US2385906A - Line take-up for power shovels, cranes, and the like - Google Patents

Description

Oct; 2, 1945. R. H. ZEILMAN 2,385,906

LINE TAKE-UP FOR POWER SHOVELS, CRANES AND 'iHE LIKE Filed Feb. is, 1944 2 sheets-sheet;

INVENTOR. Roy H. Zei/man,

Y 4 I l/3.5773015] Oct- 1945- R. H. ZEILMAN 2,385,906

LINE TAKEUP FOR POWER SHOVELS, CRANES AND THE LIKE Filed Feb 19, 1944 2 Sheets-Sheet 2 IIIIIIII;

INVENTOR Roy H. Zei/man His men Patented Oct. 2, 1945 'Roy 11. Zeilman, Lorain, ohloyassignor to The Thew shovel 'flompany, Lorain ration ol Ohi Application rebmaryjlie, 1944, Serial ntgszausj 7 Claims; (Cl. a r- 414c) This invention relates to controllingQmecha -f nisms for power operated shovel dipper latch; lines and like lines for mobile powersh ovel-orcrane mechanisms, more particularly for main-- taining such lines sufliciently taut asto-eliinie, nate unnecessary slack therein during certain periods of operation of said mobilemechanisms, or in the case of latch lines when said .lines are not in actual use for performing the ultimate:

functional purpose for which said linesarecommonly provided, and to achieve performance of said ultimate line function when desired by the; operator to be performed, I

Latch lines and tag lines for power excavating and load handling apparatus such as power shoyels and cranes commonly extend from the ,turn. table of power cranes and shovels to the excavating apparatus carried by the-boom, and during portions of the periods when said-apparatusisin,

operation frequently slackoff, as when the boom carrying the shovel or bucket is moved to a relatively more elevated position or uponretraction of a shovel dipper stick andsuch danglinglines sometimes become entangled withvarious of the, boom carried parts or with extraneous objectsprbecome displaced from sheaves, and much time is; lost in remedying the situation:

Through the provision of myimproved mech aenism comprising an improved reeling means for, yieldably exerting a winding efiort ,upon, the

maybe readily applied to power machines and whicnmay be simply and quickly operated.

The invention will be better understood by those skilled in the art to which my invention appertainsby reference to the following drawings Mickie; tb -s ecifice en an e pt o e embodiment thereof illustrated in the said drawn iwh einr- ;1,is a,side elevational view of a power hove 5 3 5 1 3 11 1 an tne'di e dumnbottom retained latch together with 1 the latch line ,for operatingv saidlatch, and apparatus enclosed by theturntable supportedcab indicatedtherein by o ed fine t. J a n Fig. 2 is'a view, partially in section and partially in; elevation, of aopower shaft end carrying a pulley and a clutch and line winding mechanism drum, the line is kept substantially taut, said means adapted to yield to permit a greater length of line to be unwound from the line drum 13 0-; cording to the line drawing movements of the; boom or shovel bucket. H

In addition to maintaining the said line sub-,- stantially taut, I provide improved controlling means for line winding means for power shovels,; whereby a greater winding eifort is imposed upon the winding drum to produce a sufliciently strong operating pull on the line to cause it, to perform its primary function, i. e.,to operate a. dipper latch. i More especially, an object vof my invention is to provide improved variably yieldable mecha-. m'sm for exerting a winding effort upon the winding drum for a line of the above character under the control ofvariably adjustable mean to vary the power of said winding efiort. Another object of my invention is to more efficiently accomplish the foregoing object through the instrumentality of a manually variably ener-. gizable electro-magnetic clutch;-;.' Another objectgof my invention is. to:provide improved simple and efficient;mechanism..:which at eche to id shaft end;

. Fig. 3 anend elevational'view of the electromechanical clutch apparatus, disposed within the clutch-casing of"Fis-,,2;

