US3512824A

US3512824A - Gripper finger mechanism for press transfer assembly

Info

Publication number: US3512824A
Application number: US675544A
Authority: US
Inventors: Frederick H Bautz; Tsuruo Otsuka
Original assignee: Verson Allsteel Press Co
Current assignee: Allied Products Corp
Priority date: 1967-10-16
Filing date: 1967-10-16
Publication date: 1970-05-19
Anticipated expiration: 1987-05-19
Also published as: CH497238A; GB1239640A; SE348653B; DE1802379B2; NL157524B; DK145012B; AT298197B; ES359193A1; FR1587522A; BE722337A; DK145012C; DE1802379A1; NL6814722A

Description

3,512,824 GRIPPER FINGER MECHANISM FOR PRESS TRANSFER ASSEMBLY Filed Oct. 16, 1967 May 19, 1970 4 II-QHIBAIUTZ ETAL v 3 Sheets-Sheet 1 I I I I l 35 J4 J4 J4 B5 l I I I I I I GRIP/2E1? #41656 TnnMsFER LOWER RETURN RE 77M or fl/PPER. FINGERS OPEN 0 Gfi/PPfR FINGERS 404/14 rvcf FEEDER/CK H 54077 I TSURUO OTSUK/I -v Ma 19,1970 F. H. B UTz-ETAL 3,512,824

GRIPPER FINGER MECHANISM FOR PRESS TRANSFER ASSEMBLY Filed Oct. 16,1967 s Sheets-Sheet z 46 41 Z0 .96 34 50 53 574-7 v 63 63 64 Z7 56 75 y lg! 5'3 76 .56- .5] 52 55 I I 54 42 5 #vvavrms.

FEEDER/CK BAUTZ TSURUO OTSUK/l May 19, 1970 F. H. BAUTZ ETAL 3,512,824 GRIPPER FINGER MECHANISM FOR PRESS TRANSFER ASSEMBLY 3 Sheets-Sheet 5 Filed Oct. 16, 196? WVEWTORS. FEEDER/CK H. 5 4072 United States Patent 3,512,824 GRIPPER FINGER MECHANISM FOR PRESS TRANSFER ASSEMBLY Frederick H. Bautz, Hazel Crest, and Tsuruo Otsuka,

Harvey, 11]., assignors to Verson Allsteel Press Company, Chicago, 11]., a corporation of Delaware Filed Oct. 16, 1967, Ser. No. 675,544 Int. Cl. B66c 1/44 U.S. Cl. 294115 19 Claims ABSTRACT OF THE DISCLOSURE A transfer assembly is provided for a press for gripping and transferring workpieces from station to station along the press. It includes at least one longitudinally movable feed bar and at least one gripper mechanism carried by said at least one feed bar for longitudinally moving gripper finger mechanisms having gripper fingers to grip and release the workpieces for transferring the workpieces as said at least one feed bar is longitudinally moved. The gripper mechanisms laterally advance and retract the gripper finger mechanisms and open and close the gripper fingers thereof. Said at least one feed bar is also raised and lowered by a lifter mechanism. In operation, the feed bars are in their lowered position, and the gripper finger mechanisms are then laterally advanced and the fingers are closed to grip the workpiece. The feed bars and gripper finger mechanisms are then raised, longitudinally moved in one direction and then lowered to transfer the workpiece from one station to the next. The gripper fingers are then opened and the gripper finger mechanisms are then laterally retracted and longitudinally returned in the opposite direction by the lowered feed bar for another cycle of operation.

A principal object of this invention is to provide an improved gripper finger mechanism in the foregoing transfer assembly which is operated by the gripper mechanism thereof. Briefly, in this connection, the gripper mechanism includes means for longitudinally moving first and second rods transversely of the feed bar, both rods being simultaneously moved between retracted and advanced po sitions and the second rod being additionally moved between said advanced position and a projected position.

The gripper finger mechanism includes a first bracket mounted on the first rod and a second bracket mounted on the second rod. A pair of gripper fingers are pivotally mounted on the first bracket and are swingable between open and closed positions. Gripper inserts are provided on the free ends of the gripper fingers for gripping a workpiece when the gripper fingers are swung to closed position and for releasing the workpiece when the gripper fingers are swung to open position. Links are pivotally connected to the second bracket and to the gripper fingers for swinging the gripper fingers from open position to closed position when the second rod is moved from the advanced position to the projected position and for swinging the gripper fingers from closed position to open position when the second rod is moved from the projected position to the advanced position. When the first and second rods are simultaneously moved between their advanced positions and their retracted positions, the gripper fingers are in their open positions. The gripper finger mechanism may be circumferentially adjustably mounted on the rods.

