Patent ID: 7226411

Claim:
In a valved plug to be fitted on a mouth piece at an inlet opening of an instrument entrance passage leading to a biopsy channel of an endoscopic insertion tube, said plug being formed of a resilient material in its entirety and having, at opposite ends of a foldable connecting strip, a generally tubular main body portion internally formed with a constricted passage of a smaller diameter as compared with said inlet opening of said instrument entrance passage, in a radial partition wall located at an intermediate portion between outer and inner ends thereof, and a nesting piece adapted to be detachably coupled with said main body portion and having a normally closed slit valve in axial alignment with said constricted passage in said main body portion to permit insertion of an instrument therethrough: an annular inward interlocking projection provided at an outer end of said main body portion to be coupled with said nesting piece, said interlocking projection being axially spaced from said radial partition wall by an internal annular groove formed around an inner periphery of said main body portion; said slit valve provided in a circular fitting body portion of said nesting piece to be fitted in said main body portion; an annular interlocking groove formed around an outer periphery of said fitting body portion of said nesting piece on an outer side of an annular interlocking flange provided at an innermost end of said fitting body portion; said annular interlocking projection on said main body portion having a thickness greater than an axial width of said annular interlocking groove on said fitting body portion of said nesting piece, and an inside diameter smaller than a root diameter of said annular interlocking groove on said fitting body portion, to hold said annular interlocking projection in a compressed state by a bottom surface and riser wall portions of said annular interlocking groove when said nesting piece is coupled with said main body portion; and said internal annular groove having a larger axial width than said annular interlocking flange on said fitting body portion to leave a free space between said radial partition wall on said main body portion and said fitting body portion of said nesting piece to permit easy inward deformation of said slit valve toward said constricted passage when opened by insertion of an instrument.