US2579440A

US2579440A - Electrostatic precipitator

Info

Publication number: US2579440A
Application number: US745314A
Authority: US
Inventors: Robert T Palmer
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1947-05-01
Filing date: 1947-05-01
Publication date: 1951-12-18
Anticipated expiration: 1968-12-18

Description

Dec. 18, 1951 -r PALMER 2,579,440

ELECTROSTATIC PRECIPITATOR Filed May 1, 1947 4 Sheets-Sheet 1 +1 E-KV P0 k151i JUPPZ. Y

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- INVENTOR. 22 19 Dec. 18, 1951 R. T. PALMER I 2,579,440

ELECTROSTATIC PRECIPITATOR Filed May 1, 1947 4 Sheets-Sheet 2 (g INVENTOR.

1386- 1951 R. T. PALMER ELECTROSTATIC PRECIPITATOR 4' Sheets-Sheet 5 Filed May 1, 1947 INVENTOR. mmv

1 '1! lluill| llllillllllia 1951 R. T. PALMER ELECTROSTATIC PRECIPITATOR 4; Sheets-Sheet 4.

Filed May 1, 1947 j attracting Patented Dec. 18, 1951 2,579,440 ELECTROSTATIC PRECIPITATOR Robert T. Palmer, Sharon, Mass., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application May 1, 1947, Serial No. 745,314

26. Claims.

This invention relates to electrostatic precipitators for the removal of small particles such as dust, from gases such as air.

The most successful electrostatic precipitators for the cleaning of air, have ionization chambers in which the foreign particles. entrained in the air, are given electrostatic charges, and have collection chambers in which the charged particles de-- posit upon oppositely charged, metal plates. After a period of use, it is necessary to clean such plates, which usually are cleaned by washingdown with liquids such as water.

. This invention provides an electrostatic pre cipitator in which a dielectric sheet is given an electrostatic charge and is moved, preferably in a plurality of passes, through the collection chamber of the precipitator, and serves as the electrodes to which the charged, foreign particles are attracted, and to which they adhere.

In one embodiment of the invention, the dielectric sheet is unwound from a first roll at, one end of the collection chamber, and is, wound upon a second roll at the other end of the collection chamber. When the first roll is used up, it is replaced, and the second roll is removed and disposed of, or cleaned.

In another embodiment of the invention, the dielectric sheet is endless and is. recirculated through the precipitator, it beingcleaned as by a suction nozzle, at a point in its travel.

In one embodiment of the invention, the dielectric sheet is electrostatically charged to one polarity, and is passed between metal plates charged to the opposite polarity, whereby the charged foreign particles are repelled by the plates towards the sheet.

In another embodiment of the invention, the two sets of electrodes in the collection chamber are formed by rows of dielectric sheets, alternate sheets being given opposite electrostatic charges whereby the charged foreign particles are re- .pelled by the sheets having the same polarity. and are attracted to the sheets having the opposite polarity.

An object of the invention is to facilitate the removal of the foreign particles collected in an electrostatic precipitator.

Another object of the invention is to provide an electrostatic precipitator for the removal of foreign particles from gases, in which the dust electrodes are electrostatically har ed, dielectric sheets movable .ther through.

Another object of the invention is to apply an electrostatic charge to .a dielectric sheet, and then to use the sheet in an electrostatic precipitator as an electrode for attracting foreign particles entrained in a gas passed therethrough.

Another object of the invention is to apply electrostatic charges to foreign particles entrained in a, gas; to apply an electrostatic charge having the opposite polarity to a dielectric sheet, and to use the sheet for attracting the charged particles.

Another object of the invention is to pass an electrostatically charged, dielectric sheet in a plurality of passes, as dust attracting electrodes, through the collecti nv chamber of an electrostatic precipitator.

