Electro-mechanical transducer

3,252,016

May 17, 1966

J. HAYER, JR,, ETAL electro-mechanical transducer Filed Sept. 11, 1962

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United States Patent Office 3,252,016 —---------—-----------------—Patented May 17, 1966 „„ 3,252,016

ELECTRO-MECHANICAL TRANSDUCER ^Jr·’ ?^{igh,and Park}> and Eric J. Straus, Westfield, NJ., assignors to Gulton Industries, Inc., Metuchen, NJ., a corporation of New Jersey

Filed Sept. 11,1962, Ser. No. 222,835 13 Claims. (CI. 310—8.4)

The principal object of this invention is to provide an improved electro-mechanical transducer, which is adaptsignal^whieh^¹¹¹² “^ecban.^{ical energy} mto an electrical signal, .which is particularly adaptable for use as an acceterometer for producing electrical signals in accordance with vibrations applied thereto, which may be adapting ίΥΤΤί?^{8 eiec}‘^{rical ener}S^y to mechanical enanTmX ^Whlj^C ♦ ^a ,^r®^latlvely high resonant frequency and also a relatively high sensitivity. ^{4 y}

Briefly, the electro-mechanical transducer of this invention includes a base, and a substantially circular disc shaped armature which is secured at the peripheral edge thereof and at an annular area of one face thereof adj! cent the peripheral edge thereof to the base with the other face thereof free from the base. At least onX p£f electric element provided with electrodes is secured in face Uded¹¹? ^relatl°ⁿ. ^t0 „^the armature, and means are proSS.fcSS* *— ‘° * «»»·» i»r ^{With this} Nation, the armature stnietnr A ^1U periphery to the base, a substantially rigid ^uctare is provided which has a relatively high resonant frequency, especially as compared to the resonant siXTat ff, t^{sabstantially} circular armature which is secured at its center, as in the electro-mechanical transducers disclosed m Dranetz Patent No. 2 808 522 and Dranetz et al. Patent No. 2,967,956, which are not So armXreto ffreT'T' ^IfP^erWrally securing the ³⁵th?^atr ? ^{th b e t0} Provide high resonant frequency the. armature were annularly secured to the base at the periphery and at both faces thereof, as byclamping Je armature to the base by an annular ring or th^hke the structure would be extremely rigid and have an extremely free to^efe^ntR^e’^UenCy;^ail^{d the armature w}°uld not be tree to flex. As a result, the sensitivity of such an electro-mechamc³! transducer would be extremely low.

• y^ev®r> ^as expressed above, in accordance with this resonant^df^1Cer °^f -^{hlS lnvention has} considerably higher resonant frequencies and greater sensitivities than the SdXems Fo^{matUre of} the aforemen- «θ uoned patents. For example, m connection with the lat, actual tests show that for same diameter armatures and same sized piezoelectric elements, the transducer with the armature peripherally secured in accordance wffhtok invention had a sensitivity (mv /g ) of 10 I® anH ’ nanl frequency of 50 kc’ M tte Muce^hX sTtTn Γη^{ίΓ31Ιϊ Secured had a} sensitivity (mv./g.) _of 8.5 to 12 and a resonant frequency of 25 kc. '

The peripheral securing of the armature to the ba^de for achieving the results of this invention may be ac“com Phshed in various ways. For example, the base may have' ^cavit^ ^{and a} substantially circular cular Hi^W 7^{D he CaVlty}’ ^{and the} substantially cirfit OTthe liS^a?^{ed armature may} secured, as by force t or the like, in the cavity with the peripheral edge therefherpnfX^{5 the cavity}’ ^{with an} annular area of one face ^{f the} ?^erlPberal edge thereof engaging the .annular shoulder and with the other face thereof free from the base. As another example, there may be proteir^eallv^afnr^bStaH^{ntialIy disc s}X^d «integrally formed on one end of the base so that the armature is effectively secured at its peripheral edge and at an annular area of one of its faces adjacent ffs pertohera edge to the base with its other face free fron/the base. . .' ^e armature may be flexed in various ways, as by applying electrical energy to the electrodes of the piezoaST ^{e emeat t0} P^roduce mechanical movement of the rmature, or by applying mechanical energy to the armature to produce electrical signals at the electrodes of ffie piezoelectric element. However, the electro-mechanical ™an T^r i°^{f thlS}f ^invention is particularly suited for use s an accelerometer and, here, means are provided for securing the base to an object to be vibrated for vibratL trie element fo^eXlnSH^the-^armt^tUre ‘° ^{Stress the} P^iez°elec“ “L L-?J°^dUC!ⁿ-^{g el},^ectrical .signals at the elecsuch vibrations. In order to increase ϊπΓίιιΛβΓ^Λβ seemed tale ^{β acceler}°“^eter’ ^a mass may be suitably the armXh X θ·.^ ^armature ** mass loading - 30 £ armature but this will operate to decrease somewhat nt the resonant frequency of the accelerometer.

