US2639995A - Process and apparatus for preparing a printing plate - Google Patents

Description

May 26, 1953 J. H. PERRY, JR., ETAL. 2,639,995

PROCESS AND APPARATUS FOR PREPARING A PRINTING PLATE Filed Feb. 28, 1949 4 Sheets-Sheet l mgl mw ATTORNEYS May 26, 1953 J. H. PERRY, JR.. Erm. 2,639,995

PROCESS AND APPARATUS FOR PREPARING A PRINTING PLATE Filed Feb. 28, 1949 4 Sheets-Sheet 2 ATTORNEYS 4 Sheets-Sheet 3 J. H. PERRY, JR., ETAL PROCESS AND APPARATUS FOR PREPARING A PRINTING PLATE INVENTO JD/// h. FfR/y ATTORNEYS May 26, 1953 Filed Feb. 28, 1949 MAY 26, 1953 J. H. PERRY, JR., ETAL 2,639,995

PROCESS AND APPARATUS FOR PREPARING A PRINTING PLATE Filed Feb. 28, 1949 4 sheets-sheet 4 ATTORNEY- Patented May 26, 1953 PRCESSL AND APPARATUS FOR-PREPARING A PRINTING PLATE` Jahn. u; rem/,3 Jr., Palm Beach. F1a., and Imbert C; Graham, Elizabeth, N. J assigning, by mesne assignments, to John H. Perry.. Jr., West Palm Beach, Fla.

Application February 28, 1949, Serial No. '78,818

. Claims.

This invention relates .to improvementsin apparatus for and the methods of preparing printing plates employed in lthe present dayA printing process. The invention also .relates to the printing plates themselves. Y

Further, the invention also pertains to certain steps in. the method. of producing one or many improved printing plates forv use on the present printing presses. Also, this invention pertains to an improvedapparatusin this art for carrying out the several-stepsin the process.

It `has longheen known in the printing industry that a printing` plate may be prepared for the press `by what is known as the etching process. However, there. have .been many drawbacksv and disadvantages to producing one or many of such plates by that prior, or old process.

The disadavntages are: lthe apparatus has been large and complicated; there have been no adeouate controls; theyoperations have been espeoially slow, such as ve or six plates per day;

half-tonescould not be included as part of thev plate without separate and special coatings of asphalt, or the like, placed thereon during each etching stepithe plates becamefwarpe'd in the process and thereforer special and additional apparatus was required to maintain them flat; the material of the original plates didnot stand up; detective printingoiten resulted due to powder beingl shifted or removedloy being touched whenv warm; and vtheetching only .carried to l0.017 depth and then it was 'necessary to'h'and'gouge or routl out 'the material between the lettera'line outs and small areas `in the half-tones.

The invention herein,V however, byreasonof experiments kand voperation of the present full size machine, does permit alternate powdering iapplyingprotective n'iatcrial) and etching so that a final depthLofthe groovesbetween .the letters and line cuts is approximately 0.625. 'tht-:reverse yof-thisstatement is that thetop of the vletters and line" cuts are 95025" higlifabove the door or bottom .of the grooves. with the improved process and 'apparatus hereinimprovedjeiective, printing plates are obtained in minimum time and with minimum vcost et `labor and minimum overhead A'cost of voperating the apparatus.

The prese-nt methods and apparatus 'of etching plates does givethe etching depth ci 1approximately 01125 for newspaper work. vHcWeyer., different types .of printing.. such as 'bookaspecial designs.v etci., areetched to.diiierent deptha'but still such etch'ingsare relatively' deep compared.

to the 0.017".

In providing efectve etched printing plates by means of the nowA preferred `etching; process.. the following outline is presented when. as an example, the nrocessis employed. in, the production of a newspaper. A typewrtteu settle or makeup for one plate. which is equivalent to one sheet of a newspaper, is provided any de sired manner, and includes the typed articles, any pictures, various kinds of art work.,` and headings of different size type, all assembled on a suitable cardboard or support. fsetuo photographed and after the development ci the photograph, it is transferred to, or burned into a sensitized emulsion spread. over en improved alloy plate, which plate later becomes the printf ins plate with letters, line cuts, and h ali ones therein. The pictures are also readily transferred 'with the typed articles to the plate, and the plates become the half-tones under the broad term art workf This plate as thus prepared, is then subjected to a first etching of desired depth- .An effective protecting material is then applied to the plate 11i-carrying forward this impro-ved-inventicn,l

there are certain steps in the process which have been improvedvand the overall eiiieiency of the process' has been greatly enhanced. An improved apparatus has been provided to efiectiveiy carry out the improvements.

