Abstract:
A railroad switch point indicator comprising a mounting plate mountable to a railroad switch point, a tubular housing mounted to the mounting plate, a piston slidably disposed in the housing and extendable to variably engage an associated railroad rail, a bias spring operatively connected to the piston for biasing the piston in an axial direction with respect to the housing and the railroad switch point, and a signal mechanism operatively connected to the piston for indicating the positional status of the switch point via an attitude of a signal flag. When the switch point is engaged with a rail, the flag is in a first attitude. When the switch point is disengaged from the rail, the flag is in a second attitude. When the switch point is positioned incorrectly, i.e., damaged, the flag may be in a third attitude intermediate between the first and second attitudes, indicating alarm.

Description:
TECHNICAL FIELD 
     The present invention relates to railroad switches for directing a train from a first set of rails to a second set of rails; more particularly, to visual indicators for informing a viewer of the positional status of a switch point in a railroad switch; and most particularly, to a system and apparatus for indicating independently the positions and conditions of both switch points in a railroad switch. 
     BACKGROUND OF THE INVENTION 
     It is well known in the prior railroad arts to provide a track arrangement including a main track and a side track, each comprising two parallel rails. The main track includes a fixed or through rail and a movable, tapering main switch rail having a main switch point, and the side track includes a fixed or side rail and a movable, tapering side switch rail having a side switch point. A switching mechanism facilitates directing of rolling stock through the switch by moving the movable switch rails to either of a first position or a second position. 
     In the first switch position, the switch directs trains along the main track by keeping the main switch point separated from the main rail (“open”) to allow train wheels to continue along the main rail, in either direction, and keeping the side switch point engaged with the side rail (“closed”) to prevent entry into the side track. 
     In the second position, the switch connects the main track to the side track by keeping the side switch point spaced apart from the side rail, to facilite entry into or exit from the side track, and the main switch point engaged with the main rail, to divert train wheels from continuing along the main rail, in either direction. (A separate arrangement known in the railroad arts as a “frog” cooperates with the switch to provide a fixed crossing for the second main rail and the second side rail at an appropriate distance from the switch mechanism.) 
     It is known in the prior art to provide a rotatable switch position indicator of the first and second positions, driven by the switch actuator beside the main track. In the first position, the indicator shows typically a green face to an approaching train engineer, indicating that the switch is set for main track travel; in the second position, the indicator shows typically a yellow face to an engineer, indicating that the switch is set for switching between the main track and the side track. In some known railroad systems, red or white is used for the side rail switch point rather than yellow. 
     As used herein, train travel through a switch in the direction wherein the through rail and the side rail diverge is defined herein as the first direction of travel, known in the railroad art as a “facing-point” movement. The opposite direction wherein the through and side rails converge is defined herein as the second direction of travel, known in the railroad art as a “trailing-point” movement. 
     It will be seen that in the first or facing-point direction of travel, on a main track entering a switch, the directing of a train is unambiguous, that is, the switch must be set in either main track or side track mode and the train will follow the switch points (when properly aligned and maintained) on the corresponding tracks accordingly. 
     It will be obvious that in a properly-functioning switch both points cannot be open at the same time, and that such a condition would lead to derailment of a train. Thus, a serious problem can arise when a train approaches a switch from the second direction in either of the possible trailing-point movements, on either the main track or the side track. If a switch is set for main line travel when a train attempts improperly to enter the main track from the side track, the weight and momentum of the train directed onto the wheel flanges will force open the closed side rail switch point by the width of the flange. This is known in the railroad arts as “running through the switch”. The main rail switch point typically is also displaced by a similar amount. However, the actuation mechanism is not moved, and the switch indicator still indicates that the switch is properly set for main track travel. Thus, the damaged switch is left in a dangerous state wherein neither switch point is fully engaged with its respective rail. The next engineer attempting to go through this switch will find that both the main rail and the side rail pathways are partially open. A train traveling into the switch on the main track in a trailing-point movement may be able to traverse the switch without derailing. Similarly, another train entering the main track from the side track, also in a trailing-point movement, will probably also be able to traverse the damaged switch. However, because the main and side rails diverge, a train traveling into the switch on the main track in a facing-point movement must become derailed. 
