US3163755A

US3163755A - Thermographic copy machine wherein the infrared radiation source is a flash lamp with a capillary bore

Info

Publication number: US3163755A
Application number: US155428A
Authority: US
Inventors: Arthur R Kotz; Roger H Appeldorn; Emil W Grieshaber; Elmer J Peterson; Norman L Giorgini
Original assignee: Minnesota Mining and Manufacturing Co
Current assignee: 3M Co
Priority date: 1958-10-20
Filing date: 1961-11-28
Publication date: 1964-12-29
Anticipated expiration: 1981-12-29

Description

DeC- 29, 1964 A. R. KoTz ETAL 3,163,755

THERMOGRAPHIC COPY MACHINE WHEREIN THE INFRARED RADIATION SOURCE 1s A FLASH l LAMP WITH A CAPILLARY BORE /M/E/vros /6 ARTHUR R KOTZ ROGER H. APPELDORN EMIL IM GR/ESHABER ELMER J. PETERSON NORMAN l.. GIORG/NI Dec. 29, 1964 A. R. KoTz ETAL 3,163,755

THERMCCRAPHIC CCPY MACHINE WHEREIN THE INFRAREDr RADIATION SOURCE Is A FLASH y LAMP WITH A CAPILLARY BoRE Original Filed Oct. 20, 1958 2 Sheets-snee?- 2 United States Patent O Ti niJ/IGGRAPIHC CPY MACHINE WIEREIN THE INFRARED RADIATlGN SOURCE IS A FLASH LAMP WTH A CAPILLARY EURE Arthur R. Kotz, Madison, Wis., and Roger H. Appeldorn,

White Bear, Emil W. Grieshaber, White Bear Township, Ramsey County, Elmer J. Peterson, Minneapolis, and Norman L. Giorgini, West St. Paul, Minn., assignors to Minnesota Mining and Manufacturing Company, St. Paul, Minn., a corporation of Delaware Original application Get. 20, 1958, Ser. No. 768,328, now Patent No. 3,656,994, dated Oct. 2, 1962. Divided and this application Nov. 28, E361, Ser. No. 155,428

7 Claims. (Cl. Z50-55) This invention relates to the reproduction of graphic originals by heat-printing, and has particular reference to economical apparatus capable of rapidly producing any required number of reproductions of printed or handwritten matter, sketches, drawings, photographic prints, and many other types of graphic originals, on heat-sensitive copy-paper. There is involved the conversion of radiant energy to heat energy at the graphic representation, and the utilization of the resulting heat-pattern in providing a corresponding visible pattern in the copypaper. Graphic representations made With colored inks or pencils as Well as with carbon inks or pencils are successfully copied, and accordingly the invention has been found particularly applicable to the copying of documents carrying signatures as well as those printed in multiple colors.

This application is a division of copending patent application Serial No. 768,328, led October 20, 1958, and now US. Patent No. 3,056,904.

Typical heat-sensitive copy-papers which, along with other types, may eifectively be used with the apparatus of this invention are disclosed in Clark U.S. Patent No. 2,813,043 and others therein cited. Such papers have been used with apparatus described in Miller U.S. Patent No. 2,740,895 and by methods described in Miller U.S. Patent No. 2,749,896, in which intense radiation from electrically heated tungsten filaments provided the required heat-pattern for visible reproduction. They have also been used with apparatus and by methods of Miller et al. U.S. Patent No. 2,844,733 employing a high potential discharge in an ionized gas as the source of radiation.

The present invention likewise calls for gas flash source of radiation but, unlike the method of the Miller et al. patent, produces a direct rather than an inverse reproduction of the printed characters, signature, or other graphic representation. Thus a signature in blue or red ink on White paper will be copied, for example, as a black signature on a White or bull background rather than as a White or bud signature on a black background. The apparatus employed is capable of reproducing originals of any length, utilizing a single ash lamp of novel construction for instantaneous llash type irradiation of successive contiguous areas of a composite graphic original and copy sheet in timed relation to the advancement of the composite past the lamp. The novel lamp construction not only provides a radiation pulse having an increased percentage of the shorter wavelength light rays facilitating reproduction of difficult-to-copy colors, but it also permits substantial reductions in the cost of the machine as well. The mechanism as Well as the electrical circuitry of the machine incorporates a number of novel features insuring the production of uniform copies of the most diverse types of graphic originals and irrespective of line voltage variation. The machine is erilcient, safe and easily operated, and is otherwise Well adapted for the purposes described.

'I'hese and other advantageous qualifications are obtained, in accordance with the present invention, by means ICC of the apparatus which will now be described in connection with the accompanying drawings, in which:

FIGURE l is a vertical sectional View taken from front to back through the copying area of a typical copying machine constructed in accordance with the invention;

FIGURE 2 is a fragmentary sectional plan view of a portion of the machine of FIGURE 1 taken along the line II-Il of FIGURE l;

FIGURE 3 is a fragmentary plan view of another portion of the machine of FIGURE l showing the timing mechanism, together with the drive means for the conveyor web and for said mechanism; and

FIGURE 4 schematically represents the electrical circuitry of the improved machine.

Referring now to FIGURES l and 2, the improved thermocopying machine is provided with a casing 5 including a ledge member 6 and a curved guide member 7 defining an inlet channel 8 and an outlet vchannel 9. Within the housing 5 is a supporting frame 10 having parallel side members ll. Mounted on the frame 10 for rotation on parallel axes in the spacial relationship shown, are a copy roll 12, a feed roll 13, a discharge roll 14 and a tensioning idler roll 15. Traversing the rolls l2 through 15 as best shown in FIGURE l is a exible endless Web or belt 16 of substantial width. A composite of a graphic original 17 and heat-sensitive copy paper 18 inserted into the entrance channel 8 is conveyed by the web 16 around the copy roll 12 and out the discharge channel 9.

The feed roll 13 and discharge roll 14 may be mounted in suitable fixed bearings, Whereas the copy roll mounting to be described hereinafter, is of the iloating type. The tensioning roller 15 may be bearinged on a shaft 22 supported in slots 19 in the frame members 1l and biased rearwardly by springs 2li carried by rods 21 extending loosely through diametrical bores in the shaft 22. The rods 21 are suitably anchored to the frame members 11, and the bias of the springs 2G exerts a strong tension upon the web 16 such that said web exerts a heavy compressive stress on all portions of the composite disposed between said web and the copy roll 12 during the passage of the composite through the machine.

