Field of the Invention

This invention relates generally to a method and vise that has a clamp for securely holding in place one or more workpieces, and more particularly to a vise with a clamp capable of compensating for tolerance differences between workpieces when simultaneously holding more than one workpiece and which is also versatile in also being able to securely hold in place a single unevenly contoured workpiece.

Background of the Invention

In the clamping of workpieces, many widely varying types of vises and clamps for vises have been developed. For the machining of workpieces by precision machine tools such as CNC machines and other precision machine tools, many of these vises and clamps are unsuitable because they cannot ensure accurate workpiece location while also securely holding workpieces that are to be precision machined. One known challenge in the field of precision machining of workpieces is maintaining the accurate location of each workpiece when clamped such that each machining operation is located accurately on the workpiece when machining is completed. A known difficulty in maintaining accurate location of each workpiece is that each workpiece can vary slightly in size, shape, and, hence, tolerance from every other workpiece, making it very challenging to precisely and accurately machine each workpiece so that each finished workpiece has a machined surface that is virtually identical to and accurately located relative to every other workpiece. This problem can be particularly acute when simultaneously precision machining more than one workpiece clamped together in a precision machine tool vise. Conventional vises are poorly suited for precision machine tool applications because they typically can only apply a clamping force against an out of tolerance workpiece at only one point along the workpiece. Therefore, even a slight contour variation in a workpiece, such as one producing a tolerance difference of only a few thousandths of an inch, can result in a

conventional vise not clamping the workpiece securely enough, which can result in a clamped workpiece undesirably moving during machining. Moreover, in the clamping of an out-of-tolerance workpiece, a vise of conventional construction will apply most, if not virtually all, of its clamping force to a relatively small area of the workpiece, quite possibly damaging the workpiece.

In another type of clamp for a machine tool vise, the clamp has a block that can pivot about a point that is generally centrally located on the jaw to enable the clamp to simultaneously hold two workpieces. Unfortunately, a clamp of this design can be rather bulky, particularly if more than one of these clamps are connected together to clamp more than two workpieces in multiples of two workpieces, making it undesirable to use in machining applications that require limited space. Additionally, the distance between a clamping point, where the clamp engages a workpiece, and its pivot cannot be too great or rather large bending moments will result, possibly causing premature failure. One final disadvantage is that this type of clamp can only hold a maximum of two workpieces at a time, no more, no less. Although it can hold multiples of two workpieces, if several of these clamps are connected together, the resulting clamping mechanism becomes so bulky as to become unwieldy.

Another problem with this type of clamp is that it also cannot securely apply clamping pressure along the entire clamping surface of a single workpiece that is unevenly contoured, dramatically limiting its versatility. Since this type of clamp is limited in the number of workpieces that it can hold at the same time, it also is not cost effective for many machining applications and automated assembly lines that require large numbers of workpieces to be machined in a very short period of time or simultaneously at one time. Another type of clamp that has been developed in an attempt to overcome these problems has a plurality of "pistons" that extend outwardly from a housing. During clamping, an end of each of these pistons bears against a resilient rubber or plastic backing that is rigidly supported by the clamp housing. When clamping workpieces, each piston is urged against the

backing, causing the backing to deform. The backing is constructed and arranged so that its deformation can vary somewhat from piston to piston thereby enabling it to "absorb" some tolerance differences between simultaneously clamped workpieces, allowing this type of clamp to compensate for some tolerance differences between simultaneously clamped workpieces. Unfortunately, the amount of tolerance compensation is limited, in part, by the thickness and deformability of the backing which can limit the effectiveness and usefulness of the clamp. Additionally, cyclic deformation of the backing can create permanent grooves in the backing, thereby reducing the effectiveness of the clamp at compensating for tolerance variations and requiring the costly replacement of backing material on a periodic and, quite possibly, relatively frequent basis. Furthermore, wear and permanent grooves in the backing can cause the clamping force to vary between workpieces simultaneously clamped possibly resulting in some workpieces being insufficiently clamped or, on the other hand, undesirably damaged. If not securely clamped, a workpiece can undesirably move during machining resulting in defectively machined workpieces. Moreover, when machining more than one workpiece having tolerance differences between them and held by the clamp in a precision machine tool vise, one or more of the workpieces can be pulled out of the vise, damaging the tooling and possibly injuring the operator.

Another known type of precision machine tool clamp has compensating jaws that consist of fingers that each have a T-shaped flange at one end, each of which is received in a complementarily grooved housing. There is a cylindrical spacer between each pair of adjacent fingers that cooperates with the adjacent fingers to enable the clamp to hold a single unevenly contoured workpiece. Unfortunately, all of the fingers of the clamp must be in contact with the workpiece to ensure that the clamping pressure of each finger is relatively balanced, significantly limiting the versatility of this type of clamp because it is only particularly well suited for clamping only a single workpiece that is large enough to be simultaneously engaged by all of the fingers of the clamp. As such, this clamp is particularly poorly suited to hold several

workpieces at one time because its clamp fingers can slide laterally within the casing requiring considerable dexterity and time to properly position and orient the workpieces and fingers before and during clamping.

Koufos, U.S. Patent No. 4,353,537, discloses a clamping device which is versatile in that it can also be used, with slight modification, to support the flat contact surface of a clutch. This clamping device utilizes a casing having openings for allowing relatively large balls, each biased outwardly by a spring, to protrude outwardly through the casing for bearing against an object being clamped. Within the casing, the large balls are in contact with a layer of smaller balls that are spaced from each biasing spring. The layer of smaller balls contact a layer of intermediately sized balls. Both the small and intermediate balls are received in complementary recesses in a rubber mat or sheet.

Unfortunately, the large balls that protrude from the casing provide a small clamping surface area, making the clamp poorly suited for clamping several workpieces at once. Even assuming that this clamp can be suitably used for clamping a single workpiece, because of the rather small area of contact between each large ball and workpiece, the rounded shape of each large ball can result in poor or insufficient clamping pressure being applied to the workpiece which can, in turn, undesirably allow a clamped workpiece to move during machining. On the other hand, the extremely small surface area of contact between each large ball of the clamping device and workpiece is typically only a single point of contact that can, in some instances, cause too much force to be applied to the workpiece, possibly damaging or permanently marring the workpiece. Moreover, due to the inward retraction of each large ball into the casing being resisted largely only by its biasing spring, any tolerance or contour compensating capability as well as the maximum clamping pressure of this clamp are, at best, extremely limited, making it poorly suited for precision machining applications. As such, this clamp design is poorly suited to handle the large clamping forces that must be applied to a workpiece being precision machined to securely hold the workpiece during machining. Moreover, should any of the

balls be pushed too far into the casing during clamping, the casing itself could undesirably directly contact the workpiece. Additionally, as a result of the construction and arrangement of the layers of balls and the mat of this clamp, deflection of the mat can occur during clamping which, in turn, can result in clamp instability by undesirably causing one or more small balls to shift so far laterally during clamping such that the balls will not return to their original positions after clamping force is released. Finally, the round shape of its clamping surface is unwieldy and also does not lend itself well to simultaneously clamping more than one workpiece at the same time. Another known disadvantage that precision machine tool vises have is that they typically require two accurately machined surfaces on the workpiece being clamped to accurately locate the workpiece upon clamping. More specifically, precision machine tool vises typically require a machined locator surface of the workpiece to be in contact with each jaw or clamp of the vise, thereby requiring each opposing jaw or clamp to also have a locator. By requiring a workpiece to already have two locator surfaces before performing additional machining operations on the workpiece, the cost to make the finished workpiece is undesirably increased. Additionally, by requiring each jaw or clamp of a vise to have a locator, the cost to construct each such vise is also undesirably increased. Moreover, by requiring a vise to be constructed with this kind of precision, the normal wear and tear associated with routine use can possibly cause vise to lose its ability to accurately locate a workpiece to be machined when it is clamped in the vise.

Summary of the Invention A vise with a clamp having a housing, at least two reciprocable clamp fingers that can move relative to each other, and at least two load transfer elements received in the housing, all constructed and arranged for securely holding more than one workpiece at the same time while compensating for tolerance differences between workpieces or for securely holding a single workpiece that has an unevenly contoured clamping surface.

The vise has a base with a pair of jaws carried by the base for securely holding one or more workpieces between its jaws. To enable clamping of a workpiece between the jaws, one jaw can be moved relative to the other jaw. To enable the clamp to securely hold more than one workpiece or a single contoured workpiece, the clamp is carried by one of the jaws. So that one jaw can be moved relative to the other jaw, the jaw that is movable is preferably supported on a guideway or guideways carried by the base. If desired, the vise can have a clamp of this invention carried by both jaws of the vise.

