FILTERING DEVICE FOR PLASTIC

Abstract: Filtering device where a fixed guiding structure (11) can receive a sliding element (12) comprising filtering means (21) which come to be placed in succession in the plastic flow. The entry (22) and exit holes (23) of the plastic are greatly reduced in comparison to the diameter of the filtering means (21). Between said holes (22 and 23) and the filtering means (21), an entry cone (26) and an exit cone (27), having an opening angle alpha between 60<o> and 89<o>, preferably 80<o>, are foreseen. The sliding element (12) is made up by two opposite half shells (18, 19) between which the filter holding plate (20) and the filtering means (21) are inserted. The latter can be fitted with a peripheral edging, of lead or other material having a coefficient of thermal expansion higher than the steel's. Between the two half shells a gasket (28) (for instance in steel) supported by a material whose coefficient of thermal expansion is higher than the steel's, can also be foreseen.

Description: "FILTERING DEVICE FOR PLASTIC" The present invention refers to a filtering device of the sliding type, carried out with a fixed guiding structure which can receive a sliding element containing filtering means normally consisting in a perforated support holding the filtering element, so that it 5. is possible to shift the sliding element by inserting in the flow a new filtering means in the place of a clogged one... - The filtering devices known at present have the following faults or disadvantages .1 . 1) considerable dimensions, so they require a great amount of 10. heat for the heating process as.they are subject to great losses (of heat). 5 _* 8HξET - 2 - 2) big section of plastic mass to v be cut during the change of the filtering element; normally in fact this section is equal or wider than the filtering surface; 3) possible stagnation of plastic material due to the great flow- 5. ing section and to the conspicuous inert masses; 4) necessity of several thermoregula ion zones which are made nec¬ essary just by the great dimensions; 5) considerable weight which lies on the other structures and must therefore be suitably supported. TO. Aim of the present invention is therefore to carry out a filtering device of simple construction and reduced dimensions, which does not cause stagnations and is easy to handle and to heat. The said aim has been reached as described in the enclosed claims. The invention will be now better illustrated with the help of an 15. exemplary embodiment which has been represented in the annexed drawings, where : Fig. 1 is a front view of the filte ing device, i.e. a view taken from side I-I of Fig. 2; Fig. 2 is a section view, i.e. taken along line II-II of Fig. 1; 20. Pig * 3 is a detail of the planned device. With reference to the drawings, it will be noted that the filtering-- device has been indicated in its whole with 10 and is composed by a fixed structure 11 and by a shell holding the filters 12 which slides within said fixed guiding structure and is controlled by 25. piston 13 so as to xiiove in the direction of arrows A. / The fixed guiding structure 11 consists in particular in two plates 14 and 15 and in two spacers 16, the said plates being joined to one another by screws 17. Inside the fixed guiding structure 11 a sliding shell is mounted, 5. generally indicated at 12, and made up of two half shells 18 and 19 which enclose the perforated plate 20 agains which the filter¬ ing means 21 leans on. This means consists in particular in one or more nets on whose pheriphery it has been applied an edging 21a, of a material having a coefficient of expansion higher that the • TO. steel's with which the rest of the apparatus is built. Lead is particularly suitable for this edging. The half shells 18 and 19 have symmetrical form and are provided respectively with an entry hole 22 and an e it hole 23, for the product to be filtered and the one jus filtered, holes extended 1 , also to plates 14 and 15. The filtering means 21 and the respe£ tive perforated plate 20 are of much bigger dimensions than holes' 22 and 23. Startirg from, said holes 22 and 23, two straight circular cones extend, indicated respectively by 26 and 27, which have a large angle o_L at the vertex, included between 60° and 89°, pre- 20. ferably 80°. If necessary, gaskets 24 and 25 are also foreseen which carry out the sealing between the shell 12 and the fixed guiding structure 11. " V The half shells 18 and 19 can foresee- a gasket made up of a steel ring 28 lodged in a groove 29 in which it is inserted a material 25. 30, such as for instance the teflon which has a coefficient of thermal e pansion higher than the steel's. As it will be noted from the description made, the weight of the f t filtering device comes to be very reduced because the entry and exit holes 22 and 23 have also greatly reduced dimensions. Moreover such limited dimensions of the filtering device allow 5. to carry out the heating of the same by very simple means. Also piston 13,which provides for the -movement of the filters holding shell 12 in the direction of arrows A, can have highly reduced dimensions because, being the passage sections of holes 22 and 23 very small, the section of plastic to be cut is limited. 10. Finally it has been experimentally verified that with the proposed embodiment, and particularly with the tapering planned no stagna¬ tion results. An excellent sealing between the filters holding shell 12 and • the fixed guiding structure 11 is obtained because the former is 15. made up of two half shells 18 and 19 free to open under the pres¬ sure thrust, so as to make each half shell 18 and 19 firmly adhere to the fixed guiding structure 11 which is next to them, carrying out in this way a perfect sealing along gaskets 24 and 25. The pressure in fact tends to ' open the half shells 18 and 19 20. coπpressing the gaskets 24 and 25 against plates 14 and 15. The sealing between the two half shells 18 and 19 is carried out with the edging 21a which expands in operation, as well as with gasket 30 which moves towards the opposite half shell as soon as the device is running.

Claims: C L A I M S 1. Filtering device where a fixed guiding structure (11) can receive a filters holding shell (12) containing filtering means- (21) which come to be placed in succession in the flow of the plas¬ tic mass, characterized in that the entry hole (22) and the exit 5. hole (23) are greatly reduced in comparison to the diameter of the filtering means (21) and ' the two connecting cones (2β, 27) between the holes (22 and 23) and the filtering means (21) having an angle o at the vertex included between β0° and 89° 3 are foreseen. 2. . Filtering device according to claim 1, characterized 10. in that the cones (26 and 27) have angles of 80°. 3. Filtering device according to claim 1, characterized J in that the filters holding shell (12) is made up of two half shells \ (18 and 19) between which the filter holding perforated plate (20) and the filtering means (21) are inserted. 15. 4. Filtering device according to claim 1, characterized ' SU SiaiUTESHEET in that the diameter of the entry (22) and exit hole (23) is included between a fourth and a fifth of the diameter of the filtering means (21). 5. Filtering device according to any of the previous 5. claims, characterized in that the filtering means (21) has an edging (21a) carried out with a material having a coefficient of expansion higher than the steel's, lead being most suitable. 6. Device according to claim 3 3 characterized in that between the two half shells (18 and 19) it is foreseen a gasket 10. (28) inserted in a groove (29) inside which is also placed a material (30) having a coefficient of thermal expansion higher than the steel's.

Inventors: DOLCI LANFRANCO, HEER SERGIO, PONTI ARMANDO, DOLCI, LANFRANCO, HEER, SERGIO, PONTI, ARMANDO
Applicants: DOLCI SPA L, ING. L. DOLCI S.P.A.
Application year: 1986
Main classification: B01D29
IPC codes: B01D29, B01D46, B29C47