GB2282218A - Refrigeration appliance with improved lamp - Google Patents

Abstract

Refrigerating appliance, in particular for domestic use, comprising one or more refrigerating circuits filled with inflammable refrigerating gases and formed by at least a compressor, a condenser, one or more associated evaporators and one or more compartments for containing the foods, said compartments being lit by at least one incandescent lamp, wherein the bulb (2) of said lamp is completely covered by a transparent, adherent, irremovable film (4) capable of hermetically enclosing the filament in the event of fracture of the glass; preferably the film is formed at least in part by silicone and is slightly coloured. <IMAGE>

Description

REFRIGERATION APPLIANCE WITH IMPROVED LAMP The invention concerns an improved type of refrigerating appliance equipped with an improved lighting device disposed in the interior of the food preservation compartment.

The invention relates in particular to all types of refrigerators, in particular domestic refrigerators, which are equipped with at least one food preservation compartment, a lamp for lighting the compartment and a refrigerating circuit of which a part, typically the evaporator, is at least partially contained in said compartment, said circuit being filled by an inflammable gas such as for example methane or butane.

For the sake of enhanced simplicity the present description will refer to a refrigerating appliance having a single compartment, but it will be appreciated that the invention can also be freely extended to refrigerating appliances having a plurality of cells and associated evaporators and lamps.

It is known that the pressure of public opinion towards products which are increasing compatible with the environment, including after they have been cast aside for utilitarian purposes, has had is effect both directly and indirectly on the industrial world in terms of developing products which are increasingly environmentally friendly; the direct effect reveals itself by a trend on the part of consumers to direct their attention with increasing emphasis towards so-called 'ecological' products, stimulated by a frequently self-interested press and advertising campaign, while the indirect effect is expressed by way of the drafting and imposition of production requirements laying down standards, and products aiming progressively to marginalise the less ecological products used at the present time.

For that second reason all types of refrigerating appliances containing chloroflurocarbons as components of the substances which are used for heat insulation have been eliminated or are in the course of being eliminated from the new productions in the more developed countries while public opinion is clearly demonstrating its own sensitivity for and interest in refrigerators which do not contain chloroflurocarbons even as the working gas in the refrigerating circuit.

It is known in fact that those types of gases or mixtures of gases have the effect of destroying the ozone present in the atmosphere, and thus the attention of public opinion to that question is very strong.

The search for gases which are alternatives to the traditionally employed gas, that is to say Freon 12, has identified a gas which is suitable for use as a refrigerating gas and which does not destroy the ozone layer, being known as R134.

However that gas suffers from the disadvantage of being harmful in terms of the effects of the so-called 'greenhouse effect' that is to say preventing the passage of in particular thermal solar radiation through the atmosphere of the earth, thereby giving rise to another type of environmental problem about which public opinion has also been alerted.

In order to eliminate such gases therefore it is necessary to have recourse to other well-known types of gases which are suitable form the technical point of view such as methane, propane, butane or mixtures thereof.

However such gases are inflammable and thus a possible leakage of such gases fro the refrigerating circuit can give rise to gas-air mixtures which can explode if the percentage of such gases is within low by well-defined limits.

It has been found therefore that, the amount of said gases contained in a refrigeration circuit being very low, any possible loss thereof to the exterior, typically being a room of medium dimensions, would not give rise to the risk of explosion having regard to the very low level of concentration of inflammable gas which would be stabilised upon being mixed with the air in the room.

For example a medium refrigerating circuit of an approximately 300 litre refrigerating appliance would need 40-50 grams of methane which, if it were completely liberated in a 30 cubic metre room, would give rise to a concentration of about 1.5 grams/cubic metre, that is to say a value which is greatly below the minimum explosiontriggering value which is about 30 grams/cubic metre.

It is also to be borne in mind that normally the room in which the refrigerating appliance is contained is never hermetically sealed so that occasional opening of doors and/or windows would contribute to further reducing the risk of explosion, in particular if the loss is not instantaneous but slow and continues over a prolonged period of time, as happens in almost all cases.

