US 3586907 A
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United States Patent Dale R. Beam;
Inventors Russell H. Van Brimer, both 01 Chillicothe, Ohio Appl. No. 877,250 Filed Nov. 17, 1969 Patented June 22, 1971 Assignee The Mead Corporation Dayton, Ohio LAMINATED COATING HEAD 14 Claims, 6 Drawing Figs.
US. Cl 317/3, 346/75, 239/15 Int. Cl ..G0ld 15/18, B05b 5/00, B05b 5/02 Field of Search 31 3,
[5 6] References Cited UNITED STATES PATENTS 2,628,150 2/1953 Gunderson 346/75 3,278,940 10/1966 Ascoli 346/75 3,298,030 1/1967 Lewis et 346/75 3,373,437 3/1968 Sweet etal 317/3 X 3,458,761 7/1969 Ascoli 317/3 3,512,173 5/1970 Damouth 346/75 Primary Examiner-Lee T. l-lix Attorney-Marechal, Biebel, French and Bugg ABSTRACT: A coating head for noncontacting coating apparatus in which the majority of the components of the head are manufactured separately as platelike members and then assembled in the proper order in laminar form to provide a laminated coating head.
PATENTED JUN22 I97! l/V VE IV TORS DALE R. BEAM 8 RUSSELL H. VAN BRIMER ATTORNEYS LAMINATED COATING HEAD CROSS REFERENCE TO RELATED APPLICATION IMAGE CONSTRUCTION SYSTEM USING MULTIPLE ARRAYS OF DROP GENERATORS, Ser. No. 768,790 filed Oct. 18, I968.
BACKGROUND OF THE INVENTION In the above noted, related application, a system is disclosed for applying a coating to a moving web or the like without contact between the coating apparatus and the material to be coated. It should be noted that the term coating is used herein in its broader's'ense to include patterned coating, as in printing, as well as the application of a continuous layer of coating. Coating apparatus constructed in accordance with the above noted related application divides a supply of coating material into a series of discrete jets which tend to break down into a series of small drops. The drops are then directed through a charge ring which may be selectively activated to either impart or not impart an electrostaticcharge to each drop. The drops then pass through an electrostatic field and are either deflected-or not deflected depending upon whether or not they have been charged by the charge rings. A catcher is pro- 'videdbeneath the electrostatic field and prevents drops which are deflected by the field from impinging upon-the web or other article being coated. Thus, by controlling the electric signals to the charge rings, drops of coating material can be deposited on theweb or other article to be treated in any desired pattern.
It will be apparent that in a coating system of the type described above the dimensions of components must be controlled with great precision. For example, the charge ring through which the droplets pass may be on the order of 0.023 inches in diameter while the orifices from which the coating material is ejected may be only 0.0015 inches in diameter.
Additionally, it will be seen that relatively small particles of foreign material could cause a malfunction if they became lodged in the system during either the manufacture thereof or as a result of impurities in the coating material.
It will also be apparent that when dealing with a system in which the components must be dimensioned within extremely fine tolerance limits, any modification of these dimensions through a build up of coating material could seriously affect the operation of the system. It is therefore desirable, if not necessary, that some provision be made for expeditiously cleaning the coating head between operations.
The environment in which coating systems of the type described above may be used to great advantage is in the application of coating material to a moving web of paper or the like, and in this type of operation it is necessary that the coating head'be suspended over the moving web. It is therefore, desirable to keep the coating head as compact as possible.
SUMMARY OF THE INVENTION In accordance with the present invention the components of the coating head are each manufactured separately and then joined in laminar relationship to form the completed coating head. In this way, each of the components may be manufactured with the degree of precision required for successful operation of the system. Constructing the coating head as an assembly of components also renders the task of insuring that each of the components is free of foreign material less complicated than would be the case if it were attempted to construct the printing head as a single unit or one or two subunits.
Additionally, should it become necessary to remove foreign material from the printing head, the head may be readily dismantled and each component carefully cleaned. In this regard it should also be noted that the laminar construction of the printing head permits the incorporation of a filter in the printing head immediately upstream of the orifices through which the coating is ejected. In this way foreign materials BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exploded perspective view showing the various components of one form of laminated coating head;
FIG. 2 is a cross-sectional view through a second form of coating head with the section through one portion thereof as taken on line A-A of FIG. 3;
FIG. 3 is a plan view of an inlet plate utilized in the present invention; I
FIG. 4 is a plan view of the upper surface of the clamp plate;
FIG. 5 is an enlargement of a portion of FIG. 2 showing a portion of the construction of F IG. 2 in more detail; and
FIG. 6 is a partialplan view of a portion of a charge ring plate. I
DESCRIPTION OF TI IE PREFERRED EMBODIMENTS As seen in FIGS. 1 and 2, the laminated printing head comprises a manifold 10 having a chamber 11 therein extending longitudinally of the manifold and opening outwardly, as at 12, along one portion thereof and a. conduit 13 for delivering coating material to the chamber 11. A filter plate 20 having a central portion 21 provided with-a series of very fine perforations therethrough is positioned with its perforated central portion over the opening 12 and a gasket member 23 interposed between the lower surface of the manifold 10 and the upper surface of the filter 20.
