US2212233A

US2212233A - Apparatus for coating printing cylinders

Info

Publication number: US2212233A
Application number: US142999A
Authority: US
Inventors: Charles L Henderson
Original assignee: Paper Patents Co
Current assignee: Paper Patents Co
Priority date: 1937-05-17
Filing date: 1937-05-17
Publication date: 1940-08-20
Anticipated expiration: 1957-08-20
Also published as: CH198975A; GB502662A; US2212234A

Description

g- 1 c. L. HENDERSON 2,212,233

APPARATUS FOR COATING PRINTING CYILINDERS Filed May 17, 1937 4 Sheets-Sheet 1 3 haw:

Aug. 20, 1940- c. L. HENDERSON 2,212,233

APPARATUS FOR COATING PRINTING CYLINDERS 4 Sheets-Sheet 2 Filed May 17, 1937 By $4 4763. (1% ,am 9- 0M Aug. 20, 1940- c.1.. HENDERSON APPARATUS FOR COATING PRINTING CYLINDERS Filed May 17, 1937 4 Sheets-Sheet 3 3% wa M on Aug. 20; 1940. c. HENDERSON APPARATUS FOR COATING PRINTING CYLINDERS Filed May 17, 1937 4 Sheets-Sheet 4 3W w cow 0 wn! Patented Aug. 20,

. 2,212,232. APPARATUS roa ooa'rmc ram'rma crnmneas cm... 1.. Henderson. Appleton. was,

to Paper Patents Company, N corporation of Wisconsin assignor eenali Win, a

' Application May 17.1931. Serial-No. 142,999 11 Claims. .(01. 91-42 My invention relates to the general art of printing and has particular reference to the preparation of etched printing cylinders for use in rotary printing presses and the like. Such cylinders have the design or pattern to be printed reproduced in intaglio on the surface thereof, and in their preparation a photographic or other reproduction of the design or pattern to be printed is photographically transferred-to the surface of a suitable, smooth finished cylinder having a coating thereon of what is known as a sensitized resist solution. This coating has the property,

that the portions thereof which are exposed to light become relatively insoluble in water and in etching solutions, Thus, when the cylinder is etched after the photographic transfer. operation,

- the exposed portions of the cylinder coating prevent or limit the etching of those areas of thesurface of the printing-cylinder which correspond to the light portions of the design or pattern to be reproduced.

Attempts have heretofore been made to coat printing cylinders with sensitized resist solutions of various types, but so far as I am aware, prior to the discovery of the apparatus and processes set forth in my co-pending applications, 8. N.

46,506 (filed October 24, 1935), and S.- N. 139,706

(riled April- 29. 1937), the attainment of uni-- form even coatings has never been successfully accomplished. Extensive tests and experimentation have established that the apparatus and methods disclosed in the above identified applications constitutes a particularly satisfactory solution of the problem with reference to the coat-' ing of small and medium size printing cylinders. .However, while it is possible to coat large diameter cylinders such as are used in newspaper work by the methods and apparatus'disclosed in these applications, some dimculty may be encountered. Y

The principal objectof the present invention, therefore, is tov provide apparatus for coating printing cylinders, particularly cylinders of large diameters, with a sensitized resist solution so as to produce even coatings of uniform and controllable thickness. In its general aspects. the present application is a continuation in part of my co-pending applications, Serial Nos.- 46,506

- and 139,706, mentioned in the foregoing.

The'invention disclosed and claimed in the above mentioned co-pending applications is based on the discovery that the even anduniform coating ofa printing cylinder with a sensitized'resist solution or the like may be. accomplished simply by applying the coating material to the longitudinal axis generally perpendicular to its longitudinal axis,

rotation of the cylinder printing cylinder, and then rotating the cylinder about its longitudinal axis and also about a vertical axis generally perpendicular to the longitudinal axis during at least a portion of the period when the coating is drying and becoming set. The coating may be initially applied to the cylinder when it is rotating about one or both of these axes'and, .ifdesired, the drying of the coating may be aided by the use of flow currents of heated air.

