The present invention relates to an arrangement in¬ tended for driving a trackbound traction vehicle with carriages coupled thereto and with track inclinations of up to 1:4, and particularly to a drive arrangement which is self-adjusting in both the forward and rear- ward directions.

The Swedish Patent Application No. 8700667-2 teaches an arrangement of a similar kind intended for driving a trackbound traction unit with carriages at said track inclinations, although this arrangement is only self- adjusting in the forward direction of the traction unit. Consequently, when this known traction unit is driven in reverse, the drive wheels and the centre rail of the drive arrangement are subjected to considerable wear and the pressure and/or driving force exerted by the drive wheels of the arrangement is reduced, and the risk of the traction unit being derailed is increased when, for instance, there is a fault in the tracks or rails or when the centre rail of the drive arrangement is warped or twisted.

The object of the present invention is to provide an arrangement for driving a trackbound traction unit which is self-adjusting in both the forward and rear- ward direction of movement, thereby to overcome the drawbacks of known arrangements of this kind when driving the traction unit in reverse.

This object is achieved with the inventive drive arran-

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gement having the characteristic features set forth in the following claims.

The invention will now be described in more detail with reference to an exemplifying, preferred embodiment thereof and with' reference to the accompanying draw¬ ings, in which Figure 1 is a longitudinal sectional view of a trackbound traction unit provided with an inventive drive arrangement, said view being taken on the line A-A in Figure 2; Figure 2 is a top view of the inventive traction unit shown in Figure 1; Figure 3 is a cross-sectional view of the traction unit and drive arrangement, taken on the line B-B in Figure l; and Figures 4 and 5 are respectively a side view and an end view of the drive arrangement with the drive wheels inclined in two mutually perpendicular vertical planes in relation to the track plane.

As will be seen from the drawings and from Figures 1, 2 and 3 in particular, the illustrated embodiment of the inventive drive arrangement includes, in a known man¬ ner, at least two drive wheels 1 with associated trans¬ missions 2, two carrier arms 3 which extend substan¬ tially parallel with the length direction of the trac- tion unit and at one end of which drive wheels are journalled, a holder 4 in which the other end of the carrier arms is pivotally mounted by means of spherical bearings 5, a hydraulic clamping piston-cylinder device 6 which is connected to the firstmentioned ends of said carrier arms, and a rail 7 which is fixedly mounted on the supporting surface in the centre of the track, wherein the carrier arms 3 are substantially perpen¬ dicular to the geometric axes of respective drive wheels 1 and are intended to pivot the drive wheels 1 into pressure abutment with the centre rail 7, through

the medium of the hydraulic piston-cylinder device 6. The inventive drive arrangement also includes a frame R of substantially elongated rectangular configuration.

The holder 4 projects from the left short side (Figure 2) of the frame and the frame is suspended from the chassis U of the trackbound traction unit by four resilient articulated piston-cylinder devices FO which are pivotally journalled at the top and at the bottom thereof by means of, e.g., spherical bearings, and which are attached to the chassis and to the frame at respective attachment points Fl and F2. Alternatively, the frame can be suspended from the chassis in tele¬ scopic rods sprung with the aid of springs.

The articulated piston-cylinder devices FO are con¬ nected to a source of hydraulic pressure which is adapted so as to balance the frame R and hold said frame positioned substantially in a horizontal plane. The frame together with associated components will then behave as though it were weightless around this plane. Consequently, when the frame R is subjected to external forces acting in a vertical plane, the frame will move either upwards or downwards, depending on the direc- tional sense of the external forces, within an interval limited by the length of working stroke of the articu¬ lated piston-cylinder devices FO.

The frame R of the illustrated embodiment is provided on both short sides thereof with a resiliently mounted pressure device T and, as a result of the aforedescri- bed suspension, is able to swing freely between support forks K within a region P defined by said support forks and having a length of about 50 mm, said pressure devices being configured so that they will be guided

into respective support forks upon movement of the frame to the lef or to the right in Figure 2. Movement of the frame is determined by the direction in which the drive wheels rotate. When contact is established between the pressure devices T on one short side of the frame and the corresponding support forks on the chassis U, pivot points TK (Figure 4) are formed which transmit the drive force responsible for displacing the chassis, and therewith the trackbound traction unit, in the direction in which the drive wheels act. The pres¬ sure devices T are mounted resiliently in elastic rubber elements L, which as a result of their elas¬ ticity distribute the pressure forces exerted by the pressure devices T equally on both sides of the centre line of the traction unit and also enable the frame R to tilt in a vertical plane both longitudinally and transversely of the traction unit.

