US 3742694 A
Apparatus for spinning and twisting yarn comprising a whorl mounted on a spindle. The spindle is rotatably journalled in a bearing housing. A coupling is provided connecting the whorl to the bearing housing. The coupling having interlocking means one portion of which is concentric abutment member, the other portion of which is a radially slideable latch.
Description (OCR text may contain errors)
United States Patent 1191 Speiser July 3, 1973  SPINNING AND- TWISTING APPARATUS 2,883,825 4/1959 Reissmueller 57/132 4  Inventor: Helmut Speiser, Grossheppach, 3028721 H962 Keyser 57/132 Germany FOREIGN PATENTS OR APPLICATIONS  Assgneei SKF Kugellagerfamken GmbH 1,128,334 4/1962 Germany 57/132 Schwemfurt, Germany 1,098,864 2/1961 Germany 57/132  Filed: June 2, 1971  Appl, No.: 149,291 Primary Examiner-Werner H. Schroeder Attorney-Richard Low and Murray Schaffer  Foreign Application Priority Data June 3, 1970 Germany P 70 20 663.2 May 10, 1971 Germany P21 22 963.0 57 ABSTRACT  US. Cl. 57/132 Apparatus f pinning and twisting yarn comprising a [5 I] IIIII. CI D0"! 7/14 whorl mounted on a pindle, The spindle is rotatably  Fleld of Search 57/130, I31, I32, j ur alled in a bearing housing A coupling is provided 57/l33', 134, 13 24/115 connecting the whorl to the bearing housing. The cou- 228 pling having interlocking means one portion of which is concentric abutment member, the other portion of  Referen es Cit d which is a radially slideable latch.
UNITED STATES PATENTS 1,383,000 6/1921 McGill 57/l32 14 Claims, 6 Drawing Figures 75 28 1 I! 52 av 30 38 "1 5' 5 arr/Cl: I as Ila;
SPINNING AND TWISTING APPARATUS The present invention relates to spring and twisting apparatus for yarns and, in particular, to means for coupling a whorl and spindle.
Textile yarns and fibers are spun or twisted on whorls or rotating spindle devices mounted on spindle shafts journalled within bearing housing. It is often necessary to remove and exchange the whorl and therefore a removeable coupling between the whorl and the spindle and bearing housing is required. In German patent publication AS 1098864, a construction is shown in which a moveable securing or latch member is arranged in the throat of the bearing housing and is adapted to engage an annular shoulder or abutment member on the spindle shaft.
The construction shown in the aforementioned patent makes it necessary to have an additional opening in the cover of the spindle bearing housing in order to effect the radial shifting of the latch member and in particular, requires the use of a tool to shift the latch member into operative engagement. This additional opening requires that the .spindle housing be carefully arranged on the spindle bank so that the opening is accessible from the front of the opening machine in order to allow entry of the tool and sufficient room to permit the adjustment. A further disadvantage of this construction lies in the fact that the latch and coupling means must be near the end of the spindle bearing housing throat causing the roller bearing assembly for the spindle to be located deep within the throat. This would make the assembly of the apparatus difficult, complex and costly. Finally, the latch element is freely mounted within the bearing housing and is capable of being rotated and twisted relative to the spindle shaft. For this reason, it had been attempted to employ springs to secure the latch elements within the throat; however, this last means urged the spindle shaft in an eccentric direction within the housing so that frequently at high rotational speeds the latch member would be so eccentrically urged that it was thereafter impossible to align the latch with the abutment to effect shifting of the upper portion or whorl of the apparatus.
It is the object of the present invention to provide a coupling means for the whorl and spindle which eliminates the defects of the prior art.
According to the present invention, this is obtained by arranging within the throat of the bearing housing and within the surrounding skirt of the whorl a coupling carrier. Either the coupling carrier or the surrounding skirt is provided with a concentric fixed abutment member and a transverse slideable latch member surrounding the carrier resiliently biased to be normally eccentric to the spindle axis and engage the abutment member. By operating the moveable latch, the whorl can be readily disengaged and separated. With the construction, it is possible to have only a small radial opening in the skirt of the whorl to manipulate the latch and the latch may be easily mounted to prevent axial movementor twisting and thus not interfere with the rotation of the spindle. The sidewise movement of the latch further insures secure interlocking between the elements and virtual elimination of an effect caused by the torque or centrifugal action of the device. Also, the eccentric position of the sliding latch with respect to the opening can be exactly maintained.
