US3757803A

US3757803A - Electrostatic cigarette filtering arrangement

Info

Publication number: US3757803A
Application number: US00294087A
Authority: US
Inventors: T Chiang
Original assignee: Individual
Current assignee: Individual
Priority date: 1972-10-02
Filing date: 1972-10-02
Publication date: 1973-09-11
Anticipated expiration: 1990-09-11

Abstract

A cigarette holder is disclosed which establishes a nonuniform electric field in a cigarette so that not only positvely and negatively charged particles entrained in the cigarette smoke may be precipitated but also so that neutrally charged particles may be precipitated. Neutrally charged particles are polarized by the presence of the electric field. Once polarized, the nonuniform entensity of the electric field exerts a net mechanical force on the particle causing it to be precipitated. The nonuniform electric field is provided between one or more needle-like electrodes which pierce the tobacco or filter tip of the cigarette and a surrounding cylindircal electrode. A power supply energizes the electrodes with sufficient voltage to provide a polarizing electric field at an intensity below the threshold that would ionize particles.

Description

United States Patent [1 1 [1111 3,757,803 Chiang 11 Sept. 1 1, 1973 [54] ELECTROSTATIC CIGARETTE FILTERING 3,028,864 4/1962 Minto 131/262 B x ARRANGEMENT FOREIGN PATENTS OR APPLICATIONS [76] Inventor: Ta-Kuan Chiang, 923 Mountain 54, 79 0 1970 Canada Ave, Berkeley Heights Township, Union County, Primary Examiner-Joseph S. Reich Oct. 2 AttorneyHoward R. Popper A cigarette holder is disclosed which establishes a nonl l 131/262 uniform electric field in a cigarette so that not only po- /150, 55/DlG. 38 sitvely and negatively charged particles entrained in the [Sl] Int. Cl A24! 13/04, A24f l3/O8 cigarette smoke may be precipitated but also so that 0 Search B; neutrally charged particles may be precipit'ated Neu- 299 trally charged particles are polarized by the presence of the electric field. Once polarized, the nonuniform en- [56] References Cited tensity of the electric field exerts a net mechanical UNITED STATES PATENTS force on the particle causingit to be precipitated. The 987,823 3/1911 Perry 131/183 X nonuniform electric field is provided between one or 1,024,930 4/1912 Fernandez I I 131/188 x more needle-like electrodes which pierce the tobacco 1.734315 1 1929 Lopez 131 133 x or filter tip of the cigarette and a surrounding cylindir- 3,064,657 11/1962 Shriner 131/262 B X cal electrode. A power supply energizes the'electrodes .070,10 1962 Hicks 61 a 131/262 3 UX with sufficient voltage to provide a polarizingelectric 3,129,] Loecl tenhofi' at an intensity below the threshold that would i0 3,423,306 l/l969 Hurwitz et al. 205/299 ize particles 3,416,540 l2/l968 Lidums 131/262 B 3,463,168 8/ I969 Troll et al. till/262 B 4 Claims, 5 Drawing Figures BACKGROUND OF THE INVENTION This invention relates to an improvement in cigarette filters and/or holders and more particularly to a cigarette filter arrangement that makes use of the ion and particle precipitating effects of applied electrical potentials.

It has been known for some time that the particles entrained in cigarette smoke have a particulate diameter of 0.1 to 0.3 microns, that approximately 40 percent of the aerosol particles are charged positively, 34 percent negatively and 26 percent are uncharged. See, for example, the work of H. L. Green and W. R. Lane entitled Particulate Clouds, Dusts, Smokes and Mists Second Edition, D. VanNostrand and Company, 1964, page 83.

The prior art cigarette filter, consisting of a short section of a random-fiber filter at the end of the cigarette, removes tar and nicotine contents in cigarette smoking on the principle of inertial effect. During a puff, smoke is drawn through the random-fiber filter and air flow in the region of each filter fiber must then diverge to pass around the fiber. The usual filter is constructed so that any particles larger than the air molecules themselves such as tar and nicotine which are of the order of 0.3 microns in diameter and above cannot follow these sudden changes in flow direction as easily as the air. Some particles will therefore have sufficient inertia to strike the fiber and adhere, resulting in less tar and nicotine transmission to the smoker than that of thenonfilter cigarettes. The removal of more tar and nicotine particles can be accomplished with prior art fiber filters either by using more fibers of smaller size, or by increasing the air velocity such as is done in the prior art air-vented cigarette filters. Either of these means will produce more rapid changes of air velocity around the fiber, and hence better inertial effect. Either of these means will however at the same time increase the resistance of the filter to air flow, and thus make it hard to draw. Because the flavor of tobacco smoking is said to be in a heated-vapor form (refer to the cited reference), any further increase of the resistance of the filter to air flow by either of the foregoing conventional arrangements also causes a further sacrifice in tobacco flavor. The filtering effectiveness of the prior art cigarette filter is therefore limited and completely deter&

mined by the taste that must remain.

