Patent ID: 6106424
Filing Date: 2000-08-22
Classification: F16H,F16J

Abstract:
A hydraulic tensioner for a traction drive having one end pivotally supported and a further end connected directly or indirectly to a tension roller, the tensioner comprising a spring-loaded piston (8) guided for sliding motion in a cylinder (6) which is arranged in an outer housing (2) and filled with hydraulic medium to an amount corresponding to the piston position, in which tensioner, a piston motion causes an exchange of volume between a high pressure chamber (9) arranged in the cylinder (6) and a hollow space (4) of the outer housing (2) which is partly filled with hydraulic medium, and, depending on a direction of motion of the piston, said exchange of volume will take place through a one-way valve (15) arranged on the cylinder (6) or through a leak gap (17), the tensioner further comprising a bellows seal (18) which is connected to a piston housing (10) and the outer housing (2) and follows the longitudinal motion of the piston (8) while bearing under pre-stress against the outer housing (2) and against a radially inward stepped portion of the piston housing (10), both ends of the bellows seal (18) comprising a retention bead (21, 22) to assure a positional fixing on the outer housing (2) and the piston housing (10), the bellows seal (18), at least in an area of one of the retention beads (21, 22), includes a recess (30) which is located against one of the piston housing (10) and the outer housing (2) so that an overpressure developing in the hollow space (4) causes a radial displacement of a part of the bellows seal (18) and the recess provides a free communication between the hollow space (4) and the atmosphere.