Abstract:
A railway vehicle safety shunt system includes a pair of axle-mounted rail wheels having outer circumferential surfaces that engage the upper surfaces of the rails, respectively, radially outwardly flange portions that engage the lateral portions of the rails, respectively, and adjacent end surfaces that are respectively engaged by a pair of spring-biased wire brushes arranged parallel with the axis of rotation of the associated rail wheel. The brushes are electrically connected by a shunt conductor, thereby to present an indication of the location of the railway vehicle at a remote vehicle position monitoring and dispatching station.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     A railway vehicle safety shunt system includes a pair of annular axle-mounted rail wheels having outer circumferential surfaces that engage the upper surfaces of the associated rails, respectively, radially outwardly directed flange portions that engage the lateral surfaces of the rails, and central hub portions having end surfaces normal to the axis of rotation of each rail wheel. A pair of collinearly-arranged axially spaced wire brushes are supported between, and parallel with the axes of rotation of, the associated rail wheels, said brushes being spring-biased axially apart into frictional electrical contact with the adjacent hub portion of the associated rail wheel. The brushes are electrically connected together by a shunt conductor, thereby to present an indication of the location of the vehicle at a remotely located vehicle position monitoring and dispatching station. 
     2. Brief Description of the Prior Art 
     As shown by the U.S. patents to Bartel, et al., U.S. Pat. No. 5,054,722 and Kruse U.S. Pat. No. 5,464,176, it is well known in the patented prior art to provide shunting devices for indicating the position of a maintenance or inspection railway vehicle on railroad tracks through which electrical monitoring signals are transmitted from a remotely located vehicle position monitoring and dispatching station. In the Bartel et al patent, a wire brush contactor rubs against the rail adjacent the rail guide wheel. Thus, the shunt is automatically engaged when the guide wheels are lowered against the rail. Similarly, in the Kruse patent, the shunting devices are attached to the high rail attachment for making electrical contact with the tracks. Consequently, the brush drags against the track as the maintenance vehicle drives down the track. 
     Referring to the Powell U.S. Pat. No. 4,488,494, it is also known in the prior art to provide convertible railway inspection and maintenance vehicles having alternately operable resilient wheel and rail wheels for transporting the vehicle along the ground and along the tracks, respectively. Hydraulic motor means are provided for vertically displacing the rail wheels relative to the chassis in order to convert the vehicle for land and rail transport, respectively. Similarly, the Pettibone Corporation of Chicago, Ill. manufactures such a convertible railway vehicle. Applicant is aware that others have proposed to provide a shunt connection between the rail wheels shown in the Powell patent, use being.make of carbon or graphite-containing ceramic contact blocks that frictionally engage the circumferential surfaces of the rail wheels. The contact blocks are electrically connected to define a shunt across the tracks, thereby giving an indication of the instantaneous position of the vehicle. This proposal has the inherent drawback that over time, both the rail wheel circumferential surface and the block contacts tend to chip and become worn through use, thereby affecting the reliability of the shunting operation. Also, mounting of the contact blocks on the vehicle has proven to be rather structurally difficult, making the replacement of the blocks difficult, time-consuming and costly. 
     The present invention was developed to produce an improved inexpensive and reliable railway shunting system that avoids the above and other drawbacks of the known devices. 
     SUMMARY OF THE INVENTION 
     Accordingly, a primary object of the present invention is to provide a railway vehicle safety shunting system including a pair of collinearly arranged axially-spaced conductive electrically connected brush members that are arranged between a pair of rail wheels, together with spring means that bias the brush members axially apart into engaged positions in continuous electrical engagement with the adjacent end surfaces of the rail wheels, respectively, whereby when the rail wheels are in engagement with the transport rails, a shunt is automatically established between the rails to provide an instantaneous indication of the location of the vehicle. 
     According to a more specific object of the invention, the brush contact members are removably connected with support members that are connected with the vehicle for axial displacement relative to the rail wheels, thereby to permit displacement of the support members axially together against the biasing force of the spring means toward retracted positions at which the brush members may be removed from the support means for replacement or repair. According to a further feature, retaining means may be provided for retaining the support and brush members in their retracted positions relative to the rail wheels. 
     Another object of the invention is to provide shunt means of the type described above that are suitable for use either with railway vehicles having only rail wheels, or with convertible type vehicles having alternately operable resilient wheels and rail wheels. In the latter case, the wire brush members are mounted for axial displacement on the axle cover member that is displaced simultaneously with the rail wheel axle when the rail wheels are displaced by hydraulic motor means between their operable and inoperable positions relative to the resilient wheels. 
