MXPA05007744A - Method and apparatus for applying a foam layer - Google Patents

Abstract

A system for applying a layer of foam comprises a first fluid supply supplying a first stream of a first fluid in a first supply line, a first flow divider splitting said first stream into primary and secondary streams, a second fluid supply supplying a second fluid in a second supply line, a second flow divider splitting said second stream into primary and secondary streams, a first mix head combining the primary stream of the first fluid with the primary stream of the second fluid, and a second mix head combining the secondary stream of the first fluid with the secondary stream of the second fluid.

Description

METHOD AND APPARATUS FOR APPLYING A FOAM LAYER The use of foam or pouring foams in manufacturing is significant and continues to increase. Polymeric foams, such as blown isocyanate, urethane- and urea-based foams in particular, are increasingly used as insulating and structural materials. These foams are rigid when cured and are commonly used with one or more additional layers of material to form a composite object having superior mechanical and / or insulating properties. Examples of foam applications include structural panels for residential construction, ship hulls, construction of refrigerator or garage doors, metal construction panels, passage chill panels, and the like.

Polymer foams typically comprise a resin and a blowing agent. This may or may not remain separate before blowing. It is common for the blowing agent to mix in one of the chemical components of the resin. When it is desired to form a foam, the components are mixed and allowed to rise at ambient pressure. The blowing agent expands and forms a gas, either as a result of a reduction in pressure, and / or as a result of a chemical reaction with the resin. Somewhat slower, the resin polymerizes in such a way that rigid bubbles are finally formed. In applications in which these foams are used it is commonly desirable to apply a substantially uniform layer of the foam along the substrate or surface. Because these foams are frothy when they occur, however, they do not flow well enough typically to level themselves. If the foam is being applied to a large area, such as a panel, it is common to provide a band, which transports the panel laterally, and an injector, which applies the foam to the moving panel. To provide a more uniform layer of foam on the panel, the injector can oscillate in a direction transverse to the direction of panel movement, moving back and forth between the edges of the panel. Since the ratio of oscillation of the injector must be a function of the speed of the band, however, it is difficult to achieve a sufficiently uniform layer in this manner at commercial speeds, and the resulting physical properties vary, within their patterns and; as a result, in the final composite panel. Figure 1 shows the zigzag pattern of the foam that is produced with this technique and illustrates the nature of the problem.

Attempts have been made to provide an injector or an applicator having multiple openings, to provide a more even foam flow towards the substrate. This has proved unsatisfactory, however, because one or more of the openings tend to clog, which tends to increase flow through the remaining openings, resulting in uneven and uncontrollable flow distribution. Therefore, it remains desirable to provide an apparatus that can provide a controlled and even distribution of foam or normal pouring foams (e.g., with water and / or pentane and / or blowing agent HFC-245) to along the surface or substrate. The desired apparatus is capable of operating in practical commercial proportions and of maintaining a constant foam distribution and performance during extended periods of use.

SUMMARY OF THE INVENTION The present invention includes a method and apparatus for applying the even and controlled foam foam distribution along a surface or substrate. The present apparatus is capable of operating in practical commercial proportions and of maintaining constant performance over extended periods of use. In one embodiment, the present invention is a foam application system comprising at least one output stream, at least one flow splitter and can be any suitable device as are known in the art., including but not limited to rotary gear flow dividers, screw driven flow splitters, spool flow splitters, and the like. In a preferred embodiment, each of at least two output streams is passed through a flow divider, and the resulting divided streams are recombined as mixed streams having desired compositions. The relative volumes of divided currents, and also of the combined currents can be controlled.

The result is that a single foam generating system (pumps, etc.) can be used to produce multiple application streams having virtually identical compositions and, if desired, identical flow rates. The flow dividers of the present invention can also be used to supply a desired pressure drop in instances.

BRIEF DESCRIPTION OF THE DRAWINGS For a more detailed understanding of the invention, reference is made to the accompanying drawings, wherein: Figure 1 illustrates a disadvantage of the prior art; and Figure 2 is a schematic representation of a system according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED MODALITIES Referring initially to Figure 1, a system constructed in accordance with a first embodiment of the invention includes a chemical supply 10, a first flow divider 20, a second flow divider 30, and a plurality of heads mixers 50. In a preferred embodiment, the present system is used in conjunction with a system of polyurethane foam, and / or polyisocyanate, and / or polyurea. As is known in the art, the chemical mixtures that form these foams typically comprise an "A side" and a "B side". A blowing agent, such as HCFC-22, HFC-134a, HFC-245Fa, hydrocarbon, water or the like, are typically included on the B side. Because the chemical components of the foam react on contact, the A side and the side B are kept separate until it is desired that foam is formed and applied. The flow dividers divide the chemical streams A and B (separately) and keep them separate before the mixing head. Therefore, the chemical supply 10 includes a first and a second supply tank 13, 14, respectively, of which the chemicals A and B flow into the first and second supply lines 12 and 14, respectively. The chemical supply 10 preferably includes pumps and controls (not shown) such that the chemicals are pumped into the supply lines 12 and 14 in a desired predetermined ratio. The first supply line 12 flows to the first flow divider 20 and the second supply line 14 flows to the second flow divider 30. Each flow divider separates the incoming fluid stream into two or more outlet streams. Accordingly, the first flow divider 20 separates the line current 12 into divided streams 32, 34, respectively. Each separate stream is directed to one of a plurality of mixing heads.