The copy roll 12 takes the form of a cylindrical sleeve of glass or other suitable material, the end portions of which extend through apertures 23 in frame members l1 and are received in bearing guide members 24 which may be of any suitable electrical insulating material, for example, the plastic material known commercially as nylon. The bearing members 24 are each formed with extended arm portions 25 which are formed with horizontal slots 26 for slidably receiving mounting screws 27 threaded into the frame members ll as shown in FIGURE 2. The cooperation of the mounting screws 27 with the slots 26 permits free floating movement of the bearing guides 24, and hence of copy roll 12, in the plane normal to the axis of said copy roll.

Bearing guides 24 are each formed with a bore 28 and with a counterbore 29 in which the adjacent open end of the copy roll l2 is rotatably received. The bearing guides 24 are also formed with a plurality of generally triangular web portions Sil joined at a central hub 31, and each is also formed with an arcuate boss 32 shown most clearly in FIGURE l. The bosses 32 are each formed with an arcuate slot 33 for receiving and supporting the adjacent end of an elongated metallic shield-reflector 34, of arcuate cross-section, the inner surface of which is preferably coated with a layer of lightreflective ceramic.

An elongated gas ash lamp 35 having a tubular cylindrical main body portion and bulbar end portions is provided at said end portions with tubular insulating mounting members 36 which engage the web portions 3G of the bearings 24 as shown most clearly in FIGURE 2, to provide a support for the lamp 35 maintaining the main body portion thereof coaxial with the copy roll 12.

Electrodes

37 and 38 which are respectively anode and cathode, are disposed within the opposite bulbarend portions of the lamp 35, as shown, and are provided with terminal portions extending outwardly of the lamp envelope for attachment to electrical connections 39 and 49 respectively. The lampy envelope -is hermetically sealed and defines an arc chamber which contains an ionizable fluid, preferably a noble gaseous fill such as commercially available xenon gas, as a fill. The main body portion of the lamp 35 preferably has a bore 41 the size of which is of the order of a capillary, i.e., not substantially larger than two millimeters in diameter, and the xenon gas is preferably under a pressure of from 500 to 760 millimeters Vof mercury.

Electrically connected to and mounted on the shieldreflector 34 is a generally U-shaped trigger electrode 42 having an elongated straight line main body portion extending parallel with the main body portion of the liash lamp 35 and adjacent the periphery thereof as shown. A suitable electrical connection member 43 is connected in circuit with the trigger' electrode 42, either directly as shown, or by connection to the shield-refiector 34, said connection member, like connection members 39 and 40, extending outwardly through the adjacent bearing guide 24 between the web portions 30 thereof as shown. Where the connection member 43 is connected directly to the trigger electrode 42, said electrode need notV be electrically connected to the shield-reliector 34. To prevent overheating of the copy roll 12, a conduit-44 leading from the outlet of a blower (not shown) is telescoped over one of the bearing guides 24 and supplies cooling air which flows longitudinally through the annular space between the flash lamp 35 and copy roll 12 and out the other bearing guide 24. Y

It will be observed that in addition to affording a support for the trigger electrode 42, the shield-reflector 34 shields a portion of the inner surface of the copy roll 12 from the radiations of the lamp 35 to thereby define on the side wall of said copy roll, and between the upper and lower edges of the shield-reflector 34, an exposure area of predetermined circumferential length through which a composite can be uniformly irradiated by the ash lamp positioned coaxially with said copy roll. In addition, of

course, the shield-reflector also functions to reliect toward the aforementioned exposure area radiations impinging thereagainst.

The tension exerted on the web 16 by the springs 20 through the tensioning roll 15 causes the copy roll 12 to be constricted within the bight portion of the web extending around the copy roll from the feed roll 13 to the khorizontal platform portion 5l). An adjustable timing mechanism 51 is mounted on the bracket 49 and comprises a generally U-shaped bracket 52 having a platform portion 53 overlaying the platform portion 5t)- of the bracket 49 and slotted as at 54 to receive screw/s55 threaded into the bracket 49 and adjustably securing the bracket 52 thereto. The bracket 52 is formed with upstanding flanges 56 and 57 affording a rotatable support for a cam shaft 58 which carries at one end a wheel 59 having a periphery of frictional material engaging the driving cone 48. A cam sleeve 60 is disposed coaxially on the cam shaft 58and has sliding frictional engagement therewith. The desired frictional engagement may be attained by proper selection of the material and of the bore of the cam sleeve 60 with respect to the cam shaft 5S therewithin. It is preferable, however, to insure the proper frictional engagement by adjustable means, for example by the use of a spring member, such as a thrust washer 61 interposed between the cam sleeve 66 and a collar 62 adjustably fixed on the'shaft 58. The washer 61 biases the cam sleeve 60 axially against an annularv shoulder 63 formed on the cam shaft 58.

-The cam sleeve 60 is provided with a shoulder 64 projecting radially from the periphery thereof as shown, and a solenoid 65 is mounted on the iiange 57 and has a plunger 66 biased toward the periphery of the cam sleeve 60 by a compression spring 67. When the plunger 66 is in the deenergized position shown, it is in the path of the Vshoulder 64 and prevents rotation ofthe cam sleeve 60 beyond the position shown, even though the cam shaft 58 may berotating therewithin. Energization of the solenoid 65l effects retraction of the plunger 66 to a position clear of the shoulder 64 permitting rotation of the cam sleeve 60 with the cam shaft 58.

The cam sleeve 60 is also formed with surface irregularities or

shoulder portions

68 and 69 which may be formed as in the illustrated embodiment by cutting away peripheral portions of the cam sleeve 60 so that the

portions

68 and 69 are in effect radial projections with respect to the cutaway portions without extending radially beyond the periphery of the remainder Vof the cam sleeve 60. Mounted on the ange 56 of the bracket 52 are a biased closed micro switch 79 a'nd a biased open micro switch 71 provided with actuating arms carrying cam following rollers 72 and 73 respectively. As will appear hereindischarge roll 14. This constriction not only affords the heavy compressive pressure .on the composite aforementioned, but it also causes the web 16 to afford substantially all of the support for the copy roll 12. The bearing guides 24 are normally operative to limit axial movement of the copy roll 12 and actually support said copy roll only when the tension on the web 16 is relieved, for exam-k ple on removal of the web from the machine. It is apparent, however, that the bearing guides 24 do afford means for retaining the copy roll 12, liash lamp 35, shieldreflector 34 and trigger electrode .42 as a unitary assemblage in which the spacial relationships of the components of said assemblage are maintained even though said assemblage can move as a unit within the limits permitted by lthe aforementitoned floating mounting.

