Patent Abstract:
This invention relates to a porous pulp mold comprising sintered particles and a plurality of drainage channels. The pulp mold of the invention can be produced in a fast and cost effective way. The molding surface of the invention comprises small pore openings, to evacuate fluid and prevent fibers from entering the pulp mold. Furthermore the pulp mold of the invention comprises drainage channels improving the drainage capabilities of the pulp mold. The molding surface can be heated to at least 200° C., due to high heat conductivity of the pulp mold and its ability to withstand high temperatures.

Full Description:
This application is a 371 of PCT/SE05/01771 filed on 25 Nov. 2005 
     TECHNICAL FIELD 
     The present invention relates to a pulp mould for moulding three-dimensional pulp objects that can be used in a wide variety of applications. More specifically the objects are formed by using fibre slurry comprising a mixture of mainly fibres and liquid. The fibre slurry is arranged in the mould and part of the liquid is evacuated and a resulting fibrous object is produced. 
     BACKGROUND OF THE INVENTION 
     Packagings of moulded pulp are used in a wide variety of fields and provide an environmental friendly packaging solution that is biodegradable. Products from moulded pulp are often used as protective packagings for consumer goods like for instance cellular phones, computer equipment, DVD players as well as other electronic consumer goods and other products that need a packaging protection. Furthermore moulded pulp objects can be used in the food industry as hamburger shells, cups for liquid content, dinner plates etc. Moreover moulded pulp objects can be used to make up structural cores of lightweight sandwich panels or other lightweight load bearing structures. The shape of these products is often complicated and in many cases they have a short expected time presence in the market. Furthermore the production series may be of relative small size, why a low production cost of the pulp mould is an advantage, as also fast and cost effective way of manufacturing a mould. Another aspect is the internal structural strength of the products. Conventional pulp moulded objects have often been limited to packaging materials since they have had a competitive disadvantage in relation to products for example made of plastic. Moreover it would be advantageous to provide a moulded pulp object with a smooth surface structure. 
     In traditional pulp moulding lines, se for example U.S. Pat. No. 6,210,531, there is a fibre containing slurry which is supplied to a moulding die, e.g. by means of vacuum. The fibres are contained by a wire mesh applied on the moulding surface of the moulding die and some of the water is sucked away through the moulding die commonly by adding a vacuum source at the bottom of the mould. Thereafter the moulding die is gently pressed towards a complementary female part and at the end of the pressing the vacuum in the moulding die can be replaced by a gentle blow of air and at the same time a vacuum is applied at the complementary inversed shape, thereby enforcing a transfer of the moulded pulp object to the complementary female part. In the next step the moulded pulp object is transferred to a conveyor belt that transfers the moulded pulp object into an oven for drying. Before the final drying of the moulded pulp object the solid content (as defined by ISO 287) according to this conventional method is in around 15-20% and afterwards the solid content is increased to 90-95%. Since the solid content is fairly low before entering the oven, the product has a tendency of altering its shape and size due to shrinkage forces and furthermore structural tensions are preserved in the product. And since the shape and size has altered during the drying process it is often necessary to “after press” the product thereby enforcing the preferred shape and size. This however creates distortions and deformations deficiencies in the resulting product. Furthermore the drying process consumes high amounts of energy. 
     Conventional pulp moulds which are used in the above described process are commonly constructed by using a main body covered by a wire mesh for the moulding surface. The wire mesh prevents fibres to be sucked out through the mould, but letting the water passing out. The main body is traditionally constructed by joining aluminium blocks containing several drilled holes for water passage and thereby achieving the preferred shape. The wire mesh is commonly added to the main body by means of welding. This is however complicated, time consuming and costly. Furthermore the grid from the wire mesh as well as the welding spots is often apparent in the surface structure of the resulting product giving an undesirable roughness in the final product. Furthermore the method of applying the wire mesh sets restrictions of the complexity of shapes for the moulding die making it impossible to form certain configurations in the shape. 
     In EP0559490 and EP0559491 a pulp moulding die preferably comprising glass beads to form a porous structure is presented, which also mentions that sintered particles can be used. A supporting layer with particles having average sizes between 1-10 mm is covered by a moulding layer with particles having average sizes between 0.2-1.0 mm. The principle behind this known technology is to provide a layer wherein water can be kept by means of capillary attraction and by using the kept water to backwash the moulding die in order to prevent the fibres from clogging the moulding die. This process is however complicated. 
     U.S. Pat. No. 6,451,235 shows an apparatus and a method for forming pulp moulded objects using two steps. The first steps wet-forms a pre fibrous object which in the second step is heated and pressed under a large pressure. The pulp mould is formed of solid metal having drilled drainage channels to evacuate fluid. 
     U.S. Pat. No. 5,603,808 presents a pulp mould where one embodiment shows a porous base structure covered by a metal coating comprising squared openings of 0.1 mm to 2.0 mm. 
     U.S. Pat. No. 6,582,562 discloses a pulp mould capable of withstanding high temperature. 
     All prior art methods related to the production of a pulp mould, including the above disclosed methods, present some disadvantage. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide a pulp mould that eliminates or at least minimizes some of the disadvantages mentioned above. This is achieved by presenting a pulp mould for moulding of objects from fibre pulp, comprising a sintered moulding surface and a permeable base structure where the moulding surface comprises at least one layer of sintered particles with an average diameter within the range 0.01-0.19 mm, preferably in the range 0.05-0.18 mm. This provides the advantage that the outermost layer of the moulding surface has fine structure with small pores in order to produce a pulp moulded object with a smooth surface and to contain fibres between a female and male mould preventing them from entering the same moulds and at the same time allowing fluid or vaporised fluid to emanate. 
