Geometrical instruments – Distance measuring – Of flexible material
Reexamination Certificate
1999-10-04
2001-08-07
Hirshfeld, Andrew H. (Department: 2859)
Geometrical instruments
Distance measuring
Of flexible material
C033S0010PT, C254S338000, C254S403000
Reexamination Certificate
active
06269547
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a position-detecting device, particularly to a digital transducer for detecting, measuring and displaying a displacement.
BACKGROUND OF THE INVENTION
A dam, a canal or a pumping station is usually provided with a gate equipped with a gatage indicator for measuring the degree of gate opening or displacement of the top of the gate. The measured value is transmitted to a display panel in the control room, wherein water discharge is controlled under monitoring. For some gates, the gate opening is converted into flow rate data for proper operations. Accordingly, precision of actual displacement is very essential to gate operation.
However, a conventional gatage indicator usually uses a circular analog meter, which is driven by mechanical gears to simultaneously drive a potentiometer to directly convert the actual displacement detected into an analog signal according to a potentiometric ratio. Thereby measured values lack accuracy, such that, for example, the displayed data converted from the analog signal in the control room changes irregularly even if the gate is in a still state. Further advancement on the conventional detecting device is needed.
Therefore, the present inventor has disclosed a Taiwanese Utility Model Patent No. 140156 entitled “Cable extension type gatage transducer”. The above mentioned shortcomings of the conventional measuring devices are improved. However, its disadvantages of higher production costs and larger occupied space should be further improved. Moreover, if an extended cable retracts at an irregular speed, the simply integrating of the drum and detecting roller will get the retracted cable disorderly winding on the drum to cause inaccurate displacement display. Besides, if extended but accidentally loosened, the cable will retract at high acceleration and release from the groove of the drum. As a result, both precision measurement and operation performance will be affected.
In addition, U.S. Pat. No. 5,236,144 “Cable Extension Linear Position Transducer” has disclosed that the displacement of an extended cable is detected by using a cable-driven drum to synchronously drive a potentiometer so that the detected displacement is directly converted into an analog signal according to potentiometric ratio. Nevertheless, no accessory is provided for guiding the extended cable to the orderly wound state when retracting at an irregular speed. Moreover, the lower accuracy occurs during the aforesaid signal conversion. In other designs, optical encoders which offer better precision are used, but these devices do not provide proper rolling up or, with the rolling wheel and the sensor wheel placed next to each other, take up a large volume. Moreover, the drawback that the breakdown easily occurs when the extended cable releases by accident or retracts at high acceleration should be improved.
In order to facilitate installation and to avoid breakdown, the present invention provides an integral structure comprising a spool, a spiral spring and a magnet-detecting element to secure greater reliability and accuracy on the actual displacement of the monitored object which is attached to the extension cable.
SUMMARY OF THE INVENTION
A digital cable extension transducer, according to one aspect of the invention, is an integral structure of a spool, a spiral spring, a magnet detecting element for sensing and directly sending out a digital signal and a cable guide assembly for guiding an extended cable orderly wound on the spool. The present invention comprises:
a housing, which comprises a side plate
20
for screwing with a base plate, a bottom plate mounted with a circuit board, a hole for a bushing provided at one side of the bottom plate and a cover integrally screwed to a front edge of the housing;
a spool, which is mounted on a shaft at the center of the base plate, wherein the shaft includes a catch. The spool comprises an outer flange and an inner flange, wherein the inner flange includes a plurality of magnets evenly spaced thereon. A socket of the flange includes a bearing, and a spiral spring is mounted between the inner flange of the spool and the catch of the shaft;
three pulleys, which are mounted on three individual cylinders surrounding the spool on the base plate to constitute a cable guide assembly, wherein the cable guide assembly guides the cable to extend or retract along grooves in the pulleys and assures orderly winding of the cable on the spool at its exact position to measure the precise displacement of the monitored object;
a baffle, which is an L-shaped plate for shielding both the spool and three pulleys and is integrally affixed to the base plate, comprises a front edge for fixing to the other ends of three individual cylinders by respective apertures thereof, wherein the distance between the inner wall of the baffle and the outer walls of the pulleys is smaller than the diameter of the cable to prevent the extended cable from derailing from the pulleys when releasing at high acceleration or loosening by accident.
The base plate further comprises a magnet detecting element sensing alternative pulse signals subject to the displacement of the magnets and dependent on the actual displacement of the monitored object attached to the cable and transmitting a digital signal to the circuit board.
The object of the present invention is to provide a digital cable extension transducer for measuring a displacement with more accuracy, which has an integral structure with improved retracting function and directly sends digital signals of the displacement of the monitored object. Accordingly, both operation performance and displacement precision are improved.
The present invention will be further understood with reference to the following description and accompanying drawings.
REFERENCES:
patent: 3494038 (1970-02-01), Quenot
patent: 3638220 (1972-01-01), Malina et al.
patent: 3812589 (1974-05-01), Schultheis
patent: 4578867 (1986-04-01), Czerwinski et al.
patent: 5236144 (1993-08-01), Kautz
Connolly Bove & Lodge & Hutz LLP
Hirshfeld Andrew H.
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