GB2468907A

GB2468907A - An improved access door for ductwork

Info

Publication number: GB2468907A
Application number: GB0905246A
Authority: GB
Inventors: Clive James Berry
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-03-27
Filing date: 2009-03-27
Publication date: 2010-09-29
Also published as: GB0905246D0

Abstract

An access door (10) for a duct, where the body portion of the door is made of plastic. There is a framework section (20) with sidewalls (21) between the door and the duct. The door has a cavity (13) with room for insulation such as rock wool, closed cell foam or fibreglass. The framework includes one or more flanges (25) to retain insulating material around the ductwork. The door is connected to the frame with a secure and tight connection including on or more clips (17) on the door engaging a corresponding clips retainer (24) on the frame. The tightness is obtained with a sealing member (23), which can be a hollow silicone tube.

Description

AN IMPROVED ACCESS DOOR FOR DUCTWORK

Field of the Invention

The present invention relates to an access door for ductwork to facilitate inspection and maintenance of said ductwork. The door is particularly applicable for use with ventilation ductwork.

Background to the Invention

The use of ductwork to convey air and heating/cooling within a building is now widespread. Leaving aside specialised ducting used, for example, for removal of fumes from a chemical laboratory, the ducting allows a centralised heating unit to control the temperature more accurately over a larger area of a building, by linking rooms together.

Ductwork, which can have square, rectangular, flat oval or circular cross-section, is predominantly constructed from folded steel or aluminium sheets, which may be galvanised to increase resistance to corrosion. The latter property can be especially important where warm, moist air is continually passed through the ducting. To reduce heat loss through the ductwork, one or more layers of insulation can be provided.

The interconnectivity described above does lead to other problems such as facilitating the spread of fire and fumes throughout a building. Measures, well known in the art, have therefore been devised to lessen this risk. For example, temperature dependent closure means can isolate an area and cut off air flow to and from that area.

At locations along the ductwork there is often a need to install an access door enabling an operator to see inside the ductwork. Access doors can be placed virtually anywhere along the length, but are usually positioned so that particular installations within the duct can be inspected, maintained or cleaned. Amongst the installations which need such attention can be listed, smoke dampers, fire dampers, volume control dampers, constant volume dampers, silencers, air-turn vanes, filters, heaters, batteries, air handling units, heat recovery equipment, fan coil units and fans. Depending upon a particular use to which the access door is to be put then the door will be so sized either to allow a person to look through or to climb through.

In order to be usable in the United Kingdom, any access door and the ductwork of which it is a part need to comply with a number of standards. For example, the ductwork needs to be installed to pass specification DW144 leakage testing to DW143 Class A to C. Ductwork components such as access doors are generally tested and certified for resistance to leakage by independent laboratory BSRIA.

In the United States, compliance with SMACNA is required.

Prior art access doors are normally formed of similar materials to the ductwork itself and are therefore constructed of a metal such as steel, although aluminium can be used, both of which can be galvanised, and which withstand fire and heat sufficiently. Nevertheless, care needs to be taken that heat does not cause a gap to be opened due to the expansion of the metal or to its warping out of its usual configuration. Moreover, metal access doors are relatively expensive. One of the reasons for the expense is that their construction requires a considerable amount of manual labour.

It is an object of the present invention to provide an access door which addresses the above problems and provides a door which complies with relevant safety standards. It is a further option of the invention to provide an access door and framework fittable to ductwork.

Summary of the Invention

According to a first aspect of the invention there is provided a device to releasably close an aperture in ductwork, the device comprising: a first framework section comprising a base having an aperture to fit over a corresponding aperture in ductwork, the base including retaining means enabling the framework section to be seemingly secured to ductwork; side walls depending from the base to receive a door, the door having a body portion, said body portion being formed of a plastics material.

Preferably, the walls of the body portion of the door define an internal void portion. The void portion provides an insulating barrier reducing heat transfer through the door. Moreover the plastics material from which the door is formed enables, due to its resilient nature, a seal to be formed between the door and the framework. The void portion advantageously contains an insulating medium such as air, rockwool, closed cell foam, fibreglass or combination thereof.

The framework section advantageously includes one or more flanges to retain insulating material around ductwork.

The door advantageously includes one or more clips, engaging a corresponding clip receiver on the framework section, engagement of the clip and clip receiver urging the door onto sealing engagement with the framework. Further advantageously, the or each clip receiver is circumferentially offset from the or each flange. This enables the provision of a simpler mould for the framework.

The base of the framework section is conveniently curved such that the curvature of the cross-section of the base matches that of the ductwork giving a better seal and easy installation.