Other objects of this invention reside in the details of construction of the gripper finger mechanism and the cooperative relationships between the component parts thereof and also in the cooperative relationships between such elements and the gripper mechanism.

3,512,824 Patented May 19, 1970 The specific lifter mechanism is disclosed and claimed in Frederick H. Bautz application Ser. No. 675,543, filed Oct. 16, 1967, now Pat. No. 3,456,814. The specific gripper mechanism is disclosed and claimed in Frederick H. Bautz and Howard J. McElroy application Ser. No. 675,625, filed Oct. 16, 1967, now Pat. No. 3,432,042.

Further objects and advantages of this invention will become apparent to those skilled in the art upon reference to the accompanying specification, claims and drawings in which:

FIG. 1 is a diagrammatic front elevational view of a conventional mechanical press having the transfer assembly of this invention applied thereto;

FIG. 2 is a diagrammatic horizontal sectional view through the press of FIG. 1 taken substantially along the line 22 of FIG. 1;

FIG. 3 is a chart illustrating the motions applied to the gripper finger mechanisms of the transfer assembly for transferring workpieces from one station to the next station in the press;

FIG. 4 is a side elevational view partly in section of the gripper finger mechanism in the retracted position and with its gripper fingers opened and taken substantially along the line 5-5 of FIG. 6;

FIG. 5 is a side elevational view similar to FIG. 4 but showing the gripper finger mechanism advanced with its gripper fingers closed and taken substantially along the line 55 of FIG. 6;

FIG. 6 is a top plan view of the gripper finger mechanism in the advanced position and the gripper fingers thereof closed and looking from the top of FIG. 5;

FIG. 7 is an end elevational View of the gripper finger mechanism and looking from the right of FIGS. 5 and 6;

FIG. 8 is a sectional view of the gripper finger mechanism taken substantially along the line .88 of FIG. 5;

FIG. 9 is an exploded sectional view of one of the grip per fingers;

FIG. 10 is an enlarged sectional view of the spring means utilized in the gripper fingers; and

FIG. 11 is an elevational view of a splined ring utilized in securing the gripper finger mechanism to the gripper mechanism.

Referring first to FIGS. 1 and 2, a conventional press, such as a mechanical press, is diagrammatically illustrated at 10. It includes a bed 11, uprights 12 supporting a crown (not shown) and a vertically reciprocable ram 13 which may be driven from a power driven crankshaft (not shown). Arranged along the length of the bed 11 is a plurality of spaced apart work forming stations, each including a die structure 14 carried by an adaptor plate 11A and bolster on the bed 11 and a punch structure 15 including an adaptor plate carried by the ram 13 for performing work functions on workpieces upon each downward stroke of the press ram 13 as they are progressively advanced along the press 10 from station to station. The initial workpieces are fed to the press 10 from a magazine 16 at one end of the press and the finished workpieces are discharged from the press 10 by a discharge mechanism 17, such as a conveyor or a chute or the like. at the other end of the press 10. The workpieces are progressively transferred from station to station in the press from the magazine 16 to the discharge mechanism 17.

The press 16 is providedwith a transfer assembly generally designated at 18 and extending lengthwise of the press. The transfer assembly 18 includes at least one longitudinally movable feed bar 19 (two being illustrated with one toward the front of the press and the other toward the rear of the press) which carry a plurality of equally spaced gripper mechanisms 20. Each gripper mechanism 20 laterally advances and retracts a gripper finger mechanism 21 and opens and closes the gripper fingers of the gripper finger mechanisms for gripping and releasing the workpieces being formed by the press. The transfer assembly 18 also includes a plurality of lifter mechanisms 22 carried by the adaptor plate 11A on the bed 11 for supporting and raising and lowering the longitudinally movable feed bars 19.

