Patent Publication Number: US-6659430-B2

Title: Winch having internal clutch mechanism

Description:
TECHNICAL FIELD OF THE INVENTION 
     The present invention relates generally to power driven winches of the type having internal planetary gears for driving the cable drum. In one embodiment, the invention relates to a winch having an internal friction clutch mechanism for selectively connecting and disconnecting the cable drum to the power input. 
     BACKGROUND OF THE INVENTION 
     Winches using one or more sets of planetary gears to transfer torque from a power input (e.g., winch motor) to the cable drum are well known. Further, it is known to provide an internal clutch mechanism in such winches for selectively connecting and disconnecting the cable drum to the winch motor whereby, for example, the clutch can first be disengaged to allow cable to be unreeled from the drum without operating the motor, and then the clutch can be engaged to allow the motor to power the drum for reeling in the cable against the load. Where it is desirable for the drum clutch mechanism be gradually engaged and disengaged while under load, the clutch mechanism must be of the type known as a friction clutch. 
     Heretofore the use of internal drum friction clutch mechanisms, especially those used in high-capacity winches, for example winches used on earth-moving machines, construction equipment or heavy trucks, has presented certain disadvantages. The reduction gear train of such winches includes multiple stages of planetary gears which take up a considerable amount of space. Typically, the drum friction clutch mechanism is located at a gear stage close to the cable drum where the torque it must transmit is relatively high, and as a result, the clutch mechanism must be physically large (e.g., large diameter) to handle the high torque requirements without failing or wearing prematurely. A first disadvantage of previous designs is that the size of such high-torque friction clutches is sometimes so large that it increases the overall size of the winch, either requiring the diameter of the winch housing to be increased, or requiring the clutch to be located to one side of the cable drum, thereby increasing the overall width of the winch. Obviously, this increased size can make it much more difficult to mount a high capacity winch on existing equipment. A second disadvantage of previous designs is that the large size and/or complexity of the high-torque friction clutches results in higher cost for their components and manufacture, consequently raising the cost of the associated winch. This of course, puts the manufacturer at a competitive disadvantage. 
     A need therefore exists, for a winch having a design which minimizes the size of the internal drum friction clutch to reduce the overall size of the winch. A need further exists, for a high-capacity winch with internal drum friction clutch having a simplified design which reduces the costs of manufacturing the winch. 
     SUMMARY OF THE INVENTION 
     The present invention disclosed and claimed herein comprises, in one aspect thereof, a winch including a drum rotatably mounted on a housing for winding a cable thereupon. A motor is attached to the housing, the motor supplying torque through a motor shaft. A special stage of planetary gears is mounted to the housing for transmitting torque between the motor shaft and the drum. The special stage of planetary gears includes a sun gear for receiving torque, a carrier/clutch unit and an annular ring gear encircling the carrier/clutch unit. The carrier/clutch unit includes a frame rotatably mounted to the housing and having walls defining a cavity therein, at least one circumferentially-spaced planet gear rotatably mounted on the frame for simultaneously engaging the sun gear and the ring gear, a selectively engagable clutch mounted within the cavity of the frame, and an output member which, when the clutch is engaged, can receive useful torque from the frame and, when the clutch is disengaged, cannot receive useful torque from the frame. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a more complete understanding of the present invention and the advantages thereof, reference is now made to the following description taken in conjunction with the accompanying drawings in which: 
     FIG. 1 illustrates a longitudinal cross sectional view through a winch in accordance with one embodiment of the current invention; 
     FIG. 2 illustrates an exploded perspective view of the static brake assembly and the drum friction clutch activation mechanism; 
     FIG. 3 illustrates an enlarged longitudinal cross sectional view through the carrier/clutch assembly of the winch; and 
     FIG. 4 illustrates an exploded perspective view of the carrier/clutch assembly. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to FIG. 1, there is illustrated a hydraulic winch in accordance with one embodiment of the current invention. The winch  100  includes a cylindrical drum  102  around which a cable  104  is wound in a conventional manner. The drum  102  is rotatably supported on a housing  106  by bearing assemblies  108  and  110  located at each end. Seal assemblies  112  and  114  are provided between the housing  106  and the drum  102  to prevent dirt, water or other foreign materials from entering the internal mechanism. 
