US2450492A - Removable screen structure for rotary beater mills - Google Patents

Description

Oct. 5, 1948. ,R.'w. STEVENSON 2,450,492 REMOVABLE SCREEN STRUCTURE FOR ROTARY BEATER MILLS Filed May 20, 1944 2 Sheets-Sheet 1 Elly-6' INVENTOR; QoaERT W jTEVENfiQN,

2G I AT-T'Y Oct, 5, 19 48.

R. W. STEVENSON REMOVABLE SCREEN STRUCTURE FOR ROTARY BEATER MILLS Filed May 20, 1944 '2 Sheet'sSheet 2 INVENTOR; -=1 ROBERT W. STEVENSON,

ATT'Y Patented Oct. 5, 1948 REMOVABLE SCREEN STRUCTURE FOR ROTARY HEATER MILLS Robert W. Stevenson, Columbus, Ohio, assignor,

by mesne assignments, to The Jeffrey ManufaoturingCoinpany, a corporation of Ohio ApplicationMay20,,1944, Serial No. 536,544

8 Claims.

This invention relates to a crusher, and an object of the invention is to provide an improved crusher capable of efliciently reducing substan-' tially any friable material.

A further object of the invention is to provide a crusher in which all or portions of the crusher bar and screen segment are removable from the crusher housing for adjustment, inspection or repair.

Another object of the invention is to provide an improved crusher screen structure wherein cross screen bars are removable from their sup-' porting rack only when the rack is removed from the crusher housing and then by longitudinal movement of the cross screen bars transversely of the cross screen bar supporting members of the rack.

Other objects of the invention will appear here- I inafter, the novel features and combinations being set forth in the appended claims.

In the accompanying drawings,

Fig. 1 is a side elevational view of the crusher of my invention;

Fig. 2 is a side sectional elevational view of the crusher in which a modified form of screen and crusher bar arrangement is provided; I

Fig. 3 is a transverse elevational view, with parts in section, and showing the mounting of one of the sliding racks and screen bars carried thereby, and taken on the line 3-3 of Fig. 2, looking in the direction of the arrows;

Fig. 4 is a combination sectional and elevational view of thefront of the crusher;

Fig. 5 is a sectional view showing one of the I sliding racks and screen bars, with the barsadjusted to one of the alternate positions in accord-.

ance with one aspect of my invention;

Fig. 6 is a plan view of a detail; and Fig. 7 is an elevational view of a supporting plate that forms a part of one of the sliding racks.

The crusher of my invention is generally designated as a primary crusher and in one physical embodiment thereof it is exceedingly large and is. 1

employed to crush metal tumings or scrap from a machine shop. The crusher, however, is adapted to crush most any friable material, including and side walls of said feed throat l2. The feed throat 12 leads to a central reducing chamber or zone l'l in which there is a rotor l5. The rotor ISinclude's a horizontal shaft it which extends through the opposite side walls of the housing or casing in and is supported in spaced bearings I! supported on integral standards on the-side L members of said housing or casing I0. I

Mounted on the shaft l6 and keyed thereto is a plurality of spaced discs [8 spaced apart by spacers l9 and tied together with cross bolts 20. Pivotally mounted near the peripheries of the discs I 8 is a plurality of swing hammers 2| which are pivoted on cross-rods 22 extending through aligned holes in the disc l8 and removably held therein by cotter keys. A pulley 23 is keyed to one end of the shaft It for driving it.

Extending transversely across the front and bottom of the throat, I2 is a heavy primary breaker bar 24 which is adjustably mounted by adjustable spacers in openings or holes in the two side plates of said housing I0. Removable bolts 25 (see Fig. 1) extend through the opposite ends of breaker bar 24 and associated spacers, as well as through the front plate of the housing 10, thereby removably and adjustably holding it in place. The breaker bar 24 may be adjusted toward and from the axis of rotation of the rotor I5 which, of course, is the axis of the shaft l'6.

Positioned below the rotor l5 and forming what is. in effect the bottom of the reducing chamber of rotation of the rotor l5, and its circumferential extent is slightly less than In view of the size of the machine the matter of adjusting, replacing and repairing individual bars is one of considerable consequence and I have provided a particular construction which make for ready and convenient inspection, repair and replacement thereof. To this end, the bar screen or cage 26 is made up of two separate units, the two units comprising two sliding racks 21 and 28. The two sliding racks 21 and 28 are slidable into and out of the housing or casing in from the front and rear, respectively. In Fig. 2 of the drawings the rack 21 is shown in its operative position and rack 28 is shown in its retracted position and is illustrated in dotted lines in its operative position.

