An Improved Pressure Reducing Valve.
Year: 1892

page_text: Date of Application, 21st June, 1892-Accepted, 13th Aug., 1892
COMPLETE SPECIFICATION.
An Improved Pressure Reducing Valve.
JOHN MOWAT NISBET 18 Tenth Avenue Heaton Newcastle-on-Tyne Marine
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 :-
In reducing valves as hitherto made, the pistons or valves passing the required
volume of steam at reduced pressures have also had to act as the controlling
agent or have been assisted by means of a spring or springs. These reducing
valves are liable to become inoperative, either owing to excessive pressure on piston
packing rings, or, from dirt collecting under valve faces, or, the pistons or valves
have been liable to pass steam, and, allows the initial high pressure steam to
accumulate on the reduced pressure steam pipes.
The main object of this invention is to obviate these difficulties by ensuring a
constancy of reduced pressure: no excessive vibrations on the controlling pistons:
no liability to stick fast: no possible accumulation of dirt on the valve faces, and
the controlling pistons to work independently of the volume of steam passing
through the reducing valve, these results are aimed at in the manner shown by
the drawings.
In the several drawings the same part will be found designated by the same
letter of reference.
Fig. 1. is a plan showing the port openings in the high pressure fixed plate A
and in the low pressure fixed plate C. and the covering sector on the slide plate
valve B.
Fig. 2. is a sectional view of the same plates A. C. & B. in position through their
lengths of port openings.
Fig. 3. is a top plan view of the same plates A. C. & B showing all ports
closed.
Fig. 4 is a side elevation showing-partly in section-how the fixed plates A. & C.
are secured, and, how the slide plate valve B. is worked. This view also shows
the high pressure control cylinder and piston D. half in section. This view also
shows the retarding oil or liquid cylinder and piston E, having half in section-and
the regulating cock and pipe F.
Fig. 5. is a top plan of the complete machine, showing how the high pressure
piston D. and the low pressure piston G operates on the double arm or lever H.
and through it gives motion to the valve spindle J. which may either be a part of―
or let into the slide plate valve B.
Fig. 6 is an end elevation of the complete machine.
The high pressure steam pipe is connected to I. and is also connected to the
flange of the high pressure control cylinder D. so that, steam enters the valve and
the control cylinder simultaneously, but, the force exerted on the piston D. and
through it to the double arm H, and, through that to the slide plate valve B. is
20% in excess of the total load on the slide plate valve B. when fully closed,
and thus the slide plate valve B. opens and allows steam to flow through the ports
in the fixed plates. & C. to the outlet O. The reduced pressure pipe is connected
to O. and also connected to the flange of the larger control cylinder G. so that when
the pressure on the piston of G becomes co-relative to the difference in the areas
of the two control cylinders an equilibrium is established, should the pressure on G.
increase, its piston will close the slide plate valve B. by its effort exerted on one
end of the double arm H. and should the pressure decrease in G. the greater
pressure in D. will exert its effort by its piston to the other end of the double
arm H, and thus open the slide plate valve B.

page_text: The areas of the steam ports in the fixed plates A & C are also co-relative to the
given and required pressures and thus equal weights are exerted on both sides of
the slide plate valve B. reducing its working friction to a minimum.
The cylinder E. being filled with liquid and only having a restricted passage
from end to end, ensures uniformity of motion on the controlling pistons and
freedom from jerks and shocks, while the motion of the slide plate valve between
its two fixed plates will prevent any accumulation of dirt on the valve faces.
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.
1. In a reducing valve, external and independent control by means of pistons, of
a co-relative area to the given and required pressures, acting on the spindle or
spindles of a slide plate valve, through which the steam or gas or water to be
reduced in pressure passes, the action of the pistons on the said valve spindle or
spindles may either be torsional or lateral in its effort or direction, and, may be
applied to the said valve spindle or spindles directly or by means of arms or
levers.
2. In a reducing valve the combination of an oil or liquid cylinder with piston or
plunger, working in unison with the controlling cylinders & piston and retarding
the sudden action of the said controlling cylinders & piston to any required extent.
The connection from end to end of the liquid cylinder may either be by cock and
pipe or by hole in cylinder jacket or may be by a simple hole in the piston or
plunger of the liquid cylinder.
3. In a reducing valve, the application of a slide plate, valve working between
two fixed plates, one or either or both of the said fixed plates may form a part of
the solid valve chest or valve chest cover or may be in separate parts and of
different metals. The said fixed plates and slide plate valve may be of disc shape
or in the form of gridiron valves or of ordinary D valves and may be acted on
either with a circular or lateral motion having ports to suit, the slide plate valve
spindle may either be part of the valve itself or loose and of different metal.
4. In a reducing valve, a valve generally suitable for reducing pressures either
of steam or of gas or for reducing the pressures in water pipes or in hydraulic
'mains.
Dated this 20th day of June 1892.