AU2002220663A1

AU2002220663A1 - Spring storage brake cylinder with emergency release device

Info

Publication number: AU2002220663A1
Application number: AU2002220663A
Authority: AU
Inventors: Philippe Berra; Herve Gumez
Original assignee: Knorr Bremse Systeme fuer Schienenfahrzeuge GmbH
Current assignee: Knorr Bremse Systeme fuer Schienenfahrzeuge GmbH
Priority date: 2000-11-02
Filing date: 2001-10-26
Publication date: 2003-05-19
Anticipated expiration: 2021-10-26
Also published as: JP4365217B2; EP1339592B1; AU2002220663B2; ATE284333T1; DE10054149A1; DE50104791D1; JP2004521827A; EP1339592A1; WO2003039933A1; DE10054149B4

Abstract

The invention relates to a spring storage brake cylinder, in particular for rail vehicles, comprising an emergency release device, a spring storage piston (8), which may be axially displaced in a housing (1), moved either by a storage spring (9) to operate the brakes on a pressure loss, or by a spring storage pressure chamber (10), pressurised by a pressure medium, for the release of said spring storage brake and a normally locked non-self-locking threaded spindle drive (12), arranged in the force path between the spring storage piston (8) and a driven piston rod (5), which may be manually unlocked by means of a stop (13), provided in the emergency release device in order to activate the spring storage brake without pressure medium. According to the invention, a reliable function of said emergency release device may be achieved in a simple manner, whereby an outer radial slide bearing surface (19), for the stop (13) held in contact therewith, is provided on that part of the threaded spindle drive (12), which may rotate relative to the housing (1), on which only one locking flank, co-operating in a positive manner with the stop (13) to lock the emergency release device, is embodied, whereby the pitch of the threaded spindle drive (12) is of such a dimension that the rotating part of the threaded spindle drive (12) achieves a maximum axial control travel in less than one complete turn.

