US2416516A

US2416516A - Variable pitch propeller

Info

Publication number: US2416516A
Application number: US292148A
Authority: US
Inventors: Walter W Everts
Original assignee: EVEREL PROPELLER CORP
Current assignee: EVEREL PROPELLER Corp
Priority date: 1939-08-26
Filing date: 1939-08-26
Publication date: 1947-02-25
Anticipated expiration: 1964-02-25

Description

Feb. 25, 1947. w. w. EVERTS 2,416,516

' VARIABLE FITCH PROPELLER Filed Aug. 26, 1939 v5 Shets-Sheet l f7 4 50 7J 14 d f6 2,/ QC) L16; 21 5;

\ 3mm/vio@ Walier WEveJ'tS' VARIABLE FITCH PRPELLEB Feb. Z5, 1947. w. w..EvER-rs 42,416,516

' 4 VARIABLE PITGH PROPELLER k y FiledAug. 26, 1959 5 sheets-sheet 3 Feb. 25, 1947. w, w, EVERTS 2,416,516

VARIABLE FITCH PROPELLER Feb. 25, 1947. w 'w, EVERTS I 2,416,516

VARIABLE PITCH PROPELLER Filed Aug. 26. 19:59 5 sheets-sheet 5 Patented Feb. 25,"11947 VARIABLE PITCH PROPELLER Walter W. Everts, Baltimore, Md., assignor to Evere! Propeller Corporation, Baltimore, Md., a corporation of Maryland Application August 26, 1939, Serial No.1292,148

v claims. v (c1. 17o- 162) My invention relates to propellers for air craft, boats, submarines or the like and fans for displacing fluids.

An important object of the invention is to provide a propeller having means to automatically vary the pitch of the blades as the elevation of the vehicle changes.

A further object of the invention is to provide means to automatically increase the pitch of the blades as the applied power increases, at any given elevation.

A further object of the invention is to provide means to automatically increase the pitch of the blades as the speed of travel of the vehicle increases.

A `further object of the invention is to provide strong and compact means to pivotally mount theblades upon thevhubof the propeller.

A further object of the invention is to arrange the means for mounting the blades within the hub to provide an enclosed structure.

Other objects and advantages of the invention will be apparent during the course of the following description.

In the accompanying drawings forming a part of this application and in which like numerals are employed to designate likeparts throughout the same,

Figure 1 is a front elevation of a propeller embodying my invention,

Figure 2 is an edge elevation Vof the same,

Figure 3 lis .a transverse .section taken on line 3-3 of Figure 1, v

Figure 4 is a transverse section taken on line 4--4 of Figurel 1,

Figure 5 is a vertical section taken in the plane of rotation of the propeller online 5-5 .of Figure 2,

Figure 6 is a transverse section taken .on line 6--6 of Figure 5, parts omitted,

Figure 7 is a transverse section taken on line 'I-l of Figure 5,

Figure 8 is a similar view taken on .line 8-8 of Figure 5,

Figure 9 `'is a transverse section taken on line B-- of Figure 5, the parts being assembled, f

Figure 10 is asection taken on line III-I0 of Figure 5, f

Figure "l1 is an exploded perspective view of the plunger and associated lug,

Figure 12 is an edge elevation of a propeller embodying .a modied form of the invention,

Figure 13 is an edge elevation of apropeller embodying a further modiedsf-orm of thelinvention,

Figure 14 is a .front Aelevation of the propeller shown in Figure 13,--

- Figure 11:a is a perspective view of the operat-Y r ing'arms and sockets carrying them,

suitable means.

