WO2006126037A1

WO2006126037A1 - A process and apparatus for manufacturing an edible product

Info

Publication number: WO2006126037A1
Application number: PCT/IB2005/001486
Authority: WO
Inventors: Jonathan Robert Lamprecht; Wolfgang Peter SCHÖNAU
Original assignee: Mars, Incorporated
Priority date: 2005-05-27
Filing date: 2005-05-27
Publication date: 2006-11-30

Abstract

Apparatus for manufacturing a sugar-based candy product comprises two sets of mould parts arranged in endless loops, A drive mechanism circulates the mould parts, which are brought into partial engagement with one another in a filling zone between a set of end plates and below a feeder which pours hot sugar syrup into the cavity' between the end plates and the mould parts. As the mould parts move, they are brought into full engagement and urged into tight contact with one another, closing the mould cavities defined between them. As the mould parts move away from the filling zone, they are cooled to promote solidification of the syrup in the mould cavities. As the mould parts separate, the set feed material is discharged for further processing.

Description

A Process and Apparatus for Manufacturing an Edible Product

BACKGROUND OF THE INVENTION

THIS invention relates to a process for manufacturing a moulded product and to apparatus for implementing the process. In particular, the process and apparatus relate to the manufacture of sugar-based candy products.

Conventionally, small sugar-based candy products, typically having a spheroidal or lenticular shape, are manufactured by feeding a heated sugar syrup mixture into a set of chilled forming rolls. The rolls are arranged with their axes parallel and the surfaces of the rolls are provided with indentations which are arranged in register so that as each pair of indentations on the surfaces of the rolls moves into alignment, the cooling syrup is forced into the respective indentations and "embossed" into a spheroidal shape. As the rollers turn and the pair of indentations begin to separate, the moulded candy product is released, with a thin web joining adjacent products. The web of candy products is set down on a cooling conveyer to set further, and is then fed into a deflash drum which breaks the products apart and removes remnants of the web adhering to each product. Subsequently, the candy products are coated and coloured, and polished to a desired finish.

The above described process requires the sugar syrup to be partially cooled from its preparation temperature and to have sufficient viscosity, or adequate stand-up properties, to prevent it from running through the gap between the chiUed forming rolls. This currently requires the. use of a scraped surface heat exchanger to cool and optionally crystallise the cooked syrup before it is applied to the forming rolls, and optionally the use of a proportion of fine sugar particles to add to the syrup. In addition, the web extending between the multiple products formed by the forming rolls is undesirable and requires removal, necessitating deflashing and smoothing of the products before they can be coated and polished. It is an object of the invention to provide an alternative process for manufacturing moulded products, particularly edible products of the kind described, and suitable apparatus for carrying out the process.

SUMMARY OF THE INVENTION

According to the invention there is provided a process for manufacturing a moulded product comprising the steps of:

preparing a flowable feed material;

pouring flowable feed material into a mould cavity defined between a pair of mould parts while the mould parts are at least partially separated;

bringing the mould parts into engagement with one another to close the mould cavity;

allowing the flowable feed material to set in the mould cavity to define a moulded product; and

separating the mould parts to release the moulded product from the mould cavity.

Preferably, a plurality of sets of mould parts are provided, the method comprising moving the sets of mould parts around respective circuits so that each mould part is moved sequentially into and out of engagement with another mould part.

For example, two sets of mould parts may be provided, each set of mould parts being arranged in an endless loop, the method including circulating the respective sets of mould parts around the loops in synchronisation with one another.

The two sets of mould parts may travel between a pair of opposed end plates as they are brought sequentially into engagement with one another, thereby defining a mould filling zone between the end plates and respective mould parts as said mould parts pass between the end plates, the method including pouring a sufficient quantity of the flowable feed material into the mould filling zone to fill the mould cavity.

The volume of the mould filling zone may vary according to the positions of the respective mould parts as they pass between the end plates.

