Screen wiper apparatus including controlled means for varying the wiping force

Screen wiper apparatus comprising:

• a drive head having a pivot axis;
• a wiper arm;
• means mounting the wiper arm on the drive head for pivoting movement with respect to the drive head about the pivot axis;
• at least one wiper blade carried by the wiper arm:
• torque applying means including a first spring means for applying substantially constant nominal torque to the wiper arm and a second spring means for applying a complementary torque to the wiper arm, said second spring means having a neutral state in which it applies no torque to the wiper arm, the torque applying mean being coupled between the drive head and the wiper arm for applying a wiping torque to the wiper arm:
• the second spring means applying a load to the wiper arm in which the algebraic value of the load is adjustable and can be additive and subtractive to the constant nominal torque such that the wiping torque applied to the wiper arm can be increased and can be reduced from the first spring means constant torque in response to vehicle operation, the second spring means neutral state defined by the value of the complementary torque being of zero magnitude, the second spring means having two springs, an elongated compression spring and an elongated tension spring that is mounted in parallel with the compression spring.

Screen wiper apparatus comprising:

• a drive head having a pivot axis;
• a wiper arm;
• means mounting the wiper arm on the drive head for pivoting movement with respect to the drive head about the pivot axis;
• at least one wiper blade carried by the wiper arm;
• torque applying means including a first spring means for applying a substantially constant nominal torque to the wiper arm and a second spring means for having a neutral state and for applying a complementary torque to the wiper arm, said second spring means having a neutral state in which it applies no torque to the wiper arm, the torque applying means being coupled between the drive head and the arm for applying a wiping torque to the wiper arm;
• the second spring means applying a load to the wiper arm in which the algebraic value of the load is adjustable and can be additive and subtractive to the constant nominal torque such that the wiping torque applied to the wiper arm can be increased and can be reduced from the first spring means constant torque in response to vehicle operation, the second spring means neutral state defined by the value of the complementary torque being of zero magnitude, the second spring means having two springs, an elongated compression spring and an elongated tension spring that is mounted in parallel with the compression spring, the tension and compression springs of the second spring means are helical springs mounted concentrically with each other.

Screen wiper apparatus comprising:

• a drive head having a pivot axis:
• a wiper arm:
• means mounting the wiper arm on the drive head for pivoting movement with respect to the drive head about the pivot axis:
• at least one wiper blade carried by the wiper arm;
• and torque applying means including a first spring means for applying a substantially constant nominal torque to the wiper arm and a second spring means for applying a complementary torque to the wiper arm, said second spring means having a neutral state in which it applies no torque to the wiper arm, the torque applying means being coupled between the drive head and the wiper arm for applying a wiping torque to the wiper arm:
• the second spring means applying a load to the wiper arm in which the algebraic value of the load is adjustable and can be additive and subtractive to the constant nominal torque such that the wiping torque applied to the wiper arm can be increased and can be reduced from the first spring means constant torque in response to vehicle operation, the second spring means neutral state defined by the value of the complementary torque being of zero magnitude, the second spring means having an actuator in the drive head and first and second elongated compression springs the first compression spring of the second spring means having one end thereof coupled to the actuator;
• an elongated support bar having a first end connected to the wiper arm, the first and second compression springs in said second means being mounted end-to-end with respect to each other on the support bar;
• the second spring means of the apparatus having a thrust plate element interposed between the two ends of the compression springs and being mounted for sliding movement on the support bar, and means coupling the thrust plate element with the actuator.

Screen wiper apparatus comprising:

• a drive head having a pivot axis;
• a wiper arm;
• means mounting the wiper arm on the drive head for pivoting movement with respect to the drive head about the pivot axis;
• at least one wiper blade carded by the wiper arm;
• and torque applying means having a first spring means for applying a substantially constant nominal torque to the wiper arm and a second spring means for applying a complementary torque to the wiper arm, said second spring means having a neutral state in which it applies no torque to the wiper arm, the torque applying means being coupled between the drive head and the wiper arm for applying a wiping torque to the wiper arm, the second spring means applying a load to the wiper arm in which the algebraic value of the load is adjustable and can be additive and subtractive to the constant nominal torque such that the wiping torque applied to the wiper arm can be increased and can be reduced from the first spring means constant torque in response to vehicle operation, the second spring means neutral state defined by the value of the complementary torque being of zero magnitude;
• the second spring means having two elongated springs, at least one of which is a compressing spring, an actuator in the drive head, at least one spring of the second spring means having one end thereof coupled to the actuator;
• said actuator comprising an output bar, a rack carried by the output bar, a motor, and gear means coupled to the motor for rotation thereby and in engagement with the said rack.