GB2219491A

GB2219491A - Crank mechanism for windscreen wiper assembly

Info

Publication number: GB2219491A
Application number: GB8912634A
Authority: GB
Inventors: Roberto Asero; Francesco Galluzzi
Original assignee: Industrie Magneti Marelli SRL; Magneti Marelli SpA
Current assignee: Industrie Magneti Marelli SRL; Marelli Europe SpA
Priority date: 1988-06-10
Filing date: 1989-06-02
Publication date: 1989-12-13
Anticipated expiration: 2009-06-02
Also published as: AR243823A1; IT1219373B; ES2015404A6; DE3918464A1; GB2219491B; FR2632589B1; BR8903025A; GB8912634D0; FR2632589A1; IT8867553A0

Description

1 1 2219491 DEVICE FOR AClUATING A WINDSCREEN WIPER ARM FOR MOTOR VEHICLES

The present invention relates in general to windscreen wipers for motor vehicles and concerns more particularly a device for actuating a windscreen wiper arm by means of which, when the latter is made to come to a standstill, this arm performs an additional travel below the normal cleaning zone, until it stops in a lowered position where it comes to lie in the immediate vicinity of the bottom edge of the windscreen so as substantially to disappear from view.

To achieve this function, actuating devices have been proposed, including a crank capable of being made to rotate in opposite directions and carrying a cylindrical pin, a connecting rod articulated with the crank by means of a ball joint mounted eccentrically on the abovemen- tioned cylindrical pin, and coupling means associated with said ball joint in order to invert its eccentricity relative to the cylindrical pin as a result of reversal of the direction of rotation of the crank. It is precisely reversal of the eccentricity of the cylindrical pin which makes it possible to obtain, prior to the windscreen wiper arm stopping, the additional travel which brings this arm and the windscreen wiper blade associated therewith into a lowered hidden position.

In the known actuating devices of this type, described for example in GB-A-2,141,021, the coupling means for inverting the eccentricity of the ball joint relative to the cylindrical pin normally comprise two spring-type engaging members, one of which is slidable axially and cooperates with the crank and the other of which is slidable radially and cooperates with the conn&cting rod, and associated cam devices for switchingover coupling between the ball joint and the connecting rod and crank, respectively.

These solutions are, from a constructional point of view, rather complex and costly, as well as being of limited operational reliability.

2 An object of the present invention is to overcome the abovementioned drawback and to provide an actuating device of the type specified above, consisting of a small number of components which are more simple and economical to manufacture and assemble as well as being able to ensure greater reliability and greater safety of operation.

According to the present invention there is provided a device for actuating a windscreen wiper arm, wherein a crank adapted to rotate in opposite directions and carries a cylindrical pin, and is articulated with a connecting rod by means of a ball joint mounted eccentrically on the cylindrical pin, and wherein coupling means is associated with said ball joint for inverting its eccentricity relative to the cylindrical pin as a result of reversal of the direction of rotation of the crank, and comprises a single bolt slidable axially through said ball joint between two opposite engaging positions, in the first of which, corresponding to rotation of the crank in a first direction, the said bolt locks said ball joint in rotation with one of said connecting rod or crank, and in the second of which, corresponding to rotation of the crank in a second direction, opposite to the first direction the said bolt locks said ball joint in rotation with the other of said crank or connecting rod, and cam means between said ball joint and the crank for switching over the bolt between said two engaging positions when rotation of the crank is reversed.

