Abstract:
A hand brake mechanism having a release hold mechanism to prevent unwanted application of the railcar brakes. The release hold mechanism includes a cam and a holding pawl having cooperating force members and a detent retaining device engaging the cam disposed within the railcar hand brake to maintain the hand brake in the released hold condition. The cooperating force members disengage the cam from the detent retaining device to allow brake application. The hand brake incorporates an indicator member having a reflective coating to indicate such release hold position of the railcar hand brake.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates, in general, to hand brake assemblies for use on railcars and, more particularly, this invention relates to a hand brake assembly with a quick release mechanism.  
         BACKGROUND OF THE INVENTION  
         [0002]    Prior to the conception and development of the present invention, railway car hand brake mechanisms were generally 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.  
           [0003]    These hand brake mechanisms further provide a clutch mechanism for facilitating a gradual release of the brake. When a hand wheel is rotated clockwise (as viewed from the front of the unit), such rotation is transmitted directly through a drive shaft, a pinion, a gear, and a winding drum to take up slack of a chain connected to the brake rigging. When resistance is offered by the chain to further rotation of the hand wheel, such resistance, acting back through the drum, the gear, and pinion, causes a nut to be advanced on a threaded portion of the drive shaft to move against a ratchet member which is clamped between respective friction surfaces on the nut and on the drive shaft, thus causing the drive shaft, ratchet, and the nut to rotate as a unit. A pawl prevents rotation of the ratchet in the opposite direction. The hand wheel torque is increased until a state of static equilibrium is reached, or at the point at which the brakes are fully applied, whereupon rotation of the hand wheel is terminated, and the clamped ratchet, by means of the holding pawl, prevents the chain from unwinding.  
           [0004]    The clutch mechanism also provides for quick release of the brakes by operating a release handle which effects disengagement of the normally engaged clutch and thereby allows free rotation of the pinion and gear to release the chain load while the nut and ratchet are held stationary by the holding pawl. 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.  
           [0005]    U.S. Pat. No. 4,714,142 titled Railway Car Hand Brake with Release Governor teaches such a hand brake having a quick release mechanism. The quick release mechanism includes a cam mounted on a manually pivotable shaft substantially attached to a quick release handle. During quick release, rotation of the quick release lever rotates the cam which engages a crank and forces it to move downwardly and disengage the pinion from the clutch collar. With the pinion disengaged from the clutch mechanism, the holding pawl and detent gear can no longer prevent its rotation, therefore it rotates freely about the drive shaft causing quick release of the brakes without rotation of the hand wheel. Opposite movement of the quick release handle releases the clutch collar and forces the clutch collar to reengage the pinion under the force of the spring acting on such collar and allow for a normal brake application.  
           [0006]    The teachings of the U.S. Pat. No. 4,714,142 are hereby incorporated in present application by reference thereto.  
           [0007]    In order for the quick release mechanism to function properly, the quick release lever, rotatable approximately 30 degrees to release the brake, must be held in the released position until the entire chain has been expelled. It has been found that when a hand brake is quick released using the lever, the lever is not left in its full released position long enough to fully expel the chain from the hand brake, thus maintaining residual tension due to lack of sufficient slack. As a result the bakes may be applied unintentionally during railcar motion, especially around the curve.  
           [0008]    As it can be seen from the above discussion, prior to the instant invention, there has been a need for a positive means for maintaining the quick release mechanism in the released hold position to avoid unintentional application of the railcar brake rigging.  
