US3306722A

US3306722A - Apparatus for precision fiberization

Info

Publication number: US3306722A
Application number: US413391A
Authority: US
Inventors: James K Duncan
Original assignee: EDWARD W O SHAUGHNESSY; JAMES K DUNCAN; TIMOTHY G LOWRY
Current assignee: EDWARD W O SHAUGHNESSY; EDWARD W O'SHAUGHNESSY; JAMES K DUNCAN; TIMOTHY G LOWRY
Priority date: 1964-11-16
Filing date: 1964-11-16
Publication date: 1967-02-28
Anticipated expiration: 1984-02-28

Description

1967 J. K. DUNCAN APPARATUS FOR PRECISION FIBERIZATION INVENTOk. Kfimma;

M/ dffjawr 3 Sheets-Sheet l Ji/W; BY

Filed Nov. 16, 1964 Feb. 28, 1967 J: K. DUNCAN 3,306,722

APPARATUS FOR PRECISION FIBERIZATION Filed Nov. 16, 1964 5 Sheets-Sheet 2 W ll/W IN V EN TOR.

52W Kfiwmwg Feb. 28, 1967 J, K. DUNCAN APPARATUS FOR PRECISION FIBERIZATION 3 Sheets-Sheet 5 Filed Nov. 16, 1964 United States Patent O APPARATUS FOR PRECISION FIBERIZATION James K. Duncan, Park Ridge, 11]., assignor to Elmer K.

Zitzewitz, Robert Gurley, Edward W. OShaughnessy,

Timothy G. Lowry, and James K. Duncan, co-partners doing business as Duncan Research Filed Nov. 16, 1964, Ser. No. 413,391 12 Claims. (Cl. 6512) This application is a continuation-in-part of my application Serial No. 69,602, filed November 16, 1960 now abandoned.

This invention relates to fiber production and concerns, more particularly, apparatus for forming fibers from molten glass, furnace slag, and the like.

Fibrous material such as is used in the construction materials industry is conventionally produced in high volumes by subjecting a molten stream of the basic material to a blast of steam. The steam blast strips thin strands from the melt which cool to form the desired fibers.

While used for many years, this method is ineflicient and difiicult to control. For example, if the melt is too cool, only limited fiberization will occur and substantial quantities of the melt will solidify in relatively large particles known as shot. If the melt is too 'hot or too great a blast of steam is used, a condition of explosiveness occurs as the stream strikes the melt which disintegrates the melt into dust and feathers. Even when operating most efiiciently, the use of steam for fiber production is not an efiicient process and it is common to experience over 50% waste in conventional fiber production.

Accordingly, it is the primary aim of the present invention to provide an improved apparatus for producing fiber from molten material in very large quantities and with exceptional efliciency. That is, by the practice of the invention, fiber can be formed at a high rate wit-h little loss through s'hot, dust or feathers.

More particularly, it is an object to provide apparatus of the above character which avoids a condition of explosiveness in the fiber forming region so that fiber can be smoothly stripped without shattering the molten material into dust and feathers.

It is also an important object to provide apparatus as referred to above which is extremely economical as compared With prior techniques of volume fiber production. More specifically, it is an object to provide an apparatus as characterized above which is economical to manfacture, long lasting in operation, and particularly inexpensive to operate. A related object is to provide an apparatus as described above that requires little or no warm up period and which can be economically started and stopped whenever desired.

A further object is to provide apparatus of the above described type which gives effective control of many variable which affect fiber production so that the most efficient use of the novel apparatus can be easily obtained.

It is also an object of the invention to provide a novel vacuum V blowcap for high volume fiber production which greatly facilitates high rates of fiber production while giving added control to the process. A collateral object is to provide a blowcap of the above type which promotes the formation of particularly elongated fibers.

Other objects and advantages of the invention will hecome apparent on reading the following detailed description and upon reference to the drawings in which:

FIGURE 1 is a longitudinal section of an apparatus embodying the invention shown fiberizing a material in accordance with the invention;

FIG. 2 is a plan of a portion of the apparatus shown in FIG. 1;

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FIG. 3 is an enlarged fragmentary elevation taken along line 33 in FIG. 2;

FIG. 4 is similar to FIG. 2 and shows an alternate form of apparatus;

FIG. 5 is similar to FIG. 1 and illustrates a further modification; and

FIGS. 6 and 7 are diagrammatic showings of coated fibers made in accordance with one aspect of the invention.

