Abstract: A microchannel device is provided with a plastic substrate having a microchannel formed therein. Polyelectrolyte multilayers are disposed along selected surfaces of the microchannel. The polyelectrolyte layers comprise alternating net positively charged layers and net negatively charged layers. A microchannel lid has a surface facing the microchannel. In making the microchannel device, selected surfaces of the microchannel are alternatively exposed to solutions comprising positively charged polyelectrolytes and negatively charged polyelectrolytes to form the desired number of polyelectrolyte layers.

Abstract: A mouse pad with improved self-cleaning and traction features. The mouse pad is a planar structure with a parallel top control layer and a bottom anti-skid coating. Formed on the top layer is a top control layer with a plurality of alternating, equal height, prismatic and pyramidal shapes, which provide improved cleaning and traction properties. Small troughs are formed between the adjacent shapes, which collect fine dirt and dust particles that are swept from the surface of the mouse ball during use. In one embodiment, the top control surface is made of flexible material that allows the prismatic and pyramidal shapes to bend slightly when the ball of a mechanical mouse rolls over the top surface. This bending action provides improved self-cleaning and traction features. In another embodiment, the top layer is made of transparent material. An ink layer may be applied to the bottom surface of the top layer.

Abstract: A semiconductor wafer diaphragm comprising a non-flat film coupled to a mounting lip is disclosed. The semiconductor wafer diaphragm is useful for reducing the edge fracture of semiconductor wafer die due to sagging of prior art semiconductor wafer tape after a semiconductor wafer adhered thereto is cut. The non-flat film of the semiconductor wafer diaphragm preferably has a surface of a convex shape and is either inherently sticky or has an adhesive layer applied to said surface. The semiconductor wafer diaphragm is used by mounting an uncut semiconductor wafer to the diaphragm in the ordinary way thereby collapsing the diaphragm, cutting the semiconductor wafer, thereafter restoring the diaphragm to the original expanded shape of the semiconductor wafer diaphragm, and removing the individually created die.

Abstract: A process for effectively bonding arbitrary size or shape substrates. The process incorporates vacuum pull down techniques to ensure uniform surface contact during the bonding process. The essence of the process for bonding substrates, such as glass, plastic, or alloys, etc., which have a moderate melting point with a gradual softening point curve, involves the application of an active vacuum source to evacuate interstices between the substrates while at the same time providing a positive force to hold the parts to be bonded in contact. This enables increasing the temperature of the bonding process to ensure that the softening point has been reached and small void areas are filled and come in contact with the opposing substrate. The process is most effective where at least one of the two plates or substrates contain channels or grooves that can be used to apply vacuum between the plates or substrates during the thermal bonding cycle.

Abstract: A heat dissipation arrangement for chip modules on multilayer ceramic substrates, in particular multichip modules, in which passages for a heat-conducting medium are provided in the ceramic substrate. The multilayer ceramic substrate is mounted on a metal heat sink. Thermal passages, in particular in the form of a hole pattern or array, are provided in the top layer of the multilayer ceramic substrate, in the region of the chip to be mounted. A cavity functioning as an evaporation chamber is provided in the layer of the multilayer ceramic substrate directly beneath the top layer, in the region of the chip to be mounted, and a trough-shaped recess functioning as a condenser is provided in the metal heat sink, in the region of the chip to be mounted.

Abstract: A coated textile fabric is disclosed for manufacturing an air holding device for a vehicle restraint system, including a base woven, knitted or non-woven base textile fabric having a first surface and a second surface. The base textile fabric is completely or partially coated with an adhesive polyurethane to form a first coating layer, the first coating layer being coated with a second composite coating layer. The second composite coating layer is preferably a polyurethane, a polysiloxane, and an epoxy resin which acts as a filler and adhesion promoter. A third coating layer is formed of a polymeric polyurethane material coated on the second composite layer. A method of producing the coated textile fabric is also disclosed. A heat sealing die for forming sealing beads to seal such coated textile fabrics to form air holding devices is also disclosed.

Abstract: The invention concerns a multiple-layer composite sheet and a method of manufacturing such a sheet. The composite sheet comprises a supporting sheet bonded to a “hetero sheet”. The hetero sheet consists of a heterogeneous blend of an elastic thermoplastic fundamental substance that cures semicrystalline or amorphous subsequent to processing and particles of added material distributed therein. The particles can be mixed and extruded along with the fundamental substance although they are heterogeneously bound therein. In the hetero sheet the particles of added material heterogeneously distributed therein are detached, by stretching for example, from the surrounding fundamental substance (2) and the material of the hetero sheet stands up at the many areas of detachment to create a fleecy surface. At least one hetero sheet (20) is enclosed in at least one supporting sheet (10 & 30).

