GB2182237A - Apparatus for supporting articles in liquid treatments - Google Patents

Abstract

Articles, e.g. aluminium extrusions, piping, to be subjected to treatment with a liquid in a tank, e.g. for etching or paint removal purposes, are supported between apertured carrier discs 6 mounted on a rotatable axle 3 journalled on frame 1. Stop plates 8 may also be mounted on the axle. The frame, which in use rests on the edges of a tank maybe provided with lifting eyes 2 to enable it to be lifted out of one tank and lowered into another. Paint may be removed from painted articles by immersing the latter, located between the carrier discs, in a paint stripping composition and rotating the discs. Further treatments e.g. a caustic treatment followed by a neutralisation treatment and rinse may be carried out using the same supporting equipment. <IMAGE>

Description

SPECIFICATION Article handling apparatus The present invention relates to an apparatus for handling articles, particularly, but not exclusivelyfor use in stripping paint from the articles. The apparatus finds particular utility in stripping paint from elongate aluminium extrusions although it may also be used in other processes involving such extrusions or similar articles such as piping.

Aluminium extrusions are commonly used, for example, in window frame material and for such purposes it has become commonplace to paint them, which term is used to include not only painting in the conventional sense but also such modern techniques as powder-coating and the like.

At times, it is desirableto remove such painted coatings. Hitherto, this has been achieved by immersing the articles in a paint stripping medium such as methylene chloride. It has been usual to support the articles in a basket type arrangement.

Rows of the articles are supported in a superposed arrangement by means ofwires at each end ofthe article. The basket is them immersed in the methylenechloride. This method has a number of disadvantages. Firstly, many extrusions have complexshapesinwhich air can become trapped when the article is immersed. This may cause the paint stripperto be ineffective in the region of such trapped air. Secondly, the paint stripped offthe articlefallstowardthe bottom ofthestripping bath.

Where the articles are arranged as has been the case, one row above another, the paint from the upper row falls onto the upper surface of the lower row, thereby such surfaces are protected from further attack bythe paint stripper. Finally, since the articles are supported on wires, there is an area where they are supported which can not be attacked by the paint stripper.

For all these reasons, it is usually necessaryforthe articles to be restacked and placed in a second stripping bath. It is an object ofthe present invention to overcome the above disadvantages and to provide anapparatusforhandling elongate articles, which can, if necessary, allow the articles to be stripped of paintorthe like in a singletreatmentstep.

According to a first aspect of a present invention, there is provided an apparatus to handle elongate articles to be treated, comprising a longitudinally extending rotatable axle, means to drive said axle and two apertured carrier plates attached at spaced locations to said axle, each ofthe apertures being dimensioned to accept an article to be treated.

Preferably the carrier plates are discs, advantageously of a material substantially inertto the chemicals used in the treatment process.

Suitable materials are polypropylene, PTFE, nylon or PVDF.

The plates may be removable from the axle to enable replacement by differently appertured plates.

The plates are advantageously selected to have apertures larger than the cross-section ofthe articles.

Two additional plates may be attached to the axle, spaced one from the other by a greater distance than are the carrier plates, the additional plates being unaperturedto prevent the article slipping from the apparatus.

The apparatus is preferably attached to lifting means whereby it may be immersed in a treatment liquid in atank, lifted therefrom at the conclusion of treatment and, if desired, transported to a further tankforadditional treatment.

According to the second aspect of the present invention,there is provided a method of stripping paint from elongate articles comprising the steps of locating the articles in carrier means, immersing the carrier means and articles carried thereby in a paint stripping medium, and, while immersed, rotating the carrier and articles about a longitudinal axis.

Preferably the articles are held loosely by said carrierto be able to move bya small amount during rotation thereof. Advantageously the elongate articles are located parallel to the longitudinal The speed of rotation may be between 1 and 10 r.p.m., most advantageously in the region of 3 r.p.m.

The articles, while located in said carrier, may pass into a succession of treatment media,for example,a composition containing methylene chloride, a caustic based etch cleaner, a dilute solution of nitric acid and one or more water rinses, in each of which the carrier is rotated.

An embodiment ofthe present invention will now be more particularly described by way of example and with reference to the accompanying drawings, in which; Figure lisa side elevation of an apparatus embodying the invention; Figure2 is an end elevation ofthe apparatus; Figure 3 shows one type of carrier plate which may be used with the apparatus; and Figure 4shows another type ofcarrier plate.

Referring now to the drawings, the apparatus comprises a frame 1, which is adapted in use, to rest on the upper surface of the tank edges as shown in more detail in Figure 2. The frame 1 is provided with lifting eyes 2to enable itto be lowered into and lifted out oftanks of treatment liquid. Journalled to the frame lisa rotatable axle 3which may be driven in the illustrated embodiment by means of a chain 4 and sprocket wheel 5, the chain being connected to an electric motor (not shown).

Fixed to the axle 3 at a predetermined spacing are two carrier discs 6 constructed of polypropylene and provided with a number of apertures 7. Also attached to the axle 3 at a greater spacing than are the carrier discs are two additional discs 8 of which at least one may be easily removed to allow loading of the apparatus.

