US3330482A - Coating control apparatus - Google Patents

Description

July 11, 1967 J. 5. CROWE 3,330,482

COATING CONTROL APPARATUS Filed May 10. 1963 2 $heets-$heet 1 BY flag;

July 11, 1967 J. s. CROWE 3,330,482

COATING CONTROL APPARATUS Filed May 10, 1963 2 Sheets-Sheet 2 i Z214 45 g 1% t if /4 INVENTOR.

57/11/144 (Rad/f BY W M United States Patent Filed May 10, 1963, Ser. No. 279,424 9 Claims. (Cl. 239-74) The present invention relates to a method of and apparatus for measuring the amount of coating being applied to a substrate material. More particularly, the invention relates to a volumetric system for monitoring the amount of coating consumption and thereby providing a running indication of the thickness of the coating as it is being applied to the substrate material from a pressurized supply line and while the coating is still in the wet or liquid state.

The industrial uses of coatings of all types are virtually endless, and, in the packaging industry alone, the use of coatings on various plastic, fiber and metal materials for either decorative, protective or adhesion purposes is a growing field. Such coating materials as natural and synthetic resins, paints, varnishes, waxes, sealant-s, adhesives and certain metals, such as solder, are customarily applied as a film to a substrate material. Common methods of applying these film coatings to the selected substrate material are spraying, immersing, or by passing the substrate material, either as a continuous web or in sheet form, over an applicator roll which carries the coating in a wet or liquid state.

Whether the coating is applied as a protective film over the entire surface of an article or sheet or merely as narrow strips of solder or adhesive to the marginal edges of a substrate web, it is generally of prime importance that the uniformity of coating deposit be carefully controlled. This is so because, in addition to the necessity of depositing an adequate but not excess thickness to assure good performance, it is equally important to avoid excessive coating thickness in order to keep waste of the normally expensive coating to a minimum.

In the past, time-consuming and rather tedious methods have been employed in measuring and controlling coating weight and thickness. A commonly used test requires a waiting period until the coating has dried to a semi-wet or solid state, after which a test sample is subjected to destructive testing to determine the coating weight. Such spot check systems are obviously slow and, accordingly, have motivated the development of more efiicient devices whereby periodic inspection can be accomplished as the coating is continuously applied and without marring or destroying the coating by direct contact. The prior art discloses, and there are commercially available, several such devices, all of which work on such principles as optics, radiation, electrical charge, thermoelectrics or the like.

Many of the available devices have distinct limitations in that they are applicable only to particular types of coatings or carrier materials. This is because the operational principles inherent in many of these prior art systems are dependent on the nature of either the surface being coated or the coating material itself, or both. Optical systems, for example, are applicable with acceptable accuracy only in situations where the light conductivity of coating and reflective characteristic of the coated surface are determinable parameters. More versatile systems are available, of course, but usually they are rather sophisticated devices which are extremely costly to install and require a certain degree of excellence in operation and maintenance. Many of these devices, although capable of highly accurate and reliable performance in the laboratory, have proven generally unsatisfactary in the practical environment of the produc- 3,330,482 Patented July 11, 1967 tion line where the variables of temperature, vibration, lighting, dirt accumulation, human judgment, and other factors are less easily controlled.

There is still a great need in the industry for a system of coating consumption control which is not only insusceptible to adverse shop conditions but which is also simple and inexpensive in construction, installation, operation and maintenance. The present invention fills this need in the industry by providing a volumetric system which accurately and directly measures the amount of coating being applied to a substrate material, from a pressurized supply line. In its basic form, the system comprises a test or measuring chamber which is connected into the coating supply line and which is provided with a predetermined amount of coating material that is maintained at a pressure substantially the same as the pressure in the coating supply line. When it is desired to measure the coating consumption, the coating applicator is temporarily disconnected from the main supply line and is temporarily connected to the test chamber, so that the coating material in the test chamber is utilized in the coating operation for a predetermined time interval. The change in volume of the coating material in the test chamber is measured and related to the quantity of substrate material coated during the time interval to establish the consumption rate in terms of volume of coating consumed per unit, per unit area, or per unit length, as the case may be. The consumption rate is then compared to a standard or desired rate and a running correction is effected based on the deviation from the standard for the selected time interval. In its preferred form, the test chamber comprises a graduated sight glass which makes possible visual measurement of the change of volume of the coating material therein.

