Friday, January 28, 2011

Planetary gear winch comprising selectively operable freewheel arrangement

A planetary gear winch broadly comprises a prime mover coupled to a winch drum through a planetary gear reduction drive train. The planetary gear reduction drive train comprises at least two serial, coacting and coaxially oriented planetary gearreduction stages, each stage comprising a plurality of planet gears journalled in a carrier therefor, said planet gears surrounding and being in engagement with a central sun gear. Each planetary gear reduction stage also comprises a ring gearsurrounding and being in engagement with said planet gears, said ring gear acting as a fixed reaction member. While separate and distinct ring gears may be utilized for each planetary gear reduction stage it is conventional to employ a single ring gearof sufficient length to house and serve the entire complement of planetary gear reduction stages, thereby simplify the construction and/or to render it more economic. Rotary power is delivered into each planetary gear reduction stage through thecentrally located sun gear thereof. In the case of the first reduction stage, the sun gear is driven by the prime mover. In the case of later stages, the sun gears are each driven by the output of the previous planetary gear reduction stage. Theplanet gears of each reduction stage are carried in a planet carrier generally comprising a plate member having a plurality of axle stubs extending perpendicularly from one surface thereof and to which axle stubs the planet gears are journalled. Conventionally, the planet carrier for each of the planetary gear reduction stages preceding the final reduction stage also comprises a centrally located sun gear rigidly affixed thereto and extending downstream therefrom, said sun gear acting, aspreviously mentioned, as the power input member for the suceeding planetary gear reduction stage.
The power output of the final planetary ger reduction stage is coaxially coupled to the winch drum in any suitable manner. For example, the planet carrier of the final planetary gear reduction stage and the bore of the winch drum element caneach define a keyway or splined recess, which recesses receive a common suitably conformed key or spline coupling member. As another example, the upstream flange of the winch drum can serve as the planet carrier for the final planetary gear reductionstage, thereby to simplify the construction of said stage and to provide a direct coupling of the output thereof to the winch drum. In this last-mentioned arrangement, axle stubs extend upstream from the upstream winch drum flange and the planet gearsof the final reduction stage are journalled thereto. Thus, said planet gears are caused to act as the power output members of the final planetary gear reduction stage driving the winch drum through said axle stubs. Another example of suitable coaxialcoupling of a final planetary gear reduction stage to a winch drum is disclosed in U.S. patent application Ser. No. 197,654 Muessel et al., filed Oct. 16, 1980, entitled Rotary Power Coupling and Planetary Gear Winch Comprising Same, now U.S. Pat. No. 4,392,635, July 12, 1983. Therein there is disclosed a flexible coupling arrangement employing an intermediate plateform coupling member whereby the planetary gear train is effectively isolated from racking loads imposed on the winch drum duringoperations.

It is in the nature of a planetary gear reduction train that the forces required to drive the train in reverse, when applied rearwardly through the final reduction stage of the gear train, are relatively great. This inherent characteristic ofplanetary gear reduction trains is employed to advantage in winch applications in that, when the prime mover is inactivated, the planetary gear train acts to produce a substantial braking of the winch drum against reverse rotation thereof under lineload. Where the load capacity of the winch is substancial it is also conventional to provide various supplemental mechanical and/or electrical braking systems to mitigate against unintentional reverse rotation of the winch drum upon shutdown of theprime mover. Generally speaking, such supplemental braking systems are located upstream from the planetary gear train thereby to ensure that full use is made of the inherent braking effects of the planetary gear reduction train and to minimize the bulkand complexity required of the supplemental braking system.

In many planetary gear winch applications it is highly desirable that the winch be provided with means by which the winch drum, in the unloaded condition, can be temporarily disconnected from the drive train therefor, thereby to be renderedfreely rotatable and to allow rapid unwinding of the line therefrom. This is a particularly desirable feature, for instance, in connection with off-the-road vehicle and boat trailer winch applications wherein a lone operator may be called upon to deploythe line from the winch drum, affix it to a fixed object or to a load and place the winch in operation. In accordance with the present invention, a winch construction comprising such selectively operable freewheel arrangement is provided.

The winch of the invention comprises a planetary gear reduction train comprising at least two planetary gear reduction stages including a final planetary gear reduction stage and a penultimate planetary gear reduction stage. The final planetarygear reduction stage is coaxially coupled to a winch drum having a central passageway through the drum element thereof. A selector shaft is received in a freely slidable manner through said passageway. To the upstream interior end of said selectorshaft there is journalled the sun gear driving the final planetary gear reduction stage. The planet carrier of the penultimate planetary gear reduction stage comprises a centrally located internal gear adapted to engage the upstream portion of saidfinal stage sun gear in driving relationship therewith. The selector shaft passes through the passageway and terminates exteriorly of the winch drum element. A two-position manually operable stop means is provided in association with said selectorshaft to position the upstream portion of the sun gear journalled to the interior end thereof in either a first "engaged" position or a second "disengaged" position with respect to the internal gear of the penultimate reduction stage planet carrier. Biasing means are provided to continuously urge said selector shaft and the sun gear journalled thereto to stroke towards the first "engaged" position.

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