US2677320A - Developing head for phtolithographic plate treating machines - Google Patents

Description

May 4, 1954 H, A COUGHUN 2,677,320

DEVELOPING HEAD FOR PHOTOLITHOGRAPHIC PLATE TREATING MACHENES Filed April 28, 1951 2 Sheets-Sheet l JCI FIG. l.

/A/fA//m HARRY A. CoucHLlN May 4, 1954 H. A. coUGHLlN 2,577,320

DEVELOPING HEAD EOE PHoToLITHoGRAPHIc PLATE TREATING MACHINES 2 Sheets-Sheet 2 Filed April 28, 1951 Patented May 4, 1954 DEVELGPNG HEAD FOR PHOTOLITHO- GRAPHC PLATE TREATING IWIACHINES Harry A. Coughlin, St. Louis, Mo., assigner to John S. Swift Co., Inc., St. Louis, Mo., a corporation of Missouri Application April 28, 1951, SerialNo. 223,620

5 Claims.

This invention relates to improvements in developing heads for photolithographic plate treating machines, the present improvements more particularly relating to a developing head assembly which constitutes a continuationin-part of the prior application of Harry A. Coughlin, SerialNo. 718,063, liled December 23, 1946, now Patent No. 2,555,874.

TheA above mentioned prior application describes the manufacture of photolithographic printing press plates in great detail. As there described, the manufacturing procedure included the steps of coating a zinc plate with a solution of albumen and ammonium bichroinate, which is sensitive to light when dry, reprod cing from a photolithographic negative the matter to be printed on the light sensitized plate and developing the sensitized plate to bring out the exposed light hardened portions whereby to the image of the photolithographic negative in the sensitized zinc plate.

In developing the exposed photolithographic press plates, the present practice is to pour a developing ink onto the sensitized coating, then spread the ink over said coating with a towel and then rub down the inked surface with a second towel to absorb the surplus ink and to dry the remaining ink. The inked plate is then placed in a pan of water or under a tap and the inked coating hand-rubbed with a large ball of cotton to soften and wash away the soft non-printing areas, leaving the hard printing areas afxed to said plate.

This hand-hiking and washing of the photolithographie press plate is a slow and arduous operation, requires a large stock of rubbing towels and cotton and results in the loss of all of the developing ink absorbed by the towels. Another objection is that the hands become stained with ink dyes, which are difficult to remove, inhalation oi the chemical :fumes causes sickness and loss of time; and physical Contact with the ammonium bichromate causes serious poisonous infections which are difcult to cure and cause some employees to seek new occupations.

It is an object of the present invention to provide an improved developing head which will replace the hand rubbing operations with means which will mechanically and uniformally rub over the entire surface of the plate to be developed, thereby avoiding the diiiiculties mentioned above.

Itis a further object of this invention to providev a plate developing head with a wraparound` fabric blanket of a material which will 2 imitate or reproduce the gentleness oi touch obtained by hand operations, and positively maintain that touch uniformly over the entire surface of the plate during the developing procedure.

It is a further object hereof to utilize a pile fabric of wool cut plush with a tightly woven Warp and weft to form a rm ground texture, such pile fabric constituting the wrap-around blanket carried by the developing head.

A further object of the present invention is to provide a hollow developing head having a water inlet and a plurality of water outlet ports arranged to direct the outgoing water against the wrap-around blanket carried by the develop ing head, thereby applying the pressure of the water against the wrap-around blanket to dis tend the same in suchmanner as to reproduce the gentle touch. obtained in the hand operation.

A still further object of the present invention is to provide mechanical operating means for moving the developing head uniformly over the surface of a photolithographie plate to be developed, and to provide the developing head with means for permitting placement of the wrap-around blanket on the developing head without disturbing the position of the head relative to the photolithographic plate.

The invention consists in a hollow developing head operatively supported in a photolithographic developing machine, by means of power operated, devices which cause the head to move in a predetermined orbit over the piates, and al pile fabric of wool cut plush positioned on the head so that the flow of the water supplied to the developing head for delivery to the photo lithographie plate will distend the fabric and cause the pile iilaments yieldingly to contact the surface of the. plate to substantially reproduce or imitate the touch or contact pressure obtained in hand operations.