     Of course, a similar problem exists, for the same reasons and with the same results, when a train making a trailing-point movement on the main track enters a switch set for side track switching. In this case, the main rail switch point will be forced open, and a subsequent train making either a trailing-point movement from the side track or a facing-point movement along the main track will be derailed. 
     All railroads keep running counts of switch derailments, which are very large causes of lost time and profit, and the prestigious industry-wide Harriman Award is earned by the company having the lowest incidence of derailments. 
     Known in the art as Human Factors Incidents, derailments are held to be the result of human error, and railroad employees are expected to visually determine that a switch is correctly set and passable before a train enters the switch; however, a switch that has been damaged as just described can be very difficult to recognize from the cab of a moving engine, especially at night or under adverse weather conditions, and even if an engineer can see it he may not be able to stop the train in time. Because the industry assumption is that an engineer a) will be guided by the system of visual signals provided, and b) will not intentionally run through an incorrectly set switch, there is great interest in providing means by which engineers and yard personnel can determine visually from either direction, at a substantial distance and with great accuracy under any weather and lighting conditions, whether a switch is properly set and, preferably, whether a switch has been damaged by a previous inadvertent running through. 
     There are numerous inventions in the prior art intended to alert railroad personnel to this dangerous situation. 
     Several patents, such as U.S. Pat. No. 5,806,809 and U.S. Pat. No. 6,588,710, employ magnetic proximity sensors in systems to detect whether a switch point is in proper closed relationship to its respective rail. All such inventions require electric power for operation, either line power or solar storage or battery power, which brings a substantial added cost and risk of failure. 
     U.S. Pat. No. 7,735,784 is directed to a mechanical indicator system employing a rectangular sleeve disposed on a tie between the switch points and housing a reciprocating slide with reflectors, attached between both switch points, selected reflectors being visible through windows in the sleeve to indicate whether the switch points themselves are set in the main track or side track position. 
     This prior art system can be easily damaged by being struck by low-hanging air hose couplings between rail cars near the track middle. Further, the indicator windows are disposed relatively low between the rails and thus may not be easily seen from a relatively low angle along the track, especially under snowy conditions. Further still, if an associated switch is run through, the indicator system may also be damaged and subsequently present faulty signals which can lead to a derailment. 
     What is needed in the art is a simple, mechanical indicator assembly that can show unequivocally and accurately the position of a switch point in relation to its cooperating rail. 
     What is further needed in the art is a system employing a pair of such indicator assemblies mounted on both switch points of a switch to show the actual position of each switch point well in advance of passage by a train. 
     What is still further needed in the art is a system employing a plurality of such pairs disposed on sequential switches along a main track in a switching yard to show at a glance the settings and conditions of all the switch points. As used herein, “condition” should be taken to mean whether a switch point is correctly or incorrectly positioned with respect to its associated railroad rail. 
     It is a principal object of the present invention to prevent switch damage by preventing the inadvertent running through of switches set in the incorrect position. 
     It is a further and larger object of the invention to prevent train derailments at switches. 
     SUMMARY OF THE INVENTION 
     Briefly described, a railroad switch point indicator in accordance with the present invention comprises a base plate mountable to a railroad switch point; a housing attached to the base plate; a piston slidably disposed in an axial bore in the housing and extendable through the base plate to variably engage the side of an associated railroad rail when the base plate is mounted to a switch point; a bias spring operatively connected to the piston for biasing the piston in an axial direction with respect to the housing and the railroad switch point; and a signal mechanism having at least one rotatable component operatively connected to the piston for indicating the positional status of the piston and hence the switch point via an attitude of a movable signal flag. 
