Method and moulding devices for moulding three-dimensional products

0001The invention relates in general to the moulding of three-dimensional, products from a mass of foodstuff starting materials which are suitable for consumption, in particular from a meat mass. More specifically, the invention relates to a moulding method, moulding devices and components which can be used in moulding devices.

0002A first aspect of the invention relates to a method for moulding three-dimensional products from a mass of foodstuff starting materials which are suitable for consumption, in particular a meat mass, comprising the steps of <ol id="ol0001" compact="compact"><li>a) filling a mould cavity, which is open on one side, with the mass of foodstuff starting materials which are suitable for consumption, which mould cavity is defined by a boundary comprising walls and base, in order to mould a moulded three-dimensional product; and</li><li>b) removing the moulded three-dimensional product from the mould cavity.</li></ol>

0003A method of this type and a device used for the method are known in the art, for example from the international patent application <patcit id="pcit0001" dnum="WO0030458A"><text>WO-A-00/30458</text></patcit> in the name of the Applicant and can be used to mould edible products from, for example, kneaded meat. This known device of the so-called "rotating drum type" has a rotatable drum which is driven continuously by an associated drive. A plurality of mould cavities which define the shape of the products which are to be produced are located on the outer side of the drum. At the filling position there is a filling member which fills the mould cavities which move past it during rotation with the mass. The products formed in this way are removed from the mould cavities at a release position located downstream of the filling position. This known moulding device uses means for exerting fixing pressure which are designed to exert a fixing pressure which acts on the mass in the mould cavity after the filled mould cavity has been Closed. This fixing pressure differs from the filling pressure which is exerted on a portion of the mass during filling of a mould cavity with this portion. The fixing pressure is used to make the pieces of the mass stick together after the filling operation and in this way to obtain a dimensionally stable product of the desired end weight which can be removed from the mould cavity.

0004In addition, this application describes a number of techniques used to assist with the removal of moulded products from the mould cavities in question under the influence of the force of gravity. In one embodiment, during each revolution of the drum a web of a film is placed in a mould cavity. For removal, stress is imparted to the web from one side, so that the web and therefore the moulded product are lifted out of the mould cavity from one side. If appropriate, the removal can be further assisted by compressed air being blown in beneath the web from a central point located in the base of the mould cavity In another embodiment, a flexible membrane is secured in a mould cavity in order to prevent contamination. The base of the mould cavity is in communication with an air source and/or vacuum means at various locations, via passages. By selective actuation, it is possible for the flexible membrane to be sucked into the mould cavity or for a moulded product to be removed. In this embodiment too, the removal can be assisted by compressed air which is blown onto the underside of the membrane from a central location and from points located in the vicinity of the peripheral edge of the base.

0005<patcit id="pcit0002" dnum="US3205837A"><text>US-A-3205837</text></patcit> dislcoses an apparatus for producing edible products, the apparatus comprising a rotary die roll having a porous wall defining a die cavity, means for introducing dough into the die cavity and means for passing a fluid such as air through the porous wall of the die while the dough is filled into the respective cavity, thereby creating a fluid film between the dough product and the die for preventing adhesion of the dough product to the die. In order to eject the shaped product from the die cavity a fluid under higher pressure is forced through the porous wall.

0006<patcit id="pcit0003" dnum="US4212609A"><text>US-A-4212609</text></patcit> discloses a method and apparatus for producing shaped and sized food articles, wherein ejection plungers having a porous bottom structure are used in the die cavities to eject shaped articles.

0007Now, it has been found that the shape of the moulded product is insufficiently uniform, in particular their edge definition This leads to product loss Defects which have been observed include the formation of lips, small pieces which break off at the edges, dents and the like.

0008Furthermore, it has been found that the service life of the plastic films used leaves something to be desired The service life is short, meaning that they have to be replaced frequently, with all the associated drawbacks relating to production idle time, maintenance work and other costs.

0009A further drawback of these known techniques is that it is difficult to monitor and maintain hygiene in these devices on account of the number of parts which come into contact with foodstuff starting material

0010It is an object of the present invention to provide a method and devices with which it is possible to provide products with a shape which is more uniform over the course of time. Another object of the invention is to provide a method and devices which can be used to produce products with a low spread in weight.. Yet another object of the invention is to provide such a method and device in which the number of components which come into contact with the foodstuff starting material is very small

0011The method according to the invention is defined in claim 1 the device according to the invention is defined in claim 4.

