US2514658A - Mechanically stoked incinerator with hinged stoker arms - Google Patents

Description

July 11, 1950 Filed Feb. 8, 1947 A. MAYER MECHANICALLY STOKED INCINERATOR WITH HINGED STOKER ARMS 5 Sheets-Sheet 1 INVENTOR. flgfasime flag 4v BY firm/ E) July 11, 1950 A. MAYER MECHANICALLY STOKED INCINERATOR WITH HINGED STOKER ARMS 5 Sheets-Sheet 2 Filed Feb. 8, i947 INVENTOR.

line/Ya I] BY Aqfm y W W 1950 A. MAYER 2,514,658

MECHANICALLY STOKED INCINERATOR WITH HINGED STOKER ARMS Filed Feb. 8 1947 5 Sheets-Sheet 3 HTTOPNEY A. MAYER MECHANICALLY STOKED INCINERATOR July 11, 1950 WITH HINGED STOKER ARMS 5 Sheets-Sheet 4 Filed Feb. 8, 1947 July 11, 1950 A. MAYER 2,514,658

MECHANICALLY STOKED INCINERATOR WITH HINGED STOKER ARMS Filed Feb. 8, 1947 5 Shee1; t 5

HTTO Y Patented July 11, 1950 MECHANICALLY STOKED INCINERATOR WITH HINGED STOKER ARMS Augustine Mayer, Jackson Heights, N. Y., as-

signor to Morse Boulger Destructor Company, New York, N. Y., a corporation of Delaware ApplicationFebruary s, 1947, Serial No. 727,413

8 Claims.

This invention relates to burning rubbish and other like waste material capable of being disposed of by incineration.

It is not uncommon to dispose of trash, garbage, waste paper and the like which is cast off by populated communities by burning this rubbish in a furnace. Furnaces for burning such rubbish are known wherein there is provided a stoker device so arranged as to mechanically stoke a pile of rubbish being burned in the furnace while causing a stream of air to pass through the rubbish serving to wholly or partially dry it while it is being burned and furnish secondary air for sustaining combustion. In the type of furnace referred to there is provided an annular hearth with a central opening through which extends a vertical shaft mounting a rotatable stoker which has arms extending outwardly to sweep over the hearth. The overlying pile of rubbish is stoked by the arms as they rotate and at the same time the arms move the rubbish outwardly onto a surrounding annular grate lying adjacent the hearth. Such combustible material as is not burned prior to the time it reaches the grate is ultimately burned on the grate and the ashes fall throrgh it into an ash pit. It is an object of this invention to provide improvements over the prior art devices.

In prior devices wherein a mechanical stoker having arms extending outwardly and adapted to sweep over the hearth as the stoker is rotated on its vertical axis is provided, there is a tendency for lumps or particles of rubbish to become lodged between the outwardly extending stoker arms and the underlying hearth. This sometimes results in forces exerted upwardly on the stoker tending to push it up out of its proper operating position. Also it puts an unwanted burden on the mechanism which drives the stoker. It is a further object of this invention to provide means to eliminate or at least to minimize the lodging of objects between the stoker arms and the hearth as the rotating arms sweep over the hearth.

To accomplish that desirable end and others which will become apparent in the more detailed description hereinafter set forth, there is provided a hearth which includes grooves or ridges in its surface extending in a direction so that particles of rubbish or objects lying adjacent the surface of the hearth are directed outwardly toward the periphery of the hearth as the stoker arms travel around in a circuitous path above the heath. Moreover, means are provided whereby the arms are attached to the stoker in Such a way as to permit them to have a limited vertical movement if an upwardly directed force is exerted on the arms as they sweep over the hearth, the purpose being to relieve the strain on the stoker mechanism which otherwise might result if the stoker arms were rigidly mounted and also to aid in the dislodgment of material causing the upwardly directed force.

