IMPROVEMENTS IN PISTONS AND PUMP BUCKETS
Year: 1885

page_text: COMPLETE SPECIFICATION.
I, WILLIAM JOHN MURGATROYD, of 21 Dross Street, Back Lane, Bowling,
Bradford in the County of York, Engineer, do hereby declare the nature of my
invention for "IMPROVEMENTS IN PISTONS AND PUMP BUCKETS
" 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 placing the piston rings wider apart at the bottom side
of a piston than they are at the top side, in the pistons of steam engines which
work horizontally or at an angle, in order to take advantage of the pressure of
Steam in the cylinder which acts upon the greater space between the rings at
the bottom side of the piston and thereby lifts the weight of the body of the piston
and reduces the friction and wear of both the piston and the cylinder.
In order to carry out my invention I form two or more grooves round the cir-
cumference of the body of the piston which grooves are not as heretofore made
parallel to each other but are made nearer to one another on that side of the
piston which is uppermost in horizontal or diagonal cylinders, whereby the rings
are wider apart at the bottom side of the piston, and upon the wider space thus
left, between the rings, at the bottom of the piston, the pressure of the steam in
the cylinder exerts a lifting force, and the greater the space between the two piston
rings, at the bottom side of the piston, in proportion to the narrow space between
the rings at the top side of such piston, the greater will be the lifting force
exerted by the steam. I therefore make the space between the rings, at the
bottom side of the piston, proportionate to the weight of the body of such piston
and to the pressure of steam in the cylinder, so that the pressure of steam in the
cylinder may, as nearly as possible, bear the weight of the body of the piston,
whereby friction is reduced, and the excessive wear of both piston and cylinder
are prevented.
My invention is not applied to any special kind of metallic piston rings, but to
any kind which fit in grooves, formed round the body of the piston, and which
work in the cylinder as nearly as possible steam tight.
The rings are prevented from turning round, or altering their position in the
grooves of the piston, by pins screwed into the body of the piston, and which
project into a hole or slot in the piston rings, or into the space between the two
ends of the piston rings, where they have been divided.

page_text: In order to enable my invention to be fully understood, I will proceed to describe
the same, with reference to the accompanying drawings, in which,
Figure 1 represents a sectional elevation of a piston, in which the piston rings
are placed at an angle to one another, as described.
Figure 2 is an elevation of the same.
Similar letters refer to similar parts in both the drawings. The body of the
piston A, has grooves G and H, formed round it, into which the rings B and C
are fitted. The space E, at the bottom side of the piston, between the two
rings B and C, is larger than the space D, between the rings at the top side of the
piston.
The pressure of steam at the bottom part of the piston, which is between the
piston rings, therefore takes effect upon a larger area than that situated between
the rings at the top side of the piston, and thereby tends to lift up, and boar
the weight of the piston, and to reduce the friction thereof upon the bottom side
of the cylinder.
The difference in distance between the piston rings at the top and bottom sido
of the pistons; is regulated according to the weight of the body of the piston, and
also according to the pressure of steam in the cylinder, that is to say, when a high
pressure of steam is employed, the excess of area acted upon by the steam on the
bottom side of the piston, over the area acted upon on the top side of such piston,
will not require to be so great as when a lower pressure is used.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I. claim is
•
"
1. The construction of pistons or pump buckets, with rings placed in grooves, at
an angle to each other, or with rings placed nearer to each other, upon the top side
of a piston working horizontally, or diagonally, and further apart at the bottom side
of such piston, in the manner and for the purpose herein set forth, or any mere
modification of the same.
2. The method of utilizing the working pressure of steam, in engine cylinders
placed horizontally or diagonally, to lift up and bear the weight of the piston,
whereby friction is lessened, and the wear upon the piston and cylinder reduced,
in the manner substantially as described.
D1 of March 1885