I'have also discovered that more satisfactory results can'be obtained when using certain types of coating materials, and particularly when coating cylinders of large diameter, by varying the speeds of rotation either about the longitudinal axis of the cylinder or about .the axis perpendicular to the longitudinal axis. of the cylinder,-

or both, during the drying operation. In ordinary instances'the coating material will be applied'to the printing cylinder when such cylinder is being rotated about its longitudinal axis at a moderate speed, although the coating material may be applied when the cylinder is bein rotated about both its longitudinal axis and about the axis perpendicular to its longitudinal axis. At least after the coating has been applied, the cylinder will be rotated both about its and about the axis which "is be desirable to increase the speed of rotation of the cylinder at least about the axis perpendicular to the longitudinal axis of the cylinder, which higher speed will preferably be continued throughout at'least' the greaterportion of the drying operation. Under certain circumstances, it may also be desirable to increase the speed of about its longitudinal axis during the drying operation, as will be hereinafter made more apparen Other objects and advantages of my invention will be mademore apparent by reference to the accompanying drawings and the followin description of In the drawings: 7

Figure 1 15a perspective view of an apparatus embodying the principles of the present inventlon with a printing cylinder in place therein. The covers and otherclosures of the device have been illustrated as opened up or cut away to make' clearthe several structural features;

one preferred embodiment thereof.-

- view is taken on the paratus illustrated generally in Figure 1., The

general line 2-2 of Figure 3;

Figure 3 is a sectional view on the general line 3-3 of Figure 2; K

Figure 4 is a sectional view on the general line 4-4 of Figure 3. A printing cylinder is also shown in place in this figure:

Figure 5 is a reduced plan view of the apparatus showing the relation of the various covers; and

Figure 6 is a perspective view of the mechanism utilized for'applying the coating solution to the roll. I

Referring to the drawings," Ill designates a hollow, cast iron base upon which is mounted a iixed vertical post ll. Rotatably mounted on the post I I by upper and lower anti-friction bearings l2 and I3 (Figure 4) is the central hub l4.

of a reinforced circular table l5. estals l5 are rigidly mounted on opposite sides of the table II and areprovided at their upper ends with open bearings I! which receive and journal the ends of the supporting shaft l3 for the cylinder to be coated.

During the coating operation, it is highly desirable that the cylinder to be coated shall be protected from dust, and to this end the table II is provided with; a generally I cylindrically shaped housing I! for enclosing the cylinder during the coating operation. The housing I! is of split construction, and the upper section 25 thereof may be swung back on suitable pivots 2| to permit the cylinder to be placed within or removed from the housing. Releasable clamp members 22 are provided for holding the upper and lower sections of the housing It together during the coating operation. The upper housing; section 20 is provided with a circular opening 23 normally tightly closed by a removable cover 25 and a fine mesh screen 25, the purposes of which will hereinafter appear. If desired, the end portions of the housing I! which engage the cylinder-supporting shaft may be provided with felt sealing rings 21 or the like for assuring a tight connection between the housing and the cylinder. When such sealing rings are used, an airtight, dust proof housing for the cylinder is made possible.

The table I5 is rotated about its vertical axis by A pair of pedcoating apparatus. The shaft of this motor 23 carries a pulley 35 which drives a belt 3| trained over two idler guide pulleys 32 and adapted to encircle a suitable ring member 33 supported at theperiphery of the table I5. The cylinder is revolved about its longitudinal axis by a variable speed motor 34 adiustably supported upon the drical in form and is preferably constructed of sheet metal'reinforced with angle irons. The

I outer housing 33 is completely covered at its top by a sheet metal cover 40 which includes two oppositely arranged, hinged sections 4| and 42, as illustrated particularly in Figures 3 and 4, The

a variable speed, electric motor 23 mounted I at one'end of the stationary structure of the closed by a hollow, open ended, hinged cover 44' of special design. The walls of this hollow cover 44 are insulated, and a plurality of electrical heater elements 45 are located in the space therebetween. The opposite ends of the hollow cover are open, as illustrated in Figure 4. The circular opening 43 in the central cover section 42 aligns with the opening 23 in the inner housing I3, as is illustrated in Figures 3 and 4, the purpose of the openings 23 and 43 and the heater units 45 being to permit the introduction of heated air. into the inner housing l9 during the drying of the coating. When the cover 25 for the inner housing I3 is in place no air will be admitted through the openings 23 and 43, and when the cover is removed to permit air to flow into the inner housing, the screen 26 serves as a filter.

