US2883898A

US2883898A - Fipple flute

Info

Publication number: US2883898A
Application number: US494885A
Authority: US
Inventors: Edward V Powell
Original assignee: Individual
Current assignee: Individual
Priority date: 1955-03-17
Filing date: 1955-03-17
Publication date: 1959-04-28
Anticipated expiration: 1976-04-28

Description

E. V. POWELL April 28, 1959 FIPPLE FLUTE 2 Sheets-Sheet 1 Filed March 17, 1955 INVENTOR fdwara 1 7 0we// 4w? ATTORNEY-5 April 1959 E. v. POWELL 2,883,898

FIPPLE FLUTE Filed March 1'7, 1955 2 Sheets-Sheet 2 T 7 W/ C ///////////////////////A lNVEN R ATTO RNEYS United States Patent FIPPLE FLUTE Edward V. Powell, Scarsdale, NY.

Application March 17, 1955, Serial No. 494,885

Claims. (Cl. 84-384) This invention relates to a fipple-flute, and embodies improvements in such an instrument to produce improved:

I. Tone-production, quality, and wide range of volume between soft and loud;

II. Means to produce half-tones; and

Ill. Mechanism for manipulation of the moving parts to simply, efiiciently and accurately produce the various tones and quality.

In regard to tone production the following factors are to be noted:

Firstwhen air is in motion with respect to a curved surface, the air tends to follow the curved surface, the degree of deflection being a function of the speed of the air, greater deflection when the air speed is greater.

Second-when a hole is pierced through the material of the curved surface and where the air is in motion over the opening, the initial action is to reduce pressure in the hole, which action is immediately followed by an equal and opposite reaction of compression at the hole opening. This paired action and reaction following in quick succession propagates a tone wave. An increase in the speed of the impressed air over the opening creates an increase in the amplitude of the wave and the addition of overtones to the fundamental tone.

The improved fipple-flute herein in its preferred form, provides (1) a body portion with a longitudinal opening or bore therein, thus forming an internal air column, and (2) a mouthpiece portion which has a confined or constricted longitudinal curved bore for part of its length, and has an open curved length for receiving and guiding the compressed air issuing from the curved bore. In addition, this mouthpiece portion has a vertical hole at the exit of the curved bore that leads to an expansion or resonating chamber that in turn leads to the internal air column of the body portion of this improved fippleflute.

Thus, the instrument functions, in general, to have the impressed air issuing from the curved bore in the mouth piece to first create air rarefaction and then air compression in the expansion or resonating chamber and thus exert an effect on the internal air column. The opera. tion of the various keys and the temporary covering of the holes along the body portion of the instrument func tions to determine the multiple tones of the chromatic scale.

The air under compression issuing from the curved bore will hereinafter be noted as an air reed, and as noted above when under different degrees of compression and passing over the vertical hole causes the air column in the body portion of the instrument to vibrate at different amplitudes. With the formation and action of the air reed and the manipulation of the keys, resonance and harmonic partials are added to the fundamental tone and provide an extended range of sonority of tone.

In regard to the structure for producing half-tones as noted under heading II, the chimney-key structure described below is provided for special changes of the lengths of the air column.

In regard to the manipulation mechanism noted under heading III, that will also be described in detail and will indicate the cooperating portions of the mechanism for varying the positions of the keys or covers over some of the openings in the wall of the improved instrument.

Further and in more particular, the invention relates to musical wind instruments, particularly wood-wind instruments of the variety known as fipple-fiutes having finger holes for easy playing of simple music. It is the purpose of this invention to extend the scope and broaden the musical qualities of this type of instrument by securing an accurate chromatic scale for at least three octaves, and for improving the tonal quality and control thereof, and for introducing in the tonal quality the factor of dynamics which is the basis of true musical expression.

Another of the features of the invention is directed to certain structures of the instrument for producing half-tones of the chromatic scale. These structures are herein called chimney-keys.

It is well known to musicians that quality of tone is dependent on the presence of overtones, or harmonic partials added to the fundamental tone, and it is known that the greater the number of overtones the richer will be the tone. The pattern of overtones forms a definite mathematical relationship of an exponential character.

