EP0574616A1

EP0574616A1 - Lift truck

Info

Publication number: EP0574616A1
Application number: EP92201756A
Authority: EP
Inventors: Hendrik De Vries
Original assignee: R BLOM BEHEER BV
Current assignee: R BLOM BEHEER BV
Priority date: 1992-06-15
Filing date: 1992-06-15
Publication date: 1993-12-22
Anticipated expiration: 2012-06-15
Also published as: DE69214131T2; EP0574616B1; DE69214131D1

Abstract

The frame (1) comprises two arms (11) which carry front wheels (2) spaced from the upright (6) in forward direction. Across the frame (1) extend upper and lower rails (17 and 18, respectively) for guiding displacement of the upright (6). The upright (6) is connected to a runner (19) guided by one of the rails (17) and to a working cylinder (20) connected to that runner (19). The working cylinder (20) is directed substantially transversely to the upright (6), one end of the working cylinder (20) is connected to the upright (6) adjacent the front thereof and the other end of the working cylinder (20) is connected direct to the runner (19).

Advantages: simple construction, good view of the area of the load carrier, lowered centre of gravity and a construction of short structural dimensions.

Description

The invention relates to a lift truck according to the preamble of claim 1.
US-A-3 490 633 discloses a lift truck whose upright is tiltable in forward and backward direction and displaceable in lateral direction relative to the frame. To that end, one end of a working cylinder is connected to the back of the upright, while the other end is connected to the frame of the lift truck, with the working cylinder directed approximately transversely to the upright. To enable the motions of the upright to be followed, the points of attachment of the working cylinder to the frame and to the upright are designed as ball-and-socket joints and it has a relatively great length. This lift truck has such a length that it is not eligible to be taken along on a lorry for loading and unloading that lorry.
The lift truck of the type described in the preamble does lend itself for this purpose and is known from NL-C-165 992. This lift truck can be suspended at the back of the lorry by inserting parts of the load carriers thereof into openings at the back of the lorry and moving the load carrier downwards relative to the lift truck, so that the lift truck itself is lifted. The lift truck can for instance be secured by means of chains.
In a light-weight lift truck intended to be taken along at the back of a lorry, compact dimensions and slight weight are of great importance. Further, the lift truck must stick out from the back of the lorry as little as possible. A lift truck of this type must therefore be built so as to be as short as possible rearwardly of the upright.
For these reasons, it is undesirable to use counterweights in such a lift truck so as to prevent the lift truck from tilting in forward direction. Instead, to prevent forward tilting of the lift truck, the frame of a lift truck of this type is provided with two arms extending substantially in forward direction on opposite sides of the load carrier, which arms carry front wheels spaced from the upright in forward direction.
Due to the presence of the wheels of a lorry, these arms cannot be moved to any point under the lorry during the loading and unloading of the lorry. The upright of a lift truck of this type should therefore be movable in lateral direction over a relatively great distance.
In the known lift truck referred to, the means for tilting the upright forwards and backwards are designed as a runner which is connected to the upright via an arm of a toggle. The runner can be moved over a rail in lateral direction across the frame of the lift truck. The other arm of the toggle is connected to an end of a working cylinder directed upwards approximately parallel to the upright, the other end of the cylinder being connected to the upright. By operating the working cylinder, the toggle pivots about its point of connection to the upright and the position of the upright is changed in forward or backward direction.
These means for tilting the upright forwards and backwards are of very compact construction in rearward direction, which is important for obtaining the desired short construction rearwardly of the upright, in particular because these means are connected to a rail extending across the frame and can be moved along that rail.
However, a drawback of this known lift truck is that the construction is laborious and relatively expensive in that it comprises a heavily loaded toggle. A further drawback of this lift truck is that the lift truck operator's view of the load carrier is obstructed by the working cylinder projecting from the toggle.
The object of the invention is to provide a lift truck which, in addition to being of light construction and compact construction, in particular rearwardly of the upright, is of simpler construction, can be manufactured at lower cost and offers a better view of the load carrier.
This object is realized according to the present invention in that in a light truck of the type described in the preamble the characterizing features according to claim 1 are used.
Inasmuch as the working cylinder is directed substantially transversely to the upright, with one end of the working cylinder connected to the upright and the other end of the working cylinder connected direct to the runner, a simple construction is obtained in that no transmission means is required for transmitting the displacement effected by the working cylinder. Inasmuch as the working cylinder is moreover directed approximately in the viewing direction of a lift truck operator and transmission means such as the toggle referred to are absent, the view of the area of the load carrier is obstructed to a considerably lesser extent.
A further advantage of the lift truck according to the invention is that is has a lowered centre of gravity in that the working cylinder does not project above the runner but extends approximately horizontally from the runner.
Notwithstanding the working cylinder extending approximately transversely to the upright, the means for tilting the upright forwards and backwards nevertheless constitute a short construction rearwardly of the upright, in that the working cylinder is connected to the upright adjacent the front thereof.
Hereinafter the invention will be further explained with reference to a most preferred embodiment, shown in the accompanying drawings, in which:

Fig. 1 is a perspective view of a lift truck according to one embodiment of the invention, and
Fig. 2 is a cutaway side elevation of a lift truck according to the invention.

The figures are overall views of the lift truck according to the invention. The lift truck comprises a frame 1, two front wheels 2 and a driven rear wheel 4 operable by means of a steering pole 3. Instead of a steering pole, other means for steering the rear wheel can be used as well, such as a steering device with a steering wheel or a joystick.
Mounted on the frame is an upright 6. The upright 6 comprises a fixed upright section 7, an upright section 8 which is movable relative to the fixed upright section 7 in the longitudinal direction thereof and a load carrier 10 which is movable relative to the movable upright section 8 in the longitudinal direction thereof. The movable upright section 8 and the load carrier 10 can be moved telescopically in the direction indicated by an arrow 9.
In the lift truck of the embodiment shown, the load carrier 10 comprises two forks 15 suspended from a fork board 16. Depending on the field of application, the load carrier may also be shaped differently, for instance without a separate fork board or with more or fewer and/or differently shaped forks.
The frame comprises two arms 11 extending substantially in forward direction on opposite sides of the load carrier 10 and carrying front wheels 2 spaced from the upright in forward direction.
Extending across the frame 1 are upper and lower rails 17 and 18, respectively, for guiding displacement of the upright 6 in lateral direction relative to the frame 1.
The upright 6 is connected to a runner 19 guided by the upper rail 17 and to two working cylinders 20, connected to that runner 19, for tilting the upright 6 backwards and forwards.
For the lateral displacement of the upright 6, a double-acting working cylinder 21 is mounted between the frame 1 and a cross beam 22 of the upright 6 (see Fig. 1). The cross beam 22 is designed as a section extending around the working cylinder 21 and the lower rail 18, so that it occupies little space, has a high rigidity and protects the working cylinder 21.
The lift truck comprises a combustion engine 13 for driving a hydraulic pump (not shown) for driving the different working cylinders and a hydromotor (not shown) connected to the wheel 4. Naturally, instead of a combustion engine, an electric motor can be used. Batteries for that purpose can be charged during driving by a dynamo which is driven by the engine of the lorry.
The steering pole 3 is fitted with a group of control handles 5 for controlling the vertical displacement of the load carrier 10 as well as the lateral displacement (side-shift) and the tilt of the upright 6 in forward and backward direction. Mounted further on the frame 1 is a control panel 14 with control means for starting and stopping the engine 13.
If, instead of the steering pole 3, an operating means, arranged adjacent to the control panel 14, such as a steering wheel or a joystick for steering the rear wheel 4 is arranged, the group of control handles for lifting, tilting and the side-shift are preferably also arranged on the control panel.
The working cylinders 20 are directed approximately transversely to the upright 6. One end of each of the working cylinders 20 is connected to the upright 6 in the area of the front of the upright 6, and the other end of each of the working cylinders 20 is connected direct to the runner 19.
This construction of the means for tilting the upright 6 forwards and backwards is of simple construction, can be manufactured at low cost and constitutes a minimal obstruction of the view of the load carrier 10. Inasmuch as the working cylinders 20 are connected to the upright 6 in the area of the front of the upright 6, they can be of sufficient length in rearward direction to obtain a sufficiently large working range for tilting the upright 6 forwards and backwards, while still projecting in rearward direction over only a very limited distance. Transmission means for arranging the working cylinders parallel to the upright are therefore not necessary.
It is observed that, instead of two working cylinders, a different number of working cylinders can be used for tilting the upright 6 forwards and backwards. It is for instance possible to use a single working cylinder, which extends centrally between standards of the upright and is connected to a cross beam interconnecting those standards. It can for instance be mounted on a central portion of an Ω-shaped element, extending between the standards of the upright, the ends of the Ω-shaped element being mounted against the back of standards of the upright. Parts which can be displaced in longitudinal direction of the upright, including the movable upright section, may in that case require an adapted design, so that they can pass the working cylinder and any elements by which it is connected to the upright.
According to the embodiment shown, the runner 19, which is connected to the working cylinders 20, runs over the upper rail 17. It is also possible, however, to make the lift truck according to the invention of such design that the runner runs over the lower rail and the upright is tiltable about the upper rail.
Preferably, however, the runner 19 can be moved over the upper rail 17 because that rail 17 can be arranged above the rear wheel 4 further to the back than the lower rail 18 without increasing the dimensions of the lift truck rearwardly of the upright 6.
The combustion engine 13 is arranged in an area lower than the upper rail 17 and laterally relative to the rear wheel 4. This offers the following advantages over the conventional location of the engine above the rear wheel:

