US1111101A - Crane. - Google Patents

Description

H. SAWYER.

CRANE. Arpmouron funn JULY 11. 191s. 1 1 1 1,101 Patented Sept. 22, 19M.

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.APPLICATION FILED JULY 11, 1913.

1,1 1 1,101 i Patented sept. l22, 191@ 5 SHEETS-SHEET 2.

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"GBANE. APPLIUATION FILED JULY 11, 1913.

Patented Sept.22,\1914.

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CRANE. APPLIUATIQN FILED JULY 11, 1913.

Patented Sept. 22, 1914.A

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.APPLICATION FILED JULY 11, 1913.

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. the boom, in operation is rocked from one .To all whom t may concern.' i

Emy SWYER, 0F MUSKEGON, MICHIGAN.

CRANE.

Specification of Letters Patent.

Patented Sept. 232, i914.

, Application filled July 1l, 1913. Serial No. 778,424.

Be it known that ll, Hnnnrz'SAwrnn, a citizen oit the United States, residing at Muskegon, county of Muskegon, State of Michigan, have made a certain new and useful Invention in Cranes, of which the'following is a specication. Y

This invention relates to cranes, and particularly to cranes of the rocking boom type. The object of the invention is to provide a craneY having a 'rochng boom and wherein side of a supporting structure-to the other.

Another object of the invention is to provide means for automatically preventing the load from rising as the crane boom` rocks' upwardly and the load from lowering as the boom rocks downwardly, whereby the overhang of the load is compensated and the power mechanism employed to rock the boom is relieved of the extra duty of raising and lowering the load as the boom rocks.

Other objects of the invention will appear more fully hereinafter.

The invention consists substantially in the construction, combination, location and relative arrangement of dparts, all as will be more fully hereinafter set orth, as shown in the accompanying drawings, and nally pointed out in the appended claims.

Referring to the accompanying drawings and to the various views and'reterence nu merals appearing thereon'z-Figure l is a.

view in side elevation of a ucrane embodying the principles of my invention, the. boom being shown in inclined position. Fig. 2 isa fi'ontelevation of the same, the boom being in vertical position. Fig. 3 is a 'broken detail. view showing cable connections for rocking the boom. Fig. 4 is a view in section on the-line t, 4, Fig. -3 looking in the direction of the arrows. Figs. 5 and 6 are broken detail views showing portions of the compensating means. Fig. 7 is a view similar to Fig. l, showing a dierent arrangement of supporting base for the crane boom, the upper end of the boom being broken 0E.

Fig. 8 is a broken view showing"tlie upper end lofthe boom of Fig. 7; Figs. 9 and 1.0, are,l respectively side and front elevations of a form ot d erriclr crane showing the application thereto ora compensating means embodying the principles 'of my invention. Fig. 1l is a diagram illustrating the edect of the compensating arniiigementl embodying my-invention, as applied to the types of cranes shown in Figs. l, 2 and 7. Fig. 12 1s a view similar to Fig. l1 showing the effect of the compensating arrangement of myinvention as applied to the type of der# riclg crane shown in Figs. 9 and 10. Fig. -13 1s a broken View showing a modied arrangement o gearing for rocking the boom.

rlhe same part is designated by the same reference numeral wherever it occurs throughout the several views.

ln the form shown in Figs. l and 2, the crane is composed of two principal parts, namely, the supporting base structure 15, and the rocking boom 16. The base structure may be provided with wheels 17 adapted to operate along track rails 18 and is desired, driven therealong by a motor indicated at 80, whereby the crane may be moved from one point to another as exigency may require. rlhe base structure is provided with vertical uprights or tower portions i9 which are preferably spaced apart a sumcient distance to permit the boom to rock and the load to'be transferred or handled to pass therebetween. The boom is composed of the side members 20 which are connected. together at both their upper and their lower ends. rlhese side members are suspended on trunnions 21in the tower portions 19 and preferably at points intermediate the top and base of the tower portions. Prei'erably the trunnions airis of the boom side members is nearer the lower end portions oit said members than the upper and provided with channel members 24: bent into. the form of drum segments concentric with the trunnions 2i. Cables 25, 26, are connected to the respective ends or veach channel member, and at their other ends are wound in reverse direction upon a drum 27, and respectively secured to said drum.,l as

indicated at 28, 29, see' Figs. 3 and ll. The

drum 27 maybe drivenin any suitable or convenient manner'. A simple arrangement ci" power mechanism for this purpose is shown'whereinamotor 30, is mounted on the base structure l5, and is suitably geared to4 a shaft 31, which drives the shafts 90, on

which thel drums are mounted, it being understood of course, that, if necessary,- and preferably a drum is provided for each side of the rocking boom. `My invention, however, as defined in the claims, is not to be limited or restricted in respect to this detail.

