US2360998A - Circuit controller - Google Patents

Description

Oct. 24, 1944. R A WOODS ET AL r2,36?,998

C IRCUIT CONTROLLER Filed May 29, 1943 5 Sheets-Sheet l Izzffala'ozz 40 Oct. 24, 1944- R. A. wooDs ETAL C IRCUIT CONTROLLER Filed May 29, 1943 5 Sheets-Sheet 2 [nulla/012 ,All

FLg. 7.

Och 24, 1944. R. A. WOODS ET Al. 2,350,993

CIRCUIT CONTROLLER Filed May 29, 1945 5 Sheets-Sheet 5 INVENTORS Hobef'lI/aod and THEIR ATTORNEY Patented Oct. 24, 1944 CIRCUIT CONTROLLER Robert A. Woods, Penn Township, Allegheny County, and William E. Smith, Edgewood, Pa., assignors to The Union Switch & Signal Cornpany, Swissvale, Pa., a corporation of Pennsylvania Application May 29, 1943, serial No. 488,918

Claims.

Our invention relates to circuit controllers, and particularly to circuit controllers for assembly 0n a control panel as one of` a compact group of similar units for controlling railway switches and signals or other apparatus.

One object of our invention is to provide a circuit controller equipped with safety contacts, that is, contacts which are positively moved to both their open and closed positions by cam action and which do not rely on spring pressure to position the movable contact fingers in either the open or closed positions of the contacts.

Another object of our invention is to provide a circuit controller having the contacts grouped and assembled in a manner which will enable the controller to withstand a 3000 volt fground test and still keep the overall size of the controller to a minimum so that it can be used in the limited space available on the control `panels of centralized traffic control systems. t

Another object of our invention is to provide a circuit controller having two groups of contacts operated by a single cam in such manner that the operation of the contacts of the one group will be completed before the operation of 'the contacts of the other group is initiated.

Another object of our invention is to provide a controller in which the contacts of each group are operated through the medium of a contact shifter clamped at one end in the contact stack and provided at the other end with an insulating contact operating member and with a cam'follower secured to saidA member and cooperating with the controller cam to provide the sequential operation of the contacts referredto in the preceding paragraph. j y Y' A further object of our inventionis to provide a controller in which the number of contacts which are provided can be readily varied.

A still further object of our invention is to provide a controller which necessitates a more positive act on the part of the operator to initiate its operation than has heretofore been customary.

According to our invention, the controller comprises an L-shaped supporting bracketl the short leg of which is adapted to be secured to the rear side of a suitable control panel and the long leg of which extends rearwardly away from the panel and is provided at its rear end with a stack of contacts comprising cooperating fixed and movable contact fingers clamped between superposed blocks of insulating material. The contacts of the stack are disposedin units of four contacts each arranged in ahorizontal row,

and the units are so constructed that as many units as desired may be assembled one above the other. The contacts of each unit are divided into groups of two or more contacts each, and each group is operated by a contact shifter comprising a iiat spring clamped at one end' in the contact stack, and provided at the other end with a return bend to increase the stiffness in the horizontal plane without interfering with the necessary flexing in the vertical plane. An insulating contact operating member provided with slots which receive with s-ome clearance the free ends of the movable contact fingers of the associated group of contacts is clamped between a vertical surface formed by the return bend and a bracket which carries a forwardly projecting cam follower. The cam followers extend into and cooperate with a cam slot formed in a cam secured to an operating shaft journaled in suitable supporting bearings. The shaft extends forwardly through the panel and carries an operating knob. vThe shaft is rotatable between two extreme positions, and the cam is so designed that when the shaft is rotated from one extreme position to the other, the one cam follower will remain stationary during one-half of the stroke of the operating shaft and the other follower will remain stationary during the other, half of the stroke, whereby a sequential operation of the two groups of contacts is obtained. The controller also includes suitable detent means to cause the operating shaft to complete its stroke in either direction with a snap action, as well as latch means which must beoperated before the operating knob can be moved away 4from either extreme position.

