Method and system for drying moulded fibre receptacle

Abstract

Method and apparatus for drying a moulded fibre receptacle 22 by directing energy 56 from a heating device 38 disposed at least partially inside the moulded fibre receptacle 22 to an inner surface 46

Description

TECHNICAL FIELD The present invention relates to methods and systems of drying moulded fibre receptacles. The receptacles may form consumer packaging, such as bottles, useful for holding liquids, powders, other flowable materials or solid objects. BACKGROUND It is desirable to reduce plastics use in consumable items, particularly packaging. Trays and other simple shapes are commonly made from paper pulp, but more complex objects, such as bottles, are more difficult to engineer. During a process for forming a fibre receptacle, a moulded fibre receptacle formed from a fibre suspension may be dried by heating the moulded fibre receptacle in a bake oven. It is desirable to provide a method for drying a moulded fibre receptacle which is faster and / or more efficient than heating the moulded fibre receptacle using a bake oven. SUMMARY According to a first aspect of the present invention, there is provided a method of drying a moulded fibre receptacle, the method comprising directing energy from a heating device disposed at least partially inside the moulded fibre receptacle to an inner surface of the moulded fibre receptacle. By using a heating device disposed inside a moulded fibre receptacle, the moulded fibre receptacle may be dried in a faster and / or more efficient way than, for example, heating the moulded fibre receptacle from the outside using a bake oven. Using a heating device disposed inside the moulded fibre receptacle may also prevent discolouration of the moulded fibre receptacle. In some examples, the moulded fibre receptacle is a bottle. In some examples, the method comprises holding the moulded fibre receptacle with a support. The directing energy to the inner surface of the moulded fibre receptacle comprises performing a heating process comprising: directing energy from the heating device to an inner surface of a neck portion of the moulded fibre receptacle according to a first set of heating process characteristics; and directing energy from the heating device to an inner surface of a body portion of the moulded fibre receptacle according to a second set of heating process characteristics different from the first set of heating process characteristics, wherein the neck portion is narrower than the body portion along a first axis. By heating the body portion according to a different set of heating process characteristics to those used to heat the neck portion, respectively different characteristics of the neck portion and body portion can be taken into account during the heating process. Optionally, the method comprises selecting the first and second sets of heating process characteristics so that the heating process provides a greater amount of heat, per unit distance along a second axis, to the inner surface of the body portion than to the inner surface of the neck portion, the second axis being perpendicular to the first axis. By providing a greater amount of heat per unit distance to the body than the neck overheating of the neck due to its narrower width may be reduced, and energy efficiency may be improved. Optionally, the method comprises selecting the first and second sets of heating process characteristics so that the heating process provides a substantially uniform distribution of heat across the inner surface of the neck portion and the inner surface of the body portion. By using a substantially uniform distribution of heat, the drying of the moulded fibre receptacle may be consistent across the neck portion and the body portion. Optionally, the first and second sets of heating process characteristics comprise first and second heating durations respectively, and the first heating duration is less than the second heating duration. By spending less time directing heat to the neck portion than the body portion, the amount of energy directed to the neck portion may be reduced. Optionally, the method comprises moving the moulded fibre receptacle relative to the heating device during the heating process, so that the first heating duration is less than the second heating duration. By moving the moulded fibre receptacle relative to the heating device, the time spent directing heat to the neck portion relative to the body portion may be controlled. Optionally, the first and second sets of heating process characteristics comprise first and second heating powers associated with the heating device respectively, and the first heating power is less than the second heating power. By directing different amounts of heating power to the neck portion and the body portion, an even temperature distribution across the neck portion and the body portion may be achieved. Optionally, directing energy from the heating device to the inner surface of the neck portion is performed in a first time interval, directing energy from the heating device to the inner surface of the body portion is performed in a second time interval, and the heating process comprises changing a heating power of the heating device between the first heating power and the second heating power at a time between the first time interval and the second time interval. By changing the heating power from the first heating power to the second heating power or vice versa during the heating process, the amount of energy directed to the neck portion relative to the body portion may be controlled in a simple way. Optionally, the inner surface comprises a coating, the coating comprising a solvent, and the directing energy to the inner surface of the moulded fibre receptacle causes the solvent to be removed from the coating. For example, the directing energy to the inner surface of the mould fibre receptacle causes at least some of the solvent to be removed from the coating, optionally substantially all of the solvent to be removed from the coating. By removing the solvent from the coating using a heating device disposed inside the moulded fibre receptacle, the coating may be dried in a fast and / or efficient way. According to a second aspect of the present invention, there is provided a method of forming a fibre receptacle, comprising drying the fibre receptacle by a method according to the first aspect. Forming a fibre receptacle using the disclosed drying method may allow a fibre receptacle to be formed in a faster and / or more efficient way. The forming method may comprise at least one additional process. The at least one additional process may comprise applying a closure to the fibre receptacle. In some examples, the method is a method of forming a bottle. In some examples, the fibre receptable is a bottle. According to a fourth aspect of the present invention, there is provided a moulded fibre receptacle drying system comprising: a support configured to support a moulded fibre receptacle; and a heating device, wherein the moulded fibre receptacle drying system is configured to insert at least part of the heating device into the moulded fibre receptacle when the moulded fibre receptacle is held by the support, and to operate to dry the moulded fibre receptacle by a method according to the first aspect. In some examples, the moulded fibre receptacle drying system is a bottle drying system for drying a bottle. Optionally, the heating device is substantially rotationally symmetric about an axis of the heating device. Using a rotationally symmetric heating device may enable an even distribution of heat along the inner surface of the moulded fibre receptacle. For example, the heating device may comprise a linear bulb. Using a linear bulb may provide a simple design that achieves