By the arrangement above described it will be seen that through the power mech- .anism provided for that purpose the boom may be rocked about its trunnions 21, so as to swing its long arm portion from one side of the supporting structure to the other, by rotating the drums 27 which causes the members of the pairs of cables 25, 26, to respectively wind upon and unwind from the drums.

As above indicated, other forms of gearing for rocking the boom may be employed with equal facilitywithout departure from the spirit and scope of my invention as dened in the claims.

By the power mechanism as above indicated, the boom can be rocked from the in-l clined position thereof shown in Fig. 1, into an upright or vertical position, as seen in Fig. 2, and then on into a corresponding inclinedposition on the other side of the supporting base structure.

A rocking boom crane having the structure and arrangement above described is adapted for general use where freight or cargo is to behandled or transferred from one point to another, and especially is s uch a crane advantageous for use in loading or;=` unloading boats, vessels, freight` cars or the 'j Flg- 13- like. In a crane for serving a marine terminal such as the loading or unloading of boats or other vessels lying alongside a dock, any part of the crane which overhangs the boat must be raised or withdrawn to clear the masts or yard arms ofthe boat when the boat is docking or sailing or when the crane structure is being shifted from one to another position relative to the boat. In the type of crane above described since the boom Irocks backward and forward with each load handled it is unnecessary to provide a separate movement for withdrawing the boom from the p'athof any part of the boat.

In the form shown in Figs. 1 and 2, a low type of supporting base structure is employed. In this type of crane of course, the space between the tracks 18, on which the base travels is not available for any other purpose. If desired, therefore, and in order to secure economy of ground area, the base portion of the crane may be supported at an elevation by means of a gantry comprising vertical leg portions 32, 33, the wheels- 17 where used, being mounted inthe lower ends of said legs, as shown in Fig. 7. By this means the base of the supporting structure may be raised to a sufcient height to permit the ground area beneath it and between the legs 32, 33, to be utilized', as, for instance, for the passage of freight cars, as-indicated Where electric motors are employed'for the power mechanism used for rocking the boom and for hoisting the load or' cargo, current may be supplied thereto in any suitable or convenient manner. In the low base type of crane shown in- Figs. 1 and 2, current may be supplied in a manner similar to the third rail system of supplying current for the operation of. electric railways, as indicated at 35, Fig. 1. In the case of the gantry type of base the current conductors may be carriedon poles as indicated at 36, Fig. 7. It will be observed that in the arrangement shown in Fig. 7 the motor 30 for rocking the boom as well as the drums 27, are laced to one side of the space between the egs 32, 33. Thisis for the purpose of leaving'the space free as much as possible for handling freight to and from cars on the railroad tracks which are not placed centrally underneath the crane.

In the foregoing description I have referred to drums and cable connections for securing the 'rocking movements of the boom. It is obvious, however, thatmy invention as defined in the claims is not to be limited to this particular construction as other forms and arrangementsare equally well adapted for this purpose. For instance, segment racks 37 and gears 38 meshing therewith may be employed as indicated in I will now 'describe the arrangement for securing an automatic compensation of the load imposed on thel power mechanism emloyed to rock the boom by the weight ofthe reight or other cargo being handled. A common practice in cranes is to reave the hoisting cable from the hoisting mechanism through a she'ave fixed at the outer or free end of the boom, thence downto the lower hoisting block and back and forth through sheaves fixed at the end' of the boom and in the lower block a suicient number of times to secure the desired liftin power,'the end of the cable, if desired, being ally anchored or secured either tothe 4end of the boom or to the lower hoisting block. In then use of 'such an arrangement in connection with a crane having a rocking boom wher'e the outer end of theboom is raised `or, rocks upwardly there is no change in the distance between manici vertical distance the load must then be lowered again. This workof raising the load is thus imposed on the motor which rocks vthe boom in addition to its normal work of merely rocking the boom, while the clination of t e boom. In

