IMPROVEMENTS IN EQUI- LIBRIUM PISTON VALVES CHIEFLY DESIGNED FOR HYDRAULIC PURPOSES
Year: 1873

page_text: PROVISIONAL SPECIFICATION left by Thomas Critchlow at the Office
of the Commissioners of Patents, with his Petition, on the 14th
April 1873.
I, THOMAS CRITCHLOW, of Baldwin, Pennsylvania, United States of
America, now of No. 8, Southampton Buildings, London, do hereby
declare the nature of the said Invention for "IMPROVEMENTS IN EQUI-
LIBRIUM PISTON VALVES CHIEFLY DESIGNED FOR HYDRAULIC PURPOSES," to be as
follows:-
My said Invention consists in the novel construction of equilibrium
piston valves chiefly designed for controlling the pressure of the water
in hydraulic engines used for various purposes, although they may be
adapted for regulating or controlling the passago of steam, air, or other,
fluid used as a motive force. But in the following description I.more
particularly refer to the use of the said valve in connection with
hydraulic machinery.
In Bessemer steel works and other works wherein hydraulic power is
employed, it is usual to have each machine provided with a valve.
whereby it is controlled, the said valve being moved or adjusted by hand.
One of the machines used in the said works is the convertor, which is
supported on trunnions, wherein it is capable of making a partial

page_text: revolution. One trunnion has fixed on it a toothed wheel which gears
into a rack connected with a piston rod, whose piston or head is caused
by the hydraulic pressure to work to and fro in a cylinder; and my
improved valves are designed to be connected with these cylinders to
of the water in the same.
control the pressure
The said improved valves may be made either single acting or double
acting, and are constructed as follows:-Inside a cylinder or casing of
cast iron or other suitable metal I fit and secure a tube or barrel prc-
Around the centre of
ferably of gun metal, which I term a bushing.
this bushing I form in the casing a receiving compartment into which I
admit the water by a suitable inlet pipe from the pressure pump. A
passage for the water is made through the bushing into this receiving
compartment, and according to one part of my Invention this passage
consists of a number of small holes or perforations. The purpose of this
contrivance is to facilitate the admission and removal of the piston;
these pistons have leather packings which if the said passage consisted of a
single large aperture would be liable to obstruction and injury thereby.
In the double acting valve annular spaces are also formed in the casing
above and below the said receiving compartment, and have outlet
apertures and pipes extending to the ends of the cylinder of the convertor
above mentioned, and the parts of the bushing enclosed within these
annular spaces are perforated with small holes around its entire circum-
ference. In the single acting valve there is an annular space at one end
only of the bushing communicating with one end of the cylinder of a
cranc or other machine..
In the said bushing I fit a double headed piston, the heads being
provided with leather packing. The said pistons are preferably con
structed as follows:-I take a bar of wrought iron or other suitable
metal and turn upon the same two collars at the proper distance apart
Then I fit upon the said collars a cup leather of suitable size and place
upon it a circular block or ring of the same diameter as the collar, or
this ring I fit another cup leather, and secure the whole in place by a
screw nut and washer. The piston of the double acting valve will hav
two cup lcathers on cach head, but that of the single acting valve maj
have two cup leathers on one head and only one on the other head.
.
The spaces at each end of the valve cylinder beyond the extremity o
the stroke of the piston are connected by a passage at the side of the sai
5

page_text: cylinder. This passage serves to equalize the exhaust pressure abovo
and below the piston, and in the double acting valve it also serves to
connect both ends of the cylinder with the ejection or waste pipe. The
said valve cylinder constructed as above described is closed by suitablo
covers at both ends, and is supported only by the aforesaid pipes. But I
sometimes construct the said valve with a cover at the upper end only of
the cylinder, its lower being attached to a base block-formed with
suitable inlet and outlet aperture with which the aforesaid pipes_arc
connected. . And instead of having in the cylinder a bushing formed of
a single tube or barrel I may place a separate bushing in each of the
aforesaid annular spaces in the casing when found desirable or necessary.
I connect with the inlet and outlet apertures a stop valve whereby water
is shut off from the equilibrium valve to permit the piston to be con-
veniently removed and replaced.
My improved equilibrium valve may also be constructed with a
cylinder which has only its lower end enclosed within an outer casing,
that is to say, the piston is fitted to work in the cylinder instead of in a
bushing in the same, but the lower end of this cylinder projects inside a.
casing, and is perforated as above described. There is an ordinary inlet.
aperture at or near the centre of the said cylinder. Each piston head
will require only one cup leather.
I also modify my said Invention as follows:-I use two cylinders
placed side by side and connected near their ends by pipes which com-
municate with the outlet pipes to the converter cylinder. In each of..
these cylinders I fit a piston, and the said pistons are attached to a lever
vibrating on a fulcrum placed between the said cylinders. The pistons
are fitted to work through hemp packing, leather packing rings, or other
suitable packing secured in the cylinders. The said pistons are closed
at both ends, and are perforated with two sets of small holes at such a
distance apart that when the pistons are in a central position in the
cylinders both sets of holes will be within the central spaces enclosed.
between the said packing. The inlet pipe opens into the central space
of one cylinder, and the central space of the other cylinder communicates
with the waste pipes.