Patent Publication Number: US-6698844-B2

Title: Earth discharging device for upward-facing shield machine

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     This application is entitled to the benefit of and incorporates by reference essential subject matter disclosed in Japanese Patent Application No. 2001-394876 filed Dec. 26, 2001. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an earth discharging device for an upward-facing shield machine, and more particularly to an upward-facing shield machine which can securely perform earth pressure control of a work face. 
     2. Description of the Related Art 
     FIG. 6 illustrates an earth discharging device for an upward-facing shield machine a previously disclosed by the present inventors. As is shown in the drawing, the upward-facing shield machine a comprises: a vertically-placed tubular shield frame b; a partition wall c which divides the interior of the shield frame b into a work face side and an interior side; and a cutter d which is rotatably mounted on the partition wall c. The shield machine a constructs a tunnel in the vertical direction by causing the cutter d to rotate using a motor e while a jack g is expanded under a reaction force to a pre-installed segment f to cause the shield frame b to rise, whereupon the jack g is caused to contract such that a segment can be provided in a tensioned state in the space between the pre-installed segment f and the jack g manually or using an erector (not shown in the drawing). 
     The earth and sand that are cut away by the cutter d are taken into a cutter chamber h and discharged by an earth discharging device i. The earth discharging device i comprises: an earth discharging pipe j which is connected to the cutter chamber h and extends downward; an elastic film-type valve k which is provided in the earth discharging pipe i and which opens and closes the interior of the earth discharging pipe i by expanding and contracting diametrically by means of fluid pressure; and an agitator  1  which kneads and fluidizes the excavated earth and sand so that this mixture can be excluded downward more easily by means of gravitational force. The agitator  1  comprises: a rotary shaft n which is disposed in the interior of the earth discharging pipe i and is rotated by a motor m; a collar o which is rotatably fitted over the part the rotary shaft n which faces the elastic film-type valve k; and a kneader blade p which is mounted on the part of the rotary shaft n inside the cutter chamber h. 
     Meanwhile, the elastic film-type valve k comprises: a tubular elastic film q (rubber film or the like) disposed at a point in the earth discharging pipe i; a tubular casing s which is disposed in a form which covers the outer side of the elastic film q and which forms a pressurizing chamber r with the peripheral surface of the elastic film q; and a supply and discharge port t which is opened in the casing s for supplying and discharging fluid (air, water, etc.) into and out of the pressurizing chamber r. The elastic film-type valve k manages adjustments to the earth pressure on the work face by supplying and discharging fluid into and out of the pressurizing chamber r through the supply and discharge port t such that the elastic film q is caused to expand and contract diametrically to adjust the amount of earth to be discharged. 
     However, in the aforementioned elastic film-type valve k, when fluid pressure acts equally on the elastic film q, the earth and sand that pass therethrough are at work face pressure (high pressure) at the inlet side and atmospheric pressure (low pressure) at the outlet side. As a result, the elastic film q does not expand equally, as is illustrated by the wavy line in FIG. 6, but is locally pressed inward, as is illustrated by the solid line in the figure, at the outlet side due to the pressure difference between the inlet side and outlet side, thereby becoming tightly pressed against the collar o. 
     As a result, when the earth and sand at work face pressure inside the cutter chamber h pass through the elastic film-type valve k to drop to the atmospheric pressure side, the earth and sand are locally pressed inward by the pressure difference at the outlet side, whereby the opening adjustment of the elastic film q by means of fluid pressure inside the pressurizing chamber r increases in sensitivity, and earth pressure control at the work face becomes unstable. More specifically, even if the sectional area of the space through which the earth and sand pass is altered in order to control earth pressure at the work face by varying the supply force of fluid to the pressurizing chamber r and varying the amount of expansion of the elastic film q, the elastic film q will be locally pressed inward at the outlet side due to the pressure difference between the upper and lower regions, thereby becoming tightly pressed against the collar o, and as a result, even small alterations in the fluid pressure of the fluid supplied to the pressurizing chamber r will invite repeated blockages and eruptions of the earth and sand, making earth pressure control at the work face unstable. 