1?ig;;- l is airansverse section taken on the iameter 4-40! Fig. 3: and i Fig, 5-is a-diagrammatic view of the electrical system ,;-,c,ompris ing as an element thereof the electro magnet ofv said electro-magnetic clutch. illustratedinfigs. 3 .a d-4.g ,l V

lteferring-now first to; the drawings of Fig. 1, there i lustrated therein a power shovelot the eli-pt nel d type mployi n dl track l9 drivemthrough-suitable gearing comprising a clrivingrpinion lla bevelled gear III, a travel shaft 3110, and suitable transmission means within the cab comprising a series of. intermeshed gears, shown by dotted lines, and-including the shaftplOS. a At, A5,;isgshown a power transmission shaft which-isgadapted'to berotated by power from the engine 12- delivered through engine pulley 49 and belt 48 to the pulley 41, a fragment of the said ee lerflre n also illustrated in F nlthoughn y invention may be applied to many and" various arrangements for operating the boom d e dipperto perform the usualpower shovel Ifnayei chosen to illustrate my inventype'of my 'co' pending application, Serial No. 5012; 54;,= filed- September 14; 1943;

"- Brieflyg-described, the more important parts of the power shovel structure, aside from the foregoin'g',"-are the' drumshaftll carrying the drums 25', 3l .':.ani1 *36,: the samebeing interchangeably operated under the control of the usual operator's control: leversynot shown but well understood, and the; rsuppleniental'ijldriving shaft 85, there hgapplied to a power shovel of the r ,2 3,965, to 3 being suitable transmission means involving chains or belts, such as shown at 13 and 61, so

interconnecting clutches, gears, sprockets and the a the urpose of elevating or lowering the boom H throughthecable 35 having an end secured to the end of the boom, thence passing over the sheave 31, its other end being wound drum 36.

Another cable 30 has a similar-winding-rela said Penrose patent is very completely described therein, the said description thereof is hereby incorporated in the present specification by referupon said tionship witha drum 3| carried upqnthe same,

shaft 49, as the drum'36, anjif islpaslsedlover; ojie'; of a pair of sheaves 32 at the end of the'boom, thence through a sheave 3Qf attached to" portion 33 of the dipper l1, and thence rearwardly' over" a twin sheave of the character of 32 rearwardly and the line26 =passedover the sheave n -the ends being then-secured at 24 and 21 to amedial portion' Hofthe'd-ippefstick Thelatch construction per-se,-indica tedat is a old its constructiomas -shewn, being that =01 the conventional type commonly employed to-remoi/ably. retain thebucket dump bottom in closed position with respect to the engaged-end wallslofsaid dipper;

While I have above briefly referred to some of the various partsofthe' power shovel and operatingcables therefor, the present-invention-fieals chiefly with the problem df maintaining 'the latch line 4 'substantia'lly taut during; all operative "periods, achieved, generally speaking; by a oom 'stantly exerted relatively Week *pullfngeifort upon @thatend of-"the line lwhiclr' extends within the cab l I and' which is wound upon-the-linereel ing drum 6, best illustrated 'in- F5252; which-constantly tends to -rotate in the windingdirection through the application -of a wea'k winding effort. constantly applied thereto through the" instrumentality of the; magneticclutch apparatus disposed w ithinthe magneticeasing -l,F'igs.'-2 to 4 inclusive, :sueh :app'aratus being best illustrated infigsrdandA; i 1 :The :operation. lofslthe electi e-magnetic clutch mechanism is controlled by variations 1 scene strength of the/current flow passingthrou'gh the electromagnetr tzbysuitable adjustment bf the electric current flow controller mechanismfgen erally-indicatedat9g Figi 5.15 ff I 5 My invention may-5e embodied in connection with th l ii ir u h i ens cti n he than that illustrated jin 'thedrawings, said draw ings illustrating one form I of'jclutch construction which Ifhave found suitabl'eifor adaptation to the performancef'f 6: the functions requ red '1 iizi the practicefof in present 'i nvetio'n: generally the s n: zi lis il-io i:eleetmmasnet b e f j iidii i a i 14 ag i ter .-w a d. c e wheelies lu rhh ia nzl :MS, LettersBatent o. enrose; datedFebn-iary 1'1,

.Qtheri. magnetic" constmctions such that disclosed.- in U.' S; i LettefszPatent ence and a brief description thereof-will suffice for incorporation'here. V v Briefly described and with reference to the adaptation of the brake mechanism of said patent to the application of the latch line winding drum-j, it will-be understood that the shaft 45, Fig." 2; is the main power shaft of the powershovel being driven during shovel operating periodsfthrough the belt 48 from the pulley 49 carried onithe crank shaft of the engine l2 and that, although the clutch and drum spindle 50 may'be'power connected to the shaft 45 in a V number- .of different ways in order to achieve rotation of the spindle by powe supplied by the engine and more to achieve the further purpose'of enabling'my invention to be applied to existing power shovels or cranes; saidspindle 5i! isfixedly mounted on the-reducedfend '5l 'of the shaft-45 either by screw threadingthe same onsaid shaft end; asillustrated, with a pin "52 pas'sing through the relatively telescoped ends Bl-oithe power shaft and 53' of the spindle; or many other suitablemanner. 7

