Improvements in or relating to Sound-regulating Devices for Pianos and like Instruments.
Year: 1895

page_text: Date of Application, 22nd May, 1895-Accepted, 22nd June, 1895
COMFLETE SPECIFICATION.
Improvements in or relating to Sound-regulating Devices for Pianos
and like Instruments.
A. communication from KARL AUGUST EDMUND SYHRE, of Dresden, in the
Kingdom of Saxony, Manufacturer.
I, ALFRED JULIUS BOULT of 323 High Holborn in the County of Middlesex.
Chartered Patent Agent, 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 :-
The well-known dumb or soft pedal in pianos-consisting of a homogeneous felt
strip to be introduced between the hammer and the strings-has for its object to
deaden the sound of the piano so strongly that, though just audible to the player, it
is not audible to bystanders in the neighbourhood of the instrument.
There are only two positions of such homogeneous felt strip which are in
conformity with a singing-accompaniment: i.e., it must be within the scope of
action of the hammer, when it renders the piano practically mute; or it is beyond
the scope of the hammer, and has, in that case no effect.
Effects, however, of a very different character are produced, if this damping strip
is not made homogeneous, but is graduated in density and thickness of material
from one side to the other. It is then possible-given, a suitable mechanism for the
actuation of the felt-strip-to permit the hammer-head to strike, at one moment.
upon a more open and softer part of the strip, and at another moment, upon
a thicker and firmer part. In this manner, not only is the strength and intensity
of the sound altered, but also its character or timbre: the note struck or played
becomes at one time fainter and duller, and at another time louder and clearer.
The accompanying drawings illustrate the improved damping strip, and in
them :-
Figure 1 represents a cross-section of the strip;
Figure 2 also shows the strip in cross-section, when constructed in another manner
as bereinafter described. In this figure also are shown a hammer head and part of
a piano-string;
Figure 3 serves to elucidate the special method of construction last above
mentioned.
and
Figure 4 represents a vertical cross-section of a pianino fitted with this invention;
Figure 5 is a plan of the lever-arrangement showing in sketch-form the operation
of the device.
I will now proceed to describe the drawings, assuming in the first instance that
felt is the material employed for the strip.
In the manufacture of this felt, the hairs are not evenly distributed from one side
to the other of the felting-board, but successively thicker. In this manner is
obtained a felt-strip a which throughout its width shows the same depth or
thickness, but increases in hardness and density regularly from one edge to the
other for example from 2 to ¹, as shown in Figure 1 by the graduated shading from
light to dark.
A strip of such felt is secured to the wooden bar extending horizontally from
end to end across all the strings and shown in cross section in Figure 4. Then in
proportion as, by means of the bar b, the said strip moved down in a greater or
less degree between the hammer-head c aud the string d the hammer-head when
27

page_text: Sorting the string will fall upon a harder and denser or upon a softer and looser
part of the strip.
As a matter of course the mechanism is so arranged that the strip can be removed
also by means of the barb, beyond the reach or out of the way of the hammer-head;
in fact it is only brought into the scope of its action as required.
The strip, further, may also not only be unequal in hardness and density
throughout its width, but likewise in absolute thickness; and it would then be
bevelled, i.e. would have a wedge-shaped form of cross-section, which would thus
be thickest at and thinnest at . Hereby the modulating effects will be very
much enhanced and extended. A very small vertical displacement of the strip of
felt will in this case correspond to a very considerable difference in the action.
As in the foregoing it has been shown, how the unequal hardness and density of
the damper-strip can be produced in one strip; so it remains to indicate in the
séquence how a similar strip is to be produced, consisting of several layers.
As material, firstly, felt is again assumed.
The felt-manufactories deliver felt for hammers and dampers in sheets of
abont 40 numbers which, by reason of different fullings (or millings) show a complete
gradation in point of hardness and density. Also, the quality of hardness is
materially influenced by a difference of the material from which the felt is
produced, i.e. whether of hair (hair-felt) or wool (woollen-felt).
If such felt-sheets, in regular gradation, are laid one on the other as in Figure 3,
and united in any suitable way, a thick sheet or plate of felt P will be obtained
which is of unequal hardness and density in its several layers p, p, p² and so on.
In Figure 3 such a thick compound sheet or plate P is shown in which the softer
layers are indicated by lighter, and the harder layers by darker proportionate
shading.
If a strip a be cut therefrom with a knife (the latter being indicated in section
by e), such a strip will, like that previously described, increase gradually and
regularly in hardness and density from to =. A strip thus formed is shown
in Figure 2 inverted and secured to the wooden bar and introduced between the
hammer e and the string d.
Of course a certain part of the width of the strip is lost, for modulation, by its
being secured as shown to the bar b for this part of the strip, this neutral
zone, so to say, layers of felt of an inferior, less fine, or stiffer quality may he
employed.
As regards uniting the different layers of felt in such a sheet as is shown in
Figure 3 together into one mass, that can be done by proper treatment or handling,
on the felting board, only when felts of the very best quality are employed, such as
felts manufactured from the very finest, softest, longest, and for the most part curly,
crisp, hair (or the like wool).
In the first place, two felt-sheets are laid upon the felting table, on which they
are joined, or CC
felted," together in the usual way by the rubbing motion imparted
to them both. This joining or felting is facilitated or promoted by strewing loose
hairs between the two sheets. To them is then added a third sheet, in the same
way, and so on, until the produced plate or sheet has attained the required
thickness.
Hereon it is necessary to remark that the thin sheets during this handling or
treatment on the felting table, become slightly harder than they were originally,
but as that is applicable to all sheets alike the regularity of the gradation of the
felt sheets joined together is in no way thereby affected.
Adhesive material may also be employed in this process of amalgamation; and in
particular gum-tragacanth may be advantageously used for this purpose, in a thin
solution and the smallest practicable quantity.
The adherence of the individual layers of the finished damper-strip a may also
be strengthened by sticking an extremely thin layer on the surface on which the
hammer falls (Figure 2): "Much better than the softest and thinnest leather, for
this purpose is the finest silk-gauze which need not be fixed by adhesive material,

