BRAKING APPARATUS

MECANISME DE FREINAGE

English Abstract

The braking apparatus is provided for a shaft conveyance system in which a
conveyance 18 is driven up and down an upright track 20 in the shaft 10. The
braking apparatus comprises a brake 22 associated with the conveyance 18 which
is operable to engage a counter-member 16 in the shaft 10 to hold the
conveyance
18 at a chosen elevation on the track 20. A load cell 34 is provided for
sensing the
vertical load on the brake when it is engaged with the counter-member. Also
provided are means operable in response to the load cell to disengage the
brake
from the counter-member when the load cell senses a predetermined load on the
brake.

Claims

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THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1.
A braking apparatus for a shaft conveyance system in which a
conveyance is driven up and down an upright track in the shaft,
the braking apparatus comprising a brake associated with the
conveyance which is operable to engage a counter-member in the
shaft to hold the conveyance at a chosen elevation on the
track, a load cell for sensing the vertical load on the brake
when it is engaged with counter-member and means operable in
response to the load cell to disengage the brake from the
counter-member when the load cell senses a predetermined load
on the brake which is present when an upward thrust applied to
the conveyance is sufficient to take at least a major part of
the dead weight of the conveyance.
2.
A braking apparatus according to claim 1 wherein the brake is
of the spring-applied type.
3.
A braking apparatus according to claim 2 wherein the brake is
of the spring-applied, hydraulically released type.

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4.
A braking apparatus according to claim 3 wherein the brake includes a caliper
carrying brake pads which are adapted to engage the counter-member between
them under spring force and wherein the means for disengaging the brake from
the
counter-member includes hydraulic actuators operable to separate the brake
pads
against the spring force.
5.
A braking apparatus according to claim 4 wherein the brake includes a housing
accommodating the caliper and a mounting plate for mounting the brake on the
conveyance and wherein the load cell is arranged between the housing and the
mounting plate and is sensitive to tension or compression applied to it.
6.
A braking apparatus according to claim 5 and including a plurality of load
cells
between the housing and the mounting plate.
7.
A braking apparatus according to claim 1 wherein the predetermined load is
approximately 90% of the upward thrust required to support the dead weight of
the
conveyance.
8.
A braking apparatus according to claim 1 when used in a mine shaft conveyance
system.

Description

CA 02037231 1999-11-23
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BRAKING APPARATUS
This invention relates to a braking apparatus to be used in a
shaft conveyance system.
It has already been proposed in PCT/GB90/00335 to provide a
mine shaft conveyance system in which linear motors are used
to transport men, ore and materials to and from the surface in
a mine shaft. This contrasts with the conventional mine shaft
conveyance system in which mine conveyances, such as personnel
cages and ore and material skips are suspended at the ends of
ropes which are paid out and wound in by surface, or in some
cases, underground, winding apparatus.
A first aspect of the present invention provides a braking
apparatus for a shaft conveyance system in which a conveyance
is driven up and down an upright track in the shaft, the
braking apparatus comprising a brake associated with the
conveyance which is operable to engage a counter-member in the
shaft to hold the conveyance at a chosen elevation on the
track, a load cell for sensing the vertical load on the brake
when it is engaged with counter-member and means operable in
response to the load cell to disengage the brake from the
counter-member when the load cell senses a predetermined load
on the brake which is present when an upward thrust applied
to the conveyance is sufficient to take at least a major part
of the dead weight of the conveyance.
64840-59

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The shaft is typically a mine shaft.
The conveyance system may be of the linear motor type disclosed
in PCT/GB90/00335. Accordingly, a second aspect of the
invention provides a braking apparatus for a shaft conveyance
system in which a conveyance carried by a reaction
64840-59

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member is driven up and down the shaft, by electromagnetic forces, relative to
a
winding support member extending vertically in the shaft, the braking
apparatus
comprising a brake on the conveyance or reaction member which is operable to
engage a counter-member extending vertically in the shaft to hold the
conveyance
and reaction member at a chosen elevation in the shaft, a load cell for
sensing the
vertical load on the brake when it is engaged with the counter-member and
means
operable in response to the load cell to disengage the brake when the load
cell
senses a predetermined vertical load on the brake.
In the interests of safety, the brake is preferably of the spring-applied,
hydraulically
released type. In a preferred brake construction, the brake includes a caliper
carrying brake pads which are adapted to engage the counter-member between
them under spring force and wherein the means for disengaging the brake from
the
counter-member includes -hydraulic actuators operable to separate the brake
pads
against the spring force.
There may be a housing accommodating the caliper and a mounting plate for
mounting the brake on the conveyance, the load cell being arranged between the
housing and the mounting plate and being sensitive to tension or compression
applied to it.
The invention will now be described in more detail, by way of example only,
with
reference to the accompanying drawings in which
Figure 1 shows a diagrammatic horizontal cross-section through a mine
shaft;
Figure 2 shows an exploded view of a braking apparatus of the
invention; and
A

