Facilitated tightening device

Abstract

A facilitated tightening device allowing a bolt to be inserted smoothly by preventing a screw block engaged with the bolt from being inclined or fallen down, comprising a base (2) having a bolt insert hole (7) partly forming a bolt receiving surface (9) and an inclined surface (8) gradually decreasing in diameter toward the insert side of the bolt (6) in the state of being continued with the bolt insert hole (7) formed therein, a screw block (3) slid along the inclined surface (8) according to the axial movement of the inserted bolt (6) to be engaged with the bolt (6), an energizing member (5) energizing the screw block (3) in inner radial direction, and guide means (10, 11) engaged with the screw block (3) to prevent the screw block (3) from being fallen down in the base (2).

Description

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a simple fastening device that can be used in various machines, such as construction, electrical, or mechanical equipment, and that can be inserted and clamped by a one-touch operation.

[0003] 2. Background of the Invention

[0004] Conventionally, there is a simple fastening device that can be inserted and clamped by a one-touch operation; this is described in Japanese Examined Utility Model Publication No. S55-48171. FIGS. 17-19 illustrate this conventional simple fastening device 100, which comprises a base 110, running screws 120, 120, and a spring 130 consisting of a coil spring.

[0005] A bolt 140 is inserted into the base 110, and a bolt-insertion hole 150 is opened in the base 110. The bolt-insertion hole 150 that is formed in the base 110 has slope portions 160, 160. The diameter of the lower parts of the slope portions 160, 160 of the bolt-insertion hole 150 is made smaller than the diameter of the upper part of the slope portions 160, 160 of the bolt-insertion hole 150, and the running screws 120, 120 are supported on the slope portions 160, 160, respectively.

[0006] The running screws 120, 120 are opposed to each other in a pair, and female screws 121, 121 that are to be engaged with a male screw 141 of the bolt 140 are formed in a longitudinal direction on the opposed faces of the running screws 120, 120. In addition, tapered faces 122, 122 that can freely slide on the above-mentioned slope portions 160, 160 are formed at the bottom of the running screws 120, 120.

[0007] A spring 130 is inserted into the base 110 in a manner so as to pressurize a pair of the opposed running screws 120, 120 from above. In order that the spring 130 can pressurize the running screws 120, 120, a cover 170 is fixed on the top end of the base 110 by pressure fitting.

[0008] In such a structure, by mounting the cover 170 onto the base 110 with the spring 130 flexed to some degree, the running screws 120, 120 are pressed to move toward the bolt-insertion hole 150. As shown in FIG. 18, the bolt 140 is inserted in the base 110 from the bolt-insertion hole 150, so that the running screws 120, 120 slide upward on the slope portions 160, 160 against the spring force of the spring 130, and thus the bolt can be inserted between the running screws 120, 120. Then, the female screws 121, 121 of the running screws 120, 120 engage with the bolt 140 due to the spring force of the spring 130, and thus the bolt 140 can be fastened by a one-touch operation.

[0009] However, this conventional simple fastening device 100 has a shortcoming that the insertion of the bolt 140 can cause the running screws 120, 120 to become inclined or to slip down in the base 110. FIG. 19 shows such a situation where the running screws 120, 120 slip down. When the inserted bolt 140 pushes up the running screws 120, 120, the top portions of the running screws 120, 120 are inclined in a manner so as to approach or lean toward each other (as shown by the arrows), or to slip down. Such a displacement causes the bolt 140 to be hooked by the running screws 120, 120 when the bolt 140 is inserted, which makes one-touch fastening of the bolt 140 difficult.

[0010] The present invention has been made in consideration of the above problems with a conventional simple fastening device, and one object of the present invention is to provide a simple fastening device that makes it possible to smoothly insert a bolt while preventing the inclination or slipping down of the running screws at the time that the bolt is inserted, and thereby makes it possible to perform fastening by a one-touch operation.

SUMMARY OF THE INVENTION

[0011] For the aforementioned purpose, the invention set forth in claim 1 is a simple fastening device wherein running screws are supported by slope portions formed on the sides of a bolt-insertion hole of a base, and a bolt is inserted in the bolt-insertion hole while the running screws are pressed by a pressing member, so that the running screws are engaged with the bolt. The invention set forth in claim 1 is also characterized such that a guide means is engaged with said running screws to prevent the running screws from slipping down in the base.

[0012] Under such a structure, by inserting the bolt into the bolt-insertion hole, the running screws are engaged and fastened with the bolt. According to the present invention, a guide means is engaged with the running screws, as a result of which the running screws will not become inclined or slip down, so that the bolt can be smoothly inserted without being hooked by the running screws.