0012In the method according to the invention, to this end step b) comprises the removal of the adhesion forces between product and boundary of the cavity substantially simultaneously at all the interface between the moulded three-dimensional product and the boundary. According to the invention, the adhesion forces are substantially eliminated, at the time of release, at all the surfaces of the moulded product which are in contact with the base and peripheral wall simultaneously It has been found that the removal of a moulded product is simpler and leads to less production loss if the adhesion forces are eliminated on all sides (apart from the open side of the mould cavity). The release occurs partly as a result of the force of gravity (the inherent weight of a moulded product, with a force of this nature simultaneously being boosted by eliminating the adhesion forces on all sides As a result of release occurring on all sides simultaneously, the edge definition of the moulded product is greatly improved compared to the prior art, and the finished moulded product more accurately corresponds to the mould cavity, since it retains the shape. It should be emphasized that in the invention, in addition to the force of gravity a force is temporarily also exerted for the purpose of removing the moulded product from a mould cavity, which force is not produced by mechanical means which are in contact with the product, such as for example a plunger Furthermore, this additional expulsion force is generated at the time of release and is not permanently present, as for example in the case of a non-stick layer, The reproducibility of the shape of the moulded products in the device according to this aspect of the invention is improved in this way, as is the reproducibility of the weight. In addition, there is no need for any additional materials, such as the disposable film used in the moulding device according to the prior art, or for the associated processing equipment

0013A means for eliminating the adhesion forces is used to remove the adhesion forces In this context, use is made of the difference in properties of the means which eliminates the adhesion forces and those of the foodstuff starting material, from which the product is moulded. According to the invention this means comprise a forcing fluid (a pressurized fluid).

0014It is more preferable to use compressed air or stream. Combinations of compressed air in which a liquid constituent is dispersed, such as water, for humidification, can also be used. Moreover, this opens up the possibility of implementing a desired addition, if necessary, to the product, for example, a (preserving) salt dissolved in water, or oil, etc. The boundary is permeable in order to allow the supply of a forcing fluid of this type.

0015For a forcing fluid to be supplied on all sides (apart from the open top side), it is advantageous for the boundary of a mould cavity to be provided with passages with openings which, distribute over base and peripheral wall of the mould cavity, open out at the surface of the boundary, with a pressurized fluid being fed to the passages. The passages may be of any desired shape, rectilinear, angled for curved, may be regular or irregular, taper or may widen out at their end The shape and size of the passages party determine the depth of penetration of the mass into the boundary and the through-flow of the fluid in the boundary, and therefore the forces exerted by the fluid. In addition, it is preferable for the size of the outlet openings of the passages to be selected in such a way that the pieces of the foodstuff starting materials are not caught in the passages. This will be explained in more detail below. Examples of a material used for this type of boundary include a perforated plate or a foil provided with openings, for example made from nickel or stainless steel. Passages can be formed, for example, using a laser treatment Etching or electroforming are other examples of suitable production techniques.

0016According to the invention the boundary comprises a porous structure of intercommunicating pores. In this way, it is possible to obtain a uniform distribution of the forcing fluid over all the interfaces between the boundary and the moulded products, which assists with the uniform removal of the product. The pore size will be selected as a function of the starting material to be processed and the forcing fluid used. By way of example, it has been found that in the case of porous boundaries made from sintered stainless steel with effective pore diameters in the range from approximately 1-20 micrometers, effective removal can be achieved for a specific meat mass. Combinations of passage structures and porous structures are also among the possible options.

0017Examples of suitable materials for the porous structure, of the boundary, include ceramic materials, plastics and metals, including in particular wintered steel,

0018It should be noted that the <patcit id="pcit0004" dnum="US4987643A"><text>patent publication US-A-4,987,643</text></patcit> and <patcit id="pcit0005" dnum="US4212609A"><text>US-A-4,212,609</text></patcit> have per se disclosed moulding machines in which the mould cavities have a base which can move up and down for removal of moulded products, which base is porous and is in communication with a supply of compressed air or the like to assist with removal of the moulded products from the mould cavities.

0019The mould cavities are advantageously formed in the porous boundary by spark erosion. The production of a mould from porous metal often uses a treatment which causes the openings of the pores which open out at the surface to be virtually completely closed up Spark erosion causes the porous structure of the boundary to be opened up again at the location of the mould cavity

0020After use, the passages and/or openings can also be used for cleaning of the mould cavities, for example by water or steam, optionally with the addition of a cleaning agent or disinfectant, being fed to them.

0021According to a further preferred embodiment, during step a) air which is enclosed between the mass and the boundary is discharged through the boundary. The boundary structure with passages and/or pores is eminently suitable for this purpose. Complete filling of a mould cavity is achieved by removing this air, for example sucking it out with the aid of suction means, so that the enclosed air does not leave any traces in the shape of the finished product or interferes with uniform removal.

