USRE16567E

USRE16567E - Machine for making offset press plates

Info

Publication number: USRE16567E
Authority: US
Publication date: 1927-03-08

Description

March 8, 1927.

A. T. KOPPE MACHINEI FOR MAKING OFFSET PRESS PLATES Original Filed June 1922 11 She nets-Sheet 1 Ilium 77. r 654 2:: 7'17 l gb ve March 8, 1927.

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UNITED STATES Re 16,557 PATENT OFFICE.

ALEXANDER KOPPE, OF CHICAGO, ILLINOIS, ASSIGNOR, BY MESN'E ASSIGNMENTS, T0 DIRECTOPLATE CORPORATION, A CORPORATION OF ILLINOIS.

MACHINE FOR MAKING OFFSET PRESS PLATES.

Original No. 1,510,007, dated September 30,1924, Serial No. 572,054, filed June 30, 1922. Application for reissue filed September 25, 1926. Serial No. 137,787.

The invention relates to photographic-machines for making ofl'set press plates from negatives carried by a frame, which frame may be quickly and accurately positioned at manner that the press plate may be substantially entirely covered withimages from the negative. The machine is particularly adapted for use in connection with a pressure frame of the type shown in Patent No. 1,396,962, issued November 15, 1921, on the application of Alexander T. Koppel,

A further object is to provide amachine for. making ofi'set press plates constructed 1 in such a manner that a negative on which a vision is disposed may be accurately po-' sit-ioned at predetermined points above a sensitized piece'of zinc used in the usual printing process, and the vision on the negative reproduced on'the press plate.

A further object is to mount the negative in a pressure frame disposed above the press plate and carried by a carriage longitudinally movable over the press plate and trans- -versely movable on the carriage, said carriage being controllable in its longitudinal movement in such a manner that it may be accurately positioned and the pressure frame provided with means whereby itmay be accurately positioned transversely on the carria e.

A further object is to provide curtains connected to the carriage whereby the por tion of thepress plate, which is not protected from the light rays by the carriage and pressure frame or disposed beneath the negative will be protected from the light. The" pressure frame has connected thereto curtains which will protect the press .plate from the light when-the pressure, frame is moved transversely of the machine A further object is to provide means whereby when the carriage or pressure frame is being moved it will be raised out of engagement with the press plate, thereby preplatel A' further object is to provide the machine with a bed plate on which is stretched a rubber sheet on which the press plate is disposed and stretched, said rubbersheet forming means whereby the sensitized press-plate. which isformed preferably from zinc, w ill closely engage the negative and conform .to

tact between the negative and press plate, thereby allowing the entire surface of the press plate to be utilized.

- A further object is to provide clamping means for holding the endsof the press plate, and means whereby said press plate may be stretched or drawn taut -on, the rubber sheet. Also to provide lever controlled sprocket and chain means for moving the carriage longitudinally and dial means whereby the distanceof movement may be accurately gauged.

A further object is to provide means whereby the spaced blocks forming the carriages at opposite sides of the machine may be spaced apart at various distances, thereby spacing the lifting bars and pressure frame supporting bars in such a manner that various sizes of pressure frames may be supported on the carriage.

With the above and other objects in view the invention resides in the combination and arrangement of parts as hereinafter set forth, shown in the drawings, described and claimed, it being understood that changes in the precise embodimentof the invention may be made within the scope of what is claimed without departing from the spirit of the invention.

In the drawings, Figure 1 is a top plan view of the left hand side of the machlnej Fig. 2 is a top plan view of the right hand side of the machine; Fig. 3 is a front elevation'of the machine; Fig. 1 is an end view of the machine; Fig. 5 is a vertical transverse sectional view through the machine taken on line 5--5 of Fig. 1; Fig. 6 is a vertical transverse sectional view through the machine taken on line 6-6 of Figure 2 and showing the carriage and pressure frame in section; Fig. 7 is 'an enlarged detail sectional View vtaken on line 7-7 of Fig. 3; Fig. 8 is an enlarged detail. sectional view tion of the carriage in section, and showing the pressure frame; Fig. 9 is a vertical transverse sectional view through one side of the machine taken on line 9-9 of Fig. 3; Fig. 10 is a vertical detail sectional View through one side of the machine and one of the side blocks of the carriage taken on line 10-10 of Fig. 3; Fig. 11 is an enlarged plan view of the left front corner of the machine;

Fig. 12 is a sectional view taken on line 1212 of Fig. 11; Fig. 13 is a plan view of the frame of the machine, portions of the carriage and controlling shafting, the bed plate and adjacent mechanism being eliminated to better show the structure; Fig. 14: is a detail sectional view taken on line 1414 of Fig. 2 and showing the carriage at the right handside of the machine; Fig. 15 is a top plan view of the central carriage block and adjacent parts; Fig. 16 is a front eleva-v tion of the dial and controlling lever; Fig.

