Chain conveyors having means for controlling chain tension

Claim 1

A chain conveyor including a driving sprocket, an electric motor arranged to drive that sprocket, another sprocket spaced from said driving sprocket, an endless chain extending between and meshing with the two sprockets so as to form upper and lower chain runs, a fluid-pressure-operable device which is so connected to said driving sprocket, and the driving sprocket being so adjustably mounted, that said device is capable of altering the distance between the driving sprocket and said other sprocket to effect adjustment in the tension of the chain, and a servo-system, of which said fluid-pressure-operable device forms a part, which includes an electrically-operable servo-device for controlling said fluid-pressure-operable device, feedback means connected between said fluid-pressure-operable device and the input side of said servo-system, and means for applying to said servo-device an electrical signal which is dependent upon the torque, at any instant, of said electric motor whereby the load on the motor is, during operation of the conveyor, continuously monitored and, in response to said signal, said servo-device can cause said fluid-pressure-operable device to effect adjustments in said distance between said driving sprocket and said other sprocket sufficient for the tension in the chain, at a point where the chain is just leaving the circumference of said driving sprocket, to be maintained at a predetermined and low value.