US 3632984 A
Apparatus for development of heat-sensitive images on sheets embodying a hollow, thin-walled, heat-conducting, rotatable cylinder or drum and a heat-resistant, perforated, flexible stationary belt wrapped about the cylindrical surface of said cylinder or drum with its bight portion in light, sliding contact therewith.
Claims available in
Description (OCR text may contain errors)
United States Patent Inventor Philip J. Brownscombe Mlllington, NJ.
Sept. 15, 1969 Jan. 4, 1972 Canadian Thermo-Images Ltd.
Appl. No. Filed Patented Assignee APPARATUS FOR REPRODUCTION MACHINES 6 Claims, 4 Drawing Figs.
US. Cl. 219/469,
219/388 Int. Cl 1105b 1/02 Field 01 Search 219/216,
9 v V References Cited UNITED STATES PATENTS 2,588,966 3/1952 Dale .L 219/469 3,012,141 12/1961 Thomiszer 219/216 Primary Examiner-Remard A. Gilheany Assistant Examiner-F. E. Bell Attorney-Johnston, Root, OKeeife, Keil, Thompson &
Shurtleff ABSTRACT: Apparatus for development of heat-sensitive images on sheets embodying a hollow, thin-walled, heat-conducting, rotatable cylinder or drum and a heat-resistant, perforated, flexible stationary belt wrapped about the cylindrical surface of said cylinder or drum with its bight portion in light, sliding contact therewith.
APPARATUS FOR REPRODUCTION MACHINES There are several classes of reproduction machines for reproducing an image on a copy sheet. The type of reproduction with which the subject invention is concerned is the class of machines wherein the image on the copy sheet is developed by heat. One well-known type of such machines are those using the diazo-type process. In this process, the copy sheet is coated with a material including diazo compounds which will decompose, when exposure action of ultraviolet light, into a form in which they are and thereafter remain colorless. The portions of the sheet which are not exposed to ultraviolet light retain the diazo compound which, upon interaction with couplers also contained in the coating, produce on the copy sheet intense azoic dyes which are insensitive to light and hence capable of forming permanent visible images. As a consequence, diazo compounds together with coupling substances may be dissolved in water which has been weakly acidified as by means of citric, tartaric, or boric acids; and auxiliary chemical compounds may also be dissolved in he water, along with the acidic, diazo and coupling components, to yield a light-sensitive coating solution which may then be applied upon a sheet of material, such as paper, after which the coated sheet is dried to remove only the water component. When such a sheet is exposed to the action of ultraviolet light, through a layer of material that is transparent to such light, and which carries opaque images thereon, the diazo compound in the coating may be destroyed except where screened by the opaque images of the original to be copied. Thereafter, by heating the exposed print-forming material, in order to produce ammonia gas therein and thus develop permanent dye images therein, the permanent dye in the coating forms an exact reproduction on the copy sheet of the light opaque image-forming portions of the original. The present invention is primarily concerned with apparatus useful in the heat development of images on a copy sheet after the latter has been exposed in the presence of the master sheet.
BRIEF DESCRIPTION OF THE INVENTION The subject invention relates to improvements in apparatus for the heat development of copy sheets in reproduction machines. It constitutes an improvement of the apparatus described in Thomiszer U.S. Pat. No. 3,012,l4l, issued Dec. 5, 1961. The basic components of the present invention are a rotatable, hollow, thin-walled, metal cylinder or drum and a stationary, perforated web or band wrapped about a portion of the cylindrical surface of the cylinder or drum with a bight portion in light, sliding contact with the rotating cylinder or drum. The thin cylindrical wall is heated by heating means preferably within the hollow interior of the cylinder or drum to a temperature sufficient to cause the image on the copy sheet to develop as the sheet passes about the cylindrical surface between the latter and the stationary web or band.
The stationary web or band is made of a heat-resistant material and has a drum-contacting surface which provides low frictional drag on the copy sheet as it is conveyed about the drum. One of the improvements of the subject invention is to use as such web or band sheet material containing a large number of small perforations which allow the escape of moisture and/or gases driven from the copy sheet as the latter progresses around the drum and is heated thereby. Another improvement of the subject invention is to utilize as the material from which said web or band is made a woven fiberglass material coated on at least its drum-contacting surface with Teflon, the latter being polytetrafluoroethylene. The perforations in said web or band are in the order of 0.03 to 0.1 inch in diameter with relatively close spacing therebetween in the order of 100 to 200 perforations per square inch. The perforations are preferably arranged so that there is little or no imperforate longitudinal lines or spaces between perforations, i.e., in the direction of travel of the copy sheet across the web or band. The invention further embodies improvements in the hardware attached to the perforated web or band for holding the latter in light, sliding contact with the cylindrical surface of the cylinder or drum.
DESCRIPTION OF THE DRAWINGS A preferred embodiment of the invention is illustrated in the drawings wherein:
FIG. 1 is a fragmentary view in cross section of the heat development section of a reproduction machine;
FIG. 2 is a fragmentary plan view thereof as seen from a eutaway on section line 22;
FlG. 3 is a fragmentary, perspective view of a perforated web or band and its associated hardware with the cylinder or drum shown in phantom; and
FIG. 4 is a fragmentary, enlarged, perspective view of the perforated web or band.
DESCRIPTION OF THE PREFERRED EMBODlMENT Referring to the drawings, the reproduction machine includes an image-developing section 11 comprising as the main component thereof a cylinder or drum 12. The cylinder or drum 12 is rotatably driven in a counterclockwise direction as viewed in FIG. 1 by a chain-driven sprocket 13. The hollow cylinder or drum 12 may be rotatably supported in the machine in any suitable manner, e.g., by peripherally spaced, grooved, idler wheels 15 and 15 coacting with the flanges 14 on each end of the drum.
