US3011354A

US3011354A - Oscillator

Info

Publication number: US3011354A
Application number: US756999A
Authority: US
Inventors: Earl T Ireton; Hans G Krauss
Original assignee: Boeing Co
Current assignee: Boeing Co
Priority date: 1958-08-25
Filing date: 1958-08-25
Publication date: 1961-12-05
Anticipated expiration: 1978-12-05

Description

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OSCILLATOR 2 Sheets-Sheet 2 Filed Aug. 25. 1958 v. @Fm

EARL T /RETO/V HANS 6."KRAU$S INVENTOR` A TTOHNE'Y United States Patent Oice 3,011,354 Patented Dec. 5, 1961 3,011,354 OSCILLATOR Earl T. Ireton, Audubon, NJ., and Hans G. Krauss, Kalamazoo, Mich., assignors, by mesne assignments, to

Boeing Airplane Company, Seattle, Wash., a corporation of Delaware Filed Aug. 25, 1958, Ser. No. 756,999 Claims. (Cl. 74-25) This invention relates to oscillators for inducing vibrations in structural units and more particularly to an oscillator for inducing a sinusoidal vibration of controlled force and frequency in an aircraft.

It is a primary object of the invention to provide an oscillator capable of producing relatively high vibratory forces at relatively low frequencies wherein those forces are generated by hydraulically actuated means which follow or are controlled by a relativelyk low power oscillating system.

It is a further object of the invention to provide an oscillator which generates a constant vibratory force throughout a range of operating frequencies.

It is a further object to provide such oscillator with means for changing the generated vibratory force independently of the frequency whereby different constant vibratory forces may be generated throughout the operating frequency range.

It is a still further object to provide an oscillator having a hydraulically actuated oscillating mass, with automatic means for varying the oscillating frequency thereof in response to manually controlled changes in the amplitude of displacement of the mass in such manner as to generate. a constant vibratory force. A still further object is to provide the oscillating mass with acceleration responsive means to cause automatic shut-down in the event a predetermined acceleration is exceeded.

Other objects of the invention, as well as the advantages thereof, will become apparent from the following description when read in conjunction with the accompanying drawings in which:

FIG. 1 is a plan view partly in section of a preferred embodiment of an oscillator constructed in accordance with the present invention;

FIG. 2 is a partial end view showing the Scotch yoke assembly by which the hydraulic control is driven;

FIG. 3 is an enlarged partial view taken along lines 3-3 of FIG. l; and

FIG. 4 is a diagram of the electrical control system.

Referring to FIG. l, the oscillator is shown to include a base comprising

beam members

11, 12 and 13 connected together by cross beams 14, and 16. The base 10 is mounted by means of bolts 17 or the like, to the structure in which it is desired to induce vibrations.

Slide rods

18 and 19 are connected at their opposite ends to the cross beams 14 and 15 and slidably support a mass 20 which is reciprocated back and forth on the

slide rods

18 and 19 by a hydraulic actuator 21. The actuator 21 comprises a cylinder 22 bolted or otherwise secured to the base 10 by means not shown, and a piston 23 connected to the mass by means of the piston rod 24 extending through one end of the cylinder 22. A second piston rod 25 extends through the other end of the cylinder 22 and has pivotally mounted on the extremity thereof a link 26, in turn pivotally connected to the spool element 27 of the actuator control valve 28. Pressure uicl from a source not shown is supplied to the control valve 28 through a line 29 containing a solenoid actuated on-ofi valve 30, while return ow to a reservoir not shown is through line 31. Ducts 32 and 33 cooperate-with the control valve 28 for communicating pressure fluid to the

end chambers

34 and 35 of the actuator 21.

A link 36 is pivotally connected at one end to the link 26 and at its other end is pivotally connected to one end of a lever 37 pivotally mounted upon the cross beam 16. A link 38 connects the lever 37 with one arm of a bellcrank 39 pivotally mounted upon the beam member 12, while the other arm of the bellcrank 39 is connected to Scotch yoke assembly 40 by means of a ylink 41. As shown in FIG. 2,

guide members

42 and 43 extend through the slotted cross-head 44 of the assembly 40 to limit its motion to one plane.

A variable speed power source or motor means, preferably ,an A.C. electric motor 45 provided with a D.C. field control, is mounted on the base 10 and drives by means of a belt 46 and pulleys 47 and 48 a shaft assembly 49. The assembly 49 is rotatably mounted upon the base 10 by means of bearings l50 and 51, and comprises an outer hollow shaft 52 having a bifurcated end portion 53 on which are carried bevel gears 54 and 55. These f gears mesh with a bevel gear 56 adapted for rotation relative to the outer shaft 52 by means of an inner shaft 57 driven by a reversible motor 58 contained within and rotatable with the outer shaft.

