US2489638A

US2489638A - Arrangement for switching on and initiating processes by means of telephone calls

Info

Publication number: US2489638A
Application number: US583696A
Authority: US
Inventors: Handschin Max
Original assignee: IPSOPHON PATENTGESELLSCHAFT A
Current assignee: IPSOPHON PATENTGESELLSCHAFT A; Ipsophon Patentgesellschaft A-G
Priority date: 1944-12-11
Filing date: 1945-03-20
Publication date: 1949-11-29
Anticipated expiration: 1966-11-29
Also published as: CH257252A; AT163570B; BE460890A; NL65337C; FR913552A

Description

Nov. 29, 1949 M. HANDSCHIN 2,489,633

ARRANGEMENT FOR SWITCHING ON AND INITIATING PROCESSES BY MEANS OF TELEPHONE CALLS Filed March 20, 1945 m a ll Jm a J;

T 3 2 I m g m M M UH AT 7 I I H I?1 v I q E 1 a I4 S II INVENTOK:

Nax Handsc/vin ATTORNEHS Patented Nov. 29, 1949 2,489,638 FOR SWITCHING 1 ON AND .ZARRANGE'IHENT PATENT INITIATING PROCESSES EY MEANS F ,TELEPHONE CALLS Arrangements ior switching eon electric ap paratusand for: initiating-processes are already known. Such devices are employe'd'in particular in connection with telephonographs which must be controlled "'by-- telephone calls either 7 for the reproduction of recorded messages or forithe re ception of communications. It .is evidentthat unauthorized persons must'be preventedwhen calling up from listening in on recorded'com munications. For this purpose devices have been invented which, after the "telephonograph has been set in -moti0n, -transmit to the caller at fixed intervals-signals such that the-caller must in turn emit-signals-after :pauses corresponding to "a"-'prearranged -key-= or=:code. -These signals, assumed always that they correspond to. the prearranged 'key set in motion-the reproducing apparatus. V

Arrangements of this type can, however, also be utilized for any other purpose, such as for switchingon electrio 'apparatus of any kind or for releasing mechanical devices. Mn this case, too, the. preliminary insertion of the abovementioned device, whicnwemay. call a "secret "lock, affords a guarantee that unauthorized persons cannot initiate theprocess. I

'The devices ioreffecting the'swit'ching'on or initiating ofproce'sses' by telephone calls dependent on' a prearrangedkey" and thereiorev on "prearranged signals given at fixed intervals are, however, "of eiitremelyfcomplicated design and construction. Secret"locks'-of""this t'ypeshould "also admitof"as"m'any"variations 0f the key as possible. "This"requirement must-*n'ot, on the other hand, render the installation economically impracticable.

The present inventiomrelates-ta-a secret lock of this kind for arrangements enabling processes to be switched 'on andrrinitiated by: telephone calls. -It is characterized by simplicity? of 13011- struction "and; aiwide rangez ofiwariationeioi the key. In the;arrangement-: ior'iinitiatingiprocesses by means of telephone. calls the subscribers calling-"circuit as}. usual actuates a" device transmitting at fixed intervals signals "f(for example aseries of numbers) between which the ca'iler :can emitorder impulses of anyidesired frequency,

which, occurring during thaprearranged pauses,

cause processes to be switched onsand initiated.

This-device :is characterised ina thatv a selector -rnechanism with -:several switchbuttons, to each pulses. :Both oi these relays-are connectedwith.

a'third, multi-ccilblock-relaycorresponding. to a switching-device insnch a way-thatthis third relaywis not excited only when bothlthe tether r-e- --1ays--are: simultaneously. excitedorisimultaneously not excited/The result is that whennosorder impulse .is received '.or .one..is.received at the wrong moment "the switch-device .is blocked.

It has beenv found convenient to design" the arrangement sothatthe circuit of each switch button .of the selector. mechanism is :Iclosedzby pressing the corresponding button. This closes the cam-controlleditzbiitaCt and consequently egcit'es the relay connected with the selector mechanism. LAnother practical measure is shift the cams controllinglthe contacts of-the switch buttons .in such awaytthat the contacts of the single. .buttonss are.-actuated successively at intervals. A suitable embodiment .of'ithe selector mechanisni'hasio buttons, giving l024*,'viz. 2 different keys. "JThegreativariety of .keys, .together with the factZthat the key 'can'be .easily altered at any time, ensures the greatest possible security .against interference by unauthorized persons.