Although the novel features which are believed to be characteristic of the invention will be pointed out in the annexed claims, the invention itself as to its objects and advantages and the manner in which it may be carried out may be better understood by reference to the following description taken in connection with the accompanying drawings forming a part hereof, in which:

Fig. l is a view in elevation in cross-section showing the general arrangement of a typical plant embodying the invention;

Fig. 2 is a section view-in elevation to larger scale showing the lower end of the furnace and more particularly the stoker mechanism, hearth and grate; n

Fig. 3 is a plan view partly in section on line 33 of Fig. 2;

Fig. 4 is a plan view partly in section, partly broken away on line 44 of Fig. 2;

- Fig. 5 is a partial view in section on line 5-5 of Fig. 4;

Fig. 6 is a partial plan view to larger scale and partly in section further illustrating the stoker and hearth arrangement, showing a hearth with spiral ridges and a stoker with hinged stoker arms; and

Fig. '7 is a view in elevation partly in section showing the hinged stoker arms.

Referring now to the drawings in which like reference characters indicate like parts, the plant as illustrated in Fig. 1 comprises a furnace A having a cylindrical side wall Ill, a roof II and an ash pit I2 in the form of a hopper, and a flue B connecting to a combustion chamber C. The combustion chamber connects with a flue D, in turn connected to a chimney (not shown). The furnace roof I l is provided with a charge port I 3 connected to a charge chute I 4 having an openable and closable charge gate l5 (shown conventionally). The ash pit has a discharge port connected to a discharge chute It provided with an openable and closable discharge gate l1 (shown conventionally) The lower end of the furnace is provided with an annular hearth E having a central opening through which extends a vertical shaft to rotate a stoker F having arms to sweep over the hearth and a tuyere head G. The hearth is surrounded by a grate H. An air heater J in the flue D is connected by a conduit H! which supplies air to the ash pit beneath the grate H and also to the stoker E and tuyere head G. The weight of the stoker Fand tuyre head G is carried on. steel structural members K, the ends of which are mounted in the walls of the furnace. understood the furnace is provided with such complement of doors I9 as maybe desired.

The annular hearth E is supported. lower part of the firebox on radially extending T bars 2 I. The outer ends of the T'barsaresupported; in the side wall of the furnace- The: walls of he. furnace are built of brick 22 and encased within a steel shell 22a. Better insulation is provided by:

additional insulation material 23. The inner ends. of the T bars 2| are supported on brackets 24 (see Fig, 2) secured to a stationary cylindrical casting 25 which in turn is carried upon structural members, designated generally by reference character K. These structural members, described in further detail hereinafter, extend across the ash pit and are suitably supported in the walls or the furnace.

The hearth E is made up of a plurality of com"- plementary cast sectors (see Figs. 3 and 6)-. When the sectors 39 are in place they form with the: top of webs 3| of the T bars 24 the annular hearth E having a central opening 32 (See-Fig. 2). The top surface of each sector 36 is provided with raised; spiral ribs 33 and the top surface 3t of the horizontal webs of the T bars at their inner ends is provided with complementary raised rib portions 33a. Accordingly, when the hearth sectors 30 are in place on the T bars 2|, the annular hearth has on its surface a continuous series of circumferentially spaced raised ribs running spirally from the central opening 32 to the peiriphery of the hearth; or, to state it another way, a series of circumferentiallyspaced spiral grooves ends by a bearing support 38a; The grate bars i extend through the wall of the-'furnace'and are provided with rocker arms 39 so that they may be rotated on their long axes. Each gr-ate sector 34 is provided with square holes 40 along one side and the grate barintermediate its ends i'ssquare and extends through the-square holes (see Fig. 6). Hence, the grate sectors are keyed to the grate bars, thus providing hinged grate sectors which may be operated from outside the furnace to dump ashes. It maybe noted that theTxbars 2 I are provided with outwardly extending flanges 4| running along the bottom, upon which t mount the hearth sectors 30'.

The stoker F and tuyre headG are carried on structural members K' (see Figs. 1, 2 and 4).. As shown, these structural members are made up-ol"; channel irons forming a pair'of hollow box beams 42 and 43 reinforced intermediate their ends by additional lengths of channels 44, 45, 46 and. Box beam 42 comprises channels Q8 and 49' and box beam 43 comprises channels-Wand 5|. The

, abutting edges of the channels formingthe box beams 42 and 63 are welded and thus the box beams provide, air conduits, for. apurpose to. be explained. It may be noted that the Webs of It Will be,

channels 49 and A5 have openings 52 and 5s (see Figs. 2 and 4) and the webs of channels 45 and 5|] have openings 54 and 55. These provide air ports from the box beams into the stoker air chamber 55. The box beams are carried on the wall of the furnace, it being noted that the ends 5- 1 andit, are, closed whilerthe: other ends 60 and SI connect with an air port-62'which in turn connects with air conduit It. If desired, the arrangement may be such that air is admitted at both ends; of? the bore beams, particularly in large furnaces- As shown inFig. 5, air port 62 is provided with an. adjustable damper 63 to regulate the amount of air passing from, conduit l8 into the box beam air conduits 42 and 43. In addition to air port 62 there is providedi another air port fi t above it and. connecting the air conduit it to the ash pit 65 below the grate H. .Port t lt is provided with an adjustable damper 66 to regulate the amount of air-passingthrough this port.