It is therefore an object of the present invention to provide an apparatus for rapidly and efiiciently measuring the amount of coating being applied to a substrate material, which apparatus is simple in construction, operation and maintenance.

Another object of the invention is to provide an apparatus of the character described which does not interfere with the speed of operation or result in loss of production and which is not destructive of either the coating or the substrate material.

A further object of the invention is to provide an apparatus which periodically measures the amount of liquid coating being applied to a selected quantity of substrate material to permit timely determination and control of the coating consumption.

A still further object of this invention is to provide a method of rapidly and efliciently measuring the amount of liquid coating being applied to a substrate material, which method embraces simple mechanical principles and which neither interferes with the continuous coating operation nor is destructive of the coating or substrate material.

Yet another object is to provide a method and apparatus for measuring and controlling coating consumption in a closed pressurized coating system, which apparatus is an integral part of the pressurized system so as to measure accurately and directly the volume of coating material being consumed without interfering with the continuous operation of the coating system.

Still another object is to provide such a method and apparatus wherein the weight of coating material being consumed can be directly measured.

Numerous other objects and advantages of the invention will be apparent as it is better understood from the following description, which, taken in connection with the accompanying drawings, discloses a preferred embodiment thereof.

Referring to the drawings:

FIG. 1 is an elevational view, partly in section, of the apparatus used in performing the objects of the present method invention, showing the valve positions when the normal spraying operation is taking place and with the coating material in the test chamber, here shown as a sight glass, at the low level which is reached at the end of the previous test cycle;

FIG. 2 i a view similar to FIG. 1, showing the valve positions after the sight glass has been filled with coating material to a predetermined level, preparatory to the next test cycle;

FIG. 3 is a view similar to FIGS. 1 and 2, showing the valve positions during a test cycle; and

FIG. 4 is an elevational view corresponding to FIG. 3, of a modified form of the apparatus.

As a preferred or exemplary embodiment of the invention, FIGS. 1 through 3 illustrate a volumetric coating control apparatus comprising a upply line containing a pressurized liquid coating material C such as a resin, paint, varnish, wax, sealant, adhesive or a metal, such as solder or the like. The coating material C is pressurized by a pump P which is in communication with a reservoir (not shown) for the material to supply coating material C to the line 10 under a predetermined pressure. The supply line 10 and a compressed air line 11 are connected to a material applicator such as a spray head 12 having an atomizing nozzle 14 which functions to spray the coating material C onto a surface to be coated, such as the interior 16 of a tubular can body 18. The spray head 12 may be of a type that is disclosed in the US. Patent 2,103,270, Murch, issued Dec. 28, 1937, which discloses a can spraying machine that could be used with the present coating control apparatus. In such a machine, the spray head operates intermittently to spray successive cans which are automatically presented to it. The present volumetric coating control apparatus, however, can be used in continuous as well as successive coating operations.

A valve 19 comprising a casing 20 and a plug 21 rotatably mounted therein is disposed in the supply line 10, and a conduit 22 is connected at one end to the valve casing 20 and at the other end to the housing 24 of a conventional, commercially available, pressure balancing or relay valve 26. A flexible diaphragm 27 is mounted within the valve housing 24 and one side thereof is in communication with the valve 19 via the conduit 22. The valve stem 28 is disposed on the other side of the diaphragm 27 and is provided with a flat head 29 which is secured to the diaphragm 27 and with an enlarged spherical portion 30 which is located adjacent one end of an orifice 32 in the housing 24. The orifice 32 connects the other side of the diaphragm 27 with an air line 34 containing air under a predetermined pressure which is greater than that in the supply line 10. The valve stem 28 extends through the orifice 32 and beyond the pherical portion 30 into a recess 35 in a plug 36 which is threaded into or otherwise attached to the valve housing 24.