Attention is now directed particularly to Figs. I

2 and 3 and'to one type of construction of rack 28. Said rack includes a pair of side plates 29 and 30 which are permanently connected together in spaced apart relation by three transversely extending bars 3 I, 32 and 33, the opposite ends of which are rigidly attached to said plates 29 and 30, as by welding.

Each f thezSiGG PIBItESxZQ andasfl isprovided:

with a series of rectangular openings whichlextend therethrough and have their inner edges formed tangent to a circle, the center of which is along the axis of rotation of the rotor when the rack 28 is in its operative position.- Extend? ing between the side plates 29 and 3flandinto each of said rectangular openings or,soolsetsais: an individual cross-bar 34, saidxcrosssbarslheln spaced apart to form a screen and beingfisufificiently rugged to co-operate With/the rotor l5 and particularly with the swing" hammers?! thereof to grind or break the friable material? being reduced.

Toprovide for ready adjustment of: the-radial.

distance between any selected bar 34 and the axis-of rotor l5,- theopposit endsofeach of the-- bars 34 are symmetrically. formed. and includeintegral. feet 3 5 (see Fig. 6 which .togethenwitn walls thereof fromsthereverse side andqthefltwo racks. cooperate to provide the complete bar screen 26. In addition; instead ofia crossbarol providea. cross channel 36 which is welded at ODPOSiterBIldS to: the-side-plates ofthe sliding. racle- 2:1. Alsoin place. of the-cross-ban 33 -1I;pr0- vide a heavier. and: generally square IOSSMbMJT: welded at opposite ends-to the side pla tesofathe:

slidingrack Z1. ,Crossohannel: 36;.,cro ss.-;bar-j31 and a bar which: corn-2spondswithdeal M rci-rack sliding rack 2-1 is.in its operative positiorn Plate 38. is'rigidly. connected Withside plates 29.,and-3D through crosschannel 35', cross-bar 3,1 and thecorner bar which. corresponds with ,cornerbar 32 of rack 28. Adjacentitsinner circular. edge,-

supporting plate 38. is fc'irmedto.v include aserles of reetangular..openings or notches which are in alignment with. theialigned rectangular openings inside plates 29- and 3.0"and these openings cooperate with those of the. side plates to support andprevent. rotationof thetcross-hars 34 when the bars are positioned in the rack21.

Tl'iesliding racks 2'1. and .23. ar slidably mounted on. individual pairs ctr-ails, therails for slidin rack 2! being, seen at 38, andtherails for sliding rack 2T8. being. seen.at40.v Thestructure. of the spaced rails. 40" is'clear1y. illustrated in Fig. dot the drawings and each includes atopv angle 41' with an upwardly extending, flang on the outside and with a horizontal flange'supporting a side member 29 or 30,215 thecase may be. Each angl'e4 'l is supported onandlweld'ed t'o a square rod 42 which in turn is welded to a bottom plate 43 preferably attached by anchor bolts 44 to a plate or framework which may be the concrete base which supports the complete crusher. The rails 39 are of similar construction.

Said rails 39 and 40 both terminate adjacent the.ce sing,v HI. Within the casing or; housing I!) thelsliding racks 21" and 28 are supported on casing bottom plates 45 (see Fig. 4) which extend both inwardly and outwardly of the side plates of saidhopsing Hi. It is, of course, obvious that the ihnerESidQS of the side plates of the housing It] form spaced opposed abutments that guide the racks 2-1-and28and their associated crossa -unit within said housing and hold their proper: positions laterally, as clearly illustrated in. Fig. 4,0f the drawings. It is to be particularly noted-that the cross-bars 34 are held age-instz,-l ongitudinal or endwise movement, that is, transverse movement with respect to the end members. 29 ,and .31) of racks: 21 andv 2 8 onl when erackszfliandz'a are .within the housing I u and then. only by the spaced opposed abutments formed by the walls of: the housing which. lie

adjacentv theaend membersv 29 and 30 and the endstorlthe cross-bars 3.4. I

To. hold the sliding rack 21 in position within thecasingpr housing), as illustrated in Fig. 2.

of the drawings, and to prevent forward move.- mentathereof. while at. the same time providing for the forwardv sliding movement thereof on railsia the sliding rackl'l is provided withv a frontplat'eAE which actsas aclosure for afront bottomaopeningin. the casing I 0 and is removabl'y. attached to. said casing. ID by removable bolts fllsee. Fig. 1), Obviously by removing the bolts 4l'th'e rack 21 and attached plate 46 may be slid forwardly in drawer-like manner on the rails until rack .21 is entirely outside the housing or casing).

