Measuring and testing – Dynamometers – Responsive to multiple loads or load components
Reexamination Certificate
2000-10-18
2002-11-19
Noori, Max (Department: 2855)
Measuring and testing
Dynamometers
Responsive to multiple loads or load components
C073S511000
Reexamination Certificate
active
06481295
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a press machine monitoring facility, and, more particularly, to a method and system for dynamically monitoring the peak compressive and tensile acceleration activity occurring within a press machine to determine an operating condition based upon a comparison of the peak load values to machine-specific capacity levels.
2. Description of the Related Art
Monitoring the load levels within a press machine plays a vital role in properly evaluating the performance of the processing activity to ensure that machine components such as the slide assembly are being operated within acceptable tolerances. The rapid identification of an out-of-bounds operating condition allows corrective action to be immediately undertaken, such as terminating machine operation or adequately adjusting the slide movement. Otherwise, the continued operation of a press machine at above-threshold levels, coupled with the inability to accurately detect the occurrence of load levels that exceed the capacity ratings, may lead to a progressive degradation in the integrity of the workpiece and eventual breakdown of the machine components. Mechanical failures could include the complete shearing or fracturing of individual coupling links in the connection assembly or physical damage to fastening elements such as slide adjustment nuts and connection screws. Complete destruction of the press machine may result if the magnitude of the operating load level exceeds the capacity threshold by a sufficient amount or if the out-of-bounds condition is sustained for a sufficient period of time. Efforts to address this problem have led to the development of various types of monitoring apparatus designed to provide process supervision aimed at detecting when the compression-type forces exhibit load values that exceed predetermined threshold capacity levels.
One conventional approach employs measurement apparatus such as stress/strain gauges configured within the uprights of the press frame structure to measure the vibrational activity present within the machine. Apparatus of this type essentially operate by registering the magnitude of the vibrational energy content occurring over a given period of time such as a press production cycle. These sensors provide a measurement of the dimensional deformation or other such physical disturbances occurring in the press machine. Any changes measured by the strain gauge sensor with respect to the dimensional characteristics of the relevant machine part represent the force or load level that is being developed within the machine at the measurement location.
These sensing devices, however, utilize a form of time-averaging which makes them unsuitable for analyzing low-speed applications and detecting peak load level conditions. The measurement data generated by strain gauge sensors represents the change in vibrational energy content that takes place over a certain measuring interval. Thus, even if a peak load level occurs and is registered by the strain gauge sensor, this event may not be recognizable in the output vibrational energy data due to its summation with other comparatively lower vibrational energy measurements. What then happens, particularly during low-speed applications, is that the measured vibrational energy which corresponds to a peak load level becomes obscured or “smoothed-out” when combined or averaged with the predominantly low levels of vibrational energy content that appear during the rest of the press machine monitoring period. Consequently, although peak load values may occur that exceed the press machine capacity levels, the occurrence of such adverse operating conditions will remain undetected during those monitoring periods where the overall vibrational energy content is sufficiently low such that the generated measurement data indicates an average energy content well below the out-of-bounds level. This presents a particular problem in adequately evaluating low-speed applications that oftentimes include rapid changes in acceleration which typically occur over relatively short time durations, thereby producing a change in the vibrational energy content, that can easily be masked by comparatively lower levels of measured vibrational energy present during other time frames of the monitoring interval.
These conventional sensor devices also do not take into account the different evaluation requirements attending a tensile process and a compression process. Press machines are typically configured so that certain load-bearing components have a higher capacity rating in one direction than the other. For example, saddle bushings and ball bushings are typically designed to provide a level of load-bearing support in the compression direction that is comparatively higher than that provided in the tensile direction. With machines of this type that are designed primarily for compressive applications, the use of the press machine for a tensile application or for an application that requires sufficient tensile acceleration has the potential of creating an operating condition that will lead to parts failure and/or workpiece malformation. Sensor apparatus that rely upon measuring the change in vibrational energy content do not have a mechanism for distinguishing between whether the measurement data is attributable to a compressive-type application or a tensile-type application. The ability to differentiate between these two types of forces has particular importance in those press machines where the compressive and tensile capacity levels vary significantly, requiring a means to incorporate this difference into the evaluation strategy. For example, in a machine having a 200 ton compression capacity rating and a tensile rating representing 10% of the compression capacity, the maximum tensile load level is 20 tons. Current approaches do not provide a facility to distinguish between compression and tensile load level measurements, nor do they incorporate load level capacity data which accurately reflects the different capacity ratings depending upon the force direction, i.e., tensile or compression.
In view of the foregoing, there is a demonstrated need for a facility capable of dynamically identifying the occurrence of adverse operating conditions arising from a compressive and/or tensile force that currently exceeds or may eventually exceed the rated capacity of the press machine.
SUMMARY OF THE INVENTION
According to the present invention there is provided a method and system for evaluating the operating condition of a press machine based upon a comparison between load level capacity data and measurement data representing peak acceleration values of the slide assembly. A measuring device in the form of an accelerometer or other such transducer dynamically generates acceleration signals representing real-time measurements of the acceleration of the slide assembly. These acceleration signals are processed to identify which ones correspond to a peak acceleration condition for the slide assembly. The peak acceleration signals represent peak operating load levels being developed within the press machine. A data means in the form of a storage facility provides load level capacity data which represents the maximum allowable compressive and tensile load levels for the press machine under study. The capacity data is preferably provided in the form of a plurality of press machine operating zones each representing a corresponding range of load values and each having a respective rating factor associated therewith. The rating factor indicates the relationship of the particular press machine operating zone to a respective one of the maximum allowable compressive and tensile load levels. A processor evaluates the peak load levels in relation to the operating zone data to determine which respective ones of the plurality of press machine operating zones encompass each respective one of the peak load levels. The operating condition of the press machine is determined in accordance with the peak operating load levels (a
Knuth Randall J.
Noori Max
The Minster Machine Company
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