US1866910A

US1866910A - Offset proof press

Info

Publication number: US1866910A
Application number: US346841A
Authority: US
Inventors: Hugo F Schmidt; Jung Louis
Original assignee: GUGLER LITHOCRAPHIC Co
Current assignee: GUGLER LITHOCRAPHIC Co
Priority date: 1929-03-14
Filing date: 1929-03-14
Publication date: 1932-07-12
Anticipated expiration: 1949-07-12

Description

July 12, 1932. H. F. SCHMIDT ET AL OFFSET PROOFPRESS Filed March 14, 1929 7 Sheets-Sheet l -wlmurnw July 12, 1932. H. F. SCHMIDT E'r AL OFFSET PROOF PRESS Filed March 14, 1929 7 Sheets-Sheet 2 dimmi* July 12, 1932. H F. SCHMIDT ET AL OFFSET PROOF PRESS Filed March 14, 1929 7 Sheets-Sheet 3 -WN ...wml

H. F. SCHMIDT ET AL- 1,866,910

OFFSET PROOF PRESS Filed March 14, 1929 7 Sheets-sheet 4 July l2, 1932.

July l2, 1932. HA F. SCHMIDT ET AL OFFSET PROOF PRES S 7 Sheets-Sheet 5 Filed MalOh 14. 1929 July 12, 1932. H. F. SCHMIDT E'r AL 1,865,910

OFFSET PROOF PRESS Filed March 14, 1929 7 Sheets-Sheet 6 July l2, 1932. I Hy F. SCHMIDT ET AL OFFSET PROOF PRESS Filea March 14, 1929 '7 Sheets-Sheet '7 WENN Patented July 12, 1932 rMen-r OFFICE HUGO F. SCHMIDT AND LOUIS JUNG, OF MILWAUKEE, WSCONSIN, ASSIGNORS TO GUGLER l'iTIG-RAFHC COMPANY, A CORPORATION OF TWISCOI\1S-3I1\T OFFSET PROOF PRESS Application led March 14, 1929. Serial No. 346,841.

This invention relates in general to printing presses and more particularly to an offset proof press of the type which includes a stationary bed and a reciprocable carriage movable back and forth along the bed and carrying a rotatable printing cylinder overlying the bed and geared to fixed racks thereon so that upon movement of the carriage in one direction the cylinder rolls over the bed and first takes an impression from a printing plate positioned on the bed and then transfers this impression to a sheet of paper held on another plate of the bed.

In all prior presses of this type considerable difiiculty has been encountered in producing high grade proofs, especially after the press has been in use for some time when, despite the exercise of care and expert skill in the operation of the press, more or less pronounced blurring or other distortion occurs in the proofs. These imperfections result largely from uncontrolled movements of the carriage and printing cylinder and although such movements are usually very slight they i are suflicient to impair the proofs. Such uncontrolled movements are due principally to back lash or lost motion in the gearing which drives the carriage and the printing cylinder and to consequent uneven application of the drive to the opposite sides of the carriage and to the opposite sides of theV printing cylinder whereby, during the printing run of the cylinder, it is slightly angled or twisted at different times, that is to say, one side of the.

cylinder Will lag slightly behind the other in one phase of the operation and perhaps advance ahead of the other in another phase of the operation. This, of course, impairs the proof as the offset printing operation in this type of machine requires that the aXis of the printing cylinder remain, during the entire printing run, at right angles to the longitudin al airis of the bed with uf'hich it has rolling contact. For the same reasons, with prio-r presses it has been difficult to obtain true registration in printing operations where successive imp 1essions are superimposed one on the other.

One of the principal objects of the present invention is to simplify the construction and operation of an odset proof press of this character while greatly improving the quality of the proofsproduced thereby, in that blurring or other distortion is precluded and true regis'tration is had. In brief, the present inven-A 55 tion avoids the bad effects of back lash, lost motion, excessive clearances, or the like, in the drive of the carriage in the printing cylinder, and so uniformly and evenly drives the printing cylinder as to cause it to remain in 50 proper relation to the printing bed during the printing run.

Another important object of the invention is to provide an offset proof press of this character which is durable in its construction and 05 which will retain its advantages even when it has been in use for some time.

A further object is to provide a press of this character and having these advantages and capacities and which is convenient and 70 safe in operation and easily manipulated to effect any of the desirable operations involved in the odset printing of proofs.

Other objects and advantages are to provide a press of compact construction in that 75 the floor space required is the very minimum in proportion to the printing size; to provide an entirely unobstructed printing bed as the grippers and registering devices incorporated in the bed are inverted and located S0 below the printing plane; to provide allaround accessibility to the blanket for cleaning or inspection since the cylinder is freely rotatable in one direction and without interfering with any of the other mecha- 35 nism of the press relative to its drivingmeans when it is positioned at either end of the press or at the center thereof; and to provide a press which minimizes the friction of all rotating parts by the use of roller bear- Q0 ings and which avoids the use of heavy machinery parts that must be moved whereby the motions and labor required of the operator are minimized, the impression time shortened, the speed increased, and the neces- Q0 sity of motor power obviated.

In carrying out these and other objects certain novel features are incorporated in the structure of theV press and for the most part w are in general as follows: Q

parts being broken away and shown in section for the salie of illustration;

Figure 2 is view of the press in top plan;

Figure 3 is a view thereof in end elevation looking toward the left in Figure 1;

Figure 4 is a view in transverse vertical section taken on line 4me of Figure 1, parts being shown in elevation for the sake of illustration g Figure 5 is a fragmentary view partly in side elevation and partly in longitudinal vertical section, the plane of the section being, for the most part, on line 5-5 of Figure 3,

. although certain parts of the machine in and adjacent to the plane of the section are broken away for the sake of illustration;

Figure 6 is a view in section taken in t-he plane of line 6 6 of Figure 5 and illustrating the differential drive for the carriage, parts being shown in elevation for the sake of illustration i Figure 7 is a fragmentary detail perspective view having parts broken away and shown in section and illustrating the structure of the one-way clutch between the hand crank and t-lie drive shaft;

Figure 8 is a fragmentary detail sectional view taken in the plane of line 8-*8 of Figure 5 and showing how one of the transverse shafts is connected at each end to a carriage frame member;

Figure 9 is a fragmentary sectional view taken on line 9-9 of Figure 2;

Figure 10 is an enlarged fragmentary plan view of the parts shown in Figure 9;

Figure 11 is a view in transverse vertical section taken on line 11.-11 of Figure 10 with parts shown in elevation for the sake of siniplicity in illustration;

Figure 12 is a detail view of one of the registering devices and illustrating the same partly in side elevation and partly in section taken on line 12--12 of Figure 10;

Figure 13 is a sectional view taken on line Y 13--13 of Figure 12;

Figure 111- is a fragmentary detail view in top plan showing one of the laterally adjustable gauges or registering devices;

Figure 15 is a detail. sectional view taken on line 15--15 of Figure 14;

