Load control power transmission

The present invention is a transmission used with a winch drum. The transmission includes a drive shaft, an output shaft, a hydraulic or pneumatic system, a cooling system, a gear coaxially mounted on the output shaft, and an electric motor for powering the gear. The drive shaft is adapted to drive the winch drum and includes a clutch disc extending generally radially outwards from the drive shaft. The clutch disc has a face. The output shaft coaxially surrounds at least a portion of the drive shaft and includes a friction surface extending generally radially inward. The friction surface has a face opposing the face of the clutch disc. The hydraulic or pneumatic system is adapted to bring the faces into contact, and the cooling system is adapted to remove heat from the friction surface via a fluid coolant.

FIELD OF THE INVENTION

The present invention relates to winches. More specifically, the present invention relates to transmissions used with winches that are subject to dynamic loading conditions, such as those conditions that arise in a marine environment.

BACKGROUND OF THE INVENTION

Towing/anchor-handling marine vessels are equipped with winches. When paying out or hauling in wire rope or holding a load stationary, the winches and their wire rope are often subjected to load surges and peaks because of wave action encountered by the vessel. These load surges and peaks can cause the wire rope to fail.

The length of wire rope to be paid out from a winch can be significant. Thus, payout of wire rope at normal winch operating speeds can require substantial amounts of time.

There is a need in the art for an apparatus and method adapted to minimize the effect of load surges and peaks on winches during payout and haul-in operations in a marine environment. Also, there is need in the art for the ability to perform high speed/horsepower dynamic payout of wire rope in a controlled manner.

BRIEF SUMMARY OF THE INVENTION

The present invention, in one embodiment, is a transmission used with a winch drum. The transmission includes a fluid cooled clutch coaxially mounted on a drive shaft adapted to drive the winch drum.

The present invention, in another embodiment, is a transmission used with a winch drum. The transmission includes a drive shaft, an output shaft, a hydraulic or pneumatic system, a cooling system, a gear coaxially mounted on the output shaft, and an electric motor for powering the gear. The drive shaft is adapted to drive the winch drum and includes a clutch disc extending generally radially outwards from the drive shaft. The clutch disc has a face. The output shaft coaxially surrounds at least a portion of the drive shaft and includes a friction surface extending generally radially inward. The friction surface has a face opposing the face of the clutch disc. The hydraulic or pneumatic system is adapted to bring the faces into contact, and the cooling system is adapted to remove heat from the friction surface via a fluid coolant.

The present invention, in another embodiment, is a transmission used with a winch drum. The transmission comprises a drive shaft, an output shaft, an actuation system, and a cooling system. The drive shaft is adapted to drive the winch drum and is operably coupled to a first clutch surface. The output shaft is adapted to be driven by a motor and is operably coupled to a second clutch surface opposing the first clutch surface. The actuation system is adapted to bring the first and second surfaces into contact. The cooling system is adapted to remove heat from at least one of the surfaces via a fluid coolant.

The present invention, in another embodiment, is a method of controlling a winch drum transmission equipped with a drive shaft and an output shaft that coaxially surrounds at least a portion of the drive shaft. The drive shaft is adapted to drive a winch drum, and the output shaft is adapted to transfer power from an electric motor to the drive shaft via a hydraulic or pneumatic clutch. The method includes setting a winch load limit, hydraulically or pneumatically causing the clutch to prevent relative displacement between the drive and output shafts when an actual winch load does not exceed the set winch load limit, allowing relative displacement between the shafts when the actual winch load exceeds the set winch load limit, and circulating a fluid coolant through the clutch to remove heat resulting from the relative displacement between the shafts.