     The piston may be urged in opposite first and second directions within the housing. When the switch point is disengaged from the associated rail, the piston is urged fully in a first direction, positioning the signal flag in a first attitude to indicate such disengagement (switch point is open). When the switch point is engaged with an adjacent railroad rail, the piston is urged fully in a second and opposite direction, positioning the signal flag in a second attitude to indicate such engagement (switch point is closed). When the switch point is positioned incorrectly and intermediately between the engaged position and the disengaged position, as can happen if the switch has been run through and damaged, the signal flag may be in a third and alarm attitude intermediate between the first and second attitudes, indicating that the switch point is improperly positioned, may cause a derailment, and needs immediate adjustment. 
     In some applications, it can be desirable that the disengaged attitude is shown when the switch point is open by only a fraction of an inch, and the engaged attitude is shown only when the switch point is closed or very nearly closed. In such applications, a switch that has been run through and damaged will show both the main rail switch point flag and the side rail switch point flag in the switch-point-open attitude simultaneously, indicating a dangerous condition of the switch that must be corrected before passage of a train through the switch. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
         FIG. 1  is a plan view of a typical railroad switch operable between a main track and a side track; 
         FIG. 1   a  is an elevational longitudinal cross-sectional view of a first embodiment of a railroad switch point indicator assembly in accordance with the present invention, mounted to a railroad switch point and showing the mechanism in both first and second positions, and the signal flag in both first and second attitudes; 
         FIG. 2  is a transverse cross-sectional view taken along line  2 - 2  in  FIG. 1   a;    
         FIG. 3  is a side elevational view of a second embodiment in accordance with the present invention, showing the flag in the first attitude; 
         FIG. 4  is a first isometric view of the embodiment shown in  FIG. 3 ; 
         FIG. 5  is a second isometric view of the embodiment shown in  FIG. 3 , showing the flag in the second attitude; 
         FIG. 6  is a cross-sectional plan view of a third embodiment in accordance with the present invention; and 
         FIG. 7  is a cross-sectional plan view of a fourth embodiment in accordance with the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIG. 1 , a typical railroad switch  10  is shown. In a first switch position, as shown, switch  10  directs trains along the main track  12  by keeping main switch point  14  separated from the main rail  16  (“open”) to allow train wheels (not shown) to continue along main rail  16 , in either direction, and keeping side switch point  18  engaged with side rail  20  (“closed”) to prevent entry into side track  22 . 
     In a second and alternative position (not shown), switch  10  connects main track  12  to side track  22  by keeping side switch point  18  spaced apart from side rail  20 , to facilite entry into or exit from side track  22 , and main switch point  14  engaged with main rail  16 , to divert train wheels from continuing along main rail  16 . (A separate arrangement  24  known in the railroad arts as a “frog” cooperates with switch  10  to provide a fixed crossing for second main rail  26  and second side rail  28  at an appropriate distance from the switch mechanism  30 .) 
     It is seen that a train making a trailing-point movement from side track  22  into switch  10  when set for main track travel as shown in  FIG. 1 , i.e., running through the switch, must force open side switch point  18  from side rail  20 , by bending and damaging mechanism  30 , in order to pass through the switch. The opposite train wheels will be forced to jump over main switch point  14  onto main rail  16 . Switch  10  will be left damaged, with both switch points open. 
     Similarly, when switch  10  is set in the side track position, a train making a trailing-point movement from main track  12  into switch  10  must force open main switch point  14  from main rail  16  in order to pass through the switch. The opposite train wheels will be forced to jump over side switch point  18  onto side rail  20 . Again, switch  10  will be left damaged, with both switch points open. 