Figure 16 is a fragmentary perspective view of certain of the elements shown in Figures 14 and 15;

Figure 17 is a fragmentary view in side elcvation showing a modified form of drive for the carriage;

Figure 18 is a fragmentary view in horizontal section taken on line 18--18 of Figure 17 and also illustrating in top plan portions of the racks underlying the carriage; and

Figure 19 is a fragmentary view in horizontal section taken on line 1919 of Figure 18, parts being shown in elevation for the sake of illustration. j

Referring to the drawings, and more particularly'to Figures 1 and 3, it will be seen that the machine comprises a base designated generally at 1 and madeup of a pair of side members or base frames 2 which, if desired, may be fastened to a suitable foundation and which are rigidly connected in proper spaced relation by cross rods 3 having reduced eX- tensions at. their ends projecting through openings in the base frames and firmly clamped thereby by nuts and washers fi. The A frame proper of the machine includes a pair of side frames 5, one side frame resting on each base frame and being securely bolted member 8 being arranged at the center there of. Stud bolts 1() securely fasten these cross members to the side frames.

Bed platesll and 12 are positioned between the side frames 5 and are supported upon the

cross members

7, 8 and 9, the plate 11 provid- I" ing a support for the printing plate or printing surface and the bed plate12 providing a support for the sheet or print receiving surface on which the proof is made. The

bed plates

11 and 12 are of identical construction and are interchangeable. As shown in Figure 2, the

bed plates

11 and 12 are formed with laterally directed guide lugs 18 engageable with the guide surface 5 formed on the side frames 5 whereby the side bed plates are hele against any lateral movement r. lthough free to be adjusted vertically. The

bed plates

11 and 12 are vertically adjusted and supported in any adjusted position by means of vertical screws 14 engaged with threaded openings provided therefor in lugs 15 integrally formed with bed plates. The upper ends of the screws are adapted to coact with a socket wrench or other suitable operatingtool1 and the lower ends thereof are smooth and bars or ledges 16 provided on the

cross niembers

7, 8 and 9. As shown in Figure 2, four vertical screws 14 are provider. for ach bed plate. there being two lugs 15 at each end of each bed plate. The lugs 15 of the bed plates located adjacent the center cross member 8 have their outer ends machined or ground to provide guiding and clamping' surfaces engageable with similarly constituted surfaces on abutment-s 17 integral with the body of the central cross member. 1li/*hen the desired vertical adjustment of the bed plates has been obtained by adjusting the vertical screws 1li the engaging surfaces of the lugs 15 and abut-- ments 17 are forced into clamping engagement by means of horizontal clamping screws 18 which are engageable with threaded bearings provided in the vertical webs 7 and 9 of the end cross members 7 and 9 and bearing against the ends of the lugs 15 located adthereto by means of stud bolts 6 (see F igure'* ieo jacent :said screws 13. This secures tlie'beds in "any verticalcadjustment but byloosening these screws 18 A`and appropriately:adjusting the 'screws v14 'the beds `rmay lne-adjusted `vertically .tosuit conditions.

A carriage, designated generally.at.20,is

supported-.on theside frames 5 .forreciproca each side frame member 5. ihe carriage 20 framemembers, which are similar in construction, Yare of approximately triangular forni and at their lower corners are connectedto the ends of horizontal shafts 24 and As shown in Figure 8, each end of the shaft 24 is snugly fitted in a bearing opening 27 provided therefor vin one lower v'corner .of cach carriage frame member rand the shaft is ield in these openings ,27and is Afixed to the carriage frame members by means of stud bolts 23 threaded into theends of the shaft 24 and bearing against a washer29which is clamped up againstthe margin of the opening 27.

As shown in Figure 4, the shaft 25 has its ends slightly reduced and snugly fitted in eccentrics which are-rotatably fitted in openings 31 provided in the other lower corner of each carriage frame member. 'The eccentrics 30 are fixed to .the'shaft 25 and are rotated therewith for the purpose of rocking or'tilting the carriage butit isqto be un derstood that during the ordinary'printing operation the yshaft 25 does not rotate. The fixing of the eccentrics 30 to the shaft 25 may be accomplished in any number of ways. As shown in Figure 4, each carriage frame 23 below its transverse bearing opening 31 is formed with a slot oropening'32 to vpermit a locating or set screw 33 to be threaded through the associated eccentric and into-clamping-engagement with the shaft VIn `addition to these screws 33, caps 34 and 35 are fitted over the ends of the eccentrics `Awhiclnas shown. in Figure 4, project slightly beyond the shaft and the carriage frames 23, the caps 34 and 35 having annular recesses which rather tightly receive the projecting Studbolts 36 and 37 are extended through openings in the caps 34 and 35 and are threaded into the opposite ends of the shaft 25.

Washers

36 and 37 are interposed between vthe heads ofthe stud '

bolts

36 and 37 and the caps 34 and 35 Aand when the

bolts

36 and 37 are tightened up they clamp and fixedlyand rigidly secure'the ageesgolo 'any one of aplurality `olf-angular adjustments lby means offa spring projected detent 39 positioned in a socket in one 'of the'carriage side frames'f23 (see Figure 4) and cooperable :with 'angularly spaced yrecesses F40 formed vinfthecaps 34. Theend ofthe dettent 39 andthe Walls ofthe :recesses 40 are beveledrso that they Aserve merely to `releasably yhold the-'shaft 25T/and iits eccentri'cs '30 in position, thus preventing accidental displacement but permitting the operator to make the desired adjustment. y

VRollers 41'fand 45-are1mounted on the shafts V24 and'25, respectively, and the 4rollers of' each shaft are located adjacent r`the 'side Vframemembers '23 of the Vcarriage. 'The rollers `'41 and 45 are of hardened'steel 'and `ride on the upper and lower walls ofthe guide grooves 21 onthe printing''andreturn run, respectively, of the carriage. At rthe ends of the guide grooves 21 stops 21a'are providedforfthe rollers.

"llo permit the rollers 141to turn freely,

vroller'bearing assemblies `42 are interposed i between the rollers 41 and the shaft l24'on which they are mountedv (see Figure I8) It is to be noted that lthe inner race member of the roller bearing assembly 42 has .one 'end abutting'a shoulder 24 provided on the shaft 'E' 24. Between the other inner race-member of 'the roller bearing assembly '42and the carriage 'framefmemberp23 a washer 43 is interposed. l

'Rollerbea-ring assemblies y'46are also in- `terposed between the rollers '45 -an'dtheir shaft 25 (see Figure'4) andareheldinposition just'like the-rollers 42 exceptthatihe washer 43 engaging the outer end ofthe inner race member of the rller'bearingas- 4Vsembly 46 engages lthe eccentrics 3() instead of the carriage "frame 23.