Further objects of this invention reside in the details of construction of the electro-mechanical transducer and pari thereof ^relatlonshiP^{s bciwe}en the component > Other objects and advantages of this invention will beo the^aac^an^{ent t0 th}°^{Se SkUled in the art u}P^on reference in which: ^mpanying specification, claims and drawing, । f ¹ ,^{IS a} Partial vertical sectional view throush one form of the electro-mechanical transducer of this inven^{2 is a} Ρ^*^ vertical sectional view through another form of this invention; “ r ^F1^G‘ ? ^{is a partiaI} vertical sectional view through a further form of this invention; ^gn a

FIG. 4 is a partial vertical sectional view throush still another form of this invention* through still tr«S«rffl„^a,X^,’&amp;ⁿFS^W1⁰' ““ '“.-««h.uicul • ^ί0™ °^{f the}„^eIectro-mechanical transducer of this

THn 1 J^{1 1S} f^eneralIy designated at 10 in FIGS. 1 and 6 It includes a base 11 which may be formed of any suitable material, such as steel or the like, and which mav be gen erally circular in configuration. The base 11 is intearlllv provided with a screw threaded extension 12 and a flange la for securing the base 11 to an object to be vibrated tions of th^brab· X ¹¹ “ ^accordance with the vibra^on . °f ^{the ob}Ject. The base 11 is provided with a substantially circular cavity 14 and a substantially circular annular shoulder 15 in the cavity.

The transducer or accelerator 10 also includes an armature 16 which is made of suitable material such as “ » + “=1. h preferably aiiXt preferablv ^{A thia} Piezoelectric element, preferably formed of a suitable piezoelectric ceramic 17k? i? ^barl?“ ^titanate> lead-zirconium-titanate or the thfr f ^pr°^{vlded Wlth} suitable electrodes on the faces rmXeT⁸ τΓ^ ^relati<*' armature 16. The ceramic element 17 is permanently

3,252,016 tion to provide relatively high resonant frequency and relatively high sensitivity. The base 27 is suitably secured in an annular recess 30, as by force fit or the like, of a base member 29 which, in turn, is provided with a screw threaded extention 31 and a flange 32 for mounting the same on an object to be vibrated.

A piezoelectric ceramic element 33 of the type described above and provided with electrodes on its opposite faces is suitably secured to the armature 26 in face abutting arrangement. The base 27 may be provided with an annular extension 34 to assist in centering the ceramic element 33 on the armature 26. As the base 27 is vibrated through the base member 29 by the object being vibrated, the armature 26 is flexed to stress the piezoelectric element 33 for producing electrical signals at the electrodes thereof in accordance with such vibrations. Accordingly, the transducer 25 of FIG. 3 operates in the same manner as the transducer 10 of FIG. 1, it having relatively high resonant frequency and rela20 tively high sensitivity. .

A modified form of the transducer of this invention is generally designated at 40 in FIG. 4, it having the same armature base and piezoelectric element as the transducer 25 of FIG. 3. Accordingly, like reference char25 acters have been utilized for like parts. In FIG. 4, however, the base member 42 is provided with a central circular boss 41 to which is secured, as by force fit or the like, the base 27. The base member 42 is provided with a screw threaded extension 43 and flange 44 for 30 mounting the same on an object to be vibrated. The essential differences between the transducer 40 of FIG. 4 and the transducer 25 of FIG. 3 is in the manner of securing the base to the base member. Outside of this difference, the transducers 40 and 25 are the same and 35 operate in the same manner to produce the same results.

The transducer generally designated at 50 in FIG. 5 corresponds to the transducer 25 of FIG. 3, and like reference characters have been utilized for like parts. Here, a piezoelectric ceramic element 51, formed of materials .40 such as described above and provided with electrodes on the opposite faces thereof, is suitably secured in face abutting relation to the armature 26 so as to be stressed in accordance with the flexing of the armature 26. Here also, a mass 52 is centrally secured to the armature. 26 45 for increasing the sensitivity of the accelerometer which, in turn, decreases somewhat the resonant frequency thereof. Basically the transducer 50 of FIG. 5 differs from the transducer 25 of FIG. 3 in substantially the same way as the transducer 20 of FIG. 2 differs from the transducer ; so 10 of FIG. 1, and accordingly, a further description of the operation of the transducer 50 of FIG. 5 is not considered necessary.

While for purposes of illustration several forms of this invention have been disclosed, other forms thereof may 55 become apparent to those skilled in the art upon reference to this disclosure and, therefore, this invention is to be limited only by the scope of the appended claims.