This invention relates to a forklift reach mechanism such as, may be carried on a forklift truck.
In particular the invention relates to reach mechanisms which allow the forklift assembly to be extended and retracted relative to a mast on which the reach mechanism is mounted.
Reach mechanisms are particularly useful in unloading a vehicle, by allowing the forks to be extended into and retracted from the vehicle interior without moving the wheels of the forklift truck.
A number of pantograph mechanisms exist to provide a reach forklift. It is an object of this invention to provide an alternative mechanism providing increased strength and stability relative to known reach mechanisms.
Accordingly there is provided a forklift reach mechanism comprising:
The mechanism provides a strong geometry with a compact size, the extensible actuating member (e.g. a hydraulic reach cylinder) being mounted in a compact fashion between the carriage and the connecting member.
The mechanism also allows for a much shorter stroke length to raise and lower the carriage along a given height of the mast as compared with a hydraulic ram acting directly on a carriage to drive it up and down as has been proposed in prior art mechanisms.
Preferably, the mechanism further comprises a secondary support connected at a distal end to the forklift assembly above the connection with the main support, and connected at a proximal end to one of the carriage, the levelling assembly or the connecting member, the secondary support being extensible and retractable to thereby tilt the forklift assembly by the relative movement between the connection points on the forklift assembly for the main and secondary supports.
This allows a tilt mechanism to be combined with the structural support of the fork assembly, and integrates the tilt mechanism into the pantograph-like reach mechanism, reducing the number of components and the complexity of the system (i.e. no tilting of the carriage is needed).
Further, preferably, the secondary support is pivotally connected at both proximal and distal ends such that it has freedom to pivot both vertically and laterally, allowing the forklift assembly to be shifted sideways relative to the carriage.
The secondary support is preferably provided by one or more tilt cylinders that run parallel to and above the main support.
Such tilt cylinder(s) are by virtue of their positioning always in tension, allowing them to be lighter and less prone to buckling than any tilt cylinder arrangement where the tilt cylinders are sometimes in compression.
Preferably the connection between the distal end of the main support and the forklift assembly is a sliding connection allowing the forklift assembly to slidably move laterally relative to the main support.
Preferably, the mechanism further comprises a side shift actuator operable between the main support and the forklift to shift the forklift assembly laterally relative to the main support along the sliding connection.
The integration of a side shift actuator into the forklift assembly allows for a more compact and simpler side shift than in conventional systems.
Preferably, a quadrilateral geometry is defined by the four points comprising (a) the first pivoting connection, (b) the second pivoting connection, (c) the connection between the upper arm and the connection member, and (d) the connection between the connecting member and the main support; wherein each of the distances (a)-(b), (b)-(c), (c)-(d) and (d)-(a) is fixed; and wherein the actuation of the extensible actuating member causes the angles at points (a) and (c) to open while the angles at points (b) and (d) close, or vice versa, with the lower arm restraining point (c) to follow an arcuate path relative to the fixed location at which it connects relative to the mast.
Preferably, the upper and lower arms form a V-shaped assembly whose apex is at the point where the upper and lower arms meet, and wherein the actuation of the extensible actuating member causes the angle at the apex to respectively open or close as the carriage moves up or down the mast.
In an independent further aspect of the invention, there is provided a forklift reach mechanism comprising:
Preferably, the levelling assembly comprises a pair of articulated arms connected at their respective proximal ends to the carriage and a fixed point relative to the mast, respectively, and connected to one another at their distal ends.
Preferably, the levelling assembly further comprises a connecting member that connects the main support to the pair of articulated arms adjacent the connection between the distal ends of the arms.
Preferably, the secondary support is pivotally connected at both proximal and distal ends with freedom to pivot both vertically and laterally, allowing the forklift assembly to be shifted sideways relative to the carriage.
Preferably, the connection between the distal end of the main support and the forklift assembly is a sliding connection allowing the forklift assembly to slidably move laterally relative to the main support.
Preferably, the forklift reach mechanism further comprises a side shift actuator operable between the main support and the forklift to shift the forklift assembly laterally relative to the main support along the sliding connection.
The invention will now be illustrated by the following description of embodiments thereof, with reference to the accompanying drawings, in which:
In
The mechanism of
A main support 16 is connected at its proximal end (i.e. the end nearest the carriage) to a first pivoting connection 18 on the carriage 14, and at its distal end (i.e. the end furthest from the carriage) to a pivoting connection 20 on a forklift assembly (not shown but represented by a connecting member 44 that forms part of a forklift carriage).
