An Improved Balanced Slide Valve.
Year: 1892

page_text: Date of Application, 13th Dec., 1892
Complete Specification Left, 13th Mar., 1893-Accepted, 20th May, 1893
PROVISIONAL SPECIFICATION.
An Improved Balanced Slide Valve.
I, ALEXANDER MELVILLE CLARK, of the firm of A. M. and Wm. Clark, of
53, Chancery Lane, in the County of Middlesex, Fellow of the Chartered Institute
of Patent Agents, do hereby declare the nature of this invention (a communi-
cation to me by John Parker, of the Village of Sturgeon Falls, District of
Nipissing, in the Province of Ontario, and Dominion of Canada) to be as
follows:-
This invention consists of an improved balanced slide valve having exhaust
passages opening through valve faces near either end of the valve which commu-
nicate alternately with ports at the opposite end of the cylinder and lead to a
common aperture extending through a piston-like disc seated in the back of the
valve and working steam tight in the manner of a slide valve against the valve
chest cover against which it is pressed by springs between it and the valve and
also by the exhaust steam in the intervening space. This balance-disc is fitted
steam-tight by means of peripheral expansion packing rings, within a ring-shaped
flange on the back of the valve and its area is about equal to that of the valve
faces through which the exhaust passages open as above mentioned, whilst
between these valve faces the front of the valve is recessed to form a space
extending to the sides of the valve and open to the valve chest to which the live
steam has access so that its pressure against the front of the valve will balance that
on the part of the back of the valve which is exposed to the steam pressure. The
exhaust opening in the balance disc is preferably of oval shape, its major axis
being in the transverse direction of the valve and it is always in register with an
aperture in the valve chest cover of similar shape but of a breadth as much greater
as is necessary to allow for the travel of the valve.
Dated this 12th dar of December 1809
A. MELVILLE CLARK,
By A. M. & Wm. Clark,
53, Chancery Lane, London, Chartered Patent Agents.
COMPLETE SPECIFICATION.
An Improved Balanced Slide Valve.
I, ALEXANDER MELVILLE CLARK, of the firm of A. M. and Wm. Clark, of
53, Chancery Lane, in the County of Middlesex, Fellow of the Chartered Institute
of Patent Agents, do hereby declare the nature of this invention (a commu
nication to me by John Parker, of the Village of Sturgeon Falls, District of
Nipissing, in the Province of Ontario, and Dominion of Canada) and in what
mauner the same is to be performed, to be particularly described and ascertained
in and by the following statement :-
This invention relates to an improved balanced slide valve of simple and durable
construction capable of being readily applied to all kinds of engines and arranged
to automatically take up all wear.
Reference is to be had to the accompanying drawings, forming part of this
Specification, in which
Figure 1 shews the valve chest cover with the exhaust pipe removed.
Figure 2 is a section of the valve chest, on line 2-2 Figure 3, shewing the back
of the valve and the balance disc thereon.
Figure 3 is a longitudinal section of the valve chest and cylinder, and
Figure 4 is a transverse section of the same on line 4-4 Figure 3.

page_text: Similar letters of reference indicate corresponding parts in all the figures.
A is the cylinder, B the piston, a and b the cylinder ports, C the valve chest,
D the slide-valve fitted to slide therein and connected with a valve-rod E, for
operation in the usual manner.
The valve D has two faces D1, D2, near its ends working over the ports a, b in
the valve seat A¹ formed on the cylinder A so that when the ports a and b are
uncovered they take live steam from the steam-chest. Between the valve faces D'
and D there is a recess F.in the valve extending across the valve and commu-
nicating, by recesses in the sides of the steam chest, with the steam space of the
latter so that live steam can enter the recess and press against the front of the
valve. Through the valve faces D', D2, lead two exhaust ports c, d, which alter-
nately coincide with the corresponding ports a, b, the ports or passages c, d, leading
to a common aperture e registering with an almond-shaped opening f formed in the
middle of a balance piston disc G fitted steam tight by means of peripheral expansion
packing rings in a cylindrical ring or flange D³ formed on the back of the
valve D. The balance disc G is pressed against the valve chest cover C₁ by
springs H held in recesses formed in the under side of the disc and bearing against
the back of the valve D. The balance disc G works steam tight in the manner of a
slide valve over an aperture g in the valve chest cover C₁ leading to the usual
exhaust pipe (not shewn) and to which the aperture in the disc is always fully
open. Two opposite sides of the aperture g are straight (see Figure 1) and the
other opposite sides are curved to correspond with the sides of the opening f in the
disc G, the length of the straight or parallel sides of the aperture g corresponding
with the length of travel of the valve, so that the communication between the two
apertures is always fully open. The area of the valve faces D' and D² is about
equal to the area of the balance disc G, so that the live steam pressure on the front
and back surfaces of the valve is equal and consequently the valve is completely
balanced.
The valve thus constructed has few parts, is not liable to get out of order, and
all wear is taken up by the springs H (assisted by the pressure of the exhaust
steam between the piston disc and the valve) pressing the disc G against the
cover C and the faces D' and D2 against the seat A'. It will be seen that by the
peculiar construction of the balance slide valve it requires only about one-third of
the travel of the ordinary slide-valve.
When the valve D is in the position shewn the port a is open to the steam chest
and the piston B is moved in the direction of the arrow a', whilst the exhaust
from the other side of the piston passes through the ports b, d, and the openings e, f, g,
to the exhaust pipe. When the valve D travels in the direction of the arrow b
the port b is uncovered and the port c registers with the port a, the admission being
then through the port and the exhaust through the ports a and c and the
openings e, f, and g.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed I declare that what I
claim is―
g
The combination, with the steam chest having the cover C₁ provided with an
exhaust steam opening 9 and the slide valve D having the exhaust ports c, d, and e,
and the live steam recess F¹ in its face, of the balance piston disc G fitted steam
tight in the back of the valve D and having an opening corresponding with
openings e, and g, and springs pressing the disc against the valve chest cover, as
shewn and described.
Dated this 12th day of M 1902
A. MELVILLE CLARK,
By A. M. & Wm. Clark,
53, Chancery Lane, London, Chartered Patent Agents.