Impact flowmeter for solids

• US 5,698,794 A
• Filed: 12/19/1995
• Issued: 12/16/1997
• Est. Priority Date: 12/19/1995
• Status: Expired due to Fees

• Current Assignee: Endress + Hauser Inc.
• Original Assignee: Thermo Sentron, Inc. (Thermo Fisher Scientific Incorporated)
• Inventors: Bussian, Gerhard
• Primary Examiner(s): Dombroske, George M.
• Assistant Examiner(s): THOMPSON, JEWEL VERGIE
• Application Number:
  US08/574,767
• Time in Patent Office: 728 Days
• Field of Search: 73/861.73, 73/861.05, 73/861.04, 248/317, 248/581
• US Class Current: 73/861.73
• CPC Class Codes: G01F 1/30 for fluent solid material
• CPC Class Codes: G01F 1/708 Measuring the time taken to traverse a fixed distance

Abstract

An impact flowmeter (10) for measuring a stream of free flowing bulk solids (60) having low mass flow rates. The flowmeter (10) includes a barrier (18) between the flowing stream of solids (60) and the sensor chamber (16). A primary sensing element (48) includes an impact plate (50) positioned to lie in flow chamber (14). A velocity sensor (39) is mounted to an inlet chute (32) for providing a velocity output signal (284) in response to the velocity of the solids in the stream of solids (60) as the stream of solids (60) passes the velocity sensor (39). The velocity sensor (39) includes a velocity circuit (278), a first capacitance sensor (41) and a second capacitance sensor (43) mounted to the side wall of the inlet chute (32) and arranged so that the solids in the stream of solids (60) pass by the first capacitance sensor (41) before passing by the second capacitance sensor (43). The velocity can then be computed as the predetermined distance divided by the travel time of the solids across the predetermined distance. A secondary sensing mechanism (92) includes a frame (94) having a horizontal plate (96) that is formed to include a circular opening (88). The plate (96) is formed to include the opening (88) to provide a space within the perimeter of the plate (96) for receiving an L-shaped arm (98) while also mimimizing the mass of the frame (94), thereby maximizing the sensitivity of the impact flowmeter (10).

Claims

1. An impact flowmeter for measuring the flow rate of solids flowing in a stream of flowing solids, the impact flowmeter comprising

a housing having an inlet, an outlet, and an interior region therebetween, the housing being positioned so that the stream flows into the inlet and out through the outlet,

an impact sensing assembly received by the interior region of the housing and including an impact plate engaging the solids and configured to move relative to the housing in a measurement direction in response to the impingement of the solids on the impact plate, transducer means fixed relative to the housing for providing an output signal in response to the movement of the impact plate, and a frame having a first end engaging the impact plate and a second end engaging the transducer means so that the frame communicates the movement of the impact plate to the transducer means, and

a cable suspension including a plurality of cables coupling the housing to the frame, the cable suspension suspending the frame between the impact plate and the transducer means for movement of the frame.

2. The impact flowmeter of claim 1, wherein the measurement direction is perpendicular to a plane and the cable suspension includes a cable coupled to the frame and coupled to the housing, the cable being substantially parallel to the plane.

3. The impact flowmeter of claim 2, wherein the cable and the plane cooperate to define an angle between -5 and 5 degrees.

4. The impact flowmeter of claim 1, wherein the measurement direction is perpendicular to a plane and the cable suspension includes a first cable and a second cable, each of the first and second cables having a first end coupled to the frame and a second end coupled to the housing, the first cable cooperating with the plane to define an angle between -5 and 5 degrees and the second cable cooperating with the plane to define an angle between -5 and 5 degrees so that the first and second cables permit movement of the frame in a direction perpendicular to the plane.

5. The impact flowmeter of claim 4, wherein the first and second cables cooperate to define an angle between 30 and 40 degrees relative to a vertical plane that is parallel to the measurement direction.

6. The impact flowmeter of claim 4, wherein the first and second cable cooperate to define an angle between 130 and 160 degrees.