To use the apparatus, a pair of carrier discs 6 is selected from a stock so that the apertures 7 are just largerthan the articles to be stripped. In this connection, it should be noted that the apertures need not be circular as shown in Figures 3 and 4 but may be any convenient shape. They may even be differently shaped on the same carrier disc. The discs are then fixed to the axle 3 at a spacing to accommodate the articles with one end almost touching one ofthe stop-plates 8. When the articles have been loaded, the other stop-plate 8 is assembled, again almost touching the end ofthe articles. It may be more convenient if thins second stop-plate 8 is constructed in two halves for easy assembly onto the axle, or even to have two halves hinged togetherto allow easy loading.Preferred material forthe axle 3 and stop-plates 8 is stainless steel, since it is regularly immersed in aggresive liquids. However, where the nitric acid treatment is omitted, mild steel will be adequate.

The apparatus is then lifted and immersed in a tank of methylene chloride based stripping medium, preferably held at a temperature of 13"C plus or minus 3"C. The drive motor is then actuated to rotate the axle 3 and its carrier discs 6 at 3 r.p.m. The speed is chosen to be sufficientlyfastto prevent the problems outlined above which occurwith static arrangements, butsufficientlyslowsoasnotto cause undue agitation ofthe liquid.

Once the treatment in the methylene chloride bath is complete, the apparatus is lifted out. In order to ensurethatthe rotation ceases before lifting occurs, limit switches may be provided to sense the instant lift begins and be connected into the drive to the motor.

In certain cases, a second methylene chloride bath follows where the treatment is similar. The apparatus then passes to a caustic based etch cleaner or even plain caustic soda bath which is preferably held ata temperature of 50"C plus or minus 5"C. The apparatus then passes to one or two flowing rinses and is neutralised by immersion in a bath of dilute nitric acid solution followed by a furtherflowing rinse. In each of these baths, the axle 3 is rotated.

As can be seen the rotation prevents build up of removed pigment on lower articles, partly because those below do not remain below and partly because the movement sweeps deposited pigmentoffthe surface. Since the apertures are slightly over-sized the articles may move within their respective aperture to be supported by different edges thereof depending on the orientation ofthe carrier disc 6.

The apparatus mayalsofind utilityin other treatment systems, particularly in pretreatment systems, for example chromate conversion coating of aluminium priorto painting. In such processes the aluminium extrusions are etched and then treated with chromic acid solution. Problems arise with trapped air and with the supportforthe articles whereby certain areas may not be properly pretreated. Use of the apparatus will overcome these problems, although it is almost certain thatthe materials ofthe apparatus would need to be selected carefully to resist the different aggressive chemicals used. In the particular pretreatment process outlined above, polyproplylene discs on a stainless steel axle are again preferable.

Claims (14)

1. An apparatus to handle elongate articles to be treated in one or moretanks of liquid, comprising a longitudinally extending rotatable axle, means to rotate said axle and two apertured carrier plates attached at spaced locations to said axle and so arranged that, during treatment, at least a portion of each plate is immersed in the liquid, each ofthe apertures being dimensioned at least to accept an article to be treated.

2. An apparatus as claimed in ciaim 1,wherein the carrier plates are discs of a material substantially inert to the or each liquid used in the treatment process.

3. An apparatus as claimed in claim 2, wherein the material is polypropylene, PTFE, nylon or PVDF.

4. An apparatus as claimed in any one ofthe preceding claims, wherein the plates are removable from the axle to enable replacement by differently apertured plates.

5. An apparatus as claimed in any one ofthe preceding claims, wherein the plates are selected to have apertures dimensioned largerthanthe cross-section ofthe articles.

6. An apparatus as claimed in any one ofthe preceding claims, further comprising two additional plates attached to the axle, spaced one from the other by a greater distance than arethe carrier plates, the additional plates being unapertured to prevent the article slipping from the apparatus.

7. An apparatus as claimed in any one ofthe preceding claims, further comprising lifting means whereby at least a portion of each plate may be immersed in a treatment liquid in a tank, the plates and axle lifted therefrom attheconclusion of treatment and, if desired, transported to a further tank for additional treatment.

8. An apparatus to handle elongatearticlesto be treated in one or more tanks of liquid substantially as described herein with reference to the accompanying drawings.

9. A method of stripping paintfrom elongate articles comprising the steps of locating the articles in carrier means, immersing the carrier means and articles carried thereby in a paint stripping medium, and, while immersed, rotating the carrier and articles about a longitudinal axis.

10. Amethod as claimed in claim 9,wherein the articles are held loosely by said carrier to be able to move by a small amount during rotation thereof.

11. A method as claimed in either claim 9 orclaim 10, wherein the speed of rotation is between 1 and 10 r.p.m.

12. A method as claimed in claim 11, wherein the speed of rotation is in the region of 3 r.p.m.

13. A method as claimed in any one of claims 9 to 12, wherein the articles, while located in said carrier, pass into a succession of treatment media, in each of which the carrier is rotated.

14. A method of stripping paint from elongate articles substantially as described herein with referenceto the accompanying drawings.