Lenslathe with vibration cancelling arrangement
A method and apparatus for substantially nullifying vibration and deflection in a single point lens turning lathe having a rapidly reciprocating lens cutting tool and shuttle assembly. The apparatus includes three or more tool shuttles of similar mass mounted for reciprocating movement along respective generally parallel shuttle paths. The shuttles are reciprocally moveable by respective actuators along their respective shuttle paths. The shuttle and tool assemblies are moved by their respective actuators in opposite directions at a rate which causes forces generated by shuttle and tool assemblies moving in one direction to cancel forces arising from the shuttle and tool assembly movement in the opposite direction. Should an odd number of shuttle and tool assemblies be used, the amount of force generated by the mass moving in one direction may be compensated by having a different rate of movement, and hence a different stroke length from the mass moving in the opposite direction.
1. A lens cutting lathe comprising:
a base;
a lens support mounted to said base for supporting said lens and spinning said lens about a lens rotational axis, said lens support being transversely moveable relative to said lens rotational axis;
a plurality of shuttles for mounting respective cutting tools mounted to said base in side by side arrangement far movement toward and away from said lens along respective generally parallel shuttle paths;
said plurality of shuttles being reciprocally movable by respectively actuators mounted to said base, said actuators being arranged to move some of said plurality of shuttles in a direction opposite to a remainder of said plurality of shuttles; and,
said plurality of shuttles being of similar mass and disposed and moved in a manner to maintain a generally fixed center of mass whereby movement of said some of said shuttles in a given direction substantially cancels linear forces imposed on said base by movement or said remainder of said shuttles in the opposite direction.
2. A lens cutting lathe as claimed in claim 1 wherein:
said plurality of shuttles are further disposed and moved in a manner to also cancel rocking forces imposed on said base by said movement of said shuttles in said opposite directions.
3. A lens cutting lathe as claimed in claim 2 wherein;
said plurality of said shuttles consists of two outer shuttles and an intermediate shuttle therebetween;
said outer shuttles move together in opposite direction to said intermediate shuttle; and
said outer shuttles move together at a rate of about one half that of said intermediate shuttle whereby the magnitude of accelerative forces generated by said outer shuttles is generally thee same as that generated by said intermediate shuttle.
4. A lens cutting lathe as claimed in claim 3 wherein:
said plurality of shuttle consists of a row of four of said shuttles arranged in two pair on either side of a central axis, said shuttles of each of said two pairs being arranged to move in opposite relative directions in phase with a corresponding shuttle of said opposite pair.
5. A lens cutting lathe as claimed in claim 3 wherein:
said shuttle paths are linear; and,
each said actuator is a linear servo motor.
6. A lens cutting lathe as claimed in claim 3 wherein:
said shuttle paths are arcuate; and,
each said actuator is a rotational servo-motor.
7. A lens cutting lathe as claimed in claim 4 wherein:
said shuttle paths are linear; and
said actuator is a linear servo-motor.
8. A lens cutting lathe as claimed in claim 4 wherein:
said shuttle paths are arcuate; and,
each said actuator is a rotational servo-motor.
9. A method of turning a non-rotationally symmetrical lens on a lens turning lathe having a lens support and at least three lens cutting tools, said method comprising the steps of:
(i) mounting a lens blank to a lens support assembly;
(ii) rotating said lens blank with said lens support assembly about a lens rotational axis;
(iii) pressing one of said at least three cutting tools against said lens blank;
(iv) moving said lens blank with said lens support assembly in a direction transverse to said lens rotational axis;
(v) reciprocally moving said one of said at least three lens cutting tools along a first tool path at a reciprocal frequency corresponding to the rotational frequency of said lens blank to produce said non-rotationally symmetrical surface; and,
(vi) reciprocally moving remaining of said at least three lens cutting tools along respective tool paths generally parallel to said first tool path at said reciprocal frequency in a direction and at a rate which counters and substantially nullifies linear forces imposed on said lathe by said one tool in step (v) without imparting a rocking movement on said lathe.