A second gasket member 24 and an inlet plate 30 are positioned beneath the filter plate 20 and, as best seen in FIG. 3, the inlet plate has an elongated slot 31 formed in one surface thereof extending longitudinally of the inlet plate and facing the opening 12 in the manifold 10. A series of uniformly spaced passages 32 are formed in the inlet plate extending from the bottom wall 33 of the slot 31 to the lower surface 34 of the inlet plate. Adjacent one end of the inlet plate a cleanout port 35 formed extending from one side of the plate into the slot 31 and a cover plate 36 and gasket 37 are secured over port 35 by means of bolts or the like 38.
Immediately beneath the inlet plate 30 an orifice plate 40 is positioned having a, series of openings 41 formed therein at regularly spaced intervals in substantial concentricity with the apertures 32 in the plate 30. A spacer plate 42 having a series of openings 43 formed therein in line with openings 41 is mounted beneath orifice plate 40 and serves to space a charge ring plate 50 from orifice plate 40a predetermined distance for a purpose to be presently described.
The charge ring plate 50, formed of a dielectric material, is positioned beneath the spacer plate 42 and is provided with a series of openings 5] extending therethrough, concentric with and appreciably greater in diameter than, the orifices 41. A discrete application of an electrically conductive coating material surrounds each opening 51, in circular outline, and covers the wall thereof to form a charge ring 52 (FIG. 5). Also applied to the plate 50 are a series of discrete lines of electrically conductive coating material which form conductors extending from each charge ring 52 t o a connector 54 mounted on charge ring plate 50 adjacent each end of a clamp plate 60. Connectors 54 engage complementary connectors 55, which in turn are in circuit with control unit 56 by means of cables 57. The charge rings 52 and conductors 53 can quite conveniently be manufactured using conventional printed circuit techniques although it will be appreciated that a somewhat higher degree of precision will be required than is usually necessary in printed circuit manufacture.
The clamp plate 60, similarly to the plates 30, 40 and 50, has a series of openings 61 extending therethrough which are substantially concentric with the openings 32, 41 and 51.
A pair of electrodes 70 are attached to the lower surface 63 of the clamp plate 60 by means of a pair of pins 71 having enlarged portions 72 attached to each of the electrodes 70 and abutting the lower surface 63 by means of the shoulder 73 formed by the enlarged portion. Each of the electrodes may conveniently e constructed of a resin impregnated fibrous material and provided with a coating of an electrically conductive material 74 along opposing faces thereof. For a purpose to be presently explained, each of the electrodes 70 is formed throughout a major portion of its length with triangularly shaped cross section 75 while distal portions 76 of each electrode are of rectangular cross section and receive the lower ends of the pins 72. It will also be noted that the lower outermost corner of each of the electrodes is beveled as at 77 and that leads 78 are attached to the'electrically conductive coatings 74 and to a source ofelectrical energy 79.
A pair of brackets 80 are also attached to the lower surface 63 of the clamp plate 60 and extend downwardly to support the catcher 81 having a blade 82 projecting outwardly thereof and at a slight angle to the horizontal. At least the upper surface and preferably both surfaces of the blade 82 are covered with a porous material, such as screening, to permit any drops of coating material which strike the blade to move inwardly into the interior of the catcher 81 from whence they are evacuated by the vacuum pump 83. The bracket 80 is preferably provided with adjusting means to permit limited movement of the catcher transversely of the coating head.
As best seen in FIG. 2, the manifold 'and the plate members 30, 40, 50 and 60 are provided with a series of aligned bolt holes 90 along their edges to provide a series of continuous passages 91 through the components of the coating head for reception of the assembly bolts 92. Bolts 92 have threaded ends 93 and clamp plate 60 is provided with threaded openings 94.
In operation, coating material is delivered through the conduit 13 into the chamber 11 of the manifold and thence out through the opening 12 and the filter plate 20. The filter plate serves to screen out any particles which may be large enough to obstruct orifices 41 during passage therethrough. By positioning the filter plate in proximity to the orifice plate, the danger of coating material having foreign particles therein reaching and clogging the orifices in the plate is reduced to a minimum. While from a filtering standpoint, it would be most desirable to have the filter plate immediately upstream of the orifices 41, it will be appreciated that faceto-face contact betweenfilter plate 20 and orifice plate 40 might result in partial blockage of orifices 41. Therefore, the inlet plate 30, with the chamber provided by the slot 31, is positioned between the filter and the orifice plate. Additionally, to channel the flow from the slot 31 and inhibit the formation of cross flows, the coating material is delivered from the slot 31 to the orifices 41 by means of the passages 32.
