US3391606A

US3391606A - Work holder

Info

Publication number: US3391606A
Application number: US518118A
Authority: US
Inventors: Sylvan J Kaminga
Original assignee: Individual
Current assignee: Individual
Priority date: 1966-01-03
Filing date: 1966-01-03
Publication date: 1968-07-09
Anticipated expiration: 1985-07-09
Also published as: DE1300802B; FR1507110A; GB1162179A

Description

S. J. KAMINGA July 9, 1968 WORK HOLDER 5 Sheets-Sheet 1 Filed Jan. 3, 1966 INVENTOR. 5711/4 J. AflM/A/GA ATTORNEYS S. J. KAMINGA WORK HOLDER 5 Sheets-Sheet 2 ATTORNEYS July 9, 1968 Filed Jan. 3, 1966 y 1963 5. J. KAMINGA 3,391,606

WORK HOLDER Filed Jan. 3, 1966 s sheets-sheet 5 Li W 2.,

ma Z m/ NVENTOR.

ATTORNEYS July 9, 1968 5. J. KAMINGA 3,

WORK HOLDER Filed Jan. 3, 1966 5 Sheets-Sheet 4 mvnm'on. 76 sum 1 MM/d/M ATTORNEYS s. J. KAMINGA 3,391,606

WORK HOLDER July 9, 1968 Filed Jan. 3, 1966 5 Sheets-Sheet 5 ATTORNEYS United States Patent 3,391,606 WORK HOLDER Sylvan J. Kaminga, 2445 Fletcher Drive,

Grand Rapids, Mich. 4950.6. Filed Jan. 3, 1966, Ser. No. 518,118 14 Claims. (Cl. 90-215) ABSTRACT OF THE DISCLOSURE This disclosure is directed to a work holder for machine tools, the work holder having work piece clamping jaws mounted for reciprocating movement past the machine tools. The jaws, on approaching work piece receiving position, opening while in movement to receive the work piece upon initiation of return movement to work piece clamping of the work piece. The jaws release the work piece upon initiation of return movement to work piece receiving positioin. The jaws incorporate work piece positioning devices which are automatically retracted as the jaws leave work piece receiving position.

This invention relates to work piece holders for machine tools for supporting the work piece as it is moved past the tool which efiects the machining on the work piece. More particularly, this invention relates to a device intended to automatically reciprocate as a continuous cycle forward and back, past the tool and to receive and release the work pieces automatically with minimum hesitation in its movement. It practically eliminates the swell periods characteristic ofconventional equipment required for either receiving or releasing the work piece. It is also designed to automatically regulate and vary the speed of movement of the work piece beneath the tool, to cause its movement to be more rapid during those portions of its travel during which the work piece and tool are not in contact. It is also designed to provide rapid and complete adjustment to adapt the tool from work pieces of one particular design to work pieces of another design.

This invention is an improvementover known tools of this type in that it continuously reciprocates back and forth between a work piece receiving position and a work piece releasing position without interruption of its motion except for the momentary hesitation when it reverses direction of movement after the machine operation and the momentary dwell necessary to drop a new work piece into place and clamp it.

It automatically releases the completed work piece during the actual return stroke of the work holder. Thus, the considerable time delay normally characteristic of these machines due to hesitation to both receive and then release the work piece, is eliminated. When machine tools are used for fabricating large quantities of similar parts on a continuous production basis, the total amount of time lost due to the necessity for the machine remaining stationary to receive and to discharge the work piece, adds up, over a period of time, to a substantial production cost factor. This invention eliminates this time loss.

The machine is so designed that itcan be quickly and readily adapted to the machining necessities of various types of machine tools and work pieces of varying designs. Further, the total stroke or distance of travel of the work piece holder can be limited to only that which is necessary to complete the machining together with the receiving and release of the work pieces. Thus, there is no time lag or waste due to the machine having to traverse unused portions of its total travel capability merely because the machine was designed to handle a work piece significantly bigger or different from than that actually being machined.

The machine provides automatic work piece locating moves the work piece past the machine tool thus eliminating interference with the rapid and automatic discharge of interference with the rapid and automatic discharge of the machined work piece when it is to be released.

These and other objects and purposes of this invention will be understood by those acquainted with the design and manufacture of machine tools upon reading the following specification and the accompanying drawrngs.

