Smoking article

Abstract: A smoking article comprising a rod of smoking material (1) and a filter portion, said filter portion including means (6) for collecting particulate matter in the smoke from the rod of smoking material in a collection zone (7), and means (3) for heating said collection zone to release the semivolatile compounds whilst allowing the involatiles to be retained in the filter.

Description: This invention relates to a smoking article according to the first part of claim 1 relating to the prior art of DE-U-1 892 093 in which the smoking material can be tobacco or any other suitable material. The composition of the cigarette smoke aerosol is complex, containing many compounds in the particulate and vapour phases. It is possible to classify the compounds contained within the particulate phase into two fractions, these are the involatile and semivolatile fractions. The semivolatile fraction can be defined as consisting of all of those compounds which evaporate from a chemically inert substrate heated to a temperature of 200°C. Many of the compounds which have been identified as contributors to the taste and flavour of cigarette smoke are contained within the semivolatile fraction. Also it is found experimentally that approximately 50% of the total particulate matter of cigarette smoke is semivolatile. It is an object of the present invention to deliver to the smoker an enhanced concentration of semivolatile compounds in the smoke and a reduced concentration of involatiles, thus maintaining taste and flavour at lower total particulate matter yields. According to the present invention a smoking article comprises a rod of smoking material and a filter portion, said filter portion including means for collecting particulate matter in the smoke from the rod of smoking material in a collection zone arranged in the upstream end of the filter portion, and means for heating said collection zone to release the semivolatile compounds of the smoke whilst allowing the involatile compounds to be retained in the filter. Preferably the rod of smoking material includes a longitudinally extending passage to feed hot gases from the tip of the article when lit to the said collection zone. In one preferred embodiment the collection zone is provided by an impervious transversely extending member on which the particulate matter is deposited by the smoke from the smoking material. The transversely extending member can be provided by a disc the centre portion of which provides said collection zone and which is surrounded by an exit opening or openings. Preferably the disc is provided in a chamber into which smoke from the smoking material is delivered and into which the longitudinally extending passage feeds hot gases to the collection zone. If desired means may be included for accelerating the hot gases from the passage into the collection zone. In another embodiment the collection zone can be provided in a high retention filter element. With this arrangement the high retention filter element can be spaced away from the end of the smoking material rod to form a chamber adjacent the collection zone and into which smoke from the smoking material is delivered and into which the longitudinally extending passage feeds hot gases to the collection zone. A secondary filter element can be provided which is located at the mouth piece end of the article. Preferably the passage in the rod of smoking material is formed by a low porosity/permeability tube. The invention can be performed in various ways but two embodiments will now be described by way of example and with reference to the accompanying drawings in which : Figure 1 is a cross-sectional side elevation of a smoking article according to the present invention; Figure 2 is a cross-sectional view on the line II-II in Figure 1; Figure 3 is a cross-sectional view on the line III-III of Figure 1; Figure 4 is a cross-sectional view on the line IV-IV of Figure 1; and, Figure 5 is a cross-sectional side elevation of another construction according to the invention. As shown in Figures 1 to 4 the smoking article according to the invention comprises a rod 1 of smoking material, for example tobacco, carried in a paper outer wrapper 2. The rod is provided with a longitudinally extending passage 3 formed by a tube of low porosity/permeability material 4 which may be made from paper or reconstituted tobacco sheet. The tube may have a diameter typically in the range of 0.5 to 5 mm. Also located within the paper wrapper 2 is a filter 5 at the mouth piece end and an impervious transversely extending member in the form of an impaction disc made of material which is temperature stable. Examples of the materials from which the disc may be constructed include metals, for example aluminium, ceramics or plastics such as nylon, polyethylene, polypropylene or cellulose acetate. Preferably the disc has a low thermal heat capacity and it may also have a low thermal conductivity, for example when constructed from a ceramic or from Nylon 66. This disc 6 has a central impaction surface 7 which is surrounded by circumferential holes 8 typically of 1 mm diameter. Between the inner end 9 of the tobacco rod 1 and the surface of the disc 6 a chamber 10 is formed in which is located a second disc 11 which can also be made from a material selected from the examples given for the disc 6, and this may be the same as, or different from, that used in the construction of the disc 6 in a particular construction. One or more (three are shown) small diameter holes 12 are provided in the disc 11 and these may typically be of 0.1 - 1 mm diameter and preferably 0.4 - 1 mm diameter. These holes act as acceleration nozzles in the manner to be described. When the article is smoked and the end 13 is lit smoke passes into the chamber 10 and through the nozzles 12, the action of passing through the nozzles 12 increases the velocity of the smoke and assists in the impaction of the smoke against the impaction surface 7 on the disc 6. This causes particulate matter to be deposited in the area 7 and to act as a collection zone. Hot gases from the burning tip pass down the passage 3, are accelerated through the holes 12 and impact on the surface 7 thus heating the collection zone and deposited particulate matter sufficiently to cause the release of the semivolatile compounds which pass radially outwardly with the smoke and through the openings 8 into the filter 5 and to the smoker. Some of the semivolatile compounds may be released as they enter the collection zone before impaction due to the heat in the collection zone. The impaction surface provided by the surface 7 is located typically 2 mm from the nozzles 12. In the embodiment shown the passage 3 is located coaxially with the smoking material rod 1 but it could be displaced to one side if desired. In the second embodiment as shown in Figure 5 the same reference numerals are used to indicate similar parts as in Figures 1 to 4. In this construction the means for collecting particulate matter in the smoke from the rod of smoking material is provided by a high retention filter element 15. The element 15 is spaced away from the end 9 of the smoking material rod and the filter 15 is located in a chamber 10 in place of the disc 11. The disc 6 is also dispensed with. In this arrangement smoke from the rod 1 impinges on the front surface 16 of the filter 15 and the filter retains a fraction of the total particulate matter over the first few (ten) mm of filter material. This is indicated by reference numeral 17. This retained total particulate matter is again heated by hot air or smoke drawn down the passage 3 as in the previous embodiment. The second filter element 5 can be spaced away from the filter element 15 as shown or it may abut it. Once again the action of the hot air or smoke heats the deposited particulate matter and releases the semivolatile fractions which are then drawn through the filter 5. The second filter element 5 may have an inclusion of activated carbon to reduce the concentration of some of the vapour components in the smoke aerosol. If desired ventilation air may be introduced through the wrapper 5 into the filter 17 through openings 18 to confine the aerosol and the hot air/smoke stream to the central part of the filter. Similarly in the construction shown in Figure 1 ventilation air may be introduced through the wrapper 5 through openings 19 to aerodynamically focus the aerosol onto the disc 6 to improve the efficiency of the filter. If desired ventilation air may also be used to cool the evaporated semivolatiles to facilitate recondensation before delivery to the smoker, for example through openings 20.