It has been known that certain of the irritant or unpleasant effects of cigarette smoke seem to be dependent upon the polarity of the ion content of the smoke. See, for example, W. I... Minto U.S. Pat. No. 3,028,864 issued Apr. 10, 1962. The latter patent attempted to make use of the contact potential of dissimilar metals or the use of dissimilar metals together with an external power supply operated at 30 volts or below the neutralize the positively charged smoke particles or to negatively charge the primarily uncharged smoke particles. The Minto patent arrangement, however, suffered from certain limitations among which the following may be noted. The filter elements and outer sleeve had to be of conductive material so that the lips of the smoker could act as an electron source, but this exposed the smoker to the danger of having his lips bumed as the burning ash of the cigarette approached the filter. Since most heat insulating materials are also electrical insulating materials, there appears no way to make the Minto arrangement work with complete safety. On the other hand, if the embodiment shown in FIG. 8 of the Minto arrangement which employs a battery source is used, it is difficult to provide an electrical gradient through the conductive sleeve 36 which surrounds the metallic filter elements 35. In addition, the surfaces of tubing elements 35 must all be at the same potential thereby eliminating the possibility of any potential field gradient among the filter elements. Consequently, the tubing elements are rather ineffective in precipitating positively charged ions. On the other hand, negatively charging smoke particles will be repelled from the negative tubing surfaces and the majority of negatively charged smoke particles will get through to the smoker.

While the foregoing brief discussion of some prior art attempts to collect the entrained ions in the smoke aerosol is of some interest, the effectiveness of the prior art collection methods has thus far left much to be desired.

SUMMARY OF THE INVENTION In accordance with my invention in one illustrative embodiment thereof, I provide a, cigarette holder having a pair of electrodes one of which is adapted tosurround and the other of which is adapted to enter the tobacco filler of the cigarette or, in the case of a cigarette having a filter tip, to enter among the fibers within the filter. The electrodes of my cigarette holder are adapted to provide a nonuniform and nonionizing electric field within the end portion of the cigarette. I have found that the nonuniform electric field established within the end portion of the body of the cigarette through which the smoke passes enhances the filtering effectiveness with respect tour and nicotine removal without detracting from the natural drawing qualities of the cigarette. As part of the body of the cigarette holder, I provide a miniaturized electrical power supply for energizing the electrodes to provide a relatively high but nonuniform electric field gradient within the end portion of the cigarette which potential gradient is kept below that which would be effective to ionize the air within the cigarette. The nonuniform electric field gradient polarizes the neutral aerosol particles in the smoke and exerts a net motive force thereon causing the particles to be more acutely diverted withinthe air stream and impinge upon and adhere to the tobacco strands or fiber particles in the immediate vicinity of the electrodes. The positive and negative polarity aerosol particles in the cigarette smoke will be driven to the tobacco strands or fiber particles by the electrostatic field and charge interaction. The filter efficiency is therefore enhanced regardless of the aerosol particle polarity. I

The electrode of my invention in one embodiment thereof are coaxial in form, the outer electrode being cylindrical and having an inner diameter proportioned to embrace the end of the cigarette or filter tip thereof and the inner electrode configured as a needle shaped rod. Advantageously, the axial lengths of the concentric electrodes are commensurate with the length of the filter tip 50 as to require the nonuniform polarizing field to exert a motive force on smoke particles throughout the entire axial length of the filter tip. The miniaturized power supply for energizing the filter of my invention converts the potential of a small battery source into an alternating current waveform signal that is applied to a ferrite core transformer primary winding, the transformer having a secondary winding connected to a diode in series with one of the aforementioned electrodes. The cigarette holder may advantageously be equipped with a switch in the primary circuit to activate and deactivate the electric polarizing field.

The foregoing and other objects and features of my invention may become more apparent by studying the ensuing specification and drawing,

FIG. 1 of which shows a side sectional view of the electrostatic cigarette holder of my invention with a filter tip cigarette installed therein;

FIG. 2 shows a side sectional view of an alternative embodiment of my invention;

FIG. 3 shows the nonuniform electric field provided by the embodiment of FIG. 1;

FIG. 4 shows and end view of the alternative embodiment of FIG. 2; and

FIG. 5 shows an electronic circuit for providing a nonuniform electrical field to the electrodes of any of the embodiments of FIGS. 1 through 4.

Referring now to FIG. 1, a cigarette 11 having a filter end 12 is inserted into the left-hand end of holder 14 which includes a pair of

concentric electrodes

21 and 22. Electrode 21 is in the form of a hollow cylinder having an internal diameter proportionedto accommodate the end of the cigarette. Electrode 22 is needle shaped and positioned along the central axis of electrode 21.

