CERTAIN IMPROVEMENTS IN STRAINING MILL SAWS
Year: 1853

page_text: LETTERS PATENT to Auguste Edouard Loradoux Bellford, of 16.
Castle Street, Holborn, City, London, Patent Agent, for the In-
vention of "CERTAIN IMPROVEMENTS IN STRAINING MILL SAWS."-
Sealed the 7th April 1854, and dated the 26th November 1853.
PROVISIONAL SPECIFICATION left by the said Auguste Edouard
Loradoux Bellford at the Office of the Commissioners of Patents,
with his Petition, on the 26th November 1853.
I, AUGUSTE EDOUARD LORADOUX BELLFORD, of 16, Castle Street,
Holborn (City), London, Patent Agent, do hereby declare the nature
5 of the said Invention for "CERTAIN IMPROVEMENTS IN STRAINING MILL
SAWS to be as follows:-
This Invention relates to the straining of the saw by the direct action
of compressed air or atmospheric pressure. It consists in attaching
the saw to pistons working in two cylinders, which are arranged in line
at opposite ends of the saw, and in which pressure is produced to act
on the pistons either by forcing in air on one side, or producing a
vacuum on the other side, of the pistons for the purpose of producing a
proper and uniform tension on the saw, and keeping it strained without
the use of a gate or saw frame.

page_text: Fig. 1, is a front view of a mill saw with its straining apparatus and
driving gear constructed and arranged according to my Invention.
Fig. 2, is a side elevation of the same, showing the air cylinders and
the framing in section. Similar letters of reference indicate corre-
sponding parts in both Figs.
The particular apparatus-represented is for straining- by compressed
air, and its description, with a little additional explanation of the
changes necessary for straining by 'atmospheric pressure, will enable
those skilled in the art to construct the apparatus for straining by either
means. The straining cylinders A, and B, are arranged directly in line
with each other; the cylinder A, being secured below the table or floor
of the mill, and the other cylinder_B, being erected upon a suitable
framing at any distance above. Each cylinder is fitted with a piston C,
furnished with a piston rod D, working through a stuffing box at that
end of the cylinder nearest the saw, which is made perfectly tight;
the other ends of the cylinders, viz., the top of the upper and the bottom
of the lower one, are left open. The piston may be made' and packed
in the simplest way, a common leather packing answering very well.
The saw E, is connected at its ends to the two piston rods in any
suitable manner, and a cross head F is applied at each end sliding on
suitable guide rods G, G. Power, either steam, water, or of any other
description; 'is applied through the shaft H, which carries two pulleys,
over one of which passes an endless band I, to a druni on the shaft J, on
the end of which shaft is secured a wheel or disc K, furnished with a
wrist or crank pin, L, which is connected with the lower cross head F,
by a connecting rod M, and serves to drive the saw. At one side of
the saw is placed an air pump M, by which the proper pressure is pro-
duced in the straining cylinders. The piston of this pump receives
motion through a connecting rod from a wrist P..on a disc, or its
equivalent secured to the end of a shaft R, which receives motion
through a pulley, over which passes an endless band V from another
pulley on a shaft H. From the top of the air pump a, pipe S leads to
and connects with a pipe T, which connects the two ends of the, cylin-
ders nearest to each other together, that is, so that the compressed air
shall be forced into the cylinders between the two, piston heads and

page_text: the packed or tight ends of the cylinders, and exert itself in forcing
apart the pistons, but the pistons being connected together by the saw
this force exerts itself in straining up the saw. A pressure valve
U, similar to an ordinarily constructed safety valve is placed on the
pipe T, to allow the excess of air to escape, and thus maintain an
uniform pressure, otherwise there is no escape of air but by leakage.
The air pump keeps up, the necessary supply, and as the piston head
in either cylinder approaches the mouth of the inlet pipe T, it drives'
the compressed air before it down or up into the other cylinder, as the
case may be, where the other piston head is receding from the inlet
pipe and making room to receive it, and is thus made to travel by the
action of the piston from one cylinder to another. If it were possible>
to make the cylinder, pistons, and packing perfectly air-tight without too
much friction, the chambers in the cylinders and the pipes being once
filled with air would continue for an indefinite period to keep the saw
strained, but as this is practically impossible the air pump is used to
start and keep up the supply of air. It is found advisable to have the
air pump so arranged that it can be operated independently of the saw,
as it will be necessary sometimes to strain up the saw before the mill is
ready to start, or at least before the feed is put on. When the saw is
cylinders nearest
strained by atmospheric pressure the ends of the
the saw will be open, and the opposite ends closed. The connecting
pipe T will then connect the ends of the cylinders furthest from the
saw, and the air pump must exhaust the air from the cylinders.
The effect thus produced is essentially the same as when the air is
forced in by the pump between the pistons, for in both cases the strain-
ing is produced by the process of pressure of the air between the pistons.
The advantages of a saw strained without a gate or saw frame are
numerous. A thinner saw can be used, requiring less power to drive it,
and wasting less stuff, and can be run at such a high speed as would
shake a heavy gate to pieces. It leaves the table or floor of the mill
unencumbered by the frame posts, and in circular sawing it allows the
board to be turned in any direction. In view of these advantages
many attempts to strain saws without a gate have been made, and
among them an attempt to use steam for the purpose, which was too

