FORKLIFT WITH REACH MECHANISM

Abstract: Forklift (1) comprising a frame (2), which supports a mast (4), a load bearer (5) with load gripping means such as forks (6) and drive means (7) gripping onto the load bearer (5) for moving the load bearer (5) up and downward along the mast (4), wherein the load bearer (5) comprises a reach mechanism construction (8) having a auxiliary mast (23) movably guided along the mast (4), a reach mechanism mast (22) supporting the load gripping means (6) and two pairs of mechanism levers, which each comprise two mechanism levers (9, 10) which are connected with their bottom end in a fixed point of rotation (11, 12) to respectively the auxiliary mast (23) or the reach mechanism mast (22) and with their top end (13, 14) to the other mast in a point of rotation slidable therealong, and which are connected to each other in a pivoting point (16) lying between the ends. The pivoting point (16) of each pair of mechanism levers (9, 10) is provided out of the centre between the points of rotation at the ends and that the constituent parts of the auxiliary mast (23), the reach mechanism mast (22) and the mechanism levers (9, 10) are positioned mutually adjacent in the direction transversely of the reach direction, such that in the retracted position the axes of the points of rotation of each pair of mechanism levers (9, 10) lie moved vertically in relation to each other and the parts of the auxiliary mast (23), the reach mechanism mast (22) and the mechanism levers (9, 10) fall substantially inside the main mast (4).

Description: The invention relates to a forklift with a reach mechanism as defined in the introductory part of claim 1. A forklift of this kind is known from US-A-2 752 058. The reach mechanism serves to be able to pick up or set down a load at a distance from the forklift, for instance when the truck cannot come close enough because of obstacles on the ground, or when work is being carried out with a rack in which pallets are disposed in two rows behind each other. A drawback of the known reach mechanism is that the carrying capacity of a forklift provided with such a mechanism is strictly limited. In the extended position of the reach mechanism the load engaging means are situated at a distance from the main mast, which corresponds with the design reach distance plus the distance which the load engaging means already have in relation to the main mast in the retracted position of the reach mechanism, as a result of the space taken up thereby. The invention has for its object to provide a forklift of the sort described in the preamble wherein the carrying capacity, taking into account the design reach distance, is as large as possible. According to the invention this object is achieved with a forklift having the characterizing measures as mentioned in the characterizing portion of claim 1. The parts of the reach mechanism, in the retracted position thereof, hereby lie at least virtually inside the main mast. The load engaging means are therefore situated at practically the same distance from the main mast as in a similar forklift without reach mechanism. In the extended position of the reach mechanism the load engaging means are thus not situated further from the main mast than the design reach distance. An additional advantage of the forklift according to the invention is that in the retracted position of the reach mechanism a load on the load bearer is situated as closely as possible to the main mast, so that driving the forklift according to the invention with a load involves no greater danger of tipping over than is the case with a similar forklift without reach mechanism. A further important advantage of the invention is that the reach mechanism in the retracted position thereof does not increase the total length of the forklift. This is particularly important for transportable forklifts, which are carried behind a truck. In accordance with traffic regulations such a transportable forklift qualifies as a load protruding behind the truck. Stringent limitations are applied to the distance over which a load may protrude. With the invention it is now possible to provide a transportable forklift provided with a reach mechanism, the length of which remains limited such that it can comply with these requirements. An additional favourable development of the invention is achieved when at least some of the corresponding ends of the pairs of scissor levers are mutually connected in torsion stiff manner by a connecting shaft. Because according to the invention the axes of the points of rotation of each pair of scissor levers in the retracted position lie vertically offset in relation to each other, the connecting shafts also come to lie underneath each other in vertical direction. In this way it is thus possible to obtain a favourable torsion stiff construction. A further improvement of the torsional stiffness is obtained when according to the invention the pivoting points of the pairs of scissor levers are mutually connected