EP0474815A4

EP0474815A4 - Apparatus for making color proof laminations

Info

Publication number: EP0474815A4
Application number: EP19910906331
Authority: EP
Inventors: Harry J. Copeland
Original assignee: Western Litho Plate and Supply Co
Current assignee: Western Litho Plate and Supply Co
Priority date: 1990-03-12
Filing date: 1991-03-11
Publication date: 1993-03-17
Also published as: WO1991013748A1; EP0474815A1; CA2055451A1; JPH05500483A

Abstract

Apparatus for producing color proofs by transferring an image in color from a sheet (22) bearing the image to an image receiving sheet (24) comprising a pair of parallel rollers (32, 34), and means for driving the rollers for feeding the sheets therebetween. At least one of the rollers (50) comprises a shaft (52) and a hollow cylindrical metal drum (54) mounted concentrically on the shaft by thermal insulation means (56) adjacent the ends of the shaft. The drum (54) is covered with a relatively thin layer (58) of thermal and electrical insulation material, and a winding (60) of electrical resistance heating wire. A relatively thin layer (62) of elastomeric material covers the winding. Electrical leads (64, 66) extend from the ends of said winding (60) to rotary contacts (68) at one end of the shaft (52). Thermal insulation (70) fills the drum (54). An electrical sensor (72) for sensing the temperature of the surface of the drum (54) is mounted adjacent to the drum (54), intermediate its ends. A controller (80), responsive to the sensor (72), provides power to the winding (60) to maintain the temperature of the surface at a preselected target temperature.

Description

APPARATUS FOR MAKING COLOR PROOF LAMINATIONS BACKGROUND OF THE INVENTION

This invention relates to color proof lamination, and in particular to apparatus for making color proof laminations.

Color proof lamination involves the application of heat and pressure to transfer a color image from an image sheet to a receiving sheet. The color proof image sheet and the receiving sheet are registered together and sandwiched between hinged carrier sheets of a high temperature resistant material. This "sandwich" or composite is then fed into the nip of a pair of heated rollers (preferably oriented one above the other) . The color proof image on the image sheet is transferred to the receiving sheet by the heat and pressure of the rollers. Upon exiting the heated rollers the composite may pass through some device for cooling the composite. The top carrier sheet and the image sheet are removed, another image sheet is registered with the receiving sheet, and the top carrier sheet is replaced. The new composite is run through the laminator. The process is repeated for each of the standard four color image sheets (magenta, cyan, yellow, and black) to make a complete four-color proof.

Various techniques have been employed for heating and controlling the temperatures of the rollers in color laminators. One technique employs a hollow, rubber-covered roller. Oil is heated in a reservoir and circulated by a pump through the hollow roller to heat the roller and the rubber cover. Although this system is commonly used in the printing industry, it has a number of disadvantages. The system is expensive and occupies a large space (due particularly to the oil reservoir and pump). Moreover, it takes a long time for the oil and the roller to warm-up for use, and the heating is inefficient because of heat losses from the oil to the pump and the plumbing. Finally, the system is slow to respond to heat loss from the roller^' surface, for example after a composite has been run through the apparatus.

Another technique employed for heating and controlling the temperature of the rollers involves a combination of internal and external heaters. This technique employs solid roller with a rubber cover. The roller has an internal heater for heating the roller, and the temperature is controlled by a thermocouple riding on the external surface of the roller. The rubber cover on the roller is heated by an external radiant heater which is activated when a composite passes over an entry sensor. This system also has some disadvantages, one being that it requires two separate heating systems and two separate control systems. The system is also inefficient because it heats the entire roller in an effort to maintain temperature stability.

