Machine element or mechanism – Gearing – Directly cooperating gears
Reexamination Certificate
1999-10-05
2001-07-10
Herrmann, Allan D. (Department: 3682)
Machine element or mechanism
Gearing
Directly cooperating gears
C188S083000, C384S125000
Reexamination Certificate
active
06257085
ABSTRACT:
CROSS-REFERENCES TO RELATED APPLICATIONS
This application claims the priority of German Patent Application Serial No. 298 18 204.1, filed Oct. 12, 1998, the subject matter of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates, in general, to an electromotive drive mechanism for a body of furniture, and in particular to a drive mechanism of a type having a worm gear activated by a motor and essentially including a gearbox casing for housing a worm and a worm wheel which is in mesh with the worm.
The type of electromotive drive, involved here, is applicable for a wide variety of different articles of furniture, for example beds, slatted bed frames or the like and is considered a small power drive. Typical drive mechanisms of this type for operating a body of furniture include a worm which is either fitted in fixed rotative engagement onto the output journal of an electric motor, or forms the output journal itself to reduce the overall dimensions. As a consequence of the geometry of the worm and the worm wheel, relatively high gearing forces are encountered that may lead to a flexure of the output journal when subject to respectively high loads. Thus, the diminished contact ratio between the worm and the worm wheel results in increased wear. In particular, the flanks of the worm wheel wear off, leading to a fracture of the output journal, so that the drive must be repaired or replaced by a new drive.
SUMMARY OF THE INVENTION
It is thus an object of the present invention to provide an improved electromotive drive mechanism, obviating the afore-stated drawbacks.
In particular, it is an object of the present invention to provide an improved electromotive drive mechanism which is simple in structure and yet at least significantly reduces a flexure of the output journal of the motor or of the wormshaft.
These objects, and others which will become apparent hereinafter, are attained in accordance with the present invention by providing a support body which is so insertable in the gearbox casing as to closely fit around the worm and includes a receiving opening for engagement by the worm wheel.
The support body is made of suitable material to keep friction to a minimum, e.g. from plastic material through an injection molding process. Through the provision of a support body according to the present invention, a sagging or flexure of the wormshaft or output journal can reliably be prevented. Thus, the worm is in optimum fit with the flanks of the worm wheel so that wear is significantly reduced. The provision of the receiving opening enables an engagement of the worm windings with the gears of the worm wheel.
According to another aspect of the present invention, the support body has a basic form of cylindrical configuration and is inserted in positive and/or non-positive engagement in a bore of the gearbox casing. Drives for articles of furniture have to be designed for realizing a self-locking action so that the attached piece of furniture is able to remain in any position, once the drive is shut down. Normally, the drive includes a spindle for driving the worm wheel, with the spindle having mounted thereon a spindle nut. In the event, the spindle is not constructed for self-locking action, but such action is desired, it is proposed, in accordance with another feature of the present invention, to provide the motor-facing end portion of the support body with several slots to realize deformable tongues. This end portion is suitably formed with an outer groove for accommodation of an annular spring retainer, whereby the spring retainer applies a precisely defined, constant friction force on the output journal of the motor to thereby effect a self-locking action of the drive mechanism, when the drive per se is not designed to include a self-locking mechanism.
The drive mechanism according to the present invention is especially suitable for articles of furniture, which require a relatively small torque for adjustment.
REFERENCES:
patent: 3431033 (1969-03-01), Dangauthier
patent: 4040307 (1977-08-01), Koster
patent: 4885948 (1989-12-01), Thrasher, Jr. et al.
patent: 4900960 (1990-02-01), Becker et al.
Bokamper Ralf
Roither Andreas
Dewert Antriebs- und Systemtechnik GmbH & Co. KG
Feiereisen Henry M.
Herrmann Allan D.
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