US2437914A

US2437914A - Quartz oscillator plate

Info

Publication number: US2437914A
Application number: US568328A
Authority: US
Inventors: Frondel Clifford
Original assignee: REEVES ELY LAB Inc
Current assignee: REEVES ELY LAB Inc; REEVES-ELY LABORATORIES Inc
Priority date: 1944-12-15
Filing date: 1944-12-15
Publication date: 1948-03-16
Anticipated expiration: 1965-03-16

Description

16, 1948. Q pfio 2,437,914 7 QUARTZ OSCILLATOR PLATE I Filed Dec. 15, 1944 INVENTOR CLIFFORD FRONDEL ATTORNEYS Patented Mar. 16, 1948 2,437,914 QUARTZ OSCILLATOR PLATE Clifiord Frondel, Flushing, N. Y.,

Reeves-Ely Laboratories, Inc., New York,

a'ssignor to N. Y.,

a corporation of New York Application December 15, 1944, Serial No. 568,328

16 Claims.

This invention relates to quartz oscillator plates and has for its object certain improvements in the method of manufacturing oscillator plates made of quartz or equivalent material.

In the manufacture of so-called BT quartz oscillator plates, for example, automatic or semiautomatic machines are generally employed in the initial and intermediate states. The final finishing of the plates is, however, still largely a hand operation, the work being done by highly skilled operatives, usually called finishers. In finishing the plates, physical dimensions of the order of sub-millionths of an inch are involved. The finisher is usually provided with a frequencychecking device, a flat glass plate, fine abrasive, an etching solution, water, a brush, cleaning solutions, lint-free towels, a micrometer, an optical fiat, a small square, etc.

The finisher receives the plates, sometimes called blanks, as they come from mechanical lapping machines, the plates having been cut to substantially proper length and width and usually brought close to, but less than, the desired oscillating frequency. In a plate desired to have a final frequency of, say, 8,000 kc., the machine lapping or other pre-hand-finishing treatment is stopped when the plate is from roughly a few hundred cycles up to ten or more kilocycles under the final desired frequency. A preliminary frequency check is then made by comparing the frequency of the plate with that of a standard plate having a known frequency. This gives the finisher a general idea how much hand lapping the plate should be given. To reduce the plate to its proper thickness, and hence to increase its frequency, the finisher grinds the plate in a mixture of the abrasive and water on the flat glass plate, keeping the faces of the plate as fiat and parallel as possible. The plate is next thoroughly cleaned and dried, after which its frequency is again tested. This is done by inserting the carefully cleaned plate in a holder, plugging the holder into an oscillator circuit and noting whether or not the plate has reached the desired oscillating frequency. The lapping of the major plane surlater-plate industry. Thus, in the so-called aciddip or etching process, the plates as obtained at the completion of the machine lapping are brought up to the desired frequency by dipping them for the required length of time into a solvent for quartz. This solvent, which may be, for example, hydrofluoric acid, removes quartz from the surface of the plate and thus acts to reduce the thickness of the plate to the desired value. This process, as with hand lapping, requires an intermittent, successive, series of treatments and measurements, especially in the final stages, to ensure that the desired frequency is exactly attained. The rate of etching of different plates of the same initial frequency is not identical, due to variations in the cleanliness of the surface, the roughness of the surface, and other factors, so that a uniform, timed, procedure for all plates can not be set out. In still another method of finishing plates to the desired frequency, the plates are tumbled with an amount of coarse abrasive in a container until the frequency apfaces of the plates usually is accompanied by a Y lapping or beveling of the edges of the plates; this operation, by removing roughness and other imperfections from the edges and by altering the edge dimensions, gives the desired degree of activity. so-called, to the plate.

The finishing of a plate to its desired frequency also may be accomplished in other ways, and a number of techniques other than hand lapping have been and are being developed in the oscilproaches that desired. The plates are then removed, cleaned, and are adjusted to the desired frequency either by etching or hand lapping.

Alternate hand lapping, cleaning and testing are required until the plate reaches the desired frequency. The activity of the plate is determined by its dimensions, contour, parallelism, absence of flaws, cleanness, etc. These physical characteristics are checked, changed, and rechecked until the desired activity is obtained. The frequency of the plate changes with changes made to the plate to obtain the desired activity, so that the finisher must coordinate the numerous variables going into the finishing operation to obtain a combination of conditions that yields a plate of predetermined activity and frequency.

