US3431889A - Fluid distribution bar - Google Patents

Description

March 11, 1969 R. E. FRAATZ FLUID DISTRIBUTION BAR Sheet 012 Filed Sept. 27, 1965 FIG. 3

lNVENTORi ROBERT E. FRAATZ IS AGENT March 11, 1969 R. E FRAATZ 3,431,889

FLUID DI STRIBUTION BAR Filed Sept. 27, 1965 7 Sheet 3. of 2 FIG. 6 FIG. 7

PRIOR ART |NVENTOR= ROBERT E. FRAATZ Bnfi H m 10% HIS AGENT United States Patent Oflice Patented Mar, 11, 1969 3,431,889 FLUID DISTRIBUTION BAR Robert E. Fraatz, Richmond, Calif., assignor to Shell Oil Company, New York, N.Y., a corporation of Delaware Filed Sept. 27, 1965, Ser. No. 490,487 US. Cl. 118-315 5 Claims Int. Cl. B05c 5/00; B05b 7/06 ABSTRACT OF THE DISCLOSURE Apparatus for applying a fluid downwardly onto a flat surface moving relative to the apparatus. The fluid distribution means comprises a horizontal pipe having a plurality of capillary tubing means positioned in openings in the pipe and of a length substantially greater than their inside diameters.

This invention relates to a machine for applying a coating of liquid material onto flat-surfaced articles passed through a curtain of the coating material, and more particularly, relates to an improved distribution means for such a machine when the liquid coating material forming the curtain is relatively viscous.

When it was necessary to coat flat-surfaced articles, such as plywood sheets, with a coating of a relatively viscous liquid material for preservation, or other purposes, it was usually necessary to apply such a coating by brush or other hand means after the plywood forms and other structural members reached their final destinations. The reason for this was that no totally satisfactory means was available by which such a viscous coating material could be applied to plywood forms to attain a coating of uniform thickness and composition. For economic reasons, it is desirable to have the coatings as thin as possible. Some commercial means for applying such thin coatings to plywood at the mill was needed. This was especially true for coatings of two-component materials where the inherent problems are multiplied, e.g., pressures, temperatures, mixing, etc., must be controlled in combination. An example is a two-component liquid epoxy formulation which, when its components are mixed and applied in one coat, gives a self-oiling, durable plastic coating. Such a material is sold under the trade mark Shellform T. The mixing and delivery of such twocomponent coating materials to a mechanical applicator of any kind is a problem in itself, as is providing a satisfactory means to flush out such a system to prevent clogging of the flow lines upon stoppage in operation. This invention is limited to the application, or distribution means for such a system.

The requirements for such a distribution means are efliciency, economy and simplicity. In the mills, plywood is treated as it is moved along on conveyor belts. It is thus necessary that the distribution means be adapted for this type of operation. The prior art shows many fluid distributions means which are adapted for use in conjunction with conveyor belts, but which fail to pro duce a satisfactory result when applied to the distribution system described for coating plywood with a thin layer of an epoxy formulation. Two of the more pertinent patents are the patents to Florio, No. 3,138,514, issued June 23, 1964 and Wrede, No. 1,981,405, issued Nov. 20, 1934. The Florio patent describes a distribution means comprising an elongated tube formed with a plurality of spaced ports, or orifices, which can be modified to produce distinct, continuous streams of adhesive for bonding plies of sheet material. Wrede shows a two-component fluid system for applying glue to pasteboard which utilizes a distribution means comprising a pipe with cooperating nozzles. Neither patent discloses a distribution means with the structural characteristics necessary to provide a thin plywood coating of uniform thickness and composition with the liquid coating materials that are commercially desirable.