         SUMMARY OF THE INVENTION  
         [0009]    A hand wheel in a handbrake mechanism for a railway car is used to rotate a gear wheel to apply the brakes. Such hand brake having a housing with a back wall and a front wall, with a chain winding drum and a main gear wheel rotatably mounted on a drum shaft thereon. There is a hand wheel having a shaft rotatably mounted on the housing and having a bearing section at a first end and a hand wheel receiving section on a second end external to such housing. A ratchet wheel is mounted on the hand wheel shaft and rotatable with such hand wheel shaft intermediate the first and second ends thereof. A holding pawl in such housing cooperates with the ratchet wheel so as to prevent reverse rotation thereof. Additionally, a freely rotatable second pinion gear on the hand wheel shaft engages the main gear wheel, such pinion having a radially extending flange cooperating therewith. A crank is pivotally mounted within the hand brake housing and has a pair of fingers engaging the collar of the clutch mechanism. A quick release mechanism cooperates with the holding pawl to allow reverse rotation of the ratchet wheel for releasing the chain. The hand brake incorporates a release hold mechanism of the preferred embodiment having a release shaft attached to a quick release lever at one end. The release shaft has a cam attached to its other end. The cam has a force receiving portion which cooperates with the force transmitting portion of the holding pawl. To quick release the brakes, rotation of the release shaft causes rotation of the cam and enables fingers of the crank to axially move the collar and disengage a second pinion gear from the main gear. At least one detent is disposed within the hand brake housing which engages the detent portion of the cam to maintain the quick release mechanism in the release and hold position. To reapply brakes, rotation of the hand wheel in the brake applied direction trips the holding pawl causing the cam to disengage from the detent position and enabling the collar to reengage the second pinion gear from the force of the spring within the clutch.  
         OBJECTS OF THE INVENTION  
         [0010]    It is therefore one of the primary objects of the present invention to provide a hand brake having a means to maintain the hand brake in the release hold position.  
           [0011]    Another object of the present invention is to provide a hand brake assembly which prevents unintentional application of the railcar brake rigging.  
           [0012]    Still another object of the present invention is to provide a hand brake having a means to re-engage the clutch mechanism after a quick release of the brake.  
           [0013]    An additional object of the present invention is to provide a hand brake having a means to visually indicate such hand brake is in a release hold position.  
           [0014]    These and various other objects and advantages to the present invention will become more readily apparent to those persons skilled in the relevant art from the following more detailed description of the invention, particularly, when such description is taken in conjunction with the attached drawing Figures and with the appended claims. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    [0015]FIG. 1 is a cross-sectional view of the hand brake.  
         [0016]    [0016]FIG. 2 is a partial perspective view of the hand brake, particularly showing the release hold mechanism of the preferred embodiment.  
         [0017]    [0017]FIG. 3 is partial planar view of the hand brake, particularly showing the release hold mechanism of an alternative embodiment.  
         [0018]    [0018]FIG. 4 is a partial elevation view of a hand brake assembly of the present invention as illustrated in FIG. 3, particularly showing the second pinion gear and the clutch collar in the applied position.  
         [0019]    [0019]FIG. 5 is a partial elevation view of a hand brake assembly of the present invention as illustrated in FIG. 3, particularly showing the second pinion gear and the clutch collar in the release hold position.  
         [0020]    [0020]FIG. 6 is a partial, front elevation view, with a portion of the cover cut away, of the present invention illustrated in FIG. 1.  
         [0021]    [0021]FIG. 7 is an exploded view of the braking governor. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0022]    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.  
         [0023]    A hand brake mechanism, generally designated  10 , includes a chain drum  21  rotatable by a gear  22 . The drum  21  is rotatably mounted on a shaft  23  which is secured to the housing back plate  24  and the housing front plate  25 . One end of a chain  27  is secured to the drum  21  by a pin  28 , and the other end of the chain  27  is secured to the railcar brake rigging so that when the chain  27  is wound up on the drum  21 , the brakes of the railcar are applied to at least limit movement of the railcar.  
         [0024]    The teeth of a first pinion gear  29 , engage the teeth of the gear  22 . The first pinion gear  29  is integral with a gear  30  and a shaft  31 , so that when the gear  30  is rotated, the first pinion gear  29  and the shaft  31  rotate which causes the gear  22  and the drum  21  to rotate.  
         [0025]    The teeth of a second pinion gear  34  are positioned to engage the teeth of the gear  30  so that a rotation of the second pinion gear  34  causes rotation of the gear  30 . The second pinion gear  34  is freely rotatable on a shaft  35  when it is not held by a clutch collar  36  which is secured to the shaft  35  so as to rotate therewith. The shaft  35  is rotatable by a hand wheel  37 . As best shown in FIGS. 3, 4, and  5 , the clutch collar  36  preferably has at least one detent release portion  100  disposed within a planar surface portion  36   a.    
