Improvements in Pistons.
Year: 1897

page_text: PROVISIONAL SPECIFICATION.
Improvements in Pistons.
I, CHARLES GEORGE EVANS, Student, of Union, in the Province of British
Columbia and Dominion of Canada, do hereby declare the nature of this inven-
tion to be as follows:
This invention relates to pistons for steam engines and has for its object to
prevent leakage of steam past the packing without causing undue friction of the
packing rings on the wall of the cylinder.
According to my invention the piston is provided with packing rings and with
followers rigidly connected with each other and fitted to slide longitudinally by
the pressure of the steam in the ends of the cylinder, the follower on one side of
the piston being connected with an expansion ring beneath the packing on the
other side of the cylinder. The followers are connected by rods or pins fitted to
slide in the body of the piston, and each follower is connected by a series of
longitudinally extending rods with its appropriate expansion ring, the rings being
received in recesses in the piston body and having bevelled peripheries which
contact with corresponding bevels on the inside of the piston rings which extend
into the said recesses. Thus when the steam enters the cylinder, its pressure
against the follower at the entering end moves the follower inward on the piston
rod and causes a movement of the other follower in the same direction thereby
sliding the expansion rings so as to cause the expansion of one of the outer packing
rings and the release of the other.
In this manner the exhaust side of the piston is packed and the packing at the
live steam side is released. The sliding movement of the followers is limited by
bevelled offsets which bear against corresponding bevelled rings in annular
recesses in the body of the piston, guard rings being provided to hold the rings
in place. These rings and the packing rings are split to permit of their being
expanded by the offsets and the expansion rings respectively while they contract
by their own resiliency.
Each ring is formed at its split end with a dovetailed tongue engaging a dove-
tailed recessed end for securely connecting the ends with each other and still
permitting of expansion and contraction thereof. The pins connecting the
followers are rigidly attached at one end to the one follower, the other end being
conical and entering a corresponding hole in the other follower, the extremity
of the pin at the latter end having a right and a left hand screw-thread engaged
by nuts which enter appropriate recesses which are filled with babbitt-metal or
other material which forms a locking pin when cooled and set to secure the two
in position. The pins of the expansion rings are similarly secured. The expan-
sion rings are preferably made in sections, the top section being of very hard steel,
the lower of ordinary steel, and the sides of soft iron, so that they wear readily
and produce an oval ring wedge which sets the packing rings properly in a worn
horizontal cylinder oval in cross-section. The faces of the body of the piston are
recessed to permit the inner ends of the offsets of the followers to move the desired
D

page_text: distance when they are pressed inwards by the steam. Thus it is evident that the
followers are pressed inward such a distance as the expansion of the rings allows
and consequently the packing rings do not expand against the inner surface of
the cylinder according to the force or pressure of the steam but only according to
the amount of movement allowed by the said rings so that the rings are uniformly
expanded with the inner wall of the cylinder irrespective of the pressure of the
steam in the ends of the cylinder, as long as the pressure is sufficient
for shifting the followers as above described. The rings encircling the followers
give sufficient resistance to the followers to prevent the same from striking hard
against their resting surfaces when adjustment takes place.
Dated this 7th day of September 1897.
A. M. & WM. CLARK,
Chartered Patent Agents, 53, Chancery Lane, London.
Дара
I, CHARLES GEORGE EVANS, Student, of Union, in the Province of British
Columbia and Dominion of Canada, do hereby declare the nature of this inven-
tion and in what manner the same is to be performed, to be particularly described
and ascertained in and by the following statement: —
This invention relates to pistons for steam engines and has for its object to
prevent leakage of steam past the packing without causing undue friction of the
packing rings on the wall of the cylinder.
The invention consists of certain parts and details and combinations of the same,
as will be fully described hereinafter and then pointed out in the claims.
Reference is to be had to the accompanying drawings forming a part of this
specification, in which similar characters of reference indicate corresponding parts
in all the figures.
