WO2002001995A2

WO2002001995A2 - Thermal insulating vessel

Info

Publication number: WO2002001995A2
Application number: PCT/IT2001/000339
Authority: WO
Inventors: Paolo Manini; Enea Rizzi
Original assignee: Saes Getters S.P.A.
Priority date: 2000-06-30
Filing date: 2001-06-27
Publication date: 2002-01-10
Also published as: IT1318098B1; AU2001271004A1; ITMI20001487A0; WO2002001995A3; ITMI20001487A1

Abstract

Thermal insulating vessel comprising a double wall container (1, 2, 3; 10, 11) and one or more evacuated panels (6, 7, 8; 12, 13) inserted into the interspace between the two walls (1, 2; 10, 11) of said container. At least one of the evacuated panels (6, 7, 8; 12, 13) preferably comprises an envelope enclosing a very fine powder of an inert material, in particular powder of pyrogenic silica.

Description

"THERMAL INSULATING VESSEL"

The present invention relates to a thermal insulating vessel. In particular, the invention refers to thermal insulating vessels used for keeping the temperature of foods and drinks constant, such as sports bottles or containers to be used at home, in restaurants and the like.

Thermal insulating vessels, also called thermos, are known, which comprise a silver-plated glass or metal double wall bottle, the interspace of which is evacuated for keeping liquids cold or warm for a certain period of time. However, these known vessels cannot be used in some fields, such as for example in the sports field, due to their relatively high cost, fragility and/or weight.

In order to avoid these problems, the double wall bottle has been made of a plastic material. However, the vacuum obtained in the interspace of a plastic bottle rapidly degrades due to the degassing of this material, as well as due to its permeation and its low tightness in the welding zones. Furthermore, the plastic flexibility involves some structural problems due to the pressure difference between the bottle exterior and the interspace.

In order to avoid the latter problem, a thermal insulating evacuated panel of the known kind, for instance those comprising an open cells polymeric foam contained in an envelope, could be inserted into the interspace. However, these panels are rigid and difficult to be adapted into the interspaces with an annular cross-section, normally present in the containers for foods and drinks. Patent application WO 96/32605 in the name of the UK company ICI discloses a method for curving panels with polymeric foams, wherein a series of grooves is obtained in the polymeric foam before its introduction into the envelope; the panel bends along the grooves at the first exposure to air. The main disadvantage of this method is that the envelope is stretched near the angles formed by the grooves, and in these zones a gas permeation into the panel may occur, thereby degrading its thermal insulating properties. It is therefore an object of the present invention to provide a thermal insulating vessel free from said disadvantages, i.e. a vessel which is light, economic and resistant. Said object is achieved with a thermal insulating vessel, the main features of which are disclosed in the first claim and other features are disclosed in the subsequent claims.

The panels of the vessel according to the present invention employ as a filling material a powder of an inert material with particles having an average size lower than 100 nanometers (rrm) and preferably comprised between about 2 and 20 nanometers. It has been found that by employing these powders, the thermal conductivity of the panels changes only slightly, and in particular remains lower than about 8 mW/m-K, for inner pressures up to some tens of mbar, unlike the panels based upon polymeric foams in which the thermal conductivity rapidly rises when the inner pressure exceeds values of about 1 mbar. For this reason, it is possible to keep in the evacuated panels of the invention pressures also greater than 10 mbar, so as to avoid the use of envelopes containing aluminum sheets, especially necessary for high temperature use. This particular arrangement, which decreases the thermal bridge down to negligible values, allows the almost complete exploitation of the insulating properties of the filling material of the evacuated panels of the invention. Thanks to their very small size, the powder particles can form, due to cohesive or electrostatic forces, aggregates having a size of some micrometers (μm) or even larger, without in any case causing changes in the thermal insulating properties of the panels.

Thanks to the evacuated panels which is provided with, the thermal insulating vessel according to the present invention can be. made up of light materials generally not suitable for keeping vacuum, such as for instance plastic, while being capable to thermally insulate the liquids contained therein for long times, also longer than 3 or 4 hours.