In the drawings:

-FIG. 1 is a plan view of this invention;

FIG. 2 is a partially broken side elevation view of this invention;

FIG. 3 is an end view of the invention taken at the right hand end of FIG. 2;

FIG. 4 is an enlarged, broken elevation view of the magazine feeder for supplying the work pieces to this machine;

FIG. 5 is a schematic plan view of the machine with the collet open ready to receive a new work piece;

FIG. 6 is a schematic side elevation view showing the work piece being fed into the open collet;

FIG. 7 is a schematic plan view of the machine with the collet closed at the moment when the feed actuator initiates its retraction stroke;

FIG. 8 is a schematic side elevation view of the invention as shown in FIG. 7;

FIG. 9 is a schematic plan view of the machine partially through its retraction stroke;

FIG. 10 is a schematic side elevation view of the invention as it is illustrated in FIG. 9;

FIG. 11 is a schematic plan view of the invention at the limit of its retraction stroke;

FIG. 12 is a schematic side elevation view of the invention as it is shown in FIG. 11;

FIG. 13 is a schematic side elevation view of the invention immediately after it has initiated its forward or return stroke;

FIG. 14 is a schematic plan view showing the collet returned to work piece receiving position;

FIG. 15 is an enlarged, fragmentary sectional view of the clamping jaw and operating ram, taken along the plane XV'IIXVII of FIG. 6;

FIG. 16 is a fragmentary central sectional view of the travel velocity control unit for the collet; and

FIG. 17 is a schematic diagram of the controls for the invention.

In executing this invention, there is provided a base frame on each end of which are mounted a pair of posts. Extending between the posts are waybars. The collet assembly is slidably mounted on these ways for travel from a work piece receiving position to a work piece releasing position between which the work piece is carried past a tool for machining it. The collet consists of a pair of jaws between which the work piece is clamped. One of the jaws is secured to a reciprocating piston which effects movement of the collet assembly back and forth along its ways. The other jaw is slidably mounted for movement toward and away from the first jaw whereby the collet may be opened to receive the work piece and closed to clamp it. The second jaw is opened and closed by a cylinder. This cylinder is mounted to travel with the collet during its work stroke.

Work stop and positioning fingers are mounted in the collet. These are automatically positioned to receive and position the work piece when it is received. The collet is then closed to lock the work piece or pieces in position. The initial position of the retraction or work stroke of the collet releases the stop fingers permitting them to retreat automatically from beneath the work piece.

The clamping of the work piece initiates movement of the collet assembly through its workv stroke. The movement of the collet is rapid until the work piece. approaches the cutter of the machine tool. At this point, a velocity control mechanism takes over to reduce the speed of travel of the collet to that which is suitable for the particular cutting tool and the type of material being cut. As soon as the piece has passed the cutting tool, the collet trips another sensor, automatically reversing the direction of travel of the collet. Immediately after reversal, a third sensor is tripped causing the second jaw of the collet to shift to release position releasing the machined work piece to drop free. The velocity control device is inoperative during the return stroke, permitting the machine to return to work piece receiving position at a rapid pace where it arrives with the jaws open ready to receive another work piece. During its hesitation in reversing direction to re-enter its work stroke, the machine automatically causes the release of a new work piece which drops into the collet, the collet is clamped, and the cycle repeated.

Referring specifically. to the drawings and to FIGS. 1 and 2, the numeral indicates a base having a pair of posts 11 adjacent each end. Extending between the posts are a pair of waybars 12 on and between which is mounted a collet assembly 13. The waybars 12 are fixed and the collet assembly 13 is mounted to slide along them.

The collet 13 has a first or backing jaw 20, the sides of which have openings therethrough for receiving the waybars 12 providing both support and guidance for the jaw during reciprocation. The backing jaw has a clamping plate 21 mounted on one face. The clamping plate 21 has a pair of vertical reliefs 22 to partially receive the hereinafter described work piece stops 51.. The clamping jaw 20 .is connected to one end of a piston 23 which is part of the actuating cylinder assembly 24. The cylinder 24, together with the piston 23, constitute the feed actuator for the invention. The cylinder 24 is stationary and is supported on the terminal plate 25 extending between a pair of the posts 11.

The collet 13 has a second or clamping jaw 30, also extending between and mounted slidably upon the waybars 12. The clamping jaw has a clamping plate 31 which cooperates with the clamping plate 21 on the backing jaw 20.

