US 2700531 A
Description (OCR text may contain errors)
Jan. 25, 1955 J. C, PATTERSON, 1R 2,700,531
AUTOMATIC TENSION 0R SLACK LINE TAKE-UP FOR LIFEBOAT WINCHES AND THE LIKE Filed D60. 12, 1952 I' l. lgl' j Z Si INVENTOR ATTORNEYS AUTOMATIC TENSION OR SLACK LINE TAKE-UP FOR LIFEBOAT WINCHES AND THE LIKE Joseph C. Patterson, Jr., Alexandria, Va.
Application December 12, 1952, Serial No. 325,735
7 Claims. (Cl. 254-187) This invention relates to power transmissions and more particularly to a mechanism for transmitting torque in hoist equipment.
In hoisting and lowering boats from a ship the problem of slack cable is presented due to the fact that the waves can and do overhaul and recede from the boat, thereby varying the proportion of the load borne by the cable and often bringing about marked variations in the load borne at a given instant by separate bow and stern cables. Slack cable in hoisting or lowering life boats with personnel aboard is, of course, very dangerous since, when a wave recedes under slack cable conditions, acute angular disposition of the boat may result. Acute shocks also lcaxccur as the slack cable is taken up by the descending oat.
The foregoing problem has long been recognized and many types of automatic cable tensioning devices have been designed in order to solve it. However, their mechanisms were complicated and involved auxiliary motors and devices. Consequently they were very costly to build. On the other hand, less costly devices have proven to be unreliable and hence unsafe.
It is, therefore, an object of this invention to provide an automatic cable tensioning or slack line take-up which is safe and reliable in use and at the same time is far less costly than the more satisfactory prior art devices. y
Other objects and advantages of this invention will be apparent from the following detailed description of a preferred embodiment thereof in conjunction with the annexed drawings, wherein:
Figure 1 is a general assembly view, largely in vertical section, showing the coacting relation of the various parts making up one half of the transmission between the power and the load; and
Fig. 2 is a fragmentary view in section taken along the line 2-2 of Figure 1.
Referring now to the drawings in greater detail, the assembly is comprised of a cable drum 10 to which one end of a hoist cable 11 is attached. The cable drum may be helically grooved on its external surface to accommodate cable wound thereon and it is assumed that cable guiding means and a drum brake may be associated with the drum 10 in accordance with prior art practice.
The drum 10 is keyed to a driving shaft 12 and to that shaft there is also keyed a driving gear 13. T'he shaft 12 is mounted in suitable bearings diagrammatically indicated at 14 and 15.
Meshing with the gear 13 is a pinion 16 which forms apart of the transmission of the present invention. The
p1n1on 16 1s connected by circumferentially arranged bolts or studs 17 to a housing 18 constituting one side l The other or end of a constant torque spring motor. side or end of the spring motor is keyed at 19 (see Figure 2) to a shaft 20 to which power is applied. The shaft 20 has keyed thereto a gear 21 which meshes with a pinion 22 which in turn is keyed to a driving shaft 23 which is connected to a power source not shown such as an electric motor.
Referring now in greater detail to Figure 2 and to the parts of Figure 1 lying immediately to the left of the pinion 16, it will be observed that the housing 18 is mounted for rotation about the shaft 20 by means of a bearing 24 at one end and the bearing 25 of the pinion 16 at the other. The housing 18 denes, as an integral part, a clutch face 26 coaxial with the shaft 20 and, within the housing 18 to the left of the clutch face 26 there is located a ball bearing nut 27, in threaded engage- United States Patent() 2,700,531 Patentedv Jan. 25, 195.5
ment with the shaft 20. The nut 27 has on its right side, as viewed in Figure 1, a clutch face registerable with the clutch face 26. Radial pins 28 extend from the nut and pass through longitudinally extending slots 29 in the housing 18. By this arrangement the nut 27 is permanently locked against rotation relative to the housing 18 although it is free to move longitudinally on the shaft 20 as a result of the screw action with that shaft. It is evident that such action will permit the clutch to be either engaged or disengaged. The parts 30 and 31 at opposite ends of the shaft 20 are merely bearings for the shaftvwhich may be made according to the prior art and hence are diagrammatically shown.
Upon reference to Figure 2 it can be seen that the spring motor is comprised of a central spindle 32 keyed to the shaft 20 at 19, and eight circumferentially spaced spindles 33 mounted in the housing 18 and extend axially thereof. Around each of the spindles 33 there is wound a prestressed coil spring, one end of which is anchored to the spindle 33 and the other end of which is anchored to the spindle 32. It can be seen, therefore, that relative rotation between the shaft 20 and the housing 18 will cause the springs to be wound back and forth between their spindles 33 and the single spindle 32. This type of device is known as a Negator motor. It has been developed by the Negator Division of the Hunter Spring Company, of Lansdale, Pennsylvania, and is fully described in an article in Machine Design for llanuary, 1951. The essence of this type of spring motor is that the torque transmitting properties between the central spindle, such as 32 here shown, and the outer spindles, such as 33 here shown, are constant irrespective of the magnitude of relative angular displacement between the shaft 20 and the housing 18. The springs themselves are so prestressed and preshaped that the torque exerted by the constant length X depicted in Figure 2 is constant irrespective of the amount of spring wound on the central spindle or one of the outer spindles. The reason for using a number of springs instead of one is to increase the over-all torque transmitting properties of the motor.
