Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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BACKGROUl'lD TO THE INV~NTIO~
The present invention relates to hydraulic
control apparatus for operating the support props o~
a mineral mining installation.
S Control apparatus is described in published
German patent speci~ication P27 49 312.5 which u~ilizes
manual-operable control valves which serve to connec-t
pressure fluid feed and return lines selectively to the
workir.g chambers of associated props. The apparatus
employs an automatic setting arrangement composed of
valve devices. This arrangement automatically connects
the prop chambers, charged with ~luid to extend tbe
props, to the pressure line once a threshold pressure
is exceeded. This ensures the props can be properly set
against the roof even if one o~ the control valves is
operated prematurely to disconnec-t the pressure line
to an associated prop chamber. The automatic setting
arrangement isolates the prop chambers from the pressure
line once the setting pressure is reached. ~xcessive
pressure is prevented irom building up in the prop
chambers by means o~ pressure-relie~ valves set -to
respond at pressure above the normal setting pressure.
The threshold pressure level at which the setting
arrangement comes into opera-tion is higher than that
present in the prop ~hambers when the props are being
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! extended freely without contact wi.th the roo:E and
less than the setting pressure. The threshold pressure
is selected so that any prop can be extended and re-
tracted by operation of the associated control valve
freely and -the prop can be extended until its roo~
; cap or the like actually contacts the roof without
the se-tting arrangement coming into action. This
enables repair and main-tenance work, and any back
filling necessary inthe event of roo~ ~alls, to be
per~ormed without the automatic setting arrangement
becoming a~fected. Generally the threshold pressure
at which the setting arrangement comes into operation
l is in the range 50 bars to 150 bars while the pressure
i in the pressure line is signi~icantly higher---typically
! 1S ahove 300 bars and in the range 350 bars to 450 bars.
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l A general object of the present invention
., is to provide improved control apparatus ~or operating
the support pxops oi a mining installation and
improved valve devicec ior use in such apparatus.
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SUMMARY OE T~IE INVENTTON
Hydraulie eontrol appara-tus construc-ted in aceor-
clanee wlth the inven-tion comprises a con-trol valve deviee
for selectively eonneetin~ first and seeond working
ehambers of an associated support prop -to pressure fluid
~eed and return lines to effeet ex-tension and retraetion
of -the prop , a pressure-relief valve deviee eonneeted or
eonneetable to the return line and to the first working
ehamber of the prop whieh is eharged wi-th pressure fluid
by the eontrol valve deviee when the prop is to be
ext_nded and set and automatic set-ting means for eonnee-
ting said first working ehamber to the pressure fluid feed
l:ine indepelldently of the eon-trol valve clevice when a pre-
cleterminecl thre~shold pressure is e~ceeded thereill sign:ifying
that the prop i.s bei.ng set allC~ :EOI~ thereafter disconnecting
said first working chambers .frorn the pressure fluid line
when a desired setting pressure is reaclled inclependently
of -the control valve device; wherein the pressure at which
the automatic means disconnec-ts the first work:i.ng chamL)er
from the pressure flulcl feecl line is just lower thall -the
; 20 response pressure of the relief~valve device at which the
. latter opens to connect -the first working chamher to the
;~ return line and the relief-va.lve device :is designed -to pass
a max.-imutrl throughflow quantity oc pressure fluicl at least
t.he same as the maximum throughflow quantity of fluid
passed through the con-trol valve device during extension
and setting of the prop.
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Control apparatus cons-tructed in accordance with -the
invention can utilize a manually-operable control valve
device which can be set with a lever to various positions
to connect the chambers of an associated roof support prop
to the pressure fluid feed and return lines to effec-t ex-
tension and retraction of the prop in a manner known per
se. Pre~erably the control valve device has -the so-callecl
"dead-man's handle" mechanism which causes the device to
adopt a neutral posi-tion when its lever is released to
0 isolate the pressure li.ne Erom -the pI'Op pressure chamber
which is used to ex-tend the prop. The pressure-~relief
valve device is connected to -the prop pressure chamber to
prevent excessive pressure bui:lclillg up.
