AU737202B2 - Air inlet arrangement and heat exchanger for spray painting booth - Google Patents

Description

P/00/011 Regulation 3.2

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

TO BE COMPLETED BY APPLICANT a 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: Air Inlet Arrangement and Heat Exchanger for Spray Painting Booth Details of Associated Provisional Application No P04621 dated 16th January 1997 The following statement is a full description of this invention, including the best method of performing it known to me:-

BACKGROUND

Spray painting booths are used for spray painting articles such as vehicles, and have the function of maintaining a controlled environment where exposure to dust, moisture, temperature and other environmental interferences can be controlled to a certain degree, as well as providing for a measure of safety for spray painters by limiting the degree of exposure to paint vapours.

The control of temperature and airflow are two important aspects of spray painting booths and it is a difficult balance to provide suitably distributed airflow in an economic way.

Additionally given the volume of air that is required, another important requirement is to provide air at the requisite elevated temperatures, for curing of the paint as economically as 15 possible, or for drying moisture from the spraying chamber.

SUMMARY OF THE INVENTION In a broad form the invention could be said to reside in a spray painting booth including, a 2 spraying chamber, said spraying chamber having a floor to support an article to be 20 sprayed, walls enclosing the chamber extending upwards from the floor, with a door for entry of the article to be sprayed positioned in at least one of said walls, and a ceiling i extending across the walls, an air distribution arrangement positioned outside of the spraying chamber, said air distribution arrangement including an inlet duct arrangement to deliver air to inlets of the spraying chamber, a spraying chamber outlet arrangement to direct air away from the spraying chamber, a fan to drive air through the air distribution •arrangement so as to provide an airflow through the spraying chamber and a heater arrangement to heat air directed through the inlet duct arrangement, said inlet duct arrangement comprising at least two channels, a heating channel, and at least one delivery channel, a plurality of spraying chamber inlets are spaced along the delivery channel to provide for air ingress through the ceiling into the spraying chamber, in use air travels through the heating channel in one direction and direction changes before entering the delivery channels, said heater arrangement including a fuel fired combustion chamber positioned towards a downstream end of said heating channel, and one or more exhaust pipes extending upstream from the combustion chamber through at least a portion of the heating channel, to exhaust flue gasses from the combustion chamber in a direction opposite to air movement through the heating channel, said one or more tubular exhaust _pipes made of a heat conductive material.

I I) 3 Preferably the combustion chamber is positioned within the heating channel, with a combustion inlet opened out from the downstream end of the heating channel.

In one form there is provided one central heating channel and two flanking distribution channel, one on either side of the heating channel It will be understood that preferably the inlet duct arrangement is positioned centrally over the spraying chamber so that there are two rows of spraying chamber inlets each spaced on either side of a medial portion of the spraying chamber, extending away from the door to the spraying chamber.

i *The heating channel is preferably defined within walls of an insulated material, and at least S'two flue pipes extend away from the combustion chamber along the heating channel, i preferably along substantially the length of the heating channel.

Preferably the at least two exhaust pipes each include at least two bends to cause turbulence within the heating channel.

Preferably the at least two exhaust pipes include a loop.

•In one form the heating channel is of rectangular cross-section, and there are four flue pipe extending along the heating channel, and a portion of a respective flue pipe extending toward corners of the rectangular cross-section.

In an alternative aspect the invention can also be said to reside in an inlet arrangement for a spray painting booth as defined or described herein. This might be retrofitted to an existing spray booth.

The invention may also be said to reside in form of the heat exchanger as defined or described herein.

BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding, the invention will now be described with reference to two illustrated embodiments wherein, Figure 1 is a sectional plan view through the inlet duct arrangement, showing the basic layout including the relative position of the central heating duct and the S 4 flanking delivery ducts, the combustion chamber and exhaust pipes, and the fan, for simplicity showing only one exhaust pipe, Figure 2 is a cross sectional view of the spraying booth through II-II in Figure 1 including showing the position of the spraying chamber air distribution arrangement, and Figure 3 is a cross sectional view of the spraying booth through III-III in Figure 1 Similar reference characters indicate corresponding parts throughout the several views of the drawings.

