US2174552A

US2174552A - Automatic tuning apparatus

Info

Publication number: US2174552A
Application number: US166661A
Authority: US
Inventors: Arthur A Collins
Original assignee: Individual
Current assignee: Individual
Priority date: 1937-09-30
Filing date: 1937-09-30
Publication date: 1939-10-03
Anticipated expiration: 1956-10-03

Description

Oct. 3, 1939.

A. A. COLLINS AUTOMATIC TUNING APPARATUS 4 Sheets-Sheet 1 Filed Sept. 30, 1937 IN a VENTOR.

(90mm, BY v ATTORNEY.

A. A. COLLINS AUTOMATIC TUNING APPARATUS Oct. 3; 11' 939.

Filed Sept. 50, 1937 4 Sheets-Sheet 2 INSULATION {4 f- INVENTOR. (?0

ATTORNEY Oct. 3, 1939.- A. A. COLLINS AUTOMATIC TUNING APPARATUS Filed Sept. 30, 1937 4 Sheets-Sheet 3 INVENTOR.

)llllllllllllllllilllll flaw/Wu a @0 BY ATTORNEY A. A. COLLINS AUTOMATIC TUNING APPARATUS 4 Sheets-Sheet 4 Filed Sept. 30, 1937 T0 540 soa /44s 94.

. INVENiOR. 2 w 61 1 lllllll lllllllll ATTORNEY Patented Oct. 3, 1939 .UNITED STATES PATENT OFFICE 2,174,552 AUTOMATIC TUNING APPARATUS Arthur A. Collins, ceasi- Rapids, Iowa Application September so, 1937, Serial No. 166,661 17 Claims. (01. 192-142) My invention relates broadly to radio transmitting and receiving apparatus and more 'particuraly to means for changing the positions of one or a plurality of tuning elements or similar mechanical devices.

This invention constitutes an improvement upon the automatic tuning systems and apparatus described in my copending applications Serial Nos. 123,453 and 160,920, filed February 1, 1937,

and August 25, 1937, respectively.

One of the objects of my invention is to provide mechanically compact, unitary, 'and efficient means for actuating variable tuning devices and setting the same tuned to any one of a plurality 5 of predetermined frequencies.

Another object of my' invention is to provide means for simultaneously and automatically adjusting the tuning devices in a plurality of circuits, regardless of the preset angular positions thereof and the variety of postset angular relations that may be required.

Still another object of my invention is to pro- .vide mechanical shaft positioning mechanism including preset stop means for establishing the shaft in a plurality of predetermined selected positions, and means for adapting the mechanism for establishing the shaft in a second plurality of different positions.

A further object of my invention is to provide 0 removable preset stop assemblies in mechanical shaft positioning mechanism so that a multiplicity of predetermined set positions may be attained by the shaft under the control of the mechanism.

A still further object of my invention is to provide a unitary type of shaft positioning apparatus for a plurality of shafts, employing motor means directly associated in the apparatus so that intercoupling of individual shaft positioning mechanisms and the motor means is effected simply and space and with a minimum of weight as a whole,

the entire assembly being especially adaptable for use aboard aircraft.

Still another object of my invention is to provide a simplified control circuit employing motor means and a minimum of relay and switch elements for effecting proper sequential operation of the apparatus.

, Another object of m'yinvention is.to provide an improved type of cam actuated sequence control switch operative together with the shaft positioning mechanism in the automatic tuning system of my invention.

without undue demand on Other and further objects of my invention reside in the structure and arrangement of the apparatus, as hereinafter more fully set forth with reference to the accompanying drawings, in

which:

Figure 1 is a front elevation of radio transmitter embodying the automatic tuning apparatus of my invention; Fig. 2 isa side elevation of the transmitter illustrating the relative arrangement of certain of the elements of the system; Fig. 3 is a front elevation of the shaft positioning mechanism embodied in a unit for a self-contained 5 the control of four tuning elements. and Fig. 4

