Patent ID: 9717395
Date: 2017-08-01
CPC Classifications: A61B,F16K

Claim:
1. A suction conduit switching apparatus for an endoscope, the suction conduit switching apparatus comprising: a cylinder that is disposed in a hand operation unit of the endoscope, the cylinder comprising: a piston passage having one end that is open; a suction connection port which is formed at an other end of the piston passage and leads to a suction conduit; and a suction source connection port which is formed in an inner peripheral surface of the piston passage and leads to a suction source conduit; a piston that is inserted into the cylinder with one end protruding from the piston passage, the piston being configured to be displaced from a first position to a second position by a pressing operation; a first communication passage that comprises: an outer peripheral surface opening which is formed in an outer peripheral surface of the piston; and an other end opening which is formed at the other end of the piston, the outer peripheral surface opening being configured to communicate with the suction source connection port when the piston is at the second position, and to be blocked by an inner peripheral surface of the piston passage when the piston is at the first position, the other end opening being configured to communicate with the suction connection port, the outer peripheral surface opening and the other end opening being allowed to communicate with each other through the first communication passage; a second communication passage that comprises: a circumferential groove which is formed in the outer peripheral surface of the piston; and a notch passage which is formed from the circumferential groove to the one end of the piston in the outer peripheral surface of the piston, the circumferential groove being configured to communicate with the suction source connection port when the piston is at the second position, and to be blocked by an inner peripheral surface of the piston passage when the piston is at the first position, the second communication passage allowing the suction source connection port to communicate with an outside atmosphere via the circumferential groove and the notch passage; and a rotation regulating unit that regulates rotation of the piston in the piston passage, wherein an increment of a communication opening width at which the suction source connection port and the outer peripheral surface opening overlap with each other is equal to or less than three times an increment of a pressing stroke of the piston when the piston is displaced from the first position to the second position by the pressing operation to the one end of the piston, and wherein at least one of the suction source connection port and the outer peripheral surface opening has a correction opening portion that has an opening width gradually increasing from the other end side toward the one end side.