IE46777B1 - Automatic load-dependent air brake - Google Patents

Abstract

An indirectly-acting, load-dependent compressed-air brake for railway vehicles, having a brake cylinder, to which compressed air can be admitted, as a function of the pay load, by a regulating valve via a compressed-air ratio device, a surge pressure, to overcome the forces of the release spring, being generated when braking is initiated in the brake cylinder, even if the vehicle is empty or only partially loaded, and the compressed-air ratio device having a balance beam which is loaded at one end by the regulating pressure via a piston and is loaded at the other end by the brake cylinder pressure via a second piston and, in the opposite direction, by the regulating pressure via a third piston and by a spring, wherein the second piston can be supported in the load direction of the brake cylinder pressure by an annular piston which is supported by the said spring in the third piston, the stroke of the annular piston in the load direction of the brake cylinder pressure and the stroke of the third piston in the opposite direction being limited by stops. [IN147277A1]

Description

This invention relates to an indirectly-acting or automatic loaddependent compressed-air brake, especially for railway vehicles. This type of brake is sometimes referred to as an automatic brake, because release of pressure from a through brake or train pipe will cause all the brakes in the train to be applied.

Such brakes may comprise a brake cylinder to which compressed air may be admitted by a regulating valve via a compressed-air ratio device, as a function of the pay load, an initial brake-actuating pressure being created in the brake cylinder even on vehicles which are empty or partly loaded, which pressure overcomes the forces of the release-spring, and said pressure converter comprising a balance beam loaded at one end by a first piston which applies the control pressure and at the other end by a second piston which applies the brake cylinder pressure, a third piston, acting in conjunction with a spring, applying the control pressure in the opposite direction.

With a known assembly of this kind, described in Czech Patent Specification No. 85144, it is impossible to cancel the effect of the third piston on the balance beam after overcoming the force of the release spring.

It is also known to use a spring loaded annular piston located in the pressure converter (see Swiss Patent Specification No. 540 800). However, this piston is lifted off the third piston by the spring force.

This means that with this arrangement it is impossible to cancel the effect which the annular piston exerts on the balance beams, after the forces of the release spring have been overcome.

According to the invention there is provided an indirectly-acting, load dependent compressed-air brake for railway vehicles, having a brake cylinder, to which compressed air can be admitted as a function of the load, by a control valve via a pressure transforming relay, a take up pressure, to overcome the forces of the release spring, being generated when braking is initiated in the brake cylinder, even if the vehicle is empty or only partially loaded, and the pressure transforming relay having a balance beam which is loaded at one end by the control pressure via a first piston and is loaded at the other end by the brake cylinder pressure via a second piston acting on the balance beam in opposition to the load from the first piston, and by the control pressure via a third piston acting in opposition to the load from the second piston and by a spring, wherein the second piston can be supported in the acting direction of the third piston by an annular piston which is supported by the said spring in the third piston, the stroke of the annular piston in the said acting direction and the stroke of the third piston in the opposite acting direction being limited by stops.

An embodiment of the air brake according to the invention will now be described with reference to the accompanying drawings, in which:Figure 1 is a schematic representation of the air brake in its 25 released state; Figure 2 shows a detail of the brake according to Figure 1 at the moment the brake is applied; and Figure 3 shows the same detail of the air brake according to Figure 2, but during service braking.

According to Figure 1, the main brake pipe 10, extending through the length of the train, is connected with an indirect-acting control valve 11, which is not shown in detail in the drawing. This control valve 11 is connected on one side with an auxilliary air reservoir 12, and on the other side with a pressure converter 13, its components being presented in the drawing in a broken line rectangle. The pressure converter 13 is moreover connected with the auxiliary air reservoir 12, and with the brake cylinder 14. The rigging which connects this brake cylinder 14 with the corresponding brake block, is not shown in the drawing.