10. A method according to claim 9 wherein:
said at least three lens cutting tools consist of a first and a last lens cutting tools with intermediate lens cutting tools disposed equidistantly therebetween and in line therewith; and,
said first and last lens cutting tools are moved in unison contra to said intermediate lens cutting tool at a rate of about half that of said intermediate late lens cutting tool.
11. A method according to claim 10 wherein:
said lens is turned in at least two stages with a different of said lens cutting tools utilized in each stage.
12. A method according to claim 9 wherein:
first, second, third and fourth lens cutting tools are provided and arranged in line;
said first and second cutting tools are moved contra to each other at a similar rate;
said third and fourth cutting tools are moved contra to each other at a similar rate; and
any rocking motion created by said first and second cutting tools is cancelled by an equal but opposite rocking motion created by said third and fourth cutting tools.
13. A method according to claim 10 including the further steps of:
(vii) measuring with a measuring device any resultant imbalance force on said lathe associated with said reciprocal movement of said lens cutting tools and generating an output signal indicative of the nature and the amount of said imbalance force,
(viii) sending said output signal to a processor;
(ix) determining with said processor how said force may be nullified by varying movement of said actuators and generating at least one output signal to at least one controller which communicates with and controls movement of said actuators;
(x) receiving said output signal with said controller and varying said reciprocal movement cause by said actuators in response to said output signal to reduce said resultant imbalance force.
14. A method according to claim 13 including the further step of:
(xi) repeating steps (vii) through (x).
15. A method according to claim 11 including the further steps of:
(vii) measuring with a measuring device any resultant imbalance force on said lathe associated with said reciprocal movement of said lens cutting tools and generating an output signal indicative of the nature and the amount of said imbalance force,
(viii) sending said output signal to a processor;
(ix) determining with said processor how said force may be nullified by varying movement of said actuators and generating at least one output signal to at least one controller which communicates with and controls movement of said actuators;
(x) receiving said output signal with said controller and varying said reciprocal movement cause by said actuators in response to said output signal to reduce said resultant imbalance force; and,
(xi) repeating steps (vii) through (x).
16. A method according to claim 12 including the further steps of:
(vii) measuring with a measuring device any resultant imbalance force on said lathe associated with said reciprocal movement of said lens cutting tools and generating an output signal indicative of the nature and the amount of said imbalance force;
(vi) sending said output signal to a processor;
(ix) determining with said processor how said force may be nullified by varying movement of said actuators and generating at least one output signal to at least one controller which communicates with and controls movement of said actuators;
(x) receiving said output signal with said controller and varying said reciprocal movement cause by said actuators in response to said output signal to reduce said resultant imbalance force; and,
(xi) repeating steps (vii) through (x).
17. A method according to claim 15 including the further steps of:
(vii) measuring with a measuring device any resultant imbalance force on said lathe associated with said reciprocal movement of said lens cutting tools and generating an output signal indicative of the nature and the amount of said imbalance force;
(viii) sending said output signal to a processor;
(ix) determining with said processor how said force may be nullified by varying movement of said actuators and generating at least one output signal to at least one controller which communicates with and controls movement of said actuators;
(x) receiving said output signal with said controller and varying said reciprocal movement cause by said actuators in response to said output signal to reduce said resultant imbalance force; and,
(xi) repeating steps (vii) through (x).
18. A method according to claim 16 including the further steps of:
(vii) measuring with a measuring device any resultant imbalance force on said lathe associated with said reciprocal movement of said lens cutting tools and generating an output signal indicative of the nature and the amount of said imbalance force;
(viii) sending said output signal to a processor;
(ix) determining with said processor how said force may be nullified by varying movement of said actuators and generating at least one output signal to at least one controller which communicates with and controls movement of said actuators;
(x) receiving said output signal with said controller and varying said reciprocal movement cause by said actuators in response to said output signal to reduce said resultant imbalance force; and,
(xi) repeating steps (vii) through (x).
19. A tool guidance assembly as claimed in claim 11 wherein:
said shuttle paths are generally parallel to said base.