US2378294A - Posting unit - Google Patents

Description

June 12, 1945. o. s. FIELD ET AL POSTING UNIT Filed June 5, 1943 5 Sheets-Sheet l 1 f" M 5 QOM -L 1L IG :1 m

WIN by Their (Ittorneg June 12, 1945. o. s. FIELD ETAL POSTING UNIT Filed June 5, 1945 3 Sheets-Sheet 3 Q S lllllllrlllqvv Mww ' 'ZSnnentors O...Fie\ l and SNWight Their (Iitorneg MJZM,

II III mm on Patented June l2, 145

UNITED STATES PATENT OFFICE pany, Rochester, N. Y.

Application June 5, 1943, Serial No. 489,776

, 13 Claims.

This invention relates in general to airway trafflc control systems, and has more particular reference to a posting unit particularly adapted for use 'in such airway traffic control systems.

In systems of the type referred to, such as disclosed, for example, in th application of Field and Wight, Ser. No. 489,774, filed June 5, 1943, now Patent No. 2,344,761, dated March 21, 1944 and entitled Airway trafific control systems," an airway flight progress board is provided on which are automatically posted various numbers, for

identifying particular planes, computed times of arrival, overtime, etc. The posting unit, such as provided for by the present invention, may be used to form the flight progress board for use in such a system to effect the postings of these various identifying numbers.

This application which is directed to the structural features of a posting unit is to be considered as a continuation in part of our prior application Ser. No. 470,018 filed December 24, 1942, insofar as the structure of the posting unit per se disclosed in such prior application is concerned. Any subject matter common between this applie cation and such prior application is intended to be covered by claims included in this application.

One of the objects of the present invention is to provide a posting unit which is very small and compact in structure and hence most economical of space on the flight board.

Another object oithe present invention is to provide a posting unit which is simple in con:- struction and still is very rugged and hence long lived in operation.

A further object of the present invention is to provide a posting unit which lends itself to'ready inspection, for adjustment, and possible repair.

A further object is to provide such a unit as can be readily reassembled without th breaking of any wire connections, in the proper former relative positions of the various parts, so as to prevent any possible error in the performance of its posting function. This is accomplished, in the main, by providing quickly detachable plug coupler type of connections between the various parts.

A further object of the invention is to provide a posting unit of an interchangeable type controllabl by different and interchangeable contact control heads.

Further objects, purposes, and characteristic features of this invention will appear as the description progresses, reference being made to the accompanying drawings, showing, solely by way of example, and in no manner whatsoever in a Y., assignors to General Railway Signal Comlimiting sense, one form which the invention can assume.

In the drawings:

Fig. 1 is a plan view of on complete posting unit in accordance with this invention.

Fig. 2 is a side elevational view of the postin unit of Fig. 1.

Fig. 3 is an end elevational view of the display portion .of the posting unit of Fig. and a sec tional view of the display portion of two adjacent posting units.

Fig. 4 is a. side elevational view of the display portion of the posting unit of Fig. l, with'parts shown in section.

Fig. 5 is a sectional view on line 55 of Fig. 4, and viewed in the direction of the arrows.

Fig. 6 is a longitudinal sectional elevation with parts shown in elevation of the contact control portion of the posting unit of Fig. I.

Fig 7 is a longitudinal elevational exploded view of Fig. 6.

Fig. 8 is a sectional view on line 8-8 of Fig. 6, and viewed in the direction of the arrows.

Fig. 9 is a sectional view on line 9-9 of Fig. 6, and viewed in the direction of the arrows.

Fig. 1G is a partial sectionai view of a second form of the invention.

Fig. 11 is a sectional View on line ii---[ i of Fig. 10 viewed in the direction of the arrows.

Fig. 12 is a schematic view of circuits employed in this invention.

Referring now to the drawings, and considering the first form of invention, (Figs, 1-9) there is here shown, by way of example, a complete posting unit, as employed in the system of the application above referred to. Although but a single posting unit is disclosed in detail in this application, it can be readily understood from the system of the application above referred to that a large number of such units is employed, but since they are identical, it is suflicient for the purpose of the present disclosure to limit the description in general to but a single unit.

