THERMO-INSULATING PANEL

Abstract: The panel comprises at least two layers of material (1) separated with a gap (2) and tightly closed at the panel's edges. The adjoining material layer (1) surfaces are covered with the coating (3) made of gastight material of a high reflectivity coefficient. The material layers (1) are fixed relative to each other by means of distancing units, each of which possesses a bearing element (4) and two complexes of mutually embedded shells (5, 6, 7, 8). The shells are suspended on the ends of the bearing element (4) and relative to each other by tension strings (9), each of which is wound around the end of the bearing element (4), the edge of the inner shell (5) and consecutively through the bottom of the smaller shell (6) and the edge of the larger shell (7) of the complex, while the ends are fixed to the outer shell (8). The panel is equipped with the gas evacuation pipe (10), tightly fastened to the coating (3), leading through the material layer (1) to the outside and ending with the cutting-off element (11). In the gap (2) between the material layers (1) a high vacuum is obtained.

Description: Description Thermo-insulating panel Field of the invention The subject of the invention is a flat, thermo-insulating panel of a very low heat pene¬ tration coefficient. Its primary fields of application are building, both housing and in¬ dustry, power industry and cold stores engineering. The panel solution can be also employed for thermal insulation of various technological devices, particularly stationa¬ ry and mobile isothermic tanks, and in portable equipment such as refrigerators, free¬ zers, as well as moveable and fixed iso-thermic load-carrying containers of trucks and refrigerator cars. Background of the invention There are panel solutions which are constructed of multilayer packets of materials of thermo-insulating properties, in which layers of material are not in direct contact, sepa¬ rated with air gap(s). In order to limit radiation the surfaces of material layers surroun¬ ding the air gap are covered with insulating material coatings of a high heat-reflectivity coefficient. One of such solutions is described in the Polish patent specification no PL-155 160. The material layers of the panel are set in fixed distances from one anot¬ her by the distancing unit, which comprises numerous connectors laid out on the sur¬ face. In such a solution heat is transported through air gaps by way of convection, gas medium conductivity and radiation; besides, a significant thermal flux penetrates thro¬ ugh the connector system. The highest parameters of thermal insulation are shown by those elements in which the heat transport path is cut off with a vacuum gap and whose walls are covered with highly heat reflective metal, e.g. with a silver or aluminum coating. The application of this construction principle is limited due to considerable atmospheric pressure on the walls of the vacuum gap. That is why the vacuum gap solutions known hitherto have the shape of coaxial solids of revolution, which are the most pressure-resistant. The realization of a flat, panel thermo-insulating element with a vacuum gap requires the employment of strutting distancing units, which would be placed between the walls of material layers. For the panels of practically useable dimensions, the technical difficul¬ ty lies in the fact that the total section of distancing units (realized in accordance with accepted technological solutions and ensuring the pressure transfer capacity of 100 kN/m 2 ) must constitute a significantly high percentage of the overall surface. As a re¬ sult, distancing units, for example frame work of hard foam or hard fibre glass plate, would transmit, by way of conductivity, a significant heat flux, which would radically deteriorate the thermal insulation properties of the panel and undermine the useful¬ ness of vacuum gap solution in panels. Disclosure of the invention The basic idea of the invention is based on the assumption that the construction of the distancing unit should ensure the conversion of compressive forces into tensile forces, for the purpose of which a system resembling a suspension bridge is employed. The load-bearing capacity resulting from tensile strength of tension strings (flaccid connec¬ tors) is dependent exclusively on the smallest cross-section area and is virtually inde¬ pendent of the length parameter. These conditions are in agreement with the measu¬ res necessary to reduce the conductive thermal flux through a given element: reduc¬ tion of the cross-section and lengthening of the heat transfer path. The nature of the panel solution, according to this invention, consists in the fact that each of the distancing units positioned in the gap possesses the bearing element and two complexes of mutually embedded shells. The shells are suspended on the ends of the central bearing element and relative to each other by means of tension strings. Each connector is wound around