The invention will now be described with ref! erence to the drawing, of which:

Fig. l is a plan view, in section, of an electro-. static precipitator embodying this invention, the section-being taken along the lines l--l of Fig. 2; Fig, 2 is a sectional view along the lines 2-2 of Fig. 1;

Fig. 3 is an enlarged, fractional view of the lower end of one of the rollers of Figs. 1 and 2, and of the bearing for same, the bearing being shown in section; I

Fig. 4 is a plan view, in section, of another electrostatic precipitator embodying this invention, the section being taken along the lines 4-4 of Fig. 5;

Fig. 5 is a sectional view along the lines 55 of Fig. 4;

Fig. 6 is a plan view, in section, of another electrostatic precipitator embodying this invention, the section being taken along the lines 6-6 of Fi Fig. 7 is a sectional view along the lines 'l-.-'| of Fig. 6;

Fig. 8 is a sectional view along the lines 8'8 of Fig. 7; v

Fig. 9 is a plan View, in section, of another electrostatic precipitator embodying this invention,

, the section being taken along the lines 9--9 of Fig. 10, and

Fig. 10 is a sectional view along the lines l0l 0 of Fig. 9.

Referring first to Figs. 1, 2 and 3, the precipitator there illustrated, includes the metal casing I0 having a gas inlet H in its upper wall, and a gas outlet [2 in its lower wall. Within the casing l0 adjacent the inlet, is the ionizer chamber l3 comprising the ionizer wires it supported by he framework 15 from the insulators I6, which n turn, are attached to opposite walls of the casing. .The tubular ionizer electrodes I! are arranged on opposite sides of the wires l4 and are supported directly from the casing walls. The

wires M are adapted to be connected to, for ex ample, the +l2,000 volt terminal of the direct current, power supply source 25, the casing Hi being grounded and connected to the negative terminal of the source. This construction is conventional and is illustrated by the E. H. R. Pegg Patent No. 2,181,147.

The collection chamber I8 is located between the ionizer chamber |3 and the outlet l2, and contains the vertically arranged, spaced, metal collector plates 9 which are supported in spaced slots in the metal bars which are attached to opposite casing walls. The plates I!) are grounded to the casing ll! through the bars 2|].

On opposite sides of the collection chamber are arranged the rollers 23 of electric insulating material, the rollers on one side having their shafts 2| in alignment with alternate of the plates IS, the rollers on the other side of the collection chamber having their shafts 2| in alignment with the others of the plates. The shafts 2| are journalled in the ball bearings 22 attached to upper and lower walls of the casing It.

To one side of the collection chamber I8, the left-hand side, facing Figs. 1 and 2 of the drawing, and of the rollers 23 on that side, are supported the

paper rolls

24 and 25, the roll 24 bein a supply roll, and the roll 25 being formed by rolling up the paper supplied by the roll 24.

The paper from the roll 24 is passed over the idler roller 24, and is then passed over the rollers 23 so that it is arranged in a plurality of passes on the opposite sides of the plates |9 as the sheet electrodes 31, as illustrated by Fig. 1, and passes out the collection chamber, and after contacting the idler roller 21 is rolled upon the roll 25.

The shaft 28 of the roll 25 is supported at its lower end in the bearing 29, and its upper end is connected through the conventional speed reducing gear box 30, to the electric driving motor 3|. The motor 3| is geared down through the box 3!] to rotate the roll 25 at a very slow speed whereby the sheet from the roll 24 is moved at low speed through the collection chamber 8.

The sheet on leaving the idler roller 26 passes between the

ionizer electrodes

34 and 35. The electrode 34 is a tubular, metal segment having a relatively large radius of curvature, and which extends the width of the sheet from the roll 24, and which is connected to, for example, the +6,000 volt terminal of the said power supp y source. The electrode 34 is supported by the tubular insulators 36 from the inner casing wall 38. The electrode is a comb type electrode extending the width of the sheet, having a plurality of sharp points adjacent the surface of the sheet, and is connected to the casing In so as to be grounded thereto.

In operation, following the energization of the direct current, power supply source, and of the motor 3|, a gas to be cleaned, such as air, is drawn into the inlet II as by the action of a fan ilvzhich is not illustrated, connected to the outlet are given positive electrostatic charges as they pass through the ionization chamber, in a process which is well known to those skilled in the art.

As the paper sheet passes between the

ionizer electrodes

34 and 35 it is given a minus electrostatic charge. This sheet charging action is disclosed in detail in the Van de Graaf Patent No. 1,991,236; the Trump Patent No. 2,252,668, and in the Delcau Patent No. 2,398,581, which patents may be referred to for an understanding of the The foreign particles entrained in the gas trostatic charges.

principles involved. The charged sheet as it passes through the collection chamber acts as a set of negatively charged electrodes 31 facing the grounded plates I9 which are positive with respect to the electrodes 31. Electrostatic fields are therefore set up between the electrodes |'9 and 31 which cause the positivel charged, foreign particles in the gas passing through the collection chamber, to be attracted to, and to adhere to the sheet.

