IMPROVEMENTS IN STEAM ENGINE EXPANSION GEAR AND GOVERNORS
Year: 1873

page_text: LETTERS PATENT to George Alfred Bridgett, of Rose Bank, Fallow-
field, near Manchester, in the County of Lancaster, for the Inven-
tion of "IMPROVEMENTS IN
STEAM ENGINE EXPANSION GEAR AND
GOVERNORS."
Scaled the 23rd September 1873, and dated the 11th June 1873.
PROVISIONAL SPECIFICATION left by the said George Alfred Bridgett
at the Office of the Commissioners of Patents, with his Petition, on
the 11th June 1873.
I, GEORGE ALFRED BRIDGETT, of Rose Bank, Fallowfield, near Man-
chester, in the County of Lancaster, do hereby declare the nature of the
said Invention for "IMPROVEMENTS IN STEAM ENGINE EXPANSION GEAR AND
GOVERNORS," to be as follows:-
:-
This Invention refers to several arrangements of gear for automatically
varying the expansion of steam in steam engines according to the
variations of the load. They may be applied either to new or to existing
engines, and the choice of any particular arrangement will be determined
by the size, speed, and construction of the engine in question.

page_text: The first part consists of a method of actuating on the main slide
valve two gridironed expansion slide valves moving in a direction at
right angles to the direction in which the main slide valve moves.
One
is at each end of the main slide, and shuts off steam from the corrc-
sponding end of the cylinder.
The following description refers to one valve only, the other being
worked in a similar manner; a spring constantly tends to keep it
shut-On the main slides moving towards the end of the valve casing,
that is, to open the cylinder port to the exhaust, an inclined or curved
projection on the expansion valve comes in contact with an inclined or
curved projection fixed to the valve casing, causing the expansion valve
to open. On its being opened a spring latch fixed to the main slide
keeps it so until such time as it is released by the latch being lifted.
This latter is accomplished in the following manner:-A revolving or
oscillating shaft passes through the valve casing, on which is a projecting
feather or cam piece (another feather on the same shaft releases the
other expansion valve), which comes in contact with the latch and
pushes it clear of the expansion valve, which then shuts by means of
the before mentioned spring. A steam displacement cushion prevents
shock. The position of this releasing shaft with regard to the crank
shaft is varied by means of the governor herein-after described, or by
means of an ordinary governor's moving endways a rifled sleeve clutch,
i.e., one containing threads of a very coarsely pitched screw.
In the case of reverseable engines the same hand lever which moves
the reversing link may also move the rifled clutch.
Another part of this Invention consists in fixing inside the valve
casing to the main slide valve a small cylinder fitted with a piston,
piston rod, and valve for the purpose of working expansion valves on
the main slide valve, whether they move transversely or parallel to the
motion of the main slide valve. The valve of this small cylinder may be
a common three-ported slide, a piston valve, or any other known kind of
distributing valve, but I prefer that there should be two passages to
each end of the cylinder, one for supply leading to the very end, and
one for exhaust entering the cylinder a short distance from the end, the
object being that compression may take place after the piston has passed
the entrance of the exhaust passage and so bring it to rest without
shock. The slide valve of the small cylinder is opperated by means of
E