To enable movement of the movable jaw, the vise has a support carried by the vise with a bore for receiving a screw that is in operable communication with the movable jaw. During operation of the vise, rotation of the screw in one direction preferably moves one jaw toward the other jaw to cause the clamp to engage a workpiece to securely hold the workpiece. Rotation of the screw in the other direction preferably moves the one jaw away from the other jaw to release the workpiece.

To ensure accurate location of a workpiece while it is clamped, one of the jaws preferably has a locator that engages a locator of the workpiece during clamping. To accurately locate the vise relative to another object, such as a machine tool, the vise is preferably accurately located relative to the machine tool.

Advantageously, a clamp of this invention does not require a locator on each jaw to engage with a locator(s) of the workpiece being clamped to ensure accurate location of the workpiece. Rather, to ensure accurate workpiece location, a vise and clamp of this invention only requires one of the jaws to have a locator that engages with a locator on the workpiece when the clamp urges the workpiece against the locating jaw during clamping.

In one preferred embodiment of a clamp of this invention, the clamp has a housing with a front wall, a rear wall, a pair of spaced apart sidewalls, and a bottom, all for defining a cavity within the housing for receiving a pair of clamp fingers and at least two load transfer elements while providing suitable room within the cavity for the fingers and elements to move relative to each other. To enable reciprocating movement of each clamp finger, the

housing front wall has a through bore extending from its exterior into the cavity, with each bore for receiving a clamp finger. To minimize friction while facilitating reciprocating movement of each finger during clamp operation, each bore can have a replaceable sleeve or liner in the bore that can be sacrificial, if desired.

Each clamp finger is elongate and has a workpiece engaging surface at one end and a load transfer element engaging surface at its opposite end. To prevent withdrawal of each finger from the clamp housing, each finger can be constructed with a head larger than the bore in the housing front wall. To urge each finger against an adjacent load transfer element, each finger preferably operably communicates with a biasing element. Preferably, the biasing element is a spring.

To enable a clamp of this invention to securely hold a wide variety of workpieces of different shapes, sizes, and contours, each clamp finger can carry an extension on the free end of the finger that extends outwardly from the clamp housing. If it is desirable to direct a portion of the clamping force in a direction other than generally parallel to a longitudinal axis of each clamp finger, the workpiece engaging surface of either one or more clamp fingers or one or more clamp finger extensions can be canted. Each load transfer element preferably has a circular cross section along at least one direction of the element. In one preferred embodiment, the element is disc-shaped, having a flat top and bottom surface with a cylindrical sidewall for providing surface area maximizing line contact between adjacent elements. If desired, each element can have a through bore and can be a drill bushing or a cylindrical roller bearing that is preferably hardened, if constructed of steel. Alternatively, each element can be of round construction, generally spherical construction, generally spherical construction with truncated flat top and bottom walls, or a puck that is a disc-shaped washer having a ball bearing in its hollow center. When received inside the clamp housing, the load transfer elements are constructed and arranged such that there is a first row of elements behind the clamp fingers and a second row of elements behind the first row of elements.

Preferably, the second row of elements are located between the rear wall of the clamp housing and the first row of load transfer elements. Preferably, the elements are constructed and arranged within the clamp housing such that there are as many elements in the first row as the number of clamp fingers and one less element in the second row than the number of clamp fingers. In the first row, each load transfer element is preferably behind the load transfer element engaging surface of a clamp finger and can move relative to the load transfer element engaging surface during clamping. Preferably, each element of the first row is arranged such that a central longitudinal axis of its clamp finger cuts through a portion of the element. During clamping, each load transfer element engaging surface of each clamp finger bears against its adjacent element in the first row.

In the second row, each load transfer element preferably is always in contact with at least two elements of the first row during clamping of a workpiece forming a triangle between the center of each element of the second row and the centers of adjacent contacting elements of the first row. Preferably, the angle between the legs of the triangle that extend from the center of the element of the second row to each center of the elements of the first row is acute and is preferably at least about 45°. During clamping, each element of the second row preferably bears against the rear wall of the housing to provide support to the assembly and transfer clamping forces to the housing and vise.

During clamping, each pair of adjacent clamp fingers is in contact with a pair of load transfer elements of the first row and those same elements in the first row are in contact with an element in the second row that has a center point that lies between both central longitudinal axes of the clamp finger pair. These contact points preferably form a four sided polygon having a first leg extending from the contact point between one of the fingers and elements of the first row and the other of the fingers and elements of the second row. A pair of legs extend from the contact point between each clamp finger and first row element to the contact point between each first row

element and the second row element. A fourth leg extends between the contact points of each first row element with the second row element.

For a clamp having more than two clamp fingers, the center point of each first row element of each interior clamp finger forms a triangle with the center points of each pair of second row elements in contact with that first row element. Preferably, the angle between legs of the triangle extending from the center point of the first row element to the center points of each contacting second row element is preferably acute and preferably does not approach or exceed 120° during clamp operation to ensure clamp stability. To encourage stability of the load transfer elements during clamp operation, within the clamp housing cavity and adjacent the front wall of the housing preferably is an inwardly extending divider or dividing wall between each pair of clamp fingers. To further encourage stability, each sidewall preferably has an inwardly extending sidewall portion to limit load transfer element movement and more particularly to preferably limit extreme outward movement of the outer second row element that is adjacent the sidewall.

Also to encourage clamp stability and to help to more equally distribute clamping forces between clamp fingers, one or preferably both sidewalls have an inwardly inclined guide surface that engages the outer first row element that is adjacent the sidewall. Preferably, each guide surface is acutely inwardly inclined at an angle of at least 5° relative to a longitudinal reference axis of an adjacent clamp finger that is parallel to the direction of movement of the finger. Preferably, each clamp housing sidewall can be constructed with a first sidewall portion that is generally parallel to the clamp finger reference axis and a second sidewall portion that is inwardly inclined to form both (a) a guide surface for the outer element of the first row, and (b) a constraining stability encouraging barrier for the outer element of the second row.

Preferably, a clamp of this construction can securely hold as many workpieces as there are clamp fingers and can also hold a number of workpieces less than the number of clamp fingers. If the clamp is holding a lesser number of workpieces than the number of clamp fingers and one or more clamp fingers are not engaging a workpiece, those clamp fingers not

engaging a workpiece preferably can be locked in place so they do not move further outwardly during clamp operation to encourage clamp stability.

In a method of this invention, a clamp of this invention can be used to securely hold a workpiece having an unevenly contoured clamping surface. To clamp the workpiece, the workpiece is received by the vise in operable communication with a jaw of the vise with the unevenly contoured clamping surface oriented so it faces the clamp fingers. Before clamping, finger extensions of the appropriate length are selected and attached to the appropriate clamp finger to ensure points of contact between each finger and the workpiece during clamping so that the workpiece will be securely clamped when clamping is completed.

During clamping, the clamp fingers are moved towards the workpiece until at least one of its fingers engage the clamping surface of the workpiece. To accomplish clamping against the contoured surface while also compensating for workpiece tolerance variations, the fingers of the clamp move relative to other fingers of the clamp causing all of the fingers to engage the clamping surface of the workpiece to securely hold the workpiece.

During clamping and after the fingers have engaged the workpiece, relative movement between the fingers occurs by urging the clamp further against the workpiece. To enable the fingers to move relative to each other, load transfer elements within the clamp move relative to other load transfer elements thereby also enabling the fingers to conform to the uneven contour of the workpiece to engage the workpiece to securely hold the workpiece. To prevent pivoting of each clamp finger extension and to provide support for each extension during clamping, each extension is preferably guided along its longitudinal axis, such as by a clamp finger extension guide assembly carried by the clamp housing and having guide bores through which the extensions are received.

The clamp can have one pair of adjacent clamp fingers spaced further apart from each other than another pair of adjacent clamp fingers. Preferably, each spaced apart adjacent pair of fingers can be spaced apart by at least one additional load transfer element in the first row and at least one additional

element in the second row. In a second preferred construction, the fingers can be spaced apart by an elongate load communicating element in one of the rows that enables all of the elements within the clamp housing to operably communicate with each other while permitting at least one pair of adjacent fingers to be spaced further apart than another pair of adjacent fingers.

During operation of a clamp of this invention, as each finger comes into contact with a workpiece, it displaces that finger slightly inwardly into the clamp housing setting off a chain reaction of load transfer element motion within the clamp housing for compensating for tolerance differences between workpieces or contour variations along a clamp surface of a single workpiece. As the clamp finger is displaced into the housing, it in turn urges its contacting first row element toward the rear of the housing causing elements in the second row also to move within the clamp housing. Advantageously, in this manner, the construction and arrangement of the clamp fingers and load transfer elements permits clamp fingers to move relative to other clamp fingers during clamping to compensate for tolerance differences between workpieces or contour variations in a single workpiece.

