Hoist cable sensor with differential drive

A hoist includes a cable deployment sensor to sense the length of a cable that is deployed from a cable drum of the hoist. The cable deployment sensor includes a stationary ring and a rotatable ring disposed coaxially on the cable drum axis. A cluster assembly is mounted to rotate about the cable drum axis simultaneously with the cable drum. The cluster assembly includes a cluster gear with a first gear engaging the stationary ring and a second gear engaging the rotatable ring. The second gear drives the rotatable ring about the cable drum axis, and the rotatable ring drives rotation of an input gear for a sensor assembly.

BACKGROUND

This disclosure relates generally to hoists. More particularly, this disclosure relates to rescue hoists for aircraft.

Rescue hoists deploy and retrieve a cable from a cable drum to hoist persons or cargo, and the rescue hoist may be mounted to an aircraft, such as a helicopter. The rescue hoist includes a drum off of which the cable is deployed. The cable drum rotates to spool or unspool the cable from the cable drum, with one end of the cable attached to the cable drum and the other end, which can include a hook or other device, deployed during operation. The length of cable that is currently deployed is an important parameter for the user to know during operation of rescue hoists. A deployment sensor is employed to determine the number of rotations of the cable drum, and a control system can calculate the deployed length based on the sensed number of rotations. Multi-turn transducers can directly sense the number of rotations, but a multiple turn transducer does not maintain the positional reading if power is lost. Single-turn transducers typically require complex planocentric drives or a bulky arrangement having multiple stages of gear reduction to achieve the high gear ratios required by the single-turn transducer.

SUMMARY

A hoist includes a cable drum rotatable about a cable drum axis; a frame supporting the cable drum; a stationary ring gear supported by the frame and disposed coaxial with the cable drum axis; a rotatable ring gear disposed coaxial with the cable drum axis; a cluster assembly mounted for rotation about the cable drum axis; and a sensor assembly supported by the frame. The cluster gear includes a first gear mounted on a shaft, the first gear interfacing with the stationary ring gear; and a second gear mounted on the shaft, the second gear interfacing with the rotatable ring gear such that the second gear drives rotation of the rotatable ring gear. Rotation of the rotatable ring gear about the cable drum axis provides an input to the sensor assembly.

A cable deployment sensing system includes a stationary ring gear having external teeth, a rotatable ring gear mounted coaxially with the stationary ring gear, a cluster assembly mounted for rotation about an axis, and a sensor assembly. The stationary ring gear is fixed such that the stationary ring gear does not rotate about the axis. The rotatable ring gear is capable of rotating about the axis. The cluster assembly includes a housing; and a cluster gear supported by the housing. The cluster gear includes a first gear mounted on a shaft, the first gear interfacing with the stationary ring gear; and a second gear mounted on the shaft, the second gear interfacing with the rotatable ring gear such that the second gear drives rotation of the rotatable ring gear. The sensor assembly includes a sensor input gear interfacing with the rotatable ring gear and fixed relative to the axis, wherein the rotatable ring gear drives rotation of the sensor input gear; and a single-turn transducer interfacing with the sensor input gear and configured to sense rotation of the sensor input gear.

DETAILED DESCRIPTION

FIG. 1is a perspective view of aircraft10and hoist12. Hoist12is mounted to aircraft10by support14. Cable16extends from hoist12. During operation, cable16is raised and lowered to deploy and retrieve objects. Crew members of aircraft10, such as the operator of hoist12and the pilot of aircraft10, need to know the deployed length of cable16to ensure that cable16does not become entangled with an object on the ground, to ensure that cable16is properly stowed, and to perform certain maintenance tasks for hoist12, among other reasons.

While hoist12is described as being supported by aircraft10, it is understood that hoist12can be any desired hoist that deploys and retrieves a cable, such as cable16, from a cable drum.