The coupling carrier intended according to the present invention can further function as the bearing ring for the spindle roller assembly and can be securely fixed within the throat of the housing to provide a secure and more or less rigid coupling connection.
The slideable latch member can take many forms.
Suitable forms can be of an oval configuration or of a U-shape which, under the effect of its rotation, can be caused to slide in the direction of the opening; i.e., the tool entrance opening. Thus, the latch member can be automatically securedly positioned in the operative relationship whenever the spindle is rotated.
In the event the coupling carrier is provided with the fixed abutment member, the slideable latch may comprise a ring-like member arranged to slide transversely of the axis of the spindle. In this instance, the upper end of the carrier may be conically formed to enable it to be pushed easily through the ring and the dimension of the bore of the ring must be greater than the extent of the concentric abutment member so that the abutment member may be axially moveable through it. When the fixed abutment member is formed on the whorl itself, the latch slide may be a ring, a U-shaped spring clip or another similar means. In this instance, however, the external diameter of the latch must be smaller than that of the abutment.
A simple and easily assembled arrangement is obtained when the radially slideable latch is an annular ring secured within a circumferential groove in the skirt of the whorl. A pin may be provided extending radially from the outer periphery of the latch into the tool opening. This locates the slide latch accurately and maintains its proper location even after considerable rotation. The ring can be supported by a spacer and fixed washer-like fastener aginst axial movement. The spacer may also be provided with flattened shoulders engaging cooperatively flattened shoulders on the ring which prevent further relative rotation or twisting of the ring during operation. In this construction, it is preferable to resiliently bias the ring to have it normally positioned in abutting engagement. It is, however, not necessary that the spring be fastened to the ring. On the contrary, a simple leaf spring can be used which chordally bridges the space in the circumferential groove and with its center portion urges the ring eccentric of the spindle axis toward the tool opening. The outer dimension and the inner bore dimension of the ring are chosen so that in its maximum movement during operation the ring does not engage the carrier or the spindle shaft and thereby avoids hindering its movement.
A second construction can be obtained where the abutment surface is formed on the whorl and the slideable latch mounted on the carrier. This embodiment has the advantage that the whorl may be maintained in operative balance, being without the eccentric latch member. The spindle can be thus free of undesireable torque or rotational imbalance. in this consturction, the carrier is formed with a reduced shank portion about which the latch is arranged. Flattened lands may also be provided to prevent rotation and or twisting even if ring latches or U-shpaed latches are used. A spring is also used which may be loose or may be fastened to the ring member. The spring is preferably located chordally between the face of the reduced shank portion and the interior of the latch.
In this second embodiment, an enclosed ring latch may be used, although it might be preferred to use the U-shape latch since the free ends of the U-shape latch can be sprung and moved resiliently over the reduced shaft portion; thus facilitaing a change of parts. Further, the U-shpaed member may be simply snaped into place within a narrow groove and thus reduce the complexity and cost of the device. The free ends of the U- shaped member may be provided with means limiting theradial movement of the latch. Also, the cross-piece of the U-shaped member. can be made with cut-out curved portions enhancing the springiness of the member and also providing means for receiving and fastening the ends of the prestressed spring.
Full details of the present invention as well as a more complete exposition of the objects and advantages follow herein.
Reference is made to the accompanying drawings wherein:
FIG. 1 is a vertical section through a whorl and spindle bearing housing assembly showing the present invention;
FIG. 2 is a section through line 22 of FIG. 1;
FIG. 3 is a view similar to that of FIG. 1 showing a second embodiment;
FIG. 4 is a section through line 44 of FIG. 3;
FIG. 5 is a view similar to that of FIG. 3 showing a second embodiment; and
FIG. 6 is a section through line 6-6 of FIG. 5.
In order to maintain the present disclosure as brief as possible, the description and the appended drawings relate just so much of a spinning and twisting apparatus as is necessary for a full understanding of the invention. Structure such as that of the spinning frame, whorl or twisting mechanism, drive means for rotating the spindle are omitted since they are conventional and readily known to those skilled in this art.