     According to further aspects of the invention:
         the pulp mould has a heat conductivity in the range of 1-1000 W/(m° C.), preferably at least 10 W/(m° C.), more preferred at least 40 W/(m° C.), which provide the advantage that heat can be transferred to the moulding surfaces during the press step in order for the press to be realised during increased temperature, which leads to a desirable vaporization of the fluid in pulp material. This vaporization helps the fluid to be sucked out throughout the moulds and helps the pressure to be equally distributed over the and thus the moulded pulp becomes equally pressurised.   the permeable base structure comprises sintered particles having average diameters that is larger than the particles in the moulding surface, preferably of at least 0.25 mm, preferably at least 0.35 mm, more preferably at least 0.45 mm and having average diameters less than 10 mm, preferably less than 5 mm, more preferred less than 2 mm, which provides the advantages with a base structure having a high fluid permeability to enable fluid and vapour to be evacuated from the moulded pulp and a base structure having a high an internal strength as to withstand the pressure imposed on the base structure during the pressing steps.   a permeable support layer comprising sintered particles is arranged between the base structure and the moulding surface where particles of the support layer have average diameter less than the average diameter of the sintered particles in the base structure and larger than the average diameter of the sintered particles in the moulding surface, which provides the advantages that support layer can minimize voids in the moulds safeguarding that the moulding surface does not collapse into the voids and if the size difference between the sintered particles of the base structure and the sintered particles of the moulding surface is very large, the support layer is added to create a smooth transition from the small particles of the moulding layer to the larger particles of the base structure and thus so by using a particle sizes in between these two extremes, which minimizes voids created between layers of different sizes.   the pulp mould has a total porosity of at least 8%, preferably at least 12%, more preferred at least 15% and that the pulp mould has total porosity of less than 40%, preferably less than 35%, more preferred less than 30%, which provides the advantage that liquid and vaporised liquid can emanate from the pulp mould.   a heat source is arranged to supply heat to the pulp mould, which provides the advantage that the can be heated during moulding.   the bottom of the pulp mould is substantially flat and free of larger voids, arranged to transmit an applied pressure, which provides a surface suitable for heat transfer and provides the advantage of a form stable pulp mould. With larger voids is meant voids larger than the voids of the drainage channels, described below, for example a relief shaped pulp mould has a large void.   a heat plate is arranged to the bottom of the mould and that the heat plate comprises suction openings, which provides the advantage that heat can be transferred to the pulp mould, thereby heating the moulding surface and that a source of suction can be arranged present a suction at the moulding surface.   the pulp mould has at least one actuator arranged to its bottom, which provides the advantage that a female and a male pulp mould can be pressed together.   the pulp mould is able to withstand temperature of at least 400° C., which provides the advantage that the mould can be heated to at least 400° C. during operation.   the pulp mould contains at least one, preferably a plurality of drainage channels, which provides the advantage that drainage of fluid and vaporised fluid can be increased in the pulp mould.   the drainage channel has a first diameter at the bottom of the pulp mould and a third diameter at the intersection between the base structure and the support layer, which is substantially smaller than the first diameter.   the first diameter is larger than or equal to a second intermediate diameter and that the second diameter is larger than the third diameter.   the second diameter is at least 1 mm, preferably at least 2 mm and that the third diameter is less than 500 μm, preferably less than 50 μm, more preferred less than 25 μm, most preferred less than 15 μm.   the plurality of drainage channels are distributed in a distribution of at least 10 channels/m2, preferably 2 500-500 000 channels/m2, more preferred less than 40 000 channels/m2, providing the advantage of good drainage capabilities.   at least one pulp mould is arranged on the heat plate and that the heat plate has suction openings and that the suction openings are arranged to mate the plurality of drainage channels.   during operation a male and a female pulp mould are pressed into contact and the temperature of the moulding surface is at least 200° C. transmitting heat to a mixture of fibres and liquid arranged between the female and male pulp mould, which provides the advantage that a large part of the liquid is vaporised and due to the expansion of the vapour the vaporised liquid emanates through the porous pulp moulds.   Complex shapes of the mould can be constructed due to the use of sintering technique in manufacturing the moulds. The pulp moulds can be constructed using graphite or stainless steel sintering moulds. These sintering moulds are easily manufactured using conventional methods and can produce very complex shapes at a low cost and short manufacture time.   The sintered mould of the invention can be manufactured with great precision.   The sintered mould of the invention can be used 500 000 times with preserved properties.   The pulp mould may comprise one or more non-permeable surface areas containing said the sintered particles, the non-permeable surface area having a permeability that is substantially less than that of the moulding surface.   If the sintered mould is outside the accuracy requirements it can be reformed by pressing the sintered mould in a second mould in which the sintered mould was created, without loss of characteristic features   Surface structures on one or both sides of the pulp object can be created. For instance a logotype can be moulded at the bottom of a dinner plate. This can be done by adding a thin sintered layer with the shape of the logotype at one or both mouldings surfaces.   A high internal strength in the resulting pulp moulded object can be produced using the pulp mould of the invention.   Smooth surfaces on both sides are provided due to the fine accurate structure of the mouldings surfaces, combined with an ability to withstand high pressure and due to the heat conductivity making it possible to press using a high temperature at the moulding surfaces, enabling the liquid to be vaporised which will act as a cushion which smoothens any small inaccuracies in the moulding surfaces.   Suction is evenly distributed due to the homogenous porosity of the mould.   Pressure between the becomes evenly distributed due too the cushion effect of the steam expansion and the evenly suction.       

