GB2361284A

GB2361284A - Insulation with vacuum cells

Info

Publication number: GB2361284A
Application number: GB0008757A
Authority: GB
Inventors: John Heffernan; Frank Robert Smith; Sean Tobias Devoy
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-04-10
Filing date: 2000-04-10
Publication date: 2001-10-17
Also published as: GB0008757D0

Abstract

A heat insulated pipe or structure comprises a plurality of vacuum cells 5 encapsulated within its wall 1,2. The pipe or structure is of a one-piece construction, and is preferably made of a moulded single polymer such as PVC. The vacuum cells 5 are encapsulated in a circumferential and longitudinal direction, allowing the vacuum to be maintained when the pipe is cut. The vacuum cells 5 may be in the form of randomly arranged bubbles within the pipe wall (as shown), or may alternatively be in the form of cavities (5; figure 1a) separated by circumferential washers (4; figure 1a) and longitudinal stringers (3; figure 1b).

Description

1 2361284 VACUUM INCLUSION PIPE STRUCTURE

BACKGROUND OF THE INVENTION

The invention relates to a vacuum insulated pipe and board material that has excellent thermal and acoustic insulation properties, as well as a process for producing the io material. Vacuum insulation materials are being used in various applications for low and high temperature storage and conveyance of liquid products due to their excellent heatinsulating properties. Current structures are for example, moulded into pipes that reduce heat loss from the liquid conveyed, boards which provide suppression of heat loss in the building and food transport industry, cylinders that reduce boiler heat loss and boards that provide noise suppression properties. The problem with current products and inventions so far is that the structure of the material to support the vacuum consist of either composites, or, if made of a single material, manufactured in more than one component. They can therefore be unnecessarily expensive to produce. It is the object of the present invention to provide a cheap, versatile, heat-insulation structure that is manufactured in a plastic 'monolith which firstly, eliminates the need for multiple manufacturing processes and secondly, reduces the volume of material required to produce.

SUMMARY OF THE INVENTION According to one present embodiment of the invention there is a heat-insulating pipe or structure of one-piece construction with a plurality of cells within the peripheral wall that are uniformly encapsulated in a circumferential as well as longitudinal direction which are manufactured and maintained in a state of vacuum, said heat- insulating pipe being constructed in one polymer.

1 1 1 According to another present embodiment of the invention there is a heat- insulating pipe or structure of one-piece construction with a plurality of cells within the peripheral wall that are encapsulated in a random cell arrangement and manufactured and maintained in a state of vacuum, said heat-insulating pipe or board being constructed in one polymer. According to another aspect of the heat-insulating structure there is provided the outline of the principle of the process to manufacture the pipe.

BRIEF DESCRIPTION OF THE DRAWINGS

The vacuum heat-insulation structure and process for producing the structure according to the present invention are hereinafter described in more detail with reference to one embodiment shown in the accompanying drawings in which:Figure 1,4 shows the heat - insulation pipe in crosssectional and end view with uif n ormly constructed vacuum cells. Figure 2,4 shows the heat - insulation pipe in cross-sectional view with vacuum cells randomly arranged. Figure 3,4 shows the manufacturing principle of the heat - insulation structure. Figure 4,4 shows a heat - insulation board in cross-sectional view with vacuum cells randomly arranged.

2s DETAILED DESCRIPTION Referring to the drawings: Figures 1 a and 1 b which shows a cross section (Fig. 1 a) and end section (Fig. I b) of a typical heat insulating tube. There is an inner tube 2 within which the fluid is contained or conveyed whose heat loss is to be minimalised, an outer tube 1 surrounding the inner tube 2 between which the vacuum is to be encapsulated in cavities 5, bulkhead washers 4 which encapsulate the vacuum in a 2 direction along the axis of the tube, and stringers 3 which brace in a circumferential direction. The pipe is moulded in one-piece. The plastic tube may be constructed in a polymer such as PVC and has a wall thickness of a strength sufficient to contain the vacuum within inner wall 2 and outer wall 1, it must also have an overall strength within the structure to withstand the io pressure exerted via the pressurised liquid within the inner tube 2 and any forces exerted via mechanical means within the normal life of a heating pipe, e.g. pipe joints being fitted, good impact and thermal stress resistance. The bulkheads 4 that provide the space in a circumferential direction between the inner 2 and outer 1 sheaths are spaced along the length of the pipe at a sufficiently minimum distance so that a vacuum of, for example 3 torr, will not be so high as to collapse or significantly alter the profile, thus sealing properties, of the outside tube 1. Equally so, the stringers 3 that run parallel to the pipe axis and encapsulate the vacuum cavities in a circumferential direction act to provide overall bending force strength, axial compression force strength and maintenance of aforementioned outside tube 1 profile. It will be evident that the bulkhead washers 4 allow the pipe to be cut at any point yet maintain overall the vacuum within the pipe wall. A second embodiment of the invention will now be described with reference to figure 2 in which the vacuum cells are randomly arranged in the pipe wall. Like parts are given like numbers to those of the first embodiment. As in the first embodiment of the heat insulating pipe the vacuum cells 5 are embedded within the pipe wall, but this time instead of being uniformly spaced around the circumference and length, they are bubbles of vacuum that have been randomly injected, or'foame&, into the wall of the pipe or board. They provide a 3 small interlaced bridge between the inner pipe 2 and outer pipe 1 so minimising heat transfer through the plastic. It will now be described with reference to Figure 3 the principle upon which the heatinsulation pipe with randomly arranged vacuum cells will be manufactured, where 1,2 and 5 are the pipe being extruded between dies 6 and 7 and the plastic being injected io is designated number 8. Boundary 10 encloses the process in a vacuum greater than that being injected through nozzle 9. As nozzle 9 injects the vacuum at a pressure lower than that which the process is bounded, it 'foams' and injects the vacuum cells into the pipe wall, thus leaving the cells in a state of vacuum when the pipe is in normal service at atmospheric pressure.

A further example of the invention is shown in figure 4, where the outer and inner boards are numbered 1 and 2 and the encapsulated vacuum cells are numbered 5. It is manufactured in a process similar to that shown in figure 3.

4

Claims

1) A heat insulating pipe or structure of one-piece construction with a plurality of closed cells encapsulated within the wall of the structure which are manufactured and maintained in a state of vacuum.

2) The structure set forth in claim 1, wherein the vacuum cells in the peripheral walls of the structure allow it to be cut yet maintain vacuum in the uncut section of the structure.

3) The structure set forth in claim 1 and 2 being constructed in one polymer.

4) A process for producing a heat insulating pipe or structure of onepiece construction as set forth in claim 1, in which process the moulded polymer structure into which the vacuum cells are injected is maintained in a state of vacuum higher than that which is being injected into the structure walls in order to create the vacuum cells.