     The pressure difference between the inlet side (work face pressure) and outlet side (atmospheric pressure) grows particularly large when advancing at great depth, and thus the elastic film q is locally pressed inward at the outlet side in accordance with this pressure difference, causing repeated earth and sand blockages and eruptions. Furthermore, in cases where the earth and sand are of a type, such as gravel with a large particle diameter or sandy soil with high frictional resistance, that is difficult to fluidize even using the agitator  1  or by injecting a mud-forming agent or the like, the earth and sand at the narrow opening of the elastic film q, which is locally pressed inward, have a tendency to become blocked such that the frequency of eruptions increases. Consequently, earth pressure control directly above the shield machine a becomes unstable, leading to the possibility of displacement at ground level. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide an earth discharging device for an upward-facing shield machine which can securely perform work face earth pressure control. 
     In order to achieve this object, the earth discharging device for an upward-facing shield machine according to the present invention is comprised of: an earth discharging pipe which is disposed in a longitudinal direction in order to discharge downward earth and sand excavated by an upward-advancing, upward-facing shield machine; an elastic film-type valve which is provided in this earth discharging pipe, and which expands and contracts diametrically by means of fluid pressure to open and close the interior of the earth discharging pipe; and a gate mechanism which is provided further toward the outlet side of the earth discharging pipe than the elastic film-type valve, and which adjusts the sectional area of the space inside the earth discharging pipe through which earth and sand pass. 
     According to the present invention, the earth pressure of the earth and sand can be raised by using the gate mechanism to narrow the sectional area of the space inside the earth discharging pipe at the outlet side of the elastic film-type valve through which earth and sand pass such that the earth and sand at the outlet side of the elastic film-type valve become slightly blocked. Thus, the earth pressure at the outlet side of the elastic film-type valve can be made substantially equal to the earth pressure at the inlet side, whereby a substantially uniform earth pressure can be caused to act upon the entire elastic film-type valve. As a result, the elastic film-type valve expands substantially uniformly, and the earth and sand are pressed inward by the entire elastic film-type valve. Thereby, blockages and eruptions of the earth and sand can be avoided, and earth pressure control can be performed securely regardless of depth or soil type. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side sectional view of an earth discharging device for an upward-facing shield machine according to an embodiment of the present invention. 
     FIG. 2 is a sectional view of line II—II in FIG. 1, explaining a gate mechanism of the aforementioned earth discharging device. 
     FIG. 3 is a view to explain a modified example of the aforementioned gate mechanism. 
     FIG. 4 is a partially enlarged view (with the gate mechanism closed) of FIG.  1 . 
     FIG. 5 is a partially enlarged view (with the gate mechanism open) of FIG.  1 . 
     FIG. 6 is a side sectional view of an earth discharging device for an upward-facing shield machine previously disclosed by the present inventors. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An embodiment of the present invention will now be explained based on the attached drawings. 
     As is illustrated in FIG. 1, an upward-facing shield machine  1  comprises: a tubular shield frame  2  which is placed vertically; a partition wall  3  which divides the interior of the shield frame  2  into a work face side and an interior side; and a cutter which is rotatably provided on the partition wall  3 . The upward-facing shield machine  1  builds a tunnel in the vertical direction by causing a cutter  4  to rotate using a motor  5  while a jack  7  is expanded under a reaction force to a pre-installed segment  6  to cause the shield frame  2  to rise, whereupon the jack  7  is caused to contract so that a segment can be provided in a tensioned state in the space between the pre-installed segment  6  and the jack  7  manually or using an erector (not shown in the drawing). 
     In more detail, the partition wall  3  is formed as an arc having an earth discharging port  8  in its central portion. An annular rotating body  9  is rotatably supported between the partition wall  3  and the shield frame  2 . The cutter  4  is mounted on the upper surface of the rotating body  9  via a support post  10 . The cutter  4  is equipped with: a central portion  11  disposed in the rotational center; a plurality of cutter spokes  12  which extend radially from the central portion  11  and include the aforementioned support post  10 ; bits  13  mounted on the work face side of each of the cutter spokes; and a kneader blade  14  which is mounted on the opposite side thereto. 
     A ring gear  15  is provided on the lower surface of the rotating body  9 . The ring gear  15  is axially supported by bearings  16  and meshed with a pinion  17  of the motor  5  so as to be rotationally driven. This upward-facing shield machine  1  builds a tunnel in the vertical direction by driving the motor  5  while causing the jack  7  which is mounted on the inner side of the shield frame  2  to expand, whereby the work face is gradually excavated by the cutter  4  to propel the machine upward under a reaction force to the pre-installed segment  6 . After expanding to a predetermined stroke, the jack  7  is caused to contract and a segment is provided in a tensioned state in the space between the pre-installed segment  6  and the jack  7  manually or using an erector (not shown in the drawing). 
