IMPROVEMENTS IN THE MEANS AND APPARATUS FOR WORKING STEAM ENGINES EXPANSIVELY.
Year: 1874

page_text: LETTERS PATENT to Bewicke Blackburn and Alexander Bewicke
Blackburn, of No. 1, York Buildings, Adelphi, in the County of
Middlesex, for the Invention of "IMPROVEMENTS IN THE MEANS AND
APPARATUS FOR WORKING STEAM ENGINES EXPANSIVELY.
PROVISIONAL SPECIFICATION left by the said Bewicke Blackburn
and Alexander Bewicke Blackburn at the Office of the Com-
missioners of Patents, with their Petition, on the 9th February
1874.
We, BEWICKE BLACKBURN and ALEXANDER BEWICKE BLACKBURN,
of No. 1, York Buildings, Adelphi, in the County of Middlesex, do
hereby declare the nature of the said Invention for "IMPROVEMENTS IN
THE MEANS AND APPARATUS FOR WORKING STEAM ENGINES EXPANSIVELY," to be
as follows:-
This Invention relates to means and apparatus for working steam
expansively in the cylinder of a steam engine. Instead of admitting
the steam from the boiler directly into the working cylinder we admit

page_text: it in the first instance into a chamber, the capacity of which may be
any desired fraction of the capacity of the cylinder. We then cut off
the communication from the boiler to this chamber, and open a com-
munication from the chamber to the working cylinder, whereupon the
charge of steam contained in the chamber expands into the cylinder
working the piston thereof.
A simple method of effecting this action is to provide at the side of
the working cylinder a slide jacket containing a slide which is moved
to and fro in the jacket by a cam or eccentric in the usual way. This
slide commands three ports, one at the middle of the jacket communi-
cating with the boiler, and one at either end communicating with the
two ends of the cylinder respectively. At each end of the jacket there
is also an eduction passage. When the slide is at or near one end of
its stroke, the one space in the jacket being then in communication
with the middle port, is receiving a charge of steam from the boiler,
while the other space in the jacket is in communication with the one
end of the cylinder, and is supplying it with the charge of steam which
it had previously received. Also, while the one end of the cylinder is
thus receiving its supply of steam from the space in the jacket the
opposite end is discharging by the eduction passage. On the slide being
moved the communications are inverted.
In order to vary the capacity of the spaces in the slide jacket which
receive the charge of steam, and thereby to vary the degree of expansion
in the working cylinder, we attach to the slide jacket on each side of
its middle port a chamber, preferably of cylindrical form, fitted with
a piston, which piston may be moved inwards or outwards at pleasure.
When it is moved inwards the capacity of the charged space is
diminished, and the engine is thus made to work with a greater
degree of expansion; when the piston is moved outwards the charge
being proportionally increased, the engine is made to work less expan-
sively. The pressure on the pistons of these variable chambers may
be balanced by permitting the boiler pressure to act on their outer
surfaces.
The variation in capacity of the charging spaces may be effected by
moving the pistons, as already described, either by hand or by means of
a governor in any known manner.
In order to equalise the strain upon the engine we prefer to make
the port by which the charge of steam passes from the chamber in the

page_text: slide jacket into the working cylinder of tapering or V shape, so that
it shall be gradually opened by the movement of the slide, presenting
a comparatively small area of ingress for the high-pressure steam of the
charge, and enlarging gradually in area as the pressure of the charge is
diminished by expansion.
Although we have described above a method of effecting the expansive
action such as we have set forth by the use of a single slide, it is obvious.
that several slides or valves might be employed for the purpose of alter-
nately charging with steam from the boiler spaces or chambers of certain
capacity, and then admitting the charges of such spaces or chambers to
the working cylinder.
And farther, when it is not desired to vary the degree of expansion
the adjustable chambers attached to the slide jacket may be dispensed
with, the jacket itself being made of capacity sufficient for receiving
at each end the desired charge, and in this case the space ordinarily
employed for jacketting the cylinder with steam, or a portion thereof
may be utilized as a charging chamber for each end of the cylinder by
dividing it into two parts, and connecting cach part with a portion of
the slide jacket on either side of the middle port.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Bewicke Blackburn and Alexander Bewicke Black-
burn in the Great Seal Patent Office on the 7th August 1874.
TO ALL TO WHOM THESE PRESENTS SHALL COME, we, BEWICKE
BLACKBURN and ALEXANDER BEWICKE BLACKBURN, of No. 1, York
Buildings, Adelphi, in the County of Middlesex, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Ninth day of February, in the year of
our Lord One thousand eight hundred and seventy-four, in the thirty-
seventh year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto us, the said Bewicke Blackburn and Alexander
Bewicke Blackburn, Her special license, that we, the said Bewicke
Blackburn and Alexander Bewicke Blackburn, our executors, admini-
strators, and assigns, or such others as we, the said Bewicke Blackburn

