US3553424A

US3553424A - Paper stabilization heater

Info

Publication number: US3553424A
Application number: US802174A
Authority: US
Inventors: Carl P Spaulding
Original assignee: Litton Systems Inc
Current assignee: Northrop Grumman Guidance and Electronics Co Inc
Priority date: 1969-02-25
Filing date: 1969-02-25
Publication date: 1971-01-05
Anticipated expiration: 1988-01-05

Abstract

Apparatus for the heat stabilization of spectrally sensitized printout paper on a continuous basis having means for forming a latent image on the paper; means for transporting the paper into thermal contact with a passive heat shunt and raising the temperature of the paper a predetermined increment; heat reservoir means in thermal contact with the paper for raising the temperature an additional predetermined increment; heater means for raising the temperature of the paper to that required for stabilization of the image; means for maintaining the stabilization temperature for a predetermined period of time while the strip is in motion; means for returning the heat from the paper to the heat reservoir; and additional means for returning heat to the heat shunt.

Description

United States Patent [72] inventor [54] PAPER STABILIZATION HEATER 13 Claims. 3 Drawing Figs.

52 u.s.c1 219/388, 96/1: 219/216, 219/347.219/530; 263/6 51 1m.c1 F27b9/06, H05b1/02 so FieldolSearch 219/388,

[56] References Cited UNITED STATES PATENTS 6/1963 Dudzik Primary Examiner- Volodymyr Y. Mayewsky Attorneys-John G. Mesaros, Alan C. Rose, Ronald W.

Reagin and Alfred B. Levine ABSTRACT: Apparatus for the heat stabilization of spectrally sensitized printout paper on a continuous basis having means for forming a latent image on the paper; means for transporting the paper into thermal contact with a passive heat shunt and raising the temperature of the paper a predetermined increment; heat reservoir means in thermal contact with the paper for raising the temperature an additional predetermined increment; heater means for raising the temperature of the paper to that required for stabilization of the image; means for maintaining the stabilization temperature for a predetermined period of time while the strip is in motion; means for returning the heat from the paper to the heat reservoir; and additional means for returning heat to the heat shunt.

PATENTED m 5 m sum 1 or 2 ArroR/My PAPER STABILIZATION HEATER BACKGROUND or THE INVENTION With the development of cathode ray tube recording systems employing fibre optics and oscillographs employing Tungsten, xenon or mercury vapor light sources; one of the primary drawbacks to the full realization of the potential of this media has been the problem relating to the stabilization of the image on the paper or fixing" the photographic emulsion to prevent the loss of image.

Generally a spectrally sensitized heat stabilized printout paper is used. A latent image is formed by exposing the paper to an image produced on a suitable electro-optical device such as a cathode ray tube. The latent image must then be stabilized by heating the emulsion for a fixed period of time at a predetermined temperature. The image is then made visible by a subsequent exposure to any source of ultraviolet or visible illumination.

It is accordingly an object of this invention to provide a new and improved printout paper stabilization heater.

It is another object of this invention to provide a new and improved paper stabilization heater for the stabilization of the latent image on a continuous basis. I

It is a further object of this invention to provide a new and improved printout paper stabilization heater which is compact and reliable.

It is still another object of this invention to provide a new and improved printout paper stabilization heater capable of instantaneous startup utilizing a heat reservoir capable of removing heat from the paper subsequent to the heat stabilization thereof. 1

It is a still further object of this invention to provide a new and improved printout paper stabilization heater employing a thermal feedback to increase the efficiency thereof.

SUMMARY OF THE INVENTION The foregoing and other objects of the invention are accomplished by providing a trough having an open end through which the paper enters and exits, the trough having reflecting surfaces on the inside thereof. Adjacent the opening is an elongate passive heat shunt having one surface thereof in proximity to the cathode ray tube which produces the original image, this surface being adapted for contact with the printout paper subsequent to the formation of the latent image in order to raise the temperature of the paper a predetermined increment. An elongate heat reservoir having an internal heater is disposed beneath the heat shunt within the trough and separated from the heat shunt by suitable insulating means. One surface of the heat reservoir is adapted for continuous contact with the printout paper for increasing the paper temperature an additional predeterminedincrement. An insulator is affixed to the lower end of the heatreservoir. A suitable heating means such as a nichrome strip heater is secured to the insulator and is in contact with the paper to bring the paper to the image stabilization temperature. The opposite surface of the heat reservoir is spaced from the strip paper and reflectively coated to substantially maintain the temperature of. the paper at the stabilization temperature for a predetermined period of time which is the time required at temperature for image stabilization. The strip then passes into contact with a second surface of the heat reservoir and returns a portion of the heat. The strip then exits the trough in thermal contact with the other surface of the heat shunt returning a portion of the heat to the shunt. With the strip in continuous movement at a predetermined speed, the temperature of the paper will be raised to the stabilization temperature in increments.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 2 shows in diagrammatic form an end view of the apparatus of FIG. 1 showing the travel of the strip of sensitize paper; and

FIG. 3 shows the heat flow within the paper stabilization heater in diagrammatic form.