With the valve plug 21 in the position shown in FIG. 3, the pressure of the coating material C in the supply line 10 is transmitted by the conduit 22 to the one side of the diaphragm 27 in the pressure balancing valve 26, while the other side of the diaphragm 27 is exposed to air pressure in a chamber 40 which is positioned adjacent thereto. When the coating material pressure on the one side of the diaphragm 27 is equal to or less than the air pressure in the chamber 40, the spherical portion 30 of the valve stem 28 occupies the position shown in FIG. 1, wherein the spherical portion 30 engages the conical seat 39 to seal the orifice 32 and prevent air under pressure from passing therethrough to the chamber 40 and the adjacent side of the diaphragm 2'7.

When the coating material pressure exceeds the air pressure in the chamber 40, the diaphragm 27 is flexed (to the left as seen in FIG. 1), thus resulting in movement of the spherical stem portion 30 away from the conical seat 39. Pressurized air from the line 34 then passes through the orifice 32 into the chamber 40 until the air pressure on the adjacent side of the diaphragm 27 again equals the pressure of the coating material C on the other side thereof, whereupon the spherical portion 30 moves into engagement with the conical seat 39 to seal the orifice 32. It will be seen, therefore, that the function of the pressure balancing or relay valve 26 is to maintain the air on one side of the diaphragm 27 at substantially the same pressure as that of the coating material in the supply line 10. For a supply line pressure of 40 p.s.i., for example, the pressure balancing valve has been found to function properly when air in the line 34 is at a pressure of 50 to 60 p.s.i.

A second conduit 41 transmits the air under the same pressure as the pressure in the supply line 10 from the pressure balancing valve 26 to a pneumatic valve 42 which comprises a casing 44 and a plug 46 rotatably mounted therein. A venting aperture 48 is provided in the casing 44 for a purpose to be described hereinafter, and the rate of venting is controlled by a bleeder valve 49 which may be operated manually or automatically. In axial alignment with the conduit 41 and on the opposite side of the valve casing 44, there is disposed a third conduit 52 which connects the valve 42 with the upper end of a test chamber which in this preferred form of the invention comprises a sight glass 54. The sight glas 54 is provided with a transparent section 55 having graduations 56 thereon. A fourth conduit 58 is connected at one end to the bottom end of the sight glass 54 and at the other end to the coating supply line 10.

During normal operation of the spray head 12, the coating material C is pumped from the reservoir (not shown) to the supply line 10 and is then transmitted by the supply line '10 through the valve 19 and to the spray head 12. The valve plug 21 is in the position shown to in FIGS. 1 and 2 to allow uninhibited flow of the coating material C through the supply line 10, while preventing flow from the supply line 10 to the conduit 22 leading to the pressure balancing valve 26. Since the conduit 58 is connected directly into the supply line 10, the coating material C in the supply line 10 is in communication with the graduated sight glass 54. The valve 46 is positioned as shown in FIG. 2 so that the pressure in the sight glass 54 is the same as the pressure in the supply line 10, and as a result, the coating material C does not flow into the sight glass 54, but remains at the lowest level produced 'by the previous test cycle.

In order to reset the system for the next measuring operation, the components are all set as shown in FIG. 1, thus, the valve 42 and bleeder valve 49 are manipulated to reduce the pressure in the sight glass 54. As shown, this is accomplished by positioning the valve plug 46, whereby the pressurized air from the conduit 41 is cut off and the conduit 52 is brought into communication with the venting aperture 48, and by opening the bleeder valve 49. The bleeder valve 49 controls the rate of venting and thus the rate at which the coating material C rises in the sight glass. When the coating material C reaches a predetermined level 60 (see FIG. 2) in the sight glass, the bleeder valve 49 is closed and the coating material will no longer rise in the sight glass, owing to the remaining air pressure in the upper portion thereof.

