Improvements in Duplex Direct Acting Pumping Apparatus.
Year: 1898

page_text: PROVISIONAL SPECIFICATION.
Improvements in Duplex Direct Acting Pumping Apparatus.
I, PHILIP FRANCIS ODDIE, of 9, Mansel Road, Wimbledon, in the County of
Surrey, Engineer, do hereby declare the nature of this invention to be as
follows:-
This invention relates to improvements in duplex direct acting pumping apparatus
and is designed to enable such pumps to be worked by means of steam used
"expansively" that is to say, to enable the supply of steam to the piston cylinders
to be cut off considerably before those pistons have completed their respective
strokes instead of the supply of steam, as is ordinarily the practice, being
continued substantially to the end of each stroke.
In carrying out my invention according to one of several arrangements of
mechanism I provide at the "water end," or part of the pump chamber behind
each plunger a separate or extra chamber into which a prolongation or plunger
extension from the end of the main pump plunger enters through suitable bushing
or packing and the extra chamber of the one (duplex) pump or main chamber is in
communication with the rear or back end of the other pump or main chamber,
whilst the extra chamber of the other pump or main chamber is in communication
with the opposite main chamber. No additional valves are required to enable the
parts to operate and other parts are substantially as usual.
In operation the steam being admitted to what, for the sake of distinction, I will
call number one steam cylinder, operating the number one steam piston and rod,
or connection to operate its coacting number one plunger in the main pump portion,
such steam may be cut off at a convenient variable or predetermined point in the
stroke, say, for instance, at a point about two thirds of its stroke. In the ordinary
construction the motion of the plunger number one would almost immediately upon
steam being cut off come to rest on account of the effective steam pressure becoming
insufficient to overcome the water pressure.
In duplex pumping apparatus arranged according to my invention whilst the
steam piston is acting upon the main plunger to pump water the plunger extension
number one in its extra chamber meanwhile is also forcing water therefrom into the
pump valve chamber behind main plunger number two until the steam piston has
reached two thirds of its entire stroke and the pump plunger the same extent, then
main plunger number two, being operated by steam piston and connection, number
two, commences its return motion in its pump cylinder, and in doing so the pressure
in rear thereof being relieved the pressure in extra chamber, number one, partakes
of that relief, facilitating the completion by plunger number one of its stroke.
When the steam, supplying pressure to piston number two, is cut off, upon it, and
its coacting main plunger having completed their strokes, to the extent of two
thirds the full stroke, cut off is effected and the stoppage of its stroke is prevented
by the main plunger number one starting on its return stroke, under the operation
of its own steam piston, and communicating the pressure of the water at its front
end to the extra chamber and additional plunger provided in like manner to the
rear end of the main pluuger number two, thereby assisting that plunger

page_text: number two in its completion of the stroke, and so on the cycle of operations is
continued repeatedly thereby constituting a compensating arrangement by which
the excess of pressure at the commencement of the stroke of the one steam piston
is through its coacting plunger utilized in aid of the deficiency of steam pressure
existing towards the end of the stroke of the opposite steam piston, and so on.
Although I have referred to two-thirds cut off this extent of cut off may be
varied. Again I have for illustration described the extra chambers as being
arranged in rear of the main plungers and chambers, but they may be arranged in
other relative positions as may be found most convenient under particular circum-
stances and the extra or extension pump plungers will be arranged in accordance
with the change of position of their chambers.
Such an arrangement of plungers and auxiliary plungers and their chambers
may be conveniently used with arrangements of steam cylinders used in what are
known as the compound type of duplex pumping engines.
Dated the 1st day of March 1898.
WM. BROOKES & SON,
55 and 56, Chancery Lane, London, Agents for the Applicant.
Improvements in Duplex Direct Acting Pumping Apparatus.
I, PHILIP FRANCIS ODDIE, of 9, Mansel Road, Wimbledon, in the County of Surrey,
Engineer, do hereby declare the nature of my invention for improvements in duplex
direct acting pumping apparatus and in what manner the same is to be perforined,
to be particularly described and ascertained in and by the following statement:-—
86
This invention relates to improvements in duplex direct acting pumping apparatus,
and is designed to enable such pumps to be worked by means of steam, used
expansively "that is to say, to enable the supply of steam to the piston cylinders
to be cut off considerably before those pistons have completed their respective
strokes; instead of the supply of steam, as is ordinarily the practice, being
continued substantially to the end of each stroke.
In carrying out my invention I provide at the "water end," or part of the pump
chamber behind each plunger a separate or extra chamber into which a prolonga-
tion or plunger extension from the end of the main pump plunger enters through
suitable bushing or packing and the extra chamber of the one (duplex) pump or
main chamber is in communication with the rear or back end of the other pump
or main chamber, whilst the extra chamber of the other pump or main
chamber is in communication with the opposite main chamber. No additional
valves are required to enable the parts to operate and other parts are substantially
as usual.
DESCRIPTION OF THE DRAWINGS.
Figure 1 represents a longitudinal section and Figure 2 a sectional plan of the
water end of a duplex pump arranged to carry
out my
invention.
Figures 3, 4, 5 and 6 by four views in sectional plan, the sequence of motions
performed by the steam pistons and auxiliary or compensating plungers, so as to
facilitate a correct comprehension of the cycle of movements perfomed during one
complete reciprocation of the co-operating parts as shown in the dawing.
Behind each pump cylinder marked I and II respectively are provided an
auxiliary chamber a3 or 63 in which an auxiliarly piston or plunger a² or b² works as
the case may be, and which auxiliarly plungers are respectively fastened to the