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the following the invention will be described in relation to the appended figures, wherein: 
         FIG. 1  shows a cross sectional view of a male part and complementary female part of a pulp mould according to a preferred embodiment of the present invention in a separate position, 
         FIG. 2  shows the same as  FIG. 1  but in an a moulding position, 
         FIG. 2   a  shows a zooming of a part of  FIG. 2 , 
       FIG.  2 ′ shows a pulp mould in a moulding position according to a second embodiment of the invention, 
         FIG. 2   a ′ shows a zooming of a part of FIG.  2 ′, 
         FIG. 3  shows a single drainage channel, 
         FIG. 4  is a cross sectional zooming of the male part of the pulp mould of  FIG. 1  showing the moulding surface the tips of three drainage channels and the upper part of the base structure, 
         FIG. 5  is a cross sectional zooming of the female part of the pulp mould of  FIG. 2  showing the moulding surface the tips of two drainage channels and the upper part of the base structure, 
         FIG. 6  is a cross sectional zooming of the embodiment shown in  FIG. 3  showing the moulding surface and the upper part of the base structure, 
         FIG. 7  is a cross sectional zooming of the embodiment shown in  FIG. 4  showing the moulding surface and the upper part of the base structure, 
         FIG. 8  shows a part of the moulding surface of the female and male pulp mould as seen from the forming space, 
         FIG. 9  shows a three-dimensional drawing of a pulp mould according to the present invention, and 
         FIG. 10  is an exploded view of a preferred embodiment of a mould combined with a heat and vacuum suction tool according to the invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a cross-sectional view of a male  100  and a complementary female  200  part of a pulp mould according to a preferred embodiment of the present invention. Both the female  200  and the male  100  part are constructed according to the same principles. A forming space  300  is arranged between the pulp moulds  100 ,  200 , where the moulded pulp is formed during operation. A base structure  110 ,  210  constitutes the main bodies of the pulp mould  100 ,  200 . A support layer  120 ,  220  is arranged upon the base structure  110 ,  210 . A moulding surface  130 ,  230  is arranged upon the support layer  120 ,  220 . The moulding surface  130 ,  230  encloses the forming space  300 . A source for heating  410  (see  FIG. 10 ), a source for suction  420  using underpressure and at least one actuator (not shown) to press the female mould  200  and the male mould  100  against each other are arranged at the bottom  140 ,  240  of the base structure  110 ,  210 . It is advantageous that the pulp moulds  100 ,  200  have good heat conductive properties in order to transfer heat to the  130 ,  230 . It is advantageous that the base structure  110 ,  210  is a stable structure being able to withstand high pressure (both applied pressure via the bottom  140 ,  240  and pressure caused by steam formation within the mould) without deforming or collapsing and at the same time having throughput properties for liquid and vapour. More specific it is preferred that the throughput properties facilitate the drainage of liquid and vapour from the wet pulp mixture inside the forming space  300  during operation of the pulp mould  100 ,  200 . It is therefore advantageous that the pulp mould has a total porosity of at least 8%, preferably at least 12%, more preferably at least 15% and at the same time to be able to withstand the operating pressure it is advantageous that the total porosity is less than 40%, preferably less than 35%, more preferably less than 30%. The total porosity is defined as the density of a porous structure divided by the density of a homogenous structure of the same volume and material as the porous structure. The throughput properties are increased by a plurality of drainage channels  150 ,  250 . It is preferred that the plurality of drainage channels  150 ,  250  are frusta conical and having a sharply pointed tip towards the intersection between base structure  110 ,  210  and support layer  120 ,  220 , e.g. the plurality of drainage channels  150 ,  250  of the present embodiment has a nail form with the nail tip pointing towards the forming space  300 . 
     As is evident from  FIG. 1  all parts of the mould  100 ,  200  are applied with the fine particles that forms the support layer  130 ,  230 . However, all parts of that surface are not used to form a pulp object, but there are peripheral surfaces  160 ,  260  that will not be used to form a pulp object. As a consequence, these surfaces  160 ,  260  preferably have a permeability that is substantially smaller than the  130 ,  230 . In the preferred embodiment this is achieved by applying a thin impermeable layer  161 ,  261  having appropriate properties, e.g. any kind of paint having sufficient strength durability to maintain its impermeable function when used under operating conditions (high heat some vibration, pressure, etc.). Alternatively this impermeable layer  161 ,  261  may be achieved by workshop machining techniques, for instance by applying a high pressure upon these surfaces  160 ,  260 , to achieve a compacted surface layer  160 ,  260  whereby the pores will be closed. Of course other methods of making these surfaces  160 ,  260  impermeable can be used as long as the result yields an impermeable surface  160 ,  260 . 
     In  FIGS. 2 ,  2   a  there is shown the position of the two mould halves  100 ,  200  during the heat press forming action. As can be seen there is formed a forming space  300  between the mould surfaces  130 ,  230 , that is about 0.8-1 mm., preferably in the range 0.5-2 mm. As can be the surfaces that will not be used to form a pulp object,  160 ,  260 A has a thin impermeable layer  161 ,  261  applied upon them. As can be seen in  FIG. 2A  the upper drainage channel  150  ends where the moulding surface  130  meets the forming space  300  and the lower drainage channel  250  ends between moulding-surface  230  and support layer  220 . The drainage channels  150 ,  250  can have its pointed ending anywhere in the interval from the border between the base structure  110 ,  210  and the support layer  120 ,  220  till the border between the moulding surface  130 ,  230  and the forming space  300 . 
     In this connection it may be mentioned that possible protruding fibre lumps, protruding on top of the slope  260 A, may easily also be handled by the use of applying a water stream, e.g. by means of an appropriately formed water jet, that will fold the protruding lumps onto the moulding surface  230  being under vacuum, such that they adhere to the rest of the fibres web. 
