US3683807A

US3683807A - Duplicating device and method utilizing heat building in an enclosed stack of sheets

Info

Publication number: US3683807A
Application number: US13359A
Authority: US
Inventors: Glenn R Anderson
Original assignee: Minnesota Mining and Manufacturing Co
Current assignee: 3M Co
Priority date: 1970-02-24
Filing date: 1970-02-24
Publication date: 1972-08-15
Anticipated expiration: 1989-08-15

Abstract

A flat hand-operated heating platen, to which is temporarily attached to an image master, produces a number of identical copies by a rhythmic ''''rubber stamp'''' dry duplicating process wherein partial depletion of reactants in the master image is compensated for by automatic increase in heat in the stack of receptor sheets.

Description

United States Patent Anderson [54] DUPLICATING DEVICE AND METHOD Duckett ..101/l34.5

2,681,005 6/l954 UTILIZING HEAT BUILDING IN AN 2,844,094 7/ 1958 Gruver 101/ 134.5 ENCLOSED STACK OF SHEETS 2,449,l 1 1 9/ 1948 Foster ..101/9 X 2 543 035 2/1951 Marston et al ..101/27 X 72 I t l l 1 351;" R Andem" Mmneapws 1,740,285 12/1929 Cornell 101 /27 x 1,952,629 3/1934 Newgard ..101/131 1 Asslgneer M so a Mining and M u c ur- 2,963,963 12/1960 Grasso ..101/287 X g'C mp y, S Paul, Mmn. 1,357,230 11/1920 Garner 101/27 22 Fi Feb 24 1970 1,993,699 3/1935 Storck l0l/l3l [21] PP N05 13,359 Primary Examiner-William B. Penn Assistant EraminerE. M. Coven 52 US. Cl. ..101/426, 101 /1345, 101/470, Attorney-Kinney, Alexander, 9" Steldt & Delahum 250/65 T, 346/76 51] 1111.0 ..B411 11/02, B411 11/06 ABSTRACT [58] held of y 1345 A flat hand-operated heating platen, to which is tem- 10 porarily attached to an image master, produces a 250/651" 346/76 number of identical copies by a rhythmic rubber stamp" dry duplicating process wherein partial deple- [56] References cued tion of reactants in the master image is compensated UNITED STATES PATENTS for by automatic increase in heat in the stack of recept 11 t8. 1,652,274 12/1927 Glass ..101/21 ms 66 3,170,395 2/ 1965 Gundlach et a1. ..101/470 2 Claims, 4 Drawing Figures 1| |I1 z4 I Z l I l 111 Z DUPLICATING DEVICE AND METHOD UTILIZING HEAT BUILDING IN AN ENCLOSED STACK F SHEETS This invention relates to dry duplicating processes and apparatus and, in particular, to a duplicating process based upon a thermally activated colorproducing chemical reaction, and to simplified handoperated apparatus for use therein.

In the dry duplicating process described in Gundlach et al., US. Pat. No. 3,170,395 a master is prepared during the making of the imaged original. A volatilizable chemical reactant is transferred to the master from a separate transfer sheet or carbon paper, as a mirror image of the original. A receptor sheet having a coreactant material thereupon is next placed on an aluminum block or the like, the master sheet is placed on top of and in alignment with the receptor sheet, and heat is applied by means of a heated roller to transfer some of the volatilizable reactant from the master to the receptor in the image areas thereby forming a right reading imaged receptor. After imaging, the receptor sheet is removed and replaced by a second sheet and the process repeated. The aluminum block used as a support for the individual receptor sheets serves as a heat sink to draw the heat away from the support surface and maintain the sheets at a uniform temperature.

While this dry duplicating process has many advantages, such as process neatness and image clarity when compared with spirit or stencil duplicating, it has heretofore suffered from a relatively serious disadvantage. While the first few copies made by dry duplicating are intense and sharp with little of the bleeding associated with a wet duplicating operation, subsequent copies are found to have images of weaker intensity and clarity due to the continually diminishing amounts of volatilizable reactant in the master.

