US2076060A - Piezoelectric crystal holder - Google Patents

Description

April 6,` 1937.

R. BECHMANN 5T A1. 2,076,060

PIEZOELEGTRIC CRYSTAL HOLDER Filed oct. 12', 19:55'

WlLHELM SCHNEIDER ATTORNEY.

Patented Apr. 6, 1937 PATENT OFFICE PIEZOELECTRIC Y rCRYSTAL HOLDER Rudolf Bechmann and Wilhelm Schneider, Berlin,

Germany, assignors to Telefunken Gesellschaft fr Drahtlose Telegraphie m. b. H., Berlin, Germany, a corporation of Germanyk Application October, 12, 1935, Serial No. 44,674 In Germany November 6, 1934 9 Claims.

This invention relates to a new and novel hold-v er for a piezo-electric crystal oscillator.

This application is a continuation in part of application Serial No. 738,454, iiledr August 4,`

In the above-mentioned patent application, ay

holder or setting means for oscillators of the piezo-electric crystal type has been disclosed, the

essential feature of which is that the crystal andA l0 the electrodes are embedded inside a casing consistingA of ceramic material.

lowing considerations.` o

'The temperature coefficient of a vcrystal device consists of the temperature coefficient of the crys-;

selfA by choosing a suitable cut. .Hence still further decrease of the temperature coeflicient of'.

the entire device is obtainable only by a reduction of the temperature coeflicient of the crystal holder. yEspecially in the case of holders of such crystal oscillators as are called upon to insure an extremely high-frequency stability or constancy, for instance, when employed as crystal monitors in connection with transmitters or as quartz clocks, it is of essential importance that the temperature coeflicient be kept small.

As a general rule, the electrodes are at an extremely small distance from the surfaces of the crystal; but this interval of space andl its stability or preservation is essential from the Viewpoint of the oscillatory state and the frequency stability of the crystal. As a result, even changes in the distance should be avoided which, per se, would be small, but which would exercise a high percentage influence. In fact, it has been for this reason that the earlier filed patent application contains the instruction that the electrodes should be confined inside a casing consisting of ceramic material, the underlying idea being to utilize the small temperature coeicient of ceramics rather than the higher temperature coefficient of metal.

Now, according to this invention, not only for the casing, but also for a portion of the principal mass of the electrodes, ceramic material is employed, such necessary metallic surface portions of the electrodes as are placed opposite the crystal being, if desired, metallized for the purpose of obtaining electric conductivity. In order to preclude soiling of the electrode surfaces by atmos- The present invenf tion discloses a further improvement of the said crystal holder which is predicated upon the :fol-

pheric agencies, for these are liable to cause irregularities of the surface and partial changes in the interelectrode distance, itis recommendable to use for metallization the surface with a kind of metal, preferably chromium, that will bc stable both in reference to atmospheric and humidity actions, I

One exemplified embodiment of the invention is illustrated in the drawing in which Fig. 1 shows `a plan view of the crystal holder, a portion 0f- Which is broken away to showk the inner construction; Fig. 2 is a cross section ofFig. l; Fig. 3 is an enlargeddetailed portion of Fig. 2. The ringlike casing made kof ceramic material l, surrounds the oscillator crystal 2 which is planar or laminar in form, and which is secured by centering ring 3. SupportingA of the crystal is effected in this manner that the crystal plate has `a peripheral groove or slot into which engage v yieldingly or elastically the peaks or supporting studs 3 inserted in the centering ring 3. The latter is clamped fast on both sides by insulating ringsA made of ceramic material 4, and the electrode holder means 5; These latter, as shown in f the drawing, are secured onthe casing I by means of a screw threadedjoint. The electrodes desig` nated Iby 6 are of ceramic material and they are metallized upon the working or` active surfaces 6 whichare located opposite `the crystal To insure adjustment of the distance between the electrode surfaces and the crystal, the electrode bodies 6 are embedded in metal rings or caps 1 which have a fine-pitched male screw thread 1', by means of which they are adjustable in the bushing-like electrode holders 5 which have female thread. In order to x the distance once adjusted, there is provided the screw-threaded rings 8 arranged on both sides. The ceramic casing caps or cover pieces l0 on both sides are united with the casing l by means of screws l2.