     In FIGS.  2 ′,  2   a ′ according to a second embodiment of the invention there is shown the position of the two mould halves  100 ,  200  during the heat press forming action. As can be seen there is formed a forming space  300  between the mould surfaces  130 ,  230 , that is about 1 mm., preferably in the range 0.5-2 mm. As also can be seen from FIG.  2 ′ the mating surfaces  161 ,  261  of the mould halves  100 ,  200 , do form a substantially smaller gap  300 ′ than the forming space  300 . The mating surfaces  161 ,  261  is somewhat tilted to the left as is shown by the angle α in order to facilitate introduction of the male  100  into the female mould  200 . Also it can be seen that the bottom surface  140  of the male mould is above the level of the upper portion  260 A of the female mould, i.e. there is formed a gap between the support and heat plate  410  (see  FIG. 10 ) of the male mould  100  and the female mould  200 , which is feasible thanks to the arrangement according to the inventive process where the applied pressure may be directly transferred to the pulp body, i.e. by means of the mould surfaces  130 ,  230 . In other words normally there is no need for external abutting means (although they may be useful in some cases) to position the mould halves  100 ,  200  during the pressing action. According to the embodiment shown in FIG.  2 ′ the design provides for using the relatively sharp edge between the horizontal surface  260 A and the vertical surface  261  to cut possible fibres lumps that protrude beyond the moulding surface  130 ,  160  of the male mould  100 . As can be seen in FIG.  2 ′,  2   a ′ the plurality of drainage channels  150 ,  250  is shown to end at the intersection between the moulding surface  130 ,  230  and the forming space  300 . Depending of an actual embodiment of the invention the drainage channels  150 ,  250  could have its pointed ending anywhere in the interval from the border between the base structure  110 ,  210  and the support layer  120 ,  220  till the border between the moulding surface  130 ,  230  and the forming space  300 . 
       FIG. 3  shows a drainage channel  150 ,  250 . The diameter Ø 1  is the diameter of the plurality of drainage channels  150 ,  250  at the bottom  140 ,  240  of the pulp moulds  100 ,  200 . The main part  151 ,  251  of the plurality of drainage channels  150 ,  250  inclines slightly from the diameter Ø 1  towards the diameter Ø 2 . The relation between diameter Ø 1  and diameter Ø 2  is at least Ø 1 ≧Ø 2  and preferably Ø 1 &gt;Ø 2 . Diameter Ø 2  is preferably above 2 mm, preferably 3 mm, i.e. preferably large enough to prevent capillary attraction. The form of the main portion t 1  of each drainage channel  150 ,  250  is dependent of the thickness of the pulp mould  100 ,  200  and therefore varies according to the desired shape of the pulp moulded object. The top portion t 2  of each drainage channel  150 ,  250  has a diameter Ø 2  that preferably decreases sharply towards diameter Ø 3 , at the border between base structure  110 ,  210  and support layer  120 ,  220 . The diameter Ø 3  is preferably substantially zero and at least less than 500 μm preferably less than 50 μm, more preferably less than 25 μm, most preferably less than 15 μm. The relation between diameter Ø 2  and diameter Ø 3  is preferably Ø 2 &gt;Ø 3  and most preferred Ø 2 &gt;&gt;Ø 3 . In the embodiment of  FIG. 1  and  FIG. 2 , Ø 2  was set to 3 mm, Ø 3  was set to 10 μm and the length t 2  of the top portion was set to 10 mm. If a drainage channel would have its tip in the border between the moulding surface  130 ,  230  and the forming space  300  and meeting an inclination of the moulding surface  130 ,  230  above 40° it may be an advantage to use a drainage channel  150 ,  250  without a conical top, i.e. Ø 2 =Ø 3 , in order to ensure a pointed opening towards the forming space  300 . Another way to ensure a pointed opening towards the forming space  300 , when the moulding surface  130 ,  230  has a steep inclination, is to increase the length t 2  of the top portion. If the drainage channels are arranged to have their tips in the border between the moulding surface  130 ,  230  and the forming space  300 , the openings Ø 3  of the plurality of drainage channels  150 ,  250  at the moulding surface  130 ,  230  are preferably very small in order to prevent fibres contained in the forming space  300  from entering the pulp mould  100 ,  200 , and also to produce a resulting surface structure of the pulp moulded object formed in the forming space  300  to be smooth. One of the reasons for the pointed tip of the plurality of drainage channels  150 ,  250  is to prevent fluid from flowing back to the pulp moulded object after pressure and vacuum is released, due to the flow resistance created by the narrowing channel. Fibres from cellulose normally has an average length of 1-3 mm and an average diameter between 16-45 μm. Preferably the diameter of the drainage channels  150 ,  250  increases gradually from the openings Ø 3  towards the diameter Ø 2  and further to the diameter Ø 1  of the drainage channels  150 ,  250 . The plurality of drainage channels  150 ,  250  of the embodiment of  FIG. 1  and  FIG. 2  was distributed with a distribution of 10 000 channels/m 2 . Normally the distribution is in the interval of 100-500000 and more preferred in the interval 2500-40000 channels/m 2 . 
       FIG. 4  and  FIG. 5  are cross sectional zoomings of  FIG. 1  and  FIG. 2  respectively showing the moulding surface  130 ,  230 , the support layer  120 ,  220 , and the upper portion of the base structure  110 ,  210 . As can be seen each drainage channel  150 ,  250  penetrates the base structure  110 ,  210  and has its pointed tip at the intersection between the base structure  110 ,  210  and the support layer  120 ,  220 . Depending of an actual embodiment of the invention the drainage channels  150 ,  250  could have its pointed ending anywhere in the interval from the border between the base structure  110 ,  210  and the support layer  120 ,  220  till the border between the moulding surface  130 ,  230  and the forming space  300 . 
