DEFLECTION CONTROL OF LIQUID STREAM DURING DISPENSING

Abstract: A method and apparatus for deflecting a liquid stream (26) during dispensing with a plurality of independently actuatable flows. A gun (20) has a nozzle (21) with an orifice (24) for dispensing a liquid stream (26). Blowout ports (33a-33f) surround the orifice (24) and are aimed at the flow path of the liquid stream (26), just beyond the end of the gun (20). The blowout ports (33a-33f) are connected via conduits (35a-35f) to a pressurized source (37).A timer (41) actuates solenoid valves (48, 38, 39) to control liquid dispensing through the orifice (24) and the flows from the blowout ports (33a-33f). By coordinating liquid dispensing with the directional flows, the liquid stream (26) may be deflected to achieve a desired dot or spray distribution pattern on a substrate (27) or uniform spray coating of the inside surface of a can.

Description: DEFLECTION CONTROL OF LIQUID STREAM DURING DISPENSING Field of the Invention This invention relates to liquid dispensing. More particularly, this invention relates to a method and apparatus for controlled deflection of a liquid stream during dispensing to achieve a complex pattern on a substrate or uniform coating of an irregular surface. One preferred embodiment of the invention relates to uniform coating of the entire interior surface of a metal can with a single nozzle. Background of the Invention In the past, a number of methods have been used to achieve a desired spray pattern for a liquid or molten product dispensed from a nozzle opening. Binary liquid spray (air spray) and airless spray are two commonly used methods for discharging a coating agent from a nozzle opening to achieve a spray pattern on a substrate. Differences among spray patterns formed by these and other methods generally relate to the varied ways in which compressed gas is used to generate the spray. Spraying of compressed air on both sides of a liquid stream may be used to provide another type of spray pattern, or to alter a known spray pattern. With any type of nozzle opening, spraying of air sideways into the liquid stream generally creates a broad deformation of the spray pattern. One method referred to as the swirl spray method creates descending spirals forming a whirlpool by discharging liquid downward through a nozzle opening and spraying a heated, compressed gas in the vicinity of the external periphery of the discharged stream from multiple openings located in regular intervals around the periphery of the nozzle. With one or more of these methods, it is possible to obtain a uniform spray pattern from a single nozzle. However, to achieve multiple or complex patterns, multiple spray guns and nozzles must be used. As a result of the additional equipment, and the increase in workers and maintenance necessitated by the additional equipment, the cost of achieving multiple or complex spray patterns increases signifi¬ cantly. In addition to higher cost, it is sometimes physically impossible to conduct certain spraying operations within the confines of a given narrow space. Another concern arises when considering continuous spray operations for coating a surface, where a reflection flow layer may form on the surface of the coated object and collide with subsequent spray, causing additional collisions, dispersion of spray and inefficient coverage of parts. This gener¬ ally occurs when the part to be coated is concave, such as the corner of a can. In addition to the inefficiency of this spraying process due to reflec¬ tion of this "air cushion", the collision and dis¬ persion of the reflected spray pollutes the spraying environment and becomes a source of contamination. It is an object of the invention to provide a method and apparatus for dispensing liquid in multiple and/or complex patterns in an economically feasible manner, within a minimum space, and in a manner which minimizes deflection and/or turbulence of atomized particles during dispensing. Summary of the Invention To these ends, this invention contemplates a liquid dispensing apparatus and method that utilizes a nozzle with a central liquid dispensing orifice and a plurality of blowout ports surrounding the orifice, with each blowout port being independently actuatable to direct a flow into contact with the dispensed liquid stream. By controlling the sequence and duration of the independently actuatable flows during liquid dispensing, a desired distribution pattern may be produced on a substrate. The invention applies to a dispensed liquid stream in the form of relatively large drops or an atomized spray. According to one embodiment of the inven¬ tion, six blowout ports are spaced equidistant around the central liquid dispensing orifice in the nozzle. The blowout ports are directed inwardly toward an axis aligned along the central liquid dispensing orifice. By sequentially actuating each of the blowout ports around the dispensing orifice during liquid dis¬ pensing, the dispensed stream is sequentially deflected in six different directions to form a generally circular deflection pattern on a substrate. Alternately, two or more of the blowout ports could be actuated simultaneously to create further variations in deflection. One particular advantage provided by this inventive method and apparatus relates to coating of the entire interior surface of a metal can with a single nozzle. Due to increased versatility and control of the direction of the liquid stream that is dispensed from the orifice of the nozzle, the inside surface of a can may be uniformly coated at a reduced cost, and with minimum of undesired air cushioning. Air cushioning is reduced by sequentially actuating the blowout ports located around the dis¬ pensing opening to supply radially inwardly directed flows from directions which rotate circumferentially around the liquid stream. Rotational deflection of the liquid stream, particularly a liquid stream that is an atomized spray, prevents undesired reflection and dispersion of the stream. As a result, a problem of prior coating