17 is an enlarged plan view of a portion of one of the. side carriage blocks, showing means for attaching a curtain thereto and a hinged shield for extending under the pressure frame; Fig. 18 isa sectional view taken on line 18-18 of Fig. 17; Fig. 19 is a sectional view taken on line 1919 of Fig. 17; Fig. 20 is a top plan view of the pressure frame showing the same mounted on carriage guide bars and portions of screening curtains; Fig. 21 is a transverse sectional view taken on line 2121 of Fig. 20.

. Referring to the drawings the numeral 1 designates the frame of the machine and2 the end members thereof. The end members 2 are connected together by means of the horizontally disposed bed plates 3 on which bed plate a rubber blanket 4 is disposed. The press plate 5 which is shown in Figure 7 rests on the blanket', and is only shown in Figures 5 and 7, being eliminated in other figures for purposes of clearness. The rubber blanket is secured at one end 6 to the bed plate 3 and at its other end is wound around a roller 7, which roller is mounted in bearings of the end members 2 of the frame and is provided with a worm gear 8, with which a worm 9 engages, said worm 9 beingcarried by a shaft 10 extending through the front of the machine and adapted to receive a crank, by means of which crank the roller 7 may be rotated and theblanket 4 drawn taut I for closely engaging the bed plate 3. One

end of the press plate 5 is clamped between bar .17 which has a sliding connection 18 with one side of the bed'plate 3. Threaded through the adjustable bar 17 are adjusting screws 19, the inner ends of which cooperate with the edge-of the bed plate 3 in such amanner that, when the adjusting screws are tightened, the press plate 5 will be drawn perfectly flat and smooth upon the rubber blanket 4, said blanket being slightly yieldable under pressure so that when the negative 20 is forced into contact with the press plate 5 by the vacuum pressure frame 21 through the means hereinafter set forth, the glass negative 20 and press plate will accommodate themselves to each other and perfect contact be obtained; Glass negative plates-are sometimes slightly warped or are thicker atpne portion than another, hence the provision of the rubber blanket to overcome these variations and also to prevent breakage of the negative incident to theabove irregularities. The vacuum pressure frame 21 is carried by a carriage 22 extend ing transversely across the machine above the bed plate, said carriage being adapted to be moved longitudinally over the bedplate and the vacuum frame to be manually moved transversely over the bed plate. Any

kind of light may be disposed'above the machine for supplylng the necessary li ht rays above the negative, no light being s own in the drawings forpurposesofclearness.

The negative 20 bearing an impression" which is to be reproduced on the sensitized i zinc plate 5, is carried by the vacuum frame 21 and mounted directly in the auxiliary negative frame 21 (see Figure 21) in which it is held by clamping plates 21 and adjust ing screws 21, as shown-in Fig. 20. The vacuum frame 21 has an annular inwardly projecting flange 21 adapted .to receive the overlying outwardly extending flange of the negative frame, as shown in Fig. 21- and the negative frame is positioned on the vacuum frame by means of pins 21 extending upwardly from the flanges 21 and engaging apertures in the outer flanges of the nega tive framev on opposite sides thereof. The under side of the vacuum frame 21 is recessed upwardly from its outer edge to receive an annular rectangular sealing ring 21 of rubber orother compressible material which is secured in position to' form, the outer wall of the annular air channel 21' from which the air may! be exhausted through a pipe as shown in my prior patent ab'overeferred to. When the vacuum frame 21 is lowered, the lower sealing ring 21' engages the upper surface of the sensitized plate 5 to form an air-tight seal around the lateral edges of the vacuum frame, and the passage of air through the spaces around the negative and around the auxiliary negalar sealing ring 21 of rectangular form the negative and thepress plate is drawn into the channel 21 and exhausted through the pipe, so that a vacuum is produced between the negative and the sensitized sheet with the result that the negative is forced by atmospheric pressure into close contact with the sensitized sheet, thus producing a close contact adapted for the reproduction of the impression ofthe negative on the sensitized plate when the negative is exposed to a suitable source of light mounted above,

the machine.