     An earth discharging device  18  is connected to the earth discharging port  8  in the partition wall  3 . The earth discharging device  18  comprises: an earth discharging pipe  19  which is connected to the earth discharging port  8  and which extends downward; an elastic film-type valve  20  which is provided in the earth discharging pipe  19  and which opens and closes the interior of the earth discharging pipe  19  by expanding and contracting diametrically by means of fluid pressure; and a gate mechanism  21  which is provided in the earth discharging pipe  19  downstream of the elastic film-type valve  20  and which adjusts the sectional area of the space inside the earth discharging pipe  19  through which earth and sand pass. 
     As is illustrated in FIG. 4, the elastic film-type valve  20  comprises: a tubular elastic film  22  (rubber film or the like) which is disposed at a point in the earth discharging pipe  19 ; a tubular casing  24  which is disposed so as to surround the elastic film  22  and which forms a pressurizing chamber  23  with the peripheral surface of the elastic film  22 ; and a supply and discharge port  25  which is opened in the casing  24  and which supplies and discharges fluid (air, water, etc.) into and out of the pressurizing chamber  23 . The elastic film-type valve  20  manages adjustments in the earth pressure at the work face by supplying and discharging fluid into and out of the pressurizing chamber  23  through the supply and discharge port  25  such that the elastic film  22  is caused to expand and contract diametrically to alter the sectional area of the space through which earth and sand pass, thereby adjusting the amount of earth to be discharged. 
     A bracket  26  which extends diametrically inward is provided in the earth discharging pipe  19  below the elastic film-type valve  20 , and a center rod  27  which extends upward is attached to the bracket  26 . The top of the center rod  27  is rotatably inserted into the central portion  11  of the cutter  4  via a rotary joint  35 . A channel  28  for mud-forming agent is formed inside the bracket  26 , center rod  27 , rotary joint  35 , and cutter  4 . The mud-forming agent that is injected through an inlet  29  formed in the earth discharging pipe  19  passes through the channel  28  inside the bracket  26 , center rod  27 , and cutter  4  to be supplied to the work face from an outlet  30  provided on the work face side of the cutter  4 . 
     The mud-forming agent that is supplied to the work face is mixed with the excavated earth and sand in accompaniment with the rotation of the cutter  4  and then this mixture is taken into a cutter chamber  31  and further kneaded by the kneader blade  14 . Thereby, the excavated earth and sand are efficiently fluidized and it becomes easier for the excavated earth and sand to drop naturally into the earth discharging pipe  19  due to a gravitational force action. Further, the center rod  27  is disposed in the center of the earth discharging pipe  19  so that when the elastic film  22  of the elastic film-type valve  20  expands, the elastic film  22  is pressed against the center rod  27  to function as a type of valve seat. 
     The gate mechanism  21  for adjusting the sectional area of the space in the earth discharging pipe  19  through which earth and sand pass is provided in the earth discharging pipe  19  below the center rod  27 . As is also shown in FIG. 2, the gate mechanism  21  is comprised of a pair of gate plates  32  disposed so as to face each other proximally with a space therebetween. The gate mechanism  21  is operated by an actuator such as a cylinder that is well-known in the art, and adjusts the sectional area of the space in the earth discharging pipe  19  through which earth and sand pass. Note that cuts  33  may be provided in the gate plates  32  and overlapped in order to ameliorate adjustment of the sectional area of the space through which earth and sand pass, as is illustrated in FIG.  3 . Further, the gate plates  32  are not limited to a pair, and instead a single swinging gate or three or more gates disposed in the fashion of a camera aperture may be employed. 
     As is shown in FIG. 1, an inspection panel  34  is provided in the earth discharging pipe  19  below the gate mechanism  21  for observing the transmission of the earth and sand. A transparent film is fitted over the inspection panel  34 . Further, an elastic film-type valve  20  and gate mechanism  21  similar to those described above are provided in the earth discharging pipe  19  below the inspection panel  34 . This lower elastic film-type valve  20  and gate mechanism  21  may be used as auxiliaries in the event of a breakdown in the upper elastic film-type valve  20  and gate mechanism  21 . Moreover, by using both the upper and lower elastic film-type valves, the stability of earth pressure control at the work face can be further improved. 
     The operation of this embodiment will now be explained. 
