GB2457131A

GB2457131A - Silver article and method of cleaning a silver article

Info

Publication number: GB2457131A
Application number: GB0724245A
Authority: GB
Inventors: Lawrence Perovetz
Original assignee: INNOVATION PATENTS Ltd
Current assignee: INNOVATION PATENTS Ltd
Priority date: 2007-12-12
Filing date: 2007-12-12
Publication date: 2009-08-12
Also published as: GB0724245D0

Abstract

A silver article 5 is provided comprising first (figure 1, 1) and second (figure 1, 2) parts. The first part (figure 1, 1) comprises silver (Ag) and the second part (figure 1, 2) comprises a material other than silver such as aluminium (Al) or zinc (Zn) or alloys of these. The first and second parts can be fixed mechanically, via a conductive adhesive or through a friction fit. The first and second parts are also in electrical contact. When the article is contacted with alkaline solution 6, an electrochemical cell is formed and tarnish is removed from the silver part. The second part can be fixed to the article 5 in a first step before cleaning. The method can be carried out in a dishwasher 3. The second part (figure 1, 2) may be removed from the first part (figure 1, 1) after cleaning.

Description

SILVER ARTICLE AND METHOD OF CLEANING A SILVER ARTICLE

The present invention relates to a silver article and a method of cleaning a silver article. In particular, the invention relates to the problem of cleaning articles which are made of silver. It is well known that silver will tarnish, particularly when used and it is desired to find a way of removing the tarnish to make the silver articles bright and clean again. A number of manually applied silver cleaning compositions are available, but are notoriously time consuming in application.

It has been known for a very long time that silver articles can be cleaned by immersing them in an alkaline solution whilst in contact with an active metal, particularly an aluminium alloy. The process was originally marketed by the Polivit Company and is described for example in GB25 8726. This has been applied in a number of way over the years, for example as an aluminium alloy vessel or plate on which or into which silver articles can be placed, whilst immersed in an alkaline solution.

It is found to be particularly suitable to place such an aluminium plate inside an automatic dish washer, because dishwashing compositions are typically alkaline. In some cases, the aluminium alloy structure can take the form of a cutlery basket or similar container. This is described for example in GB2325243.

Whilst these processes can be effective, the inventor has noted that, sometimes, the quality of cleaning or speed of cleaning are not as high as they could be, particularly when a large number of articles are washed together. The present invention sets out to provide a silver article which can be readily and reliably cleaned without special handling.

The inventor has realised that there can be a problem due to a poor level of electrical contact between the aluminium article and the silver article, which can be due to the shape of the articles or poor stacking by operatives if a large number of articles are washed at once.

Accordingly, the present inventor has realised that a repeatably high standard of cleaning can be obtained if a silver article comprises, fixed to it, a metal surface of the type which, when immersed in alkaline solution, can lead to the tarnish being removed from the silver.

Accordingly, in a first aspect, the present invention provides an article comprising a first, silver part, extending to a surface of the article, and a second part comprising a material other than silver, extending to a surface of the article, the first and second parts being in electrical contact and the second part being fixed to the article, whereby, when the article is contacted with an ilkaline solution, an electrochemical cell can be formed, so that tarnish can be removed from the silver part.

The present invention further provides, in a second aspect, a method of cleaning an article, comprising providing an article comprising a silver part extending to a surface of the article and a second part comprising a material other than silver, extending to a surface of the article, the first and second parts being in electrical contact and the second part being fixed to the article, further comprising contacting of the article with an alkaline solution to form an electrochemical cell so that tarnish is removed from the silver part.

The present invention further provides, in a third aspect, a cleaning component, comprising a material other than silver and means for fixing the cleaning component to an article comprising a silver part extending to a surface of the article, so that when the cleaning component is fixed to the article, the material other than silver is in electrical contact with the silver part, whereby, when the article with the cleaning component fixed thereto is contacted with an alkaline solution, an electrochemical cell can be formed, so that tarnish can be removed from the silver part.

Preferred and optional features of the invention will be described below.

Unless specifically indicated to the contrary, the features described below apply to all three aspects of the invention.

The article can be any article, for any purpose, at least part of the surface of which is silver. It may be a decorative article or a functional article.

