Airflow Regulator

Abstract

A louvre-type airflow regulator (10) for a mine passage comprises a plurality of louvre blades (12, 14, 16). Each blade is adapted for mounting in a frame (20). Each blade can pivot in the frame around a lengthwise axis between a predetermined position in which the louvre blades combine to close or restrict at least a portion of the passage, and an open position in which air is able to readily flow between the louvre blades and through the passage. A biasing mechanism is provided for acting on each louvre blade such that, in use, each louvre blade can be maintained in the predetermined position until a predetermined airflow against the louvre blades is reached.

Description

TECHNICAL FIELD

A louvre-type airflow regulator is disclosed. The regulator finds particular application in mining shafts, tunnels, raises, roadways etc (hereafter “mine passages”) to control or regulate airflow therethrough.

BACKGROUND ART

Underground mines may have a number of raises that act as a conduit for fresh air, with raises formed on an air intake side of an ore body and on an air return or opposite side of the ore body. Airflow at various levels in a mine is then controlled by airflow regulators arranged, inter alia, at the entrances or exits of these raises.

Known airflow regulators used in mines are referred to as drop-board regulators and have been in use for some time. An airflow regulator is also known that includes vertical louvres pivotally mounted in a steel frame.

Drop-board regulators may comprise a steel H section frame fabricated into compartments of a convenient size. Into each compartment hardwood boards are dropped down between the flanges of the H section. In this way the aperture of the regulator can be adjusted in area, thereby altering the quantity of airflow that is allowed into a given section of a mine.

Drop-board regulators require manual adjustment. In addition, before an event such as stope firing or blasting takes place, and where it is believed that the blast may physically damage the regulator, a miner has to physically remove all the boards, being a heavy, arduous and time consuming task. Major stope firings can result in large volumes of air being forced through mine passages, with the pressures generated being sufficient to permanently damage mine ventilation structures.

SUMMARY OF DISCLOSURE

In one aspect there is provided a louvre-type airflow regulator for a mine passage comprising:

• • a plurality of louvre blades, each adapted for mounting in a frame and pivoting therein around a lengthwise axis between a predetermined position in which the louvre blades combine to close or restrict at least a portion of the passage, and an open position in which air is able to readily flow between the louvre blades and through the passage portion; and
  • a biasing mechanism for acting on each louvre blade such that, in use, each louvre blade can be maintained in the predetermined position until a predetermined airflow against the louvre blades is reached.

The biasing mechanism can provide the regulator with air “overpressure” protection resulting from eg. a major stope firing or blasting event, without the need for regulator demounting. Thus, at least some of the shortcomings of drop-board regulators can be addressed. The use of louvre blades also allows for remote regulator control.

The terminology “predetermined airflow” can include within its scope predetermined air pressure, and typically though not exclusively relates to an increase in airflow/pressure from a firing or blasting (eg. a stope firing or blasting).

The predetermined position typically corresponds to a closed position or a partially opened position of the blades (the blades in the partially opened position being more closed than in the open position). The partially opened position may be assumed, for example, when the louvre is in a normal airflow control mode of operation.

The open position typically corresponds to a blade fully open position, although the blades may be less than fully open, but yet be more open than the predetermined position, hence the terminology “open position” includes such a configuration.

The biasing mechanism may comprise:

(i) a weighting arrangement operable on each louvre blade and that tends to cause it to pivot into the predetermined position;
(ii) a spring mechanism that positively urges each louvre blade to pivot into the predetermined position; and/or
(iii) a strut mechanism that positively urges each louvre blade to pivot into the predetermined position.

In (i) the weighting arrangement can comprise one or more weights operatively coupled to each louvre blade via a respective linkage, whereby due to gravity the weight(s) draw down on the linkages and thereby urge each louvre blade into the predetermined position, but at the predetermined airflow the louvre blades then act on each linkage and urge the weight(s) up as each louvre blade moves towards the open position.

For example, the weighting arrangement can comprise one or two weights, with each weight having the linkages extending therefrom at intervals spaced along the weight, and with each linkage being coupled to a respective louvre blade at a coupling that is pivotally mounted to the frame at the same point as the blade pivotal mounting.

In (ii) the spring mechanism can comprise one, a number, or a respective spring for each blade. The spring(s) pull each louvre blade into the predetermined position, but at the predetermined airflow the louvre blades act on and stretch against the spring(s) as each louvre blade moves towards the open position. For example, the spring(s) can extend between the frame and a location on or connected to a louvre blade at or adjacent to a leading or trailing edge of the blade. Also, when the louvres are interconnected via linkages, only one or a few springs may be required to pull the louvre blades into the predetermined position (eg. with the spring then acting on the linkages).

The spring(s) may, for example, comprise a helical, leaf or other spring type.

In (iii) the strut mechanism can comprise a gas strut that is connected to a linkage mechanism that acts on the louvre blades to urge them into the predetermined position. At the predetermined airflow the louvre blades can act on the linkage mechanism which in turn acts against the gas strut as each louvre blade moves towards the open position. The connection between the gas strut and the linkage mechanism can be adjustable such that the louvre blades can either be fully or partially closed by the operation of the gas strut.

The regulator may further comprise a control mechanism to separately and independently control the position of each louvre blade during normal airflow conditions in the mine passage (ie. to control airflow other than that generated by a blast). Typically the biasing mechanism is adapted to not interfere with normal airflow control and typically the control mechanism is adapted to not interfere with opening of the louvre blades at the predetermined airflow or with biasing mechanism blade return to the predetermined position.

