DESCRIPTION

The present patent concerns filtering systems for plastic materials in the molten state, more specifically it concerns systems for filtering plastic materials in the molten state during plastic recycling processes.

More specifically, the present patent concerns the opening system of filtering devices for plastic materials in the molten state during plastic recycling processes.

The problem of the recovery/recycling of plastic material for reuse in the manufacture of new products is well known and particularly felt.

The problem of the recovery/recycling of plastic materials for reuse in the manufacture of new products is known and particularly felt.

The plastic material to be recycled is subjected to a melting process and at the same time filtered to eliminate any impurities. Typically, the molten and filtered material is then properly processed to make, for example, a granular product suited to be reintroduced in the known plastic production processes.

A device of the known type that carries out the filtration of raw plastic material in the molten state is provided with a cylindrical filtration chamber equipped with a filtering element interposed between a feeding inlet for the raw plastic material to be filtered and an outlet, downstream of the filtering element, for the discharge of the filtered molten plastic material.

Filtration chambers of the known type comprise a first part with closed bottom, preferably a cylindrical first part with closed bottom, and a cover which is associated with the mouth of the first part. When the cover is associated with/fixed to the mouth of the first part, the filtration chamber is closed, and the filtering device is ready for use.

According to the known technique, the cover is fixed to the first part by means of screws and nuts. According to a known technique, the mouth of the first part is provided with a plurality of stud bolts suited to be inserted in respective holes in the cover and the same number of nuts for said stud bolts allow the cover to be fixed to the first part. The filtering devices of the known type require special maintenance operations that include, among other things, the replacement of the filtering element/filter inside the filtration chamber and/or the replacement of the cleaning elements of the filter that are usually also located inside the filtration chamber, typically scraping blades.

These maintenance operations are performed by opening the cover, after unscrewing the nuts from the respective stud bolts. Once the nuts have been unscrewed, the cover is removed from the first part, making it slide preferably on a carriage that supports it, or directly rotated through a hinge.

The cover is then closed again by tightening said nuts. The tightening operations must be carried out with care, for example in the case of torque tightening, in order to avoid the loss of plastic material or the seizure of the nuts.

The frequency with which the cover is opened/closed may depend on many factors, for example the degree of wear and tear of the filters and blades, and the cover may be opened/closed as often as once or several times a day.

A first drawback associated with maintenance operations is constituted by the need to take great care during unscrewing and especially during screwing operations to avoid damaging the closing system.

Another drawback associated with maintenance operations is constituted by the considerable amount of time required to open/close the cover, which results in machine downtime and increased running costs.

In order to overcome the above-mentioned drawbacks, a new type of filtering device for a plastic material in the molten state has been designed and constructed.

Therefore, it is an object of the invention to provide a filtering device for a plastic material that makes it easier to open the cover, in particular to facilitate maintenance operations.

It is another object of the invention to provide a filtering device for a plastic material that makes it possible to speed up the operations required to open the cover, in particular to speed up maintenance operations.

It is another object of the invention to provide a filtering device that makes it possible to detach the cover from the mouth of the hollow body and to move it away from the same in a single operation, so as to allow the rotation of the cover itself.

The above-mentioned objects are achieved by means of a filtering device for a plastic material according to the attached claim 1, to which reference is made for the sake of brevity.

More specifically, according to a first aspect of the present invention, the same concerns a filtering device for a plastic material in the molten state, said device comprising:

- a hollow body provided with a mouth and a cover suited to be associated with said mouth to define a filtration chamber, said cover and said mouth being provided with threaded means suited to allow said cover to be screwed or unscrewed with respect to said mouth;

- at least one inlet way for the introduction of said plastic material in the molten state in said filtration chamber and at least one outlet way for the outlet of said filtered plastic material in the molten state from said filtration chamber;

- an opening system suited to open said cover with respect to said mouth of said hollow body; wherein said opening system comprises rotation means suited to set a rotary flange of said cover rotating in order to cause said cover to be screwed or unscrewed with respect to said mouth and translation means suited to produce a translation movement of said cover away from said mouth of said hollow body after said unscrewing operation or to cause said cover to move towards said mouth of said hollow body before said screwing operation.