The harmonic partials are associated with the fundamental note as separate notes by themselves. These partials are superimposed upon the fundamental note to enrich it and this is accomplished by the structure of the instrument when subjected to moderate changes in blowing pressure. In the blowing of a fundamental note, there is a definite fingering for that note. If the fingering is maintained and the blowing pressure is increased, harmonic partials of higher frequency are obtained but the fundamental note is still present. With a moderate change in blowing pressure the fundamental note stands out and the partials develop and are recognized by the ear but they are of higher rate of vibration but they are still part of the harmonics of the fundamental note.

When these partials or overtones are added to the fundamental tone, the quality of the resultant note is altered in timbre and intensity.

This invention, therefore, particularly relates to an improved musical wind instrument, sometimes known as a fipple-flute, or as a chimney-keyed chromatic fippleflute, or as a chimney-keyed chromatic fiageolet, or as one of the pipes in the wind instrument field. Such an instrument is much easier to play and to learn to play than any known wind instrument that could produce like notes, and which has a definite fundamental tone. This improved instrument is simple of construction, is light of weight, and easy to hold in playing position, and may be designed of different lengths as the desired pitch of the instrument dictates.

The chimney keys, and other keys and covers, over the openings in the flute body may completely cover the air exits, or they may partially cover them. Some of the covers or keys have different thicknesses so as to provide difierent lengths of air chimneys that act to increase the length of the air column at one or more of the air exit openings, thereby to obtain variations in the pitch of the musical tones developed by this instrument, as by creating changes of half notes, or otherwise. Improved mechanical operating or fingering mechanisms act to vary these air exit openings in the tube to produce the different tones in accordance with the modified lengths of the air column due to the particular positions of the various covers or keys at a particular instant of time,

thus to produce the variations in the sounds or tones issuing from the instrument.

One of the important features of this invention resides in the type of covers or keys, employed with the air exit openings in the tube body of the instrument. in some instances, it is desired to specifically close entirely one or more of the air exit openings. In other instances, it is desired to have covers for closing one or more of the air exit openings simultaneously and to construct such covers with an opening of very small diameter or a little larger diameter, but in any event, no larger than the diameter of the opening of the air exit in the body structure of the instrument. The thickness of these covers assists in creating variations in frequency in the vibrating air column by changing the length of the air colum due to the thickness of the cover and in placing each cover in position of extending or reducing the normal size of the air exit opening. Usually the moving of one of the chimney-keys from its open position to its down or closed position changes the air column length and thereby changes a note by a half tone.

A further feature of the invention resides in the providing an improved mouthpiece at one end of the instrument, and assembling this mouthpiece in relation to the channel to allow the air blown into the mouthpiece to proceed under increasing compression through the covered part of the channel to a predetermined point and then to flow over a perforation or quasi-half moon restricted opening which leads to one end of the air column in the tubular or body part of the instrument, and thus to create vibrations in the air column. This stream of air under compression constitutes the air reed. This air reed under different degrees of compression and passing over the quasi-half moon opening causes the air column to vibrate at different amplitudes. The frequencies may be modified as desired by the operation of the several covers or keys over the air exit openings.

Further novel features of the invention provide for the range of use of the improved instrument which are readily obtained by varying some of the construction of the instrument, as, for instance, changes in diameter of the bore so as to provide a tapering air column preferably with the smaller diameter near the lower or open end of the instrument, or providing different diameters in the covers or keys over the air exit openings formed in the sides of the instrument, or by fingering the various covers so as to partially cover the exit openings even though one of the thicker covers may be pushed to position of closing the exit opening. Other variations may be made by modifying the type of channel provided for the air reed, thereby changing the direction and pressure in the air reed so as to change its effectiveness in creating other vibrations in the air column, or to change the contour of the vertical hole beneath the air reed, or to change the cubic capacity ofthe expansion or resonating chamber to produce added resonance and other values.

The dimensions and constructional relations of the several portions of the instrument controlling the direction and eifect to the air reed are designed to be in relation to the exponential character to the series of harmonic partials desirable in producing the extensive range and variable power of tone in this novel instrument.

