EP0042835B1 - Side shift fork adjustable carriage - Google Patents
Side shift fork adjustable carriage Download PDFInfo
- Publication number
- EP0042835B1 EP0042835B1 EP19800900520 EP80900520A EP0042835B1 EP 0042835 B1 EP0042835 B1 EP 0042835B1 EP 19800900520 EP19800900520 EP 19800900520 EP 80900520 A EP80900520 A EP 80900520A EP 0042835 B1 EP0042835 B1 EP 0042835B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- forks
- carriage assembly
- carriage
- tracks
- pair
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B66—HOISTING; LIFTING; HAULING
- B66F—HOISTING, LIFTING, HAULING OR PUSHING, NOT OTHERWISE PROVIDED FOR, e.g. DEVICES WHICH APPLY A LIFTING OR PUSHING FORCE DIRECTLY TO THE SURFACE OF A LOAD
- B66F9/00—Devices for lifting or lowering bulky or heavy goods for loading or unloading purposes
- B66F9/06—Devices for lifting or lowering bulky or heavy goods for loading or unloading purposes movable, with their loads, on wheels or the like, e.g. fork-lift trucks
- B66F9/075—Constructional features or details
- B66F9/12—Platforms; Forks; Other load supporting or gripping members
- B66F9/14—Platforms; Forks; Other load supporting or gripping members laterally movable, e.g. swingable, for slewing or transverse movements
- B66F9/146—Side shift, i.e. both forks move together sideways relative to fork support
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B66—HOISTING; LIFTING; HAULING
- B66F—HOISTING, LIFTING, HAULING OR PUSHING, NOT OTHERWISE PROVIDED FOR, e.g. DEVICES WHICH APPLY A LIFTING OR PUSHING FORCE DIRECTLY TO THE SURFACE OF A LOAD
- B66F9/00—Devices for lifting or lowering bulky or heavy goods for loading or unloading purposes
- B66F9/06—Devices for lifting or lowering bulky or heavy goods for loading or unloading purposes movable, with their loads, on wheels or the like, e.g. fork-lift trucks
- B66F9/075—Constructional features or details
- B66F9/12—Platforms; Forks; Other load supporting or gripping members
- B66F9/14—Platforms; Forks; Other load supporting or gripping members laterally movable, e.g. swingable, for slewing or transverse movements
- B66F9/142—Movements of forks either individually or relative to each other
- B66F9/144—Movements of forks relative to each other - independent
Definitions
- This invention relates generally to material handling equipment and more particularly to carriage assembles for fork lift vehicles. Specifically it deals with side shifting of the material handling forks and in its preferred embodiment with the associated hydraulic circuitry for operation of the side shifting arrangement.
- Material handling vehicles in order to be useful, should have a certain degree of adjustability. This is particularly true if the vehicle is to be used to handle differing types of loads. It is also true in a material handling vehicle which handles similar loads, but in a different operating environment. For example, as the vehicle approaches the load to be handled, it is usual for the vehicle to approach the load at differing aspects. Even though these differing aspects may be of a minor amount, the load handling equipment, such as forks in the case of a fork lift, may not properly align with the load. When this occurs it requires a certain degree of maneuvering of the vehicle in order to obtain alignment of the load handling elements forks and the load.
- the vehicle After maneuvering to pick up the load and subsequent to picking up the load, the vehicle is ordinarily driven to the off-loading point. The same maneuvering of the vehicle at the off-loading point that occurred at the loading point may also be necessary. That is, the vehicle may not be aligned with the loading dock, truck, or the like and thus the material handling vehicle must maneuver in order to position the load properly.
- load moment offset In providing a capability to shift the load handling elements laterally relative to the vehicle, it is important not to degrade forward visibility from the operators station. It is equally important to reduce the offset of the load, from the vehicle center of gravity, referred as load moment offset. Other desiderata include reduction of the number of hydraulic lines, closer spacing of the forks, and providing an operating system for the load handling elements that is sensitive to the load carried.
- the carriage upon which the forks are mounted has been designed to shift sideways in order to adjust or position the forks to pick up or deposit a load.
- Individual spacing of the forks upon such a side shift carriage may be accomplished manually or with additional hydraulic structure.
- the additional structure required to move the forks and carriage increases the load moment offset from the center of gravity of the vehicle by moving the forks further from the center of gravity. This, of course, reduces the load carrying capacity of the vehicle. Accordingly, reduction of the structure necessary to side shift the load, thus reducing the load moment offset, is advantageous.
- Individual fork adjustment may also be appropriate when it is necessary to pick up a load with a center of gravity laterally offset from the center line of the vehicle. One fork may then be moved laterally across the face of the carriage in orderto compensate for the offset center of gravity of the load. Once the load is picked up both forks and thus the load may be moved in the opposite direction to shift the center of gravity of the load to a point coincident with the center line of the vehicle thus eliminating or reducing the possibility of overturning the vehicle.
- a material handling vehicle such as a fork lift or the like operates in an environment having numerous obstructions
- the forks may inadvertantly contact an obstruction while the vehicle is turning, thereby placing an undesirable side load on the fork.