FIG. 2 illustrates the volumetric coating control apparatus after the coating material has risen to the predetermined level 60 in the sight glass 54 and before the measuring and testing of the coating consumption takes place. The valve plug 46 is now positioned to prevent the escape of air through the venting aperture 48 and to establish communication between conduits 41 and 52. At this time, the valve plug 21 is still in the same position as that shown in FIG. 1, whereby coating material passes via the supply line 10 from the pump P through the valve 19, and to the spray head 12. It has been found that there is no tendency for the level of the coating material in the sight glass to change to any appreciable extent during this phase of the coating operation, since the pressure is equal on both ends of the column of coating material in the sight glass 54 and in the conduit 58. The pressure is equal on both ends of the coating material column because the valves 46 is set to prevent the air at the top end of the sight glass from escaping and escape through the balancing valve 26 is impossible.

When it is desired to measure the amount of coating material being consumed, the valve plug 21 is rotated to the position shown in FIG. 3, whereby the flow of coating material C from the pump P is cut off from the spray head 12 and the coating material pressure in the supply line is re-established in the conduit 22. This causes the pressure balancing valve 26 to maintain air in the air conduit 41 at the same pressure as that of the coating material in the supply line 10, and because this pressure is transmitted through the conduit 52 to the sight glass, the coating material C in the sight glass is under the same pressure a that in the supply line 10. The pressure in the sight glass 54 immediately forces the coating material therein and in the conduit 58 into the supply line 10, and to the spray head 12 to be used for the coating operation, without interruption of the coating machine whic-h embodies the spray head 12, so that the coating material C flows out of the sight glass 54, as seen in FIG. 3.

At the end of a predetermined time interval, or, alternatively, at the end of a predetermined number of coating cycles of the spray head -12, the valve plug 21 is rotated to the position shown in FIGS. 1 and 2, thereby establishing communication between the pump P and the spray head 12. The coating material in the sight glass is now at its lowest level 62 (see FIG. 1) which is lower than the initial level 60, and the difference between these levels is an indication of the volume of coating material C consumed during the test cycle. This volume may be directly indicated by providing volumetric graduations 56 on the transparent portion 55 of the sight glass 54. The volumetric consumption, when related to the number of cans 1 8 coated during the predetermined time interval or to a predetermined number of can coating operations can then be reduced to average weight (or thickness, by further computation) of coating applied to the interior surface 16 of each can, and can be compared to a standand or desired weight or thickness to determine if a correction in the consumption rate is required. The consumption rate may be corrected, if necessary, in the conventional manner by mechanical adjustment of the spray :gun 12 or by changing the pressure of the coating material in the supply line 10.

FIG. 4 illustrates a modified form of the present invention, wherein there is no valve 19 provided between the supply line 10 and the conduit 22, with the result that there is constant communication therebetween. Instead, a valve 64 is provided at the juncture of the supply line 10 and the conduit 58, the valve 64 comprising a casing 66 and a plug 68 rotatably mounted therein. In FIG. 4, the plug 68 is positioned to cut off the coating material from the pump P and to connect the conduit 58 with the spray head 12. This position of the valve plug 68 corresponds to the active measuring phase of the coating operation disclosed in FIG. 3, wherein the valve plug 21 similarly cuts off the flow from the pump P.

During other phases of the coating operation, the valve plug 68 is rotated 90 in a clockwise direction from the position shown in FIG. 4, to connect the supply line 10 to the spray head 12 and to the conduit 58. With the valve plug 68 in this position, the valve 44 and bleeder valve 58 are turned to the positions indicated in FIG. 1 to permit the coating material C to rise in the sight glass 54 to the level 60. Except for this modification in substitution of valve 64 for the valve 19, the apparatus of FIG. 4 is identical is construction and operation to that shown in FIGS. 1 through 3.

While the coating control apparatus disclosed herein has been described with respect to individual and manual operation of the rotary and bleeder valves, it will be apparent that the valves may be connected by a suitable control system so as to function automatically at predetermined times. Also, a control system may be provided to automatically record the consumption as indicated by the graduated sight glass and correct it when there is a deviation from the standard or desired consumption. For many coating operations, such an average coating determination taken at predetermined time intervals periodically throughout the course of the day has proven more than adequate to effectively control coating quality and avoid excessive waste.

