Acoustics – Sound-modifying means – Sound absorbing panels
Reexamination Certificate
2000-04-03
2001-09-18
Nappi, Robert E. (Department: 2837)
Acoustics
Sound-modifying means
Sound absorbing panels
C181S296000, C181S285000, C428S045000, C428S138000, C052S145000, C052S742100, C052S783100
Reexamination Certificate
active
06290021
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of manufacturing a sandwich board. The invention further relates to a panel for application as a wall panel, a ceiling panel or a floor panel and to a sound insulating structure for use as a wall, a ceiling or a floor.
The invention particularly, although not exclusively, pertains to environments where space is scarce, such as in accommodations on board ships.
2. Description of the Prior Art
DE patent 34 44 992 C2 discloses a floor structure for accommodations on board ships and designed for sound insulation. According to this teaching a tile is manufactured by making out of 1 mm steel plate a shallow box with open top and pouring into this box a mixture comprising a PU based adhesive together with fillers. Once the compound has set, the tile is turned upside down and placed onto and adhered to a steel deck. Tiles made in this way are placed close together to build a floor cover layer. Where particular requirements to gas sealing prevail this floor-covering may be covered by a 0.5 mm steel plate adhered on top of the tiles and this structure may be topped by a carpet.
DE published application 27 06 969 B2 discloses a sound damping floor structure for use on ships and comprising a layer of mineral fiber material covered with a steel plating. The butt joints between sections of the steel plating are secured by fish plates arranged below the steel plating and on top of the mineral fiber material. The publication suggests adhering the fishplates to the steel platings by two-component polyurethane adhesive.
It is considered known in the art of ship building to build a sound attenuating floor structure by placing on top of a steel deck a mineral fiber wool layer, a first structural layer of steel plates, a layer of viscoelastic polyurethane, a second structural layer of steel plates and a carpet. Steel plates in the first structural layer are interconnected along the butt joints by spaced weldings for structural reasons. As part of the process of building this floor, the viscoelastic polyurethane is poured while in a viscous or fluent state on top of the first structural layer and screeded. Steel plates for the second structural layer are placed on top of the viscous layer and ballasted until the viscoelastic mass has set.
The inventor has discovered that the efficiency in terms of sound and vibration reduction capability of this floor is critically dependent on the accurate controlling of the thickness of the viscoelastic layer and on achieving full face contact between the viscoelastic layer and the steel plates of the two structural layers. However, lack of planety of the top surface of the viscous layer, unavoidable distortions of the steel plates, trapped air and the difficulty of inspecting the viscous layer while in the process of setting may give rise to difficulties during construction and imperfections in the result.
These difficulties are according to the state of the art encountered by using for the second structural layer steel plates of comparatively small formats, e.g. no more than 60×60 cm, by using heavy ballasting and by careful work. This complicates the procedure and the small formats of the steel plates of the second structural layer limits the structural rigidity provided by this floor. Furthermore, level offsets between adjacent plates require extensive filling, which has to be done using the same viscous compound as used below the second structural layer, which compound is costly and difficult to apply.
SUMMARY OF THE INVENTION
The invention, in a first aspect, provides a method of manufacturing a sandwich board, said sandwich board comprising a first sheet, a second sheet and a core, said core comprising an elastic, vibration deadening compound effectively bridging the space between and adhering together said sheets, said method comprising the steps of providing at least one through opening in said second sheet, applying a coating of compound onto at least one of said sheets, placing said first and said second sheet in overlaying, mutually spaced relationship with said coating in an intermediate position, applying a compression force onto said sheets in order to urge them together, using said opening to inspect the space between the sheets and to inspect said coating, adjusting the compression force as appropriate depending on an evaluation of the result of the inspection, and allowing said compound to set to an elastic, vibration deadening state whereby to provide said core.
According to this method at least one through opening is provided in the sheet of the second layer. A greater number of openings may be provided as appropriate. The openings permit the inspection of the space between the sheets and thus of the thickness of the viscous layer. The openings permit the escape of any trapped air. The openings further permit the injection of additional viscous mass if required. Should the inspection reveal that the space between the sheets was too wide, e.g. due to local distortions of the plates, it is easy to adjust the compression force applied on the top sheet to correct the situation. Once the viscous mass has set it adheres together the plates and the compression force may be relieved.
The method according to the invention applies to sandwich boards useful for floor coverings as well as for wall structures or ceiling structures. The sheets may comprise any kind of structural plate material, in particular plates of steel, aluminum or other metals. The sandwich board may or may not be backed by other materials also selected for sound attenuating properties, e.g. mineral fiber wool. In case no backing is used, a steel deck, a bulkhead or a ceiling plate may provide the first sheet.
The spacer means may be provided by installing a set of structural spacers, e.g. pads of wood, steel, mineral wool or other material, or the spacer means may be provided by applying a filling of viscoelastic mass and allowing it to set to form a coating on one of or both of said sheets. Pre-treatment of at least one of the sheets by applying a filling of viscoelastic mass and allowing it to set at least until assuming a viscous state prior to the step of bringing together the sheets is of particular advantage when installing the sandwich boards for wall panels or ceiling panels where a pouring in situ of a fluent mass might be difficult.
According to a preferred embodiment, the surface of the coating is textured, e.g. by pouring the viscous mass in a fluent state on to a textured foil material and placing the sheet on top. Texturing the surface of the coating provides a simple manner of controlling effectively the thickness of the coating.
According to a preferred embodiment, the filling of the viscoelastic mass is topped up subsequent to the step of bringing together the sheets by injecting additional mass in a viscous or fluent state and allowing it to set. This ensures the complete filling of the space between the sheets.
According to a preferred embodiment, injection of mass is continued until it has been observed that excess mass is being driven out past the sheet edge along the whole sheet contour.
According to a preferred embodiment, the sheets are interconnected, at least until the mass has set, by a structural component, such as a bolt, serving to secure the relative positions of the sheets. This structural component is easily introduced through an opening in the second sheet. This precaution secures the relative positions of the sheets, thus facilitating subsequent operations, such as bringing in additional ballast or adjusting the compression force since there is no danger that these operations will offset the sheet from the intended position. The additional structural component may also be utilized to apply all of or part of the compression force. E.g. a bolt could be welded to the first sheet and a nut and washer engaging the bolt could be tightened to force the second sheet closer to the first sheet. If the opening is provided in the center of the second sheet, on
Martin Edgardo San
Nappi Robert E.
Sika AG vorm. Kaspar Winkler & Co.
Vigil Thomas R.
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