The coating solution is applied simultaneously along the entire length of the cylinder being coated by means of an elongated, shallow tray 41 supported upon the table l5 near the bottom of the inner housing l3. A lifting mechanism which includes two lifting levers 48 and an operating handle 43, as illustrated particularly in Figures 3 and 6, is provided for raising and lowering the tray 41 uring the coating operation. The lifting mecha ism assures that the coating material shall be .brought into contact with the cylinder only at the proper time. The tray 41 is also used to hold water or alcohol for washing the cylinder preparatory to the coating operation, as will hereinafter appear.

The inner housing I5 is maintained closed and substantially airtight during at least the initial portions of the coating applying operation. The upper section of the housing I! is, however, provided 'with a pair of vent openings which may be opened if desired through the actuation of automatic latches. These vent openings are illustrated at 51 in Figures 3 and 4 and are normally closed by pivoted cover members 53. The cover members 53 are biased to the open position by centrifugal force when the table I5 rotates, and are held in the closed position by pivoted latches 54. The latches 54 may be readily tripped from without the inner closure l9 during the coating operation when it is desired to open the vents. The preferred method of accomplishing the coating of a printing cylinder inaccordance with my invention is substantially as follows: The cylinder to be. coated is placed in the apparatus, as illustrated in Figures 1 and 4, and is connected to the cylinder motor 34 by the belt 36. The inner housing I! is then closed, the vent covers 53 are latched in place, and the central opening 23 in the upper section 20 of the inner housing is closed by the tight cover 25. Distilled water or alcohol has previously been placed in the tray 41, and it is assumed, of course, that the surface of the cylinder to be coated has previously been carefully smoothed and prepared in eration of the motor 29.

- 41 to-flow out of the endsof the tray into the inner housing l9. Suitable spouts .55 located at the ends of the housing l8 serve to carry the water or alcohol into catch buckets 51 releasably attached to the bottom of the table. After a few minutes, the tight cover 25 for the opening 23 in the inner housing is removed and the vent latches 54 are tripped to release the vent covers 53 and open the vents Air, filtered by the screen 25, then circulates through the inner housing [9 and out the vents 5| as a result of the centrifugal action produced by the rotation of the table I5. To assure free circulation of air through the inner housing l9 at this time, the outer housing 39 should not be airtight. In the structure shown inthe drawings, a substantial opening exists between the two hinged cover sections 4| and 42. when those sections are in the closed position (see Figure-3).. Also, the opening provided in the side walls of the housing 39 for admitting the belt 5| (see Figure 2) is made considerably larger than is necessary 'to facilitate the egress of air.

When the roll is dry, the machine is stopped. ,The vents 5| are closed and the tight cover 25 is put in place. The cyiinderis then ready for coating with the sensitized resist solution. The distilled water or alcohol is removed from the catch buckets 51, and the buckets are replaced in position at the bottom of; the table; sections of the outer housing 39 may be opened to permit access to these buckets. A proper amount. of.

coating solution is then poured in the tray 41 by means of a long stemmed funnel which passes through a tube guide 59 suitably located in the upper section 2|) of the inner housing |9.- This guide is normally closed, as 'by a crok. A fine mesh screen 58 located at one end of the tray 41 'serves' to prevent. the formation of bubbles as the coating solution is pouredv into the tray. The funnel is removed and the guide tube 5! closed.

