US 3741482 A
An improved foam spray nozzle adapted, in a principal embodiment, for pneumatically driving a viscous stream of urethane foam constituents onto substrates in a controlled pattern and thickness uniform coating being projected by a gas jet arrangement in a prescribed "ballistic" fashion whereby the jet ports surround an open-ended material outlet and are disposed and tilted in a pattern reflecting the contemplated spray pattern.
Claims available in
Description (OCR text may contain errors)
United States Patent 91 Eliason et al.
[ DISTRIBUTION DEVICE  Inventors: Kay E. Eliason, Fort Madison, Iowa;
James R. James, Louisville, Ky.
 Assignee: Atlantic Richfield Company, New
 Filed: Sept. 17, 1971  Appl. No.: 181,440
 US. Cl 239/296, 239/424.5  Int. Cl B051) 7/10  Field of Search 239/290, 291, 296,
 References Cited UNITED STATES PATENTS 8/l949 Bell et al 239/291 x 3/1903 Lassoe et a1. 239/421 X June 26, 1973 2,894,691 7/1959 Sedlacsik 239/291 X 3,199,789 8/1965 James 239/549 X 3,592,391 7/1971 Bender 239/424.5 X
Primary Examiner-Allen N. Knowles Assistant Examiner-Michael Mar Attorney-John J. McCormack et al.
' [5 7] ABSTRACT An improved foam spray nozzle adapted, in a principal embodiment, for pneumatically driving a viscous stream of urethane foam constituents onto substrates in a controlled pattern and thickness uniform coating being projected by a gas jet arrangement in a prescribed ballistic fashion whereby the jet ports surround an open-ended material outlet and are disposed and tilted in a patter reflecting the contemplated spray pattern.
11 Claims, 8 Drawing Figures PAIENTEDmzs ma 3.741. 482
sum 10; 3
DISTRIBUTION DEVICE BACKGROUND OF THE INVENTION This invention relates to gas driven distribution nozzles and in particular to such nozzles as adapted for applying urethane foam or related viscous coating materials onto a substrate; and more particularly where such foam nozzles comprise a liquid delivery system including mechanical impeller means and an annular outlet slit; this delivery system being operatively coupled with a pneumatic drive system comprising jet ports surrounding the delivered viscous material and being dimensioned, disposed and tilted to project a predetermined foam coating pattern onto a substrate very uniformly and with little waste despite variations in significant operating parameters.
In the prior art, workers appreciate that pneumatic (gas driven) foam distribution devices or spray nozzles have not to date satisfactorily handled many of the operational problems typically confronted. One such problem involves the maintenance of close control over coating thickness uniformity. Typically a considerable portion of foam material is wasted on the coated substrate while the coating pattern will vary in thickness beyond the desired tolerances. Of course any unnecessary thickness in the coating and any material applied beyond the intended coating pattern (off-spray material) results in an unnecessary waste of materials and useless costs.
Moreover, in certain cases such as the application of urethane foams it is vitally important to maintain a precise uniform coating thickness entirely apart from waste considerations. For instance, coating thickness may dictate and determine the position and spacing of superposed layers such as overcoatings or applied structural members. More particularly, spraying a foam blend for thermal insulation and structural purposes can typically involve coating a substrate in a prescribed pattern as thin as a few mils (e.g. 0.004 in.as liquid before foaming), with depth tolerances as small as 1 part in 12 (or 8 percent, here 10.0003 in.). In such situations we have found that even the best foam nozzles presently available have inadequate depth control; for instance using them to produce a foam depth of approximately 1 in. minimum, thickness would typically require that one set'for a nominal thickness of about I A in. (wasting about 50 percent of the materials) supply to assure maintaining the minimum 1 in. depth everywhere across the substrate. On the other hand, we have found that using the subject invention one can reduce such excess considerably; for instance, to as little as a inch excess for a nominal of l k in. coating-a mere 8 percent excess! Now workers in the art are well aware that a very non-uniform and uneven (regarding area and volume) pattern often results using conventional foam nozzles. For example, the pneumaticmix nozzle widely used to spray a desired pattern can often involve such massive gas thruput (for mixing purposes) and such sensitivity to minor changes in conditions that a substantial overspray and loss of materials to the air and outside of the desired coating pattern results-often accompanied by unacceptable thickness variations. Mechanically mixed nozzle units may be used instead; however in either case the volume applied to selected pattern area is too unpredictable and nonuniform.