Resting upon the structural members K is a cylindrical casting 25 to which brackets. 2.4? are secured to support the inner ends of the T bars 2 (see Fig. 2). This casting 25 together with the structural members and a bottom plate m provide a Stoker air chamber 56. At the lower end of casting. 25 is a plate t? having an opening 58 in its center. It closes the gap between the. out: side of cylindrical casting 25 and the. tops. of the box beams 42 and 43. The upper end of the casting 25 has an outwardly extending annular flange or shoulder H in which is; a race tosupport ball bearings-12.

Mounted within the cylindrical, casting 25- and resting upon cover plate Hi is. a stationary'hollow center post '53 formed inv two: half sections; an upper section '15 and a lower section M kept in vertical alignment by an internal, telescoping hollow neck 76. At the top end of the neck It; is a round clamping plate T! and at the bottom a round clamping plate H5. The bottom plate 18 is welded to thelower section M, of the center postv 13'. The top plate is;weldedto the upper section 15 of the centerpost; This welding is done as shown at Bi and 82' (see Fig. 7) by providing small holes in the wall of; the center post 13. The clamping bolt l9 which extends throughthe, plates is drawn tight by nut 83.

The stoker F is rotatably mounted on the stationary center post 13. As shown in Fig. 2 a hollow sleeve shaft 83 rotates about the post. The sleeve 83' is provided with bearing surfaces 84. and 85 on the inside. At its lower end. the sleeve is provided with a flangete .(see Fig. 2) to which is secured, as by bolts 81, a bevel gear ring 88. Cast or otherwise secured to the sleeve 83 at its upper end are a plurality of radially extending webs 89 to which is securely mounted an L-shaped ring 98. This ring and its webs may conveniently be referred to as a spider ring. The vertical portion of this ring 96 extends into the cylindrical stoker air chamber and support casting 25 and the horizontal portion overlies and is secured to a bearing ring 69 which rotates 0n the ball bearings l2. Consequently, the overlying weight of the stoker F is carried on these bearings.

Securely mounted on the spider ring 90 is 3, r0- tatable hollow stoker hub 9| of generally dome shape having anopening 52 at the bottom and an opening 93 at its top. The hollow stoker hub 9| is provided with a plurality of outward extending hollow stoker arms 94. three rearwardly curved stoker arms, each of which is hinged at its inner end to the stoker hub 9| and they are arranged to sweep over the hearth As shown, there are from the interior of the dome.

E as the stoker is rotated on its vertical axis. The hinged joints are arranged to permit of limited vertical movement of the arms. The hollow interiorsof the stoker arms communicate with the hollow interior of the rotatable stoker hub. The stoker arms 94 each have a leading face 95 rearwardly curved and rearwardly inclined from bottom to top (see Fig. 7), a substantially flat top wall 96, and a trailing substantially vertical wall 91. It may be noted the top wall 96 extends a little over the vertical trailing wall 91 providing an overhanging eave 98 to keep particles from falling into the air ports 99 along the top of the trailing wall.

*Theinner ends of the stoker arms have a neck portion I fitting into a complementary collar portion IOI on the stoker hub. The neck portion of each stoker arm is hinged to a, collar portion of the stoker hub so that the arm will have a limited hinged or pivoted movement in a vertical direction. As shown, the collar portions IdI are cast to the stoker hub and extend outwardly in a radial direction from its surface. The vertical side walls I02 and I93 of the collar portion and the vertical side walls I04 and I05 of the neck portion of the stoker arm are provided with registering apertures to accommodate a hollow hinge pin I06 fastened in place by stop nuts I0! and I08. The hollow hinge pins I 96 are provided with air ports I09, the better to keep the pins cool.

