US3653594A

US3653594A - Precision coatings spray gun

Info

Publication number: US3653594A
Authority: US
Inventors: Hendrik F Bok; David A Garcia
Original assignee: EPEC IND Inc
Current assignee: EPEC IND Inc
Priority date: 1970-11-17
Filing date: 1970-11-17
Publication date: 1972-04-04
Anticipated expiration: 1989-04-04

Abstract

An automatic spray gun used for precision spray applications where coating thicknesses are required with extremely close tolerances and with a very high degree of repeatability. A valve rotor is placed in the upper portion of the spray gun construction and selectively controls the flow of solvent or coating materials through the spray gun. The valve rotates to selected positions to connect either cleaning solvent or coating material to a filter and nozzle. Provision is made for repeated coatings by selective valve rotation. Control means are included for activating the spray gun for a burst of solvent to allow prewetting of a filter area and other internal walls of the spray gun. The control means subsequently rotates the valve rotor to a coating material position to replace the solvent and the coating spraying operation ensues. Selective solvent and/or coating material cycles flushes the spray gun and eliminates the filter and nozzle orifice from being restricted. Flushing of the gun subsequent to a spray coating operational phase permits a high degree of repeatability in coating output.

Description

United States Patent Bok et al. 5] Apr. 4, 1972 [54] PRECISION COATINGS SPRAY GUN Primary ExaminerM. Henson Wood, Jr.

721 Inventors: Hendrik F. Bok, Fairhaven; David A. Garcia, New Bedford, both of Mass. y

[73] Assignee: Epec Industries, Inc., New Bedford, Mass. ABSTRACT [22] Fil d; N 17, 1970 An automatic spray gun used for precision spray applications where coating thicknesses are required with extremely close [21] APPL NOJ 90,292 tolerances and with a very high degree of repeatability. A

valve rotor is placed in the upper portion of the spray gun con- 52 us. c1 ..239/7o,239/112,239/412, Struction and selectively controls the flow of Solvent or coat- 137/625 41 I 18/7 ing materials through the spray gun. The valve rotates to [51] int. Cl ..B05b 7/12 positions to connect either cleaning solvent or coat- [58] Field of Search ..239/8, 1 1,63, 69, 70, 112, a filler f "9 made for 239/307 410412, 444446; 137/602, 625 19, peated coatmgs by selectlve valve rotation. Control means are 625.41; 1 18/7 included for activating the spray gun for a burst of solvent to allow pre-wetting of a filter area and other internal walls of the [56] References Cited spray gun. The control means subsequently rotates the valve rotor to a coating material position to replace the solvent and UNITED STATES PATENTS the coating spraying operation ensues. Selective solvent and/or coating material cycles flushes the spray gun and 3 1 10/1967 wfggms "239/112 X eliminates the filter and nozzle orifice from being restricted. 3,057,273 10/1962 Wilson "239/1 12 X Flushing of the gun subsequent to a spray coating operational 1 g i phase permits a high degree of repeatability in coating output. op ms 10 Claims, 6 Drawing Figures Patented April 4, 1972 3,653,594

4 Sheets-Sheet 1 l6 32 I I4 r 40 I F 58 t so FIG. 1

INVENTOIS HENDRIK F 80K DAVID A. GARCIA .Y Wadi/M ATTOI N EYS Patented April 4, 1972 I 50 L ATOR 4 Sheets-Sheet 5 CHARACTER 4 D TO VALVE CONTROLLING DECREASE I DIRECTION OF AIR MOTOR. CHARACTER 2 PRESSURE I SIGNAL 'FROM P AD? TRANSDUCER ADJUSTABLE RESTRICTOR CHARACTER 3 D TO vALvE D LQIZI'IKQLLL G THE INcREAsE 'SOLATOR DIRECTION OF AIR REFERENCE PRESSURE FIG 4 MOTOR CHARACTER l SOLVENT INLET D ON-OFF CONTROL U VALVE SIGNAL COATING MATERIAL INLET q CONTROL sIIaNAL U l I I I FILTER PRESSURE I I TRANSDUCER I AIR SIGNAL l l I I SELECTOR VALVE AUT. SPRAY GUN NOZZLE 8 AIR CAP INVENIOIS HENDRIK F. BOK

DAVID A. GARCIA ATTOINEYS Patented A fil 4, 1972 4 Sheets-Sheet 4.