Besides the above-mentioned block-relay the circuit of the switching device also contains a cam-controlled contact. .Tnis'can only be'j'close'd when all the cam-controlled contacts..of'the sejle'ctor mechanism have been actuated. "This means that .the circuit ofthe' switching ;device can only be closed after allthd'buttons oi'the selector mechanism have. been actuated'i'successively. If an :ordenimp'ulse is.not're'ceived"from the caller in correspondence with any parti'cular button, or if one isreceived in correspondence with a buttonwhicnwas not pressed; the block- ;relay inserted in theswitch'icircuit' is actuated. vThis relay is so designedihatnnce; actuated "it remains excited" till 'thecohtrblgprocess is terminated. -This preventstheswitchdevice', which may consist. in a relay,. being actuated "by closing the cam-controlled contactins'erted'in' the switch circuit. Only when the"impulses.:;arrive during the pauses following "the pressing of the buttons forming. the .key is the action or the block-relay excluded. "The .switchcircixitisiclosedafter the cam-controlled contactmas' .been actuated "and "the callerisconnected withtheelectricapparatus "or the'process initiated.

.details andthe general construction of. the whole circuit may be elucidated Witlithe help of the accompanying drawing representing the diagram of the circuit of a specificembodiment 'of' the arrangement according to the invention herein described.

,-.The, drawing represents "the wiring of.,p'art of a subscriber's stationpprovidedwith.aj.;telephonograph and connected with the telephone network by means of the cables [3, I4. If a call is made by any subscriber of this network destined for this subscribers station, the connection between this subscriber, the exchange ofiice, and the called subscribers station is made by means known in themselves (not shown). The calling alternating current then sent out by the exchange office, goes through the cables l3, M, the contacts l6, l1, and the condenser 55 to the relay R4, energizin the latter. contacts of this relay, which energizes the relay H6, provided with three windings, through its This closes the winding I. f the three windings of this relay,

the windings I and II serve for actuating the relay, while the winding III is bifilar incapable of setting the relay in operation. The relay H6 actuates the contacts 7, 8, ll, 16, i1 and i3 causing the following processes:

The relay MRIB is set in operation through the contact 8 and the winding I of the relay ST! 2, provided with three windings, causing this relay to become operative. The cables l3, l4 are disconnected from the relay R4 at the contacts l5, H and are connected with a circuit going through the contacts 29, 30 of the relay U49 and the outlet of the amplifier VAG3I. At this point, the contacts 1 and 73 are still inoperative. The relay MRIB, through its contact 19, closes the circuit of the motor M20 which is destined for driving the sound carrier T033 and the cam disks NKI to NKIS in forward or reverse movement. The relay STIZ, which can be energized through each one of its three windings, is, after it has been energized in the said manner through its winding I, inserted in a holding circuit, which runs through a contact 65, closed by the cam of the cam disk NK|4 in the position of rest of the latter, the operating contact 63 of the relay STI2 and the winding III of the relay STlZ. Beside the contact 63, there have also been closed the contacts 56 and BI of this relay, of which the former actuates the relay T51 and the latter the coupling magnet VK62; this magnet through a gear (not shown), couples the motor M29 with the cam disks NKI to NKI8 and the two coils S and T, on which has been wound the sound carrier T033, for example, consisting of a steel wire, so that this sound carrier in the forward movement, and the cam disks are moved in the same sense in the direction shown in the drawing at the cam disk NKI The cam disk NKI4, shortly after starting its movement, opens the contact 66, thereby opening the circuit passing through the winding III of the relay STIZ and disconnecting the relay. However, the cam disk NKI5, immediately after starting, closed the contacts 59 and 69, keeping them closed continuously during one whole rotation. In this way, there are formed two holding circuits for the relay T! and the coupling magnet VK62, which are independent of the relay STIZ. The relay Till, when energized, incidentally keeps open the circuit of the coupling magnet RK45 for the reverse movement of the sound carrier T033 and of the cam disks NKl to NKIB at the contact 43 during the entire rotation of the cam disks. The recordings existing on the sound carrier T033 which consist of a general message to the calling person and subsequently in a succession of numbers, for instance from 1 to 10, produce in the reproducing magnet SPKHJG currents which are transmitted to the calling subscriber through the amplifier VAG3I and the cables l3, I4.