The various other advantages and improved features of the invention herein will be appreciated in reading the detailed description below when taken with the drawings, wherein:

Fig. 1 is a view of the exterior of the fipple-flute showing some of the operating mechanisms and keys and showing a part of an air reed channel in the mouthpiece section;

Fig. 2 is an exterior view of the fipple-fiute when turned 90 from the view in Fig. 1;

Fig. 3 is a top planview, partially in section, of some of the keys and their operating mechanism, and the figure 4 also illustrates various heights or thicknesses of the keys and openings therein;

Fig. 4 is a view partially in section of a portion of the key operating mechanism showing an arrangement allowing independent movements of some of the keys although supported by the same shaft;

Fig. 5 is a sectional view of the operating mechanism taken on line 55 of Fig. 3;

Fig. 6 is a sectional view of the mouthpiece portion of the fipple-fiute taken on line 6-6 of Fig. 7;

Fig. 7 is an end view of the mouthpiece shown m Fig. 6;

Fig. 8 is a section taken on the line 88 of Fig. 6;

Fig. 9 is a perspective view of the mouthpiece portion of the fipple-flute showing the relations of the openings in the mouthpiece portion;

Fig. 10 is a sectional view of one of the keys and its opened relation to a hole in the body of the fipple-flute;

Fig. 11 is a sectional view as in Fig. 10 of the key properly seated in closed position against a portion of the body of the fipple-flute; and

Fig. 12 is a sectional view of a portion of the body of the fipple-flute showing its relative thickness and showing one of the keys in closed position, and showing an uncovered opening in the body of the instrument.

Referring now to these drawings, the improved fipple= flute is noted at 18 composed of mouthpiece portion 19 and 'body portion 2%) which sections overlap when joined together. The construction for overlapping is illus-' trated in Fig. 6, and the external joining shows at the annular line 21.

The improved flute body has an open bore 22', Figs. 10, 11 and 12, to the bellowed end 23 and extends into bore 24 in the mouthpiece portion it. These

passages

22 and 24 constitute the air column in the bore of the flute. Air is supplied by the player blowing into the mouthpiece 26 and which air passes along a channel 27 having a covered portion from the inlet end of the mouthpiece 26 to a plane 28 and from there the air passes a vertical opening 30 and along the remainder of the channel which is exposed and which is designated 29. The base of this latter part of the channel preferably has a convex portion.

The bore of the fipple-flute may be of uniform diameter or maybe tapered. Usually the tapered type of here is preferred.

A number of holes or openings are formed in the wall 31 at position to play certain notes of the scale. A series of these holes or openings is shown in Figs. 1, 2, 10, 11 and 12, and the openings are designated 32, 33, 34, 35, 36 and 37. Two openings covered by the

keys

38 and 39, Figs. 1 and 2, are not visible. It will be noted that

openings

32, 34 and 37 have no covers. The player covers these by manipulation of his fingers.

Opening

33 and 35 are provided, respectively, with keys 4t), and 41, and these keys with

keys

38 and 39 are manipulated by the player to cover the holes or openings in a manner to change a note by a half tone. Particular attention is also called to the fact that some of these keys have openings larger than others, and reference is made to openings 46 in key 40, opening 47 in key 41, and likewise, opening 48 in key 38, while key 39 is maintained closed and when closing over its opening closes the opening entirely. Referring to key 42, it has a large m-ain opening 49 which surrounds an upright collar 50, Fig. l, and in its manipulation does not cover the opening 36. The covering of this opening 36 is accomplished by the finger of the player.

In the preferred construction of the operating mechanism shown in Fig. 3, the operation of either key 41 or 42 will cause the operation of key 40. The operation of key 40 does not operate either key 41 or 42, as a pin 51, Fig. 5, carried by key 41 construction, engagm shoulder 52 which iskeyed to shaft 56 by .pin 54 and n t manipul t oncillat shaft 56.- When.- key; 4m

is manipulated, shoulder 52 moves away from pin 51, and, therefore, neither key 41 nor key 42 is moved. Again in reference to Fig. 3,

keys

41 and 42 are firmly fastened to shaft 57 which shaft may be hollow or may 'be solid. Key 59 is mounted on a hollow shaft 60 and is manipulated by arm 61. This key is normally closed and is independently operated and does not join with either

keys

41 or 42. Arm 61 is provided so as to al low proper manipulation with the left hand of the player. Key 62 is noted as being carried on shaft 63, Fig. 1, and is positioned so as to be easily manipulated by the thumb of the player. This particular key has an opening (not shown) which is approximately inch diameter and may be closed by the operation of the thumb. Bar 64 is provided to manipulate the key 62 by closing the pad on the hole in the instrument and leaving the 1 inch hole open. In this position just described, the position of key 62 acts as an octave key. When the hole in the instrument, and the inch hole are closed, the fundamental tones are induced. This key 62 is normally open.

