WO2000066993A1

WO2000066993A1 - Apparatus and method for measuring fluid properties

Info

Publication number: WO2000066993A1
Application number: PCT/US2000/011338
Authority: WO
Inventors: Paul S. Oliver
Original assignee: Dynisco Polymer Test Inc
Current assignee: Dynisco Polymer Test Inc
Priority date: 1999-04-29
Filing date: 2000-04-27
Publication date: 2000-11-09
Anticipated expiration: 2001-10-29
Also published as: AU4496300A

Abstract

An apparatus (10) for measuring a selected property of a fluid (15) flowing through a master flow channel (20), the apparatus comprising a tube (30) sealably connected to a port in the master flow channel and sealably connected to a sensor (100); the tube having a first upstream tube channel (42) and a second downstream tube channel (42) which are connected to each other such that fluid flows sequentially from the master flow channel through the port, the first tube channel, the second tube channel and back through the port into the master flow channel.

Description

APPARATUS AND METHOD FOR MEASURING FLUID PROPERTIES

This application claims the benefit of prior filed copending provisional application entitled, "Apparatus For Measuring Fluid Properties," Serial No. 60/131,572 filed April 29, 1999.

Background

The present invention relates to methods and apparati for measuring properties of a fluid flowing through a flow channel and, more particularly, to apparati/methods which measure properties such as viscosity, temperature, flow rate, pressure, density and the like of polymer materials being routed in fluid form through a barrel, tube, manifold, nozzle, cavity or other flow channel under high pressure such as in extruder and injection molding machines.

Summary of the Invention

In many, if not most, industrial processes for processing/converting fluids such as molten plastics and other fluids or polymers generally (e.g. chocolate mixes), implementation of the process requires measurement, monitoring or determination of various properties of the fluid which flows through the main barrel or other feed channels of the machine including properties such as viscosity, temperature, pressure, density and the like. Conventional measuring mechanisms utilize a connection of the measuring sensor or device via a fluid output port or aperture in the master flow channel to a sensor or measure mechanism and a return fluid path from the sensor/measure mechanism to the master flow channel of the master apparatus via a separate flow path and a separate port or aperture in the master flow channel. The present invention provides an apparatus and method for removing and returning a stream of the fluid to be measured through a single port in the flow channel of the master processing apparatus and preferably via a single flow path to and from the flow channel. The present invention also provides a fluid flow connector to and from a master flow channel and a fluid property measuring device or sensor, and a method and apparatus for performing a measurement of a fluid property and for using the measured property to control a processing operation or condition. In preferred embodiments, a sensor having a set of gears driven by a common drive shaft (which is in turn driven by a common motor) is connected via a hollow tubular connector to a single port in the master flow channel of a fluid processing apparatus. One or more of the commonly driven sets of gears is driven so as to direct a flow of the fluid to the sensor and other ones of the commonly driven set of gears are driven so as to direct the flow of fluid back into the master flow channel through the single port. The fluid flow connector comprises a tube having one end connected/ interconnected to the single port in the master flow channel and another end connected/ interconnected to the sensor apparatus. The connector tube has at least two separate flow channels and typically comprises a first pipe disposed within a second pipe or a single tube subdivided by a barrier which sealably separates the interior of the tube into at least two separate flow channels.

The rate of input flow from the master channel through the connector to the sensor is typically slightly less than the rate of output flow from the sensor through the channel back to the master channel and the subsets of flow control gears or other pumping controls are typically configured for achieving such differential flow rates. The measured and/or sensed properties of the fluid (e.g. viscosity, pressure, temperature and the like) may be input into a computer controlled program or algorithm to generate/calculate selected values (e.g. viscosity calculated from pressure, temperature and the like) or, such measured/calculated/sensed values may be input into a PID (proportional, integral derivative) control mechanism for automatically controlling, maintaining, setting and/or selecting selected operating parameters of the polymer processing such as flow rate, temperature and the like according to the measured/sensed property, i.e. using the value of the sensed/measured property as a variable in an algorithm/program which generates signals which control other operations and operational components of the fluid processing machine and process.

In accordance with the invention therefore, there is a provided an apparatus for measuring a selected property of a fluid flowing through a master flow channel, the apparatus comprising: a tube sealably connected to a port in the master flow channel and sealably connected to a sensor; the tube having a first upstream tube channel and a second downstream tube channel which are connected to each other such that fluid flows sequentially from the master flow channel through the port, the first tube channel, the second tube channel and back through the port into the master flow channel.

The apparatus preferably includes a fluid flow controller which routes a portion of the flow of the fluid from the master channel through the tube. The fluid flow controller routes the fluid from the master flow channel through the first upstream tube channel at a first flow rate and through the second downstream channel back into the master flow channel at a second flow rate, the first flow rate being less than the second flow rate.

