Abstract:
An apparatus for extracting juice from a comestible includes a cavity for receiving a comestible, the cavity having a cavity wall extending about an axis and movable in response to an applied hydraulic force to form a plurality of lobes spaced about the axis for applying a compressive force to the comestible. By providing such an arrangement, the applied force can be distributed evenly across the comestible, resulting in an even collapse of the comestible.

Description:
REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the priority of United Kingdom Application No. 0815990.7, filed Sep. 3, 2008, the contents of which are incorporated herein by reference. 
       FIELD OF THE INVENTION 
       [0002]    The invention relates to apparatus for extracting juice from a comestible. 
       BACKGROUND OF THE INVENTION 
       [0003]    There are a wide variety of known techniques for extracting juice from a comestible in a domestic environment. A conventional technique for domestic juice extraction from citrus fruit is to first cut the fruit in half, and then press and rotate the cut halves of the fruit against a lobed cone to extract the juice. 
         [0004]    Another technique is centrifugal juice extraction. This technique involves introducing peeled, chopped and grated comestible into a rotatable basket. The basket is then rotated at high speed in the manner of a centrifuge. Apertures provided in the basket enable juice to be extracted therethrough, whilst the pulp remains behind in the basket. 
         [0005]    A disadvantage of each of these types of juice extractor is that the comestible must be prepared by a user before the juice can be extracted. This makes the preparation of juice more time-consuming. Further, cleaning of such juicing appliances is often laborious. 
         [0006]    An alternative known technique for juicing in a domestic environment is hydraulic juicing. Examples of juicers using this principle of operation are shown and described in U.S. Pat. No. 2,414,053 and GB 2158697. These juicers each comprise a chamber having a flexible wall attached thereto. The flexible wall splits the chamber into a comestible-receiving cavity and a fluid cavity. Comestibles such as fruit or vegetables are placed into the comestible-receiving cavity and a fluid (for example, water or compressed air) is pumped into the fluid cavity. The hydraulic pressure from the fluid crushes the comestible in the comestible-receiving cavity, releasing the juice contained within the comestible. The juice is then extracted through an outlet pipe into a suitable receptacle provided by a user. 
         [0007]    A hydraulic juicing technique is advantageous in that whole fruit and vegetables can be juiced with little or no prior preparation. However, in the arrangements shown and described in U.S. Pat. No. 2,414,053 and GB 2158697, the hydraulic pressure from the fluid acts on the comestible in an uncontrolled manner. 
         [0008]    If fruit is being juiced, the uncontrolled pressure can cause the fruit to collapse unevenly or only partially. This is because fruit such as oranges are not homogeneous structures and may have weak regions where collapse will occur under a smaller applied force than at other regions. Due to the nature of a hydraulic system, the weakest points in the fruit will be caused to collapse first, leading to an uneven collapse of the fruit as a whole. Partial collapse of a fruit will reduce the yield of juice obtained. Further, uncontrolled and uneven collapse may potentially split the skin of the fruit, releasing unwanted zest and peel oil into the extracted juice. This will give the juice a bitter aftertaste. 
       SUMMARY OF THE INVENTION 
       [0009]    In a first aspect, the present invention provides apparatus for extracting juice from a comestible, the apparatus comprising a cavity for receiving a comestible, the cavity having a cavity wall extending about an axis and movable in response to an applied hydraulic force to form a plurality of lobes spaced about the axis for applying a compressive force to the comestible. 
         [0010]    By forming a plurality of lobes spaced about the axis for applying a compressive force to the comestible, the applied force can be distributed evenly across the comestible, resulting in an even collapse of the comestible. The expansion of each movable part of the cavity wall relative to the other movable parts and allows a controlled movement of the cavity wall. 
         [0011]    Preferably, the lobes formed by the cavity wall are evenly spaced about the axis. This arrangement provides the most controlled compression of the comestible in the cavity, because the hydraulic force is evenly applied around the wall. 
         [0012]    Preferably, the cavity wall is arranged to form at least three expandable lobes. More preferably, the cavity wall is arranged to form at least five expandable lobes. Increasing the number of lobes can enable the collapse of the comestible to be closely controlled. 
         [0013]    Preferably, the cavity wall comprises restraining members located thereabout, each of the plurality of lobes being formed between adjacent restraining members. By restraining, or holding the cavity wall at a plurality of restraining locations, each movable part of the cavity wall is tethered, for example to the chamber wall extending about the cavity, at two spaced locations. This controls the expansion of each movable part of the cavity wall relative to the other movable parts in response to the applied hydraulic force and allows a controlled movement of the cavity wall. This is because the tethering prevents one part of the cavity wall from expanding significantly more than the other parts, which would lead to an uncontrolled collapse. Consequently, the applied force can be distributed evenly across the comestible, resulting in an even collapse of the comestible. 
         [0014]    In a second aspect, the present invention provides apparatus for extracting juice from a comestible, the apparatus comprising a cavity for receiving a comestible, the cavity comprising a cavity wall extending about an axis, wherein the cavity wall is restrained at a plurality of restraining locations spaced about the axis, parts of the cavity wall between the restraining locations being movable in response to an applied hydraulic force so as to apply a compressive force to the comestible. A restraining member is preferably provided at each of the restraining locations. 
         [0015]    It is preferable that each of the restraining members comprises a rib which is preferably elongate and extends parallel to the axis of the cavity. Preferably, an outer wall is provided adjacent the cavity wall, the restraining members extending between the cavity wall and the outer wall. The restraining members may be integral with the outer wall and the cavity wall, or otherwise connected to each of these walls. 
         [0016]    The cavity wall and the outer wall are preferably connected together. Preferably, the cavity wall is folded to form the outer wall. This allows the cavity wall and outer wall to be formed in one piece, for example using a vacuum moulding technique. 
         [0017]    A liner is preferably removably locatable within the cavity for lining the cavity wall. By providing a removable liner, the inner surface of the cavity wall can be kept clean and requires less maintenance. Further, a removable liner can easily be removed for washing by hand or in a dishwasher. Therefore, in a third aspect the present invention provides apparatus for extracting juice from a comestible, the apparatus comprising a cavity for receiving a comestible, the cavity having a cavity wall movable in response to an applied hydraulic force so as to apply a compressive force to the comestible, and 
         [0018]    Preferably, the liner forms a pocket for receiving the comestible. By providing a pocket for the comestible, the comestible can potentially be entirely enclosed within the liner. 
         [0019]    Preferably, the liner has a reinforced open upper end. This allows the liner to be grasped by a user and also helps to keep the shape of the liner. Preferably, the liner comprises a liner wall which is shaped substantially to conform to the cavity wall. 
         [0020]    It is preferred that the liner wall has a base portion having at least a portion of greater rigidity than the remainder of the liner. Preferably, the base portion comprises a plate over-moulded into the liner wall. More preferably, the plate is formed from material having a greater stiffness than the material from which the liner wall is formed. This provides a seat for a comestible located within the cavity. 
         [0021]    Preferably, the liner wall is formed from a flexible material, preferably polyurethane. The liner is preferably formed from a washable material. 
         [0022]    Preferably, the apparatus comprises a fluid cavity for containing fluid for applying the hydraulic force to the cavity wall, at least a part of the fluid cavity being defined by the cavity wall. Preferably, the apparatus comprises a chamber having a chamber wall extending about the cavity wall, the chamber wall and the cavity wall delimiting the fluid cavity. The outer wall is preferably attached to the chamber wall. At least a part of the fluid cavity is preferably formed between the cavity wall and the outer wall. 
         [0023]    The apparatus preferably comprises a hydraulic circuit for applying a hydraulic pressure to the cavity wall. The hydraulic circuit is preferably arranged to move at least a part of the cavity wall away from the outer wall to apply a compressive force to a comestible located within the cavity, and to urge the outer wall towards the chamber wall. By arranging the hydraulic circuit to both move at least a part of the cavity wall away from the outer wall to apply a compressive force to a comestible located within the cavity, and to urge the outer wall towards the chamber wall, a compressive force can be applied to the comestible whilst simultaneously causing the outer wall to seal against the chamber wall, thereby reducing the risk of leakage of hydraulic fluid from between the outer wall and the chamber wall. Therefore, in a fourth aspect the present invention provides apparatus for extracting juice from a comestible, the apparatus comprising a chamber comprising a chamber wall, a movable member located at least partly within the chamber, the movable member comprising a cavity wall delimiting a cavity for receiving a comestible and an outer wall extending about and spaced from the cavity wall, and a hydraulic circuit for applying a hydraulic pressure to the moveable member to move at least a part of the cavity wall away from the outer wall to apply a compressive force to a comestible located within the cavity, and to urge the outer wall towards the chamber wall. 
