Improvements in Machinery or Apparatus for Drawing Gas Retorts.
Year: 1895

page_text: Date of Application, 9th Mar., 1895-Accepted, 24th May, 1895
COMPLETE SPECIFICATION.
Improvements in Machinery or Apparatus for Drawing Gas
Retorts.
I JOHN WEST, of The Albion Iron Works, Miles Platting, Manchester, in the
County of Lancaster, 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 :-
This invention relates to improvements in the drawing apparatus for which
Letters Patent No. 5806 dated 17th March 1893, were granted to me, in which in
order to economise power when reversing the piston, the pressure on the two sides
of the piston can be equalized at any part of the stroke by means of a central
passage in the valve connecting, when the valve is in its central position, the two
passages leading to the ends of the cylinder; and has for its object to provide
means for bringing the parts of the drawing mechanism to rest at the end of each
stroke without any liability of damage from the momentum of the parts; and
consists essentially in providing separate inlets and exhausts from the cylinder and
in causing the piston to close the exhaust outlet at a short distance from the end
f its stroke so that any further motion compresses the enclosed air and brings the
parts to rest. A hand release valve is provided at the back end of the motor
cylinder to enable the rake bar to be brought back to its extreme position when
required, for example after each individual drawing is completed.
In the accompanying two sheets of drawings:-
Fig. 1 is a side elevation of the drawing machine constructed according to this
invention, and
Fig. 2 is a section of the motor cylinder, showing the inlet and exhaust
connections.
Fig. 3 is an elevation of the motor cylinder showing the arrangement of levers
and connections for working the valves.
Fig. 4 is a sectional plan of the motor cylinder and valve box.
Fig. 5 is a view of the slide valve box showing the port passages, and
Figs. 6, 7 and 8 are sections of the slide valve box and slide valve showing the
slide valve in various positions.
The drawing machine consists of an upright frame on wheels provided with
gearing for propelling the machine on rails in front of the retort stack. It is
fitted with a rack R driving a pinion S for giving an alternating motion to the
chain drum T and the chains U and V attached to the rake K for driving it into
and out of the retort when drawing the coke. The rack R is cottered to the rod a
of the piston Z working in the cylinder P. Compressed air is supplied through
the inlet to the valve box ; and a slide valve p distributes the air as described
hereafter. The slide valve p is operated to start the rack in one direction or the
other by the band lever k to which is attached a connecting rods for operating the
valve, and two tappet levers tt for automatically cutting off the air supply to
the motor cylinder and place the slide valve in its central position when the piston
approaches either end of its stroke.
In carrying this invention into practical effect, the slide valve box has five ports
two pressure ports m and n and three exhaust ports b c and o, the two outer ports m
and n are for the air supply passages to each side of the piston, the two inner
ports b and c are for the exhaust from each side of the piston and the centre port o
is the outlet to the atmosphere from the two ports b and c. The slide valve p has
a bye-pass passage p through it for connecting the two ports b and c with each

page_text: other when the valve is in its central position. The passage n n leading from the
port n to the top end of the cylinder P has a check valve f in it and so arranged
that the air when going from the valve box j along the passage nn will lift the
valve and be free to pass into the cylinder and to the top of the piston Z.
When by the operation of the slide valve the air pressure below the valve fis shut
off from the top of the piston Z the check valve will close. The passage m m
leading from the pressure port m to the bottom end of the cylinder P has a check
valve g in it so arranged that the air when going from the valve box j along the
passage m m will lift the valve and be free to pass into the cylinder and to the
bottom of the piston Z. When the air pressure below the valve g is shut off
the check valve g will close. The exhaust connections b b and c c leading from
the two inner or exhaust ports b and c enter the cylinder P at points situated some
distance from the ends of the cylinder.
The piston Z in passing over the exhaust ports b b and c c in the cylinder shuts
off the exhaust before the piston arrives at the end of the stroke and compression
of air confined between the piston and the cover will take place by the continued
motion of the piston and this compressed air will act as a cushion to prevent the
piston from knocking against the cylinder covers.
When the piston Z has made say half a stroke up and it is desired to return, the
air below the piston being at the working pressure and that above it at a lower
pressure, the slide hand lever k is pushed over and as the slide valve passes over
the centre the bye-pass passager in the valve p connects the exhaust ports b and c
thereby bringing the two ends of the cylinder into communication with each other
and an equilibrium of pressure takes place immediately, and when the slide valve
is moved farther over so as to open the outer or pressure port n to admit air to the
side of the piston Z for the return stroke, the pressure on that side of the piston
will have been raised in the manner and for the purpose described in
Patent No. 5806 dated 17th March 1893.
my former
But
The cushioning of the air at each end of the stroke of the piston will cause the
piston to act quicker in the reversing of the stroke when the rake K is fully out
in the retort and when the rake is being drawn out of the retort it will not be
brought back fully home in the hanging frame. E but the stroke will be sufficient
for drawing the coke out of the retort mouthpiece. This action prevents detrimental
shocks between the stops at the end of the hanging frame and the rake bar.
when all the coke has been drawn out of one retort and it is desirable to move the
drawing machine to the next retort to be drawn it will be necessary to exhaust the
air cushion from under the piston Z to enable the rake bar to be brought fully
home in the hanging frame E so that the rake may clear the retort mouthpiece
fittings. For this purpose the release valve d is placed at the bottom of the
cylinder and a set of levers connected to this valve are provided and worked by a
hand. lever e. By moving the hand lever e the valve d will be lifted against the
pressure and the air cushion will escape to the atmosphere at a speed determined
by the size of the passage and the pressure of air on the top of the piston Z will
cause it to complete its stroke and the rake will be brought back to the end of
the hanging frame E.
It will be understood that the same arrangement as herein described will
accomplish the same ends whether the motive force be obtained from .compressed
air or any other gas or expansive vapour under pressure and I do not limit myself
to the use of compressed air only.
Having now particularly described and ascertained the nature of my said inven-
tion and in what. manner the same is to be performed, I declare that what I
claim is:
.
"
1. In a retort drawing machine, providing the motor cylinder with independent
exhaust outlets at some distance from the ends of the cylinder so that after
passing the said outlets the motor piston compresses the enclosed air or gas and is
thus brought gradually to rest, substantially as described.

page_text: 2. In a retort drawing machine in which the pressure on the two sides of the
motor piston can be equalized at any part of the stroke the arrangement of
mechanism substantially as described with reference to the drawings for bringing
the parts to rest near the end of a stroke of the piston.
3. In a retort drawing machine in which the pressure on the two sides of the
motor piston can be equalised at any part of the stroke, providing the motor
cylinder with independent exhaust outlets at some distance from the ends of the
cylinder so that after passing the said outlets the motor piston compresses the
enclosed air or gas and is thus brought gradually to rest, and in providing a hand
valve at the back end of the motor cylinder for relieving the piston from the said
pressure to permit it to complete its stroke, substantially as described.
Dated this 7th day of March 1895.
WHEATLEY & MACKENZIE,
40, Chancery Lane, London, W.C., Agents.