US3655970A

US3655970A - Portable thermographic duplicator

Info

Publication number: US3655970A
Application number: US48050A
Authority: US
Inventors: Warren F Betzler
Original assignee: Individual
Current assignee: Individual
Priority date: 1970-06-22
Filing date: 1970-06-22
Publication date: 1972-04-11
Anticipated expiration: 1989-04-11

Abstract

A portable, manually operable, miniaturized copier operable by being manually rolled across the surface of sensitized paper under which the graphic material to be copied is positioned. An electric heat lamp disposed in the copier and movable therewith, control means for said electric heat lamp, including a safety switch, and rotatable means in said copier and combined with said heat lamp exerting a degree of pressure on the work in the operation of the copier or duplicator.

Description

United States Patent 151 3,655,970 [451 Apr.1l,1972

Betzler [541 PORTABLE THERMOGRAPHIC DUPLICATOR [72] Inventor: Warren F. Betzler, PO. Box 749,-Elmira,

NY. 14902 a [22] Filed: June 22,1970 [21] Appl. No.: 48,050

[52] U.S. Cl .J ..250/65 T, 219/216, 355/84, 355/110 [51] lnt.Cl. ..G0ln 21/34 [58] Field of Search ..250/65 T; 219/216; 355/78, 355/84, 104, 110

[56] References Cited UNITED STATES PATENTS 3,219,794 11/1965 2,726,317 12/1955 2,988,979 6/1961 2,292,668 8/1942 FOREIGN PATENTS OR APPLICATIONS 937,331 1/1956 Germany ..355/84 Primary Examiner-William F. Lindquist Attorney-Peck & Peck 5 7] ABSTRACT 4 Claims, 9 Drawing Figures PATENTEDAPR H I972 3,655,970

SHEET 1 []F 4 83 INVENTOR Warren E Be/z/er ATTORNEY PATENTED APR 1 1 I972 SHEET 2 OF 4 IN VENTOR ATTORNEY PATENTEDAPR 1 1 m2 655.970

sum 3 [1F 4 INVENTOR Warren E Berz/er PATENTEDAFR 11 I972 SHEET h []F 4 INVENTOR Warren F Befz/e/ q eJa w hal PORTABLE THERMOGRAPHIC DUPLICATOR This invention relates broadly to the art of copiers, or duplicators, and in its more specific aspects it relates to such duplicators for the reproduction of graphic matter which are miniaturized, portable and manually operable; and the nature and objects of the invention will be readily recognized and understood by those skilled in the arts to which it relates in the light of the following explanation and detailed description of the accompanying drawings illustrating what I at present believe to be preferred embodiments or mechanical expressions of my invention from among various other forms, arrangements, combinations and constructions, of which the invention is capable within the spirit and scope thereof.

The duplicator of this invention is preferably, though not necessarily of the thermographic type involving the application heat energy to the graphic material to be reproduced. The thermographic sensitive copy paper is positioned over the work to be reproduced, and between said work and the heat generating means. The broad method which is practiced in using my invention for the reproduction of graphic material comprises rolling the duplicator over the sheet of sensitive material and the sheet having the graphics thereon so that the heat generated in the duplicator is applied to said papers relatively briefly. It will be understood that the clarity or sharpness of the reproduction is dependent, in part, on the speed of the device in its passage over the work and the sensitive paper.

In the development of this duplicator it has been one of my prime objects to produce a device of this character which is of small size, such a size that it may be conveniently carried or stored in a conventional attache case. The apparatus may be used on a conventional office desk, table, or the like and is provided with relatively few working parts so that the expense of maintenance is reduced to a minimum.

The apparatus has been designed as a dry duplicating apparatus, and I may use a 1,350 watt Quartz iodine infra-red lamp for producing the necessary heat so that the reproducing action will take place when the device is operated.

In the assembly of my duplicator I have provided an ingenious combination of a heat lamp and means which functions to transmit heat therefrom at a given rate, and also functions to contact and abut the work, and sensitive sheet during the operation to maintain the work and sensitive sheet flat or flush so that the heat source is projected thereon at a precise and desired angle. It is highly desirable that the aforementioned heat transmitting means be so formed and operable that a cooling effect is produced thereon. It will be appreciated that due to the relative close positioning of this means with respect to the heat lamp a cooling arrangement is salutary.

