US3141793A

US3141793A - Apparatus for coating surfaces

Info

Publication number: US3141793A
Application number: US54188A
Authority: US
Inventors: Oliphant Keith Meredith
Original assignee: Australia Res Lab
Current assignee: Research Laboratories of Australia Pty Ltd
Priority date: 1959-09-09
Filing date: 1960-09-06
Publication date: 1964-07-21
Anticipated expiration: 1981-07-21
Also published as: GB953704A; NL255695A; FR1274544A; CH365978A

Description

y 1964 K. M. OLIPHANT APPARATUS FOR COATING SURFACES Filed Sept. 6, 1960 \NVENTOR2 Kern-a MERHDITH OLIPHANT MW ATTORNEYS United States Patent 3,141,793 APPARATUS FOR COATING SURFACES Keith "Meredithfiliphant, Westhourne Park, South Aus- -tralia,.Australia, assignor to Research Laboratories of Australia Limited, South Australia, Australia Filed Sept. 6, 1960, Ser. No. 54,188 Claims priority, appiieation Australia Sept. 9, 1959 luClairns. (Cl. 118-30) This invention relates to method. and means for coating surfaces by fluid brush with coating materials such as paint, paint pigments, ink, lacquer, wax, resins, emulsions of various types, oils, dyes, gums, solutions and suspensions and the like. The surfaces to be coated may be regular or irregular or may be of sheet form or textiles or plastic sheet or board or film.

Previously surfaces have been coated by such means for example in the application of paint by means of brushes, knife coating devices, spray guns, air brushes, electrostatically assisted spray guns, and by the assisted deposition of liquid paint from the air by electrostatic means. In the use of spray guns and the like, many difiiculties arise in that the air operated gun is limited to a comparatively small volume of dispersion and also causes the coating material to be dispersed in nonuniform sized particles, and in varying patterns, and amounts in different areas. The difficulties encountered 'in this regard having given rise to an adaptation in which an electrostatic field is used to assist in distributing the particles more evenly. Further, in another adaptation an electrostatic field is used to 'drive liquid paint from an edge throughthe air on to an object to be coated.

The 'object'of the present invention is to coat the surface with greater uniformity than heretofore possible, and to coat with a greater variety of materials, and to coat with a more effective control over thickness and uniformity of deposition.

The invention consists in one embodiment in placing the material to be coated in a fixed position and moving over it a device which causes the coating material to fan out in the form which we shall call a liquid brush so as to large molecules, emulsoids or gas, as opposed to applica tion by an air brush or by a spray gun or doctor blade.

The principles underlying the invention are that when a stream of liquid is ejected under pressure from a nozzle it forms a sheet or layer which wets the surface to be coated but in this invention a suction de 'vice is introduced which sucks the excess paint or coating liquid'back into the system for re-circulation and none 'is lost. With a spray gun a mist is formed but in this invention a'bo'dy of liquid is moved under control to the desired site by ejection from one nozzle and suction of the excess immediately back into the system.

The paint loss of this method of coating is very low compared to other methods because there is no opportunity for the excess paint or coating material to escape from the painting or coating site.

In order that the invention may be more fully understood, embodiments thereof will now be described with reference to the accompanying drawings in which:

, FIG. 1 is a side elevation of one form of the apparatus,

FIG. 2.is an enlarged sectional view of the apparatus,

.FIG. 3 is a plan of the nozzle arrangement, and FIG. 4 is a view corresponding to FIG. 1 but showing a modified form of machine.

Referring first to the embodiment shown in FIGS. '1,

"ice

2 and 3 a delivery nozzle 1 is coupled by means of fiexible hose 2 to the outlet 3 of a pump 4, the inlet 5 to thepump'communicating with a tank 6 in which the paint or the like which is to be applied is carried.

The'suction'nozzle 8 is similarly connected by means of a flexible hose'9to a'pump 10, but in this case the connection is made to the inlet 11, while the outlet 12 communicates with the tank 6.