During clamping, all of these fingers and elements cooperate with each other by moving at least slightly relative to each other until an equilibrium is reached in that they can no longer move any further. When equilibrium is reached, clamping force is transferred through the fingers, elements and directly to the housing where, in turn, it is transferred to the vise resulting in a clamp having fingers that are rigid and unmoving.

Objects, features and advantages of this invention are to provide a method and vise that has a clamp with clamp fingers that can move relative to each other for compensating for tolerance differences between workpieces or contour variations along a clamping surface of a single workpiece while still being able to securely hold the workpiece or workpieces; can be constructed with load transfer elements of different sizes to suitably increase or decrease the amount of tolerance compensation that a clamp of this construction can perform; is of compact and modular construction; is readily adaptable for use with assembly lines which use pallets to transfer workpieces between

manufacturing stations; can increase production when used in precision machining applications because it can simultaneously and securely hold several accurately located workpieces despite tolerance differences between them; does not require hydraulic fluid and therefore will not leak; can be used to securely hold workpieces for a variety of manufacturing applications where a clamped workpiece is drilled, milled or broached, for example, resulting in machining forces attempting to push or pull a clamped workpiece free of the vise; is of low wear construction and can be cycled repeatedly without adversely affecting clamp operation; relatively evenly distributes clamping force amongst its clamp fingers for preventing damage to a workpiece and preventing damage and wear to the clamp; is quickly and easily adaptable for use in clamping workpieces having unevenly contoured clamping surfaces; is economical because a vise equipped with a clamp of this invention only requires one jaw to have a locator and only a single complimentary locator on the workpiece to be machined whereby location is easily and simply achieved by the clamp urging the workpiece against the locating jaw; is versatile in that it can be used to clamp workpieces of square, rectangular, oval, round or another construction; can be constructed having as few as two clamp fingers and as many fingers as are needed to clamp three or more workpieces or for providing more than one point of contact with a single workpiece or multiple workpieces; is versatile because it can be used for a variety of clamping applications without modification; and is a clamp that is rugged, simple, flexible, reliable, and durable, and which is of economical manufacture and is easy to assemble and use.

Brief Description of the Drawings

These and other objects, features, and advantages of this invention will become apparent from the following detailed description of the best mode, appended claims, and accompanying drawings in which:

FIG. 1 is a perspective view of a vise having a clamp of this invention with a portion of its housing cutaway to show clamp fingers extending from the

clamp in operable communication with a plurality of load transfer elements within the clamp;

FIG. 2 is an exploded view of the clamp shown in FIG. 1;

FIG. 3 is a top view of a clamp having more than two clamp fingers simultaneously clamping more than two workpieces with a portion of its clamp housing cutaway to show the construction and arrangement of load transfer elements within the housing and the cooperation of the elements with the clamp fingers during simultaneous clamping of multiple workpieces;

FIG. 4 is an enlarged fragmentary top view of the clamp taken along line 4—4 of FIG. 3 with a portion of the clamp housing cutaway illustrating one preferred clamp housing sidewall construction for encouraging stability of clamp operation;

FIG. 5 is a top view of a clamp having a pair of clamp fingers with a portion of its housing cutaway to show the internal construction and arrangement of load transferring elements within the clamp housing and the cooperation of the elements with the clamp fingers; and

FIG. 6 is a top view of a clamp securely holding five workpieces.

Detailed Description of the Invention

FIGS. 1 & 2 illustrate a vise 40 having a clamp 42 with reciprocable pistons or fingers 44 that cooperate with a series of load transfer elements 46 in the clamp 42 constructed and arranged for securely holding one or more workpieces 48 during machining, even though one or more of the workpieces 48 may differ slightly in size from each other such that there are tolerance variations or differences between workpieces 48. By advantageously being able to securely hold workpieces 48 having tolerance variations between them, the vise 40 and clamp 42 of this invention are well adapted for use in precision machine tool applications that require each workpiece 48 to be securely held by the vise 40 while being accurately located relative to the vise 40 to ensure accurate location and precise placement of the machining operation, even though the workpiece 48 may be slightly out of tolerance before machining.

To ensure accurate location and precise placement of any machining operation

performed on a workpiece 48 while it is held by the vise 40, a locator or locator surface 50 of each workpiece 48 is securely held against a locator or locator surface 52 of the vise 40 when clamped in the vise 40.

For the purpose of describing location and movement of individual load transfer elements 46 of the clamp 42, each load transfer element 46 of a first row 200 of elements of the clamp 42 will be designated with a capital letter, such as "A, B, C, . . ." indicating its position from left to right within the clamp housing 78 and a subscript "1" for indicating it is in the first row 200. Each load transfer element 46 of a second row 202 of elements 46 will bear a similar designation with the exception that each element label will be designated with a subscript "2" for indicating it is in the second row 202. Likewise, for the purpose of indicating the location of a particular clamp finger 44, each clamp finger 44 will be similarly labeled and will be designated with a subscript "0" for indicating it is a clamp finger 44. The vise 40 has a base 54, a support 56, a slide assembly 58 carried by the base 54, a fixed jaw 60 at one end of the slide 58, a movable jaw 62 at the other end of the slide 58, and a vise screw 64 that extends through the support 56 into the movable jaw 62 of the vise 40. To enable the vise 40 to be used for precision machining applications, its base 54 can be accurately located relative to a machine tool (not shown) for accurately locating the vise 40 relative to a cutting, drilling, abrading, reaming, grinding, broaching, threading, counterboring, or chamfering tool or another tool of a machine tool, so that workpieces 48 held by the vise 40 will also be accurately located relative to the machine tool. The base 54 of the vise 40 has notches 55 for mounting the vise 40 relative to a machine tool (not shown), such as by mounting the vise 40 on a platform or in a fixture (not shown) of the tool. Preferably, the vise 40 has at least one locator for accurately locating the vise 40 relative to the machine tool. For example, the base 54 of the vise 40 can have a locator notch or channel that mates or engages with a complementary locator when the vise 40 is mounted for accurately locating the vise 40 relative to the tool. Other types of locators and locating devices can also be used for locating the vise 40

relative to a machine tool, another tool, another object, or another device (such as a measurement device, for example).

The slide assembly 58 is preferably accurately located relative to the base 54 of the vise 40 and can be immovably affixed to the base 54 of the vise 40. To help ensure accurate location of the fixed jaw 60 and its locator surface 52, the fixed jaw 60 is preferably accurately located on the slide assembly 58 by preferably being rigidly affixed to the slide assembly 58. The fixed jaw 60 shown in FIG. 1 is depicted as being rigidly affixed to the slide assembly 58 by a connector 66, that can be an elongate key 68, for example, which extends substantially from one side of the jaw 60 to the other side of the jaw 60 and is tightly received in complementary grooves in the slide 58 and jaw 60. Although one method and apparatus for accurately locating and affixing a rigid jaw 60 is depicted in FIG. 1 and described herein, another method and/or apparatus could be used to accurately locate and/or affix a jaw of the vise 40 to the slide assembly 58 or directly to the base of the vise 40.

The slide assembly 58 shown in FIG. 1 has a pair of guideways 70 for guiding the movable jaw 62 into engagement with a single workpiece or more than one workpiece that are to be held by the vise 40 while also enabling the jaw 62 to be retracted free of engagement when it is desired to release each workpiece after machining has been completed. The movable jaw 62 has a base plate 72 that preferably is movably carried by the guideways 70 of the slide assembly 58 for enabling the movable jaw 62 to be reciprocated along the slide 58.

To advance and retract the movable jaw 62, the vise screw 64 extends through a collar 74 and the support 56, and an end of the screw 64 is preferably operably connected to the movable jaw 62. At its other end, the screw 64 preferably has a head or another type of coupling 76 for attachment to a handle, for manual operation of the vise, or for connection to a drive, for more automated operation of the vise 40. In operation, rotation of the coupling 76 rotates the screw 64 and advances or retracts the movable jaw 62 and clamp 42 toward or away from the fixed jaw 60 depending upon the direction of screw rotation. If it is desired to use the vise 40 as a conventional

vise, the clamp 42 can be modified by attaching a clamp plate with fasteners to the front of the clamp 42.

Although the clamp 42 of this invention is shown in FIG. 1 in combination with the vise 40 of the aforementioned construction, it can be used with other types and configurations of vises. For example, a clamp 42 of this invention also can be used with a vise that has a different slide assembly, such as a slide assembly that uses one or more cylindrical rods to guide the movable jaw. Additionally, the clamp 42 of this invention can also be used with a vise that has a fixed jaw adjacent the support and a movable jaw disposed from the support. A clamp 42 of this invention preferably can also be adapted for use with the type of vise shown and disclosed in Chick, et al., U.S. Patent No. 4,529,183. Alternatively, the clamp 42 of this invention is also well suited for use with vises having a pair of movable, opposed jaws. As such, it is therefore intended that the clamp 42 of this invention can be used in vises and fixtures of many diverse types, configurations, and constructions for securely holding one or more workpieces.

