Smoking article with combined ventilation and filtration efficiency adjustment

Abstract

The invention relates to a smoking article (10) comprising a tobacco rod (12) and a filter, the filter comprising a filter unit (14) comprising a first segment (16) of filtration material; a second segment comprising a tubular element (18) of filtration material upstream of the first segment (16), the tubular element (18) having an outer diameter (D2) and an inner diameter (D1). An inner surface of the tubular element (18) is substantially air impermeable. The second segment further comprises a frangible or irreversibly collapsible flow restrictor (24) disposed in the tubular element (18). When the flow restrictor (24) is in a substantially unbroken or non-collapsed state, the filter unit (14) has a first RTD. When the flow restrictor (24) is broken or collapsed, the filter unit (14) has a second RTD, the second RTD being smaller than the first RTD.

Claims

1. A smoking article comprising a tobacco rod and a filter, the filter comprising a filter unit comprising: a first segment of filtration material; a second segment comprising a tubular element of filtration material upstream of the first segment, the tubular element having an outer diameter (D2) and an inner diameter (D1), an inner surface of the tubular element being substantially air impermeable; the second segment further comprising an irreversibly collapsible flow restrictor disposed within the tubular element, the flow restrictor being collapsible upon application of a load on the filter; wherein the inner diameter (D1) is at least about 70 percent of the outer diameter (D2); wherein, when the flow restrictor is in a substantially non-collapsed state, the filter unit has a first RTD; and, when the flow restrictor is collapsed, the filter unit has a second RTD, the second RTD being smaller than the first RTD; wherein the collapsible flow restrictor is made of an open- or closed-cell, non-elastic foam material that has no shape memory or of an irreversibly deformable wax or polymeric material.

2. The smoking article according to claim 1, wherein the tubular element comprises a hollow tube defining the inner surface of the tubular element and the filtration material is arranged about the hollow tube.

3. The smoking article according to claim 1, wherein the flow restrictor has an inherent compressive yield strength of less than about 20 Newtons.

4. The smoking article according to claim 1, wherein the flow restrictor has an inherent compressive yield strength of at least about 10 Newtons.

5. The smoking article according to claim 1, wherein a compressive yield strength of the second segment is less than about 45 Newtons.

6. The smoking article according to claim 1, wherein the first RTD is at least about 120 millimetres water gauge.

7. The smoking article according to claim 1, wherein the second RTD is less than about 100 millimetres water gauge.

8. The smoking article according to claim 1, wherein a transverse cross-sectional surface area of the flow restrictor is at least about 70 percent of a theoretical free cross section of the tubular element.

9. The smoking article according to claim 1, wherein at least one cross-sectional dimension of the flow restrictor is at least about as large as the inner diameter (D1) of the tubular element, such that the flow restrictor engages with the tubular element to retain the flow restrictor in the tubular element.

10. The smoking article according to claim 1, wherein the at least one cross sectional dimension of the flow restrictor, measured in a transverse direction of the filter, is substantially equal to the inner diameter (D1) of the tubular element.

11. The smoking article according to claim 1, wherein the flow restrictor is substantially spherical.

12. The smoking article claim 1, comprising a ventilation zone at a location along the first filter segment.

13. The smoking article according to claim 12 wherein, when the flow restrictor is in a substantially unbroken or non-collapsed state, a ventilation level of the smoking article is at least about 40 percent.

14. The smoking article according to claim 1, wherein the inner surface of the tubular element is defined by a layer of a substantially air impermeable coating material.

Description

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

(2) FIG. 1 is a schematic sectional view of a smoking article in accordance with the present invention in a first configuration; and

(3) FIG. 2 a schematic sectional view of the smoking article of FIG. 1 in a second configuration.

(4) FIG. 1 shows a smoking article 10 in accordance with the present invention. The smoking article 10 comprising a tobacco rod 12 and a filter unit 14. The filter unit 14 is in alignment and in abutting arrangement with the tobacco rod 12.

(5) The filter unit 14 comprises a first segment 16 of filtration material having a length of about 15 millimetres and a second segment comprising a tubular element 18 of filtration material having a length of about 12 millimetres and arranged upstream of the first segment 16. The first segment 16 and the tubular element 18 are substantially aligned and in abutting relationship. The smoking article 10 further comprises a ventilation zone 20 at a location along the first filter segment 14.

(6) The tubular element 18 has an outer diameter D2 of about 7.8 mm and an inner diameter D1 of about 5 mm. In more detail, the tubular element 18 comprises a hollow paper tube 22 circumscribed by a layer of filtration material. An inner surface of the tubular element 18 is substantially air impermeable.

(7) Further, the filter unit 14 comprises a flow restrictor 24 disposed within the paper tube 22 at a location along the tubular element 18. The flow restrictor is spherical and has a diameter of about 4.2 millimetres. Thus, A transverse cross-sectional surface area of the flow restrictor 24 is about 70 percent of the free cross section of the hollow tube 22.

(8) In the embodiment of FIG. 1, the flow restrictor 24 is substantially spherical and has a diameter that is slightly less than the inner diameter D1 of the tubular element. Accordingly, the greater part of the mainstream smoke reaching the filter progresses through to the first filter segment 12 by flowing through the filtration material disposed about the hollow tube 22 (as indicated by arrows in FIG. 1). Accordingly, in the configuration illustrated in FIG. 1, the smoking article 10 provides high RTD values and high ventilation (as depicted by the block arrows in FIG. 1), due to a higher pressure drop across the tubular element.

(9) The flow restrictor 24 is frangible. Thus, upon application of a load greater than its inherent compressive yield strength the flow restrictor 24 breaks up into fragments 26, as illustrated in FIG. 2. Accordingly, at least part of the cross section of the hollow tube 22 previously occluded by the unbroken flow restrictor 24 becomes available for gas flow. Thus, the incoming mainstream smoke will tend, for the most part, to flow across the second segment through its hollow core to reach the first segment (as illustrated by arrows in FIG. 2). Therefore, the overall RTD of the smoking article corresponds essentially to the RTD of the first segment 14 alone. Under such circumstances, the reduced pressure drop across the hollow tube 22 results in a decreased amount of ventilation air being drawn into the filter and towards the consumer's mouth. Accordingly, a second smoking article configuration associated with low RTD values and low ventilation (as depicted by the block arrows in FIG. 2) is provided for the consumer.

(10) Tables 1 and 2 below contain parameters measured on the smoking article described above with reference to FIGS. 1 and 2 in the first configuration (that is, with the flow restrictor intact), and in the second configuration (that is, after breaking the flow restrictor), respectively. In the second configuration, an increase in the tar delivery is also observed.

(11) TABLE-US-00001 TABLE 1 RTD Ventilation Average 150.8 51.3 Standard deviation 16.20 8.71

(12) TABLE-US-00002 TABLE 2 RTD Ventilation Average 73.7 23.0 Standard deviation 6.76 6.09