Abstract:
Lateral pins are used to provide a tufting machine modular gauge assembly that allows damaged or broken gauge elements to be replaced individually. The modular gauge assembly consists of a gauge bar with a plurality of modular blocks removably attached to the bar. The modular blocks are six sided with a detent and fastener mechanism for attaching the block to the gauge bar. The gauge elements may be attached to the block by dedicated screw-pins or by a lateral pin that passes through all the gauge elements within a block. The lateral pin may either pierce the gauge elements or abut the gauge elements. Abutting pins may be malleable and segmented and secured in position by conical ended bolts.

Description:
This application is a continuation-in-part of U.S. patent application Ser. No. 10/038,219, filed Jan. 3, 2002 which is incorporated in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a tufting machine with replaceable self-aligning gauge modules and is more particularly concerned with gauge modules with individually replaceable gauge elements which can be readily installed and removed. 
     BACKGROUND OF THE INVENTION 
     Tufting machines are built with precision so that the needles and loopers of the machine are accurately spaced from each other along the needle bar or looper bars. The loopers and needles must be spaced from each other so that the looper bills pass closely adjacent to the needles to engage and hold loops of yarns carried by the needles. When assembling a tufting apparatus, errors in positioning these gauge elements may accumulate as the work progresses. The present invention seeks to establish consistency with these parts across the width of the apparatus, to provide a tufting environment, suitable even for narrow gauge configurations. The present invention also addresses the problem of replacing individual gauge elements that become broken or damaged during tufting. In most modular designs, a broken gauge element requires discarding the entire modular block containing a set of about one to two dozen gauge elements. The present invention allows for quick and efficient replacement of individually damaged gauge elements. 
     The idea of replacing individual components of assemblies in tufting machines is not new. In the past, knife holder assemblies have been devised that allow for the replacement of individual knives. The knives were arranged in pre-assembled or modular fashion in a knife holder, each knife holder having a guide mechanism which enabled groups of knives, each group in a separate holder, to be positioned on a carrying member of a tufting machine and maintained in appropriate alignment. U.S. Pat. Nos. 4,608,934; 4,669,171; 4,691,646; and 4,693,191 illustrate such prior art knife holder assemblies in which parallel knives are disposed. These prior art knife holder assemblies are then disposed in transverse bars provided with guides for positioning the holders in appropriate positions on a tufting machine. 
     Needles have previously been individually secured in modular gauge blocks as shown in U.S. Pat. No. 4,170,949, and hooks and knives have also been individually secured in gauge parts mounting blocks as shown in U.S. Pat. No. 4,491,078. These designs have used individual clamping screws to hold each gauge element in place. These blocks were not mated with slots on the carrying members and were heavily machined. In addition, the clamping screws used in these gauge blocks have typically been flat ended and have relied upon the flat tip pushing directly against the gauge element to securely position those gauge elements. When the blocks are machined from relatively soft metals such as aluminum, there has been a tendency for the threads of the block to become worn and allow too much play for all of the screws to securely hold their corresponding gauge elements. 
     More recently attempts have been made to incorporate needles and loopers into replaceable modular blocks. U.S. Pat. Nos. RE37,108, 5,896,821, 5,295,450 illustrate such modular gauge assemblies in which the gauge elements are permanently embedded into the modular block. The block is attached to the guide bar with a single screw allowing for removal and replacement of the block. One shortcoming of these modular blocks is that when a single gauge element breaks the entire modular block must be discarded. 
     SUMMARY OF THE INVENTION 
     The present invention includes a modular gauge assembly that attaches to a gauge bar. The gauge bar has a plurality of positioning recesses that allows a detent on an individual modular block to be accurately positioned along the gauge bar. Each modular block typically includes a front surface, a pair of side surfaces opposed to each other, a rear surface opposite to the front surface, and a bottom surface. 
     A tongue, which may or may not be a part of the cast block extends from a rear or bottom surface of the modular block. The tongue includes a threaded hole which along with a securing screw serves to mount the block to a gauge bar. The threaded hole aligns with the gauge bar receiving hole when the tongue of the modular block is positioned properly with a recess on the gauge bar. When sufficiently tightened, the securing screw holds the modular block to the gauge bar. 
