The object of the present invention is to provide a brake, which fulfils the requirements of the market in an effective way and which has a brake effect, which is more than three times as large as that of a common brake. The characterizing features of the invention will be stated in the enclosed claims.

Thanks to the invention a brake has been provided, which in an excellent way fulfils its purpose at the same time being also relatively cheap to manufacture.

Also, the brake according to the invention has a long life due to the fact that it has a large surface on the brake linings and that their thickness is large.

Further, it has a good cooling because of the fact that air is flowing through the brake linings, the brake disc and the brake housing. It has further a mechanical pressure setting, which is directly acting from an air clock and a well functioning, automatic self-adjust- ment.

The invention will be closer described below by aid of a preferred embodiment example with reference to the accompanying drawings, in which: Fig. 1 illustrates a schematic lateral view of the self-adjusting device when the disc brake is in a first adjusting position,

Fig. 2 illustrates the self-adjusting device accord- ing to Fig. 1 when it is in another adjusting position, Fig. 3 illustrates how the pressure setting device is built up, Fig. 4 illustrates a schematic lateral view of the disc brake, from which appears more in detail the function of the pressure setting device and the self-adjusting device, and Figs.

5 and 6 illustrate lateral views in section of the components included in the self-adjusting device for adjusting arised clearance or play.

The pressure setting device 2 included in the disc brake 1 according to a preferred embodiment of the invention has a brake housing 44 with splines 45 and ventilation openings not illustrated in the drawing, said device 2 consisting of two discs 4, 5, one side of which being formed with a number of wedge-formed seg- ments 6-9, which are illustrated more in detail in Fig.

3. Each segment consists of an elongated inclined and pressure generating wedge 6, 8 and a small steeper releasing wedge 7, 9, which make it possible for the rolls 10 situated therebetween to roll off and roll on the pressure generating wedge 6, 8. The sides with the wedge-formed segments of the discs 4, 5 are turned against each other and formed in such a manner that the segments can fit into each other. Between the discs 4, 5 there are the rolls 10, which are somewhat conically shaped and are kept in position by a roller holder. The wedge disc 4, which is closest to one of the brake discs 11, 12, is placed on splines on a splines tube

13. This wedge disc 4 cannot be turned around the center but only be displaced along the splines tube 13.

The wedge disc 5 is journaled with roller bearings 14 both radially and axially on a threaded holding-up means 15 and can be turned around the center. Between the wedge disc 5 and the holding-up means 15 there are rolls 10' for reducing the friction between these details. When the wedge disc 15 has the position, where the tips 16 of its wegde-formed segments 8, 9 are situated straight in front of the valleys 17 of the wedge disc 3, the total thickness of the wedge disc 4 and 5 is as smallest. When the wedge disc 5 is turned around so that its tips 16 approach the tips 18 of the first wedge disc 4 the total thickness is increased. In this way pressure can be activated between the threaded holding-up means 15 and a fixed holding-up means 19 provided on the splines tube 13.

When the brake linings 22, 23 included in the disc brake 1 are worn and its thickness is reduced, the threaded holding-up means must be screwed inwards against the brake discs or more exactly the brake disc 20 illustrated in order to reduce the play arised between the brake disc 20 and the brake linings 22, 23.

In the brake disc 20 there is an air gap 21 for venti- lation. Said adjustment needs to occur automatically by the movement and force which at deceleration arise in the wedge disc 5 influenced by a compressed air-driven brake clock 24 via a deceleration movement, since the brake clock 24 only has enough force during decelera- tion and since the holding-up means 15 is not pressu- rized by the wedge disc 5. To achieve this there is a program disc 26, which runs on splines 12 placed along the splines tube 13 but which cannot be turned around.

This disc 26 has a wave-formed cam 27 and is kept near the holding-up means 15 by means of an oblique screw

28, which cooperates with a slot 29 in the side of the holding-up means 15. Further, there is a feeding disc 30, which is fixed on an edge 31 on the holding-up means 15. This disc functions as a "free wheel" against the holding-up means 15, i.e. when the disc 30 is turned in one direction, rolls 33 provided thereunder in grooves 32 are released from the backing, since the space for the rolls 33 is expanded when they are press- ed against a spring 34 arranged in the groove 32 and acting against the rolls 33. When the disc 30 is turned towards the other direction the rolls 33 are wedged against the backing, i.e. against the holding-up means 15, and brings it along with itself.

On the disc 30 there is also a cam 42 having plane edges 35, 36 and a negative angle in a direction to- wards the center. Further, there is a feeding arm 37, the one end of which being via a pivot pin 38 flexibly fastened to the wedge disc 5. The other end of this arm consists of at least one journaled roll 39, 40, which by a spring 41 is pressed against the feeding disc 30 and the program disc 26.

At deceleration in a position where the holding-up means 15 must not be adjusted, as appears from Fig. 1, the rolls 39, 40 on the adjusting arm 37 will start on the lower part of the discs 30 and 26 and then climb upwards via the wave cam 27 on the disc 26 and there- after further on a second cam 42 on the feeding disc 30 without falling down over the edge of the cam 42. When the brake is released the rolls 39, 40 will return to their starting position.

When the brake linings are worn the rolls 39, 40 will move further forwards, fall down over the edge of the cam 42 and bring the feeding disc 30 a certain distance when the brake is released until the rolls 39, 40 are

lifted upwards by the cam 27, which is shown more in detail in Fig. 2. The rolls 39, 40 will now fall down on the other side of the cam 42, before the brake has been stopped in its resting position. At the next deceleration the rolls 39, 40 will press against the cam 42 and turn the disc 30, which now brings the holding-up means 15, said means being adjusted forwards a certain distance on its threads 43 until the cam 27 lifts the rolls 39, 40 up and the feeding is ended before the threaded holding-up means 15 has been press- urized by the wedge disc 5.

As a background to the invention can be mentioned how the torsional movement/brake force can be calculated on a wheel on a 12 ton axis which is braked to a non- moving position, the brake force in question being limited by the grip of the tyre against the asphalt.

This grip is calculated in . A satisfactory value is 0,9 according to information from the firm Michelin.

This applies for dry asphalt with normally rough sur- facing.

In this case the following data are actual, namely: Axle pressure: 12000 kg, 6000 kg/wheel.

The wheel grip against the road: 6000 x 0,9 = 5400 kp.

Converted to KPM and KNM: the wheel radius = 53 cm 100 cm/53cm = 1,887 (converting factor) 5400 KP/1,887 = 2862 KPM = 28,62 KNM.

The friction factor of the brake linings at a cold brake is about 0,4 . When the brake linings and the disc have been warm, 400-5000C, the friction factor has fallen to 60% of the value for a cold brake: 60/100 x 0,4 = 0,24 p. The difference between 0,4/0,24 = 1,666.

In order for a warm brake to be able to stop the wheel it needs, when it is cold, to manage 1,666 x the need, which was 28,62 KNM, 28,62 x 1,666 = 47,7 KNM. A brake according to the present invention can manage this brake moment with a good margin.