P100/OIlI Regulation 3.2 AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION INNOVATION PATENT Invention Title: Parking brake The following statement is a full description of this invention, including the best method of performing It known to us: 2 Parking Brake Field of the invention The present invention relates to a parking brake. In particular, although not exclusively, the invention relates to a spring applied, air release parking brake for a rail wagon. This 5 specification is a divisional of AU2009201856 and the reader should refer to that earlier specification for aspects described herein but not claimed. Background of the invention Existing parking brakes for railway freight wagons are generally of the type that are individually manually applied and released through the use of a hand wheel. One 0 problem with these purely manual parking brakes is that the brake force applied is inconsistent because it is dependent upon the strength of the operator. Another problem with manual parking brakes is that there is always a risk that the parking brake will be left on when the wagon is put into use. Moreover, because the application force can vary, there is a greater risk that a parking brake will be left on at a relatively low force 15 which is more difficult for the train driver to detect than if it was on at a high force. Nevertheless, parking brakes left on cause damage to rolling stock and can cause derailment. It is estimated that the cost of damage from parking brakes being left on runs to millions of dollars per year in Australia alone. Spring applied, air release parking brakes have been used on freight wagons. The 20 braking force is consistently applied by springs and a pneumatic force is required to overcome the spring force and release the parking brake. The pneumatic force is generated by a compressor on the locomotive. Thus, the use of spring applied, air release parking brakes generally relieves the problem of parking brakes being left on since the parking brakes are released automatically when the train is put into motion. 25 Automated application and release of parking brakes also reduces the time and effort required to apply and release the brakes. The braking force is also consistent because it is independent of the strength of the operator. The braking force with this type of parking brake could assist with stopping a train should the need arise. Because of the 3 magnitude of braking force, this type of parking brake is also detectable by the driver should it fail and become stuck on. However, despite the above advantages there are still situations where it may be necessary to move the freight wagon without it being attached to a locomotive e.g. 5 during workshop maintenance. However, without the presence of the locomotive, there will be no pneumatic pressure to relieve the spring force of the parking brake. Furthermore, there may be emergency situations where there is a failure of the pneumatic system and the parking brakes are stuck on. Accordingly, it is an object of the present invention to provide a spring applied, fluid 0 release parking brake for a rail wagon having an override. Reference to any prior art in the specification is not, and should not be taken as, an acknowledgment or any form of suggestion that this prior art forms part of the common general knowledge in Australia or any other jurisdiction or that this prior art could reasonably be expected to be ascertained, understood and regarded as relevant by a 5 person skilled in the art. Summary of the invention Described herein, but not claimed, is a spring applied, fluid releasable parking brake for a rail wagon, the parking brake having a manual override including a ratchet mechanism having a manual actuator, wherein the manual override is both manually applied and 20 manually released by reciprocating the manual actuator. Preferably, the manual actuator of the ratchet mechanism is in the form of a lever which is reciprocated back and forth to operate the ratchet mechanism. The ratchet mechanism may also include gears to reduce the manual force required to reciprocate the lever and overcome the spring force. Suitably, the ratchet mechanism is reversible 25 so that the manual override can be both applied and released by the same mechanism. Preferably, the manual override is in line between the rigging and the brake piston. In a most preferred form of the invention, the manual override is in line between the brake 4 piston and the application lever. For example, the brake piston may be attached to an extensible and retractable pull rod and the ratchet mechanism may be selectively operable to progressively extend or retract the pull rod in length along its longitudinal axis to release the parking brake. The pull rod may be optionally part of a piston 5 assembly including the brake piston. The piston assembly may be received within a brake cylinder. The extension of the pull rod preferably causes the brake piston to move to a position abutting against a stop e.g. formed as part of the brake cylinder, and releases the tension in the brake rigging to thereby release the parking brake. O During normal operation, preferably the parking brake operates pneumatically so that it will be released by pneumatic pressure. The pneumatic system of the parking brake may be incorporated into the pneumatic service brake system. Accordingly, the pneumatic service brake system may exert control over the pneumatic parking brake system to restrict the application of the parking brakes during normal motion. 5 In accordance with a second aspect of the present invention there is provided a spring applied, fluid releasable parking brake for a rail wagon, the parking brake including: a brake cylinder including a piston; one or more springs which apply a spring force to the piston; a manual override for the parking brake, the override including a coupling which is 20 connectable as part of a linkage extending between the piston and one or more brake force applying members, the linkage serving to transfer the spring force to the brake force applying members, wherein the coupling is selectively manually extendable to effect one of releasing and restoring the spring force and wherein the coupling is also selectively manually retractable to effect the other of releasing and restoring the spring 25 force, wherein the coupling is disposed between the piston and the brake rigging.
