GB2205485A

GB2205485A - Windscreen wiper blades

Info

Publication number: GB2205485A
Application number: GB08812844A
Authority: GB
Inventors: Bryan Nigel Victor Parsons
Original assignee: Jaguar Cars Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 1987-06-09
Filing date: 1988-05-31
Publication date: 1988-12-14
Anticipated expiration: 2008-05-31
Also published as: GB2205485B; GB8812844D0; GB8713488D0

Abstract

A windscreen wiper blade assembly comprises wiper blade 10 having body portion 11 and oppositely-extending screen-engaging portions 12, 13 forming channels 16, 17 with flanges 15 and a blade supporting arrangement comprising holder 20 and yoke member 27 connectable to a wiper arm, the wiper blade being mounted so as to be capable of pivoting about axis P which is on the screen side of a line X-X or Y-Y defined, by the angle of friction at the point of contact between the leading edge of a screen-engaging portion and the windscreen. In modifications, the blade may be mounted on a curved rod passing through a bore in the blade, the rod being mounted on a drive spindle for angular oscillating movement and provided with means at its drive end whereby it may be rotated relative to the spindle to adjust the curvature of the blade in use. Wiper blade assemblies for cleaning both sides of a windscreen utilising magnetic couplings are also disclosed. <IMAGE>

Description

WINDSCREEN \;WIPERS The present invention relates to windscreen wipers.

Conventional windscreen wiper blades have a tapered cross section which distorts during the wiping process, such that the blade is drawn across the windscreen with the tip trailing. In order to achieve this, the tip of the blade must flip over when the sweep of the the blade changes and will during this period generate noise.

The inclined blade provides a light even canter levered stiffness to all the wiper length. The spread of the load required to keep the blade in engagement with the screen is achieved by a balanced beam mechanism, the load being provided by a spring in the wiper arm, which is reacted through the driving spigot. Nevertheless, any obstructions in the path of the blade would tend to lift the trailing tip of the blade and consequently reduce its effectiveness for removing surface debris from the screen.

The height of the wiper blade is also critical as it must prevent spillage over the blade, as water builds up against it.

According to one aspect of the present invention, a windscreen wiper mechanism includes an elongate wiper blade, said wiper blade comprising a body portion and a pair of oppositely inclined screen engaging portions diverging away from the body portion, each screen engaging portion defining with the body portion a longitudinally extending laterally opening channel therebetween, the wiper blade being mounted on a wiper arm, by which it is connected to a drive shaft on which it may be traversed in reciprocating manner across a windscreen, the blade being arranged to pivot with respect to the arm about a longitudinal axis, said axis being on the screen side of the line describing the angle of friction at the point of contact between the edge of the leading screen engaging portion and the windscreen.

With the wiper blade according to the present invention, both screen engaging portions of the blade are maintained in engagement with the screen, so that for each direction of traverse of the blade, one screen engaging portion will be directed forwardly while the other will trail. The leading screen engaging portion will remove most of the water by a scoop action, the water being collected in the contiguous channel defined between the leading screen engaging portion and the body portion and being thrown outwards by centrifugal action. Any water that is not scooped up by the leading screen engaging portion, will be wiped by the trailing screen engaging portion which will function in conventional manner, the water being channelled between the two screen engaging portions and exhausted at the radially outermost tip of the blade.

The leading screen engaging portion will be. relatively stiff in the direction of traverse, due to its geometry and furthermore, any resistance to movement will tend to increase contact between the screen engaging portion and the screen. The edge of this portion will consequently remove surface debris effectively, by a chisselling action. Moreover, by selection of materials which are sufficiently stiff at low temperatures, blades of the present design could be used to remove ice and frost from the screen.

When the direction of traverse of the blade reverses, the trailing screen engaging portion becomes the leading portion and vice versa. There is consequently no need for the blade to flip over as with conventional blades and consequently the noise produced thereby will be avoided.

Pivotting of the blade about the longitudinal axis of the arm will ensure that both screen engaging portions are maintained in engagement with the screen and accommodate curvature of the screen. The positioning of the longitudinal pivot axis on the screen side of the line describing the angle of friction at the point of contact between the edge of the leading screen engaging portion and the screen provides stability so that the blade moves smoothly over the screen, without sticking and vibrating.

The blade used in the wiper mechanism according to the present invention may be mounted to the wiper drive mechanism by, for example, a balance beam arrangement, in conventional manner. Alternatively, magnetic means or vacuum means may be used to maintain an appropriate uniform loading along the full length of the blade. Furthermore, the curv-ature of the wiper blade may be adjustable to accommodate variations in the curvature of the screen.

Various embodiments of the invention are now described, by way of example, with reference to the accompanying drawings; in which: Figure 1 is a cross sectional view of a wiper blade used in windscreen wiper mechanism according to the present invention; Figure 2 is a side elevation of a wiper mechanism incorporating the wiper blade illustrated in figure 1; Figure 3 is a sectional elevation along the line III-III in figure 2; Figure 4 is a side elevation illustrating an alternative wiper mechanism incorporating a wiper blade as illustrated in figure 1; Figure 5 shows a part sectional illustration of a further alternative wiper mechanism incorporating a wiper blade similar to that illustrated in figure 1; and Figures 6A and 6B illustrate the blade profile variation with screen curvature and wipe direction, for the wiper mechanism illustrated in figure 5.

