US2684773A

US2684773A - Lift truck

Info

Publication number: US2684773A
Application number: US276509A
Authority: US
Inventors: Glenn H Boyles
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1952-03-14
Filing date: 1952-03-14
Publication date: 1954-07-27
Anticipated expiration: 1971-07-27

Description

July 27, 1954 s. H. BOYLES LIFT TRUCK 4 SheetsSheet 1 Filed March 14, 1952 Inventor.- Gle'rm H. BoL le-s,

.1.. 31.5. 3.9. 1 NI-8:] i 4.21%.. .i ai.a.!a....a.!aiii....ii I! His Attorneg.

July 27, 1954 Filed March 14, 1952 G. H. BOYLES LIFT TRUCK 4 Sheets-Sheet 2 Inventow- Glerwrw H. Bogles His Attorneg July 27, 1954 G. H. BOYLES 2,684,773

LIFT TRUCK Filed March 14, 1952 4 Sheets-Sheet 3 Glenn H. BOLJIGS,

His Att or-neg.

July 27, 1954 G. H. BOYLES 2,684,773

LIFT TRUCK Filed March 14, 1952 4 Sheets-Sheet 4 Fig.4.

/ Inventor-z Glenn l-l. Bogles,

Hi5 AttOr-ne Patented July 27, 1954 LIFT TRUCK Glenn H. Boyles, Erie, Pa

Electric Company,

., assignor to General a corporation of New York Application March 14, 1952, Serial No. 276,563

(Cl. FEM-72) 8 Claims.

My invention relates to lift trucks and more particularly to lift trucks adapted for stacking articles.

In the stacking of articles having a greater hei ht than width, it is sometimes necessary that some of the articles be placed in a vertical position and others in a horizontal position. For example in loading railroad cars with packaged refrigerators, the head room available in such cars is limited. so that two verticaily positioned refrigerator cartons cannot always be stacked on top of each other. It has been the practice in loading cars with such items to place a row of refrigerator cartons in a vertical posi ion on the floor of the car and then subsequently to place on top thereof refrigerator cartons disposed in a horizontal position. Conventional lift trucks could be used for placing the vertically disposed cartons in position, but it has been necessary to use a crew of several men to place the top horizontally-disposed row of refrigerator cartons in place by hand. By my invention a versatile lift truck is provided which is capable both of placing the lower row of vertically-disposed cartons in position and then subsequently of stacking on top thereof the horizontally-disposed cartons.

Accordingly, it is an object of my invention to provide a lift truck including an improved arrangement for stacking articles.

It is another object of my invention to provide a lift truck including an improved arrangement for stacking articles, such as refrigerator cartons, in both vertical and horizontal positions.

It is a further and more specific object of my invention to provide a lift truck including an improved arrangement for stacking articles of rectangular cross-section in a horizontal position on top of similar articles arranged in a vertical position.

It is still another object of my invention to provide a lift truck including an improved arrangement for shifting articles from the vertical to the horizontal position.

It is still a further object of my invention to provide a lift truck including an improved arrangement for lifting articles, shifting articles from the vertical to the horizontal position, and for unloading the articles from the lift truck.

Further objects and advantages of my inven tion will become apparent as the following description proceeds and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

In carrying out the object of my invention, a carriage support and a carriage slidable relative thereto are arranged on a frame for tilting movement between vertical and horizontal positions. A lifting element is movably mounted on the carri for engaging the article to be lifted. An unloading mechanism is also provided on the carriage for moving articles from the carrae'e when it is in its horizontal position.

For a setter understanding of my invention, reference may be had to the accompanying draw- 2 ich Fig. l is an isometric view of the r corp rating an embodiment of my "ention; Fig. 2 is a side elevation view of the truck showing a refrigerator carton partially Fig. 3 is a view of a portion of K of l 2 showing the carton lifted still for ye tic-a1 stacking; Fig. 4 is a view of the lift truck showing the parts in a horizontal position for unloading; Fig. 5 is a detail of the unloading chain; Fig 6 is a schematic circuit diagram; and F 7 is a view of the portion of a lift truck showing a modified form of my invention.

Referring to Fig. 1, there is shown a lift truck which includes a frame l having a plurality of wheels 2 mounted thereon for providing mobility for the truck. The drive for the wheels, which may be of any conventional type, has not been shown since it forms no part of the present invention. The frame l includes vertical members 3 at the rear portion thereof connected near the top by a cross bar 4.