- Such a load may result in damage to either the fork, the carriage, or in the event of a hydraulically operated side shift arrangement to the hydraulic circuitry. Damage which does occur as a result of contacting obstruction may result in loss of the use of the vehicle for that period of time necessary to repair it.
- the forks have been operable on a track structure with a runner or the like to locate the forks on a track structure.
- the nature of the structure is usually such that the forks may not be placed in an abutting relation, thus the total side shift of the individual forks may be reduced by the separation of the forks at their closest position.
- US-A-2,795,346 shows a vehicle with a carriage with load-clamps and an alternative carriage for providing a fork lift capability, this latter carriage being in accordance with the pre-characterizing part of claim 1.
- the forks and clamps are movable horizontally by hydraulic means, but are mounted such that their movement toward one another is limited, as is thus their maximum transverse displaceability to align with a load. Moreover, the mounting of the forks is not adapted to stabilize them against lateral tilting.
- US-A-3,075,665 shows an arrangement in which the forks may be brought together, but in which again the mounting of the forks is necessarily narrow and would not provide long-term stability.
- the present invention seeks to overcome or lessen at least these last-mentioned problems by the features of the characterizing part of claim 1.
- the invention thus concerns a track assembly for allowing lateral movement of the pair of load lifting forks from an abutting position to a spatially separated position.
- Powering means are preferably provided for selectively moving one or the other of the forks or both forks at the same time with a load thereon.
- the powering means may be sensitive to the weight imposed by the forks on the lift mechanism.
- a material handling vehicle in another aspect of this invention, includes a mast, a carriage assembly adapted for generally vertical movement on the mast and a pair of load lifting forks mounted on the carriage.
- the improvement comprises a track assembly for allowing lateral movement of the load lifting forks from an abutting position to a spatially separated position and powering means for selectively moving one or the other of the forks.
- a material handling vehicle such as a lift truck 10 is shown in Figure 1 having mounted thereupon a side shift fork adjustable carriage 12.
- Lift truck 10 includes a mast assembly 14 at one end thereof to which the adjustable carriage 12 is affixed for vertical movement.
- Adjustable carriage 12 has fitted thereon a pair of forks 16 and 18 (see Figure 2) which are adapted to receive a load.
- Operation of the lift truck 10 is well known in the art and will not be further described other than to state that loads received on forks 16 and 18 may be lifted free of the ground for transport and placement at some position remote from the point of pick up. Since the size and center of gravity of the load to be picked up may vary, the forks must be positioned properly under the load to avoid losing the load during the transport and placement operation. Placement of the forks may be accomplished in one of two manners, either by maneuvering the vehicle or by sideways adjustment of the forks after a gross positioning of the vehicle.
- Forks 16 and 18 are mounted for horizontal movement upon the carriage portion 20 of the side shift adjustable carriage 12. Such movement is facilitated by two pairs of tracks, the first pair of tracks 22, comprised of individual tracks 22a and 22b, located adjacent the top edge of the carriage portion 20 and a second pair of tracks 24, comprised of individual tracks 24a and 24b, located adjacent the bottom edge of the carriage 20.
- One pair of these tracks, preferably the first pair 22 located along the top edge of carriage 20 is oriented in a horizontal plane as illustrated in Figure 5 while the second pair of tracks, preferably the lower pair 24, is oriented in a vertical plane as illustrated in Figure 6.
- both pairs could be located in either the horizontal or vertical plane, however, the positioning of the first pair of tracks 22 at the upper edge in the horizontal plane provides greater visibility through the carriage 20 from the operator station of the lift truck. Furthermore, positioning the second pair of tracks 24 in the vertical plane as illustrated in Figure 6 reduces the weight requirements of the carriage since the vertical load placed on the forks is carried primarily by the lower set of tracks. To position the lower set of tracks in a horizontal plane would require additional strength members not necessary with the vertical arrangement as illustrated in Figure 6.
- Each fork 16 or 18 is associated with one of the tracks of the first pair of tracks 22 by an elongated bearing bar 26 or 28 having a length L and an inner end portion 26a or 28a, respectively, and one of the tracks of the second pair of tracks 24 by an elongated bearing bar 30 or 32 having a length L' and an inner end portion 30a or 32a, respectively.
- Fork 18, as shown in Figure 5, has affixed at its upper end a pair of generally triangular shaped plates 34 and 36 (see also Figure 2) which are connected at their upper end to a horizontal plate 38, for example, by welding.
- Bearing bar 28 is affixed to plate 38 by means such as bolts 40.
- a shim or spacer 42 may be appropriately affixed between plate 38 and bearing bar 28.
- the bearing bars permit sliding movement of the forks in the tracks while the length L provides more positive guidance, increased stability, while maintaining the forks substantially perpendicular relative the tracks.
- the particular arrangement of the tracks that is, the horizontal plane orientation of the first pair of tracks 22 and the vertical plane orientation of the second pair of tracks 24, permit the forks 16 and 18 to achieve the abutting relationship shown in Figure 2.
- bearing bar 28 will be described in relationship with fork 18. It should be understood that the forks are symmetrical, thus permitting utilization of substantially identical parts with either fork. It should further be noted that certain parts associated with the forks are utilized at either end; however, the part may be reversed when associated with the fork at the opposite end. When such an instance occurs this will be noted.
