Method performed in a press device, press device, and related computer program

Abstract

The method (20) is carried out on a press (1) comprising a pressure vessel (2) and a guideway (3) for guiding a pressure medium out of the pressure vessel (2) to reduce the pressure in the pressure vessel. The guideway (3) comprises a first flow restriction (5), e.g. a valve, comprising a flow restrictor (7), e.g. a valve needle, movable between a closed position and a maximum open position. The opening of the valve is controlled by an actuator (9), which exerts a first force (f1) on the flow restrictor (7) acting against a reaction mechanism (10), such as a spring element, which exerts a third force (f3), while the pressure medium itself exerts a second force (f2) biasing the flow restrictor towards the maximum open position. The actuator (9) is controlled according to a predefined relationship between the second force (f2) and the first force (f1) for a particular third force (f3), such that the pressure is reduced according to a pressure reduction sequence.

Description

[Technical field]

[0001] The present invention relates generally to the field of high pressure technology, and in particular to pressure processing. More specifically, the present invention relates to a method for a press device and a press device. The press device may be suitable for processing at least one article by isostatic pressing, such as cold isostatic pressing (CIP), warm isostatic pressing (WIP) or hot isostatic pressing (HIP), by pressure generated by a pressure medium. [Background technology]

[0002] Articles to be subjected to pressure treatment by isostatic pressing, such as cold isostatic pressing (CIP), warm isostatic pressing (WIP) or hot isostatic pressing (HIP), may be placed in a pressure vessel arranged to hold a pressure medium therein. A treatment cycle may comprise loading the articles into the pressure vessel, closing and sealing the pressure vessel, treating the articles in the pressure vessel, opening the pressure vessel and removing the articles from the pressure vessel. Several articles may be treated simultaneously. A treatment cycle may be divided into several parts or stages. After loading the articles into the pressure vessel, the pressure vessel may then be sealed, followed by introducing a pressure medium (including, for example, water) into the pressure vessel such that the pressure in the pressure vessel is increased to a certain pressure level, which may be called a pressurizing stage, whereby the articles may be exposed to an increased pressure for a selected period of time. A treatment cycle may comprise a heating stage, where the pressure medium is heated, for example, to achieve its desired or required temperature. The heating step may be performed simultaneously with the pressing step, before the pressing step, or after the pressing step. Exposing the article to the elevated pressure in the pressure vessel for a selected period of time may be referred to as the pressing step of the processing cycle. After the pressing step and before opening the pressure vessel to remove the article, the pressure in the pressure vessel is generally reduced to a sufficiently low level by withdrawing the pressure medium from the pressure vessel. This may be referred to as a pressure reduction or pressure relief step. The processing cycle may further comprise a cooling step. However, depending on the type of isostatic pressing used (e.g., whether the isostatic press is configured to perform CIP, WIP, or HIP), a cooling step may not be necessary. In some cases or applications, it may be desirable to be able to reduce the pressure in the pressure vessel during pressure reduction at different pressure decrease rates. Summary of the Invention

[0003] In some cases or applications it may be desirable or even necessary to be able to control the rate at which the pressure in the pressure vessel is reduced during the pressure reduction phase with different precision at different stages during the pressure reduction phase. For example, the inventors have found that during the pressure reduction phase and after the pressure in the pressure vessel has been reduced to some extent, it may be desirable to be able to control the rate at which the pressure in the pressure vessel is further reduced with relatively high precision, whereas prior to that stage less fine control of the rate at which the pressure in the pressure vessel is reduced may be sufficient.

[0004] In view of the above, it is a concern of the present invention to provide a means for facilitating or enabling relatively precise control of the rate at which pressure is reduced within the pressure vessel of a press apparatus.

[0005] A further concern of the present invention is to provide means for facilitating or enabling relatively precise control of the rate at which pressure is reduced within the pressure vessel of the press during selected portions of the pressure reduction phase.

[0006] In order to address at least one of these and other concerns, a method for a pressing device and a pressing device are provided according to the independent claims. Preferred embodiments are defined by the dependent claims.

[0007] According to a first aspect of the invention, a method for a pressing apparatus is provided. The pressing apparatus comprises a pressure vessel arranged to hold pressure medium therein. The pressing apparatus comprises a guideway configured to connect the pressure vessel with a pressure medium sink and to withdraw pressure medium from the pressure vessel by directing the pressure medium from the pressure vessel towards the pressure medium sink, thereby reducing the pressure in the pressure vessel. The guideway comprises at least a first flow restriction configured to control the extent to which pressure medium flow is permitted to pass through the first flow restriction, thereby controlling the extent to which pressure medium flow in the guideway is impeded or blocked. The first flow restriction comprises a flow restrictor movable between at least a closed position and a maximum open position. When the flow restrictor is moved from the closed position, an opening is created, the size of the opening increasing the closer the flow restrictor is to the maximum open position. The extent to which pressure medium flow is permitted to pass through the first flow restriction, if any, depends on the size of the opening. During controlled withdrawal of pressure medium from the pressure vessel, the size of the opening is determined by at least (i) a first force that acts on the flow restriction to urge it either toward a maximum open position or toward a closed position, which is controllably and selectively generated by the actuator, (ii) a second force that acts on the flow restriction to urge it toward a maximum open position, which is generated by the pressure of the pressure medium in the guideway, and (iii) a third force that acts on the flow restriction to urge it toward a closed position if the first force acts on the flow restriction to urge it toward a maximum open position, or to urge it toward a maximum open position if the first force acts on the flow restriction to urge it toward a closed position, the third force being generated by a counter force mechanism. For example, during controlled withdrawal of pressure medium from the pressure vessel, there may be a predetermined relationship between the second force and the first force for a particular third force.

[0008] The size of the opening may be determined at least by the first, second and third forces as described above during controlled withdrawal of pressure medium from the pressure vessel, which may be defined as withdrawal of pressure medium from the pressure vessel through the first flow restriction when the flow restrictor is away from a closed position but not in a fully open or maximum open position, where for a particular third force there is a predetermined relationship between the second and first forces. Such controlled withdrawal of pressure medium from the pressure vessel may alternatively be referred to as hindered withdrawal of pressure medium from the pressure vessel.

[0009] The predetermined relationship may be such that the combination of the first force and the second force is in equilibrium with a third force while the flow restrictor is away from the closed position but not in a fully open or maximum open position. By the combination of the first force and the second force being in equilibrium with a third force it may be meant that there is no net force or only a negligible net force acting on the flow restrictor, such that the flow restrictor is in force equilibrium or very close to force equilibrium. Thus, for each value of a plurality or set of values ​​of the first force, for a particular third force there may be a corresponding value of the second force resulting from that particular value of the first force generated by the actuator, at which value the flow restrictor is at rest or substantially at rest and away from the closed position but not in a fully open or maximum open position.

[0010] The method according to a first aspect of the invention comprises determining a plurality of values ​​of the second force such that corresponding values ​​of the pressure of the pressure medium in the taxiway correspond to a pressure reduction sequence for reducing the pressure of the pressure medium in the taxiway over time. A plurality of values ​​of the first force are determined that correspond to respective values ​​of the plurality of values ​​of the second force based on a predetermined relationship.

[0011] A method according to a first aspect of the invention comprises controlling an actuator to generate multiple values ​​of a first force such that, during at least a portion of the time that pressure medium is controllably withdrawn from the pressure vessel, pressure of the pressure medium in the guideway is reduced over time in accordance with a pressure reduction sequence.

[0012] The pressing device may be suitable for the treatment of at least one article by isostatic pressing, such as cold isostatic pressing (CIP), warm isostatic pressing (WIP) or hot isostatic pressing (HIP), by pressure generated by a pressure medium. The at least one article may comprise, for example, a food and / or beverage or foodstuff, or one or more pieces of metal, ceramic, composite or plastic components. The pressure medium may in principle comprise or consist of any suitable fluid. For example, for CIP and WIP, the pressure medium may comprise or consist of, for example, water or oil and / or any other suitable liquid. For example, for HIP, the pressure medium may comprise or consist of, for example, a gas, such as an inert gas, such as argon gas.

[0013] As mentioned above, controlling the actuator is performed during at least a portion of the time that the pressure medium is being withdrawn from the pressure vessel. At least a portion of the time that the pressure medium is being withdrawn from the pressure vessel may be defined as the time period after the pressure in the pressure vessel - and thus the pressure of the pressure medium in the induction path - is reduced below a certain pressure level. The pressure in the pressure vessel may be proportional to the pressure medium in the induction path. Thus, controlling the actuator may not be performed at the beginning of the pressure reduction phase (i.e., at the beginning of the withdrawal of the pressure medium from the pressure vessel), but only at a later stage during the pressure reduction phase. The point in time during the pressure reduction phase at which controlling the actuator begins to be performed or should begin may depend on at least one of the length and / or the specific configuration or arrangement of the induction path between the pressure vessel and the first flow restriction, and the pressure operating level(s) at which the first flow restriction may operate. For example, the induction path between the pressure vessel and the first flow restriction may have dimensions, a serpentine shape, and / or multiple bends that vary along the induction path, which may increase the flow resistance for the pressure medium being induced from the pressure vessel towards the pressure medium sink through the induction path.

