Abstract:
The invention provides an airflow regulator for a mine passage, comprising: a louver blade pivotable to a predetermined position, which is in a range from a closed position in which the louver blade restricts at least a portion of the passage to an open position in which air is readily able to flow in the passage; and a linkage mechanism for pivoting the louver blade wherein the linkage mechanism includes a biasing strut mechanism which is only activated to pivot the louver blade into the open position when a predetermined airflow is reached and biases the louver blade to its predetermined position after the airflow has reduced to less than the predetermined airflow.

Description:
RELATED APPLICATION DATA 
       [0001]    This application claims priority from AU Patent Application No. 2007905404, filed Oct. 3, 2007, which is incorporated herein in its entirety by reference hereto. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    This invention relates to an improved airflow regulator particularly to a louver type airflow regulator such as might be used in mining shafts, tunnels, raises, roadways and the like, hereinafter referred to as mine passages, to control or regulate airflow therethrough 
         [0004]    2. Description of the Prior Art 
         [0005]    Underground mines typically have a number of raises that act as a conduit for fresh air, with raises often formed on an air intake side of an ore body and on air return or opposite side of the ore body. Airflow at various levels in the mine or, in the case of metalliferous mines, individual mining areas called stopes, 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. Drop-board regulators typically comprise a steel H section frame fabricated in 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 the airflow that is allowed into a given section of a mine. However, 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 a regulator, a miner has to physically remove all the boards from the regulator. This is a heavy, arduous, and time consuming task which wastes man hours and reduces mine efficiencies. 
         [0006]    WO2006/108228, the entire contents of which are incorporated herein by reference, discloses an improved louver type airflow regulator in which airflow is controlled by adjusting the degree to which the louver blades are open and which are free to swing into a fully open position during blasting or stope firing but return to the original positions after such a firing by means of a weight, gas strut or a spring. 
         [0007]    The present invention relates to improvements in the airflow regulators disclosed in WO2006/108228. 
         [0008]    Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is solely for the purpose of providing a context for the present invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application. 
       SUMMARY OF THE INVENTION 
       [0009]    According to the invention there is provided an airflow regulator for a mine passage comprising: 
         [0010]    a louver blade pivotable to a predetermined position which in a range from a closed position in which the louver blade restricts at least a portion of the passage to an open position in which air is readily able to flow in the passage; and a linkage mechanism for pivoting the louver blade wherein the linkage mechanism includes a biasing strut mechanism which only activates to pivot the louver blade into the open position when a predetermined airflow is reached and biases the louver blade to its predetermined position after the airflow has reduced to less than the predetermined airflow. 
         [0011]    The biasing strut mechanism forms part of the linkage mechanism when not activated and is generally movable with the linkage mechanism when not activated and so it allows the louver blades to be moved between open and closed positions without a substantial input of force being required. 
         [0012]    In contrast, in the embodiments of WO2006/108228 which include a gas strut, it is not possible to pivot the louver blades without activating the gas strut. Thus, the present invention is a significant improvement on the prior art, as it means that the degree of ventilation may be easily changed without too great a force having to be exerted on the linkage mechanism. This arrangement is particularly advantageous as it allows for the air flow regulator to be easily automated, e.g. by provision of a powered actuator to move the strut mechanism. Thus the invention provides an air flow regulator that has the same strength as those of the prior art, but is reduced in weight and more flexible in its operation. Owing to the weight reduction, air flow regulators made to the present invention are easier to transport and install. 
         [0013]    In some embodiments, the regulator may comprise a plurality of louver blades. In some embodiments, the regulator may be an intake regulator and may comprise a plurality of louver blades which overlap in the closed position to close or restrict at least a portion of the passage. In some embodiments, the regulator may be an exhaust regulator and may comprise a plurality of louver blades which do not overlap in the closed position. 
         [0014]    In some embodiments, the regulator may comprise a frame in which the louver blade is mounted. The louver blade may be mounted in a frame such that it may pivot therein around a lengthwise axis. An advantage of having a frame is that the regulator is easily manufactured, transported and installed. 
