US3155539A

US3155539A - Electrostatic spray coating methods and apparatus

Info

Publication number: US3155539A
Application number: US775315A
Authority: US
Inventors: James W Juvinall
Original assignee: Individual
Current assignee: Individual
Priority date: 1958-11-20
Filing date: 1958-11-20
Publication date: 1964-11-03
Anticipated expiration: 1981-11-03
Also published as: GB941183A; DE1402627C2; DE1402627B1; DE1232047B; FR1245081A

Description

Nov. 3, 1964 J. w. JUVINALL 3,155,539

ELECTROSTATIC SPRAY COATING METHODS AND APPARATUS Filed Nov. 20, 1958 5 Sheets-Sheet 1 F/ 1 I INVENTOR.

.JAMES W. JUVINALL Attornzst Nov. 3, 1964 J. W. JUVINALL ELECTROSTATIC SPRAY COATING METHODS AND APPARATUS Filed Nov. 20, 1958 5 Sheets-Sheet 2 110 V. AC

INVENTOR.

' JAMES W. JUVINALL BY M7 W/ A Horjeysi Nov. 3, 1964 J w. JUVINALL 3 1 ELEQTROSTATIC SPRAY comma METHODS A-ND- APPARATUS Filed Nov. 20, 1958 5' Sheets-Sheet 3 Molor43o Valve 45a 1 P f\ l Solenoid R In 5 A r Solenoid PB |-4 PUSH BUTTONS R l-'! RELAYS TD l-3 TIME DELAY RELAYS JAMES W. JUVINALL BY Q R -1 5 RCI'? RELAY CONTACTS it TDC l'3 TIME DELAY CONTACTS R 6 1 -H- NORMALLY OPEN CONTACTS d- NORMALLY CLOSED CONTACTS 4 INVENTOR R65 3 Attorney Noam 3 1.. w.v JUIVINALL; 3,155,539

ELEGTRQSFMTIC: seam comma muons AND? APPARATUS Filed: Nov. 20'' 19583v 5v She'ets= Shee-t 4 INVENTOR.

F/g: 6 JAMES w. JSVINALL Nov. 3, 1964 J. w. JUVINALL 3,155,539

ELECTROSTATIC SPRAY COATING METHODS AND APPARATUS Filed Nov. 20, 1958 5 Sheets-Sheet s PBlI-l3 PUSH BUTTONS Rll-l8 RELAYS RcIs I I I l l l I I I I I PB I3 ROM R0 [5 I I I l I I, I I I I I I I I I Ron-Is RELAY CONTACTS II NORMALLY OPEN CONTACTS 1H- NORMALLY CLOSED CONTACTS RFH bqilfa RIIIIG ll x o 0 POWER SUPPLY as RGIS T I T s20 sz b 82|c RCI3 I C I 7701780 I 77b|78b l 77c Inc J ROIZ I II H new I l .J

INVENTOR.

JAMES W. J VINALL BY 5 WW AIIom ys United States Patent C) Filed Nov. 29, 1958, Ser. No. 775,315 7 Claims. (ill. 118-11) This invention relates to improvements in methods and apparatus for spray coating articles with liquid coating material. The invention is particularly useful where electrostatic forces are employed in the spray coating process and where it is desired to automatically and quickly change the type or color of coating material sprayed from a spraying device.

The application of quality finishes on articles manufactured on an assembly line basis usually involves spray coating the articles. Many automatic spray coating operations today utilize electrostatic forces in the atomization and/or deposition of the sprayed material. In spray painting conveyorized articles it is frequently desirable to change the color or type of coating material and to do so without interfering with the continuous movement of articles on the conveyor line. As an example it may be desired to coat a number of the conveyorized articles with blue paint and then immediately change over and paint the next succeeding articles with white paint. But to date no entirely satisfactory system has been developed to achieve this result.

The invention provides for changes from one type or color of coating material to another with a minimum of equipment and loss of time. It is readily usable with existing conveyor lines and with little change in plant layout or equipment. While the invention is particularly adapted for those systems utilizing electrostatic forces in atomizing and/or depositing the sprayed material, certain of its features can be used with other types of spray coating systems.

Apparatus for practicing my invention includes a conveyor for moving the articles to be spray coated successively through a coating zone and spraying means positioned adjacent the coating zone for creating a spray of liquid coating material particles to be deposited on the articles passing through the coating zone. The spraying means includes a plurality of discharge nozzles, one for each of the liquids to be used, and may embody or have associated with it a charged electrode for electrically charging the spray particles and creating an electrostatic particle-depositing field. Preferably, the spraying means is an electrostatic atomizer embodying an electrode to which liquid is supplied from the several nozzles. The apparatus also includes a plurality of sources of liquid coating material and means associated with each source for controlling the delivery of coating material from that source to the spraying means.

A common operator for the several delivery controlling means is selectively operable so as to cause delivery to the spraying means from any one of the coating material sources while preventing delivery from any other source. Power-actuated means is provided which can be energized to operate the common operator through a predetermined cycle automatically to effect successive termination of delivery of coating material to the spraying means from any one of the coating sources and, after a predetermined time delay, initiation of delivery of coating material from a pro-selected different coating material source to the spraying means. Additional features or steps may be added to the predetermined cycle of operation depending upon the spraying means employed.

