Abstract:
A locking system for trailer air brakes of the type having a supply air line with a gladhand. The locking system comprises a valve connected to the supply air line. The valve is actuatable between an open position, wherein the valve enables air conveyed in the supply air line to disengage the air brakes from the actuated position, and an exhaust position, wherein the valve exhaust air through an exhaust port thereof from the supply air line such that the air brakes remain in the actuated position. A locking device has a portion being automatically displaceable to a locking position when the valve is actuated to the exhaust position so as to lock the valve in the exhaust position, and being displaceable to a disarmed position by manual disarming means for unlocking the locking device and displace the valve to the open position.

Description:
TECHNICAL FIELD 
     The present invention generally relates to air brakes for trailers and, more particularly, to a system for locking the air brakes of a parked trailer detached from a tractor. 
     BACKGROUND ART 
     Air brakes have evolved over the years in tractor and trailer applications and have thus become safer. One such type of air brake uses two pneumatic circuits in Ad order to provide compressed air to the brakes for actuating them. These brakes are spring-loaded so as to be normally in an actuation position, i.e., such that a trailer has its brakes on when no compressed air is supplied to the brakes. When the trailer is connected to a tractor, a supply air line linking the trailer to the brake system of the tractor supplies compressed air to the brakes so as to disengage them, i.e., keep them in a retracted position. The tractor driver will then actuate the brakes of the trailer via a service air line, which also connects the tractor&#39;s brake system to the trailer. The combination of the service air with the springs of the air brakes will surpass the supply air of the supply air line to actuate the brakes of the trailer to the actuation position. The service air may then be exhausted to retract the brakes. This configuration of spring-loaded brakes with supply and service air lines provides an important safety characteristic to these air brakes: in the event of a failure to the supply air line, such as a leak therein, the brakes will be applied automatically. The connections between the tractor&#39;s brake system and the supply and service air lines are typically made by gladhands, which are well known air line connectors. The gladhands are typically positioned on both sides of a nose box at a front end of the trailer so as to be connected to the brake system thereof. When the tractor is coupled to the trailer, the supply lines from the tractor are connected to the nose box. 
     The air brakes utilize air lines which may easily be connected to the air brakes of a tractor. It is, therefore, relatively simple to steal a trailer. Obviously, this presents a plurality of problems, as the trailers are frequently filled with expensive merchandise, making them an attractive prey for thieves. Furthermore, with the quantity of tractors and trailers on the roads nowadays, stolen trailers may go virtually unnoticed. 
     Various devices and methods have been proposed in order to disable the trailer air brakes such that trailers detached from tractors cannot be stolen. One problem is that trailers very seldom have sophisticated controls nor electrical systems and, therefore, anti-theft devices are mainly mechanical. Although most of these locking systems provide adequate theft prevention, none describes a locking system which arms automatically, i.e., locking systems must be manually armed. An automatic-arming locking system has advantages, one of which is that it does not require that a driver remember to arm the locking system, as it is done automatically. Also, time is saved in the arming of the locking system. Finally, it will prevent the use of air supplies from another system or tractor to deactivate the spring brakes so as to steal the trailer. 
     SUMMARY OF INVENTION 
     Therefore, it is a feature of the present invention to provide an automatic-arming locking system for trailer air brakes to prevent theft of a trailer disconnected from a tractor. 
     According to a broad aspect of the present invention, there is provided a locking system for trailer air brakes of the type having a supply air line with a gladhand for being connected to an air supply from a tractor for disengaging the trailer air brakes from an actuated position. The locking system comprises a valve connected to the trailer supply air line. The valve is actuatable between an open position, wherein the valve enables air conveyed in the trailer supply air line to disengage the trailer air brakes from the actuated position, and an exhaust position, wherein the valve exhausts air through an exhaust port thereof from the trailer supply air line such that the trailer air brakes remain in the actuated position. The valve moves automatically to the exhaust position when the tractor air supply is disconnected from the gladhand so as to cause the trailer air brakes to be engaged in the actuated position. A locking device has a portion being automatically displaceable to a locking position when the valve is actuated to the exhaust position so as to lock the valve in the exhaust position, and being displaceable to a disarmed position by manual disarming means for unlocking the locking device and displace the valve to the open position. 
     According to a further broad aspect of the present invention, there is provided a method for automatically locking air brakes of a parked trailer in an actuated position, the trailer being of the type having a supply air line with a gladhand for being connected to an air supply from a tractor for disengaging the trailer air brakes from an actuated position. The method comprises the steps of i) providing a valve having a rod automatically displaceable to an extended position when a tractor air supply is disconnected from the gladhand of the trailer, with the rod interfering with the gladhand when displaced to the extended position, and a locking device for automatically locking the rod in the extended position; ii) disconnecting the tractor air supply from the gladhand to engage the air brakes in the actuated position, and simultaneously causing the rod to automatically move to the extended position to interfere with the gladhand; and iii) locking the rod in the extended position by the locking device automatically locking the rod in the extended position, whereby the rod interferes with the gladhand such that air cannot be reconnected to the supply air line for disengaging the trailer air brakes from the actuated position thereof unless the rod is unlocked. 