The charged sheet may be moved by the motor 3| through the collection chamber, continuously at a low speed, or intermittently. The size of the sheet, its length in the collection chamber, its speed of movement therethrough, etc., can be so correlated that the last pass of the sheet in the collection chamber, the lowermost sheet electrode 31 of Fig. 1, is sufficiently dirty under normal conditions as to prevent its further use as a collector electrode.

In the embodiment of the invention illustrated by Figs. 1 and 2, the precipitator can be shut down and the motor 3| stopped as the sheet on the supply roll 24 is unrolled to a minimum point. The sheet can then be cut adjacent the

rolls

24 and 25 and new rolls inserted. The end of the sheet adjacent the new roll 25 would then be attached to the roll, and the end of the sheet ad jacent the new roll 24 would be spliced to the outer end of the sheet on same, as is done in paper and cloth production plants. The old roll 25 would then be discarded or cleansed for reuse.

The roll 24 can be provided with a motor and gear box similar to the motor 3| and gear box 30 and adapted to rotate the roll 24 for winding up the dielectric sheet thereon. Then in case conditions are such that the last pass of the sheet through the collection chamber remains relatively clean, when the roll 24' is unwound to a minimum point, the drive for the roll 25 can be disengaged, and the drive for the roll 24 can be engaged for passing the sheet in the reverse direction to that described, through the collection chamber. When this is done the electrode 34 would be deenergized, and the similar electrode 34 would be energized for electrostatically eharging the sheet.

While for the purpose of illustration, paper has been described as being used for the electrostatically charged sheet electrodes, other dielectric materials such, for example, as silk,ri1bber rayon or nylon could be used. Preferably the sheet used should have a very low electrical conductivity so that it can easily take on and held elec- The sheet could be treatedwith a chemical such, for example, as chlorinated diphenyl which will improve its dielectric characteristics, and which will render it fireproof.

More than one set of the

electrodes

34 and 35 could be used whereby the sheet could be electrostatically charged at a plurality of spaced points, if that is necessary for adequately charging the sheet, or for maintaining it adequately charged throughout its passage through the collection chamber.

The embodiment of the invention illustrated by Figs. 4 and 5 is similar to that described in the foregoing in connection with Figs. 1-8, but differs therefrom in that the metal, plate electrodes are not used in the collection chamber, alternate of the sheet electrodes being given opposite electrostatic charges. Corresponding parts of Figs. 4 and 5 and of Figs. 1 and 2 have therefore, been given the same reference characters.

Referring now to Figs. 4, and 5, the

ionizer electrodes

44 and 45. are arranged on opposite sides of alternate passes of. the sheet through the collection chambenand the ionizer electrodes 46 and 4.1 arearranged on the opposite sides of the other passes of the sheet through the colection chamber. The pointed electrodes 15 are connected together and are grounded-to the casing Ill. The tubular segment electrodes 44 are connected together and to the -]-6,000 volt terminal of the power supply source. The pointed electrodes. 46 are connected together and to the +6,000 volt terminal of the supply source. The tubular segment electrodes 4? are connected together and are grounded to the casing H). 'With this arrangement of ionizer electrodes, the passes of the sheet moving between the electrodes is and 45 are given negative electrostatic charges,

and are identified on Fig. 4 of the drawing, as the negatively charged, collector electrodes 48. The passes. of the sheet moving between the ionizer electrodes 46 and 41 are given positive electrostatic charges, and are identified on Fig. 4 of the drawing, as the positively charged electrodes 49.

The grounded Wipers 5(! of flexible metal contact the sheet adjacent the electrodes 4!; and 4'? before it passes therebetween, and serves to remove the positive electrostatic charge from the sheet before the application of the negative electrostatic charges. The operation of the precipitator of Figs. 4 and 5 otherwise is the same as that of Figs. 1 and '2.

