The invention relates to an apparatus and method for forming end products from plastic. The invention further relates to a method for processing used plastic film bags which in many counties, in particular in developing countries such as some African countries, pollute the environment. With injection molding processes for plastic, as a rule, the raw material consists of granulate. This melts rapidly and uniformly. The blades of a rotating extrusion screw press the granulate forward in a close d-off space so that it is put under high pressure, heats up and melts. At the end of the space, the melded plastic is pressed through a small opening (tee) so that it is squirted into the mold. Then, the plastic is cooled in the mold and released from the mold by separating the mold parts and with the aid of an ejection mechanism.

In, for instance, the developing areas mentioned, granulate is not readily available. Also, particular parts which are in demand, such as for instance end plugs, shaft ends, rings for, for instance, water pumps, wheelbarrow wheels or plugs cannot be manufactured on the site. The use of recycled plastic could bring relief here.

WO 9900237 describes an injection molding process in which large pieces of used plastic are fed into an apparatus and are heated and then, with a simple plunger, are pressed through a large opening into a mold. However, the plastic is pre-processed with an extrusion mechanism and conveyed through a heated pipe with valve to a feeder cylinder where the plastic can accumulate. This apparatus is particularly suitable for forming large plastic products such as loading pallets with which the presence of polluting parts of, even, some centimetres is no objection, and not suitable for smaller pro'ducts such as, for instance, plugs. Moreover, this known apparatus is particularly expensive and complicated.

Especially in developing countries and emerging economies such as in African countries and Asiatic countries, waste of plastic film bags is a great problem. It is, potentially, a great source for recyclable plastic.

Unless it has not already been exposed to too high temperatures, used plastic film can be re-formed, as can, in principle, all thermoplastic plastics. With film bags as raw material for the production of plastic end products, the problem exists that, in practice, extrusion screws as well as 'shredders' have difficulties when processing plastic film bags which, being so light and thin, remain behind in or between the blades or stick to the walls. With granulate, this problem does not occur because this does not remain behind between the blades and it has a greater mass/surface ratio so that it does not stick to the walls.

In WO 0238276, an apparatus is described in which plastic waste material such as film is pressed in a cylinder by a press plate from a feeder through an extrusion mold, while due to heating by a heating element, the plastic near the mold transforms from a hard condition at the feeder, via a semi-melted condition, to a melted condition near the extrusion mold. Here, the plastic is pressed through the entire apparatus in one go while waste materials are separated. With this apparatus, substantially, bar stock is formed which is cut up into granulate. Moreover, the extruded bar stock has an insufficiently constant density.

The above mentioned solutions offer no inexpensive, easy to handle and simple solution for forming end products from thin, light plastic film.

There is a need for a possibility to recycle plastic bags which, especially in the sub-sarahan areas, are detrimental to the environment and the livestock, with the aid of simple means and to use them as raw material for products to be used on the site, in particular mold-formed or injection molded parts, such as end plugs, shaft ends, rings for, for instance, water pumps, wheelbarrow wheels or plugs.

The object of the invention is to provide a solution to environmental pollution by plastic film bags in, for instance, developing countries and emerging economies, in particular the sub-saharan areas and Asia.

The invention aims to provide a workable solution for forming end products from used plastic film bags.

The invention further aims to provide a durable solution for employment in developing countries and emerging economies, in particular the sub-saharan areas, while the investments will be acceptable to the local population. Another object of the invention is to provide a solution which is simple and practical in construction and use, and can be placed in a small workshop or living room without objections.

Yet another object of the invention is to provide a solution to the problem that particular products or parts are not available in developing areas.

The invention further aims to provide a method for forming parts with plastic film bags as raw material, in particular by injection molding.

At least a number of these and further objects are achieved according to the invention with an apparatus and method according to the invention.

An apparatus according to the invention is characterized by the features of claim 1.