Movement of the web 16 in the direction indicated by the arrows is provided by drive mechanism under the control of a normally open start switch 74 having an actuating arm 74a positioned within the throat of the entrance channel 8 and actuatable by insertion of a composite into the machine. The illustrated drive mechanism is associ- FIGURE 3 to which reference is now made,

after, the switch '70 is a turn-oli synchronization switch and the switch 71 is a trigger switch, it being apparent from FIGURE 3 that upon rotation of the cam sleeve 60 in the direction indicated, the switch 70 will be actuated momentarily before the switch 71, and that both of said switches are in the actuated position when the cam sleeve 69 is locked in the position shown .by the solenoid plunger 66.

Referring now to FIGURE 4, the electrical circuitry of the embodiment of the invention selected for illustration derives its power from an alternating current source 76 which is connected in circuit with the primary winding of a power transformer 77 by means of main primary conductors 7K8 and 79. All of the power to the machine is under the control of a master on-off manual switch 75 which is interposed in the conductor 78 and, as shown in FGURE 1, is mounted on the front of the casing 5. The secondary Winding of .the power transformer 77 is connected in parallel circuit relation with the flash lamp 35, more specifically the anode 37 and cathode 38 thereof, by means of the conductors 39 and 4f? respectively, the cathode 3S being grounded as at Si?. A half-wave rectilier 81 is interposed in the conductor 35 so that the current flow available from the secondary winding of the power Itransformer 77 to the conductors 39 and 4t) is in the form of unidirectional spaced pluses for a reason which will hereinafter appear. Connected across the conductors 39 and atl, as by conductors $2 and 233 is a storage capacitor $4 which is subjected to substantially the full voltage avaliable irom power transformer 77 The transformer 77, rectier 81 and conductors 39, d2, 83 and 4t) thus provide a charging circuit Ifor the storage capacitor 84:.

Triggering means is provided for effecting discharge through the lamp 35 of the electrical energy stored in the storage capicitor 84 by die charging circuit, said means comprising a voltage divider network 85 connected across the conductors 3g and itl and comprising resistors 35 and S7. The voltage divider 85 supplies a reduced voltage for storage in a trigger capacitor 88 interposed in a conductor S9 connected at one end intermediate the resistors 86 and S7 and at its other end to the conductor 4@ as shown. The trigger switch 71 is interposed in a conductor 9G along with the primary winding of a step-up trigger transformer $1, one end of the conductor 9h is connected to the conductor 89 between the capacitor 88 and the voltage divider S5 as shown, and the other end of the conductor 9@ being connected to the conductor 4d as shown. One end of the high voltage secondary winding of the trigger transformer 91-is also connected to the conductor 9d, and the other end of said secondary winding is connected in circuit with the trigger electrode 42 by the conductor d3.

While in the shut-down condition of the machine shown in FIGURE 4 the trigger switch 71 may be held closed by the cam 69, in normal operation such closure is only momentary. Thus, switch 71 is open most of the time. When the main switch 75 is closed and trigger switch 71 is opened, an electrical charge is stored in both the storage capacitor 3e and the trigger capacitor 8S. Upon momentary closure oi' the trigger switch 71 by the cam o9 the charge stored in the trigger capacitor S8 discharges through the primary winding of the trigger transformer 91 causing a high voltage charge to oe impressed across the trigger electrode 42 and the grounded cathode 33. This ionizes the gas in the lamp 35, lowering the impedance to current flow through said gas between the anode and cathode sufiiciently 'to permit the electrical energy stored in the storage capacitor 84 to be discharged through the lamp, creating thereby a flash or radiation pulse. As soon as the energy stored in the capacitor 84 is discharged, the charging circuit substantially immediately begins recharging said capacitor. Subsequent reopening of the trigger switch 71 permits recharging of the trigger capacitor 88.

Means is provided for effecting discharge of the electrical energy that may be stored in the storage capacitor 84 in the event of a power failure, said means taking the form of a safety short-out relay 93 having biased closed contacts 94 interposed in a conductor 95 which also has a resistor 92 interposed therein, said conductor having its opposite ends connected to the conductors 39 and 4d as shown. The relay 93 has a winding 26 connected in circuit with the primary conductors 7% and 79 by conductors 97 and 9S respectively. The relay 93 is normally energized to open contacts 94 whenever the main on-oi switch 7 5 is closed. ln the event of a failure of the power source 76 or opening of the main switch 75, the relay winding 9d is deenergized to close contacts 94 and permit dissipation of any charge stored in the capacitor 8d through the resistor 92.

Closure of the main switch 75 has the immediate effect, so far as the structure thus far described is concerned, only of energizing the safety short-out relay 93 and the drive motor 46 which is connected to conductors 7S and 79 by conductors 99 and 10i? as shown. Current iiow to the power transformer 77 and to the solenoid 65 of the timing mechanism 51, in addition to being under the control of the main switch 75, is also under the control of the start switch 74. The switch 74 is interposed in a conductor 101 which is connected across the

conductors

78 and 79 as shown and also has interposed therein the operato-r of a time delay relay 162. The time delay relay 102 has biased open contacts 163 and iti-fi comprising a double pole single throw switch. The contacts ttBS, together with the winding of the solenoid 65, are interposed in a conductor connected across the

conductors

78 and 79 as shown. The contacts 164, together with the winding 107 of a power relay 1%, are interposed in a conductor1tla connecting the

conductors

97 and 79 as shown. The relay H98 has biased open contacts 169 interposed in the main primary conductor 7d as shown. The turn-off synchronization switch 7d is interposed in a conductor 11@ which connects said switch in parallel circuit relation with the contacts 1&4 of relay 102 as shown.

The conductor 97 may also have one or more biased open interlock switches interposed therein as indicated at 111, said switches being positioned to be held closed by the cover or other portions of the machine when said cover or other portions are in place, said switches moving to open position by opening or removal of said cover or other portions of the housing 5. Opening of the contacts of switch or switches 111 deenergizes both the power relay 10S and the safety short-out relay 93 to thereby shut oit all power to the charging circuit and to also rapidly discharge the storage capacitor $4 through the resistance 92.

To place the machine into operation, the main switch 75 is manually closed to thereby initiate operation of the drive motor 46 and hence of the web 16, and to also energize the safety short-out relay 93 to open the contacts thereof. Referring lto FIGURE 3, operation of the motor 46 causes rotation of the driving cone 48, which in turn causes rotation of the driven wheel 59 by frictional engagement therewith. This causes rotation of the cam shaft 58, but the cam 60 is prevented from rotating with the cam shaft 58 since the solenoid plunger d6 is disposed in the path of the cam shoulder 64.

