Abstract:
A low-profile railway car retarder system comprising a fulcrum pin, an upper and a lower lever, and two braking assemblies, is disclosed. The levers are located beneath a horizontal plan drawn from the top of the rail, thereby preventing inadvertent contact with a passing car. The braking actuator comprises an air-tight bladder which is filled with fluid or drained of fluid to cause the frictional braking members to move between closed and opened braking positions, and provides greater control than prior art systems.

Description:
This invention relates to railway braking systems, and more particularly, to a low-profile pneumatically operated braking actuator for a hump-type railway car retarder system. 
     In railway classification yards, cars are separated from engines and sorted or classified based both on the type of car and the contents of the cars. In humptype classification yards, a series of side tracks are positioned on a sloped surface, leading downhill from the main track. Often, the tracks are also curved. As cars are separated from a train, each car is directed to a specific side track based on the type and content of the car, and is allowed to roll down the sloped surface. A railway car retarding system, generally comprising a frictional braking system having frictional braking members which engage and grip the sides of the passing wheels of the railway cars, is employed to slow and stop the cars on the sloped or curved side tracks. 
     In recent years, the design of railway cars has been modified in order to increase the load-carrying capacity of the cars. Increasingly, railway cars are being designed lower to the ground, such that the distance between the bed of the railway cars and the rails below is decreased. 
     Existing braking systems generally include pneumatic or hydraulic piston cylinder actuators which activate the frictional braking members. Generally, the frictional braking members are coupled to a support tube or other device which extends above and in close proximity to the adjacent rail. As the piston cylinder is activated, the motion of the support tube forces the frictional braking member towards the passing car. 
     The piston cylinder actuators of existing systems are typically controlled by a computerized control system, which activates the actuators, and determines the level of pressure to apply to a given car based on a number of factors such as rail grade, car type, car weight, and wind resistance. 
     To provide an effective retardation of the cars it is important that the frictional braking members be applied to the cars in a controlled and repeatable fashion. Pneumatic or hydraulic piston cylinder actuators, however, are problematic in this regard for several reasons. First, as noted above, in traditional hydraulic or pneumatic cylinder actuators, the frictional braking elements of the retarding system are pivoted about a point extending above the adjacent rail. When the retarding system is located at a comer, cars of the train may come into contact the with retarder system. The inadvertent contact between the car and the retarder system may cause damage to the train, the car retarder itself, or, in some cases, even derailment. 
     Secondly, a significant volume of fluid under pressure must be supplied to the cylinder of the actuator to activate the brake, and removed from the cylinder to deactivate the brake. A substantial time period is necessary, therefore, to activate and deactivate the frictional braking members. Furthermore, the fluid must be compressed to a relatively high pressure of about 16,500 pounds force to activate the piston cylinder actuator. Because of the high volume and pressure levels required to control the piston cylinder actuator, it is difficult to provide repeatable incrementally-controlled braking action. Generally, piston cylinder actuators provide on and off positions braking positions, and only a very limited range of intermediary “slowing” positions between. Therefore, when using pneumatic or hydraulic piston cylinder actuators, railway cars are not slowed to a controlled stop, but rather are stopped abruptly. 
     In addition, in piston cylinder actuators, a seal must be positioned between the movable piston and the cylinder. To assure that a vacuum is maintained between the piston and the cylinder, grease-based or graphite packing materials must be packed around the seal. The seals, however, wear with time and temperature, and may release hydraulic or other fluids into the ground around the actuator. Actuators of this type, therefore, pose an environmental problem for the classification yard. Moreover, the packing materials are very temperature sensitive and harden as the ambient temperature falls. Therefore, as the temperature falls, the amount of pressure required to move the cylinder increases, making it increasingly difficult to retard the cars, and increasingly difficult to accurately control the braking action of the frictional braking members. 
     It is therefore an object of the invention to provide a railway car retarder which does not interfere with railway car operations when placed at a comer of a classification yard. 
     It is therefore an object of the invention to provide a railway car retarder which can be activated and deactivated quickly. 
