GB2140143A - Method of filling a cavity with foamed material - Google Patents

Abstract

In a method of filling a cavity, such as the space between the shell 1 and liner 2 of a refrigerator or freezer, with foamed material, the foam-forming constituents are introduced into the cavity 3 through a tube 5 extending for a distance into the cavity from the point of introduction 4, at least the major part of the tube 5 remaining embedded in the solidified foamed material at the completion of the process. The tube 5 can be used to direct the foaming materials to restricted regions of a cavity and the use of a tube of appropriate dimensions reduces the velocity at which the materials are introduced giving a more uniform filling. <IMAGE>

Description

SPECIFICATION Method of filling a cavity with foamed material This invention relates to a method of filling a cavity with a foamed material, and more especially, though not exclusively, to a method of filling the cavity between the shell and liner of a refrigerator or freezer cabinet with foamed thermal insulating material.

In such a process a predetermined quantity of a suitable foaming plastics material in liquid form capable of being rapidly solidified in the foamed condition, for example polyurethane, together with appropriate foaming and curing agents, are injected under pressure into the cavity to be filled by means of a nozzle, the foaming agent producing a rapid expansion of the plastics material within the cavity, and the material being rapidly cured to form a solid core.

A disadvantage which is sometimes experienced with such a process, especially where the cavity contains restricted passages, is that regions of relatively high density foam can be produced and give rise to underfilling in other locations, such underfilling being difficult to detect in the finished product. Such underfilling is clearly undesirable, especially in the case of refrigerator and freezer cabinets, as regions in which the foam has less than the required density, or is competely absent give rise to inadequate performance by reason of the relatively poor thermal insulation associated with those regions. A further disadvantage is that these underfilled regions can adversely affect the structural stability of the cabinet which normally relies on there being an intervening continuous layer of foam of adequate density between the cabinet shell and liner.

An object of the invention is to provide a method of filling a cavity with foamed material in which this problem is alleviated.

According, therefore, to the present invention, in a method of filling a cavity with foamed material the foam-forming constituents are introduced into the cavity through a tube extending for a distance into the cavity from the point of introduction, at least the major part of the tube remaining embedded in the solidified foamed material at the completion of the process.

The use of such a tube, which in effect forms a continuation of the nozzle, tends to restrict the velocity at which the foam-forming constituents are introduced into the cavity, so as to prevent the formation of high-density regions of foam; by this means it is possible to obtain a foam-filling of substantially uniform density throughout the cavity being filled by suitably selecting the length and diameter of the tube.

In some cases the tube may be such that the foam-forming constituents can be directed into a region or regions remote from the filling aperture, and/or a region or regions of a restricted nature, so that subsequently the foam can more readily expand into less restricted regions, although this may not always be necessary and shorter lengths of tube, which suitably restrict the velocity of the foam-forming materials may be found to be satisfactory.

Conveniently the tube is of plastics material, and in the manufacture of refrigerator or freezer cabinets the use of what is known as "lay-flat" tubing, that is to say tubing formed of thin-walled flexible plastic material, usually polyethylene, which is initially in a flattened condition, but is openable into tubular form by the introduction into it of fluid under pressure, has been found to be particularly suitable. It is believed that as the foaming material being introduced into the cavity would need to open out the initially flat tube as it is passed along it, the velocity of the jet of material is restricted, this in turn assisting in restricting regions of high-density foam.

The length of the tubing giving the most satsifactory results will depend on the dimensions and nature of the cavity being filled but may readily be found by trial.

In some cases the end of the tube remote from the filling aperture may be closed or partly closed, and the tube provided with holes in its wall at selected positions along its length. Other modifications are also possible.

Although the invention has been found especially suitable for use in introducing foamed thermal insulating material into the cabinets of refrigerators and freezers, it will be appreciated that it can also be used to advantage in filling cavities of other kinds with foamed material, and the diameter and length of the tubing employed can readily be selected to suit the nature of the cavity being filled.

In some cases more than one tube may be employed to direct the foaming materials into two or more different regions of the cavity.

In carrying out the introduction of the foamforming materials, the tubing will normally be coupled to a nozzle of known form, commonly employed for filling cavities with foamed materials, the nozzle being withdrawn after the introduction of the materials into the cavity. If any of the tubing projects from the cavity following the foaming process this can readily be removed if desired.

The invention will be further explained by describing by way of example with reference to Figures 1 to 3 of the accompanying drawings one method, in accordance with the invention, of filling the space between the shell and liner of a refrigerator or freezer cabinet with foamed thermal insulating material.

In the drawings Figure 1 illustrates in dia grammatic form a cross-section of one such cabinet prior to the introduction of the foamed filling, Figure 2 illustrates on an enlarged scale the part of the cabinet in which the filling materials are introduced, and Figure 3 shows the same part of the cabinet during the foaming process.

In carrying out the process in accordance with the invention the shell 1 and liner 2 of the refrigerator cabinet, which may, for example, be as described in Patent No.