The invention further consists in the parts and in the combination` and arrangement of such parts, as will hereinafter be described in connection with the accompanying drawings, wherein:

Fig. l is a fragmentary top plan-view of the photolithographic plate treating machine disclosing'the parts thereof adjacent the developing head;

Fig. 2 is a greatly enlarged transverse sectional elevational view taken along line 2-2 in Fig. 1;

Fig. 3 is an enlarged top plan view of the improved developing head; Y

3 Fig. 4 is a sectional view at line 4 4 in Fig. 2; Fig. 5 is a sectional vieiv at line 5 5 in Fig. 2; Fig. 6 ig a sectional view at line E-S in Fig. 2; Fig. '7 is a sectional vieuT at line 'i-l in Fig. 2; and

Fig. 8 is sectional elevational view or" the plate rubbing blanket removed from the developing head body to show the means for securing the same to the body.

The automatic photolithographic plate treating machine of the above mentioned prior application, Serial No, comprised a table having spaced stations for receiving, inlcing, heating and developing each plate. Only a fragmentary of the machine has eeen shown in Fig. l, Wherein the table i includes the heating and developing stations C and D. The heating station C is provided with an endless belt i3 having a power driven roll iE, and the belt cooperates with cross feed rolls id at the sides thereof. The station C also includes a battery of overhead infra-red electric head lamps il in a frame Ila above the belt The developing station D (Fig. l) includes a stationary' top panel i8 for supporting a plate (not shown), a of water spray pipes i9 disposed over said panel lil at the plate receiving end, and a horizontally movable developing head 2D which engages the upper surface of the plate. The pipes SS are connected with a water supply line 2i, and the developing head 20 is connected to the same line 2i by a flexible hose Ela. The line 2i has an electrically operated cut-o valve 22 and a hand valve 23. The developing head 2d is shown more fully in connection with Figs. 2 and 5, wherein the head comprises a hollow box assembly having a top Wall 25 provided with a Water inlet nipple for the hose 2 la, a bottom wall 2'1 forming a broad, fiat face provided with a plurality of water outlet ports 28, end plates 2i?, side plates, 3:3 and intermediate transversely directe rib members Si located adjacent the water inlet nipple 2S. Each o said ribs is provided with enlarged openings 32 to permit free ilow ci the Water from the zone immediately adjacent the inlet nipple toward each end oi the hollow box or head.

The hollow head Eil (Figs. 2 and 5) is provided on its upper Wall with stirrup members 34 adjacent its opposite ends, each stirrup having outwardly extended foot elements attached to the Wall and upwardly extending guide ele-ments 3E connected at their outer ends by a bridge 3l. The bridge is provided with a threaded opening 38 in which i ounted an adjustment screw 39. In the vi y oi the water inlet nipple 28, the Wall is provided with a pair of spaced angular guide elements Il@ which supplement the function or" the guide portions of the stirrups 34.

The hollow head 2E is operatively carried on a cross (Figs. l, 2 and 3) of the photolithographic treating machine. Cross bar 42 is provided with pairs of edge notches 43 (Figs. 5 and 7) which engage the guide portions 35 of the .5tirrups 34. An additional pair of edge notches 44 cooperate with the spaced guide elements 4U. The notches in the cross bar 42 loosely engage the respective guides carried on the Wall 25 of the hollow head which permits a relative rocking movement or play between the head and the cross car in the direction defined by the guide portions 3S of the stil-rups Bil, whereby the hollow head is prevented from binding in or between these guide portions. Regulation of this relative rocking motion of the hollow head is obtained by providing the cross bar l2 with a pair of transverse members 45 (Figs. 4 and d) having their opposite end portions extending to each side of the cross bar to overlie the top surface of the wall 25. Each of the members 45 is provided With a threaded aperture to receive a leveling screw 46, there being two such leveling screivs 45 for each member 45. The members 45 are connected with the bar 42 by means 4l' or known type.

The hollow head 2g is provided with a wraparound blanlret B (Fig. 3) which is of a size to cover the lower or broad flat surface of wall 21 and provide sufficient material at its lengthwise margins to permit the blanket B to be wrapped around the opposite longitudinal sides of the head 2t. Each longitudinal margin of the blanket B is clamped between a holder bar 5e and a backing bar 5|, the bars being secured in clamp relation on opposite sides o` the blanket B by means of a plurality of threaded. elements 52 recessed in the bar 5i). The holder bar is provided with a pair of longitudinally spaced notches 53, each notch being adapted to engage with a xed pin 54 projecting from the outer surface oi the vfall 25 for that purpose.