One of the many advantages of my apparatus resides in its ability to function not solely as a duplicator or a copier, but also it may function in the production of dry mounting and photography so that the necessity for the usual expensive equipment necessary for this purpose is eliminated. It is of further significance that this duplicator may also be used for laminating, where the reproduced surface is preserved by laminating a plastic sheet thereon. This duplicator or copier may also be used in making transparencies.

Since substantial heat is generated when the heat lamp, which is combined in theduplicator, is energized, it is thus desirable to only energize the heat lamp during the actual operation of the apparatus, and for this reason I have devised novel safety electrical switching means, whereby the chance of inadvertently leaving the heat lamp energized when the device is not in operation is substantially eliminated.

All of the duplicators of which I am aware, and which are now on the market, are relatively costly, are not portable and are of substantial size and weight. For these, and other reasons, they may not be moved or carried about with facility and therefore are not immediately and conveniently available for use. The duplicator of my invention is endowed with many highly favorable characteristics, among which are portability, small size, inexpensive to purchase and to operate, light in weight and conveniently accessible at all times.

One of the significant characteristics of this development resides in means combined in the device which prevent rocking movement of the device in its rolling operation over the assembly pack including the sensitive sheet and the sheet involving the graphic material to be copied. This is essential, and results in clarity of reproduction as heat reflecting means is at all times properly positioned relative to the work and the heat sensitive sheet to thereby produce an in-focus arrangement at all times.

In a modified form of my invention I have provided an ingenious mounting arrangement for the duplicator whereby it is movably suspended over the work to be copied.

With the foregoing general objects, features and results in view, as well as certain others which will be apparent from the following explanation, the invention consists in certain novel features in design, construction, mounting and combination of elements, as will be more fully and particularly referred to and specified hereinafter.

Referring to the accompanying drawings:

FIG. 1 is a perspective view of my duplicator in operative position related to the assembly pack which includes the graphic subject matter and the heat sensitive sheet upon which the reproduction is to be made.

FIG. 2 is a view taken on line 2-2 of FIG. 3.

FIG. 3 is a view taken on line 3-3 of FIG. 1.

FIG. 4 is a perspective view of the duplicator, with the easing therefore removed.

FIG. 5 is an exploded view with parts thereof broken away disclosing the mounting and arrangement of the various elements, including the heat lamp, at one end of the duplicator.

FIG. 6 is a diagrammatic view of an electric circuit which may be used with the duplicator.

FIG. 7 is a view in perspective of a modified form of my invention.

FIG. 8 is a view in vertical section at one end of the duplicator illustrating the means for mounting the duplicator on the transverse rods.

FIG. 9 is a view in vertical section through a side of the duplicator.

In FIG. 1 of the drawings I have illustrated my miniaturized portable and manually operable duplicator in operative position on a pack assembly, including the work to be reproduced and the heat sensitive sheet of paper upon which the reproduction of the graphic material on the work is to be produced, and I have used the numeral 1 to designate, in its entirety, the duplicator or copier, and the numeral 3 to indicate, in its entirety, the pack assembly including the work embodying the graphic matter and the heat sensitive sheet upon which the reproduction is to be made. The duplicator 1 preferably, though not necessarily, may be provided with a casing consisting of a substantially imperforate top 5, sides 7 and ends 9, and it will be recognized, as this description proceeds, that the various operational elements of the duplicator are positioned in any suitable manner within the said casing comprising the top wall 5, the side walls 7 and the end walls 9. The duplicator 1 is energized and operated by means of electric power which is fed to the duplicator from any suitable source of power by means of electric lead 11 and plug 13. The switch controlling the main power source to the device projects through the top 5 of the casing, as at 15, while the safety switch, which will be particularly described hereinafter, which controls the power to the heat lamp also projects through the top 5 as at 17. An indicator light 16 also extends through top 5 of the casing.

While any suitable type of pack assembly for the work and the heat sensitive sheet may be employed, for purposes of iilustration, and not limitation, I have shown FIG. 1 such assembly, indicated generally at 3 as comprising a rectangular frame 19 which may be formed of a material which is heat resistant and preferably produces a cushioning effect, a carrier screen designated generally by the numeral 21 and comprising a mesh or the like surface 22 which is hinged at one end to the frame 19 and when the device is being operated the screen 21 is in down position as indicated by the arrow in contact with the sensitive sheet 25. While such structure is not specifically illustrated in the drawings, a bottom to the assembly 3 is provided upon which rests the work 23 which is to be reproduced, the work 23 being sandwiched below the thermographic sensi tive sheet 25, upon which the copy is to be made. It will be understood that when the work 23 and the sensitive sheet 25 are in position, as described, ready for the reproductive operation, the surface of the sensitive sheet 25 will be in substantially the same plane as the upper surface of the frame or base board 19. If desired the frame 19 may be provided with grooves forming tracks within which rollers (to be described) may travel in the rolling operation of the duplicator.

