US3313393A

US3313393A - Pallet transfer device

Info

Publication number: US3313393A
Application number: US495749A
Authority: US
Inventors: Frank A Solski; Lyman K Shepard
Original assignee: Standard Tool & Manufacturing Co
Current assignee: Standard Tool & Manufacturing Co
Priority date: 1963-06-17
Filing date: 1965-09-17
Publication date: 1967-04-11
Anticipated expiration: 1984-04-11

Description

April 1967 F. A. SOLSKI ETAL 3,313,393

PALLET TRANSFER DEVICE 6 Sheets-Sheet 1 Original Filed June 17, 1963 6 Sheets-Sheet 2 9 1 O 0 A 4 w w w W F. A. SOLSKI ETAL PALLET TRANSFER DEVICE Original Filed June 17, 1963 April 11, 19s? 1 Kg. w My m y K mg y j April 11, 1957 F. A. SOLSKI ETAL PALLET TRANSFER DEVICE 6 Sheets-Sheet 5 Original Filed June 17, 1963 W W W? W I; Z 2

April 11, 1957 F. A SOLSKI ETAL 3,313,393

PALLET TRANSFER DEVICE Original Filed June 17, 1963 6 Sheets-Sheet 4.

April 11, 1967 F. A. SOLSKI ETAL PALLET TRANSFER DEVICE Original Filed June 17, 1963 6 Sheets-Sheet 5 INVENTOR S'.

F. A. SOLSK] ETAL PALLET TRANSFER DEVICE Apr-i111, 1967 6 Sheets-Sheet 6 Original Filed June 17, 1963 United States Patent Ofifice 3,313,333 Patented Apr. 11, 1967 3,313,393 PALLET TRANSFER DEVICE Frank A. Solslri, Bloomfield Hills, Mich, and Lyman K.

Shepard, Upper Saddle River, N..l., assignors to Standard Tool & Manufacturing Company Original application June 17, 1963, Ser. No. 288,389, new Patent No. 3,237,759, dated Mar. 1, 1966. Divided and this application Sept. 17, 1965, Ser. No. 495,749 6 Claims. (Cl. 198-25) This application is a division of application Ser. No. 288,389, filed June 17, 1963, now Patent No. 3,237,759.

This invention relates to pallet transfer devices and particularly to a lowering and raising device which transfers pallets from one to another conveyor at opposite ends of a machine.

In a copending application of Solski et al., Ser. No. 266,264, filed Mar. 19, 1963, now US. Patent No. 3,271,- 840, for Automatic Machining Device, a machine is illustrated and described having a bed on which transverse bolsters are mounted for supporting ways on which pallets are advanced in steps from one to the other end of the machine. At each end of the machine, elevating and lowering mechanisms are provided which are capable of transferring the pallets between the end stations and a return conveyor in the base of the machine.

The present invention has raising and lowering mechanisms and a conveying system which are improvements over those of the above-mentioned application for Letters Patent. The return conveyor is located along one side of the base to lower the height of the machine and to have a greater coolant capacity in the tanks within the base. The raising and lowering mechanism employs a rotary motion for transferring the pallets between the two conveyors. Such structure is not to be thought of as superseding the mechanism of the above set forth application but rather as a supplement thereto which can be employed advantageously for certain applications.

The transfer mechanisms located at each end of the machine are of exactly the same construction except being of the opposite hand as the mechanism-s face each other. The conveying mechanisms embody a hub having a plurality of arms thereon herein illustrated as having three arms disposed 120 apart on each of which a forked carrier is swingably mounted and connected to a control arm fixed to the spindle thereof. A similar control arm is secured to the fixed spindle on which the hub rotates near the end of which the center of a Y-shaped leveling element is pivoted. The leveling element has three arms disposed 120 apart with the ends pivoted on the control arms of the forked carriers at a distance from the centers of the spindle which is the same as that of the center of the leveling arm from the center of the hub spindle. With this arrangement the control arms on the forked carriers are maintained at approximately 45 from the vertical at all times throughout the 360 rotation of the hub thereby maintaining the forks of the carriers horizontal in all positions.