[0013] The invention set forth in claim 2 comprises (1) a base, to which are formed (a) a bolt-insertion hole, whose one portion is a bolt-receiving face, and (b) a slope portion, whose diameter is gradually reduced toward the bolt-insertion side under a condition that it connects with the bolt-insertion hole, (2) a running screw, which slides along said slope portion and is engaged with the bolt as the bolt to be inserted moves in an axial direction, (3) pressing members for pressing the running screw downward, and (4) a guide means that engages with the running screw and prevents the running screw from slipping down in the base.

[0014] Under such a structure, when the bolt is inserted into the bolt-insertion hole, the running screw slides along the slope portion, so that the bolt can be introduced between the running screw and the bolt-receiving face. The running screw engages with the introduced bolt due to the pressure of the pressing member. A reaction force that is generated at this time is received by the bolt-receiving face, and therefore the bolt can be securely fastened.

[0015] According to the invention set forth in claim 2, a guide means is engaged with the running screw, as a result of which the running screw will not become inclined or slip down, so that the bolt can be smoothly inserted without being hooked by the running screw, as with the case of the invention set forth in claim 1.

[0016] The invention set forth in claim 3 comprises (1) a base, to which formed are (a) a bolt-insertion hole, and (b) a plurality of slope portions, whose diameters are gradually reduced toward the bolt-insertion side under the condition that the bolt is inserted into the bolt-insertion hole, (2) a plurality of running screws that slide along the slope portions and are engaged with the bolt as the inserted bolt moves in an axial direction, (3) a pressing member for pressing the running screws downward, and (4) a guide means that engages with the running screws and prevents the running screws from slipping down in the base.

[0017] Under such a structure, when the bolt is inserted into the bolt-insertion hole, a plurality of the running screws slide along the slope portion, so that the bolt can be introduced between the running screws. Furthermore, because a plurality of the running screws engage with the bolt due to the pressure of a pressing member, the bolt can be securely fastened.

[0018] According to this invention, a guide means is engaged with the running screw, as a result of which the running screw will not become inclined or slip down, so that the bolt can be smoothly inserted without being hooked by the running screw, as with the cases mentioned above.

[0019] The invention set forth in claim 4 is an invention described in any of claims 1 to 3, and is characterized in that said guide means comprises (1) a guide projection that is provided to the base in a manner so as to project toward the bolt-insertion side, and (2) a guide groove that is formed on said running screw so as to engage with the guide projection.

[0020] Under such a structure, the guide projection is engaged with the guide groove of the running screw, which slides due to insertion of the bolt, so that the running screws can be prevented from being inclined or slipping down. According to this invention, a guide means can be formed easily because of a simple structure that comprises the guide groove and the guide projection.

[0021] The invention set forth in claim 5 is an invention as described in claim 4, and is characterized such that a cover, into which said bolt can be inserted, is attached on the base in its downstream side of the bolt-insertion direction, and said guide projection is provided on the cover.

[0022] According to this invention, since the guide projection is formed on a cover that is separate from the base, the guide projection can be formed easily.

[0023] The invention set forth in claim 6 is an invention as described in claim 4 or claim 5, and is characterized such that said guide projection has a guide face, which is inclined in the same direction as a sliding direction of said running screw, and that the guide face is engaged with said guide groove.

[0024] Thus, because the guide face is formed in a manner so as to become inclined along the sliding direction of the running screw, the running screw can be surely prevented from being inclined or slipping down at the time of sliding.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG. 1 illustrates Embodiment 1 of the present invention, a plan view of which is shown by (a), a vertical cross-sectional view of which is shown by (b), and a bottom view of which is shown by (c).

[0026] FIG. 2(a) is a plan view of a base of the present invention, and FIG. 2(b) is a vertical cross-sectional view thereof

[0027] FIG. 3(a) is a front view of a running screw, FIG. 3(b) is a plan view thereof, FIG. 3(c) is a vertical cross-sectional view thereof, and FIG. 3(d) is a bottom view thereof

[0028] FIG. 4(a) is a vertical cross-sectional view of a cover, and FIG. 4(b) is a plan view thereof

[0029] FIG. 5 is a cross-sectional view showing the condition before a bolt is inserted in Embodiment 1.

[0030] FIG. 6 is a cross-sectional view showing a condition when a bolt is about to be inserted in Embodiment 1.