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

°The illustrated embodiment is a spray painting booth for the painting of vehicles. The spray painting booths comprises a spraying chamber generally rectangular in plan and which is defined within a rectangular floor four walls 4, 5, and and a ceiling A door allows vehicular access through wall to the interior of the spraying chamber. In addition to the spraying chamber the spray painting booth comprises an air •°distribution arrangement which is positioned outside of the spray painting booth. The air distribution arrangement comprises an inlet duct arrangement and spraying chamber outlet arrangement A fan (12) drives air through the air distribution arrangement and thereby provides a flow of air through the spraying chamber for adequate ventilation for spray painting an article.

The inlet duct arrangement comprises three channels, a central heating channel (15) and two flanking, air delivery channels (16, 17). The air delivery channels each leads to a plurality of spraying chamber inlets which are spaced apart therealong. In use air travels through the heating channel in onedirection as indicated by arrow (19) and then in a second direction through both of the flanking delivery channels as shown by arrows 21).

The heating channel acts as a countercurrent heater. A fuel fired combustion chamber and four exhaust pipes, shown at (26) are positioned within the heating channel. The combustion chamber (25) is positioned close to a downstream end (27) of the heating channel. A combustion chamber fan (30) blows air into the combustion chamber and provides oxygen for combustion of the fuel, and also drives flue gasses through the m exhaust pipes (26) along the heating channel in the direction indicated by the arrows, and then through the exhaust flue (28) which leads the flue gasses up out through the spraying booth into the atmosphere.

Turning now in some detail to the construction of the air inlet duct arrangement This is positioned centrally on the spraying chamber extending away from the door, which means that the spraying chamber inlets (18) are positioned in two rows (31a, 31b) on either side of a central portion of the ceiling This can perhaps best be seen in Figure 2. The spacing of these two rows (31a, 31b) can be varied depending on the desired effect. If they are spaced broader then the downdraft of air derived from each of the rows (35,36) will be kept away from the vehicle and effects of turbulence on the quality of the *finish will be kept to a minimum. It can be seen that the spraying chamber inlets each S:comprise an aperture (32) in the ceiling which leads to an inlet housing which is of dimensions larger than that of the aperture. The inlet housing may be of a pressed metal S -15 peripheral frame which is fixed to the ceiling, with a wire grid (not shown) supported at a lowermost part of the frame to cover the opening of the peripheral frame. A filter positioned over the wire grid to provide a filtering of air passing therethrough. The inlet housing chamber (34) defined within the inlet housing act as a small plenum chamber to 0.0 diffuse the directionality of air passing therethrough.

i .The construction of the air inlet duct arrangement is of insulated building panels such as marketed under the trade name Bondor. These panels are substantially a sandwich of aluminium sheeting on either side of a polystyrene insulating core. The sheeting is keyed *"together at peripheral edges, and comers are held together by an appropriate aluminium extrusion. The central heating channel (15) and the air delivery channels (16, 17) are substantially rectangular in cross section, and approximately 700mm in width. The heating channel is connected to both of the air delivery channels by duct apertures 41), whereby air flows in the direction shown by arrow (19) through the heating channel changes direction through 1800 as it passed through duct apertures (40,41) and then into the air delivery ducts. It will be understood that the combined cross sectional area of the air delivery ducts is substantially more than the cross sectional area of the heating channel. The change in direction of airflow and the increased cross sectional area results in a much reduced flow, and a further reduction in flow and decrease in directionality is achieved on entry of air into the inlet housing chamber (34).