From Figs. 1 and 2, it appears that each unit is operated from a main shaft MS which can be continuously operated by a motor or the lke, not shown, and the unit is normally automatically held out of driving connection with the main shaft. The display portion of the posting unit, as described below, is operated by a display shaft DS on the inner end or which a drive gear DG is fastened as by means of a pm Hi.

The contact control portion of the posting unit,

as described below. is operated bya shaft CS to the inner end of which a gear CG is fastened as bya pin ll. ThegearDGiswide andhasteeth i2 which are always in mesh with teeth It on gear CG. Thus, as appears more clearly below, gear DG can be moved to the left to bring a friction face 14 thereon into frictional engagement with a like face I! on a drive wheel I4 pinned to the main shaft as at H without thereby thegearsDGandCG. Bymeansofthisarrangement, the display portion and the ccmtact control portion of the posting unit can b driven from main shaft MS upon gear DG being advanced toward shaft MS all as described more fully below.

Referring now more particularly to P18. 6, shaft CS passes through a fixed housing member I! which rotatably receives main shaft MS. Received on housing I! is one part II of a two-part separable casing having a second part with both parts formed of suitable insulating material as Bakelite or the like. These two-part casings i9 and 20 fit together in a telescoping manner with part 20 slidable on a receiving portion 2i of casing part I! to form a quick detachable plug coupling arrangement as appears more clearly as the description progresses.

Casing part I! is fixed to housing I! by means of screw 22, while casing part 2| is non-rotatably held on p rtion I! by means of a positioning pin 23 in part 20 and projecting inwardly thereof to be received in a slot 24 extending longitudinally inwardly from the inner end of part ll. With this arrangement, it can be seen that if casing portion 20 be removed from IE, it can again be replaced thereon in exactly the same position as it formerly assumed, by reason of this positioning pin 23 and receiving groove 24. Removably held in the free end of casing part 20 is a plug member comprising a portion 25 slidably fitting into the end of part 20 and having a semicircular annular groove 26 in which is received a split circular ring 21 which, when in holding osition, expands outwardly into a semicircular annular groove 28 in the inner face of part 20. In this way, plug member 25 can be readily inserted into, and removed from the Carsing part 20.

Plug member 25 receives a threaded stud 28 which clamps various contact members to the plug member. These contact members include an outer cup-shaped contact ring 30 of silver or like material, having inspection openings 3| therein, and an inner cup-like contact ring 82 of silver or like material. Member 32 is in electrical contact with stud 29, while member 30 is insulated therefrom and from member 32 by insulating washers 33. A terminal member 34 is clamped by stud 29 against member 30, while a second terminal member 35 is clamped together with an insulating washer 36 against the head of stud 29 and serves as a terminal for the inner cup member 32.

These inner and outer contact cup members 32 and 30 cooperate with a plurality of contact points, such as 31, carried on contact fingers, such as 38, to which fingers are connected pushers as 39 as by riveting or the like with the contact fingers, as 38, connected to the removable casing part 20 of the plug coupler arrangement as by means of screws 40.

Though but a single contact finger has been specifically referred to above, in reality there are ten contact fingers carried by the casing part 22, and these fingers are arranged around the circumference of the member as can be clearly seen from the fingers 4], 42, 43, etc.

The ten contact fin-- and the significance gers correspond to the ten digits 0-9, respectively, of this will be seen is the description pr For each contact finger, as ll, there is a terminal wire contact part as 44, fastened in s receivingslotflbyascrew 4lincssingpart II. To theinnerendofthiscontactpartucanbe fastened an energizing wire, such as 41, by solderingitorconnectingitinanyotherdesired manner. The other end of each contact part, as

44,hssanuptumedend,asat48,tobearagainst' its corresponding contact finger when the plug coupler is connected up, two of the contact fingers having inwardly bent ends, as at 4|, for example, to aid in locking together the two parts It and 2| of the plug coupler when it is assembled.