Figure l5 is an edge velevation of a propeller embodying a further modification of the inven tion, f

Figure 16 is an edge elevation of a propeller embodying a still further modiiicationof the invention, and,

Figure 17 is an edge elevation of a propeller embodying a further modification of the invention. v

In the drawings, wherein for the purpose of illustration are shown preferred embodiments of my invention, the numeral I0 designates a hub, having a centrally arranged opening I I, to receive the crankshaft of the engine of an airplane or the like. The hub is provided with splines or ribs I2, to interlock with splines or ribs formed upon lthe crank shaft. The hub is held against longitudinal displacement .upon the crank shaft by any As an illustration, I have shown a nut I3, having screw-threaded engagement with the crank shaft. The hub comprises end portions i4, which are `oli-set laterally in opposite directions, in theplane of rotation ofthe hub, with relation to the center II of the hub. These end portions I4 have cylindrical recesses I5. The central longitudinal axes I6 of the recessesIE are oil-set -laterally `in opposite directions, in the plane of rotation of the hub, and the axes I6 are equidistantly spaced from the center. The central longitudinal axes I6 of the recesses I5 are also disposed at a right angle to a line I6', passing through the center I1, and arranged between the recesses I5,- and equidstantly spaced Vfrom the bottoms .ItaV of the recesses, which bottomsare parallel with the line l'.. The axes or cen-ter lines I6 are in a transverse plane, ,disposed at a right angle both vertically and horizontally with relation to the axis of rotationv or center line I1.

The numeral I8 designates propeller blades which are generally 4radial ywith respect to the opening II. Two of these blades are shown in opposed relation, for the purpose of illustration.

The number may be increased. Isalso contem plate using only one blade, when -a singleblade propeller is desired. The blades I8 are of :the conventional construction and .design and have the twist to produce the desired pitch. The lifting faces-I8' of the blades are convex or cambered.v The blades have ,longitudinal axes I9, which are genera-Ty radial with relation to the opening II, The blades have-leading and trait- .ing 4.surfaces 2l) and 2l, Which are unbalanced, with the trailing surface 2I being the larger.

Y Each blade I8, Figure 5, has a shank yf22. ta-

pering inwardly, .and screw-threaded, .as show-n 1 shown 3 at 23. The shank has a recess 24 formed therein, and this recess extends through the inner end of the shank,as shown, for a reason to be eX- plained. The numeral 25 designates a socket, having a screw-threaded bore 26, which tapers inwardly, as shown. The tapered shank is adapted to have screw-threaded engagement within the tapered bore of the socket 25. Preferably Y formed integral with the inner end of each socket 25 is a circular attaching flange or disc21. The socket 25 is circular in cross-section and is concentric with respect to the circular flange or disc 21, at the union of these parts, but the socket 25 becomes increasingly more eccentric with respect to the disc or flange 21 in a direction toward the outer end of the socket. The circular or cylindrical disc or flange 2 has as a center line or turning axis the line I5. The center line or longitudinal axis of each shank 22 of each blade is the line I9. The central longitudinal axis I9 of the blade and shank is therefore at an inclined or oblique angle with respect to the center line or turning axis I6 of the disc or Aflange 21. When y the disc or flange 21 turns upon its axis I6, the propeller blade will travel about the circumference of a truncated cone having the line I 6 as its center and this movement will vary the pitch of the blade.

Means are providedto lock the threaded shank l22 within the socketr25` against'turning movement so that it cannot unscrew therefrom. This means comprises a coupling-sleeve 29 which is inserted into the recess 244 and has screw-threaded engagement with the shank 22, as shown at 39. This coupling-sleeve is 'further secured to the shank by rivets 3I, so that the couplingsleeve cannot turn with respect to the shank. The numeral 32 designates a lock-sleeve, provided upon its outer surface and near its inner end with an annular set of splines or teeth 33, to'interlo-ck or intert with an annular set of splines or teeth 34 formed upon the inner end of the socket 25. The lock-sleeve is further provided upon its outer surface and near its outer end with an annular set of splines or teeth 35 to intert or interlock with teeth 36, formed upon the inner surface of the coupling-sleeve 29. It