Next, the table motor 34 is energized to revolve the cylinder about its longitudinal axis, preferably at a relatively'low speed. The tray 41 containing the coating solution is raised by operation of the handle 49, and thesurface of the cylinder picks up the coatlngsolution. After two' or three revolutions of the cylinder, the tray maybe lowered,

although this is not absolutely necessary. .Then

the table motor 291s operated to rotate'the table 15 and the cylinder about the vertical axis of the device,- also at a relatively slow speed. This slow speed rotation of the cylinder about both its longitudinal axis and about the vertical axis perpendicular to its longitudinal axis is continued for a few minutes, whereupon the speed of rotation about the vertical axis is gradually increased to several times its original value. At the same .time, the speed of rotation of the cylinder about its longitudinal axis may likewise be increased.

The high speed rotation about both axes is continued for a 'sufilcient time to permit the coating to begin to set, the actual time necessary to accomplish'this will, of course, be determined by experiment. At this pointthe vent latches 5L are tripped to open the vents 5| and the cover 25 to be coated is supported upon the table i5 within the housing l9. This housing is tightly closed,

.and the cylinder is washed in situ, preferably with distilled water or alcohol, and dried. Then,.

without opening the cylinder housing IS, the coating solution is introduced into the'tray 41 which is located within the housing. Following this,

the cylinder is rotated slowly about its own lon-' gitudinal axis, and the coating material is applied simultaneously along its entire length by raising the tray 41. Immediately following the application of the coating material, the tray 41 is lowered, and the rotation of the cylinder about the axis extending at right angles to its own longitudinal axis, 1. e., the vertical axis of the apparatus, is commenced.

The rotation of the cylinder about both axes is carried out at a slow speed for a period of a few minutes. Then both speeds of rotation are slowly and uniformly increased, the speed of rotation about the axiswhich extends at right angles to the'longitudinal axis of the cylinder being increased in the order of 15 to 20 times its original value. This high speed rotationserves to thin the film of coating material uniformly over the cylinder and is preferably continued unchanged is removed, preferably ,without slowing down the until the coating material begins to set. At such other axes are ordinarily continued unchanged during the final portions of the drying operation. When the coating is dry, the machine is stopped and the cylinder removed therefrom. The cylinder is then ready for the transfer operation whereby the design to be printed is photographically transferred to the coating thereon.

In one commercial embodiment of the invention when coating 9. cylinder about 14 inchesin diameter, the coating solution is applied at a time when the speed of rotation of the cylinder about its own longitudinal axis is approximatelyv 20 R. P. M. Immediately following the application of thercoating material, the cylinder is rotated v about the vertical axis of the apparatus at aspeed of about ,5 or 6 R. P. M., and these speeds are maintained for a period of approximately two to three minutes. Then the speed of rotation about the longitudinal axis of the cylinder is increased to about R. P. M. or even less, and the speed of rotation about the vertical axis is gradually increased to about R. P. M. These speeds are maintained for a period of approximately 10 minutes, during which time the coating sets or begins to set. The drying of the coating after the setting period does not usually require more than 4 or 5 minutes, and in this embodiment of the invention, no change in the speeds of rotation is ordinarily made during the final dry-.

ing period. It will be understood, of course, that the proper speeds during each period will vary,

dependent upon the coating material used and upon the thickness desired in the finished coating. The speeds given in the foregoing are for a coating material sold under the trade name Cold Top, which material comprises an aqueous solution of shellac containing an ammonium dichromate sensitizer. Other coating materials may well require diiferent timing and different speeds. The exact figures can, of course, be determined by test.

In the example given in the foregoing, the cylinder is rotated both about its longitudinal axis and about the-vertical axis, which is perpendicular to its longitudinal axis, during the entire period when, the coating is being distributed over the surface of the cylinder and is being dried. Tests indicate that therotation about both axes does not necessarily have to be carried on during the entire period, although it appears that the double rotation during at least a portion of the periods during which the coating is drying is of great importance in accomplishing even coating of the cylinder.

There are a number of separate, although more or less related, features which are believed responsible for the improved coating which is made possible by the apparatus of the present invention. Of particular importancein this connection is the rotation of the cylinderabout its longitudinal axis and about. an axis generally at right angles to the longitudinal axis during at least a portion of the drying and-setting of the coating. Also,v

the arrangement whereby the cylinder is completely enclosed within an air-tight housing which is not much larger than the cylinder and which rotates with the table support for the cylinder is thought to be .of importance in accomplishing the objects of the invention. This housing apparently prevents the generation of air currents which might tend to set the coating locally before .ithas spread thinly and evenly over the entire cylinder.

