Abrasive tool making process – material – or composition – With carbohydrate or reaction product thereof
Patent
1979-07-11
1982-06-08
Whitehead, Harold D.
Abrasive tool making process, material, or composition
With carbohydrate or reaction product thereof
B24B 1300
Patent
active
043332749
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to a machine for smoothing and/or polishing a non-spherical curved face of a lens, which face has a different curvature of different angular positions about an optical axis of the lens. Such a face is referred to herein and in the art as a "cylindrical" face but it will be understood that the term embraces forms which cannot be generated by the rotation about an axis of a straight line which is parallel to that axis.
To smooth and polish a cylindrical lens face, the face is rubbed on a layer of an abrasive on a complementary face of a tool. Relative movement of respective reference axes of the lens and tool must be controlled to avoid changing the curvature of the face of the lens and the relative movement must change throughout the operation to avoid the formation of marks on the face of the lens.
Known machines for smoothing and polishing cylindrical faces of lenses have complex driving means for moving one of the tool and the lens relative to the other in a manner such that the locus of a point on the lens relative to a point on the tool shows little regularity. These known driving arrangements cause abrupt changes of direction of the tool or lens and elements of the driving means undergo rapid changes in velocity. These elements must be robust and accordingly are fairly massive.
During operation, the known machines are subjected to severe vibration which is accompanied by excessive noise and by deterioration of the machine. The inertia of moving parts results in variations between the pressure under which the tool contacts the lens at different places on the face of the lens and these variations in pressure result in changes in the curvature of the lens face. A further disadvantage of the known machines is that the driving means is not capable of controlling relative movement of the reference axes of the tool and lens sufficiently accurately. Inaccuracy in such control also leads to changes in the curvature of the lens face.
SUMMARY OF THE INVENTION
According to a first aspect of the invention, there is provided a machine for smoothing and/or polishing lenses comprising at least one pair of relatively movable holders arranged for holding respective ones of a tool and the workpiece which are to be rubbed together by relative movement of the holders, constraining means for maintaining respective reference axes of the holders parallel to a reference plane and driving means for causing said relative movement of the holders wherein the constraining means comprises a first slide, means for guiding the first slide along a first rectilinear path relative to a body of the machine, a second slide and means for guiding the second slide along a second rectilinear path relative to the first slide, the second path being transverse to the first path.
Preferably, said paths are perpendicular to each other.
According to a second aspect of the invention, There is provided a machine for smoothing and/or polishing lenses comprising at least one pair of relatively movable holders arranged for holding respective ones of a tool and a workpiece which are to be rubbed together by relative movement of the holders, constraining means for maintaining respective reference axes of the holders parallel to a reference plane and driving means for causing said relative movement of the holders, wherein the driving means comprises first and second elements which are rotatable about a main axis at respective different speeds, the first element defining an auxiliary axis offset from the main axis to move around the main axis when the first element rotates and an output element mounted for rotation about the auxiliary axis, the second element being so associated with the output element as to move the output element around the auxiliary axis when the second element moves around the main axis.
The main axis may be fixed with respect to a body of the machine and there may be provided means for connecting one of the holders with the output element for displacement therewith relative to the
REFERENCES:
patent: 1001410 (1911-08-01), Johnson
patent: 1973527 (1934-09-01), DiSanto
patent: 2168843 (1939-08-01), Lockhart
patent: 3552899 (1971-01-01), Tagnon
Dollond & Aitchison (Services) Limited
Whitehead Harold D.
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