INVENTOIS HENDRIK F. BOK DAVID A. GARCIA av M ATTORNEYS PRECISION COATINGS SPRAY GUN BACKGROUND OF THE INVENTION A need exists for a spray gun for precision coatings with automatically controlled coating deliveries where coating thicknesses are required with extremely close tolerances and with a very high degree of repeatability. Such spray guns have not heretofore been available.

SUMMARY or THE INVENTION The present invention satisfies a need for a spray gun construction for precision coatings with automatically controlled coating deliveries used for precision spray applications where coating thicknesses are required with extremely close tolerances and with a very high degree of repeatability. This is accomplished by the present invention which includes a valve rotor in the upper part of the spray gun which selectively controls the flow of solvent or coating materials through the spray gun. The valve rotor upon rotation to predetermined positions connects either the cleaning solvent or the coating material to the filter and nozzle of the gun. Subsequent coatings of material can be sprayed upon an article by rotating the rotor to connect with one or more coating material sources with intermediate positions for solvent spray operational phases.

Construction and operation of the spray gun of the invention will be more readily apparent from the following detailed description of an embodiment thereof when taken together with the accompanying drawings in which:

FIG. 1 is a view partly in section through a spray gun construction in accordance with the invention;

FIGS. 2A, 2B and 2C schematically depict the spray gun in three different operational states;

FIG. 3 is a schematic of an operating control circuit for the spray gun; and

FIG. 4 is a schematic of a typical fluidic logic circuit for use with the spray gun of the invention.

Referring now in more detail to the drawings the spray gun generally designated includes spray gun housing 12 having therein a valve rotor seat 14 of truncated conical configuration in which is operatively mounted a valve rotor 16 of comparitive configuration. Shaft 18 for the valve rotor is operatively connected in a rotary actuator 20 and means such as spring 22 bias the valve rotor into sealing engagement in the rotor seat.

The valve rotor has perpendicularly disposed vertical and horizontal bores or

passageways

24, 26 therein open to the exterior of the rotor body as at 28; These passageways are intercommunicating and adapted for coaction with bores or

passageways

30 and 32 in the rotor seat which extend through the body thereof and respectively are in open communication with construction comprising, generally designated, coating material inlet 34 and solvent inlet 36. The open end of vertical bore 24 opens into chamber 38 which is in communication with compartment 40 in the valve body.

Associated with the valve body compartment is a disc filter 42 mounted by means of a threadedly engaged filter cap 44 coacting with the valve body. A communicating opening 46 permits flow from chamber 38 to one side of the filter for subsequent flow therethrough and discharge through passage 48 for mixing with atomization air.

Also operatively connected in compartment 40 is a pressure transducer assembly generally designated 50 having a transducer 52 therein. An air pressure signal-output is provided at 54 and an air inlet at 56 leading to an air atomization chamber 58. The spray gun terminates, as usual, with a nozzle 60 and air cap 62; the nozzle and air cap being operatively associated with fluid flow and atomization air passages in the spray gun. As shown in FIG. 1 the takeup spring 22 is maintained in place by end cap 64. The valve rotor is provided with a tefion rotor seat 14 and the rotary actuator for the valve rotor is preferably pneumatic.

The automatic spray gun of this construction is adapted for automatically controlled coating deliveries used for precision spray applications where coating thicknesses are required with extremely close tolerances and with a very high degree of repeatability. The valve rotor placed in the upper part of the spray gun selectively controls the flow of solvent or coating materials through the spray gun. For a single coating material, the valve rotor, by means of the rotary actuator 20, rotates 90 to connect either the cleaning solvent or the coating material to the filter and nozzle. In case two coating materials are to be sprayed, the valve rotor would, from the middle position. rotate 90 to the left to connect the coating material number one, or 90 to the right to connect the coating material number two. The valve rotor in this case always returns to the middle position.