Abstract: The invention relates to a manufacturing method for an absorbent structure (10) having at least two plies (P1, P2) each constituted of at least one embossed sheet of creped absorbent paper, wherein the plies (P1, P2) engage between two engraved metal cylinders (CG1, CG2) fitted with protrusions (R1, R2), driven in synchronized rotation, and mutually nesting with a play (J) between the tops of the protrusions (R1, R2) of one metal cylinder (CG1, CG2) and the opposite trough surface (F2, F1) of the engraving of the other cylinder (CG2, CG1), the method being characterized in that the play (J) is less than the depth of the cylinder engravings and larger than the sum of the thicknesses (E1, E2) of the plies (P1, P2) which were previously shaped in such a matching manner that the plies (P1, P2) are not compressed when being engaged between the nested engraved cylinders (CG1, CG2).

Abstract: An embossed multiple ply paper product having a nested latticework embossment pattern providing a cloth-like, quilted appearance and a process for embossing and bonding such multiple ply paper product. The multiple ply paper product comprises a latticework of cells composed of n rows of embossment elements nested within an interfacing latticework of cells composed of n+1 rows of embossment elements.

Abstract: The present invention relates to a method for making a shielded automobile component and the shielded automobile component itself. The component includes a composite formed of a metal sheet which includes protrusions which extend from a surface of the metal sheet and a blow-molded thermoplastic layer formed around the protrusions which fixes the blow-molded layer to the metal sheet during the molding process. The protrusions on the metal sheet define plain polygonal areas which are free of protrusions.

Abstract: A foam board, for fabrication of sandwich panels made of a face sheets bonded over each side of the foam board, has two opposed planar faces having an embossed pattern in the faces. The embossed pattern has three series of parallel linear indentations, each of the series intersecting the other two series at an angle of 60°, such as a series of interlinked equilateral triangles angularly offset from the other two series. The indentations into the surface of the foam boards are sufficiently deep and close together to provide escape paths for volatiles generated during the bonding. In this way, the face sheets may be bonded over the foam board and the escape paths vent the volatiles and prevents the development of excessive pressure between the face sheets that otherwise would interfere with the bonding.

Abstract: To produce a mechanically firm glued connection between two surface regions of surfaces to be connected, a method is provided which provides each of the surfaces with surface regions having a peak-to-valley thickness of less than 0.3 &mgr;m and the surface regions are brought together in such a way that an intermediate space, which is filled with the glue, is produced therebetween and the space has a small average thickness of less than 0.31 &mgr;m and extends over a surface area of at least 20×20 &mgr;m2. The glue is preferably brought into the intermediate space by capillary action and contacts of high quality can be achieved with this method.

Abstract: A multilayer ceramic device has top and bottom green ceramic layers machined and fired. Intermediate green ceramic layers are machined, have conductors laid down in the machined areas, are laminated, and are fired to form an enclosure layer. The areas of the layers which will be in contact with each other are coated with a bonding agent. The layers are aligned and bonded to form a structure having arbitrarily shaped, interior channels adjacent to the top and bottom layers which are not subject to detrimental nonplanarities.

Abstract: An all-woven inflatable fabric having areas of two layers and attachment points or “seams” where single layers of fabric are formed. Such single fabric layers are constructed solely through the utilization of basket weave patterns. These specific single fabric layers provide a relatively effective manner of reducing air permeability within the entire fabric article by decreasing the possibility of yarn shifting upon inflation of the inflatable fabric. Alternatively, the presence of at least a second single fabric layer area adjacent to the first and separated by a narrow double fabric layer can further reduce the possibility of yarn shifting in the first single fabric layer area. Such a fabric may be utilized in numerous and various applications wherein fabric inflation is desired or necessary. In particular, the inventive fabric may be incorporated within an airbag cushion.

