Filter for plastic material

Abstract

What is presented is a filter for plastic material, in particular a device that filters recycled plastic material, to clean it of extraneous bodies and foreign elements by means of several filtration units within a single body.

Claims

1. A filter for plastic melt material comprising: a hollow body defining an internal cavity; a first filtration device sealingly spanning said internal cavity and defining a first chamber upstream of said first filtration device; a second filtration device sealingly spanning said internal cavity downstream of said first filtration device and defining a second chamber between said first filtration device and said second filtration device; an inlet for introducing molten plastic material into said first chamber; an at least partially hollow, externally actuated drive shaft extending through said first and second filtration devices; a first scraper fixedly mounted on said at least partially hollow, externally actuated drive shaft such that it rotates and scrapingly engages a filtration surface of said first filtration device when said drive shaft rotates; a second scraper fixedly mounted on said at least partially hollow, externally actuated drive shaft such that it rotates and scrapingly engages a filtration surface of said second filtration device when said drive shaft rotates; a filtered melt outlet downstream of said second filtration device; a first fluid path extending through said at least partially hollow, externally actuated drive shaft in fluid communication with said first chamber for allowing egress of debris accumulated on said first filtration surface; a second fluid path extending through said at least partially hollow, externally actuated drive shaft in fluid communication with said second chamber for allowing egress of debris accumulated on said second filtration surface; and valving for controlling fluid flows such that filtration and debris removal may be separately accomplished; wherein molten plastic introduced into said first chamber passes through said first filtration device, said second filtration device and exits through said filtered melt outlet, while debris contained in said introduced molten plastic is captured by said first and second filtration devices, and is subsequently removed by said first and second scrapers, and said removed debris exits through said first and second fluid paths.

Description

DESCRIPTION OF THE DRAWINGS

(1) The technical characteristics of the invention, according to the aforesaid aims, can be seen clearly in the content of the claims reported below, and its advantages will become more readily apparent in the detailed description that follows, made with reference to the accompanying drawings, which illustrate a preferred embodiment that is purely exemplary and not limiting, where:

(2) FIG. 1 shows a front view of the filter for plastic material that is the object of the invention;

(3) FIG. 2 shows the cross-section of the object of FIG. 1 along the section line AA;

(4) FIG. 3 shows a top view of the device with the hollow body in section;

(5) FIG. 4 shows a perspective view of the hollow body according without a front cover, revealing the first filtering device and its scraper;

(6) FIG. 5 shows what is set out in FIG. 4, with the hollow body removed, to highlight the presence of two the filtration devices and relative scrapers;

(7) FIG. 6 shows what is set out above in FIG. 4 from a front plan view;

(8) FIG. 7 shows the object of FIG. 6 sectioned along the section line B-B:

(9) FIG. 8 shows a top view of the object of FIG. 5;

(10) FIGS. 9, 10 and 11 respectively show two different side views and a sectional view along the section line C-C of the drive shaft with the two scrapers fitted;

(11) FIG. 12 shows a second exploded perspective view of the drive shaft and the two scrapers;

(12) FIG. 13 shows only a front plan view of one scraper; and

(13) FIG. 14 shows a section along a vertical plane passing through the main axis of the hollow body, fitted with the filtration devices arranged in series, each provided with its own ring with key.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(14) With reference to the figures, the filtration device 1 is basically composed of a hollow body 2 within which are housed a first filtration device 3 and a second filtration device 4.

(15) Said first and said second filtration devices 3, 4, are arranged in sequence with a different filtration quality, so that the first filtering device 3, positioned upstream of the second filtration device 4 retains the largest pieces of dirt that in the molten plastic material, while the filtration device 4, which is downstream, retains the smallest dirt particles in the molten plastic material to be filtered.

(16) Each of said filter devices 3 and 4 is composed of a perforated disc 5, 6, with an appropriately sized support to withstand the mechanical stresses, having a basically circular cross-section and that rests in a suitable housing within the hollow body 2.

(17) Said perforated disc 5, 6 is likely to be a very thick perforated plate, which remains fixed with respect to the hollow body 2 when operating.

(18) Overlying and resting on a base of each of these perforated discs 5, 6, there is a perforated sheet 7, 8 with suitably sized holes. Said perforated sheet 7, 8, which does not possess the characteristics for being able to withstand the considerable work pressures within the hollow body 2, and for this reason rests on the perforated disc 5, 6 dedicated to it, has the purpose of stopping all the dirt whose size exceeds the dimensions of the holes themselves.

(19) On each of these perforated sheets 7, 8 a significant amount of material accumulates during the filtration that gradually clog the various holes and reduces the amount of molten material can be effectively be filtered.

