TECHNICAL FIELD

The present invention relates to a device in load-carrying vehicles with a so-called bogie lift, which incorporates a sprung drive shaft which carries driving wheels, and a running axle on which running wheels are suspended, the running axle being arranged, by means of a first lever operating between the running axle and one end of the spring assembly of each respective driving wheel and rotatably disposed by means of an operating device in relation to the chassis of the vehicle, to be raised and lowered by means of a second lever in relation to the frame of the vehicle in order thereby to move the running wheels of the running axle away from and into contact with the surface on which the vehicle rolls, in response to the axle pressure which is intended to be exerted on the surface, the movable, free end of' the second lever being arranged to actuate the first lever at a distance from the fulcrum of the second lever.

BACKGROUND ART

It is previously known in this art, for example from Swedish patent No. 201 306, to regulate, by means of a bogie lift, the axle pressure which is exerted by a load-carrying vehicle on the surface on which the vehicle rolls.

Such regulation of the axle pressure may be effected automatically; see for example Swedish patents Nos. 8104540-3 and 8204169-0, or manually by the driver of the vehicle. Such prior-art automatic systems pay little or no heed to the loading to which the bogie lift system proper is subjected, regulation instead taking place in response to the wanted axle pressure on the surface on which the load-carrying vehicle travels.

In manual operation of the bogie lift, an experienced and skilful driver can take into account not only the weight and payload of the vehicle but also the load to which the bogie lift is exposed. An inexperienced driver, in contrast, runs the risk of overloading and damaging the bogie lift in manual operation thereof. OBJECT OF THE PRESENT INVENTION

The primary object of the present invention is to obviate the above-outlined drawback inherent in both automatic and manual systems for operating bogie lifts so that the risk of overloading and damaging to the bogie lift will be avoided or eliminated.

SOLUTION

This object has been solved in the device described by way of introduction in that the second lever is elaborated at its movable end, with a plurality of surfaces which are located at different distances from the fulcrum of the second lever; and in that these surfaces are arranged to be rotated by the operating device about the above-mentioned fulcrum for load-transferring contact- with different parts of the first lever. Two particularly simple and advantageous embodiments of the present invention will be realized if the above-mentioned surfaces consist of two or more rotatable rollers or if the above-mentioned surfaces are interconnected to form a line of curvature. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS The nature of the present invention and its aspects will be more readily understood from the following brief description of the accompanying drawings and the discussion relating thereto. In the accompanying drawings:

Fig. 1 shows a highly simplified embodiment of the spring assembly of a driving wheel with associated parts;

Fig. 2 shows by way of definition different engagement positions for the embodiment according to Fig. 1;

Fig. 3 shows how the embodiment according to Figs. 1 and 2 is modified by a second lever of different design; and Fig. 4 schematically illustrates the- different engagement positions of this modified second lever.

In this context, it should be observed that the accompanying drawings only show one side of the rear region of a load-carrying vehicle and that the other side is of essentially identical design. DESCRIPTION OF PREFERRED EMBODIMENT

Referring to the drawings, the frame of a load-carrying vehicle, for example a truck, is designated by reference numeral

4. One end of the spring assembly of the driving wheel is pivotally secured in the frame 4 (not shown on the drawings), and its other, rear end is pivotally anchored by means of a first lever 3, in a pivot point 9 in the frame 4, as intimated in Fig.

1. Slightly further to the rear, to the right in Fig. 1, the vehicle is fitted with a running axle 2 which is rigidly connected to the first lever 3. At its end£ the running axle 2 carries two running wheels (not shown) which, together with the driving wheels

(not shown), form the disengagable and engagable bogie. In the conventional manner, the driving wheels are resiliently anchored in the frame 4 by means of the spring assembly 1, 1' (not shown), respectively. Hence, the first lever 3, at its front end seen in the direction of the vehicle, is movably connected to the rear end of the spring package 1 and is pivotally anchored in the pivot point

9 in relation to the frame 4, and its rear end supports the running wheels by means of the running axle 2. Fig. 1 shows the position assumed by the device according to the present invention when both the driving wheels and the running wheels run on the surface on which the vehicle is travelling, i.e. illustrates the bogie in the engaged state.

