US2613915A

US2613915A - Hoisting device

Info

Publication number: US2613915A
Application number: US135364A
Authority: US
Inventors: Albert L Stone
Original assignee: Standard Oil Development Co
Current assignee: Standard Oil Development Co
Priority date: 1949-12-28
Filing date: 1949-12-28
Publication date: 1952-10-14
Anticipated expiration: 1969-10-14

Description

A. L. STONE HOISTING DEVICE Oct. 14, 1952 2 SHEETS'-SHEET 1 Filed Dec. 28, 1949 Y. Re 0 TM R n V 0/ N 1 A I L T f e m A A. L. STONE HOISTING DEVICE Oct. 14, 1952 2 SHEETS-SHEET 2 Filed Dec. 28, 1949 FIG. 6.

SURGE TANK INVENTOR. Albert L. Stone,

SURGE TANK ATTORNEY.

'ous telescoping elements];

Patented Oct. 14, 1952 YHOISTING DEVICE Albert L. Stone, Redondo Beach, Calif., assignor,

bymesne assignments, to Standard Oil Development Company, Elizabeth, N. J

tion of Delaware Application December 28, 1949, Serial No. 135,364

4 Claims; (01. 254-93) My invention relates to a hoisting device. More particularly, my invention relates to a hoisting device which employs a hydraulic cylinder and a sealed flexible piston rod.

In many operations it becomes necessary to raise or to lower a load.- For example, in the drilling of boreholes by the rotary drilling method the drill pipe, casing, and various gear must be raised and lowered within the derrick above the derrick floor. This hoisting is conventionally accomplished by means of a draw :works driven by a draw works engine. The draw works and its appurtenant equipment occupy considerable space on the derrick floor and on the ground in vicinity of the derrick which could be used more efiiciently for other purposes.

The present invention contemplates the employment of at least one hydraulic cylinder having a piston mechanically connected to. a flexible piston rod for performing the function normally employed by the conventional draw works, draw works engine and subsidiary equipment. While prior art devices of this general type possessed certain advantagesfor the suspension of loads, they also possessed certain serious disadvantages. The chief advantage in the employment of aflexible piston rod in devices of this type rather than a rigid piston rod resides in the fact that the length of the piston stroke is approximately half of that required when a rigid piston rod is employed. On the-othenhand, prior art devices of this type employing a flexible piston rod have not utilized a satisfactory means for packing around the flexible piston rod so as to provide a fluid-tight seal between the rod and the piston rod end of the cylinder. Failure to provide a satisfactory sealat this point has effectively prevented widespread commercial adoption of this type of construction in a lifting device. I

Other attempts to avoid the past'difficulties encountered when employing flexiblepiston rods while at the same time avoiding the double length inherent in the use of a rigid piston rod have involved the employment'of varioustelescoping means. The telescoping means employed in some of these devices is similar in principle to the telescoping meansemployed in hydraulic jacks of conventional design. The obvious difficulty with devices employing such a telescoping means resides in thenecessity for providing a multiplicity of 'fiuid-ti'ghtseals; between the vari It'is an object of inventionto provide a hoisting device whichis' capable of hoisting a in Fig. 1;

of another embodimentof my invention;

a corporaload approximately the same distance as the length of the stroke of the. hydraulic piston used, to accomplish the lifting of theloadt It-is -fn-rther an object of my invention to provide ahy -f draulic hoisting device which utilizes a. ;i i ex ibl e piston rod provided with suitable meanss for sealing the flexible rod against the passage-=01 a hydraulic fluid. It is a furtherobjgctof any invention to provide a hydraulic hoisting. mechanism which utilizes a flexible piston-13o t which requires 'no telescoping means,

The objects and theadvantages-pf my Illvention will be readily comprehended fr o m the detailed description of the ing wherein Fig. lis an elevation, partially in cro tion, of one embodiment of my invention Fig. 2 is a top View of the embodiment shown accompanying draw- Fig. 3 is a perspectiveview of a- ;.portion .of the embodiment shown in Fig. 1; I Fig. 4 is an elevation, partly. in cross section. of a modification of the embodiment shown in Figs. 1, 2, and 3; I

