US3697313A

US3697313A - Method of spraying closed end cans

Info

Publication number: US3697313A
Application number: US13598A
Authority: US
Inventors: William C Stumphauzer; Edwin F Hogstrom; Eric T Nord; Richard E Schneider; Alvin A Rood
Original assignee: Nordson Corp
Current assignee: Nordson Corp
Priority date: 1970-02-24
Filing date: 1970-02-24
Publication date: 1972-10-10
Anticipated expiration: 1989-10-10
Also published as: JPS5620905B1; FR2080723B1; JPS546256B1; DE2100442C3; DE2100442A1; JPS5226256B1; FR2080723A1; CA923385A; GB1327125A; DE2100442B2

Abstract

METHOD AND MEANS FOR COATING THE INTERIOR CYLINDRICAL SURFACE OF OBJECTS SUCH AS METAL CANS FOR FOOD, BEVERAGES AND OTHER SUBSTANCES WHICH NEED PROTECTION AGAINST INJURIOUS REACTION WITH OR POLLUTION FROM CONTACT WITH THE MATERIAL OF THE CAN. RAPID AIRLESS SPRAY COATING OF SUCH SURFACES, WHILE THE SURFACES ARE REVOLVING AT HIGH SPEED, FROM A STATIONARY SPRAY NOZZEL EXTERNAL OF THE CAN, BY PROJECTING A SPRAY HAVING AN ASYMMETRICAL PATTERN INTO THE SINGLE OPEN END OF A CAN HAVING ONE CLOSED END, WITH THE PATTERN OF FLOW EMERGING FROM THE NOZZEL BEING MATCHED TO THE INTERNAL SURFACE CONFIGURATION TO APPLY A UNIFORM COATING. ALSO DISCLOSED ARE SPRAY NOZZELS HAVING THEIR OUTLET ORIFICES DESIGNED TO PROVIDE DESIRABLE SPRAY PATTERNS FOR USE IN THIS METHOD OF SPRAYING, AS WELL AS METHODS FOR MAKING AND SHAPING THE OUTLET ORIFICES.

Description

Oct. 1Q, 1972 w, STUMPHAUZER ETAL 3,697,313

METHOD OF SPRAYING CLOSED END CANS Filed Feb. 24, 1970 4 Sheets-Sheet 1 //V VE NT 0R5 L W/LL/AM 0. STUMPHAUZER EDW/N F. H065 TROM ERIC 7: Now 32;. E E :1. 31 It; RICHARD E. SCHNE/DER BY ALVIN 4. R000 6% 49M #M i M ATTORNEYS 10, 1972 w. c. STUMPHAUZER E A METHOD OF SPRAYING CLOSED END CANS 4 Sheets-Sheet 2 Filed Feb. 24, 1970 lA/VE/VTORS W/LL/AM C 5' TUMPHAUZER EDW/N E HOGS'T/POM ER/C r mom I R/CHARD E. SCH/VE/DER H llliil 5 J 5 BY ALVIN A. R000 5M, M HM i- M ATTORNEYS Oct. 10, 1972 w c STUMPHAUZER ETAL 3,697,313

METHOD OF SPRAYING CLOSED END CANS Filed Feb. 24, 1970 4 Sheets-Sheet 5 WILL/AM c. STUMPHAUZER ER/C 7. NORD R/CHA RD E. SCH/VE/DER J H BY ALV/N A. R000 m E; 15 iww ATTORNEYS Oct. 10, 1972 w, c. STUMPHAUZER ETI'AL 3,697,313

METHOD OF SPRAYING CLOSED END CANS 4 Sheets-Sheet 4 Filed Feb. 24, 1970 //VVE/V7U/?$ W/LL/AM C. STUMPHAUZER EDW/IV F. HOGSTROM ER/C r. NORD R/CHARD E. SCH/VE/DER BY ALV/IV A. R000 5 1 1W NM v M ATTORNEYS United States Patent (3" hio Filed Feb. 24, 1970, Ser. No. 13,598 Int. Cl. B44d 1/08 US. Cl. 117-96 8 Claims ABSTRACT OF THE DISCLOSURE Method and means for coating the interior cylindrical surface of objects such as metal cans for food, beverages and other substances which need protection against injurious reaction with or pollution from contact with the material of the can. Rapid airless spray coating of such surfaces, while the surfaces are revolving at high speed, from a stationary spray nozzle external of the can, by projecting a spray having an asymmetrical pattern into the single open end of a can having one closed end, with the pattern of flow emerging from the nozzle being matched to the internal surface configuration to apply a uniform coating. Also disclosed are spray nozzles having their outlet orifices designed to provide desirable spray patterns for use in this method of spraying, as well as methods for making and shaping the outlet orifices.

BACKGROUND OF THE INVENTION This invention relates to a method and means for coating the interiors of cylindrical objects such as metal cans and more particularly, to an improved method and apparatus for applying a uniform coating to the interior surface of a cylindrical container while one end is open.

Various methods have been proposed for coating the interiors of cans used to contain food, beverages and various liquids or gases to protect the contents from contact with the can materials. These methods and the corresponding means have varied to some extent depending upon the characteristics of the can to be coated. The prior practices described below and our invention are directed particularly to coating circular cylindrical cans.

