EP0515515B1

EP0515515B1 - Deflection control of liquid stream during dispensing

Info

Publication number: EP0515515B1
Application number: EP91904816A
Authority: EP
Inventors: Masafumi Matsunaga; Yamagata Ikuo; Kitasako Shigenori; Takamatsu Akito
Original assignee: Nordson Corp
Current assignee: Nordson Corp
Priority date: 1990-02-15
Filing date: 1991-02-15
Publication date: 1997-05-07
Anticipated expiration: 2011-02-15
Also published as: CA2075040A1; JPH03238061A; DE69126019D1; EP0515515A1; DE69126019T2; WO1991012088A1; EP0515515A4; JP2992760B2; AU7325491A

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

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 particular embodiment of the invention relates to uniform coating of the entire interior surface of a metal can with a single nozzle.
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.
US-A-4681258 discloses the uniform spray coating of a substrate in which a stream of liquid falls towards the substrate past a point towards which a plurality of nozzles are directed. Bursts of atomising gas are sprayed through the nozzles in a repeated sequence, so as to cause a repeated sequence of equal durations of spray in a plurality of directions.
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 significantly.
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 generally 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 reflection of this "air cushion", the collision and dispersion of the reflected spray pollutes the spraying environment and becomes a source of contamination.
A method of uniformly coating the inside surface of a can in accordance with the invention comprises the steps of spraying a liquid or particulate stream from a nozzle toward the inside surface of the can, characterised by directing each of a plurality of independently actuatable gas flows inwardly into contact with the sprayed stream and by independently controlling each gas flow to deflect the stream in a desired sequence of directions to coat a portion of the can uniformly without producing a spray reflection.
The can may be held in a non-rotating position and the nozzle located inside the can and then moved relative to the can iniformly to coat additional portions of the inside surface of the can.
The can may be moved past a series of nozzles, each nozzle providing a liquid or particulate spray stream directed towards a predetermined level of the inside of the can, so as to coat the entire inside surface of the can uniformly, the can being held in a non-rotating position relative to each nozzle and each nozzle being located outside the can during the coating step.
By controlling the sequence and duration of the independently actuatable flows during 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 or to a dispensed particulate stream.
Liquid or particulate dispensing apparatus in accordance with a first aspect of the invention comprises a nozzle having a discharge orifice and a plurality of ports surrounding the orifice and means for dispensing a stream of liquid or of particulate material from the discharge orifice onto a product held in a non-rotating position, characterised in that means are provided for selectively deflecting the stream with a plurality of independently actuated flows from the respective ports and in that means are provided for independently controlling the actuated flows and the dispensing means to produce a desired distribution pattern of dispensed liquid or particulate material on the surface of the product.
The product may be a hollow metal can with one open end and the entire interior surface of the sides and the closed end of the can may be coated uniformly by the deflected liquid or particulate material.
In one embodiment of apparatus in accordance with the invention, six blowout ports are spaced equidistant around the central dispensing orifice in the nozzle. The blowout ports are directed inwardly toward an axis aligned along the central dispensing orifice. By sequentially actuating each of the blowout ports around the dispensing orifice during liquid dispensing, the dispensed stream is sequentially deflected in six different directions to form a generally circular deflection pattern on a substrate. Alternatively, two or more of the blowout ports could be actuated simultaneously to create further variations in deflection.
One particular advantage provided by the methods and apparatus in accordance with the invention 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 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 a minimum of undesired air cushioning.
Air cushioning is reduced by sequentially actuating the blowout ports located around the dispensing opening to supply radially inwardly directed flows from directions which rotate circumferentially around the stream. Rotational deflection of the 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.
The selective deflecting means may comprise a plurality of conduits, each conduit connected to a pressurised gas source and terminating at a port and having a solenoid valve operatively connected thereto, each solenoid valve being electrically actuatable to permit the flow of pressurised gas from the source along the conduit and out of the port and a timer operatively connected to the solenoid valves and the dispensing means and adapted to control the dispensing of liquid or particulate material through the discharge orifice and the flow of gas from the ports.
The timer may comprise means for selecting the sequence and duration of the gas flows selectively to deflect the stream of liquid so as to produce a desired distribution pattern on the substrate.
The discharge orifice may generate a liquid stream in the form of an airless spray.
Such apparatus may include 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 milliseconds to 50 milliseconds.
By controlling the timing sequence 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.
A method of dispensing liquid or particulate material in accordance with a further aspect of the invention comprises spraying a liquid or particulate stream from a dispensing orifice of a nozzle toward a substrate, characterised by spraying a second, liquid or aerosol stream from a second orifice in the nozzle to combine the streams sprayed from both orifices in a mixed stream, and by selectively deflecting the mixed stream with a plurality of independently actuatable flows from a plurality of ports located around the periphery of the dispensing orifice so as to achieve a desired distribution pattern of the dispensed liquid or particulate material on the substrate.
The first and second liquids may be demineralised water and liquid nitrogen, respectively.
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. Alternatively, the nozzle may also include a concentric atomizing port located intermediately between the nozzle opening and the blowout ports for binary liquid spray dispensing. Such arrangements 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.
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. Methods and apparatus in accordance with the invention also reduce the cost of spraying multiple or complex patterns because a single nozzle can be used to achieve a wide range of distribution patterns. If desired, additional blowout ports may be provided to further increase versatility in achieving complex deflection patterns.
Methods and apparatus in accordance with the invention enable liquid to be dispensed 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.
The invention will now be described by way of example and with reference to the accompanying drawings in which:

Figure 1 is a cross-sectional schematic view of a first embodiment of a liquid dispensing apparatus in accordance with the invention.
Figure 2 is a view taken along lines 2-2 of Figure 1.
Figure 3 shows a dot pattern formed on a substrate by the apparatus of Figure 1.
Figure 4 is an enlarged, cross-sectional schematic view showing the liquid dispensing apparatus of Figure 1 equipped with a second embodiment of an airless spray nozzle in accordance with the invention.
Figure 5 shows a spray pattern formed on a substrate by the apparatus of Figure 4.
Figure 6 is a cross-sectional schematic view similar to the liquid dispensing apparatus shown in Figure 1, but modified to incorporate a third embodiment of a nozzle equipped for binary liquid spray dispensing in accordance with the invention.
Figure 7A is a timing diagram for operation of the apparatus of Figure 1. The timing diagram depicts current pulses that control liquid dispensing from the nozzle and gas flows from the blowout ports.
Figure 7B shows an alternative timing diagram for controlling liquid dispensing and gas flows from the blowout ports.
Figures 8A and 8B depict spray patterns formed by the apparatus of Figure 1 when operated according to the timing diagrams of Figures 7A and 7B, respectively.
Figure 9 shows a timing diagram for controlling liquid dispensing and the gas flows from blowout ports for the binary liquid gas dispenser of Figure 6.
Figure 10A depicts a spray pattern formed by the apparatus of Figure 6 when operated according to the timing diagram of Figure 9.
Figure 10B depicts a spray pattern formed by the apparatus of Figure 6, but with the timing diagram 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 of Fig. 6.
Fig. 12A depicts a spray pattern that may be formed with the liquid dispensing apparatus of Fig. 6, when operated according to the timing diagram of either Fig. 11A or Fig. 11B.
Fig. 12B depicts an alternative spray pattern that may be formed with the device of Fig. 6 and the timing diagram of either Fig. 11A or Fig. 11B where a time delay is included between initial liquid dispensing 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 includes a time delay between initial liquid dispensing and the first gas flow.
Figs. 13A, 13B, 13C and 13D depict additional, 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 fourth embodiment of a liquid dispensing apparatus in accordance with the invention which mixes aerosol with another dispensing liquid and deflects the mixture with aerosol.
Fig. 16A and 16B show dot patterns formed with a thermoplastic resin, such as a hot melt adhesive 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 alternative methods of uniformly coating the inside surface of a metallic can in accordance with the invention.

Fig. 1 shows a first embodiment of a liquid dispensing apparatus, or gun, designated generally by numeral 20, in accordance with 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 respective, radially directed bore in the nozzle 21, designated consecutively by numerals 34a-34f and shown in phantom in Fig. 2. Six conduits designated consecutively 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, respectively, 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, respectively. 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 milliseconds.
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. Dispensing 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 electrically 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 directions 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. Compressed 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 pressure 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 second embodiment of a nozzle 21 suitable for use in gun 20 in accordance with the invention. 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 embodiment of a liquid dispensing apparatus in accordance with the invention, which contemplates use of a gun 20 equipped to provide binary liquid spray to achieve atomization of the liquid stream 26. 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 modifications 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 additional 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 discharge 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 direction 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. 6. 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 patterns 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 examples 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 contacting 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.
In another embodiment in accordance with 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 connected 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, interconnect to solenoid valves 38 and 39.
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 apparatus in accordance with the 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 liquid nitrogen to create icing structures of liquid were described by The University of Gumma and other organizations in ICLAS '78 Proceedings (International Conference on Liquid Atomization and Spray System). These concepts may be readily applied to this invention by deflecting a liquid stream 26 of iced particles 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 apparatus in accordance with the 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 adhesive 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.
Liquid dispensing apparatus and methods in accordance with the invention may also incorporate electrostatic coating. 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. Otherwise, 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.
In a first method in accordance with the invention for uniformly coating the inside surfaces of a can, 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, the occurrence of air cushions within the can 109 during spray coating is eliminated. 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.
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.
In a second method in accordance with the invention for uniformly 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 11, the nozzle 21A supplies coating to a bottom portion of can 109A, while nozzle 21B at stage 112 supplies coating to a mid portion 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. Alternatively, more or less nozzles could be employed for more or less spraying stages, particularly if the dimensions of the can 109 increase or decrease.