The^" flowable feed material is preferably heated prior to pouring thereof into the mould cavity and cools in the mould cavity so that it solidifies substantially prior to separation of the mould parts.

The process may include heating the mould parts prior to pouring the flowable feed material into the mould cavity, to prevent premature solidification of the feed material as it comes into contact with the mould parts.

The flowable feed material may be poured into the mould cavity at a temperature greater than 100⁰C, with the temperature of the mould parts being heated to a temperature 1⁰C to 1O⁰C higher than that of the feed material.

The process may include cooling the mould parts after filling of the mould cavity with the heated feed material to hasten solidification of the feed material.

The flowable feed material may be a heated syrup comprising sugars and/or sugar replacers. Further according to the invention there is provided apparatus for manufacturing a moulded product, the apparatus comprising:

first and second sets of mould parts, at least some of the mould parts defining a portion of a mould cavity, so that engagement of respective mould parts of the first and second sets of mould parts defines a mould cavity between the engaged mould parts;

a feeder for pouring a flowable feed material into the mould cavity; and

a drive mechanism arranged to move the mould parts into engagement with one another to retain the feed material in the mould cavity, thereby to permit setting of the feed material, and to separate the mould parts to release the set feed material from the mould cavity.

The sets of mould parts may be movable around respective circuits so that each mould part can be moved sequentially into and out of engagement with another mould part.

The circuits may comprise endless loops, permitting the respective sets of mould parts to be circulated around the loops in synchronisation with one another.

The apparatus may comprise at least three loops, with a first feeder for pouring a first flowable feed material into mould cavities defined between mould parts of the first and second loops, and a second feeder for pouring a second flowable feed material into mould cavities defined between mould parts of the first and third loops, thereby to define a moulded product comprising the first and second feed materials.

The apparatus may include a pair of opposed end plates defining a mould filling zone between the end plates and respective mould parts when said mould . parts are located between the end plates, the mould parts being arranged to make sliding contact with the opposed end plates as they are brought sequentially into engagement with one another.

Said mould parts may define a cavity having a volume which varies according to the positions of the respective mould parts in the feed zone between the end plates.

The apparatus may include a heating arrangement for heating the feeder and/or the end plates to prevent premature solidification of the feed material as it comes into contact with the feeder and/or the end plates, respectively.

The apparatus preferably includes a heating system for heating the mould parts prior to pouring the flowable feed material into the mould cavity, to prevent premature solidification of the feed material as it comes into contact with the mould parts, and a cooling system for cooling the mould parts after filling of the mould cavity with the heated feed material to hasten solidification of the feed material.

The apparatus may include a cooling system for cooling the mould parts after filling of the mould cavity with the heated feed material to hasten solidification of the feed material.

In a preferred embodiment of the apparatus, the first and second sets of mould parts are mounted on respective first and second support frames, the support frames being movable relative to one another between respective operational positions in which mould parts of the first and second sets of mould parts can engage one another, and respective maintenance positions in which the first and second sets of mould parts are separated. The apparatus may include an actuator arrangement for urging the engaging mould parts of the first and second_vsets of mould parts into firm engagement with one another.

For example, the actuator arrangement may comprise at least one pneumatic member arranged between respective bearing surfaces defined by the first and second support frames, so that inflation of said at least one actuator member urges the first and second support frames into their operational positions.

Preferably, each mould part of the apparatus is hinged to adjacent mould parts at opposed ends thereof, to define an endless loop of joined mould parts.

