US3381834A - Lift truck - Google Patents

Description

C. D. GIBSON May 7, 1968 LIFT TRUCK 4 Sheets-Sheet 1 Filed Jan. 1967 CHRISTIAN D. GIBSON INVENTOR y 7, 1968 c. D. GIBSON 3,381,834

LIFT TRUCK Filed Jan. 4, 1967 4 Sheets-Sheet f5 CHRISTIAN D. GIBSON INVENTOR.

y 1968 c. D. GIBSON 3,381,834

LIFT TRUCK Filed Jan. 4, 1967 4 Sheets-Sheet 3 CHRISTIAN D. GIBSON INVENTOR.

C. D. GIBSON LIFT TRUCK May 7, 1968 4 Sheets-Sheet 4 Filed Jan. -i, 196'? FIG. 3e

FIG. 3h

FlG 3d CHRISTIAN D. GIBSON ZM/im/ United States Patent ABSTRACT OF THE DISCLOSURE A detachable comb-line attachment carried on the front arms of a lift truck for stripping soft loads carried on sheets off of the forks of the truck.

This invention relates to material handling machinery, and more particularly, to an attachment which may be added to a lift truck to aid in the handling of certain types of loads.

In most warehouses, loads are carried on wooden pallets designed to be handled by lift trucks having two tines, or as they are frequently termed, two forks. Rail shipment of various commodities, such as paper bags of flour or sugar, for example, may be done more economically if the bags are not shipped on wooden pallets but instead carried on cardboard sheets (sometimes called slip sheets) or the like. Because soft, non-rigid loads of that nature, if not palletized, would fall between the forks of an ordinary two-fork truck, such loads must be handled with special fork arrangements which offer more supporting surface area to the load. One satisfactory such fork arrangement involves the use of six forks spaced across the distance ordinarily occupied by two forks. While merely increasing the fork load-supporting surface area readily adapts a truck for carrying such unpalletized loads, it alone does not solve the problemof loading such loads onto the forks or the problem of removing such loads from the forks. In order to pick up such loads, means must be provided to tilt the forks downwardly, to press the fork tips against the floor, so that the forks, which are tapered, will chisel under the cardboard sheet as the forks are advanced. In order that the forks not merely push the load across the floor as they are urged under the cardboard sheet, it is necessary, of course, that the load be backed-up.

When a conventional palletized load is to be unloaded, merely lowering the forks to the proper elevation completely frees the forks from the pallet, so that the forks need not touch the pallet or the load as the forks are retracted from the pallet. When a slip-sheet mounted load is to be unloaded, however, the weight of the load and the increased load-supporting fork surface area provide a very substantial friction which, it will be seen, will interfere with retraction of the forks from beneath the load. Such loads have tended to stick to the forks as the forks have been retracted, preventing proper load placement, and sometimes damaging a load. Because handling of palletized loads is so much more convenient, it is usually desired that such loads be placed on a pallet as soon as they are unloaded from a railroad car, and thereafter handled on the pallet.

In accordance with the present invention a truck of the above described type is provided with a comb-like attachment through which the load forks may be retracted, with the teeth of the comb functioning to strip or comb the load from the forks to leave the load on a pallet. In practice, the base frame of the truck and comb are held fixed adjacent the pallet upon which the load is to be placed, and the forks are then retracted, preferably by use of a reach mechanism (such as the type shown in US. Pat. No.

2,752,058 or US. Pat. No. 3,082,894, for example), but alternatively by translation of the entire mast assembly with respect to the base of the truck in some trucks.

FIG. 1 is a perspective view of a lift truck equipped with six closely-spaced tines in its fork assembly to permit slip-sheet handling, with one form of a load stripper of the present invention shown mounted across the forwardly-extending base legs of the truck.

FIG. 1a is an enlarged perspective view of a cutaway front end portion of the truck of FIG. 1, illustrating the relationship between the load forks and the comb assembly of the present invention.

FIGS. 2a, 2b, and 2c are plan, elevation and side views, respectively, showing the load stripper mounted on the base legs of a truck.

FIGS. 3a-3h are schematic views illustrating the various operations involved as a truck of the type described removes an unpalletized load from one location, transports it to a second location and then unloads it onto a standard wooden pallet.