[0031] FIG. 7 is a cross-sectional view showing the condition when a bolt is being inserted in Embodiment 1.

[0032] FIG. 8 is a cross-sectional view showing the condition after a bolt has been inserted in Embodiment 1.

[0033] FIG. 9 is a cross-sectional view showing the condition that the bolt is being pulled out of Embodiment 1.

[0034] FIG. 10 illustrates Embodiment 2 of the present invention, a plan view of which is shown by (a), a vertical cross-sectional view of which is shown by (b), and a bottom view of which is shown by (c).

[0035] FIG. 11 (a) is a vertical cross-sectional view of a cover in Embodiment 2, and FIG. 11 (b) is a plan view thereof

[0036] FIG. 12 is a cross-sectional view showing the condition before a bolt is inserted in Embodiment 3.

[0037] FIG. 13 is a cross-sectional view showing the condition when a bolt is about to be inserted in Embodiment 3.

[0038] FIG. 14 is a cross-sectional view showing the condition when a bolt is being inserted in Embodiment 3.

[0039] FIG. 15 is a cross-sectional view showing the condition after the bolt has been inserted in Embodiment 3.

[0040] FIG. 16 is a cross-sectional view showing the condition when the bolt is being pulled out of Embodiment 3.

[0041] FIG. 17 is a cross-sectional view showing a conventional simple fastening device.

[0042] FIG. 18 is a cross-sectional view showing the condition when a bolt is about to be inserted into the conventional simple fastening device.

[0043] FIG. 19 is a cross-sectional view showing downward of the running screws in conventional simple fastening device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0044] Embodiments illustrating the present invention will be described in detail as follows. In each embodiment, the same reference number is used to refer to a given part that is found in one or more of the embodiments.

[0045] (Embodiment 1)

[0046] FIGS. 1-9 illustrate Embodiment 1 of the present invention and, as shown by FIG. 1, a simple fastening device 1 comprises a base 2, a running screw 2, a cover 4, and a spring piece 5.

[0047] A bolt 6 (FIGS. 5-9) is inserted into the base 2, and a bolt-insertion hole 7 penetrates through the base in an axial direction as shown by FIG. 2. A bolt-insertion face, into which the bolt 6 is inserted, is illustrated as 2a in FIG. 1. A moving groove 2b is formed inside the base 2. The moving groove 2b is designed in such a manner that a below-described running screw 3 moves therein, and the moving groove 2b is formed in such a way that the diameter of the bolt-insertion hole 7 varies in a prescribed way. A slope portion 8 is formed on the side of the bolt-insertion face 2a of the moving groove 2b.

[0048] The slope portion 8 is formed into a conical shape whose diameter is gradually reduced toward the bolt-insertion face 2a, in a manner so as to match the bolt-insertion hole 7. The slope portion 8 supports the running screw 3 in such a way that the running screw 3 can slide, and the slope portion 8 is formed into a shape that fits along the outer profile of the running screw 3. Accordingly, when the running screw 3 moves along the slope portion 8, a female screw 3a (which will be described later and which is shown in FIGS. 1(a), (b), and (c) and in FIGS. 3(b), (c), and (d)) of the running screw 3 that engages with the outer surface of the bolt 6 moves in a horizontal direction.

[0049] In this embodiment, the inner face of the bolt-insertion hole 7, which is opposed to the moving groove 2b (the running screw 3), is an arc-shaped bolt-receiving face 9 having approximately the same curvature as that of the bolt 6. The bolt-receiving face 9 receives the reaction force generated when the running screw 3 is engaged with the bolt 6, thereby securely fastening the bolt 6.

[0050] A cover-attaching concavity 2c is formed on the end face of the base 2 on the opposite side of the bolt-insertion face 2a. The cover-attaching concavity 2c is formed in a noncircular shape and, in this embodiment, it is formed into a noncircular shape with parallel cuts on two sides. Furthermore, the base 2 in this embodiment is molded so as to have a hexagonal nut-like outer profile, but it is not limited to this shape, and it can also be formed into other shapes.

[0051] As shown in FIG. 3, the running screw 3 has a split shape that is obtained by splitting a circular column shape into plural pieces along the direction of its diameter. On the surface that is opposed to the bolt-receiving face 9 of the bolt-insertion hole 7, there is formed a female screw 3a that engages with a male screw 6a on the outer surface of the bolt 6. Also, a slide face 3b, which is formed into a conical tapered shape and which slides on the slope portion 8, is formed at the bottom of the running screw 3. In this embodiment, one running screw 3 is used, and it is inserted in the base 2 in a manner so that the female screw 3a of the running screw 3 is opposed to the bolt-receiving face 9, in order to fasten the bolt 6 between the running screw 3 and the bolt-receiving face 9.