5 Preferably, extension of the coupling leads to release of the spring force and retraction leads to restoration of the spring force. However, the arrangement may be reversed, depending on the configuration of the linkage. The linkage typically includes a pull rod, connected to the piston, an application lever 5 and brake rigging all of which serve to transfer the spring force to the brake force applying members. The coupling is preferably disposed between the piston and the brake rigging. In a most preferred form of the invention, the parking brake force is transmitted to an application lever between the brake cylinder and the rigging, to transfer the forces from the piston to the rigging, and the coupling is disposed between 0 the piston and the application lever. The coupling may comprise any of the members of such a linkage. However, preferably the coupling is the pull rod. The spring force holds the linkage in tension during normal operation to apply the brake force applying members. During normal operation, fluid (preferably air) is applied to the cylinder to release the spring force to release the brake 5 force applying members. Preferably, a stop is also provided to define a position at which the piston comes to rest when the coupling is extended so that further extension of the coupling releases the tension in the linkage, thereby releasing the brake force applying members. The stop may be defined by the brake cylinder. The stop may comprise the end of the cylinder. Accordingly, in the normal use configuration of the 20 coupling, in order to apply the spring force, the piston is suitably spaced from the end of the cylinder. In a most preferred form of the invention, the pull rod is made up of a number of portions including a piston end portion attached to the piston and a rod end portion in connection with the application lever. The pull rod further includes an intermediate 25 threaded rod between the piston end portion and the rod end portion. The piston end portion and the rod end portion threadingly engage with the intermediate threaded rod. The override preferably includes a manually operable ratchet mechanism which is selectively operable to rotate the threaded rod and cause the threadingly engaged piston end portion and rod end portion to progressively move along the intermediate 30 threaded rod, in opposite directions to cause extension of the pull rod. This causes the 6 piston to reach the stop (e.g. the end wall of the piston) and for the tension in the brake rigging to be released. When the override is intended to be turned off, it is necessary to operate the ratchet mechanism to cause the pull rod to retract thereby enabling the spring to tension the brake rigging to reapply the park brake. 5 It will also be understood that the term "comprises" (or its grammatical variants) as used in this specification is equivalent to the term "includes" and should not be taken as excluding the presence of other elements or features. It will be understood that the invention disclosed and defined in this specification extends to all alternative combinations of two or more of the individual features o mentioned or evident from the text or drawings. All of these different combinations constitute various alternative aspects of the invention. Brief description of the figures In order that the invention may be more fully understand, one embodiment will now be described by way of example with reference to the figures in which: 5 Figure 1 is a schematic of the parking brake according to a preferred embodiment of the present invention; Figure 2 is a detailed view of the brake cylinder in accordance with a preferred embodiment of the present invention; Figure 3 is a cross-section through A-A of Figure 2; 20 Figure 4 is a plan view of the cylinder shown in Figure 2; Figure 5 is a side view in the direction B of Figure 4; Figure 6 is a partial view through E-E of Figure 5; Figure 7 is a longitudinal cross-section through C-C of Figure 4; 7 Figure 8 is a detailed view of H of Figure 7; Figure 9 is a transverse cross-sectional view through G-G of Figure 4; Figure 10 is a view through J-J of Figure 9; Figure 11 is a side view corresponding to Figure 2, except showing the piston in a 5 position corresponding to the parking brakes being released; Figure 12 is a longitudinal cross-sectional view through D-D of Figure 11; Figure 13 is a schematic view of the parking brake being applied during normal operation; Figure 14 is a schematic view of the parking brake being released during normal 10 operation; Figure 15 is a side view of the cylinder, except showing the pull rod in the extended configuration; Figure 16 is a longitudinal cross-sectional view corresponding to Figure 15; and Figure 17 is an enlarged view of Figure 8. 