Abstract:
The application discloses a base plate comprising a rigid body portion ( 50 ), means ( 51, 52′, 52″ ) arranged within the rigid body portion ( 50 ) to enable vacuum to be applied. The vacuum means comprise an open space ( 51 ) in the form of a centrally positioned recess forming a vacuum chamber ( 51 ) within the rigid body portion ( 50 ) and at least one connecting channel portion ( 52′, 52″ ) that extends in the main plane of the rigid body portion ( 50 ) arranged to connect the vacuum chamber ( 51 ) with a vacuum source ( 52 ). An assembly comprising the base plate and a pulp mould, as well as methods for producing the base plate and the assembly, are also disclosed.

Description:
BACKGROUND 
       [0001]    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. 
         [0002]    In traditional pulp moulding lines, se for example U.S. 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. 
         [0003]    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. 
         [0004]    US 2003/0051845 and US 2005/0230863 show arrangements according to the above principles. 
         [0005]    WO2006057610 describes another kind of pulp moulding lines where the product is formed on a forming tool and subsequently pressed under heat and vacuum suction in a number of pressing steps. The product is thereafter dried in a microwave oven and ready for post treatment processes. A mould suitable for such pulp moulding lines was shown in WO2006057609. The moulding surface can be heated to 200° C. and above through a heat plate arranged to the bottom of the mould. The heat plate comprises a number of drilled holes which connects the mould to a vacuum box at the opposite side of the heat plate. However drilling holes in the heat plate may be costly and also lead to undesired waste of material. Another problem is that a lot of energy is needed to heat the moulding surfaces, via the heating plate. 
         [0006]    Another kind of problem related to the tool design as presented in WO2006057609/10 is that the design of the pulp mould and also their production present some steps/features that imply high cost and/or undesired side effects. 
       OBJECTS OF THE INVENTION 
       [0007]    It is an object of the invention to provide a high quality pulp mould which is comparably cost effective to produce. 
         [0008]    It is another object of the invention to provide a pulp mould that can be produced in a time efficient manner. 
         [0009]    It is another object of the invention to provide a pulp mould whith comparably low amounts of energy to heat the moulding surface. 
         [0010]    It is another object of the invention to provide a pulp mould that can be produced at low amounts of rest materials. 
         [0011]    Further aspects of the invention will be apparent from the following. 
       SUMMARY OF THE INVENTION 
       [0012]    At least one of the above stated objects and/or problems is solved by a pulp mould and/or method as defined by the independent claims. 
         [0013]    Thanks to the invention there is achieved a pulp mould and also a tool, partly thanks to the new pulp mould which may be produced in a much more cost efficient manner, which also will require less energy during its intended use and which may in an improved manner provide high quality pulp products. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  shows a schematic view of a manufacturing process of a moulded fibrous product according to the invention, 
           [0015]      FIG. 2  shows a perspective view of the formation and pressing tools, 
           [0016]      FIG. 3  shows a perspective view of the front part of a base plate of a formation tool according to the invention, 
           [0017]      FIG. 4  shows a view from behind of said base plate, 
           [0018]      FIG. 5  shows a perspective view from above of a male pulp mould according to the invention, 
           [0019]      FIG. 6  shows a partly exploded view in perspective of one male pulp mould according to the invention 
           [0020]      FIG. 6A  shows an exemplary embodiment of a single base plate according to the invention, 
           [0021]      FIG. 7  shows an exploded view of a female pulp mould according to the invention, 
           [0022]      FIG. 8  presents a cross sectional view of pulp mould and base plate according to the invention, 
           [0023]      FIG. 9  shows an exemplary embodiment of a heating devise according to the invention, 
           [0024]      FIG. 10  shows a first embodiment of a cross section of the heating element as shown in  FIG. 9 , 
           [0025]      FIG. 11  shows a further embodiment of said heating element. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0026]    In the forthcoming text when using directional terms such as upper or lower in relation to a pulp mould, the moulding surface of the pulp mould is seen as the top and the base plate as the bottom. 
