EXPANSION ANCHOR

Abstract

An expansion anchor includes an anchor bolt, a nut, a spring washer, first and second outer metal plates, and first to fifth inner metal plates. Each of the first and second outer plates is subjected to the dovetail-correspondence elevation-angle bending-processing. The width of the first to fifth inner metal plates is set larger in the order of the fifth inner metal plate to the first inner metal plate, and the upper portions or the whole surfaces of the four side surfaces of the first to fifth inner metal plates are subjected to the chamfering-processing so that they become the continuation surfaces with the same inclination angle as the side-wall of the dovetail when the first to fifth inner metal plates are piled up in the same direction.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an expansion anchor, especially to an expansion anchor suitable to be used in combination with a dovetail.

2. Description of a Related Art

Conventionally, the drilling method in the “post-installed anchor” work is mainly carried out using a hammer drill. In this drilling method, since the intentional base-material organization destruction by the one perpendicular both-way blow movement to the object surface and the powdering by the 2-level rotational movement boring are the drilling (hole-forming) element, there are following problems.

(1) Since the hair crack occurrence caused by vibration is inescapable, the anchor power (grip power) is declined by the aged deterioration, so that the supported-material omission accidents occur frequently.
(2) Although the “edge-width dimension” security is indispensable in order to collateralize the safety margin to the intentional base-material organization destruction portion by the one perpendicular both-way blow movement, the construction which does not satisfy the “edge-width dimension” prescribed by JIS about the vending-machine fall prevention anchoring is actually rampant, so that the dangerous fixed situation where the proof stress is hardly demonstrated at the time of the earthquake calamity is becoming commonplace.

On the other hand, although the drilling by the core-drill is also performed, it is restrictively used. Because it does not give the shock mechanical vibration to the base material, but the equipments and the machines become large-scale, and it is the cutting by the water injection type.

There are the following patent document 1 and non-patent documents 1-6 as the documents which describe the problems about the “post-installed anchor.”

Patent Document 1: JP-A-2000-192926.

Non-Patent Document 1: M. Hirosawa and Y. Shimizu, “Commentary on the Goods, Structural Design and Side Execution of Post Installed Anchors”, Concrete Journal, Vol. 31, No. 4, pp. 13-30, April, 1993.

Non-Patent Document 2: Prof. Rolf Eligehausen in Stuttgart Technical University, Lecture Material “Introduction of Pouring-type Bonded Anchor and Reinforcing-Steel Establishing Method in Europe Adopted of Pouring-type Bonded Anchor”, Hilti and Japanese Hilti Sponsorship, Hilti Fastening Academy 2004.

Non-Patent Document 3: Choshiro Ogawa (Saitama Stone Business Association Youth Part Standing Director), “Miyagi Prefecture Northern Part Earthquake Damage Investigation Report”, Chapter 2.

Non-Patent Document 4: Meteorological Agency, “Seismic Intensity 5+, Many Gravestones Fall”, Meteorological Agency Intensity Scale Description Table.

Non-Patent Document 5: APAN DRIVE-IT CO., LTD., Metal Safety-Device-Against-Wind System Product Specification Dimensions Table.

Non-Patent Document 6: Diamond Product Company, Photographs Inserted in “Flatting Out of Construction.”

Non-Patent Document 7: T. Okada et. al., “Design and Construction of Post-Installed Anchor”, Japan Construction Anchor Association Recommendation Books.

In the non-patent document 1, the following matters are described.

(1) The rotation/shock-type rotary hammer drills having good drilling performance are imported from U.S.A. and Europe in the second half of the Showa 30s, and the various types of anchors come to be used widely.
(2) The 1990 fiscal-year production volume of the metal-system anchor and the adhesion-system anchor (bonded anchor) is 420 million, and shows 10-12% of elongation every year.
(3) The base metals at the use parts are also various, such as concrete, a section, brick, etc. There is also usage which can be investigated like the fixing (anchoring) of the vending machine specified by JIS, but in the other case, the kind of the anchor to be used also has the fact that the selection lacked in the dynamics consideration is performed.
(4) Moreover, there are also many questions such as a construction management, an amendment of construction mistake, an inspection method, etc., and the cures against them pose the future big problems.
(5) In Japan, there is no JIS standard about the “post-installed anchor.”
(6) Also about the construction method, there are no public standard construction specifications about the “post-installed anchor” in Japan.
(7) There are the oscillating twist drill, the hammer drill, the rock drill, and the diamond core-drill as the drilling machine.
(8) In the metal-system anchor, the construction standard is defined according to the kind and path of the bolt to be used, but when it is incongruent, the anchor efficiency declines remarkably.
(9) In the adhesion-system anchor, the remarkable efficiency degradation occurs when the removal of the powders is neglected at the cleaning of the holes.

The following analysis results are shown in the non-patent document 2.

(1) The adhesion stress (bond stress) distribution is stabilized in the embedding depth of 60 mm or more.
(2) The adhesion stress is decreased to 33% or less of the rated values when the adhesion stress determination factors (the drilling diameter, the hole-inner cleaning, and the drilling method) are neglected, especially when the hole-inner cleaning is neglected. The adhesion stress is decreased in the abbreviation half of the rated value by only one blower cleaning.
(3) When the edge-width dimension is 50 mm or less, it results in the break-down by the slight displacement and loading.
(4) The poor adhesion caused by the air remainder after the adhesives pouring occurs.
(5) Moreover, it should be constructed by the skilled manual labor (the construction grade system exists in Germany.).
(6) The conclusions of the adhesion anchor:
(a) An adhesives-pouring-type anchor is a reliable “post-installed anchor” like the conventional capsule type. However, the anchor performance depends on the hole-inner cleaning and the drilling method.
(b) About the action efficiency of the “post-installed anchor” under earthquake, the further research and experiment are required.
(c) In the concrete in which the crack has occurred, the break-down takes place by the interface between the resin and the concrete, and the break-down proof strength declines about 50% as compared with concrete without any cracks. In the concrete in which the crack has occurred, the special expansion anchor is effective. This is the anchor having the structure of maintaining the adhesion stress by the gauge pressure of the extended part of the bolt.

In the lecture entitled “Role and Importance of Post-installed Anchor in Building Equipment Earthquake-Proof Construction,” by Prof. Toshiaki Kiuchi in Kokushikan University, Technology Faculty, Architecture Design Engineering Department, in Hilti Fastening Academy 2004 sponsored by Hilti and Japanese Hilti, the following matters are stated.