A printing or transfercylinder designated generally at `"is rotatably mounted on,.a

shaft 51 supported `bythe .upper portions of the carriage vframe members. Figure v4, the lendsofthe sha'ft '51 `are jrotatably mounted in roller bearingasseniblies As shown .in

52 designed 'to'tale both radial loa'd vand axial thrust and fitted inbearing'sockets "53 provided therefor in the upper corners of the carriage framemembers. The ends of the shaft 51 projectthrough the bearings 52 .an'd'into'flanged caps 54 -secured `to the shaft ly cylindrical body portion 58 and integral end plates 59. The body 58 of the printing cylinder is formed with a gap or opening 60 fianlred with inturned flanges 61 integral with the body of the cylinder. This provides a fiat on the surface of the cylinder which functions asl will be hereinafter more fully described and it also admits of the employment of a novel form of blanket stretcher to be hereinafter more fully described. The

integr-ai ends 59 of the cylinder are cham-` bered as at 62 to receive roller bearing assemblies 63 whereby the cylinder is rotatably i mounted on the shaft 5l.

In order to rotate or roll the cylinder positively when the carriage is reciprocated along or over the beds, gear wheels 65 are provided and are secured to the shaft 5l by lreys 66 and screws 67. The gears 65 are positioned between the ends o-f the cylinder and carriage frame members, and they mesh with racks 68 secured to the side frames 5. In securing the racks 68 to the side frames 5, stud bolts 69 and dowel bushings 70 are provided,

.p1 the dowel bushings being accurately machined to properly interiit with correspondingly formed openings provided therefor in both the racks 68 and the side frames 5 (see Figure 4). Thus, the dowel bushings hold the racks against any shifting horizontally and relieve the stud bolts 69 of shearing stresses to a large extent, the stud bolts 69 serving mainly to clamp the raclrs to the seats porl vided therefor on the side frames.

The teeth of the gear wheels 65 and of the racks 68 are of helical or herring-bone formation to provide for a smooth and easy translation of the reciprocatory motion of the cyl- A ind-er into a rotary mot-ion of the shaft 5l and back-lash and lost motion is reduced to a minimum. However, in Order to eliminate the bad effects of any small amount of backlash or lost motion that may exist and to avoid the problem of obtainingthe mathematically precise alinenient of the two gear wheels 65 essential for good printing, a compensating or equalizing driving means is provided between the gear wheels 65 and the cylinder 50. Another advantage of the helical gears employed for both the carriage and cylinder drives in this organization is the avoidance of gear streaks so 'common in proof presses as heretofore constructed.

In the form of the invention illustrated this drive comprises an equalizing bar having a bearing 7 5 at its center portion pivotally supported on an inwardly directed radial stud 7.7 threadedly connected or otherwise secured to the body 58 of the cylinder (see Figures 4 and 5). A pin 78 or other suitable means prevents the bar from dropping oif of the stud 77. At its ends the equalizer bar 75 carries iXed guide pins 79 on which driving pawls are slidably fitted, the pawls 80 having sockets receiving the pins 79. Compression coil springs 8l are interposed between the ends of the bar 75 and shoulders o-n the pawls 80 and yieldably project'the pawls 80. The pawls 80 coact with ratchet teeth 82 formed on rings 83 secured to the faces of the gear wheels 65 adjacent the cylinder 50. But one ratchet tooth is provided foreach pawl as itis desirable to drive the cylinder when it is positionedvin only one particular angular relation with respect to the gear wheel. The pawls and ratchet teeth are correspondingly beveled so that they provide a one-way clutch between the gear wheels and the cylinder thereby driving the cylinder when the carriage is propelled through its printing run but permitting the same to remain stationary on the return run of the carriage. Assuming that due to back-lash, lost motion, clearance, or any other reasons, the ratchet tooth 82 on one gear wheel 65 engages its pawl 8O before the ratchet tooth 82 of the other gear wheel 65 comes into engagement with its pawl. The motion of the gear Wheel 65, which has its ratchet tooth 82 engaged with its pawl 80, willnot operate to drive the cylinder 50 but will rock the equalizer bar 75 until the other pawl 80 is engaged with the ratchet tooth 82 of its gear 65, whereupon both ratchet teeth l82 exert uniform driving force upon the pawls 80 and consequently upon both ends of the cylinder 50. As both gear wheels 65 operate to apply the same driving force on the opposite ends' of the cylinder any twisting of the cylinder, however slight, is prevented and further, one end of the cylinder is prevented from lagging behind the other during the printing run.

As pointed out, on the return run of the carriage the vone-way clutches afforded by the pawls 8O and ratchet teeth 82' permit the cylinder to remain stationary. Means is provided to releasably lock the cylinder against retrograde or reverse turning movement during the return run of the carriage, and, as shown in Figures 2, 4 and 5, comprises a retrograde locking pawl 85 iixed to a shaft 86 rotatably mounted in one of the side frames of the carriage, said pawl 85 being cooperable with a notch 87 provided in one of the gauge rings 88 shrunk on the ends of the cylinder 50. These gauge rings 88 overlie accurately machined runners 88 formed on the side frames 5 and provide a convenient means whereby the clearance in between the printing cylinder and the bed may be gauged or determined. The notch 87 is so located that the locking pawl 85 automatically snaps therein at the end of a printing run at which time the flat of the cylinder is presented at the printing bed. On the return run of the carriage the drive of the gear wheels 65 is not positively transmitted to the cylinder and any drag that may be exerted tending to rotate the cylinder 50 reversely, is ineffective for this purpose due to the action of the locking with the swivel connector whenthe rod 91 is pulled downwardly whereby to rock the crank arm 89 and consequently its shaft 8G and pawl 85 out of engagement with the notch 87. The lower end of the swivel connector is pivoted as at 93 toA a crank arm 94. integrally formed with the cap 35 and thus turned withthe shaft 25. A coil spring 96 encircles the trip Irod below the swivel connector 90 and has one end bearing against the swivel connector and has its -other end bearing against a c'rosspin 97 carried by the trip rod. VVhenthe Yshaft'25 is-in the position which it'occupieswhen the carriage is in normal or printing relation tothe bed, then the rod 91 is pushed upwardly through `the swivel Connector 90 and the spring 96-is compressed between the crossgpin 97and-the swivel connectoriand tends tofslide the swivel connector up along the trip rod and thereby press the pawl against the adjacent gauge yring 88 so that it will snap intofthe notch 87 thereof when the notch comes around tothe piwl. However, when the handle 38 is rota-ted'to turn the eecentrics-30 and-tilt -the carriage upwardly about the shaft 25 as an axis, the trip rod 91 is'automatically pulled 'downwardly-as-its lower end is connected'to'the cranlt arm 91 which, as described, is constrained to rotate with the shaft 25. rl`his, as pointed out above, automatically releases the locking pawl 85 andpermits the cylinder to be freely turned in one direction, the one way clutches also taking part in this freedom afforded Athe cylinder. This permits the cylinder to be cleaned, inspected, or ina-- nipulated yfor other purposes at any time in the printing run that'the carriage is'stoppcd.

