WO1996018511A1

WO1996018511A1 - Apparatus for supporting articles in liquid treatment tanks

Info

Publication number: WO1996018511A1
Application number: PCT/GB1995/002911
Authority: WO
Inventors: Peter William Gammage
Original assignee: Rotary Stripping Systems Limited
Priority date: 1994-12-16
Filing date: 1995-12-13
Publication date: 1996-06-20
Also published as: GB2295959B; GB9525479D0; AU4183796A; GB9425416D0; GB2295959A

Abstract

An apparatus for treating elongate articles comprising: i) a tank; ii) a longitudinally extending rotatable mounting means (5, 6) mounted on a frame (7); iii) at least two carrier plates, attached at spaced locations along said mounting means, said plates incorporating a plurality of apertures disposed about the area of each plate, each aperture being dimensioned to accept by lengthwise insertion one or more articles to be treated; iv) means to rotate said mounting means and said carrier plates, such that during treatment at least a portion of each plate and the articles therein are immersed in the contents of the tank.

Description

APPARATUS FOR SUPPORTING ARTICLES IN LIQUID TREATMENT TANKS

Field of the Invention

The present invention relates to an apparatus for treating articles in a tank, or a series of tanks, and relates particularly but not exclusively to the stripping of paint, powder coatings and other surface finishes from extrusions.

Background to the Invention

Aluminium extrusions are commonly used, for example, in window frame construction and for such purposes it has become commonplace to coat the extrusions, the term coating in this context includes not only painting in the conventional sense but also modern techniques such as powder-coating, anodizing and the like.

At times it is desirable to remove such coatings^or example when the coating is of inferior quality. Conventionally, this has been achieved by immersing the articles in a paint stripping medium such as methylene chloride or N- methyl pyrrolidone. It is usual to support the articles in a basket type arrangement. Rows of the articles are supported in a superimposed arrangement by means of wires at each end of the article. The basket is then immersed in a bath or tank of paint stripping medium. This method has a number of disadvantages. Firstly, many extrusions have complex shapes in which air can become trapped when the article is immersed. This may cause the paint stripper to be ineffective in the region of such trapped air. Secondly, the paint stripped off one article falls towards the bottom of the stripping bath. Where the articles are arranged one row above another, the paint from the upper row generally falls onto the upper surface of the row beneath, whereby such surfaces are protected from further attack by the paint stripper. Finally, where the articles are supported on wires, the area where they are supported cannot be attacked by the paint stripper. In this context the term paint stripper refers to any chemical agent suitable for removing a surface coating.

For all these reasons it is usually necessary for the articles to be restacked and placed in a second stripping bath.

A mechanical apparatus has been described in United Kingdom patent GB2 182 237 (Gammage) which overcomes these disadvantages to some extent. The apparatus, which is the closest prior art known to the inventor, comprises a series of plates mounted on an axle. Each plate has a series of apertures in its surface and these are aligned along the axle such that, starting at one end, long extrusions can be threaded through each aperture in turn until the extrusions are supported on plates along the majority of their length. The whole assembly is then lowered into a tank of stripping medium and the plates are rotated on the axle. As they rotate, different faces of the extrusions are exposed and eventually the entire surface coating is removed and the strippings fall to the bottom of the tank.

Although a considerable improvement over the manual arrangement this mechanical apparatus nevertheless suffers from a number of inherent disadvantages.

(a) The tank in which the plates rotate is rectangular in cross-section and as a consequence the strippings tend to build up in the corners. Any potential abrasive properties that the strippings might have and therefore potential to accelerate the stripping process is therefore lost. (b) The tanks have to be cleaned out periodically and this is an unpleasant and messy operation at the best of times.

(c) No hood or extraction system is provided for. This presents a real hazard in the case of certain stripping agents. The use of such agents is being more and more tightly controlled by Health and Safety

Legislation.

(d) No provision is made for stripping small items yet these are routinely used in coating systems.

(e) Use of the known apparatus is restricted to long items and it cannot accommodate irregular shapes.

It is the object of the present invention to overcome some or all of these disadvantages and to provide an apparatus which will comply with current and projected health and safety requirements.