Other objects and characteristic features of our invention will become apparent as the description proceeds.

We shall describe two forms of circuit controllers embodying our invention,Y and shall then point out the novel features thereof in claims.

In the accompanying drawings, Figs. l, 2, 3 and 4 are top plan, side elevational, left-hand and right-hand end views, respectively, showing one form of circuit controller embodying our invention. Figs. 5 and 6 are sectional viewstaken on the lines V -V and VI-VL respectively, of Fig. 2. Figs. '7, 8 and 9 are top plan,` side and front views respectively showing another form of circuit controller embodying our invention. Figs. 10 and 1l are sectional views taken onthe lines X-X and XI-Xlrespectively yof Fig. 8.

Similar reference characters referto` similar parts in each of the several views,

Referring rst to Figs. 1 to 4, inclusive, the circuit controller here shown comprises an L-shaped supporting bracket I provided with a relatively short vertical leg Ia and a relatively long horizontal leg Ib. The vertical leg Ia is adapted to .be secured tothe rear face of a control panel'indicated at 2 in the drawings, and for this purpose it is provided with two laterally spaced tapped holes 3 which receive machine screws 4 extending through countersunk holes 5 provided in the panel.

An operating shaft 6 is journaled in spaced bearing openings 'I and B providedmespectively in the vertical leg Ia of the bracket I'and'n -a bearing bracket 9 secured to thevhorizontal leg-Ib of the bracket I, and this shaft extends outwardly through the panel 2 and is provided atvits .outer end with an operating knob I by means of which the operating shaft may be rotated between ltwo extreme positions. The extreme positions of the shaft are determined "by ,detent means-comprising acam II (see Fig. 5) pinned'totheshaftf adjacent the rear jside of thevertical portion Ib of the "bracket I, Vand cooperating with a steel ball `I2. The'steel ball 14I2 is disposed kwith some clearance within `aligned vertical openings I3, I4 and I formed respectivelyinithe lower part of the bearing bracket 9, in a spacing member I6 disposed betweenthe'bracketll and theleg I'b of the bracket`lgand in the leg 1h, and is "constantly pressed into engagement with thecam I I by means lof a button -I'I securedto one end of a biasing vspring I8, the other end of which is securedito the underside/ofthe leg Ib. The cam II is formed ,withcurved shoulders IIa and IIb which cooperate with the ball I2 Vto limit the movement ofthe shaft, and with an eccentric intermediate portion I'I'cv of Vvarying radius 'so shaped that asthe'shaft approachesthe position n which either shoulder vengages the ball I2,the force of the biasing spring acting through the ball and cam surface will exert'a torque on the shaft which acts to cause the shaft to 'complete'its stroke with a snap action.Y The Ystroke of the shaft may 'be varied as conditions require, but with the partsl constructed, as5shown inthe drawingsthis stroke is 180.

"The cam I'I, in addition to 4serving'asza means to limit .the stroke of the shaft '6 vand to Vcause the shaft tocomplete itsstrokewith asnap action also'cooperates with latch means for latc'hing the shaft 'in'its two extreme positions. This .latch means vas here illustrated comprises a latch spring inthev form of a atmetal strip Zl'provided at one end with'a 'U-shaped return Ibend 20a. and at the other end with an offset'portion'Zb. The strip is'secured tothe bearing bracket 9 by means of screws v42`I passing through-the short'leg of the return bend 20a, and extends'transversely acrossthe controller directly in back of the cam II and cooperates at theoifset portion 20h with a -pu-sh button y2'2 Islidably'mounted in a bushing 23extending through andsecured tothe panel 2. A pin f24 is secured tothe-latch spring intermediate its-ends, 'and this pin cooperates with two diametrically oppositeholes`25 and v2li formed in the cam in `such positions that the hole 25 will align with the pin when andv only when'the shaft occupies its `one extreme'position and the hole 26 will -align 4with the pin when and only when the shaft occupies its other vextreme position. The latchspringis biased by its ownresiliency tothe position in which the pin 24 will enter whichever one of the`ho1es'25 and 26 is in alignment with it, and it will be seen therefore that .press .the .push button with one hand and simultaneouslyrotate the shaft with the other hand. 'The `contacts .of the controller are arranged in a stackmounted on4 the rear end of the horizontal leg Ib. of ythesupporting bracket I, and are operated by a cam i45secured to the rear end of the operating shaft in a manner which will now be madeclear.

