Sealed container, container through assembly, and method for providing

Abstract

A container, such as an evacuated solar collector, comprises a wall (1) formed from a first material having a first coefficient of thermal expansion. A penetration (2) passes through a hole (3) in a wall (1) of the container and comprises a flange (5) having a surface (5a) facing the surface of the wall (1), the penetration (2) being formed from a material having a second coefficient of thermal expansion higher than the first coefficient of thermal expansion. The resilient seal (8) is positioned between the wall (1) and the flange (5), and the clamping member is operable to move the flange (5) towards a facing surface (1a) of the wall (1) to compress the seal (8) between the wall (1) and the flange (5). A spacer is positioned between the clamping member and the flange (5), the spacer being formed of a material having a third coefficient of thermal expansion higher than the second coefficient of thermal expansion.

Description

Technical Field

[0001] The present invention relates to the sealing of containers. Background Art

[0002] Evacuated tube solar collectors often require an airtight seal between the glass vacuum tube and the metal heat exchanger tubing. In the case of a direct current collector using a single-wall vacuum tube, this seal needs to separate the vacuum from the atmospheric pressure and must therefore have high integrity. Establishing a high-integrity vacuum seal between dissimilar materials presents technical challenges, both in terms of the attachment method (whether mechanical or adhesive) and in relation to the design robustness across variable temperatures.

[0003] Similar technical challenges exist when forming a seal between dissimilar materials, and not only in evacuated tubes and other containers. Thus, the techniques disclosed herein have applications outside the field of evacuated containers.

[0004] Some sealed containers need to operate across a wide temperature range. An example is an evacuated tube solar collector. Although for building heating and hot water systems, the temperature during normal daytime operation is typically in the range of 20°C to 90°C, when the fluid is not circulating, the components can reach a wider temperature range. The temperature on a winter night can drop below freezing. During the day, if the fluid flow stops under sunny conditions (due to control or pump or component failure), the absorber inside the vacuum tube can reach 200°C to 300°C.

[0005] In some sealed containers, such as evacuated tube solar collectors, the container is made of glass, and the through-component assembly including the elastic seal includes metal components. Most metals and glass have very different coefficients of thermal expansion. The coefficient of thermal expansion of brass is 18 - 19 x 10-6 m / m K, while that of borosilicate glass (commonly used in evacuated tube solar collectors) is only 3.3 x 10-6 m / m K. This means that when the temperature changes, the brass part expands and contracts much more than the borosilicate glass.

[0006] There are various types of vacuum seals that can be used between glass and metal, including:

[0007] 1. Fused glass seals, which typically use a glass "frit" (a glass "solder" that melts at a temperature below that of the main glass components).

[0008] 2. Adhesive seals

[0009] 3. O-ring seals.

[0010] Neither the molten glass nor the bonded seal can easily accommodate temperature changes because dissimilar materials are bonded together and have different amounts of expansion. There are some specialized methods to address this problem, such as using extremely thin metal elements with mechanical elasticity (as used in Houskeeper seals). However, such seals are expensive and require precision-machined components and costly manufacturing equipment.

[0011] O-ring vacuum seals can be more adaptable to mechanical movement and temperature changes. If the metal and glass are separated by an O-ring made of an elastic material (such as ethylene propylene diene monomer rubber or Viton™), they have some freedom to expand and contract. However, in order to form a good vacuum seal, the O-ring must maintain good contact and compression, and the degree of material expansion that can be accommodated is limited.

[0012] The brass through-piece used to carry a copper tube through the wall of a glass tube or glass end cap may require a spacing of 15 mm to 20 mm between the O-ring face and the clamping nut. When a 20-mm-long brass component is heated to 300 °C, it will expand by 0.1 mm. This movement will reduce the compression of the O-ring. The reduction in compression will change the cross-sectional shape of the O-ring and reduce the contact area with the glass sealing surface. This will in turn reduce the thickness of the O-ring material that separates the vacuum from the atmosphere, and the reduction in the thickness of the O-ring material will increase the rate of air penetration through the O-ring. Therefore, the rate of air leakage through the O-ring will increase, and the service life of the vacuum tube (the duration of maintaining a good vacuum) will be shortened. In the worst case, the contact between the brass face and the glass face may disappear in a sealed area, and rapid vacuum leakage may occur.