The actual heat producing and copying apparatus of my invention which may be housed within a casing as described comprises a main, or upper body, frame designated generally by the number 27, (FIG. 4) this upper frame being of generally rectangular configuration having a portion thereof provided with a plurality of cut-outs or openings 29 in order to reduce the weight of the entire apparatus. The framework, embodying the upper plate or body portion 27, comprises a pair of end plates designated generally by the numeral 31. Each end plate consists generally of a transversely extending upper member 33 (see FIG. from which depend a pair of, what I shall term, legs 35 which are connected together by means of a central section 37. An angle iron 39 is fixed, (FIG. 4) in any suitable manner, to the outer vertical surface 33 of the right hand end plate 31 as FIG. 4 is viewed. The flange 41 of angle iron 39 extends outwardly, for a purpose to be hereinafter described. A similar flange 42 is fixed in any suitable manner to the member 33 of the end plate at the opposite end of the apparatus and its flange 44 extends inwardly.

The body portion or upper surface 27 of the frame is fastened by screws 43 to the flanges 41 and 44 of the angle irons. It will be noticed that the upper surface 27 is of rectangular elongated configuration of greater length than the distance between the end plates 31 to thereby provide a projecting portion 45 of the uppersurface 27. As this description proceeds, the purpose of the projecting section 45 will be fully explained. Adjacent to but preferably laterally spaced from one longitudinal edge of the surface 27 is a further length or strip 47 which is fixed at each end by means of screws or the like 49 to the flanges 41 and 44. For clarity of description I shall term this length, strip or elongated flat plate 47 a panel member. Adjacent to and removably spaced laterally from the other longitudinal edge of the surface 27 I affix an elongated element 51 by means of screws 53 to the flanges 41 and 44.

The main power switch 15, the indicator light 16 and the safety switch 17 for controlling energization of the heat lamp extend through the panel member 47 as clearly illustrated in FIG. 4 of the drawings. These three

operating elements

15, 16, and 17 may, as explained above, extend through the upper surface 5 of the casing 1 of the device, however it is within my contemplation, and is entirely practical, to use the duplicator in the form shown in FIG. 4 of the drawings without using the casing I as disclosed in FIG. 1.

In FIGS. 2, 3 and 5 I have illustrated in detail certain of the components of this device and their assembly into a unitary operative structure. I have used the numeral 55 to designate the heat lamp which is used in the reproduction of graphics and this heat lamp is preferably a Quartz iodine infra-red 1,350 watt lamp, and as is clearly evidenced in FIG. 3 of the drawings heat lamp 55 is generally of circular configuration in cross section. An electric lead 57 extends from one end of the heat lamp 55 through a lamp clip or supporting member 59 which is fastened to the lower portion of the section 37 of the respective end plate as at 61, by means of screws 63. This clip or supporting member is provided with an aperture 65 like element 67 is fastened to one end of the heat lamp 55 and is positioned and supported in the clip member 59. The heat lamp 55 is positioned with a reflector 71, as clearly illustrated in FIGS. 3 and 5 of the drawings. The reflector 71 is provided with an elongated slot-like aperture 73 in the lower portion thereof through which the radiant energy is directed to the thermographic sensitive copy paper which is positioned above the sheet having the graphics thereon which are to be reproduced. The heat lamp 55 when assembled in the combination is preferably on the order of one-fourth inch away from the work and the reflector and slot 73 are so angled and removed a distance from the work'so as to provide the proper focusing of the radiant energy on the work. While only one end of the reflector 71 is shown in the drawings, it is provided at each end with a pair of spaced apart threaded holes 75 so that it may be mounted at each end to a lamp support clip 59 by means of the screws 63 which pass through holes 77 in the clip, through the holes 61 in the end plate and into the holes 75 in the reflector.

It is within my contemplation to use my duplicator for blueprint, diaso printing or contact printing and when used in this manner in place of the heat lamp 55 an incandescent lamp would be substituted. The operating structure and the heart of my invention would not be altered by the change in lamp which is disposed in the reflector.