0022According to a second aspect, the invention relates as defined in claim 4 to a device for moulding three-dimensional product from a mass of foodstuff starting materials which are suitable for consumption, in particular a meat mass, comprising a moulding surface, which is provided on one side with one of more mould cavities which are open on one side and are defined by a boundary comprising walls and base, a mass feed member, which is arranged at a mass feed position, for feeding the said mass to the mould cavities

0023A device of this type, in which the moulding surface is the outer wall of a drum, is known from the abovementioned <patcit id="pcit0006" dnum="WO0030458A"><text>WO publication WO 00/30458</text></patcit>

0024According to the invention, the device also comprises means for simultaneously removing the adhesion forces between product and boundary of the mould cavity at all interfaces between a moulded three-dimensional product and the boundary. A device of this type achieves the above-described advantages relating to edge definition and uniformity of shape and weight of the moulded products.

0025The said means will be selected as a function of the embodiment in question.

0026If a forcing fluid is used as the means which eliminates the adhesion forces, the said means comprise excess-pressure means which are in fluid communication with the boundary of a mould cavity and are used to supply a pressurized fluid, such as compressed air or water. For a uniform distribution of the forcing fluid, it is advantageous for the boundary to be provided with passages with openings, which passages are in communication with excess-pressure means. The boundary comprises a porous structure of intercommunicating pores, for the reasons outlined above.

0027In yet another preferred embodiment, the device also comprises reduced-pressure means for forming reduced pressure in a mould cavity during the filling operation, so that enclosed air can be sucked out.

0028To obtain a simple structure of the device, in particular the system of lines used to supply a pressurized fluid or removed air, it is advantageous for a connecting passage to be in communication with the boundary of a mould cavity, which connecting passage can be selectively coupled to the reduced-pressure means and the excess-pressure means.

0029The moulding surface is advantageously made completely from sintered metal in which the mould cavities are formed by spark erosion. A single-piece moulding surface is a component which is easier to exchange when the moulding device needs to be used for the production of a different product shape or when the moulding device is presented for maintenance, such as cleaning, or for repair.

0030With a view to product flexibility, it is advantageous for the moulding surface to be provided with recesses in which corresponding inserts are releasably accommodated, these inserts comprising the mould cavities. In an embodiment of this type, the inserts are exchangeable, so that a variety of products can be moulded using the same moulding surface.

0031The recesses are advantageously substantially rectangular in shape, and if the outer wall of a drum is the moulding surface, the inserts comprise a substantially corresponding rectangular body, of which only the upper surface, in which the mould cavity is located, has a radius of curvature matching the radius of curvature of the drum. Recesses of this form are relatively easy to manufacture into the drum, and the corresponding inserts can also be produced in a simple way.

0032In a further advantageous embodiment thereof, the height of an insert is slightly smaller than the depth of the recess, and spacers are provided between the base of the recess and the underside of the insert, so that there is a space which can function as a collection chamber for extracted air or distribution chamber for a forcing fluid. Obviously, it is also possible for the spacers to form an integral part of the inserts, for example in the form of small legs.

0033The method described above can be carried out with various types of moulding devices, for example a turntable, a turret, a drum or an optionally stationary flat plate. With a view to achieving a high production rate, the moulding surface is preferably the wall of a drum which can be rotated in a direction of rotation by associated drive means and is provided with at least one mould cavity which is open at the outer circumference of the drum and has an associated boundary comprising walls and base.

0034The moulding surface for moulding three-dimensional products, in particular a moulding drum, from a mass of foodstuff starting materials which are suitable for consumption, in particular from a meat mass, is provided on one side with one or more mould cavities which are open on one side and are defined by a boundary comprising walls and base A moulding surface of this type in the form of a drum is known from <patcit id="pcit0007" dnum="WO0030458A"><text>WO-A-00/30458</text></patcit>, as discussed above. The walls and base which form the boundary are provided with holes which extend through the boundary. A moulding surface of this type allows the adhesion forces between the boundary and a moulded product to be removed virtually simultaneously at all the interfaces, for example using a forcing fluid as has also been explained above This leads to the abovementioned advantages with regards to simplicity and ease of removal and reduced product wastage. Furthermore, this leads to more rapid removal, so that a higher production rate can be achieved,

0035The moulding surface is advantageously a moulding drum A drum of this type has a substantially cylindrical drum wall. The drum diameter is, for example, 0.15 to 0.7 m, while the length may vary from a few tens of centimetres, for example 30 cm, to a few metres. The drum may be made from a single piece, such as for example a pipe, or from a plurality of interconnected pipe sections, reinforcements being provided if desired, for example ribs, plates or prestressing means. The mould cavities are provided in the outer side of the drum wall, for example in the form of rows which are parallel in the axial direction or offset. Other examples of moulding surfaces are straight plates, a turntable or a turret

0036The holes comprise a porous structure of intercommunicating pores. An embodiment of this type allows a uniform distribution of the holes over the boundary and therefore allows uniform removal of a moulded product from the mould cavity.

0037As has already been described above, a boundary is advantageously made from sintered metal, more particularly by means of spark erosion. The moulding surface is advantageously made from a porous sintered metal, of which the pore openings which open out at the surfaces are sealed off by the machining steps carried out during production of the molding surface, after which the mould cavities are manufactured by spark erosion, so that the pore openings are locally opened up again.