DESCRIPTION OF THE PREFERRED EMBODIMENT DESCRIPTION OF THE APPARATUS Referring now to the drawings, and particularly to FIGS. 1 and 2, there is shown a trough generally designated as It) having a bottom 12, sidewalls l4 and 16 and

end walls

18 and 20, with the sidewalls and bottom being gold plated to provide reflecting surfaces. The end walls and sidewalls define an opening 22 opposite the bottom wall 12, the length of the opening being generally that ofthe printout paper.

Positioned within the opening but spaced from the

sidewalls

14 and 16 in close proximity thereto there is located an elongate passive thermal shunt 24 which may take the form of an aluminum bar of rectangular cross section. Abutting the under surface of shunt 24 is an insulator 26 of generally uniform thickness and having a depending portion 28 at either end thereof, the purpose of which will hereinafter become obvious. A heat reservoir 30 is positioned between the depending portions 28 in abutting relationship with the undersurface of the insulator 26. The heat reservoir 30 is made from any suitable thermally conductive material such as aluminum and is generally triangular in cross section configuration. The heat reservoir 30 has a smooth continuous entrance surface 32 and an exit surface 34 being stepped inwardly at the lower portion thereof, the step portion being designated 36. An aperture 38 extends the length of the heat reservoir 30 intermediate the entrance surface 32 and the exit surface 34, the aperture 38 being in alignment with apertures 40 in the depending portions 28 of insulator 26. Internal heating means 42 extend through the aligned

apertures

38 and 40 and are mechanically held in place by suitable fastening means (now shown) at the outer surface of depending portions 28. The heating means 42 can take the form of an electrical resistance heater for example, and is energized from any suitable source of electrical power (not shown).

At the apex of the lower portion of the heat reservoir 30 there is located a longitudinal groove 44 adapted to receive an insulator 46 which has at least the bottom portion thereof rounded. The insulator 46 is secured within the groove 44 by bonding or mechanical fastening. Bonded to the curved surface of the insulator 46 is an electrical strip heater 48 made of nichrome or other similar electrical resistance material of low thermal mass (low thermal time constant) which is energized from any suitable source of electrical power (not shown). The strip heater 48 has sufficient area to efficiently transfer heat to the paper 50 at the maximum paper speed.

As shown in FIG. 2 the shunt 24, the insulator 26, and the heat reservoir 30 are so arranged to provide a continuous surface. Printout paper 50 is fed off a payout reel 52 passing in close proximity to a suitable optical device such as fibre optic tube 54 and a screen upon which the image is displayed. The sensitized surface of the paper 50 faces the image display tube 54. The back surface of the paper 50 enters the trough 10 at the entrance end designated 56in contact with the side surface of the shunt 24, the side surface of the insulator 26, and the entrance surface 32 of heat reservoir 30. The paper then reverses its path around the nichrome strip heater 48 upwardly in spaced parallel relationship with the step portion 36 of the heat reservoir 30 and into contact with exit surface 34 of the heat reservoir 30, the side surface of insulator 26, and the side surface of shunt 24 through the exit end 58 of the opening 22. The paper is then wound on a takeup reel 60.

METHOD OF OPERATION A suitable printout paper which can be utilized is Eastman- Kodak type D-l877 paper which is heat stabilized by the application of heat to a temperature of approximately 265 C.

for a period of approximately one second, and the description of operation will proceed on the basis of this particular printout paper. It is to be understood, however, that the scope of the invention is not to be limited to the utilization of any specific printout paper and is generally applicable to any flexible recording medium where a latent image is formed and must be subsequently heat stabilized at a specific temperature for a predetermined period of time in order to fix the image and make it permanent.

