AN IMPROVEMENT IN THE CON- STRUCTION OF PIANOFORTE FRAMES
Year: 1858

page_text: LETTERS PATENT to John Dewrance, of Barge Yard, in the City of
London, Engineer, for the Invention of "AN IMPROVEMENT IN THE CON-
STRUCTION OF PIANOFORTE FRAMES."
Sealed the 1st March 1859, and dated the 21st September 1858.
PROVISIONAL SPECIFICATION left by the said John Dewrance, at the
Office of the Commissioners of Patents, with his Petition, on the 21st
September 1858.
I, JOHN DEWRANCE, of Barge Yard, in the City of London, Engineer, do
hereby declare the nature of the said Invention for "AN IMPROVEMENT IN
THE CONSTRUCTION OF PIANOFORTE FRAMES," to be as follows:-
This Invention relates to an improvement in the construction of pianoforte
frames, whereby the tendency of the frames to twist under the strain of the
strings will be effectually counteracted.
The improvement relates both to metal and wooden frames, although the
former are preferred to be used, as they contract and expand equally with the
strings under differences of local temperature.
In constructing pianoforte frames, it has been usual to make them with or
to apply thereto parallel or diagonal bars stretching across the frame in the

page_text: direction of the run of the strings. By this means the frames were made
sufficiently rigid to support the direct strain of the strings, but the tendency of
the frame to twist ander the irregular lever-like action of the strings still
remained. To remove this defect which caused the sinking of the middle of
the sound board, and consequently destroyed the tone of the instrument, I
strut that division of the frame (whether of a grand, cabinet, or other kind of
piano) which is to carry the bass strings with compensating bars, which will
effectually destroy the tendency which the obtuse angle corner of the frame
has heretofore had to yield to the pull of the strings. In this part (which will
in general be rectangular) I provide two struts which cross each other and
extend respectively to the opposite angles of the division that carries the bass
strings. These cross bars are recessed or arched, so that they shall be clear
of the ribs at the back of the sound board when it is placed over or in front of
them, and the further to secure the upper end or extremity of the frame, I
cause a slight bar which springs from the junction of the cross bars, and runs
parallel with the straight side of the frame to strut the middle of that part of
the frame.
In order to destroy all unnecessary vibration in the sound board, I cause a
diagonal bar to cross one of the before mentioned cross bars near the outer
angle adjoining the wrest plank, and thus form a support at that part for the
sound board.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said John Dewrance, in the Great Seal Patent Office on the
21st March 1859.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN
DEWRANCE, of Barge Yard, in the City of London, Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-first day of September, in the year of our Lord
One thousand eight hundred and fifty-eight, in the twenty-second year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me, the
said John Dewrance, Her special license that I, the said John Dewrance,
my executors, administrators, and assigns, or such others as I, the said John
Dewrance, my executors, administrators, and assigns, should at any time agree
with, and no others, from time to time and at all times thereafter during
the term therein expressed, should and lawfully might make, use, exercise, and