In respect to one step in the process, and that is in providing a suitable protection for the side walls or `should-ers o-f the type and art Work formed by etching, a'satisfactory .material for protecting these shoulders of the type may be any commodity or material er powder that will be hardened in position and form a suitable Aprotection to the side walls of the type while the etching operation is going on. A powder which can. be fused against the vertical walls has 'been found to be satisfactory for vthis purpose,` improved-use and treatment .of this powder oonstitutes some of the improvements herein.

Usually in the improved process herein the powder 'is spread on the printing plate and the excess powder is scraped off in a novel manner, and in the scraping some of this powder is pushed or packed against the shoulders or verticals of the type and art work, and into the grooves of the half-tones. After excess powder has been scraped from the plate, it is desirable to satisfactorily set this powder to properly protect the shoulders during the etching operation. One manner of setting the powder against the verticals or shoulders is by heating it to a certain extent and have it cool by its own accord, or by actively cooling it, if such a step is desirable.

Referring to the pictures which constitute part of the original setup as photographed and transferred to the printing plate, it has been `found for newspaper work that using the 65 line engravers screen is satisfactory. The half-tones in the plate of pictures usually approximates 3600 dots per square Vinch in such a screen, and the dots are of different diameters across their tops. In the powdering and etching steps as disclosed herein, these half-tone pictures are etched to diiferent or graduated depths extending'from 0.006 for the white areas of the pictures to 0.0015 for the shadow and black printing areas. The middle tones of the pictures etch to various depths averaging approximately 0.0035" and usually these give the gray portions of the picture.

With the improved apparatus for pressing the powder against the vertical sides of the type, the same apparatus presses powder into the various grooves between the dots of the half-tones so that as the alternate powdering and etching steps take place, the white or high lights of the halftones etch to the greater depth.

It has also been found that the carrying out' of applying an acid. Any suitable etching apparatus may be employed.

It has been found from experience that the powdering and heating, and when desirable cooling, of the plate constitute steps in the etching process which in the old process were required to be carried out with great caution as those steps were delicate and complicated. The improved process herein, however, provides for the conducting of these steps in a quick and eicient manner that does not require the full attention of the attendant, as part of the operation is automatic. After the final etching, the plate is properly washed and is then curved and mounted on a base which is inserted in a printing press and the printing of the newspaper is then carried out. If desired, the plate after being curved and mounted on the base may be employed to form a matrix to receive a casting metal, which later is employed to print the paper.

For other methods of printing, the plates may be retained iiat for ilat bed printing presses. In addition, the plates may be curved to fit around a plate cylinder on an offset press, and in such a case, the use of water is eliminated, thus providing novel and efficient offset printing.

Certain parts of the improved apparatus have4 been provided to give exceptionally elcient operation and results while at the same time hav- 4 ing each plate produced without special apparatus required to prevent buckling of the plates.

There also is an improvement in the final printing plate itself. 'I'he improved plate consists of a series of letters, figures, line cuts, and halftones, `and sometimes other special showings which fall under the term art work. All of these several elements have been properly formed by etching to different depths in the plate. This situation has been accomplished substantially automatically'for there has been no change in the alternate applications of the powder and the etching steps that follow, and there has not been any special attention given to the half-tones or other art work parts of the plate over the letter parts of the plate, but the depths of the etchings are different and varied.

In carrying out this invention, it is desirable to useV an alloy plate which is satisfactorily treated in accordance with the invention herein, to thereby give the proper 4final printing plate with letters, figures, line `cuts and half-tones etched to their proper various depths as the plate moves through the powdering and etching apparatus, and to obtain these different etched depths without special attention as the plate has its regular passes through the apparatus. One of the best forms of alloy' for this purpose is a magnesium plate having approximately 96% magnesium, and the other elements of the alloy are as follows: approximately 3% aluminum, and approximately '1% of zinc, iron and beryllium. This alloy plate for this printing purpose,

gives a most satisfactory result in properly accepting the treatments of powdering and etching,v

and, as finally formed, will not show wear in theA printing, but will s tand up and permit many more printings from the same type than has heretofore been possible.