The present invention, in another embodiment, is a method of performing dynamic payout of wire rope from a winch drum coupled to a transmission. The transmission is equipped with a drive shaft and an output shaft. The drive shaft is adapted to drive the winch drum, and the output shaft coaxially surrounds at least a portion of the drive shaft and is adapted to transfer power from an electric motor to the drive shaft via a hydraulic or pneumatic clutch. The electric motor is electrically connected to an electrical load, such as resistor bank, and the clutch is fluidly connected to a cooling system. Dynamic payout of the wire rope generates energy that needs to be dissipated. In one embodiment, the method includes setting a transition point based on a percentage of the electrical load capacity. In another embodiment, the method includes setting a transition point based on a predetermined electric motor speed. For example, in one embodiment, the predetermined electric motor speed may be based on a percentage of the maximum electric motor speed. The method further includes hydraulically or pneumatically causing the clutch to prevent relative displacement between the shafts when the transition point has not been exceeded, thereby causing all of the energy, generally speaking, to be dissipated through the electrical load, and hydraulically or pneumatically actuating the clutch to allow relative displacement between the shafts when the transition point has been exceeded, thereby causing at least a portion of the energy to be dissipated through the cooling system and the remainder of the energy to be dissipated through the electrical load.

The present invention, in another embodiment, is a method of dissipating energy generated by dynamic payout of wire rope from a winch drum. The method includes setting a transition point wherein the responsibility for dissipating the energy transitions from being, generally speaking, the responsibility of a primary energy dissipation system to being shared between the primary system and a supplemental energy dissipation system, dissipating the energy through the primary system when the transition point has not been exceeded, and dissipating the energy through the primary and supplemental systems when the transition point has been exceeded. In one embodiment, the primary system is an electric motor electrically coupled to an electrical load, and the supplemental system is a fluid cooled clutch fluidly coupled to a cooling system. In another embodiment, the primary system is a hydraulic motor fluidly coupled to a hydraulic system, and the supplemental system is a fluid cooled clutch fluidly coupled to a cooling system.

DETAILED DESCRIPTION

FIGS. 1A and 1Bare, respectively, a starboard elevation and a plan view of a marine vessel1equipped with the anchor-handling/towing winch system2of the subject invention. As illustrated inFIGS. 1A and 1B, in one embodiment, the winch system2is mounted on the deck3of the marine vessel1with the winch system's wire ropes4feeding towards the stem5of the vessel from the winch system2. In other embodiments, the winch system2is mounted on the deck3of a marine vessel1so the wire ropes4feed towards other parts of the vessel1, such as the bow6.

FIG. 2is an isometric view of the anchor-handling/towing winch system2as viewed from an elevated, port/stem position. As shown inFIG. 2, in one embodiment, the winch system2includes a port tow drum10, a starboard tow drum11, an anchor-handling drum15, and a load control power transmission20. The drums10,11,15carry wire rope4.

The load control power transmission20drives and/or brakes the drums10,11,15during the winch system's various in-hauling and payout operations. As shown inFIG. 2and explained in the following discussion ofFIGS. 3 and 4, in one embodiment, the load control power transmission20employs a load limiting clutch65a,65bdirectly on each drive shaft70a,70bto eliminate the effects of motor and power train inertia. Because of each clutch's location, the speed of its associated motor45a,45b,which is operably coupled to a shaft70a,70band associated drum or drums10,11,15, does not have to remain directly proportional to the drum speed during payout. Thus, the load control power transmission20allows full control of the wire rope4for normal in-hauling and payout operations, while allowing rapid payout of wire rope4during surge or peak load situations, thereby reducing the risk of broken ropes.

In one embodiment, the clutches65a,65bare disk or axial type clutches. In one embodiment, the clutches65a,65bare rim type clutches with internal expanding shoes or external contracting shoes.

For a more detailed discussion of the load control power transmission20, reference is now made toFIG. 3, which is an isometric view of the transmission20illustrated inFIG. 2, as viewed from the same elevated, port/stem position. As shown inFIG. 3, in one embodiment, the transmission20includes a starboard power assembly25, a starboard drive shaft assembly30, a port power assembly35, and a port drive shaft assembly40. The starboard power assembly25is operably coupled to the starboard drive shaft assembly30. Similarly, the port power assembly35is operably coupled to the port drive shaft assembly40.

