Hydraulic and earth engineering – Subterranean or submarine pipe or cable laying – retrieving,... – Repair – replacement – or improvement
Patent
1995-12-01
1998-01-13
Graysay, Tamara L.
Hydraulic and earth engineering
Subterranean or submarine pipe or cable laying, retrieving,...
Repair, replacement, or improvement
405138, 175171, E21D 900
Patent
active
057071764
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an earth discharge control system for a small-diameter pipe propelling machine for laying a small-diameter pipe in the ground.
BACKGROUND ART
A conventional small-pipe propelling machine for laying a small-diameter pipe in the ground has a propelling unit disposed in a starting shaft which propels a small-diameter pipe provided at its leading end with a leading pipe in the ground to lay the small-diameter pipe underground.
A cutter head is attached to the leading end of the leading pipe, and earth excavated by the cutter head is conveyed into the starting shaft by a screw conveyor. The screw conveyor is provided at a portion in the leading pipe with a control valve, the control valve is regulated to adjust its opening according to the rate of discharge of excavated earth into the starting shaft to regulate the earth discharging rate.
When the control valve is regulated according to the rate of discharge of excavated earth into the starting shaft, the excavating efficiency of the cutting head is reduced due to excessively small excavation resulting from the abrupt change in the properties of earth, because changes in the excavating condition in the leading pipe appears in the starting shaft with a delay.
The present invention has been made in view of the aforesaid disadvantage and it is therefore an object of the present invention to provide an earth discharge control system for a small-diameter pipe propelling machine, capable of controlling the discharge of excavated earth so that excavated earth is discharged at an optimum earth discharge rate at all times.
DISCLOSURE OF THE INVENTION
With the foregoing object in view, the present invention provides an earth discharge control system for a small-diameter pipe propelling machine comprising a propelling unit installed in a starting shaft and capable of propelling a small-diameter pipe provided at its leading end with a cutting head under the ground, and a screw conveyor extended in the small-diameter pipe to convey earth excavated by the cutting head into the starting shaft, comprising a pneumatically operated control valve disposed in combination with a portion of the screw conveyor within the leading pipe, and a pressure detector for detecting the amount of excavated earth contained in a portion of a casing extending ahead of the control valve through the detection of the pressure in the pressure chamber of the control valve and to control the rotation of the screw shaft of the screw conveyor on the basis of information acquired by the pressure detector.
The earth discharge control system controls the rotating speed of the screw shaft of the screw conveyor so that a fixed amount of excavated earth is contained always in the portion of the casing extending ahead of the control valve and, consequently, troubles due to conveyance of excavated earth at an excessively high or low rate can be prevented.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a partly sectional front view of a small-diameter pipe propelling machine incorporating an earth discharge control system in a first embodiment according to the present invention;
FIG. 2 is a diagrammatic view of assistance in explaining the operation of the earth moving device of the small-diameter pipe propelling machine of FIG. 1;
FIG. 3 is a fragmentary longitudinal sectional view of assistance in explaining the operation of the earth moving device of the small-diameter pipe propelling machine of FIG. 1;
FIG. 4 is a fragmentary longitudinal sectional view of assistance in explaining the operation of the earth moving device of the small-diameter pipe propelling machine of FIG. 1;
FIG. 5 is a fragmentary longitudinal sectional view of assistance in explaining the operation of the earth moving device of the small-diameter pipe propelling machine of FIG. 1;
FIG. 6 is a flow chart of an operation to be carried out by the earth moving device of the small-diameter pipe propelling machine of FIG. 1;
FIG. 7 is a diagram of assistance in explaining the operation of t
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patent: 4506931 (1985-03-01), Haspert
patent: 4711310 (1987-12-01), Luen
patent: 5104263 (1992-04-01), Shibahara et al.
patent: 5478170 (1995-12-01), Hanamoto et al.
Graysay Tamara L.
Kabushiki Kaisha Komatsu Seisakusho
Lagman Frederick L.
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