The -contact stack as shown comprises four contacts, each consisting of a xed contact linger 30 and -an associated vlmovablecontact finger *3 I clamped adjacent their rear ends between superposed blocks 32 *3'3 -and'34 'of l'insulatingfmaterial. 'I'he :insulating blocks 'Y are lsecured to ithe horizontal leg Ib of the bracket -I by-'means of screws 355 'disposed between the` outerl and A innercontacts, and vthe middle bloekl'3'3 lis fforlned in vits lupper and lower edges with notchesl33a and grooves'33b which receivetonguesBZa and 34a'formed on the upper and ylower blocks32 and -34, respectively. The-fixed and movable fingers are l'disposed in the notchesvor-groovesas the case maybe, and it will A.be obvious, therefore, that-'the notches and grooves servefto maintain the v'fixed and movable'contactifingersfin the proper parallel spaced relation. l y

The contact 4fingers may be assembled tolform either normally closedfornormally open contacts merely yby-'reversing vthe positions-of the -fixed and movable contact fingers. 'As illustrated, the two contacts `at one side of the stack are assembled one v'way and thefremaining-two contacts are -assembled the other way. Associated with each fixed contact'iinger is a relatively lstiff 'metal stop 39 which is 4vclamped betweenthe'same two insulating blocks as the 'associated fixed nger either above or A.below *the 'nger `depending'upon Whether vthe "contact is 'arranged as a normally Vopen or `a normally .closed contact, 44and which stop cooperates .with the'associated finger to position'it whenit is not engagedby .the associated movable contact nger.

The .normallyopengcontacts comprise onegroup of contacts, rand the normally `closed contacts another group, and the contacts .of each group have,associatedttherewith a contact shifterlcomprising .a flat 4spring 40, ,an Iinsulating contact operating member 4I, and -a cam A.follower.4,2. The flat-springs .40 are disposedabove the contact ,fingers of :the associated i group `of contacts in parallelspaeed 'relation and are clamped .at theirrear ends-betweentheupper insulating block 32 and a pressure plate 52 through whichthe screws -.35 .pass. The forward ends of y the springs areeach formed with Aafreturn bend Lwat which increasesthe'stilfness of the springin'thehori- .zontal .planezwithout vinterfering with its ability ytoilex sin zthe lvertical plane. Each .return bend is :shaped to'present Vavertical surface 10b to ywhichtan Vassociated one of kthe `contact operating members `f4'I *is lsecured Vas by .'riveting. -Formed 'in'each contact operating member 4I are slots 4Ia'which:receive'the'forward'ends of the movable lcontact"'nz=;e1"s with clearance 'to thereby operatively connect the nge'rs with the contact operating members.

It should be pointed out that with the contact stack constructed in the manner just described, the screws which clamp the various parts of the stack together are disposed as farfrom the associated spring 40 at the outer side of the associated contact operating member, and the two cam followers extend into and cooperate with a` cam slot 44 (see Fig. 6) formed in the previously referred to cam 45. The cam follower support associated with the normally opencontacts is turned in the opposite direction from the one associated with the normally .closed contact, that is to say,the one extends upwardly and the other downwardly, and the parts are so proportioned that with the supports disposed in this manner, the cam followers will be on diametrically opposite sides of the axis about which the cam rotates. The cam slot is formed with a portion which is concentric with respect to the shaft 6 and a portion which is eccentric with respect to the shaft, and the parts are further so proportioned that when the shaft is in its normal extreme position in which it is shown in the drawings, the upper follower will be in the eccentric portion and the lower cam follower will be in the concentric portion. I'he parts are still further so proportioned that when the shaft is rotated from the extreme position shown to its opposite extreme position, the upper follower will remain in the part of the cam slot 44 which is eccentric with respect to the axis of the shaft until the shaft reaches its mid stroke position and will then enter the concentric portion of the slot, whereas the lower cam follower will remain in the concentric portion of the slot until the shaft reaches its mid This fact together with the stroke position and will then enter the eccentric portion of the slot.

