Electrostatic printing apparatus with heated adjustable pressure toner fixing rolls

An electrostatic printing apparatus having a fixing device wherein a transfer member, holding an unifixed toner image, is passed through, between a pair of rollers pressed down with each other and provided with a heat source within one of said rollers, for fixing said toner image, comprising:

• means for changing the fixing pressure applied between said pair of rollers in said fixing device;
• means for changing the heat generated from said heat source;
• and
• means for switching both said fixing pressure and said heat interlocked with each other, so that, when said member is a sheet of paper, said fixing pressure is set to a given high pressure and said heat is set to a given low value, while, when said member is a composite made up of plural layers of paper, said fixing pressure is set to a given low pressure and said heat is set to a given high value.

An electrostatic printing apparatus in which a toner image formed on a photosensitive member is transferred to a transfer member by a transfer charger, and said transfer member holding an unfixed toner image, is passed through, between a pair of rollers pressed down with each other and provided with a heat source within one of said rollers, for fixing, wherein:

• the transfer current of a transfer charger can be changed between a current suitable for transferring to a normal sheet of paper and another one suitable for transferring to a composite made up of plural sheets;
• and
• fixing pressure applied to between said pair of rollers can be changed between two pressures suitable respectively for the sort of mode of said transfer members;
• and provided are
• means for detecting the sort of mode of said transfer member;
• and
• means for controlling, based on a signal of said detecting means, said transfer current and said fixing pressure to those suitable for the sort of mode of said transfer member indicated by said detect signal.

An electrostatic printing apparatus having a fixing device wherein a transfer member, holding an unfixed toner image, is passed through, between a pair of rollers pressed down with each other and provided with a heat source within one of said rollers, for fixing;

• a U-turn path guiding a transfer member discharged from said fixing device to a first sheet stacker installed on top of the apparatus;
• a second sheet stacker installed nearly in the discharge direction of said member discharged from said fixing device;
• and a switching gate for changing a path of said member discharged from said fixing device between said U-turn path and a path to said second sheet stacker, wherein:
• a fixing pressure applied to between said pair of rollers in said fixing device can be changed between fixing pressures suitable respectively for said member of a normal sheet and for said member of a composite made up of plural sheets;
• and provided is
• means for interlocking said changing of said fixing pressure and said changing of said switching gate, so that, when said member is a normal sheet of paper, fixing pressure is changed to one suitable for the member as well as said switching gate is changed to one position guiding the member to said U-turn path, while, when said member is a composite, fixing pressure is changed to the other suitable for said transfer member as well as said switching gate is changed to the other position guiding the transfer member to said second sheet stacker.