The clamp 42 of this invention has a housing 78 for receiving load transfer elements 46 therein. As is shown more clearly in FIG. 2, the clamp housing 78 has a front wall 80, a rear wall 82, a pair of spaced apart sidewalls 84 & 86, a top 88, and a bottom 72. To retain the load transfer elements 46 within the housing 78, such as when the clamp 42 or vise 40 are being transported or during use, the bottom 72 (also depicted in FIG. 1 as the clamp base 72) of the housing 78 also functions as a cover 72 that can preferably be removably secured to the housing 78. Each clamp finger 44 is received through a bore 90 in the front wall 80 of the clamp housing 78. The load transfer elements 46 are received within the housing 78 and are located within the housmg 78 behind the clamp fingers 44.

The interior surfaces of the clamp walls 80, 82, 84, 86 & 88 preferably function to help limit or restrain movement of the load transfer elements 46 within the housing 78 by allowing sufficient movement of each element 46 to compensate for tolerance variations or to conform to an unevenly contoured workpiece while limiting load transfer element movement so as to encourage

and preferably maintain stability of the clamp 42 during its use and operation. Preferably, the interior surface of the clamp housing rear wall 82 is constructed and arranged to provide a guide surface for the load transfer elements 46 while also relatively rigidly supporting the load transfer elements 46 during clamping and transmitting clamping forces through the clamp housing 78 to the vise carrying the clamp 42.

Each clamp finger 44 has a load transfer element engaging surface 92 at one end and a workpiece engaging surface 94 at its other end. To minimize clamp finger friction and wear during operation of the clamp 42, each finger 44 preferably is received in a liner 96 that is, in turn, received in each bore 90 in the front wall 80 of the clamp housing 78.

To more securely retain a workpiece 48 during machining operations which tend to pull the workpiece 48 upwardly and/or out of the vise 40, such as while milling a workpiece, one or more of the clamp fingers 44 (or an extension 102) can have, carry, or support a workpiece engaging surface 94 that has a downwardly angled or canted face. With the canted face being angled, such as a 5° angle, a portion or component of the clamping force will preferably be directed downwardly against the workpiece 48 to prevent the workpiece 48 from being pulled out of the vise 40. When the clamp 42 is assembled, the opposite end of each finger 44 that is inside the clamp housing 78 preferably bears against a load transfer element 46. To urge each clamp finger 44 against a load transfer element 46, there preferably is a biasing element that is a spring 98 that is located between the interior surface of the clamp housing front wall 80 and the load transfer element engaging surface 92 of each finger 44. Preferably, each spring 98 is a coil spring telescopingly received over each finger 44 having one end of the spring 98 that bears against an outwardly extending flange 100 at the end of each finger 44 adjacent the load transfer element engaging surface 92 and the other end which bears against the interior surface of the housing front wall 80 to urge each finger 44 against a load transfer element 46.

Each clamp finger 44 can be of generally cylindrical construction having a generally circular cross section. Each clamp finger 44 can also be an

elongate clamp finger of square, generally rectangular, triangular, or another cross section. For example, each clamp finger 44 can be L-shaped and of generally square cross section with an outwardly extending, right-angled flange adjacent its load transfer element engaging surface 92 which also acts as a stop for limiting outward movement of the finger 44 to prevent its complete withdrawal from the clamp housing 78. A portion of such a flange can also function as a spring seat for the biasing spring 98.

Each clamp finger 44 is preferably constructed of a strong and resilient material capable of applying a force against a workpiece being clamped, preferably while not permanently deforming. Preferably, each clamp finger 44 is constructed of a metal such as a steel, a steel alloy, an aluminum, an aluminum alloy, titanium alloy, a tool steel such as a chrome vanadium steel alloy, or another type of suitable metal.

The clamp fingers 44 are preferably constructed of steel. If constructed of steel, at least the workpiece engaging surface 94 and load transfer element engaging surface 92 of each finger 44 is preferably hardened, such as by surface hardening, shot peening, cold working, heat treating, solution hardening, or another method of hardening. If desired, particularly for applications requiring a smaller maximum clamping force, each clamp finger 44 can be constructed of a composite material, a polymeric material, a nylon such as a glass filled nylon, a Kevlar, a urethane, an epoxy, a plastic, a rubber, wood, a ceramic material, a carbon fiber composite, or another suitable non- metal.

As is depicted in FIGS. 1 & 2, an extension 102 can be attached to each clamp finger 44 to vary and extend the useful length of each clamp finger 44 to enable the clamp 42 to hold securely a variety of workpieces of different shapes and configurations while also providing a sacrificial and wear resistant workpiece engaging surface 94. Although the clamp finger extensions 102 shown in FIG. 2 all have the same length, each clamp finger extension 102 can be of a different length for enabling a clamp 42 of this invention to be used to hold securely a single workpiece 48 that has an unevenly contoured clamping surface 49.

As is shown in FIG. 2, each extension 102 preferably has a bore or a hollow 104 (in phantom) of a cross section that is complementary with the cross section of a clamp finger 44 for enabling each extension 102 to fit over the end of a clamp finger 44. To secure each extension 102 to the finger 44 so that it does not move during clamping of a workpiece and while the workpiece is clamped, the top of each extension 102 has a threaded bore 106 in communication with the hollow 104 to receive a screw 108 that preferably is a set screw. To secure an extension 102 to a clamp finger 44, the set screw 108 is threaded into the bore 106 in the extension 102 until one end of the screw 108 firmly engages the clamp finger 44. To more securely attach the extension 102 to the finger 44, the end of each screw 108 can preferably be received in a groove in the clamp finger 44.

To prevent pivoting or other undesirable movement of each extension 102 during the clamping of a workpiece and while the workpiece is clamped, the extension 102 can be constructed with an outwardly extending flange 110 that can bear or ride against the top or bottom wall of the clamp housing 78. If desired, the flange 110 can be guided by a wall of the housing 78. If desired, a resilient damping pad 112 can be disposed between the flange 110 and the wall of the clamp housing 78 to minimize and preferably prevent vibration of a clamped workpiece during machining.

When a workpiece 48 to be clamped has an unevenly contoured surface, an extension 102 of an appropriate length to ensure engagement with the workpiece 48, is preferably selected and attached to the appropriate finger 44 such that it will bear against the clamping surface 49 when clamping is performed.

To ensure that extensions 102 can be used to hold a variety of workpieces each having an uneven clamping surface, preferably a "kit" that consists of a plurality of differently sized extensions 102 can be used by an operator of the machine tool to select extensions 102 of the appropriate length that match the contour of the clamping surface of a particular workpiece or a number of similar unevenly contoured workpieces that are to be machined. To select the appropriate length extensions 102 for a particular unevenly

contoured workpiece, the operator must measure or determine the distance from the end of each clamp finger 44 to a particular point on the clamping surface 49 of the workpiece.

For example, a "kit" of extensions can have sets of extensions, each set of which differ in length by 1/32 of an inch or in multiples of 1/32 of an inch, such as 1/32, 1/16, 3/32, etc., to enable an operator of a machine tool to select the appropriate extensions 102 from the "kit" to enable the clamp 42 to clamp workpieces of a wide variety of shapes and contours. Preferably, each set of extensions 102 can be constructed so that the difference in length, 1, of each set of extensions 102 is related to or proportional to the maximum amount of tolerance compensation, m, that the clamp 42 can provide. For example, if a clamp 42 has a maximum tolerance compensation capability, m, of seventy-five thousandths of an inch, the extension sets preferably can be constructed such that they increase in length, I, from other sets of extensions by increments of seventy-five thousandths of an inch. As such, for example, the extension sets can be constructed so that each set increases in increments of length, 1, of mil, m/3, m/4 or another divisor or formula related to the maximum tolerance compensating capability, m, of a clamp 42 of this invention when used with extensions 102. Referring additionally to FIGS. 3 & 4, the clamp housing 78 has a front wall 80, a rear wall 82, and a pair of spaced apart sidewalls 84 & 86 defining a housing cavity 87 for receiving the load transfer elements 46 inside the cavity 87. The bottom 72 of the housing 78 depicted in FIG. 2 has a removable cover 72 attached by four screws 114, such as cap screws, to the clamp housing 78. The distance between the interior surfaces of the top 88 and bottom 72 of the housing 78, defining the depth of the housing cavity 87, is greater than the height of a load transfer element 46. Preferably, the distance between the interior surfaces of the top 88 and bottom 72 of the housing 78 is only slightly greater than the height of the load transfer elements 46 within the cavity 87 for constraining the load transfer elements 46 during clamping of a workpiece and while the workpiece is clamped to help maintain stability of the load transfer elements 46.