To indicate the position of the operating knob I0 the knob is provided with an arrow Illa. This arrow also serves under certain conditions as a means for indicating the direction of a traffic route set up by operation of the controller. Moreover, the knob has attached thereto a semicircular shutter IIlb which for certain installations of the controller serves to obscure in one extreme position of the controller a legend provided on the panel, and to expose the legend in the opposite extreme position. The legend is intended to serve as a reminder to the operator of the condition of the device controlled by the controller, and as shown comprises the two words Hold East.y

`The operation of the controller as a whole is as follows: When the controller shaft occupies its normal extreme position in which it is shown in the drawings, and itis desired to reverse the controller, the operator will first press the pushV button 22 to unlock the operating shaft, and will then rotate the shaft by means of the knob IU from its normal extreme position to its reverse extreme position. During the first half of Athe stroke of the operating shaft the cam slot 44 will cooperate with the upper cam follower 42 to move' it downwardly, but will not cause any movement of the other cam follower, whereas during the lasthalf of the stroke of the operating shaft the cam slot 44 will cooperate with the lower follower to move it downwardly but will not cause any movement of the upper follower. The downward movement of the upper follower will vact through the associated contact operating member to move the associated movable contact fingers c from their closed to their open positions while the downward movement of the lower follower will act through the associated contact operating member to move the associated movable fingers from their open to their closed positions, thus providing sequential'operation of the two sets of contacts. While the shaft is moving from one extreme position to the other, the steel ball I2 will be depressed for the first half of the stroke,`

but during'the last half of the stroke the spring I8 will force the ball upwardly to exert'a torque on the shaft which causes it to complete its stroke with a snap action.

comprises a supporting bracket 60 which corre-v sponds to the supporting bracket I of the previously described circuit controller, and which is provided with a vertical leg 60a and a horizontal leg 60h. The verticall leg 60a is secured to the rear face of the control panel 2 by means of screws 4, and is provided at its upper end with an offset portion 60o containing a threaded opening 60d which receives a bushing 6I. The operating shaft 6 of the controller is journaled in the bushing 6I and in an aligned bearing opening 62a formed in a support B2 secured by means of screws 63 to the rear face of the offset portion 60o of the bracket 60, and has pinned thereto between the offset portion and the bearing bracket a gear wheel 64 which meshes with a gear segment 65 pinned to a jackshaft 66. The jackshaft 66, in turn, is journaled in aligned bearing openings formed in the leg 60a, and in a pedestalS'I secured to the leg 60h of the bracket 60, and carries a combination cam 68 which takes the place of the two 'cams I I and 45 of the circuit controller illustrated in the preceding views. The combination cam 68 is formed with a. cam'slot provided with end portions 68a and 68h connected by an intermediate connecting portion 68c. The end portions and the intermediate connecting portions are all concentric with the axis of the shaft, but the intermediate portion has a longer radius of curvature than the two end portions. The cam is also provided with a ,projection 69. The cam slot cooperates withcam followers 42 comprising part of contact Shifters .for operating the contacts of the controller, while the projection 69 cooperates with a steel ball III forming part of detent means for causing the operating shaft 6 to complete its stroke with a snap action. The contacts of the controller are similar in all respects to those of the controller shown in Figs. l to 6, inclusive, but the contact shifter for the group of normally open contacts differs from that shown in-Figs. l to 6 in that the cam support 43 extends upwardly instead of downwardly. The detent means is likewise similar to that shown in Figs. 1 vto 6 except for the fact that the spring I8 bears directly against the ball l0. Theoperating shaft- 6; extendsl outwardlg; through a, clearance hole in-,thegpanel 2, and is provided: atxits-,outer endawitbfan operating knob I D.. k y