In order that a, vacuum may be obtained and a close contact between the negative and press plate secured when the vacuum frame 21 is projected beyond the edges of the bed plate. at the front and rear sides of surface of the the machine, auxiliary sealing plates 23 are provided to act as continuations of the top ress plate. These sealing plates 23 extend chine at each side of the bed plate and are pivotally connected at 24-to the ends 2 of the frame, and after the press-plate has been inserted as above described, they are turned downwardly to the horizontal positions shownin Figures 7 and 8 with their ends 25 in engagement with the press plate, thereby forming a substantially air tight seal. The sealing plates 23 when thus closed have their upper surfaces in substantially the same horizontal plane as the top surface of the'press plate and it is obvious that when the vacuum pressure frame 21 is adjacent one of the sides of the press plate 5, the frame ma engage one of the sealing plates 23 in sue a manner that it is positioned beyond the marginal edge of the press plate while at the same time sealing the under side of the. overlapping portion of the vacuum frame so that an efiective vacuum is maintained for securing a close contact. of the negative and press plate-and obtainof the ends 2 of the frame and are provided by means of which the shafts 29 ma -with worm gears 27 (see Figs. 1 and 3) with which worms 28 carried by shafts 29 engage, said shafts being adapted to receive, on their rectangular shaped ends 30, cranks be rotated and the edges 25 of the sealing p ates 23 may be forcedinto close and binding engagementwith the edges of the press plate, thereby forming substantially air tight enlongitudinallyof the ma-' gagement which will not interfere with the operation of the vacuum pressure frame 21.

Disposed at the front and rear sides of the machine are track ways 31, on which track ways the ca-rriage 22 is slidably mounted in such a manner that the carriage may be positioned in various positions longitudinally above the bed .plate and the press plate carried thereby, thereby allowing the negative carrying frame and vacuum.

pressure frame 21 to be positioned longitudinally as desired. Disposed in opposite relation on said track ways are substantiall identical carriage blocks 32 consisting each of a center block 33 andside blocks 34, each set of blocks being connected together by a plate 35 tomove in unison. Each plate 35 is provided with aseries of notches 36 equidistant from the center of the connected middle block 33. The middle block is provided with a threaded pin 37 having threaded thereon a thumb nut 38, which thumb nut serves to clamp the plate 35 to the middle block 33. The side blocks 34 are provided with threaded pins 39 having thumbs nuts 40, which threaded pins are adapted to be received by any of the series 7 of notches'36 in the upper edge of the plate. By providing the pin and notch connections, it will be seen that the side blocks 34 of each carriage block may be positioned at different distances apart for readily locating the lifting bars 41, which connect the oppositely disposed blocks 34 together, at different distances apart' for cooperating with vacuum pressure frames of different widths, or for positioning said frames, which are usually oblong in form, lengthwise instead of crosswise in relation to the machine. v

The lift bars-.41 are rovided on their under sides at their en s with vertically disposed notches 42 which receive pins 43 carried by the side blocks 34, thereby permitting the lift bars 41 to be moved vertically, the me chanism for moving said bars vertically being hereinafter set forth The side blocks 34 are also connected together by bars 44, which bars are provided on their outer edges with accurately machined teeth 45 corresponding with the graduated mark ings 46 thereon. The bars 44, Figure 20, slidably support manually shiftable positioning blocks 47, which blocks comprise the frame supporting members 48 and the barpengaging members 49, the

members

48 and 49 of each block being adjustble in relation to each other by means of he thumb nut 50, thereby allowing said members to be accurately positioned in relation to each other and permitting the frame supporting lugs 51 carried. by the members 48 to be centered in relation to the graduated markings 46. The negative carrying frame 21 is provided with apertures 52 for the reception of the pins 51, which pin and aperture connec tion permlts the negative carrying vacuum frame to be posit oned accurately and readtermined position.

ily removed and also permits a limited up ward movement of the frame to accommo. date the lifting movements of the bars 41 as hereinafter described, without detaching the frame 21 from the pins 51. Each bar engaging member 49 is provided with a spring actuated detent 53, which is forced inwardly by means of the spring 54 and en'- gages the teeth 47 of the guide'bar 44, these teeth as well as the graduated markings on the bar being observable through the openings 55 in the slidable member 49 so that the point to which the blocks 47 and the nega-' tive carrying frame are to be shifted transversely of the machine may be easily seen and the blocks and frame quickly and accurately positioned. The .lifting' bars '41- support and carry the negative carrying vacuum frame 21 by engaging the L-shaped arms 56 carried by the frame only during the period when a shift of the carriage is made or when the negative carrying frame is being shifted transversely on the carriage, said lifting bars being raised slightly as will presently appear, to raise the negative carrying frame 21 out of contact with the press. plate so the negative and its frame will be clear of and prevented from scratching or damaging the sensitized surface of the press plate 5 in the shifting of the vacuum pressure frame and negative to a new position.

