Abstract:
A utility winch having a single planet gear assembly that commonly engages adjacent ring gears, one ring gear fixed and the other rotatable. The planet gears of the planet assembly have inner and outer portions that rotate together and have different diameters and different numbers of teeth, one ring gear engaged with an inner portion and a second ring gear engaged with an outer portion of the planet gears. Said ring gears matched to the respective planet gear portions and having different numbers of teeth and different diameters as required to achieve involute engagement of the ring gears and planet gears whereby the rotatable gear is caused to rotate at a substantially reduced rate of rotation. Said rotatable ring gear is fixed to the winch reel for reduced rotation of the reel.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates to a low cost utility winch wherein large ratios are enabled by the winch, e.g., for pulling a 2,000 pound weight, but having fewer parts than is typical for such winches.  
         BACKGROUND OF THE INVENTION  
         [0002]    A typical heavy duty winch powered by a vehicle battery and for pulling a heavy weight, e.g., to free the vehicle from a stuck condition, includes a series of planetary gear arrangements, e.g., a series of three planetary gear arrangements that reduce the rpms of a motor drive shaft (to thereby increase torque output) on the order of 200 to 1. Each planetary gear arrangement includes a sun gear, a carrier assembly including three planet gears and a ring gear and accordingly in combination, the three planetary gear arrangements collectively require a large number of parts that contribute substantially to the cost of producing the winch.  
           [0003]    A less expensive winch to be used for utility applications, i.e., having infrequent use and requiring a lesser pull power, e.g., 2,000 pounds, was developed prior to the present invention to produce the desired gear reduction (on the order of 200 to 1) but with far fewer parts. Such was accomplished using a single planetary gear arrangement. In this prior device, a sun gear is connected directly to the armature shaft of the motor and the sun gear engages three planet gears. The planet gears engage a first ring gear that is non-rotatable. The planet gears axially extend beyond their engagement with the sun gear and the ring gear. A second rotatable ring gear having the same diameter as the first ring gear is placed into engagement with the extended portions of the planet gears. The teeth of one or both ring gears are modified so that one ring gear has fewer teeth than the other, e.g., 70 teeth v. 71 teeth.  
           [0004]    To accomplish the above modification, at least one of the ring gears have teeth that do not have an involute inter-engagement with the planets as required for optimum performance. However, there is sufficient mating of the teeth to enable sequential engagement between the teeth of the planets and the teeth of both ring gears. Thus, as the planets are forced to rotate by the sun gear and because the first ring gear is fixed, the planet gears move in a circular pattern relative to the axis of the fixed ring gear. The second ring gear can rotate and with each completed circle of the planets about the ring gear axis, the second ring gear rotates the distance of one tooth, i.e., {fraction (1/70)}th of the circle. The rotatable second ring gear is fixedly mounted to the reel of the winch so that similarly the reel rotates {fraction (1/70)}th of a turn for each full circle of the planets about the axis.  
           [0005]    The problem with the above arrangement is that the non-involute or offset meshing of the teeth (between the planets and one of the ring gears) creates undesired noise, loss of efficiency and more rapid wearing of the affected parts. The present invention is also directed to a dual ring gear combination but designed to alleviate the problems of the offset meshing teeth.  
         BRIEF DESCRIPTION OF THE INVENTION  
         [0006]    The preferred embodiment of the present invention also includes a single planetary gear arrangement. A sun gear (connected to the motor&#39;s drive shaft) drives surrounding planet gears (planets) and the planets are in meshed engagement with a first ring gear. The sun gear, planets and first ring gear are cooperatively configured to provide involute gear teeth inter-engagement. A second ring gear is provided with gear teeth greater in number than the first ring gear, e.g., 71 gear teeth for the second ring gear v. 70 gear teeth for the first ring gear. The planets (three of them) are axially extended beyond the first ring gear and the extended portion is configured to have a greater number of teeth than that portion engaged with the first ring gear, e.g., 27 teeth v. 26 teeth for the portion engaged with the first ring gear. The second ring gear having 71 teeth and the planet gear portions having 27 teeth are cooperatively configured to provide involute inter-engagement and in doing so, the rotatable ring gear is slightly larger in diameter than the first ring gear, as is the extended planet portions larger in diameter than the first planet portions. With the arrangement described, the planets will rotate around their own axis 2.69 times in order for the planets to complete a full circle of movement around the first ring gear axis which is held fixed, i.e., 70÷26. The planets complete a full circle around the second or rotatable ring gear in 2.63 revolutions of the planets, i.e., 71÷27. Thus, the rotatable ring gear is rotated in reverse by about 0.06 of a revolution for every complete revolution of the planets about the first ring gear. Thus the rotatable ring gear rotates in reverse the distance of 1.5 teeth which requires 45 revolutions of the planets to produce a single revolution of the second ring gear.  
