US2007571A - Offset printer - Google Patents

Description

`Ju19,193 5@ T. wjHoRN 2,007,571

OFFSET PRINTER Filed April 1.5, 1953 5 sheets-sheet 1 July 9; 1935.

T. w. HORN OFFSET PRINTER Filed April i5, 1933 5 Sheets-Sheet 2 Arroz/vers July 9- 1935- T. w. HORN 2,007,57

OFFSET PRINTER Filed April 15, 1933 5 Sheets-Shea?l 3 M25/vrai? Fia/ms Mair/w me, wif/zw F76.' *9 Arroz/vins July 9, 1935. T. w. HORN 2,007,571

' OFFSET PRINTER Filed April l5, 1935 5 Sheets-Shea?l 4 T. w, HORN OFFSET PRINTER July 9, 1935.

Filed April l5. 1935 5 Sheets-Sheet 5 .fm Maf/:a

Patented July 9, 1935 l.UNITED STATES PATENT orrlcE f 2,007,571 OFFSET PRINTER Thomas Walter Horn, University Heights, Ohio Application April 15, 1933, Serial No. 666,298l

14 Claims.v (Cl. 1111-218) This invention relates to improvements in offset printing machines, particularly units foroflset printing whichl are so designed and constructed as to be capable of `being mounted in a known stencil printing machine in place of the cylinder Uli of that machine, so that by having interchangeable stencil and roffset printing units, either type of printing may be performed at different times upon a singlemachine. The invention in many oi' its aspects, however, is capable of general application.

One of the objects of the invention is the provision of an oset printing machine of simple construction which may be manufactured at low cost.

Another object is the provision of a unit of the character described which may be readily substituted for a portion of a known stencil printing machine, the remaining portions ofthe stencil printing machine being utilized, in connection with the substituted unit, for performing offset printing.

Another object is the provisioniof an offset printing machine capable of using dry ink, that is ink which, because of .its chemical constituents,

s is capable ci absorbing the necessary moisture from the atmosphere.

Another object of the invention is the provision of a novel mechanism for inking the plate upon the plate cylinder, and locating that mechanism within the hollow blanket cylinder, means being provided for disabling the inking mechanism while the two cylinders are in engagement for transferring an image from the plate cylinder to the blankety cylinder.

Another object is the-provision of means for supplying moist air continuously to the ink on the inking mechanism.

Still another object is the provision of throwout means for the plate cylinder, which shall be automatically operated when `a lever is moved from one position to another, such lever being so `located in the special embodiment of the invention hereinillustrated as to be operated by sheet l detector mechanism employed in the stencil machine with which the present invention is primarily intended to be used.

A further object of the invention is the provision. of a printingv plate with novel reenforcements at its ends and a novel and simple means for clamping the plate and drawing it taut over the surface of the plate cylinder.

Other objects and features of novelty will appearl as I proceedwith the description of that embodiment ofthe invention which, for the purposes of the presentl application, I have illustrated in the accompanying drawings, in which Fig. l is a View, principally in longitudinal vertical section, of a printing unit embodyingv the invention.

Fig. 2 is a transverse vertical sectional view taken substantiallylalong the line 2-2 of Fig. 1.

Fig. 3 is a side elevational view of the unit.

Fig. 4 is a detail sectional View taken substantially along the line --4 of Fig. 3. 10 Fig. 5 is a transverse sectional view of the plate cylinder, showing the means which I employ for securing the ends of the plate and stretching it over the surface of the plate cylinder.

Fig. 6 is a detail sectional View, taken substantially on the line 6-6 of Fig. 4, illustrating a part of the plate cylinder throw-oli mechanism.

Fig. '7 is a View similar to Fig. 1, but showing the cylinders in a different position, with the inking mechanism withdrawn out of contact with the plate cylinder, and with the impression cylinder withdrawnl from printing position.

Fig. 8 is a detail elevational View showing a ratchet mechanism for advancing the fountain roll rotatably step by step. .25

Fig. 9 is a detail elevational View showing adjustable means for varying thesize of the exit from the moisture dispensing container.