A structure including a carriage support 5 and a carriage is pivotally mounted on the frame I for movement between vertical and horizontal positions. On each side of the lift truck, a pair of

arms

2 and 5 are provided for mounting the carriage support 5 on the frame 5. Each of the arms "1 is pivotally connected by a pin 3 to a support or bracket it secured in any suitable manner, as by welding, to the vertical members iihe other end of each of the arms '2 is connected by a pin l to a bracket 52 secured in any suitable manner, as by welding to the carriage support Each of the other arms 8 is connected to the frame l by a pin 53 mounted in a bracket or support l4 secured to the vertical members 3. The other end of each of these arms 8 is pivotally mounted by a pin 55 on a bracket 16 which is secured to the carriage support 5.

For effecting movement of the carriage support 5 and, of course, its associated carriage 6, between the vertical ancl horizontal positions shown in *"igs. 1 and 4, for example, a mechanism including a tilt motor H is included. The motor is mounted on a plate 58 which is secured. to the brackets id. A U-shaped support is is also mounted on the plate it. A shaft 2b is rotatably mounted in bearings, one of which is shown at in the support it. This shaft includes a spur gear 22 at one end thereof and a sprocket or drum 23 at the other end. The sprocket 23 is driven by the tilt motor ll through a pinion fl: mounted on the motor shaft and engaging the spur gear For effecting movement of the car iage support by the rotation of t 1e motor ii, a chain or cable 25 is connected at one end to the upper portion or cross member 26 of the carriage support 5 and at the other end to the sprocket 23. This latter end may be secured to the sprocket 23 by a clamp 2i secured by 'lvets or other suitable fastening means to the s rocliet To facilitate movement of the carria e support, the chain 25 is passed over an idler sprocket This idler sprocket 28 is mounted on a pin 29 which is positioned in a depending bracket secured to the cross bar l in any su'table manner, as by welding.

To effect movement of the carriage support 5 and the carriage i3 from the vertical position shown in r I. to the horizontal position shown in 4, the tilt motor i? is rotated in a counterclockwise direction, as viewed in l, to cause the chain or cableiii to be wound around the sprocket or drum 23. This efiects a pivotal movement or the carriage support 5 by means of the crossed supporting arms "i and S; at each side of the lift truck. When it is desired to shit the carriage support and its associated car iage 6 from the ho izontal to the vertical posi on, the ti otcr l: is energizes to rotate in the reverse, that is, clockwise direction, unwinding the chain 25. The center or gravity or" the combined structure including carriage support 5 and carriage 6 being to the left of the pivot points provided by the pins 9 and i3, this combined structure moves by gravity toward its vertical position as the chain 25 is unwound by the tilt motor ii.

"in order to limit the movement or" the carriage support 5 and carriage 5 toward the horizontal position and to avoid overloading of the motor ll when further movement toward this position is blocked by the members 3 or the frame E, a normally closed limit switch 31 is mounted within the channel section of one of the vertical members 3 or" the tram The limit switch 3i an actuating plunger 32 which extends through ope ring in the front face or" the vertical member This actuating plunger 32 is positioned to be engaged by the cross member 2c of the carriage support when the carriage support its horizontal position. Engagement of the actuating plunger 32 by the cross bar of the carriage support 5 effects opening of the 11 it switch 3i to break the circuit of the motor 5 deenergizing the motor and stopping the counterclockwise rotation thereof. The li it switch has been shown only generally since it may be any conventional structure, and the specific structure thereof is not part of the present invention. Similarly, to limit movement of the support 5 and its associated carriage t to the vertical position, a second limit switch mounted on a portion t l of the frame The limit switch 33 includes an actuating plunger-E5 which is adapted to engage the arm l to break the circuit of the tilt motor ll when the carriage support 5 and carriage 6 reach the a vertical position and thereby stop clockwise ro tation of the motor ii.

In the schematic diagram of Fig. s power is shown being supplied. to the motor ll from power supply lines through the normally closed limit switches 35 and and a reversing switch 352: which may be manually operated by the lift truck operator. When the motor i? is to be actuated to lift the carriage pport 5, that is, when the motor ii is to be rotated in a counterclockwise direction, the reversing switch 351; is positioned as indicated by the solid lines in gig. 6. Under these conditions, power is supplied to the motor ll until the cross bar 25 engages the actuating plunger 32 of the normally closed. limit switch 36. lhis engagement opens the limit switch 3i and prevents 1 her rotation of the motor in the counterclockt e Should it then be desired to retur; car age support 5 to the horizontal position, the reversing switch 3% is shifted to the dotted position. shown in Fig. 6, thereby completing a circuit to the motor ll through the normally closed limit switch 33. The motor th '1 rotates clocst...se direction to effect loweling or" the carriage support 5 toward the vertical position. the desired limit or movement of the carriage this direction, the actuating plunger of the t switch engaged by the arm '5, as described previously, opening the limit switch 33 preventing further rotation of the motor ii in a clockwise direction. The i can, of course, still be reinstances by back to the To deener tilt motor l? regardless or the condit' 'rnit switches 3E and 33, the reversing 23 may be moved to a mid-position, fully interrupting the circuit to the motor ll from the power supply lines 3511.