As shown inFIG. 3, in one embodiment, the power assemblies25,35each include an electric motor45a,45b,a power shaft50a,50b,a brake55a,55b,a primary gear reducer60a,60b,and a fluid cooled multi-disc clutch65a,65b.Each electric motor45a,45bdrives a power shaft50a,50b that runs a primary gear reducer60a,60bcoupled to a fluid cooled clutch65a,65b.Each fluid cooled clutch65a,65b,when engaged, transfers the power of its respective electric motor45a,45bto its respective drive shaft assembly30,40. As will be explained more fully later in this specification in the discussion ofFIG. 4A, the less a clutch65a,65bis engaged, the greater the amount of slip between its power assembly25,35and the respective drive shaft assembly30,40.

As stated above, one embodiment of the invention employs electric motors45a,45bto drive the winch drums10,11,15. However, in other embodiments of the invention, the motors45a,45bare hydraulic motors or internal combustion engines.

As illustrated inFIG. 3, the drive shaft assemblies30,40each include a drive shaft70a,70bsupported by drive shaft support bearings75. The port drive shaft70ahas a port tow drum drive pinion80aand the starboard drive shaft has a starboard tow drum drive pinion80b.In one embodiment, as shown inFIG. 3, the starboard drive shaft70bhas an anchor-handling drum drive pinion80c.In another embodiment, the anchor-handling drum drive pinion80c is located on the port drive shaft70a.As shown inFIG. 3, each pinion80a,80b,80cis paired with a jaw clutch85a,85b,85c.

As can be understood fromFIGS. 2 and 3, the port tow drum drive pinion80ainterfaces with, and drives, a drive gear on the port tow drum10. When the port tow drum10is to be driven, the jaw clutch85aengages the pinion80a,causing the pinion80ato rotate with the port drive shaft70a,thereby driving the port tow drum10. When the clutch85ais disengaged from the pinion80a,the port tow drum10is not driven because the port drive shaft70ais free to rotate within the pinion80a.

As can also be understood fromFIGS. 2 and 3, the starboard tow drum drive pinion80binterfaces with, and drives, a drive gear on the starboard tow drum11. When the starboard tow drum11is to be driven, the jaw clutch85bengages the pinion80b,causing the pinion80bto rotate with the starboard drive shaft70b,thereby driving the starboard tow drum11. When the clutch85bis disengaged from the pinion80b,the starboard tow drum11is not driven because the starboard drive shaft70bis free to rotate within the pinion80b.

As can further be understood fromFIGS. 2 and 3, the anchor-handling drum drive pinion80cinterfaces with, and drives, a drive gear on the anchor-handling drum15. When the anchor-handling drum15is to be driven, the jaw clutch85cengages the pinion80c,causing the pinion80cto rotate with the starboard drive shaft70b,thereby driving the anchor-handling drum15. When the clutch85cis disengaged from the pinion80c,the anchor-handling tow drum15is not driven because the starboard drive shaft70bis free to rotate within the pinion80c.

As shown inFIG. 3, a center jaw clutch90resides between the opposed ends of the drive shafts70a,70b.When the center jaw clutch90is disengaged, the drive shafts70a,70bare independent of each other and free to rotate at different speeds and different directions, each drive shaft70a,70bbeing driven by its own power assembly25,35. Thus, for example, when the center clutch90is disengaged, the port power assembly35may drive the port drive shaft70ain one direction to cause the port tow drum10to payout its wire rope4, while the starboard power assembly25may drive the starboard drive shaft70bin the opposite direction to cause the anchor-handling drum or the starboard tow drum to haul-in its corresponding wire rope4.

As indicated inFIG. 3, when the center jaw clutch90is engaged, the drive shafts70a,70bessentially become one drive shaft. This allows the power of both power assemblies25,35to be applied simultaneously to any one or more of the pinions80a,80b,80cand its corresponding drum10,11,15.

As indicated inFIG. 3and more fully shown inFIG. 4A, which is a sectional elevation along section line AA ofFIG. 3and through the port clutch65a,port gear reducer60a,and outer end of the port drive shaft70a,the outer end portion of each drive shaft70a,70bpasses through the primary gear reducer60a,60band terminates within the clutch65a,65b.As shown inFIG. 4A, the primary gear reducer60aincludes a housing100, a drive gear105, a reducer output shaft110, support bearings115for supporting the reducer output shaft110off of the housing100, and support bearings120for supporting the reducer output shaft110off of the drive shaft70a.

