ES1229519U - Self-cleaning automatic filter for plastic material. (Machine-translation by Google Translate, not legally binding) - Google Patents

Abstract

Automatic self-cleaning filter for plastic material characterized in that it comprises a hollow cylindrical body (13) composed of at least one inlet (14) for the molten plastic material to be filtered and an outlet (15) for the already filtered material. Inside said hollow cylindrical body (13) there is a perforated support disk (16) attached to said hollow body (13) and superimposed on said perforated support (16) there is a filter (17) connected, on whose surface there is a or more doctor blades (18) in rotary motion, the holes (20) of said filter (17) having an average diameter comprised between 800 and 50 microns and the thickness of said filter (17) can be comprised between 0.5 and 2 mm . (Machine-translation by Google Translate, not legally binding)

Description

DESCRIPTION

Self-cleaning automatic filter for plastic material

State of the art

As is well known, we need to recover the plastic material for reuse. This material must be melted to give it a new use.

The internal component of the filtering device that performs such a function is a filter capable of more or less efficiently separating the waste material that is to be recycled. Said filter retains the residues and passes the molten plastic material.

This function of separation is possible thanks to several types of filters of various modalities, but the main criterion for evaluating such a device is essentially based on the costs and the degree of efficiency.

There is currently a device that is composed of a hollow cylindrical body within which the material to be filtered is propelled by an extruder. This material is heated until it becomes plastic and fluid and passes through a perforated plate (similar to a section with a limited height extracted from a round provided with a central hole and crossed by a series of small holes on the flat parts).

The waste and waste of material are stopped upstream of the dish, while downstream of this the "clean" recycled material is obtained.

This system has many drawbacks; The system must remain closed during the production of the polished plastic material in order to expel the disposable material that has accumulated in the front part of the plate.

In addition, since the plate must withstand very high pressures and temperatures, it must be removed by a wide and perforated round. The cost of preparation of said plate is very high and, however, the cylindrical holes can be clogged quickly, which entails the machine to stop and the consequent replacement of the plate.

A solution to postpone the replacement of the plate, as a filtering element, is obtained with the adoption of two rotating blades that are dragged along the surface of the plate towards the entrance and move the dirty cast away backwards, with respect to the direction of flow, of the entrance to the exit, putting the dirty material back into the melt located at the entrance of the cavity of the cylindrical body.

However, after the rotation of the blades, the material that is in the cavity of the cylindrical body needs to be pushed.

It is therefore envisaged to close the outlet of the clean material and open a different outlet conduit, with direct connection to the previous hollow part of the device. This allows that, with the entrance of the later material of the extruder that feeds the flow of the molten material to filter, eliminating a good part of the waste material can be removed and can be renewed with the input material.

The main disadvantages of this modality have to do with the machine downtime, the considerable waste of materials and the only partial replacement of the material that leaked into the cavity.

In order that the plate is not irreversibly embedded, the aforementioned operations to stop the machine must be quite frequent in time and during the processing of the material, although only slightly dirty.

However, this contradicts the high cost of the perforated plate, which tends to postpone the cleaning activity of the material, with a balance between machine downtime, the amount of material that has been discarded and the replacement costs. of the drum.

It must be said that the operations are not simple at all, and each opening of the cylindrical body cavity must be effected at the operating or operating temperature of the filtering device; that is, at a temperature between 180 and 260 degrees centigrade, depending on the type of plastic material that is being filtered, when it is still soft or fluid.

In addition, the high costs of the perforated plate are also due to the way they are manufactured: by perforation, and not by die.

Utility of the invention

The utility of the present invention is to overcome the drawbacks of the prior art technique.

A specific utility of the present invention is to provide an automatic self-cleaning filter for plastic material that meets the drawbacks of a perforated plate.

An interesting utility of the present invention is to provide an automatic self-cleaning filter whose clamping and replacement are less expensive.

An important utility of the present invention is to provide a self-cleaning automatic filter that can exceed the limits of the current production method in the filtering process.

An essential utility of the present invention is to provide an automatic self-cleaning filter that can not be easily clogged.

Another utility of the present invention is to provide a self-cleaning automatic filter that can be replaced quickly and economically.

The above-mentioned utilities and others that will appear throughout the description according to the features highlighted in the claims.

Exposition of the invention

In particular, it is a self-cleaning automatic filter for plastic material provided with a hollow cylindrical body provided with at least one inlet for the molten plastic material that will be filtered and provided with at least one outlet for the escape of the filtered molten plastic material. Inside said hollow cylindrical body there is a perforated support disc attached to said body and on top of it there is a connected filter, on whose surface there are one or more rotating squeegees having the holes a mean diameter comprised between 800 and 50 microns and a thickness comprised between 0.5 and 2 mm.

Advantages of the invention

Advantageously, said doctor blades are connected to a conveyor, said doctor blades being inclined with respect to the surface of the filter, in order to separate the waste and transport it. This conveyor is pushed by the pressure of the inflow to the outside, thus reducing the percentage of waste in relation to the amount of contamination existing in the material.