However, if at least a part of the refrigerating circuit is contained in the interior of the compartment, as frequently happens in the case of evaporators as are being considered here, in particular in refrigerating appliances of the AAA (three-star) type, and if the loss occurs at a point on that part of the circuit then the refrigerating gas diffuses in the interior of the compartment and, having regard to the reduced size thereof and its substantial sealing integrity, easily attains a level of concentration of the gas-air mixture which is potentially explosive if it is ignited for example by a spark or by a point at high temperature which accidentally comes into contact with that mixture.

In fact, in the not improbable case of fracture of the glass of a normal incandescent lamp, the temperature of the incandescent filament of the lamp which is at around 10000C is sufficient to trigger off the explosive mixture since it is significantly higher than the minimum triggering temperature of about 4000C, before the filament rapidly cools down to below the safe temperature.

To try to eliminate that danger, refrigerating appliances have been designed which comprise refrigerating circuits contained at least in part in the food preservation compartment and filled with inflammable gas, wherein all possible electrical circuits have been moved outside the compartment.

However, as will be readily appreciated, it is not possible to move the lighting lamp outside the compartment; obviously that lamp constitutes a source of danger, being potentially a source of ignition of the explosive mixture which is enclosed in the compartment since in the event of fracture of the glass the incandescent filament would immediately come into contact with the atmosphere therearound.

To eliminate that risk, appliances have been designed and constructed, which are made up of a plurality of neon lamps which operate at low temperature, that is to say around 200 cm, so that any fracture of the glass would not give rise to the feared ignition of the gaseous mixture around it; that solution, even though it is effective, has however shown itself to be seriously burdensome both by virtue of the need for suitable circuits for supplying the neon lamps and by virtue of the high cost thereof, compared to the cost of a normal incandescent lamp.

Lamps which are particularly resistant to impact fracture are known, like for example those describe din Italian industrial model patent no. 214780; however the lamps described therein do not have any property of being anti-sparking in regard to the atmosphere therearound and in addition the protective cap is removable, which is in conflict with the requirement for a very high level of safety which such laps must continue to meet, even if handled by inexpert people.

It would therefore be desirable, and this is the aim of the present invention, to provide a domestic refrigerator equipped with an improved lamp which avoids the above-described disadvantages, without involving structural complications or new technologies and at low production cost.

According to the present invention, there is provided a refrigeration appliance comprising one or more refrigerating circuits filled with inflammable refrigerating gases and formed by at least one or more compartments for containing the foods, said compartment or compartments being lit by at least one incandescent lamp, wherein the bulb of said lamp is completely covered by a transparent, adherent irremovable film capable of hermetically enclosing the filament in the event of fracture of the glass in such a way as completely to separate the atmosphere external to said bulb from the interior of said bulb.

The invention will be better appreciated from the following description given solely by way of non-limiting example and with reference to the accompanying drawings in which: Figure 1 is a diagrammatic view of the composition of a lamp according to the invention; Figure 2 is a view in cross-section of the lamp shown in Figure 1; and Figure 3 shows an improvement of the present invention.

The following description refers, solely by way of example and for the sake of enhanced simplicity, to a single refrigerating compartment which is lit by a single lamp, but it will be appreciated that what is set forth and claimed herein can be identically applied to any type of refrigerating compartment which is lit even by a plurality of lamps.

The solution which has been fundamentally conceived lies in the elimination of the possibility of contact between the filament of the lamp and the atmosphere therearound by applying to the glass of the lamp a transparent, impermeable, irremovable film which is capable of withstanding the heat of the lamp itself and which is elastic so as integrally to cover the glass and part of the adjacent threaded portion or male connecting portion; in the event of fracture of the glass of the lamp the fragments of glass would be retained within the film which, having regard to it impermeability, would prevent the surrounding atmosphere from reaching the incandescent filament.

In addition the characteristics of elasticity of the film afford the bulb with anti-impact protection, thus making accidental fracture thereof less probable.

Figures 1 and 2 show a lamp according to the invention, illustrating the filament 1, the glass bulb 2, the threaded male connecting portion 3 and the transparent film 4 which covers all the surface of the glass and part of the male connecting portion or lamp base 3, in such a way as to guarantee complete sealing integrity at the line of junction between the glass bulb and the male connecting portion.