In a preferred embodiment of the apparatus, adjacent mould parts are joined by magnetic hinges comprising a hinge pin of magnetic material and respective sets of magnets in the ends of the mould parts arranged to exert an attractive force between the mould parts.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a simplified schematic diagram of an installation including apparatus according to the present invention for manufacturing a moulded product;

Figure 2 is a schematic side view of moulding apparatus according to the present invention;

Figure 2(a) is an enlargement of the upper portion of the moulding apparatus shown in Figure 2;

Figure 2(b) is an enlargement of the lower portion of the moulding apparatus shown in Figure 2; Figure 3 is a schematic diagram corresponding to Figure 1 , showing zones of heating and cooling of the moulding apparatus;

Figure 4 is a schematic diagram showing a modified version of the moulding apparatus comprising multiple loops of mould parts;

Figure 5 is a partially exploded pictorial view of a portion of the moulding apparatus showing individual mould parts thereof;

Figure 6(a) is a partial sectional side view on the line 6 - 6 in Figure 5;

Figure 6(b) is a similar view to that of Figure 6, showing an alternative orientation of the mould parts relative to one another;

Figure 7(a) is a top view of a support structure for the moulding apparatus in a first, operational configuration thereof;

Figure 7(b) is a similar view to that of Figure 7(a) showing the support structure in an opened, non-operational configuration; and

Figure 7(c) is a side view of the support structure of Figure 7(a).

DESCRIPTION OF AN EMBODIMENT

Referring first to Figure 1 , an installation or plant for manufacturing sugar- based candy products according to the process of the invention is shown in a schematic form.

The installation comprises a mixing vessel 10 in which a syrup comprising sugars and/or sugar replacers is formed. Typically, a sugar syrup is formed by mixing water and sugar (sucrose) or sugar replacer and adding other sweeteners such as glucose syrup and other desired components such as an emulsifier and gelling agents. These components are mixed at a temperature which is usually below 100⁰C, typically 65°C, and the prepared mixture is fed to a storage tank 12.

When the sugar syrup is required for use, a pump 14 pumps the mixture through a heat exchanger such as a plate heat exchanger 16 in which the temperature of the mixture is raised to a temperature above 100⁰C and typically in the range of 1 10° to 150°C. From the heat exchanger, the hot mixture is fed to a flash-off vessel 18 in which vapour and steam are separated from the hot liquid mixture. From the flash-off vessel, the hot mixture is fed to a mixer which can be a screw with a static orifice plate pack or a screw and pin mixer, for example, in which colourants and flavourants, powdered ingredients such as castor sugar, and other ingredients such as citric acid and fat are added. Air may be injected into the mixture to aerate it to a desired extent.

Optionally, an additional heat exchanger such as a scraped surface heat exchanger can be located between the flash-off vessel 18 and the mixer 20.

The above described components of the installation are generally conventional and are well known to those skilled in the art.

The output of the mixer 20 is a hot, flowable syrup mixture at a temperature typically in the region of 115⁰C. The temperature of the mixture may be somewhat higher or lower depending on the nature of the candy product to be formed.

The output of the mixer 20 is fed to a moulding apparatus according to the invention which is illustrated in greater detail in Figures 2 to 7 and which is described in greater detail below. The moulding apparatus moulds the hot syrup mixture into individual candy products, cools the moulded products and ejects the formed products for further processing. At the output of the moulding apparatus, the moulded candy products are collected and fed to panning equipment which can be of a conventional nature and in which the moulded candy products are coated with a sugar- based coloured coating and polished, for example. The panned candy products can then be passed to a printing station and a packaging station, both of which can also be conventional.

Referring now to Figure 2, the moulding apparatus 22 of Figure 1 is shown in greater detail. The moulding apparatus comprises two adjacent loops 30 and 32 of mating mould parts, the mould parts in each loop being connected together hingedly end to end as described below. The loops 30 and 32 are arranged upright, preferably substantially vertically, by a support structure which is shown in Figures 7(a) to (c). The loop 30 is supported between respective upper and lower rollers 34 and 36 which are driven in synchronization with corresponding upper and lower rollers 38 and 40 of the second loop 32 to cause the loops of mould parts to rotate synchronously as indicated by the arrows in Figure 2.