0038In a further preferred embodiment, the moulding surface with the mould cavities therein is produced from one piece, more particularly having similarly shaped mould cavities A moulding surface of this type can be exchanged quickly and easily, for example if a product change is to be carried out, compared to a moulding surface with moulding elements which can be exchanged separately and have one or more mould cavities, with each moulding element having to be changed separately, requiting a large number of operation. Thins relatively high exchange speed reduces the time required for maintenance, repair or changeover, so that the idle time of the moulding device in which the moulding surface is used can be kept short.

0039Examples of suitable materials for the porous structure of the boundary include ceramic materials, plastics and metals, including in particular sintered steel,

0040According to a further preferred embodiment, the outer circumference of the drum is provided with recesses in which corresponding inserts are removably accommodated, which inserts comprise the mould cavities. In an embodiment of this type, the inserts are exchangeable, and consequently the changeover times from one product to another are relatively short, since the exchange of mould cavities required for this purpose can be carried out quickly and easily.

0041The recesses are advantageously substantially rectangular in shape, and the inserts advantageously comprise a substantially matching rectangular body, of which only the upper surface, in which the mould cavity is located, has a radius of curvature matching the radius of curvature of the drum Recesses of this form are relatively easy to form in the drum and it is also easy to produce the associated inserts.

0042In a further expedient embodiment thereof, the height of an insert is slightly less than the depth of the recess, and spacers are provided between the base of the recess, and the underside of the insert, so that there is a space which can function as a collection chamber or distribution chamber for air. Obviously, the spacers may also form an integral part of the inserts, for example in the form of small legs.

0043The openings of the boundary are advantageously also in communication with excess-pressure means which are designed to supply a pressure medium to the mould cavity, so that the release of products from the mould cavities as a result of their inherent weight can be assisted by a suitable pressure medium being passed through the fine openings from the inside outwards, so that the product is in this way pushed out of the mould cavity. Moreover, this opens up the option of carrying out a desired addition, if necessary, to the product, for example water or oil, etc. In this way, after use, it is also possible for the device, in particular its mould cavities, to be cleaned by rinsing with a cleaning agent.

0044In the base of the recess there are advantageously one or more openings which can be used for a number of purposes. It is preferable for a connecting passage to be in communication with the opening in the base of the recess, which connecting passage can be selectively connected to the reduced-pressure means and the excess-pressure means.

0045If desired, a release device, arranged at a release position, can be provided for removal of moulded products from the mould cavities. A release device of this type is useful primarily for the moulding device with flexible premoulds if the moulded products have a considerable tendency to stick to the flexible premoulds. The release device is designed in such a way that it has a separation element which can be introduced between the flexible premould and the moulded product without damaging either of them.

0046A preferred embodiment of a release device of this type comprises driveable endless conveyors which are arranged in parallel and describe a movement path about turning elements, between which conveyors there are connecting elements, in such a manner that the connecting elements, at the release position, pass virtually through the centre of the axis of the turning element in question. In this preferred embodiment, with this turning element, for example a turning roll or gearwheel, the movement path of the connecting elements is suddenly reversed at the release position. As a result of this reversal position being located along a tangent on the drum, in particular along the tangent on an ejected flexible premould, at a location where a moulded product moves out of the premould slightly as a result of its own weight, and as a result of the direction of movement being selected to be opposite to the tangential direction of movement of the drum, it is possible to achieve effective release. The connecting elements have a small surface area, so that the removed products do not stick to them, but rather can drop off onto a discharge belt which is guided along the bottom of the release device.

0047In an expedient embodiment of a release device of this type, the endless conveyors comprise chains, the links of which comprise an inwardly projecting part to which transverse spindles are connected.

0048It will be understood that a release device of this type can also be used for other applications, for example as what is known as a shooter belt for putting objects down in a metered manner onto another conveyor belt or onto positions where there is little space, and also in other known moulding devices.

0049The drum made, for example, from plastics or (sintered) metal - which may be solid or hollow - and is used in the preferred embodiments of the moulding devices according to the invention is difficult to produce with a constant diameter. This means that leakage may occur between the mass feed member and the outer circumference of the drum, which is undesirable with regard to loss of starting material but also on account of a resultant reduction in the quality of the moulded product.

0050To avoid this problem, the mass feed member advantageously comprises a housing in which there is a through-passage for mass to pass from an inlet to an outlet located on the drum side, the drum side bearing in a sealing manner against the drum and being designed to adapt to irregularities in the outer circumference of the drum. This ensures that the mass feed member, also known as the filling shoe, bears in a sealing manner against the drum, even when the drum is not perfectly cylindrical, so that loss of mass is limited and leakage during the application of a vacuum and/or pressure is avoided. For this purpose, the drum side of the filling shoe is flexible to a certain degree, so that it is able to follow any deviations.

