Rolling die
A rolling die is provided. The rolling die includes a bite portion having bite processing teeth at a bite starting point for a workpiece, and a finishing portion having finishing processing teeth. The bite processing teeth at the starting point in the bite portion have lower tooth height than the finishing processing teeth in the finishing portion. The bite processing teeth have a larger tooth tip angle and a larger trough angle than the finishing processing teeth.
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This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2004-103839, filed on Mar. 31, 2004, the entire content of which is incorporated herein by reference.
FIELD OF THE INVENTIONThe present invention relates to a rolling die for rolling bolts or screws. More particularly, the invention relates to a rolling die having stabilized formation precision and high durability.
BACKGROUNDFasteners, such as bolts or screws, continuously form screw crests and troughs on the peripheral surface with each single rotation by holding a rod-like workpiece between a pair of flat die pieces provided with moderately inclined processing teeth on one side surface, and relatively moving one flat die with respect to the other side surface. Typically, the processing teeth have the same cross-sectional shape, extending from a bite portion that includes a starting point on one surface side to a roll-off portion that includes an end point.
Recently, in order to increase the pinching strength and to lighten the weight, the raw material of bolts or screws has evolved from carbon steel or processed steel to relatively hard chrome molybdenum steel (SCM type steel). Corresponding to the change in raw materials of bolts and screws, cold die steel (SKD type steel) is an example of raw materials used for rolling dies.
However, since the cross-sectional shape of the processing teeth of the rolling dies is the same through a bite portion, a finishing portion, and a roll-off portion, cracking or localized damage occurs easily near the tooth tip of the bite starting point where a hardened workpiece is initially processed, and the product life of the die is shortened.
In a flat rolling die provided with a bite portion, an interim finishing portion, and a finishing portion, it has been suggested that the tooth tip line of the interim finishing portion coincide with that of the finishing portion, that the tooth height become larger closer to the bite portion, and that the tooth tip of the bite portion be sharpened more than or the same as that of the interim finishing portion. (See Japanese Laid Open Utility Model Hei 1-37800).
In a flat rolling die disclosed in Japanese Laid Open Utility Model Heil 1-37800, the teeth in the bite portion sharply cut into the raw material, and since the finishing portion presses the raw material with dispersed pressure on both sides, smooth rolling becomes possible. Because the teeth in the bite potion sharply cut into the raw material, however, there have been problems of cracking or localized damage when rolling a workpiece of a hardened raw material.
Thus, it is desirable to resolve the above problems and provide a rolling die capable of long product life and precise rolling even for processing hard workpieces. The present invention is directed to solve one or more of these problems and to provide a rolling die with processing teeth at a bite portion that include an initial bite starting point in the workpiece having a cross-sectional shape with an obtuse angle greater than that of finish processing teeth, the obtuse angle becoming successively greater from the bite portion to the finishing portion.
SUMMARY OF THE INVENTIONA rolling die is provided. The rolling die includes a bite portion having bite processing teeth at a bite starting point for a workpiece, and a finishing portion having finishing processing teeth. The bite processing teeth at the starting point in the bite portion have lower tooth height than the finishing processing teeth in the finishing portion. The bite processing teeth have a larger tooth tip angle and a larger trough angle than the finishing processing teeth.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description, serve to explain the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
Reference will now be made in detail to exemplary embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.
A rolling die according to one embodiment of the invention includes a bite portion having bite processing teeth and a finishing portion having finishing processing teeth. The bite portion includes bite processing teeth at a bite starting point for a workpiece. The processing teeth at the starting point in the bite portion have a lower tooth height than the processing teeth in the finishing portion, and the bite processing teeth at the starting point in the bite portion have a larger tooth tip angle and a larger trough angle than the finishing processing teeth in the finishing portion.
In this regard, since the processing teeth of the bite starting point are shallow and have an obtuse angle for the initial bite at a workpiece processed for bolts and the like, cracking or localized breakage becomes less likely to occur at the tooth tip at the bite portion that includes the bite starting point. Furthermore, since the cross-sectional shape of the bite processing teeth gradually changes from the bite starting point to the finishing portion, successively deeper and shaper bites are formed in the workpiece. Consequently, a desired shape of screw crest and trough can be precisely formed even in a workpiece made of a hard material. This can provide more precise processing of a workpiece with a hard material and allows a longer product life for the rolling die.
The cross-sectional shape of the bite processing teeth gradually changes to that of the finishing processing teeth from the bite starting point to the finishing portion. Tooth height as used herein refers to the distance between the tooth tip and the tooth bottom of the processing teeth, the tooth tip angle refers to the angle (so-called crest angle) having its center at the tooth tip, and the trough angle refers to the angle between two processing teeth located next to each other.