Fig. 5 is a detailed showingzof-a .p'ortion. of the device of Fig. 4; I

Fig. 6 is an elevation, partly in cross section Fig. '7 is a top view-of the embodiment;shown inFig.6;and,m

Fig. 8 is an elevation,- partly .in cross section, of a modification of the embodiments shown'in Figs. 1110 7.5 i Y 1 In the drawing like numerals refer .tolilike parts throughout; For the sake ofconvenience and clarity; the embodiment shownflin- Fi will be first described. I I

Referring to Fig; 1-, I0 designates a supporting structure, such as a derrick, on whichthe' de vice of my invention may be mounted. 'mmeg i H designates a transverse .lmemberjformin L a part of the upper portion ofjsupporting structure If]. Upright journaling members] 2 are afiixe to member ll, members 12 being adapted t ceive andsupportaxle i4 for' rot'ation abou axis. sheave I5 is mounted on axis 14 for-rotation therewith. Upright journaling member s I-3 and upright journaling members l5 are also affixed to member I I, journaling members fibeing adapted to support axle It for rotationabout its axis and journaling members 15' being adapted to support axle ll -for rotationabout its axis. Guide wheel l8 ism'ounted on axle 16 Hydraulic cylinder housing 20 defining cylindrical chamber 23 is supported in an upright position from supporting member ID and may suitably be afiixed to transverse member ll by bolts 24. Hydraulic cylinder housing 20 is mounted beneath the outer periphery 25 of sheave l and the.-buteriperiphery 26 of guide." wheel I8. I-Iydraulic'cylinder housing is so arranged that the longitudinal axis of cylindrical chamber 23 is substantially tangential to the outer pe riphery 25 of sheave l5 and to the outer periphery 26 of guide wheel [8. Upper end 2! oi hydraulic cylinder housing 20 defines passage 28. Affixed to the upper end 21 of hydraulic cylinder housing 20 by means of bolts '29 is *sealing'membe'r which will be more fully described hereinafter. Tubular member 3| fluidly Icommunicates with cylindrical chamber 23 adjacent the upper end,

dricalchamber 2'3 and carries on its outer periphery sea-ling -means 34, Which'may suitably bivanfi-"o ring or-piston ring, adapted to preventitl'ie passag'e of fluid between'the saidpiston'bndthe-walls of cylinder housing 29 which define cylindrical chamber 23. Mechanically center 'd to the ii'pper'side of piston '33 is flexibl piston-rod 35.".A'lso' mechanically affixed'tothemppei' side 35 o'fp'iston 33 is longitudinally-split tubular sealing member 31,-tu-. bula'r*-sealing =meinber 31-being arranged coaxially with fleziiblapistonrocl 3'6 anacircumsiflfiiiig thatporticn of said rodpo'sitioned withiii bylindricalchambr "23 and 'sealin'gmember 30. Longitudinally-split tubular sealing =memb51 3! "may suitably be ofany-material which willcircumscribe that portion of piston'rod 36 pb's'itionediwithin cylindrical chamber 23 and sealing member'- 30*andwhioh will "provide a fluid -tight-seal'bc'liwen-pistcn rod 36 9,1101 sealing. member 30. Longitudinally-split' tubular sealing "member 31- will-ordinarily consist of hatui'al"br"s'ynthetic rubber but may suitably be oi any material which will normally assume a tubular form toprovide a fluid-tight "sealbetwlrpistohlod 35 and sealingmember 3 0 but which is'cap'abl of assuming a fiatribbon-like configuration when rolled upon 'aflat surface. mtfnedrawmg "flexible piston red as is-shown Ta 'attfachedja't 'one end to the upper side 35 of pis on 33 'and'j'as passing "through opening 28 'and"'se'aling member 30 and over the top of j'slia'vegfijits other end being mechanically connectd to ai'suitable load gripping means 38. menticn'edibefore, longitudinally-split tubular sealingsm'em'b er 31 is arranged coaxially with flexible. piston ma 36 .while 'theas'aid. rod is confined within cylindrical chamber- 2-3-and sealtingmember 30 and in the drawing is shown as separatingfrompiston rod 3 6 above'sealing member 30 and: thereafter -passing over the top of guide wheel'l-8-and onto-reel I a-upon which it is wound; A's longitudinally-splittubular seali'ingimember 3 passe'snverl-theetop zofzguide wheel I8 it assumes aribbon-like shapeand z'main- 4 tains its ribbon-like shape while wound on reel l9.