The nozzles 1 and 8 are provided respectively with control valves 14 and 15 which serve to regulate the flow through the delivery nozzles 1 and 8, and the nozzles themselves are supported from an arcuate bracket 16 carriedon a frame member 17 connected withthe main in a socket 25 but is normally held by.a clamping nut 26 which compresses a resilient member 27 between the nut and the socket 25.

The pumps 4 and 19 are driven from a motor 30 through a belt 31, the motor 36 having on it a pulley iiz-engaged by the belt 31, each of the

pumps

4 and 10 similarly carrying pulleys 53 and 5-4 respectively engaged bythe belt 31.

35 indicates a'sheet to which the paint or the like is being applied, and it will be seen that the paint or the like is forced on to the sheet through the nozzle 1 but surplus paint or the like is removed through the nozzle 8, the control blade 23 serving to assist in distributing the paint onto the paper 35 or similar substances.

By controlling the respective speeds of the

pumps

4 and 10 and to some extent by regulation of the valves 14 and 15, :the balance required between the delivery from thenozzle 1 and the return through the nozzle 8 can be adjusted to ensure that the correct amount of coating material is applied.

It will be seen from FIG. 3 that the nozzles 1 and 8 are spread at their ends to give the required width of application of a coating material, and obviously this spread can be considerable, or a series of nozzles can be positioned end to end to give the required spread, thereby allowing for instance a paper web such as 35 to traverse'the-apparatus in a continuous manner while applying coating material thereto.

The arrows in FIG. 1 show the direction of flow of the coating material. As shown therein, the path followed by the coating material, from nozzle 1 to nozzle 8, is a curved path that is approximately tangential to the material 35 being coated. To achieve this tangential relationship, the nozzles are maintained at an obtuse anglerelative to each other, as shown in the drawings. In the embodiment shownin FIG. 4 a tank 40 contains the coating material, a control valve 41 regulating the flow from the tank to the delivery nozzle 42, the suction nozzle 43 terminating adjacent delivery nozzle as shown and communicating with a pump 44 which is capable of drawing material through the nozzle 43 and discharging it through the pipe 45 back into the tank 40. The pump 44 is driven from the motor 46 through a belt 47 passing around a pulley 48 on the motor shaft 'anda pulley 49 on the pump shaft.

The frame 'of this machine is designated 50, while a base 51 serves as asupport for the sheet 52 which is being coated, in this case again the sheet 52. forming .a continuous web that is required on to which the coating material is deposited from the delivery nozzle 42 being drawn off through the suction nozzle 43 by the pump 44 and delivered back to the tank 46.

In this case a control blade corresponding to the blade 23 is not used, but obviously such a blade could again be positioned if required.

From the foregoing it will be realised that the essential feature of this invention consists in the provision of a delivery nozzle through which the coating material is applied to a sheet or the like, and the adjacent positioning of a suction nozzle so that surplus coating material is removed from the sheet after application.

It will be obvious of course that the device can continue to function when no sheet is positioned adjacent to the delivery nozzle, the material simply then discharging through the delivery nozzle and again being drawn back through the suction nozzle to maintain a continuous circulation.

This ensures that the coating material will at all times be in a homogeneous and good condition for application to a sheet or the like and it will be realised that it would be possible in the embodiment shown in FIG. 4 to dispense with the base or table 51 and at all times to allow circulation to take place with the coating material flowing out of the delivery nozzle 42 and being sucked back into the suction nozzle 43 but during the short time that the material is disposed between the two nozzles, coating can be effected of a member passed into the path of this material.

It will be obvious that instead of using a pair of separate nozzles, that these can be formed by simply flattening or otherwise shaping a single tube and cutting the tube on one side to give the opening through which the material has access to the means which are to be coated, but generally it will be found preferable to have the delivery nozzle and the suction nozzle separately and adjustably arranged to allow the exact angle of one in relation to the other to be selected.