The gears 54 and 55 are provided with threaded

shafts

59 and 60, respectively, which extend radiallyI out through the end portion 53 of the shaft 52 and upon which are mounted a crank mechanism 61 and a counter-weight 62. The crank mechanism 61 is provided with a pin extension 63 adapted to be received in the slide block 64 of the Sctoch yoke assembly 40.

Lugs

65 and 66 on the extremity of the end portion 53 of shaft 52 embrace the sides of the crank mechanism 61 and the counter-weight 62, while a slot not shown in the crank mechanism is adapted to receive a mating pin 67 provided on the counter-weight to prevent, together with the

lugs

65 and 66, any misalignment or twisting of those two parts.

The arrangement just described is such that rotation of the gears 54 and 55 by the gear 56 causes opposite displacement of the crank mechanism 61 and the counterweight 62 to thereby substantially maintain the balance of the rotating parts. The displacement of the crank mechanism 61 produces an eccentricity between the axes of the pin 63 and the shaft 52 whereby rotation of the shaft assembly is converted to a pure harmonic motion of the crosshead 44 of the Scotch yoke assembly and through the associated control valve linkage, to the valve spool element 27. It is readily apparent that the amount of eccentricity between the pin 63 and the shaft 52 will determine the amount of displacement of the valve spool element and hence the amount or amplitude of displacement of the piston 23 and the mass 20 attached thereto. The frequency of that displacement is of course determined by the rotationl speed of the driving motor 45.

A definite mathematical relationship exists between the inertia force of a vibrating mass, the frequency of vibration and the amplitude of displacement of the mass. For a constant mass and force, it can be shown that the frequency is proportional to the square root of the reciprocal of the amplitude, or conversely, the amplitude is proportional to the reciprocal of the square of the frequency. Accordingly, if the amplitude of displacement is changed, there must also be a charge in the frequency in accordance with the relationship just stated if the force is to remain constant. Means for automatically changing the frequency in response to changes in the amplitude of displacement so as to maintain a constant vibratory force are shown in FIG. 4.

As shown therein, the electric motor 45 drives a tach generator 68, the function of which is to generate a voltage proportional to its rotational speed. This voltage is impressed, by means of the

conductors

69 and 70 and the slip rings 71 carried by the shaft assembly 49, across a potentiometer 72 mounted upon the end portion 53 of the outer shaft 52. An associated wiper 73, mounted upon the crank 61 and connected by a conductor 74 and one of the slip rings 71 to an amplifier 75, servesas means for taking off a voltage proportional to the wiper position and hence the eccentricity between the axes of the pin 63 and the shaft 52. This voltage, proportional to the rotational speed of the shaft assembly and the eccentricity of the crank mechanism, is amplified by the amplifier 75 and the amplified signal therefrom is compared by a rectifying network 76 with a reference voltage supplied by a D.C. source impressed across a potentiometer 77 having an associated manually controlled or positioned wiper 78 connected to the network 76. The difference between the reference signal and the amplified signal from the amplifier 75, is amplied by an amplifier 79 and fed to regulating means 80, the purpose of which will be explained hereinbelow.

The primary D.C. source of power 81 is connected through a switch 82 to an invertor 83, the function of which is to convert the D.C. power to a 400 cycle, 115 volt A.C. This A.C. power is utilized to energize, through connections shown in part, and thereby cause operation of the motor 45. Power from the invertor 83, as controlled by the regulator 80, is also applied to a rectifier 84, the output from which is fed directly to the control field of the motor 45 to thereby control the rotational speed of that motor. Closing the switch 82 also completes a circuit through an accelerometer switch 85 mounted upon the mass 20, and the solenoid of the solenoid actuated valve 30 in series therewith. The accelerometer switch 85 is of the type which will open the circuit if a predetermined acceleration is exceeded whereby the solenoid of the valve 30 will be deenergized which in turn will permit the valve to close and cut off the ow of pressure uid to the control valve 28 thereby suspending operation of the hydraulic actuator 21.

The D.C. source of power is connected also through a double throw switch 86 and by means of slip rings 87 to the reversible electric motor 58 whereby the motor 58 may be energized to cause operation thereof in either direction.