The pressure converter 13 comprises a first cylinder 15 which is divided by two pistons 16 and 17 into an upper chamber 18, a 15 middle chamber 19, and a lower chamber 20. The two pistons 16 and 17 are interconnected by a piston rod 21 supported at one end of the balance beam 22. A pipe 23 connects the upper chamber 18 of the first cylinder 15 with the control valve 11, and the upper chamber 18 may be connected through a pipe 24, en electropneumatic valve 25, and a pipe 26, with the middle chamber 19. When the coil 27 is excited the valve-disc 28 of the electro-pneumatic valve 25 assumes the position shown in the drawing, and the two chambers 18 and 19 are separated from each other, the middle chamber 19 thereby being connected with the atmosphere through the pipe 26 and a chamber 29. If, however, the coil 27 is not excited, the valve-disc 28 will rest on its lower valve seat so that the two chambers 18 and 19 are connected with each other, the middle chamber 19 thereby being isolated from the atmosphere.

An opening 30 in the lower chamber 20 provides a permanent connection with the atmosphere.

The upper piston 16 is considerably larger than the lower piston 17. The balance beam 22 is supported on a slidable block 31 which is connected with a piston 33 through a rod 32, said piston 33 dividing a cylinder 34 into two chambers 35 and 36.

One of these chambers 35 accommodates a spring 37 which is supported on one side at the end of the cylinder 34 and on the other side at the piston 33, Said spring tries to displace the piston towards the right-hand side, as shown in Figure 1. The other chamber 36 is connected through a pipe 38 with a weighing valve which is not shown in the drawing, and consequently the air pressure in this chamber 36 is always load-dependent. The greater the pay load on the vehicle, the higher is the air pressure in the chamber 36, and the greater is therefore the compression of the spring 37 and the displacement of the sliding block 31 towards the left.

The other end of the balance beam 22 supports a tubular piston rod 39 which is fixed to a piston 40. This piston 40, acting together with an annular piston 41, divides a cylinder 42 into an upper chamber 43 and a middle chamber 44. An additional piston 45, adjustably supported on the piston rod 39, separates the middle chamber 44 from a lower chamber 46. This lower chamber 46 is connected with the control valve 11 through a pipe 47 and the pipe 23. The upper chamber 43 is connected with the brake cylinder 14 through a pipe 48, and the middle chamber 44 is permanently connected with the atmosphere, 4677? through an opening 49. A cylinder 50, fixed to the piston 45, accommondates a spring 51 which is supported on one side against the cylinder 50 and on the other side against a ring 52. The spring 51 tries to press the ring 52 against both a stopping member 53 of the cylinder and a flange 54 of the annular piston 41. The piston 40 is located in a recess of the annular piston 41. A diaphragm-seal 55 rests against both the piston 40 and the annular piston 41.

A valve disc 56 in surface contact with a valve seat 57, separates the upper chamber 43 of the cylinder 42 from a valve chamber 58 which is connected with the auxiliary air reservoir 12 pia a pipe 59.

The valve disc 56 may be lifted off the valve seat 57 by the hollow piston rod 39. In the positions of the valve disc 56 and the hollow piston rod 39 shown in Figure 1, the chamber 43 is vented into the atmosphere through the piston rod 39, and the valve chamber 58 is isolated from the upper chamber 43.

A first stop 60 limits the downward stroke of the annular piston 41, and a second stop 61 limits the upward stroke of the piston 45.

Figure 2 and 3 depict the cylinder 42 according to Figure 1 in two additional positions. Since the arrangement is the same there is no need for details, to be discussed. Identical parts have been given the same reference numerals.

The mode of operation of the air brake described above is as follows. With the brake released, all brake components assume the positions shown in Figure 1. The through pipe 10 carries the operating pressure. The auxiliary air reservoir 12 is full, and the brake cylinder 14 has been vented into the atmosphere through a pipe 48, the chamber 43, and the hollow piston rod 39. When the vehicle is empty the slidable support 31 occupies its right-hand end position.

