Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to a control
system for a hydraulically powered, self-
advancing mine roof support.
Such supports are employed for instance
in longwall coal mining operations and incorporate
a plurality of hydraulically extensible chock
legs extending between a floor-engaging base
member~s) and a roof-engageable roof beam~s),
at least one advancing ram extending from the
support to a pan of an armoured conveyor
extending along the coal face. The support
may also include hydraulic rams to actuate
forepoling beams or for other purposes. All
these hydraulic devices are operated from a
bank of valves and a common system is for the
"adjacent control" technique to be employed
whereby the support operatorl under the
protection of a support set in its roof
supporting condition, operatés a bank of valves
in that support firstly to lower an adjacent
support from the roof J with either full or
partial disengagement of the roof beam(s) from
the roof, secondly to advance that support to
the previously-advanced conveyor, and thereafter
to re-set the support in its roof engaging
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,~ `condition by admitting pressure fluid to the
chock leg(s) to extend the latter. However,
correct setting of the chock legs is governeal
firstly by the required setting pressure
being available from the hydraulic mains
supply line and secondly by the operator holding
the relevant valve open a sufficient length
of time to allow the pressure to stabilise
between the mains supply and the chock leg(s).
The present invention is aimed at
providing a mine roof support control system
whereby the setting pressure in a leg is
positively ensured once the relevant valve
has been actuated by the operator, irrespective
of how long that valve is held open.
According to the present invention, a
mine roof support control system comprises an ~-
auxiliary valve interposed between a main
- valve and a chock leg(s) in a fluid supply
line extending from a high pressure line to the
support, a bypass line connected to the high
pressure line in advance of the main valve and
extenaling to the auxiliary valve, the auxiliary
valve being so constructed as to open upon
sensing a predetermined pressure and to close
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; upon sensing a higher predetermined pressure.
Thus, once the ni~ain valve is actuated
by the operator to supply fluid to the chock
leg(s) to effect extension thereof to set the
support to the roof, this higher pressure is
sensed by the auxiliary valve which then moves
to an open condition whereby pressure fluid
is able to bypass the main valve and to pass
from the high pressure line through the ~;
auxiliary valYe and thereafter to the chocX
leg(s), irrespective of the length of time
that the main valve is held open, the auxiliary
valve subsequently sensing the attainment of
the higher predetermined pressure whereupon it
moves into a closed condition to shut off
the bypass line. ~`
In principle, the auxiliary valve's
bypass line can be connected either to a -~
conventional mains pressure line if the latter
is able to supply hydraulic fluid at the-
required leg setting pressure or to an auxiliary -
Fressure line containing fluid at the required
leg setting pressure.
In detail, the auxiliary valve may
comprise a main port extending through the
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valve body, first and second ports intersecting
the main port and each first and second port
housing a spring loaded hydraulically balanced
poppet valve member, the first port being
intersected by an auxiliary inlet port connectable
to a bypass line, the intersection being at a :
neck between the valve member and a head
carried by the neck, the head being subjectable
to fluid pressure within the main port and -
being displaceable from the main port to unseat
the valve member upon fluid loading on the head
being greater than the spring loading in the ~`
opposite direction, a transfer port communicating
the first port downstream of the valve member
thereof to the second port, the poppet valve ~ ;
in the second port opening upon fluid passing
through the first port to the second port via
the transfer port , and thereby into the ;::;
. main port, and the second poppet valve being
closable under the influence of its spring ~ -
upon fluid pressure in the main port equalling .~uid pressure in the second port, the transfer ~;
port, and the first port.
In operation the auxiliary valve does
not interfere with any of the main valve functions
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-~but ensures that when the chock leg(s) has
been set for instance in excess of 55 bar
(800 psi f) the auxiliary valve opens allowing
the higher pressure to automatically raise
the leg pressure to the pressure existing in
the high pressure line whether this be a mains
line or an auxiliary boost pressure line.
