US3001118A - Seeking switch system - Google Patents

Description

Sept. 19, 1961 J. GOETZ SEEKING SWITCH SYSTEM 5 Sheets-Sheet 1 Filed May 25, 1960 PIP/0i? ART FIE I INVENTOR. JOHN L, 60572 ATIUENE'YS Sept. 19, 1961 J. GOETZ SEEKING SWITCH SYSTEM 5 Sheets-Sheet 2 Filed May 25, 1960 FIE E INVENTOR. Joy/v L 6'0572 ATTORNEYS Sept. 1 1961 J. L. GOETZ SEEKING swn'cu SYSTEM 5 Sheets-Sheet 3 Filed May 25, 1960 Alva/Mara)? INVENTOR. JOHN L. 'azrz Sept. 19, 19.61 J. GOETZ 3,001,118

SEEKING SWITCH SYSTEM Filed May 25, 1.960 5 SheetsSheet 5 "'FIEEI:

INVENTOR. (Jo/0v L 6'arz 3,001,118 SEEKING SWITCH SYSTEM 7 Radio Company, Cedar Rapids, Iowa, a corporation ofIowa 'j Filed May 25, 1960, Ser. No. 31,667

8 Claims. (Cl.-318--467) This invention relates generally to a seeking switch system of the shaft positioning type and, more particularly, it relates to a seeking switch system having'a motor which rotates a seeking switch until the seeking switch finds a null position (open circuit position) which in turn causes the motor to become tie-energized and cease rorating. The aforementioned null position can be preset remotely by a control switch. Such seeking switch systems are described in US. Patents 2,476,673 issued on July 19, 1949, to May and Schweighofer and entitled Shaft Positioning Control System, and US. Patent 2,676,289-issued on April 20,- 1954, to Wulfsberg and Schweighofer and entitled Shaft Positioning Mechanism for Binary Code Operation. Both of these aforementioned patents describe systems of the wire saving type, wherein a single additional lead will double the number of switch positions.

In prior art structures an individual control switch has been employed for each seeking switch. Thus, if it were desired to control (i.e., tune to a desired operating frequency) both a transmitter and a receiver by prior art structures it would be necessary to have separate seeking switches to tune the transmitter and receiver and it also would be necessary to have separate control switches for the two seeking switches associated with the transmitter operator could simultaneously tune both the transmitter and the receiver to the proper frequency.

It is an object of this invention to provide a seeking switch system in which two or more seeking switches connected in parallel arrangement can be controlled by means of one control switch.

A further object of the invention is to provide structure whereby a plurality of seeking, switches of the wire'saving type may be controlled with a single remotely located control switch.

A third purpose of the invention is to provide structure. whereby a plurality of plural system" seeking switch systems may be controlled from a common control switch system. 1 The plural system" seeking. switch system is described in United States Patent 2,800,618, issued July 23, 1957, to John P. Giacoletto entitled seeking Switch System. I 3 a A fourth aim of the invention is the improvement of seeking switches generally.

The above-mentioned -and other objects and features of the invention will be more fully understood from the, following detailed description thereof when read in conjunction with the drawings in which:

FIG. 1 is a schematic sketch of a prior art structure to facilitate the readers understanding of the invention;

3,001,118 Patented Sept. 19, 1961 FIG. 4 is a schematic diagram of an even more elaborate form of the invention; and

FIGS. 5, 5a, 5b, and 50 show the relationship ofithe threerotary switches of each seeking switch of the structure of FIG. 4 for various angular positions of said seeking switch and for various control switch settings.

Referring now to the prior art structure shown in FIG. 1, there is shown'a seeking switch within the rectangular block 10 and a control switch therefor within the block 11. Within the block 10 are shown rotary elements 12 and 13 which are fastened securely and in a fixed position with respect to each other upon a common rotatable shaft 14 which is driven by the motor 15 in a manner to be described later.

Generally speaking, in operation the rotary element (or rotor) 13 will rotate in the direction of the arrow 16 until theproper one of the two notches 17 or 18 therein aligns itself under the proper stationary contact 19, 20, or 21 at which time the rotor 13 willcease rotating. More specifically, the reason why the rotary element 13 will continue rotating until the desired position of the rotary element is obtained is that for all other positions of the rotary element 13 an energizing circuit will be established which will cause the motor 15 to remain energized.