Sealing member 30 consists of a stuffing box 39, which is affixed to the upper end 21 of cylinder housing 20 by means of bolts 29, compressible packing material 43, and plug 4|. Plug 4| is adapted to fit' slidably' withini'stu'fiingi box 33 and is secured to stuffiiigboX 39-'by-means of bolts 42, the tightening of said bolts causing compression of packing material 40 to form a .,,-fluid,-.tight seal around longitudinally-split tubula'r sealing member 31.

operation load. gripping means 38 and any '.load attachedxthereto may be raised vertically by supplying under pressure to cylindrical chamber-23 through tubular member 3|. The

fluid so. introduced .-exerts pressure against the I upper side 35 of piston 33, forcing piston 33 downwardly within cylindrical chamber 23. Flexible piston rod 36?. and longitudinally-split tubular sealingimembe'r 31 also move downwardly in cooperation :with piston 3-3.-v As: Lpiston :rcd 33 -;moves: downwardly it als'citravels .ove'r the top of sheave I15'therebyvfraisingload: gripping means 38:;together 'withtheload-:attached'thereto.-. As longitudinally-split tubular sealing. mem ber! moves downwardly in ICOOPGIHItiOIli-iWlth piston 33, itsunwind's from-:reel lfiyvtravels over the top 10f guide whee/1113 and; engages .witlrpiston rod 36- ab'0vesea1in'gmember 30; arrangingiitseli coaxially with. said piston rod. Sealing: member 33: rforces-i longitudinally-split tubularsealing member '3'1c into. fiuidtight contactiwithzzpiston fiuid-ti'ghtiiiseal' between'xztthe touter. surface of longitudinallyespiit.tubulara sealing :member; 31 and the'uppercend 2:1 =ofzcylinden housing. 20'." By arranging; Ether. :parts 'assrher'einbefore described thecescape: of. fluidcaronnctrflexibieripistom rod 33 as'itp'ass'es in and out otcylinder housing 2|] .isaprevented.

:iOrdi'narily; iti.Wl1'1fb'ef:fdeSl.-Iab18 to maintain fluid in :thenlower portion of. chamber 23 below piston 33raand infsurgeztank 52. and-conduit 53. '-Ihis: ::iiuid:must;. of .course'; beiunder .azm'uch lowerwpressureixthan;;the;i:fluid in chamber 23 aboye'piston 33.;When piston-33 i forced-downwardly inchamber. 2'3,-.the fluid below the;piston fiowsithroug-hrconduit 53-intosurgextank 52 and when-piston 33.moves upwardly in chamber 23, this nfiuid" flows from surge. tank 52 -through conduit 53winto the space in chamber 23. below pistonv33. The-purpose in-employing a surge tank is tooreduce .-:the amount of-gritoand; dirt which:would-enterxchamber 23 if the lower portion ofqthechamberwere merely vented to .-the atmosphere. =Furthermore-,.-whenfluid is maintained on-bothsides of piston 3.3,.,.sealing member 34 is-wettedfrom-bothsides-and-is thus more likely to provide a fluid tight seal.

a :When itis desired tot lower-loadgripping member; 38;together with-its attached 1oad, hydraulicwfluid iswpermitted to escape from :thespace in cylindrical chamber 23 above'piston 33- through tubularamember 3|. .-.The rate of escape of hyzd-raulicfiuid from cylindrical. chamber 23.may be .controlled by. throttling tubular member 3! in. any suitable manner as by means of a valve, .not shown. By controlling-the rate ofescape of fluid. from cylindrical .chamber 23 -the ratcof descent ofload grippingmeans 38 .is-also controlled. As fluid escapes :from;cylindrical chamber 23 through tubular-.amember 3|, piston 33 moves upwardly :within. cylindrical. chamber, 23, flexible pistoncrod 36.; :and 1 .longitudinallyesplit .embodiment'shown inFigs. l and '2.

