Abstract:
An apparatus for sensing movement of a point rail away from a stock rail by a selected distance, by closing a switch to shunt a track circuit. Manual resetting of the point rail is required to reset the apparatus to open the switch.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is a continuation patent application of co-pending U.S. patent application Ser. No. 11/057,289, filed on Feb. 11, 2005, and entitled “Non-Powered Trailed Switch Detector for Railroad Track Switching Equipment.” 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention is in the field of railroad track switching equipment used to enable railroad vehicle traffic to pass along one or the other of two sets of tracks, at a point where the two sets of tracks merge into one set of tracks or where one set of tracks diverges into two sets of tracks, specifically equipment used to monitor the position of switching equipment at the merge/diverge point. 
     2. Background Art 
     In directing railroad vehicle traffic between one set of tracks and two sets of diverging tracks, with vehicles moving in either direction, it is well known to shift a set of point rails transversely, to cause one or the other of the point rails to contact a stationary stock rail. When viewed from the perspective of the single set of tracks, if the right hand point rail aligns with the right hand stock rail, traffic will be directed from the single set of tracks onto the left set of diverging tracks, or traffic coming from the left set of diverging tracks can pass onto the single set of tracks. Conversely, if the left hand point rail aligns with the left hand stock rail, traffic will be directed from the single set of tracks onto the right set of diverging tracks, or traffic coming from the right set of diverging tracks can pass onto the single set of tracks. 
     With this common type of switching arrangement, if the right hand point rail is aligned with the right hand stock rail, and if a rail vehicle passes from the right hand set of diverging tracks onto the single set of tracks, the right hand point rail will be forced away from the right hand stock rail. In this situation, commonly called a trailed switch condition, the right hand point rail may simply deflect and then return almost to its original alignment with the right hand stock rail, but remain somewhat separated from the right hand stock rail. This results in a condition which could lead to derailment when the next rail vehicle moving along the single set of tracks passes through the switch point, since neither the right hand point rail nor the left hand point rail aligns with its respective stock rail. In other words, the right wheel of the rail vehicle will attempt to follow the right hand set of diverging tracks, while the left wheel of the rail vehicle will attempt to follow the left hand set of diverging tracks. Even if the point rail rebounds to its original position in contact with the stock rail, the switch machine which holds the point rails in position may have been damaged and rendered incapable of adequately holding the point rail in position against the stock rail. This can still result in the derailing of a rail vehicle passing through the switch. It is necessary, therefore, to send an operator to a trailed switch, to inspect the switching apparatus and reset the trailed switch detector. 
     It is known to have a shunt switch, commonly called a circuit controller switch, positioned to sense movement of the point rail away from the stock rail by a selected distance, at which point the shunt switch will shunt the associated track circuit, indicating that the point rail has moved away from the stock rail. Providing this separate circuit controller switch, possibly calling for an additional housing and connecting apparatus, obviously adds some expense and complexity to the switching arrangement. Further, some currently available switch machines are sufficiently robust that, after a train passes through the switch from the wrong set of diverging tracks, the switch machine will allow the point rail to rebound to a position sufficiently close to the stock rail that the circuit controller switch will immediately open, and the track circuit will no longer be shunted. So, in spite of the added cost of providing the circuit controller switch to detect the trailed switch condition, such known systems do not reliably sense the existence of a trailed switch condition. 
     Therefore, it is necessary to have apparatus for sensing when a trailed switch condition exists, and to prevent the trailed switch sensing apparatus from resetting itself even if the point rail moves back into contact with its stock rail. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention is an apparatus in which an actuator holds open a shunt switch, called a trailing move detector switch, in a track circuit, when the point rail is in contact with the stock rail. When the point rail moves a selected distance away from the stock rail, the actuator closes the trailing move detector switch, shunting the track circuit. The actuator will not reset and re-open the trailing move detector switch, until the point rail has been fully shifted to a reset position, thereby avoiding the situation where the track circuit might only momentarily be shunted if the point rail rebounds into contact with the stock rail. This requires an operator to go to the site and reset the sensing apparatus after inspecting the switch machine and related equipment. 
     In one embodiment, an actuator cam is spring loaded to rotate in a first direction to a first actuator position, to hold a trailing move detector switch open. A point rail position sensor, such as a rail follower piston, moves with the point rail and interacts with the actuator cam. When movement of the point rail causes the point rail follower piston to rotate the actuator cam sufficiently to pull the cam loading spring past a “high point” or point of maximum extension, the loading spring then rotates the actuator cam in a second, opposite, direction to a second actuator position, to allow the trailing move detector switch to close. Even if the point rail rebounds toward the stock rail, the actuator cam remains in the “tripped” second actuator position, fully rotated in the second direction, and it will not open the trailing move detector switch. This allows the trailing move detector switch to remain closed. 