At each end of the device I provide a pair of upper glass tube positioning and stabilizing

rollers

79 and 81, and a pair of lower glass tube positioning and

forward roll rollers

83 and 85. The pairs of rollers are operatively mounted on the respective end plates 31 in the following manner. All of the rollers 79-85 are provided with journal sleeves 87 which threadedly receive screws 79', 81', 83' and 85', respectively,- the said screws loosely extending through holes 79", 81", 83" and 85", respectively, in each end plate.

It will be appreciated that the pairs of rollers are rotatively mounted on the end plates of the frame and extend inwardly therefrom. It is to be understood that other mounting arrangements may be used for the rotatable rollers, and such other arrangements will fall within the spirit and scope of my invention.

I provide a glass roller printing tube 89 which houses the reflector 71 and the heat lamp 55. I have found that the glass tube may be formed of Coming Pyrex glass which will tolerate the substantial heat which is generated by the heat lamp. The glass roller printing tube is of substantially the same length as the reflector 71. The critical diametrical areas of the glass tube will be discussed hereinafter. Consideration of the drawings discloses that the glass tube is open at both ends, and that the heat lamp and reflector are housed therein.

The lamp support clips are affixed to an end plate at each end of the duplicator, the reflector is fixed to these clips at each end and the pairs of rollers are joumaled to an end plate at each end of the duplicator, and the reflector and heat lamp which are housed in the glass roller printing tube, which extends at each end between the pairs of rollers in the following manner. The glass tube 89 is of such diameter that its upper periphery engages the upper pair of glass tube positioning and stabilizing

rollers

79 and 81, while its lower periphery is in engagement with the sensitive sheet 25 of the assembly pack 3, see FIG. 3. The glass tube is not in engagement with the pair of glass tube positioning and

forward roll rollers

83 and 85 during the .operation of the duplicator.

A glass roller printing tube support pin 91 is fixed to each end plate and extends inwardly therefrom, one such pin extending a distance into each end of the glass tube 89 as particularly illustrated in FIGS. 2 and 3 of the drawings.

Any suitable ventilating or cooling means may be employed. As one example, from among many which may be effectively used, I provide a squirrel cage fan 93 which is operatively mounted on and driven by a shade pole motor 95, which in turn is mounted on the respective end plate 31. Any suitable type of air ducting means may be used to conduct air from the fan 93 to and into the adjacent end of the rotatable glass tube 89 for travel therethrough and exit out to the other open end of the tube to produce the desired cooling effect.

On the end of the projection 45 I affix an angle bar, or the like 97, by means of screws 99 and an electric socket, or terminal 101 is fixed to this angle bar, the plug 13 being electrically connected to terminal 101 to power the duplicator.

One type of electric circuit which may be conveniently used to power and control my duplicator is shown in FIG. 6 of the drawings wherein a lead 57 extends from terminal 101 to one end of the heat lamp 55, a lead 103 extending from the other end of the heat lamp to major power switch 15. Lead 105 is connected to lead 103 and to indicator lamp 16 from which a lead 107 extends to heat lamp control switch 17. Lead 109 is connected to switch 17, and fuse 111, lead 113 being connected to the other power lead 115 at 117 and power lead 117 being connected to switch 15.

In using the duplicator the assembly pack 3 is readied by placing the work sheet 23, having thereon the material to be reproduced, in position. The thermographic sensitive copy paper 25 is placed thereover as shown in FIG. 1 of the drawings. The assembly pack 3 may be supported on a table, desk or any other convenient surface.

The miniaturized, portable and manually operable duplicator l is then readied for operation to produce the reproduction on sensitive sheet 25. The plug 13 is connected to terminal 101 and conductor 11 is connected to any suitable and convenient power source outlet. The duplicator being positioned on the assembly pack at one end thereof so that in its manual rolling operation it will pass over the entire work and sensitive sheet area. Main power switch 15 is then actuated to close the circuit, indicator light 16 will be energized, however the safety switch 17 being open the heat lamp 55 will not at this time be energized, and not until safety switch 17 is actuated to close the circuit to the heat lamp. Safety switch 17 must be manually depressed at all times, or otherwise operated to close the circuit to the heat lamp, immediately upon withdrawal of the manual pressure the switch will open and the heat lamp will be de-energized. Switch 17 may be of any suitable type which will cause the circuit to the heat lamp to be closed only when pressure is maintained thereon, for instance, it may be spring biased to switch open position. It will be appreciated that with this safety switch combined in the circuit the danger of inadvertently leaving the heat lamp energized is eliminated.

