Abstract:
A gripper assembly is provided having an actuator, at least one jaw member and a cam pin. The jaw member includes a cam slot that is a space formed by opposed cam walls located in the jaw arm. The cam walls form a locking portion and a pivoting portion, wherein the distance between the cam walls of the locking portion is substantially equal to the distance between the cam walls of the pivoting portion.

Description:
RELATED APPLICATION 
   The present application is a Continuation of U.S. patent application, Ser. No. 09/714,354, filed on Nov. 16, 2000 now U.S. Pat. No. 6,588,816, entitled Modular Stamped Parts Transfer Gripper, which is a Continuation-in-Part of U.S. patent application, Ser. No. 09/483,794, filed Jan. 14, 2000, entitled Modular Stamped Parts Transfer Gripper, (now U.S. Pat. No. 6,227,586, issued on May 8, 2001), which is a Continuation of U.S. patent application Ser. No. 08/981,863, filed on Aug. 4, 1998, entitled Modular Stamped Parts Transfer Gripper (now U.S. Pat. No. 6,048,013, issued on Apr. 11, 2000), which is related to and claims priority to PCT Application No. US97/17795 (WO98/15392), filed on Oct. 3, 1997, which is related to and claims priority to U.S. Provisional Patent Application, Ser. No. 60/039,088, filed Mar. 14, 1997, entitled Modular Stamped Parts Transfer Gripper, and to U.S. Provisional Patent Application Ser. No. 60/027,668 filed Oct. 7, 1996, entitled Stamped Parts Transfer Gripper. To the extent not included below, the subject matter disclosed in those applications is hereby expressly incorporated into the present application. 

   TECHNICAL FIELD 
   The present invention relates to fluid pressure actuated grippers of the type employed in automated workpiece handling devices which clampingly grip and transfer a workpiece from one station to another. More particularly, the present invention relates to fluid pressure actuated grippers which can be locked in either or both of their closed or open positions and which are assembled from a plurality of modular or interchangeable components. 
   BACKGROUND AND SUMMARY 
   Fluid pressure actuated grippers are widely employed and typically take the form of a pneumatic or hydraulic differential motor whose cylinder is fixedly mounted to a transfer device. At the forward or rod end of the cylinder housing, a gripper jaw mounting structure is fixedly mounted on the cylinder to pivotally support a pair of opposed gripper jaws which are coupled to the piston rod of the motor by a linkage so arranged that, upon movement of the piston in one direction, the jaws are pivoted to an open position, and, upon movement of the piston in the opposite direction, the jaws are driven to a closed workpiece gripping position. 
   In typical operation, the gripper jaws will be closed upon a workpiece near the edge of the workpiece, and the gripper will be advanced to position the gripped workpiece in operative relationship with a work station. The gripper will then be opened to release the workpiece, and the transfer device will retract the gripper from the work station while the work operation is performed. At the conclusion of the work operation, the gripper will then advance back into the work station and the jaws will again close upon the workpiece and carry it away from the work station. Opening and closing the gripper jaws, thus, takes place when the gripper is in its closest proximity to tooling at the work station. 
   There are basically two types of linkage arrangements used in fluid pressure actuated grippers to connect the gripper jaws to the piston rods and effect movement of the gripper jaws. These are pivotable link arrangements and pivotal cam arrangements. An example of a pivotal link arrangement can be found in U.S. Pat. No. 5,152,568 to Blatt which discloses pivotal links  36  and  40  that cooperate with gripper jaws  12 A and  12 B, as shown in  FIG. 3 . 
   U.S. Pat. No. 4,518,187 to Blatt, et al. discloses a pivotal cam arrangement in which jaw plates  45  and  47  are pivoted by the cooperation of cam slots  61  provided in the jaw plates and a pivot pin  37  (and rollers  39 ) attached to the piston rod. 
   In a typical production line, there are numerous work stations with one or more fluid pressure actuated gripper devices positioned between adjacent work stations. During operation, all of the gripper devices are synchronized so that they simultaneously remove a workpiece from one work station and transfer the workpiece to the next work station. In such an operation, a problem can occur if any one of the gripper devices fails to properly grip a workpiece. For example, if a workpiece slips from its initial gripped position, it can become sufficiently out of alignment to prevent its transfer to a succeeding gripper device. A more serious problem can occur if a workpiece is transferred in a misaligned manner and subsequently positioned at a work station in a misaligned fashion. Such an incident can damage the work station. Another problem which can occur is completely losing grip of a workpiece and dropping the workpiece. Losing grip of a workpiece can occur when there is a leak or failure of fluid pressure supplied to the piston rod actuator. 
   Fluid pressure actuated grippers are generally designed for use with particular workpieces to be transferred and with specific work stations. For example, some workpieces and/or work stations may require wider or narrower gripper jaws, different types of gripper jaws, gripper jaws that open at different angles, different clearance requirements, etc. Because of the wide variety of design or performance options required of grippers, manufacturing facilities which utilize fluid actuated grippers typically have numerous sets of grippers which are designed to transport different workpieces between specific work stations. The requirement of stocking multiple sets of grippers adds to the manufacturer&#39;s costs. 
   The present invention is directed to fluid pressure actuated grippers which overcome and prevent problems associated with fluid pressure leaks or failures. Moreover, the present invention is directed to fluid pressure actuated grippers which are assembled from a plurality of modular or interchangeable components. 
   In one illustrative embodiment of the disclosure, a gripper assembly is provided comprising a body, an actuator, at least one jaw member and a cam pin. The body is coupled to the actuator. The jaw member is pivotal with respect to the body. The jaw member comprises a cam slot. The cam slot is a space formed by opposed cam walls located in the jaw arm. The cam walls form a locking portion and a pivoting portion, wherein the distance between the cam walls of the locking portion is substantially equal to the distance between the cam walls of the pivoting portion. The cam pin is attached to the actuator, wherein a portion the cam pin is located and movable in the cam slot. 
   In this and other illustrative embodiments, the gripper assembly may provide: a locking portion being substantially a straight slot portion; a pivoting portion being substantially a curved slot portion; a slot being closed at each end; a plurality of jaw members; and a rod that is engagable by an actuator and connected to a cam pin. 