1594439, are supported in a suitable jig or mould (not shown) with an appropriate space 3 between them, the space being fully enclosed apart from an opening 4 through which the foam-fforming materials are to be introduced. Within the space there is accommodated a length of "lay-flat" polyethylene tubing 5, capable of being expanded to a diameter of between one and two inches, the tubing extending from the opening 4 to a position spaced from the opening.

The protruding end 6 of the tubing 5 is held in position at the mouth of the opening 4 by means of a length of adhesive paper tape 7 iaid over the opening and its surround as can be seen in Figure 2. The tape 7 is then pierced and the injector nozzle 8, which can be of known kind commonly employed for introducing foaming materials into refrigerator and freezer cabinets, is then placed into the opening with its surrounding sealing ring 9 against the outer surface of the tape 7 to couple the nozzle firmly to the tubing 5.

A valve (not shown) is then opened to inject a predetermined quantity of foam-forming materials in appropriate proportions into the cavity 3 from the nozzle 8, the materials passing through the tubing 5 as they are introduced.

It has been found that because the initial passage of the jet of foamfforming materials through the tube 5 has to open the tube, the velocity of the jet is restricted which assists in restricting the formation of high-density pockets of foam. The end of the tube remote from the nozzle can in some cases be arranged to terminate in a restricted region of the cavity, and the foam allowed to expand into less restricted regions, which assists in the avoidance of underfilling but this is not always necessary.

When the required quantity of the foamfforming materials have been introduced into the cavity 3, sufficient to fill the cavity and cured, the nozzle is removed from the outer end of the tube, the part of the tube within the cavity remaining embedded in the foamed material and consequently retained within it.

Only a small section of the tube 5 projects from the cavity, and may be left in position.

For the above application the foam-forming materials conveniently comprise a curable liquid polyurethane resin composition, such as DALTOLAC K1 41, together with a foaming agent such as Refrigerant and a di-isocyanatodiphenylmethane-based composition such as SUPRASEC DNR for effecting the curing of the foamed resin (DALTOLAC and SUPRASEC are trade marks, the property of l.C.I. Ltd); however other suitable materials can alternatively be employed.

In a modification of the process which may be utilised with low pressure foaming systems the mouth of the "lay-flat" tubing, instead of being secured to the cabinet as described could be secured directly over the injector nozzle. Other variations are clearly practicable.

Such a variation is illustrated in Figures 4 and 5. In this method the outer end 6 of the lay-flat polyethylene tubing 5, is pushed through, and is folded around, a relatively rigid ring 10, for example of metal, of greater diameter than the opening 4 and is introduced into the opening with the main part of the tubing. The latter is then pulied tightly into the cavity so that the metal ring 10 with the intervening part of the wall of the tubing is pulled against and is thereby anchored to the wall of the outer shell around the opening as shown in Figure 5. This is conveniently effected as part of the assembly process before the liner (not shown) is fitted into the shell 1. With the liner fitted into the shell, and following the introduction of the injector 8 into the opening 4, the foam-forming materials are introduced into the cavity to fili the cavity 3 as previously described. After foaming, the ring may be left in position or it can be removed by cutting off the exposed end of the tube and re-used.

It will be appreciated that the invention may readily be applied to the introduction of foamforming materials into cavities other than those within the cabinets of refrigerators and freezers, the dimensions of the tubing and the foam-forming materials employed being readily selected to suit the cavities being filled.

Claims (9)

1. A method of filling a cavity with foamed material wherein the foam-forming constituents are introduced into the cavity through a tube extending for a distance into the cavity from the point of introduction, at least the major part of the tube remaining embedded in the solidified foamed material at the completion of the process.

2. A method according to Claim 1 wherein the tube is of plastics material.

3. A method according to Claim 2 wherein the tube is of flexible material which is initially in a flattened condition but is opened into tubular form by the introduction of the foamforming constituents.

4. A method according to any preceding Claim in which the end of the tube remote from the filling aperture is closed or partly closed, and the tube is provided with holes in its wall at selected positions along its length.

5. A method according to Claim 3 or 4 wherein the outer end of the tube is secured around the mouth of the filling aperture by adhesive paper tape.

6. A method according to Claim 3 or 4 wherein the outer end of the tube is folded around a relatively rigid ring of greater diameter than the filling aperture and extends partly into the cavity around the outside of the main part of the tube.

7. A method according to any preceding Claim in which the foam-forming material is a curable liquid polyurethane composition together with foaming and curing agents.

8. A method of filling a cavity with foamed material carried out substantially as shown in and as hereinbefore described with reference to Figures 1 to 3 or Figures 4 and 5 of the accompanying drawings.

9. A refrigerator or freezer cabinet having an outer shell and an internal liner with a cavity between the liner and the shell filled with foamed thermal insulating material, the material having been introduced into the cavity by a method according to any preceding Claim.