US3475589A

US3475589A - Thermal exposure device

Info

Publication number: US3475589A
Application number: US547587A
Authority: US
Inventors: Robert J Bartusek; Aladar L Czerna
Original assignee: Bell and Howell Co
Current assignee: White Consolidated Industries Inc
Priority date: 1966-05-04
Filing date: 1966-05-04
Publication date: 1969-10-28
Anticipated expiration: 1986-10-28

Description

0 3. 196.9 R. J. BARTUSEK ET AL 3,475,539

THERMAL EXPOSURE DEVI CE 3 Sheets-Sheet 1 Filed May 4, 1966 mm 3 I. ..J i j J d 1 5. ww \w-& H E h Jww I: I Em "W hi m2 MK, 9 9. AL NH mm 0% N LR QM m,

.12 Mm aw im J M bum R 5 B Oct. 28, 1969 Ru. RT ET AL 3,475,589

THERMAL EXPOSURE DEVICE Filed May 4, 1966 3 Sheets-Sheet 2 7g INVENTORS.

Koberz JBCU'iUsek, uqlczdar L. Czerna.

Oct. 28, 1969 BARTUSEK ET AL 3,475,589

THERMAL EXPOSURE DEVI CE 3 Sheets-Sheet 3 Filed May 4, 1966 Ill-"ill'llllll I I i I I I I l I I i I I RObenJBamusel uq ZadarL. Czerna United States Patent US. Cl. 219-216 7 Claims ABSTRACT OF THE DISCLOSURE The thermographic wax-transfer imaging process is improved by focusing radiation on the sheet assembly, comprising an original, a transfer-material-containing sheet and a copy sheet, maintained in close heat-transfer contact prior to application of sufiicient pressure to cause imagewise transfer of heat-sensitive material to the copy sheet. The exposure device, consists of a pressure roller and a transparent copy roll having a radiation lamp therein. The exposure device has means for accurately focusing the radiation on the sheet assembly before it enters the nip between the copy roll and pressure roller and deflector means for imparting drag resistance to the sheets of the assembly so as to maintain tension and heattransfer contact therebetween.

The present invention relates to methods and apparatus for the reproduction of graphic materials with radiation.

It is an object of the present invention to provide improved selective transfer of radiation activated graphic transfer material.

Another object of the present invention is to provide a method for improved and more accurate thermographic transfer of heat-activated transfer material from a supply sheet to an adjacent copy sheet in a sheet assemblage.

It is a further object of the present invention to provide a improved machine for the thermographic transfer of transfer material from a supply sheet to a copy sheet in a sheet assemblage wherein said machine has improved operating characteristics and provides a more accurate control over the transfer.

Further and more specific objects of the invention pertain to the particular arrangements whereby the aboveidentified and other objects of the invention are attained.

The invention both as to its methods and means will be better understood by reference to the following specification and the drawings forming a part thereof where- 1n:

FIGURE 1 is a cross-sectional side view of an exemplary thermal transfer machine in accordance with the present invention;

FIGURE 2 is a. cross-sectional view taken along the line 2-2 in FIGURE 1;

FIGURE 3 is a cross-sectional view taken along the line 3-3 of FIGURE 2 and drawn to scale;

FIGURE 4 is an enlarged portion of FIGURE 3;

FIGURE 5 is a cross-sectional detail of the machine of FIGURE 1 showing the means for pivotably adjusting the radiation means; and

FIGURE 6 is a cross-section view taken along the line 6-6 of FIGURE 1.

