Improvements in Compound Steam Pumps and other Compound Engines.
Year: 1892

page_text: Date of Application, 29th Aug., 1892
Complete Specification Left, 29th May, 1893-Accepted, 1st July, 1893
PROVISIONAL SPECIFICATION.
Improvements in Compound Steam Pumps and other Compound
Engines.
We, JOSEPH EVANS, of the firm of Joseph Evans and Sons, of Heath Town
Works, near Wolverhampton in the County of Stafford, Hydraulic and General
Engineers and Ironfounders, and RICHARD WILLIAM DEANS, of 93 Waterloo
Road North, Wolverhampton, aforesaid, Mechanical Draughtsman, do hereby
declare the nature of this invention to be as follows:-
This invention relates to direct-acting compound steam pumps and other com-
pound engines in which both the high and low pressure steam operate in a cylinder
fitted with a double-headed piston of which the heads are joined together by a
cylindrical portion of reduced diameter which is surrounded at the middle of the
cylinder by an annular projection from the inner wall thereof which forms a fixed
abutment, and in effect divides the cylinder lengthways into two independent
cylinders of which the piston heads form the respective pistons. The high pressure
steam operates, alternately, between one face of such annular projection and the
annular surface of the piston head on the same side of the abutment, and between
the other face of such abutment and the annular projection of the other head of the
piston; and the steam flows, alternately, from the inner face of each piston head to
the outer face thereof and is used expansively in moving the piston in the opposite
direction to that in which it was moved by the same steam when under high
pressure. The piston is thus moved in each direction by high pressure steam
acting behind the piston head which leads in the direction in which the piston is
travelling, and by low pressure steam acting at the outer face of the piston head
which is following.
Now, the main object of this invention is a combination of ports and passages
with a suitable slide valve, whereby a single steam chest and valve only may be
used to control the supply of high pressure steam to the inner faces of the piston
heads, to control the passage of the steam from the inner to the outer faces of
such heads, and to control the final exhaust of the steam to the atmosphere or
condenser.
According to a simple and convenient form of this invention, a B-slide valve,
that is a slide valve having two hollows or ports in its inner face with a central
transverse bar dividing such ports and a transverse bar at each end forming in
each case the margin of the face of the valve between one of the ports and the
outer end of the valve, is used in combination with five ports in the valve face, that
is the face against which the valve works. Of these five ports the middle one is
the exhaust port; the two outer ports communicate, respectively, by suitable
passages, with the two annular spaces between the abutinent and the inner faces of
the piston heads, and are the high pressure ports; and the two remaining or inter-
mediate ports communicate, respectively, by suitable passages, with the opposite
ends of the cylinder, and are the low pressure ports. The valve may be operated
either mechanically, in any well known or convenient manner; or it may be
operated by steam caused to flow from the main cylinder (on the uncovering of a
puff port or the opening of a valve caused by the travel of the main piston) to
each of the pistons, alternately, of a pair of pistons each formed with or attached
to the slide valve and working in a cylinder formed in the end of the steam chest,
as in the case of Tonkins' steam pump; or the valve may be operated by allowing
steam to escape (by the striking of the main piston against a tappet which allows
such steam to enter the exhaust end of the cylinder or a passage communicating
therewith), alternately, from one of snch pistons. of the valve while steam presses