         [0027]      FIG. 1  is a schematic view of a manufacturing process for producing moulded fibrous products showing a forming section  1  for forming a moulded pulp object, a drying section  2  for drying the moulded pulp object, and a after treatment section  3  for subjecting the dried moulded pulp object to after treatment steps such as lamination, finishing the edges of the pulp objects, packing the pulp objects, etc. The forming section  1  includes a plurality of rotatable holders  4 , each having two opposite located tool carriers  5 . The holder  4  alternately have female  20  or male  10  pulp mould(s) mounted on the tool carriers  5 , e.g. if the first holder has male moulds then the second holder has female moulds, and the third holder male moulds etc. The tool carrier  5  can be pushed out and pulled in, in relation to the holder  4 , thereby enabling the opposing moulds to mate each other during operation. The means for pushing and pulling the tool carriers  5  can e.g. include a telescoping hydraulically operated arm  6 . 
         [0028]    During operation, the pulp mould(s)  10  of the first holder  7  is immersed in the stock that is kept in the tank  9  to form a fibre object(s) on the pulp mould(s). The fibre object(s) is subsequently dewatered between opposing pairs of pulp moulds  10 ,  20  of the holders  4 , till it is passed to the drying section  2  by the last holder  8 . The dewatering between opposing pairs of pulp moulds  10 ,  20  is performed by pushing opposing tool carriers  5  with their female respectively male moulds against each other as is described in more detail in WO 2006057609/10, which are herewith introduced by means of reference. The dewatering operations are preferably performed under suction and heat. The first  7  and the last holder  8  rotate 90 degrees back and forth during operation, while the intermediate holders each rotate 180 degrees so that the fibre object(s) can be passed from the pulp mould(s) of the first holder  7 , to the pulp mould(s) of the second, and so on till the last holder  8 . The handover of the fibre object(s) between an opposing pair of pulp moulds  10 ,  20  can be done by releasing the suction through the delivering pulp mould(s)  10 ,  20 , and optionally give it a gentle blow, while suction is applied through the receiving pulp mould(s)  20 ,  10 . 
         [0029]    The facing surfaces of opposing pulp moulds  10 ,  20  have complementary shapes with regard to the moulding surfaces thereof, however other characteristics of the moulds may differ depending on the positional order of the moulds, for instance the mould(s) of the first holder  7  may have a coarser structure of its moulding surfaces, than the opposing mould(s) of the second holder  4 , and subsequent moulds  20 ,  10  of the following holders may have finer and finer surface structures. Further the suction means and/or the heating means may also vary between the holders, e.g. the pulp mould of the first holder  7  may have suction means but lack heating means. 
         [0030]      FIG. 2  shows a holder  4  positioned in its support structure and related sub equipment, which will not be described in greater detail, e.g. means for rotating the holder around its axis, and means pushing and pulling the tool carrier  5  outwards and inwards. On the holder  4  there are arranged two tool carriers  5 , presenting some features of one embodiment according to the invention. The tool carrier  5  here shown has six columns, where each column can hold three pulp moulds, here exemplified by male pulp moulds  10  at the first column, while the remaining columns are shown only with the base plate  50  having chambers  51  onto which a female  20  or a male  10  pulp mould can be mounted. The two carrier  5  also comprise the following; next to the backside of the base plate  50  a layer of insulation  58  and on the opposing side in relation to the base plate  50  a carrier plate  59 . Along one side end of the tool carrier  5  there is arranged vacuum pipe  52  that extends substantially along the whole length of the tool carrier  5 . From the vacuum pipe  52  there is arranged a number of branch pipes  52 ′ connected to each row of tool plates  50 , to provide for vacuum in each one of the vacuum chambers  51 , which will be described in more detail below. Accordingly the vacuum pipe  52  is fixedly attached to the tool carrier  5 , necessitating a flexible connection (not shown) to the vacuum pump to enable the desired movement of the tool carrier  5 . 