methods, that of uneven coating in the corners of the can, is eliminated. According to a preferred embodiment of the invention, this liquid dispensing apparatus includes a liquid dispensing gun with a timer actuated solenoid valve that controls flow of the dispensing liquid from an inner chamber and out of an orifice in a nozzle connected to the end of the gun. The nozzle also includes six radially directed bores which communicate with six respective blowout ports, each blowout port aimed to intersect the liquid stream from the nozzle orifice at a slight distance away from the tip of the gun. Six conduits connect to the radial bores and supply compressed gas to the blowout ports. The flow of pressurized gas through the conduits, the bores and out of the blowout ports is controlled by electrically actuated solenoid valves connected to the conduits. The solenoid valves are actuated by the timer which also controls the liquid flow valve of the gun. The timer is preferably a pulse controller capable of supplying current pulses ranging from about 4 milli¬ seconds to 50 milliseconds. By controlling the timing seguence and duration of the current pulses from the timer to the liquid dispensing valve and the valves which control the flow of blowout gas from the blowout ports, the dispensed liquid stream may be deflected in a desired manner to achieve a complex distribution pattern on a substrate. The central dispensing orifice may be a single orifice at the end of a liquid passage that extends to a liquid reservoir. The nozzle and gun may also be equipped for an airless spray nozzle. Alter¬ nately, the nozzle may also include a concentric atomizing port located intermediately between the nozzle opening and the blowout ports for binary liquid spray dispensing. These latter two embodiments enable controlled deflection of a stream of particles that have already been atomized. The gun and nozzle may also be adaptable for extruding a liquid. According to additional embodiments of the invention, the nozzle opening may include two or more orifices for liquid dispensing of two or more types of liquid. The multiple orifices may be arranged side- by-side, or concentrically. One of the orifices may be used to mix aerosol into another dispensing liquid. Additionally, aerosol may be used as the deflecting agent through the blowout ports for deflecting the mixture. Because the liquid stream may be deflected in a varied number of directions, this invention promotes increased spraying or dispensing versatility from a single nozzle within a minimum amount of space. This invention also reduces the cost of spraying multiple or complex patterns because a single nozzle can be used to archieve a wide range of distribution patterns. If desired, additional blowout ports may be provided to further increase versatility in achieving complex deflection patterns. These and other features of the invention will be more readily understood in view of the following detailed description and the drawings. Brief Description of the Drawings Fig. 1 is a cross-sectional schematic view of a liquid dispensing apparatus in accordance with a first preferred embodiment of the invention. Fig. 2 is a view taken along lines 2-2 of Fig. 1. Fig. 3 shows a dot pattern formed on a substrate by the apparatus depicted in Fig. 1. Fig. 4 is an enlarged, cross-sectional schematic showing the liquid dispensing apparatus of Fig. 1 equipped with an airless spray nozzle in accordance with a second preferred embodiment of the invention. Fig. 5 shows a spray pattern formed on a substrate by the apparatus depicted in Fig. 4. Fig. 6 is a cross-sectional schematic view similar to the liquid dispensing apparatus shown in Fig. 1, but modified to incorporate a nozzle equipped for binary liquid spray dispensing in accordance with a third preferred embodiment of the invention. Fig. 7A is a timing diagram for operation of the apparatus shown in Fig. 1. The timing diagram depicts current pulses that control liquid dispensing from the nozzle and gas flows from the blow out ports. Fig. 7B shows an alternate timing diagram for controlling liquid dispensing and gas flows from the blow out ports. Figs. 8A and 8B depict spray patterns formed by the apparatus shown in Fig. 1 when operated according to the timing diagrams of Figs. 7A and 7B, respectively. Fig. 9 shows a timing diagram for control¬ ling liquid dispensing and the gas flows from blowout ports for the binary liquid gas dispenser shown in Fig. 6. Fig. 10A depicts a spray pattern formed by the apparatus shown in Fig. 6 when operated according to the timing diagram of Fig. 9. Fig. 10B depicts a spray pattern formed by the apparatus shown in Fig. 6, but with the timing diagra of Fig. 9 slightly varied to include a delay before the initial gas flow from the blowout ports. Figs. 11A and 11B depict timing diagrams for operating the liquid dispensing apparatus shown in Fig. 6. Fig. 12A depicts a spray pattern that may be formed with the liquid dispensing apparatus shown in Fig. 6, when operated according to the timing diagram of either Fig. 11A or Fig. 11B. Fig. 12B depicts an alternate spray pattern that may be formed with the device of Fig. 6 and the timing diagram of either Fig. 11A or Fig. 11B, if a time delay is included between initial liquid dis¬ pensing and the first gas flow. Fig. 12C shows dot patterns that may be formed with the device of Fig. 1 if liquid dispensing occurs intermittently. Fig. 12D is similar to Fig. 12C, but in¬ cludes a time delay between initial liquid dispensing and the first gas flow. Figs. 13A, 13B, 13C and 13D depict addition¬ al, complex spray patterns that may be formed by the liquid dispensing apparatus of Fig. 6 if equipped with a nozzle having additional blowout ports and, with respect to Fig. 13B, Fig. 13C and Fig. 13D, additional blowout ports and either varied angles of directional gas flow or variation in volume of gas flows. Fig. 14A is a cross-sectional view of an airless spray nozzle for multiple liquid, mixed sprays. Fig. 14B is a bottom view, looking upwardly, of