EP2772451A1

EP2772451A1 - Container with expansion element

Info

Publication number: EP2772451A1
Application number: EP14154597.0A
Authority: EP
Inventors: Fredrik Brandt; Magnus Mackaldener; Fredrik Swartling; Robert NORDENHÖK; Ola SANDSTRÖM; Marcus Larsson; Raymond Reinmann
Original assignee: Scania CV AB
Current assignee: Scania CV AB
Priority date: 2013-02-28
Filing date: 2014-02-11
Publication date: 2014-09-03
Also published as: SE1350234A1

Abstract

A container (2) for a liquid medium has a wall comprising an expansion element (8), adapted to handle a volume expansion of the medium (4) upon temperature changes. The expansion element (8) has substantially an extent which coincides with the extent of the wall (6). The expansion element (8) is resilient and is adapted to exist in one of two states:
A first state, which is the normal state for the expansion element (8) and where the expansion element (8) has a convex shape (10) facing the inside of the container (2), and which is the state in which the element exists, as long as the medium (4) inside the container (8) has a pressure P which is below a predetermined threshold value P_T, and a second state, where the expansion element (8) has a concave shape (12) facing the inside of the container (2),
when the medium inside the container has a pressure P exceeding the threshold value P_T. The volume increase which the expansion plate causes prevents the container from being damaged due to e.g. freezing of a liquid medium.

Description

Field of the invention

The present invention pertains to a container according to the preamble of the independent patent claim.

Background of the invention

All liquids that have a volume increase at their freezing point may damage an enclosing component, e.g. a container, when the liquid freezes. If the inlet/outlet to the container contains liquid and it freezes, the volume in the container is locked, or if the volume is constant for any other reason, the expansion of the liquid must be managed by the container. Since the expansion occurs in a closed volume, the forces may be very great, as this is more a matter of displacement rather than an increase of pressure. If the walls of the container cannot handle the displacement, the container becomes deformed and may lose its performance or even break.
It is also conceivable that volume expansion of a liquid may take place for other reasons, e.g. upon a temperature increase.
There are a number of different solutions to handle the problem with volume changes in closed containers. A number of examples are set out in the following patent documents.
US-4883082 pertains to a valve, adapted to be used at different temperatures and which has built in protection against damage at low temperatures.
US-3404802 pertains to a container for a frozen material. In the container there is arranged a spring arrangement to absorb volume increases of the material. US-6880578 pertains to a pressure-stable cylinder, comprising a disc and a spring to handle pressure changes in the cylinder.
US-2004/0129325 pertains to a compensation arrangement, to compensate for the volume expansion of a medium, especially for a urea-water mixture, in connection with freezing. A spring-loaded piston which is enclosed by bellows is arranged so that it may be displaced in the event of volume changes in the container.
Among the prior art devices, which have been described briefly above, there are different ways of handling volume expansion, but these often have a complex design which, among other things, entails extra costs. If, for example, rubber is used in the device, there may be limitations in temperature, chemical resistance and ageing which means that the functionality is not as desired.
The objective of the present invention is to achieve an improved device, which is structurally simple and has a better resistance against chemical impact and ageing, and which functions within a broad temperature interval.

Summary of the invention

The above-mentioned objectives are achieved with the invention as defined by the independent patent claim. The preferred embodiments are defined by the dependent patent claims. The invention allows the container, when there is a risk of excessive pressure, to obtain a somewhat larger volume, lowering the pressure and reducing the risk of damaging the container. Thus the risk of a housed medium leaking and causing damage or harm to the environment is also reduced.
The expansion element consists, according to one embodiment, of a metal plate (tinplate) with a double-curved shape. It is placed so that a convex surface faces the medium, the expansion of which should be handled. The shape on the surface is designed to resist normal working pressure for the container, wherein the element is arranged inside a wall, without being buckled outwards (assuming a concave shape). When the liquid expands, e.g. due to freezing, the pressure which the double-curved shape may resist is exceeded and the tinplate changes shape from convex to concave. The volume difference between the convex and the concave shape means that the liquid may expand without damaging the container or the surrounding structure.
When the pressure falls, the expansion element resumes its original convex shape and may again resist a normal working pressure.
Several expansion elements may be used in one and the same container to ensure that the expansion volume is sufficient and/or because the placement of the expansion volume so requires.
The expansion element is a robust and cheap unit which is easy to fit. Since it is manufactured in one piece made of the same material, e.g. metal, this provides advantages in relation to the prior art devices which require e.g. rubber in order to be waterproof, having regard to temperature sensitivity (may tolerate both high and low temperatures), chemical resistance to surrounding media and ageing.
Additionally, it is space-efficient since it coincides with the walls of the container. Further distinctive advantages and features of the invention are set out in the following description of an advantageous example embodiment of the invention.

