US2389563A - Lift truck - Google Patents

Description

Nov. 20, 1945. w. sTUEBlNG, JR

LIFT TRUCK 2 sheets-sheet i Filed July 26, 1945 '22A/@wwe h//LL/AM rafa/ale, de 5y #5&7

Arrow/5K5' Nov. 20, 1945. w. sTuEBlNG, JR

LIFT TRUCK Filed July 26, 1945 2 Sheets-Sheet 2 Patented Nov. 20, 1945 LIFT TRUCK William Stuebing, Jr., Cincinnati, Ohio Application July 26, 1943, Serial No. 496,142

(c1. zar- 2) 7 Claims.

This invention relates to lift trucks, and more particularly to lift trucks which are provided with swinging steering handles where the operator walks and steers the truck.

An object of this invention is to provide a mechanism of an improved character for lifting and conveying articles such, for example, as movable platforms of the type where" a quantity of material is piled on the platform and then the loaded platform is moved from one location to another. A further object is to provide an enicient and dependable means for lifting a load. A still further object is to provide for the rapid and dependable lifting of the load so that the load may be moved in a known manner to a new location. A further object is to provide apparatus of the above character which is light in weight, sturdy in construction and inexpensive to manufacture and operate. A further object is to provide mechanism of the above character which may be operated with ease and with utmost safety. These and other objects will be in part obvious, and in part pointed out below.

The invention accordingly consists in the features of construction, `combinations of elements, and arrangements'of parts as will be exemplied in the structure to be hereinafter described, and the scope of the application of which will be indicated in the following claims.

In the drawings, in which is shown one of many possible embodiments of this invention:

Figure 1 is a side elevation of the front portion of a lift truck; Y

Figure 2 is a front view of Figure l;

Figure 3 is a plan view of Figure 1 with parts broken away to expose the central gearing mechanism;

Figure 4 is a sectional view on the line 4-4 of Figure 3; and

Figure 5 is a wiring diagram of the electrical system. l

In the illustrative embodiment of the invention, the lifting mechanism is electrically operated and the truck is propelled manually. Previously, lifttrucks have been known where the lifting operation is performed by a motor, but these trucks have been large and heavy. It has been quite universal to propel these trucks by large motors, and, in fact, the operator normally has ridden on the truck. This has resulted in the trucks being expensive to manufacture and operate so that the eld of use has been very limited. Furthermore, the size and weight of these trucks has seriously interfered with their use. For example, these heavy trucks cannot be manipulated and maneuvered in lsmall quarters, and they cannot be lifted on the usual elevators in buildings.

Small hand-operated trucks are common, but they have the objectionable characteristic that the operator must lift the load manually. This not only limits the users of the truck to workmen who could perform the lifting operation, but at times it has been an actual source of danger. With some such prior trucks, where the lifting is performed by swinging the steering handle, the workman was endangered by the flying handle; that is, when the truck was lifted by the steering handle, the latch was apt to be accidentally released with the result that the steering handle would be -suddenly thrown upwardly. Frequently this has been the cause of severe injury to workmen. In addition, manual lifting has resulted in injury to the truck because the workman failed to realize the limitation of the truck. Vlor example, workmen have attached an extension to the steering handle and then attempted to lift loads beyond the capacity of the manual lifting mechanism; the result may have been that the load was lifted but the truck parts were bent or broken. Accordingly, workmen must be watched continuously when they are using certain of the prior types of trucks. It is an object of this invention to overcome these dicultfes and to provide a truck which is satisfactory in all respects.

The lift truck shown in the drawings is provided with a chassis formed by a lower supporting frame, supporting wheels, and a steering handle. The steering handle is pivoted at the front end of the truck so that it may be swung from a Vertical to a horizontal position, and the front wheels are turned by swinging the steering handle about a vertical axis. Mounted upon the chassis is a lifting frame which is moved to and from a raised position where it engages and lifts the load. The lifting is performed by a motor lift mechanism which is mounted upon the chassis adjacent the steering handle; thus, the operator may control the lifting operation and observe the elevating of the load. In this embodiment, the lifting frame is held in the raised position by a mechanical latch and the descent is controlled by an automatic checking mechanism.

The motor lift mechanism is an electric motor operating through a cam assembly and having no direct mechanical connection with the lifting frame. The operation of the electric motor is automatically controlled so that the lifting mechanism is always returned to a predetermined initial position at the end of the lifting cycle. This predetermined initial position is such that, when the lifting cycle is started, the motor immediately starts to elevate the lifting frame. Thus, there is no time delay as might be present if the operation of the motor were controlled manually.