It has been found that this alloy plate after having been finally prepared by the process herein disclosed, and as noted above, is particularly adaptable and efficient in having matrixes made therefrom. As is well known, these matrixes are for the later casting of type for printing. It has also been found that this novel alloy plate will'` make at least 50% more matrixes than other types of alloy plates used for the same purpose. For instance, the present alloy plate has allowed A 3,000 matrixes to be made therefrom without showing hardly any wear. T'he zinc type plate, as

a competitor of the present alloy magnesium plate, would only give approximately 600 matrixes before the wearing was so great that it was necessary to replace the plate, The so-called copper alloy plate for this printing purpose breaks down when approximately 1200 or 1250v matrixes have been made.

Another feature of this invention is to provide a small size and relatively inexpensive apparatus which will quickly and easily and efficiently complete the powdering, scraping, heating and cooling steps in this process, so that one plate may. be completed in its production in a very short. space of time, say in the matter of minutes.

In conducting the improved process, it has been found desirable to provide two machine units positioned beside each other so that the proper application of the protecting material to the sides of the typeand art work, may be accomplished quickly. The plates are usually rectangular in that they are 18'] x 22" and 18" x 24, although other sizeplates may be used. Therefore, it is desirable to have the width between the guides in one unit of the apparatus constructedto receive the' 18" width and in the adjacent unit toreceive the pla-te on its 24 width. Each of these units provides for the application of the powdering to two vertical sides of the type and art work, and, therefore, the plates are preparedquickly, completely and satisfactorily by making two passes of the plate through each machine unit, where the steps of powdering, scraping, heating, and cooling, if desired, are accomplished. Then the plate is ready for an etching operation. This part of the improved invention vis nto provide these two machineunits and to operate them so that the cost of operation will be materially reduced while efficiently producing an improved printing plate. It has been found that with little experience two operators may conduct this portion of the process in a relatively short space of.

time.

Many improved structural features for properly applying the powder to the plate and scraping on the excess powder and pushing or packing the powder against the shoulders or verticals of the type and art work and to fuse the powder in position to protect the type shoulders and then to quickly and easily cool the plate so that it may be readily handled, are herein provided to easily and quickly give the improved printing plate. It will be noted that there is no routing required, that there has beenv no special attention paid to the half-tones, and that the plate has been etched to different depths.

There are many improvements in the apparatus and many detailed features which make it operate very successfully. These will be disclosed and defined in the detailed description below. It will be particularly noted that the process of producing the plates in their final form, has been greatly improved and shortened in time by reason of the novel apparatus and the steps of its operation, all as will be disclosed in detail by referring to the accompanying drawings, wherein:

Fig. 1 is a top plan view of a layout of two machine units with portions of the covers removed therefrom and of an etching machine;

Fig. 2 is a side view of the essential portions of one of the machine units shown in Fig. 1;

Fig. 3 is an enlarged view of a powder dispersing mechanism showing the powder `dropping onto one of the plates;

Fig. 4 is an enlarged view of a brush for cleaning excess powder from the plate;

' Fig. 5 is a modified view of one portion of one of the machine units of Fig. l and shows an ad- ,instable means for widening or narrowing the supporting guides to receive plates of different widths; 1

' Fig. 6 is a perspective View of a portion of the printingplate showing letter type formed in the plate by the etching process;

Figs. 7, 8, 9 and 10 illus-trate type formed in a plate by etching and shows the packing of powder protecting means on the shoulders of the type by suitable scraping and brushing means, and shows a pyramidal type of support;

Fig. 11 is a top plan view of a cooling mechanism incorporated in the machine units;

' Fig. l2 is a sectional View of Fig. 1l, taken on line |2|2 thereof;

Fig. 13 is a side view in section ltaken on line |3-|3 of Fig. 14, of a modified form of heating arrangement for setting the powder against the shoulders of the type in the printing plate;

Fig. 14 is a top plan view of a portion of the apparatus shownin Fig. 13;

Fig. 15 is a top plan view of a portion of a halftone showing dots of different sizes, and notations. of different portions of the half-tone; and

Fig. 16 is a side view of the dots of different sizes and illustrates the varied depth of etching and the pyramidal form of support.

In accomplishing the production of improved printing plates by the novel process and apparatus herein, there are provided two .machine units 2| and 22, Fig. l, preferably set side by side and particularly adapted for carrying out the'steps of applying powder, scraping off excess powder, setting the ,powder in protecting positions, cooling the plate to a temperature for ready handling, and etching.