It also appears to be important that the speed of rotation of the cylinder about the axis extending at right angles to the longitudinal axis of the cylinder (the vertical axis of the apparatus) shall be relatively low at the early stages of the coating operation. This low speed which is gradually increased as the coating sets and becomes stronger prevents the rupturing of the film of coating ma-' terial .on the cylinder, while at the same time permitting the attainment of a very thin final coating, the thickness of which may be accurately controlled by variation in the speed of rotation. The particular structural arrangement 01 the inner or cylinder-housing l9 assures that the cylinder will not be exposed to dust or other oon-. tamination between the washing, drying, and coating operations, and the vent arrangement, in combination with the filter opening through which air enters the cylinder housing during the final stages of the drying operation, permits increased speed of drying without danger of dust contamination.

The arrangement of the tray for applying the coating solution to the roll is also an important feature of the invention, for the reason that unless the coating material is applied to the cylinder at the proper instant, great difilculty willbe experienoed in the attainment of satisfactory distribution of that material. The screenfor preventing bubbles from reaching the central portions of the traywhere they might cause' spots in the finished coating is another feature of im portance.

motion shall have a speed range of approximately 20 to 1, and if the driving motor for rotating the cylinder about its longitudinal axis shall have a speed range of approximately 3 to 1.

In accordance with the patent statutes, I have herein shown and described a form of apparatus which has been found by extensive tests to permit the satisfactory carrying out of the coating methods of the present invention. It will be understood, however, that the structural details of this apparatus and the exact sequence and timing ,of the steps of the method may be varied or changed in particular instances. Accordingly, it is my desire that the accompanying claims shall be accorded the broadest possible construction consistentwith the language appearing therein and the prior art.

I claim the following as my invention:

1. In apparatus of the class described, a table supported for rotation about a central axis, means operable to rotate said table about said axis, means for supporting a printing cylinder or the like upon said table in such manner that said cylinder is free to rotate about,,its own longitudinal axis, housing means supported upon said table which may be closed about said-cylinder to provide a substantially airtight enclosure therefor, means operable to apply a coating solution to said cylinder, and meansoperable to revolve said cylinder about its longitudinal axis during the applying operation.

2. In apparatus of the class described, a table supported for rotation about a central, vertical axis, means operable to rotate said table about said axis, means for supporting a printing cylinder or the like horizontally upon said table in such manner that said cylinder is free to rotate about its own longitudinal axis, housing means supported upon said table which may be closed about said cylinder to provide a substantially airtight enclosure therefor, means operable from without said housing to apply a coating solution to said cylinder, and means operable to revolve said cylin der about its longitudinal axis during the applying operation. a

3. In apparatus ofthe class described, a generally horizontally arranged table supported for rotatable movement about a central, vertical axis, means operable to rotate said table about said axis, means for supporting a printing cylinder or the like in a generally horizontal position upon said table and in such manner that said cylinder is free to rotate'about its longitudinal axis, a housing which is supported upon said table and which may be closed about said cylinder to provide a substantially airtight enclosure therefor,

for supporting a printing cylinder or the like upon said table in such manner that said cylinder is free to rotate about its own longitudinal axis,

means for applying 'acoating solution to said aampss cylinder comprising an elongated, relatively shallow tray adjustably supported upon said table adjacent said cylinder, and means for rotating said table about said central axis and for rotating said cylinder about its longitudinal axis. k

5. In apparatus of the class described, a table supported for rotation about a central, vertical axis, means for supporting a printing cylinder or the like horizontally upon said table in such man-.

ner that said-cylinder is free to rotate about its own longitudinal axis, means for applyinga coating solution to said cylinder comprising an elon-. gated, relatively shallow tray supported upon said tablebeneath and substantially tangential to said cylinder, means operable to'raise or lower said tray, and means for rotating said table about said vertical axis and for rotating said cylinder about its-longitudinal axis.