rotational symmetry. Optionally, the support is configured to support the moulded fibre receptacle such that the moulded fibre receptacle is substantially rotationally symmetric about the axis of the heating device. Holding the moulded fibre receptacle so that its axis of symmetry is aligned with the axis of the heating device may improve the uniformity of the distribution of heat across the inner surface of the moulded fibre receptacle. Optionally, the heating device comprises a radiative bulb. A radiative bulb is a simple and efficient way of providing heat, as opposed to, for example, a water radiator or a gas burning device. Optionally, the radiative bulb comprises two terminals, and the moulded fibre receptacle drying system is configured to insert at least part of the heating device into the moulded fibre receptacle such that the radiative bulb is disposed partially inside the moulded fibre receptacle and the two terminals are disposed outside the moulded fibre receptacle. The terminals of the radiative bulb being disposed outside of the moulded fibre receptacle may allow for a simpler design of a drying apparatus including the heating device, as opposed to, for example, a radiative bulb which has one terminal inside the moulded fibre receptacle during the heating process, and a trailing wire inside the moulded fibre receptacle. Optionally, the radiative bulb may comprise two substantially straight segments and a connecting segment coupling the two substantially straight segments, each substantially straight segment protruding from a respective one of the two terminals. Optionally, the heating device comprises a plurality of radiative bulbs, each of the plurality of radiative bulbs comprising two substantially straight segments and a connecting segment coupling the two substantially straight segments, each substantially straight segment protruding from a respective terminal. The moulded fibre receptacle drying system is configured to insert at least part of the heating device into the moulded fibre receptacle such that, for each of the plurality of radiative bulbs, the two substantially straight segments are disposed partially inside the moulded fibre receptacle and the connecting segment is disposed inside the moulded fibre receptacle. Using a plurality of radiative bulbs with this shape may achieve an approximately uniform distribution of heat across the inner surface of the moulded fibre receptacle while allowing for a simpler design of the drying system. Where the distribution of heat across the inner surface of the moulded fibre receptacle is approximately uniform, the moulded fibre receptacle may not need to be rotated or otherwise moved during heating. Optionally, the radiative bulbs are of substantially the same shape and are arranged at mutually different orientations. Arranging the radiative bulbs to be at mutually different orientations may improve the uniformity of the distribution of heat across the inner surface of the moulded fibre receptacle. Optionally, a number of the plurality of radiative bulbs is greater than two, and the plurality of radiative bulbs has rotational symmetry, of order equal to the number of the plurality of radiative bulbs, about the axis of the heating device. Arranging the radiative bulbs in a ‘flower-petal’ style may improve the uniformity of the distribution of heat across the inner surface of the moulded fibre receptacle. Optionally, the moulded fibre receptacle drying system comprises a gas provision device configured to direct gas into the moulded fibre receptacle. Directing gas into the moulded fibre receptacle to replenish an internal atmosphere of the moulded fibre receptacle may improve the speed and efficiency of the drying by removing gas comprising an evaporated solvent, such as water, from the internal atmosphere and replacing it with gas having a lower concentration of the evaporated solvent. Optionally, the moulded fibre receptacle drying system comprises a further heating device configured to direct heat to an outer surface of the moulded fibre receptacle from outside the moulded fibre receptacle. Directing heat from a further heating device to the outer surface of the moulded fibre receptacle, in addition to the internal heating, may provide faster drying of the moulded fibre receptacle. The further heating device may comprise a bake oven, and the moulded fibre receptacle drying system may be configured to insert the moulded fibre receptacle into the bake oven. Optionally, the moulded fibre receptacle drying system comprises a sensor apparatus configured to receive electromagnetic radiation from the moulded fibre receptacle. The drying may be performed in conjunction with a quality control process, the quality control process using electromagnetic radiation emitted from the moulded fibre receptacle upon the heating of the moulded fibre receptacle. Optionally, the moulded fibre receptacle drying system comprises a heat shield, and is configured to insert the heat shield into the moulded fibre receptacle such that it is disposed between the heating device and the neck portion of the moulded fibre receptacle. 18 1224 By positioning a heat shield between the radiative heater and the neck portion, the amount of energy absorbed by the neck portion may be reduced. The moulded fibre receptacle drying system is configured to operate to dry the moulded fibre receptacle by a method according to the first aspect of the invention. According to a fifth aspect of the present invention, there is provided a system comprising a moulding apparatus for moulding a fibre suspension to form a moulded fibre receptacle, and, downstream of the moulding apparatus, a moulded fibre receptacle drying system according to the fourth aspect of the invention for drying the moulded fibre receptacle. In some examples, the moulded fibre receptacle is a bottle. BRIEF DESCRIPTION OF DRAWINGS Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a schematic view of an example process for making bottles from paper pulp; Figure 2 is a schematic view of an example drying system; Figure 3 is a flow chart of an example method of drying a moulded fibre receptacle; Figure 4 is a schematic view of an example variable heat delivery drying system; and Figure 5 is a schematic view of an example heat shield dry ing system including a heat shield. DETAILED DESCRIPTION The following description presents exemplary embodiments and, together with the drawings, serves to explain principles of embodiments of the invention. Figure 1 shows a process for making bottles from paper pulp (i.e., which can form the basis of an example fibre suspension). The process is merely exemplary' and is provided to give context to examples of the present invention. Broadly speaking, the exemplary process comprises providing a fibre suspension, introducing the fibre suspension into a mould cavity of a porous first mould and using the porous first mould to expel a liquid (such as water) from the fibre suspension to produce a wet precursor or embryo (which may itself be considered a moulded receptacle), further moulding the wet precursor in a mould to produce a further-moulded receptacle, coating the further-moulded receptacle to produce a coated moulded receptacle, drying the coated moulded receptacle to produce a dried receptacle, and applying a closure to the dried receptacle. As will be apparent at least from the following description, modifications may be made to the exemplary- process to provide variants thereof in which other examples of the present invention may be embodied. In this example, providing the fibre suspension comprises preparing the fibre suspension from ingredients thereof. More specifically, the preparing comprises providing pulp fibres, such as paper pulp fibres, and mixing the pulp fibres with a liquid to provide