' The drum" with g the? integrally fformed clutchcasing- 1 beingjournalled for relative rotation upon the spindleill; the clutch-mechanism disposed within the casing-{is provided tofriction ally communicate power from the shaft 45 and spindle 50 to the drum]? to cause said drum to V tend to rotate in such a directionas to'exe'rta' pulI' upon thelatch linelgwhose end portion is wound'upon said drum and whose extremeend is anchored-thereto, as at B' V To accomplish this purpose,- an annular plate '54 is secured, as a't55 and-55, to the integral unit comprising'the drumt-and theclutch casing 1. --An electro-m'agnett, preferably of the iron-- clad type is positioned tdbear against-the surface of the-plate by the small amount of pressure exerted by thespring EB encircling thejfinger 51 which projects wi thinfthe central "bore ofthe of --the-electro-magnet -8 W h'iGh 'iS' preferably annular infOrmQsaid finger 5;! being car'- ried upon the' laterally deflectible curved" arm es, which is" fulcrumed' upon a headed pivot pin' 59 whose threaded end is secured toga rotating backing plate BO -by'its'hub M-{which is splined V A lining of'the character-of brakel-ining'is-affixed -to the outer surface" of the bandmember to provide andfi'l l l v The-separable operating ends fi3 and B4 are shaped as at 68 and' -"69- 'respectively to permit of retraction about the anchor 'pinj-i59 andto as sist in retaining the -clutch shoe .62 in proper relation axially of the clutch casing. Coiled primar-y'and secondary portions 66 spring. 10 provides tension between the operat-' ing ends of the clutch shoe 82 for holding the brake in retracted position, as shown in Fig. 3.

The actuating means for controllably and variably applying the clutch shoe in clutching engagement with the inner cylindrical surface of the clutch casing 1 comprises the electro-magnet 8, the magnet supporting curved arm 58 journalled on the pin 59 and the annular flat faced disc plate 54 secured at- 55' to the inner wall of the clutch casing. The lever 58 swings about the fixed pivot 59 and comprises the curved long arm which is offset to pass around the spindle '50, the electro-magnet being disposed at a point substantially more than 90 from the pivot pin and comprises also a short arm .1] which carries a pin 72 which extends between the said separable operating ends of the clutch shoe 62.

- The pin 12 adjacent the free end of .the short arm H of the lever 58 is arranged with its axis disposed parallel with the axis of the lever pivot pin 59 but is slightly offset laterally from that vertical plane which includes the drum and lever pivot axes. In this way, changes in the effective length of the short arm are minimized during lever movement as the pin 12 engages either one of the separable operating ends of the clutch shoe. i

It will .be'understood from the foregoing description that the clutch shoe, and primary and secondary lining portions 66 and 61 will be applied upon controllably energizing the winding of the electro-magnet, as diagrammatically shown in Fig. 5.

When the winding is so energized at any current strength up to a practical maximum, force is derived continuously. and substantially without variation from the torque of the rotating drum by electro-magnetically induced friction between the electro-magnet and the magnetizable annular plate 54.

In the embodiment illustrated, the direction of rotation imposed by the power shaft 45 and spindle 50 to the curved arm 58 and electromagnet 8 is such as to preferably make the clutch action non-self-energizable and in the operation of the mechanism as adapted for the purpose of my present invention, all rotative magnetic drag efforts imposed upon the winding drum portion 5 of the integral unit 6-l is in the same direction of rotation.

Since during operation of the mechanism of the power shovel or crane, the drive shaft 45, the spindle 58 and therefore the annular plate 60, which is keyed onto the reduced end of the spindle 50, are all continuously rotated, and since the electro-magnet is secured by the anchor pin 52 to said annular disc 60, electrical conducting slip rings 73 and 14 carried on an annular disc 75 rigidly secured, as at 16, to the disc 68 and rotatable with it, .are employed in association with the brushes-ll and T8 to convey energizing electrical current through said brushes and the slip rings frictionally contacted by the brushes, and circuit conductors a and b to the electromagnet, said circuit conductors entering the clutch casing through an aperture 19 through the plate Bil and leading therefrom'tothe winding of the electro-magnet 8.