In one embodiment of the rolling die, the tooth height of the bite processing teeth becomes continuously higher toward the finishing portion, and a trough becomes deeper and wider from the bite portion to the finishing portion. The processing teeth at the bite starting point provide bites that are shallow and obtuse. Then the processing teeth next to the processing teeth at the bite starting point provide shallow obtuse bites. Another set of processing teeth at the bite portion provide deeper and sharper bites to the workpiece. Subsequently, as the workpiece is processed at the finishing portion of the rolling die, a desired shape of screw crests and troughs is precisely formed. The “trough bottom” as used here refers to a portion at a trough between the processing teeth, in which its trough angle is smaller than the trough angle at the tooth tip.
According to one embodiment of the present invention, the tooth tip angle and the trough bottom angle in the bite portion may be 60 degrees or greater, and the trough angle between the processing teeth of the finishing portion may correspond to a standard valued set for a screw. In this regard, the rolling die may process the workpiece more accurately with gradually deeper and sharper processing teeth angles and provides a longer product life. Moreover, the tooth tip and trough angle of the processing teeth at the bite starting point may be 90 degrees or greater, and the tooth tip and trough angle of the processing teeth at the finishing portion may be, for example, 60 degrees or greater.
It should be noted that, in one embodiment of the present invention, the rolling die may be provided with a roll-off portion with a roll-off angle in the finishing portion at the opposite side from the bite portion. The roll-off portion may include processing teeth having the same tooth height and tooth tip angle as the processing teeth at the finishing portion. With such a roll-off portion, it is possible to process a workpiece with desired screw crests and troughs and release the workpiece from the rolling die smoothly.
In addition, a rolling die according to one embodiment may include a pair of die members of a solid-rectangular shape that has the bite portion and the finishing portion on its side. The rolling die may provide rolling by means of a set of flat dies and extend the product life of the rolling dies. Moreover, in a pair of die members, one member may be fixed (coast side) and the other member may be movable (drive side). Alternatively, both members may be movable with respect to each other, and such a rolling die may be called a dual-drive type.
In another embodiment, the rolling die may include a pair of die members having a cylindrical shape that has the bite portion and the finishing portion on their surfaces. The rolling die having the pair of cylindrical die members may provide accurate processing of a workpiece and extend the product life of the die.
As shown in
Moreover, the dies 2, 10 may be fixed to a rolling device (not shown in figures) by clamps (not shown in figures).
One example of the cross-sectional surface of the dies 2, 10 is described as follows:
Vertical: 35 mm×Lateral: 38 mm, Length of the die 2 on the movable side: 380 mm, Length of the die 10 on the fixed side: 370 mm.
The die 2 on the movable side may be 10 mm longer than the die 10 on the fixed side to achieve a smooth bite of a workpiece between the bite portion 6 at the side surface 4 and the starting point 15 at the side surface 14. This also provides a smooth release of the workpiece from the roll-off portion 8 at the side surface 4 and the finishing point 19 at the side surface 14. In other words, when rolling the workpiece between the starting points 5, 15 at the side surfaces 4, 14, the workpiece may be prevented from being accidentally released and from being damaged during release from the finishing points 9, 19.
The processing teeth a at the starting points 5, 15 in the bite portions 6, 16 of the dies 2, 10, as shown in
The processing tooth t1 is located at the bite starting points 5, 15 in the bite portions 6, 16, and until approximately the middle of the bite portions 6, 16, the cross-sectional shape of the tooth t1 gradually becomes closer to that of the processing teeth b (processing tooth t2) by continuously changing its depth and width of the trough angle θ2.
In the bite portions 6, 16 of the dies 2, 10, the processing teeth b located approximately 60 mm from the starting points 5, 15, as shown in
A cross-sectional shape having the same shape as that of the processing tooth t2 is gradually become prevalent from the starting points 5, 15 to the middle of the bite portions 6, 16. Near the finishing portions 7, 17, the depth and width of the trough bottoms v2, v3 having a trough angle θ2 continuously becomes deeper and larger, and the cross-sectional shape of the tooth t2 gradually becomes closer to that of the processing teeth c (processing tooth t3).
In the dies 2, 10, the processing tooth c located approximately 120 mm from the starting points 5, 15, or in the finishing portions 7, 17, as shown in
Furthermore, the cross-sectional shape of the processing tooth t3 is substantially an equilateral triangle, and only the tooth tip m3 has the same shape as the tooth tips ml and m2 of the processing teeth t1 and t2. Therefore, the trough bottom v3 becomes an even narrower concave groove in comparison with the trough bottom v2.
The cross-sectional shape which is the same as that of the processing teeth t3 gradually becomes prevalent from the middle of the bite portions 6, 16 to the area close to the finishing portions 7, 17. Until the finishing portions, 7, 17, the depth and width of the trough bottom v3 having a trough angle θ2 continuously becomes deeper and larger, and the cross-sectional shape of the tooth t3 gradually becomes closer to that of the processing teeth d (processing tooth t4).
The finishing portions 7, 17 of the dies 2, 10 and the processing teeth d of the roll-off portions 8, 18, as shown in
The processing teeth t4 are located roughly 180 mm from the starting points 5, 15 and in the entire surface of the finishing portions 7, 17 and continues the same cross-sectional shape to the finishing points 9, 19 in the roll-off portions 8, 18.