page_text: vend, within the United Kingdom of Great Britain and Ireland, the Channel
Islands, and Isle of Man, an Invention for "AN IMPROVEMENT IN THE CON-
STRUCTION OF PIANOFORTE FRAMES," upon the condition (amongst others) that I
the said John Dewrance, by an instrument in writing under my hand and
seal, should particularly describe and ascertain the nature of the said Inven-
tion, and in what manner the same was to be performed, and cause the same
to be filed in the Great Seal Patent Office within six calendar months next and
immediately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said John Dewrance, do hereby declare
the nature of my said Invention, and in what manner the samo is to be
performed, to be particularly described and ascertained in and by the following
statement, reference being had to the Drawing hereunto annexed, and to the
letters and figures marked thereon (that is to say):-
This Invention relates to an improvement in the construction of pianoforte
frames whereby the tendency of the frames to twist under the strain of the
strings will be effectually counteracted. The improvement applies both to
metal and wooden frames, although I prefer the use of metal frames, as they
contract and expand like the strings under differences of local temperature.
In constructing pianoforte frames of metal, it has been usual to cast them
with or to apply thereto parallel bars stretching across the frame in the
direction of the run of the strings. By this means the frames were made
sufficiently rigid to support the direct strain of the strings, but the tendency
of the frame to twist under the irregular lever-like action of the bass strings
still remained. To remove this defect, to which is mainly due the sinking of
the middle of the sound board, and the consequent deterioration of tone and
diminution of the volume of sound of pianofortes, I propose to strut that
division of the frame (whether of a grand, cabinet, or other kind of pianoforte)
which is to carry the bass strings, with compensating bars, that will effectually
destroy the tendency which the acute-angled corner of the frame as heretofore
had to give or yield to the pull of the strings.
In the accompanying Drawing, I have shewn my Invention as applied to a
cottage pianoforte frame; Fig. 1 being a front elevation of a cast-iron cottage
pianoforte frame, constructed according to this Invention, and Fig. 2 a vertical
section of the same taken in the line 1, 2, of Fig. 1. The object being
simply to increase the resisting power of that portion of the frame which is
subject to the pull of the bass strings, I introduce no change in the construction
of the other parts of the frame, which are marked A, A, but at the bass
division of the frame (which will in general be rectangular) I provide ribbed

page_text: bars B, B, which cross each other, and extending respectively to the opposite
angles of the division that carries the bass strings, act as struts to give
stiffness to the frame. These cross bars are arched or set back, as shewn at
Fig. 2, to provide a space for and to keep them clear of the braces or belly
bars attached to the back of the sound board, and the further to secure the
frame against the tendency to yield the the unequally distributed leverage of
the strings, I cause a bar C to spring from the junction of the cross bars, and
running parallel with the straight side of the frame, to strut the middle of that
part of the frame. In order to destroy all unnecessary vibration in the sound
board, I retain the diagonal bar D, which has heretofore been used for the
like purpose, and cause it to cross one of the cross bars B near the outer
angle adjoining the wrest plank, and thus form a support at that part of the
sound board. The sound board drops into a recess made for it in the face of
the metallic frame, and it is secured in place by being glued to blocks placed
in the angles of the recess to receive it.
In applying my Invention to wooden frames, I prefer to employ an additional
metal frame made of cast or wrought iron, and provided with cross bars or
struts securing the same firmly to the back of the bass side of the wooden
frame, but a wooden frame constructed on the same principle may, if desired,
be employed. Fig. 3 shews in back elevation a wooden frame for a cottage
pianoforte, fitted with a supplementary supporting frame of cast iron, and
Fig. 4 is a vertical section of the same, taken in the line 3, 4, of Fig.3. In
these figures, E, E, is a rectangular frame, having bars F, F, extending
diagonally across the frame from one corner to its opposite. A bar G
running parallel to the side of frame, extends from one end of the frame
to the other, crossing the diagonal bars at their central point of junction.
This frame is to be secured to the wooden frame by screws or other suitable
means, and it will then impart the requisite stiffness to the wooden frame
to enable it to resist the unequally distributed leverage strain of the bass
strings.
From the above illustrations of the application of my Invention, it will be
readily understood that it applies equally to horizontal as to vertical instru-
ments, the proportions only of the strengthening parts differing according to
the construction of instruments to which the frame is to be applied.
Having now set forth the nature of my Invention of "An Improvement
in the Construction of Pianoforte Frames," and explained the manner of
carrying the same into effect, I wish it to be understood that under the above
in part recited Letters Patent, I claim the application to pianoforte frames of

page_text: diagonal bars or struts as above described, for preventing the racking or
twisting of the frame, and the consequent crippling of the sound board whereby
a larger volume of sound and a finer quality of tone may be obtained than
heretofore from a given length of strings.
In witness whereof, I, the said John Dewrance, have hereunto set my
hand and seal, the Twenty-first day of March, in the year of our Lord
One thousand eight hundred and fifty-nine.
Witness,
J. W. MOFFATT,
66, Chancery Lane.
JOHN DEWRANCE. (L.B.)