     A method for automatically locking air brakes of a parked trailer in an actuated position, the trailer being of the type having a supply air line with a gladhand for being connected to an air supply from a tractor for disengaging the trailer air brakes from an actuated position. The method comprises the steps of i) providing a valve in the supply air line automatically displaceable to an exhaust position when a tractor air supply is disconnected from the gladhand of the trailer, and a locking device for automatically locking the valve in the exhaust position; ii) disconnecting the tractor air supply from the gladhand to engage the air brakes in the actuated position, and simultaneously causing the valve to automatically move to the exhaust position; and iii) locking the valve in the exhaust position by an automatic displacement of the locking device, such that any air supplied to the supply air line is exhausted through the valve, whereby the trailer air brakes are locked in the actuated position unless the valve is unlocked. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     A preferred embodiment of the present invention will now be described with reference to the accompanying drawings in which: 
     FIG. 1 is a perspective view of a trailer with the automatic-arming locking system in accordance with the present invention; and 
     FIG. 2 is a front elevational view, partly fragmented, of an automatic-arming locking system of the present invention; 
     FIG. 3 is a front-side cross-sectional view of the air brake locking system. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     According to the drawings and, more particularly to FIG. 2, an air brake locking system in accordance with the present invention is generally shown at  10 . The automatic-arming locking system  10  is enclosed in a nose box N. As seen in FIG. 1, the nose box N is typically found on a front face of a trailer T, and comprises a supply air line gladhand G 1  and a service air line gladhand G 2 . Compressed air is supplied to the air brake line of the trailer through the supply air line gladhand G 1 , whereas the brakes are actuated by a compressed air signal through the service air line gladhand G 2 . As a safety feature, if the air pressure in the supply air line is exhausted, the brakes of the trailer will automatically engage. In this event, the brakes will only be released by repressurizing the supply air line. Therefore, when a trailer is detached from the tractor, the supply air line is depressurized by disconnecting a supply line of the tractor from the gladhand G 1  of the trailer. This ensures that the built-up pressure in the supply air line will be released and thus that the brakes are kept in an actuated position. The service air line is also disconnected and the tractor can leave the trailer in a stored and parked condition. 
     In the locking system  10  of the present invention, a valve V 1  is added to the trailer supply air line, downstream of the gladhand G 1 . The valve V 1  is typically a three-way valve with an exhaust position, wherein air enters the valve through an inlet port thereof to then be exhausted by the exhaust port, and an open position, wherein air goes through the valve to an outlet port. The valve V 1  has a rod  12  extending between a retracted position, wherein the rod  12  is kept retracted in the valve V 1  by the pressure in the supply air line, with the valve V 1  being in its open position, and an extended position, as illustrated in FIG. 2, when the supply air line is depressurized by the disconnecting of the gladhand G 1  from the tractor brake system. When the rod  12  is in the extended position, the valve V 1  is in an exhaust position, such that air supplied to the supply air line will exhaust through the valve V 1 . Accordingly, air will not reach the brakes, which will consequently remain in their actuated position. The valve V 1  is from, for instance, the Bendix PP-1 or PP-8 valve models. 
     Referring to FIGS. 2 and 3, the gladhand G 1 , as known in the art, has a connection surface  20  having a bore  21  in the middle thereof. The bore  21  is connected to the supply air line via a channel  23  in the gladhand G 1  and an elbow connector  22 , whereby air may be supplied to the air line. The gladhand G 1  has an ear  24  projecting downwardly from the connection surface  20 . The ear  24  defines a portion of an annular section and has a protrusion  26  and a guide portion  28  thereon. A cover plate  30  is positioned above the connection surface  20  and defines a gap  32  with the body of the gladhand G 1 . Normally, a corresponding gladhand from the tractor, for providing an air supply to the trailer service air line, may be connected to the gladhand G 1  by a corresponding connection surface thereof being applied to the connection surface  20  of the gladhand G 1 , and the tractor gladhand being rotated such that an ear, similar to the ear  24  of the gladhand G 1 , engages in the gap  32 , whereas a similar gap receives the ear  24  of the gladhand G 1 . The guide portion  28  is received in a corresponding groove in the cover plate of the tractor gladhand to ensure the securing of the gladhands. However, with the locking system of the present invention, a locking pin  50  emerges outwardly from the gladhand G 1  as soon as the supply line from the tractor is disconnected. The locking pin  50  may thereafter be retracted partially toward the gladhand G 1  to enable a corresponding gladhand to be connected thereto. However, the locking pin  50  is locked inside the nose box N to prevent the corresponding gladhand from being connected to the gladhand G 1 , and requires a key to be unlocked, to provide for the locking pin  50  to be retracted, as will be described in detail below. 