Description

1 Spring-brake cylinder with emergency release mechanism The present invention relates to a spring-brake cylinder, especially for rail vehicles, having an emergency release mechanism and a spring-loaded piston which is axially movable within a housing and which can be moved, on the one hand, by a pre-loaded spring for actuating the brake in the event of a loss of pressure and, on the other hand, by a spring-loaded pressure chamber which can be charged with a pressure medium to release said spring-loaded brake, as well as a normally locked, not self-locking threaded spindle drive arranged in the flux of force between the spring-loaded piston and an output piston rod, which spindle drive can be manually unlocked by means of a catch forming part of the emergency release mechanism, in order to be able to release the spring-loaded brake without pressure medium. Spring-brake cylinders of the above-described kind are preferably used as a safety-relevant assembly in rail vehicle construction to ensure that the brake is actuated in the absence of brake pressure. In a spring-brake cylinder, the brake can only be actuated by means of the pre-loaded spring, so that the spring-brake cylinder can be used as the parking brake of a stationary rail vehicle or as a safety brake during travel when a compressed air system is leaking or breaks down. A spring-brake cylinder of this type has been described in DE OS 26 08 502. The spring-brake cylinder consists essentially of a cylindrical housing with an internal pre loaded spring which, to actuate the brake, charges the piston in the event of a pressure drop in the pressure chamber from the opposite side, so that the output piston rod is extended. The brake is released by charging the pressure chamber with pressure medium, whereby the pre-loaded spring is loaded again and the piston rod is retracted. Furthermore, the spring-brake cylinder has an emergency release mechanism for interrupting and automatically returning the spring-brake cylinder to the above described normal operation, to which end a lockable and not self-locking threaded spindle drive arranged in the flux of force between the piston and the piston rod is locked or unlocked. The threaded spindle drive essentially consists of a part which is rotatable relative to the housing and a non-rotatable part. The rotatable part can be either a nut interacting with the piston, said nut being threaded onto a spindle formed on the piston rod; the spindle may also constitute the rotatable part, in which case it is mounted 004101OR7vR cinr 2 to be rotatable relative to the piston rod, whose associated nut is then non-rotatable relative to the piston. Both principles fulfil the same function. During normal brake operation - ie. when pressure is available - the rotatable part of the threaded spindle drive is locked by means of a catch, so that a firm flux of force is established between the piston and the piston rod in order to allow the piston to return under the action of pressure medium while tensioning the pre-loaded spring in the above-described manner. The emergency release device is required for the event that no pressure is available to compress the pre-loaded spring and thus to release the brake, whereas the rail vehicle must be moved - for example during shunting. In this event the transmission of power from the piston to the piston rod is manually interrupted from the outside by unlocking the not self-locking threaded spindle drive through the catch, which allows the brake to be released without pressure. The spring-brake cylinder is automatically returned to the original operating state when pressure is available again, which then effects a reverse movement of the components of the emergency release mechanism as a result of the compression of the pre-loaded spring. In the prior art this function is achieved by means of a ratchet mechanism provided on the external radius of the rotatable part of the threaded spindle drive, which engages with the catch like a locking gear mechanism. The ratchet mechanism allows a relative rotational movement of the rotatable part of the threaded spindle drive in only one direction, whereas rotation in the other direction is prevented by the stop surfaces of the toothing. This results in the problem that, when the locking mechanism engages before the rotating parts come to a halt, especially during a momentary actuation due to the catch slipping from the handle, the locking gear mechanism can be subjected to a high level of wear and suffer damage. In extremely cold conditions it is also possible, especially due to the reduced viscosity of the lubricant in such conditions, that the end position in the emergency release state is not reliably reached so that the brake cannot be released completely. This unfavourable situation is then remedied by re-engagement of the catch. Furthermore, production of the ratchet mechanism on the rotatable part of the threaded spindle drive is expensive from an engineering point of view. OA101 R'7vR cnr 3 It is therefore the object of the present invention to further improve a spring-brake cylinder of the type described above in such a manner that a reliable operation of the emergency release mechanism is achieved. This object is achieved based on a spring-brake cylinder according to the preamble of claim 1 in conjunction with its characterising features. The subsequent subclaims represent advantageous further embodiments of the invention. The invention incorporates the technical teaching that the part of the threaded spindle drive which is rotatable relative to the housing includes an external radial sliding surface for the catch which meshes with this surface, with a stop face for locking the emergency release mechanism being formed on said sliding surface which interacts in a positive manner with the catch, while the pitch of the threaded spindle drive is dimensioned such that the rotatable part of the threaded spindle drive makes less than a full rotation over its maximum axial stroke. The advantage of the invention resides in particular in that wear of the toothing due to an unfavourable engagement of the catch during movement of the rotatable part of the threaded spindle drive is prevented by avoiding a multitude of teeth on the locking gear mechanism. In the event of a brief actuation due to slipping from the handle of the catch, the catch always comes to rest on the sliding surface. The fact that the rotatable part of the threaded spindle drive can only make one full rotation at most prevents the catch from slipping a gear which could lead to damage. As a result, the meshing position of the catch is accurately defined. It is located only in the end position of the piston after the spring-brake cylinder has been returned to normal operation from the emergency release state. The sliding surface of the part of the threaded spindle drive which is rotatable relative to the housing is advantageously formed as a cam disk. In this case the stop face formed on the cam-like sliding surface preferably has a substantially radially oriented surface in order to ensure a secure engagement of the catch. The cam-shaped design of the sliding surface has the advantage that the stroke difference developing in cooperation with the catch can be used to indicate the operational state of the emergency release mechanism. The cam disk may be provided with additional attachments or recesses to allow easy external determination, with the aid of varying associated stroke differences, of the 004101 07vR doc 4 degree to which the brake was released, for example in the case of an emergency release operation. Within the scope of the present invention, the stop face formed on the sliding surface can be designed as a recess in the form of a notch or as an elevation in the form of a tooth, or in a different manner which allows it to engage with the catch. The emergency release mechanism according to the invention allows it to be used in spring-brake cylinders having a threaded spindle drive part which is rotatable relative to the housing, the threaded spindle drive being designed as a spindle which can be axially displaced together with the piston rod and which is rotatably mounted around the piston rod, the spindle interacting with a nut arranged in fixed position relative to the spring piston as the non-rotating part of the threaded spindle drive. As an alternative, it can also be used in spring-brake cylinders where the part of the threaded spindle drive which is rotatable relative to the housing is designed as a nut which can be axially displaced together with the spring piston and which is rotatably mounted coaxially on the spring piston, and which interacts with a spindle arranged in fixed position relative to the piston rod as the non-rotating part of the threaded spindle drive. In the first case of a rotatable spindle, a gear element having the external radial sliding surface with stop face according to the invention can be firmly fixed at the end of the spindle as a separate component. This simplifies the overall production of the rotatable spindle and allows a worn component to be individually exchanged by disassembly. Preferably a spring arranged between the catch and the housing is provided in order to keep the catch in permanent engagement with the sliding surface of the rotatable part of the threaded spindle drive, like a compression or tension spring. It is also feasible - in addition to manual actuation - to actuate the catch by remote control against the force of the spring by auxiliary means. A switch-operated electrical or pneumatic actuator could be used as the auxiliary means, while the required auxiliary energy may be obtained by accumulation in a battery or pressure chamber. 