Manufacturing container or tube from paper; or other manufacturi – Cigarette filter making – With shaping or compacting of filter material
Patent
1984-08-10
1987-04-28
Schmidt, Frederick R.
Manufacturing container or tube from paper; or other manufacturi
Cigarette filter making
With shaping or compacting of filter material
493 42, B31C 1300
Patent
active
046610901
DESCRIPTION:
BRIEF SUMMARY
This invention relates to the production of continuous cigarette filter rod from a tow of filter material.
An important characteristic of a cirgarette filter rod is its pressure drop per unit length, because of its close relationship to the filtration efficiency of filters produced from the rod. At low manufacturing speeds rods with a range of weights per unit length and diameters can be produced from a given tow type and these will correspondingly have a range of pressure drops. Generally, rods which have weights corresponding to the upper end of this so-called tow capability range have a greater pressure drop to weight ratio and are consequently more economical to manufacture. At high manufacturing speeds the tow capability range is reduced, so that the uppermost weights obtainable at low speeds can no longer be obtained.
Several factors may contribute to the loss in tow capability range. Tow is visco-elastic and at low speeds crimp which is removed by stretching in the tow opening process recovers before the tow reaches the garniture. At higher speeds there is insufficient time for full recovery, so that filter rod produced from the tow has fewer laterally orientated fibres and therefore presents a lower pressure drop. Another possible factor is that the tow entrains air as it is drawn through the reducing cross-section of the collating tongue leading to the garniture of a rod making machine and the entrained air is expelled, generally by counter flow to the mouth of the tongue. This counter flow air produces a drag on the tow which increases at least with the square of increase of rod speed. As a result of this drag the tension needed to pull the tow through the garniture is high, so that again the tow is stretched and crimp is lost. Drag is also induced by friction as the tow is drawn over the inner surface of the tongue.
The present invention is based on an appreciation that if the tow can be delivered to a garniture of a rod making machine in a relatively relaxed state, in particular without substantial loss of crimp, the tow capability will be retained at high rod speeds. Further at the downstream end or throat of the tongue the cross-section is relatively small and the ratio of the circumference of the tow surface in contact with the stationary tongue to that in contact with the driving tape is approaching a minimum. Therefore, if the tow can be presented at the downstream end of the tongue substantially without loss of crimp it is possible to extend the tow capability range at high manufacturing speeds. Preferably the tow is not subjected to excessive stretch, or if it is stretched it is given time to recover. In a preferred aspect of the invention the tow is subjected to conveying means between a tow opening unit and a rod forming unit the conveying means being arranged to reduce at least locally the longitudinal force required to convey the tow towards the rod forming unit, preferably at least just upstream of the rod forming unit.
The invention further relates to a machine for making continuous filter rod, comprising means such as a tongue for shaping and possibly compressing the filter tow prior to its entry into a rod forming unit, including means adapted to drive tow into at least a downstream portion of the tongue without stretching the tow in said portion. An object of the invention is to enable operation of a rod making machine at high speeds (up to 600 m/min) without loss of crimp of filter tow as it is passed through the rod making unit.
It has already been proposed, in British patent specification No. 1387404, that a driven conveyor such as a wheel or band, be used to assist driving of the tow through a tongue. Suction may be applied to the conveyor. Other arrangements for feeding tow towards a tongue are disclosed in U.S. Pat. No. 4,248,139.
The above-mentioned drive means may include pneumatic means arranged to extract entrained air from the tow as it is compressed in or upstream of the tongue and also to create an additional air flow in the direction of conveyance of the the tow to
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Molins PLC
Schmidt Frederick R.
Showalter Robert
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