0051In an appropriate embodiment, the drum side of the mass feed member comprises a flexible plate which is held against the outer circumference of the drum under pressure produced by excess-pressure means. A suitable material for the flexible plate is Teflon, which in addition to the required sealing action also imparts resistance to wear. According to a further preferred embodiment, the excess-pressure means comprise at least one pressure cushion, a number of lamellae, which are positioned transversely with respect to the direction of rotation of the drum, being arranged between the pressure cushion and the plate. These lamellae provide lines with a high rigidity in the axial direction of the drum, while the plate is able to follow deviations in the diameter of the drum. To further limit loss of mass resulting from the continuous supply, the drum side of the mass feed member, as seen in the circumferential direction of the drum, extends on either side of the outlet, over a distance which covers at least one mould cavity. If the mass feed member is operating continuously, it is if desired possible to provide a diverter passage, for example in the flexible plate, which on one side is in communication with the through-passage and on the other side is in communication with an outlet opening at a position, upstream of the outlet of the through-passage, where the next mould cavity to be filled is located. If there is no mould cavity in front of the outlet opening of the mass feed member, a partial stream of the mass is therefore introduced into the next mould cavity which is to be filled, until the latter can be filled via the ordinary outlet from the through-passage.

0052In order to enable the mass feed member, to be used for various types of foodstuff starting material, including masses which include tough (muscle) fibres, it is advantageous for a cutting device to be provided in the through-passage on the drum side, preferably at the downstream edge of the through-passage, as seen in the direction of rotation.

0053It wall be understood that the abovementioned mass feed member is also suitable for use in moulding devices with a rotating moulding drum, other than the embodiments discussed above

0054The invention is explained below with reference to the appended drawing, in which: <ul id="ul0001" list-style="none"><li><figref idref="f0001">Fig. 1</figref> shows a perspective view of an embodiment of a moulding device of the invention;</li><li><figref idref="f0002">Fig 2</figref> shows a side view of the embodiment shown in Fig- 1;</li><li><figref idref="f0003">Fig. 3</figref> shows an exploded perspective view of an embodiment of a moulding device with insert;</li><li><figref idref="f0004">Fig. 4</figref> shows a view of an embodiment of an insert with mould cavity;</li><li><figref idref="f0005">Fig. 5</figref> shows a cross section through an embodiment of a moulding device according to the invention, illustrating its operation;</li><li><figref idref="f0005">Fig. 6</figref> shows a detail of the embodiment shown in <figref idref="f0005">Fig. 5</figref>;</li><li><figref idref="f0006">Fig. 7</figref> shows a non-claimed embodiment of a moulding device ;</li><li><figref idref="f0007">Fig. 8</figref> shows an embodiment of a moulding device with release device in accordance with the invention;</li><li><figref idref="f0008">Fig. 9</figref> shows the release device presented in <figref idref="f0007">Fig 8</figref> in more detail;</li><li><figref idref="f0009">Fig. 10</figref> shows the operation of the release device illustrated in <figref idref="f0007">Fig. 8</figref>;</li><li><figref idref="f0010">Fig 11</figref> diagrammatically depicts an embodiment of a moulding device with mass feed device in accordance with the invention;</li><li><figref idref="f0011">Fig. 12</figref> shows a detail of the mass feed device shown in <figref idref="f0010">Fig.. 11</figref>;</li><li><figref idref="f0012">Fig. 13</figref> illustrates the operation of the mass feed device;</li><li><figref idref="f0013">Fig. 14-15</figref> show diagrammatic cross sections through various embodiments of a mould cavity with associated boundary;</li><li><figref idref="f0014">Fig 16-17</figref> show detailed structure of various pore forms of a boundary of a mould cavity;</li><li><figref idref="f0014">Fig. 18</figref> shows a detailed view of an embodiment of a boundary of a mould cavity with a passage structure;</li><li><figref idref="f0013">Fig. 19</figref> diagrammatically depicts a non-claimed embodiment of the method according to the invention;</li><li><figref idref="f0014">Fig. 20</figref> diagrammatically depicts another non-claimed embodiment of the method according to the invention; and</li><li><figref idref="f0015">Fig. 23-23</figref> show various embodiments of a moulding surface according to the invention.</li></ul>

0055<figref idref="f0001">Fig. 1</figref> diagrammatically depicts a perspective view of an embodiment of a moulding device 10 according to the invention, while <figref idref="f0002">Fig. 2</figref> shows a side view of this device.