   Additional features and advantages of the gripper assembly will become apparent to those skilled in the art upon consideration of the following detailed description of the illustrated embodiment exemplifying the best mode of carrying out the gripper assembly as presently perceived. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
     The present invention will be described hereafter with reference to the attached drawings which are given as non-limiting examples only, in which: 
       FIG. 1  is an exploded view of a gripper device according to one embodiment of the present invention; 
       FIG. 1   a  is an exploded view of the piston assembly of the gripper device of  FIG. 1 ; 
       FIG. 2  is a cross-sectional view of the gripper device of  FIG. 1  with the jaws in a closed position; 
       FIG. 3  is a cross-sectional view of the gripper device of  FIG. 1  with the jaws in an open position; 
       FIG. 4  is a partial cross-sectional view of  FIG. 2  taken along plane IV-IV; 
       FIG. 5  is an exploded view of a gripper device according to another embodiment of the present invention; 
       FIG. 5   a  is an exploded view of the piston assembly of the gripper device of  FIG. 5 ; 
       FIG. 6  is a cross-sectional view of the gripper device of  FIG. 5  with the jaws in a closed position; 
       FIG. 7  is a cross-sectional view of the gripper device of  FIG. 5  with the jaws in an open position; 
       FIG. 8  is a partial cross-sectional view of  FIG. 6  taken along plane VIII—VIII; 
       FIGS. 9   a  and  9   b  are side views of an adjustable gripper tip arrangement; 
       FIG. 10  is an exploded prospective view which depicts components of a modular gripper according to the present invention; 
       FIGS. 11   a – 11   g  are schematic views which depict a pivotal gripper jaw having a recessed tip seat; 
       FIGS. 12   a  and  12   b  are schematic views which depict embodiments of cone gripper tips; 
       FIGS. 13   a – 13   c  are schematic views which depict embodiments of receiver point gripper tips; 
       FIGS. 14   a ,  14   b ,  15   a  and  15   b  are schematic views which depict embodiments of padded gripper tips; 
       FIGS. 16   a – 16   d  and  17   a – 17   d  are schematic views which depict embodiments of diamond point pad gripper tips; 
       FIGS. 18   a – 18   d  and  19   a – 19   e  are schematic views which depict embodiments of reversible gripper tips that have double cone points and double diamond point pads; 
       FIGS. 20   a – 20   c  are schematic views which depict a reversible double-padded gripper tip; 
       FIGS. 21   a  and  21   b  are schematic views which depict a modular fluid activated gripper having upper and lower gripper jaws that can pivot 45° outward from the closed position; 
       FIGS. 22   a  and  22   b  are schematic views which depict a threaded plug that is designed to be inserted into bottom of the pneumatic or hydraulic cylinder; 
       FIGS. 23   a – 23   c  are schematic views which depict a reversible-threaded plug that is designed to be inserted into bottom of the pneumatic or hydraulic cylinder; 
       FIGS. 24   a  and  24   b  are schematic views which depict a modular gripper secured in a mounting plate; 
       FIGS. 25   a – 25   d  are schematic views which depict a self-aligning gripper tip according to the present invention; and 
       FIGS. 26   a  and  26   b  are schematic views which depict a modular fluid activated gripper having an upper pivotal gripper jaw  100   c  and a lower stationary gripperjaw  100   i .  FIG. 26   a  is a side view of the modular fluid activated gripper.  FIG. 26   b  is a bottom view of the modular fluid activated gripper. 
   

   DESCRIPTION OF THE INVENTION 
   The present invention is directed to fluid pressure actuated grippers of the type employed in automated workpiece handling devices which clampingly grip and transfer a workpiece from one station to another. The gripper devices of the present invention include a pneumatic or hydraulic differential motor which drives a piston rod in a reciprocal fashion, and a pair of jaws which are attached to the piston rod by a mechanical linkage that affects opening and closing of the jaws as the piston rod undergoes reciprocal motion. 
   The mechanical linkage which connects the gripper jaws to the piston rod and effects opening and closing of the jaws is a pivotal cam type linkage. That is, the gripper jaws include a cam slot which receives a cam pin that is attached to the piston rod. As the piston rod is moved in a reciprocal manner by the pneumatic or hydraulic differential motor, the cam pin slides through the cam slots causing the gripper jaws to open and close. According to the present invention, the cam slots are designed to have a particular shape which affects opening and closing of the gripper jaws, and which further causes the gripper jaws to become locked in either or both a closed position or an open position. “Locked” in position means that the position of the jaws in a closed and/or open position cannot be easily changed except by normal fluid operation of the pneumatic or hydraulic differential motor. As will be better understood from the following description, this “locking” feature prevents the gripper devices from failing in the event that fluid pressure to the pneumatic or hydraulic differential motor becomes interrupted. 
   The present invention is further directed to fluid pressure actuated grippers which are assembled from a plurality of modular or interchangeable components. For example, the modular grippers of the present invention include a common body having a yoke structure, a common piston assembly which moves in a reciprocal manner in the yoke structure, a cam pin coupled to the piston assembly, and a plurality of interchangeable components which can be assembled to the yoke structure and piston assembly to provide modular fluid pressure activated grippers having diverse performance characteristics. The interchangeable components of the modular grippers include gripper jaws, gripper tips, reversible gripper tips, pneumatic or hydraulic cylinder end closures or plugs, reversible pneumatic or hydraulic cylinder end closures or plugs, and side or impact plates. 
     FIG. 1  is an exploded view of a gripper device according to one embodiment of the present invention. The gripper device includes a yoke structure  1  which is coupled to a pneumatic or hydraulic differential motor cylinder  2  ( FIG. 2 ). The yoke structure  1  includes a through-bore  3  in the bottom portion thereof for receiving a pneumatic or hydraulic differential motor piston assembly  4  ( FIG. 2 ). The yoke structure  1  further includes a bore  5  for receiving cross piece support plate  7  which is attached to piston assembly  4 . Piston assembly  4  is received in pneumatic or hydraulic differential motor cylinder  2  ( FIG. 2 ), in a conventional manner. As shown in  FIG. 1   a , piston assembly  4  includes a piston  4   a  and piston shaft  4   b  attached thereto. Cross piece support plate  7  is received on the end of piston shaft  4   b  and supports cross piece  8 . A threaded screw  6  extends through piston  4   a , piston shaft  4   b , cross piece support plate  7 , and is secured to cross piece  8  by inserting threaded end  9  thereof into threaded bore  10  in cross piece  8 . 
   The cross piece  8  moves within yoke structure  1  as the cross piece support plate  7  moves reciprocally in bore  5 , under operation of the pneumatic or hydraulic differential motor. The cross piece  8  includes opposite ends which have cutout central portions  11 , as shown, for receiving gripper jaws  12 . In this regard, the gripper jaws  12  include stepped or narrow portions  13  which are received in the cutout central portions  11  at the ends of cross piece  8 . The narrow portions  13  of the gripper jaws  12  include cam slots  14 . The cam slots  14  have a particular shape which affects the opening, closing and locking of the gripper jaws  12 , as will be discussed below. The cam slots  14  are symmetrical to one another. Aligned through-bores  15  are provided in the ends of cross piece  8  as shown. These through-bores  15  receive pivot pins  16  which pass through cam slots  14 , and link the gripper jaws  12  to the cross piece  8 . 