     Power for the winch  100  is provided by a hydraulic motor  116  mounted to a motor support  117  forming one end of the housing  106 . A motor shaft  118  projects into the housing  106  along a longitudinal axis  120  providing torque to the reduction gear mechanism of the winch. As will be explained in further detail below, the reduction gear mechanism receives torque from the motor shaft  118 , multiplies the torque though gear sets, and delivers the torque to the drum  102  to allow the cable  104  to be reeled onto the drum against a load. 
     In the embodiment shown, the reduction gear mechanism receives torque from the motor shaft  118  at a primary sun gear  122 . The primary sun gear  122  has a longitudinally extending portion that extends along the axis  120  and abuts, but does not directly engage, the end of the motor shaft  118 . External splines  124  on the motor shaft  118  and external splines  126  on the adjoining portion of the primary sun gear  122  are received into opposite ends of an internally splined connecting collar  128 . The connecting collar  128  allows torque to be transmitted between the motor shaft  118  and the primary sun gear  122 , and further connects the reduction gear mechanism to a static brake assembly  130 . 
     The static brake assembly  130  is a safety and control feature of the winch  100  that holds the load when no power is applied to the winch and also remains applied during reel-in of the cable onto the winch drum  102 . The static brake assembly  130  includes an over-running (i.e., one-way) clutch  131  disposed in the annular space between the connecting collar  128  and an encircling multi-disc brake  132 . The over-running clutch  131  is preferably a sprag-type clutch, however, other types of one-way clutches may be used. The multi-disc brake  132  may be of conventional design, and it selectively connects the outer portion  133  of the over-running clutch  131  to the stationary motor support  117 . When the static brake assembly  130  is applied (i.e., by engaging the brake  132 ) the over-running clutch  131  allows the connecting collar  128 , and hence the motor shaft  118  and primary sun gear  122 , to rotate freely in the reel-in direction, but it immediately locks-up (i.e., immobilizes) the collar  128 , motor shaft  118  and primary sun gear  122  if they try to turn in the reel-out direction. When the static brake assembly  130  is released (i.e., by disengaging the brake  132 ), the connecting collar  128 , motor shaft  118  and primary sun gear  122  can rotate in either direction. In use, the static brake assembly  130  typically remains applied during reel-in operation of the winch. The over-riding clutch  131  will rotate freely to haul-in a load and lock up immediately to hold the load, with no “fall back,” when the winching operation is stopped. Similarly, there is no momentary “fall back” as the operator begins to haul-in as the static brake assembly  130  is not released. The static brake assembly  130  is typically released only if it necessary to rotate the motor shaft  118  and primary sun gear  122  in the reel-out direction. 
     Referring now also to FIG. 2, there are illustrated additional details of a static brake assembly  130  in accordance with this embodiment. The static brake assembly  130  is spring applied and hydraulically released, and in this case is disposed within a cavity formed by attaching the motor support  117  to a brake housing  129  (both parts  117  and  129  being portions of the winch housing  106 ). A plurality of springs  134  extend through holes in the end wall of the brake housing  129  and push via spring pucks  135  against a movable pressure plate  136 . The pressure plate  136  pushes via a spacer  137  against one side of the multi-disc brake (denoted collectively  132 ), compressing it against the end wall of the motor support  117 . As best seen in FIG. 2, the multi-disc brake  132  comprises a plurality of externally keyed discs  132   a , which engage the inner surface of the side wall of the motor support  117 , interleaved with a plurality of internally toothed discs  132   b , which engage the outer portion  133  (see FIG. 1) of the over-riding clutch  131 . A back-up ring  138   a  and a seal ring  138   b  are disposed within an annular cavity formed between the outer surface of the side wall of the motor support  117  and the concentric inner surface of the side wall of the brake housing  129 . The parts  138   a ,  138   b  and  138   c  form a piston which bears against the outer rim of the pressure plate  136  on the same side as the spacer  137 . 