Turning now to the drawings, there is shown an exemplary thermal transfer machine 10 in accordance with the present invention. The machine 10is adapted to provide an accurate transfer of thermally activated transfer material from a supply sheet to an adjacent copy sheet in a sheet assemblage 11. Preferred sheet assemblages and transfer materials are described in Patents Nos. 3,122,997 and 3,122,998 to Raczynski et a1. issued Mar. 3, 1964. A housing 12 encloses and supports the components and provides an inlet 14 into which the sheet assemblage 11 3,475,589 Patented Oct. 28, 1969 ice is fed. The sheet assemblage 11 is pulled through the machine by a copy roller 16, upon which it is exposed to radiant energy from radiation means 18, subjected to pressure by a pressure roller 20, and then discharged from the machine through outlet 22. The machine 10 performs the method of the invention on the sheet assemblage 11. However, it will be appreciated that the method of the invention is not limited to the function of the machine 10, and could be performed, for example, by hand or by various other apparatus.

Referring now in greater detail to the structure and operation of the machine 10, it may be seen that the inlet 14 has a longitudinal entrance throat defined by an entrance plate surface 24, which forms a planar lower support or floor for the entering sheet assemblage 11, and an opposing tongue 26. The tongue 26 extends longitudinally across the inlet 14 above the entrance plate 24 and is pivotably mounted at its forward edge so that its rearward edge is urged downwardly by gravity toward the entrance plate 24. Thus the tongue 26 presses downwardly upon a sheet assemblage 11 as it enters the inlet 14 to hold the sheet assemblage against the entrance plate 24. It may be seen that the entrance plate 24 slopes upwardly at a small angle and thereby directs the sheet assemblage toward the copy roller 16 at a point on the copy roller substantially spaced from the pressure roller 20.

The tongue 26, together with the entrance plate 24, provides a frictional drag resistance to the movement of a sheet assembly. As the copy roller 16 pulls the sheet assembly through the machine, this drag creates a tension upon the sheet assembly which is employed in holding the sheet assembly lightly but evenly against the copy roller 16.

Projecting downwardly into the inlet 14 is a small pivotable finger or trigger 28. Insertion of material into the machine 10 moves the finger 28, thereby rotating the shaft 30 to which it is fixed, which operates a switch 32. The switch 32 is connected to activate the lamp circuit for the radiation means 18. After the tail end sheet assembly has passed through the inlet 14, the finger 28 drops to again operate the switch 32. Preferably the lamp circuit includes a suitable conventional time delay circuit to automatically extinguished the lamp shortly thereafter.

The rearward edge of the entrance plate 24 terminates at an apex 34. At the apex 34, there is a sharp bend or change of direction of approximately 25 to a second planar surface 36 forming a sharply arcuate edge between the

surfaces

24 and 36. The second planar surface 36 is closely spaced from and generally tangential the copy roller 16 and extends toward the nip between the copy roller 16 and the pressure roller 20. The apex 34 provides several important functions. It causes a sharp change in direction or deflection of the sheet assemblage as the sheet assemblage passes over it. This causes an increase in the drag described above and provides an ironing effect upon the sheet assemblage which assists in the removal of air space between the sheets. The apex 34 is closely spaced from the outer surface of the copy roller 16, and the apex 34 together with the pressure roller 20 are the two members which hold the sheet assemblage against the copy roller 16. It may be seen that a line drawn between the apex 34 and the area of contact of the pressure roller 20 with the copy roller 16 is chordal the copy roller 16 and of a length approximately equal to the radius of the copy roller. Since the portion of the sheet assemblage between these two points is in tension as described above, it is pressed against the outwardly curving surface of the copy roller 16 between these two points. Thus a substantial wrap-around area of the sheet assemblage against the copy roller 16 is provided.

The copy roller 16 is preferably an open-ended, thinwalled tubular glass cylinder substantially larger in diameter than the pressure roller 20. It is rotatably held between the pressure roller 20 and two spaced

upper rollers

38 and 40. Preferably all three of these rollers engaging the copy roller 16 are rubber surfaced. The upper roller 40 is rotatably driven by a pulley belt 42 extending from the output of a drive mechanism 44, and the copy roller 16 is driven thereby.