is a plan view thereof; Fig. 5 is a vertical longitudinal sectional view of the apparatus shown in Fig. 3, taken substantially on line 5 -5 of Fig. 6; Fig. 6 is a horizontal sectional view looking upwardly substantially on line. 6'-6 of Fig.- 5; Fig. '7 is a horizontal partially sectional detail view taken substantially on line 1-1 in Fig. 5, and Fig. 8 is a view similar to Fig. '7 showing the operative elements thereof in opposite operative relation; Fig. 9 is a vertical sectional view, with parts in elevation and broken away, of the shaft positioning mechanism employed in the automatic tuning system of my invention, taken substantially on line 9-9 of Fig. 6; Fig. 10 is a horizontal sectional view taken substantiallyron line Ill-J0 in Fig. 9; Fig, 11 is a horizontal sectional view taken substantially on line ll-|l in Fig. 9; Figs. 12 and 13 are views similar respectively to Figs. 10 and 11 but showing operative elements in opposite operative relations; Fig. 14 is a horizontal sectional view taken substantially on line ll-H in Fig. 9; and Fig. 15 is a schematic diagram of the electrical circuit connections in the automatic tuning system of my invention. The principal object of this invention is the automatic tuning of a ;Jradio transmitter or receiver having a plurality of tuning controls, so that it may operate on a number of predetermined frequencies. I will describe the application of my invention specifically to a transmitter, although it is apparent that application to devices other than transmitters can be made. The problem of shifting the operating frequency of a transmitter is a very important one, especially on high frequencies, wherr the frequencies must be changed from time to time during the day in order to obtain satisfactory communication. It is also desirable to shift the frequency of the transmitter rapidly in order to handle traffimon 7 more than one channel with a single transmitter. Up to the present time, transmitters have been arranged for multi-frequency operation. by providing separately tuned circuits for each fre- The arrangement of my invention overcomes the practical difliculties inherent in previous systems, and, in addition, is compact and flexible in adjustment, This arrangement consists essentially of a system of mechanical positioning mechanisms applied to the rotating shafts of the adjustable tuning units of the transmitters, and interconnected in .such a way with suitable actut ating means that a group of dialed energy impulses will act to position each of the tuning shafts to the desired angular position correspond ing to the correct adjustment for each frequency. The angular position of each tuning shaft may be independently predetermined for ten or more independent tuning adjustments for each of a number of interchangeable preset assemblies, and a multiplicity of different frequencies may thus be selected by corresponding groups of dialed impulses.

The automatic tuning. system of my invention as disclosed is embodied in a self-contained radio transmitter of a type adaptable for use on aircraft. As illustrated in Figs. 1-4, the shaft positioning mechanism is constructed as a unit, Figs. 3 and 4, and combined with the main cabinet housing the transmitter and the control system, Figs. 1 and 2. Fig. -1 is a front elevation of the complete transmitter comprising the shaft positioning. mechanism mounted on the base I, and the main cabinet 4 enclosing or supporting the various elements of the transmitter including the-dial switch 44 by means of which the tuning is controlled. Fig. 2 illustrates somewhat further the arrangement of various parts, electron tubes 5, and shielded elements as at 6 being supported above a portion of the cabinet 4 and readily accessible. Also-thus mounted are a series nected in the control circuit of the system as will be hereinafter set forth in detail. Relay devices employed in the control system are conveniently mounted within the cabinet 4 in the positions indicated at 8 in Fig. 2. Standard minor switch structure of the type employed in telephone se'- lector circuits is also mounted in the cabinet 4 in connection with the dial switch 44 in the control system, as will be further defined. In Figs. 3 and 4 the shaft positioning mechanism is shown with cover removed, revealing the individual selector drum assemblies 9 provided for positioning the several tuning elements 3. In Fig. 3, I have also shown the motor 32 connected with drum switch 33. And in Fig. 4, I have indi cated the steps 22 cooperating with the drurfi assemblies 9. An indice 51 is: provided on the drum assembly for reference to dial indicia on the cover 2.

quency, and' some form of switching means for Fig. 5 shows the structure of the shaft posi-r tioning mechanism in more detail. The assembly is mounted on an aluminum casting I which is' in the shape of a box open at top and covered with plate 2 secured by bolts. Within the enclosure thus formed is an arrangement of drive shafts, gearing and spring means connected with motors 3| and 32, which are mounted respectively above and below the enclosure, with lead screws 24 and with the shafts 3a of the various'elements to be tuned, which elements are conveniently mounted under the base I by supports such as at'3b. The shafts 3a are coupled with shafts III which extend vertically through the base I and cover 2 and are rotatably mounted in bearings Illa, as shown more clearly in Fig. 9.

Referring to Fig. 6 in connection with Fig. 5,

motor 3| is shown as connected through suitable bevel gears and universal joints to shaft 30 which carries worm gears I2 for driving vertical shafts ID, as will be further described. Motor 32 is connected through similar bevel'gears and universal joints to shaft 29 for directly driving the lead screws 24 through suitable bevel gears 28. The means for driving shafts III includes worm wheel gears II engaged by worm gears I2. One of the gears II is provided with a depending offcenter pin I4 adapted to actuate a pivoted cam lever switch, indicated generally at 31, which is mounted in the base I beneath the gear having the pin I4, as shown in Fig. 5.