         [0015]    In some embodiments, the biasing strut mechanism may be a constant force biasing strut mechanism which only activates when a predetermined constant force has been reached, e.g. from the air-flow creating a force on the louver blade that is connected to the strut mechanism via the linkage mechanism. The biasing strut mechanism may activate by becoming compressible. The predetermined constant force may be chosen to have a value in a range from the maximum amount of force required to move the louver blades and the force generated by the predetermined airflow. A person of skill in the art would easily be able to determine a suitable force at which the biasing strut mechanism would activate. The predetermined airflow may be an airflow or pressure change from a deliberate or accidental explosion in a mine, for example from blasting or stope firing. The biasing strut mechanism may comprise a fluid strut, for example a gas strut. The biasing strut mechanism may have a cylinder, a piston and a piston rod. The biasing strut mechanism may comprise a spring. In some embodiments the strut mechanism is only activated when force in excess of 4000 Newton is applied to it, however the force can be varied to suit the required airflow regulator design. 
         [0016]    In some embodiments, the linkage mechanism may include a linkage bar that is operatively coupled to a louver blade via a linkage arm. For example, one end of the linkage arm may be fixed to a louver blade and the other end of which is pivotally mounted to the linkage bar to urge the louver blades to the predetermined position. In some embodiments, the linkage bar may be vertically oriented. 
         [0017]    In some embodiments, the linkage mechanism has a selectively variable length wherein the regulator is arranged so that the louver blade is in a closed position when the linkage mechanism has a maximum length and the louver blade is in an open position when the linkage mechanism has a minimum length. 
         [0018]    In some embodiments, the linkage mechanism has a position control mechanism to selectively vary the length of the linkage mechanism. The position control mechanism may be manually operated. For example, it may comprise an externally threaded rod located above a hollow strut and a handle and threaded sleeve, arranged such that by turning the handle the threaded rod may be raised or lowered into the hollow strut. The position control mechanism may be automated, for example it might be in the form of a powered actuator operated by compressed air, electrically or hydraulically. The actuator may also comprise a manually operated position control mechanism. The linkage mechanism may have a minimum length by activation of the biasing strut mechanism or by operation of the position control mechanism. 
         [0019]    In some embodiments the powered actuator may be remotely operated. Use of remote operation is particularly useful if the airflow regulator is positioned in a location that is difficult to reach or unsafe to reach due to contaminated air. Furthermore, remote operation can dramatically increase the speed at which the degree of ventilation may be altered. This leads to improved safety and efficiency. 
         [0020]    In some embodiments, the biasing strut mechanism is provided between the linkage bar and the position control mechanism. For example, one end of the biasing strut mechanism, typically the cylinder end, may be mounted to the linkage bar by a bracket or the like fixed to the linkage bar such that movement of the linkage bar moves that end of the biasing strut mechanism. The cylinder end may be pivotally mounted to the linkage bar. The piston rod may be mounted to the position control mechanism. 
         [0021]    Thus, in a broad aspect, the present invention provides a louver type airflow regulator which allows for continuous positional adjustment of the blades and uses a preferably constant force strut mechanism for return movement of the louvers which is relatively uncompressed at rest. 
         [0022]    According to the invention there is further provided a louver type airflow regulator for a mine passage comprising: 
         [0023]    a plurality of louver blades mounted in a frame and pivoting therein around a lengthwise axis between a predetermined position in which the louver blades combine to close or restrict at least a portion of the passage, and 
         [0024]    an open position in which air is readily able to flow between the louver blades and through the passage portion; and 
         [0025]    wherein when a predetermined airflow is reached, the louver blades are arranged to open or open further, unless already fully open, and including a return mechanism to cause the blades to return to their predetermined position after the airflow has reduced to less than the predetermined airflow, and 
         [0026]    wherein the return mechanism includes a biasing means in the form of a strut mechanism that is operatively connected to a linkage mechanism that acts on one or more of the louver blades to urge them into the predetermined position and wherein the return mechanism is such that the strut mechanism is not activated except when the blades open after the predetermined airflow is reached. 
         [0027]    Typically the strut mechanism is a gas strut comprising a cylinder, piston and piston rod. 
         [0028]    The gas strut is preferably a constant force strut mechanism which only moves/is activated when force in excess of 4000 Newtons is applied to it or some other predetermined force. 
