US3561628A

US3561628A - Load handling in fork-lift trucks movable fork cover for forklift truck

Info

Publication number: US3561628A
Application number: US517883A
Authority: US
Inventors: Thomas N Melin
Original assignee: Individual
Current assignee: Individual
Priority date: 1965-12-14
Filing date: 1965-12-14
Publication date: 1971-02-09
Anticipated expiration: 1988-02-09

Abstract

In a forklift truck, at least one, and preferably both, of the horizontal load-supporting tines, which extend forward in cantilever fashion from a vertically movable fork apron, are provided with load-engaging cover members which are selectively movable along the lengthwise of the tines. The cover members are movable independently of each other along their respective forks so that the angular relationship of a load supported on the forks may be adjusted relative to the length of the truck about an axis passing vertically through the load, thereby making it possible to precisely adjust the position of a load supported by the truck relative to a foundation upon which the load is to be supported without moving the truck per se.

Description

United States Patent Primary Examiner-Gerald M. Forlenza Assistant Examiner-Raymond B. Johnson Attorney-Christie, Parker & l-lale ABSTRACT: In a forklift truck, at least one, and preferably both, of the horizontal load-supporting tines, which extend forward in cantilever fashion from a vertically movable fork apron, are provided with load-engaging cover members which are selectively movable along the lengthwise of the tines. The cover members are movable independently of each other along their respective forks so that the angular relationship of a load supported on the forks may be adjusted relative to the length of the truck about an axis passing vertically through the load, thereby making it possible to precisely adjust the position of a load supported by the truck relative to a foundation upon which the load is to be supported without moving the truck per se.

PATENTEUFEB 919?: 3561628 SHEET 2 0F 2 INVENTOR.

This application is a continuation of my copending application Ser. No. 426,482 filed Jan. 15, I965, for Load Handling In Forklift Trucks, which application (now abandoned) was a continuation-in-part of application Ser. No. 401 ,413 filed Oct. 5, 1964, now abandoned, bearing the same title.

In using forklift trucks to stack articles for storage and the like, it is often very desirable, and in many cases necessary, that the article be deposited by the truck in substantially perfect angular alignment with the upper end of a partially complete stack or with a foundation for a stack. This is true whether or not the article is supported on a pallet which, in turn, is supported on the spaced forks of the forklift truck.

For example, in sawmills green lumber is arranged in unit stacks which usually are of considerable length. Several of these unit stacks are arranged vertically for drying of the lumber contained therein. Forklift trucks are used to compose the large stacks. Since the large stacks often become quite high, it is necessary, for the stack to be stable, that each unit stack be angularly aligned with the unit stack immediately below it, and that the lowermost unit stack be properly positioned on the foundation provided for it.

It is difficult, because of human errors in judgment, to properly position a lift truck adjacent a stack foundation so that a unit stack of lumber carried by the truck may be deposited properly on the foundation. Usually the truck operator positions the truck adjacent the center of the foundation only to find that the elongate extent of the truck load is skew to the elongate extent of the foundation. The truck operator thus must yo-yo, i.e., back and turn, the truck to align the load with the foundation. As a result, the proper stacking of lumber is a difficult, time consuming and uneconomical process.

It is a simple matter, on the other hand, for an operator to position a forklift truck so that a stack of lumber carried by the truck is misaligned in a given direction with a foundation for the stack. This invention relies upon this fact and provides apparatus whereby this misalignment may be corrected. The truck operator positions the truck adjacent the midlength of the foundation, and usually there is some misalignment of the load with the foundation. He then operates the apparatus to shift the position of the load (the stack carried by the truck) relative to the truck to align the load with the foundation. The load is then deposited on the foundation.

Accordingly, in general terms, this invention provides apparatus which is attachable to a forklift truck. The truck conventionally has a vertically movable fork apron to which are mounted a pair of spaced fork members adapted to support a load. The inventive apparatus comprises an elongated cover member for one of the fork members. Means are provided for mounting the cover member to the one fork member so that the cover member is adapted to engage and carry the load and so that the cover member is movable along the fork member toward and away from the fork apron. The apparatus further includes selectively operable means carried by the cover member and adapted to be connected to the fork apron. The selectively operable means is operable for moving the cover member along the one fork member.