A pair of longitudinally extending reciprocatable rods 23 is provided for longitudinally moving the feed bars 19 in one direction and in the opposite direction. A pair of longitudinally extending reciprocatable rods 24 is provided for operating the gripper mechanisms 20 to advance and retract the gripper finger mechanisms 21 and to open and close the gripper fingers thereof. A pair of longitudinally extending reciprocatable rods 25 is provided for operating the lifter mechanisms 22 to raise and lower the feed bars 19 and, hence, the gripper mechanisms 20 carried thereby. A suitable drive mechanism 26, which is operated from the crankshaft of the press in timed relation therewith, is arranged at one end of the press 10 for reciprocating the

rods

23, 24 and 25 in timed relation to each other and to the upward and downward movement of the press ram 13.

The motions imparted to the gripper finger mechanisms 21 for transferring the workpieces from the magazine 16 and progressively from station to station along the press 10 to the discharge mechanism 17 are diagrammatically illustrated in FIG. 3. With the parts in the positions illustrated in FIGS. 1 and 2, the ram 13 has been raised sufiiciently so that the punches carried thereby are clear from the workpieces, the feed bars 19 are in their lowered and their returned positions, and the gripper finger mechanisms 21 are in their retracted positions with their fingers opened. This is represented by the point A in the diagram of FIG. 3.

First, the rods 24 are moved to the left with respect to the feed bars 19 to advance laterally the gripper finger mechanisms and close the fingers thereof to grip the workpiece in that station. Next, the rods are moved to the left to raise the feed bars 19 and, hence, the gripper finger mechanisms 20 to lift the gripped workpiece from the die structure of that station. Next, the rods 23 and 24 are simultaneously moved to the left to move the raised feed bars 19 to the left to transfer the gripped and raised workpiece from that station to the next, there being no relative movement between the rods 23 and 24 during this movement. Next, the rods 25 are moved in the opposite direction to the right to lower the feed bars 19 and, hence, the gripper finger mechanisms 20 for lowering the gripped workpiece into the die structure 14 of said next station. Next, the rods 24 are moved in the opposite direction to the right to open the gripper fingers in the gripper mechanisms 20 and retract the gripper finger mechanisms. Next, the rods 23 and 24 are simultaneously moved in the opposite direction to the right to move the lowered feed bars 19 to the right to return the gripper finger mechanisms 21 with their fingers in opened position to point A in FIG. 3 for another transferring cycle. The punches 15 on the ram 13 perform their work functions on the workpieces while the gripper finger mechanisms 20 are lowered and retracted. The drive mechanism 26 may include suitable cam, linkage and lever constructions operated from the crank shaft of the press 10 for producing the foregoing timed sequences of operation of the

rods

23, 24 and 25 with respect to the operation of the press ram 13.

While the transfer assembly 18 is illustrated in FIGS. 1 to 3 as having two sets of mechanisms, one toward the front of the press and the other toward the rear, for gripping the workpieces at two points for transferring them along the press, in some instances it may be desirable to grip the workpieces at only one point for this purpose and, under such circumstances, only one set of mechanisms need be used, as for example, the one toward the front of the press or the one toward the rear thereof.

Referring now to FIG. 4, the finger gripper mechanism generally designated at 21 is illustrated as being retracted to its retracted position with the fingers thereof opened by the gripper mechanism generally designated at 20. This gripper mechanism 20 may be like that disclosed in the aforementioned Frederick H. Bautz and Howard J. McElroy application and is partially shown in FIG. 4 as including a housing 62 having a transverse opening 63 containing a splined bearing sleeve 64 for slidably mounting a first rod 65. A second rod 71 is slidably mounted within the first rod 65 and has a shoulder 73 adapted to engage the outer end of the first rod 65. Adjacent the shoulder 73 the second rod 71 is provided with an extension 74. The first and

second rods

65 and 71 are simultaneously moved from the retracted position illustrated in FIG. 4 to an advanced position wherein the gripper fingers remain open and then the second rod 71 is moved to a projected position beyond the advanced position for closing the gripper fingers as illustrated in FIG. 5. In the reverse operation of the gripper mechanism 20, the second rod 71 is moved from the projected position to the advanced position for opening the gripper fingers and then both

rods

65 and 71 are retracted to the retracted position for retracting the gripper finger mechanism with the fingers open.