Hand finishing by these methods of the oscillator plates is a tedious, slow, delicate and costly operation at best and leaves much to be desired. The human factor is an exceedingly important element in these finishing operations and the results obtained tend naturally to vary from person to person,

technique employed at the timejby each finisher.

depending upon the particular As a result of my investigation I have discovered that the frequency and certain other characteristics of piezo-electric bodies may be adjusted or varied without altering the physical dimensions of the body, such as by grinding, etching r plating with a metal or other material. The frequency of oscillation of quartz oscillator plates, for example, may be varied continuously and this variation may bebrought under continuous visual control as by an appropriate meter. This permits the frequency to be adjusted exactly to a predetermined value or range merely by following the frequency variation on a meter and stopping the treatment at the desired value or within the desired range. This is not possible in present methods of manufacture of piezo-electric bodies which, as noted above. involve a discontinuous alternatlng process of grinding or etching. cleaning and testing. The frequency of oscillation of quartz oscillator plates may, for example, be readily adiusted to a desired value with an accuracy up to 1 cycle or greater, depending primarilyontheaccuracyofthemcasuringdevice employed. 'rhis accuracy cannot be accomplished by the conventional method of grinding or etching because the amount of grinding or etching on which the change of frequency and accuracy depends cannot be accurately controlled or meassured. and the change in frequency itself cannot be observed continuously. I

The frequency of a piezo-electric body that has been put into a relatively stable state by means of baking, etching with a solvent for quartz, or other treatment. such as for the purpose of eliminating or reducing spontaneous variation with time in the frequency or activity of the piezoelectric body, can be adjusted without destroying the stability of the piezoelectric body. This is not possible by present methods of manufacture. For example, if a number of quartz oscillator 4 comprises the step of treating quarts oscillator plates to the action of cathode rays (electrons) adapted to decrease their frequency of oscillatim.

plates are brought by grinding or etching to a desired frequency, and are then baked or otherwise treated. for the P pose of stabilization, it is foimd that the frequency often changes erratically from the original value and must then be adjusted by additional grinding or etching. This action then destroys the stability of the oscillator plate and the purpose of the original stabilizing operation is lost. This readjustment can now be accomplished without grinding or etching and without loss of stability.

The frequency of oscillator plates may be adiusted, for example, without wetting them with water or other liquids and in an entirely dry condition. Water is commonly used in the conventional method of finishing to frequency by lapping with an abrasive or by etching, and has been considered to contribute substantially to undesirable ageing and other phenomena in the finished oscillator plate. This dimculty may now be obviated.

The frequency of a piezo-electric body can be adJusted while it is contained in its permanent holder, whether this is of the contact (pressure), air gap, wire suspension or other type of mount. If desired, the frequency of the piece-electric body may be adiusted before it is mounted in its permanent holder.

The change in frequenc brought about by application of the invention is downwards from the initial value, but the downwards change may be reversed. and the frequency restored to its original value, by suitable treatment. The new technique is advantageous in the recovery of oscillator plates that have been overshot by the methods of hand finishing. Oscillator plates that have increased in frequency over the upper tolerance due to ageing, or aged low activity lates that have gone over the tolerance after cleaning to bring up the activity, may be similarly readjusted to their original frequency.

In accordance with the invention, the method Cathode rays consist of a stream of electrified particles which are n atively charged. As disclosed in my co-pending application Serial No. 568,323, filed December 15, 1944, in mem'actice of the invention quartz oscillator plates were sealed an evacuated cathode-ray tube itself to bring the plates in'oontact with the cathoderays. This method is. however, ineonvmient and an electron-gun type of molmting is preferred In the electron-gun the cathode plate in the evacuated tube is replaced, for example. y I wirefllament which is heated to ce by passinganelectriccurrentthroughit. Abeamof cathode rays is shot down the tube when the filament is joined tothe negative depends on the potential difference between the cathode and the anode in the evacuated tube or electron-gun: and the desired effect may be obtained by controlled bombardment of the oscillator plates. To reduce the frequency of the oscillator plates, th y re placed in the path of the stream of cathode rays as they emerge from the window of the electron-gun. The oscillator platesmaybeplaoedinthecircuitofaf queucr meter, so that the change tahng place may be visually observed and the treatment terminated when the oscillator plates have reached a predetermined frequency, or at least fall within a pre determined frequency range.

