US2918548A - Control device - Google Patents

Description

Dec. 22, 1959 c. J. BUCCINI 2,918,548

CONTROL DEVICE Filed Dec. 21, 1956 2 Sheets-Sheet l '8 I2 ti L SIGNAL "PICKED up FROM TEST SPECIMEN 21m r l 1 VIBRATION GEN, J CUT-OFF PK; 2

IIII IHH I N VEN TOR.

COLUMBUS J. BUCCINI Dec. 22, 1959 Y c. J. BUCCINI 2,918,548

CONTROL DEVICE Filed Dec. 21, 1956 2 Sheets-$heet 2 FIG. 3

U) LL! 5 g i Z FREQUENCY SWITCH ANo//L TEST SPECIMEN AT RESONANCE 0 LL] 3: I

g I 0 (1) LL .1. 0 l6 DIRECTION OF FATIGUE B l I ,2 \START OF FATIGUE E o W 2 I25 I24 I23 I22 121 :20 H9 us 117 N6 DECREASING FREQUENCY OF TEST SPECIMEN CYCLE/SEC.

FIG. 4 INVENTOR.

COLUMBUS J. BUQCINI United States Patent CONTROL DEVICE Columbus J. Buccini, New Haven, Conn., assi'gnor to Olin Mathieson Chemical Corporation, a corporation of Virginia Application December 21, 1956, Serial No. 629,935

2 Claims. (Cl. 200-91) The present invention relates to control d vices and in particular to control devices operative to sense and to respond to changes of frequency occurring. in vibrating bodies.

A particular object of the present invention is the provision of an electrical switch device having elements thereofadapted to vibrate in synchronism or in sympathy with an extraneous vibrating body; slight changes in frequency of vibration which occur in the remote body are sensed by the control device and these changes are effective to actuate a switch.

An additional feature of the present invention is that it embraces a single reed whose effective length may be selectively adjusted to vibrate at a variety of frequencies natural to a particular selected reed length.

Another object of the invention is the provision of a novel method of sensing changes in frequency occurring in a remote vibrating body.

A still further object of the-present invention is the provision of a novel method of controlling electrical circuits.

'A control device incorporating certain features of the present invention may include a single reed adapted to be vibrated selectively'at a variety of frequencies, means for adjusting the effective length of the reed, means for driving the reed at the natural frequency corresponding to a selected length of reed, and switch means cooperating with the reed and settable to operate at a predetermined reed amplitude.

It is to be understood that the principles of the present invention may be utilized to regulate a variety of different electrical devices or operations which embrace frequency sensing or control by frequency sensing; however, for purposes of illustration, the invention wil be described in connection with a conventional fatigue tester. Reference is made to a fatigue tester wherein a sample or specimen of metallic material of a predetermined configuration is vibrated by external means to the point of failure.

A more complete understanding of the invention may be obtained from the following specification and drawing, in which:

Fig. 1 is a plan view of a device embracing the principles of the present invention;

Fig. 2 is a sectional view of Fig. 1 taken along the line 22 thereof. Certain portions are broken away for clarity. This figure also includes a wiring diagram of a typical scheme for utilizing the present invention;

Fig. 3 is a side view of the device illustrated in Fig. 1 and;

Fig. 4 is a curve showing the variations in switch reed amplitude as compared to the change in test specimen frequency occurring during and prior to specimen failure.

Referring now to the drawings and in particular to Figs. 1, 2 and 3, there is shown a steel switch reed carried by a micrometer anvil 11. The reed is restrained by a pair of opposed pressure plates 12 and is movable to and fro (from right to left as viewed in Fig. 2) be- 2,918,548 Patented De 22, 1959 tween the plates responsive to rotation of a knurled micrometer dial 13. The dial may he graduated in any suitable fashion, for example, in thousandths of an inch to indicate the increment of; distance through which the reed is advanced or withdrawn. In effect, the micrometer dial measures the effective length of the reed measured from the left face of the pressure plates to the left end of the reed. An electromagnet 14 is disposed below the reed and is utilized, in a manner which will become more apparent hereinafter, to set the reed in vibration and to drive it in synchronism with a remote vibrating body such as a test specimen vibrating in a fatigue mechanism.

Fig. 2 shows schematically the manner in which the reed 10 operates as one contact of a switch. It is noted that the positive side of a suitable source of power is con.- nected to the micrometer frame 17 by means of the lead 16. Current flows along the reed 10 where, depending uponthe amplitude of vibration of the reed as shown in dotted line at 18, the reed accomplishes a switching action with an adjustable contact 19. A lead 21 connects the contact 19 with a junction 22. The junction 22 is connected to a switch terminal 23 through a vibration generator cut off by means of the lead 24. A second switch terminal 26 is connected to the terminal 22 through a test lamp. The circuit is then completed from a mov able contact 27 to the negative side of the power source by means of the lead 28.

It is to be noted that the movable contact 27 may be set in a position to energize the test lamp or alternatively across contact 23 to include the vibration generator cut off in circuit in a manner which will become more apparent hereinafter.

A reference to Fig. 3 reveals a knurled handle 29 operative to raise and lower the contact 19 with respect to the tip of the switch reed 10.