         [0029]    The return mechanism may includes a vertically oriented linkage bar that is coupled to each louver blade via a linkage arm one end of which is fixed to the louver blades and the other end of which is pivotally mounted to the linkage bar. 
         [0030]    Preferably, one end of the gas strut, typically the cylinder end is pivotally mounted to the linkage bar by a bracket or the like fixed to the bar  25  such that movement of the bar moves that end of the strut. 
         [0031]    A free end of the piston rod is preferably mounted to means for raising and lowering that end that hence the linkage bar. 
         [0032]    In one preferred embodiment the means is an externally threaded rod located above a hollow strut and a handle and threaded sleeve, turning the handle raising and lowering the threaded rod. 
         [0033]    The term “predetermined airflow” can include within its scope  5  predetermined air pressure, and typically, though not exclusively relates to an increase in airflow/pressure due to blasting/stope firing. 
         [0034]    Airflow will typically act on the blades due to air currents which may flow in either direction through the regulator. However these flows of normal ventilation air will not typically be of sufficient force to cause the louver blades to move. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0035]    Specific embodiments of the present invention will now be described by way of example only and with reference to the accompany drawings in which: 
           [0036]      FIG. 1  is a front view of a louver type regulator according to a first embodiment of the invention with the blades in an open position; 
           [0037]      FIG. 2  is a top view of the louver type regulator as shown in  FIG. 1 ; 
           [0038]      FIG. 3  is a side view of the louver type regulator as shown in  FIG. 1  with the blades in a fully open position; 
           [0039]      FIG. 4  is a side view of the louver regulator as shown in  FIG. 1  with the blades in a fully closed position; 
           [0040]      FIG. 5  is a side view of the regulator as shown in  FIG. 1  with the blades in a partly open position as a result of airflow or manual adjustment; 
           [0041]      FIG. 7  is a front view of an automated louver type regulator according to a second embodiment of the invention; 
           [0042]      FIG. 8  is a side view of the louver type regulator of  FIG. 7  with the blades in a standard closed position; 
           [0043]      FIG. 9  is a side view of the louver type regulator of  FIG. 7  with the blades halfway between an open and a closed position; 
           [0044]      FIG. 10  is a side view of the louver type regulator of  FIG. 7  with the blades in a standard open position; 
           [0045]      FIG. 11  is a side view of the louver type regulator of  FIG. 7  with the blades in a blast open position; and 
           [0046]      FIG. 12  is a plan view of the louver type regulator of  FIG. 7 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0047]    Referring now to the drawings, a louver regulator  10  or module according to a first embodiment of the invention is shown for mounting in a mine passage in  FIGS. 1 to 4 . The regulator  10  comprises a plurality of louver blades  12 ,  14 ,  16  and  18  mounted in a rectangular steel frame  20 . The frame  20  is designed for retro-fitting to an in situ drop-board regulator frame  21  (refer to  FIG. 2 ). However, it could also be fabricated in a new frame for fitting to mine openings. 
         [0048]    Each louver blade  12 , 14 , 16 , 18  is mounted at its opposed ends in the frame  20  and is able to pivot around its lengthwise axis  22  between a closed or partially closed position in which the louver blades  12 , 14 , 16 , 18  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 more easily flow between the louver blades  12 , 14 , 16 , 18  and through the passage. As is best seen in  FIG. 3 , the axis  22  is defined by/located in a bar  22  mounted, typically welded, to the rear of the louver blade  12 , 14 , 16 , 18  and adjacent an upper edge thereof. 
         [0049]    As is best seen in  FIG. 4 , the louver blades  12 , 14 , 16 , 18  overlap in the closed position which is especially useful for an intake louver regulator as it results in the forming of a seal, due to pressure on the louver blade front faces  82 , 84 , 86 , 88  of passage ventilation air. It would also be possible to use a non lapped arrangement for an exhaust louver regulator. 
         [0050]    An adjustment and biasing mechanism  90  for acting on each louver blade  12 , 14 , 16 , 18  is provided. 
         [0051]    The adjustment and biasing mechanism  90  includes a vertical linkage bar  30  that is coupled to each louver blade  12 , 14 , 16 , 18  via linkage arms in the form of double brackets  32 , one end of which is fixed (welded) to the louver blades  12 , 14 , 16 , 18  and the other end of which is mounted by a respective coupling pivot  34  to the linkage bar  30 . 