The dry duplicating process of this invention rapidly produces an extended series of imaged receptor sheets of equal and exceptional image quality by manipulative steps analogous to rubber stamping. The several receptor sheets are imaged at a constant rate. No special support surface is required and continual manipulation of the master sheet is avoided.

The apparatus of this invention comprises a platen of the same rectangular configuration as the receptor sheet. The platen is provided with controlled heating means for uniformly heating and maintaining a uniform elevated temperature at the platen surface. and handle means for manual manipulation. The platen during use has a master sheet affixed thereto and rests upon the topmost sheet of the stack of receptor sheets as the latter is retained within the original container.

A presently preferred device for carrying out this process is illustrated in the drawings, wherein;

FIG. 1 is a perspective view of the platen device with portions broken away,

FIG. 2 is a side elevation with portions broken away,

FIG. 3 is an end elevation showing the device in use in conjunction with a stack of receptor sheets maintained in alignment within the storage tray shown partly in cross section, and

FIG. 4 is a detail plan view of the heating system components.

The platen device will be seen to comprise a heatconductive platen supported by a cover 18 and heated from an electric resistance heating element 36.

A cord 38 is electrically connected through a thermostat 20 and wires 30 to bus bars 14 which are affixed to heating element 36 by an electrically conductive adhesive, e.g., one containing conductive particles in a resinous binder. (A presently preferred heating element consists of a sheet of carbonized fiber of the type described in Filreis-Franer U.S. Pat. No. 3,367,851.) The bus bar and heater are separated from the platen 10 by a heat-conductive, electrically insulative layer 12.

Heat insulation 16, for example an open matt of fiberglass, covers the platen 10 and surrounds the thermostat 20. Attached to the platen I0 is cover 18 to which a handle 24 supported by front handle support 26 and rear handle support 27 is attached by anchoring means 28. Partially inset within the front handle support 26 is a control dial 22 for adjusting the thermostat 20, the dial being clearly visible through aperture 23 in the handle 24.

FIG. 3 illustrates the device in use. A master sheet 42 is removably attached to the platen 10, e.g., by spot application of a thermoplastic adhesive 40. The device with the attached master rests, during imaging, on a stack of receptor sheets 34 of the same rectangular configuration as the platen 10. The sheets are kept in alignment within an open-topped cardboard tray 32.

The device described above provides uniform heat over the entire surface of the receptor sheets and, by resting on the entire stack of receptor sheets as each is being imaged, causes a gradual increase in temperature at the uppermost sheet as the copying process proceeds. I

The process of this invention provides for the I production of an extended series of imaged receptor sheets having identical clear, sharp, distinct images by simple rapid manipulative steps analogous to rubber stamping. This is made possible by the increase in the amount of heat available for each sequential imaging reaction which serves to counterbalance the steadily diminishing amount of volatile reactant available on the master for each such reaction. As a result of this heat build-up, each sheet is imaged in the same short length of time.

The process of this invention utilizes a uniformly heatable platen of the same rectangular configuration as the receptor sheets, said platen maintained at a constant temperature throughout the process. The platen has a master with volatilizable material disposed in a mirror image of the original which is temporarily attached to its face by dabs of a thermoplastic adhesive preferably at each of the corners or mechanical means such as a spring clip. The heated platen is then placed atop a stacked, aligned series of receptor sheets with the alignment preferably maintained by a heat insulative material, such as an open-topped cardboard box and the first receptor sheet is imaged.

As the first sheet is imaged, the heat supplied by the platen permeates the stack. After imaging the platen is raised, the imaged sheet removed, the platen replaced,

and the second sheet is imaged. In this manner, as each sheet is imaged, heat is built up on subsequent sheets in the stack so that each subsequently imaged sheet is hotter than the one imaged immediately preceding it.

The steadily increasing supply of heat for subsequent imaging reactions directly counterbalances the steadily diminishing supply of available volatilizable reactant for each such reaction. As a result as many as 20 sheets of excellent and equal image quality may be prepared using the same length of time for each imaging and without changing the temperature setting of the device. Over 300 sheets an hour may be imaged by utilizing the teachings of this invention.