An advantage of the precipitator of Figs. 4 and 5 is that both sets of collector electrodes are continuously renewed. In prior prec'ipitators using positively charged and grounded, metal plate, collector electrodes, it was found that some foreign particles were given negative charges in the ionization chamber and were deposited upon the positively charged collector plates. While the quantity of dust which collects upon the pos itively charged, collector electrodes is small com pared to that which collects upon the negatively charged ones, it is desirable for some duties to be able to continuously renew both sets of collector electrodes.

The embodiment of the invention illustrated by Figs. 6, 7 and 8, is similar to that described in the foregoing in connection with Figs. 1 and 2 except that instead of the sheet forming the negatively charged, collector electrodes being unrolled from one roll, and rolled up on another roll, the sheet is an endless sheet, and is cleaned by suction at a point in its travel as it is recirculated through the precipitator casing. Corresponding reference characters are applied to similar parts in the precipitators of both embodiments.

Referring now to Figs. 6, 7 and 8, the endless sheet 60 is threaded over the direction changing rollers GI and 62 located in the casing It to one side of the collection chamber Iii, and over the rollers 23 which are similar to the rollers 23 of Figs. 1 and 2. The roller fil has a pulley at-' tached thereto and which is rotated through the belt 63 by the electric motor 64. The sheet is spaced, in the collection chamber, between the metal plate electrodes I9, so as to form negatively charged electrodes 31 as previously described inv connection with Figs. 1 and 2.

The suction nozzle 65 is in contact with the sheet: 50 on both sides thereoi, and. is connected atone. side of the sheet to the duct. 56 and. at the other side of the sheet to the duct 61, the ductstfi and. 6'! being connected by the duct 68 to the inlet. of the blower 69 driven by the elec- 6 tric motor 10-. The outlet of the blower '69 is connected to the outlet duct H which conveys the foreign particles collected from the sheet 50, to an external disposal .point.

In operation, the sheet 60 is electrostatically charged by the

electrodes

34 and 35, so as to act to attract the oppositely charged foreign particles entrained in the gas passing through the precipitator, as described in the foregoing. The dust attracted to the sheet, and adhering thereto, is removed by the nozzle 65. It is .prefer-red that the sheet 60 be, during the cleaning cycle. continuouslymove'd at slow speed through the collector whereby the nozzle willcontinuously remove the foreign particles adhering thereto.

Thesheetof Figs. 4 and 5 could, of course, be made endless as in Figs. 6, 7 and 8, and recirculated through a suction nozzle whereby the sheet is continuously cleaned.

, By using an endless electrostatically charged sheet, the necessity for replacementof the rolls such as are used in Figs. 1-5, is eliminated, and thev use. of a higher quality, more expensive sheet, such as silk, is therefore, justified.

The embodiment of the invention illustrated by Figs. 9 and 10 isv similar to that described in the foregoing in connection with Figs. 1 and 2, except that a wind-up roll is not used following the last pass of the dielectric sheet through the collection chamber. Instead, the sheet is passed between the rolls and. 8!, the roll 8! being rotated through the belt 82 by the electric motor 33. The sheet after passing between the rolls 8!! and BI, coils up in the. box 84 from which it can be removed for disposal when the sheet is unwound irom the roll 2-4 to a minimum point. In this embodiment of the invention, the gas fiow through the ionizer and collector chambers, is horizontal. 7

While a single dielectric sheet has been illustrated as passing in a plurality of passes throughv the collection chamber of each embodiment of the invention, each pass of the sheet through a collection chamber, may be considered as a separate sheet, and the plurality of passes of the sheet through a collection chamber, may be considered as a plurality of sheets.

While embodiments of the invention have been described for the purpose of illustration, it should be understood that the invention is not limited to the exact apparatus and arrangements of apparatus illustrated, as modifications. thereof may be suggested by those, skilled in the artv without departure. from the essence of. the invention.

What is claimed is:

1. An electrostatic precipitator comprising a casing having a gasinlet and a gas outlet, and having a collection chamber between said. inlet and. outlet, a collector electrode in said chamber, means for charging said electrode to one polarity,

a dielectric sheet, means for-moving saidv sheet through. said, chamber adjacent said electrode,

and means including ionizerelectrodes on opposite sides of said sheet for applying an. electro static charge to said sheet having a polarity op posite to that of said electrode.

