Automatic Pallet-Making Machine and Method

This invention relates to pallet-making machines and to methods for automatically assembling and stacking pallets.

Wooden pallets for transporting and storing goods are widely used in commerce and industry. A pallet is constructed by nailing a series of slats to transversely positioned stringers. Pallets are sometimes manually fabricated, but, for large-scale production, semiautomatic fabrication is more economical.

Various types of semiautomatic systems have been used to assist in assembling the components of wood pallets. Many systems require manual positioning of the slats and stringers prior to their semiautomatic nailing together. These systems usually nail only one side of the pallet. To assemble a double-sided pallet, the pallet must be flipped over after nailing one side. None provide automatic stacking of completed pallets.

It is an object of the invention to provide an automatic pallet-making machine which provides for inexpensive, automatic assembly of double-sided wooden pallets.

It is another object of the invention to provide a pallet-making machine which automatically stacks completed pallets.

These objects are achieved by providing a machine and a method for automatically assembling wooden pallets on a horizontally movable reciprocating carrier. The carrier is adapted for horizontal movement along a set of rails. First, as the carrier moves in a forward direction, a series of slat engagement means remove, respectively, the lowest slat in a vertical stack and position the slats in spaced relation on the carrier to form the bottom deck of the pallet. Second, the carrier moves to a position where stringer engagement trip-levers engage the ends of a series of stringers held in a magazine. When the carrier reverses, the trip-levers dispense the stringers. Third, the carrier passes through the slat dispenser in the reverse direction, where another series of slats is dispensed to form the top deck of the pallet. Fourth, the carrier moves through an automatic nailing station where the top and the bottom slats are nailed to the stringers by automatic nailing means. Finally, a vertical stacker automatically removes the pallet from the carrier and adds it to a stack.

FIG. 1 is a plan view of the automatic pallet-making machine according to the invention;

FIG. 2 is a side elevation of the pallet-making machine of FIG. 1;

FIG. 3 is a perspective view of the pallet carrier mounted on rails;

FIG. 4 is a detailed perspective view of a slat trip dog;

FIG. 5 is a detailed perspective view of a stringer trip lever;

FIG. 6 is an exploded, perspective view of a double-sided pallet;

FIG. 7 is a perspective view of a slat magazine;

FIG. 8 is an end perspective view of the stringer magazines for the pallet-making machine;

FIG. 9 is a perspective view of the portion of the pallet machine between the slat magazine and the stringer magazines;

FIG. 10 is a perspective view of the automatic nailing station for a pallet;

FIG. 11 is a perspective view of a nailing gun support mechanism;

FIG. 12 is a side elevation of a pallet ejector and stacking mechanism;

FIG. 13 is a detailed perspective view of an outside pallet-stacking ratchet shown in a disengaged position for removing a stack of pallets from the stacker;

FIG. 14 is a detailed perspective view of a pair of inside pallet-stacking ratchets;

FIG. 15 is a perspective view of a switch actuator operated by the pallet-stacking mechanism; and

FIG. 16 is a detailed perspective view of an outside pallet-stacking ratchet.

FIG. 17 is a perspective view of an alternate slat magazine.

FIG. 18 is a perspective view of the arms and gears of an alternate slat magazine.

FIG. 19 is a schematic of the operation of a slat magazine.

FIGS. 1 and 2 show the principal elements of a pallet-making machine which provides for automatic assembly of double-sided wooden pallets.

FIG. 6 shows a typical pallet having a top platform formed by a series of spaced-apart wooden slats 7 which are nailed or stapled to stringers 8 transversely laid with respect to the slats 7. The bottom platform is formed by another series of slats 9. Various types and configurations of pallets are known in the art and the described pallet-making machine is adaptable to assemble and to fasten a wide variety of pallet configurations.

With reference to FIGS. 1 and 2, a carrier 10 horizontally reciprocates with respect to a frame 12 along a pair of rails 22. Various work stations are located along the frame. A slat magazine 14 stores and dispenses slats from a vertical stack of 1.times.6-inch deck slat boards. A stringer magazine 16 stores and dispenses 2.times.4-inch stringers. A nailing station 18 is provided for fastening the slats to the stringers. A pallet-stacking station 20 removes a completed pallet from the carrier 10 and pushes it beneath a stack of completed pallets.