     The static brake assembly  130  of this embodiment is “applied” when the discs  132   a  and  132   b  are compressed together between the spring-biased spacer  137  and the end wall of the motor support  117 , thus frictionally locking the outer member  133  of the over-riding clutch  131  to the stationary motor support  117  and preventing its rotation. The static brake assembly  130  is “released” by introducing hydraulic fluid into a cavity  139  (see FIG. 1) through a port  140  in the brake housing  129 . The hydraulic fluid forces the piston made by O-ring  138   c , seal  138   b  and back-up ring  138   a  against the pressure plate  136 , overcoming the bias of the springs  134  and moving the pressure plate  136  and spacer  137  away from the brake discs  132  until their friction no longer provides substantial resistance to rotation of the outer member  133  with respect to the stationary motor support  117 . It will be appreciated that, as its name implies, the static brake assembly  130  is applied and released only when the winch mechanism is stationary. Further, it functions only to prevent rotation of the winch mechanism in the reel-out direction. The static brake assembly  130  does not, and cannot, function as a drum clutch (i.e., allowing the drum  102  to move independently of the motor shaft  118 ) because the motor shaft  118  and the primary sun gear  122  are constantly meshed by the brake&#39;s connecting coupling  128 . 
     As previously indicated, in this embodiment the primary sun gear  122  represents the beginning of the winch reduction gear mechanism. Multiple stages of planetary gears are then used to multiply and transmit the torque received from the motor shaft  118  to the winch drum  102 . In the embodiment shown, the first two reduction gear stages are positioned inside the cylindrical cavity  142  defined by the winch drum  102 . This arrangement makes maximum use of the space inside the winch housing  106  and thus helps to minimize the overall size of the winch. The sun gears for the three reduction stages, namely the primary sun gear  122 , the secondary sun gear  144  and the final sun gear  146 , are all located coaxially along the longitudinal axis  120 . While not required, this coaxial arrangement is often preferred because of the resulting low-profile design. 
     The axially elongated primary sun gear  122  has external teeth  148  formed on its inner end. In a conventional planetary gear arrangement as used in prior art winches, the external teeth  148  of the primary sun gear  122  engage a plurality of circumferentially spaced planet gears mounted on a conventional carrier by means of stub shafts. These planet gears simultaneously engage an encircling ring gear in the known manner. The conventional carrier typically has internal splines or teeth in fixed constant mesh with corresponding splines or teeth on the sun gear of the next reduction stage. In this manner, torque is constantly transmitted between the first and second reduction stages in a conventional winch. In the current invention, however, a special stage of planetary gears is used which does not include a conventional planet carrier. Instead, the special stage includes a carrier/clutch unit  150  which, as further explained herein, serves as both a planetary gear carrier and as a compact friction clutch for engaging and disengaging the winch drum  102  from the motor shaft  118  to allow relative motion therebetween. 
     Referring now also to FIGS. 3 and 4, there is illustrated in further detail the carrier/clutch unit  150  of this embodiment. The carrier/clutch unit  150  includes a cylindrical frame  152  defining an outer periphery  154 , an inner cavity  156  and a longitudinal axis  158 . In the embodiment shown, the longitudinal axis  158  of the carrier/clutch unit  150  is coincident with the longitudinal axis  120  of the winch  100 . The carrier/clutch frame  152  is adapted to receive a plurality of planet gear shafts  160  that are disposed circumferentially around, and oriented parallel to, the longitudinal axis  158 . A planet gear  162  is rotatably mounted on each planet gear shaft  160  by means of a bearing assembly  164  and thrust washers  166  (FIG.  4 ). In the embodiment shown, circumferential slots  167  are formed in the frame  152  to accommodate the planet gears  162 . Each planet gear  162  is sized to extend radially outward past the outer periphery  154  of the frame  152  and radially inward into the central cavity  156  of the housing after installation. As with a conventional planetary gear carrier, the carrier/clutch unit  150  serves as part of a planetary gear stage by simultaneously engaging the planet gears  162  between the primary sun gear  122  on their radially inward sides (denoted by reference numeral  168 ) and an encircling ring gear on their radially outward sides (denoted by reference numeral  170 ). In the embodiment illustrated, the encircling ring gear is provided by internal teeth  172  integrally formed on the inside surface of the winch drum  102  (see FIG.  1 ). Accordingly, when the primary sun gear  122  is rotated, the frame  152  of the carrier/clutch unit  150  rotates in the same direction at a predetermined ratio. 
