Abstract:
An apparatus engageable with a hand brake assembly for automatically applying at least one brake secured to a railway vehicle. The apparatus comprises an operating mechanism which is a two stage pneumatic cylinder having a primary portion for initial phase of the brake application and a secondary portion for the final brake application to apply high forces and to comply with AAR requirements. A source of fluid pressure is connected to the operating mechanism for periodically supplying a predetermined pressure thereto. A first control device is connected to the source of the fluid pressure for initiating the supply of such predetermined pressure to the operating mechanism. A second control device is connected to the source of the fluid pressure for regulating the supply of such predetermined pressure to the operating mechanism thereby causing an automatic application of such brake by the hand brake assembly.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
   This application is closely related to U.S. Pat. No. 6,709,068, titled “Automatic Set and Release Hand Brake”, Issued on Mar. 23, 2004; and to U.S. Pat. No. 6,848,754, titled “Automatic Application Hand Brake”, issued on Feb. 1, 2005; and to U.S. Pat. No. 6,902,042, titled “Automatic Application Hand Brake Winding Mechanism”, issued on Jun. 7, 2005. The above patents are owned by the assignee of the present invention and the teachings of these patents are incorporated herein by reference thereto. 
   FIELD OF THE INVENTION 
   The present invention relates, in general, to hand brake assemblies for use on railway type vehicles and, more particularly, this invention relates to an apparatus to automatically activate and apply the brakes on a railway vehicle without requiring an operator to manually wind the chain on such hand brake. 
   BACKGROUND OF THE INVENTION 
   Prior to the conception and development of the present invention, railway car hand brake mechanisms were well known in the art. They usually include a large, rotatable hand wheel disposed in a vertical plane and mounted on a shaft which, through a gear train, can rotate a chain drum to wind up a chain that is secured at its end remote from the chain drum to the brake rigging of the railway car. As the hand wheel is rotated in one direction, the brakes are applied and rotation of the hand wheel shaft in the opposite direction is prevented by a pawl, which engages a detent wheel on the hand wheel shaft. 
   The brakes may be released by disengaging the pawl from the detent wheel but this causes rapid rotation of the hand wheel and the gears of the gear train. To avoid rapid rotation of the hand wheel, hand brake mechanisms have been devised which are known as “quick release” mechanisms. Generally these quick release mechanisms include a releasable connecting means between the hand wheel shaft and the gear train. When the connecting means is released, the gears of the gear train rotate rapidly, without constraint by the pawl and detent wheel, but the hand wheel remains stationary. 
   The Association of American Railroads (AAR) promulgates specifications for the design and operation of railway car hand brake mechanisms. Vertical wheel, gear train, hand brake mechanisms are classified in three categories, namely:
         (1) Standard power—provides an average force on the chain of 3350 lbs. with a 125 lb. turning force applied to the rim of a wheel twenty-two inches in diameter.   (2) Intermediate power—provides an average force on the chain of 4475 lbs. with a 125 lb. turning force applied to the rim of a wheel twenty-two inches in diameter.   (3) High power—provides an average force on the chain of 6800 lbs. with a 125 lb. turning force applied to the rim of a wheel twenty-two inches in diameter.       

   After setting of the brakes, when the hand brake mechanism is released the gears of the gear train rotate rapidly. This results in the gears and other components being subjected to high forces and to shock, particularly, when the chain becomes fully let-out from the chain drum. 
   In recent times, the AAR has added a life cycle test to its specifications, and hand brake mechanisms which do not meet the life cycle test cannot be sold for use on railway cars operated in interchange service on United States railroads. The AAR life cycle test for quick release brakes requires that such latter brakes withstand 3000 quick release operations. 
