Patent Application
20120133087
The present invention relates to a method as presented in the preamble of claim 1 and an apparatus as presented in the preamble of claim 6 for manufacturing articles with the help of a mould.
Owing to its versatility of application, the method and apparatus according to the invention, i.e. the solution according to the invention, is applicable to the manufacturing of many different products in a mould. In the manufacturing, various prior-art technologies and the good aspects of them are combined so that the products to be manufactured can be small or also very large in size and manufactured from different raw materials, such as dung, straw, sawdust or woodchips, paper, plastic, rubber, metal, et cetera. In addition, the solution according to the invention is applicable to the rapid manufacture of very different composites.
Different articles that are of different sizes and composed of different materials are made with the help of moulds with solutions according to prior art with many different methods, e.g. by laminating, pressing, vacuum forming, injecting, foaming and casting. Some articles are made by hand, some with machines designed for the purpose. Large articles are generally made by laminating and small articles can be pressure moulded or cast with different methods.
Many reinforced plastic articles, i.e. plastic composites, are made according to prior art e.g. manually by laminating reinforcement material layers and resin layers in turn onto a template. The method is called open-mould lamination and one advantage of it is that also very large articles, e.g. boats, can be manufactured with it, but a problem is that open-mould lamination particularly demands professional skill, so that the quality of manufactured products can vary a lot, depending on the laminator. In addition, open-mould lamination is relatively slow. Depending on the size of the article, time ranging from a few hours to many weeks is spent on manufacturing the article. Spray-up moulding and moulding based on the vacuum bag method are reminiscent of open-mould laminating and are to some extent faster than it, but the variation in quality due to the professional skill they require and the slowness of manufacturing large articles are still a problem.
The Sheet Moulding Compound (SMC) method is used a lot, particularly in the automotive industry, for the manufacture of plastic composites. In this method hot pressing is used, which occurs as compression moulding, in which flexible SMC material that is a few millimetres thick is pressed into a mould and the preform, pressed into its shape, is cured by means of temperature. The SMC method is mainly suited to the manufacture of sheet-type moulded articles. The manufacturing time ranges from a few seconds to a few minutes, depending on the size of the article. Since moulds are extremely expensive with prior-art methods, an economically viable series size is generally at least 10,000 units. Another problem is that the strength of articles manufactured with the SMC method is not very great.
The Bulk Moulding Compound (BMC) method is also a hot pressing method. A carefully dispensed quantity of reinforced moulding material filled with a filler agent is pressed into a mould according to the compression moulding method and cured at a higher temperature. In this method also a problem is the expensive moulds, and also the fact that the equipment used is suited only for this particular method.
Resin Transfer Moulding (RTM) is a method in which reinforcement material is placed, while dry, into an airtight two-sided mould, the second side of which is e.g. a vacuum bag. Resin is injected into the space between the moulds through the reinforcements by the aid of either underpressure or overpressure. Large articles also can be manufactured with this method, but in this case also the apparatus is suited only to this purpose. Furthermore, the curing of the resin lasts a long time.
Yet another lamination technique is prepreg lamination, which is used a lot in e.g. the aviation industry. In the prepreg method, the curing of the resin is started even before performing the lamination, but the curing speed is slowed down. Prefabricated lamination sheets must be stored at a temperature of at least −18° C. so that the resin does not cure too quickly. For this reason the transportation and storage of prefabricated prepreg lamination sheets are awkward. Additionally, the epoxy resins used in prepreg methods require precise and controlled conditions for curing, e.g. a temperature of approx. 120° C.-180° C. in a pressure range of approx. 100 kg/cm2. The sealing of the laminates occurs by means of a vacuum bag and post-curing requires approx. 30-60 minutes of autoclave treatment in the aforementioned temperature range.
Compression moulding, for example, in connection with injection moulding, among other things, is generally used in the manufacture by means of a mould of plastic products other than those to be laminated and of products made from other materials. Generally, however, a problem is that a vacuum and also other casting techniques could not be economically connected to the compression moulding apparatus, but instead each apparatus had to be separately made. In addition, it has not been possible to connect adequate heating to the compression moulding apparatus for curing the article to be manufactured, so it has only been possible to make with it certain types of articles that do not need a curing reaction.