As better shown in the enlarged detail of Figure 2(a), a pair of generally triangular opposed end plates 42 (only one of which is shown) are provided at the upper end of the moulding apparatus, with which the opposed edges of the mould parts make sliding contact as the loops of mould parts rotate. Optionally the end plates can be maintained at elevated temperatures by heating means applied to the outer surface of the plates. Mounted above the end plates 42 and having an outlet 44 between them is a funnel or hopper 46 which is provided with channels 48 to allow it to be heated by steam or another heating medium. Alternatively the end plate function can be provided by extensions of all or some of the mould blocks, automatically sliding away against their mating mould blocks of the other loop when not serving this function.

Just below the outlet 44 of the funnel 46, respective lower ends of adjacent mould parts 50.1 and 50.2 come into engagement with one another as they move around the rollers 34 and 38, temporarily defining a filling zone having an open cavity 52 which is flooded with sugar syrup from the funnel. As the loops of mould parts continue to circulate, the engaging faces of the two adjacent mould parts 50.1 and 50.2 move into firm engagement with one another, enclosing a quantity of the syrup between them in complemental indentations that together define mould cavities. As the faces of the adjacent mould parts 50.1 and 50.2 come into full engagement with one another, the respective lower edges of the next set of mould parts 50.3 and 50.4 come into engagement with one another, and the process continues in this fashion.

As can be seen in Figure 2(a), an upright groove 54 is formed centrally on the inner surface of each end plate 42, which accommodates syrup squeezed out laterally between the engaging moulding faces of the mould parts as they come together.

The mould parts themselves are described in greater detail below with reference to Figures 5, 6(a) and 6(b).

Figure 2(b) shows the lower part of the moulding apparatus of Figure 1 in more detail. In this Figure, the lower rollers 36 and 40 are seen to be toothed and engage rollers 56 (or other projections) on the rear of the mould parts 50 as they turn, driving the loops of mould parts in the direction of the arrows. Within each of the loops 30 and 32 are pairs of guide rails 58, 60 and 62, 64 which are typically steel rods of circular cross-section mounted on respective frames 66 and 68, shown in Figures 7(a), 7(b) and 7(c). The frame 66 is mounted pivotably on a first set of arms 70, while the frame 68 is mounted on a second set of arms 72.

The sets of arms 70 and 72 are mounted pivotably about a shaft 74, and several of the arms 70 and 72, respectively, are mounted one below the other, supporting the respective frames 66 and 68 at intervals along the length thereof. The shaft 74 is supported by a main frame having a top plate 76 and a base plate 78. Adjacent the shaft 74 and remote from the ends 80 and 82 of the arms which support the respective frames 66 and 68, bearing surfaces 84 and 86 are formed in recesses in the arms which define between them a rectangular cavity. Received in the cavity is a pair of vertically extending pneumatic hoses 88 and 90, which are connected by a control mechanism to a source of compressed air. When the hoses 88 and 90 are inflated, adjacent plates 50.1 and 50.2 are pressed into engagement with one another by a force transmitted to the respective arms 70 and 72.

Each of the moulding plates 50 has a grooved roller 92 mounted on the rear thereof, the roller being shaped to engage the guides 58, 60, 62 and 64. Thus, inflating the pneumatic hoses 88 and 90 causes the ends 80 and 82 of the arms 70 and 72 to move towards one another, applying a force to the adjacent mould parts 50.1 and 50.2 via the guides 60 and 62 of the respective frames 66 and 68, the force being transmitted to the plates themselves via the rollers 92 mounted thereon as the mould parts travel along the respective loops.

By inflating the hoses 88 and 90 to sufficient pressure, a desired mating pressure between the mating surfaces of the mould parts can be obtained. The pressure exerted by the pneumatic hoses 88 and 90 is sufficient to urge the mating faces of the mould parts together sufficiently strongly to exclude substantially all surplus syrup from the engaging flat surfaces of the mould parts, thus ensuring that only a negligible quantity of flash is formed between the candy products.

In Figure 7(b), a locking mechanism (not shown) of the support apparatus has been unlocked and the arms 70 and 72 have been swung apart, separating the two loops of mould parts for easy maintenance.

