The present invention relates to an improved closure member construction, in particular to an improved construction of a door for use in medical, radiological, laboratory, or aseptic manufacturing installations, food preparation areas or in other areas where a high degree of cleanliness is required.

Closure members such as doors which are used in such installations and areas must also comply with fire regulations. Therefore these doors must meet the required fire rating for their particular application and also may be required to be fitted with intumescent strips which, when exposed to high temperatures, expand to form a seal between the main edges of a door and its supporting door frame. Such door construction requires the use of a number of components which can result in edges, crevices and gaps which may provide areas for the collection of dirt, dust and bacteria. These edges, crevices and gaps which can be relatively narrow are very difficult to clean and thus maintain the door in sterile condition.

One particular solution which has been used is to place the constructed door into a specifically fabricated mould and then mould a covering, typically glass reinforced polyester, around the components of the door. However, this arrangement is quite expensive, is only suitable for very high cost doors, and requires the fabrication of a separate mould for each size of door being manufactured.

The object of the invention is to alleviate the disadvantages associated with the prior art.

The present invention provides an improved closure member construction comprising one or more internal closure member components and an outer covering encapsulating the internal door components, the outer covering comprising a sheet or sheets of a plastics material formed about the closure member components and welded in position about the closure member components so as not to leave any overlapping edges, crevices or gaps, the welds being provided between adjacent or contiguous edges of the sheet or sheets of plastics material. Advantageously, the closure member is provided with smoothed corners and edges to facilitate the folding and bending of the sheets of plastics material about the internal components of the closure member. Preferably, the sheet or sheets of plastics material are joined by elongate welds of the same plastics material as the sheet material.

Depending on the dimensions of the closure member, a single sheet of plastics material may be formed about the front of the closure member and welded by a single welded joint at the rear of the closure member.

Conveniently, the sheet or sheets of plastics material and weld material are selected from the group comprising acrylonitrile butadiene styrene (ABS), polyvinyl chloride (PVC), high density polyethylene (HDPE), polypropylene (PP) and a blend comprising two or more of these materials .

The present invention provides a method of constructing a closure member, including the steps of (a) assembling internal components of the closure member to form the core of the closure member;

(b) laying down a sheet or sheets of plastic material on either side of the closure member;

(c) softening the sheet or sheets of plastics materials;

(d) forming the sheet or sheet of plastics materials about the shape of the core of the closure member; and

(e) welding adjacent or contiguous edges of the sheet or sheets of plastics material with a weld material compatible with the sheets of plastics material;

whereby the closure member is encapsulated with the plastics material without leaving any overlapping edges, crevices or gaps on the surface of the closure member.

Advantageously, the method includes providing the closure member with smoothed corners and edges so as to facilitate the folding and bending of the sheets of plastics material about the core of the closure member. Conveniently, the method includes using sheets and weld material selected for the group comprising acrylonitrile butadiene styrene (ABS), polyvinyl chloride (PVC), a high density polyethylene (HDPE), a polypropylene (PP) and a blend comprising two or more of these materials.

The invention will hereinafter be more particularly described with reference to the accompanying drawings, which show by way of example only, two embodiments of an a closure member in the form of improved door construction according to the invention. In the drawings:

Figure 1 is a cross-sectional plan view of a first embodiment of the door according to the invention and of a portion of a door frame for supporting the door (the door frame not being part of the invention);

Figure 2 is a three dimensional elevation view of the door and door frame as shown in Figure 1 ;

Figure 3 is a cross-sectional plan view of a second embodiment of the door according to the invention and of a portion of a door frame (not part of the invention) for supporting the door; and

Figure 4 is a three dimensional elevation view of the door and door frame as shown in Figure 3.

Referring to the drawings and initially to Figures 1 and 2, the first embodiment of door 100 comprises a door blank 102 surrounded by a hardwood lipping 104 in which is fitted a concealed intumescent strip 106. Encapsulating those inner components of the door 100 are two sheets 1 10 of ABS, PVC, HDPE, PP or a blend thereof. The sheets 1 10 are joined in the middle of the side faces 1 12 of the door by means of a weld 1 14. The weld 1 14 is of the same material as the sheets 1 10 and it runs the entire length of the side faces 1 12 from the base of the door to its top. The base and top of the door are also covered by corresponding sized strips of ABS, PVC, HDPE, PP or a blend thereof. The overlapping edges of these strips (not shown) with the sheets 1 10 are also welded all around by a weld of the same material so as to completely encapsulate the door. The corner edges 120 of the door between the side faces 1 12 and front and rear faces are rounded so that the sheets 1 10 may be smoothly folded about the door without damaging the sheet material. The door 100 is supported by door frame 125 which includes a metal frame extruded profile 128 fixed to internal plaster boards 130 which in turn are fixed to vertical metal studding 132. A rubber seal 134 forms a seal between the door frame 125 and door 100 when it is in the closed position. The metal frame extruded profile 128 may be covered with a timber facing or a covering material complementary with the covering material on the door 100.

The second embodiment of door 200 according to the invention is shown in Figures 3 and 4. Like parts in embodiments 100 and 200 are given like numerals. The main difference between the two embodiments is that the door 200 includes two sheets of lead 215 extending across the full area of the door 200 at both sides making the door a complete lead lined door, located between the door blank 102 and MDF sheeting 217. The door 200 is suitable for use in an x-ray or radiological department. The construction of a lead lined door is not unique, except that it is covered with sheets of material selected from the group comprising acrylonitrile butadiene styrene (ABS), polyvinyl chloride (PVC), high density polyethylene (HDPE), polypropylene (PP) and a blend comprising two or more of these materials in accordance with the invention.

Using the invention, it is possible to provide a completely encapsulated door at a considerably lower cost than possible with the prior art. The dimensions shown in the drawings are only exemplary and do not limit the sizes of the doors, or relative sizes of components of the doors, made in accordance with the invention.

It will of course be appreciated that the constructions used and method of the invention may be used in the construction of other closure members such as windows, shutters and barriers.

It also is to be understood that the invention is not limited to the specific details described herein which are given by way of example only and that various modifications and alterations are possible without departing from the scope of the invention as defined in the appended claims.