     It is another object of the invention to provide a railway car retarder which is activated by a relatively low volume of fluid at a relatively low pressure. 
     It is a further object of the invention to provide a railway car retarder which can be incrementally controlled to provide a wide range of braking levels. 
     It is yet a further object of the invention to provide a railway car retarder which operates consistently over a wide temperature range. 
     It is a still further object of the invention to provide a railway car retarder which is environmentally safe. 
     In one aspect, the present invention is a low-profile railway car retarder system, designed to prevent interference between the passing cars and the retarding system itself as the cars pass the retarder, and particularly where retarders are located at curves in the track. The low-profile car retarder system employs upper and lower levers which pivot about a fulcrum point under the rail itself. The levers are each coupled to an associated brake beam support and brake stop. The brake stops are applied to the passing railway car to stop the car. The levers and brake beam supports are all maintained at a level below the height of the adjacent rail. Therefore, all of the components of the retarding system are positioned to prevent inadvertent contact with passing cars. Furthermore, the levers are controlled by a bladder-activated braking actuator. The bladder-activated actuator is activated by a relatively low volume of compressed air or other fluids. Therefore, the bladder-activated braking actuator is smaller and has a lower profile than prior art systems. 
     In another aspect, the invention is a railway car retarder system with an improved control system. As noted above, the railway car retarder is activated by a braking actuator controlled by a bladder. The bladder is activated by a relatively low volume of compressed air or other fluids. The amount of pressure required to activate the bladder, therefore, is significantly lower than in prior art hydraulic devices. The bladder also operates at higher pressures, thereby providing a larger operating range than conventional methods. Furthermore, the bladder is not sensitive to changes in ambient, and can be repeatably controlled at any temperature. Additionally, the bladder is sealed on all sides, and does not require a lubricant. Therefore, the bladder braking actuator substantially eliminates the environmental problems often associated with the prior art. 
     Other advantages and features of the invention, together with the organization and manner of operation thereof, will become apparent from the following detailed description when taken in conjunction with the accompanying drawings wherein like elements have like numerals throughout the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view of the low-profile car retarder system of the present invention. 
     FIG. 2 is a top view of the low-profile car retarder system shown in FIG.  1 . 
     FIG. 3 is an internal view of the bladder activated braking actuator as shown in FIG.  1 . 
     FIG. 4 is an internal view of an alternate embodiment of the bladder activated braking actuator as shown in FIG.  1 . 
     FIG. 5 is an internal view of a bladder activated braking actuator for use with traditional rail systems. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the Figures and more particularly to FIG. 1 a preferred embodiment of the low-profile railway car retarder system of the present invention is shown at  10 . The railway car retarder system comprises a fulcrum pin  12 , positioned between the rail  13  of a railway track and the wood tie  15 . An upper lever  14  and lower lever  16  are pivoted around the fulcrum pin  12 . A first brake beam support  18  is positioned at the external side of the rail  13 , while a second brake beam support  20  is positioned internally of the track. A bladder activated braking actuator  22 , which is inflated to operate the car retarder system  10 , is positioned between the upper lever  14  and lower lever  16 . The upper lever  14  is positioned at a level below a horizontal plane drawn from the top of the rail, thereby preventing inadvertent contact with passing cars. 
     Referring now to FIG. 2, it can be seen that the upper lever  14 , comprises two generally parallel arms  24  and  26  extending from the fulcrum pin  12  to a position directly above the bladder activated braking actuator  22 . The aims  24  and  26  are coupled together with a support tube  28 , which is generally perpendicular to the parallel arms  24  and  26 . The support tube  28  is coupled to the arms  24  and  26  in a position horizontally below the top of the rail  13 , to prevent inadvertent contact between a passing railway car and the support tube  28 . Although a bottom view of the railway retarder system  10  is not shown, it is understood that the construction of the lower lever  16 , as will be described more fully below, is essentially a mirror image of the upper lever  14 . 
