US2211766A - Stripper for printing presses - Google Patents

Description

Aug. 20, 1940. R. c. BROWN. JR 2,211,766

STRIPPER FOR PRINTING PRESSES Filed 001:. 1, 1938 2 Sheets- Sheet 1 lhuarz i07 fiber! a Brown/g]??- Aug. 20, 1940. R. c. BROWN. JR

STRIPPER FOR PRINTING PRESSES Filed Oct. 1, 1938 2 Sheets-Sheet 2 YNN lllll'll l Patented Aug. 20, .1940

'STBIPPER ron rnmrme PRESSES Robert C. Brown, Jr., Highland Park, 111., assign- .or to Davidson Manufacturing Corporation, a

corporation of Illinois I Application October 1, 1938, Serial No. 232,815

-' 10 Claims. (Cl. 27163) This invention relatesto strippers for stripping sheets from rotating drums such as the printing drum of a printing press. It has been illustrated in, conjunction with operating mechanism which causes the point of the stripper to extend momentarily within the circumferenceof the printing drum as the sheet approaches the stripper so that it will be impossible for the sheet to pass between the drum and the stripper. The stripper can be'used without this operating mecha-.

nism, however, and in fact under any circumstances in which a stripper is desired.

The illustrated form of the stripper is more effective and satisfactory than any known here- 5 tofore and, accordingly, it finds its greatest need under the most adverse stripping conditions such as those found in offset printing, for example. In offset printing the sheet never touches the type or plate roll but instead the ink is applied by the plate to a rubber blanket which in turn applies it to the sheet. There is, however, a considerable tendency for the sheet to stick to the rubber blanket, especially if the ink coverage at the leading end of the sheet is relatively heavy.

5 Suflicient stripping force can be obtained by a stripper in the form of a flat or straight-edged blade extending the length of the blanket roll but such stripper blades are objectionable, especially with heavy inking, be'cause their continuous surfaces tend to collect ink from the printed sheet and smear the ink along the sheet. To avoid tliis' collection and smearing of ink, strippers have usually been provided with a few isolated stripping fingers which were shaped to contact the sheet along only a narrow line parallel to the movement of the sheet so that there'would be no appreciable tendency for ink to collect thereon. The result has been, however, that under the adverse conditions mentioned such strippers have not exerted sumcient force with enough uniformity to strip the sheets satisfactorily. In fact, with high grade printing presses it has been customary to provide relatively expensive and complicated stripping mechanism such 'asgrip fingers which would not only help register the sheet with the printing drum but would also positively pull or force the sheet from the drum. The present invention reconciles .theconflicting needs for a stripper blade and for a stripper which contacts the sheet only along narrow lines parallel to the movement of the sheet byproviding a corrugated stripper which contacts the sheet only along the narrow lines as required but which at very low cost provides such a large number of closely spaced contact lines that the stripping force is adequate and suiliciently uniform for any purpose commercially encountered. From the foregoing it is evident that an objectof this invention is to provide a stripper which is capable of stripping sheets from revolv- 5 ing. printing drums under adverse conditions but which will nevertheless avoid collecting or smearing the inkfrom the sheet.

A further object is to provide such a stripper which is economical to produce and easily han- 10 Y dled and adjusted.

Additional objects and advantages of the invention will be apparent from the following description and from the drawings, in which:

Fig. 1 is a fragmentary horizontal sectional 15.

view of a printing tion.

Fig. 2 is a fragmentary perspective view showing the preferred form of stripper mechanism.

press embodying this inven- Fig. 3 is a fragmentary vertical longitudinal sectional view taken approximately on the line 3-3 of Fig. 1 and illustrating diagrammatically the operation of the stripper mechanism, with the platen roll and stripper-operating cam somewhat foreshortened angularly for the sake of 25 illustration.

