US2802955A

US2802955A - Piezoelectric unit

Info

Publication number: US2802955A
Application number: US352758A
Authority: US
Inventors: Donald M Kitterman
Original assignee: Individual
Current assignee: Individual
Priority date: 1953-05-04
Filing date: 1953-05-04
Publication date: 1957-08-13
Anticipated expiration: 1974-08-13

Description

Aug. 13, 1957 D. M. KITTERMAN PIEzoELEcTRIc UNIT Filed May 4, 1955 IN V EN TOR.

United States Patent O l PmzoELEcTRic UNIT Donald M. Kitterman, Kansas City, Kans.

Application May 4, 1953, Serial No. 352,758 1 claim. (ci. 31o- 9.4)

This invention relates to the field of piezoelectricity and, more specifically, to the provisionrof an improved piezoelectricunit embodying 'improvements in the crystal element thereof, the electrode. and coupling means associated with said element and the supporting structure for said element.

The principal object of this invention is to provide a piezoelectric unit of increased piezoelectric efficiency and physical ruggedness.

4Another important object of this invention is to provide a crystal element of configuration presenting anumber of nodal, support-engaging points about its perimetric edge.

Another important object of this invention is to providey electrode and coupling means for a crystal element, wherein the electrode means are carried by the element andare physically connected to objects other than the element at nodal points on the perimetric edge of the element.

Another important object of this invention is to provide support structure adapted for line-contacting engagement with nodal points on the perimetric edge of a crystal element. K i, 2

Still otherl important objects of this invention include details of construction of the crystal element, the electrode andicoupling Ameans associated with the element and the supporting structure for the element, the way in which the element is adapted and supported for eicient operation in any position, thefway in which the damping effect of shock waves created by vibration of the element are minimized and-the speed, economy, simplicity and ease with which piezoelectric units made in accordance with this invention may be fabricated :and assembled. Many more minor objects and advantages of this invention will be made clear or become apparent as the following specification progresses.

Referring now to the accompanying drawing:

Figure 1 is `a side elevational View of a piezoelectric unit made in accordance with this invention, partsof the housing and plug assembly being Vbroken away and shown in cross-section for clearance.

Fig. 2 is an edge elevational view of said unit looking from the left of same 4as it appears in Fig. l, .parts of the.

taken on line V-V of Fig. l.

The piezoelectric unit illustrated Vbroadly includes a housing vandplugAassemblyf-, a piezoelectric crystal' element 10,- electrode-and coupling means 12'for element 10 and supporting structure 14for element 10.

Assembly 8 conventionally includes a base plate 16 65 Fig. 5y is an enlarged cross-sectional view of said unit Patented .Augx 13,l 1951.

ICC

cap 26 within channel 24 of rim 22, the whole of assem-r bly 8 being sealed in any suitable manner to exclude dust and moisture after element 10, means 12 and structure 14 have been installed as hereinafter set forth and cap 26 emplaced upon rim 22 in covering relationship thereto.4

Element 10 is formed of any suitable piezoelectric material, preferably from a quartz crystal, and, in the embodiment of the invention shown for the purpose of illus-v tration, is provided with a pair of opposed,

external faces

30 and 32, face 30 including a central section 34 circumscribed by

marginal sections

36, 38, 40 and 42, face 32 correspondingly including respectively a central section 44 circumscribed by

marginal sections

46, 48, 50 and 52.