As indicated inFIG. 4A, the drive shaft70ais supported by the support bearings75and is coaxially, rotatably displaceable within the reducer output shaft110when the clutch65ais not fully engaged. The reducer output shaft110is rotatably displaceable within the housing100and supported by the support bearings115,120. The drive gear105is coaxially mounted on the reducer output shaft110and transmits the power from the electric motor45a,via the power shaft50a,to the reducer output shaft110. As will be explained in greater detail later in this specification, the power is then transmitted from the reducer input shaft110to the drive shaft70ato a greater or lesser degree, depending on the degree of clutch engagement.

As illustrated inFIG. 4A, in one embodiment, the clutch65aincludes a clutch housing125, a swivel assembly130, a coolant inlet135, a coolant outlet140, a main hydraulic or pneumatic control pressure line145, coolant lines150, and branch hydraulic or pneumatic control pressure lines190. In one embodiment, where the each clutch65a,65bis a disk or axial type clutch, each clutch65a,65bwill also include pressure plate friction surfaces155and clutch discs160. In one embodiment, a clutch guard165encloses all of the aforementioned components of the clutches65a,65b,except the pressure line145and the coolant inlet135and outlet140. The clutch housing125is secured to the reducer output shaft110and is coaxially, rotatably displaceable about the drive shaft70awhen the clutch65ais not fully engaged. The swivel assembly130is secured to the clutch housing125.

As indicated inFIG. 4A, the clutch housing125supports pressure plate friction surfaces155that are parallel to each other, extend radially inward from the clutch housing125, and are secured to the clutch housing125. The clutch discs160are mounted on the end portion of the drive shaft70a,are parallel to each other, and radially extend outward from the shaft's outer circumference. Each clutch disc160is sandwiched between a pair of pressure plate friction surfaces155. When the pressure plate friction surfaces155are hydraulically or pneumatically actuated by a hydraulic or pneumatic engagement system170, they engage the clutch discs160.

When the pressure plate friction surfaces155are less than fully engaged, the clutch discs160may rotatably displace relative to the friction surfaces155, if a torque exerted on the drive shaft70aexceeds the frictional force between the friction surfaces155and the clutch discs160. The drive shaft70awould then rotatably displace relative to the reducer output shaft110.

Conversely, when the pressure plate friction surfaces155are fully engaged such that the torque exerted on the drive shaft70adoes not exceed the frictional force between the friction surfaces155and the clutch discs160, the clutch discs160are prevented from rotatably displacing relative to the friction surfaces155and, as a result, the drive shaft70adoes not rotatably displace relative to the reducer output shaft110. Consequently, the drive shaft70aand the reducer output shaft110rotate together as one shaft.

As shown inFIG. 4A, the coolant inlet135and coolant outlet140are connected to the swivel assembly130to circulate coolant from the cooling system175through the clutch housing125via the coolant lines150. The coolant absorbs and removes heat generated at the friction surfaces155. In one embodiment, the fluid coolant is water. In other embodiments, the coolant will be oil, air or other types of fluids.

As illustrated inFIG. 4A, the hydraulic or pneumatic control pressure line145runs from the hydraulic or pneumatic actuation system170to a connection point on the swivel assembly130, which is secured to the clutch housing125. The branch hydraulic or pneumatic lines190are in fluid communication with the main hydraulic or pneumatic control pressure line145and run from the swivel assembly130to the clutch housing125. The branch hydraulic or pneumatic lines190actuate the friction surfaces155. Other actuation systems based on magnetic, mechanical or other actuation methods may also be used.

WhileFIG. 4Adepicts one embodiment of the invention where the drive shaft70ais coaxially positioned within the reducer output shaft110, the friction surfaces155extend radially inward, and the clutch discs160extend radially outward, those skilled in the art will realize that other configurations of the invention may be developed without departing from the spirit of the invention.