     Referring to  FIGS. 1   a  and  2 , a first embodiment  100  is shown of a railroad switch point indicator assembly in accordance with the present invention, for mounting to a railroad switch point  111 . Embodiment  100  comprises a longitudinal cylindrical housing  110  having a smooth cylindrical bore  112  for receiving a reciprocable piston  114 . Preferably, housing  110  is male threaded  116  along an end portion thereof to facilitate mounting to an indicator base plate  118  via a base plate bore  120  and locking nuts  122 . (Alternatively, bore  120  may be female threaded (not shown), obviating the need for one of nuts  122 .) This arrangement permits adaptation of indicator assembly  100  to various opening gaps of various railroad switches to which indicator assembly  100  may be mounted for use, by which adaptation all such switches may be made to provide an identical stroke of piston  114  in bore  112 . Piston  114  is urged to the position shown in  FIG. 1   a  (first position) by spring  124  which is captured within bore  112  between piston  114  and housing end plate  126 . When a switch point (not shown) to which indicator assembly  100  is mounted is closed against an associated railroad rail (not shown), piston  114  is displaced along its longitudinal axis  115  to travel point  128  (second position), thereby compressing spring  124 . When the switch point subsequently is opened from engagement with the rail, spring  124  returns piston  114  to its initial position  129 . 
     It will be obvious to one of ordinary skill in the art that in an alternative embodiment of embodiment  100 , spring  124  may be captured on piston end  114   a  outside of housing  110  by compressing the spring and securing it to piston end  114   a  via a pin inserted through the piston end, e.g., such an arrangement is shown in  FIG. 3  for second embodiment  200 . 
     Housing  110  is provided with at least one helical slot  130  that begins in a radially vertical position  132  and is rotated either clockwise or counterclockwise through preferably a 90° central angle of housing  110  to a radially horizontal position  134  over precisely the stroke distance of piston  114 . Preferably, two such helical slots  130   a , 130   b  are provided, diametrically opposed. It will be seen that a pin  136  fixed in a transverse bore  138  in piston  114  and extending through opposed slots  130   a , 130   b  will cause piston  114  to be rotated 90° over the duration of its stroke. Longitudinal axis  115  thus defines a first Cartesian axis  50  ( FIG. 1 ) of rotation in accordance with the present invention. When indicator  100  is correctly mounted to a switch point, first axis  115  is horizontally transverse of the railroad track. 
     Alternatively, piston  114  may be bent 90° to form pin  136  integral with piston  114 . 
     A signal flag  140  fixed to pin  136  is displayed vertically in a first attitude  142  to indicate correct disengagement of the switch point from the associated rail. When the switch is closed and piston  114  is stroked, pin  136  and flag  140  are rotated 90° about first axis  115  to a second attitude  144 , indicating correct engagement of the switch point with the associated rail. 
     Preferably, signal flag  140  is provided with first and second flanges  146   a , 146   b  extending orthogonally from the surface edges thereof, which flanges serve to shield from view the upper reflective surface of signal flag  140  from the low-angle perspective of an approaching railroad engine when signal flag  140  is in second attitude  144 , ensuring that the flag surface cannot be seen and thus mislead. 
     Signal flag  140  preferably is provided with a highly reflective surface on both sides to make it readily visible from a distance in either direction along a railroad track. When indicator  100  is used on a main rail switch point, signal flag  140  must be colored green in accordance with railroad industry standard; when indicator  100  is used on a siding rail switch point, signal flag  140  must be colored differently, as described below. 
     In a further refinement (not shown), optionally signal flag  140  may be electrically illuminated by any of various known illumination means and methods, either on signal flag  140  itself or shined onto signal flag  140 . 
     To shield slots  130   a , 130   b  and pin  136  from the weather, preferably a cylindrical sliding cover  148  attached to pin  136  is provided around housing  110 . Cover  148  thus reciprocates and rotates with pin  136  and piston  114 . 