Accordingly, the main objects of the invention are: to provide 120 spaced arms on a driven hub on which pivoted forked carriers are retained in horizontal position at all times by a Y-shaped element which maintains crank arms on the carriers in parallel relation with each other and with a fixed arm on the stationary hub spindle; to employ the advancing bar of the machine for moving pallets to and from the fingers of the forked carriers of the transfer devices from and to the Ways of the machine, to synchronize the movement of the transfer devices with the movement of the pallets in the machine so that the devices are advanced only after the pallets have been moved to the next station of the machine, and in general,

to provide a pallet transfer device at each end of a machine which is simple in construction positive in operation and economical of manufacture.

Other objects and features of novelty of the invention will be specifically pointed out or will become apparent when referring, for a better understanding of the invention, to the following description taken in conjunction with the accompanying drawings, wherein:

FIGURE 1 is a broken perspective view of a machine having transfer devices at the opposite ends thereof embodying features of the present invention;

FIG. 2 is an enlarged perspective view of one of the pallets employed in the machine illustrated in FIG. 1 as viewed from the point 2 thereof;

FIG. 3 is an enlarged broken sectional view of the structure illustrated in FIG. 4, as viewed from the point 3 thereof;

FIG. 4 is an enlarged sectional view of the structure illustrated in FIG. 3, taken on the line 44 thereof;

FIG. 5 is an enlarged broken sectional view of the structure illustrated in FIG. 4 taken on the line 5-5 thereof;

FIG. 6 is an end view of the structure of FIG. 5 as viewed from the point 6 thereof;

FIG. 7 is a broken plan view of the structure illustrated in FIG. 4;

FIG. 8 is an enlarged broken sectional view of the structure illustrated in FIG. 3, taken on the line 88 thereof;

FIG. 9 is an enlarged sectional view of the structure illustrated in FIG. 8, taken on the line 99 thereof, and

FIG. 10 is an enlarged view in side elevation of the structure illustrated in FIG. 8.

In FIGURE 1, a machine 16 is illustrated which may be of any length having any number of stations thereon at which work is to be performed. A base 11 supports longitudinal stringers 12 across which bolsters 13 are mounted for supporting tools which operation on the workpiece carried by pallets 14 in a fixture 15 mounted thereon. The fixtures may take any form depending upon the type of workpiece to be machined and the type of machine operations which are to be performed thereon by the tools of the machine.

The pallet, as illustrated in FIG. 2, is square so that it can be turned through and advanced on the ways of the machine and a square spacer 16 is mounted between the pallet 14 and the fixture 15. The spacer is of reduced dimension to provide recesses 1'7 along the edges of the pallet which slide along fingers 13 of the fork carrier 19 when moved from or onto the ways 21 of the machine. As illustrated in FIG. 5, each of the fingers 18 has a recessed detent 22 rockable on a pin 23 against a spring pressed lunger 24. The corners of the spacer 16 are of arcuate form 25, the outermost corners being engaged by the extensions 26 on the detents to retain the pallet on the fingers 18. The cam relationship between the corners 25 of the spacer and the extension 26 of the detent, permits the pallet to be advanced from the fingers or advanced thereinto by sliding over the extension 26 which is deflected by the cam surface 27 on the forward end thereof. In this manner, the pallets with the fixture and workpiece thereon are advanced into and from the fingers of the fork carriers at the ends of the ways of the machine and at the return end of the return conveyor.

At the finishing end of the machine, the pallet removed from the ways is delivered onto the return conveyor which is continuously operating and which advances the pallet from the carrier fingers. The advancing mechanism for the machine 12 embodies sections of joined rods 30 having pins 31 extending therefrom in pairs to project upwardly at the front and rear edge of the pallet when the rod 30 is rotated to have the pins disposed vertically. The pallets 14 are accurately located in the ways 21 by rail members 32 which have extending flanges 33 projecting into the recesses 17 at the sides of the pallet. This accurately aligns the recesses of the pallet with a flange 34 on the fingers 18 to permit the recesses 17 to pass over the flanges 34 upon the next advancement of the rods 30 toward the finish end of the machine. Stop faces 35, as illustrated in FIGS. 6 and 7 limit the advancement of the pallet on the fingers 18. The stop faces 35 are located at the end of blocks 93 which are accurately positioned by a dowl 94 and secured by screws 95 to the bottom of the yoke 84 in alignment with the recess 96 along the bottom inner face of the fingers 18 of the fork carriers. The pallet slides along the recesses 96 and abuts the face 35 of the blocks 93 to locate the spacer 16 of the pallet assembly so that the extending end 26 of the detents engage the curved surfaces 25 at the extending corners of the spacer. This operation obtains for the transfer device 36 at the starting end of the machine, the facing transfer device 37 at the finishing end of the machine being structurally the same, but is located to receive the endmost pallet at the finish end of the machine.