is thus seen that when the lock-sleeve 32 is in position, it will prevent the coupling-sleeve 29 Aand shank 22 from turning with relation to the socket 25. 'I'he lock-sleeve 32 is provided with an internal flange` or shoulder 31, to be engaged by an annular flange orV shoulder 38, formed upon y a tubular lock 39. This tubular lock has screwthreaded engagement with the coupling-sleeve The tubular lock 39 may V- 29, as shown at 4D. be held against accidental rotation by any suitable means, such as a safety wirev 4 I, passing' through apertures inthe parts 32 and 39, although a cotter pin or the like may be used. YFrom the foregoing description it will be seen that theshank 22 is Ysecurely locked against imj- `properrotation with respect to the socket 25,

whereby these parts will ed in use. Y I' The attaching flange or disc 21 is mounted concentrically within the cylindrical recess I5` and is provided upon its inner sideV with a race-` remain rigidly connectway 42, to receive bearing-balls 43 operating 'within a ball racev 44. Bearing elementsfsuch Hasroller bearings'45, engage the outer side of the attaching disc oriiange 21 andare lheld in place by a ring 46 or the like,r having screw;

hreaded engagementwith the end portion I4, as

at 41. lAnysuitable form of-lock means? 48 may be employed to prevent the accidental unscrewing of the ring 46. There is a packing ring or grease seal 49, carried by a lip 50 of the ring 46, to prevent the escape of the lubricant from about the roller bearings. t

The longitudinal.` axis I9 of each blade I 8 is at an inclined or oblique angle with respect Vto the turning axis I6 of its disc or flange 21. This angle is shown as about 15, but the invention is not restricted to this precise angular arrangement, as the same may be varied as found advantageous. It is probable that this angle could vary within 10 to 40. The longitudinal axes I9 of the blades I8 do not extend through the center I1 of the hub, but are arranged upon opposite sides of this center and are spaced from the same for equal distances. This is the preferred arrangement, as it acts as a torque counterbalance, neutralizing the tendency that the blade would have to twistbodily in the plane of Arotation within the recess I5. By virtue of the arrangement of the axes I9, the pressure upon the roller bearings 45 is neutralized throughout the entire circumferences of the disc oriianges. The arrangement of the axes I9 also causes the blades to balance each other.

Means are provided to dampen or retard the movement of eachV blade about the surface of the truncated cone. This means comprises a cylindrica1 plunger 5I, having recesses 52 in its opposite ends. The plunger is mounted to reciprocate within a cylindrical bore 53 formed in the hub I Il. There are two 0f these cylindrical bores, which are eduidistantly spaced from the center I1 and circumferentially arranged so that the hub remains balanced. The ends of the bores 53 are covered by screw-threaded plugs 54. The bore 53 has annular grooves 55, receive ing packing rings 56, contacting with the plunger 5I and preventing the escape of the brake fluid between the plunger and the packing rings. The hub I9 is provided with a passage 51, arranged between the packing rings 56, and this recess receives a stud or nger 58, which is carried by `and rigidly secured to the inner face of the disc or iiange 21. The hub has a further recess 59. The stud 58 engages within a notch 66, formed in the intermediate portionrof the plunger 5I. Itis thus seen `that when the disc or flange' 21 is turned upon its axis I6, the stud or finger 58 will shift the plunger 5I longitudinally. A port 6I leads into theY opposite ends of the bore 53 adjacent to the plugs 54. The plunger 5I has notches 62 formed'therein so Vthat the ends of the port 6I: remain permanently uncovered.

lWhen the plunger moves in one direction it will force theV liquid, Ysuch as ordinary brake fluid, through the port 6I, fromone `end of the bore 53 into the other end. i The passage of the brake fluid through the port 6I is restricted or retarded, and the plunger 5I will serve to dampen or retard the movement ofthe blade in changing nected and operate separately-1.',

annale Operation The operation of the propeller is as follows:

yThe propeller is driven `counter-clockwise, viewed from the front of the airplane, which is the practice in the United States. As soon as the propeller rotates, centrifugal forceacts upon the blades I8 and tends to move Athese blades `to a radial position. This action of centrifugal force is opposed by the air thrust, which tends to swing .the blades forwardly so that the outer ends of the blades move forwardly `from, the radial position and inwardly of the maximum sweep. These two opposing forces act against each other and the blade will assume a, normal operating position between the extreme forward position and the true radial position. When the blade -is in theextreme forward position it is at the mini mum pitch and when in the true radial kposition it has the maximum pitch due to centrifugal force. Assuming that the airplane is now flying at substantially sea level, they air `thrust is then at the maximum and the blade has moved forwardly aboutthe surface of a truncated cone, to assume the forwardmost position which will impart to the blade the minimum pitch. The action of centrifugal force tends to move theblade rearwardly about the surface of the truncated cone toward the true radial position, thereby increasing the pitch of the blade. As the speed of the airplane increases, the air pressure acting upon the forward face of the blade tends to move the blade rearwardly about the surface of the truncated cone for increasing the pitch of the blade. Assuming that the propeller is being driven at 2,000 R. P. M., at sea level, the` propeller will then have the minimum pitch for this elevation. If the airplane now rises to a considerably higher elevation, the air thrust acting upon the propeller will be reduced, while the action of centrifugal force remains the same and hence the action of centrifugal force will overcome the air thrust upon the propeller blades, and the propeller blades would be moved rearwardly about the surface of a truncated cone, and therebyincreasing'the pitch of the propeller blades. This increased pitch of the propeller blades will cause the propeller to drive the airplane at an increased speed but the speed of rotation of the propeller will remain substantially constant.

When the air pressure upon the front faces of the blades I8 is sufficient to overcome the action of centrifugal' force, as when the airplane is making a nose dive, the blades are shifted rrearwardly beyond the radial position, and the pitch of the blades is increased over the maximum pitch which can be imparted to them due to the action of centrifugal force, which would occur when the blades are shifted by centrifugal force into a true radial position,

The blades I8 are free to be shifted about the surfaces of the truncated cones, within limits, to vary their pitch, as explained, and this shifting movement is dampened by the action of the plungers'SI and associated elements, and these plungers also serve as means to stop the shifting movement of the blades within the desired limits.

Attention is now called to Figure 12 of the drawings, showing the first modification vof the invention. In this form of the invention the same hub I and propeller blades I8 areernployed and the blades are mounted upon the hub linthe identical manner as described in connection with the first form of the invention. These blades uturn aboutvthe surface of a truncated cone to varyv their pitch, as explained in connection .with

the first form of the invention. In the form ofy the invention shown in Figure 12, a centrifugal pump is provided including a casing 69, Whichiis rigidly mounted upon the nut I3,.to rotate therewith. Arranged within the casing is a rotor 10,

which is driven yin an opposite direction to the direction of lrotation of the casing 5t. This rotor receives its rotation from a shaft 1I, carrying a fan or propeller l2, which drives it. The main vpropeller including the blades I8 is rotated counter-clockwise when looking into the same from the front of the airplane while the fan 'I2 is rotated clockwise when viewed from the same direction. The outlet side of the casing169 dischargesinto a pipe 13, which leads into the rear ends of the bores 53, .the plugs 54 being-removed and 4other plugs substituted therefor, which are adapted to serve as vcouplings between `the branches `Iii and the rear ends of the hores 53. In asimilar manner the plugs 54 within the forward ends of the bores Y53 are removed and other plugs substituted therefor, which are adapted to serve as couplings Vbetween the branches 15 and the vforward ends of the bores 53. The branches 15 lead into a'pipe 16, which is connected with the intake vside of the lcasing 69. The plugs 53 may be now adjusted to permit .of the maximum flow ofthe brake fluid through the port i3 I.

30 Y All other parts Vof the propeller remain identical with those shown anddescribed in connection with the first form of the invention. The operation ofthe propeller shownk in Figure l2 is as follows:

The propeller; is rotatedcounter-clockwise when looking toward `the same from the front of the airplane. The -air thrust tendsto shift thepropeller blades forwardly about the surfaces of truncated cones to decrease their pitch, while centrifugal `force tends to'move them rearwardly about. the surfaces of the truncated cones to increase their pitch. ADuring the travel of the airplane, the Yfan 0r propeller 'I2 is rotated in opposite direction to the'direction of rotation of the casing 69 of the ,centrifugal pump. The cen'- trifugalpurnp serves to force brake iiuid into 4the rear ends of the bores 53 'and to withdrawthe `same lfrom the forward ends. This action /increasesv with the increase-of the speed of ythe `airplane, and 'increased' pressure isfapplied to the rearends ofthe plungers 5 I. The forward move,-