6. In apparatus of the class described, a gen-. erally horizontally arranged table supported for rotation about a central, vertical axis, means operable to rotate said table about said vertical axis, means for supporting a printing cylinder or the like horizontally upon said table in such man ner that said cylinder is free to rotate about its ownlongitudinal axis, a housing means supported upon said table which may be closed about said cylinderto providea substantially airtight enclosure therefor, an elongated, relatively shallow tray supported within said housing beneath. said cylinder and adapted to contain the coating solution to be applied thereto, means operable from without said housing when saidcylinder .is located therein to raise said tray and thereby apply said coating material to said cylinder, and means operable to revolve said cylinder about its own longitudinal axis. a a

7. In apparatus of the class described,'a table supported for rotation about a central, vertical axis, means operable to rotate said table about said axis, means for supporting a printing cylin der or the like horizontally upon said table in such manner that said cylinder is free to rotate about its own longitudinal axis; a housing supported upon said table which is adapted to receive said cylinder and which may be c osed about said cylinder to provide a substantially airtight enclosure therefor, means operable to apply a coating solution to said cylinder, and means operable to revolve said cylinder about its longitudinal axis, said housing including vent openings located adjacent the ends thereof, an inlet opening located adjacent the axis of rotationof said table, cover means for said vent openings and for said inlet opening which may be removed when said table is being rotated, and a screen or filter which covers said inlet opening at least when the cover means for that opening has been removed.

-8. In apparatus of the class described, a table supported for rotation about a central. vertical axis, means for supporting a printing cylinder or the like horizontally upon said table in such manner that said cylinder is free to rotate about its own longitudinal axis,a housing means supported upon said table which may be closed about said cylinder to provide a substantially airtight en'- closure therefor, an-elongated, relatively shallow 3- tray supported within said housing beneath said cylinder and adapted to contain the coating solution to be applied thereto, said housing being provided with a suitably located opening where- 'by the coating solution may be poured into said tray without otherwise opening said housin'g and a cover for said opening, said tray including a tine mesh screen arranged-at one end thereof for preventing bubbles which may be formed when the coating solution is poured therein from being carried onto said cylinder during the coating operation, means operable from without said housing when said cylinder is located therein to raise said tray and thereby apply said coating material to said cylinder, and means operable to revolve said cylinder about its own longitudinal axis.

9. In apparatus of the class described, a table supported for rotation about a central vertical axis, means operable to rotate said table about said axis, means forsupporting a printing cylinder or the like horizontally upon said table in such manner that said cylinder is free to rotate about its own longitudinal axis, housing means supported upon said table which may be closed about said cylinder to provide an enclosure therefor, said enclosure being substantially airtight except for air inlet and air outlet openings, and

means-operable to revolve said cylinder aboutits longitudinal axis.

10. In apparatus of the class described, a table. supported for rotation about a central vertical axis, means operable to rotate said table about said axis, means for supporting a printing cylinder 0! the like horizontally upon said table in such manner that said cylinder is free to rotate about its own longitudinal axis, housing means supported upon said table whichv may be closed about said cylinder to provide an enclosure therefor, said enclosure'being substantially airtight except for air outlet openings located adjacent the ends thereof and an air inlet opening located adjacent the axis of rotation of said table, and means operable to revolve said cylinder about its longitudinal axis during the applying operation.

11. In apparatus of the-class described, a table supported for rotation about a central vertical axis, means operable to rotate said table about said axis, means for supporting a printing cylinhousing being provided-with air inletand air outlet openings and with cover means .for said openings which may be removed to permit circulation of air through said housing.