page_text: against the other piston thereof, as in the case of Cameron's steam pump; or the
valve may be operated in any convenient manner.
When the valve is at one end of its stroke, one of the outer ports is uncovered
and the high pressure steam passes therethrough to the annular space between the
abutment and the inner face of one of the piston heads. The low pressure port
adjacent to such outer port communicates through one of the ports in the valve
with the final exhaust port, and the exhaust steam escapes from the opposite side
of the head to that against which the high pressure steam is now pressing. The
remaining outer port and intermediate or low pressure port are in communication
with one another through the other port in the valve, and the steam from the
opposite side of the abutment to that to which the high pressure steam from the
chest is now flowing passes to the outer face of the following piston head and is
used expansively. On the reversal of the valve to the other end of its stroke the
flow of the steam is of course reversed.
The invention has been described, for convenience, as applied to a steam engine,
but it is of course applicable also to engines worked by other elastic motor, such as
compressed air.
Dated this 27th day of August 1805
STEPHEN WATKINS,
Wolverhampton, Agent for the Applicants.
COMPLETE SPECIFICATION.
Improvements in Compound Steam Pumps and other Compound
Engines.
We, JOSEPH EVANS, of the firm of Joseph Evans and Sons, of Heath Town
Works, near Wolverhampton in the County of Stafford, Hydraulic and General
Engineers and Ironfounders, and RICHARD WILLIAM DEANS, of 93 Waterloo
Road North, Wolverhampton, aforesaid, Mechanical Draughtsman, do hereby
declare the nature of this invention and in what manner the same is to be performed,
to be particularly described and ascertained in and by the following statement:-
This invention relates to direct-acting compound steam pumps and other compound
engines in which both the high and low pressure steam operate in a cylinder fitted
with a double-headed piston of which the heads are joined together by a cylindrical
portion of reduced diameter which is surrounded at the middle of the cylinder by
an annular projection from the inner wall thereof, such projection forming a fixed
abutment and in effect dividing the cylinder lengthways into two independent
cylinders of which the piston heads form the respective pistons. In such an arrange-
ment the high pressure steam operates, alternately, between one face of such annular
projection and the annular surface or inner face of the piston head on the same side of
the abutment, and between the other face of such abutment and the annular surface or
inner face of the other piston head; and the steam flows, alternately, from the inner
face of each piston head to the outer face thereof and is used expansively in
moving the piston in the opposite direction to that in which it was moved by the
same steam when under high pressure. The piston is thus moved in each direction
by high pressure steam acting behind the piston head which leads in the direction
in which the piston is travelling, and by low pressure steam acting at the outer
face of the piston head which is following.
It is unimportant, of course, so far as concerns the working of the engine,
whether the portions of the cylinder in which the respective piston heads work are
made in one piece together, or are made separately and joined together, or whether
the abutment is formed with the cylinder or fixed in place therein.
Now, the main object of this invention is a combination of ports and passages
with a suitable slide valve, whereby a single steam chest and valve only may be
used to control the supply of high pressure steam to the inner faces of the piston
heads, to control the passage of the steam from the inner to the outer faces of such

page_text: heads, and to control the final exhaust of the steam to the atmosphere or
condenser.
This object is effected, according to this invention, in a simple and convenient
manner, by the means illustrated on the drawings herewith, which we will now
proceed to describe by the aid of the letters of reference marked thereon.
Figure is a side elevation of a steam cylinder within which is fitted a double-
headed piston of the character above described, and is such as is suitable for use as
the motive power cylinder of a direct-acting pump. The valve chest is omitted,
for convenience of illustration, and the valve also is omitted so as to expose the
face against which it works.
Figure 2 is a longitudinal sectional plan taken through the centre of the cylinder,
and the valve chest and valve are also shewn as a section taken through the centre
thereof though such is at a lower level, in the arrangement shewn, than the
centre of the cylinder. The double-headed piston is shewn in plan view in this
figure, and in position when at half stroke.
Figure 3 is a section taken through the slide valve and through a portion of the
cylinder, so as to indicate more clearly than is seen in Figure 2 the arrangement of
the ports over which the valve travels and the direction of the passages with which
such ports communicate. The section is taken on the irregular line of Figure 5,
but is broken off along one side, and at each end, for convenience of illustration,
and the steam chest is omitted.
Figures 4 and 5 are transverse sections taken on lines y y and zz, respectively,
of Figure 2, supposing such figure to be a plan view instead of a sectional plan.
A is the cylinder, B the annular projection from the inner wall thereof which
forms the fixed abutment, and C the piston having the two heads D D working
within the cylinder on opposite sides of the abutment B. The abutment may be
fixed within the cylinder by means of pins passing through the wall thereof and
into the abutment, and packing rings may be inserted within a groove in the
abutment and held in place by means of a junk ring g No claim, however, is
made in respect of this arrangement of piston and abutment, as it is of a type
heretofore employed. The abutment is oniitted in Figure 3 for the sake of clearness
of illustration.
A. B-slide valve E, that is to say, a slide valve having two ports or cavities a a
in its inner face divided by a central transverse bar b, slides against a valve face F
having five ports c d d and e e. Of these ports, the middle one e is the exhaust
port which, in the arrangement shewn, communicates by means of a passage c',
which passes partially around the underside of the cylinder A, with an outlet c²
at the bottom of the cylinder casting. The ports did coming next on each side,
respectively, of the port c communicate, respectively, by means of passages d',
with openings into the opposite ends of the cylinder A. These are the low
pressure ports. The outer ports e e communicate, respectively, through passages e',
with openings into the cylinder A in position near to the annular projection
forming the fixed abutment B, and consequently with the annular spaces between
the abutment and the inner faces of the piston heads. These ports are the high
pressure ports.
The valve E may be operated either mechanically, or by steam pressure, in any
well known or other convenient manner in which slide valves are so moved. In
the illustrations, the valve is shewn to be moved by the aid of pistons i i working
in cylindrical ends of the steam chest G. These pistons may be operated by the flow
of steam to the back of one of them, alternately, while the steam is allowed to
escape from the back of the other, as in the case of the "Cornish "
steam pump
invented by Tonkin; or such pistons may be operated by the steam behind one of
them, alternately, being allowed to escape while the steam pressure remains behind
the other piston, as in the case of Cameron's steam pump.
When the valve is at the forward end of its stroke, as shewn by Figures 2 and 3,
the hinder high pressure port e is uncovered, and the steam which is supplied to
the steam chest G, through an inlet passage k or other suitable inlet, passes direct