         [0026]    A detent or ratchet wheel  40  is mounted on the shaft  35  and cooperates with a clutch mechanism, generally designated  20 , and with a holding pawl  41  which is free to ratchet thereon upon rotation of such ratchet wheel  40  in a clockwise direction so that when the hand wheel  37  is rotated in the brake applying direction, the second pinion gear  34  and the hand wheel  37  cannot rotate in the reverse direction under the tension of the chain  27 . However, the brakes may be released, after application, in small increments by rotating the hand wheel  37  in the direction opposite to the brake applying direction. In the preferred embodiment, the holding pawl  41  has a force transmitting portion  82  disposed outwardly in the direction of the cam  43 .  
         [0027]    In a particular reference to FIG. 2, there is shown a release hold mechanism, generally designated  80 , of the presently preferred embodiment comprising a cam  43  mounted on a manually pivotable release shaft  44 , which cooperates with crank  42  having fingers  42   a  and  42   b  so that when the release shaft  44  is pivoted, the fingers  42   a  and  42   b  axially move the clutch collar  36  thereby releasing the second pinion gear  34  from the clutch collar  36  and enabling the second pinion gear  34  to rotate freely on the shaft  35 . The cam  43  having a force receiving portion  84  cooperating with the force transmitting portion  82  of holding pawl  41  and a detent portion  47  cooperating with the detent  92  and stop  47 .  
         [0028]    At least one detent retaining means, generally designated  90 , is disposed within hand brake  10 . The at least one detent retaining means  90  has a detent  92  preferably engaging a detent portion  45  of the cam  43  with the brake in the released and hold condition. In the presently preferred embodiment, the at least one detent retaining means  90  further comprises a detent housing  94  substantially attached to the housing front plate  25 . A detent  92  is movably disposed within the housing  94 , protruding beyond the housing  94  and is biased by the bias spring  96  toward the detent position. It is further preferred that adjustment means  98  disposed adjacent bias spring  96  are provided to very the protrusion of the detent  92  and, more particularly, set the predetermined force of the at least one detent retaining means  90  to allow for component wear and overall tolerances of the hand brake and to provide substantial engagement of the cam  43  while brakes are in a released and hold condition while allowing release of such cam  43  to apply the brakes.  
         [0029]    Alternatively the at least one detent means  90  can be of the variety of mechanical, pneumatic, hydraulic or electrical detent means mounted internally and/or externally of the hand brake housing  14 . For example, such at least one detent means  90  can comprise a cylinder having a detent portion disposed at the end of the cylinder rod and receiving a fluid pressure signal to extend such rod in order to positively retain the cam  43  and receiving yet another fluid pressure signal to retract such rod at the beginning of the brake application cycle. Yet alternatively, the cylinder can be an electrical solenoid having similar interfaces.  
         [0030]    Additionally, a leaf spring  90  of a predetermined strength can be attached at a predetermined position within the housing  14  engaging the detent portion  45  of the cam  43  to exert a predetermined force onto the cam  43 .  
         [0031]    With further reference to FIG. 2, should it become desirable to release the brakes quickly after they have been applied, the release shaft  44  is pivoted in a clock wise direction permitting the second pinion gear  34  to rotate, and thereby permitting rotation of the gears  22 ,  29  and  30  and the drum  21 , under the tension of the chain  27 . During such rotation the detent  92  moves to the opposite surface of the detent portion  45  thus preventing the cam  43  to return to its applied position against the stop  47 .  