     Unlike conventional planetary gear carriers, the frame  152  of the carrier/clutch unit  150  has a longitudinally extending wall  174  in which are formed a plurality of longitudinal slots  176 . A clutch (denoted generally by reference numeral  177 ) including a plurality of annular separators  178  interleaved with a plurality of annular friction discs  180  is disposed inside the longitudinal wall  174  within the inner cavity  156 . The separators  178  have a plurality of tabs  182  disposed along their outer periphery which engage the longitudinal slots  176  of the carrier/clutch frame  152 , whereby the separators are rotationally locked to the housing but can move longitudinally. It will be appreciated that while the current embodiment prevents rotation of the separator discs  178  relative to the frame  152  by mating separator tabs  182  into frame slots  176 , other known locking configurations may be employed in alternative embodiments, for example, splines, gear teeth, keys and key-ways, scalloped edges, and the like. An adaptor  184  having a plurality of external splines  186  engages a plurality of teeth  188  formed on the inner annulus of each friction disc  180 , whereby the friction discs are rotationally locked to the adapter, but can move longitudinally. The elongated shaft  144  of the secondary sun gear engages the adaptor  184  by means of internal splines or teeth such that the shaft and adaptor are rotationally locked together and can transmit torque therebetween. Alternatively, the secondary sun gear and the adaptor may be formed as a single integral part. A plurality of annular wave springs  190  (best seen in FIG. 4) dimensioned to fit within the annulus of the separators  178  may be interleaved between the friction discs  180  to urge the friction discs longitudinally away from one another during disengagement of the clutch  177 . The wave springs  190  are preferred, but are not required. An annular pressure plate  192  is fitted into the open end of the carrier/clutch frame  152  and secured with a snap ring  194  to retain the friction discs  180  and separators  178 . The pressure plate  192  is provided with an inset lip  195  which allows limited axial movement of the plate with respect to the snap ring for purposes of engaging and disengaging the clutch  177 . 
     The clutch  177  of the carrier/clutch unit  150  is engaged by applying longitudinal force (i.e., a force directed parallel to the longitudinal axis  120  of the winch) inward against the frame  152  and the pressure plate  192 , thereby urging the friction discs  180  and separators  178  to move longitudinally into increasing frictional contact with one another until the friction is sufficient to allow the desired amount of torque to be transmitted therebetween (and hence between the respectively connected carrier/clutch frame  152  and adaptor  184 ). The clutch  177  is disengaged by reducing the inward longitudinal force on the housing and pressure plate, whereby the frictional contact between the friction discs  180  and separators  178  is reduced to the point that useful torque cannot be transmitted therebetween. Put another way, when the clutch  177  of the carrier/clutch unit  150  is engaged, the carrier/clutch frame  152  and the adaptor  184  (with the secondary sun gear shaft  144 ) rotate together. When the clutch is disengaged, the frame  152  and the adaptor  184  (with the secondary sun gear shaft  144 ) are uncoupled and thus may rotate with respect to one another. 