Cable16wraps around barrel36of cable drum26and is retained between first flange32and second flange34. Linear bearing24is rotatably mounted to frame18. Motor20extends from frame18and is disposed within linear bearing24. Drive train22is connected to motor20and supported by frame18. Drive train22drives rotation of linear bearing24. Cable drum26is mounted to linear bearing24. Level wind mechanism28is also mounted to linear bearing24, extends through cable drum26, and is connected to cable drum26to drive translation of cable drum26along cable drum axis A-A. Cable16is in a cable-deployed state when cable16is fully deployed from cable drum26, and cable16is in a cable-retracted state when cable16is fully retracted onto cable drum26.

CDS30senses the deployed length of cable16and can be configured to communicate that information to a user. Mounting flange42is connected to frame18. Stationary ring gear44is supported by mounting flange42and is disposed circumferentially about cable drum axis A-A. Stationary ring gear44is fixed relative to cable drum axis A-A to prevent stationary ring gear44from rotating about cable drum axis A-A. Rotatable ring gear46is supported by mounting flange42and is disposed circumferentially about cable drum axis A-A. Rotatable ring gear46is free to rotate about cable drum axis A-A. In some examples, a portion of stationary ring gear44extends under rotatable ring gear46and forms a race that rotatably supports rotatable ring gear46. In some examples, a portion of mounting flange42extends under and rotatably supports rotatable ring gear46. It is understood, however that rotatable ring gear46can be rotatably supported in any desired manner, so long as rotatable ring gear46is coaxial with cable drum axis A-A.

Cluster assembly48is supported on linear bearing24and is configured to rotate with linear bearing24about cable drum axis A-A. Housing50of cluster gear52is mounted on linear bearing24. First bearing51and second bearing53are disposed in housing50. Shaft58is rotatably supported by first bearing51and second bearing53, and shaft58extends from housing50. First gear54and second gear56are disposed coaxially on shaft58. First gear54is intermeshed with stationary ring gear44, and second gear56is intermeshed with rotatable ring gear46. In the example shown, shaft58extends from housing50such that first gear54and second gear56are cantilevered from housing50. It is understood, however, that shaft58, first gear54, and second gear56can be disposed relative to housing50in any desired manner. In addition, while cluster assembly48is described as mounted on linear bearing24, it is understood that cluster assembly48can be directly mounted to cable drum26in examples where cable drum26does not translate along cable drum axis A-A. Sensor input gear60is intermeshed with rotatable ring gear46such that rotatable ring gear46drives rotation of sensor input gear60.

Input shaft62extends from sensor input gear60into frame18. Input shaft62extends to transducer64. Transducer64is mounted to frame18and is configured to sense rotation of input shaft62. The rotation of sensor input gear60, and thus input shaft62, is directly proportional to the rotation of cable drum26. Transducer64is a single-turn transducer configured to communicate the position of input shaft62to a cable deployment calculator. The cable deployment calculator can include instructions stored on a memory that, when executed by control circuitry, convert the positional information of input shaft62into a length of cable16deployed from cable drum26. As such, transducer64can be of any suitable form for sensing the rotation of input shaft62, such as a single turn Hall Effect sensor or a potentiometer, among other options.

Differential drive38provides a reduction drive between the rotation of linear bearing24and the rotation of sensor input gear60such that sensor input gear60rotates less than or equal to 360-degrees between cable16being in the cable-deployed state and the cable-retracted state. A single-turn transducer does not lose the position of input shaft62when power is removed from transducer64. Transducer64thus maintains the positional information of cable16even where there is a loss of power to rescue hoist12. As such, CDS30maintains the positional information and can communicate that information to the user when power to rescue hoist12is restored. In examples where cable drum26can be manually rotated during a power loss, CDS30still tracks the deployment of cable16, as any rotation of cable drum26is transmitted to sensor input gear60by differential drive38.

During operation, motor20is activated and provides rotational power to drive train22. Drive train22is a gear reduction drive. Drive train22outputs rotational power to linear bearing24, thereby causing linear bearing24to rotate about cable drum axis A-A. In one embodiment, linear bearing24is a ball spline bearing, such that linear bearing24transmits torque to cable drum26to drive the rotation of cable drum26about cable drum axis A-A.

