AN IMPROVEMENT IN THE CONSTRUCTION OF PIANOFORTES
Year: 1877

page_text: LETTERS PATENT to William Glen Eavestaff, of Berners Street, Oxford Street,
in the County of Middlesex, Pianoforte Manufacturer, for the Invention of
"AN IMPROVEMENT IN THE CONSTRUCTION OF PIANOFORTES."
Sealed the 12th April 1878, and dated the 18th October 1877.
PROVISIONAL SPECIFICATION left by the said William Glen Eavestaff at the
Office of the Commissioners of Patents on the 18th October 1877.
WILLIAM GLEN EAVESTAFF, of Berners Street, Oxford Street, in the County of
Middlesex, Pianoforte Manufacturer. "AN IMPROVEMENT IN THE CONSTRUCTION
OF PIANOFORTES.
The object of this Invention is so to construct the frames of pianofortes in wood
that they will be enabled to sustain the tension of the strings, whether the tension
acts, say, in an upright instrument, in a vertical or in a mixed vertical, diagonal,
and transverse diagonal strain, without yielding or loosing their form.
In constructing a back frame for an upright pianoforte I form, first, in hard wood
a rectangular frame, the breadth and height of which will correspond with the
desired breadth and height of the back frame. I then lay upon this frame parallel
bars of suitable wood, of a length equal to the height of the frame, and I glue them
thereto at convenient distances from each other, the end bars being laid upon the
insert filling
side bars of the frame. Between the ends of these parallel bars
pieces, glueing the same to the frame, and I thus form a kind of grid frame with a
flush surface. I then take a second rectangular frame similar to that first mentioned,
and attach it by glue to the flush face of the grid frame, and I thus build up a back
frame which will be capable of resisting the parallel, cross, and diagonal strains of
the most approved modern arrangement of pianoforte strings.
For giving additional strength to the centre of the back frame I may in some
cases, before inserting the filling pieces, glue to the opposite sides of one or more of
the parallel bars stout strips of wood, of a breadth equal to the thickness of the
completed frame, and of a length equal to the height of the frame, but rebated at
their opposite ends to bring their width to an equality with the thickness of the

page_text: filling pieces. When these are used the filling pieces between the bars will be
reduced in proportion to the thickness of these additional strips.
The frame thus constructed will be fitted with a wrest plank and metal pin plates
to receive the strings.
When adapting the Invention to horizontal pianofortes, the shape of the frame 5
will be modified to suit the plan of the instrument, but in other respects its con-
struction will be similar to that above described for vertical pianofortes.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said William Glen Eavestaff in the Great Seal Patent Office on the 18th
April 1878.
WILLIAM GLEN EAVESTAFF, of Berners Street, Oxford Street, in the County of
Middlesex, Pianoforte Manufacturer. "AN IMPROVEMENT IN THE CONSTRUCTION
OF PIANOFORTES."
The object of this Invention is so to construct the back frames of upright piano-
fortes in wood that they will be enabled to sustain the tension of the strings,
whether the tension acts in a vertical or in a mixed vertical, diagonal, and transverse
diagonal strain, without yielding or losing their form.
In constructing the back frame I form, first, in birch, wainscot, or other suitable
hard wood a rectangular frame, the breadth and height of which will correspond
with the desired breadth and height of the back frame. I then lay upon this frame
bars of light wood, by preference deal, of a length equal to the height of the frame,
and I glue them thereto at convenient distances from each other, the end bars being
laid upon the side bars of the frame. Between the ends of these bars I insert filling
pieces of deal, glueing the same to the frame, and I thus form a kind of grid frame
with a flush surface. I then take a second rectangular frame similar to that first
mentioned, and attach it by glue to the flush face of the grid frame, after which I
line up the bars of deal with hard wood at back and front to make them level with
the front and back frames. By this means I build up a back frame which will be
capable of resisting the parallel cross and diagonal strains of the most approved
modern arrangement of pianoforte strings.
For giving additional strength to the centre of the back frame before inserting
the filling pieces I glue to the opposite sides of one or more of the deal bars stout
strips of wood, of a breadth equal to the thickness of the bars, and of a length equal
to the height of a frame. Where these strips occur the adjacent filling pieces
between the bars will be reduced in proportion to the thickness of these additional
strips.
The back frame thus constructed is to be fitted as usual with a wrest plank and
metal pin plates to receive the strings.
The accompanying Drawing illustrates my improved mode of building up in
wood the back frames for upright pianofortes.
Fig. 1 is a face view and Fig. 2 an edge view of a rectangular frame of hard

page_text: wood A, corresponding in height and breadth to the measurements of the pianoforte
of which it is to form a part.
Fig. 3 shews in elevation this frame A overlaid with parallel bars of deal B, B¹,
which extend from the bottom to the top of the frame, and are secured in position
by glue or other cement, thereby forming a kind of grid frame. These bars may be
placed at equal or other convenient distances apart, and either parallel, as shewn,
or some of them diagonal, according to the judgment of the maker, the object being
to give the frame the greatest strength at the part where the greatest strain of the
strings is experienced. The side bars B, B, abut the whole of their length against
the side pieces of the frame, and the bars B¹ overlie the space enclosed by the
rectangular frame A, and serve as internal string pieces to the frame. Between the
bars B, B¹, filling pieces C, C, are inserted, of such thickness as to give a flush face
to the frame. Upon this flushed face is then laid a rectangular frame A¹, Fig. 4, of
birch or other hard wood, similar to that shewn at Figures 1 and 2, and it is secured
in position by glue. The bars B¹ are then lined up at back and front with strips
of hard wood, as shewn in the sectional view, Fig. 5, at G, G. The frame will then
present the appearance shewn in face view at Fig. 4.
In order to fit the back frame thus constructed to receive the sound board and
the strings it is only necessary to apply thereto the fillets D, D, bent side E, and
wrest plank F (see the face view, Figure 6).
I have shewn at Figures 3, 4, and 6 of the Drawing the means which I prefer to
employ for giving additional strength to the middle of the back frame. This consists
in fitting to the opposite sides of one or more of the bars B¹ strips of birch or other
hard wood G¹, G', which extend from end to end of the bar or bars, and are secured
thereto by means of glue. Substantially the same result may however be attained
by bringing the parallel bars B₁ closer together near the centre of the frame in lieu
of employing a compound bar, as shewn in the Drawing, but the latter I prefer as
the more convenient arrangement.
By building up my back frame as above described it will be readily understood
that I obtain a greater power of resistance than heretofore to the strain of the
strings, especially when they are arranged in a mixed vertical, diagonal, and trans-
verse diagonal direction.
Having now set forth the nature of my Invention of "An Improvement in the
Construction of Pianofortes," and explained the manner of carrying the same into
effect, I wish it to be understood that under the above in part recited Letters
Patent I claim, the building up of back frames of vertical pianofortes in the manner
and for the purpose above described.
In witness whereof, I, the said William Glen Eavestaff, have hereunto set my
hand and seal, this Eighteenth day of April, in the year of our Lord One
thousand eight hundred and seventy-eight.
W. G. EAVESTAFF. (L.S.)