Sonic measurement of web tension
First Claim
Patent Images
1. A method of measuring web tension of a moving paper web, comprising the steps of:
- moving the paper web along a path and measuring the web speed;
applying ultrasonic vibrations to the moving paper web at a first location along the path to produce transverse waves on the paper web, including generating an electrical signal at an ultrasonic frequency and applying the electrical signal to an ultrasonic transducer at the first location;
sensing the interval between the application of the ultrasonic vibrations at the first location and the sensing of the transverse waves at the second location to determine the wave propagation velocity, including testing whether the reception time measured from the beginning of ultrasonic application falls within an interval between a minimum time and a maximum time, rejecting all measurements not within the time interval, algebraically adding the web travel time between the first and second locations as a velocity correction representing web tension.
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Abstract
Tension in a moving web is measured by subjecting the web to an ultrasonic pulse train and measuring the time interval for the resultant transverse waves in the web to proceed a known distance past a point upstream (or downstream). The composite web plus wave velocity is calculated and the web travel time is added (or subtracted) to obtain wave velocity which is related to tension in accordance with the equation T=a2 w/gc, where T=web tension, a=wave velocity, w=mass per unit area and gc =lb mass ft/lb force sec2 conversion factor.
20 Citations
10 Claims
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1. A method of measuring web tension of a moving paper web, comprising the steps of:
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moving the paper web along a path and measuring the web speed; applying ultrasonic vibrations to the moving paper web at a first location along the path to produce transverse waves on the paper web, including generating an electrical signal at an ultrasonic frequency and applying the electrical signal to an ultrasonic transducer at the first location; sensing the interval between the application of the ultrasonic vibrations at the first location and the sensing of the transverse waves at the second location to determine the wave propagation velocity, including testing whether the reception time measured from the beginning of ultrasonic application falls within an interval between a minimum time and a maximum time, rejecting all measurements not within the time interval, algebraically adding the web travel time between the first and second locations as a velocity correction representing web tension. - View Dependent Claims (2, 3, 4)
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5. Apparatus for measuring web tension of a moving paper web, comprising the steps of:
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means for moving the paper web along a path and means for measuring the web speed; means for applying ultrasonic vibrations to the moving paper web at a first location along the path to produce transverse waves, including means for generating an electrical signal at an ultrasonic frequency, an ultrasonic transducer, and means for applying the electrical signal to said ultrasonic transducer at the first location; means for sensing the transverse waves at a second location along the path; and means for timing the interval between the application of the ultrasonic vibrations and the sensing of the transverse waves to determine the wave propagation speed relative to the web, including means for testing whether the reception time measured falls within a time interval between a minimum time and a maximum time, means for rejecting all measurements not within the time interval, means for algebraically adding the web velocity to obtain wave velocity and using the wave velocity relative to the web to calculate web tension. - View Dependent Claims (6, 7, 8)
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9. Apparatus for measuring web tension of a moving paper web, comprising:
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first means for measuring the web speed and producing a representative first electrical signal, including a rotating roll supporting the paper web and a tachometer connected to said roll and producing said first electrical signal; second means located adjacent a first web location and operable to energize the paper web with ultrasonic vibrations causing transverse waves along the moving paper web, including an electro/sonic transducer mounted adjacent the paper web; third means located adjacent the paper web and spaced from said second means along the path of web travel for sensing the transverse waves, including a microphone located adjacent the paper web for picking up web vibrations; and fourth means for measuring the time between energization of the paper web with ultrasonic vibrations and the sensing of the transverse waves and providing a second electrical signal, including a microprocessor having an oscillator connected to drive said second means, and connected to said third means and operable to compute the time interval of passage of the transverse wave on the paper web between said second and third means and constituting fifth means for calculating web speed with respect to a fixed position, sixth means for algebraically adding the web speed with respect to fixed coordinates to obtain wave speed relative to the paper web, and seventh means for converting wave speed into units of web tension.
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10. A method of determining the tension in a traveling web, comprising the steps of:
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subjecting the web to an ultrasonic blast at a first location to generate transverse waves in the web; starting a timer at the initiation of the ultrasonic blast; receiving the transverse waves at a second location and converting the same to electrical signals; applying the electrical signals to stop operation of the timer; calculating the wave plus web velocity relative to a fixed position from the elapsed time posted by the timer; algebraically adding the web speed and the web plus wave velocity relative to fixed coordinates to obtain the wave velocity of the transverse waves relative to the web; and converting the wave velocity into tension units and displaying the same.
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Specification