In carrying on the invention herein by usin machine units 2| and 22, a plate 23 is introduced in unit 2| presenting the greater width ofl the plate as'its leading edge. As this plate proceeds through unit 2| and is delivered to the cooling end thereof, the operator takes the plate by hand, turns it and inserts it intomachine unit 22 which is either built or adjusted to accommodate the narrower width of the plate. When this platefinishes i-ts course through unit 22, it is again turned 90 and the operator reenters it into unit 2| with its wide width leading. 'Ihe'plate-is'nowl from its first entrance into machine unit 2|.`A After passing through unit 2|, the plate is again turned 90 and again passed through unit 22. In being removed from unit 22 all four sides of the type and art work in the plate have been protected by setting the powder in position against -the shoulders of the type and art work. The plate is then introduced into a suitable etching machine 24, where the unprotected portions of the plate are etched a desirable amount. thereby increasing the depth of ythe grooves between the various letters and between the various portions of the art work.

'The proper application of the protecting material against the sides of the type and art work, and the etching may be continued as desired .until proper or desired depth of grooves has been obtained,

. By means of the alternate powdering and etching steps, the type and points of the half-tones have supporting bases that are larger at the bottom, i. e., at the bottoms of the grooves than at the top as will be described below.

Referring now to .the structures of the machine units `2| and 22,-a frame 26 is provided for supporting the various parts. Normally unit 22 is a duplicate of unit 2| with the exception that guides 21 and 28 in unit 2| are positioned suilciently far apart to receive plate 23 vwith its wider side or edge foremost. Guides 29 and 30 in unit 22 are positioned closer together `so as to receive the plate 23 with its narrow width foremost. When desired the guides may be positioned or adjusted to receive a square plate.

A suitable means for moving the plate through each unit is provided, and usually it comprises chain Vdrives 3| and 32 having a `series of pickups 33 and 34 mounted thereon. These pickups are spaced apart, as will be noted in Fig. 2.

The plate 23 after being engaged by the moving pickups 33 and 34, moves forward into the powdering area of the machine, as will be noted in Fig. 3. The powder 36 in hopper 31 only drops to the plate 23 during the time the plate is within A suitable switch mecha the powdering area. nism is provided with a roller 38, Fig. 2, vso that as the plate 23 enters the powdering area, it engages the roller and a switch is closed to a motor, not

shown, that drives the powdering mechanismacsaeee illustrated in Fig. V3andcalmses'the powder to be'sifted throughssuitable screen `39 ontorthe plate-2L The roller I38 off the switching mechamsmv is carried by a pivoted lever arm having a longer portion 4u and atshorter vportion `4i for causing two switch points to bel closed when the roller 'is depressed. 'The switch vautomatically starts and stops the operation of the powder mechanism, as `the plate 23 passes .under the screen 395 'Any suitable powdering mechanism may be provided for properly sifting the powder, so that lumped portions thereof will not drop onto the plate. It is desirable in this preferredv structure, to provide two drum heads 42 and 43 and to assemble rods 44 between these two heads, as particularly vii'ldicated iti-Fig. l and in the end view of Fig. 3. When this powdering'mechanism is in operation, these rods 44 will move across the screen 39 and sift the-powder; It is to be under-y stood that spiral elements may take the place o! rods l44,or even rubbersqueegees may be employed in place of the rods 44.

The plate now passes from the powdering area to the scraping'area which provides for the scraping or removing of excess powder from the plate and forl pressing or packing some of the powder against the shoulders of the type and the points inthe half-tones, as'wllf'be particularly noted in Figs. 7 to 10, inclusive. Any suitable means maybeprovided for properly accomplishing this function. Inthe prior processes, the scraping mechanism had not been satisfactory without employingioonsiderable apparatus and giving it careful attention. There is provided herein an illustration of' three different types of satisfactory scrapingmeans, any one or all of which give satisfactory operations. In some instances when the grooves in the plate are quite deep, it may.

be desirable to have at least two of these scrapingy means operating. The illustrated types of Scrapers have been successfully operated in av full size'lnachine.

In the preferred apparatus for scraping the powder from the plate' and pressing some-of it against the shoulders of the letter type and the portions'of the half-tones; one of more Scrapers 46- maybe employed. In the preferred structure herein, three squeegees of'rubber or other lieiiible material. y'are shown, but experiments have shown that one squeegee will act :satisfectorily. Itis desirable to have the first squeegee 46 placed at an angle to the center line of the machine unit 2 l., thereby obtaining an increase in eulciency in the scraping operation. YIn addition tothesquee'gees, a rotary brush having separatebrushes 41, Fig. 4, is provided `for assisting in the scraping of the powder from the plate, and these several brushes alsoassist squeegee 46 in pushing or packing the powder against the sides of the type. 'The brush is helpful when the depthof the etching is relatively deep. Itis helpful that any powder remaining on the brushes 41 be removed after each contact with the printing plate and before a second contact therewith, andfo'r thispurpose a suitable bar structure 48 is .provided which engages the ends of the brushes during each revolution thereof and removes any excess powder adhering thereto. While four vseparate brushes are shown, they may be assembled in spiral form 'across their length, as in the well'known vcarpet sweeper brushes. It 'is :not necessary to operate these brushes 41 at alltimes of the operation of the machine. r In some-.in-

8 stances, `it is desirable to haves. hood 45 placed over the rotary brush.