Abstract: A method for crystallizing an amorphous silicon thin-film is provided, in which amorphous silicon thin-films on a large-area glass substrate for use in a TFT-LCD (TFT-Liquid Crystal Display) are crystallized uniformly and quickly by a scanning method using a linear lamp to prevent deforming of the glass substrate. The crystallization method includes the steps of forming an amorphous silicon thin-film on a glass substrate, and illuminating a linear light beam on the amorphous silicon thin-film from the upper portion of the glass substrate according to a scanning method. The crystallization method is applied to a polycrystalline silicon thin-film transistor manufacturing method including the steps of forming an amorphous silicon thin-film on a glass substrate, and crystallizing the amorphous silicon of the thin-film transistor according to a scanning method using a linear light beam.

Abstract: A composite material and method of forming such composite material is provided in which first and second layers of plastic film are laminated together and define a multiplicity of spaced apart, gas filled cavities therebetween, and a third layer of a fibrous or other suitable material is mechanically bonded to one of the first and second layers of plastic film.

Abstract: A laminated fibrous structure comprising at least two fibrous sheets and a method for manufacturing same are provided. At least one, and preferably two, of the fibrous sheets may be embossed. The sheets are movably joined together in a face-to-face relationship to form a laminated structure such that the sheets are able to move relative each other during the use of the laminated structure by a consumer, without tearing or separation of any one of the sheets comprising the laminated structure. The sheets comprising the laminated structure may be movably joined by using a bonding material, by mechanically engaging upstanding fibers created on the interfacing surfaces of the sheets, or by a combination of the bonding material and engaging the upstanding fibers.

Abstract: Decorative patterns for use on Venetian blind and wall paper, including a paper substrate layer, a stripe sandwiched layer and a paper face layer. A paper pulp is first laid into the paper substrate layer with a certain thickness. Then dry flowers or decorative papers are evenly sprayed over the paper substrate layer to form the stripe sandwiched layer which has high and low levels. Then a thinner paper pulp is laid over the stripe sandwiched layer to form the paper face layer. The paper face layer only covers the lower portions of the dry flowers or decorative papers of the stripe sandwiched layer so as to clamp the dry flowers or decorative papers. After dried, planed and pressed, a flexible cover article with solid structure and natural versatile solid pictures on one face is achieved.

Abstract: A printed circuit assembly and method of making the same facilitates the attachment of high density modules onto a printed circuit board. In one embodiment, the high density modules are attached to the printed circuit board using an adhesive having a conductive material disposed within at least one via. In an alternate embodiment, an adhesive layer including a plurality of non-conductive "gauge particles" disposed within a non-conductive adhesive is used to attach the module to the printed circuit board. When the adhesive layer is disposed between a module and a printed circuit, individual gauge particles are interposed or sandwiched at various points between the layers such that the diameters of the particles control the layer separation throughout overlapping areas of thereof, thereby permitting careful control over layer separation.

Abstract: A laminate having two or more plies. The plies are embossed, and adhesively joined together. The adhesive forms an essentially continuous network. The essentially continuous network increases the strength of adhesive, increases the strength of the laminate, and is disposed within the X-Y plane of the laminate coincident the embossments.

Abstract: The present invention is a microchannel mass exchanger having a first plurality of inner thin sheets and a second plurality of outer thin sheets. The inner thin sheets each have a solid margin around a circumference, the solid margin defining a slot through the inner thin sheet thickness. The outer thin sheets each have at least two header holes on opposite ends and when sandwiching an inner thin sheet. The outer thin sheets further have a mass exchange medium. The assembly forms a closed flow channel assembly wherein fluid enters through one of the header holes into the slot and exits through another of the header holes after contacting the mass exchange medium.

Abstract: A method of making a retroreflective marking material is provided, the method has the steps of: (a) providing an enclosed-lens retroreflective sheet having a top surface and a bottom surface and comprising a cover layer and a monolayer of retroreflective elements; (b) applying a conformance layer to the bottom surface of the retroreflective sheet; and (c) laminating a configuration member to the conformance layer thereby creating first portions and second portions in the sheet, the first portions being arranged in an upwardly contoured profile and the second portions being arranged in a lower, substantially planar position. A retroreflective article made by the method is also provided.

Abstract: In a method of forming a microchannel and/or microcavity structure by bonding together two elements (1, 2) having opposed plane surfaces of the same or different materials, one or both surfaces having open channels and/or cavities, bonding is effected by applying to one or both element surfaces (1, 2) a thin layer (3) of a solution of a material capable of fusing with and having a lower melting point than that of the material or materials of the two element surfaces (1, 2) in a solvent which substantially does not dissolve the element surface material or materials. The solvent is then removed, and the two elements (1, 2) are brought together and heated to a temperature where the dissolved material is caused to melt but not the element surface material or materials.