During a coating operation the common operator is set to effect delivery of a selected coating material to the spraying means and the articles arepassed succesartists Patented Nov. 3, 1964 ice sively through the spray discharged therefrom. When it is desired to change the color or type of coating material the power-actuated means is thrown into operation, as by pushing one or more buttons on a control panel, to activate the operator which proceeds through the desired cycle of operation to effect the change from one coating material to the other.

In one preferred form the invention utilizes apparatus for electrostatically spray coating articles with an atomizer of the rotating annular-edged type. The articles are moved along a path suspended from a conveyor and the atomizer mounted to one side of the path of article movement facing the articles to be coated. A plurality of liquid feeding nozzles are arranged to supply liquid directly onto the rotating atomizer surface and liquid supply lines are arranged to supply a different type or color of coating material to each one of the nozzles. In addition, one nozzle is connected to a separate line supplying a mixture of compressed air and a cleaning solvent, such as toluol, to the atomizer. Pumps and onofi valves are provided for each of the fluid feed lines. A solvent interceptor in the form of a cylindrical shroud designed to surround the atomizeris provided together with means for moving the shroud into and out of sprayintercepting position surrounding the atomizer.

A control panel remote from the atomizer provides automatic or manual means for selectively controlling the on-off valves and the pumps and the shroud moving means so as to produce a predetermined cycle of operation as follows: delivery of coating material to the atomizer is terminated, the atomizer and the interceptor are brought into spray-intercepting relation, solvent isdelivered to the atomizer for a predetermined interval to clean the atomizer while the sprayed solvent is intercepted and collected, solvent delivery is terminated, the interceptor and atomizer are moved relatively out of spray-intercepting relation, and delivery of another coating material to the atomizer is initiated. Pre-selecting means may be provided to determine which of several coating materials will be delivered to the atomizer at the termination of the operator-cycle.

In order to properly clean such a rotating atomizer of all undesired coating material more than one nozzle may be used to supply solvent or a mixture of compressed air .and solvent to the atomizer. For example, it may be desirable to direct one mixture of compressed air and cleaning solvent onto the inner surface of the rotating atomizer and to direct another mixture onto the outer surface of the atomizer.

In order to reduce the possibility of slugging, i.e., the deposit of unduly large drops of liquid coating material on the article, the atomizer, if of the rotating internally-fed type, may include a novel passageway arrangement for the liquid moving from the liquid feeding nozzle to the outer edge of the atomizer. The novel arrangement provides a sharply turning, zig-zag passageway for the liquid which serves to prevent the discharge of undesirably large slugs of liquid from the atomizer, especially when the atomizer has a diameter of more than several inches. 7

In another form the invention utilizes a plurality of air spray guns mounted on a carrier selectively movable t dispose any gun in operativespraying position. Each gun is supplied with individual liquid coating material and compressed air lines so that each gun may be individually operated to spray one particular type or color of coating; material. Mechanism is provided for rotating the guns A common operator for the several paint and air valves and for the gun carrier provides selective operation of any one individual gun while preventing operation of all of the other guns. Power-actuated means within a control panel can be energized to operate the common operator through a predetermined cycle of operation so that pressing a single button will effect termination of the flow of paint and air to the then operating spray gun, rotation of guns about their central axis until a preselected other spray gun is put into coating position, and then coating material and compressed air are supplied to the newly positioned spray gun.

The foregoing and further features of the invention will be readily apparent from the following detailed description and drawings, in which:

FIG. 1 is a detailed side view, partially broken away, of an atomizer embodying certain features of the invention;

FIG. 1A is a front view, partially broken away, taken along line 1A1A of FIG. 1;

FIG. 2 is a side view of a complete coating apparatus including the atomizer shown in FIG. 1;

FIG. 3 is a diagrammatic view of the apparatus shown in FIG. 2;

FIG. 4 is a diagram of one form of controls for the apparatus shown in FIGS. 2 and 3;

FIG. 5 is a plan view of another form of coating apparatus embodying the invention;

FIG. 6 is a side view, partially in cross section, taken along line 6-6 of FIG. 5; and

FIG. 7 is a diagram of the controls for the apparatus shown in FIGS. 5 and 6.

The apparatus shown in FIGS. 1 and 1A comprises a hoop-like atomizer 10 preferably made of nylon or other insulating material. Atomizer 10 is supported from a circular hub 11 also of nylon and afiixed thereto by several radial pins. Hub 11 is mounted for rotation with a shaft 12 comprising an insulating extension of the armature shaft of an electric motor 13 which is connected to rotate the atomizer at a speed of several hundred revolutions per minute. The atomizer-motor assembly is supported by a bracket 14 which in turn is supported from a post 15 made of insulating material.

A cylindrical interceptor member or shroud 16 is mounted concentrically about the atomizer-motor assembly and adapted for axial movement into and out of spray-intercepting position (as shown by the dotted line in FIG. 1) in which the forward end of shroud 16 will surround and lie forwardly of atomizer 10. The shroud is maintained normally in a rearward position by spring 13 and is movable into its forward spray-intercepting position by the operation of air cylinder 19, Whose piston rod 20 is attached to the rear end of shroud 16.

The motor 13, bracket 14 and shroud 16 are maintained at a high electrical potential by connection through lead line 22 to high voltage source 23, which generates a voltage in the order of 90 kv. The outer surface and back of atomizer 10 are coated with a semi-conducting material and a spring or brush 24 provides an electrical connection between motor 13 and the back of the atomizer so that the forward atomizing edge 10a of the atomizer is maintained at a voltage in the order of 90 kv.