The carrier 10, shown in FIG. 3, is designed to move along rails 22 which extend the length of the frame 12. The carrier 10 has two longitudinally extending, U-shaped side rails 30 and a cross-member 32 which connects the side rails 30. V-grooved wheels 34 are mounted near each corner of the carrier 10 and roll along the ridged top surface of the rails 22. The hooked ends of the brackets 36 which are connected to the carrier 10 slidably engage the underside of the rails 22 to hold the wheels 34 in engagement with the rails 22. A connecting arm 38 is pivotally fastened at one end to the carriage and at the other end to an endless loop roller chain 40. The chain 40 is supported by a sprocket 42 mounted to a cross-arm of the frame 12. The chain 40 is driven by a conventional gear head motor. The chain 40 moves the carrier 10 from one end to the other and back along the length of the frame 12.

A roller 44 is rotatably mounted to the connecting arm 38 near the chain 40. As the connecting arm is moved in the direction of the arrow 46 (shown in FIG. 3), the roller 44 engages the downwardly slanted near end 47 of a trip bar 48 which is pivotally mounted to the frame by a rocker arm assembly (not shown). The trip bar 48 is normally biased to an upper position, shown in FIG. 3. The roller 44 rolls along the top surface of the trip bar 48 and pushes it downwardly. The trip bar 48 actuates a conventional limit switch which operates to slow the gear head motor driving the chain 40 to approximately half-speed as the carrier passes the nailing station 18. The limit switch also signals the conventional control devices which operate the nail driving mechanism. As the carrier 10 moves in the direction shown by the arrow 46, the trip bar 48 is released when the roller 44 moves past the far end of the trip bar 48, permitting the carrier 110 to resume its normal speed. On its return, the limit switches are not actuated.

A plurality of one-way trip dog assemblies 50 (see FIGS. 3 and 4) are adjustably positioned along each side rail 30 in two parallel rows. The trip dog assemblies 50 include vertically extending support bars 52 which are removably secured to the side rails 30. At the top end of each of the support bars 52, pivotally fastened spring-loaded dogs 54 are positioned (as shown in FIG. 4). The dogs 54 pivot about pins 56 extending from the support bars 54. A spring 58 extends between a tab 60 on the support bar 52 and a tab 62 on the dog 54 and biases the trip dog 54 into a raised position. Pairs of trip dogs 54 (one on each side rail) engage the edges of the bottommost slat in the slat magazine 14 as the carrier 10 moves past the slat magazine. When the carrier moves in the opposite direction, the top edge 66 of the trip dog 54 is pushed downwardly by the edge of the bottommost slat, allowing the trip dog 54 to slip past the slat magazine without dispensing the slat. The slat is caught, however, by the trip dog 54' and dropped onto the carrier.

FIGS. 3 and 5 show spring-loaded trip-lever assemblies 70 for one-way engagement with an end of a stringer. One assembly is attached near the middle of the carrier cross-member 32 and the others, to the ends of each of a pair of adjustably positioned slide-bars 72. Each assembly 70 includes a base plate 74 which pivots in a horizontal plane about a pin 75 fastened to the slide-bar 72. A screw-threaded axle 76 is horizontally and pivotably mounted through a threaded aperture in an extended portion 78 of the base plate 74. One end of an offset lever arm 80 is fixed to a first end of the axle 76. The axle 76 is bent upward near its middle as shown. A coil spring 82 is stretched between the upturned second end of the axle 76 and the uppermost end of a right-angled support rod 84 which is welded to the slide-bar 72 as shown. The spring 82 pulls the axle 76 so that the lower part 85 of the offset lever arm 80 is stopped against the top surface of the base plate 74. The design of the assembly 70 permits the offset lever arm 80 to pivot vertically and horizontally to slide past the stringer magazine, as will be described. After the assembly 70 clears the stringer magazine, the offset lever arm 80 snaps into the position shown in FIG. 3, permitting the free end 86 of the lever arm to engage a stringer and to dispense it endwise from a storage magazine when the carrier reverses.