A fan forced gas burner (42) is used to provide heat in the heating channel The flame from the gas fired heater is contained within the combustion chamber A combustion chamber housing is made of metal, such as steel, which permits ready exchange of heat with the flames and flue gasses of the gas fired burner. The combustion chamber housing is preferably surrounded by a shroud and spaced apart therefrom to provide protection to the panels making the heating channel in the immediate vicinity of the combustion chamber from radiant heat emanating from the combustion chamber housing. It is found that otherwise damage to the polystyrene insulation within the panels may result. The shroud can take on a substantially cylindrical shape and also be made from a heat conductive material such as steel, so that it also acts as a fin to provide additional heated surfaces for heat exchange exposure to the air passing therethrough.

The four exhaust pipes (26) are each joined at a first end to the combustion chamber housing, and are flanged to provide a degree of transition from the cross-sectional dimensions of the combustion chamber to the four exhaust pipes. The exhaust pipes again are made of a heat conducting material such a steel, the metal tube is curved twice to reverse the direction of the exhaust tubing so as to describe a loop such as shown at The loops of respective exhaust pipes extend radially towards respective apices (47) of the heating channel as can best be seen in Figure 2. This acts to dampen noise occaised by the burner and also enhances the heat exchange considerably whilst being economic to "construct. At a second end each of the four exhaust pipes are joined to a flue (28) which extends upwardly out of the heating channel and into the atmosphere. The flue can be made, for example, of pressed metal.

A metal end plate (46) separates the fan (30) from the outlet of the burner, and is formed also as a deflection plate to direct air coming to the end of the heating channel through the 0 0.

respective duct apertures (40, 41). The entire heating arrangement including burner, combustion chamber, exhaust pipes and exhaust flue are substantially sealed from ingress of air from the heating channel. Seals are provided for joints, and where necessary a heat resistant sealant is used, and welds are tested for air tightness. The difficulty that arises is that the air pressure within the heating arrangement is considerably lower than the air pressure within the heating channel. The capacity of the fan (30) that feeds into the combustion chamber is very much less than the capacity of the fan (12) that is responsible for causing an air flow through the air distribution arrangement and the spraying chamber.

Where leaks occur between the heating chamber and the heating arrangement, the counter current is disturbed, or the burner can be extinguished by a reversal of the air flow. To facilitate the integrity of the seals, the heating arrangement is mounted on a frame, so as to minimise movement. In the illustrate embodiment, although not shown, a flat bar frame is used to rigidly hold the exhaust pipes in place. The combustion chamber is bolted to the end plate (46) to provide a firm mounting.

In the present embodiment, air is drawn into the heating channel either through an air intake channel (50) from above. Air passes through a bend, immediately before it enters the heating channel, thereby cause some immediate turbulence. The position of the exhaust pipes themselves enhance turbulence, and this is enhanced by the loops (45) and their extension towards the apexes of the heating channel. Additionally the flat end of the combustion chamber further enhances the turbulence of the air passage through the heating channel. It is found with this arrangement that there is a very efficient exchange of heat, and that whereas the heat in the combustion chamber is estimated to be in the vicinity of 4-500C the temperature in the flue is in the vicinity of 55 0 C, which is at least three times less than is experienced in normal cross flow heating arrangements for spray painting booths.

It can be seen from the drawings that the illustrated embodiment is a downdraft spray painting booth and is ideally suited thereto. It can be also seen that the spraying chamber 15 outlet arrangement includes a pit (52) underneath the floor of the spraying chamber. The floor comprises a grid, perhaps of pressed metal, supported on a metal frame to permit air flow therethrough. The pit leads to a services end (53) of the booth. Air coming through •the spraying chamber outlet arrangement is directed through a spraying booth exhaust S-outlet Variation of this particular layout can be used, and in some instances it may be desired to allow for recirculation. The positioning of the fan and recirculating duct are well known in the art and can be modified to suit the required arrangement.