Further specific technical operational characteristics of the device that is the subject of the present invention are described in the relevant dependent claims.

The characteristics of the new device are illustrated in greater detail in the following description making reference to the drawings, which are attached hereto by way of nonlimiting example.

Figure 1A shows an axonometric view of a filtering device according to a preferred embodiment of the invention in the closed position.

Figure IB shows the filtering device of Figure 1A from another point of view.

Figure 1C shows a cross sectional view of the filtering device shown in Figure 1A along a horizontal section plane. Figure ID shows an enlarged detail of Figure 1C.

Figure IE shows a second sectional view of the filtering device shown in Figure 1 A along a vertical section plane.

Figure 2A shows the filtering device of Figure 1A in a first operating position.

Figure 2B shows the filtering device of Figure 2A from another point of view.

Figure 2C shows a sectional view of the filtering device shown in Figure 2A along a horizontal section plane.

Figure 3A shows the filtering device of Figure 1A in a second operating position.

Figure 3B shows the filtering device of Figure 3 A from another point of view.

Figure 3C shows a sectional view of the filtering device shown in Figure 3A along a horizontal section plane.

Figure 4A shows the filtering device of Figure 1 A in a third operating position.

Figure 4B shows the filtering device of Figure 4A from another point of view.

Figure 5A shows the filtering device of Figure 1A in a fourth operating position.

Figure 5B shows the filtering device of Figure 5 A from another point of view.

Figure 6A shows a variant embodiment of the filtering device shown in Figure 1 A.

Figure 6B shows the filtering device of Figure 6A from another point of view.

Figure 7A shows an enlarged detail of Figure 6A.

Figure 7B shows the enlarged detail of Figure 7A with a special tool suited to be used by an operator applied thereto.

The Figures indicated by number 10 show a filtering device according to a preferred embodiment of the invention.

The filtering device 10 according to the invention can be preferably used in a plastic recycling process.

The filtering device 10 has the function of filtering/ stopping the impurities present in the raw plastic material to be recycled in such a way as to obtain a degree of purity that depends on the size of the meshes of the filtering element used.

To carry out this filtration operation, the raw plastic material to be recycled is first heated and brought to the molten state so that it can then be conveyed into the filtering device 10, more specifically into a filtration chamber 12 of the device 10 itself

The filtering device 10 preferably has a hollow body 14 provided with a mouth 16 (see Figure 4B) and a cover 20 suited to be associated with the mouth 16 to define the filtration chamber 12.

The hollow body 14 according to the preferred embodiment illustrated herein has a preferably cylindrical shape and the cover 20 consequently has a preferably circular crosssection.

An inlet way 22 is associated with the hollow body 14 so as to allow the introduction of the plastic material to be filtered in the molten state into the filtration chamber 12. An outlet way 24 is also associated with the hollow body 14 so as to allow the discharge of the filtered plastic material in the molten state from the filtration chamber 12.

Preferably, the inlet way 22 is associated with conveyor means, not shown and of a known type per se, suited to convey, under pressure, the material in the molten state to be filtered towards said inlet way 22.

Filtering means 38 are preferably arranged within the filtration chamber 12 in a position between the inlet way 22 and the outlet way 24.

The filtering means 38 are preferably arranged inside the filtration chamber 12 at an intermediate distance between the inlet way 22 and the outlet way 24.

Suitable automatic cleaning means 39 for the filtering means 38 are also preferably arranged inside the filtration chamber 12. Said cleaning means preferably comprise at least one scraper 39 associated with the filtering means 38 and a motor 42 driving said scraper 39.

Preferably, the device 10 is equipped with an opening system 50 suited to allow the cover 20 to be detached and moved away from the mouth 16 of the hollow body 14.

As described in detail below, said opening system 50 makes it possible to remove the cover 20 to allow access to the filtration chamber 12, in particular to allow it to be accessed, during maintenance on the device 10, in order to carry out maintenance operations on elements positioned inside the filtration chamber 12, such as the filtering means or the scraper 39. According to a first advantageous aspect of the invention, the cover 20 and the mouth 16 are provided with respective threaded means 52, 54 suited to allow the cover 20 to be screwed or unscrewed with respect to the mouth 16, as described in greater detail below.

