US1591249A - Electric safety limit switch - Google Patents

Description

J. S. TOWNSEND luly em'ze." 1,591,249

ELECTRIC SAFETY LIMIT SWITH Filed Nov.' 15, 1920 3 Shuts-Sheet 1 -IIIIII. v Illllll llll III IIIIII llll lllll July @1 26. 1,591,249

' J. 5. TOWNSEND ELECTRIC SAFETY mun swn'cn 1 Filed av. 15, 1920 s Sheets-Sheet 2 July 6 1926.

J. s. TOWN$END ELECTRIC SAFETY LIMIT SWITCH Filed Nov. 15, 1920 3 Sheets-Sheet a Patented July 6, 1926. I

Li; A

JOHN s. mownsmib, miHARVEY;uni-tiers; AssIGNoR To wnimme eoiefiorm'rion, or

HARVEY; rumors, A ooRPoRA'i Iorf oEiLLINoIsQ EL CTRIC" SAFETY L nn swr'i'oii.

This inventior is a safetyllirhit' switeh for Lise in e l'liciently stopplng any niechanism inovecl at high speed by' electrically propelled epperetus. While its application may be very general ,to devices having the same sort of mechanismthe invention Was primarily made for use in connection with eleotrio trai eliiig Cranes and willtherefore be desciibed in jeennection with sueh'hiaeh enisni. Y

it building equipped-With a travelingcrane,

movable horieontelly at a: certain given height} the efieetive useful part of the ca-v paoity oi the building; is the part; located below thehigliest point to which the-lowest part of the hook or other moving p'artpf the crane caiijbe sz fely elevatecll .For this reason crane builders always strive to 1 so eoristruet the device that'the hook-and ettechecl parts czin be moved to the highes't of i iithe bui ldiligfiflt is also 7 Well understood the-tin the use ofe high SPQCl Lorene when the hook is" elevated at "high speed and the poweris shut ofl" the book must neeessa point ithout danger to the crane mechan'is iir 'lhe object of this invention is to rproi icle enesitohietie meehenism which will out off the current, controlling the hook,- at a poi-n15 eonsisterit-vi ith high '1 speed operation I of the" machi eencl to provide a manually eontrolletl meehan sm, by WhlClL oilly .L ncler the operators constant personal control the power maybe thrloiv n inageinyinr order to l permit further elevation oi the hook and attached parts, i113 to vanother predetermined point beyoiicl whieh the current is absolute- 1ytlii ci ifiioff arid kept. off so thzttthehook meme by possibility proceed further, rm-i, thus clzlirilge the Crane mechanism;

The invention ooiisists in mechanismffor ettailiirigthe foregoing objects which can be sceinparatively easily constructed and appl-iecl to mechanism requiring-it, which is perfectly positive and effieient in operation aiicl isiiot liable to get out of Omen More par icularly the inv 'ehtion consists in r g titres and details of construction which Will s1 .t-Q.

e 11, re tullyset forth int-be speeifisetion "7 S4, 7, V

A plication 'filfed, November It is .Well ontlerstootlii-n the t eirt that in H rily' travelfe considerable V I -clistanee'upivardbeforethe brakes, or other sto -ping devices aet eii ectively, while on Y theother hand, a slow moving hook might be safely stopped at considerably higher .15, 1920. sen- 1 1%.. merge;

numerals designate th the several views 1+:

e same parts thruout V ferr ed; form,

e;nclv vi eiv of a trolley pertially in iseetioni fillListrati-iig (hie form o f-t'he riieehzuii'sin oi .thisihvention ac ti zil eppilieeti- 'Figure'3 is an liel' View alien (lithe ofFigiiije J2, certel parts, being veiit away.

Figure l is eiijeiicl iiieii" ofvtli-e switch iiieeheriism which is 'shofiri diegra iiiiriati c elljiiiri Figure 1..

side View of the m chanism n er gure Vseet oir. Figure 6 1s a tliat pzlrtof the iaheoliziiiisi i which iwhieh is aiiidu a.

of Figure G'shdwing III eiiisrii eoirir noii t o the striietiires of both Fig iirs 5 and 6 In" Figure 1- the Winding; (liiiih, I0 is sheen,

I {to the mete shift 11", dr iveii;

, Referringto the clrziwings iri which 131;

