US2933701A

US2933701A - Transmission line r.-f. lobing unit

Info

Publication number: US2933701A
Application number: US651537A
Authority: US
Inventors: Donald H Lanctot
Original assignee: Electronic Specialty Co
Current assignee: Electronic Specialty Co
Priority date: 1957-04-08
Filing date: 1957-04-08
Publication date: 1960-04-19
Anticipated expiration: 1977-04-19

Description

April 19, 1960 D H, LANCTOT 2,933,701

TRANSMISSION LINE R.F'. LOBING UNIT Filed April 8, 1957 2 Sheets-Sheet l O//g-f//Ae BY 250226 M HG, 3 Arron/evs April 19, 1960 n. H. LANcToT TRANSMISSION LINE R.F. LoBING UNIT 2 Sheets-Sheet 2 Filed -April B. 1957 INVENTOR. DONALD H. LANCTOT BY ma/523%@ P coNNEcToR 62 *1 a2 ouTPuT coNNecToR is OUTPUT ATTOR NE KS United States Patent() TRANSMISSION LINE R.F. LOBING UNIT Donald H. Lanctot, Malibu, Calif., assigner, by mesne assignments, to Electronic Specialty Co., a corporation of California Application April 8, 1957, Serial No. 651,537

15 Claims. (Cl. S33-7) This invention relates generally to high frequency elec-v trical switches and more particularly to an improved electro-mechanical lobing unit for switching high frequency electrical energy from an input transmission line to two or more output transmission lines. For convenience of terminology, the transmission lines discussed are in the form of co-axial cables, although it should be understood that parallel wire lines and wave guides could be employed as transmission carriers for the electrical energy involved.

High frequency lobing switches of the type under consideration are particularly well adapted for switching high power, high frequency electrical energy between two or more antennas such as employed in radar systems. In some instances, there may be provided a single reliecting type antenna structure fed by two separate co-axial lines arranged to `deliver energy pulses alternately to the antenna from different focus points whereby the beam of the antenna is shifted between two limits. In other instances, there may be a plurality of antennas which are sequentially energized to provide an effective lobel sweeping characteristic. It is important in all such lobing switches that minimum losses occur during the switching operation and that a proper impedance match be retained between the input and the various output lines' standpoint to insure relatively uniform and proper kirn-` pedance matching.

In order to effect switching of energy from an input line to two or more output lines at a desired rate of speed; for example, live hundred times per second, however, the problem of insuring positive connection by metal to metal contact is rendered extremely difficult. Therefore, in instances wherein a relatively rapid cyclic switching is desired, resortr is had to a capacitive coupling between the various inner conductors whereby no mechanical friction is introduced as a result of metal to metal contact. By means of such capacitive coupling, a relatively friction free unit may be provided with little mechanical diiculties. On the other hand, considerable losses are incurred as a result of capacitive coupling, and further, the various energy portions distributed among the output lines are not positively defined.

In attempting to provide relatively rapid cyclic switching by means of metal to metal contacts between the various inner conductors, there is, in addition to friction, the problem of wear between the metal to metal contact surfaces and the consequent problem of engineering a switch with suiciently close tolerances to insure a satisfactory degree of reliability, K A

iBearing the above in mind, it is a primary object of the present invcntion'to provide a greatly improved type of lobing switch in which the inner conductors of the various co-axial lines are positively connected by a metal to metal engagement to enable discrete and equal or proportioned amounts of energy to be distributed between the various lines with a minimum of electrical losses and mechanical friction and at a rate of anywhere from zero cycles to live or six hundred cycles per second.

More particularly, it is an object to provide a switch of the above type which is positive throughout in operation and in which any wear of metal to metal contact points automatically compensates itself whereby an extremely reliable and substantially maintenance free unit results. f

These basic objectives as well as many other objects and advantages of the present invention are attained,y

are adapted to be respectively connected to two output` co-axial lines between which the energy in the input line is to be periodically switched. The various co-axial connectors extend into one side of the casing and terminate in the interior thereof.