The circuit conductors a are of the well known braided wire type with a rubber or other well known cover insulation whereby to withstand the sliding flexing movements of the electro-magnet {land its, carrying arm 58, to which carrying arm:

said conductors are conveniently-secured within the casing. I

A clamp such-as that shownzat 82 is employed to clamp the wires a and b to the arm 58, although the' wires themselves fromzthe point' of their entrance within theinterior of the clutch casing are not actually shown to avoid com-5 plexities of illustration, it. will, however, -be understood that said conductors a and b entering the casing at 19 interconnect. the sliprings-13 and I4 to the winding of the iron-clad electro magnet 8 and that their-position in :thecasing is substantially parallel to the curved farm: 58, being preferably secured thereto, as at 82.

It will be understood that the annular metal plate 54, which is :rigidly carried by thecasing will be of magnetic iron orsteel of good magnetic armature quality and that at least :the faceithereof which is frictionally engageable'with the :flat face of the electro-magnet 8 will be fiat so .as to make intimate contact with the face of the magnet and durable to withstand normal sliding contact by the magnet face over the said surface without undue wear of said plate.- Preferably, the iron material of the magnet faceiwill be the softer, .for reasons of morereadyreplacement at lower cost. a i.

. The electrical circuit for effecting operation of the clutch mechanism for the. winding drum 6 is shown in Fig. 5 wherein diagrammatically the electro-magnet 8 having a.winding--8 is shown in frictional abutingfcontact with the annular plate 54 carried by thewwindingdrum' and circuit A push button switch!!!) having normally open contacts 9| bridges a, section 92 of-the resistance in the resistance unit 88..Assuming that the push mechanism is in operation and that by operationthereof, the dipper I1 hasbeen supplied with excavating material andby virtue'of the operation of the cables 30', the dipper-:I-l is rotated clockwise about its pivotal support 93 to place the dump bottom or door 5 lowermost,cthe apparatus of my invention will then be operated to withdraw ,the latch bolt 3 from the latch plate a. V w, v

To condition the apparatus fo'r operation, the adjustable rheostat blade; 81 ismoved over :the resistance portion disposed to the right of-the intermediate connection leading toua contact of the switch until the flow of current from thesource 89 to the magnetB is-sufficient 'to maintain the latch line 4 sufficiently taut while not exertingvsuch a pullithereoniias:to unlatch the dipper bottom 5. At such a-time, the electromagnet 8 being relatively weaklyxma'gnetizedwill nevertheless exert a; substantial rotative drag on: the armature disc 50 andtherefore, aupon the latch line winding drum 6 to tend'towind the line upon the drum but the tractive effort will beinsufiicientlystrong to do "more than to take" the undesirable slack" outof the line :but being not of suflicientgstrength to overcome the 'op posing force ofthe spring 3 ho1ding the:latchedbolt in latched position; v

The dipper load, being as aforesaid ready tobe dumped, the operator then will press the button v90 offthe push button switch 90 and close the contacts 9lwhereupon the magnet '8 will receive much more currentland be muchmore strongly magnetized and will exert a definite relatively strong rotative pull on the armature laterally or forwardly and rearwardly at the same time. a

Under such a condition, the drum will pay out sufficient .ofthe tag line depending upon the pendant condition of the bucketunder different adjusted positions .of thebucket and the disposition of the boom and will reel in excess line disc54, and resultantly, a relatively strong wind- 1 ing'restored by gravitywhen the dipper is again swung to such a position as illustrated in-Fig. .1 or otherwise, saidbottom is restored, the spring I03 will ensure that the latch is again operative to latch the bottom dump door.

Having hereinabove described my invention as applied tothelatch line for the ,dipperlatch of a power shovel, as previously stated, my invention has a useful application to other lines,-such as tag lines, extending rearwardly from a crane bucket in such a manner as to exert a pull on the .bucket in a direction at an angle to the lines for operating said bucket in order that said line exerting a pull on said bucket may prevent the bucket from. rotating when suspended from the end of the crane boom.