Each contact finger, as 33, has a pusher, as II, as described above, which is received in an openin as N, in the casing member 22 and projects inwardly thereof a short distance whereby to be contacted and operated by a cam member in the form of a roller I2 of fiber or like material held byapinliinabifurcatedenduofaheadli pinned, as at 54, to the contact shaft 08. When shaft CS is rotated, the cam successively operates on each pusher to move it outwardly and break the normal connection of the contact points, as It, with the inner ring 22 and make contact with the outer ring ll as shown in connection with contact point 31.

As appears from the above description, head It turns relatively to a shaft supporting member 54 which is held against rotation by means of a pin 59 carried thereby and received in the slot 24 of the casing part it. To revent accidental turning of cam 52 and its head when the plug coupler end is removed, a friction brake is employed, which comprises a spring 6| sleeved on shaft CS and urging member 54 against head 56 to compress therebetween a friction washer or brake member 52. The desirability of preventing such accidental turning of the cam will appear as the description progresses.

As can be seen from Fig. 7, which is an exploded view and similar to Fig. 6, the removable part 2| of the plug coupler can bereadily removed from, and replaced on the fixed part I9, all as described above and as here shown. Furthermore, the end portion of coupler member 20 can be readily removed and replaced as also shown in Fig. '7, and with it, the parts carried thereby including the inner and outer conducting rings ill and 32.

As shown more particularly in Fig. 4, for example, the display portion of the posting unit is controlled by the drive shaft DS which carries the drive gear DG, as described above, and which gear is pinned to its shaft as by pin II. This gear DG carries a sleeve portion 65 on the inner face of which is formed a series of teeth 66 forming V- shaped depressions 61, ten in number, to correspond to the tens digits 0-9 with a function which will appear as the description progresses.

Cooperating with these depressions $1 is a round-headed projecting pin it fixed in a fixed hub 69, which hub is carried by an electro-magnet cup-like fixed frame 1!. Shaft DS has pinned to it a magnetic plunger or core ll carrying a magnetic armature 12 of a disc-like form for cooperating magnetically with the shell-type magnetic casing or cup Hi within which is an electric winding 14.

Pinned to plunger H, as by pin 15, is a shaft 16 slidable in a yoke I1 fastened, as at II, to a base plate 18.

Shaft 16 is pinned, as at II, to a cup-like member 8| within which is received a biasing spring 82, and which cup-like member has forwardly projecting teeth 83 slidably received inapertures 84 in a bevel gear 85 received on and rotatable with shaft I6.

The bevel gear 85 is in mesh with a bevel gear 81 fastenedto a spur gear 88 which is in mesh with the teeth of a gear 89, formed on the base of a display cylinder 90 which is mounted for rotation in a bearing 9i suitably fastened to base plate 19.

Display cylinder 90 is made of translucent material such as frostedglass, milk glass, or the like,

7 and carries on its inside face, and distributed around its circumference, the ten digits 9.

Within cylinder 90 is a. source-of light in the form of a lamp 92 positioned in a receiving socket 93 whereby, when energized, the light shines I through the translucent cylinder 90 and makes can be slid into a receiving housing formed, as

shown best in Fig. 3, by vertical side plates 95 and and angle irons 91, 98, 89 and I00.

The showing in Fig. 3 includes not only the unit just described and which isdisplaying the digit l but also an adjacent unit with the front window removed, and in which the digits 2, 1, 0 are visible, and a portion of a unit IOI above this last mentioned one, and likewise a portion of a unit I02 below it. At its rear portion, the base plate is 'cut on a longitudinal central line part way towards the front end of the plate, and these portions are bent upwardly and outwardly at right angles to the floor portion to form two spaced supporting sides, one of which, I05, is shown best in Fig. 2, for supporting the electro-magnet unit. This unit is held in place as by screws I06 and I01. The front end of the base plate is turned upwardly at right angles to the floor portion and in front of the display cylinder 90 and is cut out centrally to form a.- part of a window as defined by the two spaced vertical panels I08 and I09. Connected to this upturned front end portion placein the housing. This forms a plug coupler type of display unit which can be readily removed ,from its housing and re-inserted theminto without the necessity for breaking any fixed wire connections.

The display portion, when housing, is limited in its insertion by plate H0 at its front which butts against the upper end of the housing, as at I2I.

