IMPROVEMENTS IN PIANOFORTES
Year: 1868

page_text: PROVISIONAL SPECIFICATION left by William Dawes at the Office
of the Commissioners of Patents, with his Petition, on the 28th
October 1868.
I, WILLIAM DAWES, of Blenheim Place and Kingston Grove, Leeds, in
the County of York, Engincer and Organ and Harmonium Manufacturer,
do hereby declare the nature of the said Invention for "IMPROVEMENTS IN
PIANOFORTES," to be as follows:-
My first improvement has for its object the prevention of variation of
'pitch" of the instrument consequent upon variations of temperature
of the atmosphere in which the instrument is placed; this I effect by
substituting for the ordinary wood or cast-iron "frame" of the instru-
ment a compensating frame so constructed that it shall compensate for
the alterations in length and tension of the wires or strings through
variations of temperature by its own expansion or contraction for heat
or cold in a like or necessary manner or degree to the strings themselves;
the amount of compensation being gauged or determined by the kind,
mixture, or alloy of metal or metals employed in the frame, or by tho

page_text: quantity or proportion of zinc, brass, or other expansive metal used or
fitted into or employed with wood, iron, or other metal or substance to
give the required result. I prefer to use zinc for the compensating
metal, but I do not confine myself to any or one kind of metal, nor to
one particular "make" or construction of frame, as these details may
be varied in many ways without altering the principle or effect of my
Invention.
My second improvement consists in a novel construction of "sound
board" for increasing the amount of vibration, and thereby improving the
tone of the instrument; this I effect by the use of a double sound board
constructed with a space of about one inch between the front and back
boards, and I sometimes construct this sound board with the back some-
what smaller in size or area than the front, and I attach or unite the
two firmly together in such a manner that this difference in size shall
cause compression upon the front board and tension upon the back board,
and thus increase the resonance and tone, and in some cases I produce
this tension and compression by a kind of "lattice" or open back of
separate strips or bands, each one having the necessary amount of
tension by means of screws or wedges as may be desirable. I sometimes
prefer to fix this double sound board by or upon ribs, studs, or supports
exactly coinciding in position with the "bridge" upon the sound board,
over which the strings or wires are stretched; in some cases I improve
the upper notes of the instrument by enlarging the sound board locally,
so as to give a greater area round the upper end of the bridge, over
which the wires of the upper notes of the instrument are stretched;
this enlargement may enter the "rest plank" and be continued for a
short distance beneath or behind what may be termed the rest plank
bridge.
Ny third improvement consists in the employment of a revolving or
other mechanical movement actuated by the feet or otherwise, for pro-
longing the notes of the instrument by a succession of extremely rapid
blows or strokes upon the wires (or upon additional wires placed at tlie
back of the instrument) either from the usual or ordinary hammers,
or others, or both, such blows or strokes having sufficient rapidity 'to
produce as nearly as possible the effect of an uniform and continuous
tone in imitation of a wind instrument, not as a "tremolo " or with a
distinct or palpable "beat," but on the contrary with as much smooth-
ness and connection as possible. I purpose to achieve this either by

page_text: "
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cams or fluted rollers acting by strings or otherwise upon hammers,
or by spring nobs, hammer's, or other clastic projections from wheels or
rollers, or from bands or belts running upon such wheels or rollers, the
bands being elastic and the projecting nobs, hanimiers, or other pro-
jections striking upon or or against the wires during their revolutions by
a kind of centrifugal force or blow when brought sufficiently close to the
wires by pressing down the keys of the instrument.
I also sometimes apply the "octave coupler" to this part of my
Invention so as to give additional smoothness, power, and brilliancy;
and as my fourth improvement I in some cases arrange the connection
of this movement with the keys of the instrument so that the sustained
effect is or can be produced "ad libitum" upon certain notes only by
pressing these notes down to a greater depth by a harder or greater
blow or pressure upon the key; to render this latter effect possible upon
the pianoforte I divide the back portion of each key in a sloping direction
from the bottom near the "centre pin" upwards towards the front of the
hopper block," and I joint or hinge it on the bottom side and apply a
spring on the upper side to close or "stiffen" the key as though it were
not divided; I then terminate the lift or rise of the back end of the key
by a fixed or adjustable "stop" at the proper height or distance for the
correct action of the "hoppers" or "check" of the piano action as
though the keys were not divided, the front part only of the key moving
under the extra blow or pressure of the finger; in some cases, however,
I dispense with the jointed or divided key by using an elastic pad or
packing under the centre of the key, so that when the back end is
stopped or retained at the proper height by the before-named "stop"
the front end may yield under the additional pressure; it will be obvious
that the additional tone or effect above the ordinary percussive tone of the
piano must be produced from or by a connection with the front end of
the key; the before-named mechanical arrangement (so far as regards
the keys of the instrument) being also applicable to reeds, pipes, or other
methods or "attachments" as well as to the before-named manner of
obtaining the "prolonged" effect.
My fifth improvement consists in the application of a catch or check
to the dampers or other convenient part of the "action" of the piano
for a space or compass of about two octaves at the lower or bass end or
part of the instrument similar in its action to the "tirasse tenuto "*
stop in the harmonium and organ, and enabling the player to retain or

page_text: prolong the tone of one or more bass notes whilst the free use of the
"forte" pedal is allowed for the other or higher notes of the instrument
without "damping or silencing the notes to which this action or
movement is applied.