To develop a distribution means with the necessary structural characteristics, much experimentation was needed. It was found that a throughput range of from 1100-1200 grams/min. was desirable to produce a 5 mil coating on 4 x 8 ft. plywood delivered with its length parallel to the direction of the conveyor at a line speed of about 24 ft./min. A liquid coating material of the preferred type has viscosity of from 62. to 170 centipoises in a temperature range of from 140 to 110 F. In an elfort to create a curtain of such a coating material using an elongated pipe with a series of ordinary ports or orifices along the underside thereof and an operating pressure of less than p.s.i., it was found that the fluid would run along the bottom of the pipe forming several large streams of liquid coming down upon the surface to be coated, rather than a uniform series of streams as required. Going from this type of arrangement to a distribution means utilizing an elongated pipe with cooperating nozzles as shown in the patents to Florio and Wrede, it was found that these also failed to produce a satisfactory flow pattern due to unequal distribution across the length of the bar. It was necessary to create a new bar design to handle a problem with which the prior art was not faced. The new design would have to provide for increased distribution pressure across the length of the bar to provide uniform coating.

The instant invention is directed to this improved structure. This new distribution bar consists of an elongated pipe with a plurality of openings aligned along the underside thereof, to one end of which fluid is supplied from a central distribution block. To create the necessary high resistance across the length of the pipe, capillary tubing with a satisfactory ratio of length to inside diameter is inserted in each of these openings. With the use of capillary tubing, a plurality of distinct streams is assured at an operating pressure of less than 100 psi. to produce a thin coating, e.g., 5 mil, of a relatively viscous coating material. Since the pressure decreases across the length of the pipe, the spacing between openings can be decreased as the distance from the supply end increases, to maintain even distribution.

The invention will be further described with reference to the accompanying drawings wherein:

FIGURE 1 is a schematic pictorial view showing the distribution means in position over a conveyor belt for coating sheet-s of plywood;

FIGURE 2 is a plan view of the distribution means;

FIGURE 3 is a detail view of a distribution bar connection;

FIGURE 4 is a frontal view of one of the distribution bars partially in section to show details of the capillary tubing;

FIGURE 5 is a sectional view taken on the line 55 in FIGURE 4;

FIGURE 6 is a sectional view of two standard nozzles of prior design showing the possible ambulation of fluid streams; and

FIGURE 7 is a sectional view of three capillary tubes of the instant device which prevent fluid ambulation.

When applying a thin, uniform coating of a viscous liquid material in a distribution system, it is necessary that suflicient fluid discharge ports be provided so that the entire Width of the surface to be coated is adequately covered. With a less viscous coating material, this is not as important since the liquid will tend to run more readily across the surface being coated to fill in larger areas between discharge openings. With the composition of the materials to be used with the instant device, it is critical that not only a sufficient number of discharge openings be provided, but that each downcoming stream of viscous coating material be discharged from the distribution means at a specific, predetermined location so as to ensure a uniform coating at an operating pressure of less than 100 psi. FIGURE 6 shows sectional profiles of conventional fluid nozzles 6 with fluid ducts 6a in operation and demonstrates the flow characteristics which develop when an attempt is made to decrease the spacing between nozzles to provide a greater number of nozzles per unit of length as is necessary to produce a thin, uniform coating of viscous material. When the fluid starts to flow from the standard nozzle, the surface tension of the viscous liquid is such that a liquid layer creeps across the lower discharge end of the nozzle producing a viscous film 7 by which the drops 8 can ambulate away from the discharge opening toward the edges of the nozzle as shown in FIGURE 6. The stream of fluid will then flow off the edge of the nozzle rather than directly down from the discharge opening. The same process can take place at the adjacent nozzle and if the drops ambulate toward the edge of this nozzle close to the first nozzle so that surface tension dIfilWS the drops together, the streams from two adjacent nozzles can come down in a single stream away from both discharge openings as shown by dotted lines 9 in FIGURE 6. The process can be multiplied over an entire section of nozzles so that the flow from several discharge openings form a single stream, producing a coating of viscous material which is too thick in some spots While failing to cover the surface in others. If the slightest tilt exists in the supports for such a distribution means, then the process of fluid stream ambulation will be greatly magnified. This phenomenon can be combatted without altering the design by using an operating pressure which is sufliciently great enough to actually eject the liquid streams from the nozzles with such a force that ambulation will not occur. It is, however, not desirable to operate at the high pressures required because of additional costs and increased complexity in the system. Even at high pressures, uniform flow across the entire length of the bar cannot be assured.