Abstract: A headliner for motor vehicles includes first and second sheets of material in juxtaposition to each other and adapted for positioning in a mold having two mold portions. The material of at least one of the sheets is fluid deformable with respect to another of the sheets, and is attachable to the material of the other of the sheets by the mold portions at sufficient locations to outline a potential duct between the sheets. The potential duct is adapted to receive fluid between the sheets for forming an actual duct. When fluid is received between the sheets, the material of the at least one sheet is deformed with respect to the material of the other of the sheets to define the actual duct. In one embodiment of the headliner, at least one head impact block is disposed in the duct. The headliner may also include at least one substantially air-impermeable layer disposed within the duct and attached to at least one of the the first and second sheets. Furthermore, the layer preferably includes a polymer powder.

Abstract: A sheet of paper, in particular for a sanitary paper, consists of at least one ply of absorbent, creped paper of a specific surface weight between 12-35 g/m.sup.2 evincing first and second protrusions respectively (10, 2) respectively arrayed in a first and second pattern. The first pattern is composed of pattern elements each constituted by at least one of the first protrusions (10) and is comparatively well spaced apart mutually, while the second so-called background pattern comprises the second protrusions (2) arranged in more compact manner between the pattern elements. The sheet of paper is characterized in that the pattern elements form a graphic pattern while being arrayed at a rate of at most 0.5 element/cm.sup.2 and the first protrusions (10) constituting them evince at their top a line-shaped surface with a width between 0.1-2 mm, the second protrusions (2) being arrayed at the rate of at least 30, and preferably 40, protrusions/cm.sup.2 and ensuring the essential functional features.

Abstract: A paper toweling which provides a combination of strength, bulk and absorbency while presenting an attractive appearance. Included are a single ply paper towel having areas of light and heavy embossing perforations which form diamond shaped islands of heavy embossing perforations surrounded by intersecting bands of light bosses.

Abstract: A platform is provided for the manufacture of microwave, multilayer integrated circuits and microwave, multifunction modules. The manufacturing process involves bonding fluoropolymer composite substrates into a multilayer structure using fusion bonding. The bonded multilayers, with embedded semiconductor devices, etched resistors and circuit patterns, and plated via holes form a self-contained surface mount module. Film bonding, or fusion bonding if possible, may be used to cover embedded semiconductor devices, including embedded active semiconductor devices, with one or more layers.

Abstract: A costume element having an inner layer and an at least in part transparent outer layer forming a passage therebetween, the passage having an upper opening. A fluid visible in at least a part of the passage is injected into the passage through the upper opening. A lower opening to the passage can be coupled to the upper opening by one or more tubes providing fluid communication and a pump.

Abstract: An embossed multiple ply paper product and process for producing such product displaying aesthetically pleasing decorative attributes and exhibiting functional characteristics of softness, absorbency, and drape. The decorative attributes comprise embossed patterns of indicia displaying a high quality cloth-like appearance for a softer, more quilted look. The plies are joined in a face-to-face arrangement by selective bonds which are limited to the indicia, in order to produce more permanent decorative figures that inhibit dissipation caused by compressive forces, humidity, absorption, etc.

Abstract: A ceramic packing element (500) is formed from a stack of ceramic plates (502) having parallel ribs (504) forming parallel grooves therebetween. The grooves are formed into channels by being contacted with the surface of an opposed plate. The ribs (504) may engage the end surfaces of ribs on an adjacent plate or may be interleaved with the ribs (504) of an opposed plate to form smaller channels. The plates (502) are adhered to each other by firing a stack of plates (502) in the green state or by adhering cured plates (502) by means of an inorganic adhesive such as sodium silicate. Pressure drop and cracking may be reduced, mass transfer and heat efficiencies increased by enlarging the inlets (542) to the channels and by providing perforations through the plates between the ribs (504). Elements may be preassembled into larger units before placement in a column by wrapping metal bands around an assembly of elements.

Abstract: A three layer, non-slip fabric has an upper fabric layer which is bonded through an intermediate flat plastic layer to a lower plastic layer having cup-shaped elements distributed therelong. Each cup has sidewalls and an outwardly concave end wall with one or two holes in the wall to allow the cups to deform.