Advantageously the glass temperature of the plastics material in the door body is greater than 80C, preferably greater than 90C.

Preferably the side walls of the framework section are tapered to enable the framework section to be stackable so aiding transport.

The framework section is advantageously secured to ductwork by means of a snap-fit connection.

Conveniently, the framework section includes a clip engaging a corresponding clip on the door to enhance a seal between the framework and the door.

A sealing member is advantageously included between the door and the framework to reduce fluid loss from the ductwork. Said sealing member is further advantageously a hollow silicone cube.

According to a second aspect of the invention, there is provided a door to a single aperture in ductwork, the door comprising a body portion formed of a plastics material. The door is lightweight and more durable than conventional metal doors.

Preferably, the walls of the body portion define an internal void portion, said void portion being further preferably containing an insulating medium such as air, rockwool or fibreglass.

Brief Description of the Drawings

The invention is now described with reference to the accompanying drawings which show by way of example only an access door and three embodiments of a framework. In the drawings: Figure 1 illustrates a section through an access door and a first embodiment of a frame for use on rectangular ducting; Figure 2 illustrates the section through an access door and a second embodiment of a frame for use on rectangular ducting; and Figure 3 illustrates a section through an access door and a third embodiment of a frame for use on circular ducting.

Detailed Description of the Invention

Access doors are widely used features, incorporated into conventional ductwork to allow inspection of the interior of the ductwork and any devices held therein.

Conventionally, such doors are formed on metal sheeting, such as steel or aluminium which is of a grade of metal to provide resistance to the prevailing conditions within the ductwork. Moreover, because of the high thermal conductivity of the metal, insulation needs to be provided both to reduce heat loss through a door and also where the fluid within the ductwork is hot or is chilled to reduce heat transfer from the fluid to the surroundings or vice versa.

In use, the door is positioned over an aperture in the ductwork. The sealing between the door and the ductwork is provided to prevent heat/fluid escape.

Additionally, means can be provided to secure the door in position against accidental movement. Alternatively, because metal doors can be heavy then the mass of the door then prevents this inadvertently being knocked Out of position.

The present invention seeks to remove the need for a metal door thereby reducing the weight and also reducing costs and materials. In one aspect of the invention therefore there is contemplated a door formed of plastics materials. In addition to being lighter than metal, the plastics materials also have the advantage of being resilient, a feature which is of advantage on fixing a door into position and also in forming a seal.

To assist installation and housing it is contemplated that the door be usually supplied with a framework, said framework being itself secured to the ductwork and the door then sitting within the framework.

Referring initially to Figure 1, this illustrates a door for use with a frame, said frame enabling the door to be fitted to a rectangular ductwork, i.e. the ductwork presents a flat surface on which the door can be located.

The door 10 shown in Figure 1 is made of a plastics material and comprises upper and lower skins 11, 12 sealed together around their edges to enclose a central volume 13 of depth around 25mm. Alternatively, the volume can be formed from injection-moulding a mass of plastics material to the required shape. The volume 13 forms an insulating region to reduce heat transfer to or from within the ductwork. If a greater degree of insulation is required, the volume 13 can contain, or be filled with an insulating material such as rockwool, fibreglass or synthetic polymer. Rockwool for example having a density of from around 20kgm3 to l6Okgni3 can be used, although a density of from 50-70kgm3 is preferred and a density of 45kgm3 is especially preferable.

The upper surface 14 of the door extends 15 beyond the edges of volume 13, said extension 15 being bent to form a housing 15a in which a gasket 16 is retained.

The gasket 16 can be a hollow silicone tube or other type of gasket well known in the art.

A flap 17 is hingeably mounted at 17a to the extension 15 allowing the flap 17 to move in directions shown by arrows A. Each flap 17 has a catch 18 which S 7 engages a corresponding catch 24 on the frame (see below). Although the number of flaps 17 is chosen to suit the particular use, a suitable number of flaps 17 has been found to be four, but for larger doors can be eight or more.

The frame 20 has an aperture defined by the sections 21 which aperture fits about the edge of the corresponding aperture in the ductwork; the section 21 acting to limit the movement of a frame 20 seated in the duct aperture. In order to secure the frame 20 to the ductwork, the embodiment in Figure 1 has holes 22 enabling the frame 20 to be secured to the ductwork by a rivet or other fixing means known in the art. A gasket 23 ensures that a fluid-tight seal is achieved. Attachment of the gasket 23 to the frame 20 at the time of manufacturing saves the installer of the ductwork time and also lessens the materials' transport requirement.