     According to a further object of the invention, the rail wheels each include a cylindrical circumferential surface adapted to ride on the top of the associated rail, a flange that extends radially outward from the circumferential surface for engagement with the sides of the rails, and a pair of end surfaces, the central portion of each wheel having a hub portion that is supported by the wheel bearing means. In the preferred embodiment, the collinearly arranged conductive brushes are so arranged relative to the rail wheel axle that they are biased outwardly into electrical contact with the end wall surfaces of the hub portions of the rail wheels adjacent the wheel bearing means, respectively. According to another embodiment, the brushes engage the adjacent end faces of the rail wheels at opposite locations spaced radially outwardly from the hub portions of the wheels. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects and advantages of the invention will become apparent from a study of the following specification, when viewed in the light of the accompanying drawings, in which: 
     FIG. 1 is a somewhat diagrammatic front perspective view of a railway vehicle shunt system of the prior art, and FIGS. 2 and 3 are detailed side views of the rail wheel means of FIG. 1 when in the raised and lowered positions, respectively; 
     FIG. 4 is a schematic electrical and diagrammatic illustration of the improved shunt system of the present invention; 
     FIG. 5 is a detailed longitudinal sectional view of a brush supporting means of the present invention when in the extended operable condition; 
     FIG. 6 is a sectional view taken along line  6 — 6  of FIG. 5; 
     FIG. 7 is a longitudinal sectional view corresponding to FIG. 5 with the brush supporting in the retracted inoperable condition; 
     FIG. 8 is a diagrammatic representation of the shunt means of the present invention applied to a Pettibone vehicle; and 
     FIG. 9 is a detailed sectional view of a knotted wire brush contact. 
    
    
     DETAILED DESCRIPTION 
     Referring first more particularly to FIGS. 1-3, in the convertible railway inspection and maintenance vehicle illustrated in the Powell U.S. Pat. No. 4,488,494, the railway vehicle  2  has a chassis  4  normally supported by resilient wheels  6  for transport along the ground G adjacent the pair of stationary rails R. A first pair of rail wheels  10  rotatable about an axle  12  are connected with one end of the vehicle chassis by an actuator linkage assembly  14  that is operable by hydraulic motor means  16  to raise and lower the rail wheels between their elevated inoperable and lowered operable positions relative to the rails R. 
     As shown schematically in FIG. 1, in this prior vehicle, it was proposed to provide conductive graphite or carbon-containing ceramic blocks  20  in electrical engagement with the outer circumferential surfaces  10   a  of the steel rail wheels, these block contacts being connected together by the shunt conductor wire or cable  22 . Thus, when the hydraulic motor means  16  is operated to lower the rail wheels  10  into engagement with the rails R, an electrical shorting path is established between the rails via a first steel rail wheel  10 , the associated sliding contact  20 , shunt conductor cable  22 , the other contact  20 ′, and the other steel rail wheel  10 ′. In this manner, as is known in the art, the instantaneous position of the railway vehicle is displayed on the screen of the remotely located vehicle position monitoring and dispatch station, not shown. 
     Referring now to FIG. 4, in accordance with the present invention, the railway vehicle  30  is supported by annular steel rail wheels  32  that engage rails  34  that are connected with a remotely located vehicle position monitoring and dispatch control station  36  by conductors  38 . Each rail wheel  32  has a cylindrical circumferential surface  32   a  that rides on the top of the associated rail, and a radial flange portion  32   b  that engages a side surface of the rail. The rail wheel has a pair of inner and outer end surfaces  32   c  and  32   d . The rail wheels are supported by bearings  38  for rotation about an axle  40 . The rail wheels include central hub portions  32   e  adjacent the bearing  38 . The axle  40  is connected by supports  42  with the axle cover  44  which in turn is pivotally connected with the vehicle chassis, as will be described below. 
     In accordance with the present invention, shunt connecting means  50  afford continuous electrical connection between the rail wheels  32 , thereby to provide an instantaneous position signal of the vehicle on the tracks to the monitoring and dispatch station  36 . The shunt means includes a pair of steel wire brush or twisted rope contacts  52  that are collinearly arranged in spaced relation adjacent the inner end surfaces  32   e  of the rail wheels. Preferably, the contacts  52  are supported by the axle cover  44  and the brush support means  54  at positions adjacent the end surfaces of the central hub portions  32   e  of the rail wheels. 