7. The impact flowmeter of claim 4, wherein the first and second cables cooperate to define a V-shaped cable suspension to restrict movement of the frame in directions other than the measurement direction.

8. The impact flowmeter of claim 1, wherein the housing includes a base plate positioned to lie in front of the deflection sensing assembly and a plurality of posts attached to the base plate and extending rearwardly therefrom, the posts defining a cage surrounding the frame, the cable suspension being coupled to the cage and coupled to the frame.

9. The impact flowmeter of claim 8, wherein the cable suspension includes a plurality of cables, each cable having a first end coupled to one of the posts and a second end coupled to the frame, each post being coupled to two cables.

10. The impact flowmeter of claim 1, wherein the housing further includes a base plate formed to include an opening, the impact plate being positioned to lie in front of the base plate and including a rearwardly extending stem that extends through the opening, the frame being positioned to lie behind the base plate and being coupled to the stem.

11. The impact flowmeter of claim 10, wherein the housing further includes a plurality of posts connected to the base plate and extending rearwardly therefrom, a first post and a second post being positioned to lie above the frame and a third post and a fourth post being positioned to lie beneath the frame, the cable suspension being coupled to the first, second, third, and fourth posts and coupled to the frame.

12. The impact flowmeter of claim 11, wherein the cable suspension includes a first cable coupling the first post to the frame, a second cable coupling the second post to the frame, a third cable coupling the third post to the frame, and a fourth cable coupling the fourth post to the frame, the measurement direction is substantially perpendicular to a first plane, and the first, second, third, and fourth cables are substantially parallel to the first plane, and are configured to restrict movement of the frame in directions other than the measurement direction.

13. The impact flowmeter of claim 1, wherein the frame is magnetically coupled to the housing.

14. The impact flowmeter of claim 13, further comprising a permanent first magnet fixed relative to the frame and a permanent second magnet fixed relative to the housing, the first and second magnets being in magnetic communication to resist movement of the first magnet relative to the second magnet.

15. The impact flowmeter of claim 14, further comprising a second deflection sensing assembly coupled to the housing and including a second transducer means, a secondary sensing element, and a second frame having a first end engaging the secondary sensing element and a second end coupled to the second transducer means so that the second frame communicates deflections of the secondary sensing element to the second transducer means, a third permanent magnet fixed relative to the second frame and a fourth permanent magnet fixed relative to the housing, the third and fourth permanent magnets being in magnetic communication to resist movement of the third magnet relative to the fourth magnet.

16. The impact flowmeter of claim 1, further comprising dampening means for resisting movement of the frame relative to the housing.

17. The impact flowmeter of claim 16, wherein the dampening means includes a spring having a first end coupled to the frame and a second end coupled to the housing to yieldably bias the frame toward the impact plate.

18. The impact flowmeter of claim 16, wherein the dampening means includes an air cylinder acting between the frame and the housing to yieldably bias the frame toward the impact plate.

19. The impact flowmeter of claim 1, further comprising a velocity sensor supported in fixed relation to the housing and configured to provide a velocity output signal in response to the velocity of solids in the stream of flowing solids.

20. The impact flowmeter of claim 19, wherein the velocity output signal is in response to the velocity of solids in the stream of flowing solids between the inlet and the impact plate.

21. The impact flowmeter of claim 19, further comprising a flowmeter output circuit that provides a flowmeter output that varies with the mass flow rate of solids in the stream of flowing solids in response to the output signal from the transducer and the velocity output signal.

22. The impact flowmeter of claim 19, wherein the velocity sensor includes a first capacitance sensor.

23. The impact flowmeter of claim 22, wherein the velocity sensor further includes a second capacitance sensor spaced apart from the first capacitance sensor a predetermined distance and the velocity is computed as the predetermined distance divided by the time that solids travel between the first and second capacitance sensors.