         [0024]    Preferably, the cavity wall and the outer wall are spaced by a distance no greater than 5 mm, more preferably by a distance no greater 1 mm. The outer wall is preferably attached to the chamber, and preferably abuts the chamber wall. More preferably, the outer wall lies substantially flush with part of the chamber wall. This reduces the likelihood of leakage between the outer wall and the chamber wall. 
         [0025]    Preferably, the cavity wall is formed from plastics material, preferably polyurethane. Polyurethane is inexpensive to manufacture and has a good strength and tear resistance. 
         [0026]    Preferably, at least a part of the cavity is substantially cylindrical. For example, the cavity wall may have a cylindrical portion and a domed base portion. This shape of the cavity wall is advantageous because the cavity is shaped to closely follow the shape of a comestible, such as a fruit which is routinely placed in a juice extractor, and so can achieve effective compression thereof to extract a relatively high quantity of juice from the comestible. Therefore, in a fifth aspect the present invention provides apparatus for extracting juice from a comestible, the apparatus comprising a cavity for receiving a comestible, the cavity comprising a cavity wall movable in response to an applied hydraulic force so as to apply a compressive force to a comestible received in the cavity, wherein the cavity wall has a cylindrical portion and a domed base portion. 
         [0027]    Preferably, the cavity wall extends about an axis, and at least a part of the domed base portion of the cavity wall is arranged to apply a compressive force to the comestible in a direction extending along the axis. It is desirable that the chamber wall also has a cylindrical portion and a domed base portion so that the cavity wall closely follows the chamber wall. 
         [0028]    The apparatus may comprise a biasing member for urging at least a part of the cavity wall inwardly. Advantageously, the biasing member can provide a force additional to the hydraulic force so that the cavity wall can be urged in a chosen direction to control the compression of the comestible. Therefore, in a sixth aspect the present invention provides apparatus for extracting juice from a comestible, the apparatus comprising a cavity for receiving a comestible, the cavity having a cavity wall movable in response to an applied hydraulic force so as to apply a compressive force to a comestible located within the cavity, and a biasing member for urging at least a part of the cavity wall inwardly. 
         [0029]    Preferably, the biasing member is arranged to assist the applied hydraulic force to move said at least a part of the cavity wall inwardly. 
         [0030]    Preferably, the cavity wall extends about axis and the biasing member is arranged to urge said at least a part of the cavity wall along said axis. 
         [0031]    Preferably, the cavity wall has a base portion and the biasing member is arranged to urge the base portion of the cavity wall along said axis. More preferably, the base portion of the cavity wall is domed, and the biasing member is arranged to urge a central portion of the base portion of the cavity wall along said axis. This arrangement enables the comestible to be lifted upwardly in the cavity by the combined actions of the biasing member and the hydraulic pressure. 
         [0032]    The biasing member is preferably located between the chamber wall and the cavity wall. The biasing member is preferably located within the fluid cavity. 
         [0033]    It is preferred that the biasing member comprises a resilient member, which preferably in the form of a spring. 
         [0034]    Preferably, the apparatus comprises a closure member for closing the open end of the cavity through which a comestible is introduced to the cavity, the biasing member being arranged to urge said at least part of the cavity wall towards the closure member. The apparatus preferably comprises motorised means for effecting relative rotation between the chamber and the closure member to secure the closure member to the chamber. By providing such an arrangement, the closure member can be easily and reliably secured to the chamber prior to a juicing operation. Therefore, in a seventh aspect the present invention provides apparatus for extracting juice from a comestible, the apparatus comprising a chamber having an aperture through which a comestible is introduced to the chamber, a securable closure member for closing the aperture, means for applying a compressive force to a comestible located within the chamber, and motorised means for effecting relative rotation between the chamber and the closure member to secure the closure member to the chamber. 
         [0035]    Preferably, said means for effecting relative rotation between the chamber and the closure member is arranged to rotate the chamber relative to the closure member. It is desirable that said means for effecting relative rotation between the chamber and the closure member comprises a motor drive for rotating the chamber relative to the closure member. It is also preferred that the motor drive is located beneath the chamber. 
         [0036]    The apparatus preferably comprises an outer casing within which the chamber is located. The casing preferably has a moveable lid attached thereto, with the closure member being connected to the lid. This can enable the closure member to be easily located over the aperture through simply closing the lid. Preferably, the lid is pivotable relative to the casing between open and closed positions. 
         [0037]    It is preferable that the closure member and the chamber comprise co-operating features for securing the closure member to the chamber upon relative rotation therebetween. These features preferably comprise a plurality of lugs located on one of the chamber and the closure member, and a plurality of grooves located on the other one of the chamber and the closure member for receiving the lugs upon said relative rotation. 
         [0038]    The hydraulic circuit is preferably a closed circuit located entirely within the outer casing of the apparatus. By providing a closed circuit, an external source of fluid is not required. As an external source of fluid is not required, the apparatus can be used in environments where a source of fluid is unavailable or at least not available in a convenient location. Further, because there is no external access to the hydraulic circuit, there is a reduced risk of contamination. The risk of contamination is reduced both in terms of contaminants (for example, acidic fruit juices) entering the hydraulic circuit, potentially damaging its internal components and in terms of safety for a user, whereby the risk of fluid from the hydraulic circuit becoming mixed with juice extracted from a comestible is reduced. Therefore, in an eighth aspect the present invention provides apparatus for extracting juice from a comestible, the apparatus comprising a housing within which is located a cavity for receiving a comestible, the cavity having a moveable cavity wall, and a hydraulic circuit for applying a hydraulic pressure to the cavity wall so as to apply a compressive force to a comestible located in the cavity, wherein the hydraulic circuit is a closed circuit located entirely within the housing. 
         [0039]    It is preferred that the hydraulic circuit comprises a reservoir for storing a volume of fluid for applying the hydraulic force to the cavity wall. At least a part of the reservoir is preferably deformable in response to a change in the amount of fluid within the reservoir. Preferably, the reservoir comprises a flexible material, preferably polyurethane. Preferably, the reservoir surrounds at least a part of the cavity. This arrangement allows the reservoir effectively to use the available space within the apparatus. 
         [0040]    The hydraulic circuit preferably comprises an electrically-operated pumping arrangement. An electrically-operated pumping arrangement allows the apparatus to be compact and easy to use when compared to other alternatives, for example, hand pumps, water mains connections or compressed air lines. The pumping arrangement may comprise a gear pump for pumping fluid towards, and away from, the cavity wall. Alternatively, the pumping arrangement may comprise two pumps which are preferably arranged in parallel. These pumps may have different pumping performances, and/or different pumping mechanisms. For example, one of the pumps may be a piston pump, whereas another one of the pumps may be a centrifugal pump. 
         [0041]    The pumping arrangement is preferably operable in a first mode to supply fluid to the fluid cavity and in a second mode to remove fluid from the fluid cavity. The nature of the pumping arrangement allows the fluid to be removed rapidly and easily from the cavity after a juicing operation so that the cavity wall deflates to a size that enables a user to grasp easily the remains of a comestible after a juicing operation. Therefore, in a ninth aspect the present invention provides apparatus for extracting juice from a comestible, the apparatus comprising a cavity for receiving a comestible, the cavity having a moveable cavity wall, and a hydraulic circuit for applying a hydraulic force to the cavity wall so as to apply a compressive force to the comestible, wherein the hydraulic circuit comprises a fluid cavity for receiving fluid for applying the hydraulic force to the cavity wall, and a pumping arrangement operable in a first mode to supply fluid to the fluid cavity and in a second mode to remove fluid from the fluid cavity. 
         [0042]    It is preferred that the apparatus comprises a cutter for cutting a comestible located within the cavity. The biasing member is preferably arranged to urge said at least part of the cavity wall towards the cutter. The cutter may be connected to the closure member, or it may be moveable into the chamber through an aperture formed in the closure member. Providing a cutter which is moveable into the cavity allows the cutter to be in a retracted position at the time the comestible is introduced to the cavity. This can provide an important safety feature for an appliance intended for domestic use, as the user is not exposed to any sharp cutting edge or blade of the cutter when the comestible is introduced to the cavity. Therefore, in a tenth aspect the present invention provides apparatus for extracting juice from a comestible, the apparatus comprising a cavity for receiving a comestible, the cavity having a cavity wall movable in response to an applied hydraulic force so as to apply a compressive force to a comestible within the cavity, and a cutter moveable between a retracted position in which the cutter lies outside the cavity and an extended position in which the cutter projects into the cavity. 