The construction and operation of the switch 31 are illustrated more clearly in Figs. '7 and 8.

In Fig. 7 the base I is broken-away to show the gears II and I2 and pin I4 in one limiting position. The switch 31 includes a multiple leaf contact portion comprising

spring leaves

31a, 17, c, d, e and 1, leaves b and e being movable for contact respectively with leaves a and c and leaves d and f. The actuating portion of the switch includes a lever member 31yhaving an insulated stud 31h for engaging leaves 31?) and e, and a shaft 3112 mounted in the base I and carrying the lever member 319 at the outer end and a cam lever member 31k at the inner end in operative relation to the pin I4 carried by gear II. The position shown in Fig. 7 is the normal condition of the switch for operation of the transmitter, and the alternate position assumed in the automatic tuning functions of my invention is illustrated in Fig. 8. In Figs. '7 and 8, the opposite positions that pin I4 may assume are indicated at I4'-, the are through which the pin shifts being greater than 180*.

Referringv now to Fig. 9, I have illustrated in detail the structure of the drum assembly 8, and in connection with Figs. 10-14, the structure and operation of the actuating arrangement for shaft III and the drum assembly 9. The shaft ID has a portion extending above the cover -2 on the base I, and secured thereto adjacent the cover, by key and groove or other suitable means, is a collar member 60 having oppositely extending lug portions 60a, as clearly shown in Fig. 14. A sleeve member I I has a base portion I la formed to engage the lug portions 60a accurately so that like sleeve members. may be interchangeably mountedon the collar 60 for precisely cooperating in positioning the shaft.

The sleeve member I! has a-longitudinal groove III) in the external face thereof, and a base member BI and a series of spacer washers Isa-7' splined therein, as indicated in Fig. 11, so as to be non-rotatable with respectv to the sleeve member I'I. Stop rings I8a 7' are mounted rotatably on the sleeve member |1, intermediate the spacer Fig. 9. -Handle 2| bly mounted in trated within the base eccentric arm 26a for moving washers war-7' and the base member 6|. A nut 20 engages screw threads on the upper end of sleeve member H for clamping the stop rings and spacer washers against the base member 6|, and the base portion |1a of the sleeve member. Recesses 2011 or similar means are provided on nut 20 to receive a suitable tool for moving the nut. When loosened, the stop rings Ita-j may be individually rotated'to selected position without affecting the setting of adjacent stop rings by virtue'of the splined' spacer washers l9a-7. The sleeve member |1 complete with stop rings and spacer washers clamped in position constitutes the drum assembly 9,. which is held on the upper portion of shaft III, in engagement with collar member 60 by a knurled handle 2| secured to the shaft l by bolt means 58 as shown in bears against the upper portion of sleeve member |1, permitting the nut 20 to be loosened so that with the shaft ID in manually set position, by handle 2|, an individual stop ring It! may be rotated to abut the stop 22,- in the manner shown with stop ring |8a in Fig. 11.

The stop 22 includes a body portion having a screwthreaded aperture engaged. by lead screw v 24 and a smooth bore aperture engaged by guide rod 23, as illustrated in Figs. 5 and 11. As the lead screw 24 is rotated through gears 28 and shaft 29, the stop 22 is brought opposite a selected stop ring l8, and is cooperable therewith to establish the shaft II! in a predetermined angular position.- The lower ends of screw 24 androd 23 are suitably mounted in the cover 2, and the upper ends thereof are likewise suitaa bracket support 25 extending above the cover 2 in the manner shown in Figs. 3 and 5.

The arrangement for moving shaft I0 is illusin Fig. 9, and more particularly in Figs. and 12. Gear wheel II is rotatably mounted with a sleeve bearing member 62 on an inner sleeve 26 which iskeyed or otherwise suitably mounted non-rotatively on shaft It. The sleeve 26 has an eccentric arm portion 26a extending above the gear II, and a stud l3 carried by the gear I! is adapted to engage the the shaft ID in a counterclockwise'direction as viewed in Fig. 10. The eccentric arm 26 has a pin l6 thereon engaged with the innerend of a spiral spring 21, the other end of which is secured to a pin l5 carried by the cover 2.

