GB2155168A - Improvements in insulated portable containers - Google Patents

Abstract

An insulated portable container 30 of generally rectangular prismatic form has its external walls lined with a reflective metal foil-faced plastics sheeting and is provided with a thermally insulating partition or separator 46 which is a snug fit between opposite internal walls so as to divide the space within the container into two parts of variable relative capacities depending on the volume of goods required to be thermally insulated in one part from the contents of the other part. The partition may be faced on one or both sides with the reflective plastics sheeting. <IMAGE>

Description

SPECIFICATION Improvements in insulated portable containers This invention relates to insulated portable containers such as are commonly used for the storage of food on personal journeys, picnics, etc. It has become conventional to make these containers in the form of relatively deep, substantially non-collapsible, basically rectangular prismatic boxes having external walls of a suitable wear-resistant material which are lined with a thermally insulating material, the whole presenting a more of less rigid article in the sense that it tends to retain its shape and internal capacity during normal use. This noncollapsible property is deemed herein to be implied in the term "container". Such containers commonly have loop handles for ease of carrying, and are popularly known as "picnic bags".

It is a well-known physical phenomenon that heat is reflected by polished surfaces in the same way as light, and this principle has become universally accepted in flasks and jugs such as those sold under the Registered Trade Mark "Thermos".

There is available on the market a metal foil-faced flexible plastics sheeting the foil facing component of which can be polished and hence heat reflective.

It could, therefore, form an effective insulator for the aforesaid portable containers. However, if it is preferred that such containers be manufactured by standard R.F. welding techniques using foil-faced plastics sheeting as a reflective lining, contact between the metallised surfaces must be avoided where seams have to be made because of the "flash-over" effect which results from the R.F. potential being reflected by the foil layer, so that not only does the heating not penetrate the thickness of the seam but serious damage is done to the welding machine. If, therefore, the foil faced sheeting is to be commerically successfully employed as a heat-reflective liner in an R.F. welded container, a composite material such as that described and shown in U.K. Patent No. 1,253,355 must be used.

This composite material consists of a panel of the foil-faced plastics sheeting bonded to a larger panel of PVC or the like thermoplastic material which can be R.F. welded. A seam between two panels of reflective foil-faced plastics sheeting can then be made by superimposing respective foilfree margins of the composite material and welding across their combined thickness.

Thermally insulated portable containers having relfective metal facings on their internal walls are thermally most efficient when completely filled with goods at the same temperature. However, not all articles, particularly foodstuffs, require to be at the same temperature, and in any one load there may, for example, be frozen foods, hot pies or drinks, ail requiring to be kept at their respective optimum temperatures. Similarly, wines may be required to be carried, some being chilled and others at room temperature.

In order to enable such different temperature requirements to be met in the same regular prismatic container at the same time, the present invention provides a snug-fitting thermally insulating adjustable separator or partition which can be placed at a strategic position within the container to separate the items at different temperatures.

Preferably, the separator is of relatively stiff construction so as to be able to act as a platform for articles placed above it when it is resting on other articles of different or irregular height.

Ideally, the separator or partition has at least one face having a reflecting foil surface so as to form, in conjunction with the walls and bottom or lid of a prismatic container, an enclosed fully reflective cell within which a relatively steady temperature can be maintained over a long period such as several hours.

Containers having high thermal insulation can be graded for their efficient performance on a scale recognised in the trade by a "TOG" value. This is a number which is a measure of the degree of temperature stability within a closed space, and has not hitherto normally been attributable to portable containers because of the wholly random volume of voids which vary from load to load, mainly due to unoccupied space above the contents. However, if a snug-fitting adjustable insulated partition or separator is placed on top of the contents in such a bag, so that the effective volume of the container can be adjusted according to the size of the load at any one time, such partition or separator enables the container to be calibrated on the TOG scale.

This has a marked commercial advantage since a recognisable coefficient of thermal insulation can be accorded to the product for purposes of practical comparison of performances.

A practical illustration of the invention, and of methods of its use, will now be described, by way of example only, with reference to the accompanying drawings in which; Figure 1 is a perspective view of a portable thermally insulated container having reflective internal wall surfaces and shown in its normal upright attitude; Figure 2 and 3 are perspective plan and underplan views, respectively, of a movable partition for a container as shown in Figure 1, and Figures 4 - 7 are perspective views, each partly cut away, illustrating movable partitions in use.