For example, in the particular structure shown in FIG. 1 the rotor 13 is shown in the only position in which the deenergizing circuit for motor 15 is obtained. It should be noted at this point that the motor .15 is connected across the battery 31 only when the relay winding 29 is energized to'close contacts 32. Thu-s, energization or deenergization. of motor. 15 is dependent upon energization or .de-energization' of relay winding 29. In turn, energization of relay winding 29 is dependent upon ground potential being supplied to conductor 160. Such ground potential can only, be supplied to relay winding 29 through conductor 160.

In the structure of FIG. 1 it can be seen that all circuits to ground from winding 29 are open. Specifically, contact 21 leads to an open circuit within the control switch 11, contact 20 can be traced through the switches 23 and 24 of control switch 11, the rotor 12, lead, 26, and back to contact 20 through sliding contact 22 which maintains constant contact with the conductive rotor 13. Contact 19 is obviously open-circuited at the notch 17. It is to be noted that the particular positioning of the rotorswitch 13, shown in FIG. 1, is determined by two factors. The first factor is the connecting of the arm of one of the switches 27, 23, or 28 to its ground position. In the structure of FIG. 1 switch 27 is shown as being connected to its ground position. It can be seen then, that as long as contact 19 makes with rotor 13, a

. complete circuit will be established from ground through which motor will then function to rotate and drive the FIG. 2 is a schematic diagram of a form of the inven- I 0' rotors 12 and 13 by means of the common rotatable shaft 14. However, when the contact 19 coincides witheither the notch 17 or the notch 18 (ignoring any ground potential suppliedthrough lead26), it will be apparent that the circuit for energizingthe relay winding 29 will-be opened, thus causing the contacts 32 to be opened with consequent de-energization of motor 15. It will also be apparent that since there are two notches, '17 and 18, there will be ambiguity as to which notch the contact 19 is coincident. The means for resolving this ambiguity forms the second factor which determines the angular position of the rotors 12 and 13. i

More specifically, the means for resolving the aforementioned ambiguity comprises the "switch 24 located in' the control switch 11 and the rotor 12v which hassliding contacts 33, 34,. and 35 thereon. The sliding contact 34 forms a continuous contact with the rotor 12 and is connected to the of the switch. 24 through conduc- -tor'36. Generally speaking, the function of the rotor 12. is to provide: a continuous ground return path for the relay.;winding 29 during. .a given: continuous 180" of revolution of the rotors. 13 and 12 when the switch 24 is in a given one of its two possible positions, and to pro vide a continuous ground return. path for the relay winding. 29 during the other 180 of: revolution when the switch 24 is its. other position. Thus, the motor. 15 will always be energized: during a given 180 portion. of a complete revolution of the rotor 18 soxthat one or the other ofthe notches. 17 or 18 will pass under the ground- 4 right. 'Now, since current will flow only in one direction through the conductors 41, 38, and 42 it is possible to construct a structure in which a single control switch, such as control switch 11, can be employedto control two or more seeking switches. Such a structure is shown in FIG. 2 in which control switch 11 is'- common to seekingswitch 10' and to seeking switch 43, which is identical with seeking switch 10. It is to be noted that the-rotor switches of seeking switch 43 are notconnected' in the same shaft as the rotor switches of seeking switch 10', but operate independently thereof. However, they will both rotate to the same corresponding null. position, as

. determined by the setting of control switch' 1 1', where they will stop. Since seeking switches 10' and 43 rotate independently of each other, their instantaneous: angular 7 position during the seeking period will not necessarily be different.

12, lead 26, and through the relay winding 29' to bating periphery of the rotor 12, will be simply connected to ground through switch 24. in. the control switch 11 and will have no eflect upon the relay winding 29. However,

if in this new position of'the rotors.12;and 13 the arm of the. switch 24- is moved back toitsv upper position (i.e-., to conductor 37), therelay winding 29 will become energized via aground return path-extending from the sliding contact 22 of rotor 13, contact20, lead 38,

V switch-23, lead 37, lead 36, contact 34 of rotor-12. and

'then toground potential through contact 35. The motor 15 will thereby become energized and rotate the rotors under) the contact 19.

