US2523701A - Crystal holder - Google Patents

Description

Sept. 26, 1950 c. o. KUEHL CRYSTAL nowm Filed July 13, 1948 Inventor Clifford 0. ku ehl M W, W w

Patented Sept. 26, 1950 CRYSTAL HOLDER Clifford 0. Kuehl, Sandwich, 111.," mesne assignments, to The James assignor, by Knights Company, Chicago, 111., a corporation of Illinois Application July 13, 1948, Serial No. 38,491

4 Claims.

The present invention relates to crystal holders and more particularly to crystal mount providing improved mechanical support and improved electrical contact with the crystal electrodes.

During the course of the recent intensive development of crystals and crystal holders, the use of electrodes consisting of relatively massive plates has given way to electrodes formed of a metalized coating adherently deposited on the crystal, for example by sputtering in a vacuum. Mounts for holders having various types of contact members have been devised for use with metalized crystals but in general the design has required a compromise between the mechanical and electrical requirements. Thus, those mounts in which the crystal is clamped in firm electrical contact have frequently been subject to the drawback that the clamping inhibits free internal vibration while enabling external shock and vibration to be transmitted to the crystal. The latter not only has an adverse affect on operation but may cause chipping or breakage. If, on the other hand, the crystal is shock-mounted by conventional means, the construction is bulky, almost prohibitively expensive, and may involve electrical complications. The increasing severity of service resulting from the use of crystals in aircraft and land vehicles and the necessity for meeting a competitive price has presented a problem which has defied solution using ordinary crystal mount- 0 ing techniques. The problem has recently been further complicated by the use of metalized electrodes of the wrap-around type in which the same electrode occupies portions of both faces of the crystal. I

Accordingly, it is a primary object of the present invention to provide a crystal holder which permits substantially free internal vibration of the crystal in all directions while effectively isolating the crystal against external shock and vibration. It is a related object to provide a crystal holder of the above type in which firm electrical contact is made at selected points on the crystal structure.

Another object of the present invention is to provide a crystal mount having improved mechanical and electrical characteristics which is particularly suited for use with crystals having metalized electrodes of the wrap-around type. The construction is such as to substantially insure against electrical shortcircuiting of the electrode of opposite polarity on either of the crystal faces.

' socket.

It is a further object to provide a crystal holder including the above features but which nevertheless is extremely simple and inexpensive to manufacture, and convenient to use, requiring minimum time for changing crystals. It is a more detailed but related object to provide an inexpensive holder which may be substantially universally employed, adapting itself automatically to crystals of various proportions and contours. The crystal holder may be used Without mechanical change for substantially all of the known types of cuts.

Other objects and advantages of the invention will become apparent from the following detailed description taken in connection with the accompanying drawings, in which:

Figure 1 is a general external view of the im proved crystal holder with the housing in partial section to show the location of the crystal and a trimming capacitor associated therewith.

Fig. 2 is a perspective View of one embodiment of the improved crystal holder, the external housing being removed to show the details of co struction.

Fig. 3 is a view taken along the vertical axis of the crystal and showing the bowed spring construction.

Fig. 4 is a greatly enlarged fragment of a mounting sprin showing means for attaching the same to a terminal post.

Fig. .5. is a view similar to Fig. 9. second embodiment of the present invention.

Fig. 6 is an enlarged view showing a portion of the encircling spring band and its engagement with the edge of the crystal.

Fig. '7 discloses the use of insulation which may be employed when the holder is used with crystals having other electrode arrangements.

While the invention is susceptible of various modifications and alternative constructions and uses, I have shown in the drawings and will herein describe in detail one embodiment of the invention. It is to be understood, however, that I do not intend to limit the invention by such disclosure, but aim to cover all modifications and alternative constructions and uses falling within the spirit and scope of the invention as expressed in the appended claims.

Referring more particularly to the drawings the improved holder indicated generally at l0 (Figs. 1 and 2) Will be seen to include a base H having upstanding terminal posts l2, l3 thereon. The latter are brought out to a pair ofprongs I5, 16 for plugging into a conventional type Normally the crystal is protected by a 15 which may also includes trimming if desired. The means for connect- 2, 13 to a crystal indicated generally at 18, forms the subject matter of the present invention. It will be helpful in the discussion which follows to designate the opposed housin capacitor l1, ing the terminal posts I faces of the crystal by the reference numerals I9,

20, the ends of the crystal by 2!, 22, the lateral edges by 23, 24, and the respective corner edges by the numerals 21- 30.

