Wiper motor drive system having breakaway clutch

1. A wiper motor drive system comprising:

a motor, an output shaft operatively connected to a wiper blade, and a breakaway clutch operatively connected between said motor and said output shaft;

said breakaway clutch including a torque-sensitive releasable locking mechanism having a first position wherein torque is translated from said motor to said output shaft through said breakaway clutch to drive the wiper blade across a surface to be wiped, and a second position wherein torque is interrupted between said motor and said output shaft in response to a predetermined rotational torque differential acting on said output shaft, said locking mechanism being movable back to said first position when said differential torque is reduced on said output shaft;

wherein said torque-sensitive releasable locking mechanism further includes a groove defined in said output shaft, a collar disposed about said output shaft, said collar having a slot aligned with said groove of said output shaft and being in driven relationship with said motor, and a release member disposed in said groove of said shaft and in said slot of said collar, said release member movable from said first position wherein torque is translated from said collar to said output shaft through said release member and said second position wherein no torque is translated between said collar and said output shaft.

2. The wiper motor drive system as set forth in claim 1 , wherein said slot of said collar defines a pair of edges disposed in spaced parallel relationship with respect to each other, said release member has a cylindrical body which is carried in said groove in releasable fashion and operatively engages each of said edges of said slot to thereby translate torque between said collar and said output shaft.

3. The wiper motor drive system as set forth in claim 2 , wherein said groove of said output shaft has a concave profile.

4. The wiper motor drive system as set forth in claim 1 , wherein said torque-sensitive releasable locking mechanism further includes a retaining mechanism disposed about said collar and movable between a first radial position wherein said retaining mechanism acts to keep said release member disposed in said groove of said output shaft, and a second radial position wherein said retaining mechanism allows said release member to move out of said groove in response to a predetermined rotational torque differential.

5. The wiper motor drive system as set forth in claim 1 , wherein said retaining mechanism is a cylindrical ring having a gap extending longitudinally substantially along the entire length of said retaining mechanism such that said retaining mechanism is movable from a first radial position to a second radial position in response to a predetermined radial force generated by said release member as said release member moves to said second position.

6. The wiper motor drive system as set forth in claim 4 , wherein said output shaft further includes a stop operatively attached thereto and a washer disposed between said stop and said torque-sensitive releasable locking mechanism, such that said locking mechanism is constrained longitudinally with respect to said output shaft by said stop.

7. The wiper motor drive system as set forth in claim 4 , wherein said torque-sensitive releasable locking mechanism further includes a gear operatively attached to said collar, with said gear being in driven relationship with said motor so as to translate torque from said motor to said collar.

8. The wiper motor drive system us set forth in claim 7 , wherein at least one of said gear and said collar has an alignment tab, and said retaining mechanism has at least one alignment slot, with said alignment tab being disposed in said alignment slot such that said retaining mechanism is substantially prevented from rotating with respect to said collar.

9. A wiper motor drive system comprising:

a motor, an output shaft operatively connected to said motor, an output shaft operatively connected to a wiper blade, and a breakaway clutch operatively connected between said transmission and said output shaft;

said breakaway clutch including a torque-sensitive releasable locking mechanism having a first position wherein torque is translated from said transmission to said output shaft through said breakaway clutch to drive the wiper blade across a surface to be wiped, and a second position wherein torque is interrupted between said transmission and said output shaft in response to a predetermined rotational torque differential acting on said output shaft, said locking mechanism being movable back to said first position when said differential torque is reduced on said output shaft;

wherein said torque-sensitive releasable locking mechanism further includes a groove defined in said output shaft, a collar disposed about said output shaft said collar having a slot aligned with said groove of said output shaft and being in driven relationship with said transmission, and a release member disposed in said groove of said shaft and in said slot of said collar, said release member movable from said first position wherein torque is translated from said collar to said output shaft through said release member and said second position wherein no torque is translated between said collar and said output shaft.

10. The wiper motor drive system as set forth in claim 9 , wherein said slot of said collar defines a pair of edges disposed in spaced parallel relationship with respect to each other, said release member has a cylindrical body which is carried in said groove in releasable fashion and operatively engages each of said edges of said slot to thereby translate torque between said collar and said output shaft.

11. The wiper motor drive system as set forth in claim 10 , wherein said groove of said output shaft has a concave profile.

12. The wiper motor drive system as set forth in claim 9 , wherein said torque-sensitive releasable locking mechanism further includes a retaining mechanism disposed about said collar and movable between a first radial position wherein said retaining mechanism acts to keep said release member disposed in said groove of said output shaft, and a second radial position wherein said retaining mechanism allows said release member to move out of said groove in response to a predetermined rotational torque differential.

13. The wiper motor drive system as set forth in claim 12 , wherein said retaining mechanism is a cylindrical ring having a gap extending longitudinally substantially along the entire length of said retaining mechanism such that said retaining mechanism is movable from a first radial position to a second radial position in response to a predetermined radial force generated by said release member as said release member moves to said second position.

14. The wiper motor drive system as set forth in claim 12 , wherein said output shaft further includes a stop operatively attached thereto and a washer disposed between said stop and said torque-sensitive releasable locking mechanism, such that said locking mechanism is constrained longitudinally with respect to said output shaft by said stop.

15. The wiper motor drive system as set forth in claim 12 , wherein said torque-sensitive releasable locking mechanism further includes a gear operatively attached to said collar, with said gear being in driven relationship with said transmission so as to translate torque from said transmission to said collar.

16. The wiper motor drive system as set forth in claim 15 , wherein at least one of said gear and said collar has an alignment tab, and said retaining mechanism has at least one alignment slot, with said alignment tab being disposed in said alignment slot such that said retaining mechanism is substantially prevented from rotating with respect to said collar.