In conventional practice metal cans are made in two pieces or in three pieces. In each case one piece is applied in a final operation to close and seal the can after it has been filled with food or drink. The other part of a two-piece can may be a deep drawn cylinder with a closed end. Three-piece cans, so called, comprise open ended cylindrical body shells with separate top and bottom end discs. One end disc may be coated simultaneously with the can body, as a two-piece can. The interior of the cylindrical can body is conventionally made of metal and has a seam running the length of the can. This seam may be of any common type such as a lapped seam which is soldered and crimped or cemented, or a butt seam which is welded. The bodies of three-piece cans, instead of being drawn from one piece of metal have been made as a double open end cylinder to which an end closure is fastened to seal each end, leaving a circular seam at the joint of the closure and side wall. The end closure may contain an easy open feature having a pull -tab riveted to the center of the cover.

The two or three piece cans with one closed end have heretofore been coated while being rotated about their own axes, and, using airless methods, spraying the in- 3,697,313 Patented Oct. 10, 1972 nozzle provided a fan-shaped spray pattern distributed so that a maximum amount of pain emerged from the orifice at one end of the fan with the amount of paint decreasing approximately linearly to a minimum amount at the other end of the fan.

A common method of gaging the distribution of flow from a particular nozzle is to spray a short burst of coating material against an upright, vertical substrate with the spray pattern oriented with its long axis horizontal. Typically the substrate contains alternating lands and grooves, as in a corrugated sheet, to offset the efiect of adverse influences such as the blast from the spray gun which can cause washout or distortion of the true spray pattern. Therefore, the quantity of coating material sprayed on any particular area will be reflected by the length, longer or shorter, of the rivulet in the groove running vertically downward beneath it.

A particular spray nozzle will reflect its own peculiar characteristics when gaged by the above-described method. The known drumhead nozzle has the spray pattern, FIG. 10 herein, that is skewed heavily toward one end. The commonly used prior art, fiat fan, airless paint spray nozzle has an orifice formed symmetrically with respect to the nozzle axis and slashed with a V- notch through a substantially hemispherical dome down to about the base circle of the dome. Nozzles with such orifices give, and gave, a smoothly distributed, symmetrical spray pattern having maximum flow in the middle with gradually diminished flows tapering or feathering" from the middle to the ends of the pattern. Heretofore there have been no airless spray nozzles (nor methods of making them) that provided desirable asymmetrical spray patterns between the extremes of the drumhead and the symmetrical V-notch patterns.

The drumhead nozzles in prior practice was oriented with respect to the can so that the maximum flow of coating material was directed axially the length of the can and the fanshaped pattern was directed toward the radius of the can bottom and one longitudinal line on the side wall from the bottom to the open end of the can. This procedure resulted in a substantially uniform coating being applied over the side wall of the can; the distribution of the spray fan compensating for the increasing distance the paint had to travel from the open to the closed end of the can, but the bottom of the can and the bottom circular seam received a non-uniform coating. The pattern of the drum-head nozzle is such that the place of maximum flow of paint had to be directed either at the circular seam, leaving too little material in the center of the can bottom, or the nozzle had to be directed closer to the center of the end of the can resulting in a deposit, due to centrifugal force, 'of excessive paint in the circular seam. The rivet required in the three-piece can with the easy open or pull tab feature, was particularly difficult or impossible to coat evenly. The only known remedy for an inadequately coated can was to spray more than enough paint along the side and near the seam to get a desirable minimum coating on the central part of the bottom.

Spray coating the interior of the two-piece can or threepiece can with one end closed has also been accomplished in the prior art by an air atomizing or airless spray nozzle mounted on a lance that is reciprocated into and out of the can along its axis while the can is rotated. In the lancing operation the spray may be turned on either while the lance carrying the nozzle is reciprocated from its innermost position to the outside of the can, or while moving from an external position to the inside of the can, or during reciprocation both into and out of the can.

Several difliculties attend the lancing method. The coating material tends to be applied to the wall of the can in a helical path which often results in helical streaks along the can wall. Other problems occur in timing the spray with the movement of the lance. -In particular, it is diflicult to cut off the flow of coating material at the precise instant that the spray begins to be projected outside the open end of he can as the lance emerges therefrom while supplying a sufliciently thick coating to the can wall adjacent the open end. Overspray tends to be excessive and consequently, maintenance and repair of the reciproeating device and related mechanism is often required at frequent intervals. Finally, the lancing method is quite ineflicient in that considerable time is required to move the lance into the can and to withdraw it therefrom.

SUMMARY OF THE INVENTION A general object of our invention is to provide a method and apparatus for spraying the interiors of hollow cylindrical bodies such as cans having one end open which substantially eliminates the disadvantages described above which have been encountered with prior can spraying methods and apparatus.

Another object is to provide a method and apparatus for spraying the interiors of cans having one closed end that provides a more uniform film distribution, particularly over the closed end and adjacent juncture with the side of the can.

Another object of our invention is to provide selective outlet orifices having form and contour in an airless spray nozzle giving asymmetrical spray patterns selectively related to the relative length and diameter of the can to be coated tending to provide a uniform coating over the entire interior of a can having one closed end. Such a pattern preferably gives maximum flow between one end and the middle of the pattern with smooth gradations from the point of maximum flow to each end, and an object of our invention is to provide spray patterns which will deposit paint uniformly on the sides and ends of the can in substantial proportion to the relative areas thereof.

Another object is to provide advantageous methods for cutting and forming such orifices in airless spray nozzles to achieve desirable selective distribution in spray patterns throughout a wide range commensurate with the range of sizes, shapes and proportions of cans and other hollow objects that need interior coating.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a plan view of the orifice of one form of of the body of the nozzle of FIG. 1, taken in the plane,

of the line 2-2 of FIG. 1 showing a first cut toward making the nozzle orifice.

