GB2278536A

GB2278536A - Screen wiper having means for varying the value of the wiping moment

Info

Publication number: GB2278536A
Application number: GB9410919A
Authority: GB
Inventors: Jean-Pierre Eustache
Original assignee: Valeo Systemes dEssuyage SAS
Current assignee: Valeo Systemes dEssuyage SAS
Priority date: 1993-06-02
Filing date: 1994-06-01
Publication date: 1994-12-07
Anticipated expiration: 2014-06-01
Also published as: GB9410919D0; FR2705938B1; FR2705938A1; DE4417109A1; GB2278536B

Description

a 1 2278536 A MOTOR VEHICLE SCREEN WIPER HAVING MEANS FOR VARYING THE

VALUE OF THE WIPING MOMENT This invention relates to screen wipers, especially for motor vehicles, of the type comprising a wiper arm which carries at least one wiper blade and which is articulated about a pivot axis on a drive head for driving the wiper arm.

In such a wiper, the drive head is driven in alternating rotary, or oscillating, motion by a drive shaft in order to sweep over the glass surface which is to be wiped. The wiper arm carries a wiper blade which is articulated and which is adapted to sweep over the glass surface, which is typically the windscreen of the vehicle.

In order to obtain effective wiping of the glass surface, it is necessary for the wiping strip of the blade to be applied on the glass surface with a sufficiently large pressure or wiping force. To this end it is known to provide at least one spring, for example a helical compression or tension spring, which is arranged between the drive head and the wiper arm, and which applies to the latter a force along a line of action which does not intersect with the pivot axis on which the wiper arm is articulated on the drive head. A wiping moment is thus applied to the wiper arm (this moment may also be referred to as a nominal wiping torque), its value being substantially constant.

Due to the design of this arrangement, the wiping strip is not only applied to the glass surface during the wiping motion, but also in the rest position of the wiper. Due to the constancy of the nominal wiping 2 force which is applied to the wiping strip when the wiper is in its rest position, the wiping strip tends to retain a residual deformation resulting from the squeezing of its profile against the curved surface of the glass. The result is that the wiping strip no longer produces effective wiping of the glass surface.

It is thus desirable to be able to vary the wiping force applied to the wiping strip, especially when the wiper is at rest. To this end it has previously been proposed to provide a screen wiper of the general type mentioned above, which includes means for causing the distance between the line of action of the force exerted by the spring and the pivot axis on which the screen wiper arm is articulated on the drive head, to be varied.

In one embodiment of such a known arrangement, a first end of the spring is connected with a point on the wiper arm and the second end of the spring is connected to the drive head, the means for causing the distance between the line of action of the force and the pivot axis to vary being means for causing the position of the said second end of the spring to be varied with respect to the said pivot axis, these position varying means comprising a swing arm which is mounted on the drive head for rotary swinging movement about the swing axis parallel to the said pivot axis of the wiper arm, the wiper further including a linear actuator comprising a body associated with the drive head, together with an output shaft coupled to a first branch of the swing arm, for displacement in a direction at right angles to the said pivot axis and swing axis, with a second branch of the swing arm acting on the second end of the said spring.

3 The means for controlling the swinging movements of the swing arm in this known form of screen wiper make use of a linkage which is somewhat complicated to make, and which gives rise to a danger of jamming and of parasitic action on the linear actuator during the operation of the screen wiper.

In order to overcome the above mentioned drawbacks, the invention provides a screen wiper for a motor vehicle, comprising a wiper arm which is articulated about a pivot axis on a drive head of the wiper arm, with at least one spring arranged between the drive head and the wiper arm so as to apply to the latter a linear force along a line of action in non-intersecting relationship to the said pivot axis, whereby to apply a wiping moment to the wiper arm, a first end of the spring being connected with a point on the wiper arm and the second end of the spring being connected to the drive head, the spring wiper further including means for causing the position of the said second end of the spring to be varied with respect to the said pivot axis, the said position varying means comprising a swing arm which is mounted on the drive head for rotary swinging movement about a swing axis parallel to the said pivot axis of the wiper arm, the wiper further including a linear actuator comprising a body associated with the drive head, together with an output shaft coupled to a first branch of the swing arm, for displacement in a direction at right angles to the said pivot axis and swing axis, with a second branch of the swing arm acting on the second end of the said spring, wherein the first branch of the swing arm is formed with a profiled camming surface cooperating with a cam follower element which is arranged at the free end of 1 4 the output shaft of the actuator.

According to a preferred feature of the invention, the camming surface is defined in a slot formed in the said first branch of the swing arm, the said cam follower element being a finger secured to the free end of the actuator output arm and received in the said slot.

is Preferably, the profiled camming element has two end portions joined by a central portion, each of the two end portions being associated with an end position of the swing arm with respect to the drive head.

According to another preferred feature of the invention, each said end portion of the camming surface is rectilinear so that, when the swing arm occupies the end position associated with that end portion, the latter extends parallel to the said direction of displacement of the output member of the actuator.