tubular sealing member 31 also moving upwardly in cooperation with piston 33. .As flexible piston rod 36 and longitudinally-split tubular. sealing member 31 clear sealing'member 30 in their 'upward travel, they'separate from each other, as shown most clearly in'Fig. 3. Flexible piston rod 3'6 travelsove'r the top of sheave I5 and longitudinally-split tubular sealing member 31 travels over the'top of guide wheel I8: and onto reel' I 0. 'Reel. I9 isprovided with a" suitable means, as'for example a spiral spring II, for causing it to tend to rotate in one'directio'n so as. to maintain tension on longitudinallyrsplit tubular sealing member 31 so that memberx3l will retain its ribbon-like configuration while wound on reel I9.

Flexible piston rod 36 must be ofi suflicient strength to act as a piston rod in tension when liftingror suspending the loads engaged by'load gripping means 38. It must also be suificiently flexible to travel over the top of sheave I5 without acquiring any appreciable permanent distortion or set. The outer surface of flexible piston rod 36 must be sufiiciently uniform so that when it is circumscribed by longitudinally-split tubular sealing member 31, itsouter surface will cooperate with the inner surface of member 3'! to.

while permitting the outer surface of longisealing member 30. Although any type of flexible line which will meet. the aforementioned conditions, may satisfactorily be employed, I prefer .to employ a flexible wire line of any of the types conventionally employed in hoisting equipment. 3 Figs. 4 and 5- illustratea modification of the In this modification, sealing member 30 and guide wheel 'I8'of the embodiment shown in Figs. 1 and 2 are eliminated. Referring to Figs. 4 and 5, I0 desigform a fluid-tight seal between the two surfaces nates a supporting structure, such as a der rick, and II designates a transverse member forming a part of the upper portion of supporting structure I0.

insanupright position from supporting member I0 and may suitably be afiixed to transverse member II by bolts 24. The upper end 21 of hydraulic cylinder housing 20 defines passage 28. Upright journaling members I2 affixed to transverse member support axle I I- on which is mounted sheave I5 for rotation about its axis.

Journals I2 and, accordingly, sheave I5 are so arrangedabove cylindrical housing 20 that the "outer periphery 25 of sheave I5 is substantially tangential to the longitudinal axis of cylindrical housing 20'.

Pivoting membersiGiI mounted on pivot member BI, secured to transverse member II, tend to support axle 62 on which is mounted reel 03 for rotation thereon. Spring 04 is secured'by one end of flexible piston rod 36 and one end of Iongitudinally-split tubular sealing member 31 are affixed to piston 33, while theother end of flexible I piston rod 36 passes overthe top'of sheave I5 and the other: end of longitudinally-split tubular seal- :ing member 31" iswound onto reel 63. That por- Hydraulic cylinder housing 20 defining cylindrical chamber 23 is supported 6 tion of flexible piston split-tubular sealing member 31 positioned with-- in chamber 23 and port 28 are in coaxial relation. However, as piston rod 36 and member 31 pass through port 28, they separate from each other as shown. Inasmuch as pivoting members 00 and, accordingly, reel 63' are=biased toward cylindrical housing member 20 by means of spring, the outer periphery 65 of reel 03 is always maintained substantiallytangential to the longitudinal axis of cylindrical housing member 20. Of 7 course, as longitudinally-split tubular sealing member 31 winds onto reel 63 on upward movement of piston 33, pivoting members 00 and reel 63 tend to move away from housing 20 against'the tension of spring 64. T