The carriage 6 includes two channel-shaped side members 35, an upper cross bar or member 3? and. lower cross bar or member ile. For engaging articles to be lifted, a l lting blade or element St; is slidably mounted on the carriage 6. Ihis lifting blade includes a supporting frame 39 having side portio s do which are r ceived within the channels of the members 3 3. upper end ll of the blade isoffset outwardly from the face of the carriage 6 for more readily engaging an article to be lifted and stac ed.. This lift truck is particularly adapted. for handling cartons, such as those employed for packi g household refrigerators, embocy an ove-lapping collar at the top and bottom thereof. For example, these cartons, as illustrated in Figs. 2 and 3, may be of the type as shown in Patent 2574,9653, Beach, Jr. uch cartons, which are made from corrugated paper, include overlapping dependin collar is held ."mly by a metal band surrounding the coll can best be seen by reference to Fig. 2, the offset upper end ll of the blade 3 is received within the space between the side of the main body of the carton and the 0V8: hanging depending collar 53. The collar :38 is integrated with the body of the carton to a sinlicient extent that the weight of the carton and its contents can be lifted by the blade inserted under the collar.

In order to effect movement of the blade 35 for insert on beneath the collar at and for subsequent upward movement to eiiect 1 ng of the carton 42, a chain or cable E5 is secured to the blade '38, and this chain as is driven by a blade lift motor .46.

One end of the chain 35 is connected to a lower cross member ll of the frame of lifting blade and the other end of the chain is connected to an upper cross member it of the frame The chain :35 is arranged to pass over an idler sprocket mounted at the upper end of the carriage 6 and a driven sprocket 5Q mo; at the lower end of the carriage d. The sprocket is mounted by means of a BE in a bracket which is secured to the upper cross member 3'5 of the carriage E. The driven sprocket is mounted on a shaft 53 e' tending through hearings in a bracket 54 whic 'icunted on the lower cross member did of tne frame 6. The driven sprocket so is rotated by the blade lifting motor 5 through a gear reduction un t 55 which is mounted on the 81 class bar member the of the carriage 5. can. be seen that the blade may be moved upwardly or downwardly by rotating the blade lifting motor 46 in one direction or the other.

In operation, the lift truck, and specifically the carriage 5 thereof is moved adjacent the vertical wall of a carton 52 with the offset upper edge 4! of the blade 35 in the general position indicated by the lower dotted lines in Fig. 2. The blade lifting motor 5 is then energized to rotate the driven sprocket 5b in a clockwise direc-- tion, as viewed in Fig. 1, moving the blade upwardly. The blade is moved upwardly to engage the offset upper edge 4i beneath the collar 43, and this upward movement may then be con tinued to lift the carton from the surface upon which it has been resting.

In order to limit the movement of the blade in an upward direction, a normally closed limit switch 58 is mounted on the upper cross member 3 of the carriage B. This limit switch includes a depending actuating plunger ill which is adapted to be engaged by the upper cross member 48 of the lifting blade frame 3% when the blade has reached the predetermined limit of its upward movement. Actuation of the plunger 51 by the engagement therewith of the cross member d8 opens the switch 58 and effects deenergization of the motor 46, thereby terminating clockwise rotation of the sprocket 5t and upward movement of the blade 3t. Similarly, a second normally closed limit switch 53 is provided for limiting the movement of the blade 38 in a downward direction. The limit switch 53 is mounted on one of the vertical members 36 of the frame of the carriage 6 and extends into the path or the lower cross member 5? of the frame 39 of the blade 38. The limit switch includes an upwardly extending actuating plunger 59 which is adapted to be engaged by the cross member Lil of the frame 39 of the blade when the blade reaches a predetermined lower position relative to the carriage 5. Engagement of the plunger 5% by the blade opens the switch 58 and deenergizes the blade motor 46, terminating counterclockwise rotation of the sprocket 56 and downward movement of the blade.

