Measuring and testing – Specimen stress or strain – or testing by stress or strain... – By loading of specimen
Reexamination Certificate
2000-04-05
2001-09-18
Noori, Max (Department: 2855)
Measuring and testing
Specimen stress or strain, or testing by stress or strain...
By loading of specimen
Reexamination Certificate
active
06289744
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a system for testing torsion springs. More specifically, the present invention relates to a torsion spring tester having dedicated fixtures which permit absolute measurements rather than relative measurements to be taken of the spring and further permits the results of such measurements to be repeatable.
2. Description of the Related Art
A variety of torsion spring testers have been available for a number of years. These torsion spring testing machines are designed for checking torque loads in inch ounces and inch pounds and deflections in degrees. They are intended for use with a variety of springs including torsion springs, double torsion springs, spiral springs, clock springs, motor springs and power springs. Early spring testers work in conjunction with a balance and weights to determine torque load. Such units also typically included a protractor to permit one to read deflection in degrees. More recently, various companies have developed digital torsion spring testers. Such testers typically utilized a load cell and an “electronic protractor” measuring deflection.
Testers of the type described above are manufactured by The Carlson Company of Clinton, Ark., the Spring Research and Manufacturers' Association of Sheffield, England and Link Engineering Company of Plymouth, Mich.
Testers of the type described above offer a variety of advantages. However, set up, use and recordation of information using such testers generally tends to be time consuming. Further, the results tend not to be repeatable. As such, there is a real need for a torsion spring tester which is quick and easy to use, is quick and easy to calibrate, and is capable of providing measurements which are repeatable. There is also a real need for a torsion spring tester that provides absolute measurements rather than relative measurements.
SUMMARY OF THE INVENTION
The present invention relates to a new torsion spring tester that is easy to use, easy to calibrate, generates repeatable results and provides absolute rather than relative measurements. The system includes a carriage, a first housing secured to the carriage in a fixed position, and a second housing slidable back and forth along the carriage. The first, fixed housing contains a faceplate coupled to a tube, and a microprocessor based data acquisition/control package. It also contains a specially designed load cell which measures the load and transfers the data into the electronics package. Running through the tube in the first housing is a threaded shaft which is coupled to a knob. The threaded shaft is used to couple a tooling blank to the faceplate in the housing.
The second housing includes three individually positionable stops, a sliding stop bar, and a knob used to fix the stops in place. The second housing also includes a face plate coupled to a tube. A threaded shaft running through the tube is used to couple a second tooling blank to the face plate on the housing. The tube is also coupled by a belt to an encoder. The encoder is used to measure rotation of the tube. To impart rotational motion to the tube (and thus to the face plate and tooling blank), the housing is provided with two exterior knobs. These knobs are coupled to a gearing arrangement. A switch is also provided to activate one knob or the other. Since the gearing ratio associated with the two knobs are different, one of the knobs can be used for gross rotation of the tube while the other can be used for fine rotation of the tube. Signals from the encoder are transmitted via a cable to the electronics package in the first housing.
A key aspect of the present invention is the tooling that is used in conjunction with the first and second housings. As explained above, each tooling member includes a blank which is coupled using the threaded shaft to the face plate of the specific housing. The tooling secured to the second housing, in addition to the blank, includes a mandrel and a first engagement bar. The tooling secured to the first housing includes a second engagement bar. Also provided are first and second zeroing elements. The first zeroing element is a pin that can be coupled to one of the tooling blanks. The second is a slot in the other tooling blank which receives the pin. When the first and second blanks are attached to the face plates of the first and second housings, the second housing is slid toward the first housing until the pin engages the slot. Switches associated with the electronics are then used to indicate to the electronics that the device is now in the zeroed position. Once zeroing is complete, the second housing can be slid back along the carriage and the pin can be removed. A spring can then be placed over the mandrel and easily tested. The fact that the second housing incorporates three stops allows the spring to be easily tested at three preset angles of deflection.
Another key aspect of the present invention is the use of a replaceable load cell cartridge designed to be interchangeable with other load cell cartridges. This offers significant advantages. First, it broadens the number of applications for which the spring tester can be used. Second, it makes calibration of the load cells much more efficient. For example, the National Association of Spring Testing recommends that load cells be calibrated annually. Prior to the present invention, the whole machine would have to be shipped for calibration, making it unavailable for use for a significant period of time. The present invention allows the owner to merely remove and ship the cartridge. The rest of the machine can continue to be used with a replacement cartridge.
The replaceable load cell cartridges can either be dumb or smart. Dumb cartridges include only a load cell. When calibrated, the performance characteristics are noted in writing so that the user can manually input those characteristics into the machine as part of the cartridge installation process. Smart cartridges include memory and input/output capabilities. Thus, parameters related to the calibration of the cartridge can be stored in memory during the calibration operation and electronically read by the machine. This serves to eliminate the need to manually input these parameters during installation of the cartridge.
Various other advantages and benefits of the present invention will become clear from a thorough reading of the following detailed description of the preferred embodiment in conjunction with the figures provided herewith.
REFERENCES:
patent: 3664182 (1972-05-01), Butler
patent: 3939701 (1976-02-01), Peschl
patent: 4958522 (1990-09-01), McKinlay
patent: 5948994 (1999-09-01), Jen et al.
patent: 6058784 (2000-05-01), Carroll et al.
Dixon, Jr. William R.
Larson David A.
Larson Systems Inc.
Nikolai & Mersereau , P.A.
Noori Max
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