24. An impact flowmeter for measuring the flow rate of solids in a stream of flowing solids, the impact flowmeter comprising

a housing having an inlet and an outlet, the housing being positioned so that solids flow into the inlet and out through the outlet,

an impact sensing assembly coupled to the housing and including an impact plate engaging the solids and configured to move relative to the housing in a measurement direction in response to the impingement of solids on the impact plate, transducer means fixed relative to the housing for providing an output signal in response to the movement of the impact plate, and a frame having a first end engaging the impact plate and a second end engaging the transducer means, and

cable means for supporting the frame between the impact plate and the transducer means so that the frame communicates the movement of the impact plate to the transducer means, the cable means being coupled to the housing and to the frame.

25. The impact flowmeter of claim 24, further comprising zero means coupled to the frame for urging the frame toward a zero position in which the frame engages the transducer means and is yieldably biased toward the impact plate.

26. The impact flowmeter of claim 25, wherein the zero means includes a first permanent magnet fixed to the frame, a second permanent magnet fixed to the housing, the first and second magnets being magnetically coupled.

27. The impact flowmeter of claim 24, wherein the cable means includes means coupled to the frame and to the housing for restricting movement of the frame relative to the housing in directions other than the measurement direction.

28. The impact flowmeter of claim 27, further comprising zero means coupled to the frame for urging the frame toward a zero position in which the frame engages the transducer means and is yieldably biased toward the impact plate.

29. The impact flowmeter of claim 28, wherein the zero means includes dampening means coupled to the frame for resisting movement of the frame relative to the transducer means.

30. The impact flowmeter of claim 24, wherein the housing further includes a plurality of posts fixed to the base plate and extending rearwardly therefrom, a first post and a second post being positioned to lie above the frame and a third post and a fourth post being positioned to lie beneath the frame, the cable means being coupled to the first, second, third, and fourth posts and coupled to the frame.

31. The impact flowmeter of claim 30, wherein the cable means includes a first cable coupling the first post to the frame, a second cable coupling the second post to the frame, a third cable coupling the third post to the frame, and a fourth cable coupling the fourth post to the frame, the measurement direction is substantially perpendicular to a first plane, and the first, second, third, and fourth cables are substantially parallel to the first plane, and the first, second, third, and fourth cables are configured to restrict movement of the frame in directions other than the measurement direction.

32. The impact flowmeter of claim 24, further comprising means coupled to the housing for providing a second output signal in response to movement of the housing and cancellation means for providing a third output signal in response to the first and second output signals.

33. The impact flowmeter of claim 32, wherein the cancellation means includes means for reversing the second output signal to provide a reversed second output signal and means for superimposing the reversed second output signal on the first output signal to produce the third output signal.

34. The impact flowmeter of claim 24, further comprising dampening means coupled to the frame for resisting movement of the frame relative to the transducer means.

35. The impact flowmeter of claim 34, wherein the dampening means includes a magnet fixed relative to the frame.

36. The impact flowmeter of claim 34, wherein the dampening means includes a spring coupled to the frame to yieldably bias the frame toward the impact plate.

37. The impact flowmeter of claim 34, wherein the dampening means includes an air cylinder acting between the frame and the housing.

38. An impact flowmeter for measuring the flow of solids, the impact flowmeter comprising

a housing having an inlet and an outlet, the housing being positioned so that solids flow into the inlet and out through the outlet, and

an impact sensing assembly coupled to the housing and including an impact plate engaging solids and configured to move in response to the impingement of solids on the impact plate, transducer means fixed relative to the housing for providing an output signal in response to the movement of the impact plate, and a frame having a first end engaging the impact plate and a second end engaging the transducer means so that the frame communicates the movement of the impact plate to the transducer means, the frame and the housing being magnetically coupled to yieldably bias the frame toward an initial position relative to the housing.

39. The impact flowmeter of claim 38, further comprising a first magnet having a north pole and a south pole, the first magnet being fixed to the frame, and a second magnet having a north pole and a south pole, the second magnet being fixed relative to the housing and being spaced apart from the first magnet with the north pole of the second magnet being adjacent to the south pole of the first magnet and the south pole of the second magnet being adjacent to the north pole of the first magnet, the first and second magnets being magnetically coupled so that the first and second magnets cooperate to resist movement of the first magnet relative to the second magnet.

