Field of the Invention

The present invention relates to a high-pressure press of the type which comprises a pressure vessel for high-pressure treatment of articles substances.

Background

High-pressure presses of the type stated by way of introduction are, for example, used within the food industry in which high-pressure presses can be used to prolong the shelf life of various food and beverage products.

High-pressure vessels are vessels adapted to withstand a pressure difference of at least 1 ,000 bar, preferably between 1 ,000 and 10,000 bar. To maximise their mechanical strength, high-pressure vessels commonly have a cylindrical shape.

Often liquid pressure mediums are used, preferably water, oil or an emulsion of the two and when pressurizing the pressure vessel, the pressure is increased to the desired treatment pressure by feeding pressure medium into the pressure vessel using pump and pressure intensifier unit. The pump and pressure intensifier unit is connected to interior of the pressure vessel by means of tubes arranged through the first end or second end closure. During the pressure increasing phase, the pressure medium is compressed in the pressure vessel and therefore additional medium has to be fed into the pressure vessel at very high pressures using, in addition to pumps, pressure intensifies. In fact, the pressure medium volume may be compressed during the pressurizing phase. The free-floating closures transfer pressure from the pressure vessel to the frame causing the frame to expand in the longitudinal direction of the cylinder during pressurization. In order to accommodate the expansion during pressurizing and the corresponding shrinking (to the positions of the closures in un-pressurized state) during the de-pressurizing phase, the conduits or tubes connecting the interior of the pressure vessel with the pump and pressure intensifier unit have to be flexible. Furthermore, the first end closure and the second end closure are removable and are opened during loading and un-loading of articles into the pressure vessel. The tubes or conduits have therefore also to be flexible enough to accommodate also the opening and closure of the end closures.

The required flexibility of the connecting tubes put constraints on the dimensions of the tubes. For example, the dimension cannot be too small, which limits the amount of pressure medium per time unit that can be fed into the pressure vessel during the pressure increasing phase. This, in turn, affects the cycle time. If a tube having a larger dimension can be used, it would be possible to shorten the cycle time since it would be possible to reduce the pressure increasing phase by increasing the amount of pressure medium fed into the pressure vessel per time unit, which would be beneficial.

Furthermore, the required flexibility of the connecting tubes put constraints on the length of the tube. In order to achieve the required flexibility, long connecting tubes have to be used. Increased length will result in a pressure drop between connection points and pressure drop leads to increased wear on components.

The pump and pressure intensifier unit produces heat, in particular, the pump produces significant amounts of heat, which may be troublesome since it is often desirable to have a relatively low temperature in the environment surrounding the high-pressure vessels.

Hence, to conclude, there is an interest within the industry to find im- proved high-pressure systems.

Summary of the invention

A main object of the present invention is to provide improved high- pressure systems and methods for such systems in comparison to prior art high-pressure systems.

To that end, the present invention aims at providing high-pressure systems having a reduced treatment cycle time and methods for obtaining reduced cycle time in such systems. Further, the present invention aims at providing high-pressure systems with increased durability and reduced maintenance requirements.

The present invention further aims at providing high-pressure systems with reduced pressure drop between pressure intensifier units and the pres- sure vessel.

Moreover, the present invention further aims at providing high-pressure systems with a reduced heat generation in the area close to the pressure vessel.

These and other objects which will become apparent in the following are achieved by means of a system including an isostatic press and a method for such a system as defined in the accompanied claims.

The invention relates to high-pressure equipment capable of pressure treatment at at least 1 ,000 bar above the atmospheric pressure, and preferably between 1 ,000 and 10,000 bar. The equipment according to the present invention is suitable for high-pressure food preservation, cold isostatic pressing etc.

The invention has been conceived in respect of a high-pressure pressing arrangement comprising a high-pressure vessel made up from a high- pressure cylinder and two coaxial end closures. The pressure vessel is formed by closing end apertures of the cylinder using end closures, which provide a pressure-tight seal against the environment. During operation and when the pressure vessel is pressurized, each end closure will experience an outward axial force, causing them to abut against a common frame which carries axial forces.

