Patent Application
20110079338
The present invention relates to a gas-permeable sandwich panel provided with outer surface porous stuff on one or both sides, and a honeycomb structure body at the centre thereof, in which cells of a honeycomb are filled with phenol resin foam of a linked-cellular structure.
Sandwich panels with a honeycomb structure body at the centre thereof are used for walls and floors in airplanes, railway-vehicles and houses. Among the uses of sandwich panels, sound barrier material and sound absorbing material are important.
In this specification, a sandwich panel for sound barrier material is supposed as such provided with gas barrier layers on both sides and a piece of honeycomb at the centre thereof, regardless of cells of the honeycomb being filled up or vacant. A sound absorbing material is supposed as such provided with gas permeable stuff at least on one side thereof, having cells of the honeycomb being filled up with porous material for attenuating sounds which make incidence through the gas permeable stuff. However, it is not certain, from person to person, whether a sandwich panel is called as a sound barrier material or a sound absorbing material.
Prior-art documents which may have some relationship with the present invention are raised below and explained briefly. The patent document 1 presents an example in which cells of a honeycomb are filled up with some filler material. It discloses a structure body in which a honeycomb 2 and a sheet-like filler material 1 have the same heights and widths.
The reason is that the six-sided cell walls located in the outer edge area of the honeycomb become opened when the cell walls are cut out, and the filler material can not be stably held there. When one wishes to produce a sandwich panel using the honeycomb structure body mentioned above, cutting the honeycomb structure body to fit the surface material is necessary. However, if the honeycomb and the filler material have the same dimensions, it can not be avoided the filler material from dropping off out of the outer edge area of the honeycomb due to above-mentioned reason.
Empty cells produced by the filler material that drops off deteriorate the barrier capabilities against sound and heat expected to the filler material, and damage the commodity value of the sandwich panel. Further, the filler material that have dropped off from the cells have to go to waste.
To prevent the filler material from dropping off, it may be possible to fix the filler material to the honeycomb with an adhesive agent. However, the adhesive agent will cause increase in cost and weight, besides work load, and in addition, it will cause to deteriorate the barrier capabilities against sound and heat of the sandwich panel.
The patent document 2 discloses another invention, titled “Method of producing sound absorbing panel.” The described sound absorbing panel consists of a piece of honeycomb with empty cells, having a mesh layer over a perforated metal plate on each side of the honeycomb with a very thin film-like adhesive agent of thermosetting resin. However, the described empty cells differs from the definition of a sound absorbing panel.
The patent document 3 discloses an invention titled “Method of producing panel-like core stuff.” There are described that a foam material is inserted into cells of a honeycomb with pressure, that an adhesive agent is applied to inner surface of the cells by dipping or spraying, and so on. However, no special precaution in application of the adhesive agent not to damage the gas permeability of the surface material is seen. In a drawing (
The patent document 4 discloses a utility model titled “Sandwich panel,” in which a foam sheet having a thickness smaller than the height of a honeycomb is inserted into the cells of the honeycomb to the half depth of the cells. There are described that adhesion between the honeycomb and the surface materials is made at the end of the honeycomb, that the foam material can be melt by the adhesive agent, if the end surface of the foam material (polyurethane foam) comes to the level of the end surface of the honeycomb, and that unevenness of the surface material can be made in that case. However, no special precaution in application of the adhesive agent not to damage the gas permeability of the surface material is seen.
Problems to be solved by the present invention, in producing a gas permeable sandwich panel provided with outer surface porous stuff on one or both sides, and a honeycomb structure body at the centre thereof, in which cells of a honeycomb are filled with phenol resin foam of a linked-cellular structure, are an effective measure to prevent dropping off of the filler material from the cells located in the outer edge area of the honeycomb (the first problem), and a method of applying the adhesive agent not to damage the permeability of the foam material and surface porous stuff (the second problem).
The first problem can be solved by selecting the height and width of the sheet-like foam material larger than those of the honeycomb, so that the honeycomb is surrounded by the edges of the sheet-like foam when it is pressed into the cells of the honeycomb (claim 1).
The honeycomb can be made of paper, metal, plastics, ceramics and others, and the filler material can be chosen from hard foams of phenol resin, polyurethane, polystyrene, and other plastics. A hard foam of phenol resin with a linked-cellular structure, which exhibits a superior absorbing abilities to water and sounds, is particularly suited. Laying the sheet-like filler material and the honeycomb together, and pressing them by a press machine, a honeycomb structure body in which the filler material is filled in the cells of the honeycomb is produced.
The second problem can be solved by a method of producing a sandwich panel including the steps of applying a liquid adhesive agent of a specified viscosity to a narrow band at the tips of the cell walls directing one side of the honeycomb, pushing the porous surface material against the tips of the cell walls, pressing the water-absorbing foam material into the cells of the honeycomb, from the other side of the cell where the adhesive agent has been applied, until it comes to contact with the adhesive agent, so that the foam material absorbs water from the adhesive agent to accelerate hardening (Claim 6).