Figs. 10,'11 and 12 are detail views of the links which carry the inking rolls. 30

Fig. 13 is a ragmental detail sectional view on a larger scale, showing a portion of the inking mechanism, this view being taken substantially on the line lS-IS of Fig. 1.

Fig. 14 is a detail View of the same taken sub- 35 stantially on the line lll-t4 of Fig. 13.

Fig. 15 is a further fragmental sectional View taken substantially on the line l5-l5 of Figs. l and 14.

Fig. 16 is a fragmental sectional View taken 40 upon the same section line as Fig. 4, but showing the plate cylinder in the throw-off position, that is separated from the blanket cylinder.

Fig. 17 is a fragmental side view similar to Fig.

3, showing the throw-off control mechanism in the position which it occupies when the plate cylinder is separated from the blanket cylinder.

Fig. 18 is a vertical sectional view showing in elevation the means which I employ for moving the oscillating rolls of the inking mechanism, and

Fig. 19 is a View illustrating a modiiied form of unit for use with ordinary lithographie ink.

In the drawings, I have represented in dotted lines a portion or a stencil printing machine I0, comprising'side,standards Il. An example cfa 55 machine of this character, with which my unit may be employed, is disclosed more or less in detail in Patent 1,140,883, issued May 25, i915 to A. B. Dick. The stencil cylinder ordinarily used with the machine is mounted in the standards I I, those standards having bearings I2 within which the shaft of such cylinder rotates. The stencil printing machine, as illustrated herein, also comprises a rubber-'covered impression roller I3, mounted at its ends in a pair of levers I4, which are pivotally supported in the machine frame at I5, and are urged toward printing position by coil springs I6 or the like. One or both of the arms I4 may carry an anti-friction wheel I1 for a purpose later to be described.

When the stencil cylinder of the stencil printing machine has been removed from the bearings I2, an operation which can be readily and quickly performed, the unit constituting my invention may be substituted. This unit comprises a frame having end members I8 and I9 of disc form and a transverse member connecting the end members, said transverse member consisting of flat end pieces 2G and l secured to the members I8 and I9 respectively, a transverse vertical rib E2, a. tray 23 and a sump 24 into which liquid is directed from the tray through the intermediacy of an inclined central trough 25. A threaded plug '26 at the bottom of the sump may be removed when required for clean-out purposes. At the centers of the end members I8 and I9 of the frame there are outwardly extending hubs 21 and 28 respectively. On the outer sides of these hubs I secure exterior frame members 29 and 30, the member 29 being held in place by a hollow nut 3'I with a flange which engages the outer surface of the member 2S, and the member 38 being held in place by a flanged pin 32 which is threaded into the hub 28. Cylindrical supporting elements 33 and 34 with outer knurled heads are projected through the bearings I2 and threaded tightly into threaded openings in the hollow nut 3| and pin 32, whereby the frame of the unit is clamped rigidly in place in the standards Il. It will be apparent from an inspection or" the drawings that the center of gravity of the unit frame is well below the axis of the aligned supporting elements 33 and 3,4, and hence the force of gravity tends to maintain the frame parts of the unit in the positions in which they are disclosed in the drawings, and thereby reduces the work to be done by the threaded supporting elements 33 and 34 in holding the frame against rotation in the standards I I.

Upon the hubs 21 and 28, between the inner and outer frame members, I mount rotatably my hollow `blanket cylinder 35. This cylinder comprises end members 36 and 31 and the arcuate shaped casting 38, the latter having a series of `inwardly extending iins or vanes 39. On the end Imember 31 there is a V-pulley 40 by means of which the cylinder may be power driven. It will be understood, however, that some convenient 4means for driving the cylinder by hand may be substituted if desired, or that any other suitable power means may be employed.

`On the outside of the casting 38 there is secured a blanket 4I, which may be of the usual rubber with fabric backing construction, and which may be secured to the casting in any convenient or known manner. A semi-cylindrical guard plate 42 of sheet metal may be mounted upon the .transverse members of .the frame, so as to define with thecasting 38 an arcuate air passage. The vanes 38 moving through that .passage produce a current of air for a purpose which will presently appear.