With the explanation, it is possible to describe the function of the hoist apparatus as a Whole in such an operation as lifting a boat from the water onto a ship. In that case let it be assumed that the cable is connected to a boat but is not under load. Let it likewise be assumed that the water is still so that there is no relative movement between the boat and ship due to wave action. Under such circumstances, shaft 23 is driven in a hoist direction as indicated by the arrows in Figure l. This causes the shaft 20 to turn in a counter-clockwise direction as viewed in Figure 2. Since the shaft 20 turns and since there is no load on the cable, the torque of shaft 20 is transmitted through the various springs to the spindles 33, from them to ythe housing 18 and from the housing 18 to the pinion 16 and from it to the gear 13, the shaft 12 and the drum 10. As long as there is no load on the cable the nut 27 will not move because the housing 18 will turn with the shaft 20. As soon as the load is taken by the cable, however, the springs of the spring motor 18 will no longer be able to transmit sufficient torque. The result will be that the housing 18 will be held against rotation by the load while the shaft 20 will continue to turn. This Will result in winding the springs onto the spindle 32 and, because housing 18 is immobilized, will also result in movement of the nut 27 to the right of Figure 1 to a clutch engaging position. As soon as the clutch is engaged, the load will be moved for the clutch is so designed that it can transmit all of the torque necessary to lift the design load of the equipment.
Assume now that the load is moving upwardly and is momentarily overhauled by a wave. If that happens there is a tendency for the load to be reduced sharply with a resulting tendency to produce slack cable. On the other hand, the spring motor being fully wound, instantly accelerates the pinion 16 beyond the R. P. M. at which it is driven through the clutch 26-27 and takes out the slack, at the same time disengaging the nut 27 and so disengaging the clutch. This allows the boat to go down again as the wave recedes and as soon tzasihe,loadhasfagainfewound the motor and re-engaged the clutch, hoisting .recommences vThe value of the foregoing cycle can perhaps best be appreciated if one imagines a typical use of the apparatursof. Fig-ure 1 in-whichthe apparatus of Eigure, l vis duplicatedwith one-`off the' drums connected ..to the` bow ,.c'ablefof boat.and"the other 'connected to a stern cable. f If awavelliftsthe bow.. tthe,' slack is immdiatelytaken out ofltthe cable as; justfdesciibed and,` ybecausetthe .'clutch is disengagedjithe angular portion tofthel keel V'of :the' boat. will never change exceptvwithin srrialli'lir'nits. Il -Infviewfof the. fact` thatthe running in and out of the-nut 27. 1night.under some`circlunstances occur veryrapidly, .ring' 34' is provided,connectingthe outer. ends oftlhe it 21nd,: 4lwithin the ,groove there is'. located.l an ar m35 'pivoted at' 36 and connected ,at'37 to a-dashpot' "38.".The sole .function of the dashpot .3S-istoipreventexcessively rapid.: clutch. ,engagement with resulting shocks to, the
f.' Sinceil the whole assemblyis. encased in. a Ycasingf39, I: shown. in broken lines in Figure 4l, andjsince' the vassembly operate's in an oil bath withinsaid.casing, the dash A. .potwderivesl its v oper'ating' uid :frorn the lubricants .f Iwith- '..inLthe .-.casing' 239.
WWhilethe.foregoing invention hasv been described with `respectto but a single unit appliedto but a'single cable .`;drum',.l it isto be )understood thatinv hoisting a boattwo ,units schas are fshown' in"EigL1re l are used, one `of them for each. line tto'the boat, i.- e., oneto a bowline and one Ato a .sternline 'j Both may andrareordinarily .i drivenfrorn asingle shaftsuch as 23.
.While`. from altheoretic'al, point .of View. anordinary nut will.movetashdescribed. onL the" threaded `poition 'of1 `Lthe.u shaft 20, to preventjarnmingj it: ishighlyvdesi-rable .to ..use. al .balll bearingnutand. screw arrangement [ofwthe type developed by, Saginaw"SteeringGear'Divisiong'lGenerali Motors Corporation,l Saginaw, Michigan, and de- ;sc'rib.`ed` in te'xt'v .book Mc`hine`DesignT' FirstEdition internationalTextbooK`Co.; Scranton; Pa.
'lWhatis claimed is:
l.' A power transmission particularly .suited to hoist L apparatus comprising a.'. ,dri.ving sh'aft, a rotatable part to which load is applied; a constant torquespring motor interconnecting V.said shaft .andi part, a normally. l open clutch. 'also interconnecting said shaft. and. part, .,said ,motor .being connectedto '.s'aid' clutch. :to Tcause. said vpart Irto move theclu'tch in an .engaging direction in response ..to-a..powe`rload torque Zdiferential. greaterjthan the torque transmitting, capacity of said motor.