004101087v8.doc 5 Further steps improving the invention are set out in the subelaims or are explained in greater details hereinbelow in conjunction with the description of a preferred embodiment of the invention with reference to the drawings in which: Fig. 1 is a longitudinal sectional view through a spring-brake cylinder with an emergency release mechanism according to the present invention, Fig. 2a is a plan view of a diagrammatic representation of a locking gear mechanism according to the invention in the operational state, Fig. 2b is a side view of the locking gear mechanism of Fig. 2a, Fig. 3a is a plan view of a diagrammatic representation of a locking gear mechanism in emergency release state, and Fig. 3b is a side view of the locking gear mechanism of Fig. 3a. The spring-brake cylinder according to Fig. 1 essentially consists of a two-part, substantially cylindrical housing 1 which, in its first half, contains an axially movable service brake piston 2 which can be charged via an associated service brake pressure chamber 2 with pressure medium through a connection 4 attached to housing 1, in order to transmit a braking force to a brake linkage (not shown in further detail) of a rail vehicle by means of a piston rod 5 coaxially attached to service brake piston 2 and extending in a leak-proof manner from housing 1. The return movement of service brake piston 2 takes place when service brake pressure chamber 3 is empty, essentially through the action of a return spring 6 arranged between housing 1 and service brake piston 2. Piston rod 5 also has a mechanical adjustment device 7 to compensate for tolerances arising from wear of the brake pads. In addition to the above-described service brake, the spring-brake cylinder also incorporates a spring-loaded brake, to which end an axially movable spring-loaded piston 8 is arranged in the second half of housing 1. Spring-brake piston 8 can be moved, on one sided, by a plurality of pre-loaded springs 9 which are arranged at equal radial distances and equidistantly relative to one another from spring-brake piston 8 and, on the other side, can interact with parts of housing 1 in order to automatically actuate the brake in the event of a significant drop in pressure. A spring pressure chamber 10 is located on the other side of spring-loaded piston 8. Spring pressure chamber 10 has an 004101087vRdo 6 associated connection 11 and can be charged with pressure medium in order to release the spring-loaded brake, ie. to reverse spring-loaded piston 8 against the force exerted by the pre-loaded spring. In the flux of force between spring-loaded piston 8 and output piston rod 5 is arranged a not self-locking threaded spindle drive 12 which in normal operation is locked and which can be unlocked manually by means of a catch 13 forming part of the emergency release mechanism in order to be able to release the spring-loaded brake without pressure medium. The part of threaded spindle drive 12 which is rotatable relative to housing 1 is designed as a spindle 14 which is axially movable together with piston rod 5 and which is mounted rotatably around piston rod 5. Spindle 14 is guided in housing 1 to be movable and rotatable via an external radial synthetic bush 15. A nut 16 which is in fixed position relative to spring-loaded rod 8 and non-rotatable relative to threaded spindle drive 12 cooperates with spindle 14. A rotational movement of spring-loaded piston 8 with nut 16 is prevented by a torque lock 17 which interacts with parts of housing 1 as a mechanical stop. A gear element 18 is provided to lock and unlock threaded spindle drive 12 and is attached to spindle 14 in a fixed position but can be removed. Gear element 18 has an external radial sliding surface 19 with a stop face (described in greater detail further below) for catch 13, interacting with the latter to form the emergency release mechanism. A spring 20 in the form of a compression spring is arranged between catch 13 and housing 1 in order to keep catch 13 in constant engagement with sliding surface 19 of gear element 18. Catch 13 can be manually lifted from sliding surface 19 against the force of spring 21. In the position illustrated in the drawing, the spring-brake cylinder is in the emergency release state. The spring-loaded brake has been released without pressure medium by pulling on catch 13, which cancels the positive engagement with gear element 18. Due to the resulting release of threaded spindle drive 12, spindle 14 is freely rotatable so that, due to restoring forces generated inter alia by return spring 6, piston rod 5 which is connected to spindle 14 is axially retracted to release the brake. The pitch of the 00410i OR7vR dnr 7 threaded spindle drive is dimensioned such that spindle 14 with gear element 18 makes less than a full rotation over its maximum axial stroke. According to the representation of Fig. 2a, catch 13 is in positive meshing engagement with gear element 18 against a single radially oriented stop face 22, so that threaded spindle drive 12 is locked. The remaining circumferential surface of gear element 18 is formed as a regular cam disk 19. In the locked position shown, gear element 18 - as is clear from Fig. 2b - is in an axial end position in which a positive interaction with catch 13 is still ensured. In this locked position normal braking operation can occur, while an axial displacement takes place between stationary catch 13 and axially movable gear element 18 during a stroke of piston rod 5. In the emergency release position shown in Fig. 3a, the positive engagement between catch 13 and gear element 18 has been cancelled. Threaded spindle drive 12 has been unlocked and catch 13 can slide freely along cam disk 19. After release, an axial relative movement takes place between catch 13 and gear element 18, starting from the end position shown in Fig. 3b into the end position shown in Fig. 2b, due to the axial retracting movement of piston rod 5 with spindle 14. In order to restore the operational state, a release stroke of spring-loaded piston 8 is automatically generated with compression of pre-loaded springs 9 when pressure medium is available again, while the released spindle 14 with attached gear 18 is reversed until catch 13 again positively meshes with stop face 22 and thus the locked state of threaded spindle drive 12 has been restored. Normal braking operation is once again possible. The invention is not limited to the above-described preferred embodiment. Rather, variations are conceivable which are covered by the scope of protection as defined by the claims, despite their different design. In particular, the invention is not limited to an embodiment with a rotatable spindle and a non-rotatable nut. The principle would also work in reverse, with a rotatable nut and a non-rotatable spindle. 004101087v8.doc 8 List of reference numerals 1 Housing 2 Service brake piston 3 Service brake pressure chamber 4 Connection 5 Piston rod 6 Return spring 7 Adjusting device 8 Spring-loaded piston 9 Pre-loaded spring 10 Spring pressure chamber 11 Connection 12 Threaded spindle drive 13 Catch 14 Spindle 15 Synthetic bush 16 Nut 17 Torque stop 18 Gear element 19 Sliding surface 20 Spring 21 Handle 22 Stop face 004101087v8 doc