     Referring now to  FIGS. 3 through 5 , a second embodiment  200  of a railroad switch point indicator assembly in accordance with the present invention is shown. Embodiment  200  comprises a longitudinal cylindrical housing  210  having a smooth cylindrical bore  212  for receiving a reciprocable piston  214 . Preferably, housing  210  is male threaded and mounted to base plate  218  as described above for embodiment  100 . Piston  214  is urged to the position shown in  FIG. 3  (first position) by coil spring  224  which is captured between a first end  211  end of housing  210  and a pin  213  disposed in a traverse bore in piston  214 . When a switch point (not shown) to which indicator assembly  200  is mounted is closed against an associated railroad rail (not shown), piston  214  is displaced along its longitudinal axis  215 , thereby compressing spring  224 . When the switch point subsequently is opened from engagement with the rail, spring  224  returns piston  214  to its initial position. 
     Housing  210  is provided with a cylindrical housing extension  230  that may be a separate part attached thereto as by threaded connection. Extension  230  includes a vertical slot  232  for receiving a tab  234  rotatably connected to an end of piston  214  as by a rivet or pin  236 . Tab  234  may support a separate signal flag (not shown) or may itself be a signal flag  240  as shown in  FIGS. 3-5 . 
     In operation, when the switch point is open, the piston is urged fully to the left (first position) by spring  224 , as in  FIG. 3 , thereby seating side  241  of signal flag  240  against the bottom of vertical slot  232 . Signal flag  240  is displayed vertically in a first attitude  242  to indicate correct disengagement of the switch point from the associated rail, as shown in  FIG. 4 . When the switch is closed and piston  214  is stroked to its second position, signal flag  140  is forced outwards in slot  232  and rotates by gravity about axis  215  parallel to second Cartesian axis  60  ( FIG. 1 ) orthogonal to first Cartesian axis  50  to a second attitude  244 , indicating correct engagement of the switch point with the associated rail, as shown in  FIG. 5 . (Note: spring  224  is omitted from  FIGS. 4 and 5 .) 
     Referring now to  FIG. 6 , a portion of third embodiment  300  of a railroad switch point indicator assembly in accordance with the present invention is shown; for brevity, the base plate and mounting means are omitted but should be considered as being similar to apparatus shown for embodiments  100 , 200 . 
     Embodiment  300  comprises a longitudinal cylindrical housing  310  having a smooth cylindrical bore  312  for receiving a reciprocable piston  314 . Preferably, housing  310  is male threaded and mounted to a base plate substantially as described above for either of embodiments  100 , 200 . Piston  314  is urged to the position shown in  FIG. 6  (first position  329 ) by a coil spring substantially as described above for either of embodiments  100 , 200 . When a switch point (not shown) to which indicator assembly  300  is mounted is closed against an associated railroad rail (not shown), piston  314  is displaced along its longitudinal axis  315  to second position  328 , thereby compressing the coil spring. When the switch point subsequently is opened from engagement with the rail, the coil spring returns piston  314  to its initial position  329 . 
     A mounting bracket  360  is mounted to housing  310 . A pin  362 , disposed in a bore in bracket  360 , rotatably supports a pinion gear segment  364  having teeth  366  over at least a 90° central angle. Piston  314  is provided with a rack gear  368  extending over a portion of the length of the piston and meshing with gear segment  364  such that travel of piston  314  between positions  328  and  329  serves to rotate gear segment  364  either about or with pin  362  through a 90° rotation. Signal flag  340 , fixed to pin  362  or gear segment  364 , is displayed vertically in a first attitude  342  transversely of an associated railroad rail (not shown) to indicate correct disengagement of the switch point from the associated rail. When the switch is closed and piston  314  is stroked, pin  362  and flag  340  are rotated about axis  315  parallel to third Cartesian axis  70  orthogonal first and second Cartesian axes  50 , 60  to a second attitude  344  parallel to the associated railroad rail, becoming invisible from the associated track in either direction and thereby indicating correct engagement of the switch point with the associated rail. 
     Referring to  FIG. 7 , a portion of an embodiment  400  alternative to third embodiment  300  is shown. 