- Carriage portion 20 is formed with a pair of center members 44 and 46 on which carriage rollers 48 are mounted. As is usual in the lift truck art, carriage rollers 48 roll on mast 14 for vertical movement of a carriage and fork assembly.
- a plate 50 which extends laterally across the face of the carriage forming the upper edge thereof.
- a front bearing plate 52 is affixed to plate 50 and extends downwardly therefrom as indicated in Figure 5.
- a rear bearing plate 54 is also affixed at plate 50 and extends downwardly generally at the center point or thereof. Front bearing plate 52 and rear bearing plate 54 form the bearing surfaces upon which bearing bars 28 and 26 respectively ride.
- bearing block 56 Interposed between bearing bar 28 and front bearing plate 52 and associated with bearing bar 28 is a bearing block 56 made of a plastic material such as ultra high molecular weight polyethylene. This material which is utilized in other portions of this invention will hereinafter be referred to as UHMW bearing material.
- UHMW bearing material This material which is utilized in other portions of this invention will hereinafter be referred to as UHMW bearing material.
- a similar bearing block 58 also made of UHMW bearing material is disposed between bearing bar 26 and rear bearing plate 54. It should be apparent to those skilled in the art that the load moment generated by forks 16 and 18 is generally directed in a horizontal direction as indicated in figure 5 against the front and rear bearing plates 52 and 54 respectively.
- the bearing blocks 56 and 58 serve to permit movement of the bearing bars 28 and 26 and the associated forks 18 and 16 laterally across the face of the carriage.
- a plate 60 is affixed at the end of bearing bar 28 thus effectively locking bearing block 56 into a fixed position in relation to bearing bar 28.
- a similar plate 60' is located at the opposite end of bearing bar 28.
- sliding movement of bearing bar 28 laterally across the face of carriage 20 carries with it the bearing block 56 which in turn slides against front bearing plate 52.
- a similar arrangement is provided to retain bearing block 58 in a fixed relationship with bearing block bar 26.
- front bearing plate 52 and rear bearing plate 54 form the first pair of tracks 22, specifically track 22a being the rear track and track 22b being the front track.
- track 22a being the rear track
- track 22b being the front track.
- the bearing bars 26 and 28 are permitted to extend outwardly at the end of these tracks.
- the right end of track 22a (the rear track) as shown in Figure 5 is shown covered by a curved plate member 62 affixed to a vertical member 64, which forms a right side of the carriage.
- the curved plate 62 may be used at the opposite or left hand of the carriage shown in Figure 2 if the plate is reversed as previously indicated. This is shown as curved plate 62' in Figures 2 and 4. Curved plate 62' closes the left hand of track 22b and permits the bearing bar to extend outwardly off the track.
- a bottom plate member 66 is affixed to center members 44 and 46 respectively and extends outwardly to the full extreme of the carriage.
- Bottom plate member 66 has affixed along its bottom edge a lower track 68 which forms one of the second pair of tracks 24.
- a second track member 70 oriented generally above the bottom track 68.
- a third member 72 is affixed along the top of bottom plate member 66 extending in the same manner as bottom track 68 and second track 70. More will be said about this upper member 72.
- Bearing bar 32 is affixed to fork 18 by bolts or the like as indicated in figure 6.
- bearing bar 30 is affixed to fork 16 for movement therewith.
- Disposed between bearing bar 32 and bottom track 68 is a bearing block 74, preferably of UHMW material, that is retained therewith along with a second bearing block 76 also of UHMW material by a plate 78 as indicated in Figure 6.
- a similar plate would be affixed at the opposite end of bearing bar 32.
- a bearing block 80 also of UHMW material is disposed between bearing bar 30 and second track 70 along with a UHMW bearing block 82 interposed between bearing bar 30 and plate 66.
- a plate similar to plate 78 would be positioned at each end of bearing bar 30 to retain the bearing blocks 80 and 82 respectively adjacent the bearing bars upon lateral movement of the forks 16 and 18 across the face of carriage 20.
- Second track 70 as indicated in Figure 6 has a downwardly extending portion having a generally frusto-conical cross-section as indicated in Figure 6. This generally frusto-conical cross-section is repeated in bearing bar 32 which acts in cooperation with second track 70 to retain fork 18 adjacent carriage 20. It is appropriate to position a bearing member 84 between bearing bar 30 and second track 70 to reduce wear therebetween.
- a similar shape is formed in the lower portion of upper member 72 as indicated in Figure 6 along with a corresponding shape in bearing bar 30.
- a bearing member 86 which may be bronze or the like, may be positioned between bearing bar 30 and upper member 72 as indicated in Figure 6.
- vertical member 64 extends downwardly and is affixed to plate 66.
- a similar vertical 64' extends downwardly and is affixed at that end to plate 66.
- the hydraulic system The hydraulic system
- Forks 16 and 18 are moved laterally across the face of carriage 20 by a pair of hydraulic jacks 90 and 92 respectively. Since both of these jacks are the same, reference will first be made to Figure 4 wherein jack 92 is shown affixed to fork 18. It should be noted that jack 90 is affixed in a similar manner to fork 16, however, the positions will be reversed. Jack 92 is affixed to center member 46 on a trunnion mount 94 which allows limited rotation about a bearing 96 (see Figure 4). The rod end of jack 92 is affixed by an eye 100 to a fork 18. Similarly, eye 100' of jack 90 affixes jack 90 to fork 16.
