Abstract:
On a railroad car handbrake system the main handbrake shaft, used to turn the chain, is utilized during its rotation to drive a target object to a magnetic sensor. The target object may be driven by cam plates, gears, screw mechanisms or the like and may be a magnetic or ferromagnetic object. The sensor system disclosed is rugged and easily adapted to existing handbrake systems.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to sensors capable of distinguishing when the manual hand brake setting apparatus of a railroad car is in the “Off” or “Brake Release” position. 
     2. Description of the Related Art 
     The rail industry has a very high maintenance cost related to wheel damage. The majority of this damage is the result of handbrakes being left on prior to a train departing the rail yard. If a car has the handbrake left on when the train begins to move, the wheels of that car will not turn, resulting in a worn, flat spot on the wheel. The handbrake being left on can also result in a derailment if not detected prior to the train leaving the rail yard. For these reasons it is desirable to provide the manual handbrake setting apparatus of a railcar with a sensor having an indication means whereby the railroad operator is able to determine that the manual setting of the brakes is placed in the “off” position before moving the train. 
     It is well known in the art of railroad car building to equip railcars with a manual brake system which is actuated by a manually turned wheel located on the front, or back, of said car. Generally the wheel is attached through gearing to an axle which is attached to a chain running down the front of the car and generally to the undercarriage of said car where the chain is linked to the brake rigging. Turning of the wheel gathers the chain, putting it in tension, whereby the brakes, i.e. brake pads, are pulled into the wheel assembly. Release of the chain to sufficient slack where it will not tighten and engage the brakes under any conditions, such as the rail car tilting when going around curves etc., is accomplished by turning the wheel in the opposite direction, or pulling a release arm, to unwind chain from the main axle. 
     Because the railroad car will often be subject to extremes of environment including temperature, dirt, water, and the like it is further very desirable that the sensor have a rugged construction unlikely to be susceptible to environmental degradation. It is further desirable that the sensor be located on the railroad car where it is least likely to be susceptible to such environmental degradation or contamination. 
     SUMMARY OF THE INVENTION 
     By utilizing the rotation of the main shaft, which gathers the brake chain, to drive a target object toward a sensor located near the main shaft; sensing of the chain position can be accomplished and the railroad operator can be notified when the brakes are, or should be, in the released position. An indicator electrically connected to the sensor will of course be utilized to provide some operator interface to notify the train operator. 
     Preferably, a magnetically sensitive sensor able to detect shifts in magnetic field caused by a magnetic or ferromagnetic target are utilized since such sensors are highly resistant to environmental contamination or degradation. Other environmentally rugged sensors such as a proximity sensor may be substituted for the magnetically sensitive sensor. The target object to be sensed may be driven by a variety of means linked to the main shaft such as cam plates, gears, screw mechanisms or the like. The present invention is further easily adapted to present hand brake systems, requiring minimal amounts of retrofitting. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be more fully and completely understood from a reading of the Description of the Preferred Embodiment in conjunction with the drawings, in which: 
     FIG. 1 is a highly schematic view of a railroad car showing a handbrake setting system commonly in use and a highly schematic indication of the present invention therewith. 
     FIG. 2 is a detail of a first embodiment of the present invention. 
     FIG. 3 is a detail of a second embodiment of the present invention. 
     FIG. 4 is a detail of a third embodiment of the present invention. 
     FIG. 5 is a detail view of a fourth embodiment of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Throughout the Description of the Preferred Embodiment, like components will be identified by like reference numerals. 
     As seen in FIG. 1, a railcar  11  (front end) has a body  13  mounted on a carriage assembly, or trucks (not shown), which carry the wheels  15  and the brake linkage  17 . A manual system for engaging the brake linkage  17  includes a chain  19  which is attached to a main shaft  21  which is rotatably affixed to the car body  13  by a bearing  23  near the car body  13 . At the outboard end  25  of the main shaft  21  is located a hand wheel  27  for manual rotation of the main shaft  21  in order to put the chain in tension or slack. Hand wheel  27  is turned to gather the chain  19  about the main shaft  21  and thus put the chain in tension thereby engaging the brake linkage  17  to set the brakes against wheels  15 . Normally a cover  29  is provided for the journaled end of the main shaft  21  and the gathered chain to provide some environmental protection therefor. 
     According to the present invention, as shown highly schematically in FIG. 1, a drive means  31  such as a cam plate or the like, is attached to the main or central shaft  21  and in turn drives a target  33  towards a sensing element  35 . When target  33  is placed within the sensitivity range of the sensor  35  the position of the main shaft  21  with respect to its operation of the brake chain  19  is therefore determined. Normally the most critical piece of information for the railroad operator is that the brakes are off when the train is placed under motive force. Therefore it is this condition which is most preferably sensed. The sensor  35  is then connected to suitable output electronics and operator interface indication means  37 , schematically illustrated by an LED in FIG. 1, although many forms of operator interface will be apparent to the ordinarily skilled artisan. A cover  39  is then preferably provided to protect the sensing apparatus of the present invention including the drive means, the target, and the sensor from environmental contamination or degradation. 