     Each of the parallel arms  24  and  26  of the upper lever  14  basically comprises two sections: a horizontally extending section  32 , positioned above the bladder-controlled braking actuator  22 , and an angled section  34 , extending from the fulcrum pin to the horizontally extending section  32 . The support tube  28  is coupled to the horizontally extending position  32 . As can be seen from FIG. 1, the lower lever  16  includes an extension  66  which extends beyond the fulcrum pin  12 , beneath the second brake beam support  20 . The upper lever  14 , however, substantially ends at the fulcrum pin  12 . 
     Referring again to FIG. 2, it can be seen that the first brake beam support  18  is positioned between the arms  24  and  26  of the upper lever  14  on the external side of the track adjacent the bladder actuated braking actuator  22 . The second brake beam support  20  is positioned directly opposite the first brake beam support  18 , on the internal side of the track. 
     Referring again to FIG. 1, the second brake beam support  20  includes a base  36  which extends between the fulcrum pin  12  and the rail  13 . The base  36  of the first brake beam support  18 , however, extends only as far as the rail  13 . Both the first brake beam support  18  and second brake beam support  20  are coupled to a stop block,  40  and  42 , respectively. 
     Referring now to FIG. 3, a preferred embodiment of the bladder activated braking actuator  22  is shown. Preferably, the bladder  44  comprises a hollow tubular member of a flexible material capable of expanding and contracting. Preferably, the bladder comprises a pneumatic rubber bellows manufactured by Firestone and sold under the trade name Airstroke®g. The upper and lower cover plates  30  and  46  are coupled to the open ends of the tubular bladder  44 , enclosing the bladder and providing an air-right, water impervious seal. 
     Preferably, the bladder activated braking actuator  22  includes a guiding mechanism  48 , which prevents relative lateral motion between the upper cover plate  30  and the lower cover plate  46 . In a preferred embodiment, the guiding mechanism  48  comprises a first tubular member  50  coupled to the upper cover plate  30  and a second tubular member  52  coupled to the lower cover plate  46 . The first tubular member  50  is disposed in cooperative relation with the second tubular member  52 . 
     The first tubular member  50  is located in a substantially centered position on the upper cover plate  3   0  and extends generally perpendicular to the upper cover plate  30 . The second tubular member  52  is located in a substantially centered position on the lower cover plate  46  and extends perpendicular to the lower cover plate  46 , in a telescoping relation with the first tubular member  50 . The second tubular member  52  includes a stop ring  54 , which prevents the upper cover plate  30  and lower cover plate  46  beyond a set point determined by the length of the first and second tubular members  50  and  52 . In a preferred embodiment the guiding mechanism  48  further includes a graphite impregnated bushing interposed between mating surfaces of the tubular members  50  and  52 . In addition to providing the function of preventing relative lateral motion between the cover plates  30  and  46 , the size of the guiding mechanism  48  can be used to modify the amount of fluid necessary to expand the bladder  44 . 
     Referring now to FIG. 4, the bladder activated braking actuator  22  may further include at least one retention mechanism  60  for limiting relative motion between the cover plates  30  and  46 . The retention mechanism  60  preferably comprises at least one flexible member coupled between the upper and lower cover plates  30  and  46 . The retention mechanism  60  may comprise a chain, a rubber member, or any number of known devices. In some cases, however, the bladder activated braking actuator  22  may include external guiding and retention mechanisms  61 . Preferably, the external guiding mechanism comprises a pair of generally U shaped arms forming a frame around the braking actuator. Although both internal and external mechanisms are shown, it will be apparent that either an internal retention mechanism, an external retention mechanism, or both could be used. 
     Referring again to FIG. 3, the upper cover plate  30  preferably includes an aperture  32  for receiving a hose fitting or other known device for attaching a hose  62  or other tubular member to the bladder  44 . The hose  62  carries fluid from a compressor or other fluid source (not shown) into the bladder. A fluid flow control (also not shown), preferably including a flow gauge  63 , is coupled between the hose and first plate to control the flow of fluid into and out of the bladder. Preferably, the fluid is compressed air. However, one skilled in the art will recognize that any of a number of fluids could be used. 