So-called “hydroforming” technology is also known in the art, wherein by means of hydraulic pressure and a flexible film e.g. metal sheets are pressed at room temperature into a negative or a positive mould, or a combination of these. Hydroforming technology is nowadays used a lot in e.g. the automotive industry. However, the hydroforming techniques used today are not suited to simultaneously high temperatures and high compression pressures, so that e.g. plastic composite structures that require curing cannot be made with them. In addition, the mould costs are relatively high in these also.
A problem in prior-art solutions has generally also been, in addition to expensive moulds, that fact that the product pressed or laminated into the mould is not immediately ready after the pressing or lamination, but instead drying and/or hardening often lasts for several hours after the pressing or lamination. In open-mould lamination performed by hand, in which heating is not used, articles can be detached from the mould only on the day following completion of the lamination and, in addition, detaching agents are expensive. Additionally, the autoclaves needed for curing are expensive and, being large units, also require a lot of space. There are no devices, particularly for the manufacture of large articles with extensive surfaces, which would comprise one apparatus that produces the pressure needed for compression and withstands the pressure as well as an apparatus that produces the heat needed for curing. Neither are there any devices in which, in connection with the manufacture of thermoplasts and thermosetting plastics, different metals, such as screws, various brackets or reinforcements, could be combined into the plastics.
The aim of this invention is to eliminate the aforementioned drawbacks and to achieve a method and apparatus for manufacturing articles with the help of a mould that are inexpensive, effective and suited to many applications. In addition, one aim of the invention is to achieve a solution in which the moulds are simple and inexpensive, but they nevertheless enable a high-quality end product. The aim is also to achieve a solution in which the properties and good aspects of prior-art manufacturing technologies can be easily and advantageously combined in the manufacture of different articles of different sizes such that with the same basic solution and basic apparatus large and small articles can be manufactured, and also articles manufactured with different technologies such as e.g. with laminating, compression, vacuum-forming, foaming and casting technologies.
The aim is also to achieve a solution with which the manufacture of different articles manufactured in a mould is faster than it currently is with prior-art technologies. Further, the aim is to save costs and shorten the time used by eliminating the need for separate autoclaving. In addition, the aim is e.g. to replace conventional vacuum technology with compression moulding, which enables the combining of injection moulding techniques and injection techniques. The method according to the invention is characterized by what is disclosed in the characterization part of claim 1. Likewise the apparatus according to the invention is characterized by what is disclosed in the characterization part of claim 6. Other embodiments of the invention are characterized by what is disclosed in the other claims.
One advantage, among others, of the solution according to the invention is that the manufacturing of articles is rapid and inexpensive. Small articles are quick to manufacture in a mould, because at the same time a number of different articles can be pressed into many different moulds by means of the flexible film. Another advantage is that the moulds are inexpensive so that also small series can be economically manufactured. Inexpensive moulds also enable the mechanized manufacture of large articles and also, owing to the use of heating, even large laminated articles can be manufactured quickly and inexpensively. Separate curing treatments in expensive autoclaves are not needed. Another advantage is that by means of the solution very many different types of products made from different materials, such as e.g. wood, metal, plastic, rubber, et cetera, can be manufactured. Heating and compression enable, among other things, the lignin contained in wooden material to be used as a binding agent, in which case external binding agents are not always needed. In addition, another advantage is that e.g. electronics, metal inserts, such as thread elements and various fixing parts, as well as reinforcements, et cetera, can be connected to products to be manufactured from composite materials.
Yet another advantage is that with the same apparatus the necessary moulds can also be manufactured, which moulds are inexpensive, light and easily installable into the pressure space. A further advantage is also that the solution according to the invention enables the production of articles currently manufactured with vacuum technology advantageously with compression moulding technology by means of the light mould structures to be manufactured. In this case it is possible in the manufacture of products manufactured conventionally with a vacuum technique to achieve the same very short manufacturing times as with conventional compression moulding technology. Likewise, in the solution according to the invention it is possible to manufacture large articles with extensive surfaces with compression moulding as well as with injection moulding and injection technology with the costs of manual lamination moulds.