Claims

1. Spring-brake cylinder having an emergency release mechanism, especially for rail vehicles, and having a spring-loaded piston (8) which is axially movable within a housing (1) and which can be moved, on the one hand, by a pre-loaded spring (9) for actuating the brake in the event of loss of pressure and, on the other hand, by a spring pressure chamber (10) which can be charged with pressure medium to release said spring-loaded brake, as well as having a normally locked, not self-locking threaded spindle drive (12) arranged in the flux of force between the spring-loaded piston (8) and an output piston rod (5), which threaded spindle drive can be manually unlocked by means of a catch (13) forming part of the emergency release mechanism in order to release the spring-loaded brake without pressure medium, characterised in that the part of the threaded spindle drive which is rotatable relative to the housing (1) includes an external radial sliding surface (19) for the catch (13) which meshes with said surface, with only a single stop face (22) for locking the emergency release mechanism being formed on said sliding surface (19) which interacts in a positive manner with the catch (13), while the pitch of the threaded spindle drive (12) is dimensioned such that the rotatable part of the threaded spindle drive (12) makes less than a full rotation over its maximum axial stroke.

2. Spring-brake cylinder according to claim 1, characterised in that the sliding surface (19) of the part of the threaded spindle drive (12) which is rotatable relative to the housing (1) is designed as a cam disk.

3. Spring-brake cylinder according to claim 2, characterised in that the stop face (22) formed on the cam-like sliding surface (19) is a substantially radially oriented surface.

4. Spring-brake cylinder according to claim 2, characterised in that the operational state of the emergency release mechanism can be determined by means of the stroke difference of the catch (13) from the cam-like sliding surface (19).

5. Spring-brake cylinder according to claim 1 or 2, characterised in that the stop face (22) formed on the sliding surface (19) is designed as a recess in the form of a notch or as an elevation in the form of a tooth. 004101087v8.doc 10

6. Spring-brake cylinder according to claim 1, characterised in that the part of the threaded spindle drive (12) which is rotatable relative to the housing (1) is designed as a spindle (14) which is axially movable together with the piston rod (5) and which is mounted rotatably around the piston rod (5) and interacts with a nut (16) arranged in fixed position relative to spring-loaded piston (8) as the non-rotatable part of the threaded spindle drive (12) (Fig. 1).

7. Spring-brake cylinder according to claim 6, characterised in that a gear element (18) is attached in a fixed position to the spindle (14) and has the external radial sliding surface (19) with the stop face (22) for the catch (13), interacting with the latter to form the emergency release mechanism.

8. Spring-brake cylinder according to claim 6 or 7, characterised in that the spindle (14) is guided in the housing (1) to be movable an rotatable via an external radial synthetic bush (15).

9. Spring-brake cylinder according to claim 1, characterised in that the part of the threaded spindle drive which is rotatable relative to the housing is designed as a nut which can be axially displaced together with the spring-loaded piston, which is rotatably mounted coaxially on the spring-loaded piston, and which interacts with a spindle arranged in fixed position relative to the piston rod as the non-rotatable part of the threaded spindle drive.

10. Spring-brake cylinder according to one of the preceding claims, characterised in that a spring (20) arranged between the catch (13) and the housing (1) is provided which is designed as a compression or tension spring and keeps the catch (13) in constant meshing engagement with the sliding surface (19) of the rotatable part of the threaded spindle drive (12).

11. Spring-brake cylinder according to one of the preceding claims, characterised in that the catch (13) can be actuate by remote control by means of an auxiliary device. 004101087v8.doc