Level wind mechanism28is mounted to linear bearing24and rotates about cable drum axis A-A with linear bearing24. Level wind mechanism28includes a level wind screw that is intermeshed with a follower mounted on cable drum26. The rotation of linear bearing24drives rotation of the level wind screw, and the level wind screw causes cable drum26to translate along cable drum axis A-A due to the connection of the level wind screw and the follower.

Cluster assembly48rotates about cable drum axis A-A along with linear bearing24. As cluster assembly48rotates about cable drum axis A-A, first gear54is driven by stationary ring gear44. The rotation of first gear54drives rotation of shaft58, thereby driving second gear56. Second gear56drives rotation of rotatable ring gear46about cable drum axis A-A, and rotatable ring gear46drives rotation of sensor input gear60. The interconnection of first gear54and stationary ring gear44has a first gear ratio. The interconnection of second gear56and stationary ring gear44has a second gear ratio. The first gear ratio and the second gear ratio combine to provide a total input ratio between linear bearing24and rotatable ring gear46of between 400:1 and 550:1. In a particular example, the total ratio is between 450:1 and 500:1. In one example, second gear56has a greater number of teeth than first gear54, and rotatable ring gear46has a greater number of teeth than stationary ring gear44. An output ratio between rotatable ring gear46and sensor input gear60is between about 3:1 and 3.5:1. The total ratio, which is a combination of the input ratio and the output ratio, ensures that sensor input gear60rotates less than 360-degrees from the point where cable16is in the fully-stowed position to the point where cable16is in the fully-deployed position. For example, where cable drum26rotates 160 total rotations between the fully-stowed position and the fully-deployed position, CDS30is configured such that the total ratio is greater than or equal to 160:1. Transducer40can communicate the position of input shaft62to the cable deployment calculator, which calculates the true length of the cable deployed based on the change in position of input shaft62relative to the position of input shaft62when cable16is in either the cable-deployed state or the cable-retracted state.

CDS30provides significant advantages. Transducer64is a single-turn transducer such that transducer64maintains the deployed length of cable16even where power to hoist12is lost. CDS30provides a simple, compact reduction drive between linear bearing24and sensor input gear60. The total ratio ensures that sensor input gear60advances less than a full rotation between the point where cable16is in the fully-stowed position to the point where cable16is in the fully-deployed position. The compact arrangement of CDS30reduces the weight of hoist12and provides a relatively simple arrangement for tracking the deployed length of cable16.

FIG. 3is a perspective view of cluster assembly48mounted directly to cable drum26. Housing50and cluster gear52of cluster assembly48are shown. Cluster gear52includes first gear54, second gear56, and shaft58.

In some examples, cable drum26is configured to rotate about cable drum axis A-A but is fixed such that cable drum26does not translate relative to cable drum axis A-A. In such an example, a translating payout point for cable16(shown inFIGS. 1 and 2A) ensures that cable16is level-wound onto cable drum26. A drive train, such as drive train22(shown inFIG. 2A), is directly connected to barrel36of cable drum26to cause cable drum26to rotate about cable drum axis A-A. Level wind mechanism28(shown inFIGS. 2A-2B) is meshed with the translating payout mechanism to drive oscillation of the translating payout point.

Housing50of cluster assembly48is directly mounted to inner side37of barrel36. As such, cable drum26rotating about cable drum axis A-A also causes cluster assembly48to rotate about cable drum axis A-A. Stationary ring gear44(best seen inFIG. 4), rotatable ring gear46(best seen inFIG. 4), sensor assembly40(best seen inFIG. 2A), and mounting flange42(best seen inFIG. 4) are disposed in the same manner as shown inFIGS. 2A and 2B. Stationary ring gear44causes first gear54to rotate, which causes shaft58to rotate. Second gear56rotates with shaft58, and second gear56drives the rotation of rotatable ring gear46about cable drum axis A-A. The input ratio, output ratio, and total ratio are the same as where cluster assembly48is mounted to linear bearing24. As such, CDS30provides the same advantages whether CDS30is disposed in a hoist having a translating cable drum, such as hoist12(shown inFIGS. 2A-2B), or a hoist having a fixed cable drum.

