GB2312740A - Ventilation device - Google Patents

Abstract

A ventilating device has axially displaced ring shaped elements (403 to 410). The surface area of each element presents a substantially similar cross sectional area to the axial direction of air flow. In this way, light is prevented from entering an air ventilation duct, smooth laminar flow ventilation air is allowed to pass through but high velocity turbulent air is discouraged from entering.

Description

Title: VENTILATION DEVICE The present invention relates to a ventilation device for mounting in a ventilation opening.

Static air ventilators have become increasingly desirable in order to ensure a sufficient air supply to combustion processes of oil or gas fired boilers etc, since in modem premises doors and windows are generally well sealed. Ventilators must permit an adequate flow of air but at the same time limit air forced by external winds etc. Furthermore, consideration must also be given to ensuring that the ventilator does not permit the entry of unwanted light, as described in the applicant's co-pending UK patent publication No. 2 293234.

The ventilation capacity of a ventilator will, in general be dependant upon the size of the ventilation opening and the extent to which the ventilator resists the flow of air through that opening. The calculation of air resistance is an extrernely complex matter and standards have been developed to simplify this calculation by making reference to the "free area" of the ventilated opening. Thus, at any cross section of the opening, the effective size of the opening may be considered, such that the free area of that position is represented by the total area of the ventilator opening less obscured areas due to ventilator components. Consequently, the effective free area of a ventilator may be considered as the cross section which obscures the flow of air by the largest extent. Thus, when adding constructional members within the ventilator, care must be taken to ensure that, for any cross section, the free area is not reduced beyond acceptable limits.

According to a first aspect of the present invention, there is provided a ventilating device, comprising a plurality of axially displaced ring-shaped elements, wherein the surface area of each element presents a substantially similar cross sectional area to said axial direction of air flow.

Preferably, each ring-shaped element reduces the cross sectional area of the ventilator by a permitted maximum extent. Preferably, the outer extents of said elements define a parabola when viewed in longitudinal section. Furthermore, a different parabolic shape may be defined by the inner extents of said elements compared to outer extents of said elements.

In a preferred embodiment, elements are interconnected by elongate members that maintain said elements in a spaced apart relationship. The elongate members may be arranged along longitudinal planes disposed at 120 degrees or 90 degrees to each other.

The ventilating device may be located within a liner to provide a complete ventilating assembly. Altematively, the device may be retro-fitted to existing liners so as to improve flow characteristics.

The invention will now be described by way of example only, with reference to the accompanying drawings, in which: Figure 1 illustrates the living room having a gas appliance and a ventilator to facilitate safe combustion of gas by said appliance; Figure 2 illustrates the drilling of an inside wall to facilitate the introduction of a ventilator; Figure 3 illustrates the drilling of a co-operating outside wall; Figure 4 shows a cross sectional view of a baffle incorporating the present invention; Figure 5 shows a perspective view of the baffle illustrated in Figure 4; and, Figure 6 illustrates the assembly of components to produce the ventilation assembly of the type shown in Figure 1.

A typical application for a static ventilator as shown in Figure 1. A living room has a gas appliance 101 in the form of a gas fire. Furthermore, other rooms within the house may include gas central heating boilers in addition to other gas appliances requiring a supply of oxygen to maintain safe.

combustion. Air is supplied to the room shown in Figure 1 via a ventilator 102 positioned on extemal wall 103. Thus, ventilator 102 allows fresh air from outside to enter the room shown in Figure 1, to facilitate safe and efficient combustion of gas within the gas fire 101.

The problem with ventilation systems of the type shown in Figure 1 is that, in addition to allowing a steady inflow of air, the ventilator may also be susceptible to air being forced through the ventilator due to extemal windy conditions. Under these circumstances, the inflow of air may become disturbing to occupants within the room, which may lead to said occupants obscuring the ventilator 102 so as to prevent the undesirable effects. In addition to causing inefficient combustion, starvation of air to the gas appliance may also create dangerous conditions due to a shortage of oxygen within the room and, in extreme cases, may lead to a build up of carbon monoxide. It is therefore desirable to provide a ventilation system which ensures a supply of air to combustion devices while at the same time minimising undesirable effects so as to reduce the risk of the ventilator being obscured. Thus, ventilators which allow air to enter too easily may also have dangerous effects in addition to unpleasant effects, in that, by blocking the ventilator to prevent the unpleasant effects, the system as a whole may be branded very dangerous, thus effectively creating a dangerous effect due to the type of ventilator employed. Consequently, as a safety feature, it is important that a ventilator should allow a smooth inflow of air for combustion purposes while respecting undesirable gusts of air, which are not necessary to maintain safe combustion.