The control mechanism may comprise a remotely controlled adjustment mechanism or a manual adjustment mechanism. The control mechanism can employ actuators that are eg. electrically operated and that may be remotely controlled (eg. via a fibre optic communication system at a surface of the mine). The manual adjustment mechanism can provide for multi-blade positioning, with the louvre blades being maintained at a given partially opened position using eg. a locking pin.

The regulator can further comprise the frame. The frame can, for example, form part of a module, with a plurality of such modules being mountable in a larger frame arranged in the passage. The regulator modules can also be configured such that they can be located into existing drop-board frame structures after removing the timber drop boards.

Alternatively a complete set of modules can be made up within a suitable (eg. purpose-built) frame that can be attached to the mine opening by various means. These means can, for example, comprise a plurality of mounting pins/bolts that extend from eg. the larger frame and that are adapted for fastening with respect to adjacent wall(s) of the mine passage. The pins/bolts can then be used for the mounting of suitable formwork that provides a backing for the application (eg. via spraying) of a cementitious binder (eg. shotcrete), the pins/bolts, formwork and binder then providing a structural wall to support the frame in the passage.

Each module in the set may have a plurality of selectively extendable securing pins arranged around its periphery such that, when the module is mounted in the larger passage frame, extension of the securing pins secures the module to the passage frame, and retraction of the securing pins enables module detachment from the passage frame. Each module may also have lifting points formed therein that enable it to be lifted into and out of the passage frame

In one arrangement of the regulator the louvre blades move when subject to a large air blast, and thereafter move back to the predetermined position. For the intake louvres, where normal ventilation air helps keep the louvre blades shut, the blade return mechanism (eg. the counterweight size) can be reduced or of less scale.

The regulator may further comprise a stop for preventing blade pivotal movement beyond the open position (typically a blade fully open position). The stop may comprise a dampener or shock absorber, to dampen or absorb the momentum of a pivoting blade.

Whilst the mechanism can be employed with in-use vertically (or otherwise) extending louvre blades, usually the blades extend generally horizontally in the frame in use.

BRIEF DESCRIPTION OF DRAWINGS

Notwithstanding any other forms that may fall within the scope of the louvre-type airflow regulator as defined in the Summary, specific embodiments of the regulator will now be described, by way of example only, with reference to the accompanying drawings in which:

FIG. 1 shows a front view of a louvre-type regulator;

FIG. 2 shows a front view of a louvre-type regulator module for use, inter alia, in the regulator of FIG. 1;

FIGS. 3A and 3B respectively show side schematic views of a louvre-type regulator in closed (shut) and open configurations, and illustrating the operation of a weighting mechanism for the regulator;

FIG. 4 shows a schematic plan view the weighting mechanism of FIG. 3;

FIGS. 5 and 6 respectively show front and plan views of a drop-board regulator frame but suitable for receiving one or more louvre-type regulator modules therein;

FIGS. 7A and 7B respectively show side schematic views of intake and exhaust louvre-type regulators in a mine passage and illustrating the action of blast and ventilation airflows;

FIG. 8 shows a side schematic view of two louvre blades of an exhaust louvre-type regulator in a closed configuration, and illustrating the blast and ventilation forces thereon;

FIG. 9 shows a front perspective view of a louvre-type regulator module;

FIG. 10 shows a rear perspective view of the module of FIG. 9;

FIG. 11 shows a perspective detail of the module of FIG. 9;

FIG. 12 shows a front detail of the module of FIG. 9;

FIG. 13 shows a rear view of another louvre-type regulator module;

FIG. 14 shows a side detail of the biasing mechanism for the module of FIG. 13;

FIG. 15 shows a front detail of the biasing mechanism for the module of FIG. 13;

FIG. 16 shows a side detail of the biasing mechanism of FIG. 15;

FIG. 17 shows a front detail of a securing mechanism for the module of FIG. 13; and

FIG. 18 shows a front detail of both the securing mechanism and a lifting feature for the module of FIG. 13.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Drop-board regulators are used to control air-flow to an underground mine and are typically located in (or at the entrance/exit of) so-called mine raises. These raises are typically located on each side of an ore body and comprise a number of air intake (or inlet) raises and a number of air return (or exhaust) raises. Where a stope firing or blasting occurs proximate to known drop-board regulators these can be damaged and rendered ineffective if the boards are not removed.

Louvre-based regulators have now been developed to overcome the shortcomings of drop-board regulators, including the heavy weight of the drop boards, and the arduous and time-consuming task of moving boards. Such louvre-based regulators allow for control of airflow in mine passages, but also provide for air overpressure to be accommodated (eg. as a result of proximate stope firing or blasting) and, thereafter, for louvre blade return. Thus, regulator demounting prior to a stope firing or blasting need not occur. In addition, louvre regulators can be controlled remotely (eg. from a control room at the mine surface) to regulate normal airflow levels in mine passages.

Louvre-based modules for retrofitting to in-situ drop-board regulator frames were proposed (Example 2) as a means of reducing installation cost and time.

A first stand-alone louvre design (Example 3) was proposed that incorporated manually controllable adjustment mechanisms of the louvre blades. It was noted that, due to the nature of manual control mechanisms, in some mine applications this design could be compromised by a large and/or proximate stope firing, resulting in sever air overpressure, leading to permanent louvre damage. For example, if each louvre blade is locked in a set position (eg. partial or fully opened position) it may still sustain damage due to the turbulent and non-laminar nature of airflow that can move therepast as a result of stope firing and blasting (ie. forcing the louvre blade against its lock).

