Sectional sandwich panel insert with frictional telescopic coupling

Claim 1

A grommet type insert for a sandwich panel having a low density core sandwiched between skins of supporting sheet material and provided with a through hole, comprising: a spacer including a head adapted to abut one of said skins and a tubular shank integrally joined to said head at one end and adapted to extend through said hole in closely fitted relation thereto, said shank having at its other end a counterbore and a skirt within which said counterbore is defined, said skirt having a wall thickness substantially less than that of said shank, said skirt having at said other end an extremity consisting of an annular lip of tapered thickness defined around an outwardly flaring frusto-conical throat intersecting said counterbore to define an annular shoulder of obtuse angular section; and a grommet comprising a tubular plug and an integral head at one end thereof adapted to abut the other skin of said panel, said plug having its other end externally beveled to provide a cone adapted to enter said spacer throat and to engage said annular shoulder with an expanding effect, said plug having a length such that its said other end will substantially reach the bottom of said counterbore in the fully installed insert; the outer diameter of said plug being greater than the diameter of said counterbore to an extent such that the forcible entry of said plug into said counterbore will expand said skirt beyond its elastic limit and into its plastic deformation range, and will cause said annular lip to be turned inwardly by fulcruming of said annular shoulder on said cone in response to the expansion of said skirt.