US2482730A

US2482730A - Piezoelectric crystal unit

Info

Publication number: US2482730A
Application number: US756479A
Authority: US
Inventors: Floyd W Flynn
Original assignee: PREMIER CRYSTAL LAB Inc
Current assignee: PREMIER CRYSTAL LAB Inc; PREMIER CRYSTAL LABORATORIES Inc
Priority date: 1947-06-23
Filing date: 1947-06-23
Publication date: 1949-09-20
Anticipated expiration: 1966-09-20

Description

Sept. 20, 1949. F. w. FLYNN PIEZOELECTRIC CRYSTAL 'UNIT Filed June 25, 1947 flow 14 FLY/v/v WW elk tom Patented Sept. 20, 1949 iJNITED .S TATES EATENT ()F-F [CE 'PIEZOELECTRIC CRYSTAL UNIT Floyd W. Flynn, Bellerose, N. Y., assignor to Premier Crystal Laboratories, Incorporated, New

York, N.

This invention relates to piezoelectric crystal devices, and more particularly to quartz crystal assemblies of the thickness-shear type.

A main object -of the invention is to provide a novel and improved crystal assembly which is relatively simple in construction, stable in operation and protected against the eifects of shock and vibration.

A further object of the invention is to provide an improved crystal assembly which is extremely rugged in construction, has good starting characteristics, and which is subject to a minimum degree of mechanical damping, whereby the amplitude of vibration of the crystal at resonance will be satisfactory over a wide range of operating conditions of the apparatus in which the assembly is employed and the maximum electrical output of the crystal will be available for its required functions.

A still further object of the invention is to provide improved crystal assembly employing a thickness-shear crystal which is supported by substantially rigid gripping means, but wherein the pressure exerted by the gripping means does not introduce any substantial mechanical damping of the crystal vibrations and wherein the crystal vibrates in thickness shear substantially as a free body but is at the same time securel; supported and cushioned against shock and disturbances such as are experienced in moving vehicles or in marine equipment.

A still further object of the invention is to provide a thickness-shear crystal assembly which involves only a few simple parts which are easy to manufacture and assemble.

A still further object of the invention is to provide an improved piezoelectric oscillator plate of the thickness-shear type having plated electrodes which is easy to mount, and which is not subject to frequency deviations as a result of variations in clamping pressure at the points at which it is secured to its support.

Further objects and advantages of the invention will become apparent from the following cletion claims, and from the accompanying dram. rs, wherein:

Fi ure 1 is a vertical cross-sectional view taken thro h a piezoelectric crystal assembly construc in accordance with the present invention view being taken on line !--i of Figure 2.

- Figure 2 is a horizontal cross-sectional. view taken on line 2-2 of Figure 1.

Figure 3 is an enlarged cross-sectional detail view taken on line 3-3 of Figure 1.

Figure 4 is a detail view-of the bottom support ing member of the crystal of Figure 1, taken on line li e of Figure 3.

Figure 5 is, a perspective view of an oscillator plate employed in the assembly of Figure 1, illusrating the appearance of the top edge thereof.

Figure .6 is a different perspective view of the oscillator plate of Figure 5, illustrating the appearance of the bottom edge thereof.

Figure 7 is an enlarged fragmentary detail cross-sectional view taken on the line 1-1 of Figure 5.

Figure 8 is an enlarged detail cross-sectional view taken on line -8 of Figure 1.

Referring to the drawings, ll designates a'circular base member, preferably of metal, and :secured concentrically thereto is a fiat metal ring formed at its peripheral edge with a pair of diametrically opposed upstanding apertured lugs 13, L3. Secured to and extending through base i i isa sleeve Mi and extending through said sleeve sealed therein by suitable insulatingmaterial, such as glass, is a contact prong l5 which depends below the base H. The top end of prong 1 5 extends slightly above the top edge of sleeve [4, sleeve being located within the ring l2. Also secured to base I! and depending therefrom are a plurality ofadditional prongs l5 which are electrically bonded to said base.

Secured to ring !2 are diametrically opposed vertical "hexagon-a]. post members H, H and seto the top ends of said post members is a flat ring H3, similar to and coaxial with bottom ring l2 and formed with diametrically opposed apcrtured depending lugs I9, is located in the same vertical plane as the upstanding lugs l3, l3

of the bottom ring [2. Supported in said plane by four coiled springs secured to the respective apertured lugs of the top and bottom rings is 2 is a rectangular frame member 2|, said member being formed at its corners with reduced apertured triangular lugs 22 to which the ends of the respective coil springs are secured, the springs'being thereby placed in tension.