[0013] Therefore, a design solution is needed to counteract the thermal expansion effect in the vacuum seal between materials with different coefficients of thermal expansion. This solution will be applicable to evacuated tube solar collectors, but also to other applications that require sealed containers. Summary of the Invention

[0014] Embodiments of the present invention are not limited to solving such problems and may include solutions to other problems.

[0015] The present invention content is provided to introduce in a simplified form selected concepts that will be further described in the "Detailed Description" section below. The present invention content is not intended to identify the key features or essential features of the claimed subject matter, nor is it intended to be used to determine the scope of the claimed subject matter.

[0016] Hereinafter, a sealed container is described in which two materials with different coefficients of thermal expansion are connected. A third material is added, which has a coefficient of thermal expansion higher than either of the first two materials, and this third material is used to compensate for the difference in thermal expansion.

[0017] In the following, a container is provided, which comprises:

[0018] • A wall formed of a first material having a first coefficient of thermal expansion; a penetrator passing through a hole in the wall of the container and including a flange having a surface facing the surface of the wall, the penetrator being formed of a material having a second coefficient of thermal expansion higher than the first coefficient of thermal expansion;

[0019] • An elastomeric seal located between the wall and the flange; a clamping member operable to move the flange towards the facing surface of the wall to compress the seal between the wall and the flange; and

[0020] • A spacer located between the clamping member and the flange, the spacer being formed of a material having a third coefficient of thermal expansion higher than the second coefficient of thermal expansion.

[0021] Due to the difference in the coefficients of thermal expansion, when the temperature increases, the penetrator expands much more in length than the thickness of the container wall. Normally, this would result in a reduction in the compression of the O-ring. However, since the spacer has an even higher coefficient of thermal expansion than that of the penetrator, the expansion of the spacer at least partially offsets the expansion of the penetrator, if the expansion of the penetrator is not complete. Thus, a design that is particularly robust across variable temperatures can be provided.

[0022] A penetrator assembly for a container made of a material having a coefficient of thermal expansion below 10 x 10-6 m / m K, such as glass, is also provided. The penetrator assembly may include:

[0023] • A penetrator including a flange having a surface facing the surface of the container wall in use, the penetrator being formed of a material having a second coefficient of thermal expansion higher than the first coefficient of thermal expansion; an elastomeric seal located between the wall and the flange;

[0024] • A clamping member operable to move the flange towards the facing surface of the wall to compress the seal between the wall and the flange; and

[0025] • A spacer located between the clamping member and the flange, the spacer being formed of a material having a third coefficient of thermal expansion higher than the second coefficient of thermal expansion.

[0026] A method of providing an access opening in a wall of a container made of a first material having a first coefficient of thermal expansion, such as below 10 x 10-6 m / m K, includes:

[0027] • Providing an access hole in the wall

[0028] • Arrange a penetrator to pass through a hole in a wall, the penetrator including a flange having a surface facing the surface of the wall, the penetrator being formed of a material having a second coefficient of thermal expansion higher than a first coefficient of thermal expansion;

[0029] • Position an elastic seal between the wall and the flange;

[0030] • Arrange a clamping member to be movable to compress the seal between the wall and the flange; and

[0031] • Arrange a spacer between the clamping member and the flange, the spacer being formed of a material having a third coefficient of thermal expansion higher than the second coefficient of thermal expansion.

[0032] The container, penetrator assembly, and method may include any one of the following optional features:

[0033] The clamping member can be operated from the side of the wall opposite to the flange.

[0034] The clamping member can be formed of the same material as the penetrator. This helps to avoid the risk of galvanic corrosion that may occur when the clamping member and the penetrator are formed of different materials.

[0035] The spacer can be positioned between the clamping member and the wall of the container. In this case, the elastic seal can be at least partially received in a groove formed in the surface of the flange facing the wall of the container.

[0036] The spacer can be positioned between the elastic seal and the flange. In this case, the elastic seal can be at least partially received in a groove formed in the surface of the spacer facing the wall of the container.

