provements in the Valve Gear of Direct-acting Steam Pumps and Compressors and similar Engines.
Year: 1899

page_text: Date of Application, 19th Jan., 1899
Complete Specification Left, 12th Oct., 1899-Accepted, 18th Nov., 1899
PROVIDIONAL DE PUITIVATION
Improvements in the Valve Gear of Direct-acting Steam Pumps and
Compressors and similar Engines.
I, ARTHUR KNOWLES, Mechanical Engineer, of 488, Edgware Road, London, W.,
do hereby declare the nature of this invention to be as follows:-
-
I use, in connection with the valve motion of direct-acting pumps and
similar engines, a single-acting piston and cylinder, open to the atmosphere at
one end and always open to pressure at the other end, mounted at right angles
to the line of motion of the valve gear, in such a way that the piston rod or
connecting rod of the said piston is kept constantly in compression or if the
design demands it-constantly in tension in whichever direction the valve is
moving and at every point of the stroke: thus forming a toggle combination in
which the said piston at farthest point of its stroke has no leverage on the
valve gear but exerts an increasing leverage on either side as the connecting
rod passes the centre line towards that side. The pressure in the said cylinder
may be obtained from the steam or air or fluid driving the engine, or from the
water or air delivered by the pump into the delivery pipes, or from an accumu-
lator or cistern, or the piston may be made to compress air in the cylinder, or
the piston may be actuated by springs, or a suitable spring without any cylinder
may be used. The cylinder may be oscillating or fixed. The object of the
invention is to simplify and cheapen the construction of such engines by render-
ing unnecessary the usual pistons and cylinders in the main valve chest employed
to alternate, or help to alternate, the motion of the valve.
The valve derives its motion from a pin in a crosshead which is fastened to
the piston rod. This pin is coupled by a connecting rod to a lever mounted on
a rocking shaft at right angles to the piston rod. When the piston is at the
end of its stroke, the constant pressure on the above named single-acting piston,
which is coupled to an opposite lever on the rocking shaft, & which is now
beyond its central position, causes it to swing still further in the same direction
as soon as the piston begins to reverse its stroke: and thus the connecting rod
and lever become a toggle connection of the first order to which the above
named piston & its connecting rod are a toggle connection of the second order
which assist the first toggle at its critical point. The pressure on the piston
being always in one direction effects the first toggle at the opposite end of the
stroke in the opposite direction while at its critical position.
Thus a true
motion to the valve is produced under the control of the connecting rod, which
is always in tension.
Doted this 18th day of January 1890

page_text: Improvements in the Valve Gear of Direct-acting Steam Pumps and
Compressors and similar Engines.
I, ARTHUR KNOWLES, Mechanical Engineer of 488, Edgware Road, in the
County of London, 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: —
I use, in connection with the valve motion of direct acting steam pumps and
similar engines, a single acting piston and cylinder, open to the atmosphere at
one end and always open to pressure at the other end, mounted at right angles
to the line of motion of the valve gear, in such a way that the piston rod or
connecting rod of the said piston is kept constantly in compression, or if the
design demands it, constantly in tension, in whichever direction the valve is
moving and at every part of the stroke, thus forming a toggle combination in
which the connecting rod of said piston at the farthest point of its stroke has
no leverage on the valve gear eccentric or levers, or its operating shaft, but
exerts an increasing leverage on either side as the connecting rod passes the
centre line of the shaft towards that side. The pressure in the said cylinder
may be obtained from the steam, air, or fluid driving the engine or from the
water or air delivered by the pump into the delivery pipes, or from an accumu-
lator or a cistern or the piston may be made to compress air in the cylinder and
utilize the expansion thereof on its outward stroke, or the piston may be actuated
by springs or a suitable spring without any cylinder may be used. The cylinder
may be oscillating or fixed. This auxiliary valve actuating piston or recipro-
cating rod and its connection to the valve gear are hereafter referred to as the
device." The object of the invention is to simplify and cheapen the construc-
tion of such engines by rendering unnecessary the usual pistons and cylinders
in the main valve chest usually employed to alternate or help to alternate the
motion of the valve.
"
I will now describe my invention in reference to the accompanying drawings
in which Fig. 1 is a part sectional elevation of a direct-acting steam pump
having my invention applied thereto. Figs. 2 and 3 are respectively plan and
end view of Fig. 1 partly in section and Fig. 4 is a diagram illustrating move-
ments of the improved valve gear.
A is the steam cylinder of the pump with piston A¹ the rod a of the latter extend-
ing to and carrying the pump piston in the usual manner. B is the slide valve
which derives its motion through suitable gear from a pin c on a crosshead C
which is fastened to the piston rod a. This pin c is coupled by a connecting
rod D to a double ended lever E mounted on a rocking shaft F disposed trans-
versely to the piston rod in convenient position for receiving the valve operating
eccentric G also mounted on the same shaft. F. Directly above the shaft Fis
disposed the auxiliary device consisting in this case of a single acting piston H.
working in a suitable cylinder H¹ and connected to the rocking lever E or it
may be to an extension of the eccentric sheave by a rod h, having a hinge or
ball and socket joint at h¹. This device or piston H is as described arranged
to be constantly under compression or tension according to its disposition or
arrangement so as to exert a constant pressure on its connecting rod h, which
being arranged as shown directly above or at right angles to the rocking shaft F
has no leverage upon the latter and lever E when in the central position with
the piston H at the highest point of its stroke, but has an increasing leverage
upon said rocking lever E and shaft F as it passes the centre line L on either
side.