A second stand-alone louvre design (Example 4) was proposed that incorporated self-adjusting louvre blades without manual control, with the second design being generally applicable in mines and being resistant to large and/or proximate stope firing. In this regard, the self-adjusting louvre blades were able to pivot in response to turbulent and non-laminar airflow moving therepast, but could still be independently controlled during normal airflow situations (ie. maintained at a number of set positions).

Referring now to FIGS. 1 to 4, a louvre regulator 10 is schematically depicted for mounting at or in a mine passage (eg. an air intake or exhaust raise). The regulator 10 comprises a plurality of different sized louvre blades 12, 14 and 16. Whilst the regulator can employ vertically extending louvre blades, the blades 12, 14 and 16 extend generally horizontally in use.

In the regulator 10 of FIG. 1 there are shown two louvre modules comprising eight smaller louvre blades 12, two louvre modules comprising seven medium louvre blades 14, two louvre modules comprising four large louvre blades 16. In addition, one of the lower modules can have some of the louvre blades removed (or re-sized) to enable an access door to be provided therein.

Each louvre blade is adapted at opposing ends for pivotal mounting in a respective module frame 20 (FIG. 2) to define a louvre module. In this regard, each louvre blade is able to pivot around a lengthwise axis, between a closed or partially opened position in which the louvre blades combine to close or restrict gas flow through at least a portion of the passage, and an open position in which gas (typically air) is able to easily flow between louvre blades and through the passage.

The same louvre module can be employed in both intake and exhaust raises, although the intake modules may require substantially less biasing than the exhaust raises (as described below).

As shown in FIGS. 3 and 8, the axis A may be offset with respect to a lengthwise central axis of each louvre blade. Indeed the axis may be located in a bar 22 mounted to either:

• • a front of the louvre blade and adjacent to an in-use lower edge thereof (FIG. 3); or
  • a rear of the louvre blade and adjacent to an in-use upper edge thereof (FIG. 8).

In the arrangement of FIG. 3 the louvre blades do not overlap in the closed position, whereas in the arrangement of FIGS. 7 and 8 the louvre blades overlap in the closed position (ie. lower edge and rear face of an upper louvre blade laps over the upper edge and front face of a lower louvre blade).

The overlapping arrangement is especially useful for an intake louvre as it results in the forcing of a seal, due to pressure on the louvre blade front faces of passage ventilation air (FIG. 7A). The non-lapped arrangement (FIG. 3) can be used for an exhaust louvre. However, as stated above and for expediency, typically the same louvre module is used in both intake and exhaust louvre regulator positions.

Referring again to FIG. 1, the module frames 20 are mountable in a larger frame 30 arranged in and across the mine passage as shown in FIG. 1. A number of mounting pins or rock bolts 32 extend from the frame 30 and are each adapted for being fastened with respect to (typically into) adjacent walls of the mine passage. In this regard, the pins or bolts are fastened into the wall and then formwork is mounted to the pins or bolts. Thereafter a cementitious binder 34 (eg. shotcrete comprising steel fibre reinforcement) is sprayed onto the formwork to enclose the pins or bolts therewithin.

The frame 30 is typically also braced from the front (not shown) via trusses/struts. For example, the frame can have heavy bracing at the floor level in the form of two horizontal struts at the module joins. Two 45° braces can extend up from the floor level to the frame mid-point to provide bending resistance in the vertical. Both sets of braces can be joined and bolted to the floor, and both sets can possess pin-jointed connections at the louvre frame. The braces are able to absorb much of the impact on the frame during firing/blasting.

Alternatively, the module frames 20 can be mounted in an already existing drop-board frame 40 (FIGS. 5 and 6) that may already be arranged in and across the passage.

A biasing mechanism for acting on each louvre blade is provided. In use, each blade is maintained in the predetermined position by the biasing mechanism until a stope firing, blast etc cause a predetermined airflow to act against the blades (eg. corresponding to a predetermined air pressure (or overpressure)).

In FIG. 3 it will be seen that one such biasing mechanism comprises a weighting arrangement operable on each louvre blade and that tends to cause it to pivot into a predetermined (closed) position (FIG. 3A). The weighting arrangement comprises a weight bar 50 that is operatively coupled to each louvre blade via respective linkage arms 52 which extend from respective coupling pivots 54. A coupling pivot 54 is connected to each louvre blade end and, when rotated by the linkage, causes its louvre blade to pivot about axis A. In this regard, the coupling pivot 54 can be connected to each louvre blade end at the same point as the blade pivotal mount at bar 22 (ie. to be centred on axis A).

FIG. 4 shows the weight bar 50 in greater detail. In fact the bar may comprise to back-to-back U-shaped channels 56 fastened together on either side of linkage arms 52. Adjustable ballasts 58 can be mounted within either or both of the U-shaped channels 56, with the amount of ballast being regulated responsive to the airflow/pressure which the louvre blades will be subjected to in use (eg. differential blast pressures, differential ventilation pressures at intake and exhaust louvres etc).

In any case, under the influence of gravity the weight bar 50 urges down on the linkage arms 52 to pivot and maintain each louvre blade in the predetermined (closed) position (FIG. 3A). Once a predetermined airflow/pressure is reached (directed from left side of louvre blades in FIG. 3) the blades are urged by the air to be pivoted towards an open position and now act on each linkage arm 52 against the weight of weight bar 50 (FIG. 3B). When the predetermined airflow/pressure subsides, the weight of bar 50 again urges down on the linkage arms 52 to pivot and return each louvre blade to the predetermined position.