page_text: expensive, as in mills driven by other power than steam a boiler and
other suitable apparatus, involving the use of slide valve steam
chambers and metallic packings, must be used, all of which arc of
expensive construction, and expensive to keep in repair, besides
requiring as much care and attention as a regular steam engine.
The condensation of steam in the cylinders has made the operation
of steam for this purpose so uncertain as to be of doubtful utility.
But the greatest objection found in its practical use arises from the
fact that the leakage or dripping from the cylinder falls immediately
upon the saw, soon corroding it and rendering it useless. This Inven-
tion entirely overcomes every one of the foregoing objections. It is
cheap, simple, perfectly safe, and entirely effective, and it can be used
equally well in any mill, whatever may be the driving power.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Auguste Edouard Loradoux Bellford in the
Great Seal Patent Office on the 8th April 1854.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I,
AUGUSTE EDOUARD LORADOUX BELLFORD, of 16, Castle Street (Holborn),
City, London, Patent Agent, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twenty-sixth day of November, in the
year of our Lord One thousand eight hundred and fifty-three, in the
seventeenth year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said Auguste Edouard Loradoux Bellford,
Her special licence that I, the said Auguste Edouard Loradoux
Bellford, my executors, administrators, and assigns, or such others as I,
the said Auguste Edouard Loradoux Bellford, my executors, adminis-
trators, and assigns, should at any time agree with, and no others,
from time to time and at all times thereafter during the term therein
expressed, should and lawfully might make, use, exercise, and vend,
within the United Kingdom of Great Britain and Ireland, the Channel
Islands, and Isle of Man, an Invention, communicated to me by a

page_text: foreigner residing abroad, for "CERTAIN IMPROVEMENTS IN STRAINING MILL
SAWS," upon the condition (amongst others) that I, the said Auguste
Edouard Loradoux Bellford, by an instrument in writing under my
hand and seal, should particularly describe and ascertain the nature
of the said Invention, and in what manner the same was to be per-
formed, and cause the same to be filed in the Great Seal Patent Office
within six calendar months next and immediately after the date of the
said Letters Patent.
NOW KNOW YE, that I, the said Auguste Edouard Loradoux
Bellford, do hereby declare the nature of the said Invention, and in
what manner the same is to be performed, to be particularly described
and ascertained in and by the following statement, and the Drawings
hereunto annexed (that is to say):
This Invention relates to the straining of the saw by the direct action
of compressed air or atmospheric pressure. It consists in attaching
the saw to pistons working in two cylinders, which are arranged in line
at opposite ends of the saw, and in which pressure is produced to act on
the pistons either by forcing in air on one side, or producing a vacuum
on the other side, of the pistons for the purpose of producing a proper and
uniform tension on the saw, and keeping it strained without the use of
a gate or saw frame.
Fig. 1, is a front view of a mill saw, with its straining apparatus
and driving gear constructed and arranged according to this Invention.
Fig. 2, is a side elevation of the same, showing the air cylinders and
the framing in section. Similar letters of reference indicate corre-
sponding parts in both Figs.
The particular apparatus represented is for straining by compressed
air, and its description, with additional explanation of the changes
necessary for straining by atmospheric pressure, will render the con-
struction of the apparatus for straining by either means well understood.
The straining cylinders A, and B, are arranged directly in line with
each other; the cylinder A, being secured below the table or floor of the
mill, and the other cylinder B, being erected upon a suitable framing
at any distance above. Each cylinder is fitted with a piston C, furnished
with a piston rod D, working through a stuffing box at that end of the