In the outer frame members 29 and 30 I mount rotatably a plate cylinder 43, which is so positioned as to cause an offset printing plate 44 mounted thereon to contact with the blanket 4I for the purpose of transferring an image from the plate to the blanket. The plate cylinder comprises end members 45 and 46 and a cylindrical member v41, the latter having therein a longitudinal depression 48. Within this depression I mount a bar 49 upon pivots 50 in the end members 45 and 46. Adjacent one side of the recess 48 I form a shallow rabbet 5I in the cylindrical 'member 41, and I form a similar rabbet 52 in the outer face of bar 49. Reenforcements 53 on the ends of the printing plate 44 are received within the rabbets 5I and 52. These reenforcements extend along the end edges of the plate, and are flat, lying directly adjacent one surface of the plate. A reenforcement of this kind is a new departure in the art, and has the distinct advantage that it does not interfere with the ling of the plates in a flat condition. Preferably the reenforcements are formed by bending the metal of the flexible plate upon itself one or more times. The reenforcements are held in the rabbets 5I and 52 by means of clamps 54 and 55, the clamp 54 being mounted upon pivots 55 in the end members of the cylinder, and the clamp 55 being mounted upon pivots 51 carried by the bar 49. 58 are split ring springs positioned in annular recesses at the ends of the cylinder, and bearing upon the inner arms of the clamps 54 and 55, whereby the outer ends of those clamps are swung into clamping position, and whereby the bar 43 with its clamp is swung about its pivot 50 toward the right in Fig. 5, thereby drawing the iiexible plate 44 taut over the surface of the cylinder member 41. the drawings as of square cross section. This construction of plate and arrangement of plate securing and tensioning means permits quick and easy mounting or demounting of the plate, that is to say, a screw-driver or similar tool may be thrust into the space between the clamps 54 and 55 and given a turn to swing the inner arms of the clamps away from each other, thereby swinging the outer arms of the clamps outward and permitting the plate reenforcements to be withdrawn from the rabbets 5I and 52, and the plate removed. When a new plate is to be mounted, the screw-driver or similar tool is operated in the same way, one end reenforcement is inserted into the rabbet 5I, the plate is drawn around the cylf inder, and the other end reenforcement placed in the rabbet 52,` after which the screw-driver is withdrawn and the springs 58 act to clamp the plate reenforcements and draw the plate taut.

Inking mechanism.-The inking mechanism is carried by the end plates lI8 and I9 of the frame, being located within the hollow blanket cylinder, thus utilizing space which would otherwise be wasted. This location of the inking mechanism within the blanket cylinder has the additional advantages of concealing the inking mechanism and protecting the clothing of the operator, as Well as providing a nearly closed space within which a special atmosphere with the desired moisture conditions may be maintained, this being highly desirable for the dry ink which I prefer to employ.

59 is a fountain roll which is rotatably mounted in the end plates I8 and I9. Adjacent this roll there isa plate '60, .the free edge of which runs The springs 58 are shown in Vwith `more or less force upon the cam'surface at the end of the plate, to flex the latter in order `that the amount of ink taken 'up by the roll 59 Vmay be controlled.` This roll at one end carries a ratchet wheel 63 y(Figs. 2 and 8). The roll shaft extends `through the end plate I9 of the frame and carries a crank 64 upon the extremity of .which there is a follower 55 and a pawl 66. Upon `the end member 31 of the blanket cylinder there is a cam 61 lupon which the follower 65 runs. The follower 65 and the pawl 66 are carried upon cppsite'endsof a pin 68 at the end of crank 64,

`the pawl on the inner side and the follower on thel outer side of frame member |9,.and the lat- `ter is provided with an arcuate slot 69 for the `accommodation of the pin 68.

It will be `obvious `that whenthe cam 61 engages the follower 65, the crank 64 is-swung upwardly and the pawl 66 is thereby caused to rotate the ratchet wheel 63,

fand with itthe roll 59, through a small angle.