The upper wall IIO of the hub collars I0! extends outwardly over the top wall I I I of the necks of the arms to provide a protecting eave I I2 (see Fig. 2) and a depending shoulder H3 limits the amount of angular rotation of the arm in an upward direction about the pivot pin l06. Also the bottom wall II4 of a collar provides ashoulder I I5 serving as a stop to limit the downward movement of the arm. The stops are arranged so that normally the arms rotate about the vertical axis of the stoker with the bottom wall slightly above the hearth E and so that the outer end of the stoker arm can rise a distance of the order of an inch or so.

Mounted on the center post 13 and above'the rotatable stoker hub is a plurality of superimposed truncated domes progressively smaller in diameter from bottom to top and open at both ends. Truncated dome I is carried on radial webs I2I secured to a ring I22 which rests upon a flange I23 secured to the center post. The lower peripheral edge of this dome overhangs the top opening 93 of the stoker hub and provides an annular air port I24 from the interior of the dome to a pile of rubbish overlying the stoker. Another similar but smaller truncated dome I25 is likewise mounted on the center post above the lower dome I20 and provides an annular air port are The two truncated domes I20 and I25 are surmounted by a dome-shaped cap I21 provided with webs I23 shaped to set into the hollow center post. This cap provides an annular air port I29, Thus the domes I20, I25 and the cap I21, as shown, provide a stationary tuyere head which for convenience is herein designated as Christmas tree tuyere head.

'To regulate the relative amounts of air passing to the tuyere head and to the hollow stoker arms a baflle I I6 in the shape of an inverted truncated hollow cone is mounted in central opening 93 of the stoker hub. It is mounted on the center post 13 by means of a bracket II'I. It may be noted that this bafiie IIB extends down into the stoker air chamber 50.

Mechanism is provided to rotate the stoker F about its vertical axis. It comprises a bevel pinion I30 meshing with the bevel gear ring 88 and keyed to the end of a rotatable drive shaft I3I (see Figs. 2 and 4). The drive shaft I3I rotates in bearing I32 mounted in the webs of the structural beams K and a bearing I33 outside the wall of the furnace. The drive shaft I3I is driven by a motor I34 (see Figs. 3 and 4) connected by a belt I35 to a pulley I36 of a speed reducer I31, the driven shaft of which is connected by a coupling i38 of the shear type to the drive shaft I3I.

In the operation of the furnace it maybe assumed that a pile of rubbish (indicated at I40) is charged through the charging port I4 into the firebox 20 and overlies the stoker and hearth as generally indicated in Fig. 1. The rubbish is ig-'- nited and the furnace ultimately brought up to temperature and additional rubbish is charged from time to time. The stoker F is put into operation. Air is passed through the air heater J and travels through conduit I8. The dampers 63 and are adjusted to regulate the relative amounts of air which pass into stoker air chamber 56 and to the ash pit I2. As the incineration or burning of the rubbish proceeds hot combustion gases pass through flue B to combustion chamber C where any unburned combustible gases are burned. A part of the air which is introduced into the stoker air chamber 59 passes outside the baffle H0 into the hollow rotating stoker hub 9I and thence out through the hollow arms 94 and finally through air ports 99 into the pile of rubbish as the arms sweep over the hearth. A part of the air introduced into the stoker air chamber '56 passes up through the interior of the baille II6 into the hollow tuyere head G. The air passing into the tuyre head then passes out through the annular air ports I24, I 26 and I 29 (see Figs. 2 and 7) into the pile of rubbish. The heated air passing into the rubbish helps in drying it out and also aids combustion. Upon rotation of the stoker arms about the vertical axis of the stoker hub the pile of rubbish is rabbled or stoked and is gradually moved outwardly toward the periphery of the annular hearth E and burning of the rubbish is completed on the grate H through which air passes upwardly from the ash pit I 2. It may be noted that the air passing through conduit I0 is heated by the hot combustion gases passing through flue D around the tubes of the air heater J. The combustion gases then pass to a chimney (not shown). Ashes fall through the grate into the ash pit or hopper I2 and may be removed from time to time through the discharge chute I6. The spiral grooves on the surface of the hearth E assist in directing particles of rubbish outwardly to prevent them from tending to stay in a fixed location on the hearth. Also, if the particles of rubbish on the hearth tend to lodge beneath the stoker arms thus exerting a force upwardly, strain on the stoker mechanism is relieved by reason of the hinged stoker arms which will more readily ride over any particles which tend to become lodged upon the hearth. This is an advantage in relieving undue strains upon the driving mechanism of the stoker.