Brief description of the drawings

Fig. 1 is a schematic cross-sectional view of a container equipped with an expansion element.
Fig. 2 is a schematic cross-sectional view of the container in a first state.
Fig. 3 is a schematic cross-sectional view of the container in a second state.
Figs. 4-6 shows schematic front views of different embodiments of the container
Fig. 7 shows a schematic front view of another embodiment of the container

Detailed description of preferred embodiments of the invention.

In the figures, the same or similar details have consistently been provided with the same reference numerals.
With reference first to Figures 1-3, a first embodiment of the invention will now be described. A container 2 is adapted to contain a liquid or gaseous medium 4, comprising a wall 6 which defines a space for the medium. In the figures, a schematic illustration of the container is displayed, having a rectangular shaped cross-section. The container may have any shape, e.g. rounded shapes, more complex structures and combinations of different shapes.
The container 2 comprises at least one expansion element 8 arranged in the wall 6, being adapted to handle the volume expansion of said medium 4. The wall 6 is preferably manufactured of a relatively form-stable material, e.g. metal or plastic.
The expansion element 8 has a substantially flat design with an extent which substantially coincides with the extent of the wall 6. The expansion element 8 is resilient and is adapted to be placed in one of two states (end positions):

A first state, being the normal state for the expansion element 8, and where the expansion element 8 has a convex three-dimensional shape 10 (see Figures 1 and 2), facing the inside of the container 2. The first state is the state in which the element exists, as long as the medium 4 inside the container 8 has a pressure P which is below a predetermined threshold value P_T. Also, naturally, in the case where there is no medium in the container.

A second state is the stat in which the expansion element 8 has a concave three-dimensional shape 12 (see Figure 3) facing the inside of the container 2. When the medium in the container reaches a pressure P which is equal to or exceeds the threshold value P_T, the expansion element 8 will snap directly from the first state into the second state, and remain in the second state as long as the pressure exceeds the threshold value P_T. When the pressure is below the threshold value P_T, the expansion element 8 will return to the first state with a snap.
An opening 7 is also indicated in the figures, connecting the space defined by the container with the surrounding environment, the opening 7 being e.g. connected to a pipe or a tube for supply and removal of medium in the container.
The threshold value P_T is suitably selected so that it corresponds to a temperature of the medium when it transitions from a liquid to a solid state.
Figure 1 shows the container 2, when there is no medium inside it and the expansion element 8 is in the first state.
Figure 2 shows the container 2, when it is filled with a medium, e.g. a liquid which may enter into and exit from the container via the opening 7, which is indicated with a bidirectional arrow. In this figure, there is normal usage of the container 8 [sic: 2] and the threshold value P_T is selected so that, at the pressure which the medium exhibits at normal usage of the medium, the expansion element 8 will be in the first state.
According to one embodiment, the threshold value P_T is within the interval 5-10 bar.
In Figure 3 there is a pressure P, exceeding P_T, for the medium in the container. This may have been caused by the fact that the container was subjected to cold, and if the medium was liquid it may have frozen in the opening 7, which is marked with an X, resulting in the medium inside the container being prevented from expanding through removal of medium from the container. When the medium expands because of temperature change, the pressure inside the container will increase, and when the pressure amounts to and exceeds the threshold value P_T, the expansion element 8 will transition with a snap to the second state.
As shown in Figures 2 and 3, additional volume will in this case become available for the medium to expand in, as the expansion element 8 has transitioned to the second state. Thus, the risk of the container being damaged when the medium expands is reduced.
Another effect is that one may obtain a clear indication of the pressure inside the container exceeding the threshold value, by the expansion element 8 curving outward. The expansion element may easily be identified by painting, or otherwise arranging a suitable indication on the outside, in a different colour in relation to the container's colour.
According to one embodiment, the expansion element 8 is manufactured of metal, e.g. steel, and preferably consists of a flat, disc-shaped metal plate. As shown in the figures, the expansion element has a shape which is space-efficient and structurally simple, which means that very little space outside the container is required. Other materials may also be used, as long as they meet the requirements of being able to transition into two states, as described above. Examples of materials include different plastics, carbon fibre, etc.
The expansion element 8 is secured in a hole in the wall of the container, in such a way that the container is completely sealed. The attachment is made, for example, with a laser-welded joint, a solder joint, a glued joint or clamps.
Figures 4-6 show different designs of the expansion element 8 arranged at the container 2. As shown in the figures, the expansion element 8 may have a circular shape (see Figure 4) or an elliptical shape (see Figure 5) in the plane for the container's wall, where the element is arranged. The shape may also be rectangular with rounded corners (see Figure 6). Influencing the choice of the shape is the need for the material in the expansion element to be able to handle the forces arising in e.g. corners, when the expansion element transitions from the first state to the second state.
According to one embodiment, the container comprises several expansion elements 8. One example illustrating this embodiment is displayed in Figure 7, where four elements are arranged. The reason for arranging several elements is to be able to handle a larger volume expansion. In the event the container has a rotationally symmetrical shape, e.g. a cylindrical shape, the expansion element may be arranged on its mantle surface as well as on its end surfaces.
In certain embodiments the container may normally only be partly filled with a liquid medium. In these cases, the expansion elements should primarily be arranged in that part of the container, which is filled with medium.
The container may be designed to contain volumes exceeding several litres, but it may also be adapted to contain a volume in the range of less than 10 ml, preferably one or a couple of ml. Depending on the volume changes that are to be handled, different sizes of the expansion element may be used.
According to one embodiment, the container 2 is designed to be comprised as a part of a exhaust purification system for a combustion engine. The container thereby constitutes part of a dosage equipment for urea (e.g. AdBlue®), which is used in combustion engines in vehicles to reduce the amount of nitrogen oxides in the exhaust flow. In such a case, the expansion element ensures that the container does not risk to be damaged, should the contents transition from a liquid to a solid form in connection with a temperature reduction below the freezing point.
In another embodiment, the container constitutes an expansion tank inside a liquid-based cooling system for a combustion engine, wherein similarly there is a risk that the container may be damaged if the coolant freezes into a solid form.
In an additional embodiment, the container consists of a container for flushing fluid, for cleaning the windscreens and headlights in a vehicle, wherein a sufficient amount of anti-freezing additive is not added to the flushing fluid, which in an analogous way risks freezing into ice at low temperatures.
The expansion element is described above as tinplate that directly assumes its two states by a snap-like transition. Obviously this transition may in other embodiments occur successively and more slowly.
The description has largely been made with reference to the fact that the container housed a liquid, which in connection with freezing/thawing has caused a volume increase and a pressure increase connected therewith. Obviously the container may contain another medium, such as a gas, which for some reason is subjected to a pressure increase without any phase transformation occurring. Also in such cases, the expansion element ensures that the pressure may be reduced without the container being damaged by the high pressure, and without the risk of the medium leaking into the environment.