Inasmuch as the stufling box'of Figs. 1 and'2 is eliminated from the modification shown in Figs. 3 and 4, it is necessaryin the modification shown in Figs. 3 and 4 that port 20 be of the proper dimensions to force longitudinally-split tubular sealing member 31 into sufficiently close contact with flexible piston rod 36 to cause said member 31 to provide a fiuid-tight'seal around I said piston rod. 1

While the embodiment of the hoisting device of my invention shown in Figs. 1 tof5, inclusive, utiliz'es'only one hydraulic cylinder unit including the cylinder housing, piston, piston rod,'longitudinally-split tubular sealing membensheave, and reel, the hoisting device of my invention may comprise a plurality oflsuch hydraulic cylinder units. Of course, the total number of such units employed in any particulariinstance will depend. upon the individual lifting potential of each unit and upon the magnitude of the load to be lifted. It will be appreciated that various modifications may be made in the various units themselves when a plurality are employed in order to accommodate the units to the supporting structureand to integrate the units into an efiicient working assembly. It will also be appreciated'that the supporting structure may need to be suitably modified to receive a pluralityofhydraulic cylinder'units. Portions of the hydraulic cylinder unit may even be incorporated in the supporting structureitself to-form a part thereof. For example, one or more legs of vasupporting structure, such as a drilling derrick, may be replaced bya hydraulic cylinder housing of ahydraulic cylinder unit which, in effect, will make the hydraulic cylinder housing a leg of the'derr-ick. Various other adaptations will, of course, become obvious as further embodiments of .my invention are hereinafter described. 1

In Figs. 6 and 7 an embodiment is shown in which four cylinder units are employed. Turning now to Figs. 6 and '7, I00 designatesa supporting structure, such as a derriclgon which the device of my invention may be :mounted. Numeral IOI designates a transverse'member forming a part of the upper portion of supporting structure I00,Jtransverse member I0l defining opening I02 therein. A plurality o f platform -members I04 extend laterally from supporting structure I00, the said platformmembersibeing supported :by suitable bracing: members I05. Mounted on each of the platformmembers I04 are upright journaling members" I06 and I00 and upright journal-mg members'IIlI and H01, journaling members I06 and 'I06xbeing adapted to receive and support axle I08 for rotation about its axis and journaling members 101' and 1 01' being adapted to receive and support axle I09 for rod 36 and longitudinally rotationazahoutsits. axis .Gulde. .wheel ".110 is mounted oxriaxle 'SI'UQ'JfOJE rotation-itherewitnand reek-Illismounted onlaxle I08 for-,rotationthera withp Apluralityofjournalingmembers-I I2 and] I2 are; mounted: on v the ..=transverse-member. -I II I members-I12 and i112? --b.eing adapted to receive and'support axlefl I3.-'for rotation aboutits axis. A sheavei I Miszmoun-ted on each of axles .-:I I 3 for rotationtherewithlqj gr "L-shows-thatone sheave maybe dispensed. with: entirely, hydraulic cylinder housing-member :I I 6 replacing same and forming a part of. supportingstructure -J00.

Hydraulic cylinder housing member IIB defines internal cylindrical chamber I I-8, .tulbular; member.-.I=IH fluidly communicating with internal chamberIIB adjacent the upper end I 20 of cylinder-housingmember -I I 6.. Alfixed to the upper end 120 or hydraulic. cylinder housing member .-II6 as bymeans of bolts- IZI tiszsealing member .122Z .Sealing..,mem-ber..I22 may beidentical in construction withsealing. member 30 shown in Fig. 1., the details of..which.have, beenhereinbeforedescribed, or, it. may be similar to the structureshown in Fig.-4 andhereinbefore described. Piston :I 231s slidably arranged within cylindricalchamberII aandcarries onits outer periphery sealing ,means, I 2 1, which may suitably be an .O..-.-ring or..plston ring, adapted to prevent the I .passage of. fluid between said piston and the interior wallsof cylindrical housingmember H6. Mechanically connected to the. upper side I25 of pistonIZS is flexible piston rod I26. Also affixed to the. upper end I25.of.piston I23 is longitudinally-split tubular sealing member I31, tubular sealing. member. I31 being arrangedcoaxially with flexiblepiston rod I26 and circumscribing that portion of said rod positioned within cylindrical chamber Il8 and'sealing member I22. Flexible piston rod I26 passes over the top of sheave H4, thefree end of saidrod being attached to load engaging.- member I28. longitudinally-split tubular sealing member I 21 separates from flexible piston rod I26 on'emerging from sealing member I22 and passes over the top of guide wheel III) and onto reel I I I.