The preferable plan is to make the casing fasten ing screws I2, as shown, in such a Way that one and the same bolt serves to secure, on the one hand, the electrode holder 5, and, on the other hand, the casing cap I0.

For the purpose of establishing conductive connection with the electrode metallized surfaces, there is provided a metallic spindle 9 which is fixed within the electrode body 6 and in conductive connection with the electrode rnetallized sur" faces, said spindle 9 being maintained in electrical contact with a lead-in supported in cap I0. In order to insure safe contact-making, lead Il is made yielding such that its spindle stud i I is pressed against the end surface of conductor B by virtue of spring I3 applying pressure to member 9.

Having thus described our invention, what we claim is:

l. A piezo-electric Crystal holder comprising an insulating casing, a crystal within said casing, a supporting member for said crystal, two insulating members located at each side of said crystal, said insulating members having their Surfaces that face said crystal lcoated with metal to act as an electrode for said crystal.

2. A piezo-electric crystal holder comprising an insulating casing of ceramic material, a crystal within said casing, a supporting member for said crystal, two insulating members of ceramic material located at each side of said crystal, said insulating members having their surfaces that face said crystal coated with metal to act as an electrode for said crystal.

3. A piezo-electric crystal holder comprising an insulating casing, a crystal within said casing, a supporting member for said crystal, two adjustable insulating members located at each side of said crystal, said insulating members having their surfaces that face said crystal coated with metal to act as an electrode for said crystal, and means for connecting said metal surfaces outside of said casing.

4. A piezo-electric crystal holder comprising a ring-like insulating casing having removable end caps, a crystal within said casing, a supporting member for said Crystal, two insulating members located at each side of said crystal, said insulating members having their surfaces that face said crystal coated with metal to act as an electrode for said crystal.

5. A piezo-electric crystal holder comprising an insulating casing having removable end caps, a crystal within said casing, a ring-like supporting member for supporting and surrounding said crystal, securing means whereby said supporting member is secured within said casing, two insulating members located each side of said crystal, said insulating members having their surfaces that face said crystal coated with metal, each of said metal surfaces acting as an electrode for said crystal.

6. A piezo-electric crystal holder comprising an insulating 'casing having removable end caps, a

crystal within said casing, a ring-like supporting member for supporting and surrounding said crystal, securing means whereby said supporting member is secured within said casing, two adjustable insulating members located each side of said crystal, said insulating members having their surfaces that face said crystal coated with metal, each of said metal surfaces acting as an electrode for said crystal.

7. A piezo-electric crystal holder comprising an insulating casing having removable end caps, a crystal within said casing, a ring-like supporting member for supporting and surrounding said crystal, securing means whereby said supporting member is secured within said casing, two insulating members located each side of said crystal, said insulating members having their surfaces that face said crystal coated with metal, each of said metal surfaces acting as an electrode for said crystal, and means passing through the end of said Casing for connecting said metallic surfaces outside of said casing.

8. A piezo-electric crystal holder comprising an insulating casing having removable end caps, a crystal within said casing, a ring-like supporting member for supporting and surrounding said crystal, securing means whereby said supporting member is secured within said casing, two insulating members located each side of said crystal, said insulating members having their surfaces that face said crystal coated with metal, each of Said metal surfaces acting as an electrode for said crystal, and means passing through the central portion of said insulating members and through the end of said casing for connecting said metal surfaces outside of said casing.

9. A piezo-electric crystal holder comprising an insulating casing having removable end caps, a crystal within said casing, a supporting member surrounding said crystal, securing means whereby said supporting member is secured within said casing, two insulating members having threaded bushings secured to each end thereof for adjusting said members with respect to said crystal, said insulating members having their surfaces that face said crystal coated with a metal to act as an electrode for said crystal.

RUDOLF BECHMANN. WILHELM SCHNEIDER.

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