Note: Descriptions are shown in the official language in which they were submitted.
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THIS INVENTION relates to skips.
Square or rectangular cross-sectional
bodies have been used extensively in mine skips, such
as that in USA Patent 2790569, and required reinforcing
- 5 in order to maintain their shape and to provide them
with adequate strength. This resulted in considerable
labour and material costs and required a large number
of components for each skip. In addition, the
resulting skips were often heavy and were prone to
considerable wear.
The combined mass of the skips and their
full loads and the momentum gained in their travel
resulted in the need for skip housings at the top of
shafts to provide for considerable over-run of the
relatively rapidly travelling skips, increasing the
costs of the housings.
The skip disclosed in UK publication
2l04495 (US application 30l703) has a body in whiah
the two pairs of opposed walls diverge downwardly so
that the storage chamber in the body widens downwardly
within the body~
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Provision of the downwardly diverging walls and thus
of the downwardly widening chamber can help to eliminate wear
on side, back and front walls of the body as material moves
downwardly within the chamber. However, it has been found
that the effectiveness of the downwardly widening chamber can
be increased.
Furthermore, the skip of UK Publication 2104495 does
not overcome the need for substantial reinforcing of the body
and nor does it enable the combined mass of the skip and full
load to be significantly reduced.
The present invention therefore aims to provide a
skip which, the Applicant believes, will help to alleviate
certain of the problems not fully solved by the invention of
UK Publication 2104495.
According to the invention, there is provided a skip
to be suspended in a mine shaft and comprising a body
defining a normally downwardly extending storage chamber, a
discharge opening defined in the body, and a door for closing
the discharge opening, the door being openable to allow
material to be discharged from the chamber, wherein along at
least a substantial part of the height of the chamber is of
generally circular-
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cross section with a cross-sectional area which
increases downwardly so that at least part of the
storage chamber widens downwardly within the body.
Because of the part of the body of circular
cross-section, the body need not be provided with
reinforcing comparable to that required for square or
rectangular skip bodies, in which case the mass of
the skip can be greatly reduced. In addition, this
part of the body may be formed primarily from a
single sheet of plate material bent and joined at a
single junction, for example by welding, instead of
the much greater number of junctions required in
prior art skips referred to above.
The height of the chamber may be greater
than its greatest horizontal dimension, usually more
than double this, measured in the normal operating
condition of thé skip.
The body may have a peripheral wall
encircling said chamber and an integral sloping
bottom adjacent to the discharge opening for
directing material towards the opening, the sloping
bottom extending from a top portion to a bottom
portion adjacent to a bottom portion of the discharge
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opening.
The cross-sectional area of the chamber may
preferably increase downwardly along substantially
the whole of the height of the chamber above the top
portion of the sloping bottom, the provision of the
downwardly widening chamber helping to reduce wear on
the inside of the wall of the skip as material moves
downwardly within the skip. In order to inhibit wear
still further, the inside of the peripheral wall of
the skip may be provided with deflectors, such as
rings, secured to said peripheral wall, for deflecting
downwardly moving material inwardly away from the
inside of the peripheral wall of the skip. These
deflectors are preferably provided at least at the
lower part of the inside of the wall of the skip, for
example at spaced intervals up at least a fifth of
the height of that part of the chamber above the
sloping bottom.
The door may be pivotally mounted on said
body and locatable beneath part of said chamber for
closing the discharge opening, and may be pivotable
downwardly for adopting a position defining a chute
surface beneath said opening to allow material to be
discharged from the chamber and guided away from the
opening. The door may be pivotable about an axis
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adjacent to the bottom portion of said sloping
bottom. For example, the door may be connected to
the body by suitable trunnions at opposite sides of
the door to provide for necessary movement of the
door while keeping adjacent edges of the bottom and
door in a relationship for substantially preventing
passage of material between the surfaces at the
junction.
Any suitable means may be provided for
holding the door of the skip normally in a closed
condition, and an over-centre arrangement is
particularly suitable for this purpose. In one
embodiment, the skip may have over-centre mechanisms
at opposite sides of the body and these mechanisms
may be operable to open and close the door. The
mechanisms may be movable to an over-centre condition
releasably to lock the door in its closed condition
and may be arranged so that the load on the door, the
weight of the door itself, and possibly the weight of
any operating means provided for operating the door
may be used to bias the mechanisms to remain in th'is
locked, over-centre condition.
Each mechanism may, for example, include an
arm pivotally connected to the door, a lever having
one region pivotally connected to the body and one
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region pivotally connected to the arm, and a follower
- connected to the lever and movable by a cam track in
a predetermined direction to move the arm and release
the respective mechanism from its locked over-centre
condition, enabling the door to move to its open
position.