     The automatic-arming locking system  10  of the present invention requires the gladhand GL to be modified by providing a through bore  34 , concentrically positioned an the bore  21  of the gladhand G 1 . A counter bore  36 , having tapped walls  38 , is adapted for receiving a threaded end  40  of a cylindrical tube  42 . The cylindrical, tube  42  thus extends from the gladhand G 1  to the interior of the nose box N through a through bore in a lateral wall  45  of the nose box N. The opposed end  41  of the cylindrical tube  42  is also threaded and is connected to an inner box  46  within the nose box N. The valve V 1  is partially shown with its rod  12 . The locking pin  50  is connected to the rod  12  by a bushing  52 . The connection between the locking pin  50  and the rod  12  includes a compression spring  54 , which keeps the locking pin  50  biased away from the rod  12 . A second bushing  56  is positioned between the first bushing  52  and the threaded end  41  of the cylindrical tube  42 . An annular gap  58  is thus defined between the first bushing  52  and the second bushing  56 . The locking pin  50  extends through the cylindrical tube  42  and the gladhand G 1  so as to emerge perpendicularly from the connection surface  20  of the gladhand G 1 . 
     A locking device  60 , in the form of a key cylinder, has a spring-loaded dog  62  which is constantly upwardly biased. Therefore, when the rod  12  is in its extended position as shown in FIGS. 2 and 3, the annular gap  58  is in register with the dog  62  of the locking device  60 . Therefore, the dog  62  extends into the annular gap  58 , thereby preventing locking pin  50  from being retracted in the gladhand G 1  through the stroke of the rod  12 . 
     As the rod  12  of the valve V 1  reaches its extended position as soon as the gladhand G 1  and the corresponding gladhand of the tractor are separated from one another, the locking device  60  automatically releases to lock the locking pin  50  at its outermost position with respect to the gladhand G 1 . Therefore, an air supply cannot be connected to the supply air line via the gladhand G 1 , as the locking pin  50  disables the possibility of having a mating gladhand connected to the gladhand G 1 . Furthermore, the valve V 1  is stuck in its exhaust position through the rod  12  being held by the dog  62 , whereby, if the locking pin  50  were to be cut, air could not be applied to the supply air line as the valve is stuck in its exhaust position and air going through it would be exhausted by the exhaust port thereof. This is an important aspect of the present invention, and may be used even without the locking pin  50  interfering with the gladhand G 1 . The locking pin  50  may be broken off by a thief having appropriate equipment, whereas the valve V 1  and the locking dog  62  of the locking device  60  are protected in the nose box N and in the inner box  46 . Therefore, the valve V 1 , having an exhaust position in which it may be locked by the locking device  60 , may be used without the locking pin  50  as an independent locking system. It is understood that the valve V 1  is preferably inserted directly in the supply air line when connected to it. If the valve V 1  was connected in parallel to the supply air line, one could block the exhaust port of the valve V 1  to bypass the exhaust action of the valve V 1  on the supply air line. However, by having the valve V 1  directly on the supply air line, the valve V 1  must be in its open position for air to be supplied to the brakes, whereby the locking device  60  must be unlocked. 
     In order to retract the dog  62  in the locking device  60  to allow the rod  12  and locking pin  50  to retract for the connection of mating gladhands, a key K is required to be inserted into the cylinder  60  to retract the dog  62 . Furthermore, the locking system  10  is partially accommodated in the inner box  46 , which is sealed closed and of anti-theft construction so as to prevent the locking system  10  from being broken into. Therefore, when the gladhand G 1  is to be connected with the tractor gladhand, the dog  62  is retracted by operating the key K and the locking pin  50  is pushed in against the action of the valve V 1 . The compression spring  54  is provided for instances where the tractor gladhand, which is to be connected to the trailer gladhand G 1 , is too small to accommodate a portion of the locking pin  50  while being mated to the gladhand G 1 , i.e. the rod  12  of the valve V 1  cannot retract more. Accordingly, the compression spring  54  allows for the locking pin  50  to move inwardly toward the rod  12 , so as to allow the gladhands to be connected. 
     Also, the locking pin  50  has a seal on its outer periphery within the cylindrical tube  42 , so as to prevent air, which fills the gladhand G 1  when the locking system  10  is retracted, from escaping therefrom. It is pointed out that the locking system  10  of the present invention has no bearing on the operation of the tractor, with regards to the actuation of the trailer brakes. Once the trailer is hooked up to the tractor, the air brakes of the trailer as actuated by the tractor are operated the same as they were without the locking system  10 . The locking system  10  may be installed on the trailer without having to modify the configuration of the tractor brakes. 
     It is within the ambit of the present invention to cover any obvious modifications of the embodiments described herein, provided such modifications fall within the scope of the appended claims.