The spring 21 is tensioned to maintain the shaft Ill normally rotated to its limit of movement in a clockwise it drives stud J3 and eccentric arm 26a in a counterclockwise direction increases the tension on the spring up to the limit of movement of the-shaft ll.l in the counterclockwise direct on, which is the position illustrated in Fig. 12. This is known as-the home" position of the shaft l0, wherein all stop rings l8a-j are withdrawn from the vertical path of.m ovement of the stop 22, which is the pos tion shown in Fig. 13. Moving in the reverse direction gears H with studs l3 allow the individual spiral springs to rotate the sleeves 26 and shafts ||I until the respective stop 22- in set position is engaged by the corresponding stop ring of the serie's Hal-1'. This is the position shown in-Fig. 11. Gears II are rotated through a predetermined fixed are sufficient to allow all shafts to be positioned by coaction of the stops,22 and stop rings IBw-i, and in the case mitting setting of direction, and gear II as' position shown in Fig. 10. Figs. 10 and 11, then, show the operating position of the shaft III with stop ring |6a held against stop 22 by the tension of spring 21; and Figs. 12 and 13 show the home" position of the shaft III with the spring 21 tensioned against the stud l3 in gear stop 22 being free for movement.

All of the lead screws 24 are driven from shaft 29and all ,stops 22' are located in line so that all stops 22 engage corresponding stop rings of the various drum assemblies. Also from the description given in preceding paragraphs, it will be seen that the final positioning of a stop ring against the stop, for any one shaft I0, is independent of the positioning of corresponding stop rings against respective stops for all other shafts ID. If, for any one frequency of operation of the transmitter,-one set of adjustments of all of the tuning elements is required, it will be seen that it is possible to adjust all of the tuning elements properly for as many frequency channels as there illustrated, this is the are stop rings I8 on each drum-in the present case ten channels.

' a direction as to rotate gears II in the counter clockwise direction, to home position, and relay 38 when operated serves to run motor 3| so as to drive gears II in the clockwise direction, perthe shafts Ill, the directions being the same in Figs. 10, 12 and 15. Relays 40 and 4| serve to operate motor 32 in either direction depending on which is operated so as to raise-or lower stop 22. Slow release relay 42 has a double winding and its function will be described later.

Minor switch 43 has contacts 46a-a', each of which is connected to a corresponding contact 34ai,,on drum switch '33, and also has rotating magnet 41, release magnet 48, and off normal contacts 49. This minor switch may be of telephone type in rotating magnet 41 will step contact arm 50 up to contact with succeeding points 4611-7, depending on the number of impulses. when contact arm 50 is off the normal position and making contact with any of the points 46, off normal springs 49 are moved in the direction shownby the arrow. when current is applied to release magnet 46, contact arm 5|! is returned to its home or normal'position. Impulsing' device 44 may be which case impulses delivered to a telephone dial, and control impulsing springs 44b and off normal springs 44a. The battery shown at 45 may be any source of electromotive force suitable for operation of the system, or if desired one source may be supplied for operation of the relays and another source for operation of the motors by proper connection.

The relays and switches required for operating -the system of my invention are shown schematiquence control contacts 31c and b in one lead and'contacts 42a and b in the other, and operated by contacts 49b and a.

Relays 40 and 4| are connected directly to 5' battery 45 through lead 52, a circuit returning through lead 5|, contacts 43a and 17, contacts 42, b and a, and minor switch 43, to drum switch 33 wherein relays 43 and 4| are selectively controlled through contact segments 35a and-b connected respectively to the relays.

Relay 42 is of a slow release type and is provided with dual windings, one directly controlled from the battery 45 through contacts 44a, and the other through either contacts 40b and a, or 4|b and a to lead 53, depending upon whether relay 4|! or relay 4| is actuated.

The actuating coil 41 of the minor switch 43 is directly controlled from battery 45 through dial impulse switch contacts 44b. The release coil 43 is connected with battery 45 through contacts 42d and c, the circuit returning through contacts 49a and b from lead 5| and being operated at sequence control contacts 31c and 1.

Motor 3| is shunt wound and energized from the battery 45 under control of

relays

33 and 39. The field 3ib is connected to the battery through lead 54 and controlled through contacts 38a and b, or 39a and b, and lead 53. The armature 3|a is reversibly connectible with the battery, one circuit being through contacts 390 and d to lead 54 and contacts 330 and a to lead 53; and the reverse circuit being through contacts 39c and a operation depending upon .which relay, 38 or 39, is energized, the armature normally being short circuited through contacts 38c and d and 39c and d with the field circuitopen.