Summary of the Invention

According to a first embodiment of the present invention there is provided an apparatus for treating elongate articles comprising:

i) a tank;

ii) a longitudinally extending rotatable mounting means mounted on a frame;

ϋi) at least two carrier plates, attached at spaced locations along said mounting means, said plates mcorporating a plurality of apertures disposed about the area of each plate, each aperture being dimensioned to accept by lengthwise insertion one or more articles to be treated; iv) means to rotate said mounting means and said carrier plates, such that during treatment at least a portion of each plate and the articles therein are immersed in the contents of die tank;

characterized in that the bottom of the tank is so sized, shaped and profiled that it corresponds to the size and shape of the carrier plates such that the treatment action of the apparatus may be enhanced due to the abrasive effect of any suspended solids being retained in close proximity to the articles as they rotate.

In a second embodiment a fall is introduced into the said tank such that the combination of the fall, the shape of the bottom of the tank and the agitation caused by the rotation of the articles being treated positively directs any solid waste to the lower end of the tank.

Preferably the apparatus further comprises a hood, associated with the rotating means or frame, and adapted to substantially cover the tank whilst the articles are being treated.

Preferably the hood incorporates condensing means such that any vapour associated with liquid in the tank will condense on the condensing means and thus be prevented from escaping to atmosphere.

In a particularly preferred embodiment the hood incorporates a depending skirt extending substantially around the perimeter of the hood such that the articles can be lifted clear of any liquid in the tank whilst the tank remains substantially covered by the hood and skirt in combination.

Preferably the skirt is of a concertina type, collapsing and expanding in relation to the uppeπnost-in-use edges of the tank.

In a further preferred embodiment the apparatus incorporates an extraction means adapted to prevent vapour from the treatment liquid escaping to atmosphere in the vicinity of the tank.

Preferably provision is made on the rotatable mounting means to treat small items by incorporating one or more closeable containers which rotates along with the mounting means.

Preferably the containers take the form of substantially sector-shaped drawers i.e drawers having walls tapered towards one end of the drawer, which when placed in a corresponding-shaped holder mounted on the rotatable mounting means provides a method of "containerizing" small items in self -draining containers.

In a further embodiment there is provided an apparatus for treating elongate articles comprising:

i) a tank;

ϋ) a longitudinally extending rotatable mounting means mounted on a frame;

ϋi) at least two carrier plates, attached at spaced locations along said mounting means, said plates mcorporating a pluraϋty of apertures;

iv) means to rotate said mounting means and said carrier plates, such that during treatment at least a portion of each plate and the articles inserted therein are immersed in the contents of the tank;

characterized in that articles may be loaded into some or all of the apertures from the side of the plate as opposed to being loaded by lengthwise insertion through the apertures.

In a further embodiment there is provided an apparatus for treating elongate articles comprising: i) a tank;

ϋ) a longitudinally extending rotatable mounting means mounted on a frame;

ϋi) at least two carrier plates, attached at spaced locations along said mounting means, said plates incorporating a plurality of apertures;

characterized in that the said mounting means is supported along its length at a point or points distant from each end of the mounting means, said support being provided by a supporting means operating substantially around the periphery of an appropriately positioned plate or plates and which therefore does not interfere with the rotation of articles loaded onto said plates.

Brief Description of the Drawings

Embodiments of the present invention will now be more particularly described by way of example only and with reference to the accompanying drawings in which:

Figure 1 is a side elevation of an apparatus according to the prior art but incorporating a central support means;

Figure 2 shows a cross-section through the bracketry associated with one form of support means; Figure 3 shows a cross-section through a tank with a semi-circular bottom;

Figure 4 shows a perspective of a frame incorporating a hood;

Figure 5 shows a perspective of a hood of the type illustrated in Figure 4 and which incorporates a skirt depending from the hood;

Figure 5A shows an extraction system incorporated into a hood as shown in

Figure 5;

Figures 6 and 7 show adapters suitable for processing frames or other non- elongate items;

Figure 8 shows an end elevation of a plate incorporating a series of drawers;

Figure 8A shows a front elevation of a series of plates and drawers as shown in Figure 8;

Figure 9 shows a face elevation of a plate where entry to the apertures is possible from the periphery of the plate.

Description of the Preferred Embodiments

The present embodiments represent currently the best ways known to the appϋcant of putting the invention into practice. But they are not the only ways in which this could be achieved. They are illustrated, and they will now be described by way of example only.