Referring now to Figs. 1 and 2, it can be seen that upon energization of winding I4, armature I2 and core member II move toward and into the winding, whereby to disengage the socket 61 from pin 68 and advance the drive gear DG into frictional engagement with friction drive wheel I6.

' Thereupon, main shaft MS drives gear DG which,

of the base plate is a'stop and window plate IIO To this insulating plate are fixed two contact members I I4 and H5 contacting respectively with the base and with the socket of the lamp. For energizing coil I4 there are two contact members II! and H8 fastened to the insulating plate and extending rearwardly to terminate in plug coupler ends H9 and H9 In like fashion, contacts H4 and H5 terminate at the rear of the display portion of the posting unit in plug coupler ends I20 and I2I.

Fastened to the floor portion of the receiving casing formed by the side plates and angles is an insulating strip I22 which carries four inlet contact fingers I23, I24, I25 and I26 for cooperating, respectively, with the contact members H1, H5,

, III: and [18, respectively, when the unit is in as set forth above, is always in mesh with gear CG so that contact shaft CS and display shaft D3 are rotated to operate controlling cam 52 and display cylinder 90.

As set forth in the system circuit case above referred to, and shown in Fig. 12 (and disclosed more particularly in Fig. 15A, etc. of the above identified application 489,774) the control of the posting unit depends upon placing energy on any one only of the ten contact fingers 43, etc., by

means of wire connections (not shown), which results in placing energy on coil I4 through a circuit including the inner ring 32. This energy remains on the coil, and the drive continues until the cam breaks the circuit by lifting the particular energized finger away from the inner ring. Upon this occurring, the coil becomes deenergized, and spring 82 disengages the drive and reengages the opposing one of the sockets 81, etc. with pin 68 to immediately brake the display device and center it with the proper digit accurately positioned in the display window. It should be I borne in mind that the sockets 51, etc. are so positioned as to accomplish this, and that they are ten in number to correspond with the ten digits on the display cylinder. The circuits for accomplishing these functions have not been shown since this case is concerned primarily with the structure of one of the many posting units to be employed in the system case above referred to.

When the energized contact finger is lifted from the inner ring and makes contact with the outer ring, this completes a circuit and the energizetion of such circuit, so as to check various other functions, or so as to repeat the same display accomplished by this particular'posting unit at some other location, on the same operator's control board, all as more clearly set forth in the referred to system case.

The control of the posting unit is vested in any one of a large number of tokens of a type as disclosed in application, Ser. No. 489,775, filed June 5, l943,'in the names of O. S. Field and S. N. Wight and entitled Token and receptacle for airway trafllc control systems.

It can be appreciated from the above description that for inspection, repair or replacement of parts, the structure lends itself to the ready accomplishment of such operations. The display portion of the posting unit can be withdrawn from its housing, as aunit, from'the display cylinder up to and including the drive gear DG. Furthermore, the contact control unit can be removed in the manner indicated in Fig. 7, etc., the plug coupler portion 20 can be removed, and further, the end plug'portion 25 can be removed from the portion 20.

It should be noted that each contact finger, as 44, corresponds to a paticular digit on the display inserted into its operates with finger 3| when the plug coupler is assembled and carries contact point 31 corresponding as shown in the drawings, with the digit 1. It is essential that the parts be initially positioned so that this correspondence or any other arbitrarily chosen correspondence exists. Thereafter, should the parts be removed, they must be replaced in their former positions, as otherwise, the energization of a particular finger, to display the corresponding digit, will result in the display of some other digit.

To insure maintenance of this proper correspondence, it can be seen that the display portion of the posting unit, after being withdrawn from its housing, must be replaced in its exact former position, as determined by a dowel pin I30 carried by the housing and receivable in a matching hole I3I in the electromagnet casing.

In a like manner, for maintenance of the proper correspondence between the parts, the pin 21 in the removable part oi. the plug coupler is received in slot 24 in the fixed part of the plug coupler whereby to insure the proper reassembling of the plug coupler. Also, pin 59, in the stationary head 58, is received in this same slot 24 so as to prevent this head 58 from rotating while allowing it to slide on shaft CS. This sliding of head 58 permits spring BI to compress the braking washer 52 between the head and the collar 55, whereby to prevent accidental turning'of cam 52 and its carried parts when the plug coupler is separated and the display portion of the posting unit is removed. If, under these stated conditions, the cam were rotated, the predetermined correspondence referred to above might be changed with the result or faulty posting.