A second pair of waybars 32 extends slidably through the clamping jaw 30 and are fixedly secured to the backing jaw 20. These are of sufficiently heavy construction to prevent bending resulting from the pressures exerted by the closed clamping jaws 2t) and 30. The clamping jaw 30 is equipped with bearings surrounding the waybars 32. The ends of the waybars 32 are connected by a plate 33 on which is mounted the clamp actuator 34. The clamp actuator 34 consists of a cylinder and reciprocating clamp ram 35. The ram 35 extends slidably through the plate 33 and into a blind bore within the clamping jaw 30 (FIG. 15).

The end of the ram has a head 36 chamferred at37. Where the ram enters the clamping head 30 it is surrounded by a gland nut 38 which compresses a spring 39 extending between the nut and the head 36. The spring biases the clamping jaw 30 toward the collet actuator 34 until further movement in this direction is prevented by bottoming of the head 36 on the blind end of the bore 40. When the head 36 is advanced to the bottom of the bore 40, the chamferred end 37 rides against the cam surface 41 of the trip plunger 42, forcing the trip plunger 42 outwardly against the bias of the spring 43. The purpose of this will be more fully explained hereinafter.

Retraction or opening travel of the clamping jaw 30 by the collet actuator 34 is limited by a pair of stops 44 (FIG. 1). Further retraction of the ram 35 by the collet actuator 34 withdraws the head 36 from the bottom of the bore 40, releasing the trip plunger 42. When this happens, the trip plunger shifts inwardly to the position illustrated in FIG. 14. The stops 44 are threaded through the posts 11 making them adjustable. This permits the openingof the jawstobe limited only to that which is necessary to receive the work piece. So limiting the size of the opening prevents the Work pieces from rocking sideways or falling through the jaws as they are initially dropped between them. The stops 44, once properly positioned, are locked by the locking nut 44a. I

Slidably extending through the clamping jaw 30 are a pair of rods on the ends .of which are upwardly extending work piece stops 51. Whenthe collet is opened to receive a work piece, the work piece stops are partially seated within the reliefs 22 and are held against the clamping plate 21 of the backing jaw 20. A portion of the stops extend into the opening to intercept the work piece as it enters the collet. The ends of the rods adjacent the collet actuator 34 are joined by a yoke 52.

Between the yoke 52 and the adjacent face of the c1amping jaw 30 a compression spring 53 surrounds each of the rods and urges the rods toward the collet actuator 34. Thus, the stops 51 are biased to retract into the reliefs in the lower end of the clamping plate 31 on the clamping jaw 30. Below the ram 35 is a stop 54 designed to engage the yoke 52 just before the backing jaw 20 reaches its maximum retracted position. The stop 54 presses the yoke 52 against the bias of the springs 53 toward the clamping jaw 20 shifting the stops '51 into the reliefs 22. Preferably, the stop 54 is resiliently mounted so that it will permit a limited degree of overtravel thus permitting the rods 50 to travel a limited distance with the backing jaw 20' during the last increments of movement of the backing jaw.

Mounted on one side of the machine are a pair of hexagonal control bars, one being the upper control bar and the other being the lower control bar 61. On these two control bars are mounted the sensors which control the movements of the machine. On the upper bar are the

sensors

62 and 63. The

sensors

64 and 64 are mounted on the lower control bar 61. Each of the sensors may be adjusted lengthwise of its supporting control bar and when properly positioned for the accurate actuation of the machine, may be secured to the control bar by suitable means such as set screws.

The sensor 62 is positioned to be contacted by the trip plunger 42 when the clamping jaw is shifted to collet closed or clamping position. The sensor 64 is positioned to be actuated by the trip arm 66 on the backing jaw 20 when the backing jaw reaches its maximum retracted position, that is, its maximum travel to the left as the machine is illustrated in FIGS. 1 and 2. The sensor is designed to be actuated by the trip arm 68 when the collet reaches its maximum retracted position. The sensor 63 is positioned to be actuated by the trip arm 67 on the backing jaw 20 immediately after the collet starts its retraction movement.