SUMMARY OF THE PRESENT INVENTION

It is among the objects of the present invention to provide an apparatus for making color proof laminations which has heated rollers with fast surface temperature response and recovery; it is also among the objects of this invention to provide such an apparatus which is efficient; and it is also among the objects of this invention to provide such an apparatus that is of simple, inexpensive, and compact construction. This invention relates to an apparatus for producing color proofs by transferring a color image from an image-bearing sheet to a receiving sheet superposed in registry therewith, and sandwiched between two carrier sheets. Generally, the apparatus comprises support means, and.means for feeding the composite of the image sheet, the receiving sheet, and the carrier sheets forward in the plane thereof and applying heat and pressure thereto for effecting the transfer of the image from the image bearing sheet to the image receiving sheet. This feeding means comprises a pair of parallel rollers, and means for driving the rollers for feeding the composite therebetween. At least one of the rollers comprises a shaft mounted in said support means and a hollow cylindrical metal drum mounte concentrically on the shaft by thermal insulation means adjacent the ends of the shaft. There is a relatively thin layer of thermal and electrical insulation material on the outside surface of the drum, with a winding of electrical resistance heating wire on this layer. A relatively thin layer of elastomeric material covers the winding.

Electrical leads extend from the ends of the winding to one end of the shaft and then to rotary contacts. Thermal insulation fills the drum between the shaft and the drum. An electrical means for sensing the temperature of the drum is mounted adjacent to the drum's surface, generally at the center of the drum.

The surface of the drum is heated by the winding. Because only the surface of the drum is heated, the winding can quickly respond to temperature changes and quickly restore the surface to the desired operating temperature. Moreover, because only the surface of the drum is heated, there is little wasted energy, and the apparatus operates efficiently. The apparatus has a single heat source and a single heat sensor for each roller, and thus the apparatus is of very simple, inexpensive, and compact construction. The sensor monitors the temperature of the surface of the roller. These and other advantages will be in part apparent and in part pointed out hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGURE 1 is a schematic view of a typical color proof laminating system;

FIGURE 2 is a longitudinal cross-sectional view of a roller for a color proof laminating system constructed according to the principles of this invention;

FIGURE 3 is a schematic view of a temperature control system employed with the color proof laminating system of the present invention;

FIGURE 4 is a side elevation view of a color proof laminating apparatus constructed according to principles of this invention; and FIGURE 5 is a top plan view of a color proof laminating apparatus constructed according to the principles of this invention.

Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A typical color proof laminating system, indicated generally as 20, is represented schematically in Figure 1. A color proof image sheet 22 and an image receiving sheet 24 are superposed and registered together. The image sheet 22 and the receiving sheet 24 are sandwiched between hinged carrier sheets 26 and 28 of a high temperature resistant material, such as polyimide. This composite, indicated generally as 30, is then fed into the nip of top and bottom rollers 32 and 34. The rollers 32 and 34 are heated, preferably to a temperature of between about 120° C and 130° C. The lower roller 34 is preferably mounted for rotation about a stationery location, and the upper roller 32 is urged against the lower roller 34, as by a spring device 36, to apply pressure to the composite passing between the rollers. The color proof image on the image sheet 22 is transferred to the receiving sheet 24 by the heat and pressure of the top roller 32. Upon exiting the heated rollers 32 and 34, the composite 30 is driven by transport rollers 38 and 40 through air knives 42 to cool composite 30. The top carrier sheet 26 and the image sheet 22 are then removed, another image sheet registered with the receiving sheet 24, and the top carrier sheet 26 replaced. The new composite is then run through the color proof laminating system. The process is repeated for each of the standard four color image sheets (magenta, cyan, yellow, and black) to make a complete four-color proof.

An improved roller constructed according to the principles of this invention, indicated generally as 50, is shown in longitudinal cross-section in Figure 2. The improved roller 50 comprises a shaft 52 and a hollow, generally cylindrical drum 54 mounted concentrically on the shaft 52 by thermal insulation means, such as annular spacers 56. The space between the shaft 52 and the drum 54 is filled with thermal insulation filling 70, such as fiberglass. The drum 54 is preferably a 4 inch O.D. steel tube with a wall thickness of about 0.25 inches. The spacers 56 may be made of plastic or some other suitable material. A relatively thin layer 58 of thermal and electrical insulation material covers the outside surface of the drum 54. The layer 58 preferably comprises 0.015 inch fiberglass twine wound around drum 54. A winding 60 of electrical resistance heating wire is disposed on the insulating layer 58. The winding 60 preferably comprises 0.005 inch diameter heating wire, wound with a watt density of 6.6 Watt/in² for a total wattage of about 2200 Watts. A relatively thin layer 62 of elastomeric material, such as silicone rubber, covers the winding 60. This layer is preferably about 0.125 inches thick, and is cured to a hardness of 70A durometer.

