Year: 1887

page_text: Date of Application, 26th Oct., 1887
Complete Specification Left, 25th July, 1888
Complete Specification Accepted, 12th Oct., 1888
I, ABRAHAM DAVY, Junior, of Park Iron Works, Sheffield, Engincer do hereby
declare the nature of this invention to be as follows:-
My Invention relates to self acting steam hammers (including tilt hammers) using
either compressed air or steam, and it has for its object to entirely dispense with the
usual actuated distributing valves.
For convenience, the invention will be described with reference to a steam hammer
but it will be understood that it is not limited in this respect and that the operation
is the same when compressed air is used.
According to my invention, the piston is fitted in a cylinder whose lower end is
always open to steam pressure and in which the steam is exhausted from the lower to
the upper side of the piston and thence to the atmosphere, the arrangement of the
exhaust ports and the length of the piston being such that one of the ports is always
closed by the piston. The length of the piston is about equal to its stroke and the
areas of the upper and lower faces of the piston are so proportioned that the steam
after having passed from the under to the upper end of the cylinder will, owing to
the larger area of the upper surface of the piston, overcome the pressure of the steam
on its underside.
The operation is as follows-Steam is admitted to the underside of the piston by
means of an ordinary stop cock or valve which remains always open whilst working
whereby the piston is caused to ascend. At about half its upward stroke, the piston
begins to uncover the exhaust port at the lower end of the cylinder and when this
port by the further travel of the piston, is sufficiently uncovered, the steam passing to
the upper
end of the cylinder and acting upon the larger area of the top side of the
piston, overcomes the resistance on the underside and drives the piston down. When
the piston has arrived at about half its downward stroke, it begins to uncover the
exhaust port at the upper end of the cylinder and continuing to descend, it further
opens this port and allows the steam to escape, whereupon the pressure on the underside
of the piston again asserts itself and the operation is repeated.
كيم
A. DAVY, JR.
By A. M. & Wm. Clark,
53, Chancery Lane, London,
Patent Agents.

page_text: 1, ABRAHAM DAVY, junior, of Park Iron Works, Sheffield, Engineer, do hereby
declare the nature of this invention 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 self-acting valveless power bammers whether of the direct
acting or tilt-hammer type and whether worked by steam or compressed air-and it
has for its object, whilst entirely dispensing with the usual distributing valve and
causing the piston to act as its own valve, to enable the hammer not only to operate
on a moderate thickness of material but to deliver a fairly hard blow upon the material
when required, that is to say to enable the hammer to operate upon work of variable
thickness and to deliver blows of variable force.
I am aware that similar valveless percussive engines have heretofore been proposed
but they have been so arranged and proportioned as to have but a very short stroke
and they have consequently been non-effective in practice, whereas to comply with the
above mentioned requirements it is essential that the hammer should have a long
stroke which can only be obtained by so proportioning the circulation and exhaust
ports that the former by which steam is conveyed from the lower to the upper side of
the piston shall be opened gradually and not before the piston has performed half of
its upward stroke, and similarly for the latter port on the downward stroke.
Reference is to be had to the accompanying drawing which represents in figure 1 a
vertical section of a direct acting steam hammer, and in figure 2 a development of
the interior of the cylinder shewing the dimensions of the ports. The same letters of
reference indicate like parts in both figures.
In this class of hammer, the piston A is fitted in a cylinder B whose lower end when
the hammer is in work is always open to steam pressure, the steam being circulated
through a port C from the lower to the upper side of the piston A and thence exhausted
through a port D to the atmosphere, the position and length of the ports C and D and
the length and stroke of the piston being so arranged and proportioned that one or
other of the ports shall always be closed by the piston. The length of the piston is
about equal to its stroke and the area of the upper face of the piston is so much
greater than that of its lower face that the steam acting on the upper face will, when
cut off from its source of supply, be able (supplemented by the momentum acquired
by the hammer and piston in performing half the downward stroke) to overcome the
live steam acting on the lower face sufficiently to maintain the downward impulse of
the piston. For example, let the piston be six inches diameter and have twelve inches
stroke The cylinder would be supplied by a pipe E say 14 inch diameter which
would have a full opening to the lower end of the cylinder. The circulation passage C
would, at its port or opening to the lower end of the cylinder, have an area equal to
that of the steam pipe and it would be of such proportion in length to width that its
length in the direction of the length of the cylinder would be equal to half the stroke

page_text: of the piston, i.e. six inches and its width would consequently be and inch. The
exhaust port D is of similar shape and dimensions and is so situated as never to open
to the lower side of the piston. The piston has no lap, that is to say its length is
just sufficient to cover both ports when at its mid-stroke.
The operation is as follows:--Steam is admitted to the underside of the piston by
the inlet E whereby the piston is caused to ascend. At half its upward stroke, the
piston begins to uncover the circulation port C and the steam passing to the upper
end of the cylinder and acting upon the larger area at the top side of the piston,
overcomes the steam pressure on the underside and drives the piston down. When
the piston has arrived at half its downward stroke it begins to uncover the exhaust
port D and allows the steam to escape gradually the pressure on the underside of the
piston ultimately prevailing whereupon the cycle of operations is repeated.
The hammer head or tup may either be on the end of the piston rod, as shewn, or
the piston rod may act on the beam of a tilt-hammer.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, I declare that what
I claim is
The herein-described long-stroke valveless power hammer wherein the piston controls
the admission, circulation, and exhaust of the motive fluid and wherein the circulation
and exhaust ports are narrow slits having their maximum dimension in the direction
of the stroke of the piston and each equal to about half the length of the piston stroke,
substantially as specified.