Title:
Oscillating mechanical or electromechanical system
United States Patent 2224891


Abstract:
The present invention relates to vibrating or oscillating mechanical or electromechanical systems, and more particularly to alternating current systems comprising piezo-electric resonators or oscillators. A specific object of the invention is the construction of a piezo-electric body and manner...



Inventors:
Wright, Russell B.
Application Number:
US68549933A
Publication Date:
12/17/1940
Filing Date:
08/16/1933
Assignee:
Wright, Russell B.
Primary Class:
Other Classes:
310/367, 381/162, 381/190
International Classes:
H03H9/09
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Description:

The present invention relates to vibrating or oscillating mechanical or electromechanical systems, and more particularly to alternating current systems comprising piezo-electric resonators or oscillators.

A specific object of the invention is the construction of a piezo-electric body and manner of mounting the same whereby the body will remain in a fixed position with respect to its support and electrode system, so that the resistance to vibration introduced by the support will be reduced to a minimum and maintained at a sensibly constant value.

Still another purpose is to so mount vibrating or oscillating bodies or mechanical systems in a constant space and in electrical relationship with respect to their support and appurtenances that the resistance to oscillation introduced by the support may be adjusted to a constant magnitude.

The above and other aims and objects will be more apparent from the detailed description hereinafter appearing when taken in conjunction with the drawings appended hereto and forming part hereof and in which: Fig. 1 is a vertical sectional view of one form of the invention showing a piezo-crystal and its mount; Fig. 2 is a plan view of the crystal shown in Fig. 1; Fig. 3 is a vertical sectional view similar to that of Fig. 1 but of a somewhat modified form of the invention also showing the position and arrangement of the electrode system; Fig. 4 is a plan view of the form shown in Fig. 3; Fig. 5 is a sectional view similar to Fig. 1 but of still another embodiment of the invention; Fig. 6 is a plan view of the embodiment of Fig. 5; Fig. 7 is a plan view of the invention as applied to an oscillating system, such as a tuning fork; Fig. 8 is a sectional view of the showing of Fig. 7; Fig. 9 is a plan view showing a modified form of the vibrating fork illustrated in Figs. 7 and 8; and Fig. 10 is the corresponding sectional view of the modification of Fig. 9.

A piezo-electric body maintained in a constant state of vibration by means of a vacuum tube circuit arrangement forms a most convenient source of stable and constant radio frequency current. As need for higher accuracy arose, sources of this nature were greatly improved, and led finally to the development of quite accurate and constant standards of radio frequency.

However, further progress has been retarded by one outstanding limitation. This resides in the difficulty of preventing movement of the vibrating piezo-electric body as a whole with respect to its mount or support without introducing too great a resistance to vibration. In order to overcome this impediment, I form my body or syster to comprise three principal parts or members, as will be evident from the figures of the drawings, attention being first directed to the structure shown in Figs. 1 and 2.

The character A designates a relatively thick, annular, vibrating portion of a system cut with the desired orientation from a disk or plate prepared from a quartz crystal. Although a vibrating portion of any shape may be employed, one ground in a toroidal shape is shown. As stated, the element A constitutes the vibrating section of the crystalline body. Structurally integral with this section and centrally disposed with respect thereto is a continuous, relatively thin connecting circular membrane M having a thickened portion or base B clamped between the members S, S', constituting a support or the like. A quartz body ground to form the annular portion, membrane and base, when rigidly mounted or clamped on a support, will be found to respond readily to some mode of vibration, irrespective of orientation with respect to the crystallographic axes, assuming that the electric field, or means by which it is caused to vibrate, is properly applied. However, the resistance to vibration may be further reduced by grinding away part of the membrane M to produce the modification of Figs. 3 and 4.

Here the membrane M has been cut away to provide a pair of oppositely disposed arms R, R' whose width is greater than the thickness of the original membrane. In many instances, if narrower arms be ground from a thicker membrane, so that the thickness exceeds the width, it would result in greater frequency stability by virtue of the reduced resistance to vibration thus accomplished.

The choice of points at which the arms are to terminate on the vibrating member A will depend in general upon the number of arms to be employed, the orientation of the body with respect to the crystallographic axes and the mode of operation; and more specifically upon the displacements experienced by the various points around the center of the inner periphery of the vibrating member. For example, if the geometrical axis of symmetry of the quartz body is perpendicular to both the optic and the electric axes and the mode of vibration employed responding most actively with annular electrodes placed opposite the annular vibrating surfaces, the most satisfactory points of termination will be found to be those determined by the diameter parallel to the optic axis, assuming one or two connecting arms.

The disposition of the electrode system referred to in this example is illustrated in Figs. 3 and 4, in which the electrodes are marked E, E'.

With this disposition and with the described orientation of the quartz body in relation to the optic and electric axes, and with the described arrangement of connecting arms R, RI and base member B; one of the frequencies at which the body will be found to readily vibrate may be roughly determined by the formula in which T is the thickness, or axial dimension of the vibrating member, and F is the frequency given in kilocycles per second. It may be worthy 25 of mention at this point that this or other modes of vibration may be discriminated against somewhat by choice of the number and orientation of the arms. Other orientations of the quartz body, or other shapes of the vibrating member, 30 will result in different vibration frequencies.