     As shown in greater detail in FIGS. 5 and 6, the support means  54  includes a hollow outer cylindrical steel housing  60  having an open first end adjacent the associated rail wheel  32 , the other end of the outer housing being closed by an end wall  60   a . As best shown in FIG. 6, a vertical support plate  62  is welded longitudinally of the housing by weld seams  64 , which support plate is bolted by bolts  66  to the L-shaped bracket  68  that in turn is welded to the axle cover  44  by weld seams  68 . Arranged for longitudinal sliding movement concentrically within the open first end of the housing  60  is a cylindrical inner member  70  formed of a conductive metal material such as steel, brass, or the like. At its end adjacent the rail wheel  32 , the inner member  70  contains a threaded bore into which is threadably connected the threaded shank portion  72   a  of the brush holder  72  that carries the twisted wire ropes that define the brushes  52 . A helical compression spring  74  mounted within the closed end of housing  60  reacts at one end with the support washer  76  and housing end wall  60   a  and at the other end with the adjacent end of the inner brush support member, thereby to bias the inner member outwardly to effect electrical contact between the extremities of the wire brush ropes  52  and the adjacent end face  32   e  of the hub portion of the rail wheel  32 . 
     At its other end, the inner brush support member  70  is provided with a conductive axial extension  70   a  that extends through an opening  80  contained in the housing end wall  60 . The shunt connecting means  50  includes a cable  51  connected at each end with the projecting portions  70   a  of the inner members  70  by connector means including bolt  80  and eyelets  82  and  84 . The cable  51  may include a shunt fuse  53 , if desired, for further safety protection. The inner member  70  is guided for axial displacement within housing  60  by transverse bolt means  86  that extend through diametrically opposed longitudinal slots  88  contained in the housing  60 , and a corresponding transverse through bore  89  (FIG. 6) contained in the inner member  70 . A grease fitting  90  mounted in an opening contained in the support housing  60  affords means for introducing lubricating grease into the space between the inner member  70  and the housing  60 . 
     It is important to note that in accordance with an important feature of the invention, the contact brushes  52  are biased by the compression springs  74  into continuous electrical contact with the adjacent end face  32   c  of the rail wheel  32 , thereby compensating for wear of the brushes during use. In order to replace or repair a brush  52 , the inner member  70  is displaced against the biasing force of the compression spring toward a retracted position relative to housing  60 , as shown in FIG.  7 . The inner member may be retained in this retracted position by inserting the legs of a cotter pin  94  into a transverse bore  96  contained in the projecting portion  70   a  of the inner member  70 . 
     The shunting system of the present invention may be used with a railway vehicle having only rail wheels that ride on the tracks, or with convertible vehicles having alternately operable pneumatic wheels and rail wheels for transporting the vehicle on the ground or on the tracks, respectively. Examples of the former application are bridge inspection vehicles, bridge crane equipment using railway tie handlers and inserters, maintenance trucks and track geometry trucks. Examples of the convertible type railway vehicles are those shown in the aforementioned Powell U.S. Pat. No. 4,488,494, and the Model 441-C convertible railway vehicle produced by Petibone Corporation of Chicago, Ill., illustrated diagrammatically in FIG.  8 . As shown in FIGS. 6 and 8, the rail wheel axle  40  is supported by the axle cover  44  that is pivotally connected by pivot  100  with the vehicle chassis. Hydraulic motor means  102  are connected with the vehicle chassis for lowering the rail wheels from their elevated position to the illustrated lowered position on the tracks  34 , thereby to raise the vehicle and its resilient wheels  104  upwardly from the ground  106 . Normally, when the vehicle is in the elevated position of FIG. 8, the vehicle is driven by the engagement between the resilient wheels  104  and auxiliary driven cylindrical extensions  108  on the rail wheels, as shown in phantom in FIG.  4 . 
     Instead of welding the brush support housing to the axle guard, it is appropriate that the shunting means could be connected by straps either to the axle cover members, or to other suitable parts of the vehicle. Furthermore, as shown in phantom in FIG. 4, the contact means  154  could be supported by the vehicle chassis for engagement with adjacent end faces of the rail wheels at locations spaced radially outwardly from the rail wheel hub portions. 
     Referring to FIG. 9, it will be seen that in cross section, the annular area defined by the twisted wire ropes  52  may initially be tapered to define a generally frusto conical end surface  53 , thereby to effect an improved initial contact with the associated end surface of the wheel. During extended use, the twisted wire rope brush is worn down to the level L, whereupon the brush is replaced as described above. 
     While in accordance with the provisions of the Patent Statutes the preferred forms and embodiments of the invention have been illustrated and described, it will be apparent to those skilled in the art that various changes may be made in the apparatus without deviating from the inventive concepts set forth above.