According to a further preferred feature of the invention, the said spring is a helical compression spring, the said line of action of the force exerted by the spring being defined by an orientation rod extending through the spring, with the first end of the spring bearing against a first thrust surface associated with the screen wiper arm, while its second end bears against a second thrust surface associated with the orientation rod, one end portion of the latter being connected to the second branch of the swing arm.

Preferably, the said end portion of the orientation rod is articulated on the end of the second branch of the swing arm about an axis parallel to the said swing axis.

1 Further features and advantages of the invention will appear more clearly on a reading of the description of some preferred embodiments of the invention which follows, and which is given by way of example only and with reference to the accompanying drawings, in which:- Figure 1 is a diagrammatic view in partial longitudinal cross section, showing one example of a screen wiper made in accordance with the present invention, and shown in Figure 1 in its rest position; Figure 2 is a view in cross section taken on the line 2-2 in Figure 4; Figure 3 is a view in c ross section taken on the line 3-3 in Figure 4; is Figure 4 is a partial top plan view of the screen wiper seen in Figure 1; Figure 5 is a view in cross section taken on the line 5-5 in Figure 1; Figure 6 is a view in cross section taken on the line 6-6 in Figure 1; Figure 7 is a view on a larger scale of the central part of the screen wiper shown in Figure 1; Figure 8 is a view similar to that of Figure 7, in which the screen wiper is shown in a working position; and Figure 9 is similar to Figure 8, but shows a modified embodiment of the invention.

The screen wiper 10 shown in the drawings consists 6 essentially of a screen wiper arm 12, the body or shroud 14 of which is articulated on a drive head 16, about a geometric pivot axis X-X which extends in a direction substantially at right angles to the generally longitudinal direction of the screen wiper arm.

The drive head 16 is arranged to be connected to a drive spindle (not shown), which causes it to be displaced in alternating motion about a geometric axis Y-Y which is substantially at right angles to the pivot axis X-X.

z il A helical compression spring 18 is arranged between the screen wiper arm 12 and the drive head 16, in such a way as to apply to the screen wiper arm a wiping moment which biasses it in the anti-clockwise direction with respect to Figure 1. To this end, the straight line of action D of the compressive force exerted by the spring 18 does not intersect the axis X- X, and the value of the wiping moment which is applied to the screen wiper arm 12 is a function of the product of the compressive force exerted by the spring 18 and the distance Id" (see Figure 2) between the straight line of action D and the pivot axis X-X.

An orientation rod 17 extends through the spring 18. A first free end portion 19 of the rod 17 is mounted for sliding movement in a hole 21 which is formed in a bracket element 22 of the body of the screen wiper arm 12. A first end 20 of the spring 18 bears against the corresponding abutment face of the bracket element 22, while its other or second end 24 bears against a thrust ring 26 which is fixed on the orientation rod 17.

7 Means are provided for causing the value of the wiping moment to vary, by varying the distance I'd" between the line of action D and the pivot axis X-X, this being done by varying the orientation of the line of action D, that is to say the orientation of the rod 17 itself. For this purpose, the second end portion 28 of the rod 17 is in the form of a fork in which an actuating pin 30 is received. The axis U-U of the actuating pin 30 is parallel to the pivot axis X-X. The actuating pin 30 is fixed to a swing arm 38.

The swing arm 38 is mounted for pivoting movement about a geometric swing axis T-T which is parallel to the pivot axis X-X. The swing arm 38 has a first branch 40 and a second branch 42, which extend in opposite is directions on either side of a central portion of the swing arm which is traversed by the swing axis T-T.

The second branch 42 carries the actuating pin 30 close to its free end; while a pivot pin 46, defining the axis T-T, extends through the central portion of the swing arm. The latter is thus mounted for rotation in the actuating head 16 as is shown especially in Figures 1 and 2, with the position of the geometric swing axis T-T being fixed with respect to the body of the drive head 16.

The second branch 40 of the swing arm 38 is formed with a cam slot 48, in which is received a cam follower element, here in the form of an actuating finger 50, which extends in a direction parallel to the pivot axis X-X and the swing axis T-T. The actuating finger 50 is secured at the end of a plunger 52 which is mounted for sliding movement in a guide sleeve 54, the latter being fixed to the interior of the drive head 16. The plunger 52 receives the threaded end 56 of the 8 rotatable output shaft 58 of a motor 62, the body of which is secured to the interior of the drive head 16.

The plunger 52, together with the shaft 58 and its motor 62, thus constitute a linear actuator of the screw and nut type, whereby the actuating finger 50 is displaced in back and forth sliding movement in a direction A (Figure 4) which is at right angles to the axes X-X and T-T.

is The cam slot 48 of the swing arm 38, which is best seen in Figure 7, has a camming surface which consists of a central portion 67 which joins together two end portions 66 and 70. Th.e first end portion 66 is rectilinear, and extends parallel to the direction of displacement A of the plunger 52 as can be seen in Figure 8, in which the swing arm 38 is shown in its extreme position in which the screen wiper arm 12 is at rest, i.e. the position associated with the rest position of the screen wiper itself.