The prior art has of course made available a large number of spray nozzles of various types, though relatively few are adaptable for applying foam materials. For instance, there are spray nozzles whose outlet orifices are arranged to control the shape of the spray pattern. However, these, and many similar nozzles, are unfortunately overly sensitive to minor shifts in operating conditions; e.g. with the rate of material supply, or with material viscosity and/or with nozzle height or gas drive thruput, turbulence, temperature, etc.
Also, such nozzles typically cannot feed (meter) the materials directly from the mixing unit to the distribution orifice but rather must channel it and thus have closed-ended metering. Further, various units such as the aforementioned pneumatic mixing units integrate the (foam constituent) mixing operations with the gas-driven atomizing-spray projecting operations, synergistically compounding the fickleness of each so that the resultant unit is disturbingly sensitive to operating conditions and quite difficult to get constant stable performance from.
In contradistinction to such features as those aforementioned, the present invention will be seen to provide a novel foam distribution apparatus wherein the applied pattern has no necessary relation to the shape of the (liquid or gas) ports; where pattern shape and size do not vary with material viscosity or flow rate nor with the gas thruput or turbulence, nor even with noz zle height, but rather remain constant within wide operating limits, despite such changes; and provide apparatus wherein liquid may be fed directly from a mixing station without any channeling or like constriction (i.e. open-ended metering) while yet separating the mixing function from the distribution (spray projection) functions.
US. Pat. No. 3,199,789 issued Aug. 10, I965, and the references recited therein are representative of prior art foam nozzles involving such problems.
Accordingly, one object of this invention is to provide a better answer to the foregoing problems and provide the features of improvement discussed herein. A more specific object is to provide a foam nozzle adapted to project a constant applied pattern with a high degree of depth uniformity. A related object is to provide the foregoing with minimal waste. A more particular object is to provide the foregoing for internal mechanically-mixed liquid compositions. Yet a further objectis to provide the foregoing using a prescribed projected pattern of gas jets symmetrically opposed around the liquid eject means.
LIST OF FIGURES The foregoing objects and features of invention are described hereinafter so as to enable those schooled in the art to make and use the claimed invention, this description to be read in conjunction with the accompanying drawings which comprise:
FIG. 1. A bottom perspective view of an embodiment of the invention shown in conjunction with a schematic representation of its associated spray pattern;
FIGS. 2, and 2A. An isometric view of the principal components of a mixing arrangement useful in conjunction with the embodiment of FIG. 1, the components being shown in exploded fashion; plus a sectional view of the impeller therein;
FIG. 3. An elevational section, somewhat simplified and enlarged, of the nozzle embodiment in FIG. 1;
FIG. 4. A bottom view of the gas drive (jet) ports of the embodiment in FIG. 1;
FIG. 5. An idealized representation of the disposition and relative angular orientation of the jet ports indicated in FIG. 4;
FIG. 6. A bottom view of the embodiment after the manner of FIG. 4, however with the associated spray pattern projected from the jet overlain thereon; and
FIG. 7. A sectional elevation along the lines of FIG. 3 with that embodiment being somewhat modified, here, to reduce spray diversion.
