Thermal sensor assembly

• US 5,999,768 A
• Filed: 06/03/1999
• Issued: 12/07/1999
• Est. Priority Date: 10/20/1997
• Status: Expired due to Fees

• Current Assignee: Output Technology Corporation
• Original Assignee: Output Technology Corporation
• Inventors: Casper, Robert, Gillen, John
• Primary Examiner(s): Fulton, Christopher W.
• Assistant Examiner(s): Fernandez, Maria
• Application Number:
  US09/325,519
• Time in Patent Office: 187 Days
• Field of Search: 274/121, 274/125, 274/130, 274/132, 274/153
• US Class Current: 399/92
• CPC Class Codes: G01J 5/0003 for sensing the radiant heat transfer of samples, e.g. emittance meter
• CPC Class Codes: G01J 5/04 Casings
• CPC Class Codes: G01J 5/061 by controlling the temperature of the apparatus or parts thereof, e.g. using cooling means or thermostats
• CPC Class Codes: G01J 5/12 using thermoelectric elements, e.g. thermocouples
• CPC Class Codes: G01J 5/16 Arrangements with respect to the cold junction; Compensating influence of ambient temperature or other variables
• CPC Class Codes: G03G 15/2039 with means for controlling the fixing temperature
• CPC Class Codes: G03G 21/20 Humidity or temperature control also ozone evacuation; Internal apparatus environment control

Abstract

An infrared thermal sensor assembly for sensing the temperature of a target, the sensor assembly including a heat sink having a bore therethrough; a thermopile housed in the bore; and a heater operative to heat the heat sink.

Claims

1. An electrostatic printer comprising:

a frame;

a pressure drum supported by the frame for rotation about a first axis;

an image drum supported by the frame for rotation about a second axis parallel to the first axis;

a fusing drum supported by the frame for rotation about a third axis parallel to the first axis, the fusing drum being, in operation, configured to counter-rotate against the image drum, the pressure drum being, in operation, configured to counter-rotate against the fusing drum;

a toner dispensing assembly supported by the frame and disposed to dispense toner to the image drum; and

an infrared thermal sensor assembly disposed to sense the temperature of one of the drums, the sensor assembly including a housing having an opening therethrough, a circuit board supported by the housing, a heat sink supported by the circuit board, the heat sink having opposite ends and having a bore therethrough between the opposite ends, a thermopile housed in the bore and facing the opening in the housing, a first heater element supported by the circuit board, proximate one of the ends of the heat sink, and operative to heat the heat sink, a second heater clement supported by the circuit board, proximate another of the ends of the heat sink, and configured to heat the heat sink, and a fan supported by the circuit board and configured to direct gas into the housing, and out of the housing through the opening.

2. An electrostatic printer in accordance with claim 1 wherein the first heater element comprises a power resistor supported by the circuit board, and wherein the second heater element comprises a power output stage supported by the circuit board and electrically coupled to the power resistor.

3. An electrostatic printer in accordance with claim 1 and further comprising first and second spaced apart fuse clips mounted to the circuit board, wherein the first fuse clip supports one of the ends of the heat sink, and the second fuse clip supports the other end of the heat sink.

4. An electrostatic printer in accordance with claim 1 wherein the bore includes a large diameter portion receiving the thermopile, and a small diameter portion aligned with the large diameter portion, and wherein the thermopile faces the target through the small diameter portion.

5. An electrostatic printer in accordance with claim 1 and further comprising a temperature probe operative to sense the temperature of the heat sink, and circuitry coupled to the temperature probe and to the first and second heater elements to control the temperature of the heat sink.

6. An electrostatic printer in accordance with claim 5 wherein the circuitry coupled to the temperature probe and to the first and second heater elements to control the temperature of the heat sink comprises an error amplifier.

7. An electrostatic printer in accordance with claim 5 wherein the first and second heating elements are configured to heat the heat sink in response to having power applied to the first and second heating elements, and wherein the circuitry coupled to the temperature probe and to the first and second heater elements to control the temperature of the heat sink comprises a phase compensator to compensate for delay between applying power to the first and second heating elements and temperature change of the heat sink sensed by the temperature probe.

8. An electrostatic printer in accordance with claim 1 and further comprising adjustable circuitry, accessible from outside the housing, usable to calibrate the sensor assembly for operation relative to two different temperature operating points.