FIGURE 7 shows how the use of capillary tubing 10 prohibits the ambulation of drops 11 of the viscous coating material and maintains steady, distinct streams from each of the discharge openings. The capillary tubes can be spaced close enough together to achieve a thin, uniform coating of viscous material across the entire width of the surface coated without having to cope with ambulation of fluid from one point on the nozzle tip to another, or from one nozzle to another. The thin walls of the capillary tubing effectively eliminate this problem ensuring a multiplicity of distinct, pre-located, uniform streams.

A schematic pictorial drawing of the distribution means of the instant case in operation is shown in FIGURE 1. To apply a two-component liquid epoxy formulation comprising components A and B, these components are supplied under pressure from liquid reservoirs 12 and 13 by means of fluid conduits 14 and 15 through valves 16 and 17, respectively, to a mixer 18 supported by a cross bar 19. Cross bar 19 is supported over the 'working area in any well known manner. Distribution means 20 is suitably supported from cross bar 19 through support means 21. The flat-surfaced article to be coated, such as plywood 22, is carried by a conveyor belt system 23, only part of which is shown, under the distribution means 20 which is centered therewith. The distribution means 20 comprises a central distribution block 24 connected to support means 21 by a bracket 25 through which passes conduit 26 with valve 27 therein which carries the viscous coating mixture from the mixer 18 into the central distribution block 24 through opening 28 therein (FIGURE 2). Block 24 has a hollow chamber 24a (shown by dotted lines in FIGURE 2) for receiving the mixture from the mixer and two outlet ports, 29 and 29a. Distribution or manifold bars 30 and 31 are elongated, horizontal pipes (one of which is shown in FIGURE 4) which are designed to fit into the outlet ports 29 and 29a, respectively, and remain fixed therein by means of rubber O-rings 32 (FIGURE 4) which fit into grooves 33 at one end of the distribution bars 30 and 31. The ends of the distribution bars 30 and 31 away from the central block 24 are sealed with caps 30a and 31a, respectively. FIGURE 2 shows the distribution bars 30 and 31 in operative position with respect to the central distribution block 24. A portion of FIGURE 2 is shown in dotted lines to illustrate one satisfactory method for connecting the distribution bars 30 and 31 to the block 24. This construction is shown in greater detail in FIGURE 3. The end of the distribution bar 30 connected to the block 2 4 has a cylindrical sleeve 34 fixed within its inside diameter which is machined to receive an elongated tube 35 attached to the block 24 by a cylindrical plug 36 which is fixed therein by Welds 37 and/or a set screw 38. A fluid passageway 39 within the plug 36 connects chamber 24a with the tube 35. To connect the distribution bar 30 to the block 24, it is only necessary to insert the bar 30 into the outlet port 29 so that sleeve 34 slides over tube 35 until the end of the bar 30 contacts the plug 36. The bars 30 and 31 are held in position frictionally by means of the O-ring 32.

In operation, the fluid flows from the supply means into the chamber 24a and then through passageway 39 into tube 35 from which it is discharged into the distribution bar for application. The structure and operation for distribution bar 31 is exactly the same as that described with respect to bar 30. As shown in FIGURE 4, a plurality of extended liquid discharge ducts 10 are formed of capillary tubing and aligned along what becomes the bottom of the distribution bar when the latter is in its operative position, parallel to the central axis thereof. The area 40 of the bar surface along which the tubes 10 are aligned may be machined to a flat surface to provide a more convenient surface for drilling the holes and installing the tubing. The relationship between the flat surface 40 and the capillary tubing 10 is shown in FIG- URE 5, which also shows the relative length of the tubing to the exterior wall of the distribution bar, or pipe 30.