It is of course essential that the nozzles are arranged at an angle to each other to cause the stream of the coating material to be bent and thus to give it access to the sheet or the like which is to be coated, or alternatively a member such as the control blade must be used which ensures that the material follows a curved path which will ensure that it can be applied to the sheet or the like outside of the plane of the nozzles and can again be withdrawn back into the suction nozzle when surplus coating material is present.

It will be appreciated that the deposition depends in the first instance in the full wetting of the surface by the paint or liquid and the instant removal of the excess by suction so as to given an extremely uniform paint or liquid film on the surface to be coated.

It will also be appreciated that the shape and size of the liquid brush may be controlled by the rate of ejection of the coating material in relation to the rate of return suction, by the size and shape of the hydraulic pump and by the gap between the nozzles and the surface to be coated. These will vary according to the viscosity of the paint or other liquid used.

The materials used for carrying out the invention can of course be widely varied and the coating materials used for coating can include paints and the like, liquid developers of electrostatic images and the like.

Examples of coating materials which can be applied by use of the invention are as follows:

(1) Electrophotographic Coating Grms. Zinc oxide 100 Resin 70 Cobalt naphthenate 0.7 Lead naphthenate 1.4 Toluene 200 This coating composition was milled in a ball mill for 24 hours and used in the coating apparatus.

Jet openings, pressure side A wide x A" long, suction side As X A". Pressures maintained to give correct shape of liquid brush were, suction approximately 0.5-2" water gauge in excess of pressure.

(2) Resin Emulsion Type Surface Coating Standard polyvinylacetate paint as supplied for interior decorating was used with the following nozzle openings, pressure side 7 x l", suction side x 1", gravity feed on pressure side in downhand position, otherwise positive pressure 15 pounds per square inch, suction 5" water gauge in excess.

(3) Liquid Developer for Electrophotographic Images Developer standard liquid developer suspension as described in various patent applications. Jet size, pressure x /8, suction x gravity feed to pressure side, 5" water gauge suction.

I claim:

1. Means for coating surfaces comprising a delivery nozzle for the coating material, a suction nozzle to remove excess coating material, and means to maintain the said nozzles in a spaced relationship and at an obtuse angle relative to each other to cause the coating material to follow a curved path between the delivery nozzle and the suction nozzle into the plane of the object being coated that is approximately tangential to the surface of the object being coated.

2. Means for coating surfaces according to claim 1 wherein the curvature of the path is controlled by disposing a blade between the said nozzles to deflect the said coating material.

3. Means for coating surfaces comprising a delivery nozzle for delivering the coating material to a surface along a predetermined delivery path, a suction nozzle to remove excess coating material from the surface along a predetermined removal path, means to hold the said nozzles in spaced angular relationship with the delivery and removal paths oppositely inclined with respect to the normal to said surface with their openings in proximity to each other on one side of said surface, a tank for the coating material, means coupling the said tank to the said delivery nozzle, a flow control valve in said coupling means, a suction pump, means coupling the pump inlet to the said suction nozzle, means coupling the pump outlet to the said tank, and means to drive the said pump.

4. Means for coating surfaces comprising a delivery nozzle for delivering the coating material to a surface along a predetermined delivery path, a suction nozzle to remove excess coating material from the surface along a predetermined removal path, means to hold the said nozzles in spaced relationship with the delivery and removal paths oppositely inclined with respect to the normal to said surface with their openings in proximity to each other on one side of said surface, adjustment means on the said holding means to allow angle and distance of the nozzle openings to be adjusted, a tank for the coating material, means coupling the said tank to the said delivery nozzle, a flow control valve in said coupling means, a suction pump, means coupling the pump inlet to the said suction nozzle, means coupling the pump outlet to the said tank, and means to drive the said pump.