A plurality of switching members respectively associated with the co-axial connectors are rotatably mounted on' a bearing plate within the housing. These switchingk members include tapered probes extending from a cen-A tral conducting disc for the center co-axial connector switching member, and two conducting sector plates respectively associated with the outside co-axial conductors to terminate in point contact means at the` ends of the respective inner conductors for the co-axial connectom. The central disc and sector plates are positively geared together for rotation by a motor extending from the rear of the housing. The disc and sector plates themselves are substantially co-planar and arranged such that the sector plates overlap peripheral portions of the disc. Each sector plate includes at least one sector element arranged to make a metal to metal contact with the periphery of the central disc, the sectors associated with each of the sector plates being of such relative position with respect to each other that the various connections between the sectors and the central disc are made alternately upon rotation of the plates and disc by the driving motor. With this arrangement, it ispossible to alternately switch electrical energy ,received in the center co-axial connector between the two outside co-axial connectors at anl extremely rapid rate. The casing for the various switching components is designed in a manner tok co-operate with the probes leading from the point contact means to insure a proper impedance match between the various connectors. Further, theY entire unit is hermetically sealed and lled with oil of given dielectric constant.

A better understanding of the invention and its various features and advantages will be had by referring to a more complete description of a specific embodiment thereof as illustrated in the accompanying drawings, in which: Figure 1 is a perspective view of the lobing'unit for switchingelectrical energy from an input co-axial line between two output co-axial lines; 1

Figure 2 is a plan view taken in the direction of the arrows 2 2 illustrating the various switching components employed in the unit of Figure l;

Figure 3 is an enlarged elevational view partly in cross sectionof one of the point Ycontact means employed in the unit vof Figure 2;-l y -4 l Figure 4 vis an enlarged `perspective view of one of the elements oft-the vpoint contact means; 4

Figure 5 4isfa cross sectional schematic view of a p01*' Patented Apr.y 19, 1960 f answer p y n tion ofthe switching means taken in the direction of the arrows 5 5 of lFigure 2;

Figure 6 is an enlarged cross section taken in the direction of the arrows 6 6 of Figure 5; K

Figure 7 illustrates ya modified type of sector plate which could be employed in the switching apparatus of Figure 5;

Figure 8 is another schematic diagram illustrating one possible relationship of the driving gears for operating the switching unit, taken in the direction of the arrows 8 8 of Figure 2;

Figure 9 is an elevational view ofl the driving gears taken in the direction of the arrows 9 9 of Figure 8; and,

Figure 10 is a time graph illustrating the output energy distribution effected by the switching unit of this invention.

Referring to Figure l, there is illustrated a hollow casing 11i on the front face of which is mounted a center co-axial connector 11 and two outside

co-axial connectors

12 and 13. lIn the embodiment shown in Figure 1 for the sake of illustration, the center co-axial connector 11 is adapted to be connected to an input co-axial line from a high frequency oscillator such as a magnetron or other source of high frequency electrical energy, while the two outside

co-axial connectors

12 and 13 are adaptedy to be respectively connected to two output co-axial lines leading to a pair of antennas or other type radiating or transmitting device. The switching arrangement within the casing 10 is such that energy entering the center coaxial connector 11 will be alternately switched between the

output co-axial connectors

12 and 13. A portion of the unit also includes a driving motor 14 extending from the rear of the casing 10 for effecting this switching operation. The motor 14 is provided at its rear with an inlet 15 for connection to an electrical source to drive the motor. Preferably, the motor 14 is of the synchronous type such that it will rotate at a precise, constant speed.

Referring now to the partial cross sectional plan view of Figure 2, it will be noted that the outer conductorsof the

various co-axial connectors

11, 12 and 13 are all electrically connected together through the medium of the metal casing 10 while the inner conductors associated with these connectors are isolated from the casing by suitable dielectric material. As shown in Figure 2, the hollow interior of the casing 10 is divided by a metallic bearing plate 16 extending completely across the unit to provide a first compartment 17 serving to house the various switching units to be described shortly and a second compartment 18 serving to house various gearing associated with the switching units and driven by the motor 14.

