Abstract:
A parking brake for a body mounted brake cylinder having either a single locking mechanism cooperates with a threaded shaft that is centrally mounted within the brake cylinder or with multiple locking mechanisms that are positioned symmetrically about the centerline of the brake cylinder push rod so that the push or piston rod can still accommodate arcuate motion of the level of the braking system. The locking mechanism may be controlled by a mechanical linkage or through a pneumatic circuit. Activation of the locking mechanisms prevents axial movement of the brake piston. As a result, engagement of the locking mechanism may be used to prevent a release of the brakes after then have been applied to provide an automatic parking brake.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority to U.S. Provisional Application No. 62/044,696, filed on Sep. 2, 2014. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to rail car braking systems and, more particularly, to an automatic parking brake that may be used with body mounted brake cylinders. 
     2. Description of the Related Art 
     Most rail vehicles have a manually-operated parking brake that applies the wheel brakes. Unfortunately, this requires that an operator manually apply the brake on each rail car in a train. As a result, an automatic parking brake, such as that disclosed in U.S. Pat. No. 7,163,090, has been developed that will retain the braking system of any rail car equipped with the brake in the brakes applied position if brake pipe pressure is removed from a locking mechanism position about the shaft of the brake cylinder. Body mount brake cylinders are typically constructed with a hollow rod affixed to the piston and apply the brake force to the brake rigging by means of a push rod inside the hollow rod. This arrangement accommodates angular misalignment of the push rod as the connected brake lever operates through an arc, and decouples the manual hand brake from the body mount cylinder when the cylinder is released and the hand brake applies. In this condition, the hand brake acts on the same brake rigging as the body mount brake cylinder. In the hand brake applied position, the rigging pulls the body mount brake push rod independent of the brake piston, allowing the brake piston to remain in the released position, and decouples the influence of the body mount brake cylinder return spring from the hand brake application. Accordingly, there is a need for an automatic parking brake that can be used with body mounted braking systems while still using a hollow rod, or the same functionality as a hollow rod, so that the piston rod can still accommodates angular misalignment as the connected brake lever operates through an arc. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention comprises an automatic parking brake configured for use with a body-mounted brake cylinder so that the push rod connected to the braking system can still pivot relative to the piston as the lever of the braking system moves through an arc as the brakes are applied and released. 
     In one example, the body mounted brake cylinder has a piston positioned in the brake cylinder that is moveable in response to the application of pressure to a port between a first position and a second position. A piston/push rod is positioned in abutting relation to the piston for longitudinal movement therewith and for pivoting of the piston rod as the piston moves between the first and second positions. A threaded shaft is coupled to the piston and encloses the piston rod. An automatic parking brake locking mechanism coupled to the threaded shaft for preventing movement of the threaded shaft in response to an application of brake pipe pressure to the automatic parking brake locking mechanism. The automatic parking brake locking mechanism comprises a rotatable locking nut positioned around the threaded shaft and a locking sleeve that is moveable between a locked position, where the locking sleeve engages the locking nut and prevents from the nut from rotating, and a released position, where the locking sleeve is disengages from the locking nut and the locking nut is free to rotate. The automatic parking brake locking mechanism further comprises a spring providing a force biasing the locking nut into the locked position and wherein the application of brake pipe pressure will bias the locking sleeve into the released position if the application of brake pipe pressure exceeds the force of the spring. 
     In another example, the body mounted brake cylinder comprises a piston positioned in the brake cylinder and moveable in response to the application of pressure to a port between a first position and a second position. A threaded shaft is coupled at a first end to the piston and a piston rod is connected to a second end of the threaded shaft for pivotal movement relative thereto as the piston moves between the first and second positions. An automatic parking brake locking mechanism is coupled to the threaded shaft for preventing movement of the threaded shaft in response to an application of brake pipe pressure to the automatic parking brake locking mechanism. The automatic parking brake locking mechanism has a rotatable locking nut positioned around the threaded shaft and a locking sleeve that is moveable between a locked position, where the locking sleeve engages the locking nut and prevents from the nut from rotating, and a released position, where the locking sleeve is disengages from the locking nut and the locking nut is free to rotate. The automatic parking brake locking mechanism also has a spring providing a force biasing the locking nut into the locked position and the application of brake pipe pressure will bias the locking sleeve into the released position if the application of brake pipe pressure exceeds the force of the spring. 
