GB2126918A

GB2126918A - Overspray collecting apparatus

Info

Publication number: GB2126918A
Application number: GB08224918A
Authority: GB
Inventors: Eric Charles Hopson
Original assignee: Metal Box PLC
Current assignee: Crown Packaging UK Ltd
Priority date: 1982-09-01
Filing date: 1982-09-01
Publication date: 1984-04-04

Abstract

Apparatus for collecting stray lacquer 3 from a spraying jet 2 comprises a duct 4 in which air is moved rapidly to convey the stray lacquer along the duct 4 from the jet into an expansion chamber 5 in which the lacquer settles out from the air. Separation of the air from the lacquer may be assisted by a second expansion zone 8, a mesh filter 11 and a removable glass fibre filter 12. The jet 2 applies lacquer to the side seam of a can body 1. <IMAGE>

Description

SPECIFICATION Apparatus for collecting stray lacquer from a spraying jet This invention relates to apparatus for collecting stray lacquer from a spraying jet and more particularly but not exclusively to apparatus for collecting an overspray of lacquer from a jet applying a stripe of lacquer to the side seam of a can body.

During the application a strip of lacquer to the side seam of a can it is usual to convey each can past a stationary jet from which fan shaped spray of lacquer is applied onto the side seam so that the whole length of the seam is progressively coated along its length as the can progresses past the jet. Whilst it is possible to provide sensors which control the jet to deliver lacquer only when a can is in the path of the spray it is our experience that some over spray occurs and so it is necessary, in order to minimise the risk of fire, to collect any over sprayed lacquer and any volatile constituents arising as the lacquer starts to dry.

Hitherto a large hood has been placed over the conveyor to envelope the region of the spray jet and a general movement of low velocity air has been used to move the lacquer over sprayed and volatile substances into the hood for removal along a duct: the objective being to dilute the lacquer volatiles to a non-flamable concentration which may be disposd of. In order to accommodate the large volumes of air required the hood and ducts have been large and therefore costly.

Unfortunately, a low velocity air stream permitted the lacquer to settle in the hood from which it sometimes dripped back onto the cans. Increasing the fan capacity to minimise the risk of dripping required larger ducts which are more costly.

In contrast this invention provides apparatus in which one end of the duct is adjacent the spraying jet and the other end of the duct connects with a chamber of greater cross-sectional area than the duct, the chamber having means to collect the stray lacquer and means to remove the air as the fast moving air in the duct slows down in the chamber.

The benefits arising from the use of a high velocity air movement are that the lacquer and volatiles are efficiently collected by a relatively small duct in which they do not settle, so that the lacquer and any volatiles condensing are collected in the chamber and the air is removed in a cleaned condition for discharge into the atmosphere.

In one embodiment of the apparatus a baffle plate divides the chamber into a first settling zone into which the duct leads and a second settling zone from which the cleaned air is removed.

The cleaned air may be removed through a pipe which may be spanned by a mesh. At the junction of the pipe with the chamber a drawer may be provided in which a gauze filter pad is placed. The gauze may be of fibre glass material.

The apparatus is particularly useful on apparatus applying a stripe of lacquer to the side seam of can bodies such as are made by soldering or welding because it takes the inflammable lacquers and volatiles away from the hot cans.

One embodiment of the invention will now be described by way of example and with reference to the accompanying drawings in which: Fig. 1 is a side elevation of the apparatus sectioned on the centre line of the duct; Fig. 2 is an end elevation of the apparatus of Fig. 1; and Fig. 3 is a plan view of the apparatus of Figs. 1 and 2.

As shown in Fig. 1, the apparatus is depicted in use in conjunction with apparatus for applying a stripe of lacquer to the interior of the side seam of a row of cans. Each can 1 passes over a spray jet 2 and during the short period between spraying can bodies, in which no can body lies over the jet 2, any over spray 3 is collected by a rapidly moving air flow in a duct 4 adjacent the overspray. The duct 4 leads into an expansion chamber 5 in which the lacquer is separated from the air. The cleaned air is removed up an extract pipe to by an air moving means not shown. Early trials with a domestic vacuum cleaner gave useful air-flow rates, but industrial fans are more suitable.