The plug 25 and its parts when removed from the plug coupler part 2!, can be reassembled in any position without any chance of error arising, since contact rings and 32 are continuous.

Since a large number oi posting units is required in the system, as disclosed in the system case referred to above at each of the fixes or check points, it is essential, in order that the airway flight board he not prohibitively large, that these units be very compact and economical in use of space. In this particular case, each housing member for receiving the display portion of a posting unit is in the order of a one-inch square. It can be appreciated from this that {or identifying a plane having a number, including three digits, such as 123, three complete posting units, such as described above are required, 1. e., one for each digit.

As stated above, this posting unit can be controlled by a token, as disclosed in the above referred to token application. In such application, a token when inserted in a socket completes three separate circuits in a distinctive manner to thereby energize one of the ten fingers on each of three posting units. This causes the operation of each of these three posting units until the proper number appears in the window at the front of the unit, at which time the unit is deenergized and posting of the proper plane identification is effected.

A somewhat modified form of the invention is shown in Figs. 10 and 11, wherein the contact control portion of the posting unit is of a different construction from that shown in Fig. 6, for. example, and described above. In this form, the contact control portion is changed from the former construction only with regard to the removable portion of the plug coupler arrangement.

asvaacs ries ten contact fingers, as I", arranged around the periphery of the part and having riveted to them pushers, as I", which are operated as described above by a cam I. Each finger has a contact point, as I45, biased to normally contact with an inner continuous conducting ring I" but operable by the cam to break connection with this inner ring and to make contact with the corresponding one of ten isolated outer fixed contact strips, as I", arranged around animulating block I53 and connected thereto by screws I41 Also connected to each of the pushers, as pusher I43, is a second contact finger Ill which is in electrical contact with its associated finger and extends beyond this associated finger and carries a contact point I50 which contacts with a continuous conducting outer ring I5I when in its cam operated position. These fingers I49 are biased to normallyrest against an intermediate insulating block I52, between which block and outer block I53, is clamped the continuous ring I5I. Ring I5I has a lead-out connector I54 for connection to external circuits, while the inner ring I46 has a lead-out connector I55 which is .in electrical contact with its ring by way or a clamping bolt I56 which is similar to the corresponding bolt employed in the first form of invention, but is somewhat longer than such bolt.

The connecting bolt I56 clamps the various portions together, as obvious from the drawing,

and is received in an inner block I51 of conducting material and which is detachably held in place in the removable coupler part IIII by means of grooves and a resilient split ring I60, as in the first form. The extending contact fingers, as I", are apertured, as at IBI to freely receive the contact points, as I45, on the outer fingers, as I42.

From the above description, it can be readily appreciated that the cam I, when operated, successively moves the outer fingers away from making contact with the inner ring, and into making contact with the'isolated strips, as I41, while at the same time; the extending contact fingers are moved successively, from an inactive biased position to an active operated position into contact withthe continuous outer ring I5I.

The posting unit, in the modified form Just described, differs from the posting unit as described in connectionwlth the first form only with regard to the removable part oi. the coupler. Accordingly, by simply removing this part of the plug coupler'from the fixed par-t and replacing it by the modified form of removable part, the posting unit can be changed from the one form to the other. This makes for easy and economical interchangeability of the form of posting unit and is a distinct advantage since both forms, in large numbers, of posting units are employed in the system case referred to above.

In this modified form of posting unit, the control of the posting at the fix at which the unit is located, is controlled as before by breaking contact of the proper outer finger with the inner ring all as shown in Fig. 12in connection with the first described form of invention. The function of the inner fingers in connection with the outer ring and of the outer fingers in connection with the strips, as III, is involved in the transfer or repeating of the posting at one "fix" to another fix on a difierent operator's control board.

The various circuit arrangements and connectioned to contact, respectively, with the strips tions for effecting this function are not described in this specification since they do not constitute any part of this particular invention, and for details in this connection, reference should be made to the system case referred to above.