[0052] The cover 4 is fit into the cover-attaching concavity 2c of the base 2 so as to close the face that is opposite to the bolt-insertion face 2a of the base 2. The cover 4, as shown in FIG. 4, is formed into a noncircular outer profile that is similar to that of the cover-attaching concavity 2c, and an insertion hole 4a, through which the bolt 6 penetrates, is formed at the center of the cover 4. After the cover 4 is fit into the cover-attaching concavity 2c of the base 2, the cover 4 clamps the end face of the base 2 and is thereby affixed to the base 2. A spring piece 5 and a guide projection 10 that constitutes a guide means are formed on such a cover 4.

[0053] One part of the cover 4 is bent toward the side of the base 2, so that elasticity is given to the spring piece 5. The spring piece 5 acts as a pressing means for pressing the running screw 3, which is inserted in the base 2, downward. Thus, the spring piece 5 is integrated with the cover 4, and the number of parts that constitute a simple fastening device is reduced, resulting in easy assembly, which is advantageous.

[0054] The guide projection 10 is formed on the cover 4 on the side of the spring piece 5. In this embodiment, the guide projection 10 is formed in a manner so as to project toward the base 2 (the insertion side of the bolt 6) from both sides of the spring piece 5. In this way, the guide projection 10 is formed into a triangular piece that protrudes downward, and it has a guide face 10a that is inclined in the same direction as the slope portion 8 of the above-mentioned base 2.

[0055] Guide grooves 11 constituting a guide means, together with the guide projections 10, are formed on the running screws 3. As shown in FIG. 3, the guide grooves 11 are provided on both sides of the top face of the running screw 3 and are engaged with the guide projections 10. This engagement of the guide projections 10 and the guide grooves 11 prevent the running screw 3 from slipping down.

[0056] FIGS. 5-9 illustrate the action of this embodiment. As shown in FIG. 5, a running screw 3 is inserted into the moving groove 2b of the base 2 in a manner so that a female screw 3a is opposed to the bolt-receiving face 9 of the bolt-insertion hole 7. In addition, under a free condition that the bolt is not fastened, the running screw 3 is supported by the slope portion 8. Under such a supported condition, both ends of the running screw 3, which are perpendicular to the axial direction of the running screw 3, are brought into contact with and fastened to the inner face of the base 2, and thus the running screw 3 is prevented from falling out of the base 2. In addition, both ends of the running screw 3, which are perpendicular to the axial direction of the running screw 3, protrude inside the bolt-insertion hole 7 (see FIG. 1).

[0057] The bolt 6 is formed in an upright fashion from an unfastened member (not shown), and when the simple fastening device 1 is made to approach the bolt 6, the bolt 6 is inserted into the bolt-insertion hole 7 of the base 2 from the side of the bolt-insertion face 2a. As shown in FIG. 6, due to this insertion, the bolt 6 pushes up the running screw 3. As shown in FIG. 7, due to this pushing up, the running screw 3 slides upwards along the slope portion 8, and the running screw 3 moves upward.

[0058] As a result of this movement upward, the guide projections 10 of the cover 4 are engaged with the guide grooves 11 of the running screw 3. The guide face 10a of the guide projection 10 slides in the guide groove 11 so as to achieve such an engagement. The guide face 10a is inclined in the same direction as the slope portion 8 of the base 2, so that the guide projection 10 prevents the running screw 3 from displacement, namely from slipping down or being inclined, toward the bolt-insertion hole 7. As a result, the bolt 6 is smoothly inserted in the base 2 without being hooked by the running screw 3. In this embodiment, the guide grooves 11 are formed on both sides of the running screw 3, and engaged with the guide projections 10, respectively, so that the running screw 3 can be prevented from slipping down or being inclined.

[0059] FIG. 8 illustrates the condition after the bolt 6 has been inserted into the base 2, in which the spring piece 5 of the cover 4 elastically presses the top end of the running screw 3 and presses the running screw 3 downward. Due to this pressing, the running screw 3 moves downward along the slope portion 8, and the female screw 3a is engaged with the male screw 6a of the bolt 6. Due to this engagement, the bolt 6 is bought into contact with the bolt-receiving face 9 of the bolt-insertion hole 7, and the bolt-receiving face 9 receives the reaction force of the engagement. As a result, the running screw 3 can fasten the bolt 6 without loosening. FIG. 9 illustrates the condition when the inserted bolt 6 has been returned slightly downward, and the female screw 3a of the running screw 3 is engaged with the male screw 6a of the bolt 6.

