Theft prevention system for trailers

• US 6,338,534 B1
• Filed: 12/02/1999
• Issued: 01/15/2002
• Est. Priority Date: 12/02/1999
• Status: Expired due to Fees

• Current Assignee: The Aegis Technologies Group, LLC
• Original Assignee: The Aegis Technologies Group, LLC
• Inventors: Gray, Clark W., Kee, Dan B.
• Primary Examiner(s): RODRIGUEZ, PAMELA
• Application Number:
  US09/454,236
• Time in Patent Office: 775 Days
• Field of Search: 303/89, 303/123, 303/127, 303/7, 303/9, 188/353, 188/265, 180/287
• US Class Current: 303/89
• CPC Class Codes: B60R 25/08 operating on brakes or brake systems

Abstract

There is disclosed a theft prevention system for trailers with the customary pneumatic trailer braking system. A normally closed solenoid valve is connected in the 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 transmitted over the electrical cable from tractor to trailer or may be a radio transmitted signal . The solenoid valve is provided with a pneumatic latch so that the parking brakes will remain released as long as air pressure is provided. The signal transmitter is provided with security 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 device. The solenoid valve and receiver are secured in a locked cabinet and a by pass valve is also located within the cabinet. The receiver may be programed to require the lights to be turned on in whole or in part or sequentially to release the brakes.

Claims

1. In a tractor-trailer transport vehicle having a tractor with a cab, a trailer, electrical cables and connectors therebetween, said tractor having an air pressure operated brake system with air pressure supply means and a parking air supply line to a parking brake air line of said trailer, a safety and security system comprising:

an electric signal transmitter installed in said cab;

a signal receiver in said trailer adapted to detect signals from said transmitter and produce a low voltage output;

a solenoid valve in said trailer responsive to be activated by a low voltage DC output from said signal receiver and adapted to open a normally closed valve from said parking brake air line to said parking air supply line,

wherein said solenoid valve includes a latch element responsive to high pressure air in said parking brake line to hold said normally closed valve in an open position in response to a predetermined minimum air pressure in said parking brake air line;

whereby the parking brakes of said trailer can only be released when an appropriate signal is transmitted from said cab-installed transmitter.

2. Apparatus as recited in claim 1 wherein said signal receiver is supplied with power through said electrical cables for operation.

3. Apparatus as recited in claim 1 wherein said predetermined minimum air pressure is about 20 psi.

4. Apparatus as recited in claim 3 wherein said signal receiver is supplied with power through said electrical cables for operation and for sending a low voltage output to activate said solenoid.

5. Apparatus as recited in claim 1 wherein signals from said transmitter are transmitted to said signal receiver over one or more conductors of said electrical cables.

6. A solenoid valve for use in a trailer parking brake security system for trailers having parking brakes, a parking brake air supply line connectable to a tractor for the trailer and a parking brake air line which supplies air pressure to release the trailer parking brakes, said solenoid valve comprising:

a solenoid having windings and an armature operated from a first position to a second position by electric current supplied to said windings;

a first valve element connected to said armature arranged to be closed when said armature is in the first position and open when said armature is in the second position, said first valve being in a passage between said brake air supply line and said parking brake air line;

a second valve element connected to said armature and arranged to be open when said armature is in said first position and closed when said armature is in said second position;

said second valve being located in a passage between said parking brake air line and the atmosphere;

a bias spring urging said armature to said first position;

a latch element responsive to high air pressure in said parking brake air line to hold said armature in said second position without regard to activation of said solenoid;

whereby activation of said solenoid is required to provide air pressure to said parking brake air line to release the trailer brakes, but continued activation of the solenoid is not required for release of the brakes as long as air pressure from said parking air supply line is not interrupted.

7. Apparatus as recited in claim 6 wherein said armature is restrained to sliding motion along an axis and said first valve is substantially aligned with said axis.

8. Apparatus as recited in claim 7 wherein said second valve is aligned with said first valve and said axis.

9. Apparatus as recited in claim 8 wherein the spring constant of said bias spring is great enough to move said armature to said first position if air pressure in said parking brake air line is less than 20 psi.

10. Apparatus as recited in claim 7 wherein said second valve is aligned with said first valve and said axis.

11. Apparatus as recited in claim 6 wherein the spring constant of said bias spring is great enough to move said armature to said first position if the air pressure in said parking brake air line is less than about 20 psi.

12. In a tractor-trailer transport vehicle having a tractor with a cab, a trailer, electrical cables and connectors therebetween, said tractor having an air pressure operated brake system with air pressure supply means and a parking air supply line to a parking brake air line of said trailer, a safety and security system comprising:

an electric signal transmitter installed in said cab;

a signal receiver in said trailer adapted to detect signals from said transmitter and produce a low voltage output, said signal receiver being supplied with power through said electrical cables;

a solenoid valve in said trailer responsive to be activated by a low voltage DC output from said signal receiver and adapted to close a normally open vent to atmosphere from said parking brake air line while operating a normally closed valve from said parking brake air line to said parking brake air supply line;

wherein said solenoid valve includes a latch element responsive to high pressure air in said parking brake line to hold said normally closed valve in an open position in response to a predetermined minimum air pressure in said parking brake air line;

whereby the parking brakes of said trailer can only be released when an appropriate signal is transmitted from said cab-installed transmitter.

13. Apparatus as recited in claim 12 wherein signals from said transmitter are transmitted to said signal receiver over one or more conductors of said electrical cables.

14. Apparatus as recited in claim 13 wherein said electrical cables have at least four conductors and said signal receiver is responsive to the status of electrical current or voltage for each of at least four of said conductors.

15. In a tractor-trailer transport vehicle having a tractor with a cab, a trailer, electrical cables and connectors therebetween, said tractor having an air pressure operated brake system with air pressure supply means and a parking air supply line to a parking brake air line of said trailer, a safety and security system comprising:

an electric signal transmitter installed in said cab;

a signal receiver in said trailer adapted to detect signals from said transmitter and produce a low voltage output;

a solenoid valve in said trailer responsive to be activated by a low voltage DC output from said signal receiver and adapted to open a normally closed valve from said parking brake air line to said parking air supply line;

wherein said electrical cables have at least four conductors and said signal receiver is responsive to the status of electrical current or voltage for each of at least four of said conductors;

whereby the parking brakes of said trailer can only be released when an appropriate signal is transmitted from said cab-installed transmitter;

wherein said signal receiver is supplied with power through said electrical cables for operation and for sending a low voltage output to activate said solenoid; and

wherein said solenoid valve includes a latch element responsive to high pressure air in said parking brake air line to hold said normally closed valve in an open position in response to a predetermined minimum air pressure in said parking brake air line.