Meansis provided for propelling the carriage through its printing run and accomplishes this purpose while maintaining the carriage with its aXis at right anglesto the longitudinal axis-ofthe printing bed, thereby insuring perfect registration and vpreventing blurring or other impairment of the proof. In carrying out this purpose a driving shaft 100 is provided and has its ends -mounted in Aroller bearings 101 designed to take both radial load and axial thrust and received in bearing sockets 'i101' provided therefor in the carriage frames 23 (see Figure 6). At one end the shaft 100 is provided witha'cap 102 to exclude dust,\dirt, and the like, from the adjacent bearing but freely rotatable relative to the adjacentcarriage frame member. A

hand crank 108 has its hub loosely mounted on the other end of theshaft 100 for relative rotary and siidingmovement with respect thereto. A bushing 104 is interposed bctween the hub of the hand crank 103 andthe adjacent portion of the shaft 100. A washer 105 is secured by a stud bolt 106 to the shaft 100 and holds the bushing 104 on the shaft andprevents the-crank 108 from sliding'entirely oilo of the shaft. One end of the hub ofthe hand crank 108 is formed with a clutchl jaw 107 adaptedto cooperate with a companion clutch jaw 108 keyed or otherwise suitably fixed to thershaft 100 just-inwardly ofthe-bushing 104. The jaw 108 also serves as a cap for preventing ingress of dust and dirt to the adjacent bearing 101. -As shown in Figures and 7,'the

clutch aws

107 and 108 have engaging surfaces 107:L and 108a and camming surfaces 107D and 108b and thus they are adapted to-provide a one-way clutch between the hand crank and the drive shaft whereby the hand crank may be shifted inwardly to engage the clutch and th'en turned to positively propel the carriage on the Vprinting run and yet lis automatically thrown out and remains stationary on the return run of the carriage. This is an important advantage as a rapid spinning of the hand crank on the return run of the carriage has always presented Van element of hazard to the-operators of presses of this type. The hand crank is releasingly heldin engaged or disengaged-position by means'of a spring pressed ball or detent 109 carried by the hub of the hand crank cooperable with spaced annular recesses 110 formed in the bushing 104.

Centrally, the drivesh ft 100 is formed with an enlargement 100 having a diametrical opening receiving a differential pin .111, Vthe ends of which project beyond the enlargement and provide stud shafts. Beveled planet Vpinions 112 are rotatably fitted on these studs and constantly mesh with confronting driven -bevel gears 113 fi'Xed to sleeve shafts 114; mounted for free rotaticiron journals-114 provided therefor-(inthe driving shaft. Helical or herringbone gear wheels 115 are fixed tothe sleeve shaft 1111 adjacent their outer ends'and mesh With-the racks 68. The diderential or equaliZer thus constituted is enclosed'by a short cylindrical casing 116 secured by screws 116 to the 'outer ends of studs 111 which project through the planetvpinions and the ends of the=casing snugly fit against the peripheries of the gear wheels113 although freely rotatable Arelative thereto. pin 111 may fbe Vsecured to the shaft -100 or the casing 116 maybe relied upon to hold the differential pin against axial displacement. Vith this arrangement w'hen'the crank 103 is actuated -to turn the drive shaft 100 it acts through the diiferen- The differential ly and uniformly to both sides ery of the cylinder 56 and is secured tial to turn the sleeve shafts 114 and consequently the crank wheels 115. If, due to er;- cessive clearance, back-lash, lost motion, or other reasons, the teeth on one of the gear wheel 115 engage the teeth of its rack before the teeth on thel other gear wheei 115 engages the teeth of its rachi then the differential functions, slightly but effectively, to prevent transmission of the drive through the gear wheel 115 which is positively engaged with its rack teeth until the other gear wheel 115 has its teeth engaged wit-h the teeth of its rack. Consequently, the drivingforce is always applied simultaneous? of the carriage and twisting and lagging of the carriage is precluded.

In accordance with the usual practice, a blanket 120 is wrapped around the periphg and properly and uniformly vtensioned on the cylinder by means of a novel form of blanket stretcher. Each end of the blanket is clamped between a bar 121 of rectangular cross section and a bar 122 of L-shaped cross section, by clamping screws 123 extending through openings provided in the `flange of the L-shaped bar 122 and through openings in the end of the blanket and threaded into openings found in the bar 121. The clamp-` ing bars 121 and 122 developa high degree of friction with the ends of the blanket as they reversely bend the blanket between themselves. A clamping and equalizing plate 125 extends between and engages the L-shaped bars 122 and has flaring open-ings loosely receiving screws 126 anchored in a carrier bar 127 secured by stud bolts 128 to brackets formed on the ends of the cylinder. lVing nuts 130 are threaded on the screws 126 and bear against the plate 125 so that when the wing nuts are tightened up the plate 125 and both sets of clamping bars 121 and 122 are forced inwardly. The clamping and equalizf ing action of the plate 125 serves to tighten up both ends of the blanket and to uniformly stretch and tension the same. Moreover, as the clamping plate bears against the angular clamping bar 122 adjacent the reverse bencs of the blanket ends, the blankets ends more firmly gripped between the bars 121 and 122 by the pressures exerted by the clamping plate 125.

As previously indicated, the bed plate 11 `supports a printing surface which may be the usual zinc plate designated at 135 in Figure 5. At one end, the bed plate 11 is formed with an integral downwardly inclined extension 136 to which the attaching portion of the Zinc plate is clamped by a clamp-- ing bar 1377 and clamping screws 138 which pass through the bar and the attaching portion of the zinc plate and which are threadedV into the extension 136. Due'to the o'set or downward inclination of the extension 136,

kclamping bar 1110 and clainpiro' screws 1/11 n u Lb du coacting with a downwardly oset or inclined extension .1e-2 of the printing bed 12. The surface of the metal sheet 135 is adapted to receive an impression of the crosses-orother marks ordinarily employed in effecting registration of the print receiving surface or sheet and to carry out this function the surface of the plate or metal sheet 135 may be coated with white enamel such as white Buco. WV ith a plate ofthis character the cross marks on the Zinc plate may be inked and the printing.cylinder run over the inked cross marks to take an impression thereof on theblanket. Then, as the cylinder travels over the metal sheet 135', it transfers or iinpresses the crosses or registration marks on the metal sheet. The print receiving sheet has openings therethrough which are brought over the crosses' or registration marks to properly register the print receiving surface. lt is, of course, conventional to use these crosses in this way but it is entirely noi/el to utilizo the transfer cylinder to take an impression of the crosses of the Zinc plate and apply them to the surface which underlies the proof sheet or print receiving surface. ln addition to this advantage the plate or metal sheet 135 may be raised or lowered vertically to locate it in the printing plane by shininiing it up with filler sheets of paper or the like. rlhis is advantageous as it saves the time that would otherwise have to be expended in resetting the bed plate 12.

