Machine element or mechanism – Control lever and linkage systems – Hand operated
Reexamination Certificate
1999-06-24
2001-06-05
Fenstermacher, David (Department: 3682)
Machine element or mechanism
Control lever and linkage systems
Hand operated
C074S089100
Reexamination Certificate
active
06240800
ABSTRACT:
CROSS-REFERENCES TO RELATED APPLICATIONS
This application claims the priority of German Patent Application Serial No. 298 11 566.2, filed Jun. 29, 1998, the subject matter of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates, in general, to an electromotoric operating mechanism, such as a single drive or dual drive, for height adjustment of an article of furniture, especially for furniture items useful in the field of hospitals and/or nursing, and more particularly relates to an operating mechanism of a type including an adjusting spindle actuated by a drive having a worm wheel and having mounted thereon a spindle nut which interacts with a link member in fixed rotative engagement on a shaft of an adjustable piece of furniture, with the driving relationship between the output pin of the drive and the adjusting spindle being disengageable.
An electromotoric operating mechanism for this type is applicable for a wide variety of different articles of furniture, for example beds, slatted bed frames or the like. Normally, elevating and lowering of the respective furniture component is realized at a relatively slight speed when the electromotoric operating mechanism is turned on. However, in particular hospitals or nursing homes demand occasionally a lowering of the adjustable furniture item at a significantly higher speed. Various constructions have been proposed to mechanically disengage the drive train between the output pin of the drive and the adjusting spindle.
A conventional operating mechanism includes the disposition of a first clutch disk in fixed rotative engagement on the output pin of the drive. A second clutch disk is wedged in fixed rotative engagement onto the associated end of the adjusting spindle. Both clutch disks are brought into engagement by a coupling sleeve which travels in axial direction. The clutch disk mounted on the output pin and the coupling sleeve have complementary teeth of asymmetric configuration so that the coupling sleeve is driven in synchronism by the first clutch disk when the furniture item is raised by the drive, and turns idle when the furniture item is adjusted by hand in a same direction while the first clutch disk is at a standstill.
This conventional construction suffers the drawback of requiring a relatively large number of components in order to realize the disengagement of the drive train. Moreover, as the coupling sleeve embraces the second clutch disk, the drive exhibits a substantial size. Operating systems for articles of furniture are marketed in large numbers so that cost-efficiency is of great concern.
SUMMARY OF THE INVENTION
It is thus an object of the present invention to provide an improved electromotoric operating mechanism for articles of furniture, obviating the afore-stated drawbacks.
In particular, it is an object of the present invention to provide an improved electromotoric operating mechanism for articles of furniture, which is simple in construction with a compact design and a comparably small number of components while yet enabling a reliable disengagement of the drive train.
These objects, and others which will become apparent hereinafter, are attained in accordance with the present invention by providing a drive having a worm wheel on an output side, a spindle mechanism including an adjusting spindle in driving relationship with the drive, and a spindle nut mounted on the adjusting spindle and interacting with a link member in fixed rotative engagement with a shaft of an adjustable piece of furniture, and a clutch mechanism releasably coupling the worm wheel with the adjusting spindle, with the clutch mechanism including a guide member, fixedly secured on the adjusting spindle, and a clutch gear, wherein the worm wheel is rotatably mounted on the guide member and the clutch gear is arranged on the guide member in fixed rotative engagement but axially displaceable relative thereto, and movable with respect to the worm wheel between an engaging position and a disengaging position.
In accordance with the present invention, the worm wheel is so configured that during normal operation the driving force is transmitted by the worm wheel to the adjusting spindle via the clutch gear and the guide member. In the event, the furniture item should be lowered in a shortest possible time at respectively high lowering speed, the clutch gear is disengaged from the worm wheel, whereby the adjusting spindle as well as the guide member and the clutch disk rotate idle while the worm wheel and the drive are at a standstill.
The configuration of the electromotoric operating mechanism according to the present invention results in a comparably small size which, if at all, is only negligibly different from operating mechanism without having any disengagement feature.
Suitably, the worm wheel is linked to the clutch gear by providing the worm wheel at the clutch gear confronting side with a circular ring of teeth, and by providing the clutch gear at the facing side with complementary teeth. As a result, a slip-free connection is realized which can be subjected to great loads. The teeth may be of serrated configuration, with each tooth being bounded by a steep flank and a flat flank with respect to the pivot axes of the worm wheel and the clutch gear. During normal operation, when raising the furniture item, the torque is transmitted via the steep flanks of the teeth of the worm wheel and the clutch gear. This torque transmission is realized, however, only in the respective direction of rotation. In the opposite rotation direction, e.g., when the attached furniture item is being lowered, the clutch gear rotates out of the worm wheel and travels in axial direction.
According to another feature of the present invention, the operating mechanism includes an actuator for moving the clutch gear between the engaging position and disengaging position, with the clutch gear having an outer perimeter formed with a receptacle, for example a circumferential groove, for receiving the actuator. The actuator is suitably loaded by an energy-storing member, such as a spring, which continuously seeks to urge the clutch gear against the worm wheel. When the attached furniture item should be lowered at increased speed, the actuator is used to disengage the clutch gear from the worm wheel. As the spindle drive is not self-locking, the applied load causes the spindle drive to rotate and to act upon the lifting tube which is linked to the furniture item via the link member. In this situation, the spindle drive is no longer braked by the worm drive. Examples for an actuator include a spring-loaded release lever, a Bowden cable assembly or similar device.
Suitably, the teeth of the worm wheel and the clutch gear are of serrated configuration.
According to another feature of the present invention, the clutch gear is positioned at the spindle nut distant side of the worm wheel so that the stroke of the spindle nut is not restricted.
REFERENCES:
patent: 4741226 (1988-05-01), Bernard et al.
patent: 4773518 (1988-09-01), Raad et al.
patent: 5950774 (1999-09-01), Lang et al.
Bokamper Ralf
Roither Andreas
Dewert Antriebs- und Systemtechnik GmbH & Co. KG
Feiereisen Henry M.
Fenstermacher David
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