According to another advantageous aspect of the invention, the opening system 50 comprises rotation means 60 suited to rotate a rotary flange 62 of the cover 20 so as to unscrew or screw the cover 20 with respect to the mouth 16.

The rotary flange 62 comprises a first cylindrical part 64 provided with said threaded means 52 for screwing or unscrewing it with respect to the mouth 16 and said rotation means 60 comprise at least one toothed portion 66 defined on a second part 68 of the rotary flange 62.

Preferably, the threaded means 52 comprise an external thread 52 made on said first cylindrical part 64 of the rotary flange 62 and a corresponding portion of nut screw 54 is defined in the terminal area of the mouth 16.

The cover 20 preferably comprises a main body 30 on which the rotary flange 62 rotates. The main body 30 comprises a closing portion 32 that extends from the rotary flange 62 in the direction of the filtration chamber 12. The closing portion 32 is advantageously arranged inside the filtration chamber 12 when the cover 20 is in the position in which it closes the mouth 16, as shown in particular in Figure 1C.

According to another advantageous aspect of the invention, the rotation means 60 preferably comprise a first operating gear wheel 70 cooperating with the toothed portion 66 of the rotary flange 62.

Preferably, the operating gear wheel 70 comprises a driving shaft 72 suited to set the operating gear wheel 70 rotating. Preferably, the driving shaft 72 is set rotating by means of a special tool used by the operator, for example a pneumatic gun or, according to a variant embodiment, by means of a motorized automatic system.

Acting on the operating gear wheel 70 causes the corresponding rotation of the rotary flange 62. The operator can therefore act on the driving shaft 72 during the unscrewing or screwing of the cover 20. For example, from a closed position of the device 10, as illustrated in Figures from 1A to 1C, the operator can set the operating gear wheel 70 rotating in order to bring the cover 20 to the first intermediate open position shown in Figures 2A, 2B and 2C, in which the rotary flange 62 is completely unscrewed with respect to the mouth 16. Vice versa, from the intermediate open position shown in Figures 2A, 2B and 2C, the operator can set the operating gear wheel 70 rotating in the opposite direction to bring the cover 20 in the closed position (Figures 1A-1C).

According to another advantageous aspect of the invention, the opening system 50 comprises translation means 80 suited to determine a translation movement of the cover 20 with respect to the mouth 16 of the hollow body 14.

Preferably, the translation means 80 determine the translation movement of the cover 20 away from the mouth 16 after the cover 20 has been unscrewed or towards the mouth 16 of the hollow body 14 before it is screwed.

The translation movement of the cover 20 away from the mouth 16 can be appreciated by comparing Figures 2A, 2B and 2C with Figures 3 A, 3B and 3C, the latter being related to the positioning of the cover 20 in a second intermediate open position.

Preferably, the translation means 80 comprise an operating screw 82 extending along a translation axis X, whose rotation is prevented but whose translation along said axis X is permitted within certain limits by suitable compensation means 120 (Figure ID) which are described in greater detail below. The translation means 80 comprise also a portion of nut screw 84, or metering screw, which cooperates with the operating screw 82.

More specifically, the nut screw 84 is mounted on supporting elements 87 hinged to the main body 30 of the cover 20 at the level of a hinge area 48.

As the nut screw 84 rotates, either in one direction or in the opposite direction, it is screwed on or unscrewed from the operating screw 82 and consequently translates along the main direction of translation X. The translation of the nut 84 in turn causes the translation of the cover 20 with respect to the hollow body 14.

The movement of the cover 20 with respect to the hollow body 14, during both screwing and unscrewing operations and during said translation movements, is preferably facilitated by suitable guide means 100.

The guide means 100 preferably comprise one pair of pins 102, preferably but not necessarily constituted by cylindrical elements 102 integral with the hollow body 14 and two corresponding cylindrical seats 104 integral with the supporting elements 87 sliding on said pins 102.

