US2481806A

US2481806A - Piezoelectric crystal holder

Info

Publication number: US2481806A
Application number: US767149A
Authority: US
Inventors: John M Wolfskill
Original assignee: Individual
Current assignee: Individual
Priority date: 1947-08-07
Filing date: 1947-08-07
Publication date: 1949-09-13
Anticipated expiration: 1966-09-13

Description

P 1949- J. M. WOLFSKILL PIEZQELECTRIC CRYSTAL HOLDER 3 Sheets-Sheet 1 Filed Aug. 7, 1947 JOHN M. WOLFSKILL Sept. 13, 1949. J. M. WOLFSKILL PIEZOELECTRIC CRYSTAL HOLDER Filed Aug. 7, 1947 s Shee'ts-Sheet 2 JOHN M. WOLFSKILL Sept. 13, 1949. J. M. WOLFSKILL 2,481,806

PIEZOELECTRIC CRYSTAL HOLDER Filed Aug. 7, 1947 I5 Sheets-Sheet 5 Fig 10 3 JOHN M. WOLFSKILL Patented Sept. 13, 1949 UNITED STATES PATENT OFFICE 2,481,806 PIEZOELECTRIC CRYSTAL HOLDER John M. Wlfskill, Erie, Pa. Application August 7, 1947, SerialNo. 767,149

32 Claims.

This invention pertains to an apparatus for mounting piezoelectric quartz crystals, more particularly, it pertains to mounting thin high frequency piezoelectric crystals to facilitate handling of such crystals, and provide improved performance over the prior art holders.

It is an object of this invention to provide contiguous electrodes of varying areas to elicit good response from piezoelectric crystals on difierent harmonics.

It is another object of this invention to make good electrical contacts to plated electrodes of piezoelectric crystals at such a point or area as to reduce the damping action of such contact as well as the contact resistance.

It is another object of this invention to provide a rigid support not only for lateral movement of crystal blanks but also to prevent strain in the crystal blank due to its mounting or clamping supports.

Another object of this invention is to enable the crystal blank to be plated or loaded after mounting so that it may be adjusted to an exact operating frequency by deposition of additional metal over the base plated electrode without removing it from its mounting, or have its mounting afiect this frequency adjustment afterwards.

Another object of this invention is to enable the handling of quartz blanks lapped to as thin as .001" so that they may be rigidly clamped and mounted into the holder without breakage during the operation.

It is another object of this invention to provide rigid mounting means of sufficiently small proportions, and of such materials that it may be readil sealed in a hermetically sealed holder, so that no deleterious effects will be had on the unit from the effects of the support means materials.

In the prior art the mounting of high frequency crystals either fundamental or harmonic type, was always associated with a large percentage of breakage in the quartz blanks. This tiguous electrodes. It has been'found that with these contiguous electrodes better harmonic performance is obtained, since the series capacity which is usually associated withpressure type mountings where an airgap is employed, introvl5 was'particularly true of crystals WhlCh used con- 2 quency response with less damping on the crystals oscillation.

Various methods have been employed in the prior art to mount such plated crystals including that of small metal clips which make contact and support the crystal, small wire loops in which the crystal edge is forced between the adjacent turns of a spring type loop, and sleeve type supports in which the crystal is slid between the open section.ofasmall slotted tube.

All of these methods have the disadvantage of stressing the crystals beyond its elastic limits and causing fracture. These stresses may cause twisting in the quartz blank, bending at the edges, chipping, etc., resulting in'a defective unit. Such stressing may not necessarily take place during the mounting operation, but subsequent to it, by a slight distortion in the external pin connection when the crystal unit is plugged into a socket; during the sealing operation, or during extreme changes in temperature over which most crystal units are required to operate satisfactorily. All of this is particularly true on crystal blank-s less than .010 in thickness.

