Abstract: A chain or belt tensioner comprises a plunger displaceable in a housing between retracted and extended positions. A stop ring between the plunger and housing frictionally contacts a smooth surface of the housing. A recess in the plunger has a tapered face for engagement with a bevelled surface of the stop ring. Inward movement of the plunger causes the tapered face to engage the stop ring and to force it to deform outwardly to a wedging position in which the stop ring is wedged between the tapered face and the surface thus preventing further inward movement of the plunger. The recess has a second face that engages the stop ring when the plunger moves out of the housing so as to slide it over the surface. The invention provides for a stop mechanism that enables retraction of the plunger to be prevented at an infinite number of positions.

Abstract: A chain drive assembly for an internal combustion engine comprises a chain tensioner (6) that acts upon a chain (2) that is used to drive the cam shafts (4) of the engine. The tensioner has a hydraulically actuated plunger (30) which is moveable within a housing and biasing means in the form of a solenoid (34), compression spring or motor that urges the plunger outwards of the housing at least when there is no hydraulic pressure. The tensioner is controlled by means of a control unit (8) that receives signals from various transducers that transmit signals providing information in relation to the performance of the engine. The control unit receives the measured information, calculates the desired tension to be applied to the chain and transmits the control signal to the chain tensioner so as to operate the biasing means or control the hydraulic pressure so that the desired chain tension is applied.

Abstract: A chain drive comprises a chain having a plurality of articulating chain links and a toothed sprocket. The sprocket and the chain links have bearing surfaces that contact one another during meshing of the chain. The surfaces are disposed along the length of the chain between the apertures and to one side of a sprocket tooth. One of the bearing surfaces is arcuate so that during meshing of said chain link the bearing surfaces are brought into contact such that the instantaneous centre of rotation of the meshing chain link passes from the first pivot pin of a link to the point of contact of the bearing surfaces before passing to the second pivot pin of the link. This reduces the noise generated by collision of the chain links and the sprocket teeth.