Patent ID: 7699732

Claim:
A belt- or chain-tensioning device, comprising: a fixed bracket; a moving element relative to the fixed bracket comprising: a working cam comprising an inner surface and an outer surface, wherein the working cam is mounted to the fixed bracket such that the inner surface rotates on the fixed bracket; and a pulley rotatably-mounted on the outer surface of the working cam, wherein the pulley is configured to contact a belt or a chain; an actuator configured to exert a permanent tension force between the moving element and the fixed bracket; a sensor unit configured to monitor parameters of angular displacement of the moving element relative to the fixed bracket, and a coder element positioned on the working cam, and configured to be able to rotate past a sensor positioned on the fixed bracket, wherein the fixed bracket comprises a base adapted to be fixed on a block and a tubular axial portion extending axially from the base towards the working cam and onto which is positioned the sensor, wherein the working cam comprises a radial wall extending radially outward from the outer surface and a tubular skirt extending axially from the radial wall, radially surrounding the free end of the axial portion of the fixed bracket, and comprising the coder element facing the sensor, wherein the actuator is disposed axially between the base of the fixed bracket and the radial wall of the working cam; and wherein the skirt forms with the axial portion an annular leak-tight passage to protect the coder element, the sensor, and the seat of the actuator from the intrusion of pollutant outer elements.