Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to a mine
roof support of the type of support incorporating
a plurality of hydraulically extensible chock
legs articulated at upper ends thereof to one
or more roof bars 9 and at lower ends thereof
to one or more base members.
Such supports are commonly used in :
the longwall mining o~ minerals/ notably coal,
: by being spaced along a mineral face, wi~.h an I
armoured cnnveyor interposed between ~he supports .
and the f ace, the supports being connected to
the conveyor to advance the individual pans
thereof towards the newly exposed mineral face~ ~ .
after passage of the mineral winning device,
with the support~ in their roof supp~rting
conditlon. Con~ersely, when it lS required to
advance the supports towards the advanced c~nveyor,
the ~ chock legs are retracted and the supports
~ pulled forwar~ by reacting on the conveyor.
;: 20 In pract.ice, however, there is relative
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movement between the mine roof and the mine
floor, while there also exists the possibility
: of the roof beam(s) striking a roof projection~
whilst the support is being advanced~ -Both
- 25 these effects result in the upper ends of the
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chock legs ~eing displaced. The displacement
is usually rear~ardly or a combination of
rearward and lateral displacement, but forward
displacement ls not unknown in certain conditions.
To avoid damage to the choc~ legs by this
displacement9 several proposals have been put
forward aimed not only at accommodating a few
degrees of displacemellt, but also serving to
restore the chock legs to a pre-determined
position, upon release of the support from the
roof~ However, such restoration proposals have
all incorporated a restoration device reacting
between the base member(s) of the support and
at least one chock leg thereof. This of necessity
results in the introduction of bending loads
and stresses into the chock Ieg(s).
In our U.K. Application~l74~2/77
(= U.S. Patent 4139326) is described a mine
roof support wherein the transmission of
restoration forces via ~he chock legs i~ avoided,
the invention employing permanently loaded
force supplying means operable through a shield
of ths support. If only linear displ~cement
forces (i.e. those operable along the centre
line of the roof support~ were encountered in
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practice then the location of force applying
means, e.g. rams, with lines of action parallel
to the centre line would be satisfactory. However,
non-linear Eorces are commonly encountered and a
proposal described in our U.K. Application 17442/77
(=U.S. Patent 4139326) to deal with this is to
employ two spaced apart rams located on opposite sides
of the centre line of the support and inclined with
respect to such centre line. For optimum effectiveness,
it is desirable for these rams to be spaced as far
apart as possible, i.eO one adjacent each lateral
side of the support which implies, ina four leg
support, that the rams are outside the legs. ~owever,
in certain circumstances, it is not possible to
locate the rams in this optimum position and accordingly
they must be located between the legs, thereby reducing
their effectiveness in firstly resisting displacemnt
forces and secondly in restoring a displaced roof
bar(s?, and it 1s to this form of roof support that
the present invention is directed.
According to the present invention, there is
provided a mine roof support comprising at least one
roof beam and at least one base member, a plurality
of hydraulically extensible chock legs articulated
at upper ends thereof to said roof beam and at lower
ends to said base member, a shield pivotally connected
to a rearward part of said base member and also pivotally
connected to a rearward part of said roof beam,
permanently pressurised rams, both located between a
pair of said chock legs which are laterally spaced and
one located to each side of the centre line of said
support, said rams being mutually inclined with respect
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to said cen-tre line and reacting via said shield
on said roof beam in such a manner that said rams
resist displacement of said roof beam and, upon
retraction of said chock legs from a mine roof,
restore displaced chock legs to a predetermined
position, and a pair of tie bars located one towards
each side of said support and both co].mected between
said roof beam and said shield, said tie bars readily
allowing mutual convergence of said roof beam and
said shield, and also determining the length of
effectiveness of said rams and hence maximum allowable
separation between said roof beam and said shield at
each side of said support.
Thus, with the support according to the
present invention, the tie bars ensure the presence
of greater turning moments to resist
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lateral or twisting forces on the roof beam(s)
and subsequently to restore the roof beam~-s)
to a predetermined location at the last
increment of restoration, such as when a first
ram is nearly extended and the second is not so
extended. Thus the second ram employs the fulcrum
provided by the tie bar remote Erom that ram.
Preferably, the shield is
pivotally connected via a link mechanism to
the base member~ The link mechanism may comprise
two links, one above the other, and preferably
located at each side of the support within the
overall width of the support.
