Machine element or mechanism – Mechanical movements – Reciprocating or oscillating to or from alternating rotary
Patent
1998-07-31
1999-12-21
Herrmann, Allan D.
Machine element or mechanism
Mechanical movements
Reciprocating or oscillating to or from alternating rotary
744248R, 74459, 188 67, 29736214, F16H 2524
Patent
active
060033940
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to seat actuators, primarily those used for vehicle seat recliners and possibly seat positioners.
2. State of the Art
As safety concerns for automobile and truck passengers increase, vehicle seats have become more complex. Linear actuators for allowing vehicle seats to move and the seat back to pivot are becoming increasingly complicated. One proposed linear actuator uses a leadscrew or threaded shaft. As it moves forward or backward axially due to the seat being reclined, a threaded gear nut or spin nut rotates about the leadscrew. The spin nut has a clutch that disengages the leadscrew when the user manually activates a recline lever. When the user releases the recline lever the clutch engages the shaft and prevents rotation of the spinning nut. That locks the leadscrew from further axial movement. Griswold, U.S. Pat. No. 5,320,413 (1994), Rees U.S. Pat. No. 4,881,775 (1989), and Periou U.S. Pat. No. 4,799,734 (1989), are examples of patents teaching this or similar types of seat actuators.
If a linear actuator is out of alignment, it can malfunction. That is, if the leadscrew is out of alignment (i.e., aligned up, down, to the side or at any angle to the gear nut), the gear nut does not spin freely around the leadscrew. Consequently, the leadscrew does not move freely backward and forward.
It has been proposed to use a gimbal mount for the entire mechanism as a way to overcome misalignment. The gimbal is expensive to manufacture and may require additional threaded fasteners that also are costly to make. Additionally, because of the added parts and the complexity of the gimbal mount, installation costs are high.
SUMMARY OF THE INVENTION
The principal object of the present invention is to disclose and provide a high-load linear actuator that compensates for installation and other misalignments.
The actuator includes a leadscrew that traverses the actuator housing. A gear nut within the housing surrounds and is threaded onto the leadscrew. As the leadscrew moves axially through the housing, the gear nut rotates. A ball, which is manually controlled by the user of the seat, moves in a slot radially to the gear nut. The ball can engage or disengage castellations on the gear nut. When the ball partially projects from the slot, the ball engages a gear nut castellation. The nut does not turn because the slot prevents the ball from rotating with the gear nut. Therefore, the leadscrew cannot move axially and the actuator is locked.
To prevent misalignment between the gear nut and leadscrew, the gear nut can pivot up, down, to the side or at an angle within the housing. Therefore, if the leadscrew is not aligned with the housing, the leadscrew pivots the gear nut so that the gear nut remains aligned with the leadscrew. To accomplish pivoting, the gear nut has spherical ends or inserts with spherical end surfaces, and the housing has inner walls that are spherical. The inserts or spherical radii of the gear nut itself, against the inner walls, therefore, allow gear nut rotation, and they can slide relative to each other so that the gear nut can follow the leadscrew's orientation. The spherical radii, in contact with each other also allow the gear nut to spin.
In accordance with another preferred embodiment, the gear nut includes ends or inserts which have a spherical surface. The gear nut is mounted for rotation on a conical support surface. This arrangement results in a relatively small gear nut/support surface contact area.
The actuator has a two-piece housing. The housing sections can be tightened relative to each other to squeeze against the spherical gear nut or its inserts. This minimizes "chuck," which is undesired movement of the leadscrew while the unit is locked. Alternatively, a housing may be provided with a threaded opening and cap arrangement that performs substantially the same function.
These and other objects of the invention may be seen more clearly from the detailed description of the preferred embodiment that
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Herrmann Allan D.
P.L. Porter Co.
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