It will be readily seen that the principles of the invention are not limited to the constructions disclosed in the drawings, and various other modifications may be made without departing from these principles. For example, each of the valves 19, 26, 42 and '64 may be of any suitable type or construction which is capable of functioning in the same manner as the construction disclosed herein. Similarly, various types of suitable volumetric indicators could be substituted for the graduated sight glass 54.

In addition, while the present invention has been described primarily in connection with a type of coating machine wherein individual cans are coated sequentially,

it will be understood that it is equally suited for web coating, individual sheet coating, compound lining, or any other type of coating or spraying operation where coating consumption per unit time is capable of volumetric determination and the applied material is maintained under pressure. If desired, a gravimetric rather than volumetric determination could be made of the amount of coating material drained from the sight glass during the selected testing interval. This could be accomplished, for

example, by suspending the sight glass from a balance in any suitable manner and weighing it at the beginning and at the end of a test interval to measure the weight rather than the volume of coating material consumed.

It is thought that the invention and many of its attendant advantages will be understood from the foregoing description, and it will be apparent that various other changes may be made in the form, construction and arrangement of the parts without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the form hereinbefore described being merely a preferred embodiment thereof.

I claim:

1. Apparatus for measuring the volume of coating being applied to a substrate material during a predetermined test interval, comprising means for continuously supplying said coating at a predetermined substantially constant pressure, means connected to said supplying means for directing said coating onto said substrate material, a test chamber connected to said supplying means and containing therein a predetermined volume of coating from said supplying means, pressure balancing means communicating with one end of said test chamber and said supplying means for supplying air to the coating in said test chamber at a pressure the same as that of the coating in said supplying means, valve means for disconnecting said supplying means and said directing means during said test interval, and simultaneously allowing said coating in said reservoir to flow under said pre-determined pressure to said directing means during said test interval.

2. The apparatus of claim 1 wherein said valve means is disposed between said supplying means and said pressure balancing means, and wherein said valve means is operative to connect said supplying means and said pressure balancing means during said test interval to equalize the pressure of said air supplied by said pressure balancing means to said test chamber and the pressure of said coating material in said supply line.

3. The apparatus of claim 1 wherein said pressure balancing means is connected directly to said supplying means to receive the coating pressure therefrom, and wherein said valve means is disposed between said supplying means and the other end of said test chamber.

4. The apparatus of claim 1 wherein means are provided for selectively preventing the passage of air from 7 said pressure balancing means to said one end of the test chamber and for simultaneously venting the air in said test chamber.

5. Apparatus for determining the amount of coating material being applied to a substrate material during a test interval comprising a supply line for conveying said coating material from a supply source under pressure, a material applicator on one end of said supply line, a test chamber, a coating material conduit connecting said supply line and said test chamber, a pressure balancing valve, an air line supplying said balancing valve with compressed air at a pressure higher than the pressure of said coating material in said supply line, an air conduit for conveying exhaust air from said balancing valve to said test chamber, said balancing valve operative to communicate with said supply line and equalize the pressure of said air exhausted into said air conduit, with the pressure of the coating material in said supply line, a bleeder valve for selectively decreasing the air pressure in said test chamber to a pressure below that of said coating material in said supply line to allow a pre-determined amount of said material to flow from said supply line, through said coating material conduit and into said chamber and valve means to selectively withdraw said material from said chamber or said supply source.

6. The apparatus defined in claim 5 wherein bleeder valve is operative to selectively vent said test chamber to the atmosphere.

7. The apparatus defined in claim 5 wherein said material applicator is a spray gun.

8. The apparatus defined in claim 5 wherein said means to selectively withdraw said coating material from said supply line includes a valve which is operative to put said balancing valve selectively in or out of communication with said supply line.

9. The apparatus defined in claim 5 wherein said means to selectively withdraw said coating material from said chamber is a valve operative to prevent communication of said material conduit and said supply line while permitting communication between said supply line and said material applicator or alternatively to prevent communication of said supply line with said applicator while per mitting communication between said test chamber and said applicator.