Motor 32 is series wound and energized from the battery 45 under control of relays 4|] and 4|. The series field is always energized in a given sense but the armature is reversibly connectible with respect thereto. The field 32b is connected with battery 45 through sequence control contacts 31a and b, and the circuit continues from tacts 43d and c or- 4|d and 0, depending upon which'relay is energized. In either instance, the opposite terminal of the armature is connected to lead 53 returningto battery 45, through contacts 4|c and a, or 40c and a, respectively. That is, for rotation in one direction, the motor circuit 32 includes field 32b, contacts 40d and c, the armature 32a, and contacts 4|c and a; and for I rotation in the opposite direction the circuit includes field 32b, contacts lid and c, armature 32a, and contacts 400 and a. Normally, the armature 32a is short-circuited through contacts 400 and d and He and d, and the field 32b is en-' ergized through resistor 55, which is connected in place of the armature, so that the motor32 becomes an eddy current damping device when not operating and while energized through sequence control contacts'lln and b.

The sequency of operations will now be de-. scribed. Beginning with the various elements in positions as shown at Figs. 7, 10 and 11, and with all'relay positions as shown in Fig. 15, we will assume that the transmitter is tuned to a frequency designated as frequency and that stop rings |3a are in engagement with stops 22, and we will further assume that it is desired to retune the transmitter to frequency No. 3 and that stop rings |3c have been set to give correct adjustment on this frequency. The operator inserts his finger in telephone dial 44 opposite the numeral 3 and to lead 53 and contacts 33c and d to lead 54, the

the field to the armature-32a through either conpulls it around until his finger strikes the finger stop on the dial. Off normal springs 44a will now l s comp g a circuit from battery 45, through lead 5| contacts 44a and through one winding of relay 42, thus operating this relay. Upon release of the operator's finger from the dial, the dial returns to its normal position, closing and openings springs 44b three times. Thus three current pulses will flow through the circuit from battery 45, through lead 5|, springs 44b, rotating magnet 41 and lead 52, and will cause contact arm 50 to move 'up and connect with contact point 460.

Before relay 42 can release after contacts 44a are opened at the return of the dial to normal position the other winding of relay 42 is energized through contacts a and b of either

relay

40 or 4|, as will be explained later, so that relay 42 will be kept energized. As soon as contact arm 50 moves away from the normal position, off-normal switch 49 will operate and contacts 49c and 49d will open. These may be connected in series with the plate power'supply of the transmitter in such a way as to remove plate power from the transmitter during the frequency change cycle. Contacts 49a and b will be closed, completing a circuit from battery 45, through lead 5|, contacts 49a and b, contacts 42bv and a, relay 39 contacts 310 and I: back to battery. Upon operation thusly of relay 39, connection is made to the armature and field of drum motor 3| from battery'45, through lead 53, contacts 39a and c, armature 3|a, and contacts 380 and d, and also from lead 53 in shunt through contacts 39a and b, and field 3|b, both circuits returning to battery through lead 54. Motor 3| will now run in such a direction as to move all of drive shafts l and associated equipment counterclockwise to the home position as shown in Figs. 8, 12 and 13.

In the meantime, connection has been established from battery 45, through lead contacts 49a and b, contacts 42b and a, contact arm 50, contacts 460 and 340, segment 35!), relay 4| and lead 52, causing relay 4'] to operate. This establishes a circuit from battery 45 through lead 53, contacts Ma and b, and the other winding of slow release relay 42 holding it operated for the time being. It segment 35a were contacted by contact 34c, the circuit would include relay 4|], and relay 42 would be kept energized through contacts 40a and b.

When motor 3| has operated to bring the equipment to the home position, cam driven switch 31 opens contacts 3'") and c and closescontacts 31a and 2). Opening of contacts 3Tb and c releases relay 39 and stops motor 3|. Closing of contacts 31a and b completes a circuit from battery 45 through lead 53, contacts 4|a and c, armature 32a, contacts 400 and d, series field 32b and contacts 31a and b, which starts motor 32 revolving in such a direction as to drive insulating segment 36 on positioning switch 33 toward contact with contact point 340. When insulating segment 35 contacts with point 340, the circuit before described through the operatingcoil of relay 4| is broken, causing relay 4| to release. Release of relay 4| removes voltage from motor 32 thus stopping it and also removes voltage through contacts 4| 1) and c to slow release relay 42.