The article may comprise solid silver, silver alloy or a silver plated article. It may be produced by any method by which silver or a silver alloy can be applied to an article, for example it may be Sheffield plate, chemically plated material or electroplated material The article of the first aspect of the invention may be manufactured from raw materials so that it is according to the invention, or it may comprise an existing solid silver, silver alloy or silver plated article to which a second part according to the invention is added.

According to the second aspect of the invention, the article may be according to the first aspect of the invention or may be a silver article to which, in a first step, a cleaning component according to the third aspect of the invention is applied.

A decorative article according to the invention may be selected from: table ware, being for example selected from cutlery, a knife, a fork, a spoon, a plate, a bowl, a cup, a serving vessel, a candlestick, or an accessory such as a napkin ring, cutlery rest, cruet, table decoration and the like, an accessory or adornment, such as a medal, medallion, jewellery, a closure such as a button an, embellishment and the like, any other item such as an award, sporting medal or cup, a work of art or artistic craftsmanship.

The silver part may be formed of any silver or silver alloy. By silver' or silver alloy' it is meant that it may be any material comprising a substantial amount of silver for example more than 50% by weight, mixed or alloyed with any other material, as will be known to the person skilled in the art.

The silver part will extend to at least one surface of the article, where the silver is liable to become tarnished.

The present invention is not limited by theory, but it is believed that the tarnish comprises a layer of silver suiphide, formed on the silver article.

The material of the second part may be any material which is capable of forming an electrochemical cell with silver in an alkaline solution whereby the silver surface can be cleaned. The chemistry will be described further below. The material may be a metal or metal alloy, or any electrically conductive material. For example it may comprise a carbon based material, which may contain metal or it may comprise a ceramic. Preferably, it is a metal or metal alloy. Preferably, the metal comprises aluminium, aluminium alloy, zinc, zinc alloy or a mixture thereof. Other metals include manganese, magnesium, iron and alloys thereof.

Suitable aluminium alloys comprise for example 95 -97 parts by weight of aluminium, preferably 3-2 parts by weight zinc, preferably 1-0.5 parts by weight of copper and 0.5-0.25 parts by weight of silver.

When the cleaning component of the third aspect of the invention is fixed to the article, it will act as a second part as defined for the flst and second aspects of the invention.

The second part must extend to a surface of the article and be in electrical contact with the silver part, so that when the article is contacted with an alkaline solution so that the two surfaces contact the alkaline solution, an electrochemical cell is formed. According to the method of the present invention, there is preferably a continuous body of aqueous solution extending from the surface of the silver part to the surface of the second part. This body of aqueous solution may be applied in any way, for example in the form of a bath, spray, wash or other means.

The part of the surface to which the silver extends and the part of a surface to which the other material extends are suitably adjacent to one another. They may comprise opposed surfaces of the article or surfaces which form part of the same outer surface of the article.

The second part may have any suitable shape. For example, it may comprise a thin layer applied, for example by electroplating, to the article. It may comprise a thin foil applied to the article.

By in electrical contact' it is meant that an electrical current may flow though the article from the first part to the second part. Another electrically conducting material may be present between them.

The article may comprise a structure made of the material other than silver, which has been plated in all but one selected area with silver, the selected area providing the surface of the second part.

The second part may, for example, comprise a structure of thickness at least 0.5mm which is fixed to the article. It is found that a structure of this thickness will typically have sufficient life in service and strength to remain fixed to the article for a long period.

The second part may be located on a part of the article which is not visible in normal use.

Where the article comprises solid silver, silver alloy or silver plated cutlery, the second part may be located on the handle. Preferably, it is located on a surface of the handle which is facing downwards when the cutlery is laid in a conventional position prior to use. In this way, users will not see the second part when the cutlery is laid out, nor when it is used, as the second part will be covered with the hand.

The outer surface of the second part may be provided with a decorative finish, for example, it may be given a form of a badge.

The second part or (in the third aspect of the invention) the cleaning component can be fixed to the article in any way. By "fixed" it is meant that the second part remains in contact with the article, in the same position or configuration, under the forces which are applied to the article in normal use or during at least part of the cleaning process. In this way, a good contact can be obtained, which gives good tarnish removal. It may be bonded to the article, for example, by soldering, gluing or burnishing.