The bristles -oi `thebrush may be cutat their ends to forma particularly desired thickness. /It will be `noted that the brushes rotate counterwise to the travel o1 the printing plate as it passes through the machine unit. It is to be understood that these brushes in operating alone or in assisting other scraping units, may be located at adjusted distances above the plate to cause the powder to be more or-less compacted into position or to be removed from the flat part ofthe plate.

While not necessary but in some instances'fdesirable,va verticalrbrush 49 is provided and is mounted on the frame of the machine in any suitable manner. This brush assists in removing excess powder and also assists in packing the powder against the shoulders of the type and crt work.

Usually the guides 2l and 28 maintain the printing plate in its proper travel through the machine unit, but it is desirable inv some instances to kprovide'a suitable means for holding the plate steady as rit is moving out from under the sorapingarea, For such functioning, a pair of sutable'wheels 50 is provided to engage the top edges of the plate and exert a slight pressure thereon so that the plate engages theguides and continues-a steady `movement into and through the open space 5| formed in the machine units between the powder scraping area and the beginning of the heating area. If desired the rollers may be replaced by inclined pieces mounted over the guides 2l and!!! to effect the same function.

This open space 5| is `particularly useful for two purposes. The lirst purpose is to allowthe printing plate to be introduced into the machine unit after its rst etchingand to pass through a heatingarea and a cooling area thereby providirlg a dry plate after vits travel through etchingland Washing baths. The plate thereafter is introduced at the beginning or left hand end of the machine unit 2l Where it will be subjected to all of the stepsin passing through the unit. The second reason for the provision of space 5| is for inspection of the printing plates as they pass through the machine units. Providing this space is not necessary, but it has been found to be helpful.

`It now becomes desirable to set the packed or pressed powder against the shoulders or vertical sides of the type and half-tones formed in the printing plate bythe etching, so that further etching will not eat into the sides of the type or will not undercut the type. -Any suitable means may be employed for setting this powdeiybut one form which has proven successful in the improved apparatus herein, is the provision of one or more heating units for effecting the powder to have it aiix itself to or adhere firmlyv against the side of the type formed in4 the plate. vIn the structures herein, there are provided a series of gas jets or burners 52 for heating the plate from beneath. A modied form of means for setting the powder is shown in Figs. 13Y and 14, wherein a suitable heating unit is employed above the plate. This modied structure will be described more in detail below.

As the printing plate enters the heating area, it operates a` 'suitable vswitching means which corresponds in general to the switching means for operating the powdering mechanism. The switching means in this heating area. vfunctions affect the powder which has been pressed in the half-tone depressions.

In Fig. 8 the powder 36 is shown as having been pressed against two opposite shoulders of the'type 8| by reason of the plate having passed through unit 2|, unit 22 and back on its second travel through unit 2|. With two passes through each of the machine units, the four sides of any of the type or letters 8| and the sides of the art work, will have received powder pressed against their shoulders. The plate will then be ready to be etched.

Figs. 9 and 10 show the operation of brush 41 when the depths of the grooves have been increased as will 4be noted by referring` to these figures. Fig. 9 also shows the application of the powder to one side of the shoulders of the type 8|, while Fig. l shows the application of the powder to the two opposite sides of the letter type 8|.

The alternate etching and powdering finally provides the outstanding letter type 8|, see Fig. 6, from the plate 23 and printing may be accomplished without the ink getting into the grooves 82 between any of the type letters or portions of the art work to an extent to cause trouble or defects.

