AU732201B2

AU732201B2 - A spray booth

Info

Publication number: AU732201B2
Application number: AU24702/97A
Authority: AU
Inventors: John Charles Milton
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-06-04
Filing date: 1997-06-04
Publication date: 2001-04-12
Anticipated expiration: 2017-06-04
Also published as: AU2470297A

Description

P/00/011 Regulation 3.2

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

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*5*S TO BE COMPLETED BY APPLICANT Name of Applicant: JOHN CHARLES MILTON Actual Inventor: JOHN CHARLES MILTON Address for Service: A.P.T. Patent and Trade Mark Attorneys GPO Box 772 Adelaide, SA 5001 Invention Title: A Spray Booth Details of Associated Provisional Application(s) No(s) P00245 dated 4th June 1996 The following statement is a full description of this invention, including the best method of performing it known to me:- This invention relates to a spray booth and in a preferred aspect relates to a down draught spray booth.

Spray booths are used for spray painting and create an air flow past a spray painter so as to clear vapours associated with spray painting. Often these vapours have detrimental effects on the health of the user if there is prolonged and heavy exposure. The booths are also used where the painted article is to be heated, such as for example where it is desired to bake an enamel onto the article, as is often desired for vehicles.

A variety of booth designs have been made in the past, and these generally comprise a spraying chamber, with a recirculating duct positioned to give airflow in the spraying chamber either as a down draught, from ceiling to floor, or as a through draught from end wall to end wall.

One difficulty with spray booths is a result of the air currents travelling through the spraying chamber not being uniform. Some air currents will travel upwards carrying with tem dust or other fine particles taken from the upwardly facing surface, such dust tends to spoil the finish on the article. Down draught booths have superior properties in this regard because the general movement of air is downwards and not along the ground. Even with down draught booths, however, there are localised variations in movement of air, where for example there is uneven air flow downwards. Thus some areas will have no air distribution, and typically where the areas with no air distribution are heated, such as where lights are provided at corners between walls and ceilings of a booth then eddy currents are produced with attendant disturbance of dust and the like which afterwards settles on the painted article to flaw the finish.

Another difficulty is to provide for sufficient airflow to cany away the aerosols to give minimal exposure to the painter. A substantial flow of air is desirable, however, an extremely high capacity of airflow is required to give a flow rate adequate to clear vapours from the vicinity of where the spraying occurs and also provide the same flow throughout the remainder of the booth to thereby provide an even airflow throughout the entire booth.

The costs and technica difficulties associated with attempting such an approach make it e pt uc naprah aei prohibitive.

It is an object of the present invention to provide a spray booth which obviates or minimises any one of the above problems or at least provides the public with a useful choice.

In one form, although not necessarily the broadest or only form, the invention could be said to reside in a spray booth comprising, walls and a ceiling defining therein a spraying chamber, an entrance through one of said walls to allow for entry of the article to be spray painted and a closure of the entrance, an air duct positioned outside of the spraying chamber and in communication with the spraying chamber to direct air into the chamber to thereby provide a flow of air through the chamber, a fan in communication with the air duct, to provide drive for said flow of air, at least one inlet housing having an inlet housing outlet opening into the spraying chamber said inlet housing receiving air from the air duct through a ceiling inlet in the ceiling of the booth, the inlet housing outlet directing air at least downwardly into the spraying chamber, the spraying chamber directly under the ceiling aperture receiving a greater flow of downwardly directed air than elsewhere.

1 Preferably the inlet housing protrudes into the spraying chamber, and said ceiling inlet being substantially smaller than the inlet housing outlet, an air inlet chamber being defined between the housing and the ceiling there being provided flow restriction means to reduce flow through the inlet housing outlet so that said inlet chamber acts as an inlet plenum o• chamber.

Preferably the air duct forms an air duct plenum chamber above the ceiling which is in direct communication with said ceiling inlet.