The manner in which the sensors control the actuation of the machine is set out diagrammatically in FIG. 17. It will be recognized that the machine may be operated either hydraulically or pneumatically. In either case, the pressurized fluid is supplied from a suitable source to the two

selector valves

69 and 70 through the supply lines 71 and 72 respectively. The

sensors

62, 63, 64 and 65 are poppet or pilot valves which when tripped create a pulse which actuates the selector valves. The selector valve 69 has combination supply and exhaust lines leading to each end of the collet actuator 35. The selector valve 70 has combination supply and exhaust lines leading to each end of the feed actuator 24. The

lines

72 and 73 connect the selector 69 to the collet actuator 35. The selector valve 70 is connected to the feed actuator 24 by the lines 74 and 75. Interposed in the line between the sensor 64 and the selector valve 69 is a suitable time delay mechanism such as an air operated delay timer which interposes a predetermined delay in the transmission of the signal from the sensor 64 to the selector valve 69. This delay mechanism is indicated in FIG. 17 by the numeral 76.

The rate of travel of the collet 13 under the influence of the feed actuator 24 is controlled by the velocity control mechanism (FIGS. 2 and 16). This mechanism conthe pressure plate 85, one end of which embraces the piston rod 82 between the stop nuts 83 and 84 and the other end is rigidly secured to the backing jaw 20. The

use of the nuts 83 and 84 permits the distance between them to be adjusted. I I

As best seen in FIG. 16, the piston rod extends into the

dual chambers

86 and 87 of the dash pot 8 1. -In each chamber, the piston rod is equipped with a piston head, one piston head 88 being in the chamber 86 and the other piston head 89 being in 'the chamber =87. The two chambers are separated by a bathe 90 and are connected through the baflie by a restricted bleed passage 91 through which fluid trapped in the

chambers

86 and 87 can pass only at a predetermined flow rate. The rate at which the fluid can pass through the bleed passage 91 may be adjusted by the metering screw 92. The purpose of this will appear more fully hereinafter. The restricted passage 91 is designed to limit the rate at which the fluid may pass from the chamber 86 to the chamber 87 and thus regulate the speed of travel of the collet13 as it shifts to the right, as the machine is illustrated in FIGS. 1 and 2. Movement of fluid from the chamber 87 to the chamber 86 is rapid because flow in this direction is through the check valve passage 93. The check valve 94 closes to prevent the use'o'f this passage by fluid attempting to move from the chamber 86 to the chamber 87.

As is best seen in FIG. 6, immediately above the machine is a magazine 100 designed to feed work pieces to the machine. Discharge of the work pieces from the magazine 100 is normally prevented by the gate 101 which is biased by any suitable means such as a spring into work piece holding position. MOunted on the collet 13 is a dog 102 which, when the clamping jaw is shifted to open position, engages the gate 101, withdrawing it to release one of the work pieces. The magazine 100 is shown in greater detail in'FIG. 4. It consists of a tube within which the work pieces are loaded and stored ready for release. A

spring 104 is seated with the magazine. The work pieces enter a funnel 105 whichaligns them ready one at a time, through'the lower end 106. V

In the following paragraphs the operation of this invention will be described with particular reference to FIGS. 5 through 14.

In FIG. 5, themachineis-shownfat the end of its retraction stroke with the collet {open ready to'receive a new work piece for machining. In this-position, the clamping

plates

21 and 31 are separated 'and'the workpiece stop fingers 51 are partially seated in the reliefs 22 since the yoke 52 is pressed against the stop 54 (FIG. 6). The clamping jaw is seated against the stops 44. The ram being fully retracted, the head 36 is withdrawn from the bottom of the bore 40 permitting the trip plunger 42 to retract.- Also, as is seen in FIG. '6, the gate 101 is withdrawn from the'magazine 100, permitting a new work piece A to drop between the clamping plates21 and 31 and seat on the stop fingers 51. Also at this point,as is shown in FIG. 5, the trip pin 66is engaged with the sensor '64. This engagement occurs the moment the'collet 13 reaches its maximum advance position, but the signal generated by the tripping of the sensor 64 is delayed by the delay timer 76. Thus, the selector valves actuation is delayed fora dwell period, preferably 'a fraction-ofa second. During this dwell, the work piece A is dropped intothecollet H At the end 'of the dwell period, the selector valve 69 actuates the collet actuator forcing the ram 35 to extend. This shifts the clamping jaw 30 to'a clamp position firmly locking the work piece A in the collet. As the ram 35 for discharge,

bottoms in the bore 40, the head 36' forces the trip' plunger 42 to extend, tripping the sensor 62. The pulse from the sensor'62 actuates the selector valve- 70-and starts the feed actuator moving to the right, as the machine is'illustrated in FIGS.1 and 2.