Referring particularly to Figures 1 and 3 of the drawings, the supporting frame is formed by a pair of rails 6 and 1, secured by a tie bar 8, and attached at the forward end of the truck by a head I8. Pivotally mounted in the head I8 is a fork 9 (see also Figure 2), carrying the front wheels I and II. The rear portion of the truck is not shown in the drawings but is of the type shown in my prior United States Patent No. 2,280,104, issued April 21, 1942. The lifting frame is formed by two side rails I and 2 attached at their forward ends by a saddle 3 and at the rear of the truck by frame members (not shown). The lifting frame is pivoted to the supporting frame by links 4 and 5 at the front, and by similar links at the rear.

The king bolt of fork 9 extends through head I8 and has rigidly attached toits upper end a collar I2. Pivoted to collar I2 is a steering handle I3 which is adapted to swing from the upright position shown in Figure l to a position for steering the truck, such as shown in Figure 4. The steering handle is balanced by a compression spring I4, coiled about a guide rod i between a bearing bracket I1 to which the guide rod is pivoted and a bracket IS upon the handle. The base of the handle carries a stop I9 which engages a cooperating stop portion of collar I2 to hold the handle in the position shown in Figure 1.

As indicated above, the elevating of the lifting frame is performed by an electric motor operating through suitable gearing, and controlled so that when operated, a complete lifting cycle is carried on. The entire elevating mechanism is located between the forward end of the lifting frame and head I8. At the top (Fig. 2) a battery box ZI encloses a battery 52 and is supported on the top of a gear box 20. A motor 22 is mounted on the side of the gear box (see Figure 3, and carries a pinion 82, meshing with a gear 83. Gear 83 in turn carries a pinion 84, which meshes with a gear 85 carrying a pinion 86. Pinion 86 drives a gear 81 which has a pinion driving a gear (not shown) which drives a gear 88 on a shaft 24. Shaft 24 extends transversely of the truck and is rigidly supported for rotation in bearings at the bottom of the gear box. The ends' of shaft 24 overhang, and rigidly mounted on these ends are crank arms 25 and Y26. Each of these crank arms carries at its extreme end a lifting roller 89 (see also Figure 4). Mounted upon the lifting frame in alignment with these lifting rollers are lifting hooks 30 and 3|, which are pivoted at their rear ends to saddle 3 of the lifting frame (Figures 1 and 4) and which are provided at their forward ends with hook portions 28 and 29, respectively. As will be explained below, the lifting frame is elevated by rotating arms 25 and 26 so that rollers 89 move under and engage hook portions 23 and 29, pulling the frame up.

Rigidly mounted on the frame at the side of lifting hook 39 is a guide plate 55, and extending from the hook over the top of the guide plate is a stop 92; similarly, (see Figure 3) lifting honk 3I is provided with a guide plate 56 and a stop 93. When engaged by rollers 89 on the arms, the

hooks are lifted from these plates, but when the arms move downwardly, the stops engage the plates, disengaging the hooks from the rollers; the hooks then rest on the guide plates until they are engaged again by the arms.

The lifting frame is held in its elevated position by treadle 44 (see Figure 3) mounted on the side of gear box 20, and having a hook 45 which engages a roller 46, mounted on saddle 3 of the lifting frame. Treadle 44 has a foot extension 41, which is depressed to release the frame. A

spring 50, carried at its upper end by a pin on the gear box, biases the forward end of the treadle upwardly against the stop 5I which extends from the gear box. A check 48 controls the descent of the lifting frame but does not interfere with the elevating operation.

The operation of the motor is controlled by mechanism shown at the central portion of Figure 4. At the top, a handle lever 32 is rockably mounted on a pivot 33, extending from the bottom of battery box 2I. At the right, the handle lever is provided with a cylindrical shell which encloses a plunger 90. The stem of the plunger extends from the top of the shell and is held by a pair of lock nuts 9i, and within the shell a spring 34 biases the plunger downwardly. Directly beneath the plunger, and in operative relationship therewith, isa control switch 35, which is mounted on a bracket 36 on the bottom of the battery box. The handle lever is biased to the left by a spring 49, the right-hand end of which is attached to the handle lever, and the left-hand Vend of which is carried by a pin on the side of the battery box. When the handle lever is swung clockwise from the position shown in Figure 4 to the position shown in Figure 1, the plunger engages and close switch 35, thus starting the motor.