According to a preferred embodiment of the inven- tion, the bolt is subjected to the action of a spring tending to push it axially towards the crank, and the abovementioned cam means comprise a disc inserted between the crank and the ball joint with a coefficient of friction relative to the crank greater than the coefficient of friction relative to the ball joint, and having an eccentric hole through which the cylindrical pin passes; said disc keeping, in said first direction of 3 rotation of the crank, the bolt rotationally coupled at its first end with the connecting rod, against the action of the spring, and having an opening which, in said first direction of rotation of the crank, is angularly offset relative to an engaging seat formed in the crank; coupling means being provided for locking the cam in rotation with the ball joint in said first direction of rotation of the crank, and so as to allow rotation of the cam relative to the ball joint when the crank is made to rotate in said second direction of rotation, until said opening in the cam, said engaging seat of the crank and the bolt are aligned with each other, enabling engagement of the second end of the bolt in said retaining seat owing to the action of the pressure spring. 15 The abovementioned second end of the bolt and the engaging seat of the crank advantageously have respective complementary surfaces with a ramp, so as to allow mutual disengagement thereof following reversal from said second to said first direction of rotation of the crank. 20 The invention will now be described in detail with reference to the accompanying drawings, provided purely by way of a non-limiting example, in which: Figure 1 is a schematic front elevation view of a windscreen wiper for motor vehicles, provided with an actuating device according to the invention, Figure 2 is an exploded perspective view of the actuating device, Figure 3 is a schematic plan view which shows the actuating device during its normal operation, in four successive angular positions, Figure 4 is a cross-sectional view, on a larger scale, along the line IV-IV of Figure 3, Figure 5 is a developed, cross-sectional view along the line V-V of Figure 4, Figure 6 is a view, similar to Figure 3, which shows the actuating device in three successive angular positions during a first phase of reverse operation, 4 Figure 7 is a cross-sectional view along the line VII-VII of Figure 6, Figure 8 is a developed, cross-sectional view along the line VIII-VIII of Figure 7, Figure 9 is a view, similar to Figures 3 and 6, which shows the device in three successive angular posi tions during a second phase of its reverse operation, and Figure 10 is a cross-sectional view, on a larger scale, along the line X-X of Figure 9, and Figure 11 is a view, similar to Figure 4, of a variation of a part of the device.

With reference initially to Figure 1, W denotes schematically the windscreen of a motor vehicle, with which there is associated a windscreen wiper arm T is including a wiper blade S carried by an arm B displaceable in an alternating angular movement across the windscreen W by means of an actuating device 1.

AS will be seen below, during normal operation of the device 1, the windscreen wiper blade S mounted on the arm B sweeps the windscreen W over an angular zone of amplitude A. When the device 1 is switched off the windscreen wiper blade S performs, below the normal cleaning zone A, an additional angular travel of amplitude Ce so that it comes to lie at the bottom of the windscreen W such that it is almost invisible to the occupants of the vehicle.

With reference now in greater detail to Figure 2, the actuating device 1 comprises a drive spindle 2, which is rotatable in a conventional manner by a reversible electric motor (not shown) so that it can be turned in one direction or in the opposite direction of rotation and to which a crank 3 is fixed.

The crank 3 carries a fixed cylindrical pin 4, which projects perpendicularly to the plane of the crank 3, and on which a ball joint 5 is eccentrically and rotatably mounted. In the example illustrated, the pin 5 has an axially eccentric through-hole 6 through which there passes the cylindrical pin 4 which is locked axially with respect to the ball joint 5 by means of an elastic retaining ring 7. In Figure 4, the axes of the cylindrical pin 4 and of the ball joint 5 are indicated, respectively, by X and Y, and their eccentricity is indicated by e.

The ball joint 5 is in turn coupled axially in a rotatable manner inside a cap 8 mounted on a connecting rod 9, in turn connected, in a known manner, to the arm B of the windscreen wiper T.

A cam disc 10 is inserted axially between the ball joint 5 and the crank 3 and has an axial eccentric hole 11, aligned with the hole 6 of the ball joint 5, through which the cylindrical pin 4 passes in a rotatable manner.

The arrangement is such that the coefficient of friction during sliding between the cam disc 10 and the ball joint 5 is less than the coefficient of friction during sliding between this cam disc 10 and the crank 3. This may be obtained, for example, by manufacturing the ball joint 5 from a self -lubricating plastics material, while the cam disc 10 and the crank 3 are normally metallic.