The processing teeth a-d (processing teeth t1-t4) such as those described above are illustrated in
A rolling method of a bolt by using the rolling die 1 will be described. As shown
The rolled workpiece n0 shown in
At the starting points 5, 15 of the dies 2, 10, only the tooth tip m1 of the processed tooth a(t1) moderately bite into the workpiece, and the periphery of the workpiece n0 is expanded by the shallow trough bottom v1. Thus, cracking and breakage may be prevented, and smooth elastic deformation may be achieved with a dispersed load.
As shown in
The trough bottom v2 of the processing teeth b(t2) is formed by gradually deepening and widening at the trough angle θ2 from the trough bottom v1 of the processing teeth a(t1) from starting points 5, 15. As a result, as shown in
Furthermore, as shown in
As shown in
By using the rolling die described above, the workpiece n0 is subjected to a shallow, moderate deformation between the processing teeth a, a at the starting points 5, 15. Furthermore, as it is rolled between the bite portions 6, 16, the finishing portions 7, 17, and the roll-off portions 8 and 18, the workpieces n1-n4 are smoothly and continuously formed with the crest y2-y4 with the higher tooth heights h2-h4 and the gradually deepener and narrower trough z2-z4. Furthermore, since the dies 2, 10 continuously perform each process while dispersing the load, cracking or localized breakage loss is reduced at the starting points 5, 15. Bolts and screws with more precise shapes and screw crests and troughs can be efficiently rolled, with a longer product life for the rolling die 1.
In another embodiment, both of the dies 2, 10 may be movable.
Bolts (M. diameter: 12 mm×pitch: 1 mm) were rolled by the rolling die described above from a rod type workpiece n0 made of SCM415. As a result, even after precisely rolling of multiple bolts, no cracking or damage occurred near the starting points 5, 15. When bolts were rolled by using a conventional die from workpiece made of the same material, cracking and peeling (breakage loss) occurred in the tooth tip at the starting point when a fewer number of bolts were rolled.
With the exception of the processing teeth d in finishing portions q and roll-off portions r, processing teeth a, b, c are formed in a specific position at the periphery 24 of bite portions p. Moreover, between the starting point 25 and the finish point 27, a sharp angular cut-out 23 is formed, and an axial bore 26 with a key groove 25 is formed in the center of the die member 22. A rotating axis 28 is disposed in the axial bore 26, as shown in
A cylindrical workpiece n is rolled between the starting points 25, 25 of the dies 20a, 20b, and both rotating axes 28 are rotated in a synchronized motion. As shown in
Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.
Claims
1. A rolling die, comprising:
- a bite portion having bite processing teeth at a bite starting point for a workpiece; and
- a finishing portion having finishing processing teeth, wherein the bite processing teeth at the bite starting point in the bite portion have lower tooth height than the finishing processing teeth in the finishing portion, and the bite processing teeth have a larger tooth tip angle and a larger trough angle than the finishing processing teeth.
2. The rolling die of claim 1, wherein the tooth height of the bite processing teeth becomes continuously higher toward the finishing portion, and a trough becomes deeper and wider from the bite portion to the finishing portion.
3. The rolling die of claim 1, wherein the bite processing teeth have a tooth tip angle and a trough bottom angle of 60 degrees or greater, and the trough angle between the finishing processing teeth corresponds to a standard trough angle value for a screw.
4. The rolling die of claim 2, wherein the bite processing teeth have a tooth tip angle and a trough bottom angle of 60 degrees or greater, and the trough angle between the finishing processing teeth corresponds to a standard trough angle value for a screw.
5. The rolling die of claim 1, further including a pair of solid-rectangular shaped die members having the bite portion and the finishing portion.
6. The rolling die of claim 2, further including a pair of solid-rectangular shaped die members having the bite portion and the finishing portion.
7. The rolling die of claim 3, further including a pair of solid-rectangular shaped die members having the bite portion and the finishing portion.
8. The rolling die of claim 4, further including a pair of solid-rectangular shaped die members having the bite portion and the finishing portion.
9. The rolling die of claim 1, further including a pair of cylindrical die members having the bite portion and the finishing portion.
10. The rolling die of claim 2, further including a pair of cylindrical die members having the bite portion and the finishing portion.
11. The rolling die of claim 3, further including a pair of cylindrical die members having the bite portion and the finishing portion.
12. The rolling die of claim 4, further including a pair of cylindrical die Members having the bite portion and the finishing portion.
Type: Application
Filed: Mar 4, 2005
Publication Date: Oct 6, 2005
Applicant:
Inventors: Naoshige Taniguchi (Kasugai-shi), Yoshio Nonaka (Kasugai-shi), Norishige Hayashi (Inuyama), Kazuhiko Masuo (Kasugai-shi)
Application Number: 11/071,449