The extentof this rotation may be adjustably regulated by means known in the art, as for instance by employing a guard plate over which the pawl 66 may be caused to run through part of -itsf stroke. 1

` `The ductor roll of the inking mechanism is 'shown at 18. links 1I (see Fig. 10) pivoted at 12 to the frame This roll is mounted in a pair of end members. The roll 10 turns upon a shaft which is mounted at 13 in these links. The links 1| may swing between the positions shown in Figs. 1 and 7. VA second pair of links 14, Fig.` 12, mounted in the frameend members about pivot points 15, carry pairs of guides 16 betweenlwhich `the flattened ends of a shaft 11 are mounted. An

inking roll 18 turns upon this shaft. l In the links The links 14 have formed therein arcuate slots 8|) within which run rollers or other followers 8| carried at 82 in the links 1I. The slots 80,\being eccentric to the pivot points 15, it will be apparent that, as the links 14 swing from the position shown in Fig. 1 to that showniin Fig. 7, the followers 8| 'w` l be drawn to the right and downward, thereby swinging the links 1I downward tothe position indicated in Fig. 7, and pullingthe doctor roll 10 out of contact with the fountain roll 59 and into Contact with the roll 18.

` There is a third pair of links 82, Fig. l1, pivotlallyniounted at 83 in the` frame end members. At

the points `84m their lower extremities these ilinks carry a rod 85, see particularlyFigs. 13, 14:` and l5, having a flat intermediate portion and cylindrical end portions. Y The links 82 have bosses 89 around the openings 84, which bosses 'extend through slots 81 in fthe frame end plates I8 and I9. Outside of the end plate I9, a wide faced gear '90 is mounted to rotate upon the cylindrical por- ,l

tionof rod 85, while beyond the gear v9|! there is an anti-friction roller 9 I. A similar roller is mounted to turn upon the opposite end of the rod 85, and these two rollers run in cam grooves 92 in the end members 36 and 31 ofthe blanket cylinder.

"Consequently, `as the cylinder revolves the cam` "slots cause the*y bosses 85 on the links 82 to move Y inwardly and outwardly in the slots 81 of the frame members. VIn the end `member I36 of the Ablanket cylinder directly adjacentthe cam groove 92, I mounta toothed rack 93 with which the gear .98 meshes. Accordingly, as `the blanket cylinder revolves and the rod 85 moves inwardlyfand outwardly, the'gear 98. carried by the rod rotates. v

Threeinking rolls 94, 95 and 96 are carried swings upon the two links 82 and 14, and its motion is suchthatit remains at all times parallel to a givcnplane or line, owing to the fact that Vthe distance betweenthe pivot point of the `link 82 and the connection of the rail therewith is the same as the distance between the pivot point of link `I4 and the connectionof the rail therewith. These rails carry three pairs of guides 99, and IBI, within` which slide the flatted ends of shafts |82, |69 and |64 upon which the rolls 94,95 and 96 respectively revolve. l 1

Upon the outer ends of rails 91 there are mounted yokes |85 which are adjustable to a slight extent longitudinally of the rails by means of adjusting screws |86.. Each of vthese yokes is formed at its ends with journals |91 in which shafts |88 are mounted for both longitudinal and rotational movement. Fixed tothe shafts |88 are `extends an arm I i2 of a'rocking yoke, see Fig. 18.

This yoke comprises a circular member I I3 which is mounted tolrock on a pair of trunnions I I4 that are carried by brackets` I I6 mounted in the frame end plate I9. On a diameter at right angles to the axis of trunnions I4 `a pair of anti-friction rollers `VI I1 are carried by the yoke, and these rollers run upon a cam I I8 which forms an integral part of the end plate 31l of the blanket cylinder. Accordingly, as the vcam II8 revolves with the blanket cylinder, it causes the yoke ||3 to oscillate upon its trunnions IIII. The yoke arms IIZ therefore move the shafts |08 back and forth longitudinally in `opposite directions, giving to the rolls |99 an oscillating motion, while they rotate, due to the rotation of gear 99.

l The oscillating rolls |99 have frictional contact atall times with rolls 96 and 95, roll 96 being urged into engagement vby suitable spring means, such as is indicated at |19 in Fig. 14, and the three rolls` 18, 94 and-95 being pressed` into frictional contact with each other and with the rolls |89 by suitable spring means on the links 14, as

for instance the coil springs |28 anchored in the links and exerting a pull upon slide `blocks |2I. Because of such frictional contact, all of the `rolls 96, 95, 94 and `18 are driven from the rolls |89 at all times, and the roll 18. is driven from the roll 18 while those two rolls are in contact with each other. Consequently, 'inky taken by `the ductorv roll 1I] from the fountain roll 54 when the lparts are in the position of Fig. 1, is transferred to roll 18 when the parts are in the position of Fig. 1,