     Since the carrier/clutch unit  150  is disposed within the central cavity  142  of the cable drum  102 , it is necessary to provide means for applying and releasing longitudinal force to the unit (needed to activate the clutch  177 ) while still allowing the unit to rotate freely. In the embodiment illustrated in FIG. 1, a snap ring  196  is fitted into a groove formed approximately midway along the interior wall of the drum  102 . The snap ring  196  provides longitudinal support for an abutting thrust ring  198 . The thrust ring  198 , in turn, provides longitudinal support for the carrier/clutch unit  150  by pressing laterally against the pressure plate  192  via a bearing assembly  200 . The thrust ring  198  also provides radial support for the bearing assembly  200  with its annular lip  202 . To ensure that the thrust ring  198  does not rotate under the influence of the bearing assembly  200 , the periphery of the thrust ring is preferably provided with external teeth which engage the internal teeth  172  of the drum  102 . Alternately, a key or other known securing mechanism may be provided to prevent rotation of the thrust ring. The opposite end of the carrier/clutch unit  150  is supported by a bearing assembly  203  and a race  204  that bears longitudinally against the frame  152  and surrounds the housing lip  206  (see FIG. 3) to position the unit radially. The opposite side of the race  204 , in turn, is supported by a moveable stepped piston  208  that is slidingly disposed within a cylindrical portion of the brake housing  129 . 
     Longitudinal compressive force on the carrier/clutch frame  152  (i.e., for engaging the clutch  177 ) is provided by springs  134  via the piston  208 , race  204  and bearing assembly  203 . It will be appreciated that some of the springs  134  acting on the drum clutch  177  extend through holes in the brake housing  129  and also act upon the multi-disk brake  132  as previously described, while others of the springs  134  are compressed against the end wall of the brake housing and act only upon the drum clutch. This dual-use design eliminates the need for separate springs just to activate the brake  132 , and may also reduce the overall width of the winch. A spacer  209  may be provided to position the springs  134  within the cavity formed behind the stepped piston  208 . The force from springs  134  urges the carrier/clutch frame  152  to move longitudinally toward the stationary thrust ring  198 , thereby compressing the friction discs  180  and separators  178  together in frictional engagement such that torque can be transmitted therebetween. The clutch  177  is disengaged by introducing hydraulic fluid into a cavity  210  formed between the stepped piston  208  (sealed by O-ring  208   a ) and a seal ring  211  (sealed by external O-ring  211   a  and internal O-ring  211   b ). The seal ring  211  is fixed in place longitudinally by a snap ring  213  fitted to the brake housing  129 , and the hydraulic fluid enters the cavity  210  via a port  212  in the brake housing. The hydraulic fluid in cavity  210  forces the stepped piston  208  longitudinally away from the fixed seal ring  211 , overcoming the bias of the springs  134  and allowing the frame  152  of the carrier/clutch unit  150  to move away from the pressure plate  192 . This uncompresses the separators  178  and friction discs  180  of the clutch  177  such that their frictional engagement is significantly reduced. Thus, it will be readily appreciated that the torque transmitted by the carrier/clutch unit  150  (and hence the torque transmitted from the motor shaft  118  to the winch drum  102 ), can be varied by controlling the pressure of the hydraulic fluid in the cavity  210 . 
     The carrier/clutch unit  150  allows the functions of a clutch and a planetary gear carrier to be combined into a very compact unit. If the clutch is engaged, input torque at the sun gear  122  is transmitted as multiplied output torque at the output shaft  144 . If the clutch is not engaged, input torque at the sun gear  122  is not transmitted to the output shaft  144 . This has advantages from the standpoint of cost and space requirements. 
     When the clutch  177  is fully engaged, torque is transmitted by the carrier/clutch unit  150  from the motor shaft  118  to the secondary sun gear  144  just as with a conventional planetary gear carrier. The secondary sun gear  144 , in turn, has external teeth  214  formed on the end opposite the carrier/clutch unit. These external teeth  214  of the secondary sun gear  144  engage a plurality of circumferentially spaced secondary planet gears  216  mounted on a conventional carrier  218  by means of shafts  219 . The secondary planet gears  216  simultaneously engage a ring gear encircling the carrier. In the illustrated embodiment, the encircling ring gear for the secondary planetary set is provided by internal teeth  220  integrally formed on the inside surface of the winch drum  102 . For purposes of reducing production costs, the internal teeth  220  for the secondary ring gear and the internal teeth  172  for the primary ring gear may be part of the same set of integrally formed gear teeth. In other embodiments, however, the internal teeth of the primary and secondary ring gears may have different tooth pitches and/or may be separately formed rings that are secured in place around their respective planetary set. 