hydrated pulp fibres. In this example, the pulp fibres are provided in sheet form from a supplier and the liquid comprises water and one or more additives. In this example, the liquid is mixed with the pulp fibres to provide hydrated pulp fibres having a solid fibres content of lwt% to 5wt% (by dry mass of fibres). In examples, the one or more additives includes a sizing agent, such as alkylketene dimer (AKD). The hydrated pulp fibres typically comprise AKD in an amount of 0.4wt% with respect to the total dry mass of the solid fibres in the hydrated pulp fibres. In some examples, one or more additives are present in the liquid at the point of mixing the pulp fibres with the liquid. In some examples, one or more additives are included in the hydrated pulp fibres after mixing the pulp fibres with the liquid (e.g. the pulp fibres are hydrated for a period of time, such as from 2 to 16 hours, and then one or more additives are supplied to the hydrated pulp fibres). Hie hydrated pulp fibres are passed between plates of a valley beater 11 or refiner that are in motion relative to each other. This fibrillates some, or all, of the fibres, meaning that cell walls of those fibres are caused to become partially delaminated so that wetted surfaces of those fibres comprise protruding hairs or fibrillations. These fibrillations will help to increase a strength of bonds between the fibres in the dried end product. In other examples, the valley beater 11 or refiner may be omitted. The resultant processed pulp is stored in a vat 12 in a relatively concentrated form (e.g. a solid fibres content of lwt% to 5wt%) to reduce a required storage space. At an appropriate time, the processed pulp is transferred to a mixing station 13 at which the processed pulp is diluted in further water and, optionally, mixed with one or more additives (as well as, or in place of, the one or more additives provided with the hydrated pulp fibres) to provide the fibre suspension ready for moulding. In this example, the solid fibres account for 0.7wt% of the resultant fibre suspension (by dry weight of fibres), but in other examples the proportion of solid fibres in the fibre suspension may be different, such as another value in the range of 0.5wt% to 5wt%, or 0. lwt% to 1 wt%, of the fibre suspension (by dry weight of fibres). In some examples, the one or more additives mixed with the processed pulp and water includes a dewatering agent, such as modified and / or unmodified polyethylene imine (PEI), e.g. modified PEI sold under the trade name Polymin® SK. In some examples, the one or more additives are mixed with the water, and the water and one or more additives subsequently mixed with the processed pulp; in other examples, the processed pulp and water are mixed, and the one or more additives subsequently mixed with the processed pulp and water. The fibre suspension typically comprises Polymin® SK in an amount of 0.3wt% with respect to the total dry mass of the solid fibres. Mixing of the fibre suspension at the mixing station 13 helps to homogenise the fibre suspension. In other examples, the processed pulp or the fibre suspension may be provided in other ways, such as being supplied ready-made. Downstream of the vat 12 and the mixing station 13 is a first moulding station that comprises a porous first mould 15. In this example, the porous first mould 15 comprises two half-moulds that are movable towards and away from each other, in this case using a hydraulic ram. In this example, each of the half-moulds is a monolithic or unitary tool formed by additive manufacturing (e.g. 3D-printing) that defines a mould profile, and, when the half-moulds are brought into contact with each other, their respective mould profiles cooperate to define the mould cavity in which the wet precursor or moulded receptacle is to be formed. Each half-mould may itself define a smaller moulding cavity and, when brought into cooperation with a second half-mould, the smaller moulding cavities may combine to provide the overall mould cavity7. The two half-moulds may themselves be considered “splits” or “moulds” and the overall porous first mould 15 may be considered a “split-mould” or, again, a “mould”. In other examples, the porous first mould 15 may comprise more than two splits, such as three, four or six splits, that cooperate to define the moulding cavity. In Figure 1, the fibre suspension (also known as slurry) is top-filled into the porous mould 15, in contrast to moulding processes that dip a mould in slurry. The fibre suspension is drawn under vacuum via a line 16 and into the porous mould 15, with excess suspending liquid being drawn through the porous mould 15 under vacuum via a line 18 into a tank 17. Shot mass may be controlled by measuring (e.g., weighing) the amount of liquid drawn into the tank 17. A weight scale platform supporting the tank 17 is visible in Figure 1. Once a required amount (e.g. a predetermined volume, such as 10 litres, or a predetermined mass, such as 10 kilograms) of liquid has been collected in the tank 17, suction of the suspending liquid through the porous mould 15 is stopped and the porous mould 15 is opened to ambient air. In this example, the suspending liquid drawn with the fibre suspension in line 16 is water, or predominantly water (as additives may also be present). The liquid drawn under vacuum via the line 18 and into the tank 17 is substantially free of fibres, since these are left behind against the walls of the porous mould 15 to form an embryo of the moulded receptacle. In one form, in order to remove further suspending liquid (e.g. water) from the embryo, and form or consolidate the three-dimensional shape of the receptacle, an impermeable inflation element 19, e.g., a collapsible bladder, is inserted into the porous mould 15 and expanded to act as an internal high-pressure core structure for the porous mould 15. This process strengthens the wet embryo so that it can be handled, and displaces water from in between the fibres, thereby increasing the efficiency of a subsequent drying process. Hie inflation element 19 is actuated and regulated using a hydraulic pump 20. The pump 20 has a cylinder that displaces a fluid in a line 21 into the inflation element 19, to expand the inflation element 19 radially and into conformity with the mould cavity. Fluid within the line 21 is preferably non-compressible, such as water. Water also has the advantage over other non-compressible liquids that any leaking or bursting of the bladder 19 will not introduce a new substance to the system (since the suspending liquid is already water, or predominantly water). Demoulding occurs when the porous mould 15 opens for removal of the self-supporting moulded receptacle 22. Mould cleaning 23 is preferably performed subsequently, to remove small fibres and maintain a porosity of the porous mould 15. In this example, a radially firing high-pressure jet is inserted into the mould cavity while the mould 15 is open. This dislodges fibres from the wall of the mould cavity. Alternatively, or in addition, water from the tank 17 is pressurised through the back of the porous mould 15 to dislodge entrapped fibres. Water is drained for recycling back to an upstream part of the system. It is noteworthy that cleaning is important for conditioning the porous mould 15 for re-use. The porous mould 15 may appear visibly clean after removal of the receptacle, but its performance could be compromised without cleaning. According to Figure 1, the formed but unfinished receptacle 22 is subsequently transported to a second moulding station where, in a, e.g., aluminium, mould 25, pressure and heat are applied for thermoforming a desired neck and surface finish, optionally including embossed and / or debossed surface features. After two halves of the mould 25 have closed around the