The crystal is provided with two electrodes formed by depositing an adherent coating of 2 but showingmetal in a very thin layer by any desired means. In the particular crystal shown the electrodes are of the wrap-around type in which the electrode occupies a major portion of one face and a minor portion of the opposite face. Thus, the first electrode designated at 3| covers the major portion of the face l9 visible in Fig. 2. However, the lower corners of the electrode are wrapped around the edges 23, 24 at the lower end of the crystal and occupy small triangular areas on the opposite side of the crystal. Similarly, the electrode 32 occupies primarily the face 20, and the upper corners of this electrode are wrapped around the edges 23, 24 to provide small triangular electrode areas on the face I 9. When viewed from the top it will be seenthat the electrode 32 includes all four corner edges 2730 at the upper end of the crystal while the electrode 3! includes all four corner edges at the lower end of the crystal.

In accordance with one of the aspects of the invention a combined contact and supporting member is provided at each end of the crystal for embracing the same, making electrical contact with the corner edges of the crystal. The preferred form of contact member 49 is shown in the top view of Fig. 3, and it will be understood that a similar contact member 4| is used at the bottom portion of the crystal. As illustrated, the contact member 40 is made coiled spring wire. While a number of different metals may be used for the purpose, I prefer to form the contact member of beryllium copper wire with a highly conductive coating of silver. Since the contact member 40 assumes a generally circular condition when unstressed, it maybe conveniently referred to as a garter spring.

Because of the great number of convolutions the garter spring may be extended to accommodate a wide range of crystal sizes without, however, applying undue pressure upon the crystals of larger size. Thus, the pressures exerted at the areas of contact 2l30 will in all cases be sufficiently high to establish good electrical contact without affecting the freedom of the crystal to vibrate internally.

It is to be particularly noted that since the electrode 32 extends around all four of the crystal edges, contact at but one of the corner edges 2l3ll produces a good connection. even better contact is desired, the corner edges may be rounded or bevelled slightly during the course of crystal manufacture in order to enable several successive convolutions of the garter spring to contact the electrode.

It is to be observed that in the practice of the present invention valuable use is made of the bowing of the garter spring between the points of contact. Thus, it will be noted that while the central portions 40a, 40b of the spring extend generally along the crystal faces, they are bowed outwardly sufiioiently to clear such faces by a safe margin. In a practical embodiment such bowing has been found sufiicient to prevent the opposite electrode 3! from touching the spring even under severe conditions of vibration and shock.

In accordance with another aspect of the present invention the bowed portions of the spring are used as a resilient mounting. In the arrangement disclosed in Figs. 3 and 4 this is accomplished by twisting together the ends of the spring loop and bringing them out laterally for soldering to a stationary support 44, which in the present instance is formed by the terminal post IS. The lower one of the two garter springs 4| up of a loop of resilient However, if

r of these movements applied is similarly brought out to the terminal post 12 and soldered thereto as indicated at 45 in Fig. 2. It will be apparent upon inspection of Fig. 2 that the springs 48, 4| are kept in a vertically spaced relation by the anchoring arrangement which has been used, and there is no tendency for the springs to walk toward one another even under the severest type of vibration.

It is of interest to note that an extremely effective type of two-point suspension results from the foregoing construction. The crystal may be com sidered as being pivoted for bodily movement about an axis 43 connecting the anchoring points 44, 45, such axis passing through the center of gravity of the crystal. As a result, externally applied shock and vibration may be considered to be applied at the center of gravity of the crystal and any tendency for the crystal to move under such applied force is accordingly minimized.

In the case of shock or vibration having a rotational component, it will be apparent that the two-point mounting shown enables the crystal to move with respect to the holder in all possible directions. The latter may be very simply verified merely by reference to Fig. 3. In the first place, movement of the crystal toward and away from the terminal post is is permitted by variation in the degree of bowing of the portion 40b of the spring. Movement of the crystal from right to left is permitted by compression of the convolutions on one side of the point of mounting and separation of the convolutions on the other side. Further movement of the crystal in and out of the drawing as viewed in: Fig. 3 is enabled by the upward and downward bowing of the central portion 40b of the spring. In general, shock or vibration will consist of a combination of all three at both the upper and lower points of mounting. Tests of great severity, made in an attempt to destroy either the crystal or the mounting, have shown that the resistance to damage is far in excess of any comparable crystal holder previously known, and it was found that substantially no variation in frequency occurs even at vibration amplitudes far in excess of those which would be normally encountered in use.

Attention is next directed to Figs. 5 and 6 which show an alternative embodiment employing a slightly modified spring construction and possessing modified shock characteristics. Wherever possible, corresponding numbering has been used. In this modification instead of using a coiled or garter-type spring a leaf spring is used designated at 48. Such leaf spring may consist of a loop of beryllium copper having central portions 48a, 48b and end portions 48c, 48d. The ends of the resilient band are brought out to the terminal posts l2, l3 and respectively soldered thereto at points 45, 44. Just as in the previous embodiment, the points of mounting preferably lie on an axis 46 which passes through the center of the crystal, and thus the characteristics of the modified holder are generally similar to that previously discussed.