           [0007]    As a further cost saving feature, the planet gears are rotatably mounted with bearings to provide a desired but limited friction which is overcome by providing a slightly higher powered motor than what would otherwise be required using lower friction bearings. However, the limited resistance to rotation by the planets produces substantial resistance to a force that urges rotation of the second ring gear with the motor inactive (resulting from the high ratio reduction as explained). Thus, the bearing friction produces a highly effective brake and is well within the needs of the weight rating of the utility winches contemplated herein.  
           [0008]    A further improvement is provided in the manner of mounting the second ring gear and reel to the motor and gear housing. To enable the desired fit of the clutch ring to the planets without having to critically form the holding bracket for the reel, the attachment of the bracket to the housing of the motor is a sliding interfit. This enables the bracket to be loosely mounted to the housing by a bolt-nut arrangement. It is then adjusted as necessary to obtain the desired fit between the planets and the second ring gear at which point the bolt is tightened.  
           [0009]    A further problem that was encountered and resolved is the assembly of the planets to the first ring gear, the planets being fixed at their axes relative to each other by a carrier. The planets as mounted are not symmetrical about the carrier axis (also the ring gear and sun gear axis) and the gears have to be rotatively aligned to fit the ring gears and sun gear. This rotative alignment, upon being established, is replicated for assembly by providing an alignment dot or hole on each planet to be aligned with holes in the carrier.  
           [0010]    The above will be more fully appreciated and understood upon reference to the following detailed description having reference therein to the accompanying drawings. 
       
    
    
     DESCRIPTION OF THE DRAWINGS  
       [0011]    [0011]FIG. 1 is an isometric view of a utility winch in accordance with the present invention;  
         [0012]    [0012]FIG. 2 is an exploded isometric view of the winch of FIG. 1;  
         [0013]    [0013]FIG. 3 is a section view of the winch of FIG. 1 showing the components in assembled relation;  
         [0014]    [0014]FIG. 4 is a view as taken on view lines  4 - 4  of FIG. 3; and  
         [0015]    [0015]FIG. 5 ia a sectional view as taken on view lines  5 - 5  of FIG. 3. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0016]    [0016]FIG. 1 illustrates a utility winch contemplated by the present invention which includes a motor  10 , a gear housing  12 , a rotatable reel  14  including a hub  16  and flanges  18  and  20 . The rotatable reel  14  is supported at one end by gears and the gear housing  12  (to be explained hereafter) and at the other end by a bracket  22  attached to the gear and motor housing  12  at end  24 .  
         [0017]    With reference also to FIGS. 2, 3 and  5 , motor  10  drives an armature or drive shaft  26  which directly drives a sun gear  28 . FIG. 5 illustrates the sun gear  28  in engagement with three planet gears, each having an inboard planet portion  30  and an outboard extension planet portion  38 . Planet portions  30  and planet extensions  38  are strategically assembled to carrier plate  29  via mounting pins  27 . Surrounding the planet gear portions  30  and in meshed engagement therewith is a ring gear  32 . The ring gear  32  is rotatable within gear housing  12  as provided by bearing ring  51  and is locked against rotation by spring biased lock member  34  (biased by spring  41 ) and which is unlatched by pin withdrawal tab  35 . In a winching operation, i.e., winding of a winch cable  25  onto the hub  16 , the ring gear  32  is locked against the housing  12  by the pivoting of tab  35  to release the spring urged pin  34 . The pin head is accordingly urged toward the ring gear  32  and becomes seated in a notch  37 .  
         [0018]    As best seen in FIG. 5, with the ring gear  32  non-rotatable, the sun gear  28  (e.g., having 18 teeth) is rotated at high rpms. Sun gear  28  engages planet gear portions  30 , e.g., having 26 teeth each, to provide one complete rotation of each of the planets for about every 1 ½ revolutions of the sun gear. The planet gear portions  30  are in engagement with ring gear  32  (e.g., having 70 teeth) and because the ring gear  32  is secured to the housing  12  (by lock pin  34 ), rotation of the planet portions  30  causes the planets to walk around the gear teeth  33  of ring gear  32 . As illustrated, sun gear  28  is driven clockwise which rotates the planets counter clockwise, causing the planets to “walk” around the inner periphery of the ring gear  32  clockwise as indicated by arrows  36 .  
         [0019]    Each planet rotates 2.69 times to cause the planets to make one full circle around the axis  39  of the ring gear and sun gear. This is determined by dividing the number of teeth on the fixed ring gear ( 70 ) by the number of teeth on the planet ( 26 ).  
         [0020]    It will be understood that the relationship of the sun gear, planets and ring gear are configured through calculation (known to the industry) to enable the teeth to be formed involute, i.e., so that the gear teeth roll into and out of engagement with minimal or no relative sliding there between. This is important to achieve efficient and quiet operation and to minimize wear on the teeth.  
