US2788909A - Forks for lift trucks - Google Patents

Description

E. R. KUGHLER FORKS FOR LIFT TRUCKS April 16, 1957 2 Shee ts-Sheet 1 Filed March 4, 1954 FIG.

FIG.

INVENTOR EDWIN R. KUGHLER BY $2M MBW E ATTORNEYS April 16, 1957 E. R. KUGHLER 2,788,909

FORKS FOR LIFT TRUCKS Filed March 4. 1954 2 Sheets-Sheet 2 INVENTOR. EDWIN R. KUGHLER @zil, 'MBW 17 ATTOR NEYS FIG. 9

United States O FORKS non LET TRUCKS Edwin Russell Kughler, New York, N. Y. Application March 4, 1954, Serial No.414,0ss

4 Claims. 01. 214-700 This invention relates to forks for lift trucks and has for its object to provide forks whereby a load may be elevated to a greater height than the full vertical movement of the forks to thereby permit the stacking of goods on pallets to the ceiling of a warehouse by a single operator without the operator having to leave his seat on the lift truck.

With the growing scarcity of labor it is becoming more and more important to handle materials with automatic machinery, particularly machines which require but a single operator. To this end manufactured goods which are packaged for shipment in crates and cases upon manufacture, are stored in warehouses on pallets whereby fifty or more may be handled as a unit by a single operator with a lift truck. Such trucks, as is well known, are provided with vertical guide rails or posts upon which a vertically movable cross head is moved up and down by electrical or hydraulic power supplied by the truck. As now designed the maximum lift of such trucks is limited by the length of movement of the cross head on such rails, and the cost of increasing the lift of the truck is proportionately much greater with each foot added to the length of the rails and the corresponding increase in the range of movement of the cross head.

In storage warehouses and on docks, freight depots and the like the floor space is frequently limited while the ceiling height is such that the goods can be stacked to much greater height were it possible to economically lift the pallets to and from the greater height.

The object of my invention is to provide a fork for lift trucks whereby the operator, without leaving his seat on the truck, may stack loaded pallets one upon the other to a much greater height than the lifting range of the cross head.

A further object of my invention is to provide a fork structure for lift trucks whereby the operator, without leaving his seat, may extend the horizontal length of the forks for the purpose of handling large crates and other articles which are too big to be held firmly by gravity alone on the forks of standard dimensions. My improved horizontally extensible truck may be used in conjunction with my improved structure for vertical extensible trucks whereby the capacity of a single standard lift truck as now designed may be greatly' increased both to the extent to which it can elevate a loaded pallet and the size of the crate or other article which it can safely handle.

v In the accompanying drawings:

Fig. 1 is a side elevation of a standard lift truck with my improved fork structure substituted for the conventional fork and with the fork in position to be vertically extended;

Fig. 2 is a similar view showing the verticallyextended forks;

Fig. 3 is a vertical section on an enlarged scale of a portion of the forks in the position shown in Fig. 1;

Fig. 4 is a similar view of a portion of the forks in the position shown in Fig. 2;

Fig. 5 is a perspective view of a horizontally extensible fork;

2,788,909 Patented Apr. 16, 1957- Fig. 6 is a section on line 6--6 of Fig. 5;

Fig. 7 is a perspective view of a modified structure;

Fig. 8 is a sectional view on line 8-8 of Fig 7; and

Figs. 9 and 10 are sectional views on line 9-9 of Fig. 8 showing the forks in differentpositions.

Referring to the drawings, 1 indicates the cross'head of the lift truck which moves up and down on the rails 2. As is well known, the rails 2 may be tilted both forward and backward to thereby incline the horizontal portion of the forks either downwardly or upwardly as may be necessary to pick up the load and maintain it securely on the forks. This is standard construction and in the standard lift truck each fork is. a solid integral piece having a vertical portion attached to the cross head and a horizontal portion extending forward a sufficient length to support a pallet or other load for which it is designed.

In my improved structure the vertical portion of the fork consists of a post 3 of a length about equal to the height of the rails 2 and rigidly attached to the cross head in the same manner as the vertical portion of the conventional fork. The rails 3 are provided with grooves 4 in their sides extending from near the bottom to the top of the post. On the front face of each post there is provided a series of elongated recesses shown at 5.. The recesses 5 are open slots except at their lower ends where the recesses extend below the bottom end of the opening in the face of the post as shown at 6. In the structure shown there are three such recesses. The lift forks 7 are of the usual right angle form, their vertical portions being channel shaped to embrace the posts 3 to which they are held by pins 8 fixed in the side walls of the channel sections and projecting into the vertical grooves 4 in the side walls of the posts. Pins 9 are driven or otherwise fixed in the rear face of front walls of the channel sections of the vertical portions of the forks, and project into the elongated recesses on the front surface of each post. The pins 9 have downwardly projecting heads 10 adapted to project into the extensions 6 at the bottom of the recess 5.