Advantageously, the filter has a thickness similar to the diameter of the holes through which the molten plastic material passes with a range, comprised between 800 and 400 microns, which is a great advantage from the economic point of view. This allows it to be replaced frequently and is suitable for obtaining a recycled plastic material and for injection molding.

Advantageously, the filter has a thickness greater than the diameter of the holes through which the molten plastic material passes, comprised between 400 to 50 microns, reaching a filtration quality impossible to obtain up to now. This allows recycled plastic material to be used in high quality applications, such as those obtained by extrusion.

Advantageously, the holes of said filter with an average diameter comprised of 400 to 50 microns are made with the aid of an electron beam and / or laser technology, thus surpassing the limits imposed by the technology by perforation.

Advantageously, the thickness of said filters is 2 to 20 times greater than the average diameter of the holes obtained with an electron beam and / or laser technology. This supposes the creation of much more lasting filters, with respect to the filters that can be obtained by drilling.

Advantageously, the section of the holes gradually increases from the entrance to the exit, obtaining a filter that has little possibility of clogging due to the occlusion of the holes by the waste of the material present to be cleaned.

Advantageously, said increase of the section of the holes is comprised by some tenths of degrees centigrade up to 15 degrees centigrade, since the lower end of the mentioned range, can be verified to ensure that the waste, once After the inlet section is passed, they can pass without being retained inside the filter thickness section. For its part, it has also been confirmed that the fact of increasing the section more than 15 degrees does not entail any obvious advantage.

Advantageously, said filters are subject to a hardening process, such as, for example, chromium plating, whose thickness does not obstruct the holes themselves. This makes the filters deteriorate less due to the scrapers and have greater durability before they have to be replaced.

Advantageously, the exit path for the expulsion of the waste resulting from the scrapers attached to the conveyor passes through the crankshaft coaxially by the start-up of the conveyors (19) or by a prolongation thereof. This leads to the construction of the device being much more simplified, without needing to open the rear part of the hollow cylindrical body for the evacuation of the waste and, moreover, limits the percentage thereof to only the dirt present in the material to be cleaned .

Brief description of the figures

The technical characteristics of the invention, according to the aforementioned utilities, can be clearly seen from the contents of the claims indicated below and are evident in the detailed description that describes the drawings, which illustrate a basically exhaustive and non-restrictive realization , where:

Fig. 1 shows a sectional view of a filtering device of the prior art.

Fig. 2 shows a perspective view of the device of the invention;

Fig. 3 shows a partially sectional perspective view of the device of the invention, showing the structure of the front part;

Fig. 4 shows a view of the vertical plane of the device of the invention according to a vertical plane passing through the axis of the inlet duct of the molten material to be cleaned.

Fig. 5 shows a sectional view of the device of the invention according to a horizontal plane passing through the axis of the movement crank that rotates the scrapers attached to the conveyors;

Fig. 6 shows a sectional view of the device of the invention according to a vertical plane passing through the axis of the movement crankshaft.

Detailed description of a preferred embodiment

With reference to the drawing of figure 1, example of a filtering device 1 of the prior art, it is seen that it shows a filter 2 (as filtering unit included in the same device 1), composed of a hollow cylindrical body 3, previously fed by an extruder 4, which pushes the molten plastic material that will be subsequently cleaned. Between the hollow cylindrical body 3 is located the perforated plate 5 provided with holes 7 joining the opposite flat surfaces 8, which are carried by the rotating blades 9 in order to remove the waste material to be cleaned and supported in the flat entrance surface 8. That plate 5 can be made with a thickness of more than 1 cm. and with holes, made by a drill, which are not less than 1 mm in diameter. Given the height of the cylindrical holes 7, the plate 5 can get stuck due to the occlusion of said holes 7, by the waste present in the molten plastic material to be cleaned.

The figures from 2 to 6 show the automatic self-cleaning filter object of the invention. The automatic self-cleaning filter 12 is composed of a hollow cylindrical body 13, where the filtering equipment is located.

The filtration equipment is composed of a perforated support disk 16, of a considerable and extractable thickness, located in a stop of the hollow body 13, provided with a central hole that allows the passage of the movement crankshaft.

On this perforated support disc 16, whose function is to provide support, is the filter 17, where the holes 20 retain the waste material that has been filtered.

On this filter 17, at least one doctor blade 18 is rotated by the movement crankshaft 21 to lift the debris located on the surface of said filter 17 and transport them to the exterior through a coaxial hole 22 present in the movement crankshaft 21.

Advantageously, the connection element between the doctor blade 18 and the movement crankshaft 21 is a conveyor 19 that removes the scraps from the doctor blade 18 to the exhaust channel of the hollow cylindrical body 13. In fact, it has a preferred collection channel 23 and a duct for the waste leading to the coaxial cavity 22 of the movement crank 21. Advantageously, the conveyors 19, to which the doctor blades 18 are attached, are two devices located diametrically opposite to the axis of the movement crankshaft, creating a symmetry between the construction and the effort that entails the elaboration.