Claims (10)

1. A spray painting booth including, a spraying chamber, said spraying chamber having a floor to support an article to be sprayed, walls enclosing the chamber extending upwards from the floor, with a door for entry of the article to be sprayed positioned in at least one of said walls, and a ceiling extending across the walls, an air distribution arrangement positioned outside of the spraying chamber, said air distribution arrangement including an inlet duct arrangement to deliver air to inlets of the spraying chamber, a spraying chamber outlet arrangement to direct air away from the spraying chamber, a fan to drive air through the air distribution arrangement so as to provide an airflow through the spraying chamber and a heater arrangement to heat air directed through the inlet duct arrangement, said inlet duct arrangement comprising at least two channels, a heating channel, and at least one delivery channel, a plurality of spraying chamber inlets are spaced along the 15 delivery channel to provide for air ingress through the ceiling into the spraying chamber, in use air travels through the heating channel in one direction and direction changes before entering the delivery channels, said heater arrangement including a fuel fired combustion chamber positioned towards a downstream end of said heating channel, and one or more exhaust pipes S* 20 extending upstream from the combustion chamber through at least a portion of the heating channel, to exhaust flue gasses from the combustion chamber in a direction opposite to air emovement through the heating channel, said one or more tubular exhaust pipes made of a :*heat conductive material.

2. A spray painting booth as in claim 1 wherein the combustion chamber is *o**positioned within the heating channel, with a combustion inlet opened out from the downstream end of the heating channel.

3. A spray painting booth as in claim 1 wherein the one or more exhaust pipes are wholly contained within said heating channel.

4. A spray painting booth as in claim 1 wherein the one or more exhaust pipes extend along substantially the length of the heating channel.

5. A spray painting booth as in claim 4 wherein the one or more exhaust pipes each include at least two bends to cause turbulence within the heating channel.

6. A spay painting booth as in claim I wherein the one or more exhaust pipes include a loop.

7. A spray painting booth as in claim 1 wherein the heating channel is rectilinear in cross section, and there are four exhaust pipe extending along the heating channel, and a portion of a respective exhaust pipe extending toward comers of the heating channel.

8. A spray painting booth as in claim 1 wherein the exhaust pipes are made of steel.

9. A spray painting booth as in claim 1 wherein the exhaust pipes are connected to a common flue through which the exhaust gasses are emitted to the atmosphere A spray painting booth as in claim 1 including one central heating channel and two flanking distribution channel on either side of the heating channel change direction of 180 degrees

11. A spray painting booth as in claim 10 wherein the inlet duct arrangement is positioned centrally over the spraying chamber so that there are two rows of spraying 20 chamber inlets each spaced on either side of a medial portion of the spraying chamber, 20 extending away from the door to the spraying chamber. Aspray painting booth as in claim 1 wherein the heating channel is defined within walls of an insulated material, and at least two exhaust pipes extend away from the combustion chamber along the heating channel. 25 13. An air distribution arrangement of positioning outside of a spraying chamber of the type having a floor to support an article to be sprayed, walls enclosing the chamber extending upwards from the floor, with a door for entry of the article to be sprayed positioned in at least one of said walls, and a ceiling extending across the walls, said air distribution arrangement including an inlet duct arrangement to deliver air to inlets of the spraying chamber, a spraying chamber outlet arrangement to direct air away from the spraying chamber, a fan to drive air through the air distribution arrangement so as to provide an airflow through the spraying chamber and a heater arrangement to heat air directed through the inlet duct arrangement, said inlet duct arrangement comprising at least two channels, a heating channel, and one or more delivery channels, a plurality of spraying chamber inlets are spaced along the S delivery channel to provide for air ingress through the ceiling into the spraying chamber, in use air travels through the heating channel in one direction and direction changes before entering the delivery channels, said heater arrangement including a fuel fired combustion chamber positioned towards a downstream end of said heating channel, and one or more exhaust pipes extending upstream from the combustion chamber through at least a portion of the heating channel, to exhaust flue gasses from the combustion chamber in a direction opposite to air movement through the heating channel, said one or more exhaust pipes made of a heat conductive material. Dated this 4th day of June 2001 JOHN CHARLES MILTON By his Patent Attorneys A.P.T. Patent and Trade Mark Attorneys o• oS I.