An autonomous hydraulic expansion and contraction apparatus comprises a fixing unit, a cylinder unit, a support unit, a piston unit, a valve unit and oil supply parts. By controlling the expansion and contraction length of the support part by a simple manipulation of the valve part by moving the lever, the autonomous hydraulic expansion and contraction apparatus can be easily expanded and contracted to the combined length of the expansion and contraction equipment, and additionally, the convenience of use can be enhanced.

An object of the present invention is to provide a tensioner that has a reduced number of components and lighter weight and is easy to assemble. The tensioner according to the present invention is configured such that a base member is detachably and mechanically joined to a rear end opening of a cylindrical plunger with a closed front end against the resilience of biasing means that is accommodated inside the plunger such as to be freely extend and contract. The joint between the plunger and the base member is a mechanical connection that is one of a thread engagement, a press-fit, and a pin connection.

A pressure relief valve (10) in a hydraulic tensioner for an endless loop power transmission member and method of assembly can include a check valve member (18) positioned within a fluid passage (14) defined by a housing (12) for movement toward and away from a valve seat (16) defined by the housing (12), a spring (20) normally biasing the check valve member (18) toward the valve seat (16), and a spring retainer (22) assembled within the fluid passage (14) to a variable depth in response to feedback pressure for automatically adjusting a biasing force of the assembled spring (20) to compensate for tolerances effecting a relief pressure value of an assembled pressure relief valve and allowing control of the relief pressure value to be within a predetermined range with respect to a predetermined target relief pressure value for driving the check valve member (18) away from the valve seat (16).

A product for applying tension is disclosed. A block may have a first passage opening into the block. A body may have a first manifold and may be positioned against the block so that the first passage is open to the first manifold. The body may have a flow path for providing fluid from the first manifold to a second manifold and there through to a pressure chamber. The flow path may include a series of channels and may be configured to allow substantially unimpeded flow from the first manifold to the second manifold, and to impede flow from the second manifold to the first manifold. The flow path may be free of movable components.

A hydraulic auto-tensioner for an engine accessory is provided where a sleeve fit-in hole is formed at an upper surface of a bottom portion of a cylinder accommodating a hydraulic oil, a lower end portion of a sleeve is press-fitted in the sleeve fit-in hole, and a lower end portion of a rod is slidably inserted in the sleeve to define a pressure chamber inside the sleeve. A lower end face of the sleeve is in abutment with a divided bottom surface of the sleeve fit-in hole to trap burrs produced when the lower end portion of the sleeve is press-fitted into the sleeve fit-in hole between the divided bottom surface of the sleeve fit-in hole and the lower end face of the sleeve, so that burrs are prevented from mixing into the hydraulic oil.

A tensioning device (1) for tensioning a traction mechanism of a traction mechanism drive, including a housing (2), a piston (3) that is mounted such that the piston can be displaced in an axial direction inside the housing (2), and a transport securing element (4), which in at least one transport position of the tensioning device (1) is arranged in the housing (2) transversely to the piston (3) and in abutment with the piston (3) such that a displacement of the piston (3) in at least one first axial direction is blocked. The transport securing element (4) is provided with a support portion (5), wherein in the transport position at least one first web area (6) of the support portion (5) is in abutment with one end face (7) of the piston (3), and an additional web area (8) of the support portion (5) extending in an axial direction away from the first web area (6) is supported in the housing (2), at least in a radial direction.

A resister clip (35) includes engage portions (35a) engaging with an engage groove, a spring portion (35b) and operating portions (35c). The spring portion (35b) can be designed with a high degree of freedom in terms of a coil number of turns, a winding diameter and others and the engage portions (35a) are widened centering on the spring portion (35b), so that diameter-widening resistance can be optimized.

The invention relates to a tensioner (100) comprising: a hollow body (10) provided with a bottom (12), said bottom comprising a central zone (120), a peripheral zone (121) raised relative to the central zone and an intermediate zone (122) an axis (30) two guide means (40, 50) for said axis two cups (60, 124), the cup (124) comprising a first portion (124A) in front of the peripheral zone and a second portion (124B) in front of the intermediate zone a spring (70) held between the cups and arranged around the second guide means so that there is a gap between the spring and the second guide means a valve (80) with a channel (90), the channel opening in front of the second portion of the cup (124) away from said second portion.

To provide a tensioner capable of preventing slipping between a rack portion and ratchet pawls and securing a large backlash with a simple structure. The tensioner includes a ratchet rotatably mounted on a housing and having a front pawl and a rear pawl spaced apart in a front and rear direction on a side face positioned opposite the rack portion. The ratchet includes an additional pawl formed between the front pawl and the rear pawl in the front and rear direction on the side face positioned opposite the rack portion.

A hydraulic tensioner for an internal combustion engine for tensioning a span of a chain or a belt has a piston with an internal reservoir connected to a high pressure chamber through a check valve assembly. The check valve assembly has a disk seat formed by an internal bulge within the piston; a check valve retainer within the piston, and a moveable disk that is received between the disk seat formed by the internal bulge and the check valve retainer and is moveable between a first position and a second position, and a check valve spring that is received between the check valve disk and the check valve retainer.