VARIABLE OR ADJUSTABLE TUNING FORKS
Year: 1885

page_text: I DAVID WEBSTER SEGROVE of Springfield, in the County of Clark and State
of Ohio, one of the United States of America, Musician, do hereby declare the
nature of my invention in VARIABLE OR ADJUSTABLE TUNING FORKS and in what
manner the same is to be applied, to be particularly described and ascertained in
and by the following statement :-
The nature of the invention is the employment with a tuning fork, having
graduated prongs, of a moveable bridge with projecting ends adapted to mark the
adjustment of said bridge; also the employment of concave ends or shoulders on
said bridge which rest against the prongs of the fork so that a bearing or contact
is secured only at the sides of the prongs; also the employment of backwardly
extending guides which extend from said bridge in close proximity to the prongs,
to hold the said bridge at right angles across the fork and prevent the said bridge
from being pressed out of position by the elasticity of the prongs.
My invention further employs fork prongs having enlarged or bell shaped ends
whereby the adjustment of the bridge necessary to secure a desired tone is reluced
so that a range of an octave may thus be secured in a fork of ordinary length.
My invention further employs a removeable handle at the base of the fork
which enables the fork to be more economically constructed, by bending the fork
proper from a straight bar of steel, the handle being afterwards inserted in the base
thereof.
In the accompanying drawings Fig. 1 is a perspective view of a fork embodying
my invention. Fig. 2, is a plan view of the same without the bridge, showing the
handle removed therefrom. Figs. 3 & 4, are views showing a form of the fork in
which the bridge is adapted to bear on the outside of the prongs instead of the
inside. Figs. 5, 6 & 7, are views illustrating the constructing of one form of the
bridge in which the guides are made in one piece with the bridge. Figs. 8 & 9
show a bridge with the guides made in a separate piece and secured thereon.
Figs. 10, 11 & 12, are views of the bridge adapted to bear on the outside of the
prongs, and Figs. 13 & 14, are views illustrating the manner of constructing the
fork proper.
A represents the fork proper; B the adjustable bridge or cross bar therein, and
C the handle, which is made separate from the fork and preferably screwed therein.

page_text: The adjustable bridge is adapted to slide between the prongs a a of the fork, and
is held therein by the spring or resilience of the said prongs. The prongs a a are
provided with graduations corresponding to the tones or semi-tones to be produced
by the fork.
•
In order that the bridge may be adjusted accurately at the mark or graduation
to produce a given tone, and also to hold the bridge from slipping transversely
through the fork, I provide the said bridge on either side with projections b
adapted to extend over the top of the prongs, as shown. These projections serve as
guides, or markers, whereby the exact graduation desired may be obtained.
To preserve the bridge at all times at right angles across the fork, and thus
prevent the said bridge from being forced out by the elasticity of the prongs a a,
pressing on the respective ends thereof, and at the same time to secure accuracy in
the tone produced by the fork at a given graduation, I provide the bridge with
backwardly extending guides or projections o, which extend from said bridge in
close proximity to the prongs a a. These guides c, I make in one piece with the
bridge B by first stamping the bridge out as shown in Fig. 5, and then shearing and
forcing the projections outward as shown in Figs. 6 & 7. It is obvious that the
guides may be formed in different ways for instance as shown in Figs. 8 & 9, in
which case the guides are made in a separate piece and riveted to the bridge B.
In order to reduce the length of the fork to an ordinary or moderate size, and at
the same time adapt the fork to secure a range of an octave in extent, I provide
the prongs a a with enlarged or bell-shaped ends e, the body of the prongs
between the said enlarged ends and the base e¹, being made quite slender. The
base e¹, is made heavier than the body of the prongs to secure the proper strength.
By making the handle C separate from the fork proper as above stated I ai
enabled to make the fork much more economically than could be done were the
handle stamped out in one piece with the fork, as heretofore.
In constructing the fork I take a straight bar of steel, as shown in Fig. 13, cut
to the proper length and of a size sufficient to form the width of the prongs and
the enlarged ends thereof.
This bar is then reduced by milling or swaging to the form shown in Fig. 14
after which it is bent (as indicated in dotted lines) to the form shown in Fig. 2
and the handle inserted therein.
The handle is preferably turned up round and knurled on its outer surface, and is
screwed or otherwise secured into the base e¹ of the fork proper.
In order to get a perfect bearing between the prongs a a and the bridge B, and
thus secure a perfect tone in any position of adjustment which the bridge may
occupy, I construct the ends of said bridge slightly concave, so that a bearing or
contact is secured only at the sides of the prongs. This not only secures a perfect
contact at all times between said prongs and bridge, but also lessens the friction
between said parts, rendering the bridge very easily adjustable, and at the same
time holds the bridge more firmly in its position. In Fig. 3 I have shown the
bridge formed with concaved ends or bearings adapted to engage the prongs of
the fork on the outside instead of on the inside. In this case the elasticity of
the prongs of the fork tends to force the prongs apart so that a bearing is
maintained with the bridge at any point of adjustment.
It will be seen that by the construction above described I secure a tuning-fork
which may be readily adjusted to produce any tone within the octave, and by
constructing the prongs of the shape described I am enabled to secure the adjust-
ment necessary to produce an octave in range without materially increasing the
length beyond that of an ordinary non-adjustable or single-tone fork.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is
1. The employment of the projections on the ends of a moveable bridge to mark
the adjustment of said bridge on the graduated prongs of a variable tuning-fork.

page_text: 2. The construction of the moveable bridge with concaved ends to form a bearing
on the sides of the prongs as described.
3. The construction and arrangement of the moveable bridge with the back-
wardly extending guides.
4. The arrangement and construction in a variable tuning-fork of the prongs.
having enlarged or bell shaped ends.
5. The arrangement and construction with a tuning-fork of a removeable handle
adapted to be secured to the base of said fork.