[0014] A second force acting on the flow restriction to bias the flow restriction toward the maximum open position may be generated by a pressure of the pressure medium upstream of the first flow restriction and in the guideway at the first flow restriction. The pressure in the pressure vessel may be proportional to the pressure medium upstream of the first flow restriction and in the guideway at the first flow restriction.

[0015] As mentioned above, for a particular third force generated by the counterforce mechanism during controlled withdrawal of pressure medium from the pressure vessel, there is a predefined relationship between the second force and the first force. The third force may be constant or substantially constant. The third force may be set during manufacture of the first flow restriction, for example, by selection of a particular type of counterforce mechanism. Thus, the third force may be different for different types of first flow restriction, but may be constant or substantially constant otherwise. The counterforce mechanism may comprise, for example, a spring element that may be biased to generate a third force acting on the flow restriction to bias the flow restriction towards a closed position or towards a maximum open position. In this case, the third force may be based on a spring constant of the spring element. The counterforce mechanism may comprise, for example, a spring or a gas spring (e.g., an air spring), which may be controllable.

[0016] The predetermined relationship between the second force and the first force for a particular third force may involve that for a particular third force, there is a plurality or set of values ​​of the first force, or a range of values ​​of the first force, that results in a certain plurality of respective values ​​of the second force, or a certain set of respective values ​​of the second force, or a certain range of respective values ​​of the second force. Thus, according to the predetermined relationship, for each value of the plurality or set of values ​​of the first force, there may be a corresponding value of the second force that results from that particular value of the first force generated by the actuator.

[0017] As described above, a plurality of values ​​of the second force are determined such that corresponding values ​​of the pressure of the pressure medium in the taxiway correspond to a pressure reduction sequence for reducing the pressure of the pressure medium in the taxiway over time based on the predetermined relationship. Determining the plurality of values ​​of the second force may involve selecting the second force values ​​from among a plurality of respective values ​​of the second force, or a particular set of respective values ​​of the second force, or a particular range of respective values ​​of the second force, as described above, to form a sequence of second force values ​​with which corresponding values ​​of the pressure of the pressure medium in the taxiway decrease monotonically. Such monotonically decreasing values ​​of the pressure of the pressure medium in the taxiway may form a pressure reduction sequence.

[0018] The predetermined relationship may be established or determined, for example, by a set of measurements of the second force value resulting from different values ​​of the first force generated by the actuator for a particular third force generated by the reaction mechanism, which measurements may have been performed prior to the above-mentioned steps of the method according to the first aspect of the invention, for example during the controlled withdrawal of the pressure medium from the pressure vessel. The measurement of the second force value may be performed, for example, by measuring the pressure of the pressure medium in the guideway. Thus, the second force value is not necessarily measured directly, but may be measured indirectly, for example, by measuring the pressure of the pressure medium in the guideway. The measurement of the pressure of the pressure medium in the guideway may be performed, for example, by a pressure sensor known in the art.

[0019] As described above, the first force acting on the flow restrictor to bias the flow restrictor toward the maximum open position or toward the closed position is controllably and selectively generated by the actuator. The flow restrictor may be referred to as an adjustment element of the first flow restrictor. The first flow restrictor may comprise at least one valve, such as at least one seat valve. The first flow restrictor may comprise at least one needle valve. If the first flow restrictor comprises a valve, the flow restrictor may be referred to as an adjustment element of the valve. For example, if the first flow restrictor comprises a needle valve, the flow restrictor may comprise or be constituted by a needle-shaped plunger of the needle valve. The actuator may comprise, for example, a membrane actuator and a proportional pressure regulator, which may be configured to act on the membrane actuator such that the membrane actuator generates the first force. The actuator may be configured such that the first force generated by the actuator may be changed in steps or continuously.

[0020] By the first force controllably and selectively generated by the actuator and the predefined relationship between the second force and the first force for a particular third force, a very fine control of the reduction of the pressure of the pressure medium in the guideway and therefore of the pressure vessel can be facilitated or even made possible. The precision of the control of the reduction of the pressure of the pressure medium in the guideway and therefore of the pressure vessel can in principle only be limited by the predefined relationship between the second force and the first force for a particular third force. As indicated above, the predefined relationship may involve the existence of a plurality or set of values ​​of the first force, or a range of values ​​of the first force, which results in a certain plurality of respective values ​​of the second force, or a certain set of respective values ​​of the second force, or a certain range of respective values ​​of the second force. If the predetermined relationship is (pre)determined such that a relatively large number of corresponding values ​​of the second force are known for different values ​​of the first force (interpolation between the different values ​​may be used), the pressure reduction sequence may include a relatively large number of values, thereby facilitating or enabling fine control of the reduction of the pressure of the pressure medium in the guideway - and thus the pressure in the pressure vessel - by controlling the actuator to generate multiple values ​​of the first force corresponding to multiple values ​​of the second force such that the pressure of the pressure medium in the guideway is reduced over time according to the pressure reduction sequence. In particular, this may facilitate or enable high precision in controlling the reduction rate of the pressure of the pressure medium in the guideway - and thus the pressure in the pressure vessel. Furthermore, due to the predetermined relationship, such control may be achieved without the need for, or only with a very limited need for, corrective feedback during control, for example based on measurements of the pressure in the pressure vessel. However, although not necessary, such corrective feedback may be used during control.

[0021] As described above, the size of the opening of the first flow restriction is determined by at least a first force acting on the flow restriction body to urge it either toward the maximum open position or toward the closed position, which is controllably and selectively generated by the actuator, a second force acting on the flow restriction body to urge it toward the maximum open position, which is generated by the pressure of the pressure medium in the guideway, and a third force acting on the flow restriction body to urge it toward the closed position if the first force acts on the flow restriction body to urge it toward the maximum open position, or to urge it toward the maximum open position if the first force acts on the flow restriction body to urge it toward the closed position. Thus, the first flow restriction may be either a normally closed flow restriction, if the actuator is configured to controllably and selectively generate a first force acting on the flow restriction body to urge it toward a maximum open position, and a third force may act on the flow restriction body to urge it toward a closed position, or a normally open flow restriction, if the actuator is configured to controllably and selectively generate a first force acting on the flow restriction body to urge it toward a closed position, and a third force may act on the flow restriction body to urge it toward a maximum open position.

[0022] The actuator and / or the counter force mechanism may be considered as part(s) of the first flow restriction. Thus, the first flow restriction may comprise the actuator and / or the counter force mechanism.

[0023] As mentioned above, the predetermined relationship may be that the combination of the first force and the second force is in equilibrium with the third force while the flow restrictor is away from the closed position but not in the fully open or maximum open position. By the combination of the first force and the second force being in equilibrium with the third force it may be meant that there is no net force or only a very small net force acting on the flow restrictor, so that the flow restrictor is in force equilibrium or very close to force equilibrium. Thus, for each value of a plurality or set of values ​​of the first force, for a particular third force there may be a corresponding value of the second force resulting from that particular value of the first force generated by the actuator, at which value the flow restrictor is at rest or substantially at rest and away from the closed position but not in the fully open or maximum open position.

[0024] The induction path may include a second flow restriction. The second flow restriction may be configured to control the extent to which pressure medium flow in the induction path is impeded or blocked by controlling the extent to which pressure medium flow is permitted to pass through the second flow restriction. The second flow restriction may be located upstream of the first flow restriction (e.g., the second flow restriction may be located along the induction path closer to the pressure vessel than the first flow restriction). Prior to at least a portion of the time, the second flow restriction may be controlled to not impede or block pressure medium flow through the second flow restriction, thereby allowing pressure medium to be withdrawn from the pressure vessel by being guided from the pressure vessel through the induction path towards a pressure medium sink.

[0025] The second flow restriction may be configured to either impede or obstruct the pressure medium flow or not impede or obstruct the pressure medium flow. In other words, the second flow restriction may be configured to be either "off" not impede or obstruct the pressure medium flow at all, or "on" impede or obstruct the pressure medium flow. The second flow restriction may, for example, comprise at least one valve.

[0026] The withdrawal of pressure medium from the pressure vessel may be for reducing the pressure in the pressure vessel from a high pressure level towards a low pressure level. The second flow restriction may be configured to be operable at one or more pressure levels, including at least the high pressure level. The first flow restriction may be configured to be operable at one or more pressure levels, including at least an intermediate pressure level between the high pressure level and the low pressure level. Controlling the actuator may be performed after the pressure in the pressure vessel has been reduced such that the pressure in the pressure vessel is equal to or lower than the intermediate pressure level. Controlling the actuator may be performed while the second flow restriction continues to not impede or hinder pressure medium flow.