In the following, the invention will be described in greater detail by the aid of some embodiments with reference to the attached drawings, wherein
A hydraulic press arrangement is used for manufacturing different products, such as products manufactured from one material as well as various composites and laminates, with different compression methods, which are e.g. compression moulding methods, vacuum forming methods and injection moulding methods. The solution according to the invention comprises a strong pressure-resistant frame 1 and also a pressure chamber 6 to be disposed inside it, in which pressure chamber the moulds are surrounded with high pressures and temperatures. The solution also comprises the utilization of high temperatures so that post-treatment with an autoclave of the products to be manufactured is avoided. With the solution according to the invention prior-art plastic mould techniques are applied, which have been used e.g. in injection moulding moulds.
The apparatus also comprises a hydraulic compression means between the top part 2 of the frame part 1 and the top chamber 7, of which only the hydraulic connector 5 is, however, seen in
The wedge principle can also be applied such that the top surface or base of the receiving space 1a form a wedge-shaped space in relation to each other. In this case e.g. the height of the receiving space 1a decreases linearly when proceeding towards the rear end of the receiving space 1a. When viewed from the side, the receiving space 1a can in this case be such that its base is essentially on a horizontal plane but the top surface descends when proceeding from the front towards the rear end. Or the base can ascend when proceeding from the front towards the rear end whereas the top surface remains essentially on a horizontal plane. Yet a third alternative is that both the top surface descends and the base ascends when proceeding from the front towards the rear end. Correspondingly, the pressure chamber 6, with the upper chamber part 7 and lower chamber part 8 of it placed face-to-face one on top of the other, is essentially the same shape as the receiving space 1a when viewed from the side. In this case when proceeding from the front end of the pressure chamber 6 towards the rear end, either the top surface of the upper chamber part 7 descends and the base of the lower chamber part 8 remains on a horizontal plane, or the base of the lower chamber part 8 ascends and the top surface of the upper chamber part 7 remains on a horizontal plane, or the top surface of the upper chamber part 7 descends and the base of the lower chamber part 8 simultaneously ascends. In this context, the front end of the pressure chamber 6 is that end from which the pressure chamber is pushed inside the receiving space 1a and pulled out of it.
When pushing the growing wedge shape of the pressure chamber 6 into the shallowing wedge shape of the receiving space 1a, the pressure chamber 6 is finally pressed tightly between the top surface and the base of the receiving space 1a. The compression means 16 referred to in the following ensures the staying together of the compression halves.
The pressure chamber 6 is placed into the receiving space 1a of the frame structure 1 e.g. such that first the bottom chamber 8 is pushed into the receiving space 1a starting from the first end of the receiving space 1a by the aid of some suitable pushing means 1e, until the bottom chamber 8 is in its final position inside the receiving space 1a. After this the second end of the top chamber 7 is placed on top of the first end of the bottom chamber 8 and the top chamber 7 is slid in the direction of the arrow A along the wedge surfaces between the chambers into its position on top of the bottom chamber 8. The height of the receiving space 1a as well as the combined height of the top chamber and bottom chamber 7, 8 is dimensioned such that at first there is a clearance between the top surface of the top chamber and the top surface of the receiving space 1a, but when the top chamber 7 is in its position the clearance has disappeared and the top surface of the top chamber 8 is pressed tightly against the top surface of the receiving space 1a. The final pressing of the top chamber and the bottom chamber 7, 8 against each other is implemented by the aid of a hydraulic compression means 16, which receives its working pressure from the hydraulic system or from a separate hydraulic aggregate, which is not presented in the figure.
The pressure medium is a liquid that endures high temperatures and great pressure, and which has low compressibility. It should be possible to use the pressure medium e.g. in the temperature range −40° C. . . . +450° C. One such pressure medium is e.g. a metal that melts at a low temperature, which when melted is led into the pressure chamber 6. If a temperature of the aforementioned magnitude is not needed, but instead e.g. approx. +250° C. is sufficient as a temperature, other pressure mediums can be used, e.g. ethylene glycol or corresponding substances, the compressibility of which is extremely small.
Heating of the pressure medium is implemented with heating means 13, which can be outside the pressure chamber 6, as in
The circulation pump 12 circulates the pressure medium and the process pressure for compressing the product into its mould is implemented either manually or by means of a mechanized actuator 14 with which such great pressure is caused in the pressure chamber 6 that the article to be manufactured is pressed into essentially its final shape against the mould.
