Abrading – Work holder – Clamp
Reexamination Certificate
1999-10-22
2001-05-15
Rose, Robert A. (Department: 3723)
Abrading
Work holder
Clamp
Reexamination Certificate
active
06231433
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is a blank clamping device for a machine for trimming optical lenses.
2. Description of the Prior Art
Spectacle lenses must be held in place relative to the tools of a grinding machine for trimming the lens.
During trimming, the lens must be held rigidly on an axis about which it is turned to form the various radii constituting the required shape. The axis may correspond to the optical center of the lens of the patient or to the geometrical center of the shape, for example, and does not coincide with the center of the blank. In addition to this, the great variety of geometrical shapes of the concave and convex surfaces of the lenses means that it is not possible to hold the blank in place by means of rigid interfaces.
Existing blank clamping devices for machines for trimming optical lenses have two jaws for clamping concentric faces of the blank fitted with bearing members each of which cooperates with one face of the blank, at least one of the jaws including a body and a plate carrying one of the bearing members and articulated to the body by a ball-and-socket joint.
In an arrangement of this kind the perpendicular to the mean tangent of the surface to be clamped is clearly apparent regardless of the inclination of the perpendicular and the arrangement can therefore accept all geometrical lens shapes.
However, the problem arises of transmitting rotational torque through a ball-and-socket joint. Torque can be transmitted only by friction between the male and female members of the joint, which cannot be increased by increasing the clamping force, as this would break or damage the blank, and which degrades the performance of the ball-and-socket joint.
A previous proposal for transmitting a torque in a ball-and-socket joint is such that the surfaces “stick”. Apart from the fact that transmission is then not very positive, this proposal has the drawback of requiring manual “unsticking” of the two components of the ball-and-socket joint after each operation, to avoid breaking the lens.
Another proposal associates two orthogonal pins with the two spherical members of the ball-and-socket joint. This arrangement leads to transmission of torque with too great an angular play, which can be measured in degrees.
An object of the invention is to avoid the above drawbacks and to propose a clamping device incorporating a ball-and-socket joint which improves the performance of the trimming machine in terms of speed of machining, fidelity of shapes and compliance with dimensions and with the axis of the lens.
SUMMARY OF THE INVENTION
The invention consists in a device for clamping a blank on a machine for trimming optical lenses, which machine includes two coaxial clamping jaws for clamping faces of the blank and in which machine each jaw is provided with bearing means adapted to cooperate with one face of the blank, at least one of the jaws includes a plate and a body and the plate carries one of the bearing members and is articulated to the body by a male member carried by one of the two parts of the plate/body combination and cooperating with a blind female housing in the other of the two parts, in which device the male member has at least three facets evenly distributed about its axis, each facet is generally cylindrical with generatrices orthogonal to the axis on respective opposite sides of a common transverse plane, and the female housing has plane faces parallel to its axis and each of which is delimited axially by a bottom and is adapted to cooperate with one of the facets of the male member.
The male member preferably has six facets and the female housing preferably has six plane faces.
The back of the female housing is advantageously frustoconical. Alternatively, the back of the female housing is hemispherical.
The bearing member carried by the plate is advantageously semi-elastic.
The articulation of the plate to the body is preferably protected by a bellows clipped peripherally to the plate at one end and to the body at the other end.
The male member is advantageously carried by the body and the female housing is advantageously formed in the plate.
One of the jaws being fixed and the other being movable in the axial direction, it is preferably the movable jaw which includes the plate and the body.
In one embodiment of the invention, the trimming machine comprising a clamping spindle, the body is hollow and adapted to be mounted at the end of the clamping spindle, to which it is fastened.
Alternatively, the trimming machine comprising a clamping spindle, the body consists of the end of the clamping spindle.
For a better understanding of the object of the invention, one embodiment of the invention will now be described by way of illustrative and non-limiting example only and with reference to the accompanying drawings.
REFERENCES:
patent: 1184496 (1916-05-01), Stenvall
patent: 2293291 (1942-08-01), Gaspari
patent: 3738065 (1973-06-01), Tagnon
patent: 5421770 (1995-06-01), Bobst
patent: 1 947 009 (1971-03-01), None
patent: 2 226 824 (1974-11-01), None
patent: 1 477 126 (1977-06-01), None
patent: 57-201160 (1982-12-01), None
Brechemier Bernard
Nauche Michel
Essilor International (Compagnie Generale d'Optique)
Rose Robert A.
Young & Thompson
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