Patent Publication Number: US-6338534-B1

Title: Theft prevention system for trailers

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not applicable. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     BACKGROUND OF THE INVENTION 
     The present invention principally relates to theft prevention systems for trailers, particularly those used in a over-the-road tractor-trailer vehicle combination commonly referred to as an “18-wheeler”. These trailers are almost universally provided with pneumatic braking systems which include a parking/emergency brake with brake shoes or other braking elements urged to the braking position by spring means in the absence of pneumatic pressure supplied to the braking system. 
     In this common arrangement, a parked trailer, being disconnected from the tractor vehicle with its source of air pressure will have its parking/emergency brakes (hereinafter simply “parking brakes”) urged to fill braking position preventing the trailer from rolling or being moved. However, the commonly provided system can be moved by any standard tractor vehicle having the usual air hose and electrical connections for a trailer. Once the alien tractor is connected with its air hoses to the trailer and the trailer braking system is pressurized, the parking brakes air pressure causes the spring forces to be overcome so that the parking brakes are no longer applied. 
     Numerous expedients have been employed to prevent or deter theft of a parked trailer, including systems which require some action in addition to connecting air pressure to the pneumatic brake system to release the parking brakes. Some of the theft deterrent systems incorporate a solenoid valve in the appropriate air line between the tractor and the trailer rear wheels and have a key lock switch or other device required to energize the solenoid. The valve will open when the key switch is closed to allow air pressure from the tractor to release the brakes on the wheels of the trailer (as it would if the valve were not present). These prior systems typically drew current for the solenoid from the electrical cable providing power to the trailer lights, and thus some portion of the conductors of that cable needed to be connected and energized, but this in itself was not an anti-theft feature since this would occur in the course of normal procedure by the truck driver. 
     Systems as described above are shown, for example, in U.S. Pat. No. 4,793,661 and U.S. Pat. No. 4,712,422 to Dougald, G. Munro. In these patents, the theft of the trailer is deterred by operation of a solenoid valve by a key operated switch on the trailer. Rather than being a key switch, the switch may take the form of a keyboard module switch operable only by a person in possession of the required key code. Note that the key-operated switch is on the trailer, and only standard equipment connections from a tractor are required so that an alien tractor can take the trailer if the operator is in possession of a key or a key code. U.S. Pat. No. 4,691,801 to Yale Mann and Pekka Sarssi describes a vehicle protection device which, in addition to a fuel valve block and other features, also has a parking brake lock for trailer brakes; all of these are operated by a portable infra-red transmitter (rather than the key operated switch or keyboard module switch of the Munro patents). U.S. Pat. No. 5,378,929 to Yitzchak Mor and Daniel Yuranyi describes a somewhat more complicated system of valves and alarms than those discussed above whereby the system can be manually activated using a hand-held remote control transmitter and receiver (or a hard-wired switch) located somewhere in the trailer. 
     U.S. Pat. No. 4,621,874 to Jan Gustafsson is a vehicle theft preventing device for brakes operated with compressed air having a particular valve system and which requires the operation of a code lock on the trailer to release the brakes by pressing the correct code to adjust a valve to release the brakes. U.S. Pat. No. 3,735,834 to Daniel A. St. Onge describes a brake locking system with a key operated mechanism on the trailer required to close a normally open relay by use of a proper key; the valves of the system cannot be operated to admit air pressure to release spring force applying the brakes without such a proper key even though air pressure and EMF (through an electric cable) are connected to the vehicle. 
     Other patents relevant to the background of the invention and to the state of the art are U.S. Pat. No. 4,519,653 to Paul B. Smith and U.S. Pat. No. 4,881,388 to Ronald Pruim. 