A disc-shaped electrical probe 25, made of nylon and having an outer rim 25a, is concentrically mounted on the forward face of hub 11 by means of a metal screw 26. The rear end of screw 2-5 is electrically connected by an insulation covered Wire 28 to the lower end of a high resistance 29 contained within post 15 and the upper end of resistance 29 is connected to ground. Resistance 29, in the embodiment shown, has a value of 10,000 megohrns.

The forward face and outer rim 25a of the probe is coated with a semi-conducting material so that its face and outer rim 2-5:: are electrically connected to ground through resistance 29. Probe 25 is thus electrically isolated from atomizer 10, motor 13, bracket 14, shroud 16, and the other parts of the apparatus maintained at high voltage. However, by virtue of its position adjacent to highly charged atomizing edge 10a and as the result of the voltage drop across resistance 29, probe 25 will be at a potential intermediate that of the atomizing edge and ground.

Liquid is fed to the inner surface of atomizer 10 by a plurality of liquid feeding nozzles 30 which are stationarily supported from the motor housing in circumferentially spaced relation within the rear portion of atomizer 10 as shown in FLG, 1A. A separate nozzle 30 is provided for each type or color of liquid coating material to be used and an additional nozzle is provided for the cleaning fluid, preferably a mixture of compressed air and solvent. The nozzles are supplied through fluid feed lines 31.

During the coating operation, liquid is fed from one of the nozzles 30, which remains stationary, onto the inner surface of ro ating atomizer 10. The peripheral edge of hub 11 and the inner surface of atomizer 10 form an annular slot through which the liquid must fiow in order to reach atomizing edge ltla. The transference of liquid from the stationary nozzle to the rotating atomizer surface often may produce large slugs of liquid thrown from the rotating atomizer more or less at random and such slugging is highly detrimental to the production of quality coatings. To reduce slugging, a weir 19b is built into the inner surface of the atomizer. The presence of weir 1012 provides a tortuous, zig-zag passageway for the liquid and such a passageway has been found to materially reduce slugging, especially where the atomizer is several inches or more in diameter.

FIGS. 2-3 show the atomizing apparatus just described incorporated into a complete coating arrangement in ac cordance with the invention. Atomizer 10 is supported by means of post 15 in a fixed position to one side of a conveyor track which is normally grounded. A plurality of supports 36 carry the articles 38 to be coated, shown as automobile garnish mouldings, past the atomizer.

The liquid coating materials to be used are in

individual containers

40a, 40b and 49c. Paint from container 49a is drawn by a gear pump 41a and fed to apropriate nozzle 30 through feed line 31a. The how of paint to line 31a is controlled by a compressed air operated on-otf valve 42a. Pump 41a is driven by an electric motor 43a. Compressed air for operation of paint valve 42a is supplied from a main compressed air line 44 through an on-off solenoid operated air valve 45a. In a similar manner, paint from containers 46b and 400 is fed to other nozzles.

In addition to the liquid supply arrangements just described, cleaning solvent is also fed to one of the nozzles 30. A pressurized container 46 contains a quantity of solvent, such as toluol, which is maintained under pressure by compressed air from main air line 44. A mixture of compressed air and solvent is fed to one of the nozzles 30 through a cleaning line 47 which is controlled by solenoid operated on-olf valve 48. Compressed air for operating air cylinder 19 is also supplied from air line 44 upon the opening of solenoid operated on-ofi valve 50.

A common, interconnected electrical control arrangement operates the several delivery control means (pumps 41 and valves 42, 4-5 and 43). Such an arrangement permits selective operation of any one of the delivery control means to deliver liquid from a desired source to the atomizer while preventing delivery from all the other sources. This arrangement, referred to herein as a common operator for the delivery controlling means, includes a single solenoid 51:: which controls the operation of both pump motor 430 and air valve 45a, similar solenoids 51b and c which control motors 43b and c and valves 4% and c, and a similar solenoid 52 which controls the operation of air valve 48 in cleaning line 4-7. In addition, a solenoid 53 controls the operation. of the shroud moving means (cylinder 19 and valve and solenoid 53 is preferably interconnected with the common operator for the delivery controlling means.

Solenoids

51, 52 and 53 are interconnected through a control panel 55. Panel 55 also contains power-actuated means for operating the common operator of the liquid delivery controlling means through a predetermined cycle of successive termination of delivery of one paint to the atomizer, delivery of solvent to the atomizer for a predetermined period of time to clean the atomizer, and then initiation of delivery of another paint. Preferably the cycle also includes movement of the shroud into spray intercepting relation with the atomizer before the cleaning portion of the cycle and movement of the shroud back out of spray intercepting relation after cleaning the atomizer.

The elements of one form or power-actuated means for the common operator and the relation therebetween are shown in detail in FIG. 4. Those elements physically within control panel 55 are shown in FIG. 4 within dotted line 55, while the solenoids and the motors and valves operated thereby are shown outside the dotted line. The power-actuated means contained Within panel 55 includes a number of push buttons PBl through P134, relays R1 through R7, and time delay relays TDl through TD3. Each relay and time delay relay includes one or more sets of contacts RC and TDC respectively. All these elements operate from a 110 volt alternating current line and are connected into the line as shown in FIG. 4.