Each tie bar may be constituted by
a bolt9 the bolt head being located in a slot,
e.g. provided in a bracket carried by the shiel~,
while the threaded bolt stem may pass through
an aperturP in a bracket carried by the roQf 1-
bar, with a nut applied to the threaded bolt
stem. The use of washers at the threaded end
enables the effective lengths of the bolts ~o
be readily adjusted to predetermine the leg angle,
The rams are preferably suspended from
~he roof beam(s) and react on an upper portion
of the shield. In detail, the piston rod of
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each ram may be pivotally attached to the roof
beam e.g. via a pin carried by a bracket
attached to the roof beam, while the cylinder
of eaeh ram may be similarly attached to the
shield.
Conveniently, the rams are provided
with a check valve for admission of fluid and
with a relief valve to yield when a predetermined
pressure is attained. Preferably, in an initial,
predetermined and non-displaced condition, the
piston rod of each ram is fully extended so
that should rearward roof beam displacement
for instance occurl the cylinder of each ram
remains stationary while the piston of each ram
sli ~ into its cylinder, the annulus volume
being enlarged. The maximum allowable chock leg
inclination occurs when the rams have been fully
retracted. When the roof support is released~ i
either fully or partially from the roof, re-
admission of pressure fluid to the full bore
sides of the rams, to replace that exhausted
during roof beam displacement9 causes the rams
to react on the shield to restore the roof beam[ s)
to the predete~mined position. Such readmission
may be automatically effected by permanently
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connecting the full hore sides of the rams
to th~ hydraul ic mains supplying the chock
legs, while the tie bars increase the effective-
ness of the rams towards the end of their
restoration movements.
Preferably, the two rams are so
inclined that their forward ends are adjacent
one another and their rearward ends are
remote from one another, This enables latera~
displacement to be countered and/or restored.
One may readily reverse the mode of
operation of the restoration rams if forward
roof movement is encountered, by permanently
pressurising the annulus side of the rams.
Thus for univeral use, the rams may be made
double-aeting.
The shield may be generally channel
shaped, adapted, in the retracted condition of
the roof support, to t21escope over a built up
~o rear base portion of the support which portion
becomes increasingly exposed as the shield is
lifted until the roof beam(s~ engages the
mine roof.
The invention will now be ~urther
descri~ed by way of example, with reference to
the accompanying d~awings, in whichs-
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Figure 1 is a side elevation of a
four leg, hydraulically powered, self-advancing
mine roof support in accordance with the
invention;
Figure 2 is a view in the direction
of arrow A of Figure 1 on the underside of the
roof beam;
Figure 3 is an enlarged view, partly
in section, o~ a tie bar of Figures 1 and 2;
and
Figure 4 is an enlarged view of a ram
of Figures 1 and 2.
In Figure 1, the mine roof support can
be seen to comprise a base member 1 seated on a
mine floor 2 with a roof beam 3 in engagement
; ~ith a mine roof 4, the base member 1 and roof
; beam 3 being spaced apart by two forwardly
located, hydraulically exter~sible chock legs 5
and two similar rearwardly located chock
legs 6, Each chock leg is articulated to both
the base member 1 and the roof beam 3 at known
joints incorporating arcuate bearing surfaces
~ and 8. A shield 9 is pivotally connected to
a rearward part of the base member 1 by being
~ounted at each side on pairs of upper and
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l~wer links 10, while the shield is also
pi~otally attached to a rearward part of the
roof beam 3, by means of tie bars ll and
permanently pressurised rams 12.
Each ram 12 comprises a piston rod
13 pivotally secured at 14 to a bracket 15
depending from the underside of the roof beam 3,
while the full bore cavity of a cylinder 16 is
permanently pressurised with hydraulic fluid
so that p.iston 13 is normally urged to the
extended position shownJ the cylinder 16 being
pivotally attached to a bracket 17 of the shield
9. As shown in Figure 2, each ram 12 is located
along an axis 18 inclined with respect to the
centre line 19 of the roof suppor~. .
Each tie bar 11 comprises a bolt 20
. having at one end a bolt head 21 located in
a slot 22 cf a tube 23 pivotally attached at 24
to a bracket 25 of the shield 9. At its other
en~ the ~olt 20 terminates in a threaded stem
passing through an aperture 26 in a bracket 27
carried by the roof bar 3, a nut 28 being applied
to the threaded stem to secure that bolt end to
the bracket 27.
In the drawings, the roof support
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i5 shown in a non-displaced condition. If
and when rearward displacement of tne upper
end of the chock legs 5, 6 occurs e.g. by
natural rearward movement of the roof 4, or
during advance of the roof support towards a
mineral face, the cylinders 16 remain stationary,
or substantially so, due to the non-movement
of the shield 9 ~ while the piston rods 13,
being carried by the roof beam 3, are displaced
~0 into the respective cylinders 16.