Chimney key 38 and key 39 are independent, and are easily manipulated by one finger by engaging car 67 or arm 68 or chimney-key 38 itself. It will be noted in this mechanical operation, that the shafts are held in a series of similar uprights illustrated at 69 and 70, Fig. 2, and the keys are all provided with definite types of springs such as represented by wire 71-Fig. 2-which wire engages upright 68 and the shaft 65. The wire is so positioned by sticking out of upright 69 and by engaging shaft 65 at a point that normally springs the wire so that it biases the key into either an open or closed position, as desired. Normally key 38 is in open position.

Keys

39 and 59 are normally maintained closed, while

keys

38, 40, 41 and 62 are normally maintained open.

The holes in the body of the instrument are positioned at definite and desired places along the body portion of the tube so as to play certain notes of the scale. Likewise, the keys which cover come of the openings may be of varied sizes and may have openings in them of various diameters, as illustrated in Figs. 1 and 3. In addition, the thickness of the keys may be relatively con- Siderable or less, also for the purpose of varying the musical results, and especially for changing the length of the air column in the instrument. It is preferred that

keys

38, 40 and 41 shall have thickness made up of metal 72, Figs. 10, 11 and 12, and an insulator, such as cork, '73, or any other desired material. It is desired that the metal shall have an annular collar or chimney part 74 so that when the key 40 is closed, as noted in Figs. 11 and 12, there will be an increase in the length of the air column.

In providing the suitable hole in the body 31 under the keys, it is desired to provide for actually closing the hole so that there will be no exit except through the key and along the collar 74. This is provided by preferably forming an annular sharp edge 76 which acts as a seat for receiving the cork 73. Part of the body is cut away annularly at 77 to allow for positioning of the outer end of the cork 73. The illustrations in Figs. 11 and 12 show the key 49 in its closed position, thus providing a closed additional length of air column, which additional length is called a chimney and, therefore, the keys of this structure are known as chimney-keys. Fig. 12 illustrates the body 31 with the bore 22 and uncovered opening 32.

Referring to Figs. 6, 7, 8 and 9, it will be convenient for description, to divide the disposition of constructional elements into region A and region B. The dividing line will be taken as the plane 28 perpendicular to the axis of the instrument and cutting the instrument at 8-8 where the channel 27 changes from closed to open, i.e., at one end of the mouthpiece 26 where the input of air from the mouth of the player issues into the open portion 6 of the channel 27 over an opening 30, preferably of halfmoon contour which leads into the interior part of mouthpiece portion 19.

It will be noted that the assembly of the mouthpiece 26 on the mouthpiece portion 19 of the instrument is accomplished in a way to present two adjacent openings:

(1) The preferred half-moon opening 30, Fig. 9, through the wall of the instrument into a resonance chamber, and (2) a meniscus shaped opening 31, Fig. 9, for the issue of compressed air from the mouth of the player, which air issue constitutes the air-reed.

Although invisible, this air-reed in motion and under compression, acts as tangible element having a definite shape and mass much the same as any cane or metal reed of a musical instrument. The positions of and the manner in which the two holes or openings are presented to each other, will be known as a coupling.

One of the novel features of this invention as noted above, is to effect this coupling so as to cause the air reed to initially rarefy the air at the half-moon shaped opening 30 to the air column in the body of the instrument. To accomplish this desired coupling, the curvature of the floor of the channel 27 is preferably convex for the greater part of its length under the mouthpiece 26, as noted in Fig. 6. The air reed issuing at point 28 is preferably above or outside the half-moon opening 30.

The contour of the channel 27 is further caused to change sharply at 81 on dotted line to form the curved part 82 and to lead to and meet the inner wall 83 of the bore of the instrument at a point 84.

One of the most desirable structural features of this novel instrument to insure the desired tone production which feature usually governs or controls a condition of manufacture is that of providing within limits certain contours of the inner walls and the positions or location of some cut away portions. It has been found that the desired relationship of the harmonics to a fundamental tone will result when the structure of the instrument is approximately such that the following condition exists, i.e., having two lines intersect in the region A. The first of these two lines is one drawn through the points 81 and 86, and as extended into region A, will intersect a second line that traces the inside of the upper surface of the mouthpiece 26 at the uppermost curvature thereof and extends beyond the mouthpiece. Referring to Fig. 6 of the drawings, these two lines will intersect within region A at point 87. This intersection point may vary in position but it is desired that it be somewhere within the region A. When the manufacture of the instrument is such that the lines intersect as noted, then the instrument will produce the harmonics of the fundamental tone. Also, when the line passing through points 81 and 86 is extended into region B, it will lie above the bottom of the open channel portion 29 for a distance a few times the lateral measurement of the half-moon opening, the relationship of the harmonics to a fundamental will also be maintained.