0056The moulding device 10 comprises a frame 14 which can be moved with the aid of wheels 12. A moulding drum 16 is mounted on the frame 14 in such a manner that it can be rotated about a horizontal axis and is coupled to a drive, for example an electric motor The moulding drum 16 comprises mould cavities, which are not visible in <figref idref="f0001">Fig 1</figref> and <figref idref="f0002">2</figref>. A mass feed member 18 for feeding mass which is to be moulded to the mould cavities of the moulding drum comes into close contact with the outer circumference of the moulding drum 16. The mass is fed from a displaceable storage device 19 with introduction funnel 20 and then via a releasable connecting pipe 22 to the mass feed member 18 by means of an (optionally continuously) operating pump (not shown). In the vicinity of the underside of the moulding drum 16, there is a release device 24 for releasing moulded products from the mould cavities of the moulding drum 16, as well as a discharge belt 26 beneath it. Via this discharge belt 26, the products can be fed to other processing stations, for example a protein-coating device, a freezing device or a packaging installation. The moulding device 10 also comprises a control unit 28 for controlling the various components. With a view to making the device, in particular the moulding drum 16 and the mass feed member 18, accessible for maintenance and cleaning purposes, the mass feed member 18 is secured to a subframe 30, which can be rotated about a pivot pin 34 with the aid of a piston/cylinder assembly 32, so that the mass feed member 18 can be moved out of a working position illustrated in <figref idref="f0001">Fig. 1</figref> and <figref idref="f0002">2</figref> into an at-rest position (not shown) at a distance from the moulding drum 16 after coupling 36 between connecting pipe 22 and mass feed member 18 has been released.

0057In the embodiment shown in <figref idref="f0003">Fig. 3a) and b)</figref>, rectangular recesses 42 are provided in the outer circumference 40 of the moulding drum 16, which is in this case hollow. Exchangeable inserts 44 of corresponding dimensions can be secured in these recesses 42. For this purpose, bores 46 are provided at the corners of an insert 44, aligned with threaded holes 47 in the base 48 of the recess 42, and bolts 50 can be fitted into them. In the base 48 of a recess 42 there is an opening 52 which is in communication, via one or more axial connecting passages and distribution device (not shown), with an opening 54 in an end piece 56 of the moulding drum 16. This opening 54 is in communication with excess-pressure means (not shown), such as a compressor, for supplying a forcing fluid via a flexible hose 57, and with reduced-pressure means (not shown), for example a vacuum pump, via a flexible hose 58. In its top side, the insert 44 comprises a mould cavity 60 of a shape which corresponds to the shape of the product which is to be produced.

0058In the embodiment shown in <figref idref="f0004">Fig. 4</figref>, the insert 44 together with spacer 62, forms an assembly 64. Insert 44 comprises the mould cavity 60 delimited by vertical walls 66 and base 68, while spacer 62 is a flat plate in which there is a through-opening 72, the dimensions of which are lager than the mould cavity 60. The insert 44 is made from a porous material, such as sintered steel. The pores are denoted by reference numeral 73. They open out in the base 68 and peripheral wall 66. Therefore, in the assembled state, there is a space between the underside of this insert 44 and the base 48 of the recess 42, this space also being delimited by the peripheral wall 74 of the opening 72 in spacer 62, which space is in communication with, on the one hand, the pores 73 in the insert 44 and, on the other hand, the opening 52, so that during operation the mould cavity 60 can be efficiently evacuated, and during the release operation a forcing fluid can be supplied between product and boundary. The insert 44 is a rectangular body with a flat underside and sides, apart from the top side 75, which is curved. The radius of curvature of the curved upper side 75 is identical to the radius of curvature of the moulding drum 16.

0059<figref idref="f0005">Fig. 5</figref> illustrates the way in which this embodiment of a device 10 according to the invention operates. The mass which is to be moulded is forced into the mould cavity 60, which is in a filling position, via the mass feed member 18, while air is being sucked out of this mould cavity 60 through the pores in the insert 44 in question, the opening 52 and a connecting passage 76 with the aid of reduced-pressure means. This mould cavity 60 is filled during the rotation (direction of rotation indicated by an arrow) of the moulding drum 16 past the filling position. As a result of further rotation, a mould cavity 60 moves into a release position where a moulded product 78, under the force of gravity, drops out of the mould cavity 60 onto a discharge belt 26 moving beneath it. The release is assisted by supplying compressed air or other pressure medium, for example water, to the mould cavity 60 via the connecting passage 76 and the porous insert 44. The compressed air is supplied by excess-pressure means (not shown).

0060<figref idref="f0005">Fig. 6</figref> shows the latter aspect in more detail. From the connecting passage 76, compressed air is passed through the opening 52 in the base 48 of the recess 52 in the drum 16 into distribution space 82, from where the compressed air (indicated by arrows) forces its way through the pores in the boundary of the insert 44 and expels a product.

0061For the sake of simplicity, <figref idref="f0003 f0004 f0005">Fig. 3-6</figref> in each case illustrate a combination of excess-pressure means and reduced-pressure means. As will be clear from the general description given above, the two aspects can also be employed separately.