page_text: respective pump pistons or plungers A², B², and passes through suitable bushes or
packing a, b, into the auxiliary chambers a³, 63.
The auxiliary chambers a³ of the one pump I is connected by means of a channel a³
with the back end 6 of the other pump II whilst the auxiliary chamber 63 of the
pump II is connected by a channel 65 with the opposite end a of cylinder I.
Thus no additional gear or valves are required and only those ordinarily in use are
needed.
The steam enters either the steam cylinder A or B drives the piston A¹ or B¹ and
piston rod and with it sets in motion the pump plunger A² or B2 corresponding and
an auxiliary plunger a² or b².
The steam can be cut off at a suitable point either fixed or variable, for example
two thirds of its stroke. In the ordinary construction the pump pistons A must
come to rest as soon as the steam is cut off as the effective steam pressure is not
strong enough to overcome the water pressure in the pump. In the present inven-
tion on the other hand the main piston of the one is relieved at this moment by the
motion of the auxiliary piston in the other.
In operation, referring to Figure 4 the steam being admitted, to what, for the
sake of distinction, I will call steam cylinder A, operating the steam piston A¹ and
rod, or connection to operate its co-acting plunger A2 in the main pump portion in
the direction of the arrow (1) such steam may be cut off at a convenient variable
or predetermined point in the stroke, say, for instance at a point about two thirds
of its stroke, the piston then assuming the position shown in Figure 5.
In the ordinary construction the motion of the plunger A2 would almost imme-
diately upon steam being cut off come to rest at the point shewn in Fig. 5 on
account of the effective steam pressure becoming insufficient to overcome the water
pressure.
In duplex pumping apparatus arranged according to my invention whilst the
steam piston A. is acting upon the main plunger A² to pump water the plunger
extension a² in its extra chamber a is meanwhile also forcing water therefrom into
the pump valve chamber b, behind main plunger B2 until the steam piston A¹ has
reached two thirds of its entire stroke and the pump plunger A2 the same extent,
then main plunger B² as already referred to and shown in Fig. 5, being operated by
steam piston B₁ and its connection commences its return motion in its pump
cylinder II and in doing so the pressure in rear thereof being relieved the pressure
in the extra chamber a³ partakes of that relief, facilitating the completion by
plunger A of its stroke.
When the steam, supplying pressure to piston B¹, is cut off, upon it, and its
co-acting main plunger B2, having completed their strokes, to the extent of two
thirds the full stroke a position indicated by Figure 6, cut off is effected and the
stoppage of its stroke is prevented by the main plunger A² starting on its return
stroke under the operation of its own steam piston A' and communicating the
pressure of the water at its front end to the extra chamber 63 and additional
plunger b², provided in like manner to the rear end of the main plunger B2. The
water pressure passing by channel 65 thereby assisting that plunger B2 in its
completion of the stroke.
Then referring to Fig. 3 the piston A¹ in the cylinder A continues its motion in
the direction of the arrow (7) the steam is cut off, and the piston B¹ commences its
return motion in the direction of arrow (8). Until the piston A' reaches the
position shown in this fig. about two thirds of its stroke the main plunger A2 has
been forcing water through the delivery valve of the pump exercising the
full area of its surface, and has at its opposite faces A* of its main plunger and
reduced face a of the auxiliary plunger being drawing water through the suction
valves the combined areas of these two faces A and a equalling approximately
the area of the opposite face A³. As soon as the piston A' has reached the position
indicated in this fig. the piston B₁ commences its traverse in the direction of
arrow (8) and consequently the plunger B2 and auxiliary plunger b² partake
of the same motion the motlon of the plunger B2 by its rear face B* pressing on