` ment of the plungers is transmitted to the pro peller-blades, .and coacts rwith lcentrifugal force in shifting the blades `rearwardly about the surfaces .55 of the truncated cones to increase the pitchof theblades. Thepropeller 12 yand the centrifugal pumptherefore` serve as means operated `by the travel lof the airplane, vto increase the pitch of. the bladesin proportion tothe increased speed c() of the airplane. y 4 -In Figure V13,l I have shown a second modifica;-

tion of the propeller. Figures 1-3, 14and 14ahasthesa-me hub" I0 and blades yI8, andA the yblades are mounted on the .65 hub to Vmove about the `surfaces of truncated The `liiropeller shown in is driven by the shaft 1| and fan or propeller12. This is the same arrangement as shown inl Figure l2. In the form shown in FigureV 13, I provide a pressure operated device including a cylinder 11, having an intermediate portion 18 which is'hollow, with a passage 19 for the crank shaft of the engine or a `continuation thereof. A plunger 80 is mountedr within the lower portion of the cylinder 11. This plunger is connected with a plunger rod 8l, having a universal connection with an arm 82 which is rigidly connected with the socket 25 of the blade. The opposite end of the cylinder 11 has a rod`83 rigidly secured thereto, having a universal connection with an arm 84 which is rigidly secured to the socket 25 oi the other blade. The arm 82 is disposed on the trailing edge of its socket 25 and the arm 8l!Y is disposed upon the trailing edge of its socket 25 so that when the rods 8| and 83 are'shifted outwardly they move the'arms 82 and 84 respectively, to depress the trailing Y edges of the blades and increase their pitch.

Inv the operation of this form of propeller, the centrifugal pump forces the brake fluid through a iiexible-hose 85 into one end of the cylinder 411 inwardly of the plunger 80 and withdraws the brake fluid fromrthe opposite end of the cylinder through a flexible hose 86. This moves the cylinder and plunger in opposite directions longitudinally of each other and applies the force to the

arms

82 and 84, and this force aids centrif- V ugal force in shifting the blades about the surfaces of the truncated cones to increase the pitch of the blades. The force increases in proportion to the increase in speed ofV the airplane.

' In Figure 15, the same cylinder 11, and plunger '80 are used, as described in connection with Figure 13and these parts are connected with the sockets 25 in the identical manner as shownin Figure 13. However, the centrifugal pump is dis- 11. This causes the cylinder l11 and plunger 8l)z to apply forceto the. sockets 25 tending to increase the pitch of the propeller blades. Y l

In the form of the invention shown in Figure 16, the same cylinder 81 and associatedelementst are'emoloyed. but a plunger 92 is mounted within the cylinder 81 and has screw-threaded engagement therewith. This plunger is rotated byv a f plunger rod 93, carrying a fan or propeller 94. YDuring the travel of the airplanejthe fan 94 rotates. turning the plunger 92, which in turn vforces the brake uid into one end of the cylinder 11, thus causing the cylinder and plunger 80 to coact for increasing the pitch of the blades.

vIn Figure 17, the sockets 25 are rigidly connected with the arms 84 and these arms have Y universal-connections with a iiat disc 9S, slidable upon a gwide 91. The pressure of the air upon the disc l918, due to the travel of the airplane, is transmitted to the arms 95, which aidin causing the blades to turn about the surfaces of the truncated cones to increase ythe pitch of the blades. e

' In all forms of the invention, Figures 1V to `1'!V inclusive, the same attaching discsA 21 and associatedselements are employed to mount the blades I8 upon the hub I0, in the same manner as described in connection with the first form of the invention. In all forms of the invention the discs 21 and blades |-8 have the same mode of operation, in changing the pitchrof the blades. It is to be understood that the forms of my invention herewith shown and described are to be taken as preferred examples of the same and that various changes in the shape, size, andarrangement of parts may be resorted to without departingY from the spirit of my invention or the scope of the subjoined claims. l