Electrodes

21 and 22 are mounted within the holder 14 which holder may be made of insulating plastic material. The right-hand end 26 of the holder 14 may be tapered to form a convenient mouthpiece section. Cylindrical electrode 21 is connected via lead 27 to one terminal of the miniaturized power supply housed within compartment 24. Electrode 22 is supported by spider 23 within holder 14. Lead 28 connects electrode 22 via spider 23 to the other terminal of the power supply within compartment 24. A pushbutton switch 25 is mounted in holder 14 and when actuated activates the power supply to energize

electrodes

21 and 22 to provide a nonuniform polarizing field within filter tip 12 of cigarette 11 as will hereinafter be described in more detail.

The size of power supply compartment 24 is shown in approximate scale with respect to the section of the cigarette filter 12, the principal volume of compartment 24 being taken by the battery 33 and transformer 30 schematically illustrated in FIG. 5.

FIG. 3 shows the nonuniform electric field produced.

within the body of cigarette filter 12 when the power supply is actuated. Since the same number of lines of force terminate at the cylinder 21 and at the needle 22, they will be more crowded near the axial portion thereof, and accordingly the field force will be greater at the axial portion. The needle-like shape of cylindrical electrode 22 produces an electric field gradient depicted in FIG. 3 within the filter which varies from less than 30 kilovolts per centimeter at the immediate surface of the needle to about 2 kilovolts per centimeter at the inner surface of electrode 21. Tar and nicotine particulates entrained with the smoke drawn into the non-uniform field region existing between central electrode 22 and-outer cylindrical electrode 21 within the cigarette filter 12 are subjected to both the mechanical filtration effect of the filter and the polarization forces of the nonuniform field. The mechanical effects are the usual filtration effects produced when the entrained particle impacts the filter fiber. However, the nonuniform electric field produces an additional cross-axial motive force on the particles in the gas stream, diverting them from the more or less axial gas flow towards the central electrode 22 and increasing their tendency to impinge upon the fibers of the filter, thereby increasing the mechanical filtering effectiveness without actually increasing the resistance to air flow. Furthermore, the charged tar and nicotine particulates positive and negative existing naturally in the cigarette smoke entrained with the air drawn into the nonuniform field region existing between central electrode 22 and outer cylindrical electrode 21 within the cigarette filter 12 are subjected to both the mechanical filtration effect of the filter and the electrostatic precipitation forces of the electric field and charge interaction. However, these precipitation forces will divert the positively charged tar and nicotine particulates (shown as encircled crosses in FIG. 3) towards the negative central electrode 22, and the negatively charged tar and nicotine particulates (shown as encircled dashes) away from the negative central electrode 22. Therefore, my invention increases the cigarette filter effectiveness without discrimination with respect to charged or noncharged tar and nicotine particulates. The nonuniform electric field produced by the geometry of

electrodes

21 and 22 is kept below the field intensity that would result in ionizing the smoke particles. Since no smoke particles are ionized, there is no ion currentin the filter and accordingly the current output requirement of the power supply is minimal.

The miniaturized electronic power supply for energizing

electrodes

21 and 22 is shown in detail in FIG. 5. A conventional blocking oscillating circuit including a transformer rectifier and filter may be fabricated in extremely small size. The largest elements required are the mechanical switch 25, the battery 33 and the transformer 30. All of the other components may be provided in chip-integrated circuit form. The primary winding 31 of transformer 30 is connected between the collector and base of transistor 37 in series with the parallel resistor 36 and capacitor 35. A tap on primary winding 31 is connected in series with switch 25 and wafer battery 33 to the emitter of transistor 37 to form a conventional blocking oscillator. The transformer secondary winding 32 is connected to the serial combination of diode 38 and output filter capacitor 39. The relatively highvoltage output produced across the secondary winding 32 is rectified by diode 38 and appears between

conductors

27 and 28 going respectively to outer electrode 21 and central electrode 22 of the embodiment of FIG. 1. The blocking oscillator is set into operation when switch 25 is operated to energize the center tap at the primary winding 31 of transformer 30.