the bearing element, the edge of the inner shell and, consecutively, around the bottom of the smaller shell and around the edge of the larger shell of the complex, while its ends are fastened to the outer shell. The panel is equipped with a gas evacuation pipe, linked tightly to the coating, leading through the material layer to the outside and closed with the cutting-off element. In the gap betwe¬ en the material layers a high vacuum is obtained. In such a solution, the conversion of compressive forces into tensile forces is effected through a system of tension strings of high tensile strength and a low thermal conduc¬ tivity coefficient. The system of coaxial shells, suspended on the connectors, one em¬ bedded in the other, forces a labyrinthine heat flux through the connectors, with the flow path length increased many times when compared to the depth of the distancing unit. The massive axial bearing element of the distancing unit transfers the compres¬ sive load, but does not play any role in thermal insulation. An advantageous extension of the invention is the modeling of material layer surfaces, covered with heat reflective coating, into a regular relief which consists of surfaces convex towards the outside (between the adjoining distancing units). Such modeling ensures the purely tensile stress field in all points of the coating material, which adhe¬ res to the material layer and which is made, for instance, of polyurethane foam or fo¬ amed concrete. The distancing units may constitute point or line support elements. In the point solu¬ tion there is a rod-shaped bearing element, bowl-shaped shells and strings of high-strength fibre (esp. aramid) connectors. The bowl-shaped shells may have the side surface of any shape: parabolic, conic or cylindrical. The line distancing unit has the slat-shaped bearing element, groove-like shells and their connectors may have the form of a high-strength fibre, a fibre net, foil or a fibre net sealed in foil. In each distancing unit the shells may consist of two separate, cylindrical contactless comple¬ xes, they may also be tucked into each other telescopically at both ends of the unit, which doubles the heat flow path. In order to reduce the harmful heat exchange between elements of distancing units, bearing elements, shells and connectors may be covered with the coating of highly infrared radiation-reflective material Another extension of the invention consists in the employment of antiradiation screen, positioned in the central plane of the gap. The installation of the screen, comprising the packet of metallized foils, connected pointwise with microgaps between the foils, leads to a significant reduction of heat exchange which occurs through infrared radia¬ tion. Further development of the invention concerns a unique gap closure solution at the periphery of the panel and the panels' contact junction construction which endows it with thermal insulation properties approximating those occurring in the central plane of panel interior. The margins consist of two extruded sections, double- and triple-pointed one, each tightly fastened with one of its arms to the edge of the material layer. The remaining arms form a labirynth consisting of a U-trough of the triple-pointed slat and the second arm of the double-pointed slat, inserted in the former in the axis of symme¬ try. The arms are suspended on the bearing foil, which is tightly fastened to the outer surfaces of the U-trough arms. The surfaces of double-pointed slats, triple-pointed slats and the bearing foil have the coating of a high reflectivity coefficient. The panels' junction possesses two sealing tapes whose shapes correspond to the shape of the space between the margins of the two panels which are in contact: one tape seals the space between the outer arms of the U-trough, the other - between the corners of do- uble-pointed slats. The tape sealing the comers of the double-pointed slats has a gas evacuation pipe ending with the cutting-off element. Into the gap of the panel the getter is introduced, which absorbs the residue gas re¬ maining after the air is sucked off during the assembly, and permeating, by way of dif¬ fusion, through the coating into the gap during the many years of operation. It is bene¬ ficial for the replaceable getter to have the form of a removable elastic, linear porous agent, inserted into the gap through the gas evacuation pipe, due to which its repla¬ cement is possible. The second solution which takes advantage of the general invention idea presented at the outset is that of a panel whose distancing unit consists of meshed cogs (half-co¬ lumns) and niches, occurring on both the adjoining material layer surfaces. The mate¬ rial layers are separated with the gap by means of a stressed tension string, zigzag¬ ging and fixed between cog tips of both material layers. The connector has the form of a high-strength (esp. aramid) fibre, foil or a fibre net sealed in foil. Besides the panel is equipped