Before describing the mechanism by which the lifting bars 41 are elevated, the operation of the means for adjusting the carriage to locate the negative in different ositions over the surface-of the sensitized p ate will be explained. Assuming that twelve prints are to be made on the same press plate 5, and three rows of four prints each, the first row would be made lengthwise of the machine, proceeding from the left toward the right, as viewed in Fig. 1, the spacing between the prints and the corresponding posi tions of the carriage having beendetermined and accomplished by means of the mechanism hereinafter set forth. The negative carrying frame is then shifted on the carriage 22 transversely of the machine to the predetermined point for the next row, and the carriage is returned to the starting point at the left end of the machine and another row of prints is made by moving the carriage toward the right to successive prede- The same procedure is followed for the third row of prints thereby printing three successive rows of prlnts each of which is definitely. located on the surface of the sensitized plate. The front and rear frame members 31 of the machine have journaled therein two transverse shafts58 and 60 which are located inwardly from the end frame members The shaft 60 has fixed thereon two-sprocket gears 61 located at the front and rear sides of the machine to be engaged by endless sprocket chains 62. The

endless sprocket chains 62 also pass around other sprocket gears 59 which are loosely mounted on the shaft 58 at the front and rear ends thereof. The forward end of the shaft 60 is provided with a squared portion adapted to be engaged by a crank 63 and the cha1ns'62 are connected at 64 with the middle blocks 33 of the carriage frames 32 so that when the shaft 60 is rotated by the crank 63, the movement of the chains serves to effect a movement of the carriage 22toof a lever or carriage s ifting crank 57' which is keyed'on' the outer end o'f-that shaft. The extent of the feeding movement is determined by means of a dial 7 6, this dial and a ratchet wheel 99 being supported by, and mounted for rotation on, a sleeve 103,which is keyed in a stationary position with respect to a'fixed bracket 108 and which is rotatably engaged by the shaft 58, as

shown particulraly in Fig. 8. The dial 76 and the ratchet wheel 99 are separated by a flange 104 which is formed on the sleeve 103, and the ratchet wheel is retained in position on the outer end of the sleeve by means of a plate 109 secured to the end of the sleeve. The motion of the crank or lever 57 is transmitted to the ratchet wheel 99 by a pawl 98' which is fixed on the lever as shown in Fig. 16. The reverse rotation of the ratchet wheel is normally prevented by another pawl or detent 98 which is mounted on the dial 76. The dial is normally locked against rotation on the sleeve 103 by means of a clutch member 106 formed on the dial and engaging the clutch member 107 formed in the fixed bracket 108. These clutch members are forced into and outof engagement withe'ach other by a locking lever 105 which is threaded on the sleeve 103 on the inner side of the bracket 108- and on the inner side of the frame member which carries the longitudinal scale 101 by means of which the longitudinal position of the carriage 22 is determined. The carriage 22 is provided with a pointer 102 adapted to move in proximity'to the scale 101 and, before the carriage 22 is adjusted longitudinally of the machine toward the right, the looking-lever 105 is operated to release the clutch members 106 and 107 and the dial 76 is then rotated until the desired graduation thereon is brought into position opposite the graduation on the stationary stop member 100 which is carried by the lower end of the bracket 108, this setting of the dial having been predetermined by reference to the scale 101 and the pointer 102. The locking lever 105 is then operated to lock th'dial 76 in adjusted position and the stop 95 adjacent the zero graduation on the dial 76 will then be located properly to limit the throw of the crank or lever 57 -at a point corresponding to the limit of the desired movement of the ratchet wheel 99 and the carriage 22.

The rotation of the shaft 58 by the operation of the crank 57 serves to effect a longitudinal movement of the carriage 22, toward the'right, as viewed in Figs. 1 and 2, through the operation of pinions 7 3 which are keyed on the shaft 58 at the front and rear ends thereof and which mesh with the teeth 68 of rack bars 67 mounted for move- -ment longitudinally of the frame 30 and having connection with thecarriage 22, as hereinafter described. The front and rear frame members 31 of the machine are provided on their inner sides with shoulders 65 extending the full length thereof and having V-shaped grooves 66 formed therein, as shown in- Figs. 10. and 14. Each rack bar 67 is mounted to. slide on a shoulder 65 and is provided on its inner side. with a V-shaped rib 70 adapted to engage one of the V-shaped grooves 66. On its upperside, each rack barr67 is provided with ratchet teeth 69 located opposite to the rack teeth 68 which mesh with the pinions 73. The rack bars 67 are held in sliding engagement with the grooves 66 by means of spring plates 71 secured to the frame members 31 by means of bolts 72, as shown particularly in Figs. 7 and 14. These spring plates 71 serve to hold the rack bars 67 in position and at the same time permit the rack bars to be shifted longitudinally of the machine by means of the carriage shift lever or crank 57 and the pinions 73 on the shaft 58 which is rotated by said lever.. In Fig. 14, the rack bar 67 is shown shifted to the end of its limit at the right end of the machine, this figure .of the drawings showing the parts viewed outwardly from the inner part of the machine. Each middle block 33 of the carriage carries two pivoted pawls 74 which are normally pressed into engagement with the ratchet teeth 69 by means of leaf springs 83. The ends of the pawls 74 engage the ratchet teeth 69 of the adjacent rack bar 67 and these teeth 69 are spaced apart onesixteenthof an inch, for example, to correspond with the one-sixteenth inch graduations 75 on the face of the dial 76. These dial graduations appear in Fig. 16 to be a greater distance apart than the teeth 69 because of their distance from the shaft 58. g