Each over-centre mechanism may be such that
a line extending between the axes of the pivotal
connections of the arm to the door and of the arm to
the lever is on one side of the pivot axis of the
lever when the mechanism is in its over-centre
condition and on the opposite side of that axis when
the mechanism is in its open condition. Any reaction
forces applied to the lever from the closed door will
extend along such a line and will serve to retain the
mechanism in its over-centre condition until the arm
is pivoted.
Material is normally discharged into the
skip from a loading flask, and such loading flasks
often direct material from the feed side of the skip
toward~ the opposite side of the skip, which can
result in undue wear on the inside of the wall at the
opposite side of the skip. In order to help reduce
this wear, the inside wall at the opposite side of
the skip can be provided with a wear-resistant liner
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at least at the location where the wear is otherwise
likely to be most pronounced.
An embodiment of the invention will now be
described, by way of example, with reference to the
accompanying schematic drawings, in which
Figure 1 is a partial view of a skip in a job's
bridle;
Figure 2 is a partial side view showing the
closed skip and bridle;
Figure 3 is a view of the lower part of the skip
in its open condition;
Figure 4 is a section through the lower part of
the skip;
Figure S is a section through a door mounting
; 15 trunnion;
Figure 6 is a cross-sectional plan view on line
VI-VI of Figure 2; and
Figure 7 is a side view of a cam track for
operating the skip.
Referring to the drawings in more detail', a
skip 10 is mounted in a job's bridle 12 on pivot
shafts 14 and is prevented from swinging within the
bridle by means of locks 16. The bridle may be of a
conventional construction and may be capable of
25 receiving a mancage in place of the skip.
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The bridle has suitable guides (not shown)
for co-operating with a guide assembly in a mine
shaft to guide the bridle for movement in a vertical
direction.
The skip has a body 18 comprising ~n
annular peripheral wall 20 defined about a substantially
central vertical axis of the skip and of substantially
circular cross-section, in plan view, along the major
part of its height, an upper curved wall 22, and
upper side walls 24. At its upper end, the body is
provided with a feed opening 26 between the side
walls 24 for receiving material from a loading flask
and a feeder chute.
The annular wall 20 encircles and substan-
tially defines a storage chamber 28 of generally
circular cross-section and the cross-sectional area
of this chamber increases downwardly over a height
of, for example, about 4500 mm from the top of the
chamber, which is just below the feed opening 26 and
at which the chamber has a diameter of, for exampl~e,
about 1200 mm, to a level immediately above the top
portion of a sloping bottom 32 of the body 18, the
diameter of the chamber at this level being about
1300 mm, for example. Annular rings 30 (Figure 2)
are welded to the inside surface of the annular wall
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20 up the lower part of the height of that part of
the chamber above the bottom 32 over a distance of at
least 1000 mm. These rings may be spaced at
suitable distances of, for example, from 10 to 300 mm
apart and may serve as deflectors for deflecting
downwardly moving material inwardly away from the
i~side of the wall 22 of the skip to reduce wear of
the walls at the lower part of the skip.
secause the wall 20 is of circular cross-
section, external reinforcing ribs at uniformlyspaced distances up the outside of the wall 20 are
not necessary. The absence of such ribs assists in
enabling the mass of the skip to be reduced when
compared with rectangular skips of similar load-
carrying capabilities.
The bottom of the skip is partially closedby the sloping bottom 32, which is semi-elliptical
and which is inclined downwardly at a suitable angle
with respect to the central vertical axis of the skip
and extends over approximately half of the area of
the bottom of the skip. A discharge opening 34 is
defined between a bottom portion of the sloping
bottom 36 substantially intersecting said axis and
part of the wall 20 of the body and is normally
closed by a door 38. The door and body can be
provided with wear plates 40 in a suitable manner.
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The door 38 is pivotally mounted on
trunnions 42 (shown in Figures 4 and 5). Each of
these trunnions is formed partly by a respective end
of a rigid rod 44 of substantially s~uare cross-
section along the major part of its length. The ends46 of the rod are rounded and lock washers 48 are
fitted onto the ends of the rod and trap bearings S0
in position. Each bearing 50 is received within a
bearing housing 52 provided with a cover plate 54. A
spacer 56 is provided on the rod between the square
part of the rod and the respective bearing 50 and a
labyrinth seal 58 is formed between the spacer 56 and
the bearing housing 52.