Such tag lines havelong been commonly employed in the art, their application to the bucket being well known and understood, and the same is not illustrated herein but, for the purpose of the present disclosure, reference may be had to U. S. Letters Patent No. 2,166,479, to Ruddock dated July 18, 1939, which discloses such a tag line applied to a clam shell type of crane bucket, and which, incidentally, illustrates one priorattempt to maintain such='tag line taut. The. disclosure of the above patent is'to be referred to only as illustrating the nature of such tag line and. one method of attachment thereof to an excavating clam shell bucket fora crane .1 vSuch a'line is passed rearw'ardly to the cab in some such manner as that-illustrated for the latch line of the previously described embodiment of'myinvention and the arrangement previously and maintain thezline sufficiently taut at all times. #:The present invention is also in proper size and power applicable to any or all of the :clutch mechanisms commonly employed in power shovels or; cranes illustrated .in the co-pending application of Zeilman and Smythe, Serial No. 502,354, filed September. 14, 1943.

Having thus described my invention as applied to the latch line for a dipper dump door latch, the same being to illustrate one useful application thereof, it is tobe understood that myinvention' will bewithin the skill of the art readily applicable to similar operations relating to other lines employed i power shovels or the like, power cranes or mining excavating or load handling described comprises the winding drumfor-such' a line and the inter-related mechanical friction clutch and electro-magnetic clutch will, for the purpose of this disclosure, :be consi'deredasbeing V duplicated for :such tag line of a crane bucket.

The present invention ,provides improved means for maintaining the line tautin a'more efi'icient manner and under a. greater range of I rent and the magnet of the electro-magnetic clutch to ensure that-a sufficient and ineXcessi- 'ble pull is exerted'upon said tag line to prevent unduerotation or .rotative oscillation {of the bucket during such timesaswhencarrying a load of excavatingmaterialyfreely pendant fron'r the end of the boom andaperhaps; being swung mechanisms and that the application thereof thereto will .be obvious to those skilled in the art and the scope of my invention, as claimed, com prehends such analogous uses as well as various departures from the particular structure herein illustrated and described in connection with a single, embodiment thereof.

lcla'img q l. "The combination with a dump bottom latch of a mobile xpower shovel dipper and the latch line for operating the said latch and a power driven shaft disposedupon the turntable of' such shovel, of a winding drum to which said line issecuredfor variable winding thereon, a friction type clutch :and an electromagnetic drag type clutch both adapted to 'frictionally communicate a .rotativeefiort to .said drum from said shaft, electrical current supply means normally opera-- tive to communicate a limited electrical current tothe magnet of said electromagnetic clutchto element adapted to be deflected from its normal position'responsiveto such increased drag effect and a friction clutch operating link operable by defiective movement of said mechanical element to operate said friction clutch whereby by manual 1 operation of said controller said line is given an increased. pull .over that required to maintain the line. taut to.operate said latch to release said dipper bottom; a

' 2;.The combination with a spring retracted latch for releasably retaining the dump door of a, mobile power shovel dipper in closed position of a latch line and turntable carried power mechanism comprising a prime mover and a shaft rotated thereby, a winding drum rotatably journailed on said shaft, a latch line interconnecting said latch andsaid drum adapted for partial windingof a line end upon the drum, a mechanical friction clutch and an electromagnetic drag type clutch each comprising a part carried by and rotatable with said drum, an arm movable to energize said friction clutch, said electromagnetic clutch comprising an electromagnet, 7 said magnet carried by said arm and adapted when energized by a limitedflow of an electrical .current therethrough to effect a suflicient magnetic drag frictional engagement between the said parts of said electromagnetic clutch whereby to transmit a winding effort from said shaft to said drum to maintain said latch line' tautbutinsufllcient to operate said latch against the power of its associated spring and manually operable current flow controlling meansadaptedto substantially increase the flow of current through said magnet to so increase the magnetic drag effect as to effect a limited deflection of said arm operation of said friction clutch and a resultant increase in the strength of pull upon said line whereby said latch is operated to release said dipper door.

3. Mechanism for exerting a constant relatively light pull upon the latch line of a mobile power shovel dipper dump bottom and alternately adapted to exert a stronger latch operating pull thereon, the pulling end of said line being windable upon a winding drum, comprising the combination with said drum and a power shaft with which said drum is associated, an electromagnetic friction drag type clutch adapted when energized by a normal operating electrical current flow directed through the magnet thereof to exert a winding eifort from said shaft upon said drum to merely maintain the line taut during normal operating position, and means comprising a friction clutch operably responsive to an increased energization of said electromagnetic clutch upon an increase of such current flow to exert such greater winding effort upon said drum as to operate said latch and manually operable electrical current controlling means adapted when in one position to maintain said normal current flow and in an alternate position to substantially increase said flow.