2.'.A power..transmission.. as. claimedinllclairrr 1'fur L ther .comprising meansacting .to' dampI the engagernent of said clutch.
3. A .powentransmi'ssion particularlusuited to`.h0ist vapparatus. comprising.v a driving shaft, a .rotatable part .to which load is applied, a constant torquezspringrnotor, a clutch. having .normallytldisengag'ed clutchinglelements, .onels'ide 'of saidmotorand Aone`ele1nent. of saidlclutch beingiixedlfor Arotation .with said part,`..theother.;side `of s'a`id .motor .being Xedto .saidl shaft, .the Lotherl element lof.. .said j clutch: .being ,inf .threaded-engagement with said shaftfor axial movement therealong-, and means restrain- Lingv s'aid other. Aelement of. saidA I clutchv .against rotation .relative to said part. whereby when the power-.load torque -differential exceedsthe constant torque which the spring motor.. .can transrnit the thre`ad`ed other.- element Sofi. the ,.clutch and .saidshaft relatively rotate tofmove the' clutch to. closed position while energy.. is stor`ed,.in, the spring .motor Yto .t idisengage the'. clutch: when ..theapowerfload 4 torque differential recedes to a value below the vcapacity of the spring motor.
4. power transmission particularly suited to hoist apparatus comprising a shaft to which power is applied 9 a coaxial part to which load is applied, a spring motor capable of exerting a substantially constant torque between its ends regardless of the degree to which it is wound, a clutch having@ normally disengaged clutching elements, one end of said motor and one element of "10 Ysaidfclutch "being- -tixed l to said` part for r rotation .`--therewitlrfaboutsaid'- shaftglthe-other end of said-:motor being keyed to. said shaft, the. other element of said clutch being threaded 'onto usaid shaft for a'XialV movement .therealongnand :being gxed-y Y against ,rotation relative to fl5 said part, whereby when the load on said part exceeds the torque transmitting capability Tof .said motor said clutch is engaged by the relative rotation between said other clutch element and said shaft while energy is stored in the spring motor.
.5.' A, power transmission,v particularly suitfedztojhoist apparatusv comprising a' driving sh'aft,. a rotatable .part Ato which.. load is ,applied, means exerting' af constant .torqueirrespective ofthe magnitude Lof relative angular i ,".dis'placement interconnecting said'shiaft and part, anor- :ma lly `open clutch also interconnectingv v said-shaftand T part, one element of said iclutch beingithreadedgnto said shaftlthroughi ball bearings for axial movement f lalongif thejj shaft, and 4mea-ns restraining. saidA element p ..againstgzmovement relative to sa'id p art whereby when "-the1 load. on Said vpart exceedsthej` torque transmitting capabilities 'of said torque exertingmeansgthe partand .I slaft relatively rotate 4and cause saidjelement "of said clutch to move toengaging position.
6. A power transmission,particularlyrsuited toiahoist .apparatns comprising a driving .shaft, a'rotatable partto Whichload is vapplied, a constant .torque springmQtQr,
.l alclutch, having normally disengaged. clutching elements, one. side 1of ..said ,motor.,and one element of said clutch .beingxed for rotation with said. `part, v the other side 40 of said motor beinglxed t0.. saidlshaftgf the otherele- ...mentof saidtclutch beinginb'all- Ibearing thread'edengagement With .said shaft for axial movement; therealong,
' .me.ansrestraining. said. other lelementnf isaidnelu'tch g againstrotation relativetosaid .partand damping means "40.- acting-through lsaidt restraining means. to, darnp theshock l 'of clu t ch engagement.
.7.' In hoist. apparatus.; including a c ablej drum, agpower supply, a shaftdriven byl the powersupply, a pai-tcof.aXial,to said shaft, gearing vconnecting said part to ,sa'id @Qldrurn'u inydrivingrelation, aspring motor, capable. nf exerting atsubstantially, constant torque between; its .ends regardless of the degree to which it is W011nd; sa`id, spring ...motor .comprising arhousinghaving a plurality oficircumferentally spaced spindles' thereon, a central ,spindle '5D on saidv :shaftand prestressed, springsinterconnecting said housingrspindles; and the. spindle on `saidlshaft;said. housing being connected to ,saidtpart andfhaving an.- integral ,lclutcl'lacejthereon coaxially surroundingsaid ;,shaft;f, a L `ball bearing nutthreadedly v mounted-on saidfshaftfor 601. axial. .movement1-therealong and having a 1.clu tch.fface flthereon'ior engaging, withgthe jclutch face fof said ,hous- Ling; .longitudinal Aslots. in said .housing; tand ,.radiallipins extending fromgasa'id nut. through said' slots to restrain the:v nut `aidhorlsing againstrelativerotation.
References, Cited inthe file jof. this patent UNITED STHIESy PATENTS