It is wanted to confirm that the debris approaching the filter 17 will not obstruct any hole 20 of said filter 17. These holes 20 are widened at the bottom, so that the debris will descend once they pass through the entrance section of the holes 20 being the dimensions of these debris of a size that does not pose a problem for cleaning and if they are larger than the holes of the filter, will stop before going through the holes 20. In this way, the scrapers 18 will remove them and take them to the conveyors 19 that rotate thanks to the crankshaft of movement 21. The discriminatory distinction for the size of the holes of the filters 17 of the present invention has a technological meaning, to which corresponds a quality result.

In the industry of the recycling of plastic materials there are two categories: the category of injection molding and extrusion.

For example, injection molding allows "molding" the seats of plastic chairs.

Small inclusions are usually allowed that are irrelevant with respect to the whole object obtained.

For objects that require hygiene and absence of toxicity, as is the case of products that are in contact with food, such as forks and glasses, it is necessary to use virgin plastic. On the contrary, for everything that is possible to reuse, such as plastic boxes or garden furniture, recycled plastic material is used.

For this type of applications, fine filtering is not necessary, and it is usually of a dark color to hide the impurities found in the plastic.

On the other hand, if it is going to be used as packaging, the plastic should be filtered in a more elegant way, since visually more visible inclusions are not allowed.

The device of the invention is particularly intended for this type of applications, which are the most demanded, where the recycled plastic material must be of optimum quality.

With the device of the invention it has been possible to obtain economical filters with diameters that can reach 800 mm in diameter.

In addition, it has been possible to overcome the limits of the technology by drilling (the filtering mesh is linked to the peripheral limit, same hole, same thickness), where an electron beam and / or a laser technology of less than 400 microns is used.

With the new technology, the filters 17 can have a considerably greater thickness than those obtained by the technology by drilling. For example, a filter with a thickness similar to 1 mm can have holes of 400 microns instead of 200, and even 80 microns, reaching a limit of 50 microns per hole.

This increase in thickness, with respect to the diameter of the holes, allows having an attached filter 17 with electron beam and / or laser technology whose duration is also 4 times higher than the filters made by drilling.

Finally, with the new technology, it has been possible to obtain larger and more separate holes in the direction of flow that are not obstructed by materials of a diameter similar to the holes 10, in contrast to the technology by drilling.

Claims (10)

Automatic self-cleaning filter for plastic material characterized in that it comprises a hollow cylindrical body (13) composed of at least one inlet (14) for the molten plastic material to be filtered and an outlet (15) for the already filtered material. Inside said hollow cylindrical body (13) there is a perforated support disk (16) attached to said hollow body (13) and superimposed on said perforated support (16) there is a filter (17) connected, on whose surface there is a or more doctor blades (18) in rotary motion, the holes (20) of said filter (17) having an average diameter comprised between 800 and 50 microns and the thickness of said filter (17) can be comprised between 0.5 and 2 mm . Automatic self-cleaning filter for plastic material according to claim 1, characterized in that the filter (17) with holes (20) with an average diameter comprised between 400 and 50 microns is obtained by means of an electron beam and / or laser beam. Automatic self-cleaning filter for plastic material according to the preceding claim, characterized in that the thickness of the filter (17) is 2 to 20 times greater than the average diameter of the corresponding holes (20) located in the filter (17). Automatic self-cleaning filter for plastic material according to one or more of the previously described claims, characterized in that the section of the holes (20) gradually increases from the entrance to the exit. Automatic self-cleaning filter for plastic material according to the preceding claims, characterized in that said increase in the perforated plate (20) comprises some tenths of degrees centigrade up to 15 degrees centigrade. Automatic self-cleaning filter for plastic material according to claim 1, characterized in that the filter (17) with holes (20) with a diameter between 800 and 400 microns is obtained by perforation. Automatic self-cleaning filter for plastic material according to one or more of the preceding claims, characterized in that said filters (17) are subjected to a hardening process, such as, for example, chrome-plating, whose thickness does not obstruct the holes (20). Automatic self-cleaning filter for plastic material according to claim 1, characterized in that at least one doctor blade (18) is connected to a conveyor (19), said doctor blade (18) being inclined with respect to the filter surface (17), with the the objective of separating the waste and transporting it, pushed by the pressure of the inflow to the outside. Automatic self-cleaning filter for plastic material according to claim 8, characterized in that at least one conveyor (19) is provided with a collection channel (23) and a conduit for transporting the waste coming from said doctor blade (18) to the exterior. Automatic self-cleaning filter for plastic material according to claim 9, characterized in that the outlet path for the ejection of the waste dragged by the doctor blades (18) attached to the conveyor (19) traverses coaxially the movement crankshaft (21) by putting running of the same conveyors (19) or of a prolongation of these.