Although the foregoing discussion assumes that the arm of contact '19is grounded by switch 27, it is to be understood that the arms of any. one (but only one) of the three switches 27, 23, 01 28 could be grounded; in

which case the seeking rotor- 13would rotate until. the proper notch. ofi notches 17 or 18 coincides with the be the same. In all likelihood such angular positions will Consequently, unless some means, such. as the diodes 44, 45, 46, 47, 48, 49, 56, '57, 153', and 154 are provided, sneak circuits toground potential will exist which will short circuit the, otherwise null position of either of the seeking switches 10' and thus cause: the associated motor (15) to remain energized so that the associated rotor (13) will pass by the desired .null position. A specific example will clarify the aforementioned normally be in a de-enengized condition because there is no. return path to ground potential. However, if the notch '17" of rotor 13" of seeking switch 43 has not yet rotated toa point coincidental with the contact 21.", therewill be, in the absence of the diodes 47, 48, and 49, a sneak path tolground for relay winding 29. of seeking switch. 10'.

' Such sneak path would extend from ground potential, through switch 28 diode 49, contact 21" of switch 43,

12 and 13 until the notch 17 coincides with (passes grounded contact of contacts 19, 20, or. 21. Thetanris resolvedby thesettingof switch 24, as discussed above. a It is to be noted that current-will travel in either do rcction through the lead 36, depending uponthesetting of the switch 242 For example, if the arm of" switch 24 is grounded, thenconventional current canfl'ow from battery source 31 through winding 29, lead 26,. rotor. 12,

and then from left to right in the drawing through lead 36 to ground." On the otherhand, if thearm of switch 24-is in its upper position (making contact with the-lead I 37) then, assuming rotor 12tobe making. contact with contact 35, a circuit can betraced frombattery 31 through winding 29, conductive rotor 13, contact 19; or 20, through one or the other of the switches 27 or 23. to the conductor 37, and then through switch: 24 and lead. 36

biguity produced by the fact that there are two. notches to ground potential through rotor 12; and-contact 35. It

V is. to be noted that switches27' and.23. both..have contacts leadingtoswitch 37 inasmuch as one of. the switch arms might be grounded. Thus, there will, always; be

atrleast one switch (either switch 23: or 27), through which a closed circuit will; be established: betweenrotor switch 13andlead. 37.

contact 20", lead 51 (and then assuming diode 48 to.be non-existent) through the diode 45,.sliding contact 20.

of rotary switch 13', sliding. contact 22, winding 29 to A the battery source 31. However, since diode 48 does exist, such sneak circuit is effectively blocked. In a. similar manner all the other diodes 47, 49, 44, '45, and 46 I will prevent sneak circuits to ground potential for various other null positions: of rotors 13' to 13; c

There still exists, however, the possibility of a: sneak circuit through the. fourth wires 53' and 58 which are connected: respectively to the sliding contacts 34' and 34'. of.

tacts 21" and 22, rotor 13", conductor 26, contacts 33" and 34f, lead 58, the upper contact switch 55, diode 56, through either of switches 27' or 23', rotor 13", contact 22' to the winding 29. However, diode 154=is.pres- Alternatively a cut and does block such sneak circuit. sneak circuit path: might exist solely betweenthe fourth wires 53 and 58. Assume, for examplethatthe: grounded contact 3 of seeking switch 43 makes'with. the rotor 12'. A circuit path will then be traceable from the grounded contact 35" (of seeking-switch 43) through. the rotor 12", conductor 58, the upper contactof switch 55, diode 56 and (then-asurning diode 57 to be non-existent) through the upper contact of switch 24, conductor 53 contact 34', rotor 12, contact 33', diode 153 totherela-y winding 29'. However, the diode 5'7 does exist andetfectively blocks such incipient sneak circuit. specifically pointed out that the addition of the diodes 44 through 49; and diodes 56,57, 153, and ISA-constitute important features of the invention. v p v Referring nowto FIG. 3, there is shown a 'for-mof the invention which is quite similar to that' shownin FIGL' 25, except that the form of seeking switchshcwn in: 3