Applying the adhesive agent all over the surface of the foam material or surface material should be avoided. An alternative way is to limit the amount and spot of applying the adhesive agent, not to damage their permeability. Adhesion between the honeycomb and the surface material should be made in the limited spots where the tips of the cell walls make contact with the surface material.
It is necessary to remove water from the adhesive agent to make it harden. However, evaporation of water in the sandwich panel is slow because it is a closed space, and hardening of the adhesive agent is time consuming. So, the supreme water-absorbing ability of the phenol resin foam is utilized in the present invention, by applying the adhesive agent only to the tips of the cell walls of the honeycomb, pressing the surface material against there, inserting the water-absorbing foam into the cells of the honeycomb by pressing it in the other side thereof where the adhesive agent has not been applied, until it comes in contact with the adhesive agent.
Then, water contained in the adhesive agent is rapidly absorbed, and hardening is accelerated. The water absorbed by the foam is evaporated gradually through the permeability of the sandwich panel.
According to Claim 1, because the sheet-like foam is given a greater plane size than that of the honeycomb, the foam is not cut apart to pieces by surrounding the edges of the honeycomb and the oneness of the foam is preserved even after it is inserted into the cells of the honeycomb.
The honeycomb structure body disclosed by Claim 1 gives a sandwich panel of good appearance by an easy processing, because the foam material is barely exposed around the honeycomb.
Various after-processing such as attaching a space filler connecting partly the surface material, putting a reinforcement for attachment of other elements, or inserting wooden plates or plastic plates around the panel to connect to the surface material, can be easily done by the softness and easy-process ability of the foam material barely exposed around the honeycomb.
According to the invention of Claim 6, damages to the permeability is kept to the least, as the quantity of the adhesive agent applied to the surface material is strictly limited,
For example, in case of a honeycomb having six-sided cell walls, the spots where the adhesive agent is applied are the tips of the cell walls and a hexagonal contour of the walls on the surface material, the area of which in total is very small.
Further, a precise positioning of the surface material on the honeycomb is attained, as the adhesive agent hardens fast enough for preventing the surface material from diverging from its right position, by absorbing the water in the adhesive agent with the phenol resin foam
The first preferred embodiment to the invention of Claim 1 is as follows:
In the honeycomb structure body, an upward end and/or a downward end of the honeycomb (2) project(s) by a certain length beyond the surface(s) of the foam (1). (Claim 2)
Using the honeycomb structure body having the projection(s) to produce a sandwich panel, it becomes possible to apply the adhesive agent only to the tip(s) of the projection(s) and to avoid putting the adhesive agent to the surface of the foam material.
The second preferred embodiment to the invention of Claim 1 is as follows:
One more sheet of phenol resin foam (1′) is included in the honeycomb structure body, and the two sheets (1, 1′) together are inserted into the cells of the honeycomb (2) from upper and bottom ends of the cells to make a room (5) of a certain depth between the two sheets in the middle of the height of the honeycomb. (Claim 3)
Because of the air room, the sound absorbing characteristic, in from low to high frequencies, of the embodied honeycomb structure body becomes improved, and a sound absorbing material for a full frequency band is realized.
The third preferred embodiment to the invention of Claim 1 is as follows:
One more honeycomb (2′) is included in the honeycomb structure body, in which the foam (1) has a thickness greater than the total height of the two honeycombs (2, 2′), and the two honeycombs are pressed into the foam from both sides thereof, leaving an intermediate foam layer (6) where no honeycomb is included. (Claim 4)
Because of the intermediate foam layer, the heat flow conducting in the honeycomb structure body is cut, and the intermediate foam layer makes itself an adiabatic layer.
The fourth preferred embodiment to the invention of Claim is as follows:
In any one of the above-mentioned honeycomb structure body, at least one of surface materials (8, 8′) adhered to both sides is gas permeable.
A preferred embodiment to the invention of Claim 6, which realizes a state in which the liquid adhesive agent is applied to the tips of cell walls in a narrow belt-like areas, further comprises the steps of:
selecting an emulsion adhesive agent for the adhesive agent,
pouring the emulsion adhesive agent into a flat vat,
dipping only the tips of the cell walls of the honeycomb there and pulling up. (Claim 7)
As it is hard to apply a low viscosity adhesive agent, which flows easily, to the tips of cell walls, one which exhibits an appropriate viscosity (and a surface tension, at the same time) is preferred. From that reason, an emulsion adhesive agent is selected in the present embodiment. It is convenient to dip the tips of the cell walls in the vat where the adhesive agent is poured, to apply it only to the tips in a narrow belt-like areas.
As the selected phenol resin foam has a low density, and has a hardness suited to be cut by the cell walls of the honeycomb, the foam is filled in the cells of honeycomb in a good condition.