(1) The various kinds of the earthquake-proof efficiency examinations including the anchor bolt was performed in “Tokyo Shirakami-Area Planning” about one year before the earthquake occurred off Miyagi Prefecture in 1978.
(2) The earthquake occurred off Miyagi Prefecture in 1978 during the deliberation on “Guideline of Private-Power-Generation Anti-earthquake Design” (only the “post-installed anchor technical standard” in Japan).
(3) About the post-installed anchor metal expansion type for building equipment, the permission drawing-out standard value is accepted after 1982 and afterwards. However, at the construction job site, in practice, the usage method is left in many cases to the builders who carry out the piping etc. including the site foremen, the construction supervisor engineer, the design person in charge, and the person in charge specializing in the construction company. However, since the anchor fall-out accident occurred frequently in various places, the accident preventive measures (for example, the checks of the kind, construction method, permission drawing intensity and strength have been taken in 1990 and afterwards (It will be the occurrence of Kobe Earthquake in 1995 in the midst of the measures being taken.).
(4) The post-installed anchor (HASS) standard is under deliberation in 2005 (Although about 30 years have passed since the first examination in 1977, it is the present condition that it cannot be determined.).
(5) The drawing power (tenacity) of the constructed “post-installed anchor” must fulfill the value of permission drawing power 100%. That is, there must not be any construction mistake by any means. The bad influence of one occurrence of the accident is carried out to the functionality of the whole building. There is fear of falling into the condition which cannot use the whole building depending on the case. Moreover, also especially in a big earthquake (magnitude 7 on the Japanese scale), the “post-installed anchor” must have the proof strength in all break-downs.
(6) Immediate realization of the world common standard for construction “post-installed anchor” is desired. In this case, it is conditions to keep the unified technical standard 100%.

In the above-mentioned patent document 1, the following matters are described as the weak points of the expansion-bottom anchor indicated about the anchor bolt.

(1) A crack produces to the concrete according to the power when carrying out the expansion when the anchor is inserted. Moreover, the contact surface is worn out with progress of time owing to the mechanical vibration. As a result, the anchor bolt loosens and jolts.
(2) The weak points of the adhesion-system anchor described in Paragraph 0004.
(3) The adhesive overflows from the bolt hole.
(4) Since time will be taken before solidifying, the anchor bolt shifts and inclines from the central axis of the bolt hole. Actually, the metal-system anchor and the adhesion-system anchor have the unstable grip power over the base material.

In the above-mentioned non-patent document 3, it is indicated that the anchor bolt such as a deformed bar is weak to the epicentral earthquake.

In the above-mentioned non-patent document 4, it is described “there is description of the fact that many gravestones collapsed, in Niigata Chuetsu Big Earthquake which occurred in October, 2004. Moreover, also in the gravestone in which it was equipped with the anchor bolt, the anchor bolt crawled, reached and fell out and collapsed. The cause was the vibration of the shortage of the mortar enclosure, etc. and the earthquake.”

If the size standard table of the metal extension anchor is quoted and it compares based on the frequently-used diameter of a screw [M10],

1. Internal corn placing type

Diameter of boring drill: 12.0 mm/12.5 mm, Boring depth: 40 mm>

2. Shaft-sleeve placing type

Diameter of boring drill: 14.0 mm/14.5 mm, Boring depth: 45 mm>

3. Wedge type

Diameter of Boring drill: 10.0 mm/10.5 mm, Boring depth: 60 mm>

As mentioned above, the size which guarantees the anchor intensity is specified. When the diameter of the boring twist drill is mistaken, although it is somewhat loose, it loads as it is. Or, since it is completely loose, it re-bores. As mentioned above, it is unstable and inefficient as the work which is done by a person who easily makes a misapprehension and a mistake (refer to the above-mentioned non-patent document 5).

As shown in the photograph published by the above-mentioned non-patent document 6, when the drill is held by hands, it is difficult in the stock drill operation to hold it so that the rotation core may not blur and to secure the perpendicular to the boring surface.

The defect of the boring operation using the hammer drill and the core drill, and the defect of the metal-system anchor and the adhesion-system anchor are summarized as follows:

(1) The shock boring method crushes the solid composition of the base material.
(2) When carrying out the on-site hammer drill operation, it is difficult to bore right-angled to the base material surface because of the narrow place and the influence by the hammer drill's own weight. In order to actually keep the worker's eye point on the hammer drill core drill axis-of-rotation extension, and in order to stop the bound throwing of the drill which certainly occurs at the time of the above-mentioned equipments operation, it stands and is space (1 m×1 m×less than 2 m in width) required for operation. In the job site, the place in which the drilling is possible will narrow naturally. “Slanting boring” occurs by work of the labored posture. The job called “stand curing” as a method of correcting this slanting boring becomes inescapable. It is the method of bending the external-thread bolt forcibly and making it perpendicular after the external-thread insertion after anchor wearing. Also in this case, the perpendicular standard setup is difficult. Moreover, the high-precision amendment is difficult because of the narrow working area. The perpendicular boring is difficult and is the fatal flaw which loses the anchor drawing intensity with blow boring.
(3) The edge-width-dimension reservation is difficult. When the edge-width dimension is 50 mm or less, it has almost no proof strength.
(4) When the reinforcing steel is encountered, you have to re-bore the part which made the mistake in keeping the fixed distance. Therefore, there is fear of changing the design of the related materials.
(5) In the government office order construction, the photograph of the depth of the bored hole must be taken, and the survey must be undergone.
(6) The inner cleaning is complicated, and the anchor efficiency is halved only by blower cleaning.
(7) Air will be enclosed of the pouring-type adhesion-system anchor. As a result, the adhesion stress declines.
(8) The anchor construction qualified person (journeyman) in Germany and those who pass the “post-installed anchor” construction technical expert examination in Japan are allowed the construction of the anchor.
(9) There are no anchor common protocol, standard construction technical specification, etc.
(10) The mistake and the misapprehension occur inevitably because it is complicated since there are many kinds of anchors and the diameter of the matching boring drill changes. Moreover, you have to re-bore somewhere else in that case. Therefore, it is easy to become the hotbed of the negligent construction work. After the omission accidents actually happened in succession, the construction persons concerned all over the country took the counterplan with all their might. Nevertheless, the accident will occur frequently. The reason depends the hundred percent inspection on the impossible thing.
(11) Moreover, even if it gives the high-precision anchor charge, the occurrence of the crack is inescapable as it passes through time from the characteristic of concrete. In the base material in which the crack occurs, 100% of anchor-efficiency exertion is difficult (It decreases to 50%.).
(12) Precise horizontal/vertical fixation is required of the apparatus locked up. When it must install by the slanting hole unavoidably, because the bolt axis is slanting, the screwing work with the main part of apparatus and matrix material concrete is difficult.

The incongruent anchor actually which cannot be grasped and follow-up survey are rampant.

SUMMARY OF THE INVENTION

The object of the present invention is to provide an expansion anchor which can realize the practical-use strength and the proof strength demanded in the shallow dig depth.

An expansion anchor of the present invention is an expansion anchor used in combination with a dovetail, a mouth width of the dovetail being narrower than a bottom width of the dovetail, and includes: an anchor bolt; two or more inner metal plates inserted into the dovetail; and two outer plates inserted between two side-walls of the dovetail and the inner metal plates, wherein each of the two outer plates has “L” character-like cross-sectional shape which consists of a top plate portion and a side plate portion.

An expansion anchor of the present invention is an expansion anchor (10) having an external thread at one center place of a “−” character-like shaped dovetail (31, 31′), a mouth width of the dovetail being narrower than a bottom width of the dovetail, and includes: an anchor bolt (11); a nut (12); first and second outer plates (15₁, 15₂); and two or more inner metal plates (16₁-16₅), wherein each of the first and second outer plates has “L” character-like cross-sectional shape which consists of a top plate portion and a side plate portion; and width of one inner metal plate of the two inner metal plates is set larger than width of another inner metal plate.