.and thence passes along rolls 94, 95 and |89 to roll 96. I

A To one side of 1 the inking mechanism I support upon the tray 23, a water reservoir |22from `which extends wicking or the like |23. Thisreser- Voir and the wickingprotruding therefrom.' are arranged tojbe exposed toa greateror ,lesser degree to theair circulating in the blanket cylinder by virtue of the movement of the vanes 39. Any suitable means for varying the degree of opening may be employed, but in Fig. 9 I have illustrated' for this purpose a flexible curtain |23 which extends over a pulley |24 and has a weight |25 tending to raise the curtain. The latter may be held in the desired position of adjustment by means of fastenings at its lower edge taking into selected ones of aseries of holes in the frame of the device, or in some part carried thereby.

Plate roll throw-01T.Referring now partcularly to Figs. 3, 4, 16 and 17, it may be assumed that the stencil printing machine with a portion of which the present invention may be used, is provided with means for holding the impression roller |3 out of operative position when no sheet isbeing fed. Such mechanism works in opposition to the springs I6, and holds the lever |4 down to the position indicated in Fig. 17 whenever a sheet of paper fails to enter the machine at the proper time. The lever |26 is a part of the mechanism above referred to, being pivoted at |21 and having its free end bearing upon the top of lever |4. The foregoing is a known construction, being illustrated and described in the Dick patent heretofore mentioned.

I mount upon the frame of my unit a lever |28, pivoted at |29, the free end of this lever resting upon the free end of lever |26 and following the movements thereof, due to the action of spring |30. Another lever I3| is also pivoted at |29, and tends to move with lever |28, except that it has the capacity for slight independent movement, owing to the fact that its normal engagement with lever |28 is through a pair of spring plungers |32. At its upper end the lever |'3| has a spear head |33. |34 is a pointed boss on the-blanket cylinder, which is adapted to engage the spear head of lever 3| upon one side or the other, depending upon the position of lever |28 and the corresponding position of lever |3|. The engagement ordinarily is merely enough to rock lever |3| through a slight angle against the action of the spring plungers |32, which immediately return it to its former position. On the external frame of the unit there is a channel guide |35 within which is mounted a slide |36. The spear head |33 projects into a cavity |31 in the rear face of the slide |30, which cavity is considerably Wider than the spear head in order to permit the normal oscillation of the lever |3|. The slide |36 has two positions, and it is held yieldably in either one of them by a spring detent |38 carriedrby the frame. which detent takes into either one of two sockets |39 inthe slide. |40 is a cylindrical rod which is xedly mounted in the frame members. It is surrounded by a sleeve 4| with an eccentric bore, and the plate cylinder 41 rotates upon this sleeve. At one end of the sleeve there is a gear |42 which meshes with a gear |43 of a diameter twice that of gear |42. The gear |43 turns upon a pin |44- which is fixed in the frame. On its inner side this gear |43 is provided with a series of four radial slots |45. In aligned holes in the ends 45 and 46 of the plate cylinder I mount a rod |46, which is urged toward the position of Fig. 4 by a coil spring |41, its movement in that direction being stopped by a pin |48. On the rear face of slide |36 there is a cam |49 which is adapted to engage the rod |46 and shift it longitudinally when the slide is in the proper position for that purpose. The blanket and plate cylinders are operatively connected by gears |50 tom of the tube |55.

cylinder.

