Filter manufacturing apparatus

Abstract

The invention relates to a filter manufacturing apparatus (1) to form a hollow filter body, the filter manufacturing apparatus comprising: a feed path adapted to continuously feed a filter material along a longitudinal transport direction (30); a forming device (4) connected to a terminating end of the feed path and adapted to form the filter material into a hollow rod-shaped filter body and deliver the formed filter body, the forming device including: .square-solid. a tubular forming element (8) adapted to allow the filter material to pass therethrough, .square-solid. a pin (34) extending longitudinally within the tubular forming element, the pin having a pin diameter;a diameter changing device (40), adapted to vary the pin diameter of the pin, so as to obtain a filter body having a through hole of variable diameter.

Claims

1. A filter manufacturing apparatus adapted to form a hollow filter body, the filter manufacturing apparatus comprising: a feed path adapted to continuously feed a filter material along a longitudinal transport direction; a forming device connected to a terminating end of the feed path and adapted to form the filter material into a hollow rod-shaped filter body and deliver the hollow rod-shaped formed filter body, the forming device including: a tubular forming element adapted to allow the filter material to pass therethrough, a pin extending longitudinally within the tubular forming element, the pin having a pin diameter; a diameter changing device, adapted to vary the pin diameter of the pin, so as to obtain a hollow rod-shaped filter body having a through hole of variable diameter.

2. The filter manufacturing apparatus according to claim 1, wherein the diameter changing device includes a heat generator thermally connected to the pin and adapted to change a pin temperature in order to change the pin diameter.

3. The filter manufacturing apparatus according to claim 1, wherein the pin is formed in a material comprising a metal.

4. The filter manufacturing apparatus according to claim 3, wherein the pin is formed in steel.

5. The filter manufacturing apparatus according to claim 4, wherein the pin is formed in carburized steel.

6. The filter manufacturing apparatus according to claim 1, wherein the pin defines an external surface adapted to be in contact with the filter material, and wherein the diameter changing device comprises at least two protrusions adapted to be retractable or extendable along a radial direction of the external surface.

7. The filter manufacturing apparatus according to claim 6, wherein the diameter changing device comprises at least three protrusions.

8. The filter manufacturing apparatus according to claim 6, wherein the diameter forming device includes a micrometric screw and wherein at least one of the protrusions is adapted to be retractable or extendable by means of the micrometric screw.

9. The filter manufacturing apparatus according to claim 1, comprising: a plasticizer addition unit arranged upstream an inlet of the tubular forming element and adapted to spout a plasticizer to add the plasticizer to the filter material.

10. The filter manufacturing apparatus according to claim 1, comprising: a heat treating section adapted to heat the filter material while the filter material passes through the tubular forming element.

11. The filter manufacturing apparatus according to claim 10, wherein the heat treating section comprises a steam generator fluidly connected to the tubular forming element to supply steam to the filter material.

12. The filter manufacturing apparatus according to claim 1, comprising: a cooling section located downstream the forming device to cool down the hollow rod-shaped filter body.

13. The filter manufacturing apparatus according to claim 1, wherein the forming device comprises a tapered portion, the tapered portion having its internal diameter decreasing along the longitudinal transport direction.

14. The filter manufacturing apparatus according to claim 1, wherein the pin defines an external surface adapted to be in contact with the filter tow material, and wherein the pin comprises a non-stick coating on the external surface of the pin.

15. The filter manufacturing apparatus according to claim 1, wherein the pin defines a substantially cylindrical external surface.

Description

(1) The invention will be further described, by way of example only, with reference to the accompanying drawings in which:

(2) FIG. 1 is a schematic view of an apparatus for forming a filter according to the invention;

(3) FIG. 2 is a perspective view of a portion of the machine of FIG. 1;

(4) FIG. 3 is a perspective view of a portion of the apparatus of FIG. 1;

(5) FIG. 4 is a schematic lateral view in section of an element of the portion of FIG. 3; and

(6) FIG. 5 is a perspective view of the element of FIG. 4.

(7) FIG. 1 depicts an apparatus for the production of a hollow filter body, for example to be used as a filter or as a filter component in an aerosol generating article (not depicted in the figures).

(8) Apparatus 1 comprises a transport device 3 to transport along a transport or feeding direction 30 (indicated by arrows in the figures) filter material, for example cellulose acetate or filter tow. The filter tow may be taken from a bundle (not shown). After the withdrawal from the bundle, the filter tow material by means of compressed air from different compressed air nozzles (also not shown) may be loosened up and homogenized.

