US1608875A - Resonance and amplifying chamber for banjos - Google Patents

Description

NOV. 30 1926.

- F. J. BACON ET AL RESONANCE AND AMPLIFYING CHAMBER FOR BANJOS Filed April 18, 1924 5 Sheets-Sheet 1 zlwmmtow 4 1 J Baco Nov. 30, 1926.-. 7 1,608,875

F. J. BACON ET AL RESONANCE AND AMPLIFYING CHAMBER FOR BANJOS Filed April 18, 1924 s sheets-sheet 2 gmmtou 6 if cl Bacon p pua l.

Nov. '30 1926. 7 1,608,875

F. J. BACON ET AL RESONANCE AND AMPLIFYING CHAMBER FOR BANJOS 5 Sheets-Sheet 3 Filed April 18, 1924 Patented Nov. 30, 1926.

UNITED STATES PATENT OFFECE,

FREDERICK J'. BACON, OF NEW LONDON, AND DAVID L. DAY, OF GRO'ION, CQNNECTIC'UT.

RESONANCE AND AMPLIFYING CHAMBER FOR BANJOS.

Application filed April 18, 1824. Serial No. 707,462.

This invention relates to improvements in resonating chambers for banjos and similar stringed instruments andhas as one of its objects to provide a resonating chamber which will greatly amplify and improve the tones produced by playing of the instrument, the invention contemplating the provision of an amplifying chamber so constructed that the sound waves will be greatly amplilied before they are delivered from the instrument.

Another object of the invention is to provide a resonating chamber which may be applied to the rim of any ordinary banjo and readily secured in place, and which chamber will greatly enhance the tonal qualities of the instrument.

Another object of the invention is to pro vide a. resonating or amplifying chamber for 2:) banjos so constructed as to provide against any mufiling of the tones and designed to deliver the tones or sound waves in a direction forwardly away from the instrument.

Another object of the invention is to provide a Simple and inexpensive means associated with the resonance or amplifying chamber and adapting the chamber to be applied to the rim of any ordinary banjo with out any'alteration in the construction of the rim or any mutilation of any part thereof.

Another object of the invention is to so construct the attaching means that the amplifying chamber may be readily and quickly applied and equally as readily and quickly removed, so that when employed in the rendition of concerts, the amplifying chamber may be attached or detached in accordance with the nature of the selection to be played.

In the accompanying drawings:

to Figure 1 is perspective view of resonance or amplifying chamber embodying the present invention applied to the rim of a banjo,

Figure 2 is a detail vertical transverse sectional view taken substantially on the line 2-2 of Figure 1, looking in the direction indicated by the arrows,

Figure 3 is a view in side elevation illustrating a portion of the instrument and the resonance chamber applied thereto and the means employed for holding the said chamber to the rim of the instrument,

Figure 4t is a plan view of one member of the holding or attaching means,

55' Figure 5 is a horizontal sectional View taken substantially on the line 55 of F igure 2,

Figure 6 is a view similar to Figure 3, illustrating a slight modification of the in vention as regards the attaching and holding means. I

In the drawings, the numeral 1 indicates in general a banjo which may be of ordinary or any special construction, the instrument embodying, as usual, a neck 2 extending from the usual rim 3 having the membraneous head 4; tensioned by the usual tensioning devices embodying each a shank 5, a hooked end 6 engageable over the rim 7 which engages in turn, the periphery of the membraneous head f, the fixed bearing 8 through which the stem extends and which bearing is mounted upon the outer side of the rim, and the usual nut 9 which is threaded adjust-ably onto the lower end of the stem 7 and which ordinarily bears against the under side of the said bearing 8. These parts are all of the usual construction and do not in themselves enter into the present invention except in the relationship which they bear to the resonance or amplifying chamber of the present invention.