Entry of a composite of original and copy paper into the throat of the entrance channel 8 causes actuation of the start switch 74 and immediate closure of the contacts 103 and 1M of time delay relay 102. Closure of contacts 103 effects energization of the solenoid 65 and withdrawal of the plunger 66 to a position clear of the cam shoulder 64, permitting rotation of the cam 60 with the cam shaft 58. Rotation of cam 60 moves

cam portions

68 and 69 out of engagement with the cam following rollers 72 and 73 to permit closure of the switch 70 and opening of the switch 71. Closure of contacts 104 effects energization of the power relay 10S for closure of the contacts 109 `thereof and energization of the power transformer 77. The secondary of the power transformer 77 supplies high voltage alternating current which is rectified by the rectiiier 81 and supplied to the charging circuit in the form of spaced unidirectional pulses which store electrical energy in the storage capacitor 84 and trigger capacitor 88. In the meantime the composite of graphic original and copy paper advances in heavy pressure contact over its entire area between the web 16 and the copy roll 12. This pressure contact, by virtue of the novel arrangement whereby the copy roll 12 is supported by the web 16, is substantially greater than the pressure contact impressed upon composites by prior machines.

Substantially simultaneously with the arrival of the leading edge of the composite in radial alignment with the upper edge of the shield-reiiector 34, the trigger switch 71 is actuated to closed position by the cam 69 to discharge the storage capacitor 84 through the lamp 35 and produces an intense radiation pulse which causes a direct reproduction of the graphic representations of the graphic original to appear in the heat-sensitive copy paper 18 overthe area thereof in contact with the copy roll 12 and not shielded by the shield-reiiector 34. As the original and copy leave the copy roll 12, they'are directed out the outlet channel 9 by the guide member 7 to the top of the casing where the copy is in position for immeiate visual inspection. Y

With suciently short sections of original any copy paper, a complete reproduction may be obtained with a single radiation pulse; and the apparatus is entirely satisfactory for this `class of copy. Itis equally effective, however, in the continuous copying of originals of extended length, and it is particularly useful for copying from conventional office or legal size originals, by irradiation of successive longitudinally contiguous areas thereof with multiple exposures.

As the composite continues to enter the machine and to depress the start switch. arm 74a, the

capacitors

84 and 88 are successivelyl recharged and discharged through the lamp in the manner described under thecontrol of the cam portion 69 and trigger switch 71 as successive increments ofthe composite reach the edge of the exposure area defined by the upper edge of theshield-rellector 34. Exact control of the interval between radiation pulses for synchronization of the radiation pulse with the arrival of each successive increment at the upper edge of the shieldreflector 34 is achieved by adjustment of the speed of rotation of the cam cti-with respect toy that of the web 16. This is accomplished by adjustment of the position of the timing mechanism 51 on bracket 49 to thereby adjust the position of the driven wheel 59 along the surface of the driving cone 48 as permitted by the screws 55 and slots 54. The accuracy obtainable, together with the sharpness of the image formed at the edges of the shieldreflector 34, is such that substantially no visible discontinuity is observed between contiguous exposure areas of the copy.

Passage of the trailing edge of the composite of graphic l original and copy paper into the machine and out of engagement with the start switch arm 74a causes opening of start switch 74, and after a predetermined time delay the contacts 103 and 194 of the relay 162 open. Opening of the contacts 1&4 has no effect on energization of the power relay 108, since the circuit thereto is at this time completed through the turn-off synchronization switch 70. Opening of the contacts 193, however, deenergizes solenoid 65 to permit plunger 66 to move into the path of Vthe cam shoulder 64. The cam continues to rotate with the advancement of the composite through the rnachine, and just before the leading edge of the terminal increment of the composite reaches the upper edge of the shield-reflector 34, the cam portion 68 opens turn-off synchronization switch 74B to deenergize the power relay 108 and thereby the power transformer 77. VMomentarily thereafter, simultaneously with arrival of theleading edge of the terminal increment of the composite at the upper edge of the shield-reflector 34, the cam portion 69 closes the' trigger switchv 71 to provide a radiation pulse fork exposure of said terminal increment. At substantially the same time the shoulder 64 of cam ci? moves into engagementvwith the plunger 66 to stop further movement of said cam so that the switches 70 and 71 are heldin the positions shown until another composite is inserted into the machine. Shutting off of the power supply tothe charging circuit momentarily before triggering, i.e. at a time when the charging current is minimal, insures that after discharge the residual energy in the capacitor is minimal. Low residual energy in the capacitor after discharge lengthens capacitor life, whereas shut-off of the charging circuit at a time when the charging current is The delay afforded by the f the terminal increment of the composite regardless of the length thereof or of the distance between the start switch arm and copy roll 12. VIn some instances the final radiation pulse may occur while the end portion of the composite surrounds most or substantially all of the exposure area of the copy roll. In another case the nal radiation pulse may take place after all of the composite has passed the exposure area. In all cases, however, the operational cycle is completed with the

capacitors

84 and 88 substantially fully discharged.

The permissible speed of rotation of the copy roll 12 is dependent upon the rate of voltage build up in the capacitors 84 and S8. The charging rate is dependent upon the capacity of the capacitor, which in turn is related to the energy extended in a radiation pulse of the lamp 35, and hence to the diameter of the copy roll 12 and the exposure area per flash. We have found that for the expenditure of a given amount of electrical energy in a radiation pulse, satisfactory copying requires that the characteristics, i.e. the shape, of the radiation pulse be controiledy within rather close limits. Too high a peak intensity causes destruction of the original, whereas too long a pulse duration causes low resolution, poor color pickup and low efficiency of the copying process. As will become apparent hereinafter the improved machine is provided with means for shaping the radiation pulse to afford maximum resolution, color pickup and efliciency without any deleterious effect on the original.

While wide variation is possible, it is found that a fully adequate rate of reproduction of business correspondence and analogous graphic originals is obtained when employing a iiash lamp 35 having an arc length of l0 inches and a bore of 2 millimeters mounted Within a copy roll 12 1% inches in diameter and powered from a 100 mfd. capacitor S4 having impressed thereon a voltage adjustable by adjustment of the knob 139 and potentiometer to from 229() to 3360 volts, with a l mfd. capacitor S8 supplying the triggering charge. One form Vof the machine utilizing a flash lamp, copy roll, power transformer and capacitors sized as specified, and having the circuitry previously described, produces a radiation pulse at approximately 1.5 second intervals and can expose an 81/2 x ll original in approximately 5 seconds.