A bracket 41 supports a housing 42 in which the teeth of a gear 43 meshes with the teeth of a gear 44 keyed to a shaft 40 in bearings 45. The shaft 40 also carries a pinion gear 46 which has teeth in mesh with a ring gear 47 having its teeth on the exterior surface thereof. The ring gear is located by dowls 49 on a rotatable hub 48- to which it is secured by screws 50. The cylindrical flange 51 of the housing 49 is closely contacted by the hub 48 and the encompassing flange 50 thereof to form a chamber 52 which contains a grease for the gears. The hub 48 has three equally spaced arms 53 extending therefrom 120 apart, a rib 54 strengthens the connections of the arms with the hub. The hub has a central sleeve 55 containing bearings 56 mounted for rotation on a stub shaft 57 which is located by dowls 58 and secured by screws 59 to the housing 42. The sleeve 55 rotates between a pair of end washers 62 and 63, all of which are retained in position on the stub shaft 57 by a rectangular plate 64, which is secured by a tongue and groove connection 65 to the stub shaft 57 fixed thereto by a screw 66. The plate 64 is secured at approximately 45 to the vertical on the end of the stub shaft. A Y-shaped leveling element 67 has three arms 68 extending from a central aperture 69 containing a sleeve bearing 71 which pivots on a stub shaft 72 secured to the rectangular plates 64 by a screw 73 extending from the stub shaft. Each of the arms 68 is attached to a stub shaft 72 extending through the sleeve bearing assembly 71 in the aperture 69 at the ends of the arms for pivotally connecting the arms to rectangular plates 74. The plates 74 are similar to the plate 64 and are fixed to stub shafts 75 on the ends of the arms53 by a screw 66 and a tongue and groove connection 76. The rectangular platcs64 and 74 function as crank arms and are retained parallel at an angle of approximately 45 to the vertical, at all times. The stub shafts 75 operate in sleeve bearings 77 between end washers 78 at the end of each of the arms 53.

The stubs shaft 75 has a flange 81 thereon from which a cylindrical boss 82 extends. An aperture 83 in a triangular-shape yoke 84 extends over the boss 82 and is positioned by a dowl 8-5 and secured by screws 86 extending into the flange 81. The yoke has the pair of fingers 18 extending therefrom to form a fork for the reception of a pallet having a work supporting fixture thereon. The Y- shaped element 68 maintains the crank arm 74 parallel to the crank arm 64 at all times. By maintaining the crank arm 74 in the same position at all times, the fingers 18 of each fork carrier will remain in a horizontal plane in all positions of rotation of the hub 48.

As illustrated in FIG. 7, the pallet 14 disposed within the fork carrier 19 is aligned with the ways 21 of the machine. The pallet is in position to be engaged by the endmost pin 31 when the rod 30 has advanced to the left and has been rotated 90. The pin slides the pallet from the fingers 18 onto the ways 21 when the rod 30 is moved to the right, which movement advances all of the pallets 14 along the ways 21 to the next succeeding station at which a work operation is to be performed. The fork carrier 19 of the transfer device 36 is located at station A while the next succeeding fork carrier 19 is located at station B. The fork carrier located at station B is aligned with the endmost pallet 14 on a return conveyor 97 which advances the pallets from the finishing end of the machine to the starting end thereof. The pallet is advanced at station B into the fingers 18 of the fork carrier and is retained therein by the detents 22. The third fork carrier 19 is located at station C and has a pallet 14 supported therein. Upon the next rotation of the hub 48 clockwise as illustrated in FIG. 1, the pallet at the station C will be advanced to station A and the empty fork carrier at the stat-ion A will be advanced to the station B. The fork carrier at the station B with the pallet from the conveyor 97 therein will advance to the station C. The fork carrier advanced to station B will be aligned with the conveyor 97 in position to receive the pallet 14 at the end thereof. Upon the return movement of the rod 30 to the left, as viewed in FIG. 7, upon its 90 rotation, the pins 31 will be positioned on either side of the pallet which will be advanced onto the ways 21 when the rod 31 is again advanced toward the finishing end of the machine. The pallet 14 at the station A, rests upon spaced rails 154 mounted on a top plate of a bracket 156. When the pallet 14 is advanced from the fork carrier, guide elements 157 having sloping side and bottom surfaces engage the forward corners of the pallet and accurately guide it onto the rails 21.