25 Preferably there are filter means across the inlet housing outlet leading from the inlet housing to the spraying chamber, so as to filter out impurities in incoming air, and thereby reducing flow rate. This acts also to enhance the uniformity of flow through the inlet housing outlet.

The inlet housing may include housing side walls depending from the ceiling, said housing side walls including side wall apertures therethrough to provide side streaming of air into the spraying chamber, and said inlet housing outlet including said side wail apertures and at least one downwardly facing aperture extending between the side walls to provide the downwardly directed flow of air into the spraying chamber.

The spraying chamber may be generally elongate and have dimensions to receive a _specified size range of vehicles, there being a plurality of inlet housings and corresponding 4 pairs of ceiling outlets spaced to either side of a central vehicle position, such that air streams downwardly on either side of a vehicle parked within acentral vehicle position.

Lights may be positioned on the side corners of the booth between side walls and the ceiling and said side wall apertures directing air towards the lights whereby to blow air downwards over the lights to create a cooling effect and to minimise potential for air heated by said lights to generate an upwards current.

A diffusion baffle may be placed upstream of the side wall apertures of the inlet housing whereby to restrict the flow of air through the side wall apertures over the restriction caused by the filter. It is found that otherwise it is much more difficult to regulate the extent of the side stream and if the side steam is too high then there is potential for too much turbulence. The diffusion baffle is preferably an open cellular foam, denser, or at least more restrictive to air flow than the air filter. More preferably the baffle is used over 15 the filter and is of a dimension to wedge the filter in place between the ceiling and a bottom S of the housing.

-It will be understood that the spray painting booth is preferably heated so that a heater is positioned in communication with the air duct and that the walls and ceilings of the spray 20 painting booth are insulated. It will also be understood that it will usually be desirable to make provision for the recirculation of air that has already passed through the chamber, and that is especially the case where the chamber is to be heated.

For a better understanding the invention will how be described with reference to one embodiment as illustrated in the accompanying drawings wherein: Figure 1 is a cross sectional view laterally through the illustrated spraying booth S: showing the position of the air duct above the ceiling, the ceiling outlets leading to the outlet housing, and the direction of air flow within the spraying chamber relative to a vehicle positioned within the spraying chamber, Figure 2 is a perspective elevation of the inlet housingfrom beneath showing mesh positioned over the downwardly facing aperture and the location of the side wall apertures, Figure 3 is a cross-sectional view lengthwise through one of the outlet housings, showing detail of the position of the ceiling inlet in relation to the housing, the position of the frame around the housing, the air filter positioned to filter impurities from air passing through the outlet housing, and foam diffusion baffles positioned to reduce sideways flow through the side wall apertures and to act as a beading to wedge the filters in position, Figure 4 is a somewhat schematic plan view showing the position of the outlet housings relative to the outer plenum chamber and the ceiling apertures, and, Figure 5 is a side cross sectional view of a typical spraying chamber layout showing the position of the services, including the fan and the heater, as well as the air duct on top of the spraying booth, and a pit beneath.

Similar reference characters indicate corresponding parts throughout the several views of 15 the drawings.

0 Dimensions of certain of the parts as shown in the drawings may have been modified i and/or exaggerated for the purposes of clarity of illustration.

The constructional details of the present illustrated embodiment are quite similar, apart from the inlet housings and ceiling inlets, to those in co-pending application 55847/96, which specification is incorporated herein by reference.

The spray booth comprises walls and a ceiling and an access door at a first end of the booth. The booth is divided into a spraying chamber and a services chamber by a dividing wall Sheet metal air duct is supported by the ceiling, and a pit is provided beneath the floor of the booth. A common air passageway is provided up through the services chamber through the air duct, downwardly through the spraying chamber, through the pit and back to the services chamber, with the direction of airflow being shown by the arrows. As can be seen therefore the illustrated embodiment is a down draught booth with an air recirculation facility. It will be understood an interface bhetween the. bottom of the spraying chamber and the pit in this instance at the level of the floor, acts as an outlet for airflow to leave the spraying chamber.

