Abstract A fuser system for a xerographic photocopy machine. The fuser system comprises primary and secondary fuser heating resistors connected in parallel legs across an A.C. line voltage. The primary fuser heating resistor is connected directly across the line voltage and continuously produces fusing heat. A triac is connected in series with the secondary fuser resistor and a monitoring-and-controlling circuit is connected in parallel with the first and second parallel legs, across the line voltage, for monitoring the line voltage and controlling the triac so as to cause electrical current flow through the secondary fuser heating resistor when the line voltage drops below a predetermined value. The monitoring-and-controlling circuit comprises a lamp and a photoconductor, each being connected in parallel across the line voltage. Light from the lamp controls the voltage across the photoconductor and the voltage across the photoconductor is used to control current flow through the triac.
A fuser heating system for a photocopying machine comprising: two line voltage leads for connecting said fuser heating system across a line voltage; primary and secondary fuser heating elements connected respectively in first and second parallel legs across said line voltage leads; an electronic valve connected in series with said secondary fuser heating element in said second parallel leg; a monitoring-and-controlling circuit connected in parallel with said first and second parallel legs across said line voltage leads for monitoring said line voltage and controlling said electronic valve so as to cause an increase in electrical current flow through said valve in response to a decrease in line voltage.
Claim 2
Dependent Claim
108 words
A fuser heating system for a photocopying machine comprising: two line voltage leads for connecting said fuser heating system across a line voltage; primary and secondary fuser heating elements connected respectively in first and second parallel legs across said line voltage leads; an electronic valve connected in series with said secondary fuser heating element in said second parallel leg; a monitoring-and-controlling circuit connected in parallel with said first and second parallel legs across said line voltage leads for monitoring said line voltage and controlling said electronic valve so as to cause an increase in electrical current flow through said valve in response to a decrease in line voltage.
Claim 3
Dependent Claim
46 words
A fuser heating system as claimed in claim 1 wherein said monitoring-and-controlling circuit comprises a lamp which is connected across said line voltage leads, and a photoconductor, the conductance of which varies in response to light emitted by said lamp, connected across said line voltage leads.
Claim 4
Dependent Claim
16 words
A fuser heating system as claimed in claim 2 wherein said electronic valve is a triac.
Claim 5
Dependent Claim
55 words
A fuser heating system as claimed in claim 3 wherein said monitoring-and-controlling circuit further comprises a resistor in series with said photoconductor, a capacitor in parallel with said photoconductor, and means for applying a voltage developed at the junction point between said photoconductor, said resistor, and said capacitor, to said triac as a control voltage.
Claim 6
Dependent Claim
20 words
A fuser heating system as claimed in claim 1 and including an AC voltage source for supplying said line voltage.