The control device of the present invention is placed in operation in the following manner:

Assume that a specimen of material to be fatigue tested has been placed in a conventional vibratory tester (not shown) and is being driven at a predetermined frequency by any suitable vibration generator. The specimen in the fatigue tester is usually in the form of a metal reed and is driven by a vibration generator which in turn causes the specimen to flex vigorously at its own natural frequency.

It is well know-n that the specimen will continue to vibrate at its natural frequency until the fatigue point is reached. Experience has shown that at this point, i.e., the beginning of fatigue failure, the nature frequency of the specimen experiences a marked change. Usually the value of the frequency falls off gradually until a complete break or separation of the test specimen occurs. conceivably a specimen approaching failure may show an increase in the number of flexures per cycle over the natural, frequency, but in the event of an increase or a decrease in frequency, the principles of the present invention would apply.

For the sake of explanation of the embodiment of the invention disclosed herein it will be assumed that at the point of failure the frequency of the specimen decreases (Fig. 4).

Utilizing a conventional pick-up (not shown) such as a sound head, a signal corresponding to the frequency at which the test specimen is vibrating (its natural frequency) is impressed upon the electromagnet 14. This signal through the electromagnet sets the switch reed it into vibration.

Next, an operator searches for the frequency of the test specimen by rotating the dial 13 clockwise and counterclockwise, thus advancing and withdrawing the reed 10 (actually changing its effective length) until the reed is vibrating in sympathy or in synchronism with the test specimen and at the natural frequency of the selected effective length. At this time, what is actually occurring is that the operator is searching for the particular effective length of the reed 10 which, under the influence of the signal impressed upon it by the electromagnet 14, will produce maximum amplitude in the reed 10. In this way, an effective length of switch reed is selected whose natural frequency is identical to th natural frequency of the test specimen.

After the particular length of switch reed has been selected, which produces maximum amplitude in the switch reed thus assuring sympathy or synchronism between the switch reed and the test specimen, the movable contact 27 is connected to the contact 26. Thereafter the movable contact 19 is slowly moved upwardly until the tip of the switch reed begins to tick uniformly against the contact 19. This occurrence can be observed by noting a uniform flicker in the test lamp L.

At this point, then, the switch reed is vibrating in sympathy with the test specimen and the switch reed is also developing maximum amplitude because it is vibrating at its natural frequency.

Since it is known that the natural frequency of a test specimen drops or falls off to a lower frequency just prior to the occurrence of failure, the switch reed is adjusted slightly in a direction which corresponds to a lower frequency. In actual practice, this is a matter of moving the switch reed to the right or the left several thousandths of an inch. Frequently it is desirable to calibrate the micrometer directly into frequency or at least to provide a chart or graph from which micrometer readings in thousandths may be readily converted into frequency using Well known formula.

After adjustment of the switch reed, the amplitude thereof immediately decreases since the signal impressed on the electromagnet 14 remains unchanged and does not represent the natural frequency for the new adjustment length of the switch reed. Thus, the tip of the reed no longer ticks the movable contact 19. At this time, the contact 27 is placed across the terminal 23 thus placing the vibration generator cut-off in circuit. In this condition, the fatigue tester may be left unattended with the assurance that the interval of failure may be readily recorded and that the generator will be shut off at failure of the specimen.

As stated before, prior to failure of the specimen, the frequency of vibration of the specimen will drop off. This means that the signal impressed upon the electromagnet will reflect this drop-oft and the switch reed will begin to vibrate at the new lower frequency. By virtue of the previous adjustment of the effective length of the switch reed to a point corresponding'to a selected lower value of frequency the amplitude of the switch reed will increase as the falling value of frequency begins to approach the natural frequency of the adjusted effective length of the switch reed. As soon as the test specimen and the switch reed are vibrating in sympathy or in synchronism, the switch reed will again be at maximum amplitude and the tip of the reed strikes the contact 19, the fatigue tester is immediately cut off. Termination may also include actuation of a time device, such as a time stamp, as desired.

Obviously, one of the primary features of the control device is the versatility designed into a single switch reed. It is anticipated that other modifications and variations of the present invention may be devised without departing from the spirit and scope thereof.

What is claimed is:

1. A tuned reed relay for regulating electric circuits comprising a single reed adapted to be vibrated selectively at a variety of frequencies, electrical means independent of said electric circuits for setting said reed in vibration, means for adjusting the effective length of the reed whereby the reed may be set in vibration at the natural frequency corresponding to the particular etfcctive length, and adjustable contact means cooperating with the settable reed effective to operate at predetermined amplitudes of reed vibration and further effective to regulate said electric circuit.

2 A tuned reed relay for regulating electric circuits comprising a single reed adapted to be vibrated selectively at a variety of frequencies, means for adjusting the effective length of the reed whereby the reed may be set in vibration at maximum amplitude for a given frequency, said reed constituting an electrical contact, electrical means for impressing a vibratory signal upon said reed, said electrical means being independent of said electric circuits and adjustable contact means cooperating with the settable reed effective to regulate said circuit whenever said vibratory signal corresponds to said given frequency.

References Cited in the file of this patent UNITED STATES PATENTS 524,165 Downes Aug. 7, 1894 1,174,229 Coleman Mar. 7, 1916 1,190,923 Lindquist July 11, 1916 2,179,640 Lakatos Nov. 14, 1939 2,249,649 Fielding July 15, 1941 2,361,396 Gross Oct. 31, 1944 2,450,939 Cor Oct. 12, 1948

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