(20) For this reason there is, on each perforated sheet 7, 8, a scraper 9, 10, suitably spaced apart by a ring with a key, which includes a scraper 11, 12 whose scraping edge 13, 14 is placed in contact with the perforated sheet 7, 8, and is made to rotate by a drive shaft 25. Said scraper 9, 10 lifts and removes the dirty material that is clogging the filtration holes of each perforated sheet 7, 8.

(21) Each perforated sheet 7, 8, whose scraping edge 13, 14 is in sliding contact on said perforated sheet 7, 8 and retained by an overhanging radial support 25 connected solidly to the drive shaft 25. Advantageously, each scraper 9, 10 is composed of a pair of scraper sheets 11, 12 and their supports arranged in a diametrically opposite manner.

(22) This radial support has, for the entire or a large part of its longitudinal extension, in addition to the fastening of the scraping sheet 11, 12 and all within its body, a collecting channel 15, 16 for the dirty material that when lifted by the scraping blade 11, 12, and touching it, is collected, channeled within the collection channel 15, 16.

(23) There is a window 21, 22 in the center of the connection hub of the support of the scrapers 9, 10 with the drive shaft 25, in connection with and continuing the collection channel 15, 16, to allow the transfer and the escape of said dirty material, through the hole of said windows 21, 22, to the outside of the hollow body 2.

(24) Preferably the outflow of the dirt collected by the first filtration device 3 occurs through the front cover 26 of the hollow body 2, while the outflow of the dirt collected by the second filtration device 4 occurs on the bottom 27 of the hollow body 2, through the central cavity 24 of the drive shaft 25.

(25) In fact, said drive shaft 25 is hollow in the center and has an opening 23 at the second window 22 relative to the collecting channel 16 of the radial support; while the first window 21 for the release of dirty material is connected to its own pipe 17 discharging towards the outside of the hollow body 2.

(26) Clearly, these discharge pipes 17, 18 for the release of the dirty material are closed by valves 19, 20 controlled in their opening and closing according to predetermined events, for example timed or after the pressure rises or some other event previously anticipated. It is conceivable, with particularly dirty material, that there is also a continuous rotation of the scrapers (3, 4 . . . .

(27) Said valves 19, 20 are moved by actuators 28, 29 located outside the hollow body 2 in order to facilitate their maintenance.

(28) The operation of the filtration device 1 consists of a continuous flow of material entering through an inlet opening 34 of the hollow body 2 upstream of the first filtration device 3, into the first chamber 30 between the opening cover 26 and the first perforated sheet 7.

(29) The molten material passes through the first filtering device 3, where the larger dirt particles are retained, to then pass through the holes of the corresponding first perforated support disc 5 of the first perforated sheet 7, within the second chamber 31, defined and included between the rear part of the first perforated disc 5 and the second perforated filtration sheet 8 of the second filtration device 4.

(30) Because of the pressure of the incoming molten material, this molten material, in the second chamber 31, is forced to move through the second perforated sheet 8, which prevents the passage of the finer impurities, and subsequently, through the holes of the second perforated disc 6, reaching a final collector 32 to the rear of the second perforated disc 6, connected with an outlet opening 33, which runs through the hollow body 2 to the outside.

(31) Even if there is a cleaning operation with lifting of the dirt by means of a scraper 9, 10 that partially clogs the relative holes, the input of the molten material through the inlet opening 34 of the hollow body 2 remains unchanged, or with a reduced flow.

(32) This input of the material provides sufficient pressure because the dirty material, lifted by the relative scraper blades 11, 12, which move together, being fitted onto the same drive shaft 25, scraping in a rotary manner the respective perforated sheets 7, 8, can, following the relative channels 15, 16, be channeled towards the outlet, according to the various outlet pipes 17, 18 for the release of the dirt on the outside of the filter for plastic material 1.

(33) Indeed, the exit of the dirty product will only happen if the respective valve 19, 20 is operated by the respective actuator 28, 29, to open and leave the outlet conduit free.

(34) It is evident that this actuator and respective valves can also be different from one another, for example pneumatic or hydraulic or with a different structure, such as a screw feeder.

(35) If, during the movement of the scrapers 9, 10, one of the two valves 19, 20 is kept closed, clearly the dirty product will not come out, but it will be accumulated and kept within the respective channel 15, 16 of the support of the scraper 9, 10

(36) The maintenance of the filtration device 1 is equally simple.

(37) Just open the opening cover 26, on the front of the hollow body 2, extract the first scraper 9 that holds one or two scraper blades 11; after that the perforated plate 7 and its perforated disc 5 can be removed.

(38) After removing the first scraper 9 and the first filtering device 3, you can access the second scraper 10 and the second filtration device 4, to eventually remove the various parts for maintenance and/or cleaning.