GENERAL DESCRIPTION OF PREFERRED EMBODIMENT Referring now to FIGS. 1, 3 and 4, a preferred embodiment of our invention comprising a novel foam spray nozzle arrangement 40 will now be illustrated and described as follows. Nozzle 40 will be seen to include gas drive means (jets 1-24 FIGS. 4-6) concentrically surrounding the annular foam-material delivery orifice and upstream drive (metering means) including a rotor impeller 61 arranged to help mix the viscous liquid foam constituents and thrust them through the annular orifice or meter slit EP, and beyond down and radially out to the nozzle tip, along a bevel surface 55 as indicated by the arrows. Impeller 61 will be seen to cooperate with the jet system to project different circumferentially-spaced streams of material in different selected directions to form a prescribed overall pattern of foam spray distribution according to the invention. The foam solids will be understood as mechanically mixed internally of the nozzle housing into a viscous slurry by the relatively conventional mixing arrangement (see FIG. 2 described below) and driven along the inside of the nozzle housing 41 to the nozzle tip 4l-E into operative engagement with air jet means surrounding the tip, to there be atomized and projected toward the contemplated substrate in a novel ballistic manner.
As indicated more particularly in FIGS. 2 and 2A (and described below), this nozzle embodiment includes relatively conventional mechanical mixing means adapted to mix the liquid constituents and deliver them from the end of nozzle barrel 41 at a prescribed flow rate and with prescribed (centrifugal and downward) driving force. The object, of course, is to cast the foam material in a prescribed pattern on various substrates as assisted, driven and controlled by the gas drive means according to the invention. This embodiment is particularly adapted to mix and spraydeposit a plurality of mixed liquid constituents to be sprayed onto a substrate (e.g. ss, FIG. 5) in the form of a layer of polyurethane foam having a prescribed depth kept highly uniform across the coated area.
Various types of mechanical mixing means will be recognized as applicable for this embodiment. The selected means comprises a cylindrical housing 41 (see FIG. 2, 2A, as well as FIGS. 1 and 3) with a mechanically-driven mixing blade, or impeller, 61 rotatably mounted in housing 41, being affixed on the driving end of a shaft ms driven conventionally by an electric motor or the like. Although other various mixing and driving means may be used, they will generally function to mix one, or several constituents from supply means, here indicated generally as source I-I.
Impeller 61 delivers the internally-mixed foam constituents along one of its grooves g to a meter slitEP formed by each groove end portion with the inner face of the impeller housing 41 spaced therefrom a prescribed gap. This gap (and the meter slit it creates) may if desired be made variable with shims or the like. Impeller 61 comprises a right circular cylinder approximately 3 Y4 inches long, with a l k inch diameter. It is relieved at its inject-end to include a mixing chamber 63 which is centrally-tapped at the bottom to receive drive shaft MS removable affixed there to impeller 61 for rotation thereof by motor means M or the like in the 2000 to 6000 rpm range. The sides of impeller 61 are relieved with a plurality of grooves g (e.g. 12 grooves approximately inch deep X k inch wide) disposed equidistant and symmetrically about its circumference. The transport of material from injection at mixing chamber 63 to ejection at meter slit EP is effected in a known (worm) fashion. Mixing chamber 63 is about 1 inch deep and terminates in a beveled end portion 62 dished downwardly and toward the center. Chamber 63 is adapted and intended to receive the liquid components from the supply lines indicated in FIG. 2 (to mixer H) and to facilitate the mixing and agitation thereof, thereafter to eject them outwardly and centrifugally along spiral grooves g to be driven therealong toward meter slit EP and beyond, when impeller 61 is rotated in the indicated sense. In this embodiment the mixing arrangement will be understood as providing the indicated components at a prescribed pressure such that with the impeller rotated in a range of 2,000 to 6,000 rpm a relatively constant foam thruput will be provided on the order of about 5 to about 40 lbs. per minute through slit EP. For this embodiment the mixed ejected urethane pre-foam liquid comprises a catalystadditive mixture, plus isocyanate and polyol constituents injected by supply conduits IS and PC respectively.