This invention overcomes all of these difficulties in a unique manner by providing, first of all,

two flat surfaces between which the crystal blank is clamped on its periphery. Such peripheral clamping means may be either round, square or rectangular- The ceramic or clamping rings are first lapped on the side that contacts the-crystal and then a coating of silver is fired to this flat lapped surface. Connection to this plated ring isalso fired onto the ceramic on the inner circle and on the outer surface bringing the con.- tact to the outside unlapped. side of the ceramic ring. The plated crystal is then placed between these two annular supports, which are then placed between two small spring clamps which hold the entire assembly together and make contact .to the plated crystal electrodesthrough the silver plating that has been fired. onto the ceramic. Small depressions or cavities are formed on the outside of the rings to accommodate the spring clamps. This centers the entire assembly and provides a rigid support for the crystal as well as its associated ceramic rings and contact means. If the crystal electrodes are plated over. the entire area of the blank, it is desirable to have the ceramic ring silvered around the entire periphery. If, however, only a smallarea of the crystal is used for the crystal electrode it isv only necessary to silver the lapped ceramic ring directly over the pigtail connection to the central crystalelectrode. This is a particular advantage 3 on high frequency crystals used with high order of harmonics where it is desirable to reduce the capacity of the crystal holder and any extraneous capacity outside the activated electrode area to a minimum.

Various forms of plating can be used on the crystal electrodes themselves, either evaporated, sputtered of fired spots of gold, silver, or aluminum. It is desirable from an electrolysis. standpoint and from a contact potential standpoint to provide the same metals for the plated electrodes on the crystal as is used on the ceramic rings, sinces these two metals contact and if they are dissimilar, contact potentials may be set upwhich might cause corrosion or disintegration at the point of contact of either one of the metals. Since silver or gold is easily fired to the ceramic, silver or gold electrodes on the crystal provides an excellent combination.

Once the crystal blank is mounted, the entire holder assembly may be inserted into a metal evaporating plater and the unit may then be loaded with evaporated metal to the desired frequency by having the crystal oscillate during the operation. This is a particular advantage on thin crystals because the crystal blanks need only be handled during the initial mounting operation, and the incidence of fracture due to repeated handling is greatly reduced,

Other means of holding the two annular rings may be employed such as flat leaf springs. However, it is a feature of this invention to enable the expansion of the springs by means of a simple expansion tool for the insertion of the complete assembly into the spring clips.

Another feature of the invention is the peripheral clamping of the blanks. This has a tendency to eliminate spurious responses in the crystal, and consequently small activity dips throughout a temperature range. It provides a definite electromechanical termination for the edge or edges of the crystal blank.

Further details of this invention will be apparent to those skilled in the art to which it relates from the following specification, claims and drawing, in which briefly Figure 1 is a perspective view of the thin quartz crystal and mounting with the housing removed;

Figure 2 is a vertical sectional view through the quartz crystal mounting and housing taken along the line 2-2 of Figure 3;

Figure 3 is a view taken along the line 3-3 of Fig re Figure 4 is a side view of one of the ceramic rings embracing the'quartz crystal;

Figure 5 is a sectional view along the line 5-5 of Figure 4;

Figure 6 is another side View of the ceramic ring showing the side opposite to that shown in Figure 4;

Figure 7 is a modified form of ceramic ring;

Figure 8 is a sectional view of the ceramic ring taken along the line 8-8 of Figure 'I Figure 9 is a sectional view taken along the line 9-9 of Figure '7;

Figure 10 is a view showing the other side of the ceramic ring from that shown in Figure 7;

Figure 10a is a view similar to Fig. 10 with only one coating 21 of silver or gold thereon;

Figure 11 is a view in fragmentary perspective of an embodiment of this invention housed in a glass tube, and

Figure 12 is a sectional View of the base of the tube shown in Fig. 11.

