AN IMPROVEMENT IN TRIP VALVE GEAR FOR STEAM ENGINES
Year: 1885

page_text: "
I, ROBERT MATTHEWS of Green Bank, Hyde in the county of Chester, Engineer,
do hereby declare the nature of my invention for "AN IMPROVEMENT IN TRIP
VALVE GEAR FOR STEAM ENGINES and in what manner the same is to be
performed to be particularly described and ascertained in and by the following
statement
My invention relates to the trip valve gear of steam engines, so arranged that
whilst one eccentric rod moves the valve both for supply and exhaust, the cut off
is effected by sudden closing of the supply valve at any part of the stroke as
determined by hand or by the action of the governor, as I will describe referring to
the accompanying drawings. Fig. 1 is a side elevation, partly in section, of valve
gear according to my invention and fig. 2 is a like view of a modified arrangement
of the same.
In both these figures, the same letters are used to indicate corre-
sponding parts.
Referring first to fig. 1, A is part of the eccentric rod which in making its to
and fro stroke moves two bent levers, having respectively the two arms B C
and B'C'.
The arms B and B¹ are connected through toggle joints D and D¹ respectively to
two other bent levers having arms E F and E' F¹. The arms C and C¹ are
respectively connected by links c c¹ to the cylindrical covers G G₁ of a spring
box H. The levers E F and E¹ F are fixed on the axes of partly rotating valves
of the Corliss kind, indicated by the dotted lines I and I¹. The arms F and F¹ are
connected by links ff' to pistons J J¹ fitted within the spring-box H and
pressed outwards by the springs h. An eccentric K revolving in time with the
engine shaft works two rods having on them tappets and ¹ which act on
arms L L projecting from one of the links of the toggles D'and D¹ respectively
these links having butt-tails d and d'. The eccentric K may be set by hand.on
its shaft to determine a certain cut off, or its setting on the shaft may be varied
by a governor in any known manner, as for example by means of a helical key, so
as to give a variable cut off determined by the speed of the engine. As the
eccentric rod A moves towards the left, it moves with it through the straight
toggle D¹ the lever E' and the valve J₁, closing the exhaust and opening to steam,
moving back also the cover G¹ and the piston J¹ and compressing the spring .
دلل

page_text: This goes on until the tappet acting on L¹ bends the toggle D¹ and thereupon
the spring pushes back the piston J, which by turning back I', closes the supply
port, thus effecting immediate cut-off.
.
While this is the operation at the right hand end of the cylinder, the toggle D
at the left hand end is being straightened, not moving the valve I until it becomes
straightened, during which time the arm C in travelling over the first portion of
its are scarcely moves the cover G, that movement being only that due to the versed
sine of the arc through which C moves. During the latter part of the stroke of A
when the toggle D has become straightened, the lever,E is moved, causing the valve I
to turn so as to open exhaust and at the same time the arm C moving through
the upper part of its course moves the cover G towards the left, the piston J
following it. In the stroke of A to the right a similar set of movements occur
inverted, the valve I being moved as J had been moved and I¹ being moved as J
had been moved. It will be seen that by this arrangement the covers G and G¹
are held practically stationary for a time, forming, each in its turn, an abutment or
stop to the outward stroke of J and J', when, urged by the springs h and h¹, they
close the supply, the stroke of J and J¹ being cushioned by the air between them
and G G¹ respectively.
During another portion of the time the covers G and G¹ are moved outwards
allowing the pistons J J¹ to follow them while the valves I and I open the
exhaust.
The levers B C and B¹ C¹ may be mounted respectively along with E F and E¹ Fº¹
on the axis of the valves I I' as shewn in fig. 2; their action being the same as in
the arrangement shewn in fig. 1. Also, instead of connecting arms C C¹ to moveable
covers G G¹ of the spring cylinder H, these arms and the moveable covers may be
dispensed with by introducing hydraulic stops to the pistons J J as shewn in fig. 2.
In this modification there is fitted in each end of the spring cylinder Ha
piston M M¹ pressed inwards by light springs m m sufficient to keep them in
contact with J J. From each end of the spring cylinder H there is a passage
governed by a partly rotating valve N N¹ to a compartment O containing oil or
other liquid. The valves N N¹ are worked by arms n n¹ from pins on the
eccentric rod A.
While the valves N N¹ are closed the liquid forms a stop for the pistons M M,
preventing them from being moved outwards by the strokes of J J. But when
the valves N N¹ are opened, in each case at the time when the valves I I¹ are
being opened to exhaust, the pistons M M' are not resisted by the liquid, but cau
be moved outwards by and along with J and J. Obviously, instead of holding
the covers G G practically stationary during portions of the valve grar. motion,
and moving them during other portions of the motion, by connecting them to the
arins C C¹ as described with reference to fig. 1, they might be thus held and moved
by connecting them to suitable cams on the shaft of K or on other countershafts
revolving in time with the engine shaft. And in like manner the valves N N'
which as described with reference to fig. 2 govern the passage of the liquid resisting
the pistons M M³, might be moved by cams. The object is to retain on or in the
spring cylinder H, stops or abutments, such as G G' or M M' stationary or nearly
so when the springs urge the pistons J J¹ outwards, effecting the cut off to permit
these stops or abutments to move with J J when they move farther outwards in
opening the exhaust, and to cause the stops or abutments to return with J J' to
the position where they are to remain stationary while J J proceed farther
inwards, opening the supply, until the springs again propel them outwards cutting
off the supply.
Although I have described the lever arms B E and B¹ E¹ as being connected by
toggles D D¹, they might obviously be connected by any of the trip or trigger
'connections employed for Corliss valve gear. Also, instead of employing springs h h¹,
weights might be used or steam pressure might be made to act in the known
manner instead of springs.

page_text: Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I hereby declare that
I make no general claim to valves of steam engines of the partly rotating or Corliss
kind worked by toggles to open supply until, by the bending of the toggles, they
are left free to be closed by springs, nor do I claim the bending of the toggles so
applied by the action of tappets worked by eccentrics or cams, but what I claim
in respect of trip valve gear for steam engines is
1, In combination with the levers B and E connected together by toggles D or
their equivalents, the arms C and F linked respectively to the sliding cover G and
the spring piston J, substantially as and for the purpose herein set forth.
2, In combination with the levers B and E connected by toggles D or their
equivalents, the arm F linked to the spring piston J and the valve N and
connections for working it so as to govern hydraulically the movement of the
piston M, substantially as and for the purpose herein set forth.
נית
3751 T
AT 9
Fevruary 1000.
ABEL & IMRAY,
Agents for the Applicant,
28, Southampton Buildings,
London, W.C.
ABEL & IMRAY,
Agents for the Applicant,
28, Southampton Buildings,
London, W.C.