The bearing plate 16 also serves as a mounting means for rotatably mounting a center switching member 19 and two outside switching

members

20 and 21 in co-axial alignment respectively with the center co-axial connector 11 and the two outside

co-axial connectors

12 and 13. The manner in which these switching members are mounted in the bearing plate 16 is identical and, therefore, description of the mounting arrangement and components of one will suffice for all. Referring to the lower switching member 21 of Figure 2, for example, there are provided ball bearings 22 for mounting the rear portion of the switching member to the bearing plate 16 and ball bearings 23 mounting the forward portion of the member 21 to the casing 10 adjacent the output co-axial connector 13. The switching member 21 itself includes a tapered electrically conducting probe 24 extending in the rst compartment 17 towards the output co-axial connector 13. The interior walls of the housing 10 includeV similarly tapered portions as at 25, the angle of the interior taper 25 being slightly greater than the taper 24 Such that proportionate spacing between the housing 10,

serving as the outer conductor, and the tapered probe Y24, serving as the inner conductor, with respect to the varying diameter of the inner conductor, is maintained. By this arrangement, a proper impedance match is provided from the output co-axial connector 13 to the switching member 21.

As shown in Figure 2, the tapering probe 24 terminates in a reduced diameter end portion 26 providing an end point contact surface arranged to make metal to metal contact with a point contactv means 27 positioned at the end of the inner conductor 28 of the output co-axial connector 13. The reduced end portion 26 of the probe 24 corresponds in diameter to the diameter of the inner conductor 28 of the co-axial connector 13. Suitable dielectric material serves to support the inner conductor 28 and end portion of the probe 26 in proper co-axial alignment, and the inner metal ball bearing race of the bearings 23 serves to co-operate with the tapered metallic wall portions of the housing 10 to provide an effective outer conductor for these inner conductors. The switching member 21 is rotatably mounted in the plate 16 such that rotation takes place about the central axis of the tapering probe 24 whereby the extreme end portion 26 of this probe rotates against the point contact means 27 at the end of the stationary inner conductor 28. Similar tapered probes and point contact means are included in the other two

switching members

19 and 20.

As shown in Figure 2 and in greater detail in Figure 5, the tapered probe for the center switching member 19 merges in and is electrically connected to a central conducting disc 29. The tapered probes for the switching

members

20 and 21 similarly are electrically connected to sector plates 30 and 31. The sector plates are co-planar with the central disc and dimensioned to overlap the periphery of the disc when the

rotatable switching members

19, 20 and 21 are rotated. These sector plates and central disc constitute a transfer means for alternately pass'- ing electrical energy from the central co-axial connector to the outside co-axial connectors all as will become clearer as the description proceeds.

As shown in Figure v2, the switching

members

20 and 21 include co-axial stubs including inner conductors 32 g and 33 electrically connected to the tapered probes, such as the probe 24 for the switching member 21, and extending into and terminating within the second compartment 18. These stubs 32 and 33 respectively co-operate with the mounting bearings for the respective outside switching

members

20 and 21 and the bearing plate 16 itself to provide a substantially uniform end wall lfor R.F. energy being transferred between the center co-axial connector and the outside co-axial connectors, whereby electrical losses are minimized when energy is being passed through the transfer means.

The various switching means 19, 20 and 21 are rotated by a suitablegear train in the second compartment 18. This gear train, as clearly shown in Figures 2, 8 and 9, may comprise, for example, a pinion 34 connected directly to the shaft 35 of the motor 14 and meshing with a spur gear 36 in turn connected to a second pinion 37 meshing with a center spur gear 38directly secured to the center switching member 19. The center spur gear 38 is arranged to mesh directly with two outside spur gears 39 and 40 directly secured to the switching

members

20 and 21 respectively. Rotation of the center spur gear 38 will, therefore, rotate the spur gears 39 and 40 in the same direction and at exactly the same speed in a positive manner whereby the sector plates on the other side of the partition bearing plate 16 will also be rotated exactly in synchronism with respect to the center conducting disc 29. The

gears

34, 36, and 37 are merely reduction gears to provide -a proper operating speed for the switching members.

Figure 3 shows in enlarged detail view the point contact means associated with the inner conductor 28 and tapering probe 24 for the outside coaxial connector 13.y

