The present invention relates to a locking device for a vertically adjustable support wheel of a trailer, the locking device having a support wheel holder connect¬ ed to the trailer chassis, and a locking means also con- nected thereto, which for locking the support wheel in a given vertical position is adapted to engage with a tubu¬ lar support wheel portion, which is displaceable in the support wheel holder.

Trailers as well as trailer caravans are fitted with a support wheel, which is used when the trailer is not coupled to a towing vehicle. The support wheel consists of a vertical tube, at the lower end of which the actual wheel is mounted. The tube is displaceable in a support wheel holder mounted on the trailer chassis and is lock- able in the support wheel holder in various vertical positions. The support wheel holder may consist of a yoke around the tube and a locking pin which is screwed through the yoke and which can engage with the tube so as to lock it. The problem of this type of locking device is that after being used for some time, its function deteriorates or even ceases by the locking pin jamming or snapping in two. Also, the locking pin may damage the tube.

DE-2,905,800 discloses a locking device for a ver- tically adjustable support. The locking device comprises a locking plate. A first compression spring is arranged between the locking plate and the trailer chassis and biases the locking plate in such a manner that the lock¬ ing plate is inclined relative to the support. When the lockir.c plate is pressed in the direction of the first spring, the locking plate can be angled in such a posi¬ tion that the support can move freely therethrough.

When releasing the support in its lowered position, the locking device has the drawback that the locking

plate must be pressed in a careful and controlled manner in the direction of the base, such that the locking plate is arranged perpendicular to the axis of the support and the support can move freely through the locking plate. If the locking plate is pressed too far, it will again be inclined relative to the axis of the support, whereby the support is again locked by the locking plate thus being caused to abut against the support.

The locking device according to DE-2,905,800 also suffers from the drawback that the device in its raised position cannot be secured against vertical displacement in the direction of the base. The support is maintained in its raised position by means of the compression spring only, which is arranged between the trailer chassis and the upper part of the support. Thus, using this device for trailers could imply that the support slides down when driving, for instance owing to vibrations when pass¬ ing a bump, which would jeopardise the transport safety.

The object of the present invention is to provide a locking device, which solves the problems of prior-art locking devices.

This object is achieved by means of a locking device of the type mentioned by way of introduction, whose fea¬ tures appear from the characterising clause of claim 1. The invention will now be described in more detail by means of an embodiment, reference being made to the accompanying drawings.

Fig. 1 is a side view of the front part of a trailer and illustrates the support wheel mounted in a locking device according to the invention.

Fig. 2 shows the support wheel and the locking device separately, with the locking device in a position in which the support wheel can be raised and lowered.

Figs 3 and 4 show the locking device in the direc- tion of arrows A and B in Fig. 1.

Fig. 1 shows the front part of a trailer chassis 1 and how a support wheel 2 is mounted. The support wheel

consists of an outer tube 3, in which an inner tube 14 can be screwed upwards and downwards. The actual wheel is attached to the lower part of the inner tube 14. The upper part of the inner tube is fitted with a crank 4, by means of which the inner tube can be screwed upwards and downwards a limited distance in the outer tube. This pos¬ sibility of raising and lowering the front portion of the trailer is used when connecting the trailer to and dis¬ connecting it from a towing vehicle (not shown). It is also possible to raise and lower the support wheel 2 between a transport position, in which the wheel is ele¬ vated to the chassis 1, and a parking position, in which the wheel is located in the position shown in Fig. 1. The locking of the support wheel in the respective position is carried out by means of the locking device 5 according to the invention. This consists of a support wheel holder in the form of a U-beam 6, which by means of bolts 10 is screwed to the trailer chassis 1. Between the flanges 8 and 9 of the U-beam, two locking plates 11a, b and 12a, b are inserted. The locking plates are bent and each have a shorter angular portion 11a and 12a, respectively, which abut against the respective U-beam flange 8, 9. The U-beam flanges 8 and 9 and the longer angular portions lib, 12b of the locking plates have holes 8c, 9c, lie, 12c aligned with each other and adapted to receive the support wheel tube 3. To enable locking of the tube 3, a compression spring 13 is inserted around the tube between the longer angular portions lib, 12b of the lock¬ ing plates. The compression spring will bias the locking plates to the position shown in Fig. 1. By each angular portion 11a, 12a abutting against the respective U-beam flange 8, 9, the locking plate will pivot about its point of engagement with the flange under the action of the compression spring 13. The locking plates will be slight- ly inclined and, thus, clamp the tube in the position as set. By using two locking plates, the tube will be locked against movement upwards as well as downwards.

Fig. 2 illustrates how the locking device is ope¬ rated for releasing the support wheel tube 2. If the angular portions lib, 12b of the locking plates are pressed together to an approximately parallel position, the tube is released and can be moved upwards or down¬ wards. In order not to risk that the locking plates are pressed together beyond the parallel position to a new inclined position, the spring is so designed that the locking plates are arranged in parallel, when the spring is fully tensioned. If the locking plates are released, they will resiliently move apart and again clamp the tube.

Although this embodiment comprises a support wheel holder consisting of a U-beam, other solutions are also feasible. The essential thing is that the support wheel holder secures the tube 3 perpendicular to the tube axis. Moreover, the locking plates can be hingedly mounted on the web of the U-beam. Then the angular portions 11a, 12a may be dispensed with.