       FIGS. 6 and 7  are cross sectional zoomings of  FIG. 4  respectively  FIG. 5  showing the moulding surface  130 ,  230 , the support layer  120 ,  220  and the upper part of the base structure  110 ,  210 . As can be seen from the figures the moulding surface  130 ,  230  comprises sintered particles  131 ,  231 , having an average diameter  131   d ,  231   d , provided in one thin layer. The thickness of the moulding surface is denoted by  133 ,  233  and in the shown embodiment since the moulding surface  130 ,  230  comprises one layer of particles the thickness  133 ,  233  of the moulding surface  130 ,  230  is equal to the average diameter  131   d ,  231   d . Preferably sintered metal powder  131 ,  231  with an average diameter  131   d ,  231   d  between 0.01-0.18 mm is used in the moulding surface  130 ,  230 . (In the shown embodiment sintered metal powder  131 ,  231  from Callo AB of the type Callo 25 was used to form the moulding surface  130 ,  230 . This metal powder can be obtained from CALLO AB POPPELGATAN 15, 571 39 NÄSSJÖ, SWEDEN.) Callo 25 are spherical metal powder with a particle size range between 0.09-0.18 mm and a theoretical pore size of about 25 μm and a filter threshold of about 15 μm. As is evident for a skilled person in the field of powder metallurgy the particle size ranges includes smaller amounts of particles outside the ranges, i.e. up to 5-10% smaller respectively larger particles, this however has only marginal effects on the filtering process. The chemical composition of Callo 25 is 89% Cu and 11% Sn. As a way of example a sintered structure using Callo 25 and sintered to a density of 5.5 g/cm 3  and a porosity of 40 vol-%, would have about the following characteristics; tensile strength 3-4 kp/mm 2 , elongation 4%, coefficient of heat expansion 18·10 −6 , specific heat at 293 K is 335 J/(kg·K), maximum operative temperature in neutral atmosphere 400° C. Thus in the shown embodiment the thickness  133 ,  233  of the moulding surface  130 ,  230  is in the range 0.09-0.18 mm. Generally the moulding surface  130 ,  230  comprises sintered particles  131 ,  231  in at least one layer but most preferred in merely one layer. As can be seen from the figures the support layer  120 ,  220  comprises sintered particles  121 ,  221 , having an average diameter  121   d ,  221   d.    
     The thickness of the support layer is denoted by  123 ,  223  and in the shown embodiment, since the support layer  120 ,  220  comprises one layer of particles, the thickness  123 ,  223  of the support surface  120 ,  220  is equal to the average diameter  121   d ,  221   d . (In the shown embodiment sintered metal powder  121 ,  221  from Callo AB of the type Callo 50 was used to form the support layer  120 ,  220 . This metal powder can be obtained from CALLO AB POPPELGATAN 15, 571 39 NÄSSJÖ, SWEDEN.) Callo 50 are spherical metal powder with a particle size range between 0.18-0.25 mm and a theoretical pore size of about 50 μm and a filter threshold of about 25 μm. The chemical composition of Callo 50 is 89% Cu and 11% Sn. As a way of example a sintered structure using Callo 50 and sintered to a density of 5.5 g/cm 3  and a porosity of 40 vol-%, would have about the following characteristics; tensile strength 3-4 kp/mm 2 , elongation 4%, coefficient of heat expansion 18·10 −6 , specific heat at 293 K is 335 J/(kg·K), maximum operative temperature in neutral atmosphere 400° C. Thus in the shown embodiment the thickness  123 ,  223  of the support layer  120 ,  220  is in the range 0.18-0.25 mm. The support layer  120 ,  220  may be omitted, especially if the size difference between the sintered particles  111 ,  211  of the base structure  110 ,  210  and the sintered particles  131 ,  231  of the moulding surface  130 ,  230 , is small enough, i.e. the function of the support layer  120 ,  220  increase the strength of the mould, i.e. to safeguard that the moulding surface  130 ,  230  does not collapse into the voids  114 ,  214 ,  124 ,  224 . If the size difference between the sintered particles  111 ,  211  of the base structure  110 ,  210  and the sintered particles  131 ,  231  of the moulding surface  130 ,  230 , is very large, the support layer  120 ,  220  can comprise several layers where the size of the sintered particles  121 ,  221  gradually is increased in order to improve strength, i.e. to prevent structural collapse due to the voids between the layers. 
     The base structure  110 ,  210  of the shown embodiment contains sintered metal powder  111 ,  211  of the fabricate Callo 200 from the above mentioned Callo AB. Callo 200 is a spherical metal powder with a particle size range between 0.71-1.00 mm and a theoretical pore size of about 200 μm and a filter threshold of about 100 μm. The chemical composition of Callo 200 is 89% Cu and 11% Sn. As a way of example a sintered structure using Callo 200 and sintered to a density of 5.5 g/cm 3  and a porosity of 40 vol-%, would have about the following characteristics; tensile strength 3-4 kp/mm 2 , elongation 4%, coefficient of heat expansion 18·10 −6 , specific heat at 293 K is 335 J/(kg·K), maximum operative temperature in neutral atmosphere 400° C. The pores  112 ,  212  of the base structure  110 ,  210  in the first embodiment has thus a theoretical pore size  112   d ,  212   d  of 200 μm, enabling liquid and vapour to be evacuated through the pore structure. 