     In addition to use of key-operated switches, numeric keypads for entry of key codes, or combination switches that may be used to generate a locking or unlocking signal in a vehicle security device, there are other security applications in which unauthorized operation is controlled by provision of a card reader which identifies an ID card of an operator seeking to operate the device. Such apparatus for management of the operation of a centrifuge is shown In U.S. Pat. No. 5,871,435 to Satoshi Numata, et al. Portions of such apparatus may be employed in an ID card reader version of Applicant&#39;s invention. As evidencing the state of the art relevant to the enablement of Applicant&#39;s disclosure, the Numata et al. patent and the other relevant patents above are to be considered incorporated by reference here. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention is directed to a theft prevention system for tractor-trailer transport vehicles. In particular, such trailers usually employ an air brake system using two air lines where one parking air line controls the trailer&#39;s parking/emergency brakes and another system air line controls the regular operating brakes. Air supplied by an air pressure supply means at the tractor controls both brake systems. In accordance with DOT specifications, the emergency brakes should set automatically when the trailer is parked and/or the air supply is disconnected. A major problem as mentioned above is that the thieves, if not otherwise deterred, can steal an entire parked trailer by coupling a tractor to the trailer, releasing the parking brakes in the customary manner, and driving away with the trailer in tow. 
     While previous anti-theft systems have provided locking means for parked trailers which prevented the release of parking brakes, the present invention has advantages and special features which primarily relate to a regimen of preventing alien tractors not belonging to a trucking company from releasing the parking brake in a trailer belonging to a trucking company equipped with the system of the present invention. The receiver and solenoid valve of the present invention are responsive only to a special transmitter installed in an authorized tractor. Thus, only authorized tractors can couple to and successfully deactivate the parking brakes. Although a wireless transmitter in a tractor may be utilized to transmit the signal to release the parking brakes, it is preferred that a signal be transmitted over existing conductors in the electric cable connected to the trailer for controlling and powering the lighting of the trailer. Numerous types of signaling may be employed including DC, AC, audio frequency and radio frequency transmission. The coding of the signal required by the receiver to actuate the solenoid valve to release the emergency brakes can be as complex as desired to prevent would-be thieves from sending a false signal not originating from an authorized tractor to release the trailer brakes. In a preferred embodiment, the electrical and pneumatic components of the system are configured so that continued receipt of the parking brake release signal is not required as long as air pressure to the trailer is maintained above a minimum value and the electrical power to the lighting system or theft prevention system are not interrupted. 
     Another optional feature of the system requires that the driver of the truck have a key, key code, or key card to activate the transmitter rather than to simply flip a switch in the tractor cab. This gives additional security that upon gaining access to the tractor cab, one cannot release the tractor brakes without having a necessary key, key code or key card. 
     In accordance with another optional feature of the system, the receiver and the decoder forming a part thereof may require that several or all of the trailer light circuits be energized to operate the solenoid brake release valve. Thus the driver could be required to test the lights before releasing the brakes. A more sophisticated version may require that trailer lighting circuits be energized in a particular sequence. In the latter case, this could operate as an additional “code” making the theft of the trailer using an unauthorized tractor more difficult. The present theft prevention system has an advantage over previous systems in that it does not require removal, replacement or modification of the standard trailer air brake system. It does not interact with the service line for the regular operating brakes at all and requires only the insertion of a solenoid valve in the parking air supply line which can be conveniently done near the point where such air line enters the trailer. The theft prevention receiver unit of the present invention also requires a simple connection to two or more conductors of the standard electrical cable connected to the trailer to supply power to the various lighting circuits. The transmitter in the tractor cab only requires connection to the electrical system of the tractor, preferably being connected into a circuit or circuits for the trailer lights. If desired, the trailer solenoid may be provided with a bypass air line and a manual control valve so that the theft prevention system can be effectively disabled if necessary without requiring the services of a technician. Of course, the bypass manual valve would have to be locked and/or within a locked cabinet. Preferably the trailer receiver and solenoid valve are positioned in a locked cabinet to deter a thief from “hot-wiring” or otherwise defeating the theft prevention system. 
     In addition to providing the features and advantages described above, it is an object of the present invention to provide a theft prevention system for tractor-trailer transport vehicles that is implemented without modification of trucks or trailers other than by adding a transmitter in the tractor cab and a receiver and solenoid valve in the trailer leaving the air line connections and electrical cable connections without modification and allowing the tractor to be coupled to the trailer in conventional fashion. 