the airless spray nozzle stream in Fig. 14A. Fig. 14C is a bottom view, similar to Fig. 14B, of a binary liquid spray nozzle for multiple liquid, mixed sprays. Fig. 15 is a cross-sectional view of a liquid dispensing apparatus which mixes aerosol with another dispensing liquid and deflects the mixture with aerosol, according to a fourth preferred embodi¬ ment of the invention. Fig. 16A and 16B show dot patterns formed with a thermoplastic resin, such as a hot melt adhe¬ sive agent, wax or a similar substance. Fig. 16C shows a dot pattern similar to those of Figs. 16A and 16B, but formed with multiple, parallel nozzles. Figs. 17A, 17B, 17C, 17D and 17E show various dot patterns that may be formed in accordance with the teachings of this invention. Fig. 18 depicts a uniform spray pattern particularly suitable for coating the inner surface of a metallic can. Figs. 19A and 19B show alternate methods of uniformly coating the inside surface of a metallic can according to the invention. Detailed Description of the Invention Fig. 1 shows a liquid dispensing apparatus, or gun, designated generally by numeral 20, according to a first preferred embodiment of the invention. The gun 20 is connected to a nozzle 21 for dispensing of a liquid therefrom. The aligned gun 20 and nozzle 21 form a central liquid passage 23 which terminates in an orifice 24 through which liquid is dispensed. While this invention contemplates liquid dispensing as drops, droplets or atomized particles in a spray, the dispensed liquid is generally referred to in the application as a liquid stream, and designated by numeral 26. The surface upon which the stream 26 is dispensed and distributed is referred to generally as substrate 27. The dispensing liquid is contained within the gun 20 inside an annular chamber 28. Fluid supplied to the chamber 28 is provided by an external pump 29 connected to the gun 20. Flow control of dispensing liquid from chamber 28 is accomplished by operation of a liquid valve 30 which extends through chamber 28 and seats within an upper end of central liquid passage 23. Nozzle 21 includes six blowout ports, designated consecutively by numerals 33a-33f. Gas blown from the blowout ports deflects the dispensed liquid stream 26 to provide a desired deflection distribution on substrate 27. While six blowout ports 33a-33f are shown, it is contemplated that an optimal arrangement would include up to thirty-six blowout ports. Each blowout port communicates with a respec¬ tive, radially directed bore in the nozzle 21, des¬ ignated consecutively by numerals 34a-34f and shown in phantom in Fig. 2. Six conduits designated consecu¬ tively by numerals 35a-35f connect to the outer circumference of the nozzle 21 for fluid communication with radial bores 34a-34f, respectively. Valves 36a-36f are located along conduits 35a-35f, respec¬ tively, although only valves 36a and 36d are shown in Fig. 1. The valves 36a-36f regulate the flow of pressurized gas toward blowout ports 33a-33f, respec¬ tively. At least two solenoid valves 38 and 39 are operatively connected to the conduits 35a-35f to control flow of pressurized gas from a pressurized gas source 37, along the conduits 35a-35f, through the bores 34a-34f and eventually out of the blowout ports 33a-33f. Solenoid valves 38 and 39 are electrically connected to a timer 41, and, as depicted, each of these valves 38 or 39 control gas flows from three of the blowout ports. If additional blowout ports are used, additional solenoid valves may be necessary. The timer 41 actuates the solenoid valves 38 and 39 according to a desired sequence and duration to produce a predetermined distribution pattern of the liquid stream 26 onto the substrate 27. Preferably, the timer 41 is a current pulse controller capable of providing square wave current pulses of selectable durations. Particularly in spray coating applications, since disturbances referred to as air cushions may cause undesired reflection of the gas flows, as described in the background, it is best if the time duration of the current pulses from timer 41 are kept under 500 milliseconds. Preferably, the timer 41 should be capable of delivering current pulses ranging in duration of several milliseconds, i.e., about 4 milliseconds, up to about 50 milli¬ seconds. The timer 41 is also electrically connected to a solenoid valve 42 which controls the supplying of dispensing liquid from pump 29 to chamber 28. Dis¬ pensing liquid may be supplied from a liquid tank 44, a pressurized liquid tank 45 or a gravity pressure tank 46. A feedback line 47 may also be used to connect chamber 28 with pump 29 to assist regulation of pressure and/or flow conditions of dispensing liquid in chamber 28. With the liquid in chamber 28 pressurized by pump 29 and its peripherally connected components, raising of valve 30 from its seated position within passage 23 causes pressurized liquid in the chamber 28 to flow along passage 23 and out of orifice 24. To raise valve 30, the timer 41 elec¬ trically actuates a solenoid valve 48 to permit pressurized gas flow into a cylinder 50 at the top of the gun 20. The pressurized gas moves a piston 51 upwardly within the cylinder 50 to raise the valve 30. When no pressurized gas is supplied from solenoid valve 48, downward force from a spring 52 acts against the top surface of the piston 51 to hold valve 30 in a normally closed position. A valve 49 may be used to variably control the volume of gas that flows into cylinder 50 when solenoid valve 48 is actuated. Fig. 2 shows the radial orientation of the six blowout ports 33a-33f with respect to orifice 24. From this view, it can be readily seen that the alignment of the blowout ports 33a-33f enables a liquid stream 26 to be deflected from the opening 24 in any one of six radial directions, the six direc¬ tions being spaced 60° around the exterior of the orifice 24. Fig. 3 shows a dot pattern formed on a substrate 27 using the gun 20 depicted in Fig. 1. When valve 30 is raised to an "open" position, the liquid in chamber 28 moves through passage 23 and out orifice 