When the

switches

15 and 17 are closed, as described, the heat lamp being energized, the duplicator is rolled over the assembly pack to produce the reproduction of the graphic material on sensitive sheet 25.

When the duplicator is rolled over the assembly pack, including the sensitive sheet and the sheet having the graphic material thereon to be copied, the glass roller printing tube 89 makes slight contact with the sensitive sheet, is thereby rotated, and exerts a degree of pressure on the two

sheets

23 and 25, thereby maintaining these sheets flush or flat so that the heat from the heat source is projected thereon at the desired precise angle for clarity of reproduction.

In this reproducing operation the glass tube 89 transmits heat to the sensitive sheet at a given rate. During this operation the glass tube is rotating and the diameter thereof is suffrcient so that a part of the peripheral surface of the tube is removed from the heat below opening 73 in the reflector 71 a sufficient time for cooling of said peripheral surface before it again rotates to position below said opening 73.

Consideration of the drawings, and particularly FIG. 3 thereof, indicates that the lower tube positioning and

forward roll rollers

83 and 85 do not engage glass tube 89, however they function as the wheels for the rolling movement of the duplicator in its reproducing operation, traveling on frame 19.

Roller

83 and 85 act not only as wheels, but also function to prevent rocking of the duplicator so that the reflector 71 is always properly positioned relative to the work to produce an in-focus arrangement at all times. It will be appreciated that when the duplicator is grasped and manually rolled this undesirable rocking would occur were it not for

rollers

83 and 85.

The glass tube positioning and stabilizing

rollers

79 and 81 are in contact with and rotated by the glass tube during the rolling reproducing operation. When normal downward pressure is applied to the duplicator in the manual rolling operation it will be realized that the glass tube will be urged upwardly and into limiting contact with

rollers

79 and 81, thus, these rollers maintain the glass tube 89 in proper position at all times during operation of the device.

The pins 91 which project into each end of the glass tube engage the upper periphery thereof when the duplicator is not in operation, to keep the glass tube from falling out of the duplicator, however during operation the pins are not in engagement with the glass tube, see FIG. 3.

It will be appreciated that the reflector must be slightly angled with respect to the vertical so that the point of focus from the heat lamp meets the work slightly ahead of the forward movement of the duplicator.

In FIGS. 7, 8 and 9 of the drawings I have illustrated a modified form of my invention and have used the same reference numerals to designate parts which are the same as those described above. In this form of the invention I provide a duplicator housing, which I have designated by the numeral 121, and fixed on the top of this housing I provide a handle 123, of any suitable type, in order to facilitate the manual movement of the duplicator over the work, in a manner which will be hereinafter described. Adjacent to but inwardly spaced from each end of the duplicator housing I provide aligned apertures 127 in each side 129 of the housing. As in the previously described apparatus I provide an end plate 31 at each end of the duplicator and this end plate may be connected to the housing in any suitable manner. Rotatively mounted at each end of each transversely extending upper member 33 of each end plate are a pair of upper wheels, or rollers, 13] and 133, these rollers being operatively mounted on studs which are fixed to each end plate. The wheels, or rollers, 131 and 133 are preferably provided with concave surfaces, as clearly illustrated in FIG. 9 of the drawings. Spaced below the pair of transversely spaced apart

rollers

131 and 133 is a further wheel, or roller 137 which is rotatively mounted by means of a stud 139. This roller or wheel 137 is spaced below the

rollers

131 and 133 and positioned intermediately thereof.

In the form of the invention illustrated in FIGS. 79 I provide any suitable type of assembly means for the work 23 and the sensitive sheet 25 and about this pack or assembly I provide a framework of generally rectangular configuration, which I have designated by the numeral 141, the framework having sides 142 and ends 144. At each corner of the framework posts 143 are fixed thereto to extend upwardly therefrom, said posts being in alignment. Fixed to and extending between aligned posts 143 along the sides of the framework are traverse rods 145 which are of cylindrical configuration in cross section. Each rod at each side of the framework extends through the aligned openings 127 adjacent each end of the duplicator housing 121, and rods 145 extend along the concave surfaces of the wheels or

rollers

131, and 133 and also along the concave surface of the wheel or roller 137, all as clearly disclosed in FIGS. 8 and 9 of the drawings. It will now be recognized that the duplicator and its housing are suspended for movement over the sensitive sheet 25 along the pair of traverse rods 145 so as to reproduce the work 23.