page_text: but can be effectually fixed by a few stitches with the finest silk thread. In this
way the surface exposed to the action of the hammer offers a perfectly smooth and
even surface, so that the repetitive action is in no way prejudicial in this case.
Inasmuch as the strips are cut directly across the successive layers, the material
advantage follows of itself, that the hairs of the felt lie mainly perpendicularly
across the piano-string struck.
It is a speciality with American hammer-felt manufacturers, to secure a
corresponding position of the hair constituting the hammer-felt, in order to obtain,
on the stroke of the hammer, a particularly clear and fine tone.
Further also such hammer-felts last longer because the hair is utilised in the longi-
tudinal direction and does not lie transversely to the direction in which the hammer
moves on to it.
Both these advantages may be placed to the credit of the damper-strip, and
result from the use of the ordinary felt because the hairs mainly lying as they do
in the plane of the sheet are cut transversely across.
By the proper and judicious selection of the layers in sequence in the given case,
we are enabled to take advantage of the differences established by the processes of
manufacture; thus for the first and softest layer the softest hair-felt may be advan-
tageously selected; for the middle layers a lambswool felt; and for the last and
firmest layer a felt made of sheepswool.
Next to felt as a material for the manufacture of damper-strips in the second
category comes silk or soft leather more especially the latter which is sometimes
employed to manufacture the firmer strips in the compound damper-strips above
described. For this purpose however the use of adhesive substances is above all
essential; but care must be taken in the selection because in the technics of
manufacture numerous similar substances are known which do not become
dry and hard. For example therefore rubber-solution is a suitable adhesive
substance.
The damper-strip applied across all the strings of the instrument may without
departure from the principle and scope of the invention be formed in short
sections for separate groups of chords; or small supplementary pieces may be
laid on for any individual string. The same are then chosen thinner and softer
in gradations from the bass upwards to the treble-analogous to the variations
in felting the hammer-heads.
For the movement of the wooden bar b carrying the damper strip or strips a
lever actuated by the performer's knee may advantageously be employed.
In Figure 4 the modulation device is shown in one of its working positions; the
knee-actuated lever g being represented in full lines while its normal position is
indicated in dotted lines.
A coiled spring constantly tends to maintain the lever in the normal position
or to bring it back thereto after displacement. The notion of the lever is
transmitted by the lever i (having equal arms) to the vertical rod k which acts
upon one of the arms carrying the bar b.
l
For the support of the knee and foot
in actuating the lever (and the rest of the lever arrangements) a sliding
plate m serves as a foot-rest, when drawn out from beneath the bottom of the
instrument.
In Figure 4 is shown the application of this modulating apparatus to a pianino with
an over-damper; the damper-strip a in this case extends upwards from the bar b.
In instruments fitted with under-dampers on the other hand the strip a extends.
downwards from the bar b as shown in Figure 2.
This system is applicable to harpsichords, grands, and other kinds of pianos,
just as well as to pianinos, cottages cabinets and other kinds; only that a suitable
change must be made in the mechanism to obtain the displacement of the damper
strip in a horizontal instead of in a vertical plane.
Lastly it is possible also to employ in a single instrument two damper bars b
with damper strips a or separate damper pieces, which may operate separately or
together between the hammer and the strings.

page_text: Having now particularly described and ascertained the nature of the said inven-
tion as communicated to me by my foreign correspondent, and in what manner
the same is to be performed, I declare that what I claim is :-
1. A sound-regulating device for pianos and like instruments consisting of a strip
of felt or equivalent damping-material graduated in density hardness or texture
substantially as and for the purpose described.
2. A sound-regulating device for pianos and like instruments consisting of a strip
of felt or equivalent damping-material graduated in thickness and also in density
hardness or texture substantially as and for the purpose described.
3. A damping-strip such as is claimed in either of the preceding claiming-clauses
made up of superposed portions which possess relatively different degrees of density
hardness or texture with or without a facing of thin silk gauze substantially as and
for the purpose described.
4. The manufacture of damping strips by superposing layers of felt or equivalent
damping material which possess relatively different degrees of density hardness or
texture and so cutting the series of layers into strips that the strips are compound
and graduated substantially as and for the purpose described.
Dated this 22nd day of May 1895.
BOULT & WADE,
Agents for the Applicant.