The transfer device 37 at the opposite or finishing end of the machine will have the fork carrier at station A disposed in alignment with the ways 21 to receive the pallet 14 having the finished workpiece thereon. The pallet will be advanced onto the fingers 18 by the pins 31 on the rod 30 when the rod is advanced toward the finishing end of the machine. The fork carrier at the station B will hold a pallet 14 for advancement to station C while the fork carrier at the station C has delivered its pallet to the conveyor 97. Upon the counterclockwise rotation of the hub 48 as viewed in FIG. 1, the fork carrier at station B will deposit its pallet onto the conveyor 97 while the pallet on the fork carrier at the station A will be advanced 120 to the station C. The fork carrier at the station C will move upwardly to the station A with its fingers 18 aligned with ways 21 at the flushing end of the machine for receiving the endmost pallet when the rod 30 advances it therefrom.

Automatic means may be provided for removing and inserting a new workpiece in the fixture 15 of either transfer device. The finished workpiece may -be removed and a new workpiece to be machined may be inserted in the fixture manually. Such a change of workpieces may be performed in the transfer device 36 at the station B before the pallet is advanced to station A or in the device 37 at the station B before the pallet is advanced to station C.

The shaft 88 of the gear 43 is connected to a shaft 89 of a motor 92 by a key 91. The motor 92 is preferably of the fluid type, driving the shaft 89 at an accelerated speed until near the end of the 120 advancement of the hub 48 when the speed is reduced and the hub 48 substantially stopped.

A stop pin 98 is carried by the housing 42 within a bushing 99 to accurately position the hub 48 in each of the 120 positions of advancement. A tapered end 101 of the pin 98 enter the tapered end of one of three bushings 102 secured to the hub 48 by a plurality of screws 103. A piston within a cylinder 104 ope-rates a piston rod 105 which is releasably connected by the head of a screw 106 to the stop pin 98. The opposite end of the rod 105 carries a pair of

washers

107 and 108 which operate switches 109 and 111. In the advance position of the stop pin 98, the washer 107 actuates the switch 109 while the washer 108 has moved out of engagement with the operating finger of the switch 111.

After the stop pin 98 been withdrawn, the motor 92 is energized for driving the hub 48 toward the next 120 stop position. The fluid motor accelerates to drive the gears and hub to advance the fork carriers toward the next 120 positions. As the hub approaches the 120 positions, the motor is rapidly decelerated and stopped when the stop pin 98 is advanced to engage a bushing 102 to therefore acurately locate the hub and the fork carriers at the end of each 120 advancement. The hub is provided with a ring 112 having three sloping cam surfaces 113 capable of engaging a ball 114 of a plunger 115 which engages a wheel 116 on a plunger 117 of a valve 118. As the ball rides up the cam surface 113, it depresses the plunger 117 thereby progressively cutting off the flow of fluid to the fluid motor 92 and thereby rapidly decelerating the motor and the driving of the hub 48 to the next 120 stop position. The ring 112 is supported by bolts 119 eX- tending through slots 121 in the hub which permits the ring to be accurately adjusted to locate the stop positions. When the switch 109 is energized upon the advancement of the pin 98, a circuit is completed which permits the transfer bar 30 to be operated in the normal sequence of operation of the machine. This operation can only occur when the stop pin 98 is in forward position and when in such position the hub 48 and the fork carriers cannot be advanced. When the stop pin is retracted, the switch 111 completes a circuit which permits a valve to be energized in the normal operation of the machine cycle for delivering fluid to the motor 92 in a circuit shunted about the circuit of the valve 118 which remains depressed until the hub advances to have the cam surface 113 pass over the ball 114 to permit the plunger 117 to retract. A dog 122 is carried on the end of each of the arms 55 in position to strike an arm 123 of a switch 124 for the purpose of operating a valve for admitting fluid to the cylinder 104 to advance the stop pin 98 at each 120 advancement of the hub 48.

