An Improved Valve Gear for Duplex Pumping Engines.
Year: 1893

page_text: Date of Application, 1st Aug., 1893
Complete Specification Left, 28th May, 1894-Accepted, 14th July, 1894
PROVISIONAL SPECIFICATION.
An Improved Valve Gear for Duplex Pumping Engines.
1 JOHN FIELDING of Somerset Lawn in the City and County of Gloucester
Engineer do hereby declare the nature of this invention to be as follows:-
1
The object of my invention is to overcome a well known and important defect
in the working of duplex pumping engines as usually constructed, viz., that under
some conditions they are liable to work short strokes, thus reducing their pumping
capacity whilst using as much steam as if working full stroke.
This defect arises from the action of the ordinary valve gear which causes each
piston to reverse the valve of the opposite cylinder as it passes the half stroke.
Therefore as the valves are usually without lap, it is quite possible to have the
pistons making such short strokes that the pumping capacity may be almost reduced
to nothing whilst the full consumption of steam is going on.
According to my invention the valves are so operated that their reversal cannot
take place until their operating pistons have completed their full stroke, whilst the
construction of the valve gear is simpler than that now in use.
My improved valve gear consists of a pair of swinging levers connected to and
operated by the piston rods, after the manner at present in use, except that, instead
of being pivoted upon two shafts working in bearings carried upon the engine frame,
one lever only works upon a pivot so carried.
The said pivot takes the form of a long boss of considerable size which may be
made in one piece with its lever or the latter may be keyed or otherwise secured
to it.
An eccentrically situated hole is bored in the said lever boss parallel to its axis
and in the same line radially as the lever.
•
Within this hole is placed the shaft upon which the second swinging lever is
carried & secured. At either end of this shaft are two short levers, placed in a
line with the swinging lever and opposite to each other.
These levers operate the
valves by means of connecting links, or their equivalents.
These levers stand directly opposite to each other and therefore move in opposite
directions as the second swinging lever vibrates.
The result of this arrangement is that each valve receives a compound movement,
partly due to that of the eccentric hole in the boss of the first swinging lever, and
partly to that of one of the short levers upon the shaft of the second swinging
lever.
The action of the gear is such that each piston reverses the valve of the opposite
cylinder from full port open at one end to a slight lead opening at the other,
whilst it moves the valve of its own cylinder from the lead opening to full port
open.
Dated this Thirty-first day of July 1893.
JOHN FIELDING.

page_text: COMPLETE SPECIFICATION.
An Improved Valve Gear for Duplex Pumping Engines.
I JOHN FIELDING of Somerset Lawn in the City and County of Gloucester
Engineer 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 :-
The object of my invention is to overcome a well known and important defect
in the working of duplex pumping engines as usually constructed, viz., that under
some conditions they are liable to work short strokes, thus reducing their pumping
capacity without a corresponding reduction in the consumption of steam.
This defect arises from the action of the ordinary valve gear which causes each
piston to reverse the valve of the opposite cylinder as it passes the half stroke.
Therefore as the valves are usually without lap, it is quite possible to have the
pistons making such short strokes that the pumping capacity may be almost
reduced to nothing whilst the full consumption of steam is going on.
According to my invention the valves are so operated that their reversal cannot
take place until their operating pistons have completed their full stroke whilst the
construction of the valve gear is simpler than that now in use.
My improved valve gear consists of a pair of swinging levers connected to and
operated by the piston rods after the manner at present in use, except that instead
of being pivotted upon two shafts working in bearings carried upon the engine
frame, one lever only works upon a pivot so carried.
The said pivot takes the form of a long boss of considerable size which may be
made in one piece with its lever or the latter may be keyed or otherwise secured
to it.
An eccentrically situated hole is bored in the said lever boss parallel to its axis
and in the same line radially as the lever.
Within this hole is placed the shaft upon which the second swinging lever is
carried and secured. At either end of this shaft are two short levers placed in a
line with the swinging lever and opposite to each other, these levers operate the
valves by means of connecting links, or their equivalents.
These levers stand directly opposite to each other and therefore move in opposite
directions as the second swinging lever vibrates.
The result of this arrangement is that each valve receives a compound movement
partly due to that of the eccentric hole in the boss of the first swinging lever, and
partly to that of one of the short levers upon the shaft of the second swinging
lever.
The action of the gear is such that each piston reverses the valve of the opposite
cylinder from full port open at one end to a slight lead opening at the other whilst
it moves the valve of its own cylinder from the lead opening to full port open.
DESCRIPTION OF THE DRAWINGS.
+
The steam cylinders A. and B. are placed side by side and are so combined as to
act reciprocally upon the steam valves of each other.
The piston rods C. and C' each carry a crosshead a. one of which connects with
the lever D. and the other with lever D'.
The lever D. is provided at its upper end with a cylindrical enlargement or boss
which forms a movable bearing d. which latter may be integral with the lever or
keyed thereto, and is mounted in a bearing d' rigidly secured in position to any
convenient portion of the apparatus. This boss extends transversely across the
apparatus, and as the piston C. to which lever D is connected, is reciprocated, it
will be seen that the boss is given a semi-rotary movement in its bearing.
+