         [0021]    Referring now to FIGS. 3 and 4, the planets are configured to each have an extended portion  38 , i.e., extended axially of the sun gear  28  and ring gear  32 . The extended portions  38  can be machined separately and secured to the planet portion  30  by a locking fit as shown or the planet portions can be machined from a single piece. Regardless, the extended portion  38  is fixed to the planet portion  30  and travels with the planet portion  30  both in rotation around axis  40  of each planet and in circling about the axis  39  of the ring gears.  
         [0022]    The extended planet portions  38  are in engagement with a second rotatable ring gear  42  which rotates independent of ring gear  32  and is formed integral or fixed to flange  20  of the reel  14 . Thus, rotation of the ring gear  42  produces rotation of the reel  14 .  
         [0023]    It will be observed from FIG. 3 that the inner diameter of ring gear  42  (defined by the teeth  43 ) is slightly larger in diameter than the inner diameter of ring gear  32  (defined by teeth  33 ) to enable the greater number of teeth, e.g., 71 teeth in ring gear 42 v. 70 teeth in ring gear  32 . The planet extensions  38  are similarly larger in external diameter (defined by teeth  31 ). The planet extensions  38  are provided with 27 teeth v. 26 teeth for the planet portions  30 . Again, the selection of teeth are formulated to provide involute engagement between planet extensions  38  and ring gear  42 .  
         [0024]    As previously explained, the planets  30  rotate 2.6 times to produce one complete cycle of the planets around the ring gear  32 . The planet extensions  38  rotate 2.63 times to complete a full circle about the axis of ring gear  42 . Thus, the planet extensions  38  will complete the circle around ring gear  42  before the planets  30  complete the circle around ring gear  32 . Because the planet portions  30  and planet extensions  38  are integral (securely fixed together), the ring gear  42  is caused to rotate in reverse, i.e., counter to the circling of the planets. This reverse rotation is in the order of about one and one-half teeth per cycle of the planets about ring gear  32  and thus the reverse rotation of ring gear  42  and reel  14  is in the order of one revolution for every 45 revolutions of the circling planets. The sun gear rotates about five times for every revolution of the planets and thus about 225 times (in practice 222 times) for every revolution of the second ring gear.  
         [0025]    Reference is now made to FIG. 2 with emphasis on the pins  27  that mount the planets to the carrier plates  29 . These pins provide the bearing surfaces about which the planets rotate. The planets rotate 2.69 times for each cycling of the planets about the sun gear or ring gear axis and thus about 121 times for each revolution of the second or rotatable ring gear. A pull of 2,000 pounds on cable  25  attempting to unwind the cable from the reel  14  will be met with overmatching resistance with but a small resistance to rotation applied by the bearings to the planets. Thus, further braking is unnecessary and the less expensive, less efficient bearing pins  27  provide the required braking function when the motor  10  is inoperative. Whereas the ratio of drive to driven power as between the drive shaft and planets is reversed, a motor with but slightly greater drive power will provide the same drive power as would be required with a state of the art bearing support for the planets.  
         [0026]    Reference is now made to FIGS. 2 and 3 with particular reference to the bracket  22 . The bracket is L-shaped with a long support leg that extends from the gear housing  12  to the end of the reel. A vertical leg of the bracket carries a bearing ring  50  which rotatably supports the rim  18  of reel  14 . Because ring gear  42  is part of rim  20  of reel  14 , the reel needs to be properly seated with the ring gear of rim  20  secured in position relative to the planet extensions  38 .  
         [0027]    To achieve the desired seating of ring gear  42 , the L-shaped bracket  22  must be properly fitted to the housing  12  so as to correctly accommodate the length of the reel. To avoid the necessity of precision manufacture of the bracket, the bolt hole  52  in housing  12  (see FIG. 3) is elongated to provide extra clearance for a bolt  54 . A nut  56  is provided at the inner side of the housing and bolt  54  is inserted through a fitted hole in the bracket end  24  and through oversized hole  52  and into loose engagement with nut  56 . With the ring gear  42  properly seated, the bolt is tightened to secure the components (reel and planets) in the desired relationship. The sliding fit described allows for desired manufacturing tolerances for bracket  22  and contributes to the desired cost reduction of the winch.  
         [0028]    A problem that is encountered in assembly of the planets and carriers to the ring gear and sun gear is that the planets need to be rotatably aligned to enable assembly onto the ring gear and sun gear. This relationship is determined and the planets and carrier are appropriately marked as shown in FIG. 2. The carrier plates  29  are provided with alignment holes  44  and notch  45 . Holes or other markings  46  on gears  38  are rotated into alignment with holes  44  and notch  45  to establish the required alignment for assembly of the planet and carrier to the sun and ring gears.  
         [0029]    The above disclosure is but an example of numerous embodiments that will become obvious to those skilled in the art. Terms as used to define the invention in the claims appended hereto are intended to have their common meaning encompassing a desired broad scope of the invention and are not intended to define merely the disclosed embodiment.