FIGS. 2A, 2B and 2C show the spray gun with solvent inlet and one coating material inlet in three different phases or states. In drawing 2A the spray gun is shown in the Off mode. The valve rotor, controlled by the selector valve and actuated I by the rotary actuator, is in the solvent position, and since the solvent On/Off valve is in the Off position, the spray gun is at rest.

FIG. 2B shows the spray gun after the gun On signal has been received. The solvent On-Off valve is momentarily activated and a burst of solvent is fed via a valve rotor opening (valve rotor is in the solvent position) through the filter and the nozzle. This action allows pre-wetting of the filter area and other internal walls of the spray gun.

Immediately after the solvent burst, the valve rotor is rotated to the material position, FIG. 2C, allowing coating material to replace the solvent and the spray operation commences. After the spray gun Off signal is received, the valve rotor is rotated back to the solvent position. In addition, the solvent On-Off valve is time-cycled to allow a timed solvent flush through the gun which eliminates restriction of the filter and nozzle orifice. By wetting the internal parts of the spray gun prior to the spray operation, and by flushing the spray gun immediately after the spray operation, all solids have been flushed out of the gun and a high degree of repeatability in coating output is assured, even after the gun has been in the Off position for a long period of time.

The present invention also provides automatic coating pres sure readout with self-adjusting pot pressure control. Since the applied coating thickness is in direct proportion to the coating material output from the gun, and since the coating material output changes with the pressure of the coating material in the nozzle (assuring a constant nozzle orifice opening), a pressure readout or indication of the coating material pressure, at a place following the filter and above the nozzle, is an indirect method of checking the obtained film thickness. In addition, this pressure information can be compared against a reference pressure to produce a readout and/or a signal which will adjust the pot pressure to a level whereby the pressure information equals the reference pressure.

As shown in FIG. 1, the pressure transducer is placed between the outlet side of the filter and the nozzle of the spray gun. Air atomization pressure of the spray gun is controlled by circuitry and means as shown in FIG. 3 of the drawings. This includes a large diaphragm precision pressure regulator 66 in air supply line 68. The air supply can for example be between p.s.i. and regulator 66 is for a range of between for example 10 20 p.s.i. Pressure gauge 70 operable in a range of 0 20 p.s.i. serves to indicate the pressure of the air supply for atomization and the transducer. The pressure regulator 66 is self-compensating and assures a constant air supply output, unaffected by possible upstream pressure fluctuation of the air supply. The regulator 66 is also provided with a one micron filter to remove possible line contamination.

The precisely pressure-controlled air output of regulator 66 is fed into the gun 10 for atomization of the coating material. In addition, as shown in FIG. 3, a very small amount of air is used as an input into the pressure transducer 52. Air atomization is generally indicated at 72. Solvent and coating material inputs are also indicated at 34 and 36. The pressure transducer senses the coating material pressure behind the built-in filter and just above the nozzle. It, in operation, converts this pressure information into an air output with a pressure which is in direct proportion to the coating material pressure variation. The air output signal from the transducer is fed into a three way signal pilot operated valve 74 having a lead 76 to a booster valve in the On-Off controller. The three way valve 74 allows the output signal from the transducer to flow into a fluidic logic circuit, FIG. 4 only if the spray gun is in the On mode.

In the spray gun Off mode the reference pressure is placed as a double but equal signal into the fluidic logic circuit. The logic circuit assembly is generally shown at 76 in FIG. 3. In this case, no differential is sensed and the fluidic logic circuit is placed in a state whereby the readout shows the nominal valve configuration, and no signal is sent to either one of three way signal pilot operated valves 78 or 80. In addition, in the spray gun off mode, the reference pressure is fed through line 82 into the pressure pot as the head of pressure for the coating material supply at 84. Operatively incorporated in the line is a reference pressure gauge and valve assembly 84, an air motor driven pressure regulator 86 with valve 88 with the outputs going through a three way single pilot operated valve 90. The logic circuit assembly 76 has operatively connected a readout 92 with indicators 94 for nominal, 96 for low and 98 for high.