receptacle 22, a pressuriser is engaged. For example, a bladder 26 (e.g., a thermoforming bladder 26) is inserted into the receptacle 22. The bladder 26 is inflated via a line 27 by a pump 28 to supply pressurised fluid, e.g., air, water, or oil. Optionally, during supply, the pressurised fluid is heated with e.g. a heater or, alternatively, is cooled with e.g. a heat exchanger. An external mould block 24 of the mould 25, and / or the mould 25 itself, may also, or alternatively, be heated. A state of the moulded receptacle 22 after thermoforming is considerably more rigid, with more compressed side walls, compared with the state at demoulding from the porous mould 15. A drying stage 29 is performed downstream of the thermoforming, as shown. In one example, the drying stage 29 is performed before thermoforming. However, moulding in the mould 25 requires some water content to assist with bonding during the compression process. Figure 1 illustrates a further drying stage 30 after the drying stage 29, which may utilise hot air circulated onto the moulded receptacle 22, e.g., in a “hot box”. In some examples, drying processes may be performed at plural stages of the overall manufacturing process. The drying stage 29, and / or the further drying stage 30, may be conducted in accordance with the methods disclosed herein and / or using the drying systems disclosed herein. The moulded receptacle 22 is then subjected to a coating stage during which, in this example, a spray lance 31 is inserted into the moulded receptacle 22 and applies one or more surface coatings to internal walls of the moulded receptacle 22. In another example, the moulded receptacle 22 is instead filled with a liquid that coats the internal walls of the moulded receptacle 22. In practice, such coatings provide a protective layer to prevent egress of contents into the bottle wall, which may permeate and / or weaken it. Coatings will be selected dependent on the intended contents of receptacle 22, e.g., a beverage, detergent, pharmaceutical product, etc. In some examples, the further drying stage 30 is performed after the coating stage (or both before and after the coating stage). In this example, the moulded receptacle 22 is then subjected to a curing process 34, which can be configured or optimised dependent on the coating, e.g., drying for twenty-four hours at ambient conditions or by a flash drying method. The curing process 34 may be conducted in accordance with the methods disclosed herein and / or using the drying systems disclosed herein. In some examples, e.g. where the further drying stage 30 occurs after the coating stage, the curing process 34 may be omitted. At an appropriate stage of production (e.g., during thermoforming, or before or after coating) a closure or mouth forming process may be performed on the moulded receptacle 22. For example, as shown in Figure 1, a neck fitment 35 may be affixed. In some examples, an exterior coating is applied to the moulded receptacle 22, as shown in the further coating stage 32. In one example, the moulded receptacle 22 is dipped into a liquid that coats its outer surface, as shown in Figure 1. One or more further drying or curing processes may then be performed. For example, the moulded receptacle 22 maybe allowed to dry in warm air. Alternatively, the moulded receptacle 22 may be dried with the methods disclosed herein and / or using the drying systems disclosed herein. The moulded receptacle 22 may therefore be fully formed and ready to accept contents therein. In other examples, the receptacle 22 may be considered fully formed without the neck fitment 35 being affixed. Figure 2 shows a dry ing system 36 according to an example. The drying system 36 is configured to perform at least one of the drying stages described above with reference to Figure 1, for example drying stage 29, on the moulded fibre receptacle 22. The drying system 36 comprises a support 37 configured to support the moulded fibre receptacle 22, and a heating device 38. Hie drying system 36 is configured to insert at least part of the heating device 38 into the moulded fibre receptacle 22 when the moulded fibre receptacle 22 is held by the support 37, and to operate to dry the moulded fibre receptacle 22. This may be performed by holding the moulded fibre receptacle 22 stationary in the support 37, and extending at least part of the heating device 38 into the moulded fibre receptacle 22. Alternatively, the heating device 38 may be held stationary, and the support 37 may be configured to move the moulded fibre receptacle 22 so that at least part of the heating device 38 is inserted into the moulded fibre receptacle 22. Alternatively, both the heating device 38 and the moulded fibre receptacle 22 may be moved, so that the heating device 38 is inserted into the moulded fibre receptacle 22. The moulded fibre receptacle 22 may thus be dried in a faster and / or more efficient way than, for example, prior art methods in which the moulded fibre receptacle 22 is heated from the outside using a bake oven. Performing heating by disposing the heating device 38 inside the moulded fibre receptacle 22 may also prevent discolouration of the outside of the moulded fibre receptacle 22. In this example, the heating device 38 is substantially rotationally symmetric about a heating device axis 42. Using a rotationally symmetric heating device may enable an even distribution of heat along the inner surface 46 of the moulded fibre receptacle 22. “Rotational symmetry about an axis” as used herein may refer to rotational symmetry of finite order or circular symmetry, unless explicitly specified. It will be understood, of course, that it is not essential for the heating device 38 to be substantially rotationally symmetric. The heating device 38 has a heating element 39. The heating element 39 may comprise a linear radiative bulb which has circular symmetry around an axis of the linear radiative bulb, or any other suitable component. In this example, the drying system 36 comprises a first wire 43 and a second wire 44 configured to deliver electrical current to the heating element 39, which is in the form of a linear radiative bulb, through a first terminal 40 and a second terminal 41 respectively. The first wire 43 and the second wire 44 are spaced apart and each run substantially parallel to a heating device longitudinal axis 42. In other examples, the first terminal 40 and the second terminal 41 may both be positioned on the heating device axis 42 at opposite ends of the linear radiative bulb 39. Hie linear radiative bulb, as well as other radiative bulbs described herein, is configured to radiate, for example, infrared radiation. In some examples, the infrared radiation comprises medium infrared radiation, having a wavelength in the range 1.4pm to 3pm. Radiation in this range may be particularly efficient in removing a solvent (e.g. water) in examples where the inner surface 46 comprises a coating. Hie drying system 36 may comprise a power source (not shown) configured to deliver electrical current to the heating device 38. Alternatively, or additionally, the heating device 3 8 may comprise a water radiator and / or a gas burning device for performing the heating. Hie dry ing system 36 may comprise a water and / or gas supply, as appropriate. Alternatively, or additionally, the heating element 39 of the heating device 38 may comprise a U-bulb heating device, the U-bulb heating device comprising a radiative bulb which has two substantially straight segments and a connecting segment coupling the two substantially straight segments. Each substantially straight segment protrudes from a respective one of two terminals. Hie two substantially straight segments have the same length. The two substantially straight segments may be parallel to one another. The two