Magnetic rail brake

Abstract

A magnetic rail brake for a rail vehicle is disclosed of the type comprising a magnet ( 5 ) supported from the rail vehicle a small distance above the rail ( 4 ). The magnet is supported by springs which are overridden on actuation of the magnet. A guide assembly guides the magnet for movement in a substantially vertical plane while allowing limited lateral movement. The magnet is provided with an extension arm ( 20 ) arranged to contact the rail vehicle at a distance from the magnet which is substantially greater than either the maximum extent of vertical movement or the maximum extent of lateral movement. By controlling the motion of the extension arm within these limits of lateral and vertical motion, unwanted and excessive tilting of the magnet can be avoided.

1 . A magnetic rail brake for a rail vehicle comprising: 
 a magnet supported from the rail vehicle;    a guide assembly to guide the magnet for movement in a substantially vertical plane while allowing limited lateral movement; and    an extension arm, the extension arm arranged to contact the rail vehicle at a distance from the magnet which is substantially greater than either the maximum extent of vertical movement or the maximum extent of lateral movement of the magnet to thereby reduce tilting of the magnet.    
   
   
       2 . The magnetic rail brake according to  claim 1 , wherein the extension arm is rigidly attached to the magnet and extends generally therefrom.  
   
   
       3 . The magnetic rail brake according to  claim 1 , wherein the extension arm comprises a first stop surface for interacting with the rail vehicle to prevent tilting of the magnet in a first direction.  
   
   
       4 . The magnetic rail brake according to  claim 3 , wherein the extension arm comprises a second stop surface for interacting with the rail vehicle to prevent tilting of the magnet in a second direction opposite to the first direction.  
   
   
       5 . The magnetic rail brake according to  claim 1 , wherein the extension arm extends laterally outwardly away from a centreline of the rail vehicle.  
   
   
       6 . The magnetic rail brake according to  claim 1 , wherein the extension arm extends generally vertically.  
   
   
       7 . The magnetic rail brake according to  claim 1 , wherein the extension arm comprises two branches extending in different directions.  
   
   
       8 . The magnetic rail brake according to  claim 1 , wherein the extension arm comprises adjustable stop means.  
   
   
       9 . The magnetic rail brake according to  claim 1 , wherein the rail vehicle is provided with adjustable counterstop means.  
   
   
       10 . The magnetic rail brake according to  claim 1 , further comprising an actuation device causing the magnet to be attracted to a rail on which the rail vehicle travels.  
   
   
       11 . The magnetic rail brake according to  claim 10 , further comprising a tilt detection device adapted to prevent actuation of the actuation device on tilting of the magnet by more than a given angle.  
   
   
       12 . The magnetic rail brake according to  claim 1 , wherein the guide assembly comprises a laterally sliding pivot arranged on the rail vehicle and the extension arm is rigidly attached to the magnet and extends laterally to the sliding pivot whereby the magnet and extension arm can rotate around the pivot and slide laterally with respect to the rail vehicle.  
   
   
       13 . The magnetic rail brake according to  claim 12 , wherein the laterally sliding pivot comprises a profiled slot.  
   
   
       14 . The magnetic rail brake according to  claim 1 , wherein the guide assembly comprises a pivot arranged on the rail vehicle and the extension arm comprises an extendable arm, rigidly attached to the magnet and extending laterally to the pivot whereby the magnet and extension arm can rotate around the pivot and the extension arm can extend to allow lateral movement of the magnet with respect to the rail vehicle.  
   
   
       15 . The magnetic rail brake according to  claim 1 , wherein the magnet is constrained to tilt no more than 6° in either direction.  
   
   
       16 . The magnetic rail brake according to  claim 1 , wherein the magnet is constrained to tilt no more than 3° in either direction.  
   
   
       17 . The magnetic rail brake according to  claim 1 , wherein the magnet is supported from the rail vehicle by a suspension device comprising a compression or tension spring.  
   
   
       18 . The magnetic rail brake according to  claim 1 , wherein the magnet is supported from the rail vehicle a suspension device comprising an actuator device.  
   
   
       19 . A method of controlling the maximum permitted tilt of a magnet in a magnetic rail brake, the magnet being arranged for vertical and lateral movement, comprising attaching an extension arm to the magnet and controlling the movement of the end of the extension arm distant from the magnet, the length of the extension arm being substantially greater than either the maximum extent of vertical movement or the maximum extent of lateral movement of the magnet, to thereby control tilting of the magnet.  
   
   
       20 . (canceled)  
   
   
       21 . A rail vehicle movable along a rail, the rail vehicle comprising: 
 a magnet supported from the rail vehicle in close proximity to the rail;    a guide assembly for guiding the magnet for movement in a first direction towards and away from the rail while allowing limited lateral movement in a second direction;    an actuator for causing movement of the magnet in the first direction; and    an extension arm extending from the magnet the extension arm arranged to contact the rail vehicle at a distance from the magnet which is substantially greater than the maximum extent of movement of the magnet in either the first or second directions thereby reducing tilting movement of the magnet.