The print receiving surface which, as indicatedyis usually in the forni of a sheet of paper,.is clamped against the undersurface of a combined gripping and index plate 145, the top surface of which is located just below the printing plane. As shown to advantage in Figure 11, the plate 145 is supported on the central cross member 8 of the frame by means of spacing and supporting members 146 which have their lower ends engaging the cross member 8 and their upper ends enlarged and engaging the underside of the plate. Screws 1117, which have their heads countersunk in the plate 145, pass through the plate Vand, the members 146 and are threaded into the cross member 8 whereby to rigidly secure the plate 145 in position. For clamping the print receiving sheet up against the underside of the plate 145, gripping fingers,

designated generally at 148, areprovidedr'. (see F 1gnres 9 and 10) ,the gripping/'fingers being'- of resilient metal and each having-oneendbearing against av spacing-blockr149 andfas tened throughV thezvblock 149. to the plate145 by. nie-ans of screws orother suitablefastening devices 150.. The inherent.resiliencyrof! thefingers .148- bias thernto releasedposition wherein their freegripping ends148 which are offset toward the plate 145, are spaced? fromplate 145 to .admit of the free passage of the print receiving sheet to the spacebetween themselves and -theplate 145. When the sheet has its end'V edge positioned in between the lingers 148 and the plate 145 the lingersareforced up against the paper and clamp the paper between themselves. and the plate.

This is accomplished by means of a camshafty 151 havingV a plurality of cams 152 fixed;

thereto, there being one cam 152 engaged with each gripping finger 148. As'shown-in Figures 9'to 11, the cam shaft extends transversely of the machine and of the gripping fingers and itl issupported forrotary movement in bearings provided therefor inthe supportingmembers 1'46. The cam-shaft '1513 is rotated fromtaffinger lever 154 which is fixed to the'outer end of-a shaft lirotatably` mounted in ar bearing 156secured to the underside-of thel plate 145.1 A beveled" gear wheel 157 is fixed to the shaft 155 andmeshesvv with a beveled gear`v wheel 158-fiXed"to -th'e cam shaft 151'. Vhen thev fin-ger lever is inthe position shown in Figures 9,10 and 11, the cam shaft isso positioned that the grippingfingers 148'are released; By turningI the fingerlever 154 andthe` shaft 155'in' counter-clockwise direction, asfviewed irl-Fig' ure 11, th-e cani shaft is tu-rnedto bring the highest pointY of the camsV against thegripping fingers 148 and press# these grippingY fingers into sheet gripping position.

lVhen the gripping fingers are in sheet gripping position the finger lever-'154" is lo;

cated in ahorizontal position butlhas been rotated to 18()O in a counterclockwisedirectionV fromV theposition shown- 1n Figure 11.

Thus, in both positions of 4the lfingerflever-itis located below the `printing plane.` Forftlie purpose` of preventing4 the operatorl of" the machine from inadvertently leaving l'the fin ger-lever in an intermediate position-inwhich-v it might projectup above ithe printing plane andE present an obstructionin'the way-of a printing cylinder, aselfeacting springgbiased" toggle is associatedwith the finger'lever; As

shown in'ligurerll, this-toggle includes anarmf160 which* may he formedas a continuation ofthe finger lever inwvhi'c'hit 1s p1v' otally: connected as at@ 1601 'to -one end'of the sliding linkv 161; The lowerl en-d'of the/linkl 16`1Fslides through-an-opening provided there-v. for in a swivelzpin'a162, pivotallyrmountedf on afbracketf. arm 1163 `w'liihzlmay:hie-.convene 5' iently. formed .integralwitli the.bearir'zg'156f (see Figure 9).- coil' spring 165encircles the link.161 and hasone end abuttinga shoulder formed; atthe upper end ofithe link and has its .other'errd abutting the swivel piin 162. rIhe` spring.' 165.isunderv compression and inthe toggle arrangement shown biases the thusshortensthe distance between the ends.

of the' spring. After thel finger lever passes the vertical position, further-swingingfmove ment in acounter-eloekwise direction is accompanied by expansion-off the: spring 161 which, of course, tends to throwr the finger lever to I itsother vhorizontal position.

To facilitateI proper positioning ofy the.v print receivingfsurface the plate145ispro videdv with longitudinallyv and transversely adjustable gauges.-

rlhe longitudinally adjustable gauges (see Figures 9,10, 12 andl) are two in numbery and are in the form ofblocks 170r having beveledfforwardi extensions Y171- and provided with beveled guide piecesA 172 fastened theretobyscrews A178'and operating in longitudinal slots 174-formedinvthe plate 145.- Grad# nations or scales-175 are provided on the* plate 145' adjacent the slots 174Jand facili tate` precise adjusting of the gauges. Thegauge blocks 170 areI carried at the. forward ends of rods 176 and the rearwardends off the rods are screw threaded asvat 177 and passlooselyY through spaced guides 178'fiXed' tothe-underside of the platef145. Knurl'ed thumb nuts 179, which are engaged with the threads-of the .rods-176, operate between the guidesl 1781and/project up through slots or' openings.180-formedinfthe plate 145'. (Db` viously, by' turning the nutsl/'Q in one di.- rection.` the gauge block-s- 170 are advanced and ,byv turning the thumb nuts- 179in-v an opposite directionthe gauge blocks'lTO are retracted.

The transversely adjustable gauges include gauge plates 182'located one adjacent each endA of theA plate 145 and travelingacross'- scales 183 provided along the for-wardedge off'plate 145adjacent: each end thereof'(see Figure: 10). rllhelgauges 182are mounted ontheplate 1451 for. transverse slidingmove- Y ment andfa'rereleasably secu-red in any adjustment; 'I'hevguiding an-dmounting-of the gauges 182 is preferably effected by means of a guide memh'er'184. (see Figures 14,15

and 16), which has an upwardly directed flange 185..- alongwits: forward edge snuglyfitted in';aguide/clrannell186 provided inthe undersideoffplatez145. 'Ehe guide. membersl 184.- proj ectzrearwardly beyondthe plate.v 145 l and each has an integral enlargementl 187 spaced rearwardly from the plate 145 and designed to provide a lixed wedge and also to permit of the convenient connection of the gauge plate 182 to the guides 184. Thus, each gauge plate 182 is fastened to the enlargement 187 of its guide 184 by means of screws or rivets 188. And the forward wall of the enlargement 187 of each guide 184 is beveled at 187 to provide the fixed wedge structure. F or releasably securing each gauge plate 182 in adjusted position a shiftable wedge 189 is provided and has its rearward end portion formed with a tapering or gradually inclined and enlarging portion 190 'which coacts with the fixed wedge constituted by the inclined surface 187 of the guide 184. The wedge 189 is of L-shaped form and between the wider portion thereof n and the enlargement 187 an expansible coil spring 191 is provided and tenus to shift the wedge member 189 to the left as viewed in Figure 10, thereby causing the shiftable Wedge to have binding engagement with the J' plate 145 and the enlargement 187 of the guide and consequently releasably securing the gauge plate 182 in adjusted position. By pressing the shiftable wedge 189 to the right, as viewed in Figure 15, the wedge surfaces 187 and 190 are disengaged and the gauge is freed or released for adjustment. rIhe thumb and forelinger may be conveniently used to release the wedge 189 and shift the gauge. v