The mixer barrel or housing 41 has an outer diameter of about 2 inches with walls about one-fourth inch thick, being tapered almost to a point at its eject tip end (where tip 41-E presents an annular flat a few mils wide). The taper or beveled portion 51 along the inner end of barrel 41 is about three-fourths inch long and disposed at a few degrees with respect to nozzle center line C-L and housing sides. When impeller 61 is mounted and rotated concentrically within barrel 41, a clearance of about one thirty-second inch is realized with inner barrel wall making annular exit slit EP one thirty-second inch wide between grooves. Of course other clearances may be provided and a variableclearance means may be incorporated in the device as known in the art.
GAS DRIVE DETAILS In general it is intended that the gas drive for projecting foam materials toward the substrate according to the invention be circumferentially distributed in the form of jet ports symmetrically and uniformly surrounding the path of foam ejection (proceeding from slit EP along bevel 55 to flat tip 4l-E) and adapted to provide a gas stream of sufficient thruput (pressure, flow rate) and so oriented as to project a prescribed application pattern onto a given substrate-doing so in a manner that provides a smooth coating of uniform thickness despite normal variations in substrate distance, material thruput and viscosity and gas drive characteristics. Accordingly and according to these features, housing 41 is provided with an annular slot 41-S cut into its exterior wall adjacent its delivery end and bevel 55; being about 60 to mils deep by onehalf inch high. Housing 41 is surrounded by, and attached to, an air supply ring arrangement A comprising an annular cylinder 51 2 A: inches in diameter by about three-fourths inch high and relieved inwardly across its midsection to define a Slot A-S adapted to communicate congruently with housing slot 41-8, being the same height and about 400 mils deep so that together, the slots form a plenum chamber PC about one-half inch square adapted to be supplied with pressurized air (e.g. as indicated by air supply conduits 31,31). Plenum PC thus comprises an annular chamber adapted to distribute the injected gas stream relatively evenly to an array of jet ports j comprising ports labeled 1 through 24 in FIG. 4. These ports communicate with plenum PC and exit at the delivery end of nozzle 40 at the outer circumferential end thereof so as to project associated air streams for interacting with, engaging and projecting an associated stream of foam materials driven from an associated groove exiting at slit EP. Plenum chamber PC preferably is supplied by symmetrically opposed supply conduits so that air pressure may be distributed relatively evenly throughout; of course for higher air pressures and increased gas thruput, etc. four or more (rather than two) opposed conduits may be employed.
As particularly shown in FIGS. 3 and 4, jet ports j are formed in this embodiment by cylindrical channels drilled from the outer periphery of tip 41-E to the floor of slot 41-8 in a prescribed manner (tilt angle indicated below; thru a distance of one-half to three-fourths inch). Thus, at theouter circumference of tip 41-13 a number of exit points of the ports are disposed symmetrically and equidistant (here, 15 apart) along the circumferential locus of the outer diameter of housing 41, concentric with centerline C-L and equidistant from annular eject slit EP. For example, FIG. 3 shows, in section, typical ports 19 and 13 indicated also in'FIG. 4 and FIG. 5.