[0027] The one or more pressure operating levels at which the second flow restriction may be operable may be, for example, up to 16000 bar, up to 10000 bar, up to 8000 bar, or up to 6000 bar.

[0028] The one or more pressure operating levels at which the first flow restriction may be operable may for example be below 800 bar, or below 400 bar. Thus, the intermediate pressure level may be, for example, 800 bar or 400 bar.

[0029] The pressing device may optionally include one or more additional flow restriction portions, each of which may be included in the induction path. Any of such one or more additional flow restriction portions may be located downstream of the first flow restriction portion (i.e., further away from the pressure vessel along the induction path than the first flow restriction portion), or upstream of the first flow restriction portion (i.e., closer to the pressure vessel along the induction path than the first flow restriction portion), and optionally between the first flow restriction portion and the second flow restriction portion, or in parallel with the first flow restriction portion. Each or any of such one or more additional flow restriction portions may be located similarly or identically to the first flow restriction portion, and may thus be configured to control the degree to which the pressure medium flow in the induction path is impeded or blocked by controlling the degree to which the pressure medium flow is allowed to pass through the additional flow restriction portion, and the additional flow restriction portion may include a flow restrictor movable between at least a closed position and a maximum open position, as for the first flow restriction portion described herein. For each or any of such one or more additional flow restriction portions, an actuator and / or a counter force mechanism may be associated similarly or in the same manner as for the first flow restriction portion described herein. The associated actuator and / or counter force mechanism may be considered as part(s) of the additional flow restriction, and thus the additional flow restriction may comprise an associated actuator and / or counter force mechanism. For each or any such one or more additional flow restriction, the associated actuator may be controlled similarly or in the same manner as controlling the actuator associated with or included in the first flow restriction described herein.

[0030] The first flow restriction and each additional flow restriction (if any) may be configured to have different pressure operating levels at which they are operable. For example, the first flow restriction may be operable at one or more pressure levels between 0 bar and 800 bar, and the additional flow restriction, which may be located downstream of the first flow restriction, may be operable at one or more pressure levels between 0 bar and 400 bar. Such a configuration may further facilitate high accuracy in controlling the rate of reduction of the pressure of the pressure medium in the induction path, and thus the pressure in the pressure vessel, particularly over a relatively wide range of pressures of the pressure medium in the pressure vessel.

[0031] According to a second aspect of the present invention, a pressing device is provided. The pressing device comprises a pressure vessel arranged to hold pressure medium therein. The pressing device comprises a guideway configured to connect the pressure vessel with a pressure medium sink and to withdraw pressure medium from the pressure vessel by directing the pressure medium from the pressure vessel towards the pressure medium sink, thereby reducing the pressure in the pressure vessel. The pressing device comprises at least a first flow restriction included in the guideway and configured to control the extent to which the pressure medium flow in the guideway is impeded or blocked by controlling the extent to which the pressure medium flow is allowed to pass through the first flow restriction. The first flow restriction comprises a flow restrictor movable between at least a closed position and a maximum open position, where an opening is created when the flow restrictor is moved from the closed position, the size of the opening increasing the closer the flow restrictor is to the maximum open position. The extent to which the pressure medium flow is allowed to pass through the first flow restriction, if any, depends on the size of the opening. During the controlled withdrawal of pressure medium from the pressure vessel, the size of the opening is determined by at least (i) a first force acting on the flow restriction to urge it either towards a maximum open position or towards a closed position, which is controllably and selectively generated by an actuator, (ii) a second force acting on the flow restriction to urge it towards a maximum open position, which is generated by the pressure of the pressure medium in the guideway, and (iii) a third force acting on the flow restriction to urge it towards a closed position if the first force acts on the flow restriction to urge it towards a maximum open position, or to urge it towards a maximum open position if the first force acts on the flow restriction to urge it towards a closed position, the third force being generated by a counterforce mechanism. During the controlled withdrawal of pressure medium from the pressure vessel, for a particular third force, there may be a predetermined relationship between the second force and the first force. The pressing device comprises at least one control and / or processing unit.The at least one control and / or processing unit is configured to determine a plurality of values ​​of the second force such that corresponding values ​​of the pressure of the pressure medium in the guideway correspond to a pressure reduction sequence for reducing the pressure of the pressure medium in the guideway over time, and to determine a plurality of values ​​of the first force corresponding to respective values ​​of the plurality of values ​​of the second force based on a predetermined relationship. The at least one control and / or processing unit is configured to control the actuator to generate the plurality of values ​​of the first force such that the pressure of the pressure medium in the guideway is reduced over time in accordance with the pressure reduction sequence during at least a portion of the time that the pressure medium is controllably withdrawn from the pressure vessel.

[0032] The at least one control and / or processing unit may comprise a processing unit and a control unit, the processing unit may be configured to perform the determination of a plurality of values ​​of the second force and the control unit may be configured to perform controlling the actuator.

[0033] The at least one control and / or processing unit may, for example, include or be configured by one or more of any suitable central processing unit (CPU), microcontroller, programmable logic controller (PLC), digital signal processor (DSP), application specific integrated circuit (ASIC), field programmable gate array (FPGA), etc., or any combination thereof. The at least one control and / or processing unit may optionally be capable of executing software instructions stored, for example, in a computer program product in the form of a memory. The memory may, for example, be any combination of read-write memory (RAM) and read-only memory (ROM). The memory may comprise a persistent storage device, which may, for example, be a magnetic memory, an optical memory, a solid-state memory, or a remotely mounted memory, or any combination thereof.

[0034] According to a third aspect of the invention there is provided a computer program comprising instructions which, when executed by one or more processors comprised in at least one control and / or processing unit, cause the at least one control and / or processing unit to perform a method according to the first aspect of the invention.

[0035] According to a fourth aspect of the invention there is provided a processor readable medium having a computer program loaded thereon, the computer program comprising instructions which, when executed by one or more processors comprised in at least one control and / or processing unit, cause the at least one control and / or processing unit to perform a method according to the first aspect of the invention.

[0036] Each or any of the one or more processors may comprise, for example, a CPU, microcontroller, PLC, DSP, ASIC, FPGA, etc., or any combination thereof. The processor readable medium may include, for example, a digital versatile disk (DVD) or a floppy disk, or any other suitable type of processor readable means or processor readable (digital) medium, such as, for example, a memory such as, for example, but not limited to, non-volatile memory, a hard disk drive, a compact disk (CD), Flash memory, magnetic tape, a universal serial bus (USB) memory device, a Zip drive, etc.

[0037] Further objects and advantages of the present invention are described below by way of exemplary embodiments. It should be noted that the present invention relates to all possible combinations of the features described in the claims. Further features and advantages of the present invention will become apparent upon review of the appended claims and the description herein. Those skilled in the art will understand that different features of the present invention can be combined to create embodiments other than those described herein.

[0038] Exemplary embodiments of the invention are described below with reference to the accompanying drawings. [Brief description of the drawings]

[0039] [Figure 1] FIG. 1 is a schematic diagram of a press device according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic diagram of a pressing device according to one embodiment of the present invention. [Diagram 3] FIG. 3 is a schematic diagram of a first flow restriction according to one embodiment of the present invention. [Figure 4] FIG. 4 is a schematic graph illustrating the principle of an embodiment of the present invention. [Diagram 5] FIG. 5 is a schematic flow chart illustrating a method according to an embodiment of the present invention. [Figure 6] FIG. 6 is a schematic flow chart illustrating a method according to an embodiment of the present invention. [Figure 7] FIG. 7 is a schematic diagram of a press device according to one embodiment of the present invention. [Figure 8] FIG. 8 is a schematic diagram of a pressing device according to one embodiment of the present invention. [Figure 9] FIG. 9 is a schematic diagram of a pressing device according to one embodiment of the present invention. [Figure 10] FIG. 10 is a schematic diagram of a first flow restriction according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] All drawings are schematic, not necessarily to scale, and generally show only those parts necessary to clarify an embodiment of the invention, where other parts may be omitted or merely suggested.

[0041] The present invention will now be described with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. However, the present invention may be embodied in many different forms and should not be construed as being limited to the embodiments of the invention set forth herein, but rather, these embodiments are provided as examples so that this disclosure will convey the scope of the invention to those skilled in the art.

[0042] 1 is a schematic diagram of a pressing apparatus 1 according to one embodiment of the present invention. It should be noted that all illustrated components of the pressing apparatus 1 are only shown very diagrammatically in FIG.

[0043] The pressing apparatus 1 comprises a pressure vessel 2 arranged to hold a pressure medium therein. The pressure vessel 2 may for example be cylindrical in shape. The pressing apparatus 1 may be suitable for the treatment of at least one article (not shown in FIG. 1 ) by pressure generated by the pressure medium, for example by isostatic pressing, such as cold isostatic pressing (CIP), warm isostatic pressing (WIP) or hot isostatic pressing (HIP). The at least one article may for example comprise a food and / or beverage or foodstuff, or one or more pieces of metal, ceramic, composite or plastic components. The pressure medium may in principle comprise or be constituted by any suitable fluid. For example, for CIP and WIP, the pressure medium may comprise or be constituted by, for example, water or oil and / or any other suitable liquid. For example, for HIP, the pressure medium may comprise or be constituted by, for example, a gas, for example an inert gas such as argon gas.

