GB2561663A

GB2561663A - Door closure system and a method of manufacture thereof

Info

Publication number: GB2561663A
Application number: GB1802290.5A
Authority: GB
Inventors: Philip Barnes Matthew
Original assignee: Ralph Ellerker 1795 Ltd
Current assignee: Ralph Ellerker 1795 Ltd
Priority date: 2017-02-21
Filing date: 2018-02-13
Publication date: 2018-10-24
Also published as: GB201702784D0; GB201802290D0

Abstract

The door structure is for controlling an opening between a first environment at a first temperature and a second environment at a second, colder temperature, and includes a door formed by first and second spaced walls 3, 5 which define a cavity 7 therebetween, with air movement means 9 to cause the movement of air into and through the cavity, a sensing means to sense the temperature, relative humidity or air pressure of the first environment, and heating means for heating the air to a temperature above the dew point of the first environment, the air being introduced into the cavity from an upper portion of the structure. The sensing means may calculate the dew point temperature of the first environment. The first environment may be at an ambient or room temperature and pressure. The second environment may be chilled or refrigerated. The structure may comprise a frame formed from spaced side members, and a top member 13 having an elongate chamber 15 with a downwardly-tapered cross section, with an elongate slot 17 along its lower length through which the air is expelled into the cavity. The structure may be used in a walk-in fridge.

Description

(54) Title of the Invention: Door closure system and a method of manufacture thereof Abstract Title: Door structure for use between chilled and ambient environments (57) The door structure is for controlling an opening between a first environment at a first temperature and a second environment at a second, colder temperature, and includes a door formed by first and second spaced walls 3, 5 which define a cavity 7 therebetween, with air movement means 9 to cause the movement of air into and through the cavity, a sensing means to sense the temperature, relative humidity or air pressure of the first environment, and heating means for heating the air to a temperature above the dew point of the first environment, the air being introduced into the cavity from an upper portion of the structure. The sensing means may calculate the dew point temperature of the first environment. The first environment may be at an ambient or room temperature and pressure. The second environment may be chilled or refrigerated. The structure may comprise a frame formed from spaced side members, and a top member 13 having an elongate chamber 15 with a downwardly-tapered cross section, with an elongate slot 17 along its lower length through which the air is expelled into the cavity. The structure may be used in a walk-in fridge.

At least one drawing originally filed was informal and the print reproduced here is taken from a later filed formal copy.

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Door Closure system and a method of manufacture thereof

The invention to which this application relates is a door closure system of the type which is particularly, although not necessarily exclusively, of use to be movable between an open and closed position with respect to an environment, on one side, which is held in, for example, chilled temperatures for the storage of goods therein and, on the other side an environment which is substantially at ambient temperature.

A problem which is often experienced with openings between environments which are required to be held at different temperatures, is the need to provide a closure in the form of a door for the opening, which door is operable to move between opened and closed positions and in particular, once opened, to return to a closed condition as quickly as possible so as to be able to maintain the temperature in the cooler environment and thereby allow the maintenance of the goods in the cooler environment at the required temperature. A further problem which is experienced is the creation of condensation on the door itself which can lead to, in examples where the cooler environment is that of a chilled or refrigerated environment, the gathering of water or liquid in the vicinity of the door, creating puddles of water which can become a slip hazard.

By mounting a standard (single skin) high speed door in between two areas of differing air temperature and humidity, a barrier is formed where condensation can occur. Condensation is caused when water vapour contained within the high humidity atmosphere comes into contact with the cold surface of the door blade (the blade having been cooled by the air within the chilled ambient atmosphere).

The warm air within the high humidity atmosphere can hold more water vapour than the cold air on the opposite side of the door. When the warm air makes contact with a colder surface, it cools down and cannot retain the same amount of water vapour. The excess water vapour is released and forms condensation (water droplets) on the door blade. The condensed water droplets then leak down the blade and on to the floor below.

Typically, problematic conditions synonymous with high temperature and humidity differentials tend to be found within, for example, bakeries and food preparation factories where a high speed door has been installed to separate the warm moist air within the bakery (ambient environment) with the cold (drier) air of an adjoining chilled storage area. The relatively warm, humid air found within bakeries / food preparation factories and the cold dry air of a chilled ambient storage area provides a substantial temperature and humidity delta between the two atmospheres where condensation around the barrier is almost certain to occur.