40. The impact flowmeter of claim 39, wherein the housing includes a base plate and a magnet support fixed to the base plate and extending inwardly from the base plate generally toward the transducer means, the second magnet being fixed to the magnet support.

41. The impact flowmeter of claim 40, wherein the frame further includes a generally vertically extending elongated back portion having a first end and a second end, the back portion engaging the transducer means at an engagement point spaced-apart from both of the first end and the second end, and the first magnet being connected to the first end.

42. The impact flowmeter of claim 38, further comprising a second transducer means fixed relative to the housing for providing a second output signal in response to undesired inputs such as uncontrolled movement of the housing so that the second output signal is generally the equivalent of a noise portion of the output signal of the transducer means.

43. The impact flowmeter of claim 42, further comprising a second frame engaging the second transducer means, the second frame and the housing being magnetically coupled so that the second frame tends to both move to an initial position relative to the housing and to resist movement of the second frame away from the initial position of the second frame.

44. The impact flowmeter of claim 43, further comprising first, second, third, and fourth magnets, the first magnet being fixed to the first frame, the second magnet being fixed relative to the housing and spaced apart from the first magnet, the first and second magnets being magnetically coupled so that the first and second magnets cooperate to resist movement of the first magnet relative to the second magnet, the third magnet being fixed to the second frame, and the fourth magnet being fixed relative to the housing and spaced apart from the third magnet, the third and fourth magnets being magnetically coupled so that the third and fourth magnets cooperate to resist movement of the third magnet relative to the fourth magnet.

45. An impact flowmeter for measuring the mass flow rate of a flow stream of solids, the impact flowmeter comprising

a housing,

a primary sensor fixed to the housing and configured to provide a first signal in response to the mass flow rate of the flow stream of solids,

a secondary sensor fixed to the housing and configured to provide a second signal in response to undesired movement of the housing, and

means coupled to the primary sensor and the secondary sensor for providing a third signal in response to the first and second signals.

46. The impact flowmeter of claim 45, further comprising primary sensing element having an impact surface engaging the flow stream of solids, a first frame having a first end engaging the primary sensing element and a second end engaging the primary sensor, a secondary sensing element, and a second frame having a first end engaging the secondary sensing element and a second end engaging the secondary sensor so that the first and second frames communicate the positions of the primary and secondary sensing elements respectively to the respective primary and secondary sensors.

47. The impact flowmeter of claim 46, wherein the secondary sensing element is positioned to lie above the flow stream of solids and above the impact surface.

48. The impact flowmeter of claim 47, wherein the housing further includes a base plate having a first opening and a second opening, the base plate being positioned to lie in front of the deflection sensing assembly and behind the impact surface and the secondary sensing element, the impact surface being formed on an impact plate having a back surface opposite the impact surface and a rod connected to the back surface and extending rearwardly therefrom, the rod extending through the first opening and being connected to the first frame, the secondary sensing element including a rod extending rearwardly therefrom, the rod of the secondary sensing element extending through the second opening and being connected to the second frame.

49. The impact flowmeter of claim 45, further comprising a flowmeter output circuit for providing a flowmeter output signal that varies with the mass flowrate of the flow stream of solids in response to the third signal and in response to the velocity of the stream of solids.

50. The impact flowmeter of claim 49, further comprising a velocity sensor for providing a velocity output signal in response to the velocity of the stream of solids, the flowmeter output circuit providing the flowmeter output signal in response to the third signal and in response to the velocity output signal.

51. The impact flowmeter of claim 45, wherein the velocity sensor includes a counter electrode carried by the chute and a capacitance sensor carried by the chute and opposing the counter electrode, the capacitance sensor providing a first capacitance output signal that varies in response to changes in capacitance between the counter electrode and the capacitance sensor.

52. The impact flowmeter of claim 45, wherein the velocity sensor further includes a second capacitance sensor spaced apart from the first capacitance sensor a predetermined distance and opposing the counter electrode, the second capacitance sensor providing a second capacitance output signal that varies in response to changes in capacitance between the counter electrode and the second capacitance sensor, the velocity sensor providing the velocity output in response to the first and second capacitance output signals.