FIG. 2a corresponds to FIG. 2, showing however, the second cut independently of the first cut to illustrate making the nozzle orifice.

FIG. 1a is a view corresponding to FIG. 1 showing the first cut only toward making the nozzle orifice.

FIG. 1b is a view corresponding to FIGS. 1 and 1a showing however the second cut of making the nozzle orifice, independently however for illustration, of the first cut.

FIG. 3 is a fragmentary view of the cutting edge of one of the wheels for ma'king the first cut of the orifice shown in FIGS. 1, 1a and 2.

FIG. 4 is a fragmentary view of the cutting edge of the other wheel for cutting the other part of the orifice shown in FIGS. 1, lb and 2a.

FIG. 5 is a plan view of the orifice of a preferred form ofour controlled distribution nozzle.

FIG. 6 is a longitudinal, vertical as viewed, section of the body of vthe nozzle of FIG. 5 taken in the plane of the line 6-6 of FIG. 7 illustrating our preferred method ofcutting this orifice.

FIG. 7 is a top plan view corresponding to FIG. 5, showing, however, steps employed in cutting the finished orifice of FIG. 5.

FIG. 8 illustrates a typical asymmetrical spray pattern obtained from both forms of our nozzles illustrated in FIGS. 1 and 5.

FIG. 9 is a top plan view corresponding to FIGS. 1 and 5 showing, however, the form of the orifice of the familiar prior art drumhead nozzle.

FIG. 10 shows the known spray pattern of prior art drumhead nozzles in which the place of maximum flow is at or closely adjacent the one end ofthe pattern and the place of minimum fiow at the other end.

FIG. 11 is a plan view of the orifice of another preferred form of our controlled distribution nozzle.

FIG. 12 is a longitudinal, vertical as viewed, section of the body of the nozzle of FIG. 11 taken in the plane of the line 12-12 of the axis of the nozzle.

FIG. 13 is a view corresponding to FIG. 11, but showing the configuration or nominal configuration of both of the cuts or gashes which together produce the finished orifice.

FIG. 14 is a fragmentary view of the cutting edge of the wheel for making the narrower cut or gash.

FIG. 15 is a fragmentary view of the cutting edge of the Wheel for making the broader cut or gash.

FIG. 16 is substantially a mirror view of FIG. 8 showing the reversed, right to left, pattern of our controlled distribution nozzle of FIG. 11.

FIG. 17 is a fragmentary plan view, partly in section and partly diagrammatic, of known means for rotating the can, or other hollow body, to be coated interiorly and advanced to a baking oven.

FIG. 18 is a longitudinal section of a hollow body such as a beer can with one closed end and with an opposite open end through which spray is projected according to our preferred method of coating the interior of such bodies.

FIG. 19 is a transverse sectional view taken in the plane of the line 19-19 of FIG. 18, showing the spray nozzle through the open end of the can and suggesting the plane of the fan of spray projected into the can.

DESCRIPTION OF THE PREFERRED EMBODIMENTS (A) The controlled distribution nozzle Illustrative and preferred embodiments of our airless spray nozzle orifices for controlled selective distribution spray patterns, are shown in FIGS. 1, 5 and 11 in their final form. The figures related to FIGS. 1, 5 and 11 depict the nozzles at various stages of cutting of the nozzle orifices, the steps of the methods of making them. It is a purpose of these nozzles to produce fiat, fan-shaped airless spray patterns having a predetermined distribution which will match ideally with the internal surface configuration of a can or other hollow body, with a closed end to apply a uniform coating thereover.

In the spray pattern of the controlled distribution nozzle, as shown in FIG. 8, the maximum flow of paint, or coating material, occurs at a point 10 approximately 75% distant from the far end of the fan F and 25% from the near end. Reasonable tolerances within good commercial practice are i5%. The amount of material flowing in the rest of the fan tapers smoothly and substantially linearly from the point of maximum flow 10, to points of minimum flow at each end of the fan. In contrast, the prior art drumhead nozzle, FIG. 9, produced the familiar fan pattern, FIG. 10 with maximum flow at the point 11 at or quite closely adjacent one end of the pattern and tapering linearly to minimum flow at the other end; substantially in a %-5% flow distribution.

(B) First nozzle embodiment An illustrative embodiment of a controlled distribution nozzle adapted to produce a spray pattern with a distribution similar to FIG. 8, is illustrated in FIG. 1, and comprises an orifice O slashed or cut in the top as viewed, of the hollow cylindrical body B, the workpiece until completed, FIGS. 2 and 2a, with an internal cylindrical approach passage P terminating in the plane 36, its upper end in the base circle, or eclipse, of a substantially hemispherical internal dome D. The wall of body B is, for convenient illustration, shown to be of substantially uniform thickness over and about the dome. The orifice O is of size, shape and position tending to yield a distribution profile similar to FIG. 8, and is cut into the dome D by two rotary cutting wheels, W and W having different cutting angles, i.e., different degrees of peripheral sharpness, FIGS. 3 and 4. The wheels may have appropriate known qualities for coping with the material of the nozzle tip.