While the invention will be described in connection with a preferred embodiment, it will be understood that I do not intend to limit the invention to that embodiment. On the contrary, I intend to cover all alternatives, modifications and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.

Turning now to the drawings, there is shown an apparatus 10 embodying an aspect of the invention and arranged to fiberize a stream of molten material 11 which flows from a furnace 12. In the illustrated embodiment, the material being fiberized is common blast furnace slag so as to produce a mineral fiber known as slag wool. It will be appreciated by those skilled in the art, however, that the invention is equally applicable to the formation of any fiber so long as its constituents can be heated to a fluid condition or can be rendered fluid by the addition of a suitable solvent. Of course, the furnace 12 can be of any convenient type, depending upon the nature of the material being fiberized. Since the incipient melting temperature of slag is approximately 2000 F., the furnace 12 preferably heats the material 11 to a flowing temperature of 2650 F. In this temperature range, the slag is molten, that is, syrupy but not watery.

In accordance with the invention, a stream of the material 11 just above its melting temperature is poured in front of a blowcap 20 and is struck with a blast of hot gases from the blowcap so as to strip the stream into elongated fibers, the hot gases being at a temperature substantially equal to the incipient solidification temperature of the fiberized material and being formed of dry, non-combustible or completely burned constituents. In the present case, the material I11 drops from the furnace 12 into a forehearth pool 21 from which it falls in a plurality of streams 22 from a group of adjacent spillways 23. The blowcap 20 directs a blast of hot gases against each one of the streams 22.

In the illustrated case, the molten material 11 in the streams 22 assumes a temperature of about 2550 F., the free flowing melting temperature of the slag material, and is struck by a high velocity blast of gases from the blowcap 20 having a temperature of approximately 1900 to 2000 F. The hot gas blast strips elongated fibers 24 from each of the streams 22 and, because of the nature of the gas blast, substantially all of the material in the streams is stripped into usable elongated fibers. Little shot is formed because the high temperature of the gas blast avoids sudden solidification of the molten material. The temperature difference between the hot gases in the 'blast and the'molten material is just sufficient to slightly solidify the fibers as they are stripped from the streams 22. Since the gases are dry, no sudden expansion occurs as when water vapor in steam strikes molten material at the temperature ranges involved. Also, since the gases in the blast are formed of non-combustible or completely burned constituents and are already at the approximate temperature which is the incipient solidification temperature of the molten material, no condition of explosiveness occurs as the gas blast strikes the molten streams 22.

In carrying out the invention, the hot gases are generated in the apparatus 10 by a device for burning fuel which device, in the preferred construction, takes the preferred form of a gas turbine 25 of a commercially available type. Quite briefly, the turbine includes a main shaft 26 journaled in a frame 27 and carrying compressor elements 28. Air enters the turbine through inlets 29 and is directed outwardly by the compressor elements 28 into a generally annular combustion chamber 29 into which fuel is injected through a nozzle 30 from a fuel line 31. The gaseous products of combustion from the chamber 29 are directed through turbine elements 32 and out an exhaust pipe 33.

To adapt the turbine 25 for use with the apparatus 10, the driving end of the shaft 26 is covered by a housing 35 and the turbine is rigidly secured to a frame 36 so that its exhaust 33 is directed toward a chamber 37 behind the blowcap 20. In other words, rather than being a torque generator, the turbine 25 is utilized as a relatively inexpensive, compact and economically operated device capable of generating large quantities of hot gases. In the construction shown, the turbine 25 delivers gases at an approximate temperature of 1250 F.

To effect an adjustment of the amount of gas delivered by the turbine 25, a shiftable choke member 40 is mounted behind the turbine exhaust pipe 33 on a bracket 41 that is slidably supported on the frame 36. The member 40 includes a cylindrical portion 42 slidably fitted within a cylindrical portion 43 forming an extension of the chamber 37. The member 40 also includes a funnelshaped section 42a adapted to surround the exhaust pipe 33. A lever 44 is pivoted at 45 on the frame 36 and is coupled to the bracket 41 through a pin and slot connection 46 so that rocking movement of the lever slides the choke member 40 toward and away from the turbine 25.