In Fig. 1 the apparatus comprises the duct 4 which leads into a first settling zone 7 of the chamber 5. The first zone 7 is separated from a second settling zone 8 by a baffle plate 9 and a box wall 10. The box wall 10 and walls of the chamber support a mesh filter 1 1 which spans the exit path of the air. A drawer 12, shown partly in open in Fig. 1, contains a fibrous pad 13 which may be of glass fibre. The drawer 12 spans the entry to the extract pipe 6 and permits easy removal of the pad when saturated.

Referring to Figs. 1, 2 and 3 the duct 4 can be seen to be rectangular in cross-section so that it is able to generally conform to the cross-section of the fan shaped spray emerging from the jet 2. The cross-section area of the duct 4 is much less than the cross-section of the chamber 5 which defines the cross-sectional area of the first settling zone 7 so that as the velocity of the air and lacquer arriving in the first settling zone 7 abates the lacquer falls out of the stream for collection in the bottom of the chamber 5. Any volatile material condensing along the length of the chamber 5 is collected in the first or second settling zones 7, 8.

In this particular apparatus the duct 4 has a cross-section 20 mm wide by 60 mm along the path of can travel making a cross-sectional area of 1,200 sq.mm. The chamber is a rectangular box approximately 400 mm long and has a crosssection of 100 mm deep by 120 mm wide making a cross-sectional area of 12,000 mm. Therefore the ratio of duct cross-section to first zone crosssection is 120 to 1,200 or 1:10 giving a reduction in air speed in the zone to approximately one tenth of the duct speed.

The air flow past the baffle 9 gives a further opportunity for an expansion of the air so permitting further removal of the airborne lacquer.

The mesh filter 11 provides a further surface on which precipitation can occur. Any droplets forming on the mesh may fall back into the chamber for collection. If, however, droplets are carried onwards from the mesh filter 11 they are caught in the fibrous pad 13.

In Fig. 1 and 2 the floor 14 of the chamber 5 can be seen to slope downards to a drain hole 15 which, in operation, is kept closed. However, the drain hole may be kept open if the tube is connected to the drain hole to lead below the meniscus of fluid in a collecting vessel (not shown).

The chamber 5 is provided with a removable lid 16 which is held in air tight closure by toggle fasteners. The lid may be removed to inspect the level of the lacquer collected. As the apparatus described is quite small and will contain only about a gallon of lacquer it is quite practicable to simply invert the chamber to pour out the lacquer collected if this is found more convenient.

The invention may be applied in various forms not limited to the shape and size of the specific embodiment described; and may be applied to various situations when an overspray of lacque or the like occurs. For example the apparatus may be used to catch over spray from a jet applying an external stripe of lacquer to a can body.

Claims

1. Apparatus for collecting stray lacquer from a spraying jet, said apparatus comprising a duct in which air is moved to convey the stray lacquer along the duct, characterised in that, one end of the duct is adjacent the spraying jet and the other end of the duct connects with a chamber of greater cross-sectional area than the duct, the chamber having means to collect the stray lacquer and means to remove the air.

2. Apparaus according to claim 1 characterised in that a baffle plate divides the chamber into a first settling zone into which the duct leads and a second settling zone from which the air is removed.

3. Apparatus according to claim 1 or claim 2 characterised in that the means to remove the air from the chamber is a pipe spanned by a mesh.

4. Apparatus according to any preceding claim characterised in that the means to remove the air from the chamber is a pipe spanned by a fibreglass filter supported in a drawer.

5. Apparatus according to any preceding claim when mounted on apparatus for applying a stripe of lacquer to a side seam of a can body.

6. Apparatus, substantially as hereon before described and shown in the accompanying drawings.