In the schematic diagram of Fig. 6, power is shown being supplied to motor at through the normally closed limit switches 56 and 5B and a reversing switch 59c which may be manually actuated by the lift truck operator. When the blade lifting motor 46 is to be actuated to lift the blade 38, that is, when the sprocket 59 is to be rotated in a clockwise direction, the switch 59a is moved to the position indicated by the solid lines in Fig. 6. Under these conditions, power is supplied to the motor 46 until the upper cross member 48 of the lifting blade frame 39 engages the actuating plunger 57 of the normally closed limit switch 56. Actuation of the plunger 5? opens the limit switch 56 and prevents further rotation of the sprocket 50 in the clockwise direction. Should it then be desired to lower the blade 33, the reversing switch 59a is shifted to the dotted line position shown in Fig. 6, thereby completing a circuit to the motor 46 through the normally closed limit switch 58. The motor then rotates to drive the sprocket 50 in a counterclockwise direction to lower the blade 33. At the desired lower limit of movement of the blade, the cross member 37 of the frame 39 engages the actuating plunger 58 of the limit switch 58, opening the limit switch 58 and preventing further rotation of the sprocket 50 in a counterclockwise direction. I'he motor can, of course, still be rotated in a clockwise direction to lift the blade under these circumstances by shifting the reversing switch 59a back to the solid line position shown in Fig. 6. To deenergize the motor 46 regardless of the position of the limit switches and 58, the reversing switch 59a may be moved to a mid-position, fully interrupting the circuit to the motor 46 from the power supply lines 3511.

The movement of the lifting blade 3% is surficient to move the carton 42 only a limited distance from the surface upon which it has been resting. In order to effect a substantially greater upward movement of the carton, for ex ample for vertically stacking the carton on another object or carton 60 in the manner illustrated in Fig. 3, and also for assisting in positioning and unloading cartons in the horizontal position, the carriage 6 is mounted for a substantial sliding movement relative to the carriage support 5. To provide for this movement, the carriage support 5 includes two parallel inwardly extending channels, one of w ich is shown at El in Fig. 1. These channels 5! provide guides or ways for receiving outwardly facing channel members 62. As can be seen in Fig. l, the members and 62 interlock to provide for sliding movement of the carriage 6 r lative to the carriage support 5.

In order to effect movement of the carriage 6 relative to the carriage support 5, a carriage lifting motor $3 is provided. Although for simplicity no gear reduction unit has been illustrated in connection with motors 63 and il, it will be apparent that a gear reduction unit similar to that shown at 55 would normally be employed in order that the motors i1 and st may satisfactorily handle the relatively large loads involved. The motor 63 is mounted on a hori zontal plate 64 which is secured to the carriage support 5 in any suitable manner, as by welding. The motor 53 drives a sprocket 65 mounted on a shaft 66 of the motor. A second sprocket 6? is driven from the sprocket 65 by an endless chain 68 which engages both sprockets. An opening 89 is provided in the plate 64 to allow passage of the chain 63 therethrough. The sprocket 5? is mounted on a shaft '56 which extends through bearings provided in the vertical side members 16a of the carriage support 5. A sprocket, one of which is shown at H, is rigidly mounted on each end of the shaft 70 so as to be driven by this shaft. In order to translate rotation of the sprockets H into sliding movement of the carriage 6 relative to the carriage support 5, two endless conveyor chains I2 are provided. For guiding each of the chains 12 two sprockets l3 and 74 are rotatably mounted on the carriage r 2 support 5 and two=additional sprockets l5 and Y6 are rotatably mounted. at the upper and lower ends respectively of the vertical side members 36 of the carriage t. Alsornounted on each of the side members 35 of the carriage 6 at the lower portion thereof is a solenoid-actuated locking device, one such device being shown at El. Each locking device'l'l includes a plunger 28 which is normally, that is, when the solenoid 58a is deenergized, spring'biased into engagement with the teeth of the corresponding sprocket it so as to prevent rotation of this sprocket. With rotation of the sprocket it bein normally clocked by the engagement of the locking device Ti therewith, it can be seen that energization of the carriage lifting rotor 63 to effect, for example, coun erclockwise rotation of the sprocket H, as viewed in Fig. l, is effective to cause a lifting of the carriage 5 relative to the carriage support 5. In this manner the carriage can be lifted, for example, from the position shown in 2 to that shown in Fig. 3, this substantial upward movement of the carriage aiiorcling stacking of a carton 32 in a vertical position on a lower object cc. Conversely, energization of the carriage lifting motor $3 for rotation in a clockwise direction to efiect clockwise rotation of sprocket ii is efiective to move the carriage 6 downwardly relat've to the carriage support 5.