The cover member is 'not a mere extension device for the fork member. Rather it is a load-carrying and load-driving member. The truck is positioned adjacent the foundation for the load so that, in the preferred case, the end of the load carried by the cover member is farther out of alignment with the foundation than the other end of the load. The cover member is then moved toward the foundation to move the load on the fork members. The cover member is moved sufficiently to align the elongate extent of the load with the length of the foundation. If desired, the truck can be moved closer to the foundation to position the load directly over the foundation. The load is then lowered onto the foundation.

Only one of the pair of fork members need be provided with a cover member for the successful practice of this invention.

This is true since the direction of the error of alignment of the truck relative to the load foundation is easily controlled by the truck operator. Moreover, the extent of this error, between limits, is easily controlled by the truck operator. Accordingly, in the large majority of situations only one cover member is needed. The invention is described below, however, as including a cover member for each fork member in order to be complete.

The above mentioned and other features of the invention are more fully set forth in the following detailed description of the invention taken in conjunction with the accompanying drawings wherein:

FIG. 1 is a top plan view of apparatus according to this invention mounted to the front end of the forklift truck;

FIG. 2 is an enlarged perspective view with parts broken away of a fork member fitted with apparatus according to this invention;

FIG. 3 is a side elevation view showing the connection of a fork member to the fork apron of the truck;

FIG. 4 is a perspective view, similar to FIG. 2, of a fork member fitted with another apparatus according to this inven tion; and

FIG. 5 is a side elevation view of the apparatus shown in FIG. 4.

FIG. 1 shows an industrial forklift truck 10 having a chassis II to which are mounted front wheels I2. A vertical elevator 13 is mounted to the truck chassis between the front wheels. The elevator includes a pair of C-shaped structural channels 14 which open toward each other to define elevator tracks. The channels are disposed parallel to one another and are extended vertically from a support plate 15 movably mounted to the front end of the truck.

A fork apron 16 is mounted to the elevator for movement along the tracks. The fork apron includes a vertically oriented planar frame 17 disposed transversely of the truck. A fork apron carriage 18 is secured to the rear central portion of frame 17 and carries a plurality of wheels 19 on opposite sides of the carriage. The wheels are engaged between the flanges of the channels to movably engage of the carriage with the elevator. An extensible hydraulic ram 20 is connected between carriage I8 and channel support plate 15 and is operable to move the carriage vertically in the elevator tracks.

FIGS. 1 and 3 show a pair of fork members 21 connected to the fork apron on opposite sides of the elevator. Each fork member is a right angled, elongated forged member which has a vertically extending leg 22 and a horizontally extending leg 23. The upper end of leg 22 is connected to a support pin 24 carried by the fork apron frame. Leg 23 extends forwardly from the front face the fork apron adjacent the lower edge of the frame. A bearing plate 25 is secured to the lower front surface of frame 17 and bears against the lower rear surface of fork member leg 22.

Each fork member 21 is a common type of fork member occurring in a typical industrial forklift truck. Fork member 21 is shown merely for the purposes of example. It is within the scope of this invention that the structure of the fork member may vary from that shown and described. Preferably, however, the vertical thickness of the horizontal portion of the fork member decreases progressing forwardly of the fork from the structure to which it is connected, as shown in FIG. 3.

An elongated cover plate 30, shows in FIGS. 1 and 2, is disposed adjacent the upper surface of each fork member. Preferably each plate 30 has a width greater than the horizontal width of fork member leg 23 and has a length less than the length of the leg. A flange 31 (see FIG. 2) depends from each longitudinal side of each cover plate along the length of the plate. The opposing surfaces of the flanges on each cover plate are spaced apart a distance greater than the width of the fork member. An inturned lip 32 extends from the lower extremity of each flange toward the opposite flange of the cover plate. As shown in FIG. 2, the upper surfaces of the lips are spaced from the lower surface of the cover plate a distance greater than the thickness of the fork member. The cover plate is thus configured to be slipped longitudinally over the fork member and to be retained thereon by lips 32 and flanges 31.

Each cover plate is mounted to its fork member for movement along the fork member toward and away from the fork apron. As shown in FIG. 2, a roller bearing cage plate 35 is disposed between each cover plate and the adjacent fork member. Preferably, the cage plate has a length substantially equal to the length of the cover plate. A plurality of roller bearings 36 are mounted in each cage plate at locations spaced along the cage plate. The roller bearings are disposed transversely of the fork member and extend above the upper surface of the cage plate to engage the underside of cover plate 30. The bearings and cage plates mount each cover plate to its fork member so that the weight of a load engaged with the cover plates is transferred to the fork members. Moreover, they assure that the loaded cover plates are movable along the fork member.