This point contact means is characteristic of the other two connections to tapered probes for the switching

members

19 and 20 and, therefore, description of one will suice for all. As shown in Figure 3, the inner conductor 28 has a tapered surface portion 41 conical in shape and thence merging into a reduced diameter nose portion 42. The point contact means 27 itself comprises a highly conductive cup element having a plurality of slots in its sides to define

ngers

43, 44, 45 and 46 as best seen in Figure 4. The ends of these figures are adapted to ride on the conical surface 41 and are biased laterally inwardly thereby tending to move the element 27 in anaxial direction as indicated by the arrow to the right, such that the bottom ofthe element 27 engages the contactsurface 47 of the end portion 26 of the probe. The nose portion 42 serves as a guide for this axial movement. This bottom portion of the cup 27 is made with precious metal to insure a long wearing contact with the probe end. Because of the biasing of the springngers in engagement with the conical surface 41, any Wearing of the inner engaging surfaces at 47, which may result under ordinary conditions in a loss of contact, is accommodated bythe constant urging of the cup bottom towards the probe and by the action of the fingers against the conical surface 41. Thus, there is provided an automatic adjustment which is continuously in action to rinsure positive electrical contact between the inner conductor 28 and the probe end portion 26.

The manner in which the transfer means comprising thevarious sector plates 30 and 31 and the central disc 29 as described in connection with Figure 2 operate, will nowybe describedin detail with reference to Figures 5 and `6. InrFigure 5, it will be noted that the sector plate 30 includes two

sectors

48 and 49. In the embodiment `shown for illustrative purposes, these sectors may have an arcuate peripheral extent of substantially forty-` ve degrees each and extend diametrically as shown. Similarly, the sector plate 31 includes two diametrically oppositely extending

sectors

50 and 51 each of substantially forty-five degrees of arc. The

sectors

50 and 51 are positioned at ninety degrees relative to the

sectors

48 and 49 suchy that alternate contact with the central conducting disc 2.9 will be made by the respective sectors. The overall diameters of the sector plates 30 and 31 are such that their peripheries will overlap the periphery of the'conducting disc 29. As shown best in Figure 6, the

kcentral discV 29 in a preferred embodiment, actually includes' two coaxial discs 5.2 and 53 secured together at their hubs to define a peripheral slot 54. The overlapping ofthe sectors is accommodated by reception of the sectors between the discs inthe slot 54. As a result of the differential speed` created by the overlapping, a wiping contact .will be made between the sector plates and the central conducting disc comprising thedual discs S2 and 53.

If it is assumed that the gear train drives the central conducting disc 29 in a counter clockwise direction as viewed in Figure 5, then the sector plates 30 and 31 will be driven in a clockwise direction simultaneously and .at the same rate of speed, all as indicated by the arrows. In this event, the sector portion 49 as shown will be entering the peripheral slot 54 and thus while so sandwiched within this slot electrical energy will be passed from the center coaxial connector 11 to the outside coaxial connector 12. Y

Just prior to termination of contact of the sector 49 with the inner side walls of the discs defining the slot 54 in thek conducting disc 29, the sector 51 associated with the sector plate 31 will enter the slot 54 to make contact with thel conducting disc 29. The arcuate extent and degreegof overlapping of the various plates and central disc may be designed such that one contact will be made before the other contact is broken. By having a contact made before the other is broken, possible arcing occasioned'by open circuits is avoided.

'In the cross sectional view of Figure 6 taken in the direction of the arrows 6-6 of Figure 5, it will be noted that the peripheral disc surfaces forthe

discs

52 and 53 dening the slot 54 are directed inwardly slightly to enable introduction of a spring bias so that the

discs

52 and 53 tend to grip opposite sides of the sector 49 thereby providing a positive engagement as at 55 and 56. To facilitate entry of the sectors, the edge and end portions thereof such as at 57 for the sector 49 are tapered slightly.

This manner of interconnection of the sector plates with the conducting disc 29 is an important feature of the invention. to provide consistent contact pressure coupled with the natural differential speeds introduced as a result of the overlapping, there is provided a self cleaning action between these engaged metal to metal surfaces. Further, the inh'erent additional advantages of capacitance coupling is realized because of the relatively large contact area between the metal contacting portions of the

dual discs

52 and 53 sector 49.

The duration of the electrical connection between any one sector and the disc may be varied by altering the arcuate extent of the sector. Further, the sectors on one sector plate may be dimensioned diierently from the sectors on the other sector plate in order to provide a distinguishing characteristic in the electrical signal transmitted to one of the coaxial connectors as compared to the other.

In Figure 7, for example, there is illustrated a sector plate 58 having

sector portions

59 and 60 provided with notches 61 such that several make and break connections are eected while the

sectors

59 and 60 aresandwiched within the slot 54. Thus, the output energy from the corresponding coaxial connector is distinguished over that` fed to the other coaxial connector. As an alternative to the notching such as at 61, the overall arcuate extent of the

sectors

59 and 60 may be made dilferent from that of the sectors on the other sector plate whereby a distinguishing means is provided for the two output signals.

