Abstract:
A hand brake mechanism having a mechanism to disengage a release lever disposed within a clutch and release assembly at the beginning of the brake application cycle. These mechanism includes a holding pawl having a force transmitting member which cooperates with a force receiving member disposed within the release lever to effect rotational motion onto the release lever at the beginning of the brake application cycle. At least one spring is provided to substantially complete rotational motion of the release lever.

Description:
CROSS-REFERENCES TO CO-PENDING APPLICATION 
       [0001]    This application is related to co-pending U.S. Ser. No. ______ entitled “Release Holding Mechanism for ASR Hand Brake, filed concurrently herewith and assigned to the assignee of the present invention. The teachings of this co-pending application are hereby incorporated herein by reference thereto. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates, in general, to hand brake assemblies for use on railway type vehicles and, more particularly, this invention relates to a hand brake assembly equipped with a quick release mechanism. 
       BACKGROUND OF THE INVENTION 
       [0003]    Railway car hand brake mechanisms are well known in the railway art. They usually include a relatively large, rotatable hand wheel disposed in a substantially vertical plane and mounted on a shaft which, through a gear train, can rotate a chain drum in order 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. 
         [0004]    These hand brake mechanisms further include a clutch mechanism for facilitating gradual release of the brake. When the 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. 
         [0005]    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. 
         [0006]    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. 
         [0007]    To avoid rapid rotation of the hand wheel, hand brake mechanisms have been devised which are known as “quick release” mechanisms. U.S. Pat. No. 4,368,648 titled Hand Brake for Railroad Car teaches such a hand brake having a quick release mechanism. 
         [0008]    Such quick release mechanism includes 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 teachings of U.S. Pat. No. 4,368,648 are hereby incorporated into present application by reference thereto. 
         [0009]    The co-pending U.S. patent application filed concurrently herewith and having Ser. No. ______ and entitled “Release Holding Mechanism for ASR Hand Brake” teaches a release lever being positively retained by the spring holding means. In order to apply brakes, the release lever must be repositioned so as to allow brake application. As it can be seen from the above discussion there is a need for means to reposition such release lever to a starting position for brake application. 
       SUMMARY OF THE INVENTION 
       [0010]    In a handbrake mechanism for a railway car, a hand wheel is used to rotate a gear wheel to apply the brakes. Such handbrake 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. The hand wheel having a shaft rotatably mounted on the housing 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 the hand wheel shaft intermediate the first and second ends thereof. A holding pawl in the housing cooperates with the ratchet wheel so as to prevent reverse rotation thereof. Additionally, a freely rotatable pinion on such hand wheel shaft engages the main gear wheel. The pinion has a radially extending flange cooperating therewith. A quick release mechanism cooperates with the holding pawl to allow reverse rotation of the ratchet wheel for releasing the chain. The holding pawl comprises a force transmitting means which cooperates with a force receiving means disposed within such release lever to effect rotational motion onto the release lever at the beginning of a brake application cycle. At least one spring means is provided to substantially complete rotational motion of the release lever. 
       OBJECTS OF THE INVENTION 
       [0011]    It is therefore one of the primary objects of the present invention to provide a hand brake having a means to return the release lever to a starting position in order to allow a brake application. 
         [0012]    It is an additional object of the present invention to provide a hand brake means to return a release lever to a starting position to allow a brake application, which is easily convertible for use with the presently disclosed hand brake. 
         [0013]    Although a number of objects and advantages of the present invention have been described in some detail above, various additional objects and advantages of the hand brake mechanism of the present invention will become more readily apparent to those persons who are skilled in the relevant art from the following more detailed description of the invention, particularly, when such detailed description of the invention is taken in conjunction with both the attached drawing figures and with the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a perspective view of a hand brake assembly of a presently preferred embodiment of the invention. 
           [0015]      FIG. 2  is a cross-sectional view of the hand brake assembly, taken along the lines  2 - 2  of  FIG. 1  showing a chain component. 
           [0016]      FIG. 3  is a cross-sectional view of the hand brake assembly, taken along the lines  3 - 3  of  FIG. 1  showing a clutch and release mechanism. 
           [0017]      FIG. 4  is a cut-away perspective view of a hand brake assembly of the present invention, particularly showing the holding pawl of the present invention when the hand brake is in a released and hold position. 
           [0018]      FIG. 5  is a cut-away perspective view of a hand brake assembly of the present invention, particularly showing the holding pawl of the present invention in the brake applied position. 
           [0019]      FIG. 6  is a perspective view of the presently preferred holding pawl according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0020]    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. 
         [0021]    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. 
         [0022]    A hand brake, generally designated  10 , for railroad cars embodying the invention, as shown in  FIGS. 1 and 2 , comprises a housing, generally designated  14 , having a front plate  16  and a back plate  18 . A driving mechanism, generally designated  20 , is disposed in the upper portion of housing  14 , such driving mechanism comprising a hand wheel  22  secured to a drive shaft  24 , the drive shaft  24  being journaled for rotation in bearings  26  and  28  secured in front plate  16  and back plate  18 , respectively. 
         [0023]    The drive shaft  24  has secured thereon, for rotation therewith, at the end adjacent bearing  28 , a pinion  30  which engages with a gear  32  for rotating a chain drum  34  journaled for rotation in bearings  36  and  38  secured on front plate  16  and back plate  18 , respectively, in the lower portion of housing  14 . Chain drum  34  is engageable with alternate links of a chain  37  for taking-up the chain. 