The magazine 14 for a stack of slats 102 (shown in FIG. 7) includes a vertically extending guide channel 90 adjustably positionable on the frame. The guide channel 90 includes a vertically extending back panel 92 and a pair of oppositely spaced side panels 94,96 which obliquely extend from the side panel 92 as shown. The lower end of the channel 90 terminates in an angle bracket 98 which extends downwardly from the lower end of the back panel 92 and which has a horizontally extending shelf portion 100 for holding the end of a deck slat.

A guide bracket 110 is adjustably positionable on the side of the machine opposite the guide channel 90. The bracket 110 has an upper end 112 which angles outwardly and a lower end terminating in an angle bracket 114 which performs the same function as the oppositely positioned angle bracket 98. A vertically extending rail 116 serves as a stop for the stack of slats 102. The angle brackets 98,114 each have clearance on each side so that a slat may be horizontally removed from the bottom of the vertical stack of slats 102 by a pair of trip dog assemblies 50. A pair of guide bars 118 push a slat downwardly after the slat is dispensed from the stack.

In operation, as the carrier 10 moves beneath the slat magazine 14, a one-way trip dog assembly 50 on each side rail 30 (as shown in FIG. 3) engages the bottom slat of the stack 102 and pushes the slat onto the carrier 10. Some assemblies 50 along the length of the carrier 10 are arranged to dispense slats as the carrier moves in a forward direction, while other assemblies 50 are arranged to dispense slats when the carrier 10 moves in the reverse direction. The movement of the carrier 10 in the forward direction dispenses slats for the bottom deck of a pallet, while movement of the carrier 10 in the reverse direction dispenses slats for the top deck.

An alternate means for dispensing slats is shown in FIGS. 17-19. Two shafts 400 and 402 extend substantially perpendicular to the carrier's movement. Each shaft 400 or 402 has a plurality of crescent-shaped arms 404 projecting from it. The arms 404 on shaft 400 are designed to extend toward the right in their operative position, while the arms of shaft 402 extend toward the left. The arms 404 hold a stack of slats when in the operative position and allow slats to be slid from the stack in the directions in which they extend. The arms 404 on shaft 400 are slightly offset from those on shaft 402 so that both sets of arms may contact the bottom slat of the stack simultaneously (as shown in FIG. 17).

In operation, the slats lie on the arms 404 of shaft 400. The carrier 10 moves toward the right to engage slats for the bottom deck. When the carrier 10 reaches the stringer magazine assembly 16, the roller 44 engages a trip bar 406 which activates a limit switch 409 to turn shaft 402. The turning is coordinated as follows (FIG. 19). The limit switch activates a pneumatic cylinder 411 which draws rack 412 to the left to turn gear 414. Gear 414 is keyed to shaft 402 and turns the arms to contact the bottommost slat. Simultaneously with that contact, the roller contacts a second trip bar 407 to activate a limit switch 408, pneumatic cylinder 410, rack 416, and gear 418 to turn shaft 400. As the carrier 10 returns through the slat magazine, a top deck of slats is dispensed. At the nailing station 20, a second set of trip bars 420 and 421 is contacted, which activates the limit switches to reverse the process just described. Thus the arms of shaft 400 recontact the slats, while the arms of shaft 402 rotate out of the way.

FIG. 8 shows a stringer magazine assembly 16 which includes three chutes 120. Each chute 120 is designed to be loaded with a plurality of 2.times.4 stringers. A chute 120 includes an inclined feed table 122 which has upturned side rails 124 formed along its front and back edges. Stringers 8 are positioned with their ends adjacent the rails 124 and with their wider sides lying against the inclined table 122. The stringers 8 slide by gravity into a curved throat portion 126. At the bottom end of the throat 126, an inwardly extending lip 128 supports a narrower side of the bottom stringer.

In operation, as the carrier 10 moves forward past and beneath the stringer magazine, the offset lever arms 80 spring back until the carrier reaches the far end of the assembly. The lever arms 80 then recoil so that their free ends 86 can engage the ends of the lower stringers 8 in the respective magazines. As the carrier 10 moves in the reverse direction, each lever arm slips along the opening slot provided by the lip 128 to draw a stringer 8 out of each chute. The stringers 8 are longitudinally aligned on their narrower sides along the direction of motion of the carrier 10 transverse to the bottom slats 9.