The predetermined position may also correspond to a blade partially opened position, in which case the bar 50, via linkage arms 52, can pivot and return each louvre blade to this position, and this position may in turn be delineated by one or more appropriately positioned stops acting on the bar, linkage arm(s) and/or blade(s).

The weighting arrangement may also comprise two (or more) spaced-apart weight bars, and when two weight bars are present they can be located on either side of a louvre module.

In a first alternative to the weighting arrangement (or as an addition to the weighting arrangement), a spring mechanism that positively urges each louvre blade to pivot into the predetermined position can be provided. The spring mechanism can comprise one, a number, or a respective spring for each blade. The spring(s) pull each louvre blade into the predetermined position, but at the predetermined airflow the louvre blades act on and stretch the spring(s) as each louvre blade moves towards the open position.

The spring(s) can act between the frame and the lever arms or weight bar, or a respective spring can act on each louvre blade to urge it into the predetermined position. For example, each spring can extend between the frame and a mounting point located on the louvre blade at or adjacent to a leading or trailing edge of the blade.

Each spring may comprise a helical spring (eg. of steel), a leaf spring etc. The tension in each spring may also be adjustable.

At the predetermined airflow/pressure the louvre blades act on and stretch the spring(s) as each blade pivots towards the open position, with the spring(s) returning each blade to the predetermined position as the airflow/pressure subsides.

Referring now to FIGS. 9 to 17, where like reference numerals are used in these Figures to denote like parts, a louvre module 60 comprises a frame 62 which is mountable into a larger frame (for example in larger frame 30), with the larger frame typically having been pre-arranged in and across a mine passage.

The module 60 comprises four large louvre blades 64, with each blade having a support shaft 65 affixed (eg. welded) to a rear thereof, and with opposing ends of shaft 65 being pivotally mounted in a respective part of the frame 62 (see FIGS. 12 and 13). In this regard, each louvre blade is able to pivot around a lengthwise axis extending through the shaft 65, between a closed or partially closed (partially opened) position in which the louvre blades combine to close or restrict gas flow through the module, and an open position in which gas is able to easily flow between louvre blades.

The frame 62 further incorporates two tyne-receiving lifting sleeves 66 in a base member 68 thereof. The lifting sleeves 66 can each receive therein a respective tyne of a forklift vehicle to enable module lifting and transfer to and from the larger frame.

Referring to FIGS. 10, 12 and 17, side members 70 of the frame 62 each have four spaced securing pin barrels 72 mounted thereto via angle iron brackets 74. Each barrel houses a respective securing pin 76 for sliding therein. A release bolt 78 is attached to and projects transversely from the pin 76 to travel in tracking 80 defined in the barrel 72. The tracking 80 terminates at two locking slots 82 and 83 to accommodate any variations in the larger frame when mounting the module therein.

Each securing pin is slidable to extend beyond the periphery of frame 62 and is lockable in that extended position by moving the bolt 76 into one of the two locking slots 82 and 83. Thus, when the module has been located in the larger frame (eg. via a forklift vehicle) extension of the pins secures the module to the larger frame.

Thereafter, retraction of the securing pins enables the module to be detached from the larger frame. This provides a rapid and robust means of mounting and demounting each module.

Referring now to FIGS. 10, 11, 13, 14 and 18 a biasing mechanism for acting on each louvre blade is provided behind a protective cover plate 84 connected to extend upwardly from frame base member 68. In use, each blade is maintained in a predetermined (eg. closed) position by the biasing mechanism until a stope firing, blast etc causes a predetermined airflow A (FIG. 14) to act against the blades (with the airflow corresponding to a predetermined air pressure (or overpressure)).

In FIGS. 14 and 15 it will be seen that the biasing mechanism comprises a gas strut 86. The strut 86 has a housing 88, with a rod 90 being connected to the frame base member 68 at pin mounting arrangement 92. The housing 88 is moved by gas pressure in the strut up along rod 90 to generally be urged up with respect to the frame 62 (in the direction of arrow F—FIG. 15). This movement imparts the self-closing tendency in the biasing mechanism.

In this regard, and as best shown in FIGS. 15 and 16, an upper end of the housing 88 has upwardly extending lugs 94 fastened thereto, with each lug having a hole therethrough. The lugs 94 receive a downwardly extending lug 96 therebetween, with lug 96 also having a hole therethrough. Lugs 94 are connected to lug 96 via a retention pin 98. The lug 96 extends downwardly from a plate 100, with the plate 100 in turn being connected to a linkage bar 102 for louvre blade adjustment (as described below).

To control the amount of louvre blade closure an adjustment mechanism is provided. This mechanism comprises opposing spaced guide rods 104, each with a plurality of holes 105 defined therethrough. Each rod 104 is also connected to the frame base member 68 at a respective pin mounting arrangement 106 and extends upwardly therefrom and through apertures in the plate 100. The rods can thus help to guide plate movement up and down. An adjustment pin 108 is insertable through a selected one of the holes 105 of each rod 104 to extend between the rods as best shown in FIG. 15. As shown, the pin 108 sits above plate 100 and thereby restricts its upward travel, being that travel resulting from the gas strut urging upwardly on the plate. Because the plate is connected to the linkage bar 102 for louvre blade adjustment, the extent of louvre blade closure can thus be controlled through appropriate location of the adjustment pin 108.