With the choke member 40 slid to the left in the drawing, virtually a continuous connection is provided between the exhaust pipe 33 of the turbine 25 and the chamber 37 so that a substantial back pressure is exerted on the turbine. Sliding the choke member 40 toward the right, spaces, in increasing amounts, the funnel portion 42a of the member 40 from the exhaust pipe 33 so as to open up the front of the turbine and thus reduce the back pressure while diverting a portion of the exhaust gases into a duct 47 where they are conveyed forwardly for a purpose discussed below. It can therefore be seen that swinging the lever 44 so as to position the choke member 40 adjusts the amount of hot gases delivered from the turbine 25, both by affecting the operation of the turbine and by diverting a portion of the gases into the duct 47.

For raising the temperature of the turbine exhaust gases to the incipient solidification temperature of the molten material 11, the chamber 37 is formed as an afterburner and for this purpose includes a rearwardly opening air intake valve 50 and a fuel injection nozzle 51. The valve 50 is made up of a valve plate 51 sandwiched between a pair of wall members 52 and 53. A worm 54 drivingly engages a plurality of teeth (not shown) formed in the periphery of the plate 51 and the worm is coupled to a hand wheel so that by rotating the hand wheel the plate 51 can be rotated between the wall members 52, 53. The valve plate 51 and the Wall portions 52, 53 have a plurality of peripherally spaced apertures 54 arranged so that rotating the plate 51, by manipulating the hand wheel 55, causes the apertures in the plate to move into and out of alinement with the apertures in the wall members. In this way, the size of the openings through which air may be taken into the chamber 37 is conveniently varied.

The amount of fuel, preferably natural gas, injected into the chamber 37 through the nozzle 51 and the positioning of the valve plate 51 are selected so as to raise the temperature of the gas stream passing through the chamber 37 to slightly below the incipient solidification temperature of the melt being fiberized or, in this case, approximately 1900 to 2000 F. It is also important to note that the afterburner effect created in the chamber 37 assures that there is complete combustion of the exhaust gases from the turbine 25 so that the gases supplied to the blowcap 20 comprise non-combustible or completely burned constituents.

To control the amount of gas delivered from the chamber 37 to the blowcap 20, a vent 60 is formed in the upper wall of the chamber and is provided with a slidable cover 61. An adjusting screw 62, anchored to the upper wall of the chamber 37, adjustably controls the position of the cover 61, so that by rotating the screw the extent of the opening in the chamber can be adjusted. A duct 63 extends from the opening 60 to the duct 47. It will be appreciated that upon sliding the cover 61 to the left in the drawing, the opening 60 is enlarged so as to vent greater quantities of gas from the chamber 37 and thus reduce the amount of gas supplied to the blowcap 20. By closing the opening 60, all of the gas passing through the chamber 37 is delivered to the blowcap 20.

Pursuant to a further aspect of the invention, the blowcap 20 is a vacuum V type having an orifice adjustable in size so as to provide a final control of the velocity of the gas blast which impinges on the molten material being fiberized. In the illustrated arrangement, the blowcap 20 is provided with eight adjacent V-shaped orifices each defined by the space between a downwardly extending V-shaped projection 71 and the upper surface of a plate 72 which has notches 73 conforming to and alined with the projections 71. The plate 72 is slidably mounted on the front of the blowcap 20 and adjusting screws 74 are provided for varying the vertical position of the plate 72 and thus controlling the width of the orifices 70.

Each of the projections 71 are hollowed out at 75 back from the plane of the outer face of the blowcap so that the streams 22, one falling in front of each of the projections 71, are held back by the vacuum effect developed in the hollowed portions 75 by the blasts of hot air emerging from the orifices 70.

As observed above, the plurality of spillways 23 are disposed above the blowcap 20 so that one stream 22 falls adjacent each of the hollowed out portions 75 and thus each stream 22 is subjected to a V-shaped blast of hot gas from one of the orifices 70. To minimize the effect that each one of the blasts might have on the adjacent streams, a plurality of shroud plates 76 are vertically positioned in forwardly extending relation between the adjacent projections 71.

It will be appreciated that the streams 22 of molten material are stripped and fiberized only by the uppermost layers of hot gas projected through the orifices 70 so that lowering the plate 72 affects the fiberization operation primarily by increasing the aperture through which the hot gases escape from the chamber 37 and thus decreasing the velocity of those gases. By vertically positioning the plate 72, it is therefore possible to obtain precise control of the velocity of the stripping gases at the blowcap 20 and thus the most effective velocity compatible with continuous filament formation speed for stripping the particular melt being worked upon can be easily selected and maintained.