In operation, components A and B of the two-component liquid epoxy formulation are supplied to mixer 18 where they are thoroughly mixed before being carried to the distribution means 20. The mixture enters chamber 24a of the central distribution block 24 where it is directed toward outlet ports 29 and 29a and distribution bars 30 and 31, respectively. The mixture enters the distribution bars and is discharged through the capillary tubing 10 in a plurality of closely spaced but distinct streams forming a uniform curtain of liquid through which the articles to be coated pass. It is the high resistance offered by each individual capillary tube which provides for the increased distribution pressure across the entire length of the distribution bars. The pressure drop across the bars is not nearly as great as it would be if standard nozzles were used.

To achieve the desired results, it is necessary that capillary tubing having a satisfactory ratio of length to inside diameter be used. This controls the resistance across the length of the bars. Thus, if it is desirable to increase the bore Within the capillary tubing, the length of the tubing has to be correspondingly increased to compensate for the decrease in resistance created by a larger fluid discharge opening so as to maintain adequate operating pressure across the bars. To illustrate the criticality of the bar design for achieving satisfactory results, the following test data has been included. Table 1 illustrates the characteristics of viscosity vs. temperature of a suitable liquid coating material, in this case Shellform T mentioned previously.

TABLE 1 Temperature F.): Viscosity (poises) 75 15.00 100 2.75 110 1.70 120 1.20 140 0.62 160 0.30

As would be expected, consumption requirements for coating plywood with a 5 mil coating vary proportionally to the line speed. For plywood sheets 4 ft. in width, about 40-60 grams/min. of coating fluid are applied for each ft./min. of line speed, e.g., 1510 grams/min. are applied in a typical operation using a plywood rate of 32 ft./min.

In the desirable application range of 110-140 F. (Table 1), tests were conducted with a spray bar A which consisted of two 24 in. long sections of in. steel pipe (ID=0.39 in.) mounted in an offset manner on a center distribution block as previously described. Holes mils in diameter were drilled on A in. centers across the bars, providing 192 fluid orifices. The results of these tests are given in Table 2.

TABLE 2 Test 011 Bar Flow viscosity pressure (g./min.) Remarks (poise) (p.s.i.)

5. 0 1, 615 Poor distribution pattern. 7. 5 1, 645 Do. 10. 5 1, 675 D0. 16. 0 2, 470 D0. 8. 0 1, 320 Do. 6. 0 l, 010 Do.

Thus, spray bar A produced an unsatisfactory spray pattern in the desired throughput range of 1100-1200 grams/min. -In fact, even at 2500 g./min., uneven distributions were observed. Bar pressures ranged from 5 to 16 p.s.i. (Table 2). It was obvious that a new bar design was needed in order to increase operating pressure and thus improve the flow distribution across the bar. Two such bars were designed, built and tested on a laboratory scale set-up. Both utilized the capillary tubing of the instant invention.

Spray bar B consisted of two sections, each 24 in. long, of in. brass pipe, schedule 40 with holes drilled on A; in. centers across the bar, providing 384 orifices total for 2 sections. Into these holes were soldered 24 gage stainless steel capillary tubing inserts in. long (5 mil wall, 22 mil OD and 12 mil ID with variance from 11 to 12.5 mil). The flow characteristics of spray bar B are given in Table 3 at an appropriate operating viscosity.

TABLE 3 Test oil viscosity Bar pressure Flow (g./min.) Remarks (poise) (p.s.i.)

69 1, 440 Good pattern. 58 1, 208 Do. 56 1, 176 Do.

To determine the efiect of non-uniform spacing of the capillary tubes, spray bar C was constructed in exactly the same way except that holes were drilled on graded centers across the two sections from a spacing of 250 mil at the center block to 125 at the ends of the sections providing 134 holes in a 2 ft. section, 56 (41.8%) on the half toward the central block, 78 (58.2%) on the outer half. The test results for spray bar C are given in Table 4.