The time required for imaging is dependent to some extent on the type of paper used for the master and receptor sheets, platen temperature, and perhaps other factors. Of these factors, platen temperature is the more important. The components of the device are selected to provide and maintain a platen temperature at any desired point between about 225 F. and 310 F. Any point within this temperature span will produce satisfactory images with an extremely broad spectrum of reactant materials with minimal effect on the paper.

For systems employing dithiooxamides (hereinafter DTO) and nickel salts or equivalent reactants, a temperature between about 260280 F. is especially preferred. These temperatures provide rapid duplicating with efficient utilization of materials. Only 5 seconds is needed to complete the imaging of a DTO- nickel salt reactant system or its equivalent when the platen is maintained at a temperature of 270 F. Although temperatures as low as 225 F. may be used, imaging takes somewhat longer, i.e., seconds in the case of the DTO-nickel salt system.

Examples of the presently preferred embodiments of the process of this invention follow. These examples are merely illustrative of the process of this invention.

EXAMPLE 1 Ingredient Parts by Weight N ,Ndibenzyldithiooxamide acetone Candellila Wax Dicyclohexylphthalate Triphenylphosphate Ethylcellulose Paricin 8 (Paricin 8 is a waxy lubricant plasticizer made by Baker Castor Oil Co.)

Receptor sheets were made from paper having a base weight of 38.5 lbs/3,300 sq. ft. The sheets were roll coated with the following fluid mixture to provide a coating weight of 3.85 lbs/3,300 sq. ft.

Ingredient Parts by Weight Starch (gelatiniaed) 24.1 Ni rosinate 19.7 Aluminum oxide (paper grade) 42.0 CaCO (pigment) 6.0 Thiourea 6.1 Dispersants 2.9

A master was prepared by typing on a sheet of standard bond paper having a weight of 49.8 lbs/3,300 sq. ft. in contact with a donor sheet. The coating on the donor adhered to the back side of the original which back side was then used as the donor surface of the master. The receptor sheets were stacked in an open box which was of the same general rectangular configuration as the sheets, but slightly larger. The master sheet was sp0t-adhered't0 the platen, preheated to a temperature of 270 F, with a United Shoe Co. glue stick thermoplastic adhesive sparingly applied at the corner areas of the heated platen. The heated platen, with the attached master sheet, was placed against the topmost receptor sheet, allowed to rest thereon for five seconds, and removed. The imaged top sheet was removed, and the process repeated until a total of 20 sheets had been imaged. During this period the temperature of the remaining stack of receptor sheets gradually increased. Uniformly sharp, clear and distinct purple images were produced on all 20 of the copy sheets.

EXAMPLE 2 Example 1 was repeated in all particulars using the identical components except that the platen temperature was 225 F. Imaging time for each sheet was 15 seconds and each of the 20 sheets imaged had clear, sharp, distinct and substantially identical images.

EXAMPLE 3 The N,N'dibenzyl DTO used in the first two examples on the donor paper was replaced with an equal amount of dimethyl-glyoxime. Otherwise, the donor and receptor papers were coated using identical form ulas. The two masters were prepared as in the preceding examples and two lots of receptor paper were imaged as in the preceding examples. The first lot was imaged for 5 seconds with the platen heated to 270 F. and the second lot was imaged for 15 seconds with the platen at a temperature of 225 F. The images produced in each lot were of the same quality as the images of the preceding examples, but were red in color.

These examples illustrate the presently preferred method of applicants invention. It should be noted that aligning means are preferred to maintain the alignment of the stack. A cardboard container is the preferred aligning means because it is a heat insulator to prevent the escape of heat from the remaining receptor sheets. The cardboard container is also cheap and may be provided as the container for the sheets thereby eliminating the need for separate aligning means. An alternative to an open-topped aligning container for the sheets is to extend the sides of the cover of the device to serve as aligning means and to use a spring loaded support or other means to urge the diminishing stack of receptor sheets against the platen. The advantage to the latter embodiment is that the surface of the platen would be less likely to come in contact with the operator although it would add to the cost of the device. The extended sides may also be vertically moveable to protect the operator and eliminate the need for urging means at the bottom of the stack. Other variants for practicing the teachings of this invention will suggest themselves to those skilled in the art in view of the foregoing description.