A further reason for needing to prevent the building and pooling of condensation is that water which is allowed to settle can become particularly problematic when it is allowed to warm above 20°C. Above this temperature, bacterial germs and legionellosis can thrive, which may contaminate and cause severe illnesses.

Various high speed door closure systems exist with “conditioned air” vestibules and have been developed over the years. These doors attempt to prevent the air masses of two separate environments from mixing when the door blade is open as well as delivering warm air to the door blade surface. The primary function of these doors is to maintain temperature differentials between the two environments, thus reducing energy costs. The conditioned air is ducted horizontally through the opening at high level only, leaving the lower level of the door blade susceptible to condensation accumulation. Alternative solutions that attempt to insulate two environments do so using an insulated door blade material to increase the thermal capacity (energy required to increase the temperature of the blade) thus reducing condensation or icing (depending on application). These doors are proven ineffective due to the inherent way in which the door blade is constructed using the insulated material. (The insulated material must be joined and re-enforccd to withstand regular heavy use, therefore thermal bridging occurs at the areas where the joints are placed. Thermal bridging breaks the insulated barrier.)

It is therefore an aim of the present invention to provide an apparatus for preventing the accumulation of condensation on the surfacc(s) of a door closure system, for example, a high speed door located in between a chilled air atmosphere and a high humidity / high air temperature atmosphere that overcomes the aforementioned problems associated with the prior art.

According to a first aspect of the invention there is provided a door structure for controlling an opening between a first environment at a first temperature and a second environment at a second, colder temperature, said door structure including a door selectively movable between open and closed conditions, the door, when in the closed position, formed by a first wall forming an external surface at a first side of the opening and a second, spaced wall defining an external surface to the second side of the opening, said first and second walls defining a cavity therebetween, and air movement means are provided to cause the movement of air into and through the said cavity, characterised in that the air is introduced into the cavitv from an

J upper portion of the structure at a temperature above the dew point of the first environment.

The dew point of a particular environment is the atmospheric temperature — which varies according to pressure and humidity — below which water droplets will begin to condense and dew can form. A higher dew point indicates that there is more moisture in that environment, and measurement of the same is closely related to the humidity of the environment. Thus, in order to prevent the build-up of condensation on, for example, the first wall of the door at or adjacent the first, relatively warmer, environment, the temperature and humidity of the first environment may be assessed and the dew point calculated. Air above this temperature may then be introduced into the cavity of the door structure, thereby heating the door wall to this temperature and thus preventing the formation of condensation thereon. Such a feature is particularly advantageous over what is currently available in the prior art, as in instances whereby the relative humidity of the first environment is less than 100%, the dew point (in C) will be slightly less than the actual temperature (in °C) of that environment. Thus, in such circumstances the air introduced into the cavity will only need to be above the dew point temperature and not the absolute temperature of the first environment, thereby requiring less energy to heat the same, saving costs and being more environmentally friendly.

In one embodiment, the first environment is provided to be at an ambient or room temperature and pressure, and the second environment is provided to be a chilled or refrigerated environment.

In one embodiment, the door structure includes a frame formed from spaced side members and a top member which, in combination with a floor on which the structure is located, define the opening in which the door is positioned.

In one embodiment, the cavity extends substantially across the area of the opening.

In one embodiment, sensing means are provided to sense / measure at least the temperature and relative humidity of the first environment. Typically, said sensing means may also measure the air pressure of the first environment.

In one embodiment, the said sensing means are provided with further means by which to calculate the dew point temperature of the first environment.

In one embodiment, said sensing means are provided integrally with the door structure. In another embodiment, said sensing means can be provided independently of the door structure.

In one embodiment, heating means are provided associated with the air movement means. Typically, said heating means are provided to heat air to a temperature above the dew point of the first environment.

In one embodiment, control means are provided associated with said heating means. Typically, said control means are provided to enable temperature adjustment of said heating means. Further typically, said control means may be manually adjustable in order to permit a user to adjust the temperature of the heating means.

In one embodiment, sensing means arc provided in electrical communication with said heating means, via control means. Typically, said sensing means, upon calculation of a required dew point, can communicate such data with the control means, permitting automatic adjustment of the temperature of the heating means.

In one embodiment, air movement means draws air therein from the second, cooler environment. Typically, air drawn in from the second environment is of a lower humidity (drier) than that of the air in the first environment. Typically, air drawn in through the air movement means is arranged to be subsequently heated by said heating means.