Extending downwardly from handle lever 32 is a latch finger 40. Pivoted on the gear box directly beneath the latch finger is a trip lever 31, which is formed by a downwardly extending release arm 39, a stop portion 43 at the top and, at the left, a latch portion 38. A spring 4I, having its left end fixed to the gear box and its right end attached to the trip lever, biases the trip lever in a clockwise direction. When in the position shown in Figure 4, stop portion 43 limits the counterclockwise swinging movement of handle lever 32.

Lifting arm 26 has integral therewith an arcuate member 21 which rotates in alignment with release arm 39. When the cam member 21 is opposite the release arm 39, the release arm is engaged, and the trip lever is held in the position shown in Figure 4 with spring 4I held under tension. However, when the cam member moves away from the release arm, the trip lever tends to swing to the right due to the action of the spring toward the position shown in Figure 1. Thus, when the handle lever is swung to close switch 35, and the arcuate member 21 has moved away from release arm 39, the latch portion 38 swings below the latch linger 40, thereby latching the lever handle in the position shown in Figure l with switch 35 closed. Subsequentlycam member 21 engages release arm 39, swinging latch lever 31 counterelockwise with the result that latch finger 48 is released. This permits spring 49 to swing handle lever 32 counterclockwise with the result that switch 35 opens, stopping the motor.

The electric circuit for the motor is shown in Figure 5. The motor 22, one side of switch 35 and the negative side of battery 52 are all grounded to the frame, and the other side of each is connected to arelay 53. Relay 53 is of known construction and is such that when switch 35 is closed', motor 22 is connected to the positive side of the battery `soV that the motor starts; and when switch`35 is lreopened, the motoris stopped.

When a load is to be lifted, the handle lever 32 `is swung from the position shown in Figure 4 to the positionwshown in Figure 1, thereby closing switch 35. The motor immediately starts with the result that arms 25 and 26 are rotated. R'eferring specifically to Figure 1, rollers 89 engage hooks 28 and 29, and the lifting frame is pulled bythe hooks into the elevated position shown in AFigure 4. At this time roller 4B and hook 45 of treadle 44 become engaged, holding the lifting frame in the elevated position. However, during this initial movement, cam member 21 engages release arm 39 and holds latch lever 31 in the position of Figure 4. Thus, at any time during this initial movement, if the operator so desires, he can release the handle lever and the motor is immediately disconnected; -the load will then recede of its own weight.` However, at the time hook 45 engages roller 46, cam Vportion 21 moves from engagement with release arm 39 with the result that the handle lever is latched in the position shown in Figure 1, and the releasing of the handle lever will not result in stopping the motor. The motor continues to run, and arms 25 and 25 carry hooks 30 and 3l down so that stops 92 and 93 engage plates 55 and 56, and the arms move away from the hooks, When arms 25 and 26 reach the position shown in Figure 1, release arm 39 is engaged by cam portion 21, and further movement of the cam portion releases handle lever 32 and stops the motor. However, the motor coasts so that at the time it stops, arms 25 and 25 are so positioned (as shown in Figure 4) that upon the restarting of the motor, rollers 89 on the arms will immediately engage their lifting hooks.

When it is desirable to lower the load, foot portion 41 of treadle 44 is depressed, releasing the engagement between hook 45 and roller 45 and permitting the load to descend under the control of check 48. When the truck is descending, hook stops 92 and 93 ride along the tops of guide plates 55 and 56, thus, positioning the hooks to be engaged for lifting the lifting frame again.

As many possible embodiments may ibe made of the above invention and as many changes might be made in the embodiment above set forth, it is to be understood that all matter hereinbefore set forth, or shown in the accompanying drawings, is to be interpreted as illustrative and not in a limiting sense.

I claim:

1. In a lift truck construction, the combination of: a chassis comprising a supporting frame, a plurality of wheels supporting said frame, and a steering handle; load engaging means mounted on said frame and adapted to be moved from a lowered position to a position in which it engages and lifts the load; and elevating means to elevate said load engaging means comprising a motor mounted on said frame and having associated therewith means constituting a source of electric power and a switch to be closed to operate the motor, a lifting arm assembly rotatably mounted and connected to said motor to be rotated upon the operation of said motor, cooperating means mounted on said load engaging means in alignment with said lifting arm assembly and adapted to be engaged by said lifting arm assembly upon the rotation thereof by said motor with the result that said lifting arm assembly elevates said load engagingmeans, and latch means to hold the switch closed after the load has been elevated and until the lifting arm assembly has been moved to "a predetermined initial position.