       FIG. 8  shows a part of the moulding surface  130 ,  230  as seen from the forming space  300 . The moulding surface  130 ,  230  comprises sintered particles  131 ,  231  having an average diameter of  131   d ,  231   d . The pores  132 ,  232  of the moulding surface  130 ,  230  have a theoretical pore size  132   d ,  232   d . In the above described embodiment the theoretical pore size  132   d ,  232   d  is about 25 μm. The pores  132 ,  232  are preferably small enough in order to prevent cellulose fibres from entering the interior of the pulp mould  100 ,  200 , but at the same time enabling liquid and vapour to be evacuated through the pores  132 ,  232 . Fibres from cellulose normally have an average length of 1-3 mm and an average diameter between 16-45 μm. 
       FIG. 9  shows a three-dimensional drawing of a pulp mould  100 ,  200  according to the present invention. The bottom opening Ø 1  of the plurality of drainage channels  150  of the male mould  100  are shown in the drawing. A source for heating, a source for suction using underpressure and at least one actuator to press the female mould  200  and the male mould  100  against each other can be arranged at the bottom  140 ,  240  of the base structure  110 ,  210 . For instance a heated metal plate can be used to transfer heat to the flat bottom  140 ,  240 . 
       FIG. 10  is an exploded view of the heat and vacuum suction tool  400  of a preferred embodiment. A plurality of male pulp moulds  100  are arranged upon a support and heat plate  410 . Of course the same heat and vacuum suction tool  400  can be used to attach female pulp moulds  200 . The support and heat plate  410  is heated by means of induction. The support and heat plate  410  is divided into a plurality of locations  411 , where in the preferred embodiment up to eight pulp moulds  100 ,  200  can be placed side by side. Of course the invention is by no means limited to this number, but it is rather depending outside production factors outside the scope of the present invention, i.e. the surface area of the support and heat plate  410  can be increased or decreased and/or the bottom area of the pulp mould  100 , could likewise be increased or decreased. The support and heat plate  410  comprises a plurality of suction openings  412  which are connected to the vacuum chamber  420 . Each male pulp mould  100  have its bottom side  140  being substantially flat, as mentioned below this may be achieved by machining. A machining action of a sintered porous surface will make the pore openings to clog. Thanks to the drainage channels  150  that will have no negative effect on the process, since sufficient throughput surface is achieved by the drainage openings despite the clogging of the pores at the bottom  140  of the pulp moulds  100 . On the contrary it will be shown that this is rather an advantage in the present invention. The support and heat plate  410  comprises a plurality of suction openings  412  and these are preferably arranged to mate the openings Ø 1  of the plurality of drainage channels  150  at the bottom of the pulp mould  100 . Since the bottom area between the drainage channels  150  is meeting the solid part of the support and heat plate  410 , no suction would have occurred through the pore openings  112  at the bottom surface  140  in this embodiment. The clogging of the pores  112  at the bottom surface  140  presents an advantage due to the fact that this area is in contact with the solid part of support and heat plate  410  and hence heat is better transferred to the clogged machined bottom surface  140  and thereby to the pulp mould  100 . The same principles of above will naturally yield for a female mould  200  attached to the heat and vacuum suction tool  400 . The vacuum chamber  420  is arranged at the bottom of the support and heat plate  410 . A plurality of spatial elements  421  are arranged to support the heat plate  410  and prevent the support and heat plate  410  from bend deformations due to the negative pressure in the vacuum chamber  420 . An isolation plate  430  is arranged to the bottom of the vacuum chamber  420 . The task appointed for the isolations plate  430  is to prevent heat from the support and heat plate  410  to transfer further to the process equipment. The isolation plate is preferably made of a material with low heat conductivity. A cooling element  440  is constructed from a first  441  and second  442  cooling plate. In the bottom side of the first cooling plate  441  and the front side of the second cooling plate  442  there is formed a machined cooling channel  443  having channel openings  443   a ,  443   b . A fluid can flow into the cooling channel  443  or out from the cooling channel  443  through the channel openings  443   a ,  443   b . The cooling channel  443  is formed in a meandering pattern from the first channel opening  443   a  towards the second channel opening  443   b . To the bottom of the cooling element  440  there is arranged a plurality of attach devices  450 . These plurality of attach devices  450  are used for attaching the heat and vacuum suction tool  400  to a pressing tool (not shown in the drawing). 
     According to a preferred embodiment the pulp mould is produced in the following manner. For the sintering process a basic mould (not shown) is used as is known per se, e.g. made of synthetic graphite or stainless steel. The use of graphite provides a certain advantage in some cases, since it is extremely form stable in varying temperature ranges, i.e. heat expansion is very limited. On the other hand stainless steel may be preferred in other cases, i.e. depending on the configuration of the mould, since stainless steel has a heat expansion that is similar to the heat expansion of the sintered body (e.g. if mainly comprising bronze) such that during the cooling (after sintering) the sintered body and the basic mould contracts substantially equally. In the basic mould there is formed a moulding face that corresponds to the moulding surface  130 ,  230  and also non-forming surfaces  160 ,  260  of the pulp mould (that is to be produced), which moulding face may be produced in many different ways known in the art, e.g. by the use of conventional machining techniques. Since a very smooth surface of the pulp mould is desirable the finish of the surface of the moulding face should preferably be of high quality. However, the precision, i.e. exact measurement, must not be extremely high, since an advantage with the invention is that high quality moulded pulp products may be achieved even if moderate tolerances are used for the configuration of the pulp mould. As described above, the first heat pressing action (when producing a moulded pulp product according to the invention), creates a kind of impulse impact within the fibre material trapped in the void  300  between the two mould halves  100 ,  200 , that forces the free liquid out of the web in a homogeneous manner, despite possible variations of web thickness, which as a result provides a substantially even moisture content within the whole web. Hence it is possible to produce the basic moulds with tolerances that allow cost efficient machining. 
