Dither tuned microwave tube
United States Patent [191 Landau [451 Apr. 8, 1975 DITHER TUNED MICROWAVE TUBE Melvin Landau, Manchester, NH.  
 Varian Associates, Palo Alto, Calif.  
 Mar. 22, 1974 Inventor:  
 Assignee:  
 Filed:  
 Appl. No.:  
 US. Cl. 3l5/39.6l; 315/3955; 315/3977; 332/25; 74/390 Int. Cl. H0lj 25/50 Field of Search 315/3951, 39.55, 39.61, 315/3977; 74/390; 332/25 References Cited UNITED STATES PATENTS Glcnficld 3l5/39.55  
 Chun 315/3961 Hynes et a1 315/3961 Stoke 315/3961 3,731,137 5/1973 Foreman 3l5/39.77  
 Primary Examiner-Alfred E. Smith Assistant E.\&#34;aminerSaxfield Chatmon, Jr. Attorney, Agent, or F irmStan1ey Z. Cole; Harry E. Aine; D. R. Pressman 5 7 ABSTRACT A mechanically actuated tuner of a microwave tube, such as a coaxial magnetron, is driven into reciprocal rectilinear translation relative to the microwave circuit for tuning thereof at a relatively high rate, as of 200Hz, over a relatively wide band of frequencies, as of 250MHz. The tuner is driven via a motorized tuner actuator assembly including a circular rail cam having a scalloped rail on which a pair of followers ride for converting circular motion of one of the members into the reciprocal rectilinear translation of the other which is coupled to the tuning structure.  
 6 Claims, 3 Drawing Figures DITI-IER TUNED MICROWAVE TUBE The invention herein described was made in the course of or under a contract or subcontract thereunder, with the Department of the Navy.  
  BACKGROUND OF THE INVENTION The present invention relates in general to dither tuned tubes and, more particularly, to an improved tuner actuator structure employing a circular rail cam and a pair of cam followers riding thereon for converting rotary motion to reciprocal rectilinear translation of the tuner.  
 RELATED CASES The present invention is an improvement on the invention of copending US. application of R. C. Stoke, Ser. No. 450,964, filed 14 Mar. 1974, now US. Pat. No. 3,852,638, issued 3 Dec. 1974, and assigned to the same assignee as the present invention. The original application discloses and claims a circular cam track with cam follower means riding thereon for converting rotary motion into reciprocal rectilinear translation for actuation of a tuner of a dither tuned microwave tube, such as a coaxial magnetron.  
 DESCRIPTION OF THE PRIOR ART Heretofore, coaxial magnetrons have been dither tuned by means of a tuner actuating mechanism adapted and arranged for converting rotary motion of a motor into reciprocal rectilinear translation of a tuning structure adjacent the microwave circuit ofa coaxial magnetron for tuning thereof. Tuners of this type are disclosed and claimed in US. Pat. No. 3,414,761, issued Dec. 3, 1968; US. Pat. No. 3,441,795, issued Apr. 29, 1969; and US. Pat. No. 3,590,313, issued- June 29. 1971, all assigned to the same assignee as the present invention. These prior tubes utilized an eccentric crankshaft driven by an electric motor for cranking the tuning structure to and fro (dithering same) adjacent the microwave circuit of the tube for dither tuning thereof.  
  It is also known from the prior art to employ a motordriven circular cam track having a scalloped circular cam groove in which to receive a cam follower and rotating one of the cam and cam follower means while affixing the other member to the tuning structure for con verting rotary motion into reciprocal rectilinear trans lation of the tuner. This latter arrangement has the dual advantages of substantially reducing the profile height of the tuning actuating structure while also reducing certain whipping motions heretofore encountered in the eccentric crankshaft type of tuner actuating structure. The circular scalloped cam track and follower arrangement is disclosed and claimed in the aforecited copending US. Patent application Ser. No. 450,964.  