As thecollet initiates its movement toward the cutter B, both the trip plunger 42 and the trip pin 6'6 disengage their

respective sensors

62 and 64. Also, the yoke 52 is moved away from the stop 54 and by reasonof the bias of the springs 53 (FIG. 1),the rods 50 and their fingers 51' retractinto thesockets 55, leaving the space below the work piece A free andunobstructed. I

During the movement ofthe clamping jaw to clamping position, the dog 102 shifts to the right, as the machine isillustrated, permitting the gate 101 to move under the magazine, preventing the discharge of another work piece.

During the initial increment of movement of the loaded collet toward the tool B, the pressure plate 85 traverses the gap between the stop nuts 83 and 84 on the piston rod 82 (FIG. 2'). Thus, the velocity control mechanism is inactive and the feed actuator'is free to move as fast as'fl'uid is supplied to it. The machine is so designed that the rate of travel durin this interval is quite rapid. Just before the work piece makes contact with the tool B; the pressure plate 85 engages the stop nuts 84. Thereafter the collet has to shift the piston82with 'it. The rate at which the collet can shift the piston 82 is governed by the rate at which the fluid trapped in the chamber 86 can be transferred to the chamber 87 through the bleed passage 91. The rate of flow through this passage has been previously metered by means of the metering valve 92 to that which will move the work piece past the cutter atthe precise speed required by the particular machining operation to be executed. It will be understood that this will vary, depending on the particular tool being used and the particular material being machined."

FIGS. 7 and 8 show the equipment just as the machine initiates its retraction movement toward the cutter. FIGS. 9 and 10 illustrate the equipment in transit between loading position and the cutting tool B.

FIGS. 11 and 12 illustrate the eqiupment at themoment it reaches the limit of its retraction stroke, after the work piece A has been carried past the cutter and the operation on it has been completed. It will be noted that the trip pin 67 has a pivoted end 77 which constitutes a one-way dog. This permits the trip pin67 to pass the sensor '63 without activating it. The end of the retraction stroke is reached when the sensor 68 trips the sensor 65. At this point, the trip pin 67 has just passed the sensor 63 a sufficient distance to permit the dog 77 to pivot into operating position where, upon reversal of movement, the dog will wipe across the sensor 63 tripping it. The tripping of the sensor 65 shifts the selector valve 70 reversing the direction of movement of the feed actuator 24. Immediately the direction of travel of the collet is reversed and the collet starts to advance toward the loading position at the left hand end of the machine as illustrated.

Immediately upon initiation of the advance move- =ment of the collet, the trip pin 67 trips the sensor' 63. This actuates the selector valve 69 causing the collet actuator to retract the ram 35. This opens the collet to' maximum jaw opening, freeing the completed work piece A to drop through the collet into suitable collection equipment. It will be noted that the pins 51 are retained in retracted position by the springs 53 during this period, and thus, do not interfere with the free drop of the completed work piece. It is important to note that the machine does not pause to unload. Further, it unloadsbefore the work 'piece is moved back past the cutter B,

as is clearly shown'in FIG. 13.

Due to the presence of the check valve passage 93 and the check valvev 94, the transfer of fluid from the chamber 87 to the chamber 86 in the velocity control device, may progress rapidly and thus, the velocity control to the left during the advance stroke, resetting it for the next operating cycle. This arangement permits the collet to return to its load-receiving position rapidly and without interference from the piston 82.

As the collet approaches the loading station, the clamping jaw 30 engages the stops 44 preventing further return movement. However, since the backing jaw will not have reached a position to trip the sensor 64, its re: turn movement will continue until the sensor 64 is tripped. Its continued movement partially. closes the opening between the jaws until it once again is only sufficient to receive the work piece. Just before contact is made be tween the clamping jaw 30 and the stops 44, contact will have occurred between the yoke 52 and the stop 54 extending the stop pins 51 to a position which will partially seat them in the channels 22 when the backing jaw reaches its maximum return position. This restriction in the size of the jaw opening permits the jaw opening to be set at just that which will receive the part. Thus, parts of various sizes and shapes can be accommodated. For example, it permits use of the machine with a headed part which must be delivered to the collet head down.