     For the actual production of the pulp mould  100 ,  200  the whole portion of the formed surface of the basic mould is arranged with an even layer of the very fine particles, that will form the surface  130 ,  230 ;  160 ,  260  of the pulp mould, which is performed by providing a thin layer to the basic mould that will adhere the particles  131 ,  231  of the surface layer  130 ,  230 ;  160 ,  260 . This may be achieved in many different ways, for instance by applying a thin sticky layer (e.g. wax, starch, etc.) on to the basic mould, e.g. by means of spray or by applying it with a cloth. Once the sticky layer has been applied an excessive amount of the fine particles  131 ,  231  (which form the surface layer of the pulp mould) are poured into the mould. By movement of the basic mould, such that the excessive amount of particles  131 ,  231  move around onto every part of the surface within the basic mould, it is accomplished to arrange an even layer of the fine particles  131 ,  231  on each part of the surface in the basic mould. This process may be repeated to achieve further layers, for instance the support layers  120 ,  220 . In the next stage pointed elongated elements, e.g. nails, which preferably have a slightly conical shape, are arranged on top of the last layer. These objects will form enlarged drainage passages  150 ,  250  in the basic body, which will facilitate an efficient drainage of fluid from the pulp web and providing a flow resistance hindering fluid to pour back. Thereafter further particles  111 ,  211  are poured into the basic mould forming the basic body  110 ,  210  of the pulp mould, on the top of the surface layer  130 ,  230 . Normally these further particles have a larger size than the particles in the surface layer. Preferably the bottom surface  140 ,  240  of the pulp mould, i.e. the surface that is now directed upwardly, is evened out, before the entire basic mould is introduced into the sintering furnace, wherein the sintering is accomplished in accordance with conventional know how. After cooling, the sintered body  100 ,  200  is thereafter taken out of the basic mould and the sharp pointed objects taken out from the body, which is especially easy if these are conical. (It may be preferred to apply the “nails” to a plate, which allows for introduction and removal of the “nails” in an efficient manner). Finally the rear surface of the pulp mould  140 ,  240  preferably is machined in order to obtain a totally flat supporting surface. The provision of a flat surface leads to advantages, since firstly it facilitate exact positioning of the mould half  100 ,  200  onto a supporting plate  410 , secondly it provides for transmitting the applied pressure evenly through the whole mould  100 ,  200  and finally it provides a very good interface for transmitting heat, e.g. from the support plate  410 . However, it is understood that there is no need to always use a totally flat surfaces, but that in many cases the substantially plane surface that is achieved directly after the sintering is sufficient. 
     Moreover, some parts  160 ,  260  of the surface  130 , 230 ;  160 ,  260  are not used to form a pulp object, but there are peripheral surfaces  160 ,  260  that will not be used to form a pulp object. As a consequence, these surfaces  160 ,  260  are given a permeability that is substantially smaller than the  130 ,  230 . As mentioned above, this may be achieved by applying a thin impermeable layer  161 ,  261  having appropriate properties, e.g. any kind of paint having sufficient strength durability to maintain its impermeable function when used under operating conditions. 
     The pulp moulds  100 ,  200  are operated by pressing the moulds  100 ,  200  together so that the  130 ,  230  face each other. In the forming space  300  between the moulding surface  130 ,  230  a wet fibrous content is arranged on one of the moulding surfaces  130 ,  230 , preferably by means of suction. The pulp moulds  100 ,  200  can be heated during the pressing operation and the resulting temperature at the moulding surfaces is preferably above 200° C., most preferred around 220° C. By pressing the pulp moulds  100 ,  200  quick with impulse pressing under high pressure and high temperature, large parts of the water in the fibrous content vaporises and the steam quickly expands and tries to escape the narrow area. The steam can evacuate the pulp moulds  100 ,  200  by means of the porosity of moulding surface  130 ,  230 , the support structure  120 ,  220 , the base structure  110 ,  210  and the plurality of drainage channels  130 ,  230 . 
     Means of vacuum suction can further increase the evacuation speed and increase the amount of liquid and steam leaving the fibrous content. When the pulp moulds  100 ,  200  again are separated from each other, the moulded pulp object which has been created from the fibrous content, is held to one of the  130 ,  230  preferably by means of suction. Possibly also a gentle blow is applied through the opposite surface  230 ,  130  at this moment to safeguard that the pulp object leaves with the desired mould half. When separating the pulp moulds  100 ,  200  a negative pressure can occur in the forming space  300 , this negative pressure is far smaller than the pressing pressure. The conical endings of the plurality drainage channels  150 ,  250  together with the small openings Ø 3  as well as the difference between the pore sizes  132   d ,  232   d  in the moulding surface  130 ,  230 , the pore sizes  122   d ,  222   d  of the support layer  120 ,  220  and the pore sizes  112   d ,  212   d  of the base structure  110 ,  210 , functions as a flow resistance and restrain backflow to the forming space  300 , thereby restraining backflow to the fibrous content. 
     The invention is not limited by what is described above but may be varied within the scope of the appended claims. 