As shown in FIG. 10, a nailing station 18 includes a plurality of pneumatically operated nailing gun assemblies 130 for driving nails 132 through upper slats 7 and lower slats 9. The assemblies 130 are positioned on opposite sides of a series of stringers 8. The nails 132 are attached to tapes to form chains which are contained in magazines 133. The nails 132 are automatically dispensed by the nail guns. Each of a pair of conventional light source/receiver modules 134 is positioned above the path traversed by a pallet. Each module projects a light beam onto a mirror 136 located below. The light beam is reflected back from the mirror 136 to the module 134. A pallet interrupts the light beam to activate conventional pneumatic control devices (not shown) for a plurality of air-operated cylinders 138. The pneumatic control devices are armed initially by the roller 44 depressing the trip bar 48, shown in FIG. 3. Each cylinder 138 moves a vertically movable support plate 140 against the biasing force provided by a spring 142 (which is connected at one end to the movable support plate 140 and at the other end to a fixed support bracket 143). Each movable support plate 140 has a conventional pneumatically operated nail gun 145 mounted thereon which is actuated when its head 147 contacts the surface of a slat. The nail guns 145 are guided by a pair of rods 148 which slide within cylindrical guides 149 fixed to the movable support bracket 140. Each end of the cylinder 138 is respectively coupled to the plate 140 and the bracket 144 by a pin 150. The cylinder 138 is operated by air from a pressure source controlled by the light source/receiver modules 134. As shown in FIG. 10, the rods 148 are pivotally mounted to a bracket assembly 152 which permits the nailing gun assemblies 130 to pivot if a jam develops. A spring 154, attached between a rod 156 fixed to the frame and the plate 140, provides a biasing force to keep the nailing guns 145 vertically aligned.

In operation, a series of nails 132 are inserted into the top and bottom sides of a pallet. The nailing guns 145 are moved into contact with the top slat 7 and bottom slat 9 of a pallet by means of the air cylinders 138, controlled by the light source/receiver modules 134. The carrier 10 is slowed to approximately half-speed as the carrier passes through the nailing station in the direction of the arrow 46 shown in FIG. 3.

After the pallet components have been nailed together at the nailing station 18, the carrier, with a completed pallet thereon, moves to the stacking station 20, shown in FIG. 12. A carrier-sensing switch assembly 200, shown in FIG. 15, includes an electrical assembly switch 202 and a roller 203 which is mounted on a pivotable bracket 204 biased by a spring 206 away from the switch 202. The entire assembly is mounted to move with the end of a connecting arm 210. As the carrier 10 moves to the end of the rails, a cam bar 212 horizontally fixed to the carrier 10 engages the roller 203 and pushes the roller so that the pivotable bracket 204 contacts and actuates the electrical switch assembly 202. The electrical switch assembly 202, when actuated, disables the gear head motor 220 (shown in FIG. 12), which drives the roller chain 40 connected to the carrier 10. The switch 202 also activates a solenoid-operated air valve (not shown) which controls the operation of an air cylinder 222 which causes the connecting arm 210 to pivot toward the end of the pallet-making machine. The roller 203 moves in an arc on the end of the arm 210 and rolls along a curved bar 213. When the roller moves past the end of the bar 213, the roller 203 and the bracket 204 are biased away from the roller switch assembly 202, the air supply to the air cylinder 222 is cut off, and the gear head motor 220 is again activated to move the carrier 10.