As mentioned hereinbefore, the fiash lamp 35 is characterized by tue main body portion having a bore of substantially capillary size, i.e. of the order of 2 millimeters. This novel type of lamp construction produces several unexpected and very desirable results. First, the reduced diameter bore affords the lamp increased efficiency, i.e. greater usableL light output for a given energy input. Further, the reduced diameter bore produces, for a given peak current fiow through the lamp, a radiation pulse which is substantialiy richer in the shorter wave length rays, more specifically blue rays, than the radiation pulse produced by the same peak current fiow through a ash lamp having a larger diameter bore. Since the difficultto-copy colors are usually blue absorbers, the radiation pulse rich in blue rays produced by the improved lamp 35 contributes substantially to the ability of the improved machine to reproduce difcult-to-copy colors. It is thought that the radiation pulse .rich in the blue rays is caused by a higher current density occurring within the restricted bore for a given peak current fiow. To produce in a lamp having a larger bore a current density suf'dcient to generate a radiation puise correspondingly rich in blue rays would require an extremely high peak current ow through the lamp. Such extreme current ow would generate excessive heat deleteriously affecting both the composite and the conveyor web 16.

, Still anotheradvantage of the use of the restricted bore lamp 35 results from the fact that a reduction in the bore of a fiash lamp effectively lengthens the duration of the radiation pulse and reduces the peak intensity of the current iicw through the lamp. This is thought to be the result of impedance to current dow presented by restriction of the bore. The pulse lengthening effect of the reduced bore is the same effect as would be produced in a larger bore lamp by increasing the capacitance of the storage capacitor S4. Thus, for a given desired length of radiation pulse, the use of the lamp 35 having a restricted bore permits the use of a storage capacitor 84 having substantially less capacity than would be required of said capacitor to produce the same length of pulse in a flash lamp having a larger bore. This feature is particularly desirable, since large capacitance capacitors are relatively large, heavy and expensive, and the bulk, weight and cost of such capacitors varies substantially directly with the capacitance thereof. Thus, the use of the restricted bore flash lamp 35 cuts down very substantially on the cost, as well as on the size and weight of the machine.

The electrical energy expended in a radiation pulse is represented by the formula E=1/2CV2, wherein E represents the electrical energy expended in watt seconds or joules, C represents the capacitance of the storage capacitor 84 in farads, and V represents the voltage stored in the storage capacitor in volts. For a given value of electrical energy expended, and a given peak intensity a reduction in the capacitance of the capacitor 84 made possible by the improved flash lamp requires that the voltage impressed upon said capacitor be increased; This increase in voltage can be readily supplied by a change in the design of the power transformer 77, however, without any substantial increase in the bulk, Weight or cost of the machine.

Conversely the restricted bore lamp affords a circuit element for controlling the shape of a current pulse therethrough. The shape of the arc chamber Within the lamp is determinative of the impedance to current flow through the lamp and thus is determinative of the shape of the current pulse. Control of the shape of a current pulse by such a circuit element is possible by the selection of a lamp arc chamber shape of the character which produces the desired shape of pulse. The control of pulse shape thus provided is preferable to the control of pulse shape by external circuit means, for example by the use of a different capacitor or the use of inductors or resistors with the capacitor.

A further novel feature of the improved flash lamp 35 resides in the use of a xenon gas fill under substantially greater pressure than has been used heretofore in ash lamps, for example a pressure of 500 to 760 mm. of mercury as compared with a pressure of 300 mm. of mercury used in conventional ash lamps. Several unexpected and desirable advantages flow from the use of the higher pressure ll. More specifically the increased ll pressure affords, like the restricted bore of the lamp, substantially increased efficiency, i.e. greater usable light output for a given value of energy expended in a radiation pulse. The higher pressure lill, like the reduced diameter bore, also tends to increase the amount of shorter wave length blue rays in the radiation pulse. In addi-tion, the higher pressure lill raises the stand-off potential of the lamp 35, i.e. it raises the level of the minimum voltage at which the storage capacitor can spontaneously discharge through the lamp, thereby permitting a higher voltage to be stored in the storage capacitor without spontaneous discharge through the lamp. An- Y other novel feature of the machine facilitating servicing and contributing to the eciency of the machine is the structure and mounting of the trigger electrode 42. Mounting of the trigger electrode 42 on the shield-reliector 34 permits removal and replacement of the lamp 35 without removal of the trigger electrode. 1t will also be observed that the trigger electrode, being disposed on the side of the lamp 35 facing the shield-reflector 34 does not in any way obstruct the travel of light rays from the lamp bore to the exposure area of the copy roll 12. Experience has shown that after prolonged operation, a deposit forms on the outer surface of asrh lamps adjacent the trigger electrode. With Vthe improved trigger electrode structure, any deposit formed would likewise not in any way obstruct the travel of the light rays from the lamp bore to the exposure area of the copy roll. For these reasons the improved trigger electrode structure is substantially more efficient than a trigger electrode of conventional form helically wound about its associated dash lamp.

Reproduction of the graphic originals by the multiple ash means afforded by the improved machine can be effective in producing fully satisfactory copies only if the contiguous exposure areas are so carefully joined and so uniformly exposed as to provide practically no distinguishable inter-edges or density variations. Inter-edges are eliminated through adjustment of the timing mechanism 51 as aforedescribed, and variation in density is avoided by insuring strict uniformity of the peak intensity of the radiation pulse. It has been found, for example, that variations of more than i2% in the voltage impressed upon the capacitor 84 produce observable and undesirable variations in density `and copying ability. The present invention provides means for maintaining the voltage stored in the capacitor 34 Well within this limit of variation in spite of any substantial variations in the voltage supplied by the source 76.

In the illustrated embodiment of the invention', the aforementioned voltage control means includes a voltage sampling circuit 112 connected across the conductors 39 and 4t) as shown and including resistors 113 and 114, potentiometer 115 and variable resistor 116. The voltage sampling circuit 112 samples the voltage supplied to the storage capacitor 84, and supplies a predetermined fraction of said voltage, through conductors 117 and 118 to a voltage comparing and error signal amplifying circuit 119 including a source 120 of stable reference voltage which in the illustrated embodiment takes the form of a Zener diode, but which may take any other suitable form, such as a mercury battery or a standard cell. When the voltage supplied to the storage capacitor 84 is of the proper value, the fraction thereof supplied to the circuit 119 substantially matches .the voltage supplied by the stable voltage source 120.

The voltage comparing and error signal amplifying circuit 119 suppliesl to a second amplifying circuit 121, through

conductors

122 and 123, a current signal which varies inversely with variations in the sampled voltage with respect to the stable voltage source 120. Upon amplication in the circuit 121, this signal is supplied, through conductors 125 and 126, to variable impedance means 124, which may take the form of a saturable rcactor. The saturable reactor 124 has load and control windings 127 and 128 respectively, the load winding 12'7 being connected in parallel circuit relation with the control winding 129 of a load reactor 130 and also with a reset capacitor 131. The load reactor also has a load winding 132 which, with the control Winding 129 is wound on an iron core which preferably has substantially rectangular hysteresis curve characteristics affording maximum changes in impedance in the load winding for a given current change in the control winding. The load Winding 132 is interposed in the conductor 40 between the power transformer 77 and the conductor 83 as shown. Power is supplied to the circuits 119 and 121 from a transformer 133 having a primary Winding 134 supplied from 'the source 76 through

conductors

135 and 136 connected to the conductors 7g and 79 respectively as shown. The transformer 133 has secondary windings 137 and 13S connected respectively into the circuits 121 and 119 as shown.