   As shown in  FIG. 1 , the upper portion of gripper jaws  12  are approximately as wide as the gap  17  in yoke structure  1 . Through-bores  18  are provided in the wide portion of gripper jaws  12 . These through-bores  18  receive pivot pins  19  which pivotally connect the gripper jaws  12  to yoke structure  1 , so that the gripper jaws  12  can pivot within yoke gap  17 .  FIG. 1  depicts bores  20  in the yoke structure  1  which receive pivot pins  19 . Pivot pins  19  can be secured in bores  20  in any convenient manner, such as snap rings, cooperating threaded structures, etc. 
   Also, illustrated in  FIG. 1  are adjustable slide plates  21 . These plates can be adjustable so that edge  22  thereof extends slightly beyond surface  23  of the yoke structure  1 . In operation, there is a tendency for surface  23  of yoke structure  1  to become worn as it repeatedly contacts workpieces. Slide plates  21  can be positioned so that workpieces come into contact with edge  22  thereof, thus preventing wear on surface  23  of yoke structure  1 . Slide plates  21  can be adjustably positioned by loosening screws  24  which pass through elongated slots  25  and into threaded bores  26 , and are preferably made from a tempered or otherwise hard metal. Slide plates  21  can be easily adjusted and replaced as required. 
   Also, illustrated in  FIG. 1  is a mounting plate  27  for mounting the gripper device to an articulated support or transfer device. Mounting plate  27  includes two plate portions  28  which can be secured together by screws or bolts which extend into threaded bores  29 . As shown in  FIG. 2 , the pneumatic or hydraulic differential motor cylinder  2  of the gripper device is defined by a wall  30  that includes a stepped or narrow portion  31 . This narrow portion  31  is cylindrical, as opposed to the overall general rectangular shape of the wall  30 . When secured together, mounting plates  28  define an opening  32  which extends around narrow cylindrical portion  31  so that the gripper device freely rotates with respect to the mounting plate  27 . Mounting plate  27  also includes an opening  33  which can receive a spherical collar  34  that can be clamped therein in a fixed orientation and used to mount the gripper device to an articulated structure. 
     FIG. 2  is a cross-sectional view of the gripper device of  FIG. 1  with the gripper jaws  12  in a closed position. As depicted, gripper tips  35  and  36  secure a workpiece  37  therebetween. Gripper tip  35  is a serrated point tip and is attached to the gripper jaw  12  by a threaded screw  38   a  which is inserted into threaded bore  38   b  provided in the gripper jaws  12 . Threaded screw  38   a  is received into corresponding threaded bore provided in the gripper tip  35 . Gripper tip  36  is a cone point tip which is threaded directly into threaded bore  38   b . The illustrated gripper tips are presented as examples of various other tips which can be used in conjunction with the gripper device. 
     FIG. 2  depicts one manner in which pneumatic or hydraulic differential motor cylinder  2  can be defined by end walls which are secured, e.g., threaded, into cylinder bore  3 . 
   As illustrated in  FIG. 2 , piston  4  is urged upward by fluid pressure which is applied to port  39  of pneumatic or hydraulic differential motor cylinder  2 . As piston  4  moves upwardly, as depicted in  FIG. 2 , cam pins  16  connected to cross piece  8  slide through cam slots  14  in gripper jaws  12 , causing the gripper jaws  12  to pivot about pivot pins  19 . This upward or forward movement of piston  4  causes the gripper jaws  12  to pivot into a closed position. 
     FIG. 3  is a cross-sectional view of the gripper device of  FIG. 1  with the gripper jaws  12  in an open position. As depicted in  FIG. 3 , piston  4  is urged downward by fluid pressure which is applied to port  40  of pneumatic or hydraulic differential motor cylinder  2 . As piston  4  moves downward, as depicted in  FIG. 3 , cam pins  16  connected to cross piece  8  slide through cam slots  14  in gripper jaws  12 , causing the gripper jaws  12  to pivot about pivot pins  19 . This downward or rearward movement of piston  4  causes the gripper jaws  12  to pivot into an open position as shown. 
     FIG. 4  is a partial cross-sectional view of  FIG. 2  taken along plane IV-IV.  FIG. 4  depicts the manner in which the cross piece  8  is received in gap  17  of yoke structure  1  and how the narrow portions  13  of gripper jaw  12  are received in the cutout portions  11  of the cross piece  8  and pivotally secured therein by cam pins  16 . 
   The embodiment of the gripper device depicted in  FIGS. 1-4  is designed to lock in both the closed and open position. This locking function is achieved in part by the particular design or shape of the cam slots  14 . That is, the cam slots  14  depicted in  FIGS. 2 and 3  include three distinct segments, including two locking segments at either end and a central pivoting segment. When the cam pins  16  are positioned in either of the locking segments at the ends of the cam slots  14 , the gripper jaws  12  are locked in corresponding closed or open positions. In these locked positions, the gripper jaws  12  cannot be pivoted about pivot pins  19 . For example, as can be seen in  FIG. 2 , when the piston  4  is moved to its full upward or forward position, cam pins  16  are positioned at one end of the cam slots  14 . This segment of the cam slots  14 , identified by reference numeral  41 , causes the gripper jaws  12  to be locked in their closed position, because the configuration of locking segments  41  prevents the gripping jaws  12  from pivoting about pivot pins  19 . As can be seen from  FIG. 2 , gripper jaws  12  can only pivot about pivot pins  19  when cam pins  16  are moved slightly downward by piston  4 . In a similar manner, when cam pins  16  are in locking segments  42  of cam slots  14 , as shown in  FIG. 3 , the gripper jaws  12  cannot be pivoted about pivot pins  19 . 
   As the cam pins  16  move between locking segments  41  and  42  of the cam slots  14 , gripping jaws  12  are pivoted between their closed and open positions. Thus, the central cam slot segments between the locking segments are referred here to central pivoting segments  43 . 
   As can be seen, the locking segments  41  and  42  are configured to prevent pivotal movement of the gripping jaws  12  about pivot pins  19 . The central pivoting segment  43 , on the other hand, generally has a continuous curving shape which can be varied to affect the manner in which the gripping jaws move between their closed and open positions. For example, a portion of the slots having a smaller radius of curvature would cause quicker movement of the gripper jaws than a portion having a larger radius of curvature for a constant piston speed. In addition to affecting the speed or rate at which the gripper jaws move, the curved shape of the cam slots have been varied to effect the amount of torque applied between the gripper jaws. Thus, it is to be understood that the shape of the central pivoting segments  43  of the cam slots  14  can be varied as desired. 
     FIG. 5  is an exploded view of a gripper device according to another embodiment of the present invention. The gripper device depicted in  FIG. 5  can be used with the mounting plate  27  shown in  FIG. 1 . However, since the mounting plate  27  is not shown in  FIG. 5 , the narrow cylindrical portion  31  of the pneumatic or hydraulic motor wall  30  can be seen in perspective. 