     It is another object of the present invention to provide a theft prevention system in which an operator of an authorized tractor-trailer can connect a trailer to the tractor in customary fashion and, by activating a transmitter within the cab, proceed to release the parking brakes in the customary manner in a simple and expeditious manner. 
     It is yet another object of the present invention to provide a theft prevention system for trailers in which normally locked parking brakes in compliance with DOT specifications require for brake release that a signal be transmitted to a receiver in the trailer by activating a transmitter in the cab and the action required by the driver to activate the transmitter is wiping a suitably encoded magnetic strip card through a card reader in the cab. 
     It is a further object of the present invention to provide a theft prevention system for trailers having a solenoid valve in a trailer air line which must be open to release the trailer parking brakes wherein the solenoid valve has an integral pneumatic latch so that once opened by the solenoid, the valve is open as long as pressure is applied to the trailer parking brake air line. 
     It is a still further object of the present invention to provide a theft prevention system for trailers having a solenoid valve controlling release of the parking brakes is activated to release the brakes only upon energization of a plurality of the lighting circuits for the trailer. 
     Further objects and advantages of the present invention will be understood by those skilled in the art by reference to the following description and the appended drawings. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     FIG. 1 is a partially schematic side view of a tractor-trailer transport vehicle having an anti-theft system according to the invention; 
     FIG. 2 is a schematic diagram of a conventional trailer pneumatic brake system having a solenoid valve and associated receiver connected to control the air supply in the parking brake air line; 
     FIG. 3 is a schematic, partially sectional view of a solenoid valve particularly adapted for use in a system of the present invention, in the closed position; 
     FIG. 4 is a schematic, partially sectional view of a solenoid valve particularly adapted for use in a system of the present invention, in the open position; 
     FIG. 5 is a schematic diagram partially broken away showing within a locked cabinet the solenoid valve of FIGS. 3 and 4 wherein a manually valved bypass is provided for the solenoid valve. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings, and particularly FIG. 1, a trailer transport vehicle is shown including a tractor  8  with a cab  10  and a trailer  11  to which the theft prevention system for trailers according to the invention is applied. Typically the invention will be applied to a tractor-trailer transport vehicle  6  of a common type referred to as an “18-wheeler”. Although the invention is particularly adapted to such tractors and semi-trailers, it may be used with any truck/trailer combination in which the trailer has air brakes and a pneumatic system supplied with pressurized air from the tractor or truck pulling the trailer. 
     Trailer  11  is equipped with a conventional pneumatic braking system which includes brakes and brake control valves (not shown in detail) at  16  for the wheels on the two trailer axles. Conventionally connected air hoses  13  and  14  constitute an air pressure supply means including a service air supply line and a parking air supply line, respectively. 
     A conventional electrical cable  12  provides power and control for the lights of the trailer and also is adapted to power a solenoid valve  17  and a signal receiver  18  of the theft prevention system. Preferably, the solenoid valve  17  and the signal receiver  18  are secured in a limited access cabinet  25  provided with a key lock or other means to limit access only to those authorized to perform maintenance or repair or the like. Normally the input to the solenoid valve  17  will be connected to the parking air supply line  14  while the output of the solenoid valve  17  will be connected to a parking brake air line  15  whereby the pressure in the parking brake air line is in part controlled by the solenoid valve  17 . It will also be noted that electrical cable  12  connects to the receiver  18  (in addition to providing power for the trailer lights in a manner not shown). Thus, two or more conductors of cable  12  are available to provide power to receiver  18  which in turn powers the solenoid valve  17 . 