page_text: a revolving or oscillating shaft passing through the valve casing, on
which shaft slides endways, being pushed backwards and forwards by
the main slide, a cam or a lever for working the small valve. The
position of this shaft with regard to the crank shaft is varied in the same
manner as that of the releasing shaft before mentioned.
Another part of this Invention refers to another method of actuating
the before mentioned gridironed expansion valves working at right
angles to the motion of the main valve, the two valves being secured
together so as to move at the same time, the one to open when the other
shuts; a small steam cylinder is bolted to the side of the valve casing
with its piston rod projecting into the same. At the end of the piston
rod and at right angles to it is a long slot; a projection from the
expansion valves engages into this slot, so that they may be carried
along with the main slide, but will be moved across it on the piston
rod's being pushed in or out. The same kind of valve may be used to
distribute steam to this cylinder as was described for the one fixed to
the slide valve. It may also be opperated in the same manner, except
that as the cylinder is fixed and not carried along with the main slide
so neither will the cam or lever which actuates the valve be pushed
backwards and forwards by the main slide valve on the oscillating or
revolving shaft, which latter may if preferred be outside the valve
casing. Instead of the slot at the end of the piston rod engageing a
projection on the expansion valves it may engage a pin at the end of
one arm of a bell-crank lever working on a centre fixed to the main
slide, the other arm of the bell-crank lever opperating expansion valves
moving parallel with the motion of the main slide.
Another part of this Invention refers to a method of actuating
expansion valves on the main slide, working parallel to the motion of
the same.
On a revolving or oscillating shaft passing through the valve.
casing is a cam which opperates the expansion valves, and which is itself
carried backwards and forwards by the main slide on a square or on
feathers on the revolving or oscillating shaft, which latter is advanced
or delayed with regard to the crank shaft by the governor.
In combination with any of the foregoing arrangements of expansion
gear, except the first, a spring being in its normal position when the
expansion valves are at mid-stroke, may with advantage act on the
latter

page_text: In some cases the governor spindle being driven by gearing instead of
causing the sleeve on the governor spindle to opperate a rifled clutch I
fix to each suspension arm of the governor a bevelled toothed segment
gearing into a bevel wheel on a sleeve on the governor spindle. As
the balls open the sleeve turns round with regard to the spindle. On
this sleeve is either a cam to work the before mentioned oscillating,
i.e., rocking shaft, or a wheel to work the before mentioned revolving
haft
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said George Alfred Bridgett in the Great Scal Patent
Office on the 11th December 1873.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, GEORGE
ALFRED BRIDGETT, of Rose Bank, Fallowfield, near Manchester, in the
County of Lancaster, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Eleventh day of June, in the year of
our Lord One thousand eight hundred and seventy-three, in the thirty-
sixth year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said George Alfred Bridgett, Her
special licence that I, the said George Alfred Bridgett, my executors,
administrators, and assigns, or such others as I, the said George
Alfred Bridgett, my 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 Inven-
tion for "IMPROVEMENTS IN STEAM ENGINE EXPANSION GEAR AND GOVERNORS,"
upon the condition (amongst others) that I, the said George Alfred
Bridgett, 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 performed, and cause the same to

page_text: be filed in the Great Seal Patent Office within six calender months next
and immediately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said George Alfred Bridgett, do hereby
declare the nature of my said Invention, and in what manner the
same is to be performed, to be particularly described and ascertained
in and by the following statement (that is to say) :—
This Invention refers to several arrangements of gear for automatically
varying the expansion of steam in steam engines according to the
variations of the load. They may be applied either to new or to existing
engines, and the choice of any particular arrangement will be determined
by the size, speed, and construction of the engine in question.
In order that my Invention may be more clearly and particularly
understood I have hereunto annexed a Sheet of Drawings, to which the
following description refers :-
Fig. 1 shows an arrangement for releasing the cross gridironed
expansion slide valves a, a, acted on by springs b, b, by means of cam
pieces c, c, on a revolving shaft d. The valves a, a, are forced open
against the springs b, b, by inclines e, e, on the valve casing o, and are
kept so by latches f, f, until the latches are lifted by the cams c, c, on
the revolving shaft d; h is a displacement cushion to prevent shock.
Instead of the cams c, c, being made so long as to act on the latches in
all positions of the main slide valve they may be made short, and the
shaft be carried along endways by the main slide g, or they may be
mado loose, and be themselves carried backwards and forwards on a
square or on feathers on the shaft d.
Fig. 2 shews a modification in which the expansion valves a, a, after
being forced open by the inclines e, e, on the valve casing o are kept so
by the high parts of the cams c, c, on the revolving shaft d, and are
released when the high parts of the cams have passed clear of the
bearing pieces k, k, on the expansion valves, that is to say, the latches
are done away with and the cams act directly on the expansion valves to
keep them open the requisit amount of time.
With regard to the next part of my Invention, since filing my
Provisional Specification I have discovered that the use of a small
cylinder fixed on the main slide to work expansion valves thereon is not
new, I therefore make no further general claim. to this, but my novel