It is to be is as wire systemlinstead of a 3 wire system and has a Sixth 'wirewhich Will double the capacity of the seeking switch to provide positions for each seeking switch. In the case of the structure shown in FIG. 2, a 3 wire system is usedwith a fourth wire which'doubles the capacity to provide six positions. A further diiference between the structures of FIG. 3 and FIG. 2,, is that the function of the switches 55 and 24' and the diodes-56 and 57 of the control switch 11' of FIG. 2 are replaced with switch 56, relay winding 57, switches 58 and 59 which are operated by relay winding 57, and diodes 60, 61, 62, and 63 which are grouped in two pairs of diodes. An examination of the switches 5'9 and 58 and theactivating relay winding 57 will show that ground potential is placed on leads 53 and 58 when the arm of switch 56 is connected to ground potential to energize relay .winding 57. Such grounding of leads 53' and 58' corresponds to-the grounding of the arms of the switches 55 and 24' of FIG. 2. When the switch 56 is open the relay winding 57 is de-energi zed and the arms of switches 58 and 59 make with the upper contacts 65 and 64, as shown inFIG. 3. The said upper contacts 65 and 64 connect to the common cathode junction of the diodes .62 and 6-3 and to the'common cathode junction of diodes 60 and 61, respectively. One function of diodes 60 and 61 is to permit completion of a circuit from ground po,- tential, at the contact 35" through the rotary switch 34", the lead 53, contact 64, lead -66,and through diode60 or 61 to either the contact 67 or 68 through the rotor 13", and dream the relay winding contained within the block 70. It is to be noted that the block 70 contains a relay winding and associated contacts, a battery supply, and a motor similar to a relay winding 29, contacts 3 2,

battery source 31 and the motor shownin FIG. 1. Another function of the'diodes 60 and 61 is to prevent undesirable sneak circuits. 'For example, assume that'theswitch 71 was open instead of closed, as shown, and that the arm of switch 72, instead, was closed to ground potential. A sneak circuit would then exist from ground potential'through switch 72, lead 73, diode 75 (and assuming diode 61 to be non-existent, i.e., short-circuited), through diode 60, contact 67 and through the "rotary switch 13" to the relay winding in the block 70. Another sneak circuit path might start from the same source (switch 72.) and extend through conductor 73, conductor 66, switch 59, rotor 34', lead 26 to the 'relayywinding in block 70.- However, the presence of diodesv 60, 61, 62, and 63 effectively block all such sneak circuit paths, thus completely isolating seeking switch system 79 from seeking switch system 80, although they both are controlled by the same control 1 switch 81.? A

Referring now to FIG. 4, there is shown a more elaborate form of the invention. More specifically, there is.

shown in FIG. 4 two seeking switches, each of which -.has five wires. plus a sixth wire and a seventh wire. The -five wiresof seeking switch system 88 are identified by referencejcharacters 82, 83, 84, 85, and 86-, each wire being connected to a separate sliding contact -(91) which makes with the conductive periphery of the rotary switch 87. The sixth wire 163 functions to double the capacity 'of. the five-wires to provide ten angular. positions of the rotary element 87 and the seventh wire 164 functions to doublethe. aforementioned ten angular position capacity I of the rotary element to provide a twenty discrete angu- --lar position capacity rotary switch 87..

The details of the seeking switch represented by the a block 89 are not shown since they are identical with the 1 seeking switchshown within the block 88. The control switch,f which is that structure shown within dotted block 90,,is common to both of the seeking switch systems 88 and 89. Y I'Referring now to the seeking switch shown within the block 88, thej-rotary element 87 can be seen to have four snatches,101,102,103, and'104 spaced 90 apart around the periphery thereof. The five sliding contacts 91 connected to the conductors 82 through 86, respectively, are spaced at equal distances along the periphery of rotary element 87 and span an angular distance somewhat less than so that the entire five contacts 91 can be located between two adjacent notches in the rotary element 87.