The above rather specific description of two forms which the invention can assume, has been given solely by way of example and is not intended, in any manner whatsoever, in a limiting sense. It is to be understood that various modifications, adaptations and alterations may be applied from time to time to meet the requirements of practice without, in any manner, departing from the spirit or scope of the invention, except insofar as limited by the appended claims. Having described our invention, we now claim: 1. In posting units for airway traffic control systems, in combination, a posting unit having a display part and a contact control part, a driven shaft for each part. a main drive shaft. means for operably and simultaneously connecting the main shaft. to the two driven shafts, the control part including. a fixed casing, a removable casing quickly detachably securable on the fixed casing,

a plurality of contact strips onthe fixed casing, a like pluralityof. contact fingers on the removable casing' positioned to contact, respectively, with the strips. when the two casings are interconnected, a removable plug in the removable casing, an inner-land a spaced outer. conducting part including, a fixed casing, a removable casing quickly. detachably securable on the fixed casing, a plurality of contactstrips on the fixed casing,

a like plurality of contact fingers on the removable casing and positioned to contact, respectively,

when the two casings are interconnected, a removable plug inthe removable casing, an inner,

and a spaced outer, conducting ring carried by the plug. the control part shaft extending throu h.

the fixed casing and into the removable casing,.

a, contact operating cam on the shaft, contact P ints on the contact fingers movable by the cam from one ring to the other, an operating pusher on each contact finger, an aperture in the removable casing for each pusher and'loosely receiving its pusher, the contact fingers being biased to position the pushers toextend inside of the casin and opposed to the cam, and mechanicallyinter-' engaging means on the fixed and removable casings; respectively, for requiring assembly of the casings always in the same relative position.

4. In posting units for airway trafiic control systems, in combination, a posting unit having a display part and a contact control part, a driven shaft for each part, a main drive shaft, means for operably and simultaneously connecting the main shaft, to the two driven shafts, the control part including, a cylindrical fixed casing, a cylin- V drical removable casing quickly detachably securable to the fixedcasing, a plurality of contact strips on and around the outside of the fixed casing, a like plurality of contact fingers on and around the outside of the removable casing, and positioned to contact, respectively, with the strips,

when the two casings are interconnected, arewith the strips when the two casings are inter- 7 connected, a removable plug in the removable casing, an inner and a spaced. outer, conducting ring carried by the plug. the control part shaft extending through the fixed casing and into. the removable casing, a contact operating cam on the shaft. and contact points on the contact fingers movable by the cam from contact with one ring to contact with the other, the contact fingers and the-contact strips being positioned around the outside of their casings,'an operating pusher on each contact finger, an aperture in the removable casing for each pusher and loosely receiving its pusher, the contact fingers being biased to. position the pushers to extend inside of the casing and opposed to the cam.

I 3. In posting units for airway traflic control systems, in combination, a posting unit having a display part and a contact control part, a driven shaft for each part, a main drive shaft, means for operably and simultaneously connecting the main shaft to the two driven shafts, the control part including, a cylindrical fixed casing, a removable cylindrical casing quickly detachably securable on the fixed casing, a plurality of contact stripson and spaced around the fixed casing, a like plurality of contact fingers on and spaced around the removable casing and posimovable plug in the removable casing, an inner, and a spaced outer, conducting ring carried by the plug, the control part shaft extending through the fixed casing and into the removable casing, a contact operating cam on the shaft, contact points on the contact fingers movable by the cam from contacting with one ring to contacting with the other ring, an operating pusher on each contact finger, an aperture in the removable casing for each pusher, and loosely receiving its pusher, the contact fingers being biased to position the pushers to extend inside of the removable casing and opposed to the cam, and friction brake means between the shaft of the contact control part and the fixed casing, to prevent accidental turning of the shaft whenthe removable casing is removed. 7 v5. In posting units for airway trafiic control systems, in combination, a posting unit having a display part and a contact'control part, a driven shaft for each'part, a main drive shaft, means foxoperably and simultaneously connecting the main shaft, to the two driven shafts, the control part including, a cylindrical fixed casing, a cylindrical removable casing quickly detachably securable to the fixed casing, a plurality of contact strips on and around the outside of thefixed casing, a likeplurality of contact fingers on and points on the contact fingers movable by the cam from contacting with one ring to contacting with the other ring, an operating pusher on each contact finger, an aperture in the removable. casing for each pusher, and loosely receiving its pusher, the contact fingers being biased to position the pushers to extend inside of the removable casing and opposed to the cam, polarizing means on the fixed and removable casing for requiring assembly of the casings always in the same position, and friction brake means between-the shaft of the contact control part and the fixed casing, to prevent accidental turning of the shaft when the removable casing is removed. 7