Referring first to Figure 1, this shows a side elevation of the general type of apparatus described in GB 2,182,237 with an additional central support in the form of carrier plate 1. This additional plate is formed to a similar profile to the other carrier plates and contains identical apertures. In this example it is constructed from heavier gauge material, and is locked in place between the two halves of the longitudinal axle 5 and 6. This central plate is fitted with two rolled stainless steel angle hoops 2 of slightly greater circumference than the central plate itself. The angle hoops are placed one on each side of the plate and are bolted through the plates to act as a guide for a chain support 3, which in turn is fed over the top of the main frame via a sprocket located between bearings 4 bolted to main frame. The chain thus encircles the outer perimeter of disk 1 and passes over the top of the main frame 7.

The length of the chain is adjusted so that the axle is supported in use in a horizontal position even when the carrier plates are fully loaded.

In this example the support plate 1 is not driven but this need not be the case. There are circumstances where driving the system from at or near the mid¬ point of the axle may be a positive advantage and this arrangement makes this possible.

Although in this example a chain is used as support means it is intended to cover any suitable mechanical equivalent such as a strap or belt.

As well as or instead of being supported by a chain as described above the centre plate may also be supported by steel load bearing wheels located beneath the rim of the stainless steel hoops and fixed in position via bracketry bolted through the underside of the main frame. This arrangement is shown ^grammatically in more detail in Figure 2. Brackets 10, 11 are mounted beneath main frame 7 and are used to support bearing wheels 12 which rotate on bearings 13. Steel hoops 2 attached to the perimeter of carrier plate 1 are thus supported by bearing wheels 12 the whole assembly being constructed in such a way as to take the weight of the fully laden assembly.

When the materials in excess of 8 metres in length are being processed, it may well be that additional support using one or both of the aforementioned methods has to be placed at strategic intervals along the longitudinal length of the axle. That is to say, two or more of these support assembϋes can be introduced as necessary.

Turning now to Figure 3, this shows a cross-section of a tank, looking along the line of the axle, where the_. tank is no longer rectangular in profile. Instead of a flat bottomed rectangular tank, as would normally be used, this embodiment employs a tank with a semi-circular base 20. The shape of the base has in fact been chosen to follow approximately the contours of the plates 23. By avoiding having any defined corners in the bottom of the tank this ensures that any soϋds resulting from the treatment process remains in suspension and these can act as a mild abrasive to improve the efficiency of the whole treatment system. This novel arrangement can significantly increase the speed of treatment and thus reduce throughput times and thereby increase the output of the process.

Another very positive advantage stems directly from this novel tank design. By introducing a sϋght fall on the tank there is created what is in effect an archemedies screw type action, giving positive displacement of waste towards the lower end of the tank. This not only makes for easier waste removal but allows, for the first time, the option of mechanical, as opposed to manual, emptying. For the first time it is possible to automate the emptying process by sucking or pumping out waste soϋds as they are produced and providing a constant volume device for mamtaining the level of liquid in the tank. Such constant volume devices are known per se.

Alternatively, a mixture of ϋquid and solids can be withdrawn from the lower end of the tank in a constant or intermittent manner, taken to a filtration system where unwanted soϋds are removed and then the filtered liquid returned to the tank. Where the treatment process requires heating or cooling of this stripping agent this arrangement has the advantage that the temperature of the liquid can be adjusted during this recycling process. This avoids the necessity of having heating or cooling elements in the tank itself, where they are prone to damage. The incorporation of a heating system is particularly advantageous in the case of N-methyl pyrroϋdone as stripping agent which performs significantly better at temperatures above ambient.

The volatile nature of the solvents used in stripping treatment processes, such as methylene chloride based chemicals, and the less volatile but more pungent N-methyl pyrrolidone-type chemicals result in obvious health and safety problems. This invention also provides for fitting a hood to the main frame and this arrangement is shown in Figure 4. A rectangular hood 30, arranged and adapted to form a close fitting seal with the top of the tank is attached to the main frame. This hood arrangement means that during the time that the stripping process is going on the tank contents are substantiaUy completely covered, only being uncovered during transference of the articles from one tank to another or while the liquid is being allowed to drain off.

