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 saw apparatus includes a guide bar, a chain driver, and an endless cutting chain trained about the guide bar and the chain driver. A hydraulic chain tensioning apparatus has a hydraulic actuator configured to be driven by a hydraulic power source to act against the guide bar to maintain tension in the cutting chain. A tension release valve is provided between the hydraulic power source and the hydraulic actuator. The tension release valve has a check valve, and a manual override press-button configured to maintain the check valve in an open condition while depressed. The tension release valve has a spring detent configured to maintain the manual override press-button in a depressed condition until selectively released.

A belt-tensioning device includes an electric machine having a drive belt pulley, which is driven about a drive axis, and a further drive belt pulley, where an endless belt wraps around the drive belt pulleys. The device has a housing in which a first and a second spring arm are mounted, in each of which spring arms a tension roller having axes of rotation which are parallel to the drive axis is rotatably mounted. The spring arms are supported against one another and press the endless belt together via the tension rollers in the region of the drive belt pulley. A first and a second further spring arm are provided adjacent to the spring arms which are adjustable by an adjustment element such that the spring forces of the further spring arms either do or do not support the spring forces of the spring arms acting on the endless belt.

A stack of disk springs are placed between a second piston of a dual hydraulic variable force tensioner system and a hydraulic tensioner arm to allow much higher spring rates if desired. The springs may be stacked in multiple configurations to provide different spring rates. Package space can be reduced depending on the number of springs and orientations of said springs within the tensioner arm.

An articulated chain with alternating inner chain links and outer chain links which are each connected to each other by means of a chain joint, wherein each outer chain link comprises at least two outer link plates and two chain studs connecting them to each other, each inner chain link comprises at least two inner link plates and two joint sleeves connecting them to each other, and for forming a chain joint, one chain stud each of the outer chain link extends through a joint sleeve of the inner chain link. The joint sleeves of the inner chain links are embodied as winding sleeves and firmly connected to the inner link plates, wherein the sleeve joints of the two winding sleeves are positioned on the same side of a link plate's longitudinal axis and face each other, and the sleeve joints are arranged at a distance to the link plate's longitudinal axis and at a distance to an upper apex or to a lower inflection point of the winding sleeve.

A work machine having a belt tensioning system is described. A belt is engaged with an engine drive sheave and a driven sheave of a rotor having a plurality of cutting tools configured for reducing wood infeed material. An idler pulley is mounted to an idler arm that is hinged to the machine frame. An actuator is hinged to the idler arm and the frame. The actuator may be extended and retracted in order to press the idler pulley into stronger and weaker engagement with the belt in order to set the desired amount of tension in the belt. One or more sensors may be used to sense the amount of tension in the belt, and the one or more sensors may be in communication with a control system that controls the actuator to monitor and adjust the belt tension so that it is maintained within desired limits.

Systems are provided for a belt tensioner. In one example, the belt tensioner comprises a fluid chamber divided into a first portion and a second portion via a dividing wall. An eccentric housing, which defines the fluid chamber, rotates relative to the dividing wall based on a spring force and a belt force.

A chain guide and tensioning apparatus is disclosed that is configured for engagement (contact) with a driven chain (e.g., in an automotive engine). The chain guide and tensioning apparatus includes a guide body and a guide face overlying the guide body. The guide face defines an inner surface and an opposite outer surface that is configured to guide and tension the driven chain. The guide face includes a plurality of spacers that extend therefrom into engagement (contact) with the guide body so as to define at least one channel that is configured to facilitate air and/or lubricant circulation between the guide body and the guide face to reduce heat and friction generated by engagement of the driven chain with the guide face.

An auto tensioner is supported on one side surface of a cylinder block 4-(the outer surface of a front wall part) via a bracket. The auto tensioner includes: a tension pulley that is pressed against a belt; an arm that rotatably supports the tension pulley and is swingably supported to the bracket; and a hydraulic actuator that is supported by the arm and bracket to adjust the pressing force of the tension pulley to the belt using a predetermined position of the arm as a supporting point. The hydraulic actuator is disposed outside the water pump 8-on the front wall part of the cylinder block.

A hydraulic tensioner (10) and method of assembly can include a housing (12) having an aperture and a piston (16) received within the aperture for movement between an extended position and a retracted position. A tensioner spring (36) positioned within the aperture for bias the piston (16) toward the extended position. The piston (16) and the aperture of the housing (12) defining an expandable fluid chamber (18). The hydraulic tensioner (10) can include a cantilever spring (20) having a first end (22) attachable to the housing (12) and a second end (24) releasably engageable with the piston (16) for retaining the piston (16) in the retracted position against urging of the tensioner spring (36) during storage, shipment, installation, and service. The second end (24) can be disengageable from the piston (16) allowing movement of the piston (16) outwardly toward the extended position during operation in a working environment.