A switch actuating arm 125 extends from a quadrant 126 which is mounted on a pivot 127. The quadrant and arm are urged upwardly by a spring 128, the former being stabilized between the ends of pins 129 carried by arms 131. A block 132 extends at right angles to the end of the arm 125 and is provided with a slot to receive a roller 133 pivoted on a pin 134. As illustrated in FIGS. 3 and 7, when a pallet is disposed in the device 36 located at station A, it engages the roller 133 and deflects the arm 125 downwardly to have an extending block 135 operate an arm 136 of a switch 137. The block has an adjusting screw 138 which is set to assure the operation of the switch when the roller 133 on the arm 125 is deflected by a pallet. The switch 137 prevents the transfer device 36 from being operated when the pallet is located at station A. When the pallet is removed, the spring 128draws the arm 125 upwardly and the arm 136 of the switch 137 is moved to its initial position. When the arm 125 is depressed, the switch 136 also sets up a circuit which permits the bar 30 to be drawn towards the finishing end of the machine after the cycle of machine operations are completed. If no pallet is present the arm 125 is not deflected and the bar 30 cannot be advanced.

The conveyor 97 is composed of two silent chains 139 which are driven over a pair of sprockets 141 and 142 at the opposite ends of the machine. The chain runs ride in troughs 143 .at the top and 144 at the bottom of the conveyor. The chains have central guides which engage central recesses in the teeth of the sprocket to main tain the chains aligned thereon. The sprockets 142 are mounted on a shaft 145 carried by spaced plates 146. The plates are aligned with screws 147 by which the plates 146 and sprockets 142 are moved outwardly of the end of the machine to tighten the chains. Studs 148 on the frame of the conveyor extend through slots 149 in the plates 146 to secure the plates in adjusted position. The

sprockets 141 are driven by a shaft 151 through a speed reducer 152 from a motor 153. The chains are driven continuously and the speed may vary over a substantial range, a speed of 2 feet a second has proven satisfactory.

A plunger 158, as illustrated in FIG. 4 is disposed in the path of advancement of the pallet 14 on the conveyor 97 at the starting end of the machine urged toward the endmost pallet by a spring 159. When the plunger 158 is deflected by a pallet sufliciently to assure the complete advancement of the pallet in the fingers 18, a rod 161 on the plunger engages an arm 162 of a switch 163. If the arm is no longer deflected, the switch 163 permits the operation of the valve to reverse the flow of fluid to the cylinder 104 to retract the stop pin 98. When this occurs, switch 111 is energized to operate a valve which bypasses the decelerating valve 118 and provides a flow of fluid to the motor 92 to drive the hub 48. As the pallet is advanced by the conveyor 97 to station C from which they are raised, the endmost pallet strikes a lockout detent 170 which is aligned with the slot 17 formed by the spacer 16 with the pallet. The

end

164 or 164 will be struck by the spacer 16 and the shock of the striking force is taken by a spring 165 on the slide block 166 supporting the detent. The detent is secured to the block by a pivot pin 167 with the end 164' having an extending finger 168 containing a downwardly facing slot 169. A pin 171 carried by an L-shaped bracket 172 is supported on a boss 173 and guided on a pin 174 in a sleevelined aperture 175 in the boss. The downwardly eX- tending portion of the bracket 172 is connected to a piston rod 176 of a piston within a cylinder 177. When a pallet is to be advanced, the piston rod 176 is moved to the left as viewed in FIG. 8, rocking the detent 170 clockwise, thereby releasing the forward end of the spacer 16 and the pallet 14 while having the end 164 engage the spacer of the next succeeding pallet and thereby retaining it from advancing. When the piston rod 176 is moved to the right, the arm 178 of a switch 179 is released by a washer 181 on the remote end of the piston rod from that engaging the bracket 172. The washer 181 strikes an arm 182 of a switch 183 to operate the contacts thereof.