- Hydraulic circuit 102 in addition to jacks 90 and 92 includes a third jack 104 which is operable to raise and lower the carriage 20 on mast 14.
- Hydraulic fluid under pressure is provided by a pump 106 drawing fluid from a tank 108. Fluid is provided from pump 106 to a conduit 110 which branches into a conduit 112 leading to a lift valve 114 and a conduit 116 leading to a side shift valve 118.
- Lift valve 114 is a three-position three-way valve having a normally closed center position and operated by a cane 128.
- a conduit 120 from lift valve 114 leads leading to the head end of lift cylinder. With the valve in the position shown in Figure 7, no fluid is passed through lift valve 114; therefore, the lift jack 104 will remain in the position last set.
- a pressure sensing relief valve 122 is controlled by pressure in conduit 120 through a pilot line 124. The purpose of pressure sensing relief valve will become apparent in the ensuing discussion; therefore, suffice it to say that pilot line 124 acts on a spring biased check valve 126 to relieve pressure in jacks 90 or 92 as appropriate.
- Shift valve 118 is preferably a four-way three-position valve as shown in Figure 7, operable by a cane 130 to provide pressure to jacks 90 and 92 thereby shifting forks 16 and 18 leftwardly or rightwardly as the case may be.
- Interposed between shift valve 118 and jacks 90 and 92 are a pair of two-position four-way valves 132 and 134 that, when used in conjunction with shift valve 118, serve to move the individual forks 16 or 18 either rightwardly or leftwardly as the case may be. This will become more apparent in the discussion of the operation of this system.
- Valve 118 feeds a pair of conduits 136 and 138, each of which feeds a branch conduit 140 and 142, respectively, leading to a double check valve 144 with a lead 147 to spring biased check valve 126.
- Normally closed check valve 126 blocks communication of lead 147 to a conduit 149 which communicates with tank 108.
- Conduit 136 leads to valve 134 while conduit 138 leads to valve 132.
- conduit 136 With valve 134 in a straight through position, conduit 136 is interconnected with a conduit 146 leading to the head end of jack 90.
- conduit 138 With valve 132 and valve 134 in the straight through position as shown in Figure 7, conduit 138 leads to a conduit 148 which leads to the head end of jack 92.
- a third conduit 150 branches to the rod ends of both jacks 90 and 92.
- the forks 16 and 18 are adjustable on the carriage 20 with the carriage in any position on the mast. Further, the forks 16 and 18 may be adjusted with any load thereupon. Specifically, forks 16 and 18 may be positioned as closely as shown in Figure 2, that is in an abutting relationship, or as a widely separated as shown in phantom in Figure 2, specifically at the extreme edges of the carriage. The forks are individually operable or operable together to move either to the left or to the right. Operation of the forks is accomplished by manipulation of side shift valve 118 in conjunction with valves 132 and 134. The following table illustrates the resulting action on jack 90 and jack 92 indicating the direction to the right or left as shown in Figure 7.
- jack 90 and 92 operation of jack 90 and 92 is accomplished from pressure provided by pump 106 that also provides pressure to lift jack 104.
- pilot line 124 biases spring bias check valve 126.
- pressure supplied to jacks 90 and 92 may be relieved through double check valve 144 should the pressure in either conduit 140 or 142 exceed that of the bias of spring bias check valve 126. Should this occur, pressure is bled off from conduit 140 or 142 and is returned to sump 108 via line 149.
- the pressure sensitive relief valve 122 offers one additional feature not found elsewhere. Should the operator inadvertantly hit an obstruction with one of the forks 16 or 18 while turning, the lateral force imposed thereupon would be transmitted back to either jack 90 or 92.
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- Forklifts And Lifting Vehicles (AREA)
Abstract
Description
- This invention relates generally to material handling equipment and more particularly to carriage assembles for fork lift vehicles. Specifically it deals with side shifting of the material handling forks and in its preferred embodiment with the associated hydraulic circuitry for operation of the side shifting arrangement.
- Material handling vehicles, such as fork lifts, in order to be useful, should have a certain degree of adjustability. This is particularly true if the vehicle is to be used to handle differing types of loads. It is also true in a material handling vehicle which handles similar loads, but in a different operating environment. For example, as the vehicle approaches the load to be handled, it is usual for the vehicle to approach the load at differing aspects. Even though these differing aspects may be of a minor amount, the load handling equipment, such as forks in the case of a fork lift, may not properly align with the load. When this occurs it requires a certain degree of maneuvering of the vehicle in order to obtain alignment of the load handling elements forks and the load.
- After maneuvering to pick up the load and subsequent to picking up the load, the vehicle is ordinarily driven to the off-loading point. The same maneuvering of the vehicle at the off-loading point that occurred at the loading point may also be necessary. That is, the vehicle may not be aligned with the loading dock, truck, or the like and thus the material handling vehicle must maneuver in order to position the load properly.
