Improvements in Valve Gear for Steam Engines.
Year: 1887

page_text: Date of Application, 1st Sept., 1887.
Specification Accepted, 4th Oct., 1887
Improvements in Valve Gear for Steam Engines.
1, HENRY CHRISTIAN LOBNITZ, of the Slip Dock, Renfrew, in the County of
Renfrew, North Britain, 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, that is to say:-
My said Invention has for its object to improve the construction of or mode of
combining or arranging valve gear for steam engines, my improved gear being
specially designed for triple-expansion marine engines made with three cranks.
The nature of my Invention and the manner of performing the same will be easily
understood from the following particular description of an example of its practical
application diagrammatically shown on sheet, 1, of the explanatory drawings hereunto
appended. It is however to be understood that some of the details of the arrangement
are susceptible of variation to suit different applications and requirements.
The figures on sheet, 1, of the accompanying drawings represent portions of a set
of triple-expansion inverted-cylinder engines suitable for driving the screw propeller,
the parts being indicated in elevation in figure, 1, and in inverted plan in figure, 2,
and the same reference letters and numerals being used to mark the same or like parts
wherever they are repeated.
The piston rods of the three cylinders, HP, IP, LP, are connected respectively to
three equidistant cranks, C1, C2, C3, and the valve casings are arranged so that the
three valve rods are in a vertical plane, 3-3, parallel to the vertical plane, 4-4, of
the cylinders and crank shaft. The valve rod, V, figure, 1, of the high-pressure
cylinder, HP, is directly acted on by a curved link, M, arranged and adjusted like
that of an ordinary link valve motion, but instead of this link, M, being worked in the
ordinary way by means of a pair of eccentrics on the crank shaft, it is worked by
rods, 5, jointed to its ends and having their other ends jointed to short levers, L, on
rocking shafts, R. The valve rods of the other cylinders, IP, LP, are worked by
motion links connected by rods to short levers, L, on rocking shafts in the same way
as the valve rod, V, of the cylinder, HP, but to avoid confusion the motion links and
the rods working them are not shown.
The rocking shafts, R, of which three are required are worked by levers, L1, L2, L3,
connected by links, 6, to the slide blocks, B of the piston rods of the cylinders, HP,

page_text: IP, LP, respectively; or as indicated by a dotted line in figure, 1, each lever may
be connected by a link, 7, to the respective crank or to any suitable part of the
respective connecting rod. The rocking shaft, R 1, having fast on it the lever, L1,
connected to the piston rod of the cylinder, HP, is a central solid shaft, carried in
suitable bearings (not shown) and having fixed on it short levers, L, connected by
rods, 5, to the motion links (M) of the other two cylinders, IP, LP. The rocking
shaft, R 2, having fast on it the lever, L2, connected to the piston rod of the inter-
mediate cylinder, IP, is a tubular shaft carried on and concentric with the rocking
shaft, R 1. A part of the tubular shaft, R2, is cut away all but a segment, 8,
connecting the two ends, to allow of the working of the short levers, L, which work
the valves of the intermediate cylinder, IP, the tubular shaft, R 2, having fixed on it
short levers, L, in positions for being connected to the motion links (M) of the
cylinders, HP, and LP. The rocking shaft, R 3, having fast on it the lever, L3,
connected to the piston rod of the cylinder, LP, consists of three tubular parts
concentric with and carried by the rocking shaft, R 1, the three parts being connected
by a segmental piece, 9. Each rocking shaft, R1, R2, R3, has fast on it two short
levers, L, and whilst it receives its motion from the piston rod of one cylinder it gives
motion to the valve gear of the other two cylinders, acting like a forward eccentric
for one and like a backward eccentric for the other. It follows that the valve gear of
each cylinder gets its forward motion from one of the other cylinders and its backward
motion from the remaining cylinder.
With this arrangement all the conveniences and advantages of an ordinary link
motion in reversing and varying the cut-off are obtained with simple levers and a
combination of concentric rocking shafts and without eccentrics on the main crank
shaft.
Instead of working the rocking shafts, R1, R2, R3, by levers, L1, L2, L3,
moved by the piston-rod slide blocks or connecting rods they may be worked by
eccentrics E1, E2, E 3, as shown in figure, 3, on sheet, 2, of the explanatory
drawings hereunto appended, a modified arrangement of the rocking shafts being
shown in figure, 4, to suit the eccentrics when placed on the forward end of the crank
shaft. When convenient, however, the eccentrics may be placed in other positions on
the crank shaft the rocking shafts being modified accordingly; and in some cases the
rocking shafts may be worked partly by levers connected to the piston-rod slide blocks
or connecting rods and partly by one or more eccentrics on the crank shaft.
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-The improved arrangement or combination of valve gear details substantially as
herein before described and as shown on sheet, 1, of the accompanying drawings.
2-The modified arrangement or combination of valve gear details in which the
rocking shafts are worked by eccentrics substantially as herein before described with
reference to sheet, 2, of the accompanying drawings.
3-The modified arrangement or combination of valve gear details in which the
rocking shafts are worked partly from the piston-rod slide blocks or connecting rods
and partly by one or more eccentrics on the crank shaft substantially as hereinbefore
described.
Dated this Thirty-first day of August 1887.