A pivoted shaft 184 carries an arm 185 which is urged upwardly into the path of the pallet by a spring 186. The arm carries a stop finger 187 having an adjusting screw 188 thereon for limiting the upward movement of the arm 185. The shaft has an arm 189 fixed thereto supporting an adjusting screw 191 which engages the arm of a switch 192. As the pallet is advanced, the forward edge engages the arm 185 and causes it to deflect to thereby operate the switch 192 near the end of its advancement. When passing beyond the arm 185, the spring 186 urges the arm upwardly and prevents the pallet from rebounding from the fingers of the fork carrier. The closing of the contacts of the switch 192 removes another lockout which prevented the transfer device 36 to operate until the pallet is locked within the carrier.

The conveyor 97 is supported on uprights 280 having cross members 281 carrying longitudinally extending rails 282 which support the upper channel members 143. Cross members 203 are secured to the lower part of the uprights and support an upwardly presenting channel member 204 on which the channel members 144 are secured. Uprights 205 having cross members 206 at the top are joined by an upper longitudinally extending element 207 and bottom elements 208. Rectangular frames 209 enclose the transfer devices 36 and 37. The frames 209 and the uprights 285 are covered by expanded metal sheets 211 or sheets of other type of screen material. The conveyor 97 and the transfer devices 36 and 37 are enclosed by the screen material and are protected from having articles and large particles fall thereinto.

After machine operations have been employed on the workpieces clamped in the fixtures 15 at all of the stations, and when the pallets carried by the fork carriers are properly located at stations A, B, C, A and B, the

rod 30' is moved to the right, toward the finishing end of the machine. The movement of the rod to the right will advance all of the pallets along the ways 21 and from the fingers 18 of the fork carrier at station A onto the ways adjacent thereto and from the finishing end of the machine into the fingers 18 of the fork carrier at station A. The transfer mechanism 36 will then be advanced 120 clockwise to move the pallet from station B to station A before or after the rod 30 has been moved to the left. At the same time, or subsequent thereto, the transfer device 37 can be advanced 120 counterclockwise moving the fork carrier at station B to station C and moving the fork carrier at the station C to the station A in position to receive the endmost pallet at the finishing end of the machine. The pallet at station B will be moved to the station C onto the conveyor 97 which will advance the pallets from the fingers 18 of the fork carrier. The pallet at the forward end of the conveyor 97 will be moved into the fingers 18 of the fork carrier at station of the transverse device 36 and if the pallets are properly located in the carriers at stations A, C and A, the rod 30 with the pins 31 disposed vertical can advance toward the finishing end of the machine when all of the interlocking servo mechanisms have unlocked the control system. Valves, pistons and cylinders are employed with the transfer devices 36 and 37 and the conveyor 97 interlocked with each other and the devices of the machine to prevent the operation of the machine and the transverse devices at all times when the pallets are not accurately located in the fingers 18 of the fork carriers and when not accurately located at the various stations. The operating mechanism for the rod 30 is locked out and prevented from operating when the transfer devices are being operated or are in condition to be operated. If the transfer devices are not properly located or the pallets are not in proper position either on the conveyor or in the fingers of the fork carriers, the machine and devices will not operate. This interlock also embodies the control for the stop pin 93 which must be in the position to locate the hub before the rod 30 can be advanced with the transfer devices locked out of operation until the stop pin 98 has been retracted.

As has been pointed out hereinabove, the fixture has not been described in detail since the fixtures will take many forms depending upon the type of workpiece and the places thereon at which operations must be performed. The one herein illustrated is merely shown by way of example.

What is claimed is:

1. In a transfer device, a rotatable hub, arms fixed to said hub and spaced a predetermined distance apart, pivoted carriers on said arms, crank arms fixed to and extending from the pivots of the carriers and from the center about which the hub rotates, an element pivoted to the crank arms for retaining said carriers in horizontal planes, said hub arms being spaced an equal angular distance apart, stop means carried by the hub spaced the same distance apart as said hub arms, a pin projectable into said stop means for locating the hub at each advanced position, a machine having one of said transfer devices at each end oppositely disposed to have the hub and arm facing each other, means on said machine for the reception of workpiece supporting pallets which are advanced to stations therealong, and means on said machine located below said pallet advancing means for returning said pallets to the starting end of the machine, said transfer devices at each end of the machine transferring the pallets from and to the advancing means and the returning means.