Referring first to Figures 1 - 3, a thermally insulated "picnic" bag 30 of generally rectangular right prismatic shape and comprises, essentially, a smooth outer shell or casing 32 of a wear-resistant plastics material and a liner 34 which provides the heat insulating property. Suitable stiffeners can be incorporated in the construction as necessary. The liner 34 consists of a side wall panel in the form of a tubular sleeve 36 of composite foil-faced plastics material bonded to a wider sheet of thermoplastic material to provide the foil-free margins for R.F.

seam welding. To the sleeve 36 is welded a base panel 38 of the same composite sheeting and a lid panel 60 also of the same composite sheeting. The bag is completed by the usual handles 42 and a separate adjustable-level partition 44 (Figures 2 and 3) which may or may not have one or both surfaces formed by heat-reflective composite sheeting. Its prime function is to act as a separator or baffle separating, physically and thermally, a lower compartment for, say, more highly temperature-sensitive substances from the remainder of the internal volume. Its thermal separation purpose is mainly realised by the thermal insulating capacity of the partition 44, but a significant contribution to the efficiency of thermal separation can be achieved by merely preventing, or severely restricting, convection currents passing between the upper and lower compartments.Thus the contents on opposite sides of the partition 44 can be stored at different temperatures. Its physical separation purpose is enhanced by the provision of a stiff or rigid core material such as expanded polystyrene. The use of foil-faced sheeting on one or both sides of the partition will increase the thermal insulation of the compartment towards which it is directed, although the provision of some means of gripping and removing the partition 44 - such as the overlying strap handle 46 on the upper surface of the partition - will tend to reduce the heat-reflective characteristic of that surface.

The tubular wall panel 36 is formed by wrapping a composite sheet of the appropriate size on itself, foil face inwards, until the two originally opposite vertical foil-free margins overiap and are turned out to be seam-welded at 37 (Figure 1) in the conventional manner. Similarly, the bottom margin of the tubular sleeve 36 is out-turned to register with the margin of the base panel 38 and seam-welded thereto.

The lid panel 40 has a shallow skirt 50 attached around its periphery, and the rim of this skirt carries one track 52 of a sliding clasp fastener the other track 54 of which surrounds the top of the casing 32 at a depth below the rim equal to the depth of the shallow skirt 50. Although in Figure 1 a visible gap is indicated between the adjacent edges 36a of the foil flanking the line of the seam 37, it will be understood that in practice this would be effectively masked by the fullness of the liner.

Figures 2 and 3 show an adjustable-level partition 44 having its underface metallised but a plain upper face on which an overlying strap handle 46 is fixed. The partition is dimensioned so as to be a snug fit, when horizontal, within the bag 30 and movable at will to any desired height above the base 38 so as to rest upon goods or packages such as frozen foods -- whose temperature needs to be controlled within the limits of accuracy obtainable in a heat insulated container, and to isolate them thermally from the space above the partition. In Figure 4, the partition 44 is shown resting on top of packages or containers 60 of goods which are to be protected from an undesirable temperature change by exposure to the ambient temperature of the empty space above the partition 44.

In Figure 5, the space above the partition 44 is shown filled with goods whose temperature may be uncritical or which may be required to be stored at an elevated temperature - such as the ingredients of a hot meal. Thus, one or more hot courses may be stored at 62 while a cold dessert may be stored at 60.

In Figure 6, the entire contents 64 of the space within the bag 30 may be required to be kept at the same elevated or depressed temperatLre relative to ambient. Thus, a bag 30 according to the present invention and having a heat-reflecting metal foil faced partition 44 can be put to a wider range of uses than a conventional "picnic" bag having no heat-reflecting internal wall surfaces, and no partition or separator 44.

It is to be understood that the upper surface of the partition 44 may be metallised as well, while different handle patterns may be adopted - such as cord loops at each end - to minimise masking of the upper foil. Alternatively, all foil facings 12 can be omitted from the partition 44, although such treatment would reduce the thermal insulation performance of the bag 30.

Figure 7 shows a variant of the arrangement of Figures 2 - 6. In Figure 7, the bag 30 is adapted for the transport of bottles, either solely - for example, wines - or in conjunction with other items for example, bottled milk and other foodstuffs. In either case, it is convenient to pack bottles upright, and to thermally insulate one or more from other contents in the bag by an upright partition 66.

Thus, red and white wines can be carried at their respective optimum temperatures, or cold milk can be separated from other foods at ambient temperatures.

The upright partition 66 can be designed as a snug fit between opposite side walls of the bag 30 either on the shorter or the longer medial dimension of a bag shaped as shown in Figure 1. To accommodate these different widths, the partition 66 may be made to an overall with equal to the longer dimension of the bag but be formed with fold lines to accommodate the shorter span. In any case, the reflective composite material is non-rigid so that lateral deflections up to a certain limit are possible and will often facilitate the separation of items of unequal or irregular size and shape.

For maximum efficiency, the partition 66 must be provided with reflective surfaces on both sides.

This can easily be achieved by R.F. welding two composite panels together around their plain plastics margins. Alternatively, a single composite panel of twice the desired width can be folded in half and the overlapping foil-free edges can be seam welded.

A popular variant (not illustrated) of the design shown in Figure 1 is a shoulder bag style. In this style, the hinged lid 40 of Figure 1 is replaced by an integral top wall having a sliding clasp fastener running thereacross between a pair of lugs or ears which are formed, as will be described later, by deformation of the top wall at each end of the fastener and constitute an anchorage for a shoulder strap which connects them. When the sliding clasp fastener is opened, an aperture is formed through which articles can be inserted or withdrawn.