The attachment apparatus provided by this invention also includes selectively operable means for moving each cover plate along its fork member. As shown in FIGS. 1 and 2, a double-acting hydraulic ram assembly 40, having a cylinder 41 and a piston 42, is carried by each cover plate. A bracket 43 extends laterally from that cover plate flange which, when the cover plate is engaged with its fork member, is disposed opp site from elevator 13. Each bracket carries a vertical plate 44 which opens to the rear end, i.e., the apron end, of the cover plate to which it is connected. The cylinder of a respective ram assembly is connected to plate 44 and extends from the plate toward the fork apron. The ram assembly is aligned parallel to the elongate extent of the cover plate. The ram piston carries a lug 45 adapted to be connected to a cooperating lug 46 carried by the fork apron adjacent the rear end of the horizontal portion of the fork member. It will be understood, however, that lug 46 may be connected to the fork if desired, as when the forks are movably laterally relative to the apron. it is preferred that the ram assemblies be disposed below a horizontal plane defined by the upper surfaces of cover plates 30 so that no portion of the weight of a load placed on the cover plates is borne by the ram assemblies.

Each ram assembly 40 is operable independently of the other ram assembly to move its cover member along the adjacent fork member. Each cover member is guided in such motion by flanges 31.

Ram assemblies 40, described above, are exemplary of means which are provided to move the cover plates along their cooperating fork members. The invention, however, is not restricted to the use of such devices. For example, a motor driven jackscrew may be connected between each cover plate and the adjacent end of the fork apron. It is required only that whatever device which is provided for moving the cover plate along the fork member be operable independently of the mechanism provided for so moving the other cover plate.

As indicated above, the present invention is useful in positioning a load accurately in a preselected position even when the forklift truck which carries the load is located adjacent this position but is somewhat out of alignment therewith. The area enclosed in FIG. l by dashed line represents a preselected position in which a load, represented by phantom lines 52 and carried by truck 10, is to be deposited. The truck is disposed so that the longitudinal axis of the truck is slightly skew to the elongate extent of position 50. The load is disposed on the cover plates so that its midlength is centered between the cover plates. The cover plates are positioned immediately adjacent the fork apron.

Points

54 and 55 represent the centers of pressure of the load upon the right and left cover plates, respectively, assuming a uniform distribution of the load on each of cover plates 3%. I

To properly deposit the load in position St), the left end of the load (as viewed by the operator of the truck) must be moved forwardly of fork apron ll. Accordingly, the operator of truck l0 actuates ram assembly 40 associated with the cover plate engaged with the left fork of the truck to move the cover plate (and center of pressure 55) forwardly along the cover plate a distance B, the chord by an arc A swung about point 54. Such operation of the ram assembly drives the load into alignment with position 50 as the load pivots about the centers of pressure of the load on the respective cover plates. The operator then need only lower the fork apron relative to the truck chassis to deposit the load in proper alignment with position 50.

By providing each cover plate with a separate selectively operable means for moving the cover plate along its associated fork member, a forklift truck equipped with this invention has the capacity to pivot a load in either a clockwise or counterclockwise direction. As indicated above, however, the direction and extent of misalignment of the initial position of the load relative to the position in which the load is to be deposited is easily controllable by the operator of the truck. For example, the operator can position the truck so that the left end of the load is away from the foundation so that the error of alignment is from 7% to 15 and requires a clockwise movement of the load relative to the truck to align the load with the foundation. This error can be reproduced at will. Accordingly, a cover member need by provided only on the left fork member for the practice of this invention.

FIGS. 4 and 5 show a second cover member 60 according to this invention. Cover member 60 is fabricated of heavy gauge sheet metal arranged to form a sheath which encloses the horizontal leg 23 of a fork member 21. The cover member has a closed end 61 for enclosing the toe of the fork, i.e., the end of the fork spaced from fork apron 16. The cover member has a lower surface which curves upward to the front end of the cover member; this curvature facilitates insertion of the fork and cover member under a load and also assures that the fork can be withdrawn from under a load without damaging either the cover member or the structure on which the load is deposited. The length of the cover member is such that a rear end 62 of the cover member is spaced from the vertical leg of the fork when ram 4-0 is disposed in the midposition of its operating range; this is the normal or at rest position of the ram. A roller bearing cage plate 35 is mounted inside the cover member between it and the upper surface of the fork.