(9) Further, the apparatus 1 includes an inlet unit 2 adapted to form a continuous stream or strip of filter material, moistened with a hardening fluid or plasticizer, such as triacetin. The filter material is fed to the inlet unit 2 by the transport device 3. The moistening of the filter material with plasticizer takes place in a plasticizer unit, not shown in the drawings and known in the art. The plasticizer unit is located upstream the inlet unit 2.

(10) After the impregnation unit, the transport device 3 transports the impregnated filter tow material to the inlet unit 2, which includes preferably a cone-shaped element 54 (see FIG. 3). In the inlet unit 2, the filter tow material is subjected to compressed air. This procedure may cause homogenization of the filter tow material, which is pushed along an interior channel 41 of the inlet unit 2 realized along a longitudinal direction of the inlet unit itself. The interior channel 41 is preferably cylindrically shaped and it defines a longitudinal axis preferably parallel to the transport direction 30.

(11) Downstream the inlet unit 2, the apparatus includes a rod forming unit 4, arranged in series to the inlet unit 2 and adapted to receive the flow or strip of filter material and to cause the hardening material present in the filter material to react to transform the filter material into a continuous axially rigid hollow rod filter body.

(12) Preferably, the hollow filter body exiting the rod forming unit 4 is a non-wrapped acetates filters (NWA filters). In order to avoid an expanding of the rod filter body after shaping it in the rod forming unit 4, without such a wrapping paper presence, such as in standard filters, inside the rod forming unit 4 the filter material receives already during its shaping a sufficiently large stability, so that it is used and processed without the wrapping paper.

(13) The production of such filtering ranks takes place in particular in a pultrusion procedure. During this procedure the filter material stream passes through the rod forming unit 4.

(14) The rod forming unit 4 comprises a tubular forming element 8, shown in an enlarged view in FIG. 4, adapted to receive the filter material saturated with hardening material, for example along the transport direction 30 depicted in FIG. 4 which is the transport direction of the transport device 3, and to shape the filter material crosswise so as to transform it into a moist, generally cylindrical filter body and to advance the filter body in the feed direction of the mentioned arrow to the further components of the apparatus 1.

(15) Tubular forming element 8 defines a through hole 20 through which the filter material can pass. Preferably, the through hole 20 comprises an inner surface 21 which compresses the filter material to form a substantially cylindrical rod-like shaped continuous strip of material. Further, preferably the tubular element 8 includes a steam generator 9 comprising one or more nozzles 11 which can emit steam in the interior of the tubular element 8. The steam can harden the plasticizer present in the filter material and transform it into the substantially rigid filter rod or body.

(16) The apparatus 1 is adapted for the production of a hollow filter body, that is, of a filter body having a through hole of a desired size, for example of a desired diameter. For this purpose, a guidance pin 34 is located in the interior of the inlet unit 2 and rod forming unit 4. This guidance pin 34 extends in the transport direction 30. In other words, the pin 34 essentially defines a longitudinal extending direction which is substantially parallel to the transport direction 30. Preferably, the pin 34 is coaxial to channel 41 of inlet unit 2 and through hole 20 of the tubular element 8, as shown in FIG. 3. Guidance pin 34 defines a diameter in a cross section perpendicular to the transport direction 30 or axis of the pin. The diameter is selected depending on the desired size of the through hole of the filter body.

(17) Preferably, the pin 34 has an outer surface 36, preferably cylindrical, which is coated in a non-stick coating. The coating could be a plastic or ceramic coating. Preferably, the pin 34 may be realized in metal such as steel and may be surface-treated.

(18) The guidance pin 34 preferably comprises a first section 51 and a second section 53. The first section 51 of the guidance pin 34 extends within the inlet unit 2. The second section 53 of the guidance pin 34 extends within the rod forming unit 4. First and the second section 51, 53 are one connected to the other and in particular they are along the same longitudinal axis. Preferably the pin 34 defines an outer substantially cylindrical surface.

(19) A length of the guidance pin 34 measured in transport direction 30 is thus longer than a length of the interior of the inlet unit 2 and of the rod forming unit 40 measured in same direction.

(20) Preferably the filter material is pushed inside the tubular element 8 along arrow 30 by means of a fluid jet, for example a pressurized air jet, generated by a pressurized fluid generator (not shown in the drawings).