page_text: This boss is provided as shown with an eccentrically located hole for the passage
of the shaft E. which latter is located parallel to the axis of the boss and in the.
same line radially as lever D.
Secured to shaft E. is the second swinging lever D¹ which latter is connected at
its lower end to the crosshead carried by the piston C¹.
This shaft E is provided at either end with two short levers F. F¹ placed in a
line with lever D₁ and opposite to each other.
g. or
These levers operate the valves G and G¹ by means of the connecting links,
their equivalent. As these levers stand opposite each other and are on opposite
sides of the axis of shaft E, it follows that they move in opposite directions as the
lever D' vibrates. The result of this arrangement is that each valve G and G¹,
receives a compound movement partly due to that of the eccentric hole in the boss
of the lever D. and partly to that of one of the short levers F. F¹ upon the
shaft E.
The action of the gear is such that each piston reverses the valve of the
opposite cylinder from full port open at one end to a slight lead opening at the
other end, while it moves the valve of its own cylinder from the lead opening to
full port opening.
The movement of the parts is clearly shown in Figs. 3 to 6.
These four figures show the positions occupied by the gear at the commencement
of each of the four strokes which form the cycle.
In Fig. 3 valve G is traveling from left to right just opening the left hand steam
port and the right hand exhaust, while valve G is at the extreme left hand of its
stroke, the right hand steam and left hand exhaust ports being fully open, now by
moving lever D, which as before stated, is actuated by one of the piston rods, the
boss d. is turned in its bearing which shifts shaft E to the right, without turning
said shaft into the position shown in Fig. 4. In this figure, valve G is shown with
its left hand steam and right hand exhaust open, while valve G¹ has also traveled
from left to right enough to open left hand steam port and the right hand exhaust
slightly.
The piston rod which actuates lever D' now moves from left to right carrying
with it lever D', and the latter actuating shaft E. and short levers F. F' moves the
valves from right to left as shown in Figure 5. the positions then being the reverse
of those shown Fig. 3. and the movement of lever D. from right to left brings the
parts into the positions shown in Fig. 6, where they are exactly reverse to those
shown in Fig. 4. The next movement of D' from right to left completes the cycle
of movements and brings the parts into the positions as in Fig. 3.
By the above arrangement of parts the valves are so connected and operated
that their reversal cannot take place until their operating pistons have completed
their full stroke, whilst at the same time the construction of the gear is not less
simple than that now in use generally known as the Worthington duplex valve
gear.
It is evident that many slight changes might be resorted to in the relative
arrangement and construction of parts without departing from the spirit and scope
of my invention hence I would have it understood that I do not restrict myself to
the exact construction of parts herein described.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1st. In a double cylinder engine the combination with the cylinders, valves and
piston rods of a shaft mounted eccentrically in a movable bearing, means connecting
said movable bearing with one of the piston rods, and means connecting the valves
with the shaft, substantially as set forth.
2nd. In a double cylinder engine, the combination with the cylinders, valves and
piston rods, of a moveable bearing, a lever actuated by one of the pistons for giving
said bearing a semi-rotary motion, a shaft eccentrically mounted in said moveable

page_text: bearing and provided with short levers, devices connecting said short levers and
valves, and means actuated by the other piston rod for rocking the shaft,
substantially as set forth.
3rd. In a double cylinder engine, the combination with the cylinders, valves and
piston rods, of a cylinder boss or bearing a lever attached to said boss or bearing
and engaging one piston rod, a shaft eccentrically mounted in said boss or bearing,
a lever connected to said shaft and actuated by the other piston rod, and devices
-connecting the shaft and valves, substantially as set forth.
4th. In a double cylinder engine the combination with the cylinders, valves and
piston rods, of a cylindrical boss or bearing, a lever attached thereto and actuated
by one of the piston rods, a shaft eccentrically mounted in said boss or bearing
and provided with short levers so located as to move in opposite directions as the
shaft is rocked, a lever connected to the said shaft and actuated by the other piston
rod, and links connecting the short levers and valves substantially as set forth.
Dated this 25th day of May 1894.
JOHN FIELDING.