A first rotary cutter, such as a diamond charged wheel W, FIG. 3, and see FIG. 1a, for cutting tungsten carbide, is narrowly tapered with an included angle of about 22 /2 at and comprising the cutting edge. It may have a radius R of 3 inches, for example, to cut the narrow, leftward, as viewed, part of orifice 0, FIGS. 1, 1a and 2. The wheel W has its center angled leftwardly from the longitudinal axis aa of the body B, and cuts an inclined tapered gash along and down to the line 37 through the wall of the body above and adjacent the dome D down to the leftward point x at the base circle of the dome and down to the point x above the base circle on the right side of the dome as shown in FIGS. 1a and 2. The line of the bottom of the cut 37 is angled to the base of the dome and the inclined aspect of the wheel to the axis a-a of the paS- sage P being for this example 7 /z as shown.

In this illustration the movement of the Wheel W, as well as W discussed below, will be in the plane 2-2 of the axis aa. A 3 inch wheel cutting an orifice .015 inch long, for example, will have a substantially straight line 37 for the bottom of the cut even if the bodily movement of the center of the wheel advances the wheel only along its radius R on the

line

45, 41, 43 inclined at said 7 /2" to the axis aa. The line 45-43 is the perpendicular bisector of the line 37 between the points x and x and passes through the center of the base circle of the dome, i.e. the intersection of a-a and plane 36 normal thereto. The same cut may be made with inclined rightward and leftward bodily movement of the wheel so long as the 7 /2 inclined aspect of the wheel to the work is preserved.

In this illustration the cuts or gashes made by the wheels W and W respectively, are shown in FIGS. 2, 2a, 1a and 1b as if each were a first cut. In practice the cuts are made successively so the second cut is made in part in the void of the first cut and is more awkward to explain in the first instance than the fiction of each cut being first and original. In FIGS. 1, 1a and lb the circle, or eclipse of the base of the dome is suggested in dotted lines. As shown in FIG. 2, the line 37 intersects the outside of the body at points 39 and 49 which define the ends of the gash in the exterior of the body.

Points

45 and 41 show the places of greatest width of the cut at the outside and inside, respectively, of the wall of the dome, and are offset from the axis by

distances

44 and 40 respectively. Vertical projections of

points

41 and 45 intersect the diameter of the base of the dome in

points

42 and 46 respectively. The equivalent of

points

41, 43 and 45 in the wheel W when cutting at full depth on the line 37 are shown at points 41a, 43a and 45a respectively in the wheel whereby to visualize the

maximum widths

48 and 47 of the gash in the exterior and interior of the wall of the dome. These lines of width are transposed to FIG. 1a passing through the

points

46 and 42 respectively and show the effect of tipping the gash and moving the places of maximum width leftwardly of the axis aa. As seen in FIG. 1, this leftward inclination of 0' makes the widest part of it join the gash 0", FIG. 1b, more harmoniously than were the line 37 to lie in the plane 36. This also results in a smoother line from the point in FIG. 8 to the left end of the spray pattern. This inclination of the 6 line 37 tends in minor degree to move the point 10 leftward in the spray pattern, of FIG. 8.

A second cutting wheel W of greater included angle of taper in the cutting edge, taken arbitrarily at 50 for this illustration, and radius R, FIG. 2 equal to R has its center offset rightwardly from the axis aa of body B, and cuts a broader rightward gash 0 through the dome, the bottom line 61 of which is inclined at 30", also taken arbitrarily, to the axis and plane 36. Wheel W cuts through the wall above and about the dome D down to the point y on the right of the base circle of the dome diametrically opposite the point x. This puts the ends of the exterior of the cut at the points 59 and 60 as shown in FIGS. 2a and lb, and puts the actual and tentative ends of the part 0" of the orifice O at the points y and y in the surface of the dome. When this is literally a second cut, the points y and 59 will lie in the void of the left ward part of the first cut. Following the procedure used above, the perpendicular bisector of the part y'-y of the line 60 originates at point 53 and passes through the intersec'tion of the axis and plane 36 and the

points

51 and 55 in the dome and external wall above it. These points are offset

distances

50 and 54 respectively from the axis and project downwardly to points 52 and y in the diameter of the base of the dome. Transposition of corresponding points 53a, 51a and 55a in the wheel W, FIG. 4, permits the measurement of maximum width of the cut in the dome and in the wall above it at

lines

57 and 58, the transposition of which to FIG. 1b depicts the whole cut and orifice containing the part 0" in plan view, as if the cut were made through solid material in the first instance. It remains merely to superpose FIGS. 1a and 1b to show the effect of the successive steps and cuts to make the composite orifice O and the exposed surfaces of the cut in the wall above and about the dome. The orifice O has sharp cusp at both ends. Particularly the right, as viewed, end which distinguishes it radically from the prior drumhead nozzles, and provides smoothly curved lines joining the place of maximum flow, corresponding to the point 10, to the ends of the pattern. The line 57 of greatest width of the orifice 0 corresponds approximately with the place of greatest flow in the pattern, and by its length and offset from the axis a-a plays the major part in placing the point of maximum flow, like point 10, where it may be desired in the spray pattern.

In FIG. 8, the oval area F at the top of the pattern is the place or target of impact of the fan F with the corrugated sheet or substrate. The point 10 lies at the bottom of the longest line of fiow of paint from the oval and shows the whereabouts in the spray fan of maximum flow. The lesser lines of flow of paint from different parts of the oval down the sheet measure the relatively lesser quantities of paint in corresponding parts of the fan. We have called the part H of the pattern to the left of the line of point 10 the heavy part, and the part L to fl1e right, the light or lighter part. This is convenient in respect to relating the different parts of the pattern to different parts of the can or hollow body being painted. This explanation is made to avoid confusion between one usage and the logical description of the heavy part of the pattern as that containing the maximum flow. In our usage we speak of the line or path of maximum flow as the line of division between parts H and L, or as an appreciable part of the pattern comprising the great flow to the point 10, as the context will suggest.