4. The combination with a mobile power shovel comprising a turntable, a prime mover and a shaft rotatable thereby carried by the turntable, a latch line winding drum journalled upon said shaft, a boom dipper stick and dipper adjustably carried by said turntable and in extensible relation thereto, a dump bottom for said dipper, a spring retracted latch for normally maintaining said bottom in closed position, a latch operating line interconnecting said drum and said latch, a magnetic drag type clutch adapted when energized by a limited electrical current flow through the magnet thereof to transmit a sufficient line winding effort upon said drum to maintain said line winding taut and insufficient to overcome the power of the latch spring a friction clutch adapted when energized.

to transmit from said shaft to said drum a stronger winding effort sufiicient to overcome the latch spring -to operate the latch, an element associated with said electromagnetic clutch responsive to an increased driving torque thereof adapted to operate said friction clutch to a degree commensurable to the driving torque at the time transmitted to said drum by said electromagnetic clutch, and electrical current flow controlling means to alternately vary the current flow to said magnet to effect operation of only said electromagnetic clutch to maintain said latch line taut, or to operate both said clutches to operate said latch.

5. The combination with power shovel mechanism comprising a rotatable turntable, a boom hingedly connected to the turntable adapted to be swung thereby and to have its free end portions variously adjusted in a vertical plane, a

dipper stick longitudinallyri adj ustable. transversely of said boom and carried thereby, a dip: per having a I dump bottom -;secured to an end ,of the dipper stick, power means and ashaft driven thereby, on said turntable, anoscillatable latch for releasably holding said dumpbottom-in dip,- per closed position and a latch li QeQ 1 drum journalled on said power shaft, said linm xr tending between :said latch: and; said drum-and secured in ,winding'relation to said 1 d um; ,cluj; ch means comprising afriction-.clutch andangelec; tromagnetic clutch, each for separately communicating a driving effort from said shaft to said drum, each of said clutches comprising a shaft carried and a drum carried part, the two said parts for the magnetic clutch being disposed in face-to-face magnetic drag relation and one of said parts being yieldably mounted upon its carrier for limited angular displacement thereon, responsive to the torque load imposed upon 7 said part, mechanical means for said friction clutch, movable responsive to the deflection movement of said magnetic clutch deflectable part to energize said friction clutch to a degree commensurable to said torque load, a source of electrical current supply for normally energizing the magnet 01' said electromagnetic clutch to a limited degree of energization, and manually operable strength-of-current controlling means adapted to substantially increase the supply of current to said magnet, whereby said drum normally maintains said latch line taut by limited operation of said clutch means upon a lesser energization of said electromagnetic clutch and whereby said line may exert a sulficiently strong pull upon said latch to oscillate it to dump bottom releasing position, and retracting means to restore said latch to dipper bottom latching position against the pull normally exerted upon said latch line as a result of normal energization of said magnet.

6. Mechanism for maintaining taut lines such as latch lines, tag lines or the like leading from a rotatable turntable to an excavating shovel or bucket implement comprising in combination with said line a power driven shaft disposed upon the turntable, a winding drum upon which an end of said line is disposed in winding relation, said drum rotatably carried by said shaft, a mechanical friction clutch and an electromagnetic drag type clutch each comprising a part carried by and rotatable with said shaft and a part carried by and rotatable with said drum. an arm movable to energize said friction clutch, said electromagnetic clutch comprising an electromagnet, said magent carried by said arm and adapted when energized by a limited flow of an electrical current therethrough to the operator may limit the pull upon said lineto that degree of pull within the power of pullmg eifort capable of being communicated by said electromagnetic clutch or to effect a greater pull by co-operative pulling efforts of both such related clutches.

7. Mechanism for maintaining taut lines such as latch lines, tag lines or the like leading from a rotatable turntable toanexcavating shovel or bu'ok'et implement comprising in combination with-' said line a power driven'shaft disposed upon the turntable ,-a winding drum upon which an end of said line is disposed in winding relafien -said drum rota-tably carried-by said shaft, an electromagnetic friction drag-"type ciut'ch adapted when energizedbyanormal operating electrical current flow "directed through the magnet thereof to exerta winding effort from said shaft upon said drum; and means compris- ROY: H.

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