         [0043]    The cutter is preferably movable along an axis about which the cavity extends. The apparatus preferably comprises a linear drive for driving the cutter between the retracted position and the extended position. The linear drive preferably comprises a motor and a gear arrangement drivable by the motor to drive the cutter between the retracted position and the extended position. The gear arrangement preferably comprises at least one rack and pinion gear arrangement, more preferably two rack and pinion arrangements each located on opposing sides of the cutter. By locating two gear arrangements on opposing sides of the cutter, there is no resultant torque when the cutter is driven into the cavity, reducing the strain on the apparatus. 
         [0044]    The apparatus preferably comprises inhibiting means for inhibiting contact between the cavity wall and the cutter. Inhibiting contact between the cavity wall and the cutter can improve the reliability of the apparatus by significantly reducing the risk of the cavity wall becoming ruptured during a juicing operation. The inhibiting means may comprise a shield member located between the cavity wall and the cutter. The shield member can thus provide a physical barrier which prevents the cutter from contacting the cavity wall. Preferably, the shield member is located adjacent the cavity wall to maximise the distance by which the cutter may extend into the cavity. The shield member is preferably moveable with the cavity wall, and may form part of the removable liner. 
         [0045]    Alternatively, the inhibiting means may be arranged to control movement of the cutter relative to the cavity so that the cutter is prevented from contacting the cavity wall. The inhibiting means may comprise a sensor or other means for detecting the position of the cutter relative to the cavity wall. A signal emitted from the sensor may be used to control movement of either the cutter or the cavity wall to inhibit contact therebetween. For example, the inhibiting means may be arranged to control movement of the cutter in response to the volume of fluid in the fluid cavity. 
         [0046]    The hydraulic circuit is preferably arranged to apply a first, relatively low hydraulic force to the cavity wall to cause the cavity wall to support the comestible within the cavity for cutting thereof by the cutter, and a second, relatively high hydraulic force to the cavity wall subsequent to the cutting of the comestible to cause the cavity wall to compress the comestible to extract juice therefrom. This two-staged application of a hydraulic force to the cavity wall can enable the comestible to be supported by the cavity wall prior to contact between the cutter and the comestible, thereby preventing the comestible from slipping out of position when the cutter contacts the comestible. This can enable accurate and reproducible cutting of a comestible prior to the extraction of juice therefrom. Therefore, in an eleventh aspect the present invention provides apparatus for extracting juice from a comestible, the apparatus comprising a cavity for receiving a comestible, a hydraulic circuit and a cutter moveable relative to the cavity to cut a comestible located therein, the cavity having a cavity wall movable in response to a hydraulic force applied thereto by the hydraulic circuit to contact a comestible in the cavity, wherein the hydraulic circuit is arranged to apply a first, relatively low hydraulic force to the cavity wall to cause the cavity wall to support the comestible within the cavity for cutting thereof by the cutter, and a second, relatively high hydraulic force to the cavity wall subsequent to the cutting of the comestible to cause the cavity wall to compress the comestible to extract juice therefrom. 
         [0047]    Preferably, the hydraulic circuit is arranged to apply a first hydraulic force to the cavity of sufficient magnitude to apply a pressure in the range from 0.3 to 0.7 bar to the cavity wall. Preferably, the hydraulic circuit is arranged to apply a second hydraulic force to the cavity of sufficient magnitude to apply a pressure in the range from 5 to 20 bar to the cavity wall. This pressure is sufficient to crush most comestibles to extract juice therefrom. 
         [0048]    In a twelfth aspect, the present invention provides a method of extracting juice from a comestible. The method preferably comprises the steps of: 
         [0049]    locating a comestible within a cavity having a moveable cavity wall extending about an axis; and 
         [0050]    applying a hydraulic force to cause the cavity wall to form a plurality of lobes spaced about the axis for applying a compressive force to the comestible. 
         [0051]    Preferably, the apparatus is in the form of a domestic juice extractor. 
         [0052]    Features described above in connection with the first aspect of the invention are equally applicable to any of the second to twelfth aspects, and vice versa. Features described above in connection with apparatus aspects of the invention are also equally applicable to the method aspect of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0053]    An embodiment of the invention will now be described with reference to the accompanying drawings, in which: 
           [0054]      FIG. 1  is a perspective view of a juice extractor according to the present invention; 
           [0055]      FIG. 2  is a section through the juice extractor of  FIG. 1 ; 
           [0056]      FIG. 3  is a perspective view of a juicing chamber of the juice extractor of  FIG. 1 ; 
           [0057]      FIG. 4  is a plan view of the juicing chamber of  FIG. 3 ; 
           [0058]      FIG. 5  is a section through the juicing chamber of  FIG. 3  taken along the line A-A of  FIG. 4 , and with a flexible member and a removable liner located therein; 
           [0059]      FIG. 6  is a perspective view of the flexible member of  FIG. 5 ; 
           [0060]      FIG. 7  is a side view of the flexible member of  FIG. 6 ; 
           [0061]      FIG. 8  is a section through the flexible member of  FIG. 6  taken along the line B-B of  FIG. 7 ; 
           [0062]      FIG. 9  is a magnified view of a part of  FIG. 8 ; 
           [0063]      FIG. 10  is a perspective view of a removable liner forming part of the juicing chamber shown in  FIG. 5 ; 
           [0064]      FIG. 11  is a plan view of the removable liner of  FIG. 10 ; 
           [0065]      FIG. 12  is a section through the removable liner of  FIG. 10  taken along the line C-C of  FIG. 11 ; 
           [0066]      FIG. 13  is a perspective view of a lower chassis of the juice extractor of  FIG. 1 ; 
           [0067]      FIG. 14  is a front view of the lower chassis of  FIG. 13 ; 
           [0068]      FIG. 15  is a side section of the lower chassis of  FIG. 13  taken along the line D-D of  FIG. 14 ; 
           [0069]      FIG. 16  is a schematic of a hydraulic circuit forming a part of the juice extractor of  FIG. 1  in a first mode; 
           [0070]      FIG. 17  is a schematic of the hydraulic circuit of  FIG. 16  in a second mode; 
           [0071]      FIG. 18  is a perspective view of a flexible reservoir forming part of the juice extractor of  FIG. 1 ; 
           [0072]      FIG. 19  is a plan view of the flexible reservoir of  FIG. 18 ; 
           [0073]      FIG. 20  is a side view of a reversible valve removed from the remainder of the juice extractor; 
           [0074]      FIG. 21  is a section taken along the line E-E of  FIG. 20  showing the reversible valve in a first mode of operation; 
           [0075]      FIG. 22  is a section taken along the line E-E of  FIG. 20  showing the reversible valve in a second mode of operation; 
           [0076]      FIG. 23  is a section through the juice extractor of  FIG. 1  showing a juice collection unit in a first configuration; 
           [0077]      FIG. 24  is a section through the juice extractor of  FIG. 1  showing the juice collection unit in a second configuration; 
           [0078]      FIG. 25  is a perspective view of the juice extractor of  FIG. 1  showing an access door in an open configuration; 
           [0079]      FIG. 26  is a side section through the juice extractor as shown in  FIG. 25 ; and 
           [0080]      FIG. 27  is a section through the flexible member similar to  FIG. 8  but showing the flexible member in an expanded state. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0081]      FIG. 1  illustrates a juice extractor  10  according to the present invention. The juice extractor  10  is in the form of a small domestic appliance and is appropriate for domestic use, for example in a kitchen environment. The juice extractor  10  has a substantially cuboid outer casing  12 . The outer casing has an upper surface  14  and a front surface  16 . A spout  18  is located in the front surface  16  of the outer casing  12 . The spout  18  is extendible to dispense juice from the juice extractor  10 . However, in  FIG. 1  the spout  18  is shown in a retracted position in which the spout  18  is stored within the outer casing  12  of the juice extractor  10 . 
