NZ513123A - An improved blade for a vent grille - Google Patents

Abstract

A vent blade has a transverse cross-section defining the blade thickness. The blade has ends, a leading edge, a trailing edge, an upper surface, and a lower surface in use. The shape of the transverse cross section of the blade is selected to reduce fluid drag and fluid turbulence over at least one of the surfaces. The blade has at least two portions, wherein at least one of the portions has different stiffness characteristics to the other portion.

Description

No.: 513123 Date: 25 July 2001 NEW ZEALAND PATENTS ACT 1953 COMPLETE SPECIFICATION "A Vent Blade" Firepro Systems Limited, a New Zealand company, of 8 Botha Road, Penrose, Auckland, hereby declares the invention, for which it prays that a patent may be granted to it, and the method by which it is to be performed, to be particularly described in and by the following statement: ! ' v, o.: i' . j 1 o Jl-'L i i »■ ■ ■->" - ■ This invention relates to a vent member or blade. The invention is directed particularly, but not solely, toward grilles, dampers, gratings, grids, latticed screens, ducting inserts, ducting covers or vent covers.

BACKGROUND OF THE INVENTION Vent blades or grilles or vent covers having blades are used to cover or fit within apertures or openings or ducts or tunnels or passageways in members or structures such as doors, walls, ceilings and buildings etc. Even passageways etc in the ground may need to have access restricted by vent blades or grilles. Grilles or covers restrict unwanted entry while allowing 10 the passage of air in normal use. They are also used as vent covers for outlet for air conditioners, ventilation units and heating apparatus etc. The vent blade(s) or grilles can assist in directing and/or speeding up fluid/airflow eg by placing blade members of the grille at an angle to the airflow or changing the aperture size and shape.

As well as the normal use of allowing air through, the grilles or vent blades in specific positions in a structure must also be able to meet fire safety requirements.

Commonly, these grilles or vent covers comprise an inner barrier means eg a blade(s) and an outer frame member. The grilles or covers can be modular or integral in structure. The 20 inner barrier means and frame can be fire rated to meet certain safety requirements. The inner barrier means are commonly elongate planar blade members being rectangular in cross-sectional shape, set at various angles to the airflow. A grille can have any number of inner barrier means and/or the barrier means can be in any pattern.

However, known grilles impede the airflow, by having adverse cross-sectional shapes with frictional surface characteristics which, create air drag and air turbulence which significantly slows the air speed therethrough. Air turbulence can have an adverse effect on the performance of the grilles or vent blades. For example, square blades produce significant air turbulence or eddying. This air turbulence or eddying creates a lower air pressure further 30 along the cross section of the blade and a backwash which in turn reduces the so called free flow gap between adjacent blades. The greater the free flow gap between biade(s) the better the capacity of the system, which can mean reduced pressure on motors etc and smaller pipes etc meaning reduced material costs. 2 Reduced air speed in turn reduces the amount of air going through in a certain period, which can reduce the capacity of the grille or connected ducting, or heating or ventilation or air conditioning devices. This capacity reduction can mean that larger ducting is required which can in turn mean, larger ceiling cavities which in turn significantly increases construction 5 costs. For heaters or air conditioners etc, the capacity reduction through the grille can mean greater loading which in turn can increase power consumption and reduce the life of the heater or air conditioner. The capacity reduction of grilles in a smoke venting situation of toxic gases, is also undesirable.

It is the object of the present invention to provide an improved blade or vent member which will obviate or minimize the aforementioned problems or which will at least provide the public with a useful choice.

STATEMENT OF INVENTION Accordingly in a first aspect the invention consists in a vent blade, the blade having a transverse cross-section defining the blade thickness, the blade having ends, a leading edge, a trailing edge, an upper surface, and a lower surface in use, wherein the shape of the transverse cross section of the blade is selected to reduce fluid drag and fluid turbulence over at least one of the surfaces the blade has at least two portions, wherein at least one of 20 the portions has different stiffness characteristics to the other portion.

Preferably the fluid is air.

Accordingly in a second aspect the invention consists in a vent blade, the blade having a 25 transverse cross-section defining the blade thickness, the blade having ends, a leading edge, a trailing edge, an upper surface, and a lower surface in use, wherein the blade thickness increases from a first minimum thickness adjacent the leading edge to a maximum thickness between the leading edge and the trailing edge, and the blade thickness decreases from the maximum thickness to a second minimum thickness adjacent the trailing edge the blade has 30 at least two portions, wherein at least one of the portions has different stiffness characteristics to the other portion.

