INTERMITTENT CONTROL DEVICE

• US 3,643,145 A
• Filed: 04/18/1969
• Issued: 02/15/1972
• Est. Priority Date: 04/18/1969
• Status: Expired due to Term

• Current Assignee: David Tann, Robert A. Noetzold
• Original Assignee: David Tann, Robert A. Noetzold
• Inventors: Tann, David, Noetzold, Robert A.
• Primary Examiner(s): Hix, L. T.
• Assistant Examiner(s): Hickey, Robert J.
• Application Number:
  US04/817,451
• Time in Patent Office: 1,033 Days
• Field of Search: 318/443,472,473WW 15/250.02,250.12
• US Class Current: 318/443
• CPC Class Codes: B60S 1/0807 using electronic control means, e.g. tubes, semiconductors B60S1/0818, B60S1/0896 take precedence
• CPC Class Codes: Y10S 15/15 Moisture responsive

Abstract

A control device for operating windshield wiper blades intermittently with a dwell period between wiping cycles. The length of time of the dwell periods is determined by a thermistor. The resistance of the thermistor is varied by the wiper motor current so that the length of time of the dwell periods is varied inversely with the moisture on the windshield.

Claims

1. In combination, wiper drive means including an electric motor for driving a wiper blade over a windshield in repeating wiping cycles, and automatic control means for activating and deactivating said drive means intermittently to drive said wiper blade through repeating wiping cycles interrupted by dwell periods, said control means including variable-resistance means and automatically varying the value of said variable-resistance means in response to the moisture on the windshield while the drive means is activated and controlling the length of time of said dwell periods in response to the value of said variableresistance means, the length of time of the dwell periods varying inversely with the moisture on the windshield, said variableresistance means comprising a thermistor and a heating element for varying the temperature of said thermistor, the temperature of said heating element being responsive to and proportional to the motor current, said control means including a capacitor and connecting said capacitor with said thermIstor to control the length of time of said dwell period.

2. In combination, wiper drive means including an electric motor for driving a wiper blade over a windshield in repeating wiping cycles, and automatic control means for activating and deactivating said drive means intermittently to drive said wiper blades through wiping cycles interrupted by dwell periods, said control means including a thermistor and a heating element for varying the temperature of said thermistor, the temperature of said heating element being varied in response to and proportional to the motor current to automatically vary the value of said variable resistance means in response to and proportional to the drag encountered by the wiper blade on the windshield so that the length of time of the dwell periods varies inversely with the moisture on the windshield.

3. The invention as defined in claim 2 wherein said thermistor is a positive temperature coefficient thermistor.

4. In combination, wiper drive means including an electric motor for driving a wiper blade over a windshield in repeating wiping cycles, and automatic control means for activating and deactivating said motor intermittently to drive said wiper blades through wiping cycles interrupted by dwell periods, said control means including a discharge circuit having variable resistor means for determining the length of said dwell periods, said resistor means having a resistance during each dwell period initially determined directly by the level of motor current during the preceding wiping cycle, so that the resistance increases with the drag encountered by the wiper blade and the length of said dwell periods varies inversely with the moisture on the windshield.

5. The invention as defined in claim 4 wherein said discharge circuit includes a capacitive element which is charged during each wiping cycle and discharged through said variable resistor means during each dwell period.

6. The invention as defined in claim 5 wherein said variable resistor means includes a resistive element having a resistance which increases with heat and a thermal element in circuit with said motor operatively positioned for heating said resistive element in direct response to motor current.