Patent Description:
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.

<CIT> relates to a forklift linkage system for movement has a levelling carriage assembly movably contained within a channel assembly. A main long link pivotally connects to the levelling carriage assembly at a first pivot point and a fork carriage assembly at a second pivot point. A short link pivotally connects near a midpoint of the main long link at a third pivot point and at a fixed pivot point relative to the channel, near a vertical offset position from the pivot point of the main long link to the levelling carriage assembly at a fourth pivot point. A levelling link pivotally connects to the levelling carriage assembly at a fifth pivot point and at the opposite end to a fork carriage assembly at a sixth pivot point, such that the travel path of the second pivot point connecting the main long link to the fork carriage assembly remains substantially perpendicular to the channel when the linkage system is moved between retracted and extended positions. The angle through the second pivot point connects the main long link to the fork carriage assembly. The sixth pivot point connects the levelling link to the fork carriage assembly substantially constant in relation to the channel when the linkage system is moved between retracted and extended positions.

Accordingly there is provided a forklift reach mechanism according to claim <NUM>.

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 non-claimed 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 <FIG> there is indicated, generally at <NUM>, a forklift reach mechanism shown in three different states. In <FIG> the mechanism is shown in a retracted state; in <FIG> it is shown in a partially extended state; and in <FIG> it is shown in a fully extended state.

The mechanism of <FIG> is shown in simplified form as a geometry of connected members and connection points, mounted on a mast <NUM> and a carriage <NUM> which is vertically moveable along the mast <NUM>. Connecting members shown in solid lines are of fixed length in this embodiment, while those shown in broken lines are extendable and retractable (e.g. using hydraulic cylinders).

A main support <NUM> is connected at its proximal end (i.e. the end nearest the carriage) to a first pivoting connection <NUM> on the carriage <NUM>, and at its distal end (i.e. the end furthest from the carriage) to a pivoting connection <NUM> on a forklift assembly (not shown but represented by a connecting member <NUM> that forms part of a forklift carriage).

A V-shaped levelling assembly is provided by an upper arm <NUM> and a lower arm <NUM> connected to one another at their respective distal ends (at the apex of the "V" shape) at a pivoting connection <NUM>. As seen moving from <FIG>, the V shape can move from an open angle to a closed angle, i.e. the internal angle at the apex becomes more acute between <FIG>. The upper arm is connected at its proximal end to the carriage at a second pivoting connection <NUM> which is positioned above the first pivoting connection <NUM> on the carriage. The proximal end of the lower arm is connected using a pivoting connection <NUM> at a fixed location relative to the mast <NUM>, below the carriage.

A connecting member <NUM> (not visible in <FIG> as it is hidden behind a portion of the lower arm <NUM>) is connected at one end to the levelling assembly at or adjacent the connection <NUM> between the upper and lower arms, and at another end to the main support <NUM> at an intermediate point <NUM> along the main support between the proximal and distal ends of the main support.

It can be seen that a quadrilateral geometry is defined by the four points comprising (a) the first pivoting connection <NUM>, (b) the second pivoting connection <NUM>, (c) the connection <NUM> between the levelling assembly and the connection member <NUM>, and (d) the connection <NUM> between the connecting member <NUM> and the main support <NUM>.

Each of the distances <NUM> - <NUM>, <NUM> - <NUM>, <NUM> - <NUM>, and <NUM> - <NUM> is fixed, and the preferred geometry of this quadrilateral is approximately that of a parallelogram (hence the distance of the connection <NUM> on the main support is chosen to be approximately the same distance from the first pivoting connection <NUM> as the length of the upper arm <NUM>).

An extensible actuating member <NUM> is connected between the carriage at a connection <NUM> and the connecting member <NUM> at a connection <NUM>. The actuating member can be extended (<FIG>) or retracted (<FIG>) to drive the carriage vertically along the mast, thereby drawing the forklift assembly <NUM> towards or away from the mast.

It is the action of this actuation member <NUM> that changes the geometry of the quadrilateral previously described, to implement the reach function shown in the transition between <FIG>.

The actuation member <NUM> only requires a very short stroke length to fully raise or lower the carriage, i.e. the length changes by approximately <NUM>% 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 <FIG> that this extension and retraction draws the forklift assembly in a generally horizontal line towards or away from the mast, keeping the load level.