     As previously discussed, an important feature of the preferred embodiment of the invention is that the solenoid valve  17  and the receiver  18  cannot be operated by the driver of a tractor which has not been equipped with a transmitter  22  to cooperate with the theft prevention system. In the cab  10  of tractor  8  is installed transmitter  22  which transmits a coded or otherwise appropriate signal to receiver  18  to effectuate release of the parking brakes by operation of solenoid  17 . Preferably, electrical cable  12  is connected to transmitter  22  so that the signal to receiver  18  is transmitted on cable  12  and only on cable  12  using two or more of the conductors in that cable. Transmitter  22  is provided with a driver control element  21  which in a simple form of the invention could be a push button or lever switch for sending a DC, AC, audio frequency, or radio frequency signal to receiver  18 . Obviously, it is desirable that the signal sent be sufficiently complex or encoded to prevent a false or counterfeit signal easily being injected into cable  12  to release the parking brakes of trailer  11 . 
     In most cases it will be preferable that driver control element  21  provides extra security by requiring a conventional key to operate the switch or have the form of some access-limiting device such as a magnetic strip card reader, an optical card scanner, fingerprint scanner, a numerical touch pad, computer microchip controlled, or computer interfaced with onboard computer to initiate the signal from transmitter  22  to receiver  18 . When interfaced with an onboard computer communicating by satellite with a base station, two-way coupling between driver control element  21  and onboard computer makes data on operator ID, etc. available at the base station and, optionally, permits remote control of brake release over the satellite link. 
     It will be understood that driver control element  21  may be represented by any of these access-limiting devices as well as by a simple push button or key lock switch. By way of example, driver control element  21  may take the form of a magnetic strip card reader and associated data processing means as shown and described in the U.S. patent to Numata et al., U.S. Pat. No. 5,871,435 for Centrifuge Management System. 
     FIG. 2 shows a schematic diagram of a typical conventional pneumatic truck/trailer braking system with the addition of a solenoid valve  17  and a receiver  18  to implement the theft prevention system according to the present invention. The service line  13  for normal braking in on the road operation connects to emergency relay valve assemblies  31  from which service line branches  34  lead to the respective spring brakes  35  which actuate friction braking elements such as brake shoes or the like (not shown in FIG.  2 ). 
     As previously described, parking air supply line  14  is connected to the inlet of solenoid valve  17  and the air pressure communicated by parking air supply line  14  through solenoid valve  17  when open is imparted through parking brake air line  15  to parking/emergency relay valve assemblies  31  and thence through parking air branch lines  33  to appropriate inlets of spring brakes  35 . Although a solenoid valve such as  17  could also be utilized in service line  13 , it is preferred that the service line and the related normal operation of the brakes for decelerating on the road shall not be modified in any way and that normal braking be totally unaffected by addition of the theft prevention system of the present invention. 
     It will be noted that, as previously mentioned, receiver  18  preferably receives both power and control signals through cable  12  already present for transmitting power to the trailer lights. As few as two of the half dozen or so conductors in the common form of electrical cable  12  may actually be connected to the receiver  18 . Alternatively, a greater number or all of the conductors may be so connected. As shown in FIG. 2, the cable  12  from the tractor has a continuation cable  19  which is routed to the trailer lighting in normal fashion. 
     A preferred form of solenoid valve  17  is shown schematically in FIG.  3  and FIG. 4 with FIG. 3 showing the valve closed causing the parking brakes to be applied while FIG. 4 shows the valve open and latched to release the parking brakes by supplying air pressure to the parking brake air line from the parking air supply line. 
     Solenoid valve  17  is provided with a conventional solenoid actuator  41  having a winding  43 . Solenoid valve  17  has an inlet  44  which is provided with a suitable hose connector (not shown) to receive parking air supply line  14 . Similarly, an outlet  45  is provided with a suitable connector (not shown) for connecting parking brake air line  15 . Inlet  44  leads to a chamber  47  which, in the position shown in FIG. 3, is closed by disc  49  urged upward by spring  55 . It will be noted that in the position shown in FIG. 3 a vent  57  is open so that outlet  45  communicates with the atmosphere, thereby bleeding off any pressure that might exist in parking brake air line  15 . When solenoid  41  is activated by a current to windings  43  from receiver  18  in response to a signal received over cable  12 , solenoid armature  53  extends as shown in FIG. 4 causing valve stem  51  to move disc  49  to close the vent  57  while opening a passage from inlet  44  to outlet  45 . This causes the pressure present at inlet  44  (at least about 100 psi) to be communicated to the parking brake air line  15  allowing release of the trailer brakes. The extension of armature  53  also opens a path between a pilot chamber  61  and chamber  47 . The pressure in pilot chamber  61  is caused to be the same as that at outlet  45  by the pilot channel  59 . 