References Cited UNITED STATES PATENTS 2,826,067 3/1958 Braunlich 73-168 3,000,207 9/1961 Goife 73223 X 3,172,779 3/1965 Warshaw et al. 118-9 3,179,291 4/1965 Umbach et al 73l68 ALFRED L. LEAVITI, Primary Examiner.

E. B. LIPSCOMB, Assistant Examiner.

Claims (3)

1. APPARATUS FOR MEASURING THE VOLUME OF COATING BEING APPLIED TO A SUBSTRATE MATERIAL DURING A PREDETERMINED TEST INTERVAL, COMPRISING MEANS FOR CONTINUOUSLY SUPPLYING SAID COATING AT A PREDETERMINED SUBSTANTIALLY CONSTANT PRESSURE, MEANS CONNECTED TO SAID SUPPLYING MEANS FOR DIRECTING SAID COATING ONTO SAID SUBSTRATE MATERIAL, A TEST CHAMBER CONNECTED TO SAID SUPPLYING MEANS AND CONTAINING THEREIN A PREDETERMINED VOLUME OF COATING FROM SAID SUPPLYING MEANS, PRESSURE BALANCING MEANS COMMUNICATING WITH ONE END OF SAID TEST CHAMBER AND SAID SUPPLYING MEANS FOR SUPPLYING AIR TO THE COATING IN SAID TEST CHAMBER AT A PRESSURE THE SAME AS THAT OF THE COATING IN SAID SUPPLYING MEANS, VALVE MEANS FOR DISCONNECTING SAID SUPPLYING MEANS AND SAID DIRECTING MEANS DURING SAID TEST INTERVAL, AND SIMULTANEOUSLY ALLOWING SAID COATING IN SAID RESERVOIR TO FLOW UNDER SAID PRE-DETERMINED PRESSURE TO SAID DIRECTING MEANS DURING SAID TEST INTERVAL.

5. APPARATUS FOR DETERMINING THE AMOUNT OF COATING MATERIAL BEING APPLIED TO A SUBSTRATE MATERIAL DURING A TEST INTERVAL COMPRISING A SUPPLY LINE FOR CONVEYING SAID COATING MATERIAL FROM A SUPPLY SOURCE UNDER PRESSURE, A MATERIAL APPLICATOR ON ONE END OF SAID SUPPLY LINE, A TEST CHAMBER, A COATING MATERIAL CONDUIT CONNECTING SAID SUPPLY LINE AND SAID TEST CHAMBER, A PRESSURE BALANCING VALVE, AN AIR LINE SUPPLYING SAID BALANCING VALVE WITH COMPRESSED AIR AT A PRESSURE HIGHER THAN THE PRESSURE OF SAID COATING MATERIAL IN SAID SUPPLY LINE, AN AIR CONDUIT FOR CONVEYING EXHAUST AIR FROM SAID BALANCING VALVE TO SAID TEST CHAMBER, SAID BALANCING VALVE OPERATIVE TO COMMUNICATE WITH SAID SUPPLY LINE AND EQUALIZE THE PRESSURE OF SAID AIR EXHAUSTED INTO SAID AIR CONDUIT, WITH THE PRESSURE OF THE COATING MATERIAL IN SAID SUPPLY LINE, A BLEEDER VALVE FOR SELECTIVELY DECREASING THE AIR PRESSURE IN SAID TEST CHAMBER TO A PRESSURE BELOW THAT OF SAID COATING MATERIAL IN SAID SUPPLY LINE TO ALLOW A PRE-DETERMINED AMOUNT OF SAID MATERIAL TO FLOW FROM SAID SUPPLY LINE, THROUGH SAID COATING MATERIAL CONDUIT AND INTO SAID CHAMBER AND VALVE MEANS TO SELECTIVELY WITHDRAW SAID MATERIAL FROM SAID CHAMBER OR SAID SUPPLY SOURCE.

7. THE APPARATUS DEFINED IN CLAIM 5 WHEREIN SAID MATERIAL APPLICATOR IS A SPRAY GUN.

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