In a preferred embodiment, each mixing head receives a current from each flow divider. The chemicals supplied by the separate streams are mixed into each mixing head and flow out through an application injector 52. Since lines 12 and 14 preferably contain the chemical components in a predetermined proportion and the flow dividers are in a predetermined proportion. , 30 can be placed so that each one divides their respective currents in the same fractions, the relative volumes of the separated currents can be controlled. Thus, if the ratio of the volume of current 24 to current 22 is the same as the ratio of the volume of current 34 to current 32, currents 22 and 32 and currents 24 and 34 can be combined to form mixed streams having the same composition desired. Therefore, the present system allows the output flow of a single current to be provided as a plurality of equivalent currents. Moreover, the output volume for each mixed stream can be controlled, so it is not necessary to provide identical fluid flow rates in each mixing head 50. It will be understood that, each flow divider can divide the incoming flow stream into more than two output currents, if desired, as shown in phantom. These divided streams may be directed to additional mixing heads, also shown in phantom.

Similiarly, while Figure 2 illustrates a system with two flow dividers 20, 30, more than two flow dividers can be used in parallel to provide equal fluid flow to the multiple application injectors. In the same way, flow dividers can be provided in series. For example, the flow dividers 20, 30 can each generate two streams, which in turn are fed to four additional flow dividers later. The output of these four flow dividers can be used in four mixing heads at the time 50 (partially shown in the ghost of Figure 1). In some preferred embodiments, a recycling line may be provided to optionally recycle fluid from the outlet of at least one of the flow dividers back to the receptacle or tank containing that fluid. The flow through these recycling lines is preferably controlled each by its corresponding valve 23, 25, 33, 35. This is disadvantageous at the beginning, when the pressure in the system has not obtained its operational level, as the fluid may be recycled through the supply tank until the hot fluid and / or sufficient pressure is present in the system to provide adequate mixing in the mixing heads. In addition, each flow divider can be configured to provide a desired pressure drop. In systems where the pressure pumps available at the outlet of the chemical supply 10 are greater than desired, flow dividers 20, 30 can be used to bring the fluid pressure to a decrease to a desired level, without the need for circulate the pump and provide a fluid receptacle to maintain fluid flow. An added advantage is that the flow dividers can be used to reduce the pressure between the outlet of the chemical supply 10 and the inlets of the mixing heads 50 so that the pressure decreases along each mixing head 50 and is below a level default maximum. For example, certain blowing agents are gases under ambient conditions. These are stored at more than atmospheric pressures before being used. As mentioned above, the blowing agent is typically dissolved in one of the liquid components of the resin mixture. The pressure under the pump in the chemical supply 10 can be from 15 to 3500 psi and it is preferable for the pressure of the components of the liquid entering the mixing heads 50 to be in the range of 20 to 600 psi.

If three or more chemical sources are available (other than only A and B), then they can be fed separately to their own fluid splitters and separated into separate streams and fed to the mixing heads. While the preferred embodiments of the invention have been described herein, it will be understood that various modifications may be made without departing from the scope of the invention. For example, the number, size and type of each piece of equipment described herein, and the manner in which they are connected and configured can be modified.

Claims (14)

NOVELTY OF THE INVENTION
1. Having described the invention, it is considered as a novelty and, therefore, what is contained in the following clauses is claimed: 1. A system for applying a foam layer, comprising: a first supply of fluid supplying a first stream of a first fluid in a first fluid supply line; a first flow divider, separating said first current into primary and secondary currents; a second supply of fluid supplying a second fluid in a second supply line; a second flow divider separating said second current into primary and secondary currents; a first mixing head combining said first stream of said first fluid with said primary stream of said second fluid; and a second mixing head combining said secondary current of said first fluid with said secondary current of said second fluid.
2. 2. The system in accordance with the one mentioned in clause 1 where the foam is foamed foam.
3. 3. The system according to that mentioned in clause 1, subsequently including at least one recycling line of at least one of said flow dividers to at least one of said fluid supplies.
4. 4. A method for applying a foamed foam layer, comprising: a) supplying first and second fluid stream; b) dividing each of said first and second stream into a desired number of divided streams; and c) combining the selected ones of said divided streams to form a plurality of mixed streams having substantially the same composition.
5. 5. The system according to that mentioned in clause 4, subsequently including the step of recycling fluid from at least one divided stream.
6. 6. The method according to that mentioned in clause 4 wherein step c) includes controlling the proportions of relative volume of said divided streams.
7. 7. The method according to that mentioned in clause 4, subsequently including the step of providing a desired pressure drop in step b).
8. 8. The method according to the one mentioned in clause 4,. subsequently including the step of ejecting each of the mixed streams through an injector.
9. 9. The method according to the one mentioned in clause 8 where there are four mixed streams and there are four nozzles.
10. 10. A method for applying a foamed foam layer, comprising: a) providing first and second fluid streams; b) dividing each of said first and second fluid stream into a desired number of divided streams; c) combining the selected ones of said divided current; and d) ejecting each of the mixed streams through an injector.
11. 11. The system according to the one mentioned in clause 10, subsequently including the step of recycling fluid of at least one divided stream.
12. 12. The method according to that mentioned in clause 10, wherein step c) includes controlling the relative volume proportions of said streams "divided to form a plurality of mixed streams, each stream mixed having a desired composition.
13. 13. The method according to that mentioned in clause 10, subsequently including the step of providing a desired pressure drop in step b).
14. 14. The method according to the one mentioned in clause 10 where there are four mixed streams and there are four injectors.