WO1995030618A1

WO1995030618A1 - Forklift with fork support

Info

Publication number: WO1995030618A1
Application number: PCT/US1995/005619
Authority: WO
Inventors: Eeuwe Durk Kooi
Original assignee: Teledyne Industries Inc.
Priority date: 1994-05-09
Filing date: 1995-05-05
Publication date: 1995-11-16
Also published as: NL9400772A; AU2471095A

Abstract

The invention relates to a forklift comprising a vehicle (2), a lifting mast (3) mounted on this vehicle and a reach mechanism construction (4) which is guided slidably along the lifting mast and which supports on its outreaching end a fork carrier (5). A fork (6) is arranged thereon, wherein close to the end of the fork connected to the fork carrier a support (8) movable over a loading floor (11) is arranged and moving means are arranged for moving the support downward relative to the underside of the fork.

Description

FORKLIFT WITH FORK SUPPORT

The invention relates to a forklift which in typical manner comprises a vehicle, a lifting mast mounted on this vehicle, a reach mechanism construction which is guided slidably along the lifting mast and which supports on its outreaching end a fork carrier, on which a fork is arranged. With such a forklift loads can be picked up and set down at a distance from the lifting mast.

The reach of such a forklift is limited to the so- called limit distance. This is the distance within which the backward acting moment of the forklift is greater than the forward acting moment caused by the load. In other words, the distance within which a load can still just be picked up without the forklift tipping forward with the load.

The reach distance can be enlarged by increasing the counter-weight of the forklift. In particular cases an increase of the counter-weight is problematic, particularly when this involves so-called transportable forklifts.

This is because a transportable forklift must preferably have the lowest possible weight since the weight of the forklift reduces the effective load capacity of the truck with which it is transported.

The invention now has for its object to provide a fork¬ lift which has a very large reach without a great weight of the forklift being required for this purpose. This object is achieved with the forklift as characterized in claim 1. The furthest reach of a forklift with reach mechanism construction is required when the load for picking up or placing is located a far distance away on a loading floor or must be placed thereon. This occurs for instance in the case of trucks on which two pallets lie mutually adjacently in transverse direction and it is desired to unload these two pallets from one side of the truck. With the forklift according to the invention a far remote pallet can now also be picked up and set down because the support prevents tipping over. When the reach is greater than the reach distance the support with the moving means is placed in contact with the loading floor, wherein the load is held just clear of the loading floor.

The support can for instance be formed by a carriage, although in preference the step of claim 2 is applied. The forklift according to the invention can then also function in reliable manner on uneven and rough loading floors. A very suitable embodiment of the forklift according to the invention is characterized in claim 3.

When the fork is tilted with the support in contact with the loading floor, the fork rises upward whereby the load is cleared of the loading floor and can be moved. The support can be embodied very simply and robustly.

The means for backward tilting of the fork carrier can suitably be the lifting mast tilting means. When a load is picked up with the support in contact with the loading floor, the lifting mast is simultaneously tilted backward and the reach mechanism construction moved downward along the lifting mast, thus resulting in the desired tilting of the fork carrier.

A suitable stable construction with a short path of force is obtained with the step according to claim 5. The forces exerted by the load are transmitted directly to the loading floor via the fork and the support.

Another suitable embodiment is characterized in claim 7. The convenience of operation of the apparatus is hereby increased. The invention will be further elucidated in the following description with reference to the embodiments shown in the figures.

Fig. 1-3 show three schematic side views of the use of a forklift according to a first embodiment of the invention. Fig. 4 shows a partly perspective view of a forklift according to the embodiment of fig. 1-3 at the position of the support. Fig. 5 shows a view corresponding with fig. 4 of another embodiment.

Fig. 6 shows a simplified hydraulic diagram of the control means for the embodiment of fig. 5. The forklift 1 comprises a vehicle 2 on which a lifting mast 3 is arranged in usual manner.

A reach mechanism construction 4 is mounted for vertical displacement along this lifting mast 3. The reach mechanism construction bears on its outreaching end a fork carrier 5 to which in turn a fork 6 is mounted. The forklift 1 described up to this point is per se known and is for instance known, as shown, as transportable forklift.

As the figure shows, the forklift 1 comprises a support 7 close to the end of the fork 6 connected to the fork carrier 5. In the embodiment shown, the support is formed by a wheel 8. The support can move, in this case travel , over the loading floor 11 of a truck 12.

Fig. 1-3 show three stages during pick-up from the truck 12 of a load 9 placed on a pallet 10. Even if the load 9 is so heavy that it normally lies outside the reach distance of the forklift 1 for a load of such a weight, it can nevertheless be picked up without problem with the fork¬ lift 1 according to the invention.

From the position shown in fig. 1 the forklift 1 drives to the left:, wherein the fork 6 is inserted in the usual manner into the recess of the pallet 10 intended for this purpose. If the forklift driver were now only to move the reach mechanism construction 4 upward to lift up the load 9, this would result in the forklift 1 tipping forward while the load 9 would simply remain on the loading floor 11. However, unloading is made possible by the wheel 8. The operative tilts the lifting mast 3 of the forklift to the rear and simultaneously moves the reach mechanism construction 4 slightly downward along the lifting mast. This is the situation shown in fig. 2. The wheel 8 hereby comes into supporting contact with loading floor 11 and the fork 6 tilts upward on the point of rotation of the wheel 8, whereby pallet 10 is lifted from loading floor 11. The operative can then retract the reach mechanism construction 4, wherein wheel 8 rolls over loading floor 11. As soon as the load 10 has moved within the reach distance, so that the forklift can carry it without tipping, the wheel 8 can be lifted from the loading floor 11 and the load 9 on pallet 10 can be transported in the usual manner.