Inside the halves 7 and 8 of the pressure chamber 6 is a pressure space 17, 17a, which is connected to the hydraulic system 10 of the apparatus via pressure connectors 9. The pressure space 17 of the upper half 7 is closed off from the bottom part of the pressure space in a pressure-resistant manner, i.e. from the side of the lower half 8, with an elastic film 18, such as with a silicone film or Teflon film, that withstands pressure and heat. Correspondingly the pressure space 17a of the lower half 8 is closed off from the top part of the pressure space, i.e. from the side of the upper half 7, with an essentially thin mould element 19, e.g. with a thin mould element that is formed into the shape of the mould of one large-sized article or the shape of the moulds of a number of small articles to be made simultaneously and that is made with a metal sheet, plastic sheet or plastic composite sheet or from another suitable material. In the following a mould element refers to an entity that comprises either the mould of one large product or a number of moulds of a smaller product to be simultaneously manufactured in the same element.
The lower half 8 of the pressure chamber 6 comprises means for supporting the mould element 19 in its position during filling of the mould and during manufacture of the product. Preferably these means are the edges of the lower half 8 that meet against the upper half. In this case the edges of the mould element 19 extend in the lateral direction to outside the outer edges of the lower half 8 of the pressure chamber 6, in which case when manufacturing articles the mould element 19 is pressed at its edges between the halves 7 and 8 of the pressure chamber 6.
The gap between the halves 7 and 8 of the pressure chamber 6 is sealed, e.g. with an elastic sealing means 9c, which behind the seal surface is connected via a pressure duct 9b, a pressure amplifier 9a and a pressure connector 9 to the hydraulic system 10 of the apparatus. The pressure amplifier 9a is thus connected to the process pressure and owing to its amplification ratio, which is implemented with pistons of different sizes, always causes greater pressure on the sealing means 9c than the process pressure that is prevailing at that moment in the pressure space 17, 17a of the pressure chamber 6. Thus the process pressure is not able to leak out of the pressure space 17, 17a.
On top of the mould element 19 is material 20 to be pressed into a product, which material is disposed in all the desired points on top of the mould element 19 when the lower half 8 of the pressure chamber 6 is still preferably free and outside the receiving space 1a of the frame structure 1. In this case it is easy to place all the material needed for manufacturing a product into the mould.
The upper mould element 19a is also essentially thin and can be essentially similar in its material and structure to the lower mould element 19, but it can contain different mould patterns than those in the lower mould element 19, in which case the products to be manufactured will not necessarily be of equal thickness. In this solution the elastic film 18 is pressed against the rear surface of the upper mould element 19a when the process pressure is switched on and the products are finished by pressing between the lower mould half and the upper mould half.
Each of the mould elements 19, 19a can be of such a structure that their top half and bottom half are of a different material. In this case e.g. the rear side of a mould element 19, 19a can be wholly metal whereas the front side is composite, or vice versa.
The solution according to
In the situation according to
The apparatus also comprises regulating means, with which the compression speed and the increase in the pressure prevailing in the pressure chamber and also the temperature prevailing in the pressure chamber are adjusted if necessary during the pressing. Correspondingly the apparatus comprises regulating means for regulating the timing of the pressurizing cycles. The regulating means are not depicted in the figures. Prior-art techniques known from e.g. injection moulding technology are used for removing air from the mould elements 19.
Characteristic to the solution according to the invention is, among other things, the heating and/or the curing of the mould element 19, 19a or of the material to be compressed that occurs by means of the liquid heating or other suitable heating, as well as the formation of hydraulic pressure directly behind essentially thin mould elements 19, 19a. The properties of the halves of the mould elements 19, 19a that give a surface to the product are selected to be such that they withstand variations in pressure and temperature. In this case the surfaces of the mould elements 19, 19a are preferably e.g. metal or composite structures.
The speed of the manufacturing process of a product can be increased because a number of mould elements 19 are used. In this case the next mould element 19 can already be filled simultaneously with when the previous mould element 19 is in the pressure chamber 6 in the heating phase, pressing phase, or drying/hardening phase. When the previous mould element 19 is taken out of the pressure chamber 6 to cool, the next mould element 19, which is already filled, can immediately be put inside the pressure chamber 6 and a new pressing process can be started.
