IMPROVEMENTS IN HIGH SPEED ENGINES
Year: 1885

page_text: I WILLIAM LOWRIE, Engineer, of 18 Gibson Square, Islington, N. in the County
of Middlesex, do hereby declare the nature of my Invention for IMPROVEMENTS IN
HIGH SPEED ENGINES to be as follows:-
In high speed engines where two or more cylinders or tandems of cylinders are
used & where the ordinary method of steam compression is insufficient to overcome
the momentum & inertia of the reciprocating parts & prevent reversal of strains on
the connecting rods, I use an independant steam cushion piston rigidly attached
to each set of reciprocating parts to hold them tightly in one direction against
the crank.
These cushion pistons work in cylinders open at one end to the atmosphere or
condenser, and all opening at the other end into one common steain chamber.
This common steam chamber may be the steam chest from which the working
cylinders are fed or be a separate chamber for the cushion pistons only to work
into & where any desired pressure may be maintained.
I so arrange the cylinders around a crank, or the cranks, on a shaft, that the
steam pressure, on the system of cushion pistons whatever their number, may be
in equilibrium on the shaft and their reciprocating action does not alter the area
of the common steam chamber into which they work, therefore causing no
compression or expansion therein.
The engine may be either double or single acting & if single acting the steam
pressure may be applied either in the same or in the opposite direction to the steam
pressure on the cushion piston to which it is attached.

page_text: Fig. I is a vertical section through the 2 cylinders of a single acting high speed
steam engine. A A' are the working pistons, B B' are the cushion pistons, C is the
steam chest D is the exhaust chamber open to atmosphere or condenser, E is the
crank chamber,
I have not shewn in the drawings any valves for controlling the steain supply as
they may be of any ordinary or special construction.
The pistons B B¹ being open at one end to the steam pressure in the chest C and
at the other end to the chamber E balance each other on the crank shaft at any
part of the stroke when no steam is acting on the pistons A A', if however steam
is admitted under piston A¹ and piston A is open to the exhaust chamber piston A¹
would move upwards and piston B would do work downwards on its crank in
proportion to the work being done by piston A¹, thus each working piston destroys
the equalibrium of the cushion pistons and allows the cushion piston attached to
the other working piston to do work on the crank shaft.

page_text: At the commencement of the up stroke the inertia of either set of moving parts
will keep sufficent pressure on the crank pin, and as the steam would be cut off,
from the working cylinder before full speed was attained on the reciprocating
parts, the gradual diminuition of pressure therein, would allow the pressure on the
cushion piston to bring the mass to rest without a reversal of strains, and the
whole area of the cushion piston will be available for commencing the mass on its
downward stroke.
Fig. II is a vertical section through the cylinders of a single acting high speed
steam engine, here A A¹ are the working pistons B B' are the cushion pistons C is
the steam chest D is the exhaust chamber E is the crank chamber, F is the
cushion piston chamber, in which any desired pressure may be maintained. In
this fig. the cushion pistons will be in equalibrium as described in Fig. I, but the
working pistons are acting in the same direction, the full pressure on the cushion
pistons therefore is allways acting in a direction to prevent reversal of strains on
the connecting rods.
It is obvious that Figs. I and II could be combined to make a double acting
engine either with or without the chamber F. Either form could be compounded
by putting other pistons rigidly connected in tandem with each set That any
number of sets of pistons could be employed, either on seperate cranks set at equal
angles to each other or work on to one crank, the pistons being set at equal angles
around it. That the chamber in which the cushion pistons work in Fig. I might
be a seperate chamber as in Fig. II. The cushion pistons can be placed in any
position in relation to the working pistons.
Having thus described the nature of my invention and the manners of performing
the same I would have it understood that I claim-
First. The use in combination with the pistons or tandems of pistons of single
acting engines where two or more are used of cushion pistons rigidly attached to
each set, and balanced on the crank shaft by each other, and with the steam
pressure acting on them in the contrary direction to the steam pressure on the
working pistons substantially as herein before described.
Second. The use in combination with the pistons or tandemns of pistons of single
acting steam engines, where two or more are used of cushion pistons rigidly
attached to each set, and balanced on the crank shaft by each other, and with the
steam pressure acting on them in the same direction to the steam pressure on the
working pistons substantially as herein before described.
Third. The use in combination with the pistons or tandams of pistons in double
acting steam engines, where two or more are used, of cushion pistons rigidly
attached to each set, and balanced on the crank shaft by each other substantially
as herein before described.