An Improved Process for the Production of Sounding Boards.
Year: 1898

page_text: Date of Application, 4th Mar., 1898-Accepted, 7th May, 1898
COMPLETE SPECIFICATION.
An Improved Process for the Production of Sounding Boards.
I, REGINALD HADDAN, of the Firm of Herbert Haddan & Co., of 18, Buckingham
Street, Strand, W.C., London, Patent Agent, do hereby declare the nature of this
invention, a communication to me from abroad by Constantin Schmidtlein, of
22, Luisenstrasse, Berlin, in the Empire of Germany, and in what manner the
same is to be performed, to be particularly described and ascertained in and by
the following statement:-
It has hitherto been sometimes usual to stretch or bring into tension sounding
boards which has hitherto been done by means of mechanical devices after they
have been made whereby of course only a very limited success could be obtained.
The process of the present invention is intended to give an automatic intense
and always increasing molecular tension or stress in the sounding board. The
process is as follows:-
If several (two or more) boards, in such condition that they would have a
tendency to contract or expand if brought into the atmospheric conditions that
the sounding board will be subject to when in use, are glued over one another so
that the fibre directions cross one another such boards when glued together are
prevented from naturally contracting or expanding. A sounding board produced
in this manner will have an intense interior molecular tension or stress. Where
the state of the wood at the time of making the sounding board and its state
when in use have the greatest difference, the tension or stress of the sounding
board in the state of use will be correspondingly intense. One can obtain this
difference between the state of the production and that of use in two ways:-
1. For producing sounding boards glued across and over one another, dry
boards are taken and exposed for several days to a high temperature, which is
far beyond the limit of the climatic maximum temperature to which they will be
The boards must
subjected and they are then glued together in such dried state.
of course be chosen so strong that they endure the continuous enormous tension
during the state of use; after being glued together there will be a tendency
in each layer of wood to expand laterally of the fibre direction because the high
temperature of the drying chamber in which the wood was placed for several
By means
days, differs from that prevailing when the sounding board is in use.
of this expansive tendency there will be effected a tension or stress of the molecules
of the wood, since the longitudinal fibres glued cross wise over one another, do
not allow an expansion of the board.
2. In a reverse manner one can glue boards crosswise over one another that
have not been entirely dried and may utilize the subsequent drying for producing

page_text: the desired tension or stress.
The last process will therefore be especially recom-
mendable, as it is then not necessary to leave the wood for sounding boards for
years in the drying chamber. The use of undried wood will of course have its
limits, as the gluing over one another requires a certain amount of previous drying
of the wood. In this manner one obtains, nearly in a directly opposite way to
the previous method, an automatic molecular tension or stress in the sounding
board which in consequence causes these boards to improve from year to year.
Warping is prevented after the boards are glued together since they are im-
mmediately mounted on the frame or support which in effect is a necessary adjunct
of any ordinary sounding board.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed I declare that what I
claim is:
-
1. The process for the production of sounding boards based upon the glueing
together of superposed boards of sufficient thickness, with the direction of the
grain crossing one another, the condition of said boards in respect of greater or
less dryness of the wood being so chosen as to differ from the condition they will
attain when the sounding board is in use in such manner as to set up molecular
tension or stress in the sounding board substantially as set forth.
2. The process for the production of sounding boards having molecular tension,
or stress consisting in glueing together superposed partially dried boards of
sufficient thickness with the direction of the grain crossing one another, mounting
same upon a frame and suffering the same to dry substantially as and for the purpose
set forth.
3. The process for the production of sounding boards having molecular tension
or stress consisting in glueing together superposed excessively dry boards of
sufficient thickness with the direction of the grain crossing one another, mounting
same upon a frame, and exposing the same to moister atmospheric conditions
substantially as and for the purpose set forth.