Turning to Figure 2(b) it can be seen that vibrating blocks 94 and 96 are mounted adjacent the respective loops 30 and 32 near the lower ends thereof, on the return routes of the mould parts. As the mould parts separate at the lower end of the moulding apparatus, the moulded candy products 96 tend to fall out as shown. However, some of the moulded products may stick to the mould surfaces, requiring mechanical removal. The vibrating plates 94 and 96 are grooved longitudinally, with the grooves oriented upright, in the direction of travel of the mould parts, and are caused to vibrate from side to side by small pneumatic motors 98 and 100, respectively, connected to a source of compressed air. This tends to shake loose any products which adhere to the mould surfaces. Finally, air knives 102 and 104 are located adjacent the loops above the plates 94 and 96, to remove any remaining stuck candy products or detritus with a strong blast of compressed air.

Referring now to Figure 3, a schematic diagram corresponding to the arrangement of Figure 2 is shown, indicating heating and cooling zones applicable to the moulding apparatus. As indicated by the legend in Figure 3, the mould parts circulating upwardly towards the funnel 46 are heated by steam from a position near the lower end of the apparatus, with increasing heat being applied as the mould parts move towards the upper end of the apparatus. As the mould parts reach the upper rollers 34 and 38, they are subjected to heating by steam at approximately 100°C, and the mould parts continue to be heated until shortly after they have been brought into engagement with one another. The heating of the mould parts prevents sudden cooling and solidification of the syrup as it comes into contact with the mould parts.

As the engaged mould parts move downwardly with the hot syrup contained between them, they are subjected to increasing degrees of cooling, as indicated, up to and just beyond the point where they separate at the lower end of the apparatus. The cooling of the mould parts is carried out using chilled water or brine, for example. The cooling treatment helps with demoulding due to the action of solidification and contraction.

By actively heating and cooling the apparatus, the length of the loops 30 and 32 can be shortened and the moulding time can be reduced. The candy products 96 are typically spheroidal or flattened-spheroidal in shape and may be in the region of 5mm to 20mm in diameter. However, it will be appreciated that this range of dimensions is purely exemplary.

Figures 5, 6(a) and 6(b) show the individual mould parts in greater detail. Each mould part 50 is generally ingot shaped, with a flat mould surface 106 defining a plurality of part-spheroidal indentations 108. When the mould faces 106 of two mould parts 50 are brought into engagement with one another, with the mould cavities 108 correctly aligned, a plurality of separate, closed mould cavities are defined by the matching indentations. The mould surfaces 106 are preferably provided with a non-stick coating to facilitate ejection of moulded products from the mould parts.

At opposite ends of the mould parts 50, inclined end faces 110 and 112 have transversely extending grooves 114 formed at the edges thereof which adjoin the mould surfaces 106, sized to received cylindrical hinge pins 116. The hinge pins in the prototype apparatus were formed from chromed steel, while the mould parts 50 were machined from solid aluminum billets. It will be appreciated that the mould parts could be formed with a composite structure, for example, with interchangeable mould plates securable to a base portion of the mould part. It will also be appreciated that the number, shape and configuration of the indentations in the mould surfaces can be varied as required, to define moulded products of the required shape and size.

As best seen in Figures 6(a) and 6(b) slots 118 are machined in the end faces 110 and 112 of each mould part 50 to receive rare earth magnets 120, with the poles of the magnets 120 at opposite ends of each mould part being oriented oppositely. The slots 1 18 are located as close as possible to the hinge pins 116 and the magnets in the slots, together with the hinge pin, define a magnetic hinge which holds adjacent mould parts 50 together firmly but permits relative movement thereof about the hinge pins 52 (as shown in Figure 6b) as the mould parts pass around the loops 30 and 32 of the apparatus. With suitable tolerances and magnetic material a strong, even attractive force is exerted between the hinge components, so that the hinges are self cleaning and resist the ingress of sugar syrup in use. However, it will be appreciated that alternative, mechanical hinge structures can also be used.