The rim 3 and head f of the instrumentconstitute, as usual, a resonance chamber, and the present invention contemplates disposing against the open back of the rim, an alnplifyingchamber which will increase the resonance of and amplify the tone before delivery from the instrument, thus improving not only the quality but also the volume of the tone. The said amplifying chamber is indicated in general by the numeral 10 and the same is spun from sheet metal. The said chamber comprises a substantially fiat, annular top wall indicated by the numeral 11, which wall is provided at its inner periphery with a depending annular flange 12 which is relatively shallow and which is of a diameter substantially equal to the external diameter of the rim 3 of the instrument. From the lower edge of the flange 12, an annular partition wall 13 projects inwardly a suitable distance and defines an opening 14 located centrally of the said. wall. Viewed in another light, the resonancechamber includes a top wall which is provided centrally with an opening and which, between its inner and outer peripheries, is stepped downwardly so as to accommodate the open side of the rim 3 of the instrument 110 in connection with which the amplifyingi chamber is to be employed. The top wall 11 at its outer periphery is provided with a downwardly extending annular flange which constitutes the circumscribing wall 15 of the said chamber, and this wall is of somewhat greater depth than the flange 12, as clearly shown in Figure 2 of the drawings. The numeral 16 indicates a resonant back which may be of any resonant material such as wood, and this back is of circular form and preferably bulged as indicated by the numeral 17, the back being provided with a peripheral rabbet 18 which receives the lowor edge portion of the wall 15, screws 19 being secured to said lower edge portion of said wall and into the periphery of the said back 16.

As heretofore stated, the open side or back of the rim 3 is adapted to be more or less snugly received within the circumference of the flange 12, as shown in Figure'2 of the drawings, and against the adjacent portion of the partition wall 13., the resonance chamber of the instrument and the amplifying chamber of the present invention being placed in communication with each other by way of the opening 14 which is, as'stated, defined by the inner periphery of the partition wall 13. By reference to Figure 5 of the drawings, in particular, it will be observed that the top wall 11 of the amplifying chamber of the invention surrounds the rim 3 of the instrument and is formed at equally spaced intervals with openings 20'which are of relatively large diameter; openings 21 which are of smaller diameter; and, openings 22 which, in a manner to be presently explained, accommodate elements of the attaching devices for holding the amplifying chamber to the, instrument. The openings 20 and 21 are alternately arranged as illustrated in the drawings, and by reference to Figures 1 and 5, it will be observed that the openings 20 are located immediately below the tensioning nuts 9.

In that form of the invention shown in Figures 1 to t inclusive, the attaching means for holding the resonance and amplifying chamber to the rim of the instrument is indicated in general by the numeral 23 and the same comprises, in part, a bridge in the nature of a flat arcuate plate 24; disposed with its concave edge presented toward the outer side of the rim 8 and having its end portions formed with slots 25, the said plate being formed intermediate its ends and in its convex edge with a notch 26. In mounting the plate in place, the threaded lower end portions of an adjacent pair of the clamps 5 of the head tensioning devices are fitted through the slots 25, and the nuts 9 of'the'said devices then applied to their respective stems and suitably tightened. In this manner, the bridge plate 24 is secured 11 place in position extending between two adjacent ones of the head tensioning devices and is, therefore, rigidly secured with relation to the rim 3 of the instrument. The numeral 27 indicates a bolt which is fitted through a respective one of the openings 22 in the top wall 11 of the resonance and amplifying chamber and which has a headed end 28 located within the said chamber, a spring 29 being arranged upon the said bolt within the chamber and bearing at one end the head28 and at its other or upper end against the under side of the said wall 11. The upper endof the bolt is threaded as indicated by the nruneral 30 and extends upwardly through the notch 26 in the bridge plate 24L, and a thumb nut 31 is adjustablv fitted-on said threaded end of the bolt and may be adjusted to bear upon the upper side of the bridge plate and through its adjustment draw the bolt 2'! in an upward direction, hus tensioning the spring 29 and causing the partition wall 18 of the amplifying chamber to bind firmly against the rear edge of the rim 3, this arrangement of the parts being most clearly shown in Figures 2 and 3 of the drawings. The openings 22 are preferably located at diametrically opposite sides of the amplifying chamber 10 on a diametri'c line substantially at right angles to the neckof' the instrument, and while only two of the attaching'and holding devices are illustrated as employed in connection with the amplifying chamber embodying the invention, it will be understood that a gre aternumb'er may be employed if found desirable or expedient.

