WO1998021141A1

WO1998021141A1 - Arrangement for adjustment of the forks on a forklift or similar

Info

Publication number: WO1998021141A1
Application number: PCT/SE1996/001455
Authority: WO
Inventors: Rolf Åke HELLGREN
Original assignee: Smidesprodukter Skövde Ab
Priority date: 1996-11-12
Filing date: 1996-11-12
Publication date: 1998-05-22

Abstract

The present invention concerns a fork carrier equipped with forks which are adjustable by means of hydraulic control devices installed in the machine cab, designed for mounting on work machines of the front loader or excavator type. Two hydraulic cylinders, supplied by a pump are installed in an upper member of a parallelipedic cross section to prevent obscurement of the view from the operator's station. The movable piston ends are attached to yokes which, in turn, support the forks. A lower member is provided to maintain the forks in position. The forks perform an inward or outward symmetrical movement when the hydraulic fluid pump operates.

Description

Arrangement for adjustment of the forks on a forklift or similar State of the art Rational handling methods are essential in all industries, such as construction, in which materials are moved. The use of load carriers of various types has become increasingly common. The unitisation of loads, for example using loading pallets, enables loads to be moved efficiently by means of forklift trucks. Despite this, however, the truck forks must be adjusted from time to time. In this context, it should be noted particularly that the practical and user-friendly forklift principle has, so to speak, been extended to other vehicles. For example, loading machines of the front -loader type and even tractor excavators can be equipped with forks. Since machines of this type have a wider field of application than the forklift truck, a practical method of adjusting the forks is not only of major interest, but is also necessary to facilitate rational materials handling. It is further advantageous if this operation can be carried out from the cab of the machine. The literature describes many different methods of adjusting the forks of a forklift truck, or the forks mounted on another type of vehicle, from the operator's cab. In this context, another factor considered of major importance in the literature is the view, from the cab, of the forks and the load being handled. Thus, it is possible to define an area of technical interest in terms of the following characteristic features: adjustment of the loading device on a vehicle from the cab, with the advantage of a clear view of the forks and the load to be handled. The invention described below refers particularly to front loaders and excavators which can be fitted with forks for handling loads. In such cases, it should be noted particularly that unlike a forklift truck, the view from the operator's cab is not obscured by a heavy, centrally mounted hydraulic cylinder. Many fork arrangements on vehicles of this type employ a heavy plate to support the forks, which interferes with the field of vision at the very point where a good view is most important, that is at the tips of the forks. At this juncture, it should be emphasised that a fork which is adjustable from the cab may either be of the conventional type used to lift the load from underneath or may consist of a grapple, such as the type used to handle bales. In the latter case, the design is one which permits a gripping action; in other words, the forks are deployed mainly in a vertical rather than a horizontal plane as normal. Various arrangements are shown in the following patent documents: WO 95/02552, EP 0489255, EP 0628511, EP 0478245 and EP 06311975.

General description of invention

The present invention consists of a light, simple arrangement for adjusting the forks on a vehicle equipped with a lifting device simultaneously and symmetrically. The device may be provided with parallel arms as on a front loader or with an axle as on an excavator bucket. In most cases, all of these are operated with hydraulic power assistance. In symmetrical adjustment, the forks are assumed to move symmetrically relative to the direction of travel. In other words, the forks move either inward or outward as a pair. The vehicle is a loader or excavator of a common type, but is fitted with a standard tool fixture. In this context, the term 'tool' may refer to a bucket, a brush unit, lifting arms for use as a crane, or similar devices. On modern machines, these standard fixtures may be operated entirely from the driver's station by means of hydraulic controls.

The forks run on a fixture which is attached to the vehicle in a standard manner as described above, An example of this is the design used by Volvo on its type LM loaders. The fixture is attached to the loader or excavator by means of an ordinary claw attachment. This fixture consists of an upper and a lower member with vertical crossmembers to provide stability. The members are both made from hollow sections (such as VKR tube) ; in other words, the interior of the member is hollow.

This is particularly important in the case of the upper member, as that which houses hydraulic cylinders and on which the yokes rest. The forks are mounted, normally suspended, on individual yokes which, in turn, are also suspended from the upper member. The top of the upper member is provided with a rail which holds the yoke in position and prevents it from moving in the forward direction. This member houses two identical hydraulic cylinders. The top and bottom sides of the member are each provided with a slot extending more or less along half of the length of the member, and located respectively to the left and right. Each slot is arranged so that the inward-facing mounting element on the aforementioned yoke is inserted in the slot. Within the member, the two cylinders are located respectively alongside the slots in the sides and are arranged so as to operate in opposite directions. The cylinders are attached to the member at its outer ends. The other, movable end of each cylinder is provided with a bearing in which a journal is seated, the other end of the journal being attached to the yoke. The cylinders are supplied with hydraulic fluid from a hydraulic unit with the aid of the usual valves and their operation. This causes the pistons to execute a mutually opposed movement which, through the yokes and forks, causes the forks to move symmetrically relative to the axis of symmetry in the direction of travel of the vehicle.

The following, more detailed description refers to Figs. 1 and 2.

Fig. 1 shows the location of the cylinders on the bottom surface of the member, the upper part of which has been removed for clarity.

Fig. 2 is a cutaway view of the upper member as seen from the side. In the upper member 1, the cylinders 2 are mounted on the bottom surface of the member. This is achieved by means of the journal 3, which is fixed to the bottom of the member 4. The other end of the cylinder is provided with a journal bearing 5 in which a journal is seated. The yoke 6 is attached to the other end of the journal. Thus, the yoke 6 moves in the member 1 when the cylinder operates following the admission of hydraulic fluid. This causes the journal 3 to move in an open slot 7 in the top of the upper member. The yoke for the second fork is operated in the same manner, with the exception that the fixed part of this cylinder is attached to the upper section of the member, but on the opposite side, and that the corresponding movable journal runs in a slot in the bottom of the upper member, in the figure, the second cylinder is indicated by broken lines.

Some of the features which are essential to the function of the invention are shown more clearly in Fig. 2, in which the yoke 6 is shown resting on the rails 8 and 9 attached respectively to the top and bottom of the upper member. The purpose of the rails is to guide the movement of the cylinder pistons. The rails may, furthermore, be made of a material other than steel, such as PE . The figure also shows the two cylinders 2, which act on their respective yokes.

Claims

PATENT CLAIMS

Fork carrier consisting of two forks suspended from yokes on an upper member and with a lower member as support, which support also includes two stabilising crossmembers connecting the upper and the lower member, designed for mounting on a standard loading machine fixture with forks which are adjustable from the operator's station, characterised in that the forks are adjusted symmetrically in the opening or closing direction with the aid of two hydraulic pistons mounted symmetrically inside the supporting member on the fork adjusting device, the moving part of the pistons being attached, through a slot, to the yokes on which the forks are mounted.