GB2028114A - Improvement relating to wiper drive assemblies - Google Patents

Abstract

This invention relates to wiper drive assemblies particularly for use as windscreen wiper drive assemblies. The invention provides an assembly comprising two parallel crank members (12, 13) rigidly spaced apart by a first crank pin (14) on which a connecting rod (15) is pivoted. A second crank pin (18) is provided on the opposite side of the crank member (13) to the first crank pin (14) and a second connecting rod (19) is pivoted thereon. The connecting rods (14, 18) are in turn pivotally connected to windscreen wiper arms. The crank members are rotated by a motor drive shaft (10) and thus the rotary movement of the motor is converted into reciprocating movement of the connecting rods which is in turn converted into a wiping motion of the wiper arms (20). <IMAGE>

Description

SPECIFICATION Improvements relating to wiper drive assemblies This invention relates to wiper drive assemblies and in particular, but not exclusively, to windscreen wiper assemblies.

There are two basic types of known wiper drive assemblies.

First, there are those which are driven by a motor having a rotatably reciprocatable drive shaft. These comprise a crank member rigidly attached to the drive shaft of the motor, two crank pins being mounted on the crank member on the same side or opposite sides of the axis of rotation thereof, each pin having one end of a connecting rod pivotally attached thereto and the other end of each connecting rod being attached to a wiper arm. Thus the reciprocating movement of the motor is transmitted to the wiper arms which undergo a wiping action.

Secondly, wiper drive assemblies are known which comprise two crank pins on opposite sides of the axis of rotation of a gear, the gear being driven from a gear or gears on the drive shaft of a rotary motor. Again, one end of a connecting rod is pivotally attached to each of the pins and the other ends of the rods are attached to wiper arms. Thus the rotational movement of the motor drive shaft is transformed by the mechanism into reciprocating movement of the connecting rods and thus a wiping action of the wiper arms.

Both of these known types of wiper drive assemblies involve the use of expensive specialised equipment. In the first case, a motor having a rotatably reciprocatable drive shaft, and in the second case a gear box with a crank on each of two opposite sides thereof.

An object of the invention is to provide a new and improved wiper drive assembly.

According to a first aspect of the invention we provide a wiper drive assembly comprising a drive shaft rotatable about an axis and a first crank member rigidly attached to the drive shaft, the first crank member having connected thereto, one end of a crank pin, the crank pin extending therefrom on the opposite side of the first crank member to the drive shaft, the other end of the crank pin being connected to a second crank member the first and second crank members being fixed relative to one another, the second crank members having a further crank pin extending therefrom on the opposite side to the crank pin connecting the first and second crank members, the crank pins each having an axis, the axes of the drive shaft and each of the crank pins being substantially parallel and spaced apart, each of the crank pins having connected therewith, a connecting rod, each connecting rod also being connected to a wiper arm which is adapted to undergo a wiping action, whereby rotational movement of the drive shaft is connected to a reciprocating movement of the connecting rods which is in turn transmitted to a wiping movement of the wiper arms.

Each of the wiper arms may be pivoted along its length so that the reciprocating movement of the connecting rods is converted into a "clap-hand" movement of the wiping arms.

The distance between the connecting rod and the pivot of the wiper arm, or the distance between the crank pin and the axis of rotation of the crank member may be varied for a particular application to achieve a desired sweep of the wiper arms.

The drive shaft may be the output shaft of a motor or alternatively the drive shaft may be driven by any other means such as a pulley or gear driven directly or indirectly from a motor.

The invention will now be described by and with reference to the accompanying drawings in which Figure 1 shows a plan view of a windscreen wiper drive assembly according to the invention, Figure 2 is a side view of the assembly of Fig. 1, and, Figure 3 is a side view of a typical linkage system as may be used in accordance with the invention.

Referring to Figs. 1 and 2 of the drawings, there is shown a windscreen wiper drive assembly for use in a vehicle, the assembly comprising a drive shaft 10 of a rotary motor (not shown) which is rigidly attached to a first crank member 1 2 by a nut 11 and is rotatable about an axis 7. A second crank member 1 3 is rigidly attached parallel to and spaced from the first crank member 12, by a crank pin 14, having a central axis 14a. Pivoted on the pin 14 is one end of a connecting rod 1 5.

