Geometrical instruments – Distance measuring – Of flexible material
Reexamination Certificate
1999-12-22
2002-08-13
Bennett, G. Bradley (Department: 2859)
Geometrical instruments
Distance measuring
Of flexible material
C033S0010PT
Reexamination Certificate
active
06430836
ABSTRACT:
BACKGROUND AND SUMMARY OF THE INVENTION
1. Field of the Invention
The invention concerns a pull element travel sensor and a lifting apparatus embodied with such elements.
2. Background of the Invention
Pull element travel sensors occur in many different configurations for example in order to determine the precise positioning of a given component which in particular can move over considerable travel distances, for example the cabin of an elevator. A typical pull element travel sensor of that kind has a tensile or pull element, for example a cable, which is wound on to a winding drum which is biassed in the winding-on direction. The free end of the pull element is connected to that component whose position is to be determined, for example as mentioned above an elevator cabin. A prestressing force for urging the winding drum in the winding-on direction is produced for example by way of a flat spiral spring which for example is arranged coaxially with respect to the winding drum and is non-rotatably connected thereto.
The winding drum is also typically connected to a detection unit for recording the revolutions or angular distances through which the winding drum passes in the winding-on or unwinding direction, and which in addition by way of a suitable electronic evaluation system determines the length of the pull element which has been drawn off the cable drum.
In order to simplify that operation of determining the drawn-off length of the pull element, for example a cable, the pull element is wound in only a single layer on the periphery of the winding drum, with the turns of the pull element on the winding drum being in axially juxtaposed relationship. As a result, one revolution of the winding drum will always correspond to exactly the same length of the pull element.
In order to ensure that the pull element is wound on to the drum in only a single layer and in order to prevent the pull element from jumping over on to the first layer to start a second layer there over when winding the pull element on to the winding drum, it is generally necessary to take suitable mechanical steps involving appropriate structure on the travel sensor to obviate that occurrence.
Instead of determining the rotary movement of the winding drum, it is also known for the length of the pull element, which has been drawn off the winding drum, to be determined directly, for example by arranging a counting device at the location at which the pull element issues from the housing of the winding drum, wherein the pull element has portions which are always of the same size and which are of different configurations, for example in the form of holes or perforations which are arranged uniformly in the longitudinal direction. Those different portions such as holes can be suitably counted by the counting device and converted in a suitable system into a measurement corresponding to the length of the pull element which has been drawn off the winding drum.
A disadvantage with that structure is that it is necessary to use a pull element of a special configuration whose differing portions must remain unchanged, even over a long period of time and even after a large number of operations of being wound on to and unwound from the winding drum. In the case of portions of different configurations on the pull element, such as for example holes, tooth arrangements and the like, they tend to be subjected to a high level of mechanical wear and thus enjoy only a limited service life.
In contrast thereto, determining the rotary movement of the winding drum by means of a rotary angle sensor which is operatively coupled to the rotary movement of the winding drum involves structure which is virtually wear-free and thus enjoys a very good overall service life.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a pull element travel sensor of simplified mechanical structure, thereby to afford a pull element travel sensor of minimised axial length.
Another object of the present invention is to provide a pull element travel sensor capable of winding the pull element on the winding drum thereof without involving complicated mechanical components.
Still another object of the present invention is to provide a handling apparatus such as a lifting apparatus including a pull element travel sensor, capable of providing for precise vertical positioning of an object connected to the handling apparatus.
In accordance with the principles of the present invention, the foregoing and other objects are attained in a first aspect by a pull element travel sensor comprising a pull element winding drum and a biassing unit operatively connected thereto for biassing the winding drum in the direction of rotation thereof for winding the pull element on to the winding drum. A detection unit is operable to detect the length of the pull element which has been drawn off the winding drum. The pull element is wound on the winding drum in a single radial plane of the winding drum in a spiral configuration in a plurality of layers in mutually superposed relationship.
Further in accordance with the present invention, in a second aspect thereof, the foregoing and other objects are attained by a handling apparatus such as a lifting apparatus for lifting a load, comprising at least first and second lifting units and at least one travel sensor. Each lifting unit includes a pull element winding drum and a biassing unit operatively connected thereto for biassing the winding drum in the direction of rotation of the winding drum for winding the pull element on to the winding drum. A motor drives the winding drum at least in the winding-on direction. The lifting units are arranged with downwardly facing free ends of the pull elements. At least one of the lifting units is provided with a detection device for detecting the length of the pull element which has been drawn off the winding drum and all pull elements engage the same load.
In accordance with the principles of the present invention moreover in a third aspect the foregoing and other objects are attained by a pull element travel sensor comprising a winding drum for winding a band on an external winding surface of a winding cylinder portion of the winding drum, and a housing in which the winding drum is rotatably mounted. At least one braking magnet is arranged at a point non-rotatable with the winding drum in such a way that it acts brakingly against the direction of rotation in contact-less magnetically on the winding drum at an eccentric region of action thereof, the winding drum at least in the region includes electrically conductive material.
Further in accordance with the principles of the invention in a fourth aspect the foregoing and other objects are attained by a pull element travel sensor comprising a winding drum for winding a band on to an external winding surface of a winding cylinder portion of the winding drum, and a housing in which the winding drum is rotatably mounted. At least one braking magnet arranged eccentrically on the winding drum is operable to brakingly act on the housing in the direction of rotation in contact-less mode magnetically, the housing, at least in the region in which the magnet acts thereon, has electrically conductive material.
Additionally in accordance with the invention the foregoing and other objects in a fifth aspect are attained by a pull element travel sensor comprising a winding drum for winding a band on the external winding surface of a winding cylinder portion of the winding drum, and a housing in which the winding drum is rotatably supported. At least one holding magnet is arranged on the winding drum radially within the winding surface of the winding cylinder portion of the winding drum and is operable to hold the band radially inwardly to the winding surface, the band having magnetisable material.
In accordance still with the principles of the invention in a sixth aspect the foregoing and other objects are attained by a pull element travel sensor comprising a winding drum for winding a band on to an external winding surface of a winding cylinde
ASM Automation Sensorik Messtechnic GmbH
Bennett G. Bradley
Crowell & Moring LLP
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