     At least the front surface of the block contains a plurality of spaced parallel slots so that gauge elements may be positioned in the slots with proper spacing. The proximal ends of the gauge elements may have apertures or channels recessed therein. In one embodiment of the present invention the proximal ends of the gauge elements are inserted into the block and secured there by a lateral pin that enters the block on one of the opposing side surfaces and passes through apertures on the proximal ends of the gauge elements. An alternative embodiment biases a lateral pin resting in a channel on the proximal ends of the gauge elements by tightening a securing bolt that is in communication with the lateral pin through an opening on the block. The preferred securing bolts have conical ends to exert a wedging or camming force against the lateral pin. In either case the gauge elements are secured by a lateral pin engaging the gauge elements. Individual gauge elements can be replaced by demounting the affected block, removing the lateral pin and removing a selected gauge element. After the selected gauge element is removed a new gauge element may be re-inserted into the proper vertical slot and secured by the lateral pin and securing bolt. 
     A plurality of modular blocks are arranged along the surface of the gauge bar and are vertically positioned on the gauge bar by a horizontal surface of the gauge bar or of a guide bar that passes through a guide bar channel on the gauge bar. The width of each block is substantially equal to the distance between the positioning recesses of the gauge bar so that the edges of the blocks abut one another and the blocks are laterally positioned. 
     In an alternative embodiment of the present invention each modular gauge assembly attaches to a gauge bar having a plurality of positioning recesses that allows the detent on the individual modular block to laterally position the block on the gauge bar. Each modular block typically includes a front surface, a pair of side surfaces opposed to each other, a rear surface opposite to the front surface, and opposing bottom and top surfaces. The rear surface contains a rectangular tab or detent that includes a threaded hole to receive a securing screw. The threaded hole aligns with the gauge bar receiving hole when the modular block is positioned properly on the gauge bar. When tightened, the securing screw holds the modular block securely to the gauge bar. A plurality of gauge holes extend from the bottom toward the top surface, in some cases passing through the modular block. Gauge elements with proximal ends adopted to be received within the gauge holes may be positioned with proper spacing in the block. Gauge elements that have the proximal end inserted into the block are securely positioned by pin-screws that enter the block below the tab on the rear surface. The pin-screws are positioned beneath the tab. In this fashion, the pin-screws can be accessed without removing the modular block from the gauge bar. When engaging rounded gauge elements such as tufting needles, the pin screws may advantageously have conical ends to hold the gauge elements by wedging or camming force. 
     Accordingly, it is an object of the present invention to provide a tufting machine where the gauge elements of the tufting machine are accurately positioned within a modular block assembly. 
     Another object of the present invention is to provide in a tufting machine, a system which can facilitate the rapid change over of one or more damaged gauge elements, reducing to a minimum the downtime of the tufting machine. 
     Another object of the present invention is to provide in a modular block assembly, a system which can facilitate the rapid change over of individual damaged gauge elements, reducing the cost of repairing broken gauge elements and removing the need to replace entire modular blocks when a single gauge element becomes damaged. 
     Other objects, features, and advantages of the present invention will become apparent from the following description when considered in conjunction with the accompanying drawing wherein like characters of reference designate corresponding parts throughout several views. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a fragmentary perspective view of a modular block assembly with single looper modular blocks in place on a gauge bar. 
     FIG. 2 is an exploded perspective view of the modular block assembly of FIG. 1 with modular blocks removed from the gauge bar, and one looper modular block disassembled. 
     FIG. 3 is a perspective view of the rear surface of a modular block of FIG.  1 . 
     FIG. 4 is a fragmentary perspective view of a double looper modular block assembly with modular blocks in place on the gauge bar. 
     FIG. 5 is an exploded perspective view of the modular block assembly of FIG. 4, with modular blocks removed from the gauge bar and one block disassembled. 
     FIG. 6 is a fragmentary perspective view of a modular needle block assembly with modular blocks in place on a gauge bar. 
     FIG. 7 is an exploded fragmentary perspective view of the modular needle block assembly of FIG. 6 with the modular blocks removed from the gauge bar and one block disassembled. 
     FIG. 8 is a rear perspective view of a modular block of FIG.  6 . 
     FIG. 9 is an exploded perspective view of a modular assembly having a single row of loop-pile hooks held in place by a lateral pin and securing bolts. 
     FIG. 10A is an exploded view of a modular block having a double row of loop-pile hooks held in place by lateral pins and securing bolts. 
     FIG. 10B is a top perspective view of the relative positions of the gauge elements, lateral pins and securing bolts of FIG. 10A when mounted in the block. 