After being unscrewed (position as shown in Figures 2A-2C) the cover 20 can therefore be advantageously arranged in the second intermediate open position (Figures 3A, 3B and 3C) and from this position it can be rotated around the hinge area 48 to be arranged in convenient open operating positions, for example in a first open position shown in Figures 4A and 4B and in a completely open position shown in Figures 5 A and 5B.

Vice versa, the cover 20 can be moved from the second intermediate open position (Figures 3 A, 3B and 3C) to the first intermediate open position (Figures 2A, 2B and 2C).

According to a preferred embodiment, a kinematic mechanism 86 is suited to set the nut screw 84 rotating in one direction, or in the opposite direction, when the rotary flange 62 rotates in a corresponding direction, or in the opposite direction.

The kinematic mechanism 86 preferably comprises a transmission gear wheel 88 integral with said nut screw 84 and cooperating with the toothed portion 66 of the rotary flange 62 of the cover 20.

Therefore, the rotation movement of the rotary flange 62 of the cover 20 is transmitted to the nut screw 84 through the transmission gear wheel 88.

Therefore, if the operating gear wheel 70 is set rotating by an operator by means of the driving shaft 72, analogously to what has been explained above, this results in the corresponding rotation of the rotary flange 62 of the cover 20 and, in turn, in the translation of the cover 20 through said transmission gear wheel 88 and said nut screw 84.

According to the preferred embodiment illustrated in the figures, the operating gear wheel 70 and the transmission gear wheel 88 are arranged on opposite sides with respect to the rotary flange 62 of the cover 20, as shown in Figure IE.

Therefore, according to what has been described above, the filtering device 10 according to the invention, equipped with the described opening system 50, allows an operator to carry out the opening of the cover 20 by means of a first step of unscrewing the cover 20 followed by a step of translating the cover 20 itself, wherein said steps are advantageously and automatically carried out one after the other by the operator who simply needs to act on the driving shaft 72 (for example, using a pneumatic gun).

Similarly, vice versa, the filtering device 10 according to the invention, equipped with the described opening system 50, allows an operator to close the cover 20 by means of a first step of translating the cover 20 followed by a step of screwing the cover 20 itself, wherein said steps are advantageously and automatically carried out one after the other by the operator who simply needs to act on the driving shaft 72 (for example, using a pneumatic gun).

Cover opening/closing operations, particularly during maintenance, are therefore facilitated and/or speeded up compared to the known systems.

According to another aspect of the present invention, the device 10 is advantageously provided also with compensation means 120 suited to compensate for the movements of the operating screw 82 with respect to the hollow body 14.

The compensation means 120 preferably comprise elastic thrust means suited to act on the operating screw 82 to move it towards a predetermined fixed position with respect to the hollow body 14.

The elastic thrust means 122 (Figure ID) preferably comprise a first plurality of Belleville washers 122a suited to thrust a flange 83 of the operating screw 82 along a first direction and a second plurality of Belleville washers 122b suited to thrust said flange 83 of the operating screw 82 along a second direction opposite to the first direction.

The gear ratios between the transmission gear wheel 88 and the toothed portion 66 of the rotary flange 62 of the cover 20 and between the operating gear wheel 70 and the toothed portion 66 of the rotary flange 62 of the cover 20 and the thread pitches of the nut screw 84/operating screw 82 and the threaded means 52/54 are conveniently dimensioned to allow for correct synchronism during movements.

Any differences, however, are conveniently compensated for by said compensation system 120, which allows temporary, slight shifts of the operating screw 82 with respect to the hollow body 14 along the direction of translation X.

According to the embodiment illustrated and described above, the device preferably comprises an operating gear wheel 70, on which the operator acts, and a transmission gear wheel 88 associated with the translation means 80. In a preferred variant embodiment, however, the operating gear wheel may not be provided, and its function may be performed by the transmission gear wheel, wherein a convenient system should be provided to allow the operator to directly set the transmission gear wheel rotating. In other words, in said embodiment, the operating gear wheel coincides with the transmission gear wheel, as better described below with reference to the embodiment shown in Figures 6A, 6B, 7A and 7B. The kinematic mechanism 86 is designed in such a way that it stops automatically once the maximum stroke of the nut screw 84 on the operating screw 82 has been reached, that is, the maximum translation of the cover 20 along the direction X (operating position shown in Figures 3A, 3B, 3C), before the elastic means 122 have been completely compressed. This is a safety feature, especially in the case where the opening operation is carried out manually or using a pneumatic gun and the operator continues to act on the driving shaft 72 even when the maximum translation of the cover 20 has already been reached.

