US2589246A - Oscillator - Google Patents

Description

OLJHMM HUJL H. H. GRIMM OSCILLATOR arch 18, 1952 3 Sheets-Sheet 1 Filed Dec. 29, 1944 INVEN TOR. #[MV 6. aim/)7 BY W mam- H. H. GRIMM March 18, 1952 OSCILLATOR 3 Sheets-Sheet 2 Filed Dec. 29, 1944 March 18, 1952 H. H. GRIMM 2,589,246

OSCILLATOR Filed Dec. 29, 1944 :s Sheets-Sheet s Patented Mar. 18, 1952 OSCILLATOR Henry H. Grimm, Dayton, Ohio, assignor to the United States of America as represented by the Secretary of War Application December 29, 1944, Serial No. 570,421

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) 3 Claims.

The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

The invention to be hereinafter described relates to wide range cavity oscillators.

In oscillators of this general type one serious objection and disadvantage has been a high noise level during tunin of the oscillator due, primarily, to engagement of the sliding contacts. In known oscillators of this type it has been common practice to use what is known as the double concentric cavity construction involving a considerable number of parts with total considerable length and corresponding complexity of adjustments. In the known oscillators of this general class there are serious restrictions controlling the tracking of the feed-back capacity with I and I0.

the main capacity, as the feed-back capacity needs to be increased as the resonant frequency decreases to insure that the oscillator output does not cease at low frequencies.

The main objects of the present invention are to overcome the above and other objections and disadvantages and provide a simple, efiicient, compact, wide range cavity oscillator of few parts and capable of relatively low cost production.

In order to more clearly disclose the construction, operation and use of the invention, reference should be had to the accompanying drawings forming part of the present application.

Throughout the several figures of the drawings like reference characters designate the same parts in the different views.

In the drawings:

Fig. 1 is a longitudinal cross section through a preferred form of the invention;

Fig. 2 is a like view through a modified form;

Fig. 3 is a circuit diagram through the invention, in the modification; and

Fig. 4 is a like diagrammatic view showing the circuit through the preferred form.

Referring to the drawings in detail, I indicates the wall or barrel of the oscillator in which the cavity exists. The opposite ends are closed by heads 2 and 3. Beyond the head 2 and suitably supported thereon is a cylindrical section, frame or other suitable support or guide 4. Frame 4 carries a block or head 5 in which is removably mounted the bearing block or head 6, of rod I5.

From the base 3 a stub I extends longitudinally toward head 2 concentrically within the cylinder I. The upper portion of this stub is tapered or conical, the top being cut off on a plane parallel with the base, producing a frustum 8. Coopcrating with frustum 8 is the movable cup 9. Cup 9 comprises a head mounted to travel longitudinally back and forth within I. Cup 9 is of very slightly less outside diameter than the inside diameter of I. It is provided with a skirt or wall I0 perpendicular to its base. In assembled, operative position, this skirt will be, as shown, concentric with but very slightly spaced from the adjacent wall of I. There will be no actual physical contact between the surfaces of This reduces to the minimum the noise during tuning of the oscillator.

Concentric with skirt I0 is a cylindrical block in which is provided a socket or well II the lower inner portion of which has dimensions substantially the same as corresponding dimensions of the frustum 8. The adjacent and cooperating surfaces of 8 and II are substantially complementary.

In order to travel the cup 9 longitudinally within the cylinder I toward and from the stub I, a stem, post or tube I2 is connected thereto concentrically thereof. This tube has sliding longitudinal movement centrally in and through the head 2, but is held against rotary movement therein by a spring pressed detent or any other suitable device I3 working in a longitudinal groove HI in I2, in well known manner. For reciprocation of tube I2, the upper portion thereof is interiorly screw threaded to receive the cooperating threaded rod I5. This rod is not threaded through the bearing block or head 6 but, instead, is integral therewith and both the rod and the bearing block rotate as a unit relative to head 5. Shaft I5 and bearing block or head 6 are held yieldingly in place by leaf springs 25 or the like. By rotating rod I5 by a knob or any other suitable means not shown, the lateral distance or air-gap between II and 8 may be varied as may be desired. Also, and at the same time, the effective lengths of the overlapping walls or surfaces of 8 and II may be correspondingly varied, all for purposes well understood in the art. By adjustment of the tapered surface I I relatively to the tapered surface 8 the lateral distance between the two may be reduced to two or even one thousandth of an inch which makes it possible to control or regulate the capacity over a wide range and with a fine degree. However, mechanical difiiculties in manufacture make efforts at this extreme adjustment inadvisable. The tolerances necessarily permissible in manufacture result in irregularities which, at such extreme adjustment, result in actual contact or pacitor.

such near contact, relative to other portions of the cooperating surfaces 8 and II, as will render inoperative the capacitor 8-| I. However, within the practicable range of adjustment, the capacitor 8-|| is capable of giving much finer control and better results than other constructions for the same general purpose.

As will be readily understood, the cylinder I and. skirt ID, in spaced relation, provide a construction and arrangement capable of acting as a condenser of fixed capacity which may serve or function as a radio frequency by-pass.

To complete the assembly as an oscillator, a triode tube, indicated as a whole by IT, is suitably mounted in the cavity between 9 and 3. This tube may be one of several known types such as that generally referred to as the lighthouse type tube or that known as the acorn type. As illustrating the invention, the lighthouse type has been selected and is indicated, generally, at H. Should the acorn type be substituted for the lighthouse, those skilled in the art will readily understand that the tube capacities themselves supply sufficient feedback, requiring no such feed-back arrangement as that advisable with the lighthouse type. The tube plate is connected to the power supply (B+) and to a by-pass condenser. The other side of the by-pass condenser is connected to the stub 1 and through it to the variable capacitor.