24 in a downward direction. If the liquid has a relatively low pressure in contrast to a relatively high viscosity, a high cohesive force is created. For instance, a rubber type liquid substance or a hot-melt adhesive agent would fit this description and produce a high cohesive force. As a result, the effluent flow will create a linear form of discharge flow. Com¬ pressed gas is then blown out sequentially from each of the multiple, independently actuatable gas blowout ports 33a-33f. As the gas blowout flows strike the linear outgoing flow, the liquid stream 26 is deflected, or redirected in a different direction. As shown in Fig. 3, when liquid with a high cohesive force is deflected from a downward linear direction, a dot pattern is achieved, the size and spacing of the dots depending upon the blowout pres¬ sure of the distribution gas. « Fig. 3 shows dots 55a-55f produced by gas flows from blowout ports 33a-33f, respectively. It is noted that each dot resides on the opposite side of the blowout port from which it was deflected. Fig. 4 shows an enlarged view of a nozzle 21 suitable for use in gun 20 in accordance with a second preferred embodiment of the invention. According to this embodiment, the nozzle 21 is equipped with an airless spray orifice 57, which makes it possible to obtain a complex spray pattern from a liquid stream 26 that is atomized. All of the other elements of the gun 20 are similar to those shown in Fig. 1, although higher liquid pressures may be necessary. The liquid used to produce the dot pattern of Fig. 3 had a relatively high viscosity, but the liquid used with the airless spray orifice 57 has a relatively low viscosity (for instance a solvent, coating agent, emulsion, oil, atomized gas, etc.). Because the liquid stream 26 is atomized during discharge, the resulting pattern which appears on substrate 27 is a spray coating pattern, as shown in Fig. 5. Instead of the dots 55a-55f of Fig. 3, the airless spray orifice 57 produces spray regions 58a-58f of atomized droplets corresponding to directional gas flows from the blowout ports 33a-33f, respectively. Fig. 6 shows a third preferred embodiment of the invention, which contemplates use of a gun 20 equipped to provide binary liquid spray to achieve atomization of the liquid stream 26. According to this embodiment of the invention, the gas blowout ports 33a-33f surround the periphery of a nozzle orifice 59 and atomization of the dispensed liquid is achieved by discharging atomizing gas from the nozzle 21 via a concentric atomizing gas outlet 60 located at an end of a longitudinal, concentric passage 61. The atomization creates a spray flow for the liquid stream 26. Similar to the first and second embodiments described above, the atomized liquid stream 26 combines with multiple distribution gas blowout flows from the blowout ports 33a-33f. When the gas blowout ports 33a-33f are actuated sequentially to produce gas flows which strike the atomized liquid stream 26, deflection occurs and it is possible to obtain a desired complex spray pattern as shown in Fig. 5. The binary liquid spray gun 20 of Fig. 6 is similar to that of Fig. 1, except for the modifica¬ tions necessary to spray atomizing air along passage 61 and from outlet 60 into the liquid stream 26. More particularly, the gun 20 includes the passage 61 which terminates in a bore 64, and the bore 64 is connected to a conduit 65 which is in turn connected to the pressurized source 37 via a solenoid valve 68. Solenoid valve 68 is electrically actuated by timer 41 to permit pressurized air flow along conduit 65, through bore 64, along passage 61, and eventually out of outlet 60 during liquid dispensing from orifice 23, thereby to atomize the liquid stream 26. An addition¬ al flow valve 67 may be used along conduit 65 to provide additional control over the flow of atomizing gas therethrough. Fig. 7A depicts current versus time for the current signals from timer 41 which control operation of the liquid dispensing valve 30 and gas flows from the blowout ports 33a-33f. Curve 70 represents the timing of the discharge of the liquid from orifice 24. When a signal is received from the timer 41 or pulse controller 41 in Fig. 1, the operational position of the solenoid valve 48 will be the "open" position, and the operating air will be connected directly to the gun 20 so that it will penetrate inside the air cylinder 50 to raise piston 51 and valve 30 to dis¬ charge the liquid. Numerals 73a-73f represent the current pulses that generate the gas flows from respective multiple distribution gas blowout ports 33a-33f. When the distribution blowout ports (six in this case) have identical allocations for liquid discharge time, sequentially distributed gas is blown out from each of the blowout ports 33a-33f during only one allocated time pulse. Fig. 7A shows blowout from the first blowout port 33a occurring simultaneously with the pulse 70 which initiates discharge of the liquid stream 26. Subsequently, the other blowout ports 33b, 33c, 33d, 33e and 33f are actuated sequentially by respective pulses 73b, 73c, 73d, 73e and 73f. When a gas flow from a blowout port strikes the liquid stream 26, the two flows combine to create a deflected directional flow that eventually lands on the surface of the substrate 27. With six distribution gas blowout ports, six liquid agglomerates can be gradually distributed into respective locations, sequentially and one by one. According to the timing of the liquid signal 70 and the pulses 73a-73f shown in Fig. 7A, the substrate 27 will be coated according to the following sequence of coating regions 74a, 74b, 74c, 74d, 74e and 74f. If the timing is modified, the sequence will be altered. Furthermore, if necessary, when the gas flow is interrupted, the liquid stream 26 will flow vertically downward and form a central region 80 residing within the center of the six regions 74a-74f on the substrate 27. Fig. 7B depicts a timing diagram in which the first gas flow commences a time delay 76 later than initial discharge of the liquid stream 