Figs. 4 and 5 are fragmentary sectional views taken approximately on the line 4-4 of Fig. 1 and showing diagrammatically successive positions of the stripper as it moves from the posi- 30 tion shown in Fig. 3, Fig. 5 showing the normal position of the stripper.

A preferred embodiment of the invention has been shown in the drawings and will hereinafter be described all as required by see. 4888 of the 35 Revised Statutes but the appended claims are not to be'limited bythe disclosure except as required by the'prior art.

The invention is illustrated as embodied in a printing press, the general nature of which is seen best from Figs. 1 and 3. Although the invention can be used with any form of printing press, including small duplicating machines, it has been illustratedas embodied in an oflset printing press. The printing rolls of the illustrated press include a blanket roll or printing drum II and a platen roll i2. There would of course also be the usual plate roll, not shown, with suitable means for inking it so that it would apply the ink to the rubber blanket l3 of the 50 blanket roll it which in turn would print the ink on the successive sheets of paper I. The paper is fed to the printing rolls II and I2 by conveyor belts l6 and feeding mechanism indicated generally by ll, and a'stripper from the 55 Git blanket roll II by a stripping mechanism indicated generally at l8. 7

As seen in Fig. 1, the conveyor belts I6 are disposed at an angle so as to feed the sheets against an edge guide 2|, thus assuring their accurate lateral registry. Accurate longitudinal registry is assured by the feeding mechanism At the beginning of the feeding cycle-the stop fingers 23 are positioned vertically so as to obstruct the path of the sheets. A sheet is then fed by the belts l6 against the stop fingers 23 which accurately position the front edge of the sheet. While the sheet is thus held stationary, the pressure roller 24 is lowered to press the sheet against advancing roller 26. After the sheet is thus firmly gripped by the feed rollers 24 and 26, the roller 26 is driven to feed the sheet forwardly to the printing rolls H and I2. The stop fingers 23 are mounted on the shaft which drives the roller 26 so that they necessarily move out of the way of the advancing sheet.

The advancing roller 26 is driven by means of a pinion 21 and gear segment 28 which in turn is driven through a lever 29 by a. cam, not shown, mounted in, conjunction with and rotating with the blanket roll II. This cam is so shaped as to cause the advancing roller 26 to accelerate its speed smoothly but quickly so that there will be no slippage between it and the sheet, but so that when the sheet reaches the bite between the printingrolls H and I2 it will-be moving at the peripher'alspeed of these rolls so that there will be no slippage between the sheet and the printing rolls. As soon as the sheet has been gripped in the bite formed by the printing rolls l and i2, a cam carried by the blanket roll ralses the pressure roller 24'through a suitable lever 3|.

Immediately afterthis, the high point of the cam. which drives the advancing roller 26 is reached. so that the forward movement of this roller ceases. As the cam continues to rotate to the starting position, it permits the roller 26 and the stop fingers 23 to be returned to their starting position by a return spring 33. This spring also acts to take up all slack in the driving mechanism so that substantially perfect uniformity of the feeding is obtained. The feeding cam which drives the roller 26 is so positioned as to cause the sheet to be fed to the blanket roll H in the relative positions shown in Fig. 3 with the sheet i l having its leading edge portion 36 projecting .beyond the leading edge 33 of the blanket iii. In-

other words, the leading edge portion 36 of the sheet overlaps or extends over a recess or opening 39 in the blanket roll Ii. It may be noted that this opening is normally provided in blanket rolls for the purpose of securing the blanket to the roll and stretching it. If the printing drum H were some other form of drum than a blanket roll, a special recess could be provided since thisrecess is very helpful in the operation of the stripping mechanism.

Stripping mechanism The stripping mechanism Ii] includes a stripper d! which is carried by a cross bar 42, the ends of which are bent downwardly to form arms 13 which are pivoted to the press frame i l by suitable screws 35.