FIG. 1 shows the general arrangement of one embodiment of the invention incorporated on a lift truck equipped for slip-sheet load handling. The truck comprises a base frame carried on one or more dirigible, powered drive wheels 12, only one of which is shown in FIG. 1, and a pair of non-steerable load-carrying front wheel assemblies 14 and 15 mounted on forwardlyextending straddle arms 16 and 17 which project forwardly from the base of the truck. An operators platform, various control apparatus, and the truck electrical storage battery (mounted Within compartment 18) are all carried on the main base frame of the truck, together with a mast or gallows formed by a pair of inwardly-facing channel members 19 and 20. A pair of telescopic uprights shown as comprising I-shapes 21 and 22 are nested within channels 19 and 20 and are raised and lowered by hydraulic cylinder 23. A rectangular frame or load carriage 24 is carried on rollers (not shown) within the tracks formed by the flanges of I-shapes 21, 22, and hydraulic cylinders 25 and 26 serve to raise and lower carriage 24 with respect to telescopic I-shape uprights 21, 22. Carried on load carriage 24 and attached thereto by means of an extensible and retractable scissors reach mechanism is fork carriage assembly 26. The reach mechanism preferably comprises an arrangement of the type disclosed in my prior Pat. No. 3,082,894. Fork carriage assembly 26 carries a plurality of tines of forks 31 through 36 which are spaced laterally across the fork carriage. Fork carriage assembly 26 also carries mechanism which allows all of the forks 31-36 to be tilted upwardly and downwardly, 4 degrees from the horizontal in each direction being the maximum amount of tilt provided in one embodiment of the invention. The utility of the truck in FIG. 1 may be considerably increased if it can be used for normal palletized load handling with a two-tine fork as well as slipsheet load handling. Toward that end it is highly desirable that at least four of the tines or forks be easily and rapidly removable and replaceable, and accordingly, the truck advantageously may include a fork carriage assembly of the type shown in copending appl. Ser. No. 607,315, filed on even date herewith by Stanford B. Jones and myself.

Shown in FIG. 1 extending between and connected to straddle arms 16 and 17 is a comb assembly 37 having a plurality of fingers 38, 39 and 40 in the form of plates spaced laterally inbetween various pairs of the forks, with the front faces of plates 38-40 parallel with the forward ends of arms 16, 17. The details of comb assembly 37 are shown in FIGS. la and 2a2c, to which reference now may be had.

In the exemplary embodiment of the invention shown in FIGS. la and 2a-2c, the vertically extending fingers 38-40 comprise upward extensions of a front plate 41 which extends entirely across the space between arms 16 and 17, and which is mounted flush with the forward faces 16a and 17a of arms 16 and 17. It is essential that at least two vertical fingers extend upwardly sufficiently to extend above the top of a standard-size pallet lying on the floor, and in one successful embodiment of the invention they extended approximately ten inches above the floor. The fingers may extend upwardly much higher, however, just so that they do not interfere with lowering of the fork carriage to a level where the fork tips may touch the floor when tilted maximum downwardly. It will be understood that comb assembly 37, in extending between the two arms 16 and 17 extends perpendicular to the direction of extension and retraction of the reach mechanism of the truck. Also it will be appreciated that if a truck equipped with the assembly 37 is driven up to an empty pallet on the floor to a point where one or more fingers 38-40 engages the side of the pallet, that the assembly provides a flat surface which will rotate the empty pallet if necessary to correctly align it with the direction of travel of the truck reach mechanism. The comb assembly also includes a plurality of braces 44, 45 (7 are shown) which interconnect front plate 41 and rear plate 43. Braces 44, 44 support finger members 38-40.

It is desirable that the comb assembly be easily removable and replaceable in order that the truck be readily converted between pallet handling and sheet handling modes, and toward that end comb assembly 37 is arranged to hook onto the front of arms 16 and 17 and to be held in place by merely two bolts 47, 47. Each straddle arm is shown in FIG. 242-20 as having a pair 14, 15 of load rollers or wheels mounted near its front end in a pair of recesses within the assembly. The front recess in each arm is provided with an upper lip or edge 50 (see FIG. 20) adapted to be engaged by a hook portion (52 or 53) attached at each end of cross-piece 41. While the embodiment of the invention disclosed herein includes three fingers (38-46), it should be apparent that as few as two fingers would be sufficient in some embodiments of the invention, and that more than three fingers might be preferred in others.

