Multi-stroke parking brake variable ratio apply and release mechanism

Claim 1

A parking brake actuation and release mechanism comprising: a fixed mounting bracket; a parking brake lever pivotally mounted on said mounting bracket to pivot arcuately about a pivot axis through a first maximum predetermined arc between a rest position and an applied position; a toothed ratchet member pivotally mounted on said mounting bracket to pivot arcuately about the pivot axis through a second maximum predetermined arc which is more than twice as wide as said first arc; an eccentic cable take-up member pivotally mounted on said mounting bracket to pivot arcuately about the pivot axis through said second maximum predetermined arc and having drive means between said toothed ratchet member and said eccentric cable take-up member to drive said eccentric cable take-up member by said toothed ratchet member arcuately in the brake applying direction; a first releasable pawl pivotally mounted on said mounting bracket and selectively normally engaging said toothed ratchet member to prevent brake releasing movement thereof; means for selectively releasing said first pawl to disengage it from said toothed ratchet member; a second releasable pawl pivotally mounted on said parking brake lever and normally engaging said toothed ratchet member to drive said toothed ratchet member and said eccentric cable take-up member in the arcuate brake actuating direction with the brake actuating strokes of said parking brake lever from its rest position and to ratchet over said toothed ratchet member as said parking brake lever returns to the rest position while said first pawl is in toothed engagement with said toothed ratchet member and preventing brake releasing movement thereof; a parking brake cable having one end secured to said eccentric cable take-up member at a maximum effective radius from the pivot axis, said cable being received by said eccentric with a decreasing effective radius from the pivot axis as said eccentric take-up member is arcuately driven in the brake actuating direction to continually increase the mechanical advantage of the cable travel relative to pedal lever movement as the mechanism applies the parking brake by tensioning the cable; said first and second pawls cooperating with said toothed ratchet member to permit multiple parking brake lever strokes from the rest position within said first arc to drive said toothed ratchet member and said eccentric cable take-up member through said second arc to exert a maximum parking brake take-up and apply force through said cable; said first pawl when released allowing the brake actuating tension force in said cable to return said toothed ratchet member and said eccentric cable take-up member to the brake released position; and trip means on said fixed mounting bracket engaging said second pawl as said pedal lever is returned to the rest position to hold said second pawl out of engagement with said toothed ratchet member while said pedal lever is at the rest position, said second pawl being moved during initial brake actuating movement of said pedal lever to be disengaged from said trip means and to engage said toothed ratchet member in driving relation.