6. In posting units for airway traffic control systems, in combination, a posting unit having a display part and a contact control part, a driven shaft for each part, a main drive shaft, means for operably and simultaneously connecting the main shaft, to the two driven shafts, the control part including, afixed cylindrical casing, a removable cylindrical casing quickly detachably securable'to the fixed casing, a, plurality of contact strips on and arranged around the fixed casing, a like plurality of contact fingers on and arranged around the removable casing and positioned to contact, respectively,'with the strips, when the two casings are interconnected, a removable plug in the removable casing, an inner and a spaced outer, conducting ring carried by the plug, the control part shaft extending through the fixed casing and into the removable casing, a contact operating cam on the shaft contact points on the contact fingers movable by the cam from contacting with one ring to contacting with the other, an

operating pusher on each contact finger, an aperture in the removable casing for each pusher and loosely receiving its pusher, the contact fingers being biased to position the pushers to extend inside of the casing and opposed to the cam, an extending contact finger and contact point on each pusher and in electrical contact with the other finger on the pusher, and a second outer conducting ring on the plug and cooperating with the contact points of the extending fingers.

7. In posting units for airway trafilc control systems, in combination, a posting unit having a display part and a contact control part, a driven shaft for each part, a main drive shaft, means for operably and simultaneously connecting the main shaft, to the two driven shafts, the control part including, a fixed cylindrical casing. a removable cylindrical casing quickly detachably securable to the fixed casing, a, plurality of contact strips on and arranged around the fixed casing, a like plurality of contact fingers on and arranged around the removable casing and positioned to contact, respectively, with the strips, when the two casings are interconnected, a removable plug in the removable casing, an inner and a spaced outer, conducting ring carried by the plug. the control part shaft extending through the fixed casing and into the removable casing. a contact operating cam on the shaft, contact points on the contact fingers movable by the cam from contacting with one ring to contacting with-the other, an operating pusher on each contact finger, an aperture in the removable casing for each pusher and loosely receiving its pusher, the contact fingers being biased to position the pushers to extend inside of the casing and opposed to the cam, the extending fingers passing between the inner. and the first said outer ring, and an aperture in each extending finger loosely receiving the contact point of the other finger on the same pusher.

8. In posting units for airway trafilc control systems, in combination, a posting unit having a display part and a contact control part, a driven shaft for each part. a main drive shaft, means for operably and simultaneously connecting the main shaft, to the two driven shafts, the control part including, a fixed cylindrical casing, a removable cylindrical casing quickly detachably securable to the fixed casing, a plurality of contact strips onandsrrangedaroimdthefixedcasinmalike plurality of contact fingers on and arranged around the removable casing and positioned to contact, respectively, with the strips, when the two casings are interconnected, a rmnovable plug in the removable casing. an inner and a spaced outer, conducting ring carried by the plug, the control part shaft extending through the fixed casing and into the removable casing. a contact operating cam on the shaft, contact points on the contact fingers movable by the cam from contacting with one ring to contacting with the other,'an operating pusher on each contact finger, an aperture in the removable casing for each pusher and loosely receiving its pusher, the contact fingers being biased to position the pushers to extend inside of the casing and opposed to the cam, and mean anchoring the removable casing against rotation when in assembled position on the fixed casing.