         [0031]    In  FIG. 3  there is shown in a perspective view, and in greater detail, one of the tool plates  50  presented in  FIG. 2 . The tool plate  50  is in the form of a rigid body  50  and arranged with a number of holes  54  for attachment of moulds  10 ,  20  e.g. three moulds. For each mould  10 / 20  there is arranged a centrally positioned recess  51  forming the vacuum chamber for each mould  10 / 20 . The extension of the vacuum chamber  51  is in general as large as possible, considering the fact that there is a need of a surrounding support surface  55  to safely attach and seal along the attachment area of the mould. Also in connection with each vacuum chamber  51  there is a vacuum outlet  52 ″ leading to a channel  52 ′connecting each vacuum chamber  51  with the vacuum pipe  52 . The channel  52 ′extends, at least partly, within tool plate  50 , i.e. extending in a plane that is parallel with the plane of the extension of the main plane of the plate  50 . Moreover there are passages  53  for connection of electricity and preferably also sensors for each one of the moulds  10 / 20 . The tool plate  50  could be produced in almost any kind of material, but is preferable made from some kind of light weight material having good ability to fulfill all needs, e.g. aluminum. 
         [0032]    In  FIG. 4  there is shown the backside  57  of a tool plate  50 . Here the connecting vacuum channel  52 ′ is clearly presented, in the form of channel in the back of the plate  50 . Also small channels  53 ′ are provided for electric cables (not shown) to the electrical contacts (and possible sensor/s  48 , see  FIG. 8 ) intended for fitting into the passages  53 . 
         [0033]    In  FIG. 5  there is shown a set of three male moulds  10  intended for interfit with a tool plate  50  as described in relation to  FIGS. 3 and 4 . Each mould  10  is arranged with a moulding surface  13  that is porous to enable vacuum to pass through. Further there is a support part  16  surrounding the moulding surface area  13  which support part presents impermeable areas  16 . The interfit between the tool plate  50  and the mould  10 / 20  will be described more in detail in relation to  FIG. 8 . 
         [0034]    In  FIGS. 6 and 7  there are shown exploded views of male pulp mould  10  and a female mould  20 , respectively, according to the one embodiment of invention. As is evident for a skilled person the same inventive features are of course applicable to both the male and female moulds. The mould  10 / 20  forms an integral body  11  (see  FIG. 8 ) wherein a heating coil  40  and a sealing barrier  47  are built in, in connection with sintering of the mould  10 / 20 . In the sealing barrier  47  there are formed holes  47 ′,  47 ″ of corresponding size and form as the cross-section of the element (heating wire and/or sensor body) intended to pass through. Further there is an interface unit  41  for connecting the heating means  40  and also possibly a sensor.  FIG. 6A  shows a perspective view of a pulp plate  50  intended to merely carry one mould  10 / 20 . The main purpose of this figure is to present that indeed there are a big variety of the modifications within ambit of the invention, e.g. merely have one mould on top of each base plate  50 . Also this figure presents a different solution for providing vacuum to the vacuum chamber  51 , which is achieved by drilled holes  52 ′ leading into the vacuum chamber  51  via appropriate connecting channels  52  (not shown), e.g. branch pipes  52 ′ leading to a common vacuum pipe  52 . Further it is shown that there are positioning pins  56  intended to facilitate fitting of the mould  10 / 20  onto the base plate  50 . Moreover it is presented that the base plate  50  may be formed to have a vacuum chamber  51  in the form of through passage and accordingly then use backing plate in connection with the insulating layer at the back of the base plate  50 , to provide for reliable sealing and support. 
         [0035]      FIG. 8  presents a cross sectional view through a female pulp mould  20  being attached to a tool plate  50 , in accordance with the invention, wherein a rigid body  50  is used for the tool plate having the vacuum chamber  51  integrated therein such that that the rear wall  570  forms an integrated portion. In the following the details of the inventions will be described with reference to a mixture of  FIGS. 6-11 . The pulp mould  10  includes a porous body  11  with an inner permeable surface  12  and an outer permeable moulding surface  13 . The porous body  11  is preferably a loose sintered body from metal powder. In particular copper based powders, preferably bronze powders have been shown to provide very good results. The porous body  11  may be of metal particles of the similar sizes throughout the body  11  or be layered by powder of different size and/or content, to fulfil different needs and mostly having a finer powder at the outer moulding surface. (Regarding the sintering it is referred to the WO-document referenced above.) 