The. illustrative embodiment shown in the drawings includes an ash hopper but it will be understood that a furnace may be constructed in accordance with other features of the invention where no ash hopper is provided. In such a case the stoker mechanism need not be supported on box beams extending into the walls but may be supported on the concrete serving as the bottom 7 of-the ash' pit. and air conduits of. less strength may be utilizedto; carry air to thestoker.

The. terms. and expressions. which have. been employed herein are used as terms of description and'not of limitation and there is no intention in theme of such terms and. expressions of excluding'any equivalentof the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of invention claimed.

What is claimed is z 1. An incinerator furnace for burning, rubbish and the like which comprises a firebox, an' annular hearthhaving a central opening in the lower part of the firebox, a grate surrounding said hearth, a rotatable stoker having a verticalshaft through said central opening and outwardly extending arms sweeping over the surface of said hearth upon rotation of said stoker about its vertical axis, said hearth having outwardly extending, channels spaced 'circumferentially over substantially its entire area, to direct particles of rubbish on the hearth toward its periphery as said arms sweep over the hearth.

2. An incinerator furnace for burning rubbish and the like which comprises'a firebox, an annular hearth having a central opening in the lowor part of the firebox, a grate surrounding said hearth, a rotatable stoker having a vertical shaft through said central opening and outwardly extending arms sweeping over the'surface of said hearth upon rotation of said stoker about its vertical axis, said hearth surface having a continuous series of circumferentially spaced, outwardly extending, spiral ribs providing'channels therebetween to direct particles of rubbish. on the of rubbish on the hearth toward its periphery as said arms sweep over the hearth and hinging means connecting said arms to said-hub-member to permit of limited vertical movement of said arms, said hinging means including a hollow member providing passageway from said hollow hub for the passage of air therethrough into the interior of said arms.

4. An incinerator furnace for burning rubbish and the like which comprises a firebox, an annular hearth having a, central opening in the lower part of the firebox, a grate surrounding said hearth, a rotatable stoker having a hollow hub member for supporting stoker arms, a vertical shaft through said central opening, said hub member having outwardly extending hollow stoker arms sweeping over the surface of said hearth upon rotation of said stoker about its, vertical axis, said hearth surface having a continuous series of outwardly directed, circumferentially spaced, spiral ribs extending from said central opening to the periphery of said hearth, and hinged connections securing the inner ends of said stoker arms to said hub member to permit of limited vertical movement of said arms, each of said hinged connections including hollow members secured to. said hub providing, passageway for air from the interior of said hub into itsadjacent hollow arm.

5. An incinerator apparatus for burning rubbish which comprises a firebox, an annular hearth in said firebox havinga central opening, an annular grate at the periphery of said hearth, said hearth having raised ribs extending from said central opening to its periphery, a hollow rotatable stoker hub, hollow arms each having a. hinged connection to said stoker hub:for stoking a pileof rubbish on said hearth and having air ports, a hollow sleeve connected to said stoker hub, a normally closed ash pit below saidgrate, a hollow tuyere head surmounting said rotatable stoker hub, power means to rotate said sleeve whereby to rotate said stoker hub on its vertical axis together with said arms, means for supplying a stream of air to said grate, means including a conduit for supplying a stream of air to said stoker hub and tuyerehead, each of said hinged connections. comprising a hollow collar on the hub and a hollow neck on the arms protruding into said collar, and a hollow pin pivotallyconnecting said collar and neck permittingof limited vertical movement of said arms, a bevel ringgear secured to said sleeve, a rotatable shaft, a bevel pinion connected to said shaft and meshing with said ring gear and means to rotate said shaft whereby to rotate said stoker, each of said collars providing passageway for air from said hub to its connected arm and each of said pins providing passageway for air for cooling the pin.

