US3701367A

US3701367A - Wire wrap tool

Info

Publication number: US3701367A
Application number: US97704A
Authority: US
Inventors: Daniel Whitney Ackerman
Original assignee: Universal Instruments Corp
Current assignee: Delaware Capital Formation Inc
Priority date: 1970-12-14
Filing date: 1970-12-14
Publication date: 1972-10-31
Anticipated expiration: 1989-10-31

Abstract

A wire wrapping tool having an elongated cylindrical bit with an aperture in the end thereof for receiving a terminal stud and a wrapping sleeve which telescopes on the bit to lock a length of wire thereon. A flange on the wrapping sleeve cooperates with a relieved and grooved surface and a wire slot on the bit to hold the wire properly as both bit and sleeve are being rotated on the stud to effect a wirewrap.

Description

United States Patent Ackerman 51 Oct. 31, 1972 [s41 WIRE WRAP TOOL [72] Inventor: Daniel Whltney' Ackerman, Binghamton, NY.

[73] Assignee: Universal Instruments Corporation, Blnghamton, N.Y.

[22] Filed: Dec. 14, I970 [2]] Appl. No.: 97,704

[52] US. Cl ..140/119, 242/7.17 [51] Int. Cl. ..B2lf 15/04 [58] Field of Search .....l40/l24, H9, 122; 242/7.06, 242/7.17

[56] References Cited UNITED STATES PATENTS '.,006,563 10/1961 Bos et a]. ..242/7.l7

3,244,202 4/1966 Huang ..242/7. 17 2,758,797 8/1956 Miklau ..242/7.l7 2,885,764 5/1959 Shulters et al. ..242/7. 1 7

Primary Examiner-Lowell A. Larson Anomey-Fidelman. Wolfte & Leitner [57] ABSTRACT A wire wrapping tool having an elongated cylindrical bit with an aperture in the end thereof for receiving a terminal stud and a wrapping sleeve which telescopes on the bit to lock a length of wire thereon. A flange on the wrapping sleeve cooperates with a relieved and grooved surface and a wire slot on the bit to hold the wire properly as both bit and sleeve are being rotated on the stud to effect a wirewrap.

11 Claims, 11 Drawing Figures PAIENTEDUBI 31 I912 SHEET 1 BF 4 8 INVENTOR DANIEL ACKERMAN BY M 1% ATTORNEY PATENTEDBBHI um I SHEET 2 0F 4 INVENTOR ATTORNEY PATENTED nm a 1 m2 SHEET 3 0F 4 now vOm INVENTOR DANIEL W. ACKERMAN ATTORNEY rATENTEflucrsl m2 SHEET l 0F 4 INVENTOR 03K m3 Qm wow New mow lax 244 ATTORNEY WIRE WRAP TOOL This invention relates to a wire wrapping tool for use in a semi-automatic operation of wrapping wire leads around terminal studs and is an improvement of the tool shown and disclosed in my copending application Ser. No. 62,825 filed Aug. ll, 1970, now U.S. Pat. No. 3,670,784 entitled WIRE WRAPPING TOOL, and the contents of that application are hereby incorporated by reference.

In manufacturing electrical and electronic equipment, it is desirable to interconnect terminals on portions of the equipment, e.g., on printed circuit boards. This is usually done by wrapping the stripped ends of a measured length of insulated wire strand onto the terminals to form wrapped connections. Most wrapping machines today are semi-automatic and such operations can be perfored at relatively high speeds.

In the process of wrapping wire leads around terminal studs, a partially stripped section of wire is placed into engagement with a wrapping bit either automatically or by a machine operator. The bit retracts up into a sleeve which locks the section of wire into a wrapping head. The previously retracted bit and sleeve then descend onto a preselected terminal stud and the head rotates, thus wrapping the wire securely around the stud.

Various wrapping bits and sleeves have been designed to accomplish such an operation and they are generally well known. The problems of wire wrapping, which still exist, center around achieving a proper wrap on the terminal stud.

Generally there are two types of wirewraps. The first is the standard wrap" where there'is no insulation involved in the wrapped spirals of the wire. The second is the modified wrap which provides two turns of insulation around the post prior to wrapping the stripped portion of the wire. While the subject matter of this in-. vention deals primarily with the latter, it is understood that the instant invention can be adapted to provide a standard wrap.