If desired, the bottom 72 can have a downwardly extending bracket (not shown) with a bore that can be threaded to receive the vise screw 64 to enable the clamp 42 to be moved back and forth along the guideways 70 of the vise 40 during clamping and releasing of one or more workpieces. Alternatively, the clamp 42 may be carried by or received in a fixture (not shown) that is in operable communication with the vise screw 64 to enable the clamp 42 to be reciprocated toward and away from the fixed jaw 60 during vise operation. To prevent each load transfer element 46 inside the cavity 87 from being displaced between a pair of clamp fingers 44, the front wall 80 of the clamp housing 78 has an inwardly projecting dividing wall 116 between each pair clamp finger bores 90. Preferably, each divider 116 extends far enough inwardly into the housing cavity 87 to help maintain the location of each load transfer element 46, at least in the first row 200, relative to every other load transfer element 46 during clamp operation by preventing any load transfer element 46 adjacent a divider 116 from being displaced into any region adjacent the clamp housing front wall 80 between clamp fingers 44. Each inwardly projecting divider 116 can preferably be constructed with an angled face 118 that generally faces an adjacent load transfer element 46 for bearing against that adjacent load transfer element 46, should it become slightly displaced toward the divider 116 during clamp operation.

Referring to FIGS. 3-5, to guide a load transfer element 46 during clamping while helping to maintain the stability of load transfer elements 46 during clamping and while a workpiece is clamped, one and preferably both clamp housing sidewalls 84 & 86 have an interior load transfer element engaging surface 120 that extends inwardly into the housing cavity 87 and which is preferably in contact with a load transfer element 46 adjacent the clamp housing sidewall. Preferably, the load transfer element engaging surface 120 is an inwardly inclined surface 126, such as is depicted more clearly in FIGS. 3-5, but also can be an abutment or a projection that extends inwardly into the clamp housing cavity 87 for engaging an adjacent (outer) load transfer element 46 of the first row 200 (i.e. load transfer element A _j ) during clamping of a workpiece to help guide and restrain that load transfer element 46.

Although only one clamp housing sidewall 86 is depicted in FIG. 4, one sidewall 84 or 86, or both sidewalls 84 & 86 (FIG. 3), of this preferred clamp housing construction preferably can be constructed with (a) a first sidewall portion 122 that is generally parallel to an axis 124 of one of the clamp fingers 44 substantially parallel to the direction of motion that the clamp finger 44 follows during the clamping and releasing of a workpiece, and (b) a second sidewall portion 126 that is acutely inclined relative to the first sidewall portion 122 and clamp finger axis 124 for providing a guide surface 120 for engaging a load transfer element 46 (outer load transfer element A _t or E of the clamp shown in FIGS. 4 & 5) to help guide or restrain the movement of one or more of the load transfer elements 46 during clamping of a workpiece and while the workpiece is clamped.

Preferably, each load transfer element engaging surface 120 is capable of guiding the movement of an adjacent load transfer element 46 during clamping while also supporting and restraining one or more of the load transfer elements 46 during and after a workpiece has been clamped to help maintain stability of preferably all of the load transfer elements 46. Preferably, the inwardly inclined guide surface 120 helps maintain stability of the clamp assembly 42 by preventing the load transfer elements 46 adjacent each outer clamp finger 44 from moving too far outwardly towards the clamp housing sidewall 84 and/or 86, binding or locking, and becoming immovable, thereby locking an exterior clamp finger 44 in place and preventing it from being able to adequately move in a manner necessary for it to enable the clamp fingers 44 to adjust to tolerance differences between workpieces being clamped. The inclined sidewall portion 120 also preferably helps maintain stability of the load transfer elements 46 by constraining outward movement of both the outer element 46 (element A^ in the row of elements immediately behind the clamp fingers 44 (first element row 200) and the outer element 46 (A ₂ ) in the row of elements that bear against the rear wall 82 of the clamp housing 78 (second element row 202). Although the second sidewall portion 126 can have a stepped transition 128 with the rear wall 82, it can also be

constructed having a smooth transition portion 130 (in phantom) with the rear wall 82.

The second sidewall portion 126 preferably forms an acute included angle, ct, with the first sidewall portion 122 for guiding an outer load transfer element 46 while helping to maintain stability of the rest of the load transfer elements 46. Preferably, the second sidewall portion 126 can be constructed and arranged to be angled relative to the clamp finger axis 124 at an angle of at least about 5°. If desired, the second sidewall portion 126 can be angled relative to the clamp finger axis 124 at an angle falling within the range of between about 20° and 60°. Since the first sidewall portion 122 preferably is also parallel with axis 124, the second sidewall portion 126 forms an acute included angle, α, with the first sidewall portion 122 such that α can fall within the range between about 20° and 60°. Preferably, the second sidewall portion 126 of this clamp construction can be constructed and arranged so it forms an acute included angle, α, with the first sidewall portion 122 that can be between about 30° and 40°, and, for example, α can preferably be between about 33° to about 36° for the clamp construction shown in FIGS. 4 & 5.

Some routine testing and experimentation may be done to determine an optimal guide sidewall angle, α, for a given clamp construction. For example, routine testing and experimentation may be done to determine an optimal guide sidewall angle, , for load transfer elements 46 of different shapes, sizes, and configurations, as well as for clamps of this invention having a varying number of clamp fingers 44 and different distances between fingers 44. Additionally, α may be dependent upon clamping forces or other clamp design criteria and may, therefore, vary from clamp construction to clamp construction.

The clamp housing 78 can be constructed having a sidewall without an inwardly inclined portion in contact with a load transfer element 46. If desired, a clamp housing 78 of this construction can be made with an inclined sidewall portion 132 that is not in contact with a load transfer element 46. Alternatively, for example, the clamp housing 78 can also be constructed

with sidewalls that are not inwardly inclined whatsoever, thereby lacking any inclined sidewall portion in contact with a load transfer element 46.

The clamp housing 78 is preferably constructed of a strong and resilient material such as steel, aluminum, an aluminum alloy, titanium, a titanium alloy, magnesium, a magnesium alloy, or another suitable metal or metal alloy. Preferably, the housing 78 is constructed of steel, such as a high strength low alloy steel or another suitable type of steel. Alternatively, for some clamp applications, the clamp housing 78 can be constructed of a composite material, such as a reinforced carbon or glass fiber composite, a nylon, an aramid or aramid fibrous composite, a suitable plastic or polymeric material, a urethane, a type of plastic, or another type of suitable synthetic material. If constructed of a metal, the housing 78 can preferably be cast and thereafter machined. If constructed of steel or another metal, interior surfaces of the housing 78 that come into contact with load transfer elements 46 are also preferably hardened. To minimize wear and facilitate smooth movement of load transfer elements 46 within the housing cavity 87, the interior surfaces of one, several, or all of the walls of the housing 78 can be lubricated or impregnated with a petroleum lubricant, molybedenum, TEFLON or a coating or layer of friction reducing material. As is shown in FIG. 1, there are at least three and, where a clamp 42 of this invention has more than two clamp fingers 44, a plurality of load transfer elements 46 received inside the clamp housing cavity 87. The load transfer elements 46 are constructed and arranged within the housing cavity 87 to receive the force from each clamp finger 44 that a finger 44 receives during the clamping of one or more workpieces while allowing each element 46 to move as is needed within the cavity during clamping to compensate for tolerance variations between workpieces or to conform to the contour of a single workpiece. When clamping is completed, the load transfer elements 46 are in engagement with each other and preferably cannot move any further for transmitting clamping force from the workpiece through the clamp housing 78 to the jaw 62 carrying the clamp 42, and to the vise 40.

Each load transfer element 46 preferably has a circular cross section along at least one direction of the element 46. Preferably, each load transfer element 46 is constructed of a durable and strong material that is preferably also wear resistant, such as preferably a steel, aluminum, an aluminum alloy, titanium, a titanium alloy, magnesium, a magnesium alloy, a tool steel, a high strength low alloy steel, or another suitable metal or metal alloy. For other applications not requiring the strength of a metal, each element can be constructed of plastic, rubber, or a composite, such as a thermoplastic, a thermoset plastic, a nylon, an epoxy, a urethane, an aramid, a glass filled nylon, a carbon fiber composite or another suitable non-metallic material. If constructed of steel or another metal, the outer surface of each element 46 is preferably hardened or is constructed of a material having good toughness. For example, a suitable load transfer element 46 can be a steel drill bushing having a hardness of sixty-two R _c along its exterior surface. Since each load transfer element 46 is in contact with at least one other element 46 during use and operation of the clamp 42 and relative movement between elements 46 can occur during clamping, each load transfer element 46 can be lubricated or impregnated with a lubricant, such as a petroleum lubricant, graphite, molybdenum, teflon, or another lubricant for minimizing friction. If desired, the load transfer element 46 can be a circular disk having a truncated generally cylindrical construction and a generally circular cross section. The element 46 has a top wall, a bottom wall, and an endless sidewall that is generally perpendicular to either the top wall 142 or the bottom wall 144 for forming a contact line 150 (FIG. 5) with another element 46 when it bears against the element 46 during clamping thereby maximizing the surface area of contact between adjacent load transfer elements 46 which maximizes the amount of clamping force that can be applied against a workpiece being clamped.