work of again lowering the load is imposed on the load hoisting motor' which wcrk'is done in the form of brake application. The' same results follow if the load is transferred in the reverse direction, that is, from a position corresponding to the substantially vertical position .of the boom into a position correspondin to the position of extreme inthis case the load would have to be' raisedy bythe hoisting motor a vertical distance thirty feet greater than the height thereof required in the eX- lcontiguous to the base treme inclined position to be ultimately as-l sumed by the boom in completing the transfer,

this case there is the increased hoisting work imposed on vthe hoisting motor and the increased braking work on the boom rocking motor. lt may be true that the two movements, namely, the hoistingland lowering or the lowering and hoisting movements, as the case may be, of the load may be carried on simultaneously so as to cause the load to move in substantially a horizontal plane but the fact remains, nevertheless7 that whether these movements of the load are accomplished consecutivelyy or simultaneously, unnecessaryor increased work is being done by one motor and is beingvused up in the brake application of the other motor. ln other words, in transferring a load removed from the base fr ame into position'contiguous` thereto the boom rocking motor must draw current-,from the line supply to hoist the required, and this work is convertedinto heat by the applicav'tion of the hoisting motor` brakes when the load is again lowered and similarly if the load is to be transferred from a position intoa position. remote therefrom, then the `load hoisting motor `must drawv current from the line in order to hoist the load through the required vertical distance, and the work ofagain lowering the load as the boom swings downwardly into its extreme inclined position is converted intofheat in the brake whichcontrols this movement. It is among the special purposes of my .present invention to provide means rfor compensating this unnecessary eXtra in order to make up for the lowering' Dprocess due to the rocking of the boom Adownwardly into its inclined position. ln

that is, a drum is located ateach side of the boom, as shown; As the reaving of the hoisting cable is the same at each side of the boo-m a description thereof for one cable will answer for both.

rllhe hoisting'cable 43, leads from the hoist ing drum 4l or 42, mounted on the rocking boom at its base, along the boom arm 20 to and around a sheave 44 Vat the outer or free end of the boom, thence inwardly toward the centerline of the cross beam 22, to and around one of a pair of sheaves 45 carried by said beam, thence down and around a sheave in the lower hoisting block 46, thence up and around another of the pair of sheaves 45 on the beam 22, thence outwardly to and around a sheave 4'?, thence downwardly to and around a sheave 48 mounted in the upper ends of the base tower 19, above the journal axis 2l of the rocking boom, thence u wardly to and around a sheave 49 carried y the overhanging end of the beam 22vat the upper end of the boom, thence downwardly to and around a second sheave 50 andthence upwardly and the end of said cable is anchored or otherwise suitably secured, as indicated at 5l', to a bracket or other conven-4 ientpart at the upper end of the boom. lt isobvious that the sheaves respectively at the upper' ends of the boom and the base tower maybfeincreased as' desired to secure ,anydesired number of runs or legs of the lhoisting lcable between thesepoints. Since the'ed'ective-leverage of the runs orv legs of the cable between the said pulleys respectivelyl at the top of the boom and tower acts ing about the trunnions on which lthemboorn rocks, is less than theoverhang of the load,

the number of runs or legs of the cable between said sheaves must be'propolrtionally greater `than the number of runs or legs of the portion of the cable carrying the load.. ln the particular arrangement of crane whichl have shown" to illustrate my invention the' edective leverage of the compensating cable actingA about the fulcruln of the rocking boom, is only about-one half of the.

overhang of the load so the number of legs or runs of the cable between the sheaves at the tops of the"boonrand tower is twice as many as those' supporting the load.

With the compensating arrangement as above described the operation is as follows: As the boom rocks upwardly from its extreme incline'd position, the overhang ofthe load as well as the effective leverage of the compensating portions of the hoisting cable is gradually reduced so that by the time the boom attains its vertical position, both the overhang of the load and the eiective leverage of the compensating portion ofthe cable is reduced to zero. Similarly, when the boom moves from its vertical position toward its extreme inclined position the overhang of the load as well as the eiective leverage of the cable increases rom zero to the maximum with the result that in the one case there is a gradual lengthenin of that bight or portion of the cable whic carries the load, and in the other case there is a gradual shortening of said -bight or portion and consequently, in either case the load travels in a substantially horizontal line and i without imposing any material or substantial load on the motors either in hoisting or brakin Work. Since gravity always acts in vertica and-consequently parallel lines while the direction of pull of the compensating cable is constantly changing as tlie boom rocks in one direction or the other the overhang of the load and the effective leverage exerted by the cable do not increase or decrease in exact proportional relation and consequently there is a failure to secure absolute and perfect compensation. The compensation secured, however, in the arrangement described, is ysuiiicient for all practical purposes. I