The pressure vessel can be installed horizontally. According to an aspect of the present invention, there is provided a system for high-pressure treatment. The system comprises a high-pressure vessel comprising a high- pressure cylinder and coaxial first and second end closures. A first and a second closure manipulator is arranged to open and close a respective end closure. Only one or both end closures may be opened for enabling insertion/removal of the load. According to embodiments of the invention, the cylinder is installed horizontally and both its end closures can be opened. At least one pressure intensifier unit is connected to the pressure vessel via a respective at least one tube extending through the first and/or second end closure via a respective through passage. The pressure intensifier units are configured to increase the pressure inside the pressure vessel by feeding pressure medium into the pressure vessel via the at least one tube during a pressurizing phase. The pressure intensifier unit is arranged to move in a longitudinal direction of the pressure vessel in response to an axial movement of the first end closure and/or second end closure.

According to a further aspect of the present invention, there is provided a method for high-pressure treatment in a system including a high-pressure vessel comprising a high-pressure cylinder and coaxial first and second end closures, first and a second closure manipulator arranged to open and close a respective end closure and at least one pressure intensifier unit connected to the pressure vessel via a respective at least one tube, the at least one tube extending through the first and/or second end closure via a respective through passage in the closure, the method comprising the steps of:

increasing the pressure inside the pressure vessel by feeding pressure medium into the pressure vessel via the at least one tube during a pressurizing phase; and

moving the at least one pressure intensifier unit in a longitudinal direction of the pressure vessel in response to an axial movement of the first end closure and/or second end closure.

The present invention is based on the idea of arranging the pressure intensifier unit or units in close proximity to the pressure vessel and arranging the pressure intensifier unit (-s) to be movable in an axial direction of the pressure vessel in response to movements of the end closures during pressurizing phases and de-pressurizing phases, and also in response to opening and closure of the end closures. Thereby, several advantages can be achieved.

For example, it is possible to reduce the treatment cycle time and, in particular, the pressurizing phase can be shortened. This is due to the fact that by arranging the pressure intensifier unit (-s) to be movable in an axial direction of the pressure vessel, connecting high-pressure tubes between the pressure intensifier unit (-s) and the pressure vessel in which the pressure medium is fed during a pressurizing phase with a large diameter can be used. Such tubes can withstand very high pressures, for example, pressures between 1 ,000 and 10,000 bar. Thereby, it is possible to increase the pressure increasing rate during the pressurizing phase. These tubes are expensive and therefore it is also an advantage that the present invention allows that the pressure intensifier unit (-s) can be located very close to the pressure vessel, for example, as shown in Figs. 2, 3 and 4.

A further advantage of the present invention, is that the pressure drop between the pressure intensifier unit (-s) and the pressure vessel can be limited, which is due to the location of the pressure intensifier unit (-s) close to the pressure vessel.

Yet another advantage of the present invention is improved durability and reduced maintenance needs due to separation of pumps and pressure intensifier unit (-s), which entails to a reduced wear of the pressure intensifi- ers. This also provides the advantage of reduced heat generation in the area around the pressure vessel since the pumps do not need to be located close to the pressure vessel due to the separation between the pumps and pressure intensifier unit (-s).

In certain embodiments of the present invention, a surrounding force- absorbing frame is provided for resisting outward axial movement of the first and second end closures when closed during operation.

In embodiments of the present invention, pre-stressing means is provided around an envelope surface of the pressure vessel so as to provide a radial compressive pre-stress in the pressure vessel wall.

According to embodiments of the present invention, the pressure intensifier unit (-s) is connected to the first and/or second closure manipulator such that the at least one pressure intensifier moves in a longitudinal direction of the pressure vessel in response to an axial movement of the first end clo- sure and/or second end closure.

In embodiments of the present invention, the pressure intensifier unit (- s) is mechanically connected to a closure manipulator via connection means such that the pressure intensifier moves in a longitudinal direction of the pres- sure vessel in response to an axial movement of the first end closure and/or second end closure.

In embodiments of the present invention, each pressure intensifier unit is arranged on a movable carriage. The carriage is mechanically connected to a closure manipulator via connection means such that the carriage moves in a longitudinal direction of the pressure vessel in response to an axial movement of the first end closure and/or second end closure.

In further embodiments of the present invention, the movable carriage is arranged to slide over at least one rail and wherein the carriage is me- chanically connected to a closure manipulator via connection means such that the carriage moves in a longitudinal direction of the pressure vessel in response to an axial movement of the first end closure and/or second end closure.

In embodiments of the present invention, the movable carriage is pro- vided with at least one wheel arranged to roll on a corresponding track and wherein the carriage is mechanically connected to a closure manipulator via connection means such that the carriage moves in a longitudinal direction of the pressure vessel in response to an axial movement of the first end closure and/or second end closure.