The tube typically comprises a first hollow pipe disposed within a second hollow pipe and has a first flow channel and a second flow channel.

The fluid flow controller typically comprises a first fluid flow drive mechanism and a second fluid flow drive mechanism, each fluid flow drive mechanism being disposed within the flow of fluid through the tube and being driven at a different rate by a common drive mechanism.

Further in accordance with the invention there is provided a method for measuring a selected property of a fluid flowing through a master flow channel, the method comprising: routing a portion of the flow of the fluid from the master flow channel in one direction through a first channel in a tube sealably connected at one end to a port in the master flow channel and sealably connected at another end to a sensor; measuring a selected property of the fluid with the sensor; and, routing the flow of fluid from the first channel in a direction opposite to the first direction through a second tube channel in the tube through the port back into the master flow channel.

Brief Description of the Drawings The invention is described below with reference to the following figures which depict embodiments of the invention but is not limited to such embodiments.

Fig. 1 is a side schematic view of an apparatus and method according to the invention; Fig. 2 is an exploded isometric view of an apparatus according to the invention showing a typical connection to a master fluid flow channel of a polymer processing machine;

Fig. 3 is a side, close-up partial cross-sectional of certain components of the Fig. 2 apparatus which connect into the master flow channel of the polymer processing machine;

Fig. 4 is a side schematic isometric view of an alternative embodiment of a dual channel tube component of an apparatus according to the showing a tube divided into two channels by a barrier or plate. Detailed Description of The Invention

Figs. 1-2 show a fluid flow routing and measuring apparatus 10 attached to the barrel 20 of a material processing machine (not shown) such as an injection molding machine or an extruder through which a fluid flow 15 of a selected material is flowing under elevated pressure and temperature, typically a polymer which is convertible to fluid at elevated temperature and pressure such as a polyolefins, polycarbonates, polyamides, polyesters, thermoplastic elastomers, polystyrenes, chocolate mixes, polymer solutions (i.e. solutions that are liquid at room temperature) and the like. The apparatus 10 is sealably interconnected to the barrel 20 via a master pipe or tube 30 which has a secondary pipe or tube 40 disposed within the master tube 30 for routing or siphoning off a relatively small stream 50 in one direction out of the path of the main stream 15 and eventually back in the opposite direction as a return stream 60 into the main process stream 15. As shown, the two tubes 30, 40 are sealably connected to the wall 70 of the barrel 20 through a single aperture or port 75 in the wall of the barrel 20. The sealed interconnection is effected in a conventional manner depending on the materials of which the wall 70 of the barrel and the tube 30 are comprised, typically in the case of metal materials, typically in the case of metal materials, a face sealed screwed in connection 57, Fig. 3, is employed although welding, brazing and other common fluid sealing attachment methods may be utilized. The siphoned off stream 50 flows through the hollow channel of the inner tube 40 the end of which communicates with the main flow stream 15, and the return stream 60 flows separately through the unoccupied portion or annular section 32 of the tube 30, both the siphoned off 50 and return 60 streams thus flowing/travelling through a single port 75 in the barrel 20 of the processing machine. As can be readily imagined, the shape/geometry of the tubes 30, 40 may be of any desired configuration, e.g. in cross section - circular, rectangular, square, triangular, as selected by the user, and may be rigid or flexible as selected by the user. Typically the tubes/pipes 30, 40 comprise high grade, high strength rigid metal materials which are resistant to deformation and corrosion when subjected to elevated temperatures and pressures as required in typical materials processing operation such as injection molding and extrusion.

In the embodiment shown in Figs. 1-3, the apparatus 10 comprises an enclosed, fluid sealed passage 105 configured within a spatially compact housing which is readily mountable on the outside surface of a barrel or other channel 20 via the single port or aperture 75. In the embodiment shown in Figs. 2-3, the outer surface of tube 40 has spacer ribs 200, Fig. 3, projecting from the outer surface which serve to mount tube 40 securely within the inner cavity of tube 30 and to establish/maintain the integrity of the outflow channel 32 between the outer surface of tube 40 and the inner surface of tube 30. In the embodiment shown in Fig. 4, the dual inflow and outflow channels in tube 30 are formed via a plate or barrier 37 which divides the interior of tube 30 into two separate channels, the inflow 50 and outflow 60 channels.

As shown in Figs. 1-3, two pair of precision gears 80, 90 are disposed in the path of flow 105 of the fluid flowing through the apparatus 10. The two sets of gears 80, 90 are both commonly driven by a single servo-motor 100 although each set of gears may be driven by separate motors as an alternative. The intake set of gears 80 are disposed in a fluid sealed housing 82 which is positioned upstream in the flow path of the siphoned off stream relative to another fluid sealed housing 92 in which the second set of driven gears 90 are disposed. The driven sets of gears 80, 90 thus act as a pump to force the siphoned off/redirected fluid stream from the master channel of the barrel to flow 106 through the fluid path(s) 105 of the apparatus 10 and back into the main stream 15 of master tube or barrel 20.