     While in the open position, shown in FIG. 4, solenoid valve  17  is latched open as long as a predetermined minimal pressure is present in chamber  47  sufficient to overcome the force of spring  55 . Preferably, the spring constant of spring  55  is determined to allow the spring force to be overcome if the pressure differential between chamber  47  and the atmosphere at vent  57  is greater than 15-25 pounds psi. Thus, it will be seen that in usual operation, the solenoid valve  17  will cause the path therethrough to remain open as long as pressure of approximately 20 lbs. Psi, but when the source of the pressure is disconnected, spring  55  will cause the valve to close and it cannot thereafter be opened without an appropriate signal received at receiver  18  to operate the solenoid  41 . 
     FIG. 5 shows cabinet  25  for preventing unauthorized access to the receiver  18  and the solenoid valve  17  and also shows an alternative embodiment of the invention including a manual bypass to permit the brake system to function as if the theft prevention system were not present, as may be desired for purposes of maintenance, repair, or other contingencies. 
     Cabinet  25  may be of conventional form with hinges  27  and a key lock  29  with whatever degree of security against intrusion might be desired. For simplicity, solenoid valve  17 , solenoid  41  and receiver  18  are shown without the electrical cable connection that would be present to power solenoid  41  and receiver  18 . In FIG. 5 a bypass line  71  provides a path around solenoid valve  17  and a two position valve  73  is connected in line  15 . In the position shown in FIG. 5 all air flow is through line  15  and solenoid valve  17  so that solenoid valve  17  controls the operation of the brakes of the trailer. In a rotated position of 90° of lever  75 , valve  73  disconnects line  15  from valve  17  connecting it instead through bypass  71  to parking air supply line  14  whereby solenoid valve  17  no longer has any affect on the operation of the parking brakes. The bypass line  71  and valve  73  of FIG. 5 is an optional feature of the apparatus and other means might be employed to override the operation of solenoid valve  17  or spring  55  as desired. 
     It will thus be seen that the theft prevention system for trailers according to the invention interacts with the customary pneumatic trailer braking system having spring actuated parking brakes that apply when in absence of pressure in an air supply line to the trailer from a tractor-mounted compressed air tank. A normally closed solenoid valve is connected in series with the pressurized air supply line that supplies air to release the trailer parking brakes and a signal receiver adapted to receive an electrical signal from a transmitter in the tractor cab must be caused to actuate the solenoid to open the valve to release the trailer parking brakes. The signal from the transmitter to the receiver may be a dc, ac, or high frequency signal transmitted over the normally provided electrical cable from tractor to trailer from tractor to trailer or may be a radio transmitted signal wherein of the kind employed for garage door openers. 
     The solenoid valve is preferably provided with a pneumatic latch so that the parking brakes will remain released as long as air pressure is provided to the trailer once an enabling signal is received by the receiver. The signal transmitter is preferably provided with appropriate security means to prevent unauthorized use which may be a key switch, a key pad for entry of an identification number, a magnetic strip card reader or other conventional device. The solenoid valve and receiver in the trailer may be secured in a locked cabinet and, if provided, a manual by pass valve for the solenoid valve may also be within the cabinet. The receiver and the solenoid valve are powered from the same electrical cable which provides power to the trailer lights and the receiver may be programed to require the lights to be turned on in whole or in part or sequentially to release the brakes. 
     Reviewing the operation of the theft prevention system according to the invention, it will be noted that no special action is required on the part of the driver to set the trailer brakes when it is parked and disconnected from the tractor. When standard hose connectors are uncoupled to disconnect the tractor, there is no longer any source of pressure for the parking air supply line  14  and the parking brake air line  15  so that the normal operation of the trailer braking system causes the parking brakes to be set. This is facilitated by the fact that spring  55  returns disc  49  from the position shown in FIG. 4 to the position shown in FIG. 3 thereby opening outlet  45  and parking brake air line  15  to atmospheric pressure. 