     In a further example, the body mounted brake cylinder has a piston positioned in the brake cylinder and moveable in response to the application of pressure to a port between a first position and a second position. A piston rod is positioned in abutting relation to the piston for longitudinal movement therewith and for pivoting of the piston rod as the piston moves between the first and second positions. A central shaft is coupled to the piston and encloses the piston rod. A plurality of threaded shafts are positioned equidistantly about the central shaft and coupled to the piston for movement therewith. A corresponding plurality of automatic parking brake locking mechanisms are coupled to the plurality of threaded shafts for preventing movement of the plurality of threaded shafts. The automatic parking brake locking mechanism has a rotatable locking nut positioned around the threaded shaft and a locking sleeve that is moveable between a locked position, where the locking sleeve engages the locking nut and prevents from the nut from rotating, and a released position, where the locking sleeve is disengages from the locking nut and the locking nut is free to rotate. The automatic parking brake locking mechanism also has a spring providing a force biasing the locking nut into the locked position and wherein the application of brake pipe pressure causes a biasing of the locking sleeve into the released position. A brake pipe pressure activating assembly is used for biasing the locking sleeve into the released position, and the brake pipe pressure activing assembly includes a second piston moveable between a first position and a second position in response to the application brake pipe pressure to a face of the piston. In one embodiment, the brake pipe pressure activing assembly comprises a plurality of cams, each of which is associated with each of the plurality of the automatic parking brake locking mechanisms and the second piston is interconnected to the plurality of cams so that movement of the second piston between the first position and the second position causes movement of each of the plurality of cams into each of the locking sleeves of the plurality of automatic parking brake locking mechanisms such that each of the corresponding locking sleeves are moved into the unlocked positions. In another embodiment, the brake pipe pressure activing assembly comprises a plurality of conduits extending from the second piston to each of the plurality of the automatic parking brake locking mechanisms. As a result, movement of the second piston between the first position and the second position causes pressure to be applied through the plurality of conduits to the locking sleeves of the plurality of automatic parking brake locking mechanisms such that each of the corresponding locking sleeves are moved into the unlocked positions. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
       The present invention will be more fully understood and appreciated by reading the following Detailed Description in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a perspective view of an automatic parking brake for a body mounted brake cylinder; 
         FIG. 2  is a cross-section of an automatic parking brake for a body mounted brake cylinder; 
         FIG. 3  is a perspective view of another automatic parking brake for a body mounted brake cylinder 
         FIG. 4  is a cross-section of the automatic parking brake for a body mounted brake cylinder seen in  FIG. 3 ; 
         FIG. 5  is a perspective view of a further automatic parking brake for a body mounted brake cylinder; 
         FIG. 6  is a cross-section of the automatic parking brake for a body mounted brake cylinder see in  FIG. 5 ; 
         FIG. 7  is a perspective view of the automatic parking brake for a body mounted brake cylinder seen in  FIGS. 5 and 6 ; 
         FIG. 8  is a perspective view of an additional automatic parking brake for a body mounted brake cylinder; 
         FIG. 9  is a cross-section of the automatic parking brake for a body mounted brake cylinder seen in  FIG. 8 ; 
         FIG. 10  is a perspective view of the automatic parking brake for a body mounted brake cylinder seen in  FIGS. 8 and 9 ; and 
         FIG. 11  is a perspective view of the exterior of the automatic parking brake for a body mounted brake cylinder seen in  FIGS. 5 through 10 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings, wherein like reference numerals refer to like parts throughout, there is seen in  FIGS. 1 and 2  a first embodiment of an automatic parking brake  10  interconnected to the non-pressure head of a body mounted brake cylinder  12 . Brake cylinder  12  includes a piston  16  that moves in response to pneumatic pressure applied to an inlet  18 , such as a source of brake cylinder pressure. A spring  20  biases piston  16  into a brakes released position, and pressure applied to inlet  18  moves piston  16  into the brakes applied position. A piston rod  14  is pushably coupled to the piston  16  at one end and is connected to the braking system at the other end to apply the brakes of a rail car. A threaded shaft  22  having a hollow cavity is also coupled to piston  16  and extends axially around piston rod  14  for movement therewith. Piston rod  14  connected to piston  16  such that piston rod  14  is free to pivot relative to piston  16  within the bounds of the inside of threaded shaft  22  to accommodate angular misalignment of piston rod  14  as the brake lever of the braking system to which piston rod  14  in connected operates through an arc. 