When the spray gun commences the spraying operation, the pressure signal from the pressure transducer is compared to the reference pressure by the fluidic logic circuit (FIG. 4). If the pressure signal is too low the fluidic logic circuit produces a combination of signals to form the low display configuration, 96, and a signal is fed to three way valve 78 which allows air motor 86 to rotate in such a direction that the pressure regulator 88 produces a high head of pressure in the pressure pot. If the pressure signal of the pressure transducer is too high, a high display 98 is shown and the air motor rotates the pressure regulator 88 to lower the head of pressure of the pressure pot.

A typical fluidic logic circuit as shown in FIG. 4 senses a pressure differential between the two pressure signal inputs from the transducer and reference pressure and produces three output conditions for the fluidic readout and pressure compensation signals as indicated.

Manifestly minor changes in details can be effected without departing from the spirit and scope of the invention as defined in and limited solely by the appended claims.

We claim:

1. A. precision coatings spray system comprising:

A. a spray gun;

B. a spray propellant source operatively connected to said spray gun adapted for atomizing and dispensing material from said spray gun;

C. a solvent supply source for said spray gun;

D. a coating material supply source for said spray gun; and

E. means operable for selectively controlling flow of solvent and coating material into and through said spray gun in discrete pre-determined interval sequences, that means being operable to initially introduce a burst of solvent into said spray gun prior to introduction of coating material for pre-wetting internal components and areas of the spray gun.

2. A precision coatings spray system as claimed in claim 1, wherein following said pro-wetting solvent burst, coating material is supplied to said spray gun for application to an article to be coated and subsequently a second increment of solvent at a time-cycled interval is introduced into and through said spray gun for flushing coating material from the spray gun components and interior to prevent restriction and flushing all solids out of the gun whereby a high degree of repeatability in coating output is assured conjointly by said pre-wetting and flushing with solvent even subsequent to the spray gun being inoperative for a substantial period of time.

3. A precision coatings spray system as claimed in claim 1, and including a ported rotatable valve in said spray gun, means for rotating the valve to pre-determined positions for interconnecting respectively said solvent supply source and said coating material supply source, a filter in said spray gun and a spray nozzle on said spray gun, said valve selectively controlling solvent and coating material flow, and means for cycling valve positioning to initially introduce a burst of solvent through said gun, a subsequent supply of coating material through said gun and a subsequent supply of solvent through said gun, said solvent increments serving initially to pre-wet the interior and components of the spray gun with the subsequent solvent introduction serving to cleanse the spray gun interior including said filter and spray orifice to flush solid materials therefrom and prevent clogging of said spray gun.

4. A precision coatings spray system as claimed in claim 3, including a pressure transducer operatively connected into said spray gun in an area intermediate said filter and the spray gun nozzle, said pressure transducer being operable for a pressure indication of coating material pressure subsequent to said filter and prior to said nozzle, said pressure indication constituting an indication of coating thickness which is in direct proportion to coating material output from the spray gun and with the pressure of the coating material in the spray gun nozzle, and means for comparing the pressure information against a reference pressure to produce a signal operable to adjust pot pressure to a level whereby the pressure information equals the reference pressure.

5. A precision coatings spray system as claimed in claim 4, including a precision pressure regulator from said spray propellant source, said pressure regulator being self-compensating and assuring constant air supply output unaffected by possible upstream pressure fluctuations of an air supply, the pressure controlled air output from said regulator being fed into said spray gun for atomization of the coating material, a minor increment of the air being introduced as an input into said pressure transducer, said pressure transducer sensing coating material pressure behind said filter and just prior to the nozzle, said transducer converting the measured pressure information into an air output with a pressure which is in direct proportion to the coating material pressure variation.

6. A precision coatings spray system as claimed in claim 5, and further including a three-way single pilot operated valve for receiving the air output signal from the transducer, a fluidic logic circuit, said threeway valve permitting an output signal from said transducer to flow into the fluidic logic circuit only during periods when said spray gun is in an on" mode, the reference pressure with the spray gun in an off mode being introduced as a double but equal signal into the fluidic logic circuit and, no pressure differential being sensed places said fluidic logic circuit in a no flow control setting, reference pressure being fed as head pressure for the coating material supply with said spray gun in the off" mode.