The following description of our two preferred forms of nozzle orifices will exemplify different advantageous ways of following the principle while altering the form of the orifice 0 described above. Preliminarily, it will be evident from the discussion about the orifice O that reducing the inclination of the line 60 from 30 to 20 about the point y, for example, that the wide cut from the wheel W will be extended leftward, tending to move the point 10 leftward in the fan pattern, and increasing the light part L of the pattern at the expense of the heavy part H. This will also tend to lengthen the cusp up from the point y and improve the quality of distribution in the part L of the pattern. Foreshadowing our preferred orifice in FIG. 11 (which is turned right for left from FIGS. 1 and 5), our teaching includes changing the depth as well as the inclination of any cut through the dome; specifically-raising and/or tipping the bottom line 60 of the cut, to diminsh the size and effect of o"- in relation to in the orifice O.

(C) The first preferred nozzle A first preferred embodiment of our controlled distribution, or controlled pattern, nozzle is shown in FIGS. 5, 6 and 7,'and differs from the embodiment described above in both the shape of the discharge orifice and in the method of cutting it. As shown in FIG. 5, the orifice O0 is approximately tulip-shaped, or arrowhead-shaped, comprising two minor divergent

cusped lobes

23 and 24 on the right as viewed, side of the axis aa of nozzle body B which merge into a major cusped lobe that terminates at the point x, see also FIGS. 6 and 7, on the opposite side of axis aa. The

lobes

23 and 24 join at the point 34, or line 34-35, diametrically opposite the point x but higher on the curve of the dome from the base thereof, FIGS. and 6. The section of maximum width 28 of the orifice lies near the point 34 substantially in a plane at right angles to theplane containing the axis and points x, 34 and 35. Approximately 25% of the coating material output from the orifice 00 appears to emerge from

lobes

23 and 24 while about 75% of the material appears to emerge from the remaining portion of the orifice to form the spray pattern of FIG. 8.

The tulip or arrowhead orifice 00, FIG. 5 is preferably cut and formed as shown in FIGS. 6 and 7 by the cutting wheel W2 making two chordal gashes down to the base circleof the dome; both gashes passing through the point x on the left, as viewed, with one passing through the point y and the other through y on the right side of the base circle of the dome. The first cut is shown in full; the second in dotted lines in FIG. 7. The bottom of the first out and the intersection of the central plane thereof with the plane of the base circle of the dome follows the imaginary line K, FIG. 7, at the angle 0 from the central longitudinal plane 6-6of the body B. After the first cut is made the work piece, i.e. the unfinished body B, is rotated relative to the wheel W about a line parallel to axis aa andvpassing through the point x so that the second cut will follow the line Q at an equal and opposite angle 0 on the opposite side of the central plane 66. The second cut is shown in dotted lines; the two gashes together form the arrowhead orifice 00, FIG. 5. The finished orifice 00 has major sloping side surfaces 30' and 31 and minor side surfaces 32 and 33 which lie on opposite sides of the uncut wedge-like part 38 of the wall ofthe dome. The

surfaces

32 and 33 intersect in the line 34-35 in the plane 66, FIG. 7. It will be appreciated that when the lines K and Q coincide a simple symmetrical pattern will result and the point like of maximum flow will be shifted to the middle of the pattern. Conversely as the angle of divergence 2c between lines K and Q increases, the point of maximum flow will be moved more nearly to the right, as viewed, in FIG. 8, of the pattern. Presently we have not tested the advantageous limits of such divergence beyond shifting the point 10 to about an 85 pattern.

An example of a controlled distribution nozzle formed in this manner has an orifice of about .015 inch equivalent diameter and projects a fan spray having an output rate of flow of water of about 120 cc. per minute at about 40 p.s.i. The width of the fan-shaped spray pattern produced by this orifice is approximately 8-10 inches measured normal to the nozzle axis at about 10 inches from the nozzle to the target. The cutting edge of wheel W2 is tapered at an included angle of about 25 and has a radius of 3 inches. Angle c in FIG. 7 is approximately 8 /2 (D) The second preferred nozzle This preferred form of our nozzle invention and method of making an embodiment thereof is illustrated in FIGS. 11-15. An illustrative spray pattern from this nozzle is shown in FIG. 16, which is a mirror view of FIG. 8. The orifice 03, FIG. 11, is a composite resulting from two successive cuts made by two different Wheels W3 and W4, FIGS. 14 and 15, both moving in the central longitudinal plane 1212 and making cuts of different inclination, breadth and depth.

As shown in FIGS. 12 and 15, and in full lines in FIG. 13, this first cut is quite conventional and made with the wheel W3 having a cutting edge with faces inclined at a 37 included angle, down to the line 70 in plane 36 of the base of the dome at the orthodox points x and y. Such a cut would give a conventional symmetrical fan pattern as if the point 10 were in the middle. The center of wheel W3 is aligned with the axis aa of the dome D, approach passage P and nozzle body B, so the line 70 is horizontal and the perpendicular bisector of x-y coincides with the axis aa. The widest part of the cut through the dome is suggested at 75 and through the outer wall at 76, FIG. 12, and translates to

lines

75b and 76b taken through the wheel W3 at

points

75a and 76a, corresponding points 75 and 76 in the work, and to the cut as viewed in plan and seen in full lines in FIG. 13. The line 70 of the first cut crosses the axis aa at point 72, FIG. 12, as suggested at the point 72a at the extreme edge of the wheel, FIG. 14.