Having thus described my invention, What-I claim is: f

1-. A propeller comprising a, hub having an axis of rotation and a plane of rotation normal there'-I to, blades to be carried by the hub, rotatable attaching means to secure each blade to the hub, the attaching means having a center turning line and lying'in said plane, each blade having a lon-v gitudinal axis disposed diagonally with respect to the center line of its attaching means, whereby centrifugal force acting on the blades tends to move the blade axes into said plane of rotation and thereby rotate said attaching means about theirturning line in a direction to increase the pitch of the blades, fluid pressure means applying a force in addition to centrifugal force to the blades for rotating the attaching means in said pitch increasing direction, and an element actuated by the air stream in response to the relative velocity thereof .in the line`of flight during the travel of the vehicle to operate the fluid pressure means.

2. A propeller comprising awhub having an axis of rotation and a plane of rotation normal thereto,V blades to be carried by the hub, rotatable attaching means to secure each blade to the hub, the attaching means having a center turning line lying as said plane, each blade having a longitudinal axis disposed diagonally with respect to the center line of the attaching means, whereby centrifugal-force acting on the blades tends to move the blade axes into said plane of rotation and thereby rotate said attaching means about their Vturning line in a direction to increase the pitch of the blades, Viiuid pressure devices connected with the attaching means to apply a force thereto in addition to centrifugal force on the blades to rotate the same in said pitch increasing direction, .a rotary compressor to supply iluid pressure to the devices to operate them, and means independent -of the propeller for driving Y the compressor including a rotary fan Ahaving blades at an angle of attack to the air stream and moved thereby in response to the relative velocity thereof.

3. A propeller comprising a hub having an axis of rotation and a plane of rotation normal thereto, blades to be carried by the hub, rotatable attaching means to secure each blade to the hub, the attaching means having a center turning line and lying in said plane, each blade having alongitudinal axis disposed diagonally with respect to the center line of the attaching means, whereby centrifugal force .actingV on the blades tends to move the blade axes into said plane of rotation and thereby rotate said attachingmeans about their turning line in a direction to increase the pitch of the blades, a iluid pressure device connected with the attaching means to apply a` rotating force thereto in addition to centrifuga-l force lto rotate the attaching meansv Vin said pitch increasing direction, a cylinder having communication with-'the -fluid pressure device to supply iiuid pressure thereto, a plunger within the cylinder, and an element in the air stream and movable in response to the relative velocity thereof in the direction of flight, said element being connected with the plunger to actuate the same.

4. A propeller comprising a hub having an axis of rotation, blades to be carried by the hub, attaching means to secure eachblade to the hub, the attaching means having a center turning line, each blade having a longitudinal axis disposed diagonally With respect to the center line of the attaching means, each blade being shiftable inone direction by centrifugal force to increase its pitch, a iiuid pressure device connected with the blades to apply a force thereto in addition to centrifugal force to shift the blades for increasing their pitch, a cylinder having communication with the fluid pressure device to supply fluid pressure thereto, a plunger having screw-threaded engagement within the cylinder, and a fan connected with the plunger to turn the same.

5. A propeller comprising a hub having an axis of rotation and recesses, said hub also having bores, discs having center lines and mounted within the recesses to turn therein upon the center lines, the center lines of the discs, when extended, being perpendicular to a plane containing the axis of rotation and spaced on opposite sides of the axis of rotation, blades attached to the discs and having longitudinal axes arranged diagonally with respect to the center lines of the discs, a plunger arranged within each bore, each bore having a lateral opening intermediate its ends communicating With one of the recesses, means on each side of said lateral opening to seal the plunger Within said bore, a stud secured to each disc and extending through the lateral opening in the bore to engage the adjacent plunger to move it, each bore being adapted to receive fluid between the ends thereof and the plunger, and means to regulate the flow of fluid in a retarded manner from one end of the bore to the opposite end.

