US1872896A - Constant-frequency generator - Google Patents

Description

Aug. 23, 1932. F. CONRAD CONSTANT FREQUENCY GENERATOR Original Filed Jan, 18, 1929 2 Sheets-Sheet Aug. 23, 1932.4 F, CONRAD 1,872,896

CONSTANT FREQUENCY GENERATOR Original Filed Jan. 18, 19,29 n 2 Sheets-Sheet 2 www l lil-.Ila f4 lc la 2o Sethd /oaoa mu-1 Currenf 80 BY 76 8/ 77 7 TTORNEY a constant-frequency-generator Patented Aug. 23, 1932,

1,872,8img

FRANK CONRAD, .orjPENN TowNSHIP. ALLEGHENY COUNTY, PENNsYL'vAN'iA, .as-

SIGNOR TO WESTINGHOUSE ELECTRIC MANUFACTURING COMPANY, A CORPORA- TION F PENNSYLVANIA CONSTANTFREQUENCY GENERATOR 1930. Serial This application is a division of my applifation, Serial No. 333,374, filed January 18, 1929.

My invention relates to high frequency generators of the tuning-fork or vibrating-reed type.

The object of my invention is to provide means for maintaining the yfrequency of a generator of the above-mentioned type` oonstant. p

In practicing my invention, I em loy a tuning fork which is mounted in a b ook of metal and driven by electromagnetic means; The frequency of vibration of the tuning fork is maintained constant by periodically heating the tuning fork by an amount that is dependent upon t-he departure of the vibrations from the desired fre uency. The heat is applied periodically to t e'tun'ing fork by means of a heater element which is 1n contact wlth the metal block and is connected to a system including an electric clock and a synchronous motor, as Will be more fully described hereinafter.

Other features and advantages of my invention will appear from the yfollowing description, taken in connection with the accompanying drawings, in which, s

Figure 1 is a diagrammatic -view'of the apparatus and electrical connections employed in my constant-frequency generator; i

Fig. 2 is a diagram to aid in describing the operation of my constant-frequency generator:

Fig. 3 is a diagrammatic view of the -heating box and heating apparatus for the constant-frequency-generator tuning fork;

Fig. 4 is an end elevational view ofthe tuning fork and its holder and driving mechanism, and l v Fig. 5 is asectional view, taken along the line V-V of Fig. 4. i

Referring to the drawings, the portion o f system, indicated in Fig. 1 by the legend heater yand Vfork, is shown schematically in Fi 3. This portion of the system .comprises al eat-insulated boX 67 within which are locatedr two electric heaters 68 and' 69. The uppery heater 68 is connected to a source of 'current' through Original application tiled January 18,r i929, Serial No. 333,374. Divided and this application iiledMarch',

a thermostatic relay 70 of the bimetallic type,

A condenser 7l is shunted across the relay contacts to reduce sparking. The interior of the heater box is maintained at a substantially constant temperature by means of the heatv yer 68 and the thermostatic relay 70. The

f tors and v7 6, respectively, arey electromagnetic devices for drivingl the tuninfr fork.

The construction of the tuning-flink holder 7 2, the tuning` fork, andthe electromagnetic driving means `73 and 74 can best vbe understood by referring to Figs. 4 and 5. The holder 72 comprises two solid metallic blocks 77 and 78,- preferably of brass, each v having a vertical hole 79 drilled off center, therein. Each block has a larger threaded hole, drilled at right-angles to the vertical hole 79 and communicating with` it, in which one of the electromagnetic driving units 73 and 74 is supported. The two blocks 77 and 78 are clamped together by means of bolts 80, with their thin walls adjacent to `each other and .with a sheet yof magnetic material 81 between them. In this Way, two well portions 79 are formed, separated by a thin partition of magnetic material 81 and nonmagnetic material 82. A square notch 83 is cuty in the middle of the upper edge of the partition. by means of bolts 85, between two solid metal blocks 86 and 87, preferably of brass. Blocks 86 and v87 are secured, by bolts 88, to the blocks 77 and 78 in such position that a portion of the tuning fork 84 is located within the notch 83 cut in the partition, While the prongs 99 are located within the wells 79. A clip 10() is attached at the top of the block for holding a thermometer 101.` n

The tuning-fork-driving elements 73 and 74 comprise telephone-receiver units having pole pieces adjacent to the prongs 99 of the tuning fork 84. The pole pieces are soft- `iron pieces attached to the'poles of a permanentr magnet 102. .They have coilsnl03y The tuning fork 84 is clamped,

. the forli heater 69. y

,plied to the fork 84 is controlled by means of asynchronous motor 108 (preferably of the mounted thereon which are connected to the binding posts 104. The driving elements are held in place by means of set screws 105.

