Abstract:
A brake mechanism for activating the brake rigging of a railway car, the brake mechanism comprising a shaft having axial splines formed on one end thereof, a handle rotatably coupled to the shaft so that the handle is rotationally fixed to the shaft in a first direction and rotates relative to the shaft in an opposite second direction. A first gear is connected to the railway car brake rigging, a second gear is in operative engagement with the shaft splines, and a clutch is operatively disposed between the first gear and the second gear, the clutch having a coupler for rotationally coupling the first gear and the second gear and at least one spring operatively disposed intermediate the first gear and the second gear for biasing the coupler into engagement with the second gear. The coupler is moveable between a first position in which the first gear is rotationally coupled to the second gear, and a second position in which the first gear rotates with respect to the second gear.

Description:
CLAIM OF PRIORITY 
     This application claims priority to U.S. Provisional Patent Application No. 60/718,292, filed Sep. 19, 2005, the entire disclosure of which is incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to hand operable brake mechanisms and particularly, to a handbrake load limiter for railway cars. 
     Railway car handbrake mechanisms are well known and may include a rotatable wheel or lever that provides upward tension on a chain that is secured at its distal end to a brake rigging of the railway car. Sufficient force must be applied on the brake shoes of the railway car to releasably secure the wheels in a locked position to prevent the railway car from moving. An under applied brake can result in unwanted movement of the car, for example a runaway car. On the opposite end of the spectrum, an over applied brake may result in damage or failure to the brake rigging. 
     Previously, it has been industry standard to apply 125 pounds of force to the end of the brake lever or 125 pounds of torque force on a wheel to properly apply the handbrake. Currently, certain segments of the railway industry have lowered the 125 pound requirement to 74 pounds. This lowered threshold can result in many more instances when the handbrake is over applied. When the brake is to be fully applied with 125 pounds, there exists the possibility of the handbrake being under applied. Thus, a mechanism is needed that alerts the operator when the brake is properly applied to within a predetermined range and prevents the application of excessive input force. 
     SUMMARY OF THE INVENTION 
     The present invention recognizes and addresses the foregoing disadvantages, and others, of prior art constructions and methods. 
     The present invention provides a brake mechanism for activating the brake rigging of a railway car. The brake mechanism comprises a housing, a handle mechanism coupled to the housing, a quick release mechanism mounted in the housing and in operative engagement with the first shaft, and a chain drum mechanism. 
     The handle mechanism has a first handle, a first shaft rotatably received in the first handle and the housing, a first ratchet wheel rotationally fixed to the first shaft, and a first pawl mounted proximate to, and in operative engagement with the first ratchet wheel. The first pawl is biased into engagement with the first ratchet wheel and rotationally fixes the first ratchet wheel in a first direction while ratcheting over the first ratchet wheel in an opposite second direction. 
     The quick release mechanism has a second handle rotatably coupled to the housing, a second ratchet wheel rotationally fixed to the first shaft, and a second pawl rotatably coupled to the housing and in operative engagement with the first and the second handles. The chain drum mechanism has a second shaft, a first gear connected to the railway car brake rigging, a second gear rotatably mounted on the second shaft and in operative engagement with the first shaft, and a clutch mounted on the second shaft intermediate the first gear and the second gear. The clutch is moveable between a first position in which the first gear is rotationally coupled to the second gear, and a second position in which the first gear rotates with respect to the second gear. 
     The first shaft may define axial splines thereon that rotationally couple the second gear to the first spline so that rotation of the first shaft in the first direction causes the second gear to rotate in the opposite second direction. The second gear may define a plurality of ramped teeth on an end thereon, and the clutch may define a plurality of ramped teeth on an end thereon, wherein the second gear and the clutch are positioned so that the second gear teeth and the clutch teeth are in engagement with each other. When the second gear rotates in the second opposite direction, the second gear can rotate with respect to the clutch when a predetermined input torque is reached and the second gear is rotationally fixed with the clutch in the first direction. 
     The clutch may have a splined hub rotatably received on the second shaft, the splined hub being rotationally fixed to the first gear. A clutch may also contain a coupler received on, and rotationally fixed to, the splined hub, where the coupler is positioned between the second gear and the splined hub. At least one spring is positioned intermediate the splined hub and the coupler for biasing the coupler into engagement with the second gear. The clutch may also have an adjustment plate for adjusting the level of the predetermined torque required for the second gear to rotate with respect to the clutch. 