- In providing a capability to shift the load handling elements laterally relative to the vehicle, it is important not to degrade forward visibility from the operators station. It is equally important to reduce the offset of the load, from the vehicle center of gravity, referred as load moment offset. Other desiderata include reduction of the number of hydraulic lines, closer spacing of the forks, and providing an operating system for the load handling elements that is sensitive to the load carried.
- Various solutions to these problems have been developed for material handling vehicles. Specifically side shifting forks to handle varying widths of loads are available. In a related field, that is in a vehicle that incorporates a pair of load clamps rather than forks, side shifting of the load has been provided along with the clamping feature. Such side shifting of the load in a clamping type vehicle permits pick up and subsequent placement of the load at a more specific location than would be readily available through maneuvering of the vehicle as discussed above. In the past the side shifting mechanism along with the necessary track structure to support the forks or clamps has degraded forward visibility because of the relatively massive track structure and further has required extensive hydraulic plumbing.
- In other solutions the carriage upon which the forks are mounted has been designed to shift sideways in order to adjust or position the forks to pick up or deposit a load. Individual spacing of the forks upon such a side shift carriage may be accomplished manually or with additional hydraulic structure. In an arrangement such as the sideshift carriage with hydraulically adjustable forks, the additional structure required to move the forks and carriage increases the load moment offset from the center of gravity of the vehicle by moving the forks further from the center of gravity. This, of course, reduces the load carrying capacity of the vehicle. Accordingly, reduction of the structure necessary to side shift the load, thus reducing the load moment offset, is advantageous. The reduction of the load moment offset by elimination of the structure to shift the carriage and concentration of the side shift capability in the forks alone also reduces weight of the overall attachment. It should be readily apparent that reduction of the overall weight and reduction of the load moment offset permits an increase in the load carrying capacity of the vehicle itself.
- Individual fork adjustment may also be appropriate when it is necessary to pick up a load with a center of gravity laterally offset from the center line of the vehicle. One fork may then be moved laterally across the face of the carriage in orderto compensate for the offset center of gravity of the load. Once the load is picked up both forks and thus the load may be moved in the opposite direction to shift the center of gravity of the load to a point coincident with the center line of the vehicle thus eliminating or reducing the possibility of overturning the vehicle.
- Side shifting of either the carriage or of the forks in previous vehicles has usually been accomplished by a separate hydraulic circuit which shifts the carriage or the forks at a constant pressure. Providing sufficient pressure and flow to the hydraulic cylinders to move a fully loaded carriage or pair of forks has been the aim of these earlier structures. It is equally likely the forks or carriage will be shifted with no load. With the high pressure and flow provided in available fork or carriage shift mechanisms the shift feature when operated without a load has resulted in a rather abrupt and sometimes rather startlingly rapid shift of the forks or carriage.
- When a material handling vehicle such as a fork lift or the like operates in an environment having numerous obstructions, the forks may inadvertantly contact an obstruction while the vehicle is turning, thereby placing an undesirable side load on the fork. Such a load may result in damage to either the fork, the carriage, or in the event of a hydraulically operated side shift arrangement to the hydraulic circuitry. Damage which does occur as a result of contacting obstruction may result in loss of the use of the vehicle for that period of time necessary to repair it.
- Finally, in those vehicles in which a side shift capability has been provided to the forks, the forks have been operable on a track structure with a runner or the like to locate the forks on a track structure. The nature of the structure is usually such that the forks may not be placed in an abutting relation, thus the total side shift of the individual forks may be reduced by the separation of the forks at their closest position.
- US-A-2,795,346 shows a vehicle with a carriage with load-clamps and an alternative carriage for providing a fork lift capability, this latter carriage being in accordance with the pre-characterizing part of
claim 1. The forks and clamps are movable horizontally by hydraulic means, but are mounted such that their movement toward one another is limited, as is thus their maximum transverse displaceability to align with a load. Moreover, the mounting of the forks is not adapted to stabilize them against lateral tilting. - US-A-3,075,665 shows an arrangement in which the forks may be brought together, but in which again the mounting of the forks is necessarily narrow and would not provide long-term stability.
- The present invention seeks to overcome or lessen at least these last-mentioned problems by the features of the characterizing part of
claim 1. The invention thus concerns a track assembly for allowing lateral movement of the pair of load lifting forks from an abutting position to a spatially separated position. Powering means are preferably provided for selectively moving one or the other of the forks or both forks at the same time with a load thereon. The powering means may be sensitive to the weight imposed by the forks on the lift mechanism. - In another aspect of this invention, a material handling vehicle includes a mast, a carriage assembly adapted for generally vertical movement on the mast and a pair of load lifting forks mounted on the carriage. The improvement comprises a track assembly for allowing lateral movement of the load lifting forks from an abutting position to a spatially separated position and powering means for selectively moving one or the other of the forks.
- In this embodiment to be described of this invention, the problem of side shifting of a load on a material handling vehicle such as a fork lift, which in the past had required rather extensive structure that degraded forward visibility, has been solved by overlapping tracks thereby increasing the forward visibility while concurrently reducing the load moment offset and weight of the fork and carriage structure. Furthermore, hydraulic circuitry is provided that conditions the side shift pressure to be proportional to the load on the forks, thereby eliminating excessive pressures in the side-shift mechanism.