The second cut has the orifice and function of moving the line or path of greatest flow in the spray pattern from the middle leftwardly as viewed in FIG. 16 over to about the quarter point about midway between the center and left end of the pattern and giving the light side L about 25 and the heavy side H about 75 of the flow of paint. This second cut is made with the wide (115) angle cutting edge wheel W4, FIG. 15, inclined along line 71 at 16% to the plane 36 and line 70 with the center of the wheel angled 16 /2" from axis w-a when it coincides with the perpendicular bisector 72-74 of the part 77 79 of line 71 where the latter intersects the hemisphere of the'dome, actually in the voidinvthe first cut. The bottom of the second cut at its greatest depth reaches only about 40% of the way down the radius 7273 of the dome whence the extreme ends of the first cut in the plane 36, FIGS. 11, 12 and 13, are untouched by the wheel W4,

and their narrow sharp cuspcd ends persist in their benign influence at and within the edges of the parts H and L of the spray pattern.

Projecting the

points

77, 74, 73, 79 and the intersection of line 71 with the outside of the wall of the dome down in the plane 1212 to the diametric line x-y and 70, the

respective points

87, 84, 83, 89 and 71a are established to locate these points in plan view in FIGS. 11 and 13. The projection of the. intersection of line 71 with the left interior surface of the dome is substantially coincident with the intersection of the line 70 with the same surface. These projected points locate the ends and places of greatest width of the orifice and gash cut by the wheel W4. The respective widths are found, as above, by translating the

points

73 and 74 into the wheel at

points

73a and 74a; the point 78a translating extreme edge of the wheel contacting the point 78. At the

points

73a and 74a in the wheel, the width thereof, which reflects the maximum width of the orifice and gash is shown in

lines

73b and 74b, and translating these lines into FIG. 13 establishes the plan view of the outline, shown in dotted lines, of the gash through the wall above the dome and the orifice in the dome.

As shown in FIGS. 11 and 13, the bluntness of the wheel W4 make the gash, and orifice cut thereby, almost as wide as long and loses the theoretical ends of the orifice in the void of the first cut. In FIG. 11, the dominance of the part 91, of the final orifice 03, made by the wheel W4 is shown realtive to the part 90 cut by the wheel W3 in the right part of orifice O3, and a small part of the orifice and gash cut by the wheel W3 at the left end of the orifice 03, FIGS. 11 and 13.

Our present tests and observation of nozzles having the orifice 03 appear to show that their orifice can give much the same pattern, FIG. 16, as the nozzle '00, FIG. 8, when the place of maximum flow, point 10, is midway between the middle and the near end of the pattern. The nozzle 03 presently appears to be more predictable in respect to its pattern as the second cut is inclined, and/or cut more deeply, to move the point 10 of the pattern nearer the end of the pattern. Conversely reducing the inclination of the second cut, as from 16 /2 to 13 will tend to move the point 10 of the pattern toward the middle, reducing H and increasing I...

-(E) The method of coating generally In FIGS. 17, 18 and 19, our preferred method of coating the interiors of hollow bodies, like cans, is illustrated. The cans to be coated must be indexed one by one to a spraying station where they are revolved rapidly, by known mechanism as in the Eberhart, US. Pat. No. 2,189,- 783, and sprayed by a stationary automatic airless spray gun and our nozzle. The cans, still rotating, are then dropped or stepped out of the indexing apparatus to an inclined belt or chute on which they continue to rotate and roll to a baking oven. The belt and/or chute is of a length and inclination such that the cans will roll for a suflicient time and for a suflicient number of revolutions to allow the coating to become so tacky that it will no longer flow, and therefore not impair the uniformity of coating obtained during spraying, before the coating is fixed by baking. The cans then are moved into the oven where the coating is baked at a prescribed temperature for a proper time. Illustrative can indexing and rotating apparatus is suggested diagrammatically in FIG. 17.

Preferably, the spraying of the can interiors should result in a uniform film distribution with a weight of coating of a particular number of milligrams per square inch according to prescribed specifications related to the use and proposed contents of the can. Coating materials may be vinyl, epoxy, butoxy, phenolic, acrylic, alkyd, modifications of the above, or other suitable coatings.

Film distribution is commonly determined electrically by measuring the resistance of the film at a plurality of points on the interior surface of the can. A method of determining overspray is to measure the weight gain of the can and the weight of oversprayed material which is capture during the spraying process. The captured overspray material then may be calculated as a percentage of the total weight of the material emerging from the nozzle.

In FIG. 17, an illustrative can indexing and rotating apparatus 1 is shown rotating a can C having one closed end 7 at a spraying station where gun G with nozzle N is positioned at the open end of the can to spray and coat the interior thereof, see also FIGS. 18 and 19'. Nozzle N is oriented with respect to the longitudinal axis ss of the can, its direction of rotation and the intended line and angle of contact of the spray fan with the inside of the can to provide the very rapid coating of uniform thickness discussed more fully below. Nozzle N and automatic gun G therefore is rotatably, pivotally and adjustably mounted on indexing table 2 which allows the nozzle to be positioned bodily and aimed about horizontal and vertical axes with respect to the interior of the can to be coated. Appropriate hoses, not shown, supply paint at desired temperatures and pressures to the Each can is rotated in a direction that advances the exposed edge of the lapped joint 17 of the can to receive head-on a tangential component of a spray fan, FIG. 19. The can is rotated at high speed, characteristically between 500 and 3000 revolutions per minute, a typical example being 1 650 r.p.m. The coating material is sprayed into the interior of the can during a little more than three revolutions; e.g. for about to 200 milliseconds. A uniform coating of desired thickness, for example, 3.5 to 6-.5 milligrams per square inch is deposited in this short time. The coating material has advantageously, properties of good wettability and adhesion. Viscosity is characteristically Within a range of 14 to 40 seconds as measured with a Zahn No. 2 efilux cup at 77 F. The coating is deliberately sprayed olf the proximate edge 16 of the can for a distance of, for example, about V to insure full coating thickness to and on the edge.