The horizontal sections of the forks may be formed as usual of a single solid piece of metalor may be provided, as shown, with an adjustable tread whereby the forks may be horizontally extended to accommodate loads of unusual size.

The extensible tread consists of a channel shaped sec tion 13 overlying the horizontal portion of the fork 14 and held against vertical displacement by inturned flanges or bevels 15 on the side flanges of the treads. The tread portion is held against free movement on the horizontal portion of the fork by a bolt 16 which is threaded into the face of the tread and projects into a grove 17 formed in the upper face of the horizontal portion of the fork. The groove 17 extends substantially the full length of the horizontal portion of the fork and formedv in each end of the groove is a recess 18 which is slightly deeper than the groove. The bolt 16 is recessed at itsv ends to receive a ball 19 and a spring 29 which holds the ball normally projecting below the bottom face ofthe bolt. Additional recesses 18 may be at intermediate positions in the groove 17 if desired. By this arangement the ball will be forced into the recesses 18 in the groove 17 when the extension tread isin a corresponding position, and thereby holds the extension 13 against displacement in such positions but permits its movement back and forth along the horizontal member 14 of the fork when suflicient force is exerted in a horizontal direction to overcome the-pressure of the spring 20. The recesses 18in the groove are slightly less in depth than the radius of the balls and consequently a horizontal push or pull on the extension of sufiicient force will force the ball back into the pin against the tension of the spring and allow the extension 13 to be shifted on the fork.

In operation, the lift truck is used in the ordinary manner except when the load is to be lifted to a greater height than permitted by the elevating mechanism of the lift truck. The forks 7 remain in their lowermost positions on the posts 3 with the pins 9 in the lowermost recesses on the posts. The pins 8 in the'sides of the vertical portion of the forkhold' the forks against tilting forward at the upper portion, while the pins 9 support the forks against further downward movement. If the operator is using the truck tostack pallets to a greater height than permitted byt'he amplitude of vertical movement of the cross head 1, he places 'a stack of'pallets adjacent the area where'the goods are to be stored, this stack of pallets having its top surface just under the height to which the fork can be lifted when positioned in their lowermost positions on the vertical posts 4. Such stack is shown at 11 in Fig. 'l'. The operator Picks up a pallet on the forks, elevates theforks to where they will clear the upper surface of the stack 11, and then drives his truck so as to bring he ends of the forks over the stack 11 as shown. The crosshead 1 is then lowered slightly to lift the heads 10 of the pins 9 0m of the undercut ends of the recesses 5. The operator then, through the usual tilting mechanism, tilts the rails forward at the upper ends, thereby likewise tilting the posts 3 forward at their upper ends, with the result that the forms which are 'held'against tilting movement by resting on top of the stack 11 swing forward on the Pins 8 until the heads 10 of the pins 9 are clear of the recesses 5 in the front face of the posts. The operator now lowers the cross head and with it the posts 3 until the pins 9 are opposite the receses 5 at the upper ends of the posts. He now returns the rails and thecross head to vertical position so that the pins 9 enter the recesses at the upper end of the post and hold the forks against downward movement. The cross head is now elevated sufficiently to lift the load off the stack 11 and the truck is then operated to take the load to the position where it is to be stacked. When this position is reached the cross head is again elevated, thereby lifting the load to a further height where, as shown in Fig. 2, it may be stacked on top' of a tier of pallets which is already as high as the pallets can be lifted by the truck without using the vertical extension.

In order to return the empty fork to its lowermost position after the forks have been withdrawn from under the pallet, the operator has only to tilt the rails carrying the cross head forward at their upper ends so that pins 9 will clear the top recesses in the poss. He then brings his truck alongside the stack 11' and lowers the cross head until the forks rest on the stack. The continued downward movement of the cross head causes the forks to swing on their pins 8, thus withdrawing the pins 9 from the recess in the front wall of the post 3 so that the cross head may again beelevated, but without'lifting the forks. When the cross head is elevated sufficiently for the pins 9 to be opposite the lowermost receses in the front face of the post the rails 2 are again turned to vertical position, thereby causing the pins 9 to enter the bottom recesses in the, posts and thus restore the forks to their initial position ready to pick up another pallet.