Relay R1 is connected across the line in series with the normally open push button FBI and the normally closed contacts TDC3 of time delay relay TD3. Relay R1 has a pair of normally closed contacts R01 which open to prevent energization of the paint-control relays R4, R5, and R6 and of relay R7. Relay R1 also has three pairs of normally open contacts RC1, one in parallel with push button PET, a second pair in series across the line with time delay relay TDl, and a third pair in series across the line with time delay relay TDZ and a pair of normally open contacts RC2 of relay R2 Tiime delay relay TDl has a single pair of normally open contacts TDCl in series across the line with relay R2. and with a pair of normally closed contacts RC7 of relay R7.

Relay R2 has, in addition to the aforesaid contacts RC2 in series with time delay relay TDZ, three other pairs of normally open contacts RC2, one in parallel with the aforesaid contacts TDCl, a second pair controlling energization of interceptor-actuating solenoid 53, a third pair in series across the line with solvent-controlling solenoid '52 and the normally open contacts RC3 of relay R3.

Time delay relay TDZ has a single pair of normally open contacts TDC 2 controlling relay R3 which, in turn, has a single pair of normally open contacts RC3 that control time delay relay TD3. The latter has the normally closed contact TDC 3 above mentioned in the circuit of relay R1.

Delivery of the several coating materials is selectively controlled by relays R4, R5, and R6. Circuits including those relays and corresponding push-button switches PB2, PB3, and P34 are connected across the line in parallel with each other and in series with a common pair of normally closed contacts RC7 of relay R7. Each of the relays R4, R5, and R6 has three pairs of normally open contacts, one pair in series across the line with the corresponding delivery controlling solenoid 51, and a second pair in a holding circuit bridging both the corresponding push button and the associated relay contacts RC7. The third pairs of normally open contacts of the relays R4, R5, and R6 are connected in parallel with each other across the line in series with the relay R7.

In describing the operation of the apparatus shown in FIGS. 1-4, it is assumed that liquid coating material A is in container 43a, material B in container diib, and material C in container 400. To begin the painting operation with, for example, material A push button PB2 is pushed. This energizes relay R4 whose several contacts RC4 close to actuate solenoid 51a and initiate delivery of coating material A, to complete the holding circuit around PB2, and to energize relay R7.

The resultant opening of the contacts RC7 associated with the push buttons PB2, PB3, and PB4 is without effeet on relay R4, since those contacts are bridged by the holding circuit completed when relay R4 was energized. Opening of said contacts RC7 does, however, prevent energization of either of the other delivery-com trolling relays R5 and R6, and thus prevents the system from being inadvertently operated to deliver two different coating materials, simultaneously. Delivery of coating material A continues until its termination is desired.

To initiate the predetermined cycle of terminating delivery or" material A and cleaning the atomizer, push button PBl is pressed. The resultant energizaticn of relay R1 opens the normally closed contacts RC1, thus de-energizing relay R4, and closes all normally open contacts RC1 one pair of which is in circuit with relay R2 which operates to cause supply of current to time delay relay TD as above described. De-energization of relay Rd opens the circuit including solenoid 51a to terminate the delivery or" material A and also opens both the holding circuit around PB2 and the circuit of relay R7. De-energiz'ation of relay R7 closes the contacts RC7 in circuit with relay R2, so that when relay TD} operates after expiration of the time delay for which it has been set the resultant closing of contacts TDCl will complete a circuit through relay R2.

Energization of relay R2. operates, as above described, first to energize solenoid 53 and cause advance of the interceptor 16 to the dotted-line position of FIG. 1, and then, after the delay provided by relay TD2, to close relay R3, actuate solenoid 52, and initiate delivery of the cleaning mixture of air and solvent through cleaning line 47 and appropriate nozzle 3% If desired, line 57 can also be connected to feed cleaning fluid to a second nozzle 56 lying outside atomizer 1t} and mounted on interceptor 16 to direct a spray of cleaning fluid onto the outside edge of atomizer it? as shown in FIG. 1. The time delay provided by relay TDl is sufiicient to permit all material A in the atomizer to be discharged therefrom before the interceptor advances, while the delay provided by relay T132 insures that the interceptor will be in advanced position before the cleaning solvent is delivered to the atomizer.

The operation of relay R3 which initiated solvent delivery also caused current to be supplied totime delay relay T133 which operates, after the delay for which it is set, to open the contacts TDC3 in circuit with relay R1, and the resultant de-energization of that relay, by opening all normally open contacts RC1, causes the deenergization of relays TD} and TD2, followed by the de-energization of relays R3 and T333. The opening of relay R3 de-energizes solenoid 52 to terminate the delivery of solvent; but, as relay R2 remains energized by virtue of the holding circuit around contacts TDCl, solenoid 5'3 remains energized to hold the shroud 16 in advanced, or operative, position where it will collect all solvent discharged from the atomizer after the valve 48 in the solvent delivery line was closed.

The shroud 16 is of conducting material and, because of its connection to the housing of motor 13, has the same potential as the atomizer ll). In its retracted position it lies well back of the front edge of the atomizer where it does not interfere with the existence of the desired field strength at the atomizer edge. When the shroud is in advanced position, however, it electrically shields the atomizer and thus prevents the existence at and adjacent the atomizer of any field which would cause discharged material to be attracted to the work. Thus, solvent or other material discharged from the atomizer ,1 when the shroud is advanced will all be collected in the shroud. The shroud may be provided with a drain line 57.