Variable exposure in the machine is provided by varying the speed of the paper assemblage through the machine. This is accomplished by changing the speed output of the variable speed drive mechanism 44. The drive mechanism 44- comprises an axially movable roller 46 frictionally driving the surface of a rotatable cone 48. The roller 46 is driven by an electric motor 54 which also drives a blower 56. Variably positioning the roller 46 along the surface of the cone 48 changes the relative rotation between the two and thereby controls the speed of a Worm 50 connected to the cone 48. The worm 50 drives a worm gear 52 which is fixed to a pulley for driving'the pulley belt 42.

The blower 56 is preferably of a conventional centrifugal construction. The output of the blower 56 is fed through an air tube 58 and supplies the air for cooling the radiation means 18.

Considering now the pressure roller 20, it is axially rotatably mounted at each end to an arm 60. Each arm 60 is in turn pivotably mounted to the housing 12 about an axis 62 at the forward end thereof. The rear end of each arm 60 is pulled upwardly by a spring 64 from the housing thereby pulling the pressure roller 20 into a pressure contact with the copy roller 16, which pressure is exerted on the sheet assembly 11 passing therebetween. A suitable structure provides a zone of contact and pressure 66 between the pressure roller 20 and the copy roller 16 of approximately .090 to .100 inch in width extending evenly the length of the copy roller 16. The pressure zone 66 is centered upon the line between the axis of the copy roller 16 and the axis of the pressure roller 20. Within this pressure zone 66 there is a transfer pressure sufficient to accomplish transfer of heated transfer material onto a copy sheet, preferably at least three pounds per square inch. The sheet assembly 11 is subject to a transfer pressure only within this pressure zone 66. The pressure exerted upon the assemblage 11 at any other area of the copy roller 16 is due only to the drag tension provided thereon as described above and is insuflicient to accomplish a transfer of the transfer material even when in a sufliciently heated state.

Turning now to the radiation means 18, the source of radiation therein is preferably a conventional infrared lamp 68 approximately coextensive in length with the copy roller 16. A suitable lamp 68 is the GE. lamp 1,350 Watts/T2 1/2/CY1-115 v. The lamp 68 is mounted within an elliptical reflector and heat sink 70 which in turn is enclosed by a cooling duct 72. The entire radiation means 18 is preferably mounted completely inside the copy roller 16. The cooling duct 72 is secured to the reflector 70, and the reflector 70 is in turn supported at each end by an angle bracket 74. The bracket 74 is adjustably fastened to the housing 12.

The reflector 70 may be constructed as a gold anodized aluminum extrusion and is adapted to hold the lamp 68 closely spaced from the inner wall of the copy roller 16. Preferably, the reflector 70 contains the lamp 68 within a reflective recess 76. The upper wall of the recess 76 is in the form of a reflector for focusing the emission from the lamp 68 into a high intensity band of radiation which is projected through the transparent wall of the copy roller 16 at a radiation zone 78 onto the sheet assemblage 11. While the outlet opening from the recess 76 is approximately .260 inch, most of the emitted radiation is focused by the reflector 70 onto the radiation zone 78 which is approximately .050 inch in width. The preferred distance between the center of this radiation zone 78 and the center of the pressure zone 66 in the machine 10 is approximately .150 inch. Thus, it may be seen that the bulk of the thermal energy applied to the sheet assemblage is applied thereto prior to the passage of the sheet assemblage through the pressure zone 66, although there may be some overlap of radiation in the pressure zone.

The above mentioned distance between the radiation zone 78 and the pressure zone 66 is critical to the effective transfer operation of the machine 10, and there is therefore provided an arrangement for the continuous fine adjustable positioning of the radiation means 18 in relation to the pressure roller 20. This is accomplished herein by a continuously adjustable pivotable mounting of the radiation means 18. An arcuate projection or knife edge on the bracket pivotably engages a corresponding recess in the top of the reflector 70 to provide a pivot 82 between the radiation means 18 and the bracket 74. It may be seen that the pivot 82 is located near the axis or. center of rotation of the copy roller 16. Thereby a substantial purely arcuate movement of the radiation means with respect to the copy roller 16 is provided by the pivoting of the radiation means about the pivot 82. Screws 84a and 84b are spaced at opposite sides of the pivot 82 and extend through the bracket 74 into threaded engagement with the reflector 70. Accordingly, turning these screws causes a finely controllable arcuate pivoting of the radiation means 18 and thereby a .fine movement of the radiation zone 78 toward or away from the pressure zone 66. i

It may be seen that each bracket 74 also contains a pair of vertical slots through which the bracket 74 is bolted to the housing 12. This allows adjustment in the vertical position of the radiation means 18 with respect to the copy roller 16.

