ELECTRONIC TRAILER BRAKE ACTUATOR

• US 3,738,710 A
• Filed: 02/25/1971
• Issued: 06/12/1973
• Est. Priority Date: 02/25/1971
• Status: Expired due to Term

• Current Assignee: Charles J. Corris, Jordan J. Pokrinchak
• Original Assignee: Charles J. Corris, Jordan J. Pokrinchak
• Inventors: Pokrinchak, Jordan J., Corris, Charles J.
• Primary Examiner(s): Caldwell, John W.
• Assistant Examiner(s): Leimer, Kenneth N.
• Application Number:
  US05/118,883
• Time in Patent Office: 838 Days
• Field of Search: 340/22,52,53,54,60,69,71 188/3,156,158,163 303/7,20 280/400,422,423,428 317/141S,148.5
• US Class Current: 303/20
• CPC Class Codes: B60T 13/74 with electrical assistance or drive

Abstract

A trailer brake actuator is normally signaled into operation upon energization of the brake light circuit in the towing vehicle. Closure of the brake light switch supplies charging current to a capacitor, and the increasing voltage developed thereacross is amplified and used to control the conductance of a series current regulator connected in an energizing circuit for the trailer brakes. A separate switch permits more rapid charging of the capacitor and actuation of the trailer brakes independently of the vehicle brakes.

Claims

1. A braking system for a tractor-trailer unit, said system comprising, in combination:

A. a brake light circuit carried by the tractor, said circuit including a battery and a brake light and a brake light switch connected in series between first and second output terminals of said battery;

B. electrical trailer brakes having a first input terminal and a second input terminal electrically connected to said second battery output terminal;

C. a timing circuit connected across said first and second battery output terminals upon closure of said brake light switch for deriving a control signal proportional to the duration of brake light switch closure;

D. electronic amplifier means connected to said timing circuit for selectively amplifying said control signal; and

E. electronic control means connected between said first battery output terminal and said first trailer brake input terminal and responsive to said amplified control signal for regulating current flow to said trailer brakes in accordance with the duration of brake light switch closure.

2. said control means comprises a power transistor having its base connected to the output of said amplifier network and its collector-emitter circuit connected in the circuit between said first battery terminal and said first trailer brake input terminal.

3. The braking system defined in claim 2, wherein said first resistor is adjustable to vary the charging rate of said capacitor and thus the rate of increase of said signal voltage during the period of closure of said brake light switch.

4. The braking system defined in claim 2, which further includes a manual over-ride switch operable upon closure to by-pass said brake light switch and connect a second resistor in parallel with said first resistor, thereby to accelerate the charging rate of said capacitor and the rate of increase of said signal voltage.

5. The braking system defined in claim 4, which further includes a diode connected between said first junction and a second junction connectable to said first battery terminal through either said brake light switch or said manual over-ride switch and to said second battery terminal through a third resistor, said diode being back-biased during closure of either said brake light switch or said manual over-ride switch and unbiased upon opening of the previously closed switch to rapidly discharge said capacitor.

6. The braking system defined in claim 5, wherein

7. The braking system defined in claim 6, wherein said amplifier network further includes a variable interstage resistor for adjusting the relationship between the amplitude of said signal voltage and the conductance level of said power transistor.

8. The braking system defined in claim 6, which further includes a variable resistor connected in the base circuit of said powEr transistor for adjusting the relationship between the amplitude of said signal voltage and the conductance level of said power transistor.

9. The braking system defined in claim 6, which further includes a second capacitor connected between said brake light switch and the base input circuit of the output transistor of said amplifier network, said second capacitor serving to anticipate the controlling effect of said signal voltage by causing said power transistor to pass an initial current surge and thereby to compensate for worn trailer brakes.

10. The braking system defined in claim 6, which further includes a pilot lamp and a quenching diode connected across said trailer brake input terminals.