[0060] In such an embodiment, the guide projections 10, which constitute a guide means, and the guide grooves 11 are engaged with each other so as to prevent slipping down or inclination of the running screw 3, and thus the bolt 6 can be smoothly inserted without being hooked by the running screw 3. Thereby, fastening can be surely performed by one-touch insertion. Also, in this embodiment, because the spring piece 5 is integrated with the cover 4, the number of parts can be reduced, and the entire axial length of the device can be shortened.

[0061] (Embodiment 2)

[0062] FIGS. 10 and 11 illustrate Embodiment 2 of the present invention. In this embodiment, as shown in FIG. 10, a moving groove 2b, which has a slope portion 8, is formed opposite to both sides of the bolt-insertion hole 7. Furthermore, a pair of running screws 3 are supported by the slope portion 8 in such a way that the running screws 3 face each other. A pair of the running screws 3 are inserted in the base 2 in such a way that the female screws 3a face each other.

[0063] Guide grooves 11 are formed on the top faces of the running screws 3 and, as shown in FIG. 11, the guide projections 10 to be engaged with the guide grooves 11 are formed on the cover 4 in such a way that the number of the guide protrusions 10 equals the number of running screws 3. Furthermore, the spring pieces 5 for pressing each of the running screws 3 downward are formed at positions of the cover 4 that correspond to the running screws 3.

[0064] In this embodiment, when the bolt 6 is inserted in the bolt-insertion hole 7 from the side of the bolt-insertion face 2a, a pair of the running screws 3 move upward along the slope portion 8. Due to this movement, the guide projections 10 are engaged with the guide grooves 11 of the running screws 3. As a result, the running screws 3 can be prevented from inclining or slipping down, and the bolt 6 can be smoothly inserted. After the bolt 6 is inserted, the pair of running screws 3 are pressed by the spring piece 5, and thus the running screws 3 are engaged with the bolt 6 in such a way that the running screws 3 clamp the bolt 6 from both sides of the bolt 6. Thereby, the force for fastening the bolt 6 becomes large, so that the bolt 6 can be stably fastened.

[0065] (Embodiment 3)

[0066] FIGS. 12-16 illustrate Embodiment 3 of the present invention. In this embodiment, a spring-accommodating groove 12 is formed at the end opposite to the bolt-insertion face 2a of the base 2. The spring-accommodating groove 12 is formed so as to have a predetermined length in the axial direction of the base 2, so that a coil spring 13 can be partially inserted therein.

[0067] Because the coil spring 13 is inserted into the spring-accommodating groove 12, one part of the coil spring 13 is positioned in the moving groove 2b of the base 2, and thus the coil spring 13 presses the running screws 3, which are inserted in the grooves 2b, downward. Accordingly, in this embodiment, a spring piece 5 is not formed on the cover 4, and therefore the shape of the cover 4 is simple.

[0068] Guide projections 10, which are to be engaged with the guide grooves 11 of the running screws 3, are formed on the cover 4. The guide projection 10 projects from the cover 4 in an upright fashion on the bolt-insertion face 2a of the base 2, in the condition that the guide projection 10 has the guide face 10a so as to be engaged with the guide groove 11 of the running screw 3.

[0069] FIGS. 12 and 13 illustrate the condition before a bolt is inserted into the base 2 in this embodiment, FIG. 14 illustrates the condition while a bolt is being inserted, FIG. 15 illustrates the condition after a bolt has been inserted, and FIG. 16 illustrates the condition when the bolt 6 is returned slightly downward and the female screw 3a of the running screw 3 is engaged with the male screw 6a of the bolt 6. When the bolt 6 is inserted in the base 2, the running screw 3 moves upward along the slope portion 8. Because the guide projection 10 of the cover 4 is engaged with the guide groove 11 of the running screw 3, the running screw 3 can be prevented from inclining or slipping down. Further, because the coil spring 13 presses the running screw 3 downward, the female screw 3a of the running screw 3 can be engaged with the bolt 6. In addition, because the bolt-receiving face 9 of the bolt-insertion hole 7 receives the reaction force from this engagement, the bolt 6 can be securely fastened.

[0070] The present invention is not limited to the above embodiments, and it can be implemented in various ways. For example, the cover 4 can be omitted from the base 2.