   The gripper device of  FIG. 5  includes a yoke structure  44  and a piston assembly  58  which moves in a reciprocal manner in the yoke structure  44 . Movement of the piston assembly  58  is affected by a pneumatic or hydraulic motor having a cylinder  46  which is formed in the lower portion of the yoke structure  44  (see  FIG. 6 ). Rather than have a cross piece as in the gripper device of  FIG. 1 , the gripper device of  FIG. 5  includes a single cam pin  47  that is attached to supporting cross piece  45 , which in turn is attached to the free end of the piston assembly  58 . As shown in  FIG. 5   a , the piston assembly  58  includes a piston  58   a  and a piston shaft  58   b . Supporting cross piece  45  is attached to the end of piston shaft  58   b  by a threaded screw  6  having a threaded end  9  which is received in a correspondingly threaded bore  9   a  in supporting cross piece  45 . Supporting cross piece  45  includes a through-bore  45   a  which receives cam pin  47  as depicted. The cam pin  47  passes through cam slots  48  in gripper jaws  49 , and the ends of the cam pin  47  are received in bushings  50  which slide freely in a pair of longitudinal slots  51  in the side walls of the yoke structure  44 . It is noted that the bushings have flat parallel sides which slide along the inner surfaces of longitudinal slots  51 . These flat sides avoid a point contact and allow for the body or yoke structure to be made of a softer material such as an aluminum alloy. The bushings  50  are held in place in the longitudinal slots  51  between the gripper jaws  49  and side plates  52 . Side plates  52  can be attached to the yoke structure  44  by mechanical fastener means, such as screws  53 . Spherical surfaced bearings  54  are provided on the ends of cam pin  47  to ensure free movement of the cam pin  47  in cam slots  48 . 
   Gripper jaws  49  are pivotally connected to the yoke structure  44  by means of a pivot pin  55  which passes through aligned through-bores  56  in the side walls of the yoke structure  44  and through-bores  57  in the gripper jaws  49 . 
     FIG. 5  also depicts end closure  60  for pneumatic or hydraulic cylinder  46 . 
     FIG. 6  is a cross-sectional view of the gripper device of  FIG. 5  with the gripper jaws in a closed position. As depicted, gripper tips  61  and  62  secure a workpiece  63  therebetween. Gripper tip  61  is a serrated point tip and is attached to the gripper jaw  49  by threaded screw  64   a  which are inserted into threaded bore  64   b  provided in the gripper jaws  49 . Threaded screw is received into corresponding threaded bore provided in gripper tip  61 . Gripper tip  62  is a cone point tip and can be directly threaded into threaded bore  64   b . The illustrated gripper tips are presented as examples of various other tips which can be used in conjunction with the gripper device. 
     FIG. 6  depicts one manner in which pneumatic or hydraulic differential motor cylinder  46  can be defined by a bore  66  formed in the bottom of the yoke structure  44  which has an end wall or plug  60  secured, e.g., threaded, in the end of bore  66 . 
   As illustrated in  FIG. 6 , piston  58  is urged upward by fluid pressure which is applied to port  65  of pneumatic or hydraulic differential motor cylinder  46 . As piston  58  moves upwardly, as depicted in  FIG. 6 , cam pin  47  connected to supporting cross piece  45  slides through cam slots  48  in gripper jaws  49 , causing the gripper jaws  49  to pivot about pivot pin  55 . This upward or forward movement of piston  58  causes the gripper jaws  49  to pivot into a closed position. 
     FIG. 7  is a cross-sectional view of the gripper device of  FIG. 5  with the gripper jaws  49  in an open position. As depicted in  FIG. 7 , piston  58  is urged downward by fluid pressure which is applied to port  67  of pneumatic or hydraulic differential motor cylinder  46 . As piston  58  moves downward, as depicted in  FIG. 7 , cam pin  47  connected to supporting cross piece  45  slides through cam slots  48  in gripper jaws  49 , causing the gripper jaws  49  to pivot about pivot pins  55 . This downward or rearward movement of piston  58  causes the gripper jaws  49  to pivot into an open position as shown. 
     FIG. 8  is a partial cross-sectional view of  FIG. 6  taken along plane VIII-VIII.  FIG. 8  depicts the manner in which the bearings  54  mounted on the ends of the cam pin  47  are positioned in the cam slots  48  of the gripper jaws  49 , and how the cam pin  47  extends into bushings  50  which are located in longitudinal slots  51 . Side plates  52  are not shown in  FIG. 8 . 
   The embodiment of the gripper device depicted in  FIGS. 5-8  is designed to lock only in the closed position. This locking function is achieved by providing the cam slots  48  with locking segments at one end and pivoting segments throughout the remaining portion thereof. When the cam pin  47  is positioned in the locking segments of the cam slots  48 , the gripper jaws  49  are locked in a closed position as shown in  FIG. 6 . In this locked position, the gripper jaws  49  cannot be pivoted about pivot pin  55 . That is, as can be seen in  FIG. 6 , when the piston  58  is moved to its full upward or forward position, cam pin  47  is positioned at one end of the cam slots  48 . These segments of the cam slots  48 , identified by reference numeral  68 , cause the gripper jaws  49  to be locked in their closed position, because the configuration of locking segments  49  prevents the gripping jaws  49  from pivoting about pivot pin  55 . As can be seen from  FIG. 6 , gripper jaws  49  can only pivot about pivot pin  55  when cam pin  47  is moved slightly downward by piston  58 . 
   In contrast, when cam pin  47  is in opposite ends of cam slots  48  as shown in  FIG. 7 , the gripper jaws  49  can be pivoted about pivot pin  55 , because at this opposite end of the cam slots  48  the slots have a curvature which allows the gripper jaws  49  to pivot about pivot pin  55 . As the cam pin  47  moves between locking segments  68  and the opposite ends of the cam slots  48 , gripping jaws  49  are pivoted between their closed and open positions. As can be seen, the locking segments  68  are configured to prevent pivotal movement of the gripping jaws  49  about pivot pin  55 . On the other hand, the remaining portion or segment of the cam slots  48  have a continuous curving shape which can be varied to affect the manner in which the gripping jaws move between their closed and open positions. For example, a portion having a smaller radius of curvature would cause quicker movement of the gripper jaws than a portion having a larger radius of curvature for a constant piston speed. Thus, it is to be understood that the shape of the curved segments of the cam slots  48  can be varied as desired. 