         [0036]    The pulp mould  10  includes a heating means  40 , preferably in the form of resistor heating coils  40  commonly used in electrical stoves. The heating coils have an inner core  402  (see  FIG. 10 ) which is heated by means of electrical resistance. An intermediate layer  401  surrounds the inner core  402 . Preferably the intermediate layer  401  is electrically non conductive, but is a good heat conductor for transferring heat to the porous body  11 . However, as indicated in  FIG. 11  the intermediate layer may comprise an upper portion  404  and lower portion  403 , where the upper portion  404  is in a material that is a much better heat conductor than the lower portion  403  which forms an heat insulator, so that heat is directed towards the moulding surface  13 . An outer layer  400  preferably of a metallic material surrounds the intermediate layer  401 . The outer layer  400  is sintered to the porous body, forming sintering necks to the particles of the porous body  11  which provides for a good heat transfer to the porous body  11 . 
         [0037]    Since the pulp mould  10 / 20  will be heated during use it is desirable that the heating coefficient of the powder particles and the material of the outer layer  400  are similar. When using bronze powder in the body it has been shown that copper or a copper based alloy is a good material for the outer layer  400 . Copper and bronze can also be sintered at much lower temperature than steel powder in connection with steel heating elements  40 ; however such a combination may also be possible. The cross-section of the resistor heating coils  40  can be circular as shown in  FIGS. 10 and 11 , however the cross-section could very well be rectangular or having any other kind of cross-sectional shapes. 
         [0038]      FIGS. 6 and 7  present that there is preferably a sealing stripe  47  arranged in the mould  10 / 20 , preferably made in copper to provide a seal between the permeable area (including the outer moulding surface  13 ) and the area  16  where it is desired not having the mould permeable to vacuum. Accordingly in a preferred embodiment both the heating element  40  and the sealing stripe  47  are positioned into the basic mould (not shown) in connection with the production of the pulp mould  10 / 20  by means of sintering. When using bronze powder in the body it has been shown that copper or a copper based alloy is a good material for the sealing stripe  47 ; however other alloys may also be used as the material for sealing stripe  47 . 
         [0039]    As is evident from the cross section shown in  FIG. 8  the heating means  40  and also the sealing stripe  47  will be integrated/embedded into the body  11  of the mould  20 . Furthermore it is shown that said sealing stripe  47  is arranged between said outer area  16  and a central portion  11 A of said porous body  11 . A novel feature presented in  FIG. 8  is the use of a limited surrounding machined rear surface  14  of the mould. This rear surface  14  is the only part of the inner moulding surface  12  that is machined after sintering. Accordingly merely a sufficient area is machined to allow for appropriate interfit onto the support surface  55  of the tool plate  50 . 
         [0040]    Thanks to this arrangement a number of advantages are gained. Firstly it means that merely a minor fraction of the material used in connection with sintering will be wasted, compared to the traditional manner where the whole backside of the mould  20  would be machined to make it flat. Further it will allow for better permeability of the inner surface  12  of the mould, due to the fact that machining will negatively affect that surface by at least partly blocking the pores at the surface  12 . 
         [0041]    Also the use of sealing stripe  47  will provide considerable advantages. The stripe  47  in an efficient manner seals the outer portion surface  16  of the mould  20  that otherwise will have to be sealed in some other manner that have shown to be either costly and/or not totally reliable. Further it implies that the holes  54  or the screws connecting the mould  20  with the tool plate  50  is also sealed off in an efficient manner, due to positioning the sealing stripe  47  closer to the inner edge  55 A of the supporting surface  55  than the outer edge  55 B, thereby providing a relatively wide area adjacent the periphery of the mould  20  for the holes  54 . 
         [0042]    Another evident advantage with the principles of the novel features is that the arrangement of vacuum supply to the vacuum chambers  51  may be achieved in a very compact and cost efficient manner, by forming the vacuum chambers as integrated spaces in the rigid body  50  of the tool plate and also by integrating the connecting channels  52 ′,  52 ″ directly into the tool plate  50 . As is evident from  FIG. 8  and also  FIG. 2 , this leads to a very compact arrangement. 
