Method for producing protected metal bases for aerosol valves and the like

Abstract

 According to the method, after the metal base for the aerosol valve or the like has been formed by conventional methods from sheet metal, a layer of protective plastics material such as polyethylene or polypropylene is applied to at least one of its sides. This application can be done by known methods such as spraying or immersion.
The metal base can be formed from unprotected steel which is tin-, nickel- or chromium-plated, or from varnished aluminium alloy.
The plastics material is preferably applied differentially to obtain selectively different layers on the metal base, for example a greater thickness on the inside of its rim, this being the region where the base is clinched or otherwise fixed to the container.

Description

[0001] This invention relates to a method for producing metal bases for delivery devices such as aerosol valves, metering pumps and/or atomizers and the like, where said bases are used to fix said devices onto the aperture of a metal can or other vessel which is to contain the product or products to be delivered.

[0002] The invention also relates to the metal base produced.

[0003] The bases in question are produced by pressing steel or aluminium alloy sheet. The steel sheet can be tin-, chromium- or nickel-­plated to protect it form oxidation. In the case of aluminium alloy, the sheet is varnished with a protective varnish, for example epoxide-bases.

[0004] Recently, tinned steel sheets coated on one side with a layer of polyethylene have been also used.

[0005] In no case is the base obtained from such sheets protected against oxidation and chemical attack at its punched edges, this representing a serious drawback.

[0006] The main object of the present invention is therefore to provide a method for producing a base which not only obviates the aforesaid drawback but also enables the seal between the base and the vessel on which it is fixed to be made without the need to use the conventional gasket.

[0007] A further object of the present invention is to provide a method which enables bases to be produced in two colours, thus satisfying certain commercial requirements.

[0008] These and further objects which will be apparent from the detailed description given hereinafter are attained according to the invention by a method characterised essentially in that after the base has been formed from sheet metal which is untreated in the sense that it has no plastics coating, it is at least partly coated with plastics material such as polyethylene, polypropylene or the like, for example by spraying or immersion or fluidized-bed application.

[0009] The invention will be more apparent from the detailed description of a preferred embodiment thereof given hereinafter by way of non-limiting example with reference to the accompanying drawing in which:

Figure 1 is a diagrammatic axial section through an aerosol vessel provided with the base of the invention;

Figure 2 is an inverted diametrical section through the base of the invention;

Figure 3 is a view similar to Figure 2 showing a base provided with two different types of coating.

[0010] In Figure 1 the reference numeral 1 indicates an aerosol container comprising a preferably metal can or vessel 2 for containing the product or products to be delivered plus the propellant. The can 2 upperly comprises a wide aperture flanged at its edge 3. A base 4 which supports the delivery valve 5 in conventional manner is fixed onto this aperture by clinching along its edge. This valve is also conventional and can be different from that shown, which in this case comprises a delivery button 6, a valving element 7 on which the button is mounted, a gasket 10, a compression spring 8 acting on the valving element, and a member 9 which retains the entire assembly and on which there is fixed a dip tube 11 through which the product is withdrawn from the bottom of the container 2.

[0011] According to the invention, the base 4 (Figures 2 and 3) is formed by conventional methods (pressing) from untreated steel or aluminium alloy sheet. The term "untreated" as used in the text and in the accompanying claims signifies that no layer or coating of plastics material exists on the starting sheet. The steel sheet can however be tin-, chromium- or nickel-plated.

[0012] After it has been formed, the base is hot-coated with a layer of plastics material, preferably polyethylene or polypropylene, by immersion or spraying, or in a fluidized-bed, or by other conventional methods. In particular, although this does not constitute a limitation to the invention, the polyethylene can be dissolved (if necessary with heat) in an organic solvent such as cycloaliphatic or aromatic hydrocarbons, and sprayed on the preferably hot base by usual spray guns, or alternatively the base can be immersed in such a solution. The known fluidized-bed method can also be used to coat the base. Hot polythene in the liquid state can also be sprayed onto the base or the base can be immersed in a polyethylene bath. It is in any event clear that the spraying method enables different plastics materials, for example in terms of their colour, to be applied to the base. In addition, using this known method it is possible to apply a thicker coating to given regions of the base than to other regions. This thickness difference can however also be obtained by immersion.

[0013] In this case after the base has been immersed and allowed to drip, it is maintained in its inverted position as shown in Figures 2 and 3. The applied material thus accumulates in the clinching groove 13 in the base.

[0014] After drying, this accumulation constitutes an effective seal element when the base is fixed to the vessel 2. Such an accumulation can be obtained during spraying by accentuating the application in the appropriate points. The spraying method is also suitable for applying two different materials, one on the inner surface and the other on the outer surface. The two materials can be different in terms of physical properties. For example a more elastic material can be applied to the inner side A and a different colour material can be applied to the outer side B. One example of this is shown in Figure 3. The base 4 of this figure is hot-sprayed at points C and D with elastic, chemically resistant plastics material able to provide good sealing on fitting to the vessel. At the points E, coloured protective plastics material is hot-sprayed.

[0015] As can be seen from Figures 2 and 3, the invention also enables the coating to be obtained at the punch-cut points of regions Z, so that in contrast to known bases, the base of the invention is effectively protected in these regions against oxidation.

[0016] The invention is not limited to the described embodiments, and covers all modification within the same inventive scope. The coating can also be only partial and be applied only to those regions which it is required to protect.

Claims

1. A method for producing metal bases (4) for delivery devices (5) such as aerosol valves, metering pumps and/or atomizers and the like, where said bases are used to fix said devices onto the aperture (3) of a metal can (2) or other vessel which is to contain the product or products to be delivered, characterised in that after the base (4) has been formed from untreated sheet metal, it is at least partly coated (12) with plastics material such as polyethylene, polypropylene or the like.

2. A method as claimed in claim 1, characterised in that the plastics material is applied to the base by spraying, immersion or fluidized-bed methods.

3. A method as claimed in the preceding claims, characterised in that the coating is also applied to its punch-cut edges (Z).

4. A method as claimed in at least one of the preceding claims, characterised in that the coating is differential in terms of material and/or thickness.

5. A method as claimed in at least one of the preceding claims, characterised in that the coating comprises at least one selective accumulation, preferably in the clinghing groove (13) of the base (4).

6. A base, characterised by being coated at least partially with plastics material applied after its forming.

7. A base as claimed in claim 6, characterised in that its inner and outer surfaces are coated with different materials (in terms of physical and/or chemical properties).

8. A base as claimed in claim 6 or claims 6 and 7, characterised in that its groove (13) carries an increased application of plastics material.

Drawing