[0044] The processing cycle may comprise loading the item(s) into the pressure vessel 2, closing and sealing the pressure vessel 2, processing the items in the pressure vessel 2, opening the pressure vessel 2, and removing the items from the pressure vessel 2. The pressure vessel 2 may have one or more closures (not shown in FIG. 1 ) that may be opened and closed to place the item(s) into the pressure vessel 2 prior to processing of the item(s) and to remove the item(s) from the pressure vessel 2 after processing is completed. For example, if the pressure vessel 2 is cylindrical in shape, an end closure may be located at one or each end of the pressure vessel 2. The press apparatus 1 may comprise a loading compartment (not shown in FIG. 1 ) in which the item(s) are placed. For example, the loading compartment, which may comprise a loading basket, may be removably positioned within the pressure vessel 2 such that it may be placed within and subsequently removed from the pressure vessel 2.

[0045] The treatment cycle may be divided into several parts or stages. After loading the article into the pressure vessel 2, the latter may then be closed and sealed, followed by introduction of a pressure medium into the pressure vessel such that the pressure in the pressure vessel 2 is increased to a desired pressure level, which may be called the pressurization stage. Means for introducing a pressure medium into the pressure vessel 2 are known per se in the art and are not illustrated in FIG. 1. The pressure in the pressure vessel 2 may be maintained at or near a desired pressure level for a selected period of time. Thereby, the article may be exposed to an elevated pressure for a selected period of time. The introduction of the pressure medium into the pressure vessel 2 and the exposure of the article to an elevated pressure for a selected period of time may be called the pressing stage. The treatment cycle may comprise a heating stage, in which the pressure medium is heated, for example, to achieve its desired or required temperature. The heating stage may be carried out simultaneously with the pressing stage, before the pressing stage or after the pressing stage.

[0046] After the pressing stage and before opening the pressure vessel to remove the articles, the pressure in the pressure vessel 2 should be reduced to a sufficiently low level by withdrawing the pressure medium from the pressure vessel 2. This may be called a pressure reduction stage. To that end, the pressing device 1 comprises a guideway 3, which connects the pressure vessel 2 with a pressure medium sink 4 and is configured to withdraw the pressure medium from the pressure vessel 2 by directing the pressure medium from the pressure vessel 2 towards the pressure medium sink 4, thereby reducing the pressure in the pressure vessel 2. The guideway 3 may be defined, for example, by the interior of one or more pipes, tubes or conduits which may fluidly couple the pressure vessel 2 with the pressure medium sink 4. Thus, the guideway 3 may be implemented or realised, for example, by one or more pipes, tubes or conduits which may fluidly couple the pressure vessel 2 with the pressure medium sink 4.

[0047] The processing cycle may further include a cooling step, however, depending on the type of isostatic pressing used (e.g., whether the isostatic press is configured to perform CIP, WIP, or HIP), a cooling step may not be necessary.

[0048] The pressure medium sink 4 may for example comprise a pressure medium reservoir, which may be configured to hold the pressure medium and enable reuse of the pressure medium in the pressure vessel 2. The pressure medium sink 4 may alternatively - at least in case the pressure medium does not contain harmful substances, for example in case the pressure medium comprises pure or substantially pure water - comprise a drain, which may be coupled to a sewer line under the building in which the press apparatus 1 is installed. It is to be understood, however, that the pressure medium sink 4 may in principle comprise any body, element, component, etc., which is capable of at least temporarily storing the pressure medium and / or placing the pressure medium.

[0049] The pressing device 1 comprises a first flow restriction 5 which is included in the guideway 3 and which is configured to control the extent to which the pressure medium flow is obstructed or impeded in the guideway 3 by controlling the extent to which the pressure medium flow is allowed to pass through the first flow restriction 5. The first flow restriction 5 may comprise at least one valve, such as for example at least one seat valve. The first flow restriction 5 may for example comprise or be constituted by at least one needle valve.

[0050] The guideway 3 may be configured to provide a constant flow resistance to the pressure medium guided from the pressure vessel 2 towards the pressure medium sink 4 when the first flow restriction 5 is kept fully "open" while the pressure medium is being withdrawn from the pressure vessel 2, i.e. when the first flow restriction 5 does not obstruct or impede the pressure medium flow at all. As an alternative or in addition to the guideway 3 being so configured (e.g. by its structure or design), the guideway 3 may be provided with any component, element, unit, etc. that provides such a flow resistance. A constant flow resistance may be desirable or even necessary to obtain a certain pressure drop over the length of the guideway 3 and to ensure that one or more pressure levels at which different components (e.g. the first flow restriction) are operable are not exceeded, in order to ensure that the wear of the components in the press 1 exposed to the flow of the pressure medium does not become too high due to cavitation that may occur in the pressure medium or flow at a combination of a relatively low pressure medium flow rate and a relatively high pressure medium flow rate.

[0051] According to the embodiment of the invention shown in FIG. 1, the press device 1 comprises a second flow restriction 6. Like the first flow restriction 5, the second flow restriction 6 is also included in the guideway 3. Also like the first flow restriction 5, the second flow restriction 6 is configured to control the degree to which the pressure medium flow is blocked or impeded in the guideway 3 by controlling the degree to which the pressure medium flow is allowed to pass through the second flow restriction 6. As shown in FIG. 1, the second flow restriction 6 is located upstream of the first flow restriction 5 (i.e., closer to the pressure vessel 2 along the guideway 3). The second flow restriction 6 may comprise, for example, at least one valve. The second flow restriction 6 may be configured to either block or impede the pressure medium flow, or not block or not impede the pressure medium flow. In other words, the second flow restriction 6 may be configured to be either "off" which does not block or impede the pressure medium flow at all, or "on" which impedes or impedes the pressure medium flow. The second flow restriction 6 may be in a normally off or open state. The second flow restriction 6 may be, for example, a normally open valve.

[0052] The taxiway 3 may be configured, for example by constructing or designing it in a special way, to provide a constant flow resistance to the pressure medium guided from the pressure vessel 2 towards the pressure medium sink 4 when the first flow restriction 5 is kept fully "open" while the pressure medium is withdrawn from the pressure vessel 2. For example, the taxiway 3 may be configured to have a constant cross-sectional area perpendicular to the longitudinal direction of the taxiway 3, and / or the taxiway 3 may be constructed, for example, such that it is not straight, but has multiple bends along the longitudinal direction of the taxiway 3 over a certain length of the taxiway 3, or at least viewed from a certain direction, meanders along the longitudinal direction of the taxiway 3 over a certain length of the taxiway 3. At least a part of the taxiway 3 between the second flow restriction 6 and the first flow restriction 5 may be constructed or designed in this way. As shown in FIG. 1, the taxiway 3 may have at least two bends between the second flow restriction 6 and the first flow restriction 5. FIG. 2 shows the case where the taxiway 3 meanders between the second flow restriction 6 and the first flow restriction 5. Except for the meandering of the guideway 3 between the second flow restriction 6 and the first flow restriction 5, the pressing apparatus 1 shown in Figure 2 is the same as the pressing apparatus 1 shown in Figure 1. Such meandering may be implemented in the guideway(s) of any other disclosed embodiment of the invention, such as, for example, the guideway(s) of any of the illustrated embodiments of the invention in Figures 7-9 described below.

[0053] 3 is a schematic diagram of a first flow restriction 5 according to one embodiment of the present invention. It should be noted that all illustrated components of the first flow restriction 5 are only shown very diagrammatically in FIG.

[0054] The first flow restriction 5 comprises a flow restrictor 7 which is movable at least between a closed position and a maximum open position. According to the embodiment shown in Fig. 3, the flow restrictor 7 is movable upwards and downwards in Fig. 3. The part of the guideway 3 which is illustrated in Figs. 1 and 2 is illustrated in Fig. 3. The part of the guideway 3 which is in the lower part of Fig. 3 is at the inlet of the first flow restriction 5 (i.e. towards the second flow restriction 6 in Figs. 1 and 2) and the part of the guideway 3 which is in the right part of Fig. 3 is at the outlet of the first flow restriction 5 (i.e. towards the pressure medium sink 4 in Figs. 1 and 2).

[0055] When the flow restrictor 7 is moved from the closed position, an opening 8 is created, the size of the opening 8 increasing the closer the flow restrictor 7 is to the maximum open position. The extent to which pressure medium flow is permitted through the first flow restriction 5, if any, depends on the size of the opening 8. According to the embodiment of the invention shown in Figure 3, the closed position of the flow restrictor 7 is reached by the flow restrictor 7 moving downwards in Figure 3 and the maximum open position of the flow restrictor 7 is reached by the flow restrictor 7 moving upwards in Figure 3.

