Axial drive mechanism

An axial drive mechanism consisting of a worm gear, a first planetary gear system having a carrier, helical planet gears in meshing engagement with the worm gear and mounted on the carrier, and a ring gear on the carrier. An electric motor can be used to drive the worm gear and a second planetary gear system can be arranged in a coaxial relation with the first system to achieve a desired gear reduction while retaining the axial arrangement of the drive. The second planetary gear system has planet spur gears arranged about and in meshing engagement with the first ring gear and a secondary ring gear encircling the planet spur gears. The second planetary gear system includes a carrier on which the planet spur gears are mounted and an output pinion gear formed integral with the last mentioned carrier. The stationary ring gear is conveniently formed as a part of the housing for the electric motor.

BACKGROUND AND SUMMARY OF THE INVENTION 
This invention relates generally to drive mechanisms and more particularly 
to an axial drive mechanism that has the advantage of being compact and 
can thus be used in installations, such as adjustable seat mechanisms, 
where space availabilities limit the size and shape of the drive mechanism 
that can be used. The drive mechanism is conveniently driven by an 
electric motor with a coaxial drive shaft but it can also be driven by a 
remote drive. 
The axial drive assembly of this invention includes a worm gear, a 
planetary gear system having a carrier, helical planet gears mounted in 
inclined positions on the carrier in meshing engagement with the worm 
gear, and a ring gear which is formed integral with the carrier, the 
planetary gear system being in a coaxial relation with the worm gear. The 
ring gear can then be used to drive a variety of other mechanisms. 
A second planetary gear system having planet spur gears arranged about and 
in meshing engagement with the first ring gear can be disposed in axial 
alignment with the first planetary gear system to obtain a further gear 
reduction. The second planetary gear system includes a stationary ring 
gear which encircles the planet spur gears and is integrally formed with 
the housing for the drive assembly. The second planetary gear system also 
includes a carrier on which the planet spur gears are mounted and an 
output pinion gear that is formed integral with the last mentioned 
carrier. 
The drive shaft, worm gear, carriers and ring gears are in substantial 
axial alignment to thereby confine the transverse dimension of the drive 
assembly. In one embodiment of the invention, this dimension is 
substantially the same dimension as the transverse dimension of an 
electric motor used to drive the worm gear. 
It can thus be seen that in the drive mechanism of this invention, the two 
planetary gear systems are structured and arranged so that they are 
coaxial with each other and with the worm gear and operate to provide an 
output which is of reduced speed and of increased torque relative to the 
output from the electric motor drive shaft. Such a drive assembly has 
applicability to numerous mechanical environments wherein components must 
be selectively moved.