If, due to inertia, motor 32 causes insulating segment 36 to pass contact 340, the circuit is completed through switch 50, contacts 460 and 34c, segment 35a and relay 40, which relay provides a control similar to that of relay 4|, but to, run motor 32 in the reverse direction, current to the armature being reversed; so as to return insulating segment 36 to contact with contact point 340. Resistor 55 allows current to flow-through series field 32b from lead 53 when armature 32a. is disconnected therefrom and short-circuited through contacts 40c and a. and (Z and c. The motor 32 thus acts as an eddy current damping device to prevent hunting when insulating segment 36 is seeking contact with contact point 340. The release time of relay 42 is such'that it remains actuated if motor 32 oscillates in a forward or backward direction before coming' to rest, but will release a fraction of a second after motor 32 has come to rest.

Release of relay 42 opens contacts 42a and b and closes contacts 420 and d, completing a circuit'from battery 45 through lead 5|, contacts 49a and b, contacts 31c and d, and relay 38, back to contacts 42d and c and to battery 45 through lead 52, which causes relay 38 to operate. Another circuit is now completed from battery 45 through lead 53, contacts 38a and b and field 3 lb, as well as a circuit from lead 53 in shunt through contacts 33a and c, armature 3|a and contacts 390 and d, both circuits returning through lead 54 back to battery, which causes motor 3| to rotate in opposite direction, current to the armature being reversed, to cause gears l I to rotate in a clockwise direction.

Drive shafts ID will also rotate in a clockwise direction under action of springs 21 until stop'rings I80 have individually contacted with stops 22, whereupon drive shafts I will individually cease rotating in their position as now determined. Motor 3| will continue to rotate until pin l4 has operated cam 31k as shown in Fig. 7, thus opening contacts 31d and e, thereby opening the circuit to relay 38 and stopping motor 3|, and closing contacts 31c and f.

A circuit is now completed from battery 45, through lead contacts 49a and b, contacts 31c and f, release magnet 48, and contacts 42d and 0 back to battery through lead 52. Operation of release magnet 48 restores minor switch 43 to its normal position and closes contacts 490 and d, allowing plate power to be reapplied to the trans mitter. Contacts 490. and b are opened, preventing operation of any of the relays until another number has been dialed. Current is removed from switch arm 50,before its return to normal position, at open contacts 42a and b.

The operation of the system of my invention may be briefly described as follows: An impulse transmitter 44 of the type commonly used in dial telephone circuits is operated to condition the circuits of a selector drum switch 33 and simultaneou'sly to actuate a slow release relay device 42 which operates to energize the minor switch 43 of the impulse transmitter, supplying energy to the selector switch 33, and relay means 39 controlling a motor 3| for moving all shafts to home position. Cam switch means 31 operated by the motor disconnects the relay means 39 con- I trolling the motor 3| when'the shafts reach home position, and simultaneously energizes motor means 32 for moving all stops to the position determined bythe selector switch 33; The last mentioned motor means is controlled by

relay devices

40, 4| energized through the selector switch 33 for determining the direction of rotation of the motor means. When the switch 33 is established in selected position, the relay devices and motor means are deenergized by the same selector switch. The slow release relay device 42 has been held operative through one of these last,

mentioned relay devices, and upon their release is deenergized so that after a given time it releases, deenergizing the minor switch and operating to connect an additional relay 38 which adapts the circuits of the first mentioned motor 3| for reverse operation, permitting all shafts to move away from home position under the force of spring means to set positionsas determined by the respective stop rings. The cam switch 31 is again operated by the motor 3| after a maximum predetermined rotation thereof, disconnecting the last mentioned relay and energizing a release magnet 48 in the minor switch of the impulse ransmitter for releasing the minor switch which then operates off-normal contacts 49 to remove power from the release magnet.

As indicated in Figs. 2 and i5, rotaryswitch means 56 may besynchronized with the operation of the selectordrum switch 33 by properly gearing and coupling the switch arm 56a. to ,motor 32, as shown suggestively in Fig. 2. The rotary switchmaybe used to connect crystals and tuned circuits of the oscillator and low powered stages of a radio transmitter where the large tuning elements controlled by the positioning mechanisms are not necessary. In actual construction, the entire low powered radio frequency system is mounted on a plate approximately 8 /2" x 8 which is removable from the transmitter proper simply by removing a few screws. It contains sockets for the oscillator and first amplifier tubes, sockets for ten crystals, sockets for small adjustable tank circuits for the first amplifier stages, a tap switch for selecting crystals and small tank circuits as well as necessary resistors, condensers and wiring; connections to it being made by a small multi-contact, easily detachable plug. The positioning switch 33 is also mounted on this unit and it is geared directly to the tap switch shaft in'the general manner indicated in Fig. 2.