Referring to the drawings in detail, the thin quartz crystal I0 is shown embraced by a pair of ceramic rings I I that are disposed so as to clamp the circumferential portions of the crystal I0 therebetween by the spring action of the resilient wire supports I2. Each of the spring clamps I2 is provided with projections I3 fitting into small cavities formed in the ceramic rings II so that the assembled rings and quartz crystal are supported by the springs I2 in suitably rugged fashion to withstand handling such: as the unit will receive in the course of ordinary use. The mid portions I4 of the members I2 are bent into a loop to substantially encircle the upper ends of the contact pins I5 that are suported on the base I6 of the housing by glass insulation beads I1. These mid portions I4 may be soldered or welded to the ends of the pins I5 and the glass beads I! are also firmly joined both to the pins I5 and to the base IS. The whole crystal and mounting assembly is supported on the base IG and enclosed in the housing IBa that fits into the groove I8b formed in the base and may be soldered therein.

The piezoelectric crystal blank I0 may be employed for frequency stabilization, and generation and absorption of high or ultra-high frequency electrical oscillations, This piezo-electric crystal blank consists of a crystal element that may have a thickness as small as A of an inch and the major faces thereof may be cut substantially parallel to the X-axis of the mother crystal and at an angle between +20 and +40 to the optic axis. An angle of 30' or 35 with respect to the optic axis has been found satisfactory. However, other types of piezoelectric crystal cuts may be employed and these cuts may be either parallel to or at an angle with respect to the X-axis or the optic axis. Furthermore, the crystal may be made of slightly convex contour and the surfaces of the major faces of the crystal blank should be free from even minute depressions.

Suitable electrodes I8 and I9 are provided to each major face of the quartz crystal II) by processes such as plating, sputtering, evaporation in vacuum and the like. The lead of electrode I8 is connected by a solder or silver connection 20a to a suitable metallic coating 20 extending around one of the ceramic rings H in contact with the projection I3 formed on one of the spring clamps I2 as shown in Figures 1, 2 and 3 and the other electrode I9 is connected to a similar metallic coating 2 I on the other ceramic ring I I contacting a projection I3 on the other spring clamp I2. As a result the contact pins I5 are connected, one to the quartz crystal electrode I8 through the metallic coating 20 on a portion of one of the ceramic rings I I and the other electrode I9 is connected to the other pin I5 through the metallic coating 2I on a portion of the other ceramic ring II. The electrodes I8 and I9 are each preferably of an area that is small compared to the area of each of the major faces of the crystal blank I0. For example in a crystal blank having a diameter about inch the diameter of the electrode may be about A; inch. Furthermore, the electrodes I8 and I 9 may be of the same diameters or they may be of different diameters and the crystal blank may be of circular or rectangular shape or any other convenient shape. The electrodes may likewise be of circular, rectangular or other convenient shapes. Each of the electrodes [8 and I9 are provided with a pig-tail connection, the pig-tail connection of the electrode I8 being connected through the globule 20a of solder or silver to the coating 20 and one of the pins I2, and the electrode I9 being connected to a suitable f pig-tail connection to the coating 2 I, this coating 2I being connected also through a globule of solder or silver to th pig-tail associated with theelectrode I9.

"Details of construction of the ceramic rings II are shown in Figures 4 to inclusive, Figures 7 to 10 inclusive showing a modified form. In Figure 4 is shown a side view of a ring H such as shown in Figure 1 and this ring may be made of various insulation materials such as synthetic porcelain, fused quartz; glass, as Well as synthetic resins. The rings I I instead of being made of the materials set forth above may be cut from quartz crystal material the same as-the piezoelectric crystal blank and in this case these rings may be out from blanks that are cut atsubstantially the same angle or angles at which the piezoelectric crystal blank is cut so as to have a linear coefficient of expansion the same as the piezoelectric crystal blank and thereby prevent any slippage between the rings II and the piezoelectric crystal blank I0 through temperature cycling referred to as hysteresis effect. Hysteresis effect may be explained as follows. If the frequency of the piezoelectric crystal blank is measured at room temperature and the temperature of the crystal blank is then raised or lowered and then brought back to the initial temperature and the frequencymeasured after this temperature cycle, it is frequently found that the second frequency is no longer exactly the same as the initial frequency and that the initial frequency can be restored by jarring the piezoelectric crystal blank or by taking it through a temperature cycle in the opposite direction.