A more elaborate type of hood system is shown in Figure 5 wherein a concertina-type skirt 31 is suspended from all four edges of the hood 30 such that the tank remains substantially covered even when the main frame assembly is withdrawn from the ϋquid in the tank to allow the liquid to drain from the articles being cleaned. A concertina-type arrangement is just one way in which this feature can be incorporated and a positive sealing system, for example using magnetic strips, can be incorporated to keep the lower most edges of the skirt in contact with the rim of the tank.

The hood can also incorporate a condenser system (not shown) which is particularly advantageous because of the volatile nature of the stripping agents which, coupled with the constant agitation of the articles within the tank, means that evaporation losses can be considerable. This is particularly true when the stripping agent is being heated.

Known apparatus of this type cannot be used with irregularly shaped articles or with small items. Both these short comings have been addressed by this invention. Firstly, Figures 6 and 7 show adapters suitable for processing frames and the like or for processing small sheets or panels. Turning first to Figure 6 this shows an apparatus for holding window frames or simϋar objects which may be regular or irregular in shape but similar in size. The apparatus is designed to hold one or many similar objects up to the working depth of the holder. The apparatus consists of two sections 41, each section being attached to the main axle 42 either by clamping around the axle shaft as an adapter or by sϋding on to the shaft as a unit during assembly of the axle components. Each of the two sections consists of four pivoting arms 43 positioned as shown in Figure 6B. Each arm can be locked in place at any point in a 90° arc extending between the axle axis and an axis perpendicular to the axle by means of locking pivot 46. Each section of four arms may be positioned at any point along the shaft.

At the end of each arm and at 90° to the arm there is a support 44 covered with polypropylene (or other suitable material) on which the frames 45 to be treated are positioned. These supports are adjustable along the length of the arms to give overall adjustment in every direction allowing irregular shaped frames to be held in place. Once loaded all frames are loosely locked on to the holder by polyproylene bars 47 or discs 48. Thus practically any shape of frame can be accommodated providing it can be rotated within the working width of the tank, shown as a dotted line in Figure 6A

Turning next to Figure 7, this shows an apparatus for holding small sheets or panels. The apparatus consists of two end sections 51 and an intermediate section 52. The number of intermediate sections employed wϋl depend upon the length of the items to be stripped. If they are relatively short it may be that no intermediate sections are required.

Each section is clamped to the main frame 53 as an adapter or slid on to the shaft as a fixture, generally forming a mirror image on both sides of the main shaft. In this respect, the assembly of this device resembles that described in Figure 6. Each section consists of two arms 51, 52 fixed at their mid-points at substantially 90° to the main shaft. At the end of each arm and at 90° to the arm are located positioning supports 54. The positioning supports are made from thick-walled polyproylene tube which is slotted at regular intervals, these slots 55 providing support for the sheets or panels 56. The polypropylene tube may be supported internally by a rod or bar provided with fixings at each end.

To load the device, the sheets or panels are passed through the slots 55 in the supports 54, the end or corner supports are then twisted to 90° to lock the sheets in place. The supports 54 are adjustable along the length of the arms and each section is also adjustable along the main shaft to accommodate virtually any length of sheet. By these means any item which is of a size that can be locked in place within the maximum diameter of the circle created by rotating the work piece within the confines of the tank may be processed in this fashion.

The processing of small items (from paper-clips upwards) can be simpϋfied using a "containerized" system as shown in Figures 8 and 8A. A series of drawers 60 made up of a main compartment 61 and a detachable lid 62 are fitted in a holder 65 mounted around the longitudinal axle. The drawers 60 are self draining and uniformed in size and shape though naturally the side walls of the drawers taper towards the axle. The drawers are locked in place by retaining bars 63 and R cups 64. This containerized system can be incorporated as part of the main system or if desired could be a system in its own right. In use, the drawers are filled or partially filled with small items or items of irregular shape, closed by ϋd 62, and placed within a drawer housing formed between two adjacent plates 65. Once all the drawers have been loaded retaining bars 63 are slid through the handles on both the lids and the drawer bottoms and the retaining bars held in place by R cups 64. The whole assembly is then immersed into a tank and the contents cleaned or processed in the same way as elongate articles. On occasions it is necessary to process articles having a long but irregular shape, for example the hangers which carry extrusions through a powder coating process need cleaning on a regular basis. Such an irregular shape does not lend itself to length-wise insertions through a series of carrier plates. This difficulty has been overcome by a specially modified carrier plate as shown in Figure 9. Rather than a flat plate per se a substantially circular supporting structure 69 is formed which incorporates a number of apertures 70, 71 which can be loaded from the edge of the plate. Removal of bars 72 and 73 give so-called "side-access" so that irregularly shaped articles can be loaded directly without the need to pass them through adjacent plates, although there is still provision for this through, for example, apertures 74 and 75. Bars 72 and 73 are repositioned once all the articles have been loaded and the treatment process carried out as previously described. By this modification the supports commonly used in powder coating processes can be cleaned in a similar manner and along with the extrusions themselves. Since these items are generally made of steel, the speciaUy shaped supporting structure 69 can be made of the same material. If more aggressive chemicals are going to be used, then stainless steel would be a suitable option.