     The second handle may be rotated to cause the second pawl to disengage from the second ratchet wheel allowing the first shaft to rotate in the second opposite direction. The second pawl is releasably maintained in the disengaged position so that the torque applied to the railway car brake rigging is fully released. The second pawl may be biased back into engagement with the second ratchet wheel by rotating the first handle to prevent the first shaft from rotating in the second opposite direction. 
     A chain may be in operative engagement with the first gear and the railway car brake rigging such that rotation of the first shaft in the first direction causes the chain to engage the railway car brake rigging. 
     The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate one or more embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended drawings, in which: 
         FIG. 1  is a side view of the hand brake mechanism of the present invention; 
         FIG. 2  is an exploded perspective view of the hand brake of  FIG. 1 ; 
         FIG. 3  is front view of the hand brake mechanism of  FIG. 1 , with the front housing cover removed; 
         FIG. 4  is a cutaway view of the handbrake mechanism of  FIG. 1  along lines A-A; and 
         FIGS. 5A-5C  are partial front views of the coupler mechanism used in the handbrake mechanism of  FIG. 1 . 
     
    
    
     Repeat use of reference characters in the present specification and drawings is intended to represent same or analogous features or elements of the invention. 
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Reference will now be made in detail to presently preferred embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that modifications and variations can be made in the present invention without departing from the scope and spirit thereof. For instance, features illustrated or described as part of one embodiment may be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents. 
     Referring to  FIG. 1  a handbrake mechanism  10  generally comprises a housing  12 , a handle  14  rotatably coupled to a gear mechanism (not shown), a quick release handle  16  operatively connected to the gear mechanism, a chain  18  coupled to the gear mechanism, a weight  20  coupled to one end of chain  18 , and a pair of mounting flanges  22  and  24  to facilitate mounting of the handbrake to a railway car. 
     With reference to  FIG. 2 , housing  12  is shown having a casing  26  and a cover  28 , which is secured to the casing by fasteners  30  and  32 . In one preferred embodiment, fasteners  30  and  32  are screws. Also referring to  FIG. 3 , casing  26  has a first side wall  34 , a second side wall  36 , a top wall  38  and a bottom wall  40  that all connect to a back wall  42 . A dividing wall  44  is mounted vertically in casing  26  and is generally parallel to first side wall  34 . A first compartment  46  is defined between first side wall  34  and dividing wall  44  and a second compartment  48  is defined between dividing wall  44  and second wall  36 . The purpose of the two compartments will be discussed herein. 
     Referring again to  FIG. 2 , the handbrake mechanism of the present invention can generally be separated into three distinct parts: a handle ratchet mechanism  50 , a quick release mechanism  52  and a chain drum mechanism  54 . 
     Handle mechanism  50  comprises handle  14 , a ratchet wheel  56 , a pawl  58 , a spring  60  and a pinion shaft  62 . Handle  14  is formed in two halves which allows for the handle ratchet mechanism to be located in a compartment  15  formed in handle  14 . Ratchet wheel  56  is placed in compartment  15  and is received on a first end  64  of pinion shaft  62  against a ledge  66  formed on the shaft. Shaft end  64  extends into handle compartment  15  and has a polygonal shaped cross-section that matches to a polygonal shaped bore  68  formed through ratchet wheel  56 . The polygonal shaped bore and shaft end rotationally lock the ratchet wheel to the shaft. Ratchet wheel  56  defines a plurality of teeth  70  on an outer circumference thereon that interengage with pawl  58 . Pawl  58  is rotatably mounted in compartment  15  about a pawl shaft  72  that is received through a bore  74  formed through pawl  58 . Spring  60  is mounted in compartment  15  proximate pawl  58  such that the spring rotationally biases pawl  58  into engagement with ratchet wheel teeth  70 . Handle  14  is axially secured to shaft end  64  by a fastener  76  and washer  78  into bearing  79 . Fastener  76  is threadedly received in a blind bore formed in shaft end  64 . 