' Hydraulic cylinder housing member I I 6, sheave "I I 4, and guide wheel I ID are so arranged with respect-to each other that periphery I30 of sheave H4 and periphery 'I3I of guide wheel I I'IJ' are substantially tangential to the longitudinal'axis "of hydraulic 'cylind'er housing -member II 6. This "arrangement 'isnecessary so that flexible piston rod I2Bamayreadily pass over-the top of sheave "Il l while longitudinally-split tubular sealing member I3I imayiproperly separate from-piston rod I26 to pass LOVBI the top of guide wheel I Ill and onto lreel II'I.

Sincethe operation of each of the individual hydraulic cylinderrunits. shown in Figs.:6 and'7 isnidenticarwith thecoperation of the hydraulic .icylinder iunitshown inw-Fig. i its =operationwi1l not again be described in=:detail.;. Itwill be suffici'ent tov state::thatj all of itherhydraulic; cylinder,

units smart. bezsimultaneouslyxsupplied.: with.by- .draulia fluid. to actuate air of. ithem, simultaneously; orittmay be.-des.irable in some instancesto supplyzhydraulic. fluid .tolessxthan all. Izirvthis lastem'entione'd instanceathev units not-:actually being supplied with hydraulic fluid will go through their. normal cycle; but-"without accomplishing any useful work-.1 Of'course', itlwill be understood that one or more .or-the hydraulic cylinder. units may be takenout of seryicez'whilethe. remainder are required to perform the: requiredhoi'sting service by the simple expedient of disconnecting flexible piston. rod: I26'-fromaload engaging member I28.

In the description of. Figs. 1 to '7 hereinbeiore given, the sealing member employedifor-provid inga seal :between :flexible piston rod 36 and :the upper end 2-! of. hydraulic cylinder :housing '20 has'been designated by numeral 31; andv has: been described as a longitudinally split, 4 resilient; normally tubular. sealing-.member. I-twill be'understood, however,: that the resilient sealing- :mem b'er adapted topass through :port 28 in the upper end 21- of cylindrical housing member 20=-need not necessarily be normally tubular in formv but may normally b'e -ribbon-like inform as shown in Fig. 8. In Fig. 8 the sealing member 31' adapted to move-longitudinally through port 28 defined in'the upper: end zlofyhydraulic cylinder housing ZU in'OOO DGIatlOIIWith flexible piston rod 36 to provide a fiuid-tight' seal betweenflex.- ible piston ro'd iit and 'upper end- "21 normally possesses a fiat ribbon-like configurationand only assumes a tubular configuration whenitcircumscribes flexible piston rod 36v as the said rod passes through port 28; Resilient sealing member3'l is of such a width that as it passes throughi port 28 in cooperation with flexible piston rod"36,.it arranges itself coaxially around piston rod 36, the outer edges I5Il and IEO meetingQas at 2I5I, to completely circumscribe flexible piston rod 36 without any substantial gap-between edges and I 50 and without 'any' substantialoverlapping of 'said edges. Inasmuch as resilientsealing member'3'I' normally possesses aribbon-like configuration,. that portion of member '31 not actually confined within. port .28 around flexible piston rod '36 will normally possess th-isribbon-like configuration as shown-clearly inFig. 8;- Resilient sealing member 3lawill ordinarily consist of natural or synthetic rubberbut may suitably be of i any resilient material "normally having a fiat ribbon-like configuration but'whichis capable .of assuming 'a' tubular configuration whemapassed through a restricted opening, as for example when passed throughport 28.; Itwillfurther be. understood, of. course, that. resilient sealingmember 3'I-may be usedin. any of. the embodiments'or modifications shown in Figs. 1 to 7, inclusive-in place of the longitudinally split, resilient, normally tubular sealing member 31.