FIGS. 10 and 11 shows a variation on the adjustment pin 108. An elbow 109 extends from the pin and can extend through the next overlying hole 105. A retaining clip 109A can fasten an end of the elbow into position, to fasten the pin 108 in place.

In this regard, the linkage bar 102 is pivotally connected to a double bracket arrangement 110 (as best shown in FIG. 13). Each of the double brackets in an arrangement 110 is, at one end, fixed (eg. welded) adjacent to an upper edge of a respective louvre blade 64. The opposite end of each of the double brackets pivots about a pin 112 extending through a hole (eg. 114) at linkage bar 102.

Thus, when the louvre blades are each at least partway open (eg. from an increase in passage air pressure) to self-close the blades the gas strut acts to move the strut housing 88 upwardly. This urges plate 100 upwardly, which simultaneously urges linkage bar 102 upwardly, causing the double bracket arrangement 110 to pivot upwardly (ie. around the lengthwise axis of the louvre blade shaft 65). This causes each of the louvre blades 64 to be moved back towards the predetermined (eg. closed) position, with the gas strut then tending to maintain each louvre blade in this position. However, pin 108 can be employed at various positions along the rods 104 so that plate 100 will engage the pin, thereby stopping louvre blade movement to the fully closed position (with this stop resistance being depicted by arrow S in FIG. 15). Hence the pin 108 can be used to maintain the louvre blades in a partially closed (partially open) position. For example, pin 108 may be employed when it is desirable or necessary to allow some, or a normal/natural flow level of eg. air in the passage in which the module 60 is employed.

Arrow A in FIG. 14 depicts a predetermined airflow/pressure being reached whereby the blades 64 are urged by the airflow to be pivoted (in the direction of arrow P in FIG. 14) towards an open position. This causes the linkage bar 102 (via the double bracket arrangement 110 and plate 100) to be moved against the gas strut force F, causing the strut housing 88 to be driven downwardly along rod 90. When the predetermined airflow/pressure has subsided, the gas strut again urges the plate 100 and thus the linkage bar 102 upwardly to pivot and return each louvre blade to the predetermined position (partially or fully closed).

Because the gas strut can be interchanged, different self-closing forces can be selected based on a given strut's specifications. The strut itself may also be adjustable, such that it is only compressible once a certain air pressure (eg. from a stope firing or blast) is reached.

Usually the regulator comprises a control mechanism to separately and independently control the position of each louvre blade during normal airflow control in the mine passage (ie. for the flow control of non-blast generated airflow). In this regard, the biasing mechanism does not interfere with the control mechanism during such normal airflow control. Conversely the control mechanism does not interfere with opening of the louvre blades at the predetermined airflow or with biasing mechanism blade return to the predetermined position. In other words, these mechanisms operate independently of each other.

The control mechanism can be manually adjustable or comprise a remotely controlled adjustment mechanism. The remotely controlled adjustment mechanism employs actuators that are electrically operated and remotely controlled via a fibre optic communication system located at a surface of the mine to adjust the blades to a set position. The actuators can operate in conjunction with air flow meters located at each regulator site, and an operator typically remotely adjusts the blades to obtain a desired airflow under normal mine operating conditions.

The manually adjustable mechanism can provide for multi-blade-position adjustment, whereby the louvre blades can be maintained at a number of different positions using locking pin(s). However, this adjustment must be performed in situ by an operator.

The regulator typically comprises a stop in the form of a dampener or shock absorber for preventing/restricting blade pivotal movement beyond the open position (typically a blade fully open position). A dampener or shock absorber can be provided for each blade, or again one or just a few dampeners or shock absorbers may be arranged to act on the weight bar or the linkage arms. Each dampener or shock absorber can absorb the momentum of one or more rapidly pivoting blades under the influence of an air blast.

EXAMPLES

Non-limiting examples of louvre-based regulators will now be described.

Example 1

New Louvre Construction

In the construction of a new louvre regulator such as shown in FIG. 1, rock bolts were first installed into the mine wall. Pins, consisting of RHS steel section, were then cut to length, welded to the rock bolt and then welded to the larger regulator frame. At each attachment point two pins or braces were provided, one being directly in line with the frame and one extending at 45 degrees thereto, to provide a truss like effect.

Formwork was then mounted to the pins/bolts and shotcreting took place (typically a wet process concrete spraying with the concrete comprising steel fibre reinforcement). A standard frame generally required 5 cubic metres of concrete to meet structural requirements.

The applicant noted that the time for construction of the louvre regulator of FIG. 1 could in many mines take up to three 12 hour shifts (a substantial down-time cost), with the cost of providing the regulator with a new shotcrete surround also being substantial. Thus, for many mines (especially existing mines) it would be easier to simply install separate modules into each existing regulator site.

Example 2

Louvre Retrofit to Drop-Board Frames

Rather than replacing the existing drop-board surrounds, louvre modules were designed that could be retrofitted into eg. a known six partition drop-board regulator frame.

FIGS. 5 and 6 schematically depict part of a steel drop-board regulator frame 40 to which the louvre modules could be mounted. Known frames were constructed from 150 UC30 section and comprised three vertical partitions 60, each divided into a top and bottom half by horizontal partitions 62. In some of the drop-board regulator frames examined, partitions were missing, however were easily welded back into place.