When it is desired to re-initiate the delivery of a coating material to the atomizer, the'appropriate push button PBZ, P133, or P34 is pushed. Pushing of either of buttons PB3 or PBd causes the same operations as follow pushing of button PR2 except that material B or C, rather than A, would be delivered to the atomizer. The energization of relay R7 which follows closing of any of the push button switches PBZ, P332, or P134, by opening the contacts RG7 in circuit with relay R2, causes opening of that relay and consequent de-energization of solenoid 53 and retraction of the shroud 16, thus restoring the electrostatic field to the discharge edge of the atomizer 19.

Other forms of delivery-controlling means, common operators, and power-actuated means for operating the operators through a predetermined cycle in accordance with my invention will be apparent to those skilled in the art. By appropriate selection of elements for the poweractuated means the pushing of a single button can, for example, initiate a complete predetermined cycle of successively timed termination of delivery of coating material, movement of the shroud into spray-intercepting position, delivery of solvent to the spraying device for a predetermined time, retraction of the shroud, and initiation of delivery of a preselected different coating material to the atomizer or spraying means. Another form of the invention adapted for use with a plurality of air spray guns is shown in FIGS. 5-7.

In the coating apparatus in FIGS. 5 and 6 the spraying means comprises a plurality of compressed air spray guns 66 arranged like the spokes of a wheel around a central hub 61. A separate gun 61) is used for each color or type of liquid coating material to be sprayed. Eight guns are shown in FIG. 5 however, the control mechanism will be described as it relates to only three

guns

66a, 60b and 600, it being understood that the invention is not dependent upon the number of guns or coating materials which are used.

Hub 61 is aflixed to the upper end of a shaft 62 which is made of insulating material. The lower end of shaft 62 is mounted for rotation in a bearing 63. Guns 60, hub 61 and shaft 62 are enclosed within a cylindrical housing 64-, preferably of insulating material. The upper end of housing 64 contains an opening 64a through an arc of about 45, which opening faces directly toward a conveyor line 65 designed to carry a plurality of articles 68 past the spraying means.

Articles 68 are grounded through conveyor 65. The guns 65} are maintained at high voltage in the order of 100 kv. through hub 61 which is connected through a spring 72 to a high voltage source 73. Two parallel electrode wires 74 arranged on opposite sides of the opening 6411 are also maintained at about 100 kv. by direct connection to the high voltage source 7 3.

Each gun 60 is supplied by an individual paint line 75 and compressed air line 76. These lines are flexible and of suilicient length to permit shaft 62 to rotate approximately one revolution in either direction without fouling or breaking the lines. The flow of paint and compressed air to lines 75 and 76 for each gun are simultaneously controlled by a pair of on-off valves 77 and 73 respectively monuted adjacent bearing 63. Each pair of valves 77 and 78 are simultaneously controlled by a single paint and air solenoid 79.

The position of guns 69 is changed by rotation of shaft 62 about its center. Power for rotating shaft 62 is supplied by a DC. motor 80 which is connected to rotate shaft 62 through suitable gearing within a gear box 81. Shaft 62 can thus be rotated in either direction depending upon the direction of rotation of motor 80. The operation of motor 80 is controlled by a plurality of positioning solenoids 82 arranged about shaft 62, a motor switch 33 mounted eccentrically on the side of 8 shaft 62 and a motor-reversing switch 84 mounted adjacent to shaft 62. Each of the solenoids 82 has a springretracted core which, upon energization of the solenoid, is projected into the path of switch 83.

A common, interconnected electrical control arrangement, referred to herein as the common operator, opcrates the delivery contol means (paint valves 77, compressed air valves 78, and motor so as to permit selective operation of any one pair of paint and air valves serving a single preselected spray gun (for example, valves 77a and 78a serving gun 60a) While preventing delivery of paint and air to any other gun, and also to permit positioning the preselected gun (for example, gun 60a) in coating position in opening 64a. The common operator includes solenoid 79a which controls the operation of both valves 77a and 78a, other similar paint and air solenoids 79 controlling other pairs of paint and air valves, solenoid 82a and other similar solenoids 82 controlling the position of the guns 60, and switches 83 and $4 controlling the operation of rotation of motor 80.

Solenoids '79 and S2 and switches 83 and 84 are interconnected through a control panel 85, which contains power-actuated means for operating the common operator of the delivery control means through a predetermined cycle which includes termination of delivery of paint and air to one spray gun, movement of another preselected spray gun into coating position, and then initiation of delivery of paint and air to such other spray gun. The elements of one form of power driven means are shown in detail in FIG. 7. Those elements physically within control panel 85 are shown in FIG. 7 within dotted line 85, while the solenoids, motor and switches operated by the power driven means are shown outside the dotted line.

The power-actuated means within panel 85 includes a number of push buttons PB11 through P1313, relays R11 through R18, a DC. power supply 88 for operating motor 89, and a variable low-braking resistance 89. Each relay includes a plurality of contacts RC, some of which are normally open and others normally closed. All of the foregoing elements operate from a volt alternating current line and are connected into the line as shown in FIG. 7.

