A device for operating a motor-vehicle windscreen-wiper arm

Abstract: A device for operating a windscreen-wiper arm includes a crank (2) which is rotated in opposite senses and carries a cylindrical pin (4), and a connecting rod (28) articulated to the crank (2) by means of a ball (6) mounted eccentrically on the cylindrical pin (4). Means are associated with the ball (6) for reversing its eccentricity relative to the cylindrical pin (6) as a result of the reversal of the sense of rotation of the crank in order to achieve an additional stroke of the windscreen-wiper arm which brings it to a concealed rest position. A coupling peg (18) is slidable axially through the ball (6) between two opposite engagement positions, in the first of which it engages a seat (24) with an inclined profile formed in the crank (2) and in the second of which it engages a cavity (36) in a cap member (26) carried by a connecting rod. The cap member (26) has a projection (32) which cooperates with a groove (34) in the ball (6) and the cavity (36) is recessed with respect to a reaction surface (30) against which one end of the peg (18) is urged.

Description: The present invention relates to a device for operating a windscreen-wiper arm, of the type comprising: a crank which can be rotated in opposite senses and carries a cylindrical pin, a ball mounted eccentrically and rotatably on the cylindrical pin, a cap member carried by a connecting rod and rotatable on the ball, a coupling peg slidable axially through the ball between two opposite engagement positions, in the first of which - corresponding to the rotation of the crank in a first sense - it engages a seat with an inclined profile formed in the crank and makes the ball fast for rotation with the crank and in the second of which - corresponding to the rotation of the crank in a second sense opposite the first - it engages a cavity in the cap member, and cam means between the ball and the crank for switching the peg between its first and second engagement positions when the rotation of the crank is reversed from the first sense of rotation to the second. A device of the type specified above is described in the same Applicant's Italian patent application IT-A-8867553 corresponding to GB-A-2 219 491 published on 13.12.89 and therefore not being part of the state of the art as defined in Art. 54(2) EPC in conjunction with Art. 89 EPC. The operating sequence of the aforesaid device is as follows. During normal operation, the crank is rotated in the first sense, for example anticlockwise. The peg engages the cavity in the cap and makes the connecting rod fast for rotation with the ball. The latter rotates on the cylindrical pin and is entrained for rotation by the crank. When the windscreen-wiper is switched off, a control unit reverses the sense of rotation of the electric motor which drives the crank when the crank reaches its end of travel position, so that it rotates through 360° in the second sense (clockwise) before stopping. During this rotation, the peg engages the seat in the crank and makes the ball fast with the crank; the ball thus reverses its eccentricity relative to the normal operating configuration and enables the windscreen-wiper arm connected to the connecting rod to perform an additional angular stroke which brings the blade to a lowered rest position. When the windscreen-wiper is switched on again, the control unit supplies the electric motor so that it rotates through 180° in the second sense of rotation (clockwise). During this rotation, the peg re-engages the cavity in the cap member, as is necessary for the normal operation of the windscreen-wiper. The control unit then reverses the sense of rotation of the motor, returning the crank to its normal sense of rotation. The aforesaid rotation through 180° in the clockwise sense when the windscreen-wiper is switched on makes the control unit more complicated. The object of the present invention is to provide an operating device of the type specified at the beginning of the present description which does not need to rotate in the second sense of rotation when the windscreen-wiper is switched on. According to the present invention, this object is achieved by the provision of an operating device of the type defined above, characterised in that the cap member has a projection which cooperates with a groove formed in the ball and which is adapted to abut an end of the groove when the crank rotates in the second sense so that the ball applies to the peg a lateral force which causes the peg to come out of the seat in the crank as a result of its reaction against the inclined profile of the seat, and in that the cavity in the cap member is recessed with respect to a reaction surface against which an end of the peg presses as a result of the force due to friction between the ball and the cap member. The present invention will now be described with reference to the appended drawings, provided purely by way of non-limiting example, in which: Figure 1 is an exploded perspective view of the device according to the present invention, and Figures 2, 3 and 4 are sections taken on the line II-II of Figure 1 in various operating conditions. With reference to the drawings, a device for operating a windscreen-wiper arm is indicated 1 and includes a crank 2 fixed to the drive shaft of a reversible electric motor (not shown). A cylindrical pin 4 is fixed to the crank 2 and a ball 6 is mounted rotatably and eccentrically thereon. A cam disc 8, which is also mounted eccentrically on the cylindrical pin 4 and has a peripheral notch 10, is interposed in known manner between the ball 6 and the crank 2. In known manner, the cam disc 8 has a tooth 12 which engages an arcuate groove 14 in the ball 6. An axial aperture 16 is formed in the ball 6 and a peg 18 slidable therein is urged by a helical spring 20 in the direction indicated by the arrow A in Figure 1. The peg 18 has a lower, wedge-shaped portion 22 for cooperating with a seat 24 with an inclined profile formed in the crank 2. A cap member 26 carried by a connecting rod 28 to which the windscreen-wiper arm (not shown) is fixed is rotatable on the ball 6. The cap member 26 has a reaction surface 30 with a projection 32 which cooperates with a groove 34 in the ball 6. A cavity 36 engageable by an end 38 of the peg 18 is also formed in the reaction surface 30 and is recessed therein. When the windscreen-wiper is operating normally, the device described above behaves in exactly the same way as that described in the Italian patent application IT-A-67553 cited above. In the normal operating configuration shown in Figure 4, the peg 18 is restrained with its end 38 engaged in the cavity 36 in the cap member 26, since the notch 10 in the cam disc 8 is offset from the position of the peg 18 and the end 22 of the latter bears against the surface of the cam disc 8. The tooth 12 of the disc 10 reacts frontally against an end of the groove 14 so that, during the rotation of the crank 2, the cam disc 8 is fast for rotation with the ball 6 and its angular position relative to the peg 18 does not, therefore, change. Thus, in normal operation, during which the crank 2 rotates in the sense indicated by the arrow K in Figure 1, the cap member 26 and the ball 6 are fast for rotation and the ball 6 rotates on the cylindrical pin 4. When the windscreen-wiper is switched off, a control unit, not shown, reverses the sense of rotation of the electric motor, in known manner, so that the crank 2 performs one complete turn in the sense indicated by the arrow H in Figure 1 before stopping. As described in detail in the aforementioned Italian patent application IT-A-67553, during this rotation in the sense indicated by the arrow H, the cam disc 8 is no longer entrained by the tooth 12 and remains stationary as a result of friction with the surface of the crank 2. The notch 10 in the disc 8 is positioned in correspondence with the seat 24 in the crank 2. The ball 6 rotates until the peg 18 is in correspondence with the notch 10 in the disc 8. The peg is urged into engagement with the seat 24 by the spring 20 so that its end 22 makes the ball 6 fast for rotation with the crank 2. During this reverse rotation, the eccentricity of the ball 6 is reversed with respect to the normal operating configuration, increasing its throw and enabling the connecting rod 28 and the windscreen-wiper arm to perform an additional angular stroke which brings the arm to a lowered rest position outside the driver's field of view. When the device according to the present invention is switched on again, the crank 2 is immediately rotated in the sense of normal operation indicated by the arrow K without a preliminary rotation in the reverse sense indicated by the arrow H. At first, the ball 6 rotates with the crank 2 as long as the peg 18 remains engaged in the seat 24 of the crank 2. The projection 32 of the cap member 26 abuts the end 34b of the groove 34 as a result of the rotation of the ball 6 relative to the cap member 26 of the connecting rod 28. At the same time, the cavity 36 is positioned in correspondence with the axis of the peg 18; the peg 18 is no longer forced to engage the seat 24 by the reaction surface 30 of the cap member 26. The peg 18 is acted on laterally by the ball 6 which in turn is entrained by the projection 32 in abutment with the end 34b of the groove 34. The peg 18 is moved axially as a result of the reaction between the peg 18 and the inclined seat 24 and engages the cavity 36, enabling the ball 6 to rotate freely relative to the crank 2. At this point, the device 1 is in the configuration shown in Figure 3, with the cap member 26 made fast with the ball 6 by means of the peg 18 and by means of the projection 32 which bears against the end 34b. After the peg 18 has engaged the seat 36, the cam disc 8 rotates relative to the ball 6, into its normal operating position.