with a gas evacuation pipe, fastened tightly to the coating, leading thro¬ ugh the material layer to the outside and closed with a cutting-off element, in the gap between the material layers a high vacuum is obtained. In such a realization, the cog-reliefed walls of material layers must be suitably rigid and deformation resistant, as cog tips play the role of support pillars(half-columns). The pattern of cogs and niches of material layers may be point-based or linear. In the point solution, cog tips mark out a plane with a chessboard-display system of points. With the linear support of material layers cog tips mark out a plane with the system of parallel lines. It is beneficial to use as a tension string the foil covered on both sides with the coating of material of a high reflectivity coefficient, which also serves the function of antira¬ diation screen. Further development of the panel consists in a unique construction of the periphery, adapted to the full-surface glued contact with the adjoining panel. At the panel perip¬ hery there is an overlap made of a material layer which ends with a niche, and has the surface which is concave relative to the central plane. The tension strip, made of foil, is tightly fastened to the front surface of the overlap. The invention offers the solution whose method of construction is more complex than solutions known hitherto, and requires a higher technology level, but the obtained in¬ sulation increase effect is incommensurably high. The panel version with shell distan- cing units, which takes advantage of all rationalizations of the invention, allows the heat penetration virtual coefficient to approximate λ=0,0002 W/m/K, whereas the sculptured, integral version - λ=0,0005 W/m/K, which are the values several dozen times lower than the parameters of the most effective insulation materials known so far. Brief description of the drawings The full understanding of the nature of the invention will be made possible by the de¬ scription of model realizations of two panels visualized in the figures. Figure 1 shows the cross-section of the first panel with its shell distancing units, Figure 2 - the axial section through the distancing unit in schematic realization, Figure 3 - the cross-sec¬ tion through the panel edge junction zone, while Figure 4 - the cross-section through the jointed complex of panels in the second realization, with cogged material layers. Modes of carrying out the invention The panel shown in Figure 1 possesses two material layers 1, placed at a distance from each other which constitutes the gap 2. Each of the material layers 1 , which is made of high-strength thermoplastic PET foil, is covered with rigid polyurethane foam coating 3, 0.5 mm thick, laminated on both sides with aluminum, inox or metallic glass foil. The polyurethane foam, apart from its high thermal insulation, is also characteri¬ zed by strong adhesion to metal foil and low polymerization temperature from the liqu¬ id state. The coating 3 has the surface regularly reliefed with surfaces which are con¬ cave towards the outside of the material layer 1 , with the positions of reliefs determi¬ ned by the positioning of distancing units. For the making of foil relief the partial vacu¬ um thermoplastic stampling method is the most beneficial, while for the sheet metal coating solution, pressure stamping is necessary. Each distancing unit consists of a bearing element 4, two complexes comprising at le¬ ast three shells: the inner shell 5, the smaller shell 6, the larger one 7, and the outer shell 8, as well as the tension strings 9. In the three-shell complex the inner shell 5 is simultaneously the smaller shell 6. The bowl-shaped shells 5, 6, 7, 8 are made of plas¬ tic, metal or glass, and enclose each other contactlessly, suspended on high-strength aramid fibres of kevlar or PBO type, which constitute the bearing element 9. The fibres are wound around the tip of the bearing element 4, and then through the consecutive shells to the outside. The wound fibre forms a zigzag line consisting of sections of al¬ ternating tangency with outer surface halves of consecutive shells and the linking con¬ tactless sections, which run between each tip zone of the smaller shell 6 and the edge of the larger shell 7. The ends of the fibres are glued or bighted to the outer shell 8. The path of the fibre is shown clearly on Fig. 2, which, in addition, illustrates the leng¬ thened path of the thermal flux "s", the forces compressing the particular shells (dar¬ kened arrows) and the tensile forces (arrows with white arrow-heads). All the elements of distancing units are covered with a thin layer of highly thermally reflective metal. Material layers 1 are wrapped with extemal screening layers 25, made of hard plastic or sheet metal. The gas evacuation pipe 10 is tightly fastened to the coating 3 of one material layer 1 , through which it leads outside, where it ends with the clamp-shaped cutting-off element 11. The gas evacuation