Turning now to FIGS. 1 and 2 which show one embodiment of the invention, there is seen a lower whorl supporting spindle assembly comprising a spindle bearing housing 10 formed to have a receiving throat at its upper end. A spindle shaft 12 connected to a drive means and source of power (not illustrated) is concentrically mounted within the housing 10 and is rotatably supported by a roller bearing assembly 14 secured within the receiving throat. The roller bearing assembly 14 is also conventional, comprising a lower retaining ring, an annular cylindrical race and a plurality of rollers engaging the surface of the spindle shaft 12.
Mounted above the end of the spindle bearing housing is a whorl or other conventional spinning or twisting device 16. The whorl is generally conventional in form and is provided with a depending annular skirt surrounding the throat of the spindle bearing housing 10. The spindle shaft 12 extends into the whorl l6 and is scparably connected or keyed to it so that rotation of the spindle causes the whorl to rotate. The skirt or lower portion of the whorl is spaced from the bearing housing 10 to permit rotation and a degree of radial movement.
Removeably coupling the lower bearing assembly with the whorl is a connecting carrier generally defined by the numeral 18. The carrier is provided with radially outwardly directed flanges 20 and 22 at its lower and upper ends respectively. The lower flange 20 grips the wall of the bearing housing 10 within the throat and lies on the race of the roller bearing assembly 14 to form the upper retaining ring. The upper edge of the bearing housing 10 is bent over to form a lip 24 which secures itself on the flange 20 and thereby holds the connecting carrier 18 fast within the throat against axial movement. The carrier 18 has an elongated shank 26 surrounding the spindle shaft 12. The inner wall of the shank 26 is spaced from the spindle shaft to permit free rotation and also some degree of radial clearance.
The upper flange 22 of the connecting member has a planar lower face which forms an impact or abutment shoulder while its upper face is conically formed. The abutment surface of the upper flange 22 lies above the slideable securing member generally defined by the numeral 28. The securing member or latch 28 takes the form of a ring or annular member and is secured within a circumferential groove 30 formed in the inner wall of the skirt of the whorl 16. The ring latch 28 has a generally oval shape of smaller overall diameter than the skirt of whorl 16 and is thus radially slideable transversely to the axis of the spindle. The latch 28 is supported by a fastening element 32 mounted in a second groove and a spacer or washer 34 on which the latch 28 lies. The fastening element 32 and spacer 34 have an inner diameter at least larger than the diameter of the flange 22.
As will be clearly seen in FIG. 2, the oval securing latch ring 28 has an inner bore 36 eccentric to the outer circumference and is located to surround the shank 26 of the connecting carrier 18. The skirt of the whorl 16 is provided with an entrance opening 38 located along the transverse plane of the securing ring 28. The securing latch ring 28 is also provided with a radially extending pin 40 adapted to enter into the entrance opening 38. The bore 36 of the latch ring 28 is dimensioned so that it is at least slightly larger than the diameter of flange 22 and also that it is continuously spaced from the shank 26 even when the ring is transversely shifted to its maximum extent toward the entrance opening 38; i.e., when its outer peripheral surface contacts the inner wall of the whorl skirt. It will be understood that the latch 28 rotates with the whorl 16 because of the connection between the opening 38 and pin 40 and because of its eccentricity and oval shape may tend to move toward the opening 38; however, the diameter of the bore 36 provides the necessary spacing between it and the shank 26 so as not to impede rotation.
The diameter of the bore 36 is furthermore made at least as large as the radial extent of the upper flange 22 of the connecting carrier 18 so that the flange may move through it and so that in tis operative position (FIGS. 1 and 2) the latch 28 underlies at least a portion of the abutment face of the upper flange 22. The whorl 16 is thus prevented from moving axially upward by the engagement of the securing ring latch 28 and the abutment surface of the flange 22 even under high rotational speeds and centrifugal action. The latch 28 is further prevented from relative rotation with respect to the whorl by providing the spacer washer 34 with upwardly or axial extending parallel guide rails 42, 44 to either side of the ring 28. The rails 42 and 44 are opposed to each other and are provided with smooth faces 46. Similarly, the latch 28 is formed with parallel opposed smooth lands 48 and 50 cooperatively engaging the rails 42 and 44 respectively. Thus, the ring latch 28 is permitted to move transversely of the spindle axis from right to left as seen in FIG. 2. The latch 28 is, however, normally biased by a chordally arranged leaf spring 52 located opposite and normal to the entrance opening 38 within the groove 30 formed in the inner wall of the whorl. The ends of the spring 52 are secured in the wall of the whorl while its central portion abuts the outer circumference of the ring latch 28 so as to resiliently urge the latch toward the entrance opening 38. As noted before, the diameter of the bore 36 of the securing ring latch 28 is dimensioned so that even in maximum extent of movement toward the entrance opening at least a small space and radial clearance is provided between the wall of the bore 36 and the wall of the shank 26.