s cllltvge 19 is moved to anopen position when tn ating element 3i is engaged by th 3?, thereby deenergizing the carriage -i tor and terminating the clockwise rotation of the motor the downward movement of the carriage -elative to the carriage support 5. For limiting the upward movement of the carriage 5 a normally closed 'rnit sw tch 82 is on the J63? s ace oi the carriage support This limit switch includes a forwardly extending actuating element 3* adapted to he engaged by upper surface of the gear reduction unit o5 at the limit or" the desired upward movement of the carriage 8 relative to the carriage support 5. The limit switch 32 is adapted to he moved to the open position through engagement of the actuating element 83 by tr e gear reduction unit thereby deenergizing the carriage iii a motor and terminating the counterclockwise rotation of the motor 53 the upward movement of the carriage 6 relative to the carriage support 5.

In the schematic diagram of F l. shown being supplied the c rriage lifting Inst 83 through the normally closed limit switches and 52 and, a reversing switch which may be manually operated oy the lift truck operator. When the motor as is to be actuated to lift the carriage 5 relative to the carriage support 5, that is, when motor is to be rotated in a counterclockwise oirection as shown in Fig. l, the reversing switch 83a is positioned as indi cated by the solid lines shown in Fig. 6. Under these conditions, power is supplied to-the motor 53 through the normallyclosed limit switch until the upper surface of the gear reduction unit 55 engages the actuating element c3 of the imit switch 82. This engagement opens limit switch S2 and prevents further rotation of the motor 63 in a counterclockwise direction. Should it then be desired to lower the carriage i5 relative to the carriage support 5, the reversing switch is shifted to the dotted. line position shown in Fig. 6, thereby completing a circuit to otor 53 through the normally closed limit tor E9. The motor 63 then rotates in a clockwise c1 rection to effect lowering of the carriage relative to the carriage support 5. At the desired. lower limit of such movement of the cart, the cross member 3? of the frame of c rriage 5 engages the actuating element 35 of the normally closed limit switch 9, opening this limit switch and preventing further rotation of motor in a clockwise direction. The motor can, of course, still be rotated in a counterclockwise direction to lift the carriage 5 unde these circumstances by shifting the reg switch $3a back to the solid line position the motor 5 3 ng switch 8321 may he moved -posit on, fully inter-run g the circuit to the motor from the power supply lines l 'fo enient of the carriage 6 relative to the 5 is also employed in the he i- ;oning of carton 52 as well as .J. ting or vertical stacking thereof. for example, it can be seen u of the carriage can be ng th carriage from the solid o to the clotted line position shown. This shah-es the carton to be properly positioned le 'tially overhanging a lower carton or object upon which it is to be stacked before the of the carton s2 is begun. Thu the carriage and the support may s ung to the horizontal position in the locatioh shown by the solid lines in i. The go 8 may then be moved by energization the carriage lifting motor 63 to shift the carge and the carton 'leld thereon to a position, for example, shown oy'the dotted. lines in Fig. i. in order to eiiect unloading of the carton movement thereof to its horizontally stacked position, the conveyor chains l2 are provided. The use of the chains 52 for effecting movement of the carriage 6 relative to the carriage support 5 been described above. In order to afford proper movement of each of the chains '62 for unloading of cartons in the horizontal position shown in Fig. 4, the solenoid lfia of locking device ll is energized, retracting the plunger it out of engagement with the sprocket 78, so as to permit rotation of this sprocket ES. Energization of the motor 83 and resultant rotation of the sprockets ii is then efiective to move the conveyor chains l2 relativeto the carriage ii for unloading cartons supported on the carriage. To insure that the rotation of the sprockets i under the circumstances is directed entirely to movement of the chains relative to the carriage for unloading purposes and is not efiective for moving the carriage 5 relative to the carriage support a second locking device 8 5 is provided. his locking device 34 is mounted on the carriage supp by rivets $5 or other suitable fastel -ng devices. The locking devi e 83 includes a lever 86 adapted to en age a rack ill secured to or formed integral with the carriage E. This lever 86 is normally biased out of engagement with the rack E'l by a-spring 23 and is adapted to be moved into engagement with the rack 87 by a solenoid S8 of the locking device. Hence, to

the vert- Refer that this look the carriage 6 against movement relative to the carriage support 5, the solenoid 89 of the locking device 8% is energized, moving lever 86 into engagement with the rack 3'5. circuit pplying power to the solenoids i311, and 89 of the locking devices ll and t l, respectively, is arranged so that both solenoids are energized and deenergized simultaneously, for example by employing a single switch 96 in series with the solenoids lSa and 58, as shown schematically in Fig. 6.