The overall operation of the entire lobing unit will be apparent from the above description. Referring once again to Figure 2 and to the plot in Figure l0, a source of electrical energy is connected to the electrical inlet 15 for the motor 14 to drive the motor at a constant rate of speed. An inlet co-axial line passing from an electrical energy source (not shown) is connected to the center co-axial connector 11, and two output co-axial lines (notshown), leading to other units such as antennas between which the energy from the input co-axial line is to be switched, are connected to the outside

co-axial connectors

12 and 13. The input high frequency energy in the co-axial connector 11 is passed through the inner conductor thereof and the point contact cup means such as illustrated in Figures 3 and 4 to the center probe associated with the switching member 19 so that this energy appears on the conducting disc 29. This disc is being rotated at' a given speed through the medium of the gear train by motor 14 and simultaneously the outer sector plates 30 and 31 are similarly being rotated. As best shown yin Figure 5, the sector plates'stl and 31 will thus alternately make electrical contact with the conducting disc 29 thereby passing the high frequency energy at disc 29 to one or the other of the sector plates 3i) and 31. From the sector plates 39 and 31, this electrical energy will pass down a corresponding tapered probe and point contact cup to the corresponding inner conductor of the outside

co-axial connectors

12 and 13 to pass to the output co-axial lines. The provision of the bearing plate partition 16 as described heretofore, in co-operation with the co-axial stubs 32 and 33 minimizes electrical losses during the transferring operation between the disc and sectors and delines essentially, with the remaining Walls Y' By sandwiching the sector within the slot 54 acens/or `As mentioned heretofore, the unique point contact means 27 in the formof the split cup Vof Figures 3 and 4 insures substantially maintenance free and reliable operation ofthe unit. Further, the sandwiching provision in the central conducting disc 29 provided by the dual disc construction with the peripheral portions of the sector plates, insures positive electrical contact during the switching operation. Any wear during these contacting periods is accommodated by biasing in of the side of the walls of the

discs

52 and 53 against the sector therewithin. The differential speed as a result of the overlapping of the sectors and central disc provides wiping action as well as a cleaning action between these contacting surfaces.

Because of the positive mechanical gearing and constant speed of the motor 14 as well as the positive arcuate dimensioning of the various sectors, a discrete proportioning of the input electrical energy is maintained. In Figure l0, for example, the distribution of this high frequency energy between the two output

co-axial connectors

12 and 13 is illustrated. Thus, with respect to time, the output of electrical energy from the co-axial connector 12is indicated by the shaded wave formk 62 and the output of the co-axial connector 13 is indicated by the shaded portion 63. It will be noted that the durationy of each of the energies distributed between the output connectors is exactly equal as indicated by P. Each output ofthe lobing unit thus provides a substantially perfect square wave, and to this end the lob-ing unit may readily be employed as a square wave generator.

As mentioned heretofore, it may be desirable that the output from one of the co-axial connectors be distinguishable from the output from the other co-axial connector, and to this end one of the sector plates may be dimensioned differently from the other. In the event such dimensioning took the form of decreasing the arcuate extent of the sectors on the sector plate, this would effectively change the period P for the particular energy coming from one of the outputs as compared with the period P for the energy from the other output.

In the actual embodiment of the lobing switch unit, the entire interior of the casing as illustrated in Figure 2 is filled with oil 64 of given dielectric constant and the whole unit is hermetically sealed. Sealing between the first and second compartments 17 and 18 insofar as the oil is concerned, however, is not necessary nor desirable. Actually, the oil will permeate the motor 14 itself and ser-ve to lubricate all the gearing as well as the various ball bearings and will provide an excellent operating and lubricating medium for the sector plates and conducting disc. Any sparking, for example, will be immediately quenched by the oil and any generated heat will be readily transferred to the casing 10 and properly dissipated. Further, the given dielectric constant of the oil is ysuch as to provide a uniform impedance between the tapered probes and interior tapering of the case 10 such that impedance matching is maintained throughout.

