Positioning device

Claim 1

A positioning device for positioning two components relative to one another in each of three mutually perpendicular co-ordinate directions, said device comprising a first component having at least one bore therein, said bore having an opening in a substantially planar outer surface portion of said first component and having a substantially conical wall surface portion disposed symmetrically with respect to an axis extending substantially perpendicularly of said outer surface portion and passing through said bore, said substantially conical wall surface portion being of increasing cross-section towards said opening, and a second component provided with a positioning element having a free end portion thereof extending outwardly from a substantially planar outer surface portion of said second component and received within said bore by way of said opening, said free end portion of said positioning element having a substantially spherical centering portion of reducing cross-section towards the outer extremity of said free end portion and having an axis of symmetry alignable with said first mentioned axis of symmetry, the major diameter of said inserted portion being less than that of said opening, whereby -- on said first and second components being urged towards one another to cause said positioning element to enter said bore -- said substantially planar outer surface portions of said first and second components are brought into mutually abutting relationship to define an interface between said first and second components whilst only said substantially spherical centering portion of said positioning element is brought to bear against said substantially conical wall surface portion of said bore, said substantially conical wall surface portion being tapered to include at said axis an angle smaller than that subtended thereat by any two notional tangents to said substantially spherical centering portion at points thereon disposed symmetrically relative to said axis and inwardly of said bearing surfaces, said conical wall surface portion extending outwardly from said bearing surfaces to be spaced apart from the surface portion of said positioning element facing said conical wall surface portion, said substantially spherical centering portion being brought to bear with sufficient force to cause material deformation of at least one of said substantially conical wall surface portion and said substantially spherical centering portion thereby to enlarge at least one of said bearing surfaces and to positively locate said positioning element in said bore free of play in a first of said co-ordinate directions parallel with said axis and in each of two further ones of said co-ordinate directions.