The cylindrical wall 16 of the cylinder or drum 12 is a thin, heat-conductive wall, e.g., a cylindrical, thin metal wall. Within the hollow interior of the cylinder or drum 12 there is a heating means 17 for substantially evenly heating the cylindrical wall of the drum or cylinder, eg, a tube extending coaxially through the hollow cylinder or drum 12 and emitting radiant heat.
The second essential element of the invention is the perforated stationary belt or band 20 which is wrapped about slightly more than half the cylindrical surface of the cylinder or drum to provide a bight portion in light, sliding contact therewith. One end 21 of the perforated belt or band is rigidly attached by bracket 22 to a wall 23 of the machine. The end 21 is gripped between a leg 24 of the bracket 22 and the bar 25 held together by a plurality of screws26. The leg 24 has on its outer face a plurality of L-shaped guide pins 27, the leg 28 of which is rigidly attached to the outer face of the leg 24 by welding or the like. The outwardly extending leg 29 of each L- pin extends diagonally upwardly from the end 21 of the belt or band with the upper ends thereof resting in longitudinally spaced, annular grooves 30 in the roller 31 which is rotatably driven by the belt 32.
The opposite end 35 of the web or band is held between a pair of bars 36 and 37 which are riveted together with the end 35 gripped therebetween. These bars 36 and 37 contain two or more longitudinally spaced apertures 38.
The belt or band 20 is wrapped about a roller or round bar 40 having an axle or shaft 41 at each end mounted in respective slots 42 of the machine frame. The light, frictional contact between the band or belt 20 and the cylinder or drum 12 is maintained by two or more springs 43, each having one end 44 extending through the apertures 38 and the outer end 45 extending through apertures in a bracket mounting bar 46 rigidly attached to the machine frame.
Exposed copy paper is fed to the developing section 11 by feeding it into the nip between a pair of feed rollers 31 and 51 and is discharged between the nip of rollers and 51. The shaft supports both rollers are preferably mounted in a diagonal slot 52 in frame members or frame plates of the machine.
After passingthrough the nip of the rollers 31 and 51, and the leading edge of the .copy paper is guided between the tingers 27 and the guide plate 57 through the paper feed passage 58 to the nip 56. When the copy paper reaches the point of departure between the belt or band 20 and the cylindrical wall 16, it is guided by the guide plate 53 and a thin stripper plate 54 mounted on plate 53 between the rotating drum or cylinder 12 and the stationary perforated web or band to the nip of the roller 50 and the roller 51. The latter rollers pick up the paper and convey it out of the machine. The tension in the web or band 20 is sufficient to cause the leading edge of the paper to be frictionally engaged by the outer surface of the cylindrical wall 16. The paper is conveyed about the drum or cylinder 12 between the latter and the bight portion of the web or band 20 in light contact therewith. In the course of such travel, the heated, heat-conductive wall 16 sufficiently heats the copy paper to cause the permanent images to be formed thereon.
The belt or band 20 contains a large number of perforations 60 (FIG. 4). These perforations permit the escape of moisture and/or gas, particularly the former. The moisture develops when the copy paper is heated by the cylinder or drum 12 as it passes between the latter and belt or band 20. if the belt or band 20 is imperforate or substantially imperforate, the trapped moisture causes the copy sheet to wrinkle. As will be seen in Flg. 4, the perforations 60 are of small size and are closely spaced. They preferably have a dimension of about 0.03 to 0.1 inch and are sufficiently closely spaced to provide a density of about 100 to 200 perforations per square inch. The material from which the belt or band is made is a heat resistant material. A preferred material is woven fiberglass coated on one or both sides with polytetrafluoroethylene.
The perforations 60 may be arranged in any pattern which allows the moisture to escape through the perforations. One preferred arrangement is shown in Flg. 4 wherein the perforations are arranged in traversely staggered, longitudinally aligned rows with an overlapping between edges of perforations in respective longitudinal rows or with only a narrow spacing between edges of projections in respective longitudinal rows, longitudinal as used here being the direction of copy paper travel across the web or band, which direction of travel is indicated in Flg. 4 by the arrow 61. These perforations extend over at least the portion of said band forming said bight and may extend over the entire band.
It is thought that the invention and its numerous attendant advantages will be fully understood from the foregoing description, and it is obvious that numerous changes may be made in the form, construction and arrangement of the several parts without departing from the spirit or scope of the invention, or sacrificing any of its attendant advantages, the form herein disclosed being a preferred embodiment for the purpose ofillustrating the invention.
The invention is hereby claimed as follows:
1. Apparatus for the development of heat-sensitive copy sheets comprising a hollow, thin-walled, rotatably cylinder nested in the bight of a flexible band wrapped about a portion of the surface of said cylinder, said band having a plurality of small perforations of a predetermined pattern extending over at least the portion of said band forming said bight; means for holding said band in a fixed position as said cylinder is rotated; and means for heating the wall of said cylinder.
2. Apparatus as in claim 1 wherein said perforations have respective diameters in the range of 0.03 to 0.1 inch and are sufficiently closely spaced to provide to 200 perforations per square inch.
3. Apparatus as in claim 2 wherein said band is made of woven fiberglass coated with polytetrafluoroethylene.
4. Apparatus as in claim 1, and spring means attached to one end of said band to maintain a light tension in said band.
5. Apparatus as in claim 4 wherein said one end ofsaid band has a rigid member extending thereacross, and said spring means being attached to said rigid member.
6. Apparatus as in claim 5 wherein the opposite end of said band is fixedly attached to a rigid bracket extending thereacross and a plurality of thin guide fingers extending outwardly from said bracket.