US1728754A - Stringed musical instrument - Google Patents

Description

I Sept. 17, .w ESPIE I STRINGED MUSICAL INSTRUMENT Filed march 8, 1927 A TTORNE Y.

Patented Sept. 17, 1929 JOHN W. GILLESPIE, OF CINCINNATI, OHIO S'IBINGED MUSICAL INSTRUMENT Application filed March 8, 1927. Serial No. 173,744.

My invention relates to stringed musical instruments of the type of banjo. ukulele or the like, in which music is produced by playing on strings which cause the vibration of a tympanum or diaphragm which is mounted in a tubular supporting member.

It is the object of my invention to construct the support for the tympanum, so that a maximum of strength will be achieved, and so that the additional strengthening means which I provide will greatly clarify the tone of the notes and cause more mellow, bell-like tones to be emitted from the instrument than has been possible in such instruments prior to my invention.

Referring to the drawings in which I have shown a preferred structure in a banjo which embodies my invention Figure 1 is a plan View of a banjo head.

Figure 2 is a section of the head taken along the lines 22 in Figure 1.

Figure 3 is a detail section taken along the lines 33 in Figure 1.

Figure 4 is a diagram of the probable audio principle involved in my novel structure.

The banjo illustrated in Figures 1-3 is composed of a tympanum 1 mounted on a wooden tubular casing member 2, which I will refer to as the head. 7 The tympanum which is ordi- 36 narily made from some strong animal fibrous membrane is bound at its edges in adjustable annular members which will permit the tympanum to be tightened and released in accordance with the conditions to which the instrument is subjected. For supporting the edges of the tympanum I have shown, as is in accordance with standard banjo manufacturing practice. a hoop 3 and a stretcher band or wire 4. The edges of the tympanum 0 are passed under the band 4, then up on the bearing downwardly on the top surface of the hoop. The posts are mounted in lugs 6 which are interspaced about the outer periphery of the tubular support and secured to the support with screws such as are indicated at 7. The posts have threaded ends which extend through the lugs and nuts 8 are mounted on the threaded ends. By tightening up the nuts one after another, it will be obvious that the tympanum or diaphragm may be tightened, and by slacking off on the nuts the tympanum will be loosened.

The playing strings for the banjo are inclicated at 9. The usual method of securing the strings is in a plate 10, which is secured to the tubular support as indicated in Figure 2 with pin posts 11 which extend through an outwardly flanged portion 12 of the plate. The pin posts have threaded ends Which pass through lugs 13 which are attached to the tubular support in a similar manner as are the lugs 6, by screws 14. The plate 10 has grooves therein and in each one of the grooves a string is engaged usually by knotting the end of the string. The strings pass up over the face of the tympanum over a bridge 15 mounted on the tympanum in the usual manner.

The description of the construction, so far given. forms no part of my invention, being explained merely so as to enable one skilled in the art to copy the exact structure which I have found most satisfactory in a banjo instrument.

My invention consists primarily in the structure of the wooden tubular support 2 for the tympanum which is that part of the instrument which contributes to the quality of the music thereof. I have shown at the base of the member 2 an internally flanged wooden rib 16 which it will be apparent is of considerable importance in supporting the tubular member against a collapsing strain which is often present in such instruments as a banjo. Banjos are very often provided with cross ribs which extend across the opening in the tubular support, and although I may equip a banjo made in accordance with my invention with such a rib, its presence or lack does not materially affect the practical result that the wooden reinforcing rib 16, which is preferably beveled from lines parallel to the sides of said head toward lines projected along radial lines extending from the axis of the head, materially increases the anticollapsing strength of the tubular sound box.

In Figure 4 I have illustrated diagrammatically my theory of the effect of the rib on the tone of the instrument. I have shown a tympanum which is indicated at a. The tubular support is indicated at Z). The effect of sound waves on one side of the tympanum without the rib 0 is indicated by the dotted lines at the bottom of the figure. WVhile a vibration of the tympanum causes impulses on one side of the tympanum, counter impulses are caused by the inward movement of the tympanum on the other side thereof. The cycle is alternately reversed and repeated on each of the sides of the tympanum in accordance with the rate of vibration of the sound wave. If the tubular support is not provided with anything to interfere with the free travel around the corner edge of the support, the effect is for the plus and minus waves, as they may be called, to neutralize each other, as is indicated by the dotted lines at the lower end of the figure. With the flanged reinforcing rib, however, indicated at the upper side of the figure, the tree path of tone vibrations from one side of the tympanum to the other is restricted and a Louder and more vibrant sound is heard, due to the sound waves being turned inwardly toward the axis of the head. It will be observed that the sound waves within the tubular support are turned back, each on the other, and they reverberate within the head. A resonance which gives the tonal quality of a bell results. I have indicated the path of travel of the sound vibrations in an instrument constructed in accordance with my invention by the wavy solid lines shown in Figure 4.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent, is

1. In a stringed musical instrument, a tympanum and a wooden tubular resonant support for said tympanum, said support being open at its ends, and a Wooden reinforcing peripheral rib extending about one end to reinforce the tubular support, said rib acting as a battle to increase the resonance of said support, said rib extending inwardly adjacent the outer periphery of said tubular support, and having a concaveinner Wall.

2. In a stringed musical instrument, a tympanum and a wooden tubular resonant support for said tympanum, said support being open at its ends, and a wooden reinforcing peripheral rib extending about one end to reinforce the tubular support, said rib acting as a bafile to increase the resonance of said support, said rib extending inwardly adjacent the outer periphery of said tubular support, and portions of said rib concavely beveled to deflect sound Waves inwardly toward the axis of said support.

3. In a banjo, an open ended resonant support for the diaphragm thereof, and a wooden rib formed adjacent the open end of said support, said rib being beveled from lines parallel with the Walls of said support and curving concavely toward the axis of said support whereby sound waves within said support will tend to be deflected back into said support, whereby the tonal quality of said banjo will be improved.

JOHN WM. GILLESPIE.

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