GB2146401A - Ducting - Google Patents

Abstract

A flanged fitting 1, such as a right angle or 45 DEG bend or a T piece, for ducting, has flanges 2 and 3 integrally moulded in plastics material, preferably by a blow, injection or dip moulding process. The fitting 1 and flanges 2 and 3 are preferably covered with a coating 4 of glass fibre reinforced plastics material, and in order to improve the bond, the fitting 1 and flanges 2 and 3 are coated with a layer of polyvinyl chloride paint or like material prior to covering with a mat of glass fibre. <IMAGE>

Description

SPECIFICATION Ducting This invention relates to ducting, and more particularly to ducting of comparatively large diameter, e.g. for air ducting.

Ducting for air is normally made in a range of diameters from 6 inches (15cm) to 24 inches (60cm), with various standard sizes between these extremes. Such ducting is frequently made from extruded polyvinylchloride or other plastics material.

Much ducting of this kind is in use and many of the accessories, such as bends and T pieces, are not very satisfactory. Bends are often made, with considerable expenditure of labour and skill, by fitting together lengths of standard ducting with their ends cut at different angles.

However, where a good tight joint is required, resort is often had to welding flanges onto the ducting. This can be a very expensive procedure as it involves much skilled labour.

This invention has as an object an improvement in the field of extruded plastics duct work.

According to the present invention there is provided a flanged fitting for ducting in which the fitting and flanges are integrally moulded in plastic material, preferably by a blow, injection or dip moulding process.

The fittings to which the invention may be applied include, without being exclusive, right angle and 45 bends and also T pieces.

Such fittings may be moulded in a range of sizes to match up with conventional extruded ducting, which will have flanges attached thereto as required.

It is frequently required that ducting of this nature, particularly for external or exposed use, should be covered with a layer of glass fibre reinforced plastic. This is not simple to achieve with a smooth finish, such as that achieved by dip moulding, which is too smooth to provide good adhesion for the applied layer of plastics material.

It has been found that by coating the surface of the moulded article with a layer of polyvinyl chloride paint or like material, and then applying a layer or mat of glass fibre, a good bond can be achieved between the moulded article and the plastics material eventually impregnated into.the glass fibre mat. The fittings may be moulded in polyvinylchloride or other plastics materials, and naturally the paint or like material is chosen to form a good bond with the material of the basic fitting.

The invention will be further described with reference to the accompanying drawing, of which the sole figure is a sectional view of a typical flanged fitting manufactured in accordance with the teaching of the invention.

The drawing shows a moulded right angle bend fitting 1 of plastics material, such as polyvinylch bride or the like, having integrally moulded end flanges 2 and 3. The fitting 1 is shown as having bonded to the outer surface of the moulded part a protective and reinforcing coating 4 of glass-reinforced plastics material, such as a polyester resin.

The coating 4 may for example be of 600 gm/m2 chopped strand glass fibre saturated with the resin and rolled to expel all air. A fire retardant exterior coat may also form part of the coating 4, which is applied green and cured in situ. The coating 4 is of substantially even thickness over the body of the fitting 1, but in the region of the flanges 2 and 3 it is much thicker. As an example, the body and flanges may have a basic nominal thickness of 4 mm and the coating 4 may be of 2 mm nominal thickness, built up to 10 or llmm in the region of the flanges 2 and 3. In order to improve the bonding of the coating 4 to the fitting 1 and the flanges 2 and 3, the fitting 1 and flanges 2 and 3 may be coated with a layer of polyvinylchloride paint or like material prior to application of the coating 4.

Various modifications may be made within the scope of the invention.

1. A flanged fitting for ducting, in which the fitting and flanges are integrally moulded in plastics material.

2. A flanged fitting as claimed in claim 1, in which the fitting and flanges are moulded by an injection moulding process.

3. A flanged fitting as claimed in claim 1, in which the fitting and flanges are moulded by a blow moulding process.

4. A flanged fitting as claimed in claim 1, in which the fitting and flanges are moulded by a dip moulding process.

5. A flanged fitting as claimed any of in claims 1 to 4, in which the fining and flanges are covered with a layer of glass fibre reinforced plastics material.