. The forks may be extended horizontally by the operator without leaving his seat. Where loads of variable size have to be handled, as is common in freight depots, steamshipwharves and the like, this is accomplished by operating the truck to project the forks under a loaded pallet and then operating the elevating mechanism to a sufiicient extent to bring the upper surface of the extensions into firm contact with the under side of the pallet.

If, now, the operator backs away from'the pallet the frictended forks against the wall of the depot or warehouse to thereby overcome the pressure of the spring against the ball and push the extensions back.

The forks may be positioned in advance in either fully open, full closed, or intermediate position, as may be needed for the particular operation at hand, and locked in that position by screwing the bolt down until the end of the screw at the end of the ball firmly engages the metal of the fork surrounding the recess.

In Figs. 7, 8, 9 and 10 I have illustrated a modified are for the vertical'extension of the works. As here shown the upright members attached to the cross head 1 consists of two channels 23 connected together in the manner shown by three transverse bars 24 which are welded to the side flanges of the channels at the bottom, middle and near the top, respectively. The channels are also connected by a top piece and by the eye bar 2:3 by which the two uprights are connected to thecross head 1 of the'lift truck.

The forks 27 have fixed to the rear face of their upright portions, blocks 28 of a width slightly less than the distance between the edges of the facing flanges of the two channels 23. Short cross shafts 29 are fixed in the upper part of blocks 28 and rollers 30 are mounted on the ends of the shafts 29, the rollers being of a diameter slightly less than the distance between the innerfaces of the side flanges of the channels whereby the channels serve as tracks for the rollers in the vertical movement of the forks with respect to the channels.

The bottom ends of the blocks 28 are somewhat wider than the transverse webs of the channels so that when the vertical portions of the forks 29 rest against the front faces of the flanges of the channels the bottom portions of the blocks 28 will project rearwardly beyond the channels so as to overlie the transverse bars 24. The bottom faces of the rearwardly extending portions of the blocks 28 are upwardly and inwardly inclined'and the top surfaces of the bars 24ers similarly inclined so that when the rearwardly projecting portions of the blocks 28 rest on the bar 24 the, vertical portions of forks 27 will be held firmly against the flanges of the channels 23.

The operation of the above described modification is the same as that of the first described structure. The modified structure has the advantage that it may be fabricated with little labor from bars, rods, channels, etc. of conventional shapes and dimensions which are obtainable at low cost. It will be understood that my improved fork structure may be modified otherwise than in the manner described, and that my invention is not limited to the specific embodiments disclosed but covers all modifications thereof as fall within the scope of the appended claims. a 1

I claim:

1. A fork structure for lift trucks, comprising a ver-v tically movable member having horizontally extending load supporting bars, load engaging tread portions mounted on said bars for movement longitudinally of the bars and means for limiting the, relative movement of said tread portions and said load. supporting portion, said means yieldingly holding said parts against relative movement at a plurality of points in the permitted range of movement.

2. The structure of claim 1 wherein means are providedfor'locking said extensions in different positions of adjustment.

3. The combination with a lift truck having forked supporting guides mounted for tilting movement in a vertical plane, a cross head and means for moving the same longitudinally of said guides, of a second pair of guides connected to said cross head for movement in parallelism with said first pair of guides, a second cross head mounted for movement longitudinally of said second pair of guides, lifting forks having load receiving tines and suspending portions at right angles to said tines, said suspending portions being pivotally mounted at their upper ends on said second cross head and interengaging projections on said fork members and said second guides for holding said forks against movement under the weight of the load thereon when said guides 5 are in vertical position and said forks are moved downwardly relatively thereto.

4. The combination of claim 3 wherein the intercugaging projections are shaped to prevent swinging movement of said forks with respect to said guide. 10

References Cited in the file of this patent UNITED STATES PATENTS 1,580,698 Stag; Apr. 13, 1926 15 6 Grab July 16, 1935 Cochran Feb. 3, 1942 Ulinski Ian. 11, 1944 Hawkins May 31, 1949 Lehmann Apr. 4, 1950 Lehman Ian. 2, 1951 OSullivan Dec. 16, 1952 'Lepkowski Apr. 27, 1954 Hobson May 4, 1954 FOREIGN PATENTS Austria Mar. 10, 1953 France Nov. 7, 1953

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