26. Figs. 7A and 7B show timing for continuously discharged liquid with sequentially blown out gas. With continuous liquid dispensing, some of the direc¬ tion of the liquid stream 26 will be retained during distribution as it existed before the change of the direction. More particularly, a tail, such as those shown in Figs. 8A and 8B will be added to each of the dot shapes or coated regions 74a-74f. Note that central dot 80 remains unaffected in Fig. 8B. Fig. 9 shows an example of the coordination of the current pulses 70, 78 and 73a-73f for producing discharge of liquid, atomized gas and distributed gas flows, respectively, using the binary liquid spray gun 20 shown in Fig. 5. The timing pulses of Fig. 9 produce distribution of the liquid stream 26 on a substrate 27 in the pattern shown in Fig. 10A. If a time lag between signal 70 and signal 73a were to be used, and all of the other gas flows were sequenced and of the same duration, the pattern shown in Fig. 10B would be produced on substrate 27. Fig. 11A depicts current pulses which produce intermittent discharge of liquid stream 26 and intermittent actuation of atomized gas. Fig. 11B depicts current pulses which produce intermittent discharge of the liquid stream 26 with continuous blowing out of atomized gas. In both of these cases, when the intermittent liquid stream 26 strikes the gas from the ports 33a-33f, the direction of the flow during the previous change of each of the spray flows is not maintained. In other words, since there is a discontinuation in liquid dispensing, i.e., signal 70, the spray distribution patterns of Figs. 12A and 12B are produced without tails. Again, Fig. 12B depicts a central coated region 80 that would be caused if the first gas flow were to lag behind initial liquid dispensing. This current control scheme is not depicted. In both Fig. 11A and Fig. 11B the current pulses to actuate the gas flows, i.e., 73a-73f, are sequenced and staggered. Although the above examples relate to an atomized liquid stream 26, it is also possible to use current pulses to intermittently actuate the liquid stream 26 produced by the device of Fig. 1 for the purpose of obtaining dot shape patterns, as shown in Figs. 12C and 12D. Note that Fig. 12D depicts a pattern that would be formed if a time lag were used between initiation of liquid dispensing and the first gas flow from the blowout ports. In all cases, if the liquid dispensing is intermittent, the spray pattern will not have tails. Although the explanation above describes six distribution gas blowout ports 33a-33f and the pat¬ terns have a generally circular shape, the number of these distribution gas blowout ports may be increased to twelve to obtain a ring shape, such as the one shown in Fig. 13A. This example and the prior exam¬ ples all used identical angles for the blowout ports, as well as identical blowout pressures and blowout times. However, if these variables are changed, it becomes possible to obtain more complex patterns, such as those shown in Figs. 13B, 13C and 13D. For instance, the patterns shown in Figs. 13B and 13C require a total twelve ports, similar to Fig. 13A, but with some of the ports angled differently than the others. Alternately, the same designs could also be achieved if the durations of the current pulses were varied to change the volumes of the gas flows con¬ tacting the liquid stream 26. The pattern of Fig. 13D requires sixteen blowout ports and variation in the angles of the ports, or alternately, variation in the duration of the current pulses which generate the gas flows. While Figs. 13A-13D show the effects of variation in blowout port angles or current pulse duration for the spray, the same techniques can also be applied to the apparatus shown in Fig. 1 to obtain dot shaped patterns. While use of the blowout ports to achieve single directional deflection has been described, it is also possible to use a combination of intersecting gas flows. It is also possible to use gas flows to create a twist to the liquid stream 26. Such a technique is a particularly efficient method of applying dot shapes in a desired distribution pattern. According to another embodiment of the invention, multiple liquids may be discharged from multiple nozzles, as shown in Figs. 14A, 14B and 14C. By mixing the discharged liquids, a combined flow is achieved. This would enable the addition of a hardening agent or similar agent for mixing in advance, so that the dispensed liquid would harden more readily. Figs. 14A and 14B show an airless spray nozzle 85 for mixing liquids dispensed from an inner orifice 86 and an outer, concentric orifice 87. Both orifice 86 and orifice 87 reside within the blowout ports 33a-33f. Fig. 14C shows a variation for spraying a liquid stream 26 of liquid from three orifices 89, 90 and 91, located within a concentric atomizing outlet 92, with blowout ports 33a-33f located further outside. One of the additionally mixed liquids may also be liquid aerosol, as shown in Fig. 15, with aerosol supplied by one, or both, of the conduits 95 or 96 connected to tanks 97 and 98, respectively. Flow of liquid aerosol to orifice 87 of the gun 20 via line 104 is controlled by a solenoid valve 101 con¬ nected to timer 41. Valve 102 provides additional control of aerosol flow through line 104. Fig. 15 also shows that aerosol conduits 96 and 99 from tanks 97 and 98, respectively, inter¬ connect to solenoid valves 38 and 39. Thus, according to this invention, the aerosol is supplied to the blowout ports 33a-33f and used as the blowing agent to deflect the mixed liquid stream 26 formed from both liquids dispensed out of nozzle 21. It would also be possible to supply different aerosols to each of the blowout ports 33a-33f, provided that additional pipe lines were used for each of the aerosols. Mixing of the liquid that forms the aerosol can be conducted with a solvent, a catalyst, a hardening agent, a liquified gas, etc. When a solvent is used, it is more effective to use self-cleaning of the orifice 23 and of the distributed gas blowout ports 