in torsion stiff manner by a connecting shaft. Further advantages and features of the forklift according to the invention are elucidated in the following description of an embodiment thereof, with reference to the annexed figures. Fig. 1 shows a schematic side view of a forklift according to the invention, with extended reach mechanism. Fig. 2 shows a partially broken away perspective view of a portion of the forklift from fig. 1. Fig. 3 shows a front view according to arrow III in fig. 2. Fig. 4 shows a vertical section along line IV-IV in fig. 3. The forklift 1 shown in the figures comprises a frame 2 which can move over a ground surface by means of wheels 3 connected thereto. As shown the forklift 1 is of the transportable type, wherein the front wheels 3 normally lie at a distance in front of the mast construction 4, so that the centre of gravity of a transported load lies within the support surface defined by the wheels. Therefor, no counter weight is necessary and the forklift can have a light construction. Mounted on the mast structure 4 is a load bearer 5 which is provided with load engaging means such as forks 6. Drive means, here in the form of piston cylinder devices 7, engage the load bearer to move the load bearer 5 up and downward along the mast 4. The load bearer 5 comprises a reach mechanism here generally designated 8, which makes it possible to displace the lifting forks 6 between a retracted position, wherein the lifting forks are situated close to the mast 4, and an extended position, as shown in fig. 1. The reach mechanism 8 is operated using a piston cylinder device 15. In the forklift 1 the lifting forks 6 can be moved to a position in front of the front wheels 3, by extending the reach mechanism 8. When unloading a truck the lifting forks 6 can thus be inserted into a pallet on the load carrying floor of the truck and this pallet can be picked up, even when the wheels 3 cannot travel beneath the truck because for instance a wheel of the truck is situated at that location. As is shown in more detail in fig. 2 the reach mechanism 8 comprises an auxiliary mast 23 guided movably along the main mast 4, a reach mechanism mast 22 supporting the load engaging means 6 and two pairs of scissor levers, each comprising two scissor levers 9, 10. The scissor levers 9 are connected with their lower ends to the auxiliary mast 23 in a fixed point of rotation 11, while the scissor levers 10 are connected with their lower ends to the reach mechanism mast 22 in a fixed point of rotation 12. As can be seen from the figures the main mast 4, the auxiliary mast 23 and the reach mechanism mast 22 are each assembled from two pillars placed at a mutual distance. The upper ends of the levers 9 and 10 are connected respectively to the reach mechanism mast 22 and the auxiliary mast 23 by means of a point of rotation slidable along the respective mast. The main mast 4 comprises an outer mast 25 connected to the frame and an inner mast 24 slidable therein. The auxiliary mast 23 is again mounted slidably in the inner mast 24 by means of rollers 31, 32. The piston cylinder devices 7 are connected with a bottom end to the outer mast 25 and with their top end to a beam connecting the inner masts 24. On either side at the top and bottom the inner mast 24 supports the respective pulleys 26 and 28. A cable 27 is tensioned around each pair of associated pulleys 26 and 28. The outer portion of the cable 27 is fixedly connected in each case to the outer mast 25, close to the upper end thereof. The inner portion of the cable 27 is connected in each case to the auxiliary mast 23, close to the upper end thereof. As a result of extending the piston cylinders 7 the inner mast 24 is thus moved upward in relation to the outer mast 25. Simultaneously however the auxiliary mast 23 is moved upward at double speed. The vertical displacement of the auxiliary mast 23 and thus of the load bearer 5 connected thereto therefore amounts to twice the stroke of the piston cylinders 7. As is shown the upper ends of the pairs of scissor levers 9 and 10 are in each case connected to each other in torsion stiff manner by the respective connecting shafts 19 and 18. The ends of these shafts carry rollers slidable in the respective reach mechanism mast 22 and auxiliary mast 23. The lower ends of the scissor levers 9 are likewise connected to each other in torsion stiff manner by means of a connecting shaft 18. The ends of this connecting shaft are mounted rotatably in the auxiliary mast 23 and in line therewith rollers 31 are arranged, by means of which the auxiliary mast 23 can be moved in the inner mast 24. Arranged at the upper end of the auxiliary mast 23 are corresponding rollers 32. The scissor levers 9 and 10 are rotatably connected to each other in a pivoting point 16. The levers 9 are mutually connected in the pivoting point 16 in torsion stiff manner by the connecting shaft 20, while the levers 10 are rotatably mounted in line with this shaft 20. As can be seen most clearly in fig. 1 