US1996569A - Piezo-electric device - Google Patents

Description

April 2, 1935. l. F BYRNES El' AL 1,996,569

I PIEzo ELECTRIC DEVICE Filed Nov. 16, 1929 /zo F191. f/F ,/7\ J2 /4 C C C C w y C ze Figa..

20 z/ /9 /o I 24 2 5-nfl; /6

,4 Z5 zz u Ihvemtorl Irvlhg E' Bgrhes, Harrg RMeahL.

b9 MM Hleir Attorney.

l Patented Apr. 2, 1935 UNITED STATES PATENT OFFICE PIEZO-ELECTRIC DEVICE Irving F. Byrnes and Harry R. Meahl, Schenectady, N. Y., assignors to General Electric Company, a corporation of New York Application November 16, 1929, Serial No. 407,785

2 Claims. (Cl. 219-19) Our invention relates to piezo-electric devices crystal I! through the leads 20 and 2|, which are such as are used to control the operating freconnected respectively to an electrode 22 and an quency of oscillation generators. It has for its electrode 23 which forms the bottom of the cell. principal object the provision of an improved de- A thermometer 24 may be provided for observavice of this character which operates at a fretion of the cell temperature. It will of course be quency substantially independent of ambient apparent that the upper electrode 22 and the temperature. lower electrode 23 are electrically insulated from It is well known that a piezo-electric crystal one another by any suitable means. The illussuch as a slab of quartz or the like tends to vibrate trated type of crystal mounting is well known and at a frequency dependent on its mechanical need not be described in further detail. 10 dimensions when it is subjected to an electrical In 3 the crystal C611 iS indicated at 25 by field. It is also known that the natural vibration dotted lines, and the 'thermo-regulator I6, the period of the crystal is dependent to some extent crystal I9, and the heater or heating layer I2 on the temperature to which it is subjected durare shown diagrammatically as enclosed within ing its operation, and various means have been the cell. Heating current is supplied to the heatprovided in the past for regulating the temperaing layer I2 from any suitable source such for ture of the crystal. Our invention relates to an example as an alternating current source 25 improved apparatus whereby changes in the temthrough a relay 21. The relay 21 is provided with perature of the crystal are minimized to a degree an operating coil 2l which is connected in the not heretofore realized. plate circuit of an electron discharge device 29, 20

Our invention will be better understood from through which the supply of current to the heatthe following description when considered in coning layer is controlled. nection with the accompanying drawing, and its It will be observed that the electron discharge scope will be pointed out in the appended claims. device 29 includes a cathode 30, a control grid 3 I,

Referring to the drawing, Figs. 1 and 2 are and an anode or plate 32. Heating current is 25 vertical and horizontal sectional views of a piezo supplied from the source 26 to the cathode 30 electric cell wherein our invention has been emthrough a transformer 33.v Plate and grid conbodied, and Fig. 3 is a wiring diagram of the control potentials are applied to the device 29 through trol circuits through which temperature control a transformer 34, the plate circuit of the device 30 of the crystaliseffected. 2! being connected across one section of the 30 As indicated by Figs. 1 and 2, the cell comprises secondary circuit of the transformer 34 and the an outer protective layer I0 which may be of grid 3| being connectedtothe cathode 30 through basswood or the like, an insulation layer Il which a capacitor and another section of the may be any suitable material, a heating layer I2, secondary circuit of the transformer 34. A

35 a heat distributing layer I3, a heat attenuating smoothing capacitor 3S is connected in shunt to 35 layer I4, and a heat storing layer I5. The heat the operating coil 28 of the relay 21, and a reattenuating layer, which is shown as an enclosed sistor 31 is connected between the thermo-reguair space may include a layer of hair felt or other lator 46 and the grid 3l. The operation of the suitable material, and is arranged to enclose a device will be readily understood without detailed thermo-regulator I6 of any suitable type. The explanation. Assuming that the temperature of 40 heat distributing layer comprises any suitable the cell increases above the desired value, the material having high heat conductivity and low mercury within the thermo-regulator I6 expands heat storage capacity. The thermo-regulator I6 and a connection is completed between the termiis preferably mounted near theheat distributing nals I1, thus connecting the grid 3i directly to layer I3, and in the illustrated embodiment of the the cathode 3l, through resistor 31 which limits 45 invention is a mercury contact device provided current through contacts I1 permitting the transwith a pair of terminals I1 which, as hereinafter mission of current through the device 29 to the explained, are arrangedto control the grid potenoperating coil 28 of the relay 21, which is opertial of a vacuum tube device through which the ated to its upper or open position, interrupting supply of heating current to the heating layer I2 the supply of heating current to the heating 50 is controlled. This heating current is supplied layer I2. When the temperature of the device through leads I8. The piezo-electric crystal is decreases below the desired value the mercury indicated at I9 andis enclosed within the heat within the thermo-regulator Il contracts, the storing layer I5, which is preferably made of circuit between the terminals I1 is interrupted,