12. In apparatus ofthe class described, a table supported for rotation about a central vertical axis, means operable to rotate said table about said axis, means for supporting a printing cylinder or the like horizontally upon said table in such manner thatsaid cylinder is free to rotate about its own longitudinal axis, a housing sup-. ported upon said table which is adapted to receive said cylinder and which may be closed about said cylinder to provide a substantially airtight enclosure therefor means operable to apply a coating solution to said cylinder, and means operable to revolve said cylinder about its longitudinal axis' during the applying operation, said housing being provided with vent openings located adiacentthe ends thereof and an air inlet located adjacent the axis of rotation of said table, and removable closure means for said vent openings. 4

13, .In apparatus of the class described, a table supported for rotation about a central vertical axis, meam operable to rotatesaid table about 15 said axis, means for supporting a printing cylinder or the like horizontally upon said table in such manner that said cylinder is free to rotate about its own longitudinal axis, a housing supported upon said table which is adapted to receive said cylinder and which mayv be closed about said cylinder to provide a substantially airtight enclosure therefor, means operable to apply a coating solution to said cylinder, and means operable to revolve said cylinder about its longitudinal axis during the applying operation, said housing being provided with vent openings located adjacent the ends thereof, an air inlet opening, and cover means for said openings which may be removed to open said inlet and vent openings when said table is being rotated.

14. In apparatus of the class described, a table supported for rotation about a central vertical axis, means operable to rotate said table about said axis, means for supporting a printing cylinder or the like horizontally upon said table in such manner that said cylinder is free to rotate about its own longitudinal axis, a housing sup- I ported upon said table which is adapted to receive said cylinder and which may be closed about said cylinder to provide a substantially airtight enclosure therefor, means operable to apply a coating solution to said cylinder, means operable to revolve said cylinder about its longitudinal axis, said housing being provided with vent openings located adjacent the ends thereof, an air inlet opening located adjacent the axis of rotation of said table, pivotally supported cover means movable into engagement with said housing to close said vent openings and away from said housing to open said vent openings, said cover means being biased away from said housing by centrifugal force when said table is being rotated, and latch means, releasable from without said housing, for latching said cover means in the vent closing position.

15. In apparatus of the class described, a generally horizontally arranged table supported for rotation about a central vertical axis, means includingbearings and a pair of pedestals rigidly mounted upon said table for supporting a printing cylinder or the like in horizontal. position upon said table in such manner that said cylinder is free to rotate about its own longitudinal axis, a housing which comprises two hingedly connected complementary sections supported upon said table for receiving said cylinder, said housing sections being movable into engagement with each other so as enclose said cylinder, means for applying a coating solution to said cylinder comprising an elongated, relatively shallow tray supported within said housing beneath said cylinder .and operable from without said housing when said housing is closed to raise or lower said tray, and means operable to revolve said cylinder about its own longitudinal axis during the applying operation.

16. In apparatus of the class'described, a table supported for rotation about a central vertical axis, means operable to rotate said table about said axis, means for supporting a printing cylinder or the like horizontally upon said table in such manner that said cylinder is free to rotate about its own longitudinal axis, a housing supported upon said table which is adapted to receive said cylinder and which may be closed about said cylinder to provide an enclosure therefor, said housing when closed being substantially airtight except for air outlet openings located ad- Jacent the ends thereof and an air inlet opening located adjacent the axis of rotation'of said table, means operable to apply a coating solution to said cylinder, means including a motorsupported upon said table operable to revolve said cylinder about its longitudinal axis during the applying operation, and an outer housing for enclosing said table, said outer housing being provided with an air inlet opening adapted to align with the air inlet opening in said inner housing during the operation of 'said apparatus, and means for heating the air drawn into said inner housing.

17. In. apparatus of the class described, a table supported for rotation about a central vertical axis, means for supporting a printing cylinder or the like horizontally upon said table in such manner that said cylinder is free to rotate about its own longitudinal axis, a housing means supported upon said table which may be closed about said cylinder to provide a substantially airtight enclosure therefor, means for applying a coating solution to said cylinder comprising an elongated, relatively shallow tray vertically adjustably supported upon said table beneath said cylinder, said tray being provided with a fine mesh screen located at one end thereof for preventing bubbles formed when the coating solution is poured therein from being carried onto said cylinder' during the applying operation, and means operable to revolve said cylinder about its own longitudinal axis.

a CHARLES L. HENDERSON.