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Figure 3 shows a side view of the assembled braking apparatus.
In Figure 1, the numeral 10 designates a vertical, circular cross-section mine
shaft.
Fixed in the shaft is steelwork which includes structural members 12 and 14.
The
members 14, which are located at vertically spaced intervals in the shaft,
have T-
section brake reaction rails 16 fixed to them as illustrated, the members 16
extending in the shaft from the top to the bottom thereof.
Figure 1 also shows two mine conveyances 18, such as ore, personnel or
equipment
conveyances which are driven vertically up and down the shaft as required by
electromagnetic forces generated by linear motors indicated generally with the
numeral 20. Each linear motor is constituted by a vertically extending winding
support member and a reaction member, typically incorporating permanent
magnets, as described in the specification of PCT/GB 90/00335. The conveyances
18 are carried by the reaction members of the linear motors.
Caliper brakes 22 are mounted on the conveyances 18, although it is also
within the
scope of the invention for the brakes to be mounted directly on the reaction
members. Referring to Figures 2 and 3, each caliper brake has a mounting plate
24 which is secured to the ~,:nderside of the conveyance and a pair of
hydraulic
brake actuators 26 which act on a caliper carrying brake pads 28 of friction
material.
The brakes 22 are mounted on the conveyances 18 in such positions that the
webs
30 of the counter-members 16 are located between the brake pads 28. The brakes
are of the spring-applied, hydraulically released type. Thus the normal
operation
of the springs in the actuators is to apply the brakes, i.e. to force the
brake pads 28
together to clamp the webs 30 between them. When the brakes are to be
released,
hydraulic fluid is supplied to release cylinders in the actuators which pull
the brake

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pads apart and off the webs 30.
Between the mounting plate 24 and the caliper housing 32 of each brake 22 is a
series of load cells 34 which may be of a conventional type designed to sense
vertical loads tending to force the plate 24 towards the housing 32 or tending
to
force the plate and housing apart.
When a conveyance 18 is travelling vertically in the shaft 10 under
electromagnetic
forces and it is desired to brake the conveyance at a desired elevation, an
electromagnetic control is used to decelerate the conveyance to zero speed and
then
hold the conveyance in a "hover" mode at the desired elevation. Hydraulic feed
to
the actuators is terminated and the springs apply the brakes to clamp the
conveyance relative to the counter-members 16. The electrical supply to the
winding support members of the linear motors can now be terminated and the
conveyance remains in a stationary position, held only by the mechanical
braking
forces.
If it is now desired to cause the conveyance to rise or descend, the
electrical supply
to the winding support members is re-established. It will be appreciated that
it will
take a short time for the linear motors to build up sufficient thrust to
support the
weight of the conveyance and its contents, and in the case of upward movement,
to
lift it. It would clearly be extremely dangerous for the brakes to be released
too
early, since this could have the result that the conveyance falls down the
shaft under
gravity.
Assuming that the conveyance is to be lifted up the shaft by the linear
motors, the
load cells 34 will come under tension as the linear motors build up thrust. It
is only
when a predetermined thrust has been attained that the load cells relay a
signal to
a hydraulic control circuit (not shown) which operates, in response to that
signal,

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to feed hydraulic fluid to the actuators to pull the brake pads 28 apart.
Normally the load cells will not permit the brakes to be released until at
least about
90% of the thrust required to take the dead weight of the conveyance and its
contents is attained. This will permit the conveyance to drop a small distance
before the full thrust is attained to take the weight of the conveyance and
contents,
whereafter further thrust which is generated will serve to lift the conveyance
and
contents.
If it is intended that the conveyance will descend in the shaft from its
braked
position, the load cells will again sense when sufficient thrust has been
built up to
take at least the major part of the dead weight of the conveyance and
contents, and
only then will a signal be transmitted to the hydraulic control circuit to
cause the
brakes to be released.

Representative Drawing