Even and effective cooling of the radiation means 18 and the copy roller 16 is important to the proper function of the machine 10. The cooling air from the blower 50 is provided through the air tube 58 which is connected to the cooling duct or shield 72. The duct 72.has a relatively large cross-sectional area and evenly distributes incoming air along the radiation means 18 since the housing 72 extends along the principal length of the reflector 70. It may be seen that the duct 72 substantially surrounds the reflector 70 and is generally cylindrical.

Preferably, the sole outlet of air from the cooling duct 72 is from a multiplicity of-similar small air outlets 86 comprising notches in the edges of the duct 72 where the edges of the duct 72 abut the sides of the reflector 70. Thus, the air outlets 86 directly overlie and discharge air over the surface of the reflector 70. It will be observed that the spacing between the air outlets 86 increases from inch at the center of the reflector 70 to inch at the outer end so that a subtsantially greater number of air outlets per unit length are located toward the center of the cooling duct 72 than toward the outer ends thereof. Thereby the overall outlet area for air discharge decreases in proportion to the distance from the center of the radiation means 18. Thus, more cooling air is provided at the areas of increasing heat concentration, and, consequently, an even cooling is provided.

The air discharged from the air outlets 86 is directed, due to the downwardly projecting position of these outlets, toward the lower inside surface of the copy roller 16. This provides maximum air flow over the area of the copy roller which is being heated by the radiation means. The air then flows through the copy roller 16 andv out the open ends thereof, which it heats.

Considering particularly the method of the invention, it will be appreciated that in prior thermographic transfer methods and particularly in processes involving a wax transfer process whereby both heat and pressure are needed to accomplish the transfer of a waxy material, as for example those described in the above cited Raczynski et al. patents, it is taught that heat and pressure should be simultaneously applied for transfer. However, it is the teaching of the improved process of the invention that, where heating of the transfer material is substantially accomplished prior to the application of pressure, improved transfer control is possible. The period of the delay between the substantial completion of the thermal radiation and the pressure application may be carefully controlled so that the transfer material is still in a softened transferable condition when pressure is applied to provide an optimum transfer.

While the exact theory is not completely understood, it is believed that the process involves a controlled cooling or heat distribution or change in condition ofthe transfer material in the controlled period following the bulk of the heating and prior to the application of transfer pressure. It is known that controlling the wax temperature by controlling the lamp temperature is very diflicult. The heat actually applied to the transfer material is subject to variations due to the conditions of ambient temperature, the period of operation of the machine, the power supplied to the lamp, etc. It has been found that that application of pressure simultaneously while heating the transfer material results in distortion and blurring of the image to a much greater degree than where transfer takes place under pressure applied very shortly after most or substantially all of the heating is completed and prior to a substantial cooling of the transfer material to the point where selective adhesion will not occur. Thus, in the method of the invention, the sheet assemblage is first subjected to suffieient thermal radiation to selectively soften the transfer material at the image areas but not subjected to pressure suflicient to transfer the transfer ma terial to the copy sheet. Then, after a preset period after the thermal radiation is substantially terminated, but While the transfer material is still sufficiently soft to effect transfer, which period is controlled by the presetting of a time delay, or spacing delay for a moving sheet assembly, transfer pressure is applied.