the pivoting point 16 of each scissor lever 9, 10 is arranged out of the middle between the points of rotation at the ends. In particular, the distance between the point of rotation 12 and the pivoting point 16 is smaller than the distance between the point of rotation 13 and the pivoting point 16 of the lever 10. In similar manner the distance between the point of rotation 14 and the pivoting point 16 is smaller than the distance between the point of rotation 11 and the pivoting point 16 of the levers 9. In the embodiment shown the mentioned distances of the respective levers 9 and 10 are in each case equal on the same side of the pivoting point 16. For proper operation, that is, a guiding such that the reach mechanism mast 22 remains in each case parallel to the auxiliary mast 23, it is sufficient that only the ratio of these distances is equal in each lever. As a result of the location of the pivoting point 16 out of the middle between the respective points of rotation of each lever it is achieved in favourable manner that in the retracted position of the mechanism the points of rotation lie vertically above each other. This is clearly apparent from fig. 4. The connecting shaft 18 lies in the retracted position above the connecting shaft 19 while the connecting shaft 17 lies beneath the points of rotation 12. Because in addition, as shown in fig. 3, the scissor levers 9 lie inside the scissor levers 10 it is possible to fold in the scissor levers almost entirely. As is shown in the figures the levers 10 are provided close to the connecting shaft 18 with a notch 30, in which, in the retracted position, the connecting shaft 19 can be taken up. In addition the respective pillars of the reach mechanism mast 22 are disposed at a distance such that in the folded in state the outer scissor levers 10 again fall inside them. The pillars of the auxiliary mast 23 are again placed at a distance such that the pillars of the reach mechanism mast 20 again fall between them. The whole reach mechanism therefore falls in the retracted position at least virtually within the space defined by the outer mast 25 of the main mast 4. As is further shown in the figures the mast construction according to the invention can be used in combination with a so-called "side shift". As shown schematically this comprises a transverse guide bar 36 arranged in the frame and on which the mast construction rests using wheels 33. These wheels 33 are mounted in a beam fixedly connected to the outer mast 25. This construction is per se known and will not be further described in detail. Although the invention is described with reference to an application thereof in a so-called transportable forklift, where this has particular advantages as earlier described, the invention is also applicable with equal advantage to other forklifts. In the retracted transporting state a load can be carried in each case closely against the mast, so that a stable positioning of the forklift is achieved. As a result of the very torsion stiff embodiment of the mechanism according to the further development of the invention, this is in practice easy and safe to use.

Claims: Forklift (1) comprising a frame (2), which supports a main mast (4), a load bearer with load engaging means (6) such as forks and drive means (7) connected to the load bearer for moving the load bearer up and downward along the mast (4), wherein the load bearer comprises a reach mechanism (8) having an auxiliary mast (23) movably guided along the main mast (4), a reach mechanism mast (22) supporting the load engaging means (6) and two pairs of scissor lever mechanisms (8) connecting the reach mechanism mast (22) parallel movable to and fro, to the auxiliary mast (23) wherein the pivoting point (16) of each pair of scissor levers (9, 10) is arranged out of the middle between the points of rotation at the ends such that in the retracted position the axes of the points of rotation of the scissor levers (9, 10) of each pair are vertically offset relative to each other characterized in that the main mast (4), the auxiliary mast (23) and the reach mechanism mast each comprise two pillars placed at a mutual distance, whereby the scissor levers (9, 10) fall inside the reach mechanism mast (22), the reach mechanism mast (22) falls inside the auxiliary mast (23) and the auxiliary mast (23) falls inside the main mast (4). Forklift as claimed in claim 1, characterized in that at least some of the corresponding ends of the pairs of scissor levers are mutually connected in torsion stiff manner by a connecting shaft. Forklift as claimed in claim 1 or 2, characterized in that the pivoting points of the pairs of scissor levers are mutually connected in torsion stiff manner by a connecting shaft. Forklift as claimed in any of the foregoing claims, characterized in that the forklift is a transportable forklift to be carried along behind a truck.

Inventors: KOOI, HESSEL
Applicants: KOOI BEHEER B.V.
Application year: 1989
Main classification: B66F9
IPC codes: B66F9