It will be seen from the above description that this invention provides a work holder and collet which reciprocates back and fourth past the tool or cutter with a minimum of delay in its operating cycle. At the loading end of the stroke, its dwell period is only that fraction of a second necessary to receive and clamp a new work piece. This can be reduced to a fraction of a second. At the opposite end of the stroke, the dwell period is only that necessary to reverse the direction of movement of the feed actuator 24. No dwell is required for discharge of the completed work piece. Thus, the machine operates with maximum efliciency. Further, the machine is so designed that it may be adapted to the machining of a wide variety of work pieces. It is entirely possible to use the machine to perform consecutively, several operations during the retraction stroke. It is also possible to adjust the operating speed of the machine during the actual machining operation to feed rates consistent with a wide variety of materials. While the machine has been illustrated as used with a milling cutter, it will be recognized that numerous other types of machining operations can be performed on the work pieces utilizing this particular machine. Further, the machine is completely automatic and requires no manual intervention throughout any portion of its operating cycle. It is readily adjustable to strokes of varying lengths. Therefore, there is no wasted time interval while the machine traverses unnecessary distances, not utilized in the particular operation to which it is applied. The length of the stroke is variable by shifting the

sensors

63 and 65 along the stop bars 60 and 61. The sensors can be shifted and locked in any location required by the particular operation.

While the machine has been described. as having hydraulic or pneumatic sensors, it will also be recognized that the sensors could be electronic and the selector valves operated by solenoids. Such changes are to be considered as within the scope of this invention. It will be recognized that other changes can be made in the construction of this invention without departing from the principles of the invention. Such modifications are to be considered as within the scope of the hereinafter appended claims, unless these claims by their language expressly state otherwise.

I claim:

1. A work holder having a collet with work clamping jaws and means mounting said collet for reciprocating movement between a first position and a second position and a regulator element for controlling the reciprocation of said collet; a first actuator for continuously reciprocating said collet between said positions; a second actuator for opening and closing the jaws of said collet; said regulator element activating said second actuator to close the jaws of said collet when said collet reaches said first position; a delay member connected to said regulator element for causing said collet to dwell during the closing of said jaws at said first position; a speed control member operatively associated with said collet for varying the speed of travel of said collet during at least one portion of its movement in one direction, said speed control member being a dual chambered dash pot having a pair of pistons one in each chamber mounted on a common rod; both of said chambers being fluid filled; an arm connecting said rod to said collet and adjustable means on said rod cooperating with said arm and forming a lost motion connection between said rod and said arm; a restricted passage connecting said chambers for the passage of fluid when said collet and rod are moving in said one direction; a check valve connecting said chambers and openable to permit the free flow of fluid therebetween when said collet and rod are moving in the opposite direction. 7

2. A work holder as described in claim 1 wherein said speed control member has an adjustable valve member mounted in said restricted passage for prcdetermining the speed of travel of said collet during said one portion of its movement.

3. A work holder having a collet with work clamping jaws and means mounting said collet for reciprocating movement between a first position and a second position and a regulator element for controlling the reciprocation of said collet; a first actuator for continuously reciprocating said collet between said positions; a second actuator for opening and closing the jaws of said collet; said regulator element activating said second actuator to close the jaws of said collet when said collet reaches said first position; a delay member connected to said regulator element for causing said collet to dwell during the closing of said jaws at said first position; a workpiece positioning element in said collet; stop means urging said positioning element into workpiece intercepting position when said collet is in said first position; resilient means urging said positioning element into retracted position removed from the opening between said jaws when said jaws are open and said collet is adjacent said second opening.

4. A fork holder as described in claim 3 wherein said position-ing element is a pair of fingers and a spring biasing said fingers into retracted position; said stop means being a resilient stop engaging said fingers and shifting them against one jaw of said collet as said collect ap proaches said one position.

5. A fork holder as described in claim 4 wherein sai one jaw has reliefs in the face thereof to partially receive said fingers; the other jaw of said collet being recessed to receive said fingers when they are retracted by said spring.

6. In a work holder designed to hold and move a work piece past the tool of a machine, said work holder having a pair of jaws forming a work clamping collet and a supporting way on and along which said collet may slidably travel between work piece receiving and work piece releasing positions; first actuator means mounted to said collet for travel therewith and for opening and closing said jaws of said collet; second actuator means for moving said collet lengthwise of said ways, the improvement in said work holder comprising: a first sensor tripped by said first actuator when the jaws of said collet reach closed position at said work piece receiving position; said first sensor being operatively connected to said second actuator for initiating retraction travel of said collet past the tool; a second sensor actuated by said collet at the limit of its travel toward work piece releasing position, operatively connected to said second actuator for reversing its direction of travel; a third sensor actuated by said collet upon initiation of its advance travel toward work piece receiving position'and operatively connected to said first actuator for reversing its travel and opening said jaws for releasing the work piece as said collet returns to its work piece receiving position; a speed control element operatively connected to said collet for sensing the position thereof along said way and for varying the rate of travel of said collet in response to its position on said way; a work piece positioning member mounted on one of said jaws; a spring biasing said positioning member into retracted position toward said one jaw and removed from the opening between said jaws; means at said work piece receiving position engaging said positioning member and urging it into advanced work piece intercepting position between said jaws.