In the diagram of Fig. 11, I have shown the compensating action secured in the use of the arrangement above described. The line a, indicates the line of travel of the load from one extreme limit of inclination of the rocking boom 20 to the other, the lines b, indicating the various positions of the boom, and the lines c, the lines of inclination of the compensating portions of the cable, and d, the line indicating the shifting of the effective center of gravity .of the load. In eX- planation of this line d, it will be understood that, without compensation, when the load is imposed on the end of the boom when the latter is in its extreme inclined position, the leverage through which theload acts is the distance between the vertical'lines respectively containing the axis of the boom and the load block 46. But the compensating cables exert a moment in the opposite direction with the result that the net leverage through which the load acts is correspondingly shortened. This net leverage varies as the boom rocks from its extreme inclined po'- sition on one side, to that on the other side.

- The line d, which I call the line indicating the shifting of the effective center of gravity of the load, represents this varying net 1everage exerted vby the load. It will be seen that the line a, rises more raplidly from the extreme inclined positions of t e boom. This is the time whenthere is the greatest eiective overhang of the load, that is, the 'time when the compensation is less complete. As the line a, reaches a point where it 1s strictly horizontal it indicates perfect compensation action, and at that point the line d, crosses the vertical center of the crane. As the lower hoisting block 46 approaches the vertical center line of the crane it is slightly lowered below the true horizontal line, thereby indicating over compensation as shown by the loop in the center of gravity curve d.

From the foregoing it will be readily understood that the portions, of the hoisting cable whichy extend between the sheaves 'at the upper ends, respectively, of the boom and tower exert a leverage or'movement on the boom in opposite direction to and practically equal to that exerted by the overhanging vload with the result 4that as the boom rocks the load is maintained at a substantiall horizontal line without imposing any additional duty uponl either lthe hoisting or the boom rocking motors.

The advantages and benefits of the compensating arrangement above set forth are not confined to the application thereof to the structure of crane above described but are attainable with equally useful results in other types and structures of cranes. In Figs. 9 and l0, I have shown another form of crane wherein a boom 60 is pivotally mounted to rock or swing upon a fulcrum 61, on a base frame 62, the rocking of the boom being secured in any sui-table manner, as, for instance, by the pivo-ted screw rod 63. In this arrangement the hoisting cable 64 leads from the hoisting .mechanism 65, carried by the base frame, over sheaves 66 at the upper end of the boom, thence to and around a sheave in the hoisting block 67 thence back over sheaves 68 at the upper end of the boom to and over sheaves 69, at the base of the boom and to and over sheaves 70 on the base frame, the runs or legs of the portion of the cable operating over the sheaves 69 and 70 varying in the proportional relation to the number of runs or legs in the bight which carries the block 67 in the same manner and ,with the same compensating result as above described with reference to the structure shown in Figs. l and 2. -The diagram of Fig. 12 illustrates the compensating action of the crane structure shown in Figs. 9 and 10, the lines a and d thereof corresponding to the lines a, and d of the diagram of Fig. 11.

While I have shown the hoisting motor as carried by the swinging boom it is to be understood that my invention, in its broad- .aneans .carnieol by lroclisaid'laoom.

aesinet est scope as defined Vthe claims, is not to he restricted or limited in vthis respect. lt 1s also to be understood that the .particular reevng of .the 'hoisting ropes as well asI and relieving :the boom rocking motor 'of the extra cluty ,of raising and lowering the load as the boom. rocks. llt will be under. stood, ofcourse, that with the arrangements shown, tiais compensation .is .always .piroporfy tionslfto the load and consequently is equally ecient .whether the whether it foe light.

ture oi my iunvention-7 .and various construc-g tions embodyingthe .principles ,thereofgyvhat l claim as new 'fand useful and .of .my .own in;

:vention anni desire :to secure .fby .Letters yPat- .ent'isz- 1 'ln a crane,.a.s1lpportingbase, a laventi` caliy rochnboom carried ,thereby toreok .ii'oin `one si e of the ibase to `.the other, load supponting devices amounted on vIthe-:hangin?, :me-ansior operating. said de viQQs, ,nienns carried loy ,the base to rockglooomian means to cause the load ,to nieve-1in :ja-'substantially .straight line ysturing the groclfiing movements of the boom..