Central sections

34 and 44 are each substantially at and are disposed in spaced, parallel, opposition to each other. Correspondingly opposed pairs of marginal sections 36-46, 38-48, 40-S0 and 42-52 are acutely bevelled from the planes of their corresponding central sections 34 .and 44 and intersect each other in acutely converging relationship forming a peripheral portion 54 of V-shaped cross-section on element 10 in circumscribing relationship to the latter, thereby presenting an extremely thin, linelike perimetric edge 56 on element l0 at the zoneof juncture between marginal sections 36-4e3, 38-48,

40-50 and 42-52. Edge 56 is planar and circumscribes adapted for line-contacting interengagement with Asupporting means therefor and that such application of said principles is contemplated as within the spirit hereof, vit will be equally apparent that the specicconguration of element wherein described for purposes of illustration. will be found particularly suited for crystal elements in` tended to oscillate in the shear mode identified, for instance, with the so-called AT-cut type of quartz crystal element. With such type of element Ill), it is significant that edge 56 will be found to be disposed along the central, nodal plane of element l0 and that, while

central sections

34 and 44 of

faces

30 and 32 will displace themselves relatively to each other, said control plane and the v axis of element lil during oscillation of element 10 in such AT-cut mode ot shear vibration, all points on edge S6 will remain xed relative toeach other and the axis of element l0 and are, therefore, nodal.

As shown in the accompanying drawing, element 10 is essentially square and of relatively small 'thickness as compared with the other dimensions thereof. lt wiil be understood, however, that the'shapes, proportions and dimensions of crystal elements may be varied substantially, depending upon the particular piezoelectric material of which they are formed, the desired rfrequency of oscillationand other factors, and that the applicability ofthe presentinvention is not limited to elements 10 of the precise configuration and proportions shown. Thus,

with appropriate, obvious, minor modications of other' parts of the unit herein illustrated and described, ele# ments 10 of diiferent sizes and shapes, but having a nodal, perimetric,linelike edge comparable to edge' 56, could be equally well employed.. Further, `itfslhould be notedl that, although as a matter of convenience in productionr Y it is to be preferredv that the entire areas of marginal sections v,36, 3P, 40, 42, 46, 4S, 59 and 52 vbe bevelled, from a purely operational viewpoint the bevalling of correl o@ spondingly opposed, spaced-apart, areas on said marginal sections to present an interrupted, line-like edge 56 would be satisfactory.

Electrode and coupling means 12 for element 10 include a thin electrode 58 of conducting material for face of element 10, preferably formed by plating, evaporating or otherwise suitably depositing a continuous film or coating of gold, copper or the like upon element 10 in permanently adhered relationship thereto, a similarly formed electrode 6i) for face 32 of element 10, and a pair of

flexible conductors

62 and 64. Conductor 62 connects electrode 58 to pin 18 of assembly 8, and conductor 64 connects electrode 60 to pin 20, to permit coupling of element 18 with an external electrical circuit (not shown).

It will be understood that, in Figs. l, 4 and 5, the thickness of

electrodes

58 and 60 has been exaggerated for purposes of illustration. From said iigures, it will be clear that electrode 58 covers central section 34 of face 30, a minor part 66 of marginal sections 36, a minor ginal section 46, a minor part 78 of edge 56 adjacent part 76 of marginal section 46, and a minor part 80 of marginal section 36 adjacent part 78 of edge 56 and directly opposite part 76 of marginal section 46, conductor 64 being connected with electrode 60 at a point 82 thereon adjacent part 78 of edge 56, Electrodes 5S and 60 are not contiguous at any point.

It is obvious, therefore, that

conductors

62 and 64 are physically connected to

electrodes

58 and 60 of element 10 only at nodal points 72 and 82 adjacent parts 68 and 78 of nodal edge 56 of element 10, so that such connections at points 72 and 82 will have no damping effect on element 10, will be at points of no vibration during oscillation of element 10, and may be of a physical nature best suited for ruggedness without critical regard to the mass of the means used for effecting the connections.

Supporting structure 14 is formed of insulating material and includes a pair of spaced-apart parallel, perforated, plate-

like members

84 and 86 secured to a base slab 88 disposed therebelow and extending therebetween adjacent their lowermost extremities as illustrated in Figs. 1, 2 and 5, slab 88 in turn being mounted in any suitable manner upon base plate 16 of assembly 8 and being provided with clearance openings for

pins

18 and 20. Members are also interconnected by a number of bridging

arms

941, 92, 94, 96, 98 and lill) and by a bridging piece 102, arms 90 and 92 overlying slab 88 as the unit is disposed in Fig. l,

arms

94 and 96 being adjacent the left-most and

arms

98 and 100 adjacent the right-most extremities of

members

84 and 86 as depicted in said figure, and piece 182 being adjacent the uppermost extremities of

members

84 and 86 in said figure.