     FIGS. 9   a  and  9   b  are side views of an adjustable gripper tip arrangement. As depicted in  FIGS. 9   a  and  9   b , the facing ends of the gripper jaws  70  (one shown) have a concave radial surface  71  which mates with a corresponding convex radial surface  72  on the gripper tip  73 , e.g., a serrated tip or threaded stud. These mating radial surfaces allow the gripper tip  73  to be rotated at installation so that they are perpendicular to a workpiece surface. In this regard, the gripper jaws  70  will close at slightly different angles depending on the thickness of a workpiece. For example,  FIG. 9   a  depicts a gripper jaw  70  which is 2.00° off parallel (open) from the surface or central axis of a workpiece which is 0.242 inch (6.147 mm.) thick.  FIG. 9   b  depicts a gripper jaw  70  which is parallel with the surface or central axis of a workpiece which is 0.094 inch (2.388 mm) thick. In each case, the gripper tip  73  is perpendicular to the surface or central axis of the workpiece. The gripper tips  73  are adjusted to a particular workpiece thickness, by loosening bolt  74  which attaches the gripper tips  73  to the gripper jaws  70 , and moving the gripper jaws  70  to a closed position on a workpiece. In this position, the gripper tips  73  are rotated against the concave surface  71  of the face of the gripper jaws  71  until the gripper tips  73  are perpendicular to the surface or central axis of the workpiece. Bolts  74  are then tightened to secure the gripper tips  73  in position. 
   In  FIGS. 10-26   d  common reference numbers have been used to identify similar elements wherever possible for convenience. 
     FIG. 10  is an exploded view which depicts the components of a modular gripper according to the present invention. The “common elements” of this gripper include the body  101 , the piston assembly  102 , jaw pivot pin  105 , and the jaw driver assembly. The piston assembly  102  includes piston  106 , piston seal  107 , piston shaft  108 , and piston shaft seal  109 . The jaw driver assembly includes cross piece  110  which is attached to piston shaft  108 , cam pin  111  which is coupled to cross piece  110 , and jaw bushings  112  which are received in cam slots  103  of the jaw members  100  and slider bushings  113  which are received in longitudinal slots  114  formed in the side walls of the yoke structure of the body  101 . 
   The term “common elements” referred to above is used to identify the basic elements of a modular gripper to which numerous interchangeable parts or elements can be attached or assembled. The “common elements” include the gripper body and the mechanical elements which are used to drive the gripper jaws. 
     FIG. 10  depicts a number of different interchangeable gripper jaws  100   a  to  100   i  which can be assembled in the body  101  and coupled to the jaw driver assembly  102 . As depicted, each of the different jaws  100   a  to  100   i  have different tip end designs and/or cam slots  103  that effect different movement characteristics. As depicted in  FIG. 10  and discussed in more detail below, the modular gripper of the present invention can be assembled to include gripper jaws having different tip designs that can be used for handling, e.g., transporting or transferring, different types of workpieces. Also, as discussed below, the modular gripper can be assembled with gripper jaws  100  having different cam slot  103  configurations which can affect the angle at which one or both jaws open or close, and which determine whether or not the jaws lock in an open and/or closed position. 
   Jaw  100   a  includes a recessed tip seat  115  and is designed to open either 22.5° or 45° from a closed position. Jaw  100   b  includes a recessed tip seat  115  and is designed to open 75° from a closed position. Jaw  100   c  includes a tip seat which can be recessed and is designed to open 55° from a closed position. Jaw  100   d  includes a double chisel point and is designed to open 22.5° from a closed position. The chisel point includes threaded bores for receiving a cone point or cone gripper tip discussed below. Jaw  100   e  is similar to jaw 100 d  except jaw  100   e  includes a single chisel point. Jaw 100 f  includes a double chisel point and is designed to remain stationary. Jaw 100 g  is similar to jaw  100   e  except jaw  100   g  includes a single chisel point. Jaw  100   h  includes a recessed tip seat  115  and is designed to remain stationary. Jaw  100   i  is a flange jaw and includes a tip seat at the end thereof. Jaw  100   i  is designed to open 22.5° from a closed position. Jaws  100   a – 100   i  are examples of different gripper jaw designs which can be used in various combinations. As will be understood from the following description, the shape and configuration of the slots in the jaws can be varied to affect a desired movement of the jaws, including angular degree of opening and closing, rate of opening and closing and force applied to a workpiece in the closed position. The dimensions depicted throughout the figures are relative and can be scaled up or down as desired. 
   The side or impact plates  104  depicted in  FIG. 10  are both adjustable and interchangeable with other impact plate designs, which are discussed below. In addition, the end closure or plug  60  for the pneumatic or hydraulic cylinder is interchangeable with plugs  60  of different lengths which can be used to limit the travel of the piston assembly and hence the angular movement of the gripper jaws  100 . 
     FIGS. 11   a – 11   g  depict a pivotal gripper jaw having a recessed tip seat  115 . The gripper jaw  100  of  FIGS. 11   a – 11   g  is designed to pivot 45° outward from the closed position.  FIG. 11   a  is a perspective view of the pivotal gripper jaw  100 .  FIGS. 11   b  and  11   c  are inverted back side views of the pivotal gripper jaw  100 .  FIG. 11   d  is a top view of the pivotal gripper jaw  100 .  FIG. 11   e  is a front side view of the pivotal gripper jaw  100 . 
   Collectively,  FIGS. 11   a – 11   e  depict the pivotal gripper jaw  100  as including a through-bore  116  for receiving a pivot pin  105  which connects the gripper jaw  100  to body or yoke structure  101 , as discussed above. Cam slot  103  has a generally curved shape with a substantially straight end portion  118  which affects locking of the gripper jaw  100  when the gripper jaw  100  is in its closed position, as discussed above. Through-bore  116  is aligned with the central axis of the substantially straight end portion  118  of cam slot  103 . As the pivot pin  105  moves along the curved portion of the cam slot  103 , angular movement is imparted to the gripper jaw  100  so that the gripper jaw  100  moves 45° between an open and closed position. 
   The pivotal gripper jaw  100  of  FIGS. 11   a – 11   g  includes a gripper tip seat  115 . The recessed tip seat  115  includes a threaded bore  117  for receiving a screw which is used to secure a gripper tip within the recessed tip seat  115 . The recessed tip seat  117  provides parallel recessed edges which engage opposed edges of a gripper tip, as discussed below, and relieve shear forces which would otherwise, i.e., absent the parallel recessed edges, be applied directed to a screw used to secure a gripper tip to the gripper jaw  100 . According to one embodiment, the recessed seat  115  can have a concave curved surface for receiving a gripper tip having a corresponding curved shape as indicated in  FIGS. 9   a  and  9   b . This embodiment would allow the gripper tip to be adjusted parallel to the surface of a workpiece. 
     FIGS. 1   f  and  11   g  are schematic views of the shape and alignment of the cam slot  103  and through-bore  116 . It is to be understood that the angular degree of movement of the pivotal gripper jaw  100  of  FIGS. 11   a – 1   g , and other pivotal gripper jaws disclosed herein, can be increased or decreased by appropriately lengthening or shortening cam slot  103 . In this regard, the measurements of reference points shown in  FIGS. 11   a – 11   g  that are used to define the curved shape of the cam slot are merely relative to one particular example. It is to be understood that the dimensions given in  FIGS. 11   a – 11   g  are relative and can be scaled up or down as desired. It is further to be understood that the cam slot in  FIGS. 11   a – 11   g  is illustrative only, and that the shape of the cam slots used in the gripper devices of the present invention can vary. Accordingly,  FIG. 10  depicts pivotal gripper jaws which move 22.5°, 45°, 55°, and 75°. It is obvious from these examples that pivotal gripper jaws can be designed with a variety of angles of movement. 