In describing the operation of the apparatus shown in FIGS. 57, the liquid coating material containers and main supply line for compressed air are not shown but it is assumed that gun 60a is connected to a pressurized source of liquid coating material A, gun 60b to material B, and gun 600 to material C. Delivery of coating material to the several spray guns 60 is controlled by a series of relays R11, R12, and R13 adapted respectively for initial energization by push buttons P1311, P1312, and P1313. Each of such relays has three pairs of normally open contacts RG11, RG12, and RG13. The first such pairs of contacts of each relay is connected in a holding circuit bridging the relay-controlling contacts of the associated push button switch. The second pairs of contacts of the relays are in circuit respectively with the several positioning solenoids 82a, 82b, and 820, while the third pairs of contacts are respectively in circuit with the solenoids 79 which control the delivery of coating material and compressed air to the several spray guns 60.

Associated respectively with the several relays R11, R12, and R13 are other relays R14, R15, and R16. The push button PIE-11 has a second set of normally open contacts in circuit with relay R14; the push button PB12, a second pair of normally open contacts in circuit with relay R15; and the push button P1313, a second pair of normally open contacts in circuit with relay R16. The relays R14, R15, and R16 have normally open pairs of cont-acts RG14, RG15, and RG16 connected in parallel with each other and in series across the line with a motorcontrolling relay R17. Each of the relays R14, R15, and R16 also has two pairs of normally closed contacts RG14, RG15, or RG16. The circuit of relay R11 includ s nor- 9 mally closed, series COIIIIECtCd contacts RG and RG16 of relays R15 and R16; the circuit of relay R12 contains normally closed, series connected contacts RG14 and RG16 of relays R14 and R15; and the circuit of relay R13 contains normally closed series connected contacts RG14 and RG15 of relays R14 and R15.

The relay R17 is a latching relay provided with a latch which, when the relay is energized, engages the armature of the relay to hold it in advanced position, even after de-energization of the relay, until an associated latch-release coil is energized.

The latch release coil of relay R17 is controlled by the switch 83 to be energized when such switch strikes the projected core of any of the solenoids 82. Since the push buttons PB11, R1312, and PB13 are biased toward open position and since the holding circuit associated with each of such push buttons does not bridge the contacts controlling the respectively associated relays R14, R15, and R16, the relay R17 is energized only momentarily; and after it is de-energized its armature is held in advanced position only by the latch. As a result, when the switch 83 strikes the projected core of the solenoid 82 to release the latch, all contacts of the relay 17 return to their normal conditions. Such contacts control operation of the motor 80 in a manner to be hereinafter described.

In order to prevent fouling of the paint and air hoses 75 and 76, rotation of the shaft 62. is limited to somewhat less than 360. It is therefore necessary to provide for rotation of the shaft 62 in both directions. The direction of rotation of the shaft and of the motor 81 is controlled by a relay R18 which has a set of contacts RG1$ constituting, in effect, a double pole, double throw, motorreversing switch. The relay 13 is of a well-known type embodying two windings and so constructed that when the armature is moved to one controlling condition by energization of one Winding it will remain in that position, even after de-energization of such winding, until the other winding is energized. The relay R18 is controlled by a reversing switch 34 mounted adjacent shaft 62 and operated by a pin (not shown) supported from such shaft in an eccentric position. When, in the course of rotation of shaft 62, the pin engages the operating member of switch 84, such switch operates to reverse the relay R18 and its associated contacts RG18, thereby reversing the direction of motor rotation. The switch 84 and its operating pin are so disposed that reversal of the switch 84 occurs while the shaft 69 is rotating to bring a new gun 611 into operative position.

The circuit of the motor fill is supplied with current from a DC. power supply 83. The circuit of the motor 8% includes two sets of normally open contacts RG17 which must be closed by operation of the relay R17 in order for motor 81 to operate. The relay R17 also in cludes two sets of normally closed contacts RG17 connected in series with a braking resistance 8% across the armature of motor 8%. So long as relay R17 is in condition to cause supply of current to the motor 859, such motor rotates in the direction determined by the condition of relay R18 until the switch 83 engages the projected core of one of the solenoids 82, whereupon the latch of relay R17 is released and such relay returns to normal position to interrupt the supply of current to the motor 8% and throw the braking resistance 89 into circuit with the motor-armature, thus retarding coasting of the motor and promptly bringing the shaft 62 to rest.

in order to insure against delivery of coating material to any of the guns 6% while the guns are changing position, the circuits of the delivery controlling solenoids 79 are connected to the power supply 88 through an additional set of normally closed contacts RG17 of relay R17.

To explain operation of the system of FIGS. 5, 6, and 7, it will be assumed that the system is operating in the steady-state condition brought about by depression of push-button P1313. In this condition, gun 61% is in operative position as shown in FIG. 5 and relay 13 is being held in a state of energization through the holding circuit bridging the switch P813. Since the movement of gun 6130 into operative position actuated switch 83 to release the armature of relay R17, the motor fill is at rest and the contacts RG17 of relay R17 which control connection of the power supply to the circuits of solenoids 79 are closed. Since relay R13 is energized its pair of contacts RG13 in circuit respectively with

solenoids

82c and 790 are closed and such solenoids are energized. As a result of the energization of solenoid 790, the valves 77c and 78s are open and air and coating material C are being supplied to the operatively positioned gun 60c to be discharged therefrom as a spray which is deposited on the work by the electrostatic field existing between the high voltage electrodes 74 and such work.