The partition above-specified is provided for electrically shielding the driving elements 73 and 7 l from each other.

Since the tuning forl 84 is in contact with the brass blocks 86 and S7, which are good heat conductors, the temperature of the forli 84 may be controlled by varying the amount of heat applied to these blocks. This is done by setting the fork holder72upon an electric heater 60, as shown in Fig. 3, and by controlling the amount of current flowing through the heater by means of the circuit shown in Fig. 1. VReferring to'Fig. 1, the constant-frequency current is generated by so connecting the forlvdriying elements 73 and 7 4 to an amplilier 106 that the fork 34 is vibrated at its natural frequency. In the example being described, a 500G-cycle current is generated. rlhe driving element l. is connected to the input of the amplifier 100 by conductors 6, while the driving element 7 3 is connected to .the output of the amplifier 106 by conductors from the Vamplifier output.

The frequency of the current generated is controlled by varying the amount of heat supplied through the heater circuit 107 to The amount of heat supphonic-wheel type.) connected to the forkainplifier output through an amplifier 109,

and byr means of an electric clock 110.

When a current ofthe desired frequency is being generated, the synchronous motor 10S connects the forlcheater circuit 107 to a source of. current at regular intervals, while It-heelectric clock 110 disconnects the heater circuit 107 from the source at like intervals.

In this way, the fork heater 60 is alternately connected to, and disconnected from, the source of current, which. 1n the example illustrated, is a 110-volt alternating-current supply. p l,

',The circuit connecting the current supply tothe forli heater 69 may be traced from one dicator lamp 117 and resistance 118, in parallel, a conductor 119, one conductor of line 107, the forl heater 69, the other conductor of'line107 and the conductor 120, back to the rother terminal of the alternating-current supply. The winding of relayV 114, which pulls upthe armature 113 an'd'thereby con- 'nects the fork heater 69 to the alternating:

current supply, has one terminal connected to ground and the other terminal connected, through a resistance 121 and a conductor 122, to one terminal of a battery 23, the other lterminal of the battery 123 heilig connected armature'113 of the relay 114C is pulled up to connect the fork heater 69 to the 110 volt supply. Vhen the armature 125 of the polar relay 1241- rests against the right-hand contact, the Winding of the relay 11-l is short circuited, and the armature 113 drops down, thus disconnecting the fork heater 69 from the 110 volt supply.

The armature 125 of the polar relay 124 is pulled over to the left, to connect the fork heater 69 to the 110 volt supply, each time the upper terminalrof the left-hand windin g 127 of said relay is connected to ground by means of the synchronous motor 108 through the conductor 128, brush 120, contact elei ent 130, shaft 131, ring 132 and brush 133. Vle shaft 131 is connected tothe synchronous rootor 103 through a gear reduction unit so that contact between element 130 and brush 129 is made once every two seconds if the tuning fork 8l. is vibrating at the proper frequency.

The polar relay armature 12o pulled against the right-hand contact, to disconnect the fork heaterf69 from the 110-volt supply, each time the electric clock 110 pulls the armature 134 of the polar relay 135 against the left-hand contact. Since the electric clock 110 actuates the polar relay 135 at regular intervals, (once every two seconds, in the example illustrated) the forli heater 69 will be disconnected from the 110-volt supply at like intervals. The synchronous motor 103 and the electric clock 110 are so adjusted with respect to each other that they alternately conneet and disconnect the fork heater' 69 and the current supply. The electric clock 110 preferably, of the type described an d claimed in my copending application. Serial No. 176,061, liled'March 17, 1927, in which the pendulum is driven by charging and discharging a condenser through a driving coil. The'coil of the polar relay 135 is connected in series with this driving coil.