     Embodiment  400  comprises a longitudinal cylindrical housing  410  having a smooth cylindrical bore  412  for receiving a reciprocable piston  414 . Preferably, housing  410  is male threaded and mounted to a base plate substantially as described above for either of embodiments  100 , 200 . Piston  414  is urged to the position shown in  FIG. 7  by a coil spring substantially as described above for either of embodiments  100 , 200 . When a switch point (not shown) to which indicator assembly  400  is mounted is closed against an associated railroad rail (not shown), piston  414  is displaced along its longitudinal axis  415  to position  428 , thereby compressing the coil spring. When the switch point subsequently is opened from engagement with the rail, the coil spring returns piston  414  to its initial position  429 . 
     A mounting bracket  460  is mounted to housing  410 . A pin  462 , disposed in a bore in bracket  460 , rotatably supports a pivotable lever arm  464  having a slot  466 . Piston  414  is provided with a pin  468  extending into slot  466 . Travel of piston  414  between positions  428  and  429  serves to rotate lever arm  464  through a 90° rotation. As in embodiment  300 , signal flag  440  fixed to lever arm  464  is displayed vertically in a first attitude  442  transversely of an associated railroad rail (not shown) to indicate correct disengagement of the switch point from the associated rail. When the switch is closed and piston  414  is stroked, lever arm  464  and flag  440  are rotated about third axis  415  to a second attitude  444  parallel to the associated railroad rail, becoming invisible from the associated track in either direction and thereby indicating correct engagement of the switch point with the associated rail. 
     Note that in each embodiment  100 , 200 , 300 , 400 , correct operation of the associated switch point with respect to its associated railroad rail is indicated by one or the other extreme position of the piston and its associated signal flag. It is a very important advantage of the present invention that any of these embodiments will show that a switch has been damaged by a run through. Because a run-through leaves the switch point in an intermediate position between fully open and fully closed, which unacceptable open spacing may be as little as a fraction of an inch, the stroke of the piston will be stopped somewhere between the extremes x 28  and x 29  described above. The result will be that the signal flag may be stopped in a third attitude intermediate between first and second correct attitudes x 42  and x 44  described above, which intermediate attitude is an alarm attitude indicating that the switch point is improperly positioned and can cause derailment of the next train to pass through the switch. 
     In some applications, it can be desirable to adjust the action of each of the switch point indicators such that the switch-open attitude of the signal flag is displayed when the switch point is open by as little as a fraction of an inch, as can occur when the switch has been run through and damaged. In such case, the signal flags of both switch points will show a switch-open attitude. Since in a properly-functioning switch, both flags are never visible (switch-open attitude) at the same time, an engineer seeing both flags of a switch will know immediately that the switch is damaged and a derailment can occur. 
     A railroad switching yard comprising first and second railroad switch point indicators on all the switches defines a system for reducing railroad derailments at switches. Each switch is provided with two switch point indicators, one indicator having a green signal flag being mounted on the main-rail switch point, and the other indicator having a different colored signal flag being mounted on the side-rail switch point. In various railroad systems, the known side track indicator may be yellow, red, or white. An engineer entering the switching yard on a main track can tell immediately and at a glance a) whether all switch points are in proper adjustment and repair, and b) which side tracks if any are enabled, indicated by the green flag visible and the differently colored flag not visible. Likewise, an engineer entering a main track from a side track can tell a) whether the switch points ahead are in proper adjustment and repair, and b) whether the switch is properly set to enable such entry and thereby avoid a destructive run-through of an incorrectly set switch. With diligent attention by all engineers and switch yard personnel to switch point indicator positions and conditions, all derailments resulting from running through incorrectly-set switches can be avoided, at great savings to the railroad company and improved personnel safety. 
     While the invention has been described by reference to various specific embodiments, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the described embodiments, but will have full scope defined by the language of the following claims.