Since the band 48 does not include spaced convolutions enabling relative edgewise vibration of the crystal with respect to the sides of the holder, this function is to a large extent performed by the flexible tabs 50, SI which connect the spring loops to the terminal posts. Operation of the coil spring can be approached, however, merely by providing a series of accordion-like pleats in the central portions of the band as indicated at 52.

In operation the band 48 is formed so that its major diameter is considerably shorter than the width of the crystal. Upon inserting the crystal the loop is squeezed to elongate it, whereupon the crystal can be readily inserted. Due to the resilient nature of the band 48, firm electrical contact occurs at the corner edges 21, 28 of the crystal. If desired, as a still further modification, the portion 48a of the band may be removed by severing at points 54 to form a more or less C-shaped spring as distinguished from the complete loop. The latter alternative is not preferred, however, since the engagement with the crystal is not as secure as that obtained in the previous two embodiments and since there is some possibility that unlike pressure will be developed at the corner edges 2l-30. In addition, use of a C-shaped spring requires that a heavier and consequently less resilient band be used in order to obtain sufficient pressure at the points of contact.

Crystal holders constructed in accordance with the present invention have been employed with all types of crystal cuts conventionally used, particularly the types AT and BT. Regardless of type of cut it has been found that internal vibration may take place along all three of the mechanical axes of the crystal, or along angularly arranged planes in the shear mode, with substantially no restraint. Consequently, it is possible to work a crystal at a higher current than is feasible with conventional types of holders without danger of fracture or other damage.

While the invention has been specifically discussed in connection with wrap-around elec trodes, it will b apparent to one skilled in the art that the invention is likewise well adapted for use with crystals having electrodes of the more conventional type in which the electrodes of opposite polarity completely cover the respective faces. For example, if it is desired that the spring loop 46 of Fig. 3 be isolated from electrical contact with any of the corner edges 27-30, it is sufiicient merely to insulate such corner by insertion of a small amount of suitable insulating material between the contact member and the crystal. This is indicated at 56 in the fragmentary view of Fig. '7 and is obviously applicable to the construction shown in Figs. 5 and 6 as well. The insulating material should be such as not to dampen the vibration and may, if desired, be dispensed with by the simple expedient of not allowing a metal layer to extend into the area of physical contact with the spring loop of opposite polarity.

The foregoing crystal holder in any one of its modifications may be very inexpensively constructed from commercially available spring elements and without necessity for special jigs or fixtures. Due to the large range through which the springs may be extended, the contact member readily adapts itself to crystals of a wide range of sizes and shapes, and the number of holders which must be kept in stock is correspondingly reduced.

I claim as my invention:

1. In a crystal holder for use with crystals having metalized electrodes of the wrap-around type in which one of the electrodes extends around opposite edges of the crystal at one end thereof, the combination comprising a closed smoothlycurved spring loop adapted to encircle said crystal for engagement with said opposite edges, said loop having bowed portions adapted to extend along the opposed faces of said crystal and out of contact therewith, and a support member at tached to one of said bowed portions at the center thereof for the resilient support of the crystal against the effects of shock and vibration.

2. In a crystal holder for crystals having metalized electrodes of the wrap-around type enabling edge contact, the combination comprising a pair of contact loops adapted to encircle said crystal for contact with the edges thereof, said contact loops each including tension means for constantly urging said loops into firm electrical and mechanical contact with the crystal edges, and support members connected to said loops, the points of attachment to said loops being symmetrically arranged with respect to the center of gravity of said crystal.

3. In a crystal holder for use with crystals naving metalized electrodes providing contact at the crystal edges, the combination comprising a garter spring encircling said crystal and in firm electrical and mechanical contact therewith at the crystal edges and terminal means connected to said garter spring for establishing electrical contact therewith.

4. In a crystal holder for use with crystals having metalized electrodes of the wrap-around type enabling electrical contact at the crystal edges, the combination comprising, a pair of terminals, contact posts extending upwardly from said terminals in spaced relation to provide space for mounting a crystal therebetween, crystal contact springs formed of closed loops of resilient metal for the encircling engagement of the upper and lower ends respectively of an inserted crystal and having portions bowed outwardly from the faces of the crystal, and a resilient connection between said contact posts and the outwardly bowed portions of the springs adjacent the opposite faces of the crystal to provide a floating type mounting for said crystal.

CLIFFORD O. KUEHL.

REFERENCES CITED UNITED STATES PATENTS Number Name Date Bokovoy June 8, 1943

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