When the armature 13a is pulled against the left-hand contact. a circuit is completed Afrom a battery 136, through a resistance 137,

a conductor138, a relay winding 139, a conductor 140, the relay armature lil-lf and the left-hand contact, back to the battery 136. This pulls the relay armature 141 against the upper contact and connects the upper terminal of the right-hand winding 14.2 of the polar relay 124 to ground through conductor 5Lavasee 143 and armature 141. The" armature 125'of the polar relay 124 is then pulled 'against the right-hand contact, and relay armature 113 drops, 'thereby disconnecting the heater 69 from the current supply. i

A special circuit is provided for passing current through the polar- relay windings 127 and 142 in response. to they closing of either the synchronous motor or the electric-clock contacts. The circuit comprises the battery 123 which is connected, throuo'h aconductor 144, a resistance 145 of a fewtliundred ohms anda second resistance 146 of several me ohms, to one terminal of a condenser 14 The other terminal of the condenser 147 is connected to the other terminal of the battery 123 through ground. A circuitis likewise completed from one terminal of the battery 123, through the conductor 144, the resistance 145, a second resistance 148 similar to resistance 146, a condenser 149 similar to condenser 147 and, through ground, to the other termi-` nal of the battery 123. e

By means of the circuit described above,

. the condensers 147 and 149 are kept charged.

Accordingly, when the upper terminal yof either polar-relay winding 127l or winding 142 is connected to ground, by means of the synchronous motor 108 or the electric clock 110, the condenser to which the windinr is connected discharges through that winding. This momentary yflow of current through the winding is suiicient to pull the armature 125 against a contact. Because of this arrangement, the 4armature 125 of the polar relay 124 may be pulled away from a contact very shortly after it is pulled against it, since the rush of currents lasts a very short time.

I Therefore, the armature 125 of the relay may fio CIS

be pulled away from a relay contact even though the contacts of the synchronous motor 108 or those of electric clock 110, which pull the armature 125 against the relay contact, are still closed.

The condensers 150 and resistances 151 are employed` to reduce sparking at the relay contacts. 2 y f The following values of capacity, resistance and voltage have been found satisfactory although, obviously, other values may be employed, if desiredzkresistances 146 and 148 equal 5 megohms; resistance 145 equals 1000 ohms; resistance 112 equals 50 ohms resistance 116 equals 800 ohms; resistance 118 equals ohms; condensers 147 and 149 equal .25 micro-farads; resistance 121 equals 10,000 ohms; and the voltage of battery 123 equals 350 volts.

The operation of the circuit will be more fully understood by yreferring to the diagram of Fig. 2 which greatly exaggerate-s the rapidity with which changes in the fork frequency occur. In ythis diagram, the( curl rent applied to the fork heater 69 is plotted against time in seconds. From zero to four from, the vcurrent supply at one-second ini" tervals. 'When the fork 84 begins to vibrate too slowly, the synchronous motor 108 slows down,'and, after the heater 69 hasbeen disconnected from the current supply (as after the four-secondnterval) it is not again connected to the current supply until a longer time than one second. The electric clock 110, however, is not affected by the frequency of the tuning fork 84 and continues to disconnect the current from the fork heater 69 at two second intervals. The current supply is accordingly disconnected from the heater 69 at the six-second interval. It will be noted from the diagram that, as a result, less heat is applied to the fork 84 than when it is vibrating at the proper frequenc Accordingly, the tuning fork 84 wil be cooled slightly and kits frequency will increase. In the diagram, the fork frequency begins to increase after the ten-second interval. After the twelve-second interval, the fork 84 begins to vibrate too rapidly, and the synchronous motor 108 speeds up. This results in heat being applied to the fork 84 an instant sooner than 1t would be'if the forkwere vibrating at the 5000-cycle frequency. lThe temperature ofthe fork 84 is, accordingly, increased and its frequency is changed the desired amount. It will be noted that, at the sixteen-second interval, the fork 84 is vibrating so rapidly that the synchronous motor 108 connects the heater 69 to the current supply as soon as it is disconnected by the. electric clock 110. It is evident that, if the fork 84 vibrates still more rapidly, the synchronous-motor speed will be so high that its contact 130 will connect the fork heater 69 to the current supply ]'ust before the contacts of relay 139 are closed by the electric clock 110 to disconnect the current supply from the heater. When this happens, less, instead of more, heat is applied to the fork 84 than is applied when it runs at the proper frequency, and the system will not correct the fork frequenc VIn such case, a manual adjustment must made to increase the fork temperature. Under ordinary conditions, no such adjustment is necessary. In the 500G-cycle generator described, the synchronous motor I cla-iin asmy invention:

1'.' A constant-frequency generator comprising a mechanical element havingv a nat ural period of vibration, means for vibrating said element at its natural frequency, and means responsive to changes in the frequency of the output of said generator for maintaining the frequency of vibration of said element constant.