Lowering of the plate 72 does however, also create a layer of hot gases underlying the fibers 24 as they are stripped from the melt which tends to carry the fibers forwardly from the blowcap and promote their elongation. Preferably, the fibers 24 are directed through a hood 80 into a chamber 81 that is heated by directing the vented gases from the duct 47 into the chamber through an opening 82. The hood 80 and the chamber 81 have the effect of containing the hot gases from the blowcap so as to keep the newly formed fibers 24 in a hot gaseous environment. In the embodiment illustrated, the gases within the hood 81 have a temperature of approximately 1500 F.

As a result of this construction and mode of operation, it will be seen that the melt in the streams 22 and the newly formed fibers 24 are not subject to any sudden cooling action. Rather, the molten material is only gradually brought through its incipient solidification temperature so that the fibers being formed are substantially more stress free than those produced by previous high volume production methods.

If desired, a fiber coating material to act as a binder or to waterproof the fibers may be added by driving the material in spray form onto the fibers as they are formed. In the illustrated apparatus, fiber coating is accomplished by positioning a coating material tank 85 approximately above the blowcap 2i) and by driving the material from the tank 85 through a nozzle 87 by means of air pressure from a line 86. The effect of the air pressure on the coating material is to atomize the material and smoothly disperse it about the fibers 24 as they are stripped. The heat of the gas blast issuing from the blowcap 20 and the heated chamber 81 serve to cure the coating material on the fibers as the fibers pass through the chamber 81. Preferably, a belt form of conveyor receives the fibers 24 and transports them through the curing chamber 81.

As a feature of this aspect of the invention, the coating material added through the nozzle 87 can be a thermosetting plastic so that, with reference to FIG. 6, resulting fibers or filaments 111, 111a will have a uniform coating 112, 112a of thermosetting material that is partially cured by the heat in the chamber 81. Upon knitting or weaving the coated fibers 111, 111a into an interlocking pattern, as suggested in FIG. 7, a further heat treatment will result in final curing and setting up of the coating material to produce resilient sheaths 11% and 1120 which give the inter-locked fibers a permanent set tending to resist unraveling of the fibrous filaments. In this Way, otherwise smooth fibers can be knitted or woven into fabrics that will resist running upon the breaking of one or two filaments.

In the modification illustrated in FIG. 4, characteristics of the fiberizing blast are controlled by delivering compressed air to the combustion chamber through lines 103a which are provided with control valves.

The modification shown in FIG. employs, in lieu of a gas turbine, a source 88 of compressed air and a tank 99 containing an inflammable gas such as propane. The compressed air is led into a compression chamber 100 through lines including a control valve 10311 and a pressure regulator 105a. The fuel gas is directed to the combustion chamber 100 through control valves 104a and 104b, a pressure regulator 106a and a safety check valve 109. Preferably, combustion is insured in the chamber 100 by a high temperature spark plug 101 which is kept continuously arcing under power received from a high voltage alternating current transformer 102. Spark plugs for this purpose are well known and normally operate at 10,000 to 20,000 volts.

An afterburner chamber 110 is provided to insure complete combustion and both compressed air and inflammable gas are selectively directed to the afterburner chamber through suitable control valves and pressure regulators 10512 and 10612. A bleed or escapement pipe 107 preferably opens from the afterburner 110 to provide control of the gas velocity'issuing through the blowcap 108.

It is desirable that the compressed air regulator 108 maintain the air supply at a pressure higher than the pressure in the combustion chamber 100, but lower than the gas pressure maintained by the gas pressure regulator 106a. This relationship prevents choking ofl? of the gas supply. Accidental ignited gas backup is positively prevented by the check valve 109.

It is particularly important to appreciate that the apparatus described above, both in the form shown in FIGS. 1 to 3 and in FIGS. 4 and 5, permits exacting control of a number of factors which are critical to the efiicient production of desirable fiber. The several temperature controls permit adjustment of the blast temperature to approximately that of the incipient solidification temperature of the material being fiberized; for the reasons already set forth in detail above. The several controls affecting the velocity of the blast emitting from the blowcap permits the obtaining of a blast velocity compatible, and usually slightly below, the continuous attenuation rate associated with the viscosity of the material being fiberized. This results in long, virtually continuous filaments being formed. Also, the controls which permit regulation of the gas volume constituting the fiberizing blast allow adjustment of the forces exerted against the material being fiberized; both the vacuum created holding force and the force serving to strip the material into filaments. Finally, the viscosity of the material being fiberized is controllable consistent with the nature of the material by adjusting the heat and feeding rate of the material as it is directed into the fiberizing blast.