   To meet such life cycle test requirements, even standard power hand brake mechanisms had to be modified when the life cycle test was adopted. When intermediate power hand brake mechanisms of the type sold prior to the adoption of the life cycle test were subjected to the life cycle test, it was found that the components thereof wore prematurely or were damaged, and it was found to be necessary to add a shock retarder, or absorber, external to the hand brake mechanism, to overcome such wear and damage. Of course, such an external shock retarder is undesirable not only because it is external to the hand brake mechanism but also because of the additional cost and because it requires field modification of the equipment on a railway car if the intermediate power hand brake mechanism is used to replace a standard power hand brake mechanism. 
   High power hand brake mechanisms sold prior to the adoption of the life cycle test were similarly unable to pass the life cycle test. It should be borne in mind that such high power brake mechanisms normally have additional gears to provide the desired force on the chain, and this results in a higher speed of rotation of at least some of the gears during release of the hand brake mechanism. 
   Although the use of an external shock retarder might have solved the problems with the higher power hand brake mechanism, a change in the AAR specifications would have been required to permit the use of such an external shock retarder. Attempts were made to redesign the high power hand brake mechanism, such as by making it stronger, so that it would meet the life cycle test without the use of an external shock retarder, but the attempts were not successful. 
   One of the characteristics of railway car brakes with which the invention is concerned is that the force applied to the chain, and hence, the parts of the hand brake, is non-linear and depends on the extent to which the brakes are applied or released. Thus, as the brakes are applied, relatively little force is required to take up the slack in the chain and the brake rigging, but to meet AAR requirements, the final force on the chain must be as set forth above, namely, 3350 lbs. for a standard power brake, 4475 lbs. for an intermediate power brake and 6800 lbs. for a high power brake. 
   After slack in the rigging is taken up, which may require, for example, 5–15 inches of chain travel, the force on the chain increases exponentially, e.g. from 200 lbs. to the final value, as the brake hand wheel is further turned to set the brakes. In reaching the final value after the slack is taken up, the chain may travel only two or three inches. 
   Similarly, when the hand brake is released, the chain force decreases exponentially and reaches a relatively small value shortly after the hand brake is released. The aforementioned co-pending application teaches a single stage, double acting cylinder which displaces the same volume of fluid pressure with each stroke regardless of the resulting force in the hand break mechanism. As a result, a partial amount of fluid pressure is being wasted at the beginning of the brake application cycle, where relatively little force is required to take up the slack in the chain. Since the source of said fluid pressure is typically an emergency reservoir having a predetermined volume, less fluid pressure will be available at the end of the brake application to meet chain force requirement. 
   As it can be seen from the above discussion, it would be advantageous to optimize the consumption of fluid pressure so that less fluid is consumed during the first stage of brake application leaving more fluid available during the critical end stages of brake application when higher pressure is necessary to meet the minimum chain force requirements. 
   SUMMARY OF THE INVENTION 
   The present invention comprises a two-stage application cylinder, having a primary drive rod and a secondary drive rod. A drive arm is attached to the primary drive rod at one end and engages a lever at the distal end. An operating pawl is attached to the lever and a spring means is provided for urging the operating pawl into contact with a ratchet. This ratchet is engageable with at least one gear of a hand brake gear assembly disposed in a housing member of the hand brake assembly. At the beginning of the braking cycle, application of a force within the application cylinder causes the primary drive rod and drive arm to move outwardly from the cylinder and apply a downward force to the lever, which causes the operating pawl to engage a tooth within the ratchet. A primary return spring is provided within the application cylinder to urge the drive arm back to its original position. Rotation of the ratchet causes the gear of the hand brake gear assembly to rotate in a direction, which will cause an application of the brake means. Repeated applications of pressure within the application cylinder enables the gear of the hand brake gear assembly to rotate a sufficient amount to result in an application of the brakes. A holding pawl is also provided which cooperates with the ratchet. At the end of the braking cycle, continuing application of the fluid pressure within the cylinder causes the secondary drive rod to move outwardly from the cylinder and apply a required force to complete a braking application. At least one control valve means is engageable with the trigger attached to lever to control the operation of the application cylinder. At least one control valve means is also provided to redirect the path of the fluid pressure to the other side of the cylinder and aid a return spring in completely returning the primary piston to its original position. 