page_text: the water in b communicates that pressure through channel as to the auxiliary
chamber a³ in rear of auxiliary plunger a² and presses on the face a of that
auxiliary plunger assisting the piston A to complete the stroke.
As soon as this has been accomplished the piston B₁ (see Fig. 4) still moving in
the direction of the arrow 2 arrives at the point where its steam supply is cut off
and piston A¹ is about commencing its return traverse in the direction of arrow 1,
and doing so the water pressure in front of plunger A2 being relieved that relief of
pressure is by the channel 65 communicated to the chamber 63 in rear of the
auxiliary plunger 62 and thereby the completion of the stroke of piston B' is assisted.
And so on the cycle of operations is continued repeatedly thereby constituting a
compensating arrangement by which the excess of pressure at the commencement
of the stroke of the one steam piston as A¹ is through its co-acting plunger as B
utilized in aid of the deficiency of steam pressure existing towards the end of the
stroke of the opposite steam piston and so on.
Although I have referred to two-thirds cut off this extent of cut off may be
varied.
Again I have for illustration described the extra chambers as being arranged in
rear of the main plungers and chambers, but they may be arranged in other relative
positions as may be found most convenient under particular circumstances and the
extra or extension pump plungers will be arranged in accordance with the change
of position of their chambers.
Although in the drawings I have shown each plunger as being provided with
auxiliary plungers and as being of the same area, I in some cases however make the
auxiliary plungers of different areas or dispense with the auxiliary plunger on one
pump cylinder altogether. Thus in the case of a duplex pumping engine with one high
and one low pressure steam cylinder placed side by side I prefer to make the
compensating plunger connected with the high pressure piston rod considerably
larger than that connected with the low pressure piston rod and thus obtain an
earlier cut off of steam in the high pressure cylinder than would otherwise be
possible.
Again, although I have also shewn the compensating plungers single-acting it is
evident that they may be made double-acting pistons or have plungers working in
separate cylinders.
The usual difficulty attendant on expansive working of steam has been overcome
in the present improved construction of pump, for it is evident for obvious reasons
that without some compensating device the pistons must come to rest almost
directly after the steam has been cut off. In the present improved pump apparatus
however when the pressure of steam on the steam pistons is reduced owing to
expansion after cut off, the net area of the pump plunger or piston is also reduced;
in other words, the work done is less to suit the diminished power, the water
pressure remaining constant.
To obtain this desirable end, advantage is taken of the fact that one piston starts
when the other has completed say two-thirds of its stroke. The plunger or pump
piston is so constructed that up to two-thirds of its stroke it is pumping with its
full area, but as soon as the other piston starts moving it is relieved by this move-
ment of say one-third of its load, thus enabling the reduced steam pressure to
finish its work by completing the stroke of the piston.
By referring to the section it will be seen that each plunger is provided with an
extension which works in an auxiliary chamber at the rear of the pump.
The auxiliary chamber of one pump is in constant connection with the main
pump chamber of the other and vice-versa.
In operation, after the steam supply to the first cylinder has been cut off and the
piston has completed say two thirds of its stroke, the second piston commences its
is
travel; the pressure in the auxiliary chamber of the first pump consequently
relieved, thus reducing the load on the piston to the extent of the sectional area of
the plunger extension.

page_text: This enables the piston to complete its stroke in spite of the fact that the steam
pressure has, owing to expansion, fallen below the water pressure in the pump.
This action is, in turn, repeated for all four strokes, and a simple and automatic
compensation obtained by means of the plungers themselves without the use of any
external mechanism, additional valves, or other complications.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what mauuer the same is to be performed, I declare that what I
claim is :-
1. In a duplex pumping engine, the combination with the two steam actuated
pistons, (as A and B), and their connected plungers, (as A and B²,) of auxiliary
plungers, (as a², 62,) respectively, auxiliary chambers therefor and water passages
(as a and b) connecting the spaces between the suction and delivery valves of the
inain plungers with the opposite chambers in rear of the auxiliary plungers
respectively, substantially as shown and described by the drawing.
2. In a duplex pumping engine, a pair of main steam pistons and cylinders
and connected main plungers and cylinders, an auxiliary plunger connected to the
one face of one of the said main plungers, an auxiliary chamber in rear thereof,
a connecting channel connecting said auxiliary chamber with the chamber of the
other of the said main plungers, a second auxiliary plunger connected with the
other main plunger, a second auxiliary chamber therefor and a second connecting
channel connecting said second auxiliary chamber with the chamber of the first
mentioned main plunger, as set forth.
3. In a duplex pumping engine, steam pistons as A¹ and B¹, cooperating plungers
as A2, B2, auxiliary plungers as a², 62, and cylinders for the same to reciprocate in
combination with connecting pressure relieving passages between the plunger
chambers for the liquid to pass from one chamber to the other to enable the one
plunger to operate in relief of the other plunger towards the end of the stroke of
the latter and when the steam pressure is reduced owing to the expansion of the
steam after the steain thereto has been cut off.
4. In duplex pumping engines (characterized by one plunger commencing to
move before the other has completed its stroke) the use of means for dividing up
the effective pumping area of the plunger into two distinct parts, each part acting
in separate chambers; connecting one of the chambers in which one of the parts
work with one of the pump chambers of the other pump cylinder, so that the motion
of one plunger tends to relieve the other plunger of work to the extent of the area
of one of the parts of which it is composed and vice versa, and the effective work
done by each plunger is thus reduced during the latter part of its stroke; the fluid
pressure remaining constant throughout, substantially as and for the purpose set
forth.