Preferably the blade thickness increase or blade decrease is a substantially smooth gradient. 3 INTELLECTUAL PROPERTY OFFICE OF N2 3 I JUL 2003 received Preferably the first minimum thickness is substantially the same as the second minimum thickness.

Alternatively the first minimum thickness is substantially greater than the second minimum 5 thickness.

Alternatively the first minimum thickness is substantially less than the second minimum thickness.

Preferably the blade thickness is symmetrical about a transverse cross-sectional axis.

Preferably the upper surface slopes gradually from the trailing edge to the leading edge with respect to the central transverse cross section.

Preferably the lower surface slopes gradually from the trailing edge to the leading edge with respect to the central transverse cross section.

Preferably the blade has at least one portion.

Preferably the at least one portion is formed of a blend of materials.

Preferably the at least one portion is formed of at least an intumescent material.

Alternatively the blade has at least two portions.

Preferably at least one of the portions has different stiffness characteristics to the other portion.

Preferably at least one of the portions is formed substantially of a material including a metal.

Preferably the metal is aluminium.

Alternatively the metal is an aluminium alloy.

Preferably at least one of the portions is formed of an intumescent material. 3 I JUL 2003 received Preferably the intumescent material comprises a graphite based material.

Preferably the intumescent material includes a transverse slot adapted to receive the metal 5 portion.

Preferably the metal portion, in cross section, is thicker at the trailing edge than the leading edge of the blade.

Preferably the first portion protrudes from the second portion.

Preferably the metal portion, in cross section, is arrow headed in cross-sectional shape.

Preferably the blade has a beveled edge.

Preferably the beveled edge comprises an angled surface.

Preferably the angled surface is located at the trailing edge of the blade.

Accordingly in a third aspect the invention may broadly be said to consist in a barrier member comprising at least one blade according to any one of the preceding paragraphs.

Preferably the at least one blade is supported by a frame.

Preferably the frame supports a plurality of blades.

Preferably the plurality of blades are spaced apart in a first parallel formation in the frame.

Alternatively there is a second parallel formation of blades.

Preferably the first and second parallel formations of blades are at an angle to each other. Alternatively the plurality of blades are not parallel within the frame.

INTELLECTUAL PROPERTY OFFICE OF N.Z 3 1 JUL 2003 received BRIEF DESCRIPTION OF THE DRAWINGS Preferred forms of the invention will now be described with reference to the accompanying drawings.

Figure 1 shows a cross-section of the blade of the invention.

Figure 2 shows a plan view of several blade members in a frame.

Figure 3 is a cross-section of the figure shown in figure 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A blade 1 or vane or slat or insert or flap can be part of a vent cover or grille cover or shutter or damper or louvre and can be thought of as a barrier member or deflecting member. The 15 blade 1 of figure 1 can have a cross sectional shape similar to an aerofoil shape having an airfoil transverse cross-section. The blade cross section is non-rectangular in cross section and will therefore provide reduced air resistance. The blade 1 has the following structural characteristics of a leading edge 4, a trailing edge 5 and also an upper surface 6 and a lower surface 7. The blade 1 of figure 1 shows this non-rectangular cross sectional shape whereby 20 the blade adjacent to the trailing edge 5 is thinner than the blade adjacent to the leading edge 4.

As shown in figure 1 the blade has a transverse axis A-A which separates the upper surface 6 from the lower surface 7. Axis A-A can also be a central transverse axis as shown in figure 25 1, with the upper surface and lower surfaces being equidistant from the axis. It is also envisaged that in other cross sectional shapes, the transverse axis will not be central. For example, as in an aerofoil shape. Therefore the upper surface 6 will not be equidistant from the transverse axis.

In a first alternative construction the blade 1 can be formed of at least two portions 2 and 3. At least one of the portions 2 and 3 can be formed of a stiffer or stronger or more heat resistant material than the other material. Each portion 2 and 3 in itself can be formed of at least one main or substantial material type. At least one of the portions can be formed of a 6 INTELLECTUAL PROPERTY OFFICE OF N.Z 3 1 JUL 2003 received metal material. It is preferred that the metal material can be an aluminium alloy. The first portion 2 can be an aluminium alloy. The second portion 3, is formed of a second material. In a preferred form, the second portion 3 is substantially an intumescent material such as intumescent graphite based material.

