Fixing roller device

Claim 2

A fixing roller device, comprising: a heating roller having a surface and two ends, said surface having a middle zone, including the axial middle of said surface, and a first and second end zone disposed respectively axially and symmetrically to either side of said middle zone between said middle zone and a respective one of said ends; first means for sensing temperature of said surface at said axial middle; second means for sensing temperature of said surface in one of said first and second end zones; a control system responsively connected to said first and second temperature sensing means; and means responsively connected to said control system and arranged inside said heating roller, for producing at said heating roller surface a surface temperature distribution which exhibits a first value at said axial middle, symmetrically tends toward a second value at either end of said middle zone, and then substantially uniformly maintaIns said second value substantially throughout said first and second end zones; wherein said first value is a local maximum.

Claim 3

A fixing roller device as claimed in claim 1 wherein said second value differs from said first value by a quantity which ranges from about 2° to 10° C.

Claim 4

A fixing roller device, comprising: a heating roller having a surface and two ends, said surface having a middle zone, including the axial middle of said surface, and a first and second end zone disposed respectively axially and symmetrically to either side of said middle zone between said middle zone and a respective one of said ends; first means for sensing temperature of said surface at said axial middle; second means for sensing temperature of said surface in one of said first and second end zones; a control system responsively connected to said first and second temperature sensing means; and means responsively connected to said control system and arranged inside said heating roller, for producing at said heating roller surface a surface temperature distribution which exhibits a first value at said axial middle, symmetrically tends toward a second value at either end of said middle zone, and then substantially uniformly maintains said second value substantially throughout said first and second end zones; wherein said second value differs from said first value by a quantity which ranges from about 2° to 10° C; and wherein said quantity is selected according to the particular copying materil being used.

Claim 5

A fixing roller device, comprising: a heating roller having a surface and two ends, said surface having a middle zone, including the axial middle of said surface, and a first and second end zone disposed respectively axially and symmetrically to either side of said middle zone between said middle zone and a respective one of said ends; first means for sensing temperature of said surface at said axial middle; second means for sensing temperature of said surface in one of said first and second end zones; a control system responsively connected to said first and second temperature sensing means; and means responsively connected to said control system and arranged inside said heating roller, for producing at said heating roller surface a surface temperature distribution which exhibits a first value at said axial middle, symmetrically tends toward a second value at either end of said middle zone, and then substantially uniformly maintains said second value substantially throughout said first and second end zones; wherein said second value differs from said first value by a quantity which ranges from about 2° to 10° C; and wherein said quantity is selected according to the particular copying materil being used.

Claim 6

A fixing roller device as claimed in claim 3 wherein said first value is a local minimum.

Claim 7

A fixing roller device as claimed in claim 3 wherein said surface temperature distribution producing means comprises first and second heating elements disposed within said heating roller and responsively connected to said control system.

Claim 8

A fixing roller device as claimed in claim 5 wherein said first and second heating elements are disposed substantially parallel to an axis of said heating roller.

Claim 9

A fixing roller device as claimed in claim 4 wherein: said first heating element comprises a middle coil arranged primarily within said middle zone; and said second heating element comprises first and second end coils arranged primarily within said first and second end zones respectively.

Claim 10

A fixing roller device as claimed in claim 7 wherein said middle coil overlaps at each end with an adjacent end of each of said end coils.

Claim 11

A fixing roller device as claimed in claim 8 wherein said middle coil overlaps at each end with an adjacent end of each of said end coils by up to about 5 mm.

Claim 12

A fixing roller device as claimed in claim 7 wherein said middle coil has a length of at least equal to the width of DIN-A3 format paper.

Claim 13

A fixing roller device as claimed in claim 7 wherein each of said end coils has a length at least equal to about 150 mm.

Claim 14

A fixing roller device as claimed in claim 5 wherein said middle coil is caused to heat if DIN-A4 and DIN-A3 format paper is being copied upon.

Claim 15

A fixing roller device as claimed in claim 12 wherein said end coils are also caused to heat if said second temperature sensing means senses a temperature more than 2° C. to 10° C. lower than that sensed by said first temperature sensing means.

Claim 16

A fixing roller device as claimed in claim 7 wherein both of said first and second heating elements are supplied current, if a DIN-A2 or DIN-A1 format sheet is being copied upon.

Claim 17

A fixing roller device, comprising: a heating roller having a surface and two ends, said surface having a middle zone, including the axial middle of said surface, and a first and second end zone disposed respectively axially and symmetrically to either side of said middle zone between said middle zone and a respective one of said ends; first means for sensing temperature of said surface at said axial middle; second means for sensing temperature of said surface in one of said first and second end zones; a control system responsively connected to said first and second temperature sensing means; and means responsively connected to said control system and arranged inside said heating roller, for producing at said heating roller surface a surface temperature distribution which exhibits a first value at said axial middle, symmetrically tends toward a second value at either end of said middle zone, and then substantially uniformly maintains said second value substantially throughout said first and second end zones; wherein said second value differs from said first value by a quantity which ranges from about 2° to 10° C.; and wherein said heating roller has a silicone rubber coating terminating within said end zones about 30-33 mm from either end of said heating roll surface, leaving an uncoated segment to either end of said surface, said surface temperature distribution in said first and second zones having a maximum temperature in each of said uncoated segments.

Claim 18

A fixing roller device, comprising: a heating roller having a surface and two ends, said surface having a middle zone, including the axial middle of said surface, and a first and second end zone disposed respectively axially and symmetrically to either side of said middle zone between said middle zone and a respective one of said ends; first means for sensing temperature of said surface at said axial middle; second means for sensing temperature of said surface in one of said first and second end zones; a control system responsively connected to said first and second temperature sensing means; and means responsively connected to said control system and arranged inside said heating roller, for producing at said heating roller surface a surface temperature distribution which exhibits a first value at said axial middle, symmetrically tends toward a second value at either end of said middle zone, and then substantially uniformly maintains said second value substantially throughout said first and second end zones; wherein said second value differs from said first value by a quantity which ranges from about 2° to 10° C.; and wherein said heating roller has a silicone rubber coating terminating within said end zones about 30-33 mm from either end of said heating roll surface, leaving an uncoated segment to either end of said surface, said surface temperature distribution in said first and second zones having a maximum temperature in each of said uncoated segments.