A skeg 65 is welded to the underside of the fork at the heel of the fork and is spaced from the end of the cover member, when ram 40 is in its normal position, by an amount equal to one-half the travel of piston 42. The skeg has a lower surface 66 curved convexly downward and faired into the curvature of the heel of the fork. The skeg provides a stop for the cover member and also enables the fork to be withdrawn from under a load, after a load has been deposited, by sliding easily over whatever structure the load is placed on.

Cover member 60 has sidewalls 68 which have extensions 69 extended to the rear of the vertical leg of fork as shown in FIGS. 4 and 5. The extensions have upper edges 70 which lie substantially in the plane of the top of the cover member. The extensions are particularly useful where the load handled by truck 10 is lumber. In the absence of the extensions and with the cover member in its normal position, it is possible for a piece of lumber from the load to drop into the space between the rear end of the cover member and the front surface of fork leg 22. When this happens the cover member cannot be moved toward the fork apron without crushing the piece of lumber, nor can the fork be withdrawn from under the load without taking the piece of lumber with it. The extensions, however, prevent a piece of lumber from falling into the space between the rear of the cover member and the front face of the fork leg 22, thereby preventing these problems from arismg.

Lug 45 to which ram piston 42 is connected is notched as at '72 to receive the adjacent cover member sidewall extension.

The structural strength of cover member 6th is provided in its top, bottom and sidewalls. Borrowing a phrase from the aeronautical industry, the cover member is skin stressed." The cover member is sufficiently strong that it can receive a load within the capacity of truck l0 and be moved in response to operation of ram 49 to move a load as described above.

it is a feature of the apparatus described above that the longitudinal dimension of a forklift truck is not increased by the addition of the apparatus to the truck, and the apparatus is light in weight. Accordingly, the load carrying capacity of the truck is not reduced. Moreover, operation of the apparatus does not produce any substantial shift in the center of gravity of a load carried by the truck. There is substantially no lateral shifting of the center of gravity of the load since the center of gravity of the load moves along a line which extends longitudinally of the vehicle. Accordingly, lateral stability of the vehicle is not impaired. Moreover, as shown above, this longitudinal shift in the center of gravity of the load relative to the truck is small. There is substantially only rotational movement of the load relative to the truck chassis rather than rotational and translatory motion. Accordingly, the truck operator need concern himself only with positioning the truck at the desired location lengthwise of the position in which the load is to be deposited; he need not worry about lateral shifting of the load as the angular relation of the load relative to the position is adjusted.

It is a further feature of this invention that an existing forklift truck can readily be equipped with the inventive apparatus. All that is required is to slip a cover plate or cover member in accord with the above description over one of the forks of the truck and to connect the cover-plate-moving mechanism between the cover plate and the fork apron adjacent the one fork. The only structural modification required to the truck is the connection of the lug 46 to the fork apron adjacent the rear end of the fork. The conversion apparatus, composed of the cover plate and the ram assembly, may be removed from the truck at will if desired. Where a hydraulic ram is used to move the cover plate along the fork member, certain modifications obvious to one skilled in the art must be made to the hydraulic system of the truck. Alternatively, a supplemental hydraulic system may be attached to the truck.

The above described apparatus is to be distinguished from certain prior art structures such as those disclosed in US. Pat. No. 2,774,498 issued to Cordes et al. on Dec. l8, 1956, and in U.S. Pat. No. 2,788,909 issued to Kughler on Apr. 16, i957. Both of these patents disclose devices for extending the length of the forks of a forklift truck to enable the truck to be used for handling large crates and the like which are too large to be held firmly by gravity on forks of standard dimensions. They do not disclose apparatus for driving a load along the forks to change the position of the load relative to the truck.

The present apparatus is also to be distinguished over a structure like that shown in US. Pat. No. 2,536,068 issued to Lehmann on Jan. 2, 1951. This patent shows movable extensions fitted to each of a pair of forks in a conventional forklift truck. The extensions are movable along the forks by hydraulic rams. The Lehmann rams, however, operate in unison and cannot be operated independently of one another. There is no disclosure that the angular relation between the load and the truck be altered. Accordingly, such a device such as that shown in the Lehmann patent is like those structures shown by Cordes et al. and Kughler in that the extensions merely increase the capability of the truck for handling large cartons and the like.