Here, length of the another inner metal plate of the two inner metal plates may be set larger than the width of the one inner metal plate, so that side surfaces of the two inner metal plates become surfaces having the same inclination angle as a side-wall of the dovetail when the one inner metal plate is turned 90 degrees to be piled on top of the another inner metal plate of the two inner metal plates.

Width of at least one inner metal plate of the two inner metal plates may be set larger than the mouth width of the dovetail; and a penetration-hole, a bore of which is larger than a diameter of the anchor bolt, may be provided in a center portion of the at least one inner metal plate of the two inner metal plates.

An expansion anchor of the present invention is an expansion anchor (50) having internal threads at two end portions of a “−” character-like shaped dovetail (31, 31′), a mouth width of the dovetail being narrower than a bottom width of the dovetail, and includes: first and second anchor bolts (51₁, 51₂); first and second outer plates (55₁, 55₂); and upper inner metal plate (56₁) and lower inner metal plate (56₂), wherein each of the first and second outer plates has “L” character-like cross-sectional shape which consists of a top plate portion and a side plate portion; and first and second upper internal threads (56a₁₁, 56a₁₂) and first and second lower internal threads (56a₂₁, 56a₂₂), by which tap-processing is carried out to screw with the first and second anchor bolts, are formed in the upper inner metal plate and the lower inner metal plate.

Here, width of the upper and lower inner metal plates may be set smaller than the mouth width of the dovetail; a sectional shape of the lower inner metal plate seen from a perpendicular direction to length direction of the lower inner metal plate when cutting in the length direction of the lower inner metal plate is made into a reverse-trapezoid shape; and each width of the side plate portions of the first and second outer plates is set smaller toward a bottom portion from a central portion when seeing along height direction of the side plate portion.

An expansion anchor of the present invention is an expansion anchor (60) having internal threads at four end portions of a “+” character-like shaped dovetail (32, 32′), a mouth width of the dovetail being narrower than a bottom width of the dovetail, and includes: first to fourth anchor bolts (61₁-61₄); first to eighth outer plates (65₁-65₈); and upper innermetal plate (66₁) and lower innermetal plate (66₂), wherein each of the first to eighth outer plates has “L” character-like cross-sectional shape which consists of a top plate portion and a side plate portion; the upper inner metal plate and the lower inner metal plate have shape similar to the shape of the dovetail when seen at a plane; first to fourth upper internal threads (66a₁₁-66a₁₄), by which tap-processing is carried out to screw with the first to fourth anchor bolts, are formed in first to fourth upper projection portions of the upper inner metal plate; and

first to fourth lower internal threads (66a₂₁-66a₂₄), by which the tap-processing is carried out to screw with the first to fourth anchor bolts, are formed in first to fourth lower projection portions of the lower inner metal plate.

Here, each width of the first to fourth upper projection portions of the upper inner metal plate and the first to fourth lower projection portions of the lower inner metal plate may be set smaller than the mouth width of the dovetail; tip portions of the first to fourth lower projection portions of the lower inner metal plate are cut by an acute angle toward a bottom portion of the lower inner metal plate; and each width of the side plate portions of the first to eighth outer plates is set smaller toward a bottom portion from a central portion when seeing along height direction of the side plate portion.

That is, the expansion anchor (dovetail anchor) of the present invention is the metal expansion anchor, and is locked up in the dovetail, which is formed in the base material by the rotation of the blade and chain (for example, the diamond saw and the diamond chain saw) in order to overcome the defects of the conventional circular-hole boring expansion anchor.

The shape of the dovetail dug to the base material and the shape of the matching anchor are “−” character-like and “+” character-like on the looking-down plan view. Moreover, the screwing portions are prepared in many parts including one center place or the end portions. Furthermore, either the internal thread or the external thread can be used according to the demanded proof strength and conditions.

The expansion anchor of the present invention tends to acquire the pull proof strength and shearing proof strength of the anchor using it in combination with the dovetail (the slot the mouth width of which is set smaller than the bottom width). Therefore, it is impossible to be inserted into the dovetail with one parts and one-article parts because it is the component corresponding to the width of the dovetail, so that the parts are molded into plurality and the parts are separately inserted into the dovetail. After the insertion of the parts, each of the parts is made one, connected and expanded utilizing the bolt screwing function to demonstrate the stress and the power-proof which are demanded to the anchor.

Conventionally, the group effect (namely, the dramatic reduction of the anchor proof strength by the lap of the project area) in the cone break-down is inescapable when four anchors are locked up at the high-density places and the narrow places. However, the expansion anchor of the present invention has the technical effect to realize the practical-use strength and the proof strength demanded in the shallow dig depth, because the cause of the proof-strength attenuation combined with the base-material break-down according to the mechanical vibration at the time of forming the anchor hole can be avoided 100%.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a drawing showing the composition of an expansion anchor 10 according to the first embodiment of the present invention.

FIGS. 2A and 2B are drawings explaining the forming method of a “−” character-like dovetail, FIG. 2A is a diagram showing a diamond wheel saw 21 used for forming the dovetail, and FIG. 2B is a drawing showing a diamond chain saw 25.

FIGS. 3A-3D are drawings explaining the forming method of a“−” character-like dovetail, and show the steps of forming a dovetail 31 in a base material 30 using the diamond wheel saw 21 shown in FIG. 2A.

FIGS. 4A and 4B are drawings showing the shape of the “−” character-like dovetails 31, 31′, FIG. 4A is a drawing showing the shape of the dovetail 31 formed using the diamond wheel saw 21 shown in FIG. 2A, and FIG. 4B is a drawing showing the shape of the dovetail 31′ formed using the diamond chain saw 25 shown in FIG. 2B.

FIGS. 5A-5D are drawings showing the state of the locked-up expansion anchor 10 shown in FIG. 1, FIG. 5A is a looking-down plan view, FIG. 5B is a looking-up plan view, FIG. 5C is a side view, and FIG. 5D is an elevation view.

FIG. 6 is a drawing showing the composition of an expansion anchor 50 according to the second embodiment of the present invention.

FIGS. 7A-7D are drawings showing the state of the locked-up expansion anchor 50 shown in FIG. 6, FIG. 7A is a looking-down plan view, FIG. 7B is a looking-up plan view, FIG. 7C is a side view, and FIG. 7D is an elevation view.

FIG. 8 is a drawing showing the composition of an expansion anchor 60 according to the third embodiment of the present invention.

FIGS. 9A-9D are drawings explaining the forming method of a “+” character-like dovetail, and show the steps of forming a dovetail 32 in a base material 30 using the diamond wheel saw 21 shown in FIG. 2A.

FIGS. 10A and 10B are drawings showing the shape of the “+” character-like dovetails 32, 32′, FIG. 10A is a drawing showing the shape of the dovetail 32 formed using the diamond wheel saw 21 shown in FIG. 2A, and FIG. 10B is a drawing showing the shape of the dovetail 32′ formed using the diamond chain saw 25 shown in FIG. 2B.

FIGS. 11A-11D are drawings showing the state of the locked-up expansion anchor 60 shown in FIG. 8, FIG. 11A is a looking-down plan view, FIG. 11B is a looking-up plan view, FIG. 11C is a side view, and FIG. 11D is an elevation view.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of an expansion anchor according to the present invention will be described with reference to the drawings.