If it is desired to terminate the supply of coating material C and initiate the supply of, for example, coating material A, the switch PB11 is momentarily closed to energize relays R11 and R14. Energization of relay R14 opens the normally closed contacts RG14 in the circuit of relay R13, thus tie-energizing the latter relay and opening its normally closed contacts RG13 to break the holding circuit around switch P1313 and to de-energize solenoids 79c and 820, thus terminating the supply of coating material C to the gun 66c and permitting the core of solenoid 820 to retract. Energization of relay R14 also closes the contacts RG14 in circuit with the relay R17, thus initiating operation of the motor 80 and rotation of the gunpositioning shaft 62. Even though the energization of relay R14 is only momentary, so that the relay R17 is only momentarily energized, the latch of the latter relay maintains the contacts RG17 in the motor circuit closed, and the motor continues to operate. Energization of the relay R11, eifected jointly with that of relay'Rl l by closing of the switch P311, completes the holding circuit across the switch P1311 to maintain relay R11 energized and also closes the contacts RG11 in circuit with solenoid 82a to advance the core of such solenoid. The contacts RG11 in circuit with solenoid 7% also close at this time, but this is without eilect since the contacts RG17 in series with them were simultaneously opened by energization of relay R17.

if it is assumed that shaft 62 can rotate far enough to bring gun 60d into operative position without tripping switch 84, rotation of the motor 80 will continue until gun 69a approaches operative position at opening 64a and the operating member of switch 83 engages the projecting core of solenoid 82a. When this happens, the armature of relay R17 is released to open the motor circuit and close the motor-braking circuit, with the result that gun otla comes to rest in operative position. With the release of relay R17, its contacts RG17 in circuit with solenoid 79 close to energize solenoid 79a through the associated and previously closed contacts RG11. With energization of solenoid 7%, the valves 77a and 78a are opened and coating material A is sprayed from the operatively positioned gun 611a.

If coating with material B is subsequently desired, push button P312 is pushed to energize relay R12 and momentarily energize relay R15. The normally closed contacts RG15 of relay R15 in series with relay R11 open momentarily to de-energize gun 60a. Latching relay R17 is again latched through the momentary closing of the normally open contact RG15 of relay R15 in series with relay R17. The normally closed relay contacts RG17 in series with the line are latched open to de-energize all paint and air solenoids during the re-positioning of the guns.

At the same time the normally closed relay-contacts RG17 in series with resistance 89 are opened and the normally open contacts RG17 between DC. power supply 38 and motor so are closed to supply power to the armature of motor 89. The normally open contacts RG12 in series with positioning solenoid 8212 close to energize the 11 t solenoid 8212. Motor 80 rotates shaft 62 until spray gu 60b is operatively positioned at opening 64a. Thereupon the motor 80 is de-energized by contact between switch 83 and the pin of positioning solenoid 8212. This in turn causes de-latching of relay R17 so that normally closed contacts RG17 in series with solenoids 79 will close and coating material B will be fed to and atomized from gun 60b.

If, in the operation of bringing a selected gun 65) to operative position, the switch 84 is tripped, the relay R18 and its contacts RG18 are reversed to reverse the motor 30 and the shaft 62, and such shaft will then continue to rotate in the opposite direction until the selected gun reaches operative position.

The two systems above described as examples of my invention have in common a multi-color spraying means which can be selectively controlled from a remote point by a power-actuated means which automatically terminates delivery of one liquid to the spraying means and then, after a time delay, initiates delivery of another liquid. In the system of FIGS. 1 to 4, which employs a single atmoizer that must be washed with solvent before a color change can be completed, the second liquid is the cleaning solvent and the time delay is utilized to position the spray-intercepting shroud, which pervents the discharged solvent form being deposited on the work. In the other system, where the spraying means embodies a plurality of atomizers each of the which discharges a single liquid, the time delay is utilized to substitute atomizers in spraying position. Both systems, as shown and described, are electrostatic, but some features of the invention can be employed in non-electrostatic systems.

I claim:

1. In combination with spraying means for forming a spray of liquid coating material particles, a plurality of sources of liquid coating material, means associated with each of said sources for controlling delivery of coating material therefrom to said spraying means, a source of solvent, means for controlling the delivery of solvent therefrom to the spraying means, a common operator for the several delivery-controlling means, said operator being selectively operable to cause delivery to the spraying means from any selected one of said sources while preventing delivery from the other sources to the spraying means, and power-actuated means energizable during the delivery of coating material from the selected coatingmaterial source to operate said operator through a predetermined cycle automatically to effect successive termination of delivery of coating material to the spraying means from such selected coating-material source, delivery of solvent for a predetermined time from the solvent source to the spraying means, and de-energization of said poweractuated means.

2. The combination of claim 1 with the addition of a spray interceptor for collecting liquid sprayed from the spraying means, said spraying means and spray interceptor being relatively movable into and out or" a spray-intercepting relation in which spray from the spraying means is collected by the interceptor, and means controlled with said operator for disposing the spraying means and sprayinterceptor in said spray-intercepting relation during delivery of solvent to the spraying means.

3. The combination of claim 1 further characterized in that there are at least three coating-material sources and that said operator, after termination of solvent-delivery and before de-energization of said power-actuated means, initiates the delivery to the spraying means of coating material from a different coating-material source, the combination including means for pre-seleeting such different source.