One problem encountered has been the so-called spir wrap where the turns of wire taken around the terminal studs tend to loosen because of spacers between the turns, i.e., the successive turns are not in contact with each other.

Another problem encountered in wrapping wire on a stud has been opposite from that just previously described, i.e., the problem of overwrap. An overwrap situation is where one turn is taken around the post over turns previously made, causing overlap and looseness in the connection.

Open wrap is still another unacceptable result in wrapping terminals. This occurs when the turns are grouped, i.e., several turns are made in proper fashion and then the next turn is spaced considerably apart. This leaves an open gap in the wrap.

Other problems encountered includethe absence of sufficient turns of insulation around the base of the stud and the pigtail left by the end of the wire projecting out from the side of the stud after the wrapping is completed.

All of these problems and more are basically caused by wrapping bits which are not properly designed. Too large a wrapping radius, an improper wire, guiding radius, slippage or binding between the bit and the sleeve and other considerations cause bad wraps as previously discussed.

A proper modified wrap is where a bit will tightly wrap about one and a half to two turns of the unstripped wire around the stud, then tightly wrap the remaining stripped wire around the stud so that each turn abuts the next and the end of the wire is left flush against the stud. When such a wrap is accomplished, a cold weld actually takes place between the wire and stud when the wire is wrapped. This is true fora standard wrap, also. The studs are usually square or rectangular in cross section so that the corners are actually welded tothe wire because of the high pressure with which the wire is wrapped.

This invention overcomes all the difficulties discussed and insures a proper, tight and acceptable wrap. The bit of the present invention has a convex wire bearing surface containing a relieved wire groove which merges with a wire slot and cooperates with a flange on the sleeve to securely and accurately hold the wire as it is being fed onto the stud as the tool rotates. The slot is of generally U-shaped configuration to properly support the length of the portion of wire within the slot to insure proper presentation of the wire to the bit, i.e., to guide the wire into position. The bit is relieved at the end of the slot and a countersunk area merges with the relieved area and the merger is further relieved.

Accordingly, it is an object of the present invention to provide a new and improved wire wrap tool.

Another object of this invention is to provide an improved wrapping tool to accurately and reliably provide acceptable wire wraps on a terminal stud.

A further object of this invention is to provide an improved wrapping tool for insuring proper presentation of the wire to the wrapping bit.

A further object of this invention is to provide the proper amount of tension in the spiral portion as the wire is being wrapped, i.e., not too loose or too tight.

Another object of this invention is to provide a new and improved wire wrap tool having a convex wire bearing surface having a relieved groove therein and a wire slot merging into a countersunk area for guiding the wire onto a terminal.

With these and other objects in view, reference is had to the accompanying drawings in which:

FIG. 1 is a perspective view of the wrapping bit of this invention;

FIG. 2 is a side view of the wrapping bit of this invention,

FIG. 3 is a side view of the wrapping bit of FIG. 2, only rotated clockwise by FIG. 4 is an enlarged side view of the bit as shown in FIGS. 1 and 2;

FIG. 5 is an end view of the wrapping bit of FIG. 4;

FIG. 6 is a perspective view of the wrapping sleeve;

FIG. 7 is a side view of the wrapping sleeve shown in FIG. 6;

FIG. 8 is a side view of the wrapping sleeve as shown in FIG. 7 only rotated counterclockwise by 30;

FIGS. 9-11 show an alternative embodiment of the End portion 51 is connected to the main portion of the bit by a reduced cylindrical portion 50. The purpose of reduced portion 50 is to allow a spring means in a rotary chuck (not shown) to engage therein and hold the bit therein.

A hole 101 is positioned about midway of the length of the bit and is for receiving a pin (now shown) to cooperate with a slot in the wrapping sleeve.

The bit is notched to provide a convex wire guiding surface 104 and arc-

shaped areas

102 and 103. Area 102 is planar and generally perpendicular to wire guiding surface 104 but area 103, as seen in FIG. 4, is angled with respect to surface 104 and gradually merges therewith as at 119.

The end of bit 100 is flat as at 105. and has therein a countersunk portion 106 which provides a guide for receiving the stud and may assist in maintaining the turns of wire in a tightened condition as the wire is wrapped about a terminal stud. A stud receiving hole 107 merges with countersunk portion 106 and, as shown in FIG. 2, extends up under surface 104 and terminates in inner countersunk portion 108.