As illustrated in figure 1, the wiper blade 10 used in the wiper mechamisms according to the present invention, is of uniform cross section having a body portion 11 with a pair of oppositely inclined wedge shaped screen engaging portions 12 and 13, these screen engaging portions decreasing in thickness from the body portion to the screen engaging edge and diverging one with respect to the other away from the body portion 11 and into engagement with a screen 14. A pair of flange portions 15 are provided on the body portion 11 to provide channels 16 and 17 on opposite sides of the blade 10.

In use, when blade 10 moves in the direction of arrow M in figure 1, portion 12 of the blade 10 will scoop water off the screen 14 and into the channel 16, from where it will be expelled by centrifugal action at the radially outer tip of the blade 10. Any water missed by portion 12 will be wiped by portion 13, the water thus collected being channelled between portions 12 and 13 and expelled at the outer tip of blade 10.

In the wiper mechanism illustrated in figure 2 and 3, the blade is supported by blade holder 20, which has a pair of grooves 21 in which are located the outer extremities of flange portions 15. The blade holder 20 is rigid transversely of the blade 10 but permits flexing of the blade longitudinally. The blade 10 is connected via blade holder 20 to a balanced beam wiper arm 23. This balanced beam wiper arm 23 is of conventional design and comprises a main arm 24 which is connected to the blade holder 20 at several points along its length, by means of a series of inter-pivotted levers 25 to 29. The main arm 24 is pivotally attached to the wiper drive spindle 30 and a tension spring 31 acts between the main arm 24 and spindle 30, so that the wiper blade 10 is loaded evenly along its length. A pivotted cover 32 may be provided to cover the balance beam arrangement in order to improve the aesthetic appearance of the wiper assembly. Also for this purpose, the arrangement of levers 26 to 29 may be designed to provide its most compact profile, when the wiper is in the parked position.

A blade holder 20 is attached to the levers 26 to 29 of the balance beam arm 23 in a manner which will allow a small amount of pivotting of the blade 10 about a longitudinal axis denoted by pivot point P. This ability to pivot will ensure that both screen engaging portions 12 and 13 of blade 10 will be maintained in engagement with the screen 14, in spite of varying curvature of the screen. The wiper mechanism is designed, so that pivot point P is located on the screen side of the lines X-X and Y-Y, which describe the angle of friction between the point of engagement of portions 12 and 13 with the screen, for movement of the wiper when the respective portion 12, 13 is leading. This configuration ensures that the blade 10 moves smoothly over the screen 14 without sticking or vibrating.

In the alternative wiper mechanism illustrated in figure 4, the blade 10 is mounted on an arm 40, which is rigid transversely of its longitudinal axis, but which is flexible in the direction normal to the screen 14. An inner element 41 is driven coincidentally with arm 40, against the inner surface of the screen 14. A magnetic element is provided on the arm 40 or on the inner element 41, along the length thereof corresponding to the length of, blade 10. A ferromagnetic element or magnetic element is also provided on the other member 41 or 40, so that the arm 40 will be magnetically attracted to the inner element 41, thereby maintaining engagement between the blade 10 and screen 14. Spring means in the form, for example of a Belleville washer 42 is provided between the drive spindle 43 and arm 40, in order to ensure good initial magnetic coupling.

The inner element 41 of this mechanism, may be provided with a blade or sleeve, for wiping the inside of the screen for de-misting purposes. However, as the inside of the screen will normally be dry, frictional engagement of this surface should be reduced as far as possible. An alternative would be to have roller means mounted on the inner element 41 which would run against the inside of the screen 14.

In an alternative embodiment (not shown) the blade 10 may be mounted on an arm similar to arm 40 of the embodiment illustrated in figure 4. However, rather than using magnetic coupling to maintain the blade 10 in engagement with screen 14, a vacuum could be provided in the void 45 (see figure 1) defined between the two screen engaging portions 12 and 13 and the screen 14. The vacuum could be provided by tapping manifold depression or by means of an engine driven pump, one or more bores being provided in the blade 10 opening into the channel between the screen engaging portions 12,13, for connection thereof by means of a vacuum line. As with the magnetically coupled wiper assembly, spring means will be required to provide initial contact between the wiper blade 10 and screen 14 and to restore contact if contact is momentarily lost.

In the embodiment illustrated in figures 5, 6A and 6B, a flexible blade 10 is mounted on a spine 51 of circular cross section, said spine 51 locating through a longitudinal bore 52 in the body portion 11 of blade 10 and stop means 53 being provided at the end of spine 51 to retain the blade 10.

Spine 51 is curved to curvature corresponding to the maximum curvature of screen 14 and is mounted on the drive spigot 54, in a manner such that it may be rotated relative to the spigot 54 to vary its orientation relative to the screen 14. Means, for example crank 55, is provided adjacent the spigot 54, by which the spine 51 may be rotated by for example a cam driven lever, to rotate spine 51 relative to spigot 54 as the blade 10 is traversed across the screen 14 about spigot 54.

