IMPROVEMENTS IN PIANOFORTES
Year: 1861

page_text: PROVISIONAL SPECIFICATION left by Charles Glassborow at the Office of
the Commissioners of Patents, with his Petition, on the 28th June
1861.
I, CHARLES GLASSBOROW, of Rheidol Terrace, Islington, in the County of
Middlesex, Pianoforte Manufacturer, do hereby declare the nature of the said
Invention for "IMPROVEMENTS IN PIANOFORTES," to be as follows:
My Invention of improvements in pianofortes relates to various improve-
ments upon the action of pianofortes, and applies more particularly to upright
pianofortes.
The instrument is constructed with a double-sounding board, or rather two
sounding boards placed back to back, and glued or otherwise secured to the
strong timber framing on all sides, except the top side, which is left open, so
that the sound may escape from the interior. By thus boxing in the framing
and forming a kind of sound or wind chest, great sonorousness is produced.
A double set of strings are employed, one set is placed in front as usual, and
these are the strings which are struck by the hammers. The other set of
strings is placed on the reverse side of the 'sound chest, that is, on the other
sounding board, and when both these sets of strings are drawn up in time the
tension of one set will be found to counteract the tension of the other, and
therefore the instrument will not be liable to get out of tune by any undue
strain upon its parts, as is the case in pianofortes of the ordinary construction.
The back and front pin plates in instruments of the ordinary construction are
made in separate and distinct pieces, and are screwed on to the back and front

page_text: of the wooden framing. Instead of forming the back and front plates of
separate pieces, as heretofore, I propose to unite the two plates, and make
them in the form of a trough or shoe that shall embrace and fit the under side
of the framing, so that when the strings are drawn up tightly on the pins they
will draw up the trough or shoe plate, and hold the parts firmly together.
This trough or shoe may for convenience be divided into two, three, or more
sections, as may be desired. As there are two sets of strings, one at the front
and the other at the back of the instrument, there must of course be two sets
of dampers, one to act on each set of strings, and either one of the back
strings will be set in vibration by striking the corresponding string of the front
set. The corresponding dampers of both sets are made to act simultaneously,
as they are actuated by the same mechanism, which is set in motion by the
keys which actuate the hammers. The motion from the mechanism in front
is transferred to the back dampers by rods, which pass transversely through
the instrument. The whole of both sets of dampers may be operated simul-
taneously by means of a pedal lever, which by means of suitable rods transfers
the motion to both sets. In order to prevent the hammers from returning and
striking the strings a second time after the desired blow has been given, I
employ a check action, which is made to bring a stop up against either the
head or the butt of the hammer. This check action is separate and distinct
from the ordinary action of the pianoforte, and is made and adapted to a
separate frame, so that it may be removed when desired. It consists prin-
cipally of a rod or sticker, the lower end of which rests upon a block or lever
attached to the inner end of the key, which raises it when the key is depressed.
The upper end of this rod or sticker is connected by a butt joint to a block or
stop piece, which, when the hammer strikes, comes up against it and prevents
it from striking a second time until the key is again depressed. This im-
proved check action may be adapted to ordinary upright pianofortes with
facility, and by lengthening or shortening the connecting sticker or rod this
contrivance may be adapted to either cabinet, cottage, or piccolo intruments.
In order still further to improve the action I have devised an improved jack
with a double escapement or regulator, and with an adjusting screw to regulate
the action and compensate for wear.