2. An electrostatic precipitator comprising a casing. having a gas inlet and a gas outlet, and having a collection chamber between said inlet and. outlet, a plurality of; spaced collector electrodes in. said chamber, means for charging said electrodes. to. one: polarity, a. dielectric sheet,

means formoving said; sheetv through saidichambar-between said electrodes, and means includingionizer electrodes onv opposite: sides or said sheetv if for applying an electrostatic charge to said sheet having a polarity opposite to that of said-electrodes. 1

3. An electrostatic precipitator as claimed in claim 2 in which the sheet is moved through the collection chamber in a plurality of passes be-' tween and along opposite sides of the electrodes.

4. An electrostatic precipitator comprising a casing having a gas inlet and a gas outlet, and having a collection chamber between said inlet and outlet, a dielectric sheet, means for moving said sheet in a plurality of passes through said chamber, and means including ionizer electrodes on the opposite sides of said sheet for applying electrostatic charges of one polarity to alternate passes of said sheet, and for applying electrostatic charges of the opposite polarity to the other passes of said sheet.

5. An electrostatic precipitator comprising a casing having a gas inlet and a gas outlet, an ionizer chamber between said inlet and outlet, a collection chamber between said ionizer chamber and said outlet, means in said ionizer chamber for applying an electrostatic charge of one polarity to the foreign particles in the gas passing therethrough, a dielectric sheet, means for moving said sheet through said collection chamber, and means including ionizer electrodes on opposite sides of saidsheet for applying an electrostatic charge to said sheet having a polarity oposite to that of said particles.

6. An electrostatic precipitatorias claimed in claim 5 in which the sheet is moved in a plurality of passes through'the collection chamber.

7. An electrostatic precipitator comprising a casing having a gas inlet and a gas outlet, an ionizer chamber between said inlet and outlet, a collection chamber between said ionizer chamber and said outlet, means in said ionizer chamber for applying an electrostatic charge having one polarity to the foreign particles in the gas passing therethrough, a, dielectric sheet, means for moving said sheet in a plurality of passes through said collection chamber, and means including ionizer electrodes on the opposite sides of said sheet for applying an electrostatic charge having the same polarity as said particles to al-' ternate passes of said sheet, and for applying an' electrostatic charge having the opposite polarity to the other passes of said sheet.

8. An electrostatic precipitator comprising a casing having a gas inlet and a gas outlet, an ionizer chamber between said inlet and outlet, a collection chamber between said ionizer chamber and said outlet, means'in said ionizer chamber for applying an electrostatic charge having one polarity to the foreign particles in the gas passing therethrough, a plurality of collector electrodes in said collection chamber, means for applying an electric charge to said electrodes having the same polarity as said particles, a di-' electric sheet, means for moving said sheet in a plurality of passes between said electrodes, and means for applying an electrostatic charge to said sheet having the opposite polarity to said electrodes.

9. An electrostatic precipitator comprising a casing having a gas inlet and a gas outlet, a collection chamber between said inlet and outlet, a supply roll having a dielectric sheet wound thereon at one end of said chamber, sheet moving means at the other endof said chamber, means for passing sheet'from' said supply roll through said collection chamber to said sheet moving means, and means'including ionizer electrodes on the opposite sides of said sheet for 8. applying an electrostatic charge'to said sheet when it enters said chamber.

10. An electrostatic precipitator as claimed in claim 9 in which the sheet is arranged in a plurality of passes in the collection chamber.

11. An electrostatic percipitator comprising a casing having a gas inlet and a gas outlet, a collection chamber between said inlet and outlet, a plurality. of spaced, collector electrodes in said chamber, means for electrically charging said electrodes to one polarity, a supply roll having a dielectric sheet wound thereon at one end of said chamber, sheet moving means at the other end of said chamber, means for passing sheet from said supply roll in a plurality of passes between said electrodes, to said sheet moving means, and means including ionizer electrodes on the opposite sides of said sheet for applying an electrostatic charge to said sheet, opposite in polarity to that of said electrodes.

12. An electrostatic precipitator comprising a casing having a gas inlet and a gas outlet, an ionization chamber between said inlet and outlet, a collection chamber between said ionization chamber and said outlet, means in said ionization chamber for applying an electrostatic charge of one polarity to the foreign particles in the gas passing therethrough, a plurality of spaced, collector electrodes in said. collector chamber, means for electrically charging said electrodes to the same polarity as said particles, a supply roll having a dielectric sheet wound thereon at one end of said chamber, sheet moving means at the other end of said chamber, means for passing sheet from said supply roll in a plurality of passes between said electrodes to said sheet moving means, and means for applying an electrostatic charge to said sheet onposite in polarity to that of said electrodes.