In further embodiments of the present invention, a controller unit is configured to instruct a driving unit to move the movable carriage in a longitudinal direction of the pressure vessel in response to an axial movement of the first end closure and/or second end closure.

In further embodiments of the present invention, at least one pump is connected to at least one pressure intensifier unit via a tube in order to feed pressure medium to the at least one pressure intensifier.

In embodiments of the present invention, a first pressure intensifier unit is connected to the pressure vessel via at least one tube, the at least one tube being arranged in a through passage in the first end closure and a sec- ond pressure intensifier unit connected to the pressure vessel via at least one tube, the at least one tube being arranged in a through passage in the second end closure. However, an arbitrary number of pressure intensifier units may be used in the invention. Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a/an/the [element, device, component, means, step, etc]" are to be interpreted openly as referring to at least one instance of the element, device, component, means, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.

Other objectives, features and advantages of the present invention will appear from the following detailed description, the attached dependent claims, and from the appended drawings.

Brief description of the drawings

The above, as well as additional objects, features and advantages of the present invention, will be better understood through the following illustra- tive and non-limiting detailed description of preferred embodiments of the present invention, with reference to the appended drawings, where the same reference numerals will be used for similar elements, wherein:

Fig. 1 is a schematic cross-sectional view of an isostatic press that can be used in systems according to embodiments of the present invention;

Fig. 2 is a schematic view from above of a system according to an embodiment of the present invention;

Fig. 3 is a schematic perspective view of the system shown in Fig. 2;

Fig. 4 is a more detailed schematic perspective view of the system shown in Fig. 2 and 3;

Fig. 5 is a schematic cross-sectional view of an isostatic press used in a system according to an embodiment of the present invention;

Fig. 6 is a schematic view of a system according to an embodiment of the present invention;

Fig. 7 is a schematic side view of a pressure intensifier unit carriage according to an embodiment of the present invention; and

Fig. 8 is a schematic view from above of a system according to an embodiment of the present invention. Detailed description of embodiments

Fig. 1 is a schematic cross-sectional view of an isostatic press 10 that can be used in a system in accordance with at least one embodiment of the invention.

The press 10 comprises a generally cylindrical pressure vessel 12 having an outer envelope surface 14 and an inner surface 16. The inner surface 16 defines a generally cylindrical delimitation of a pressure chamber 18 in which substances are to undergo pressure treatment. The pressure chamber 18 is also delimited by two end closures 20a, 20b.

Substances are introduced into the pressure chamber 18 by removing one or both of the end closures 20a or 20b. Next, the end closure 20a or 20b or both is/are returned into place and a pressure medium, such as water, is supplied from pumps and pressure intensifiers through conduits or tubes (see e.g. Figs. 2 - 5 ) leading into the pressure chamber 18, e.g. via one of the end portions of the isostatic press 10.

In the exemplary embodiment of the pressing arrangement, a liquid pressure medium is used, preferably water, oil or an emulsion of the two.

When the pressure chamber 18 is filled with pressure medium, more pressure medium is introduced in order to increase the pressure to a desired high-pressure state. When the treatment is finished, the pressure chamber 18 is decompressed and the end closure 20a or 20b is removed so that the treated substances can be taken out from the pressure chamber 18, and thereby allowing new substances to be introduced.

In order to assist the pressure vessel 12 in taking up axial loads the press 10 is provided with a surrounding force-absorbing frame 24.

In order to assist the pressure vessel wall 12 in taking up radial loads, the outer envelope surface 14 thereof is provided with a pre-stressing means in the form of a package of wound steel bands 26. The bands 26 are wound tightly, substantially in circles, around the envelope surface 14 so as to pro- vide a radial compressive pre-stress in the pressure vessel wall 12. The band package 26 has a longitudinal extension essentially equal to the length of the pressure chamber 18, i.e. the distance between the end closures 20a, 20b, and is delimited by two end walls 28a, 28b arranged in respective circumfer- ential recesses. As illustrated in the figure, the frame 24 may also be provided with a package of wound steel bands 27.

In Fig. 2 - 8, schematic views of systems according to embodiments of the present invention are shown.

The system 50 comprises a press 10 (for example, of the type shown in Fig. 1 and described above). The end closures 20a, 20b can be opened and closed by means of closure manipulators 52a, 52b in an axial direction (indicated by arrow 40) of the pressure vessel 12, i.e. in a direction of the longitudinal axis of the pressure vessel 12.