In operation, when the motor 58 has been energized to position the crank pin 63 eccentric to the axis of the shaft assembly 49, closing of the switch 82 causes actuation of the valve 30 to permit the supply of pressure fluid to the control valve 28, and causes operation of the motor 45. The shaft assembly 49 is thus caused to rotate and through the eccentric crank pin 63 and Scotch yoke assembly 40 an up and down motion is imparted to the link 41. When the link 41 moves downwardly the bellcrank 39 is caused to rotate in a clockwise direction, which through link 38, lever 37, link 36 and link 26 moves the spool element 27 to the left as shown. In this position, pressure fluid is admitted to the end chamber 35 through duct 32 which causes the piston 23 and mass attached thereto to move to the left. Piston rod 25 is carried to the left and carries with it the lower end of the link 26 whereby the link 26 is rotated in a clockwise direction to return the spool element 27 to its neutral position. Similarly, when the link 41 moves upwardly as the shaft assembly continues to rotate, the spool element 27 is moved to the right thereby directing pressure uid through duct 33 to the end chamber 34 which causes the piston 23 to move to the right. This again causes rotation of link 26 and the return of the spool element 27 to its neutral position.

It is apparent that the speed of operation of the motor 45 is dependent upon the position of the wipers 73 and 7,8. When the speed of operation is such that the output signal from the amplifier 75 is balanced by Athe reference signal taken off the potentiometer 77, the speed of the motor will remain constant. However, any change in the position of the crank mechanism and hence the position of the wiper 73, will produce a different signal across the

conductors

70 and 74, which signal when amplified by the amplifier 75 and compared with the reference signal taken off the potentiometer 77 will produce a signal at the amplifier 79. This signal, when amplified and fed to the line regulator 80, will cause either an increase or decrease in the power supplied to the control field of the motor 45, depending upon the direction of the signal, and hence either an increase or decrease in the speed of the motor until the output signal from the amplifier is again balanced by the reference signal. Similarly, any change in the position of the wiper 78 to change the reference signal will produce a signal at the amplifier 79, which results in an increase or decrease in speed of the motor 45, depending upon the direction of the signal, until the output signal from the amplifier 75 is again balanced by the reference signal.

Although shown and described in what is believed to be the most practical and preferred embodiment, it is apparent that departures therefrom will suggest themselves to those skilled in the art and may be made without departing from the spirit and scope of the invention. We therefore do not wish to restrict ourselves to the particular form of construction illustrated and described, but desire to avail ourselves of all modifications that may fall within the scope of the appended claims.

Having thus described our invention, what we claim is:

1. An oscillator for producing vibrations comprising a mass adapted for oscillating motion, a hydraulic actuatorv` connected to said mass and'provided with-acontrol valve, crank mechanism having a variable throw and operatively connected to said control valve, motor means for rotatably driving said crank mechanism, means for generating a first signal proportional to the rotative speed of said motor means and means for generating a second signal proportional to the throw of said crank mechanism, a reference signal, means for comparing said first and second signals with said reference signal, and means responsive to the difference in the signals so compared for controlling the rotative speed of said motor means.

2. An oscillator for producing vibrations comprising a mass adapted for oscillating motion, a hydraulic actuator connected to said mass and provided with a control valve. crank mechanism having a variable throw and operatively connected to said control valve, manually controlled means for varying the throw of said crank mechanism, motor means for rotatably driving said crank mechanism, means for generating a first signal proportional to the rotative speed of said motor means and means for generating a second signal proportional to the throw of said crank mechanism, a reference signal, means for comparing said first and second signals with said reference signal, and means responsive to the difference in the signals so compared for controlling the rotative speed of said motor means.

3. An oscillator for producing vibrations comprising a mass adapted for oscillating motion, a hydraulic actuator connected to said mass and provided with a control valve, a second valve for controlling the fiow of pressure fluid to said control valve, acceleration responsive means mounted upon said mass for controlling said second valve, crank mechanism having a variable throw and operatively connected to said control valve, motor means for rotatably driving said crank mechanism, means for generating a first signal proportional to the rotative speed of said motor means and means for generating a second signal proportional to the throw of said crank mechanism, a reference signal, means for comparing said first and second signals with said reference signal, and means responsive to the difference in the signals so compared for controlling the rotative speed of said motor means.

4. An oscillator for producing vibrations comprising a mass adapted for oscillating motion, a hydraulic actuator connected to said mass and provided with a control valve having a link operatively connected to said hydraulic actuator to provide4 a follow-up motion to said control valve, crank mechanism having a variable throw operatively connected to said link for imparting reciprocating motion to said control valve, motor means for rotatably driving said crank mechanism, means for generating a first signal proportional to the rotative speed of said motor means and means for generating a second signal proportional to the throw of said crank mechanism, a Ireference signal, means for comparing said rst and second signals with said reference signal, and means responsive to the dilerence in the signals so compared for controlling the rotative speed of said motor means.

5. Apparatus as claimed in claim 4 characterized by the provision of a second valve'for controlling the ow of pressure fluid to said control valve and acceleration responsive means mounted upon said mass for controlling said second valve.

References Cited in the ile of this patent UNITED STATES PATENTS OTHER REFERENCES Product Engineering, Hydraulic Vibrators, Dec. 9, 1957, pages 9498.