Another characteristic is that a projection 4 of the honeycomb 2 is formed above the surface of the foam material 1. This projection 4 is formed by pressing in the honeycomb 2 having the height of 30 mm into the foam material 1 whose thickness is 28 mm, and stopping motion when the lower surface of the honeycomb comes to that of the foam material, leaving the projection 4 of 2 mm above the surface of the foam material 1.
The projection 4 works for a surface-guard of the foam material, and at the same time, makes it possible to apply the adhesive agent only to the tip of the projection 4, not to the surface of the surface of the foam material 1.
There can be a case, depending on the usage, where no projection is produced, by selecting the height and thickness of the honeycomb and the foam material to be equal.
By pressing in the two foam sheets into the cells of honeycomb from the upper and/or lower end, the honeycomb is surrounded by the rims of the foam sheets, each has 15 mm width, and an air room 5 having the height of 10 mm between the two foam sheets is formed in the middle of height of the honeycomb.
The reference sign 3a denotes a support which is inserted between the rims to maintain the air room 5 there. The support 3a can be formed by producing frame-like banks on top of the surface of the foam sheet in advance, or by inserting four-faced rods of the foam material in-between the foam sheets from the four sides.
Items other than that the thickness of the foam material is 50 mm, and that two honeycombs whose height is 20 mm each are used, are the same as those in the example 1. Each height of the pair of honeycombs can be 25 mm and 15 mm
In this example, the honeycomb is surrounded by the rim 3, and projections 4, 4′ of the honeycomb are formed from both surfaces of the foam material.
In the honeycomb structure body of the example 3, heat flow conducting in the body is cut by the intermediate foam layer 6, the foam material consisting the intermediate foam layer 6 makes itself an adiabatic layer. With a thicker intermediate foam layer 6, a greater adiabatic nature is attained.
The honeycombs positioned near the surfaces of the foam material can serve as surface protection.
In the honeycomb structure body, as shown in
The projection 4 can be formed on one or both surface(s) of the foam material, or no projection at all.
The sandwich panel of the example 4 was produced by:
applying a well agitated two-liquid epoxy adhesive agent 7 on the aluminium plates 8, 8′ at a rate of 300˜600 g/m2, the projections 4 are pushed against the aluminium plates 8, 8′ to adhere each other. After the adhesive agent hardened, edge parts of to panel is cut to fit the dimensions of the aluminium plates. It is easy to process the panel as the edge parts thereof are covered with rims 3.
In the examples shown above, cases in which dimensions in height and width of the foam sheet(s) are both larger than those of the honeycomb, However, if either of height and width is larger than that of the honeycomb, the same advantage can be obtained.
The honeycomb 2 can be made of paper, metal, plastics, inorganic substance, and above all, paper is preferable from the view point of weight. In this example, a paper honeycomb soaked with magnesium silicate was used. The shape of the cells is not restricted to a hexagon, but triangle, square, pentagon, circle, wavy pattern are acceptable.
Though an aluminium fibre cloth was adopted for the gas permeable surface material in this example, a glass fibre cloth, woven plastic fibre cloth, and so on will be usable.
The vat 9 is as large as it can take in a honeycomb having dimensions of 1000×1000×30 mm in height·width·thickness, and the emulsion adhesive agent poured in there has a viscosity of 45,000˜85,000 MPa·s, containing 42˜46 wt % of non-volatile components and 54˜58 wt % of moisture.
The honeycomb was immersed in the vat, and the adhesive agent was applied to the height of 1˜2 mm from the tip of the cell walls.
In
Because the thickness of the foam material is 28 mm, and the height of the honeycomb is 30 mm, an allowance of 2 mm is given, and it produces a projection above the surface of the foam material, when the honeycomb is fully pressed in the foam material. In the drawing, a reference sign 4 is assigned to the projection. The projection 4 supports the surface of the surface material where the adhesive agent is applied material, not to closely touch with the surface of the foam material, and prevent the linked-cellular of the foam material from being clogged.
For the gas barrier surface material, aluminium plate is preferable because of light weight, easy process ability, and back up effects in obtaining a self sustaining strength. For the adhesive agent 7, epoxy compounds (urethan compounds or acrylic compounds) which harden at normal temperature, are preferred. One of these adhesive agent is applied all over the surface of the aluminium plate to adhere it to the projections 4. With this treatment, corrosion prevention against moisture can be expected.
On the other hand, as mentioned above, the phenol resin foam has a strong water absorbing ability. When the foam material filled in the cell spaces comes in contact with the adhesive agent 7, a rapid absorption of water in the adhesive agent occurs, and hardening of the adhesive agent is accelerated.
| Number | Date | Country | Kind |
|---|---|---|---|
| JP 2005-167921 | Jun 2005 | JP | national |
| JP 2005-251877 | Aug 2005 | JP | national |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11792311 | Feb 2008 | US |
| Child | 12926810 | US |