What I wish to claimj as .newand usefuland-zto secure by Letters Patent is: 1

1. A hydraulic hoisting device-.comprising-iin combination, a housing having walls .definingza chamber .and a port communicating with-said chamber, the axis of said port being substantially coincident with thealongitudinal axis of.;'-said chamber, .said chamber beingfiuidly connectible with a source of fluid under. pressure; alpiston slidably "arranged in; said :chamberwforilongitudinal movement therein .in fluid-tight .relationw'ith .thewalls. .iorming said chamber, a. rotatable v sheavemounted in rspacedrelation :fromvsai'd housing, the outer periphery of :said shearetbem'g from said housing for receiving in the form of an elongated strip the resilient sealing member when said piston moves toward the piston rod end of said chamber and for payin 1f Said resilient sealing member when said piston is moving away from the piston rod end of said chamber.

2. A hydraulic hoisting. device comprising, in combination, at least one housing havin walls defining at least one chamber and a port communicating with said at least one chamber, the axis of said port being substantially coincident with the longitudinal axis of said at least one chamber, the said at least one chamber being fluidly connectible with a source of fluid under pressure, a piston slidably arranged in said at least one chamber for longitudinal movement therein in fluid-tight relation with the walls forming said at least one chamber, a rotatable sheave for each said at least one chamber mounted in spaced relation from said housing, the outer periphery of said sheave being substantially tangential to the longitudinal axis of said chamber, a flexible piston rod aflixed at one end to said piston and extending through said port and over said sheave, a resilient sealing member adapted to move longitudinally through said port in cooperation with said flexible piston rod to provide a fluid-tight seal between said flexible piston rod and the walls of said housing defining said port, and a reel mounted in spaced relation from said housing for receiving in the form of an elongated strip the resilient sealing member when said piston moves toward the piston rod end of said chamber and for paying off said resilient sealing member when said piston is moving away from the piston rod end of said chamber.

3. A hydraulic hoisting device comprising, in combination, a housing having walls defining a chamber and a port communicating with said chamber, said chamber being fluidly connectible with a source of fluid under pressure, a piston slidably arranged in said chamber for longitudinal movementtherein in fluid-tight relation with the housing walls forming said chamber, a flexi- .ble piston rod afiixed at one end to said piston and extending through said port, the other end of said rod being adapted to engage with a load for hoisting said load, a longitudinally-split, resilient, normally tubular sealing member arranged coaxially with that portion of the flexible piston rod positioned within said chamber and said port and adapted to provide a fluid-tight seal between said flexible piston rod and the walls of said housing defining said port, and a reel mounted in spaced relation from said housing for receiving in the form of an elongated strip said longitudinally split, resilient, normally tubular sealing member when said piston moves toward the piston rod end of said chamber and for paying off said sealing member when said piston is moving away from the piston rod end of said chamber.

4. A hydraulic hoisting device comprising, in combination, at least one housing having walls defining at least one chamber and a port communicating with said at least one chamber, said at least one chamber being fluidly connectible with a source of fluid under pressure, a piston slidably arranged in said at least one chamberfor longitudinal movement therein in fluid-tight relation with the housing walls forming said chamber, a flexible piston rod aflixed at one end to said piston and extending through said port, the other end of said rod being adapted to engage with a load for hoisting said load, a longitudinally-split, resilient, normally tubular sealing member arranged coaxially with that portion of the flexible piston rod positioned within said at least one chamber and said port and adapted to provide a fluid-tight seal between said flexible piston rod and the Walls of said housing defining said port, and a reel mounted in spaced relation from said housing for receiving in the form of an elongated strip the longitudinally split, resilient, normally tubular sealing member when said piston move toward the piston rod end of said chamber and for paying off said sealing member when said piston is moving away from the piston rod end of said chamber.

ALBERT L. STONE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,094,124 Huffman Sept. 28, 1937 2,253,069 Eckel et al Aug. 19, 1941