33a-33f. Furthermore, it is well known that when a catalyst and a hardening agent are used, adding amine to epoxy-type paints is an effective manner of vapor curing. Also, when liquified gas is used, the high amount of energy created by expansion during mixing of the gas and liquid accelerates atomization. It is also possible to use this invention for deflecting fine particles of ice. Recently, Taiyo Oxygen KK Co. and Mitsubishi Electronics KK Co. proposed the injection of demineralized water into liquid nitrogen to create icing particles as a method to clean wafers. Other methods of using liguid nitrogen to create icing structures of liquid were described by The University of Gumma and other orga¬ nizations in ICLAS '78 Proceedings (International Conference on Liquid Atomization and Spray System) . These concepts may be readily applied to this inven¬ tion by deflecting a liquid stream 26 of iced parti¬ cles formed by mixing demineralized water and liquid nitrogen. This mixture would preferably be atomized by injection of the demineralized water into the liquid nitrogen. It is also to be understood that molten liquids may be used with this invention to produce a thermoplastic resin, a hot melt adhesive agent, wax, or a similar substance with a relatively low viscosity under 200°C. According to prior methods for dot shaped coating of hot melt adhesives onto substrate, the adhesive was discharged intermittently from a nozzle opening while the substrate was moved relative to the nozzle in order to achieve a straight line of coating. Figs. 16A and 16B show distribution patterns of dots that can be attained with the gun shown in Fig. 1. Fig. 16C shows a dot distribution pattern obtainable with multiple, parallel guns 20 of this type. Figs. 17A-17D also show distribution patterns attainable with a gun 20 of the type shown in Fig. 1, but with additional blowout ports added and liquid dispensing during relative movement of the gun 20 and substrate 27. It is also possible to apply prior art electrostatic coating methods to this invention. By charging the liquid with static electricity when the liquid is supplied to the gun, or attaching a corona pin to the vicinity of the nozzle orifice 24 for the liquid, the liquid can be charged as it is dispensed from the gun 20. Charging of the liquid stream 26 accelerates atomization, thereby reducing particle size to microscopic dimensions and improving the adhesion characteristics on a coated substrate 27. Perhaps the most important commercial advantage of the invention relates to coating the interior surfaces of a hollow product such as a metallic container. To prevent the contamination of the food contents of a can by the metal of the can, it is generally necessary to coat the entire interior surface of the can in a uniform, even manner. Other¬ wise, the food contents in the can may lose their aroma or taste. According to one prior method of coating the interior of a can, a spray nozzle was located inside the can and the can was revolved until the entire inside circumferential surface had been coated. However, it is known that centrifugal force created by rotation of the can causes some of the spray coating to accumulate in the corners of the can, resulting in uneven coating of the inside corners of the can. Moreover, the corners of the can were particularly susceptible to spray reflection. This invention proposes two methods for uniformly coating the inside surfaces of a can. First, adjustments are made to the timer 41 to produce a spray distribution pattern of the type shown in Fig. 18, with seven generally circularly shaped spray regions. Then, as shown in Fig. 19A, the nozzle 21 is inserted into the inside of a can 109 and spraying is conducted near the bottom of the can 109. The liquid stream 26 is distributed by changing the direction of each of the gas flows from the blowout ports 33a-33f so that there are no reflection flows within the can 109. Because the direction of the liquid stream 26 may be shifted within a short period of time, i.e., 20 milliseconds or less, this invention eliminates the occurrence of air cushions within the can 109 during spray coating. With this method and apparatus, the time of one cycle of gas flows, i.e., one gas flow from each blowout port 33a-33f, is approximately 120 milliseconds. With this method, it is not necessary to revolve the can 109 during coating, as required by prior methods. However, even if the can is revolved, it may be revolved at a relatively low speed so that the influence of centrifugal force is relatively small. By raising the nozzle upward with respect to the fixed can 109, or lowering the can 109 with respect to the nozzle 21, coating is applied uniformly to the inner surfaces of the can 109 by a number of additional spraying cycles, with each cycle directing a coating at a predetermined position or level of the can 109. Spraying may occur while there is continuous relative movement between the gun 20 and the can 109, or while the gun 20 is stationary within the can 109 at each of a finite number of different spraying positions. According to another method of coating the inside surface of a metal can, as shown in Fig. 19B, three different coating steps or stages are used. Each stage supplies coating to a different region of the can 109, and each stage employs a gun located outside of the can but pointed toward the can. For instance, at stage 111, the nozzle 21A supplies coating to a bottom portion of can 109A, while nozzle 2IB at stage 112 supplies coating to a midportion of the can 109B and nozzle 21C at stage 113 supplies coating to an upper portion of can 109C. Fig. 19B shows coating the internal surfaces of cans 109A, 109B and 109C with three different nozzle and gun set ups, one for each coating stage. Alternately, more or less nozzles could be employed for more or less spraying stages, particularly if the dimensions of the can 109 increases or decreases. From the above disclosure of the general principles of the present invention and the preceding detailed description of the preferred embodiments, those skilled in the art will readily comprehend the various modifications to which the present invention is susceptible. Therefore, we desire to be limited only by the scope of the following claims and equiva¬ lents thereof. We claim:

Claims: 1. A method of uniformly coating the inside surface of a can comprising the steps of: (a) spraying a liquid stream from a nozzle toward the inside surface of the can; and (b) directing each of a plurality of independently actuatable gas flows radially inward into contact with the sprayed liquid stream to deflect the stream in a desired sequence of directions to uniformly coat a portion of the inside surface of the can without producing a spray reflection. 2. The method of claim 1 and further comprising the steps of: performing steps (a) and (b) with the nozzle inside the can and then moving the nozzle relative to the can to uniformly coat additional portions of the inside surface of the can. 3. The method of claim 2 and further comprising the steps of: repeating said spraying, directing and moving steps a finite number of times to uniformly coat the entire inside surface of the can in a series of steps, wherein one cycle of spraying and directing occurs during each of the steps and each cycle has a duration of about 120 milliseconds. 4. The method of claim 3 wherein the gas flows are directed radially inwardly from six external blowout ports and each cycle further comprises: deflecting the liquid stream with six gas flows, each gas flow having a duration of about 20 milliseconds. 5. The method of claim 1 wherein steps (a) and (b) are performed at a first stage with the nozzle located outside of the can and directed toward a predetermined level in the can and further comprising the steps of: performing steps (a) and (b) again at a finite number of additional stages, each additional stage equipped with a nozzle directed toward a differ¬ ent predetermined level in the can, thereby to uni¬ formly coat the entire inside surface of the can without inserting any of the nozzles into the can. 6. The method of claim 1 and further comprising the step of: electrostatically charging the liquid stream during the spraying step. 7. A liquid dispensing apparatus comprising: a nozzle with a discharge orifice and a plurality of blowout ports surrounding the orifice; means for dispensing a liquid stream from the discharge orifice onto an interior surface of a hollow product; and means for selectively deflecting the liquid stream with a plurality of independently actuated flows from the respective blowout ports, thereby to produce a desired distribution pattern of dispensed liquid on the interior surface of the hollow product. 8. The liquid dispensing apparatus of claim 7 wherein the hollow product is a metal can with one open end and the entire interior surface of the sides and the closed end of the can are uniformly coated by the deflected liquid. 9. A method of dispensing liquid comprising the steps of: flowing a liquid stream from a dispensing orifice of a nozzle toward the interior surface of a hollow product; and selectively deflecting the liquid stream with a plurality of independently actuatable flows from a plurality of blowout ports located around the periphery of the dispensing orifice, thereby to achieve a desired distribution pattern of the dis¬ pensed liquid on the interior surface of the hollow product. 10. The method of claim 9 wherein the hollow product is a metal can with one open end and the liquid stream is flowed and deflected to uniformly coat the entire interior surface of the sides and closed end of the can. 11. A liquid dispensing apparatus comprising: a nozzle with a discharge orifice and a plurality of blowout ports surrounding the orifice; means for dispensing a liquid stream from the discharge orifice onto a substrate; and means for selectively deflecting the liquid stream with a plurality of independently actuated flows from the respective blowout ports, thereby to produce a desired distribution pattern of dispensed liquid on the substrate. 12. The liquid dispensing apparatus of claim 11 wherein said means for selectively deflecting further comprises: a plurality of conduits, each conduit connected to a pressurized gas source and terminating at a blowout port; at least two solenoid valves, one solenoid valve operatively connected to each conduit and electrically actuatable to permit pressurized gas flow from the pressurized gas source along the respective conduit and out of the respective blowout port; and a timer operatively connected to the solenoid valves and the dispensing means and adapted to control liquid dispensing through the discharge orifice and gas flows from the blowout ports. 13. The liquid dispensing apparatus of claim 11 wherein the nozzle further comprises: six blowout ports spaced equidistantly around the outside of the orifice for directing six radially inwardly directed flows against the liquid stream. 14. The liquid dispensing apparatus of claim 12 wherein the timer further comprises: means for selecting the sequence and dura¬ tion of said gas flows, thereby to selectively deflect the liquid stream to produce a desired distribution pattern on the substrate. 15. The liquid dispensing apparatus of claim 11 wherein the discharge orifice generates a liquid stream in the form of an airless spray. 16. The liquid dispensing apparatus of claim 11 wherein the nozzle includes an atomizing outlet between the discharge orifice and the blowout ports to generate the liquid stream in the form of a binary liquid spray. 17. The liquid dispensing apparatus of claim 11 wherein the nozzle further includes an additional orifice located adjacent the discharge orifice and the blowout ports. 18. The liquid dispensing apparatus of claim 17 wherein the additional orifice is concentric with the dispensing liquid discharge orifice and further comprising: means for spraying pressurized gas from the additional orifice to atomize the liquid stream dispensed from the discharge orifice. 