An expansion anchor 10 according to the first embodiment of the present invention is used as an expansion anchor which has an external thread at one center place of a “−” character-like shaped dovetail 31 (refer to FIGS. 4A and 4B). As shown in FIG. 1, the expansion anchor 10 includes an anchor bolt 11 (a hexagonal-head bolt) made from steel, a nut 12 made from steel, a spring washer 13 made from steel, an anchorage metal plate 14 made from steel, the first and second outer plates 15₁, 15₂ made from steel or a plastic, and the first to fifth inner metal plates 16₁-16₅ (4.5 mm in thickness) made from steel.

Here, each of the first and second outer plates 15₁, 15₂ has “L” character-like cross-sectional shape which consists of a top plate portion and a side plate portion formed in one. The side plate portions of the first and second outer plates 15₁, 15₂ are bent to the top plate portions at the inclination angle so that the side plate portions become parallel to the side-walls of the dovetail 31 when inserting the first and second outer plates 15₁, 15₂ into the dovetail 31 so that the end surfaces of the top plate portions face each other. That is, the first and second outer plates 15₁, 15₂ are subjected to the dovetail-correspondence elevation-angle bending-processing. Although it is more desirable that the first and second outer plates 15₁, 15₂ are subjected to the dovetail-correspondence elevation-angle bending-processing, they may be ones which are manufactured by cutting the ready-made article angle (for example, a right-angled bending material like an iron-material angle cutting plane).

Moreover, the first and second outer plates 15₁, 15₂ have the function for transmitting the short-term load and the long-term load (tensile force and shearing force), which are generated after providing the anchor, to the side-walls of the dovetail 31 uniformly and on the average. The first and second outer plates 15₁, 15₂ may be made from metal such as steel in the usual application, but they may be made from plastic in the special-purpose application such as electric-insulation goods.

In the center portion of the anchorage metal plate 14, a penetration-hole, the bore of which is the almost same size as the diameter of the anchor bolt 11, is provided.

Moreover, in the center portions of the first to fifth inner metal plates 16₁-16₅, penetration-holes, the bore of which is larger than the diameter of the anchor bolt 11 (that is, with a margin), is provided.

The width (the length of the width direction of the dovetail 31) of the first to fifth inner metal plates 16₁-16₅ is set so that “the width 1W of the first inner metal plate 16₁”<“the width 2W of the second inner metal plate 16₂”<“the width 3W of the third inner metal plate 16₃”<“the width 4W of the fourth inner metal plate 16₄”<“the width 5W of the fifth inner metal plate 16₅”. The length (the length of the longitudinal direction of the dovetail 31) of the first to fifth inner metal plates 16₁-16₅ is set so that “the length 1L of the first inner metal plate 16₁”<“the length 2L of the second inner metal plate 16₂”<“the length 3L of the third inner metal plate 16₃”<“the length 4L of the fourth inner metal plate 16₄”<“the length 5L of the fifth inner metal plate 16₅.”

Here, the width 5W of the fifth inner metal plate 16₅ is set larger than the mouth width W1 of the dovetail 31.

However, if the sum of the thickness of the side portion of the first outer plate 15₁, the width 5W of the fifth inner metal plate 16₅ and the thickness of the side portion of the second outer plate 15₂ is larger that the mouth width W1 of the dovetail 31, the width 5W of the fifth inner metal plate 16₅ may be smaller than the mouth width W1 of the dovetail 31.

Moreover, the upper portions (or the whole surfaces) of the four side surfaces of the first to fifth inner metal plates 16₁-16₅ are subjected to the chamfering-processing so that they become the continuation surfaces with the same inclination angle as the side-wall of the dovetail 31 when the first to fifth inner metal plates 16₁-16₅ are piled up in the same direction in order of the fifth to first inner metal plate 16₅-16₁. However, although it is more desirable that the first to fifth innermetal plates 16₁-16₅ are subjected to the chamfering-processing, they may be ones which are manufactured by being extracted by the press-working machine and are not subjected to the chamfering-processing.

Moreover, the length 1L of the first inner metal plate 16₁ is set larger than the width 5W of the fifth inner metal plate 16₅ (namely, 5W<1L), the chamfering-processed upper surfaces of the side surfaces of the first to fifth inner metal plates 16₁-16₅ become the continuation surfaces having the same inclination angle as the side-wall of the dovetail 31 when the fifth inner metal plate 16₅ is turned 90 degrees to be piled on top of the first inner metal plate 16₁.

Thereby, even when the tolerance between the width of the dovetail 31 formed in a base material 30 and the original marking width occurs, the optimal expansion width can be gained. For example, when a set of the inner metal plates in which the first inner metal plate 16₁ is used as the lowest stage and the fifth to second inner metal plates 16₂-16₅ are turned 90 degrees to the first inner metal plate 16₁ to be piled on top of the first inner metal plate 16₁ in this order (1L>5W>4W>3W>2W) is used, the optimal width accommodating even to the dovetail 31 the bottom width of which becomes larger than the width of the fifth inner metal plate 16₅ by the tolerance occurring can be gained. Therefore, the failure of the digging can be made zero (namely, the digging-work yield can be pushed up to 100%).

In addition, by creating an exclusive gauge, the optimal width (namely, the combination of 1W-5L) may be instantly expressed as color by putting this gauge in the fixed position of the dug dovetail 31.

Next, the usage of the expansion anchor 10 according to this embodiment is explained with reference to FIGS. 2-4.

First, two cuts, the sectional shape of which is an arc, are formed using a diamond wheel saw 21 shown in FIG. 2A in the base material 30 (such as a concrete and a stone) by the rotational movement of the wheel in which the diamond chips 22 are provided.

Thereafter, using the diamond wheel saw 21, an auxiliary cut is formed to a predetermined depth so that the shape of the two cuts and the auxiliary cut is like “Z” character as shown in FIG. 3A. Then, as shown in FIG. 3B, the acute-angle portion of the auxiliary cut (the portion applied black in this drawing) of the “Z” character-like cuts is hit using the chisel. Then, while the unnecessary base material 30 is removed, the remaining portion (the portion applied black in this drawing) of the “Z” character-like cut is hit using a chisel as shown in FIGS. 3C and 3D. When the remaining base material 30 is not exfoliated, the bottom thereof is swept away using the chisel.

Thereby, the “−” character-like dovetail 31 with the mouth width W1 and the bottom width W2 (W1<w2) as shown in FIG. 4A is formed in the base material 30.

When only the imperfect dovetail is formed in this method, the dovetail is suitably formed using the diamond wheel saw 21, a diamond cutter, a diamond disc sander, or a diamond chain saw. The smoothness of the surface of the dovetail 31 is unnecessary. Rather, when the unevenness remains, the effect of the adhesive becomes better.

Moreover, when the cutting-slant is not applied, after removing the marking dimensions, the dovetail 31 the bottom width W2 of which is lager than the mouth width W1 can be easily formed by repeating the operation in which the blade edge of the diamond wheel saw 21 is pushed and leaned.

Furthermore, since the anchor design, in which the expansion anchor 10 spreads to the internal fixed distance even in the shorten portion of the blade, is applied, the anchor effect can be demonstrated in the whole contact dovetail surface.