0062<figref idref="f0013">Fig. 14</figref> shows an embodiment of a mould cavity 60 with a permeable boundary with a complete pore structure for the base 68 and peripheral wall 66. In addition to the pores 73, passages 200 are provided in the base 68. In the situation illustrated, the pores 73 are fed with a gaseous forcing fluid, such as compressed air, via a separate feed 202. The passages 200 are provided with a liquid forcing fluid, such as water, via a separate feed 204. As an alternative to a separate supply, it is also possible to use a mixture of liquid and gaseous forcing fluids.

0063<figref idref="f0013">Fig. 15</figref> shows yet another embodiment, in which the boundary of a mould cavity 60 is of layered structure. An innermost boundary layer 206 comprises a pore structure, while the outermost boundary layer 208 is provided with passages 200. A forcing fluid is introduced into a distribution chamber 212 via feed 210. From there, the fluid flows through the passages 200 and then via the pores 73 and into the mould cavity.

0064<figref idref="f0014">Fig. 16 and 17</figref> show two different pore structures. One is composed of sintered, substantially round metal grains (<figref idref="f0014">Fig. 16</figref>) and one is composed of sintered, irregularly shaped metal particles. In the case of the pore structure shown in <figref idref="f0014">Fig. 17</figref>, the risk of a meat mass or small pieces of meat sticking in the pores is lower than in the case of the structure shown in <figref idref="f0014">Fig. 16</figref>, since the depth of penetration of the mass is lower on account of the relatively high resistance caused by the irregular nature of the pores.

0065<figref idref="f0014">Fig. 18</figref> shows a boundary part with irregular passages 200 which taper from the outside towards the mould cavity 60.

0066<figref idref="f0013">Fig 19</figref> shows a boundary of a mould cavity 60 in which the boundary comprises a coating layer 220 which is given a surface, charge by a reversible chemical reaction, repelling the oppositely charged particles (indicated as dipoles) from the product starting material.

0067<figref idref="f0014">Fig. 20</figref> illustrates a method in which an additional electromagnetic repulsion force is generated in order to release a product from the mould cavity 60 with the aid of an electromagnet 222.

0068<figref idref="f0006">Fig. 7</figref> shows another embodiment of a moulding device 10 , in which components which correspond to those shown in <figref idref="f0001 f0002 f0003 f0004 f0005">Fig 1-6</figref> are denoted by the same reference numerals. The moulding drum 16 comprises recesses 42 which are distributed over its circumference and in which a filler piece 81 is positioned. In this case, the mould cavity 60 is delimited by the top side 83 of filler piece 81 and side walls 84 of the recess 42. The top side 83 in this case has a surface which is provided with a contour, so that an attractively shaped appearance can be imparted to the product. The mould cavities 60 of the moulding drum 16 can once again be selectively coupled to either reduced pressure means or feed means, as described for a different embodiment with reference to <figref idref="f0005">Fig. 5 and 6</figref>. For this purpose, an opening 52, which is aligned with bore 85 in filler piece 81, is provided in the base 48 of the recess 42. A web or strip 86 is wound around the moulding drum 16. This strip 86 has a sandwich structure and comprises an upper layer 88 made from a plastics material, in which flexible premoulds 90 are provided, substantially corresponding to a mould cavity 60, and a lower layer 92, which during operation is in contact with the outer circumference of the moulding drum 16 and is made from a more rigid material, in which there are round openings 94, the diameter of which in this case substantially corresponds to that of the premoulds 90 and therefore to that of the mould cavities 60. The two layers 88 and 82 are connected to one another in a suitable way. One end 96 of the web 86 of a sandwich structure is provided with securing means which interact with securing features on the drum 16. An example is a row of small openings 98 which are positioned over short projections on the drum 16. The free end 102 of the web may be fixed to the drum 16 or to itself, for example using adhesive tape or the like. To protect the web 86, there is a wear-resistant material, for example stainless steel, protective strip 104, in which openings 106 which likewise correspond to the flexible premoulds are provided. One end of the protective strip 104 has a flanged edge 108 which, during operation, engages in an axial groove 110 provided in the outer circumference of the drum 16. The other end 112 has spring securing means 114 at its corners, and these means can be fixed to projections on the drum 16, so that the protective strip 104 can be clamped taut around the drum 16 and in this way also holds the flexible strip 86 beneath it in place.

0069During operation, at the filling position the flexible premoulds 90 in the mould cavities 62 are filled with mass or a portion of mass, it being possible for the air which is present beneath the flexible premould 90 in the mould cavity 60 to be sucked out, for example via the central bore 85 in filler piece 81 and opening 52 connected to it in the base 48 of recess 42, which opening can be connected to reduced-pressure means via an axial connecting passage in the manner described above. At the release position (<figref idref="f0007">Fig. 8</figref>), the flexible premould 90 is pushed out of the mould cavity 60 with the aid of compressed air, which is led to the mould cavity 60 in the manner which has likewise already been described, and the moulded product 78 can be released, if desired with the assistance of a release device, for example a spindle belt which is to be described bellow.