The switch is normally open so the solenoids are deenergized and hence the plunger engages the sprocket lit to prevent rotation. th reof and the lever as is out of engageent with the rack ill. Under these circumstances energizetion of the motor 53 is effective, as explained previously, to move the carriage 6 relative to the carriage support When it is desired to unload a carton in the horizontal position shown in Fig. 4, the switch 9:? is closed energizing the solenoids lac and $9, thereby retracting the plunger 73 out of engagement with the sprocket l; and moving the lever 8E; into engagement with the rack This simultaneously locks the carriage support 5 and the carriage against relative move-- ment and initiates, when the motor 63 is energized, movement of the conveyor chains TEE around the sprockets ll, it, it, '55 and it. While the upper longitudinal of each of the conveyor chains l2 may sag to some extent in its middle portion when the carriage 5 is in the horizontal position, the chains nevertheless engage the carton l2 at least in the region i l adjacent the forward end thereof rotation of the sprockets ii in a clockwise direction, as viewed in Fig, 4, is effective to cause movement of the carton 42 to the right for stacking in a horizontal position on top of another object, for example, a vertically positioned carton. As indicated in 4, the carriage may, if desired, be first advanced horizontally relative to the carriage support 5, for example to the position indicated by dotted lines 82, and then movement of the conveyor chain may be initiated for eilecting unloading of the carton 52.

A detail of the conveyor chain is shown in Fig. 5. It will be noted from this figure that the links f the conveyor chain have mounted thereon upwardly extending segments 94. These segments are provided at the upper edge with teeth or serrations adapted to engage the carton for eirecting unloading thereof.

In describine the movement of the carriage support 5 and the carriage between the vertical and horizontel positions, it has previously been mentioned that this combined structure is moved from the vertical to the horizontal position by the winding of the chain 25 on the sprocket 23 and that the combined structure is returned to the vertical position by gravity as the chain is unwound upon reverse rotation of the motor ll. It was there mentioned that this gravity return is effected because the center of ravity of the combined structure including the carriage support and carriage is positioned to the left of the pivot points 9 and i3 of the arms I and 8 on the frame 5. However, in providing for substantial movement of the carriage s relative to the carriage support 5 to secure adequate vertical lifting, for example in the form of operation llustrated in Fig. 3, the permissible movement of the carriage 5 is such that, when fully extended to the right in the horizontal position shown in Fig. 4, the center of gravity of the coml0 bined structure may be to the right of the afor mentioned pivot points. Under such circum-- stances, the unwinding of the chain would, of course, have no effect in returning the combined structure to the vertical position. More importantly, it would be possible to effect a substantial unwinding of the chain hg slack therein, and then a movement of the carriage G to the left until the center of gravity of the comhined structure reached a point to the left of the pivot points 9 and it of the arms and Under these circumstances, there would then be an abrupt swing of the combined structure toward the vertical position, imposing a severe strain on the cable 25 at the time the slack was taken up. In a similar manner, should the combined struc ture be started from the vertical to the horizontal when the carriage $5 were in a fully extended upward position, as illustrated in Fig. 3, the center of gravity of the combined structure might be such that, when moved partially to the hori-- zontal position by the tilt motor ll, it would swing rapidly by its own weight the remainder of the distance, causing a danger of impact damage to the mechanism.

To avoid the possibility of the above occurrences a limit switch SE is mounted on the carriage support 5. This limit switch is con nected in the circuit of the tilt motor ll, as shown in Fig. 6. lT-he switch as includes an actuating element 5'5 adapted to be engaged by a dog 58 mounted on the carriage 5. When the carriage 6 has moved upwardly, as viewed in Fig. l, a predetermined distance relative to the carriage support 5, the dog 98 engages the actuating element throwing the limit switch to its open position and breaking the supply circuit to the tilt motor ll. Thus, when the carriage i has moved a relatively short distance which is substantially less than the upward movement permitted by the limit switch 82, the so ly circuit to the tilt motor l? is interrupted energization of this motor is prevented. The tilt motor I I cannot then be energized to move the combined structure of the carriage support 5 and the carriage E from the vertical to the horizontal position until the carriage 6 has been moved downwardly, as viewed in l, to a sufficient extent that the dog 98 again engages the actuating element 9? throwing the limit switch to its closed position. Similarly, if the carriage 8 has been extended suihcientl to the right in a position shown in Fig. 4, that the dog 98 has passed beyond the actuating element 9? of the imit switch the tilt motor ll cannot be energized to unwind the chain 25 until the 6 has first been retracted to a suni ient again conditioning the limit switch for provid a circuit to the tilt motor H.

in the specific embodiment of the invention illustrated the carriage support 5, the carriage 6 and the operating mechanism associated therewith including the tilt motor ii and its mounting and the arms l and a and their supporting brackets are shown supported on the vertical members 3 which form part of the frame I. If, for any reason, it is desired to secure a greater vertical movement of the mechanism, this structure could alternatively be mounted on slides received in the channels formed by the vertical members 3, the entire mechanism being movable vertically in the slides by any conventional hydraulic lifting system.