     When the point rail is driven through its full stroke, however, a reset plate driven by the movement of the point rail follower piston rotates the actuator cam in the first direction until the cam loading spring moves back past its high point, thereafter again biasing the actuator in the first direction to the first actuator position, thereby “resetting” the actuator cam. Then, returning the point rail to contact with the stock rail will cause the actuator cam to again open the trailing move detector switch. 
     In a second embodiment, when the point rail is in contact with the stock rail, a contactor base holds an actuator pawl in a first rotational direction in a first actuator position, in which the actuator pawl holds the trailing move detector switch open. The actuator pawl is biased to rotate in a second, opposite, direction by a loading spring, to rotate away from the trailing move detector switch and toward the contactor base. Movement of the point rail away from the stock rail by a selected distance causes the point rail follower piston to displace the actuator pawl away from the contactor base, or vice versa, allowing the pawl loading spring to rotate the actuator pawl in the second direction away from the trailing move detector switch to a second actuator position, allowing the trailing move detector switch to close, thereby shunting the track circuit. Even if the point rail rebounds toward the stock rail, the actuator pawl remains in its “tripped” second actuator position, fully rotated in the second direction, and it will not open the trailing move detector switch. This allows the trailing move detector switch to remain closed. 
     When the point rail is driven through its full stroke, however, the actuator pawl contacts a reset bar mounted to the housing of the apparatus, which rotates the actuator pawl in the first direction again, until the actuator pawl is retained in its first position by a latch, thereby “resetting” the actuator pawl. Then, returning the point rail to contact with the stock rail will cause the actuator pawl to again open the trailing move detector switch. As the actuator pawl moves into contact with the trailing move detector switch, once the actuator pawl is again held in its first position by the contactor base, the contactor base releases the actuator pawl from the latch. 
     Either of these embodiments can also incorporate a circuit controller switch and actuator, as discussed above. This type of actuator, however, will open the circuit controller switch without being reset. An example of such an actuator would be a lever adapted to be rotated by movement of the point rail follower piston, to open and close the circuit controller switch. Incorporating this type of circuit controller switch in the same housing with the trailing move detector switch, and using the same point rail follower piston to actuate the circuit controller switch, can reduce the cost and complexity associated with providing a circuit controller switch. 
     The novel features of this invention, as well as the invention itself, will be best understood from the attached drawings, taken along with the following description, in which similar reference characters refer to similar parts, and in which: 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a perspective view of a first embodiment of the apparatus of the present invention; 
         FIG. 2  is a circuit diagram of a switching arrangement according to the present invention; 
         FIG. 3  is a plan view of a portion of the apparatus shown in  FIG. 1 ; 
         FIGS. 4 and 5  are plan views showing the tripping of the switches shown in  FIG. 1  to shunt the track circuit; 
         FIG. 6  is an elevation view of a second embodiment of the apparatus of the present invention; 
         FIGS. 7 and 8  are elevation views showing the tripping of the switch shown in  FIG. 6  to shunt the track circuit; 
         FIG. 9  is an elevation view of the apparatus shown in  FIG. 6 , in the reset position; and 
         FIGS. 10 and 11  are elevation views showing the opening of the switch after resetting of the apparatus, as shown in  FIG. 9 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As shown in  FIG. 1 , a first embodiment of the apparatus  100  of the present invention includes a housing  110  in which are mounted one or more point rail follower pistons  112 . A collar  114  is fixedly mounted on each follower piston  112 , and a distal end  116  of each follower piston  112  is adapted to remain in contact with and follow a point rail PR, as shown in  FIG. 3 . Only half of the apparatus  100  is shown in  FIG. 3 , for simplicity.  FIG. 3  also shows that a spring  160  can be used to bias the follower piston  112  to remain in contact with the point rail PR. 
     An actuator cam  118  is positioned to interact with the collar  114  on each follower piston  112 , and each actuator cam  118  selectively opens a pair of trailing move detector switches  122 ,  126  or  132 ,  136 . A circuit controller lever  120  can also be provided for each follower piston  112 , with each circuit controller lever  120  actuating a pair of circuit controller switches  124 ,  128  or  134 ,  138 . As shown in  FIG. 2 , the trailing move detector switches  122 ,  126 ,  132 ,  136  and the circuit controller switches  124 ,  128 ,  134 ,  138  are connected to selectively shunt one or two track circuits to alert operators of a possible trailed switch condition. All eight switches can be connected to a single track circuit, such as Track  1 , by connecting the terminal bars as shown in dashed lines. If there are two adjacent tracks to be monitored, the switches are segregated by removal of the dashed portion of the terminal bars. Closing of any one of the switches will shunt its respective track circuit. All of the switches are biased toward the closed position. 