Referring now to the formation of the air column within the body of the instrument, there is provided an expansion chamber 88 of the bore joining the half-moon opening 30 with the general internal air column. This expansion or resonance chamber below the half-moon opening 30 is preferably formed by enlarging somewhat the bore at that region.

In noting the air reed as a tangible mass quantity, it will be understood that the initial rarefaction set up at the half-moon opening 30 in the instrument by the air reed, is met immediately by an equal and opposite com pression, which rarefaction and compression follow one another in quick succession with the air reed fluttering to and fro over the half-moon shaped opening, thus sustaining the tone in desired pitch. Increased input, as by the force of the players breath, produces increase in power of tone without distortion of pitch. This novel effect, much desired in music, is, it will be noted, made a possible by this novelcombination of exponentially provided constructional features acting in correlation with the natural measurements of the instrument governing tones.

Considering the aero-dynamic principles involved, it will be evident that the presence of exponentially curving structure as described, forces the air-reed to follow along the curved surfaces of the channel and later along outer Surface 29 of the floor or base of channel 27 to a greater or lesser degree, depending upon the rate of input of air at the will of the player. These combined airactions and reactions therefore, impart in a large measure, elasticity to the air-reed, thereby resulting in the desired musical shadings.

With the desired construction of the mouthpiece portion 19 of the improved instrument, it will be noted the line drawn through the points 81 and 86 is tangent at the point 31 to the floor of the channel 27. When the player blows air into the mouthpiece 26, it will be noted in Fig. 6 that the air becomes compressed as the floor of channel 27 rises and thereby requires the air to be compressed to form the air reed, and the highest point of compression is at exit point 81. The air then issues from underneath the mouthpiece 26 at the meniscus opening 31, where the channel is open at its top and passes over the opening 30 and along the curvature of the floor of the channel 27 in the open region B. The radius of the floor of channel 27 is the same as that under the moutl piece for a distance, and then the curve becomes concave and continues to the top wall of the instrument, and thus the air reed is forced out of and away from the instrument. Thus, the depth of the channel 27 varies. The floor of the channel 27 may vary somewhat in length of the convex and concave portions and such variations may be governed or controlled or dictated by a desired coupling which permits the musical impressions desired. The structure simulated in Fig. 6 for these preferred curvatures has been found to be satisfactory.

It will be evident from the description and the structural features outlined that this invention discloses a novel construction to utilize air in motion as a reed affording most of the qualities heretofore ascribed only to cane or metal reeds.

This invention also provides for the novel arrangement for changing the length of air column in the body of the instrument by including different novel types of keys, some noted above as chimney-keys.

It will be understood that various modifications and changes may be made in the preferred form of the invention herein, and such modifications and changes are to be understood as part of this invention, as outlined in the following claims.

The invention claimed is:

1. A musical instrument comprising the combination of a tube, a mouthpiece at one end of the tube, said tube and mouthpiece having a bore extending longitudinally therethrough, said tube having a series of radial tone holes therethrough communicating with the bore for playing notes of different pitch, said mouthpiece being open at one end for the reception of a stream of air, the mouthpiece having a channel communicating with the opening and directing the stream of air along a path externally of the bore and longitudinally thereof, the chan nel having a floor, side walls and a roof, the roof extending substantially parallel to the axis of the bore, the floor having a convex curvature sloping upwardly from the opening toward the roof and then downwardly away from the roof from a point in nearest proximity to the roof, the floor having an orifice opening through the floor and forming a communication between the channel'and the bore, said orifice being located in proximity to but beyond the said point of nearest proximity of the floor to the roof so that the cross sectional area of the chan nel constantly diminishes to said point of nearest proximity andthen increases to the near, edge of the orifice, and the u roof terminating above the near edge of the orifice so that the channel is open to atmosphere above and beyond the orifice.