One of the principal features in the structure herein disclosed is the removable drum assembly 9 as previously described. The drum assembly, including all of the stop rings,.may be removed from the drive shaft without disturbing the setting of the stop rings by merely removing screw 58, as no bearing is located on the shaft, above the drum. In replacing the drum the base portion |1a thereof and the lugs 60a. on the collar member 60 are arranged to be engaged in only one position, as by virtue of a pin 60b in one of the lugs adapted to enter an aperture in the base portion l1a, or any other suitable means. Hence for a transmitter operating on twenty difierent frequencies it would be possible to change from one set of tenfreque-ncies to another set of ten merely by changing crystals and drum assemblie I have shown my invention in Figs. 1 and 2 applied to a low power, self-contained transmitter suitable for use aboard aircraft or small mobile units. It will be understood however that thethe structure and the arrangement of the elementsthereof, and that no limitations are intended as to the form or application of my invention, except as are imposed within the scope of the appended claims.

What'I claim as new and desire to secure by Letters Patent of the United States is as follows:

1. Shaft positioning mechanism including a winged collar member on the shaft, an interchangeable sleeve member supported on the collar member in angularly fixed relation, a plurality of stop rings adjustably mounted on said sleeve member for individually coacting with a movable stop, and means connected with said shaft for clamping said sleeve member in respect to said collar member, said means being releaseableto permit the removal of said sleeve member with said stop rings maintained in adjusted relation for replacement by a similar sleeve member having similar stop rings adjustably mounted thereon in different positions for coaction with said stop to effect different set positions of the shaft.

2. Shaft positioning mechanism including a winged collar member on the shaft, an interchangeable sleeve member removably mounted in angularly fixed relation on said collar member, a plurality of stop rings adjustably mounted on said sleeve, member and individually engageable with a movable stop, and independent motive means for moving said shaft and said stop, means for defining a limiting home position of said shaft, said shaft being moved to said limiting position when it is desired to move said stop and subsequently being moved to a set position with the stop engaged with one of the stop rings, said shaft being moved to the limiting position also for interchanging sleeve members for providing differently adjusted stop rings cooperable with 1 mitting said spring means to establish said shaft in desired position as determined by the stop and the cooperative stop ring.

4. Shaft positioning mechanism comprising a box-like casing having a shaft extending therethrough, a stop ring assembly mounted on said shaft external of said casing and cooperative with a movable stop supported from said casing, a motor mounted on one side of said casing, a second motor mounted on the opposite side of said casing, and shaft and gear means interconnecting said motors separately with said shaft and said movable stop, the connection to said shaft including means for permitting relative movement between said shaft and the motor con nected thereto.

5. Shaft positioning mechanism as set forth in claim 4 and including a plurality of shafts having individual stop ring assemblies and cooperative -movable stops mounted in said casing,-said shaft tending therethrough, a stop ring assembly mounted on each said shaft external of said casing and separately cooperative with movable stops supported from said casing, shaft and gear means within said casing interconnectig said shafts and said movable stops respectively, means in the connection to each shaft for permitting relative movement of the respective shaft and the associated shaft and gear means. v

7. Shaft positioning mechanism as set forth in claim 6 and including separate external motor means connected with the shaft and gear means within said casing, for effecting movement of said stops and of said shafts, respectively.

8. Shaft positioning mechanism including adjustable stop means for a shaft, drive means for the shaft arranged for movement between two limiting positions with means for permitting relative movement between said shaft and said drive means, electrical control means for said mechanism including a switch for controlling a sequence of operations including actuation of said drive means to'one limiting position, adjustment of said stop means and actuation of said drive means in reverse to the opposite limiting position, and cam lever means actuated by said drive means at alternate limiting positions for actuating said switch, said switch being maintained in preactuated condition as said 'drive means moves from one limiting position to the other.

9. Shaft positioning mechanism comprising a box-like casing having a. plurality of shafts extending therethrough, a stop ring assembly mounted on each said shaft external of said casing and separately cooperative with movable stops supported from said casing, a motor mounted on one side of said casing, asecond motor mounted on the opposite side of said casing, shaft and gear means within said casing interconnecting the first said motor and said movable stops, additional shaft and gear means within said casing interconnecting the said second'motor and said shafts, means individual to the connections to the shafts .for permitting relative movement of the shafts and said second motor, said second motor being controlled for operation in reverse directions and for a fixed period in both. direc tions, electrical control means for both said motors including a switch mounted on said casing and operable for controlling a sequence of operations, and cam lever means mounted on said casing and actuated by said additional shaft and gear means at the end of each period of operationl of said second motor for actuating said switch, said switch being maintained in preactuated condition as said second motor is operated in the reverse direction for the said fixed period.