To provide for this sliding of the plate 46 the bottoms lthereofkare notched to clear the rails 39'; and laterally spaced'anchorages. or handlesifi.

are provided, to Whicha block and tackle, tractor, truck, or other pulling device. may be attached. Upon remoValLof'rack 21"the bars 34 arereadily aco5ible for: adjustment, as for example, by u-rningthem' over inspection or removal. To remove theba'rs 34 after the rack 21 is slid for- Wafrd'outsidethe casing Iii, it is. only necessary to slide them axiall of themselves or, in other words, transversely of the side plates of said rack 21. After the bars 34 have. been adjusted, in.- spected, or replaced, the complete rack 2! with the/bars 34 in place may be slid to the full line position illustrated in Fig. 2, and the closure plate 46 bolted rigidly by bolts 41.

The removability; of the "sliding rack 28 is generally the same, except for certain differences which shall now zbepointed out. The rails 39 are generally left inposition. However, the rails 40 arepn'ormally. removed .and the. tie bolts 44 normallyanchor the bottom of a tramp material bin 48'which sis-a part of thehousing I0. Under certaincondltions thetramp material bin 48 maybe eliminatedland rails ill left in place, in which case a plate, similar .to .plate46, will be attached at the rear of the-casing 10 to close it and also. hold the sliding rack 28 in place. In the preferred embodiment, however, the tramp material bin 48 is employed. This bin, as above stated, is to the rear of the mainportion of the housing l0, and adiaoentthetoprear portion is provided with a pivoted inspection door 49.

Alsoacross the top of the tramp material bin- 48 is a pivoted deflector plate 50 pivoted at its of said bin 48. The lower end of the deflector plate 50 is provided with attaching lugs 5-2 on opposite ends thereof, which are adapted to be attached by removable bolts to any one'of a plurality of holes 53 in the side plates of the bin 48 positioned on the arc of a circle, the center of which is the pivot point of the plate 50. As illustrated in Fig. 1 of the drawings, cover and reinforcing plates 54 are attached to the side plates of the bin 48 through which the holes 53 extend so as to reinforce the support for the bottom of said deflector plate 58 and to cover holes 53 not occupied by bolts. Plate 54 has a series of holes complementary to the holes 53, but only one of each is in alignment at one time. Sliding of plate 54 brings desired ones into alignment, all other holes 53 being effectively closed by plate 54.

When the sliding rack 28 is in its operating position or the dotted line position of Fig. 2, it is held in place by an upstanding plate or partition 55 which extends laterally between the side platesof the housing l and forms the rear bottom portion ofsaid housing Ill and the forward wall of the bottom portion of the tramp material bin 48. This plate 55 is held loosely and remov-- ably in place by bolts 51 (see Fig. 1), which also attach the bottom portion of the bin 48 to the main side plates of the housing or casing l0.

To remove the sliding rack 28, the bolts 51 and anchor bolts 44 are disconnected and the complete tramp bin 48 is removed. Plate 55 is then removed. Rails 40 are then attached to the anchor bolts 44, and the sliding rack 28 is slid in drawer-like manner rearwardly over said rails 48, thus providing for inspection, adjustment or re newal of the screen bars 34. Attention is now directed particularly to certain important characteristics of the sliding racks 21 and 28 and associated cross-bars 34. As illustrated in Fig. 2 of the drawings, the bars 34 are spaced apart circumferentially to provide a screening function so that when material is reduced sufiiciently to pass between adjacent bars, it can freely do so and be discharged to the open bottom of the housing l0 and through a discharge opening 58 formed in a supporting base 53 which may be of concrete.

The bars 34 also co-operate with swing hammers 2| to reduce or grind the material, following the first reducing action which takes place by the hammers 2| striking the material in the throat l2 and impelling it against the breaker plates [3. The very heavy primary breaker bar 24 also co-operates with the swing hammers 2| to effect some of the initial breaking, and it is subjected to very severe loads and thus-is called upon to perform exceedingly heavy service. That is the reason'for its large size as compared with the screen bars 34.