         [0082]    An access door  20  is formed in the outer casing  12 . The access door  20  is L-shaped and forms a part of both the upper and front surfaces  14 ,  16  of the outer casing  12 . The access door  20  has a hinge  22  adjacent the upper surface  14  to enable it to be pivotably opened in an upward direction. When the access door  20  is open, comestibles (for example, fruit or vegetables) can be inserted into the interior of the juice extractor  10  for juicing. The juice extractor  10  has a control panel  24  located on the upper surface  14  for operating the juice extractor  10 . 
         [0083]      FIG. 2  is a section through the juice extractor  10  showing the internal components in more detail. The juice extractor  10  comprises a juicing unit  100 , a pump arrangement  200 , a hydraulic reservoir assembly  300  and a juice collection unit  400 . 
         [0084]      FIGS. 3 and 4  illustrate a juicing chamber  102  of the juicing unit  100 . The juicing chamber  102  has a chamber wall  104 . The chamber wall  104  has a cylindrical upper portion  105  and a domed base portion  106 . Returning to  FIG. 2 , a closure member  108  is provided for closing an open upper end of the chamber  102  during a juicing operation. The closure member  108  is connected to the access door  20  so that the closure member  108  pivots upwardly with the access door  20  when the access door  20  is opened. This will be described in more detail later. 
         [0085]    The closure member  108  seals the upper end of the chamber wall  104  by means of three lugs  110  located on the outer periphery of the closure member  108  which engage with cooperating grooves  112  formed in the upper end of the chamber wall  104 . The lugs  110  engage with the grooves  112  in a bayonet-type fitting by means of relative rotation between the closure member  108  and the chamber  102 . 
         [0086]    Relative rotation between the chamber  102  and the closure member  108  is achieved by means of a motor and bearing assembly  114  located below the chamber  102 . The motor and bearing assembly  114  is located in a sealed position below the chamber  102 , away from potential contamination from extracted juice and solids. This improves the robustness of the appliance and provides further safety for the user, because the motor and bearing assembly  114  is hidden below the chamber  102 , reducing the risk of injury to a user through accidental contact with these components. In this embodiment the motor and bearing assembly  114  rotates the chamber  102  about an axis X-X shown in  FIG. 5 . This enables the closure member  108  to be sealed to the chamber  102 . 
         [0087]      FIG. 5  illustrates a movable member  116  located within the chamber  102 . The movable member  116  is attached to the chamber wall  104  by two annular rings  118 ,  120  integral therewith, and substantially conforms to the inner surface of the chamber  102 .  FIGS. 6 to 9  illustrate the movable member  116  removed from the chamber  102 . 
         [0088]    The movable member  116  is formed from a flexible, hard-wearing plastic material such as polyurethane. It is preferred that the movable member  116  is formed in one piece, although this is not essential. The movable member  116  comprises an inner, cavity wall  122  having a cylindrical portion  123  and a domed base portion  124 , and an outer wall  126 . The outer wall  126  is located concentric with, and spaced from, the cavity wall  122  in the radial direction. The cavity wall  122  and the outer wall  126  are integral with one another and connected by a connecting portion  128  located at an upper end of the movable member  116 . The cavity wall  122 , the outer wall  126  and the connecting portion  128  are arranged such that the cavity wall  122  of the movable member  116  appears to have been folded back on itself to form the outer wall  126 . In this embodiment, the cavity wall  122  and outer wall  126  are spaced by 1 mm to form a narrow annular pocket  130  therebetween. The annular pocket  130  has a sealed upper end, and an open lower end. The purpose of the annular pocket  130  will be described later. 
         [0089]    A plurality of ribs  132  are formed between the cavity wall  122  and outer wall  126 . The ribs  132  form a part of the movable member  116  and are formed integrally with the cavity wall  122  and the outer wall  126 . In this embodiment, five ribs  132  are provided. The ribs  132  extend parallel to, and are equi-spaced about, the axis X-X. The ribs  132  extend between the cavity wall  122  and the outer wall  126  and function as restraining members which tether the cavity wall  122  to the outer wall  126  at a plurality of spaced restraining locations. 
         [0090]    The two annular securing rings  118 ,  120  are formed on the outer periphery of the outer wall  126  at the upper end and at the lower end thereof respectively. The securing rings  118 ,  120  secure the movable member  116  to the chamber wall  104  of the chamber  102  in a fluid-tight manner. 
         [0091]    Referring back to  FIG. 5 , the cavity wall  122  of the movable member  116  delimits the chamber  102  into two cavities, namely a comestible cavity  134  and a fluid cavity  136 . The fluid cavity  136  is delimited at a lower end by the domed base portion  124  of the cavity wall  122  and the domed base portion  106  of the chamber wall  104 , and at an upper end by the cavity wall  122  and the outer wall  126 . The annular pocket  130  thus forms a part of the fluid cavity  136 . The annular securing rings  118 ,  120  ensure that the fluid cavity  136  is sealed tightly. 
         [0092]    Further, the chamber  102  has a shallow step in the region where the cylindrical upper portion  105  of the chamber wall  104  meets the domed base portion  106  of the chamber wall  104 . This ensures that the outer wall  126  lies substantially flush with the domed base portion  106  of the chamber wall  104 , enhancing the sealing therebetween. 
         [0093]    As shown in  FIG. 5 , at rest the domed base portion  124  of the cavity wall  122  substantially conforms to the inner surface of the domed base portion  106  of the chamber wall  104 . The domed base portion  124  of the cavity wall  122  contacts the domed base portion  106  of the chamber wall  104  over the majority of the surface area of the domed base portion  124 . The purpose of this will be described later. 
         [0094]    A removable liner  138  is located within the comestible cavity  134  and is shaped substantially to conform to the inner surface of the cavity wall  122  of the movable member  116 . The removable liner  138  is removable upwardly out of the comestible cavity  134  through the open upper end of the chamber  102 . 
         [0095]    The removable liner  138  is shown in more detail in  FIGS. 10 to 12 . In these figures, the removable liner  138  is shown removed from the remainder of the juice extractor  10 . The liner  138  forms a pocket arranged to receive a comestible. The pocket is sized and shaped to contain the whole of a comestible which may be accommodated within the chamber  102  and to prevent contact between the comestible and the cavity wall  122  when the removable liner  138  is located in the comestible cavity  134 . The removable liner  138  has a cylindrical liner wall  140  with a domed base portion  142 . The liner wall  140  is made from a flexible and washable material. In this embodiment, the liner wall  140  is formed from a thin sheet of polyurethane, which has the added advantage of having a good strength and having a good resistance to tearing. 
         [0096]    The open upper end of the liner  138  has a seating ring  144  moulded therein. The seating ring  144  helps to maintain the substantially cylindrical shape of the removable liner  138  and aids seating the removable liner  138  inside the comestible cavity  134 . 
         [0097]    A cylindrical plate  146  is located in the domed base portion  142  of the removable liner  138 . The cylindrical plate  146  is over-moulded into the removable liner  138 , although this is not essential. The cylindrical plate  146  is made from a more rigid material than the remainder of the liner wall  140 . In this embodiment, the cylindrical plate  146  is made from a rigid plastics material such as Perspex or ABS. Alternatively, the cylindrical plate  146  may be formed from a metallic material. The cylindrical plate  146  functions as a platform to support a comestible and, as described later, as a shield member for protecting the liner wall  140 . 
         [0098]    The removable liner  138  is removable from the comestible cavity  134  for cleaning following a juicing operation. Referring back to  FIG. 5 , when inserted into the comestible cavity  134 , the removable liner  138  is positioned such that the cylindrical plate  146  is located at the base of the comestible cavity  134 . 
         [0099]    A biasing member  148  is located within the fluid cavity  136  and attached to the inner surface of the domed base portion  106  of the chamber wall  104 . In this embodiment, the biasing member  148  is a coil spring biased so as to urge the domed base portion  124  of the cavity wall  122 , and the cylindrical plate  146  of the removable liner  138 , inwardly, that is, towards the centre of the chamber  102 . 
         [0100]    In this embodiment, the biasing member  148  urges the domed base portion  124  of the cavity wall  122  upwardly in an axial direction, i.e. in the direction of the axis X-X passing through the centre of the chamber  102  and about which the chamber wall  104  extends. This is so that a comestible inserted into the comestible cavity  134  is pushed upwardly by the combined action of the biasing member  148  and the hydraulic pressure of the fluid within the fluid cavity  136  at the start of a juicing operation. In other words, the biasing member  148  acts to assist an applied hydraulic force to move the cavity wall  122  inwardly away from the chamber wall  104 . The purpose of this movement will be described later. 