The pressure at which the automatic se-t-ting arrange-
men-t disconnects the pressuIe line from the prop pressure
chamber is preferably not more than 10% lower and expedi-
ently 5% less than the response pressure ot the relief
valve device. This development permits the props to be
set with a force in the range of their full rated loading
without the possibility Oe damage to the relle~f valv~
devices. To achieve the high setting force, the workillg
pressure in the pressure flu:id feed line must be corres--
pondingly high to take account of` unavoidable pressure
drops and fluctuations. The working pressure is prefer-
ably somewha-t bigher than the se-tting pressure. Because
of pressure f`luctuations which occur -the pressure prevaili.ng
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at the onset of the setti.ng operation e~fected by the manual
actuation of the main control device can easily reach a peak
value which causes the assoc:iated pressure-relie:e valve device
to respond. However, by making the latter valve device pass
a hi.gher quarltity o e pressure .fluid than is norl~al and at least
the same as that passing through the control valve device the
entire quantity of fluid passed through the control valve device
can be conveyed away safely by the relie~ valve device unti.l
the prevailing pressure falls back below the response pressure.
A pressure-relief valve suitable for this task can be based on
that described in German published Paten-t Specifications 1750834
and 2803283. However, the in-ternal fluid i`low cross-section
Oe the valve must be increase~cl to permit the aforesaid :Larger
throughflow characteristics.
The present invention also provides a hydraulic control
apparatus Ior controlling a pressure-fluid operated roof support
prop of mining appara-tus; said appa.ratus comprising main pressure
fluid feed and return lines; a manually-operable control clevice
for selectively connecting the feed ar~d return lines to
worklng chamber of -the prop -to effec-t e~ten~ion and retrac-tion
thereof; a setting valve~ device connec-ted to a :first work:ing
ch~mber o~ the prop which is charged with fluid to e~ec-t
extension o~ the prop and to the pressure line, said valve
device being settable to a firs-t state where connection is
established between said working charnber and the pressure
line or a second state, where connection is bro~sen between
the pressure line and said working chamber;
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a flrst control piston of the valve dev:ice l`or causing the
valve device -to adopt said firs-t state when exposed to pres~
s~re above a threshold level signifying the prop is being
set; a pressure-relie~ valve clevice connected to said
working chamber to respond and open at a pressure signifying
setting of the prop has been effected; a further control
: piston of the setting valve device to cause the setting
valve device to adopt the second s-tate when the setting pres-
; sure has been esta~lished in said vor~sirlg chamber and a
0 second pressure-relief valve device conrlected to the worlcing
chamber of the prop, the second relief valve device being
set to respond and open to relieve pressule in the working
; chamber of the prop at a reSpOrlSe p:ressure sl:i.ghtly ~reater
than that at which the fi.rst pressure-rel:ief v~lve device
]5 responds and the second reliei valve devi.ce serving to pass
a maximum pressure fluid quantity ~vhen opened at least
equal to that passed by the control device when the latter
connects the pressure line to the working chamber of the
:~ prop.
The inventlon may be understood more readily, and
: various other aspects and features of the invention may
become apparent, from consideratlon of the following
description.
BRIEE DESCRIPTION OE DRA~YING
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An embodiment of the invention will now be clescr:ibed, by wa~7of ex ~ple
only, with reference to the acccmpanying drawing, wh:ich is
a!sch~l-tlc representation of hydraulic con-trol a~aratus const~rcted
in accord,~nce with the inven-tion.