From the face of the cam disc 10 directed towards the ball joint 5 there extends a projection 12 which engages slidably inside a curved slot 13 formed in the corresponding face of the ball joint 5. The arrangement is such that, during normal operation of the windscreen wiper T, the projection 12 comes up against one end of the slot 13, as a result of which the cam disc 10 is driven in rotation integrally with the ball joint 5. As will be seen below, when the windscreen wiper T is actuated in reverse, the projection 12 is free to slide inside the slot 13, as a result of which, owing to the greater coefficient of friction between the disc 10 and the crank 3, angular displacement of this cam disc 10 relative to the ball joint 5 is produced.

The cam disc 10 has, moreover, a peripheral notch 14 6 designed to cooperate in the manner explained below with an engaging seat 15 formed in the surface of the crank 3 on which the disc 10 rests. As can be seen more clearly in Figure 5, the engaging seat 15 has at one end a ramp 5 15a, for the purposes explained below.

A bolt 17 is mounted so as to be able to slide axially through a throughopening 18 in the ball joint 5. The end 17a of this bolt 17, directed towards the connect- ing rod 9, is designed to cooperate with a retaining seat 19 formed on the inside of the cap 8. The other end 176 of the bolt 17 is formed in the manner of an inclined ramp such as the ramp 15a of the engaging seat 15 of the crank 3, so as to cooperate with the latter in the manner described below.

A helical compression spring 20 reacting between the ball joint 5 and a support arm 21 of the bolt 17 tends to press the latter in tho- direction of the crank 3.

The mode of operation of the actuating device 1 described above is as follows.

With reference initially to Figure 3, it is assumed that the windscreen wiper T has been operated normally by actuating (via an appropriate known switch normally of the lever type) the electric motor associated with the drive spindle 2, in its normal direction of rotation indicated by the arrow H in Figures 3 and 4. During normal operation, the arm B moves across the cleaning zone A on the windscreen W; the arrangement of the components of the device 1, shown in detail in Figures 4 and 5, is such that the eccentricity e is displaced from the region of the pin 2, i.e. the axis Y of the ball joint 5 is arranged radially on the inside with respect to the axis X of the cylindrical pin 4, in the initial position corresponding to the start of the angular cleaning path A. This position is indicated in Figure 3 by 00. The arrangement is moreover such that the notch 14 of the cam disc 10 is situated in a position diametrically opposite to the 7 engaging seat 15 of the crank 3, and the bolt 17 is held with its end 17a in engagement inside the seat 19 of the connecting rod 9, against the action of the spring 20. The projection 12 of the disc 10 comes up, at the front, against one end of the channel 13 of the ball joint 5 such that, during the entire rotation of the cylindrical pin 4 with the crank 3, the cam disc 10 is locked in rotation with the ball joint 5 and hence its angular position relative to the bolt 17 does not change. In this position the notch 14 of the cam disc 10 is angularly offset with respect to the end 17b of the bolt 17 and, as a result of engagement of the end 17a inside the seat 19, the cap 8 and the connecting rod 9 are locked in rotation with the ball joint 5. The latter rotates obviously on the cylin- drical pin 4.

As is clear from Figure 3, the arrangement described above remains unchanged during the movement into the successive positions indicated by 900, 1800 and 2700, except for the relative displacement between the crank 3 and the other components of the device 1.

In practice, therefore, during normal operation of the windscreen wiper T, the cam disc 10 keeps the connecting rod 9 and the ball joint 5 constantly connected in rotation, so that each time the arm B of the windscreen wiper T arranges itself in the initial 00 position, it is located at the bottom ofi. the cleaning zone A and, therefore, at a certain distance from the bottom edge of the windscreen W.