page_text: methods of actuating an auxiliary slide valve on the back of the main
slide valve by cams on a shaft passing through the valve casing are
applicable to the actuating of the small slide valve of a small steam
cylinder fixed on the main slide valve, and the use of two passages to
each end of such a cylinder to prevent shock is new, I therefore continue
my claim to these in connection with such cylinder.
Fig. 4 shews a small cylinder n fixed on the back of a steam engine
slide valve g to work expansion valves a thereon transversly to its
motion. There are four passages, two to each end of the cylinder, the
outside ones are for the admission of steam, and the inside ones are for
its exhaust. The small slide valve p to this cylinder is actuated in the
following manner:-A revolving shaft d has a cam c on it capable of
sliding backwards and forwards on it along with the main slide valve g.
Now the cam c may act on one bearing piece k on the small slide and
move it in one direction, and a spring e be employed to move it in the
other, as shewn in Fig. 4, or the cam c may act on two bearing
pieces k, k, one on each side of it, and cause the movement of the
valve p both ways without the assistance of a spring, as shewn in
Fig. 5, and instead of the cam c sliding endways along the revolving
shaft d, as shewn in Fig. 4, it may be fixed to it, and be made so long
that the bearing piece k on the small slide valve p will not move beyond
it by the motion of the main slide valve g, as shewn in Fig. 5, or it
may be fixed to the shaft d, and the shaft itself be carried backwards
and forwards endways, in which latter case the shaft d must either be
telescopic or it must slide through the wheel which revolves it.
Fig. 3 shews the form of cam employed to work the small slide valve
of a cylinder (n) fixed on the main slide (g) to work expansion valves (a)
parallel with the motion of the main slide (g). Instead of this cam
moving endways along the revolving shaft d it may be fixed to it, and
the shaft itself be carried endways along with the main slide.
This cam
may be also arranged to work the small valve only one way, a spring
being caused to move it the other.
In the case of small engines, or where the use of a steam cylinder
fixed on the main slide is inadmissable, as for instance, from want of
room in the valve casing, the expansion valves themselves may be
actuated in the same manner that the slide of the small cylinder is shewn
to be actuated in Figs. 3, 4, 5.

page_text: Fig. 2 shews one example of thus directly actuating the expansion
valves without the cylinder, substantially in the same manner as the
slide of the small cylinder is shewn to be actuated in Fig. 4. The
valves a, a, are forced open by the cams c, c, and kept so by them until
the high parts of the cams have passed clear of the bearing pieces k, k,
on the expansion valves, when they shut in obedience to the action of
springs not shewn in this view.
The parts not shewn in Figs. 2° & 2 are supposed to be similar to
those of Fig. 1, though if preferred the displacement cushion may be
done away with.
The arrangement shewn in Fig. 2ª is similar to that shewn in Fig. 2,
except that the inclines on the valve casing are done away with, and
the cams force the expansion valves open themselves.
The arrangement of a bearing piece on each side of the cam, as shewn
in Fig. 5, may be applied directly to the expansion valves, substantially
as shewn in that Figure. I have therefore thought it unnecessary to
give any further Drawing of such application, though I may remark
that the expansion valves may be fastened together and worked by
one cam, or they may be separate and worked by two cams, one to
each.
The application of a cam somewhat similar to that shewn in Fig. 3
to the working of expansion valves moving parallel to the motion of
the main slide is shewn in Fig. 6. The only difference is that bearing
pieces k, k, of the form shewn are used in Fig. 6 for the cam to work
against, instead of the pin shewn in Fig. 3, though of course in the
case of a very small engine a pin for the cam to act against may be
fixed into the expansion valves, and visa versa, in the case of a very
large engine hardened bearing pieces, similar to those shewn in Fig. 6,
may be fixed to the small slide of Fig. 3. Also the pin instead of being
round may be modified into a projection, such as would be formed by
the bearing pieces k, k, Fig. 6, put back to back.
With regard to Fig. 6, instead of the cam moving the expansion
valves both ways it may move them only one, a spring being employed
to move them the other. Where the main slide valve is made long for
the sake of shortening the steam passages, or for the convenience of
relieving the back of it of pressure by a ring or otherwise, the expansion

