US2454769A - Piezoelectric crystal support - Google Patents

Description

Nov. 30, 1948. F. A. M. BUSNEL PIEZOELECTRIC CRYSTAL SUPPORT Filed March 1, 1945 LEILIL.

[N V ENTO R Fwy/Yea lsA /v lfiusnfL ATl ORN EY Patented Nov. 30, 1948 PIEZOELECTRIC CRYSTAL SUPPORT Francoise A. M. Busnel, Lyon,'France, assignor to International Standard Electric Corporation, New York, N. Y., a corporation of Delaware Application March 1, 1943, Serial No. 477,643. InFrance January 23, 1942 1 Claim. 1

The present invention relates to a piezo-electric mounting, and, more particularly, to a mounting for quartz crystal discs which are required to operate at very high frequencies.

One object of the invention is to provide a piezo-electric mounting having a very weak electrical capacity in its support element.

Another object of the invention is to provide a quartz crystal mounting of small dimensions and of very simple construction.

Still another object of the invention is to provide a piezo-electric mounting in which the distance between the electrodes can be easily adjusted to any desired value.

A still further object of the invention is to provide a mounting of this type which can be assembled and taken apart without difficulty, and in which all elements are easily accessible and replaceable.

These and other objects are accomplished, according to the present invention, by the arrangement and combination of elements set forth in the following description, defined in the appended claim and illustratively exemplified in the accompanying drawing, in which Fig. 1 is an axial section through a piezo-electric mounting according to the invention, and

Fig. 2 is a top elevation of the device according to Fig. 1 after removal of the protective hood.

In the drawing, I denotes a cylindrical protective hood, preferably of insulating material, which rests with its rim on an insulating support plate 2 of circular outline. The plate 2 may be secured to the hood I by means of screws (not shown) to be countersunk in recesses 3 formed in the bottom face of the support plate 2.

The support plate 2 is provided centrally with a cylindrical boss 4. A conductor strip 5 rests on and extends radially of the support plate 2 into a cut-out of the boss 4 beyond the center of the latter. An insulating disk 9 rests on the boss 4 and supports, in turn, a cylindrical metal element 1, the upper face 6 of which forms one of the electrodes for the quartz crystal. A metal screw 8 passes through threaded aligned perforations of the support plate 2, the conductor strip 5, and the insulating disk 9 into a threaded axial bore of the electrode element I, thus securing all these parts together and also providing a continuous metallic connection between the electrode 6 and a connecting plug I screwed into the conductor strip through the support plate 2.

The insulating disk 9 and the metal element I form the bottom of a casing for the quartz crystal. The peripheral wall of this casing is formed by a cylindrical insulating sleeve I I, which rests on the disk 9 and surrounds the metal element I without, however, being mechanically connected with either the disk 9 or the element I. The quartz crystal disk I I a, which has a diameter substantially equal to that of the electrode element 1, is disposed in the casing and rests on the electrode face 6. The insulating sleeve II projects upwardly beyond the upper face of the quartz crystal disk Ila.

The quartz crystal casing is closed by a metal cover disc I2 which rests on the end face of the sleeve II at a distance from the upper face of the quartz crystal disk Ila. The cover disc I2 is provided with a central threaded bore traversed by a metal screw plug I3, the inner face I4 thereof constituting the second electrode for the quartz crystal IIa. By turning the screw plug I3 in clockwise or counterclockwise direction the distance between the electrodes 6 and I4 can be varied in order to change the vibration frequency of the quartz crystal disk. A look nut 20 serves to secure the plug I3 in its adjusted position. The cover disc I2 merely rests on the end face of the sleeve I I and is not mechanically connected with the sleeve which forms the circumferential wall of the quartz crystal casing.

The various parts of the casing are held together, after being placed in position, by means of an electrically conducted spring blade I5 provided at its inner end with a centering pin I6 adapted to engage in a central recess in the top face of the screw plug I3. This centering pin insures also, owing to the pressure of the spring band I5 upon the screw plug I3, an excellent electrical connection between the electrode I4 and a second connecting plug H. The plug I1 is screwed through the support plate 2 into one arm of angular metal bracket I8 which is, in this manner, secured to the support plate. The outer end of the spring blade I5 is secured to the other arm of the bracket by means of a set screw 19. The screw l9 can be tightened to hold the spring band I5 in a radial position in which it acts upon the screw plug I3, or the screw I9 may be loosened to permit the spring band I5, after disengagement of the centering pin I6 from the recess in the screw plug I3, to be swung about the screw I9 into an inoperative position, in which the cover elements I2, I3 and the sleeve II with the quartz crystal disk Ila can be taken apart without any further detaching operation.

The quartz crystal mounting described permits a definite adjustment of the crystal frequency by a simple tightening or loosening of the screw plug 13. Moreover, a mounting of this type can be easily and cheaply manufactured and it may be assembled and taken apart without difiiculty, so that the control and the replacement of parts is greatly facilitated. The electrical capacity of the mounting is very small and consists almost exclusively of the adjustable capacity between the electrodes.

It will be understood that the invention is not limited to the embodiment described and shown, but is capable of various modifications and alterations within the scope of the following claim. e

I claim:

A piezo-electric mounting comprising a support, two terminals secured to said support, a cylindrical electrode element mounted on said support, means electrically connecting said-electrode with one of said terminals, a quartz crystal disk having substantially the same diameter as said electrode element and resting on a flat electrode face of the latter, a casing for said quartz crystal disk, said casing including a cylindrical insulating sleeve surrounding said electrode element and quartz crystal disk and extending axially beyond the latter, a cover plate resting against one end face of said sleeve at a distance from said quartz crystal disk, said cover plate being provided with a central threaded bore, a screw plug electrode screwed into and traversing said bore to have its inner electrode face disposed at an adjustable distance from the electrode face of said cylindrical electrode element, and resilient means mounted on said support to press said cover plate against said sleeve, including a spring blade extending substantially radially of said screw plug electrode at about the level of the outer face thereof, a centering pin mounted on the inner end of said blade and adapted to engage a central recess provided in said outer face of said screw plug so as to urge the latter and said cover plate against said sleeve, and means electrically connecting said screw plug electrode with said second terminal, including a metal bracket mounted in said support and electrically connected with said second terminal, said bracket carrying and being electrically connected with the outer end of said spring blade.

FRANCOISE A. M. BUSNEL.

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

UNITED STATES PATENTS Number Name Date 1,572,773 Crossley Feb. 9, 1926 1,790,355 Peterson Jan. 27, 1931 1,844,705 Tripp Feb. 9, 1932 FOREIGN PATENTS 30 Number Country Date 279,595 Great Britain Nov. 3, 1927

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