Year: 1886

page_text: I, JOSEPH DELERUE, of 2 Rue Sainte Appoline, Paris, France, Pianoforte
Manufacturer, 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:—
One of the great difficulties to overcome in the manufacture of pianos, and
particularly in those pianos having oblique strings is to provide sufficiently firm
and strong cross bars to resist the traction of the strings.
Many means have been proposed. The number of bars has been increased,
which renders the means cumbersome, without giving a satisfactory result as to
solidity. Iron frames have also been employed. The latter are commonly used:
they certainly have the advantage of simplifying the construction, are economical,
and increase the firmness of the instrument, but at the same time there are many
disadvantages connected with their use.
It injures the qualities of the sound of the instrument; in fact, when a cast plate
is introduced into the piano it can never be prevented from participating in the
general vibration, and so much the more as it is identified with the instrument.
Iron which can be introduced with impunity into a piano to increase the solidity,
ought not to participate with the vibration of the sounding board, which latter
alone ought to act the part assigned to it in the instrument.
In order to prevent the metallic apparatus influencing the resonance of the
sounding board, while at the same time efficaciously contributing to the solidity
of the instrument, it is necessary that the parts constituting the apparatus are not
welded or connected to one another so as to render its combination homogeneous.
Another disadvantage in iron frames arises from the fact that expansion is
effected in a transverse direction to the cords; regularity in the tone of the
instrument cannot therefore be obtained.
In fact, the application of iron frames renders the piano heavy, and tends to force
asunder the string frames..
The object of the improvements forming the present invention is, whilst
continuing to use wooden string frames in pianos, to give same a firmness or
solidity at least equal to the iron framed pianos, and at the same time augmenting
their sounding qualities.
The principal improvements by which I attain these results consist essentially:
1st In the application to the bars of the string frames of a brace which I call
a compensator with double plates connected to it," to be hereinafter described.
I thus avoid the deflection of the string frames in causing the traction of the cords
to be supported by these compensators.
2nd In the application to the string plate and wrest plank of a regulating bar
preferably metallic, which serves at one and the same time as a stay or support for
the compensators, and as a nut or holdfast as hereinafter described.

page_text: 3rd In the manner of supporting the sounding board upon a sharp edged support
or splint, with the object of augmenting the sensibility of the vibration.
4th In the application of a string regulating bar serving to draw in the cords of
the string plates.
This my metallic apparatus distends or expands in the direction of the length
of the corda. It is that which has caused me to give it the name of compensating
apparatus. It changes the point of flexion, and transports it to one of the ends of
the cord, and it does not affect, or influence the sounding board, as it is not in
contact with same.
Figure 1 of the accompanying drawings is a longitudinal section of my com-
pensator fitted in position. This section is taken through line 7-8 Figure 8.
Figure 2 represents a side view of my compensator fitted in position. The
wrest plank and string plate d, the regulating bar f, and the sounding board g,
being in section through line 9-10, Figure 8.
Figure 3 is a transverse section through line 1-2, Figure 2.
Figure 4 is a plan of the compensator.
Figure 5 shews a slight modification of the upper part of compensator in side
view. In this view the plate r, instead of butting against the regulating bar f, is
stopped against a shoulder all of the compensator plate.
Figures 6 and 7 represent a side view, and inverted plan of the string regulating
bar n serving to draw the strings in towards the wrest plank l.
Figure 8 represents front view of wooden framing fitted with 2 compensators,
the sounding board being removed.
Figure 9 is a vertical section through line 11-12 Figure 8.
Figure 10 is a vertical section through line 13-14 Figure 8.
Figure 11 is a vertical section through line 15-16 Figure 8.
Figure 12 is an underside view of string plate d fitted with plate k, and Figure 13
is a section through line 17-18 Figure 12.
Figures 8, 9, 10, 11, 12, 13, are all drawn to one scale, being half that of
Figures 1 to 7.
The compensator consists essentially of two distinct parts; the one a formed of
either forged or cast iron or other metal, or other suitable material, rolled or cut
out to a T shape.
The rib a¹ of this T piece is of a variable breadth, as seen in Figures 1 and 2.
The part of this T is swelled out at its upper part a. Upon all are fixed,
in any convenient manner, bolts, pins, or ferrules 6 61 611, which are formed
cylindrical; and with a shoulder, upon their upper part, of a conical or other
convenient form.
Upon this piece a, fitting on the ferrules b 6' 6" there is a plate r of iron, copper,
aluminium, or other suitable metal, or material, corresponding exactly with the
height of the swelled part a¹¹, Figures 1, 2, and 8. Or, it may butt against a
shoulder al as in Figure 5. The two pieces together form the "compensator with
double plates." The other ferrules c c pass through the lower double plates k of
the string block d, and serve to keep same in place. Wood screws or bolts e e¹ keep
the whole together.
с
These compensators are fitted upon the uprights of the string frames as will be
seen at Figures 8 and 11; the hinder rib a' fitting in a mortice, and the front
part a pressing against the regulating bar f fitting against the lower edge of
wrest plank l
The number and dimensions of the compensators necessary to balance the tension
of the cords of a piano, are determined by the various arrangements of such cords-
perpendicular, oblique, or superposed-and also by the acoustic scale (pitch) of the
instrument.
The drawings shew clearly that heat expanding the cords, will at the same time
expand the compensator, which latter will elongate in a downward direction, and
draw with it the string plate d. It follows that these two expansions will be equal,
L