page_text: (
and Alexander Bewicke Blackburn, our executors, administrators, 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 for "IMPROVEMENTS IN THE MEANS AND
APPARATUS FOR WORKING STEAM ENGINES EXPANSIVELY," upon the condition
(amongst others) that we, the said Bewicke Blackburn and Alexander
Bewicke Blackburn, our executors or administrators, by an instrument
in writing under our or their hands and seals, or under the hand and
seal of one of us or them, should particularly describe and ascertain the
nature of the said Invention, and in what manner the same was to be
performed, 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 Alexander Bewicke Blackburn,
on behalf of myself and the said Bewicke Blackburn, 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 thereof, reference being had to the accom-
panying Sheet of Drawings, and to the figures and letters marked
thereon, that is to say :-
This Invention relates to means and apparatus for working steam
expansively in the cylinder of a steam engine. Instead of admitting
the steam from the boiler directly into the working cylinder we admit
it in the first instance into a chamber, the capacity of which may be
any desired fraction of the capacity of the cylinder. We then cut off
the communication from the boiler to this chamber, and open a com-
munication from the chamber to the working cylinder, whereupon the
charge of steam contained in the chamber expands into the cylinder
working the piston thereof.
A simple method of effecting this action is to provide at the side of
the working cylinder a slide jacket containing a slide which is moved
to and fro in the jacket by a cam or eccentric in the usual way. This
slide commands three ports, one at the middle of the jacket communi-
cating with the boiler, and one at either end communicating with the
two ends of the cylinder respectively. At each end of the jacket there

page_text: is also an eduction passage. When the slide is at or near one end of
its stroke the one space in the jacket being then in communication
with the middle port is receiving a charge of steam from the boiler
while the other space in the jacket is in communication with the one
end of the cylinder and is supplying it with the charge of steam which
it had previously received. Also while the one end of the cylinder is
thus receiving its supply of steam from the space in the jacket the
opposite end is discharging by the eduction passage. On the slide being
moved the communications are inverted.
In order to vary the capacity of the spaces in the slide jacket which
receive the charge of steam, and thereby to vary the degree of expansion
in the working cylinder, we attach to the slide jacket on each side of
its middle port a chamber, preferably of cylindrical form, fitted with
a piston, which piston may be moved inwards or outwards at pleasure.
When it is moved inwards the capacity of the charged space is
diminished, and the engine is thus made to work with a greater
degree of expansion; when the piston is moved outwards, the charge
being proportionally increased, the engine is made to work less expan-
sively. The pressure on the pistons of these variable chambers may
be balanced by permitting the boiler pressure to act on their outer
surfaces.
The variation in capacity of the charging spaces may be effected by
moving the pistons, as already described, either by hand or by means of
a governor in any known manner.
In order to equalise the strain upon the engine we prefer to make
the port by which the charge of steam passes from the chamber in the
slide jacket into the working cylinder of tapering or V shape, so that
it shall be gradually opened by the movement of the slide, presenting
a comparatively small area of ingress for the high-pressure steam of the
charge, and enlarging gradually in area as the pressure of the charge is
diminished by expansion.
Although we have described above a method of effecting the expansive
action, such as we have set forth by the use of a single slide, it is obvious
that several slides or valves might be employed for the purpose of alter-
3 nately charging with steam from the boiler spaces or chambers of certain
capacity, and then admitting the charges of such spaces or chambers to
the working cylinder.

page_text: And farther when it is not desired to vary the degree of expansion
the adjustable chambers attached to the slide jacket may be dispensed
with, the jacket itself being made of capacity sufficient for receiving
at each end the desired charge, and in this case the space ordinarily
employed for jacketting the cylinder with steam, or a portion thereof,
may be utilized as a charging chamber for each end of the cylinder by
dividing it into two parts, and connecting each part with a portion of
the slide jacket on either side of the middle port.
DESCRIPTION OF THE DRAWINGS.
Fig. 1 represents a longitudinal section of a steam cylinder provided
with a slide to act in accordance with our Invention. C is the steam
cylinder, and P, the piston. On the side of the cylinder is formed
a slide jacket fitted with a slide having three piston bosses V, V¹, V².
The two extreme bosses V1, V2, work respectively over the cylinder
ports c', c², and the middle boss V works over the steam inlet port A.
Passages E¹, E, are formed at each end of the jacket for exhaust.
The middle boss V of the slide always separates the jacket into two
chambers S¹, S2, which may be made to have such capacity in pro-
portion to the capacity of the cylinder C, as may be desired, for
expansion. When the slide is in the position shewn in Fig. 1, the
piston P then moving in the direction of the arrow, the chamber C²
is receiving a charge of steam from A, while the steam contained in
the chamber S¹ is expanding into the cylinder and propelling the
piston, the waste steam of the previous stroke issuing by E². As the
piston approaches the end of its stroke the slide is moved by an
eccentric or otherwise so as to bring its bosses past the ports A, c¹, c²,
respectively. The other end of the cylinder then receives steam from
the chamber S2, while the steam expanded in the cylinder during the
previous stroke escapes by the passage E'. Thus at every stroke the
piston is worked by steam which expands from the volume occupying
either of the chambers S1, S2, to the joint volume of the cylinder and the
chamber. If, for example, either of the chambers S¹ or S² has a capacity
of 1, while the capacity of the cylinder is 8, the volume of steam would
during the stroke expand from 1 to 9.
When it is desired to vary the degree of expansion cylindrical vessels
B1, B2, may be fitted on the side of the slide jacket communicating
respectively with the chambers S¹, S³, and fitted with pistons b¹, b²,

page_text: and eduction at each end, and the supply to the expansion chambers
in the middle, substantially as herein described.
In witness whereof, I, the said Alexander Bewicke Blackburn,
have hereunto set my hand and seal, this Thirty-first day of
July, in the year of our Lord One thousand eight hundred and
seventy-four.