Patent ID: 8029246

Claim:
A pressure-operated mechanism comprising: a pressure chamber; an operation portion that drives a driven portion or controls a controlled portion, according to a change in pressure in the pressure chamber; a connection passage, at least part of which is attachable and detachable to and from the pressure chamber; a disconnection detecting portion for detecting disconnection of the connection passage from the pressure chamber, based on a change in a condition of flow in the connection passage; a pressure path, one end of which is connected to the pressure chamber, the other end of which is branched and respectively connected to a first pressure area and a second pressure area in which pressure is lower than the pressure in the first pressure area, the pressure path including the connection passage, wherein the disconnection detecting portion is connected to the pressure path, and a passage cross section of a section of the pressure path between a detachable portion of the connection passage and a connection portion of the disconnection detecting portion has a predetermined size such that detection of disconnection by the disconnection detecting portion is possible; a switching portion, provided on the pressure path, for changing a state of communication between the pressure chamber and the pressure areas in order to cause a change in pressure in the pressure chamber; and a pressure transmission-reducing portion, provided on the pressure path, for preventing pressure in the pressure chamber from rapidly changing when the switching portion is switched, wherein: the switching portion is configured to be selectively switched between a state in which the switching portion causes the pressure chamber to communicate with the first pressure area and a state in which the switching portion causes the pressure chamber to communicate with the second pressure area; and the pressure transmission-reducing portion includes a throat portion, of which a passage cross section is smaller than the predetermined size, on the pressure path.