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Capacitive melt pressure measurement with center-mounted electrode post

  • US 5,492,016 A
  • Filed: 12/14/1993
  • Issued: 02/20/1996
  • Est. Priority Date: 06/15/1992
  • Status: Expired due to Fees
First Claim
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1. A melt pressure measurement device for measuring the pressure of a melted substance useful in cooled state for forming solid objects, the device comprising a probe for insertion through an aperture in a wall of a melt-containing vessel, the probe having a pressure-deflectable end portion for contact with pressurized melt, pressure-resistant securing means associated with said device for fixing the device in the wall with said end portion of the probe exposed for contact with the melt in a non-flow obstructive relationship, and a seal surface on said probe between said end portion of the probe and the securing means, for cooperative sealing action with a mating sealing means associated with the wall to prevent exposure of said melt to said securing means, and pressure detection means internal of the probe, responsive to deflection of the end portion of the probe, for detecting pressure of said melt, said pressure detection means comprising a temperature-compensated capacitive sensor having, effectively, a capacitor, one plate of the capacitor defined by the end portion of the probe exposed to the melt, the opposite plate of said capacitor mounted within the probe in spaced relation to said end portion, a capacitive gap being defined by said end portion and said opposite plate, and electronic circuitry remote from the melt-exposed end portion of the probe and connected to said capacitor in a manner to compensate for change of temperature effects on the capacitor and to generate an output signal proportional to said melt pressure, said electronic circuitry comprising circuitry means mounted within a portion of the probe to generate a signal proportional to the capacitance of said capacitive sensor and wherein said pressure-deflectable end portion of said probe at a center region has a connection member, a peripheral outer region of said end portion of the probe being substantially undeflected by said melt pressure, and thereby substantially fixed from translating as compared to the center region of said end portion of the probe, which translates axially in response to said melt pressure, said outer region of the end portion of the probe forming said one plate of said capacitor, and said opposite plate of said capacitor comprises a rigid disk having a first face joined at its center to said connection member, a conducting region on said first face, located radially outward of said connection member, forming said capacitor with said outer region of the end portion of the probe.

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