[0037] The clamping member can surround a portion of the penetrator. For example, the clamping member can include a threaded nut that can move along a corresponding threaded surface provided on the portion of the penetrator extending outside the container. This portion of the penetrator can extend outside or inside the container.

[0038] The wall of the container can be formed of a ceramic material, and / or the penetrator can be formed of a metal. For example, the wall of the container can be formed of glass, and / or the penetrator can be formed of brass.

[0039] The third coefficient of thermal expansion can be at least 5 times the first coefficient of thermal expansion.

[0040] The material of the spacer can be polytetrafluoroethylene.

[0041] The container can be evacuated. For example, the container can include a solar collector. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Some embodiments of the present invention will be described by way of example with reference to the following drawings, in which:

[0043] Figure 1 is a cross-sectional view of a part of the wall of a container provided with a penetrator;

[0044] Figure 2 is a cutaway perspective view of a solar collector, Figure 1 the container wall and the penetrator of which can be included in the solar collector; and

[0045] Figure 3 is Figure 3 a perspective view of a parallel array of solar collectors of the kind shown in. DETAILED DESCRIPTION

[0046] Aspects of the present invention will be understood from the following detailed description of embodiments, which are intended to be illustrative only and not restrictive. For the sake of brevity, some well-known features, methods and systems, program components and circuits are not described in detail.

[0047] Figure 1 is a cross-sectional view of a part of the wall 1 of a container provided with a penetrator 2. Relative to Figure 2 Examples of the container are further described. The penetrator provides an inlet from one side of the wall to the other side, for example, from the outside to the interior of the container. The penetrator can include an annular member, although other shapes are possible, the annular member having a thickness greater than that of the container wall so as to project from the wall on both sides, for example, projecting into the container and extending outside the container.

[0048] The penetrator can be hollow or solid. For example, a fluid penetrator can include a channel that can receive a pipe or pass through or enter the container in use. The pipe is generally sealed relative to the penetrator. An electrical penetrator can include a solid conductor, and electrical connections can be made to the conductor, for example, on both sides of the wall. The penetrator needs to be sealed against the wall of the container.

[0049] The container wall 1 is formed of a first material having a first coefficient of thermal expansion. For example, the container wall 1 can be made of glass. The penetrator 2 is made of a material having a coefficient of thermal expansion higher than that of the material of the wall 1. For example, the penetrator can be made of brass.

[0050] The penetrator 2 passes through the hole 3 in the container wall 1 and includes: an extension portion 4 on one side of the container wall 1, and a flange 5 on the other side of the container wall 1, the flange having a surface 5a facing the surface 1a of the container wall 1.

[0051] The elastic seal 8 is positioned between the wall 1 and the flange 5, for example, between the corresponding surfaces 1a and 5a. Various materials and shapes can be suitable for the seal, as is familiar to those skilled in the art. For example, the seal 8 can include an O-ring. Additionally or alternatively, the seal 8 can also be formed of fluororubber (such as Viton™).

[0052] To compress the seal and ensure good surface contact between the seal 8 and the corresponding surfaces it contacts, a clamping member is provided, which can be operated to move the flange 5 towards the wall 1 to compress the seal 8 between the wall 1 and the flange 5. In Figure 1 it, the clamping member includes a threaded nut 19, which can move along a corresponding threaded surface provided on a portion 4 of the penetrator extending outside the container 1. A washer 18 or an annular disc is provided between the nut and the container wall 1.

[0053] The seal does not necessarily have to be in direct contact with the flange 5. For example, one or more spacers can be present between the seal and the flange 5 while still enabling the seal 8 to be compressed between the wall 1 and the flange 5 and thus form good surface contact with the surface 1a of the wall 1.

[0054] The elastic seal can be provided with grooves for positioning the seal on the surface facing the container wall 1 against which it is compressed in use. For example, as Figure 1 shown, the elastic seal 8 can be positioned or at least partially received in a groove 5b formed in the surface 5a of the flange 5. For example, the groove 5b can include an annular channel.

[0055] Other suitable clamping members can be used, such as but not limited to those that surround a portion of the penetrator 2, which portion extends on the side of the container opposite to the flange 5. Generally, the clamping member can be operated from the side of the wall 1 opposite to the flange 5, for example, by a human operator, and the same is true for the case of the threaded nut 19.