In operation, the beds 11 vand 12 are first adjusted to their proper vertical height and are clamped in such position. The zinc plate or other printing surface is then applied and clamped to the bed plate 11 and a sheet of L paper or other print receiving surface is placed on the bed plate 12 and after being properlypositioncd with the aid of the registering devices or gauges, is clamped thereon by means of the gripping lingers 148 and the i plate 145. The Zinc plate having been inked,

the operator grasps the hand crank 103 and pushes it in towards the carriage to engage the

clutch jaws

107 and 108. The crank is j then turned in a counter-clockwise direction,

ESOy

3* as viewed in Figure 1, and acting through the differential uniformly propels both sides of the carriage to the left, as viewed in Figure 1. As soon as the carriage starts in motion the gear wheels 65, due to their meshing with the fixed racks 68, are rotated and through the equalizing or compensating cylinder drive apply the driving force to the center of the printing or transfer cylinder thereby evenly driving the same without any twisting or angling. The blanket is thus caused to roll over the Zinc plate and the impression is transferred from the zinc plate to the blanket. As the motion of the carriage and cylinder r`continue the carriage comes over the print receiving surface and the impression 1s transferred from the blanket to the print receiving surface. At the end of the printing run the flat of the cylinder lies over the bed of the press and the locking pawl 85 snaps into its notch 87 and these parts remain in this position and prevent retrograte movement of the cylinder during the return run of the carriage. In moving the carriage through the return run the operator grasps a handle 289 provided for this purpose and pushes the carriage back along the side frames. During the return run, the crank handle remains stationary as it is automatically thrown out by the camming surfaces of its

clutch jaws

107 and 108. The cylinder also is held against rtation, as described, although it moves bodily with the carriage. If, at any time during the print-ing run, it becomes necessary or desirable to move the printing cylinder out of printing contact with the bed, this may be done by manipulating the lever 138 to tilt the carriage and release the retrograde lock that disengages the pawl 85 from its notch 87. Moreover, this throwing out of the cylinder does not interfere with motion of the carriage.

In Figure 17 to 19, inclusive, a modified form of mounting and drive is proposed for the printing cylinder. In all other respects the press is the same as that shown in F igures 1 to 16, inclusive, and the foregoing description applies thereto. Referring now to Figure 18, it will be seen that the printing cylinder in the modified form of the invention is fixed to the inner ends of stud shafts 200 by means of nuts and washers 201 which force the inner tapered ends 200 of the stud shaft into tight engagement with ta` pered bearing openings 50a provided in the ends of: the cylinder. The stud shafts also extend loosely` through bushed openings in the hubs of gear wheels 202 meshing with the racks 68 of the printing bed. As shown, the hubs are somewhat extended on one side of the gear wheels 202 and the extended portions of the hubs project through roller bearing assemblies 203 supported in bearing recesses 204 provided on the carriage frames. The roller nearing assemblies 208 are designed to take both radial load and axial thrust and their inner race members have secure enengagement with the extension of the hubs at the gear wheels 202- while their outer race members have tight gripping engagement with the walls of the bearing recesses in which they are positioned. Theouter ends of the stud shafts are provided with washers 205 held in place by stud bolts 206 and operating to exclude dust from the bearing assembly. The equalizing or compensating one-way drive between the gear wheels 202 and the cylinder is exactly the same as in the other form of the invention. The modification also proposes the elimination of the differential in the carriage drive. This may be desired under some circumstances although usually the differential would be employed in order to obtain a very accurate registration and is especially desirable where colors are superimposed one on the other or in other work where even a minute uncontrolled shifting of the cylinder or carriage will produce blurring or otherwise impair the proof. In the carriage drive shown in the modification, Vthe drive shaft is designated at 210 and is rotatably mounted in roller bearings 211 provided in the frame of the carriage. Gear wheels 212 are keyed to the shaft 210 and mesh with the racks 68. A hand crank 103, exactly the same as that employed with the other form of the invent-ion, is also employed here and has the same one-way clutch or one-way driving connection with the drive shaft.

- From the foregoing it will be understood that the modified form of the invention is exactly the same in construction as the preferred form except that the differential in the carriagev drive is omitted and that the cylinder driving gears are loosely instead of rotatably mounted on the shafts provided for mounting the printing cylinder on the car-v riage. The operation of the press with this modified cylinder mounting and modified carri age drive is precisely the same as that of the preferred form of the invention which has been hereinbefore described.

The invention claimed is:

1. An offset proof press of the character described comprising a bed, a carriage reciprocable along the bed, a traveling transfer cylinder rotatably mounted on the carriage and adapted to have rolling contact with the bed, a pair of fixed racks associated with the bed a drive shaft rotatably mounted on the carriage, a pair of carriage driving gears meshed with the racks, means for transmitting the driving force from the drive shaft to said driving gears only when the teeth of both exert uniform driving pressure on the teeth of their racks, cylinderY driving gears meshed with the racks and movable relative to the cylinder, and motion transmission means between said cylinder driving gears and said cylinder operable to transmit the driving force to the cylinder only when the teeth of both cylinder driving gears exert uniform driving pressure on the teeth of their respective racks.

2. A press of the character described comprising a bed, a carriage reciprocable along' 'the bed, a cylinderv rotatably mounted on the carriage and adapted to have rolling contact with the bed, fixed helical racks associated with the bed, a drive shaft rotatably mounted on the carriage, helical carriage driving gears meshed with the racks, means for transmitting the driving force from the drive shaft to said driving gears only when the teeth of both exert uniform driving pressure on the teeth of their racks, helical cylinder driving gears meshed with the racks and movable relative to the cylinder, and motion transmis sion means between said cylinder drivingv gears and said cylinder operable to transmit the driving force to the cylinder only when the teeth of both cylinder driving gears exert uniform driving pressure on the teeth of their respective racks.

3. A press of the character described com-y prising a bed, a carriage reciprocable along the bed, a differential drive for the carriage7 a. cylinder rotatably mounted on the carriage and an equalized drive for the cylinder.

4f. An offset proof press of the character described comprising a frame, a bed carried thereby, a carriage reciprocable along the bed, means for driving the carriage including racks fixed to the bed frame, and driving gears rotatably mounted on the carriage and meshed with the racks, a transfer printing cylinder rotatably mounted on the carriage7 cylinder driving gears meshed with the racks and mounted on the carriage for rotation relative to the cylinder, and means for transmitting the drive from the cylinder driving gears to the cylinder and including a one-way driving` connection cooperable with each driving gear and an equalizer between said driving connection and the cylinder.

5. An offset proof press comprising a bed, a cylin der, means for supporting the cylinder for rolling Contact with the bed, and means for rotating the cylinder as it travels over the bed including driving gears, a one-way clutch cooperable with each driving gear and an equalizer carrying said clutches and connected to the cylinder.

