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AssigneeIndustrial Sensors, Inc.
InventorsGino A. Pinto, Leif E. Lawhite, Gerard Eggleston, Robert B. Carr, Boruch B. Frusztajer
Estimating the term…
A melt pressure measurement probe for insertion through wall of melt-containing vessel has a pressure-deflectable end portion for contact with pressurized melt. Pressure-resistant securing means fixes the end surface in a non-flow obstruction relationship. A seal surface on the probe prevents exposure of the melt to the securing means. Pressure detection means internal of the probe, responsive to deflection of the probe end surface to detect melt pressure, comprises a temperature-compensated capacitive sensor, one capacitor plate defined by the end portion and an opposite capacitor plate in the probe with a capacitive gap in-between. Electronic circuitry remote from the melt-exposed end, including circuitry within the probe to generate a signal proportional to the capacitance, compensates for change of temperature of the capacitor to generate an output signal proportional to melt pressure.
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.
A pressure measurement device comprising a probe having a pressure-deflectable end surface and pressure detection means internal of the probe, responsive to deflection of the end surface of the probe, for detecting pressure, said pressure detection means comprising a capacitive sensor having, effectively, a capacitor, one plate of the capacitor defined by the end surface of the probe, the opposite plate of said capacitor mounted within the probe in spaced relation to said end surface, a capacitive gap being defined by said end surface and said opposite plate, means for detecting the temperature of said end surface, and electronic circuitry remote from said end surface and connected to said capacitor in a manner to generate an output signal that is linearly proportional to pressure, said circuitry including means for storing a plurality of pressure versus capacitance and temperature data that is characteristic of the device, means for generating a first signal based on the capacitance of said capacitive sensor, means for generating a second signal based on the temperature of said end surface, and means for generating said output signal using said first and second signals with a predetermined functional relationship between capacitance, temperature, and pressure, wherein said electronic circuitry further comprises means for generating a linearization signal based on said first and second signals, said linearization signal indicating the difference between said first signal, as it relates to the measured capacitance of said capacitive sensor, and the desired linearized output signal, and means for adding said linearization signal to said first signal to produce said output signal, whereby said output signal is linearly proportional to the melt pressure.
Dependencies are inferred from the claim text.
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Transmitting or indicating the displacement of flexible diaphragms: using variations in capacitance
By making use of variations in capacitance , i.e. electric circuits therefor: with temperature compensating means
Details of, or accessories for, apparatus for measuring steady or quasi-steady pressure of a fluent medium insofar as such details or…
Measuring force, stress, torque, work, mechanical power, mechanical efficiency, or fluid pressure
Term ended 14 Dec 2013 (estimated)
USPTO file history isn’t available for this patent, so only indexed dates are shown.
This invention relates to pressure transducers.
In a key respect, the invention relates to melt pressure measurement of plastically deformable materials, for example, synthetic resins, pastes, slurries, and food substances. Plastic materials such as these are melted or mixed and then extracted or injection molded to form solid objects such as injection molded parts, extruded shapes, fibers, extruded film, and shaped food stuffs. During the process, the material is typically heated to a desired temperature, which may range as high as 1000.degree. F., and worked under a desired pressure, which may range as high as 20,000 or 30,000 psi or higher.
It is important to accurately measure the pressure of the material while it is processed in both manufacturing and laboratory settings. In rheological studies, for example, the mixing, flow, viscosity, and separation properties of the plastic material being extruded through a vessel are all detected and analyzed as a function of the melt pressure of the material within the vessel. In manufacturing applications, the melt pressure of the material being extruded or injection molded is monitored for quality control of the process parameters as well as to guard against dangerous conditions resulting from equipment malfunction.
This invention is pointed out with particularity in the appended claims. The above and further advantages of this invention may be better understood by referring to the following description of a preferred embodiment taken in conjunction with the accompanying drawings, in which:
FIG. 1a is a diagrammatic illustration of a prior art extrusion system.
FIG. 1b is a side view of a prior art melt pressure transducer.
Referring to FIG. 2a, the melt pressure capacitive transducer 30 of the preferred embodiment includes a multi-sectional housing, consisting of a circular diaphragm cap 32 having an integral diaphragm 33 at its end, a hollow, cylindrical connecting body 34, referred to as a "snout tip", a hollow, cylindrical extension rod 36 mechanically connected to the connecting body 34, and an electronics housing 38.
Also referring to FIGS. 2b and 2c, the transducer housing is designed to threadably mount within a standard extruder barrel aperture 11 of an extruder barrel assembly 12. As shown in FIG. 2b, multiple transducers 10 are installed along the length of the barrel, each providing, e.g., process control monitoring or safety checks. The extruder barrel aperture typically has a 0.375 inch-wide opening into the extruder bore 46 and includes a 2 to 4 inch-thick steel extruder barrel 44, a surrounding 0.5 inch-thick heater band 42 and a 2 inch-thick layer of insulation 40. The extruder barrel 44, has an inner surface which defines the extruder bore 46. The bore 46, having a diameter between 1 inch and 6 inches, which surrounds a driven extruder screw; the screw works the semi-molten material under high pressure and delivers it in melted form to an outlet such as an extruder die.
Outer threads 50 on the transducer snout tip 34 engage with corresponding mounting threads in the extruder aperture 11 when the transducer is rotated down into the extruder aperture. When the beveled edge surface 54 of the snout tip seals properly on a mating surface of the extruder barrel, the radial position of the diaphragm 33 on the end of the diaphragm cap 32 is tangent with the inner wall of the barrel bore 46. This seating edge surface 54, provides the seal against the corresponding edge in the aperture 11, which, in addition to limiting the transducer's inward travel, prevents escape of the melt around the transducer housing to the threads. Precise positioning of the transducer diaphragm is necessary because protrusion of the diaphragm into the barrel bore would subject it to abrasive wear by the melt and possible damage by the passing extrusion screw, while excessive recession would provide a space in which material could stagnate, degrade, and harm the process as well as the diaphragm itself. If necessary, a shim of some appropriate material may be sandwiched between the two seating surfaces to act as a spacer for backing off the transducer diaphragm from the barrel bore to the proper position.