It will thus be appreciated that the arrangement seen in FIGS. 1 and 2 provides a secure interlocking coupling-or connection between the spindle bearing housing and the whorl 16. Inoperation, the upper surface of the securing ring latch member 28 will engage with the raially extending abutment surface of the flange 22 preventing axial movment, avoiding separation of the parts, even under extreme speeds of spindle rotation. The spring 52 maintains the ring member 28 securely located in position while the opening 38 and pin 40 together with the side guide rails and lands prevent unwanted rotation and movement. Should the forces operating on either the upper lower assemblies tend to cause the whorlto lift the impact surface and the entrance opening will prevent disengagement.
To remove the whorl; i. e., the upper portion of the device from the spindle bearing housing, it is only necessary to insert a pencil-like object into the entrance opening 38 and to push the securing ring latch 28 to the left (as seen in FIGS. 1 and 2). The latch 28 is thus movedagainst the bias of the spring 52 until the eccentric bore 36 is aligned with the flange 22 at the upper end of the carrier 18. The upper portion or whorl can then be easily moved since the flange 22 will pass axially through the bore 36, spacer 34 and fastening element 32, allowing separation of the two parts.
To assemble the two separate parts, the pencil-like tool is not required, since the conical upper surface of flange 22 will permit the two portions to be easily pushed together. The conically tapered edge engages the interior of the latch 28 in keylike fashion, pushing it to the left against the bias of spring 52 until the abutment surface of the flange 22 snaps over the latch, Thereafter, the spring 52 causes the ring 28 to assume its operating position beneath the abutment surface.
In the embodiment seen in FIGS. 3 and 4, the device is basically constructed in the same way as in the prior embodiment except that the abutment surface is formed on the inner wall of the whorl itself and that the upper part of the connecting carrier is modified. Otherwise, the spindle bearing housing, the whorl, and the lower portion of the connecting carrier are identical with the first embodiment and shall not be further described.
As seen in FIGS. 3 and 4, the connecting carrier, generally defined by numeral 60, is fixed within the throat of the spindle bearing housing 62, extending axially outwardly therefrom in a shank or neck portion 64 of smaller diameter spaced from the inner most edge of the interior wall of the whorl. Extending upwardly from the shank 64 is a second neck portion 66 of even a smaller diameter, forming an inwardly tapering steplike end to the carrier 60. The step 64 and 66 define an annular shoulder 68 on which a latch member generally having the numeral 70 rests. The extending step portion 66 is provided with a pair of parallel opposed flattened land portions 72 and 74 on each side and the latch is also provide with similarly formed flattened lands 76 and 78 corresponding therewith. Thus, the ring latch 70 is prevented from rotating about the step 66.'The latch 70 is provided with a central bore 80 which has a greater extent in the transverse direction; i.e., parallel to the lands 76 and 78, than the diameter of the step 66. Thus, the latch 70 is radially slideable from right to left as seen in the figures. A leaf spring 82 is located in the space between the step 66 and the inner wall-of the bore 80. The leaf spring has its ends secured in the wall of the bore 80 and its central portion abut in the engagement against the cylindrical surface of the shank 66. The leaf spring 82 thus urges the latch 70 to the right as seen in FIG. 4. The whorl 84 is provided with an entrance opening 86 positioned on the right adjacent to the edge of the latch 70. The latch 70 has an outer dimension approximately equal to the diameter of the shank 64 and is dimensioned so as not to engage the surface of the whorl. Because of the lands 72 and 74 on step 66, the latch 70 is prevented from rotating. The latch 70 is prevented from moving axially by a spacer washer 88 set in a groove at the end of the connecting carrier 60 and fastened by a nut or other fastening element 92.