With an apparatus according to the invention, the advantage is achieved that a plunger can be used as pressing means. By having the plunger fit the inner walls of the shell accurately, it is guided through the shell and plastic can be pressed forward in front of the plunger. Preferably, the plunger fits the inner wall of the shell so accurately that air can escape therealong while thin film, with a thickness of, for instance, approximately between 15 micrometers and 1000 micrometers, will not escape along the plunger. Such a

plunger is simple in construction and, in a particular embodiment, can be manually operated.

The shell guides and protects the plastic to be inserted and the plunger. The shell is simple in construction and offers the possibility to locally couple elements such as, for instance, a feeder, thermal means, a liquid bath, a reduced portion, a closure and a mold. By adding these elements, in an easy-to- construct manner, the shell is divided into a feed chamber, heating chamber and discharge.

Against the discharge, at the end of the shell, a mold can be provided. This offers the advantage that the entire process, from feeding the plastic into the feeder until pouring the end products, can take place in one production run.

The reduced portion in the shell near the heating chamber will ensure that the pressure on the plastic increases locally so that the plastic is compressed further in melted condition and further air inclusions are pressed therefrom (degassing). Such a reduced portion is easy to construct and has appeared particularly effective.

The invention further relates to a method characterized by the features of claim 22. In a first step, the plastic is compressed in the cold feed chamber between the plunger and the plastic situated further on. This first pressing step ensures the removal or air inclusions in a first degassing. A first cold compression also prevents loose, thin film parts from sticking to the wall. Hence, the compressed mass can simply be shifted in the direction of the heating chamber.

In a second step, the meanwhile at least partly melted plastic is compressed by movement of the plunger at the location of the reduced portion in the warm heating chamber. This second step ensures the final air inclusions to the forced away and the end product to obtrain the desired density.

Herein, cold is at least understood to include a temperature below the melting temperature of the plastic, while warm is at least understood to include a temperature above it, at least such that at that temperature, the plastic melts at the prevailing pressure. Herein, film is at least understood to include plastic material with an average thickness between 5 and 1500 micrometers, in particular between 10 and 300 micrometers, more in particular between 18 and 45 micrometers. In a still further embodiment, the invention is characterized by the features of claim 26. An apparatus according to the invention comprises substantially one mold, consisting of at least two mold parts and a liquid bath. The amount of material and parts processed in this apparatus is limited to a minimum. The apparatus is very small and very simple in construction and operation.

In a still further embodiment, the invention is characterized by the features of claim 32.

This provides a simple plastic forming process in which for instance plastic film can be formed into end products of relatively large dimensions at relatively low prevailing pressures. The required apparatus is simple and relatively inexpensive and applicable with all sorts of different energy sources. The apparatus and methods described offer solutions to forming end products from used plastic, so that they can be constructed, maintained and used in developing countries with the means available on the site.

By way of illustration of the present invention, exemplary embodiments of the injection molding apparatus according to the present invention will be further elucidated with reference to the drawing. In the drawing:

Fig. 1 shows, in partly cross-sectional side view, a schematically represented embodiment of an apparatus according to the present invention for injection molding end products from plastic;

Fig. 2 shows, in front view, a schematically represented embodiment of a press-on means according to the present invention;

Fig. 3 shows, in side view, a schematically represented embodiment of a cooling means according to the present invention; Fig. 4 shows, in side view, a schematically represented embodiment of an insulating means according to the present invention;

Fig. 5 shows, in partly cross-sectional side view, a schematically represented embodiment of the apparatus according to the present invention, with different zones indicated in the longitudinal direction of the apparatus; Fig. 6 shows, in cross-sectional side view, a different embodiment of an apparatus according to the present invention in the form of a mold for a wheel to be placed in a liquid bath;

Fig. 7 shows, in cross sectional side view, a different embodiment of an apparatus according to the present invention in the form of a mold to be placed a liquid bath.