page_text: and that the tension of the cords, and in consequence the tone of the instrument
will remain the same.
In Figures 1 and 2 it will be observed that the rib a¹ is swelled out at a, also
that the sounding board g fitted with bridge h occupies an intermediate position
between the two connected plates and all, and that it is intersected by the
ferrules b 61 61 of the compensator without being in contact with same.
Tension being caused through cord o upon the two points o¹ oll on the wrest
plank, and upon string block d, a power exercised to cause the equilibrium of the
apparatus will be the more efficient as the distance between the cord and the organ
of resistance lessens; or in other words, as the point where the resistance should
be the maximum is nearer the cord, and the point of flexion nearer one of the
extremities of the cord.
With the arrangement shewn at Figures 1 and 2, the double connected plates
are adjacent to the centre of effort and carry the point of flexion towards the
lower end of the cord, the point coinciding with the swelled part a of the rib a¹
of compensator a.
As before stated this compensator presses against a regulating bar finterposed
between it, and the wrest plank l. This regulating bar f which may be of iron,
copper, bronze, aluminium, or other suitable metal or material, takes the place, in
the whole length of the wrest plank of the appliance generally used for determining
the striking of the hammers.
The application of this regulating bar f which I call the "harmonic bar," inter-
posed between the compensating apparatus, and the wrest plank, is of great
importance, serving to characterize the system.
1st One perceives the great advantage in the solidity of tone, resulting from this
arrangement, in that the metallic apparatus does not rest directly on the wrest
plank, but upon the aforesaid "harmonic bar" (preferably of metal) which is
interposed in the whole thickness of the wrest plank, and forms an absolutely firm
bed for same.
2nd This metallic "harmonic bar" serves also as striking regulator, and I give
it the name of "harmonic bar" in consequence of considerations dependent upon
the theory of acoustics which I have formulated in the following manner :-
"The emission of sound in a piano, and particularly in the higher octaves, will
"be the purer and more liquid according to the density or homogeneousness of the
"base upon which the point of repose of the cord is situated."
My "harmonic bar "frealizes these conditions by reason of the enormous traction
of the cords exercised, the one part on the wrest plank l, and the other part on the
string block d, the compensating system presses upon the "harmonic bar" f and
holds it against the wrest plank in such manner as not to allow it the least
movement.
Besides, this "harmonic bar" f being of metal, the cords cannot cut into it.
It follows that the vibrations of the cords will not be in the least counteracted
against by the vibrations of striking regulator not sufficiently maintained in
position; and that the sounds will preserve all their purity and limpidness.
Referring to Figures 8, 9, and 10, it will be seen that the splint or support m of
the sounding board g is shaped with a bevil so as not to be in contact with the
sounding board, except by its sharp edge. The object of this arrangement is to
give greater sensibility of vibration to the sounding board.
The sounding board g is attached to this support at intervals by screws, pins, or
other convenient means.
In order to draw the cords or strings near the wrest plank before they pass over
the "harmonic bar" f, I fix upon said wrest plank by means of screws a piece n
which I call the "string regulating bar." Seen in section Figures 1 and 2, and in
inverted plan and side view Figures 6 and 7.
The cords or strings passing in the spaces between two teeth n' n¹ are brought
for attachment close to the base of the pins o¹, and act upon these latter by a small
lever arm. At the base of each tooth n¹ there is a screw taking into the wrest

page_text: plank so that said "string regulating bar" cannot vibrate except in unison with
the wrest plank, and does not influence the vibrations of the cords.
Having now particularly described and ascertained the nature of this invention,
and in what manner the same is to be performed I declare that what I claim is :
1. The application of metallic compensators in pianos, each formed of two pieces
of metal connected by pins, bolts, or ferrules, to a metal rib; forming for part of
the length of same a sort of strengthened beam; for the purpose of resisting flexion,
substantially as set forth.
2. In metallic compensators for pianos the application of a rib placed perpen-
dicularly with the lower plate, and strengthened or swelled out for a part of its
length; substantially as and for the purposes set forth.
3. In metallic compensators for pianos the arrangement of the lower ferrules
passing through holes in the plates fixed under the string block; the connection of
the compensator and the string block being, besides, maintained by screws or bolts:
substantially as herein before set forth.
4. The application and mode of joining these my metallic compensators to the
string frames of pianos, so as to consolidate, and compensate for, the distension of
the cords; substantially as herein before set forth.
5. The application beneath the wrest plate of a metallic regulating bar following
the curve of the striking regulating mechanism, and which for this reason I call
the "harmonic bar," substantially as hereinbefore set forth.
6. The means for supporting the pressure of the compensators against this my
"harmonic or regulating bar:" with the double view of consolidating the framing,
and of maintaining the "harmonic or regulating bar" firmly pressed against the
wrest plank; substantially as set forth.
7. The arrangement of plates, pierced with holes, and fixed under the string
block the holes being destined to receive the lower ferrules of the compensators―
for the purpose of supporting the string block by the lower plate of the com-
pensator; substantially as set forth.
8. The application to the framing of pianos, of a bevilled bed to hold the
sounding board, with the object of augmenting the sensibility of the vibration of
same an arrangement which completely isolates the sounding board from the
metallic apparatus, substantially as set forth.
9. In pianos, the application to the wrest plank of a string regulating bar screwed
firmly to same for the purpose of drawing in the cords to the wrest plank, sub-
stantially as set forth.
"
10. The combination of compensators connected to double plates, and of the
'harmonic or regulating bar; substantially as above described.
"
11. In pianos the arrangement and combination of the compensators connected
to double plates, of the "harmonic or regulating bar," of the string block, of the
bevilled bed, and of the string regulating bar; all for the purpose of constructing
a piano with wooden framing, which shall be more solid than iron frame pianos;
substantially as hereinbefore set forth and illustrated in the accompanying
drawings.