Claims: A smoking article comprising a rod of smoking material (1) and a filter portion (5), said filter portion including means (6) for collecting particulate matter in the smoke from the rod of smoking material in a collection zone arranged in the upstream end of the filter portion, characterized by means for heating (3) said collection zone to release the semivolatile compounds of the smoke whilst allowing the involatile compounds to be retained in the filter. A smoking article as claimed in claim 1 in which said rod of smoking material includes a longitudinally extending passage to feed hot gases from the tip of the article when lit to the said collection zone. A smoking article as claimed in claim 2 in which said collection zone is provided by an impervious transversely extending member on which the particulate matter is deposited by the smoke from the smoking material. A smoking article as claimed in claim 3 in which said transversely extending member is provided by a disc the centre portion of which provides said collection zone and which is surrounded by an exit opening or openings. A smoking article as claimed in claim 4 in which said disc is provided in a chamber into which smoke from the smoking material is delivered and into which the longitudinally extending passage feeds hot gases to the collection zone. A smoking article as claimed in claims 2 to 5 including means for accelerating the hot gases from the passage into the collection zone. A smoking article as claimed in claim 6 including means for accelerating the hot gases from the passage and the smoke into the collection zone. A smoking article as claimed in claims 6 and claim 7 in which the means for accelerating the hot gases or hot gases and smoke includes a disc of impervious material having one or more holes within the range of 0.1 to 1.0 mm diameter. A smoking article as claimed in claim 2 in which said collection zone is provided in a high retention filter element. A smoking article as claimed in claim 9 in which said high retention filter element is spaced away from the end of the smoking material rod to form a chamber adjacent the collection zone and into which smoke from the smoking material is delivered and into which the longitudinally extending passage feeds hot gases to the collection zone. A smoking article as claimed in claims 1 to 10 in which a secondary filter element is located at the mouth piece end of the article. A smoking article as claimed in claims 2 to 9 in which said passage in the rod of smoking material is formed by a low porosity/permeability tube.

Inventors: MOLLOY PETER JOHN, MOLLOY, PETER JOHN
Applicants: ROTHMANS INTERNATIONAL LTD, ROTHMANS INTERNATIONAL SERVICES LIMITED
Application year: 1991
Main classification: A24D1
IPC codes: A24D3, A24D1