With reference to the drawing, the axial drive mechanism of this invention, 
indicated generally at 10, is shown in FIGS. 1 and 5 as including a worm 
gear 16 having an axis 15 and a planetary gear system 20. The planetary 
gear system 20 is positioned in a driven relation with the worm gear 16 
and includes a carrier 22 of irregular shape. The carrier 22 has a central 
cavity 24 and is positioned so that the worm gear 16 extends into the 
cavity 24. 
An annular gear support section 28 surrounds the cavity 24 and encircles 
the worm gear 16. This gear support section 28 includes a plurality of 
support surfaces 30 (FIG. 3), shown as three in number, which are inclined 
at an angle of substantially 45.degree. to the axis 15 of the worm gear 
16. A plurality of helical planet gears 32, shown as three in number, are 
mounted on the support surfaces 30 as shown in FIG. 3 so that the teeth on 
the gears 32 will mesh with the teeth on the worm gear 16. 
Each of the gears 32 rotates about a shaft 34 carried by the carrier 22 and 
located so that the gear 32 can be positioned substantially flat against 
the inclined surface 30. As a result, the gears 32 are likewise inclined 
at an angle of about 45.degree. to the axis 15. 
The carrier 22 has an extension 36 which extends axially away from the 
cavity 24 and is provided with integral teeth forming a ring gear 38. 
An electric motor 12 having an axial drive shaft 14 formed integral with 
the worm gear 16 is shown in FIG. 1 for driving the worm gear 16 about the 
axis 15. Axially beyond the worm gear 16, the drive shaft 14 terminates in 
a thrust or bearing portion 18 which engages the bottom wall 26 of the 
carrier cavity 24. 
A second planetary gear system 40 is shown in FIG. 1 axially aligned with 
the worm gear 16 and the axial drive mechanism 10. The system 40 has a 
plurality of spur gears 42 arranged about and in meshing engagement with 
the ring gear 38 in the planetary system 20. The spur gears 42 rotate 
about shafts 44 mounted on a carrier 46 (FIG. 3). A stationary ring gear 
48 is formed as an integral part of the housing 52 for the mechanism 10 
and is in meshing engagement with the teeth on the planet gears 32 and the 
spur gears 44. An output pinion gear 50 is formed integral with the 
carrier 46 and is located in a coaxial relation with the shaft 14. 
FIG. 5 illustrates an embodiment of the invention in which the axial drive 
mechanism 10 is mounted in a housing 70 and the ring gear 38 is in a 
driving relation with a gear 72 that drives a shaft 74. The worm gear 16 
is bearing supported on the carrier 22 and the housing 70 and is connected 
through a coupling 76 to a remote power source such as a motor (not 
shown). A bottom plate 78 on the housing 70 carries a spindle 80 that 
extends into a central bore 54 in the ring gear 38 and rotatably supports 
the carrier 22. 
From the above description, it is seen that this invention provides an 
axial drive mechanism 10 which includes a worm gear 16 and an axially 
aligned planetary gear system 20. In the embodiment shown in FIGS. 1-4, a 
second planetary gear system 40 is interconnected and arranged in a driven 
relation with the planetary 20 so that the high speed, low torque output 
of the shaft 14 is translated into a low speed, high torque output of the 
pinion gear 50. The drive torque of the worm gear 16 provides the force 
that moves the pinion gear 50 and the stationary ring gear 48 provides the 
reaction force from which the drive force for the pinion gear 50 is 
generated. 
As shown in FIG. 1, the drive mechanism 10 is of a compact size and of a 
small dimension in a direction transversely of the motor drive shaft 14 so 
that the transverse dimension of the mechanism 10 does not substantially 
exceed the transverse dimension of the motor 12. This enables use of the 
drive mechanism 10 in mechanical environments in which space is limited. 
In the assembly 55 illustrated in FIG. 4 utilizing drive mechanisms 10, a 
pair of motors 12 are arranged side-by-side in a common housing 52a and 
the drive mechanisms are supported on a rail 56. Mounting members 58 are 
mounted at their lower ends on the rail 56 and at their upper ends have 
support spindles 80 that are telescoped into the central bore 54 in the 
ring gear 36 and a coaxial bore 60 in the output pinion gear 50. The 
connectors 58 thus constitute supports for the axial drive mechanisms 10. 
As shown in FIGS. 2 and 4, a geared lever 62 can be mounted on a support 64 
on the rail 56 so that it is in meshing engagement with the output pinion 
50 for driving the lever 62 back and forth about its pivot 64. Similarly, 
the pinion gear 50 on the adjacent drive mechanism 10 can be arranged in a 
driving relation with a toothed member such as shown at 66. 
The drive mechanism 10 is particularly applicable to adjustable seat 
assemblies in vehicles and an embodiment of the invention is shown in FIG. 
6 for this use and indicated generally at 80. The assembly 80 is like the 
assembly 55 in that it includes a plurality of electric motors 12 in a 
common housing 52b. Two of the motors 12 drive axial drive mechanisms 10 
that are associated with planetary systems 40 that drive pinion gears 50 
and the third drive mechanism 10 drives a gear system 81 that drives a 
pinion gear 82 on a shaft 84 mounted in a bearing support 86. The shaft 84 
in turn drives an output gear 88. 
In the assembly 80, two of the mechanisms 10 are used to adjust the seat in 
up and down directions and the third mechanism 10 is used to move the seat 
forward and back. 
During operation of the mechanism 10, the rotating worm gear 16 drives the 
helical gears 32 so as to rotate the carrier 22 about the axis 15. 
Rotation of the carrier 22 results in rotation of the ring gear 38 which 
can be used to drive many different mechanisms. The ring gear 38 is used 
in FIG. 1 to drive the spur gears 42 which mesh with the stationary ring 
gear 48 to in turn drive the carrier 46 and rotate the output pinion gear 
50 at a reduced speed relative to the speed of rotation of the drive shaft 
14. The result is a compact axial drive mechanism which efficiently 
translates the high speed, low torque rotation of the electric motor shaft 
14 into a low speed, high torque rotation of the output pinion gear 50 
which can be effectively utilized in a variety of mechanism installations.