The first rod 65 is externally splined as indicated at 30, these splines cooperating with the internal splines in bearing sleeve 64 to prevent rotation of the second rod 65 with respect to the housing 62. Near the outer end of the splined first rod 65, it is provided with a pair of grooves, a wide groove 31 and a narrow groove 32. An internally splined ring 36 is slipped over the end of splined first rod 65 past the narrow groove 32 into the wide groove 31 where it may be rotatably positioned. A snap ring 33 is then snapped into the narrow groove 32. A first bracket 34 has a circular recess which is received over the end of the splined first rod 65 and it has an annular shoulder 35 engageable with the end of the rod 65, the first bracket 34 being rotatably positionable with respect to the first rod 65. The splined first rod 65, for example, has 20 splines and the ring 36 has 20 internal splines along with 3 equally circumferentially spaced holes as shown in FIG. 11. One of the holes is radially lined up with the centerline one tooth space of the splines, the other holes not being so lined up due to the use of 3 holes and 20 splines. After the first bracket 34, which also has 3 equally spaced tapped holes, is positioned in the desired rotative position over the end of the first rod 65, the splined ring 36 is rotated in the groove 31 until the splines therein line up with the splines 30 on the first rod 65 and holes therein line up with the tapped holes in the first bracket 34. Screws 37 are then extended through the holes in the splined ring 36 and the first bracket 34 to draw up the splined ring 36 against the snap ring 32 and the shoulder 35 on the bracket against the end of the rod 65 with the internal splines in the ring 36 engaging the splines on the rod 65 between the

grooves

31 and 32. In this way, the first bracket 34 is securely clamped to the end of the first rod 65 with the rotative position of the bracket 34 fixed with respect to the rod 65. Since there are 3 holes and 20 splines, the bracket 14 may be positioned in 60 different positions on the rod 65, with an angular displacement of 6 between each position. This allows for a multitude of selective rotative positions of the gripper finger mechanism 21 with respect to the gripper mechanism 20 and lends considerable versatility to the transfer assembly in gripping and transferring various kinds of workpieces in various orientations.

The bracket 34 is provided with a pair of spaced arms 38 which carry a pair of pivot pins 39 therebetween for pivotally mounting the gripper fingers. The gripper fingers as shown more clearly in FIGS. 7 to 9 are essentially outwardly acute bell crank gripper fingers which are in the form of two-part fingers, one part being designated 41 and the other part being designated 42. The finger part 41 is provided with a recess 43 for providing a pair of ears 44 having holes therein for mounting part 41 on the pivot pin 39. Part 41 also includes an attachment portion 45 and a portion 46 having a circular recess 47 therein concentric with a hole passing therethrough.

The other part 42 has a tongue portion 49 received within the recess 43 of the part 41 which is provided with a hole for also pivotally mounting the part 42 on the pivot pin 39. The part 42 also has a portion 51 provided with a circular recess 52 concentric with a tapped hole and also with an ear provided with a hole therethrough. A spring means 53 such as a plurality of conical washers or the like, as illustrated in FIG. 10, are inserted between the

recess

47 and 52 in the pivoted

parts

41 and 42 for resiliently urging these parts apart. A screw 54 extends through the opening in the part 41 and the spring means '53 into the tapped hole in part 42 for fixing the amount by which the spring means can separate the

parts

41 and 42. Thus, there is provided a resilient lost motion connection between the pivoted

parts

41 and 42 to allow a limited amount of resilent motion of the part 42 with re spect to the part 41.

The ear 50 on the part 42 carries a pivot pin 55 upon which one end of a pair of links is pivotally mounted. The other ends of the pair of links 56 are pivotally mounted to pivot pins 57 carried by a second bracket 58. This second bracket 58 is secured to the extension 74 of the second rod 71 by means of a snap ring 59, the snap ring 59 holding the second bracket 58 against the shoulder 73 on the rod 71. The portions 45 of the parts 41 of the gripper fingers carry gripper inserts 75 by means of screws 76 extending through holes in the portions 45 of the parts 41. Preferably the gripper inserts 75 are electrically insulated from the parts 41 by electrical insulating

sheets

77 and 78 and insulating sleeves 79. The gripper inserts 75 grip a workpiece 80 when the gripper fingers are closed as illustrated in FIGS. 5 and 7.