One side of this ring I I is provided with a metallic coating 20 extending at least partially around the ring so as to contact one of the electrodes Is for example and this coating also extends into the cavity 22 receiving the projection I3 of the sprin clamp I2 that is employed for supporting the crystal assembly and connecting one of the crystal electrodes to one of the pins I5. The other side of the insulation ring II is provided with 'acavity 23 for receiving one of the projections I 3 of the other spring clamp I2. However, no metallic coating surrounds this cavity inasmuch as no connection is to be made to the springclamp I2 from this side of this insulation ring. The surface of the ring I 'I next to the quartz crystal I0 is provided with a metallic coating 24 that consists of silver fired to the surface of the ring and this silvered surface engages the opposite surface of the quartz crystal. This silvered surface of each of the rings I'I may be used to cement these rings directly to the opposite surfaces of the crystal blank III and for this purpose cements of various types including a low temperature fired silver bondin cement such as now on the market may be employed. Both of the rings II are made in this manner and each of these rings is provided with a metallic'coating such as coating 22, the coating of one ring making contact with one of the supporting clamps I2 and the coating on the other ringmaking'contact with the other supporting spring clamp I2. In Figures 8, 9 and 10 is illustrated a ring 25 similar to the ring II except that the ring 25 does not engage the quartz crystal throughout its circumference inasmuch as the ring 25 has two cut-away I portions 26. -As a result only the silvered surfaces 2'! engage the corresponding surfaces of the quartz crystal. These silvered surfaces 21 may be employed to cement the ring 25 to the opposite surfaces of the crystal blank III and furthermore,

if desired, only oneof the projecting areas of the ring 25 need be provided with a coating 21 as shown in Fig. 10a. These rings 25 are particularly adapted for use with high frequency crystals employing high order harmonics where it is desirable to reduce the capacity of the crystal holder. The rings 25 are also provided with

cavities

22 and 23 for receiving ends I3 of the spring clamps and one of these cavities of each ring 25 is also provided with a metallic coating for the purpose of connecting the associated spring clamp I2 to an electrode of the quartz crystal.

InFigs. 11 and 12 is illustrated an embodiment of this invention in which the piezoelectric crystal blank and associated members are positioned in a glass housing 28 which may be similar to glass housings providedto vacuum tubes. This glass housing is provided with a base 29 sealed to the contact pins I5 that project out of the base and are adapted to be used for connecting the piezo electric crystal blank III to an electric circuit. These pins l5 are sealed to the glass base 29 in air-tight fashion and for this purpose various glass to metal seals may be employed. The base 29 is sealed to the housing 28 around the circumference of the base and this operation is accomplished by suitable glass working technique. The interior of the glass housing 28 may be evacuated if desired so that the piezoelectric crystal blank I0 may be operated substantially in a vacuum or an atmosphere of inert gas such as neon. nitrogen, helium and the like, may be provided inside of the housing.

While I have described this invention in detail with respect to a preferred embodiment, it is of course apparent that modifications therein may be made without departing from the spirit and scope of this invention and therefore I do not desire to limit this invention to the exact details shown and described except as defined by the following claims.

What is claimed is: I

1. A piezoelectric crystal apparatus assembly for extremely thin piezoelectric crystal blanks comprising a piezoelectric crystal blank having a thickness between 0.01 inch and 0.001 inch, means for reinforcing said crystal blank without substantially impairing the operation thereof and means for'connectin said crystal blank to an electrical circuit.

2. A piezoelectric crystal apparatus assembly for extremely thin piezoelectric crystal blanks comprising a piezoelectric crystal blank having a thickness between 0.01 inch and 0.001 inch, means cemented to said crystal blank for reinforcing said crystal blank without substantially impairing the operationthereof and means for connecting said crystal blank to an electrical circuit.

3. A piezoelectric crystal apparatus assembly for extremely thin piezoelectric crystal blanks comprising a substantially circular piezoelectric crystal blank having a thickness between 0.01 inch and 0.001 inch, ring-shaped means for reinforcing said crystal blank without substantially impairing the operation thereof and means for connecting said crystal blank to an electrical circuit.