         [0101]    A fluid port  150  is located in the domed base portion  106  of the chamber wall  104  and is arranged to operate as both an inlet and an outlet for fluid. The fluid port  150  is preferably located at, or towards, the base of the chamber  102 , and preferably so that the axis X-X passes through the fluid port  150 . This ensures an even distribution of fluid entering the fluid cavity  136  and an even pressure distribution within the fluid cavity  136 . In this embodiment, the fluid port  150  is arranged symmetrically about the axis X-X. 
         [0102]    A fluid conduit  152  is in communication with the fluid cavity  136  via the fluid port  150  and is arranged both to supply fluid to the fluid cavity  136  and to receive extracted fluid from the fluid cavity  136 . When fluid is introduced into the fluid cavity  136 , the cavity wall  122  of the movable member  116  moves under the action of the applied force generated by the hydraulic pressure of the fluid. This will be described later. The fluid conduit  152  preferably extends along the axis X-X. The fluid conduit  152  also provides an axle for the rotation of the chamber  102  by the motor and bearing assembly  114 . 
         [0103]      FIGS. 13 to 15  illustrate a lower chassis of the juice extractor  10 . In these figures, the juicing unit  100 , the pump arrangement  200  and the hydraulic reservoir assembly  300  are shown in more detail. The fluid cavity  136 , which is part of the juicing unit  100 , the pump arrangement  200  and the hydraulic reservoir assembly  300  form a hydraulic circuit  350 . The hydraulic circuit  350  is illustrated schematically in  FIGS. 16 and 17 . 
         [0104]    The hydraulic circuit  350  contains a hydraulic fluid. In this embodiment, the fluid is water. Water is non-toxic and food safe, making it ideal for use in domestic food preparation equipment such as the juice extractor  10 . However, other fluids suitable for use in a domestic environment may also be used instead of water. Further, additives may be added to the water in the hydraulic circuit  350 , for example anti-bacterial compounds or sterilising compounds which maintain the water in the hydraulic circuit  350  in a sanitary state. 
         [0105]    The hydraulic circuit  350  is sealed and is a closed circuit. By this is meant that an external source of fluid (e.g. a mains water supply) is not required in order to operate the juice extractor  10 —the hydraulic circuit  350  is contained entirely within the juice extractor  10 . As an external source of fluid is not required, the juice extractor  10  can be used in environments where a source of fluid is unavailable or at least not available in a convenient location. Further, because there is no external access to the hydraulic circuit  350  there is a reduced risk of contamination. The risk of contamination is reduced both in terms of contaminants (for example, acidic fruit juices) entering the hydraulic circuit  350 , potentially damaging its internal components, and in terms of safety for a user, whereby the risk of fluid from the hydraulic circuit  350  becoming mixed with juice extracted from a comestible is reduced. 
         [0106]    The pump arrangement  200  is electrically-operated and comprises a first pump  202 , a second pump  204 , a connecting conduit  206 , and a reversible valve  208 . Both of the first pump  202  and the second pump  204  are preferably electrically operated. The first pump  202  is a centrifugal pump arranged to move fluid through the hydraulic circuit  350  and the second pump  204  is an electromagnetically operated piston-type pump arranged to provide up to 15 bar of hydraulic pressure to compress a comestible and extract juice therefrom. The first pump  202  and the second pump  204  are connected in parallel, and are arranged to be operated simultaneously to pump the fluid around the hydraulic circuit  350 . The connecting conduit  206  is a T-piece which connects the pumps  202 ,  204  to the reversible valve  208 . 
         [0107]    With reference to  FIGS. 14 and 15 , the hydraulic reservoir assembly  300  comprises a flexible reservoir  302  providing a source of fluid for pumping around the sealed hydraulic circuit  350 . The flexible reservoir  302  is located towards the base of the lower chassis of the juice extractor  10  and is connected to the pump arrangement  200  by a reservoir conduit  304  extending therefrom. The flexible reservoir  302  is located within a reservoir space  306  formed in the base of the juice extractor  10 . 
         [0108]    The flexible reservoir  302  surrounds a part of the juicing chamber  102  (and thus surrounds a part of the cavity  122 ). This arrangement ensures that the available space within the outer casing  12  of the juice extractor  10  is used efficiently, concomitantly allowing the overall size of the juice extractor  10  to be reduced. 
         [0109]    The flexible reservoir  302  is shown removed from the remainder of the juice extractor  10  in  FIGS. 18 and 19 . The flexible reservoir  302  is substantially U-shaped and has rectangular outer side walls  308  and curved inner walls  310 . A curved upper part  312  of the inner walls  310  is arranged to conform to the shape of the outer surface of the chamber  102 . The reservoir conduit  304  is formed in an inner wall  310  and supplies fluid from the flexible reservoir  302  to the fluid cavity  136  via the pump arrangement  200  and hydraulic reservoir assembly  300 . 
         [0110]    The flexible reservoir  302  is deformable. By this is meant that the flexible reservoir  302  is designed to collapse when the fluid therein is extracted and passed through the hydraulic circuit  350  to the fluid cavity  136 . In order to withstand repeated juicing operations, the flexible reservoir  302  is made from a robust, yet flexible material such as polyurethane. 
         [0111]    When in use, it is necessary for the fluid in the hydraulic circuit  350  to be pumped in both directions between the flexible reservoir  302  and the fluid cavity  136 . During a juicing operation, fluid is pumped in a first direction from the flexible reservoir  302  and into the fluid cavity  136 . This applies a hydraulic force to the cavity wall  122  in order to compress a comestible within the comestible cavity  134 . However, at the end of a juicing operation, it is necessary to deflate the cavity wall  122  to enable the user to remove the remaining parts of the comestible from the comestible cavity  134 . Therefore, the fluid is subsequently pumped in a second direction, opposite to the first direction, from the fluid cavity  136  and back to the flexible reservoir  302 . 
         [0112]    In this embodiment, the presence of the reversible valve  208  enables fluid to be pumped in both first and second directions around the hydraulic circuit  350 . The reversible valve  208  is required because the first pump  202  and the second pumps  204  are only able to pump fluid in a single direction. However, as an alternative, the pumps  202 ,  204  and the reversible valve  208  could be replaced by a pump which is able to pump fluid in two directions, for example a gear pump. 
         [0113]    The reversible valve  208  is shown in  FIGS. 20 to 22 . The reversible valve  208  connects together the flexible reservoir  302 , the fluid cavity  136  and the pumps  202 ,  204 . The reversible valve  208  has first and second modes of operation. In the first mode of operation, the pumps  202 ,  204  operate to pump fluid in the first direction. In the second mode of operation, the pumps  202 ,  204  operate to pump fluid in the second direction. 
         [0114]      FIG. 21  shows the reversible valve  208  in the first mode, and  FIG. 22  shows the reversible valve  208  in the second mode. The reversible valve  208  comprises a reservoir connector  210  connected to the reservoir conduit  304  to convey fluid to and from the flexible reservoir  302 , and a cavity connector  212  connected to the fluid conduit  152  to convey fluid to and from the fluid cavity  136 . A first pump connector  214  is connected to the connecting conduit  206  which leads to the pumps  202 ,  204 , and the second and third pump connectors  216 ,  218  are connected to outlets from the pumps  202 ,  204  respectively. A non-return valve  220  is located between the second and third pump connectors  216 ,  218 . The purpose of the non-return valve  220  will be described later. 
         [0115]    A channel  222  is located within the reversible valve  208  to provide a communication path between the reservoir connector  210  and the pump connectors  214 ,  216 ,  218 , and between the cavity connector  212  and the pump connectors  214 ,  216 ,  218 . A valve body  224  is located in the channel  222  and is moveable therein between a first position (which corresponds to the first mode shown in  FIG. 21 ) and a second position (which corresponds to the second mode shown in  FIG. 22 ). The movement of the valve body  224  is driven by a motor  226  via a rack and pinion gear arrangement  228 . 
         [0116]    The flow path through the hydraulic circuit  350  when the reversible valve  208  is in the first mode is shown in  FIG. 16 . In this mode, the reservoir connection  210  is in fluid communication with the first pump connector  214  which leads to the connecting conduit  206 . The outlets of the pumps  202 ,  204  are connected to the second and third pump connectors  216 ,  218  respectively, which are in fluid communication with the cavity connector  212  so that fluid can flow therethrough to the fluid cavity  136 . 