terminals are spaced along a first axis in the form of a transverse axis 55, the transverse axis 55 being perpendicular to the longitudinal heating device axis 42. The drying system 36 is configured to insert at least part of the U-bulb heating device into the moulded fibre receptacle 22 such that the radiative bulb is disposed partially inside the moulded fibre receptacle 22. The drying system 36 is configured to insert at least part of the U-bulb heating device into the moulded fibre receptacle 22 such that the two substantially straight segments are disposed partially inside the moulded fibre receptacle 22 and the connecting segment is disposed inside the moulded fibre receptacle 22. The two terminals are positioned on a platform outside the moulded fibre receptacle 22. Disposing the terminals outside of the moulded fibre receptacle 22 may allow for a simpler design of the drying system 36 than, for example, a heating element which has one or more terminals and a trailing wire(s) inside the moulded fibre receptacle 22 during the heating process. In a case where the heating device 38 does not have circular rotational symmetiy. for example the U-bulb heating device described above, the moulded fibre receptacle 22 may be rotated around the heating device longitudinal axis 42 during the heating process. For example, the drying system 36 may be configured to rotate the support 37 during the heating process. Additionally, or alternatively, the drying system 36 may be configured to rotate the U-bulb heating device during the heating process. In some examples, the U-bulb heating device comprises a plurality of multisegment radiative bulbs. For example, the plurality of multi-segment radiative bulbs may comprise three radiative bulbs. However, in some examples, the plurality of multisegment radiative bulbs may comprise more than three radiative bulbs. The dry ing system 36 is configured to insert at least part of the U-bulb heating device into the moulded fibre receptacle 22 such that, for each of the plurality of multi-segment radiative bulbs, the two substantially straight segments are disposed partially inside the moulded fibre receptacle 22 and the connecting segment is disposed inside the moulded fibre receptacle 22. In some examples, each of the plurality of multi-segment radiative bulbs are arranged at mutually different orientations. In such examples, the substantially straight segments of one of the plurality of multi-segment radiative bulbs may each be parallel to the substantially straight segments of each of the other of the plurality of multi-segment radiative bulbs. Arranging the plurality of multi-segment radiative bulbs to be at mutually different orientations may improve the uniformity of the distribution of heat across the inner surface 46 of the moulded fibre receptacle 22. In some examples, the plurality of multi-segment radiative bulbs has rotational symmetry, of order equal to the number of the plurality of radiative bulbs, about the heating device longitudinal axis 42. For example, the plurality of multi-segment radiative bulbs may comprise three radiative bulbs and have rotational symmetry of order three about the heating device longitudinal axis 42. Arranging the plurality of multi-segment radiative bulbs in a ‘flower-petal’ style in this way may improve the uniformity of the distribution of heat across the inner surface 46 of the moulded fibre receptacle 22. In the example of Figure 2, the support 37 is configured to support the moulded fibre receptacle 22 such that the moulded fibre receptacle 22 is substantially rotationally symmetric about the heating device longitudinal axis 42. Holding the moulded fibre receptacle 22 so that its axis of symmetry is aligned with the longitudinal axis of the heating device 38 may improve the uniformity of the distribution of heat across the inner surface 46 of the moulded fibre receptacle 22. In this example, the moulded fibre receptacle 22 is substantially rotationally symmetric about a longitudinal axis of the moulded fibre receptacle 22. The support 37 is configured to support the moulded fibre receptacle 22 such that the longitudinal axis of the moulded fibre receptacle 22 is aligned with the heating device longitudinal axis 42. The moulded fibre receptacle 22 comprises a body portion 54 and a neck portion 53. The neck portion 53 is narrower than the body portion 54 along the transverse axis 55. With reference to the above-mentioned axes, the total length of the moulded fibre receptacle 22 may be between 160mm and 230mm. The neck portion 53 may comprise a cylindrical or otherwise prism-shaped portion of length between 4mm and 15mm along the longitudinal axis of the moulded fibre receptacle 22. A width of the body portion 54 may be between 65mm and 90mm. A width of the neck portion 53 may be between 38mm and 50mm. A radius of curvature of a transition portion 59 between the body portion 54 and the neck portion 53 may be 14mm or greater. In methods according to the present invention, as shown in Figure 2, energy 45 is directed from the heating device 38 to an inner surface 46 of the moulded fibre receptacle 22. The energy 45 comprises heat energy. The heat energy may cause water and / or moisture on the inner surface 46 to evaporate. Water vapour resulting from the evaporation may pass through an opening 48 in the moulded fibre receptacle 22. In some examples, the inner surface 46 comprises a coating, and the drying system 36 is for drying the coating. The coating comprises a solvent, which in some examples is water, but in other examples, other solvents may be used. The heat energy causes the solvent to evaporate, and thereby be removed from the coating. Vaporised solvent resulting from the evaporation may pass through the opening 48. When the inner surface 46 comprises a coating, directing energy from a heating device inside the moulded fibre receptacle 22 may reduce or prevent discolouration of the moulded fibre receptacle 22 and / or its outer surface 47, as compared with heating the moulded fibre receptacle 22 from the outside. The drying system 36 of the present invention may additionally or alternatively be used to dry the outer surface 47 of moulded fibre receptacle 22, for example following the application of an exterior coating in the further coating stage 32. In some examples, the energy 45 heats the inner surface 46 of the moulded fibre receptacle 22. By thermal conduction, the heat then spreads to the outer surface 47 of the moulded fibre receptacle 22. The heat causes water and / or moisture and / or other solvent on the outer surface 47 to evaporate. Figure 3 shows a method 100 of drying a moulded fibre receptacle 22 according to an example. Broadly, the method 100 comprises directing energy 45 from a heating device 38 disposed at least partially inside the moulded fibre receptacle 22 to an inner surface 46 of the fibre receptacle. The method 100 may be implemented using the drying system 36. In the example of Figure 3, the directing energy 45 to the inner surface 46 of the moulded fibre receptacle 22 comprises performing a heating process. The heating process comprises a step 102 of directing energy 5 7 from the heating device 3 8 to the inner surface of the neck portion 53 of the moulded fibre receptacle 22 according to a first set of heating process characteristics. The heating process comprises a step 104 of directing energy 56 from the heating device 38 to the inner surface of the body portion 54 of the moulded fibre receptacle 22 according to a second set of heating process characteristics different from the first set of heating process characteristics. The order of steps 102 and 104 may be reversed, or the steps 102 and 104 may be carried out simultaneously. By heating the body portion 54 according to a different set of heating process