The presetting of the delay period is quite critical. For example in the machine the optimum is approximately :.020 inch. Arcuate movement of the radiation zone 78 either way from its optimum position by greater than this amount will result in a poor transfer. Movement too far away from the pressure zone will result in an incomplete transfer, whereas movement of the radiation zone too close to the pressure zone will cause the characters to fill in or become distorted or blurred. Changing the speed of the machine 10 effects the optimum spacing. At a slower copy speed the two zones can be closer together, and at a higher speed they are preferably further apart.

For the machine 10, the copy speed range is from 4.12 to 7. 84 inches per second. Optimum speed for a Spirit Master is 5.72 inches per second and for facsimile copies 6.5 inches per second.

In view of the foregoing disclosures, it is clear that there has been provided hereby improved means and methods for thermographic transfer. While the means and methods described herein are presently considered to be preferred, it is contemplated that numerous variations and modifications within the purview of those skilled in the ares can be made herein and it is intended to cover in the appended claims all such variations and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1'. A graphic transfer machine for the selective transfer of radiation-activated transfer material from a supply sheet to an adjacent copy sheet in a sheet assemblage, said machine comprising:

a housing,

a copy roller in said housing,

means in said housing for lightly engaging a sheet assembly against said copy roller,

a pressure roller in said housing adapted to compress a sheet assemblage at a pressure area on said copy roller,

radiation means in said housing adjacent said copy roller for radiating an exposure area on said copy roller substantially adjacent said pressure area so that the principal portion of the radiation therefrom does not overlie said pressure area,

a bracket adjustably mounted to said housing,

pivot means between said bracket and said radiation means and continuous adjustment means connecting said bracket means and said radiation means spaced from said pivot means for pivoting said radiation means about said pivot means to selectively move said exposure area toward and away from said pressure area.

2. The graphic transfer machine of claim 1 wherein said pivot means are located within said copy roller adjacent the central axis thereof.

3. A graphic transfer machine for the selective transfer of radiation-activated transfer material from a supply sheet to an adjacent copy sheet in a sheet assemblage, said machine comprising:

a housing,

a copy roller in said housing,

a pressure roller in said housing adapted to compress a sheet assemblage at a pressure area on said copy roller, radiation means in said housing adjacent said copy roller for radiating an exposure area on said copy roller substantially adjacent said pressure area so that the principal portion of the radiation therefrom does not overlie said pressure area, said radiation means being positioned inside said copy roller and practically enclosed by an air-cooling housing extending along the principal length of said radiation means, said air-cooling housing having an air opening means inside said copy roller and overlying said radiation means, said air opening means having an area of opening which decreases in proportion to its distance from the center of said radiation means,

and continuous adjustment means for said radiation means to selectively move said exposure area to- Ward and away from said pressure area.

4. A graphic transfer machine comprising:

a housing,

copy support means in said housing,

radiation means in said housing adjacent said copy support means,

a bracket adjustably mounted to said housing,

pivot means between said bracket and said radiation means,

and continuous adjustment means connecting said bracket means and said radiation means spaced from said pivot means for pivoting said radiation means about said pivot means.

5. A graphic transfer machine for the selective transfer of radiation-activated transfer material from a supply sheet to an adjacent copy sheet in a sheet assemblage, said machine comprising:

a housing,

a copy roller in said housing,

deflector means in said housing for lightly engaging a sheet assembly against said copy roller in said exposure area to maintain said sheet assembly under tension between said deflector means and said copy roller,

and continuous adjustment means for said radiation means to selectively move said exposure area toward and away from said pressure area.

6. The graphic transfer machine of claim 5, wherein said deflector means comprises a sheet assembly deflector having an arcuate apex closely spaced from the surface of said copy roller, said apex of said deflector and said pressure area of said pressure roller being chordal said copy roller.

7. The graphic transfer machine of claim 6 wherein said deflector means further comprises drag means positioned to engage said sheet assembly prior to said sheet assembly deflector.

References Cited UNITED STATES PATENTS 0 JOSEPH V. TRUHE, Primary Examiner C. L. ALBRITTON, Assistant Examiner Us. or. X.R.