As the coating material passes through the orifices 41, there is a natural tendency for each of the jets to break into a series of fine drops. However, these drops would not be generated naturally at a uniform rate nor would they normally be of a uniform size. Therefore, to insure uniformity an externalstimulation is applied to the coating head. As seen in FIG. 1 of the drawings, this may take the form of a sonic vibrator 100 attached to the manifold 10 and imposing a sonic signal of a predetermined frequency on the system Alternatively, the signal may be an electric signal applied to the jets as they leave the orifices 41 by means of an electrohydrodynamic plate 101 (FIG. 2) which may be substituted for spacer plate 42 (FIG. 1) and which may have a series of openings 102 formed therethrough. Electrohydrodynamic plate 101 is preferably provided with an electrically conductive coating on the upper surface thereof and an insulating coating over the electrically conductive coating. Stimulation is achieved by connecting the conductive coating to an oscillating voltage source and thereby producing traction forces at the surfaces of the unbroken fluid filaments.
In either case, a series of drops of uniform size are projected from each of the orifices 41 at a uniform rate and pass through the charge rings 52 in charge plate 50. Control unit 56 controls the charge rings 52 and causes each drop passing through each of the charge rings to be charged or not, as desired. If a drop is charged, as it passes between the electrodes 70 it will be deflected from its normally vertical path a slight amount, to the right as seen in FIG. 2, where it is caught by the blade 82 of the catcher 81. Conversely, if the charge ring does not charge a particular drop it will continue in a substantially vertical path and be imprinted on the web or the like W.
It should also be noted that is is desirable to charge the drops just before they break away from their respective jets. The point at which they break away will vary, of course, under different operating conditions but will generally occur a short distance downstream of the outlets of the orifices 41. Therefore, the thickness of spacer plate 42 (or electrohydrodynamic plate 101 as the case may be) is selected to position charge ring plate 50 at the jet breakup point. Minor variations in the breakup position are compensated for by extending each charge ring 52 to cover the entire wall of its corresponding opening 51.
In a typical installation, the screen 20 is 0.001 inches thick and the central portion thereof provided with 41,000 holes of one-half mil in diameter and arranged in a 90 array. The inlet plate is 0.250 inches thick and has 50 passages 32, each 0.0635 inches in diameter and spaced on 0.1000 inch centers. The orifice plate is 0.011 inches in thickness and is provided with 50 orifices of 1.5 mils in diameter. If an electrohydrodynamic plate 101 is utilized, this plate may be 0.105 inches in thickness and have a series of 50 openings therethrough of 0.040 inches in diameter. The charge ring plate is 0.093 inches thick and also has 50 holes 51 therethrough of 0.025 inches in diameter.
The clamp plate 60, which also serves as an insulating shield between the charge ring plate and the electrodes 70, may be seven sixty-fourths of an inch in thickness with 50 openings 0.0635 inches in diameter extending therethrough. The electrodes may be 0.500 inches in thickness and spaced apart a distance of 0.065 inches.
As best seen in FIG. 2, the web W of paper or the like is trained past the coating head at an appreciable angle to the horizontal. This arrangement lessens the tendency of the droplets projected onto the web to assume a noncircular shape and gives a more symmetrical imprint. In this regard, the corners of the electrodes are beveled as at 77 to permit the coating head to be positioned beveling of the right-hand electrode as seen in FIG. 1 has no effect upon the proximity of the coating head to the web, it will be appreciated that by manufacturing all electrodes identically the necessity for stocking two different types of electrodes is eliminated.
In assembly the coating head, the filter plate 20, inlet plate 30 and orifice plate 40 are assembled on a jig in proper position with respect to each other. A cleaning fluid is then pumped through the filter plate 20 and into the slot 31 and compressed air is pumped through the orifices 41; the air and cleaning fluid exiting the inlet plate through the cleanout port 35. After these three components have been cleaned in this manner, the cover plate 36 is attached to the inlet plate and the remaining components of the coating head stacked on a jig in their proper position with respect to each other. Bolts 92 are then placed in each of the passages 91 with the screwthreaded lower end 93 of each bolt engaging complementary threads 94 in the openings in the clamp plate. The electrodes are then attached to the assembly by inserting the pin 71, which is coated with a resilient material, into the openings in the lower surface of the clamp plate where they frictionally engage the walls of the openings. The catcher 81 is next attached to the clamp plate and precisely positioned by means of the brackets just to one side, the right-hand side as seen in FIG. 2, of the path the nondeflected drops take from the orifice 41. It will be noted that by forming the electrodes 75 as triangular in cross section throughout most of their extent, the space between the electrodes and the bottom of the clamp plate 60 may be readily cleaned.