[0056] According to the embodiment of the invention shown in Figure 3, the first flow restriction 5 comprises an actuator 9 and a counter force mechanism 10, both of which are shown very diagrammatically in Figure 3. The actuator 9 is configured to controllably and selectively generate a first force acting on the flow restrictor 7 to urge the flow restrictor 7 either towards a maximum open position or towards a closed position.

[0057] During controlled withdrawal of pressure medium from the pressure vessel 2, the size of the opening 8 is varied by at least (i) a first force f1, which is controllably and selectively generated by the actuator 9, acting on the flow restrictor 7 to urge the flow restrictor 7 either towards the maximum open position or towards the closed position, and (ii) a pressure of the pressure medium in the guideway 3 (e.g., the pressure of the pressure medium in the guideway 3 upstream of the first flow restriction 5 and at the first flow restriction 5) to urge the flow restrictor 7 towards the maximum open position. and (iii) a third force f3 acting on the flow restriction body 7 to urge the flow restriction body 7 toward the closed position when the first force f1 acts on the flow restriction body 7 to urge the flow restriction body 7 toward the maximum open position, or to urge the flow restriction body 7 toward the maximum open position when the first force f1 acts on the flow restriction body 7 to urge the flow restriction body 7 toward the closed position, the third force f3 being generated by the reaction force mechanism 10.

[0058] Thus, the first flow restriction portion 5 can be either - normally closed when the actuator 9 is configured to controllably and selectively generate a first force acting on the flow restriction body 7 to urge it towards the maximum open position, and a third force f3 acts on the flow restriction body 7 to urge it towards the closed position, or - normally open when the actuator 9 is configured to controllably and selectively generate a first force acting on the flow restriction body 7 to urge it towards the closed position, and a third force f3 acts on the flow restriction body 7 to urge it towards the maximum open position.

[0059] A normally closed first flow restriction 5 is shown in FIG. 3. A normally open first flow restriction 5 is shown in FIG. 10. Except for the fact that the normally open first flow restriction 5 shown in FIG. 10 (and a different position of the reaction mechanism 10), the first flow restriction 5 shown in FIG. 10 is the same or substantially the same as the first flow restriction 5 shown in FIG. 3. The reaction mechanism 10 in the first flow restriction 5 shown in FIG. 3 may include, for example, a compression spring. The reaction mechanism 10 in the first flow restriction 5 shown in FIG. 10 may include, for example, a compression spring if the reaction mechanism 10 is attached to the actuator 9 as shown in FIG. 10, or may include a tension spring if the reaction mechanism 10 is attached to the other side of the actuator 9 (as shown in FIG. 3).

[0060] It should be noted that in Figures 3 and 10, the lengths of the arrows indicating the first force f1, the second force f2, and the third force f3, respectively, do not necessarily mean anything about the relative magnitudes of the forces f1, f2, and f3 with respect to one another. These arrows are included in Figures 3 and 10 merely to show the directions in which the first force f1, the second force f2, and the third force f3 may act relative to one another.

[0061] The flow restrictor 7 may in some cases be referred to as an adjustment element of the first flow restrictor 5. If the first flow restrictor 5 comprises a valve, the flow restrictor 7 may be referred to as an adjustment element of the valve. For example, according to the embodiment of the invention shown in Figures 3 and 10, the first flow restrictor 5 may comprise a needle valve or the like, and the flow restrictor 7 may comprise or be constituted by a needle-shaped plunger of the needle valve. Again, it is noted that Figures 3 and 10 are schematic diagrams of the first flow restrictor 5, and it is further noted that certain components that may be included in the first flow restrictor 5 are omitted in Figures 3 and 10. For example, if the first flow restricting portion 5 comprises or is constituted by a needle valve, the first flow restricting portion 5 may further comprise a valve seat not shown in FIG. 3 or FIG. 10, and the shape of the needle-shaped plunger corresponds to the shape of the valve seat such that the needle-shaped plunger (or the flow restricting body 7) fits into the valve seat when the needle-shaped plunger is in the closed position.

[0062] The actuator 9 may, for example, comprise a membrane actuator and a proportional pressure regulator configured to act on the membrane actuator such that the membrane actuator generates a first force f1. The actuator 9 may be configured such that the first force f1 generated by the actuator 9 can be varied in steps or continuously.

[0063] The reaction force mechanism 10 may comprise, for example, a spring element that may be biased to generate a third force f3 that acts on the flow restrictor 7 to urge the flow restrictor 7 towards a closed position when the first force f1 acts on the flow restrictor 7 to urge the flow restrictor 7 towards a maximum open position or a third force f3 that acts on the flow restrictor 7 to urge the flow restrictor 7 towards a maximum open position when the first force f1 acts on the flow restrictor 7 to urge the flow restrictor 7 towards a closed position. The reaction force mechanism 10 may comprise, for example, a spring or a gas spring (e.g., an air spring), which may be controllable. The third force f3 generated by the reaction force mechanism 10 may be constant or substantially constant when the first force f1 acts on the flow restrictor 7 to bias the flow restrictor 7 toward the closed position or when the first force f1 acts on the flow restrictor 7 to bias the flow restrictor 7 toward the closed position and bias the flow restrictor 7 toward the maximum open position. The third force f3 may be set during manufacture of the first flow restrictor 5, for example, by selection of the particular type of reaction force mechanism 10 used for the first flow restrictor 5. Thus, the third force f3 may be different for different types of first flow restrictors 5, but may otherwise be constant or substantially constant. When the reaction force mechanism 10 comprises a spring element, the third force f3 may be based on the spring constant of the spring element.

[0064] The first force f1 is selectively and controllably generated by the actuator 9 and is therefore variable. Since the pressure of the pressure medium in the guideway 3 (or the pressure of the pressure medium in the guideway 3 upstream of and at the first flow restriction 5) will generally vary during withdrawal of pressure medium from the pressure vessel 2, the second force f2 will typically vary during the controlled withdrawal of pressure medium from the pressure vessel 2.

[0065] For a particular third force, during the controlled withdrawal of pressure medium from the pressure vessel 2, there may be a predefined relationship between the second force and the first force. The predefined relationship may involve that for a particular third force, there is a plurality or set of values ​​of the first force, or a range of values ​​of the first force, which results in a certain plurality of respective values ​​of the second force, or a certain set of respective values ​​of the second force, or a certain range of respective values ​​of the second force. Thus, according to the predefined relationship, for each value of the plurality or set of values ​​of the first force, there may be a corresponding value of the second force resulting from that particular value of the first force generated by the actuator 9. The predefined relationship may, for example, be established or determined by a set of measurements of values ​​of the second force resulting from different values ​​of the first force generated by the actuator 9 during the controlled withdrawal of pressure medium from the pressure vessel 2 for a particular third force generated by the counterforce mechanism 10.

[0066] The set of measurements may not be taken during an actual processing cycle in which at least one article is processed in the press apparatus, but during a "test" or "training" cycle that may be performed prior to the actual processing cycle and with the purpose of determining the above relationship. During such a "test" or "training" cycle, the pressure in the pressure vessel 2 may be raised to a pressure level at which processing of the article is intended to take place by introducing a pressure medium into the pressure vessel 2, and after the pressure in the pressure vessel 2 reaches this pressure level, the pressure medium may be withdrawn from the pressure vessel 2 via the induction path 3 in order to reduce the pressure in the pressure vessel 2. The set of measurements may be taken during such a "test" or "training" cycle, during the controlled withdrawal of pressure medium from the pressure vessel 2. During such a "test" or "training" cycle, the actuator 9 may be controlled to generate a certain value of the first force and then it may be measured what the resulting value of the second force is. This may be performed for a series of different constant values ​​of the first force generated by the actuator 9 in order to obtain a set of measurements that are used to establish or determine the predetermined relationship.

[0067] During the controlled withdrawal of pressure medium from the pressure vessel 2, for each different value of the first force generated by the actuator 9, it can be measured what is the resulting value of the second force. The measurement of the value of the second force can be performed, for example, by measuring the pressure of the pressure medium in the guideway 3. Thus, the value of the second force is not necessarily measured directly, but can be measured indirectly, for example, by measuring the pressure of the pressure medium in the guideway 3. The measurement of the pressure of the pressure medium in the guideway 3 can be performed, for example, by pressure sensors (not shown in the figures) known in the art. Although not shown in Figures 1 and 2, the press device 1 can comprise one or more pressure sensors, for example, for sensing or measuring the pressure of the pressure medium in the guideway 3. For example, a pressure sensor configured to sense or measure the pressure in the guideway 3 at the point where the guideway 3 enters the pressure vessel 2 and / or a pressure sensor configured to sense or measure the pressure in the guideway 3 upstream of and at the first flow restriction 5 can be provided. Any pressure sensor can be arranged or attached, for example, at a selected position along the guideway 3. Any pressure sensor may be located or attached, for example, to one or more pipes, tubes or conduits that may implement or realize the induction path 3. Alternatively or additionally, any pressure sensor may be located or attached to some other component (not shown in the figures) that may be coupled to the pressure vessel 2, such as, for example, a pipe, tube, conduit or circuit for a pressure medium, etc.