In the following description, identical or corresponding parts will be indicated with identical or corresponding reference numerals. These exemplary embodiments are merely shown by way of illustration and should not be construed to be limitative in any manner. In Fig. 1, in cross-sectional side view, an apparatus is shown comprising a shell 100 with a feed chamber 3, at heating chamber 9, a reduced portion 11 and a discharge 19, and a mold 14, 15 consisting of two parts with a mold cavity in 18 therein. A press-on means 1 and a feeder 2 are provided in or adjacent the feed chamber 3. A lever transmission 5 is hingedly connected with a plunger 4, movable in the feed chamber 3, and a foot 102 of the apparatus (Fig. 5). Plunger 4 extends substantially within feed chamber 3 and is moveable in a feed-through direction 101. At the location of the feed chamber 3, a cooling means 6 is provided and adjacent the heating chamber 9 an insulating means 8 is provided. Heating chamber 9 is surrounded by an oil bath 10 having an electric heating element 12 therein. After oil bath 10, an

insulating means 13 has been provided. In the embodiment of Fig. 1, molds 14,

15 also function as cooling means. Cooling means 6, 14, 15, are provided with cooling liquid from a reservoir 7. Fig. 1 further shows an ejection mechanism

16 and a lever transmission 17 for releasing the end product from the mold cavity 18 of the mold 14, 15.

An apparatus according to Fig. 1 can be used as follows: plastic, in particular plastic film, is inserted into the feeder 2 after which it is fed into the feed chamber 3 by the press-on means 1. The feed chamber 3 is closed off by press-on means 1 at the location of the opening towards feeder 2, and plunger 4 can press the raw material in the direction of the heating chamber 9 with the aid of the transmission 5. Transmission 5 is a lever, shown in Fig. 5, hingedly connected with the foot 102 of the apparatus by a connection 103, and slideably and hingedly connected with the plunger 4 by a connection 104, so that by hinging the lever transmission 5 over the connection 103 with the foot 102, the plunger 4 moves through the feed chamber 3 in a feed-through direction 101. The length between the connections 103, 104 is less than the length between the connection 103 and a point of engagement 105 against which pressure is applied for allowing the plunger 4 to press so that a lever principle enters into operation and the plunger 4, by means of manual operation, allows plunger 4 to press with sufficient force. This transmission should not be construed to be limitative in any manner. This can for instance also be a motorized transmission, a hydraulic transmission or, for instance, a screw to be manually rotated.

Between plunger 4 and feed chamber 3, space is present so that during pressing, air can escape along the plunger 4. By contrast, thin plastic film at the side of the plunger 4 leading in the feed- through direction must not end up between plunger 4 and the inner walls 170 of the feed chamber 3. As plastic film has an average thickness in the order of between 5 and 1500 micrometers, in particular between 10 and 300 micrometers, more in particular between 18 and 45 micrometers, the tolerance of the fit of the

plunger 4 in the feed chamber 3 of the shell 100 is in the order of 10 to 1500 micrometers, in particular between 40 and 400 micrometers, more in particular 200 micrometers. This appeared sufficiently effective to, on the one side, prevent film bags from ending up between the plunger 4 and the inner walls 170 of feed chamber 3 and, on the other side, allow movement of the plunger 4 through feed chamber 3.

The shell 100 is substantially built up from a first part 21 comprising the feed chamber 3, a second part 22 comprising the heating chamber 9 and the reduced portion 11, and a third part 23 comprising a discharge 120. In the embodiment shown, these parts are all substantially cylindrical with a circular cross section. However, naturally, also other cross sections can be opted for.

The three parts 21, 22, 23 are arranged one behind the other in the feed-through direction 101. On the side facing the second part 22, the first part 21 is provided with a first flange 42. The second part 22 is provided, on both ends, with a second and third flange 43, 44, respectively, and the third part 23 is provided on the end facing the second part 22, with a fourth flange 45. The first and second flange 42, 43 are attached against each other with interposition of a thermally insulating ring 41, forming the insulation 8. The third flange 44 and the fourth flange 45 are attached to each other with interposition of a further insulating ring 46, forming the insulation 13.