A notch is cut in the end of the bit 100 to provide planar area 109 (see FIG. 5), planar triangularly shaped wall 1 and planar wall 1 11 which merges with an arcuate wall 112 (FIG. 5).

Walls

110, 111 and 112 all intersect the countersunk portion 106 and are generally perpendicular to area 109. As seen in FIG. 4, planar area 109 is spaced slightly inward from the end of hole 107.

A wire slot 113 (FIG. 1) connects the notch with guiding surface 104.'The slot 113 consists of substantially

parallel walls

116 and 115 and rounded bottom portion 114. Since the radial depth of slot 113 is greater than the surface 104, the rounded portion 114 is extended into a groove 117 in surface 104. Groove 117 extends a substantial amount along surface 104 and terminates in a rounded area 118.

The slot 113 extends through a forward area, generally designated as 108 in FIGS. 1 and 4.

The end of slot 113 does not terminate abruptly in area 109. A relieved bearing surface 120 is provided having two edges 121 and 122 which tend to intersect.

The relieved area provides for a transition bearing surface for the wire to be guided out of slot 113 and around the terminal studs.

Referring now to FIG. 5, there are shown certain angles and radii. While FIGS. 4 and 5 do not represent the actual size of the wrapping unit, they are in scale so that the relative proportions of the configuration are correct. The x-y axis is representative of the position of the bit as it is presented to the stud. A denotes the angle between they axis and wall 110. B denotes the angle between the y axis and the radial line on which the center of radius of arcuate bottom portion 114 of slot 1 13 is on.

C and D indicate the angle and distance measured to determine the radius E of curved wall 112, which may act as a bearing wall also in turning the wire tail onto a terminal stud.

F is the radius of theibottom surface 114 of slot 113 and is determined by the distance I. J is the distance between the tangent to the periphery of bit 100 and the tangent to the bottom most point on rounded surface 114.

This distance, J, is determined by the diameter of wire to be wrapped. The wire, with its insulation is preferably of a diameter that protrudes out beyond the circumference of bit by a predetermined amount, say 0.001 to 0.003 inch so as to provide for an interference fit with the sleeve. Such a procedure establishes the bottom point of slot 113 and dimension J.

I represents the width of the notched

area containing walls

110, 111 and 112. Once wall 112 is determined, wall 111 is at an angle A to the y axis (i.e., parallel to wall and tangential to wall 112. The wall 110 is then established by measuring the distance I.

H is the radius of surface 104 and the center thereof is at a distance K from the x axis.

G is the radius of relieved are as shown in FIG. 4. The center of radius is at a distance L from the face 105 of the bit.

M is the angle at which are 103 deviates from being perpendicular to surface 104.

For a typical 24 gauge wrapping bit, the dimensions would be as listed below:

.030" radius .116" radius .065"

These dimensions would be for a bit of an outside diameter of 156 inches, having a bore of 0.067 inch diameter and a countersink of 60.

N is the distance from the intersection of surface 104 to the axis of the bit (FIG. 5).

O, P and 0 represent the distances from the end of the tool to area 102, portion 118 and area 103, respectively. For the same bit, these dimensions would be as follows:

Referring now to FIGS. 6-8, there is shown the wrapping sleeve designated generally as 200. It consists of a main tapered portion 201, a cylindrical portion 202, a reduced cylindrical portion 203, and a cap portion 204 with a bevel 205 on the end thereof.

In portion 202, there is an aperture 207 in one wall and a slot 28 having stops 209 in the opposite wall thereof. Slot 208 receives a projecting part of a pin (not shown) which is mounted in aperture 101 in bit 100. This allows for bit 100 to slide within sleeve 200 for the length of slot 207.

Extending through

portions

201, 202, 203 and 204 is tout slot 214 which has a curved wall 218 which merges at one end with wall 217 and merges at the other end with a perpendicular wall 220 through rounded wall portion 219.

The combined shape of the two slots produces a wire holding flange 221 which is adapted to slide down over slot 113 to hold that portion of the wire having insulation thereon. The end of the sleeve is flat as at 222.

FIG. 7 shows a side view of the sleeve shown in perspective in FIG. 6. It is taken looking in at VII along the x axis of FIG. 6. FIG. 8 shows the side view of FIG. 7 only rotated counterclockwise 30. The angle which wall 218 makes with the axis of sleeve 200 in the rotated 30 position is shown as R.