6. A propeller comprising a hub having a, recess therein, a disc mounted in said re-cess, a blade receiving socket internally threaded and carried by said disc, said socket and disc having registering openings therein providing access to the internally threaded portion of the socket, a blade having a screw threaded shank mounted within the internally screw threaded portion of the socket, said shank having an axial recess formed therein, a coupling sleeve fixedly mounted in the interior of said shank,.an axially slidable tubular locking member inserted within the opening of said disc and extending into said sleeve and having external splines cooperating with said coupling sleeve and with said disc to secure said shank and coupling sleeve against rotational movement within said socket, and means extending through said locking member and having a screw threaded engagement With said coupling sleeve for retaining said locking member in locking position.

7. A propeller for aircraft comprising a hub having an axis of rotation a, blades to be carried by the hub b, attaching means to secure each blade to the hub, the attaching means having a center turning line c, each blade having a longitudinal raxis disposed diagonally with respect to the center line of the attaching means d, each blade being so constructed and positioned as to be shiftable in one direction by centrifugal force to increase its pitch, a fluid pressure device connected with the attaching means to apply a rotating force therein in addition to centrifugal force to rotate the attaching means in said pitch increasing direction, a cylinder having communication with the iluid pressure device to supply huid pressure thereto, a plunger within the cylinder, and an element presenting a surface normal to the air stream in the direction of flight and movable in response to the relative velocity thereof, said element being connected with the plunger to actuate the same.

WALTER W. EVERTS.

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

UNITED STATES PATENTS Number Name Date 2,117,062 Jablonsky May 10, 1938 1,943,210 De Lavaud Jan. 9, 1934 997,884 Wells July 11, 1911 2,134,661 Everts Oct. 25, 1938 1,786,644 Davis Dec. 30, 1930 2,221,613 De Lavaud Nov 12, 1940 1,786,644 Davis Dec. 30, 1930 1,802,648 Heath April 28, 1931 1,879,935 Hill l Sept. 27, 1932 1,380,406 Mott June 7, 1921 2,250,826 Everts July 29, 1941l 2,192,034 Briggs Feb. 27, 1940 2,127,264 Lampton Aug. 16, 1938 1,620,968 Heath Mar. 15, 1927 1,829,437 Clay Oct. 27, 1931v 2,223,081 Thomas Nov. 26, 1940 1,940,200 Wingler Dec. 19, 1933 758,020 Robinson Apr. 19, 1904 833,232 Lemp Oct. 16, 1906 2,075,682 Weiman Mar. 3o, 1937 2,141,552 Ratie Dec. 27, 1938 2,219,303 Fraser Oct. 29, 1940 2,234,196 Prewitt Mar. 11, 1941 1,233,858 Farmer July 17, 1917 1,401,537 Hill Dec. 27, 1921 1,425,922 Wesnigk Aug. 15, 1922 1,825,768 Barbarou Oct. 6, 1931 1,872,337 Pllard Aug. 16, 1932 1,967,461 Ballew July 24, 1934 1,972,337 Gardner Sept. 4, 1934 2,133,656 Caldwell Oct. 18, 1938y 2,152,419 Platt Mar. 28, 1939 2,243,046 Algarsson May 20, 1941 FOREIGN PATENTS Number Country Date 652,753 French Oct. 29, 1928 469,124 British July 20, 1937 796,840 French Feb. 3, 1936 601,459 French Nov. 30, 1925 499,932 British Jan. 31, 1939 670,448v French Aug. 19, 1929 496,750 British Dec. 5, 1938 447,424 British May 19, 1936 37,393 French Aug. 26, 1930 645,878 French 147,228 Swiss Aug- 17, 1931 18,445 British Aug. 9, 1897 444,320 British Mar. 18, 1936 450,854 British July 24,1936

476,852 British Dec. 16, 1937 488,477 British July 7, 1938 501,054- British Feb. 20, 1939 684,120 French June 21, 1930 820,653 French Apr. 2, 1937