GB2043872A

GB2043872A - A Spiral Box for a Fume Escape Hood

Info

Publication number: GB2043872A
Application number: GB7942475A
Authority: GB
Original assignee: Elektrobau Mulfingen and Co EBM GmbH
Current assignee: Elektrobau Mulfingen and Co EBM GmbH
Priority date: 1979-03-12
Filing date: 1979-12-10
Publication date: 1980-10-08
Also published as: GR69681B; GB2043872B; IT7983476A0; DE2909622A1; ES484658A1; NL7907565A; IT1125350B; FR2451232A1; DE2909622C2; NL183436B; FR2451232B1; BE880208A; NL183436C; CH648740A5

Abstract

To obviate the need for complex adjustments or control arrangements and to obtain a high rate of air flow therethrough, a spiral box for a fume escape hood (e.g. for removing fumes from a kitchen) comprises a housing 6 having a front wall 7 and a rear wall 4 between two adjacent ends of which extends an oblique wall 2. A fan is fastened on the front wall 7. The rear wall has an inlet ring 1 of diameter D1 and the front wall has at opposite ends thereof respectively a rectangular outlet for recirculated air A, and a circular outlet for exhaust air C. A conical wall portion 3 extends obliquely from the rear wall adjacent one end thereof and forms part of a ring edge 10 having a diameter d and through which exhaust air B can escape. One edge 8 of the front wall is, above abscissae axis x, curved at 11 toward the ring edge 10. The other edge 12 of the front wall has, also above axis x, two curved portions 14, and 15 which are flush with and extend from respective ends of a curved portion 16. <IMAGE>

Description

SPECIFICATION A Spiral Box for a Fume Escape Hood This invention relates to spiral boxes for fume hoods, said spiral boxes comprising air inlet rings.

Already known are spiral boxes for use with fume escape hoods. Usually backwardly-curved radial wheels are used for fume escape hoods and these are adjustable by a single manipulation from recirculated air to exhaust air. In general backwardly-curved radial wheels do not need a spiral bousing. However, by providing a housing which is spiral the air flow therethrough can be increased. However, a disadvantage of a completely spiral housing is that only one exhaust direction is available.

An object of the present invention is to provide a spiral box for a fume escape hood which has at least two air directions for optimum efficiency, thereby achieving a high air performance and extensive noise dampening.

With this object in view the present invention provides a spiral box for a fume escape hood comprising an air inlet ring, characterised in that said spiral box further comprises a housing having substantially rectangular cross-section, said housing having an oblique lower transverse wall, a rear wall which is widened in its upper region by a correspondingly-curved, conical, oblique wall, and a front wall one edge of which is, above an abscissae axis, curved towards a ring edge whilst its other edge has, in the upper region, an undulatory shape having inwardly curved portions flush with an outwardly curved portion and extending toward the ring edge.

An advantage of the spiral box of the present invention is that there is provided, with the least possible losses three air outlet directions for recirculated air or exhaust air without need complicated adjustments or corresponding control arrangements being needed.

The invention will be described further, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a front view of a preferred embodiment of the spiral box of the present invention; Fig. 2 is a side view of the embodiment of Fig.

1,and Fig. 3 is a plan view of the embodiment of Figs.

1 and 2.

The preferred embodiment of the spiral box illustrated in the drawings is used in an environment from which it is desired to remove fumes, for example, in a kitchen. The spiral base is connected to a fume escape hood by way of associated flanges. The spiral box is made from one piece of material. This material is either steel or plastics. During production of the spiral box an air inlet ring 1 (Figs. 1 and 2) is introduced into one wall thereof. This production is analogous when using either metallic or non-metallic material or when using a combination of both metallic and non-metallic material. Naturally, it is also conceivable to produce the spiral box in individual parts and then welding the parts together. As an alternative to steel or plastics the spiral box is made of a non-separable and flameretardent foam material.

As is illustrated in Figs. 1 and 2 the spiral box has a housing 6 having a substantial rectangular cross-section. As more clearly illustrated in Fig, 2 the housing 6 has a lower transverse wall 2, which is disposed obliquely relative to a front wall 7, for example, at an angle of 450. The transverse wall 2 can, of course, be disposed at any desired angle from the front wall 7 or alternatively may be arched. A rear wall 4 of the housing 6 has an air inlet ring 1 having a diameter D,. The front wall 7 has a recirculated air outlet opposite the transverse wall 2 and an exhaust outlet at the opposite end of the housing 6 to the recirculated air outlet. Air is deflected through the recirculated air outlet, at an angle of about 900, to atmosphere as shown by the direction of arrow A.

One could, instead of the obliquely-placed transverse wall 2 provide an additional transverse wall and in this region form the housing in itself differently, although this is disadvantageous. The rear wall 4 is widened in its upper region by an oblique wall 3 which is conical and which is disposed at an angle of 300 to 450 relative to the rear wall 4. The oblique wall 3 forms part of a ring edge 10. In this way, with a minimum of disturbance and energy loss an offtake of the exhaust air from the ring edge 10 in the direction of arrow B is made possible. At the same time or, separately, the exhaust air could be conducted away through the exhaust air outlet, in the direction of arrow C.

Referring to Fig. 1, and more particularly to the shape of the spiral box in its upper region above an abscissae axis x, a portion 11 of one edge of the front wall 7 is curved and links a rectilinearlyextending piece 8 of the edge above the axis x and the ring edge 10. A commerically-available tube having the same diameter d can be connected to the ring edge 10 for removing exhaust air.

The radius of curvature r4 of the portion 11 has a dimension from 1.25 to 1.65 rimes D1. Ideally it is 1.42 times D.