and |5|`, which have a two to one ratio. The

teeth of the gears are long enough to permit the desired separation of the cylinders without going out of mesh. When the cam |48 is brought into operative position, the rotation of the plate cylinder causes the rod |46 to ride up onto the cam and forces the opposite end of the rod into one of the radial grooves |45. The rotation of the plate cylinder then causes the rod to turn gear |43 through an angle of 90, when the rod leaves the groove. This 90 rotation of gear |43 produces a 180 rotation of gear |42, and a similar rotation of eccentric sleeve |4|. The slide |36 carries two oppositely directed spring pressed detents |52 and |53. When the slide is shifted from the position of Fig. 4 to that of Fig. 16, detent |52 is withdrawn from a hole in sleeve |4|, and detent |53 is drawn into contact with the sleeve. As soon as the 180 rotation of the sleeve is completed, detent |53 snaps into the same hole and secures the sleeve against further rotation. When the movement of the slide is reversed the detent |53 is withdrawn and the detent |52 moves into contact with the sleeve ready to enter the hole as soon as the rotation of the sleeve is completed.

The position of the parts in Fig. 3 is that which they occupy during normal running. In Fig. 17 they are shown in the positions which they occupy when the plate cylinder is thrown out of engagement with the blanket cylinder, the lever |26 at this time being lowered below the position which it occupies in Fig. 3. 'I'he movement of lever |28 from one position to the other may of course be accomplished by hand, but it is primarily my intention to have this movement performed automatically whenever the lever |26 is raised or lowered in connection with a sheet detector mechanism of the paper feed, such as previously referred to. A latch |54 may be used to hold lever |28 in its raised position of Fig. 3, vthat is by swinging the handle of the latch to the right, as viewed in that figure, the lever |3| being thereby held in the position of Fig. 3, or the handle of latch |54 may be swung to the left until it engages and pushes the lever |3| to the left and holds it in the position of Fig. 17, the lever |28 being then held in its lowered position by the lever |3|. The latch |54 is intended for use only when the machine is being set up for a job of printing, or when it is being cleaned or the like.

For the convenient cleaning of the inking mechanism, the unit is So arranged that benzene or other cleaning fiuid may be poured yover the inking rolls, being then discharged into the tray 23, and iiowing thence through the trough 25 into thesump 24. A siphoning tube |55 extends from a position near the bottom of the sump upwardly into and through an opening |56 in the hub 28 of the end member I9 of the frame. Consequently, as soon as the level of the liquid in the sump and tray reaches the opening |56, the liquid will be siphoned out down to the bot- Any sludge that collects in the sump can be drawn off by removing the plug 26.

In Fig. 19 I have shown a modification wherein dampening rolls |51, |58 and |59 are mounted in the external frame members above the plate The rolls |58 and |59, which contact with the plate 44, may be felt-covered, and the roll |51 may be of brass. Such rolls may be employed in the event that ordinary lithographie ink is used, and the air moistening means herei movement of the vanos tofore described isomitt'ed. A small; amount of water poured -uponthe brass rollVv |151' is sufficient forfa considerablerung; if c i Operatio11,.--The `operation oflr the vunity in connection with a portion of the stencil yprinting machinelwithwhich the invention may be` employed,

:,willrbe largelyapparent romthe foregoing description'oi'` the nfiechanismfV When the operator desires vto employ theoffset printing unit, heremoves l the stencil cylinder' of vthe 1 machine, puts the unit inposition between "the standards li, inserts fthe supporting elements 33, and 3&3v through thebearings I2 inthestandards, and screws the supporting elements into theiramelhubs, therebyy fixing the unit in position.` Xhenl theprinting plate lili 'has been mounted upon the plate cylinder"andl`the, machine otherwise made ready for operation, the blanket cylinder ismrevolved by power Aor hand,-a`s" the case ymaybe,4fa'nd'the paper sheets fed through "the machinejinfa manner apparent to thoseskilled inthear't. -lnk is applied'to the plaite-llf7i bythe inkingr roll'ei during approximately one-halt :oi A the rotation of4 `the blanket cylinder. As theforward Aedge ofthe blanket 4| approaches the plate. cylinder the earn groove `QZyacts throughfanti-friction rollers 9| to carry rod; 5 inwardly,- thereby swinging links 82 and 'Mito the positions of Figp'l `andwithdrawing the rollfputofthe path of thecasting 3B land accompanyingnparts. Thisv motion of links lil pulls links 1| downwardly, bringing the two rolls 18 and lli intocontacuthereby rotating roll lll andfcausingthe ink thereupon to be wiped over the surface `enroll 13', bywhich it is transferred through the intermediate rolls to roll' Siti. Furtherrotation of the blanket y,and plate cylinders causes theinked imagevuponplate M'to be transferred to `blanket lilthisv operation being illustrated in Fig.` 7.` Asy the forward edge of the blanket approaches impression roller |3",fa sheet otpaper'is fed into position Iabove itheiinpression roller and the latter rises topress tl'ieA paper against fthev blanket for the printing. Voperationl A cam plate lton the blanket cylinder permits thespringslii toact at the' proper time. The