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DESCRIPTION OF PREFERRED EMBODIMEN~S
As shown in Figure 1, con-trol apparatus has a settin~
valve device 11 connec-ted by way of example through conduits
or lines 13, 14 to the working chambers 10l, 10" of an
h~draulic prop 10 and to pressure ~luid Eeed and return lines
P, R. It is also possible to connect the valve device 11 to
several props instead of a single prop as shown. The valve
device 11 is capable of adopting one of three se-ttings or
states depicted schematically in the drawing. The valve device
11 preferably has a housing with flat surfaces for face-to-face
mounting at some convenient location and employs a rotary slide
valve actuated by a pivotable control lever accessible at the
exterior of the housing. The valve device 11 is provided with
an automatic return mechanism - the so-called 'dead man's
handle' - which automaticall~ brings the control lever back
to a neutral position when released. This neutral position
corresponds to a neutral state or setting designated O and
shown to be adopted in Figure 1. In the state O~ the device 1
connects the chamber 10" to the return line R while isolating
the chamber 10' from the pressure line P.
With the valve device 11 set to the control state designated 1
the chamber 10' is connected to the pressure feed line P via
the non-return valve 43 while the chamber 10" is connected to
the return line R. This setting state 1 initiates extension
and setting of the prop 10. With the valve device 11 set to
the control state designated 2, the chamber 10' is connected
to the return line R while the chamber 10" is connected to the
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pressure feed l:ine P. This setting state 2 initiates posi.tive
retraction of the prop 1. With the device 11 set to the acti~e
states 1 or 2, the typical flow rate of pressure fluid through
the device 11 is 50 litres per minute at a typical working
pressure in the feed line P of about 4QO bars. In practice,
the pressure in the feed lines fluctuates from time to time
and changing the valve device 11 -to the setting state 1 does
not always ensure that the prop or props associated therewith
will become set in roof contact with a setting pressure corres~
ponding to their proper full rated loading. A pressure-relief
valve device 12 is connected to the line 13 leading to the
chamber 10' and hence to the chamber 10l of the prop 10. The
device 12 is also connected to -the fluid return R. The device
12 is set to open at a response pressure approximately
corresponding to the rated loading-typically 370 bars. Thus,
when this pressure is established in the cha,mber 10', after
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the valve device 11 has been set to state 1, the device e
12 opens -to preclude any pressure r:ise due to surges and
closes once the pressure falls agairl. The valve device
12 is also capable of' passin~ high quan-tities of fluid
S therethrough - preferabl~ at least the flow rate of
the valv~ deviLce 11 i.e.at 5~ litres ner minlite. ~'ence,
if wheIl the -~a1Ye ^'evice il is set to stat~ l, t~le
pre$surg in the,-ee~ line I3 is_a~ove the r~sponse
setti~g of the~v~.}ve de~ic~ J,2,then~the"valve device 12
will respond instantly. The valve device 12 will open
so the entire quantity oi fluid ilowing through the
device 11 to the,conduit 13 will be drawn o~ througl
the device 12 to return. This prevents any possibility
o-f pressure building up in the chamber 10' above the
setting response pressure o-i the device 12. Once the
pressure falls below the response setting of the device
12, the device 12 will close perrnitting the ~luid to
pass through the device 11 to charge the chamber 10'.
By cons-tructing the valve device 12 so it can
pass relatively high quantities of pressure fluidJ
çommensurate with the device 11 and unlike conventional
pressure-relief valve devices, damage and xapid wear
of the device 12 can be prevented. The valve device 12
can be constructed in a manner known per se.
2~ r~he device 12 may thus have a spring-loaded
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piston member slidably mounted in a guide bore oI a
guide piece provided with an O-ring seal engaging
on the shank of -the piston member. I'he piston member
S has an axial bore leading through radial bores which
open into fluid outlets a-t the exteriQr surface of
the shank. The guide piece wi-th the associated piston
member are retained in a housing containing the spring
which bears on the piston member via a thrust plate
0 to hold the piston member in a position with i-ts out-
lets closed by the O-ring seal. As the pressure of
fluid acting on the piston member rises above a pre-
determined level the piston member moves in the guide
bore to bring the outlets passed the O-ring seal to
lS permit fluid discharge. With the piston member dis-
placed to open the valve the fluid path cross~sectlon
is sufficiently large to permit -the necessarily-
large flow rates discussed above.