The bars 34 in the rack 21 may be'all turned 180, in which case the feet 35 on the ends there" of will extend inwardly toward the axis of the rotor l rather than outwardly, in which case the bars 34 will be spaced apart from the circle generated by the ends of the swing hammers 21, a greater distance as determined by the thickness of the feet 35. Another alternate arrangement of the bars 3d in the rack 21 is illustrated in Fig. 5 of the draw ings, in which case the bars 34 are in staggered relation radially; that is, every other bar 34 is at a different radial distance from the axis of the concentric circles as to which they aretangent. As illustrated in Fig. 5 of the drawings,

the first, third and fifth bars 84 are tangent to a circle of greater diameter than the second and fourth bars. This provides for an appreciably increased grinding action by the bars 34 during travel of the swing hammers 2! over the bottom forward quadrant of rotation of rotor l5.

Also, as illustrated by arrows in the lower portion of Fig. 2 of the drawings, it will be noted that the radius of the circle as to which the working surfaces of the bars 34 of sliding rack 28 are tangent, has a greater diameter than the concentric circle as to which the working surfaces of the'bars 34 of rack 2l'are tangent. This arrangement may be employed where the principal grinding action is to take place in the forward lower quadrant of the reducing zone, with the rearward lower quadrant acting more as a screen than as a reducing'sectio'n; Under some conditions, the sliding rack 28 and all the bars may be completely removed and the material allowed to discharge freely through the bottom of the casing l0 over the rear lower quadrant.

There is another difference between the sliding racks 21 and 28 which is of significance. As previously pointed'out, the bar 31 which connects the side members of rack 21 as well as intermediate member 38 thereof, is considerably heavier tha'n the cross-bar 33 of rack 28. By virtue of this heavy construction of bar 31, it may be employed to aid in supporting the bar 34 directly across from it, and this is frequently desirable, particularly where said bar 34 across from it is the last reducing bar in the lower forward quadrantof the reducing chamber I4, since such last bar always takes a heavier load than the other bars. This reinforcement may be effected by placing intermediate feet on the bar 34 or by providing a reinforcing bar which fills the space between the bar 34 and the bar 31. Of course, if the bar 34 is rotated 180 from the position illustrated, the bottom thereof then will lie fiat on the top of the bar 31 and be reinforced.

It may also be mentioned that the plane of severance between thesliding racks 21 and 28.

as illustrated in Fig. 2 of the drawings, i along a vertical plane passing through the axis of rotation of rotor l5, and the two inner ends of the racks 2'! and 28 abut each other, thus co-operating to maintain themselves in proper position.

A slightly different arrangement of the bars 34 and slide racks' is illustrated in Fig. 1 of the drawings. Here all of the screen bar 34 are tangent to the same circle, the center of which is along the axis of shaft l6 so that substantially the entire area of the bar screen 26 acts as both a reducing member and screen member. Also in this arrangement, the split between the two sliding racks 21 and 28 is not vertical but is along a radial line 50.

In addition to the breaker bars and rack bars previously mentioned, in the upper rear quadrant of the reducing chamber 14 and what constitutes entrance to 'the tramp material bin 48, I

'preferably'provide a pair of adjustable breaker bars 6| and 62 adjustably mounted in the side plates of the casing or housing H]. In addition, there is' also a transverse breaker bar 63 provided at the rear portion of the casing l8 and substantially opposite the primary breaker bar 24. Breaker bar 53 is mounted in the side plates of the'casing Ill and 'is provided with adjusting shims, as clearly illustrated in Figs. 1 and Zof the drawings.

'- Also' in the up'per'rear portion of the casing I ll 'isi'a'n adjustable trampmaterial deflector plate smprovided. with upwardly extending, end flanges which are bolted by removable boltsextendingthrough selected onesof'a plurality of holes in the side plates of said casing l covered byout-- side cover plates 65 (see Fig. 1) The? deflector plate 64 extends in a" horizontal or nearlyhorizontal position but may be inclined upwardly and rearwardly.