Ill-gore lis e cliagremme-tie-"YieWof inec h .a-111s111; l-ll ustretlng this IHYEfilJlOil iii its preright l; eertei i parts sheen in S6611 We q ie lf ii-b o s 1 i i di- Y fiecl ZOnStI'HQtlOH Of the SWlftQll meehar sm used in the dev ce of; Flgures 2 1 F'gure 211's ess cle viewofe craneencl i ,e fi l fie? thri l n 'ately the center of Figure e, but ir pleee e egmmmeeau ceneeetee; by 1 i a .eorivei tionel rem of eleet'r'ie e ror-101516,,

preview vwith siiiteble 'w'viriiig-lsof eoriventiomil leading toeiiisrii provided with the ps ial oonventioiiel resistance 21 and in the case here illustr'eitecl-,siiitebly eoiiiiected to ipair of normally open sw'itehes eoinmoiily celled alternating cu'i'ireiit is used and r is.

applied to the device frame suitable source etthegioi nts 2 8 v 11i: the plrys'icl meeher ism appliee' to ii traveling. zine,'insi1letors. .?i()

are applied at lili iell for the cr 'a iebmdge rmcl thet em t ef the twangmeehen sm; at

eorit iotor' and s'iiigl'e rriernij l ly opercited switch 5% all ofoonventional form 1 11-.

the lest of the'insulators is applied tofand 1 One end of carried by the crane bridgeinconventional manner whereas the other parts of thewir-v ing system are located at some other con- ,venient point, usually at theopeiating station, on the crane bridge. 1 e i In connection wlth the foregoing conven- .tional mechanism a special stop and switch mechanism is. applied for operation'by the crane hook block 32, which is conventionally suspended from the drum 10 by a hoisting rope In the case'illustrated in Figure 1, block 32 does the mechanical portion of the stopping-by engaging a transversely'd1s-' posed rope 36, passing as shown betweenthe ropes 84., sothat the block cannot fail,'in its upward travel, regardless of its lateral swinging movement, to' engage this rope 36.

while the'opposite end portion PP Q 5 after passing over suitable pulof the rope,

ley l- 0, is wound around finally secured at one poi'it on thecircumfercnce of a wneel 42, carried by shaft 46 suitably mounted to 2 leys 54. and 56.

' 7 Switch 24 is so' 'connectedin drive pinion 48, which in turn, ,thru a gear '50actuates shaft 52. A spring la connected to hub and to a fixed support i7, is

adapted to move the wheel and attached parts contrary to the pull of rope .36. Mounted on this shaft 52 which is common to both of the switch mechanisms heretofore referred to, are two parallel segmental'puh remain in such engagement or contact during a. much longer portion of theIarc of travel of shaft'52r Both pulleys 54; and 56 are so positioned and arranged that'there is asubstantial portion of the arc of travel of shaft 52 during which there is no contact with the adjacent switch points on either one of thee pulleys. Contact is so connectedinto the wiring circuit 18 thru a wire 66 that whenever block 32 strikes rope 36 and thus ultimately rotates shaft 52 to the point where surface 58 of pulley 5st is disen gagedfrom contact 60, magnet 26'is deenergized thus allowing the spring 22 to open connector 22 and thus throw off the current from .motor 16 and stop the powerful elevation ofthe hook bloclr32.

therope is fastened to a fixed The pulleys 545 and 56ers the circuit that when it'is manually closed, magnet 26 is operated, even thomembers 58Iand 60 may will continueas long asswitch 2&remains closed; except as hereafter provided.

The relatively long circumferential 0011- tact surface is sopositioned and connected into the circuit thru wire .701 leading from contact tl l that switch 24 can operate asQdescribed in the last sentence so long as menr.

bore 64- remain in engagement with surface 62 but that when block 32*mov s rope 36.11pward sufficiently so that'shaft 52 rotates far surface 62, the circuitiwhich switch 24' controls is in fact broken with the result that the operator holding switch 2% closed is no longer effective and contactor 22 automatically opens as heretofore described;thusp'erinanently preventing any further upward movement of the hook under thepower ofmotorlfi.

In actual practice the pulleys 5 tand56 are. so proportioned and positioned that when block 32 engages rope 86 it causes the enough to move contacts 6 1 as froin'contact breaking or opening of contact'58-60 at apoint or timevinthe unwardtravel of L D an a e 1 clock e2where 1i it is moving at high speed.

ithas sinncient space within which to travel upwardso that the'brake and other" niechanism can stop it beforc 1t actuallyengages and thereby injures the cranemechanism and that if the operator'maintains his hold 7 on switch2 l the contact at62+67l will-not;

nism as it can possibly go withsafety at any speed, beyond which it cannot be moved further. In actual practice the operator is not supposed to close switch 24 when the crane is working at high speed until the block has been automaticallystopped by breaking contact mechanism 586() and he' thereafter sees that the momentum upward of the block isnot going to carry it high enough. i V is working very slowly he may close switch 2% at or before the time contact 58 60 is broken and maintain it until switch opens. This does away with the temptatiom not to say necessity, of operators of ordinary cranes having only 'a safety limit switchat the level at which switch 58- -60 operates to run the load up at high speed in order to make it carry up by momentum to the upper limit of travel, viz.: with this invention the operator can operate slowly all the way up and be sure of gettingthe load up to the maximum point without subjecthe broken as described'until the hook lock .82 has traveled as near toithe cranemecha On the otherhand, the crane,

I when block move 1 36 upward to manipulate the mechanism as described, the pull of rope 36 compresses spring 44 whichreturns theparts to-normal' position just as soon as the crane operator manipulates the device to cause block 32 to start to descend.