A housing of cluster gear52, such as housing50(shown inFIGS. 2A-3), is attached, either directly or indirectly, to cable drum26such that housing50and cluster gear52rotate about cable drum axis A-A. Mounting flange42is connected to a grounded component of a rescue hoist, such as a frame of the rescue hoist. Stationary ring gear44is supported by mounting flange42and fixed relative to cable drum axis A-A such that stationary ring gear44does not rotate about cable drum axis A-A. Rotatable ring gear46is supported by mounting flange42and is in a floating arrangement such that rotatable ring gear46can rotate about cable drum axis A-A. Cluster gear52is connected to both stationary ring gear44and rotatable ring gear46. First gear54and second gear56are disposed coaxially on shaft58. Stationary ring gear44drives rotation of cluster gear52and cluster gear52drives rotation of rotatable ring gear46. Sensor input gear60is intermeshed with rotatable ring gear46such that rotatable ring gear46drives the rotation of sensor input gear60. Input shaft62extends to a single-turn transducer, such as transducer64(shown inFIG. 2A), that senses the rotation of input shaft62. The transducer is configured to provide positional information regarding input shaft62to a cable deployment calculator, and the cable deployment calculator can calculate the deployed length of a cable based on the position of input shaft62.

During operation, CDS30provides a total reduction ratio between rotation of the cable drum and rotation of sensor input gear60such that sensor input gear60rotates less than or equal to 360-degrees from the point where the cable is fully stowed on the cable drum and the point where the cable is fully deployed from the cable drum. The housing of cluster assembly rotates about cable drum axis A-A as the cable drum is driven about cable drum axis A-A. The housing of cluster assembly48carries cluster gear52such that cluster gear completes a full rotation about cable drum axis A-A for each rotation of the cable drum about cable drum axis A-A.

First gear teeth70of first gear54are intermeshed with stationary ring teeth66of stationary ring gear44such that stationary ring gear44drives rotation of first gear54as cluster assembly48rotates about cable drum axis A-A. First gear54drives rotation of shaft58, and shaft58drives rotation of second gear56. Second gear teeth72of second gear56are intermeshed with rotatable ring teeth68, such that second gear56drives rotation of rotatable ring gear46about cable drum axis A-A. Rotatable ring teeth68are intermeshed with input gear teeth74such that rotatable ring gear46drives rotation of sensor input gear60.

The interconnection of first gear54and stationary ring gear44has a first gear ratio. The interconnection of second gear56and stationary ring gear44has a second gear ratio. The first gear ratio and the second gear ratio combine to provide a total input ratio between linear bearing24and rotatable ring gear46of between 400:1 and 550:1. In a particular example, the total ratio is between 450:1 and 500:1. In one example, second gear56has a greater number of teeth than first gear54, and rotatable ring gear46has a greater number of teeth than stationary ring gear44. An output ratio between rotatable ring gear46and sensor input gear60is between about 3:1 and 3.5:1. The total ratio, which is a combination of the input ratio and the output ratio, ensures that sensor input gear60rotates less than 360-degrees from the point where cable16is in the fully-stowed position to the point where cable16is in the fully-deployed position. For example, where cable drum26rotates 160 total rotations between the fully-stowed position and the fully-deployed position, CDS30is configured such that the total ratio is greater than or equal to 160:1. In one example, first gear54includes thirty-two first gear teeth70and has a pitch of thirty-two, stationary ring gear44includes 140 stationary ring teeth66, second gear56includes thirty-four second gear teeth72and has a pitch of thirty-four, and rotatable ring gear46includes 149 rotatable ring teeth68. In such an example the gear ratio between first gear54and stationary ring gear44is 32:140, and the gear ratio between second gear56and rotatable ring gear46is 34:149. The gear ratios and epicyclic movement of cluster assembly48causes rotatable ring gear46to advance about 0.17% of a rotation for each rotation of cluster assembly48about cable drum axis A-A. With cable drum26configured to rotate 160 revolutions between the fully-stowed position and the fully-deployed position, the gear ratio causes rotatable ring gear46to advance about 0.27 of a full revolution. In such an example, sensor input gear60can have forty-three input gear teeth74. Sensor input gear60would thus advance 0.93 of a full revolution between the fully-stowed position and the fully-deployed position due to the gear ratio between sensor input gear60and rotatable ring gear46.