     To operate the railway car retarding system  10  shown in FIG. 1, a computerized controller (not shown) preferably signals the fluid flow controller to allow fluid to flow into the braking actuator  22 , expanding the bladder  44 . The position of the upper lever  14  and the first brake beam support  18  are held constant as the bladder activated braking actuator  22  expands. The expansion of the bladder  44  forces the lower cover plate  46  downward. As the lower cover plate  46  is forced downward, the lower lever  16  rotates about the fulcrum pin  12 , causing the extended portion  66  of the lower lever  16  to contact the base  36  of the second brake beam support  20 , forcing the braking beam support  20  upward toward the rail  13 . The total volume and the pressure of the fluid allowed into the bladder  44  is varied based on any number of parameters. These parameters may include the type of car, the weight of the car, and the contents of the car. For example, cars which contain fragile cargo may be slowed, rather than stopped abruptly. In an alternative embodiment, as the bladder expands, the upper cover plate  30  and lower cover plate  46  are forced apart, thereby causing the levers  14  and  16  to move relative to each other. The levers  14  and  16 , in turn, cause the stop blocks  40  and  42  to move into the closed braking position, in which the stop blocks  40  and  42  grip the wheel or wheels of the car to retard the motion. 
     When the car is retarded to the desired level, the controller signals the fluid flow control to slow or stop the flow of fluid to the braking actuator bladder  44 . The fluid flow control may activate a release valve or other device to drain the bladder, therefore causing the bladder to contract, forcing the lower cover plate  46  up, thereby forcing the lower lever up and releasing the second brake beam support  20 . Upon release of the second brake beam support  20 , the car is allowed to move freely along the track. In an alternative embodiment, the upper cover plate  30  and lower cover plate  46  are forced together, and causing the levers  14  and  16  to move relatively towards each other. As the levers  14  and  16  move, the brake beam supports  18  and  20  are forced to the open braking position, and the car is allowed to move freely along the track. 
     Referring to FIG. 5, a bladder activated braking actuator for use with a traditional retarder system as opposed to the low profile car retarder system  10  described above, is shown at  70 . The bladder activated braking actuator  70  includes a guiding mechanism  72  which extends through concentric apertures  74  and  76  in the upper and lower cover plates  78  and  80 , respectively. The guiding mechanism  72  generally comprises a guide bushing sleeve  82  and guide rod  84 . 
     The guide bushing sleeve  82  is positioned between the concentric apertures  74  and  76  and provides a channel for the guide rod  84  to move in an up/down direction. The guide bushing sleeve  82  is substantially centered and extends generally perpendicularly between the upper and lower cover plates  78  and  80 . The body of the bushing sleeve  82  is substantially tubular. Internally, however, the walls of the bushing sleeve  82  are of two or more thicknesses to provide a stop point for motion of the guide rod  84  in the bushing sleeve. The stop point is provided by an internal ledge  94  established by the thicker portion of the bushing sleeve  82 . A flange for coupling the bushing sleeve to the upper cover plate  78  extends circumferentially from the upper portion of the bushing sleeve  84 . 
     The guide rod  84  is located in a substantially centered position in the guide bushing sleeve  82  in a telescoping relation to the guide bushing sleeve  82 . The guide rod  84  includes threading on both an upper and lower section. A stop ring  90 , dimensioned to allow motion of the guide rod  84  through the thinner portions of the bushing sleeve  82 , while preventing motion through the thicker portions, is coupled to the threads at the upper end of the guide rod  84 . A cylinder rod  92  is coupled to the lower end of the guide rod  84 . As the bellows are expanded, and the upper and lower cover plates  78  and  80  move relative to one another, total motion is limited by the interaction of the stop ring  92  and the internal ledge  94 . 
     While preferred embodiments have been illustrated and described, it should be understood that changes and modifications can be made thereto without departing from the invention in its broadest aspects. Various features of the invention are defined in the following claims.