Figure 1 is a longitudinal section of the improvement;
Figure 2 is a transverse section of the same, on the line 2-2 of Figure 1; and
Figure 3 is a plan view of the ends of one of the packing rings.
The improved piston is provided with a body A, secured on a piston rod B,
connected in the usual manner with the driving shaft of the engine, the piston
being reciprocated in the cylinder C by the pressure of the steam or other motive
agent alternately acting on the ends of the said piston.
On the front face of the piston body A is arranged a follower D, fitted to slide
longitudinally on the piston rod B, and rigidly connected by rods or pins E with
a follower Di, held on the other face of the body A, the said rods or pins being
fitted to slide in suitable bearings in the body_A. The follower D is connected
by a series of longitudinally-extending rods F, with a ring G, fitted to slide
longitudinally in a recess A₁ formed in the body A, and the other follower D¹ is
similarly connected by rods F1 with a ring G, fitted to slide in a recess A³, likewise
formed in the body A. The rings G and G¹ are formed on their peripheries with
bevels engaging corresponding bevels on the inside of the packing rings H and H¹
extending through the recesses A¹ and A³, to engage with the inside of the
cylinder C and form a packing for the piston.
The packing ring H is arranged near the face of the piston having the
follower D¹, and the other packing ring H is arranged near the face having the
follower D, as is plainly shown in the drawings, so that when the steam enters
the right hand end of the cylinder C and presses against the follower D, the latter
moves to the left, and in doing so, causes a sliding of the other follower in the

page_text: same direction, and a sliding of the rings G and G¹ in the same direction, to cause
an expansion of the packing ring H and a releasing of the packing ring H¹.
When the steam enters the left hand end of the cylinder C, it presses on the
follower D', and the latter is caused to slide to the right, carrying the follower D
and the rings G, G¹ in the same direction, whereby the packing ring His
expanded, and the previously expanded packing ring H is released. Thus that
side of the piston containing the exhaust steam is packed by the corresponding
packing ring, while the ring on that side of the piston containing the live steam.
is in a release position.
It will be seen that by the arrangement described, the followers D) and D as
well as the expanding and releasing rings G and G¹, move in unison in longitudinal
directions, the followers on one side of the piston directly actuating the expansion
and releasing ring for the opposite side of the piston.
In order to limit the inward sliding motion of the followers D and D', I provide
the inner faces of the followers D and D¹ with bevelled offsets D2, D³, respectively,
engaging the inner bevels of rings I, I¹, respectively, held in annular
recesses A3, A4, respectively, formed in the body A. Guard rings J, J¹, secured
on the piston body, extend a short distance over the faces of the rings I, I', so as
to hold the same in their recesses, against longitudinal movement.
The rings H, H, I, I¹ are made in the form of split rings, so as to permit of
expanding the rings and allowing the same to contract by their own resiliency,
the rings H, H¹ being expanded by the movement of the rings G, G', respectively,
and the rings I, I' being expanded by the bevelled offsets D³, D³, respectively, on
the followers D and D¹.
As shown in Figure 3, each of the rings H, H¹ is formed at its split end with
a dovetailed tongue H, engaging a dovetailed, recessed end H³, for securely con-
necting the ends with each other, and still permit of expansion and contraction
thereof, for the purpose above described. The ends of the rings I, I' are similarly
constructed,
Each of the pins E is rigidly secured at one end to the follower D, and the other
end is formed with a conical offset E' engaging in a corresponding aperture in
the follower D¹. The extreme outer end of the pin is formed with a right hand
screw thread E and a left hand screw thread E³, of which the former is engaged
by a nut K and the latter by a nut K¹, both having registering recesses K³, K³
countersunk at their adjacent ends, and adapted to be filled with babbitt-metal
or other material, which when cooled and set forms a locking pin for securing
the two nuts in position. A similar fastening is arranged for the pins or rods F, F1
which are secured at one end in the rings G, G¹, and at their other end by nut locks
as described, for the followers D, D¹.