[0068] Optionally, a pressure relief device, such as, for example, a safety valve or a rupture disk or the like (not shown in Figures 1 and 2), may be coupled to the first flow restriction 5 and may be used in case of any malfunction of the first flow restriction 5.

[0069] With further reference to FIGS. 1 and 2, the pressing apparatus 1 comprises at least one control and / or processing unit, indicated diagrammatically at 11 .

[0070] The at least one control and / or processing unit 11 is configured to determine a plurality of values ​​of the second force such that corresponding values ​​of the pressure of the pressure medium in the taxiway 3 correspond to a pressure reduction sequence for reducing the pressure of the pressure medium in the taxiway 3 over time, and to determine a plurality of values ​​of the first force corresponding to respective values ​​of the plurality of values ​​of the second force based on a predetermined relationship. The at least one control and / or processing unit 11 is configured to control the actuator 9 to generate a plurality of values ​​of the first force such that the pressure of the pressure medium in the taxiway 3 is reduced over time according to a pressure reduction sequence during at least a portion of the time that the pressure medium is controllably withdrawn from the pressure vessel 2. The pressure reduction sequence may also be referred to as a pressure gradient.

[0071] Thus, the predetermined relationship may first be used to define a pressure reduction sequence, and then the actuator 9 may be controlled such that the pressure of the pressure medium in the taxiway 3 is reduced over time according to the pressure reduction sequence, by controlling the actuator 9 to generate a plurality of values ​​of the first force that will result in the pressure of the pressure medium in the taxiway 3 being reduced over time according to the pressure reduction sequence. Determining the plurality of values ​​of the second force may involve selecting the second force values ​​from among a plurality of respective values ​​of the second force, or a certain set of respective values ​​of the second force, or a certain range of values ​​of the second force, as described herein, to form a series of second force values ​​with corresponding values ​​of the pressure of the pressure medium in the taxiway 3 decreasing monotonically. Such monotonically decreasing values ​​of the pressure of the pressure medium in the taxiway 3 may form a pressure reduction sequence.

[0072] With further reference to Figures 1 and 2, the at least one control and / or processing unit 11 may be configured to control the second flow restriction 6 so as not to impede or inhibit pressure medium flow through the second flow restriction 6 prior to at least a portion of the time, thereby allowing pressure medium to be withdrawn from the pressure vessel 2 by being guided from the pressure vessel 2 via the guide path 3 towards the pressure medium sink 4.

[0073] The above-mentioned predetermined relationship may be such that, for the predetermined relationship, the combination of the first and second forces is determined to be in equilibrium with the third force while the flow restrictor 7 is away from the closed position. By the combination of the first and second forces being in equilibrium with the third force, it may be meant that there is no net force or only a very small net force acting on the flow restrictor 7, so that the flow restrictor 7 is in force equilibrium or very close to force equilibrium. Thus, for each value of a plurality or set of values ​​of the first force, for a particular third force, there may be a corresponding value of the second force resulting from that particular value of the first force generated by the actuator 9, at which value the flow restrictor 7 is at rest or substantially at rest and away from the closed position.

[0074] The at least one control and / or processing unit 11 may be connected to the first flow restriction 5, the second flow restriction 6, and / or any other components in the press apparatus 1, for example, to control their operation (e.g., to control the actuator 9 of the first flow restriction 5). Such a connection may be implemented or realized, for example, by any wireless and / or wired means as known in the art. Such a connection may be a communication connection, whereby the at least one control and / or processing unit 11 may be able to communicate with the first flow restriction 5, the second flow restriction 6, and / or any other components in the press apparatus 1, for example, via any suitable wired and / or wireless communication means or techniques as known in the art, for transmitting messages, instructions, data, commands, etc. from the at least one control and / or processing unit 11 to the first flow restriction 5, the second flow restriction 6, and / or any other components in the press apparatus 1, and possibly vice versa.

[0075] Figure 4 is a schematic graph illustrating the principles of an embodiment of the invention as described above, for example with reference to Figures 1-3 and 10. More specifically, Figure 4 is a schematic graph of pressure P versus time t (both P and t in arbitrary units) within the pressure vessel 2 during at least a portion of the time that pressure medium is being withdrawn from the pressure vessel 2.

[0076] Curve P1 shows how the pressure P in the pressure vessel 2 may decrease over time if the first flow restriction and, if present, the possibly second flow restriction would be in a fully "open" state during withdrawal of pressure medium from the pressure vessel 2, i.e. if the first flow restriction and, if present, the possibly second flow restriction would not impede or hinder the pressure medium flow at all during withdrawal of pressure medium from the pressure vessel 2. This may correspond to the case where the actuator 9 is controlled to generate a first force having a sufficiently high value to ensure that the flow restrictor 7 is maintained in a maximally open position during withdrawal of pressure medium from the pressure vessel 2 (e.g. if the first flow restriction 5 is a normally closed flow restriction).

[0077] Curve P2 shows how the pressure P in the pressure vessel may decrease over time when a first flow restriction is used in accordance with one or more embodiments of the present invention, in particular when actuator 9 is controlled as described herein, for example as described above with reference to Figures 1-3 and 10, during at least a portion of the time that pressure medium is controllably withdrawn from pressure vessel 2.

[0078] Lines F1-F7 in FIG. 4 show certain values ​​of the first force generated by the actuator 9. Line F7 coincides with the horizontal axis. The value of the pressure P in the pressure vessel at each point where the lines F1-F7 intersect the curve P1 corresponds to a pressure of the pressure medium in the guideway 3 where the combination of the respective values ​​F1-F7 of the first force and the second force generated by the pressure medium pressure in the guideway 3 and acting on the flow restriction body 7 to urge it towards the maximum open position is not sufficiently large compared to the third force to move the flow restriction body 7 out of the closed position (e.g., when the first flow restriction 5 is a normally closed flow restriction).

[0079] At least some of F1-F7 may correspond to monotonically increasing or continuously different values ​​of a first force that may be generated by the actuator 9. For example, if the actuator 9 comprises a membrane actuator and a proportional pressure regulator configured to act on the membrane actuator such that it generates the first force, F1-F7 may correspond for example to pressures of 0 bar, 1 bar, 2 bar, 3 bar, 4 bar, 5 bar and 6 bar, respectively (for example, if the first flow restriction 5 is a normally closed flow restriction).

[0080] F7 may correspond to a first force value sufficient to ensure that the flow restrictor 7 is maintained in a maximum open position while pressure medium is being withdrawn from the pressure vessel 2, i.e. that the first flow restriction 5 is maintained fully "open" while pressure medium is being withdrawn from the pressure vessel 2, i.e. that it does not obstruct or impede the pressure medium flow in any way.

[0081] As mentioned above, for a particular third force, during the controlled withdrawal of pressure medium from the pressure vessel 2, a predetermined relationship exists between the second force and the first force. A plurality of values ​​of the second force may be determined such that corresponding values ​​of the pressure of the pressure medium in the taxiway 3 correspond to a pressure reduction sequence for reducing the pressure of the pressure medium in the taxiway 3 over time. The curve P2 may correspond to such a pressure reduction sequence. Based on the predetermined relationship, a plurality of values ​​of the first force may be determined corresponding to respective values ​​of the plurality of values ​​of the second force.

[0082] According to the embodiment shown in FIG. 4, by controlling the actuator 9 such that the first force varies between F2 and F6 for at least a portion of the time, the pressure medium in the guideway - and therefore the pressure P in the pressure vessel, which is proportional to the pressure medium in the guideway - can be reduced over time according to a curve P2, which in the example shown is a straight line with a certain negative slope from time t1 to time t2. Thus, from time t1 to time t2, the reduction rate of the pressure P in the pressure vessel can be controlled to be constant, or at least substantially constant. At each point on the curve P2, the combination of the first and second forces is in equilibrium with the third force, while the flow restrictor 7 is away from the closed position but not in a fully open or maximum open position. Thus, by controlling the actuator 9 as described herein, a high degree of precision in controlling the reduction rate of the pressure of the pressure medium in the guideway 3 - and therefore of the pressure P in the pressure vessel 2 - can be achieved. Although FIG. 4 shows the curve P2 as a straight line, it should be understood that the curve P2 can have another shape. Thus, the rate of reduction of the pressure P in the pressure vessel from time t1 to time t2 is not necessarily constant, or at least substantially constant, but may be controlled to vary at least instantaneously during the time period from time t1 to time t2. For example, instead of a straight line, the curve P2 may be a curve that resembles or has a shape similar to a parabola. Thus, the pressure P in the pressure vessel does not necessarily have to be reduced over time according to a straight line with a certain negative slope from time t1 to time t2, this is just one example of how the pressure P in the pressure vessel may be controlled to reduce over time.