The air cylinder 222 has a piston rod 224 which is pivotally pinned to one end of a lever arm 226. The other end of the lever arm 226 is perpendicularly fixed to a horizontal shaft 228 which is journaled near each end by bearing assemblies 230 attached to the lower frame members 232 of the machine. The connecting arm 210 is fixed to the horizontal shaft 228, which is turned by the air cylinder 222. Fixed to each end of the shaft 228 is one end of a pair of elevating arms 234. The other end of each elevating arm 234 is pivotally pinned to one end of a pair of brackets 236, which have a guide rod 238 attached thereto. Each guide rod 238 fits within a guide cylinder 240 which is vertically aligned and fastened to a pallet elevating frame 242. The frame 242 has a series of rollers 244 fastened along each side, which rollers 244 engage the bottom deck of a pallet. The connecting arm 210, shown in FIG. 12, is pinned at its free end to one end of a horizontal connecting rod 246. The other end of the horizontal connecting rod 246 is pinned to the free end of a second connecting arm 248. The other end of the arm 248 is perpendicularly fastened to a second horizontal shaft 250, which has elevating arms 254 fixed at each end. Each of another pair of brackets 256 is pivotally pinned to one of the elevating arms 254, and the brackets 256 are each attached to another one of a pair of guide rods 258 which fit within guide cylinders 260 attached to the pallet elevating frame 242. The connecting rod 246 couples the two shafts 228,250 together for movement so that as the air-cylinder rod 224 is extended, the pallet elevating frame 242 is moved vertically. When the air-cylinder rod 224 is extended, the rollers 244 engage the bottom of a pallet and lift the pallet from the carrier 10. The switch 202 and the bracket 204 mounted at the end of the connecting rod 246 move in an arc when the air cylinder 222 is operated. When the roller 203 moves past the end of the bar 213, the air supply to the air cylinder 222 is cut off and the pallet elevating frame 242 returns to its lowered position.

Each pallet removed from the carrier 10 is pushed into the bottom position in a stack of pallets, as shown in FIG. 12. A pair of inside ratchet mechanisms 270 (see FIG. 14) are welded to a cross-member of the machine frame. Each ratchet mechanism 270 includes a catcher assembly 272 which includes a step portion 274 and a curved guide portion 276. The catcher assembly 272 pivots about a pin 278 which is fixed to a stacker guide rod 280. The catcher assembly 272 is biased by a spring 282 so that the step portion 274 is normally in a horizontal position. The step 274 engages the bottom pallet in the stack and rests against one of the slat faces. One half of the entire pallet stack is supported by the inside ratchet mechanisms 270. When a new pallet is pushed up into the bottom position in the stack, the edges of the outside slats 284 of a pallet engage the curved guide 276 and pivot the free end of the step 274 upwardly until it clears the pallet. The ratchet mechanism 270 is then biased back to a position beneath the pallet 284. When the pallet elevating frame 242 returns to a lowered position, the pallet is supported on the steps 274, as shown in FIG. 14.

FIGS. 13 and 16 show an outside ratchet mechanism 300 provided for supporting the outside half of the pallet stack. A pair of elongated arm members 302 are held in a spaced-apart relationship by a transverse brace 303. FIG. 13 shows the members 302 pivotably attached at their lower ends to the machine frame. A catcher bracket 304 attached to each arm member 302 includes a step portion 306 and an inclined ramp portion 308. A transverse post 310 is attached between the midportions of the arm members 302 and has one end of a pusher arm 312 journaled to it. The pusher arm 312 includes a telescopically slidable portion 314 which is outwardly biased by a concentric compression spring 316. The end of the slidable portion 314 has an end block 318 which pivots inwardly (as shown in FIG. 13). The end block 318 engages a pocket 320 formed in the frame. A handle 322 is attached to the end block 318. When the end block 318 is engaged in the pocket 320 (as shown in FIG. 16), the spring 316 biases the arm members 302 against the pallet stack. As a new pallet is pushed up into the bottom position in the stack, the arms 302 are pivoted outwardly by the slats riding against the inclined ramps 308. When the stack is lowered, the steps 306 support the pallet stack. When it is desired to remove a stack of pallets from the stacker, the stack of pallets is raised away from the ratchet steps 276, 306 and the handle 322 is operated to pivot the end block 318 (shown in FIG. 13) out of the pocket 320. The arms 302 are then moved from their upright orientation (as shown in FIG. 16) to a substantially horizontal orientation (as shown in FIG. 13), and the pallet stack is rolled away onto a handling frame or the like.

While particular embodiments of the invention have been shown and described, the invention is not to be limited thereto since many modifications to it may be made. This application covers all modifications that fall within the true spirit and scope of the basic underlying principles disclosed and claimed.