The inner wall is provided in the plane of the shank portion 64 with a radially inwardly extending ledge 94 forming a flat annular shoulder on its upper surface and having a conical outwardly tapering face on its lower surface. The ledge 94 defines an inner space or radial clearance therebe tween. The annular shoulder ledge 94 has a flattened abutment surface which is located beneath the plane of the securing ring member 70, which at least in part is seen in FIGS. 3 and 4 engagingly overlies its surface. Thus, the latch 70 and the ledge 94 interengage and cooperate to interlock the upper portion or whorl with the lower portion or bearing housing. They, of course, react in the same manner as the construction seen in FIGS. 1 and 2.
To disengage the upper portion from the lower portion a pencillike tool is inserted within the opening 86 and the latch 70 is pushed to the left (as seen in the figures) so far that is outer surface or periphery becomes coaxial with the opening formed by the annular ledge 94. When this occurs the whorl may be lifted and removed. To assemble the mechanism, the conical lower surface of the ledge 94 permits the whorl to be pressed on to the bearing housing since the ring member can be easily moved against the spring 82 The embodiment shown in FIGS. 5 and 6 is similar to that of FIGS. 3 and 4 in that the abutment ledge is also provided on the. inner wall of the whorl. However, here modification has been made to the upper end of the connecting carrier 60. In other-respects, the construction is the same as shown in FIGS. 1 and 2 and therefore the structure of the lower end of the carrier, the bearing housing and roller assembly are not described again.
In the embodiment, the securing latch holding the upper and lower sections together comprises a U-- shaped member, generally depicted by the numeral 100. The outer dimension of the member is no larger than that of the shank of the carrier 60 and is inserted through its open bight within a circumferential groove 102 formed within the shank. The groove 102 is defined at its bottom by a shoulder 104 formed by a cylindrical section 106 of the carrier and at its top by a radial flange 108. The latch 100 is slideable within the groove and extends eccentric to one side of the cylindrical circumference of the shank portion 106 of the carrier 60. The groove 102 is located just above the plane of the inwardly extending annular ledge 94 so that at least a portion of the latch 100 may be caused to lie over the ledge 94, thus, causing the upper section; i.e., whorl, and the lower section; i.e'., spindle bearing housing, to interlock so that the two can not be separated.
The latch 100 is U-shaped and is provided with a pair of lateral legs 110 and 112 connected by a cross-piece 114. This arrangement provides a resilient element allowing the lateral legs to be flexed spring-like with respect to the cross-piece. Both lateral legs 110 and 112 have inner slide edge portions 116 and 116 which are parallel to each other and which have tip-like ends 118 and 118 respectively which are adapted to partially encircle the shank portion 106. The shank portion 106 itself has a pair of parallel diametrically opposed flattened lands 120 and 120' on which the slide edge 116 and 116' respectively ride, and in the manner previously noted prevent the latch ring from rotation. The inner edge 122 of the cross-piece 114 is curved to conform to the curvature of the shank 106 opposite to it. The distance between the lips 118 and 118' and the inner edge 122 is greater than the diameter of the shank portion 106 so that a space 124 is defined between the inner edge 122 and the shank. The leaf spring 126 is located in this space 124 and serves to bias the securing member toward the right (as seen in the drawings) maintaining the securing member 100 normally eccentric of the carrier 60. The tips 118 and 118 at the ends of the legs 116 and 116' respectively limit the normal movement of the securing member 100 since they engage the surface of the shank 106. The outer dimension; i.e., diameter, of the securing member 100 is choosen such that its out wall edge does not touch the wall of the whorl and that sufflcient radial clearance is allowed to permit free rotation of the whorl.
The leaf spring 126 is prestressed or tensioned to normally maintain the securing member 100 in operative postion over the flat abutment surface of the ledge 94. As seen in FIG. 6, the seucring member 100 is provided with cut-out portions 128 and 128' between the ends of the cross-piece 114 and the legs 116 and 116 respectively. These cut-out portions provide arches 130 and 130 in which the ends of the leaf spring 126 may seat and be retained. In this manner, the spring 126 may be maintained out of contact with the inner edges of the securing latch 100 and in particular, the spring 'allows the latch 100 to be accurately moved in the radial direction.
To disengage the whorl from the spindle, the whorl must frst be rotated so that the entrance opening 86 is aligned with the back of the cross-piece 114 of the securing member 100. A pencil-like tool may then be inserted to radially move the latch 100 against the force of the spring 126 so that the inner shoulder or ledge 94 is freed from engagement with the securing member and the parts may be separated. Assembly is similar to that obtained in the preceding embodiment, in that the conical surface permits the sections to be pressed together.