A fan (10) driven by a motor (11) that is mounted on a box section frame (12) (shown only in part) made of RHS structural steel, and a heater shown in part at (13) is also supported by the frame. Also provided, but not shown, are fresh air intake and an air exhaust so that with appropriate control the spray booth can be operated in the normal manner, perhaps by using louvred closures to appropriately control the direction of airflow.

The spraying chamber is elongate so as to accommodate a vehicle, and spaced along the length of the spraying chamber are five inlet housings (20) each fastened to the ceiling.

The air duct supported above the ceiling is fanned out from a relatively narrow cross section above the services chamber to take the form of an air duct plenum chamber (21) above the ceiling of the spraying chamber, as best seen in Figure 4. It is also seen that the air duct and plenum chamber formed therefrom is tapered vertically being wider at the services chamber end of the booth and narrower at the access door end of the booth.

This reduces variation of the rate of air flow along the length of the air duct. Ten apertures forming ceiling inlets (22) pass through the ceiling, two spaced apart apertures for each inlet housing to direct air flow from the recirculating duct to the inlet housings.

o. 15 The construction of the inlet housings can best be seen by reference to Figures 2 and 3.

An inlet housing side wall (23) defines the periphery of the inlet housing. The side wall is made of sheet metal and includes an, upper, fastening flange (24) which is fastened by fasteners such as bolts (25) through the ceiling. Preferably the housing can be opened.

Hinges may be provided at one end, and quick release fasteners being provided around the remaining three sides. A lower part of the housing is defined by a metal mesh (26) which rests on a supporting flange (27) of the inlet housing side wall. It can be seen that the inlet housing has a generally open bottom which can be described as a downwardly open aperture The side walls of the inlet housing have a plurality of spaced apart side wall apertures (28) cut therethrough. It will be understood that the downwardly open aperture S. 25 (29) and the plurality of spaced side wall apertures (28) collectively constitute an inlet housing outlet. It may in some instances however be preferred only to have the downwardly open aperture, and no side wall apertures, in which case the former would constitute the inlet housing outlet. It might also be desired to have smaller downwardly open apertures, and perhaps not spaced directly beneath a corresponding ceiling inlet, to thereby further reduce the flow of air in the inlet housing.

An appropriate air filter (32) is layered over the outlets of the inlet housing, including the downwardly open aperture (29) through the bottom of the inlet housing, and the side wall apertures This may be of a type typically used to remove aerosols and dust particles in a spray booth. A denser foam strip (31) acts as a beading to wedge the filter between the supporting flange (27) and an opposing portion of the ceiling. The denser foam strip Ralso reduces the rate of air flow through the side wall apertures relative to the rate of air flow through the downwardly open aperture (29) and diffuses air passing therethrough to act as a diffusion baffle.

It can be seen that the ceiling inlets are considerably smaller than the open bottom housing.

An inlet chamber (35) is thus defined between the inlet housing and the ceiling. As a result of the baffle effect that the filter (32) and the denser foam strip (3 1) has as well as the relative size of the ceiling inlets (22) relative to the inlet housing outlet, the inlet chamber acts as a further plenum chamber of reduced air flow to assist with the redirection of the air. The extent of distribution in a sideways direction and downwards direction can be varied to suit the requirements by varying the relative size and position of the ceiling inlets the sizes of the side wall apertures (28) and the extent to which flow is restricted through the side wall apertures and the downwardly open aperture (29).

In the configuration as illustrated the booth width is approximately 4 metres, the inlet "15 housing is approximately 3 metres in length by 1 metre in width, and the ceiling inlets are approx 600mm by 600mm. The depth of the inlet housing is approximately 100mm.