     As seen better in  FIG. 3 , the actuator cam  118  pivots about a cam shaft  152 . When the apparatus  100  is in the fully reset position shown in  FIGS. 1 and 3 , a cam loading spring  154  biases the actuator cam  118  in a first, clockwise, direction, causing the switch contact face  142  on the actuator cam  118  to contact and open the related trailing move detector switches  122 ,  126 . This is the first actuator position of the actuator cam  118 . Rotation of the actuator cam  118  farther in the clockwise direction past this point is prevented by contact between the actuator cam  118  and a cam position stop post  144 . A start clasp  140  is pivotally mounted to the actuator cam  118 , with its left hand hooked end engaging the collar  114  when the collar  114  is in its farthest right position, corresponding to the position in which the point rail PR contacts its respective stock rail. The hooked left hand end of the start clasp  140  is held in engagement with the collar  114  by a clasp spring  156  which pulls the right hand end of the start clasp  140  away from the follower piston  112 . The circuit controller lever  120  pivots about a lever shaft  150 . One end of the circuit controller lever  120  is biased against the collar  114  by a lever spring  162 . When the collar  114  is in its farthest right position, as shown, it holds the contact face  146  of the other end of the lever  120  in contact with the related circuit controller switches  124 ,  128 , holding these switches in the open position. 
     As shown in  FIG. 4 , when the follower piston  112  and the collar  114  move to the left, along with the point rail PR, the collar  114  moves the start clasp  140  to the left, causing the actuator cam  118  to rotate counter-clockwise under the action of a suitable mechanism for providing a biasing force, such as the cam loading spring  154 . At approximately three-sixteenths of an inch of movement in the left direction, the cam loading spring  154  reaches its “high point” as it passes over the center of rotation of the actuator cam  118 , at the cam shaft  152 . In this first portion of the range of motion of the actuator cam  118 , the cam loading spring  154  biases the actuator cam in the clockwise direction. After this point, in the second portion of its range of motion, the actuator cam  118  is biased in the counter-clockwise direction to the second actuator position of the actuator cam  118 . It can be seen that as the start clasp  140  rotates about the clasp shaft  172  relative to the actuator cam  118 , the clasp spring  156  brings the right hand end of the start clasp  140  into contact with the cam shaft  152  to stop rotation of the start clasp  140  relative to the actuator cam  118 . It can also be seen that at approximately this point, the contact face  142  of the actuator cam  118  no longer contacts the contact button  168  of the trailing move detector switch  122 . The circuit controller lever  120  is omitted from  FIG. 4  for clarity. 
     As shown in  FIG. 5 , when the collar  114  has moved to the left by one fourth of an inch, the contact button  168  of the trailing move detector switch  122  has been completely released, closing the switch and shunting the related track circuit. This is the second actuator position of the actuator cam  118 . Further, the start clasp  140  has continued to rotate with the actuator cam  118 , until the hooked end of the start clasp  140  has cleared the collar  114 . It can also be noted that, at this point, the circuit controller lever  120  has rotated counterclockwise, biased by the lever spring  162 , as the distal end of the circuit controller lever  120  follows the collar  114 , until the contact face  146  of the circuit controller lever  120  has released the contact button  170  of the circuit controller switch  124 . This closes the circuit controller switch  124 , also shunting the track circuit. 
     If the point rail PR were to rebound to the right at this point, it can be seen that the circuit controller lever  120  would rotate to the right, opening the circuit controller switch  124 . However, the actuator cam  118  would remain in its counter-clockwise rotated second actuator position, held there by the cam loading spring  154 . Therefore, the actuator cam  118  will not open the trailing move detector switch  122 , and the track circuit will remain shunted. An operator can then go to the site and inspect the necessary equipment. The operator can then manually stroke the switch machine through its full stroke and return it to its original setting. When the point rail is moved to the left end of its stroke, the collar  114  moves to the left until it contacts an upright lip  158  on the left end of the reset plate  130 , and move the reset plate  130  to the left against the bias of the plate spring  164 . An extension  165  on the right end of the reset plate  130  has an upright lip  166 . As the reset plate  130  moves to the left, the lip  166  on the plate extension  165  contacts the edge of the actuator cam as indicated best in  FIG. 5 . Continued movement of the collar  114  to the left end of its stroke pulls the lip  166  farther left, causing the actuator cam  118  to rotate in the clockwise direction. As the actuator cam  118  rotates in the clockwise direction, the cam loading spring  154  passes back over its “high point”, after which the cam loading spring  154  biases the actuator cam  118  fully in the clockwise direction until it reaches its “reset” first actuator position, contacting the position stop  144 . Thereafter, as the point rail PR is moved back to the right to contact the stock rail, the collar  114  moves back to the right, deflecting the hooked end of the start clasp  140  as it passes. This returns the apparatus  100  to the condition shown in  FIG. 3 . 
