Patent ID: 8726928

Claim:
A method suitable for boring a portion of a pipe wall of an existing pipe to form an opening in the pipe wall with a boring machine, inserting a gate valve body into a line of the existing pipe to stop a flow of a water through the existing pipe, and removing the inserted gate valve body, the method using an apparatus, the apparatus comprising: a sealing case including first and second separate cases separated from each other in a circumferential direction of the existing pipe and enclosing a portion of the existing pipe, and a valve cover portion attached to a branch pipe portion formed integral with the first separate case and protruding upwardly in a radial direction of the existing pipe, an axis of the branch pipe portion being set to be in an up-down direction; the gate valve body accommodated by the valve cover portion and the branch pipe portion to be intruded into the existing pipe to stop the flow of the water through the existing pipe; an operation valve body having an arc-shaped lateral cross section for opening/closing a branch hole formed in the branch pipe portion by rotating in the circumferential direction of the existing pipe between an inner periphery surface of the sealing case and an outer periphery surface of the existing pipe; a valve seat provided on the inner periphery surface of the first separate case with which the operation valve body contacts in a valve-closed state; and a rotation mechanism for rotating the operation valve body, the rotation mechanism comprising: an operation portion rotated outside the sealing case; a driving gear unit which rotates following the rotation of the operation portion; and a driven gear provided on the operation valve body for rotating the operation valve body in the circumferential direction of the existing pipe following the rotation of the driving gear unit, the method for removing the gate valve body comprising the steps of: forming the opening by the boring machine attached to the branch pipe portion with the water flowing inside the existing pipe; moving the operation valve body from the valve-open position to the valve-closed position and then taking out the boring machine; attaching the valve cover portion accommodating the gate valve body to the first separate case; rotating the operation valve body in the circumferential direction and moving the operation valve body to the valve-open position; after moving the operation valve body to the valve-closed position, taking out the valve cover portion accommodating the gate valve body from the first separate case and removing the gate valve body; after removing the gate valve body, attaching a tectal plate to a joint portion of the first separate case and sealing the branch hole of the first separate case.