The circuit 121, variable impedance means 124, reset capacitor 131 and load reactor 130 comprise error signal sensitive Variable impedance means for supplying impedance to the charging circuit for the storage capacitor S4 as required to adjust the voltage at said capacitor to the predetermined proper value. The variable impedance means 124 and reset capacitor 131 provide means for resettingand reorienting the iron of lthe core of the `load reactor 130 during the intervals between successive current pulses through the load winding 132. Thus the interval between successive current pulses must be of sufoient duration to permit such resetting. The half wave rectiier S1 is uniquely suited to provide unidirectional pulses spaced sutliciently to permit resetting of the core iron during the intervals between successive pulses. The degree of resetting, and hence the magnitude of the impedance afforded to kcurrent flow through the winding 132, is variable in accordance with the impedance of the variable impedance means 124. The impedance of the variable impedance means 124, i.e. the impedance of load winding 127 thereof, is variable inversely with variations in the amplified signal supplied to the windings 128 from the circuit 121.

The ilow of `a direct current pulse through the load winding 132 of load reactor 130 effects a predetermined orientation of the molecular structure of the iron of the core of said reactor and simultaneously induces a voltage in the Vcontrol winding 129, which voltage is impressed upon the reset capacitor 131, charging the latter. This action aords a predetermined impedance to the iiow of the direct current pulse through the winding 132. On terminationrof the direct current pulse aforementioned, the capacitor 131 tends to discharge through the load reactor control winding 129, as well as through the saturable lreactor load winding 127. Currentl dow from the capacitor 131 through the winding 129 of reactor 131i is effective to reset or reorient the` molecular structure of the core Vof said reactor, and the degree to which the iron of said core is reset is determinative of the impedance to ow through the winding 132 presented to the next succeeding direct current pulse.

The percentage of the stored energy in the reset capacitor 131'which can discharge through the load reactor winding 129 is dependent upon the impedance presented by the saturable reactor winding 127 to the flow of said discharging current therethrough. Since the impedance presented to current flow through the winding 127 is variable inversely with the magnitude of Vthe signal supplied to the windings 128, and the signal supplied by the Voltage comparing circuit lli to amplifying circuit 121 varies inversely with variations in the sampled voltage, 'if the voltage supplied to the storage capacitor 84 exceeds the desired predetermined voltage, the impedance to current dow through the saturablereactor load winding 127 is correspondingly increased. This causes a greater percentage of the stored energy in the reset capacitor 131 to discharge through the load reactor control winding 129,

thereby increasing the degree of resetting of the` iron ofV the load reactor core and correspondingly increasingrthe impedance presented to the next direct current pulse through the load reactor load winding 132.

n The increase in impedence to current iow through the load winding 132 of the load reactor reduces the current ow into the storage capacitor 84 on the next succeeding pulse such that the recharge current is less than the drain of the voltage sampling network112 until the charge lin Y the capacitor 84 decays to the predetermined desired value.

succeeding current pulse through the load reactor load i' winding l132', less'impedance is present to the dow thereof, and the Voltage to which the storage capacitor 84 is subjected is returned to the predetermined desired value.

With the improved circuitry just described, the voltage to which the storage capacitor 84 is subjected can be maintained Within i2% of t'ne predetermined desired voltage, in spite of voltage changes at a normally 115 volt source 76 of from 105 in 125 volts. Similar control is possible where the source 76 is normallyof 20() volts.

Variations in graphic originals, for example as between black and white and colored, or variations in the types of heat-sensitive copying papers used necessitate the provision of means for adjusting the energy level of the radiation pulse produced by the lamp 35. Copying of a black and white original, for example, takes less radiation than does copying an original including other colors. Manual adjustment of the energy level of radiation available from the lamp 35 is afforded by a rotary knob 139 on the front of the casing 5 (see FIGURE 1) directly controlling the adjustment of the potentiometer 11S in the voltage sampling circuit 112. By this adjustment, the sampledV Voltage suppled to the voltage comparing circuit 119 through conductors 117 and 118 is a largeror smaller fraction of the total voltage impressed upon the storage capacitor 84. Since` the voltage control means supplies impedance to the charging circuit as required to maintain the voltage impressed on the capacitor 84 at a value such Ithat the sampled voltage substantially matches the stable reference voltage, -Aadjustment of the potentiometer 115 by rotation* of the knob 139 adjusts the voltage at the storage capacitor 84- to a new level which is automatically maintained by said voltage control means.

Having thus described the structure and organization of thermoprinting apparatus illustrating one specilic embodiment of the presentinvention, it is to be understood `that the iliustrated form was selected to facilitate the disclosure of the invention, rather than to limit the number of forms which it may assume. Various modifications, adaptations, and alterations may `be applied to the speciiic form shown to meet the requirements of practice without in any manner departing from the spirit or scope ofY theV present invention, and all of such modifications, adaptations, and alterations are contemplated as may come within the scope of the appended claims.

What is claimed as the invention is:

l. A machine for reproducing graphic originals, comprising means deiining an inlet, an outlet and a copy station,'means for conveying a composite of a graphic original and a copy sheet from said inlet through said copy station toward said outlet, means for irradiating a composite at said copy station, said irradiating means comprising a flash lamp, capacitor means in a circuit with said lamp, a charging circuit for storing energy in said capacitor means, and means for discharging the stored energy through said lamp including a triggering switch, a power cut-ot switch in said charging circuit, switch actuating cam means, drive means `tending to rotate said cam means in one direction, electro-responsive cam K locking means operable to prevent rotation oi said cam means beyond a given position, power switch-activating shoulder means on said cam means positioned to actuate said power switch to power cut-ott position at a predetermined short time interval prior to said cam means reaching said given position, said shoulder means holding said switch in said power cut-oit position until said cam means is rotated beyond said given position following subsequent release by said cam locking means, trigger switch actuating shoulder means on said cam means positioned to actuate said trigger kswitch after actuation of said power cut-ofi switch by its actuating shoulder means and momentarily preceding disposition of said cam means in said given position, and time delay switch means having a member positioned at said inlet for actuation by in- Y sertion of a composite, said last mentioned switch means being connected to etect, on actuation of said member, a release of said cam locking means for rotation of said cam means by its said drive means, said rotation of said cam means affording cycling actuation of said trigger switch and correspondinggeneration of radiation pulses by said flash lamp in timed relation to the advance of said sneetjes composite through said copy station for irradiation of successive longitudinal areas of said composite, said time delay switch means being operable, after a predetermined time interval following disengagement of the trailing edge of said composite from said member, to render said cam locking means operative to prevent rotation of said cam means beyond said given position, the disposition of said cut-oli and trigger switch actuating shoulder means insuring interruption of said charging circuit and discharge of said capacitor means when said cam means is in said given position.

