IMPROVEMENTS IN STEAM ENGINES
Year: 1875

page_text: PROVISIONAL SPECIFICATION left by Robert Carey and Robert
Porter at the Office of the Commissioners of Patents, with their.
Petition, on the 24th June 1875.
We, ROBERT CAREY and ROBERT PORTER, both of No. 172, Fen-
I church Street, in the City of London, Engineers, do hereby declare the
nature of the said Invention for "IMPROVEMENTS IN STEAM ENGINES," to
be as follows:―
This Invention consists in the novel construction and arrangement of
the parts of engines of a special form, some of which improvements are
applicable to other steam engines.
These engines are constructed with two cylinders connected by a
central chamber, all of which together with the bed plate of the engine
are cast in one piece, passages being formed in the bed plate for the
steam and exhaust. The two cylinders are in the same line, so that they
both may be bored through at one operation; they take the steam only
at the outer end, being open towards the central chamber. The pistons
are made comparatively long in the form of a trunk, and when at the
extent of the stroke they project a short distance into the central

page_text: chamber, thereby avoiding any rapid wearing or the formation of a
shoulder. A crank shaft passes through the central chamber at equal
distance from both cylinders, the crank being made to work in the
central chamber. The connecting rods from the pistons both made
exactly alike are coupled together upon the crank, so as to give the 5
greatest amount of wearing surface.
The connecting rod ends are made in the following manner :—A block
or casting is made, upon one end of which are lugs, and on the other
end at a corresponding distance a groove is turned on the outside. The
block is bored through to suit the crank pin, allowing for the variation 1
of the rods as the crank revolves. When the block has been prepared
in the manner described it is divided through the centre of the hole
prepared for the crank pin. The two parts are then reversed so as to
bring the groove formed at one end of either part opposite the lugs
upon the other part. A cap is made to fit into each groove, and is 1
secured to the opposite lug by bolts or other suitable means. The said
two caps are fitted accurately by bolting them together, and boring them
out to suit the groove turned in the said block before it is divided.
The action of the engine is controlled or reversed by actuating the
slide valve in the following manner :-The slide valve is connected by a 2
rod to a sliding plate, which is caused to traverse or slide in a straight
line between guides upon another plate by the direct action of an
excentric, which is keyed upon the crank shaft exactly in the opposite
direction to the crank.
The said guide plate which carries the sliding plate is fitted loosely on 2
the crank shaft and is adjustable to any angle, and it is retained in
position by a quadrant or other suitable means. When the guide plate
is adjusted and set, so that the sliding plate is caused to work at right
angles to the slide valve, the latter remains almost still midway of its
traverse, and the steam is shut off from both cylinders. The lead of 8
the slide valve is obtained in either direction by setting the sliding plate
aforesaid to work at a suitable angle by adjustment of the guide plate.
The connection between the eccentric and slide valve is formed by a
ring being fixed on to the sliding plate in a central position with
respect to the jaws upon the sliding plate, between which jaws the 8
eppentric works. A strap is. fitted on to this ring, and to one end of the

page_text: connecting rod, the other end of which rod is connected to the slide rod
of the slide valve in any convenient manner.
"When it is convenient to let the crank shaft terminate flush with the
eccentric the jaws upon the sliding plate between which the eccentric
works are connected beyond the eccentric by a plate, upon which
midway between the two jaws is fixed a stud, upon which one end of
the connecting rod to the slide valve is fitted.
The ordinary form of slide valves is employed, one valve for each
cylinder. There is one passage into the end of the cylinder, and one
passage for the exhaust for each cylinder. The slide valves therefore
only have to work in regard to the two passages or ports. By this
means a great advantage is gained as the slide rods may be lengthened
or shortened, and thus with the same valve a greater range of cut off is
obtained.
In the said reversing gear by placing the ring or stud, as the case may
be, slightly out of the centre with respect to the jaws in which the
eccentric works, so as to vary the distance between the two slides
according as the guide plate is moved into different positions the slides
always retain the same lead.
When the reversing gear is not used the slides are actuated by an
eccentric keyed on the crank shaft and working into a frame, and the
two slide rods are taken from each side of the frame respectively, the .
whole working in a straight line.