4. A piezoelectric crystal apparatus assembly for extremely thin piezoelectric crystal blanks comprising a piezoelectric crystal blank having a thickness between 0.01 inch and 0.001 inch, means for clamping said crystal blank for reinforcing said crystal blank without substantially impairing the operation thereofv and means for connectin saidscrystal blank .to.:an;electricaltcira wit:

5. A: piezoelectric. crystal" apparatus assembly: for extremely thin piezoelectric crystala blanks comprising a piezoelectric crystal-blank-having a: thickness between: 0.01 inch and.0.001 inch,- means engaging peripheral portions of. said crystal blankifor; reinforcing said crystal blank without substantially impairing theoperation thereof and meansvfor. connecting said crystal blank to an electrical :circuit.

6. A piezoelectric crystal apparatus assembly for. extremely thin: piezoelectric crystal blanks comprising; a piezoelectric. crystal blank. havingv a. thickness between- 0.01 inch and 0.001 inch, ring shapedtl elements engaging peripheral: portions of said' crystal blank for. reinforcing; said crystal blank without substantially impairing the: operation thereof and means for: connecting saidicrystalblank to. an electrical circuit.

'7. A: piezoelectric crystal apparatus assembly for extremely thin piezoelectriccrystalblanks as set; forth inclaim. lwherein'the means for reinforcing thecrystal blank-comprises .ceramic elementsengagingonly the peripheral. portions of saidcrystal :blankmajorfaces, the surfaces of said ceramic elements. .engaging;said major faces being lapped;

8; Piezoelectriccrystalapparatus comprising a thinpiezoelectric crystal .having a thickness be-. tween 0.01 inch and 0.001 inch, apair of ceramic rings; each 'of saidrrings having onesurface thereof lapped to a high degree of flatness, means for cementing the lapped, surfaces;ofeach of said rings .to'peripheral portions of the majorfaces of. said crystalblank forreinforcingsaid crystal blank, said ceramic rings each'havingsmall holes in substantially; diametrically opposed portions thereof; andspringmeans positioned in sa-idsmall holes for. supporting said crystal blank-and .said rings in assembled relation.

9. Piezoelectric crystal apparatusv comprising a thin piezoelectric crystal of circular configuration having a thickness'between 0.01. inch'and 0.001 inch, a pair-of ceramic'rings, each ofesaid rings having one surface-thereof lappedtoahigh degree of-flatness, means for cementingthe lapped surfaces of. each of said rings'tov peripheral portionsiof the maj or faces of said crystal blank. for reinforcing said crystal blank, said-ceramicrings each having small holes in substantially. diametrically opposed portionsithereof; andspring'means positioned in said-smallholes for; supporting said crystal blank and said; ringsin assembledrela tion';

10: Piezoelectric crystal apparatus comprisinga thin: piezoelectric, crystal having athickness be tween 0.01 inch and :0.001 inch, .a pair 10f .lceramic rings, each of said rings having one surface there-. of lapped to a high degree of'fiatness, means. for cementing the lapped surfaces of" each: of said rings to peripheral portions of themajorsfaces of said crystal 'blank' for. reinforcing said crystal blank, said-ceramic rings each having smallholes in substantially diametrically opposed: portions thereof, resilientwire elements having the ends thereof lodged in-said small holes, and; means attached. to said wire elements for supportingsaid crystal blank andsaidmingsin assembled relation.

11. Piezoelectric crystal apparatuscomprisingia thinpiezoelectriccrystal, a pair of .ceramicrings, each of said ringshaving one; surface thereof lapped to a-highdegree of flatness,-means:for cc"- menting;the.-lapped:surfacespreach of saidrrings toperipheral portionspf the-.majorfacespf said crystal blank for reinforcing saidlcrystal blank, said ceramic. rings: each having; smallv holes, in substantially diametrically opposed. portions thereof, and springmeanspositioned. in said small holes for supporting-said crystal blank and. said ringsin assembled relations.