first, above the rear wheel 4, rearwardly of the upright 6, there is more free space for the upper rail 17 and for the passage of the runner 19;
secondly, the view of the area of the load carrier 10 is obstructed to a lesser extent;
thirdly, the centre of gravity of the lift truck is located at a lower point.

In this position, viewed in side elevation, the engine is disposed within the profile of the lift truck, so that this position of the engine 13 entails no drawbacks with regard to the extent to which the lift truck projects from a lorry at the back of which the lift truck is suspended.
In the lift truck according to the embodiment shown, the engine 13 is located laterally of the middle of the frame 1. In a lift truck with two rear wheels, however, the position laterally of a rear wheel can also be obtained by arranging the engine centrally between the rear wheels.
The engine 13 is located at a lateral distance from the rear wheel 4, such that the rear wheel 4 can be swivelled at least into a position directed substantially transverse to the front wheels 2. Thus, the contribution of the rear wheel 4 and the steering pole 3 to the size of the profile of the lift truck in side elevation, can be limited to a minimum when the lift truck is suspended behind a lorry.
For limiting the size of the profile of the lift truck in side elevation when the lift truck has been arranged in the transit position, it is further advantageous when steering pole 3 is located at least partly above the engine 13 when the back of the rear wheel 4 has been swivelled towards the engine 13 into the position directed at least substantially transverse to the front wheels 2.
Inasmuch as in the lift truck according to the embodiment shown the upper rail 17 is located above a bridge portion 24 of the frame 1 that extends upwards from the arms 11, behind the upright 6, it is possible to arrange the rail, at a given length of the lift truck, further backwards rearwardly of the upright 6 than in the known lift truck, where the rail is disposed in front of this bridge portion of the frame. Further, as a consequence thereof, the working cylinders 20 for tilting the upright 6 forwards and backwards are located at a relatively large distance from the tilting shaft of the upright 6, so that the forces exerted thereon are relatively low.
Inasmuch as in the lift truck according to the embodiment shown two working cylinders 20 for tilting the upright 6 forwards and backwards are mounted on opposite sides of the upright 6, an optimum view through the upright 6 is obtained and a considerably smaller torque is exerted on the standards of the upright 6 than in the conventional construction, where a toggle engages the upright centrally. Further, the standards are stabilized in that the upright 6 comprises a cross beam 23 between the standards, at the level of the points of engagement of the working cylinders 20. Owing to the working cylinders 20 engaging the upright 6 adjacent to the standards, this cross beam 23 can be of relatively slender and light construction, which saves weight and is advantageous for obtaining a proper view through the upright 6.
In the lift truck according to the invention, the load on the cross beam 23 is further limited in that it is not loaded with a force parallel to the upright for operating a toggle as is the case in the conventional construction with a toggle and a working cylinder parallel to the upright.
The upper rail 17, which guides the runner 19 connected to the working cylinders 20, has a cylindrical outside surface. At spaced points along its length, the rail is connected to the frame 1. This rail 17 is easy to manufacture and can be of light construction because it is supported by the frame at spaced points along its length. The upper rail 17 moreover does not have a recess or the like on the outside where dirt can accumulate and water may collect.
In order to obtain low-friction guidance of the runner 19 relative to the rail 17, the runner 19 is fitted with rollers 25 (Fig. 2). These rollers 25 each have a tread of concave cross-section, viewed in side elevation, and can roll over the rail 17. The rollers 25 centre the runner 19 relative to the rail 17 and do not prevent the runner 19 from following the tilt of the working cylinders 20. To obtain this effect, the rail can optionally be shaped as well, with, for instance, only the part of the outer surface that faces away from the upright being of cylindrical shape, instead of the entire outer surface.
The runner comprises a retaining piece opposite the rollers 25, which retaining piece is located at such a distance from the rollers 25, that, when the rollers 25 rest against the rail in centred position, the retaining piece is disposed against the rail 17 or located at a very minor distance therefrom. It is thus achieved that the runner 19 embraces the rail 17 in a reliable manner, also when the working cylinders 20 are subject to a pressure load and a rearward force is exerted on the runner 19 away from the upright 6. This can for instance occur when the truck is driven backwards with a load on the load carrier 10 and the brakes are applied abruptly. To absorb shocks which may arise as a result of the retaining piece striking against the rail and to prevent rattling in the case of a light load on the runner 19, the retaining piece is made of plastics.
The lower rail 18, too, has a cylindrical outer surface and is connected to the frame at spaced points along its length. The upright 6 comprises a tube 26 (Fig. 2) having a slot in its longitudinal direction, which tube 26 embraces the cylindrical outer surface of the lower rail 18 and can be shifted over it.
The lower rail 18 is simple to manufacture and can be of light construction inasmuch as it is supported by the frame 1 at spaced points along its length. The connection between the frame 1 and the rod 18 extends through the slot in the tube 26. The lower rail 18 has a convex surface, so that accumulation of dirt and moisture is avoided. The tube 26 is prevented from becoming dirty inasmuch as the slot of the tube 26 is located at the underside of that tube.