         [0052]    The biasing mechanism  90  includes a constant force gas strut  50  including a cylinder  52  and piston rod  54 . The gas strut  50  is set to activate (i.e. the piston rod  54  moves into the cylinder  52  compressing the gas inside) when a blast force superimposed on the louver blades transmits a force through the linkage bar and (typically of 4000 Newton or more) is applied to the piston rod  54 . The cylinder end  53  of the gas strut  50  is pivotally mounted to the linkage bar  30  by a bracket or clevis  55  or the like fixed to the bar  30  such that movement of the bar  30  moves that end of the strut  50  and vice versa. 
         [0053]    A free end  56  of the piston rod  54  is pivotally mounted to an externally threaded rod  59 . A position control mechanism  58  which includes a handle  60  in the form of cruciform intersecting levers, or a wheel, is fixed to an internally threaded sleeve  62  located above a hollow strut  64 . 
         [0054]    In use, turning the handle/levers  60  in one sense (either clockwise or anti-clockwise) will cause the threaded rod  59  to rise vertically and at the same time push upwardly the piston rod  54  of the gas strut  50  against the weight of the linkage rod  30 . The weight of the linkage rod  30  is not sufficient to compress the gas strut  50 . When the module  10  is “at rest”—i.e. not during blasting or at times where the airflow is below the predetermined level, in the fully open position shown in  FIG. 3  or the fully closed position shown in  FIG. 4 , or any intermediate position, the constant force gas strut  50  is not compressed. This makes adjustment of the louvers  12 , 14 , 16 , 18  easier and safer as the gas strut  50  does not have to be compressed or decompressed as the louvers  12 , 14 , 16 , 18  are adjusted to change the degree of ventilation. Adjustment is also continuous between the fully open and closed positions by simple rotation of the handle/levers  60 , to set the louver blades  12 , 14 , 16 , 18  to allow the required amount of ventilation. 
         [0055]    With reference now to  FIGS. 4 and 5 , the gas strut  50  only becomes compressed during greatly increased air flow  100  such as would occur during blasting or stope firing when the position of the threaded rod  59  remains fixed and the louver blades  12 , 14 , 16 , 18  rotate in an anti-clockwise or upward direction “A”, pushing the piston rod  54  into the cylinder  52  and compressing the gas strut  50 . Such action provides a bias to return the louver blades  12 , 14 , 16 , 18  to their set position after the greatly increased air flow  100  has subsided after firing. 
         [0056]    In  FIGS. 7 to 12 , a second embodiment of a louver regulator  110  according to the present invention is shown. Louver regulator  110  is an automated louver regulator in that the manually operated mechanism  58  of the first embodiment for adjusting the position of the strut  50  is replaced by a powered actuator. Like features of the second embodiment to features of the first embodiment are identified by like reference numerals. 
         [0057]    Louver regulator  110  comprises a plurality of louver blades  112 , 114 , 116 , 118  mounted in a rectangular steel frame  120 . The frame  120  is designed for retro-fitting to an in situ drop-board regulator frame  121  shown in  FIG. 12 . However, the regulator  110  could also be fabricated in a new frame (not shown) for fitting to a mine opening or a passage way. Each louver blade  112 , 114 , 116 , 118  is mounted at its opposed ends (one of which is indicated as  122   a  in  FIG. 7 ) in the frame  120  and is able to pivot around its lengthwise axis  122  between a closed or partially closed position (such as that shown in  FIGS. 7 and 8 ) in which the louver blades  112 , 114 , 116 , 118  combine to close or restrict gas flow through at least a portion of the passage and an open position (shown in  FIGS. 10 and 11 ) in which gas, typically air is able to more easily flow between the louver blades  112 , 114 , 116 , 118  and through the passage. The axis  122  is defined by/located in a bar  122  mounted, typically welded, to the rear of the louver blade  112 , 114 , 116 , 118  and adjacent an upper edge thereof. 
         [0058]    As is best seen in  FIG. 8 , the louver blades  112 , 114 , 116 , 118  overlap in the closed position which is especially useful for an intake louver as it results in the forming of a seal, due to pressure on the louver blade front faces  182 , 184 , 186 , 188  from passage ventilation air. It would also be possible to use a non lapped arrangement for an exhaust louver. 