With the method according to the invention, one or more mould elements 19, 19a of essentially thin structure and the filling of the mould, i.e. the material of the article to be manufactured, are placed into the pressure chamber 6, after which the pressure chamber 6 is pushed with the aid of a pushing means 1e inside a frame structure 1 that endures the pressure needed for manufacturing the article, after which process pressure of essentially the same magnitude is directed onto both sides of the mould element 19, 19a by means of a pressure medium that is in liquid form. In addition to compressive pressure, the temperature in the pressure chamber 6 needed in the manufacturing process is directed at the material of the article to be manufactured and/or the article to be manufactured, which temperature is produced either via the pressure medium or by the aid of a heating means connected to the mould element 19, 19a.
The top half and the bottom half 7, 8 of the pressure chamber 6 are pressed advantageously against each other with the hydraulic compression means 16 that is between the frame structure 1 and the pressure chamber 6. In addition, the sides and, if necessary, the ends of the top half and the bottom half 7, 8 of the pressure chamber 6 are supported with a compression means corresponding to the compression means 16, and to ensure the sealing, reinforced pressure from the process pressure is led to the sealing 9c that is on the joint face of the top half and the bottom half 7, 8 of the pressure chamber 6, which reinforced pressure is greater than the process pressure inside the pressure chamber 6. A metal or a metal alloy, for example, in liquid form and that melts at a low temperature is led into the pressure chamber 6 as a pressure medium.
Composite structures are manufactured in one or more mould elements 19, 19a disposed in the pressure chamber 6 by placing the manufacturing material needed into the mould elements 19, 19a one manufacturing phase at a time, which material comprises e.g. plastics and reinforcing agents, and by performing the necessary pressing and heating one phase at a time.
It is obvious to the person skilled in the art that different embodiments of the invention are not limited to the example described above, but that they may be varied within the scope of the claims presented below. Thus, for example, the frame structure and the other structures of the apparatus can be different to what is described in the examples above. A supportive and strong frame structure that does not allow the halves of the pressure chamber to detach from each other is, however, essential. In this case e.g. a rock cave can also function as a frame structure.
Likewise it is obvious to the person skilled in the art that the structure of the pressure chamber can be different to what is described above. The bottom half of the pressure chamber can be e.g. shallower than the top half, and the pressure space below the mould element can be smaller than the pressure space of the top half above the elastic film.
It is further obvious to the person skilled in the art that the material of the mould elements can, in addition to the aforementioned metal, plastic or plastic composite, also be e.g. rubber, wood, ceramic, concrete or any other suitable material whatsoever that can easily be formed and that withstands the necessary pressure and temperature. The mould element can be manufactured from e.g. metal alloys, which have a low melting point, e.g. Rose's metal, tin foil and Eutectic solder. The aforementioned metal alloys are cast onto or into the template inside the pressure chamber, where the temperature is greater than the melting point of the metal in question. The metal alloy can be selected according to the temperature needed at that time. It must be noted, however, that changes in pressures and temperatures may not cause changes in the moulds, so that the moulds must not melt at the temperatures used.
It is also obvious to the person skilled in the art that the moulds can be cast from mould silicones onto or into a template in the pressure chamber e.g. with the following phase: the dispensed amount, of e.g. RTV silicone, is fed into the pressure space and vacuumized. A precise casting mould, from which copies can be made with the same principle, is obtained by pressurizing. Two-component silicone elastomer, which is cast around the mould or moulds, is advantageously utilized in connection with the mould elements. In this case the silicone layer enables the second mould half to be cheap. Likewise the silicone layer prevents sealing leaks and enables a high process pressure and operating pressure and also a high temperature.
It is also obvious to the person skilled in the art that the apparatus can comprise separate heating tanks and cooling tanks for the pressure medium that are connected to the hydraulic system of the apparatus.
It is further obvious to the skilled person that discharge routes for air and for excess material are connected to the mould elements, as also are vacuum connections for vacuum treatment.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20090194 | May 2009 | FI | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/FI2010/050382 | 5/11/2010 | WO | 00 | 1/27/2012 |