(21) Advantageously, the apparatus 1 further includes a wrapping unit 6, to wrap the hollow rod filter in a wrapping paper 90. Further, the apparatus may comprise a cutting unit 7, normally a rotating cutting head of known type, arranged downstream of the rod forming unit 4 and wrapping unit 6 and adapted to cut the hollow filter rod crosswise into filter segments (not shown). The desired length of the units in which the filter body is cut is for example obtained with the assistance of a measurer apparatus (also not shown). The cut units are made available in following processing steps or are buffered.

(22) Wrapping unit 6, transport device 3 and cutting unit 7 are known in the art and not further detailed below.

(23) Further, the apparatus 1 includes a diameter changing device 40. The diameter changing device, schematically shown in FIGS. 1 and 3, is connected to the pin 34 in order to change the diameter of the same. Diameter changing device 40 may include a heat generator so as to change the temperature of the pin. In FIG. 5, a different embodiment of the pin 34 and diameter changing device 40 is shown. Pin 34 includes a plurality of protrusion 35 departing from its outer surface 36 and angularly spaced. The protrusion, with the aid of the diameter changing device, may be expanded or retracted in the radial direction. The length of protrusions 35 defines the diameter of the pin 34.

(24) Apparatus 1 may also include a central control unit 100. Central unit 100 is adapted to command the rod forming unit 4. Preferably, central unit 100 commands the steam generator 9 and the pressurized fluid generator (not visible in the drawings). The central unit 100 is adapted to change the pressure of the steam produced by the steam generator and, in alternative or in addition, the pressure of the fluid pushing the filter material into the tubular forming element 8. Central control unit 100 is also adapted to command diameter changing device 40 in order to properly change the diameter of the pin 34.

(25) The functioning of the apparatus 1 is as follows. According to the specification of the desired filter body to be produced, the diameter adjusting device is regulated, for example imputing a desired diameter of the pin 34, and the pin 34 reaches the desired inputted diameter. The filter tow is transported along the transporting direction 30 and a plasticizer is added to it. By means of compressed air it is then inserted into the inlet unit 2, and in particular in the cone-like element, where it is shaped around the pin 34, that is, it is compressed between the pin 34 outer surface and the inner surface of channel 41. As previously mentioned, the filter tow is transported along the interior of the inlet unit 2 by means of compressed air along transport direction 30, preferably parallel to the axis of channel 41, and homogenized at the same time. For this purpose, the inlet unit 2 may include compressed air ports not represented. The filter tow distributes itself under the influence of compressed air evenly around the pin 34. At an outlet 36 of the inlet unit 2, a filter material stream emerges, which surrounds the pin 34.

(26) The filter material stream enters the tubular forming element 8, in which a sleeve-like channel is defined between the internal surface 21 of the through hole 20 and the external surface of the pin 34. The channel likewise essentially extends in transport direction 30. Inside the channel of the tubular forming element, nozzles 11 introduces the fluid, such as steam, from steam generator 9 serving as sources of energy. In particular hot-air or superheated steam is used as process fluid. The filter material stream 22 existing from the tubular forming element 8 is solidified by effect of the warmth transported by the process fluid, so that a non-wrapped hollow tubular body is manufactured. The hollow filter body can possibly also undergo a further wrapping step in a wrapping unit, not further described and considered standard in the field.

(27) The shaping of the hollow filter body takes place by means of the effect of the internal surface 21 of the through hole 20 of the tubular forming element 8 on the one hand and of the opposite outside surface 36 of the second section 53 of the guidance pin 34 on the other hand. These two surfaces 21, 36 acts as guide surfaces for the filter material stream and form together the format channel for the shaping of filter material.

(28) The format channel is substantially shaped as a mantel or sleeve. The selected pin diameter defines the dimension of the through hole of the filter body, that is, the thickness of the channel. Preferably, the dimension of the internal surface 21 remains constant, and only the dimension of the outside surface 36 is changed.

(29) Advantageously, when a different hollow filter body is desired, for example a hollow filter body having a different diameter of its through hole, the diameter of the pin 34 is changed, acting on the diameter changing device 40. For example, the temperature of the pin may be changed, or the extension of protrusions 35 may be varied, and a new diameter can be set. The filter material entering the apparatus 1 after the diameter change of the pin is subjected in the inlet unit 2 and in the rod forming unit 4 to the new pin diameter and therefore a new hollow filter body is produced.