IMPROVEMENTS IN METALLIC PISTON PACKING
Year: 1887

page_text: Date of Application, 29th Mar., 1887.
Specification Accepted, 29th Apr., 1887
I, WILLIAM W. ST. JOHN, of No. 280 Broadway, in the City and State of New
York, United States of America, Engineer, do hereby declare the nature of my
invention for "IMPROVEMENTS IN METALLIC PISTON PACKING," and in what manner
the same is to be performed, to be particularly described and ascertained in and by
the following statement :-
My invention relates to improvements in Metallic Packing Rings for pistons, for
steam engines and other purposes, and is an improvement on the devices for that
purpose shown and described in Letters Patent No. 10,177 of 1885, to Alfred Julius
Boult, as a communication from William W. St. John of New York, United States
of America.
The object of my invention is to produce a packing ring for pistons by which they
can be packed perfectly tight, and also to so construct the ring, that the cylindrical
surface of the ring bearing against the inner curved surface of the cylinder, and the
face or bearing side of the ring placed against the piston body shall wear in a pre-
determined proportionate manner.
For this purpose the face, or side of the ring that is vertical in a horizontal
cylinder, has a slightly greater area of bearing surface than the cylindrical edge of
the ring; furthermore, in order that this proportion may remain constant I form a
portion of the face of the ring with a bevel sloping inward so that it may be acted
upon by the steam with the effect of forcing the ring outward.
My invention consists of a packing-ring of an shaped cross section, the longer
arm of the forming the flat or face surface of the ring and the shorter arm forming
the cylindrical surface. I preferably form the outer edge of that portion of the ring,
(which is the shorter. arm of the L in section), with a bevel sloping inward at such
an angle that a line corresponding with this bevel and at right angles with the ring
at any point will just touch the opposite corner of the ring also preferably leaving a
small shoulder below the bevelled portion.
My invention further consists in the construction of certain details and in the
arrangement of parts, as will be more definitely described hereinafter, and specifically
pointed out in the claims, reference being had to the accompanying drawings and

page_text: letters of reference marked thereon. Like letters indicate similar parts in the different
Figures of the drawings, in which:
Figure 1, is a plan view of a portion of the piston of a steam engine to which my
improved packing ring has been applied.
Figure 2, is a plan view of one of my packing rings.
Figure 3, is a cross section, on a much enlarged scale, of the packing ring on the
line,, of Figure 2.
Figure 4, is an enlarged view of a portion of the piston shown in Figure 1, a part
of the main ring being broken away to show the pin at the joint of the packing ring.
Figure 5, is a side elevation of a piston provided with my packing rings.
Figure 6, is a vertical section of a solid piston provided as above.
Figure 7, is a vertical section of a piston formed with a ring and follower, and
having my ring applied.
In the drawings, A, represents the main packing ring of a steam piston. B, B, are
my shaped spring packing rings each cut as shown at b, and sprung into a groove a,
in the ring A, these are more particularly hereinafter described. C, Figures 5, 6,
and 7, is the main body of a steam piston, D, is the piston rod, having a collar d,
and a nut d². C, C, are set-screws which secure the follower plate E; to the body of
the piston C; these details are however, unimportant and may greatly vary.
My packing-ring B, consists of a spring metallic ring somewhat larger than the
internal diameter of the cylinder and of a cross section such as is shown in Figure 3;
that is shaped with the shorter arm forming the outer cylindrical surface of the
piston, and cut off at a bevel as shown. The ring is cut apart at b, the longer flange
or portion of the lying against the body of the piston or at right angles with the
cylinder is cut out at the meeting point to leave a notch 6, which fits over a large
headed T pin, set in the ring A, or in the body of the piston C.
The face or flat surface of the spring packing ring B, is made greater than the
cylindrical surface of the same ring, in order that the pressure of steam may keep the
ring pressed closely against the body of the piston or the ring A, and thus keep a
steam tight joint.
If the face were made flat upon its entire surface, as the cylindrical-surface wore
away the relative proportion between the cylindrical and face surface would vary
and the efficiency of the ring would suffer materially.
It is to correct this fault that I bevel the end of the shorter arm of the L in section
as shown, making this part appear as a narrow angular ring sloping inward.
The result of this form is that as the cylindrical surface wears away diminishing
of course the length of the under flange, the cylindrical surface also diminishes in
like proportion keeping the relation of the two surfaces nearly or quite constant.
Though I have found in practice that the bevel shown will give the proper relative
proportions in the two surfaces, yet this bevel may vary a little, either one way or
the other.
In vertical engines a joint-piece is used instead of the pin at the joint.
The operation is as follows: the rings are first sprung into the grooves b, b, and
the pin inserted in its hole in the piston-body to prevent the rings from revolving.
The steam pressure in the cylinder will force the rings out against the inner curved
surface of the cylinder by first pressing against the bevelled sides, and the steain
will then pass under the inner curved surface of the ring, as well as against the sides
of the ring, and force it against the body of the piston, thereby preventing any
leakage. It will be readily understood that the surface of the face or side which is
vertical in a horizontal cylinder being greater than the cylindrical surface, the steam
has a greater area to press it against the body of the Piston, and passing against the
bevel surface, the ring will be always packed against the inner curved surface of the
cylinder, in whatever direction the piston is travelling.
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 :-
1. A packing ring for pistons cut at one point only, having a portion of its outer

page_text: face bevelled so that the side bearing against the inner curved surface of the cylinder,
and the side bearing against the body of the piston shall wear in proportionate degree
substantially as specified.
2. In a piston a packing ring cut only at one point and having a cross-section such
that the face bearing against the piston body is greater in width than the cylindrical
surface bearing against the inner curved surface of the cylinder and having its outer
exposed face bevelled as shown and for the purpose set forth.
3. A packing ring for pistons having an L shaped cross-section of which the face
bearing against the piston body is of greater width than its curved edge bearing
against the inner curved surface of the cylinder and having a portion of its face
bevelled and provided with a shoulder substantially as described.
4. A piston packing ring having a side placed toward the piston body of greater
depth than its curved edge, and its outer side bevelled, in combination with a headed
pin set in the body of the piston substantially as described.
Dated this 28th day of February 1887