[0071] In this case, the running screw 3 can be prevented from inclining or slipping down by forming the guide projection 10 at a portion of the base 2 that faces the running screw 3. Also, when a plurality of running screws 3 are provided, more than one pair can be provided.

Possibility of Industrial Utilization

[0072] According to the invention set forth in claim 1, because the guide means is engaged with the running screw so as to prevent the running screw from slipping down, the bolt is not hooked by the running screw, so that the bolt can be inserted smoothly.

[0073] According to the invention set forth in claim 2, because the bolt can securely fastened by the running screw and the bolt-receiving face of the bolt-insertion hole, and because the running screw is prevented from slipping down, the bolt is not hooked by the running screw, so that the bolt can be inserted smoothly.

[0074] According to the invention set forth in claim 3, because a plurality of running screws are engaged with the bolt, the bolt can be securely fastened and the running screws are prevented from slipping down. Thereby, the bolt is not hooked by the running screws, so that the bolt can be inserted smoothly.

[0075] According to the invention set forth in claim 4, in addition to the same effects of the invention set forth in any of claims 1-3, a guide means can be formed easily.

[0076] According to the invention set forth in claim 5, in addition to the same effects of the invention set forth in claim 4, because a guide projection is formed on a cover that is separate from the base, the guide projection can be formed easily.

[0077] According to the invention set forth in claim 6, in addition to the same effects of the invention set forth in claim 4 or 5, the running screw can be surely prevented from slipping down at the time of sliding.

Explanation of Numbers in the Drawings

[0078] 1. Simple fastening device

[0079] 2. Base

[0080] 2a. Bolt-insertion face

[0081] 2b. Moving groove

[0082] 2c. Cover-attaching concavity

[0083] 3. Running screw

[0084] 3a. Female screw

[0085] 3b. Slide face

[0086] 4. Cover

[0087] 5. Spring piece

[0088] 6. Bolt

[0089] 6a. Male screw

[0090] 7. Bolt-insertion hole

[0091] 8. Slope portion

[0092] 9. Bolt-receiving face

[0093] 10. Guide projection

[0094] 10a. Guide face

[0095] 11. Guide groove

[0096] 12. Spring-accommodating groove

[0097] 100. Simple fastening device

[0098] 110. Base

[0099] 120. Running screw

[0100] 121. Female screw

[0101] 122. Tapered face

[0102] 130. Spring

[0103] 140. Bolt

[0104] 141. Male screw

[0105] 150. Bolt-insertion face

[0106] 160. Slope portion

[0107] 170. Cover

Claims

1. A simple fastening device wherein a running screw is supported by a slope portion that is formed in a bolt-insertion hole of a base, and a bolt is inserted into the bolt-insertion hole under the condition that the running screw is pressed by a pressing member, so that the running screw is engaged with the bolt, and wherein a guide means is engaged with said running screw, so that the running screw is prevented from slipping down in the base.

2. A simple fastening device that comprises (1) a base, to which are formed (a) a bolt-insertion hole whose one portion is a bolt-receiving face, and (b) a slope portion whose diameter is gradually reduced toward the bolt-insertion side under the condition that it connects with the bolt-insertion hole, (2) a running screw that slides along said slope portion and is engaged with the bolt as the bolt to be inserted moves in its axial direction, (3) a pressing member for pressing the running screw downward, and (4) a guide means that engages with the running screw and prevents the running screw from slipping down in the base.

3. A simple fastening device that comprises (1) a base to which are formed (a) a bolt-insertion hole, and (b) a plurality of slope portions whose diameters are gradually reduced toward the bolt-insertion side under the condition that they connect with the bolt-insertion hole, (2) a plurality of running screws that slide along the slope portions and are engaged with the bolts as the inserted bolt moves in its axial direction, (3) a pressing member for pressing the running screws downward, and (4) a guide means that is engaged with the running screws and prevents the running screws from slipping down in the base.

4. A simple fastening device, as set forth in any of claims 1-3, wherein said guide means comprises (1) a guide projection that is provided to the base in a manner so as to project toward the bolt-insertion side, and (2) a guide groove that is formed on said running screw so as to engage with the guide projection.

5. A simple fastening device, as set forth in claim 4, wherein a cover into which said bolt can be inserted is attached to the base on the lower side of the bolt-insertion direction, and such that the aforementioned guide projection is provided on the cover.

6. A simple fastening device, as set forth in claim 4 or 5, wherein said guide projection has a guide face that is inclined in the same direction as the sliding direction of said running screw, and such that the guide face is engaged with said guide groove.