Using a chain saw 25 shown in FIG. 2B instead of the diamond wheel saw 21, a “−” character-like shaped dovetail 31′ with the mouth width W1 and the bottom width W2 (W1<W2) shown in FIG. 4B may be formed in the base material 30 by the rotational movement of the chain in which diamond chips 26 are provided.

When the dovetail 31 is formed in the base material 30 as mentioned above, the anchor bolt 11 (refer to FIG. 1) is inserted into the dovetail 31 so that the bolt head turns down. Then, after the anchor bolt 11 is penetrated in the penetration-hole of the fifth inner metal plate 16₅, the fifth inner metal plate 16₅ is inserted into the dovetail 31 by the fifth inner metal plate 16₅ being inclined aslant against the mouth surface of the dovetail 31 (namely, making the plane-projection-area small) and is made to pass through the mouth of the dovetail 31 utilizing the margin of the penetration-hole. Thereby, even if the fifth inner metal plate 16₅ the width 5W of which is larger than the mouth width W1 of the dovetail 31 is used, it is possible to insert it into the dovetail 31.

Then, the fourth to first inner metal plates 16₄-16₁ are inserted into the dovetail 31. At this time, the fourth to first inner metal plates 16₄-16₁ the width of which is larger than the mouth width W1 of the dovetail 31 are inserted by inclining aslant as well as the fifth inner metal plate 16₅. The direction of the first to fifth inner metal plates 16₁-16₅ is the same (an anchor-bolt and inner-metal-plate insertion step).

At this time, when the base material 30 is a floor, the anchor bolt 11 and the first to fifth innermetal plates 16₁-16₅ are dropped into the bottom of the dovetail 31 using attraction.

Moreover, when the base material 30 is a ceiling, any one of the first to fifth inner metal plates 16₁-16₅, the width of which is larger than the mouth width of the dovetail 31, is caught, so that the inserted anchor bolt 11 and the first to fifth inner metal plates 16₁-16₅ do not fall. When the drop of the anchor bolt 11 and the first to fifth inner metal plates 16₁-16₅ is prevented by another method such as by pressing down by a hand, the widths 1W-5W of the first to fifth inner metal plates 16₁-16₅ may be smaller than the mouth width W1 of the dovetail 31.

Thereafter, while the inserted anchor bolt 11 and first to fifth inner metal plates 16₁-16₅ are pushed against the bottom of the dovetail 31, the first and second outer plates 15₁, 15₂ are inserted into the dovetail 31 one by one so that the external surfaces of the first and second outer plates 15₁, 15₂ may touch the side-wall of the dovetail 31 certainly and naturally (an outer-plate imposition step).

Since a space of a certain size is generated in the bottom of the dovetail 31 in this step by experience, the smooth imposition operation to the dovetail 31 and the most important anchor-axis-upright-rectification can be carried out freely.

Moreover, when the side-walls of the dovetail 31 do not face each other at equal intervals of the longitudinal direction of the dovetail 31, the following measures are taken.

(1) An elastic adhesive, epoxy adhesive, or a cement mortar is poured between the side-wall of the dovetail 31 and the first and second outer plates 15₁, 15₂ and is stiffened.
(2) The position adjustment is carried out by inserting the wedges at one to four places between the first and second outer plates 15₁, 15₂ and the first to fifth inner metal plate 16₁-16₅ from the right and left of the longitudinal direction of the dovetail 31, and then they are locked up eternally. In this case, it is safer to fill up the cavity of the dovetail 31 with an adhesive or a cement mortar.

Then, the anchorage metal plate 14 is inserted into the anchor bolt 11 by passing the bolt-screw portion of the anchor bolt 11 through the penetration-hole of the anchorage metal plate 14 (an anchorage mount step).

Thereby, the anchorage metal plate 14 bridges the side-wall of the dovetail 31 on the surface of the base material 30. Since the anchorage metal plate 14 planarly contacts with the surface of the base material 30 together with the anchorage after being locked up, the short-term load and the long-term load (tensile force and shearing force) are transformed into the compression force against the base material 30.

Furthermore, the anchorage metal plate 14 is effective in not causing the partial displacement of the first and second outer plates 15₁, 15₂ when they are locked up as mentioned later.

Finally, the locked-up operation is carried out using the spring washer 13 and the nut 12 (a locked-up step).

Thereby, the first to fifth inner metal plates 16₁-16₅ begin the displacement in the mouth direction of the dovetail 31, and the first and second outer plates 15₁, 15₂ stick to the side-walls of the dovetail 31 to begin to demonstrate the anchor adhesion. However, it is not necessary to apply the unnecessary torque, and the shakiness should just be solved.

FIGS. 5A-5D show the states of the locked-up expansion anchor 10.

In the expansion anchor 10 according to this embodiment, it is not necessary to give the anchor-expansion stress, because the anchor itself does not theoretically need to be fixed to the base material 30 unlike the conventional circular-hole anchor. That is, since only the value of the real number of the generated load serves as the adhesion force and acts to the base material 30, the structure in which any superfluous stress is not given at all is realized. Therefore, the locking-up operation may be carried out without causing the shakiness to the respective parts and components. Furthermore, in case of the permanent anchoring, it is sufficient to stop the shakiness by filling up the cavity of the base material 30 with silicon coking or a cement mortar. In the established base material concrete, the “concrete stiffener method by epoxy resin pouring” which is already announced by the Japanese Concrete Institute may be performed.

In comparison with the hammer-drill boring method (the vibration to the base material is unescapable) used abundantly in the conventional technology, the dig method using the diamond wheel saw 21 (sandblast) and the expansion anchor 10 according to this embodiment do not give any unnecessary stress (mechanical vibration and internal expansion force) to the base material 30. Therefore,

(1) In the precast concrete, the strength on the test result table by the public institution which the maker announced (in the new-building cast-in-place concrete, the concrete strength after the care-of-health period progress of the requirement observance, and in the established building, the strength by the test method of the Schmidt hammer in the job site etc.).
(2) The material strength of the steel product, the plastic, etc. used for the expansion anchor 10
(3) Tensile test value
Anchor conditions: Ordinary-structural rolled steel (Suspended Solids JIS G 3101)
1. Dig depth 40 mm
2. Anchor outer depth 30 mm
3. Anchor outer dimensions 30×60xt=2 Two right and left
4. Anchor inner dimensions (46 to 48)×(26 to 30)xt=4.5 4 sheets
(a) A concrete (test-specimen dimensions: 150×150×100 mm) non-reinforcing steel

27. 2 kN/bolt (M12) base material crevice break-down (relief break-down to the crevice and the side surface on the basis of the intersection of the side surface and the bottom of the dovetail)

(b) Black granite (test-specimen dimensions: 182×152×117 mm)

40.0 KN/bolt (M12) base material crevice break-down (one dovetail wall extension surface crevice break-down on the basis of the intersection of the side surface and the bottom of the dovetail)

The architecture of the anchor bolt and the strength calculation can be performed only for the above value, so that the pulling-out examination after the construction of the on-site becomes unnecessary.

That is, the maximum tensile strength of the expansion anchor 10 becomes the lower value of the base-material bending moment strength and the bolt yield-stress strength. As a result, if the 150 kN-super-high strength concrete and the 800 mega pascal super-high tension steel which are put are utilized for the raw material and the composition elements of the expansion anchor 10, the drastic super-high-strength-post-installed anchor will be born.