characteristics to those used to heat the neck portion 53, respectively different characteristics of the neck portion 53 and body portion 54 can be taken account of during the heating process. Examples of methods of vary ing the heating process characteristics according to which the neck portion 53 and body portion 54, respectively, are heated are described below with reference to Figures 4 and 5. Figure 4 shows an example of the drying system 36, in the form of a variable heat delivery drying system 36a. The variable heat delivery drying system 36a is arranged to direct heat differently to the body portion 54 and the neck portion 53 of the moulded fibre receptacle 22 in accordance with the method 100 of Figure 3. The variable heat delivery' drying system 36a includes a heating device 38a, which may take the same form as the heating device 38 described above in relation to Figure 2 and may have a relatively short heating element 39a, as described below. The variable heat delivery dry ing system 36a is configured to move the heating device 38a relative to the moulded fibre receptacle 22 and selectively heat the neck portion 53 and the body portion 54. In this example, the variable heat delivery drying system 36a may be arranged to direct energy to the inner surface of the neck portion 53 and the inner surface of the body portion 54 simultaneously. However, the amount of power absorbed by a given area of the inner surface depends on the distance between the given area and the heating device 38a, or on an integral of a function of the distance between the given area and a given point on the heating device 38a over all points on the heating device 38a. Hence, the heating device 38a may be arranged to be sufficiently short as measured along the heating device longitudinal axis 42, such that when the heating device 38a is located in a body portion position inside the body portion 54, labelled position 1, the body portion 54 typically absorbs more power than the neck portion 53, and when the heating device 38a is located in a neck portion position inside the neck portion 53, labelled position 2, the neck portion 53 typically absorbs more power than the body portion 54. In some examples, the length of the heating element 39a of the heating device 38a along the heating device axis 42 is less than a length of the body portion 54 and / or a length of the neck portion 53. For example, the length of the heating element 39a of the heating device 38a along the heating device axis 42 may be approximately one-third of the length of the moulded fibre receptacle 22. Additionally, or alternatively, the length of the heating element 39a of the heating device 38a along the heating device axis 42 may be less than half of a total length of the moulded fibre receptacle 22. Due to the neck portion 53 being narrower than the body portion 54, for a heating device which supplies a constant amount of power, the amount of power absorbed by the neck portion 53 per unit surface area when the heating device is at position 2 is typically more than the amount of power absorbed by the body portion 54 per unit surface area when the heating device is at position 1. In order to avoid a resultant undesirable variance between the energy provided to the neck portion 53 and the energy provided to the body portion 54, in some examples, the first and second sets of heating process characteristics are selected so that the heating process provides a greater amount of heat, per unit distance along the longitudinal axis of the heating device 42, to the inner surface of the body portion 54 than to the inner surface of the neck portion 53. By providing a greater amount of heat per unit distance to the body portion 54 than to the neck portion 53, overheating of the neck portion 53 due to its narrower width may be reduced, and energy efficiency may be improved. In some examples, the first and second sets of heating process characteristics are selected so that the heating process provides a substantially uniform distribution of heat across the inner surface of the neck portion 53 and the inner surface of the body portion 54. For example, the amount of heat absorbed by the inner surface of the neck portion 53 per unit area may be similar to the amount of heat absorbed by the inner surface of tire body portion 54 per unit area. The maximum temperature reached by the inner surface of the neck portion 53 during the heating process may be similar to that reached by the inner surface of the body portion 54. By using a substantially unifonn distribution of heat, the drying of the moulded fibre receptacle 22 may be consistent across the neck portion 53 and the body-portion 54. The energy efficiency of the heating process may be improved by this consistency. Furthermore, burning or other overheating damage of the neck portion may be prevented. In some examples, the first and second sets of heating process characteristics comprise first and second heating durations respectively. Tire first heating duration is an amount of time spent heating the inner surface of the neck portion 53. The second heating duration is an amount of time spent heating the inner surface of the body portion 54. The first duration is less than the second duration. This enables the amount of energy directed to the neck portion 53 to be reduced. For example, the heating device 38a may first be inserted such that it is at position 1, and used to direct energy 56 to the body portion 54 for a time equal to the second duration. The heating device 38a may be turned off, moved to position 2, and used to direct energy 57 to the neck portion 53 for a time equal to the first duration. Alternatively, or additionally, the moulded fibre receptacle 22 may be moved relative to the heating device 38a during the heating process, so that the first heating duration is less than the second heating duration. For example, the heating device 38a may be inserted such that it is at position 1, and used to direct energy 56 to the body portion 54 for a time equal to the second duration. The heating device 38a may be stationary relative to the moulded fibre receptacle 22 during this time. Then, while continuing to direct energy to the inner surface 46 of the moulded fibre receptacle 22, the heating device 38a is moved, for example at a predetermined speed, relative to the moulded fibre receptacle 22 so that it is closer to the neck portion 53. In some examples, the heating device 38a is moved in a continuous motion from an initial position in the body portion 54 to a final position outside the moulded fibre receptacle 22. The heating device 3 8a may be moved in a straight line parallel to the heating device longitudinal axis 42. The heating device 38a is then used to direct energy 57 to the neck portion 53 for a time equal to the first duration. By moving the moulded fibre receptacle 22 relative to the heating device 38a, the time spent directing heat to the neck portion 53 relative to the body portion 54 may be controlled without needing to van- the power supplied to the heating device 38a during the heating process. Alternatively, or additionally, the first and second sets of heating process characteristics may comprise first and second heating powers associated with the heating device 38a respectively. In this example, the first heating power is less than the second heating power. For example, the first heating power may be 650-850W, and the second heating power may be around 1. IkW. Directing energy 57 from the heating device 38a to the inner surface of the neck portion 53 is performed in a first time interval. Directing energy 56 from the heating device 38a to the inner surface of the body portion 54 is performed in a second time interval. For example, the heating device 38a may be inserted such that it is at position 1, and used