Improvements in the Construction of Pianos.
Year: 1896

page_text: Date of Application, 1st July, 1896-Accepted, 29th Aug., 1896
COMPLETE SPECIFICATION.
Improvements in the Construction of Pianos.
I, LOUIS PAUL FRANCOIS DE SMET, of 99 Rue Royale, in the City of Brussels,
in the Kingdom of Belgium, Manufacturer of Pianos, do hereby declare the
nature of this invention, and in what manner the same is to be performed to be
particularly described and ascertained in and by the following statement :-
This invention relates to the construction of pianos. In all systems of con-
struction of upright or vertical pianos hitherto employed the particular position
of the strings, in respect to the woodwork or frame and the sounding board, produces
the inevitable result of putting the contour of the sounding board under the influence
of the pressure produced by the tension of the strings. The pressure tends to crush
the woodwork and by springing the contour of the sounding board renders the
isolation of the latter doubtful and takes away its elasticity and freedom of
impression so as to completely annihilate its influence, the result being that a short
and dry tone of the instrument is produced. The continuous action of the tension
of the strings often in the end crushes the sounding board so as to split it. In
order to overcome these grave disadvantages, in certain systems of upright pianos
two or more strong iron bars or metallic struts are employed which are disposed
between the strings the one in the bass and the other in the treble so as to
maintain a fixed distance at the extreme parts of the construction that is to say
the girder or upper transverse beam of the frame which carries the pegs and the
lower part of the frame to which are fixed the points of attachment. Now these
bars, under the compressive and bending strains produced by the enormous tension
set up by the stretching of the strings, are bent or curved from which the crushing
of the structure results bringing with it the numerous disadvantages hereinbefore
described.
Further these bars give to the neighbouring notes a bad quality of sound
producing inequality which is offensive to the practised ear.
This invention has for its object the obviation of these inconveniences; it consists
in balancing by tensional strains or resistance the forces of pressure resulting from
the tension of the strings and in this way to render the sounding board absolutely
independent of and protected from all pressure.
This principle of construction which is represented diagrammatically in Figure 1
can be compared to that which obtains in a bow-saw.
The pull of the strings acting in the direction of arrows a a on the arms cc of
the levers is counterbalanced by the resisting forces b b applied to the arms c¹ c² of
the levers, so as to maintain the total of these forces balanced on a fixed point, dd,
which is the centre of the construction of the piano where crushing is impossible.
One can readily understand that by now disposing the sounding board M at a
point somewhere between the points of application of the pressure a a resulting
from the tension of the strings and the points of support d d it will be always
relieved of all compression.
Figures 2 to 4 represent an upright piano constructed according to this
system;
Figure 2 being a front view of the piano.
Figure 3 being a back view and Figure 4 a vertical section to a larger scale
on the line X-Y Figure 2.
The upper ends of the strings A are attached as in well known constructions to
pegs B fixed to the girder or upper transverse beam C but the lower ends are
attached to points D projecting from a metal plate E having a form adapted to
WL

page_text: the curve of the acoustic logarithms corresponding to the length and diameter of
the strings. This plate is bent or angled so as to present a base F, Figure 4, on
which the standards G are supported. At the back edge of this base Fare fixed
vertical iron bolts H, which follow the standards G from bottom to top so as to
join to an iron bar I preferably of square section, upon which they are tightened
by means of nuts J or other equivalent devices. In this plate are also fixed by
means of nuts the back ends of horizontal bolts K which pass through the
girder or upper transverse beam C and the heads of which are supported against
an iron bar L.
It will be seen from Figures 2 and 3 that the direction of compensating or
tension bolts H correspond essentially to that of the oblique strings, which assures
not only the perfect balance of the pressure of the strings but contributes at the
same time to maintain the absolute stability of the construction.
It follows from these explanations and the examination of the drawings, that the
sounding board is relieved of all pressure, the girder or upper transverse beam
and the standards of the frame being only loaded by the forces acting on one
part through the bolts K and on the other part through the base F of the plate E.
It results that the sounding board can vibrate with ease and give a pure and deep
tone.
The sounding board will not only not be damaged by long use but on the contrary
will become better, the fibres being permitted without restraint to conform to the
influences which occur in the ageing of the wood.
Further by reason of the balancing of the forces of resistance, the initial turning
of the instrument can be maintained in an absolute manner and can be with
difficulty destroyed by the variations of circumstances and temperature.
This construction which is largely distinguished by its great lightness permits
also the enlargement of the sounding board so as to give an upright piano, a power
of sound equal to that of a grand piano, further that the board can be detached
with great facility for repairing or replacing it when necessary.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1st. A system of construction of upright piano in which the pressure produced
by the tension of the strings and acting on the front part of the frame or wood-
work is balanced by tensional or resisting forces applied on the back part of the
wood-work, so as to concentrate these forces on the centre of the girder or upper
transverse beam and the standards of the frame and to completely relieve the
sounding board disposed between the strings and the standards of the frame.
2nd. An upright piano, as claimed in Claim 1, in which the lower extremities
of the cords A are attached to the pins D of a metallic plate E formed so as to
present a base F upon which rest the standards of the frame and in which are fixed
compensating tie rods H combined with the upper transverse beams or girder C
by means of plates I and L, and horizontal bolts K traversing the upper trans-
verse beam or girder, the whole arranged so that the sound board M can be
completely disengaged.
3rd. In an upright piano as claimed in Claim 2 the arrangement of the com-
pensating tie-rods H in such a manner that they follow the standards of the frame,
and have a direction coincident with that of the strings.
Dated this 30th day of June 1896.
FELL & JAMES,
Agents for the Applicant.