In the preferred construction, a lighthouse tube I! being used, a variable feed-back condenser is included, comprising a small capacitative tab |8 fixed at its outer end to the framework supporting the tube. It is resilient. Its inner free end is yieldingly adjustable toward a plate l9 which is mounted on stub I. A threaded and insulated rod or a rod 20 of insulating material extends through head 3 and engages the under side of I8. Thus the free end of l8 may be yieldingly forced toward l9 but will return to its originally greater spaced relation therefrom as soon as the force on 20 is removed. As will be well understood, 8 and I9 constitute an external variable feed-back condenser for tube l1. With the variable capacitor 8-| I in a given relation or position, the plate 18 may be manually adjusted to properly effect the desired corresponding feed-back. Thus, the feed-back is variable and adjustable. However, it must be changed for the respective changed relation between 8 and In Fig. 2, a modification is illustrated including a variable feed-back condenser, automatically operated, the variation in the feed-back corresponding with the variation in the variable ca- In this form, plate |9 is omitted and a filament lead is substituted for rod 20. The variable feed-back condenser in this modification operates automatically and in such manner that its operation changes in accordance with the variation of the variable capacitor 8-| I. It consists of two stationary spaced plates 2| and 22 and the movable plate 23. Plate 2| is carried by a rod, bar, strip or other suitable support passed through the wall of and connected to ance to the travel of 9. It is so positioned as to extend between plates 2| and 23. As it is moved back and forth between 2| and 22 by travel of 9 it will have the same condenser effect or action as obtained by movement of tab l8 relatively to plate IS in the preferred form. However, a very important feature of difference between the two types of variable feed-backs results from the fact that plate 23 producing the variation in the modification is, carried by and travels with cup 9 of the variable capacitor 8| As a result of that relation, the variation in the feed-back will, approximately, correspond with the variations in the variable condenser 8-, thereby giving a wider frequency range without feed-back adjustment.

As will be clear from the drawings of the modified form, particularly as indicated in the diagram, all leads to the oscillator are brought in at the shorted end of the stub which makes up the inductance of the resonating circuit.

Referring particularly to Fig. 3 the oscillator, briefly, is what is known as a grounded grid untuned cathode oscillator circuit. It may be traced in the diagram of Fig. 3 substantially as follows: The tuned circuit inductance consists of stub I, head 3 and the wall The variable capacitor consists of adjacent surfaces 8| The radio frequency by-pass condenser consists of skirt HI and wall I. The blocking and radio frequency by-pass condenser |0|l isolates the plate voltage from the metal structure of the cavity. The grid condenser |0| is built in the side of the cavity. Chokes I02 and I03 are required in the cathode and filament leads of the grounded grid oscillator, as will be well understood. The variable feed-back capacity is shown at 2|22. The tube used in this diagram is a lighthouse triode.

Fig. 4 is a schematic diagram of the preferred embodiment illustrated in Fig. 1. Fig. 4 is essentially the same as Fig. 3 except that instead of the feedback capacitor 2|-22 of Fig. 3, there is shown the feedback capacitor |8--|9 which is not automatically operated, but is manually operated to perform the same function as capacitor 2|22. In all other respects both circuits operate in the same manner.

It is thought that the construction, operation and use of the invention will be clear from the preceding detailed description.

Changes may be made in the construction, arrangement and disposition of the several parts of the invention, within the scope of the appended claims without departing from the field of the invention and it is meant to include all such within this application wherein only a preferred form and one modification have been disclosed by way of illustration and with no thought or intent to, in any degree, limit the invention thereby. i

Having thus described my invention, what I i claim and desire to protect by Letters Patent is: 1. A cavity oscillator including a cylindrical 65, b dy, a first member connected to and forming a closure at one end of said cylindrical body, said first member being provided with a stationary stub extending within said cylindrical body concentrically therewith, said stub having a conical surface on the end thereof, connecting means disposed within and insulated from said stub, said connecting means cooperating with said stub to form a coupling condenser having a low reactance to the radio frequency energy generated by said oscillator, an electron tube having QLHHLJH MUUL a cathode, an anode and a control electrode, means insulated from said stub for connecting said anode to said connecting means, means for connecting a source of space-current voltage between said connecting means and said first member, a first condenser element connected to said control electrode and arranged in spaced relationship with respect to said cylindrical body, a second condenser element connected to said anode, a third condenser element connected to said cathode and arranged in spaced relationship with respect to said second element, a second member longitudinally movable within said body relative to said stub and provided with a fourth condenser element cooperating with the conical surface of said stub, said second member also carrying a cylindrical flange in spaced relationship to said cylindrical body to form a fixed condenser, and means for moving said movable 3. A cavity oscillator according to claim 1, wherein said tube is disposed with the top thereof within said cylindrical body and adjacent to said stub, the axis of said tube being substantially perpendicular to the axis of said cylindrical body, said tube having an anode terminal on the top thereof, and wherein said means for connecting said anode to said connecting means includes a cap connected to said anode, said cap including a stud passing through and insulated from said stub and contacting said connecting means.

HENRY H. GRIMM.

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

UNITED STATES PATENTS Number Name Date 2,223,835 Smith Dec. 3, 1940 2,248,227 Gantet July 8, 1941 2,328,561 Lavoie Sept. 7, 1943 2,408,355 Turner Sept. 24, 1946 2,435,442 Gurewitsch Feb. 3, 1948 ,438,832 Turner Mar. 30, 1948 2,443,907 Gurewitsch June 22, 1948 2,458,650 Schreiner Jan. 11, 1949

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