Improved Means for Balancing Main and Cut-off Slide Valves.
Year: 1899

page_text: Date of Application, 8th Apr., 1899-Accepted, 2nd Sept., 1899
COMPLETE SPECIFICATION.
Improved Means for Balancing Main and Cut-off Slide Valves.
I, OLOF MAGNUS HOFWOLT, of Patriotischer Weg 106, Rostock, Germany, Manu-
facturer, 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:―
For the purpose of balancing the main slide valve as also the cut-off slide valve,
there is provided a closed cut-off hollow slide valve, having two lower helical
ports for altering the cut-off by means of rotation; and the balancing is effected
by means of a semi-cylindrical balancing plate, which is provided with a hollow
piston for admitting the steam into the cut-off hollow slide valve. This balancing
plate bears steam-tight against the main slide valve, and also against the cut-
off hollow slide valve, and is held from the outside by means of its hollow
piston in such a manner that it keeps the steam pressure from off the slide
valves.
Figures 1, 2 and 3 are respectively a longitudinal section, a cross-section, and
an elevation of the balancing device. Figure 4 shows the main slide valve, with
the extension slide valve inserted to the extent of one-half. Figure 5 shows the
development of the slide valve surfaces.
The valve gear, which is similar to a Rider valve gear, consists of the main
slide valve a, having on its lower side straight ports and on its back helical
ports, and of the cut-off slide valve b, which is formed as a closed hollow slide
valve, and has in its bottom face two helical ports, and on its back one straight
port. Over both slide valves there bears steam-tight the balancing plate c, with
a hollow piston d, which is jointed steam-tight in a cylindrical part of the cover
of the valve chest o, by means of inserted rings e, against the entering steam.
The balancing plate e is immovable in the direction of the slide valve movement,
but it can be shifted at right angles thereto by means of the screws s provided
thereon. The steam enters through the pipe f into the chamber h, which is
closed by means of a cover g, and which is arranged on the outside of the cover
of the valve chest o. From this chamber the steam can pass through the
aperture into the piston d, and further on through the port k in the balancing
plate e to the port 7 into the cut-off hollow slide valve b, whence the steam can
pass through the two ports m into the main slide valve a, and into the steam
cylinder. From the foregoing it will be perceived that the pressure steam can
never enter the valve chest o, and press therein upon the slide valves, because the
hollow piston d is jointed steam tight by means of the rings c, and the main slide
valve and the cut-off slide valve b work steam-tight between the slide valve
seat and the balancing plate c. The steam can therefore only press upon the
hollow piston d, which is prevented by the adjustment by means of the screws s
from transmitting the pressure to the slide valves, and consequently relieves both
slide valves from the steam pressure,

page_text: 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:-
Balanced main and cut-off slide valve gear characterised by a semi-cylindrical
balancing plate c, which is provided with a hollow piston d and which bears
steam-tight upon the main slide valve a, and also upon the closed cut-off hollow
slide valve b, and which is held adjustably from the outside in such a manner
by means of a hollow piston d (which is provided on the balancing plate and
which is jointed steam tight against the valve chest, and admits the steam
into the cut-off hollow slide valve b), that it keeps the steam pressure from off
the slide valves.
n day or April 1899.
ROBERT E. PHILLIPS, Assoc.M.Inst.C.E., M.I.Mech. E.,
Chartered Patent Agent,
70, Chancery Lane, London, W.C., Associate Agent.