past thev opening in `thelmoistening apparatus |22. The air thereby moistenedflows 'over theinkfon `the inking rolls, particularly roll 95, enabling that ink. to; extract' the necessary moisture from the air. It will be apparent that the yoke mechanism, illustrated in Fig. 18 of the drawings, oscillates the rolls ille continuously, whether they are in the inner or outer position, the yrelation of the yoke arms to the shafts |08 when the rolls are withdrawn inwardly being indicated in dotted lines in Fig. 18. l

The operation will be continuous so long as sheets are properly fed to the machine. If there should be an interruption in the sheet feed, the

free end of lever |25 would drop and lever |28 would follow it. Lever |3l would then swing toward the left into the positionshown in Fig. 17.

The boss |34 upon its next approach would then move to the right of the spear head |33 and.`

shift the lever i3| to the left, carrying with it the slide |36 which moves far enough to permit spring detent itil to leave the lower one of sockets |39 and enter the upper one.` When this movement occurs, cam |48 is `brought into the path of rod M6, and causes the opposite end of the rod to engage with one of the radial grooves |45, operating as heretofore described to turn` eccentric sleeve |4| throughan angle oi 180, separating the plate cylinder from the blanket cyl- 39 carries a supply of air inder Awithout interrupting the geared travel of the platecylinder.l Theparts thereafter remain in the lposition of Fig'. 17 until the feed of sheets isresumed, whereupon the levers |26 and |28 rise againj to the positions shown in Fig. 3, causing the lever,A ISI to move back into the position of. that ligure. When the boss |311 on its next revolution approaches the spear head |33 it contacts the inner side oi the same and shifts the lever 13|- 'to theright, shifting the slide |36 accordingly, and causing the rod to ride over the ycam U39 so asto engage the next'radial groove illingear v|43 `and produce through the mechanism previously `descrlbedra second 180 rotation of sleeve lei, whereby the plate` cylinder is` returned-toengagement with the blanket cylinder and'the'transfer of the image to the blanket; is resumed. i

While I have described and illustrated my'invention as applied to a unit which may be inserted into `a known stencil printing machine, I'desire the .invention herein disclosed are vequally susceptible of application to complete oiiset printing machineshavingno mechanical connection with other printing machines of any character. i Having thus described myinventiom I claim:

l. In combination, a frame having aligned supporting elements adapted to be received in aligned bearings,a blanket cylinder mounted for` rotation upon said frame, means for Idriving said cylinder, and a plate cylinder carried by said frame in` position to cooperate with said blanket cylinder. V

2. In combination, a frame comprising end members, said end members having aligned supporting .elements adapted to be lreceived in aligned bearings, a blanket cylinder mounted upon said frame for rotation about an axis within said aligned supporting elements, andl a plate cylinder carried iby said frame in position to cooperate `with said4 blanket cylinder.

3; .In combination, va frame having aligned, d

supporting elements adapted to be received in aligned bearings, a hollow blanket cylinder surroundingv the `intermediate portion of said frame, the `said `blanket cylinderghaving rotative bearingsfwuponl :said aligned supporting elements, rameextensions outside of said blanket cylinder,- and a plate cylinder carried by said extensions in position to cooperate with said blanket cylinder.

4. In a unit for printing machines, a frame, means for supporting said frame exclusively comprising aligned supporting elements adapted to be received in aligned bearings, a hollow cylinder mounted for rotation upon said frame, means for driving said cylinder, a plate cylinder carried by said frame adapted to .contact with the said hollow cylinder intermittently, and inking mechanism also carried by said frame and adapted to apply ink to said plate cylinder while it is out of contact with the said hollow cylinder.

