Improvements in Cocks.
Year: 1894

page_text: Date of Application, 8th May, 1894
Complete Specification Left, 7th Feb., 1895-Accepted, 4th May, 1895
PROVISIONAL SPECIFICATION.
Improvements in Cocks.
We JOHN DEWRANCE and GEORGE HENRY WALL, both of 158 Great
Dover Street, London, S.E., Engineers do hereby declare the nature of this
invention to be as follows:-
Upon the stem or spindle of the plug of a cock we form a shoulder upon which
a suitable loose flange or plate rests; this flange which we prefer to make oval
has a hole through which the upper part of the stem of the plug passes but not
the part beyond the shoulder, and it is attached and drawn toward the cover of
te cock by studs and nuts, or one stud and nut can be made to serve the purpose
if a suitable support is provided, so that the end of the plate opposite to that of
the plug takes a bearing upon the cover.
The flange is adjusted to put pressure upon the shoulder on the stem of the
plug of the cock to press the plug sufficiently against the surfaces that are
depended upon to keep the cock tight in the direction of the way.
We prefer that the flange should have a limited amount of spring or suitable
springs may be added to allow the plug to rise somewhat when expansion would
otherwise cause it to work hard. This arrangement is independent of the stuffing
box that makes fluid tight joint around the stem of the plug of the cock, and is
applicable to the form of cock illustrated and described in the Specification of
Patent (No. 4922, 1890) or to any system or construction of cock whether asbestos
packed or ground in plug. For the larger sizes of cocks we prefer to use a cock
such as is shown by the before-named Specification so that as much as possible of
the upward pressure of the fluid is balanced, but for smaller sizes the stuffing box
may be around the larger end of the taper part of the plug as it can be more
easily arranged in connection with the packing in the grooves if the cock is
asbestos packed, in this case the flange has to resist all the upward thrust due to
the pressure acting upon the area of the plug at its largest part.
In all compound gland cocks as hitherto constructed the stuffing box has to
perform two duties, it has first to make a tight joint around the stem of the plug
and secondly the pressure of the gland has to be transmitted to the plug through
the medium of the packing for the purpose of keeping the plug down sufficiently
hard on its surfaces. In the best form hitherto made the pressure of the fluid
passing through the cock acts upon the unbalanced area of the stem of the plug
and compresses this packing and more particularly so when the plug is revolved.
The least compression of this packing by the plug demands a corresponding
adjustment of the gland as it lessens the pressure that it is necessary that the
packing should exert upon the shoulder of the plug to keep the plug tight upon
its surfaces; if this adjustment is neglected the result is a leakage in the direction
of the way of the cock.
With the arrangement hereinbefore described the stuffing box can be screwed up
with freedom as it is only required to make a joint around the stem of the plug. The
pressure required to be put upon the plug is effected by the flange which being
constructed of a relatively incompressible material maintains the amount of
pressure originally put on by means of the nuts.
To effect the same object we sometimes form a circular projection at the
smaller end of the plug; this projection passes out through a stuffing box at the
lower end of the cock and its diameter is determined by the amount of pressure