         [0117]    The flow path through the hydraulic circuit  350  when the reversible valve  208  is in the second mode is shown in  FIG. 17 . In this mode, the cavity connector  212  is in fluid communication with the first pump connector  214  which leads to the connecting conduit  206 . The outlets of the pumps  202 ,  204  remain connected to the second and third pump connectors  216 ,  218  respectively, which are now in fluid communication with the reservoir connector  210  so that fluid can flow therethrough to the flexible reservoir  302 . 
         [0118]    The mechanism by which juice is extracted, from the comestible and supplied to a user will now be described.  FIGS. 23 and 24  illustrate the juice collection unit  400  in two different configurations. Referring first to  FIG. 23 , the juice collection unit  400  is located above the juicing unit  100 . The closure member  108  forms a base for the juice collection unit  400 . The juice collection unit  400  comprises a juice reservoir  402 , a cutter  404  and a cutter drive mechanism  406 . 
         [0119]    The juice reservoir  402  is located between the closure member  108  and the upper surface  14  of the juice extractor  10 . The juice reservoir  402  has a lower portion  408  which is attached to the closure member  108  and an upper portion  410  which is movable with the cutter drive mechanism  406 . A dispensing conduit  412  is connected to the interior of the juice reservoir  402  and is in communication with the spout  18  such that juice can be dispensed from the spout  18 . 
         [0120]    The cutter  404  is shown in a retracted position in  FIG. 23 . The cutter  404  is mounted substantially centrally in the juice reservoir  402  and comprises a hollow cylindrical sleeve  414 . The sleeve  414  has a blade  416  for cutting into a comestible and a plurality of apertures  418 . The apertures  418  are dimensioned and arranged such that juice from the comestible is able to flow out through the apertures  418  into the juice reservoir  402 . 
         [0121]    A plunger  420  is located inside the cylindrical sleeve  414 . The plunger  420  is slidably moveable inside the sleeve  414 . A spring  422  biases the plunger  420  into a position in which it lies at the lower end of the sleeve  414  and substantially level with the lower surface of the closure member  108 . In this position, the plunger  420  lies immediately above the comestible cavity  134  when the closure member  108  is in the closed position. 
         [0122]    In this embodiment the cutter drive mechanism  406  is in the form of a liner drive for moving the cutter  404  relative to the chamber  102  along the axis X-X. The cutter drive mechanism  406  comprises a sleeve drive  424  attached to an upper end of the sleeve  414  and to the upper portion  410  of the juice reservoir  402 . The sleeve drive  424  includes two drive racks  426 ,  428  each located on a respective side of the upper portion  410  of the juice reservoir  402 . The cutter drive mechanism  406  further comprises first and second drive shafts  430 ,  432  each having a respective pinion gear  434 ,  436 . Each pinion gear  434 ,  436  engages with a respective drive rack  426 ,  428 . The drive shafts  430 ,  432  are connected to a cutter motor  438  (shown in  FIG. 26 ). By providing two separate drive shafts  430 ,  432 , the cutter motor  438  applies an equal and opposite torque to each drive shaft  430 ,  432 . This results in no net applied torque when the cutter motor  438  is operated, reducing the load applied to the structure of the juice extractor  10 . 
         [0123]    The cutter drive mechanism  406  is thus arranged to move the cutter  404  (including the sleeve  414 , the sleeve drive  424  and the upper portion  410  of the juice reservoir  402 ) along the axis X-X between the retracted position and an extended position.  FIG. 24  illustrates the cutter  404  in an extended position. The extended position is used during juice extraction from a comestible. When the cutter  404  is in the extended position, the sleeve  414  cuts into and penetrates a comestible, for example a fruit  450 , so that juice can be extracted therefrom. 
         [0124]      FIGS. 25 and 26  illustrate the juice extractor  10  with the access door  20  in an open position to allow a comestible to be inserted into the comestible cavity  134 . The juice reservoir  402 , the cutter  404  and a part of the cutter drive mechanism  406  move with the access door  20  when it is pivotably opened and closed. However, the cutter motor  438  is located within the outer casing  12  of the juice extractor  10  and does not move with the access door  20 . The cutter drive mechanism  406  separates into two separate portions when the access door  20  is lifted. Each of the drive shafts  430 ,  432  is formed in two separable portions  440 ,  442  connectable by a ball which engages with a hexagonal drive dog. This arrangement does not require the cutter motor  438  to be mounted on the access door  20 , which reduces the weight of the access door  20 . Further, it improves the safety of the juice extractor  10  because the cutter  404  cannot be operated by the cutter motor  438  when the access door  20  is opened. 
         [0125]    When the access door  20  is in this position, the juice reservoir  402  is removable for cleaning. The juice reservoir  402  can be secured to the access door  20  by any suitable means, such as clips, screws or a push fit arrangement (not shown), which enable the juice reservoir  402  to be readily disconnected from, and reconnected to, the access door  20  by the user. 
         [0126]    In use, a user presses a button on the control panel  24  to release the access door  20 . The access door  20  pivots upwardly about the hinge  22 , revealing the internal parts of the juice extractor  10 . The access door  20  is L-shaped and is spring loaded so that the access door  20  opens easily without undue effort from the user. When pivoted upwardly, the separable portions  440 ,  442  of each of the drive shafts  430 ,  432  separate so that the cutter  404  is disengaged from the cutter motor  438 . This can be seen most clearly in  FIGS. 25 and 26 . 
         [0127]    The following description relates to the juicing of a fruit, such as an orange. However, this is not to be taken as limiting and other comestibles may also be juiced in a similar way. 
         [0128]    Once the access door  20  is open (as shown in  FIGS. 25 and 26 ), the juicing chamber  102  is exposed and visible to the user. The user now has access to the comestible cavity  134 . The removable liner  138  is located inside the comestible cavity  134  and substantially conforms to the shape of the movable member  116  which defines the comestible cavity  134 . The domed base portion  142  of the liner wall  140  conforms to the domed base portion  124  of the cavity wall  122 . The domed base portions  124 ,  142  are of sufficient diameter to receive a fruit such as a large orange or grapefruit. 
         [0129]    The user then places a fruit  450  within the removable liner  138  located in the comestible cavity  134 . Alternatively, the user can lift the removable liner  138  from the comestible cavity  134  and insert the fruit  450  therein before replacing the removable liner  138  within the comestible cavity  134 . When located in the comestible cavity  134 , the fruit  450  will sit at the domed base portion  142  of the removable liner  138  so that the fruit  450  is surrounded by the removable liner  138  and the cavity wall  122 . 
         [0130]    Once the fruit  450  has been loaded into the comestible cavity  134 , the user closes the access door  20  and operates the juice extractor  10  using the control panel  24 . When the juice extractor  10  starts a juicing operation, the spout  18  extends from within the outer casing  12 . When in an extended position, the spout  18  projects from the outer casing  12 . This allows extracted juice to be dispensed from the spout  18  into a suitable receptacle such as glass or mug. 
         [0131]    When the access door  20  is closed, the closure member  108  is positioned directly above the chamber  102 . The chamber  102  is then rotated by the motor and bearing arrangement  114  to secure the closure member  108  to the chamber  102  through engagement of the lugs  110  with the grooves  112  in a bayonet-type fashion. This ensures that the closure member  108  cannot be opened accidentally by the user during a juicing operation, for example by opening the access door  20 . 
         [0132]    Once the closure member  108  is secured to the chamber  102 , the pumps  202 ,  204  are operated. The reversible valve  208  is placed in the first mode of operation so that the fluid flows in the first direction when the pumps  202 ,  204  are operated. Fluid from the flexible reservoir  302  is drawn along the reservoir conduit  304  to the reservoir connector  210 . With the valve body  224  in the first position, the fluid passes through the channel  222  to the first pump connector  214  and thereon to the connecting conduit  206 . 
         [0133]    Fluid exhausted from the outlets of the pumps  202 ,  204  flows back into the reversible valve  208  through the second and third pump connectors  216 ,  218  respectively. In the first position of the valve body  224 , the second and third pump connectors  216 ,  218  are placed in fluid communication with the cavity connector  212  so the fluid passes through part of the channel  222  to the cavity connector  212 , and is subsequently conveyed to the fluid cavity  136  by the fluid conduit  152 . 