The change is frequency produced in oscillator plates by the cathode rays (electrons) is downwards from the original value. The change is progressive and continuous during irradiation but finally reaches a limiting value, determined by factors within the quartz, beyond which there is no further change. The rate of change appears to depend primarily on the intensity of the radiation, but in part on variations in the Properties of the quartz from specimen to specimen and on pre-treatment of the quartz. The continuity of the change is of great importance from a manufacturing point of view. The downward direction of the change is also of particular advantage.

The downward change in i brought about by the cathode rays is permanent under ordinary conditions, but can be revemed and the oscillator plate brought back to its original frequency by baking at a suitably elevated temperature or by irradiating the plate with ultra-violet rays. Ultra-violet rays reverse the action of the other type of radiation. The ability to reverse the downward change is a great advantage, In other words, the oscillator plates may be adjusted downwards and upwards in frequency r peatedly by the proper treatment.

The rate at which the downward change in frequency of the oscillator plates can be effected and the total amount of change is influenced by the temperature at which the quartz is held during irradiation, and by previously baking the quartz at a suitably elevated temperature.

These and other features of the invenflon will be better understood by referring to the accompanying drawing, taken in coniimction with the following description, in which:

Fig. 1 is a ditic representation of a cathode ray (electron) gun showing a quartz oscillator plate positioned before a window for anode terminal l3 and a plurality of anodic defining shields I4, I42. The other end of the tube is provided with a window l5 through which the cathode rays (electrons) l6 may freely pass. A quartz oscillator plate I! is shown in front of the window, the plate being held on a sliding holder l8 movable in an upper track l9 and a lower track 20 by means of a handle 2 l.

Referring next to Fig. 2, the apparatus shown comprises a similar evacuated cathode ray (electron) gun l with a quartz oscillator plate I! located in front of the window i of the tube. in this case, however, the oscillator plate is mounted in a holder 25 of conventional construction. The casing of, and the electrode within, the holder around the oscillator plate are shown broken away, for convenience. The holder is, in turn, connected with a frequency meter 26 by means of a pair of leads 21 and 28. The frequency meter may be of conventional design, having a needle 29 adapted to move back and forth over a graduated frequency scale 30, preferably divided to indicate cycles per second.

When cathode filament I2 is joined to a negative terminal and anode terminal i3 is joined to a positive terminal of a source of direct current (not shown), and such direct current is passed through the filament, it is heated and results in the thermionic emission of the stream of cathode rays (electrons) IS. The cathode rays (electrons) i6 are made to form a beam of desired cross section by means of deflecting shields H,

M, which also direct the cathode rays to and through window i5 onto quartz oscillator plate ii. The effect of the cathode rays (electrons) on the oscillator plate is gradually to decrease its frequency of oscillation. The bombardment of the oscillator plate with the beam of cathode rays may be conducted until the oscillating characteristics of the oscillator plate fall within a predetermined range or reach a predetermined value.

When using apparatus such as that disclosed in Fig. 2, the predetermined frequency range or value may be noted visually on frequency meter 26. When needle 29 is deflected until it points at the desired frequency or frequency range indicated by scale 30, the oscillator plate is taken out of the beam of cathode rays or the beam of cathode rays is shut off.

The rate of change of frequency during irradiation is rapid, at first, but drops off with time and distance, finally to approach a limiting value. The magnitude of the limiting value varies with different specimens of quartz. This variation, which in the extreme cases so far encountered is about tenfold, appears to depend primarily on a predisposing feature in the quartz itself. The actual rate of change in frequency in a given oscillator plate varies with the conditions of treatment, and primarily with the intensity of radiation. The decrease in frequency during irradiation is accomplished with little, if any. significant change in activity.

As previously noted, the frequency of quartz oscillator plates also undergoes a change when the plates are treated with ultra-violet rays; the change in frequency, however, being upwardly tions.

instead of downwardly. Oscillator plates irradiated as described above in order to decrease their frequency may be reverted in frequency to their initial value when exposed, for example, to a powerful quartz-mercury lamp. The'change is accelerated by heating the quartz oscillator plates to 150 C. during irradiation with the ultra-violet rays.