         [0024]    Also disposed in the upper portion of housing  14  and associated with the driving mechanism, is a clutch and quick release mechanism, generally designated  40 , which may best be seen in  FIG. 3 . The clutch and quick release mechanism  40  comprises an annular stationary cam member  42  which is restrained from both axial and rotational movement, and a movable cam member, generally designated  44 , rotatably disposed concentrically within the stationary cam  42 , the movable cam  44  being rotatable relative to the stationary cam member  42  by means of complementary fast pitch threads (not shown) formed thereon. 
         [0025]    An internally splined annular clutch collar  48  is provided with an annular flange  50  and concentrically surrounds the drive shaft  24 , the collar  48  engaging with an externally splined nut, generally designated  52 , attached to threaded portion  25  of such shaft  24 . Nut  52  has a flange  54  which has an annular friction surface  56  for making abutting contact with one side of a ratchet wheel  58 , the other side of the ratchet wheel  58  being abuttable with a friction surface  57  of a friction plate  59  concentrically secured to shaft  24  adjacent bearing  26 . 
         [0026]    A clutch and quick release mechanism  40  includes a release lever, generally designated  70 , best seen in  FIGS. 4 ,  5 , and  6 , having a shaft  72  journaled in a release shaft bushing  73  perpendicularly secured in housing front plate  16  above the driving mechanism  20 . A release handle, generally designated  120 , engages an external end of release shaft  72  while the other end of such release shaft  72  is provided with a main portion  74 , thereby preventing axial displacement of release lever  70 . A holding pawl, generally designated  90 , best shown in  FIG. 6 , having a mounting cavity  94  disposed within locating portion  92  is rotatably mounted on release shaft bushing  73 . The ratchet engaging portion  96  of holding pawl  90  engages ratchet wheel  58  and is free to ratchet thereon upon rotation of such ratchet wheel  58  in a counter-clockwise direction, as viewed in  FIG. 1 . A force transmitting tab portion  98  of holding pawl  90  cooperates with a force receiving tab portion  86  of release lever  70  and engages the force receiving tab portion  68  during a brake application cycle. At least one detent retaining means  100 , engages a detent portion  82  of the release lever  70  with the brake in the released and hold condition. 
         [0027]    At least one spring means, generally designated  130 , has a first attachment portion  132  and a second attachment portion  134 . The first attachment portion  132  engages with the release lever portion  78  attached to the pin portion  76  at one, end and the second attachment portion  134  engages a mounting hook  128  attached to the housing  14  at the distal end. In the preferred embodiment such at least one spring means  130  is a well known compression spring. 
         [0028]    In operation, in order to apply the brakes, hand wheel  22  is rotated counter-clockwise, as viewed in  FIG. 1 , such rotation being transmitted through drive shaft  24 , and pinion  30  to cause rotation of gear  32  in a counterclockwise rotation and thereby take-up slack of chain  37 . Until such time that tension starts to build up in chain  37 , shaft  24 , pinion  30 , nut  52 , and clutch collar  48  all rotate as a unit during rotation of hand wheel  22 . When tension begins to build up in the chain  37 , such tension is reflected in gear  32  and transmitted back through pinion  30  to clutch collar  48 . 
         [0029]    A resistance to rotation by clutch collar  48 , which is splined to nut  52 , causes nut  52  to advance on threads  25  and thereby clamp ratchet member  58  between friction surfaces  56  and  57 . With ratchet  58  so clamped, continued rotation of wheel  22  causes drive shaft  24 , the ratchet member  58 , and nuts  52  (along with friction plates  59 ) to rotate as a single unit until the desired tension is attained on chain  37 , while holding pawl  90  ratchets on such ratchet member  58 . The ratchet engaging portion  96  of the holding pawl  90  moves in an upward direction from the root of the ratchet tooth to its external surface. Force transmitting tab portion  98  of holding pawl  90  engages the force receiving tab portion  86  of release lever  70  effecting rotational movement of such release lever  70  in a clockwise direction as viewed in  FIGS. 4 and 5 . Such rotational movement causes disengagement of the detent portion  82  of the release lever  70  from the detent retaining portion  104  of the leaf spring  100 . Furthermore, an extension spring  130  applies an additional force onto release lever  70  effecting completion of the release lever  70  rotational movement and disengagement from the leaf spring  100 . 
         [0030]    Subsequent engagement of pin portion  76  with first fork portion  47  of movable cam  44 , causes counter-clockwise rotation of the movable cam  44 . As was hereinbefore noted, stationary cam  42  and movable cam  44  are provided with complementary fast-pitch threads  43 , so that as movable cam  44  rotates counter-clockwise, it moves axially outwardly of such stationary cam  42 , in a downward direction as viewed in  FIG. 3 , and carries with it clutch collar  48  by engagement of flange  50  thereof. A groove (not shown) in movable cam  44  serves to constrain the collar flange  50  from relative axial and lateral movement with respect to movable cam  44  but allows free clutch collar  48  rotation. Stationary cam  42  is restrained against both rotational and axial movement by engagement of lugs  62  formed on the periphery thereof and engaged in respective T-shaped elements  63  fixed to the inside surface of housing  14  (see  FIG. 3 ). Thus, downward axial movement of movable cam  44  causes axial engagement of external splines  64  formed on clutch collar  48  from internal splines  65  formed on pinion  30 , thereby constraining the rotation of the pinion  30  and gear  32  for applying the load on chain  37 , while drive shaft  24 , nut  52 , collar  48 , and ratchet  58  are allowed to rotate freely. The continued rotation of the hand brake wheel  22  can now apply and hold the required load. When desired tension has been achieved on chain  37 , rotation or application of torque on wheel  22  is terminated, and the holding pawl  90  engaged on clamped ratchet member  58  prevents the chain from unwinding, since the pawl permits only counter-clockwise rotation of such ratchet member  58 . 
         [0031]    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.