  One of the problems encountered in this prior art arrangement i.e., a circular scalloped cam groove within which the follower means rides is that it is extremely difficult to so precisely dimension the cam track groove or slot such that excessive play does not develop between the cam follower and the scalloped surfaces of the cam track groove. When such play exists, it results in a hammering action between the follower and the guiding scalloped surfaces of the cam track as the reciprocating member changes direction at opposite ends of its travel in its reciprocal rectilinear mode of transla tion. This hammering type of action produces excessive wear and results in shortening the operating life of the bearing assemblies, particularly when the tuner is operating at high tuning rates, as of greater than 15OHz.  
 Therefore, it is desired to obtain an improved tuning actuator structure for converting rotary motion into reciprocal rectilinear translation of the tuning member.  
 SUMMARY OF THE PRESENT INVENTION The principal object of the present invention is the provision of an improved dither tuned microwave tube.  
  In one feature of the present invention, rotary motion of a drive motor is converted into reciprocal rectilinear translation of a tuning structure of a microwave tube by means of an actuator mechanism including a scalloped circular cam rail having a pair of cam followers riding on opposite sides of the scalloped rail, whereby rotary motion of one of said cam and cam follower members is converted into reciprocal rectilinear translation of the other which is then coupled to the tuning structure.  
  In another feature of the present invention, the cam rail is rotated and captured against axial translation, whereas the cam followers are affixed to the tuning structure for effecting reciprocal rectilinear translation of the tuning structure in response to rotation of the rail cam.  
  In another feature of the present invention, the follower means are adjustable in the axial direction of the circular rail cam so as to permit an adjustment which avoids play between the rail cam and the followers which ride in rolling engagement with the circular rail cam track. I  
  Other features and advantages of the presentinvetion will become apparent upon a perusal of the following specification taken in connection with the accompanying drawings wherein:  
 BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary longitudinal sectional view of a coaxial magnetron incorporating a tuner of the present invention,  
  FIG. 2 is an enlarged detail view of a portion of the structure of FIG. 1 delineated by line 2-2, and  
  FIGS. 3 is an enlarged detail view similar to that of FIG. 2 depicting an alternative embodiment of the present invention.  
 DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 11, there is shown a dither tuned coaxial magnetron microwave tube 11 incorporating features of the present invention. Microwave tube 11 is of the type generally described in the aforecited U.S. Pat. No. 3,441,795 and only partially shown herein. It includes a main body portion 22 housing a toroid-shaped cavity resonator 23 coaxially surrounding an array of vane resonators 24 which in-turn surround a cathode emitter 25 to define an annular magnetron interaction region between the vane resonators 24 and the cathode emitter 25. The vane resonators are carried at their outer edges from a cylindrical anode wall 26 forming a common wall of the resonator 23 and the vane resonator system 24. An array of longitudinally directed coupling slots 27 are provided communicating through the common wall 26 with alternate vane resonators for locking the 7r mode of oscillation of the vane resonator system 24 to the TE circular electric mode in the coaxial cavity 23.  
  The upper end wall 28 of the cavity resonator 23 is axially movable for tuning the resonant frequency of the resonator 23 and thus the frequency of the &#39;n&#39; mode and the output frequency of the tube. Movable end wall 28 is carried from dependent legs 29 of a spider structure 31. The body portion 31 of the spider is an annular disc sealed to the body of the tube via a pair of axially spaced bellows represented by broken lines 32 and 33. The spider 31 is axially translatable via an axially directed actuating rod 34 which is affixed at its lower extremity via a nut to the bottom of a cup-shaped member 35 which is affixed at its outer periphery to the spider 31. A fixed cylindrical slide linear motion ball bearing assembly 36 is affixed to the body of the tube at 37 for guiding and supporting the axially translatable actuating rod 34.  