cams 84 which are 'splined on the longitu dinal shafts 82 and which are adapted to contact with the projecting extremities 85 of the cam levers, as shown particularly in Fig. 14. The cam shafts 82 extend longitudinally of the machine at the front and rear sides thereof within the frame members 31 and they are actuated by a transverse shaft connected by worms and worm wheels 81 with the shafts 82, as shown in Fig. 13. The shaft 80 is in turn actuated by a longitudinal shaft 78 with which it is connected by the beveled gears 79 and this shaft 78 extends through one end frame 2, as shown in Fig. 13, where it is engaged by the rela-- tively fixed actuating lever 77 mounted for angular movement adjacent a stationary quadrant secured to the end of the machine, as illustrated in Fig. 4. When the lever 77 is in the neutral position illustrated by full lines in Fig. 4, the detents 74 are moved out of engagement with the ratchet teeth v69 against the pressure of the springs 83, thereby permitting 'the carriage 22 to be withdrawn toward the left, as viewed in Fig. 1, by the operation of the crank 63. When the lever 77 is rocked in one direction or the, other from the neutral position, as hereriage in that position after it has been shifted. This mechanism comprises'a pair of longitudinall extending toothed bars 86 having accurate y machined teeth which are adapted to be engaged b carried by the center bloc s33 of the carriage,- as shown particularly in Fig. 15. These detents are spring-actuated and have accurately machined V-shaped

points

87 and 87 which are normally out ofengagement with the; toothed bars 86 but which are adapted to be moved into engagement therewith by means of the

cams

88 and 89 WlllCll are splmed on the shafts 82 adjacent the cams 84. All of these cams-84, 88 and 89 are located between arms of the carriage blocks 33 so that they move longitudinally of the machine with the carriage by reason the detents 87 of their splined connection with the shafts 82. Two of the

detents

88 and 89 are pro.- vided for each shaft 82' so that one detent of each pair will engage the adjacent toothed bar 86, dependin upon the position of the lever 77 by whic ,the angular positions of the shafts 82 are controlled. The teeth ofthe

detents

88 and 89 areso arranged that one of them will engage the adjacent toothed bar 86 at either a one-sixteenthror a oneeighth inch movement of the carriage 22, to correspond with the action of the pawls 74 by which the feeding movement of the ,carrla e is effected through the motion of the rac bars 67 The angular movement of the shafts 82, efiectedby the actuation of the lever 77, is also utilized to elevate the lifting bars 41 of the carriage 22. This lifting movement is effected by means of four cams 90,-one of which is splined on one of theshafts 82 be:

- the lifting bars 41, coil springs may preferalbly be mounted on the plungers 91 between the upper sides of the carriage blocks 34 and the heads 93, asshown in Fig. 14. The cams are mounted to move longitudinally of the shafts 82 when the carriage 22 is shifted longitudinally of the frame. For this purpose, the cams 90 have collars 90 which are adapted to fit over projections 203 formed on the under sides of the carriage blocks 34, as shown in Fig. 14, the cams being retained in position with respect to these carriage block members by means of pins 205 which are actuated by springs 206 to occupy the normal positions illustrated in Fig. 14 wherein the lower ends thereof en age the annular grooves 204 formed in t e cam projections 90. The annulargrooves 204 permit the cams to rotate and at the same time retain them in proper position beneath the plungers 91. When all of the cams 90 are simultaneously actuated by the turning of the shafts 82, the lifting bars 41 of the carriage 22 are elevated and the vacuum frame 21 is raised until all parts of the vacuum frame and parts carried thereby are out of engagement'with the surface of the press plate 5, thereby permlttlng the carriage 22 to be shiftedfrom one POSI- tion to another and permitting the vacuum frame to be shifted in its position on the carriage while supported by the lifting bars, without causing injury to the surface of the press plate. When the vacuum frame is elevated by the operation of the earns 90, the pins 51 retain their engagement with the holes in the vacuum frame, as heretofore indicated, so that the vacuum frame moves with the carriage in its adjustment or may be moved on the bars 41 by the movement of the positioning blocks 48 longitudinally on the side carriage bars 44. When the lever 77 is in the neutral position s'hownby full lines in Fig; 4, the longitudinal shafts 82 are in such positions that the lifting bars 41 are elevatedby the cams 90, the