The top arm of the frame member 2! is enlarged in thickness at its mid-portion, as shown at 23, and threaded through said enlarged midportion is a vertical set screw 24 formed with a conic 1 point at its bottom end. Set screw 24 is lwith the rings 83 and i2. A lock nut 25 ..readed on the upper portion of set screw 24, 'l by tightening same the set screw may be ri idly locked with respect to the frame member 22!.

The'bottom arm of the frame member 2i is enlarged in thickness at its mid-portion, as shown at 26, and is formed with an aperture 21 in which is tightly secured a stud 28 of insulating material. Stud 28 is formed with a flange 29 which overlies the upper surface of the bottom arm of the frame member, and with an upstanding rectangular central lu 30. Stud 23 is coaxial with the rings l8 and I2.

Supported on the flange 29 is a relatively stiff bar member 3| formed with a central rectangular aperture 32 which fits over the lug 30 and is nonrotatively engaged therewith. symmetrically spaced on each side of the aperture 32 the bar member has secured thereto

upstanding pin members

33, 33, the top ends of said pin members being conically pointed. The plane defined by the set screw 24 and the

pin members

33, 33 is at right angles to the plane of frame member 2| and passes through the vertical axis of the rings l8 and |2.

Connected to one of the pin members 33 is one end of a conductor wire 34, the other end of which is connected to the top end of the prong I5.

Clampingly engaged at its respective top and bottom edges by the respective set Screw 24 and the

pointed pin members

33, 33 is an oscillator plate 35, said oscillator plate being engaged by said set screw and pin members at its median plane parallel to its major faces, so that said major faces are transverse to the plane of frame member 2 l. The oscillator plate 35 is of the thickness-shear type, so that its median plane is a nodal plane and the points at which it is thus clamped are not driven to any appreciable degree during oscillation of the plate, whereby mechanical damping due to the restrictive effect of the clamping means is minimized.

The oscillator plate 35 is provided on one major face thereof with a plated electrode 35. Continuous with said plated electrode 36 is a small central plated area 31 on the top edge of the plate. Said top edge is formed at its mid-point and in the median plane of the plate with a conical recess 38, which is included in the small plated area 31. Deposited in said recess over the plating is a small quantity of soft silver solder 39. When the plate is clamped, the pointed conical tip of set screw 24 engages and deforms the solder spot 39 and causes a certain amount of flow of said solder spot around the screw tip in the plated recess 33, said flow insuring a good electrical contact at said screw tip, and the recess 38 insuring that the screw tip is centered in the median plane of the oscillator plate.

The opposite major face of the oscillator plate is provided with a plated electrode 43. Continuous with said plated electrode 48 are a pair of small plated areas 4|, 4| on the bottom edge of the plate, said areas being symmetrically located with respect to the vertical axis of the plate and being spaced apart substantially the same distance as the distance between the pin members 33. The bottom edge of the plate is recessed at the plated areas 4|, 4| in the median plane of the plate in the same manner as illustrated in Figure '7 for the top edge of the plate, the recesses being spaced apart by exactly the same distance as that which separates the pin members 33. 33 and being symmetrically located with respect to the vertical axis of the plate. Over the plating in each recess is deposited a spot 42 of soft silver solder similar to spot 33. The pointed tips of

pin members

33, 33 are adapted to engage the

solder spots

42, 42 when the oscillator plate is clamped and to provide the same type of electrical contact and centering effect described 4 above in connection with the contact made by the point of set screw 24 with the top solder spot 39.

The degree of clamping pressure applied to the crystal plate is not critical and may be regulated by set screw 24. The clamping pressure is cushioned somewhat by flexure of the bar member 3| under the force transmitted thereto by the plate 35 at the

pin members

33, 33.

The springs 20 function as shock absorbing supports for the frame member 2| so that the frame member and the oscillator plate 35 clamped therein are mechanically insulated against shock and vibration. The

solder spots

39 and 42, 42 insure that electrical contact with the respective crystal electrodes will be constantly maintained at the set screw 24 and the

pin members

33, 33 respectively. Electrode 40 is connected through

pin members

33, 33, bar 3| and conductor wire 34 to the prong l5. Electrode 36 is connected through set screw 24, frame member 2|, springs 20, ring I 2 and base member to the other prongs 3.

A suitable cylindrical housing 43 is secured to the base member H and encloses the oscillator plate and its supporting means to thereby protect the plate against the entry of dust or moisture.

While a specific embodiment of a piezoelectric crystal assembly for crystals of the thicknessshear type has been disclosed in the foregoing description, it will be understood that various modifications within the spirit of the invention may occur to those skilled in the art. Therefore it is intended that no limitations be placed on the invention except as defined by the scope of the appended claims.

