Improvements in the Construction of Pistons.
Year: 1894

page_text: Date of Application, 22nd May, 1894-Accepted, 20th Oct.. 1894
COMPLETE SPECIFICATION.
Improvements in the Construction of Pistons.
I, JOHN HIND, of 8 Ulster Chambers, Belfast, Ireland, Engineer, 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:-
These improvements refer to the pistons described in the Specifications of
Rowan's Patents dated respectively May 23rd of 1877 No. 2013 and February 6th
of 1883 No. 649.
The
1. According to the 1877 Patent the flat steel spring was arranged to bear at
intervals upon projections cast upon the inner surface of the packing-ring.
friction which took place at the point of contact soon cut through the steel spring
rendering it useless, and the method of manufacture was abandoned. The construc-
tion was subsequently modified by cramping pieces on to the steel, but as these
pieces were cramped into square notches in the steel bars for the purpose of keeping
them in their places, the steel was still liable to fracture. I propose by my present
invention to avoid breakage, first by a multiplicity of springs, so that in case of one
breaking the others will retain their action, and secondly, by making the notch of
curved form instead of square or if wire is used by slightly flattening it where the
pieces are cramped on.
2. According to both the above named Patents the wave-spring was free to
revolve independently of the packing rings, and it thus happened that the pressure
of one wave might be bearing upon one end of the packing-ring (where it is cut)
and that the other end of the said ring was left without any pressure and was there-
fore liable to breakage.
According to my present invention I provide means for keeping the wave spring
from revolving and arrange it so as to avoid breakage of the ring as hereinafter
described.
3. In the 1877 Patent no special cod or tongue-piece was provided for, but the
rings have latterly been fitted with that described in the 1883 Patent. This how-
ever, while it is excellent when the rings are first fitted and remain of their original
size, ceases to bear in a steam-tight manner upon the ring, after wear has begun and
the ring has expanded.
To correct this defect I now propose to make the surfaces in contact to a circle
of a larger radius than that of the rings, as hereinafter described.
4. In the 1883 Patent, the helical spring used for expanding the packing ring
was so applied that its end thrust was made to force the ends of the ring apart, and
the pressure obtained by its curved form was used to keep the tongue-piece in
contact with the packing ring, but as the curve is very slight the pressure is insuffi-
cient for the purpose and is less for large diameters than for small. I propose to
overcome this by causing the internal hoop with its lugs to overlap the tongue-piece
and hold it in position.
5. In the 1883 Patent there was not sufficient provision for keeping the helical
spring in its place and there was a liability for it to get out and cause a breakage.
I provide against this by completely enclosing the spring as will be presently
described.
6. Neither of the former Patents provided sufficiently for resistance to the
extreme high pressures of steam now being used. To meet this difficulty I propose
to abandon the spring for outward pressure, and to build up the packing rings of
strong sections bound together by an iron hoop, in such a way that it may be

page_text: adjusted by hand to the diameter of the cylinder, forming a practically solid ring
which will not be affected by steam pressure either within or without.
1st improvement which relates to the method of making and applying the wave
springs for outward pressure as by the 1877 Patent is illustrated by Figures 1, 2,
5 and 6 in which the spring for outward pressure, instead of consisting of one band
or ribbon is constructed of two or more wires C of round, square or other section,
bound together at intervals by clamps or knuckles D which serve, not only to hold
them together, but also cause the wires to take a wavy form and thus to exert a
pressure upon the internal surface of the packing ring A which pressure may be
regulated with minute nicety by the number and thickness of the wires, and by the
distance at which the clamps D are spaced apart. The clamps may be so arranged
as to hold all the wires as shown in Figure 5, or a portion of them alternately as
shown in Figure 2, in which latter case the pressure is more evenly distributed
round the ring. Under certain circumstances two or more flat ribbons of steel may
be bound together in one clamp as shown in Figure 6 instead of wires. When flat
steel is used a curved notch is made in the edge of the steel where the clamp is-
attached to prevent it sliding along the steel; in the case of wire it is flattened
slightly for the same purpose.