The sequence of operation of the truck will be clear from the successive views of FIG. 3, to which reference now may be had.

In FIG. 3a the truck is shown positioned adjacent a load of small packages carried on a cardboard sheet. The reach mechanism has been fully extended and the fork tilt mechanism tilted maximum downwardly, and the carriage lowered so that the fork tips all press tightly against the floor. The operator then drives the truck forward, slowly until all fork tips are under the load, and then more rapidly in one continuous motion, to chisel the forks all the way under the cardboard sheet, as shown in FIG. 3b. Next, the forks are tilted partly upward, the carriage elevated slightly, and the truck backed slowly for a short distance to separate the load from any adjacent loads or walls, and then the forks are tilted maximum upwardly (typically four degrees from horizontal) to cradle the load within the forks, and FIG. 3c illustrates the truck after such operations have been performed. The carriage is then elevated high enough for the tops of the fork (i.e. the bottom of the cardboard sheet) to clear the tops of the comb members of the load stripper and then the reach mechanism is retracted, as shown in FIG. 3d. The truck is then ready to be driven out of the boxcar or other site to the warehouse dock or other location where the load is to be unloaded onto a pallet.

In FIG. 3c the truck has been driven up to a pallet, to a point where the front faces of the comb members of the load stripper are substantially contiguous to the side of the pallet. The reach mechanism is then. extended until the back of the load is beyond the front faces of the comb members, and then the load carriage is lowered until the forks are only a few inches above the pallet, as shown in FIG. 3f. The forks are then tilted downwardly (and the carriage again lowered, if necessary) until the forward (outward) of the load is resting on the pallet. The forks are then withdrawn by retracting the reach mechanism. FIG. 3g shows the truck just beginning to retract the forks. Even though there may be considerable friction between the forks, the pallet and the load, the vertical comb members of the load stripper will hold both the pallet and the load stationary and in place while the forks slide out from between them. While most lift truck reach mechanisms do not extend and retract far enough to completely withdraw the forks from between the pallet and the cardboard sheet, enough of the weight of load will rest on the pallet when the forks are perhaps half-withdrawn (FIG. 3/2) that neither the load nor the pallet will move if the truck is then backed to completely withdraw the tips of the forks from under the load.

As mentioned above, the invention is applicable as well to lift trucks provided with traveling masts in lieu of scissors reach mechanisms, and because adaptation of the invention to such a truck should now be obvious as a result of this disclosure, no detailed description of such alternative arrangement is deemed necessary.

It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained, and since certain changes may be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Having described my invention, what I claim as new and desire to secure by Letters Patent is:

1. In a material handling vehicle comprisin a base with a pair of forwardly-extending arms each having a wheel assembly near its outer end, a fork carriage carrying a plurality of forwardly-facing generally L-shaped load forks spaced at intervals across said fork carriage, means for translating said fork carriage relative to said base in generally up and down vertical directions and forward and rearward directions, and means for tilting said load forks to raise and lower the tips thereof, the combination of a comb member mounted between said arms, said comb member having a plurality of fingers laterally spaced between said load forks and extending vertically from an elevation below the top of a standard height pallet up more than the maximum downward tilt distance of said tips of said load forks.

2. Apparatus according to claim 1 in which said fingers comprise plates the forward faces of which are coterminous with the forward ends of said arm members.

3. Apparatus according to claim 1 in which said L- shaped load forks include generally horizontal lower portions to collectively provide a generally horizontal loadsupporting surface area and generally vertical back portions to provide a generally vertical load-supporting surface area, and in which said fingers comprise plates, the forward faces of which are located slightly rearwardly of said vertical load-supporting surface area with said fork carriage translated to its forwardmost position.

References Cited UNITED STATES PATENTS ALBERT J. MAKAY, Primary Examiner.

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