With this arrangement, the curvature of the blade 10 may be adjusted by rotating the spine 51 relative to spigot 54, so that when the screen is at its greatest curvature, the spine 51 will be positioned so that it is parallel to the curvature of the screen 14 a projection thereof providing a straight line on the plane of screen 14 as illustrated at positon A in figure 6A. As the blade 10 is traversed over the screen in the direction of arrow M in figure 6A, the spine 51 is rotated so that the curvature of the blade 10 matches that of the screen 14, the curvature of the screen 14 decreasing towards the centre of the screen. As the spine 51 is rotated, the blade 10 is curved in the plane of the screen 14, so that its outer end trails, as illustrated at position B in figure 6A.Rotation of the spine 51 is continued until when the blade 10 is at the centre of the screen, position C, where the screen is flat, the blade 10 will also be flat. Rotation of the spine 51 will then be reversed gradually increasing curvature of the blade 10 until it will again form a straight projection in the plane of the screen at position D, at the end of its sweep.

On the reverse sweep as illustrated in figure 6B, the spine 51 will be rotated in the opposite direction, so that the blade 10 will again conform to the curvature of the screen 14, but will be bent backwards in the plane of the screen 14 relative to the new direction of movement. With this system, the flexibility of the blade will accommodate any small errors that may occur between the curvature of the spine 51 and the screen 14.

Various modifications may be made without departing from the invention. For example, the wiper blade used in the wiper mechanisms described above would normally be made in one part, from a resilient material, for example a rubber composition. However the body portion 11 and screen engaging portions 12 and 13 may alaternative be made separately and joined together in suitable manner. With this two part construction, the screen engaging portions 12 and 13 may be made of a resilient material such as a rubber composition and the body portion could be made, for example of a plastics material which while permitting flexing of the blade normal to the screen would be rigid transversely, thus avoiding the need for a separate blade holder.

Furthermore, with a wiper assembly of the form described with reference to figure 4, a blade of two part construction may be used in which the body portion 11 of the blade 10 constitutes the arm 40.

Claims

1. A windscreen wiper mechanism- including an elongate wiper blade, said wiper blade comprising a body portion and a pair of oppositely inclined screen engaging portions diverging away from the body portion, each screen engaging portion defining with the body portion a longitudinally extending laterally opening channel therebetween, the wiper blade being mounted on a wiper arm, by which it is connected to a drive shaft on which it may be traversed in reciprocating manner across à windscreen, the blade being arranged to pivot with respect to the arm about a longitudinal axis, said axis being on the screen side of the line describing the angle of friction at the point of contact between the edge of the leading screen engaging portion and the windscreen.

2. A windscreen wiper mechanism according to Claim 1 in which the screen engaging portions are of wedge shaped cross-section, reducing in thickness from the body portion towards the screen engaging edge.

3. A windscreen wiper mechanism according to Claim 1 or 2 in which the body portion and screen engaging portions are of integral construction.

4. A windscreen wiper mechanism according to any one of Clains 1 to 3 in which the wiper arm is a balanced beam arm.

5. A wiper mechanism according to Claim 4 in which the balanced beam arm is provided with a pivotted cover.

6. A wiper mechanism according to Claim 4 or 5 in which the balanced beam arm is designed to provide its most compact profile when the wiper mechanism is in the parked position.

7. A windscreen wiper mechanism according to any one of Claims 1 to 3 in which the blade is mounted on an arm which is rigid relative to the direction of reciprocating movement but is flexible in a direction normal to the plane of movement, an inner element being disposed on the opposite side of the windscreen to the arm and being driven coincidentally with the arm, the arm and inner element being coupled magnetically to maintain the blade, along its length, in engagement with the windscreen.

8. A windscreen wiper mechanism according to any one of Claims 1 to 3 in which the blade is mounted on an arm which is rigid relative to the direction of reciprocating movement but flexible in a direction normal to the plane of movement, means being provided to produce a vacuum in the void defined between the screen engaging portions of the wiper blade and the screen, said vacuum acting to maintain the blade, along its length, in engagement with the screen.

9. A windscreen wiper mechanism according to any one of Claims 1 to 3 in which the arm is in the form of a curved spine, the spine being rotatable to vary the curvature of the blade along its length, means being provided to rotate the spine as the blade is traversed across the windscreen, thereby varying the curvature of the blade to conform with the curvature of the windscreen.

10. A windscreen wiper mechanism according to Claim 9 in which the curved spine is formed by a rod of circular section, said rod being located through a longitudinal bore in the body portion of the blade.

11. A windscreen wiper mechanism according to Claim 10 in which a crank is provided at the end of the rod adjacent the drive shaft, means being provided for rotation of the crank to vary the curvature of the blade as it traverses across the windscreen.

12. A wiper mechanism substantially as described herein with reference to, and as shown in, Figures 1 to 6 of the accompanying drawings.