As the air is taken from a chilled or refrigerated environment, the air has already been processed and is drier (lower humidity) than the air at the ambient side; this is important in ensuring that the air is non-saturated, and has a greater ability to absorb water vapour from within the door structure cavity. Thus, drier, lower humidity air is drawn into the door structure from the cooler environment and as it is heated by the heating means, the air remains at this lower humidity. As such, lower humidity, non-saturated air has the capacity to absorb more water vapour than higher humidity (saturated) air. This is beneficial as it means that while the air is heated and introduced into the cavity, condensation in the cavity on the second door wall at or adjacent the second, chilled environment is much less likely to form because the air has increased capacity to absorb moisture. This is further aided by the movement of the air within the cavity. Circulating air above the dew point around the cavity then serves to eliminate water condensation forming on the door wall at or adjacent the warmer / ambient first environment.

In one embodiment, the top frame member is provided as, or further includes therewith, an elongate member having a chamber located therein.

In one embodiment, the air movement means is arranged to draw air in from the second environment and move the same into the said chamber. Typically, heating means are arranged to heat the air en route to the said chamber. Thus, air that has been drawn in is heated above the required dew point temperature as it enters the chamber.

In one embodiment, the chamber is located along a length of the elongate member, typically, along a substantially horizontal axis. In one embodiment, said chamber is provided with a downwardly-tapered cross-section. Typically, said chamber is provided with a substantially V- or Y-shaped cross section, or similar. Further typically, the cross-section of the chamber tapers towards an outlet portion of the chamber.

In one embodiment, the chamber is provided with an outlet. Typically, said outlet is provided as an elongate slot substantially along the length of a lower end of the elongate member.

In one embodiment, the air drawn into the chamber from said second environment is arranged to be expelled through the outlet into an upper portion of said cavity. Typically, air is arranged to be expelled through the outlet provided in the form of an elongate slot.

In one embodiment, air is directed to be expelled downwardly into the said cavity. Typically, said chamber is pressurised.

Thus, the upper portion of the cavity has air introduced thereto, and the air subsequently circulates throughout the cavity. Tapering the chamber serves to pressurise the air and discharge it therefrom and into the cavity in an evenly distributed manner along the outlet. Consequently, the introduction of air into the cavity heated above the dew point of the first environment serves to prevent the formation of condensation on the door wall at or adjacent the first environment or, if already present, will serve to reduce and/or remove it therefrom.

In one embodiment, air circulated within the cavity serves to reduce the thermal difference between air in the first environment and the surface of the door at or adjacent that environment. Thus, this reduces or prevents the future formation of condensation on the surface of the door.

In one embodiment, one or more apertures or ducts are provided associated with the door structure. Typically, said one or more apertures or ducts are provided to act as ventilation holes for the expulsion of air from said cavity.

In one embodiment, said one or more ventilation holes are arranged to expel air from the said cavity into the first environment.

In one embodiment, said one or more ventilation holes are located at a lower portion of the door structure. Typically, the said holes are located substantially at or adjacent the floor.

In one embodiment, said one or more ventilation holes can be located in the frame side members.

In one embodiment, said first and second door wall portions are connectable at a lowermost edge or point of the said door. Typically, the said walls are connectable via a connecting member.

In one embodiment, said connecting member extends substantially the width of the door. Typically, said connecting member maintains movement of the door between the frame side members and within a cross-section of the same.

In one embodiment, one or more apertures or ducts are provided associated with the connecting member. Typically, said one or more apertures or ducts are provided to act as ventilation holes for the expulsion of air from said cavity.

In one embodiment, said one or more ventilation holes are provided as a plurality of perforated, punched, or punctures apertures located along at least part of the length of the connecting member.

In one embodiment, said one or more ventilation holes are located in a side of the connecting member at or adjacent the first environment, Typically, said one or more ventilation holes are arranged to expel air from the said cavity into the first environment.

In one embodiment, one or more baffle means are provided on the connecting member, associated with said one or more ventilation holes. Typically, one or more baffle means are provided associated with each of said ventilation holes.

In one embodiment, said baffle means are provided as adjustable baffle means. Typically, said baffle means are provided as adjustable so as to control the amount of air expelled from said cavity.

In one embodiment, said baffle means may be located on an exterior surface of the said connecting member. Typically, said baffle means are manually adjustable.