It is to be noted that the function of the rotary element 92 is the same as the rotary element 12 of FIG. 1, which tunction is to resolve a 180 ambiguity of the rotor 87. More specifically, the rotary element 92 will always com plete the ground path for energization of the relay winding contained in block 93 during a continuous 180 segment of the cycle of the rotary element 87. However, since the element 87 has 20 discrete positions (five positions in each 90 sector thereof), there will be an ambiguity in the selected 180 portion of the'cycle of the rotary element 87. The function of the rotary element 94 is to resolve the ambiguity of the two 90 sectors of the selected 180 sector. Thus, the rotary elements 94 and 92 will function in cooperation with associated control unit switching network, to be discussed later, to provide continuous ground potential to the relay winding of block 93 during the time intervals that three of the four 90 sec tors of the rotary element 87 are passing-under the five sliding contacts 91. Only during one 90 sector (with any given settings of the associated control unit circuitry to be discussed later) will the seeking switches 8801 89 function to cooperate with the control switch 90 to prm duce a null or open circuit condition so that the motor in block 93. will be de-energized and stopped. The aforementioned statement can be seen to be true when it is considered that when the proper notch on the rotary switch 87 is passing under the sliding contacts'91 during the selected 90 segment of rotation of the rotary switch 87, that ground potential for the relay winding can be supplied only through the conductive rotaryswitch87.

The particular switching circuitry which determines which of the 90 sectors of the rotary switch 87 will be the one during which a null can occur is found in the control switching unit 90' and, more specifically, comprises switches and 106. Switches 105 and 106, respectively, energize relay winding 107 and 108. The relay winding 107 controls switches 110 and 111 which in turn control, respectively, the return-to-ground circuit for therelay winding of block 93 through rotary element 94, and a similar return-to-ground in the seeking switch 89. Relay winding 108 controls switches 112 and 113 whichin turn control, respectively, the return-to-ground path for the relay in block 93 through the rotary element 92 and a similar returnt0-.ground path in the second seeking switch unit 89. Y

A specific example of the operation of the structure shown in FIG. 4 will now be described. 8 First, however, it should be specifically noted that the combination of one seeking switch with one control unit is old in the art and the operation of such combination, as has been described in conjunction with the structures of FIGS. 1, 2, and 3, and as is about to 'be described in conjunction with the structure of FIG. 4, are described herein only because such description is considered necessary to facilitate an understanding of the invention. As indicated hereinbefore, the invention is essentially comprised of the circuitry required to control two or more seeking switches with a single control unit. Such required circuitry in the structure of FIG. 4 is comprised of the relays 107 and 108 and the associated switches 110 to 113. 'Such required circuitry also comprises diodes to 147, inclusively.

With respect to the operation of the structure shown in FIG. 4,'assi1me that inthe control switch 10 the switch 114 is closedto ground potential as shown, and that switches 115, 116, 117, and 118 are all open. As indicated hereinbefore, this means that when the appropriate one of the notches 101 through 104 in rotary'switch- 87 coincides with the position of the grounded sliding contact 119, all possible return -to-ground circuits for the relay winding in block as'win be open so that said relay wind- V will be deeenergi zcd and the motor in block 93 will therefore also be de ener'giz'ed. Now, as indicated hereinheforaonly one of the four notches, 101 through 104, will provide such a null position. When any of the other three notches pass under the contact 119, the relay windmg in block 93 will be grounded either through the rotary switch 94 or the rotary switch 92 "(referring only to seeking switch 88 andigncfin seeking switch 89'). In the particular arrangement *ofycont'acts shown in FIG. 4, the

pro er notch ofthe notches "1-0'1 through 104 is notch 101, which is shown as passing under the contact 119. Thus, all return to ground for therel'a'y winding of block "93 are open, which defines. a null position and which will cause the motor and the rotary switches to stop rotating. Now, assume that switch 106 is closed by the operator. The re- J'a' windinglllli will be energized in a circuit extending from ground potential through switch 106, relay winding ms, to battery source 121. 'Ihearms of switches 112 and 113 will then be connected toground potential (oppes'ite {re-the connection show in 4) establishing a rctur'n-to-ground path for the relay winding {inlblo'ck 93) extending from the relay winding (in bloclc "93), through conductor "122., 1iding contact 128, sliding contact 127,

switch 112m ground. The motor in block 93 will be energized and will rotate the rotary switch consisting of rotary elements 87, 9'2, and 94 until the appropriate notch fof notches 101 through 104 passes under contact 119. Such appropriate notch is notch 103, which means that a "the rotary switch must be rotated exactly 180 to find its 7 new nulli c'sinoh; Since the rotary elements 92. and 94 yare rigidly secured on the same shaft 165 as rotary elemath 87, they alsov'vill be rotated 180". From an ex- "innination of FIG. 4 it will be apparent that since rotary element 94 is symmetrical about its axis its new angular position is, for all purposes, the same as shown in FIG. 4.