It will be apparent that placing of a load outside the normal reach distance can take place in the same manner, but in reverse sequence of fig. 3-1. Fig. 4 shows the construction of the forklift at the position of the support in more detail. As is shown, the support 7 is arranged directly onto the fork arm 13. The support 7 is arranged non-movably in vertical direction and at a distance in the direction to the mast, that is, to the left in fig. 4, so that during the tilting of the fork carrier described with reference to fig. 1-3 the fork 6 tilts upward on the rotation axis of wheel 8 to lift the pallet from the loading floor.

Fig. 5 shows a view corresponding with fig. 4 wherein a support 15 is applied with separate moving means. The support 15 comprises a guide tube 16 which is connected fixedly to the fork carrier construction 5 and in which a sliding tube 17 is received for vertical sliding. A roller 19 is mounted on the bottom end of the sliding tube. In the guide tube and the sliding tube 17 is mounted a hydraulic cylinder 18, the cylinder of which is fixedly connected to the guide tube 16 and the piston rod of which is fixedly connected to the sliding tube 17. By supplying hydraulic oil under pressure to cylinder 18 via conduit 20 the sliding tube 17 is pressed downward and roller 19 is placed in contact with the loading floor. The support 15 is simpler to use than the fixed support 7 of the foregoing embodiment. The operative has only to slide the fork 6 into the recesses of the pallet intended for that purpose, whereafter the cylinder 18 is fed with hydraulic oil under pressure, whereby the roller 19 is pressed into contact with the loading floor and the fork 6 lifts up the pallet. The coordinated movement of tilting and downward movement of the reach mechanism construction necessary in the foregoing embodiment is thus superfluous here.

Fig. 6 shows the operation of the hydraulic cylinders 18. A support 15 with associated cylinder 18 is arranged on either side of the fork carrier close to each fork arm.

The cylinders 18 are single-action and provided with resetting springs 21 so that the rollers 19 are moved upward in the non-active state of the cylinders 18.

The cylinders 18 on either side are connected in parallel and connected to a three-position valve 23. In the shown position of valve 23 the oil in cylinders 18 can flow away to the return conduit 22 under the influence of the action of the springs 21.

If the operative moves the valve 23 fully to the left by means of the manual control 24, the oil pressure conduit 25 is placed in communication with the conduit 20, whereby the piston rods having the rollers 19 connected thereto are pressed downward counter to the action of springs 21. When the valve is moved into the middle position the adjusted position is maintained.

As will be apparent from the foregoing, the invention is particularly suitable for use in a transportable fork¬ lift, wherein a low own weight is a great advantage. Despite a low own weight, a load at a great distance can nevertheless be handled by the invention without the danger of the forklift tipping over.

Claims

1. Forklift comprising a vehicle, a lifting mast mounted on this vehicle, a reach mechanism construction which is guided slidably along the lifting mast and which supports on its outreaching end a fork carrier on which a fork is arranged, wherein close to the end of the fork connected to the fork carrier a support movable over a loading floor is arranged and moving means are arranged for moving the support downward relative to the underside of the fork.

2. Forklift as claimed in claim 1, wherein the support is a wheel.

3. Forklift as claimed in claim 1 or 2, wherein the support is arranged non-movably in vertical direction and at a distance from the fork in the direction to the mast and the moving means are formed by means for tilting the fork carrier to the rear.

4. Forklift as claimed in claim 3, wherein the means for tilting the fork carrier to the rear are lifting mast tilting means.

5. Forklift as claimed in any of the foregoing claims, wherein a support is arranged on each fork arm.

6. Forklift as claimed in any of the claims 1-5, wherein a support is arranged on the fork carrier close to each fork arm.

7. Forklift as claimed in claim 1 or 2, wherein the moving means are formed by a jack connected to the fork carrier and the support is arranged on a vertically movable part of the jack.

8. A forklift comprising a vehicle, a vertically extending lifting mast mounted on the vehicle, a reach mechanism having an inner end mounted on the lifting mast for vertical movement and a free outer end, a fork carrier mounted to said outer end of the reach mechanism including one or more outwardly extending lift forks; a support member mounted near an inner end of the liftforks for movable engagement over a loading floor supporting a load, at least the forward end of said fork selectively movable upwardly relative to said loading floor.

9. The forklift defined in claim 8 wherein said support member comprises a rotatably mounted wheel and said lifting mast is mounted to said vehicle for tilting rearwardly away from said fork carrier to cause said lift forks to rotate in a vertical direction about the axis of said wheel.

10. A method of lifting a load with a pair of lift forks mounted to a fork carrier connected to the outer end of an extendable reach mechanism mounted to a vertically tiltable lift mast for vertical movement wherein each of said lift forks carry a rotatably wheel disposed near an inner end of each lift fork for engagement with a loading floor supporting said load, comprising the steps of extending said reach mechanism and said lift forks outwardly relative to said mast and into engagement with said load; tilting said lift mast rearwardly relative to said lift forks and lowering said reach mechanism on said lift mast to cause said lift fork to pivot upwardly about the axis of said wheels; and retracting said reach mechanism and lift forks toward said lift mast with said wheels in rolling engagement with said loading floor and carrying the weight of a load placed upon said lift forks.