Claims

A light-weight lift truck comprising
a frame (1),
an upright (6), and
a load carrier (10) on the front of the upright (6), which is guided by the upright for upward and downward displacement, wherein
the frame (1) is provided with two arms (11) extending substantially forwards on opposite sides of the load carrier (10), said arms (11) carrying front wheels (2) spaced from the upright (6) in forward direction, and with upper and lower rails (17 and 18, respectively), extending across the frame (1), for guiding displacement of the upright (6) in lateral direction relative to the frame (1), and wherein
the upright (6) is connected to a runner (19) guided by one of the rails (17) and to at least one working cylinder (20), connected to said runner (19), for tilting the upright (6) backwards and forwards,
characterized in that
the working cylinder (20) is directed substantially transversely to the upright (6),
one end of the working cylinder (20) is connected to the upright (6) adjacent the front of the upright, and
the other end of the working cylinder (20) is connected direct to the runner (19).
A lift truck according to claim 1, characterized by two working cylinders (20) on opposite sides of the upright (6) for tilting the upright forwards and backwards.
A lift truck according to claim 1 or 2, characterized in that the runner (19) can be displaced over the upper rail (17).
A lift truck according to claim 3, characterized by an engine (13) for driving at least the working cylinders (20) for operating the upright (6), said engine being located in an area lateral to the rear wheel (4) and lower than the upper rail (17).
A lift truck according to claim 4, characterized in that the engine (13) is located at a lateral distance from the rear wheel (4), such that the rear wheel can be swivelled at least into a position directed substantially transversely to the front wheels (2).
A lift truck according to claim 4, characterized by a steering pole (3) which is located at least partly above said engine (13) when the back of the rear wheel (4) has been swivelled towards the engine (13) into the position directed at least substantially transversely to the front wheels (2).
A lift truck according to any one of claims 3-6, characterized in that the frame (1) comprises a bridge portion (24) extending upwards from said arms (11) behind the upright (6), with the upper rail (17) located above this bridge portion (24).
A lift truck according to any one of the preceding claims, characterized in that the rail (17) which guides the runner (19) connected to the working cylinder (20) has an at least partly cylindrical outer circumference and is connected to the frame (1) at least at a plurality of points spaced along its length.
A lift truck according to claim 8, characterized in that the runner (19) comprises at least one wheel (25) whose tread has a concave profile viewed in cross-section and can roll over the corresponding rail (17).
A lift truck according to any one of the preceding claims, characterized in that the other rail (18) has an at least partly cylindrical outer circumference and is connected to the frame (1) at least at a plurality of points spaced along its length and the upright (6) comprises a tube (26) having a slot extending in longitudinal direction, which tube (26) embraces the cylindrical bar and can be shifted over said bar.