pipe 10 with the cutting-off element 11 enables the sucking-off of the air and obtaining the vacuum in the gap 2 after the as¬ sembly, and additionally allows the operating control and vacuum improvement. Thro¬ ugh the gas evacuation pipe 10 an elastic, porous bar 26, saturated with powder get¬ ter: silica gel, zeolite, activated carbon, barium alloy, etc. is inserted in the gap 2. In the central plane i-l of the gap 2 an antiradiation screen 12 is situated, suspended on ultrathin polymer fibres 13; it is made of a packet of several dozen, contactless sheets of metallized foil, 3-5 mm thick, sewn through with very thin polymer fibres and welded or glued. On the margins of the panel the gap 2 is closed with a unit composed of two deep¬ ly-extruded sections: one double-pointed 14 and one triple-pointed 15, and of the bea¬ ring foil 18. The slats 14 and 15, made of plastic, are hermetically glued or seam wel¬ ded with one arm to the edges of the material layer 1. The remaining arms of the slats 14 and 15 together form a labyrinth: two arms of the triple-pointed slat form the U -shaped trough 16, while the second arm 17 of the double-pointed slat 14 is intro¬ duced in the axis of symmetry into the U -trough 16. A strip of thin, high-strength Mylar bearing foil 18, metallized on both sides, or inox foil or strip of metallic glass, is glued or seam welded tightly with its edges to the outer surfaces of the arm which form part of the U -trough 16. The width of the bearing foil strip 18, corresponding to the distan¬ ce between the material layers 1 , is slightly smaller than the double depth of the U - trough 16. The bearing foil 18 performs the following tasks: it seals the gap 2 on the periphery, supports the distancing of periphery material layers 1 and transfers the la¬ teral atmospheric pressure. Due to its negligible depth and considerable width it stron¬ gly reduces heat conductivity transfer, while its metallized surface simultaneously con¬ stitutes a screen for radiation heat exchange between the slats 14 and 15. For the purpose of insulating larger surfaces, the junction created between the mar¬ gins of the panels which are in contact is equipped with two sealing tapes 19 and 20 or glued together. The shape of the tapes corresponds to the shape of the gaps bet¬ ween the extemal arms of the U-trough 16 and between the comers of the double-po¬ inted slats 14. The sealing tapes 19 and 20 are made of ageing-resistant silicon mic- rogum with closed pores or metallic tape. The sealing tape 20 has the gas evacuation pipe 10 pasted in, which ends with the cutting-off element 11. After the panels and seals have been pressed against each other, a vacuum pomp is connected to the gas evacuation pipe 10. The vacuum obtained in the junction causes the reduction of the thermal flux which flows through this zone, and simultaneously evokes strong pressu¬ re of the panels against each other. In the case of the need to disassemble the ther¬ mal insulation panels' screening layer, it is sufficient to allow aeration of the junction through the cutting-off element 11. Figure 4 shows the panel according to the second realization of the invention. The task of the distancing unit is taken over by the walls of material layers 1 , meshed with each other and reliefed with cogs 21 and niches 22. The material layers 1 are kept in a distance from each other, secured against the implosion by the tension string 9 which is stretched in a zigzag fashion, and alternated and fixed between neighbouring cog tips 21 of both layers. The tension string 9 is constituted by a net of kevlar or PBO fibres, covered on both sides with metallized polymer foil, which also serves as anti- radiation screen. In this realization the coating 3 of the material layer 1 is formed by a deep negative-pressure thermal-stamping method from a rigid polymer sheet cove¬ red with alluminum or inox foil, or alternatively, it is stamped from metal, esp. inox, sheets. In the solution with the coating 3, the material layer 1 ending with the niche 22 has the peripheral overlap 23 whose surface is concave relative to the central plane l-l. The tension strip 9 made of metallic or metallic glass foil is tightly glued or seam welded to the front surface 24 of the overlap 23. In the junction which is created when two panels of mirror-image overlaps 23 have been pressed and glued against each other, the thermal flux must flow through a foil strip of small cross-section area and considerable length. The panel's junction realization with the concave-surface, foil-covered and glued over¬ lap, as described above, may obviously be introduced also in the panel realization ac¬ cording to Figure 1, to replace the double- and triple-pointed slats as the periphery complex. The cases presented above do not limit the possibilities of realizing the invention, be¬ ing only illustrative examples of the basic idea of the conversion of compressive forces into tensible forces by means of the distancing units.