In the third aspect of the invention, the cleaning component may be removed by a user after cleaning has taken place. This allows a user to take an existing silver article, apply a cleaning component to it, wash it in alkaline solution to remove tarnish and then remove the cleaning component (if it has not all been consumed chemically in the washing process) if it is not desired to leave the cleaning component in position for aesthetic or other reasons.

The second part or (in the third aspect of the invention) the cleaning component may be adhered to the article. Preferably, an electrically conductive adhesive is used.

This may comprise an adhesive matrix with conductive particles distributed in the adhesive matrix.

The second part or (in the third aspect of the invention) the cleaning component may consist of the conductive particles contained in the adhesive. The cleaning component may comprise a paste or resin which can form an electrochemical cell with silver to remove tarnish from silver.. Preferably, it is an electrically conducting paste or resin.

The second part may be of any suitable size. It should be of a size which is sufficient to allow a good cleaning effect over at least one wash.

According to one embodiment of the invention, the second part has a size sufficient to give a good cleaning effect over many washes. However, it is also possible that the second part can be of such a size that it will only last for substantially one wash.

In this way, articles which are only cleaned infrequently may have a second part applied to them specifically for the wash, the second part being fixed to the article, the second part being substantially consumed during the washing process. In this way, either none of the second part is left after the washing process or the amount that is left can be easily removed.

The second part may be fixed mechanically. For example, the article may comprise a receiving portion having a first shape, the second part comprising a fixing portion having a shape which is complementary to the shape of the receiving portion, the second part being fixed to the article by interference fit, positive fit or frictional fit.

The alkaline solution used in the present invention is preferably an aqueous alkaline solution.

The scope of the present invention is not limited to any particular understanding of the chemistry but it is understood that the following reactions are occurring.

As noted above, it is understood that the tarnish on the silver comprises a layer of silver sulphide. In the past, it has been understood that when aluminium metal, or other metals, are immersed in an alkaline solution, a reaction occurs by which hydrogen is generated, sometimes referred to as nascent hydrogen, which reacts with the suiphide to generate hydrogen suiphide which is dissolved in the alkaline solution, leaving a clean, untarnished silver surface: 2A1 + 6H20 -Al (OH) + 3H2 (1) Al. + NaOH -Na [Al (OH) } (2) Ag2S+H2-2Ag+H2S (3) The reaction may alternatively be described in terms of electrochemical half equations 4 and 5 set out below.

At+3H20 -Al(OH)3+3H+3e (4) Ag+e-Ag (5) The equations have been written on the assumption that the metal is aluminium, but it is noted that many other metals will give a similar reaction. In this case, the reaction will proceed if the sum of the redox potentials of the reactions (4) (5) is correct.

The alkaline solution used in the method of the present invention is an aqueous alkaline solution. It must have a small pH in excess of 7, preferably in excess of 9 and more preferably in excess of 10. The alkaline solution may be provided by dissolving foi example alkali metal or alkaline earth metal hydroxide, carbonate, bicarbonate or silicate in water.

In a preferred embodiment, the alkaline solution is produced by dissolving a dishwashing composition in water, for example at the mixing ratios commonly employed in automatic dishwashing machines.

The alkaline solution may be at ambient temperature or at a temperature raised above ambient temperature, preferably in excess of 50°C and more preferably in excess of 60°C, in order to speed up the reaction.

The method of the invention can be carried out by hand, or by machine, for example in any washing apparatus, in particular silver cleaning apparatus or a dishwasher.

The present invention will be described further below by way of example only with reference to the accompanying drawings, in which: Figure 1 is a sketch view of an article, according to the first or third aspect of the present invention, comprising a spoon.

Figure 2 is a schematic view of the method of the present invention being carried out in a conventional automatic dishwasher.

Figure 3 is an isometric view of a cleaning component according to the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

Figure 1 shows an article, in the form of a spoon. The spoon 1 is suitably formed as solid silver or silver plated material. In the handle of the spoon there is formed a badge or an escutcheon 2 of an aluminium alloy. The badge 2 is rigidly fixed to the spoon 1 and not removable from it in the normal use. It is in electrical contact with the silver surface of the spoon 1. When in contact with an alkaline solution, an electrochemical cell is set up which leads to the removal of tarnish from the silver surface of the spoon 1.