In the operation of the machine, friable ma-- terial, such as-stone, coal, metal turnings, orany other ofa wide variety'of materials-which can be broken down by a crusher, will be fed through the throat l2 from the hopper l-l; 'I'herotor: [5 will be rotated in-the' direction indicated by the arrow, and the swing hammers 2| will strike the material-as it comes down through the throat and in effect support the materialinafloating. condition, breaking. or chopping the bottom thereof and disintegrating it at leastiir part and throwing it against the breaker plate l13'. This, ofcourse, will produce additional breaking'down of the material.v The swing hammers 21' will also-co-operate with the primary breaker bar 2 1 tobreak down material further and this breaking action will continue together with what is more in the nature of a grinding action, in connectionwith the breaker or screen bars 34 of'the sliding rack 2'! which are within the lower forward quadrant of the reducing zone or chamber l4. If the bars 34' are in the staggered relation as illustrated in Fig. 5, there will be a greater breaking and less grinding action in this zone. Simultaneously with this breaking action, the spacing of the bar 3-4 provides a screening. action and the material which is sufiiciently reduced will pass through the spaces between-the bars 34 and downwardly out the open bottom of the casing, l0 and through the'discha rge opening5'8; As the material reaches the lower rear quadrant of the reducing chamber N, there will be an expansion of said chamber'by virtue of" the greater radial distances oi thebars 34 and consequently there will be less breaking, action and more screening" action through thi zone.

Tramp material which passes through. the reducing'zone will be thrown by the'rotor l 5 against the first deflector plate 64-which will deflect it toward the second deflector plate 50 which in turn will deflect it to the bottom of. the tramp material bin 48. The deflector plates 64 and 50 may be adjusted in their angular relations, depending upon the materialbeing. treated, so as to provide for a proper guiding ofisaid tramp material into the material" bin 48. Any particlesv of" reduced material which reach the upper rear zone of the reducing, chamber I' lv will be reduced. by the'cross-bars Bl and'GZand, of course,.the crossbar 63 will also aid in reducingmaterial which strikes it.

As previously suggested, one of the important considerable size and consequently eventhe bars 34 are. of such weight that itis very difficult for a man to lift them. Purely by way of example, one crusher is almost eight feet from the'foundation to the top of the throat l2. Itis to be As above mentioned,- in oneembodiment of my invention, the crusher lsof understood; however, that thefeatures: of myxinvention may be employed with crushers of an size.

Obviously those skilled .in the art may make various changes in the details and arrangement of parts without departing from the spirit and scope of the invention as defined by the claims hereto appended, and I therefore wish not to be restricted'to the precise construction herein.

disclosed.

Having thus described and shown anembodimentof my invention, what I desire to secure by Letters Patent of the United States is:

1. In a-crusher, a housing, a rotor in saidhousing, an adjustable screen in said housing adaptedv to co-operate with said rotor for crushing, and grinding material fed into the crusher including,-

a plurality of. cross screen bars having ofiset symmetrical ends, a rack supporting the said cross screen bars slidable into and out of the housing in a drawer-like manner including a pair of spaced interconnected end members having pairs of, aligned symmetrical openings extending therethrough, each pair of aligned symmetrical'openings receiving the offset ends of one of said cross screen bars whereby the rack and cross screen bars are slidably removable from said housing asa unit and thecross screen bars individually removable and rotatably positionable within the aligned symmetrical openings in said rack to provide for the adjustment of the cross screen bars relative to the rotor, said cross screen bars being.

removable from said rack by movement transverse of said rack end members.

2. In a crusher, a housing having side walls forming spaced opposed abutments, a rotoriin said. housing, an adjustable screen in said housing adapted to co-operate with saidrotor for crushing and grinding material fed into the crusher including a plurality of cross screen bars extending within said housing between said opposed abut-- ments and having offset symmetrical ends, the said abutments being adapted to arrest endwise movement of said cross screen bars, and arack supporting said cross screen bars slidable into and cross screen bars relative to the rotor, saidcross:

screen bars bein removable from said rack by movement transverse of said rack end members.-

3. In a crusher, a housing, a rotor in said housing, a screen in said housing adapted to co-operate with said rotor for crushing and grinding material fed into the crusher including a plurality of cross screen bars having symmetrical ends, a

racksupporting said cross screen bars slida'ble into and out of the housing in a drawer-likemanner includinga pair of spaced interconnected end members having pairs of aligned symmetrical.

openings extending therethrough, each pair of aligned symmetrical openings receiving the ends of one of said cross screen bars whereby the rack and cross screen bars are slidably removable .fromsaid housing as a unit and the cross bars individually removable and rotatably positionable 9 7 within the aligned openings in said rack only b movement transverse of said rack end members.

