IMPROVEMENTS IN APPARATUS FOR ACTUATING THE VALVES OF STEAM ENGINES
Year: 1874

page_text: PROVISIONAL SPECIFICATION left by Robert William Page at the
Office of the Commissioners of Patents, with his Petition, on the
2nd January 1874.
I, ROBERT WILLIAM PAGE, of High Holborn, in the County of
Middlesex, Engineer, do hereby declare the nature of the said Invention
for "IMPROVEMENTS IN APPARATUS FOR ACTUATING THE VALVES OF STEAM
ENGINES," to be as follows:-
:
My Invention relates to apparatus used for driving the valves of steam
engines, which are worked by excentrics fixed upon the revolving shaft
of such engines in the method well understood and practised, and has
for its objects an improved construction and arrangement of apparatus
by which the action of a single excentric may be so applied to the valve
that the engine may be reversed or stopped or the movement of the
valve modified for the purpose of working the steam expansively without
the use of two excentrics connected by a "link" motion or of a single
excentric loose upon the driving shaft as ordinarily used.
For the purpose. of carrying out my Invention I connect the rod or
spindle, which is attached to and drives the valve of the engine to the

page_text: rod which is attached to and driven by the excentric upon the driving
shaft by means of joints at the extremities of a link, which is itself
jointed at or near its centre. The joints at each end of this link are
connected to slides or guide bars, or to the ends of vibrating links, the
other ends of which turn upon fixed centres, so that they are guided in
a line straight or very nearly straight. If now the jointed connecting
link already described be bent, so that its central joint is removed to a
considerable distance from the straight line joining its extremities, and
if this central joint is then connected to guides, by which it is only
allowed to travel in a direction parallel or nearly parallel to the line of
motion of the valve spindle and the excentric rod, then when the
excentric is made to revolve, its rod together with the jointed connecting
link and the valve spindle and valve receive a motion practically the
same as if the end of the excentric rod were jointed to the end of the
valve spindle without the intervention of the jointed link described. If
on the other hand the central joint of the jointed connecting link be
connected to guides, by which it is only allowed to travel in a direction
at right angles, or nearly-at right angles to the line of motion of the
valve spindle and the excentric rod, then when the excentric is made to
revolve the action of its rod is to increase or decrease the angle at which
the jointed connecting link is bent, and thus practically to lengthen or
shorten the distance between its ends. If under these conditions the
excentric be turned, so that its rod is forced toward the valve its action
is to decrease (by further bending it) the angle at which the jointed
connecting link is bent, and thus to draw the valve spindle and valve
toward the excentric. If the excentric be turned so that its rod is forced
from the valve its action is to increase the angle of the jointed con-
necting link, and thus to force the valve spindle from the excentric. In
this position therefore of the guides which restrain and regulate the
i movement of the centre joint of the jointed link, the action of the
excentric upon the valve is exactly the opposite of its action in the
position of the guides first described, and the movement of the engine is
accordingly reversed. In any position of the guides between the two
described the action of the excentric upon the valve partakes more or
less of that in the two positions described, and the travel of the valve
can thus be diminished and the steam worked expansively, whilst in a
central position between the two first described the action of the
excentric is neutralized and the engine is stopped.

page_text: In order to vary as desired the position of the guides which regulate
the movement of the central joint of the jointed link as above described
I prefer to connect such central joint to one end of a bar or rod of
suitable length, the other end of which is jointed to a pin, which can be
fixed either in such a position that the bar or rod is at right angles to
the line of motion of the valve spindle and valve or parallel with it.
For this purpose I prefer to attach such pin to one end of a lever, which
turns upon a fixed centre at or near the central joint of the jointed link,
round which fixed centre it can be turned into the desired position by
means of a handle, which can be fixed where required.