Ventilators of the type shown in Figure 1 may be fitted to existing houses, usually by drilling holes through external walls or by removing a single brick. Equipment for drilling a hole through wall 103 is shown in Figure 2. Circular drill 201 is powered by an electric drilling device 202 to create a hole 203 through internal wall 103. Usually, extemal walls are fabricated from two physical walls with a cavity therebetween. Consequently, a similar operation to that shown in Figure 2, for creating hole 203 through the internal wall, is repeated, as shown in Figure 3, to form a hole 301 through an extemal wall 302.

The hole drilled through the extemal wall shown in Figure 3 should align with the hole drilled through the internal wall as shown in Figure 2 whereafter said holes are connected by a cylindrical liner. In this way, a ventilation duct is created between the extemal ambient conditions and the internal room as shown in Figure 1.

Vents could be added to the holes on either side and it is also known to apply a cowl to the extemal hole so as to prevent rain water entering therethrough and also to prevent the direct entry of sunlight etc. Such an arrangement would provide a good flow of air, but the arrangement would also be susceptible to sudden bursts of air, thereby creating undesirable effects within the room.

Systems for preventing or at least minimising unwanted bursts of air entering through the ventilator usually consist of baffles as shown in the applicants aforesaid patent publication. Baffles introduce resistance which is particularly effective against high velocity flows, thereby significantly mitigating undesirable effects within the room. However, the introduction of baffles within the ventilation duct will reduce the effective free area of the duct, thereby making the effective size of the duct smaller and subsequently reducing the amount of air which may pass through the duct during normal ventilating conditions.

A baffle 401 embodying the present invention is illustrated in Figure 4.

The baffle member 401, preferably formed in a one-piece plastics moulding, has a series of plate-like baffle rings of substantially equal axial thickness, spaced axially apart at subsequently equal distances. The rings decrease successively in their extemal and internal radial diameter. Air enters into the baffle in the direction of arrow 402. A first baffle element 403, in the form of a ring, effectively extends from the cylindrical liner, such that all of the air passes through a circular orifice having a slightly smaller diameter than that of the liner itself.

The next baffle element 404 is displaced in the direction of arrow 402 but is radially concentric with element 403. Element 404 again takes the form of a ring having an external diameter slightly larger than the internal diameter of ring 403. In this way, there is no direct line of sight through the baffle, thereby preventing the direct entry of sunlight. The internal diameter of ring 404 is smaller than the internal diameter of ring 403 however the distance between the internal diameter and the external diameter of ring 404, ie the thickness of the ring, is slightly larger than the thickness of ring 403. This difference in thickness is calculated such that the total area of the ring is substantially similar to the area of ring 403. In this way, the total obscured area presented by the baffle remain substantially constant. Similarly, the free area of the baffle also remains substantially constant with smaller diameter rings being proportionally thicker so as to present a substantially similar cross sectional area.

Following in the direction of arrow 402, baffle ring 405 again has an external diameter slightly larger than the intemal diameter of baffle ring 404, with an intemal diameter such as to present a substantially similar area to that presented by the previous baffles. This relationship continues for baffle elements 406,407,408,409 and 410.

Baffle element 411 is presented in the form of a complete circular disc and the area of this disc is substantially similar to the area presented by all of the preceding rings. In the preferred arrangement, the disc 411 is presented to the intemal ventilator and as such allows part numbers and trade marks etc to be carried thereon such that the component type may be inspected from the inside of the room. Alternatively, if desired, the orientation of the baffle may be reversed, effectively reversing the direction of arrow 402, with the extemal wind striking circular disc 411 before being presented to the other baffle elements. However, tests have suggested that the baffle is equally effective in either orientation, although the advised orientation presents a better aesthetic appearance when viewed from inside the room.

However, in many situations, very little of the baffle would actually be visible, due to the presence of an intemal grill.

Interconnecting elongate stub members 412 are provided to maintain the rings in a spaced apart relationship and are disposed with their longitudinal axes extending axially of, and parallel to, the central longitudinal axis 413 of the ventilator.

The overall constraint when designing the concentric baffles is to ensure that, at any baffle position, the obscuring area of the baffle remains substantially constant. Or, from a mathematical point of view, the area of each baffle element may be calculated by subtracting the area of a circle present within the internal radius, from a similar circle defined by the size of the extemal radius. The area of a circle is given by the product of pi and the radius squared and, as previously suggested, the area of the ring may then be calculated by subtracting the smaller area from the larger area.

The external radius of each ring diminishes in the axial direction in such manner that the extemal peripheries lie on an extemal parabola.

Likewise, the intemal diameters diminish successively along an intemal parabola. The concavity of the generatrix of the intemal parabola is greater than that of the extemal parabola so that the intemal and extemal parabola may be considered as being defined by different functions. These functions are determined so as to ensure that the total cross sectional area of each baffle element remains substantially constant.

When inserted within a ventilating device, the baffle provides a plurality of axially displaced ring shaped elements, which may be circular, as shown in the embodiment, or may adopt any regular or irregular polygonal outline. Another preferred shape is a quadrilateral or rectangular arrangement, particularly configured to occupy the space of a single house brick such that the ventilation system may be inserted within the space made available when a house brick is removed. Alternatively, such an arrangement is particularly attractive when being incorporated during the building process, wherein the ventilation system occupies the space which would normally be occupied by a house brick.