4. In combination with spraying means for forming a spray of liquid coating material particles, a plurality of sources of liquid for delivery to the spraying means, means associated with each of said sources for controlling the delivery of liquid therefrom to said spraying means, a common operator for the several liquid delivery-controlling means, said operator being selectively operable to cause delivery to the spraying means from any selected one of said sources while preventing delivery from the other sources to the spraying means, power-actuated means energizable during the delivery of coating material from the selected liquid source to operate said operator through a predetermined cycle automatically to effect successive termination of delivery of liquid to the spraying means from the selected coating material source, then after a predetermined time delay initiation of delivery of liquid from a different liquid source to the spraying means, and then de-energizing said power-actuated means, and means operable prior to the expiration of such predetermined time delay for pre-selecting said different liquid source.

5. In electrostatic spray coating apparatus, a conveyor for moving articles to be coated successively through a coating zone, spraying means adjacent said coating zone for creating a spray of electrically charged coating material particles for electrostatic deposition on the articles as they pass through the coating zone, said spraying means including a highly charged electrode and a plurality of liquid discharge nozzles, a plurality of sources of liquid, means associated with each of said sources for controlling the delivery of liquid therefrom to a corresponding one of said nozzles, a common operator for the several liquid delivery-controlling means, said operator being selectively operable to cause delivery to the spraying means from any selected one of said sources while preventing delivery from the other sources to the spraying means, power-actuated means energizable during delivery of liquid from the selected liquid source to operate said operator through a predetermined cycle automatically to effect successive termination of delivery of liquid to the spraying means from the selected liquid source, and then after a predetermined time delay initiation of delivery of liquid from a different liquid source to the spraying means, and means operable before termination of said predetermined time delay for preselecting said diiicrent liquid source.

6. Apparatus for use in a spray coating system comprising an atomizer, a shroud adapted to surround said atomizer for intercepting particles of liquid projected from said atomizer while said shroud surrounds said atomizer, means for moving said shroud in and out of its postion surrounding said atomizer, a first line for supplying liquid coating material A to said atomizer, a second line for supplying a cleaning fluid to said atomizer, a third line for supplying liquid coating material B to said atomizer, said three lines running to said atomizer to supply liquid thereto for atomization as a spray of liquid particles, a first valve in said first line, a second valve in said second line, a third valve in said third line, and a common control means operatively associated with the three valves and the shroud-moving means and operative to place the shroud in atomizer-surrounding position while said first and third valves are closed and to both open and later close said second valve while the shroud remains in such atomizer-surrounding position.

7. In electrostatic spray coating apparatus, a conveyor for moving articles to be coated through a coating zone, spraying means adjacent said coating zone for creating a spray of electrically charged liquid particles for electrostatic deposition on the articles, said spraying means including a plurality of spray guns and a highly charged electrode, a plurality of sources of liquid coating material, means associated with each of said sources for controlling the delivery of liquid material therefrom to one of said spray guns, means for moving said spraying means to locate different ones of said spray guns in coating position in said coating zone, a common operator for the several dclivery controlling means and said spray gun moving means, said operator being selectively operable to cause delivery of liquid material to one of said spray guns from one of said sources while preventig delivery from the other sources to the other spray guns, power-actuated means energizable to operate said operator through a predetermined cycle automatically to effect successive termination of delivery of liquid material to any of the spray guns from any of the liquid material sources, operation of said spray gun moving means to position a different spray gun in coating position, and then initiation of delivery of liquid material to said difierent spray gun, and means operable before operation of the spray gun moving means for preselecting the different spray gun to be positioned in coating position.

References fitted in the file of this patent UNITED STATES PATENTS Fleming Sept. 23, 1941 Miller Mar. 5, 1-957 Faber June 11, 1957 Sherratt et a1. June 11, 1957 MacArthur et a1. Oct. 22, 1957 Sherman Mar. 18, 1958 FOREIGN PATENTS Great Britain Apr. 16, 1903

Claims

1. IN COMBINATION WITH SPRAYING MEANS FOR FORMING A SPRAY OF LIQUID COATING MATERIAL PARTICLES, A PLURALITY OF SOURCES OF LIQUID COATING MATERIAL, MEANS ASSOCIATED WITH EACH OF SAID SOURCES FOR CONTROLLING DELIVERY OF COATING MATERIAL THEREFROM TO SAID SPRAYING MEANS, A SOURCE OF SOLVENT, MEANS FOR CONTROLLING THE DELIVERY OF SOLVENT THEREFROM TO THE SPRAYING MEANS, A COMMON OPERATOR FOR THE SEVERAL DELIVERY-CONTROLLING MEANS, SAID OPERATOR BEING SELECTIVELY OPERABLE TO CAUSE DELIVERY TO THE SPRAYING MEANS FROM ANY SELECTED ONE OF SAID SOURCES WHILE PREVENTING DELIVERY FROM THE OTHER SOURCES TO THE SPRAYING MEANS, AND POWER-ACTUATED MEANS ENERGIZABLE DURING THE DELIVERY OF COATING MATERIAL FROM THE SELECTED COATINGMATERIAL SOURCE TO OPERATE SAID OPERATOR THROUGH A PREDETERMINED CYCLE AUTOMATICALLY TO EFFECT SUCCESSIVE TERMINATION OF DELIVERY OF COATING MATERIAL TO THE SPRAYING MEANS FROM SUCH SELECTED COATING-MATERIAL SOURCE, DELIVERY OF SOLVENT FOR A PERDETERMINED TIME FROM THE SOLVENT SOURCE TO THE SPRAYING MEANS, AND DE-ENERGIZATION OF SAID POWERACTUATED MEANS.