Claims: Caims 1. A thermo-insulating panel, constructed of a multilayer packet of materials of ther¬ mo-insulating properties, comprising at least two layers of material separated with a gap and tightly closed at the panel's periphery, and furthermore, whose adjoining material layer surfaces are covered with a coating made of gastight material of a high reflectivity coefficient and whose material layers are fixed relative to each other by means of distancing units, characterized in that the panel has distancing units conver¬ ting the compressive forces into tensile forces and each of the distancing units pos¬ sesses a bearing element (4) and two complexes of mutually embedded shells (5, 6, 7, 8), suspended on the ends and relative to each other by tension strings (9), each of which is wound around the end of the bearing element (4), the edge of the inner shell (5) and consecutively through the bottom of the smaller shell (6) and the edge of the larger shell (7) of the complex, and fixed with the ends to the outer shell (8), further¬ more, the panel being equipped with the gas evacuation pipe (10), tightly fastened to the coating (3), leading through the material layer (1) to the outside and ending with the cutting-off element (11) through which a high vacuum is obtained in the gap (2) between the material layers (1). 2. The panel in accordance with claim 1, characterized in that between the distancing units the surfaces of material layers (1) covered with the coating (3) are reiiefed with surfaces which are concave towards the outside of the material layer (1). 3. The panel in accordance with claim 1 , characterized in that the bearing element (4) has the form of a rod, the shells are bowl-like, and the tension strings (9) are made of high-strength, esp. aramid or PBO fibre. 4. The panel in accordance with claim 1 , characterized in that the bearing element (4) has the form of a slat, the shells (5, 6, 7, 8) are groove-like and the tension strings (9) are made of a high-strength, esp. aramid, fibre, a fibre-net, foil or a fibre-net sealed in foil. 5. The panel in accordance with claim 3 or 4, characterized in that the bearing ele¬ ment (4), the shells (5, 6, 7, 8) and the tension strings (9) are covered with a coating made of the material of a high reflectivity coefficient. 6. The panel in accordance with claim 1, characterized in that in the central plane (l-l) of the gap (2) the multilayer antiradiation screen (12) is installed. 7. The panel in accordance with claim 6, characterized in that the antiradiation screen (12) has the form of a packet of metallized foils, connected to each other pointwise with microgaps between the foils, and suspended between material layers (1) by me¬ ans of polymer ultrathin fibres (13). 8. The panel in accordance with claim 1, characterized in that its margins constitute two deeply extruded sections: the double-pointed (14) and the triple-pointed (15) ones, each tightly fastened with one ami to the edge of the material layer (1), and whose remaining arms form a labyrinth comprising the U- trough (16), the triple-poin¬ ted slat (15) and the second arm (17) of the double-pointed slat (14), introduced in the former in the axis of symmetry, the arms being suspended on the bearing foil (18), tightly fastened to the outer surfaces of the U-trough (16) arms. 9. The panel in accordance with claim 8, characterized in that the surfaces of doub¬ le-pointed (14) and triple-pointed slats (15) as well as the bearing foil (18) have the coating of material of a high reflectivity coefficient. 10. The panel in accordance with claim 8, characterized in that it possesses two sea¬ ling tapes (19, 20), whose shapes correspond to the shape of the space between the margins of the two panels which are in contact: one tape seals the space between the outer arms of the U -trough (16), the other - between the comers of double-pointed slats (14). 11. The panel in accordance with claim 10, characterized in that the tape (20) sealing the comers of double-pointed slats (14) has the gas evacuation pipe (10) which ends in the cutting-off element (11). 12. The panel in accordance with claim 1, characterized in that replaceable getter is introduced into the gap (2). 13. The panel in accordance with claim 12, characterized in that it possesses a repla¬ ceable elastic, linear porous agent (26), saturated with powder getter, inserted into the empty layer (2) through the gas evacuation pipe (10). 14. A thermo-insulating panel, constructed of a multilayer packet of materials of ther- mo- insulating properties, comprising at least two layers of material separated with a gap and tightly closed at the panel's periphery, and furthermore, whose adjoining material layer surfaces are covered with a coating made of gastight material of a high reflectivity coefficient and whose material layers are fixed relative to each other by means of distancing units, characterized in that the distancing unit is created by the meshed cogs (21) and niches (22) made on both the adjoining surfaces of the mate¬ rial layers (1), separated with the gap by means of a stretched tension string, zigzag¬ ging and fixed between cog tips (21) of both material layers (1), having the form of a high-strength, esp. aramid, fibre, foil or a fibre net sealed in foil, furthermore the pa¬ nel being equipped with a gas evacuation pipe (10), tightly fastened to the coating (3), leading through the material layer (1) to the outside and closed with the cutting-off element, due to which in the gap (2) between the material layers (2) a high vacuum is obtained. 15. The panel in accordance with claim 14, characterized in that the cog tips (21) mark out a plane with a chessboard-display system of points. 16. The panel in accordance with claim 14, characterized in that cog tips (21) mark out a plane with the system of parallel lines. 17. The panel in accordance with claim 15 or 16, characterized in that the foil which constitutes the tension string (9) is covered on both sides with the coating of material of a high reflectivity coefficient. 18. The panel in accordance with claim 14, characterized in that it has an overlap (23) made of the material layer (1) which ends with the niche (22), the glued or wrinkled overlap surface (23) has the surface which is concave relative to the central plane (l-l) and the foil tension strip (9) is tightly fastened to the front surface (24) of the over¬ lap (9).

Inventors: PASZKOWSKI MARIUSZ, PASZKOWSKI, MARIUSZ
Applicants: PASZKOWSKI MARIUSZ, PASZKOWSKI, MARIUSZ
Application year: 1997
Main classification: E04B1
IPC codes: B32B3, E04B1