Abstract: A multilayered insulating panel having improved acoustic insulating properties and mechanical strength has two outer facings and a soft synthetic foam core having cavities. The foam core with the cavities is in intimate contact with the facings. The cavities are arranged so that the gaps between the core material and the outer facings are in alternate patterns with respect to the opposing outer facings.

Abstract: Microstructured articles of the invention comprising, in order: a) a retroreflective microstructured member; b) a sealing layer melt-bonded to the microstructured member; and c) a backing member. The backing member is a fibrous web comprising a plurality of multifilament strands and is melt-bonded to the second surface of the sealing layer.

Abstract: A wood preservative wrap includes a body divided by liquid impervious grid lines into a plurality of pockets filled with wood preservative. The body is trimmable along the grid lines without compromising the containment of the wood preservative.

Abstract: A roofing membrane has a quantity of water-retaining particles fixed in the upper surface of the membrane. A fleece web affixed to the membrane surface in a quilt-like manner may provide zones of selectable size for holding the particles in place. By varying the amount of the absorber particles, the water-retaining capacity of the roofing membrane may be varied to the particular intended use, such as on a flat roof or a sloped roof.

Abstract: A laminated fibrous structure comprising at least two fibrous sheets and a method for manufacturing same are provided. At least one, and preferably two, of the fibrous sheets may be embossed. The sheets are movably joined together in a face-to-face relationship to form a laminated structure such that the sheets are able to move relative each other during the use of the laminated structure by a consumer, without tearing or separation of any one of the sheets comprising the laminated structure. The sheets comprising the laminated structure may be movably joined by using a bonding material, by mechanically engaging upstanding fibers created on the interfacing surfaces of the sheets, or by a combination of the bonding material and engaging the upstanding fibers.

Abstract: There is provided a cavity included decorative sheet having tremendously excellent design and decorative features by the cavities formed in the plane region in which colorless or colored light transmissible uneven pattern formed as the light refracts and reflects in complicated manner, by which the cavities appear to be brilliant water bubbles.

Abstract: An impact energy absorptive structure is made of usual plastic materials suitable for molding processing, and is designed to suit different degrees of impact loading anticipated in various applications. The impact energy absorptive structure is composed of a base member 11 and protruding rib members including long and short members, in which the proportion of the cross sectional area of the long rib members is between 0.3 to 0.8 of the total cross sectional area of the rib members. Other design modifications can be made readily to customize the impact resistance of the impact energy absorptive structures.

Abstract: A paper toweling which provides a combination of strength, bulk and absorbency while presenting an attractive appearance. Included are a single ply paper towel having areas of light and heavy embossing perforations which form diamond shaped islands of heavy embossing perforations surrounded by intersecting bands of light bosses.

Abstract: Redetachable, self-adhesive fastening device having a base plate, the front side of which serves for fastening and the rear side of which has a strip of an adhesive film which is adhesive on both sides and is adhesively attached in such a way that one end of the adhesive film protrudes beyond the base plate as a grip, the adhesive film being of such a kind that the adhesive bond achieved with it can be released again by pulling in the direction of the adhesive bonding plane, stretching the strip, characterized in that the rear side of the base plate has duct-like depressions in the region in which the strip of adhesive film is adhesively attached, these depressions extending at least partially beyond the region of the strip of adhesive film.

Abstract: A multilayered flexible sheet for absorbing liquids comprises a nonsegmented flexible layer comprised of woven or nonwoven materials having the capacity to absorb liquids and a segmented flexible layer of woven or nonwoven materials having the capacity to absorb liquids being tacked face-to-face to the nonsegmented layer, the segments of the segmented layer being separated by substantially straight boundaries extending across one dimension of the sheet. The multilayered sheet can be easily folded along the boundaries between the segments of the segmented layer and therefore can be used unfolded as walk on mats, wipes, absorbent pads and response pads or folded as pillows or socks for absorbing liquids.

Abstract: The disclosed gelatinous cushion comprises a gelatinous material enclosed in a membrane fixed to a support. The membrane has at least one told and the gelatinous material assumes the shape of the fold. The fold is arranged in such a way that the membrane unfolds when pressure is exerted on the cushion. Advantages: the elimination of the membrane effect due to the compression of the gelatinous material in the membrane, the improvement of wearing comfort and of dampening properties. Application in particular to the making of highly comfortably nose-pads for eyeglass frames.

