AN ACTUATING DEVICE FOR A VEHICLE BRAKE RIGGING

Abstract: An actuating device for a vehicle brake rigging, compris­ ing a service brake and a spring parking brake. The device comprises, apart from a service brake cylin­ der (1) and piston (2) and a parking brake cylinder (15, 17) and piston (12), a ratchet wheel (8) disposed between the two pistons, non-permanent connection means (6, 7) provided between the ratchet wheel and the service brake piston; and further connection means (10, 12) provided between the ratchet wheel and the parking brake piston; the ratchet wheel being controllable in translation and in rotation-translation, depending on whether a chamber (B) of the parking brake cylinder is either emptied or fed.

Description: AN ACTUATING DEVICE FOR A VEHICLE BRAKE RIGGING Technical Field This invention relates to an actuating device for a vehicle brake rigging, comprising a service brake and a spring parking brake. The invention applies more particularly but not exclusively to brake riggings for railway vehicles. Background of the Invention A device of this kind has the object of applying a brake force either by supplying pressurized fluid to the service brake or by holding the parking brake applied by its springs, when the fluid pressure in the vehicle has decreased inadvertently through exhaust (leak) or wilfully by remote control from the drivers cab (electric valve). Such device can moreover be manually deactivated to permit the vehicle to be driven in the absence of pressure and automatically reactivated as soon as the pressure has increased when the vehicle has been brought into operation again. This last manipulation can be effected where it is desired to neutralize the parking brake while leaving the service brake usable following an incident such as breakage of a feed hose. The Invention The device according to the invention is characterized in that it comprises, apart from a service brake cylinder and piston and a parking brake cylinder and piston, a ratchet wheel disposed between the pistons; non-permanent connection means provided between said ratchet and said service piston; and further connection means provided between the ratchet wheel and the parking piston; the ratchet wheel being controllable in translation and rotation-translation, depending on whether a chamber of the parking brake cylinder is either emptied or fed. The parking brake cylinder and the service brake cylinder are placed in opposed relationship. Brief Description of the Drawing The invention will be described in further detail below under reference to the accompanying drawing, which is a side-view, partly in section, of a device according to the invention. Description of a Preferred Embodiment A device according to the Invention comprises a service brake cylinder 1, controlled by pressurized fluid, a piston 2, provided with a return spring 3 and axially movable in the cylinder and connected to a slack adjuster 4 which transmits a brake force to a rod 5 (errded by an ear); a pulling sleeve 6 secured to the service brake piston 2; an axial ball bearing 7 disposed on a rotatable ratchet wheel 2, on the one hand prevented from rotation relative to a housing 9 by a pawl 10, normally held in engagement by a spring 11, and on the other hand connected to a parking brake piston 12 via a helical ramp thereon, the latter piston 12 moving axially in a parking brake cylinder 15, 17 to the left in the drawing under the action of forceful springs 13 and 14, the parking brake cylinder being disposed in an opposed relationship in respect to the service brake cylinder 1; and a pulling means 16 for lifting up the pawl 10. The parking brake cylinder Is actually constituted by a cylinder 15 proper and a sleeve 17 that can be screwed or unscrewed in said cylinder thereby to increase or diminish a control distance 11A" of the slack adjuster 4. The operation is as follows: When the service brake is released its piston 2 rests under the action of the spring 3 on the bottom of the cylinder 1 while maintaining a clearance between the ball bearing 7 and the pulling sleeve 6. At service brake application fluid flows into a chamber C and pushes the piston 2 as well as the rod 5 to the left in the drawing via the slack adjuster 4, which is provided for maintaining the piston stroke and consequently the clearance or slack between the brake shoe or block and wheel or disk constant- independently of the wear. When the vehicle runs the parking brake is in the released brake position, i.e. the pressurized fluid in chamber B maintains the springs 13 and 14 compressed through the piston 12, itself supported by the housing 9 and the ratchet wheel 8, such that there is provided a clearance between the ball bearing 7 and the pulling sleeve 6. Upon parking, when fluid pressure disappears in the chamber B, the piston 12 moves forward (to the left in the drawing) under the action of springs 13 and 14 thereby pulling also the ratchet wheel 8, which is non rotationally connected to the piston 12 through the pawl 10. Consequently the ball bearing 7 pulls the service brake piston 2 via the pulling sleeve 6 thereby transmitting the force of the springs 13 and 14 to the rod 5 and the wheel or disk, diminished by the force of the return spring 3. After parking braking pressure reappears in chamber B, and all the parts reassume their positions for released brake. Unlocking or deactivating is effected by pulling up the pulling means 16 thereby to disengage the pawl 10 and rotationally release the ratchet wheel 8. Consequently, the service brake piston 2 with the pulling sleeve 6 returns to its released brake position under the action of the return spring 3 while pulling the ratched wheel 8 via the ball bearing 7. Furthermore, as the chamber B is not supplied with pressurized fluid, the parking brake piston 12 moves to rest on the bottom of the cylinder 15 thereby neutralizing the force of springs 13 and 14. Relocking or reactivating is automatic and is effected when the fluid pressure increases in chamber B of the parking brake thereby causing the piston 12 to move to the right in the drawing under compression of springs 13 and 14 and the ratchet wheel 8 to rotate under the action of the helical ramp on the piston 12. It is to be noted that in this case the pawl 10 is lifted by the passage thereunder of each tooth of the ratchet wheel 8.

Claims: CLAIMS 1. An actuating device for a vehicle brake rigging, comprising a service brake and a spring parking brake, characterized in that it comprises, apart from a service brake cylinder (I) and piston (2) and a parking brake cylinder (15,17) and piston (12), a ratchet wheel (8) disposed between the pistons; non-permanent connection means (6, 7) provided between the ratchet wheel and the service brake piston; and further connection means (10, 12) provided between the ratchet wheel and the parking brake piston; the ratchet wheel being controllable in translation and in rotation-translation, depending on whether a chamber (B) of the parking brake cylinder is either emptied (contact between the non-permanent connection means - translation of the ratchet wheel - application of the parking brake) or fed (release for rotation and translation of the ratchet wheel - clearance between the non-permanent connection means - release of parking and service brakes). 2. A device according to claim 1, characterized in that the parking brake cylinder (15, 17) and the service brake cylinder (l) are placed in opposed relationship. 3. A device according to any of claims 1 and 2, characterized in that the non-permanent connection means consist of a pulling sleeve (6) and a ball bearing (7). 4. A device according to any of the preceding claims, characterized in that the further connection means consists of a helical ramp on the piston (12) in engagement with said ratchet wheel (8), a pawl (10) causing rotational blocking of ratchet wheel (8) in one direction, as long as it is not pulled away from said ratchet wheel. 5. A device according to any of the preceding claims, characterized in that the parking brake cylinder (15, 17) comprises a cylinder (15) proper and a sleeve (I7) that can be screwed or unscrewed in said cylinder thereby to increase or decrease a control dimension (A) of a slack adjuster (4) connected to the service brake piston (2).

Inventors: ROGER, MICHEL
Applicants: SAB NIFE AB
Application year: 1986
Main classification: B60T17
IPC codes: F16D65, B60T13, B60T17