9. In posting units for airway traffic control sysstems, in combination, a posting unit including a control part and a display part, a main drive shaft, a driven shaft in each of said parts, biased lock means for normally positively locking both driven shafts against rotation, release means operable for unlocking the driven shafts and simultaneously drivsbly connecting them to the main shaft, a plurality of conducting contacts operably connected to the control part shaft so as to be successively operated when their shaft turns, a turnable display box operably connected to the display part shaft so as to turn when its shaft turns, and different indicia of a number equal to the number of said plurality of contacts, distributed around the box, the control part including a plug member and a plug member receiving socket member, each of said plurality of contacts including a plug portion carried on the plug member, and a socket portion normally in contact with its plug portion and carried on the socket member, the plug and socket members being quickly, detachably connectable together, and cooperating mechanically interengnging means in the two members respectively for requiring the connection of the two members in an invariable position in which the same plug and socket portions of contacts are-always electrically interconnected when the members are interconnected.

10. In posting units for airway traffic control systems, in combination, a posting unit includ- -ing a control part and a display part, a, main drive shaft, a driven shaft in each of said parts, means operable for drivably connecting the driven shafts to the main shaft, a plurality of contacts operably connected to the control part shaft so as to be successively operated when their shaft turns, a turnable display means operably connected to the display part shaft so as to turn when its shaft turns, and different indicla, of a number equal to that of said plurality of contacts, distributed around the means, the control part including quickly detachable plug and socket members, each of said plurality of contacts including a plug portion carried on the plug member, and a socket portion carried on the socket member, cooperating pin and slot means in the two members for assuring the interconnection of the two members in an invariable position in which the same plug and socket portions of contacts are electrically interconnected when the members are interconnected, and a secondalternative plug member, having a different arrangement of contact plug portions. removably securable on the said socket member, so

that the contact plug portions cooperate with the socket contact portions.

11. In a posting unit for an airway traffic control system, a driven shaft located longitudinally of the unit and normally biased longitudinally in one direction, electromagnetic means for actuating said shaft longitudinally against its bias for engaging a power-driven clutch to cause rotation of said shaft, detent means for normally preventing rotation of the shaft when it is in its normal biased position but releasing said shaft for rotation when it is actuated by said electromagnetic means, a display drum mounted on an axis at right angles to the axis of said driven shaft, and means operatively connecting said drum to said shaft irrespective of the position of the shaft to thereby cause the display drum to be rotated when said power-driven clutch is engagedbut to be held in its existing position when said shaft is in its biased position.

12. Ina posting unit for an airway traffic control system, a driven shaft located longitudinally of the unit, a coil spring surrounding the shaft and normally biasing it longitudinally in one direction against a stop, an electromagnet having a winding surrounding said shaft and a circular armature attached to said shaft for causing the endwise movement of said shaft against said biasing spring when said winding is energized, a centering detent means including a circular member attached to said shaft and having a recess for each of a plurality of positions and a fixed centering member receivable in the nearest one of said recesses when said shaft is biased to its normal position by said coil spring, a powerdriven clutch engaged by said shaft when it is caused to he moved endwise by said electromagnet for causing rotation of the shaft, a display drum mounted on an axis at right angles to said driven shaft, and means including a beveled gear mounted on said shaft to allow endwise movement of the shaft with respect to the gear but causing the gear to be rotated when the shaft rotates for causing the rotation of said drum to its different positions.

13. In a posting unit for an airway traffic control system, a display drum having a plurality of different display positions and mounted to be rotated on an axis parallel with the plane of an aperture in the face of the unit, a, driven shaft located longitudinally of the unit and normally biased longitudinally in one direction against a stop, an electromagnet having a winding surrounding said shaft and a circular armature attached thereto for causing the actuation of said shaft away from the stop when said winding is energized, a power-driven clutch engaged by said shaft when it is in an actuated position for causing rotation of the shaft, means operatively connecting saidshaft with said display drum to cause rotation to its different positions when said power-driven clutch is engaged, a separate contact unit having a contact for eachposition of said display drum and operably connected to said shaft through a sliding gear connection, and a centering detent means including a circular member having a toothed recess for each position of said display drum and a fixed centering member receivable into said recesses when said shaft is biased against the stop, whereby said display drum is caused to be centered in the selected display position and the contact for the corresponding position is positively held when said electromagnet is deenergized irrespective of the slight off center stopping of said shaft for any selected position when said power-driven clutch is disengaged.

, OSCAR S. FIELD.

SEDGWICK N. WIGHT.

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