IMPROVEMENTS IN MOTIVE-POWER ENGINES
Year: 1878

page_text: PROVISIONAL SPECIFICATION left by Andrew Barclay at the Office of the
Commissioners of Patents on the 29th April 1878.
ANDREW BARCLAY, of Kilmarnock, in the County of Ayr, North Britain, En-
gineer. "IMPROVEMENTS IN MOTIVE-POWER ENGINES."
The improvements constituting this Invention relate to that class of motive-
power engines which are driven by steam, gas, air, or equivalent motive agent.
The first part of the improvements relate to the slide valves of such engines, and
this part consists in the adaptation of a packing ring to the back of such valves
for the purpose of displacing the pressure of the motive agent from the back of
such valves. The packing ring has two working surfaces at right angles to each
other, viz., the vertical or cylindrical surface, which fits and works in the cylin-
drical receptacle on the back of the valve, and a horizontal surface, which bears
against the under side of the steam chest cover or equivalent surface. The packing
ring herein-before mentioned is kept in its place when the steam is off by one or
more springs.
The second part of the improvements relate to the working of the slide valve in
engines which are not provided with a rotating crank or equivalent shaft. This
part of the improvements consists of a tappet rod driven from the piston rod of
the engine. The tappets on this rod are for the purpose of actuating the levers by
means of which the slide valve is moved into some of its several positions, and for
freeing the cataracts by which the valve is moved into certain of its other posi-
tions. The outer portion of the valve spindle has formed on it or is fitted with a
frame with slots and cross pieces, in and upon which the wipers by which the valve
is driven act. The valve gearing is also provided with interlocking quadrants for
the purpose of holding the valve gear and its connections in a locked or free con-
dition.
In place of using the ordinary water cataract, as applied to Cornish pumping and
other engines, I employ a steam cylinder fitted with a piston in direct connection
with the steam pipe or other conduit for the conveyance of the motive agent, the
pressure of the steam or other motive agent.acting in place of the ordinary weights
in operating the cataract.
:

page_text: In place of the foregoing arrangements for operating the valve, what is known
as a weighted tumbling lever in combination with tappets and levers, with the
cataract, may be used.
The third part of this Invention relates to apparatus for controlling the action
of the motive agent admission valve of engines. This consists of a small cylinder
provided with a pair of valves opening outwards to the atmosphere, and with
another pair of valves, one between each end of the cylinder, and another smaller
cylinder connected thereto. Both cylinders are fitted with a piston and piston rod.
The piston of the cylinder first referred to is connected by levers to the piston rod
of the engine, and by these the piston of the one cylinder is operated. The effect
of so operating the piston is to form a partial vacuum under the piston of the
smaller cylinder, and in opposition to the tension of a spring tending to draw that
piston outwards. The extent of vacuum is regulated by a variable orifice by which
the admission of air is controlled. The piston rod of the small cylinder last referred
to is connected with the lever which opens and closes the admission or throttle
valve, and a lock is provided for keeping the valve entirely closed when neces-
sary.
The fourth part of these improvements relate to the expansion and slide valve
gear of motive-power engines, and the object of this part of the improvements is
to enable the engineman to have full control over the engine by the expansion gear
alone, and for preventing the wire-drawing of the steam or other motive agent. In
this improved gear the expansion valve handle and the main valve handle are
mounted preferably on the same centre, and they are preferably provided with inter-
locking gear so that they can be united and work as one when the engine is not
working expansively, or when stopping and starting. Or the handles may work
separately when the engine has been operated expansively. The levers herein-before
referred to are connected to the ordinary link motion.