6. An offset proof press comprising a bed, a traveling transfer cylinder cooperable with the bed, a pair of fixed racks` a pair of driving gears meshed with the racks and rotatable relative to the cylinder, and motion transmission means between the gears and the ovlinder including an equalizer operable to transmit the driving force to the cylinder only when the teeth of both gears exert uniform driving pressure against the teeth of the racks whereby to propel the cvlinder without angling or twisting. l'

7. An offset proof press comprisingr a bed, a traveling transfer cylinder eooperable with the bed, a pair of fixed racks, a pair of driving gears meshed with the racks and rotatable relative `to the cylinder, an equalizer bar fioatably connected to the cylinder, and means affording driving connection between the equalizer bar and the driving gears and perf mittin g the bar to move relative to the cylinder to withhold the application of the driving force to the cylinder until the teeth of both gears exert uniform pressure on the teeth of their respective racks.

8. A press of the character described comprising a bed, a cylinder supported for rollsv ing contact with the bed, and means for rota@ ing the cylinder comprising driving elements and motion transmission means between the driving elements and the cylinder including an equalizer.

9. An offset proof press comprising a stationary bed, a traveling transfer cylinder, means for supporting the cylinder for rolling contact with the bed, and means for rotating the cylinder as it travels over the bed and including fixed racks, cylinder driving gears disposed adjacent the ends of the cylinder rotatable relative thereto and meshed with the racks, a one-way clutch associated with each driving gear, and an equalizer connecting the driven members of the clutches to the cylinder.

10. An offset proof press comprising a bed, a cylinder, means for supporting the cylinder for rolling contact with the bed, and means for rotating the cylinder as it travels over the bed including driving gears adjacent the end-s of the cylinder and fixed racks on the bed with which the drivingr gears mesh, each driving gear having a ratchet, a pawl cooperablewith each ratchet, an equalizer bar pivoted to the cylinder and carrying said pawls, and means for biasing the pawls to engage the ratchets.

l1. A press ofthe character described comprising a bed, a carriage mounted on the bed for reciprocatory movement and carrying a cylinder adapted to have rolling contact with the bed and a drive for the carriage embodying a differential.

12. A press of the character described comprising a bed, a carriage reciprocable along the bed, a cylinder rotatably mounted on the carriage and adapted to have rolling contact with the bed, fixed racks associated with the bed, a drive shaft rotatably mounted on the carriage, carriage driving gears meshed with the racks, and means for transmitting the driving force from the drive shaft to said driving gea-rs only when the teeth of both exertuniform driving pressure on the teeth of their respective racks.

13. A press of thecharacter described comprising a bed, a carriage reciprocable along the bed, a cylinder rotatably mounted on the carriage and adapted to have rolling contact with the bed, fixed racks associated with the bed, a drive shaft rotatably mounted on the carriage, carriage driving gears meshed With the racks, sleeve shafts rotatably mounted on the drive shaft and to which said gears are fixed and a differential actuated from the drive shaft and driving the sleeve shaft.

lll. A press of the character described comprising a bed, a carriage reciprocable along the bed, a cylinder rotatably mounted on the carriage and adapted to have rolling contact with the bed, fixed racks associated with the bed, a drive shaft rotatably mounted on the y carriage, carriage driving gears meshedwith the racks, sleeve shafts rotatably mounted o-n the drive shaft and to which said gears are fixed, radial stud shafts constrained to rotate with the drive shaft, planet pinions rotatably mounted on the stud shafts, and driven gear wheels meshed with the planet pinions and fixed to the sleeve shaft.

15. An offset proof press of the character described comprising a frame, a bed carried thereby, a carriage reciprocable along the bed, means for driving the carriage including racks fixed to the bed frame, and driving gears rotatably mounted on the carriage and meshed with the racks, a transfer printing cylinder rotatablyV mounted on the carriage, cylinder drivinggears meshed with the racks and mounted on the carriage for rotation relative to the cylinder, and means for transmitting the drive from the cylinder driving gears to the cylinder.

16. An offset proof press comprising a bed, a traveling transfer cylinder, a carriage on which the cylinder is rotatably mounted, said cylinder being adapted foiirolling contact with the bed and having a flat or gap located adjacent the bed at the end of the printing run and during the return run, means for reciprocating the carriage, a one- Way drive for rotating the cylinder as the carriage is moved through a printing run and means for preventing retrograde movement of the cylinder.

17. An offset proof press comprising a bed, a traveling transfer cylinder, a carriage on which the cylinder is rotatably mounted, said cylinder being adapted for rolling contact With the bed and having a flat or gap located adjacent the bed at the end of the printing run and during the return run, means for reciproca-ting the carriage, driving elements geared to the bed so as to be rotated when the carriage is reciprocated, a one-Way driving connection between the driving elements and the cylinder for rotating the cylinder during the printing run, and pawl and ratchet means between the carriage and the cylinder for holding the cylinder against retrograde movement during the Areturn run while leaving the saine free to rotate for- Wardly during the printing run.

18. An offset proof press comprising a bed, a traveling transfer cylinder, a carriage on which the cylinder is rotatably mounted,

said cylinder being adapted for rolling contact with the bed, means for reciprocating the carriage, a one-way drive for rotating the l cylinder during printing runs, means for preventing retrograde movement of the cylinder, means for throwing the cylinder out of printing relation to the bed, and a release for the means which prevents retrograde move- ISG with. the bed and having a flat or gap located adjacent the bed at the end of the printing run and during the return run, means for reciprocating the carriage, driving elements geared to the bed so as to be rotated when the carriage is reciprocated, a one-way driving connection between the driving elements and the cylinder for rotating the cylinder during the printing runs, a retrograde loclr for holding the cylinder against reverse movement during return runs, a throwout for the cylinder, and a. release for the retrograde lock interconnected with and actuated by the throwout whereby the cylinder may be freely rotated in any phase of the operation when out of contact with'the printing bed.

20.v An offset proof press comprising anbed, aI carriage reciprocable along thebed, a travcling transfer cylinder rotatably supported on the carriage and having a flat or gap disposed adjacent the bed atthe end of each printing run and during each return run, means for'supporting and guiding the carriage to constrain it to maintain the cylinder in such position as to be adapted to have rolling contact with the bed during each printing run, a throwout associated with said supporting means and operable to tilt the carriage toelevate the cylinder out'of printing rela,- tion to the bed in any phase of the operation, a drive for rotating thecylinder during each printing run, holding means for preventing rotation of the cylinder during each return run, and a release for the holding means.

21. An offset proof press comprising a bed, a carriage reciprocable along` the bed, a traveling transfer cylinder rotatably supported on the carriage, means for supporting and guiding the carriage to constrain it to maintain the cylinder in such position as to be adapted to have rolling contact with the bed during each printing run, and throwout associated with said supporting means and operable to tilt the carriage relative to its supporting means to elevate the cylinder out of printing relation to the bed.

