IMPROVED VALVE-GEAR FOR ROCK DRILLS, PUMPS AND THE LIKE to be as follows:
Year: 1884

page_text: I ARTHUR EDWARD MARSTON of Enderby in the county of Leicester, Gentleman
do hereby declare the nature of the said invention for "IMPROVED VALVE-GEAR
FOR ROCK DRILLS, PUMPS AND THE LIKE to be as follows:-
"
The valve casing is by preference cast or formed in one piece with the cylinder
and the valve which may be cylindrical is parallel with the cylinder. Two tappets
or levers are arranged to project into the cylinder so that the piston strikes each in
turn as it travels backwards and forwards in the cylinder. The tappets are
pivotted and have each an arm extending beyond the pivot which takes into a
recess near one. end of the valve. There is one pressure port in the casing and
two exhaust ports (or vice versa if the motion be reversed) and two pressure ports
or passages in the valve.
The steam or other compressed fluid enters the casing and passes by one port in
the valve to one end of the cylinder, drives the piston along until it strikes the
tappet at the other end and so reverses the position of the valve, and the pressure
is then upon the other side of the piston, the first side being by the motion of the
valve now open to the exhaust. Upon the return of the piston the tappet at the
first end of the cylinder is struck and the valve again reversed and so on.

page_text: I ARTHUR EDWARD MARSTON of Enderby, in the county of Leicester Gentleman,
do hereby declare the nature of this invention for "IMPROVED VALVE GEAR FOR
ROCK DRILLS PUMPS AND THE LIKE" and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement:-
.
This invention will be best understood by reference to the accompanying
drawings.
Figure 1 is an elevation half in section, showing the general arrangement suitable
for pumps and so forth where there is no special rebound of the piston; Figure 2
is a complete section of the apparatus particularly suitable for rock drills and the
like where the piston rebounds.
Figure 3 is a longitudinal section thro' the valve and exhaust branch.
A is the cylinder B the piston and C the piston rod.
D. E are the tappets pivotted at D' and E' and having their shorter ends D' E'
projecting into recesses F in the valve F.
These tappets-work in the ports or passages S through which the steam or
equivalent passes to and from the cylinder A. The valve is provided with ports
or passages P. G through which the steam or other fluid pressure is admitted and
released. In Figure 1 the valve is shown in full with the ports dotted inside it:
the opening opens into the port G and delivers the exhaust into the exhaust
branch H through a corresponding port I in the casing, shown in dotted lines in
the non-sectioned half of Figure 1.-In Figure 2 the valve is in section as well as
the rest.
The action is as follows:-
The fluid under pressure enters by the branch K in the direction indicated by
the arrow, and with the valve in the position shown is just entering the back
port P, previous to driving the piston B forward. The piston is at present in
contact with the back tappet E which is driving the valve forward in the direction
of the arrow thus bringing the back part under the pressure opening K¹ this is
more clearly shown in Figure 2.
The first steam or other pressure serves to cushion the piston but by the time
the piston has reached the end of its stroke, the tappet E has moved the valve F
to its full extent forward; and the full pressure behind the piston drives it forward
when its front end coming in contact with the lappet D. the operation is repeated
and the valve driven back. This series of operations is repented again and again
while the machine works.
The object of the port Q in the valve (Figure 1) is to let the steam have access
to the space at the end of the valve which is thus driven over and held there-
This is of importance especially when the valve is not in a horizontal position.
This form of the valve motion is well suited for pumps and the like where no
uncontrollable force comes into action upon the piston.
If however the drill bit in a rock boring machine strikes the rock before the
piston has travelled far enough forward to move the tappet and valve a sufficient
distance to open the port for the return stroke and then rebounds the valve may
never be opened at all and the machine will stick until the valve is operated by
hand so as to start it again.
To get over this difficulty the form shown in Figure 2 is provided.
The general arrangement of the valve and method of operating it are similar
to those of Figure 1 but in connection with the pressure entrance K' there is a

page_text: passage L which communicates with the space in which the valve works somewhat
as shown in the drawing. Near the end of the valve is another passage M which
when the valve is in the right position comes under the end of passage L thus
forming a direct communication between the inlet K¹ and the space R at the end
of the valve. There is also a recess N in the casing which at proper times is in
communication with the passage O in the valve. There is also at the other end of
the valve a passage Q communicating with the space R at that end of the valve.
The action is as follows:-
Suppose the piston to be travelling in the direction shown by the arrow and the
valve of course in the opposite direction this continues until each occupy the
positions represented in Figure 2 when the port P begins to take steam through K¹
and continues to do so until the pressure in that end of the cylinder is sufficient to
reverse the direction of the piston but before this has taken place the steam has
entered through the passage Q, completed the travel of the valve if necessary and
now holds it at one end of its stroke the steam in the space R at the other end
escaping into the main cylinder through the recess N and passage O So far
passages L and M do not come into use Now for the return stroke-both tappets
are close to the casting on the left hand sides, the piston travels outwards until it
encounters the tappet D when it moves the valve until the port G is on the point
of opening to K¹ when the drill bit in the piston rod strikes the rock and instantly
the piston rebounds; but the passage M by this time is on the point of opening
to Land the passage O has passed the recess N. thus shutting off communication
through it therefore the valve by its momentum travels on a short distance when
steam enters by L and M to space R thus driving the valve back to the other
cover.
Any steam behind the valve escaping through Q into the cylinder and so to the
exhaust and live steam entering the main cylinder through port G.
The exhaust escapes as before.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed I declare that what
I claim is
1. In a valve gear the combination with the cylinder A of the valve F. operated
by tappets D. E located in the passages S between A and F and receiving
motion directly from the main piston B substantially as set forth.
2. In a valve gear the combination with cylinder A of the valve F operated as
set forth and having passages or ports G. P which receive the steam or equivalent
from the branch K₁ and deliver it to the cylinder through the passages S which
contain the tappets substantially as set forth.
3. In a valve gear the combination with the supplementary valve ports M. O.
of the supplementary casing passages L. N. substantially as and for the purpose
specified.
Dated this 10th day of November 1884