     FIGS. 12   a – 20   c  depict different gripper tips which can be used interchangeably with gripper jaws having gripper tip seats, or the flange jaw grippers depicted in  FIG. 10 . 
     FIGS. 12   a  and  12   b , are schematic views which depict embodiments of cone gripper tips.  FIG. 12   a  is a side view of a cone gripper tip  121 , and  FIG. 12   b  is an end view of the same tip. The cone gripper tip  121  of  FIGS. 12   a  and  12   b  includes a base  122  which is depicted as having a hexagonal shape, a cylindrical tip  123  which extends from the base  122 , and a threaded stud  124  which extends from the base  122  on an opposite side from the cylindrical tip  123 . The cylindrical tip  123  terminates at a point  125  which can be defined by any desired angle. The base  122  is depicted as having a hexagonal shape. However, it is to be understood that the base  122  can be of any desired shape such as square, rectangular, round, round with parallel flat sides, etc. The base  122  is used to tighten the threaded stud  124  into a corresponding threaded bore on the tips of a gripper jaw. Accordingly, the periphery of the base  122  should include surfaces which can be easily gripped with a wrench for tightening purposes. The cylindrical shape of the tip  123  is a matter of convenience. This tip  123  can have any cross sectional shape such as square, rectangular, oval, etc. 
     FIGS. 13   a – 13   c  are schematic views which depict embodiments of cone point gripper tips which are designed to receive tip elements.  FIG. 13   a  is a side view of a cone point gripper tip, and  FIGS. 13   b  and  13   c  are front and end views of the same tip. The cone gripper tip  121 ′ of  FIGS. 13   a – 13   c  includes a base  122  which is depicted as having a hexagonal shape, and a threaded stud  124  which extends from one side of the base  122 . The base  122  has a tip receiver end  123 ′ defined by a tapered portion which terminates at an internal bore  126 . This bore  126  is designed to be used with the cone point  121  shown in  FIGS. 12   a – 12   b . The bore  126  allows a workpiece being gripped between the cone point  121 ′ of  FIGS. 13   a – 13   c  and the cone point  121  of  FIGS. 12   a – 12   b  to be bent away from the point  125  causing a cavity in the workpiece that improves the gripper&#39;s ability to hold the workpiece. The base,  122  is depicted as having a hexagonal shape. However, it is to be understood that the base  122  can be of any desired shape such as square, rectangular, round, round with parallel flat sides, etc. The base  122  is used to tighten the threaded stud  124  into a corresponding threaded bore on the tips of a gripper jaw. Accordingly, the periphery of the base  122  should include surfaces which can be easily gripped with a wrench for tightening purposes. It is noted that the length of the cone gripper tips and the receiver point gripper tips can vary as desired to achieve any necessary clearance. 
     FIGS. 14   a ,  14   b ,  15   a  and  15   b  are schematic views which depict embodiments of padded gripper tips.  FIG. 14   a  is a side view of a gripper tip  127  and  FIG. 14   b  is an end view of the same tip. The padded gripper tip  127  of  FIGS. 14   a  and  14   b  includes a base  128  which is depicted as having a square shape, and a pad portion  129  which is bonded to the base  128  and depicted as having a cylindrical shape. The base  128  includes an internally threaded bore  130  by which the padded gripper tip  127  can be attached to the end of a gripper jaw by passing a threaded member though the end of the jaw and into threaded bore  130 . Alternatively, the base  128  could be provided with a threaded stud similar to that depicted in  FIGS. 12–13 . 
   The pad portion  129  can be bonded to the base  128  by any suitable chemical means such as adhesives, epoxies, thermal bonding or welding, etc. In addition, the padded portion  129  can be mechanically secured to the base  128 . For example, the portion of the base  128  which extends into the pad portion  129 , as depicted, could include external threads, bayonet mounting structure, securing projections, etc. by which the pad portion  129  could be secured to the base  128 . 
   Neither the base  128  nor the pad portion  129  is limited to the shapes depicted in  FIGS. 14   a  and  14   b . That is, the base  128  and pad portion  129  can have any suitable cross sectional shape, including round, triangular, square, hexagonal, oval, etc. The face  131  of the pad portion  129  is provided with an uneven, or grooved surface to increase gripping friction. As depicted, the face  131  of the pad portion  129  is provided with a series of concentric grooves or ribs  132 . Other uneven or grooved or ribbed surface patterns can be used including any combination of linear and/or curved grooves or ribs, patterns of protrusions or indentations, or random surface structures. 
   As in the case of all the non-padded gripper tips, the base  128  is made from a sturdy wear- and impact-resistant material such as a metal. The pad portion  129  can be made out of any suitable plastic, resinous, or polymeric material such as urethane. 
     FIG. 15   a  is a side view of a padded gripper tip and  FIG. 15   b  is a front view of the same tip. The padded gripper tip  127  of  FIGS. 15   a  and  15   b  differ from the padded gripper tip  127  of  FIGS. 14   a  and  14   b  in the length of the base  128 . From these drawings it can be understood that the base  128  can be any suitable length. 
     FIGS. 16   a – 16   d , and  17   a – 17   d  are schematic views which depict embodiments of diamond point pad gripper tips.  FIG. 16   a  is a prospective view of a diamond point pad gripper tip  133 .  FIG. 16   b  is a top or face view thereof.  FIG. 16   c  is an end view thereof.  FIG. 16   d  is a side view of the same tip. The diamond point pad gripper tip  133  of  FIGS. 16   a – 16   d  includes a substantially rectangular body  134  having opposed sides  135  which extend beyond a lower surface  136  thereof so as to define a saddle-like structure. This saddle-like structure is designed to be received in and mate with the recessed or stepped structure of the gripper tip seats  115  depicted in  FIGS. 10 and 11 . The extended portions of the sides  135  restrict linear movement of the diamond point pad gripper tip  133  in one direction and the edges of the recessed or stepped portion of the gripper tip seat  115  restrict linear motion in an orthogonal direction. As depicted, the junction between the lower surface  136  of the body and the inner surfaces  137  of the extended side portions  135  may include a recessed area rather than a 90° angle in order to accommodate any burs, dents, or other imperfections on the corresponding mating portion of the gripper tip seat structure  115 . 
   The face  138  of the diamond point pad gripper tip  133  is formed with a matrix of protrusions which can be cast or machined into the surface during manufacture. Opposed edges of the face  138  can be beveled as depicted in  FIG. 16   b . A stepped through-bore  139  is provided in the face  138  of the diamond point gripper tip  133  as depicted. The stepped bore  139  has a larger diameter portion at the surface of face  138  which allows a threaded member used to secure the tip  133  to a gripper jaw to be counter sunk in the bore  139 . 