When the windscreen wiper T is deactivated, an appropriate automatic switch, not shown, in a manner known per se reverses the direction of rotation of the electric motor and hence of the drive spindle 2, as soon as the device 1 assumes the 00 position again. Angular displacement of the device 1, through a complete revolution of 3600, in the direction of the arrow indicated by K in Figures 6, 7 and 9, is then performed. This complete rotation has been divided up, for the sake of clarity, 8 into two successive phases from 0 to 1800 (Figures 6 to 8) and from 1800 to 00 (Figures 9 and 10).

During the f irst phase, as a result of reversal of the direction of rotation of the crank 3, angular 5 displacement of the cam disc 10 relative to the ball joint 5 occurs, owing to entrainment thereof by the crank 3 and owing to sliding of the projection 12 inside the slot 13 of the ball joint 5. Passing from the 00 position to the 1800, the cam disc 10 performs a corresponding angular displacement of 1800, into the position shown in Figures 7 and 8. In this position the notch 14 of the cam disc 10 is arranged in axial alignment, on one side, with the engaging seat 15 of the crank 3 and, on the other side, with the bolt 17. As a result of the pressure exerted by the spring 20, the end 17b of the bolt 17 engages inside the receiving cavity 15, while the end 17a disengages from the seat 18 of the cap mounted on the connecting rod 9. In this manner, rotational coupling of the ball joint 5 is switched over, the latter being freed relative to the cap 8 and hence to the connecting rod 9 and being locked in rotation with the crank 3. As can be seen clearly in Figure 7, in the 1800 position, the eccentricity e between the ball joint 5 and the cylindrical pin 4 is diametrically opposite to that corresponding to the initial 00 position; in other words, the axis Y of the ball joint 5 is situated radially on the outside of the axis X of the cylindrical pin 4.

During the second phase of reverse rotation, shown in Figures 9 and 10, the device reaches, in succession, the 2700 position and the final 00 position. During this rotation, the relative arrangement of its components does not change: the only relative angular movement during this phase is that between the cap 8 of the connecting rod 9 and the ball joint -5. Consequently, when the device 1 stops in the final 00 position, the abovedescribed reversal of the eccentricity e allows the arm B of the windscreen wiper T to perform the additional travel C, so 9 as to arrange the blade S in the immediate vicinity of the bottom of the windscreen W.

When the windscreen wiper T is activated again, as a result of rotation of the device 1 in the direction of the arrow H there occurs, when the 1800 position is reached, disengagement between the end 17b of the bolt and the receiving seat 15 of the crank 3, owing to the inclined surface 15a and the corresponding configuration of the end 17b. The bolt 17 then rises again against the action of the spring 20, rearranging itself with its end 17a engaging in the seat 19 of the cap 8, and is kept in this position as a result of the subsequent rotation of the cam disc 10 relative to the ball joint 5 into the position where the lug 12 comes up against the end of the channel 13.

obviously the constructional details and the embodiments may be varied with respect to that described and illustrated, without thereby departing from the scope of the present invention.

A possible variation is shown in Figure 11, in which parts identical or similar to those described previously are indicated by the same reference numbers. In this variation the ball joint 5 (which is normally made of plastic, as is the cam disc 10) has, in the region of the crank 3, an annular cover in the form of an axial lug 5a which surrounds the cam disc 10. This cover 5a advantageously protects the internal parts of the device from the ingress of external agents.

Furthermore, in order to increase during operation the friction between the ball joint 5 and the cap 8 of the connecting rod 9, necessary for entrainment of the former by the latter so as to allow disengagement of the bolt 17 from the receiving seat 15, the ball joint 5 advantageously has an external circumferential groove 5b which is formed on its widest diametral point and inside which an oring made of elastomeric material 5c is accommodated. In the assembled condition of the device 1, this 0-ring 5c is arranged in frictional contact against the internal side wall of the cap 8.

