Safety device for a kneading machine using rolls

Abstract

A safety device detects when a worker's hand enters a hazardous region between rollers of a kneading machine, and stops rotation of the rolls to prevent an accident. Each time the rollers are stopped, the orientation of photoelectric sensors is switched from the vicinity of the gap between the two rollers to a test reflection member, and the quantity of received light is compared to a predetermined value, to prevent workers form starting work without knowing a fault or accident has happened. More specifically, a bar electrode of an electrostatic capacitance sensor is disposed above and near the gap between the two rollers, for detecting a physical quantity that is changed by entry of a worker's hand. When the electrostatic capacitance detected by the sensor exceeds a predetermined value, a judging circuit supplies a control signal to stop a driving unit that operates the kneading machine. Heat ray sensors or photoelectric sensors may be used as alternatives to electrostatic sensors. As an additional feature, case housing light projectors and photoelectric sensors are rotatably disposed above and near the gap between the two rollers, and a test reflector is disposed on the side of the case. When the rollers are stopped, a light receiving object switching circuit rotates the case and a test circuit tests the light receiving states of the photoelectric sensors.