     Some common parts of the brake mechanism and railroad car assembly have been left out for purposes of clarity of explanation but will be recognized by the ordinarily skilled artisan of railroad car construction and are not deemed necessary to a further exposition of the present invention. 
     Referencing FIG. 2, the main shaft  21  has affixed concentrically therewith a cam wheel  41  having a spiral groove or track  43  therein for the provision of camming action. A cam follower  45  is affixed within the spiral track  43  at one end thereof by a pin  47 . The cam follower  45  is prevented from rotating by a grooved cover or the like (not shown). The cam follower  45  is shown as an elliptical ring  49  whose center void  51  overlies the main shaft  21 . An elongated member  53  carrying the pin  47  is affixed at one end of the elliptical ring  49  in order to provide connection to the spiral track  43 . A sensor such as a magnetically sensitive Hall element sensor or the like  35  is located in a fixed position outside of the cam wheel  41  such that rotation of the main shaft  21  in turn causes rotation of the cam wheel  41 , drawing the cam follower  45  towards the sensor  35 . The cam follower is preferably constructed of ferromagnetic material or may have a feature thereon such as a magnet  54  for disturbing the field of the Hall sensor  35 . The cam follower  45  is shown in phantom placed in position to be sensed by the sensor  35 . The sensing apparatus of FIG. 2 might be constructed and arranged as an end cap addition to the main shaft wherein, e.g. the cam wheel  41  is approximately the same diameter as the shaft itself, thereby making the sensing apparatus very compact. 
     Referencing FIG. 3, a second embodiment shows the main shaft  21  with a threaded central bore  57  at either the rear or front end thereof, i.e. proximal or distal to the car. Riding within the threaded central bore  57  is a screw, or threaded member,  59  with a square or rectangular head  61  captivated in a housing  63  attached over the end of the main shaft  21 . Turning of the main shaft will cause the screw  59  to ride up and down within the threaded central bore  57 , presenting the rectangular head  61  to the magnetic sensor  35 . The sensor is affixed to sense the screw head  61  at its extended position where the main shaft is in position to provide sufficient slack to the brake chain  19 . The housing, or screw head holder  63  may have an opening or slot (not shown) placed therein at point where the screw head  61  reaches the sensitivity range of the sensor  35  in order that the screw head holder  63  does not interfere with the magnetic interaction between sensor  35  and screw head  61 . 
     The sensing apparatus of FIG. 3 might desirably be constructed and arranged as an end-cap add-on to the main shaft rather than having a threaded bore within the main shaft as shown. 
     Referencing FIG. 4, a third alternative of the preferred embodiment shows the main shaft  21  having on its back end (closest to the car) an eccentric pin  67 . The eccentric pin  67  engages a partially toothed gear wheel  69  rotatably affixed to the back of main shaft bearing housing  71 . Rotation of the main shaft  21  will cause the eccentric pin  67  to engage a tooth of the partially toothed gear wheel  69  once per revolution of the main shaft thus rotating one tooth, or a feature thereon, or a lack of teeth, toward the sensor  35  to determine the appropriate position of the main shaft  21  in a position where sufficient slack is given the brake chain (not shown) to release the manual actuation of the brakes. A cap  39  is preferably provided to prevent environmental contamination and degradation of the sensing apparatus. 
     Referencing FIG. 5, a fourth alternative embodiment shows the main shaft  21 , or suitable extension thereof, having affixed concentrically thereto a drive gear  73 . The drive gear  73  engages a driven gear  75  with a magnet or other ferromagnetic-magnetic feature  77  mounted thereon. A Hall sensor  35  is fixedly located on the apparatus so as to be placed where its sensitivity range will detect the magnet  77  which is placed to be aligned with the sensor  35  when the main shaft  21  is placed in position to allow sufficient chain slack for the brakes to be fully off. Commonly, five full rotations of the main shaft  21  are required to fully tension or slack the chain placing the brakes from full on to full off respectively. Thus the driven gear  75  shown in FIG. 5 is selected to have a reduction ratio of 5:1 with the driving gear  73 . 
     All of the above embodiments may be suitably constructed and arranged to provide a low profile environmentally rugged sensing apparatus for main shaft chain release position and would require minimal rework or retrofitting to existing brake mechanisms. 
     Although several alternative embodiments have been shown, numerous variants will occur to the artisan of ordinary skill in the art of sensing apparatus and the present invention is intended to be limited only by the claims herein.