Electrical leads 64 and 66 extend from the ends of the winding 52 to one end of the shaft 52. A rotary contact means, such as rotary contact 68, connects the leads 64 and 66 to a source of electrical power while permitting the shaft 52 and drum 54 to turn. The rotary contact 68 may be a Mercotac Model 230 rotary contact (available from Mercotac, Inc., San Diego, California).

An electrical means for sensing the temperature of the drum 54 is mounted adjacent the surface of the drum, preferably at about the center of the drum. The sensing means detects the temperature of the surface of the drum. This means may be, for example, an infrared radiation (IR) sensor 72 spaced approximately 1 inch from the surface of the drum and focused on the surface to detect infrared radiation from the surface to thereby determine the surface temperature. This type of IR sensor can be obtained from Raytek, Inc. of Santa Cruz, California.

A high limit safety sensor may mounted inside the drum contiguous with the inside surface. This sensor may be, for example, a bimetallic device 73. Second electrical leads 74 and 76 extend from the sensor 73 to a rotary contact means, such as a rotary contact 78, at the end of the shaft 52 opposite rotary contact 68. The rotary contact 78 permits the shaft 52 and the. drum 54 to turn, while operatively connecting the sensor 73 via leads 74 and 76 to a normally open relay 79 controlling the main power supply. The rotary contact 78 may be a Mercotac Model 590 rotary contact. Thus, if there is a malfunction in the controller for the apparatus (described below) such that the temperature of the roller increases beyond the set temperature, when the sensor 73 detects that a preselected high limit temperature has been exceeded, power to the apparatus is cut off by relay 79. The temperature sensed by. the sensor 72 is provided to a controller, represented schematically as 80 in Figure 3. The controller 80 selectively powers the winding 60 to maintain the temperature of the surface of the drum 64 at a preselected temperature. As shown in Figure 3, the sensor 72 preferably comprises a lens 82 for focusing infrared radiation from the drum 54 onto a infrared detector or thermopile 84. The signal from the thermopile 84 and a signal from an ambient temperature detector 86, for example a thermocouple, are provided to a pre-amplifier 88. The output of the pre-amplifier 88, which is non-linear, is provided to a signal conditioner 90. The output of the sensor 72, i.e.. the output of the signal conditioner 90, is provided to the controller 80. The controller has comparator means 92 for comparing the signal from the sensor 72 with the temperature set at a control 94. If the temperature sensed by sensor 72 is below the temperature set at control 94, then the comparator means 92 sends a signal to a relay 96 to energize the winding 60 via rotary contact 68 and leads 64 and 66, with a 230V input.

Figures 4 and 5 show an apparatus constructed according to the principles of this invention, and indicated generally as 100, for making color proof laminations. The apparatus 100 comprises a support means such as frame 102. Top and bottom rollers 104 and 106 are mounted parallel with each other in the frame 102. At least the top roller 104, but preferably both top and bottom rollers 104 and 106 are constructed similar to roller 50 described above. Each of the rollers 104 and 106, has a drive sprocket 108 (Figure 5), by which the roller can be driven, as by a motor and a chain. Preferably, the bottom roller 106 is mounted at a fixed elevation for .rotation about a horizontal axis. However, the top roller 104 is preferably mounted so that its horizontal axis of rotation can be moved vertically with respect to the bottom roller 106. This vertical movement permits adjustment of the pressure applied by the rollers to a composite passing between them.

The ends of the roller 104 are preferably journaled in end blocks Ϊ10. Each end block 110 is slidably mounted for vertical movement between two vertical tracks 112 and 114. Each block 110 has a threaded socket 116 for receiving a vertically extending threaded rod 118 journaled in the frame 102. Rotation of the rod 118 in the socket 116 causes the its respective block 110 to move vertically up or down, depending on the direction of rotation. This permits initial alignment of the roller 104 with the roller 106. A spring 120 is mounted on rod 118, with the upper end engaged by the frame, and the lower end engaged by a nut 119 on the rod. The spring 120 applies a biasing force on roller 104, urging it against roller 106. A cam 122 is pivotally mounted at the top of each rod 118, and can be pivoted with handle 124. When the cam 122 is in the vertical position, the rod 118 is pulled up against the force of the spring 120 so the roller 104 is not urged against the roller 106. Moving the handle 124 to the horizontal position shown in Figure 4 causes the cam 122 to pivot, releasing the rod 118 so that the spring 120 urges the roller 104 against roller 106, to apply pressure to composites passing between the rollers.