     As the secondary sun gear  144  rotates, the secondary carrier  218  will rotate in the same direction at a predetermined ratio, thereby multiplying the transmitted torque in the known manner. The secondary carrier  218  maintains fixed constant engagement with the final sun gear  146  by means of splines  222  such that torque can be transmitted therebetween. The final sun gear  146  has external teeth  224  formed on the end opposite the secondary planetary stage. These external teeth  224  may be integrally formed as part of the final sun gear  146 , or alternatively, the final sun gear may be formed from a separate shaft portion and a separate toothed portion which are splined or otherwise joined together. The external teeth  224  of the final sun gear  146  engage a plurality of circumferentially spaced final planet gears  226  mounted on a conventional carrier  228  by means of shafts  230 . The final planet gears  226  simultaneously engage a ring gear  232  encircling the final carrier  228 . It will be appreciated that, as the torque increases with each succeeding planetary stage, the size of the associated sun gear, planet gears and carrier will also increase to handle the necessary loads. Thus, in the illustrated embodiment, the final ring gear  232  is much larger than the secondary ring gear  220 , and is therefore mounted to one side of the winch drum  102 . As the final sun gear  146  rotates, the final carrier  228  will rotate in the same direction at a predetermined ratio as previously described, thus further multiplying the transmitted torque. The final carrier  228  is splined to one end of a drum shaft  234 , and the opposite end of the drum shaft is splined to an internal drum spline  236  on the drum  102 . In this manner, the output torque from the final carrier  228  is transmitted to the winch drum  102 , thus completing the transfer of power from the motor shaft  118  to the winch drum. 
     It will be readily apparent that the winch  100 , which includes the drum friction clutch after the first stage of gear reduction, substantially reduces the torque-carrying requirements for the clutch in comparison to a winch where the friction clutch is provided after the second or third stage of gear reduction (i.e., where the torques being transmitted are proportionally higher). Thus, the winch  100  can use a friction clutch that is much smaller and/or less expensive to manufacture than other designs. In addition, the use of the carrier/clutch unit  150  incorporating both a planetary carrier and a friction clutch in a single unit further simplifies production of the winch and reduces costs. Further still, use of a common set of springs to activate both the drum clutch and the static brake of the winch also reduces the parts count, further simplifies production, and reduces costs for the winch. Finally, mounting the carrier/clutch unit within the internal cavity of the winch drum makes excellent use of the available space within the winch housing so as to provide for a more compact unit. 
     Although the preferred embodiment has been described in detail, it should be understood that various changes, substitutions and alterations can be made therein without departing from the spirit and scope of the invention. For example, in another embodiment of the invention, the carrier/clutch unit may be disposed between the secondary sun gear and the final sun gears, rather than between the primary sun gear and the secondary sun gear. In yet another embodiment, the winch may have only two stages of gear reduction, and the entire gear reduction mechanism, including a carrier/clutch unit, maybe disposed within the internal cavity of the winch drum. In still another embodiment, the winch may have only a single stage of gear reduction, but will incorporate a carrier/clutch unit sharing common springs with the static brake assembly. In yet another embodiment, all of the reduction gear sets, including the set incorporating the carrier/clutch unit, may be disposed outside the winch drum. In still another embodiment, some of the winch&#39;s reduction gear sets including the carrier/clutch unit may be disposed along a first longitudinal axis, other of the reduction gear sets may be disposed along a second, parallel longitudinal axis, and the gear sets on the two axes are connected by a set of engaged gears, a chain/sprocket arrangement, or other torque transmitting means. In yet other embodiments, the relative movements of the components of planetary gear sets may be rearranged in the known manner. These and other embodiments are defined by the claims as appended hereto.