     FIG. 10C is a bottom perspective view of the relative positions of the gauge elements, lateral pins and securing bolts of FIG. 10A when mounted in the block. 
     FIG. 10D shows in isolation a side elevation view of the relative positions of a single gauge element, lateral pin and securing bolt when mounted in the block. 
     FIG. 11A is an exploded view of a modular block having cut-pile hooks with lateral pins, and securing bolts. 
     FIG. 11B is a side elevation view of the block of FIG.  11 A. 
     FIG. 11C is a side elevation view of the relative positions of the gauge elements, lateral pins and securing bolt of FIG. 11B when mounted in the block. 
    
    
     DETAILED DESCRIPTION 
     The present invention is designed for use in tufting machines of the type generally including a needle bar carrying one or more rows of longitudinally spaced needles that are supported and reciprocally driven by a plurality of push rods. In the tufting zone, the needles carry yarns which are driven through a backing fabric by the reciprocation of the needles. While penetrating the backing fabric, a plurality of longitudinally spaced hooks cooperate with the needles to seize loops of yarns and thereby form the face of a resulting fabric. In some cases the hooks will cooperate with knives to cut the loops of yarn seized on the hooks and thereby form a cut pile face for the fabric. The present invention is directed to modular units for holding loopers or hooks and for holding needles to facilitate their cooperation during the tufting process. 
     Referring in detail to FIG. 1, a modular block assembly  5  is illustrated having a single row of gauge elements  10 , in this case loopers, housed in a series of modular blocks  15 . The individual gauge elements  10  are fastened to each block  15  by a lateral pin  20 . As better illustrated in FIG. 2, the lateral pin  20  enters the modular block  15  at one of the opposing side surfaces  22   a,    22   b.  The gauge bar  25  and guide bar  30  are used in concert to position the modular blocks  15  relative to one another. The guide bar  30  extends laterally through channel  35  substantially the entire length of the gauge bar  25 . The tab breaks  115  of the modular blocks  15  engage with guide bar  30  as shown in FIG. 3, to vertically align the individual blocks  15  in the modular block assembly  5 . 
     FIG. 2 illustrates a portion of the modular block assembly  5  with the blocks  15  detached from the gauge bar  25 . The gauge bar  25  has a plurality of vertical recesses  40 . The recesses  40  are crossed by lateral channel  35  so that guide bar  30  fits between the gauge bar  25  and the rear surfaces  45  of the modular blocks  15 . Guide bar  30  creates upper face  31  and lower face  32  which are normal to the side walls of recesses  40 . When tab breaks  115  of modular blocks  15  engage these faces  31 ,  32 , the faces serve as restraining surfaces to hold blocks  15  in vertical alignment. 
     One modular block  15  in FIG. 2 is disassembled and removed from the gauge bar  25  to reveal spaced parallel slots  50  divided by vertical walls  51  located on the front surface  55  of the block for receiving the proximal ends  75  of the gauge elements  10 . The illustrated proximal ends  75  of the gauge elements  10  contain apertures such as pinholes  70 . When the gauge elements  10  are positioned in the modular block  15  the pinholes  70  align with apertures formed in side surfaces of the block such as pin opening  85 . Lateral pin  20  is then inserted through pin opening  85  in one of the opposing side surfaces  22   a,    22   b,  and the pinholes  70  for each gauge element  10  to fasten the gauge elements  10  in block  15 . 
     In illustrated modular blocks  15  containing only a single row of gauge elements  10 , a tongue portion  60  extends from the rear surface  45  of the modular block  15 . The tongue  60  has an opening, preferably in the form of hole  90 , as shown in FIG.  3 . When the modular block  15  is positioned on the gauge bar  25 , threaded hole  90  aligns with another hole  100  located in a gauge bar recess  40 . Once a modular block  15  is positioned a securing screw  65  can be inserted through hole  90  and tightened into the hole  100  on the gauge bar  25 . A modular block  15 , once fixed in place by the securing screw  65 , is prevented from lateral and vertical movement. The screw  65  and side walls of vertical recesses  40  resist against horizontal movement while the screw  65  and faces  31 ,  32  of the guide bar  30  resist against vertical movement. The fixed position of the blocks  15  insures that the gauge elements  10  remain properly aligned during the tufting process. 
