US 6,146,300 AGranted

Tensioner device for chain drive mechanism

AssigneeTsubakimoto Chain Co.

InventorsTadasu Suzuki, Katsuya Nakakubo, Shigekazu Fukuda

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Abstract

A tensioner device for adjusting a tension in a chain wound around two sprockets includes a tensioner lever held in sliding contact with a slack run of the chain, an oil-filled tensioner provided on a stationary member, and a ratchet tensioner provided on the tensioner lever. The oil-filled tensioner includes a piston movable back and forth relatively to a housing attached to the stationary member, and a spring urging the piston in the forward direction. The ratchet tensioner includes a plunger movable in the forward direction relative to a housing formed integrally with the tensioner lever, and a spring urging the plunger in the forward direction. The piston and the plunger are held in face-to-face abutment with each other. The spring of the oil-filled tensioner has a larger spring coefficient than the spring of the ratchet tensioner. With this construction, when a sag of the chain is in excess of the forward stroke of the piston of the oil-filled tensioner, the plunger of the ratchet tensioner moves forward to cover a shortage of forward stroke of the piston. The tensioner device can continue proper tension-adjusting operation over a long period of use of a chain drive mechanism in which it is incorporated.

Claims5

Dependent claims

A tensioner device for a chain drive mechanism including at least two sprockets spaced from each other on a stationary member, and an endless chain wound around the sprockets, said tensioner device comprising:

a tensioner lever having one end pivoted to the stationary member, said tensioner lever being in slide contact with the chain between the sprockets to adjust a tension in the chain;
a first tensioner assembly including a first housing, a plunger movable in a forward direction relative to said first housing, a spring urging said plunger toward the forward direction, and a stop means for preventing backward movement of said plunger;
a second tensioner assembly including a second housing, a piston movable in a forward and a backward direction relative to said second housing, a spring urging said piston toward the forward direction, and means for restricting backward movement of said piston while allowing forward movement of said piston;
one of said first and second tensioner assemblies being provided on said tensioner lever, and the other tensioner assembly being provided on the stationary member;
said plunger and said piston being in face-to-face abutment with each other;
and
said spring of said first tensioner assembly having a spring coefficient smaller than a spring coefficient of the spring of said second tensioner assembly.

4 more elements

Dependencies are inferred from the claim text.