The use of ultra-violet rays offers an impor tant advantage. If for some reason the frequency of an oscillator plate should be decreased too much by the other type of radiation disclosed.

.its frequency may be increased to the desired value. The use of ultra-violet light rays is more particularly described and claimed in my copending application Serial No. 568,330, filed December 15, 1944.

It will be clear to those skilled in this art that the invention lends itself to numerous modifica- The oscillator plates may be irradiated whether plated or unplated, coated or uncoated. In accordance with the invention the oscillator plates may, for example, be plated with a metal such as gold, silver, aluminum or an alloy which may serve the purpose of making a better or more intimate electrical contact with or act as electrodes; or which may serve as a protective or stabilizing films. The plates may, for example, be coated with amorphous silica or organic plastic or other material which may serve the purpose of protective or stabilizing films. In the case of oscillator plates that have been protected or stabilized by a plating, coating or other treatmerit, including heating and ageing, the radiations herein contemplated are adapted nevertheless to modify the oscillator plates so as to vary their oscillating characteristics; and irradiation of the plates may be conducted until their frequency of oscillation reaches the desired value without substantial loss of stability. The plates may be adjusted upwards or downwards in frequencyrepeatedly by use of the proper radiations.

It also is possible to adjust the plate to have a desired frequency at a given temperature by irradiating the plate, and bringing it to frequency, while it is held at that temperature in a suitable heating or cooling contrivance. This is not easily accomplished by the conventional lapping or etching techniques of finishing plates.

The rate of change of frequency of the plate during irradiation and also the total amount of frequency change that can be obtained (saturation value) can be modified by baking the quartz plate at a suitable temperature before it is irradiated. Thus, baking the quartz plate at a suitably elevated temperature has been found to increase both the rate of change and the amount of change of frequency over that which would obtain if the plate had not been baked beforehand. The increase in rate brought about by baking between 250 and 350 C. ranges up to two-fold. and there is an accompanying increase so that the change in frequency of oscillation which takes place may be visually observed and the irradiation stopped when the plates have attained the desired frequency. The type of permanmt holder, for example, may be of-the pressure or clamp, air-gap, combined pressure and air-gap, wire-support, mechanically or hermetically sealed, temperature-controlled or temperature protected, or the multiple-type. If the oscil lator plates are mounted in a Permanent holder, the radiations go right through the plastic, glass or metal shell or housing of the holder. A sufficiently penetrating radiation must, of course, be eml w This practice isespecially useful in the case of oscillator plates supported between wire mounts in thin-walled vacuum holders. If the oscillator plates are not .mounted in a holder, they may be held, for example, in paper or aluminum foil envelopes which protect them from moisture, dust and grease spots from handling.

It also is convenient under certain circumstance; to irradiate a large number of plates simultaneously. This can be done, for example, y stacking the plates together and placing the stack directly in front of the window, face on. line amount of frequency change thus brought about is not uniform through the stack, but is greatest in the first plate, considerably less in the second, and then decreases more slowly in succeeding plates.

While the practice of the invention has been described with respect to memo-electric material in the form of quartz, it will also be clear to those skilled in this art that the invention is applicable to the treatment of other piezo-electric materials, such as Rochelle salts, tourmaline, tartrates, etc. The invention is applicable to the treatment of any useful pieao-electrl material the frequency and oscillating characteristics of which are to be varied under controlled conditions.

I claim:

'1. In the manufacture of quartz oscillator plates,]the hnprovement which comprises treating each oscillator plate with cathode rays adapted to decrmse its frequency of oscillation.

2. In the manufacture of quartz oscillator plates, the improvement which comprises treating each oscillator plate with cathode rays adapted to decrease itsfrequency of oscillation, and terminating the treatment of each plate with said cathode rays when its frequency of oscillation reaches a undetermined value.

3. In the manufacture of quartz oscillator plates, the improvement which comprises treat-- ing each wclllator plate while mounted in a holder connected to a frequency meter to the action of cathode rays adapted to decrease the frequemy of oscillation of the plate, and terminating the treatment of each plate with said cathode rays when its frequency of oscillation reaches a predetermined value.