In that form of the invention shown in Figure 6 of the drawings, the attaching and holdingnneansembodies a bridge plate 32 corresponding to the bridge plate 24;, and fitted through an opening 33 in the said plate intermediate its ends, is an adjusting screw 34: having a slotted head 35 adapting it for the application thereto of a screw driver, the threaded shank of the screw being fitted through an opening 36 in the top wall 11 of the resonance and amplifying chamber and threaded through an openii 37 formed in a disc or plate 88 welded or otherwise secured to the under side of the said wall 11 and of a thickness to have a number of threads formed in the wall of it; said opening 87. In this construction it is only necessary to apply a screw-driver to the head of the screw and adjust the screw so as to draw the resonance and amplifying chamber to the rear edge of the rim of the instrument.

From the foregoing description of the invention it will be evidentthat the sound waves developed in the resonance box of the'instrument will enter the resonance and amplifying chamber embodying the invention, by way of the opening 14L defined by the annular partition wall 13, and due to the greater diameter of this chamber as compared to the rim of the instrument, the resonant nature of its back 16 and its double component walls, and due to the firm contact of the rear edge of the rim 3 against the metallic partition wall 13 of the said chamber, the sound waves will be reverberated, the quality of the tone improved, and the volume increased, before the sound waves finally are delivered from the said chamber through the openings 20 and 21 in the wall 11 thereof. Inasmuch as in the playing of the instrument the said wall 11 will be presented in a forward direction from the player, the sound waves will be delivered in a corresponding direction and will, therefore, not be muffled by the clothing of the musician and will carry to a greater distance than would be the case if the resonance chamber were not employed.

It will furthermore be evident that the resonance and amplifying chamber embodying the invention may be readily and quickly applied to and removed from any ordinary banjo, the rim of which is of a diameter exteriorly to fit within the stepped top wall of the said chamber.

Having thus described the invention, what we claim is:

1. A resonant amplifying chamber for banjos having a continuous annular portion constituting a seat for the edge of the wall of the resonance box of the banjo and spaced inwardly from its outer periphery and of a diameter to receive the. said resonance box, and attaching means carried by the chamber, the said chamber being provided in one of its walls outwardly beyond the seating portion with sound wave exit openings.

2. A resonant amplifying chamber for banjos having oppositely arranged resonant walls and a circumferential connecting wall, one of said first mentioned walls having a continuous annular seat for the rear edge of the wall of the resonance box of a banjo and having an opening located within the circumference of the said seat.

3. A resonant amplifying chamber for banjos having oppositely arranged resonant walls and a circumferential connecting wall, one of said first mentioned walls having a continuous seat for the rear edge of the wall of the resonance box of a banjo and having an opening located within the circumference of the said seat, said wall being provided, outwardly of the seat, with sound wave exit openings.

i. A resonant amplifying chamber for banjos comprising an annular wall having a portion between its inner and outer peripheries constituting a continuous annular seat for the open back of the resonance box of the banjo, acircumferential connecting wall extending about the outer periphery of the first mentioned wall, and a resonant back disposed within the circumference of said circumferential wall, the first mentioned wall being provided with sound wave exit openings between its seating portion and its outer periphery.

5. A resonant amplifying chamber for banjos comprising a plane annular wall defining an opening, the inner peripheral portion of said wall being offset to provide a depressed seat for the edge of the wall of the resonance box of the banjo, the said wall being provided outwardly beyond the seating portion with sound wave exit open- I ings, a circumferential wall surrounding the outer periphery of the first mentioned wall, and a resonant back disposed within the circumference of the said circumferential wall.

6. The combination with a banjo including the usual resonance box, head and tensioning devices for the head, of an amplifying chamber having a plane annular wall provided at its inner periphery with an annular flange extending inwardly from the plane of said wall, said flange being provided with an inwardly extending resonant partition wall having a central opening located within the bounds of the wall of the resonance box, the edge of the wall of the resonance box seating against the partition wall and within the circumference of the said flange, a circumferential wall extending about the outer periphery of the first mentioned wall, a resonant back supported within the circumference of the said circumferential wall, the first mentioned wall having sound wave exit openings, and means extending between the said first mentioned wall and certain of the said tension ing devices for holding the said chamber to the resonance box.

In testimony whereof we afiix our signatures.

FREDERICK J. BACON. '[L.s.] DAVID L. DAY. [L.S.]

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