Jet ports j are preferably all 0.042 inch in diameter, though this is readily variable within limits as seen below, depending primarily upon the maximum total gas flow rate desired and other factors. As will become more evident from thedescription of FIG. 5, ports j are, according to a feature of novelty, tilted at a prescribed degree with respect to the nozzle centerplane, defined by the aforementioned nozzle centerline -1. and horizontal centerline CL' (indicated in FIG. 4) in such a manner as to project a prescribed pattern onto the contemplated substrate. For example, for this embodiment it will be evident that ports j are tilted to a degree directly proportional to their distance from this nozzle center plane and so that their projections onto a prescribed substrate about two feet away from the nozzle tip to locate a prescribed array of index points (see FIG. 5 where points are numbered and keyed to the port numbers in FIG. 4), defining a pattern of prescribed shape and size. Here the pattern is an ellipse with a major axis A-Mlabout 18 inches long, (along direction C-C) and a minor axis A-MN about 1 6 inches long, along the scan direction as indicated. Thus ports 1 and 13 are not tilted at all; ports 14, 24, 2 and 12 are all tilted at 17 with respect to the reference plane, ports 3, ll, 15 and 23 tilted at 15; ports 16, 22, 4 and tilted at 21; ports 17, 21, 5 and 9 tilted 25 and ports l8, 19, 20, 6, 7 and 8 tilted at 28. Of course the foregoing angular orientation was chosen simply to define the indicated elliptical pattern of index points indicated in FIG. 1 by the ports projections on a flat substrate at a reference distance of 2 feet from nozzle tip 41-E. It will be understood that a different pattern size and/or shape may be rendered in like manner by a different angular orientation of ports. For instance, it has been found that compressing the width of the indicated minor axis A-MN to about one-half inch and scanning the nozzle perpendicular to the direction indicated in FIG. 1 (that is, along direction C-C) can render a thin, beautifully-defined, uniform thickness pencil pattern along a substrate" better, even', than a single nozzle orifice or the like! Of course it is recognized that the pattern defined by the port projections as indicated in FIG. 1 is not a full-width pattern as coated, since the normal impingement of the material from each nozzle will result in some spray outside of this locusthat is the effective length (lp) and width (wp) of the applied pattern will be somewhat greater than indicated in FIG. 1. This is schematically indicated in FIG. 6 wherein the bottom of nozzle 40 is shown as superimposed over its associated pattern in this embodiment wherein the locus of index points is indicated at L-I while the effective length and width (lp and wp) are indicated with respect thereto.
Turning now to the operation of the gas driven foam nozzle described in this embodiment and referring especially to FIG. 3, it will be noted that impeller 61 thrusts the viscous foam material downwardly and outwardly across annular beveled face 51 (generally in 12, relatively-separate strings from each of the 12 spiral grooves in 61) to the outer edge of tip 41-13 where this material is acted upon by one or several of the air jets j, to be projected downwardly and outwardly in a prescribed and controlled array of angles toward the substrate. For instance, streams projected adjacent jets 19 and 13 and there beyond are indicated schematically by the dotted line arrows in FIG. 3. It has been observed in practice that when this embodiment is operating optimally, diagonal streams (or strings) of material can be seen projected from the nozzle for a distance 1 to 2 inches; thereafter the pattern becomes foggy or masked over-presumably by atomization and interparticle'action being completed with the particles being carried by air jets and the force of gravity in a ballistic projectory toward the substrate. It is further believed that with the material thus being imparted with sufficient momentum vector that their impact upon the substrate causes a subsequent puddling, a leveling action takes place with the jet streams (including those from successive coating passes with the nozzle) helping to level and smooth the overall coating, and all contributing toward developing a uniform thickness as well. Thus, it would be apparent that the ballistic effect imparted by the described nozzle jet drive system is important for distributing the foam material on the substrate and smoothing it. More particularly it is believed that the energy imparted by the mechanical impeller to the foam materials is important. This centrifugal, downward thrust can, of course, be a function of rotor speed and the exit velocity of the materials from gap EP, this vector being resolved together with that given by the associated jet stream later. For instance, it has been found that with the indicated embodiment and pattern. at a material thruput of 13 lbs. per minute constant (ARGO-Foam 1 or 2) and a constant air jet pressure, using the foregoingembodiment rotating impeller 61 at 2,000 rpm yielded a pattern about 2 /2 inches wide by about 17 inches long. Increasing impeller velocity lengthened the pattern only in the major axis direction, however, since a speed of 2750 rpm gave a pattern length of 19 inches while 3700 rpm gave about 24 inch length. Substantially beyond this rpm, however, the distribution pattern seems to blow out since at 4500 rpm the major axis lengthened to about 30 inches, while the minor axis suddenly balloons-out to about 36 inches. The foregoing indicates that within moderate rpm limits, the change in impeller speed imparts more velocity to the material at the jets along the extremities of the major axis A-MJ in FIG. 1 (that is at jets 17, 18, 19, 20 and 21 plus 5, 6, 7, 8 and 9).