Referring now to FIG. 2, the paper 50 moves at approximately 1.67 inches per second past the fibre optic tube 54 where a latent image is formed on the paper. For purposes of discussion the paper is at room temperature or approximately 20 C. Prior to this internal heater 42 has been energized on a standby basis to maintain the heat reservoir at an average temperature of 135 C. A certain portion of the heat is lost (approximately 4 watts) through the insulator 26 to thereby maintain the temperature of the heat shunt 24 at an average temperature of 80 C. The nichrome strip heater 48 is thermostatically controlled or maintained at a temperature of approximately 260 C. The strip heater 48 can be energized upon initial movement of the paper 50 and due to its low thermal mass it will reach operating temperature by the time the first image reaches the strip heater 48.

The heat flow diagram shown in FIG. 4 is based on the specific aforementioned paper and temperatures and heat quantities stated are in reference to this paper. After the latent image is formed the paper 50 passes in contact with the shunt '24 where about 55 watts of heat is absorbed and the temperatact with the entrance surface 32 of heat reservoir 30. An additional 120 watts of heat is conducted from the reservoir to the paper 50 raising its temperature to about 130 C. The paper then passes over an open gap and is wrapped around the nichrome strip heater 48 where the temperature of the paper is raised to 260 C., the temperature required for stabilization. Next, the paper 50 passes over the step portion 36, the portion 36 having a length in the direction of travel of approximately 1.7 inches. Gold plating of the step portion 36 and the internal surface of the sidewall 14 of the trough l minimize radiation and convection losses to substantially maintain this temperature. The length of the step portion 36 is chosen to require one second for the paper 50 to traverse the step portion 36 with the one second being the time period required at the stabilization temperature at 260 C., for heat stabilization of the image of this specific printout paper.

After stabilization the paper slides over exit surface 34 of the heat reservoir 30. Since the paper 50 is hotter than the reservoir 30 it gives up about 120 watts of heat. The paper then passes over the insulating section 26 and comes into contact with the heat shunt 24 which is still cooler, the paper 50 giving up an additional 55 watts and its temperature is reduced to that of the shunt 24- about 85 C.

The remaining heat is stored in the takeup roll 60 of the paper 50. This heat may be transferred by convection to the outsideair or may, to some extent, be transferred to the feed roll to raise the temperature of the unexposed paper.

With this particular apparatus approximately five inches of paper lie between the fibre optic tube 54 and the viewing area. At the stated speed of 1.67 inches per second, this means that approximately three seconds are required between receipt of a message at the tube 50 and its appearance in the viewing area. When the paper 50 is not moving the heater 42 is switched to standby condition the heat at standby being as hot as possible i but not so hot as to char or mechanically weaken the paper50 threaded through the apparatus and not moving. ln standby the nichrome strip heater 48 is turned off and the internal heater 42 is turned on and is thermostatically controlled to maintain the temperature of the heat reservoir at about 135 C. As soon as a message is received the paper 50 begins moving and the nichrome strip heater 48 is switched on and the internal heater 42 is turned off. With the application of power the nichrome strip heater temperature is raised from C standby to 260 C., operating temperature within one second or less than the time required for the paperto travel from the tube 54 to the nichrome strip heater 48';

in summary, there has been shown anddescribed a printout paper stabilization heater which is compact and efficient, employing heat transfer means to return heat figom the paper to the transfer means thereby reducing'the,. 1 power requirements from external sources and rendering thegdevice more efficient than heretofore known prior artdeyicesslt is to. be understood, however, that other adaptationsand,modifications may be made within the spirit and scope of the invention,

and the invention is not to be limited by the specificstructure shown nor the specific paper described.

lclaim:

1. Apparatus for the continuous heat stabilization of images formed by exposing to light a strip of light sensitive paper, said apparatus comprising:

a. a heat reservoir having a first surface in thermal contact with said paper subsequent to the formation of the latent image for raising the" temperature of said. paper a predetermined increment; l i an electrical heating element adjacent to but spaced from said heat reservoir, said heating element being 'in thermal contact with said paper to raise the temperature .of said paper an additional increment to the temperature required for heat stabilization of the latent iniage;

c. transport means for moving f'i d'ipap'er along a path of travel at a predetermined speed, .j'

d. reflecting means for maintaining 'the paper at the stabilization temperature for a predetermined period of time while said paper is moving at the predetermined speed;

e. thermal conduction means for returninga portion of the heat of said paper to said heat reservoiraft rt he l'ap'seof said predetermined period of time; and I f. enclosure means for'substantially containing said heat reservoir, said heating element, said reflecting means and said thermal conduction means.