     FIG. 3 shows the rear surface  45  of a modular block  15  having a single row of gauge elements  10 . On the rear surface  45  is a detent in the form of an elongated tab  110  extending vertically from the top  165  of the block to the bottom of the tongue portion  60  of the block. Tab  110  has a horizontal break  115  that engages with guide bar  30  to vertically position block  15  on the gauge bar  25 . The walls of break  115  are preferably substantially planar and parallel so that a part of the rectangular cross section of guide bar  30  closely fits within break  115 . The lower segment  120  of the tab contains the opening  90  where the securing screw  65  enters and attaches to a receiving hole  100  in the gauge bar  25 . 
     FIG. 4 illustrates a section of a modular block assembly  5  with three double gauge element modular blocks  130  mounted on the gauge bar  26 . Each modular block  130  contains two transverse gauge element rows  125 , the forward gauge elements  12  forming a first row  125  and rear gauge elements  11  forming a second row. Modular blocks  130  have two apertures such as pin openings  85   a,    85   b  that are spaced apart on the side surfaces  22   a,    22   b  of the block  130 . Unlike blocks  15  in FIG. 1, a portion of the double gauge modular blocks  130  rests on top of the gauge bar  26  to vertically position blocks  130 . This is accomplished by using a downwardly extending detent such as tongue  60  illustrated near the center of the bottom  135  of blocks  130 . 
     FIG. 5 shows an exploded view of modular block  130  containing two rows  125  of gauge elements  11 ,  12 . The gauge bar  26  in FIG. 5 has a plurality of vertical recesses  40 . Vertical recesses  40  receive tongues  60  to horizontally position blocks  130  along the gauge bar  25 . Vertical positioning is accomplished by resting part of the bottom surface  135  of gauge blocks  130  on the top surface of gauge bar  25 . Modular block  130  in FIG. 5 is disassembled and removed from the gauge bar  26  to reveal the spaced parallel slots  50   a,    50   b  located on the front  55  and rear surface  45  of the block  130  for receiving the proximal ends  77 ,  78  of the front and rear gauge elements  12 ,  11 . 
     The proximal ends  77 ,  78  of the gauge elements  12 ,  11  contain openings such as pin holes  71 ,  72  which when positioned in slots  50   a,    50   b  of modular block  130  align with pin openings  85   a  or  85   b,  respectively. The lateral pins  20   a,    20   b  are inserted through the pin openings  85   a  or  85   b  on one of the opposing side surfaces  22   a,    22   b  and through pin holes  71 ,  72  in the proximal ends of each gauge element  11 ,  12  to fasten the gauge elements  11 ,  12  in the modular block  130 . 
     In the illustrated modular blocks  130  the tongue portion  60  of the modular block  130  extends centrally from the bottom surface  135 . Tongue  60  defines an opening (not shown). When modular blocks  130  are positioned on gauge bar  26 , this opening aligns with a threaded receiving hole  100 , located in vertical recesses  40  of gauge bar  26 . Once the modular block  130  is positioned a securing screw  65  can be inserted through the opening in tongue  60  and tightened into threaded receiving hole  100 . Modular blocks  130 , once fixed in place by securing screws  65 , are prevented from lateral movement by the securing screw  65  and interface of the detent against walls of vertical recesses. Similarly, modular blocks  130  are prevented from vertical movement by securing screw  65  and interface of bottom surface  135  against the top surface  26   a  of gauge bar  26 . The fixed position of the block  130  insures that the gauge elements  11 ,  12  remain properly aligned during the tufting process. 
     Referring now to FIG. 6, another aspect of the present invention depicts a section of a modular block assembly  5  having a row of gauge elements, in this case needles  13 , housed in clamping modular blocks  140 . FIG. 6 shows four clamping modular blocks  140  attached to gauge bar  27 . The clamping modular blocks  140  are positioned such that the lower portion  150  of the block  140  extends beneath the gauge bar  27 . This exposed lower portion  150  contains individual clamping elements, such as screw-pins  145 , shown in FIG. 7, that hold the gauge elements  13  in place in the block  140 . The gauge bar  27  has a horizontal shelf portion  27   a  and a vertical portion  27   b  which join to form an interior right angle into which the blocks  140  are positioned. 