While the instant invention has been described with respect to a particular embodiment in which a center coaxial connector is arranged to switch electrical energy between only two output co-axial connectors, it should be readily understood that additional output co-axial connectors and associated tapered probes and switching units including properly designed sector plates may be incorporated without departing from the spirit of the invention. Thus, for example, because of the symmetry of the unit with respect to the central axis thereof passing through the center co-axial connector 11, two additional coi-axial connectors similar to 12 and 13l could be arranged above and below the connector 11 as viewed in Figure l whereby electrical energy may be uniformly distributed between four output co-axial connectors. It is also possible to serially connect another set of switching members in co-axial tandem fashion with the switching members 19, 2t), and 21 and employ the same motor driving means for rotating these mcmberson common shafts. Other such modifications falling within the scope and spirit of this invention will readily occur to those skilled in the art. The transmission line R.F. lobing switch is, therefore, not to be thought of as limited to Y the particular embodiment described and shown for illustrative purposes.

What is claimed is:

l. A lobing unit for switchingV high frequency electrical energy from an input co-axial line between at least two output co-axial lines, comprising, inV combination: a central conducting disc and two conducting sector plates; means rotatably mounting said disc and each of said plates in substantially co-planar relationship; means for rotating said disc and each of said plates in synchronism to produce synchronous rotation of said disc and said plates; said plates each including a sector portion alternately making electrical contact with said central disc upon said synchronous rotation; and means electrically connecting said disc to the center conductor of said input co-axial line, and means respectively connecting electrically each of said sector plates to the corresponding inner conductor of said output co-axial lines.

2. A lobing unit according to claim 1, in which said means electrically connecting said disc into the center conductor of said input co-axial line and said means respectively connecting said sector plates to the inner conductors of said output co-axial lines, each include a cupshaped conducting element having a plurality of slots in its side walls to dene a plurality of fingers; the end p0rtions of said inner conductors tapering to a reduced diameter to dene conical surfaces against which said' fingers seat; probes on said central disc and outside sector plates respectively extending `towards said inner conductors to terminate adjacent the bottom of each cup associated therewith and to make point Contact therewith, said fingers on each cup being biased laterally outwardly by the corresponding conical surface at the end portion of the corresponding inner conductor whereby said cup is axially urged towards the ends of said probes to maintain said point contact.

3. A lobing unit for switching high frequency electrical energy from an input co-axial line between at least two output co-axial lines, comprising, in combination: a hollow casing; a center coaxial connector and two outside co-axial connectors passing into said casing, said center co-axial connector being adapted for connection to said n input co-axial line and said two outside co-axial connectors being respectively adapted for connection to said two output co-axial lines; a bearing plate positioned in said casing to divide the hollow interior thereof into `iirst and second compartments; a center switching means and two outside switching means rotatably mounted in said bearing plate in co-axial alignment respectively with said center co-axial connector and saidtwo outside co-axial connectors; said center switching means including a probe extending into said first compartment and terminating inV a contact surface adjacent the end of the inner conductor of said center co-axial connector; point contact means -positioned between said'contact surface and said inner conductor for passing said electrical energy fromssaid center co-axial connector to said center switching means; transfer means for alternately passing saidelectricalienergy to said outside switching means upon rotation ofy said center switching means and said outside switching.

means, said outside switching means respectively including probes extending into said first compartment and terminating in contact surfaces adjacent the ends of the inner conductors of said outside co-axial connectors; point contact means positioned between said contact surfaces and said inner conductors for passing said electrical energy from said outside switching means to said voutside co-axial connectors; gear means in Vsaid second compartment positively interconnecting said center switching means with said two outside switching means; and motor means for driving said gear means to rotate Said Center 9 switching means and said two outside switching means whereby said energy is passed by said transfer means from said center switching means alternately to said two outsideV switching means.

4. A unit according to claim 3, in which said point contact means for passing electrical energy from said center co-axial connector to said center switching means and said point contact means for passing said electrical energy from said outside switching means to said outside co-axial connectors comprise cup-shaped highly conductive elements having lateral slots in their side walls defining a plurality of fingers, the terminal end of said inner conductor for said center co-axial connector and the terminal ends of said inner conductors for said outside co-axial connectors each tapering to a reduced diameter to define a conical surface adapted to be engaged by the ends of said fingers to bias said cup-shaped elements respectively in axial directions against said contact surface on the end of said probe for said center switching means and said contact surfaces on the ends of said probes for said outside switching means.