The more anchor-imbedding depth is deep, the more the safety rate seems to improve as long as there is the instability in the base-material compression intensity such as the neutralization, cracks, etc. of concrete. However, it can reason from the base material break-down and the break fact in the tensile test concerned that since the origin of the anchor proof strength is the counter force over the base-material bending moment in the expansion anchor 10, the warping cone break-down secondarily generates, but the imbedding depth and the warping cone break-down can be free from the anchor-proof-strength origin.

On the practical use target, the practical anchor proof strength can be obtained when any deterioration such as the neutralization does not occurred within the depth limit (namely, within the “wear” limits) to the reinforcing steel placed under the concrete surface at 3-5 cm, and it is judged in the Schmidt hammer test that there is the sufficient anchor proof strength. That is, the reinforcing-steel investigation is beforehand performed like the conventional anchor construction using the technical drawing and the probe. When the reinforcing steel is encountered, the digging is stopped if the depth of around 35 mm is secured, and the anchor establishment may be performed in this depth. Furthermore, when the depth is surely secured, the reinforcing steel can be cut off and removed using the diamond saw under the careful examination. In this case, it is important to reinforce the base-material concrete by the epoxy resin being poured in and filled up in the air gap of the dovetail 31 after the anchor being fixed.

According to the above-mentioned non-patent literature 7 (T. Okada et. al., “Design and Construction of Post-Installed Anchor”, Japan Construction Anchor Association Recommendation Books), there is the description of the experience value “there was 30% or more of reinforcing-steel encounter in case of the boring depth of 50 mm or more.” The expansion anchor 10 according to this embodiment opens 100% from the accompanying operation and defect caused by the reinforcing-steel encounter.

Next, an expansion anchor according to the second embodiment of the present invention is explained.

An expansion anchor 50 according to this embodiment is used as an expansion anchor having internal threads at two end portions of a “−” character-like shaped dovetail 31, and has, as shown in FIG. 6, the first and second anchor bolts 51₁, 51₂ (hexagonal-head bolts) made from steel, the first and second spring washers 53₁, 53₂ made from steel, an anchorage metal plate 54 made from steel, the first and second outer plates 55₁, 55₂ from steel or plastic, and upper and lower inner metal plates 56₁, 56₂ made from steel.

Here, in the both ends on the center line of the longitudinal direction of the anchorage metal plate 54 (the longitudinal direction of the dovetail 31), the first and second penetration-holes the diameter of which is the almost same as the diameter of the first and second anchor bolts 51₁, 51₂ are formed, respectively.

In the places corresponding to the first and second penetration-holes of the anchorage metal plate 54 on the center line of the longitudinal direction of the upper inner metal plates 56₁ (the longitudinal direction of the dovetail 31), the first and second upper internal threads 56a₁₁, 56a₁₂ by which the tap-processing is carried out to screw with the first and second anchor bolts 51₁, 51₂ are formed, respectively. Similarly, the places corresponding to the first and second penetration-holes of the anchorage metal plate 54 on the center line of the longitudinal direction of the lower inner metal plates 56₂ (the longitudinal direction of the dovetail 31), the first and second lower internal threads 56a₂₁, 56a₂₂ by which the tap-processing is carried out to screw with the first and second anchor bolts 51₁, 51₂ are formed, respectively.

In the expansion anchor 50 according to this embodiment, in order to secure two screw parts on the upper and lower sides or the right and left sides, the length (the length of the longitudinal direction of the dovetail 31) and height (the length of the depth direction of the dovetail 31) of the upper and lower inner metal plates 56₁, 56₂ are set larger than the length and height of the first to fifth inner metal plates 16₁-16₄ shown in FIG. 1.

Since the height of the upper and lower inner metal plates 56₁, 56₂ is set large, the upper and lower inner metal plates 56₁, 56₂ cannot be inserted into the dovetail 31 like the fifth inner metal plate 16₅ mentioned above. Therefore, the width of the upper and lower inner metal plates 56₁, 56₂ is set smaller than the mouth width W1 of the dovetail 31.

In order to secure the width larger than the mouth width W1 of the dovetail 31 after inserting the first and second outer plates 55₁, 55₂ and the upper and lower inner metal plates 56₁, 56₂ into the dovetail 31, the thickness of the first and second outer plates 55₁, 55₂ is set larger than the thickness of the first and second outer plates 15₁, 15₂ shown in FIG. 1.

Since the height of the upper and lower inner metal plates 56₁, 56₂ is set large, the sectional shape of the length direction of the lower inner metal plate 56₂ is made into a reverse-trapezoid shape so that it can be inserted into the dovetail 31 whose sectional shape along the length direction is a semicircle shape.

Since each of the first and second outer plates 55₁, 55₂ has “L” character-like cross-sectional shape which consists of a top plate portion and a side plate portion and the height of the first and second outer plates 55₁, 55₂ is set larger than the height of the first and second outer plates 15₁, 15₂ shown in FIG. 1, the width of the side plate portion is set smaller toward the bottom portion from the center portion to be able to be inserted into the dovetail 31 whose sectional shape of the length direction is semicircle-like.

The upper portions (or the whole surfaces) of the two side surfaces of the upper and lower inner metal plates 56₁, 56₅ are subjected to the chamfering-processing so that they become the continuation surfaces with the same inclination angle as the side-wall of the dovetail 31 when the upper inner metal plate 56₁ is piled up on the lower inner metal plate 56₅ in the same direction. Although it is more desirable that the upper and lower inner metal plates 56₁, 56₅ are subjected the chamfering-processing, they may be ones which are manufactured by being extracted by the press-working machine and are not subjected the chamfering-processing.

Moreover, the side plate portions of the first and second outer plates 55₁, 55₂ are bent to the top plate portions of the first and second outer plates 55₁, 55₂ at the inclination angle so that the side plate portions become parallel to the side-walls of the dovetail 31 when inserting the first and second outer plates 55₁, 55₂ into the dovetail 31 so that the end surfaces of the top plate portions face each other. That is, the first and second outer plates 55₁, 55₂ are subjected to the dovetail-correspondence elevation-angle bending-processing. Although it is more desirable that the side plate portions of the first and second outer plates 55₁, 55₂ are subjected to the dovetail-correspondence elevation-angle bending-processing, they may be ones which are manufactured by cutting the ready-made article angle (for example, a right-angled bending material like an iron-material angle cutting plane).

Next, the usage of the expansion anchor 50 according to this embodiment is explained.

First, the dovetail 31 shown in FIG. 4A is formed in the base material 30 using the diamond wheel saw 21 shown in FIG. 2A like the case of the expansion anchor 10 according to the first embodiment mentioned above.

Thereafter, the lower inner metal plate 56₂ is dropped into the dovetail 31, and then the upper inner metal plate 56₁ is dropped on the lower inner metal plate 56₂ (an inner-plate imposition step).

Thereafter, the first and second outer plates 55₁, 55₂ are inserted into the dovetail 31 one by one so that the external surfaces of the first and second outer plates 55₁, 55₂ may touch the side-wall of the dovetail 31 certainly and naturally (an outer-plate imposition step).

Thereafter, the anchorage metal plate 54 is placed on the surface of the base material 30 to cover all the opening portions of the dovetail 31 (an anchorage mount step).