carriage locking detents

88 and 89 are out of engagement with the toothed bars 86, and the pawls 74 are out of engagement with the ratchet teeth 69 on the rack bars 67, so that the carriage 22 can be moved to the starting point at the left-hand end of the machine, as viewed in Fig. 1, by means of the crank 63 on the outer end of the shaft 60. When the lever 77 is moved to either of the intermediate posi-.

tions, indicated by the numeral 94 in Fig. 4 of the drawings, the carriage feeding'pawls 74 are movedinto engagement with the a ratchet teeth of the rack bar 67, but the carriage locking and

positioning detents

88 and 89 are still held out of engagement with the toothed bars 86, and the cams 90 are still in such positions that they hold the lifting bars 41 in their elevated positions, so that, with the lever 77 in either of the intermediate positions referred to, the carriage 22 can be given a feeding movement toward the right, as viewed in Fig. 1, by the acuation of the lever or crank 57. The feeding movement, of the carriage 22 takes place through a predetermineddistance according to the previous setting of the dial 76 and its stop 95. When the carriage 22 has been shifted to the predetermined position, a full throw of the lever 77 to one ofthe extreme positions 96 or 97, shown in Fig. 4, will cause one of the detents 88-0189 of each setof detents to engage certain notches of thetoothed bars 86, thereby locking the carriage 22 positively at a certain graduation depending upon the previous. setting of the dial and at the same time effecting a final positioning movement of the carriage so that it is seenrately located in the predetermined position. The position of the lever 77 indicated by the numeral 96 in Fig. 4'corresponds to the operation of the detents for a one-eighth inch graduation on the dial, and the lever position-'97 shown in Fig. 4 corresponds to a onesixteenth inch setting on the dial. The angular movement of the. shafts 82 by turning the lever 77 to either of the positions 96 or 97 also operates to turn the cams 90 so that the lifting bars 41 are free to move downwardly by gravity and thereby permitthe vacuum frame 21 to lower until its lower sealing ring comes into contact with the press plate. After the sealing ring engages side curtains .111.

the press plate the operation" of the vacuum system will exhaust the air from the region between the nega-tiye and the press plate and produce a close contact between them in readiness for exposure to the source of light.

The locking

detents

88 and 89 are accurately machined and cooperate with the toothed bars 86 with such precision that the slightest lost motion in the caniage feeding means willdie corrected by the wedge-shaped ends of the detents as they are forced into engagement with the teeth of the bar, thereby causing the carriage to be moved into the precise position required by the setting of the dial. Exact equal spacing movements of the carriage for corresponding settings of the dial are thushobtained and a positive locking of the carriage is obtained at the same-time.

When the lever 57 is moved in the direction of the arrows a in Fig. 16, the spring pawls 98 engage the ratchet wheel 99 and cause this wheel to rotate until the lever 57 engages the stop 95, at which time the lever returns to the step 100, the return movement of the lever not causing a rotation of the ratchet wheel 99 so that the carriage may be intermittently moved toward the right to various predetermined positions corresponding to the desired predetermined positionsof the negative over the press plate as determined by the scale 101 and the pointer 102.

Since the source of light is located above and separately from the machine, it is necessary to provide means for protecting from the light rays those portions of the press" plate which are not disposed below the vacuum pressure frame or below the negative during the time that the negative-is being exposed and also during the move ments of the carriage and vacuum frame in case the light is inoperation during those movements. For this purpose of protecting the sensitizedpress plate from the action of light, curtains are employed. These curtains include two end curtains 110 and two These curtains windon self-winding spring rollers 112 which are carried by the end members of the frame 2 and by rollers 113 carried by the central blocks 33 of the carriage as shown in Fig. 1. The curtains 110'pass downwardly and inwardlv over guide rollers 114 and are attached to the undersides of L-shaped metal members llz'j shown in Figs. 17 to 19 inclusive. 'The L-shaped members are provided with hinged plates 116 and end blocks 117,