The circuit may now be explained with the help of a number of examples of correct, incorrect and repeatedly incorrect command, considering a selector mechanism with 10 buttons. Let the secret key be the number 146. This presupposes that of the keys TI to Til), the keys Tl, T4, and T6 have been confirmed by the owners of the telephonograph so that the contacts 84, 87, and 89 are closed. As will be seen from the subsequent description in detail, it is, for a correct control by the calling subscriber, now necessary for the latter, immediately after sounding those numbers of the series of numbers, emitted by the telephonograph, which correspond to the numbers of the secret number, thus, in the present case, after the numbers 1, 4, and 6, to speak into his microphone each time at least two impulses consisting of one sound each. 0n the other hand, when the remaining numbers of the series of numbers are sounded, in the present case after the numbers 2, 3, 5, 7, 8, 9, and 10, he must not give any sound impulses to his microphone.

1. Correct control Immediately after the calling subscriber has heard the number 1, he will be switched from the amplifier VAG3 I, which serves for the amplification of the sounds coming from the reproducing magnet SPKIOO, to the amplifier VEG32 which serves for the amplification of the sounds coming from this subscriber. This is done by cam NKI! and relay U49 over the following circuit:

(1) Earth, NKI'I, contact battery.

Hll, relay U49,

(2) Earth, Tl, contact 84, NKI, contact 14,

relay P98, battery.

When the calling subscriber speaks the first of the two sound impulses to be sent out after the number 1, into his microphone, the relay L50 is actuated in the following circuit:

(3) Earth, NKI6, contact 58, contact 53,

contact 5|, relay L59, battery.

The relay C48 is provided with two windings I and II. However, it can be energized only through the winding I, since the winding II is bifilar. Before the relay L51) is energized, the winding I of the relay C48 is without current because of the open contacts 5!, so that closing the contacts 53 of the relay J28 in regard to the relay C48 remains inefiective for the time being. If the relay L50 in the circuit 3 has been actuated and if the contact 53 is still closed, the relay C48 stillcannot be energized, since on both ends of its winding I there is the same potential, that is through contacts 58, 53, and 41, on the one hand, and the contacts I02 and 51, on the other hand.

" itientifcal hq itftrti nt af r umber ad; 3 aithfhklri' ittaet liJ Zf cOntact lt n f t t tt gr .cbyntiatt 1 teatim ttt'ety. re a iate a? =1. hwte o w et-1 9 v K ea e tx 'ar..l. 3 f he mb "l fl y 1 td attheeetqit jfir 6 "We hat e the the onditions as after numd tt p f qt 'thei a ng I ex: e. 'it'itt'o it p jes-sedjjtiq'sitig'cotttt tt at, W es the ground potential, "so 'that {as P 98 is ezzcited by the ciosingf of een e'stablis edthrou'gh the contacts *hnta ct 'm i cant The remaining buttons ,8; 53, 1ai d Mat th sereni y; t -t wineries I "to "i to'jrmj'vtitn contacts at, exist-'93 the the 'of'therei'ay 8,"'to'"'be disconnectedx This're- "ti ties eas g, cams-N111 BQSQ 'wi t s lay is now actuated in the following circuit: g e as i fl' tp th t t 1mm- (5) Earth, b t m fb 5t 'tiofi'isidentical withthat corresponding to biitg yf winH -f ifiia winding 4: tons T113 and 5 The correct control IIIIIDHIISQS a r' 5 ,hlavednow been glven and the following clrcuit 18 L M 1 t I rd ruim ulse v n'by'. thepaller I a r v r a tra cts're'layflfi"and'the following-circuit (10) Earth, Contact 95, Contact relay'ANSG, battery.

contact 5%, contacti ti b Uponlputtfnglbh relay ANQB into Operation h a 41l ontact 1 "relay X24, the contact'35 is closezi by which any mechanical w h t f jor electricalprocess may be released. This process may, for example, consist inconnecting the in line l3, M of the telephonograph with a producing"inaiiet' belonging 'totjthe I p ,l'atter,Whiehimagnet operates 'in conjunction 1365 the relay X251 remems "with'asteel band-on tvhichther'e are any, jc1esired igj lbyiousythat the order impulses emitted by thecaHer or 'byiflthe exchange wiitriot'alt'trays ength. In order to hring about t a A h la Pas h e nfq neyt teeerdin' s whichthe calling subscriber Wishes I X 2 4',1wh1 c h possesses three w ndings 1n to heat 11; i wh fie on fused for Its 3 A'ss tion as circuit--10 isclosedhonta'ct 12 of is insert-edin the-fol the r'eIayANfiGis interrupted. This prevents a. g circuit: second passage Of t he sound carrier T033, as