When received in the cavity 87 of a clamp housing 78, the bottom 144 of each load transfer element 46 bears against the interior surface of the bottom wall 72 of the housing 78 such that each element 46a can move or slide along the bottom 72 of the housing 78. Therefore, during clamping, the

elements 46 are capable of moving or sliding within the housing 78 relative to each other as is necessary until they achieve a condition of equilibrium within the housing 78 such that when the workpieces are clamped, the elements 46 cannot further move. In an alternative load transer element embodiment, the load transfer element 46 can have an opening if it is not necessary to have a load transfer element of completely solid construction. An example of a suitable load transfer element 46 having a hollow or bore therethrough is a washer, a roller bearing, or a drill bushing of generally cylindrical construction. The load transfer element 46 can also be a round ball of spherical construction and which has a generally circular cross section. An example of a suitable load transfer element 46 of this construction is a ball bearing. When received in the clamp housing cavity 87, each ball bearing element 46 forms a contact point with the clamp housing bottom and each adjacent ball bearing element 46 thereby minimizing friction between contacting surfaces.

The load transfer element 46 can also be a puck 154 having a round ball received in a disc-shaped washer. When received in the clamp housing cavity 87, the ball preferably makes point contact with the clamp housing bottom 72 while the washer makes line contact with another load transfer element 46 when it contacts an adjacent element 46.

The load transfer element 46 can also be generally disc-shaped having a generally spherical sidewall that is truncated on its top and bottom to form a flat top wall and a flat bottom wall. When received in the clamp housing cavity 87, the load transfer element 46 preferably makes point contact with another similarly shaped load transfer element 46 when it contacts an adjacent element 46.

The load transfer elements can be interlocked with each other to provide enhanced stability during the clamping of a workpiece and while the workpiece is clamped. One of the load transfer elements 46 can have a concave sidewall, an interlock ridge along its top, and an interlock ridge along its bottom. The other of the interlocking elements 46 has a convex sidewall that is preferably complementary with the concave sidewall of an interlocking

element 46 so that the two interlocking elements fit together, at least somewhat loosely.

If interlocking pairs of load transfer elements are used, the load transfer element engaging surface 92 of each clamp finger 44 can be of a configuration that is preferably complementary to the sidewall shape of the load transfer element it contacts during use and operation of the clamp 42. The load transfer element engaging surface 92 of each clamp finger 44 preferably can have a convex surface for engaging with the concave sidewall of an adjacent interlocking load transfer element 46 to interlock with that element 46 while allowing some relative movement therebetween.

Additionally, the rear wall 82 and sidewalls 84 & 86 of the clamp housing 78 can be constructed with an interior load transfer element engaging surface that is complementary in shape with an adjacent interlocking load transfer element sidewall to further enhance the interlocking and stability of the entire assembly of load transfer elements. Adjacent interlocking elements preferably interlock with each other to increase the stability of the entire assembly during use and operation while allowing each pair of contacting interlocking elements 46 & 46 to move relative to each other to compensate for contour variations or tolerance differences between workpieces. Preferably, stability of the assembly is increased by preventing any interlocking load transfer elements 46 from deviating from the plane they are in and/or becoming completely disengaged from each other during clamping of a workpiece and while the workpiece is clamped.

Referring to FIG. 5, the clamp 42 has a pair of spaced apart clamp fingers 44 carried by the clamp housing 78 with a load transfer element 46 behind each finger 44 forming a first row 200 of load transfer elements and a single load transfer element 46 behind the first row of elements 200 forming a second row 202 of load transfer elements. Although a clamp 42 of this invention can be constructed such that each element 46 in both rows 200 & 202 are of substantially the same size, the load transfer elements 46 of the first row 200 can be larger or smaller in diameter than the load transfer elements 46 of the second row 202.

The clamp 42 has a load transfer element 46 in the first row 200 directly behind each clamp finger 44. Preferably, there is one less load transfer element 46 in the second row 202 than the number of load transfer elements 46 in the first row 200. For the clamp construction 42 shown in FIG. 5, the clamp 42 has the same number of load transfer elements 46 in the first row 200 as the number of clamp fingers 44. In the second row 202, there is one less load transfer element 46 than the number of clamp fingers 44. Also, there is one less element 46 in the second row 202 as the number of elements 46 in the first row 200. Therefore, there are two elements 46 in the first row 200 and only a single element 46 in the second row 202 because the clamp 42 depicted in FIG. 5 has only two clamp fingers 44.

Each element 46 in the first row 200 is positioned behind a clamp finger 44 and is preferably positioned directly behind a clamp finger 44 such that a central longitudinal axis 204 of the clamp finger 44 passes through at least a portion of that element 46 that is behind the finger 44. The clamp 42 shown in FIG. 5 has the central longitudinal axis 204 of each clamp finger 44 passing through a center point 206 of its immediately element 46 in the first row 200. Although this generally can be true when each workpiece 48 has exactly the same length from the clamp finger workpiece engaging surface 94 to the fixed jaw 60 of the vise 40 as every other workpiece 48 simultaneously being clamped, the center 206 of an element 46 in the first row 200 may shift away from the axis 204 of its adjacent clamp finger 44 when clamping a pair of workpieces of different lengths and having a tolerance difference between them.

As is also shown in FIG. 5, there preferably is a load transfer element 46 in the second row 202 that has a center point 208 between each pair of adjacent clamp fingers 44 and which engages the load transfer elements 46 in the first row 200 that are in contact with the pair of clamp fingers 44. The center point 208 lies preferably between the central axis 204 of both clamp fingers 44. When a workpiece clamped by one of the clamp fingers 44 is longer than a workpiece clamped by the other of the fingers 44, the load

transfer elements will cooperate with each other within the clamp housing 78 such that the center point 208 of the load transfer element 46 of the second row 202 will shift toward the central axis 204 of the clamp finger 44 that is engaging the shortest workpiece. The center point 208 of the load transfer element 46 of the second row

202 preferably forms a triangle 210 with the center points 206 of the load transfer elements 46 of the first row 200 that are in contact with that load transfer element 46 of the second row 202. Preferably, the contact point 212 of the load transfer element 46 of the second row 202 with each of the load transfer elements 46 of the first row 200 and the contact point 214 of each load transfer element 46 of the first row 200 with its clamp finger 44 define a four sided polygon 216.

The legs of the triangle 210 that extend from the center point 208 of the load transfer element 46 of the second row 202 to the center point 206 of each of the load transfer elements 46 of the first row 200 define an acute angle, β, that preferably can be at least 45°, depending upon the size of the load transfer elements 46, the spacing between clamp fingers 44, as well as the amount of the tolerance difference between multiple workpieces being simultaneously clamped. With the clamp 42 securely holding two workpieces of exactly the same size and having no tolerance differences between them, β is preferably between about 60° and about 70° and can vary during clamp operation.

Angle, β, will vary depending upon the amount of the tolerance difference between workpieces clamped as well as the spacing between clamp fingers. Additionally, β can vary also vary if the size of the load transfer elements 46 of the first row 200 differs from the size of the load transfer elements 46 of the second row 202.

During clamping, each element 46 in the first row 200 that is behind a clamp finger 44 that is in contact with a workpiece 48 preferably can move in any direction as is needed, as is indicated by an unidirectional directional arrow indicator on load transfer element 46 at position A _t shown in FIG. 3. Each element 46 in the second row 202 preferably can only move side to side

as is indicated by a lateral directional arrow indicator on load transfer element 46 at position c ₂ .

For elements 46 in the first row 200 that are behind a clamp finger 44 that is restrained, those elements 46 can move only laterally across the load transfer element engaging surface 92 of each restrained finger 44. For elements 46 in the first row 200 that are not behind any clamp finger 44, the elements 46 can only move laterally substantially in the direction indicated by the lateral position indicator.

It is noted that an element 46 in the first row 200 of a clamp 42 that can theoretically move in any direction may be limited in its direction of actual movement by one or more factors, such as for example, a sidewall of the clamp housing 78, the magnitude or direction of applied clamping force, or the size, workpiece contour, or the tolerance differences between more than one simultaneously clamped workpiece. Other factors may also influence or limit first row element movement.