     If an alien truck attempts to move the trailer, the driver will find that the brakes cannot be released normally by applying pressure to the parking air supply line in the absence of a coded signal transmitted to receiver  18  due to the action of solenoid valve  17 . Solenoid valve  17  has assumed an unlatched position as shown in FIG.  3  and spring  55  causes disc  49  to close the path between inlet  44  and outlet  45  and also open outlet  45  to the vent  57  and to atmospheric pressure. The coded signal required by receiver  18  needs to be sufficiently complex so that it cannot be provided by a would-be thief and such signal coding arrangements are well-known, in the remote garage door opener art for example. Although not the preferred arrangement, a remote transmitter such as used in the garage door opener art could be permanently installed in the cab of the tractor with the receiver  18  having the remote receiver for such transmitter. Such remote transmitter and receiver arrangements employ radio transmission which is considered less desirable than transmitting the coded signal over conductors of electrical cable. Thus it would be desirable to modify the garage door type remote transmission and reception units so that a lower frequency signal was transmitted over conductors of electrical cable  12 . This would avoid a problem of radio frequency transmissions that trailer brakes could be released by a hand-held transmitter or by the transmitter of a tractor near to, but not connected to, the trailer. 
     A preferred form of the invention for deterring theft comprises a card reader operated transmitter  22  in which the driver operated device  21  is a card reader of the type disclosed in U.S. Pat. No. 5,871,435 and which is generally known in the art. In a manner known in the art, the data on a magnetic strip card would be read and, if such data indicated an authorized operator, then a suitably coded digital signal would be sent over conductors of cable  12  to receiver  18 . Such technology is well known in the employee attendance and time accounting art and elsewhere and will not be described in detail here. Numerous other possibilities for communicating a coded signal to receiver  18  as discussed above are available. Another example of using well-known technology is the use of a telephone touch tone keypad at the transmitter and a touch tone decoder at the receiver  18 . In such case, the signal would be transmitted over two of the conductors of cable  12  which may be unused conductors or conductors which are also used for transmission of DC current to the lighting circuits. It will be seen that the desirable attributes of having a transmitter of special characteristics in the cab and utilizing the electrical cable  12  for transmission of coded signals to receiver  18  can be accomplished in a variety of different ways utilizing known techniques taken from the communication and other arts. 
     Considering now the actions that may be required of an authorized driver operating an authorized tractor in connecting to and releasing the brakes of a trailer equipped with the theft prevention system according to the invention, it will first be noted that all actions required of the driver in addition to the normal hookup are performed in the cab. Assuming that the driver operated control of the transmitter in the cab is a magnetic strip card reader, and the running or marker lights of the trailer are the electrical circuit selected to power the receiver and the solenoid valve, then the following actions need to be taken. The normal hookup procedures, including connecting air hoses and electrical cable are performed in the normal manner. The marker or running lights are turned on from the tractor cab, and any brake release procedure required in the cab is performed. The driver takes a designated appropriate magnetic strip card and inserts it in or wipes it through the magnetic card reader of the transmitter. 
     These actions will send a coded signal to the receiver in the trailer while the pressure from the tractor is applied to the parking air supply line, thus latching open the solenoid valve to apply and maintain pressure in the parking brake air line to release the parking brakes and keep them in the released position as long as pressure is received from the tractor. Thus it will be seen that virtually the only extra steps required by the driver are to turn on some trailer lights and pass a magnetic strip card through a reader to unlock the anti-theft system and proceed with the trailer in tow. In many cases the magnetic strip card used by the driver may be a magnetic strip card provided by the company to drivers and/or other employees for use in other company procedures. 
     In addition to the modifications and variations to the invention that have been shown, described, or suggested, other variations and modifications will be apparent to those of skill in the art and, accordingly, the scope of the invention is not to be limited to those specific variations and modifications disclosed but is to be determined by reference to the appended claims.