A polished foil insulated shoulder bag according to the present invention is made by R.F. welding to each other a pair of equal-sized composite panels each of a length equal to the depth of the bag pius half its width when full. Two equal-sized plain panels of the material of the external wall 32 are overlaid, one of each composite liner panel 34, and all four panels are united at one end across their width by seam-welding to a sliding clasp fastener of a little less length than the common width of the composite liner panels 34 and external wall panels 32. Thus, the sliding clasp fastener unites two similar pairs of panels, and these are then folded flat against each other about the line of the fastener, foil to foil, and the long edges are seam welded to each other down each side. The result is a doublewalled, foil lined pocket open at the end remote from the fastener.

If desired, sheets of extra insulating material can now be inserted between composite panel and its associated external wall panel. When this has been done, the pairs of liner and external panels are separated at the open end of the pocket and an oval composite base panel, already pre-formed, is registered with the rim of the open end of the pocket and R.F. seam welded thereto, in a manner generally similar to that of the attachment of the base panel 38 in Figure 1. The pocket is now sealed at what was its open end and closed at the other end by the sliding clasp fastener.

The bag is now stood on its base panel and the side seams which run up the length of the bag are now pinched at either end of the fastener and the external surface flanking the fastener is depressed so that the top ends of the seams form the points of a pair of opposed lugs or ears. Each lug or ear is capped by an inverted U-shaped cap between the arms of which is inserted a metal D-ring or half-buckle to which can be attached the ends of the shoulder strap. Each cap is then riveted to its lug or ear, and a linered shoulder bag according to the present invention is complete. A partition or baffle like that shown in Figures 2 and 3 is also provided.

As has already been noted, the foil-faced plastics sheeting is a proprietary article, and has a thickness of 0.005 in. (=0.125 mm). In practical tests, this material was welded onto a backing sheet having a thickness of 0.008 in. (=0.20 mm). The use of the foil faced plastics sheeting was shown to be very effective as an insulator by placing a pan of boiiling water direct from the boiling ring onto the polished foil face of a sheet, and after 2 minutes the temperature rise on the underside of the sheet was only just sensible to the touch. The presence of the heat reflecting foil layer imparts a higher overall heat resistance to the plastics base.

The deliberate avoidance of foil-to-foil contact at all R.F. welded seams is a precaution against arcing during welding. The area of non-metallised plastics can be kept to 5% or less of the total wall surface of the liner and by suitable control of the panels during the welding process the natural resilience thereof will cause the welded panels to bulge sufficiently to bring the metallised layers into virtual or actual contact, thus minimising a heat loss path between them.

Instead of using foil faced plastics sheeting, foil faced polyethylene foam can be substituted.

Claims (15)

1. The method of making a thermally insulated portable container comprising forming a hollow rectangular prismatic body with a lining of a plastics material having a reflective metal layer deposited on one surface thereof; closing one end of the hollow body with a fixed panel having a lining of the same material; forming a similarly lined openable closure at the other end thereof, and making a thermally insulating partition to be a snug fit within the container between opposite internal wall surfaces thereof so as to thermally insulate one part of the internal space of the container from the remainder.

2. The method according to claim 1 wherein the thermally insulating partition is of relatively stiff or semi-rigid construction so as to be capable of forming a platform for the support of goods placed thereon.

3. The method according to claim 1 or 2 wherein at least one face of the insulating partition carries a reflective metal foil facing.

4. The method according to claim 1, 2 or 3 wherein the partition is a snug fit in the horizontal plane between opposite sides of the body when the container is in an upright attitude.

5. The method according to claim 1, 2 or 3 wherein the partition is a snug fit between a pair of opposite internal walls when the container and the partition are both in an upright attitude.

6. The method according to claim 1 wherein a lid of approximately the same dimensions as the fixed panel is lined with the same metallised plastics material as forms the lining of the body and is hinged to the upper end of the body and provided with a skirt which embraces the upper end of the body in the closed position of the lid.

7. The method according to claim 1 wherein the top of the body is closed by pinching together the top edges thereof and securing them by means of a sliding clasp fastener.

8. A thermally insulated portable container having a generally rectangular right prismatic body whose internal walls are lined by a metal foil-faced flexible plastics material, and having a thermally insulating partition which is a snug fit within the container.

9. A container according to claim 8 wherein the partition has a reflective metal foil facing on at least one side.

10. A container according to claim 8 or 9 having a generally rectangular prismatic shape and the partition is a snug fit in the container parallel to the base thereof.

11. A container according to claim 8 or 9 having a generally rectangular prismatic shape and the partition is a snug fit between a pair of opposite walls when inserted thereinto in an upright attitude.

12. A container according to any of claims 8 11 wherein the bottom of the container is closed by a base panel having its top surface lined with the foil-faced plastics material while the top is closed by a hinged lid having its underface also lined with the foil-faced plastics material.

13. A container according to any of claims 8 11 wherein the top of the body is closed by a sliding clasp fastener and the container is suspended by a strap to constitute a shoulder bag.

14. The method of making a thermally insulated container substantially as hereinbefore described.

15. A thermally insulated container substantially as hereinbefore described with reference to the accompanying drawings.