In mounting the wrap-around blanket B on the head 20, one of the holder bars is first positioned with its notches 53 engaged over the pins 54, the blanket is then disposed about the lower wall 2l of the head, and the opposite holder b r 5G is then brought into position whereby its notches 53 engage the pins 54 provided therefor. In this manner, the pile 55 or the fabric B naturally assumes an erect position projecting normal to the broad flat face of the Wall 2T, so that the tip portions of the erect nlaments constitute the portions of the blanket which rub the surface oi' the photolithographic plate which is to be developed and are receptive to the ink on such plates In use, the hollow head 20 is supplied with Water through the flexible hose 21a under a low pressure condition. In one commercial machine, wa er was supplied to the machine at about 55 to 6G' pounds per square inch, gauge. The valve 23 was turned toward closed position until the pressure in the head 2Q was approximately one pound or less. This low pressure resulted due to the large volume of the head 2U compared to the one-half inch hose 21a, and the back pressure effect produced by the tightly woven Warp and Weit of the blanket B. Thus, the dynamic pressure effect of the flowing liquid caused the blanket to belly outwardly or assume a distended and somewhat curved position relative to the ilat surface of Wall 2T so that the erect filaments of the pile 55 in the central longitudinal zone of the blanket El moved away from the Wall and was yieldingly held by the flow of the Water. This action eiIectively reproduces or imitates the gentleness of touch which can be achieved by hand developing operations, but which is very difllcult to maintain uniform.

It is preferred, in connection with the wraparound blanliet B, to employ a pile fabric of wool cut plush with a tightly woven warp and weft to form a nrm ground texture which will offer a desired degree of resistance to the free now of the Water through the interstices of the warp and weft. The plate to be developed passes adjacent the erect filaments so that their tip portions become eiective to reproduce a gentle but uniform rubbing touch on the surface of the plate to be developed and the blanket is more receptive to the inlr. This use of a pile fabric of wool cut plush prevents an undesirable hard or hard gemeen rubbing or scrubbing action on the photolithographic plate surface, so that the mechanical movement or the hollow head produces a uniformly gentle rubbing action over the full Ysurface of the photolithcgraphic plate vand leads to better developing results.

It has been found, furthermore, that the Wool out plush has a greatly to be desired useful life. The life of a typical wool cut plus fabric has been found, in some instances, to extend over the developing of 150,000 square feet of photolithographic plate surface. This is important, since it practically eliminates the high cost of the wiping cloths required in the hand operation of developing such plates.

The mechanical operation of lthe present developing head is obtained from a suitable source of power as a motor (not shown) connected to the drive shaft 5l located at one side of the frame of table This power input to the drive shaft 51 may be seen in connection with Figs. 1 and 2. The drive shaft El' is provided with a beveled gear 5t which meshes with a second beveled gear 55 hired to a vertically directed shaft member te carrying at its upper end a bearing plate 6| provided with an eccentrically located drive pin 52. A cross shaft 5t is provided at one end with a bevel gear 6s meshing with the bevel gear 59 and having at its opposite end a bevel gear 65 which meshes with bevel gear S5 carried by a second vertically directed shaft 61 having a bearing plate St at its upper end carrying an eccentrically located pin The cross bar 42 which supports the hollow head is provided with a bearing aperture lil at its drive end and with a slotted bearing opening 1i at its opposite end. These bearin@` openings l and 1i are engaged respectively by the drive pins 62 and 6g carried by the respective bearing plates tl and 68. It is obvious that rotation of the drive shaft 51 produces simultaneous rotation of the bearing plates and the pins thereon so that the cross bar 42 is caused to move in a circular orbit which produces both crosswise and longitudinal movement relative to the photolithographic plate being moved therel below.

The hollow head 20 may be leveled or angularly adjusted with respect to the normal horizontal position of the photolithographic plate by means of the leveling screws 4%, previously described. I

In Fig. fl, will be observed that the leveling screws it contact the exposed surface of the blacking bars 5i and that by threading up or backing oir the leveling screws at one longitudinal side or the other of the head, the head may be moved or singularly rocked relative to the guide portions and is to change the position of its leading edge, thereby permitting the photolithographic plate to pass beneath the hollow head without striking a portion of the head or digging into the blanket B.