' which .end blocks are provided with "spring pressed pins 118 adapted to engage the annular: grooves 119 of pins 120 extending fromthe sides of the side blocks 31 of the carriage. These curtains are as wide as the bed plate 3 and the hinged plates 116 thereof are adapted to extend beneath the tooth cross bars 44 of the carriage andin close relation to the underside thereof thereby. excluding light rays from the sensitized press-plates as shown in Fig. 7. The curtains automatically wind on conventional forms of rollers, such for instance as window shade rollers and wind up and follow the carriage as it is shifted longitudinally of the machine. The curtains are detachable from the carriage blocks by simply raising the spring pressed pins 118, the members or blocks 117 sliding on rods 121 extending from end to end of the machine 1 to hold the freed ends of the curtains off of the press plate 5 when applying or detaching the same from'the carriage, it being necessary to detach the curtains, as it is n ecessar to remove the cross members of the carnage when applying or removing the press plate from the machine. The hinged. plates 116 may be swung to an upright position as shown by dotted lines in Figure 18 when the curtains are detached and curtains wound on their rollers in order that the sealing plates 23 may be raised and lowered without interference from adjacent mechanism.

The side curtains 111 extend upwardly and inwardly over the guide rollers 122 and are provided at their ends with L-shaped plates 123 which carry looped members 124 which engage over pins 125 on the negative carrying frame, and which also wind and unwind as said frame is shifted transversely of the machine. All four curtains have a marginal overlapping relation so as to exclude light from the sensitized press plate 5 not covered by the negative in the shifting operation of the latter. The ends of these curtains are also easily detachable from the vacuum pressure frame.

loo

- From the above it will be seen that an' offset press plate machine is provided, which is simple in construction, positive in its operation, and one wherein a vacuum pressure frame may be accurately positioned at predetermined positions abovea press plate, then moved into engagementwith the press plate. locked to position until after the printing operation, then raised out of en gagement and moved to a new position. It will also be seen that by providing the sealingbars the entire surface of the press plate 5 may be utilized.

Iclaim: 1. The combination with the bed plate of a machine for photographically preparing ofi'set press plates, of a resilient blanket 2. The combination with a bed plate'of a 'machine for photographically preparing press plates, of a resilient blanket extend lng over said bed plate, and means operable lfor stretching and holding -said blanket no i whereby it will closely engage the bed plate.

3. The combination with the bed plate of a machine for photographically preparing press plates, of a resilient blanket covering said bed plate, one end of said blanket being.

a -machine for photographically preparing press plates, said bed plate being adapted to vreceive a sensitized press plate, amovable negative carrying frame disposed above the bed plate and press plates, of adjustable means cooperating with the ends of the press plate whereby said negative carrying frame may be positioned beyond the end of the press pla K 5. The combination with the bed plate of a machine for photographically preparing press plates, said bed plate being adapted to receive a press plate, a negative carrying frame disposed above the bed plate, of sealing bars disposed adjacent the ends of the bed plate and adapted to engage the ends of the press plate and form an extended base for the negative carrying frame.

6. The combination with the bed-plate of a machine for photographically preparing press plates, said-bed plate being adapted to receive a press late, a movable negative carrying frame isposed above the bed plate, of pivoted sealing bars'adjacent the ends of the bed plate and forming means whereby the side of the negative carrying frame may be disposed beyond the ends of the press plate carried by the bed plate.

7. The combination with the bed plate of I a machine for photographically preparin press plates, said bed p ate being adapte to receive a press plate, a negative carrying frame disposed above the bed plate, of a sealin bar disposed adjacent the end of the bed plate and engagin the end of the press plate and forming a hase for a portion of the negative carrying frame.

8. The combination with the bed plate of a machine for photographically preparing press plates, said bed plate being adapted to receive a press late, a movable negative carrying frame isposed above the bed plate, of a pivoted sealing bar adjacent the ends of the bed plate and adapted to have its free end engage the end of the press plate thereby allowing a portion of the negative carrying frame to be disposed beyond the edge of the press plate.

9. The combination with the bed plate of a machine for photographically preparing press plates, said bed plate being adapted to receive a press plate, a movable negative carrying frame disposed above the bed plate, of. pivoted sealing bars disposed adjacent the ends of the bed plate, the free ends of said bars coo crating with the press plate to form a su stantially airtight seal and support the negative carrying frame beyond the ends of the press plate, and means whereby said sealing bars may be simultaneously controlled.

10. The combination with abed plate of a ,machine for photographically preparing press plates, said bed plate being adapted to receive a press plate, a movable negative earrying frame disposed above the bed plate, of pivoted sealing bars disposed adjacen the free endslof the bed plate and cooperating with the press plate and support the negative carrying frame beyond the ends of the press plate, and means whereby said sealing bars may be controlled in their pivotal movement.

11. The combination with a bed plate of a machine for photographically preparing press plates, said bed plate beingadapted to receive a press plate, a'movable negative carrying frame disposed above the bed plate, of pivoted sealing bars disposed adjacent the free ends of the bed plate and cooperating with the press plate and support the negative carrying frame beyond the ends of the press plate, and shaft and gear means whereby said sealing bars may .be controlled in their pivotal movement.