   OBJECTS OF THE INVENTION 
   It is therefore an object of the present invention to provide an automatic application hand brake, which reduces the consumption of fluid pressure during the first stages of brake application when minimal force is realized within the winding apparatus hence conserving fluid pressure for the critical end of the application during which time higher pressure is required to achieve the minimum chain force required for braking. 
   It is a further object of the present invention to provide an automatic application hand brake, which can be converted for use with the presently used automatic activation hand brake winding mechanisms. 
   In addition to the various objects and advantages of the present invention which have been generally described above, there will be various other objects and advantages of the invention that will become more readily apparent to those persons skilled in the relevant art from the following more detailed description of the invention, particularly, when the detailed description is taken in conjunction with the attached drawing figures and with the appended claims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic illustration of the presently preferred control configuration for use with an automatic activation hand brake winding mechanism including the presently preferred application cylinder. 
       FIG. 2  is a schematic illustration of the present invention with the primary rod in the substantially retracted position. 
       FIG. 3  is a schematic illustration of the present invention with the primary rod in the substantially extended position. 
       FIG. 4  is a schematic illustration of the present invention with the primary rod and secondary rod in the substantially extended position. 
       FIG. 5  is a front elevation view of a hand brake assembly incorporating the present invention, with the application cylinder primary rod in a substantially retracted position. 
       FIG. 6  is a front elevation view of a hand brake assembly incorporating the present invention, with the application cylinder primary rod in a substantially extended position. 
       FIG. 7  is a front elevation view of a hand brake assembly incorporating the present invention, with the application cylinder primary rod and secondary rod in substantially extended positions. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The following background information is provided to assist the reader to understand the environment in which the invention will typically be used. The terms used herein are not intended to be limited to any particular narrow interpretation unless specifically stated otherwise in this document. 
   Prior to proceeding to the more detailed description of the various embodiments of the present invention, for the sake of clarity and understanding of such invention, it should be noted that identical components having identical functions have been identified with identical reference numerals throughout each of the figures illustrated herein. 
   In reference to  FIGS. 2 through 7 , the automatic application hand brake of the invention comprises an operating means, generally designated  300 , engageable with such hand brake. In the presently preferred embodiment operating means  300  includes a spring return, two-stage cylinder. The presently preferred pressure fluid is pneumatic. Alternatively, hydraulic fluid pressure can be utilized when required. Pneumatic cylinder  300  comprising an outer cylindrical casing member  324 , a primary piston member  308  having a first surface and an opposed second surface and being mounted for reciprocal movement within a cylindrical casing formed by the inner surface of the secondary rod  304 . 
   Upon the application of pneumatic pressure thereto, a convention seal member  326  adjacent a first end of the piston  308  and contacting the inner surface of the secondary rod  304  so as to provide an airtight chamber at one end of the cylindrical member such that application of pneumatic pressure therein and against the first end of the piston  308  enables forward movement of piston  308 . A primary return spring  312  is provided to return the piston  308  to its initial position. The opposed second end of the piston  308  is attached to a first portion of primary drive rod  302 . A second portion of the primary drive rod  302  is connected to a first portion of the drive arm  306 , having a second portion engageable with a lever  152 . 
   Furthermore, pneumatic cylinder  300  includes a secondary piston member  310  having a first surface and an opposed second surface and being mounted for reciprocal movement along the inner surface of cylindrical casing  324 . Upon the application of pneumatic pressure thereto, a conventional seal member  328  adjacent a first end of the piston  310  and contacting the inner surface of the cylindrical casing member  324  so as to provide an airtight chamber at one end of the cylindrical member such that application of pneumatic pressure therein and against the first end of the piston  310  enables forward movement of such piston  310 . 