It will be appreciated that one or more supporting structures 69 can be introduced into the overall assembly as necessary, resulting in still further flexibility.

The reader is directed to this disclosure of patent specification GB 2,182,237 for any further detaϋs he may need to put the invention into practice.

In this context the term plate is intended to have a very broad meaning. It encompasses any structure, flat or otherwise that can support items in a tank in the manner described above.

Claims

1. An apparatus for treating elongate articles comprising:

i) a tank;

ϋ) a longitudinaUy extending rotatable mounting means mounted on a frame;

in) at least two carrier plates, attached at spaced locations along said mounting means, said plates mcorporating a plurality of apertures disposed about the area of each plate, each aperture being dimensioned to accept by lengthwise insertion one or more articles to be treated;

iv) means to rotate said mounting means and said carrier plates, such that during treatment at least a portion of each plate and the articles therein are immersed in the contents of the tank;

2. An apparatus for treating elongate articles as claimed in Claim 1 wherein a fall is introduced into the said tank such that the combination of the faU, the shape of the bottom of the tank and the agitation caused by the rotation of the articles being treated positively directs any soϋd waste to the lower end of the tank.

3. An apparatus for treating elongate articles as claimed in Claim 1 or Claim 2 wherein the apparatus further comprises a hood, associated with the rotating means or frame, and adapted to substantially cover the tank whilst the articles are being treated.

4. An apparatus for treating elongate articles as claimed in Claim 3 wherein the hood incorporates condensing means such that any vapour associated with ϋquid in the tank will condense on the condensing means and thus be prevented from escaping to atmosphere.

5. An apparatus according to Claim 3 or Claim 4 wherein the hood incorporates a depending skirt extending substantially around the perimeter of the hood such that the articles can be lifted clear of any liquid in the tank whilst the tank remains substantially covered by the hood and skirt in combination.

6. An apparatus as claimed in Claim 5 wherein the skirt is of a concertina type, coUapsing and expanding in relation to the uppeπnost-in-use edges of the tank.

7. An apparatus according to Claims 3-6 wherein the apparatus incorporates an extraction means adapted to prevent vapour from the treatment liquid escaping to atmosphere in the vicinity of the tank.

8. An apparatus according to any preceding claim wherein provision is made on the rotatable mounting means to treat small items by incorporating one or more closeable containers which rotate along with the mounting means.

9. An apparatus as claimed in Claim 8 wherein the said containers take the form of substantiaUy sector-shaped drawers i.e drawers having walls tapered towards one end of the drawer, which when placed in a holder mounted on the rotatable mounting means provides a method of "containerizing" small items in self-draining containers.

10. An apparatus for treating elongate articles comprising:

i) a tank;

ϋ) a longitudinally extending rotatable mounting means mounted on a frame;

iϋ) at least two carrier plates, attached at spaced locations along said mounting means, said plates incorporating a plurality of apertures;

11. An apparatus for treating elongate articles comprisingX

i) a tank;

ϋ) a longitudinally extending rotatable mounting means mounted on a frame;

characterized in that the said mounting means is supported along its length at a point or points distant from each end of the mounting means, said support being provided by a supporting means operating substantially around a periphery of an appropriately positioned plate or plates and which therefore does not interfere with the articles loaded onto said plates.

12. An apparatus for treating elongate articles substantially as herein described with reference to and as illustrated in any combination of the accompanying drawings.