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- Figure 1 is a diagrammatic perspective view of a fork lift incorporating side shifting forks which form an exemplary embodiemnt of the present invention.
- Figure 2 is a diagrammatic front elevational view of the side adjusting forks shown in Figure 1.
- Figure 3 is a diagrammatic side elevational view partly in section of the fork lift structure depicted in Figure 2.
- Figure 4 is a diagrammatic detail of the trunnion mounting of the power structure for the fork lift arrangement.
- Figure 5 is a diagrammatic detailed view taken at section line V-V of Figure 2.
- Figure 6 is a diagrammatic detailed view partly in section taken at section line VI-VI of Figure 2.
- Figure 7 is a schematic diagram of the hydraulic control circuit for the side shifting fork arrangement.
- A material handling vehicle such as a
lift truck 10 is shown in Figure 1 having mounted thereupon a side shift forkadjustable carriage 12.Lift truck 10 includes amast assembly 14 at one end thereof to which theadjustable carriage 12 is affixed for vertical movement.Adjustable carriage 12 has fitted thereon a pair offorks 16 and 18 (see Figure 2) which are adapted to receive a load. Operation of thelift truck 10 is well known in the art and will not be further described other than to state that loads received onforks -
Forks carriage portion 20 of the side shiftadjustable carriage 12. Such movement is facilitated by two pairs of tracks, the first pair oftracks 22, comprised ofindividual tracks carriage portion 20 and a second pair oftracks 24, comprised ofindividual tracks carriage 20. One pair of these tracks, preferably thefirst pair 22 located along the top edge ofcarriage 20 is oriented in a horizontal plane as illustrated in Figure 5 while the second pair of tracks, preferably thelower pair 24, is oriented in a vertical plane as illustrated in Figure 6. It should be understood that both pairs could be located in either the horizontal or vertical plane, however, the positioning of the first pair oftracks 22 at the upper edge in the horizontal plane provides greater visibility through thecarriage 20 from the operator station of the lift truck. Furthermore, positioning the second pair oftracks 24 in the vertical plane as illustrated in Figure 6 reduces the weight requirements of the carriage since the vertical load placed on the forks is carried primarily by the lower set of tracks. To position the lower set of tracks in a horizontal plane would require additional strength members not necessary with the vertical arrangement as illustrated in Figure 6. - Each
fork tracks 22 by anelongated bearing bar inner end portion tracks 24 by anelongated bearing bar inner end portion Fork 18, as shown in Figure 5, has affixed at its upper end a pair of generally triangular shapedplates 34 and 36 (see also Figure 2) which are connected at their upper end to ahorizontal plate 38, for example, by welding. Bearingbar 28 is affixed to plate 38 by means such asbolts 40. A shim orspacer 42 may be appropriately affixed betweenplate 38 and bearingbar 28. The bearing bars, as will be seen, permit sliding movement of the forks in the tracks while the length L provides more positive guidance, increased stability, while maintaining the forks substantially perpendicular relative the tracks. The particular arrangement of the tracks, that is, the horizontal plane orientation of the first pair oftracks 22 and the vertical plane orientation of the second pair oftracks 24, permit theforks forks forks - Referring now to Figure 5, the structure of bearing
bar 28 will be described in relationship withfork 18. It should be understood that the forks are symmetrical, thus permitting utilization of substantially identical parts with either fork. It should further be noted that certain parts associated with the forks are utilized at either end; however, the part may be reversed when associated with the fork at the opposite end. When such an instance occurs this will be noted. -
Carriage portion 20 is formed with a pair ofcenter members carriage rollers 48 are mounted. As is usual in the lift truck art,carriage rollers 48 roll onmast 14 for vertical movement of a carriage and fork assembly. Affixed to the upper ends ofcenter members plate 50 which extends laterally across the face of the carriage forming the upper edge thereof. Afront bearing plate 52 is affixed to plate 50 and extends downwardly therefrom as indicated in Figure 5. Arear bearing plate 54 is also affixed atplate 50 and extends downwardly generally at the center point or thereof.Front bearing plate 52 andrear bearing plate 54 form the bearing surfaces upon which bearing bars 28 and 26 respectively ride. - Interposed between bearing
bar 28 andfront bearing plate 52 and associated with bearingbar 28 is abearing block 56 made of a plastic material such as ultra high molecular weight polyethylene. This material which is utilized in other portions of this invention will hereinafter be referred to as UHMW bearing material. Asimilar bearing block 58 also made of UHMW bearing material is disposed between bearingbar 26 andrear bearing plate 54. It should be apparent to those skilled in the art that the load moment generated byforks rear bearing plates forks plate 60 is affixed at the end of bearingbar 28 thus effectively lockingbearing block 56 into a fixed position in relation to bearingbar 28. A similar plate 60' is located at the opposite end of bearingbar 28. Thus sliding movement of bearingbar 28 laterally across the face ofcarriage 20 carries with it the bearingblock 56 which in turn slides againstfront bearing plate 52. A similar arrangement is provided to retain bearingblock 58 in a fixed relationship with bearingblock bar 26. - Referring to Figure 5,