The teeth of each set of gears 80, 90 are configured such that the teeth receive fluid and drive the fluid in a forward direction 106 through the fluid flow path 105 of the routing/measuring apparatus 10 as the gears are drivably rotated by motor 100. In a preferred embodiment the teeth of gears 80 and gears 90 each have a different selected volume or capacity for receiving fluid. In a most preferred embodiment, the teeth of the downstream set of gears 90 have a greater fluid receiving volume than the upstream set of gears 80 such that flow rate generated by gears 90 is greater than the flow rated generated by gears 80 and the apparatus is thus assured of not having a fluid pressure build up within the flow path 105 of the apparatus 10. As can be readily imagined any conventional high performance fluid pump mechanism(s) may be employed as an alternative to gear pumps 80, 90 such pumps having a structural integrity sufficient to withstand the high pressure and temperature of the fluid being rerouted from the main stream 15 of the main channel 20, such fluid pressures typically ranging between about 0 and about 500 psi and fluid temperatures ranging between about 25° Centigrade and about 400° Centigrade in extrusion and injection molding processes. Metering pumps are most preferably used as the pump mechanism, e.g. pump 80 and/or 90, in an apparatus according to the invention, typical examples of metering pumps being gear pumps and screw pumps.

The gear pumps 80, 90 may alternatively have the same fluid receiving volume/capacity or, also alternatively, gears 80 may have a greater fluid receiving volume/capacity than gears 90. In such cases, the downstream gears 90 or other selected pump is driven at a faster selected rate than the upstream gears 80 or pump such that the flow rate generated by the downstream pump is assured of being greater than the flow rate generated by the upstream pump so that a pressure buildup within the flow path 105 of the apparatus 10 is assured of being avoided. As shown in the Figs. 1-3 embodiment, the path of the fluid exiting pump 80 leads to/through a channel 110 of predetermined length and volume having a pair of pressure transducers 120, 130 positioned at opposite ends of the channel 110. A temperature sensor 125 is positioned at a selected position within the flow path of the fluid, preferably within or near the channel 110 so as to sense a fluid temperature that is as close to the temperature of the fluid flowing between the transducers 120, 130 as possible. The pressure transducers 120, 130 record/sense the pressure of the fluid at each end of the channel 1 10 and the sensed pressure data and/or sensed temperature data is input into an algorithm of a processor (not shown) which calculates the melt index or viscosity of the fluid and displays a value therefor to the user of the machine. The determined/calculated viscosity value, and/or the sensed pressure, temperature, or other selected sensed property, may also separately be utilized as a variable input to another algorithm of a data processor or computer 140 which is interconnected to and controls the drive or other control mechanisms used to drive, operate or control other operating components of the processing machine, e.g. drive motors 210 for components such as for an injection screw of an extruder or injection molding machine (e.g. for controlling the drive or on off/start/stop operation or the screw speed/rotation), or the drive mechanisms 220 for actuators for valves which may control the on/off operation or flow rate of fluid being distributed or injected, or for controlling the voltage or current inputs 230 to heaters which may be used to heat injection fluid or other machine components which are in contact with and control the temperature of the fluid.

As can be readily imagined, a sensor for detecting a selected property of the fluid may be positioned at any position along or within the flow path 105 of the fluid such that the fluid flows past the sensor or the operative component of the sensor otherwise interacts with, views or touches the fluid 106 flow past or through the sensor, e.g. the tip end of a temperature or pressure sensor contacts the fluid, or the emitted beam of a photoemitting sensor interacts with the fluid flow such that the beam is altered by the fluid flow.

Control of the operation of the servomotor 100 may also be effected via an algorithm or computer program which causes the motor 100 to adjust the flow rate according to any predetermined program. The apparatus 10 may also be operated with a single pump as opposed to dual pumps 80, 90, whereby a pressure buildup within channel 105 is avoided.

The polymer material is typically a solid at room temperature which is liquified by the processing machine, e.g. by shear forces created by the main barrel screw and/or by heaters arranged throughout various components of the processing machine. The polymer material may also be a liquid or in liquid solution form at room temperature.

Claims

1 Apparatus for measuring a selected property of a fluid flowing through a master flow channel, the apparatus comprising: a tube sealably connected to a port in the master flow channel and sealably connected to a sensor; the tube having a first upstream tube channel and a second downstream tube channel which are connected to each other such that fluid flows sequentially from the master flow channel through the port, the first tube channel, the second tube channel and back through the port into the master flow channel.