By using a block of very fine powder of an inert material as a filler, it is possible to obtain evacuated panels which can be bent or curved, so as to be inserted into the interspace between two curved surfaces of the walls of the container. Furthermore, at the same thermal insulation, the panel of the invention is thinner and more resistant, as well as bears higher imier pressures, than the known panels based on polymeric foams, with a consequent longer duration of the functionality of the thermal insulating vessel.

According to a particular aspect of the invention, the inert material of the powder is silica preferably mixed with mineral fibers, so as to be easily compressed for making blocks with a thickness of few millimeters only, which can be enveloped, evacuated and subsequently curved with a relative easiness.

Further advantages and features of the thermal insulating vessel according to the present invention will be clear to those skilled in the art from the following detailed and non-limiting description of some embodiment thereof, with reference to the attached drawings wherein:

- figure 1 shows a side view of a first embodiment in a cross-section taken along plane I-I of figure 2;

- figure 2 shows a bottom view of the embodiment of figure 1 in a cross-section taken along plane II-II of figure 1; — figure 3 shows a cross-sectioned side view of a second embodiment; and

- figure 4 and 5 show two diagrams of the temperature progress of liquids contained in known vessels and in vessels according to the present invention.

In the first illustrated embodiment the evacuated panels of the invention are employed for the thermal insulation of a bottle-shaped vessel, for instance for sports use. Referring to figures 1 and 2, it is seen that the thermal insulating vessel according to this embodiment of the invention comprises in a known way a substantially cylindrical-shaped bottle having an outer diameter comprised for example between 5 and 10 cm, which is provided with two walls: an outer wall 1 and an inner wall 2. These walls are preferably joined to each other at a neck 3 provided with an opening 4 for the liquid passage, wliich can be closed by a cap 5.

Walls 1, 2 and neck 3 of the bottle are preferably made of a light material, for instance plastic. In the interspace between the two walls is inserted at least one evacuated panel 6 with a substantially parallelepiped shape, which is curved so as to form a tube which can be arranged between the lateral surfaces of walls 1 and 2. A second evacuated panel 7 with a substantially circular shape can be inserted between the lower bases of walls 1 and 2, while a third evacuated panel δ with a substantially annular shape can be inserted between the upper bases of the same walls.

Evacuated panels 6, 7 and 8 have a thickness comprised for example between 4 and 8 mm and are made of an envelope of laminated plastic, possibly metallized, in which a very fine powder of an inert material, in particular silica, is enclosed. The plastic material used for the envelope can be any known material considered suitable for manufacturing evacuated panels of the conventional kind, for instance polyolefin. The pressure in the envelope is lower than 50 mbar, while the silica powder is preferably mixed with mineral fibers, in particular glass fiber. Silica is preferably pyrogenic silica, a form of silica obtained by burning in a suitable chamber SiCl₄ with oxygen, according to the reaction:

SiCl₄ + O₂ → SiO₂ + 2 Cl₂

Silica produced in this reaction is in form of particles of size comprised between few nanometers and some tens of nanometers, which may agglomerate for making up particles having greater sizes, as previously disclosed. Pyrogenic silica is produced and sold for example by the US company CABOT Corp. with

® the name Nanogel or by the German company Wacker GmbH.

In. a second embodiment, the panels of the invention are employed for the thermal insulation of cylindrical containers for keeping foods or drinks at a desired temperature, such as pots or water tanks for preparing warm or cold drinks. With reference to figure 3, it is seen that a container 9 of this kind can comprise two walls: an outer wall 10 and an imier wall 11. At least an evacuated panel 12 of the above described kind, curved in a cylindrical shape, and preferably a further evacuated panel 13 with a circular shape are inserted into the interspace between these two walls and into the base of the container, respectively. Containers according to this embodiment are generally bigger that the bottle of figures 1 and 2, and in particular have a diameter which can be comprised between 10 and 50 cm. In this case panel 12, being curved with a curvature radius greater than the radius of the sports bottle, can be thicker, up to 10-15 mm. Container 9 generally provides for an upper closure member, for instance a cover (not shown in the figure) wliich in turn can be preferably made with a double wall defining an interspace for containing a thermal insulating panel.