         [0134]    When fluid enters the fluid cavity  136 , the fluid will initially fill the free space within the fluid cavity  136  without changing the shape thereof. During this phase, the non-return valve  228  functions to allow fluid flow from both pumps  202 ,  204  to pass through to the fluid cavity  136 . However, once the fluid cavity  136  is filled with fluid, the pressure in the system increases. As mentioned previously, the second pump  204  is able to generate a pressure of up to 15 bar, whereas the first pump  202  has a maximum pressure delivery of only around 2 bar. When the pressure in the hydraulic circuit  350  exceeds pressure which can be delivered by the first pump  202 , a pressure differential is created between the second and third pump connectors  216 ,  218 . This pressure differential causes the non-return valve  228  to close thereby isolating the second pump connector  216  from the cavity connector  212 . The second pump  204  remains in fluid communication with the cavity connector  212  and so acts to pressurise the fluid in the fluid cavity  136  up to a maximum deliverable pressure of 15 bar. 
         [0135]    The hydraulic pressure of the fluid in the fluid cavity  136  exerts a force on the movable member  116 . This force will act through the point of least resistance. The fluid port  150  (through which the fluid enters the fluid cavity  136 ) is located at the base of the chamber  102 . Therefore, the initial force on the cavity wall  122  will be at the domed base portion  124  thereof. This effect is enhanced by the close contact between the domed base portion  124  of the cavity wall  122  and the domed base portion  106  of the chamber wall  104  because only a small volume of fluid is required to fill the region of the fluid cavity  136  therebetween before deformation of the cavity wall  122  occurs. 
         [0136]    Additionally, the biasing member  148  urges the domed base portion  124  of the cavity wall  122  upwardly, working with the applied hydraulic force to deform the cavity wall  122 . The biasing member  148  is located such that the biasing member  148  applies a force to the cylindrical plate  146  forming a part of the removable liner  138 . 
         [0137]    The overall effect of the forces acting on the movable member  116  is that the domed base portion  124  of the cavity wall  122  will initially deform upwardly. This action raises the fruit  450  in the comestible cavity  134  until the fruit  450  is held firmly between the domed base portion  124  of the movable member  116  and the underside of the closure member  108 . This ensures that the fruit  450  does not move sideways relative to the axis X-X when the sleeve  414  of the cutter  404  commences its downward motion from the retracted position into the extended position. 
         [0138]    As fluid is pumped into the fluid cavity  136 , the hydraulic pressure will force fluid into the annular pocket  130  between the concentrically-arranged cylindrical upper portion  123  of the cavity wall  122  and the outer wall  126 . The hydraulic pressure will urge the cylindrical upper portion  123  of the cavity wall  122  and the outer wall  126  apart. In this embodiment, the spacing of 1 mm between the cylindrical upper portion  123  of the cavity wall  122  and the outer wall  126  enables the fluid to flow easily therebetween but allows the annular pocket  130  to have a relatively small volume. This reduces the time required to fill the annular pocket  130  with fluid before deformation of the cylindrical upper portion  123  of the cavity wall  122  occurs. 
         [0139]    Usefully, the fluid will apply a force to the outer wall  126  in the direction of the chamber wall  104 . This reduces the risk of leakages occurring and ensures that a good seal is formed between the cylindrical upper portion  105  of the chamber wall  104  and the outer wall  126  of the movable member  116  when the pressure within the fluid cavity  136  is relatively high. By urging the outer wall  126  against the chamber wall  104 , a more reliable seal can be achieved than with conventional seals which connect at a single point and so would be pulled apart from the chamber wall  104  when under pressure. 
         [0140]    Parts of the cylindrical upper portion  123  of the cavity wall  122  are attached to the outer wall  126  by the ribs  132 . These parts of the cylindrical upper portion  123  of the cavity wall  122  are restrained, or held, relative to the chamber  102 . In other words these parts of the cylindrical upper portion  123  of the cavity wall  122  do not move, or only move by a relatively small amount, relative to the chamber  102  when the hydraulic force is applied to the cavity wall  122 . It will be appreciated by those skilled in the art that, because the ribs  132  are manufactured from polyurethane, some movement is inevitable due to the elastic properties of such a plastics material. 
         [0141]    However, the parts of the cylindrical upper portion  123  of the cavity wall  122  between the ribs  132  are able to move to a greater degree under the applied hydraulic force. These parts expand towards the centre of the comestible cavity  134  in a balloon-like fashion to form a plurality of lobes  460  spaced about the axis X-X (the lobes can be seen in a fully expanded state in  FIG. 27 ). The lobes  460  will continue to expand until the fruit  450  is held firmly in a radial direction by the expanded lobes of the cylindrical upper portion  123  of the cavity wall  122 . We have found that approximately 0.5 bar of pressure in the hydraulic circuit  350  is required to hold the fruit  450  firmly within the chamber but not to compress it to any significant degree. When this pressure is reached, the pumps  202 ,  204  stop temporarily. 
         [0142]    An advantage of using a hydraulic arrangement is that substantially the same pressure is required to hold fruit of different sizes. This is because the applied hydraulic force will be distributed evenly around the cavity wall  122  of the movable member  116 . 
         [0143]    The cutter motor  438  is then activated to drive the sleeve  414  of the cutter  404  into the fruit  450 . The blade  416  located on the sleeve  414  is sharp enough to cut through the skin of the fruit  450  and to penetrate the flesh. The sleeve  414  will continue to penetrate the interior of the fruit  450  until it reaches the extended position (as shown in  FIG. 24 ). As the sleeve  414  penetrates the fruit  450 , a part of the fruit  450  (known as the core) will enter the hollow interior of the sleeve  414  and will push the plunger  420  upwardly. 
         [0144]    It is possible that, in some circumstances, the sleeve  414  may move too far along the axis X-X and contact the domed base portion  124  of the cavity wall  122 , for example, if a small fruit is being juiced. If the cavity wall  122  were to be cut by the blade  416 , the juice extractor  10  would no longer function as hydraulic fluid would simply leak from the hydraulic circuit  350 . Further, there is a risk of contamination of any extracted juice by the water leaking from the hydraulic circuit  350 . 
         [0145]    The cylindrical plate  146  formed in the removable liner  138  is arranged to prevent such an occurrence. The cylindrical plate  146  is made from a solid plastic material which cannot be penetrated by the blade  416 . In other words, the cylindrical plate  146  functions as a shield member to inhibit the blade  416  of the cutter  404  from contacting the cavity wall  122  of the movable member  116 . Therefore, should the sleeve  414  travel too far down into the comestible chamber  134 , the blade  416  will impinge upon the cylindrical plate  146  to prevent the blade  416  from puncturing the movable member  116 . 
         [0146]    Once the cutter  404  is located in the extended position projecting into the cavity  134 , the pumps  202 ,  204  are operated again in the first direction to generate further hydraulic pressure in the fluid cavity  136  and to expand further the lobes  460  of the cylindrical upper portion  123  of the cavity wall  122 . This applies a force to the fruit  450  which is greater than that used to grip the fruit  450  before operation of the cutter  404 . With the types of pumps  202 ,  204  described above, up to 15 bar of pressure can be applied to extract juice from the fruit  450  within the comestible cavity  134 . 
         [0147]      FIG. 27  shows a section through the movable member  116  when the cylindrical upper portion  123  of the cavity wall  122  is in a fully expanded configuration. The five ribs  132  are equi-spaced from one another about the axis X-X and define five expanded lobes  460  therebetween formed by the inflated cylindrical upper portion  123  of the cavity wall  122 . The lobes  460  expand at substantially the same rate under the applied hydraulic force. This is because the hydraulic force is evenly distributed around the cylindrical upper portion  123  of the cavity wall  122 . 
         [0148]    The lobes  460  of the cylindrical upper portion  123  of the cavity wall  122  reduce the volume of the comestible cavity  134  and concomitantly crush the fruit  450  located therein. The lobes  460  compress the fruit  450  in an approximately radial direction. However, other parts of the movable member  116  will apply a force to the fruit  450  in different directions; for example, the domed base portion  124  of the cavity wall  122  will apply a substantially axial force, that is a force along axis X-X, at the lowermost end thereof. 
         [0149]    The use of the five ribs  132  results in five expanding lobes  460  being formed by the cavity wall  122  to enable the fruit  450  to be compressed in a controlled manner. By this is meant that an approximately even force will be applied around the periphery of the fruit  450 , irrespective of variations in the structural integrity of the skin or internal parts of the fruit  450 . The ribs  132  thus prevent one part of the cavity wall  122  from expanding significantly more than the other parts, which would lead to an uncontrolled collapse. 