For example, as illustrated inFIG. 4B, which is a sectional elevation similar toFIG. 4A, except of an alternative embodiment, the port clutch65aand the port gear reducer60ahave reversed positions and the drive shaft70ais no longer coaxially within the reducer output shaft110. Furthermore, the clutch discs160extend radially inward from the drive shaft70aor, that is to say, an extension of the drive shaft70a,and the friction surfaces155extend radially outward from the reducer output shaft110, or in other words from a clutch housing125mounted on the output shaft110.

As shown inFIG. 4B, the coolant inlet135, coolant outlet140, and main hydraulic or pneumatic control pressure line145connect to a swivel assembly130on the end of the output shaft110. A branch hydraulic or pneumatic line190leads from the swivel assembly130, through the output shaft110, and to the friction surfaces155. Coolant supply and return lines150run from the coolant inlet135and outlet140, through the output shaft110, and to the friction surfaces155. Like the embodiment illustrated inFIG. 4A, the gear reducer60acauses the output shaft110to rotate, which causes the drive shaft70ato rotate to a greater or lesser degree, depending on the degree of clutch engagement.

To illustrate another embodiment of the invention, reference is now made toFIG. 4C, which is a sectional elevation similar toFIG. 4A, except of an alternative embodiment, wherein the port clutch65aand the port gear reducer60ahave reversed positions and the drive shaft70ais no longer coaxially within the reducer output shaft110. As shown inFIG. 4C, the clutch discs160extend radially outward from the drive shaft70a,and the friction surfaces155extend radially inward from the clutch housing125, which is attached to the end of the output shaft110.

As illustrated inFIG. 4C, the coolant inlet135, coolant outlet140, and main hydraulic or pneumatic control pressure line145connect to a swivel assembly130on the end of the output shaft110. A branch hydraulic or pneumatic line190leads from the swivel assembly130, through the output shaft110, and to the friction surfaces155. Coolant supply and return lines150run from the coolant inlet135and outlet140, through the output shaft110, and to the friction surfaces155. Like the embodiment illustrated inFIG. 4A, the gear reducer60acauses the output shaft110to rotate, which causes the drive shaft70ato rotate to a greater or lesser degree, depending on the degree of clutch engagement.

To illustrate another embodiment of the winching system2of the subject invention, reference is now made toFIG. 3A, which is a schematic plan view of an alternative embodiment of the winching system2. As shown inFIG. 3A, a power shaft50extends between a motor45and a gear box60. A brake55is located along the power shaft50. A first shaft70extends between the gear box60and a clutch65.

As shown inFIG. 4D, which is a sectional elevation taken along section line BB ofFIG. 3Aand through the clutch65and outer end of the first shaft70, in extending into the clutch65, the first shaft70is coaxially surrounded by a second shaft110and a first gear105mounted on the second shaft110. In one embodiment, a clutch housing125radially extends from the second shaft110. Pressure plate friction surfaces155are mounted on the clutch housing125and configured to engage clutch discs160that radially extend from the first shaft70.

As can be understood fromFIG. 3A, the first gear105drives a second gear106, which is mounted on a third shaft111. A fourth gear113is coaxially pivotally mounted on the third shaft111and in engagement with a drum gear114on the winch drum10. The fourth gear113is brought into engagement with the third shaft111via a jaw clutch85arrangement as previously described in this Detailed Description. When the fourth gear113is engaged with the third shaft111, it will drive a drum gear114and, as a result, the winch drum10.

To discuss the function of the load control power transmission20and its components, reference is now made toFIGS. 3,4A and5.FIG. 5is a flow diagram illustrating the function of the transmission20. In operation, the winch operator sets the winch load limit at an operator's control panel180(block500). In other words, the operator sets the clutch65a,65bsuch that the clutch discs160will not rotatably displace relative to the friction surfaces155, unless the torque imposed on the clutch65a,65bby the load in the wire rope4exceeds the frictional force between the friction surfaces155and the clutch discs160. In one embodiment, the winch load limit will be based on a percentage of the structural load limit of the winch or a component of the winch (e.g., the structural load limit of the wire rope).