Claims

A method of uniformly coating the inside surface of a can (109) comprising the steps of spraying a liquid or particulate stream (26) from a nozzle (21) toward the inside surface of the can (109), characterised by directing each of a plurality of independently actuatable gas flows inwardly into contact with the sprayed stream (26) and by independently controlling each gas flow to deflect the stream (26) in a desired sequence of directions to coat a portion of the can (109) uniformly without producing a spray reflection.
A method according to claim 1 wherein the can (109) is held in a non-rotating position and the nozzle (21) is located inside the can (109) and then moved relative to the can (109) uniformly to coat additional portions of the inside surface of the can.
A method according to claim 1 wherein the can (109) is moved past a series of nozzles (21A,21B,21C), each nozzle providing a liquid or particulate spray stream directed towards a predetermined level of the inside of the can (109), so as to coat the entire inside surface of the can (109) uniformly, the can (109) being held in a non-rotating position relative to each nozzle and each nozzle (21A,21B,21C) being located outside the can (109) during the coating step.
A method of dispensing liquid or particulate material comprising spraying a liquid or particulate stream (26) from a dispensing orifice (59,86) of a nozzle (21) toward a substrate (27), characterised by spraying a second, liquid or aerosol stream from a second orifice (60,87) in the nozzle (21) to combine the streams sprayed from both orifices (59,86,60,87) in a mixed stream (26) and by selectively deflecting the mixed stream (26) with a plurality of independently actuatable flows from a plurality of ports (33a-33f) located around the periphery of the dispensing orifice (59,86), so as to achieve a desired distribution pattern of the dispensed liquid or particulate material on the substrate (27).
A method according to claim 4 characterised in that the first and second liquids are demineralised water and liquid nitrogen respectively.
Liquid or particulate material dispensing apparatus (20) comprising a nozzle (21) having a discharge orifice (24,59,86) and a plurality of ports (33a-33f) surrounding the orifice (24,59,86) and means (28,30) for dispensing a stream (26) of liquid or of particulate material from the discharge orifice onto a product (109) held in a non-rotating position, characterised in that means are provided for selectively deflecting the stream with a plurality of independently actuated flows from the respective ports (33a-33f) and in that means are provided for independently controlling the actuated flows and the dispensing means to produce a desired distribution pattern of dispensed liquid or of particulate material on the surface of the product (109).
Apparatus according to claim 6 characterised in that the product is a hollow metal can with one open end and in that the entire interior surface of the sides and the closed end of the can are coated uniformly by the deflected liquid or particulate material.
Apparatus according to Claim 6 or 7 characterised in that the selective deflecting means comprises a plurality of conduits (35a-35f), each conduit being connected to a pressurised gas source (37) and terminating at a port (33a-33f) and having a solenoid valve (38,39) operatively connected thereto, each solenoid valve (38,39) being electrically actuatable to permit the flow of pressurised gas from the source (37) along the conduit (35a-35f) and out of the blowout port (33a-33f) and a timer (41) operatively connected to the solenoid valves (38,39) and the dispensing means (28,30) and adapted to control the dispensing of liquid or of particulate material through the discharge orifice (24,59,86) and the flow of gas from the ports (33a-33f).
Apparatus according to claim 8 characterised in that the timer (41) comprises means for selecting the sequence and duration of the gas flows selectively to deflect the stream (26) of liquid or particulate material so as to produce a desired distribution pattern of dispensed liquid or particulate material on the product (109).
Apparatus according to claim 8 or 9 characterised in that the discharge orifice (24,59,86) generates a liquid stream (26) in the form of an airless spray.