12. The combination with a bed plate a machine for photogra hioally preparing press plates, said bed p 'ate being adapted to receive a press plate, a movable negative carrying frame disposed above the bed late, of pivoted sealin bars disposed adacent the free ends of t e bed plate and cooperating with the press plate and support the negative carrying frame beyond the ends of the press late, and shaft and gear means whereby saitFsealing bars may be simultaneously moved into and out of engagement with the press plate.

13. A machine for photographically preparing oflset press plates including a base to support a'sensitized press plate, a carriage disposed above the base, said carriage being movable towards opposite sides of the machine, a negative carrying frame carried 14. The combination with a machine for photographically preparing offset press plates, said machine comprising a bed plate for the reception of a press plate, a carriage movable abovethe bed plate, a negative carrying frame movable on the carriage at an angle to the direction of movement of the carriage, of curtains attached to and controlled by said carriage and frame whereby the sensitizedplate which is not'exposed to the negative will be covered.

15. The'combinationwith a machine for photographically preparing offset press plates, said machine comprising a bed plate for the reception of a press plate, a. carriage movable adjacent said press plate, of curtains for protecting the unexposed'portion of the press. plate, a negative carrying frame carried by said carriage, said curtains having their free ends connected to the-carriage and controlled by the movement thereof.

. 16. The combination with a machine for photographically preparing offset press plates, said machine comprising a bed plate for the reception of a press plate, a carriage movable above the bed plate, a negative carrying frame movable on the carriage, of curtains carried adjacent the sides of the machine, the free ends of opposite curtains being connected to the carriage, the free ends of the other opposite curtains being connected to the negative carrying frame, whereby the movement'of said carriage and frame controls the movement of theecurtains. I 17 The combination with a machine for photographically preparing offset press plates, said machine comprising a bed plate for the reception of a press plate, a carriage movable above the bed plate, curtains car ried at the opposite sides of the machine, the free ends of said curtains being detachably connected to the carriage and the movement of the carriage controlling the movement of the curtains. v

18? The combination with a machine for photographically preparing offset press plates, said machine comprising a bed plate for the reception of the press plate, a carriage movable above the bed plate, curtains carried at opposite sides of the machine, said curtains having their free ends detachably connected'to the carriage, and hinged extension members carried by the free ends of the curtains and underlying the opposite sides of the carriage. r

19. The combination with a machine for photographically preparing plates, said machine comprising a bed plate for the reception of a press plate, a carriage movable above said bed plate, a negative carrying frame movable on the carriage at an. angle to the direction of movement of the carriage,'-of roller carried curtains at the opposite sides of the machine, the .free ends of opposite curtains being detachably connected to the carriage and the free ends of the other oppositely disposed curtainsbeing detachably connected to the negative carrying frame and means cooperating with the rollers for winding up the curtains whereby the curtains play vout and wind up under movement of said carriage and frame.

offset press 20. The combination with amachine for photographically preparing offset press plates, said machine comprising a bed plate for the reception of a press plate, ofa carriage carried by said machine for supporting a negative carrying frame, of means for adjusting the distance between the carriage members bearing the negative carrying frame, whereby different sizes of negative carrying frames may be supported by. said carriage.

21. The combination with a machine for photographically preparing offset press plates, said machine comprising a bed plate for the reception of a press plate, of a carriage movable on said machine above the bed plate, said carriage comprising spaced supporting blocks mounted on trackways,

bars connecting opposite blocks, means for supporting a negative carrymg frame on said bars and means whereby said blocks may be adjusted in'relation to each other whereby different sizes of negative carrying frames may be received.

22. The combination with a machine for photographically preparing offset press plates, said machine comprising a bed plate for the reception of a press plate, of a car riage carried by saidimachine above the bed plates, of a negative carrying frame carriage for said machine, said carriage being provided with means for varying the dimensions thereof whereby negative carrying frames of different size may be received.

24.'The combination with a machine for photographically preparing offset press plates, of a negative carrying frame carmounted on trackways at opposite sides of the machine, the ends of the carriage being formed from spaced blocks, connecting bars between the block s at each end of the carriage, means whereby said blocks may be adjusted towards and away from each other, negative frame supporting bars connecting the end blocks together and extending across riage for said machine, said carriage being the machine, and means whereby the negative carrying frame may be positioned on the carriage at apredetermined point. 1

25. The combination with the bed plate of a machine for photographically preparing'press plates, said bed plate having a IBSlhQIIt blanket thereon, of means for bolding a press plate in'close engagement with the blanket, said means comprlsmg a clamp-