CDS30provides a compact, simple arrangement for transmitting the rotation of the cable drum to sensor assembly40. The compact arrangement reduces the weight of the rescue hoist and allows CDS30to be implemented in either a rescue hoist having a translating cable drum or a rescue hoist having a fixed cable drum. In addition, the simple arrangement of CDS30reduces the downtime required for any maintenance.

Discussion of Possible Embodiments

A hoist includes a cable drum rotatable about a cable drum axis; a frame supporting the cable drum; a stationary ring gear supported by the frame and disposed coaxial with the cable drum axis; a rotatable ring gear disposed coaxial with the cable drum axis; a cluster assembly mounted for rotation about the cable drum axis; and a sensor assembly supported by the frame. The cluster gear includes a first gear mounted on a shaft, the first gear interfacing with the stationary ring gear; and a second gear mounted on the shaft, the second gear interfacing with the rotatable ring gear such that the second gear drives rotation of the rotatable ring gear. Rotation of the rotatable ring gear about the cable drum axis provides an input to the sensor assembly.

The housing of the cluster assembly is mounted on an interior of a barrel of the cable drum.

A linear bearing supported by the frame, wherein the cable drum is supported by the linear bearing, and the housing of the cluster assembly is mounted on the linear bearing.

A first gear ratio between the first gear and the stationary ring gear is larger than a second gear ratio between the second gear and the rotatable ring gear.

The first gear ratio is 32:140 and the second gear ratio is 34:149.

The first gear includes thirty-two teeth and has a pitch of thirty-two, and wherein the second gear includes thirty-four teeth and has a pitch of thirty-four.

The sensor assembly includes a sensor input gear intermeshed with the rotatable ring gear; a sensor shaft extending from the sensor input gear through the frame; and a transducer interfacing with the sensor shaft and configured to sense rotation of the sensor shaft.

The transducer is a single-turn transducer.

The single-turn transducer is selected from the group consisting of a potentiometer and a single turn Hall Effect sensor.

An output ratio between the rotatable ring gear and the sensor input gear is between 2.5:1 and 4:1.

The output ratio between the rotatable ring gear and the sensor input gear is between 3:1 and 3.5:1.

A total input ratio between rotation of the cable drum about the cable drum axis and rotation of the rotatable ring gear about the cable drum axis is between 400:1 and 550:1.

The total input ratio is between 450:1 and 500:1.

The shaft of the cluster gear extends from the housing of the cluster gear and the first gear and the second gear are cantilevered from the housing.

A cable deployment sensing system includes a stationary ring gear having external teeth, a rotatable ring gear mounted coaxially with the stationary ring gear, a cluster assembly mounted for rotation about an axis, and a sensor assembly. The stationary ring gear is fixed such that the stationary ring gear does not rotate about the axis. The rotatable ring gear is capable of rotating about the axis. The cluster assembly includes a housing; and a cluster gear supported by the housing. The cluster gear includes a first gear mounted on a shaft, the first gear interfacing with the stationary ring gear; and a second gear mounted on the shaft, the second gear interfacing with the rotatable ring gear such that the second gear drives rotation of the rotatable ring gear. The sensor assembly includes a sensor input gear interfacing with the rotatable ring gear and fixed relative to the axis, wherein the rotatable ring gear drives rotation of the sensor input gear; and a single-turn transducer interfacing with the sensor input gear and configured to sense rotation of the sensor input gear.

The first gear has a first number of gear teeth and the second gear has a second number of gear teeth, and wherein the first number is less than the second number.

The stationary ring gear has a third number of gear teeth and the rotatable ring gear has a fourth number of gear teeth, and wherein the third number is less than the fourth number.

The first gear and the second gear are coaxial.

The shaft of the cluster assembly extends from the housing of the cluster assembly such that the first gear and the second gear are cantilevered relative to the housing of the cluster assembly.

The sensor assembly further comprises a sensor shaft extending from the sensor input gear, and wherein the single-turn transducer interfaces with the sensor shaft to sense rotation of the sensor shaft.