2. The apparatus of claim 1 further comprising a fluid flow controller which routes a flow of the fluid from the master channel through the tube.

3. The apparatus of claim 2 wherein the fluid flow controller routes the fluid from the master flow channel through the first upstream tube channel at a first flow rate and through the second downstream channel back into the master flow channel at a second flow rate, the first flow rate being less than the second flow rate.

4. The apparatus of claim 1 wherein the tube comprises a first hollow pipe disposed within a second hollow pipe.

5. The apparatus of claim 1 wherein the tube comprises a hollow tube having a first flow channel and a second flow channel.

6. The apparatus of claim 2 wherein the fluid flow controller comprises a first fluid flow drive mechanism and a second fluid flow drive mechanism, each fluid flow drive mechanism being disposed within the flow of fluid through the tube.

7. The apparatus of claim 2 wherein the fluid flow controller comprises a first fluid flow drive mechanism and a second fluid flow drive mechanism, each fluid flow drive mechanism being disposed within the flow of fluid through the tube and each fluid flow drive mechanism driving the fluid at a different predetermined rate of flow in the same direction through the tube.

8. The apparatus of claim 7 wherein the first fluid flow drive mechanism is disposed within the path of flow of the fluid within the tube at a position upstream of a position at which the second fluid flow drive mechanism is disposed, the first fluid flow drive mechanism being driven at a rate such that the rate of fluid flow through the first fluid flow drive mechanism is less than the rate of fluid flow through the second fluid flow drive mechanism.

9. The apparatus of claim 6 wherein the first and second fluid flow drive mechanisms are driven by a common drive mechanism.

10. Apparatus for measuring a selected property of a fluid flowing through a master flow channel, the apparatus comprising: a tube sealably connected at one end to the master flow channel and sealably connected at another end to a sensor; the tube having a first tube channel wherein fluid flowing through the master channel travels through the first tube channel to the sensor; the tube having a second tube channel communicating with the first fluid channel wherein the fluid flowing through the first tube channel travels downstream through the second tube channel back into the master flow channel.

11. The apparatus of claim 10 wherein the tube comprises a first hollow pipe disposed within a second hollow pipe.

12. The apparatus of claim 10 wherein the tube comprises a hollow tube having a first flow channel and a second flow channel.

13. The apparatus of claim 10 wherein the one end of the tube is sealably connected to a single fluid flow port in the master channel.

14. The apparatus of claim 10 further including a fluid flow controller disposed within a path of travel of the fluid within the tube.

15. The apparatus of claim 14 wherein the fluid flow controller comprises a first fluid flow drive mechanism and a second fluid flow drive mechanism, each fluid flow drive mechanism being disposed within the flow of fluid through the tube.

16. The apparatus of claim 14 wherein the fluid flow controller comprises a first fluid flow drive mechanism and a second fluid flow drive mechanism, each fluid flow drive mechanism being disposed within the flow of fluid through the tube and each fluid flow drive mechanism driving the fluid at a different predetermined rate of flow in the same direction through the tube.

17. The apparatus of claim 16 wherein the first fluid flow drive mechanism is disposed within the path of flow of the fluid within the tube at a position upstream of a position at which the second fluid flow drive mechanism is disposed, the first fluid flow drive mechanism being driven at a rate such that the rate of fluid flow through the first fluid flow drive mechanism is less than the rate of fluid flow through the second fluid flow drive mechanism.

18. The apparatus of claim 15 wherein the first and second fluid flow drive mechanisms are driven by a common drive mechanism.

19. The apparatus of claim 16 wherein the first and second fluid flow drive mechanisms are driven by a common drive mechanism.

20 Method for measuring a selected property of a fluid flowing through a master flow channel, the method comprising: routing a portion of the flow of the fluid from the master flow channel in one direction through a first channel in a tube sealably connected at one end to a port in the master flow channel and sealably connected at another end to a sensor; measuring a selected property of the fluid with the sensor; routing the flow of fluid from the first channel in a direction opposite to the first direction through a second tube channel in the tube through the port back into the master flow channel.

21. The method of claim 20 further comprising routing the portion of the flow from the master flow channel through the first channel of the tube at a flow rate which is different from the rate of flow through the second channel of the tube.

22 The method of claim 21 wherein the flow rate through the first channel is less than the flow rate through the second channel.

23. The method of claim 20 wherein the flow of fluid through the first and second channels is driven by a common drive mechanism.

24. The method of claim 21 wherein the flow of fluid through the first and second channels is driven by a common drive mechanism.

25. The method of claim 22 wherein the flow of fluid through the first and second channels is driven by a common drive mechanism.