Similarly, the second end portion 70 of the cam slot 48 is also rectilinear and, when the swing arm 38 occupies its other extreme position, i.e. that shown in Figure 7, the end portion 70 extends parallel to the direction A.

Command and control means (not shown) enable the position of the output plunger 52 of the actuator to be varied between either of the above mentioned two extreme positions shown in Figures 7 and 8. In the rest position shown in Figure 8, the distance "d" between the geometrical pivot axis X-X and the line of action D is at a minimum, the nominal wiping moment which is applied to the screen wiper arm 12 being then v 1 1 9 itself at a minimum; while, in the position shown in Figures 1 to 7, the distance I'd" is at a maximum, so that a maximum wiping torque is applied to the screen wiper arm 12.

is It is of course possible, without departing from the scope of the present invention, to control the actuator in such a way that the plunger 52 occupies an intermediate position between these two extreme positions, so that a nominal wiping moment is applied to the screen wiper arm 12 at a value lying between the above mentioned minimum and maximum values.

The straight end portions 66 and 70 of the cam slot 48 and their orientations, described above, enable the application of forces to the actuator to be avoided in the two extreme positions. The displacements of the motor shaft 58 can be controlled by means of a suitable detection device, such as a device 264 indicated diagrammatically in Figure 4, this being in this example of the electric rheostat type.

Reference is now made to Figure 9, which shows a modified embodiment of the invention in which the second branch 40 of the swing arm 38 is formed with an external camming surface 148, on which the actuating finger 50 slides.

central portion 1 joined together various portions their directions, the portions 64, above.

This camming surface 148 has a 64 and two end portions 166 and 170, by the central portion 164. These of the surface 148 correspond, as to substantially with the directions of 66 and 70 of the cam slot 48 described The invention is of course not limited to the embodiments described above. In particular, it is applicable in the case where the spring 18 is a helical compression spring.

It is also possible to conceive numerous modifications which will enable a law or pattern of variation of the wiping moment to be obtained which is more complex than in the embodiments described above. This may be done by modifying the profile of the central or connecting portion 64 of the cam slot 48 or the central portion 164 of the camming surface 148 in Figure 9.

z A

Claims

1. A screen wiper for a motor vehicle, comprising a wiper arm which is articulated about a pivot axis on a drive head of the wiper arm, with at least one spring arranged between the drive head and the wiper arm so as to apply to the latter a linear force along a line of action in nonintersecting relationship to the said pivot axis, whereby to apply a wiping moment to the wiper arm, a first end of the spring being connected with a point on the wiper arm and the second end of the spring being connected to the drive head, the spring wiper further including means for causing the position of the said second end of the spring to be varied with respect to the said pivot axis, the said position varying means comprising a swing arm which is mounted on the drive head for rotary swinging movement about a swing axis parallel to the said pivot axis of the wiper arm, the wiper further including a linear actuator comprising a body associated with the drive head, together with an output shaft coupled to a first branch of the swing arm, for displacement in a direction at right angles to the said pivot axis and swing axis, with a second branch of the swing arm acting on the second end of the said spring, wherein the first branch of the swing arm is formed with a profiled camming surface cooperating with a cam follower element which is arranged at the free end of the output shaft of the actuator.

2. A screen wiper according to Claim 1, wherein the profiled camming surface is defined in a slot formed in the said first branch of the swing arm, the said cam follower element being a finger secured to the free end of the actuator output arm and received in the said 12 slot.

3. A screen wiper according to Claim 1 or Claim 2, wherein the profiled camming surface has two end portions joined by a central portion, each of the two end portions being associated with an end position of the swing arm with respect to the drive head.

4. A screen wiper according to Claim 3, wherein each said end portion of the camming surface is rectilinear so that, when the swing arm occupies the end position associated with that end portion, the latter extends parallel to the said direction of displacement of the output member of the actuator.

5. A screen wiper according to any one of the preceding Claims, wherein the said spring is a helical is compression spring, the said line of action of the force exerted by the spring being defined by an orientation rod extending through the spring, with the first end of the spring bearing against a first thrust surface associated with the screen wiper arm, while its second end bears against a second thrust surface associated with the orientation rod, one end portion of the latter being connected to the second branch of the swing arm.

6. A screen wiper according to Claim 5, wherein the said end portion of the orientation rod is articulated on the end of the second branch of the swing arm about an axis parallel to the said swing axis.

7. A screen wiper for a motor vehicle, substantially as described in the foregoing description with reference to Figures 1 to 8 of the accompanying drawings.

z 13

8. A screen wiper according to Claim 7, save that it incorporates the modification described in the foregoing description with reference to Figure 9 of the accompanying drawings.