Static structures (e.g. – buildings) – With synthetic resinous component – Foam
Reexamination Certificate
2000-07-07
2002-06-11
Stephan, Beth A. (Department: 3635)
Static structures (e.g., buildings)
With synthetic resinous component
Foam
C052S309900, C052S745150, C052S784150
Reexamination Certificate
active
06401414
ABSTRACT:
The present invention relates to weather resistant panels. In particular, the present invention relates to weather resistant doors and most particularly temperature resistant doors. For ease of reference the term “panel” when used herein shall include “door”. Whilst the invention will be described with particular reference to the panel being a door, it is also applicable to other panels such as, for example, false walls, wall facias, office dividers and the like.
By “weather resistant” we mean that the panel is resistant to damage caused by climatic features such as temperature and humidity. In particular we mean damage that is caused by changes in climatic features and in particular changes in temperature. In addition, we mean damage that is caused when opposed faces of the panel are exposed to different climatic features in particular different temperatures.
Where the panel is, for example, an exterior door, the external face of the door may be exposed to high temperatures during the summer months whilst the internal face of the door is exposed to cool temperatures caused by, for example, air conditioning. In contrast, in the winter months the outer face of the door is exposed to cold temperatures whilst the inner face is exposed to warmer temperatures due to heating inside the building. The door will also be exposed to different temperatures during a 24-hour period as the ambient temperatures change or as a result of being exposed to direct sunlight and then in shade. Even where the panel is for use internally, the panel may be exposed to different temperatures during a period as heating is switched on and off, is altered over time or differs between rooms.
Damage to the panel caused by these differences in temperature and/or humidity includes crack failure on the surface of the panel, the development of curvature, known as “bowing” or other distortion of the entire surface of the panel. Distortion of a panel, such as a door, may have several severe consequences. First the appearance of the door may be marred. Secondly, the ease of the operation of the door may be affected, in particular it may become difficult to open or shut the door.
Most seriously, the air-tightness, water-tightness and sound insulation of the door may be reduced.
It is therefore desirable to provide “weather resistant” panels which are able to withstand these changes in temperature and/or humidity and which therefore have a longer useful life. Further it is advantageous if the panel exhibits an ability to insulate the face of the panel remote from a heat source from the heat. That is to say the panel reduces the transmission of heat through the panel.
Panels which are resistant to the transmission of heat have various applications. Heat resistant panels are desirable for use in domestic, industrial and commercial buildings and are required in buildings that have multiple occupancy such as hospitals, residential homes, offices and the like. These panels may be for internal or external use. Many countries set minimum safety requirements which building materials must meet before they can be used in the aforementioned situations. The ability of the panels to not only retard heat transmission but also to withstand changes in ambient temperature is particularly advantageous as the frequency at which panels have to be replaced is reduced.
Panels may be made from a variety of materials. Historically, wood has been the material of choice, either used alone or glazed to allow visibility through the panel. However, wooden panels can suffer from warping and splitting when subjected to changes in temperature. In recent years it has been desirable to replace wood as the preferred material with plastics materials which are generally cheaper and easier to handle than wood.
Panels formed from plastics material often comprise a pair of vacuum formed thermoplastics skins, attached to opposed faces of a frame, eg of wood and having a core of a filler material which may be, for example, glass fibre, foamed plastics or the like. Panels of this type are difficult to manufacture and do not overcome the disadvantages of wooden panels with regard to temperature resistance. Indeed for some plastics materials the damage caused by changes in ambient temperature can be greater than for panels made from wood. In particular, panels formed from plastic materials tend to suffer from bowing when exposed to increased temperature on one side of the panel. This is believed to be due to the different levels of expansion of the plastics skins on the “hot” and “cold” sides of the panel. Since the skins are bonded at their edges to the frame, the only way in which the different levels of thermal expansion of the skins can be absorbed is by bowing.
Further, it has been difficult to obtain panels formed from plastics material which meet the heat resistant criteria set down by the legislative bodies.
We have now discovered that the above-mentioned disadvantages can be overcome and that a panel having a vacuum formed thermoplastics skin can be formed which exhibits improved resistance to bowing and which exhibits substantial heat resistance.
Thus, according to a first aspect of the present invention there is provided a panel comprising a substantially open-cell, rigid foam core and at least one vacuum formed thermoplastic skin adhesively bonded to said foam core. The at least one skin preferably comprises vinyl chloride polymer such as PVC or, more preferably uPVC. The panel preferably comprises two skins adhesively bonded to opposing faces of the panel. More preferably the panel also includes a frame or frame members which are suitably of wood.
Without wishing to be bound by any theory, it is believed that when the opposed faces of a panel according to the invention are exposed to different temperatures, the rigidity of the core, to which the heated skin is adhesively bonded, provides a counter force to the thermal effect on the skin and inhibits the skin from expanding. It is further believed that the substantial stress which would be created in the skin due to the inability to expand fully is possibly absorbed, at least to some extent, by material flow within the skin. In any event, whether or not this theory is correct, it has been found that when the skin of the panel is exposed to changes in temperature and/or humidity, cracking, bowing and other damage caused by exposure to heat are substantially reduced over what been achieved heretofore. Further the transmission of heat through the panel is also reduced.
The foam core preferably has at least one face containing pores which when the, or each, skin is in place are open to the rear face of the skin. In this arrangement, the adhesive can percolate into and key to the surface of the foam, thereby forming a stronger bond. This serves to lock the skin to the foam.
Where a panel is faced with vacuum formed plastics skins, it is difficult to provide them with the depressed zones of moulding detail which are found in traditional panelled wooden panels. This is because in order to achieve the depressed zones it would be necessary either to use preformed foamed core parts of complicated shape or to leave space behind the depressed zones empty. Both methods are disadvantageous. The first is costly and the second results in a panel having zones of weakness and an unacceptable lack of rigidity. One method of overcoming this problem is to provide the moulding detail as raised portions in the skin. However, these are not as aesthetically pleasing as the preferred depressions and further, if these are hollow, the air inside the raised portions expands when the panel is exposed to increased temperatures and the mouldings may burst.
Therefore, according to a second aspect of the present invention there is provided a moulded panel comprising at least one vacuum formed skin, having depressed zones adhesively bonded to a foamed plastics core wherein the core comprises a substantially rigid plastics foam having frangible cell walls.
By a foam having frangible cell walls we mean that under compression the foam c
Albertelli Aldino
Steel Iain
Acell Holdings Limited
Slack Naoko
Stephan Beth A.
LandOfFree
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