What is claimed is as follows:

l. A duplicating process for utilizing the reaction between a volatilizable chemical disposed in an image configuration on a master sheet and a co-reactive chemical on a series of paper receptor sheets, said process comprising temporarily attaching said'master sheet to a manually movable device having a sheet-supporting platen maintained at a uniform elevated temperature over the entire platen surface, then placing said device upon the topmost sheet of a stack of aligned receptor sheets, supported within a heat-retaining enclosure, for a time and with said platen at a temperature sufficient to cause a progressive increase in temperature in the remaining sheets of said stack and to image the topmost receptor sheet by heat volatilization thereto of a portion ofsaid chemical depleted from said master, removing said device and said topmost sheet and promptly replacing said device and substantially exactly repeating the process with subsequent topmost receptor sheets at a substantially constant rate selected to permit the temperature in the remaining stack to increase proportionately with depletion of said chemical so that substantially the same time may be consumed for imaging each sheet with an equal image.

2. Apparatus for utilizing a master sheet containing a volatilizable reactant in an image configuration in the substantially identical imaging of a series of rectangular co-reactant paper receptor sheets, said apparatus ineluding, in combination, an open-topped rectangular heat-retaining box-like enclosure containing a stack of said receptor sheets and a manually movable device fitting within said enclosure and upon the uppermost sheet of said stack of sheets and comprising a flat heatconductive master-supporting platen, means for establishing and maintaining a uniform elevated temperature over the entire platen surface, means for removably attaching a said master sheet to said surface, and handle means for manual manipulation of .said device in lifting it from said enclosure to permit removal of an imaged uppermost sheet from said stack and then replacing it within said enclosure and upon the next uppermost sheet of said stack, the said combination permitting progressive increase in temperature at said stack, during the preparation at substantially constant rate of a series of copies from a single master, as the supply of volatilizable reactant in said master becomes progressively depleted.

Claims

1. A duplicating process for utilizing the reaction between a volatilizable chemical disposed in an image configuration on a master sheet and a co-reactive chemical on a series of paper receptor sheets, said process comprising temporarily attaching said master sheet to a manually movable device having a sheetsupporting platen maintained at a uniform elevated temperature over the entire platen surface, then placing said device upon the topmost sheet of a stack of aligned receptor sheets, supported within a heat-retaining enclosure, for a time and with said platen at a temperature sufficient to cause a progressive increase in temperature in the remaining sheets of said stack and to image the topmost receptor sheet by heat volatilization thereto of a portion of said chemical depleted from said master, removing said device and said topmost sheet and promptly replacing said device and substantially exactly repeating the process with subsequent topmost receptor sheets at a substantially constant rate selected to permit the temperature in the remaining stack to increase proportionately with depletion of said chemical so that substantially the same time may be consumed for imaging each sheet with an equal image.

2. Apparatus for utilizing a master sheet containing a volatilizable reactant in an image configuration in the substantially identical imaging of a series of rectangular co-reactant paper receptor sheets, said apparatus including, in combination, an open-topped rectangular heat-retaining box-like enclosure containing a stack of said receptor sheets and a manually movable device fitting within said enclosure and upon the uppermost sheet of said stack of sheets and comprising a flat heat-conductive master-supporting platen, means for establishing and mAintaining a uniform elevated temperature over the entire platen surface, means for removably attaching a said master sheet to said surface, and handle means for manual manipulation of said device in lifting it from said enclosure to permit removal of an imaged uppermost sheet from said stack and then replacing it within said enclosure and upon the next uppermost sheet of said stack, the said combination permitting progressive increase in temperature at said stack, during the preparation at substantially constant rate of a series of copies from a single master, as the supply of volatilizable reactant in said master becomes progressively depleted.