The square part of the rod 44 is welded to
ribs 60 spaced along the bottom 36 of the skip and
mounting plates 62 are fixed rigidly to the bearing
housing 52 at each side of the skip. The door 38 is
fixed rigidly to the mounting plates 62 at a position
such that it is eccentrically mounted with respect to
the ax~s of rotation 64 of the trunnion. The
mounting of the door is such that, in the closed ,
condition of the door shown in Figure 4, the wear
plate 40 of the door presses against the lower edge
of the bottom 36 of the skip. However, as the door
is pivoted in the direction of arrow 66 in Figure 4,
the door moves away from the lower edge of the bottom
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36 and swings through an arc about the axis 64 until
it reaches a position shown in Figure 3 where it is
almost parallel to the bottom 36 with its upper end
below the level of the lower part of the bottom 36.
In this position, the bottom and door form a chute
for guiding material flowing from the skip. The door
is provided with side plates 68 to further improve
the guiding of the material.
The skip shown has shock pads of suitable
rubber between the wear plates 40 and lower plates 72
of the bottom 36 and door 38. These assist in
avoiding the 'nut cracker' effect that sometimes
arises when doors close in a manner similar to that
illustrated. However, if it is considered that a
'nut cracker' effect is likely to arise when the door
of the skip shown is closed, it is possible to
provide the bottom 36 of the hopper with a wedge-like
formation which tapers to a point at the lower part
of the plate 72 of the bottom 36. This arrangement
can result in particles that would normally be
subject to a 'nut cracker' action being squeezed out
from between the bottom 36 and the door 38 as the
door closes.
The door of the skip shown is normally held
in its closed condition by a door control means
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including over-centre mechanisms 74 at opposite sides
of the body 18. Each such mechanism includes a
follower 76 in the form of a tipping wheel, an arm 78
pivotally connected to a respective pivot 80 on the
door and a lever 82 pivotally connected to a mounting
84 on the body 18 of the skip by a pivot 86. The
mounting 84 may be a relatively simple member welded
to the wall 20, and may be of any suitable shape, as
shown in Figures 2 and 6.
The end of each lever 82 furthest from the
respective pivot 86 is provided with a pivot 88
connecting to the free end of the arm 78, the
follower 76 being located on the lever 82 between the
pivots 86 and 88.
As shown in Figure 2, each arm 78 is
cranked so that, with the door in its normal closed
condition, it rests against a supporting shaft of the
follower 76 in a locked over-centre condition. If
required, guides may be provided on the body for
guiding the arm to move to this position. The ar~ is
cranked to such an extent that an imayinary line 90
passing through the axes of the pivots 80 and 88 is
on one side of the axis of the pivot 86 when the door
is in its closed condition and moves to the opposite
side of the axis of the pivot 86 when the door is
moving to its open condition. Thus, when the door is
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in the position shown in Figure 2, forces applied to
the closed door by a load in the skip, and the weight
of the door itself, serve to provide a reaction force
along the imaginary line and increase the locking
S effect of the mechanissms. The door is opened by
causing each follower 76 to follow a path such as the
path 92 of Figure 3 as the skip moves upwardly into
the head gear of a mine.
In order to cause the followers,76 to
follow such a path, the skip is used with a skip head
which includes cam tracks 96 and 98 arranged on
opposite sides of the skip head and facing towards
one another for receiving the followers 76 of the
respective over-centre mechanism. When the skip
moves upwardly into the skip head, the followers 76
move upwardly between the respective cam tracks 96
and 98 in the direction of arrow lO0 and are guided
between the cam tracks, the cam tracks 98 forcing the
followers to move the méchanisms 74 from their over-
centre locked condition and the cam tracks 96supporting the followers 76 to prevent excessivel~
rapid opening of the door 38 once the mechanisms have
moved from the over-centre condition. The tracks 96
support the followers 76 until the door 38 is fully
Open.
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When the skip is again moved downwardly,
the cam tracks 96 force the followers 76 to move in
the opposite direction and, in due course, force the
mechanîsms 74 to return to the over-centre condition
so that the door 38 is again locked.
Although the downwardly diverging shape of
the skip and the rings 30 can assist in reducing
undue wear of the annular wall 20 of the skip, it may
be found that material flowing into the skip from a
loading flask will be projected across the width of
the skip and strike the inside wall surface of the
skip at the side of the skip facing the feed opening
but usually below the level of the feed opening 26.
In order to inhibit undue wear as a result of this, a
wear-resistant liner 102 may be bonded to the inside
of the wall of the skip where the wear resulting from
flow of material into the skip would otherwise be
most pronounced.