     Quick release mechanism  52  comprises a quick release handle  16 , a ratchet wheel  80 , a pawl  82  and two mounting shafts  84  and  86 . Quick release handle  16  is rotatably mounted in first compartment  46  about a shaft  86 . Shaft  86  is formed with threads on a first end  86   a  and a slot on a second end  86   b . Thus, shaft  86  is threadedly received in a threaded bore (not shown) formed in dividing wall  44  and can be positioned using a flat head screwdriver engaged in slotted shaft second end  86   b . Ratchet wheel  80  defines a plurality of teeth  88  on an outer circumference thereon and a splined bore  90  therethrough that is countersunk on a side facing handle  14 . Ratchet wheel  80  is received on a splined portion  92  of pinion shaft  62  such that the countersunk portion of the bore is adjacent a smooth surface  94  of pinion shaft  62 . Splined bore  90  and pinion shaft splines  92  rotationally fix ratchet wheel  80  to pinion shaft  62 . A bearing  96  is received in an opening  98  formed in first side wall  34  and rotationally supports pinion shaft  62  at shaft smooth surface  94 . The bearing facilitates rotation of the shaft during operation. 
     Pawl  82  is rotationally received in compartment  46  about shaft  84 . Shaft  84 , like shaft  86 , has a threaded first end  84   a  and a slotted second end  84   b . Shaft  84  is threadedly received in a threaded bore (not shown) formed in dividing wall  44  and can be positioned using a flat head screwdriver engaged in slotted shaft second end  84   b . Pawl  82  has two fingers  100  and  102 , the former coupled with a spring and the latter received between two radial extensions  104  and  106  extending from quick release handle  16 . Pawl finger  100  is coupled to a pivoting yoke pin  108  that receives a spring  110 . The end of yoke pin  108  is received through a hole  109  ( FIG. 3 ) so that as pawl  82  pivots about shaft  84 , yoke pin  108  rotates about finger  100  while the compression of spring  110  is maintained against the surface defining hole  109 . Second pawl finger  102  includes a threaded bore  112  that receives a threaded shaft  114 . One end of shaft  114  extends through an oblong opening  120  formed through first side wall  32  and engages with a sustained release extension  122  on handle  14 , as described herein. 
     Quick release handle radial extension  104  includes a opening  126  that receives one end of a spring  128 , and the opposite end of spring  128  is coupled to top wall  38  ( FIG. 3 ). Spring  128  biases the quick release handle into a vertical resting position, as shown in  FIGS. 1 and 3 . In particular, when quick release handle  16  is rotated upward and released, spring  128  biases the handle back down into its resting position. 
     Still referring to  FIG. 2 , chain drum mechanism  54  includes an adjusting plate  130 , a load plate  132 , a first thrust washer  134 , a thrust bearing  136 , a second thrust washer  138 , a gear wheel  140 , a first coupler  142 , spring plates  146 , a splined hub  148  and a chain drum  150 . 
     Adjusting plate  130  is generally circular in shape and contains a bore therethrough. Three load screws  152  are received in respective threaded bores  154 , which extend from the opposite side of adjusting plate  130  into contact with load plate  132 . Load plate  132  contains a bore therethrough that defines a plurality of radially inward pointing splines  156 . Thrust bearing  136  contains a plurality of radially oriented rollers  158 , and is sandwiched between thrust washers  134  and  138 . A bearing  160  is received in a bore  162  formed through gear wheel  140 . Gear ring  140  defines a plurality of teeth  164  on an outer circumference thereon that interengage with a plurality of gear teeth  168  on pinion shaft  62 . Spring plates  146  are Belleville type spring plates, model no. 096042 manufactured by Dodge. Hub  148  is generally cylindrical in shape and contains a plurality of axially extending splines  176  formed on an outer circumference thereof. Additionally, hub  148  contains a discontinuous radially extending flange  177  formed at a first end  179  thereof. Chain drum  150  contains a plurality of radially extending teeth  182  that engage the loops of chain  18 . 
     In one preferred embodiment, first coupler  142  contains a plurality of axially extending teeth  170  that couple with a plurality of axially extending teeth  172  ( FIG. 3 ) on a second coupler  174  ( FIG. 4 ) that is rotationally and axially fixed to gear wheel  140  by weldments or other suitable means for fastening the two parts together such as rivets or staking. First coupler  142  further defines a plurality of radially inward extending splines  178  formed on an inner circumference of a bore  180  formed therethrough. First coupler  142  is formed from AISI 1144 steel and second coupler  174  is formed from AISI 1141 steel. The material for each coupler is oil quenched to 48 to 52 Rockwell C hardness and tempered at 600 degrees Fahrenheit to 40 to 44 Rockwell C hardness. The ramp angles of each tooth on the couplers are formed at a 10 degree angle. It should be understood that second coupler  174  may be formed integrally with gear wheel  140 . 