Immediately after each can is coated and while still rotating, it is stepped forward to a releasing station general-1y indicated as 3, FIG. 17, where it is released from the rotating and indexing apparatus and caused to roll down a long inclined ohute 4 at a rate of rotation that prevents the still mobile coating material from moving its place of uniformdeposition.

Continuing rotation causes the material to set with uniform thickness before baking. The length of the inclined chute 4 is much greater than shown in FIG. 17, and is such that the can is caused to make a generous minimum number of setting revolutions, fifty for example, during which the paint becomes tacky so that it will not flow. At the same time some volatiles have time to escape the can 'before it enters the baking oven. At the end of inclined chute 4 the can may enter the oven 5 where the paint is baked at a prescribed temperature; e.g. at 300 F. for about 6 minutes, sufircient to cure and harden the applied film of the particular coating material.

(F) Coating cans with a single open end The internal surface of a single open end can is coated, as shown diagrammatically in FIGS. 17 to 19 with a spray gun employing our novel controlled distribution nozzle, preferably having the orifice form of FIG. 5 or 11. Only one nozzle N is employed, the axis n of which is positioned to spray into the open end with the fan F at a small angle 1, FIG. 19, measured horizontally with respect to the vertical plane v of the longitudinal axis s-s of can body, and with axis n of the nozzle at an angle e, FIG. 18 measured vertically with respect to the horizontal plane h, of the axis of the can body. The nozzle orifice is located a distance 18 from the open end of the can, FIG. 18 and about half that distance about the plane I: and enough to the left of v to provide the angle 1, FIG. 19. Consequently the line 6 of maximum flow in the spray fan (see point 10 of FIGS. 8 and 16), is intended to be directed at the circle of intersection between the closed end 7 of the can and its cylindrical side 8. The heavy portion H of the fan is directed along the side of the can body while the lighter part L is directed toward the closed end 7 of the can. The width and direction of the fan shaped pattern from the nozzle orifice is such that the outside edge 9 of the lighter portion L of the fan is directed at the center of the circular bottom or closed end of the can, and the opposite edge 15 of the fan is directed at, or very slightly without, the edge 16 of the open end of the can.

With this orientation the distribution pattern of the spray nozzle is ideally matched to the areas and portion of the internal surfaces of the can to be coated. The heavy part H of the fan spray falling between the open edge 16 of the can, and the closed bottom end 7 provides a uniform coating on the sidewall 8, all portions of which are rotating at the same lineal speed. The lighter portion L of the spray fan decreases from a maximum flow along the line 6 to a minimum desirable flow at the outer edge 9 of the spray fan which is directed at or slightly beyond the dead center of the circular closure end 7. The amount of coating material applied to can end 7 is greater at the places further from the center so that the amount of coating material decreases with the decreasing radius of can end 7 to the dead center thereof.

Our method is premised on, and permits the novel matching of the spray pattern to the shape and proportion of the interior of the can. Should the area of the bottom of the can be one-third the size of the area of the side, our method would employ a nozzle giving a theoretical 25%-75% pattern with A of the flow of coating material in the part L and in the part H, FIG. 18, having in mind, however, our collateral teaching that (1) the seam 19 needs a controlled quantity of paint more than enough to cover a pure geometric circle, (2) the rivet and die cut in pull-tab end closures may need paint more than normal smooth surfaces, '(3) centrifugal force tends to wash mobile, wet paint off the end closure, (4) a little overspray must be lost from part H at the open end of the can and (5) the effusion of solvents from the fan and target area probably impair the flow of paint to the closed end more than to the side of the can. Depending on the ratio of can length to diameter, among other things, our present experience suggests that these collateral considerations may make a 25%-75% pattern advantageous in a can having a closed end of noticeably less than 25% of the whole internal area and a side wall area correspondingly greater than 76% the total area.

The fact that a prior art drumhead nozzle would serve to coat the inside of a very long can of small diameter, and a conventional nozzle with a symmetrical pattern would coat a shallow can of large diameter, bottom area about equal to side area, does not diminish the advantage and economy of our method and means for coating the interiors of cans whose proportions lie between these extremes.

In contrastwith prior practice of using the prior drumhead nozzle to spray the sidewall and end of such a can, our controlled distribution nozzle puts substantially equal, desirably minimum, quantities of paint on every square inch of the whole interior surface in the first instance. When the circle of juncture between the side and closed bottom of the can comprises also a seam 19 that may have raw edges and minute voids, our nozzle and method puts the maximum flow right on the circle and seam whereour selected distribution and pattern insures proper covering'of the seam without the hazard of flooding the annular corner.

The proportions of the can also influence the most advantageous location of the nozzle N, the inclination of its axis ss and the disposition of the fan in relation to the interior of the can. A preferred position of nozzle N is off the axis ss of can C as shown in FIGS. 18 and 19. When the can is rotated clockwise, as viewed in FIG. 19 and suggested by the arrow, the spray fan F is inclined at angle 1 to have a tangential component where it meets the side of the can to meet the raw leading edge of the lap seam 17 head-on whereby to insure a proper covering of the edge, and voids, if any, in the lap, of the seam with ample coating material.