To operate the bogie lift, an operating device 8 is provided in the form of, for instance, a cylinder with a movable piston, which, in the activated state, rotates a rotatable shaft 10 disposed in the frame 4, the shaft 10 in its turn rotating a second lever 5 into cooperation with the upper side of the first lever 3, as particularly illustrated in Fig.2. It should here be observed that this shaft 10 naturally runs across to the other side of the vehicle where a corresponding second lever 5', a corresponding first lever 3' etc. (not shown) are disposed.

It will be apparent from Fig. 1 that the second lever 5 is provided with two projections 5a, 5b which are disposed at different distances from the fulcrum of the shaft 10 with the lower roller 6, seen in Fig. 1, rotatably disposed at a shorter distance from this fulcrum than the rotary anchorage of -the roller 7.

As a result of this design, on activation of the cylinder 8, the lower roller 6 will first enter into engagement with the first lever 3 and the additional roller 7 .will only assume this engagement when a further rotation of the shaft 10 has been realized, see Fig. 2. In the position where only the first roller 6 is in engagement with the first lever 3, less force will thus be required to turn the first lever 3, the strain will be lower and the rear running wheels will, by means of the running axle 2, have here been raised only insignificantly. By means of a limit switch on the cylinder (not shown) the piston of the cylinder 8 will execute a stroke which is only of such length as is required to obtain desired load distribution between the driving wheels and running wheels of the bogie, but not further than that only the first roller 6 is in engagement with the first lever 3. If, on the other hand, the load of the vehicle is sufficiently light, the above-mentioned limit switch may thereafter be bypassed and full stroke of the piston of the cylinder 8 obtained, in which event the additional roller 7 enters into engagement with the first lever 3 and the running axle 2 is raised to full height, this situation corresponding to the lowermost position illustrated in Fig. 2 by broken lines and corresponding to fully raised running wheels.

Whether the limit switch can be opened or not is determined automatically in that the load-sensing switch (not shown) disposed at the rear axle governs the limit switch, or, if no such arrangement is provided on the vehicle, the limit switch is provided with load-sensing equipment of, for instance, the same type as is employed as a load-sensing valve in the brake system of commercial vehicles.

Fig. 3 illustrates a variation of the second lever 5 and Fig. 4 illustrates the different engagement positions of this second lever.

In Fig. 4, the rollers 6 and 7 according to the embodiment of Figs. 1 and 2 have been intimated by broken lines so as to illustrate that these rollers 6 and 7 may, from the functional viewpoint, be wholly replaced by a second lever according to Figs.

3 and 4 without such rollers.

The above-mentioned second lever 5 according to Fig. 3 is - as is particularly apparent from Fig. 4 - of integral design with configurated surfaces, marked with reference numerals 5a-5j, these being disposed along a curve or line of curvature at different distances from the fulcrum of the second lever 5, namely the shaft

10. These surfaces 5a-5j - in contrast to the rollers 6 and 7 according to Figs. 1 and 2 - are stationary in relation to the second lever 5 and, in actual fact, are included as integral, inseparable surfaces in the second lever 5 although these surfaces

■ 5a-5j have been marked in Fig. 4 for purposes of clarity.

Since the second lever 5, on turning thereof by means of the operating device 8 according to Fig. 3 about the shaft 10, makes contact, by means of the various surfaces marked 5a-5j in Fig. 4, with different parts of the upper side of the first lever 3, the contact point or contact line between the second lever 5 and the upper side of the first lever 3 is changed without generating any appreciable sliding friction between them, i.e. the second lever 5 will "roll" in relation to the upper side of the first lever 3 although no rollers are provided in this particular case.

The precondition enabling this to take place is that the length, configuration and fulcrum - the shaft 10 - of the second lever 5 are adapted to the configuration of the upper side of the first lever 3 and to its fulcrum - the pivotal point 9 - or that, conversely, mutual adaptation is effected of the relevant contact surfaces and pivotal points to this end, namely that the second lever 5 "rolls" in relation to the first lever 3.

The present invention should not be considered as restricted to that described above and shown on the drawings, many modifications being conceivable without departing from the spirit and scope of the appended Claims.