12. Piezoelectric crystal apparatuscomprising a. thin. piezoelectric crystal, a.- pair. of ceramic rings; eachiof said rings having one surfacethere of-lapped-to. a highdegree of flatness, meansfor cementing the-lapped. surfacesof each of said rings ,to peripheral. portions-of. the major. faces of said crystal blank. forreinforcing, said crystal blank, andmeans for supportingsaid crystal blank and-said ringsinassembledrelations.

1 13;- Piezoelectric crystal apparatuscomprisinga thin piezoelectric crystal, a pair of :ceramic :rings, each: of said rings having; one surface thereof lapped to. a high degree-ofxflatness; meansrfor cementingthealapped.surfaces of eachof said rings .to peripheral portions of the major faces of said. crystal blankfor: reinforcing. said' crystal blank, said ceramic ringseach havingsmall holes in substantially diametrically; opposedportions thereof, resilient wireelements having the ends thereof positioned in saidsmall. holes; and means attachedto said wireelements for supportingsaid crystal. blank and saidrings-in assembled rela tions.

14. A. piezoelectric crystal apparatus assembly for extremely thinpiezoelectric crystal blanks comprisinga. piezoelectric crystal .blank having ;a thickness between 0.01 inch and:0.001 inch, a pair of electrodes for said crystal. blank cone tiguousto-the centralportions of the major faces ofsaidcrystaLblank, an .element'having substan+ tiallyf greater /meehanical.strength than. said piezoelectriccrystal blank cemented toperipheral portions ofloneecfzsaidmajorfaces .of said crystal blank for strengthening said crystal blankand connectionssto said-electrodesfor connectingsaid crystal .blankto a'desired circuit:

15. A piezoelectric crystal apparatus-assembly forextremelythin piezoelectric. crystal blanks comprising; a .piezoelectric crystal. blank having a thicknessbetween 0.01-. inches and.0.001 inches, a .pair of electrodes.- for: said .crystal blankcon tiguous to thecentral portionsof the major faces ofsaid-.crystal blank, elements having v substan-- tiallygreater. mechanical strength than said piezoelectric crystal blanksengagingrperipheral-portions of: said. major faces. of said: crystal; blank for strengthening said crystal blank and having said crystal-blank therebetween, resilient members for engaging said. elements.' and. pressing said elementsragainst said crystalblank and connections between. said resilient members: and .selectedrones of said electrodesfor connectingsaid-crystal.blank toa'desired circuit.

16. A piezoelectriccrystalapparatus assembly for extremely thin; piezoelectric crystal! blanks comprising, a piezoelectric crystal: blank having at thickness-between 0:01-inch and 0.0012inch'; a.- pairrof. electrodes for. said: crystal blankcon tinguous. to: the, central; portions; of the major facesof saidprystal blank; ring,-shaped;elements having substantially: greater mechanical strength than saidzpiezoelectric crystal. blank, said ring shaped elements being cemented: one. on each side of -.saidt.cr:ystal-blank:forengaging peripheral portions-of;saidmajor-faces of said crystal blank forrstrengthening said -.crystal blank 1 and holding said.crysta'1 blank therebetweem resilient meme bersforengaging saidfelementsand pressings cas nos L.. 9 elements against/said crystal blank and connections between said resilient members and'selected ones of said electrodes for connecting said crystal blank to a desired circuit.

.17. A piezoelectric crystal apparatus assembly for extremely thin piezoelectric crystal blanks comprising a piezoelectric crystal blank having a thicknesslbetween 0.01 inch and 0.001 inch, a pair of electrodes for said crystalblank contiguous to the central portions of the major faces ofsaid crystal blank, elements having substantially greater mechanical strength than said piezoelectric crystal blank cemented to peripheral portions of-said major faces of said crystal blank for strengthening said, crystal blank and holding said crystal blank therebetween, resilient members for engaging said elements and pressing said elements against said crystal blank and connections between said resilient members and-selected ones of said'electrodes for connecting said crystal blank to a desired circuit.