The oircuitecontroller. alsoincludeslatchlmeans comprising; the spring 2.0;. As here shown, how.-V ever, this spring is, secured l. to i thel offsetf` portion. 60o of. thefbracket 6l!J and; extends: transversely" of the controller directly in.,back,of the panel 2.` and; cooperates @tits-onset portion, Zbwiththelzfis; made slightlylongergthanlinsligs.: 1",to,.6,anfl extends through a.;clearance.,holey inthe pane112'; andy cooperateswwith holes: luc, and.y I d lformedlinl the control knob;,inssuchpositionlthat the hole.. I Gc willlreccive` the pin-:whenthe knob is rdt'atedl to itsone-,extreme position and the; hole 4I Dilwill; receive. the ninwhen-theknob isrotated to its, otherextremeA position,4 ItJ will.y be.,- obvious., of; course,A that the pinf2v4,c.a n befwithdrawn-from the holes [0c and ldb-y. operating,- the push button 22.

The parts are soproportionedrthat the operating knob is; free to rotatethrough an anglel of 1809, and that: rotation of, the knob,I through .this angle williact, through ,the gear Bland gear, seg;- ment: 65to rotate the cam throughvan yangleofl 80. The parts are further so proportioned that, when either cam follower` is in the end portion 68u, or; 68h of the-camslot, the, other. pinwilllbe. in the intermediate-vconnecting lportion l 685e, and4 thatthe difference in ltheradiusvnt curvature between theend portions .andthe centralconnecting, portion is` suflicientf to cause. the necessary, vertical movement of s the contactshifters .in response to rotation of the voperating-:shaft from one extreme position to ,the othentotopenthe contacts of-theonegroup, and.closethe,contacts of the other groun It followsftherefore, that with the controller constructedlas shownrin Figs.` '7,to 11, inclusive, operation of the-,controlknob I0`lbe-.- tween-its.two extreme positions, will.cause sequential operation; ofV the, contacts, of the two groups, in `a ,manner equivalentE to :that obtained* with theconstruction-shownin,Eigs.1 izo-6L. in. elusive.r

It1should-be notedlthat infbothformstor conetrollersl the means for` latchingg they controller, imite-.two extreme positions mayfnot bef-required forcertainapplications, and .when this is thecase this latching Lmeansf'm-ay beomitted.-

It `should also ibeenoted ath-at lin lboth forms-ofcontrollersthe metal, stopsty 39`la-re -sol designed. thatftheywill break-,apart the contacts iff they fuse together due togcufrrentiarcs.A

Although lwe have herein-shownfand, :described only..y two forms of@ circuit controllers embodying our invention, it is understood* that. Various; changes and modifications imay be;r made -therein` withinithe scope ofwfthe: Vappended claims-without. departing from the'fspiritgand .r scope-r of: our@ in-fl ventigon.- i

Havingfthus describedfour; invention, what `We claim is:

l. Ai circuit controller-'comprisingasupporting bracket; a stach ofz contacts l secured;I to" said bracket, each-said contactcomprisingfarmed andy a .movable Contact vngeri vclampedwat one end` .in

vparallel spacedfrelation between insulating'fblocks;

. push bu tton-.22-.v The pin 24 carriedbythespring, 10i

effective, tot positively. move said shifter in. opposite directions between two extreme positionsto operate said. contacts in response to. operation l of said-shaft between .itstwo extreme positions.