Here, in case of using the expansion anchor 50 as objects for fixing a hand-rail etc. which is attached to the wall, a hand-rail-leg-wheel flat plate is used as the anchorage metal plate 54. At this time, the hand-rail-leg-wheel flat plate may be designed to be larger than the dovetail 31 in order to cover the dovetail 31.

Thereafter, the first and second anchor bolts 51₁, 52₂ are passed through the first and second penetration-holes of the anchorage metal plate 54 after being equipped with the first and second spring washers 53₁, 53₂, and then the first and second upper internal threads 56a₁₁, 56a₁₂ of the upper inner metal plate 56₁ and the first and second lower internal threads 56a₂₁, 56a₂₂ of the lower inner metal plate 56₂ are fastened by the brake torque being averagely applied to the first and second anchor bolts 51₁, 51₂ by turns, (a locked-up step).

Thereby, the upper inner metal plate 56₁ and the lower inner metal plate 56₂ begin the displacement in the mouth direction of the dovetail 31, and the first and second outer plates 55₁, 55₂ stick to the side-walls of the dovetail 31 to begin to demonstrate the anchor adhesion. However, it is not necessary to apply the unnecessary torque, and the shakiness should just be solved.

FIGS. 7A-7D show the states of the locked-up expansion anchor 50

Next, an expansion anchor according to the third embodiment of the present invention is explained.

An expansion anchor 60 according to this embodiment is used as an expansion anchor having internal threads at four end portions of a “+” character-like shaped dovetail 32 (refer to FIG. 10A), and has, as shown in FIG. 8, the first to fourth anchor bolts 61₁-61₄ (hexagonal-head bolts) made from steel, the first to fourth spring washer 63₁-63₄ made from steel, an anchorage metal plate 64 made from steel, the first to eighth outer plates 65₁-65₈ made from steel or plastic, and upper and lower inner metal plates 66₁, 66₂ made from steel.

In FIG. 8, only the first and fourth anchor bolts 61₁, 61₄ among the first to fourth anchor bolts 61₁-61₄ are showed, and only the first and fourth spring washers 63₁, 63₄ among the first to fourth spring washer 63₁-63₄ are showed.

Here, in the both ends on two center lines (length and width) of the anchorage metal plate 64, the first to fourth penetration-holes the diameter of which is the almost same as the diameter of the first to fourth anchor bolts 61₁-61₄ are formed, respectively.

Moreover, the upper inner metal plate 66₁ and the lower inner metal plate 66₂ has the shape similar to the shape of the “+” character-like dovetail 32.

That is, the upper inner metal plate 66₁ has the plane shape in which two sticks are intersected in the shape of “+” character (hereafter, to a simplification of explanation sake, the projection portions of the upper inner metal plate 66₁ are called the first to fourth upper projection portions.), and the first to fourth upper internal threads 66a₁′-66a₁₄ by which the tap-processing is carried out to screw with the first to fourth anchor bolts 61₁-61₄ are formed in the places of the first to fourth upper projection portions which correspond to the first to fourth penetration-holes of the anchorage metal plate 64.

Similarly, the lower inner metal plate 66₂ has the plane shape in which two sticks are intersected in the shape of “+” character (hereafter, to a simplification of explanation sake, the projection portions of the lower inner metal plate 66₂ are called the first to fourth lower projection portions.), and the first to fourth lower internal threads 66a₂₁-66a2₂₄ by which the tap-processing is carried out to screw with the first to fourth anchor bolts 61₁-61₄ are formed in the places of the first to fourth lower projection portions which correspond to the first to fourth penetration-holes of the anchorage metal plate 64.

In the expansion anchor 60 according to this embodiment, in order to secure four screw parts on the upper and lower sides and the right and left sides, the length (namely, the length from the tip of the first upper projection portion to the tip of the third upper projection portion, and the length from the tip of the second upper projection portion to the tip of the fourth upper projection portion) and height (namely, the length of the depth direction of the dovetail 32) of the upper and lower inner metal plates 66₁, 66₂ are set larger than the length and height of the first to fifth inner metal plates 16₁-16₄ shown in FIG. 1.

Since the height of the upper and lower inner metal plates 66₁, 66₂ is set large, the upper and lower inner metal plates 66₁, 66₂ cannot be leaned and inserted into the dovetail 32 like the first to fifth inner metal plate 16₁-16₅ shown in FIG. 1. Therefore, the width of the first to fourth upper projection portions of the upper inner metal plate 56₁ and the first to fourth lower projection portions of the lower inner metal plate 56₂ is set smaller than the mouth width of the dovetail 32.

In order to secure the width larger than the mouth width W1 of the dovetail 32 after inserting the first to eighth outer plates 65₁-65₈ and the upper and lower inner metal plates 66₁, 66₂ into the dovetail 32, the thickness of the first to eighth outer plates 65₁-65₈ is set larger than the thickness of the first and second outer plates 15₁, 15₂ shown in FIG. 1.

Since the height of the upper and lower inner metal plates 66₁, 66₂ is large, the tips of the first to fourth projection portions of the lower inner metal plate 66₂ are cut by the acute angle to be inserted into the dovetail 32 whose sectional shape of the longitudinal direction is the semicircle shape.

Each of the first to eighth outer plates 65₁-65₈ has the “L” character-like cross-sectional shape which consists of a top plate portion and a side plate portion, and since the height of the first to eighth outer plates 65₁-65₈ is set larger than the height of the first and second outer plates 15₁, 15₂ shown in FIG. 1, the width of the side plate portions is set smaller toward the bottom portion from the center portion to be inserted to near the bottom of the dovetail 32 whose sectional shape of the longitudinal direction is the semicircle shape.

Moreover, the upper portions (or the whole surfaces) of the two side surfaces of the longitudinal direction of the first to fifth upper projection portions of the upper inner metal plate 66₁ and the first to fifth lower projection portions of the lower inner metal plate 66₂ are subjected to the chamfering-processing so that they become the continuation surfaces with the same inclination angle as the side-wall of the dovetail 32 when the upper inner metal plate 66₁ is piled up in the same direction on the lower inner metal plate 66₂. However, although it is more desirable that the upper and lower inner metal plates 66₁, 66₂ are subjected the chamfering-processing, they may be ones which are manufactured by being extracted by the press-working machine and are not subjected the chamfering-processing.

Moreover, the side plate portions of the first to eighth outer plates 65₁-65₈ are bent to the top plate portions of the first to eighth outer plates 65₁-65₈ at the inclination angle so that the side plate portions become parallel to the side-walls of the dovetail 32 when inserting the first to eighth outer plates 65₁-65₈ into the dovetail 32 so that the end surfaces of the top plate portions face each other. That is, the first to eighth outer plates 65₁-65₈ are subjected to the dovetail-correspondence elevation-angle bending-processing. Although it is more desirable that the first to eighth outer plates 65₁-65₈ are subjected to the dovetail-correspondence elevation-angle bending-processing, they may be ones which are manufactured by cutting the ready-made article angle (for example, a right-angled bending material like an iron-material angle cutting plane).

Next, the usage of the expansion anchor 60 according to this embodiment is explained with reference to FIGS. 9-11.

