Abstract: A ventilated litter box in which a lower pan removably receives an enclosing cover having a pet access opening, a ventilation opening, and a fan housing surrounding the ventilation opening which includes an electric fan positioned to withdraw air through the ventilation opening from an interior space while an exhaust outlet in the fan housing provides for escape of the air withdrawn from the space. An electronic circuit controls the operation of the fan. An apparatus for sensing the presence of a pet entering the interior space is provided with a capacitive pick-up in the form of a pair capacitive plates preferably located at or near either side of the access opening. The electronic circuit is responsive to the change of capacitance between the plates indicating the presence of the animal. A first time-out circuit delays the operation of the ventilating fan motor following the entrance of a pet into the interior of the box to avoid frightening the pet.

Abstract: A protective PTC device is heated by a heater PTC device or by a resistor to an elevated temperature greater than ambient but less than its switching temperature. The elevated temperature of the protective PTC device reduces its switching response time, and minimizes variations in such response time with variations in ambient temperature. The protective PTC device is connected in series with an electrical load to reduce current to a load when the protective PTC device is switched to its high-resistance state by a temperature increase resulting from overcurrent. The heater PTC device or the heater resistor may be in parallel or in series with the protective PTC device. The heater PTC device does not carry load current, but the heater resistor may be placed in series with the load and the protective PTC device so as to carry load current along with the protective PTC device.

Abstract: A combined pressure cutoff and pressure relief valve includes a normally closed switch movable between closed and open contact positions. A normally closed pressure relief vent is located in a common housing with the switch. A pressure responsive diaphragm applies force to a switch snap disc and a vent snap disc. Under high pressure conditions, the switch snap disc snaps and opens a pair of contacts. In the event an abnormal pressure condition occurs, the vent snap disc operates and causes a pin to rupture the diaphragm for opening the relief vent.

Abstract: A protective PTC device is heated by another PTC device to an elevated temperature greater than ambient but less than its switching temperature. The elevated temperature of the protective PTC device reduces its switching response time, and minimizes variations in such response time with variations in ambient temperature.

Abstract: Temperature responsive apparatus includes a housing having a pair of spaced-apart probes, each receiving a different thermistor. The housing includes a one-piece hollow plastic shell having the pair of spaced apart probes formed integral therewith. The entire hollow interior of the shell, including the probes, is filled with plastic material to encapsulate the thermistors received within the probes.

Abstract: A thermal cutoff is mounted adjacent a bleed opening in a hot air duct. Hot air flowing through the bleed opening mixes with ambient air before contacting the thermal cutoff. If a predetermined air temperature is exceeded, the thermal cutoff operates, and de-energizes the air heater.

Abstract: A PTC polymer assembly in which a sheet of PTC polymer is sandwiched between two electrodes, and electric terminations are mechanically and electrically connected to the electrodes, at least one of the terminations is a looped spring connected at one end to one of the electrodes and at another end to a mounting element, with a loop between the electrode and the mounting element to which it is mechanically connected.

Abstract: A thermally actuatable electrical switch construction having a housing carrying an electrically insulating end plug provided with an opening passing therethrough and in which a portion of a conductive lead is disposed so that opposed ends of the lead extend beyond opposed ends of the plug and respectively define a fixed contact inside the housing and a terminal outside the housing, the portion of the lead being retained in the opening by a sealing compound disposed in the opening and extending around the portion of the lead and interlocking therewith to tend to prevent axial movement of the lead into the housing as well as to tend to prevent rotational movement of the lead relative to the end plug.

Abstract: A normally open temperature sensitive electrical switching device includes a heat fusible electrically conductive pellet which melts and provides an electrically conductive path through the switching device at a predetermined temperature level and, further, includes arc contacts defining an air gap across which arcing will occur when a sufficient potential is supplied to the switching device. A first electrically conductive electrode and second electrically conductive electrode are electrically connected to first and second electrical leads provided for an electrical connection to the device. A nonconductive mounting arrangement holds the first and second electrodes in spaced relation. The heat fusible conductive pellet is positioned in contact with the second electrode and defines the air gap of predetermined dimension with the first electrode.