9. An electrostatic printer comprising:

a frame;

a pressure drum supported by the frame for rotation about a first axis;

an image drum supported by the frame for rotation about a second axis parallel to the first axis;

a fusing drum supported by the frame for rotation about a third axis parallel to the first axis, the fusing drum being, in operation, disposed to counter-rotate against the image drum, the pressure drum, in operation, being disposed to counter-rotate against the fusing drum;

a heating assembly configured to heat the fusing drum; and

an infrared thermal sensor assembly for sensing the temperature of the fusing drum, the sensor assembly including;

a housing having an opening therethrough;

a circuit board supported by the housing;

a heat sink supported by the circuit board, the heat sink having opposite ends and having a bore therethrough between the opposite ends, the bore including a first portion, having a first diameter, receiving the thermopile, and a second portion having a second diameter less than the first diameter, the second portion being aligned with the first portion;

a multi-junction thermopile housed in the first portion of the bore and facing the opening in the housing through the second portion, whereby the field of view of the thermopile is controlled;

a first heater element supported by the circuit board, proximate one of the ends of the heat sink, and operative to heat the heat sink in response to having power applied to the first heater element, the first heater element including a power resistor supported by the circuit board;

a second heater element supported by the circuit board, proximate another of the ends of the heat sink, and configured to heat the heat sink in response to having power applied to the second heater element, the second heater element including a power output stage supported by the circuit board and electrically coupled to the power resistor;

a temperature probe operative to sense the temperature of the heat sink;

circuitry coupled to the temperature probe and to the first and second heater elements to control the temperature of the heat sink, the circuitry including an error amplifier and a phase compensator to compensate for delay between applying power to the first and second heating elements and temperature change of the heat sink sensed by the temperature probe; and

a fan supported by the circuit board and configured to direct gas into the housing, and out of the housing through the opening.

10. An electrostatic printer in accordance with claim 9 and further comprising first and second spaced apart fuse clips mounted to the circuit board, wherein the first fuse clip supports one of the ends of the heat sink, and the second fuse clip supports the other end of the heat sink.

11. An electrostatic printer in accordance with claim 9 and further comprising adjustable circuitry, accessible from outside the housing, coupled to the first mentioned circuitry, and usable to calibrate the sensor assembly for operation relative to different temperature operating points.

12. An electrostatic printer comprising:

a frame;

a pressure drum supported by the frame for rotation about a first axis;

an image drum supported by the frame for rotation about a second axis parallel to the first axis;

a fusing drum supported by the frame for rotation about a third axis parallel to the first axis, the fusing drum being, in operation, disposed to counter-rotate against the image drum, the pressure drum, in operation, being disposed to counter-rotate against the fusing drum to define a nip;

a support member supported by the frame and configured to direct a continuous printable media to the nip;

a toner dispensing assembly supported by the frame and disposed to dispense toner to the image drum;

an image forming assembly disposed to operate on toner dispensed on the image drum to form an image, the imaging drum being configured to transfer the image to the fusing drum, the fusing drum being configured to transfer the image to the continuous printable media;

a heating assembly configured to heat the fusing drum; and

an infrared thermal sensor assembly for sensing the temperature of the fusing drum, the sensor assembly including;

a housing having an opening therethrough;

a circuit board supported by the housing;

first and second spaced apart clips mounted on the circuit board;

a heat sink supported from the circuit board by the clips, the heat sink having opposite ends and having a bore therethrough between the opposite ends, the bore including a first portion, having a first diameter, and a second portion having a second diameter, less than the first diameter, the second portion being aligned with the first portion;

a thermopile housed in the first portion of the bore and facing the opening in the housing through the second portion;

a first heater element supported by the circuit board, proximate one of the ends of the heat sink, and operative to heat the heat sink in response to having power applied to the first heater element, the first heater element including a power resistor supported by the circuit board;

a second heater element supported by the circuit board, proximate another of the ends of the heat sink, and configured to heat the heat sink in response to having power applied to the second heater element, the second heater element including a power output stage supported by the circuit board and electrically coupled to the power resistor;

a temperature probe operative to sense the temperature of the heat sink;

temperature control circuitry coupled to the temperature probe and to the first and second heater elements to control the temperature of the heat sink, the temperature control circuitry including an error amplifier and a phase compensator to compensate for delay between applying power to the first and second heating elements and temperature change of the heat sink sensed by the temperature probe;

adjustable circuitry, accessible from outside the housing, coupled to the temperature control circuitry, and usable to calibrate the sensor assembly for operation relative to different temperature operating points and;

a fan supported by the circuit board and configured to direct gas into the housing, and out of the housing through the opening.