Abstract: A process is disclosed for producing reinforced twin-sheet thermoformed articles comprising the steps of heating first and second sheets of thermoplastic material; forming the sheets in molds; heating a reinforcing insert of thermoplastic material; placing the heated insert on the first sheet in its mold at the location to be reinforced; pressing the second sheet into contact with the heated first sheet and the heated insert to form the insert between the sheets so that a fusion of the thermoplastic sheets and the insert takes place to produce a reinforced section of the article having a desired shape and thickness. Alternative processes are disclosed wherein a heated quantity of thermoplastic liquid material is extruded or injected between the first and second sheets within the first and second molds either by inserting the liquid material before the molds are closed or by injecting it through one of the molds.

Abstract: The component has a movable section (2) over a substrate (1), in which spacers (3) preferably made of fluorocarbon are present on the top side of the substrate and prevent the movable section from adhering to the support.

Abstract: A composite shelf in a shelf frame supports a plurality of disk drives and attenuates vibrations in the shelf. In the composite shelf, there is a double wall having an outer wall and an inner wall for supporting the disk drives mounted on the shelf. A stiffener between the inner wall and outer wall strengthens the composite shelf to reduce flexure in the composite shelf when the shelf is loaded by disk drives mounted on the shelf. A damping layer is placed between the stiffener and one of the inner wall or outer wall. This damping layer attenuates vibrations in the composite shelf so as to reduce vibrations transmitted from the composite shelf to the disk drives supported by the composite shelf. A second damping layer is placed between the stiffener and the other wall. Both damping layers attenuate vibrations in the composite shelf so as to reduce vibrations transmitted from the composite shelf to the disk drives supported by the composite shelf. A third damping layer may be placed within the stiffener.

Abstract: The present invention provides a windshield frame utilizing composite technology. More particularly, the windshield frame preferably comprises a fiber reinforced plastic molded upper frame section bonded with a structural grade adhesive to a fiber reinforced plastic molded lower frame section. According to the invention, steel reinforcements and tapping plates are bonded on or molded into the frame sections to stabilize the structure and provide hardware attachment points. Continuous carbon fibers may also be molded in the frame sections in critical high stress areas. The strength of the bonding between the frame sections is enhanced by a tongue and groove geometry along the interface. In addition, dowel pins and bushings are used to mechanically tie the frame sections together near body side attachment points.

Abstract: A ceramic packing element is formed from a stack of ceramic plates having parallel ribs forming parallel grooves therebetween. The grooves are closed into channels by the surf ace of an opposed plate. The ribs may engage the end surfaces of ribs on an adjacent space or may be interleaved with the ribs of an opposed plate to form smaller channels. The plates are adhered to each other by firing a stack of plates in the green state or wrapping film or bands around a stack of pre-fired plates. The elements may be preassembled into larger units before placement in a column by wrapping metal bands around an assembly of elements.

Abstract: Disclosed is an injection-molded hollow article having large hollow portions 1 which securely provide the strength required by the injection-molded hollow article without depending upon ribs as more solid remaining portions being unstable in position and size.A melted resin and pressurized fluid are injected under pressure into a metal mold cavity 4, a movable core 5 projected into the metal mold cavity 4 is moved and then a support portion 2 is formed at the position from which the movable core 5 is moved.The position and size of the support portion 2 can be determined by selecting the position and size of the movable core 5.

Abstract: A laminated bubble wrap packaging material is provided with has a tackifier, such as a polybutene, dispersed homogeneously throughout the packaging material. The packaging material is adherent to itself as well as and does not leave a residue. The tackifier is incorporated into the plastic material during extruding of the layers of plastic material into thin plastic films.

Abstract: An absorbent multi-layer sheet, with at least two layers each constituted of at least one embossed ply of creped absorbent paper having a specific surface weight between 10 and 40 g/m.sup.2 per ply, with an external surface forming the outer side of the multi-layer sheet and an inner surface, the inner surface of the first layer including first and second protrusions and the inner surface of the second layer including third protrusions nested between the-protrusions of the first layer, the two layers being bonded together by at least part of the protrusion tips of one layer adhesively joined to the other layer between two protrusions, is characterized in that the bonding is implemented by the first protrusions of the first layer, the second protrusions having a lesser height than the first ones and their tips being adhesive-free.