         [0150]    As an example, a citrus fruit such as an orange is a non-uniform sphere. A part of the skin of the orange may be thinner, softer or weaker than the remainder of the skin. If the ribs  132  were not present, then the applied hydraulic force would be focussed at the weakest point on the surface of the orange and the initial collapse would be at this point. The result will be a non-uniform collapse centred on the weak spot of the orange. As a result, other regions of the orange may not experience sufficient force to extract the juice contained therein, reducing the yield of juice obtainable from the fruit. 
         [0151]    By use of the juice extractor  100 , a significantly greater amount of juice can be extracted from the fruit. In the case of an orange, an optimum yield of 40-45% by weight can be achieved. Further juice extraction is not desirable, because peel oils in the skin of the fruit may be extracted and become mixed with the juice, giving a bitter taste to the extracted juice. In this respect, a further advantage of the described arrangement is that the evenly-applied hydraulic pressure results in a controlled collapse which is less likely to break the skin of the fruit. Therefore, extraction of peel oils from the skin of the fruit is less of a problem. 
         [0152]    The applied hydraulic pressure from the fluid in the fluid cavity  136  forces the juice from the fruit  450 . Since the comestible cavity  134  is sealed by the movable member  116  and the closure member  108 , the only outlet for juice from the cavity is through the apertures  418  in the sleeve  414  of the cutter  404 . Consequently, juice pushes the plunger  420  upwardly and then flows up into the juice reservoir  402 . From the juice reservoir  402 , the juice flows by gravity along the dispensing conduit  412  to the spout  18 . The juice then flows out of the spout  18  into the receptacle provided by the user. 
         [0153]    Once the juice within the fruit  450  has been extracted, the pressure within the interior of the fruit  450 , and within the comestible cavity  134 , will reduce. This causes the plunger  420  to move downwardly under the action of the spring  422 . This action pushes the core of the fruit  450  (which is forced into the interior of the sleeve  414  when the cutter  404  moves from the retracted position into the extended position) out of the interior of the sleeve  414  and back inside the husk of the fruit  450 . This is convenient for the user to dispose of because there is only a single item to throw away. 
         [0154]    Once a juicing operation is completed, the user may wish to commence another juicing operation immediately. In order to commence a further juicing operation, the husk of the juiced fruit  450  must first be removed and another comestible (for example, another fruit) placed in the juicing unit  100  of the juice extractor  10 . In order to allow convenient access to the husk, the motor  226  and gear arrangement  228  of the reversible valve  208  is driven to move the valve body  224  into the second mode so that the hydraulic circuit  350  is in the configuration shown in  FIG. 17 . The pumps  202 ,  204  are then operated in order to pump fluid in the second direction to remove fluid from the fluid cavity  136 . Fluid is pumped from the fluid cavity  136  back to the flexible reservoir  302  which will then inflate as the fluid is returned thereto. 
         [0155]    As the pressure in the fluid cavity  136  and the amount of fluid in the fluid cavity  136  are reduced, the lobes  460  formed in the cylindrical upper portion  123  of the cavity wall  122  by the applied hydraulic force will gradually contract and the comestible cavity  134  will concomitantly expand. After a short period, sufficient fluid will have been removed from the fluid cavity  136  so that the movable member  116  is returned back to its natural shape as shown in  FIG. 2 . 
         [0156]    The chamber  102  is then rotated by the motor and bearing arrangement  114  relative to the closure member  108  to disengage the lugs  110  from the grooves  112  to release the closure member  108  from the chamber  102 . The access door  20  can then be opened by the user by lifting the access door  20  so that the access door  20  pivots upwardly about the hinge  22  to reveal the comestible cavity  134 , as shown in  FIGS. 25 and 26 . 
         [0157]    The comestible cavity  134  has by now expanded sufficiently that the user can manually remove the husk of the fruit  450  from the comestible cavity  134 . As a variation, it could be arranged for a small amount of hydraulic pressure to be retained in the fluid cavity  134  so that the domed base portion  124  of the cavity wall  122  lifts the husk of the fruit upwardly such that the husk is easily graspable by a user. Another fruit can then be inserted into the comestible cavity  134  for juicing, as described above. 
         [0158]    As mentioned above, parts of the juice extractor  10  may be removed therefrom for cleaning. With the access door  20  open, the user can grasp the removable liner  138  by the seating ring  144  located at the upper end thereof. The seating ring  144  is moulded from thicker polyurethane than the remainder of the removable liner  138  and helps to maintain the shape of the removable liner  138  and provide a graspable surface for the user. The user can then pull the removable liner  138  away from the inner surface of the cavity wall  122 . Any juice or comestible remaining in the chamber  102  will be removed with the removable liner  138  and so the movable member  116  will not require cleaning. 
         [0159]    The removable liner  138  can be cleaned either by manual cleaning in clean water or by cleaning in a dishwasher. If the removable liner  138  becomes damaged, torn or cracked, it can simply be thrown away and replaced. Therefore, the removable liner  138  forms a sacrificial protective layer which protects the movable member  116  from dirt, wear and tear. Consequently, there should be no need to replace the movable member  116  during the lifetime of the juice extractor  10 . 
         [0160]    As previously mentioned, the juice reservoir  402  is also removable for cleaning after a juicing operation. 
         [0161]    It will be understood that the invention is not to be limited to the precise details described above. Other variations and modifications will be apparent to the skilled reader. 
         [0162]    A variety of comestibles may be juiced. The term “comestible” is to be interpreted broadly and is intended to cover all juice-bearing foodstuffs; for example, fruits, vegetables, meats, fungi, plants and herbs. 
         [0163]    There need not be five expandable lobes formed in the cavity wall  122 , nor need there be five ribs  132 . In order to achieve a controlled compression of the comestible, at least three lobes are desired. However, any number above three may be provided. 
         [0164]    Further, the lobes (and ribs) need not be equi-spaced about the axis of the chamber. The spacing between the lobes (and the ribs) may be varied as appropriate; for example, to achieve a specific type of controlled compression. 
         [0165]    The cavity wall may also include an imprinting arrangement. A sign (for example, a logo, lettering or an image) may be formed in relief on the cavity wall, i.e. the sign may take the form of a raised projection in the cavity wall. In this manner, when a comestible is juiced, the sign will be formed on the outer surface of the comestible as hydraulic pressure is applied to the cavity wall. Alternatively, the imprinting arrangement may take the form of an item insertable into the cavity which is forced against the outer surface of the fruit during a juicing operation, leaving an imprint thereon. 
         [0166]    The biasing member may take a form other than a coil spring. Whilst a resilient member (such as a spring or other suitable part under tension) is preferred, other biasing members may be used. For example, a solenoid could be used to urge the base of the cavity wall. Alternatively, a second hydraulic circuit or arrangement could be used. 
         [0167]    Further, the biasing member need not be located at the base of the chamber and need not apply an upward force. The biasing member could be located anywhere within the chamber or the cavity, and could apply a force at any point in the chamber or cavity where it is required. However, it is desired that the biasing member applies a force in a substantially inward direction relative to the cavity such that the biasing member assists the applied hydraulic force in moving the cavity wall. 
         [0168]    The closure member need not form part of the access door. A separate closure member may be provided, which may be released by a user once the access door has been opened. Alternatively, the closure member may be formed in the outer casing of the juice extractor. 
         [0169]    Whilst it is desired that the closure member and chamber secure to one another by relative rotation, it is merely preferred that the chamber rotates relative to the closure member. Alternatively, the closure member may rotate relative to the chamber, either manually or by mechanical or electrical means. 
         [0170]    Other securing mechanisms may be used; for example, bolts, pins, cams or locks which are engaged by relative rotation between the closure member and the chamber. Additionally, if lugs and grooves are to be used in a bayonet type fitting, then the positions of these could be reversed, i.e. the lugs may be located on the chamber and the grooves in the closure member. Additionally, the closure member need not be at the upper end of the chamber and may be located at the base or side of the chamber. 
         [0171]    Alternative mechanisms for preventing the cutter from damaging the cavity wall may be used. There need not be a cylindrical plate located, in use, below the cutter. Instead, a detector may be used to detect the position of the cutter relative to the cavity wall. This could be achieved by any one of the following examples: a photodetector, a torque detector which detects an increased torque when the cavity wall is contacted, a fluid meter which monitors how much fluid has been introduced into the fluid cavity (and, hence, can determine the position of the cavity wall therefrom), and an arrangement which limits the amount of fluid available in the reservoir.