-(7) Earthjcondenser 22, Contact 23, relay v,ftj il eg xbla d inid ailbefllow The two cam x24, vtinding I, battery. TQZ ALN L-Q d N'K j r er n h W I t I V 3 wayjthatflehiringjihe flescribledrotation of the 'The c w r m the cam now j'e'ameigkSiwKt NKta, the contacts tt and ta are 1si'i'c 'es'sij/e!y shQrt-circuited once. While i 'ng thei'contact 6 1,:'bcause of the opened pe H onal'contactfit of the r'eIayKBB, remains tv i't outjaniy ,e'fie'ct, the contact closes the following circuits:

relay X24 in t following ay; ('l'lY-G'rouhd; contacttfi, winding I of the ,cdfimct e .felay ixzawwmdingwmt J I 'l he rel ay K69 starts to operate and is kept in a the circuit: I g I .fi. \f Z .01ssnipe;9t hr a watb au f th (12) g fiizgi f fi fi g jg vther leynQflii so hat these Q la s a e ai to "relay battery b 0 15 ai t a p itie wo es 7 1 131 m a ime t canr of the cam disIg NKZ has magie 'contact m Assoorfi 'as 'thecircuit 10 is closed in the above the lowercontact spring of the contactlfi, As, :ci'e'scrib'eg"marinenthe circuit 1211s again inter- ,however,;key T2 isnot pressed, contact 15 101, rupted bcause thewntact 12 of the relay ANSG c11os ed, s 0 thatno circuit is formed and relay 3981 5 m opened. As a result the relay K59 becomes cannot b e e gcit'ed The calling subscriber has inoperative. When the forward moveme'nt'fis .noty receivedthe number} and circuit lis again fgorhpletedfrio'wer" magnet VKtE and relay I51 c1osed. -As it iyasassumed that the order imarecutjo ut by NK'fit. Making the magnet V3162 milses e 'iven..co ec 1y, no. impulse is given 0 t1t,'aus s heflsot na carrier oss and aitenthefnumber 2, so that relays'Lfitl' and 6481 3 the cam disk'sNK! to'NKIQ to'stop. The inactiare; no,t:actuated,; k v yation of the re ay rst has the additional result "i'Ihe-samel process i jepeatedavi-ththe' num- ;that'it"s" resting contact 33 is closed, which forms 'ber 3',;in connectionwith which'likewjse qnlycirthe "following circuit for the coupling magnet Quit: is formemasfbutton 3 lsojgremains' un- RKEE that produces the reverse movement of -presseglrandnoii npulse'is receiyeskv Qn theecon- -iwnthe sound carrier T033 and of the cam disks '-trar-y,; the procedure in connection, Withnurnber ,NK l-NKI B.

4, i. e. after subscriber has received the number 4, V i v v r v ;resemb1es;that. fo11owing number-Land the 'fol- (13) Q Contact "lowing circuit is formed: power magnet Pat/Gary r; z T :1 tccord ingly the sonnd carrier T033 andthe (9) ct fcam'disks 'NK!-NKt3 retum'to initial position, yv 11' eatsesinjtne latter the" opening of the Relay P98 is" attracted and circuit 8' interc cuit of the magnet P0565 at contact at of the "ru htedfcirc'uits 1"and 3"to Barereform'ed'prethe position of rest of the cam disks, the contact 42 of the cam disk NKiB is open also, the relay H6 cannot continue operating through its winding II and becomes inoperative. This opens all circuits which are still operating, and stops the telephonograph. In order to prevent any possibility for the subscriber to hear in reverse the message recorded on the sound carrier T033 during the reverse movement of the latter, the reproducing magnet SPKIUO, during this reverse movement, is short-circuited by the contact I95 belonging to the relay T! which remains inoperative during the reverse movement.

2. Incorrect control and repetition of message Let it be assumed that the calling subscriber emits two impulses in connection with the number 2. The first impulse, as relay P98 was not excited, closes circuits 3, 4 and 5; whereas the second impulse closes the following circuit:

(14) Earth, contact 58, contact 53, contact 41, contact #36, relay S21, winding I, battery.