In one embodiment, said baffle means ate movable in a substantially linear direction. Typically, said baffles means are movable between a first position, wherein the ventilation holes are fully open, a second position, wherein said ventilation holes are fully closed, and an intermediate position, wherein said ventilation holes are partially closed.

In another embodiment, said baffle means may be automated or remotely adjustable. Typically, said baffle means may be linearly and/or rotatably movable between first open, second closed, and intermediate positions. Further typically, said baffle means may be located adjacent or within said ventilation holes.

According to another aspect of the present invention, there is provided a method of manufacturing a door structure forcontrolling an opening between a first environment at a first temperature and a second environment at a second, colder temperature as described above, said method including the steps of: providing a door that is selectively movable between open and closed conditions, such that the door, when in the closed position, is formed by a first wall forming an external surface at a first side of the opening and a second, spaced wall defining an external surface to the second side of the opening so as to provide a cavity therebetween, providing air movement means so as to cause the movement of air into and through the said cavity, and characterised in that the door structure is formed such that the air is arranged to be introduced into the cavity from an upper portion of the structure at a temperature above the dew point of the first environment.

Embodiments of the present invention will now be described with reference to the accompanying figures, wherein:

Figure 1 illustrates a perspective view of a door structure, in accordance with an embodiment of the present invention;

Figures 2a — b illustrate front and plan views of a door structure, in an open position, in accordance with an embodiment of the present invention;

Figure 3 illustrates a front view of a door structure, in a closed position, in accordance with an embodiment of the present invention;

Figure 4 illustrates a cross-sectional view of a top portion of a door structure, in accordance with an embodiment of the present invention; and

Figure 5 illustrates a connecting member and associated ventilation holes of a door structure, in accordance with an embodiment of the present invention.

Referring now to the Figures there is shown a door structure in the form of a high speed door 1, which is provided to allow access between a first environment and a second, relatively colder environment. In the examples described, the first environment may be referred to as an ambient environment, at standard room temperature and pressure. The second environment is a chilled or refrigerated environment — usually a walk-in fridge or similar. The door itself is movable between a raised, open position (Figures 1 - 2b), and a lowered, closed position (Figure 3). Further, the door is formed from first 3 and second 5 walls, which are spaced apart from one another, thereby forming a cavity 7 (shown in Figure 4) between the two walls. Air movement means in the form of a duct and fan 9 are provided in order to draw air in from the external environment and move it through the door structure, ultimately introducing it into the cavity 7. In particular the air is introduced into an upper portion of the cavity 7 from an upper part of the structure 1, and is done so at a temperature that is above the calculated dew point of the first, ambient environment. As described above, the dew point of a particular environment is the atmospheric temperature — which varies according to pressure and humidity — below which water droplets will begin to condense and dew can form, and the present invention therefore provides a distinct advantage over the prior art in being able to asses such a feature and introduce air into the cavity 7 above this particular point. The structure further includes a frame comprising side members 11 and a top portion 13, extending over and between the side members 11. The frame is located on a floor thereby defining the opening in which the structure is located, and the cavity 7 formed between the walls 3, 5 extends substantially across the area of that opening.

The door structure may further be provided with sensing means (not shown), which may be provided in order to read and measure the temperature, relative humidity and, in some cases, the pressure of the first, ambient environment. Based on the readings obtained, the sensing means may then be provided with further means by which to calculate the dew point of the first environment. Heating means in the form of a heater fan or similar is provided in association with the duct and fan 9. Thus, as the air is drawn in, it may subsequently be heated to the required temperature. Once the dew point is calculated by the sensing means, the heater may be programmed to heat the drawn-in air to a desired temperature above the dew point. Programming of the heater may occur in several ways. If the sensing means used to determine the relevant dew point are provided detached from the door structure 1, control means may be provided with the heater such that a user may manually set the required temperature. If the sensing means are provided in electronic communication with the heater, control means in the heater may automatically set the required temperature based on the calculated dew point made by the sensing means. This will enable the door structure to be left unmanned and if there is any sudden change in the temperature of the ambient environment, this will automatically be detected and a change in the temperature of the heater will occur automatically. An override may also be provided with the heater, in order for a user to manually change the temperature, if required.