4. In a crusher, a housing having side Walls forming spaced opposed abutments, a rotor in said housing, a screen in said housing adapted to co-operate with said rotor for crushing and grinding material fed into the crusher including a plurality of cross screen bars extending within said housing between said spaced opposed abutments, said abutments being adapted to arrest endwise movement of said cross screen bars, and a rack supporting said cross screen bars slidable into and out of said housing from between said abutments, said rack including a pair of spaced interconnected end members having pairs of aligned openings extending therethrough, each pair of aligned openings receiving the ends of one of said cross screen bars whereby the rack and cross screen bars are slidably removable from said housing as a unit and the cross screen bars are individually removable from said aligned openings in said rack by movement transverse of said rack end members.

5. In an adjustable bar screen assembly adapted to co-operate with the rotor of a crusher, a rack including a pair of spacedend plates, means interconnecting said end lates, said end plates having a plurality of rectangular openings formed therein substantially upon the arc of a circle, the openings in each end plate aligning with corresponding openings in the other end plate, and a plurality of screen bars each having rectangular offset end portions adapted to be received by said rectangular openings in said end plates, the screen bars being removable from said rack only by longitudinal movement thereof transverse of said end plates and being rotatably replaceable therein for adjustment of the screen.

6. A rack adapted to carry cross screen bars of a crusher screen having rectangular bearing sections including a pair of spaced end plates, means permanently interconnecting said end plates, said end plates each having a plurality of rectangular openings formed therein and lying substantially upon the arc of a circle, the openings in each end plate aligning with corresponding openings in the other end plate for receiving rectangular end bearing sections of cross screen bars, and a member spaced between said end plates and interconnected therewith having rectangular openings therein aligned with said aligned openings in the end plates for receiving other rectangular bearing portions of said cross screen bars whereby the cross screen bars carried by said rack are removable therefrom by endwise movement transverse of said end plates.

7. A rack adapted to carry cross screen bars of a crusher screen having bearing sections including a pair of spaced end plates, means permanently interconnecting said end plates, said end plates each having a plurality of openings formed therein and lying substantially upon the arc of a circle, the openings in each end plate aligning screen bars, and a member spaced between said end plates and interconnected therewith having openings therein aligned with said aligned openings in the end plates for receiving other bearing portions of said cross screen bars whereby the cross screen bars carried by said rack are removable therefrom by endwise movement transverse of said end plates.

8. A rack adapted to carry cross screen bars of a crusher screen having rectangular end bearing portions including a pair of spaced end plates, means permanently interconnecting said end plates, said end plates each having a plurality of rectangular openings formed therein substantially upon the arc of a circle, the openings in each end plate aligning with corresponding openings in the other end plate for receiving the rectangular end bearing portions of cross section bars whereby the cross screen bars carried by said rack are removable therefrom by endwise movement transverse of said end plates.

ROBERT W. STEVENSON.

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

UNITED STATES PATENTS Number Name Date 183,653 Douglas et al Oct. 24, 1876 204,849 Sherwin June 11, 1878 604,283 Albrecht May 17, 1898 625,212 Straker May 16, 1899 757,969 Schoellhorn Apr. 19, 1904 758,288 Williams Apr. 26, 1904 806,383 Williams Dec. 5, 1905 811,679 Williams Feb. 6, 1906 842,430 Simpson J an, 29, 1907 916,697 Gruendler Mar. 30, 1909 1,182,575 Langevin May 9, 1916 1,185,620 Blum June 6, 1916 1,286,757 Patterson Dec. 3, 1918 1,427,842 Plaisted Sept. 5, 1922 1,424,923 Knittel Aug. 8, 1922 1,668,717 Bell Nov. 30, 1926 1,624,886 Borton Apr. 12, 1927 1,647,730 Hartman Nov. 1, 1927 1,691,951 Alfred Nov. 20, 1928 1,742,511 Kuntz Jan. 7, 1930 2,122,965 Swenson July 5, 1938 2,149,571 Battey Mar. 7, 1939 2,227,090 Hughes Dec. 31, 1940 2,253,733 Sheldon Aug. 26, 1941 2,298,712 Mank'off Oct. 13, 1942 2,411,302 Stine Nov. 19, 1946 FOREIGN PATENTS Number Country Date 142,396 Germany July 4, 1903 322,368 Germany June 28, 1920 193,985 Great Britain Mar. 6, 1923

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