The relay S21 is provided with three windings I, II, and III, of which each one can be used for actuating the relay. The relay, by its operating contact 52, is inserted in the following holding circuit:

(15) Earth, NKIB, contact 58, contact 52,

relay S21, winding III, battery.

The make and break contact 94 of relay S21 is inserted in the circuit of relay AN95 which it interrupts when excited. As soon as relay S21 is excited all other order impulses are rendered ineffective by this relay. If an impulse is received at a wrong moment, i. e. when the corresponding button has not been pressed, relay S21 is in any case excited and if, after the passage of all the button circuits, contact 95 of cam NKH is actuated, a special circuit 36 is closed. This circuit can, for example, transmit a busy signal to the calling subscriber in the usual way. The following circuit is formed:

(16) Earth, NKH, contact 95, contact 94,

relay ABS'I, battery.

Shortly before the cam NK!5 has made a com- ;plete revolution, there is effected in the described manner the disconnection of the magnet VKGZ Holding the relay H6 is taken over by the circuit:

(18) Earth, contact Hi6, contact 7, relay H6, Winding II, and bifilar winding III, battery.

Connecting the relay STIZ produces another forward movement of the sound carrier T033 of the cam disks NKI--NKI8 which makes possible another emission of the sound impulses by the calling subscriber. At this second forward movement relay Z65 which is provide-d with two windings I and II can be excited over circuit:

( 19) Earth, NKI3, contact 61, contact 64, re-

lay Z65, winding I, battery,

because at the first forward movement NKI 2 closed the circuit of winding I of relay 69 over contact 68. This relay is held over contact H and its winding II. At the first forward movement relay Z65 could not be actuated over contact 64, as NKIS closes contact 61 before NKI2 closes contact 68.

Relay Z65 is held in the circuit:

(20) Earth, contact I3, contact 12, contact 10, relay Z65, winding II, battery.

If the correct control impulses are given at the second forward movement, circuit I0 is closed, as described above. If other incorrect control impulses are given, the following circuit is formed after the completion of the return movement:

(21) Earth, NKIB, contact 99, contact 44, relay H6, bifilar winding 111, battery.

This again cuts out relay H6 and all the relays return to their normal position.

So far the procedure occasioned by incorrect control impulses has been described. If, however, at a prearranged point, in the present case for example after the number 1, no impulse is emitted, circuits 3 to 7 are not excited. On the other hand, relay P98 is nevertheless attracted so that condenser I04 can be charged. On cutting out relay P98 the following circuit is formed:

(22) Earth, condenser I04, contact 25, contact 26, relay S21, winding II, battery.

Relay S21 is now held by circuit l5. As already repeatedly mentioned, the attraction of relay S21 excludes the possibility of actuating relay AN 96. It also closes the special circuit 36 with the help of relay A1391.

Iclaim:

1. In a control system for remotely actuating an apparatus, an electrical line, and a station comprising said apparatus, an impulse relay actuated by current impulses arriving over said line, a first intermediate relay connected with the contacts of said impulse relay and energized when said impulse relay is actuated by a current impulse, means for holding said first intermediate relay independently of said impulse relay after the first intermediate relay was actuated, a second intermediate relay connected with the contacts of the first intermediate relay to prepare its actuating circuit and also connected with the contacts of said impulse relay to be actuated on the end of the impulse operating said first intermediate relay, means for holding said second intermediate rela after its actuation independentl of said impulse relay, electrical switching means, and an actuating circuit for said electrical switching means, said actuating circuit including contacts of said impulse relay and contacts of said second intermediate relay and actuating said electrical switching means upon recei-pt of at least two current impulses transmitted over said line.

2. In a control system for remotely actuating an apparatus, an electrical line and a station, in which said apparatus is located, a, transmitter for transmitting signals over the line, means for causin the transmission of a number of signals by the transmitter at predetermined time intervals, a first set of switches to be manually actuated in accordance with a prearranged code, a

second set of switches including means for operating the switching of said second set one by one and each within one of said time intervals, a first relay, a set of circuits, each circuit being provided with a switch of each set of switches and adapted to operate said first relay when both switches are simultaneously in the operated position, a second relay adapted to be actuated by electrical impulses arriving over the line, a third relay, a circuit comprising contacts of said first and second relay and adapted to operate the third relay upon the arrival of electrical impulses not corresponding to said code, and circuit means for actuating the apparatus, the operation of the latter means being controlled by contacts of the third relay for preventing the apparatus from being actuated when the third relay has been operated.