The other edge 12 of the front wall 7, above the axis x has an undulatory shape 13 and has two inwardly curved portions and one outwardly curved portion. This undulatory shape 13 starts at the abscissae axis x with an inwardly curved portion 14 and ends at the ring edge 10 with another inwardly curved portion 1 5. Provided therebetween is at least one outwardly curved portion 16, which merges into the inwardly curved portion 1 5. This undulatory shape 13 can also be shaped differently. The radius of curvature r1 of the inwardly curved portion 14 extends up to an angle dof about 270 to 450 and then merges into the outwardly curved portion 16, having a radius of curvature r2. The outwardly curved portion 16 then merges into the inwardly curved portion 15, having a radius of curvature r3.The radius of curvature r should have a dimension from 0.7 to 1.1 times D,. Ideally it should be 0.9 times D1. The radius of curvature r2 should have a dimension of from 0.2 to 0.45 times D,. Ideally it should be 0.31 times D,. The radius of curvature r3 should have a dimension from 1.1 to 1.4 times D,. Ideally it should be of 1.25 times D,.

When use is made of plastics the wall thickness of the spiral box is usually from 0.07 to 0.1 times the diameter of D,. Ideally it is 0.085 times D,.

The recirculated air outlet is rectangular and will generally have a maximum dimension of dl x a. Here, generally, no tube will be connected because the recirculated air for example flows once more into the environment, for example the kitchen.

The front wall 7 (fig. 2) can if necessary be abolished in the case of the spiral box, because this wall is present in the fume escape hoods.

Generally the exhaust outlet will be circular and the recirculated air outlet will be rectangular. A motor fan is fastened on the front wall 7 be it in the spiral box, be it in the fume escape hood.

Claims

1. A spiral box for a fume escape hood comprising an air inlet ring, characterised in that said spiral box further comprises a housing having a substantially rectangular cross-section, said housing having an oblique lower transverse wall, a rear wall which is widened in its upper region by a correspondingly-curved, conical, oblique wall, and a front wall, one edge of which is, above an abscissae axis, curved towards a ring edge whilst its other edge has, in the upper region, an undulatory shape having inwardly curved portions flush with an outwardly curved portion and extending toward the ring edge.

2. A spiral box as claimed in claim 1, characterised in that the oblique lower transverse wall is disposed relative to the front wall at an angle of 450.

3. A spiral box as claimed in claim 1 or 2 characterised in that an additional transverse wall is inserted.

4. A spiral box as claimed in claim 1, 2 or 3, characterised in that the oblique wall is disposed at an angle of 300 to 450 relative to the rear side wall.

5. A spiral box as claimed in any preceding claim characterised in that said one edge of said front wall has a radius and curvature which is from 1.25 to 1.65 times the diameter of the inlet ring.

6. A spiral box as claimed in claim 5 characterised in that said radius of curvature hasa value which is 1.42 times the diameter of the inlet ring.

7. A spiral box as claimed in any preceding claim, characterised in that said one edge starts with a rectilinearly-extending piece and terminates with the ring edge.

8. A spiral box as claimed in any preceding claim, characterised in that one inwardly curved portion of said other edge has a radius of curvature which is from 0.7 to 1.1 times the diameter of the inlet ring.

9. A spiral box as claimed in claim 8 characterised in that said radius of curvature has a value which is 0.9 times the diameter of the inlet ring.

10. A spiral box as claimed in claim 8 or 9 characterised in that said one inwardly curved portion lies on the abscissae axis and ends with a straight portion of said other edge.

11. A spiral box as claimed in any preceding claim, characterised in that the other inwardly curved portion of said further edge has a radius of curvature which is from 1.1 to 1.4 times the diameter of the inlet ring.

12. A spiral box as claimed in claim 11 characterised in that the radius of curvature is 1.25 times the diameter of the inlet ring.

13. A spiral box as claimed in claim 11 or 12 characterised in that said other inwardly curved portion is joined to the one outwardly curvedportion and the ring edge.

14. A spiral box as claimed in any preceding claim, characterised in that the outwardly curved portion of said further edge has a radius of curvature which is from 0.2 to 0.45 times the diameter of the inlet ring.

15. A spiral box as claimed in claim 14 characterised in that the radius of curvature is 0.31 times the diameter of the inlet ring.

16. A spiral box as claimed in claim 14 or 15 characterised in that the outwardly curved portion lies between and is flush with the two inwardly curved portions.

1 7. A spiral box as claimed in any preceding claim, characterised in that it is made from one piece of material.

18. A spiral box as claimed in any preceding claim, characterised in that it is made of steel.

19. A spiral box as claimed in any preceding claim, characterised in that the air inlet ring is introduced in one piece into the rear wall and is merged therewith by means of a rounding.

20. A spiral box as claimed in any preceding claim, characterised in that it is made from plastics material, for example, by injectionmoulding or casting.

21. A spiral box as claimed in any preceding claim, characterised in that it is made from a nonseparable and flame-retarding foam material.

22. A spiral box as claimed in any preceding claim, characterised in that its wall thickness when plastics material is used, is for example from 0.07 to 0.1 times the diameter of the inlet ring.

23. A spiral box as claimed in claim 22 characterised in that its wall thickness is 0.085 times the diameter of the inlet ring.

24. A spiral box as claimed in any preceding claim, characterised in that the housing has, in the region of the air outlet, at least one crosssectional widening.

25. A spiral box as claimed in claim 24, characterised in that the cross-sectional widening is diverging oblique wall having a conical crosssection.

26. A spiral box for a fume escape hood as claimed in claim 24 or 25, characterised in that the widening is so shaped to enable a tube of the same to be connected thereto.

27. A spiral box substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.