Furthermore, the engaging arrangement of the bolt 17 could be reversed compared to that described with reference to the example illustrated, and provide during normal operation of the windscreen wiper T the rotational connection between the ball joint 5 and the crank 3 by means of the bolt 17 and, during the phase of reverse operation, engagement between this bolt 17 and the connecting rod 9. In practice, therefore, during normal operation, sliding occurs between the ball joint 5 and the cap 8 of the connecting rod 9, while, during reverse operation where there is additional travel, sliding occurs between the ball joint 5 and the cylindrical pin 4. In such a case, if R, is the increase in the radius of the crank 3 necessary for obtaining the additional angular travel, the eccentricity necessary for obtaining the required increase R, will be e = R,/2, instead of e = R, as in the case described above.

Finally, in the case of a windscreen wiper T with two blades, the ball joint 5 could have a double con figuration, i.e. with two axially superimposed portions with a cylindrical surface, for connecting both associated connecting rods to the blades. In this case, the general arrangement of the device 1 does not change, since a single bolt 17 is sufficient to invert the eccentricity e of both ball joints.

J 11

Claims

A device for actuating a windscreen wiper arm, wherein a crank adapted to rotate in opposite directions carries a cylindrical pin, and is articulated with a connecting rod by means of a ball joint mounted eccentrically on the cylindrical pin, and wherein coupling means is associated with said ball joint for inverting its eccentricity relative to the cylindrical pin as a result of reversal of the direction of rotation of the crank, and comprises a single bolt slidable axially through said ball joint between two opposite engaging positions, in the first of which, corresponding to rotation of the crank in a first direction, the said bolt locks said ball joint in rotation with one of said connecting rod or crank, and in the second of which, corresponding to rotation of the crank in a second direction, opposite to the first direction the said bolt locks said ball joint in rotation with the other of said crank or connecting rod, and cam means between said ball joint and the crank for switching over the bolt between said two engaging positions when rotation of the crank is reversed.
2. A device according to Claim 1 wherein said bolt is subjected to the action of a pressure spring tending to push it axially towards the crank, and wherein said cam means comprise a disc inserted between the crank and the ball joint with a coefficient of friction relative to the crank greater than the coefficient of friction relative to the ball joint and having an eccentric hole through which the cylindrical pin passes; said disc keeping, in said first direction of rotation of the crank, the bolt rotationally coupled at a first end with the connecting rod against the action of said pressure spring, and having an opening which, in said first direction of rotation of the crank, is angularly offset relative to an engaging seat 12 formed in the crank; coupling means being provided for locking the cam in rotation with the ball joint in said first direction of rotation of the crank, and so as to allow rotation of the cam relative to the ball joint when the crank is made to rotate in said second direction of rotation, until said opening in the cam, said engaging seat of the crank and the bolt are aligned with each other, enabling insertion of the second end of the bolt in said retaining seat owing to the action of said pressure spring.
3. A device according to Claim 2, wherein said second end of the bolt and said engaging seat of the crank advantageously have respective complementary surfaces with a ramp, so as to allow mutual disengagement thereof following reversal from said second to said first direction of rotation of the crank.
4. A device according to Claim 2, wherein the ball joint has, in the region of the crank, an annular covering lug which encloses the abovementioned cam disc.
5. A device according to Claim 2 or 4, wherein the ball joint has an external circumferential groove inside which an 0-ring made of elastomeric material is accommodated, and wherein the connecting rod has a cap-type member which is engaged on the ball joint and the internal wall of which is in friction contact with said 0-ring.
6. A device for actuating a windscreen wiper arm substantially as hereinbefore described with reference to Figures 1 to 10 or Figures 1 to 10 as modified by Figure 11 of the accompanying drawings.

Published 1989 atThe PatentOffice, State House. 6&7 Fu_-,her copies rnkvbe obtaxnelrom The Patent Office- gton. Kent BR5 3RD. Printed by Multiplex techniques ltd, St Msz7 Cray. KenL, Con. 1187 Sales Branch, St Mary Cray, Orpir 1 High Holborn. London WCIR 4TP.