2. A machine for reproducing graphic originals, comprising means defining an inlet, an outlet and a copy station, means for conveying a composite of a graphic original and a copy sheet from said inlet through said copy station toward said outlet, motor drive means for said conveyor means, means for irradiating a composite at said copy station, said irradiating means comprising a flash lamp, capacitor means in circuit with said lamp, a charging circuit for storing energy in said capacitor means, and means for discharging the stored energy through said lamp including a triggering switch, a power cut-oliC switch in said charging circuit, switch actuating cam means having a frictional drive connection with said motor drive means tending to rotate said cam means in one direction therewith, lirst shoulder means on said cam means, electroresponsive cam locking means having a detent member biased toward an obstructing position in which it is engageable by said lirst shoulder means to prevent rotation of said cam means beyond a given position and cause slipping of said frictional drive connection, second shoulder means on said cam means positioned to actuate said power switch to power cut-oft position at a predetermined short time interval prior to said cam means reaching said given position, said second shoulder means holding said switch in said power cut-off position until said cam means is rotated beyond said given position following subsequent release by said cam locking means, third shoulder means on said cam means positioned to aotuate said trigger switch after actuation of said power cut-01T switch by said second shoulder means and momentarily preceding disposition of said cam means in said given position, and time delay switch means having a member positioned at said inlet for actuation by insertion of a composite, said last mentioned switch means being connected to effect, on actuation of said member, energization of said electroresponsive cam locking means for movement of said detent toward a non-obstructing position releasing said cam v means for rotation by said motor drive means, said rotation of said cam means affording cycling actuation of said trigger switch and corresponding generation or radiation pulses by said tlash lamp in timed relation to the advance of said composite through said copy station for irradiation of successive longitudinal areas of said composite, said time delay switch means being operable, after a predetermined time interval following disengagement of Ithe trailing edge of said composite from said member, to deenergize said cam locking means for return of said detent to said obstructing position, the disposition of said second and third shoulder means insuring interruption of said charging circuit and Vdischarge of said capacitor means when said cam means is in said given position.

3. In a machine for reproducing graphic originals, having means dening an arcuately-shaped copy station and having means for positioning a composite of a graphic original and a heat-sensitive copy sheet in copyingvposition at said copy station, the combination of: means disposed coaxially with said copy-station for subjecting said composite while at said copy station to a brief radiation pulse, said means comprising an hermetically sealed envelope formed with an elongated transparent tubular main body portion having a capillary bore, electrodes within said envelope at opposite ends of said bore, and an ionizable iluid within said envelope; and means in circuit with said electrodes for impressing a predetermined Voltage thereon to produce a radiation pulse; the reduced diameter of said `capillary bore causing, for a given peak current and pulse length,the radiation pulse thus produced to be richer in shorter wavelength rays than said pulse would be if said bore were of larger diameter.

4. In a machine for reproducing graphic originals, the combination with means dening a copy station and means for positioning a composite of a graphic original and a heat-sensitive copy sheet in copying position at said copy station, of means for subjecting said composite while at said copy station to a brief radiation pulse, said means comprising an hermetically sealed envelope formed with an elongated transparent tubular main body portion having a bore not substantially larger than 2 millimeters, electrodes within said envelope at opposite ends of said bore, an ionizable fluid Within said envelope, and means in circuit with said electrodes for impressing a predetermined voltage thereon to produce a radiation pulse, the reduced diameter of said bore causing, for a given peak current and pulse length, the radiation pulse thus produced to be richer in shorter wavelength rays than said pulse would be if said bore were ol larger diameter.

5. In a machine for reproducing graphic originals, the combination with means deiining a copy station and means for positioning a composite of a graphic original and a heat-sensitive copy sheet in copying position at said copy station, of means for subjecting said composite while at said copy station to a brief radiation pulse of given peak intensity and duration, said means comprising at least one ash lamp including an hermetically sealed envelope formed with an elongated transparent tubular main body portion having a capillary bore, capacitor means in circuit with said lamp for storage of electrical energy for discharge through said lamp, and means for charging said capacitor means, the reduced diameter or" said capillary bore affording, on discharge of said lamp, a radiation pulse of lengthened duration and reduced peak intensity for a given voltage charge in said capacitor means, Wherefore a radiation pulse of said given peak intensity and duration can be generated by said lamp when the capacitance of said capacitor means is reduced and the voltage of the electrical charge stored therein by said charging means is increased as compared respectively with the values of said capacitance and voltage required to produce a radiation pulse of said given peak intensity and duration if said dash Vlamp had a larger bore.

6. In a machine for reproducing graphic originals, the combination with means deining a copy station and means for positioning a composite of a graphic original and a heat-sensitive copy sheet in copying position at said copy station, of means for subjecting said composite while at said copy station to be a brief radiation pulse of given peak intensity and duration, said means comprising at least one ash lamp including au hermetically sealed envelope formed with an elongated transparent tubular main body portion having a bore diameter of the order of 2 millimeters, capacitor means in circuit with said lamp for storage of electrical energy for discharge through said lamp, and means for charging said capacitor means, the reduced diameter of said bore affording, on discharge of said lamp, a radiation pulse of lengthened duration and reduced peak intensity for a given voltage charge in said capacitor means, wherefore a radiation pulse of said given peak intensity and duration can be generated by said lamp when the capacitance of said capacitor means is reduced and the voltage of the electrical charge stored therein by said charging means is increased as compared respectively with the values of said capacitance and voltage required to produce a radiation-pulse of said given peak intensity and duration if said flash lamp had a larger bore.

7. In a machine for reproducing graphic originals, the combination with a transparent tubular copy roll and means for positioning a composite of a graphie original and a heat-sensitive copy sheet in copying position in pressure contact with the periphery of said copy roll, of means for uniformly subjecting said composite while in said copying position to a brief radiation pulse of given peak vintensity and duration, said means comprising a Hash lamp'including an hermetically sealed envelope formed with an elongated transparent tubular cylindrical main body portion 'having a capillary bore and extending coaxially within said copy roll, capacitor means in circuit with said lamp for storage of electrical energy for discharge through said lamp, and means for charging said capacitor means, the reduced diameter of said capillary bore affording, on `discharge of said lamp, a radiation pulseof lengthened duration and reduced peak intensity for a given voltage charge in said capacitor means, wherefore a radiation pulse of saidV given peak 15 intensity and duration can be generated by said lamp when the capacitance of said capacitor means is reduced Y 's" and the voltage of the electrical charge stored therein by said charging means is increased as compared respectively with the values of said capacitance and voltage required to produce a radiation pulse of said given peak intensity and duration if said flash lamp had a larger bore.