In addition, air jet thruput must be kept high enough for a given thruput of foam solids so that the foam is properly aerated and does not choke" the pattern. For instance, for a 24 hole nozzle the air thruput associated with a 29 mil jet will do a good application job at lbs. per minute but will not properly apply 30 lbs. per minute unless the diameter is opened up to about 42 mils.
Referring to the spray patterns described above, it should also be borne in mind that while the typical elliptical spray pattern approximates that shown in FIG. 1, being somewhat larger than the ellipse traced by the index points (see the pattern shown in plan view in FIG. 6 in association with nozzle 40 superposed thereover observing that the effective pattern width wp of about 3 k inches to 4 inches and effective length lp of about 19 inches to 20 inches) and has an even, uniform thickness, a halo" is also developed outside this pattern, comprising an off-spray halo", OS. This off-spray halo" (FIG. 6) surrounds the effective uniformthickness coating pattern and comprises an outwardlytapering annulus of waste materials. Halo OS will be understood as about 4 inches wide surrounding the effective coating pattern and tapering from the nominal coating thickness of 1 A inches to virtually nothing at its outer periphery, the total off-spray volume in this penumbra comprising on the order of less than 10 percent of the total volume of material sprayed-a considerable saving over conventional methods today.
Jet port diameter appears to be one factor in this offspray phenomenon. For instance, a port diameter of about 40 mils may lay down the satisfactory given pattern at 30 psi air pressure and operating foam thruput, whereas reducing the diameter to about 35 mils or less will render a smaller effective pattern with a larger percentage of off-spray. Similarly, increasing the diameter substantially provides that a 29 mil 24 hole head operating at 13 pounds per minute gives an increased amount or percentage of off-spray when the thruput is increased to 30 pounds per minute unless the diameter is opened up to about 42 mils.
Table I below summarizes a few illustrative cases indicating how the jet port diameter/foam thruput relation affects coating quality (e.g. illustrating choking effect).
TABLE I For nozzle as in EXAMPLE I, with a 24 port, 30 psi head with everything kept constant:
Port Diameter Foam Thruput Coverage Quality Case A 0.040 inches at 13 lb./min very good, uniform Case A 0.040 inches at 30 lb./min very good, uniform Case A 0.030 inches at 30 lb./min unsatisfactory Case B 0.030 inches various mixed qualit (not ood" Case C 0.030 inches various etter 48 ports In summary, the results achieved with the foregoing embodiment have been quite satisfactory and a distinct improvement over present-day alternatives. Using the aforedescribed 42 mil jets at 30 psi pressure with the described urethane materials provided at about 13 pounds per minute thruput will be seen to yield a uniform V4 inch thick urethane foam layer (nozzle height about 24 inches) above the substrate forming the indicated elliptical (about 3 /2 inches X 20 inches) relatively flat level pattern following closely the contours of the substrate SS. The same resultant coating is rendered in strips of indefinite lengths by simply scanning nozzle 40, together with associated supporting equipment repeatedly across the substrate to build up enough layers to develop the desired total thickness. For instance, a number of layers like the foregoing were laid down superimposed one on the other in a sixlaminate foam layer about 1 la inch thick by simply scanning the nozzle six times over the same substrate strip length, allowing a few seconds curing time between passes. A nozzle moving at about 2 feet per second and provided on a 3 inch head stagger was found useful resulted this purpose. A very high degree of thickness uniformity was achieved in that thickness variations of only about i /8 inch were found or 1 part in 12 (8 percent). This is a signal achievement in this art as workers will attest. These laminates were laid down at a rate of 45 to 54 board feet per minute using an automatic spray machine, assuming 30 pound per minute through the nozzle which when added to the typical down time (e.g. scanning turn-arounds, etc.) )resulted in an average 18 pounds per minute effective thruput" (i.e. at the substrate).
Moreover, it was found that considerable variations in operating conditions, such as air jet pressure (within the range of 30 to 50 psi) and foam thruput (e.g. from a few pounds up to about 25 to 30 pounds per minute) produced no significant changes in the pattern applied. This operating stability and insensitivity to changes in liquid thruput and gas thruput will be recognized as significant, highly advantageous and quite unexpected by those skilled in the art.