The operator then causes the winch to perform a payout or haul-in operation or causes the winch to hold a load in place. If the actual load in the wire rope4does not exceed the set load limit (block510), then there is no relative motion between the clutch discs160and the friction surfaces155(block520). As a result, there is no relative motion between the drive shaft70a,70band the reducer output shaft110, and these shafts operate as one shaft (block520).

If the actual load in the wire rope exceeds the set load limit (block510), then there is relative motion between the clutch discs160and the friction surfaces155, because the clutch discs160slip (block530). Consequently, there is relative motion between the drive shaft70a,70band the reducer output shaft110(block520). This situation may arise, for example, during a payout or haul-in procedure when a large wave causes the vessel1to surge upwards, suddenly decreasing the slack in the wire rope and causing the wire rope load to peak. Once the actual load in the wire rope returns below the set load limit (block510) (e.g., the vessel1rides down the wave and the slack in the wire rope increases), the friction surfaces155relock on the clutch discs160and the relative motion between the drive shaft70a,70band the reducer output shaft110ceases (i.e., the these shafts again operate as one shaft) (block520).

The load control power transmission20facilitates dynamic, high speed/high horsepower wire rope payout by providing two modes for dissipating the energy generated during the dynamic payout process. In the first mode, during a dynamic payout, the load control power transmission20generates energy via a motor45a,45band the energy is dissipated at an energy dissipation system185connected to the motor45a,45b.For example, in one embodiment, the energy is generated at an electric motor45a,45band the energy is dissipated at an electrical load, such as a resistor bank185, electrically connected to the electrical motor45a,45b.In the second mode, during a dynamic payout, the load control power transmission20generates energy via both an electric motor45a,45band a clutch65a,65b,and the energy is dissipated via the resistor bank185coupled to the motor45a,45band a cooling system180coupled to the clutch65a,65b.

As explained above, in one embodiment of the first mode, the dynamic payout energy may be dissipated at an electrical load (e.g., resistor bank185) coupled to an electric motor45a,45b.However, in another embodiment of the first load, wherein the electrical motor45a,45band the electrical load185are replaced with a hydraulic motor coupled to a hydraulic system, the dynamic payout energy is dissipated via the hydraulic system. In either case, in the second mode, the energy generation/dissipation method of the first mode (i.e., the electric motor/electrical load combination or the hydraulic motor/hydraulic system combination) is combined with the energy generation/dissipation capability of the fluid cooled clutch65a,65bcoupled to the cooling system180.

FIG. 6is a flow diagram illustrating the dynamic payout process. In operation, the winch operator uses the operator's control panel180to set a transition point wherein the load control power transmission20shifts from the first mode to the second mode (block600). In other words, the transition point determines when the energy generation/dissipation responsibilities shifts from being, generally speaking, the responsibility of the primary energy generation/dissipation system (i.e., the electric motor/resistor bank combination) to being shared between the primary energy generation/dissipation system and the supplemental energy generation/dissipation system (i.e., the clutch/cooling system combination).

In one embodiment, the transition point may be based on a percentage of the resistor bank capacity. For example, in one embodiment, the setting is 66% of the maximum resistor bank dissipation capacity.

In one embodiment, the transition point may be based on a predetermined electric motor speed, winch drum speed, and/or torque perceived by the motor. For example, in one embodiment, the predetermined electric motor speed and/or torque may be based on a percentage of the maximum payout motor speed and/or torque.

Once the transition point has been set (block600), the operator causes the winch to perform a dynamic payout operation. If the power generated by the electric motor45a,45bdoes not exceed the setting (e.g., 66% of the maximum resistor bank dissipation capacity or a predetermined payout motor speed) (block610), then the electric motor45a,45bcontinues to handle the dynamic payout forces by itself (i.e., the electric motor/resistor bank combination is, generally speaking, responsible for the generation and dissipation of all the dynamic payout energy) and there is no relative motion between the clutch discs160and the friction surfaces155(block620). As a result, there is no relative motion between the drive shaft70a,70band the reducer output shaft110, and these shafts operate as one shaft (block620). Thus, when the load control power transmission20is operating in the first mode during a dynamic payout, the speed of the winch drum is controlled by the braking effect of the motor45a,45band associated electrical load (e.g., resistor bank185).