10. A shaft positioning system comprising adjust'ed stop means for the shaft cooperative with a movable stop, separate means for rotating the shaft and formoving the stop, and an automatic control system for actuating the last said means including adial impulse switch operative to condition 'the circuits of a selector switch and to energize one winding of a dual-wound slow release relay, said slow release relay being operative to energize, through said selector switch, control means for conditioning the means for moving said stop; said slow release relay being operative also to energize control means for operating the said means for rotating the shaft for establishing the shaft in home position, cam and switch means actuated by the last mentioned means to deenergize the last said control means and to motor mounted on said casing and connectedwlth energize the means for moving said stop for establishing the stop in selected position, the other'winding of said slow release relay being energized through the first said control means and deenergized by said selector switch with the stop in selected position; said slow release relay being operative after a fixed time period to energize control means for operating the said means for rotating the shaft for' effecting establishment of the shaft in desired position, said cam and switch means being actuated by the last mentioned means to 'deenergize the last said control means.

11. A shaft positioning system comprising adjusted stop means for the shaft cooperative with a movable stop, separate motor means for rotat ting the shaft and for moving the stop, and an automatic control system for actuating said motor means including a selector switch actuated by the motor means for moving said stop, a slow release master control relay, a sequence control switchactuated by the motor means forrotating the shaft, motor control relays separately connected with said motor means, a power source,

and circuit means interconnecting said master control relay and said sehuence control switch with said motor control relays and said power source for operation of said motor control relays and said motor means in predetermined sequence, said selector switch being connected with the motor control relays connected with the motor means for moving said stop, for establishing the stop in selected position.

' 12. A shaft positioning system including niotor means connected with the shaft, a selector switch connected with motor control relays for determining the operation of said motor means, and a controlled switch proportionatein construction to. said selector switch and actuated by said shaft.

13. A shaft positioning system including motor means connected with the shaft, separate motor means connected with position determin-' ing means for said shaft, a selector switch connected with motor control relays for determining the operation of the second said motor means, a sequence control switch connected with motor control relays for determining the operation of the first said motor means, and a master control slow release relay energized with the second said motor means and operative to control the functioning of the first said motor means in accordance with the condition of said sequence control switch.

14. Shaft positioning apparatus for tuning 'aircraft radio devices including a cabinet for housing the radio device, a box-like casing mounted on said cabinet and having a shaft extending therethrough, position determinin means for said shaft engageable therewith, a

said shaft, a motor mounted on said casing and housed within said cabinet and connected with said position determining means, a selector switch and'a dial control switch constituting ele-; T

ments of automatic control means for said motors, said selector switch being housed in said cabinet and mechanically connected with the second said motor, and said dial control switch constituting the sole manual control for operating said automatic control means.

15. Shaft positioning apparatus as set forth in claim 14 for a shaft extending through the said casing, and including in combination with said apparatus a switch arm and a series of switch contacts arranged in proportionate angular rela tion to the structure of saidselector switch, and means for driving said switch arm in synchronous relation to said selector switch by the second said motor for positioning said switch arm in accordance with the operation of said selector switch under the control of said dial control switch.

16. Shaft positioning mechanism including'a box-like casing having a shaft extending therethrough, position determining means for said shaft engageable therewith, drive means for said shaft disposed within said casing and including a gear member coaxial with said shaft and arranged for movement between twolimiting positions, said drive means also including means for permitting relative movement between said gear member and said shaft with the shaft in determined position, a depending pin member carried by said gear member, a cam device pivotally mounted in said casing adjacent said shaft and engageable by said pin member in the limiting positions thereof, and an electrical switch device mounted on saidcasing and operable by said cam device.

17. Shaft positioning mechanism as set forth in claim 16, with said cam device comprising a U- shaped member mounted at the base thereof on a stud shaft pivoted in a wall of the casing and extending parallel to the axis of said gear memher, said U-shaped member extending in a plane beneath the plane of said gear member and having the arms thereof substantially embracing the axis of said gear member and disposed in the path of said depending pin member, the ends of said arms, being formed at an angle with respect to the tangential line of contact with said pin member for effecting limited movement thereof by said pin member; and a crank member connected with said stud shaft and operative in a limited are upon actuation of said U-shaped member by said pin member, said electrical switch iicvice including a spring contact switch member engageable by said crank member in either of the limiting positions thereof on said are.

' ARTHUR A. COLLINS.