In the preferred embodiment of this sleeve, R would be approximately 10. The slot 213 would be approximately 1.06 inches long and radius of portion 219 would be approximately 0.062 inch as shown in FIG. 8. The center of radius would be a distance S from the end of the sleeve as seen in FIG. 8. S is about 0.250 inch in the preferred embodiment.

The operation of the device is as follows: The sleeve 200 is in retracted position when the operator or automatic feeding device (not shown) lays the wire across the convex surface 104. The sleeve 200 is lowered over the bit 100. As the descent takes place, the flange 221 of the sleeve forces the wire to pivot around curved corner 119. Continued retraction forces the wire down into groove 113 where it is held by

walls

115 and 116, the inner surface of the sleeve 200 and groove 117.

The tool is rotated and the end of the wire containing the insulation is wrapped around a stud. The tool is further rotated and the wire, by guiding area 120, is wrapped around a stud.

The bit 100 is biased downwardly to maintain pres sure on the wire but it is the torque on the wire portion that is out of the slot 113 and not yet wrapped on the stud that insures that the wire is securely wrapped around the stud in proper fashion rather than wall 112 engaging the wire. As the wire is wrapped around stud 31, the bit is forced upwardly.

The wrapping tool of the instant device provides an improved wrap of proper tightness and more uniform characteristics. Further, the wire slot and groove in the bit surface and the flange on the sleeve cooperate to define a wire feeding passage which is near the rotational axis of the bit which is important since the wire is not unduly stressed and a more uniform wrap of proper tightness is achieved. The U-shape of the slot and the merging notch 120 also provide for a smoother feed of the wire. The shape of the slot and notch also provide for a smooth feed of the wire without creating undue stress and fatigue therein.

The particular arrangement of the convex surface 104 with flange 221 of the sleeve and the relationship of the sleeve flange and slots 213 and 214 afford an accurate bending of the wire into slot 113 and groove 1 17 as the bit is retracted. The sleeve 200 provides no obstruction to the wire pivoting across surface 104 as the bit is retracted.

The stripped wire fits into slot 113 an is fed onto a stud resulting in spiral wire wrap. The wire, as it passes over portion 120, does not completely follow the radius G. It flows out into space at a lesser angle. The angle the radius can bend the wire can vary from 0 to 90.

The wire is thus under three-dimensional torque for a portion of its length, the torque being caused by the relationship of slot 113 and area 120 to the stud and the shape of area 109. The portion 120 only puts enough torque on the wire toallow radius G to influence the bendings of the wire as it goes into space.

Arcuate wall 112 is shaped so as to engage the end of a stripped wire portion and whip it onto a stud, thus eliminating any pigtail in the wrap. This surface does not effect the wire as it is being wrapped, however. It is, in essence, a terminal camming surface.

As is shown, the relieved area 109 does not merge with countersunk area 106.

While countersunk area 106 does not effect the wrap as the wire is being fed, it is understood that the bit is biased downwardly to offset the upward thrust on the bit by the torqued portion of the wire. At the conclusion of the wrap, the tool is allowed to be biased downwardly so the countersunk area 106 in conjunction with

areas

109 and 112 engage the top of the wrapped wire and guide and compress the last spiral.

FIGS. 9-11 show an alternative embodiment of the lead supporting and wrapping portions of the bit and sleeve.

Referring to FIG. 9, but 300 resembles bit inasmuch as it has an end face 305, a countersunk portion 306, a stud receiving hole 307, a planar area 309, and a planar triangular shaped wall 310. It has the same end view configuration as bit 100.

A wire slot 313 extends from the front of the bit merges with slot 314 as it tapers toward the rear where slot 314 ends in relieved portion 318. The slots have

planar side walls

317 and 321.

In the area 308 of the bit, the slot 313 has a rounded area 320 which is similar to rounded area in bit 100. There is no cutout surface similar to 204 on the earlier embodiment.

The alternative bit 300 is used in conjunction with a modified sleeve 400 as seen in FIG. 10. It is similar to sleeve 200 inasmuch as it has a main tapered portion 401, the taper being seen in FIGS. 10 and 11.

The sleeve 400, in area 401, has an end face 410, a flange 409 having an edge 408 and a cut out area 402.