22. An offset proof press comprising a bed, a carriage reciprocable along the bed, a. travelingr transfer' cylinder rotatably supported on the carriage and having a flat or gap disposed adjacent the bed at the end of each printing run and during each return run, means for supporting and guiding the carriage to constrain it to maintain the cylinder in such position as to be adapted to have rolling contact with the bed during each printing run, a throwout associated with said supporting means and operable to tilt the carriageto'elevate the cylinder out of print-v ing relation to the bed in any phase ofthe operation, a one-way drive for rotating'the cylinder during printing runs, a retrograde lock for peventing reverse rotation of the cylinder during return runs, and a release for the lock` automatically operated by the throvvout.

23. An offset proof press comprising a bed, traveling transfer cylinder, a carriage on which the cylinder is rotatably mounted, said cylinder being adapted for rolling contact with the bed, means for reciprocating the carriagea one-way drive for rotating the cylinder during printing` runs, a throwout for elevating the cylinder out of printing relation to the bed, a ratchet on the cylinder, a pawl mounted on the carriage and biased to engage the ratchet to prevent reverse turning of the cylinder, and a release actuated from the throwout and cooperable with the pawl to disengage it from the ratchet when the cylinder is elevated out of operating relation to the bed. y

24. An offset proof press comprising a bed, a printing cylinder, a carriage on which the printing cylinder is rotatably mounted, means for normally supporting and guiding the carriage in printing relation to the bed and operable to tilt the carriage upwardly, said cylinder being adapted for rolling contact with the bed and having a flat or gap overlying the bec at the end of the printing run and during the return run, means for reciprocatingl the carriage, means for rotating the cylinder the carriage is moved through a printing run while permitting the same to remain stationary during the return run and comprising driving elements geared to the bed so as to be rotated when the carriage isreciprocated, a one-way driving connection between the driving elements and the cylinder, pawl and ratchet means between the car riage and the cylinder for holding the cylinder against retrograde movement while leaving the same free to rotate forwardly during the printing run, and arelease for the pawl and ratchet means interconnected with the means for tilting the carriage so as to be au tomatically operated when the carriage is tilted. Y i

25. In a press of the character described, a bed, a carriage including a carriage frame member atv each side of the bed, means for connecting the carriage frame members and supporting the carriage for movement over the bed including cross shafts connecting the carriage frame members and carrying rollers, eccentrics on one of the shafts cooperable with the carriage frame members whereby the carriage may be tilted and a printing cylinder mounted on the carriage and adapted to have rolling contact with the bed.

26a In a press of the character described, a rotatable cylinder, a oneway drive therefor, a retrograde lock for preventing reverse rotation of thecylinder, a throwout for the cylinder, a release for the retrograde lock, and common means for actuating the throwout and the release.

27. An odset proof pressrof the character described comprising a frame having a bed and also having guide-ways therein, a carriage reciprocable over the bed, cross shafts connected to the carriage and having rollers rotatably mounted thereon and operating in the guide-ways, eccentrics fixed to one of the cross shafts and cooperable with the carriage for tilting the same, a printing cylinder mounted on the carriage and adapted for rolling contact with the bed, and means for driving the carriage and the cylinder.

28. An offset proof press comprising a frame having guide-ways, a printing surface and a print receiving surface supported on said frame, 4a carriage including carriage frame members adjacent the sides of the frame, cross shafts extending between said carriage frame. members, rollers rotatably mounted on the cross shafts and operating in the guide-ways of the frame, eccentrics between one of said cross shafts and the carria-ge frame members, means for turning the cross shaft having the eccentrics whereby to tilt the carriage when desirable, and a printing cylinder rotatably mounted on the carriage and adapted for rolling Contact with said surfaces.

29. An offset proof press comprising a frame having guide-ways, a printing surface and a print receiving surface supported on said frame, a carriage including carriage frame members adjacent the sides of theY frame, cross shafts extending between said carriage frame members. rollers rotatably mounted on the cross shafts and operating in the guide-ways of the frame, eccentrics between one of said cross shafts and the Vcarriage frame members, means for turning the cross shaft having the eccentrics whereby to tilt the carriage when desirable, a printing cylinder loosely mounted on the carriage, means for causing the printing cylinder to have rolling contact with said surfaces dur-- ing the printing run of the carriage, said cylinder having a flat disposed adjacent said surfaces at the end of the printing run and during` the return run of the carriage, means for holding the cylinder against retrograde movement during the return run and a release for the holding means automatically operated when the carriage is tilted.

30. A printing press of the character described including a frame having a bed, a carriage supported on the frame for reciprocatory movement therealong, means for reciprocatingl the carriage including helical racks fixed to the frame, helical driving gears mounted on the carriage and meshed with the racks, means for rotating said gears including a drive shaft and a diierential actuated from the drive shaft and having its driven gears connected to the helical gears, a printing cylinder rotatably mounted on the carriage, and helical drive gears meshed with the racks and having a driving connection with the cylinder.

31. A printing press of the character described including a frame having a bed, a carriage supported on the frame for reciprocatory movement therealong, means for reciprocating the carriage including helical racks fixed to the frame, helical driving gears mounted on the carriage and meshed with the racks, means for rotating said gears, a printing cylinder rotatably mounted on the carriage, and helical drive gears meshed with the racks and having an equalized driving connection with the printing cylinder.

32. An offset proof lpress comprising a printing bed having a printing surface and a print receiving surface, an offset printing cylinder adapted to have rolling contact with the surfaces of the printing bed, a carriage upon which the cylinder yis rotatably mounted, means for supportingthe carriage for reciprocatory movement along the bed, means for driving the carriage including gear wheels rotatably mounted on the carriage and racks fixed to the bed and meshed with the gear wheels and means for rotating the printing cylinder and comprising gear wheels rotatably mounted on the carriage meshing with the racks and having driving connection with the cylinder.

33. A press of the character described including a bed, a reciprocable carriage carrying a cylinder adapted to have rolling contact with the bed, and means for driving the carriage including a drive shaft, a hand crank, and a one-way clutch between the hand crank and the drive shaft. l

34. A press of the character described includingra bed, a carriagemounted on the bed for reciprocatory movement and carrying a cylinder adapted to have rolling contact with the bed, means for driving the carriage including a drive shaft, hand crank, and cooperable clutch jaws between the hand crank and the drive shaft engageable to permit the hand crank to be turned to actua-te the drive shaft in one direction and having camming surfaces for throwing out the hand crank upon reverse movement of the drive shaft.

35. In a printing press of the character described, a frame, ai printing bed, vertical screws coacting with the bed and with the frame to support the bed on the frame in various vertical adjustments, cooperating guide means between the sides of the bed and the frame for constraining the bed to vertical movement, coonerable abutments integral with one end of the bed and the frame, and clamping means engageable with the other end of the bed for forcing said abutments into engagement.

36. In an offset proof press of the type having a reciprocable carriage and a rotating cylinder mounted on the carriage and movable bodily with the carriage as well as rotated