If the power regenerated by the electric motor45a,45bexceeds the setting (e.g., 66% of the maximum resistor bank regeneration dissipation capacity or a predetermined payout motor speed and/or torque) (block610), then the load control power transmission20transitions to the second mode and the excess percentage of the resistor bank capacity or the motor speed and/or torque is accommodated by the fluid cooled clutch65a,65b(block630). Specifically, the clutch discs160begin to slip allowing relative motion between the clutch discs160and the friction surfaces155(block630). As a result, there is relative motion between the drive shaft70a,70band the reducer output shaft110, which, in one embodiment, allows the motor45a,45bto slow and decreases the power being sent to the resistor bank185(block630). In another embodiment, relative motion between the drive shaft70a,70band the output shaft110at least prevents the motor speed and/or the power being sent to the resistor bank from increasing further.

The heat generated by the slipping clutch discs160is carried away by the cooling system175(block630). Thus, when the load control power transmission20is operating in the second mode during a dynamic payout, the speed of the winch drum is controlled by the braking effects of the motor45a,45band associated electrical load (e.g., resistor bank185) and the slipping discs160of the fluid cooled clutch65a,65b.Also, in the second mode, the relative motion between the shafts70,110allows the speed of the payout to be maintained, although the electric motor45a,45bhas been allowed to slow or at least the motor's speed and/or torque has not continued to increase.

Once the power to be dissipated during the dynamic payout process decreases to a level that does not exceed the setting (block610), the friction surfaces155fully engage the clutch discs160to stop the relative motion between these aspects of the clutch65a,65b(block620). At the same time, the electric motor45a,45b,if necessary, speeds up to match the payout speed, and the resistor bank185again, generally speaking, becomes responsible for dissipating all of the power being generated by the dynamic payout (block620).

In one embodiment, the dynamic payout power being generated by the electric motor45a,45band sent to the resistor bank185is monitored via power sensor means as are known in the art. As the power increases, additional resistors are brought on line (i.e., the electrical load is increased incrementally). Once, the transition point (i.e., a percentage of the electrical load capacity) has been reached, the clutch65a,65bis progressively released and relative rotational displacement between the drive shaft70a,70band the output shaft110progressively increases. As the dynamic payout process continues, the power being sent to the electrical load185is continuously monitored and the clutch will be adjusted accordingly.

In one embodiment while the system is operating in the second mode, if the power to the electrical load begins to decrease, the power sensors will determine this as an indication that the overall dynamic payout power is decreasing. Consequently, the clutch65a,65bwill be actuated to progressively decrease the rotational displacement between the drive and output shafts. If the monitoring system determines that the overall dynamic payout power has decreased to a point that does not exceed the transition point, then the system will begin to transition to the first mode by progressively actuating the clutch to progressively increase the torque perceived by the electrical motor until the system is fully operating in the first mode.

As explained above, in one embodiment, as the energy generated during the dynamic payout process causes the set percentage of maximum motor speed or electrical load capacity to be exceeded, the clutch65a,65bbegins to slip and the cooling system175begins to assume responsibility for at least a portion of the necessary energy dissipation. In other words, the energy dissipation responsibilities transitions from being, generally speaking, the responsibility of the electrical motor45a,45band its associated electrical load185, to being at least partially shared with the clutch65a,65band the cooling system175.

However, the responsibilities and sequencing may be reversed. For example, the energy dissipation responsibilities could initially be, generally speaking, the responsibility of the clutch65a,65band the cooling system175. When a set point associated with the clutch (e.g., a percentage of the maximum clutch speed or a percentage of the maximum cooling capacity of the cooling system) is exceeded, the electrical motor45a,45band its associated electrical load185begin to assume at least partial responsibility for energy dissipation.

In the event of an emergency stop or drum over-speed condition, the fluid cooled clutch65a,65bis fully applied, along with the drum brakes and the electric motor brakes55a,55b,in a controlled sequence. This provides maximum stopping power to the winch.