19. The liquid dispensing apparatus of claim 17 wherein the additional orifice is concentric with the dispensing liquid discharge orifice and further comprising: means for dispensing a second liguid into the liquid stream dispensed from the discharge orifice to form a combined liquid stream that is deflected by said flows. 20. The liquid dispensing apparatus of claim 19 wherein said second liguid is an aerosol. 21. The liquid dispensing apparatus of claim 20 wherein said means for selectively deflecting includes means for introducing aerosol into the combined liquid stream. 22. The liquid dispensing apparatus of claim 11 wherein the nozzle further includes: multiple discharge orifices through which multiple liquids are dispensed and a concentric atomizing outlet outside of the multiple orifices and inside of the blowout ports. 23. The liquid dispensing apparatus of claim 11 wherein said dispensing means further comprises: a dispensing gun, the gun having a central liquid passage with one end terminating at the orifice and another end terminating at an internal chamber; means for supplying dispensing liquid to the chamber and pressurizing the liquid; a normally closed valve coacting with the liquid passage to prevent flow of dispensing liguid from the chamber to the passage; and means for opening the valve to dispense liquid from the orifice, the opening means operatively connected with the selectively deflecting means to coordinate deflection of the liquid stream onto the substrate in a desired distribution pattern. 24. A method of dispensing liquid comprising the steps of: flowing a liquid stream from a dispensing orifice of a nozzle toward a substrate; and selectively deflecting the liquid stream with a plurality of independently actuatable flows from a plurality of blowout ports located around the periphery of the dispensing orifice, thereby to achieve a desired distribution pattern of the dis¬ pensed liquid on the substrate. 25. The method of claim 24 wherein the indepen¬ dently actuatable flows are gas flows from a source of pressurized gas. 26. The method of claim 24 wherein the flowed liquid stream is atomized prior to deflection. 27. The method of claim 26 wherein the atomized liquid stream is produced by an airless spray nozzle. 28. The method of claim 26 and further com¬ prising the step of: flowing atomizing gas into the liquid stream from an atomizing outlet in the nozzle located between the dispensing orifice and the blowout ports, thereby to atomize said liquid stream prior to deflection. 29. The method of claim 24 and further com¬ prising the step of: flowing a second liquid stream from a second orifice in the nozzle to combine said flowed liquids from both orifices in a mixed liquid stream prior to said selective deflecting step. 30. The method of claim 29 wherein said second liquid is an aerosol spray. 31. The method of claim 29 wherein said second liquid is a hardening agent. 32. The method of claim 29 wherein said first and second liquids are demineralized water and liquid nitrogen, respectively. 33. The method of claim 29 and further com¬ prising the step of: atomizing the mixed liquid stream with an atomizing flow from a third concentric orifice in the nozzle located exteriorly of the first and second orifices and inside of the blowout ports. 34. The method of claim 29 wherein said second liquid stream flowing step further comprises: spraying an aerosol from a second orifice concentric about the first orifice. 35. The method of claim 34 wherein said mixed liquid stream is selectively deflected by aerosol flows from the blowout ports. 36. The method of claim 35 wherein the deflecting aerosol flows are produced by aerosols of different liquids. 37. The method of claim 34 wherein said second aerosol liquid stream is a hardening agent. 38. The method of claim 31 wherein said second aerosol liquid stream is demineralized water and said first flowed liquid stream is liquid nitrogen. 39. The method of claim 24 and further com¬ prising the steps of: selectively coordinating the flowing of the liquid stream with a desired sequence and duration of directional flows from the blowout ports to achieve a predetermined distribution pattern on the substrate. 40. The method of claim 39 wherein each of the directional flows has a duration ranging from about 4 milliseconds to 50 milliseconds. 41. The method of claim 26 and further com¬ prising the steps of: selectively coordinating flowing of the atomized liquid stream with a desired sequence and duration of directional flows from the blowout ports to achieve a predetermined distribution pattern on the substrate. 42. The method of claim 41 wherein each of the directional flows has a duration ranging from about 4 milliseconds to 50 milliseconds. 43. The method of claim 24 wherein the liquid stream is flowed continuously and the blowout ports are sequentially actuated during one cycle of opera¬ tion, and the flow of the liquid stream and a first of the directional flows are initiated simultaneously. 44. The method of claim 24 wherein the liquid stream is flowed continuously and the blowout ports are sequentially actuated during one cycle of opera¬ tion, and the flow of the liquid stream is initiated a predetermined time duration prior to a first of the directional flows. 45. The method of claim 28 wherein both liquid flow and atomizing occurs continuously during sequen¬ tial actuation of the directional flows. 46. The method of claim 28 wherein the atomizing flow operates continuously and the liquid stream is flowed intermittently. 47. The method of claim 28 wherein the atomizing gas operates continuously and the liquid stream is flowed intermittently. 48. The method of claim 28 wherein both the atomizing gas and the flowing of the liquid stream are actuated intermittently.

Inventors: AKITO TAKAMATSU, IKUO YAMAGATA, MATSUNAGA MASAFUMI, SHIGENORI KITASAKO, AKITO, TAKAMATSU, IKUO, YAMAGATA, MATSUNAGA, MASAFUMI, SHIGENORI, KITASAKO
Applicants: NORDSON CORP, NORDSON CORPORATION
Application year: 1991
Main classification: B05D1
IPC codes: B05B1, B05B7, B05B12, B05D1, B05D3