The rotation of the driving shaft once the maximum translation of the cover 20 has been reached causes a translation movement of the operating screw 82 along the direction X, but in the opposite sense, and a consequent compression of the elastic elements 122. However, the length of the operating screw 82 has been designed in such a way that the nut screw 84 is unscrewed completely before the elastic means 122 are completely compressed, thereby stopping the kinematic mechanism 86. Successively, when the rotation direction of the driving shaft 72 is reversed, the nut screw 84 is screwed back on the operating screw 82 due to the effect of the compression force exerted by the operating screw 82 on the nut screw 84, thereby restoring the operation of the kinematic mechanism 86.

To ensure tightness against any leakage, the filtering device 10 is equipped with a taper fit between the filtration chamber 12 and the cover 20, as indicated by the reference number 15 in Figure 1C.

Appropriate seats 131a, 131b are also provided so as to allow the installation of special metal gaskets 130a, 130b, also shown in Figure 2C, to increase tightness, if necessary, especially in the presence of very high process pressures or particularly fluid materials, which makes tightness independent of the preload applied to the cover 20.

The gaskets 130a, 130b are integral with the closing portion 32 (or the hollow body 14). In this way, they cannot slip out of their seat during opening, closing and cleaning.

A variant embodiment of the filtering device 10 according to the invention is shown in Figures from 6A to 7B and described herein. Component parts corresponding or equivalent to those of the first embodiment are identified by the same reference numbers.

Said embodiment differs from the embodiment illustrated above in that it comprises only the transmission gear wheel 88 while there is no operating gear wheel. Preferably, an operating system 200 is associated with said transmission gear wheel 88 and allows the operator to directly set the transmission gear wheel 88 rotating. The transmission gear wheel 88 driven/rotated by means of said operating system 200 serves the function of the operating gear wheel described above, that is, carries out the steps of unscrewing or screwing the cover 20.

In greater detail, the operating system 200 is obtained simply by creating a hexagonal coupling portion 284 or an equivalent system, as shown in the detail of Figure 7A, on the nut screw 84, said coupling portion 284 being suited to receive a manoeuvring tool U, a bushing or an equivalent tool fitted therein by an operator (as shown in the detail of Figure 7B).

The manoeuvring tool U can be set rotating by a special tool used by the operator, for example a pneumatic gun or other motorized or hydraulic versions suited to automate the process.

Even in this embodiment, the kinematic mechanism 86 stops automatically when the maximum translation of the cover 20 is reached, as described above.

From an operational point of view, starting from the situation in which the cover 20 is in the closed position, the operator inserts the tool U and, rotating it, rotates the nut screw 84 and the transmission gear wheel 88 that is integral with it. The transmission gearwheel 88, cooperating with the toothed portion 66 of the flange 62, causes the rotation of the latter and the consequent unscrewing of the cover 20, until bringing the device 10 in the first intermediate open position (as shown in Figures 2A, 2B and 2C).

As the rotation of the tool U continues, the nut screw 84 is screwed onto the operating screw 82 and consequently translates along the main direction of translation X. The translation of the nut screw 84, in turn, causes the translation of the cover 20 with respect to the hollow body 14. The device 10, therefore, moves from the first intermediate open position to the second intermediate open position (as shown in Figures 3 A, 3B and 3C) and from this position it can be rotated around the hinge area 48 to be arranged in convenient open operating positions (as described above). Before carrying out the rotation movement around the hinge 48, the tool U is conveniently removed. The reverse closing operations, from a position in which the cover 20 is open to the position in which it is closed, will be carried out in an intuitive manner by means of said tool U It is therefore clear from what has been described above that the device according to the invention makes it possible to achieve the set objects.

Therefore, with reference to the above description and the attached drawings, the following claims are made.