2. A constant-frequency generator coinprising a mechanical element havingI a natural period of vibration, means for vibrating said element at its natural frequency, and means for applying heat to said element, said means being responsive to changes in the frequency of the output of said generator for changing the amount of heat applied to said element.

8. A constantfrequency generator comprising a mechanical ele-nient having a natural period of vibration, means for vibrating said element at its natural frequency, means for applying heat to said element at periodic intervals, and ineans responsive to the frequency of vibration of said element for controlling the time between said intervals.

4. A constant-frequency generator comprising a mechanical element having a natural period of vibration, means for vibrating said element at its natural frequency, and means responsive to the frequency of vibration of said element for applying heat thereto in increments having a magnitude dependent upon said frequency.

5. A constant-frequency generator coinprising a mechanical element having a n at ural period of vibration, means for vibrating said element at its natural frequency, means for heating said element, a source of current, means responsive to the frequency of said element for connecting said source Vto said heating means and means for disconnecting said source from said heating means at regular intervals.

6, A constantffrequency generator comprising amechanical element having a natural period of vibration, means for driving said element at its natural frequency, means including an electric heating element, for heating said mechanical element, a source of current, means for connecting said source to said heating element at intervals dependent upon the frequency of vibration of said element, and means for disconnecting said source from said heating element at regular intervals.

7. A constant-frequency generator comprising a mechanical element having a natural period of vibration, means for vibrating said .element at its natural freque- Jy, means, including an electric heating element, for heating said element, source of current, means for alternately connecting and disconnecting said source and said heating G5- element and 'means for making the time between said connection and disconnection dependent upon the frequency of vibration of said element.

S. A constant-frequency generator eoniprising a mechanical element having a natural period of vibration, means for vibrating said elementat its natural frequency, means, including an electric heating element, for heating said mechanical element, a source of current, means for connecting said source to said heating element after said mechanical element has vibrated a predetermined number of cycles and means for disconnecting said source from said heating element at intervals independent of the frequency of vibration of said mechanical element.

9. A constant-frequency generator comprising a mechanical element having a natural period of vibration, means, including an electric heating element, for heating said mechanical element, a source of current, means, including a synchronous motor driven by said generator, for connecting said source to said heating element and means, including an electric clock, for disconnecting said source from said heating element.

l0. A constant-frequency generator comprising a mechanical element having a natural period of vibration, means for vibrating said element at its natural frequency, means responsive to the frequency of said element for heating it and means for making said heating means ineffectivev at fixed intervals.

1l. A constant-frequency generator comprising a mechanical element having a natural period of vibration, means for vibrating said element at its natural frequency, means for heating said element, means for making said heating means ineffective at intervals spaced apart by a predetermined number of vibrations of said mechanical element and means for making said heating means ineffective at evenly spaced time intervals.

12. A constant-frequency generator comprising a mechanical element having a natural period of vibration, means for vibrating said element at its natural frequency, means for heating said element, means for making said heating means effective at intervals spaced apart by a pe fiod of time proportional to alpredetermined number of vibrations of said element, and means for making said heating means ineffective the same number of times it is made effective and at regular intervals, independent of the frequency of said element.

13. A constant-frequency generator comprising a mechanical element having a natural period of vibration, means for vibrating said element at its natural frequency, means for heating said element, a polar relay, a plurality of condensers connected to said relay, means for charging said' condensers, means for operating said relay and making said heating means effective when one of said condensers is discharged and means for operating said relay and making said heating means ineffective when another of said condensers is discharged.

14. A constant-frequency generator comprising a mechanical element havinga natural period of vibration, means for vibrating said element at its natural frequency, means for heating said element, a polar relay having an armature and two windings, each of said windings having. a condenser connected thereto, means for charging said condensers, means for making said heating means effective when current isv passed through one relay winding, means for making said heating means ineffective when current is passed through the second relay winding, means responsive to the frequency of vibration of said element for discharging one of said condensers through said one relay winding, and means independent of the frequency of said element for discharging the other condenser through the second relay winding at regular intervals.

15. A constant-frequency generator com-- prising a mechanical element having a nat@ ural period of vibration, means for vibrating said element at its natural frequency,l

heating means for heating said element, means for alternately making said heating means effective and ineffective,y and means for making the time between the instant'the heating means is made effective and the instant it is made ineii'ective dependent upon the frequency of vibration of said element.

In testimony whereof, I have hereuntosubscribed my name this 26th day 'of February, 1930.

FRANK CONRAD

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