  A motor 38 drives the tuner actuating rod 34 in a reciprocal rectilinear manner axially of the rod 34 via a suitable gear train assembly 39 and cam arrangement 41 (FIG. 2). The cam arrangement 41 serves to convert the rotary motion of the motor driven gear train 39 into reciprocal rectilinear translation of the tuner actuating rod 34. More particularly, the cam arrangement 41 includes a disc-shaped rail cam 42 which has, at its outer periphery, circular rail cam track which is scalloped out of the mean plane of the circular cam track in a desired manner such as in a sinusoidal deviation taken around the perimeter of the rail cam 42. In a typical example, the rail cam has two periods of sinusoidal deviation taken around the perimeter thereof with the peakto-peak deviation A of the center line 40 of the cam rail from the mean plane 30 of the cam rail comprising, for example, 0.021 inch.  
  A pair of cam followers 43 ride at the outer periphery of the cam rail 42 on opposite sides thereof in a mutually opposed relation. The cam followers are fixedly coupled to the outer end of the tuner actuating rod 34, as by set screws 44. Each of the cam followers 43 includes a cylindrical cam follower 45 riding in rolling engagement with the opposite sides of the cam rail 42 and being affixed to the tuner drive shaft 34 via a pair of cam follower axles 46 which are radially directed of the circular cam rail 42. Radial ball bearing assemblies 47 are provided between the cylindrical followers 45 and the axle 46. The cam rail 42 is fixedly carried from a shaft 48 which in-turn is supported at its ends in thrust bearing assemblies 49 which are mounted in a gear plate 51 and in an opposed mounting plate 52. The mounting plate 52 is affixed to the end of the tube body 22 via suitable mounting screws, not shown. The gear plate 51 is supported from the mounting plate 52 via a pluality of standoff spacers 53 (FIG. 1).  
  The gear train 39 includes a first drive gear 54 affixed to the end of the drive shaft 55 of the motor 38 via a set screw 56. The first drive gear 54 drives a first idler gear 57 which in-turn drives a second idler gear 58 which drives a gear 59 fixedly secured to the drive shaft 48 of the rail cam 42. A housing 61 is fixedly secured to the mounting plate and covers the gear train 39 and cam assembly 41. An electrical generator 62 is coupled to the other end of the drive shaft 55 of the motor 38 for generating a time varying electrical output in synchronism with the reciprocal translation of the tuner shaft 34. This output, at rated speed of the motor 38, tracks the motion of the tuner to derive an electrical output for tuning the local oscillator of a receiver which is to receive the returned echoes of the transmitted signal transmitted by the tube 11.  
  In operation, rotation of the cam rail 42 produces reciprocal rectilinear translation of the cam followers 43 and thus the tuning rod 34 to which they are fixedly secured. This is true because the cam rail 42 is captured against reciprocal translation by thrust bearings 49. The cam followers 43 are adjusted on the tuner rod 34 so as to be brought into firm bearing engagement with opposite sides of the cam rail 42 to prevent play therebetween as the followers 43 follow the reciprocal deviations of the cam rail 42. By assuring that there is no play between the cam followers 43 and the cam rail 42, the undesired hammering action encountered in the prior art system disclosed in the aforecited copending application 450,964 is avoided, thereby increasing bearing life and thus the operating life of the tuner. In a typical example of the tuner of the present invention, 250MHz tuning range is obtained at a rate of 200Hz with a peak-to-peak displacement of the tuning ring 28 of 0.021 inch. The tuning actuating rod 34 is captured against rotation by bellows 32 and 33 which allow axial translation of the rod 34 without turning thereof.  
  Referring now to FIG. 3, there is shown an alternative embodiment of the cam arrangement 41 of FIGS. 1 and 2. More particularly, in this embodiment, the cam followers 43 are captured against axial translation, whereas the circular and scalloped cam rail 42 is fixedly secured to the tuning shaft 34 via a set screw 65 passing through a threaded hole in a collar portion 66 of the cam rail 42. The cam followers 43 have their axles 46 fixedly secured to axially spaced rings 67 and 68 in diametrically opposed positions in respective ones of the rings 67 and 68. The rings 67 and 68 are ax ially splined to a drive gear 69 which surrounds the cam follower rings 67 and 68. A set screw 71 fixedly secures the axial position of the lower cam follower ring 68 relative to the drive gear 69. Thrust bearings 72 are provided between the rings 67 and 68 and the lower mounting plate 52 and a threaded plug portion 73 of the upper gear plate 51.  