page_text: from the steam chest into, the annular space h between the abutment B and the
hinder piston head D, and drives the piston in the direction indicated by the
arrow j, Figure 2. The forward port or hollow a in the face of the valve E is
over both the forward high pressure porte and the forward low pressure port d,
placing such ports e and d in communication with one another. The high pressure
steam thus passes from the annular space between the front of the abutinent B
and the forward piston head into the forward end of the cylinder, and acts
expansively in driving the piston backwards in the direction indicated by the
arrow, that is to say, in the direction in which it is also being driven by the
high pressure steam acting against the inner face of the hinder piston head.
The hinder port or hollow a in the face of the valve E is over both the
hinder low pressure port d and the exhaust port c, placing these ports d and c in
communication with one another and allowing steam to escape from the hinder or
outer face of the hinder piston head D into the exhaust port, and away to the
atmosphere or condenser. The direction of the flow of the steam is indicated by
the arrows in Figures 3, 4 and 5.
When the valve is moved back to the opposite end of its stroke, the reverse
movement of the steam, of course, takes place. The forward high pressure port e
is uncovered, the hinder high pressure port e and the hinder low pressure port d
are placed in communication with one another, and the forward low pressure
port d and the exhaust port e are also placed in communication with one another.
High pressure steam from the steam chest flows consequently into the annular
space between the front of the abutment B and the forward head D of the
piston. The high pressure steam from between the back of the abutment B
and the hinder piston head expands into the cylinder on the opposite side of
such piston head. And the steam exhausts from the forward side of the forward
piston head into the atmosphere or condenser.
The invention has been described in its application to a steam engine fitted with
a double-headed piston, and the description has referred more especially to a direct
acting steam pump. The invention, however, is applicable, as will be obvious, to
compound engines generally whether worked by steam or by other elastic motor
such as compressed air, and whether a double-headed piston operating in the manner
above described is employed or whether separate pistons are used working in
separate cylinders. In the case of a compound engine having a high pressure
cylinder distinct from the low pressure cylinder the two high pressure ports e e
communicate with passages which open into the opposite ends, respectively, of the
high pressure cylinder, and the low pressure ports d d communicate with passages
which open into the opposite ends, respectively, of the low pressure cylinder, and
thus a single slide valve is used for the two cylinders.
Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed, we declare that what
we claim is :-
1. In a compound steam pump or other compound engine fitted with a double-
headed piston in the manner described or having separate pistons working in
separate cylinders, the combination of ports and passages with a slide valve in
such manner that a single valve serves to control the supply of high pressure steam
(or other fluid motor) to both the high pressure chambers or to each end of the
high pressure cylinder, to control the passage of the steam (or other fluid motor)
from both the high pressure chambers or from both ends of the high pressure
cylinder to both the low pressure chambers or to both ends of the low pressure.
cylinder, and to control, through the medium of a single or common exhaust'
port in the face against which the valve works, the final exhaust from both the
low pressure chambers or both ends of the low pressure cylinder to the atmosphere
or condenser, substantially as herein before described.
2. The combination, in a compound steam pump or other compound engine, of a
double-headed piston operated. by both high and low pressure steam (or other fluid.

page_text: motor) in the manner described, with a B or double-ported slide valve and five
ports in the face against which the valve slides, said ports communicating,
respectively, with suitable passages for the purpose set forth, substantially as
described.
3. The combination, in a compound steam pump or other compound engine, of a
double-headed piston operated by both high and low pressure steam (or other fluid
motor) in the manner described, with a slide valve and ports and passages
constructed and arranged substantially as described and shewn by.the drawings
herewith, for the purpose set forth.
Dated this 26th day of May 1893
STEPHEN WATKINS,
Wolverhampton, Agent for the Applicants.