Sliding rack ratchet tensioner
AssigneeBorgWarner Inc.
InventorAnand Arun Barve
Life of this patent
Estimating the term…
Abstract
The high-performance sliding rack ratchet tensioner is inexpensively manufactured. A rack having rack teeth is slidingly received in a rack slot on the side of the piston. The rack slot is preferably open-ended on the end facing the tensioner arm. The rack and piston are both received in a piston bore in the tensioner body. The rack length is preferably shorter than the rack slot length to provide backlash. A pawl mounted in a pawl bore perpendicular to the rack bore engages the rack. The open-ended rack slot allows the rack to be inserted after the piston during assembly. The rack and pawl preferably have shark fin-shaped teeth. The pawl preferably has dummy teeth to ensure that the load is shared by the center teeth.
Claims24
A ratchet tensioner comprising:
- a tensioner body having a piston bore open at one end and a pawl bore extending into the piston bore;
- a piston having an outer circumference slidably received in the piston bore and a rack slot axially extending and formed as part of the outer circumference, the rack slot having an open end at an outward end of the piston;
- a first biasing member biasing the piston in a protruding direction;
- a rack comprising a plurality of rack teeth and slidably received in the rack slot;
- a pawl slidably received in the pawl bore, the pawl comprising a plurality of pawl teeth;
- and
- a second biasing member biasing the pawl toward the rack;
- such that the pawl teeth engage the rack teeth, thereby permitting travel of the piston in the protruding direction but resisting travel of the piston in a retracting direction opposite the protruding direction above a designed backlash.
A pawl for engaging a rack, having a plurality of rack teeth, of a ratchet tensioner, the pawl comprising:
- a pawl body having an outer circumference slidably received in a pawl bore;
- and
- a plurality of pawl teeth comprising a first dummy tooth, a first center tooth adjacent to the first dummy tooth, a second center tooth adjacent to the first center tooth on a side opposite the first dummy tooth, and a second dummy tooth adjacent to the second center tooth on a side opposite the first center tooth;
- wherein a distance between a vertical surface of the first center tooth and a vertical surface of the second center tooth is equal to a pitch of the rack teeth, a distance between a vertical surface of the first dummy tooth and the vertical surface of the first center tooth is less than the pitch of the rack teeth, and a distance between the vertical surface of the second center tooth and a vertical surface of the second dummy tooth is greater than the pitch of the rack teeth;
- such that the vertical surface of the first center tooth and the vertical surface of the second center tooth bear load from the rack teeth and the vertical surface of the first dummy tooth and the vertical surface of the second dummy tooth do not contact the rack teeth and are not loaded by the rack.
A ratchet tensioner comprising:
- a tensioner body having a piston bore open at one end and a pawl bore extending into the piston bore;
- a piston having an outer circumference slidably received in the piston bore and a rack slot axially extending and formed as part of the outer circumference;
- a first biasing member biasing the piston in a protruding direction;
- a rack comprising a plurality of rack teeth and received in the rack slot, the rack teeth being convexly curved in the plane perpendicular to the length of the rack;
- a pawl slidably received in the pawl bore, the pawl comprising a plurality of pawl teeth, the pawl teeth being concavely curved complementary to the rack teeth;
- and
- a second biasing member biasing the pawl toward the rack;
- such that the pawl teeth engage the rack teeth, thereby permitting travel of the piston in the protruding direction but resisting travel of the piston in a retracting direction opposite the protruding direction above a designed backlash.
A method of assembling a ratchet tensioner comprising the steps of:
- a) inserting a piston into a tensioner body having a piston bore open at one end and a pawl bore extending into the piston bore, the piston having an outer circumference slidably received in the piston bore and a rack slot axially extending and formed as part of the outer circumference, the rack slot having an open end at an outward end of the piston;
- b) after step (a), slidably inserting a rack comprising a plurality of rack teeth in the rack slot.
Dependencies are inferred from the claim text.