[0056] The clamping member can be formed of the same material as the penetrator 2. Thus, for example, the threaded nut 19 and optionally also the washer 18 can be formed of brass.

[0057] The surface 5a of the flange 5 can face the inner surface or the outer surface of the container wall 1. The advantage of the flange 5 on the inner surface is that the clamping member is more accessible on the outside. However, the flange 5 and the seal 8 can also be on the outer surface. For example, in the case of a vacuum, this has certain advantages because the force due to atmospheric pressure also compresses the seal. For example, this is feasible when the penetrator is installed before the formation of the container is completed and / or before it is evacuated.

[0058] The spacer is positioned between the clamping member and the flange 5 and is formed of a material having a higher coefficient of thermal expansion than the container wall 1 or the penetrator 5. In Figure 1 the arrangement, the spacer includes an additional washer or an annular disc 20 positioned between the washer 18 and the wall 1. In the case where the container is glass and the penetrator is brass, a suitable material for the spacer 20 is polytetrafluoroethylene.

[0059] In Figure 1 the arrangement shown, the wall 1 separates the spacer from the flange, for example, separates the polytetrafluoroethylene washer 20 from the flange 5. In other words, the spacer is positioned between the clamping member and the wall 1 of the container. In an alternative arrangement, the spacer can be positioned between the elastic seal 8 and the flange. Then, under the action of the clamping member, the elastic seal 8 will be compressed between the spacer and the wall. The spacer can be provided with grooves to position or at least partially accommodate the seal.

[0060] Figure 1 An example of a container is shown where the wall is formed of a first material having a first coefficient of thermal expansion, the penetrator is formed of a material having a second coefficient of thermal expansion higher than the first coefficient of thermal expansion, and the spacer is formed of a material having a third coefficient of thermal expansion higher than the second coefficient of thermal expansion. This provides a design that is particularly robust across variable temperatures.

[0061] Taking glass, brass, and polytetrafluoroethylene as an example, when the temperature increases, the brass penetrator expands much more in length than the glass plate (thickness). Thus, the compression of the O-ring is reduced. However, the polytetrafluoroethylene washer has an even higher coefficient of thermal expansion than brass, and the expansion of this part offsets the expansion of the brass. Due to the appropriate selection of the dimensions of the container wall, penetrator, and spacer, the compression of the O-ring can be maintained at a substantially constant amount, independent of temperature. The following calculations show how these expansion amounts offset each other.

[0062]

[0063] In this example, when the temperature rises by 300 °C, the brass penetrator expands by 7.9x10 -2 mm, but the polytetrafluoroethylene also expands by 6.3x10 -2mm, resulting in a total change in O-ring compression of only 5x10 -3 mm, which is negligible.

[0064] More generally, the thickness of the "clamped portion" (i.e., the portion between the clamping member and the flange) and the length of the through-piece between the clamping member and the flange can be selected such that the difference in compression within the desired temperature range is within a predetermined threshold or tolerance.

[0065] For example, as Figure 1 shown, the through-piece, the seal, and the clamping member form a through-piece assembly, which can be provided as a separate item for installation in a container.

[0066] A method of providing an access opening in a wall of a container may include:

[0067] • Providing an access hole in the wall, the wall being formed of a first material having a first coefficient of thermal expansion,

[0068] • Arranging a through-piece to pass through the hole in the wall, the through-piece including a flange having a surface facing the surface of the wall, the through-piece being formed of a material having a second coefficient of thermal expansion higher than the first coefficient of thermal expansion;

[0069] • Positioning an elastic seal between the wall and the flange;

[0070] • Arranging a clamping member to be movable to compress the seal between the wall and the flange; and

[0071] • Arranging a spacer between the clamping member and the flange, the spacer being formed of a material having a third coefficient of thermal expansion higher than the second coefficient of thermal expansion.

[0072] Figure 1 The container of which the wall 1 is a part may include a solar collector. Figure 2 An example of a solar collector is shown in cutaway perspective, and the through-piece assembly as described herein can be incorporated into the solar collector. Examples of solar collectors are described in more detail in EP2898270A1 and EP3722698A1.