2. In a transfer device, a rotatable hub, arms fixed to said hub and spaced a predetermined distance apart, pivoted carriers on said arms, crank arms fixed to and extending from the pivots of the carriers and from the center about which the hub rotates, an element pivoted to the crank arms for retaining said carriers in horizontal planes, said hub arms being spaced an equal angular diso tance apart, stop means carried by the hub spaced the same distance apart as said hub arms, a pin projectable into said stop means for locating the hub at each advanced position, a machine having one of said transfer devices at each end, means on said machine for the reception of workpiece supporting pallets which are advanced to sta' tions therealong, a means on said machine located below said pallet advancing means for returning said pallets to the starting end of the machine, said transfer devices at each end of the machine transferring the pallets from and to the advancing means and the returning means, said carrier having spaced fingers thereon for receiving and supporting said pallets.

3. In a transfer device at each end of a machine which advances pallets to stations at which work operations are to be performed on workpieces carried by the pallets, said machine having conveyor means on which the pallets are advanced and a return conveyor on which the pallets are returned to the starting end of. the machine, each said transfer device having a rotatable hub containing spaced bushings, fork carriers having stub shafts located within said bushings, means for preventing said stub shafts from rotating as said hub is rotated and means for driving said hub to distance between said bushings for advancing the fork carriers to the conveyor means and to said return conveyor.

4. In a transfer device at each end of a machine which advances pallets to stations at which work operations are to be performed on workpieces carried by the pallets, said machine having conveyor means on which the pallets are advanced and a return conveyor on which the pallets are returned to the starting end of the machine, each said transfer device having a rotatable hub containing spaced bushings, fork carriers having stub shafts located within said bushings, means for preventing said stub shafts from rotating as said hub is rotated, means for driving said hub the distance between said bushings for advancing the fork carriers to the conveyor means and to said return conveyor, and means for driving said return conveyor for advancing a pallet from a fork carrier of the transfer device at the finishing end of the machine and advance a pallet into a fork carrier of the transfer device at the starting end of the machine.

5. In a transfer dewice at each end of a machine which advances pallets to stations at which work operations are to be performed on workpieces carried by the pallets, said machine having conveyor means on which the pallets are advanced and a return conveyor on which the pallets are returned to the starting end of the machine, each said transfer device having a rotatable huh containing spaced bushings, fork carriers having stub shafts located within said bushings, means for preventing said stub shafts from rotating as said hub is rotated, means for driving said hub the distance between said bushings for advancing the fork carriers to the conveyor means and to said return conveyor, means for driving said eurn conveyor for advancing a pallet from a fork gill: of the transfer device at the finishing end of the machine and advance a pallet into a fork carrier of the transfer device at the starting end of the machine, and means for advancing the pallets on the conveyor means and moving a pallet from a fork carrier of the transfer device at the starting end of the machine onto the conveyor means while advancing a pallet at the finishing end of the machine from the conveyor means into the fork carrier of the transfer device located thereat.

6. In a transfer device at each end of a machine which advances pallets to stations at which work operations are to be performd on workpieces carried by the pallets, said machine having conveyor means on which the pallets are advanced and a return conveyor on which the pallets are returned to the starting end of the machine,

each said transfer device having a rotatable hub containing spaced bushings, fork carriers having stub shafts located within said bushings, means for preventing said stub shafts from rotating as said hub is rotated, means for driving said hub the distance between said bushings for advancing the fork carriers to the conveyor means and to said return conveyor, means for driving said return conveyor for advancing a .pallet from a fork carrier of the transfer device at the finishing end of the machine and advance a pallet into a fork carrier of the transfer device at the starting end of the machine, means for advancing the pallets on the conveyor means and moving a pallet from a fork carrier of the transfer device at the starting end of the machine onto the conveyor means While advancing a pallet at the finishing end of the machine from the conveyor means into the fork carrier of the transfer device located thereat, and stop means on References Cited by the Examiner UNITED STATES PATENTS 8/1960 Heimlecher 198-25 9/1965 Kile 214-46 EVON C. BLUNK, Primary Examiner.

RICHARD E. AEGERTER, Examiner.