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Automatic wiper actuator for a vehicle window

  • US 4,567,412 A
  • Filed: 11/29/1984
  • Issued: 01/28/1986
  • Est. Priority Date: 11/29/1984
  • Status: Expired due to Term
First Claim
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1. A control system for a motor driven wiper on a vehicle window comprising, in combination:

  • an oscillator effective to generate a rectangular voltage wave of supply and ground voltage levels having a substantially constant frequency and duty cycle;

    an AND gate with three inputs and an output;

    an inverter effective to invert the rectangular voltage wave and apply the inverted rectangular voltage wave to the first AND gate input;

    first wave transformation means comprising a series diode and inverter with a first capacitor and first resistor connected from the junction of the diode and inverter to ground, the resistance of the first resistor being variably controllable by an operator of the vehicle, the first wave transformation means being connected from the oscillator to the second AND gate input, whereby it applies to said input the rectangular voltage inverted and delayed by a first time period;

    second wave transformation means comprising a diode followed by two series inverters with a parallel second capacitor and second resistor connected from the junction of the diode and one of the series inverters to ground, the second wave transformation means being connected from the oscillator to the third AND gate input, the second capacitor being located adjacent the lower edge of the wiped portion of the vehicle window and responsive in capacitance to the presence of moisture on said wiped portion, whereby the second wave transfomation means applies to the third AND gate input the rectangular wave delayed by a second time period varying with said capacitance and thus with the moisture on the window;

    a retriggerable monostable multivibrator connected to the output of the AND gate and effective, when triggered by common supply voltage levels on all three inputs, to generate an energized output of period longer than a cycle of the rectangular voltage wave; and

    means responsive to the energized output of the retriggerable monostable multivibrator to activate the motor driven wiper to perform a wipe cycle, whereby the wiper system is automatically activated in response to moisture on the windshield and is further adjustable by the vehicle operator in sensitivity to moisture.

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