4. In the manufacture of quartz oscillator plats, the improvement which comprises treating each plate while mounted in a holder connected to a frequency meter to the action of cathode rays adapted to pass through the housing of the holder and to decrease the frequency of oscillation of the plate, and terminating the treatment of each plate with said cathode rays when its frequency of oscillation reaches aprevalue.

5. In the manufacture of quartz oscillator plates, the improvement which comprises treating each plate while at a predetermined temperature 8 with cathode rays adapted to decrease its frequency of oscillation, and terminating the treatment of the plate with said cathode rays when its frequency of oscillation reaches a predetermined value.

6. In the manufacture of quartz oscillator plates, the improvement which comprises maintaining each oscillator plate at a predetermined temperature while mounted in a holder connected to a frequency meter, treating the plate while at said temperauire with cathode rays adapted to decrease the frequency of oscillation of the plate, and terminating the treatment of the plate with said cathode rays when its frequency of oscillation reaches a predetermined value.

7. In the manufacture of quartz oscillator plates, the improvement which comprises maintalning each oscillator plate at a predetermined temperature while mounted in a holder connected to a meter, treating the plate to the action of cathode rays adapted to pass through the housing of the holder and to decrease the frequency of oscillation of the plate, and terminating the treatment of the plate with said cathode rays when its frequency of oscillation reaches a predetermined value.

8. In the manufacture of quartz oscillator plates, the improvement which comprises grinding each oscillator plate to a thickness beyond that required to increase its frequency to a predetermined value, and treating the ground plate with cathode rays adapted to decrease its frequency of oscillation.

9. In the manufacture of quartz oscillator plates, the improvement which comprises grinding each oscillator plate to a thickness beyond that required to increase its frequency to -a predetermined value, treating the ground plate with cathode rays adapted to decrease its frequency of oscillation, and terminating the treatment of each ground plate with said cathode rays when its fre quency of oscillation reaches a predetermined value.

10. In the manufacture of quartz oscillator plates, the improvement which comprises etching each oscillator plate to a thickness beyond that required to increase its frequency to a predetermined value, treating the etched plate with cathode rays adapted to decrease its frequency of oscillation, and terminating the treatment of the etched plate with said cathode rays when its frequency of oscillation reaches a predetermined value.

11. In the manufacture of quartz oscillator plates that have been stabilized by baking, acid washing or other treatment and that have a frequency of oscillation hisher than desired, the improvement which comprises treating each stabilized oscillator plate with cathode rays adapted to decrease its frequency of oscillation, and .terminating the treatment of each stabilized plate with said cathode rays when its frequency of oscillation reaches a predetermined value.

12-. In the manufacture of quartz oscillator plates, the improvement which comprises treating each plate to the action of cathode rays adapted to decrease its frequency of oscillation, treating the plate to the action of ultra-violet light rays adapted to increase its frequency of oscillation. and terminating the treatment of the plate with the ultra-violet rays when its frequency of oscillation reaches a predetermined value.

13. In the manufacture of quartz oscillator plates, the improvement which comprises heating each plate to an elevated temperature to sensitize it to frequency change, treating each sensitized plate to cathode rays adapted to decrease its frequency of oscillation, and terminating the treatment of each plate with said cathode rays when its frequency of oscillation reaches a predetermined value.

14. In the manufacture of quartz oscillator plates, the improvement which comprises heating each plate to an elevated temperature to sensitize it to frequency change, treating each sensitized plate to the action of cathode rays adapted to decrease its frequency of oscillation, treating the plate to the action of ultra-violet light rays adapted to increase its frequency of oscillation, and terminating the treatment of the plate with said ultra-violet light rays when its frequency of oscillation reaches a predetermined value.

15. In the manufacture of quartz oscillator plates, the improvement which comprises heating each plate to an elevated temperature to sensitize it to frequency change, treating each sensitized plate to the action of cathode rays adapted to decrease its frequency of oscillation, heating the plate so treated to increase its frequency of oscillation, and terminating the heating of the plate when its frequency of oscillation reaches a pre determined value.

16. In the manufacture of oscillator plates the step comprising reducing the frequency of the oscillator plate by treating the same with cathode rays.

CLIFFORD FRONDEL.