Alternatively the blade construction can comprise at least a single portion having an upper and lower surface 6 and 7. The single blade portion can be formed of a material having stiffer or stronger properties in different parts or portions thereof. It is preferred to have greater stiffness characteristics in the middle and trailing end 5 and more intumescent type 10 characteristics on the upper or lower surface areas. Alternatively, the single portion could have at least intumescent qualities.

In an alternative shape, the cross sectional shape of the blade could include a thicker middle with thinner thickness adjacent the blade edges. Other combinations of the thick and thin 15 middle and thickness adjacent the blade edges are also envisaged. For example the position of the thicker middle can be transversely sited anywhere between the leading edge and trailing edges. All these combinations of thickness variations have surface slopes or gradients that are even or gradual and not abrupt or rough from a frictional perspective. These alternative cross sectional shapes also have reduced fluid or air drag characteristics. 20 Other cross sections such as airfoil shapes can also be used.

It is preferred that the second portion 3, which can be an intumescent material, substantially surrounds the first portion 2. The intumescent material is a material that expands or swells when heated to a certain temperature. In a fire situation, this swelling is used to block ducts 25 or apertures etc in walls etc to stop the spread of fire and smoke for a certain period of time, between adjacent rooms or fire cells. This period of time is termed a fire rating.

In one form of use with respect to airflow, the blade 1 has the following structural characteristics of the leading edge 4, the trailing edge 5 and also the upper surface 6 and the 30 lower surface 7. As shown in figure 1, these characteristics of the blade 1 apply when the blade is in use so the term 'leading edge' refers to one edge that leads or faces the air flow when the blade is in use. However, the blade can also be used in reversed airflows.

The blade thickness increases from a minimum thickness at the leading edge to a maximum 35 thickness between the leading edge and the trailing edge. The blade thickness can then 7 iniellectual ( OFFICF OF N.Z 31 JUL 2003 received decrease from the maximum thickness to a minimum thickness at the trailing edge. This increase or decrease in thickness is preferably gradual in its slope. Preferably the upper surface is not a constant distance from the transverse axis A-A but changes with respect to the axis ie is sloped. The slope of the upper surface can be similar or substantially different 5 to that of the lower surface. For example the upper surface can reach a maximum distance from the axis A-A different to that maximum distance of the lower surface from the axis A-A. As previously disclosed in preceding paragraphs the axis A-A can also not be equidistant between the upper and lower surfaces and in its broadest form, the A-A merely represents the transverse axis between the upper and lower surfaces.

As shown in figure 1, in a preferred form, the first portion 2 is made up of a head portion 8 and a body planar portion 9. It is preferred to have the head portion 8 shaped as an arrowhead. It is also preferred to have the body portion 9 shaped as a slender planar portion which is completely surrounded by the second portion 3 and has a major cross-sectional axis 15 parallel and coincident to the axis A-A of the transverse cross section of the blade. The head portion 8 protrudes from the intumescent material or second portion 3 at the trailing edge 5 of the blade, to protect the blade from damage. The intumescent material of the second portion 3 is weaker than the material in use for the first portion 2(i.e. the aluminium alloy) and therefore would be liable to be damaged when the blade is being handled or being used.

Alternatively the cross sectional shape of the first portion can vary from the arrow headed version to one where the minimum requirement is to have a portion of the first portion 2 protruding at the trailing edge 5. The body portion 9 being any shape that is both structurally viable and cost effective.

The head portion 8 or the trailing edge can have a chamfer or beveled surface or angled surface 10. The bevel can be on the upper surface 6. Alternatively the second portion may not be shaped as an arrowhead portion 8 and/or slender portion 9. The first and second portions can have any cross sectional shape that fits the aerofoil cross section. The angled 30 surface 10 has the function of reducing any vibration and consequential sounds which can arise when air is passed around the blade. Further angled surfaces in the form of chamfers or bevels may be provided on the blades as found necessary.