First, two cuts whose sectional shape is an arc are formed, using the diamond wheel saw 21 shown in FIG. 2A, in the base material 30 (such as a concrete and a stone) by the rotational movement of the wheel in which the diamond chips 22 are provided as shown in FIG. 9A, and then two other cuts whose sectional shape is an arc are formed in parallel in the base material 30 to cross right-angled at the center of the two cuts.

Thereafter, as shown in FIG. 9B, the intersection portion of the four cuts (the portion applied black in this figure) is hit using the chisel. Then, while the unnecessary base material 30 is removed, the remaining portions (the portions applied black in this figure) between the two parallel cuts are hit using the chisel as shown in FIGS. 9C and 9D. When the remaining base material 30 is not exfoliated, the bottom thereof is swept away using the chisel.

Thereby, the “+” character-like dovetail 32 which has the mouth width W1, the bottom width W2, the mouth intersection-portion diagonal-line length W3 and the bottom intersection-portion diagonal-line length W4 (W1<W2<W3<W4) as shown in FIG. 10A is formed in the base material 30.

Using the chain saw 25 shown in FIG. 2B, a “+” character-like shaped dovetail 32′ shown in FIG. 10B may be formed in the base material 30 similarly.

Thereafter, the lower inner metal plate 66₂ is dropped into the dovetail 32, and then the upper inner metal plate 66₁ is dropped on the lower inner metal plate 66₂ (an inner-plate imposition step).

Thereafter, the first to eighth outer plates 65₁-65₈ are inserted into the dovetail 32 one by one so that the external surfaces of the first to eighth outer plates 65₁-65₈ may touch the side-wall of the dovetail 32 certainly and naturally (an outer-plate imposition step).

Thereafter, the anchorage metal plate 64 is placed on the surface of the base material 30 to cover all the opening portions of the dovetail 32 (an anchorage mount step).

Here, in case of using the expansion anchor 60 as objects for fixing in the leg portion of the angle stiff pipe pillar, the round stiff-pipe pillar, etc., the flat-bar sheet steel which is attached in the leg portion of the pillar by welding and so forth and in which four holes are formed is used as the anchorage metal plate 64.

Thereafter, the first to fourth anchor bolts 61₁-62₄ are passed through the first to fourth penetration-holes of the anchorage metal plate 64 after being equipped with the first to fourth spring washers 63₁-63₄, and then the first to fourth upper internal threads 66a₁₁-66a₁₂ of the upper inner metal plate 66₁ and the first to fourth lower internal threads 66a₂₁-66a₂₂ of the lower inner metal plate 66₂ are fastened by the brake torque being averagely applied to the first to fourth anchor bolts 61₁-61₂ by turns, (a locked-up step).

Thereby, the upper inner metal plate 66₁ and the lower inner metal plate 66₂ begin the displacement in the mouth direction of the dovetail 32, and the first to eighth outer plates 65₁-65₈ stick to the side-walls of the dovetail 32 to begin to demonstrate the anchor adhesion. However, it is not necessary to apply the unnecessary torque, and the shakiness should just be solved.

FIGS. 11A-11D show the states of the locked-up expansion anchor 60

In the above explanation, although the anchorage metal plates 14, 54, 64 made from steel are used, the roves made from steel may be used.

Claims

1. An expansion anchor for use in combination with a dovetail, a mouth width of said dovetail being narrower than a bottom width of said dovetail, the expansion anchor comprising:

an anchor bolt;

two or more inner metal plates inserted into said dovetail; and

two outer plates inserted between two side-walls of said dovetail and said inner metal plates,

wherein each of said two outer plates has a substantially L-shaped cross-section which comprises a top plate portion and a side plate portion.

2. An elongated expansion anchor having a threaded portion in a center portion thereof, the expansion anchor being configured to engage a dovetail, a mouth width of said dovetail being narrower than a bottom width of said dovetail, the expansion anchor comprising:

an anchor bolt;

a nut;

first and second outer plates; and

two or more inner metal plates,

wherein each of said first and second outer plates has a substantially L-shaped cross-section, which comprises a top plate portion and a side plate portion; and

wherein a width of a first inner metal plate is selected to be greater than a width of a second inner metal plate.

3. The expansion anchor according to claim 2, wherein a length of said second inner metal plate is selected to be greater than the width of said first inner metal plate, so that side surfaces of said first and second inner metal plates become surfaces having the same inclination angle as a side-wall of said dovetail when said first inner metal plate is turned 90 degrees to be stacked with said second inner metal plate.

4. The expansion anchor according to claim 2, wherein

a width of at least one inner metal plate of said two or more inner metal plates is selected to be larger than the mouth width of said dovetail; and wherein

a penetration-hole, a bore of which is larger than a diameter of said anchor bolt, is provided in a center portion of at least one inner metal plate of said two or more inner metal plates.

5. An elongated expansion anchor having threaded portions in opposed end portions thereof, the expansion anchor being configured to engage a dovetail, a mouth width of said dovetail being narrower than a bottom width of said dovetail, the expansion anchor comprising:

first and second anchor bolts;

first and second outer plates; and

an upper inner metal plate and a lower inner metal plate,

wherein each of said first and second outer plates has a substantially L-shaped cross-section, which comprises a top plate portion and a side plate portion; and

wherein each of said upper inner and lower inner metal plates includes first and second upper internal threaded portions formed in respective holes defined therein, to enable threaded engagement with said first and second anchor bolts.

6. The expansion anchor according to claim 5, wherein

a width of each of said upper and lower inner metal plates is selected to be smaller than the mouth width of said dovetail;

a cross-sectional shape of said lower inner metal plate viewed from a side thereof is substantially trapezoidal; and

a width of said side plate portions of said first and second outer plates is selected to be less in a bottom portion thereof than in a central portion thereof.

7. A substantially cross-shaped expansion anchor having internal threaded portions defined in four end portions thereof, the expansion anchor being configured to engage a dovetail, a mouth width of said dovetail being narrower than a bottom width of said dovetail, comprising:

first to fourth anchor bolts;

first to eighth outer plates; and

an upper inner metal plate and a lower inner metal plate, each including first through fourth projection portions, wherein:

each of said first to eighth outer plates has a substantially L-shaped cross-section, which comprises a top plate portion and a side plate portion;

said upper inner metal plate and said lower inner metal plate have a shape similar to the shape of said dovetail when viewed from a the same direction; and

said first to fourth projection portions of each of the upper and lower internal plates respectively include threaded portions formed in respective holes defined therein, to enable threaded engagement with respective ones of said first to fourth anchor bolts.

8. The expansion anchor according to claim 7, wherein

a width of each of said first to fourth upper projection portions of said upper inner metal plate and said first to fourth lower projection portions of said lower inner metal plate is selected to be smaller than the mouth width of said dovetail;

tip portions of said first to fourth lower projection portions of said lower inner metal plate are cut by an acute angle toward a bottom portion of said lower inner metal plate; and

a width of each of said side plate portions of said first to eighth outer plates is selected to be less in a bottom portion there of than in a central portion thereof.

9. The expansion anchor according to claim 3, wherein

a width of at least one inner metal plate of said two or more inner metal plates is selected to be greater than the mouth width of said dovetail; and

a penetration-hole, a bore of which is larger than a diameter of said anchor bolt, is defined in a center portion of said at least one inner metal plate of said two or more inner metal plates.