Although specific structure has been shown and described in the foregoing explanation of a preferred embodiment of the invention, this has been by way of example only and is not to be considered as limiting the scope of the invention.

lclaim:

1. Attachment apparatus for a forklift truck having a verti cally movable fork apron carrying a pair of substantially identical spaced horizontal fork members adapted to support a load, the apparatus comprising an elongated cover member for enclosing one of the fork members, the cover member having a length as long as the horizontal length of the one fork member, the cover member having an open end and a closed end for enclosing the tip of the one fork member, means for mounting the cover member to the one fork member independently of the other fork member for movement of the cover member along the upper surface of the one fork member toward and away from the fork apron, means carried by the cover member operable for moving the cover member along the one fork member independently of the other fork member, and a skeg secured to the underside of the one fork member adjacent the fork apron and having a lower surface including a first portion faired into the surface of the one fork member adjacent the apron and a second portion substantially coplanar with the undersurface of the cover member.

2. Apparatus according to claim 1 wherein each fork member has a vertical leg mounted to the fork apron and a horizontal leg extending forwardly of the truck from the apron, the cover member enclosing the horizontal leg of the one fork member, the cover member has side extensions which, when the cover member moving means is in a normal at rest condition thereof with the open end of the cover member spaced from the vertical leg of the one fork member, extend on opposite sides of said vertical leg, the extensions having upper surfaces disposed substantially in the plane of the top of the cover member.

3. In a forklift truck having a vertically movable carriage including an apron and a pair of spaced lifting fork members, said fork members supporting respective portions of a load engaged therewith and extended in a cantilevered fashion forwardly of the truck from the apron to unsupported tip ends spaced from the apron, apparatus comprising an elongated cover member supported by one of the fork members substantially enclosing the one fork member from its unsupported end to adjacent its supported end, the cover member having a closed end enclosing the tip end of the one fork member and an open end disposed adjacent to and forwardly of the apron, the cover member including a portion disposed over and aligned with the length of the one fork member for engaging the adjacent portion of a load supported by the fork members, the cover member having guide means cooperating with the one fork member for guiding the cover member in load-bearing movement along the length of the one fork member, bearing means mounting the cover member to the one fork member wholly independently of the other fork member for load-bearing guided movement of the cover member along the one fork member, cover member moving power means connected to the cover member and the carriage operable for moving the cover member along the one fork member to move the portion of a load supported by the cover member relative to the portion of the load supported by the other fork member to move the load angularly about a vertical axis through the load, and means cooperating between the open end of the cover member and the supported end of the one fork member for preventing foreign bodies from wedging between the open end of the cover member and the one fork member sufficiently to hinder movement of the cover member toward the apron in response to operation of the power means.

W i-v F PO-WJO UNITED N r \f CERTIFIQAI I, ()I CQRRILLIION Patent No. 3 561 Dated February 197] Inventor(s) Thomas N Melin It is certified that: error appears in the above-identified pace: and that said Letters Patent are hereby corrected as shown below:

Column 2, line 40, after "engage" delete -of--;

line 63, for "shows" read -shown--.

Coluinn 3, line 35, for "lug 46" read --che ram pistc lug--' I line 36, after "desired," read -as shown in 4, o

Signed and sealed this 21st day of September 1971.

(SEAL) Attest:

EDWARD M-FLETCHERJR- ROBERT GOTTSCHALK Attesting Officer Acting Commissioner of Pa

Claims

1. Attachment apparatus for a forklift truck having a vertically movable fork apron carrying a pair of substantially identical spaced horizontal fork members adapted to support a load, the apparatus comprising an elongated cover member for enclosing one of the fork members, the cover member having a length as long as the horizontal length of the one fork member, the cover member having an open end and a closed end for enclosing the tip of the one fork member, means for mounting the cover member to the one fork member independently of the other fork member for movement of the cover member along the upper surface of the one fork member toward and away from the fork apron, means carried by the cover member operable for moving the cover member along the one fork member independently of the other fork member, and a skeg secured to the underside of the one fork member adjacent the fork apron and having a lower surface including a first portion faired into the surface of the one fork member adjacent the apron and a second portion substantially coplanar with the undersurface of the cover member.