7. A work piece holder as described in claim 6 wherein said one jaw is recessed to receive said positioning mem her when it is retracted.

8. A work piece holder as described in claim 7 wherein all of said sensors are mounted for adjustment lengthwise of said way for increasing or decreasing the distance traveled by said collet.

9. A work holder having a collet with work clamping jaws and means mounting said collet for reciprocating movement between a work piece receiving first position and a second position; a first actuator for continuously reciprocating said collet between said positions; a second actuator for opening and closing the jaws of said collet; said second actuator opening said jaws of said collet during the collets return movement from its second to its first position; a stop member engaging one of the jaws of said collet as said collet approaches said first position, said stop member restraining further movement of said one jaw to effect a partial closing of said jaws by cont-inued movement of the other of said jaws.

10. A work holder as described in claim 9 wherein a work piece positioning element is provided in said collet; stop means urging said positioning element into work piece intercepting position when said collet is in said first position; resilient means urging said positioning element into retracted position removed from the opening between said jaws when said jaws are removed from said first position.

11. A work holder as described in claim 10 where-in said stop means is resiliently mounted and resiliently urging said work positioning element against the other of said jaws, said stop means permitting said work positioning element to travel with said other jaw against the bias of the stop means resilient mounting.

12. A work holder having a collet with work clamping jaws and means mounting said collet for reciprocating movement between a work piece receiving first position and a second position and a regulator element for controlling the reciprocation of said collet; a first actuator for continuously reciprocating said collet between said positions; a second actuator for opening and closing the jaws of said collet; said regulator element activating said second actuator to open said jaws of said collet after said collet has reached said second position and has initiated its return movement toward said first position to discharge a work piece during its return movement.

13. A work holder having a supporting way and a collet mounted thereon for reciprocation therealong, a first actuator for reciprocating said collet along said way from a work piece receiving position to a work piece completed position remote therefrom and returning said collet to said work piece receiving position, said collet having a pair of work piece receiving jaws and a second actuator for opening and closing said jaws, the improvement in said work holder comprising: said second actuator closing said jaws when a new work piece has been received therebetween; a delay member connected to said first actuator for causing said collet to dwell during the closing of said jaws at said work piece receiving position; a member sensitive to and actuated by the resistance pressure exerted by said jaws when fully closed upon a work piece deactivating said delay member to initiate travel of said collet toward said work piece completed position.

14. A work holder having a collet with work clamping jaws and means mounting said collet for reciprocating movement between a first position and second position and a regulator element for controlling the reciprocation of said collet; a first actuator for continuously reciprocating said collet between said positions; a second actuator for opening and closing the jaws of said collet; said regu lator element activating said second actuator to close the jaws of said collet when said collet reaches said first position; a dash pot having a piston and a cylinder, one of said piston and cylinder being secured against lineal movement and the other having a lost motion connection to said collet for varying the speed of travel of said collet during at least a portion of the collets movement from said first to said second positions.

References Cited UNITED STATES PATENTS 1,355,167 10/ 1920 Rich 9-0-21 1,976,105 10/1934 Archea -21.5 2,542,986 2/1951 Bowen 9021.02 2,577,766 12/1951 Johnson et a1 90-21.02 2,582,012 1/ 1952 Currier 90-2102 FRANCIS S. HUSAR, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,391,606 July 9, 1968 Sylvan J. Kaminga It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 15, "upon initiation of return movement to work piece clamping of the work piece" should read and initiating advance movement upon proper clamping of the work piece Column 2, line 1, "moves the work piece" should read devices which are automatically removed as the machine moves the work piece Column 4, line 35, "The

sensors

64 and 64" should read The

sensors

64 and 65 Column 8, line 42, "A fork holder" should read A work holder line 48, "A fork holder" should read A work holder Signed and sealed this 13th day of January 1970.

(SEAL) Attest:

Edward M. Fletcher, Jr.

Attesting Officer Commissionerof Patents WILLIAM E. SCHUYLER, JR,