I claim as my invention:

1. An apparatus for fiberizing a stream of molten material comprising, in combination, a blowmember having an orifice, a spillway for directing a stream of molten material in front of said orifice, means defining a chamber behind said blowmember, a gas turbine alined with said chamber for delivering hot burned gases to said chamber, means for adjusting the temperature of said gases at said blowmember to a point substantially equal to the incipient solidification temperature of said material, and an adjustable opening in said chamber for venting a portion of said gases from said chamber so that the discharge velocity of said gases from said orifice is such to smoothly strip said stream into elongated fibers.

2. An apparatus for fiberizing a stream of molten material comprising, in combination, a blowcap having an orifice, a spillway for directing a falling stream of molten material in front of said orifice, means defining a chamber behind said blowcap, a gas turbine preceding said chamber for delivering hot burned gases to said chamber, means interposed between said turbine and said chamber for funneling selected amounts of gas from said turbine into said chamber, means for adjusting the temperature of said gases at said blowcap to a point substantially equal to the incipient solidification temperature of said material, and means for venting a portion of said gases from said chamber so that the discharge velocity of said gases from said orifice is such to smoothly strip said stream into elongated fibers.

3. An apparatus for fiberizing a stream of molten material comprising, in combination, a vacuum V blowcap having an orifice, :a spillway for directing a falling stream of molten material in front of said orifice, means defining a chamber behind said blowcap, a gas turbine adjacent said chamber for delivering gases to said chamber, means for adjusting the temperature of said gases at said blowcap to a point substantially equal to the incipient solidification temperature of said material, an adjustable opening in said chamber for venting a portion of said gases from said chamber so that the discharge velocity of said gases from said orifice is such to smoothly strip said stream into elongated fibers, means for applying heat cur able coating material onto said fibers as they are stripped, and a duct for transferring said vented gases to said fibers so as to facilitate curing of said coating material.

4. An apparatus for fiberizing a stream of molten material comprising, in combination, a blowmember having an orifice, a spillway for directing a stream of molten material in front of said orifice, means defining a chamber behind said blowmember, a device for burning fuel so as to generate hot combustion gases, said device being prior to said chamber so as to deliver said gases to said chamber, an afterburner for assuring complete combustion of the constituents of said hot gases and for adjusting the temperature of said gases at said blowmember to a point sub- 'stantially equal to the incipient solidification temperature of said material, and an adjustable opening in said chamber for venting a portion of said gases from said chamber so that the discharge velocity of said gases from said orifice is such to smoothly strip said stream into elongated fibers.

5. An apparatus for fiberizing a stream of molten ma 7 terialscornprising, in combination, a member having a plurality of vacuum V orifices, spillways for directing a fall ing stream of molten material in front of each of said orifices, means defining a chamber behind said blowcap, a device for burning fuel so as to generate hot combustion gases, said device being alined with said chamber so as to deliver said gases to said chamber, an afterburner for assuring complete combustion of the constituents of said hot gases and for adjusting the temperature of said gases at said blowcap to a point substantially equal to the incipient solidification temperature of said material, and means for venting a portion of said gases from said chamber so that the discharge velocity of said gases from said orifices is such to smoothly strip said streams into elongated fibers.

6. An apparatus for fiberizing a stream of molten material comprising, in combination, a blowcap having an orifice, a spillway for directing a falling stream of molten material in front of said orifice, means defining a chamber behind said blowcap, a device for burning fuel so as to generate hot gases, said device being prior to said chamber so as to deliver said gases to said chamber, an afterburner for assuring complete combustion of the constituents of said hot gases and for adjusting the temperature of said gases at said blowcap to a point substantially equal to the incipient solidification temperature of said material, and an adjustable opening in said chamber for venting a portion of said gases from said chamber so that the discharge velocity of said gases from said orifice is such to smoothly strip said stream into elongated fibers, means for applying a spray of heat curable coating material onto said fibers as they are stripped, and a duct for transferring said vented gases to said formed fibers so as to facilitate curing of said coating material.

