Work holders – Holder mounted for movement – With plural means for changing holder positions
Reexamination Certificate
1999-02-17
2001-02-27
Banks, Derris H. (Department: 3723)
Work holders
Holder mounted for movement
With plural means for changing holder positions
C359S391000
Reexamination Certificate
active
06193226
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a mechanism for a positioner and to a positioner having such a mechanism, more especially to a multi-axis positioning mechanism.
Positioners have many scientific and industrial applications.
One application, for example, is the positioning of optical fibres relative to each other, relative to waveguides, laser diodes, detectors etc, prior to testing and joining. This type of positioning has to be very precise, typically of sub-micron precision, and is commonplace in research and production facilities in the telecommunications industry.
Another application is for positioning optical or non-optical components, such as mirrors, lenses or samples beneath microscopes.
There are two main types of precision positioning stage, those based on bearings and those based on flexure hinges. The simplest form of both types of design produce linear motion, so called x-positioners. Both types of design can however be adapted to produce rotary motion with additional linkages and the like, so called &thgr;-positioners.
Many applications require not one, but several, axes of motion. This is obtained by stacking several stages. For example, bolting the top plate of one bearing stage to the base of another linear stage so that the respective positioning axes are at right angles to each other will produce a two-axis positioner, or so-called xy-positioner. Moreover, by then bolting an L-bracket onto the top-plate of the y-stage and a further bearing stage onto the upright of the L-bracket, a three-axis positioner, or so-called xyz-positioner, is produced.
Sometimes multi-axis positioners are supplied as integrated units. For example, in an xy-positioner, the top plate of the x-stage can also serve as the base plate of the y-stage, to reduce size and weight.
Flexure stages can also be nested in various ways to make them more compact.
However, the integration of parts in this way does not affect the basic principle of operation which is to use a number of similar mechanisms connected serially.
There are however several drawbacks to the use of a series of single axis mechanisms for multi-axis positioners:
1. The complexity and cost tends to increase with the number of axes.
2. The mass of moving parts increases with the number of axes, making the positioner slower to respond and more susceptible to ambient vibrations.
3. The force of adjusting a micrometer (other than that of the first stage) is transmitted through the preceding stages, causing disturbance to the position of the stages.
4. The stiffness of the positioner decreases as the number of axes increases.
BRIEF SUMMARY OF THE INVENTION
According to the present invention there is provided a mechanism for a multi-axis flexure positioner, the mechanism including a fixed part and a movable part, the movable part being connected to the fixed part via a plurality of transmission means, one for each axis, for transmitting actuation forces for the respective axes to the movable part, the transmission means for each axis including a flexure member arranged to transmit actuation forces for that axis to the movable part and to flex between the fixed part and the movable part in response to actuation forces associated with the or each other axis, wherein there are three flexure members arranged to extend along three mutually-perpendicular axes so that each flexure member is flexible along the axes of extent of the other two flexure members, each of the three flexure members comprising a pair of flexure linkages arranged to extend parallel to each other, the three pairs of linkages thus defining three mutually-perpendicular planes.
Preferred embodiments of the invention incorporate up to six axes of motion into a positioning mechanism of this kind. Once fitted with actuators, such as micrometers, the positioning mechanism forms a multi-axis positioner, preferably a micropositioner, with a corresponding number of axes of motion.
In the preferred embodiments, the movable block of the positioner is supported by six linkages, each linkage being thinned towards each end to give the linkage flexibility to bend in two directions and to twist about its axis of extent.
The new design allows multi-axis positioners to be made which have one or more of the following advantages:
1. Low mass of moving parts—better response time, more resistance to ambient vibrations.
2. Adjusting a micrometer, or other actuator, for one axis does not result in force being transmitted through the mechanics of the stage and disturbing the positions set by the or each other stage.
3. Greater stiffness resulting from the parallel rather than serial action of the linkages.
4. Because there are fewer parts in series, lost motion among adjacent parts is minimized and the overall precision is improved.
5. Simpler design, lower cost.
These advantages become more significant as the number of axes increases.
A sub-micron positioning precision is achievable.
Further aspects of the invention are exemplified by the attached claims.
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Banks Derris H.
Melles Griot Limited
Renner , Otto, Boisselle & Sklar, LLP
Shanley Daniel
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