The apparatus 100 preferably also comprises two pairs of rollers 126 and 128 for driving a composite past air knives 130 to cool the composite. OPERATION

In operation, a composite is assembled by superposing an image-bearing sheet 22 and a receiving sheet 24 in registry, and sandwiching the sheets between carrier sheets 26 and 28. The color proof laminating apparatus is. prepared for use by adjusting the temperature controls for the rolls 104 and 106 to a temperature of between about 120° C and about 130° C. The positions of the rolls are adjusted so that they will apply the appropriate pressure to composites passing between them. Typically this pressure corresponds to about 10 - 15 Kg/cm². The rollers are set in motion, typically to move the composite at a linear speed of about 2-3 feet per minute. The composite 30 is fed into the nip of the rollers (on the. right side as seen in Figure 4) . The rollers 104 and 106 heat and press the image sheet 22 and the receiving sheet 24.

As the composite passes between the rollers 104 and 106, it absorbs heat from the rollers, thus reducing the surface temperature of the rollers. If the temperature of a roller drops below the target temperature set by control 94 for the roller, the controller 80 energizes the winding 60 to restore the roller to the proper temperature. Since the roller is substantially hollow, only the surface must be heated, and thus temperature response is relatively fast.

After the composite 30 has passed through the rollers, they are transported by pairs of rollers 126 and 128 past air knives 130 for cooling the composite. The top carrier sheet is removed, the image-bearing sheet is replaced with a new image bearing sheet, the carrier sheet is replaced, and the new composite is fed through the apparatus. Because of the fast response time, the rollers have returned to the proper operating temperature for good image transferral. In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Claims

AME.NDED CLAIMS

[received by the International Bureau on 18 July 1991 (18.07.91⁾; original claims 7 and 8 amended; new claims 16-20 added; other claims unchanged (7 pages)]

1. Apparatus for producing color proofs by transferring an image in color from a sheet bearing the image to an image receiving sheet with one of said sheets superimposed on the other and with the two sheets sandwiched between two carrier sheets and held in registry one with the other between the carrier sheets, said apparatus comprising supporting means, means mounted on said supporting means for feeding the composite comprising the two carrier sheets and the image bearing and image receiving sheets forward in the plane thereof and applying heat and pressure thereto for effecting the transfer of the image from the image bearing sheet to the image receiving sheet, said means comprising a pair of parallel rollers, and means for driving the rollers for feeding the composite therebetween,

wherein at least one of the rollers comprises:

a shaft;

a hollow cylindrical metal drum mounted concentrically on the shaft by thermal insulation means adjacent the ends of the shaft;

a relatively thin layer of thermal and electrical insulation material on the outside surface of the drum;

a winding of electrical resistance heating wire on said layer;

a relatively thin layer of elastomeric material covering said winding; 18

7. The apparatus according to claim 1 further comprising secondary temperature sensing means inside the drum, contiguous to its inside surface intermediate its ends, second electrical leads for said sensing means extending to an end of the shaft, rotary contact means for said second leads, and means responsive to said secondary temperature sensing means to cut off power to the apparatus if a preselected high-limit temperature is exceeded.

8. Apparatus for producing color proofs by transferring an image in color from a sheet bearing the image to an image receiving sheet with one of said sheets superimposed on the other and with the two sheets sandwiched between two carrier sheets and held in registry one with the other between the carrier sheets, said apparatus comprising supporting means, means mounted on said supporting means for feeding the composite comprising the two carrier sheets and the image bearing and image receiving sheets forward in the plane thereof and applying heat and pressure thereto for effecting the transfer of the image from the image bearing sheet to the image receiving sheet, said means comprising a pair of parallel rollers, and means for driving the rollers for feeding the composite therebetween, wherein at least one of the rollers comprises:

a shaft;

a relatively thin layer of thermal and electrical insulation material on the outside surface of the drum, 17

electrical leads for said winding extending from the ends of said winding to an end of the shaft;

rotary contact means for said electrical leads; and

a thermal insulation filling in the drum between the shaft and the drum;

and wherein the apparatus further comprises means for sensing the temperature of the drum.