Figure 4 shows a diagram 14 of the temperature progress of a liquid at about 0 °C placed in a known thermal insulating vessel, for instance comprising a plastic bottle with a double wall having the interspace filled with a non-evacuated material. The same figure shows diagrams 15 and 16 of the temperature of the same liquid at about 0 °C placed in two vessels according to the present invention. These two vessels comprise the same plastic bottle with double wall of the known vessel, but evacuated panels 5 and 7 mm thick, respectively, are arranged in their interspaces. As it can be noted, the liquids contained in the above three vessels reach the temperature of about 12 °C, shown with a broken line, after about 1.5, 4 and 5 hours, respectively. This particular temperature is significant since it represents the physiological threshold value of the human sensation of cold liquid.

Figure 5 shows instead a diagram 17 of the temperature progress of a liquid at about 90 °C placed in a known thermal insulating vessel, for instance comprising a plastic bottle with a double wall having the interspace filled with a non-evacuated material. The same figure shows diagrams 18 and 19 of the temperature of the same liquid at about 90 °C placed in two vessels according to the present invention. These two vessels comprise the same plastic bottle with double wall of the known vessel, but evacuated panels 5 and 7 mm thick, respectively, are arranged in their interspaces. As it can be noted, the liquids contained in the above three vessels reach the temperature of about 40 °C, shown with a broken line, after about 2.5, 4 and 5 hours, respectively. This particular temperature is significant since it represents the physiological threshold value of the human sensation of warm liquid.

Modifications and/or additions, if any, may be made by those skilled in the art to the above described and illustrated embodiment remaining within the scope of the same invention. It is for example obvious that in other embodiments of the thermal insulating vessel according to the present invention the container may not be cylindrical, but have other shapes, for instance half-cylindrical, prismatic, etc.

Claims

1. Thermal insulating vessel comprising a double wall container (1, 2, 3; 10, 11), characterized in that one or more evacuated panels (6, 7, 8; 12, 13) are inserted into the interspace between the two walls (1, 2; 10, 11) of said container, at least one of said panels comprising an envelope enclosing powder of an inert material with an average size of the particles lower than 100 nanometers.

2. Thermal insulating vessel according to the previous claim, characterized in that the powder of inert material has particles with an average size comprised between 2 and 20 nanometers.

3. Thermal insulating vessel according to one of the previous claims, characterized in that the envelope is made of a plastic material, possibly metallized.

4. Thermal insulating vessel according to one of the previous claims, characterized in that the powder of inert material is mixed with mineral fibers.

5. Thermal insulating vessel according to the previous claim, characterized in that said mineral fibers are glass fibers.

6. Thermal insulating vessel according to one of the previous claims, characterized in that the inert material is silica.

7. Thermal insulating vessel according to the previous claim, characterized in that said silica is pyrogenic silica.

8. Thermal insulating vessel according to one of the previous claims, characterized in that the walls of the container (1, 2, 3; 10, 11) are made of a plastic material.

9. Thermal insulating vessel according to one of the previous claims, characterized in that at least one surface of both walls (1, 2; 10, 11) of the container is curved, and that the evacuated panel (6; 12) comprised in the relevant interspace is curved.

10. Thermal insulating vessel according to the previous claim, characterized in that the container has a substantially cylindrical shape and includes an evacuated panel (6; 12) with a substantially parallelepiped shape, which is curved and inserted into the interspace between the lateral surfaces of the walls (1, 2; 10, 11) of the container.

11. Thermal insulating vessel according to one of the previous claims, characterized in that a second evacuated panel (7; 13) having a substantially circular shape is inserted between the lower bases of the walls (1, 2; 10, 11) of the container.

12. Thermal insulating vessel according to one of the previous claims, characterized in that the container is a bottle.

13. Thermal insulating vessel according to the previous claim, characterized in that a third evacuated panel (8) with a substantially annular shape is inserted between the upper bases of the walls (1, 2) of the bottle.

14. Thermal insulating vessel according to claim 12 or 13, characterized in that at least one of the evacuated panels (6, 7, 8) has a thickness comprised between 4 and 8 mm.

15. Thermal insulating vessel according to one of claims 1 to 11, characterized in that the container is a pot or a tank (9).

16. Thermal insulating vessel according to the previous claim, characterized in that at least one of the evacuated panels (12, 13) has a thickness comprised between 4 and 15 mm.