front bearing plate 52 andrear bearing plate 54 form the first pair oftracks 22, specifically track 22a being the rear track andtrack 22b being the front track. Referring to Figure 2, it should be noted that the bearing bars 26 and 28 are permitted to extend outwardly at the end of these tracks. However, the right end oftrack 22a (the rear track) as shown in Figure 5 is shown covered by acurved plate member 62 affixed to avertical member 64, which forms a right side of the carriage. Thecurved plate 62 may be used at the opposite or left hand of the carriage shown in Figure 2 if the plate is reversed as previously indicated. This is shown ascurved plate 62' in Figures 2 and 4.Curved plate 62' closes the left hand oftrack 22b and permits the bearing bar to extend outwardly off the track. - Referring again to Figure 2, a
bottom plate member 66 is affixed to centermembers Bottom plate member 66 has affixed along its bottom edge alower track 68 which forms one of the second pair oftracks 24. Generally at the midpoint ofbottom plate member 66 is asecond track member 70 oriented generally above thebottom track 68. Athird member 72 is affixed along the top ofbottom plate member 66 extending in the same manner asbottom track 68 andsecond track 70. More will be said about thisupper member 72. - Bearing
bar 32 is affixed to fork 18 by bolts or the like as indicated in figure 6. Similarly bearingbar 30 is affixed to fork 16 for movement therewith. Disposed between bearingbar 32 andbottom track 68 is abearing block 74, preferably of UHMW material, that is retained therewith along with asecond bearing block 76 also of UHMW material by aplate 78 as indicated in Figure 6. A similar plate would be affixed at the opposite end of bearingbar 32. Similarly, abearing block 80 also of UHMW material is disposed between bearingbar 30 andsecond track 70 along with aUHMW bearing block 82 interposed between bearingbar 30 andplate 66. A plate similar toplate 78 would be positioned at each end of bearingbar 30 to retain the bearing blocks 80 and 82 respectively adjacent the bearing bars upon lateral movement of theforks carriage 20. -
Second track 70 as indicated in Figure 6 has a downwardly extending portion having a generally frusto-conical cross-section as indicated in Figure 6. This generally frusto-conical cross-section is repeated in bearingbar 32 which acts in cooperation withsecond track 70 to retainfork 18adjacent carriage 20. It is appropriate to position a bearingmember 84 between bearingbar 30 andsecond track 70 to reduce wear therebetween. A similar shape is formed in the lower portion ofupper member 72 as indicated in Figure 6 along with a corresponding shape in bearingbar 30. A bearingmember 86, which may be bronze or the like, may be positioned between bearingbar 30 andupper member 72 as indicated in Figure 6. - Referring to Figure 2, it can be seen that
vertical member 64 extends downwardly and is affixed to plate 66. Similarly, at the opposite end a similar vertical 64' extends downwardly and is affixed at that end toplate 66. -
Forks carriage 20 by a pair ofhydraulic jacks jack 92 is shown affixed to fork 18. It should be noted thatjack 90 is affixed in a similar manner to fork 16, however, the positions will be reversed.Jack 92 is affixed to centermember 46 on atrunnion mount 94 which allows limited rotation about a bearing 96 (see Figure 4). The rod end ofjack 92 is affixed by aneye 100 to afork 18. Similarly, eye 100' ofjack 90 affixes jack 90 to fork 16. - Referring now to Figure 7, the schematic of a
hydraulic circuit 102 capable of operating the aforedescribed system is shown. A novel feature of this hydraulic circuit is the reduction in the number of hydraulic lines provided to the carriage in order to operate the side shift arrangement of the forks. This will become apparent in the ensuing description.Hydraulic circuit 102 in addition tojacks third jack 104 which is operable to raise and lower thecarriage 20 onmast 14. - Hydraulic fluid under pressure is provided by a
pump 106 drawing fluid from atank 108. Fluid is provided frompump 106 to aconduit 110 which branches into aconduit 112 leading to alift valve 114 and aconduit 116 leading to aside shift valve 118. - Lift
valve 114 is a three-position three-way valve having a normally closed center position and operated by acane 128. Aconduit 120 fromlift valve 114 leads leading to the head end of lift cylinder. With the valve in the position shown in Figure 7, no fluid is passed throughlift valve 114; therefore, thelift jack 104 will remain in the position last set. A pressuresensing relief valve 122 is controlled by pressure inconduit 120 through apilot line 124. The purpose of pressure sensing relief valve will become apparent in the ensuing discussion; therefore, suffice it to say thatpilot line 124 acts on a springbiased check valve 126 to relieve pressure injacks -
Shift valve 118 is preferably a four-way three-position valve as shown in Figure 7, operable by acane 130 to provide pressure tojacks forks shift valve 118 andjacks way valves 132 and 134 that, when used in conjunction withshift valve 118, serve to move theindividual forks -
Valve 118 feeds a pair ofconduits branch conduit 140 and 142, respectively, leading to adouble check valve 144 with a lead 147 to springbiased check valve 126. Normally closedcheck valve 126 blocks communication oflead 147 to aconduit 149 which communicates withtank 108. - .