While we have mentioned our preference for particular speeds of rotation of typical cans while the coating spray is being applied, we also prefer that the can be rotated no less than a whole revolution, obviously, and also that the can be rotated a whole number of revolutions plus afraction of a revolution corresponding to the circumferential distance the can rotates while the flow from the nozzle builds up from zero to full-flow, and vice-versa, i.e. while the valve in the paint gun is moving from closed to open, and vice-versa. ,With a solenoid actuated pneumatically operated valve the time taken for valve opening and closing is small but long enough to permit the rapidly moving coated surface to move an appreciable distance and .be covered with a circumferential wedge of coating of increasing depth while the valve is opening, and, desirably, should be covered with an equal and opposite wedge of decreasing depth while the valve is closing. The same problem and same solution pertain to the end wall as to the side wall of the can. Our teaching is to effect the overlap as fully as practicable, as precise 12 timing will suggest and examination of a few trial runs will check. It will also occur to those skilled in the art that-imperfection or omission of the overlap will diminish in importance as the number of painting revolutions and coatings increase beyond the first ones.

(G) Example of spray coating single open end can According to our preferred method of spraying the single open end can C, nozzle N was positioned with its axis n at an angle 2 of 43 with respect to plane h, and at an angle f of 0 the axis lying in the vertical plane v. The distance 18 from the nozzle N to the plane of the can opening, FIG. 18, was about inch. The nozzle N was located about twice as high above plane h as that shown in FIGS. 18 and 19 to be about 5 inch from the top edge of can C and, correspondingly, inclined more steeply; maximum flow along line 6,'FIG. 18, still was aimed at the circular seam as shown.

The can C was about 2 inches in diameter and 4 inches long. The nozzle flowed 208 cc. of water per minute at 40 p.s.i. and gave a distribution pattern at 10. inches distance of 74.5%25.5%, H to L with a fan width between 10 inches and 10% inches. In this example the paint was sprayed at 700 p.s.i., and -140 F. The spray was turned on for 167 milliseconds while the can was rotating at 1650 r.p.m. The coating material was lacquer reduced in a 1 to 1 ratio with a suitable solvent such as MIBK (methyl-isobutyl-ketone) and xylene to a viscosity of 23 seconds measured with a Zahn No. 2 cup at 77 F. After spraying and coating, the can was released from the spraying station and continued to be rotated and rolled for about two minutes at 250 r.p.m., and low velocity air was moved through the can to remove solvent vapor during the second minute before delivery to the baking oven. In the oven the can was baked for about 6 minutes at a temperature of 300 F. Before the can was formedthe metal had been precoated to a thickness of 4 milligrams per square inch. The material which we added by spraying was 5.9 milligrams per square inch so that the total coating thickness was 6.3 milligrams per square inch. Maximum variation in thickness was measured as 1.2 milligrams per square inch.

While we have illustrated and described exemplary and preferred forms of our invention, changes and improvements will occur to those skilled in the art who understand its advantages and uses, and we do not want to be limited to the embodiments and examples specifically disclosed herein, nor in any manner inconsistent with the progress by which we have promoted the art.

What we claim is:

1. The method of coating the interior of one end surface and the inner cylindrical surface of a body having a longitudinal axis and one open end with a peripheral edge and having one circular closed end surface normal to said axis, comprising rotating said body about its said axis, projecting an airless spray fan of liquid coating material from a fixed nozzle having a central axis into said rotating body through the open end thereof, providing said fan with an asymmetrical pattern with the point of maximum flow about midway bewteen the middle of said pattern and one end thereof, aiming said fan into said body with said point of maximum flow substantially contacting the junction of said closed end and said cylindrical surface.

2. The method of claim 1 with the step of placing said fan in a chordal plane parallel with and spaced from the axis of said body and on the side of said axis which directs paint into contact with said cylindrical surface with a tangential component moving opposite the direction of movement of said surface.

3. The method of claim 2 with the axes of said nozzle and body respectively appearing to intersect at an acute angle when viewed at right angles to said fan.-

4. The method of claim 1 wherein the pattern of said fan provides the greater flow between said place of maximum fflow and one end of said pattern herein called the heavy part of the fan, and places the lesser flow between said place of maximum flow and the other end of said pattern, herein called the light part of the fan, with the step of directing the heavy part to the surface of greater area and directing the lesser part to the surface of lesser area.

5. The method of claim 4 with the step of proportioning said heavy and lesser parts to deposit coating material at uniform depth through all surface areas of the body.

6. The method of claim 5 with the step of diverting more than the proportionate share between said heavy and light parts based on relative areas to the light part when the light part is directed toward the closed end of the body and the closed end is of markedly less area than the side of the body.

7. The method of claim 1 With the steps of directing one point of minimum flow in said pattern at about the center of said closed end and directing the other point of minimum flow slightly outside the edge of the open end of said body.

References Cited UNITED STATES PATENTS 3,259,673 7/1966 Ericson 117-105.1 3,445,262 5/1969 Greek et a1 118-302 X 2,048,912 7/1936 Ziska et al 118-302 EDWARD G. WHITBY, Primary Examiner US. Cl. X.R.

29-157 C; 117-97, 105.4, 161 'UZ, 161 ZB, 161 K; 118-318; 239-601