copper. Electric potential is applied to the and thegrid 3|,whichis connected to the cathode 55 3@ through the capacitor in the left-hand section of the secondary circuit oi the troer 3d, is subjected to a potential which interrupts or reduces the current of the device 2@ and permits the relay 2l to move to its lower or closed position, thus connecting the heating layer i@ to the source 26.

It has been found in the operation of the device that the range of temperature variation of the crystal is dependent on several factors not heretofore well mi Br smug, the range of temperature variation of the crystal depends on the sensitivity oi the thermo-regulator and on the size of the heater. ln the operation of the device it has been found that the heat distributing layer i8 is of great importance. It has also been found that the .best results are secured when the thermo-regulator is mounted inproximity to the heating layer whereby it is sensitively responsive to heat produced thereby, and is suciently removed from the `Wall i5 to permit the latter to act as a relatively constant temperature heat reservoir, or balance wheel. Ii the thermo-regulator is mounted betvveen the insulation layer ii and the hting layer i2, for example, a change of about 1 C. is found to exist for each 8 C. change in room temperature. When the hwt distributing layer i@ is provided and the thermo-regulator is mounted in proximity to this layer, it rf i.. been found that the range of variation in the crystal temperature is about 111; of 1 for each 20 C. change in room temperature. The heat distributing layer and the proper location of the thermo-regulator are therefore important considerations in the construction oi the type of crystal cell herein described.

The large heat storing mass of the base plate 28 and Walls i5 aiords a relatively co f m temperature reservoir of heat, or heat mi :n ce wheel, thereby very greatly reducing temperature variations Within these operation of the cl a considerable cunt of heat is dissipated in the crystal due to its operation. Since the crystal is in intimate heat conducting relation with the base 23 and walls i5 this heat is quickly absorbed in the reservoir without produling large temperature variation in the c asi ce wir we cl as new and d m secune by Letters Patent oi' the United Sta, is,-

incasso l. The combination, in a temperature control device for piezo-electric crystals, of a chber having a wall ci high heat conductivity and low heat storing capactiy, a heating winding wound about the exterior surface oi said wall thereby evenly to distribute heat over said surface, an inner chamber enclosed by and spaced from said walls, said inner chamber having massive Walls of high heat retg capacity, one of said massive walls being in intimate heat conducting relation with the crystal and a temperature responsive means for controlling said heating ding, said temperature responsive means being located in suiiciently close heat conducting relation with said heating winding to produce sensitive response to temperature variations produced thereby and sumciently removed from saidI massive wall to permit the latter to act as a relatively constant tem'perature heat reservoir thereby to protect the crystal from heat variations produced by said heating means.

2. The combination, in a temperature control device for piezo electric crystals, a housing for said crystal having thick massive walls of high heat storing capacity, one of said walls being of greater thickness and mass than the others, the piezo electric crystal being mounted in intimate heat conducting relation with said wall of greater thickness and mass whereby heat dissipated in the crystal is quickly absorbed in said walls, a heat attenuating chamber enclosing said housing, the walls thereof being spaced from the Walls of said housing and having high heat conductivity and low heat storing capacity, a heating winding wound upon the exterior surface of said attenuating cber thereby evenly to distribute heat about said crystal, and temperature responsive means to control said said means being located in suiciently close heat conducting relation with said heating winding to produce sensitive response to temperature variations produced thereby and suiiiciently removed from said housing to permit said housing to act as a relatively constant temperature heat reservoir to protect the crystal from temperature varlations produced by said heating winding.

Images