with the first heating power to direct energy 56 to the body portion 54 in the second time interval. The heating device 38a may be moved relative to the moulded fibre receptacle 22 such that it is at position 2, and used with the second heating power to direct energy 56 to the body portion 54 in the first time interval. By directing different amounts of heating power to the neck portion 53 and the body portion 54, an even temperature distribution across the neck portion 53 and the body portion 54 may be achieved. Figure 5 shows another example of the drying system 36, in the form of a heat shield dry ing system 36b, comprising a heating device 38b, which may take the same form as the heating device 38 described above in relation to Figure 2. The heat shield drying system 36b comprises a heat shield 58 which is arranged partially to absorb or reflect the energy 57 directed to the neck, so that the energy absorbed by the inner surface of the neck portion 53 is less when the heat shield 58 is disposed between the heating device 38b and the neck portion 53 than otherwise. The heat shield drying system 36b is thereby configured to direct heat differently to the body portion 54 and the neck portion 53 of the moulded fibre receptacle 22, in accordance with the method 100 of Figure 3. The heat shield 58 may be made of a thermally insulating material. In some examples, the heat shield drying system 36b may be configured to insert the heat shield 58 into the moulded fibre receptacle 22 such that it is disposed between the heating device 38 and the neck portion 53 of the moulded fibre receptacle 22. For example, the heat shield drying system 36b may include an arm (not shown) which extends the heat shield 58 into the moulded fibre receptacle 22, so that the heat shield 58 is disposed between the heating device 38b and the neck portion 53 of the fibre receptacle 22. The heat shield 58 may be disposed concentrically outside the heating device 38b during the heating process. The heat shield 58 may be an annular cylinder. A longitudinal axis of the annular cylinder may be aligned with the heating device longitudinal axis 42 and / or the longitudinal axis of the moulded fibre receptacle 22. In this example, the first set of heating process characteristics comprises the substantially unobstructed provision of heat from the heating device 38b to the body portion 54 and the second set of heating process characteristics comprises the heat shield 58 being disposed between the heating device 38b and the neck portion 53. The heat shield 58 may be allowed to cool down, or be replaced, between use for a first moulded fibre receptacle and use for a second moulded fibre receptacle. In some examples, since the heat shield 58 reduces the amount of heat incident on the neck portion 53, step 102 of directing energy 57 from the heating device 38b to the inner surface of the neck portion 53 can be performed at the same time as step 104 of directing energy 56 from the heating device 38b to the inner surface of the body portion 54. Because of the presence of the heat shield 58, different heating process characteristics can be applied to the neck portion 53 from those applied to the body portion 54, without requiring the heating device 38b to be controlled to provide differential heating between the neck portion 53 and the body portion 54, thus simplifying configuration and operation of the heating device 38b. For example, as shown in Figure 5, the heating device 38b may provide substantial heat to the neck portion 53 and the body portion 54 simultaneously. The length of a heating element 39b of the heating device 38b along the heating device longitudinal axis 42 may be longer than the length of the body portion 54 and / or the length of the neck portion 53, or may be longer than the total length of the moulded fibre receptacle. Ure heating process may therefore be started and completed without moving the heating device 38b relative to the moulded fibre receptacle 22. In some examples, the drying system 36 comprises a gas provision device. Tire gas provision device comprises a gas source and a pipe. Tire pipe is at least partially inserted into the moulded fibre receptacle 22. The gas provision device is configured to direct gas into the moulded fibre receptacle 22 through the pipe. Directing gas into the moulded fibre receptacle 22 may allow an internal atmosphere of the moulded fibre receptacle 22 to be replenished during drying, and may thus improve the speed and / or efficiency of the drying. For example, directing gas into the moulded fibre receptacle 22 may cause a greater volume of moisture-containing fluid to flow out of the opening 48. This may allow an overall concentration of evaporated water or vaporised solvent in the internal atmosphere of the moulded fibre receptacle 22 to remain lower during the drying than without the gas provision device. In some examples, the dry ing system 36 comprises a sensor apparatus. The sensor apparatus is configured to receive electromagnetic radiation from the moulded fibre receptacle 22. For example, the moulded fibre receptacle 22 may receive and partially absorb the energy 45, causing the temperature of the moulded fibre receptacle 22 to rise. The moulded fibre receptacle 22 may then emit the electromagnetic radiation outwards, some of which is received by the sensor apparatus. Hie greater the power supplied to the heating device 38, the greater the temperature reached by the moulded fibre receptacle 22, and hence the greater the intensity? of electromagnetic radiation emitted by the moulded fibre receptacle 22. The sensor apparatus may comprise, for example, an infrared sensor configured to receive the electromagnetic radiation and indicate an intensity of the electromagnetic radiation. The electromagnetic radiation received by the sensor apparatus may be analysed by a processor to determine properties of the structure of the moulded fibre receptacle 22. For example, the electromagnetic radiation received by the sensor apparatus may be indicative of the distribution of fibres in a wall of the moulded fibre receptacle 22. The wall may include the inner surface 46 and / or the outer surface 47. The electromagnetic radiation received by the sensor apparatus may be indicative of the temperature of the moulded fibre receptacle 22. The temperature and the amount of energy supplied to the moulded fibre receptacle 22 may be used to infer the water and / or other solvent content of the coating of the inner surface 46, by, for example, determining the amount of energy that has been used to cause the water and / or other solvent to evaporate. In some examples, the drying system 36 comprises a further heating device configured to direct heat to the outer surface 47 of the moulded fibre receptacle 22 from 5 outside the moulded fibre receptacle 22. The further heating device may comprise a bake oven held on the support 37. The moulded fibre receptacle 22 may be placed on a surface of the bake oven, such that the bake oven supports the moulded fibre receptacle 22, and the moulded fibre receptacle 22 is completely contained by the bake oven. The inner surface 46 of the moulded fibre receptacle 22 may be heated by the heating device 38 10 described above with reference to Figures 2, 4 and 5 while the outer surface 47 is heated by the bake oven. Directing heat from die further heating device to the outer surface 47 of the moulded fibre receptacle 22, in addition to the internal heating, may provide faster drying of the moulded fibre receptacle 22. Example embodiments of the present invention have been discussed, with 15 reference to the examples illustrated. However, it will be appreciated that variations and modifications may be made without departing from the scope of the invention as defined by die appended claims.