The above described apparatus essentially permits a continuous hot moulding operation which can accept a hot sugar syrup feed at, say, 115°C, compared with prior art chilled roller apparatus which requires a syrup feed which has been cooled to 90°C. The syrup fed to the apparatus of the present invention can be liquid and does not need to have substantial stand-up properties or viscosity.

Because the syrup is formed into a candy product in individual closed mould cavities, the product has little or no flash and thus requires little or no deflashing or smoothing treatment prior to panning thereof. In addition, the relatively uniform shape of the product 96 tends to require less panning. No additional cool web conveyer is required, with a concomitant reduction in the requirement for conditioned air. A further advantage of the invention is a simplification of upstream equipment and processes ahead of the moulding apparatus. The moulding apparatus is relatively compact and is expected to cost substantially less than the prior art system of chilled rolls and cooled web conveyers.

A variation of the moulding apparatus is shown in Figure 4, which illustrates how the invention can be applied to the manufacture of multi-part candy products. In Figure 4, a moulding apparatus is shown which is generally similar to that of Figure 2. However, the left side loop 1 12 of the apparatus is a full-sized loop, while the right side loop 124 is shortened. The mould parts 126 of the left side loop each have an indentation 128 formed in the mould surface thereof, while the mould parts 130 of the right side loop are formed with flat mould surfaces. Thus, at the bottom of the loop 124, where the mould parts 130 separate from the mould parts 126, the mould parts 126 contain a hemispherical or hemispheroidal candy product. A third loop 132 is located below the loop 124 and a hopper or chute 134 is arranged to direct heated sugar syrup into a cavity 136 defined between the mould parts 126 of the first loop 122 and mould parts 134 of the third loop 132. The mould parts 134 are formed with hemispherical or hemispheroidal indentations 136, which are aligned with the indentations 128 in the mould parts 128.

By using a sugar syrup of a different colour or having another different characteristic from the sugar syrup introduced at the top of the apparatus, two-component or two-coloured candy products can be obtained. Optionally the two halves could have different shape profile or surface detail.

It will be appreciated that, in principle, any number of additional loops can be provided, allowing multi-component or multi-layer candy products to be manufactured. Realistically, four-component candy products can be produced in this way.

The end plates 42 and the mould parts 50 at the upper end of the apparatus are preferably heated to a higher temperature, preferably in a range 1 °C to 10⁰C higher, than the temperature of the sugar syrup supplied to the apparatus. The value of the temperature differential will depend on the product in question. For example, the differential will be greater in the case of hard candy products, and less in the case of softer products. The heat differential lowers the viscosity of the product where it contacts the mould plates, allowing excess syrup to be squeezed out between the mould parts relatively easily, with less force than would otherwise be required.

It will be appreciated by those skilled in the art that although the invention has been described with reference to a process adapted for the production of sugar-based candy products, the invention can be applied to the production of other products.

Claims

1. A process for manufacturing a moulded product comprising the steps of:

preparing a flowable feed material;

2. A process according to claim 1 wherein a plurality of sets of mould parts are provided, the method comprising moving the sets of mould parts around respective circuits so that each mould part is moved sequentially into and out of engagement with another mould part.

3. A process according to claim 2 wherein two sets of mould parts are provided, each set of mould parts being arranged in an endless loop, the method including circulating the respective sets of mould parts around the loops in synchronisation with one another.

4. A process according to claim 3 wherein the two sets of mould parts travel between a pair of opposed end plates as they are brought sequentially into engagement with one another, thereby defining a mould filling zone between the end plates and respective mould parts as said mould parts pass between the end plates, the method including pouring a sufficient quantity of the flowable feed material into the mould filling zone to fill the mould cavity.

5. A process according to claim 4 wherein the volume of the mould filling zone varies according to the positions of the respective mould parts as they pass between the end plates.