6. A flanged fitting as claimed in claim 5, in which the fitting and flanges are coated with a layer of polyvinyl chloride paint or like material prior to covering with a mat of glass fibre, so as to provide a bond between the basic plastics material of the fitting and flanges and the reinforced plastics material.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Ducting This invention relates to ducting, and more particularly to ducting of comparatively large diameter, e.g. for air ducting. Ducting for air is normally made in a range of diameters from 6 inches (15cm) to 24 inches (60cm), with various standard sizes between these extremes. Such ducting is frequently made from extruded polyvinylchloride or other plastics material. Much ducting of this kind is in use and many of the accessories, such as bends and T pieces, are not very satisfactory. Bends are often made, with considerable expenditure of labour and skill, by fitting together lengths of standard ducting with their ends cut at different angles. However, where a good tight joint is required, resort is often had to welding flanges onto the ducting. This can be a very expensive procedure as it involves much skilled labour. This invention has as an object an improvement in the field of extruded plastics duct work. According to the present invention there is provided a flanged fitting for ducting in which the fitting and flanges are integrally moulded in plastic material, preferably by a blow, injection or dip moulding process. The fittings to which the invention may be applied include, without being exclusive, right angle and 45 bends and also T pieces. Such fittings may be moulded in a range of sizes to match up with conventional extruded ducting, which will have flanges attached thereto as required. It is frequently required that ducting of this nature, particularly for external or exposed use, should be covered with a layer of glass fibre reinforced plastic. This is not simple to achieve with a smooth finish, such as that achieved by dip moulding, which is too smooth to provide good adhesion for the applied layer of plastics material. It has been found that by coating the surface of the moulded article with a layer of polyvinyl chloride paint or like material, and then applying a layer or mat of glass fibre, a good bond can be achieved between the moulded article and the plastics material eventually impregnated into.the glass fibre mat. The fittings may be moulded in polyvinylchloride or other plastics materials, and naturally the paint or like material is chosen to form a good bond with the material of the basic fitting. The invention will be further described with reference to the accompanying drawing, of which the sole figure is a sectional view of a typical flanged fitting manufactured in accordance with the teaching of the invention. The drawing shows a moulded right angle bend fitting 1 of plastics material, such as polyvinylch bride or the like, having integrally moulded end flanges 2 and 3. The fitting 1 is shown as having bonded to the outer surface of the moulded part a protective and reinforcing coating 4 of glass-reinforced plastics material, such as a polyester resin. The coating 4 may for example be of 600 gm/m2 chopped strand glass fibre saturated with the resin and rolled to expel all air. A fire retardant exterior coat may also form part of the coating 4, which is applied green and cured in situ. The coating 4 is of substantially even thickness over the body of the fitting 1, but in the region of the flanges 2 and 3 it is much thicker. As an example, the body and flanges may have a basic nominal thickness of 4 mm and the coating 4 may be of 2 mm nominal thickness, built up to 10 or llmm in the region of the flanges 2 and 3. In order to improve the bonding of the coating 4 to the fitting 1 and the flanges 2 and 3, the fitting 1 and flanges 2 and 3 may be coated with a layer of polyvinylchloride paint or like material prior to application of the coating 4. Various modifications may be made within the scope of the invention. CLAIMS

1. A flanged fitting for ducting, in which the fitting and flanges are integrally moulded in plastics material.

2. A flanged fitting as claimed in claim 1, in which the fitting and flanges are moulded by an injection moulding process.

3. A flanged fitting as claimed in claim 1, in which the fitting and flanges are moulded by a blow moulding process.

4. A flanged fitting as claimed in claim 1, in which the fitting and flanges are moulded by a dip moulding process.

5. A flanged fitting as claimed any of in claims 1 to 4, in which the fining and flanges are covered with a layer of glass fibre reinforced plastics material.

6. A flanged fitting as claimed in claim 5, in which the fitting and flanges are coated with a layer of polyvinyl chloride paint or like material prior to covering with a mat of glass fibre, so as to provide a bond between the basic plastics material of the fitting and flanges and the reinforced plastics material.