Year: 1888

page_text: I CHARLES HAMPTON 139 Barry Road Dulwich S.E. in the county of Surrey
Pianoforte Manufacturer do hereby declare the nature of this invention to be
as follows:-
The object of this invention is to gain greater power of the wood back quality of
tone than has heretofore been obtained.
It is well known that the present method of applying a metal frame (usually of
cast iron) to resist the tension of heavy stringing is partly or mainly situate in front
of the belly (or sound board) and upon the wrest plank under the blow of the hammers.
The result being that the musical quality of tone is deteriorated.
To avoid this disadvantage while providing the extra power of resistance needed I
so arrange a series of steel or iron girders (5 more or less) edgewise behind the belly
that no portion of the metal is in front of the belly or wrest plank but takes the
strain of the strings from behind and leaves the belly perfectly free as in a wood
back Piano.
The metal girder back having a rabbit at the top of the girders to receive the
wrest plank and a bottom plate similar to those in use in wood back Pianos but
forming part of the metal back the front edge of the bottom plate being a continuation
of the hitch pin plate from treble to bass forming one complete casting firmly built
into the wood back.
Thus I have two backs in combination first a wood back which sustains the sound-
board and secures the wood back quality of tone secondly I add a metal girder back
behind the belly which gives the extra strength required for heavy stringing and to
which all the strings are attached.

page_text: In
helping to insulate the sound from the metal frame. Cast in the same piece as the
bottom plate a and hitch pin plate c are vertical bracings a³, the whole casting
forming the framing which takes the strain of the strings from treble to bass,
and forming also the foundation upon which the wood back is built up.
order to resist the vertical strain or "down pull" of the strings a deep metal
rabbet a³ is formed upon the upper end of the bracings a³, and upon this
separated by woollen cloth or other suitable sound insulating material is supported
the wrest plank d, secured by bolts e to the metal frame, to resist the "overpull"
of the strings.
The wrest plank & I construct in two separate parts, d' d' of different thicknesses,
the thicker part d', which is supported by the rabbet a³, receiving the wrest pins f, and
bearing the tension of the strings g, and the thinner portion d² forming the support
for the upper end of the belly or sound board h. In this manner the metal frame is
almost entirely insulated from all sympathy with the sound board, ii are bolts to
secure the wrest plank d to the wood back b. The strings g pass over the belly
bridge k and are secured at their lower ends to the bottom edge of the metal plate a
in the usual manner by pins 7 affixed therein. The lower ends of the wood bracings b
resting in the recesses a in the bottom plate a, and their upper ends pressing against
the underside of the rabbet a³ a dead end abutment is obtained, and compactness and
solidity so conducive to pure tone is secured. By these end abutments shrinkage is
moreover prevented, there being no wood disposed to give sideway shrinkage, and the
metal frame and strings contract and expand together. In order to strengthen and
more effectually insulate the metal bracings a² struts 62 are secured at or about the
centres of the wood bracings b.
The metal frame it will be seen does not extend along the entire length of the piano.
The object sought is to maintain the present wooden-back with its musical quality
and at the same time increase its strength by providing independent resisting power
to the tension caused by heavy stringing whilst avoiding the metallic "ring" which
obtains in pianos as at present constructed where a metal frame of the ordinary
construction is applied.
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 :-
The construction of upright pianoforte backs of wood and metal parts as described
uniting the metal and wood so as to effect their respective purposes without either part
interfering with the functions of the other. The metal affording the resisting power
to the tension of heavy stringing, the wood parts affording the quality of tone
characteristic of a wood back, by reason of the sound board being dependent upon
the wood back, which is freed from the tension of the strings, which tension is borne
by the metal back: metal in front of the sound board being dispensed with.
Dated the 4th day of December 1888.
WM. BROOKES & SON,
55 & 56, Chancery Lane, London,
Agents for the Applicant.