     Threaded shaft  22  is selectively locked and unlocked by the action of a locking nut  24  positioned between two thrust bearings  26  and  28  and threaded to shaft  22  via high helix threads, and a locking sleeve  30  that is rotationally fixed but free to move into and out of engagement with locking nut  24 . When engaged with nut  24 , locking sleeve  30  prevents nut  24  from rotating, and thereby locking shaft  22  in place. When sleeve  30  is disengaged from nut  24 , nut  24  is free to rotate, thereby allowing shaft  22  to translate between the brakes applied and brakes released position. Sleeve  30  is biased into engagement with nut  24  and a pressure port  32 , which is preferably connected to a source of brake pipe pressure, allows pressure to be applied directly to sleeve  30  to move it out of engagement with nut  24 . As a result, the removal of brake pipe pressure after the application of brake cylinder pressure will automatically lock brake cylinder  12  in the brakes applied position, and the restoration of brake pipe pressure will release automatic parking brake  10 . A pin  34  may be positioned between a shoulder  34  of sleeve  30  and nut  24  and, more particularly, in a groove formed in shaft  22 , to prevent rotation of sleeve  30  about shaft  22 . A protective boot  36  may be positioned about the end of shaft  22  to protect against outside elements. 
     There is seen in  FIGS. 3 and 4  another embodiment of an automatic parking brake  110  interconnected to the non-pressure head of a body mounted brake cylinder  112 . Brake cylinder  112  includes a piston  116  that moves in response to pneumatic pressure applied to an inlet  118 , such as a source of brake cylinder pressure. A spring  120  biases piston  116  into a brakes released position, and pressure applied to inlet  118  moves piston  116  into the brakes applied position. A threaded shaft  122  is coupled to the piston  116  at one end and is interconnected to the braking system at the other end via a connecting rod  140  that is connected to threaded shaft  122  by a ball joint  142 . The push rod (not shown) of a conventional braking system may be positioned over connecting rod  140 . Threaded shaft  122  is selectively locked and unlocked by the action of a locking nut  124  positioned between two thrust bearings  126  and  128  and threaded to shaft  120  via high helix threads, and a locking sleeve  130  that is rotationally fixed but free to move into and out of engagement with locking nut  124 . When engaged with nut  124 , locking sleeve  130  prevents nut  124  from rotating, and thereby locking shaft  120  in place. When sleeve  130  is disengaged from nut  124 , nut  124  is free to rotate, thereby allowing shaft  120  to translate between the brakes applied and brakes released position. Sleeve  130  is biased into engagement with nut  124  and a pressure port  132 , which is preferably connected to a source of brake pipe pressure. Pressure port  132  allows pressure to be applied directed to sleeve  130  to move it out of engagement with nut  124 . As a result, the removal of brake pipe pressure after the application of brake cylinder pressure will automatically lock brake cylinder  112  in the brakes applied position, and the restoration of brake pipe pressure will release automatic parking brake  110 . A pair of pins  134  may positioned between a shoulder  134  of sleeve  130  and nut  124 . A protective boot may be is positioned about shaft  122  to protect against outside elements. 
     There is seen in  FIGS. 5 through 7 , another embodiment of an automatic parking brake  210  for a body mounted brake cylinder  212  having a pair of locking assemblies  240  oriented symmetrically about the centerline of the push rod, thereby preventing the piston from tipping when the brake force is applied through locking assemblies  240 . Although a configuration with two locking assemblies  240  is disclosed, any number greater than one could be utilized, provided that the locking assemblies  240  are oriented symmetrically about centerline of the push rod. Brake cylinder  212  includes a piston  216  that moves in response to pneumatic pressure applied to an inlet  218 , such as a source of brake cylinder pressure. A spring  220  biases piston  216  into a brakes released position, and pressure applied to inlet  218  moves piston  216  into the brakes applied position. A piston rod  214  is coupled to the piston  216  at one end and is interconnected to the braking system at the other end. 
