GB2109108A - Suction hood - Google Patents

Abstract

A suction hood, particularly for a metal treatment bath, includes opposed longitudinal walls (3, 4) with inspection apertures (5) and being surmounted by oppositely inclined roof shaped surfaces (12, 13) defining a slot (9) at the ridge with upstanding walls (10, 11) at its edges. A series of extraction pipes (14) connected to a collecting duct (15) are provided in the inclined surfaces (12) which is higher and steeper than the other surface (13). Lights (18) to aid observation of the process being carried out inside the hood can be provided on the underside of the flatter inclined surface (13). <IMAGE>

Description

SPECIFICATION Suction Hood The invention relates to a suction hood for a longitudinally extending diffused emission source, in particular for a metal treatment bath, with an upper component which is roofshaped in cross-section and which has a longitudinal slot at the ridge for the location of suspension means for the parts to be treated in the flow of material, doors at the ends and openable and closable inspection apertures arranged in its longitudinal walls, forming the lower component of the hood, wherein the emissions from the metal treatment bath are dischargeable by means of extraction pipes arranged on one of the inclined surfaces of the roof-shaped component, which pipes are connected so as to discharge into a suction collecting duct.

Such a suction hood is known from "I N- FORMATIONSFORUM" published in August 1981 by the Staatlichen Gewerbeaufsichtsamt Dortmund. This known suction hood is made symmetrically roof-shaped in cross-section at the upper component and the extraction pipes are arranged centrally on one of the incline surfaces, whereby the emissions cannot be completely withdrawn economically and partly escape upwardly from the longitudinal slot, due to the action of thermal up-draughts. A more or less complete extraction can be attained by means of this known suction hood only by an enormous expenditure of energy or by imposing high driving loads on the suction fans, which can no longer be effected economically, however.

From this standpoint, the purpose of the invention is to provide a suction hood of the kind mentioned initially, which enables optimum extraction of the emissions from a metal treatment bath with the least possible consumption of energy.

According to the invention, this problem is solved in that the inclined surface with the extraction pipes is made higher and steeper than the other opposite surface, whereby the thermal currents from the diffused emission source are utilized and the extraction pipes are displaced from the longitudinal slot corresponding approximately to their diameter, the longitudinal slot having walls projecting above the ridge.In an advantageous manner, the suction collecting duct is graded from a portion at one end of the suction hood having double the cross-section corresponding to one of the extraction pipes, to a portion which corresponds to double the sum of all crosssections of the extracton pipes, whereby an approximately equal-pressure extraction is achieved, giving an approximately uniform sub-pressure distribution in the longitudinal slot and therefore producing a suction flow from above downwardly, which opposes the thermal currents and thus effectively prevents escape of the emissions from the slot.

For observation and control, lamps or other illuminating means are provided in a suitable manner inside the suction hood on the flatter surface opposite the steep surface provided with the extraction pipes.

The advantages of the suction hood according to the invention are to be seen particularly in the optimum economical extraction Of emissions from metal treatment baths, which can be achieved in a structurally simple way.

In the accompanying drawing, the suction hood according to the invention is shown iri more detail by means of an exemplary embodiment. In the drawings: Figure 1 shows a suction hood in plan view; Figure 2 shows the suction hood according to Fig. 1 in cross-section.

As can be seen from Figs. 1 and 2, the suction hood 1, which is arranged above a longitudinally-extending metal treatment bath 2, consists of opposed longitudinal walls 3,4 which contain openable and closable inspection apertures 5, end doors 6,7 and an upper component 8 which is roof-shaped in crosssection, having at the ridge a longitudinal slot 9, with walls 10,11 projecting above the ridge for the location of suspension means (not shown) for the parts to be treated in the flow of material, wherein, for the extraction of the emissions from the metal treatment bath, an inclined surface 1 2 of the roof-shaped component 8, which is arranged to be higher and steeper than the opposite inclined surface 13, whereby the thermal currents are utilized, includes a plurality of extraction pipes 14, which discharge into a suction collecting duct 15.

The extraction pipes 14 are displaced by about their own diameter from the longitudinal slot 9, which means that the extraction of the emissions takes place in the region of the longitudinal slot 9.

In order to achieve an approximately equalpressure extraction and obtain an approximately uniform sub-pressure distribution in the longitudinal slot 9 and thus an extraction flow directed from above downwardly, which opposes the thermal flow and thus effectively prevents escape of the emissions from the longitudinal slot 9, the suction collecting duct 1 5 is graded from a portion 1 6 of double the cross-section corresponding to one extraction pipe 14, at one end of the suction hood 1, to a portion 1 7 which corresponds to double the sum of all cross-sections of the extraction pipes 14.

Since an accumulation space for the emissions is provided by the shape of the upper component 8 of the suction hood 1 in the region where extraction occurs, illumination means 1 8 for ob'servation and control are suitably provided, advantageously on the other side, on the flatter surface 1 3 inside the suction hood 1.

Claims (4)

1. A suction hood for a longitudinallyextending diffused emission source, particularly for a metal treatment bath having an upper component which is roof-shaped in cross section, which has a longitudinal slot at the'ridge for the location of suspension means for the parts to be treated in the flow of material, doors at the ends and openable and closable inspection apertures arranged in its longitudinal walls, wherein emissions from the metal treatment bath are dischargable by means of extraction pipes arranaged on one of the inclined surfaces of the upper component and connected to a suction collecting duct, wherein the incline surface with the extraction pipes is higher and steeper than the opposite surface and the extraction pipes are displaced from the longitudinal slot corresponding approximately to their diameter, the slot having walls which project above the ridge.

2. A suction hood according to claim 1, wherein the collecting duct is graded from a portion at one end of the suction hood having double the cross-section of one extraction pipe to a portion corresponding to double the sum of all cross-sections of the extraction pipes.

3. A suction hood according to claim 1 or 2, wherein illuminating means are provided inside the suction hood on the flatter surface opposite the surface provided with the extraction pipes.

4. A suction hood according to claim 1, substantially as described with reference to Figs. 1 and 2 of the accompanying drawings.