   A secondary return spring  314  is provided to return piston  308  to its initial position. The opposed second end of piston  310  is connected to the second portion of the secondary drive rod  304 . A first pneumatic fluid pressure communications means  320  disposed within cylindrical casing  324  enables the application into and the evacuation of the pneumatic fluid pressure from the piston cavity. 
   The first fluid pressure communication means  320  may be any well known type capable of supplying pneumatic fluid pressure into the piston cavity. A second pneumatic fluid pressure communication means  316  disposed within cylindrical casing  324  enables application into and evacuation of the pneumatic fluid pressure from the rod side of the secondary piston  310  cavity. Furthermore, such fluid pressure communication means  316  enables application into and evacuation of fluid pressure from the rod side of the primary piston  308  cavity when the secondary rod is in the steady state position shown in  FIGS. 2 and 3 . 
   Additionally a third fluid pressure communication means  318  of predetermined geometry disposed within cylinder  300  enables the application and evacuation of fluid pressure between the rod side of the primary piston  308  cavity and the rod side of the secondary piston  310  cavity as well as to allow for a predetermined rate of flow of pneumatic fluid, acting in cooperation with fluid pressure communication means  316 , to maintain a predetermined range of fluid pressure acting against the rod side of the secondary piston  310  in cooperation with spring  314  to maintain the secondary piston in a steady state during forward travel of primary piston  308  as shown in  FIG. 2 . 
   Furthermore, fluid pressure communication means  318  enables application and evacuation of fluid from the rod side of the primary piston  308  cavity when the secondary rod  304  is in an extended position as shown in  FIG. 4 . At least one operating pawl (not shown) is attached to the lever  152  and a spring means  156  is provided for urging the operating pawl (not shown) into contact with a ratchet (not shown). This ratchet (not shown) is engageable with at least one gear  14  of a hand brake gear assembly  40  disposed in a housing member of the hand brake assembly  20 . Initial application of fluid pressure through first fluid communication means  320  produces a force against the primary drive rod piston  308  of the operating cylinder  300  which causes the drive arm  306  to move outwardly from the cylinder and apply a downward force to the lever  152  which causes the operating pawl (not shown) to engage a tooth within the ratchet (not shown). Upon retraction, primary rod return spring  312  is provided within the operating cylinder  300  to urge the drive arm  306  back to its original position with the aid of fluid pressure entering through secondary rod orifice  318 . Rotation of the ratchet (not shown) causes the gear  14  of the hand brake gear assembly  40  to rotate in a direction which will cause an application of the brake means. A holding pawl (not shown), is also provided which cooperates with a ratchet (not shown). At least one control valve is engageable with the trigger  172  attached to lever  152  to control the operation of the operating cylinder  300 . This control valve system includes a first reciprocating valve means  220  and a second reciprocating valve means  230 . At least one control valve means  240  is also provided to redirect the path of the fluid pressure through end fluid communication means  316  and through secondary rod orifice  318  of the cylinder  300  to aid a primary rod return spring  312  in completely returning the piston  308  to its fully returned position. 
   Refer now, more particularly to  FIG. 1 , where under steady state conditions, the primary cylinder piston  308  is completely returned by it&#39;s spring  312 . Consequently, there is no air pressure behind the piston  308 , and to start an application all that is required is to activate pushbutton  202  attached to application valve member  200  which begins the process of winding up the brake. It allows a source of fluid pressure  50  from an emergency reservoir (not shown) to flow through the valve  200  and into pilot  212  attached to activation valve  210 . The build-up of pressure in the pilot  212  to a predetermined value causes valve  210  to open and allow fluid pressure  50  to flow through the valve  210  to a first reciprocating valve  220  and a second reciprocating valve  230 . 