The stripper 5| is urged toward the position shown in Fig. 3 by means of a coil spring 36 but is normally held in the position shown in Fig. 5 by means of a cam ll and cam following roller 38. The cam following roller 48 is carried by an arm t?) which in turn is rigidly mounted on the cross bar 42. As the blanket roll approaches the position shown in Fig. 3, the reducing portion 5| of the cam 41 reaches roller 48 so that under the influence of spring 46 the stripper 4| is tilted rearwardly toward the position shown in Fig. 3 so that the forward tips or points 52 of the stripper 4| are positioned radially inwardly of the sheet 4. As a matter of fact, these tips 52 have been illustrated as actually projecting between the side walls of the blanket roll II, but this is of course further inwardly than they need to extend, it being suflicient if they extend a little further inwardly than the periphery of the blanket l3, or it maybe found that even less inward movement than that will suffice.

As the blanket roll continues to rotate, the leading edge or projecting portion 36 of the sheet |4 passes under the points 52 and at the same time the enlarged portion of the cam 41 reaches the follower 48 so that the stripper 4| is moved from the position shown in Fig. 3 to the position shown in Fig. 5. As the stripper ll passes from one position to the other, the points 52 strike the inside of the projecting portion 36 of sheet M as seen in Fig. 4. It will be obvious-from the foregoing description that because of the way in which-the stripper 4| ducks inside of the sheet Hi there is no possibility that the sheet will pass between the stripper 4| and the blanket roll Hence, satisfactory stripping is assured providing that the stripper 4| has proper engagement with the sheet.

This stripping mechanism has been described as the preferred use of the stripper of this invention, but of course this stripper may be used in a stationary manner or with any other suitable mechanism, being especially advantageous wherever the stripping conditions are adverse.

- The conventional strippers of the past which were-of the spaced-finger type have not been reliable in their stripping action. Under adverse conditions as when the ink coverage on the leading portion of the blanket l3 is heavy, the sheet will adhere to the blanket l3 quite firmly with the result that the strip fingers would wrinkle the sheet or even tear it in the process of removing it. The necessity of separate adjustment of the various fingers to space them uniformly from the printing drum was a nuisance. If a straight edge stripper blade is used extending uniformly across the width of the printing roll I these difflculties are avoided but another difficulty is encountered. The ink from the inner surface of the sheet M tends to collect on the straight edge of such a stripping blade and to be smeared along the sheet. This is of course disastrous and must be avoided.

According to the present invention all of the advantages of both forms of stripper are combined by providing a large number of closely spaced strip fingers which in their most economical form comprise the corrugations 53 of a corrugated stripping plate which comprises the stripper 6|, seen best in Fig. 2. The individual stripping fingers or corrugations 53 have their bottoms formed by extremely narrow line-like surfaces which do not collect or smear ink as the sheet slides along them. The forward ends of these bottom surfaces form the points 52 which, as seen in Fig. l, are slightly rounded so as to minimize the danger of puncturing the sheets.

The danger of puncturing the sheets is substantially eliminated in any event by the correct positioning of the stripper 4| as seen in Fig. 5

and by the movement of the stripper such that 7 its points duck in behind the sheet as the leading edge of the sheet approaches the stripper. Thus, the sheet is first contacted by the bottom edges of the stripper 4| rather than by the tips of the points 52. When the stripper 4| returns to its normal position as seen in Fig. 5, its sheetengaging surfaces are at the proper angle for best stripping action so that they neither tend to cause the sheet to buckle nor tend to puncture the sheet.

