US2468537A - Ultra high frequency vibrator - Google Patents

Description

H. BENIOFF ULTRA HIGH FREQUENCY VIBRATOR Filed July 23, 1945 INVENTOR. 'Huso BENIOFF Hll H N ll FIG. I

Patented Apr. 26, 1949 2,468,537 ULTRA HIGH FREQUENCY VIBRATOR Hugo Beniofl, Pasadena, Calii'., assignor, by mesne assignments, to Submarine Signal Company, Boston, Mass, a corporation of Delaware Application July 23, 1945, Serial No. 606,498

' 6 Claims. (01. 25942) 1 The present invention relates to an ultra high frequency vibrator used principally for vibrating liquids. More particularly in the present inventiona small volume of liquid is vibrated within a container which is particularly adapted to fit into the vibrator andhave an intimate acoustic coupling with the vibrating surface.

The vibrator in the present invention maybe formed as a piezoelectric crystal of quartz, or other suitable piezoelectric materials may be used producing vibrations over a uniform surface which is covered with a liquid film forming acoustic contact with a very thin membrane. The membrane may alsobe covered with a liquid in which the container holding the liquid substance to be ilbrated is placed. The device is preferably operable at very high frequencies with comparatively high power and it may be built in varying sizes for vibrating small test samples or larger quan ties for industrial production purposes.

"The invention will be more fully described in the specification attached when taken in connection with the drawings showing an embodiment of the invention in which:

Fig.1 shows a plan view of the device with fragmentary portions broken away;

Fig.2 shows a section taken on the line 2--2 of Fig. ,3.

Fig. 3 shows a section taken'on the line 3-3 ofFig; 1;

Fig. 4 shows a detail of the piezoelectric oper--.

ating element;

Fig. 5 shows a section on the line 5-5 of Fig. 4; and

Fig. 6 shows a circuit diagram of the device of Fig. 1.

In the arrangement in Fig. 1 the unit as assembled may comprise a wooden base I on which stands a casing or cover 2 which is preferably made of copper or other shielding material. A copper shield partition 3 within the casing 2 separates the upper part of the casing from the lower part in which the tuned power oscillating circuit is positioned. This comprises a transformer 4 with an inner primary coil 5 and an outer secondary coil 6 within which is positioned a copper vane or disc 1 whose position is adjusted by the external knob 8 until a maximum current is indicated on the secondary current meter 9. Both the tuning dial knob 8 and the meter 9 are mounted on a metallic panel ill at the front of the device, the panel also containing th input .plug II to which the desired high frequency cur-' rent is conducted. The transformer 4 is a step up transformer so that the voltage within the device is at a much higher potential than that brought to the device from the outside.

As indicated in Fig. 3 both primary and secondary coils may be wound on insulating forms l2 and I3, respectively, which-may be made of plastic or other suitable material. The secondary of the coil is shunted by a vacuum or mica condenser M of a very high voltage rating. This condenser is mounted on suitable insulating-supports l5 extending from the base of the case.

The vibrating unit itself is. shown in section in Fig. 2. This comprises a piezoelectric crystal vibrating element 20 which has an annular groove 2| in its top face and a substantial heavy ring portion 22 by means of which the crystal is firmly The crystal preferably is of clamped in place. quartz but other suitable piezoelectric material may be used. While the frequency of operation used may be considered high for compressional wave vibration, a frequency of 500 kc. has been found satisfactory.

The bottom face of the crystal is coated with a conductive electrode 23 of gold or other highly conductive material. The center 24 of the crystal element preferably has a surface parallel to a thin diaphragm 25 which'is positioned just above it and separated only from the top of the'crystal by an oil film of very little thickness. The electrode 23 on the bottom face serves as one electrode of the system while the thin diaphragm 25, which may be of Monel metal, or the like, serves as the top electrode acting through the oil film. The lower clamping member 26, which is recessed at the center to leave the bottom of. the piezoelectric crystal free, except at the edges, serves as the conductive connection for the bottom electrode. This lower clamping element is held in place by means of screws 28 inserted from the top of an insulating supporting plate 29 of Lucite, Mycalex, or other suitable material. The screws 28 draw the lower clamping plate 26 tightly against the lower surface of the insulating plate 29 and hold the rim of the crystal element tightly against a shoulder 3li'recessed in the sides of the plate adjacent the central opening 3| in the plate. An outer casing 32 is attached by means of screws 33; or otherwise, to the sides of the clamping plate 26. This cover 32 is made of copper or other suitable conductive material and serves as a conductive path to the crystal electrode through the spring contact 34 connected to the rod 35 in sulated through the glass bushing 33. I serves to conduct heat away from the crystal. At its lower end the rod 35 connects through the conductor 31 to the secondary 6 of the trans- It also former.

or diaphragm 2s. The ring as threads onto the f end of the cylindricaltube 38 and clamps, the

- diaphragm between the-fiangeof the; ring and The top. electrode ",comprising the. Monelmetal thin disc, is retained in place bymeans of metallic sleeve 38 with an inwardly extendingflange extending over therim of the disc providing a free release at this surface of'the crystal in aim-gas or vacuum surroundings; The bellows, with its oil filled chamber 4! connecting with the chamber 44, provides. for expansion of the end of the tube. Both thering andtube are conductiveand preferably are made ofaluminum alloy or some such similar light conductive metal.