13. An electrostatic precipitator comprising a casing having a gas inlet and a gas outlet, a collection chamber between said inlet and outlet, an endless dielectric sheet, means supporting said sheet in a plurality of passes in said chamber, means for rotating said sheet, and means including ionizer electrodes on the opposite sides of said sheet for applying an electrostatic charge to said sheet.

14. An electrostatic precipitator as claimed in claim 13 in which means is provided for continuously cleaning the sheet during the rotation thereof.

l5.An electrostatic precipitator as claimed in claim 13 in which means including a suction nozzle is provided for continuously cleaning the. sheet during the rotation thereof.

16. An electrostatic precipitator comprising a casing having a gas inlet and a gas outlet, a collection chamber between said inlet and outlet, a plurality of spaced collector electrodes in said chamber, means for electrically charging said electrodes to one polarity, an endless, dielectric sheet, means supporting said sheet in a plurality of passes between said electrodes, means for rotating said sheet, and means including ionizer electrodes on the opposite sides of said sheet for applying an electrostatic charge to said sheet opposite in polarity to that of said electrodes.

17. An electrostatic precipitator as claimed in claim 16 in which means is provided for continu ously cleaning the sheet during the rotation thereof.

18. An electrostatic precipitaor as claimed in claim 16 in which means including a suction nozzle is provided for continuously cleaning the sheet during the rotation thereof.

19. An electrostatic precipitator comprising a casing having a gas inlet and a gas outlet, an ionizer chamber between said inlet and outlet, a collection chamber between said ionizer chamber and said outlet, means in said ionizer chamber for applying an electrostatic charge of one polarity to the foreign particles in the gas passing therethrough, an endless dielectric sheet, means for supporting said sheet in a plurality of passes in said collection chamber, means for rotating said sheet, and means including ionizer electrodes on the opposite sides of said sheet for applying an electrostatic charge to said sheet opposite in polarity to said particles.

20. An electrostatic precipitator as claimed in claim 19 in which means is provided for continuously cleaning the sheet during the rotation thereof.

21. An electrostatic precipitator as claimed in claim 19 in which means including a suction nozzle is provided for continuouslycleaning the sheet during the rotation thereof.

22. An electrostatic precipitator comprising a casing having a gas inlet and a gas outlet, an ionizer chamber between said inlet and outlet, a collection chamber between said ionizer chamber and said outlet, means in said ionizer chamber for applying an electrostatic charge of one polarity to the foreign particles in the gas passing therethrough, a plurality of spaced, collector electrodes in said collection chamber, means for applying an electric charge to said electrodes having the same polarity as said particles, an endless, dielectric sheet, means for supporting said sheet in a plurality of passes between said electrodes, means for rotating said sheet, and means including ionizer electrodes on the opposite sides of said sheet for applying an electrostatic charge to said sheet opposite in polarity to said electrodes.

23. An electrostatic precipitator as claimed in claim 22 in which means is provided for continuously cleaning the sheet during the rotation thereof.

24. An electrostatic precipitator as claimed in claim 22 in which means including a suction nozzle is provided for continuously cleaning the sheet during the rotation thereof.

25. An electrostatic precipitator comprising a casing having a gas inlet and a gas outlet, and having a collector chamber between said inlet and outlet, a dielectric sheet, means for moving said sheet through said chamber, and means including ionizer electrodes on the opposite sides of said sheet for applying an electrostatic charge to said sheet by providing an excess of ions having the same polarity thereon.

26. An electrostatic precipitator comprising a casing having a gas inlet and a gas outlet, and having a collector chamber between said inlet and outlet, a dielectric sheet, means for supporting said sheet for movement in a plurality of passes through said chamber, means for moving said sheet, and means including ionizer electrodes on the opposite sides of said sheet for applying an electrostatic charge to said sheet by providing an excess of ions having the same polarity thereon.

ROBERT T. PALMER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Winchester Sept. 8, 1931 Christofierson Dec. 4, 1934 Dollinger Oct. 8, 1935 FOREIGN PATENTS Number Number