Planetary gearbox with integral electric motor and steering means.

[00002] Field of the Invention

[00003] 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.

[00004] 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.

[00005] 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.

[00006] 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.

[00007] 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.

[00008] 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.

[00009] 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.

[00010] 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.

[00011] 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.

[00015] With respect to FIG. 1, two wheel motor assemblies 10 are shown in a paired relationship with an interconnecting tie bar assembly 12 which is pivotably connected at each end to spindle brackets 14. Spindle brackets 14 are pivotably mounted on a shaft (not shown) extending downwardly from brackets 16. Brackets 16 can be mounted to the appropriate undercarriage of the scissor lift or other scaffold equipment (not shown). Tie bar assembly 12 is 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.

[00016] With reference to FIGS. 2 and 3, wheel motor assembly 10 comprises spindle bracket 14 to which is mounted motor 18. The upper end 15 of spindle bracket 14 has a hollow cylindrical opening 20 formed throughout which is dimensional to receive the cylindrical shaft (not shown) mounted on bracket 16 so that the spindle bracket 14 can pivot about vertical axis 22.

[00017] Electrical power is supplied to motor 18 through electrical cable 24 which is connected to an appropriate power source. The application of electrical power through cable 24 causes output shaft 26 or motor 18 to rotate. Output shaft 26 is supported for rotation by shaft bearing 28 positioned within a circular opening 29 through the lower end 57 of spindle bracket 14. An O-ring seal 30 is provided around the edge of motor 18 to prevent dust and debris from entering the motor compartment and to support the motor 18. Additionally, a shaft lip seal 32 is provided to further seal the shaft 26 to prevent lubricant from exiting and dust and debris from entering the gear compartment 31. Gear compartment 31 comprises a hollow interior portion of the lower end 57 of spindle bracket 14. Shaft bearing 28 is retained in position by a retaining ring 34. Mounted on the end of output shaft 26 is input sun gear 36 which is retained on the end of shaft 26 by a retaining ring 38 which engages a recess on the end of shaft 26. Sun gear 36 comprises a plurality of gear teeth which engage corresponding gear teeth on input planet gears 40 (only one of three shown). A ring gear 42 having a plurality of gear teeth is positioned to engage the teeth of input planet gears 40 so that rotation of the input sun gear 36 causes the input planet gears 40 to rotate within ring gear 42 to cause the input planet gears to circle around sun gear 36. Planet gears 40 are mounted for rotation on input planet pins 44 by lock ring 41, and are supported for rotation about input planet pins 44 by needle bearings 43. Pins 44 are mounted to an input carrier 46 which is joined to output sun gear 48. Input carrier 46 is locked to output sun gear 48 by a locking ring 49. Sun gear 48 is mounted for rotation around shaft 26. Thus, when input planetary gears 40 are caused to circle about sun gear 36 as sun gear 36 rotates, carrier 46 and joined output sun gear 48 are caused to rotate about shaft 26 in the same direction.

[00018] Output sun gear 48 has teeth which engage gear teeth on output planet gears 50 which are mounted for rotation to the spindle bracket 14 by output planet pins 52. Thrust washers 54 are provided on each side of output planet gears 50 around pin 52 and needle bearings 56 support the output planet gears 50 for easy rotation.

[00019] Mounted for rotation about lower end 57 of spindle bracket 14 is generally cylindrically shaped hub 58. Hub 58 is supported for rotation by bearings 60 and 62. Bearings 60 are retained in position by retaining ring 61. Joined to the interior surface 59 of hub 50 is an output ring gear 64 which engages output planet gears 50. Rotation of the output planet gears 50 caused by the rotation of the output sun gear 48 causes the output ring gear 64 to rotate causing joined hub 58 to rotate. Thus, the application of electrical power to motor 18 causes output shaft 26 and attached input sun gear 36 to rotate which in turn causes input planet gears to rotate around the interior of ring gear 42 which in turn rotates input carrier 46 and attached output sun gear 48 about shaft 26. The rotation of output sun gear 48 in turn causes output planet gears 50 to rotate which in turn causes output ring gear 64 and integrally joined hub 58 to rotate. A rubber wheel (not shown) is normally attached to the exterior surface 55 of hub 58 by bolts (not shown) screwed into threaded recesses 66 formed on a vertical face 68 of hub 58.

[00020] A cover 70 overlies the open exterior end of hub 58 and is retained in position by a locking ring 72 which engages a groove at the open exterior end of hub 58. An O-ring seal 74 is positioned around the edge of cover 70 to prevent lubricant from exiting and dust and construction debris from entering the planetary gear compartment 31. Also, a lip seal 76 is provided around the interior edge of hub 58 and the edge of spindle bracket 14 to prevent lubricant from exiting and dust and construction debris from entering the interior of the mechanism from the back side.

[00021] Electric motor 18 has a braking mechanism 79 contained at the exterior end of motor 18 and is covered by cover 78. The braking mechanism operates to lock shaft 26 to prevent rotation of shaft 26 when electrical power is removed from motor 18 but to release shaft 26 for rotation whenever electrical power is applied to motor 18. This locking mechanism prevents movement of the wheels any time electrical power is not being applied. Thus, if wheel motor assembly 10 is 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 motor 24.