The air duct and fan 9, as discussed above, serve to draw air in from the external environment, which is subsequently heated. In particular, the air is drawn in from the second, chilled environment (arrow A) and into the duct and fan 9, which is subsequently heated. As the air is taken from a chilled or refrigerated environment, the air has already been processed and is drier (lower humidity) than the air at the ambient side; this is important in ensuring that the air is non-saturated, and has a greater ability to absorb water vapour from within the door structure cavity 7. Thus, drier, lower humidity air is drawn into the door structure 1 from the cooler environment and as it is heated by the heater, the air remains at this lower humidity. The top portion 13 of the frame is formed as or is provided with an elongate member containing therein a chamber acting as an air box 15. After the air has been drawn in from the drier, refrigerated environment (Arrow A) and subsequently heated to the dew point, it is then introduced into the air box 15 along Arrows B. The air box 15 acts as a pressurised chamber and serves to pressurise the air as it is introduced thereto. In order to aid this, along the length of its axis, the air box 15 is provided with a downwardly-tapered cross-section (Figure 4), for example, such as like a V- or Y-shaped cross-section. At the lowermost point of the tapered section, an outlet nozzle 17 from the air box 15 is provided, and forms an elongate slot along the length of the air box 15. As the heated, dry air is drawn into the air box 15, it is pressurised and subsequently expelled out of the box 15 (see arrows C) through the outlet nozzle 17 and downwardly into the cavity 7 between the walls 3, 5 of the door. Thus, the upper portion of the cavity 7 has air introduced thereto, and the air subsequently circulates throughout the cavity — shown as arrows D in Figure 3, wherein the door is in the closed position. Tapering the air box 15 serves to pressurise the air and discharge it therefrom and into the cavity 7 in an evenly distributed manner along the outlet 17. Consequently, the introduction of air into the cavity 7, heated above the dew point of the first, ambient environment serves to prevent the formation of condensation on the door wall 3 at or adjacent the ambient environment or, if already present, will serve to reduce and/or remove it therefrom.

As the air is circulated throughout the cavity 7, the thermal difference between the door wall 3 adjacent the ambient environment, and the ambient environment itself will reduce. This will have the effect of reducing or preventing future formation of condensation on the outer surface of the door. Once circulated through the cavity 7, the air is subsequently expelled from the structure. This is enabled by the provision of one or more ducts or apertures in the form of ventilation holes in the door structure. These can, in one embodiment, be provided at or near the base of the frame side members 11. However, in preferred embodiments, they are provided along the length of the bottom of the door itself. This may be achieved by providing a connecting member in the form of a bottom beam 19, which serves to connect and link the two wall portions 3, 5 of the door at their lower edges. The beam 19 extends across the width of the access opening of the door and locates between the frame side members 11. This also aids in maintaining the vertical movement of the door within the boundaries of the frame given that it moves at relatively high speeds.

Within the beam 19, a plurality of ventilation holes 21 may be provided so as to permit the expulsion of air from within the cavity 7. The ventilation holes 21 may be provided as perforations, holes, punctures, ducts or slots along the beam and are formed such that the air, when expelled (arrows E), is done so into the warmer, ambient environment. Additionally, and in order to provide a means to control the rate of air flow exiting the cavity 7, a number of adjustable baffles 23 may be provided on the beam 19 and in association with the said ventilation holes

21. As the baffles are provided to control the air flow exiting the system, this will also therefore provide a means by which to alter the back pressure and/or air flow around the door blade cavity 7. In a preferred embodiment, the baffles 23 are located on an exterior surface of the beam 19 — on the warmer, ambient side — and located above each of the ventilation holes 21. The baffles 23 are provided to be movable in substantially vertical directions, and are manually adjustable to be moved downward to cover the ventilation holes 21 as required, and kept in place via bolts, screws, studs 25 and/or the like. In other embodiments of the present invention, the baffles 21 may be provided to be automated or remotely adjustable, thereby negated the need for manual adjustment each time they are required to be moved. The baffles 23 may also operate horizontally or even as rotatable members located adjacent or within the ventilation holes 21 which, when activated, may rotate to partially or fully block the ventilation holes 21, as may be required by the user. Such automated baffles may also therefore be located on an interior surface of the beam 19, if so desired.

The present invention therefore provides a novel solution to the problems discussed above, and which serves to reduce and prevent the formation and subsequent pooling of condensation from the surfaces of doors located between chilled and ambient environments. The advantage of circulating the air throughout the cavity 7 by introducing it thereto from an upper part and expelling it at a lower end, ensures that the entire surface of the door is ventilated properly. Furthermore, by heating the air above the calculated dew point of the warmer, ambient environment, the thermal difference between that environment and the surface 3 of the door is reduced, thereby removing and preventing the future formation of condensation.