In order to hold the door 10 in the closed position, a catch 24 is provided which engages the catch 18 on the flap 17. The resilient nature of the flap 17 and catch 18 facilitates the action of closure and opening.

As indicated above, insulation is often provided with respect to the ductwork, which insulation often takes the form of a layer of insulating material around the ductwork. The framework 20 includes a sealing flange 25, around 25mm in length, which holds such a layer in place around the framework 20 and the ductwork and creates a continuous barrier against escape of fluid. Although not required for the installation of an access door, the base portion of the framework is tapered so that framework sections can be stacked together during transit, minimising the space required for said transit.

It will be appreciated that the size of the door and the framework are chosen to suit a particular use. Typical sizes (length cm) x (width cm) are however: 200 x 125; 300 x 150; 460 x 250; 530 x 360; 635 x 430. In addition the components ideally have a glass temperature of greater than 80C to ensure that shape is retained even at higher working temperatures. In addition, flame retardant S 8 materials known in the art can be included to reduce the speed with which any plastics material used catches fire or to prevent the materials from supporting a fire.

The use of plastics materials has a number of advantages over metals. Firstly, the installation time is reduced as the amount of sealing, often a neoprene mastic.

Secondly, the use of plastics does not lead so easily to sharp edges, capable of cutting a user, being produced; the safety of the product is thereby enhanced.

Thirdly, the chemical resistance of plastics materials, particularly towards aqueous environments, is in many situations higher than that of metals, increasing the durability of the doors. Finally, the resilient nature of many plastics materials gives advantages in features which can be included, such as fastenings and seals.

Turning to Figure 2, a second embodiment of door with framework is shown, also designed to sit on rectangular ductwork as with the embodiment of Figure 1. The primary difference between the two embodiments lies in the means of attachment of the framework 30 to the ductwork. To facilitate installation, a snapfit means is provided. The base section 31 of the framework 30 has a clip 32 to engage a retaining clip 33. A gasket 34 separates the framework 30 and the ductwork and yields a fluid type seal. The clip 33 fits around and underneath the gasket 34, and a hingeably mounted clip 35 closes around the clip 32 to compress the framework and ductwork together. The gasket 34 can be attached either to the framework or the clip 33.

In Figure 3, a framework 40 suitable for use with curved ductwork is shown. The framework 40 is secured by conventional means to the ductwork through the use of holes 41 in the framework 40. The diameter of the basal section 42 of the framework 40 is designed to be complementary to that of the ductwork.

It will of course 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 within the scope of the invention.

Claims

Claims 1. A device to releasably close an aperture in ductwork, the device comprising: a first framework section comprising a base having an aperture to fit over a corresponding aperture in ductwork, the base including retaining means enabling the framework section to be seemingly secured to ductwork; side walls depending from the base to receive a door, the door having a body portion, said body portion being formed of a plastics material.
2. A device according to Claim I, wherein the walls of the body portion of the door define an internal void portion.
3. A device according to Claim 2, wherein void portion advantageously contains an insulating medium such as air, rockwool, closed cell foam, fibreglass or combination thereof.
4. A device according to any preceding Claim, wherein the framework section includes one or more flanges to retain insulating material around ductwork.
5. A device according to any preceding Claim, wherein the door includes one or more clips, engaging a corresponding clip receiver on the framework section, engagement of the clip and clip receiver urging the door onto sealing engagement with the framework.
6. A device according to Claim 5, wherein the or each clip receiver is circumferentially offset from the or each flange.
7. A device according to any preceding Claim wherein the base of the framework section is curved such that the curvature of the cross-section of the base matches that of the ductwork.
8. A device according to any preceding claim wherein the glass temperature of the plastics material in the door body is greater than 80C.
9. A device accordingly to Claim 8 wherein the glass temperature is greater than 90C.
10. A device according to any preceding claim, wherein the side walls of the framework section are tapered to enable the framework section to be stackable so aiding transport.
11. A device according to any preceding claim, wherein the framework section is secured to ductwork by means of a snap-fit connection.
12. A device according to any preceding claim, wherein the framework section includes a clip engaging a corresponding clip on the door to enhance a seal between the framework and the door.
13. A device according to any preceding member, wherein a sealing member is included between the door and the framework.
14. A device according to Claim 13, wherein the sealing member is further a hollow silicone tube.
15. A door to a single aperture in ductwork, the door comprising a body portion formed of a plastics material.
16. A door according to Claim 15, wherein the walls of the body portion defme an internal void portion.
17. A device substantially as herein described with reference to and as illustrated by the accompanying drawings.