An advantageous result has been obtained by practicing the method herein with the preferred apparatus. That result is that by the time the plate is etched to a depth of approximately 0.025", each letter or number or line cut has a supporting base of pyramidal construction. This pyramidal construction results by reason of the alternate powdering and etching as each successive powdering covers the prior powder and the side of the letter which is unpowdered by reason of the last etching. It will, therefore, -be noted that as each alternate powdering and etching takes place that the final metal support for each letter, line cut, and the like, has a widened base, as will be noted in the right ends of Figs. 8 and 10. After the nal etching takes place, the plate is thoroughly scrubbed in water and solvent powder, and all of the set powder is removed leaving the pyramidal type of support for each letter and line cut. This widened supporting base for each letter and line cut is helpful in giving more supporting strength to each letter during the printing of the newspaper. Also this pyramidal type of support for each letter and line cut portion and half-tone points, Fig. 16, permits the making of a matrix in a most efficient manner as there is no opportunity of the matrix material getting in under any of the letters or line cuts and the matrix is, therefore, easily pulled from the printing plate.

On the half-tones, the white or high lights etch down to approximately 0.006 depth. lIhe middle tones etch down to 0.0035". These are the gray part of the picture. The shadow areas are formed by reason of the first etch and are not usually deeper etched by any further operation. The white or high lights are noted in any half-tone picture as being the very light or small dots.

Any half-tone prints by reason of the diameters of the dots give the high lights, middle tones, shadow areas or the black part of the pictures, see Fig. 15.

The half-tones are only dots so far as printing is concerned, and the diameters of the dots show up in the printing as graduated from black to substantially white, Figs. and 16.

An advantageous feature or result which has been found in the practice of the invention herein in the preferred apparatus also disclosed, is that any picture included in the original typewritten setups or makeups, can be carried through the developing, burning-in steps and to the alternate powdering and etching steps and still only have an etched depth suitable for printing the picture itself. This result comes about by reason of the fact that after the first one or two etchings which only give a final depth of approximately 0.006" in the picture portion of the plate, it has been found that these pictures will not etch deeper, because with the squeegee type of scraper the powder is pressed or packed into the fine openings in the half-tone and act as a resist to further etching. This result usually comes about automatically and is particularly advantageous as the picture reproduces in the newspaper in excellent fashion without smearing or without leaving out important portions of the picture.

In reproducing pictures by the improved method herein, it is helpful to have the screen of the picture approximately 65 lines per inch in each direction for newspaper work. With a screen lined as thus indicated for newspaper work, it has been found that the etching depth is approximately 0.006. When using this process for book work instead of newspaper work, it is desirable that the picture have about 120 lines in each direction per inch.

In the half tone printing, the pictures are spoken of as S5-line engravers screen." In this 65-line screen there are approximately 3600 dots per square inch, each dot being of different diameter across its top. g

Usually the center of each dot is equidistant from the four adjacent dots even though the diameters of the adjacent dots are different. In some few instances in the printing art, there may be some small changes from the above arrangement, but they are considered as being within the foregoing general statement.

Referring now to the modified form of structure shown in Fig. 5, the guides 21 and 28 are shown as being movable back and forth to accommodate the narrow width of the plate 23 or the wider width of that plate. Thus, withthe adjustment shown in Fig. 5, one machine unit may be employed when desired to properly powder, scrape, set the powder and cool the plate. In this modification in Fig. 5, the driving chains 3| and 32 are preferably positioned near the outer edges of the frame 28 and are driven by a. suitable shaft 86. In such an instance, the propelling means for moving the plate 23 through the machine unit, takes the form of a relatively wide belt 81 preferably having two pickups 88 thereon for engaging the plate and moving the same forward. This belt is driven by the shaft 88 and may have a series of pickups fastened thereto.

In the modification of structure shown in Figs. 13 and 14, Fig. 13 shows the plate 23 being moved under a burner provided with jet openings 8| so that a burning gas 82 preferably issues on the slant against the leading edge of the shoulders of the type 8|, and thus acts to properly heat the powder so as to set it or afllx it against the shoulders to protect them against etching acids. The heat from the burner 90 may be of so-called blast formation, or may be reduced in intensity and nearness to the plate.

On this top or down-heating modified structure shown in Figs. 13 and 14, it is desired to obtain suitable heating to accomplish the powder setting without heating the body of the plate too high. If desired, a series of burners may be ing said plate out of said heating area, moving said plate at an increased rate of speed to a cooling area, applying cooling medium to a side of said plate opposite said letters and said art work While it is being moved at the higher speed, applying additional cooling medium to the wet side of said plate after said plate has moved from the higher speed area, and repeating the steps with the plate orientating into positions at right angles until the four sides of the letters of the words and symbols are coated and the powder set.