Although the clamps 42 shown in FIGS. 1-4 differ from the clamp shown in FIG. 5 in that they have more than two clamp fingers 44, they preferably are also constructed in a manner very similar to and preferably virtually identical to the clamp of FIG. 5, having the same number of elements 46 in the first row 200 as the number of clamp fingers 44 and one less element 46 in the second row 202 as the number of clamp fingers 44. These clamps 42 also have one less element 46 in the second row 202 as the number of elements 46 in the first row 200.

FIG. 3 illustrates a clamp 42 of this invention having more than two clamp fingers 44 clamping more than one workpiece at the same time. The clamp 42 has five clamp fingers 44 for clamping as many as five workpieces or for applying force along five contact points to hold a single workpiece that can have a contoured clamping surface.

In the first row 200, the clamp 42 has as many load transfer elements 46 as there are clamp fingers 44 with each load transfer element 46 in the first row 200 in contact with a clamp finger 44 when that clamp finger 44 is holding a workpiece. Preferably, each load transfer element 46 of the first row 200 is

behind an adjacent clamp finger 44. Preferably, a central axis 204 of each clamp finger 44 cuts across at least a portion of an adjacent load transfer element 46.

When several workpieces of the same length are clamped at the same time, such as is depicted in FIG. 3, load transfer elements 46 of the first row 200 in contact with the clamp fingers 44 that lie inside the outer clamp fingers 44 also contact at least two other load transfer elements 46 of the second row 202. The load transfer elements 46 of the first row 200 that are in contact with the outside clamp fingers 44 contact at least one element 46 of the second row 202.

In the second row 202, the clamp 42 has one less load transfer element 46 than there are clamp fingers 44. While one or more workpieces are clamped, each element 46 of the second row 202 is preferably in contact with one other element 46. While clamped, each element 46 of the second row 202 is preferably in contact with an element 46 of the first row 200.

Although the clamp 42 shown in FIG. 3 has five clamp fingers 44, the clamp 42 can be constructed with a lesser or greater number of clamp fingers 44. For example, a clamp 42 of this invention can be constructed with three, four, seven, eight, nine, ten, fifteen, twenty, or even more clamp fingers 44, if desired. As such, if a clamp 42 is constructed with ten clamp fingers 44, it preferably has ten load transfer elements 46 in its first row 200, and nine load transfer elements 46 in its second row 202. For example, if a clamp 42 is constructed with fifteen clamp fingers 44, it preferably has fifteen elements 46 in its first row 200, and fourteen elements 46 in its second row 202. As such, a clamp 42 of the preferred embodiment shown in FIGS. 4-6, preferably has as many load transfer elements 46 in the first row 200 as there are clamp fingers 44. Additionally, a clamp 42 of this preferred embodiment preferably has one less load transfer element 46 than the number of clamp fingers 44 of the clamp 42. Therefore, as is depicted in FIG. 3, there are five clamp fingers 44, five load transfer elements 46 in the first row 200, and four load transfer elements 46 in the second row 202.

The triangle relationship 210 and polygon relationship 216 of the load transfer elements 46 and contact points for the clamp with the single pair of clamp fingers 44 shown in FIG. 5 preferably also holds true for the load transfer elements 46 cooperating with each pair of fingers 44 for clamps having more than two clamp fingers 44, as is depicted by the representative clamp 42 shown in FIG. 3. As such, a clamp 42 of this preferred embodiment has a contact point 214 between each clamp finger 44 and a load transfer element 46 of the first row 200, and a contact point 212 between each load transfer element 46 of the first row 200 and an adjacent load transfer element 46 of the second row 202 with the contact points 212 & 214 between the clamp fingers 44 and load transfer elements 46 being constructed and arranged such that the contact points 214 between clamp fingers 44 and adjacent load transfer elements 46 of the first row 200 and contact points 212 of adjacent load transfer elements 46 of the first row 200 and the common load transfer element 46 of the second row 202 form a four sided polygon 216.

As is depicted in FIG. 3, for each pair of clamp fingers 44, the legs of the triangle 210 that extend from the center point 208 of the load transfer element 46 of the second row 202 to the center point 206 of each of the load transfer elements 46 of the first row 200 define an acute angle, β, that preferably can be at least about 35°, depending upon the size of the load transfer elements 46, the spacing between clamp fingers 44, the amount of the tolerance difference between workpieces being clamped, and perhaps other factors, as well. With the clamp 42 securely holding five workpieces of exactly the same size and having no tolerance differences between them, β is between about 60° and about 70° and is about equal for each pair of clamp fingers 44. Of course, angle, β, can vary from that discussed above depending upon a number of factors. For example, the amount of the tolerance difference between workpieces clamped as well as the spacing between clamp fingers 44 may also cause β to vary, β will also vary if the size of the load transfer elements 46 of the first row 200 differs from the size of the load transfer elements 46 of the second row 202.

Another triangle relationship 211 can be defined for the load transfer elements 46 in contact with each clamp finger 44 and which lie inside of the outer clamp fingers 44. For each interior clamp finger 44, such as for fingers 44 located at positions B ₀ , C ₀ , & D ₀ of the clamp shown in FIG. 3, a triangle 211 can be formed between the center point 206 of the load transfer element 46 in the first row 200 contacting the interior finger 44 and the center points 208 of the two load transfer elements 46 of the second row 202 contacting that first row element, with a preferably acute angle, ε, being formed by two legs of the triangle 211. As an interior clamp finger 44 (B ₀ , C ₀ & D ₀ ) adjacent the triangles 210

& 211 is displaced into the clamp housing 78 and is displaced inwardly relative to the other of the clamp fingers, β for that clamp finger preferably increases, at least slightly. When the clamp 42 reaches equilibrium upon clamping, such as the equilibrium shown in FIG. 3, with all of the fingers 44 of the clamp 42 securely holding workpieces of the same size, having no tolerance differences between them, and all of the load transfer elements 46 within the clamp housing being of the same size, ε and β are preferably substantially about equal or within a few degrees of each other. Preferably, ε of any triangle 211 of a clamp 42 does not reach 180° during operation of a clamp of this construction to maintain stability of the clamp 42. Preferably, ε of any triangle 211 of a clamp 42 of this preferred construction does not substantially exceed 120° during normal clamp operation.

A pair of clamps 42 can be carried by a vise for holding round workpieces between the clamps 42, while accurately locating each round workpiece about a locator point, that preferably can be common to all of the workpieces (such as the center), for enabling a machining operation to be accurately located on each workpiece.

A clamp 42 can be constructed having an adjacent pair of clamp fingers 44 spaced apart by a distance, M, that is greater than a nominal distance, M,, between other clamp fingers 44. The distance M is preferably greater than the diameter of a single load transfer element 46 while still providing tolerance compensating and uneven contour conforming capabilities to each clamp.

In use, as is depicted in FIG. 3, a clamp 42 of this invention can be used to simultaneously clamp several workpieces having slightly different lengths while compensating for tolerance differences between the workpieces. A clamp 42 of this invention can also be used to clamp a single workpiece 48 having a contoured clamping surface. Additionally, a clamp 42 of this invention can be used to clamp a single contoured workpiece that has a portion or all of its contoured clamping surface out of tolerance.

In operation, the clamp 42 shown in FIG. 1 is depicted clamping a pair of workpieces 48 against a locator surface 52 of the fixed jaw 60 of the vise 40. As clamp fingers 44 are brought to bear against each workpiece 48, each workpiece 48 is urged against the locator surface 52 of the vise 40 thereby accurately locating each workpiece 48 relative to the vise 40, as well as, preferably a machine tool or another device that is to perform an operation on the workpieces 48. During clamping, as the clamp fingers 44 are brought to bear against the workpieces 48, clamping force is transmitted from the clamp fingers 44 to the load transfer elements 46 within the clamp housing 78. Since the housing cavity 87 is larger than the load transfer elements 46 within the cavity 87, as clamping pressure continues to be applied by an operator of the vise 40, at least some of the load transfer elements 46 move relative to each other as clamp fingers 44 in contact with a workpiece 48 are displaced inwardly into the housing cavity 87. As the clamp fingers 44 that are in contact with a workpiece 48 are displaced into the housing 78, the clamp fingers 44 not engaging a workpiece 48 can be displaced slightly outwardly from the clamp housing 78 as a result of cooperation between load transfer elements 46 within the housing 78 with the clamp fingers 44.

In this manner, a clamp 42 of this construction having five clamp fingers 44 can be used to clamp a single workpiece with all of its fingers, a single workpiece 48 with one of its fingers, a pair of workpieces 48 with two of its fingers 44, three workpieces with three of its fingers 44, four workpieces 48 with four of its fingers 44. and a workpiece securely held by each finger 44, as is shown in FIG. 3.

As is depicted in FIG. 5, for the case of the clamp 42 having two clamp fingers 44, the clamp 42 is shown clamping a pair of workpieces 48. Both of the workpieces have about the same length from the end of each clamp finger, Ao & B ₀ , to the locator surface 50 of the fixed jaw 60. During clamping, both clamp fingers, AQ & B ₀ , are displaced into the clamp housing 78 substantially about the same amount because the workpieces 48 are substantially the length.