7. A precision coatings spray system as claimed in claim 6, wherein upon commencement of spray operation of said spray gun, a pressure signal from said pressure transducer is compared to the reference pressure by said fluidic logic circuit, a too low pressure signal resulting in the fluidic logic circuit producing a combination of signals to form a low display configuration and initiate a signal to control rotation of and produce a higher head pressure on the coating material source and conversely if the pressure signal of the pressure transducer is too high, a high display is shown and the head pressure on the material source is lowered.

8. A spray gun comprising:

A. a housing having a chamber therein;

B. a valve seat having a truncated cone shaped main passage therethrough and opening into secondary passages leading respectively to a coating material inlet and a solvent inlet;

C. a valve rotor of mating shape and size with main passage through said seat and having a passage therethrough for selective connection to the coating material and solvent passages upon rotation of said rotor and communicating with discharge from said rotor seat for subsequent passage through said spray gun;

D a source of air under pressure operatively connected to said spray gun for atomization of coating material and flow through said spray gun.

9. A spray gun as claimed in claim 8, and including a spray nozzle at the discharge end of said spray gun, a filter placed subsequent to the discharge end of said rotor seat, a pressure transducer assembly positioned intermediate said filter and said spray nozzle in an area after the filter and the spray nozzle adapted for an indication of coating material pressure and for

Claims

1. A. precision coatings spray system comprising: A. a spray gun; B. a spray propellant source operatively connected to said spray gun adapted for atomizing and dispensing material from said spray gun; C. a solvent supply source for said spray gun; D. a coating material supply source for said spray gun; and E. means operable for selectively controlling flow of solvent and coating material into and through said spray gun in discrete pre-determined interval sequences, that means being operable to initially introduce a burst of solvent into said spray gun prior to introduction of coating material for prewetting internal components and areas of the spray gun.

2. A precision coatings spray system as claimed in claim 1, wherein following said pre-wetting solvent burst, coating material is supplied to said spray gun for application to an article to be coated and subsequently a second increment of solvent at a time-cycled interval is introduced into and through said spray gun for flushing coating material from the spray gun components and interior to prevent restriction and flushing all solids out of the gun whereby a high degree of repeatability in coating output is assured conjointly by said pre-wetting and flushing with solvent even subsequent to the spray gun being inoperative for a substantial period of time.

6. A precision coatings spray system as claimed in claim 5, and further including a three-way single pilot operated valve for receiving the air output signal from the transducer, a fluidic logic circuit, said three-way valve permitting an output signal from said transducer to flow into the fluidic logic circuit only during periods when said spray gun is in an ''''on'''' mode, the reference pressure with the spray gun in an ''''off'''' mode being introduced as a double but equal signal into the fluidic logic circuit and, no pressure differential being sensed places said fluidic logic circuit in a no flow control setting, reference pressure being fed as head pressure for the coating material supply with said spray gun in the ''''off'''' mode.

8. A spray gun comprising: A. a housing having a chamber therein; B. a valve seat having a truncated cone shaped main passage therethrough and opening into secondary passages leading respectively to a coating material inlet and a solvent inlet; C. a valve rotor of mating shape and size with main passage through said seat and having a passage therethrough for selective connection to the coating material and solvent passages upon rotation of said rotor and communicating with discharge from said rotor seat for subsequent passage through said spray gun; D. a source of air under pressure operatively connected to said spray gun for atomization of coating material and flow through said spray gun.

9. A spray gun as claimed in claim 8, and including a spray nozzle at the discharge end of said spray gun, a filter placed subsequent to the discharge end of said rotor seat, a pressure transducer assembly positioned intermediate said filter and said spray nozzle in an area after the filter and the spray nozzle adapted for an indication of coating material pressure and for producing a signal to adjust head pressure on the coating material for flow control through said gun.

10. A spray gun as claimed in claim 9, and including a rotary actuator operatively connected to said valve rotor and means for controllably time cycling positionment of said valve rotor to selectively control flow of solvent and coating material into and through said spray gun in discrete predetermined interval sequences.