A V-shaped levelling assembly is provided by an upper arm 22 and a lower arm 24 connected to one another at their respective distal ends (at the apex of the āVā shape) at a pivoting connection 26. As seen moving from
A connecting member 32 (not visible in
It can be seen that a quadrilateral geometry is defined by the four points comprising (a) the first pivoting connection 18, (b) the second pivoting connection 28, (c) the connection 26 between the levelling assembly and the connection member 32, and (d) the connection 34 between the connecting member 32 and the main support 16.
Each of the distances 18 - 28, 28 - 26, 26 - 34, and 34 - 18 is fixed, and the preferred geometry of this quadrilateral is approximately that of a parallelogram (hence the distance of the connection 34 on the main support is chosen to be approximately the same distance from the first pivoting connection 18 as the length of the upper arm 22).
An extensible actuating member 36 is connected between the carriage at a connection 38 and the connecting member 32 at a connection 40. The actuating member can be extended (
It is the action of this actuation member 36 that changes the geometry of the quadrilateral previously described, to implement the reach function shown in the transition between
The actuation member 36 only requires a very short stroke length to fully raise or lower the carriage, i.e. the length changes by approximately 25% in a complete traversal of the carriage along the mast. This allows for a significantly more compact mechanism than one which must act directly on the carriage.
It can be seen from the heavy broken line across
A secondary support 46 is connected at its proximal end to the carriage above the first pivoting connection. This pivoting connection is hidden in
While the secondary support 46 in this embodiment is extensible-retractable, no extension or retraction occurs in the transition between
The actuation of the extensible actuating member 36 causes the angles at pivoting connection points 28 and 34 to open while the angles at pivoting connection points 18 and 26 close, or vice versa.
The lower arm restrains pivoting connection 26 to follow an arcuate path relative to the fixed location at which it connects relative to the mast. The connecting member 32 draws the connecting point 34 on the main support downwards and outwards as a result, implementing the reach function.
The ghosted mechanism of
Thus, in
The mast 12 shown in
The main support 16 comprises a pair of arms, one at each side (only one visible in
The secondary support 46 is provided by a pair of hydraulic tilt cylinders parallel to one another and disposed more centrally than the main support arms 16. These cylinders can be extended and retracted in order to tilt the forklift assembly relative to the main support and mast.
The tilt cylinders 46, being mounted above the main support 16, are in tension rather than in compression, which reduces the required size (a cylinder that is in compression generally needs to be heavier and thicker to prevent buckling).
Referring to
The main support bridging structure 50 receives a journaled shaft 52 mounted between a pair of brackets 54 carried on the rear of the forklift assembly 44. The shaft 52 is free to slide laterally within the main support bridging structure 50, so that the forklift assembly can be shifted sideways relative to the main support.
The shifting force is applied and controlled by a hydraulic side shift cylinder 56 which couples the main support bridging structure 50 to the bracket 54.
In order to accommodate the sideward motion, the tilt cylinders 46 are each provided with a spherical bearing 58 mounted on a shaft 60 running between two inner brackets 62. Similar bearings are provided at the proximal ends to mount the tilt cylinders to the carriage.
As seen with reference to
The side shift is integrated into the forklift assembly, and close to the fork hanging position on the main support, which reduces the stress on this side shift cylinder. This also allows the mast to remain static during the side shift, meaning that the mast can abut against the side of a vehicle during loading and unloading, increasing stability when a heavy lift needs to be side shifted, particularly with the reach mechanism at full extension.
Referring to
It can be seen that tilting is thereby integrated into and a function of the supporting connections between the forklift assembly and the mast. Because the tilt cylinders carry part of the load, they remain in tension at all times.
It can be seen that the point of support between the main support and the forklift assembly, at the journaled shaft 52, is very close to the heel 64 of the forks (i.e. the 90-degree internal angle at the proximal end of the forks). This reduces the load moment as the load is tilted backwards (
A different embodiment is shown in
Whereas the embodiment of
Therefore the forklift assembly 44 is again supporte4d by a main support 16 and a secondary support 146, and the secondary support 146 again provides an integrated tilt function that is always in tension, but the secondary support 146 in this case runs from the levelling assembly pivot point 26 (or one of the upper and lower arms 22, 24) to the pivot point 46 positioned on the forklift assembly above the connection point 20 for the main support.
As in the embodiment of
Number | Date | Country | Kind |
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2012974.8 | Aug 2020 | GB | national |
Filing Document | Filing Date | Country | Kind |
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PCT/EP2021/072670 | 8/16/2021 | WO |