' Thecontroll'er mechanism 20- is of'abs'olutely standard conventionalform and the switch devices herein provided are only con which the 'ope reaches after. passing-over suitably disposed pulleys 80. Weight 78 is nected into it on its side which'isusedin'the the various switch devices entering intofthis' invention as described; v c

In the modified form of construction shown in Figures 2, '3' and 6 the spring 44 is dispensed with and its place istaken by a rope and weight mechanism. In this modi- Vfied construction the wheel 42wiil be desig nated as 72. To a suitable pointin its circumference a rope 7 4 is secured intermediate 7 of its ends so that it hasone free end carrying a relatively small weight 76 and its other end carrying a relatively large weight 78,

perforated or otherwise provided with guides thru which ropes passto insure the; weight 78 following tlie swinging movement of block 32. In the construction of Figures 2 and 8 weight 7 8 1S enough heavier than weight 76 so that when both. weightsv have controlof the 'pulley,'weight 78 predomivnates and thereby: holds. the. switch mechanisnifin the position of Figure 1, that is-to say in the same position, against stop mechanism '82 inwhich-the. parts are heldv by spring 44. Vhen, however, block device 32 ascends far enough to engageand' lift weight 7 78-, weight '76 is thrown incontrol with the result that: it moves the parts: in the same manner in which they are moved in the other construction when. block a 32 moves "upward and pulls on rope 36'.

This weight mechanism form oi -device: has

the advantage of doing away with thespring and thus avoiding what inighthappenif the spring broke or'otherwisefailed to operate:

It hardly seems necessary to describe the conventional form of crane shown in which the main crane girder 86 carrying the wheels 88 on which the trolley 90 hearing the crane mechanism described travels in the ordinary manner. The main operating switch devices described are enclosed in a conventional form of box 92 mounted on the trolley in convenient position for operation;

Having thus'described my invention what I claimas new and desire tosecure by Let icrsfatent is i v 1 In a, power mechanisms moving" merry- Ina power mechanism, ber, electrically operated, means propelling shaftymean' partially rota,

her, power meanspropelling it, 'two' power.

cut off devices, automaticallyoperatable insuccession by themoving memberto, provided the power 18 on,,cut it off and norm-al-.

vly inoperativemechanism, vrendered operative by constant manual holding, in connection with: the:- second cut oil mechanism,

adaptedwhileso manually operated to 'rea store the 'pov've'r to the propelling mechanism trom the timeth-efirstcut off operates until the second cutoiii itself operates.

52. In a power mechanism, a moving'meniit, twopower-cut oil" devices,automatically opera-tablein succession by the moving inemher to, providedthe power is on, cut it off and normally inoperative mechanism rendered opera-bleby constantmanual holding,

in connection with the second i cut oli mecha;

nism, adapted while so' manually-operated to restore'the power to the propelling mechanism fronrthevtime the first cut oii operates until the second-cut oil itself operates;

13-. In a poWerniechanism, a movingmem}v s o0 henpower-"means propelling it, two power cut ofi"- device's automatically operatable 1'11 holy, electrical-lymperated means propelling succession by the" moving member to, pro

v'i-d'ed the power is on,'cut it off and normally inoperative mechanism rendered operative by constant-manual holding, in connection with. the second cut oii mechanism, adapted while so manuallyoperatedto restore the power to the propellingmechanism from the time-thefirst cut off oper t until the s econ 1 Cut Off s l "op fates; a e

a moving me'mit, two power cutoli devices automatically- :operata'ble in: succession -by the moving ,member to, provided the power is on, cut it off and normally inoperative mechanism rendered operative by constant manual holding, in connection with-the secondcut operated to' restore the power to the propel"- ling'niechanismfrom the time the first out off operates'until; the second cut ofi itself operates. v

5: In mechanism of the class described, a movable member, electrically operated mechanismfor propelling themoving member, fan autdmafilc switfih, operated by the moving member at' a predetermined point in its oti mechanism, j adapted while somanually travelitocut-off the current from the operat- 7 ing mechanism, -a normally" open switch closable by constant manual holding,adaptedrwhen soclosedto restore" said current, and means o'peratable at a more distant point in -the travel olfthe moving member finally cuttingofl the current.