Then, in each drop-board regulator frame the timber slabs were removed and six louvre modules 20 were then positioned within the frame. However, prior to positioning the louvre modules within the frame four lugs were welded onto the sides of each module to be slotted into the regulator frames and the modules were then dropped down to fit inside the existing frame. Any gaps were able to be covered by steel cover plate.

Five of these frames were fully bladed and the sixth (right-hand lower section) contained a man-door together with some of the louvre blades (optionally modified in length, width etc).

Advantages of using modules included their rapid and easy removal (eg. for repairs, replacement) and their ability to be installed within any existing frame in the mine.

Example 3

First Trial Louvre-Type Regulator

An initial trial louvre regulator design employed a normal airflow control mechanism using manual fixing of the louvre blades in each module via linking rods to a rigid manual blade adjustment mechanism (but which could also employ a motorised drive).

Before stope firing the blades were moved to a fully opened position and were locked into place. The trial louvre design was subjected to several blasts, and it was observed that the closest blast caused damage to the blades and their attached blade mounting shafts. In some trials, when stope firing took place on the same level as the louvre, the blades and shaft attachment were so damaged that the module was rendered inoperative.

In the trials it was also noted that the air-blast from firings within surrounding levels subjected the louvre blades to forces from other directions (eg. originating from the raise). Even though this represented the least flow resistance to an air blast, the swirling action of the turbulent air was observed to subject the blades and attached linkages to excessive pressures, thereby potentially sustaining damage.

The applications of regulators comprising manually controlled louvre blade adjustment was therefore considered to be more limited.

Example 4

Second Trial Louvre-Type Regulator

As discussed in Example 3, the initial trial louvre regulator design incorporating manual louvre blade adjustment did not satisfy all operating conditions within the mine and, it was noted, would likely sustain damage at some stage, rendering it inoperative. A second trial louvre regulator design was conceived (a so-called “MkII” design) which was designed to minimise the damage to the louvre blades, attached linkages and frame structure. The MkII design was developed to lessen the initial impact on the frame that secured the components.

In this regard, in the MkII design the blades (and any linkages) were free to move during a firing and did not absorb as much energy as a manual blade fixing system. The blades were therefore self-adjusting.

In the design and construction of the MkII design, the following design features were developed:

1. The louvre blade pivot point was located as close to the leading edge (edge closest to the air-flow from within the adjacent stope) as possible so that damage was minimised during stope firing. Also, for the blades to hang freely and close against each other the pivot point was located close to the leading edge.
2. The blade design had a low resistance to passing air so that energy losses were minimised.
3. The louvre blades were self-adjusting such that, before stope firing, mine ventilation officers did not have to make any adjustment to the louvre.
4. The blades within a louvre module rotated freely on their shafts and could self-closed under mine ventilation pressures (except at blasting overpressures).
5. The blades were fabricated to be sufficiently heavy to assist in achieving movement to a predetermined position (closed or partially open) against ventilation pressures.
6. The required weighting was different for louvre regulators situated next to intake passages compared to those situated next to exhaust passages.
7. There was no restraint on the blades being able to fully open (eg. towards horizontal) from a set position (predetermined—closed or partially open) during firing and the blades dropped back (fell) to the predetermined position even after being further opened by the blast.
8. A pre-set guide (eg. stop) was not rigidly attached to the blade linkage.
9. The louvre frame was braced from the front, as there was no bracing access from the rear (or within the raise) in use.
10. An option to have one of the in-use bottom modules hinged, to enable user access through the louvre regulator, as necessary.
11. The blades could be independently coupled to an actuator (eg. employing a motor drive) for normal airflow control in the raise.

Example 5

Exhaust and Intake Louvre-Type Regulators

FIGS. 7A and 7B respectively and schematically illustrate louvre regulators subject to intake or exhaust pressure. A typical maximum ventilation pressure within any raise was noted to be up to 2000 Pa (with the maximum fan pressure at the top of the raise as illustrated). This pressure was dissipated as air traveled through a raise and/or as air paths were split. This pressure was used for the design of the louvre blades.

In the intake louvre regulator of FIG. 7A a stope airblast lifted the louvre blades, whereas ventilation air pressure tended to close the blades.

In the exhaust louvre of FIG. 7B both the stope airblast and the ventilation air pressure lifted open the blades. Thus, blade weight and, where necessary, additional weighting and/or spring biasing was employed to counteract ventilation air pressure lift on the louvre blades and maintain them in the predetermined position. To further assist blade self-closure:

1 A blade design was employed that located the blade pivot point towards its top edge;
2 A blade design was employed where the blade was tilted so that a component of the blade weight resisted the ventilation air-flow;
3 The weight distribution of the blade was closely examined.

Example 6

Louvre Blade Design

Calculations were performed to determine whether a louvre blade weight could be employed that would resist the force of the ventilating air. The calculations assumed that the blade shaft was offset towards the blade top and that the blades sat against each other in a tilted configuration (FIG. 8).

The calculations were based on a blade that was 475 mm wide, manufactured from 8 mm plate and, for simplicity, was 1 metre in length. The blade was assumed to be welded to a 30 mm diameter shaft and offset 100 mm, giving 100 mm overlap for each pair of adjacent blades. The blade shaft centres were assumed to be spaced 375 mm. It was assumed that the offset blade design needed to resist a 2 kPa ventilation pressure without opening. The calculations were as follows:

$\begin{array}{c}\mathrm{Blade}\mathrm{weight}=0.008\times 0.475\times 9800N\\ =360.3N\end{array}$

In FIG. 8 offset blades are shown attached to 30 mm shafts centred on an axis A. In FIG. 8:

F_s is the resultant force of a steel blade;

F_v1,2 are the forces on the blade due to the ventilation exhaust air.

