GB2100794A - Spring-loaded brake cylinder - Google Patents

Abstract

In a spring-loaded cylinder a breathing chamber accommodating an energy-storing spring is connected to atmospheric air by way of a conduit 29 leading to a bore 33 in a support flange of the spring-loaded cylinder, and a filter 36 and a labyrinth insert 39 are provided in the bore to prevent dirt, dust and spray water from entering the breathing chamber. The filter and the labyrinth insert are fixed in position by, on the one hand, a shoulder 35 in the bore 33 and, on the other hand, by the inserted end 32 of the conduit 29. The atmospheric air connection 33' for the chamber is located downstream of the filter 36. <IMAGE>

Description

SPECIFICATION Improvements in or relating to spring-loaded cylinders, particularly spring-loaded brake cylinders for road vehicles.

The present invention relates to spring-loaded cylinders, particularly spring-loaded brake cylinders for road vehicles.

One type of spring-loaded cylinder (German Auslegeschrift 1,238,792) has a supporting flange for securing the cylinder to a support member, and an energy-storing spring fitted in a breathing chamber which is provided between a cylinder base and a spring-loaded piston and which is connected to an atmospheric air connection by way of a separate line which leads to the support flange where it opens into a bore which is provided in the support flange and in which a filter is fitted.

The use of spring-loaded cylinders of this kind as brake-cylinders involves the problem of venting the breathing chamber whose volume changes each time the brakes are actuated and released.

Reliable communication must exist between the breathing chamber and the atmospheric air if it is desired not to reduce the efficacy of the energystoring spring.

However, ventilation of the breathing chamber is particularly problematical when the springloaded cylinder is used as a spring-loaded brake cylinder for a vehicle, since, in the case of rain, snow and/or a dusty road, the dirt in the installation region under the vehicles is such that the breathing of the breathing chamber draws a large number of corrosive substances and other particles into the breathing chamber. These substances and particles are deposited on the energy-storing spring and in the spring-loaded cylinder and have a detrimental effect on the operation of the spring-loaded mechanism. It is particularly disadvantageous when a piston and a sliding surface for the latter are provided in the spring-loaded cylinder, since corrosion or dirt has a particularly disadvantageous effect on the movability of the spring-loaded mechanism.

Although the problem could be solved to a certain extent by using a diaphragm piston, a diaphragm piston of this kind in the spring-loaded cylinder has the disadvantage that it has to be guided owing to the fact that the energy-storing spring does not supply its power in an axially parallel direction. Moreover, it is difficult to obtain a desired linear characteristic of the pressure curve with a diaphragm piston owing to the fact that the effective surface of the diaphragm varies during the stroke, particularly during auxiliary braking in cooperation interacting with the braking of a trailer.

In order to avoid the disadvantage of the drawing-in of dirt, oil or water, it has already been proposed, in the case of combined single-chamber spring-loaded brake cylinders, to connect the breathing chamber of the spring-loaded cylinder to the spring chamber of the brake cylinder by way of a pipe (Austrian patent specification 300,599).

However, a construction of this kind is complicated.

According to the present invention there is provided a spring-loaded cylinder, particularly a spring-loaded brake cylinder for road vehicles, having a support flange for securing the cylinder to a support member, and an energy-storing spring fitted in a breathing chamber which is provided between a cylinder base and a spring-loaded piston, in which the breathing chamber is connected to an atmospheric air connection by way of a separate line leading to the support flange where it opens into a bore which is provided in the support flange and in which a cylindrical filter and a labyrinth insert are provided.

A spring-loaded cylinder embodying the present invention can have the advantage that communication between the breathing chamber of the spring-loaded cylinder and the atmospheric air is established over a relatively short path and that this connection can prevent the intrusion of injurious substances into the breathing chamber without great expenditure.

The invention will be further described by way of example with reference to the accompanying drawings in which: Fig. 1 is a section through a combined singlechamber spring-loaded brake cylinder, and Fig. 2 is a section through a support flange of the cylinder of Fig. 1.

A spring-loaded cylinder has a cup-shaped, sheet metal housing 1 which is closed by a cast cover 2. The housing 1 has an operating cylinder 3 whose end facing a base 4 has a step 5 to which a spring reception cylinder 6 of smaller length is contiguous.

A nut 7 for an emergency release screw 8 is secured centrally in the base 4. In this manner, a screw location is formed. The free end 9 of the screw 8 extends into the spring-loaded cylinder where it carries a disc 10 which is secured to the emergency release screw 8 by means of a smaller screw 1 The end 9 of the screw together with the disc 10 and the screw 11 are accommodated in a tubular piston rod 12 of circular cross section and are longitudinally movable therein.

That end of the tubular piston rod 12 which is remote from the base 4 is closed by a radial wall 13 and, sealed by means of an O-ring seal 14, passes centrally through the cover 2. The other end of tubular piston rod 12 is connected to a spring-loaded piston 1 7 made from sheet metal.

The piston 1 7 is sealed relative to the operating cylinder 3 by means of a seal 19, comprising a softer annular collar 20 and a harder guide ring 21. The piston 1 7 constitutes a movable wall of a spring-loaded pressure chamber 1 6.

A spring abutment plate 22 abuts against the piston 1 7 and its shape is adapted to that of the spring-loaded piston 1 7. An energy-storing spring 23 is mounted on the spring abutment plate 22 and is clamped between the spring abutment plate 22 and the base 4.