V 6'. Ina'deviceof the kind described, a moving member, an Veletric' circuited power mechanism normally moving said member, a

bY WhZ LClI the movingmember I 5 allel segmental cont-act members, of different circumferential lengths, on the shaft, a con-- tactor in the electric circuit adapted to CQIL trol the power, a contact member opposite the shorter segmental contact adapted when disengaged from the segment to cause the contactor' to shut off the power, a manually operated switch in a circuit arrangedto restore the power so shut off and contact members, engageable with the longer segmental contact on the shaft so connected into the last mentionedcircuit that so long as the segment remains in position to maintain such contact, and said manually operated switch is ope'rated,the efiect of said switch action operated by the shorter segment is negatived; V

7. In mechanism of the classdescribed, a' moving load controlled member, an electric c ircuited power -mechanism normally moving said controlled member, a movable switch 'm'ember," means by which at a predetermined time in the travel of said ccontrolled member it movesthe switch member,

to maintain 'said circuit closed, the effect of the ,power shut off by the shorter circuitcomp'leting member is negatived.

, 8. In mechanism of the class described, a moving load controlled member, an electric circuited power mechanisn normally mov ing said controlled member, a movable switch member, means by which at a predetermined time in the travel of said controlled member it moves the switch member a pair of separated, parallel circuit-completing members of different operating lengths on the switch member, a contactor in the electric circuit adapted to control the power,

' a cooperating member opposite the shorter circuit completing member on the switch member adapted when disengaged therefrom topermit the contactor to shut off 1the power, a manually controlled switch in a c rcuit arranged to restore. the power'so' shut olf and another cooperating member cooperating with the'longer of said circuit-completing members on the switch member, so connected into the lastmentioned circuit that so long as the longer circuit-completin member remains in position to maintain eai -the opposite direction.

circuit closed and said switch is operated,;.

the effect of the power shut off by the shorter circuit-completing member is negatived.

9. In mechanism of the class described, a

moving load controlled mcmber,an electric oircuited power mechanism normally moving said controlled 'member, a movable switch member, means by which at a predetermined time in the travel of saidcontrolled member it'moves the switch mem-r her, a pair'of separated, parallel circuitcompleting members of different operating lengths on the switch member, a contactor in the electric circuit adapted to control the power, a cooperating member opposite the shorter circuit-completing member on the switch member adapted when disengaged therefrom to permit the contactor to shut off the power, a circuit arra'ngedto restore the power so shutoff and another cooperat said circuit-completing members on the switch member, so connected into the last mentioned circuit that so long as the longer circuit-completing member remains ini-position to'maintain said circuit closed, the effect of the power shut off by the shorter circuitcompleting memberis negatived, and means resisting'said movement of the switch member, returning said switch to original position when the controlled member moves in 10. In mechanism of moving load controlled member, an electric circuited power mechanism normally mov-I ing said controlled .member, a movable switch member, means bywhich at a predetermined time inrthe travel of said controlled member, it moves the switch meming member'coo'perating with the longer of theclass described, a 7

her, a pair of separated, parallel circiiitcompleting members of different operating lengths on the switch member, a contactor in the electric circuit adapted to control the power, a cooperating member opposite the shorter circnit-completing membei on the switch member adapted when disengaged therefrom to permit the contactor to shut off the power, a manually controlled switch in acircuit arranged to restore the power completing members on'the switch member, so connected into the lastimentioned circuit that so long as the longer circuit-completing member remains in position to maintainsaid circuit closed and said switch is operated, the effect of the power shut off by the shorter. circuit-completing member is negatived, and means resisting said movement of the'switch member, returning said switch to" original position when controlled member moves in theopp'osite direction.

11. In mechanism of theclass described,

a mevablexswitch member, means automati I so shut off and another cooperating member cooperating with thelonger of said circuittion, a pair of separated, circuit-completing.

' members of different lengths carried by the switch member, stationary cooperating mem- .;bers opposite said circuit-completing members adapted when the switch is moved to open circuits in which they are respectively included during periods oftime determinedby the lengths ofthe respective circuit com-' pleting devices on the movable switch.

a rotatable switch member, means automatically restoring said switch to initial posi- .:'sWitch.

12. In mechanism of theclass described,

scribed my name. r 1 v p a Y JOHN S. TOWNSEND,

members of different lengths carried by the tion, a pair of separated, circuit-completing J I switch member, and stationary cooperating members opposite said circuit-completing members adapted when the switch is moved tively included during periods of time decircuit completing devices on the movable In witness whereof,

1 toopen circuitsin which they are respecc I have hereunto sub:

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