Conduit 136 leads to valve 134 whileconduit 138 leads tovalve 132. With valve 134 in a straight through position,conduit 136 is interconnected with aconduit 146 leading to the head end ofjack 90. Withvalve 132 and valve 134 in the straight through position as shown in Figure 7,conduit 138 leads to aconduit 148 which leads to the head end ofjack 92. Athird conduit 150 branches to the rod ends of bothjacks - In operation the
forks carriage 20 with the carriage in any position on the mast. Further, theforks forks side shift valve 118 in conjunction withvalves 132 and 134. The following table illustrates the resulting action onjack 90 andjack 92 indicating the direction to the right or left as shown in Figure 7. - It should be noted that operation of
jack pump 106 that also provides pressure to liftjack 104. As previously noted,pilot line 124 biases springbias check valve 126. Concurrently, pressure supplied tojacks double check valve 144 should the pressure in eitherconduit 140 or 142 exceed that of the bias of springbias check valve 126. Should this occur, pressure is bled off fromconduit 140 or 142 and is returned tosump 108 vialine 149. The pressuresensitive relief valve 122 offers one additional feature not found elsewhere. Should the operator inadvertantly hit an obstruction with one of theforks jack sensing relief valve 122, the sudden pressure spike resulting from the impact of one of the forks against an obstruction is relieved throughdouble check valve 144 and springbias check valve 126. This saves considerable wear and tear on the machinery and prevents inadvertant damage to not only the mechanical parts but also the hydraulic parts. Equally important is the fact that pressure supplied to thejacks lift jack 104. Thus, the motion offorks
Claims (13)
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
PCT/US1980/000015 WO1981002001A1 (en) | 1980-01-07 | 1980-01-07 | Side shift fork adjustable carriage |
Publications (3)
Publication Number | Publication Date |
---|---|
EP0042835A4 EP0042835A4 (en) | 1981-11-11 |
EP0042835A1 EP0042835A1 (en) | 1982-01-06 |
EP0042835B1 true EP0042835B1 (en) | 1985-08-21 |
Family
ID=22154143
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP19800900520 Expired EP0042835B1 (en) | 1980-01-07 | 1980-01-07 | Side shift fork adjustable carriage |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP0042835B1 (en) |
DE (1) | DE3071001D1 (en) |
WO (1) | WO1981002001A1 (en) |
Families Citing this family (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE3071512D1 (en) * | 1980-09-22 | 1986-04-24 | Towmotor Corp | Carriage assembly with shiftable forks |
US5326217A (en) * | 1990-09-24 | 1994-07-05 | Clark Material Handling Company | Lift truck with negative drop upright |
DK84893D0 (en) * | 1993-07-16 | 1993-07-16 | E L M Kragelund A S | HYDRAULIC CONTROLLED BEARING AND GRIBING EQUIPMENT, PRELIMINARY FOR USE ON FORK LIFTERS |
CN102167269B (en) * | 2011-05-03 | 2013-06-05 | 中国人民解放军总后勤部建筑工程研究所 | Integrated type forklift sidesway mechanism with internally-installed di-oil cylinder |
US9309099B2 (en) | 2014-06-20 | 2016-04-12 | Cascade Corporation | Side-shift limiter |
CN114803959B (en) * | 2022-04-29 | 2023-10-27 | 顺德职业技术学院 | Multi-pivot cargo handling forklift structure and fork arm positioning control method thereof |
Family Cites Families (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2613830A (en) * | 1948-03-15 | 1952-10-14 | Louie H Ponnequin | Lift truck fork |
US2795346A (en) * | 1953-07-16 | 1957-06-11 | Hyster Co | Load grip side shift for lift trucks |
US2748966A (en) * | 1953-08-03 | 1956-06-05 | Gerlinger Carrier Co | Laterally adjustable tines for a lift truck |
US2958436A (en) * | 1957-10-21 | 1960-11-01 | Sebben S Skutle | Article handling method and apparatus |
US3075665A (en) * | 1960-12-05 | 1963-01-29 | Clark Equipment Co | Adjustable load engaging means for lift truck |
FR2274546A1 (en) * | 1974-06-14 | 1976-01-09 | Blereau Peg | Forklift truck fork adjustment mechanism - spring-loaded rollers lift forks clear of apron when unloaded |
FR2322085A1 (en) * | 1975-08-27 | 1977-03-25 | Bergerat Monnoyeur Sa | Fork mounting for lift truck - has rams pivoting and sliding fork frame on horizontal shaft fixed to slide by rotary sliding joint |
US4185944A (en) * | 1978-06-29 | 1980-01-29 | Cascade Corporation | Slide structure for parallel arm clamps and the like |
-
1980
- 1980-01-07 DE DE8080900520T patent/DE3071001D1/en not_active Expired
- 1980-01-07 EP EP19800900520 patent/EP0042835B1/en not_active Expired
- 1980-01-07 WO PCT/US1980/000015 patent/WO1981002001A1/en active IP Right Grant
Also Published As
Publication number | Publication date |
---|---|
DE3071001D1 (en) | 1985-09-26 |
EP0042835A1 (en) | 1982-01-06 |
EP0042835A4 (en) | 1981-11-11 |
WO1981002001A1 (en) | 1981-07-23 |
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