As shown in figure 2 in plan view to the cross sectional view of the blade of figure 1 the blade 35 1 is an elongate member having a length 20 and having a transverse cross-section defining 8 INTELLECTUAL PROPERTY OFFICE OF N.Z 3 1 JUL 2003 received the blade thickness. The blade length 20 has ends 21 and 22, a leading edge, a trailing edge, an upper surface 6, and a lower surface 7 in use. The ends 21 and 22 are used to fix the blade to a support or frame 11.

Wind tunnel tests for the blades 1 of the invention have shown much lower fluid flow resistance and fluid turbulence or backwash than other blades/louvres/slats/vanes. The blades 1 preferably have to perform as efficiently as possible in normal use (non fire) and in a non normal use or fire situation. The free flow gap 23 (see figure 3) is generally defined as a gap between adjacent blades that has already allowed for frictional characteristics such as 10 drag and turbulence. In normal use the blade 1 of the invention combines reduced fluid drag and/or turbulence characteristics which effect the free flow gap 23 and capacity, in normal use with fire rated characteristics. With increased turbulence one gets increased pressure drop which effects the free flow gap 23 between blades 1 which effects air flow capacity therethrough. A 'fluid' has a general definition of being any substance that flows. For 15 example air or water.

The frame 11 to house and support the blades 1, can be any shape or configuration and can comprise members of any suitable cross section needed to contain the blades 1. For example the cross-section of figure 3 shows the orientation of the blades 1 within the frame 20 11 which shown to be a rectangular shape. The blades 1 as shown in figure 3 can also be at any angle to the frame 11. This depends on the frictional or air flow characteristics that are required.

The frame 11 shape can be circular or square or rectangular or any shape as needed for 25 whatever aperture is found. The fixing of the blades 1 into the frame 11 can be done using slots for the blade ends (not labeled or shown) in the frame member 11 or they may even be glued in place. Alternatively the blades may be pinned to the frame members ( not shown in the drawings). These pins may be fixed or rotatably fixed to allow rotational positioning of the blades. The pins may be fixed centrally with respect to the blade length(s) or at the ends 30 of the blades. The blades 1 shown in figure 2 are only shown as one series of parallel blades. Any number of configurations or patterns for the blades 1 can be selected. The blades 1 need not be parallel or regularly spaced. The blade pattern can be criss-crossed, or unequally angled to each other. 9 INTELLECTUAL PROPERTY OFFICF OF 3 \ JUL 2003 RECEIVED The blades 1 can be combined with other fire related devices such as fusible links or may be used in a fume cupboard or may even be part of lighting fixtures such as ceiling lights. The fusible link may be part of a centre pin linkage for several blades which can initiate an automatic drop down of the blades in a fire situation.

The spacing of the blades 1 can be determined with regard to factors such as the physical requirements of the swelling of the intumescent material and or the air interference between the blades. Other factors may be the capacity of the connecting ducting or heating/air conditioning devices, or the free flow gap between blades which is in turn related to the 10 pressure drop and turbulence characteristics.

The blade(s) 1 may be used as part of grilles, grids or latticework or screens, ducting inserts or vents of heaters or air conditioners or ventilation units etc or they may be fixed directly to apertures, ducts or pipes or doors, hatches or ceilings etc or they may be used in wall vents 15 or louvres or dampers.

To those skilled in the art to which the invention relates, many changes in construction and widely differing embodiments and applications of the invention will suggest themselves without departing from the scope of the invention as defined in the appended claims. The 20 disclosures and the descriptions herein are purely illustrative and are not intended to be in any sense limiting.

Throughout the description and claims of this specification the word "comprise" and variations of that word, such as "comprises" and "comprising", are not intended to exclude 25 other additives, components, integers or steps.

The vent blade has the following advantages: 1. Reduced fluid frictional characteristics. 2. Reduced fluid turbulence and pressure loss. 3. Pleasing appearance. 4. Easy to manufacture.

INTELLECTUAL PROPERTY OFFICE OF N.Z 3 I JUL 2003 received

Claims (35)

What we claim is:

1. A vent blade, the blade having a transverse cross-section defining the blade thickness, the blade having ends, a leading edge, a trailing edge, an upper surface, and a lower surface in use, the shape of the transverse cross section of the blade is selected to reduce fluid drag and fluid turbulence over at least one of the surfaces, the blade has at least two portions, wherein at least one of the portions has different stiffness characteristics to the other portion.