As a result, the feed chamber 3 and the heating chamber 9 on the one side, and the heating chamber 9 and the discharge 120 on the other side are thermally separated from each other, so that the feed chamber 3 and the discharge 120 can be kept relatively cold and the heating chamber 9 can be strongly heated, virtually without mutually influencing each other. A continuous shell 100 is obtained from the feed chamber 3, via the heating chamber 9 to the discharge 120 as far as into the mold cavity 18 of the mold 14, 15.

Preferably, the temperature in the cold chambers 3, 120 is below the melting temperature of the inserted plastic and will preferably vary between approximately 0 and 50C°. More in particular, this temperature will be approximately 30 C°. It is preferred that the temperature of the heating chamber 9 is above the melting temperature of the plastic raw material and will preferably be between 100 C° and 250 C°, more in particular between 160 C° and 190 C°.

The inner space of the shell 100 has a cross section that is sufficiently favorable for heating plastic bags. In the embodiment of Fig. 1, the cylindrical shell 100 has a diameter of approximately 4 centimetres in front of the reduced portion 11. In other embodiments, the cross section of the inner space of the shell 100 may have a length, width and/or diameter between, for instance, approximately 0.5 and 20 centimetres, in particular less than 10 centimetres, more in particular, the approximately 4 centimetres mentioned has appeared the most favorable. Preferably, the shell 100 is cylindrical, but elliptical or angular shapes can also be used. In all cases, the plunger 4 will have to fit the walls of the feed chamber 3.

Feed chamber 3 is kept cool by means of cooling means 6, in the exemplary embodiment of Fig. 3 shown as a collar 34 around the feed chamber 3, while in the collar 34, in particular at the top and bottom of the collar 34, openings have been provided for allowing cooling liquid to flow through the collar 34. Feeding the cooling liquid, for instance water, is carried out in this embodiment of the invention by means of hoses 130, conveying liquid from cooling liquid reservoir 7 to cooling means 6. Other hoses 130 convey liquid from reservoir 7 to mold parts/cooling means 14, 15. Feeding the cooling liquid in the holes of means 6, 14, 15 could, for instance, can also be done by means of a bucket of water, instead of, for instance, a reservoir 7 with hoses 130. Preferably, thermal insulating means 8 is arranged such that the plastic transforms from a solid condition to a liquid condition in the heating chamber 9 and remains cold in the feed chamber 3. Insulating means 8 has also been

provided to prevent the formation of too long a zone with an undesired and uncontrolled temperature between the cold feed chamber 3 and the warm heating chamber 9. With too long a zone which is warmer than the feed chamber 3 and colder than the heating chamber 9, plastic can start sticking to the wall. Plastic starts sticking to the wall with too long a zone with a temperature transition from, for instance, 50 to 130 C ⁰ , in particular from approximately 60 to 80 C°. To prevent this sticking, it is preferred that temperature transition zones adjacent the transition from chamber 3 to 9 and from chamber 9 to 120 are approximately 2 cm or less and, in exceptional embodiments at most 10 cm. These temperature transition zones will be situated adjacent the thermally insulating means 8, 13.

Adjacent oil bath 10, feed chamber 3 merges into heating chamber 9. When the plastic enters the heating chamber 9, it will directly be heated and will melt when the plastic has been heated sufficiently long. Heating chamber 9 is provided with the reduced portion 11 through which the plastic is further compressed in a simple manner. At the location where the plunger 4 is wider than the reduced portion 11, the reduced portion 11 prevents the plunger 4 from moving further forward.