The stripper 4| may bar 42 in any suitable manner be secured to the cross but it is preferably secured in a manner to be adjustable. One

'carrying the cam follower multaneously.

of theadvantages of this form of stripper is that it is in the form of a rigid unit so that all of its points 52 are adjusted simultaneously. The adjustment may be obtained by means of slots 56 in'the cross bar through which screws 51 extend to screw into nuts 58 welded or otherwise seside of the corrugations 53 or at least above the bottom of the stripper 4|. Of course, the screws 51 may be threaded directly into the upper portions of the corrugations or threaded studs may be secured to the stripper 4| and be secured in the slots 56 by suitable nuts screwed on the studs. The arm' 49 48 is preferably likewise adjustably secured by means of slot 59 and screw 6|. In order to facilitate adjusting the stripper 4| independently in angular and longitudinal directions the cam following roller 48 may be carried by an eccentric pin 63 which may be locked in any position by a lock nut 54. I

With these various adjustments it is seen that the mechanism may be adjusted so that the points 52 will pass quite close to the leading edge 58 of the blanket l3. Consequently, it will not be nece essary for the sheet l4 to project very far beyond the leading edge 38," especially since the feeding mechanism |1 provides absolute uniformity in the length of this projection. A length of approximately or {s of an inch has been found quite satisfactory. The projection 36 should not be too short or the points 52 might tear through and nick the edge of the sheet.

From the foregoing it is seen. that a stripper has been provided which combines the advantages of the prior blade and spaced-arm strippers. Thus, the stripper engages the sheet substantially all along the length of its leading edge so that its action is thoroughly dependable even under adverse cond'tions and yet the stripper also engages the sheet only along thin longitudinallyextending lines so that there is no danger of collecting ink from the sheet or.smearing the ink on the sheet. Furthermore, the stripper is one which may be manufactured very easily and ecod may be adjusted with great ease since all of the stripping fingers are adjusted si- In that re-pointing should be necessary, this may be done without requiring separate adjustment of the points but merely by grinding the points evenly on a suit:- able machine. The grinding and adjusting are not made more difiicult as the number of fingers is increased and hence as many fingers may be provided as are found to be advantageous.

I claim: K

1. A stripper comprising a plate bent to form closely spaced sheet-contacting surfaces positioned along parallel lines and terminating in stripper points adapted to lie close to a revolving drum, said surfaces and points being suiiiciently narrow to avoid the collection 5 of ink thereon.

,3. A stripper comprising a corrugated plate having one end cut substantially on a taper to form points at the crests of the corrugations on one side adapted to be disposed closely adjacent a roll with the crests of the corrugations lying close to a plane tangent to the drum at the point where extensions of said crests would strike the drum.

4. Stripping mechanism for strippin a sheet from a rotating roll, including stripping means normally positioned stationarily with its forward end adjacent the surface of the roll, and means for causing the forward end of the stripping means. to approach relatively closer to the axis of the roll as the leading edge of the sheet appreached the stripping'means to prevent the sheet from passing between the stripping means and the roll, said stripping means comprising a form a plurality of closely spaced sheet-contacting surfaces positioned along parallel lines and terminating in stripper points lying close to the rotating roll.

5. A printing press including a printing drum having a recess therein, a sheet-feeding means 30 for feeding a sheet in accurate registry with the with the leading edge portion of the sheet extending partially over the recess, stripping means normally positioned close to the surface of the printing drum to strip the sheet therefrom, and means for moving the stripping means into the recess ahead ofthe leading edge of the sheet and then out of the recess in a path passing through the original position assumed by the leading edge portion of the sheet with respect to the printing drum to prevent passage of the sheet between stripping means, said stripping means comprising a plate bent to form a plurality of closely spaced sheet-contacting surfaces positioned along parallel lines and terminating in stripper points lying close to the printing drum.

6. A stripper comprising a rigid support member, a plate member rigidly secured to the-support member and having a plurality of parallel a plurality of channels bounded by parallel stripping edges providing narrow longitudinally extending sheetengaging surfaces terminating in stripper points. '1. A strippercomprising a sheet member havmeans for supporting said member with the longitudinal dimension-of the creased portions extending edges terminating in stripper points adapted to lie close to a printing member 9. A stripper comprising a plate member having a plurality allel channels therein di- 65 of par vided one from another by narrow sheet-contactstripper tints adapted channel therein termi tacting ridges nating adapted to lie close to a printing member. ROBERT 6. BROWN. JR.

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