     Of course the configurations of the female  200  and male  100  moulds can differ from each other. The sintered particles  131 ,  231  in the moulding surface  130 ,  230  may differ in sizes, i.e.  131   d  and  231   d  may have different values. Likewise the sintered particles  121 ,  221  in the support layer  120 ,  220  may differ in sizes, i.e.  121   d  and  221   d  may have different values. Similarly the sintered particles  111 ,  211  in the base structure  110 ,  210  may differ in sizes, i.e.  111   d  and  211   d  may have different values. The thickness  133 ,  233  of the moulding layer  130 ,  230  preferably lies within 0.01 mm-1 mm and it is evident for the skilled person that the thickness  133  and the thickness  233  may differ from each other. The thicknesses of the support layer  123 ,  223  may also differ from each other. It is also to be understood that in some embodiments the plurality of drainage channels  150 ,  250  may be used in only one of the moulds  100 ,  200  or in none of the moulds  100 ,  200 . Also the spatial placement of the plurality of drainage channels  150 ,  250  may differ between the moulds  100 ,  200  as well as the size parameters Ø 1 , Ø 2 , Ø 3 , t 1 , t 2  and other shape characteristics of the plurality of drainage channels  150 ,  250 . Obvious the distribution density of the plurality of drainage channels  150 ,  250  may also differ between the female  200  and the male  100  mould. Furthermore the skilled person realises that the plurality of drainage channels  150 ,  250  may differ in size and shape within an individual mould  100 ,  200 . Furthermore the moulding surface  130 ,  230  may comprise particles of different materials, shapes and sizes and may be divided into different segments, each segment comprising a certain particle type. Likewise the support layer  120 ,  220  may comprise particles of different materials, shapes and sizes and may comprise different substantial layers, e.g. each substantial layer comprising a certain particle type. For instance the support layer  120 ,  220  may comprise several layers where the size of the sintered particles  121 ,  221  gradually is increased whit the smallest particles adjacent to the moulding surface  120 ,  220  and the largest particles adjacent to the base structure  110 ,  210 . Similar the base structure  110 ,  210  may comprise particles of different materials, shapes and sizes and may be divided into different substantial layers comprising, e.g. each substantial layer comprising a certain particle type. The shape of the sintered particles of the base structure  110 ,  210 , the support layer  120 ,  220  and the moulding surface  130 ,  230  may for example be spherical, irregular, short fibres or of other shapes. The material of the sintered particles may for example be bronze, nickel based alloys, titanium, copper based alloys, stainless steel etc. Furthermore it is to be understood that the shape of the mould  100 ,  200  is decided by the wanted shape of the fibrous object and that the shape of the embodiments are by means of example. Since the pulp moulds  100 ,  200  are produced using a sintering technique very complex shapes can be formed. For example a graphite form or a stainless steel form can be used for the sintering process and such a graphite form or stainless steel form can easily be manufactured in a workshop in complex shapes and with high accuracy. This makes it easy and cost effective to test alternative shapes for the fibrous object. Furthermore low production series of fibrous objects can be commercial possible due to the relative low cost of manufacturing a pulp mould  100 ,  200  of the present invention. It is further to be understood that both pulp moulds  100 ,  200  can be heated during operation as well as only one of the pulp moulds  100 ,  200  as well as none of the pulp moulds  100 ,  200 . The pulp moulds  100 ,  200  can be heated in a wide variety of ways, a heated metal plate  410  can be attached to the bottom  140 ,  240  of the pulp moulds  100 ,  200 , hot air can be blown at the pulp mould  100 ,  200 , heating elements can be added inside the base structure  110 ,  210 , a gas flame can heat the pulp mould  100 ,  200 , inductive heat may be applied, microwaves may be used, etc. Furthermore a vacuum source can be applied to the bottom  140 ,  240  of both pulp moulds  100 ,  200 , as well as to the bottom  140 ,  240  of only one of the pulp moulds  100 ,  200 , as well as to none of the pulp moulds  100 ,  200 . Moreover the source of pressing the pulp mould  100 ,  200  together can be imposed on both pulp moulds  100 ,  200  or to only one of the pulp moulds  100 ,  200  fixating the other pulp mould  200 ,  100 . Furthermore merely one of the pulp moulds  100 ,  200  could be used as a stand alone forming tool, to form a wet fibrous object in a conventional manner, i.e. normally by means of suction and thereafter normally dried in an oven, i.e. without any pressing steps. Furthermore the skilled man realises that the voids  114 ,  214 ,  124 ,  224  can be filled with particles of appropriate sizes depending of the manufacturing technique used in creating the sintered pulp mould  100 ,  200 . Moreover in some situations there might not be necessary to have an outermost layer having such small particles as the moulding surface  130 ,  230  of the invention. It is to be understood that the pulp mould of the invention can be used without the moulding layer, i.e. the support layer  120 ,  220  on top of the base structure  110 ,  210 , as well as only the base structure  110 ,  210  as the outermost layer. For instance in the forming step of the pulp moulding process, the pulp mould  100 ,  200  may have larger particles in the outermost layer than in forthcoming pressing steps. Depending of an actual embodiment of the invention the drainage channels  150 ,  250  could have its pointed opening Ø 3  anywhere in the interval from the border between the base structure  110 ,  210  and the support layer  120 ,  220  till the border between the moulding surface  130 ,  230  and the forming space  300 . Moreover, using the support and heat plate  410  beneath the pulp mould  100 ,  200  where the suction openings  412  are arranged to mate the bottom openings Ø 1  of the plurality of drainage channels  150 ,  250 , it is obvious that it is preferred that the mating is a close match as possible and preferably every suction opening  412  always mate a corresponding bottom opening Ø 1 , but of course the invention is not limited to a perfect match rather the suction openings  412  could differ in diameters contra the bottom openings Ø 1  and the number of suction openings  412  could be larger as well as smaller than the corresponding bottom openings Ø 1 . Since the pulp mould  100 ,  200  preferably are constructed by metal particles and since the pulp mould does not have a relief shape, i.e. the thickness of the pulp mould  100 ,  200  is not constant following the contour of the pulp moulded object, but has preferably a flat bottom  140  resulting in that the thickness of the pulp mould  100 ,  200  varies depending of the shape of the pulp moulded object, the pulp mould is able to withstand very high pressure without deforming or collapsing compared to a pulp  100 ,  200  mould having a relief shape and/or comprised by a material of less strength, for instance glass beads.

Technology Classification (CPC): 3