A modified form of my invention is shown in Fig. '7. The structure of this modified form is the same as that of the lift truck previously described with the single exception that a positive unload bar E9 is provided in lieu of relying on the frictional engagement of the conveyor chains '9'? with the carton d2. Referring to Fig. '2, it can be seen that the unload bar 98 is secured at its ends to the chains "42 so that movement of the chains 72 in the manner previously described for unloading is effective for moving the unload bar 99 along the carriage 5. The unload bar 99 includes two outwar iv extending ears which, in the horizon 1 position of the carriage 5, are adapted to engage the rear end of the carton so that movement of the unload her under those circumstances to the right, in the position of the structure corresponding to Fig; 4, is effective for pushing the carton t2 positively off the carriage 5 and stacking it in horizontal position on top of other objects. The construction illustrated in Fig. '7 has an advantage in that the outwardly extending ears of the unload har may be employed for assisting in lifting a carton :2 vertically. Under these circumstances the entire reliance for support the carton in its vertical position need not he placed on the blade since the ears its may he brought into engagement with the bottom of the carton to assist in sunporting the carton in the vertical position and in lifting the carton. In the form previously described the chains '52 are ,s driven in one direction. in the form shown in Fig. '1, it is necessary to reverse the chain-driving motor to retract the unload ba 2 9 in order to condition it for the next unloading operation.

While I have shown and described specific embodiments of my invention, I do not desire my invention to he lirnitedto the partic ar construction shown and described and I intend hi the appended claims to cover all modifications within the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

*1. A lift truck comprising a frame, a carriage support pivotally mounted on said frame, a pair of crossed arms pivotally mounted on said frame and pivotally connected to said support for mounting said support on said frame and for guiding said support between elevated horizonta and vertical positions relative to said frame, a carriage slidably mounted on said support, means for moving said carriage relative to said support, a lifting element slidably mounted on said carriage and adapted to engage an article to he lifted, and means for moving said lifting element relative to said carriage.

2. A lift truck comprising a frame, a carriage support pivotally on said frame, means for moving said c ,rriage s port between vertical and horizontal positions, a carriage slidably mounted on said support, a first sprocket rotatably mounted said carriage at one end thereof, a second sprocket rotatably mounted on said carriage at the other end thereof, a drive sprocket mounted on said ca riage support, an endless chain en aging said sprockets, means for rotating said drive sprocket, means for preventing rotation of one of s first mentioned sprockets whereby rotation of said drive sprocket efiects longitudinal movement of said carriage relative to said carriage support, a lifting element s idably mounted on said carriage and adapted to engage an article 12 to be lifted, and means for moving said lifting element relative to said carriage.

3. A lift truck comprising a frame, a carriage support pivotally mounted on said frame, means for moving said carriage support between vertical and horizontal positions, a carriage slidably mounted on said support, a first sprocket rotatably mounted on said carriage at one end thereof, second sprocket rotatably mounted on said carriage at the other end thereof, a drive sprocket mounted on said carriage support, an endless chain engaging said sprockets, means for rotating drive sprocket, means for preventing rotation of one of said first-mentioned sprockets whereby rotation of said drive sprocket efieots longitudinal movement of said carriage relative to said carriage support, a lifting blade slidaloly mounted on said carriage and arranged for insertion under the collar of a shipping carton for lifting the carton, and means for moving said blade relative to said carriage.

4. A lift truck comprising a frame, a carriage support pivotally mounted on said frame, means for moving said carriage support between vertical and horizontal positions, a carriage slidaloly mounted on said support, a first locking means mounted on said carriage support and adapted to engage said carriage for preventing relative movement of said carriage and said carriage support, said first locking means being norinally disengaged from said carriage, a solenoid for actuating said means into engagement with said carriage, a first sprocket rotatably mounted on said carriage at one end thereof, and a second sprocket rotatably mounted on said carriage at the other end thereof, a drive sprocket mounted on said carriage support, an endless chain engaging said sprockets, means for rotating said drive sprocket, a second locking normally engaging one of said first mentioned sprockets for preventing rotation thereof whereby rotation of said drive sprocket effects longitudinal movement of said carriage relative to said carriage support, a second solenoid for actuating said second locking to its disengaged position, and means for simultaneously energizing said solenoids for moving said first locking means to its engaged posit on and for moving said second locking means to its disengaged position and for simultaneously deenergizing said solenoids for inc 3 said first locking means to its disengaged position and for moving said second locking means to its engaged position.