         [0032]    Yet another alternative embodiment of the release hold mechanism  80  is illustrated in FIGS. 3, 4, and  5 . In a particular reference to FIG. 3, at least one detent means  90  are disposed adjacent the clutch collar  36  and the detent  92  engages the side surface  36   b  of the collar  36 , best shown in FIG. 4. If it is desired to release the brakes quickly after they have been applied, upon rotation of release shaft  44  by way of a release lever (not shown), the fingers  42   a  and  42   b  axially move the clutch collar  36  and thereby release the second pinion gear  34  from the clutch collar  36  and enable the second pinion gear  34  to rotate freely on the shaft  35 . Axial movement of the clutch collar  36  enables the detent  92 , normally engaging the collar side surface  36   b , to move linearly and engage clutch collar planar surface  36   a , best shown in FIG. 5, thus preventing return of the clutch collar  36  into the applied position. The release of clutch collar  36  may be accomplished by rotating the hand wheel  27  during brake application, enabling at least one detent releasing portion  100  disposed within the planar surface  36   a  to disengage the detent  92  from the planar surface  36   a  and further enable the clutch collar  36  to return to the applied position from the force of the spring  33  disposed within clutch mechanism  20 .  
         [0033]    It should be understood that detent  90  may engage at least a portion of the crank  42  in the release hold position and that such detent  90  may be disengaged by such modified at least one detent release portion  100  without departing from the intent of the present invention.  
         [0034]    It will be further understood that at least one detent release portion  100  could be disposed within the surface of the ratchet wheel  40  adjacent the crank  42  and apply force on the crank  42  during the rotation of the hand wheel  37  to disengage crank  42  from the hold position to apply brakes.  
         [0035]    The hand brake mechanism  10  may also include an indicator member  110 , having a coating  112  applied thereto, attached to the outer end of the manually pivotable release shaft  44  to provide visual indication of the hand brake in the release hold position. Preferably, the coating  112  is a reflective tape easily recognizable from a distance.  
         [0036]    The hand brake mechanism  10  may further include a brake governor, generally designated  60 , disposed intermediate gears  29  and  30 , best illustrated in FIGS. 6 and 7.  
         [0037]    The brake governor  60  is coupled to the gear  30  and provides a limited braking force which varies its retarding force dependent upon the speed of rotation of the gear  30 . Thus, such brake acts as a governor and increases the retarding force with an increase of the speed of rotation of the gear  30  from a negligible value when the speed of rotation is low to a larger value which has no significant effect on the speed of rotation when the hand brake is first released.  
         [0038]    The brake governor  60  comprises a hollow cylinder or braking drum  65  which is non-rotatably secured to the back plate  24 . The drum  65  has a shaft  66  integral therewith, the shaft  66  having a groove  67  for receiving a retaining ring  68 . The shaft  66  carries a cylindrical bearing  69  on which a gear  70  with a flange  71  having a plurality of wedge shaped slots  72 , which are open at their radially outermost ends, is rotatably mounted. A plurality of brake shoes  73 , one for each slot  72 , are slidably received in, and substantially fill, the slots  72  between the collar  71  and the braking drum  65 .  
         [0039]    The teeth of the gear  70  mesh with the teeth of the gear  30  so that, depending upon the gear ratios, the gear  70  rotates approximately thirty-two times faster in the embodiment illustrated, than the drum  21  upon release of the railcar brakes. Such rate of rotation of the gear  70  causes the shoe  73  to be thrown outwardly by centrifugal force against the inner wall of the drum  65 . By reason of the friction between the shoes  73  and the inner wall of the drum  65 , there is a braking force applied to the gear  30  which, after release of the hand brake and the braking force on the chain  27  is substantially reduced, reduces the speed of rotation of the gears  22 ,  29 ,  30  and  34  and the chain drum  21 , as compared to the speed of rotation thereof in the absence of the gear  70 , shoes  73  and drum  65 . Also, because of the gear ratios, a smaller braking force is required for retarding the rotation of the chain drum  21  than would be the case if the braking force were applied directly to the chain drum  21 , such as by the gear  22 .  
         [0040]    Thus, the present invention has been described in such full, clear, concise and exact terms as to enable any person skilled in the art to which it pertains to make and use the same. It will be understood that variations, modifications, equivalents and substitutions for components of the specifically described embodiments of the invention may be made by those skilled in the art without departing from the spirit and scope of the invention as set forth in the appended claims.