Moreover, unlike many alternative foam distribution systems, the present invention is also quite tolerant of radical shifts in the viscosity and/or temperature of the foam (the latter affecting viscosity). That is, where alternative devices will experience a radical variation in the applied pattern accompanying a change in viscosity and/or temperature of foam materials (e.g. especially using one of the common pneumatic mixing-projecting nozzles) the instant device is practically unaffected. As a result, the much higher viscosities as well as lower material temperatures may be used with the present device; much less Freon or other blowing agent is typically lost.
Of course, various changes and modifications inthe components of the foregoing embodiment may be made as contemplated by those skilled in the art to achieve the described functions and results. For instance, one might substitute a different but equivalent mechanical mixing system, or gas jet supply system to render the same of modified pattern. Furthermore, for certain applications the relative disposition of the air jet and liquid supply systems may be shifted while still performing the indicated functions; for instance, one may locate plenum P within the walls of housing 41 to emerge at some point along the length of beveled section 51 in FIG. 3, being angled outwardly from from center-line C-L to provide the selected degrees of outward thrust. However, the same ballistic projection phenomenon will be seen to be implemented within the spirit and scope of the subject invention.
Also, various features of the invention may be changed to produce higher and more intricate levels of sophistication. For instance, the jet port diameters need not be kept uniform for a given nozzle design, but may be varied to produce different coated thicknesses at different portions of the applied pattern. For instance, if the port diameters for nozzle 40 were increased going from right to left in FIG. 1 so that the smallest and narrowest ports were located on the right (e.g. ports 5, 6, 7, 8, 9 at 20 mils) with the ports getting progressively larger as one proceeds to the left so that v the largest ports are located at the left extremity (e.g.
ports 17, 18, 19, 20, 21 at 40 mils), one might produce a pattern having a graduated, increasing thickness in a leftward direction assuming the same indicated scan direction and other operating conditions. (Scanning across a stripseveral times could amplify this thickness differential.) Similarly, one might graduate the thickness in two directions, outward from the center to produce a relatively U-shaped coated strip (cross-section, looking in the direction of scan). Of course, workers in the art will visualize other applications for using such ballistic-projection foam nozzles; eg with different but related viscous i liquids materials, such as high build epoxy coatings or the like.
. Nozzle plugging is a problem endemic to all devices like that described, although the subject nozzle appears to be much'less prone, being self-cleaning and having no flow-constrictions between the mixing station and the ejection station'(that is open-ended metering). However in extreme cases if the catalyst level is so high relative to the speed of application that the material is setting up in the nozzle and before it has reached the substrate, a plugging problem can result, of course. (I-Iigh'temperatures like high catalyst projections can give this problem--too-rapid curing). In situationsv where the foam is to be applied in a scanning operation for one or more layers, it has been found that, with the necessary (turn-around) down-time at the end of each pass, it is reasonable to equate minimum risetime with twice this down-time, (conversely with a 6 second rise-time, the head can never be shut-down more than about 3 seconds before plugging will begin). Here, it is also preferred to make the head and impeller components readily demountable for cleaning and replacement.
Associated with this plugging problem is the problem of minor foam build-up along the face of the plenum ring (see face A-F in FIG. 3). It has been found that material will build up on face A-F, especially adjacent end jets (such as 17 to 20 and 5 through 9 in FIG. I). Accordingly, and especially to minimize any such buildup problem, the embodiment modification indicated in FIG. 7 is recommended for such situations. Here, the air jet ring is beveled, as indicated on face 51-B, away from and back from the area of nozzle tip 4l-E so as to present a minimum overhang outwardly adjacent the exit portion of the jets (e.g. jet ports 19 and 13 in FIG. 7). Similarly, the inlet supply conduits should be relocated back away from the face of the nozzle as indicated for conduit 31'. The embodiment in FIG. 7 also indicates (schematically) a modification whereby plenum chamber A-C is incorporated within the walls of housing 41, for instance being fashioned as the breakaway-tip indicated as removable mounted on the forward end of barrel 41.
