Thermographic copying machines

Claim 2

A thermographic machine comprising a body including means for defining a feed path through a heating station in the machine, feed means for advancing heat sensitive sheet assemblies therealong, said heating station being defined by a pair of rolls, at least one of said rolls being hollow and having a wall for engaging said sheet assemblies, and electrically energized heating means within said one roll for furnishing radiant heat at the heating station, the improvement comprising: a. a temperature sensing means, b. means for mounting said temperature sensing means at a position adjacent to said wall and also in the path of radiation from said heating means to provide an output signal which is dependent upon a combination of the temperature of said wall and radiant heat from said heating means, c. control means responsive to said output signal for reducing and raising the heat furnished by said heating means in response respectively to the rise and fall of the temperature sensed by said sensing means at least partly to counteract the temperature variation of said sheet assemblies at said heating station, d. said means comprising an electrically energized heating element, e. said hollow roll being made of a material which will transmit radiation from said heating element to each of said sheet assemblies, f. said control means comprising a circuit in which said element is connected and which includes a current controlling means settable in response to said output signal provided by said temperature sensing means, g. said current controlling means comprising a pulse forming sub-circuit for supplying pulses of current to said heating means, h. said circuit including means for varying the mark/space ratio presented by said pulses of current in dependence upon the magnitude of said output signal from said temperature sensing means.

Claim 3

A thermographic machine comprising a body including means for defining a feed path through a heating station in the machine, feed means for advancing heat sensitive sheet assemblies therealong, said heating station being defined by a pair of rolls, at least one of said rolls being hollow and having a wall for engaging said sheet assemblies, and electrically energized heating means within said one roll for furnishing radiant heat at the heating station, the improvement comprising: a. a temperature sensing means, b. means for mounting said temperature sensing means at a position adjacent to said wall and also in the path of radiation from said heating means to provide an output signal which is dependent upon a combination of the temperature of said wall and radiant heat from said heating means, c. control means responsive to said output signal for reducing and raising the heat furnished by said heating means in responsive respectively to the rise and fall of the temperature sensed by said sensing means at least partly to counteract the temperature variation of said sheet assemblies at said heating station, d. said heating means comprising an electrically energized heating element, e. said hollow roll being made of a material which will transmit radiation from said heating element to each of said sheet assemblies, f. said control means comprising a circuit in which said element is connected and which inCludes a current controlling means settable in response to said output signal provided by said temperature sensing means, g. said current controlling means comprising a pulse forming sub-circuit for supplying pulses of current to said heating means, h. said circuit including means for varying the mark/space ratio presented by said pulses of current in dependence upon the magnitude of said output signal from said temperature sensing means, i. said circuit including a switch means, j. said switch means being operable to cut off and establish respectively a supply of current to said electrically energized heating means, k. said switch means has an operating member disposed in an approach section of said feed path to said heating station, so as to be operable by each sheet assembly when advanced therealong by said feed means, l. said circuit further includes a time delay subcircuit, m. said time delay sub-circuit is electrically connected with said switch means and with said current controlling means to maintain establishment of current through said heating means for a predetermined period after reversion of said switch means to an unoperated condition, upon passage of a trailing edge of said sheet assemblies past said operating member whereby said electrically energized heating means is maintained energized for a period sufficient to ensure proper reproduction of matter contained in the trailing margin of an original sheet included in each of said sheet assemblies.

Claim 4

A thermographic machine comprising a body including means for defining a feed path through a heating station in the machine, feed means for advancing heat sensitive sheet assemblies therealong, said heating station being defined by a pair of rolls, at least one of said rolls being hollow and having a wall for engaging said sheet assemblies, and electrically energized heating means within said one roll for furnishing radiant heat at the heating station, the improvement comprising: a. a temperature sensing means, b. means for mounting said temperature sensing means at a position adjacent to said wall and also in the path of radiation from said heating means to provide an output signal which is dependent upon a combination of the temperature of said wall and radiant heat from said heating means, c. control means responsive to said output signal for reducing and raising the heat furnished by said heating means in responsive respectively to the rise and fall of the temperature sensed by said sensing means at least partly to counteract the temperature variation of said sheet assemblies at said heating station, d. said heating means comprising an electrically energized heating element, e. said hollow roll being made of a material which will transmit radiation from said heating element to each of said sheet assemblies, f. said control means comprising a circuit in which said element is connected and which inCludes a current controlling means settable in response to said output signal provided by said temperature sensing means, g. said current controlling means comprising a pulse forming sub-circuit for supplying pulses of current to said heating means, h. said circuit including means for varying the mark/space ratio presented by said pulses of current in dependence upon the magnitude of said output signal from said temperature sensing means, i. said circuit including a switch means, j. said switch means being operable to cut off and establish respectively a supply of current to said electrically energized heating means, k. said switch means has an operating member disposed in an approach section of said feed path to said heating station, so as to be operable by each sheet assembly when advanced therealong by said feed means, l. said circuit further includes a time delay subcircuit, m. said time delay sub-circuit is electrically connected with said switch means and with said current controlling means to maintain establishment of current through said heating means for a predetermined period after reversion of said switch means to an unoperated condition, upon passage of a trailing edge of said sheet assemblies past said operating member whereby said electrically energized heating means is maintained energized for a period sufficient to ensure proper reproduction of matter contained in the trailing margin of an original sheet included in each of said sheet assemblies.