2. A circuittcontroller comprising a supporting bracket,. a. stack of. contacts securedl tof said? bracket, eachrsaid. contact comprising a flXed. aridi amovable contactl'nger clamped insuperposed spaced parallel relation betweeninsulating blocks, ar contact shifter. associated witlisaid contacts andlcomprisinga flat spring clamped atone end' in said-.stack andfprovided at, the other end" with a return bend which increases the stiffness of the springinthe horizontal'plane while permitting' said springtoflex inthe Verticalplane, an insulating. contact operating member secured tosaid' return bendfandlproyidedwith slots which receive thejree ends ofsai'dc'ontact ng'ers t'o operatively connect the fingers" with` said Contactv operating" member, an' operating shaft journaled in said" bracket, and cam means operatively' connecting said.' shaft with' said-l Contactl shifter and eiective to positively move said'shifterinzopposite direc# tions between two extremepositionsinresponse' to rotation ofsaid'sha'ft between itstwo extreme( positions.

3J A' circuit .controller comprising a supporting* bracket, a stack ofi contacts secured' to said" bracket, said" contacts being dividedl intoI twov groups and each said contact' comprsinga-xed" anda movablec'ontact finger clamped insuperi posed l'parallel lspaced relation betweeninsulating" blocks; a contact shiftenassociatedwith each r group'of contacts'and` comprising'v a flatl springv clampedat one-'end'in said stack and-extending parallelto the'contact" fingers of thea'ssociat'edl contacts and anl insulating Contact,v operating member secured to the reeendlof each said spring and eaclrprovided with" slots which receivethe freeendsv of the/movable c :onta'ctnn` gers of thecontacts--ofthe associatedlgroups; an'A operatingV shaft journaled in said"bra`cket; and' cam means operatively--connecting each 'said-'con'- tact shifter withssa'id-shaft kand-eiiectiveV to sequentially move said contact shi'f ters 'between two f extreme'lpositionstosequentially--operate `the contacts of said'two groupssin responsetofoperation* of'said'shaft between its `two'extreme positions# 4. A circuit controller comprising a supportingI bracket; astack of'Y contactsf secured tol said bracket; each said Contact comprising alired Yandf a movable' contactl finger-clamped i' atfr one endi-y in parallel f spaced-f' relation between insulating:` blocks, a contact-shifter'- coniprisin'gt a x-atf'sprin'g clamped vat'oneendfin said@ sta-oki and i" provided-l at theI other endfiwithfanI'insulatingfconta'ctop;- eratingmember formedA A"with" slotsfwhich f receive the free ends oflsaidirnovablefcontact r1gers` an` operating f shaft journaledflin'saidV bracket,l cam?v means L- connectingrsaidf shaftf. with` said: contacti-` shifter 'andr effectiveto' positivelyirfmove said Yshiftef erf in opposites directions i between: two v extremeNv positions tonroperate saidocontacts.zint response-'to 'a operation ofc said fshaftubetween itsfxtwoextreme positions; and Idetentmeans l.connected with Ssaidw operating shaft' andreffectiveffto cause .-said'4 sha-ttf to `complete rits :st-rokeftozeither extreme-:position withi asnapaction;v l

5.i Afcircuitfcontrollercomprising aff-supporting;V bracket,;astack-of contacts securedvto said brack;'- et,` each :saidi contact rcomprising.I af'xedif andfa@ movableI contact-` linger clampedatl one Vendsin. parallel spaced relation betweenI insulating-blocks, acontact shifterl'comprising-z ax fiat spring clamped at 'l oneend" in said stack@ and providedY at f ther other end with an insulating contact operating member formed with slots which receive the free end of said movable contact fingers, an operating shaft journaled in said bracket, cam means connecting said shaft with said contact shifter and effective to positively move said shifter in opposite directions between two extreme positions to operate said contacts in response to operation of said shaft between its two extreme positions, detent means connected with said operating shaft and effective to cause said shaft to complete its stroke to either extreme position with a snap action, and latch means connected with said shaft for latching said shaft in its extreme positions.