[0073] Figure 2 The solar collector of includes a container in the form of a sealed elongated transparent tube 201, the sealed elongated transparent tube containing a solar absorber assembly 202. As Figure 3 shown, a plurality of tubes 201 can be arranged in a parallel array 200, each tube containing a solar absorber.

[0074] Figure 2 The tube 201 shown in is provided with Figure 1Two penetrator assemblies 210 of the type shown are positioned in the circular end wall 230 of the tube 201. Some details are not shown, but it can be seen that each penetrator assembly 201 includes a clamping member, which in this example is a threaded nut 219 that can be operated from the outer surface of the circular end wall 230 of the container or tube 201. In Figure 2 this example, spacers 220 are provided between the end wall 230 and each threaded nut.

[0075] It should be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments. Embodiments are not limited to embodiments that solve any or all of the stated problems or have any or all of the stated benefits and advantages.

[0076] Any reference to "a" item means one or more of these items. The term "comprising" is used herein to mean including the identified method steps or elements, but such steps or elements do not include an exclusive list, and the method or apparatus may include additional steps or elements.

[0077] The drawings illustrate exemplary methods. Although these methods are shown and described as a series of acts performed in a particular order, it should be understood and appreciated that these methods are not limited by the order of the sequence. For example, some acts may occur in a different order than described herein. Additionally, one act may occur concurrently with another act. Further, in some cases, not all acts may be required to implement the methods described herein.

[0078] It should be understood that the above description of the embodiments is given by way of example only, and various modifications can be made by those skilled in the art. The above description includes examples of one or more embodiments. Of course, it is not possible to describe every conceivable modification and change of the above-described devices or methods for the purpose of describing the above aspects, but those of ordinary skill in the art can recognize that many further modifications and permutations of the various aspects are possible. Accordingly, the described aspects are intended to cover all such changes, modifications, and variations that fall within the scope of the appended claims.

Claims

1. A container, comprising: a wall formed of a first material having a first coefficient of thermal expansion; a penetrator passing through a hole in the wall of the container and including a flange having a surface facing the surface of the wall, the penetrator being formed of a material having a second coefficient of thermal expansion higher than the first coefficient of thermal expansion; an elastomeric seal positioned between the wall and the flange; a clamping member operable to move the flange towards the facing surface of the wall to compress the seal between the wall and the flange; and a spacer positioned between the clamping member and the flange, the spacer being formed of a material having a third coefficient of thermal expansion higher than the second coefficient of thermal expansion.

2. The container according to claim 1, wherein The clamping member is operable from a side of the wall opposite the flange.

3. The container according to claim 1 or claim 2, wherein, The clamping member is formed of the same material as the penetrator.

4. The container according to any one of the preceding claims, wherein, The spacer is positioned between the clamping member and the wall of the container.

5. The container according to claim 4, wherein, The elastomeric seal is at least partially received in a groove formed in the surface of the flange facing the wall of the container.

6. The container according to claim 1, 2 or 3, wherein The spacer is positioned between the elastomeric seal and the flange.

7. The container according to claim 6, wherein, The elastomeric seal is at least partially received in a groove formed in the surface of the spacer facing the wall of the container.

8. The container according to any one of the preceding claims, wherein, The clamping member surrounds a portion of the penetrator.

9. The container according to claim 8, wherein, The clamping member includes a threaded nut movable along a corresponding threaded surface provided on the portion of the penetrator extending outside the container.

10. The container according to any one of the preceding claims, wherein, The wall of the container is formed of a ceramic material and the penetrator is formed of metal.

11. The container according to any one of the preceding claims, wherein, The wall of the container is formed of glass.

12. The container according to any one of the preceding claims, wherein, The penetrator is formed of brass.

13. The container according to any one of the preceding claims, wherein, The third coefficient of thermal expansion is at least 5 times the first coefficient of thermal expansion.

14. The container according to any one of the preceding claims, wherein, The material of the spacer is polytetrafluoroethylene.