18. A piezoelectric crystal apparatus assembly for extremely thin piezoelectric crystal blanks comprising a piezoelectric crystal blank havin a thickness between 0.01 inch and 0.001 inch, a pair of electrodes .for said crystal blank contiguous to the central portions of the major faces of said crystal blank, ring-shaped elements having substantially greater mechanical strength than said piezoelectric crystal blank engaging peripheral portions of said major faces of said crystal blank for strengthening said crystal blank and holding said crystal blank therebetween, resilient members for engagin said elements and pressing said elements against said crystal blank and connections between said resilient mem bers and selected ones of said electrodes for connecting said crystal blank to a desired circuit.

19. A piezoelectric crystal apparatus assembly for extremely thin piezoelectric crystal blanks comprising a piezoelectric crystal blank having a thickness between 0.01 inch and 0.001 inch, means having substantially the same coefficient of expansion as said crystal blank for reinforcing said crystal blank without substantially impairing the operation thereof and means for connecting said crystal blank to an electrical circuit.

20. A piezoelectric crystal apparatus assembly for extremely thin piezoelectric crystal blanks comprising a piezoelectric crystal blank having a thickness between 0.01 inch and 0.001 inch, means havin substantially the same coefficient of expansion as said crystal blank cemented to said crystal blank for reinforcing said crystal blank without substantially impairing the operation thereof and means for connecting said crystal blank to an electrical circuit.

21. A piezoelectric crystal apparatus assembly for extremely thin piezoelectric crystal blanks comprising a substantially circular piezoelectric crystal blank having a thickness between 0.01 inch and 0.001 inch, ring-shaped means having substantially the same coefficient of expansion as said crystal blank for reinforcing said crystal blank without substantially impairing the operation thereof and means for connecting said crystal blank to an electrical circuit.

22. A piezoelectric crystal apparatus assembly for extremely thin piezoelectric crystal blanks comprising a piezoelectric crystal blank having thickness between 0.01 inch and 0.001 inch, ringshaped insulation means having substantially the same coefficient of expansion as said crystal blank for reinforcin said crystal blank without substantially impairing the operation thereof and 10 means for connecting'said crystal blank to an electrical circuit.

23. A piezoelectric crystal apparatus assembly for extremely thin piezoelectric crystal blanks comprising a piezoelectric crystal blank having a thickness between 0.01 'inch and 0.001 inch, means having substantially the same coefficient of expansion as saidcrystal blank engaging peripheral portions of said crystal blank for reinforcing said. crystal blank without substantially impairing the operation thereof and means for connecting said-crystal blank to an electrical circuit. I

24. A piezoelectric crystal apparatus assembly for extremely thin piezoelectric crystal blanks comprising. a piezoelectric crystal blank having a low temperature coefiicient of expansion and having a thickness between 0.01 inch and 0.001 inch, said crystal blank being cutat an angle between ,20 and 40 degrees with respect tothe crystalline optic axis, means having substantially the same coefficient:of expansion as said crystal blank for reinforcing said crystal blank without substantially impairing the operation thereof and means for connecting said crystal blank to an electrical circuit. a l

25. A piezoelectric crystal apparatus assembly for extremely thin piezoelectric crystal blanks comprising a piezoelectric crystal blank having a low temperature coefficient of expansion and having a thickness between 0.01 inch and 0.001 inch, said crystal blank being cut at an angle substantially 35 with respect to the crystalline optic axis, means having substantially the same coeflicient of expansion as said crystal blank for reinforcing said crystal blank without substantially impairing the operation thereof and means for connecting said crystal blank to an electrical circuit.

26. Piezoelectric crystal apparatus comprising a thin piezoelectric crystal blank having a thickness between 0.01 inch and 0.001 inch, a pair of quartz rings, each of said rings having one surface thereof lapped to a high degree of flatness, means for cementing the lapped surfaces of each of said rings to peripheral portions of the major faces of said crystal blank for reinforcing said crystal blank, and means for supporting said crystal blank and said rings in assembled relation.