3. In a control system for remotely actuating an apparatus, an electrical line and a station, in which said apparatus is located, a sound carrier having numerals of a numerological series recorded at intervals thereon, a device for reproducing said numerals electrically and for transmitting them over the line, a first set of switches to be manually actuated in accordance with a prearranged code, a second set of switches, a first relay, a set of circuits of which each is provided with a switch of each set of switches and is adapted to operate said first relay when both switches are simultaneously in the operated position, a second relay adapted to be actuated by electrical impulses arriving over the line, rotatable cam means adapted on the one hand to operate the switches of said second set of switches, each during the interval between the transmission of two numerals, and on the other hand to cause said second relay to be connected with the line during each of said intervals, driving means adapted to move the sound carrier and the cam means, a third relay, a circuit comprising contacts of said first and second relay and adapted to operate the third relay upon the arrival of electrical impulses not corresponding with said code, and circuit means for actuating the apparatus, the operation of the latter means being controlled by said cam means for actuating the apparatus after the transmission of said numerals and being further controlled by contacts of the said third relay to prevent the apparatus from being actuated when the third relay has been operated.

4. In a control system an electrical line and a station in which is located an apparatus to be actuated by electrical impulses transmitted over the line and corresponding to a predetermined code, electrical impulse receiving means responsive to impulses transmitted over the line, selective circuit elements set in accordance with said code, control means adapted for cyclic operation causing the selective circuit elements to become efiective one after the other during each cycle, starting means connected with the control means for causing the latter to operate through one cycle, a relay and circuit connections between the contacts of the relay and the starting means for operating the latter by this relay, contact means controlled by said electrical impulse receiving means and said selective circuit elements, and a test circuit including said relay and said contact means for operating the relay upon the arrival of impulses not corresponding with the code and thereby causing the control means to operate through a further cycle.

5. In a control system, an electrical line and 10 a station, in which is located an apparatus to be actuated by electrical impulses transmitted over the line and corresponding to a predetermined code, electrical impulse receiving means responsive to impulses transmitted over the line, selective circuit elements set in accordance with the code, control means adapted for cyclic operation from an initial position and causing the selective circuit elements to become efiective one after the other during each cycle, driving means for moving the control means out of said initial position and for automatically restoring them to this position, a test circuit comprising a relay and contact means, said contact means including contacts controlled by said electrical impulse receiving means and contacts controlled by said selective circuit elements for operating the relay upon the arrival during a first cycle of the control means of impulses not corresponding with the code, a starting circuit for said driving means including contacts of said relay and contacts associated with said control means and arranged to be operated thereby in their initial position, the starting circuit being provided to initiate the control means to operate through a further cycle when the impulses transmitted during said first cycle did not correspond with the code.

6. In a control system in combination with a transmitter, an electrical line and a station in which is located an apparatus to be actuated by electrical impulses transmitted over the line and corresponding to a predetermined code, electrical impulse receiving means including contacts to be operated by impulses transmitted over the line, circuit means including a relay and selective circuit elements set in accordance with the code, a time delay switch operating through a fixed range and adapted to govern said transmitter to transmit signals at predetermined time intervals over the line and to cause the circuit means to connect said selective circuit elements one by one and each during one of said time intervals with the said relay for operating it in accordance with the code, control means for causing the switch to move through said range, and a test circuit including the contacts controlled by the impulse receiving means, the contacts of said relay and the control means, which contacts are arranged to operate the control means and thereby to effect the repetition of a foregoing movement of the switch during which a series of impulses transmitted over the line did not correspond to the code.

MAX HANDSCHIN.

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

UNITED STATES PATENTS Number Name Date 1,595,241 Nelson Aug. 10, 1926 1,665,622 Chauveau Apr. 10, 1928 1,719,535 Davis July 2, 1929 1,888,904 Brauer Nov. 22, 1932 2,072,079 Blodgett Mar. 2, 1937 2,141,551 Phinney Dec. 27, 1938 2,194,559 Koch Mar. 26, 1940 2,230,486 Durant Feb. 4, 1941 2,238,976 Hadel et al Apr. 22, 1941 2,276,646 Boswau Mar. 17, 1942 2,306,654 Triman Dec. 29, 1942 2,368,826 Hailes Feb. 6, 1945 2,399,738 Howe May 7, 1946