What is claimed is:

l. A piezoelectric crystal assembly comprising a piezoelectric oscillator plate, a support, a frame member resiliently secured to said support, inwardly projecting clamping means carried by said frame member and engaging opposite edges of the oscillator plate in the median plane of said plate parallel to the major faces thereof, said median plane being transverse to the plane of the frame member, and deformable material carried on the plate edges at the points of engagement of said clamping means therewith.

2. A piezoelectric crystal assembly comprising a piezoelectric oscillator plate, a support, a frame member resiliently secured to said support, inwardly projecting clamping means carried by said frame member and engaging the mid-point of one edge of the plate and two points at the opposite edge of said plate symmetrically located with respect to the mid-point thereof, said points of engagement lying in the median plane of the plate parallel to the major faces thereof, said median plane being transverse to the plane of the frame member, the plate edges being recessed at said points of engagement, and deformable material contained in said recesses.

3. A piezoelectric crystal assembly comprising a piezoelectric oscillator plate, a support, a rectangular frame member, resilient means connecting each corner of said rectangular frame member to said support and suspending said frame member in a vertical position, an inwardly projecting vertica1 clamping member carried at the mid-portion of the top arm of said frame member and engaging the mid-point of the top edge of the oscillator plate, and a horizontal bar member supported on the mid-portion of the bottom arm of the frame member and extending transversely thereof, said bar member carrying two upwardly projecting clamping members spaced symmetrically with respect to said bottom arm and engaging the bottom edge of the oscillator plate at points spaced symmetrically on each side of the midpoint of said bottom edge, the points of engagement of the clamping meinbers lying in the median plane of the oscillator plate parallel to the major faces thereof.

4. The structure of claim 3, and wherein the crystal plate edges are formed with recesses at said points of engagement receiving said clamping members.

5. The structure of claim 3, and wherein the crystal plate edges carry deposits of deformable material at points of engagement.

6. The structure of claim 3, and wherein the crystal plate edges are formed with recesses at said points of engagement, said recesses containing deposits of deformable material.

7. In a piezoelectric crystal assembly, an oscillator plate comprising a crystal blank having a first electrode plated on one face thereof, said first electrode extending over the mid-portion of one edge of the blank, a second electrode plated on the opposite face of the blank and having a portion thereof extending over the opposite edge of the blank, a deposit of deformable material which is electrically conductive on the electrode extension at said one edge at the midpoint of said one edge, and a pair of deposits of electrically conductive deformable material on the electrode extension at said opposite edge and being spaced substantially symmetrically with respect to the midpoint of said opposlte edge, said deposits being located substantially in the median plane of the blank parallel to the plated faces thereof.

8. In a piezoelectric crystal assembly, an oscillator plate comprising a crystal blank having a first electrode plated on one face thereof, said first electrode extending over the mid-portion of one edge of the blank, a second plated electrode on the opposite face of the blank and extending over the opposite edge of the blank, said one edge being formed with a recess at its midpoint and said opposite edge being formed with two recesses spaced symmetrically on each side of the mid-point of said opposite edge, the electrode extensions including said recesses, the recess centers lying substantially in the median plane of the blank parallel to the plated faces thereof, and a deposit of deformable conductive material in each recess.

9. A piezoelectric crystal assembly comprising a piezoelectric oscillator plate, a support, a frame member, means connecting said frame member to said support and supporting said frame member in a vertical position, an inwardly projecting clamping element carried at one side of said frame member and engaging one edge of the 0scillator plate, and a bar member supported on the opposite side of the frame member and extending transversely thereof, said bar member carrying a plurality of inwardly projecting clamping elements engaging the opposite edge of the oscillator plate, the points of engagement of the clamping elements lying in the median plane of the oscillator plate parallel to the major faces thereof.

10. A piezoelectric crystal assembly comprising a piezoelectric oscillator plate, a support, a frame member, resilient means connecting opposed portions of said frame member to said support and suspending said frame member in a vertical position, an inwardly projecting clamping element carried at the top portion of said frame member and engaging the top edge of the oscillater plate, and a bar member supported on the bottom portion of said frame member and extendiz transversely thereof, said bar member ca ing a plurality of inwardly projecting cl.....1ping elements engaging the bottom edge of the oscillator plate, the points of engagement of the clamping elements lying in the median plane of the oscillator plate parallel to the major faces thereof.

FLOYD W. FLYNN'.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,077,204 Bechmann Apr. 13, 1937 2,133,647 Pierce Oct. 18, 1938 2,203,486 Bond June 4, 1940 2,315,392 Bokovoy Mar. 30, 194.3 2,443,700 Sylvester et a1. June 22, 1948