     FIG. 7 illustrates a portion of a modular block assembly  5  with screw-pin modular blocks  140  detached from the gauge bar  27  and one block  140  disassembled. The gauge bar  27  has a plurality of vertical recesses  40  on the inner surface of vertical portion  27   b  of the gauge bar  27 . As illustrated, the recesses  40  do not extend the entire height of the wall portion  27   b  of the gauge bar  27 . Each recess  40  preferably contains a clearance hole  100  which receives a securing screw  65  to attach blocks  140  to the gauge bar  27 . The rear surfaces  45  of modular blocks  140  have a detent such as tab  160  with an opening, such as threaded hole  90  (shown in FIG.  8 ), positioned to align with holes  100 , located in the vertical recesses  40  of gauge bar  27 . Once a modular block  140  is positioned in the interior right angle between the shelf portion  27   a  and wall portion  27   b,  with tab  160  received in a vertical recess  40 , the securing screw  65  can be inserted through the corresponding hole  100  in the wall portion  27   b  into the threaded hole  90  in the tab  160  and tightened to hold the modular block  140  in place. Once fixed in place by securing screw  65 , the modular block  140  is prevented from lateral movement by the action of the tab  160  fitting between the vertical walls of the vertical recess  40 , by the screw  65 . Vertical movement is restrained by action of the screw  65  and the interface of the top surface  165  of block  140  with the bottom of shelf portion  27   a  of the gauge bar  27 . The fixed position of the block  140  insures that the gauge elements  10  remain properly aligned during the tufting process. 
     FIG. 7 also depicts a disassembled clamping modular block  140  thereby revealing the spaced parallel gauge element openings  155  which extend from the top surface  165  to the bottom surface  135  of the block  140 . Openings  155  need not extend completely to the top surface  165  for satisfactory operation, however, it is convenient for manufacture. The individual needles  13  are fastened to the block  140  by dedicated clamps such as screw-pins  145  that fix individual gauge elements  10  within the block  140 . Screw pins  145  enter the block  140  at the rear surface  45  of the block  140  on its lower portion  150 . When the block is attached to the gauge bar  27  the screw-pins  145  remain accessible so that individual gauge elements  10  can be removed and replaced. 
     FIG. 8 illustrates the top  165  and rear surface  45  of the block  140 . Gauge element openings  155  can be seen on the top surface  165  of the block  140 . A rectangular tab  160  for positioning the block  140  on the gauge bar  27  is located centrally on the rear surface  45  of the block  140 . The rectangular tab  160  defines the opening  90  which aligns with the holes  100  in vertical recesses  40  and with securing screw  65  fixes the block  140  to the gauge bar  27 . Openings  170  for screw pins  145  are located horizontally along the lower portion  150  of block  140 . 
     Referring now to FIG. 9, a preferred embodiment of the present invention depicts a modular block assembly  5  having a single row of gauge elements, in this case loop pile hooks  10 , housed in a single gauge modular block  15 . The modular block  15  may be mounted and attached to the gauge bar  25  with securing screw  65  extending through the block  15  into the gauge bar  25 . The gauge elements  10  are inserted in and removably secured to the block  15  by use of lateral pin  20 . The lateral pin  20  may be divided into two or more sections, or be formed of somewhat malleable material, to compensate for various differences in the heights of the gauging elements  10 . 
     Unlike the previous embodiments, the illustrated lateral pin  20  does not extend through openings in the gauge elements  10 , but merely abuts proximal ends of gauge elements  10  so that the gauge elements  10  are resting on the lateral pin  20 . The lateral pin  20  is then biased against the gauging elements  10  by a clamp such as securing bolt  38  received in threaded opening  39  on the top surface  165  of modular block  15 . Tightening securing bolts  38  biases the lateral pin  20  against the gauging elements  10 . In a preferred embodiment the lateral pin  20  is made of a soft metal such as brass so that when urged by the securing bolt  38 , the lateral pin  20  deforms slightly and compresses within channels  79  of individual gauge elements  10 . As a result of the clamp, the lateral pin  20  is held in place preventing lateral movement of the pin  20  into or out of the block  15 . 
     Due to differences in the width of the proximal ends  75  and channels  79  of the various gauge elements  10 , varying amounts of pressure are required along the length of pin  20  to sufficiently compress and restrain the gauge elements in a fixed position. Thus a preferred construction divides the pin  20  into segments to prevent the necessity of compressing a single pin  20  into all the gauge elements  10 . 