Preferably, the reduced portion 11 tapers so that the plastic is pressed through the reduced portion more easily. In the embodiment of Fig. 1, the diameter of the inner space of shell 100 in front of the reduced portion 11 is approximately 4 centimetres and behind the reduced portion approximately 2.5 centimetres. Here, the constriction of the inner space of shell 100 from 4 to 2.5 centimetres takes place over a distance of approximately 5 centimetres. In other embodiments where the inner space of the shell 100 is of a different order of magnitude or, for instance, has a different shape, this length of the reduced portion 11 will preferably vary between 0.5 and 20 cm.

Oil bath 10 is a tank with thermally insulating walls in which oil is stored. In this embodiment, the oil is heated by at least one heating element 12. With this heating element 12, the oil is heated to and held at a desired

temperature by means of a thermostat. In this embodiment, the temperature can be regulated between for instance 160 C° and 190 C°. In other advantageous embodiments, a heating element can for instance consist of fire beneath the oil bath 10, or, for instance, a gas burner. After the oil bath 10, the shell 100 proceeds until mold 14, 15. Mold

14, 15 is cooled by means of cooling liquid so that the plastic in the mold 14, 15 sets, at least cures. In one embodiment, mold 14, 15 consists of a female part 14 and a male part 15. The female part 14 is fixedly arranged on the shell. The male part 15 is provided so as to be extendable and has an ejection mechanism 16 so that the plastic part 18 can be released. The second insulating means 13 ensures that heat transmission from oil bath 10 disturbs the cooling of mold parts 14, 15 as little as possible. In one embodiment, the male part is extended by means of a lever transmission 17.

Further, a closure 150 may be arranged in front of the beginning of mold 14, 15 and after oil bath 10, which ensures that no plastic leaves the apparatus unwontedly when, for instance, the mold is open or during curing of the plastic in the mold. In a favorable embodiment, this closure 150 is a thin plate or valve closing off the shell, for instance at the location of insulating means 13. In Fig. 2, in cross-sectional front view, the press-on means 1 is shown. The pressing, round end 160 of the press-on means 1 presses plastic through feed 2 in the direction of the feed chamber 3, until the round end 160 is in line with the inner wall 170 of the feed chamber 3, and is in register with the circumference of plunger 4. Fig. 3 shows an embodiment of cooling means 6 of the apparatus, where a cooling liquid reservoir 7 with cooling liquid 32 can be seen, while the cooling liquid flows from and towards the cooling means 6. In an advantageous embodiment, the liquid flows from bottom to top through the collar 34 so that it flows into the bottom of the collar 34 in cold condition, and leaves the top of the collar 34 in warm condition.

In Fig. 4, in side view, insulating means 8 is shown which screens from the heat given up by the oil bath 10. This insulating means 8 consists of an insulating material 41 with two plates 42, 43 on the outside, extending outwards as flanges from the respective ends of the feed chamber 3 and the heating chamber 9. The three layers 41, 42, 43 are attached to each other by, for instance, screws 44.

Fig. 5 shows a schematic representation of an embodiment of the apparatus according to the present invention wherein four zones are indicated which correspond with particular parts of the apparatus. The first zone 51 is the transmission to the plunger 4 which, as indicated, can be mechanized or motorized. The second zone 52 is the compression zone where the plastic is compressed for the first time in the feed chamber 3 by the plunger 4. The third zone 53 is the zone of heating over the length of the oil bath 10 and further compression by the reduced portion 11. The fourth zone 54 is the zone of injection, cooling and release. In this zone, the plastic is pressed into the mold. After this, the manual or mechanized release of the mold parts 14, 15 follows.

A different embodiment of the invention relates to a mold 60, comprising mold parts 14, 15 which can be laid into a heated oil bath 10 separately. This embodiment may be considered as a simplified embodiment of the present invention as shown and described in Figs. 1 - 5. In this embodiment, oil bath 10 is heated by, for instance, fire. Plastic, in particular plastic film bags can be directly inserted into a mold and then pressed. An exemplary embodiment of such a mold is shown in Figs. 6, 7.