     The connection of the parts of the gear mechanism  54  will now be described with reference to  FIGS. 3 and 4 . Each of the parts of gear mechanism  54  is mounted directly or indirectly on an output shaft  184  ( FIG. 4 ). Output shaft  184  is threaded on one end  184   a  thereof and is threadedly received in a threaded bore  186  formed in dividing wall  44 . A second end  184   b  of output shaft  184  is received in an opening  194  ( FIG. 2 ) formed in second side wall  36 . 
     Chain drum  150  is rotatably received on output shaft  184  over a bearing  204 . Hub  148  is received over output shaft  184  and is rotationally fixed to the chain drum by a polygonally shaped blind bore  190  formed in hub  148  that receives a polygonally shaped portion  192  of chain drum  150 . Spring plates  146  are placed on hub  148  so that the inner diameter of the spring plates abut hub flange  177 . Next, first coupler  142  is inserted on hub  148  so that first coupler splines  178  engage with hub splines  176  rotationally fixing first coupler  142  to hub  148 . Gear wheel  140  is rotatably received on hub  148  and rotates about the hub on bearing  160 . First coupler  142  and gear wheel  140  are positioned such that first coupler teeth  170  engage with second coupler teeth  172 . Thrust washers  134  and  138  and roller bearing  136  are placed on hub  148  adjacent to gear wheel  140 . Load plate  132  is received on hub  148  adjacent to thrust washer  134  and is rotationally fixed to the hub via load plate splines  156  and hub splines  176 . Lastly, adjusting plate  130  is threadedly received on hub  148  by a threaded inner bore  189  formed through adjusting plate  130  and a thread  191  formed on an end of hub splines  176 . Thus, once adjusting plate  130  is threaded onto hub  148 , it is rotationally fixed to the hub via a set screw  188  ( FIG. 2 ). This set screw may also be a radial pin press-fitted into a bore. An inner bore  189  of adjusting plate engages with threads  191  formed on the end of hub splines  176 . 
     Referring to  FIG. 4 , a chain guide  196  is secured to second side wall  36  proximate chain drum teeth  182 . Chain guide  196  facilitates the proper orientation of chain  18  as it rides on chain drum teeth  182 . A chain stripper  198  mounted proximate to the bottom of chain drum  150  strips chain  18  off of chain drum teeth  182  to ensure that the chain does not stick to the teeth as they rotate around output shaft  184 . Two bearings  202  and  204  are received on output shaft  184 , the first inside hub  148  and the second inside chain drum  150 . 
     The operation of handbrake  10  is described herein with reference to FIGS.  4  and  5 A- 5 C. To begin operation of the handbrake, the operator lifts upward on handle  14 , which in turn imparts counterclockwise rotation on ratchet wheel  56  (with respect to  FIG. 4  looking to the right). As ratchet wheel  56  rotates counterclockwise, pinion shaft  62  also rotates counterclockwise due to the coupling of polygonal pinion shaft portion  64  and polygonal ratchet wheel bore  68 . Ratchet wheel  80  also rotates counterclockwise with pinion shaft  62  due to the interaction of pinion shaft splines  92  and ratchet wheel splines  90  ( FIG. 2 ). As ratchet wheels  56  and  80  rotate, their respective pawls  58  and  82  ratchet over their respective teeth and into engagement with successive teeth, which prevents rotation of the ratchet wheels in the clockwise direction. 
     As pinion shaft  62  rotates counterclockwise, pinion teeth  168  interengage with gear wheel teeth  164  causing gear wheel  140  to rotate clockwise. Gear wheel  140  can rotate with respect to adjusting plate  130  and load plate  132  because of roller bearing  136  and plain bearing  160 . Gear wheel  140  can also rotate with respect to first coupler  142  when the first coupler teeth are not engaged with second coupler teeth  172 . As a result of the interconnection of all of the parts, first coupler  142  and second coupler  174  rotationally fix gear wheel  140  to chain drum  150  through hub  148 . Thus, as the gear wheel rotates clockwise the hub and chain drum also rotate clockwise causing the chain to be pulled upward through housing  12 . Upward tension on chain  18  causes the railway car brakes to engage to hold the car stationary. 