With the parts in the position shown in FIG. 4, the gripper finger mechanism 21 is retracted and the gripper fingers thereof are opened. When the gripper mechanism 20 advances the gripper finger mechanism 21 from the retracted position to the advanced position, the gripper fingers remain open and they overlie the workpiece 80 to be gripped. As the second rod 71 is advanced from the advanced position to the projected position, the second bracket 58 is moved outwardly and the links 56 operated thereby move the gripper fingers toward the closed position for gripping the workpiece 80 as illustrated in FIG. 5. In this finger closing movement, the links 56 preferably move over center as illustrated in FIG. 5 to provide a toggle action, the links 56 operating as toggle links. By reason of this toggle action the force required to grip the workpiece 80 is relieved from the second rod 71 to prevent undue strain therein while the workpiece 80 is gripped and being transferred. While the links 56 for both gripper fingers are illustrated as being toggle links in FIG. 5, in

some instances it may be desirable to make only one of the links 56 a toggle link.

The resilient lost motion connection 53 between the

parts

51 and 42 of the gripper fingers operate effectively to compensate for variations in the thickness of the workpiece 80 and also to provide a resilient gripping force for the gripper inserts 75 as they grip the workpiece 80. The resilent lost motion connection 53 also assists in allowing the toggle links 56 to move over center, the resilient lost motion means 53 being compressed during this over center movement of the toggle links 56. As illustrated in the drawings, the upper and lower gripper fingers have different configurations but they may have the same configuration if this be desired. Generally speaking, the configurations of the gripper fingers are determined by the shapes and positions of the workpieces to be gripped thereby and many different configurations may be utilized toward this end. Electrical connections may be made to the screws 76 which carry the gripper inserts 75 and these electrical connections may be led to a suitable indicating or control device for operating the same when and if a workpiece is not gripped by the gripper inserts when the gripper fingers are moved to their closed positions. In this connection when a proper gripping contact on the workpiece 80 is made by the gripper fingers 75, a suitable electrical signal may be produced through the workpiece 80.

While for purposes of illustration one form of this invention has been disclosed other forms thereof may become apparent to those skilled in the art upon reference to this disclosure and, therefore, this invention should be limited only by the scope of the appended claims.

What is claimed is:

1. A gripper finger mechanism for a press transfer assembly for transfering workpieces along the press and having a gripper mechanism including first and second longitudinally movable rods which are simultaneously moved between retracted and advanced positions and wherein the second rod is additionally moved between said advanced position and a projected position, said gripper finger mechanism comprising a first bracket mounted on the first rod, a pair of outwardly acute bell crank gripper fingers pivotally mounted on said first bracket and swingable between open and closed positions, gripper inserts on the forward free ends of said gripper fingers for gripping a workpiece when the gripper fingers are swung to closed position and for releasing the workpiece when the gripper fingers are swung to open position, a second bracket mounted on the second rod, links pivotally connected to said second bracket and to the rearward ends of the gripper fingers for swinging the gripper fingers from open position to closed position when the second rod is moved from said advanced position to said projected position and for swinging the gripper fingers from closed position to open position when the second rod is moved from said projected position to said advanced position.

2. The combination of claim 1 wherein said first rod is hollow, said second rod is slidably mounted in said first rod, and said second bracket carried by said second rod is arranged within the confines of said first bracket carried by said first rod.

3. The combination of claim 1 wherein said first bracket is detachably mounted on said first rod, and said second bracket is detachably mounted on said second rod.

4. A gripper finger mechanism for a press transfer assembly for transferring workpieces along the press and having a gripper mechanism including first and second longitudinally movable rods which are simultaneously moved between retracted and advanced positions and wherein the second rod is additionally moved between said advanced position and a projected position, said gripper finger mechanism comprising a first bracket mounted on the first rod, a pair of gripper fingers pivotally mounted on said first bracket and swingable between open and closed positions, gripper inserts on the free ends of said gripper fingers for gripping a workpiece when the gripper fingers are swung to closed position and for releasing the workpiece when the gripper fingers are swung to open position, a second bracket mounted on the second rod, links pivotally connected to said second bracket and to the gripper fingers for swinging the gripper fingers from open position to closed position when the second rod is moved from said advanced position to said projected position and for swinging the gripper fingers from closed position to open position when the second rod is moved from said projected position to said advanced position, at least one of said links being a toggle link which moves over center when the gripper fingers are swung thereby to the closed position for locking the gripper fingers in closed position and for relieving the force on said second rod while the gripper fingers are closed.