However, the rotary element 92 in its new position has a configuration reversed fro'm that shown in FIG. 4and thus 'will *make contact with grounded sliding contact 126.

*There willbe no ground return path for the relay windi'ng in block 93, however, since the sliding contact 127 or-rotary switch 92 is connected also to ground, and

' "since the sliding contact '128 of rotary switch 92 no longer contact with the periphery of conductive rotary element 92. V

K The live diodes 130, 131, 132, 133, 134, and the five diodes 135, 136, 137, 138, 139 function to prevent sneak circuits between seeking switch units 88 "and 89 through the ill) leads to which they are connected. The four pairs ofdiodes consisting of diodes 140, 141, 142, 143-, 144, 145, 146, and 147 function to prevent sneak circuits within "citherof the two seeking 's'witch units 88 -or8 9. It is to be noted that in the structure of FIG. 4, .as well as in the structur of FIG. 3, that the extra wire circuits, i.e.,

the sixth 58' a1'1d53' of FIG." 3 and the sixth and "seventh extra wires such as sixth and seventh wires 163' and 16 1 of 4 are. isolated one from the other so ftliat there is no danger Or sneak circuits 'thereb'etween.

"Rather, as will bediscussed later herein,"the possibility of sneak j'circuifs lies between 'pairs of the live basic tie leads,

such as l ads 82'through 85 which connect the control unit to a seekin switch can. M I

Itwill be observed that the upper contacts of switches 110, 111, 112, and 11 3each lead'to "ajcommon cathode ijflildtidnf of an individual "paircf diodes. NOW, as discussed connection with the structure of FIG. 3, this type cqnnecriontunc icnstc .provide'a'ground return path from the relay :wi'n'dings (such as therel'a'y winding in block 9306f seeking's'witehes "88 and 89 to the grounded sliding contacts such as contacts 150 and 1260f rotary "elements 94 and "92, and also functions to block sneak 'i'cireu'its. In both seeking switch units "88 and 89 such ground return path is connected to tw leads of leads -=*sn'eh as leads 82--86= since,-*at any given instant or time,

one cr the twcieans might be npenchcnitcn at the rotary tact ('91) connected to said lead. For example, in FIG; 4

it is apparent that a ground return path could not "be established through the lead 82 since the contact .119 is open. However, a complete circuit can'be traced from the junction between the diodes 140 and 141, through diode 141, lead 83, conductive rotary element "87,"sli'd ing contact 151, to the relay winding in block 93.

It is to be noted that if either the contact 114 or 1115 were closed a sneak circuit would beestablished in the absence of diodes 140 and 141. For example, assuming as shown, that contact 114' is closed, a ground return sneak path could then be established from ground potential through switch 114, diode 130, and in the absence of poled in.the proper polarity to prevent a sneak circuit path. v The three other pairs of diodes 142, 143, and 144, $145., and '146, 147 function in the same manner as diodes 1'40 and 141 but, of course, in connection with different of connecting leads and in connection with difierent rotary elements.

In the discussion of the structure of FIG. 4it was stated hereinb'efore that only one 90? sector of the rotary ele- ' ments 87, 92 and 94 was able to provide a null position for the seeking switch for any given setting of the switches 105 and 106. Since switches 105 and 106 are two in number, each having an open and a closed position, there are four combinations possible, which will 'sel'ectively enable each of the four difie'rent 90 sectors of the rotary element 87 to provide a null position. "These four combinations of the switch settings of switches 105 and 106 are shown in FIGS. 5, 5a, 5 b, and 5c with the rotary 'elements being shown in the proper position so that the notch shown passing under the first-0f the five sliding contacts (91) is just entering the portion of the cycle :in

which a null position is obtainable, i.e., will not be shortcircuited through one of the other two rotary elements 92' or 94'. It is to be noted that switches and .106

are shown as having their arms connected directly to the r a sliding contacts 124 and 127 of the rotary elements '94 and 92', respectively. For purposes of this portion of the.

isolation is needed since the operation of only oneiseekin switch is being described. a h

For purposes-of convenience the notches 101, 102, 1061 and 104 are labeled in each of the FIGS. 5, 5a, 5b,'and5c and it will be further observed that the notches are advanced 90 in each of the four FIGS. 5 through 50.