A secondary support <NUM> is connected at its proximal end to the carriage above the first pivoting connection. This pivoting connection is hidden in <FIG>, as is the proximal half of the secondary support <NUM> behind the upper arm <NUM>, but the proximal pivoting connection is approximately coaxial with the second pivoting connection <NUM> in this embodiment. At its distal end, the secondary support is connected to the forklift assembly <NUM> above the connection <NUM> with the main support <NUM>.

While the secondary support <NUM> in this embodiment is extensible-retractable, no extension or retraction occurs in the transition between <FIG>. The secondary remains at a fixed length in these figures, and as will be appreciated from these drawings and as described further below, the purpose of the variable length of this secondary support is to enable a tilt mechanism for the forklift assembly, allowing e.g. member <NUM> to be tilted about the pivoting connection <NUM> as the secondary support is shortened or lengthened.

The actuation of the extensible actuating member <NUM> causes the angles at pivoting connection points <NUM> and <NUM> to open while the angles at pivoting connection points <NUM> and <NUM> close, or vice versa.

The lower arm restrains pivoting connection <NUM> to follow an arcuate path relative to the fixed location at which it connects relative to the mast. The connecting member <NUM> draws the connecting point <NUM> on the main support downwards and outwards as a result, implementing the reach function.

<FIG> shows the geometric layout from <FIG> overlaid on a ghosted and partially cutaway forklift reach mechanism. In <FIG>, the mast <NUM> and carriage <NUM> are identified, as are each of the pivoting connections <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM>. The connecting members are shown but for clarity are not identified with reference numerals, to allow the underlying components to be seen.

The ghosted mechanism of <FIG> is shown in full detail in <FIG> in side, front perspective and rear perspective views, respectively. The same reference numerals as in <FIG> will be used to refer to actual components in this mechanism where appropriate.

Thus, in <FIG> there is seen the mast <NUM> and carriage <NUM>. The main support <NUM> runs from the carriage <NUM> to the forklift assembly <NUM> which is shown with forks <NUM> visible. The upper arm <NUM> and lower arm <NUM> form a levelling assembly to which the connecting member <NUM> is connected at one end, the other end being connected to the main support <NUM>. The forklift assembly is in the extended reach position due to the extension of the hydraulic cylinder <NUM> serving as the extensible actuating member.

The mast <NUM> shown in <FIG> is a reach mast, used for the raising and lowering of the carriage <NUM> as the forks <NUM> are retracted or extended. This mast <NUM> is carried on a lift mast (not shown) with a chain drive <NUM> provided to raise and lower the reach mast <NUM> relative to the lift mast on which the chain drive <NUM> is mounted. Thus the chain drive <NUM> is used to lift and lower the forks themselves, both in the extended reach position and in the retracted position (seen in <FIG>).

<FIG> shows that the upper arm is a rectangular frame member with pivot points at each of the four corners, while the lower arm is provided by a pair of arms <NUM>, one at each side (only one visible in <FIG>).

The main support <NUM> comprises a pair of arms, one at each side (only one visible in <FIG>), a and a bridging structure <NUM> reinforcing and connecting the two sides and coupling the main support to the forklift assembly as detailed further in <FIG>.

The secondary support <NUM> is provided by a pair of hydraulic tilt cylinders parallel to one another and disposed more centrally than the main support arms <NUM>. These cylinders can be extended and retracted in order to tilt the forklift assembly relative to the main support and mast.

The tilt cylinders <NUM>, being mounted above the main support <NUM>, 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 a non-claimed aspect depicted in <FIG>, the coupling of the main and secondary supports to the forklift assembly can be seen.

The main support bridging structure <NUM> receives a journaled shaft <NUM> mounted between a pair of brackets <NUM> carried on the rear of the forklift assembly <NUM>. The shaft <NUM> is free to slide laterally within the main support bridging structure <NUM>, 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 <NUM> which couples the main support bridging structure <NUM> to the bracket <NUM>.

In order to accommodate the sideward motion, the tilt cylinders <NUM> are each provided with a spherical bearing <NUM> mounted on a shaft <NUM> running between two inner brackets <NUM>. Similar bearings are provided at the proximal ends to mount the tilt cylinders to the carriage.