5. The combination of claim 4 wherein both of said links are toggle links.

6. A gripper finger mechanism for a press transfer assembly for transferring workpieces along the press and having a gripper mechanism including first and second longitudinally movable rods which are simultaneously moved between retracted and advanced positions and wherein the second rod is additionally moved between said advanced position and a projected position, said gripper finger mechanism comprising a first bracket mounted on the first rod, a pair of gripper fingers pivotally mounted on said first bracket and swingable between open and closed positions, gripper inserts on the free ends of said gripper fingers for gripping a workpiece when the gripper fingers are swung to closed position and for releasing the workpiece when the gripper fingers are swung to open position, a second bracket mounted on the second rod, links pivotally connected to said second bracket and to the gripper fingers for swinging the gripper fingers from open position to closed position when the second rod is moved from said advanced position to said projected position and for swinging the gripper fingers from closed position to open position when the second rod is moved from said projected position to said advanced position, said pivotally mounted gripper fingers being two part fingers, one part carrying the gripper inserts, the other part being pivotally connected to the links, and both parts being pivotally mounted on the first bracket, and including spring means for resi iently separating said parts, and stop means for limiting the amount of such separation, whereby the gripper inserts resiliently grip the workpiece when the gripper fingers are swung to the closed position.

7. The combination of claim 6 wherein at least one of said links is a toggle link which moves over center when the gripper fingers are swung thereby to the closed position for locking the gripper fingers in closed position and for relieving the force on said second rod while the gripper fingers are closed, said spring means also facilitating over center movement of said at least one toggle link.

8. The combination of claim 7 wheren both of said links are toggle links.

9. A gripper finger mechanism for a press transfer assembly for transferring workpieces along the press and having a gripper mechanism including first and second longitudinally movable rods which are simultaneously moved between retracted and advanced positions and wherein the second rod is additionally moved between said advanced position and a projected position, said gripper finger mechanism comprising a first bracket mounted on the first rod, a pair of gripper fingers pivotally mounted on said first bracket and swingable between open and closed positions, gripper inserts on the free ends of said gripper fingers for gripping a workpiece when the gripper fingers are swung to closed position and for releasing the workpiece when the gripper fingers are swung to open position, a second bracket mounted on the second rod, links pivotally connected to said second bracket and to the gripper fingers for swinging the gripper fingers from open position to closed position when the second rod is moved from said advanced position to said projected position and for swinging the gripper fingers from closed position to open position when the second rod is moved from said projected position to said advanced position, the

mounting of the first bracket on the first rod comprising a V groove in said first rod near the end thereof, a snap ring in said groove, an annular portion on said first bracket receiving the end portion of said first rod and engaging the end thereof, a ring about said first rod and engaging the snap ring, and screws engaging said ring and the annular portion of said first bracket for drawing said ring against said snap ring and the annular portion of said first bracket against the end of said first rod to clamp said first bracket on said first rod.

10. The combination of claim 9 wherein said first rod and said ring have interlocking splines for preventing rotation of said first bracket with respect to said first rod.

11. The combination of claim 10 wherein said first rod has a second groove into which said splined ring may be backed to provide for rotative positioning of said ring and said first bracket.

12. The combination of claim 11 wherein said first rod and said ring have twenty splines and said screws are three in number and equally circumferentially spaced to provide sixty rotative positions for said first bracket with respect to said first rod, said positions being at six angular degree intervals.

13. A gripper finger mechanism for a press transfer assembly for transferring workpieces along the press and having a gripper mechanism including first and second longitudinally movable rods which are simultaneously moved between retracted and advanced positions and wherein the second rod is additionally moved between said advanced position and a projected position, said gripper finger mechanism comprising a first bracket mounted on the first rod, a pair of gripper fingers pivotally mounted on said first bracket and swingable between open and closed positions, gripper inserts on the free ends of said gripper fingers for gripping a workpiece when the gripper fingers are swung to closed position and for releasing the workpiece when the gripper fingers are swung to open position, a second bracket mounted on the second rod, links pivotally connected to said second bracket and to the gripper fingers for swinging the gripper fingers from open position to closed position when the second rod is moved from said advanced position to said projected position and for swinging the gripper fingers from closed position to open position when the second rod is moved from said projected position to said advanced position, said gripper inserts being electrically conducting and electrically insulated from said gripper fingers, and means including electrical connections to said gripper inserts for electrically sensing the gripping of the workpiece by the gripper inserts.