The object of this improvement is to give increased facilities for adjustment of
the pressure produced by the spring and to reduce the risk arising from breakage
of the springs, it being unlikely that all the wires would break at the same time.
2nd improvement which relates to the arrangement and control of the helical
spring for outward pressure described in the 1883 Patent Specification, is illustrated
by Figures 10, 11, 12, 13 and 14. In this improvement the cod or tongue-piece B
is sunk into the packing ring A so that its inner surface is flush and concentric with
that of the ring. The lugs L which are rivetted to the steel hoop O carry the
helical spring C and receive its pressure to transmit it to the packing ring. They
are brought close together, so as to overlap the tongue-piece B, thus keeping the
latter more firmly in its place against the outward pressure of steam than is the case
with those made under the 1883 Patent. One of the lugs L is made to receive a
pin P upon which swings a bridle M of iron or other suitable material. This bridle
may be swung to one side as shown in Figure 11 when the rings are out of the
piston for the purpose of inserting or withdrawing the spring C, but when the ring
is in the piston the bridle M is kept in the position shown in Figure 10 completely
enclosing the spring and preventing it from getting out of its place. The other end
of the bridle is fitted with a set screw N by which the spring may be compressed to
facilitate its removal from the cylinder and by which also the pressure of the spring
may be confined within predetermined limits, by fixing the set screw N at any pre-
scribed position. The spring C may be of oval section and made of flat steel and
provided in the 1883 Patent as shown in Figure 12 but may also be made of round
section as shown in Figure 13 and of round, square or other suitable section of
steel.
The object of this improvement is to keep the tongue-piece B securely fixed in
its seat, and to provide better means for keeping the spring C in its place, and for
facilitating the removal and adjustment of the same.
3rd improvement relates to the cod or tongue-piece for the piston ring as
described in the 1883 Patent Specification and is also applicable to the piston of the
1877 Patent. This improvement is illustrated by Figures 1. 7. 9. 10 and 11. It
consists in forming the outer surface B¹ of the cod or tongue-piece B to an arc of a
materially larger radius than that of the inner diameter of the packing-ring and of
grooving out the latter to a corresponding arc, instead of making them of the radius
corresponding to that of the ring, as has been done hitherto.
The object of this improvement is to ensure the tongue-piece retaining its full,
steam-tight contact after the packing rings are worn and have consequently opened
out to a larger diameter.
4th improvement relates to the mode of making and applying the wave spring
between the piston rings described in both Patent Specifications. This is

page_text: illustrated by Figures 3 and 4. It consists in bending up the two ends of the
wave-spring in opposite directions as shown in Figure 3 and forming a recess in
each of the packing rings for these beat up ends to rest in. By a modification the
wave-spring may as shown in Figure 4 be made of square steel or of round steel, a
suitable groove being turned in one of the packing-rings for it to lie in, in which
case a hole bored in the rings to receive the turned up ends takes the place of the
recess described above.
The object of this improvement is to ensure the wave spring being kept in such
relative position to the packing rings that one of the waves may always exert a
pressure equally on both the free ends of the same, the wave spring and the packing
rings being prevented from revolving independently of each other.
5th improvement relates to a new construction of piston rings whereby the spring
for outward pressure is done away with and the rings are made adjustable by hand.
This improvement is specially applicable to pistons for extreme high pressures and
for piston valves; it is illustrated by Figs. 7. 8. 9 and 9^.
This improvement consists of forming the packing rings A with an internal
groove H of suitable size to receive a hoop or band G of iron or steel upon which
are rivetted one or two pairs of lugs I and J which are held together by bolts and
Duts. The packing-rings A are cut into two or more sections according to their
diameter, a round, countersunk hole being bored through at the point of section in
which is inserted a pin K round which each section is free to turn slightly. One of
the sections is fitted with a cod-piece B (instead of the pin K) which is held in
place by the lugs I and bolt and nuts. The sections are strung upon the hoop or
band G which is screwed together by the lugs I J and bolts and nuts and adjusted
to the size of the cylinder by the insertion of a small.packing in the joint under the
tongue-piece, when the whole is screwed up to form practically a solid ring.