page_text: that is required to keep the plug down on to its surfaces; in this arrangement
the head or stem of the plug is loose and arranged to turn the taper part of the
plug at its largest end but the upward thrust due to the pressure of the fluid
acting upon the area of the stem is taken by a shoulder that bears against the
under side of the cover; in this case also a stuffing box is required to make a
joint around the stem but the flange is not required as the plug is drawn down to
its surfaces by the pressure acting upon the unbalanced area of the projection.
Dated this 8th day of May 1894.
JOHN DEWRANCE.
GEORGE HENRY WALL.
Improv COCKS.
We JOHN DEWRANCE and GEORGE HENRY WALL, both of 158 Great
Dover Street, London, S.E., Engineers, 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 :--
On the accompanying sheet of drawings Fig. 1 is a sectional elevation, and
Fig. 2, is an end elevation of a cock constructed according to our invention.
Upon the stem or spindle of the plug J, we form a shoulder upon which a suitable
loose flange or plate rests. This plate is hereinafter called the holding-down
plate and is shown by A, on the drawing. We prefer to make it oval and to be
drawn toward the cover F, by studs and nuts B, B. It is obvious that one stud
and nut may be made to serve the purpose. The holding-down plate is adjusted
by the nuts B, B, to put pressure upon the shoulder of the plug J, to press the
plug sufficiently against the surfaces that are depended upon to keep the cock
tight in the direction of the way. We prefer that the holding-down plate A,
should have a limited amount of spring to allow the plug to rise somewhat when
expansion would otherwise cause it to work too hard. Between the holding-down
plate and the shoulder of the plug J a thin washer of non-metallic material may
be inserted to prevent abrasion, but it is essential that the washer should be of
practically incompressible material, so that as long as the adjustment of the
nuts B, B, remains unaltered the adjustment of the plug J on its conical bearing
will also remain unaltered. C is the gland and D, D are the bolts and nuts with
which the gland is screwed down to compress the packing E, to make a tight
joint around the stem J. F is the cover and G. G, are the bolts and nuts by
which the cover is jointed to the body of the cock H. L is the space between the
plug J and cover into which the pressure is admitted by the hole M, to balance
the plug to that extent. K, K, are strips of indurated asbestos that surround
the ways, and on which the plug bears to make the cock fluid tight in the direction
of the way.
In solid bottom compound gland cocks as hitherto constructed the stuffing box
has to perform two duties; it has first to make a tight joint around the stem of
the plug and secondly to transmit the pressure of the gland to the plug through
the medium of packing for the purpose of keeping the plug down sufficiently hard
on the conical surfaces that are depended upon to keep the cock fluid tight in the
direction of the way of the cock.
The pressure of the fluid passing through the cock acts upon the unbalanced
area of the plug and this together with the changes of temperature and other
circumstances compresses or shrinks the packing in the stuffing box.
The least compression or shrinkage of this packing lessens the pressure that it
is necessary that the packing should exert upon the shoulder of the plug to keep
the lug fluid tight upon its surfaces.

page_text: Readjustment of the gland corrects this but in practice it is apt to be forgotten
and if the readjustment is neglected the result is a leakage in the direction of the
way of the cock.
It has been suggested that by omitting the packing in the stuffing box just
described or substituting some incompressible material in place of the usual
packing the same result may be obtained as by the use of our holding-down plate
but in such case it would not be possible to admit the pressure to the space
corresponding to the space L between the top of the plug and the cover to partly
balance the upward pressure on the plug as described in the Specification of
Patent No. 4922 of 1890 granted to us; with that arrangement it is essential that
there should be an efficient stuffing box and such can only be made by packing that
is too yielding in its nature to give a constant and reliable adjustment of the plug
on its bearing. Furthermore when the upward pressure is not partly balanced as
aforesaid the whole of the upward pressure due to the fluid pressure acting on the
largest diameter of the plug would have to be counteracted by the gland. On
a 3" cock this upward pressure may amount to upwards of a ton.
The gland must be screwed down hard enough to prevent the plug rising when
the fluid pressure is in the cock.
If the gland has any spring it will obviously force the plug down on to its
conical bearing with a pressure more than a tou when the fluid pressure is not in
the cock, and such a pressure in that direction would cause the cock to work
too hard.
On the other hand if the gland were made strong enough not to spring or yield
at all when sufficient pressure was put upon it by the nuts to counteract the
upward fluid pressure, the plug when suddenly expanded by the heat of the fluid
passing through it would not only be difficult to move but the surfaces of the
packing which form the conical bearing would be unduly compressed and the
adjustment of the plug on its bearing would be altered thereby.
With the arrangement shown by the drawing the fluid pressure
admitted to
the space L, and the upward pressure only amounts to the fluid pressure that acts
upon the diameter of that part of the stem of the plug J surrounded by the
gland C.
The stem is made of as small a diameter as will afford sufficient strength to
turn the cock.
The holding-down plate A has to press the plug J down upon the strips of
packing K, K, with sufficient force to keep the cock fluid tight, and in addition it
has to resist whatever upward pressure may be exerted by the pressure of fluid in
the cock, but on a 3" cock this upward pressure would be 695 lbs. instead of
a ton.
When there is no pressure of fluid in the cock the upward pressure is not exerted
and the force of the spring holding-down plate is exerted upon the plug J to force
it down upon the strips of packing K, K, but this pressure being so much reduced
is not sufficient to make the cock work too hard.
Having now particularly described and ascertained the nature of our said
invention, and in what manner the same is to be performed, we declare that
what we claim is :-
The improved apparatus and arrangement consisting of a solid bottom cock
having a spring holding down plate and a stuffing box each to perform a specific
purpose substantially as hereinbefore described and illustrated in the accompanying
drawings.
1
1005
JOHN DEWRANCE.
GEORGE HENRY WALL.