0070The release device 24 shown in <figref idref="f0007 f0008 f0009">Fig. 8-10</figref> is arranged beneath the moulding drum 16 at the release position and in the situation illustrated comprises an endless conveyor. This conveyor comprises two endless chains 120 which are arranged parallel to one another and are guided in a fixed path over toothed wheels 122. Toothed wheels 128 arranged on a common driven axle 126 engage in the vicinity of the centre of a top part 124, moving towards the drum 16, of the conveyor. A drive unit is denoted overall by reference numeral 130. The links 132 of the chains 120 (cf. <figref idref="f0009">Fig. 10</figref>) are lengthened on the inner side by an extension piece 134 which projects inwards. Extension pieces 134 of corresponding links 132 of the two endless chains 120 are connected to one another by thin transverse spindles 136, in such a manner that the transverse spindles 136, at the reversing point, pass through the centre of the axis of the toothed wheel 122 in question. This results in the formation of a pointed nose which is responsible for further removing moulded products 78 from the mould cavity 60.

0071<figref idref="f0010">Fig. 11</figref> diagrammatically depicts an embodiment of a mass feed member 18, in which identical components are once again denoted by identical reference numerals. The mass feed member 18 comprises a virtually semicircular housing 140 with a through-passage 142 extending in the radial direction (cf. also <figref idref="f0012">Fig. 13</figref>) with an inlet 144 for the mass which is to be moulded from a storage device 19 and an outlet 146 for the mass to pass to a mould cavity 60. Side walls 148 and 150 of the housing 140 are provided with openings 152 extending in the radial direction. Radially movable lamellae 154, for example made from metal, are arranged between corresponding openings 152 in the side walls 148, 150. The central part of the mass feed member 18 comprises a filler block 156 which is fixedly connected to the housing and in which the through-passage 142 is provided. That side of the mass feed member 18 which faces towards the moulding drum 16 comprises a plate 158 made from a flexible plastic, for example Teflon, in which the outlet 146 to a mould cavity 60 is provided. Between the inner wall of the housing 140 and the lamellae 154 there is a pressure cushion 160 which can be pressurized using a suitable pressure medium, such as compressed air or pressurized water or other liquid. In this way, during operation, the Teflon plate 158 is pressed onto the moulding drum 16 in such a manner as to form a seal, the lamellae 154 forming a large number of ribs which extend in the axial direction of the moulding drum 16 and impart the required rigidity, while the Teflon plate 158 is able to adapt to possible deviations in the radius of the moulding drum 16. On one side of the through-passage 152 there is a cutting blade 170 for cutting through tough pieces, such as muscle fibres.

0072In the embodiment of the moulding drum 16 illustrated in this figure, there are provided, in its outer wall, recesses 42 which have a widened base 162, extend in the longitudinal direction and into which corresponding inserts 44 with a mould cavity 60 can be pushed from the corresponding end of the moulding drum 16.

0073<figref idref="f0015">Fig. 21</figref> shows a perspective illustration of an exchangeable moulding drum 16 as an embodiment of a moulding surface according to the invention. The moulding drum 16, which can rotate about an axle 250, comprises a cylindrical drum wall 252. The outer side of the cylindrical drum wall 252 comprises recesses 42. In each recess 42 there is an insert 44, which insert 44 comprises a mould cavity 60 which is defined by a boundary provided with holes, namely walls 66 and base 68. In the embodiment illustrated, all the mould cavities 60 are identical in shape. It is also possible for the shape of the mould cavities to differ, for example for each annular drum-wall part to have identically shaped mould cavities, while the shape of the mould cavities differs from one annular drum-wall part to another. It is therefore relatively easy to make a range of products of different shapes and then package these products.

0074<figref idref="f0015">Fig. 22</figref> shows a moulding drum similar to that shown in <figref idref="f0015">Fig. 21</figref>, except for the fact that the exchangeable inserts 44 are elements which extend in the longitudinal direction of the drum and are each provided with four mould cavities 60.

0075<figref idref="f0015">Fig. 23</figref> shows a particularly preferred embodiment of a moulding drum 16 according to the invention which can be exchanged in its entirety. The moulding drum 16 comprises a piece of porous metal, the surface pores of which have been sealed at the outer surface and the inner surface. The mould cavities 60 are formed by spark erosion, with the result that the boundary, comprising base 68 and side walls 66, has acquired the porous structure, since the pores are uncovered as a result. It is easier to replace one moulding drum with another than to exchange the removable inserts as used in the embodiments shown in <figref idref="f0015">Fig. 21 and 22</figref>.