Implements or apparatus for applying pushing or pulling force – Screw
Patent
1998-08-17
2000-08-29
Scherbel, David A.
Implements or apparatus for applying pushing or pulling force
Screw
254103, B66F 308
Patent
active
06109594&
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention concerns a mechanical device able to: system, translation-free.
BACKGROUND OF THE INVENTION
The solution currently used consists of uncoupling the reversible screw
ut system from its drive motor by means of a claw coupling controlled externally or by a lever whose movement depends on the axial force applied to the screw of the jack.
The external mechanical device located between the load and the screw of the jack drives the lever when the force exceeds a pre-established value.
The drawbacks of this system are: which needs to be regularly reset, causes inaccuracy concerning the positioning of the load linked to the jack,
SUMMARY OF THE INVENTION
The device of the invention is able to resolve these drawbacks.
This device includes two elements, one integral with the screw of the jack and the other integral with the load able to rotate with respect to the other on a given axis. The axial translation movement between these two elements cannot take place.
Disposed between these two elements is a friction system. At rest, the rotation of the two elements with respect to the other is prevented by this friction system. The screw of the jack is therefore rendered integral with the load and this blocks rotation of this screw and creates a torsion torque on the friction system when the jack is functioning.
Two cases of functioning appear:
1. Dynamic force limiter of the jack when the latter moves the load:
The friction torque between the screw and the nut tends to move the screw in rotation. This rotation is prevented until the friction system slides and separates the screw from the load which is no longer translation-driven.
This therefore produces a limitation of the force of the jack.
2. Static force limiter supported by the jack when the latter does not move the load:
The device uses the reversibility of the screw
ut system.
Reversibility means that, under the action of an axial force on one of the screw or nut elements, the other, blocked in an axial direction, starts to rotate.
The force applied by the load in the axis of the screw tends to drive it in rotation. This rotation is prevented until the friction system slides and separates the screw from the load.
The rotation of the screw causes the latter to advance into the nut and actuates a linear movement of the load.
This device functions both on traction and on compression.
The friction system used may be a device with balls, friction disks, multipolar permanent magnets or be of another type.
When the jack has stops for cutting off feeding of the drive motor when the end of travel is reached, the device of the invention involves the use of end of travel stops whose functioning is symmetrical around the axis of the jack as the screw is rotating.
These stops ensure the same total travel of the rotating screw, regardless of its angular position.
According to particular embodiments, the end of travel stops can be made up of: breaker, a pneumatic or optical detector or another type of detector. <<Hall>> effect detector using a semiconductor or similar type of device.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings illustrate the invention:
FIG. 1 is a cutaway view of the device of the invention.
FIG. 2 is a cutaway view of a first variant of this device.
FIG. 3 is a cutaway view of a second variant of this device.
FIG. 4 is a cutaway view of a variant of the device according to FIG. 2.
FIG. 5 is a cutaway view of a third variant of the device of FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
With reference to these drawings, the jack itself, which has been simplified so as to understand the invention, comprises a body (15) containing a nut (8) immobilised along the axis between two rolling stops (12) acting against end surfaces of nut (8). This nut is driven in rotation with the aid of a motor (11) by means of a gear train with two pinions (9) and (10). The nut (8) moves the screw (7) which transforms the rotating movement of the nut into a translation movement of this s
REFERENCES:
patent: 4015824 (1977-04-01), Profet
patent: 4221363 (1980-09-01), Jasper
patent: 4234151 (1980-11-01), John et al.
patent: 4339113 (1982-07-01), Vosper
Waligora Julien
Waligora Laurent
Scherbel David A.
Shanley Daniel C.
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