For the purpose of measuring a field of force such as, for example, the earth's gravitational field, the membrane M may be ground away, leaving an arm R2, as shown in Figs. 5 and 6, which 35 is of sufficient length compared to its lateral dimensions to be deflected by the action of the force upon the vibrating member which it supports. The resulting displacement of the vibrating member with respect to the mounting and 4 appurtenances will be manifested as an alteration in the vibration frequency. The shape of arm R2 illustrated is chosen to indicate that the arm may conveniently be made any number of degrees of arc in extent, up to 7200, or that there 4may be two or more similar arms. Obviously, these arms may be ground in other shapes, for instance helical.

To illustrate the general application of the invention to vibrating bodies of constant frequenl0 cies, there is illustrated in Figs. 7 and 8 a crystalline or fused quartz tuning fork F mounted or clamped by means of arms R3 and R4 and base B3 on a support constituting arms S', S2. The fork is supported in a constant or definite space 55 or electrical relationship with respect to its mounting. As indicated, if the tuning fork is prepared from crystalline or fused quartz, it is ground in the shape depicted in Figs. 7 and 8.

The point or points on the fork member F at 60 which the arm or arms R3, R4 are to terminate will depend principally upon the ratio of the median length of the curved part or yoke of the fork to the "over-all" median length. A change in this ratio would result in an alteration of the 65 displacements experienced by points on the yoke of the fork. If this ratio is one half and two arms symmetrically related, as shown in the figures, are employed, the angle included by the arms should be approximately 86Y/2, if it is 70 desired that the radial component of the displacements experienced by the points of attachment be reduced substantially to 0; whereas for forks whose ratio is as small as A, the angle to be included is practically 180°.

75 As in the embodiments previously described, the base B3 is designed to be rigidly clamped between members S', S2 forming the mounting.

If it is found desirable in this modification, or that of Figs. 3 to 6 inclusive, the arms and base member may be arranged externally. As an llustration, a possible external arrangement is shown in Figs. 9 and 10, in which the vibrating portion of the fork F' is seen to be supported by the arms R5 and R6 which terminate in the externally disposed base member B4. It is evident that forks of this nature, whether designed with external or internal supports, may be constructed of materials other than quartz.

For some purposes, a fabricated metal fork of this type would prove practicable. Forks of piezo-electric material may be coupled to an electrical circuit arrangement either piezo-electrically, dielectrically or acoustically. Forks of fused crystalline material, such as fused quartz, may be coupled dielectrically or acoustically. Forks of magnetic material may be coupled magnetically, magneto-strictively, or acoustically.

It will be appreciated that forks of the design shown in Figs. 7, 8, 9 and 10 may find diversified application. If constructed from crystalline or fused crystalline material, a fork of this nature would undoubtedly be intended for use in conjunction with vacuum tube circuit arrangements of great refinement, such as are at present employed in precision standards of radio frequency. If constructed of magnetic material, the fork might be intended for use in a vacuum tube circuit arrangement of lesser refinement or merely for such purposes now satisfied by conventional tuning forks, acoustically or magnetically excited.

Without resorting to additional illustration, it will be apparent that the invention may be incorporated in a vibrating or oscillating system, such as a pendulum. The uncertain or erratic 46 behavior of pendulum supports, such as knife edges, may be avoided by the use of a pendulum comprising an oscillating member or part connected to a base member, the latter designed to be rigidly secured to a flexible interlinking member. The latter member is preferably in the form of a fused crystalline membrane designed to bend very readily to allow the oscillating member to swing freely.

Other modifications and applications will be apparent to those skilled in the art, and all such are considered to fall within the spirit and scope of the invention as defined in the appended claims.

I claim: 1. A piezo-electric resonator comprising a vibrating portion and a flexible member integral with the portion, said flexible member serving to mount the resonator on a support.

2. A piezo-electric resonator comprising an annular vibrating portion and an inner member integral with the vibrating portion operable to rigidly mount the resonator on a support.

3. An annular piezo-electric resonator having a central integral web constituting a membrane for mounting the same.

4. An annular piezo-electric resonator having an integral web centrally thereof constituting a membrane for mounting the same.

5. An annular piezo-electric resonator having a central integral web constituting a membrane of materially reduced thickness with respect to its vibrating portion.

6. An annular piezo-electric resonator having a membrane centrally thereof of materially reii lilli Ii II _ : -- -----~-. _..~-r---I· -_ .·L 1 duced thickness with respect to its vibrating portion.

7. A crystal resonator comprising a slab of piezo-electric quartz and an arm fashioned from the crystal for rigidly supporting the same.

8. A crystal resonator comprising a vibrating portion, a connecting element and a base portion.

9. A crystal resonator comprising a vibrating portion, a connecting element, and a base portion, the connecting element being of less thickness than the vibrating portion.

10. A resonator comprising a vibrating portion, a connecting element and a base portion all formed from a single crystal.

11. A resonator comprising a vibrating portion, a connecting element and a base portion, all formed from a single crystal, the connecting element being of less thickness than the vibrating portion.

12. Elastically oscillating oscillator having a small damping action comprising an oscillator cut from a block of material in such a manner that said block provides the support for said oscillator.

13. Elastically oscillating oscillator having a small damping action comprising a piezo-electric oscillator cut from a block of quartz material in such a manner that said quartz provides the support for said oscillator.

RUSSELL B. WRIGHT.