The expanding and releasing rings G, G₁ are preferably made in sections, of
which the top section is made of very hard steel, the lower section of ordinary
steel, and the side sections of soft iron, so that they wear readily and produce an
oval ring wedge which sets the packing rings H, H³ properly in a worn horizontal
cylinder, oval in cross section.
It is understood that the rings I, I¹ wear on their inner faces about in pro-
portion to the wear of the packing rings H, H¹, so that an automatic adjustment
always takes place as the offsets D, D³ move further inward on the rings I, I',
and consequently an expansion of the rings H, H¹ in a corresponding degree takes
place, so as to insure at all times a perfect packing of the piston in the cylinder.
The faces of the body A are recessed at A5 and A6, to permit the inner ends of the
offsets D and D³ to move the desired distance when the followers are pressed
inward by the motive agent.
By the arrangement described, it is evident that the followers D, D' are pressed
inward such a distance as the expansion of the rings I, I¹ allows, and consequently,
the rings Hand H' do not expand against the inner surface of the cylinder C
according to the force or pressure of the steam, but only according to the amount
of movement allowed by the said rings I and I¹, so that the rings are uniformly

page_text: expanded with the inner wall of the cylinder C, irrespective of the pressure of the
motive agent in the ends of the cylinder, as long as the pressure is sufficient for
shifting the followers as above described. The rings I, I encircling the followers,
give sufficient resistance to prevent the latter from striking hard against their
resting surfaces when adjustment takes place.
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 piston, provided with packing rings, and followers rigidly connected with
each other, and fitted to slide longitudinally by the pressure of the motive agent
in the ends of the cylinder, the follower on one side of the piston being connected
with the packing ring for the other side of the piston, substantially as shown and
described.
2. A piston, provided with packing rings, followers rigidly connected with each
other and fitted to slide longitudinally by the pressure of the motive agent in the
ends of the cylinder, the follower on one side of the piston being connected with
the packing ring for the other side of the piston, and a device for limiting the
sliding motion of the followers and the expansion of the rings, substantially as
shown and described.
3. A piston, provided with packing rings, a device for expanding and releasing
each of the said packing rings, and followers rigidly connected with each other
and fitted to slide longitudinally, the follower on one side of the piston being
rigidly connected with the expansion and releasing device on the other side of the
piston, substantially as shown and described.
4. A piston, provided with packing rings, a device for expanding and releasing
each of the said packing rings, followers rigidly connected with each other and
fitted to slide longitudinally, the follower on one side of the piston being rigidly
connected with the expansion and releasing device on the other side of the piston,
and a limiting device for each follower, for limiting the sliding motion of the
same, substantially as shown and described.
5. A nut lock, comprising a rod having right and left hand threads, and nuts
on the said threads, and formed with registering apertures adapted to be filled
with a setting or hardening substance, the said apertures being counter-sunk at
their adjacent ends, substantially as shown and described.
6. A piston, provided with an expansion ring for the packing ring, and made
in sections of metal of different degrees of hardness, substantially as shown and
described.
7. A piston having a body, a follower at each end of the body, two packing rings
running around the body, an expanding ring beneath each packing ring, and con-
nections respectively between the followers and the expanding rings furthest
therefrom, substantially as described.
8. A piston having a body, a follower at each end of the body, expansive pack-
ing rings, and connections respectively between the followers and the packing
rings furthest therefrom, whereby upon the movement of one follower the packing
ring furthest from said follower will be expanded, substantially as described.
9. A piston having a body, a follower thereon, an expansive packing ring, an
expanding ring having connection with the packing ring and moving to expand
the same, and a connection between the follower and the expanding ring, sub-
stantially as described.
101
1
L
1000
A. M. & WM. CLARK,
Chartered Patent Agents, 53, Chancery Lane, London.