6. A process according to any one of claims 1 to 5 wherein the flowable feed material is heated prior to pouring thereof into the mould cavity and cools in the mould cavity so that it solidifies substantially prior to separation of the mould parts.

7. A process according to any one of claims 1 to 6 including heating the mould parts prior to pouring the flowable feed material into the mould cavity, to prevent premature solidification of the feed material as it comes into contact with the mould parts.

8. A process according to claim 7 wherein the flowable feed material is poured into the mould cavity at a temperature greater than 100⁰C, with the temperature of the mould parts being heated to a temperature 1 ° C to 10° C higher than that of the feed material.

9. A process according to any one of claims 1 to 8 including cooling the mould parts after filling of the mould cavity with the heated feed material to hasten solidification of the feed material.

10. A process according to any one of claims 1 to 9 wherein the flowable feed material is a heated syrup comprising sugars and/or sugar replacers.

11. Apparatus for manufacturing a moulded product, the apparatus comprising: first and second sets of mould parts, at least some of the mould parts defining a portion of a mould cavity, so that engagement of respective mould parts of the first and second sets of mould parts defines a mould cavity between the engaged mould parts;

a feeder for pouring a flowable feed material into the mould cavity; and

12. Apparatus according to claim 11 wherein the sets of mould parts are movable around respective circuits so that each mould part can be moved sequentially into and out of engagement with another mould part.

13. Apparatus according to claim 12 wherein the circuits comprise endless loops, permitting the respective sets of mould parts^' to be circulated around the loops in synchronisation with one another.

14. Apparatus according to claim 13 comprising at least three loops, with a first feeder for pouring a first flowable feed material into mould cavities defined between mould parts of the first and second loops, and a second feeder for pouring a second flowable feed material into mould cavities defined between mould parts of the first and third loops, thereby to define a moulded product comprising the first and second feed materials.

15. Apparatus according to any one of claims 11 to 14 including a pair of opposed end plates defining a mould filling zone between the end plates and respective mould parts when said mould parts are located between the end plates, the mould parts being arranged to make sliding contact with the opposed end plates as they are brought sequentially into engagement with one another.

16. Apparatus according to claim 15 wherein said mould parts define a cavity in the mould filling zone, the cavity having a volume which varies according to the positions of the respective mould parts in the feed zone between the end plates.

17. Apparatus according to claim 15 or claim 16 including a heating arrangement for heating the feeder and/or the end plates to prevent premature solidification of the feed material as it comes into contact with the feeder and/or the end plates, respectively.

18. Apparatus according to any one of claims 11 to 17 including a heating system for heating the mould parts prior to pouring the flowable feed material into the mould cavity, to prevent premature solidification of the feed material as it comes into contact with the mould parts.

19. Apparatus according to any one of claims 11 to 18 including a cooling system for cooling the mould parts after filling of the mould cavity with the heated feed material to hasten solidification of the feed material.

20. Apparatus according to any one of claims 11 to 19 wherein the first and second sets of mould parts are mounted on respective first and second support frames, the support frames being movable relative to one another between respective operational positions in which mould parts of the first and second sets of mould parts can engage one another, and respective maintenance positions in which the first and second sets of mould parts are separated.

21. Apparatus according to claim 20 including an actuator arrangement for urging the engaging mould parts of the first and second sets of mould parts into firm engagement with one another.

22. Apparatus according to claim 21 wherein the actuator arrangement comprises at least one pneumatic member arranged between respective bearing surfaces defined by the first and second support frames, so that inflation of said at least one actuator member urges the first and second support frames into their operational positions.

23. Apparatus according to any one of claims 11 to 22 wherein each mould part is hinged to adjacent mould parts at opposed ends thereof, to define an endless loop of joined mould parts.

24. Apparatus according to claim 23 wherein adjacent mould parts are joined by magnetic hinges comprising a hinge pin of magnetic material and respective sets of magnets in the ends of the mould parts arranged to exert an attractive force between the mould parts.