     FIG. 17   a  is a perspective view of a diamond point pad gripper tip  133 .  FIG. 17   b  is a top or face view thereof.  FIG. 17   c  is an end view thereof.  FIG. 17   d  is a side view of the same tip. The diamond point pad gripper tip  133  of  FIGS. 17   a – 17   d  differs from the diamond point pad gripper tip  133  of  FIGS. 16   a – 16   d  in the height of the body  134 . From these drawings it can be understood that the body  134  can have any suitable height. 
     FIGS. 18   a – 18   d  and  19   a – 19   e  depict reversible gripper tips  140  which have double cone points  141  and double diamond point pads  142 .  FIG. 18   a  is a perspective view of a reversible gripper tip  140 .  FIG. 18   b  is a top of view thereof  FIG. 18   c  is cross sectional view taken along C—C in  FIG. 18   d .  FIG. 18   d  is a front view of the reversible gripper tip  140 . 
   The reversible gripper tip  140  of  FIGS. 18   a – 18   d  includes a central body portion  143  which extends between two reversible tip ends  144 . Each of the reversible tip ends  144  includes opposed gripping surfaces. In the example shown in  FIGS. 18   a – 18   d , the reversible tip ends  144  include a double cone point on one face  141  and a double diamond point pad on the opposing face  142 . The central body portion  143  includes a through-bore  145  by which the reversible tip  140  can be secured in the recessed or stepped portion of a gripper tip seat  115 . The manner in which the reversible tips  144  extend beyond the upper and lower surface of the central body portion  143  provides saddle-like structures which can mate with the recess or stepped portion of a gripper tip seat  115 , as discussed above. 
   As depicted, the junctions between both the upper and lower surfaces of the central body portion  143  and the inner surfaces of the reversible tips  144  may include a recessed area rather than a 90° angle in order to accommodate any burs, dents, or other imperfections on the corresponding mating portion of the gripper tip seat structure. The structure of the double cone points  141  and the double diamond point pad  142  are similar to the corresponding structures on the non-reversible tips discussed above. 
     FIG. 19   a  is a perspective view of a reversible gripper tip  140 .  FIG. 19   b  is a top of view thereof.  FIG. 19   c  is an end view thereof.  FIG. 19   d  is a front view of the reversible gripper tip  140 . The reversible gripper tip  140  of  FIGS. 19   a – 19   e  is similar to that of  FIGS. 18   a – 18   d  except that the reversible gripper tip  140  of  FIGS. 19   a – 19   e  includes bores  146  in the double diamond point pads  142 . 
   It is noted that the height of the reversible tips  144  and the attachment position of each to the central body portion  143  can be modified to affect the “height” of each of the opposed gripping face structures as desired. It is also noted that the double diamond point pad gripping faces can include a bore  146  or a structure defining a conical region (see  FIGS. 18   a – 18   d ) which will enhance gripping of a workpiece. 
     FIGS. 20   a – 20   c  are schematic views which depict a reversible double-padded gripper tip  150 .  FIG. 20   a  is a cross-sectional side view of the reversible double-padded gripper tip  150 .  FIG. 20   b  is a top view thereof.  FIG. 20   c  is a bottom view thereof. The reversible double-padded gripper tip  150  includes a central body portion  151  and opposed tip members  152  which extend orthogonally to the central body portion  151  at either end thereof. According to one embodiment, as shown, the central body portion  151  includes through-bores members  153  near opposite ends thereof through which the opposed tip  152  extend. The central body portion  151  further includes a central through-bore  154  through which a threaded member can be used to secure the reversible double-padded gripper tip  150  to a gripper tip seat  115 . The embodiment of the double-padded gripper  150  tip depicts how the tip members  152  can be shaped to provide wider or narrower gripping pads on opposite sides of the central body portion  151 . In an alternate embodiment, the height of the tip members  152  and the attachment position of each to the central body portion  151  can be modified to affect the “height” of each of the gripping faces of the tip members  152 , as desired. 
   For the reversible double-padded gripper tip  150 , the central body portion  151  can be made from a sturdy wear and impact resistant material such as a metal, and the tip members  152  can be made out of any suitable plastic, resinous, or polymeric material such as urethane. 
     FIGS. 21   a  and  21   b  are schematic views which depict an example of a modular fluid activated gripper that has upper and lower gripper jaws  100   a  which can pivot 45° outward from the closed position.  FIG. 21   a  is a side view of the modular fluid actuated gripper which depicts the upper and lower gripper jaws  100   a  in their closed position. The open position of the gripper jaws  100   a  is depicted in phantom. Each of the gripper jaws includes a gripper tip seat  115 .  FIG. 21   b  is a bottom view of the modular fluid actuated gripper of  FIG. 21   a . It is also pointed out that  FIGS. 21 and 26  illustrate the use of side or impact plates  104  that have different shapes. More particularly, the side or impact plates have impact surfaces which extend outward at the side or sides of the gripper where pivotal gripper jaws are used since the gripper can be moved towards a workpiece until the leading edge of the impact plates contact the workpiece, proper adjustment of the impact plates may need to be made to ensure alignment and position of the workpiece in the jaws of the gripper. As seen in the drawings, these extended impact surfaces are not required for stationary gripper jaws. 
     FIGS. 22   a – 22   b  and  23   a – 23   c  are schematic views which depict embodiments of the end closure or plug  60  that is illustrated in  FIG. 5 .  FIGS. 22   a  and  22   b  depict a threaded plug  60  which is designed to be inserted into bottom of the pneumatic or hydraulic cylinder  46 .  FIG. 22   a  is a cross-sectional view of the plug  60  and  FIG. 22   b  is an end view thereof. The plug  60  includes a threaded portion  160  by which it is secured into a corresponding bore in the bottom of the pneumatic or hydraulic cylinder  46 . A groove  161  is provided on the periphery of the plug  60  and used to secure an o-ring or similar sealing gasket. In order to tighten plug  60  in the bottom of the pneumatic or hydraulic cylinder  46 , a keyed bore or tightening tool receiving structure  162  is provided in the bottom  163  of the plug  60 . This keyed bore  162  can have any convenient shape which allows it to receive a tightening tool, such as hexagonal for receiving an allen wrench, a groove for receiving a screw driver, or any similar shape. 
   The length of the plug  60 , when inserted in the bottom of the pneumatic or hydraulic cylinder, can limit the distance the piston assembly moves, and thus the angle at which pivotal gripper jaws open. Therefore, according to the present invention, a variety of plug lengths can by used interchangeably to control the angle at which pivotal gripper jaws open. According to one embodiment, a threaded plug  60  can be used with indicia corresponding to the depth at which it is threaded into the bottom of the cylinder. The position or depth of this plug  60  could be adjusted, using the indicia as a reference, to limit the distance the piston assembly moves. It is also possible to use a locking element, e.g., threaded ring or nut, to keep the position of the plug  60  fixed. 