'In FIG. So the notch 102" is shown as passing under the contact 119". An examination of the circuit show that there are no return paths to groundirom the I conductor 1%". To eflectthis null condition the armof switch 105 must be connected to ground potential andthe arm of switch 106" must be connected to its upper contact.

In FIG. 5b the arm of switch 105" is shown as being connected to its upper contact and the arm of switch 106"" is shown as being connected to ground potential; The

notch 1'03'" of rotary element 87" is shown as passing under sliding contact 119"; An examination of-the circuit will show there is no-sneakcircuit path to groun potential under these conditions. I

In F-I-GVSC the-fourth and last setting of switches 10 and 106"" is shown; bbth switches having their anus eonnected :to ground potential. Under these conditions iit mi condition will exist w en the notch 104" passes It is to be noted that the forms of the invention shown herein and described arebut preferred embodiments there- 'tact, each seeking switch unit comprising a rotatable shaft and a first rotary element mounted on said rotatable 'shaft, said first rotary element having a plurality of notches in the periphery thereof spaced substantially equidistant apart around said periphery, a pluralitygof first sliding contacts arranged to make contact with the periphery of said first rotary element and" spaced apart substantially equidistant in such a manner that the total angular distance spanned by said plurality of first sliding contacts is less than the angular distance between two adjacent ones of said notches, a plurality of diodes individually connecting each of said plurality of said first sliding contacts to an individual one of said arms of said first switches of said control unit, second sliding contact means constructed and arranged to make continuous contact with said first rotary element, motor means including a rotor coupled to said rotatable shaft, said motor means responsive to ground potential being supplied to said second sliding contact means to cause energization of said motor means, said first rotary element responsive to energization of said motor means to rotate until one 1 of said notches passes underneath a grounded one of said plurality of first sliding contacts, individual ambiguity resolving means for each of said seeking switch units, each ambiguity resolving in cans constructed to supply ground potential to said second sliding contact means during a selectable one half cycle of the two half cycles forming a complete revolution of said first rotary element, thus maintaining energization of said motor means during said selected half cycle regardless of any notch passing under the grounded contact of said first plurality of sliding contacts, each of said ambiguity resolving means comprising a second rotary element, third sliding contact means connected to ground potential, fourth sliding contact means connected with said second sliding contact means, and fifth sliding contact means continuously in contact with said second rotary element, said rotary element being constructed to have a 180 sector of its periphery make contact with the third and fourth sliding contact means, and other switching means for selectively applying ground potential to the fifth sliding contact or to connect said fiith sliding contact to at least one of the contacts of said plurality of first sliding contact in contact with said first rotary element.

2. A seeking switch system in accordance with claim 1 in which each of said other switching means comprises a single pole double throw switch having a first contact connected to ground potential and a second contact, in which at least two switches of said plurality of first switches comprise a second contact, diode means connecting said second contact of each of said other switching means to the second contacts of said first switches, said last mentioned diode means being poled in the same polarity as the polarity of said first diode means with respect to said motor means in a circuit extending through the second contacts of said first switches.

3. A seeking switch system in accordance with claim 1 in which said first rotary element comprises four notches in the outer periphery thereof spaced apart at 90 intervals, and in which each of said seeking switch units comprises a second ambiguity resolving means including' a third rotary element, a sixth sliding contactconnected to ground potential, a seventh sliding contact connected to said second'sliding contact, and an eighth sliding contact constructed to be in continuous contact with said third rotary element, said third rotary element constructed to provide a continuous ground return path 'to said second sliding contact means to cause energization of said motor means during a sector of the operable sector of said first rotary element to resolve the ambiguity of said operable 180 sector, said third rotary element comprising two 90 sectors which make contact with said sixth and seventh sliding contacts, said two 90' sectors being position so that they are each bisected by a diametrical line passing through the rotatable shaft upon which said third rotary element is mounted, and means for selectively applying ground potential to said eighth sliding contact or to connect said eighth sliding contact to at least two of said first sliding contacts. 1