Should the workpiece 48 in contact with clamp finger be even slightly longer than the workpiece 48 in contact with clamp finger B ₀ , indicating a tolerance difference between the workpieces, the finger A _Q in contact with the longest workpiece 48 will be displaced further into the housing than the other finger B ₀ and load transfer element A ₂ will be displaced such that its center 208 will move toward the axis 204 of the finger B ₀ bearing against the shortest workpiece 48. Of course, the direction of movement of element A ₂ relative to elements A _j & B _j will be reversed if the workpiece in contact with finger B ₀ is longer than the workpiece in contact with finger AQ. When clamped, any tolerance difference between workpieces will preferably increase, at least slightly, the angle, β, between load transfer elements A A ₂ & B^ To maintain stability of the clamp 42, the clamp housing 78 and load transfer elements 46 are constructed and arranged such that at no time does the center point 208 of element A ₂ become aligned with the center point 206 of either element A _t or element B, in a direction parallel to a central axis 204 of any clamp finger 44 of the clamp 42.

As is shown in more detail in FIG. 6, for the case of the clamp 42 having more than two fingers 44 and holding securely two workpieces 48, the positions of each load transfer element 46 relative to each other load transfer element 46 are shown. As the two clamp fingers B ₀ & D ₀ are brought to bear against a workpiece 48, they are displaced inwardly into the clamp housing 78 causing load transfer elements 46 to shift around within the housing 78.

As each finger, B ₀ & D ₀ , is displaced, it displaces load transfer elements 46 in the first row 200 and load transfer elements 46 in the second row 202. Each load transfer element, B _! & D _v of the first row 200 in contact with clamp fingers, B ₀ & D ₀ , moves relative to its adjacent clamp finger at least

slightly outwardly toward a sidewall 84 or 86 of the housing 78. As they move, the center point 206 of each adjacent load transfer element, B _] & D _1; moves outwardly of the central longitudinal axis 204 of the finger, B ₀ & D ₀ , and the angle, e _l &ε ₃ , between center points 208 of adjacent pairs of contacting load transfer elements, A ₂ & B ₂ , and, C ₂ & D ₂ , the center point 206 of load transfer elements, B, & D„ increases.

As fingers, B ₀ & D ₀ , are urged inwardly into the clamp housing 78, each contacting load transfer element, B, & D„ is urged toward the rear wall of the housing, spreading apart, respectively, load transfer elements, A ₂ & B ₂ , and, C ₂ & D ₂ , causing εi &ε ₃ , to increase. As the elements, A ₂ & B ₂ , and, C ₂ & D ₂ , are spread apart from each other, elements, B ₂ & C ₂ , are urged toward each other, decreasing ε ₂ and causing ε ₂ to be less than ε, &ε ₃ . As the load transfer elements 46 cooperate with each other, they reach a point where no further movement is possible, thereby causing the clamping force to each workpiece 48 being held by the fingers, B ₀ & D ₀ , to increase. When clamping is completed, the clamping force is substantially equally distributed between workpieces 48 as a result of the relatively symmetric arrangement of the load transfer elements 46 within the clamp housing 78.

For a single clamp finger C ₀ clamping a single workpiece 48, the finger C ₀ is urged inwardly into the clamp housing 78 displacing load transfer element C, toward the rear wall 82 and separating slightly elements, B ₂ & C ₂ , and increasing angle ε ₂ . When the single workpiece 48 is completely clamped, ε ₂ preferably is greater than both ε _t &ε ₃ and the center point 206 of elements, Bi & D lie outside of the axis 204 of the clamp finger, B ₀ & D ₀ , in contact with the element.

For a clamp 42 holding three workpieces 48, the fingers A _Q , C ₀ & E ₀ are urged further into the clamp housing 78, displacing elements, A,, C _t & E _v toward the rear wall 82 of the housing 78. As elements, A _v & E„ are displaced, elements A ₂ & B ₂ and C ₂ & D ₂ are urged toward each other and elements B ₂ & C ₂ are urged away from each other, decreasing £χ &ε ₃ while increasing ε ₂ .

When less than the full number of fingers 44 of a clamp 42 engage a workpiece 48 or clamping surface of a workpiece 48, the dividers 116 of the clamp housing 78 preferably can be constructed and arranged so that outward displacement of each clamp finger, B ₀ & D ₀ , not engaging a workpiece is limited by its immediately adjacent load transfer element B _! & D ₂ bearing against one or more adjacent dividers 116 thereby stopping its movement toward the adjacent clamp finger. If desired, the length of each divider 116 or distance between adjacent dividers 116 can be selected so as to suitably limit the forward travel of an adjacent load transfer element 46. Advantageously, as a result of limiting forward displacement of a load transfer element 46 bearing against an unrestrained clamp finger 44, the stability of the entire assembly of load transfer elements is increased and preferably maintained under all clamp conditions.

To further enhance stability of the clamp 42, each finger 44 not in contact with a workpiece can be restrained or locked in place for limiting or preventing excessive clamp finger movement in an outward direction relative to the clamp housing 78.

For a clamp 42 holding four workpieces 48, fingers A„, B ₀ , D ₀ & E ₀ are urged into the housing relative to finger C ₀ , thereby urging elements B ₂ & C ₂ toward each other and causing ε ₂ to be less than ε _t &ε ₃ . When clamped, elements B, & D move relative to their immediately adjacent clamp fingers B ₀ & D ₀ such that their center points 206 lie interiorly of the central axis 204 of the fingers B ₀ & D ₀ in contact with those elements B, & D _t .

For a clamp 42 holding five workpieces 48 which all have substantially the same length, L, all of the load transfer elements 46 cooperate with each other to securely hold the workpieces 48 against the locator surface 52 of the fixed jaw 60. When clamped, ε,, ε ₂ and ε ₃ are substantially equal.

Example FIG. 6 illustrates a clamp housing 78 having a length from sidewall 84 to sidewall 86 of about 5 inches and a depth from front wall 80 to rear wall 82 of about 4 inches with each sidewall 84 & 86 having a thickness of about 0.449

at its thinnest point. The front wall 80 has a thickness of about 0.75 inches and the rear wall 82 has a thickness of about 1.5 inches, although a thinner rear wall could be used. Each bore 90 (FIG. 2) for receiving a clamp finger 44 has a diameter of between about 0.376 and 0.377 inches. Each load transfer element 46 has a diameter of about 0.75 inches and a thickness of between about 0.456 and 0.458 inches with the interior surfaces of the top and bottom of the clamp housing 78 being spaced apart sufficiently to accommodate all of the elements 46 while allowing them to freely move within the housing cavity 87. To guide the outer load transfer elements A, & E, of the first row 200 and promote stability of the clamp 42, each sidewall 84 & 86 has an inwardly inclined guide wall 120 that has an inclined portion 126 that is inclined at an angle, α, of between about 31° and about 35° and preferably is between about 33° and 34°. Preferably, this inwardly extending portion 120 of each sidewall 84 & 86 also helps to maintain clamp stability by restraining outward movement of each outer load transfer element A ₂ & D ₂ of the second row 202 of elements 46. Alternatively, a small block of generally rectangular cross section (not shown) having a length of about 0.5 inches, a width of about 0.375 inches and a depth of about 0.375 inches could be substituted for the inclined wall portion 120 to encourage stability of the clamp 42.

The clamp 42 is shown in FIG. 6 clamping five workpieces having tolerance differences between them. Workpieces 48 have a length, L, that is about 1 inch and workpieces 48a have a length, L', of about 0.969 inches amounting to a tolerance difference, t, of about 0.031 inches. During clamping, fingers B ₀ & D ₀ are urged slightly further inwardly into the clamp housing than fingers A _Q , C ₀ & E ₀ , thereby urging elements B ₂ & C ₂ toward each other and causing elements A _x & E, to move relative to fingers Ag & E ₀ such that the center point 206 of those elements A _x & E _x lie slightly outside the central longitudinal axis 204 of the fingers A _Q & E ₀ they are contacting. Preferably, the center point 206 of elements A _t & E _j lie about 0.007 inches outside of axis 204 when the workpieces 48 & 48a are clamped.

When the workpieces are clamped. ε ₂ is less than ε _t &ε, as a result of elements B ₂ & C ₂ being urged toward each other. When clamped, β _! &β ₄ are approximately between about 68° and 69° and are preferably about 68.62°. When clamped, β ₂ &β ₃ are between about 67° to about 68° and are preferably about 67.98°. Preferably, a clamp 42 of this construction can compensate for tolerance differences (such as differences in workpiece length) between workpieces simultaneously clamped of at least as much as fifty thousandths of an inch.