Improvements in Valve Gears for Steam Engines.
Year: 1893

page_text: Date of Application, 31st Jan., 1893-Accepted, 20th May, 1893
COMPLETE SPECIFICATION.
Improvements in Valve Gears for Steam Engines.
CHARLES FREDERIC LITTLEJOHN, of Bridgeport, Fairfield County,
Connecticut, United States, Gentleman, 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 :—
This invention relates to certain novel and useful improvements in valve gears
for steam engines, more especially intended for marine engines, although applicable
to engines of other kinds, and the object thereof is to provide a simple and certain
means for varying the cut-off according as the engine is performing light or heavy
duty. With this end in view my invention consists and resides in the construction
and combination of elements hereinafter fully explained and then recited in the
clains, and particularly in the employment of the adjustable cam whereby the
throw of the valve is determined through suitable connections.
In order that those skilled in the art to which my invention appertains may
fully understand its construction and method of operation I will describe the same
in detail, reference being had to the accompanying drawings which form a part of
this Specification, and in which,
Figure 1, is an end elevation of a vertical engine containing my improvement.
Figure 2, is a side elevation.
Figure 3, a vertical section on the line - of Figure 2.
Figure 4, comprises two small sections of the adjustable cam ring, the upper one
transverse to the shaft, and the lower longitudinal.
Figure 5, is a detail plan view of the hand lever.
In the engine shown in the drawings 1 denotes a suitable frame upon which tho
cylinder 2 is supported. The steam chest 3 is mounted alongsido tho cylinder and
is connected therewith by means of ateam ports 4, see Figure 3. Steam is
admitted to the chest through a steam pipe 5. A shaft 6 is journalled longitudinally
in the steam chest, which latter, as shown at Figure 3, is circular in cross section,
and upon this shaft is borne a rocker valve 7 which is adapted- alternately to cover
and thereby connect the steam ports 4 with the exhaust port 8 which, as shown at
Figure 3, lies between the steam ports. As this is a common and well known form
of valve it needs no further description in this place. The piston 9 having piston
rod 10 is connected through a pitman 11 with a driving crank 12 upon the main
shaft 13, which, in a marine engine, carries the propeller wheel. To the end of
the shaft 6, which projects outside the steam chest, is affixed the crank 14 which
has a slotted engagement with another crank 15, which latter is borne upon a rock
shaft 16 mounted in vertical bearings. The lower end of this shaft is furnished
with a laterally projecting rod or bar 17, said bar being hung in bearings 18 on
the lower end of the rod. The outer end of the rod 17 has hinged thereto a
shoe 19. Upon the main shaft 13 is secured a hub 20, and around this hub is
placed a ring 21 having in its periphery a groove 22. This ring is connected to
the hub 20 by means of gimbals 23 upon which it may have a rocking movement.
The shoe 19 just referred to enters the groove in this ring, as shown at Figuro 1.
Hung in bearings on the frame is a vertical rock shaft 24 similar in construction to
the rock shaft. 16, and on its lower end it carries an outwardly projecting crank 25,
as appears at Figure 1. The end of this crank carries a shoe 26, see Figure 2,
and this shoe runs in a groove 27 in a hub 28, which latter part is splined to the
shaft 13. Through a connecting link 20 the hub 28 is connected with the ring 21 in
auch manner that a sliding movement of the hub along the shaft will rock the ring
upon its gimbal joints for the purpose of changing its plane of rotation. The
upper end of the shaft 24-is provided with a lever 30 ɓaving a screw stud or

page_text: fastening 31 which runs in a slot 32 in a plate 33, and this lever is provided with a
handle whereby it may be operated.
The operation of my invention is as follows. If the ring 21 stood in a plane at
right angles to the plane of the shaft 13 uo movement would be imparted to the
valvo 7, but in direct proportion as the ring is swung upon its gimbal joints so as
to stand oblique to the shaft 13 it operates upon the shoe 19 after the manner of
cams, and through said shoe imparts an oscillatory movement to the shaft 16 and
thenco through the parts 15, 14 and 6 to the valve itself. The throw of the valve
is varied by means of the levor 30 which, by moving the hub 28, determines the
augle at which the ring 21 stands to the shaft, and this forms an exceedingly
simple and positive device for this purpose.
I have shown simply the hand lever for actuating the ring and determining the
throw of the valve, but I do not confine myself to this specific moans, since if
required a governor may be used in place of the lever in such manner as to cause
the throw of the valve to automatically adjust itself for any duty either light or
heavy which may devolve upon the engine.
I have shown the ring as borne upon the main shaft, and this I deem to be
preferable, but it will readily be understood that it may be secured upon any other
element of the machine which has a rotative movement properly timed to the
stroke of the engine.
The gear shown may also, as will be readily apparent to any one skilled in the
art, be applied to or combined with valves other than the rocker valve shown in
the drawings.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declaro that what I
olaim is :-
1. In a machine of the character described, the combination with the main shaft,
of a grooved ring hung thereon, means for changing the plane of rotation of the
ring, and a connection substantially as described between said ring and the valve,
whereby the position of the ring will determine the throw of the valve, substantially
as described.
2. The combination with the cylinder and steam chest having suitable ports, of
a rocker valve mounted in the steam chest, a shaft whereon said valvo is borne,
and whereby it is actuated, a grooved ring pivoted upon the main shaft, a connection
between the valve shaft and the ring, and means as described for varying the plane
of rotation of said ring, substantially as specified.
3. In a machine of the character described, the shaft 13 bearing a hub, and a
grooved ring hung on gimbals to said hub, in combination with a rock shaft actuated
by said grooved ring, a connection between said rock shaft and the valvo, and
means as described whereby the plane of rotation of the grooved ring may be
controlled and varied.
4. In a machine of the character described, the shaft 13, the hub mounted
thereon, and a ring provided with a peripheral groove and secured to said lub by
a gimbal connection, in combination with the rock shaft 16 actuated from the ring,
the valve and suitable connection between it and the rock shaft, a sliding hub
splined on the shaft 13 and connected to the ring, and an operating lever and means
for connecting it with the splined hub, the whole arranged substantially as
described.
Dated this 31st day of January 1893.
GEO. H. RAYNER,
37, Chancery Lane, London, W.C., Agent for the Applicant.