As seen with reference to the non-claimed aspects depicted in <FIG>, in this way the main support bridging structure <NUM> remains static during side shift, and the forklift assembly <NUM> translates sideways under the action of the hydraulic side shift cylinder <NUM>, with the distal ends of the tilt cylinders <NUM> being carried sideways with the forklift assembly and accommodating a lateral pivoting motion at the spherical bearings <NUM>. The forklift assembly can thereby be displaced to the left (when seen from above as in <FIG>) or right (<FIG>), regardless of whether the reach mechanism is extended or retracted, and regardless of tilt (although the tilt cylinders will compensate for the side shift by extending a corresponding small amount to accommodate the side shift increasing the distance to the carriage).

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 the non-claimed aspects depicted in <FIG> the mechanism is shown with the forks <NUM> tilted back (<FIG>) and forward (<FIG>). This is accomplished by retracting and extending the tilt cylinders <NUM> which provide the secondary support to the forklift assembly.

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 <NUM>, is very close to the heel <NUM> of the forks (i.e. the <NUM>-degree internal angle at the proximal end of the forks). This reduces the load moment as the load is tilted backwards (<FIG>), i.e. the load comes closer to the mast as it is tilted back.

<FIG> show the same forklift reach mechanism when the forklift assembly <NUM> is in the retracted position. The carriage <NUM> has been raised due to the retraction of the hydraulic cylinder <NUM> (extensible actuating member) just visible in <FIG>, which has drawn the midpoint of the connecting member <NUM> towards the carriage <NUM>. The levelling assembly, comprising upper and lower arms <NUM>, <NUM> and the pivoting connection <NUM>, has been drawn inwards, with the internal angle at the pivoting connection becoming more obtuse. The main support <NUM>, <NUM> has been drawn upwards and almost parallel with the mast <NUM>, thereby pulling the forklift assembly <NUM> back to the mast.

A different embodiment is shown in <FIG>, illustrated as in <FIG> to show the geometry. For ease of understanding, this can be compared with <FIG>. Like parts are indicated with like reference numerals and they need not be described again. Whereas the embodiment of <FIG> had a secondary support <NUM> in the form of a pair of tilt cylinders running from the carriage <NUM> to the forklift assembly <NUM>, the embodiment of <FIG> has a secondary support <NUM>, again in the form of a pair of tilt cylinders, running from the levelling assembly <NUM>, <NUM>, <NUM>, to the forklift assembly. Therefore the forklift assembly <NUM> is again supporte4d by a main support <NUM> and a secondary support <NUM>, and the secondary support <NUM> again provides an integrated tilt function that is always in tension, but the secondary support <NUM> in this case runs from the levelling assembly pivot point <NUM> (or one of the upper and lower arms <NUM>, <NUM>) to the pivot point <NUM> positioned on the forklift assembly above the connection point <NUM> for the main support.

Claim 1:
A forklift reach mechanism comprising:
a vertical mast (<NUM>);
a carriage (<NUM>) that is movable vertically along the mast;
a main support (<NUM>) connected at a proximal end thereof to the carriage at a first pivoting connection and connected at a distal end thereof to a forklift assembly, wherein the proximal end is the end nearest the carriage and the distal end is the end furthest from the carriage;
a levelling assembly comprising upper (<NUM>) and lower (<NUM>) arms connected using a pivoting connection (<NUM>) at their distal ends, wherein the proximal end of the upper arm (<NUM>) is connected to the carriage at a second pivoting connection, and the proximal end of the lower arm (<NUM>) is connected using a pivoting connection (<NUM>) at a fixed location relative to the mast below the carriage;
a connecting member (<NUM>) connected at one end to the levelling assembly adjacent the connection between the upper and lower arms, and at another end to the main support (<NUM>) at an intermediate point along the main support (<NUM>) between the proximal and distal ends thereof;
an extensible actuating member (<NUM>) connected between the carriage and the connecting member;
wherein the first pivoting connection (<NUM>) is below the second pivoting connection on the carriage;
wherein the actuating member (<NUM>) can be extended or retracted to drive the carriage vertically along the mast, thereby moving the forklift assembly towards or away from the mast.