page_text: cylinder nearest the saw, which is made perfectly tight; the other ends
of the cylinders, viz., the top of the upper and the bottom of the lower
one, are left open. The piston may be made and packed in the simplest
way, a common leather packing answering very well. The saw E, is
connected at its ends to two piston rods in any suitable manner, and a
cross head is applied at each end sliding on suitable guide rods G, G.
Power, either steam, water, or of any other description, is applied
through the shaft H, which carries two pulleys, over one of which
passes and endless band I, to a drum on the shaft J, on the end of which
shaft is secured a wheel or disc K, furnished with a wrist or crank pin L,
which is connected with the lower cross head F, by a connecting rod M,
and serves to drive the saw. At one side of the saw is placed an air
pump N, by which the proper pressure is produced in the straining
cylinders. The piston of this pump receives motion through a con-
necting rod O, from a wrist P, on a disc Q, or its equivalent, secured
to the end of a shaft R, which receives motion through a pulley, over
which passes an endless band V from another pulley on the shaft H.
From the top of the air pump a pipe S leads to and connects with
a pipe T, which connects the two ends of the cylinders nearest to each
other together, that is, so that the compressed air shall be forced into
the cylinders between the two piston heads and the packed or tight
ends of the cylinders, and exert itself in forcing apart the pistons, but
the pistons being connected together by the saw this force exerts itself
in straining up the saw. A pressure valve U, similar to an ordinarily
constructed safety valve is placed on the pipe T, to allow the excess of
air to escape, and thus maintain an uniform pressure, otherwise there
is no escape of air but by leakage. The air pump keeps up the
necessary supply, and as the piston head in either cylinder approaches
the mouth of the inlet pipe T, it drives the compressed air before it
down or up into the other cylinder, as the case may be, where the other
piston head is receding from the inlet pipe, and making room to receive
it, and it thus is made to travel by the action of the piston from one
cylinder to the other. If it were possible to make the cylinder, pistons,
and packing perfectly air-tight without too much friction, the chambers
in the cylinders and the pipes being once filled with air would continue

page_text: for an indefinite period to keep the saw strained, but as this is practi-
cally impossible the air pump is used to start and keep up the supply
of air. It is found advisable to have the air pump so arranged that
it can be operated independently of the saw, as it will be. necessary
sometimes to strain up the saw before the mill is ready to start, or at
least before the feed is put on. When the saw is strained by atmo
spheric pressure the ends of the cylinders nearest, the saw, will be open,
and the opposite ends closed. The connecting, pipe T will then connect
the ends of the cylinders farthest from the saw, and the air punip
must exhaust the air from the cylinders. The effect thus produced is
essentially the same as when the air is forced in by the pump between
the pistons, for in both cases the straining is produced by the excess of
pressure of the air between the pistons. The advantages of a saw
strained without a gate or saw frame are numerous. A thinner saw
can be used, requiring less power to drive it, and wasting less stuff, and
can be run at such a high speed as would shake a heavy gate to pieces.
It leaves the table or floor of the mill unencumbered by the frame
posts, and in circular sawing it allows the board to be turned in any
direction. In view of these advantages many attempts to strain saws
without a gate have been made, and among them an attempt to use
steam for the purpose, which was too expensive, as in mills driven by
other power than steam a boiler and other suitable apparatus, involving
the use of slide valves, steam chambers, and metallic packing, must be
used, all of which are of expensive construction, and expensive to
keep in repair, besides requiring as much care and attention as a
regular steam engine. The condensation of steam in the cylinders has
made the operation of steam for this purpose so uncertain as to be of
doubtful utility. But the greatest objection found in its practical use
arises from the fact that the leakage or dripping from the cylinder
falls immediately upon the saw, soon corroding it and rendering it
useless. This Invention entirely overcomes every one of the foregoing
objections. It is cheap, simple, perfectly safe, and entirely effective,
and it can be used equally well in any mill, whatever may be the
driving power.
I claim, straining the saw by the action of compressed air upon

page_text: pistons attached to opposite ends of the saw, and working within
cylinders, when the said cylinders are so connected with each other
that the compressed air shall alternately pass from one cylinder to the
other during the reciprocating action of the saw, and combined with a
compressing pump and pressure valve for the purpose of maintaining
and regulating the intensity of the strain, substantially as herein
represented and described. And, as equivalent to the above, I claim
effecting the strain by producing a vacuum on one side of each piston,
with the modification of the same apparatus, as described.
In witness whereof, 1, the said Auguste Edouard Loradoux
Bellford, have hereunto set my hand and seal, this Eighth day
of April, in the year of our Lord One thousand eight hundred
and fifty-four.
A. E. LORADOUX BELLFORD. (L.S.)