  The cam system 41 is loaded by first positioning the lower follower ring 68. The cam rail 42 is then brought into bearing engagement with the upper surfaces of the cylindrical followers for loading the lower follower ring and then the cam rail 42 is fixedly secured to the tuner actuating rod 34 in this position by tightening set screw 65 in the collar 66 of the cam rail 42. The drive gear 69 is fixedly secured to the lower cam follower ring 68 by tightening one or more set screws 71. Next, the upper cam follower ring 67 is brought into engagement with the upper surface of the cam rail 42 and the threaded plug 73 is tightened down on the assembly to assure firm bearing engagement between the upper cam followers 45, the upper surface of the rail cam 42.  
  While there have been described and illustrated several specific embodiments of the invention, it will be clear that variations in the details of the embodiments specifically illustrated and described may be made without departing from the true spirit and scope of the invention as defined in the appended claims and their legal equivalents.  
 What is claimed is: 1. In a dither tuned microwave tube: cathode emitter means for emitting a stream of electrons; microwave circuit means disposed in electromagnetic wave energy exchanging relation with the stream of electrons; means for applying an anode potential to said microwave circuit means relative to said cathode means for drawing the stream of electrons from said cathode means toward said microwave circuit means and for generating wave energy on said microwave circuit means as a result of electromagnetic wave interaction with said stream of electrons; tuning means for displacing electromagnetic fields of said microwave circuit means for tuning of said microwave circuit means and thus the frequency of the wave energy generated on said microwave circuit, said tuning&#39;means including, a tuning structure movable relative to said microwave circuit for variably displacing fields of said microwave circuit means, tuner actuator means coupled to said tuning structure for effecting reciprocal rectilinear translation of said tuning structure, and motor means for imparting rotary motion to said actuator means for actuation thereof; said tuner actuator means including, cam means having a circular cam rail to receive cam follower means, said circular cam rail being scalloped in a direction normal to the mean plane of said circular cam rail, and cam follower means including cam follower means disposed adjacent said cam rail for following said circular scalloped cam rail to derive reciprocal rectilinear translation of one of said cam means and said cam follower means relative to said microwave circuit means, and means for coupling said reciprocating one of said cam means and said cam follower means to said tuning structure to effect reciprocal rectilinear translation thereof. 2. The apparatus of claim 1 wherein said cam follower means includes a pair of cam followers riding on opposite sides of said scalloped cam rail means taken in the direction of rectilinear &#34;translation of one of said cam and cam follower means.  
  3. The apparatus of claim 2 wherein said motor means includes a rotatable drive shaft, and wherein the axis of revolution of said drive shaft is generally parallel to the axis of rectilinear translation of said tuning structure.  
  4. The apparatus of claim 2 wherein said cam follower means includes a pair of rotatable cylindrical follower members riding on opposite sides of said cam rail in rolling engagement therewith and each having an axis of revolution radially directed of said circular cam rail.  
  5. The apparatus of claim 2 wherein said reciprocating one of said cam means and said cam follower means is said cam follower means, and including means for rotating said cam means adjacent said cam follower means, and means for capturing said rotatable cam means against reciprocal rectilinear translation, whereby rotation of said cam means adjacent said cam follower means results in effecting reciprocal axial rectilinear translation of said cam follower means.  
  6. The apparatus of claim 2 wherein said reciprocating one of said cam means and said cam follower means is said cam means, and including means for rotating said cam follower means around said scalloped circular cam track of said cam means, and means for capturing said rotatable cam follower means against reciprocal rectilinear translation, whereby rotation of said cam follower means around said cam rail results in effecting reciprocal axial rectilinear translation of said cam means.