2., ln a crane, a supporting-base z'aanynig -trunnions, a vertically rocking :boem having ;bearingsfonsaiol trunnion's, load suppoeting devices-carried by said hooin, a hoisting motor mounted on and arranged' to ceunter-v halance said rocking boom, .conneot iqns,o .elated by `said -inotor .and leading to said supporting devices-to .openate the sante, and

the supportlnggbase to ibase? a :venti 3.131 a crane a supporting -miemteol- Eon cally rocking -booni plvtal .y

:to l.the other, yloaol supporting olev'vieesl eanriecl :by thelooom, means for operating sani ole-4 vices, a motor .carried loytlie base, connec :tions operated lby saidvinotor toxrocl .saiol ing movements of the booin. y.

el. in a crane, a supporting lease9 a vergt -cally ,rocking fbooin .pivotall'y mounted inter-` -inetiiate'its ends on said base to Vrock from fone side ofthe vhase to `the athena .motor ;monnted on the lower end of the boom, load l'snppnaf'ting-ievieescarried by the boom, con- `sections -aotnatecl bysaia motorini' control.

l llne -during lthe les@ fb@ been. 0.11 l i "f v,tacitamente Qtthetoomftolcaus the. loedlto .Having .now set forth the obyect land .nay

ling said devises, and .means ion rocking said boom, I

V5. j nacijane, a sapportin base, a vertisI .callyroclnng hoorn Apivotallgy mounted on said base to rock 'from one side of the base to the other, loadslpporting devices carrie by the abonne, .means vfor .operating said devices, :including cable connections, guides for saicl connections operating to cause the same to inove" the loaol in .a substantially straight rocking movements of the booniand-power operated .mechanism for rocking said booms -v '-6. nacrane, a suppontirngbase having an luprightorgtovver portion, aboom pivotally .snspendedeintermedate its ends upon said tower .position loaol supponting devices car- ',nied hysaielboom :means fior .operating said devices, meensto 'rocksaid 1000m from ,011e

sfide of the ibase to .the other and means op- .enating: automatically .during the rocking travel. in a substantially straight line. f7. lima erano, `a.supporting lease having vertice 1y estemline'ltower .nortons .spaced spant omeaehot er, a vertically .rocking been! -givotally supported intermediate its .ends between .'-saiiol ftower -poiftions, load sup- ?eetlag devices Gareediby saidA booms means or gigeratinggsaidelevices, ineens tor rock- 111g seid bww 'emol --means oper-ating .automatically during the rockinggof theinooin to .cause the Eliegst-tn travel en ,a substantially straight tine..

.@fn te stese a eenvertieeitesc Ihaving 'vertieailvf sweating towers seated sont toni ,seele @then i a V'vertically rocking boom including sicefnaenibens respectively jour:

Maisel intennieeliate-theic enfle on lsaid tower povtionsganel connected together at their respective encls, ieajdsiipporting devices car- ,rae lay-'Sem flffono,"cahle connections for opferetingxsaiei deviees nieans for rocking saisi tenement-seems to auteniatcaily nay est teiipisaidf ealileconneetiens Toy the the n-a certaine .a :supporting floase having -asttieailv enemies tower .sett-ions Aspaces apart 'Jtroi'n each ot er, a vertically ,rocking ieelefiee :site members respectively ionsnaieol iateifnietiiate theii'nenols .on saici ,teveeffnetiese and contestes together et .ith nnper anti lowerfendjs, ii-hoisting motor Q?llfifby,tiie booin its lower encl, loaol zsllipvtllldeviees inclnling cable connecftiens actuateii-fioysaici motor, and means for rocking saiclloooin., y

k- 110., ina' craneyasuplportinghase having- -verticaliy :extending towers. portions spacecl apart :trein each other, a vertically rochng lio'oin incintling .sie inemhers respectively v iournaleel intermetliate their ends on saici towerV noiftonsanol connected together at @their n -pperanclfiovver enfle, load supporting devices carried by said boom, and including cable" connections, means carried by the lower end of the boom for operating said devices, and power operated devices for rocking said boom.