The con-trol apparatus also employs auto-
2~ matic setting means. This means includes a further
setting valve device 15 which can adop-t one o~ two
states designated a and b . The device 15 is connected
at a~ inlet to a conduit or line 16 leading to the
pressure line P and at an ou-tlet to a conduit or line
17 leading to the line 13 and thence to the prop
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working chamber 10'. A non-return valve 18 is incorpor~ted
in the line 17. In setting state a the line 17 is
isolated -from the pressure fluid feed line P while in
the setting state b the line 17 is connected to the
Spressure line P. Unlike the device 11, ihe device 15
is solely pressure-actuated. As illustrated in Figure 1,
.the device 15 has a control piston 19 connected
through a conduit or line 20 with the line 17, down- ¦
stream of the valve 18, and thence with the line 13.
10The device 15 also has a second control piston 21 with
a larger working area than the piston 19. The piston
21, which opposes -the action of the piston 19, is
connected through a condui-t or line 22, and a conduit
or line 25 containing a non-return valve 26 to the
lSline 17 downstream of the valve 18. A pressure-relief
valve device 24 has its inlet connected to the line 17
to lead directly to the line 13 and hence -the prop
working chamber 10'. The device 2a has its outlet
connected to the line 22 and directly to the piston 21.
20Th~ response pressure of the relief valve device 24
is equal -to or slightly less than -that of the device 12.
.~ Typically where -the device 12 is set to open at 370
bars the device 24 would be set to open at around 360
.bars~ With both pistonsl~, 21 of the device 15 exposed
25to the same pressure the piston 21 will prevail because
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of its larger area and the device 15 will adopt the
sta-te a. State a is also the normal non-functioning
sta-te of the device 15 when neither piston 19, 21
is exposed to pressure or when -the pis-ton 19 is
exposed to pressure below a set threshold. Only
when the piston 19 solely is exposecl to pressure above
the set threshold will the device change from state a
to b.
Assume that the prop 10 is retracted as
illustrated in Figure 1. In order to extend and set
the prop 10 the device 11 is set to state 1 by moving
its control lever. So long as th~ roof-engaging part of
the prop 10 ox i-ts roof bar does not contact -the roof
of the working the pressure which builds up in the
chamber 10' is determined essentially by the resistance
to extension of the prop and the weight of its roof-
bar and is relatively low-typically 50 bars or less.
When the roof-engaging part of the prop 10 or its
roof bar actually contacts the roof the pressure in the
chamber 10' rises towar~s the pressure in the line P
so long as the device 12 remains closed and so long as
the device 11 remains in the setting state 1. If the
device 11 is changed from state 1 prematurely however
the pressure in the chamber 10' may be considerably
lower than the ideal-setting pressure which can be
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extrernely dangerous. The automati.c setting means or
arrangement enclosed by chain-dotted lines in Figure
1 is designed to preven-t this from happening. T~le
automatic setting arrangement is dec:igned to come
into operation at a pre-determined pressure threshold
value - typically above 50 bars and below 150 bars
e.g.120 bars. As soon as this pressure thresl~old value
. prevails in the chamber 10', signifying the prop 10
has been extended to contact the roof and is not
0 extending or retracting freely,the piston 19 acts
to change the device 15 from state a to sta-te b auto-
matically. This results in the charnber 10' being
connected to the pressure line P via the device 15
and the lines 13~ 17 effectively by-passing the
device 11. Hence any premature change of the device
11 will not affect che correct setting of the prop 10
and if the device 11 is maintained in state 1 as
would be normal the devices 11, 15 act in parallel to
charge the chamber 10' to the desired setting pressure.
Whether the device 15 is passing fluid to the chamber
10' singly or in combination with the device 11 when
the pressure in the chamber 10' reaches the response
pressure of the relief device 24, e.g. 360 bars J the
latter will open. The opening of the device 24 causes
the piston 21 of the valve device 15 to become
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exposed to pressure and the piston 21 prevails over the piston
19 to change the device 15 back to state a thereby breaking
the path from the line P through the device 15 to the chamber
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