     In a second embodiment of the apparatus  200  shown in  FIG. 6 , a follower block  214  is mounted to the point rail follower piston  212 . A contact base  246  is mounted to the housing  210 , with a trailing move detector switch  250  mounted to the contact base  246 . The trailing move detector switch  250  can be, for example, a simple circuit board with a flexible contact arm  252  biased toward the circuit board. When the contact arm  252  contacts the switch  250 , the switch is closed. An actuator pawl  216  is pivotably mounted on a pawl shaft  224  on the follower block  214 . A suitable mechanism for providing a biasing force, such as a pawl spring  226  biases the actuator pawl  216  in the counter-clockwise direction. A latch  230  is pivotably mounted on a latch post  238  to the follower block  214 . A latch spring  236  biases the latch  230  in the counter-clockwise direction.  FIG. 6  shows the apparatus  200  in its “reset” position, with the trailing move detector switch  250  open, corresponding to the farthest right position of the point rail PR. It can be seen that the contact extension  220  of the actuator pawl  216  is pushing the contact arm  252  of the trailing move detector switch  250  to the open position. The contact extension  220  can pass through a notch in the circuit board of the switch  250 . The contact extension  220  is held in this position by the pawl position stop face  248  of the contact base  246 . This is the first actuator position of the actuator pawl  216 . It can be seen that the latch  230  does not engage the actuator pawl  216  at this point. 
       FIG. 7  better shows this position, with the switch contact face  258  of the actuator pawl  216  contacting the switch contact arm  252 , and with the latch contact face  256  of the lower extension  254  of the contact base  246  being contacted by the base contact face  242  of the latch  230 . The lower lip  222  of the actuator pawl  216  does not engage the hook  234  of the latch  230 . As the point rail PR moves to the left, away from the stock rail, the follower piston  212  and the follower block  214  move to the left. After one fourth inch movement to the left, the contact extension  220  of the actuator pawl  216  clears the pawl position stop face  248  of the contact base  246 . This allows the pawl spring  226  to rotate the actuator pawl  216  in the counter-clockwise direction until the reset extension  218  of the actuator pawl  216  contacts the pawl stop post  228 , as shown in  FIG. 8 . This is the second actuator position of the actuator pawl  216 . It can be seen that the contact arm  252  contacts the circuit board, closing the trailing move detector switch  250 . It can also be seen that, even if the point rail PR rebounds to the right, the actuator pawl  216  will not open the trailing move detector switch  250 . 
     However, after inspecting the necessary equipment, an operator can move the point rail PR through its full stroke to reset the apparatus  200  as well as the switch machine.  FIG. 9  shows the point rail follower piston  212  moved fully to the left. The reset extension  218  of the actuator pawl  216  has contacted a reset bar  260  mounted to the housing  210 . This rotates the actuator pawl  216  in the clockwise direction, until the lower lip  222  on the actuator pawl  216  contacts and deflects the hook  234  on the latch  230 , ultimately latching the lip  222  behind the hook  234 . The latch spring  236  holds the latch  230  against the latch stop post  240 , and the pawl loading spring  226  maintains the lower lip  222  in engagement with the hook  234 . This holds the actuator pawl  216  in its reset position. 
     As shown in  FIG. 10 , as the point rail PR and the follower block  214  are moved back to the right, the contact extension  220  of the actuator pawl  216  moves underneath the pawl position stop face  248  of the contact base  246 , with the latch  230  holding the actuator pawl  216  in its reset first actuator position. As shown in  FIG. 11 , as the contact extension  220  of the actuator pawl  216  moves under the pawl position stop face  248 , the contact extension  220  also opens the trailing move detector switch  250 . Further, the latch contact face  256  of the contact base  246  urges the latch  230  in the clockwise direction against the bias of the latch spring  236 , releasing the lower lip  222  on the actuator pawl  216  from the hook  234  on the latch  230 . This allows the contact extension  220  of the actuator pawl  216  to be held in position against the bias of the pawl loading spring  226  only by the pawl position stop face  248 , and the apparatus  200  has been returned to its fully reset position as shown in  FIG. 6 . 
     This disclosure is merely illustrative of the preferred embodiments of the invention, and no limitations are intended other than as described in the appended claims.