Temperature control means for toner fusing device in an electrostatic copier

A temperature control network for a toner fusing device having an electrical heater and including a cooling means in an electrostatic copier comprising:

• a temperature sensing member responsive to the temperature prevailing within the toner fusing device,
• a toner fusing device temperature regulating circuit including a temperature control bridge having therein said temperature sensing member and a resistor for setting a toner fusing temperature and controlling the electric current supplied to the heater in the toner fusing device for regulating the temperature in the toner fusing device at a first predetermined level in response to said temperature sensing member,
• a second circuit for sensing a third predetermined fuser temperature including a bridge having said temperature sensing member and a resistor for setting said third predetermined temperature, and means responsive to said second circuit for disabling said cooling means upon the temperature in the toner fusing device falling below said third predetermined fuser temperature after said heater is deenergized on the termination of copying,
• thereby, sensing two different temperatures through the medium of one temperature sensing member, and as the result maintaining the temperature in the toner fusing device substantially constant and causing the cooling means non-operable on the terminationn of copying.

A temperature control network for a toner fusing device having an electrical heater in an electrostatic copier including copying motivating means and cooling means comprising:

• a temperature sensing member responsive to the temperature prevailing within the toner fusing device,
• a toner fusing device temperature regulating first circuit including a temperature control bridge having therein said temperature sensing member and a resistor for setting a toner fusing temperature, and controlling the electric current supplied to the heater in the toner fusing device for regulating the temperature in the toner fusing device at a first predetermined level in response to said temperature sensing member,
• a second electric circuit for sensing a toner fusible temperature including a differential amplifier having an input connected to said temperature control bridge, means responsive to the output of said amplifier for disabling said copy motivating means until said fusing device temperature reaches a second predetermined level as detected by said temperature sensing member, and
• a third circuit for sensing a third predetermined fuser temperature including a bridge having said temperature sensing member and a resistor for setting said third predetermined temperature, and means responsive to said third circuit for disabling said cooling means upon the temperature in the toner fusing device falling below said third predetermined temperature after said heater is deenergized on the termination of copying,
• thereby, sensing three different temperatures through the medium of one temperature sensing member, and as the result maintaining the temperature in the toner fusing device substantially constant, causing the copying operation of the copier operable upon starting of the operation of the copier and causing the cooling means non-operable on the termination of copying.