Since the duplicator in this form of my invention is suspended from the traverse rods 145 the supporting rollers 83 which are provided in the form of the invention previously discussed are not required and are therefore eliminated.

It will now be appreciated that the upper rollers constituting a part of the suspending mechanism are in slidable engagement with the uppermost arc of the traverse rod while the lower roller of the mechanism is in slidable engagement with the lowermost arc of the traverse rod. It will further be understood that the utilization of the pair of upper rollers and the single lower roller insures that the duplicator will at all times in its operation over the work and the sensitive paper be maintained in proper angular relation thereto so that the energy 1. A miniaturized portable and manually operated thermographic duplicator, adapted to be rolled over the work having the graphic material thereon and over the thermographic sensitive paper upon which the graphic material is to be reproduced, including in combination, a stationary supporting surface for the work and the thermographic sensitive paper, a framework in said duplicator, forward roll rollers operatively mounted on each end of said framework and partially supporting said duplicator in its rolling movement over the work and thermographic sensitive paper, a heat lamp affixed to said framework, electric energizing means for said heat lamp, in-

cluding an electric circuit and a source of power and an open ended cylindrical rotatable, radially incompressible heat transmitting means operatively positioned in said duplicator between said heat lamp and the thermographic sensitive paper and in rolling contact with said thermographic sensitive paper and partially supporting said duplicator in its rolling movement, means fixed on the ends of said framework and extending therefrom into the open ends of said heat transmitting means and engageable thereby solely when said heat transmitting means is out of contact with said thermographic sensitive paper, and further means fixed to said framework and engageable with said heat transmitting means solely when said heat transmitting means in in rolling contact with said thermographic sensitive paper.

2. A miniaturized, portable and manually operated duplicator, in accordance with claim 1, wherein said further means is rotatably mounted in said framework in engagement with said rotary heat transmitting means and rotated thereby when said duplicator is operative and said heat transmitting means is rolled over the work and the thermographic sensitive paper to thereby limit radial movement of said cylindrical rotary heat transmitting means in a direction away from said work and thermographic sensitive paper. v

3. A miniaturized, portable and manually operated duplicator in accordance with claim 1, wherein said framework is of elongated configuration and includes an end plate at each end thereof, and said means and said further means are operatively fixed on each end plate, said further means comprising a pair of horizontally spaced apart rotatable members operatively fixed on each end plate, said means being fixed on each end plate in a projected vertical plane below the area between said spaced apart rotatable members, providing a free area between said means and said further means and said rotatable heat transmitting means extends at each end into the free area.

4. A miniaturized, portable and manually operated thermographic duplicator, in accordance with claim 1, wherein said heat transmitting means is freely moveable between said means and said further means.

Claims

1. A miniaturized portable and manually operated thermographic duplicator, adapted to be rolled over the work having the graphic material thereon and over the thermographic sensitive paper upon which the graphic material is to be reproduced, including in combination, a stationary supporting surface for the work and the thermographic sensitive paper, a framework in said duplicator, forward roll rollers operatively mounted on each end of said framework and partially supporting said duplicator in its rolling movement over the work and thermographic sensitive paper, a heat lamp affixed to said framework, electric energizing means for said heat lamp, including an electric circuit and a source of power and an open ended cylindrical rotatable, radially incompressible heat transmitting means operatively positioned in said duplicator between said heat lamp and the thermographic sensitive paper and in rolling contact with said thermographic sensitive paper and partially supporting said duplicator in its rolling movement, means fixed on the ends of said framework and extending therefroM into the open ends of said heat transmitting means and engageable thereby solely when said heat transmitting means is out of contact with said thermographic sensitive paper, and further means fixed to said framework and engageable with said heat transmitting means solely when said heat transmitting means in in rolling contact with said thermographic sensitive paper.

2. A miniaturized, portable and manually operated duplicator, in accordance with claim 1, wherein said further means is rotatably mounted in said framework in engagement with said rotary heat transmitting means and rotated thereby when said duplicator is operative and said heat transmitting means is rolled over the work and the thermographic sensitive paper to thereby limit radial movement of said cylindrical rotary heat transmitting means in a direction away from said work and thermographic sensitive paper.