-3. In an apparatus for producing an etched printing plate for use on printing presses, the combination of a frame for supporting various parts of said apparatus, guides in said frame for receiving and guiding the plate through most of said apparatus, travelling means engaging said plate for moving it along said guides, first supports carried by said frame near the front end of said apparatus, a powder reservoir mounted on said first supports and above said guides for holding and dropping powder onto said plate as the plate passes thereunder, second supports affixed to said frame back of said first supports, a squeegee mounted in said second supports for engaging said plate as it moves from in under said powder reservoir, to press the opwder against the shoulders and the art work raised on said plate and for removing excess powder therefrom, third supports mounted on said frame beyond said squeegee, means mounted in said third supports for causing said powder to firmly adhere against the shoulders of said type and art work, and means following said powder adhering means for cooling said printing plate without affecting the type formed in the surface of said plate 4. In an apparatus for producing an etched printing plate for use on printing presses, the combination of a frame for supporting various parts of said apparatus, guides in said frame for receiving and guiding the plate through most of said apparatus, travelling means engaging said plate for moving it along said guides, first supports carried by said Aframe near the front end of said apparatus, a powder reservoir mounted on said first supports and above said guides for holding and dropping powder onto said plate as the plate passes thereunder, second supports afhxed to said frame back of said first supports, a squeegee mounted in said second supports for engaging said plate as it moves from in under said powder reservoir to press the powder against the shoulders and the art work raised on said plate and for removing excess powder therefrom, third supports mounted on said frame beyond said squeegee, means mounted in said third supports for causing said powder to firmly adhere against the shoulders of said type and art work, additional engaging means for gripping said plate as it passes from in under said powder adhering means for moving said plate at an increased speed and away from said travelling means, and cooling means for receiving said plate from said additional engaging means for cooling the under side of said plate.

5. In a powdering apparatus for preparing printing plates, the combination of a frame, a guide supported in said frame for receiving the plate, travelling means for engaging the plate and moving it through some portions of said apparatus, a support mounted on said frame near the front end thereof, a powdering mechanism including a reservoir mounted on said support for applying powder toone surface of said plate as the same passes under said powdering mech- ,16. 'anism, second supports mounted back of said powdering mechanism, a rubber squeegee mounted in said second supports and positioned at an angle to the axis of travel of said plate, said plate passing under said squeegee for removing some of said powder and for pressing other portions of said powder against type shoulders of said plate, third supports near said second supports, additional squeegees mounted in said third supports for assisting in removing excess powder and additionally pressing powder against said shoulders, fourth supports mounted on said frame, a brush mounted in said fourth supports and rotating in opposite direction to the movement of said plate for also removing excess powder from said plate, holding means mounted in said frame beyond said fourth supports for engaging said plate to hold it from vibrating, fifth supports mounted in said frame, means mounted in said fifth support for setting said powder against the upright sides of the type letters formed in said plate, a gripping means positioned in said frame beyond said fifth supports for engaging said plate and for moving it at an increased speed through another portion of said apparatus, a first cooling means for engaging said plate while it is issuing from said gripping means, a second cooling means mounted in said frame beyond said gripping means and positioned to receive said plate, and a doctor means mounted in said frame beyond said second cooling means for scraping liquid from the bottom of said plate as it is removed from said apparatus.

6. In an apparatus for preparing printing plates for use on printing presses, the combination of a frame, a guide supported in said frame for receiving and guiding a printing plate through each of the treating positions in said apparatus, means for engaging and moving said plate along said guide, a support carried by said frame near and above the front end of said apparatus, a powder reservoir mounted on said support for dropping the powder onto one surface of said plate as it moves thereunder, second supports mounted on said frame next to said powder reservoir support, a squeegee carried by said second supports and positioned at an angle to the travel axis of said plate as it passes from in under said powder reservoir, said squeegee engaging said plate for pressing some of said powder against type shoulders and art work formed in said plate and for removing excess powder therefrom, and heating means carried by said frame next to and in succession to said squeegee supports for setting said powder tightly against said shoulders as said plate passes thereunder.

7. In a system of producing an etched printing plate, an apparatus for applying a protecting element to the shoulders of the printing type and art work of said plate, said apparatus including a frame, a guide for supporting and guiding the plate through said apparatus, a travelling means for moving said plate along said guide. a powder reservoir, a support on said frame near the front of said apparatus for holding said reservoir over the travel of said plate, a mechanism in said reservoir for agitating said powder to have it drop in substantially uniform thickness onto said plate as said plate moves under said reservoir, a second support mounted on said frame beyond said powder reservoir, a squeegee mounted in said second support in position to engage said plate for pushing some of the powder against the upright shoulders of the type and art work and for removing excess powder, third supports, heating means mounted in said third supports to nx the powder to the shoulders of the type and art Work to prevent etching material from eating said shoulders, and cooling means mounted in said frame beyond said heating means for cooling said plate as it moves from the heating area in said frame.