The connecting rod comprises a shaft 8 having an internally threaded bore into one end of which a screw threaded part 1 6 of a pivot member 9 is threadedly engaged. Antifriction bearings 21 are provided between the pivot member 9 and the crank pin 14 to facilitate relative rotation between the pivot member 9 and the crank pin 14. A lock nut 1 7 is also provided on the threaded part 1 6 to lock the pivot member 9 in the shaft 8.

The end of the connecting rod 1 5 remote from the pivot member 9 is pivotally connected to a wiper arm 20 at 22, but may alternatively be connected to a lever (not shown) connected to the wiper arm 20.

The second crank member 1 3 is provided with a second crank pin 1 8 having an axis 1 8a, the pin 18 extending therefrom on the opposite side of the crank member 1 3 to the first crank pin 14.

The pin 1 8 has a second connecting rod 19 similar to the first connecting rod 15, pivoted thereon, the rod 1 9 being pivotally attached to a wiper arm 20 at its other end. The axis of the drive shaft 10, and the axis 1 4a, of the first crank pin 14, and the axis 1 8a of the second crank pin 18, are parallel but spaced apart, the axis 1 4a and 1 8a being equi-distant from the axis of rotation 7 of the drive shaft 10.

In use, the drive shaft 10 rotates the crank members 12 and 13 about axis 7 and thus the pins 14 and 18 will move as indicated by the circle 25 (Fig. 2) and thus the connecting rods 15, 1 9 will be reciprocated simultaneously in opposite directions. As the wiper arms 20 are pivoted along their length at 22, they will undergo a "clap-hand" movement.

This movement of the wiping arms 20 defines sweep angles a and b (Fig. 3) which may be increased or decreased for a particular application by selecting the lengths of the wiper arms 20, and the position of pivot 22, and the distance of the crank pins 14 and 1 8 from the axis of rotation 7 of the drive shaft 10, to achieve a desired sweep.

The drive shaft 10 need not be attached to the first crank member 12 by a nut, but may be welded or riveted for example or attached in any other manner.

The drive shaft 10 need not be the output shaft of a motor, but may be rotated by any other means such as a pulley or gear driven directly or indirectly by a motor.

The crank members 1 2 and 13 may be substantially rectangular in side view as shown in Fig. 2 of the drawings, or may be elliptical, semi-circular or any other desired shape.

The connecting rods 1 5 and 1 9 need not comprise a shaft 8 and pivot member 9, but may be made in one piece, and/or comprise a solid rectangular bar or any other elongate member.

Claims (8)

1. A wiper drive assembly comprising a drive shaft rotatable about an axis and a first crank member rigidly attached to the drive shaft, the first crank member having connected thereto, one end of a crank pin, the crank pin extending therefrom on the opposite side of the first crank member to the drive shaft, the other end of the crank pin being connected to a second crank member the first and second crank members being fixed relative to one another, the second crank members having a further crank pin extending therefrom on the opposite side to the crank pin connecting the first and second crank members, the crank pins each having an axis, the axes of the drive shaft and each of the crank pins being substantially parallel and spaced apart, each of the crank pins having connected therewith, a connecting rod, each connecting rod also being connected to a wiper arm which is adapted to undergo a wiping action, whereby rotational movement of the drive shaft is connected to a reciprocating movement of the connecting rods which is in turn transmitted to a wiping movement of the wiper arms.

2. A wiper drive assembly according to Claim 1 wherein each of the wiper arms is pivoted along its length so that the reciprocating movement of the connecting rods is converted into a "clap-hand" movement of the wiping arms.

3. A wiper drive assembly according to Claim 1 or Claim 2 wherein the distance between the connecting rod and the pivot of the wiper arm is variable for a particular application to achieve a desired sweep of the wiper arms.

4. A wiper drive assembly according to Claim 1 or Claim 2 wherein the distance between the crank pin and the axis of rotation of the crank member is variable for a particular application to achieve a desired sweep of the wiper arms.

5. A wiper drive assembly according to any one of the preceding claims wherein the drive shaft is the output shaft of a rotary motor.

6. A wiper drive assembly according to any one of claims 1 to 4 wherein the drive shaft is driven directly or indirectly from a rotary motor.

7. A wiper drive assembly substantially as hereinbefore described with reference to the accompanying drawings.

8. A vehicle having a wiper drive assembly according to any one of the preceding claims.