As noted earlier, the latch 100 is retained within the groove 106. It is easily mounted therein or demounted if desired by moving it in a radial direction. This takes advantage of the resilient nature of the structure and the desired cooperation with the shank portion of the carrier on which it is mounted. The construction has the advantage of removing any imbalance from the whorl which might occur if the latch were mounted on the whorl itself.
It will be apparent that various modifications and changes can be made to the structure described without departing from the concept of the present invention. Accordingly, the disclosure is to be taken as illustrative and not limiting of the present invention.
What is claimed is:
1. Apparatus for spinning and twisting yarn comprising a housing having a throat at one end, a spindle journalled within said housing for rotation about its axis, said spindle extending outwardly of said throat, a whorl concentrically connected to said spindle for rotation therewith and extending at least in part about the throat of said housing, a coupling comprising a carrier mounted at one end within said throat and extending axially about said spindle within said whorl, said carrier and said whorl having means cooperating to interlock said whorl and carrier against axial movement, com prising a fixed member having an abutment surface extending transversely to and concentric with the axis of said spindle and a slidable securing latch resiliently biased to be normally eccentric to the axis of the spindle to selectively engage said abutment surface of said fixed member, including means for securing said latch against rotation relative to the axis of said whorl, said fixed member and said latch being axially movable one within the other on transverse movement of said latch, to effect disengagement thereof permitting separation of said whorl from said carrier.
2. The apparatus according to claim 1 including an opening in said whorl permitting access to said latch to move the same.
3. The apparatus according to claim 2 wherein said carrier comprises an elongated shank secured at one end within the throat of said housing and having a radially outwardly directed flange at its other end, said flange forming an abutment surface on its lower face, and wherein said slideable securing latch comprises a ring mounted about said shaft below said abutment face, means connecting said ring to said whorl for conjoint rotation, said ring having an eccentric inner bore greater than the diameter of said flange permitting said ring under centrifugal action caused by the rotation of said whorl to slide beneath and engage at least a portion of said abutment surface and to be slideable so as to be aligned with said flange to permit axial separation.
4. The apparatus according to claim 3 wherein said securing ring is mounted within a circumferential groove within the wall of said whorl and provided with means for preventing axial movement along said shank.
5. The apparatus according to claim 4 including spring means acting on said ring to normally bias said ring eccentric of said shank.
6. The apparatus according to claim 5 wherein the upper face of said radially extending flange is conically tapered to permit entry of said flange within said ring.
7. The apparatus according to claim 4 wherein the means for interconnecting the ring and the whorl comprises a pin extending radially from the periphery of said ring into the entrance opening.
8. The apparatus according to claim 2 wherein said carrier comprises an elongated shank secured at one end to said housing, and is provided at its other end with means for receiving said slideable securing latch, said receiving means comprises a shank portion of reduced diameter about which said slideable securing member is located, said slideable securing member having an interior bore greater than the diameter of said reduced shank portion and an exterior dimension substantially equal'to said shank, the inner wall of the whorl being formed with a radially extending ledge forming an abutment surface on its upper face located beneath said slideable securing member and radially spaced from said shank portion, and means for resiliently urging said slideable securing member eccentric of said shank to abuttingly engage at least a portion of said ledge, and to be slideable into alignment with the shank portion to permit axial movement through said ledge.
reduced shank portion and said slideable securing member are provided with cooperating means to prevent relative rotation therebetween.
12. The apparatus according to claim 11 wherein said cooperating means comprise cooperating flattened land surface on each of said reduce shank portion and said slideable member.
13. The apparatus according to claim 8 wherein said slideable member comprises a ring, the inner bore of which is greater in dimension than the diameter of said reduced shank portion and includes spring means arranged within said bore and acting on said reduced shank portion and said reduced shank portion and said ring to bias said ring normally into engagement with said abutment surface.
14. The apparatus according to claim 8 wherein said slideable securing member is U-shaped having a pair of lateral legs and a cross-piece resiliently secureable about said reduced shank portion, said reduced shank portion and said lateral legs having cooperating flattened land surface to prevent relative rotation, spring means located with said U-shapedmember between the reduced shank portion and saidcross-piecefor biasing said U-shaped member eccentric of said shank, and means at the end of each of said lateral legs to limit the extent of such bias.