Cut out area 402 has beveled

side portions

406 and 403. Portion 406 merges with portion 405.

Portions

405 and 403 connect through beveled portion 404.

Portion 406 merges into the edge 407 of flange 409.

FIG. 11 shows the bit 300 within sleeve 400, it being understood that no relative rotation between the two can occur. As seen in FIG. 11, slot 313 is in an angular position with respect to flange 409 such that a wire laid into the cutout area 402 is forced into slot 313 by the edge 407 of flange 409 as the bit 300 descends within sleeve 400.

That is, the operator places the wire to be wrapped into sleeve 400, the open space between flange edge 408 and the remainder of the working portion 401 of the bit sleeve permitting the operator to merely slide the wire in and hold it against the edge 407 so that it will be forced into slot 313 as bit: 300 descends. The subsequent wrapping operation is identical to that defined with regard to FIGS. 1-8.

Control of the operational sequence of either of the tools and wire feed can be accomplished in any of a number of convention a ways, e.g., a punched tape NC control system may be used for directing the various operational steps. A cam system and solenoids whose sequence is controlled by the cam system and a motor driven cam shaft may be used. A closed loop digital control system using D.C. servo motors may be a further way of automatically running the sequence of operations.

it is understood that the wrapping tools shown and described are merely illustrative of this invention and other modifications and changes will occur to those of ordinary skill in the art without departing from the scope of the appended claims.

What is claimed is:

l. A wire wrapping tool for wrapping connection leads onto terminal studs comprising:

a. a tubular sleeve member; and

b. a cylindrical bit received in said sleeve member and adapted to move longitudinally therein;

c. said bit having a bore in one end for receiving a terminal, said bore being recessed, and

d. a flared surface means between the end of said bit and the beginning of said bore; and

e. an external slot means in said bit, one end of which merges with said flared surface means, the merger of said slot means and surface means being cut away so as to form a relieved area, the merger of said relieved area and said slot being relieved so as to provide a wire bending radius surface;

f. a convex surface formed along one side of said bit and inwardly of said end so as to form two arcuately-shaped end walls; and I g. the other end of said slot means merging with said convex surface and said slot means having an extension of said slot means therein in the form of a groove;

h. said sleeve having an elongated opening therein which cooperates with said convex surface to allow a wire to be pivoted upon retraction of said bit within said sleeve; and

i. flange means on said sleeve cooperating with said slot means to define a wire supporting passage; whereby when a wire is laid across said planar surface, retraction of said bit within said sleeve causes the wire to pivot on said convex surface and be grasped in said passage. I

2. A wire wrapping tool as in claim 1 wherein the lowest point of said slot means is below said convex surface.

3. A wire wrapping tool as in claim 1 wherein said flared surface means comprises a countersunk area between the end of' said bit and the beginning of said bore.

4. A wire wrapping tool as in claim 1 wherein pin and slot means are provided on said bit and sleeve to prevent relative rotation therebetween.

5. A wire wrapping tool as in claim 1 wherein said groove means'has an arcuate portion, the radius of said arcuate portion being slightly larger than the diameter of the insulation of the wire to be wrapped.

6. A wire wrapping tool as in claim 1 wherein said groove means is of a size whereby the diameter of the insulation of the wire to be wrapped protrudes out beyond the peripheral surface of the bit.

7. A wire wrapping tool for wrapping wires onto terminal studs comprising:

a.atubular sleevemember; b. a cylindrical bit received 111 said sleeve member and adapted to move longitudinally therein;

c. means to prevent relative rotation between said bit and sleeve;

. a stud receiving passage in said bit, said passage being located along the longitudinal axis of said bit;

e. a counterbore in said bit of larger diameter than said passage and located between the end of said bit and said passage, a portion of said counterbore being relieved and providing a camming surface;

f. an external wire receiving slot means in said bit,

one end of said slot means merging with said relieved portion of said counterbore, the merger of said slot means and relieved counterbore portion being further relieved to provide a wire guiding surface means and said slot means defining two wire supporting walls;

g. a convex surface formed along one side of said bit and inwardly of said end so as to form two arcuately-shaped end walls;

. the other end of said slot means merging with said convex surface, the merger of one of said wire supporting walls of said slot means and one of said end walls being relieved to form a rounded corner means adapted to allow a wire to be pivoted into position as said bit retracts into said sleeve;

. said sleeve having an elongated opening therein which cooperates with said convex surface to allow a wire to be pivoted upon retraction of said bit within said sleeve;

j. flange means on said sleeve cooperating with said wire supporting walls to define a wire supporting passage; whereby when a wire is laid across said planar surface, retraction of said bit within said sleeve causes the wire to pivot on said corner means and it is grasped in said slot means between said flange means and said wire supporting wall and said camming surface forces the end of said wire to lie flat on said stud at the conclusion of said wrapping.