The general direction of airflow within the spraying chamber can be seen by reference to Figure 1. A vehicle (40) is shown in dotted outline. Strong air streams (41,42) with 20 greater air flow than elsewhere are achieved directly beneath the ceiling inlets As can be seen the ceiling inlets are positioned on either side of a central vehicle position (43).

o Accordingly the strong air streams provide a very effective means of driving vapour laden air from a position where a painter will be working to spray the vehicle. Additionally a positive air pressure is maintained in other parts of the spraying chamber by reason of air passing through sidewall apertures (28) so as to maintain a further, even, downward airflow over the remainder of the booth, including over an area where lights (44) are positioned. This then ensures that the potential updraught effects of the strong air streams are obviated or at least minimised.

It may be desired to have a control to change the size of the ceiling apertures so as to reduce the flow rate of the strong air streams. Whilst the inlet chambers are shown across spraying chamber it may also be desired to have the inlet chambers forned longi'-"'tudinally: along the length of the spraying booth, or alternatively to have a single intermediate layer formed under the ceiling, going across the entire length and width of the spraying chamber.

Claims

1. A spray booth comprising, walls and a ceiling defining therein a spraying chamber, an entrance through one of said walls to allow for entry of the article to be spray painted and a closure of the entrance, an air duct positioned outside of the spraying chamber and in communication with the spraying chamber to direct air into the chamber to thereby provide a flow of air through the chamber,. a fan in communication with the air duct, to provide drive for said flow of air, at least one inlet housing having an inlet housing outlet opening into the spraying chamber said inlet housing receiving air from the air duct through a plurality of pairs of ceiling inlets in the ceiling of the booth, the inlet housing outlet directing air at least downwardly into the spraying chamber, the spraying chamber directly under the ceiling inlet receiving a greater flow of downwardly directed air than elsewhere. The spraying chamber being generally elongate and having dimensions to receive a specified size range of vehicles, the plurality of pairs of ceiling inlets spaced to either side of a central vehicle position, such that air streams predominantly downwardly to either side of a vehicle parked within acentral vehicle position. 20

2. A spray booth as in claim 1 wherein the inlet housing protrudes into the spraying o* o chamber, and said ceiling inlet being substantially smaller than the inlet housing outlet, an air inlet chamber being defined between the housing and the ceiling there being provided flow restriction means to reduce flow through the inlet housing outlet so that said inlet ooooo S•chamber acts as an inlet plenum chamber.

3. A spray booth as in either claim 1 or 2 wherein the air duct forms an air duct S.plenum chamber above the ceiling which is in direct communication with said ceiling inlet.

4. A spray booth as in claim 2 wherein filter means are positioned across the inlet S 30 housing outlet leading from the inlet housing to the spraying chamber, so as to filter out impurities in the recirculated air, and to also act as the means to reduce flow.

A spray booth as in any one of claims 2, 3, or 5 wherein the inlet housing includes housing side walls depending from the ceiling, said housing side walls including side wall apertures therethrough to provide for side streaming of air into the spraying chamber, and said inlet housing outlet including said side wall apertures and at least one downwardly -R facing aperture extending between the side walls to provide the downwardly directed flow of air into the spraying chamber. 9

6. A spray booth as in any one of the preceding claims wherein lights are positioned on the side corners of the booth between sided walls and the ceiling and said side wall apertures directing air towards the lights whereby to blow air downwards over the lights to create a cooling effect and to minimise potential for air heated by said lights to generate an upwards current.

7. A spray booth as in claim 5 wherein a baffle is placed upstream of the side wall apertures of the inlet housing whereby to restrict the flow of air through the side wall apertures over the restriction caused by the filter.

8. A spray booth as in claim 7 wherein the baffle is an open cellular foam, denser, or at least more restrictive to air flow than the air filter.

9. A spray booth as in either claim 7 or 8 wherein the baffle is used over the filter and is of a dimension to wedge the filter in place between the ceiling and a bottom of the housing. A spray booth substantially as hereinbefore described with reference to the 20 illustrations. .00: S"Dated this 5th day of February 2001 0••o :o0 25 JOHN CHARLES MILTON By his Patent Attorneys, A. P. T. Patent and Trade ~Mark Attorneys 00..