2. The vent blade as claimed in claim 1 wherein the fluid is air.

3. A vent blade, the blade having a transverse cross-section defining the blade thickness, the blade having ends, a leading edge, a trailing edge, an upper surface, and a lower surface in use, the blade thickness increases from a first minimum thickness adjacent the leading edge to a maximum thickness between the leading edge and the trailing edge, and the blade thickness decreases from the maximum thickness to a second minimum thickness adjacent the trailing edge the blade has at least two portions, wherein at least one of the portions has different stiffness characteristics to the other portion.

4. The vent blade as claimed in claim 3 wherein the blade thickness increase or blade thickness decrease is a substantially smooth gradient.

5. The vent blade as claimed in claim 4 wherein the first minimum thickness is substantially the same as the second minimum thickness.

6. The vent blade as claimed in claim 4 wherein the first minimum thickness is substantially greater than the second minimum thickness.

7. The vent blade as claimed in claim 4 wherein the first minimum thickness is substantially less than the second minimum thickness.

8. The vent blade as claimed in and one of claims 3 to 7 wherein the blade thickness is symmetrical about a transverse cross-sectional axis.

9. The vent blade as claimed in claim 8 wherein the upper surface slopes gradually from the trailing edge to the leading edge with respect to the central transverse cross section. 11 3 I JUL 2003 received

10. The vent blade as claimed in claim 9 wherein the lower surface slopes gradually from the trailing edge to the leading edge with respect to the central transverse cross section. 5

11. The vent blade as claimed in claim 10 wherein the blade has at least one portion.

12. The vent blade as claimed in claim 11 wherein the at least one portion is formed of a blend of materials. 10

13. The vent blade as claimed in claim 12 wherein the at least one portion is formed of at least an intumescent material.

14. The vent blade as claimed in anyone of claims 11 to 15 wherein at least one of the portions is formed substantially of a material including a metal. 15

15. The vent blade as claimed in claim 16 wherein the metal is aluminium.

16. The vent blade as claimed in claim 16 wherein the metal is an aluminium alloy. 20

17. The vent blade as claimed in any one of claims 11 to 18 wherein at least one of the portions is formed of an intumescent material.

18. The vent blade as claimed in claim 19 wherein the intumescent material comprises a graphite based material. 25

19. The vent blade as claimed in claim 19 wherein the intumescent material includes a transverse slot adapted to receive the metal portion.

20. The vent blade as claimed in claim 21 wherein the metal portion, in cross section, is 30 thicker at the trailing edge than the leading edge of the blade.

21. The vent blade as claimed in any one of claims 11 to 22 wherein the first portion protrudes from the second portion.

22. The vent blade as claimed in claim 21 wherein the metal portion, in cross section, is arrow headed in cross-sectional shape.

23. The vent blade as claimed in any one of claims 3 to 24 wherein the blade has a beveled 5 edge.

24. The vent blade as claimed in claim 25 wherein the beveled edge comprises an angled surface. 10

25. The vent blade as claimed in claim 26 wherein the angled surface is located at the trailing edge of the blade.

26. A barrier member comprising at least one blade according to any one of the claims 1 to 27. 15

27. The barrier member as claimed in claim 28 wherein the at least one blade is supported by a frame.

28. The barrier member as claimed in claim 29 wherein the frame supports a plurality of 20 blades.

29. The barrier member as claimed in claim 30 wherein the plurality of blades are spaced apart in a first parallel formation in the frame. 25

30. The barrier member as claimed in claim 29 wherein there is a second parallel formation of blades.

31. The barrier member as claimed in claim 30 wherein the first and second parallel formations of blades are at an angle to each other. 30

32. The barrier member as claimed in claim 30 wherein the plurality of blades are not parallel within the frame. 35

33. A vent blade as claimed in claim 1 as herein before described with reference to the accompanying drawings. 13 'NTELLECTIML pr°pertY office OF 3 I JUL 2003 RECEIVED

34. A vent blade as claimed in claim 3 as herein before described with reference to the accompanying drawings. 5

35. A barrier means as claimed in claim 28 as herein before described with reference to the accompanying drawings. 10 END OF CLAIMS PIPER KNOWLES Attorneys for Firepro Systems Limited 15 14 INTELLECTUAL PROPERTY OFFICE OF N.Z 31 JUL 2003 RECEIVED