     Each locking assembly  240  comprises a threaded shaft  222  coupled to piston  216  and positioned in parallel with piston rod  214 . Threaded shaft  222  is selectively locked and unlocked by the action of a locking nut  224  that is threaded to shaft  222  via high helix threads. A locking sleeve  230  is positioned proximately to locking nut  224  and is rotationally fixed but free to move axially into and out of engagement with locking nut  224 . Locking nut  224  is held in place by a bushing  226  and a thrust bearing  228 . Locking sleeve  230  is biased into engagement with each locking nut  224  by a spring  232 . When engaged with nut  224 , locking sleeve  230  prevents nut  224  from rotating, and thereby locking shaft  222  in place. When each sleeve  230  is disengaged from each nut  224 , each nut  224  is free to rotate, thereby allowing each shaft  222  to translate between the brakes applied and brakes released position. Pins  234  may be used to prevent rotation of sleeve  230 . Each locking assembly  240  may be protected by a boot  256  positioned in covering relation to the cover  258  enclosing spring  232  in the non-pressure head  254  of brake cylinder  214 . 
     The pair of locking assemblies  240  are interconnected to each other by an activating assembly  242  comprising a piston  244  having a tapered edge  246  in contact with a pair of pins  248  so that translation of piston  244  from a non-pressurized position to a pressurized position caused pins  248  move linearly outwardly as the tapered edge  246  gradually pushes against pins  248 . Pins  248  extend outwardly from tapered edge  246  of piston  244  into contact with a pair of cams  250 . Each cam  250  is mechanically interconnected to each locking sleeve  230  of each locking assembly  240  by a shoulder  252  on the opposing end of cam  250  so that, when rotated, engages a corresponding shoulder  254  on locking sleeve  230  and moves locking sleeve  230  axially out of engagement with locking nut  224 . As a result, the linear movement of pins  248  in response to the movement of piston  244  will cause cams  250  to rotate and the rotation of cams  250  will force locking sleeves  230  to move out of engagement with locking nuts  224 . Thus, when a source of pressure is applied to or removed from a pressure port  262  associated with the face  260  of piston  244 , such as brake pipe pressure, locking assemblies  240  are unlocked or locked, respectively. A manual piston knob  264  may be coupled to piston  244  to allow for a manual application or release of locking assemblies  240 . 
     There is seen in  FIGS. 8 through 10 , another embodiment of an automatic parking brake  310  for a body mounted brake cylinder  312  having a pair of locking assemblies  340 . Brake cylinder  312  includes a piston  316  that moves in response to pneumatic pressure applied to an inlet  318 , such as a source of brake cylinder pressure. A spring  320  biases piston  316  into a brakes released position, and pressure applied to inlet  318  moves piston  316  into the brakes applied position. A piston rod  314  is coupled to the piston  316  at one end and is interconnected to the braking system at the other end. 
     Each locking assembly  340  comprises a threaded shaft  322  coupled to piston  316  and positioned in parallel with piston rod  314 . Threaded shaft  322  is selectively locked and unlocked by the action of a locking nut  324  that is threaded to shaft  322  via high helix threads. A locking sleeve  330  is positioned proximately to locking nut  324  and is rotationally fixed but free to move axially into and out of engagement with locking nut  324 . Locking nut  324  is held in place by a bushing  326  and a thrust bearing  328 . Locking sleeve  330  is biased into engagement with each locking nut  324  by a spring  332  into a locked position. When engaged with nut  324 , locking sleeve  330  prevents nut  324  from rotating, and thereby locking shaft  322  in place. When each sleeve  230  is disengaged from each nut  224 , each nut  224  is free to rotate, thereby allowing each shaft  222  to translate between the brakes applied and brakes released position. Each locking assembly  340  may be protected by a boot  356  positioned in covering relation to the cover  358  enclosing spring  332  in the non-pressure head  354  of brake cylinder  314 . Pins  334  may be used to prevent rotation of sleeve  330 . 
     The pair of locking assemblies  340  are interconnected to each other by an activating assembly  342  comprising a piston  344  that can selectively apply pressure via a pair of conduits  346  directly to locking sleeves  330  to move them out of engagement with the corresponding locking nuts  324 . Piston  344  is preferably biased so that no pressure is supplied to locking sleeves  330  and may be automatically actuated, such as by connecting a source of brake pipe pressure, or by providing a manual point of connection to the face  360  of piston  344 . Referring to  FIG. 10 , piston  344  may include a manual release nut  350  that, when rotating, will withdraw piston  344  so that pressure is applied to locking sleeve  330  to move into the disengaged position relative to locking nut  324  so that brake piston  316  may return to the brakes released position. Piston  344  may include one or more O-rings  352  to seal piston  344  within the non-pressure head  354  of brake cylinder  314 .  FIG. 11  shows the outer structure of a brake cylinder according to  FIGS. 5 through 7 , or  8  through  10 .