` 2. In a lift truck constructionin which a lift- Ationftorotate said cam means one complete revolution from a predetermined initial position, and cooperating means mounted on said lifting frame -to be engaged byv said cam means duringthe initialportion of the rotary movement of said cam means whereby said cam means elevates said lifting frame and thereafter ccntinues'to move from engagement with said cooperating means. 3. In a lift truck constructionin which a lifting frameis mounted on achassis to be moved to and from an elevated position wherein it engages ancl lifts a load, a'pair of lifting arms rotatably mounted on said chassis at the opposite sides thereof, motive means geared to said lifting arms and adapted upon energization to rotate said lifting armsone complete revolution from a predetermined initial position, a pairof hooksl pivotally mounted on said' lifting frame to be engaged by said lifting arms during the initial portion Aof the rotary movement of said lifting .arms whereby said cam means elevates said lifting frame and thereafter continues to move from engagement with said hooks, a pair of guide plates mounted respectively at the sides of said hooks, and stop means on each of said hooks extending over the top of the adjacent guide plate, whereby said stops hold said hooks from falling below a substantially horizontal position.

4, In a lift truck construction in which a lifting frame is mounted on a chassis to be moved to and from an elevated position wherein it engages and lifts a load, a gear casing mounted on said chassis between the front end of the chassis and the front end of the frame, cam means rotatably mounted on said casing, motive means mounted on said casing and geared to said cam means and adapted upon energization to rotate said cam means one complete revolution from a predetermined initial position, and cooperating hook means mounted on said lifting frame to be engaged by said cam means during the initial portion of the rotary movement of said cam means whereby said cam means elevates said `lifting frame and thereafter continues to move from engagement with said cooperating means.

5. In a lift truck construction in which a lifting frame is mounted on a chassis so as to be raised from a lowered. position to an elevated position wherein it engages and lifts the load, means for automatically raising the lifting frame comprising, link means pivotally attached to the lifting frame and having engaging means eX- tending forwardly with respect to the lifting frame, crank arm means rotatably mounted and adapted to engage said engaging means and to exert a lifting force which is eective to raise the lifting frame, a motor geared to said crank arm means to rotate said crank arm means, a control switch which is closed to operate said motor thereby to elevate the lifting frame, an arm adapted to beA moved manually to close said switch, a spring actuated dog to engage said arm and hold said switch closed, and means mounted to `rotate with said crank arm to engage said `dog iand release said 'arm to stop the `motor after lifting frame is swingably mounted on a Vchassis whereby the lifting frame swings from a lower position to an elevated position upon a plurality of similar links one end of each of which is pivoted to the chassis and the other end of each of which is pivoted to the lifting frame and wherein the lifting frame is held in the elevated position by a releasable latch means, means to elevate vthe lifting frame comprising, a pair of elongated hook links mounted upon the opposite sides of the Ilifting frame each of said hook links being attached at one end to the lifting frame and having at its other end a hook portion which is open downwardly, a gear casing positioned between said hook portions and mounted on said chassis, a pair of crank arms associated respectively with the two hook links, a crank shaft rotatably mounted on said gear casing and having said crank arms rigidly mounted on its ends, a motor mounted on said gear casing and geared to said crank shaft through a speed reduction gear 'train in said gear casing, and motor control means to operate said motor thereby to cause the crank arms to engage the hook links and elevate the lifting frame.

7. In a lift truck construction, the combina'- tion of: a vchassis `comprising 'a supporting frame, a plurality `of wheels supporting said frame, and a steering handle; loadengaging means mounted on said frame and adaptedto be moved from a lowered position to a position in which it engages and lifts the load; and elevating means to elevate said load engaging means comprising, a motor mounted on said frame and having associated therewith means constituting a source Vof lelectric power 'and control means to operate the motor including a lever Which is moved Vfrom an off position to an on position to -start the motor., a lifting arm assembly rotatably mounted and connected to said motor to be rotated upon the operation of said motor, and cooperating means mounted on said load engaging means in alignment with said lifting arm assembly and adapted to be engaged by said lifting arm assembly upon the rotation thereof by said motor with the result that said lifting arm assembly elevates said load engaging means, said lifting arm as- -sembly including a cam vwhich is effective to cause said lever to be moved from its on position tov 'its 01T position when the liftingarm assembly has completed one revolution with the result that the motor is automatically stopped.

WnJLiAM sTUEBINQ-JR.

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