11. In a crane, the combination with a supporting base, a boom pivotally mounted thereon to rock from one side thereofto the other and load supporting devices carried by said boom, of means made effective by the rocking movements of the boom to cause the load to move in a substantially horizontal line when said boom is rocked.

12. In a crane, a supporting base, a boom pivotally 'mounted thereon, load supporting devices carried by said boom, and means for rocking said boom vertically from one side of the base to the other in combination with means made effective by the rocking movement of the boom for automatically causing the load carried by the boom to move in substantially a horizontal line when said boom is rocked.

13. In a crane, a supporting base, a boom pivotally mounted thereon, load supporting devices suspended from the upper end of said boom, and means for rocking said boom vertically from one side of the base to the other, in combination with means for automatically preventing the load from rising as the boom rocks from an inclined toward an upright position. f

14. In a crane, a supporting base, a boom pivotally mounted thereon, supporting devices suspended from the upper end of said boom, and means for rocking said boom vertically from one side of the base to the other in combination with means for automatically raising the load relative to the upper end of the boom, as the boom rocks from an upright toward an inclined position. 15. In a crane, a supporting base, a boom pivotally mounted to rock thereon from one side thereof to the other, and load supporting devices carried b said boom, said load supporting devices aving connection with said supporting baseO to automatically vary the eective leverage of the load as the boom is rocked.

16. In a crane, a supporting base, a boom pivotally mounted to rock thereon from one side thereof to the other, load supporting devices carried by the boom lincluding a cable, and pulleys carriedby the supporting base over which said cable operates, and located so as to vary the effective leverage of the load as the boom rocks.

17. In a crane, a supportin base having a tower portion, a boom pivota ly suspended from sald tower portion, load supporting devices carried by the boom and. including a cable, pulleys respectively located at the' [upper ends of the boom and tower portion over' which said cable operates, means to\ pivotally boom, said operate the cable and means for locking said boom from one side to the other o said e tower ortion. l

18. n a crane, -a supporting base having a tower portion, a boom pivotally supported upon said tower portion, load supporting devices carried by the boom and including a cable, means to o crate the same, 'pulleys respectively locate at the upper ends of the boom and tower portion'over which the cable operates, the )tower pulle being located above the pivotal axis o the boom, and means for rockin said boom from one side to the other of said base.

19. In a crane, a supportin base having tower portions, a boom pivota ly suspended intermediate' its ends between said 4tower portions to rockvfrom one side thereof to the other, pulleys respectively located at the upper ends of the boom and tower portions, load supporting devices carried by the boom and including a cable, said cable operating over said pulleys, the pulleys on the tower portions being located above the pivotal axis of the boom, means for operating the cable, and means for rocking said boom.

20. In a crane, a supporting base, a boom pivotally mounted thereon to rock or swing vertically from one' side of said base to the other, a load supporting device suspended from the end of said boom and means made effective by the rocking. movements of the boom for automatically moving said device relatively to theI end of the -boom as said boom swings.

21. In a crane, a supporting base, a boom mounted thereon to swing in a vertical plane from one side of the base to the other, sheaves respectively carried by said boom and base, a load supporting device, and a cable for' suspending said load supporting device, said cable operating over said respective sheaves to eiect a moment in opposite' direction and substantially equal to that exerted by the load.

22. In a crane, a supporting base, a boom. mounted thereon to swing in a vertical plane from one side thereof to the other, means for rocking said boom, sheaves respectively carried by said boom and base, a load supporting device, a cable for suspending said device from the end of the cable operating over said respective sheaves to effect a moment in opposite directionl and substantially equal' to that exerted by the load and a hoisting motor connected to said cable.

23. In a crane, a base, a boom pivotallyA mounted thereon to swing in a vertical plane from one side thereof to the other,'sheaves respectively carried by saidboom andbase, a load supporting device, a cable suspendin the same from the end of the boom, said cable operating over `said respective sheaves,

said sheaves being so relatively' arranged my hand in the presence of the subscribing thatthe sheaves on the boom approach a Witnesses, on this rl7th day of July A. D., line drawn through the pivotal axes of the 1913.

boom and the basesheaves as the load sup- E 1'? RY SAWYER.

5 porting device approaches the vertical line Witnesses: v

through the pivotal axis of the boom. OTTO AIBERT, Y

In testimony whereof I have hereunto set vP. J. KULPERST.

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