   In further reference to  FIG. 5 , trigger  172  engages pushbutton  232  attached to valve  230  and allows fluid pressure  50  to flow through valve  230  into pilot  224  attached to first reciprocating valve  220 . The predetermined pressure in the pilot  224  will cause the valve  220  to shift and allow fluid pressure  50  to flow through valve  220  in four directions. The primary directions of the fluid pressure will be to the backside of the piston  308 , causing the piston  308  to now drive the primary rod  302  down pushing the air back out of the cylinder to atmosphere through quick exhaust valve  290  and, more importantly, rotating lever  152  in a clock-wise direction, causing the hand brake  20  to wind up. Additionally, when the load is fully applied, the fluid pressure will flow to the pilot  214  attached to the activation valve  210  causing the valve  210  to shift into the vented position and cut-off fluid pressure supply  50  from the emergency reservoir. 
   Furthermore, the fluid pressure will flow through the quick exhaust valve  280  to the pilot  242  attached to the change-over valve  240 , causing valve  240  to shift and allow fluid pressure supply  50  to flow to the front side of the piston  308  further aiding its return to the original position. 
   Yet additionally, the fluid pressure will be exhausted to atmosphere through choke  282 . Once the piston  308  reaches the bottom of its stroke, the trigger  172  will activate pushbutton  222  attached to the first reciprocating valve  220 , closing valve  220 . Furthermore, the return spring  312  is going to drive the piston  308  to its original position pushing the air back out of the cylinder to atmosphere  284  through quick exhaust valve  290 . The trigger  172  engages pushbutton  232 , opening valve  230 , which is going to cause air to go back in the cylinder again through first reciprocating valve  220 . In the first stages of brake application when minimum force is required, winding of the brake mechanism is accomplished solely through the reciprocation of the primary rod  302  by repeated applications of pressure within the operating cylinder  300  through the control valve means and return spring  312  described above, which enables the gear of the hand brake gear assembly to rotate a sufficient amount to eliminate the slack within the brake application mechanism. 
   As the slack within the brake mechanism is diminished, the force required to urge rotation of the hand brake gear increases. Ultimately, the force transmitted through the primary rod  302  is not of sufficient magnitude to overcome the resulting force in the mechanism. Fluid pressure  50  entering through first fluid communication means  320  accumulates in the cylinder and produces an increasing force on the secondary rod piston  310 . As this force increases, the secondary rod  304  becomes active and begins to move outwardly. At a predetermined point in this extension, secondary rod orifice  318  is restricted thus preventing fluid pressure from entering the primary cylinder. Exhaust means disposed within such secondary rod are provided to exhaust fluid pressure outward upon movement of the secondary drive rod. In the presently preferred embodiment the means include a longitudinal cavity  322  disposed in the outer surface of the secondary rod  304 , such cavity  322  is oriented parallel to the secondary rod axis, producing an exhaust path to vent fluid residing in the drive rod cavity of the cylinder at a second predetermined point in its travel, hence allowing further extension of the secondary drive rod  304 . 
   Alternatively, the exhaust means can also be created using other well-known means, including a plurality of valves, which do not rely on similar cross sectional variations of the secondary rod. During its outward movement, the secondary rod  304  leading end encounters the drive arm  306  attached to the primary rod, and, in cooperation with the primary rod, urges additional rotation of the brake gear to achieve the desired braking force. Upon achieving such load, the pressure in the line between valve  220  and valve  290  will increase causing valve  210  to shift and vent to atmosphere, but more importantly, closing the supply of the fluid pressure  50 . At the same time, the predetermined pressure in the pilot  242  will cause valve  240  to shift allowing fluid pressure to flow to the bottom side of the cylinder  300  and cooperate, with return springs  312  and  314  to disengage the holding pawl (not shown) within brake apparatus  20 . 
   While the presently preferred embodiment and various additional alternative embodiments for carrying out the instant invention have been set forth in detail in accordance with the Patent Act, those persons skilled in the hand brake art to which this invention pertains will recognize various alternative ways of practicing the invention without departing from the spirit of the invention and scope of the appended claims.