References Cited in the lile of this patent UNITED STATES PATENTS 10 2,181,879 Edgerton Dec. 5, 1939y 2,517,031v v Rochester Aug. 1, 1950 2,844,733 Miller et al. July 22,` 1958 2,891,165 Kuhrmeyer et al June 16, 1959 2,927,210 OMara fMar. l, 1960 3,012,141 Thomiszer Dec. 5, 1961 3,065,667 Edgerton Nov. 27, 1962

Claims

1. A MACHINE FOR REPRODUCING GRAPHIC ORIGINALS, COMPRISING MEANS DEFINING AN INLET, AND OUTLET AND A COPY STATION, MEANS FOR CONVEYING A COMPOSITE OF A GRAPHIC ORIGINAL AND A COPY SHEET FROM SAID INLET THROUGH SAID COPY STATION TOWARD SAID OUTLET, MEANS FOR IRRADIATING A COMPOSITE AT SAID COPY STATION, SAID IRRADIATING MEANS COMPRISING A FLASH LAMP, CAPACITOR MEANS IN A CIRCUIT WITH SAID LAMP, A CHARGING CIRCUIT FOR STORING ENERGY IN SAID CAPACITOR MEANS, AND MEANS FOR DISCHARGING THE STORED ENERGY THROUGH SAID LAMP INCLUDING A TRIGGERING SWITCH, A POWER CUT-OFF SWITCH IN SAID CHARGING CIRCUIT, SWITCH ACTUATING CAM MEANS, DRIVE MEANS TENDING TO ROTATE SAID CAM MEANS IN ONE DIRECTION, ELCTRO-RESPONSIVE CAM LOCKING MEANS OPERABLE TO PREVENT ROTATION OF SAID CAM MEANS BEYOND A GIVEN POSITION, POWER SWITCH-ACTIVATING SHOULDER MEANS ON SAID CAM MEANS POSITIONED TO ACTUATE SAID POWER SWITCH TO POWER CUT-OFF POSITION AT A PREDETERMINED SHORT TIME INTERVAL PRIOR TO SAID CAM MEANS REACHING SAID GIVEN POSITION, SAID SHOULDER MEANS HOLDING SAID SWITCH IN SAID POWER CUT-OFF POSITION UNTIL SAID CAM MEANS IS ROTATED BEYOND SAID GIVEN POSITION FOLLOWING SUBSEQUENT RELEASE BY SAID CAM LOCKING MEANS, TRIGGER SWITCH ACTUATING SHOULDER MEANS ON SAID CAM MEANS POSITIONED TO ACTUATE SAID TRIGGER SWITCH AFTER ACTUATION OF SAID POWER CUT-OFF SWITCH BY ITS ACTUATING SHOULDER MEANS AND MOMENTARILY PRECEDING DISPOSITION OF SAID CAM MEANS IN SAID GIVEN POSITION, AND TIME DELAY SWITCH MEANS HAVING A MEMBER POSITIONED AT SAID INLET FOR ACTUATION BY INSERTION OF A COMPOSITE, SAID LAST MENTIONED SWITCH MEANS BEING CONNECTED TO EFFECT, ON ACTUATION OF SAID MEMBER, A RELEASE OF SAID CAM LOCKING MEANS FOR ROTATION OF SAID CAM MEANS BY ITS SAID DRIVE MEANS, SAID ROTATION OF SAID CAM MEANS AFFORDING CYCLING ACTUATION OF SAID TRIGGER SWITCH AND CORRESPONDING GENERATION OF RADIATION PULSES BY SAID FLASH LAMP IN TIMED RELATION TO THE ADVANCE OF SAID COMPOSITE THROUGH SAID COPY STATION FOR IRRADIATION OF SUCCESSIVE LONGITUDINAL AREAS OF SAID COMPOSITE, SAID TIME DELAY SWITCH MEANS BEING OPERABLE, AFTER A PREDETERMINED TIME INTERVAL FOLLOWING DISENGAGEMENT OF THE TRAILING EDGE OF SAID COMPOSITE FROM SAID MEMBER, TO RENDER SAID CAM LOCKING MEANS OPERATIVE TO PREVENT ROTATION OF SAID CAM MEANS BEYOND SAID GIVEN POSITION, THE DISPOSITION OF SAID CUT-OFF AND TRIGGER SWITCH ACTUATING SHOULDER MEANS INSURING INTERRUPTION OF SAID CHARGING CIRCUIT AND DISCHARGE OF SAID CAPACITOR MEANS WHEN SAID CAM MEANS IS IN SAID GIVEN POSITION.

3. IN A MACHINE FOR REPRODUCING GRAPHIC ORIGINALS, HAVING MEANS DEFINING AN ARCUATELY-SHAPED COPY STATION AND HAVING MEANS FOR POSITIONING A COMPOSITE OF A GRAPHIC ORIGINAL AND A HEAT-SENSITIVE COPY SHEET IN COPYING POSITION AT SAID COPY STATION, THE COMBINATION OF: MEANS DISPOSED COAXIALLY WITH SAID COPY-STATION FOR SUBJECTING SAID COMPOSITE WHILE AT SAID COPY STATION TO A BRIEF RADIATION PULSE,SAID MEANS COMPRISING AN HERMETICALLY SEALED ENVELOPE FORMED WITH AN ELONGATED TRANSPARENT TUBULAR MAIN BODY PORTION HAVING A CAPILLARY BOR, ELECTRODES WITHIN SAID EVELOPE AT OPPOSITE ENDS OF SAID BORE, AND AN IONIZABLE FLUID WITHIN SAID ENVELOPE; AND MEANS IN CIRCUIT WITH SAID ELECTRODES FOR IMPRESSING A PREDETERMINED VOLTAGE THEREON TO PRODUCE A RADIATION PULSE; THE REDUCED DIAMETER OF SAID CAPILLARY BORE CAUSING, FOR A GIVEN PEAK CURRENT AND PULSE LENGTH, THE RADIATION PULSE THUS PRODUCED TO BE RICHER IN SHORTER WAVELENGTH RAYS THAN SAID PULSE WOULD BE IF SAID BORE WERE OF LARGER DIAMETER.