2. The combination according to claim 1 wherein said'apparatus is provided with heat transfer means in thermal contact with said paper prior to said heat reservoir means for raising the temperature of the paper an initial predetermined increment, said heat transfer means extracting an additional portion of heat from said paper subsequent to said means for returning a portion of the heat of the paper to said heat reservoir.

3. The combination according to claim 1 wherein said heat ing element includes an elongate strip heater having a low thermal mass.

4. The combination according to claim 2 wherein said heat.

transfer means includes an elongate bar having first and second generally parallel surfaces, said first surface being in thermal contact with said paper subsequent to the formation of the latent image and said second surface being in thermal contact with said paper after stabilization for extracting the heat.

5. The combination according to claim 1 wherein said heat reservoir includes a thermally conductive block of generally triangular cross section. I

6. The combination according to claim 5 wherein said strip heater is secured to and insulated from the apex of said block, said strip heater being generally arcuate in configuration for generally reversing the direction of travel of said paper.

7. The combination according toclaim 6 wherein said block is provided with a secondgenerally opposite surface vhaving a first portion and a second portion stepped inwardly from said first portion, said first portion being adapted for thermal conf tact with the paper for returning heat to said block and said second portion being spaced from the path of travel of said paper, said secondportion at least partially reflecting heat for maintaining the paper at the stabilization temperature.

8. The combination according to claim 7 wherein said second portion is reflectively coated and the length ol -said' second portion in the direction of travel of the paper is sufficient to substantially maintain the paper at the stabilization temperature at said predetermined speed.

9. The combination according to claim 5 wherein said block is provided with internal heating means.

10. The combination according to claim 9 wherein said internal heating means are energized electrically independent from said strip heater, said internal heatingmeans being energized on a standby basis prior to movement of the paper to provide an initial heat content to said block, said strip heater being energized upon movement of the paper.

Claims

1. Apparatus for the continuous heat stabilization of images formed by exposing to light a strip of light sensitive paper, said apparatus comprising: a. a heat reservoir having a first surface in thermal contact with said paper subsequent to the formation of the latent image for raising the temperature of said paper a predetermined increment; b. an electrical heating element adjacent to but spaced from said heat reservoir, said heating element being in thermal contact with said paper to raise the temperature of said paper an additional increment to the temperature required for heat stabilization of the latent image; c. transport means for moving said paper along a path of travel at a predetermined speed; d. reflecting means for maintaining the paper at the stabilization temperature for a predetermined period of time while said paper is moving at the predetermined speed; e. thermal conduction means for returning a portion of the heat of said paper to said heat reservoir after the lapse of said predetermined period of time; and f. enclosure means for substantially containing said heat reservoir, said heating element, said reflecting means and said thermal conduction means.

2. The combination according to claim 1 wherein said apparatus is provided with heat transfer means in thermal contact with said paper prior to said heat reservoir means for raising the temperature of the paper an initial predetermined increment, said heat transfer means extracting an additional portion of heat from said paper subsequent to said means for returning a portion of the heat of the paper to said heat reservoir.

3. The combination according to claim 1 wherein said heating element includes an elongate strip heater having a low thermal mass.

4. The combination according to claim 2 wherein said heat transfer means includes an elongate bar having first and second generally parallel surfaces, said first surface being in thermal contact with said paper subsequent to the formation of the latent image and said second surface being in thermal contact with said paper after stabilization for extracting the heat.

5. The combination according to claim 1 wherein said heat reservoir includes a thermally conductive block of generally triangular cross section.

7. The combination according to claim 6 wherein said block is provided with a second generally opposite surface having a first portion and a second portion stepped inwardly from said first portion, said first portion being adapted for thermal contact with the paper for returning heat to said block and said second portion being spaced from the path of travel of said paper, said second portion at least partially reflecting heat for maintaining the paper at the stabilization temperature.

8. The combination according to claim 7 wherein said second portion is reflectively coated and the length of said second portion in the direction of travel of the paper is sufficient to substantially maintain the paper at the stabilization temperature at said predetermined speed.

10. The combination according to claim 9 wherein said internal heating means are energized electrically independent from said strip heater, said internal heating means being energized on a standby basis prior to movement of the paper to provide an initial heat content to said block, said strip heater being energized upon movement of the paper.

11. The combination according to claim 8 wherein said enclosure means includes a trough.

12. The combination according to claim 11 wherein said trough has an open end for entrance and exit of the paper and oppositely disposed sidewalls in proximity to the path of travel of the paper.

13. The combination according to claim 12 wherein said trough has end walls and a bottom wall said sidewalls and said bottom wall being reflectively coated.