We imagine now that the traction unit is driven to the left in Figure 2, which implies, as described above, that the pressure devices T on the left short-side of the frame R will move into engagement with correspond¬ ing support forks K on the chassis U and therewith form pivot points TK. Corresponding pressure devices T on the other short-side of the frame are thus free from engagement with corresponding support forks K within the region P, which as mentioned above means that the frame R is free to tilt upwards or downwards in a vertical plane, both along and across the pivot thus formed.

In this starting position, the frame R is substantially parallel with the plane of the track, the pressure devices T, the support forks K and the centre points C of the drive wheels 1 being located in one and the same

plane substantially parallel with the track plane 7.

In the event of a deviation from the frame position in which said frame is substantially parallel with the plane of the track, for instance due to a track fault or a warped centre rail, the frame R with the drive wheels will be pivoted, or rotated, by the vertical reaction drive-force component (F _nv ) acting on the drive wheels (1) and/or by the substantially horizontal reaction pressure force (F _TH ) acting on the drive wheels (1) to the height position on the rail 7 in which the total drive force of the drive wheels again acts pressingly in a direction towards the pivot point TK. Those force moments which result in pivotal move- ment of the frame cease when this height position is reached.

When the traction unit is driven in the opposite direc¬ tion, i.e. to the right in Figure 2, for instance when reversing said unit, the pressure devices T on the right short side of the frame move into engagement with corresponding support forks K on the chassis and there form pivot points TK, which means that the pressure devices on the left side of the frame are free from engagement with corresponding support forks. The same procedure as that described above takes place when the position of the frame deviates from the position in which said frame is substantially parallel with the plane of the track, for instance due to a track fault or a warped centre rail.

Figures 4 and 5 illustrate, by way of example, the manner in which the frame is returned automatically to the height position on the centre rail in which the total drive force exerted by the drive wheels 1 acts in

a direction towards the pivot points TK established when driving on one side.

We imagine that the traction unit first moves along a fully horizontal track of which one rail, the left rail, abruptly begins to drop in relation to the other rail, which is still horizontal. The drive wheels will then be positioned slightly obliquely in relation to the centre rail, partly in a vertical plane parallel with said rail (Figure 4) and partly in a vertical plane perpendicular to said rail (Figure 5).

At each positive or negative angular deviation between the rolling direction of the drive wheels and the track plane, there will then be produced in the vertical plane parallel with the rail 7 a vertical reaction drive-force component or a transverse force F _DV on each drive wheel, this force being directed upwards or downwards depending on the angular deviation. This transverse force endeavours to rotate the frame R with the drive wheels to its starting position parallel with the track plane through the moment of force F-..-.A, where A is the distance between the mutual point of contact of the pressure devices and support forks, i.e. the pivot points TK, from the centre points C of res¬ pective drive wheels 1, whereupon the transverse force ceases.

In the vertical plane perpendicular to the rail 7, on the other hand, in the event of an angular deviation a between the circular base or top surface of the drive wheels 1 and the track plane, each drive wheel 1 is subjected to a substantially horizontal reaction pressure-force or transverse force T _H . This transverse force endeavours to rotate the frame R with the drive

wheels via the elastic elements L, through the moment of force F _T --.B, where B is equal to the width or height of the drive wheel, such that the angular deviation ceases and the transverse forces F„„ return to the centre points C of the drive wheels 1. The vertical reaction-pressure force components which also act on each drive wheel at the aforesaid angular deviation are, however, negligible at the small angles concerned, i.e. angles of 1-2°.

The drive arrangement also includes two hydraulic holding piston-cylinder devices H which are pivotally connected to the frame R and to the chassis U and which function to ensure contact between the pressure devices T and the support forks K in the drive direction should the traction unit roll faster than the peripheral speed of the drive wheels 1 along the centre rail 7, for instance due to gravity when rolling along an inclined plane, wherewith the support forks K on the chassis move away from the pressure device T on the frame. The holding piston-cylinder devices H can thus be used to maintain the pivotal connection in the drive direction, irrespective of the slope of the track plane. The holding piston-cylinder devices H are located sub- stantially parallel with the long sides of the frame R. The pivotal connections of the piston-cylinder devices H with the frame and the chassis preferably have the form of spherical bearings, thereby enabling said piston-cylinder devices to tilt freely in a vertical plane, both transversely and longitudinally of the trackbound traction unit.

The pivot points formed by mutual coaction of the pressure devices T and the support forks K can also be locked firmly with the aid of (not shown) automatically

operated hook locks which function to lock the pressure devices in the support forks.

The upper spherical bearing 5 of respective carrier arms 3 in the holder 4 is surrounded by a sleeve HY having excentric outer and inner cylinder surfaces and is rotatable to enable the holder axes to be adjusted to a preset angle of inclination, therewith to compen¬ sate for elastic deformation of the carrier arms and the holder among other things, and thereby enabling the whole peripheral drive surface of the drive wheels to be brought into abutment with the centre rail.