15 Description of embodiment Figure 1 shows schematically the form of a parking brake 10 for a freight wagon according to a preferred embodiment of the invention. The parking brake 10 includes a brake cylinder 12 having a brake cylinder body 14 which houses a piston assembly 16. The piston assembly 16 includes a piston 18 and a packing cup 22 fitted on the piston 20 18 to seal against the air pressure. The piston is attached to an extensible/retractable pull rod 20. The pull rod 20 is guided through a front plate 24 of the brake cylinder 12. Furthermore, one or more applications springs 26 are housed within the cylinder 8 between the front plate 24 and the piston 18. The applications springs 26 apply a spring force to urge the piston 18 in the direction of arrow PAPPLY. The pull rod 20 is made up of three portions including a piston end portion 30 which is attached to the piston 18, a rod end portion 32 and a threaded rod 46. The piston end 5 portion 30 and the rod end portion 32 have their longitudinal axes aligned and their adjacent ends 34, 36 are spaced from each other. The spaced ends 34, 36 are also provided with aligned threaded bores 38, 40. The spaced ends 34, 36 of the pull rod portions 30, 32 receive the threaded rod 46. A manual override is provided in the form of a ratchet mechanism 42 with actuating lever 0 44. The ratchet mechanism 42 is connected to the threaded rod 46. The ratchet mechanism operates when the user reciprocates the manual actuator 44 back and forth which in turn rotates the threaded rod 46 about its longitudinal axis. Rotation of the threaded rod 46 causes the piston end portion 30 and the rod end portion 32 to move away/towards from each other in a direction along their aligned longitudinal axes, 15 thereby causing extension/retraction of the pull rod 20. The ratchet mechanism 42 can operate in either direction so that the pull rod 20 can either extend or retract to restore the normal operation of the parking brake. The parking brake also includes an application lever 50 which pivots about fixed pivot 52. One end of the application lever is connected by a flexible link 54, suitably in the 20 form of chain and shackles, to the outermost end of the rod end portion 32. The opposite end of the application lever 50 is connected to the brake rigging 56. The rigging 56 is then connected to the one or more brake force applying members in the form of friction member(s) (not shown) e.g. brake shoe which frictionally engages a friction receiving member such as a brake drum or the wheel directly. Such brake 25 components will be understood by those persons skilled in the art and therefore need not be described in detail in this specification. The parking brake illustrated in Figure 1 has two modes of operation. Firstly, the parking brake may function in a normal use mode and secondly, there is a manual override mode.
9 In the normal use mode, the application springs 26 normally push the piston in the direction of arrow PAPPLY which causes the pull rod 20 to pull on the lower end of the application lever 50 which pulls on the rigging 56 to apply the friction member to the receiving member and thereby operate the parking brake. To release the parking brake, 5 pneumatic pressure is applied to the opposite side of the piston in the direction indicated by arrow PRELEASE at a pressure of approximately 425 KPa. This pressure acts against the application springs 26 permitting the pull rod 20 to move to the left which releases the force applied to the rigging 56, disengaging the frictional brake members. The pneumatic pressure system operating in the parking brake may be connected to the 0 service brake pneumatic system. In such a set-up, it will be understood that the pneumatic release of the park brake will not operate when the freight wagon is not connected to a locomotive. Thus, due to the application springs 26, the park brake is held on when the freight wagon is not connected to a locomotive or if the air pressure fails. 5 Accordingly, there may be situations where it is desirable to release the parking brake and for this reason the manual override 41 is provided. The manual override 41 enables the parking brake 10 to be pumped off. This is achieved by reciprocating the actuation lever 44 to extend the pull rod 20. This causes the piston 18 to reach a stop at the end of the cylinder and releases the tension in the brake rigging. This will enable the freight 20 wagon to be moved. When it is desired to reinstate the parking brake, the ratchet mechanism 42 may be reversed so that reciprocating the actuation lever 44 causes the pull rod 20 to retract, enabling the springs to apply tension in the direction of the arrow PAPPLY . Figures 2 to 16 are detailed drawings of the brake cylinder and override corresponding 25 to the schematic illustration of Figure 1. Accordingly, like numerals are used to represent like parts. As shown in Figures 2 and 3 front plate 24 is bolted to the body of cylinder 12.