   The closure or plug of  FIGS. 23   a – 23   c  is reversible and has two different lengths or depths which can be used to limit the distance the piston assembly moves in the cylinder.  FIG. 23   a  is a cross-sectional view of the plug  60 ′.  FIGS. 23   b  and  23   c  are opposite end views thereof. The reversible plug  60 ′ has an externally threaded center portion  160  with grooves  161  adjacent either side of the central threaded portion  160 . These grooves  161  are provided to receive o-rings or other similar sealing members. Each end of the reversible plug  60 ′ has a keyed bore or tightening tool receiving structure  162 , as discussed, with reference to  FIGS. 22   a – 22   b . As depicted in  FIG. 23   a , the central threaded portion  160  is actually offset from the center of the length of the plug  60 ′ so that the distance from the threaded portion  160  to either end of the plug  60 ′ is different. This provides a plug  60 ′ that has two different lengths or depths when inserted and secured into a bore at the bottom of the pneumatic or hydraulic cylinder. Reversing the plug  60 ′ allows selection between the two lengths or depths, and thus adjustment of the angle at which a pivotal gripper jaw moves. 
     FIGS. 24   a  and  24   b  depict a modular gripper secured in a mounting plate  27 .  FIG. 24   a  is a side view of the assembly, and  FIG. 24   b  is an end view of the assembly. As discussed above in reference to  FIG. 1 , plate  27  includes an opening  33  which can receive a spherical collar  34  that can be clamped therein in a fixed orientation and used to mount the gripper device to an articulated structure. The spherical collar  34  receives a support  165 , as depicted in  FIG. 24   a , allows the mounting plate  27  and modular gripper attached thereto, to be adjusted over an angular range defined between the support  165  and mounting plate  27  by rotating the spherical collar  34  in opening  33 . 
   As depicted in  FIG. 24   b , the modular gripper can be adjusted 360° by rotation thereof in opening  32 . These adjustments allow the modular gripper to be positioned at virtually any angle with respect to support  165 . 
   The range of angular adjustment between the support  165  and mounting plate  27  which is affected by rotating the spherical collar in opening  33  is dependent on the spherical shape of the spherical collar and clearance between the support and mounting plate. Angular ranges of 30° off center are easily provided, however, larger ranges are possible. 
   As discussed above, the mounting plate  27  includes two halves which are secured together by screws or bolts which extend into threaded bores  29 . The use of three threaded bores allows separate loosening and angular adjustment of either the spherical collar  34  or the modular gripper. In this regard, loosening only the screw or bolt at one end of the mounting plate  27  is sufficient to loosen the adjacent spherical collar  34  or modular gripper, while maintaining the other in a secured manner. This feature allows easy and separate adjustment of the mounting plate  27  with respect to the support  165  or the modular gripper with respect to the mounting plate  27 . In order to provide a tighter grip, the spherical collar  34  can have a roughened, e.g., ribbed, grooved, etc., outer surface. Making the spherical collar  34  out of a hard metal and making the mounting plate  27  out of a softer steel or an alloy of aluminum, brass, etc. will also allow better gripping between the two. It is also possible to provide open  33  with a roughened inner surface. 
     FIGS. 25   a – 25   d  depict a self-aligning gripper tip.  FIGS. 25   a  and  25   b  are prospective views of different embodiments of the self-aligning gripper tip  170 .  FIG. 25   c  is a side view of the self-aligning gripper tip in the end of a gripper jaw  100 .  FIG. 25   d  is an end view of  FIG. 25   c  which depicts how the self-aligning gripper tip  170  is secured in the end of a gripper jaw  100 . 
   The self-aligning gripper tip  170  is designed to rotate as needed to align the gripping surface thereof with a workpiece. The self-adjusting gripper tip  170  includes a cylindrical body  171  having a projecting structure  172  along one side thereof which projecting structure  172  includes a gripping surface  173 . The gripping surface  173  can be roughened, include teeth structures, grooves, or any suitable surface structures. According to the embodiment of the self-aligning gripper tip  170  depicted in  FIG. 25   a , one end of the cylindrical body  171  includes a flange  174 , and the other end is provided with an internally-threaded bore which can receive a threaded member  175 . The threaded member  175  includes a flange  176  which is used to secure the self-aligning gripper tip  170  in a gripping jaw  100 , as discussed below. 
   In the embodiment of the self-aligning gripper tip  170  depicted in  FIG. 25   b , a groove  177  is provided on one end of the cylindrical body  171 . This groove  177  can receive a snap ring  178  that can be used alone or in combination with a washer to secure the self-aligning gripper tip  170  in a gripper jaw  100 . Although  FIG. 25   b  depicts the use of a snap ring  178  and corresponding groove  177  on one end of the self-aligning gripper tip  170 , it is to be understood that the flange  174  in  FIG. 25   b  and in  FIG. 25   a  could be replaced with groove  177  and a snap ring  178 . 
     FIGS. 25   c  and  25   d  depict how the self-aligning gripper tip  170  is secured in a gripper jaw  100 . As shown, the gripper jaw  100  includes a through-bore  179  which intersects a lower surface  180  thereof, so that a slot is formed at the lower surface  180 . The self-aligning gripper tip  170  is inserted in through-bore  179  and secured in place by the flange  174  which abuts one side of the gripper jaw  100  and by threaded member  175  (and optional washer  181 ) which is threaded into the self-aligning gripper tip  170 . In the alternative embodiment depicted in  FIG. 25   b , the snap ring  178  (an optional washer) would be used to secure one or both ends of the self-aligning gripper tip  170  in through-bore  179 . 
   As depicted in  FIG. 25   c , the projecting structure  172  is allowed to rotate in the direction of double-headed arrow “a” as the cylindrical body  171  of the self-aligning gripper tip  170  rotates in through-bore  179 . This rotation of the projecting structure  172  allows the gripping surface  173  to align with the surface of a workpiece. 
     FIGS. 26   a  and  26   b  are schematic views which depict a modular fluid activated gripper having an upper pivotal gripper jaw  100   c  and a lower stationary gripper jaw  100   i . The lower stationary gripper jaw has a gripper tip seat which faces outward or forward from the modular fluid actuated gripper, as depicted in  FIG. 26   b . The upper pivotal gripper jaw  100   c  has a curved shape which allows it to pivot so that the gripper tip seats  115  of each gripper jaw are in face-to-face alignment, as depicted in  FIG. 26   a , when the upper gripper jaw is in its closed position. The open position of the upper gripper jaw is depicted in phantom in  FIG. 26   a.    
   Although the present invention has been described with reference to particular means, materials and embodiments, from the foregoing description, one skilled in the art can easily ascertain the essential characteristics of the present invention and various changes and modifications may be made to adapt the various uses and characteristics without departing from the spirit and scope of the present invention as set forth in the following claims.