According to the third aspect of the invention, the badge 2 could have been prepared separately and applied to the spoon for the purposes of cleaning the spoon. For example, it may be adhered in place using an electrically conducting adhesive.

Figure 2 is a schematic drawing of a conventional dishwashing machine 3 comprising a tray for holding an article of cutlery, for example, a spoon 5 which is sprayed with a solution of conventional dishwashing composition dissolved in hot water 6. The spray of alkaline solution 6 wets the entire surface of the spoon I to such an extent that the electrochemical cell is set up and tarnish is removed from the silver surfaces of thea spoon.

Figure 3 shows a schematic isometric view of a cleaning component according to the invention, in the form of a strip having a layer 7 of material which can form an electrochemical cell with silver to remove tarnish from silver, in this case aluminium or aluminium alloy. There is a further layer 8 of adhesive material for fixing the component to a silver article for cleaning. The adhesive layer is made electrically conductive by including dispersed aluminium powder. The component of figure 3 is supplied in the form of strips or sheets with a removable backing material or in the form of a roll, like adhesive tape. In use, a section of component is taken, for example by un rolling from a roll and adhered to a silver article. The silver article is then immersed in an alkaline solution, for example in a dishwasher. As a result, an electrochemical cell is formed and tarnish is removed from the silver article. The component may be removed from the silver article afler use.

The present invention has been described above by way of example only and modifications can be made within the present invention. ii

Claims

CLAIMS: 1. An article, comprising a first, silver part, extending to a surface of the article, and a second part, comprising a material other than silver, extending to a surface of the article, the first and second parts being in electrical contact and the second part being fixed to the article, whereby, when the article is contacted with alkaline solution, an electrochemical cell can be formed, so that tarnish can be removed from the silver part.
2. The article according to claim 1, comprising solid silver, silver alloy or a silver plated article.
3. The article according to claim 1 or 2, wherein the second part comprises aluminium, aluminium alloy, zinc, zinc alloy, manganese, magnesium, iron or alloys thereof.
4. An article according to claim 3, when the second part comprises aluminium or aluminium alloy.
5. An article according to any preceding claim, wherein the.second part is mechauilcally fixed to the article.
6. An article according to claim 5 wherein the article comprises a receiving portion having a first shape, the second part comprising a fixing portion having a shape which is complementary to the shape of the receiving portion, the second part being fixed to the article by interference fit, positive fit or frictional fit.
7. An article according to any of claims 1 to 4, wherein the second part is adhered to the article.
8. An article according to claim 7, wherein the second part is adhered to the article using an electrically conductive adhesive.
9. An article according to claim 7 or 8, wherein the second part comprises aluminium foil.
10. A method of cleaning an article, comprising providing an article comprising a silver part extending to a surface of the article and a second part comprising a material other than silver, extending to the surface of the article, the first and second parts being in electrical contact and the second part being fixed to the article, further comprising contacting the article with an alkaline solution to form an electrochemical cell so that tarnish is removed from the silver part.
11. A method according to claim 10, wherein the alkaline solution comprises a solution of dishwashing composition.
12. The method of claim 10 or 11, carried out in cleaning apparatus.
13. The method of claim 12, carried out in a dishwasher.
14. The method of any of claims 10 to 13, further comprising the initial step of fixing the second part to the article.
15. The method of claim 14, wherein an aluminium foil is adhered to the article.
16. The method of any of claims 10 to 15, further comprising the subsequent step of removing the second part from the article after cleaning.
17. A cleaning component, comprising a material other than silver and means for fixing the cleaning component to an article comprising a silver part extending to a surface of the article, so that when the cleaning component is fixed to the article, the material other than silver is in electrical contact with the silver part, whereby, when the article with the cleaning component fixed thereto is contacted with an alkaline solution, an electrochemical cell can be formed, so that tarnish can be removed from the silver part.
18. The claiming component of claim 17, comprising a metal foil with an adhesive backing.
19. The cleaning component of claim 18, comprising aluminium foil with an adhesive backing.
20. The cleaning component of claim 17, comprising a paste or resin.
21. An article substantially as herein described with reference to figure 1 of the accompany drawings.
22. A method substantially as herein described with reference to the accompanying drawings.
23. A cleaning component substantially as herein described with reference to figure 3 of the accompanying drawings