Claims

1. A door structure for controlling an opening between a first environment at a first temperature and a second environment at a second, colder temperature, said door structure including:

a door selectively movable between open and closed conditions;

the door, when in the closed position, formed by a first wall forming an external surface at a first side of the opening and a second, spaced wall defining an external surface to the second side of the opening;

said first and second walls defining a cavity therebetween;

and air movement means are provided to cause the movement of air into and through the said cavity, characterised in that the air is introduced into the cavity from an upper portion of the structure at a temperature above the dew point of the first environment.

2. A door structure according to claim 1, wherein the first environment is provided to be at an ambient or room temperature and pressure, and the second environment is provided to be a chilled or refrigerated environment.

3. A door structure according to claim 1, wherein the door structure includes a frame formed from spaced side members and a top member which, in combination with a floor on which the structure is located, define the opening in which the door is positioned.

4. A door structure according to claim 1, wherein sensing means are provided to sense / measure any or any combination of the temperature, relative humidity and/or the air pressure of the first environment.

5. A door structure according to claim 4, wherein said sensing means are provided with further means by which to calculate the dew point temperature of the first environment.

6. A door structure according to claim 4, wherein said sensing means are provided integrally with the door structure.

7. A door structure according to claim 4, wherein said sensing means can be provided independently of the door structure.

8. A door structure according to claim 1, wherein heating means are provided associated with the air movement means, provided to heat air to a temperature above the dew point of the first environment.

9. A door structure according to claim 8, wherein control means are provided associated with said heating means, provided to enable temperature adjustment of said heating means.

10. A door structure according to claim 8, wherein sensing means are provided in electrical communication with said heating means, via control means provided therewith.

11. A door structure according to claim 10, wherein said sensing means, upon calculation of a required dew point, is arranged to communicate such data with the control means, permitting automatic adjustment of the temperature of the heating means.

12. A door structure according to claim 1, wherein said air movement means is arranged to draw air therein from the second, cooler environment.

13. A door structure according to claim 1, wherein the top frame member is provided as, or further includes therewith, an elongate member having a chamber located therein.

14. A door structure according to claim 13, wherein the air movement means is arranged to draw air in from the second environment and move the same into the said chamber.

15. A door structure according to claim 14, wherein heating means are arranged to heat the air en route to the said chamber.

16. A door structure according to claim 13, wherein the chamber is located along a length of the elongate member, along a substantially horizontal axis.

17. A door structure according to claim 13, wherein said chamber is provided with a downwardly-tapered crosssection.

18. A door structure according to claim 13, wherein the chamber is provided with an outlet, provided as an elongate slot substantially along the length of a lower end of the elongate member.

19. A door structure according to claim 13, wherein the air drawn into the chamber from said second environment is arranged to be expelled through the outlet into an upper portion of said cavitv.

20. A door structure according to claim 1, wherein one or more apertures or ducts are provided associated with the door structure, provided to act as ventilation holes for the expulsion of air from said cavity.

21. A door structure according to claim 20, wherein said one or more ventilation holes are arranged to expel air from the said cavity into the first environment.

22. A door structure according to claim 20, wherein one or more baffle means are provided associated with each of said ventilation holes.

23. A door structure according to claim 22, wherein said baffle means are provided as adjustable, thereby arranged to control the amount of ait expelled from said cavity.

24. A door structure according to claim 22, wherein said baffle means may be automated or remotely adjustable.

25. A method of manufacturing a door structure for controlling an opening between a first environment at a first temperature and a second environment at a second, colder temperature as defined in claims 1-24, said method including the steps of:

providing a door that is selectively movable between open and closed conditions, such that the door, when in the closed position, is formed by a first wall forming an external surface at a first side of the opening and a second, spaced wall defining an external surface to the second side of the opening so as to provide a cavity therebetween;

providing air movement means so as to cause the movement of air into and through the said cavity, and characterised in that the door structure is formed such that the air is arranged to be introduced into the cavity from an upper portion of the structure at a temperature above the dew point of the first environment.

Intellectual

Property

Office

Application No: GB1802290.5 Examiner: Mr Joshua Nolan