Gasket for use in manhole bases and the like

Claim 1

An annular gasket for providing a fluid-tight seal between a sewer pipe and an annular opening in a wall of cast material through which said sewer pipe passes, said opening having a central axis, said gasket comprising a length of a linear extrusion of elastomeric material having first and second ends and having a cross-sectional configuration comprising a central portion having a substantially pear-shaped cross-section defining a wide and a narrow end and tapered sides extending between said wide and narrow ends; said length being bent into an annular gasket so that said first and second ends are joined to oppose each other; an outer radial embedment portion of substantially T-shaped cross-section defining a cylindrical-shaped flange portion of the annular gasket and defining a web portion integrally joined at one end thereof to the mid region of said flange portion and integrally joined to the mid region of the wide end of said pear-shaped central portion; said flange portion and part of the web portion being embedded in said wall when it is cast; said annular gasket having a radially inwardly end portion remote from said embedment portion comprising an elongated lip having a cross-section defined by an elongated rectangle ending in a bead at the free end thereof, the thickness of said lip except for the bead in cross-section being less than the width of the narrow end of said central portion and having a first end integrally joined to the narrow end of said central portion, said lip extending away from said central portion and terminating in a second free end, said lip extending in a direction diagonal to an imaginary plane passing through said web portion and said central portion when said gasket is in an unstressed state, said imaginary plane being substantially perpendicular to the central axis of said opening; the web portion and the central portion lying along said imaginary plane when in the unstressed state, the second free end of said lip defining an opening which is smaller in diameter than the outer diameter of a sewer pipe to be inserted into the gasket; and said lip and at least a portion of one of the tapered surfaces adjacent said narrow end of said central portion being so related as to embrace said sewer pipe when said sewer pipe is forced into the gasket.