FIGS. 2 and 4 show respectively the sectional and end views of an alternative electrostatic cigarette filter embodiment. The embodiment of FIGS. 2 and 4 contains a number of needle-shaped electrodes to reduce the voltage requirement at the output of the power supply of FIG. 5. Reduced output voltage has the advantageous effect of reducing the size of transformer 30. The alternative embodiment of FIGS. 2 and 4 includes a cylindrical electrode 221 mounted in a plastic holder 14. However, instead of a single central electrode connected to the hot output of the power supply of FIG. 5, the central electrode 221 is instead connected to the ground output of the power supply. A cluster of needie-like electrodes 222 is arranged on a metallic ring 223 which is fitted into plastic holder 14 and insulated from electrodes 221 and 221'. Metallic ring 223 is connected to the high voltage output of the power supply. As seen in FIG. 2, the needle electrode 221' is mounted in a cross member 223 and is spaced from the ring 223 so as to be non-conductive therewith. The member 223 is conductive and is arranged to be in electrical contact with the cylindrical electrode 221 by means not shown. A nonuniform electric field is thus provided between each needle-shaped electrode 222 in ring 223 and the outer cylindrical electrode 221 as well as between the needle-shaped conductor 222 and grounded center electrode 221. The decreased spacing between

electrodes

222, 221 and 221 permits voltage gradients comparable to that shown in FIG. 3 to be provided by the power supply of FIG. 5 with a net decrease in the output voltage required to be delivered by the power supply.

Referring now to FIG. 3, there is shown the electric field forces acting on an uncharged particle entrained in the air stream passing through the filter of the embodiment of FIG. 1. It will be apparent that positively charged particles will be repelled by the outer electrode 21 and attracted to inner electrode 22. The opposite effect will be produced on negatively charged particles.

A neutrally or uncharged particle 41 is shown greatly enlarged in FIG. 3. Such a particle will become polarized because of the electric field existing between central electrode 22 and cylindrical electrode 21. The electric field lines of force 3a, 3b emanating'from the inner periphery of cylindrical electrode 21 must all terminate on the much similar periphery of central electrode 22. Consequently, the electric field intensity is greater in the regionclose to the central electrode than it is in the region immediately adjacent cylindrical electrode 21 and so is nonuniform. Since particle 41 is neutrally charged, it may be represented as having an equal number of positive and negative charges which are randomly distributed on its surface. The electric field p0- larizes the individual plus and minus charges on neutrally charged particle 41, drawing the positive charges towards that surface of particle 41 that is nearest central electrode 22 and drawing the negative charges closest that surface of particle41 which is closest to central electrode 21. Since particle 41 is assumed to be neutrally charged, there will be as many positive particles displaced by the polarization as negative particles. However, the polarization of the particles puts the positive charges of particle 41 in a region of greater field intensity than the negative charges because the positive charges are closer to central electrode 22. Accordingly, the neutrally charged particle 41 will be impelled towards central electrode 22 because of the nonuniform electric field gradient. Thus, in accordance with my invention not only positively and negatively charged particles entrained in the air stream are caused to be divetted, but also neutrally charged particles are diverted orthogonally to the normal direction of the air stream. This enhances the filtering effectivenss of the cigarette filter significantly reducing the amount of tars, nicotine and other particulate matter reaching the smoker.

Since the embodiments of the present invention produce an electric field intensity which is nonuniform and nonionizing, the current requirements of the power supply may be minimal, it merely being necessary to overcome the leakage current due to moisture entrained within the cigarette smoke. Advantageously, the power requirement may further be reduced by employing a moisture blocking filter preceding the fiber cigarette filter.

What is claimed is:

1. An arrangement for improving the filtering effectiveness of a cigarette without materially increasing the smoke flow resistance thereof to the smoker comprising an electrically insulating cigarette holder having an outer hollow electrode for embracing an end portion of said cigarette and at least one needle-shaped electrode within said hollow electrode located within the fibers of said end of said cigarette, and means for energizing said electrodes to produce a nonuniform electric field gradient in the end of said cigarette between said electrodes, said electric field gradient having a value varying from less than 30 kilovolts per centimeter immediately adjacent to the sharp end of said needle electrode to approximately 2 kilovolts per centimeter adjacent the surface of said cylindrical electrode.

2. An arrangement according to claim 1 wherein said holder includes a compartment for containing a miniaturized electronic power supply for energizing said electrodes.

3. An arrangement according to claim 1 further comprising a ring member supported within said insulating holder, said ring member providing a mounting base for a plurality of said needle-shaped electrodes. r

4. An arrangement according to claim 3 wherein said needle electrode is centrally supported within said holder and insulated from said ring member and wherein one terminal of said power supply is connected to both said outer cylinder and said inner central elec-- trode and the other terminal of said power supply is connected to said ring member of the needle-shaped electrodes protruding from said ring member being interposed between said central electrode and said outer cylindrical electrode.

* I 8' I i

Claims

3. An arrangement according to claim 1 further comprising a ring member supported within said insulating holder, said ring member providing a mounting base for a plurality of said needle-shaped electrodes.

4. An arrangement according to claim 3 wherein said needle electrode is centrally supported within said holder and insulated from said ring member and wherein one terminal of said power supply is connected to both said outer cylinder and said inner central electrode and the other terminal of said power supply is connected to said ring member of the needle-shaped electrodes protruding from said ring member being interposed between said central electrode and said outer cylindrical electrode.