2. The apparatus according to claim 1 wherein the rollers are similarly constructed.

3. The apparatus according to claim 1 further comprising control means, responsive to the temperature sensing means, for providing power to the winding to maintain the temperature at a preselected target temperature.

4. The apparatus according to claim 3 wherein the control means comprises means for preselecting the target temperature.

5. The apparatus according to claim 1 wherein the temperature sensing means comprises an infrared detector mounted adjacent the drum.

6. The apparatus according to claim 5 wherein the infrared sensor is spaced from the surface of the drum, generally intermediate the ends. a winding of electrical resistance heating wire on said layer;

a relatively thin layer of elastomeric material covering said winding;

rotary contact means for said electrical leads;

a thermal insulation filling in the drum between the shaft and the drum;

and further comprising electrical means for sensing the temperature of the surface of the drum; and

control means, responsive to the temperature sensing means, for providing power to the winding to maintain the temperature at a preselected target temperature suitable to effect transfer of the image from said image-bearing sheet to said image-receiving sheet.

9. The apparatus according to claim 8 wherein the temperature sensing means comprises an infrared detector.

10. The apparatus according to claim 8 wherein the rollers are similarly constructed, and wherein there is a separate means for sensing the temperature of the surface of each drum.

11. The apparatus according to claim 10 wherein there is a separate controller for each roller. 12. The apparatus according to claim 10 wherein each temperature sensing means comprises an infrared detector.

13. The apparatus according to claim 12 wherein the control means comprises means for preselecting the target temperature.

14. The apparatus according to claim 8 wherein the control means comprises means for preselecting the target temperature.

15. The apparatus according to claim 8 further comprising secondary temperature sensing means inside the drum, contiguous to its inside surface intermediate its ends, and means responsive to the secondary temperature sensing means to cut off power to the apparatus if a preselected temperature is exceeded.

16. A method of producing a color proof by transferring an image in color from an image-bearing sheet bearing the image to an image-receiving sheet with one of the sheets superposed on the other and with the two sheets sandwiched between two carrier sheets and held in registry one with the other between the carrier sheets, said method comprising the following steps:

placing said image-bearing sheet and image-receiving sheet in superposed relation;

placing the superposed sheets with the sheets in registry between two carrier sheets to form a composite; feeding the composite forward in the plane of the composite between a pair of rollers thereby to apply heat and pressure to the composite for effecting transfer of the image from the image-bearing sheet to the image-receiving sheet;

at least one of said rollers comprising a shaft, a hollow cylindrical metal drum mounted concentrically on the shaft by thermal insulation means adjacent the ends of the shaft, a relatively thin layer of thermal and electrical insulation material on the outside surface of the drum, a winding of electrical resistance heating wire on said layer, a relatively thin layer of elastomeric material covering said winding, electrical leads for said winding extending from the ends of the winding to an end of the shaft, and rotary contact means for said electrical leads,

sensing the temperature of the outer surface of the drum to determine if said temperature is below a preselected target temperature, and

if the temperature of the outer surface of the drum is below said preselected target temperature, energizing said winding of said heating wire to heat the drum to said preselected target temperature suitable to effect transfer of said image from said image-bearing sheet to said image-receiving sheet as the composite is fed between said rollers.

17. A method as set forth in claim 16 wherein said temperature sensing is effected at a location spaced from the outer surface of the drum. 18. A method as set forth in claim 16 further comprising de-energizing said winding of said heating wire if the temperature of the outer surface of the drum exceeds a high limit temperature greater than said preselected target temperature.

19. A method as set forth in claim 16 wherein said preselected target temperature is in the range of about 120-130 degrees Celsius.

20. A method as set forth in claim 16 wherein said composite is fed forward between said rollers at a speed of about 2-3 feet per minute, and wherein the rollers apply a pressure of about 10-15 Kg/cm2 to the composite.