page_text: valves may be made separate from each other, and a separate cam used
for each of them. Further, instead of the cam c being moved backwards
and forwards along the revolving shaft d inside the valve casing by a
carrier fixed on the main slide valve g, it may be moved backwards
and forwards along the revolving shaft d outside the valve casing by a
carrier fixed to the main slide spindle, and communicate motion to the
expansion valves through the intervention of bearing pieces fixed on an
expansion slide valve spindle.
The next part of my Invention is shewn in Fig. 7, and consists of a
double-acting steam cylinder m fixed to the side of the slide valve
casing o, and fitted with a slide valve p, a piston r, and a piston rods,
having a long slot t fixed across the end of it and engaging a pro-
jection u from the expansion valves a for the purpose of working them
across the main slide valve g. If it be desired that the expansion
valves should move parallel to the motion of the main slide this may
be accomplished by the intervention of a bell-crank lever working on a
pin fixed in the main slide, a pin at the end of one arm of the lever
engaging into the slot, and the end of the other arm being attached by
a link or otherwise to the expansion valves. d is a revolving shaft, on
which is a cam c to work the small slide spindle.
In the before mentioned arrangements of expansion gear, except
where the expansion valves are moved in one direction by springs, I
prefer to cause a spring to act on the expansion valves, being in its
normal position when the expansion valves are at mid-stroke, thereby
increasing the smartness of their action. Such a spring marked y
shewn in Fig. 3, but it may be used in connection with the other
arrangements, and may be made of any suitable shape and placed in any
convenient position.
is
The next part of my Invention refers to varying the relative position
of the crank shaft and the shaft marked d in the Drawings so as to
vary the point of the stroke at which the steam is cut off. This may
be accomplished by several known arrangements of mechanism, such as
the rifled sleeve clutch, or the three bevel wheel method, and the
ordinary governor may act on these.
Fig. 10 shews how the governor may act on a rifled sleeve clutch,
but I prefer to use two toothed segments x, x, Fig. 9, attached to the
weights on to the suspension arms of the covernor

page_text: Having described the nature of this Invention, and the manner of
performing the same, I declare that what I claim as the Invention to be
protected by the herein-before in part recited Letters Patent is,―
1st. Actuating auxiliary valves on the backs of steam engine slide
valves by the several modifications of cams on a shaft passing through 5
the valve casing, substantially as described and shewn.
2nd. The several combinations of mechanism for actuating gridironed
expansion slide valves on the main slide valve, substantially as described
and shewn.
3rd. The use of two passages to each end of a small steam cylinder 1
employed to work expansion valves on the main slide valve substantially,
as described and shewn.
4th. In combination with any of the herein-before mentioned arrange-
ments of expansion gear I claim varying the relative position of the
crank shaft and the shaft marked d in the Drawings, substantially as 1
described and shewn.
5th. In combination with any of the hercin-before mentioned arrange-
ments of expansion gear I claim the use of a spring, being in its normal
position when the expansion valves are at mid-stroke, substantially as
described and shewn.
6th. The use of two toothed segments attached to the weights or to
the suspension arms of a centrifugal governor for the purpose of causing
it to vary the point of cut-off by altering the relative position of two
revolving shafts, substantially as described and shewn.
2
In witness whereof, I, the said George Alfred Bridgett, have here- 2
unto set my hand and seal, this Second day of December, in
the year of our Lord One thousand eight hundred and seventy-
three.
GEORGE ALFRED BRIDGETT. (L.S.)