Air pressure was resolved into equivalent forces about a line of thrust as shown.

F_v1=0.275×1×2000=550 N (lever arm 137.5 mm)
F_v2=0.100×1×2000=200 N (lever arm 50.0 mm)

By resolving moments about the centre A of the shaft it was determined whether the blade force was sufficient to close against the ventilation pressure.

Hence

$\begin{array}{c}{M}_A=365.3\left[N\right]\times 21.93\left[\mathrm{mm}\right]+200\left[N\right]\times 50\left[\mathrm{mm}\right]\\ =18\mathrm{kN}.\mathrm{mm}\end{array}$

Ventilation pressure on the blade below the shaft should therefore resist the moment M_A. The moment due to the ventilation pressure on the portion of the blade below the shaft was:

$=550\left[N\right]\times 137.5\left[\mathrm{mm}\right]=75.625\mathrm{kN}.\mathrm{mm}$

The imbalance of 57.6 kN.mm needed to be overcome in order to maintain the blades in the predetermined position. The following possibilities were then considered as possible solutions:

1 Add a solid block of 40 mm square steel to the blade tip (but this was calculated to provide only an additional 7.845 kN.mm).
2 Offset the blade another 50 mm from pivot A (but this was calculated to add only another moment of 50×365.3=18.27 kN.mm).

Thus, an increase in blade weight and/or an increase in the blade pivot arm were each calculated to be insufficient in overcoming the ventilation air pressure. In addition, because the blade edges seal against the frame, the amount of offset was accordingly limited. Centralizing the pivot point A was noted to balance the ventilation pressure on the blade, however the blades could then sustain damage during a stope firing/blast.

Thus, one solution as outlined in the description of FIG. 3 was developed, namely, arranging a balance weight on the raise side of each module, the weight being attached to blades via respective lever arms. This ensured the blades were maintained in the predetermined position under normal ventilation pressures.

Typically a steel weight was employed. The option of guiding and containing the steel weight's movement up and down within a pipe was also investigated. A return spring mechanism was also noted to perform the same function and was advantageously also tension adjustable.

It was noted that further experiments were to be conducted to measure the pressure-time profile of the effects of production firing at a trial site. Software was to be written to describe the forces on each louvre component at any given blade angle or at any given time. The software was to have as input the pressure time profile for any overpressure event.

Example 7

Exhaust Louvre-Type Regulator Design Solution

Referring again to FIGS. 3A and 3B an exhaust louvre is schematically depicted. This design was based on incorporating a weight that can act against a 1000 Pa ventilation pressure on 300×1200 mm blades (an approximate louvre module size). The total mass of each weight bar on opposing sides of a module was 54 kg (a bar located on one side of the louvre could have a bar weight of approximately 108 kg).

In operation of the exhaust louvre it was noted that as the louvre blades opened the resistance to airflow lessened (ie. the lever arm effectively shortened) with each blade becoming easier to open the more open it became. This had a tendency to lessen the blast impact on the blades and structure as a whole.

Ideally the link bar weight was adjustable (eg. using the ballast). Also, because the blades had a tendency to accelerate as they shut the regulator design needed to account for impact against a set-point mechanism.

Example 8

Louvre Blade, Module and Frame Fabrication

Each louvre blade was formed from painted mild steel (350 grade steel). The painting of the steel louvre was undertaken after sandblasting. Frames were also formed similarly. A two-part epoxy paint (Joatacoat 605) was employed to provide effective corrosion protection. Such paint was found to give good results in underground mines where known ventilation controls painted with such paint did not need to be refurbished until after a period of six years.

316 stainless steel was used for louvre shafts, and nylon bushes were employed at the blade mountings.

Design Specifications

The louvre modules were designed to control airflow to surface air raises that service up to six or seven levels within each part of a mine. Each louvre blade, module and frame:

• • Was designed to withstand a blast overpressure of 5 psi (34 kPa);
  • Was manually adjustable by one operator without assistance;
  • Typically had an opening size 4.5 metres in height and 3.5 metres in width;
  • Had a modular construction so that its configuration was variable;
  • Was able to be shotcreted into place;
  • Was able to be controlled remotely;
  • Was unaffected by ground movement during installation;
  • Was corrosion resistant (eg. to saline water vapour present in down-casting air);
  • Had the option for control in pairs of modules, whereby eg. three actuators could fully open or fully close the louvre blades. To provide incremental airflow control, additional controls could be added to the actuators.

Louvre Modules

The louvre regulator typically comprised six equally sized removable modules, each with a set of horizontal louvre blades for ease of removal and replacement of damaged modules (see FIG. 1). Lifting lugs were provided for the safe removal of each module.

In a manual control version, horizontal louvre blades were able to be set in multiple positions. In such case, the louvre blades in each module were adjustable to and lockable in the positions: Open, 20%, 40%, 60%, 80% and Closed.

The louvre framework was also able to be welded to existing drop-board regulator steel frames, however each such application required careful examination and measurement for compatibility.

Louvre Automation

Automatic (and remote) control of blades in each louvre blade frame was achieved using a Tyco double acting electric actuator, which employs a rack and pinion, with the pinion connected to the louvre blades via connecting rods. These actuators could easily be remotely controlled. The actuators also had an anodised aluminium body to protect against corrosive environments. Three actuators were mounted on a horizontal frame that separated each pair of louvre modules.

