Geometrical instruments – Distance measuring – By flexible tape
Reexamination Certificate
2000-11-15
2002-12-31
Fulton, Christopher W. (Department: 2859)
Geometrical instruments
Distance measuring
By flexible tape
C033S761000
Reexamination Certificate
active
06499225
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to measuring cable travel sensors, and in particular, to cable travel sensors which operate on the basis of a measuring cable principle.
BACKGROUND OF THE INVENTION
Measuring cable travel sensors comprise a precisely defined and positioned cable drum on to which a measuring cable is wound, generally only in a single layer, and fixed at one end.
The other free end of the measuring cable is secured to the article of which the variation in the position is to be precisely measured.
When the article moves in relative terms away from the cable drum of the measuring cable travel sensor, the angular movements of the measuring cable drum are converted into a precise travel length by means of a rotary angle sensor which is non-rotatably coupled to the measuring cable drum. A rotary torsion spring, which is operatively connected generally in coaxial relationship to the measuring cable drum, ensures that the measuring cable is wound on to the measuring cable drum when the article to be measured moves towards the cable drum.
Measuring cable travel sensors of this kind are used in various technical assemblies, for example, for determining the position of an elevator cabin in an elevator shaft for continuously monitoring the angular position of ailerons or control elevators and vertical rudders in aircraft or the like.
In order to achieve the desired level of measurement accuracy for such measuring cable travel sensors, it is necessary on one hand, to ensure absolute angular truth as between the measuring cable drum and the rotary angle sensor. This requires, inter alia, free unimpeded rotary movement of the measuring cable drum, under all operating conditions, as any impediment to the cable drum would grossly falsify the measurement result. In particular, rubbing of the cable drum against the housing, for example, as a consequence of a mechanical loading, thermal distortion of parts of the housing and so forth, must be avoided.
For this reason the housings of the measuring cable travel sensors have hitherto generally been composed of metal parts. Production using injection molding procedures with plastic material or light metal or alloy has hitherto scarcely been wide-spread by reason of the generally unsatisfactory degree of accuracy and the complicated co-operation of the individual components.
On the other hand the extent of use of measuring cable travel sensors of that kind can be increased in proportion to reduced manufacturing cost thereof and the enhanced universality of the design configuration for example of the means for securing the sensor with respect to a surrounding structure.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a measuring cable travel sensor which is inexpensive to produce and which nonetheless functions precisely and which in particular permits a wide variety of possible ways of fixing same with respect to its surroundings.
A further object of the present invention is to provide a method of assembling such a sensor, which permits fast and thus inexpensive assembly of the sensor, thereby to reduce the manufacturing costs of a sensor of that kind in regard to their aspect which depends heavily on the amount of time involved in assembly of the sensor.
These objects are attained by the invention as set forth herein.
Advantageous features and configurations are further set forth in the appendant claims.
As will be apparent from the description hereinafter of a preferred embodiment of the invention the fact that the housing which encloses the mechanical internal space or cavity and which therefore accommodates the cable drum and the flat spiral spring has at least two and preferably four flat outside surfaces which are at a right angle to each other and on each side has one or preferably two mutually parallel outwardly open grooves which are each at the same spacing from the contact edges of the outside surfaces means that the housing and therewith the travel sensor can be fixed in the most widely varying orientations by means of the same clamping claws or brackets to a component of the surroundings, that is with the cable exit of the travel sensor parallel or perpendicular to the component supporting the travel sensor.
If the end faces of the housing also extend at a right angle to the outside surfaces bearing the grooves and screw means which are present in the corners of the housing which is not only rectangular but preferably square as viewed in the longitudinal direction terminate openly visibly in those end faces, then by arranging the nuts on the corresponding screws in corresponding hexagonal recesses in the end faces, it is possible to use nuts into which the corresponding screws which hold the housing together only partially penetrate from the one end, so that other screws are used from the other side, for fixing with respect to the surrounding structure. If then fixing with respect to the surrounding structure is implemented by means of a mounting angle member which, by virtue of arcuate or mutually parallel diagonal slots, permits variability in its angular positioning either with respect to the surrounding component or with respect to the sensor, the most widely varying mounting options can be implemented in a simple fashion.
The internal structure of the travel sensor is also so selected that on the one hand assembly is very simple and quick, while on the other hand production is possible using plastic injection molding, that is to say with the dimensional deviations which necessarily occur in that situation, both in manufacture and also in operational fitment of the sensor.
In that sense the housing which encloses the mechanical internal space for containing the flat spiral spring and the cable drum and which is in the form of a cuboidal portion with a smaller cuboidal portion fitted thereon, more specifically the cable fitment portion through which the cable extends outwardly from the housing in which the cable drum is rotatably disposed, does not as was hitherto conventionally the case comprise two housing portions in the form of half-shell portions, the plane of contact of which extends through the cable fitment portion.
Instead, the housing comprises one mounting plate which accommodates the flat shaped spring and which therefore involves a smaller extent in the longitudinal direction of the travel sensor, that is to say the axial direction of the rotary trunnion or journal of the rotary angle sensor, as already known hitherto, is a cup-shaped mounting plate which however is kept as small as possible in respect of its depth in the longitudinal direction so that this mounting plate, in regard to the cable fitment portion, just also involves a side wall of the latter, while the whole of the remainder of the cable fitment portion is a component part of the other mounting plate which is therefore of a substantially greater longitudinal extent.
Because of its greater axial extent in the longitudinal direction, that other mounting plate is precisely not cup-shaped, that is to say with a closed bottom, but is of such a configuration as to be open at both axial sides or ends. The outwardly directed end face is closed by a separate component which is connected non-rotatably to the rotary angle sensor. As the rotary angle sensor can also be a potentiometer, or pot, that separate component which carries the rotary angle sensor can also be referred to as the pot mounting plate member. This involves advantages in regard to manufacturing procedures, in terms of production tolerances, and also facilitates zero position adjustment of the rotary angle sensor.
In this connection, the screw means, disposed in the four corners of the two mounting plates, can be used in different ways relative to each other, by virtue of the selected radial spacing of the through openings provided for that purpose in the corners of the housing, with respect to the pot mounting plate member.
When using screws without an additional washer, the screw heads no longer project into the region of the pot mounting plate mem
ASM Automation Sensorik Messtechnik GmbH
Fulton Christopher W.
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