The system 50 further comprises at least one pressure intensifier unit

54 including a number of individual pressure intensifier devices 56.

In the illustrated embodiments, the system 50 comprises two pressure intensifier units 54 each including two pressure intensifier devices 56. The pressure intensifier units 54 are adapted to feed pressure medium into the pressure chamber 18 to increase the pressure. According to embodiments of the present invention, the pressure intensifiers 54 feeds pressure medium via tubes 60. Each tube 60 is arranged in a respective lead-through 61 a, 61 b provided in respective closure 20a, 20b.

It should be noted that a system according to the present invention may comprise, for example, one, three or four pressure intensifier units and that each pressure intensifier unit may comprise less than six or more than six pressure intensifier devices.

As shown in Fig. 6, at least one hydraulic pump 62 is connected to the pressure intensifier units 54 by means of tubes 64. The at least one pump 62 is arranged to feed pressure medium to the pressure intensifiers 54 at a pressure of, for example, 100 bar or more via the tubes 64. Since the pumps 62 are separated from the pressure intensifiers 54, they can be located at a distance from the press 10. The relative low pressure (e.g. about 125 bar) of the pressure medium being fed from the pumps 62 to the pressure intensifiers 54 entails that the tubes 64 can be dimensioned with a relatively large diameter compared to the diameter of the tubes 60 (see Fig. 5) connecting the pressure intensifier units 54 with the press 10. Further, this also entails that the tubes 64 connecting the at least one pump 62 to the pressure intensifier units 54 relatively long. In the embodiment of the present invention shown in Fig. 6, two pumps are illustrated but an arbitrary number of pumps may be used.

In embodiments of the present invention, each pressure intensifier unit 54 is arranged on a movable carriage 58 as illustrated in Figs. 2 - 4. In this illustrated embodiment, the movable carriages 58 are arranged to slide back and forth in an axial direction of the pressure vessel 12 thereby moving the respective pressure intensifier unit 54 so as to compensate for axial movements of the end closures 20a, 20b and opening/closing of the closures 20a, 20b. The pressure intensifier units 54 are mechanically connected to the clo- sure manipulators 52a, 52b via rods 66a, 66b, 67a, 67b or other means.

Hence, when the closure manipulators 52a, 52b are operated to open or close a respective closure 20a, 20b, the respective carriage 58 connected to the closure manipulators 52a, 52b will be forced to slide on, for example, rails 59 and move a corresponding distance by means of the connecting rods 66a, 66b, 67a, 67b. When the carriages 58 are moved, the pressure intensifier units 54 will also be moved the same distance.

Furthermore, during the pressurizing phase, when the end closures 20a, 20b moves in an axial, outward direction (seen from the pressure vessel 12), the respective carriage 58 connected to the closure manipulators 52a, 52b will be forced to slide on the rails 59 and move a corresponding distance by means of the connecting rods 66a, 66b, 67a, 67b. When the carriages 58 are moved, the pressure intensifier units 54 will also be moved the same distance. Correspondingly, when the pressure is released and the end closures instead moves in an axial, inward direction (seen from the pressure vessel 12), the respective carriage 58 will be forced to slide on the rails 59 and move a corresponding distance by means of the connecting rods 66a, 66b. When the carriages 58 are moved a certain distance along the rails 59 by the influence of the connecting rods 66a, 66b, respective pressure intensifier unit 54 will hence also move the corresponding distance.

In alternative embodiments of the present invention, the carriages 58' are provided with wheels 68 arranged to roll, for example, in tracks 69 during the movement as schematically illustrated in Fig. 7. There are also other conceivable embodiments, such as having the carriages to move in grooves or on a sliding plate.

In alternative embodiments of the present invention, movement of the carriages 58 are controlled by means of a controller unit 70 (see Fig. 8), which also controls the closure manipulators 52a, 52b. The controller unit 70 thus controls each carriage 58 via a driving unit (including e.g. a motor) 72 to move in order to compensate for expansions/shrinkage of the pressure vessel 12 and/or to compensate for opening/closure of a closure 20a, 20b. For example, the driving unit 72 moves the carriages 58 electrically or hydraulically. The driving unit 72 may also drive the closure manipulators 52a, 52b.

Although the invention has been illustrated and described in detail in the drawings and preceding description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments.

Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that cer- tain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.