Data processing: generic control systems or specific application – Specific application – apparatus or process – Mechanical control system
Reexamination Certificate
1998-10-20
2001-04-03
Stamber, Eric W. (Department: 2163)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Mechanical control system
C702S041000, C702S056000
Reexamination Certificate
active
06212445
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to improved methods and apparatus for generating a linear vibratory output force (also sometimes called a reciprocating output force) having a controllable amplitude.
A pair of eccentric masses rotating in opposite directions about a common axis in respective closely spaced parallel planes, or rotating in opposite directions about respective parallel axes in a common plane, cooperate to produce an approximately linear vibratory force, assuming (1) that the rotating force vectors of the individual masses have the same amplitude, (2) that both masses rotate at the same speed, and (3) that the masses are properly phased relative to one another. The vibratory output force acts along a line that is parallel to the plane or planes in which the eccentric masses rotate. This line is also perpendicular to a line between the centers of gravity of the two masses when the two masses are at phase angles that differ by 180°.
Two pairs of masses, each pair counter-rotating as described above, can be operated together with their vibratory output forces aligned. Assuming that all four masses rotate at the same speed, the phase relationship between the two pairs influences the extent to which the output forces of the two pairs add to or subtract from one another. Thus the phase relationship between the two pairs controls the amplitude of the net vibratory output force (the vector sum of the vibratory output forces of the two pairs).
There are applications of vibratory force generators in which it is desirable to be able to control amplitude substantially independently of frequency and phase. For example, vibratory force generators may be used to counteract the effect of helicopter rotor blades passing over the fuselage of the helicopter. In general, the frequency and phase of the vibratory force generator output must be matched to rotor speed and angular position. At any given rotor speed, however, the angle of attack of the rotor blades may vary, and this will change the amplitude of the vibratory force generator output that is required to counteract the effect of the rotor blades on the fuselage. Hence the requirement to be able to change vibratory force generator output amplitude substantially independent of frequency and phase.
Austin et al. U.S. Pat. No. 3,208,292 shows a system of four rotating masses in two pairs of two counter-rotating masses powered by a single motor with phase adjustment between the pairs. However, the Austin et al. patent does not disclose or suggest a system which is capable of high-speed, dynamic variation of such vibratory output force parameters as frequency, phase, and amplitude. Nor does the Austin et al. patent disclose or suggest a system which is adapted to produce amplitude variation substantially independently of frequency and phase.
Jensen U.S. Pat. No. 5,005,439 shows a system in which each of four rotating eccentric masses is powered by a separate motor. Assuming separate control of the motors, the Jensen system can produce a wide range of output parameter combinations. But four separate motors may undesirably increase the cost, size, weight, complexity, etc., of the system.
In view of the foregoing, it is an object of this invention to provide improved and simplified linear vibratory force generator apparatus and methods.
It is a more particular object of this invention to provide relatively simple linear vibratory force generator apparatus and methods which can perform such functions as varying the amplitude of the output force substantially independently of the frequency and phase of that force.
SUMMARY OF THE INVENTION
These and other objects of the invention are accomplished in accordance with the principles of the invention by using two pairs of eccentric masses, each pair including two counter-rotating eccentric masses that rotate in a fixed relationship to each other through a mechanical linkage. The masses in each pair are oriented such that the net force generated by the pair lies along a line that is perpendicular to an axis of rotation of the pair. The pairs of masses are oriented such that the net forces produced by each pair interact to form a resultant linear vibratory output force in a direction substantially along the same line. The phase relationship between the net force generated by the first pair and the net force generated by the second pair is adjustable such that the resultant amplitude of the combination of the net forces of the pairs is between zero and the sum of the values of the amplitudes of the net forces of both pairs. Furthermore, when adjusting the amplitude of the vibratory output force, the phase (and also substantially the frequency) of the output force may be maintained by advancing the phase of one rotating pair by a specific amount with respect to the phase of the original output force, while retarding the phase of the second rotating pair by the same amount with respect to the phase of the original output force. The phase of one pair is advanced by increasing the frequency of rotation of that pair for a specific amount of time and then returning to the original desired frequency. Likewise, the phase of the other pair is retarded by decreasing the frequency of rotation of that pair for a specific time and then returning to the original desired frequency. A suitable control system is utilized to adjust the phase relationships between the mass pairs and the starting output force function. The control system may be designed so that the output force generated maintains the phase, frequency, and amplitude dictated to the control system from an external source. For example, the external source may be a computer located on a helicopter for the purpose of determining the output force frequency, amplitude, and phase necessary to cancel unwanted vibrations in the helicopter.
Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments.
REFERENCES:
patent: 3208292 (1965-09-01), Austin et al.
patent: 3617020 (1971-11-01), Gerstine et al.
patent: 4627576 (1986-12-01), Hahn et al.
patent: 5584375 (1996-12-01), Burgess, Jr. et al.
patent: 5675083 (1997-10-01), Nakamura
patent: 5903077 (1999-05-01), Garnjost et al.
patent: WO 91/08842 (1991-06-01), None
patent: WO 96/06290 (1996-02-01), None
English langauage translation of WO 91/08842.
Barba Valentin G.
Crook David J. C.
Shube Eugene E.
Egbert, III Walter M.
Fish & Neave
Jackson Robert R.
Smiths Industries Actuation Systems Inc.
Stamber Eric W.
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