Fig. 6 shows a schematic drawing of a cross-sectioned side view and a top view of a mold 60 for a plastic wheel to be injection molded. The mold 60 comprises at least two approximately annular tubes as two mold parts 14, 15 with a approximately semi-circular cross section, laid against each other along a dividing face 63, indicated by a broken line. The two mold parts 14, 15 are held in position relative to each other by plates 64, 65. Plate 64 is screwably connected to the top mold part 14, and plate 65 is likewise screwably connected

to the bottom mold part 15. A riser 66 with press-on means 67 is connected with the mold.

When using the embodiment shown in Fig. 6, at least one mold part 14 and/or 15 is filled with plastic. This is possible by for instance separating mold parts 14, 15 at a sufficient distance from each other and placing plastic, for instance film, in the cavity 18 by hand. Then, mold parts 14, 15 are pressed towards each other by means of, for instance, screws 69. To ensure that the cavities of the mold parts 14, 15 fittingly link up with each other, the plates 64, 65 have been attached to respective mold parts 14, 15, holding the opposite mold part in position relative to the mold part against which they have been attached. Riser 66 collects the plastic which is pressed outwards and can increase the pressure of the plastic in the mold with a press-on means 67. Also, via the riser 66, optionally, plastic can be refilled in the mold, for instance after the mold parts have already been pressed together. Then, the entire mold 16 is laid in heated oil so that the plastic melts and homogenizes.

Subsequently, the mold is taken from the bath 10 and cooled down, whereupon the formed product can be taken out.

In Fig. 7, schematically, a side view is shown of a further embodiment of the apparatus according to the present invention. This embodiment exhibits the same basic principles as the embodiment of Fig. 6. The complete Figure shows a mold 60 with a press-on means 67 comprising a spindle 1 and a plunger 2. The Figure schematically shows a mold cavity 18. By means of spindle 1, plunger 2 is moved in the direction of the mold cavity, for instance by means of a helical movement, so that the plastic is compressed in the mold cavity 18. In different advantageous embodiments, also, several press-on means 67 can be connected with mold cavity 18 while the cavity 18 may have different forms, for instance the form of bar stock, rings, wheels or beakers. For heating the mold, an oil bath 10 to be heated is present. The use of the embodiment shown in Fig. 7 has the same characteristics as the use of the embodiment shown in Fig. 6. When using mold

60, first, the mold cavity 18 is filled with plastic. After the mold cavities 14, 15, have been pressed together, then, by means of riser 66 and press-on means 67, the pressure of the plastic in the cavity 18 can be increased. If necessary, also, plastic can be refilled by means of the riser 66 and press-on means 67. When the plastic has been sufficiently compressed in cavity 18, mold 60 filled with plastic can be laid in its entirety in separate oil tank 10 which is heated by fire 180. When the plastic has melted and homogenized, the mold 60 is taken from the oil bath 10 again and the mold 60 is cooled down, after which the end product can be released from the cavity 18. Different embodiments from the embodiments described hereinabove are possible, for instance by using molds in which the plastic passes the mold, as is the case with extrusion, for, for instance, producing bar stock or granulate. With extrusion, instead of being pressed by a plunger, plastic can also be pulled with a pulling means. The invention is not limited in any manner to the embodiments represented in the description and drawings. Many variations thereon are possible within the framework of the invention as outlined by the claims. For instance, different parts of the embodiments shown can be combined and/or be exchanged. For instance, with the embodiment shown in Fig. 1, a fire can be used as heating means and, with the embodiment shown in Figs. 6 and 7, electric heating means may for instance be used. Further, instead of or in addition to the film as raw material, also other plastic parts can be used in apparatus according to the invention, for instance granulate or plastic waste parts. Several reduced portions can be used, for instance if a more powerful compression is desired or a smaller force can be applied. Also, several heating chambers can be provided and different feeder means and/or discharge means can be used. The mentioned products to be manufactured are only indicated by way of illustration and are not construed to be limitative in any manner.

These and many comparable variations are understood to fall within the framework of the invention.