Abstract: A thermally responsive motor protector device particularly adapted for protecting a small electrical motor against both overcurrent and overtemperature conditions in an environment requiring hermetic sealing of the protector has a structure which provides the device with the desired hermetic seal and with a very small thermal mass for achieving the desired speed of response to overcurrent and overtemperature conditions in a small motor while also permitting mass production and automatic calibration of the device at low cost and inexpensive installation of the device without risk of loss of calibration.

Abstract: A miniature motor protector device incorporates a flat, open-ended, electrically conductive metal can having a flange around its open end and having a terminal extending from the flange. A generally flat, electrically conductive metal lid is sealed to and electrically isolated from the can by an electrically insulating gasket which fits between the lid and the can flange. A thin electrically insulating film is disposed on the surface of the lid exteriorily of the can and a flat serpentine resistance heater element is positioned in heat transfer relation to the lid on top of the film. One end of the heater element is electrically connected to one end of the lid while the opposite end of the heater element extends from the opposite end of the lid to a second terminal. End portions of the lid and film are crimped over the heater element to secure the element and film to the lid.