15. The container according to any one of the preceding claims, wherein, The container is evacuated.

16. The container according to any one of the preceding claims, wherein, The container includes a solar collector.

17. A penetrator assembly for a container formed of a material having a first coefficient of thermal expansion less than 10 x 10-6 m / m K, the penetrator assembly comprising: a penetrator including a flange having a surface facing the surface of a container wall in use, the penetrator being formed of a material having a second coefficient of thermal expansion higher than the first coefficient of thermal expansion; an elastomeric seal positioned between the wall and the flange; a clamping member operable to move the flange towards the facing surface of the wall to compress the seal between the wall and the flange; and a spacer positioned between the clamping member and the flange, the spacer being formed of a material having a third coefficient of thermal expansion higher than the second coefficient of thermal expansion.

18. The penetrator assembly according to claim 17, the penetrator assembly being configured such that the clamping member is operable from a side of the wall opposite the flange.

19. The through-component assembly according to claim 17 or claim 18, wherein The clamping member is formed of the same material as the penetrator.

20. The through - piece assembly according to claim 17, 18 or 19, wherein the through - piece assembly is configured to position the spacer between the clamping member and the wall of the container.

21. The through-component assembly according to claim 20, wherein, A groove is formed in the surface of the flange facing the wall of the container to at least partially accommodate the elastic seal.

22. The through - piece assembly according to claim 17, 18 or 19, wherein the through - piece assembly is configured to position the spacer between the elastic seal and the flange.

23. The through-component assembly according to claim 22, wherein, A groove is formed in the surface of the spacer facing the wall of the container to at least partially accommodate the seal.

24. The through-component assembly according to any one of claims 17 to 23, wherein, The clamping member surrounds a portion of the through - piece.

25. The through-component assembly according to claim 24, wherein, The clamping member includes a threaded nut that is movable along a corresponding threaded surface provided on the portion of the through - piece.

26. The through-piece assembly according to any one of claims 17 to 25, wherein, The through - piece is formed of brass.

27. The through-piece assembly according to any one of claims 17 to 26, wherein, The third coefficient of thermal expansion is at least 5 times the first coefficient of thermal expansion.

28. The through-component assembly according to any one of claims 17 to 27, wherein, The material of the spacer is polytetrafluoroethylene.

29. A method of providing an access opening in a wall of a container, the container being formed of a first material having a first coefficient of thermal expansion, the method comprising: Providing an access hole in the wall; Arranging a through - piece through the hole in the wall, the through - piece including a flange having a surface facing the surface of the wall, the through - piece being formed of a material having a second coefficient of thermal expansion higher than the first coefficient of thermal expansion; Positioning an elastic seal between the wall and the flange; Arranging a clamping member to be movable to compress the seal between the wall and the flange; And Arranging a spacer between the clamping member and the flange, the spacer being formed of a material having a third coefficient of thermal expansion higher than the second coefficient of thermal expansion.

30. The method according to claim 29, wherein, The through - piece is positioned outside the wall of the container.

31. The method according to claim 29, wherein, The through - piece is positioned inside the wall of the container.

32. The method according to claim 29, 30 or 31, comprising: Arranging the clamping member to be operable from a side of the wall opposite the flange.

33. The method according to any one of claims 29 to 32, wherein, The clamping member is formed of the same material as the through - piece.

34. The method according to any one of claims 29 to 33, comprising: Positioning the spacer between the clamping member and the wall of the container.

35. The method according to claim 34, comprising: Forming a groove in the surface of the flange facing the wall of the container to at least partially accommodate the elastic seal.

36. The method according to any one of claims 29 to 33, comprising: Positioning the spacer between the elastic seal and the flange.

37. The method according to claim 36, comprising: Forming a groove in the surface of the spacer facing the wall of the container to at least partially accommodate the seal.

38. The method according to any one of claims 29 to 37, wherein The clamping member surrounds a portion of the through - piece designed to extend outside the container in use.

39. The method according to claim 38, wherein, The clamping member includes a threaded nut that is movable along a corresponding threaded surface provided on the portion of the through - piece.

40. The method according to any one of claims 29 to 39, comprising: The through - piece is formed of brass.

41. The method according to any one of claims 29 to 40, wherein The third coefficient of thermal expansion is at least 5 times the first coefficient of thermal expansion.

42. The method according to any one of claims 29 to 41, comprising: The spacer is formed of polytetrafluoroethylene.

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