     This method of securing gauging elements to a block may also be employed for double gauge modular blocks  130  as seen in FIG.  10 A. Rear and forward gauging elements  11  and  12  are arranged in parallel transverse rows on block  130 . The rear row of gauging elements  11  is held in position by rear lateral pin  20   a.  Pin  20   a  is biased against the rear gauging elements  11  by securing bolts  38   a  which are received by threaded openings  39   a.  Likewise, the forward gauging elements  12  are held in place by forward lateral pin  20   b  biased against the forward gauging elements  12  by securing bolts  38   b  which are received by threaded openings  39   b.    
     In FIGS. 10B and 10C, the gauge elements  11 ,  12  are shown with lateral pins  20   a,    20   b  and securing bolts as they would be positioned in blocks  130 , however, the blocks are not shown. Of particular interest is the conical point  89  of securing bolts  38   a,    38   b.  The conical points  89  are aligned alightly off center of lateral pins  20   a,    20   b,  so that the side wall rather than the vertice of the conical point makes contact with the pins  20   a,    20   b.  This causes a wedge like or camming effect to pressure pins  20   a,    20   b  against gauge elements  11 ,  12 . When securing bolts  38   a,    38   b  utilize camming action rather than mere frontal clamping pressure as would typically be the case if the bolts had flat ends, the bolts  38   a,    38   b  will continue to function even when wear and operating stresses have introduced some play between the threads of the bolts  38   a,    38   b  and their openings  38   a,    39   b.    
     FIG. 10D shows a single securing bolt  38   a  with conical point  89  applying camming type pressure against lateral pin  20   a  which is engaged in channel  79  of rear gauge element  11 . The modular block  130  that would hold these components is not shown so that the interaction of the gauge element, lateral pin  20   a  and securing bolt  38   a  can be clearly illustrated. 
     An additional embodiment of the invention is illustrated in FIG.  11 A. The gauge elements, in this case cut-pile loopers  14 ,  18  are shown removed from block  15 . When mounted in block  15 , the gauge elements  14 ,  18  fit between lateral bracing pins  16   a,    16   b  and secured lateral pin  20 . The bracing pins  16   a,    16   b,  are slidably press fit within the block  15  and then gauge elements  14 ,  18  are positioned. Bracing pins  16 a,  16   b  preferably fit in channels  79   a,    79   b  (shown in FIG. 11C) of gauge elements  14 ,  18 . Pin  20  is also biased against the gauge elements  14 ,  18  by a clamping device such as securing bolts  38  proceeding through threaded openings  39  to engage the pin  20 . Once the gauge elements  14 ,  18  are placed in the block  15  and the bracing pins  16   a,    16   b  are positioned in channels  79   a,    79   b  of those gauge elements  14 ,  18  and lateral pin  20  is in place in block  15 , the securing bolts  38  are tightened to bias the securing pin  20  against the gauge elements  14 ,  18 . 
     FIG. 11A shows a series of four securing bolts  38 . In a preferred embodiment, each securing bolt  38  contacts a dedicated segment of the pin  20 . Pin  20  may be made of a malleable metal such as brass and either cut or scored to create segments. Thus, pin  20  may be comprised of four separate pieces. The bolts  38  are sufficiently spaced across the block  15  so that each securing bolt  38  can contact a segment of the securing pin  20  and thereby bias between about two and about four individual gauge elements  14 ,  18 . 
     FIGS. 11B and 11C are side plan views of the modular block  15  and cut pile loopers  14 ,  18  of FIG. 11A, however, FIG. 11C shows the gauge elements  14 ,  18 , lateral pins  16   a,    16   b,    20 , and securing bolts  38  without the modular block  15 . It can be seen that cut pile loopers  14 ,  18  are designed to engage with rear and front rows of needles respectively, although a single length of looper could be used if only one row of needles was to be used to create cut pile tufts. As best seen in FIG. 11B, the side wall of conical point  89  exerts camming pressure against lateral pin  20 . Lateral pin  20  in turn engages with the proximal ends of gauge elements  14 ,  18 . FIG. 11C shows that lateral pins  16   a,    16   b  and  20  are advantageously set in channels  79   a,    79   b,    79  formed in the proximal ends of the gauge elements  14 ,  18 . 
     Although a preferred embodiment of the present invention has been disclosed in detail herein, it will be understood that various substitutions and modifications may be made to the disclosed embodiment described herein without departing from the scope and spirit of the present invention as recited in the appended claims.