5. A lift truck comprising a frame, a carriage support pivotally mounted on said frame, means including a motor for moving said carriage support between vertical and horizontal positions, a carriage slidaloly mounted on said carriage support, means for moving said carriage relative to said carriage support, a limit switch for deenergizing said motor when said carriage support reaches its vertical position, a second limit switch for deenergizing said motor "1311 said carriage support reaches its horizontal position, a third limit switch for deenergizing motor when said carriage has moved beyond a predetermined position relative to said carriage support.

6. A lift truck comprising a frarne, a carriage support pivotally mounted on saidfrarne, means including a first motor for moving said carriage support between vertical and horizontal positions, a limit switch for deenergizing said first motor when said carriage support reaches vertical position, a second limit switch for deenergizing said first motor When said carriage reaches its horizontal position, a carriage slidably mounted on said support, means including a second motor for moving said carriage relative to said support, third limit switch for deenergizing said second motor to limit movement of said carriage relative to said carriage support in one direction, a fourth limit switch for deenergizing said second motor to limit movement of said carriage relative to said carriage support in the opposite direction, a fifth limit switch for deenergizing said first motor when said carriage moves beyond a predetermined position relative to said carriage support in one direction, a lifting blade slidahly mounted on said carriage and adapted to engage an article to be lifted, means including a third motor for moving said blade relative to said carriage, a sixth limit switch for deenergizing said third motor to limit movement of said blade relative to said carriage in one direction, a seventh limit switch for deenergizing said third motor to limit movement of said blade relative to said carriage in the opposite direction, a conveyor chain mounted on said carriage, and means including said second motor for driving said conveyor chain to unload articles from said carriage in the horizontal position.

7. A lift truck comprising a frame, a carriage support pivotally mounted on said frame, means including a first motor for moving said carriage support between vertical horizontal positions, a limit switch for deenergizing said first motor when said carriage support reaches its vertical position, a second limit switch for deenergizing said first motor when said carriage reaches its horizontal position, a carriage slidably mounted on said support, a first sprocket rotatably mounted on said carriage at one end thereof, a second sprocket rotatably mounted on said carriage at the other end thereof, a drive sprocket mounted on said carriage support, an endless chain engaging said sprockets, a second motor for rotating said drive sprocket, a first locking means for preventing rotation of one of said first-mentioned sprockets whereby rotation of said drive sprocket effects longitudinal movement of said carriage relative to said support, a third limit switch for deenergizing said second motor to limit movement of said carriage relative to said carriage support in one direction, fourth limit switch for cleenergizing said second motor to limit movement or" said carriage relative to said carriage support in the opposite direction, a fifth limit switch for deenergizing said first motor when said carriage moves beyond a predetermined position relative to said carriage support in one direction, a lifting blade slidably mounted on said carriage and adapted to engage an article to be lifted, means including a third motor for moving said blade relative to said carriage, a sixth limit switch for deenergizing said third motor to limit movement of said blade relative to said carriage in one direction, a seventh limit switch for deenergizing said third motor to limit movement of said blade relative to said carriage in the opposite direction, said chain being arranged to engage an article carried on said carriage in the horizontal position thereof whereby movement of said chain is effective to unload the article from said carriage, a second locking means for preventing movement of said carriage relative to said support, and means for actuating said first locking means out of engagement with said one of said first-mentioned sprockets to aficrd movement of said chain for unloading said carriage.

8. A lift truck comprising a frame, a carriage support pivotally mounted on said frame, means for moving said carriage support between vertical and horizontal positions, a carriage slidably mounted on said support, a first sprocket rota ably mounted on said carriage at one end thereof, a second sprocket rotatably mounted on said carriage at the other end thereof, a drive sprocket mounted on said carriage support, an endless chain engaging said sprockets, neans for rotating said drive sprocket, a first locking means normally engaging one of said first-mentioned sprockets for preventing rotation thereof whereby rotation of said drive sprocket effects longitudinal movement of said carriage relative to said carriage support, said chain being arranged to engage an article to be stacked for unloading the article from said carriage in the horizontal position of said carriage, means for disengaging said first locking means for affording movement of said chain relative to said carriage for unloading, and a second locking means for preventing movement of said carriage relative to said carriage support.

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