From the above if will be seen that the present invention provides a laminated coating head in which each of the components thereof may be manufactured separately with the high degree of precision necessary for a system of this type. Additionally, the system may be readily cleaned both before assembly and after, and means are provided for filtering the coating material immediately upstream of a majority of the components of the coating head. It will also be noted that the unit is exceptionally compact and therefore ideally suited for suspension over a moving web or the like and yet may be readily dismantled if necessary for cleaning and repair.
While the forms of apparatus herein described constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to these precise forms of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.
What I claim is:
l. A laminated coating head comprising:
a. an orifice plate having a series of regularly spaced orifices I formed therethrough,
b. means for supplying fluid under pressure to each of said orifices,
c. a charge ring plate extending coextensively with one surface of said orifice plate and having a series of openings therethrough concentric with said orifices,
d. a charge ring positioned in each of said charge ring plate openings,
e. means for selectively applying an electrical charge to each of said charge rings,
. means for securing said fluid supplying means, orifice plate and charge rig plate together in laminar relationship,
g. means for establishing an electrostatic field beneath said charge ring plate, and
h. means for catching drops of fluid ejected through said orifices.
2. The apparatus of claim 1 further comprising:
a. a filter interposed between said fluid supplying means and said orifice plate.
3. The apparatus of claim 1 further comprising:
a. an inlet plate interposed between said fluid supplying means and said orifice plate,
b. said inlet plate having an elongated slot formed in a surface thereof adjacent said fluid supplying means.
4. The apparatus of claim 1 further comprising:
a. an electrohydrodynamic plate interposed between said orifice plate and said charge ring plate,
b. said electrohydrodynamic plate having a series of openings therethrough concentric with said orifices, and
c. means for applying an electrical signal of a predetermined frequency to said electrohydrodynamic plate.
5. The apparatus of claim 1 wherein said means for establishing an electrostatic field comprises:
a. a pair of elongated electrodes, and
b. means mounting said electrodes in spaced relationship to a lower portion of said coating head and in parallel spaced relation to each other.
6. The apparatus of claim 5 wherein:
a. each of said electrodes is of substantially triangular cross section throughout a major portion of its length.
7. The apparatus of claim 6 wherein:
a. distal portions of said electrodes are substantially rectangular in cross section, and
b. said mounting means extends from said distal portions to said lower portion of said coating head.
8. A laminated coating head comprising:
a. a coating material manifold having means defining a chamber therein extending longitudinally of said coating head and opening outwardly along a portion thereof,
b. an inlet plate extending coextensively with said manifold and having an elongated slot in one surface thereof facing said manifold opening,
. a filter plate interposed between said manifold and said inlet plate,
(1. a cleanout opening having a removable cover thereover extending from one side of said inlet plate into said slot,
e. an orifice plate abutting said opposite surface of said inlet plate and extending coextensive therewith,
f. said orifice plate having a series of orifices therein,
g. a charge ring plate extending beneath one surface of said orifice plate and having a series of openings thcrethrough concentric with said orifices,
h. a charge ring positioned in each of said charge ring plate openings,
. a clamp plate abutting one surface of said charge ring plate and having a series of openings therethroug'h concentric with said charge ring plate openings,
k. fastener means extending from said manifold to said clamp plate and securing said manifold, inlet plate, filter plate, orifice plate, charge ring and clamp plate together in laminar relationship,
I. a pair of electrodes attached to a lower surface of said clamp plate, and
m. a catcher attached to said lower surface of said clamp plate and extending beneath said electrode.
9. The apparatus of claim 8' further comprising:
a. an electrohydrodynamic plate positioned between said clamp plate and said orifice plate,
b. a series of openings in said electrohydrodynamic plate concentric with said orifices,
c. means for applying an electric signal of a predetermined frequency to said electrohydrodynamic plate.
10. Apparatus for imparting an electric charge to individual drops of coating comprising:
a. an elongated plate member of dielectric material,
b. means defining a series of regularly-spaced openings through said plate member,
c. a discrete application of electrically conductive material surrounding each of said openings, and
d. a conductor extending from each of said discrete applications to a source of electric energy.
11. The apparatus ofclaim 10 wherein:
a. said electrically conductive material extends into and covers the wall of each of said openings but does not block said openings.
12. The apparatus of claim 11 wherein:
a. each of said discrete applications is substantially circular in outline.
13. The apparatus of claim 10 wherein:
a. each of said conductors comprises a line of electrically conductive material applied to said plate member.
14. The apparatus of claim 10 further comprising:
a. means for selectively energizing each of said discrete applications of electrically conductive material.