Window lifter installation

Claim 1

A circuit arrangement for the purpose of driving a movable window element or the like in motor vehicles, comprising: an operating switch, an electric motor fed out of a voltage source and controlled by way of a switching element and a motor current supervising stage affecting the switching element, wherein the motor current supervising stage at least at times recognizes a reset signal derived from a given change in time of the motor current, wherein the motor current supervising stage recognizes a reset signal derived from a given static motor value, wherein the maximum torque of the motor exceeds by 20 percent, the torque necessary to drive the movable element in the most unfavorable case of operation, wherein the drop in voltage on a measuring resistor in the motor circuit serves as a reset signal, to which measuring resistor a voltage divider with a resistor and a parallel circuit consisting of a preferably variable resistor and a capacitor is connected in parallel, whereby the reset signal may be measured on the voltage divider tapping, wherein the load inrush current of the motor is absorbed by a capacitor, wherein the motor current supervising stage affects the switching element via a bistable toggle stage which may be quenched by the reset signal and be brought back to the other switching condition only by means of a switching process of the operating switch, wherein the operating voltage may be conducted to at least one switching member of the toggle stage via the operating switch, wherein a switching member of the toggle stage is connected with the switching element and the operating switch is connected in series to the voltage source, wherein the toggle stage is provided with two transistors of which one is located in the control circuit of the switching element as switching member and is controlled by the second transistor, whereby the output signal of the first transistor is fed back to the control voltage, wherein the reset signal is conducted to the second transistor as control voltage, wherein the reset signal is conducted to the first transistor via a further switching stage, wherein the motor is switched off via the toggle stage and a further switching element is controlled to reverse the direction of rotation of the motor, whereby the control circuit of said second switching element is interrupted, when the current supervising device detects a reset signal, wherein a further transistor switching stage serves for the control of the control circuit of the second switching stage serves for the control of the control circuit of the second switching element, whereby the reset signal is conducted to said transistor switching stage, wherein the control circuit of the second switching element is affected by the transistor switching stage which also controls the toggle stage, and wherein the two switching elements comprise one changeover relay each through which the motor may be depolarized or short-circuited, whereby shorting of the motor winding takes place before reversing the motor.