8. In a system of producing an etched printing plate, an apparatus for applying a protecting element to the shoulders of the printing type and art work of said plate, said apparatus including a frame, a guide mounted in said frame for supporting and guiding the plate as it moves through said apparatus, a travelling means for moving said plate along said guide, a powder reservoir, a support on said frame near the front of said apparatus for holding said reservoir over the path of travel of said plate, a mechanism in said reservoir for agitating said powder to have it drop in substantially uniform thickness onto said plate as said plate moves under said reservoir, a second support mounted on said frame beyond said powder reservoir, a squeegee mounted in said second support in position to engage said plate for pushing some of the powder against the upright shoulders of the type and art work and for removing excess powder, third supports, heating means mounted in said third supports and being held adjacent said printing plate as it moves under said heating means to fix the powder to the shoulders of the type and art work, and a cooling mechanism comprising a support held in said frame for receiving said plate after said powder has been set, a cooling pad carried by said frame and in near relation with said support, means also carried by said frame for removing said support from said plate and allowing said plate to engage said pad for further cooling said plate.

9. In the method of preparing printing plates for use on printing presses, the steps of conveying a printing plate through successive treating zones, applying powder to the plate as it moves under a powder supply mechanism, pressing the powder against the shoulders of type and art 4 work in said plate by engaging said plate by a squeegee, removing excess powder from the plate as it moves through the apparatus, holding the plate from vibration during the pressing step, semi-liquefying said powder by heating, cooling the semi-liquid powder, thereafter moving said plate at an increased speed beyond said heating means, and cooling said plate as it issues from the increased speed area.

10. In the method of preparing printing plates ior use on printing presses, the steps of conveying a printing plate through successive treating zones, applying powder to the plate as it moves under a powder supply mechanism, pressing the powder against the shoulders of type and art work in said plate by engaging said plate by a squeegee, removing excess powder from the plate as it moves through the apparatus, holding the plate from vibration during the pressing step, semi-liquefying said powder by heating, cooling the powder as so semi-liquied, thereafter moving said plate at an increased speed beyond said heating means, cooling said plate as it issues from the increased speed area, and cleaning the conveyor preparatory to receiving the next plate.

JOHN H. PERRY, JR. ROBERT C. GRAHAM.

References Cited in the file 0f this patent UNITED STATES PATENTS Number Name Date 770,912 Leavitt Sept. 27, 1964 354,675 Spitzer May 21, 1907 854,676 Spitzer May 21, 1907 1,225,477 Murray May 8, 1917 1,243,431 Leitner Oct. 16, 1917 1,651,906 Powers Dec. 6, 1927 2,032,771 Scherer Mar. 3, 1936 2,175,272 Lipsius Oct. 10, 1939 2,328,904 I-Iiers Sept. 7, 1943 2,459,396 Solana et al. Jan. 18, 1949 OTHER REFERENCES Commercial Engraving and Printing; Commercial Engraving Publ. Co., Indianapolis, Ind.

5 (1921), page 338.

Ilford Manual of Process Work; Ilford Ltd., Ilford, England (4th ed. 1946), pages 135-113.

Claims (1)

10. IN THE METHOD OF PREPARING PRINTING PLATES FOR USE ON PRINTING PRESSES, THE STEPS OF CONVEYING A PRINTING PLATE THROUGH SUCCESSIVELY TREATING ZONES, APPLYING POWDER TO THE PLATE AS IT MOVES UNDER A POWDER SUPPLY MECHANISM, PRESSING THE POWDER AGAINST THE SHOULDERS OF TYPE AND ART WORK IN SAID PLATE BY ENGAGING SAID PLATE BY A SQUEEGEE, REMOVING EXCESS POWDER FROM THE PLATE AS IT MOVES THROUGH THE APPARATUS, HOLDING THE PLATE FROM VIBRATION DURING THE PRESSING STEP, SEMI-LIQUEFYING SAID POWDER BY HEATING, COOLING THE POWDER AS TO SEMI-LIQUIFIED, THEREAFTER MOVING SAID PLATE AT AN INCREASED SPEED BEYOND SAID HEATING MEANS, COOLING SAID PLATE AS IT ISSUES FROM THE INCREASED SPEED AREA, AND CLEANING THE CONVEYOR PREPARTORY TO RECEIVING THE NEXT PLATE.

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