Although certain embodiments have been indicated by way of example and illustration, it is obvious that various modifications in the structures and techniques shown may be made, alone or in combination, by those skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims. For example, equivalent elements may be substituted for parts described, parts may be reversed andlor various features used independently, while certain other features are eliminated; all without departing from the spirit of the invention.
What we claim is:
1. An improved nozzle device for applying coatings of controlled depth to a prescribed substrate in a predetermined pattern comprising:
Nozzle housing means including an annular tip portion; metering means comprising an array of annular orifices adapted to provide a prescribed semiviscous liquid at a predetermined rate and a prescribed velocity along selected circumferential portions of said tip portion and gas drive means disposed to circumferentially surround said tip and adapted to operatively engage associated portions of said liquid flow there so as to project these toward an associated part of said substrate pattern in a prescribed ballistic manner.
2. The device as recited in claim 1 wherein said nozzle tip includes an annular end-flat portion; wherein gas drive means includes a source of pressurized gas, a plenurn chamber adapted to be filled with said pressurized gas and an array of similar gas conduits extending between said plenum and an associated portion of said annular flat to present an array of jet ports on said tip symmetrically surrounding said metering means and equidistant therefrom; wherein said liquid comprises foam materials; and wherein said metering means comprises an open-ended foam delivery system.
3. The device as recited in claim 1 wherein mechanical mixingsimpelling means are provided to impart said velocity; and wherein said velocity vector together with the thrust imparted by said gas jets combine to impart a prescribed projection energy to each associated liquid stream at said tip and thereby develop said ballistic projection.
4. The combination as recited in claim 2 wherein said gas drive means is arranged to provide a prescribed gas thruput through each jet port and wherein said metering means is adapted to supply said foam materials at a prescribed foam thruput, matched to said jet thruput, so as to accomodate said ballistic projection and uniform coating of said pattern, yet without producing any substantial off-spray or other waste.
5. The combination as recited in claim 4 wherein said jet ports are arranged to have a diameter less than that which produces an excess off-spray.
6. The combination as recited in claim 4 wherein said metering means and said gas drive means are conjunctively arranged so that the flow rates of gas and liquid materials are matched and wherein the means for delivery of each are so oriented relative one another and said pattern as to render an elliptical coating pattern on said substrate.
7. The combination as recited in claim 6 wherein associated nozzle motive means are also provided in operative relation with said nozzle device and adapted to transport said device at a prescribed rate across said substrate so as to sweep said pattern thereacross in a prescribed direction, laying down one or more layers of said coating foam materials.
8. The combination as recited in claim 6 wherein said liquid materials comprise mixed foam constituents adapted to be sprayed on the substrate; wherein said gas conduit diameters are in the range of a few hundredths of an inch; wherein said liquid material thruput is on the order of from a few to several dozen pounds per minute and wherein said gas thruput rate is equivalent to that resulting from a pressure of a few dozen pounds per square inch through gas conduits.
9. The combination as recited in claim 4 wherein said gas drive means includes an annular plenum ring disposed surrounding said nozzle housing adjacent said tip and attached thereto, this ring adapted to provide at least a portion of said plenum chamber.
10. The combination as recited in claim 9 wherein said ring is tapered backward and away from said tip in a prescribed manner adapted to minimize any foam deposition thereon.
ll. The combination as recited in claim 2 wherein said annular nozzle flat is centered on a prescribed nozzle-axis extending normal to the plane of this flat; wherein said gas drive means comprises an array of gas conduits surrounding the outer radial circumference of said flat and equidistant from one another and from said metering means, opposed first ones of said conduits being aligned along first axes parallel to one another and to said nozzle axis; the rest of said conduits being tilted at prescribed respective axes to the reference plane forward by said axes, each being disposed so that its projected longitudinal axis intersects a prescribed portion of said pattern on said substrate.