5. Means for coating surfaces comprising a delivery nozzle for the coating material, a suction nozzle to remove excess coating material, means to hold the said nozzles in spaced angular relationship with their openings 1n proximity to each other, a tank for the coating material, a delivery pump, means coupling the pump inlet to the said tank, means coupling the pump outlet to the said delivery nozzle, a suction pump, means coupling the pump inlet to the said suction nozzle, means coupling the pump outlet to the said tank, means to drive the said pumps, and flow control valves in the means coupling the respective pumps to their associated nozzles.

6. Means for coating surfaces comprising a delivery nozzle for the coating material, a suction nozzle to remove excess coating material, means to hold the said nozzles in spaced relationship with their openings in proximity to each other, adjustment means on the said holding means to allow angle and distance of the nozzle openings to be adjusted, a tank for the coating material, a delivery pump, means coupling the pump inlet to the said tank, means coupling the pump outlet to the said delivery nozzle, a suction pump, means coupling the pump inlet to the said suction nozzle, means coupling the pump outlet to the said tank, means to drive the said pumps, and flow control valves in the means coupling the repsective pumps to their associated nozzles.

7. Means for coating surfaces comprising a delivery nozzle for delivering the coating material to a surface along a predetermined delivery path, a suction nozzle to remove excess coating material from the surface along a predetermined removal path, means to hold the said nozzles in spaced angular relationship with the delivery and removal paths oppositely inclined with respect to the normal to said surface with their openings in proximity to each other on one side of said surface, a blade disposed between the two said nozzles in the path of the coating material, a tank for the coating material, means coupling said tank to the said delivery nozzle, a flow control valve in said coupling means, a suction pump, means coupling the pump inlet to the said suction nozzle, means coupling the pump outlet to the said tank, and means to drive the said pump.

8. Means for coating surfaces comprising a delivery nozzle for delivering the coating material to a surface along a predetermined delivery path, a suction nozzle to remove excess coating material from the surface along a predetermined removal path, means to hold the said nozzles in spaced relationship with the delivery and removal paths oppositely inclined with respect to the normal to said surface with their openings in proximity to each other on one side of said surface, adjustment means on the said holding means to allow angle and distance of the nozzle openings to be adjusted, an adjustable blade between the two said nozzles in the path of the coating material, a tank for the coating material, means coupling 6 the said tank to the said delivery nozzle, a flow control valve in said coupling means, a suction pump, means coupling the pump inlet to the said suction nozzle, means coupling the pump outlet to the said tank, and means to drive the said pump.

9. Means for coating surfaces comprising a delivery nozzle for the coating material, a suction nozzle to remove excess coating material, means to hold the said nozzles in spaced angular relationship with their openings in proximity to each other, an adjustable blade between the two said nozzles in the path of the coating material, a tank for the coating material, a delivery pump, means coupling the pump inlet to the said tank, means coupling the pump outlet to the said delivery nozzle, a suction pump, means coupling the pump inlet to the said suction nozzle, means coupling the pump outlet to the said tank, means to drive the said pumps, and flow control valves in the means coupling the respective pumps to their associated nozzles.

10. Means for coating surfaces comprising a delivery nozzle for the coating material, a suction nozzle to remove excess coating material, means to hold the said nozzles in spaced relationship with their openings in proximity to each other, adjustment means on the said holding means to allow angle and distance of the nozzle openings to be adjusted, an adjustable blade between the two said nozzles in the path of the coating material, a tank for the coating material, a delivery pump, means coupling the pump inlet to the said tank, means coupling the pump outlet to the said delivery nozzle, a suction pump, means coupling the pump inlet to the said suction nozzle, means coupling the pump outlet to the said tank, means to drive the said pumps, and flow control valves in the means coupling the respective pumps to their associated nozzles.

References Cited in the file of this patent UNITED STATES PATENTS 1,338,624 Heppes et al Apr. 27, 1920 1,728,043 Christman Sept. 10, 1929 1,989,800 Gustin Feb. 5, 1935 2,471,330 Knight et al May 24, 1949 2,899,339 Rakus Aug. 11, 1959