7. An apparatus for fiberizing a stream of molten material comprising, in combination, a body having an outer face, said face having an orifice with a V-shaped projection extending downwardly from the upper edge of said orifice, said projection being hollowed out back from the plane of said outer face above its V-shaped edges, a plate adjustably mounted on said body for movement across said orifice toward and away from said projection, said plate having a V-shaped notch conforming to and alined with said projections, a spillway for directing a stream of molten material in front of said V-shaped projection, means defining a chamber behind said blowcap, means prior to said chamber for delivering hot gases to said chamber, means for adjusting the temperature of said gases at said body to a point substantially equal to the incipient solidification temperature of said material, and means for venting a portion of said gases from said chamber so that the discharge velocity of said gases from said orifice is such to smoothly strip said stream into elongated fibers.

8. An apparatus for making filaments from a stream of plastic material comprising, in combination, a blowmember having an orifice, a spillway for directing the stream across said orifice, means defining a chamber behind said blowmember, a gas turbine prior to said chamber for delivering hot burned gases to said chamber, means for adjusting the temperature of said gases at said blowmember to a point substantially equal to the incipient solidification temperature of said material, and means for adjusting the discharge velocity of said gases from such orifice to smoothly strip substantially all of said stream into continuous filaments.

9. An apparatus for making filaments from a stream of plastic material comprising, in combination, a blowmember having an orifice, a spillway for directing the stream across said orifice, means defining a chamber behind said blowmember, a gas turbine prior to said chamber for delivering hot burned gases to said chamber, an afterburner for adjusting the temperatureof said gases at said blowmember to a point substantially equal to the incipient solidification temperature of said material and means for adjusting the discharge velocity of said gases from said orifice to smoothly strip substantially all of said stream into continuous filaments.

10. An apparatus for making filaments from a stream of molten material comprising, in combination, a blowmember having an orifice, a spillway for directing the stream of material in front of said orifice and into the path of a gaseous blast from said orifice, means defining a chamber preceding said blowmember, a gas turbine prior to said chamber for delivering hot gases to said chamber, means for controlling the pressure of said hot gases received by said chamber, means for adjusting the temperature of said gaseous blast to a point substantially equal to the filament stripping temperature of the stream, and means for adjusting the discharge velocity of said gaseous blast from said orifice to smoothly strip substantially all of the stream into continuous filaments.

11. An apparatus for making filaments from a stream of plastic material comprising, in combination, a vacuum V blowmember having an orifice emitting a gas blast, at spillway for directing the stream across said orifice, means defining a chamber behind said blowmember, a device for burning fuel prior to said chamber for delivering hot burned gases to said chamber, means for adjusting the temperature of said gas blast to establish linear filament stripping from the stream simultaneously with the incipient solidification of the filaments as they arev formed, means for varying the pressure in the chamber so that the discharge velocity is compatible with the viscosity of the material as the filament is being stripped to sustain the formation of substantially all of the material of the stream into continuous linear filaments, and means for applying a coating material to said filaments as they are stripped.

12.. An apparatus for making filaments from a stream of plastic material comprising, in combination, a vacuum V blowmember having an orifice emitting a gas blast, a spillway for directing the stream across said orifice, means defining a chamber behind said blowmember, a device for burning fuel prior to said chamber for delivering hot burned gases to said chamber, means for adjusting the temperature of said gas blast to establish linear filament stripping from the stream simultaneously with the incipient solidification of the filaments as they are formed, means for varying the pressure in the chamber so that the discharge velocity is compatible with the viscosity of the material as the filament is being stripped to sustain the formation of substantially all of the material of the stream into continuous linear filaments, and means including a variation of the blast orifice area for adjusting the discharge velocity of said gases from said orifice to smoothly strip substantially all of said stream into continuous filaments.

References Cited by the Examiner UNITED STATES PATENTS 1,765,026 6/1930 Miller -3 2,376,043 5/ 1945 Freeman et a1 18-25 2,554,486 5/1951 Austin 65-5 3,015,127 1/1962 Stalego 18-2.5 3,065,614 11/1962 Lebino 65-16 3,138,444 6/1964 Searight et al 65-21 DONALL H. SYLVESTER, Primary Examiner.

R. L. LINDSAY, Assistant Examiner,