4. A seeking switch system in accordance with claim 3 in which the last mentioned means comprisesa pair of diodes connected back-to-back between a given-pair of said first sliding contacts, relay winding means, means for selectively energizing-or de-energizing said relay winding means, a relay arm connected to said eighth sliding contact and operable by said relay winding means, and front and back contacts connectable to said relay arm, one of said front and back contacts being connected to ground potential and the other of said contacts being connected to the junction between said back-to-back diode.

5. A seeking switch system comprising a common control unit and a plurality of seeking switch units operable by said common control unit, said common control unit comprising a pluralityof first switches each including an arm and a first contact connected to a reference potential, each seeking switch unit comprising a rotary switch having a rotatable shaft and a first rotary elemen-t mounted thereon, said seeking switch system responsive to the connecting of the arm of a selectable one of said plurality of first switches to the first contact thereof, said first rotary element being of a conductive material and having notches in the periphery thereof, said rotary switch further comprising a plurality of first sliding contacts which make contact with said periphery of said first rotary element, first individual diode means connecting each of said first sliding contacts to an individual one of said arms of said first plurality of switches, second sliding contact means constructed and arranged to make continuous contact with said first rotary element, motor means comprising a rotor coupled to said rotatable shaft, actuating means constructed and arranged to respond to the supplying of said reference potential to said second sliding contact to energize said motor means and to cause said rotary switch to rotate until one of said notches in the periphery of said first rotary element passes underneath the particular one of said first sliding contacts which is connected to said reference potential through the arm of one of said plurality of first switches, a second rotary element of conductive material mounted on said rotatable shaft, third and fourth sliding contacts connected respectively to said reference potential and said second sliding contact and arranged substantially 180 apart with respect to said rotatable shaft, said second rotary element being constructed and arranged to make contact alternately with said third and fourth sliding contacts during substantially exclusive 180 continuous sectors of rotation of said second rotary element to cause said motor means to be energized continuously during a first of said exclusive 180 sectors, a fifth sliding contact constructed to make continuous contact with said second rotary element, and means including other switching means for selectively connecting said fifth sliding contact to said reference potential or to at least one of said first sliding contacts which is making contact with said first rotary element,

said means including \diodevmeans co blocl; sneak pnises iaflsingle pole double ,throw svn'tch having a first contact connected ,to. said reference potential and; a second :contactain which attleast two switches of said plurality of first (switches comprise a second contact, idiode means 7 connecting said second contact of each of said other "switching means to the second contact of said =first switches, :said last mentioned diode means being ,poled 5 in .ithe same apolarit-y as the-polarity rot? :said first diode imeans withmespect tosaidmotor means in a circuit extending through theisecond contacts of said first switches. 7.- -A.-seeking.switch.system .in accordance withtclairn 5 in which @the first rotary .elernent contains four notches in :the touter periphery thereof spaced apart :at 9.0 in- ,tenvals, rand .-compri,sing.-a third rotary element, a sixth sliding contact connected tosaid reference potential and in seventh gslidingicontact connected "to said second sliding :contaet, and an .eighth';-sliding (contact constructed *to be :iin {continuous contact wvith said third rotary element,

said'third rotary element constructed to provide a-circuit I 3 3th Tim said reference potential to said second sliding .eontact means to r cause energization of said motor -means vrotary element having two 9.0 :sectors ,which :make eond ning-e90 sector of thersecond of said-exclusive 489 Sector. ,of-said .second ,rotary \elementto resolve the am big uity of the second exclusive 180 sector, saiddliilid diodes connected backed-back bet-ween a ,given ,pair of said first sliding contacts, relay winding means, km'eans .for selectively energizingor ,de-energizingr-said relay wind- :ing means, a relay .arm operable .bysaid relay winding means and connected tosaid eighth sliding contact, anda front and back contacts connectable {to said relay arm,

one of said ,front and back contacts being connected .to said reference potential and .the other of said contacts being-connected to the junction between said-thack-JQ- ':baok1diodes.- V n No references cited."

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