Planetary gearbox with integral electric motor and steering means.

A new, useful and compact wheel motor drive arrangement for applications on such construction equipment as scissor lifts and other similar scaffolding equipment where hydraulically driven systems have historically been used to provide power to the wheels to move the equipment is disclosed. An electric motor is mounted to a spindle bracket which is pivotably connected to the frame of the equipment to allow the unit to be pivoted around a vertical axis for steering purposes. A gear reducing planetary gear system is mounted around the drive shaft of the motor is positioned totally within the rotating wheel hub. The output ring gear of the planetary gear system is integrally formed to the interior of the wheel hub so that there is a direct application through the planetary gear system to the wheel hub to provide greater efficiency.

BACKGROUND OF THE INVENTION

Field of the Invention

This invention relates generally to electrical wheel motor drive systems for construction equipment and more particularly for small, compact construction equipment such as scissor lifts and scaffolding. More particularly, this invention combines a planetary gear box, an electrical motor and steering arm into one compact package which allows the wheel motor to act as both the drive wheel and steering wheel for the equipment.

SUMMARY OF THE INVENTION

The present invention comprises a useful and compact wheel motor drive arrangement for applications on such construction equipment as scissor lifts and other similar scaffolding equipment where hydraulically driven systems have historically been used to provide power to the wheels to move the equipment. The invention includes an electric motor mounted to a spindle bracket which is pivotably connected to the frame of the equipment to allow the unit to be pivoted around a vertical axis for steering purposes. A gear reducing planetary gear system is mounted around the drive shaft of the motor which is contained within the rotating wheel hub. The output ring gear of the planetary gear system is integrally formed to the interior of the wheel hub so that there is a direct application through the planetary gear system to the wheel hub to provide greater efficiency.

The present invention provides decided advantages over the low speed hydraulic wheel motors that are presently used to drive such compact scissor lift and other scaffolding equipment used in the construction industry. Hydraulic wheel motors have historically been used for such equipment due to their small size and relatively inexpensive cost. However, such hydraulic motors require an electrical motor and hydraulic pump to drive the hydraulic wheel motors which causes substantial loss of efficiency for the system. The present invention provides a highly efficient compact motor and planetary gear system which is far more efficient than the prior art hydraulic wheel motors, and which provides greater direct power to the wheels than prior art systems.

Historically, electrical motor/gearbox combinations have been too large and too complex to supplant hydraulic wheel motors for small compact scaffold and scissor lift equipment. However, the present invention provides a unique, compact, and efficient arrangement which reduces the overall size while maintaining and increasing the power and efficiency to the drive wheels. Further, present invention allows much quieter operation with the elimination of hydraulic fluid leaks which can cause safety and cleanliness problems at construction sites. The present invention is typically mounted in pairs that are interconnected by a tie bar so that both the wheel motors can be pivoted about the vertical axis of the spindle to permit the steering of the equipment during movement.

Finally, the present invention provides for an automatic locking arrangement which locks the wheels in position any time the power is removed from the motor so that the equipment remains stationary during use.

Thus, it is a primary object of the present invention to provide a compact, efficient electric wheel motor arrangement for scissor lifts and similar scaffolding equipment which can be economically used to eliminate low speed hydraulic wheel motors.

It is yet another object of the present invention to provide a steerable wheel motor for scissor lifts and other scaffolding equipment which can be used both to drive the movement of the equipment as well as steer the equipment during movement.

It is yet another object of the present invention to provide a steerable wheel motor for scissor lifts and other scaffolding equipment which contains an electrically operated brake arrangement that locks the wheels when electrical power is removed from the motor and the wheels are stopped and releases the brake when power is applied to the motor and the wheels are rotated.

These and other obvious advantages and features shall hereinafter appear and for the purposes of illustration, but not for limitation, the following preferred embodiments are described.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With respect toFIG. 1, two wheel motor assemblies10are shown in a paired relationship with an interconnecting tie bar assembly12which is pivotably connected at each end to spindle brackets14. Spindle brackets14are pivotably mounted on a shaft (not shown) extending downwardly from brackets16. Brackets16can be mounted to the appropriate undercarriage of the scissor lift or other scaffold equipment (not shown). Tie bar assembly12is connected to the steering mechanism of the equipment (not shown) so that the tie bar can be moved laterally to cause the wheel motor assemblies to pivot around the shaft to steer the equipment.