2. A musical instrument comprising the combination of a tube, a mouthpiece at one end of the tube, said tube and mouthpiece having a bore extending longitudinally therethrough, said tube having a series of radial tone holes therethrough communicating with the bore for playing notes of different pitch, said mouthpiece being open at one end for the reception of a stream of air, the mouthpiece having a channel communicating with the opening and directing the stream of air along a path externally of the bore and longitudinally thereof, the channel having a floor, side walls and a roof, the roof extending substantially parallel to the axis of the bore, the floor having a convex curvature sloping upwardly from the opening toward the roof and then downwardly away from the root from a point in nearest proximity to the roof, the floor having an orifice opening through the floor and forming a communication between the channel and the bore, said orifice being located in proximity to but beyond the said point of nearest proximity of the floor to the roof so that the cross sectional area of the channel constantly diminishes to said point of nearest proximity and then increases to the near edge of the orifice, the roof terminating above the near edge of the orifice so that the channel is open to atmosphere above and beyond the orifice, the orifice having a diameter which increases as it progresses from the floor to the bore so that the far edge of the orifice forms an acute angle with the floor and presents an enlarged chamber.

3. A musical instrument comprising the combination of a tube, a mouthpiece at one end of the tube, said tube and mouthpiece having a bore extending longitudinally therethrough, said tube having a series of radial tone holes therethrough communicating with the bore for playing notes of diiferent pitch, said mouthpiece being open at one end for the reception of a stream of air, the mouthpiece having a channel communicating with the opening and directing the stream of air along a path externally of the bore and longitudinally thereof, the channel having a floor, side walls and a roof, the roof extending substantially parallel to the axis of the bore, the floor having a convex curvature sloping upwardly from the opening toward the roof and then downwardly away from the roof from a point in nearest proximity to the roof, the floor having an orifice opening through the floor and forming a communictaion between the channel and the bore, said orifice being located in proximity to but beyond the said point of nearest proximity of the floor to the roof so that the cross sectional area of the channel constantly diminishes to said point of nearest proximity and then increases to the near edge of the orfice, the roof terminating above the near edge of the orifice so that the channel is open to atmosphere above and beyond the orifice, the orifice having a diameter which increases as it progresses from the floor to the bore so that the far edge of the orifice forms an acute angle with the floor and presents an enlarged chamber, and the floor continuing beyond the far edge of the orifice in said convex curvature.

4. A musical instrument comprising the combination ofa tube, a mouthpiece at one end of the tube, said tube and mouthpiece having a bore extending longitudinally tzerethrough, said mouthpiece being open at one end for the reception of a stream of air, the mouthpiece having a channel communicating with the opening and directing the stream of air along a path externally the bore and longitudinally thereof, the channel having a floor, side walls and a roof, the roof extending substantially parallel to the axis of the bore, the floor having a convex curvature sloping upwardly from the opening toward the roof and then downwardly away from the root from a point in nearest proximity to the roof, the fioor having an orifice opening through the floor and formingv a communication between the channel and the bore, said orifice being located in proximity to but beyond the said point of nearest proximity of the floor to the roof so that the cross sectional area of the channel constantly diminishes to said point of nearest proximity and then increases to the near edge of the orifice, the said tube having a series of radial tone holes therethrough communicating with the bore for playing notes of different pitch, two of the tone holes of the series being positioned for playing one note when the lower hole is open and the upper hole is closed, and a second note, a whole tone higher than the first note when both holes are open, a cylindrical key adapted to be superimposed over the upper hole coaxially therewith, having a bore of a diameter and length to sound the fiat of said second note when the key is positioned over the upper hole with its outer extremity open so that the bore of the key is in communication with and forms an extension of the bore of the tube, and a manually operable finger piece associated with said key to depress said key in said position while leaving its outer extremity open.

5. The musical instrument as defined in claim 4 in which the diameter of the bore of said cylindrical key approximates the diameter of said upper hole.

References Cited in the file of this patent UNITED STATES PATENTS 527,742 Devault Oct. 16, 1894 638,385 Evette Dec. 5, 1899 1,786,833 Dytch Dec. 30, 1930 2,202,410 Walberg May 28, 1940 2,330,379 Powell Sept. 28, 1943 FOREIGN PATENTS 246,255 Italy Apr. 1, 1926 431,185 Germany July 1, 1926 841,597 France Feb. 13, 1939 724,046 Germany Aug. 17, 1942