Claims

1. A method of drying a moulded fibre receptacle, the method comprisingdirecting energy from a heating device disposed at least partially inside the moulded fibre receptacle to an inner surface of the moulded fibre receptacle, wherein the directing energy to the inner surface of the moulded fibre receptacle comprises performing a heating process comprising:directing energy from the heating device to an inner surface of a neck portion of the moulded fibre receptacle according to a first set of heating process characteristics; anddirecting energy from the heating device to an inner surface of a body portion of the moulded fibre receptacle according to a second set of heating process characteristics different from the first set of heating process characteristics,wherein the neck portion is narrower than the body portion along a first axis.

2. The method of claim 1, comprising selecting the first and second sets of heating process characteristics so that the heating process provides a greater amount of heat, per unit distance along a second axis, to the inner surface of the body portion than to the inner surface of the neck portion, the second axis being perpendicular to the first axis.

3. The method of claim 1 or claim 2, comprising selecting the first and second sets of heating process characteristics so that the heating process provides a substantially uniform distribution of heat across the inner surface of the neck portion and the inner surface of the body portion.

4. The method of any one of the preceding claims, wherein the first and second sets of heating process characteristics comprise first and second heating durations respectively, and the first heating duration is less than the second heating duration.

5. The method of claim 4, wherein the method comprises moving the moulded fibre receptacle relative to the heating device during the heating process, so that the first heating duration is less than the second heating duration.

6. The method of any one of the preceding claims, wherein the first and second sets of heating process characteristics comprise first and second heating powers associated with the heating device respectively, and the first heating power is less than the second heating power.

7. The method of claim 6, wherein:directing energy from the heating device to the inner surface of the neck portion is performed in a first time interval,directing energy from the heating device to the inner surface of the body portion is performed in a second time interval, andthe heating process comprises changing a heating power of the heating device between the first heating power and the second heating power at a time between the first time interval and the second time interval.

8. The method of any one of claim 1 to claim 7, wherein the inner surface comprises a coating, the coating comprising a solvent, and the directing energy to the inner surface of the moulded fibre receptacle causes the solvent to be removed from the coating.

9. A method of forming a fibre receptacle, comprising drying the fibre receptacle by a method according to any one of claim 1 to claim 8.

10. A moulded fibre receptacle drying system comprising:a support configured to support a moulded fibre receptacle; anda heating device,wherein the moulded fibre receptacle drying system is configured to insert at least part of the heating device into the moulded fibre receptacle when the moulded fibre receptacle is held by the support, and to operate to dry the moulded fibre receptacle by a method according to any one of claims 1 to 9.

11. The moulded fibre receptacle drying system of claim 10, wherein the heating device is substantially rotationally symmetric about an axis of the heating device.

12. The moulded fibre receptacle drying system of claim 11, wherein the support is configured to support the moulded fibre receptacle such that the moulded fibre receptacle is substantially rotationally symmetric about the axis of the heating device.

13. The moulded fibre receptacle drying system of any one of claim 10 to claim 12, wherein the heating device comprises a radiative bulb.

14. The moulded fibre receptacle drying system of claim 13, wherein the radiative bulb comprises two terminals, and the moulded fibre receptacle drying system is configured to insert at least part of the heating device into the moulded fibre receptacle such that the radiative bulb is disposed partially inside the moulded fibre receptacle and the two terminals are disposed outside the moulded fibre receptacle.

15. The moulded fibre receptacle drying system of any one of claim 10 to claim 12, wherein the heating device comprises a plurality of radiative bulbs, each of the plurality of radiative bulbs comprising two substantially straight segments and a connecting segment coupling the two substantially straight segments, each substantially straight segment protruding from a respective terminal, and the moulded fibre receptacle drying system is configured to insert at least part of the heating device into the moulded fibre receptacle such that, for each of the plurality of radiative bulbs, the two substantially straight segments are disposed partially inside the moulded fibre receptacle and the connecting segment is disposed inside the moulded fibre receptacle.

16. The moulded fibre receptacle drying system of claim 15, wherein the radiative bulbs are of substantially the same shape and are arranged at mutually different orientations.

17. The moulded fibre receptacle drying system of claim 16 when dependent on claim 11, wherein a number of the plurality of radiative bulbs is greater than two, and the plurality of radiative bulbs has rotational symmetry, of order equal to the number of the plurality of radiative bulbs, about the axis of the heating device.

18. The moulded fibre receptacle drying system of any one of claim 10 to claim 17, comprising a gas provision device configured to direct gas into the moulded fibre receptacle.

19. The moulded fibre receptacle drying system of any one of claim 10 to claim 18, comprising a further heating device configured to direct heat to an outer surface of the moulded fibre receptacle from outside the moulded fibre receptacle.

20. The moulded fibre receptacle drying system of any one of claim 10 to claim 19, comprising a sensor apparatus configured to receive electromagnetic radiation from the moulded fibre receptacle.

21. The moulded fibre receptacle drying system of any one of claim 10 to claim 20, comprising a heat shield, and configured to insert the heat shield into the moulded fibre receptacle such that it is disposed between the heating device and the neck portion of the moulded fibre receptacle.

22. A system comprising a moulding apparatus for moulding a fibre suspension to form a moulded fibre receptacle, and, downstream of the moulding apparatus, the moulded fibre receptacle drying system of any one of claim 10 to claim 21 for drying the moulded fibre receptacle.

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