6. A circuit controller comprising a supporting bracket, a stack of contacts secured to said bracket, said contacts being divided into two groups, a contact shifter operatively associated With each group of contacts and each provided with a cam follower, an operating shaft journaled in said bracket, a cam secured to said shaft and provided with a cam slot a part of which is concentric with respect to the axis of said shaft and the remainder of which is eccentric with respect to the axis of said shaft, said cam followers extending into said slot at diametrically opposite points and the` parts being so proportioned that when one follower is in the eccentric portion of the slot the other follower will be disposed in the concentric portion and vice versa.

7. A circuit controller comprising a supporting bracket, a stack of contacts secured to said bracket, said contacts being divided into two groups, a contact shifter operatively associated with each group of contacts and each provided with a cam follower, an operating shaft journaled in said bracket, a first cam secured to said shaft and provided with a cam slot a part of which is concentric with respect to the axis of said shaft and the remainder of which is eccentric with respect to the axis of said slot, said cam followers extending into said slot at diametrically opposite points and the .parts being so proportioned that when one follower is in the eccentric portion of the slot the other follower will be disposed in the concentric portion and vice versa, a second cam secured to said shaft, said second cam being provided with curved shoulders and with an eccentric intermediate portion of varying radius, and spring pressed means engaging said second cam and cooperating with said shoulders to limit the extreme positions of the shaft and with said eccentric portion to urge the shaft to its extreme positions with a snap action.

8. A circuit controller comprising a supporting bracket, a stack of contacts secured to said bracket, said contacts being divided into two groups, a contact shifter associated with each group of contacts and each provided with a cam follower, an operating shaft journaled in said bracket, a first cam secured to said shaft and provided with a cam slot a part of which is concentric with respect to the axis of said shaft and the remainder of which is eccentric with respect to the axis of said shaft, said cam followers extending into said slot at diametrically opposite points and the parts being so proportioned that when o-ne follower is in the eccentric portion of the slot the otherfollower will be disposed in the concentric portion and vice versa, a second cam secured to said shaft, said second cam being provided with curved shoulders and with an eccentric intermediate portion of varying radius and with a pair of spaced holes, spring pressed means engaging said second cam and cooperating with said shoulders to limit the extreme positions of the shaft and with said eccentric portion to urge said shaft to its extreme positions with a snap action, and latch means comprising a spring carrying a pin adapted to enter one of the holes in said second cam in one extreme position of the shaft and another one of said holes in said cam in the other extreme position of said shaft.

9. A circuit controller comprising a supporting bracket, a stack of contacts secured to said bracket, said contacts being divided into two groups, a contact shifter operatively associated with each group of contacts and provided with a cam follower, an operating shaft journaled in said bracket, a cam operatively connected with said shaft and provided with a cam slot having two end portions and an intermediate connecting portion all concentric with respect to the axis of rotation of the cam, said end portions having a different radius of curvature from said intermediate connecting portion and said cam followers being so disposed that when said shaft occupies its extreme positions one of said cam followers will be disposed in a corresponding end portion of said slot and the other follower will be disposed in the intermediate connecting portion and that as the one follower moves out of either end portion into the intermediate portion the other follower will simultaneously enter the intermediate portion to provide sequential operation of said contacts.

10. A circuit controller comprising a supporting bracket, a stack o-f contacts secured to said bracket, each said contact comprising a fixed and a movable contact finger clamped at one end in parallel spaced relation between insulating blocks, a contact shifter comprising a flat spring mounted at one end in said stack and provided at the other end with an insulating contact operating member formed with slots which receive the free ends of the movable contact fingers to operatively connect the fingers with said contact shifter, an operating shaft journaled in said bracket, a jackshaft journaled in said bracket and connected with said operating shaft by gear means, a cam secured to said jackshaft, and a cam follower secured to said contact shifter and cooperating with said cam to positively7 move said shifter in opposite directions between two extreme positions to operate said contacts in response to operation of said operating shaft between its two extreme positions.

ROBERT A. WOODS. WILLIAM E. SMITH.

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