10 Piston end 30 of pull rod 20 is screwed into the stem of piston 18 at one end. The piston end 30 passes through front plate 24 supported by guide bush 60. Rod wiper 62 lodged inside guide bush 60 prevents dust and moisture ingress inside cylinder 12. As shown in Figure 7, the front plate 24 has integrally formed projections 63 extending inwardly into 5 the cylinder 12. These projections guide the piston guide rollers 66 (Figure 9). Piston guide pin 64, on which piston guide rollers 66 are retained by circlip 68, is fitted through piston end 30. The piston guide rollers 66, which are constrained by projections 63, prevent the piston 18 from rotating when the pull rod 20 is being extended and retracted. 0 Rubber locking ring 70 is lodged inside locking nut 72, which is screwed over the end of piston end 30. The locking ring 70 is compressed between locking nut 72 and rod end 30 when the locking nut is turned clockwise. This compressive action will cause the locking ring 70 to deform and lock together threaded rod 46, rod end 30 and locking nut 72. While locked, this prevents turning of ratchet mechanism 42, (to which threaded rod 5 46 is connected) under normal wagon shock and vibrations conditions. As shown in Figure 5, strainer assembly 74 is retained inside front plate 24 and allows air flow to and from the non-pressurized side of the cylinder. The actuating lever 44 is held within casing 76 which is attached to cylinder body 12 via bolts 78. The actuating lever 44 is retained inside casing 76 via a lock bolt mechanism 20 and release spring 80 (see Figure 6), which is held in place by split pin 82. Operating Modes As shown schematically in Figure 13, the brake force is created by springs 26A and 26B, which are compressed between front plate 24 and piston 18, and applies tension via pull rod 20 to the brake rigging 56 to apply the brake blocks to the wheels. 25 Depending on the means used to apply and release the spring force there are two operating modes: 11 A) Normal (automated) operating mode B) Manual operating mode Automated operation of tension spring park brake In automated operating mode, which is predominant throughout a freight wagon life, 5 park brake application and release is effected by using control air pressure. A control air pressure is supplied through air supply port 84 during normal operation when the freight wagon is connected to a locomotive. In order to apply the brakes, the control air pressure is exhausted via the air supply port 84, which causes the piston to retract under the force of compressed springs 26A and 26B, and apply a tensile force to 1O the flexible link 54. This tensile force is multiplied or reduced, as required, via application lever 50 and bogie rigging 56, and applied as brake force to the wheels 86 through the brake blocks 88. It is important that the bogie rigging 56 is set up in such a way that the piston 18 is well 5 clear of the cylinder bottom when the brakes are in applied condition. Figure 3 shows a distance of 13mm between the two in applied condition. In order to release the brakes, air pressure has to be applied via the air supply port 84. The build up of air pressure behind the piston 18 will result in a force capable of overcoming the force of the compressed springs 26A and 26B, allowing the piston 18 to 20 move out and release the brakes. Manual operation of tension spring park brake Manual release of the spring park brake 10 will be required whenever there is no air supply available to release and apply the park brake 10 automatically, or the air pressure behind the piston 18 cannot be maintained (such as in the case of leaking 25 piston seal).
12 In order to carry out a manual release, the actuating level 44 is taken out of its casing 76 (Figure 5), fitted inside socket of locking nut 72 (Figure 8) and actuated counter clockwise in order to decompress rubber locking ring 70 and unlock the threaded rod 46, enabling it to be turned by ratchet mechanism 42. 5 Then, actuating level 44 is fitted inside the socket of ratchet mechanism 42 whose ratcheting directional switch is set for release, and actuated forth and back until the pull rod 20 extends so that the piston 18 moves against the cylinder end 90, while the rod end 32 extends out (see Figure 16). Once the piston 18 rests against cylinder body 12 there is no more spring force 0 transmitted to pull rod 20, and with the rod end 32 moving out and the overall extension of the pull rod 20, any residual tension in the bogie rigging 56 will also be released. In order to reapply the park brake manually, the directional switch on the ratchet mechanism 42 is reset for take up, and the actuator lever 44 is moved back and forth until rod end 32 is pulled back in and the pull rod 20 is shortened in length, and piston 5 18 moves out away from cylinder end 90 to the position shown in Figure 3. The locking nut 72 is relocked by turning clockwise. The foregoing describes one embodiment of the present invention and modifications may be made thereto without departing from the scope of the present invention.