14. A gripper finger mechanism for a press transfer assembly comprising a first bracket having spaced apart arms, a pair of centrally aligned gripper fingers pivotally mounted between said arms of said first bracket and swingable between open and closed positions and each having a centrally aligned ear, gripper inserts on the free ends of said gripper fingers for gripping a workpiece when the gripper fingers are swung to closed position and for releasing the workpiece when the gripper fingers are swung to open position, a second bracket mounted between said arms of said first bracket and longitudinally movable between one postiion and a projected position and having a pair of centrally aligned ears, a pair of spaced apart links pivotally connected to one of the centrally aligned ears on said second bracket and the centerally aligned ear on one of said gripper fingers and a pair of spaced apart links pivotally connected to the other centrally aligned ear on said second bracket and the centrally aligned ear on the other of said gripper fingers for swinging the gripper fingers from open position to closed position when the second bracket is longitudinally moved from said one position to said projected position and for swinging the gripper fingers from closed position to open position when the second bracket is longitudinally moved from said projected position to said one position.

15. A gripper finger mechanism for a press transfer assembly comprising a first bracket having spaced apart arms a pair of gripper fingers pivotally mounted be tween said arms of said first bracket and swingable between open and closed positions and having an ear, gripper inesrts on the free ends of said gripper fingers for gripping a workpiece when the gripper fingers are swung to closed position and for releasing the workpiece when the gripper fingers are swung to open position, a second bracket mounted between said arms of said first bracket and longitudinally movable between one position and a projected position and having a pair of cars, a pair of links pivotally connected to one of the ears on said second bracket and the ear on one of said gripper fingers and a pair of links pivotally connected to the other ear on said second bracket and the ear on the other of said gripper fingers for swinging the gripper fingers from open position to closed position when the second bracket is longitudinally moved from said one position to said projected position and for swinging the gripper fingers from closed position to open position when the second bracket is longitudinally moved from said projected position to said one position, at least one of said pairs of links constituting a toggle link which moves over center when the gripper fingers are swung thereby to the closed position for locking the gripper fingers in closed position and for relieving the force on said second bracket while the gripper fingers are closed.

16. The combination of claim 15 wherein both of said pairs of links constitute toggle links.

17. A gripper finger mechanism for a press transfer assembly comprising a first bracket having spaced apart arms, a pair of gripper fingers pivotally mounted between said arms of said first bracket and swingable between open and closed positions and having an ear, gripper inserts on the free ends of said gripper fingers for gripping a workpiece when the gripper fingers are swung to closed position and for releasing the workpiece when the gripper fingers are swung to open position, a second bracket mounted between said arms of said first bracket and longitudinally movable between one position and a projected position and having a pair of ears, a pair of links pivotally connected to one of the ears on said second bracket and the ear on one of said gripper fingers and a pair of links pivotally connected to the other car on said second bracket and the ear on the other of said gripper fingers for swinging the gripper fingers from open position to closed position when the second bracket is longitudinally moved from said one position to said projected position and for swinging the gripper fingers from closed position to open position when the second bracket is longitudinally moved from said projected position to said one position, said pivotally mounted gripper fingers comprising two part fingers, one part carrying the gripper inserts and having spaced apart mounting ears by which it is pivotally mounted between the arms of the first bracket, the other part carrying the ear by which it is pivotally connected to the pair of links and having a mounting ear between the spaced apart mounting ears of the first part by which it is pivotally mounted between the arms of the first bracket, and including spring means for resiliently separating said parts, and stop means for limiting the amount of said separation, whereby the gripper inserts resiliently grip the workpiece when the gripper fingers are swung to the closed position.

18. The combination of claim 17 wherein at least one of said pairs of links constitute a toggle link which moves over center when the gripper fingers are swung thereby to the closed position for locking the gripper fingers in closed position and for releasing the force on said second bracket while the gripper fingers are closed, said spring means also facilitating over center movement of said at least one of said pairs of links.

19. The combination of claim 18 wherein both of said pairs of links constitute toggle links.

References Cited UNITED STATES PATENTS 2/1962 Harry 294- 9/1968 Bende 294-115