The head 20, furthermore, carries a photolithographic plate hold down arm which is shown at 13. This hold down arm comprises a longitudinal guide bar 'M having a beveled leading face which is positioned to direct the leading edge of the photolithographic plate down and under the head 20. The bar 'i4 is pivotally mounted at the opposite ends of the head by arm members 16 (Figs. 3 and 4) carried thereon by pivot elements 11 which cooperate with xed stop elements 18 to limit the downward pivoting motion of the guide bar 14.

The hold down means 13, of course, may be pivoted upwardly and rearwardly to a position lout of the way when it is necessary to remove blanket Band replace it by a new blanket. The removal of the blanket B may be easily accomplis'hed without disturbing the desired setting of the leveling screws 46 by threading the screws A3?: to permit'the head '20 `to drop away from the leveling screws a suiilcient distance so that the back bar 5| engaging the longitudinal edge of the blanket B may be lifted away to disengage the bar 50 from the stop pin 54 without striking the leveling screws.

The present invention has been described in connection with a preferred construction in which there is employ-ed a pile fabric of wool cut plush. However, itis obvious that changes may be made in the construction of the developing head and certain variations may be had the characteristic of the pile fabric of wool cut plush without departing from the scope of the invention donned by the appended claims.

What I claim is:

l. In a photolithographic plate treating ma chine for removing excess non-printing ink from the plate, a panel to support the plates moved through the machine, a movable hollow body eX- tending substantially the width of said plate supporting panel and having a perforated bottom face spaced from said panel, drive means relatively loosely connected with said body for moving the same in a circular orbit over said panel on which the plates move, a blanket carried on said body covering said bottom face, said blanket being of a character receptive to the printing ink and consisting of pile fabric of wool cut plush with a tightly woven warp and weft forming a nrm ground texture, and conduit means connected with said body supplying a fluid at relatively low pressure thereto for flow through said perforated bottom face, the fluid escaping through the said blanket and simultaneously distending the blanket into a position yieldable to the thickness of the plate and erecting the filaments of the pile out plush into gentle yielding contact with the plate and flushing away the excess of the non-printing ink contacted and loosened by the distended filaments, the pressure of said uid distending said blanket causing said loosely connected body to assume a position relative to said drive means for controlling the precsure of contact of the filaments with the plate.

2. In a photolithographic plate treating machine, a supporting panel over which the exposed inked plates move during the developing treatment to remove excess non-printing ink, a hollow body extending substantially the width of said supporting panel and having inlet for developing fluid and a large area bottom face with outlet ports therein, a conduit connected to said body inlet to conduct developing uid thereto under relatively low pressure, a movable cross bar on the machine extending over said panel, power operated means on the machine connected with said cross bar for moving said cross bar in a circular orbit, cooperating members on said body and cross bar adjustably and loosely mountinfy said body spaced above said panel, and a blanket covering the bottom face area of said body, said blanket being of a character receptive to the printing ink and comprising a pile fabric of wool cut plush with a tightly woven warp and weft to form a firm ground texture, said fluid escape through said body outlet ports being resisted by said blanket with the pile filaments becoming distended and yieldingly held in touching relation with the plate being treated to dislodge the ex- 7 cess non-printing ink for removal by the flushing action of the uid, the pressure of said fluid distending said blanket causing said loosely mounted body to assume a position for controlling the contact of the laments with the plate.

3. The photolithographic plate treating machine set forth in claim 2, in which removable clamp means is provided to hold said blanket along opposite margins, said clamp means tightening said blanket over the bottom face of said body.

4. The photolithographic plate treating machine set forth in claim 2, in which cooperating clamping members hold said blanket along opposite margins, and pin elements in the upper surface of said body locate said clamping members with said blanket tightened over the bottom face of said body.

8 5.`The photolithographic plate treating machine set forth in claim 2, in which plate hold down means is carried on said body, said means including a guide member located to guide the plates beneath said body for contact by the distended pile laments of said blanket.

References Cited in the iile of this patent UNITED STATES PATENTS Number Name Date 2,325,867 Matsalcas Aug. 3, 1943 2,347,511 Scarzello Apr. 25, 1944 FOREIGN PATENTS Number Country Date 130,055 Germany Apr. 23, 1902 609,072 France May 3, 1926

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