[0083] It should be understood that the graph in Fig. 4 may show the reduction of the pressure P in the pressure vessel from time t1 to time t2 according to ideal or near-ideal operating conditions of the press apparatus 1. For example, the graph in Fig. 4 may ignore any pressure medium leakage that may occur in one or more components of the press apparatus 1, such as, for example, in the first flow restriction 5, in any pipe(s), tube(s) or conduit(s) implementing or realizing the guideway 3, etc. In the presence of such pressure medium leakage, the curves F1-F6 in Fig. 4 may not, for example, follow exactly a straight line as shown in Fig. 4, but may deviate somewhat from the shape of such type of curve and may, for example, exhibit one or more kinks.

[0084] If the press apparatus 1 is equipped with a second flow restriction 6 as shown in Figures 1 and 2, both curves P1 and P2 assume that the second flow restriction 6 is in a completely "open" state, i.e. that the second flow restriction does not obstruct or impede the pressure medium flow in any way while the pressure medium is being withdrawn from the pressure vessel 2.

[0085] FIG. 5 is a schematic flow chart of a method 20 according to an embodiment of the present invention. The method 20 is a method for a pressing apparatus. The pressing apparatus comprises a pressure vessel arranged to hold pressure medium therein. The pressing apparatus comprises a guideway configured to connect the pressure vessel with a pressure medium sink and to withdraw pressure medium from the pressure vessel by directing the pressure medium from the pressure vessel towards the pressure medium sink, thereby reducing the pressure in the pressure vessel. The guideway comprises at least a first flow restriction configured to control the extent to which pressure medium flow is permitted to pass through the first flow restriction, thereby controlling the extent to which pressure medium flow in the guideway is impeded or blocked. The first flow restriction comprises a flow restrictor movable between at least a closed position and a maximum open position. When the flow restrictor is moved from the closed position, an opening is created, the size of the opening increasing the closer the flow restrictor is to the maximum open position. The extent to which pressure medium flow is permitted to pass through the first flow restriction depends on the size of the opening, if any. During controlled withdrawal of pressure medium from the pressure vessel, the size of the opening is determined by at least (i) a first force, controllably and selectively generated by the actuator, acting on the flow restriction to urge the flow restriction either toward a maximum open position or toward a closed position, (ii) a second force, generated by pressure of the pressure medium in the guideway, acting on the flow restriction to urge the flow restriction toward a maximum open position, and (iii) a third force, generated by a counterforce mechanism, acting on the flow restriction to urge the flow restriction toward a closed position if the first force acts on the flow restriction to urge the flow restriction toward a maximum open position, or to urge the flow restriction toward a maximum open position if the first force acts on the flow restriction to urge the flow restriction toward a closed position. During controlled withdrawal of pressure medium from the pressure vessel, a predetermined relationship exists between the second force and the first force for a particular third force.

[0086] The method 20 comprises determining a plurality of values ​​of the second force such that corresponding values ​​of pressure of the pressure medium in the taxiway correspond to a pressure reduction sequence for reducing the pressure of the pressure medium in the taxiway over time at 21. A plurality of values ​​of the first force are determined at 22 corresponding to respective values ​​of the plurality of values ​​of the second force based on a predetermined relationship. At 23, during at least a portion of the time that pressure medium is controllably withdrawn from the pressure vessel, the actuator is controlled to generate the plurality of values ​​of the first force such that the pressure of the pressure medium in the taxiway is reduced over time according to the pressure reduction sequence.

[0087] Fig. 6 is a schematic flow chart of a method 30 according to another embodiment of the present invention. The method 30 shown in Fig. 6 is similar to the method 20 shown in Fig. 5 and includes the same operations 21, 22 and 23 as the method 20 shown in Fig. 5. In contrast to the method 20 shown in Fig. 5, in the method 30 shown in Fig. 6, the guideway further comprises a second flow restriction, which is configured to control the degree to which the pressure medium flow in the guideway is obstructed or blocked by controlling the degree to which the pressure medium flow is allowed to pass through the second flow restriction, and the second flow restriction is arranged upstream of the first flow restriction. Furthermore, in contrast to the method 20 shown in Fig. 5, the method 30 comprises, at least a part of the time before, at 24, controlling the second flow restriction so as not to obstruct or block the pressure medium flow through the second flow restriction, whereby the pressure medium is withdrawn from the pressure vessel by being guided from the pressure vessel through the guideway towards the pressure medium sink.

[0088] 1 and 2 illustrate a single first flow restriction 5, it should be understood that the pressing apparatus 1 may optionally include one or more additional flow restrictions, each of which may be included in the guideway 3. Figures 7 and 8 show, in a schematic manner, different alternative configurations to those shown in Figures 1 and 2. Thus, each of Figures 7 and 8 is a schematic diagram of a pressing apparatus 1 according to an embodiment of the present invention. The same reference numbers in Figures 7 and 8 and in Figures 1 and 2 indicate the same or similar components having the same or similar functions.

[0089] According to the embodiment of the invention shown in Figure 7, there are two first flow restriction parts 5 connected in parallel. More than two first flow restriction parts connected in parallel can be provided. In the embodiment of the invention shown in Figure 7, the second flow restriction part 6 can be omitted. The second flow restriction part 6 can also be omitted in the embodiment of the invention shown in Figures 1 and 2.

[0090] According to the embodiment of the invention shown in Figure 8, there are two first flow restriction parts 5 connected in series. More than two first flow restriction parts connected in series may be provided. In the embodiment of the invention shown in Figure 8, the second flow restriction part 6 may be omitted.

[0091] In some cases, multiple first flow restrictions may be provided, some of which may be connected in parallel and some of which may be connected in series.

[0092] Each or any of the one or more additional flow restriction sections, if any, may be similarly or identically positioned to the first flow restriction section 5 and may therefore be configured to control the extent to which pressure medium flow in the guideway 3 is obstructed or impeded by controlling the extent to which pressure medium flow is permitted to pass through the additional flow restriction section, and the additional flow restriction section may comprise a flow restrictor movable between at least a closed position and a maximum open position, like the first flow restriction section 5 described herein.

[0093] Figure 9 is a schematic diagram of a pressing device 1 according to another embodiment of the present invention. The same reference numbers in Figure 9 and in Figures 1 and 2 indicate the same or similar components having the same or similar functions. The embodiment of the present invention shown in Figure 9 differs from the embodiment of the present invention shown in Figures 1 and 2 in that according to the embodiment of the present invention shown in Figure 9, the first flow restriction part 5 and the second flow restriction part 6 are connected in parallel.

[0094] In conclusion, a method is disclosed in a press apparatus comprising a pressure vessel and a guideway for directing pressure medium out of the pressure vessel to reduce pressure within the pressure vessel, the guideway comprising a first flow restriction comprising a flow restrictor movable between at least a closed position and a maximum open position. When the flow restriction is moved from the closed position, an opening is created, the size of the opening being determined by a first force acting on the flow restriction to urge it either toward a maximum open position or toward a closed position, generated by the actuator during controlled withdrawal of pressure medium from the pressure vessel, a second force acting on the flow restriction to urge it toward a maximum open position, generated by the pressure of the pressure medium in the guideway, and a third force acting on the flow restriction to urge it toward a closed position if the first force acts on the flow restriction to urge it toward a maximum open position, or to urge it toward a maximum open position if the first force acts on the flow restriction to urge it toward a closed position, the third force being generated by a counterforce mechanism. The actuator is controlled according to a predetermined relationship between the second force and the first force for a particular third force such that the pressure of the pressure medium in the guideway is reduced over time according to a pressure reduction sequence.

[0095] While the present invention has been illustrated in the accompanying drawings and the foregoing description, such illustrations should be considered as exemplary or illustrative and not restrictive, and the present 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 appended claims, the term "comprising" does not exclude other elements or steps, and the indefinite articles "a" or "an" do not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be interpreted as limiting the scope.

