IMPROVEMENTS IN SAFETY VALVES
Year: 1878

page_text: LETTERS PATENT to Thomas Adams, of West Gorton, near Manchester, in
the County of Lancaster, Engineer, for the Invention of "IMPROVEMENTS
IN SAFETY VALVES."
Sealed the 28th May 1878, and dated the 18th January 1878.
PROVISIONAL SPECIFICATION left by the said Thomas Adams at the
Office of the Commissioners of Patents on the 18th January 1878.
THOMAS ADAMS, of West Gorton, near Manchester, in the County of Lancaster,
Engineer. "IMPROVEMENTS IN SAFETY VALVES."
This Invention has for its object improvements in safety valves, and applies
especially to that class of valves in which the prompt opening and closing of the
valve is ensured by means of a properly proportioned hood on the valve extending
over and slightly overlapping the edge of the valve sent.
In such valves as hitherto made the amount of the overlap has, for a three-inch
valve, not exceeded three sixty-fourths of an inch, and this amount cannot be
increased (unless the interior form of the hood be modified, as herein-after explained)
otherwise the valve would not close until the pressure had descended far below that
to which the valve is set. Hence it happens that valves of this class, properly pro-
portioned so that they open and close with the necessary promptitude, do not lift
more than about one-tenth of an inch, or say, one-thirtieth of the diameter.
According to my Invention I am able without disturbing the adjustment of the
valve in other respects to extend the lift nearly to a quarter of an inch, or say, to
one-twelfth of the diameter. This I do by adding to the lower edge of the hood a
lip which is curved or inclined outwards or away from the edge of the valve seat
which it faces, so that now in the sectional form of the interior of the hood there is
a double curvature; the part around the centre is concave as heretofore, but the
curvature becomes convex in the lip which I add to the edge of the hood, as
as already
stated.

page_text: In the annexed Drawing the valve and seat are shown in section; the full lines
indicate a properly proportioned valve and seat such that the valve will lift promptly
to about a tenth of an inch from the seat, and will there stand until the pressure has
been reduced about one pound, when it will close at once.
The dotted lines indicate the lip, which according to my present Invention I add
to the valve, and by which addition I cause the valve, without interfering with its
proper adjustment to lift, to nearly one quarter of an inch. The form of this lip
admits of some variation, but it should be so proportioned that as the valve litts, the
area of the orifice by which the steam enters the hood, and the area of the orifice by
which it leaves the hood, should maintain a constant ratio.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Thomas Adams in the Great Seal Patent Office on the 18th July
1878.
THOMAS ADAMS, of West Gorton, near Manchester, in the County of Lancaster,
Engineer. "IMPROVEMENTS IN SAFETY VALVES."
This Invention has for its object improvements in safety valves, and applies
especially to that class of valves in which the prompt opening and closing of the
valve is ensured by means of a properly proportioned hood on the valve, extending
over and slightly overlapping the edge of the valve seat.
In such valves as hitherto made the amount of the overlap has, for a three-inch
valve, not exceeded three sixty-fourths of an inch, and this amount cannot be
increased unless the interior form of the hood be modified, as herein-after explained,
otherwise the valve would not close until the pressure had descended far below that
to which the valve is set. Hence it happens that valves of this class, properly pro-
portioned so that they open and close with the necessary promptitude, do not lift
more than about one-tenth of an inch, or, say, one-thirtieth of the diameter.
According to my Invention I am able, without disturbing the adjustment of the
valve in other respects, to extend the lift nearly to a quarter of an inch, or, say, to
one-twelfth of the diameter; this I do by adding to the lower edge of the hood a
lip, which is curved or inclined outwards or away from the edge of the valve seat
which it faces, so that now in the sectional form of the interior of the hood there is
a double curvature; the part around the centre is concave, as heretofore, but the
curvature becomes convex in the lip, which I add to the edge of the hood as already
stated.
the
In the annexed Drawing, Figure 1, the valve and seat are shown in section;
full lines indicate a properly proportioned valve and seat, such that the valve will
lift promptly to about a tenth of an inch from the seat, and will there stand until
the pressure has been reduced about one pound, when it will close at once.
The dotted lines indicate the lip which according to my present Invention I add
to the valve, and by which addition I cause the valve, without interfering with its

page_text: proper adjustment, to lift to nearly one-quarter of an inch. The form of this lip
admits of some variation, but it should be so proportioned that as the valve lifts,
the area of the orifice by which the steam enters the hood, and the area of the orifice
by which it leaves the hood should maintain a constant ratio, viz., the ratio of
Rx V to R' x V₁, where the values assigned to these symbols are those indicated in
the schedule written upon the Drawing.
The vertical height of the hood, or in other words the dimension on the line 1, 1,
is immaterial, and may be varied, the relation between the inlet to and the outlet
from the cavity being the point of importance.
I would remark that an obvious equivalent for the lip upon the hood is a cor-
responding lip upon the valve seat overlapping the valve, or overlapped by it; such
an arrangement is seen at Figure 2. The convexity may be either on the seat or
the valve; in Figure 2 it is on the former, and in Figure 3 it is on the latter. The
arrangement shewn by Figure 1 is that which is preferred.
What I claim is, the construction of safety valves, substantially as described, and
with the lip to the hood herein referred to, or its equivalent, as herein set forth.
In witness whereof, I, the said Thomas Adams, have hereunto set my hand
and seal, this Eighteenth day of July, in the year of our Lord One thousand
eight hundred and seventy-eight.
THOMAS ADAMS. (L.S.)