27. Piezoelectric crystal apparatus comprising a thin piezoelectric crystal blank of circular configuration having :a thickness between 0.01 inch and 0.001 inch, a pair of quartz rings, each of said rings having one surface thereof lapped to a high degree of flatness, means for cementing the lapped surfaces of each of said rings to Deripheral portions of the major faces of said crystal blank for reinforcing said crystal blank, said quartz rings each having smal1 holes in substantially diametrically opposed portions thereof, and spring means positioned in said small holes for supporting said crystal blank and said rings in assembled relation.

28. Piezoelectric crystal apparatus comprising a thin piezoelectric crystal blank having a thickness between 0.01 inch and 0.001 inch, 9. pair of quartz rings, each of said rings having one surface thereof lapped to a high degree of flatness, means for cementing the lapped surfaces of each of said rings to peripheral portions of the major faces of said crystal blank for reinforcing said. crystal blank, said quartz rings each having small holes in substantially diametrically opposed portions thereof, resilient wire elements having the 1 1:1 ends'thereof lodgedimsaid small-holes, and means attached to the said wire elementsfior supporting said :crystal blank *and "said *rmgs'in assembled relation.

29. Piezoelectric crystal "apparatus comprising a"thin"piezoelectricrcrystal blarikra pairof rings having substantially the same-coem'cient o'f expans'ion as said"crystafblankfieach o'fsaid rings having one surface theredflappeiitoa high degree of 'flatnesa'means for'cementingthe lapped surfaces'of each of said*ringstojiperipheral portions ofthe -majori aces 'of'said crystal blank for reinforcing said crystal blank saici quartz'rings each "having small holes in substantiallyniametrically "opposed portions thereof, "and sprin means positioned in said -sm'all 'holes for supporting said crystal blank -an'dsai'd rings in assembled relation.

30. Piezoelectric -crysta1-apparatus comprising *athin piezoelectric crystaI bIank a-pair ofrings having substantially the same coem'cient of expansionassaid crystalblanheach of said rings having one surface thereof lapped" to -a high "degreeof fiatness,"means for cementing the lapped surfaces of each ofsaidringsto peripheral portions of the major faces of said *crystal'blank for reinforcing said crystal blankpand means forsupporting "said "crystal blank and said =rings 'in assembled. relation.

31. Piezoelectric -crystal apparatus comprising a thin piezoelectric crystal blank having a thicknessbetween 0.01 inch and "0.001 inh, a 'pair of quartz rings, each of said wings "having one sur- Iace thereof lapped to a hi'g'hdegree of "flatness, means -for= cementing the iappflsuriza'ccesofleach of said-rings to "peripheraiportions of the major faces "6f said "crystal blank for "reinforcing said crystal blankysaid quartz rings'each having small holes in substantially diametrically opposedportionsthereof,"and'springmeans' positioned in said small holes for. supporting'said crystal blank and saidrings in' assembledrelation.

"32. A piezoelectric crystal mounting for 'extremely thin piezoelectric 'crystal blanks comprisinga piezoelectric'crystal-blank having a low temperature coefficient of expansion 'an'd having a thiknessbetweenQOl in'ch'anii 01001 inch-said crystal blank being cut at-an angle of 30 with respect' to the "crystalline optic axis, means having substantially" the same 'coefiicient of expansion'as saidcrystalblank for reinforcing said crystal "blank-without substantially impairing the operation thereof and means for connecting said 'crystalbianlctoan-electrical circuit.

JOHNM. W'OIFSKILL.

" REFERENCES CITED The iollowing references are of record-in the file of this patent:

UNITED STATES PATENTS Number Name Date 1",9'57',299 'Staubel -JMay' 1, 1 934 2,224,891 'Wi'ight Dec. 1'7, 1940 2,249,933 Bechmann July 22, 1941 221343359 Hight Feb. 29, .1944 2,353,089 Shapiro July 4, 1944 2,362,056 Drews et al. Nov.'7, 1944 2,392,429 Sykes Jan. "8, 1946