Claims

1. 1. A method (20) in a press apparatus (1) comprising a pressure vessel (2) arranged to hold pressure medium therein, and a guideway (3) configured to connect the pressure vessel with a pressure medium sink (4) and to withdraw pressure medium from the pressure vessel by directing pressure medium from the pressure vessel towards the pressure medium sink, thereby reducing the pressure in the pressure vessel, the guideway comprising at least a first flow restriction (5) configured to control the extent to which pressure medium flow is permitted to pass through a first flow restriction, thereby controlling the extent to which pressure medium flow in the guideway is obstructed or impeded, the first flow restriction comprising a flow restrictor (7) movable between at least a closed position and a maximum open position, when the flow restrictor is moved from the closed position an opening (8) is created, the size of the opening increasing the closer the flow restrictor is to the maximum open position, the extent to which pressure medium flow is permitted to pass through the first flow restriction, if any, depending on the size of the opening, and the pressure in the pressure vessel is withdrawn by a pressure vessel and a guideway (3) configured to withdraw pressure medium from the pressure vessel by directing pressure medium from the pressure vessel towards the pressure medium sink, the guideway comprising at least a first flow restriction (5) configured to control the extent to which pressure medium flow is permitted to pass through the first flow restriction, the first flow restriction comprising a flow restrictor (7) movable between at least a closed position and a maximum open position, when the flow restrictor is moved from the closed position an opening (8) is created, During controlled withdrawal of medium, the size of the opening is determined by at least: (i) a first force (f1) controllably and selectively generated by an actuator (9) acting on the flow restriction to urge the flow restriction either towards the maximum open position or towards the closed position; (ii) a second force (f2) generated by the pressure of a pressure medium in the guideway acting on the flow restriction to urge the flow restriction towards the maximum open position; and (iii) a third force (f3) acting on the flow restriction to urge the flow restriction towards the closed position if the first force acts on the flow restriction to urge the flow restriction towards the maximum open position or to urge the flow restriction towards the maximum open position if the first force acts on the flow restriction to urge the flow restriction towards the closed position, the third force being generated by a reaction force mechanism (10), and for a particular third force there is a predetermined relationship between the second force and the first force, the method comprising: Determining (21) a plurality of values ​​of the second force such that corresponding values ​​of pressure of the pressure medium in the guideway correspond to a pressure reduction sequence for reducing the pressure of the pressure medium in the guideway over time; determining (22) a plurality of values ​​of the first force corresponding to respective values ​​of the plurality of values ​​of the second force based on the predetermined relationship; controlling (23) the actuator to generate a plurality of values ​​of the first force such that the pressure of pressure medium in the guideway is reduced over time in accordance with the pressure reduction sequence during at least a portion of the time that pressure medium is controllably withdrawn from the pressure vessel; A method comprising:

2. 2. The method of claim 1, wherein the predetermined relationship is determined for a particular third force generated by the reaction mechanism by a set of measurements of values ​​of the second force resulting from different values ​​of the first force generated by the actuator, performed prior to the method steps of claim 1.

3. 3. The method of claim 1 or 2, wherein for the predetermined relationship, a combination of the first force and the second force is in equilibrium with the third force while the flow restrictor is away from the closed position but not in the maximum open position.

4. The induction path further comprises a second flow restriction (6) configured to control the extent to which pressure medium flow in the induction path is obstructed or impeded by controlling the extent to which pressure medium flow is allowed through a second flow restriction, the second flow restriction being located upstream of the first flow restriction, and the method further comprises the steps of: prior to at least a portion of the time: controlling (24) the second flow restriction so as not to impede or impede pressure medium flow through the second flow restriction, whereby the pressure medium is withdrawn from the pressure vessel by being guided from the pressure vessel via the guide path towards the pressure medium sink. The method (30) according to any one of claims 1 to 3.

5. 5. The method of claim 4, wherein the withdrawing of pressure medium from the pressure vessel is for reducing the pressure in the pressure vessel from a high pressure level towards a low pressure level, the second flow restriction is configured to be operable at one or more pressure levels including at least the high pressure level, the first flow restriction is configured to be operable at one or more pressure levels including at least an intermediate pressure level between the high pressure level and the low pressure level, and the controlling of the actuator is performed after the pressure in the pressure vessel has been reduced such that the pressure in the pressure vessel is below the intermediate pressure level.

6. 6. The method according to claim 4 or 5, wherein said controlling of said actuator is performed whilst said second flow restriction remains unimpeded or unhindered to pressure medium flow.

7. 6. The method of claim 5, wherein the one or more pressure operating levels at which the second flow restriction is operable are less than or equal to 6000 bar and / or the one or more pressure operating levels at which the first flow restriction is operable are less than or equal to 400 bar.

8. A press device (1), comprising: a pressure vessel (2) arranged to hold a pressure medium therein; a guideway (3) connecting the pressure vessel with a pressure medium sink (4) and configured to withdraw pressure medium from the pressure vessel by directing pressure medium from the pressure vessel towards the pressure medium sink, thereby reducing the pressure in the pressure vessel; and at least a first flow restriction (5) included in the guideway and configured to control the extent to which pressure medium flow in the guideway is obstructed or impeded by controlling the extent to which pressure medium flow is allowed to pass through the first flow restriction, the first flow restriction comprising a flow restrictor (7) movable between at least a closed position and a maximum open position, wherein when the flow restrictor is moved from the closed position an opening (8) is created, the size of the opening increasing the closer the flow restrictor is to the maximum open position, the extent to which pressure medium flow is allowed to pass through the first flow restriction depending on the size, if any, of the opening, and during controlled withdrawal of pressure medium from the pressure vessel the size of the opening increases at least by: (i) moving the flow restrictor (7) towards the maximum open position, the size of the opening increasing at least by a movement of ... (ii) a second force (f2) generated by pressure of a pressure medium in the guideway, acting on the flow restriction body to urge the flow restriction body toward the maximum open position; and (iii) a third force (f3) acting on the flow restriction body to urge the flow restriction body toward the closed position if the first force acts on the flow restriction body to urge the flow restriction body toward the maximum open position, or to urge the flow restriction body toward the maximum open position if the first force acts on the flow restriction body to urge the flow restriction body toward the closed position, the third force being generated by a reaction force mechanism (10), and for a particular third force, a predetermined relationship exists between the second force and the first force, The press device is determining a plurality of values ​​of the second force such that corresponding values ​​of pressure of the pressure medium in the guideway correspond to a pressure reduction sequence for reducing the pressure of the pressure medium in the guideway over time; determining a plurality of values ​​of the first force corresponding to respective values ​​of the plurality of values ​​of the second force based on the predetermined relationship; controlling the actuator to generate a plurality of values ​​of the first force such that the pressure of pressure medium in the guideway is reduced over time in accordance with the pressure reduction sequence during at least a portion of the time that pressure medium is controllably withdrawn from the pressure vessel; The pressing apparatus further comprises at least one control and / or processing unit (11) configured to:

9. The pressing apparatus of claim 8 , wherein the first flow restriction comprises at least one valve.

10. 10. The pressing apparatus according to claim 8 or 9, wherein the first flow restriction comprises at least one seat valve.

11. The pressing apparatus according to any one of claims 8 to 10, wherein the first flow restriction comprises at least one needle valve.

12. 12. The press apparatus according to claim 8, wherein the actuator comprises a membrane actuator and a proportional pressure regulator configured to act on the membrane actuator such that the membrane actuator generates the first force.

13. The press apparatus according to any one of claims 8 to 12, wherein the actuator is configured to be capable of varying the first force generated by the actuator in a stepwise manner.

14. The press apparatus according to any one of claims 8 to 12, wherein the actuator is configured to be capable of continuously changing the first force generated by the actuator.

15. 15. The press apparatus of claim 8, wherein the reaction force mechanism comprises a spring element biased to generate the third force acting on the flow restrictor to bias the flow restrictor either towards the closed position or towards the maximum open position.

16. a second flow restriction (6) included in the guideway and configured to control the extent to which the pressure medium flow in the guideway is obstructed or impeded by controlling the extent to which the pressure medium flow is allowed through a second flow restriction, wherein the second flow restriction is arranged upstream of the first flow restriction, The at least one control and / or processing unit, prior to at least a portion of the time, configured to control the second flow restriction so as not to impede or inhibit pressure medium flow through the second flow restriction, whereby the pressure medium is withdrawn from the pressure vessel by being guided from the pressure vessel via the guide path towards the pressure medium sink. The pressing device according to any one of claims 8 to 15.

17. 17. The pressing apparatus according to claim 16, wherein the second flow restriction is configured to either impede or obstruct the pressure medium flow or not impede or not obstruct the pressure medium flow.

18. 18. A pressing apparatus according to claim 16 or 17, wherein the second flow restriction comprises at least one valve.

19. 19. The press apparatus according to claim 16, wherein the withdrawal of pressure medium from the pressure vessel is for reducing the pressure in the pressure vessel from a high pressure level towards a low pressure level, the second flow restriction being configured to be operable at one or more pressure levels including at least the high pressure level, and the first flow restriction being configured to be operable at one or more pressure levels including at least an intermediate pressure level between the high pressure level and the low pressure level.

20. 20. The pressing apparatus of claim 19, wherein the one or more pressure operating levels at which the second flow restriction is operable are equal to or lower than 6000 bar and / or the one or more pressure operating levels at which the first flow restriction is operable are equal to or lower than 400 bar.

21. A computer program comprising instructions which, when executed by one or more processors comprised in at least one control and / or processing unit (11) of a press apparatus (1) according to any one of claims 8 to 20, cause the at least one control and / or processing unit to perform the method (20, 30) according to any one of claims 1 to 7.

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