The cylindrical tube 38 is flared outward con ically at 40 and merges into a supportingstructurell which has a heavyflange ring 42" by means of which theelement 4| is clamped tight 1y to the rim of the plastic or-Lucite element 29, making a full liquid seal. Aszwill be noted, liquid.

seals are also provided between the piezoelectric crystal element and the top clamping shoulderil as wellas between "the Lucite element 28 and the lower clamping ring 26.

' A liquid bellows element 42 is'attached to the.

bottom of the clamping ring 26, at its outer edge by welding, soft solder, or any other suitable method. A passage is also drilled through the insulatingplate 29. connecting the inside of the bellows with the chamber M formed between the f element and the insulating plate. This chamber 44, the inside of the bellowsvand the entire surface of the crystal element is filled with oil, i

I preferably a good insulating oil. A second chamber is formed above thediaphragm .25 within the hollow cylinder 39 and its flared out conical ertion 40. This second chamber 45 is filled with a "liquid which may be, the same as the. insulatins oil in the chamber 44.

The supporting structure 4| is provided with an inwardly extending horizontal flange, and

also with an upwardly extending wall 41 adapted to receive a cylindrical cover it over its top and side surfaces. The inwardlyextending flange 40 serves as a support for the container 48' which is provided. with a shoulder 49 adapted to rest oil produced'by heat generated in unit. It will also be noted that vibrational energy may be transmitted not only throughthe bottom of the container but also through the side walls by means of the liquid contact of the chamber ll.

The device herein described may be used for testing purposes by putting samples of the aubstances to, be tested within the container 48'.

.Ihe'se preferably should be liquid but other types or materials, such as plastics, semi-plastics. or 15 r even solids, may be similarly tested by immersing the materials in the container. I Having now described my invention, I claim:

l. An ultra high frequency vibrator compris ing a piezoelectric crystal having a rear surface and a. front-surface, a gas confining container covering said rear surface whereby said rear surface maybe exposed to a gasor vacuum medium,

said front surface covered with a liquid medium and a container in intimate contact with the liquid medium. l

2. An ultra high. frequencypiezoeiectric crys tal vibrator having a conducting electrode attached to one face of the vibrator and another electrode comprisinga thin conductive membrane insulatedly mounted "with respect to the first-mentioned electrode'n'ear the other face of the 'vibratorand having onlyan oil'film between it and said otherfalce of the vibrator, and'acon- I tainer positioned adjacent said membrane and a against the flange it. The top part ofthecover I is perforated also to make a free fltfor the container 48'. The container 48" is removable and preferably is provided witha thin lower wall II and a thin bottom diaphragm ll. The con-, tainer also may be covered by a cover "with one or more vent holes 53.

The top diaphragm ",which serves as the secondelectrode, is electricallyconnected through the supporting platefiorgstructure 4| which may begrounded to the case through a supporting second liquid medium acting between. said'mem- .brane and said container. l l l 3. An ultra high frequency vibrator compris 'ing a piezo, electric crystal plate, a conductive electrode positioned in parallel relation to said plate, near one face thereof, having only an oil film between the electrode and said face of the plate, means on the other side of said electrode from said plate forminga liquid chamber over said electrode having means supporting a container and said container having the bottom thereof immersed in said liquid chamber,

4. An ultra high frequency vibrator comprising a piezoelectric crystal plate having a top surface and a bottom surface and a thin compliance rim, a gas confining containerqcovering said bottom surface whereby said bottom surface may be exposed to a gas medium, an oil chamber formed on top of the piezoelectric crystal plate, a conprises the transformer, the shunting condenser and the crystal oscillator. The vibrations gen! erated by the crystal oscillatorwill be transmitted through the thin oil film between the top. surface the short liquid pathbeneath the bottom ii of the container 48' effectively providing an acoustic coupling for transmitting acoustic vibrations to the liquid 60 within the container 40;. i

It will be noted that the lower surface or elec- 1 of the crystal and the diaphragm 25 and through ductive electrode positioned parallel to the piezoelectric crystal platenear said top surface and having only an oil film of said chamber between i the electrode and the plate, a second oilchamber formed over said electrode, a container havin the substance to be treated positioned in said second chamber over the electrode and means for supporting said second container in said chamber.

clamped at its edge and free around the rest of the surface of the plate, an oil chamber formed above the plate, an expandable bellows element trode of the piezoelectric crystal is not immersed in a liquid medium but that only the upper surface is in contact with the liquid medium thus positioned beneath said bottom electrode and having a passageway to said; chamber, a membrane forming a thin electrode positioned directly over the plate having an oil film between it and the plate, a second chamber formed over said membrane and a container adapted to bcposi- 5. An ultra high frequency vibrator comprising a piezoelectric crystal plate, an electrodeat the bottom surface of said plate, said plate being 5 tioned within said chamber, said container adapted to contain material to be vibrated.

6. An ultra high frequency vibrator comprising a piezoelectric crystal plate having a thin compliance ring, means clamping the piezoelectric crystal plate beyond said thin compliance ring, one of said clamping members comprising a large plastic non-conductive plate, the other a conductive flanged ring making electrical contact with a bottom electrode of said plate, a liquid chamber formed over said plastic plate, a cover covering said liquid chamber, a thin membrane, means provided within said cover for supporting said thin membrane, said cover and membrane being of conductive material and said membrane being parallel to said plate and sewing as an electrode therefor, a thin film separating said mem- 6 brane from said plate and means formed within said cover comprising a second liquid chamber over said membrane and a container sup- P rted within said second chamber.

HUGO BENIOFF.

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

UNITED STATES PATENTS

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