6. An incinerator furnace for burning rubbish and the like, which comprises a firebox, an annular hearth having a central opening in said firebox, a grate surrounding said hearth, and a stoker and tuyere device, said stoker and tuyre device comprising a rotatable hollow truncated domeshaped hub having an opening at its bottom and an opening at its top, hollow stoker arms adapted to sweep over the surface of said hearth secured to said rotatable hub and extending outwardly therefrom and having air ports in their walls, a plurality of hollow members circumferentially spaced about said hub providing means for pivotally connecting said arms, each of said arms having a neck portion pivotally connected to one of said hollow members so that the interiors ofsaid arms communicate with the interior of said rotateable hub and so that each arm has limited vertical movement about its pivot, a rotatable hollow sleeve secured to and depending from said rotatable hub, a stationary hollow casting surrounding said rotatable sleeve providing a wall for a stoker air'chamber and providingabearing surface for said stoker hub, said rotatable sleeve extending downwardly through said stationary hollow casting, a stationary post extending upwardly through said sleeve, a plurality of stationary superimposed truncated hollow domes carried by said post, each having anopening at its bottom and top and surmounting said rotatable hub, and a stationary capping dome closed at its top crowning said stationary truncated domes, said stationary domes being vertically spaced to provide air ports at their peripheral edges through which to pass air into rubbish piled on said hearth, and means including. a prime mover to rotate said sleeve and stoker hub.

7. An incinerator furnace for burning rubbish and the like, which comprises a firebox, an annular hearth having a central opening in said firebox, a grate surrounding said hearth,and a stoker and tuyre device, said stoker comprising arotatable hollow truncated dome-shaped hub having an opening at its bottom and an opening at its top, hollow stoker arms adapted to sweep over the surface of said hearth secured to said rotatable hub and extending outwardly therefrom and having air ports in their walls, a plurality of radially extending hollow collars secured to and circumferentially spaced about said hub providing means for pivotally connecting said arms, each of said arms having a neck portion extending into an adjacent collar, a pivot pin for each arm pivotally mounting it on its adjacent collar for vertical movement so that the interiors of said arms communicate with the interior of said rotatable hub, a rotatable hollow sleeve secured to and depending from said rotatable hub, a stationary hollow casting surrounding said rotatable sleeve providing a wall of a stoker air chamber and providing a bearing surface at its upper end for said stoker hub and also providing a support for said hearth, said rotatable sleeve extending downwardly through said stationary hollow casting, a stationary center post extending upwardly through said sleeve, a plurality of stationary superimposed truncated hollow domes carried by said post, each having an opening at its bottom and top and surmounting said rotatable hub, and a stationary capping dome closed at its top crowning said stationary truncated domes, said stationary domes being vertically spaced to provide air ports at their peripheral edges through which to pass air into rubbish piled on said hearth, means including a prime mover to rotate said sleeve and stoker hub, structural members to support said stationary casting and providing an air conduit to said stoker air chamber, and means to support said stationary center post.

8. An incinerator apparatus for burning rubbish which comprises a firebox, an annular horizontally disposed hearth in said firebox and having a central opening, an annular grate at the periphery of said hearth, a dome-shaped hollow rotat- 10 able stoker hub, a plurality of rectangular-shaped hollow collars radially disposed and circumferentially spaced on said hub and providing a passage= way for air from the interior of said hub, a hollow stoker arm extending in a radial direction from each of said collars, each stoker arm having a rectangular-shaped hollow neck portion snugly and sliolably fitting in its adjacent collar and pro viding a passageway for air into said arm, a pivot pin on each of said collars mounting each of said neck portions for vertical movement of said arms about said pivots, each of said collars having a portion extending over the neck portion of its adjacent arm providin an eave preventing particles of overlying rubbish from entering into said hub and arms and each of said collars having a portion engageable with its adjacent arm providing a stop limiting the amount of upward movement of said arms when swung upwardly on their pivots, a hollow sleeve connected to said stoker hub and extending down through said central opening, a hollow tuyere head surmounting said rotatable hub, power means to rotate said sleeve whereby to rotate said stoker hub on its vertical axis together with said arms, means for supplying a stream of air to said grate and means including a conduit for supplying a stream of air to said stoker hub and tuyere head.

AUGUSTINE MAYER.

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

UNITED STATES PATENTS Number Name Date 548,254 Horsfall Oct. 22, 1895 386,665 Solvay July 24, 1888 1,655,320 Lummis Jan. 3, 1928 2,122,384 Scott June 28, 1938 2,232,556 Nichols Feb. 18, 1941 2,402,436 Nichols June 18, 1946

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