Claim 5

A thermographic machine comprising a body including means for defining a feed path through a heating station in the machine, feed means for advancing heat sensitive sheet assemblies therealong, said heating station being defined by a pair of rolls, at least one of said rolls being hollow and having a wall for engaging said sheet assemblies, and electrically energized heating means within said one roll for furnishing radiant heat at the heating station, the improvement comprising: a. a temperature sensing means, b. means for mounting said temperature sensing means at a position adjacent to said wall and also in the path of radiation from said heating means to provide an output signal which is dependent upon a combination of the temperature of said wall and radiant heat from said heating means, c. control means responsive to said output signal for reducing and raising the heat furnished by said heating means in response respectively to the rise and fall of the temperature sensed by said sensing means at least partly to counteract the temperature variation of said sheet assemblies at said heating station, d. said feed means for advancing said sheet assemblies including adjustment means for varying the speed of advancement, e. said adjustment means being operable by a manually movable control member, f. indicator means being provided in operative association with said manually operable control member for indicating a plurality of different speed settings or ranges thereof for different classes of work, g. said feed means for advancing said sheet assemblies comprising i. a motor, ii. a rotatable drive element on and driven by said motor, iii. a rotatable driven element drivingly connected with said at least one of said rolls, iv. the respective peripheral surfaces on said drive element and said driven element being in rolling engagement with each other for transmitting a driving motion therethrough from the motor to the driven element, at least one of said peripheral surfaces being of generally conical form, v. motor mounting means providing for movement of said motor and said driving element collectively in a direction axially of said generally conical surface to bring different axial zones thereof into rolling engagement with said driven element and thereby steplessly vary the velocity ratio afforded between said elements, vi. means connecting said manually movable control member with said motor to move same to diffErent positions for different classes of work indicated by said indicator means.

Claim 6

A thermographic machine comprising a body including means for defining a feed path through a heating station in the machine, feed means for advancing heat sensitive sheet assemblies therealong, said heating station being defined by a pair of rolls, at least one of said rolls being hollow and having a wall for engaging said sheet assemblies, and electrically energized heating means within said one roll for furnishing radiant heat at the heating station, the improvement comprising: a. a temperature sensing means, b. means for mounting said temperature sensing means at a position adjacent to said wall and also in the path of radiation from said heating means to provide an output signal which is dependent upon a combination of the temperature of said wall and radiant heat from said heating means, c. control means responsive to said output signal for reducing and raising the heat furnished by said heating means in response respectively to the rise and fall of the temperature sensed by said sensing means at least partly to counteract the temperature variation of said sheet assemblies at said heating station, d. said feed means for advancing said sheet assemblies including adjustment means for varying the speed of advancement, e. said adjustment means being operable by a manually movable control member, f. indicator means being provided in operative association with said manually operable control member for indicating a plurality of different speed settings or ranges thereof for different classes of work, g. said feed means for advancing said sheet assemblies comprising i. a motor, ii. a rotatable drive element on and driven by said motor, iii. a rotatable driven element drivingly connected with said at least one of said rolls, iv. the respective peripheral surfaces on said drive element and said driven element being in rolling engagement with each other for transmitting a driving motion therethrough from the motor to the driven element, at least one of said peripheral surfaces being of generally conical form, v. motor mounting means providing for movement of said motor and said driving element collectively in a direction axially of said generally conical surface to bring different axial zones thereof into rolling engagement with said driven element and thereby steplessly vary the velocity ratio afforded between said elements, vi. means connecting said manually movable control member with said motor to move same to diffErent positions for different classes of work indicated by said indicator means.