Electrical generator or motor structure – Dynamoelectric – Oscillating
Reexamination Certificate
1999-10-29
2001-07-24
Enad, Elvin (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Oscillating
C310S037000, C310S038000, C310S039000
Reexamination Certificate
active
06265794
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to crossed-flexure pivot galvanometers, and more particularly to the precise tuning of the resonant frequency thereof.
2. Description of the Related Art
Crossed-flexure pivot galvanometers are often used in applications such as laser printers. These galvanometers typically comprise a torsional resonant rotor attached to a stationary frame by a series of flexures, with a mirror or other load attached to the rotor for oscillation therewith. The flexures are usually comprised of pairs of springs along an axis of rotation. Each of a pair of these springs is mounted at an angle to its mate so that they cross at the axis of rotation, making an “X” shape as viewed along this axis. One end of each spring is attached on a distal side of the rotor, and the remaining ends are attached to the stationary frame of the galvanometer.
Crossed-flexure pivot galvanometers are generally used in fixed-frequency application. Specifically, the effective spring constant of the flexures and the moments of inertia of the rotor and flexure masses, as well as that of any load attached to the rotor operator to set this frequency combines to provide a torsional resonance at a desired frequency.
Since the physical attributes of the galvanometer flexures, such as their dimensions and the Young's modulus of the material from which they are made, always vary over a small range from unit to unit, and since the dimensions, stiffness, and density of the rotor materials similarly vary from to unit, it has been necessary in the former art to provide such galvanometers with a compensatory means for adjusting the resonant frequency of each unit during or after manufacture.
Traditional techniques of adjusting the resonant frequency after manufacture have been the:
(1) addition of a weight or weights, the galvanometer having been designed with an intentionally low moment of inertia; (2) removal of selected material from the rotor assembly, the galvanometer having been designed with an intentionally high moment of inertia; or (3) the variation of the effective radius of an inertial mass or masses to changed their moments of inertia.
One potential disadvantage to the above-described methods of adjusting the resonant frequency is that additional parts are needed either before or after manufacture. Another disadvantage is that small incremental adjustments require additional effort and may require several incremental masses to be added, removed or moved to arrive at the desired resonant frequency of the galvanometer. This adds additional cost and effort to the manufacture and or calibration of these devices.
It is therefore an object of the present invention to provide a method of precisely tuning the resonant frequency of a crossed-flexure pivot galvanometer, which compensates for manufacturing variability and, which employs the existing components of the pivot galvanometer without requiring the addition or removal of mass from the galvanometer.
Other objects will, in part, be obvious and will, in part, appear hereinafter. The invention accordingly comprises an article of manufacture processing the features an properties exemplified in the constructions described herein and the several steps and the relation of one or more of such steps with respect to the others and the apparatus embodying the features of construction, combination of the elements and the arrangement of parts, which are adapted to effect such steps, all as exemplified in the following detailed description, and the scope of the invention will be indicated in the claims.
DESCRIPTION OF THE INVENTION
BRIEF SUMMARY OF THE INVENTION
In accordance with the present invention I have provided a method which uses adjustment of parts of the galvanometer already present and essential, to wit the permanent-magnetic armature of the rotor and the poles of the stator, to adjust a magnetic spring which works in cooperation with the flexure springs to vary the effective overall spring constant of the device.
More specifically, the invention makes use of the fact that with a flexured rotor support, the axis of the rotor undergoes a displacement relative to the stator axis. The magnetic structure urges the rotor in the direction of maximum displacement and then acts as a torsional spring. Adjusting the stator axis relative to the rotor axis can vary this torsional spring force.
In a preferred embodiment, the present invention provides an adjustment of the stator axis with respect to the rotor along the line passing through the poles of the armature.
REFERENCES:
patent: 4187452 (1980-02-01), Knappe et al.
patent: 4700090 (1987-10-01), Bianchi et al.
patent: 5959757 (1999-09-01), Plesko
patent: 0 523 413 A2 (1992-06-01), None
Cesari & McKenna LLP
Enad Elvin
GSI Lumenics, Inc.
Lam Thanh
LandOfFree
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