A hole 25 having an outwardly extending annular rim 26 is disposed at a top location of the side wall of a breathing chamber 24 accommodating the energy-storing spring 23. A 90" arcuate member 27 made from plastics material is secured in the rim 26 by means of a snap-in flange 28 and is thus secured in position.

A straight conduit 28' is inserted into the free end of the arcuate member 27, the other end of the conduit 28' being inserted into a second 90" arcuate member 29 also made from plastics material. The arcuate member 29 is mounted in an axially parallel through bore 30 of a support flange 2' in the region of the said end of the conduit member. The other end of the arcuate member 29 is provided with a flange 31 (Fig. 2) and, contiguous thereto, an axial extension 32 by means of which the arcuate member is inserted into a bore 33 in the support flange and is fixed in position by the flange 31.

The bore 33 in the support flange is disposed parallel and perpendicular to the axis 34 of the spring-loaded cylinder. Although the bore 33 is a through bore, it has a shoulder 35 which serves as an abutment for a cylindrical filter 36. The filter 36 is inserted in the bore 33. A sleeve-shaped labyrinth insert 38 is disposed upstream of the filter 36, so that the labyrinth insert 38 and the filter 36 are located one behind the other in the bore 33 in the support flange. The sleeveshaped labyrinth insert 38 has a transverse wall 39 and radial bores 39' in the wall of the sleeve, so that axial flow-through is only possible by a circuitous route. The filter 36 and the labyrinth insert 38 are held and fixed in position between the shoulder 35 and an end 37 of the axial insert 32. An atmospheric air connection of the bore is designated 33'.

A single-chamber brake cylinder 40 is assembled with the housing 1 of the springloaded cylinder to form a single-chamber springloaded brake cylinder unit. The brake cylinder 40 has a piston rod 41 which is disposed coaxially of the tubular piston rod 12 and which, when in its illustrated position, is operatively connected to the piston rod 12. A free end 42 of the piston rod 41 extends out of the single-chamber brake cylinder 40 in a sealed manner and, in a manner not illustrated, is provided at this location with hinge or pivot point for a brake-rod linkage. Screws 43 inserted into the single-chamber brake cylinder 40 serve to secure the single-chamber spring-loaded brake cylinder to a part (not illustrated) of the vehicle. A diaphragm piston 44 is movable in the brake cylinder 40 against the force of a return spring 45 by the pressure in a pressure chamber 46.

The pressure cylinder operates as follows: During normal braking with the service brake, the spring-loaded pressure chamber 1 6 is subjected to supply pressure. The energy-storing spring 23 is stressed. The pressure in the pressure chamber 46 of the single-chamber brake cylinder 40 rises, whereupon the diaphragm piston 44 moves the piston rod 41 to the right. Any spray water, dirt or dust entering the spring chamber of the single-chamber brake cylinder 40 is of no great consequence, since the piston of the singlechamber brake cylinder is in the form of a diaphragm piston.

When braking with the spring-loaded mechanism, the supply pressure is discharged from the pressure chamber 16, whereupon the energy-storing spring 23 moves the tubular piston rod 1 2 to the right by way of the spring abutment plate 22, and the piston rod 1 2 moves the two pistons 1 7 and 44 together with the piston rod 41 to the right. The same movement is effected even in the event of failure of the supply of compressed air.

If the brakes are to be released from the position in which braking is effected by the springloaded mechanism, in order, for example, to drive the vehicle to a workshop, this operation is referred to as "emergency release". For this purpose, the emergency release screw 8 is turned in its nut 7, so that it is screwed out of the springloaded brake cylinder 26. The disc 10 secured to the screw 8 thereby comes into abutment against the spring abutment plate 22, whereupon the latter tensions the energy-storing spring 23, so that the brake-rod linkage is released.

The breathing chamber 24 breathes by way of the conduit 27, 28' and 29 and through the bore 33 in the support flange which accommodates the labyrinth insert 38 and the filter 36. The labyrinth insert and the filter ensure that dirt, water and oil cannot enter the breathing chamber 24 from the outside. Such contamination is retained by the filter 36 and by the labyrinth insert 38, so that nothing can be soiled or corroded in the breathing chamber 24.

Claims (4)

1. A spring-loaded cylinder, particularly a spring-loaded brake cylinder for road vehicles, having a support flange for securing the cylinder to a support member, and an energy-storing spring fitted in a breathing chamber which is provided between a cylinder base and a spring-loaded piston, in which the breathing chamber is connected to an atmospheric air connection by way of a separate line leading to the support flange where it opens into a bore which is provided in the support flange and in which a cylindrical filter and a labyrinth insert are provided.

2. A spring-loaded cylinder as claimed in claim 1, in which the labyrinth insert and the filter are disposed one behind the other in the bore in the support flange.

3. A spring-loaded cylinder as claimed in claim 1 or 2, in which the bore in the support flange has a shoulder for mounting the filter, and the labyrinth insert and the filter are disposed in the path to the atmospheric air connection, with the labyrinth insert disposed upstream of the filter.

4. A spring-loaded cylinder constructed and arranged and adapted to operate substantially as hereinbefore particularly described with reference to and as illustrated in the accompanying drawings.