When the packing rings are worn, the small packing is replaced by a larger
one Q Figure 94 and the lugs tightened up to the increased diameter as shewn in
Figure 9 which represents the full extent to which such adjustment can conveniently
be made.
The object of this improvement is to form a rigid packing-ring which cannot be
expanded by steam leaking to the interior of the piston and thus setting up
excessive friction, while at the same time providing a convenient means of
adjustment for wear and providing against breakage of packing rings by binding
them together with a wrought iron hoop.
NOTE. The first second and fifth improvements are each of them to be used in
combination with the improved cod or tongue-piece described as the 3rd improvement
and also with a wave-spring made either in accordance with the 1883 Patent or
with the 4th improvement described above.
The complete packing generally consists of two packing rings A turned to fit the
cylinder and cut at one place to admit of being expanded by the outward pressure
of the spring C so as to fill inequalities in the bore of the cylinder or to take up
wear of the rings and cylinder. Each packing ring is fitted with a cod or tongue-
piece B to cover the cut and prevent steam leaking in thereby which is kept in its
place by the pressure of the spring C transmitted in Figure 1 through the
socket E and in Figure 10 through the lugs. L. The two packing rings are kept
apart and in close contact with the flanges of the piston body by the wave spring F.
In the modification shown in Figures 7, 8, 9 and 9ª the packing rings are cut in
more than one place and the spring C is dispensed with.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. A spring for exerting outward pressure on piston packing-rings said spring
consisting of two or more steel hoops clamped together by knuckles cramped upon
them at intervals, the hoops being slightly flattened where the clamps are placed to
prevent them shifting or the hoops having a semicircular notch cut in their edges

page_text: for the same purpose the knuckles only being in contact with the packing ring
while the hoops are kept at sufficient distance from it to admit of their bending in
towards the ring between the knuckles, when the ring is closed in to the size of the
cylinder, the pressure being produced by the tendency of the spring to resume its
true circular form as described with reference to Figures 1, 2, 5 and 6.
2. The formation of the cod or tongue-piece and of that portion of the inner
surface of the packing-ring against which it bears, to a curve of a radius, sensibly
greater than that of the inner diameter of the packing-ring as described with
reference to Figures 10, 11, 12, 13 and 14.
3. The turning up of the two ends of the wave spring in opposite directions and
the formation of grooves or holes in the edges of the packing-rings for keeping the
wave spring in place as described with reference to Figures 3 and 4.
4. The combination of the spring for outward pressure as firstly claimed with the
cod and packing-ring as secondly claimed and the improved wave spring as thirdly
claimed to be applied to pistons either with or without junk rings, the complete
packing consisting of two packing rings each with its cod and spring and with
wave-spring between them.
5. The lugs L and bridle M with screw N for enclosing, adjusting and easily
removing the springs C Figures 10, 11, 12, 13 and 14.
6. The recessing of the packing-ring for the cod to such a depth that the inner
surface of the cod shall be concentric with that of the ring, the cod and ring being
made in accordance with second claim, in combination with the improved lugs L and
bridle M the two packing rings and the wave-spring as described.
7. The combination of two packing rings each of which is cut into two or more
sections and held together by a hoop of iron or steel lying in a suitably formed
groove on the inner surface of the ring and kept steam tight at one of the sections
by a suitably formed cod and at the other sections by a pin fitted into countersunk
holes bored through the plane of section, the whole of each ring being held
together and formed to the correct size of cylinder by the lugs, bolts and packings
as described with reference to Figures 7, 8 and 9 and with or without a wave spring
between the rings.
Dated this 22nd day of May 1804
JENSEN & SON,
77, Chancery Lane, London, W.C., Patent Agents.