The covering film 4 can be produced from and formed by various substances but it has been found that a preferable solution is the adoption of a very thin but continuous layer of silicone which is applied by means of various procedures that are already available and known to the man skilled in the art. For example it has been found that a particularly effective treatment for adapting a lamp to the present invention comprises powder coating of the bulb, covering it with a protective elastic layer of material which at the end of the treatment is of a thickness of at least two microns.

However it may happen that the film, composed of any material, may have regions in which the bulb remains uncovered, just as it can also happen that a lamp of the type described can be easily replaced by an equivalent lamp but without the transparent protective film, thereby unwittingly nullifying the predisposed anti-explosion safeguard.

A first improvement to the present invention therefore involves being able to verify immediately and by any person if the lamp to be fitted is completely covered with the described film; that is possible if the film is not completely transparent but slightly coloured in such a way that it is possible immediately to distinguish both the type of lamp and if the lamp has regions in which it is not covered by the film, which can be distinguished immediately by virtue of the possible lack of or irregularity in the external colouring of the bulb.

Since however protection for the filament from the surrounding atmosphere does not constitute the only potential danger for the lamp when surrounded by a potentially explosive atmosphere, but there is also the possibility of sparks shooting between the screwthread of the lamp or at any rate its electrical terminal and the electrical contact terminal on the feed conductor, a second improvement involves adopting particular types of engagement between said contacts of the type referred to as 'sure' that is to say of the type which is not subject to accidental disengagement or wrong or intermittent contacts, as for example may happen with a lamp which is badly screwed in.

There are many types of such sure contacts available in the art, such as for example of the bayonet type with a retaining spring, or of the so-called 'faston' type (using a permanently secured pin), or other types such as PVC insulated wires 5 as shown by way of example in figure 3.

Therefore the present invention affords the following advantages: a) rapidity of connection between the lamp and the associated electrical supply circuit; b) the ease of preparation of the lamp and the possibility of using normal lamps to be prepared in accordance with the invention; c) improvement in the anti-fracture characteristics of the bulb and good anti-deflagration security in the event of fracture in a gas-saturated compartment; d) good anti-deflagration security in the event of unsure electrical contacts in relation to the feed point of the lamp in a gas-saturated compartment; and e) overall economy in construction and the use of known simple and sound technologies.

It will be appreciated that each lamp may also be produced in shapes different from those shown without thereby departing from the scope of protection of the present invention.

Claims (5)

1. A refrigeration appliance comprising one or more refrigerating circuits filled with inflammable refrigerating gases and formed by at least one or more compartments for containing the foods, said compartment or compartments being lit by at least one incandescent lamp, wherein the bulb of said lamp is completely covered by a transparent, adherent irremovable film capable of hermetically enclosing the filament in the event of fracture of the glass in such a way as completely to separate the atmosphere external to said bulb from the interior of said bulb.

2. A refrigerating appliance according to claim 1 wherein said film is formed at least in part by silicone and has a minimum thickness of 2 microns.

3. A refrigerating appliance according to claim 1 or claim 2 wherein said film is slightly coloured.

4. A refrigerating appliance according to any one of the preceding claims wherein the electrical contacts of the lamps for lighting the compartment are of 'sure' type.

5. A refrigerating appliance constructed and arranged to operate substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

5. A refrigerating appliance constructed and arranged to operate substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

Amendments to the claims have been filed as follows 1. A refrigeration appliance comprising one or more refrigerating circuits filled with inflammable refrigerating gases and formed by at least one or more compartments for containing the foods, said compartment or compartments being lit by at least one incandescent lamp, the lamp comprising a glass bulb and a connecting portion for mounting the lamp in a socket, wherein the bulb of said lamp is completely covered by a transparent, adherent irremovable film capable of hermetically enclosing the filament in the event of fracture of the glass in such a way as completely to separate the atmosphere external to said bulb from the interior of said bulb, the film extending at least part way over the connecting portion of the lamp in such a way as to guarantee complete sealing integrity at the line of the junction between the glass bulb and the connecting portion.

2. A refrigerating appliance according to claim 1 wherein said film is formed at least in part by silicone and has a minimum thickness of 2 microns.

3. A refrigerating appliance according to claim 1 or claim 2 wherein said film is slightly coloured.

4. A refrigerating appliance according to any one of the preceding claims wherein the electrical contacts of the lamps for lighting the compartment are of 'sure' type.