Geometrical instruments – Distance measuring – By flexible tape
Reexamination Certificate
1999-07-26
2002-02-19
Gutierrez, Diego (Department: 2859)
Geometrical instruments
Distance measuring
By flexible tape
C033S755000, C033S762000
Reexamination Certificate
active
06347462
ABSTRACT:
FIELD OF THE INVENTION
The invention concerns a measuring cable travel sensor and more particularly a measuring cable travel sensor with housing.
BACKGROUND OF THE INVENTION
Measuring cable travel sensors are travel or distance-measuring sensors which operate on the principle of a measuring cable, with a housing which is suitable for use in industrial situations. A typical travel sensor of that kind comprises a precisely defined and positioned cable drum on to which a measuring cable is wound, generally only in a single layer on the drum, with one end of the measuring cable being suitably fixed to the cable drum. The other free end of the measuring cable is secured to that body or article, the variation in the position of which is to be precisely measured.
When the movable body or article moves away from or towards the cable drum of the measuring cable travel sensor, the resulting angular movements of the measuring cable drum about its axis are converted into a precise travel or distance length by means of a rotary angle sensor which is non-rotatably coupled to the cable drum. A rotary torsion spring which is operatively connected to the cable drum, generally in coaxial relationship therewith, ensures that the measuring cable is wound on to the cable drum again when the movable body whose position is to be measured moves towards the cable drum, thereby to ensure that the measuring cable is properly wound on to the drum and is kept in a reasonably taut condition.
The housing for a typical measuring cable travel sensor of such a kind which in particular has receiving regions for accommodating the cable drum and the spring is assembled from individual parts, in particular by screw means. The one individual part provides a receiving region for accommodating the spring, a further part provides a receiving region for accommodating the cable drum and there is possibly yet a further part which provides a receiving region for the rotary angle sensor. The individual parts constituting the housing of the measuring cable travel sensor of such a configuration are generally produced more particularly from light metal or alloy by a die casting process and subjected to finishing machining by procedures such as milling and boring, but they may also be produced from the solid by cutting machining. The parts constituting the housing can also be produced by deep drawing.
It has been found however that housings of that nature suffer from a number of specific disadvantages according to the respective mode of manufacture involved.
Thus for example all forms of housing which are produced by means of an initial shaping mold as is the case for example with die casting or deep drawing are an economical proposition only when relatively large numbers of housings are produced.
On the other hand housing parts which are produced for example by milling from solid material are uniformly expensive in regard to individual item price.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a measuring cable travel sensor whose parts and in particular the parts of the housing thereof can be easily and inexpensively produced.
Another object of the present invention is to provide a measuring cable travel sensor in which in particular moving parts of the sensor and more especially the cable drum thereof are to be of the lowest viable inertial mass.
Still another object of the present invention is to provide a measuring cable travel sensor having a housing which can be produced in a compact and robust design configuration by a simple operating procedure.
Yet another object of the present invention is to afford a measuring cable travel sensor having a housing whose design configuration is such as to provide a highly advantageous relationship between quality and price by suitable selection of the material involved and the operating procedure applied thereto.
Still a further object of the present invention is to provide a measuring cable travel sensor which is so designed that assembly thereof is a readily implementable procedure.
In accordance with the principles of the present invention the foregoing and other objects are attained by a measuring cable travel sensor comprising a housing accommodating a measuring cable drum and a rotary spring for urging the cable drum in the cable winding-on direction. A rotary angle sensor is mounted to the housing. The housing at least partially comprises a straight profile portion with a cross-section which is uniform in the longitudinal direction.
As will be appreciated from the description hereinafter in greater detail of preferred embodiments of the present invention, the fact that the measuring cable travel sensor is at least partially manufactured from straight profile portions which are not produced in the required length directly from manufacture, it is possible to use inexpensive extruded profile portions which then only have to be cut to the desired length in order to serve as a portion of the housing or as a part of the cable drum.
The profile portion may include integrated longitudinal grooves of an undercut configuration, whereby it is further possible for covers to be fixed on the open sides of the profile portions by means of self-tapping screws, without requiring further preliminary preparation or machining thereof. Thus the only preliminary preparation operation is that of providing openings on the appropriate profile portion for fitting therethrough the shaft of the measuring cable travel sensor, which carries the rotary members thereof.
It is possible in that way to produce a compact robust housing at low cost, while in addition the relationship between price and quality can also be influenced by the choice of the material used, in particular involving a selection between plastic material and light metal or alloy.
It will be noted in that respect that it is possible to use different profile shapes for the housing, for example either open profile shapes such as a plate profile, an L-shaped profile or a C-shaped profile, or closed profile shapes such as a box profile or a double-box profile. When the open profile shapes are adopted, the cable drum is arranged parallel to one of the main limbs or sides of the profile shape, the shaft carrying the cable drum passing through that limb. More particularly in that case the cable drum is disposed in the free space defined within a C-shaped profile or in the free space between the legs of an L-shaped profile. In such a case the cable drum on the one hand and the rotary spring on the other hand, and possibly additionally also the rotary angle sensor on the other hand, may be disposed in respective separate housing portions which can be releasably fixed to each other, more particularly by screw means.
In particular upon assembly of the rotary spring which is generally a shaped flat spring wound in a spiral configuration in one plane, the procedure involved is such that the spring is on the one hand non-rotatably connected to the shaft and on the other hand fixedly connected to the housing, and the part of the housing which accommodates the spring, which can be referred to hereinafter as the spring shell portion of the housing, is then turned relative to the other parts of the housing, about the shaft, until the spring is in its prestressed condition. It is only then that the spring shell portion constituting part of the housing is connected to the other parts of the housing as for example by screw means or in some other suitable fashion.
When box profile portions are used, on the one hand the spring and on the other hand the cable drum can each be disposed in a respective box profile portion, while in some cases the rotary angle sensor can also be disposed in a further box profile portion. In that case the three box profile portions constituting the housing can be connected directly or indirectly by means of longitudinal covers which engage thereover and which are secured for example by screw means to all three profile portions.
When the housing is made up at least in part by the use of a multiple-box profile
ASM Automation Sensorik Messtechnik GmbH
Gonzalez Madeline
Gutierrez Diego
Jacobson & Holman PLLC
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