TABLE 4 Test oil viscosity Bar pressure Flow (gJmin. Remarks (poise) (p.s.i.) for 4 it.)

36 1, 160 Good pattern. 38 1, 240 Do. 49 628 D0. 56 728 Do. 65 864 Do. 79 1, 074 Do.

With bar B (Table 3), flow patterns were excellent at 1100-1200 g./min. and bar pressures of 50-70 p.s.i. were realized. Decreasing the orifice diameter from 15 to 12 mils could only partly explain the rise in operating pressure. Principal cause is theincrease in the orifice length/diameter ratio from 5 to 30 which greatly restricts the flow, improves the exudate pattern and elirninates the mergence of streams.

Similar results were obtained on bar C (Table 4), except that as a result of the fewer number of orifices, higher head pressures were necessitated at a fluid viscosity of 1.48 to yield the desired flow rates of 1100-1200 g./min. A distribution study substantiated the theory that graded centers are necessary to offset the pressure drop across a bar. It is evident that for the test conditions, a less severe gradient of 200-125 mils would have led to a better flow pattern. In addition, the spacings between orifices used in this test appears to be excessive and hinders proper flowout of the coating on the plywood substrate.

Satisfactory results seem to be realized when the length of the tubing is 10 to times as long as its inside diameter. The inside diameter of the tubing used during the testing was 0.012 inch while the length was .375 inch giving a ratio of .032 to 1. The cross sectional area of each tube was about .00112 sq. inch while that of the horizontal pipe in. ID) was about .126 sq. inch. Thus, with 384 tubes, the ratio of total capillary tube inside diameter cross sectional area to pipe inside diameter cross sectional area was approximately 1 to 3.

What has been described is an improved distribution means for applying a thin coating of a relatively viscous material to flat-surfaced articles.

I claim as my invention:

1. In a machine for applying a viscous fluid in a continuous curtain stream onto a flat, horizontal surface moved relative to said machine, a high-pressure fluid distribution system comprising:

(a) fluid supply means;

(b) two elongated, horizontal pipes with a plurality of openings aligned along the undersides thereof;

(c) capillary tubing positioned in each of said openings and extending beyond the exterior wall of the pipes, tforming a row of high resistance fluid ducts with axes normal to the longitudinal axes of the pipes; and

(d) connecting means for attaching the fluid supply means to the horizontal pipes, said pipes being parallel and offset from one another so as not to overlap.

2. A high-pressure distribution system for viscous fluids as defined in claim 1 wherein the fluid supply means is centered between said two pipes and attached to one end of each of the pipes through said connecting means and the spacing between adjacent openings is graduated along the length of the pipes, varying from a maximum value at the ends of the pipes attached to the fluid supply means to a minimum value at the opposite ends thereof.

3. In the machine of claim 1 wherein the length of the capillary tubing positioned in each of said openings is from 10 to 100 times as long as the inside diameter of said tubing.

4. In the machine of claim 1, wherein said connecting means is disposed at one end of said'horizontal pipes and the spacing between adjacent openings in said horizontal pipes is graduated along the length of said pipes, varying from a maximum value at the end to which the fluid supply means is conected to the horizontal pipes to a minimum value at the opposite end thereof.

5. In the machine of claim 1 wherein the ratio of total cross-sectional area of the inside diameter of said capillary tubing to the cross-sectional area of the inside diameter of said pipes is approximately 1 to 3.

References Cited UNITED STATES PATENTS 2,543,013 2/1951 Glassey 118401 2,733,171 1/19'56 Ransburg 118315 X 5 3,059,610 10/1962 Mentz 118-315 X 3,256,581 6/1966 Thal et al. 11831S X WALTER A. SCHEEL, Primary Examiner.

10 ROBERT I. SMITH, Assistant Examiner.

Images