5. In combination, a frame having aligned cylindrical supporting elements adapted to be received in aligned bearings, the center of gravity of said frame lying below the axis of said aligned supporting elements, a hollow cylinder mounted upon said frame for rotation about said cylindrical supporting elements, and a plate cylinder carried by said frame exclusively and adapted to contact with the said hollow cylinder.

' 6. In combination, a frame comprising aligned horizontal supporting elements, aligned bearings carried by the frame, a hollow cylinder mounted to rotate upon said bearings, inking mechanism carried by said frame substantially within said hollow cylinder, a plate cylinder carried by said frame externally of said hollow cylinder, said hollow cylinder being open throughout a peripheral portion thereof, and means for causing said inking mechanism to apply ink to said plate cylinder through the opening in said hollow cylinder as the cylinders rotate.

Y 7. In combination, a frame comprising aligned horizontal supporting elements, aligned bearings carried by the frame, a hollow cylinder mounted to rotate upon said bearings, inklng mechanism carried by said'frame substantially within said hollow cylinder, said inking mechanism comprising an ink applying roller, a plate cylinder carried by said frame externally of said hollow cylinder, said hollow cylinder being open throughout a peripheral portion thereof, and means for projecting said ink applying roller into contact with said plate cylinder through said opening and for retracting said ink applying roller and holding it within the hollow cylinder while the latter is in contact with the plate cylinder.

8. In an offset printing machine, a frame having horizontally arranged aligned supporting elements, a hollow blanket cylinder rotatable about said supporting elements, inking mechanism p carried by said frame substantially within said hollow blanket cylinder, and an air moistener carried by said frame within the blanket cylinder.

9. In an oiset printing machine, a frame having horizontally arranged aligned supporting elements, a hollow blanket cylinder rotatable about said supporting elements, inking mechanism carried by said frame substantially within said hollow blanket cylinder, an air moistener carried by said frame within the blanket cylinder, and means for creating a draft ofair over said moistener and thence to said inklng mechanism.

l0. In an offset printing machine, a frame having horizontally arranged aligned supporting elements, a hollow blanket cylinder rotatable about said supporting elements, inking mechanism carried by said frame substantially within said hollow blanket cylinder, an air moistener carried by said frame within the blanket cylinder, and a plurality of vanes on the inner side of said blanket cylinder for creating a draft of air past said lrnoistener and over said inking mechanism.

11. In a printing machine, a hollow cylinder, a plate cylinder arranged for cooperative movement with said hollow cylinder, said hollow cylinder being open throughout a peripheral portion thereof, a xed frame within said hollow cylinder, inking mechanism carried by said trame, said mechanism comprising a series o1' rollers, means actuated by said rotating hollow cylinder for driving said rollers, and means for moving said rollers inwardly and outwardly to project the outermost roller through said opening into contact with said plate cylinder and to retract the said roller within the hollow cylinder while the latter is in contact with said plate cylinder.

12. In an offset printing machine, a frame having horizontally arranged aligned supporting elements, a hollow blanket cylinder rotatable about said supporting elements, said'frame intermediate the ends of the blanket cylinder comprising a tray and a sump in communication therewith, inklng mechanism carried Aby the frame above said tray, .and a siphoning tube extending from said sump'upwardly through one of said aligned supporting elements.

13. In an oil'set printing machine, a plate cylinder, an inking mechanism, a container therefor permitting the application of ink to said plate cylinder, and means for maintaining a substantially constant degree of humidity of the air within said container.

14. In a. printing machine, inklng mechanism, a frame upon which said mechanism is mounted, said frame having at the ends thereof two supporting elements arranged in alignment, a hollow cylinder rotatably mounted upon said supporting elements and sux-rounding said inking mechanism in the normal position of the latter, a printing plate adapted to move in printing relation with said cylinder, said hollow cylinder being open throughout a peripheral portion thereof, said inklng mechanism comprising an ink applying roller, and means for projecting said roller through said opening into contact with -said plate and for retracting said roller and holding it within the hollow cylinder while the latter is in contact with said plate.

THOMAS WALTER HORN.

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