If, as assumed, the coil 27 of the electro-pneumatic valve 25 is excited as shown in the drawing, there will be no air in the chamber 19; only the upper chamber 18 is connected with the control valve 11 through the pipe 23, and so long as the brake is released, there will be no pressure in this chamber 18.

When the brake is applied, the pressure in the through brake pipe 10 is reduced, and the control valve responds, an initial pressure of approximately 0.8 kg/cm being created above the piston 16 in chamber 18, and below the piston 45 in the chamber 46. If, as assumed, the slidable support 31 is in its end position at the right-hand side, the force exerted by the piston 16 on the hollow piston rod 39 via the piston rod 21 and the balance beam 22 is only small. However, the initial actuating pressure is such that the piston 45 is thrown into its uppermost position against the stop 61; the annular piston 41 is thereby similarly forced upwards, together with the piston 40, by the spring 51 and the flange 54, so that they, too reach their highest positions.

The respective positions of the three pistons 45, 41 and 40, are shown in Figure 2. This spontaneous upward movement of the three pistons 45, and 40, however, depends on the fact that the middle chamber 44 and the upper chamber 43 are under atmospheric pressure, as explained above. When the piston 40 is raised as shown in Figure 2, the valve disc 56 is lifted off the valve seat 57, and consequently compressed air is admitted from the auxiliary reservoir 12 into the upper chamber 43 through the valve chamber 58, and into the brake cylinder 14 through the pipe 48. In consequence of this, pressure builds up in the upper chamber 43 so that the annular piston 41 is forced downwards against its stop 60, compressing the spring 51. Figure 3 shows the corresponding positions of the three pistons 45, 41 and 40. When the pistons 45 and 41 assume the positions shown in Figure 3, the pressure in the upper chamber 43 and consequently also in the brake cylinder depends solely on the surface ratio of the two pistons 16 and 40 and on the position of the slidable support 31. However, before the two pistons 45 and 41 may assume the positions shown in Figure 3, a pressure must have built up in the chambers 43 and 46 which is high enough to compress the spring 51. Whether an initial brake actuating pressure can be produced in the brake cylinder 14 thus depends on the initial pressure in the chamber 46 and on the resistance of the spring 51, and this is independent of the load carried on the vehicle, that is to say, on the position of the slidable support 31. In this manner it may be ensured that a minimum initial pressure is available in the brake cylinder 14 on every vehicle of a train, whatever its load may be.

The transmission ratio of the pressure converter 13 can be reduced when the current to the electro-pneumatic valve 25 is disconnected.

As soon as the coil 27 ceases to be excited, a connection is established between the chambers 18 and 19 in the cylinder 15. In this case the pressure at the two sides of the piston 16 is identical and the piston 15 is therefore inoperative. The control pressure is admitted only to the smaller piston 17, and the brake force is thereofore correspondingly smaller.

Claims (2)

1. An indirectly-acting, load dependent compressed-air brake for railway vehicles, having a brake cylinder, to which compressed-air can be admitted as a function of the load, by a control valve via a 5 pressure transforming relay, a take up pressure, to overcome the forces of the release spring, being generated when braking is initiated in the brake cylinder, even if the vehicle is empty or only partially loaded, and the pressure transforming relay having a balance beam which is loaded at one end by the control pressure via a first piston 10 and is loaded at the other end by the brake cylinder pressure via a second piston acting on the balance beam in opposition to the load from the first piston, and by the control pressure via a third piston acting in opposition to the load from the second piston and by a spring, wherein the second piston can be supported in the acting 15 direction of the third piston by an annular piston which is supported by the said spring in the third piston, the stroke of the annular piston in the said acting direction and the stroke of the third piston in the opposite acting direction being limited by stops.

2. An indirectly-acting load dependent compressed-air brake for 20 railway vehicles, substantially as described herein with reference to the accompanying drawings.