With reference toFIGS. 2 and 3, wheel motor assembly10comprises spindle bracket14to which is mounted motor18. The upper end15of spindle bracket14has a hollow cylindrical opening20formed throughout which is dimensional to receive the cylindrical shaft (not shown) mounted on bracket16so that the spindle bracket14can pivot about vertical axis22.

Electrical power is supplied to motor18through electrical cable24which is connected to an appropriate power source. The application of electrical power through cable24causes output shaft26or motor18to rotate. Output shaft26is supported for rotation by shaft bearing28positioned within a circular opening29through the lower end57of spindle bracket14. An O-ring seal30is provided around the edge of motor18to prevent dust and debris from entering the motor compartment and to support the motor18. Additionally, a shaft lip seal32is provided to further seal the shaft26to prevent lubricant from exiting and dust and debris from entering the gear compartment31. Gear compartment31comprises a hollow interior portion of the lower end57of spindle bracket14. Shaft bearing28is retained in position by a retaining ring34. Mounted on the end of output shaft26is input sun gear36which is retained on the end of shaft26by a retaining ring38which engages a recess on the end of shaft26. Sun gear36comprises a plurality of gear teeth which engage corresponding gear teeth on input planet gears40(only one of three shown). A ring gear42having a plurality of gear teeth is positioned to engage the teeth of input planet gears40so that rotation of the input sun gear36causes the input planet gears40to rotate within ring gear42to cause the input planet gears to circle around sun gear36. Planet gears40are mounted for rotation on input planet pins44by lock ring41, and are supported for rotation about input planet pins44by needle bearings43. Pins44are mounted to an input carrier46which is joined to output sun gear48. Input carrier46is locked to output sun gear48by a locking ring49. Sun gear48is mounted for rotation around shaft26. Thus, when input planetary gears40are caused to circle about sun gear36as sun gear36rotates, carrier46and joined output sun gear48are caused to rotate about shaft26in the same direction.

Output sun gear48has teeth which engage gear teeth on output planet gears50which are mounted for rotation to the spindle bracket14by output planet pins52. Thrust washers54are provided on each side of output planet gears50around pin52and needle bearings56support the output planet gears50for easy rotation.

Mounted for rotation about lower end57of spindle bracket14is generally cylindrically shaped hub58. Hub58is supported for rotation by bearings60and62. Bearings60are retained in position by retaining ring61. Joined to the interior surface59of hub50is an output ring gear64which engages output planet gears50. Rotation of the output planet gears50caused by the rotation of the output sun gear48causes the output ring gear64to rotate causing joined hub58to rotate. Thus, the application of electrical power to motor18causes output shaft26and attached input sun gear36to rotate which in turn causes input planet gears to rotate around the interior of ring gear42which in turn rotates input carrier46and attached output sun gear48about shaft26. The rotation of output sun gear48in turn causes output planet gears50to rotate which in turn causes output ring gear64and integrally joined hub58to rotate. A rubber wheel (not shown) is normally attached to the exterior surface55of hub58by bolts (not shown) screwed into threaded recesses66formed on a vertical face68of hub58.

A cover70overlies the open exterior end of hub58and is retained in position by a locking ring72which engages a groove at the open exterior end of hub58. An O-ring seal74is positioned around the edge of cover70to prevent lubricant from exiting and dust and construction debris from entering the planetary gear compartment31. Also, a lip seal76is provided around the interior edge of hub58and the edge of spindle bracket14to prevent lubricant from exiting and dust and construction debris from entering the interior of the mechanism from the back side.

Electric motor18has a braking mechanism79contained at the exterior end of motor18and is covered by cover78. The braking mechanism operates to lock shaft26to prevent rotation of shaft26when electrical power is removed from motor18but to release shaft26for rotation whenever electrical power is applied to motor18. This locking mechanism prevents movement of the wheels any time electrical power is not being applied. Thus, if wheel motor assembly10is used to drive a scissor lift or other scaffolding type equipment, such equipment is locked and prevented from movement once the electrical power is removed from motor24.