page_text: In operation, assuming the steam cylinder piston A¹ to be at the end of, its
stroke as shown in Fig. 1 and the parts to have arrived at position marked 1 on
the diagram Fig. 4, the constant pressure on the auxiliary piston H (the con-
necting rod of which is now beyond its central position) causes it to impart
to the rocking lever E and shaft F a further movement in the same direction
and the parts assume the position marked 2 in the diagram, thus the eccentric G
is operated so as to move the slide valve B and open the steam port to the
piston A, and simultaneously therewith the movement of the rocking shaft F
and lever E carries the connecting rod D over its critical point, that is to say to
the other side of a centre line marked L' between the pin c and rocking shaft F.
Then on forward movement of the piston A' and crosshead C the lever D,
still assisted by the auxiliary device, rocks the lever E and eccentric G still
further to the position 3 in the diagram when the steam port will be fully
open. The lever D and other parts then reverse their movements following
the positions 4, 5, 6 and 7 on the diagram until the completion of the stroke
of piston A and crosshead C when the same movements are repeated on the
opposite side of the centre line L of shaft F and the device or piston H with
corresponding action upon the slide valve B. The pin hole e in lever E must
be in the form of a short slot (see Figs. 1 and 3) to allow the connecting rod D
to swing across the centre line L' L' from positions marked 1 to 2 in the
diagram.
From the above it will thus be seen that the pressure of the device being
always in one direction, supplementary movement is imparted to the first toggle
formed by lever D and E while at its critical position at the end of the piston
stroke so as to alternate or assist to alternate the motion of the valve B impart-
ing an initial movement thereto which serves to open the steam ports to the
piston A at the proper time for its return stroke. Thus I am enabled to dis-
pense with the pistons and cylinders and complicated passages usually employed
in the main valve chest for this purpose and at the same time the construction
is cheapened and simplified.
In order to prevent any straining of the gear the connecting rod D and the
lever E on the rocking shaft F may be made of such a combined length that
when the piston A¹ touches the cylinder covers at each end (for instance at o o¹
in the diagram) their centre lines will form a straight line between the cross-
head pin and the rocking shaft. Should the piston have a tendency to go beyond
its proper stroke the valve will open the steam port against the piston and so
protect the cylinder cover whilst the valve gear levers will be brought to a more
favourable position for assisting the action of the auxiliary device thereon;
this action will take place without any abnormal motion of the valve gear.
I prefer to give a slight lap inside and outside the valve B to prevent any
possibility of the steam blowing through when the valve is in mid position.
This outside lap tends to advance the point of cut-off; but this can be corrected
by giving "lost motion" to the valve. This "lost motion" will also assist the
action of the auxiliary device by causing the levers E and D to move further
over the centre line at the moment when the piston H comes into action to
swing the connecting rod D over the centre line L' from the points marked 1
to 2.
When the valve has lap it is possible that the pump might be stopped when
both steam ports are covered and thus be unable to start again on turning
on steam. To obviate this it is necessary to provide a hand starting gear such
as that shown in Fig. 3, herein the double ended rocking lever E is adapted
to slide in a part g which is fixed to the shaft For is in one with the sheave
of eccentric G. This allows of the lever E having a small sliding motion in
the direction of its length and the pin c¹ at the top end of the lever is pro-
longed so as to form a handle k. The small amount of play thus given to the
lever E allows the eccentric G and valve B to be moved by hand so as to uncover
the ports. The pressure of the auxiliary device will always keep the sliding
1

page_text: lever E in its proper position when working. This construction also forms a
means of safety in preventing the buckling of the connecting rod or straining
of the parts in case of racing.
Although I have described the eccentric operating shaft as connected by a
lever to the crosshead C it is to be understood an auxiliary device such as
described may be readily applied to other valve motions with like object and
effect.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what.
I claim is:-
1. The arrangement of gear for alternating or imparting an initial movement to
the main steam valve or valves in which a piston contained in a cylinder or an
equivalent device adapted to be always under a sufficient pressure acts in the
hereindescribed manner to impart a supplementary movement to the admission
valve gear at the ends of the piston stroke, substantially as set forth.
2. In the valve gear of direct acting steam pumps and so forth, the use of a
device such as above referred to under constant compression (or tension) and
disposed and reciprocating on a centre line at right angles to the axis of a rock-
ing shaft operating the valve eccentric, lever or equivalent, so that the said
piston exerts pressure thereon on either side of its centre line and imparts an
initial or supplementary movement thereto, substantially as and for the pur-
poses set forth.
3. The improvements in valve gear of direct acting steam pumps and com-
pressors and similar engines, comprising the combination of a rocking lever
and shaft operating the valve eccentric, a rod connecting said rocking shaft at
one end to and so as to receive motion from a motion block or crosshead upon
the main piston rod, a pistón and connecting rod reciprocating under pressure
and connected to said rocking lever at its other end and disposed at right angles
to the rocking shaft so as to impart an initial or supplementary rocking motion
thereto both ends of its stroke, substantially as and for the purposes set forth.
4. The combination of parts comprising the improved valve gear and means
for operating same to alternate or impart an initial movement to the main
steam valve or valves, all arranged and adapted to operate substantially as
herein described and as illustrated in the accompanying drawings.
Data 104 1
For the Applicant,
J. C. CHAPMAN & Co.,
Chartered Patent Agents, 70, Chancery Lane, London, W.C.