The auxiliary valve is therefore fully
automatic, and can be manufactured of small
size and hence relatively inexpensively. It
can be mounted in single or any multiple bank
- unit to suit the hydraulic circuit or mounting
facilities. The body of the auxiliary valve
may be made from brass and the poppets from
stainless steel. A shut-off valve may be
provided to lock out the auxiliary valve should
the need ever arise.
The invention will now be further described
by way of examples, with reference to the
accompanying drawings in which
Figure 1 is a first embodiment of
schematic circuit of the mine roof support
control system in accordance with the present
invention;
Figure 2 shows a second embodiment of
such a circuit; and
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;.,~ Figure 3 shows a suitable auxiliary valve.
In all Figures like reference numerals
are employed for like components.
In the circuit of Figure 1, the mine
roof support control system can be seen to
comprise a hydraulica]ly extensible chock leg 1
- of a hydraulically ~owered, self-advancing
mine roof support shown at lA a high pressure
line 2, a main valve 3, a fluid supply line 4
extending between the main valve 3 and the
chock leg 1, the supply line 4 incorporating
an auxiliary valve 5, while.a by-pass line ~
connects the auxiliary valve 5 to the high pressure ;
line 2 at a location upstream of the main
valve 3, the by-pass line 6 incorporating a
- shut-off valve 7. -~
In the circuit of Figure 2, a boost
pressure line 8 is provided and the by-pass
line 6 connects the auxiliary valve 5 to the ~;
boost pressure line 8-. Otherwise the circuit
is as described with respect to Figure 1.
For the circuit of both Figures 1 and
2, the auxiliary valve is as shown in ~igure
37 and comprises a main port 9 extending through ~ ;
the valve body 10, first and second ports 11 ;
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"and 12 respectively intersecting the main port
9 and each first and second port 11, 12 housing
a spring loaded hydraulically balanced poppet
valve member 13, the first port 11 being
intersected by an auxiliary inlet port 14
connectable to the bypass line 6, the inter-
section being at a neck 15 between the valve
member 13 and a head 16 carried by the neck,
the head being subjectable to fluid pressure
within the main port 9 and being displaceable
from the main port 9 to unseat the valve member
13 upon fluid loading on the head 16 being
greater than the spring loading in the opposite
direction. A transfer port 17 communicates
the first port 11 downstream of its valve member
13 to the second por.t 12, the poppet valve 13
in the second port opening upon fluid passing
through the first port 11 to the second port 12
via the transfer port 17, and thereby into the
main port 9, and the second poppet valve 13
being closable under the influence of its spring
upon fluid pressure in the main port 9 equalling
fluid pressure in the second port 12, the transfer
port 17, and the first port 11.
In use, to extend the chock leg 1, the
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~operator moves a control handle (not shown)
on the main valve 3 to connect the high pressure
line 2 to the supply line 4. The resulting
increase in pressure iII the main port 9 of
the auxiliary valve 5 acts both on valve member
13 of port 12 to urge that valve member into
tighter seating engagement and on head 16 to
displace the latter away from the main port 9
and hence unseat the valve member 13 of port :~;
11. This puts the auxiliary inlet port 14
into communication with transfer port 17, the
auxiliary communication port 14 being connected
to the by-pass line 6, so that with the circuit :
of Figure 1 the fluid in high pressure line 2 :
is in communication with the transfer port 17
or with the circuit of Figure 29 the boost
pressure line 8 is in communication with the `~
transfer port 17. Such pressure in the transfer : .
port 17 unseats the valve member 13 in the ~ `
port 12 thereby transferring fluid from the
transfer port 17 into the main port 9 and hence
via the supply line 4 to the chock l~g 1. This
flow of fluid continues until fluid pressure in
the main port 9, the first and second ports 11
and 12 and the transfer port 17 are equal,
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~hereupon the valve mem~r 13 in the second
port 12 closes under the influence of its
spring loading and the operating cycle is
complete.
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