Claims: A device for operating a windscreen-wiper arm, comprising: a crank (2) which can be rotated in opposite senses and carries a cylindrical pin (4), a ball (6) mounted eccentrically and rotatably on the cylindrical pin (4), a cap member (26) carried by a connecting rod (28) and rotatable on the ball (6), a coupling peg (18) slidable axially through the ball (6) between two opposite engagement positions, in the first of which - corresponding to the rotation of the crank in a first sense (H) - it engages a seat (24) with an inclined profile formed in the crank (2) and makes the ball (6) fast for rotation with the crank (2) and in the second of which - corresponding to the rotation of the crank (2) in a second sense (K) opposite the first - it engages a cavity (36) in the cap member (26), and cam means (8) between the ball (6) and the crank (2) for switching the peg (18) between its first and second engagement positions when the rotation of the crank (2) is reversed from the first sense of rotation to the second, characterised in that the cap member (26) has a projection (32) which cooperates with a groove (34) formed in the ball (6) and which is adapted to abut an end (34b) of the groove (34) when the crank (2) rotates in the second sense (K) so that the ball (6) applies to the peg (18) a lateral force which causes the peg (18) to come out of the seat (24) in the crank (2) as a result of its reaction against the inclined profile of the seat (24), and in that the cavity (36) in the cap member (26) is recessed with respect to a reaction surface (30) against which an end of the peg (18) presses as a result of the force due to friction between the ball (6) and the cap member (26).

Inventors: PEDANI GIUSEPPE, PEDANI, GIUSEPPE
Applicants: MAGNETI MARELLI SPA, INDUSTRIE MAGNETI MARELLI S.P.A.
Application year: 1990
Main classification: B60S1
IPC codes: B60S1