         [0043]    As depicted in  FIG. 8A , which is a partial cross sectional area including the sealing stripe  47  the part  11 B of the mould comprising the surface  16 A not intended to be permeable may adjacent the surface thereof be provided with a thicker layer of finer powder particles F to thereby provide extra safety to have it impermeable, i.e. a sufficiently thick layer of fine particles F such that impermeability is achieved, whereas on the inside of the stripe  47  that layer F is very thin to achieve a fine and permeable surface  13 . As is evident the sealing stripe  47  may assist in efficient building of different kind of layers on the outside and inside respectively thereof  47 . Moreover it is evident that the latter kind of functionality may be achieved by using a pre-fabricated frame portion (not shown) which is impermeable and to position that frame portion into the basic mould (not shown), to thereafter use powder to produce the inner permeable body  11  of the mould  20 . 
         [0044]    The heating means  40  are preferably placed close to the outer moulding surface  13  for good heat transfer to the moulding surface. How close is dependent on the geometry of the pulp mould  10 . Preferably though the heating element has at least one active section thereof located at a distance within 20 mm from lowest portion of the moulding surface, preferably within 10 mm, even more preferred within 5 mm. 
         [0045]    In  FIG. 7  the heating means  40  is shown to be arranged substantially in one level within the central part of the porous body  11 , while in  FIG. 6  the heating means  40  is arranged substantially in two levels within the central part. It may be possible in simple geometries to let the heating elements follow the contour of moulding surface  13 . 
         [0046]    The heating means in the form of heating coils  40  may of course be wound in different shapes before sintering them into the porous body  11 . For instance they may be wound in a circular manner as shown in  FIG. 9  or in meander patterns as shown in  FIGS. 6 and 7 , but of course there are numerous ways of winding the heating elements. 
         [0047]    By having the heating means  40  embedded in the porous body  11  much less energy needs to be used to achieve the same temperature at the moulding surface  13  in comparison to the use of a heat plate below the mould as known prior art. Further since the heat plate may be eliminated the pulp moulds may be positioned closer to the rotational centre of the pressing tools  4  which has several advantages: 1) the strike distance may be increased or each mating pressing tools  4  may be placed closer to one another maintaining the same strike distance, 2) the momentum required to rotate the pressing tools  4  is reduced since the weight distribution is moved closer to their rotational centre, thereby enabling a faster rotation and/or a rotation at lower power needs. Further since less energy is used less heat will also reach the machinery of the pressing tools  4 . It may therefore be possible to further decrease the heat insulation plate as well as eliminate possible cooling element without risking undue heating of the machinery of the pressing tools, providing even better weight distribution. 
         [0048]    Thanks to the new kind of heating element drastic savings may be achieved, especially due to the fact that the new kind of heating means can be used in the form of standard equipment that is very cheaply produced in connection with stoves etc. Also thanks to the embedding thereof, by means of the sintering and eliminating any need of machining in connection with the heating elements, will all lead to considerable cost savings. Further, the improved permeability will give the advantage that in most cases there may not longer be any need for providing broader drainage channels through the porous body  11 . However such drainage channels, which e.g. is described in WO2006/057609 and hereby incorporated by reference, may be used to further increase drainage through the pulp mould, e.g. drainage channels running from the inner surface  12  towards the outer surface  13 , preferably with decreasing diameter in the direction to the outer surface  13 . The new principle of merely machining the portion of the inner surface  12  will also lead to an increase of the production capacity since the reduced amounts of machining will merely take a fraction of the time compared to today&#39;s technology. 
         [0049]    The elimination of the backing plate between vacuum box and the tool also leads to considerable savings since for instance such a backing plate will need a large number of drill holes, etc. 
         [0050]    The invention is not limited by what is described above but may be varied within the scope of the appended claims. For instance for the skilled person it is evident that many different kind of heating means may be used to achieve the desired heating of the mould phase itself, i.e. a variety of the heating devises know per se which may be embedded into the sintered body in accordance with the invention. In the same manner it is evident for the skilled person that a variety of sensors may be integrated into the sintered body. More over it is evident that many of the different features described above, e.g. the none grinding of the back side of the mould, the separate arrangement for achieving good sealing within the attachment area of the mould (eliminating leakage through the screw holes), etc. may be the subject for divisional separate applications in the future. Further, to facilitate heat transfer from the outer layer  400  of the heating means to the porous body  11  of the pulp mould  10 ,  20 , the surface of the outer layer  400  may be roughened and/or to have finer metal powder particles adjacent to the heating means  40 , to thereby enhance a sintering neck formation between the heating means  40  and the porous body.