         [0059]    An adjustment and biasing mechanism  190  for acting on each louver blade  112 , 114 , 116 , 118  is provided. 
         [0060]    The adjustment and biasing mechanism  190  includes a vertical linkage bar  130  that is operably coupled to each louver blade  112 , 114 , 116 , 118  via linkage arms in the form of double brackets  132 , one end of which is fixed (welded) to the louver blades  112 , 114 , 116 , 118  and the other end of which is mounted by respective coupling pivots  134  to the linkage bar  130 . 
         [0061]    The biasing mechanism  190  includes a constant force gas strut  150  including a cylinder  152  and piston rod  154 . The gas strut  150  is set to activate (i.e. the piston rod  154  moves into the cylinder  152  compressing the gas inside) when a strong force (typically of 4000 Newton or more) is applied to the piston rod  154 . The strong force is selected to be approximately the force applied to the louver blades  112 , 114 , 116 , 118  by air flow created during blasting in a mine. The cylinder end  153  of the gas strut  150  is pivotally mounted to the linkage bar  130  by a bracket  155  or the like fixed to the bar  130  such that movement of the bar  130  moves that end of the strut  150  and vice versa. 
         [0062]    The powered actuator  175  comprises a body  171 , rod housing  172  and an extendable rod  173 . Free end  156  of piston rod  154  is attached to free end  174  of actuator rod  173  by connector  178 . 
         [0063]    The actuator  175  is arranged such that through movement of actuator rod  173  from an extended position to a retracted position, as shown respectively in  FIGS. 8 and 10 , the louver blades  112 , 114 , 116 , 118  may be moved from a closed position (under regular air flow) to an open position. Thus, under regular conditions, when the actuator rod  173  is extended the louver blades  112 , 114 , 116 , 118  are closed, and when the actuator rod  173  is retracted the louver blades  112 , 114 , 116 , 118  are open. When the actuator rod  173  is partially extended for example to a predetermined position, the louver blades  112 , 114 , 116 , 118  are partly open (as shown in  FIG. 9 ). The actuator rod  173  may be extended and retracted by remote operation such that a desired rate of flow of ventilation air may be obtained, for example as shown in  FIG. 9 . 
         [0064]    When the module  110  is “at rest”—i.e. not during blasting or at times where the airflow is below the predetermined level, in the fully open position shown in  FIG. 10  or the fully closed position shown in  FIG. 8 , or any intermediate position such as that shown in  FIG. 9 , the gas strut  150  is relatively uncompressed. This makes adjustment of the louvers  112 , 114 , 116 , 118  by actuator  175  easier and safer as the gas strut  150  does not have to be compressed or decompressed as the louvers  112 , 114 , 116 , 118  are adjusted to change the degree of ventilation. Accordingly, actuator  175  does not have to overcome the resisting force of the gas strut  150  to effect adjustment of the position of the louvers  112 , 114 , 116 , 118 . Thus the power consumption of the actuator  175  is less than that required in the prior art, as the force required to move the louvers  112 , 114 , 116 , 118  is much less. As the actuator  175  is attached to the gas strut  150 , the actuator  175  has to be rated to at least the resisting force of the gas strut  150  or greater so that it is able to withstand transmitted forces on the louver blades  112 , 114 , 116 , 118 , e.g. from the impact of the increased air flow  100  from an explosion. This is in order that the actuator  175  is not deflected from its predetermined position by the impact of the increased air flow  100 . 
         [0065]    The actuator  175  is provided with a mechanism (not shown) for manual operation such that if electric power is not available the louver regulator  110  may still be operated by manual extension and retraction of the extensible rod  173  of the actuator  175 . 
         [0066]    In the present embodiment the actuator  75  is a Linak® LA36 actuator, but it will be appreciated that any suitable actuator might be used. 
         [0067]      FIG. 11  shows the louver regulator  110  with its louver blades  112 , 114 , 116 , 118  having been forcibly rotated into an open position by increased air flow  100 , such as from blasting, thereby compressing the gas strut  150 . 
         [0068]    The present invention provides a low cost, light-weight louver blade base regulator which is easy to adjust and which provides continuous adjustment of the position of the louver blades. 
         [0069]    It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.