     As is illustrated in FIG. 4, during advance of the upward-facing shield machine  1 , the sectional area of the space in the earth discharging pipe  19  through which the earth and sand pass is appropriately narrowed by the gate mechanism  21 , thereby causing a slight blockage in the earth and sand on the outlet side of the elastic film-type valve  20  so as to raise the earth pressure thereof. As a result, the earth pressure on the outlet side of the elastic film-type valve  20  can be made substantially equal to the earth pressure (work face pressure) on the inlet side, and a substantially uniform earth pressure can be caused to act upon the entire elastic film  22 . Accordingly, the elastic film  22  expands substantially uniformly without being pressed inward locally (as shown in FIG.  5 ), and is pressed inward by the entire elastic film-type valve  20 . Thereby, earth pressure control at the work face can be performed securely regardless of the depth of advance or the type of soil being excavated. 
     In other words, as is shown in FIG. 5, if the gate mechanism  21  is left fully open, fluid pressure inside the pressurizing chamber  23  acts uniformly on the elastic film  22  such that the earth and sand passing through are at work face pressure (high pressure) on the inlet side and atmospheric pressure (low pressure) at the outlet side. As a result, the elastic film  22  does not expand uniformly but is pressed inward locally at the outlet side due to the pressure difference between the inlet side and the outlet side, thereby becoming tightly pressed against the center rod  27 . 
     Consequently, the supply force of the fluid to the pressurizing chamber  23  in order to control earth pressure at the work face changes such that even when attempts are made to alter the sectional area of the space through which the earth and sand pass by varying the amount of expansion of the elastic film  22 , the elastic film  22  is pressed tightly inward at its lower end due to the difference in pressure at the upper and lower ends, and thereby pressed tightly against the center rod  27 . As a result, repeated blockages and eruptions of the earth and sand occur in response to only slight changes in the fluid pressure supplied to the pressurizing chamber  23 , and earth pressure control at the work face becomes unstable. 
     The pressure difference in the elastic film-type valve  20  between the inlet side (work face pressure) and outlet side (atmospheric pressure) grows particularly large when advancing at great depth, and thus the elastic film  22  is locally pressed inward at the outlet side in accordance with this pressure difference, causing repeated earth and sand blockages and eruptions. Furthermore, in cases where the earth and sand are of a type, such as gravel with a large particle diameter or sandy soil with high frictional resistance, that is difficult to fluidize even using the kneader blade  14  or by injecting a mud-forming agent or the like, the earth and sand at the narrow opening of the elastic film  22 , which is locally pressed inward, have a tendency to become blocked such that the frequency of eruptions increases. As a result, earth pressure control directly above the shield machine  1  becomes unstable, leading to the possibility of displacement at ground level. 
     Accordingly, as is illustrated in FIG. 4, by using the gate mechanism  21  to appropriately narrow the sectional area of the space inside the earth discharging pipe  19  through which the earth and sand pass, the earth pressure (back pressure) on the outlet side of the elastic film-type valve  20  increases such that a substantially uniform earth pressure is caused to act upon the entire elastic film  22 . As a result, the elastic film  22  expands substantially uniformly, and, while pressed inward by the entire elastic film-type valve  20 , becomes pressed against the center rod  27  at a strength which accords with the injection pressure of working fluid injected into the pressurizing chamber  23 . Thus, by altering the injection pressure to a pressure which accords with the work face earth pressure, blockages and eruptions can be avoided, and secure earth pressure control of the work face can be performed regardless of the depth of advance or type of soil being excavated. Accordingly, displacement at ground level directly above the machine can be suppressed. 
     Further, when lumps of earth that cannot be discharged downward appear at an intermediate opening point of the gate mechanism  21  during such earth pressure management of the work face, it is possible to discharge these lumps of earth while maintaining the work face earth pressure by increasing the pressure of the fluid supplied from the elastic film-type valve  20  into the pressurizing chamber  23  such that the elastic film  22  expands to capacity, thereby causing [the gate mechanism  21 ] to close completely, and then by opening the gate mechanism  21  completely after the work face earth pressure has been maintained by the elastic film-type valve  20  [in this way]. 
     As was described above, according to the earth discharging device for an upward-facing shield machine pertaining to this embodiment, the elastic film-type valve  20  inside the earth discharging pipe  19  can be caused to expand uniformly regardless of depth or soil type, whereby secure earth pressure control at the work face can be performed. 
     Note that the present invention is not limited to or by the aforementioned embodiment, and may be implemented in modified form within the scope of the patent claims.