Members

84 and 86, slab 88 and

arms

90, 92, 94, 96, 98 and 100 are preferably integrally formed of a suitable plastic material by injection molding or other conventional process, piece 102 being separately formed and then permanently mounted upon

members

84 and 86 in any suitable manner, as by thermoplastic joinder, after element 10 is in place as hereinafter explained.

Arms

90, 92, 94, 96, 98 and 100 and piece 102 are disposed at spaced intervals about perimetric edge 56 of element 10 for contining and supporting the latter in the position illustrated when it is in normal position between

members

84 and 86.

Arms

90, 92, 94, 96, 98 and 100 and piece 102 are respectively provided with V-

shaped notches

110, 112, 114, 116, 118, and 122, each disposed and adapted to receive edge 56 in substantially linecontacting relationship in the manner shown in the ac` companying drawing, the angular divergence of each notch 110 etc. being greater than the angular convergence of the corresponding marginal sections 36-46, S18- 48, 40-50 or 42-52 defining that part of peripheral portion 54 of element 10 disposed therewithin. Notches 110 etc. preferably are located with their vertexes midway between

members

84 and 86, so as to adapt arms 90 etc. and piece 102 for supporting element 10 between and spaced from

members

84 and 86.

Members

84 and 86 are respectively provided with

openings

124 and 126 in the part thereof opposite

central sections

34 and 44 of element l() and with apertures 128 and opposite

marginal portions

36 and 46 of element 10. The provision and disposition of

such clearances

124, 126, 128 and 130 is significant in the minimization of the damping elfect which otherwise would result from shock waves of air created by vibration of element 10 within the space between

members

84 and 86, the axis of symmetry of

openings

124 and 126 being substantially in alignment with the centers of

central sections

34 and 44 of element 10.

It will now be evident that the overall improvement of piezoelectric crystal units which is the subject of this invention contemplates and includes the mounting of an improved type of crystal element 10 provided with an irnproved type of electrode and coupling means 12 in an improved type of supporting structure 14 to produce a unit of improved physical ruggedness and piezoelectric efficiency which will operate in any position without material damping of the element 10 or sacrificing of the units ability to withstand rough treatment.

It will be further appreciated that various minor moditications and changes could be made in the structures shown and described for the purpose of illustration, without departing from the principles or spirit of this invention; accordingly, it is intended that this invention shall be limited only by the scope of the appended claim.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

In a holder for a rectangular, piezoelectric, crystal element having each marginal portion thereof beveled to present sharp edges thereon, an element support comprising a pair of spaced apart, parallel, substantially rectangular, plate-like members of greater dimensions than the element and each having an opening therein; and a plurality of bridging arms interconnecting the members and each provided with a V-shaped element-receiving notch therein, there being at least one arm for each edge respectively of the element, said arms being disposed for supporting and conining said element between said members and in spaced relationship thereto with the sharp edges of the element in engagement with corresponding arms at the vertexes of the notches of the latter, the angle between the opposed surfaces of each beveled, marginal portion of the element being smaller than the angle dened by the sides of the notch of the corresponding arm.

References Cited in the le of this patent UNITED STATES PATENTS 2,161,980 Runge June 13, 1939 2,232,277 Schneider Feb. 18, 1941 2,399,919 Garrison May 7, 1946 2,423,081 Bokovoy July 1, 1947 2,434,266 Fruth Ian. 13, 1948 2,505,121 Knights Apr. 25, 1950 2,575,819 Laird Nov. 20, 1951 2,677,775 Font May 4, 1954 2,706,326 Mason Apr. 19, 1955