Abstract: An inverted tooth transmission chain with articulating link plates has improved wear resistance and life expectancy. The articulating link plates are blanked from steel having an aluminium content of 0.01% to 0.08% by weight and a grain size number of at least 8 ASTM. The link plates are then carburised by heating them to a temperature in the range 800° C. to 1000° C. for a period of between 10 to 60 minutes in a conventional carburising atmosphere including, for example, methane or propane. The link plates are then quenched or austempered in an oil or salt bath. The final hardness of the carburised link plate is in the region of 600 to 700 Hv (Vickers hardness value).

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 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.

Abstract: The link plates, bushes or rollers of a transmission chain are treated so as to produce a surface layer of iron bisulphide. The surface improves the resistance of the chain to wear and also accelerates the running-in process.

Abstract: A chain or belt tensioner comprises a plunger displaceable in a bore of a housing between retracted and extended positions. A radially resilient stop ring disposed in the bore between the plunger and housing is engaged in frictional contact with a smooth surface of the housing. A recess in the plunger is defined opposite the smooth bore and has a tapered face for engagement with a bevelled surface of the stop ring. The tapered face tapers radially inwardly in the direction towards the open end of the bore so that movement of the plunger relative to the housing towards the retracted position causes the tapered face to engage said surface of the stop ring and to force it to deform in a radial direction to a wedging position in which the stop ring is wedged between the tapered face and the bore surface so as to prevent further inward movement of the plunger.