5. A unit according to claim 3, in which said transfer means comprise: a central conducting disc mounted to said center switching means for rotation therewith; and two conducting sector plates respectively mounted to said outside switching means for rotation therewith, the peripheries of said sector plates overlapping the periphery of said central disc, said sector plates having sector portions adapted to make alternate electrical contact with said central disc upon rotation of said switching means.

6. A unit according to claim 5, in which said central conducting disc is substantially co-planar with said sector plates and includa a peripheral slot of thickness sufficient to receive the thickness of said sector plates whereby the overlapping portions of the peripheries of said sector plates are alternately sandwiched in said slot upon rotation of said switching means.

7. A unit according to claim 3, in which said gear means include a center spur gear secured to said center switching means for rotation therewith, and two outside spur gears co-planar with said center spur gear, secured respectively to said two outside switching means and intermeshing `at diametrically opposite points with said center spur gear; said motor means being coupled to drive said center spur gear whereby rotation thereof rotates said outside spur gears and associated outside switching means at the same speed and in the same direction.

8. A unit according to claim 3, in which said probe for said center switching means and said probes for said outside switching means include electrical conductors of given diameter gradually tapering to a reduced diameter in a direction respectively towards the inner conductor of said center co-axial connector and the inner conductors of said outside co-axial connectors, said side walls in said first compartment including tapered portions partially surrounding the respective tapering portions of the probes whereby a relatively constant impedance is maintained between the co-axial connectors and switching means.

9. A unit according to claim 8, in which said outside switching means each respectively include co-axial stubs extending from` said probes into and terminating in said second compartment whereby the portions of said switching means mounted in said bearing plate in combination with said stubs provide with said bearing plate a substantially uniform R-F cavity end wall whereby losses of said electrical energy passing from said center switching means to said outside switching means are minimized.

10. Agunit according to claim 5, in which each of said sector plates includes at least one sector of given circumferential arcuate extent and relative position such that one of said sector plates will make contact with said central disc before the other of said sector plates breaks contact with said central disc.

11. A unit according to claim 10, in which one of said sector plates includes a sector dimensioned differently from a sector on the other of Said sector plates whereby the electrical energy transferred to said one of said sector plates is distinguished from the electrical energy transferred to the other of said sector plates.

12. A unit according to claim 3, in which said hollow casing is hermetically sealed and is filled with oil having a given dielectric constant.

13. A transfer means for alternately passing electrical energy from an input conductor to two output conductors, comprising, in combination: a central disc connected to said input conductor; two outside plates connected respectively to said two output conductors; means rotatably mounting said central disc and plates in co-planar relationship such that the peripheries of said plates respectively contact and overlap opposite peripheral portions of said central disc; means for rotating said disc and each of said plates in synchronism to produce synchronous rotation of said disc and said plates; and conducting portions in each of said plates positioned to make alternate contact with said central disc upon'rotation of said plates.

14. Thek subject matter of claim 13, in which said central disc includes a pair of co-axial conducting discs secured together at their hub portions and defining a peripheral slot therebetween, the thickness of said slot being sufiicient to accommodate said conducting portions on said plates; said means for rotating said plates including means for rotating said plates including means for simultaneously rotating said central disc at the same speed whereby the overlapping surfaces of said slot and said conducting portions move at differential speeds to provide a wiping contact.

15. A point contact means for passing electrical energy between two electrical conductors in co-axial alignment having their adjacent ends terminating in opposed relation to each other and in which one of said conductors is rotated about its axis, comprising: a cup-shaped element positioned between said adjacent ends and having lateral slots defining a plurality of ngers, the end portion of the other of said conductors tapering to a reduced diameter to define a conical surface adapted t0 be engaged by the ends of said fingers, the base of said cup making point contact with the end of said one of said conductors, said fingers being biased radially inwardly to exert pressure on said conical surface of said other of said conductors thereby urging said cup base axially against said end of` said one of said conductors.

References Cited in the file of this patent UNITED STATES PATENTS 1,272,677 Krantz July 16, 1918 2,064,585 Atienza Dec. 15, 1936 2,449,138 Phillips Sept. 14, 1948 2,695,385 Shunemann Nov. 23, 1954 2,757,341 Lundstrom July 31, 1956