Measuring and testing – Dynamometers – Responsive to force
Reexamination Certificate
1998-12-01
2001-04-03
Noori, Max (Department: 2855)
Measuring and testing
Dynamometers
Responsive to force
C073S082000
Reexamination Certificate
active
06209403
ABSTRACT:
FIELD OF INVENTION
This invention relates to an apparatus for measuring positively-sensed force of an electrical connector, in particular to a device that provides at least one strain gauge on an elastically deformable sheet. In the device deformation of the elastically deformable sheet to which the strain gauge attaches, serves as a measure for measuring strain of the sheet and for acquiring the positively-sensed clamping force of the connector terminals.
BACKGROUND OF INVENTION
In engineering an electrical connector, electrical connector terminals must consist of positively-sensed clamping force of a certain amplitude in order to rub off oxides or sulfides of contact surfaces between a circuit board and the terminals thereby attaining acceptable conductive effects, maintaining sufficient contact area between the circuit board and the connector, and preventing fretting corrosion failure due to vibration. On the other hand, if other factors, such as wear reduction, spring rigidity and stability, are taken into account in engineering the connector, the positively-sensed clamping force of the electrical connector terminals effecting to the circuit board is preferred to be minimized so as to optimize connector performance. Therefore, how to maintain an appropriate positively-sensed clamping force being effected to the circuit board is an important engineering issue being intensively observed while engineering new electrical connectors or modifying existing electrical connectors. Because amplitude of the positively-sensed clamping force that an electrical connector effects to a circuit board will eventually affect connector reliability and force required for inserting or withdrawing the connector into or from the circuit board, manufactures of electrical connectors have given much consideration to the amplitude of clamping force while engineering electrical connectors. However, apparatus for measuring positively-sensed clamping force of an electrical connector is currently unavailable in the commercial market, where most of the time, connectors are split apart such that positively-sensed clamping force is measured by conducting tensile test thereto. The majority of manufactures also rely on past experiences, repetitive experiments and design modifications attain the desired positively-sensed clamping force. It is sometimes necessary to rely on the customers to evaluate whether the ultimate positively-sensed clamping force that the electrical connectors effect to the circuit board qualifies the customers' specifications. The only prior art known so far involves U.S. Pat. No. 4,380,171 issued on Apr. 19, 1983. Hence, manufacturers of electrical connectors in general cost considerable experimental or trial-run expenditures and take an extended engineering term to attain the desired connectors, where such an engineering approach is obviously disadvantageous to the manufacturers in contending orders and in product manufacturing.
Currently, amplitude of the positively-sensed force of an electrical connector is obtained through two measures, including analysis and experimentation, wherein the method of analysis mostly involves finite element analysis, from which the overall stress distribution and the positively-sensed clamping force of the electrical connector can be calculated. However, since in such a method numeral results are derived from specific mathematical modes, it is essential to select proper modes and to modify the results based on existent conditions in order to attain correct values. Thus, implementation of the method of analysis still relies on actual measurements of the positively-sensed force to verify the results of the finite elements analysis, to serve as a reference for modifying the analysis modes, and to help engineers who design the electrical connector to acquire feeling for the amplitude of the positively-sensed force. Therefore, taking actual measurements of the positively-sensed force is an extremely vital technique in engineering electrical connectors.
In addition, recent development of electronic industry has gradually reduced thickness of common circuit boards down to approximately 1 mm, or even thinner; compact and high density designs are thus trends that electrical connectors must follow, which trends eventually result in reduction of terminal volume and intensify difficulty for measuring the positively-sensed force of such miniature products. Most researches related to taking actual measurements of positively-sensed clamping force of electrical connector terminals being conducted by research teams, are still in the conception stage. It is to the applicant's knowledge that commercial products that are equipped with such functions are currently unavailable in the market
SUMMARY OF INVENTION AND RELEVANT PRIOR ART
It is a primary object of this invention to provide an apparatus for measuring positively-sensed force of an electrical connector, such that manufacturers of electrical connectors may conveniently, and easily measure the positively-sensed clamping force of their connector products effecting to circuit boards.
Conventional. technology implemented in this invention includes utilization of a resistive strain gauge being attached to a surface of a deformable article and conversion of resistance variation of the strain gauge into voltage variation (i.e., signal outputs), where such concepts are similar to those being implemented in the load sensor of implant bones disclosed in the allowed ROC (Taiwan) Pat. Pub. No. 245634 which was filed by the same Applicant on Sep. 24, 1993 and published on Apr. 21, 1995 for ROC (Taiwan) Pat. Appln. No. 82108047. This invention implements two L-shaped pads and a thinner elastically deformable sheet provided between the pads, wherein the elastically deformable sheet is affixed with at least one strain gauge, such that upon simultaneous insertion of the two L-shaped pads and the elastically deformable sheet into an electrical connector, the elastically deformable sheet having a lower thickness is deformed while experiencing lateral pressure exerted by the connector terminals at one side thereof, so as to cause deformation of the strain gauge provided thereon. Because the strain gauge itself is a resistive component having resistance value being linearly dependent on length variation thereof, converting the resistance variation into electronic signals which are subsequently output to a signal amplifying device, allows one to obtain strain value of the strain gauge.
Prior to using this invention, a calibration instrument is utilized to obtain a calibration curve of load (positively-sensed force) vs. strain value and another calibration curve of displacement vs. strain value, such that upon insertion of this invention into the electrical connector, value of the positively-sensed force is obtainable by matching the strain value displayed in the signal amplifying device with the two calibration curves. Detailed structure of such a calibration instrument and calibration method thereof are disclosed in a co-pening patent application entitled “Micro Positively-sensed Force Calibration Instrument and Calibration Method” filed by the same Applicant.
The structure and advantages of this invention may be clearly understood by referring to the following illustrations and descriptions of preferred embodiments.
REFERENCES:
patent: 3969935 (1976-07-01), Shoberg
patent: 4038867 (1977-08-01), Andrews et al.
patent: 4294015 (1981-10-01), Drouin et al.
patent: 4380171 (1983-04-01), Smith
patent: 5313022 (1994-05-01), Piroozmandi et al.
patent: 5578754 (1996-11-01), Kato et al.
patent: 245634 (1995-04-01), None
Chen Li-Sen
Jao Wei-Tai
Liao Yen-Jang
Yen Hung-Ju
Industrial Technology Research Institute
Merchant & Gould P.C.
Noori Max
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