     The connection of first coupler  142  to second coupler  174  is facilitated by the interaction of first coupler teeth  170  and second coupler teeth  172  ( FIG. 3 ). In particular, adjusting plate  130  is axially fixed to hub  148  and exerts axial pressure (to the right with respect to  FIG. 4 ) against load plate  132  by load screws  152 . Therefore, the axial load against gear wheel  140  and second coupler  174  can be adjusted by turning load screws  152 . At the opposite side of hub  148 , spring plates  146  exert an axial load (to the left with respect to  FIG. 4 ) against first coupler  142 , thereby pressing first coupler teeth  170  against second coupler teeth  172 . As previously discussed, each of coupler teeth  170  and  172  are angled at 10 degrees such that the face of one tooth matches up to the face of an opposite tooth ( FIG. 5A ). 
     The angle of each tooth is chosen so that a predetermined input force can be exerted on handle  14  and chain  18  before the coupler teeth slip over each other. Thus, if the rotational torque exerted by the movement of lever  14  is less than the input set point sufficient to cause the coupler teeth to slip over each other, then once handle  14  reaches the top of its full swing, the operator lowers the handle to return it to vertical. 
     As handle  14  is lowered, pinion shaft  62  is held rotationally still since pawl  82  restricts the rotation of gear wheel  80  in the clockwise direction. Because pawl  58  will ratchet over ratchet wheel teeth  70 , the handle will rotate clockwise with respect to ratchet wheel  70 . Once handle  14  is substantially vertical, the operator once again lifts up on handle  14  and additional input force is exerted on pinion shaft  62 . As such, pinion shaft gear teeth  168  rotate in the counterclockwise direction (looking to the right with respect to  FIG. 4 ) causing gear wheel  140  to rotate clockwise. As long as the input force exerted between the couplers remain less than the predetermined input set point, movement of handle  14  upward will cause chain drum  150  to exert tension on chain  18 . 
     Referring to  FIG. 5B , first coupler teeth  170  are shown beginning to slip over second coupler teeth  172 . This occurs because the input force exerted by the operator on handle  14  is nearing the axial force exerted by spring plates  146 . As the force exerted on handle  14  nears the predetermined input set point, first coupler  142  begins to move axially to the right (with respect to  FIGS. 4 and 5B ) and the first coupler teeth  170  begin to slip over second coupler teeth  172 . Once the input force on handle  14  reaches the predetermined input set point, first coupler  142  moves axially further to the right and first coupler teeth  170  slip completely past second coupler teeth  172 . Based on a 10 degree tooth angle, the axial displacement of first coupler  142  with respect to second coupler  174  is 0.041 inches. Once the coupler teeth slip past each other, a loud clicking noise is generated to alert the user that the maximum input force has been achieved. Therefore, the couplers act as a torque indicator to alert the user when the proper input force has been exerted on the railway car brake rigging. After the maximum input force has been reached, additional rotation of handle  14  will not impart additional tension on chain  18  by chain drum  150 . Thus, the couplers prevent the operator from over applying the brake rigging or under applying the rigging since the user should continue to rotate lever  14  until the clicking noise is heard. 
     To release the tension exerted on chain  18 , the operator lifts quick release handle  16 . Referring to  FIGS. 2 and 3 , as handle  16  rotates about shaft  86 , handle radial extension  104  exerts downward pressure on pawl finger  102 . As a result, pawl  82  is forced to rotate about pawl shaft  84  causing a third pawl finger  200  ( FIG. 2 ) to disengage from ratchet wheel  80 . Once third pawl finger  200  disengages from ratchet wheel  80 , pinion shaft  62  is free to rotate in the clockwise direction (looking to the right with respect to  FIGS. 2 and 3 ). Accordingly, gear wheel  140  rotates counterclockwise with hub  148  allowing chain drum  150  to release the tension on chain  18 . Pawl  82  is maintained in the quick release position even after quick release handle  16  is released since yoke pin  108  rotates over center and spring  110  exerts a bias to maintain the pawl in the released position. In order to reapply tension on chain  18 , handle  14  is once again lifted. As the handle rotates counterclockwise, sustained release handle extension  122  exerts an upward force on the end of threaded shaft  114  causing the pawl to rotate counterclockwise on shaft  84  moving third pawl finger  200  back into engagement with the teeth on ratchet wheel  80 . 
     While one or more preferred embodiments of the invention have been described above, it should be understood that any and all equivalent realizations of the present invention are included within the scope and spirit thereof. The embodiments depicted are presented by way of example and are not intended as limitations upon the present invention. Thus, those of ordinary skill in this art should understand that the present invention is not limited to these embodiments since modifications can be made. Therefore, it is contemplated that any and all such embodiments are included in the present invention as may fall within the scope and spirit thereof.