Example 9

Louvre-Based Regulator Advantages

In a self-adjusting louvre-type regulator:

• • The ventilation officers did not have to adjust the louvre before and after a stope firing.
  • Blades were free to swing away from the blast during a stope firing.
  • Blades returned to their original (predetermined) positions after a stope firing.
  • Returned blades remained in the predetermined position against the normal mine ventilation flow, and in the closed position provided better sealing performance than known regulators, especially with blade overlap.
  • Blade modules were able to be retrofit into existing drop-board regulator frames.
  • Regulators were provided that were suitable for use within corrosive saline environments and that required minimal servicing.

Where an adjustment mechanism was employed with the self-adjusting louvre-type regulator it did not need to be directly attached to the louvre blade controls, and could comprise a simple mechanism.

Whilst specific embodiments of a louvre-type regulator have been described, it should be appreciated that the regulator can be embodied in many other forms.

Claims

1. A louvre-type airflow regulator for a mine passage comprising:

a plurality of louvre blades, each adapted for mounting in a frame and pivoting therein around a lengthwise axis between a predetermined position in which the louvre blades combine to close or restrict at least a portion of the passage, and an open position in which air is able to readily flow between the louvre blades and through the passage;

a biasing mechanism for acting on each louvre blade such that, in use, each louvre blade can be maintained in the predetermined position until a predetermined airflow against the louvre blades is reached; wherein

the predetermined position is adjustable and includes at least one partially open position of the blades between a closed position and a fully open position.

2. (canceled)

3. A regulator as claimed in claim 1 wherein the biasing mechanism is:

(i) a weighting arrangement operable on each louvre blade and that tends to cause it to pivot into the predetermined position;

(ii) a spring mechanism that positively urges each louvre blade to pivot into the predetermined position; and/or

(iii) a strut mechanism that positively urges each louvre blade to pivot into the predetermined position.

4. A regulator as claimed in claim 3 wherein in:

(i) the weighting arrangement comprises one or more weights operatively coupled to each louvre blade via a respective linkage, whereby due to gravity the weight(s) draw down on the linkages and thereby urge each louvre blade into the predetermined position, but at the predetermined airflow the louvre blades then act on each linkage and urge the weight(s) up as each louvre blade moves towards the open position;

(ii) the spring mechanism comprises a respective spring that pulls each louvre blade into the predetermined position, but at the predetermined airflow the louvre blades act on and stretch each respective spring as each louvre blade moves towards the open position; and/or

(iii) the strut mechanism is a gas strut that is connected to a linkage mechanism that acts on the louvre blades to urge them into the predetermined position, but at the predetermined airflow the louvre blades act on the linkage mechanism which in turn acts against the gas strut as each louvre blade moves towards the open position.

5. A regulator as claimed in claim 4 wherein in:

(i) the weighting arrangement comprises one or two weights, with each weight having the linkages extending therefrom at intervals spaced along the weight, and with each linkage being coupled to a respective louvre blade at a coupling that is pivotally mounted to the frame at the same point as the blade pivotal mounting;

(ii) each spring extends between the frame and a location on the louvre blade at or adjacent to a leading or trailing edge of the blade; and/or

(iii) the connection between the gas strut and the linkage mechanism is adjustable such that the louvre blades can either be fully or partially closed by the operation of the gas strut.

6. (canceled)

7. (canceled)

8. (canceled)

9. A regulator as claimed in claim 1 further comprising the frame, and a plurality of mounting pins/bolts extending from the frame and adapted for being fastened with respect to adjacent wall(s) of the mine passage.

10. A regulator as claimed in claim 9 wherein the pins are used for the mounting of formwork that provides at backing for the application of a cementitious binder, whereby the pins/bolts, formwork and binder then provide a structural wall to support the frame in the passage.

11. A regulator as claimed in claim 1 wherein the frame forms part of a module, with a plurality of such modules being mountable in a larger frame arranged in the passage.

12. A regulator as claimed in claim 11 wherein each module has a plurality of selectively extendable securing pins arranged around its periphery such that, when the module is mounted in the larger passage frame, extension of the securing pins secures the module to the passage frame, and retraction of the securing pins enables module detachment from the passage frame.

13. A regulator as claimed in claim 11 wherein each module has lifting points formed therein that enable it to be lifted into and out of the passage frame.

14. A regulator as claimed in claim 1 further comprising a stop for preventing blade pivotal movement beyond the open position.

15. A regulator as claimed in claim 14 wherein the stop comprises a dampener or shock absorber.

16. A regulator as claimed in claim 1 wherein the blades extend generally horizontally in the frame in use.

17. A blast proof regulator for a mine passage comprising:

a plurality of louvre blades, mounted in a frame and pivoting therein around a lengthwise axis between at least a predetermined position in which the louvre blades combine to close or restrict at least a portion of the passage, and an open position in which air is able to readily flow between the louvre blades and through the passage;

a biasing mechanism for acting on each louvre blade such that, in use, each louvre blade can be maintained in the predetermined position until a predetermined airflow against the louvre blades is reached; wherein

the predetermined position is adjustable and includes at least one partially open position of the blades between a closed position and a fully open position; and wherein the louvre blades are adapted to pivot open at a predetermined airflow in the mine passage and return to their respective predetermined positions after removal of the predetermined airflow.

18. A blast proof regulator as claimed in claim 17 wherein a plurality of frames are mountable in a larger frame arranged in the mine passage.