The surface area of each element presents a substantially similar cross sectional area to the direction of airflow. It can therefore be seen that a cross sectional area may be selected which represents the maximum possible cross sectional area so as to ensure that the remaining cross section provides the required level of free area. The cross sectional areas remain substantially constant, therefore as the average radius decreases, the actual thickness of the ring may also increase. The parabolic shape results from the fact that the area of any particular ring is proportional to the square of its radius thus, it can be appreciated, that the total free area may be increased by increasing the number of baffle ring elements present within the baffle assembly, with each individual baffle having a thinner ring. However, in practice, it can be appreciated that an optimal number of rings exists so as to provide a trade-off between free area reduction and the mechanical integrity of the baffle itself.

A perspective view of the baffle element of Figure 4 is shown in Figure 5, having similar reference numerais. It can clearly be seen in Figure 5 that the area presented by each baffle to the flow of air remains substantially constant by the radial thickness of each baffle reducing as the average diameter increases. Figure 5 also clearly shows the elongate stub members 412 arranged to interconnect the concentric baffles. Thus, the outermost baffle 403 is retained within the cylindrical liner. Smaller baffles 404 to 411 are effectively fastened to the outermost baffle by the elongate stub members 412.

It can be appreciated that, due to the presence of combustion devices, air will tend to enter from outside through the vent and into the room The nature of the flow of air may take basically two forms. Firstly, as part of the ventilation process, a smooth laminar flow of air is encouraged, the velocity of which is relatively low and does not cause a nuisance to occupants within the room. The purpose of the baffle is to introduce turbulence and resistance to high velocity air, encouraging it to enter a turbulent mode of transport such that a substantial proportion of its energy and hence its velocity, is absorbed within the baffle structure. Aerodynamically, the baffle structure shown in Figure 4 and Figure 5 is substantially symmetrical and external air could enter from the small end through the baffle towards the wider end or altematively, the air could enter from the wider end and out of the smaller end. The smaller end consists of a solid disc and as such this disc provides a useful platform for conveying information such as the manufacturers name and the device type. For this reason, it is preferable to arrange the baffle in the orientation as shown in Figure 6, with the small end ring facing towards the room and with the wider end, that is the end of the baffle having the larger circumference ring, being positioned towards the outside wall.

After the intemal and extemal holes have been drilled, as shown in Figure 2 and Figure 3 respectively, a ventilation liner 601 is inserted within the resulting holes so as to define the ventilation duct. The liner is telescopic with a first portion 602 being arranged to slide within a second portion 603, thereby allowing the length of the liner to be adjusted without requiring a portion of the liner to be removed.

After the liner 601 has been inserted within the holes, the baffle 401 is inserted from the inside and secured within the ventilation ducts 601 by fixing attachments. Furthermore, it can be appreciated that the baffle 401 could be added to existing ventilation ducts of the type shown in Figure 6.

After the baffle 401 has been secured within the ventilation duct, a suitable grill 604 is applied to the inside and a downward facing cowl 605 is secured to the outside. Thus, with the arrangement shown in Figure 6, ventilation may be provided to the room shown in Figure 1 while turbulent high velocity air has its velocity significantly reduced by the presence of the baffle 401.

The baffle structure provides a solution which prevents light entering through the ventilation duct, baffles the effects of high velocity air introducing turbulence and resistance, while at the same time maximising the free area at any cross section so as to minimise the resistance to slow velocity laminar flow, required for combustion purposes.

Claims (10)

Claims

1. A ventilating device, comprising a plurality of axially displaced ring-shaped elements, wherein the surface area of each element presents a substantially similar cross sectional area to said axial direction of air flow.

2. A device according to claim 1, wherein each ring-shaped element reduces the cross sectional area of the ventilator by a permitted maximum extent.

3. A ventilating device according to claim 1 or claim 2, wherein the outer extents of said elements define a parabola when viewed in longitudinal section.

4. A ventilating device according to claim 3, wherein a different parabolic shape is defined by the inner extent of said elements compared to the outer extents of said elements.

5. A device according to any one of claims 1 to 4, wherein the elements are interconnected by elongate members that maintain said element in spaced apart relationship.

6. A device according to claim 5, wherein said elongate members are arranged along longitudinal planes disposed at 120 degrees or 90 degrees to each other.

7. A device according to any one of claims 1 to 6, wherein the larger end baffle is provided with a baffle locating ring.

8. A device according to claim 7, wherein the smaller end baffle member is provided with a circular disk having its extemal periphery overlapping the internal periphery of said smaller end baffle member considered axially.

9. A ventilating assembly comprising a liner having a device according to any of Claims 1 to 8, arranged in said liner.

10. A ventilating device substantially described with reference to the accompanying drawings.