IMPROVEMENTS IN THE CONSTRUCTION AND ARRANGEMENT OF VALVES FOR STEAM ENGINES AND IN THE MODE OF WORKING THE SAME
Year: 1876

page_text: PROVISIONAL SPECIFICATION left by Grosvenor du Vallon at the Office of
the Commissioners of Patents on the 4th November 1876.
GROSVENOR DU VALLON, of Birmingham, in the County of Warwick, Engineer.
"IMPROVEMENTS IN THE CONSTRUCTION AND ARRANGEMENT OF VALVES FOR STEAM
ENGINES AND IN THE MODE OF WORKING THE SAME."
My Invention has for its object the construction and arrangement of the valves
of steam engines in such a manner that instead of having as usual to set the
steam valve crank or eccentric a certain number of degrees over ninety in advance
of the piston crank, in order to give the valve its proper lead, and to shift the
said crank to a corresponding position behind the piston crank when required to
reverse the engine, the valve crank can be set once for all ninety degrees in advance
of the piston crank, the steam chest being made capable of being shifted round the
centre of the crank shaft a number of degrees equivalent to the amount of lead
desired in a direction to the left of the cylinder if the crank travels from left to
right, and to the right if the crank travels from right to left, thereby effecting the
reversing when required. For this purpose my Invention consists in the combi-
nation of two valves applicable generally to steam engines with cylinders, and more
particularly to steam engines with several cylinders (two, three, or four) in which
the pistons are directly connected with the cranks without piston rods whether the
cylinders be single or double acting. One of such valves (the steam valve proper) is
set in motion by the crank shaft direct, and its face, instead of sliding or revolving
against a fixed surface or seating (as usual) in which the cylinder ports are cut out,
is made to slide by rotary motion on the face of a circular valve in which certain
ports are cut out corresponding in number to the number of cylinders if single
acting, or twice the number if double acting, and communicating ultimately with
the respective ports of the said cylinders, but so extended and arranged on the
above-mentioned face that, combined with the motion of the rotating valve they
may give to the latter the proper amount of lead for each cylinder respectively. This
second valve, which constitutes an important feature in the combination, is provided
with a spindle which prolonged to the outside through a stuffing box carries a lever by
which the valve can be slightly turned on its axis, and the lead thereby altered and
reversed as required, each port in the valve still preserving its communication with
the same cylinder port.

page_text: The rotating valve has two radial grooves next to the shifting valve, and one
circular groove on its back face.
Of the two radial grooves one communicates with a hollow cavity in the centre
of the valve where steam is first admitted, and from whence it is supplied through
the said radial groove to the shifting valve; the other groove occupies about two-
thirds of the opposite radius, and is carried through the thickness of the valve to
the circular groove at the back, which groove is in constant communication with the
exhaust pipe.
The admission of steam to the centre cavity of the rotating valve is so made
that this valve is kept pressed between the shifting valve and the exhaust face,
thereby preventing leakage on either face. The amount of such pressure can be
regulated so as to produce almost an equilibrium. Both the valves are contained in
a steam chest, and can be made in the form of two cylinders placed on end and
having their axis in a line with that of the crank shaft at one end of the latter, or
of two concentric cylinders, one within the other, or of two concentric cones one
within the other; or the shifting valve may be made in the form of a circular. plate
with chambers cast round its centre, corresponding in number with that of the
cylinders, and containing slide valves all worked by the same excentric or crank
fixed on the crank shaft, which is prolonged through the said plate or shifting
valve; or the steam chest itself may be made to act as a shifting valve,
provided it be connected with the body of the engine by means of a trunnion joint
to allow of shifting without leakage.
In all the above or in other suitable forms of the valves it is to be observed as a
prominent feature of my Invention that the steam valve proper does not supply
steam directly from the steam chest, but that the steam is first passed through the
shifting valve.