Claims

Container (2), adapted to contain a liquid medium (4) and comprising a wall (6) which defines a space for the medium, the container (2) comprising at least one expansion element (8) arranged in the wall (6), wherein the expansion element (8) is adapted to handle a volume expansion of said medium (4) on a transition from a liquid to a solid state, characterised in that the expansion element (8) has a substantially flat design with an extent substantially coinciding with the extent of the wall (6), and that the expansion element (8) is resilient and adapted to exist in one of two states,
- a first state, which is the normal state for the expansion element (8) and wherein the expansion element (8) has a convex three-dimensional shape (10) facing the inside of the container (2), and which is the state in which the expansion element exists, as long as the medium (4) in the container (8) has a pressure P which is below a predetermined threshold value P_T,

- a second state, where the expansion element (8) has a concave three-dimensional shape (12) facing the inside of the container (2),
wherein, when the medium in the container has a pressure P which amounts to and exceeds the threshold value P_T, the expansion element (8) will transition from the first state to the second state and exist in the second state as long as the pressure amounts to and exceeds the threshold value P_T, and when the pressure is below the threshold value P_T, the expansion element (8) will revert to the first state.
Container (2) according to claim 1, wherein the threshold value P_T is selected so that, at the pressure P, which the medium has in normal usage of the medium in the container (2), the expansion element (8) will be in the first state.
Container (2) according to claim 1 or 2, wherein the threshold value P_T is within the interval 5-10 bar.
Container (2) according to any of the claims 1-3, wherein the expansion element (8) is manufactured of metal and preferably consists of a flat, disc-shaped metal plate.
Container (2) according to any of the claims 1-4, wherein the expansion element (8) has a circular or an elliptical shape.
Container (2) according to any of claims 1-5, wherein the expansion element (8) is fixed in a hole in the wall of the container, in such a way that the container is entirely sealed.
Container (2) according to claim 6, wherein the expansion element (8) is attached with a laser-welded joint, a solder joint, a glued joint, or clamps.
Container (2) according to any of claims 1-7, wherein the container comprises several expansion elements (8).
Container (2) according to any of claims 1-8, wherein the container (2) is adapted to contain a volume in the range of less than 10 ml.
Container (2) according to any of claims 1-9, wherein the container (2) is designed to constitute a part of dosage equipment for urea (e.g. AdBlue®), used to reduce the amount of nitrogen oxides in an exhaust purification system for a combustion engine.