8. A wire wrapping tool as in claim 7 wherein said convex surface has a wire receiving groove therein which merges with said slot means.

9. A wire wrapping tool as in claim 7 wherein pin and slot means are provided, on said bit and sleeve to prevent relative rotation therebetween.

10. A wire wrapping tool as in claim 7 wherein said slot means has an arcuate portion, the radius of said arcuate portion being slightly larger than the diameter of the insulation of the wire to be wrapped.

11. A wire wrapping tool as in claim 7 wherein said slot means is of a size whereby the diameter of the insulation of the wire to be wrapped protrudes out beyond the peripheral surface of the bit.

Claims

1. A wire wrapping tool for wrapping connection leads onto terminal studs comprising: a. a tubular sleeve member; and b. a cylindrical bit received in said sleeve member and adapted to move longitudinally therein; c. said bit having a bore in one end for receiving a terminal, said bore being recessed, and d. a flared surface means between the end of said bit and the beginning of said bore; and e. an external slot means in said bit, one end of which merges with said flared surface means, the merger of said slot means and surface means being cut away so as to form a relieved area, the merger of said relieved area and said slot being relieved so as to provide a wire bending radius surface; f. a convex surface formed along one side of said bit and inwardly of said end so as to form two arcuately-shaped end walls; and g. the other end of said slot means merging with said convex surface and said slot means having an extension of said slot means therein in the form of a groove; h. said sleeve having an elongated opening therein which cooperates with said convex surface to allow a wire to be pivoted upon retraction of said bit within said sleeve; and i. flange means on said sleeve cooperating with said slot means to define a wire supporting passage; whereby when a wire is laid across said planar surface, retraction of said bit within said sleeve causes the wire to pivot on said convex surface and be grasped in said passage.

3. A wire wrapping tool as in claim 1 wherein said flared surface means comprises a countersunk area between the end of said bit and the beginning of said bore.

5. A wire wrapping tool as in claim 1 wherein said groove means has an arcuate portion, the radius of said arcuate portion being slightly larger than the diameter of the insulation of the wire to be wrapped.

7. A wire wrapping tool for wrapping wires onto terminal studs comprising: a. a tubular sleeve member; b. a cylindrical bit received in said sleeve member and adapted to move longitudinally therein; c. means to prevent relative rotation between said bit and sleeve; d. a stud receiving passage in said bit, said passage being located along the longitudinal axis of said bit; e. a counterbore in said bit of larger diameter than said passage and located between the end of said bit and said passage, a portion of said counterbore being relieved and providing a camming surface; f. an external wire receiving slot means in said bit, one end of said slot means merging with said relieved portion of said counterbore, the merger of said slot means and relieved counterbore portion beIng further relieved to provide a wire guiding surface means and said slot means defining two wire supporting walls; g. a convex surface formed along one side of said bit and inwardly of said end so as to form two arcuately-shaped end walls; h. the other end of said slot means merging with said convex surface, the merger of one of said wire supporting walls of said slot means and one of said end walls being relieved to form a rounded corner means adapted to allow a wire to be pivoted into position as said bit retracts into said sleeve; i. said sleeve having an elongated opening therein which cooperates with said convex surface to allow a wire to be pivoted upon retraction of said bit within said sleeve; j. flange means on said sleeve cooperating with said wire supporting walls to define a wire supporting passage; whereby when a wire is laid across said planar surface, retraction of said bit within said sleeve causes the wire to pivot on said corner means and it is grasped in said slot means between said flange means and said wire supporting wall and said camming surface forces the end of said wire to lie flat on said stud at the conclusion of said wrapping.

9. A wire wrapping tool as in claim 7 wherein pin and slot means are provided on said bit and sleeve to prevent relative rotation therebetween.