System for accurately weighing solids and control mechanism for same

• US 7,683,271 B2
• Filed: 03/27/2006
• Issued: 03/23/2010
• Est. Priority Date: 04/12/2005
• Status: Active Grant

• Current Assignee: DuPont Safety & Construction, Inc. (DuPont de Nemours, Inc.)
• Original Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.)
• Inventors: Newton, Christopher William
• Primary Examiner(s): Gibson; Randy W
• Application Number:
  US11/911,145
• Publication Number:
  US 20080223626A1
• Time in Patent Office: 1,457 Days
• Field of Search: 177116-122, 222/55, 222/56, 222/77, 141/83, 406/14, 406/31, 406/79, 406/146
• US Class Current: 177/116
• CPC Class Codes: G01G 13/003 Details; specially adapted accessories details of weighing apparatus in general G01G21/00; auxiliary devices for weighing apparatus in general G01G23/00
• CPC Class Codes: G01G 21/30 Means for preventing contamination by dust

Abstract

A system for accurately weighing a mass of material, including a closed chamber (20) having a gas inlet (22) and a gas outlet (24). A scale (30) is disposed in the closed chamber (20). An inert gas supply, under positive pressure, is connected to the gas inlet (22) and a vacuum powered pressure regulator (100) is connected to the gas outlet (24) to maintain a predetermined pressure level within the closed chamber (20) and to substantially inhibit pressure fluctuations within the chamber (20) that may affect accuracy of the scale (30).

Claims

1. A system for accurately weighing a mass of material, comprising:

a) a closed chamber (20) including a chamber gas inlet (22) and a gas outlet (24);

b) an inert gas supply under positive pressure connected to the gas inlet (22);

c) a scale (30) disposed in the closed chamber (20) ; and

d) a vacuum powered pressure regulator (100) operatively connected to the gas outlet (24) to maintain a predetermined pressure level within the closed chamber (22) and to substantially inhibit pressure fluctuations within the closed chamber (22), wherein the vacuum powered pressure regulator (100) comprises;

a container including a compartment (110) partially filled with a liquid (111) so as to define a head space above the liquid (111);

a vacuum supply in fluid communication with the head space;

a first dip tube (117) having one end extending into the liquid (111) and an opposite end operatively connected with the gas outlet (24); and

a second dip tube (122) having one end extending into the liquid (111) and an opposite end operatively connected to a container vent.

2. The system of claim 1, wherein the container includes a liquid trap zone (112) disposed between the compartment (110) and the chamber gas outlet (24).

3. The system of claim 2, wherein the container includes a second liquid trap zone (114) disposed between the compartment (110) and the container vent.

4. The system of claim 1, wherein the system is capable of measuring a 20 kg mass of material within +/−

0.1 gm.

5. The system of claim 1, further comprising a receptacle (40) connected to the scale (30).

6. The system of claim 5, further comprising a material supply line (29) disposed above and physically unconnected from the receptacle (40), and a material dispensing conduit (50) disposed below and physically unconnected from the receptacle (40).

7. A process for accurately weighing and dispensing a mass of material, comprising the steps of:

i) providing a closed chamber (20) including a scale (30) disposed therein and a receptacle (40) operatively connected to the scale (30);

ii) adding a mass of material to the receptacle (40) from a material supply line (29) that is disposed above and physically unconnected from the receptacle (40);

iii) controlling pressure within the closed chamber (20) through operation of a vacuum powered pressure regulator (100) connected to the closed chamber (20); and

iv) dispensing the mass of material from the receptacle (40) via a dispensing conduit (50) disposed below and physically unconnected from the receptacle (40);

wherein said vacuum powered pressure regulator (100) comprises;

a) a compartment (110) partially filled with a liquid (111) so as to define a head space above the liquid (111);

b) a vacuum port (132) in fluid communication with the head space, so that an environmental pressure of the head space is negative;

c) a vent line (120,121,122) for regulating pressure in the head space, the vent line (122) adjustably extending into the liquid (111);

d) a process line (115,116,117) including a first end connected to the closed chamber (20), and an opposing second end adjustably extending into the liquid (111).

8. The process of claim 7, further comprising the step of:

continuously sweeping the closed chamber (20) by introducing an inert gas under positive pressure into the closed chamber (20) through a gas inlet (22).

9. The process of claim 8, further comprising the step of:

continuously exhausting the inert gas from the closed chamber (20) through a gas outlet (24).

10. The process of claim 7, wherein the vacuum powered pressure regulator (100) further comprises a first liquid trap zone (112) for the process line (115,116,117).

11. The process of claim 10, wherein the vacuum powered pressure regulator (100) further comprises a second liquid trap zone (114) for the vent line (120,121,122).

12. The process of claim 7, wherein the process is capable of measuring a 20 kg mass of material within +/−

0.1 gm.

13. A process for accurately weighing a mass of material, comprising the steps of:

i) providing a closed chamber (20) including a scale (30) disposed therein and a receptacle (40) operatively connected to the scale (30);

ii) adding a mass of material to the receptacle (40) from a material supply line (29) that is disposed above and physically unconnected from the receptacle (40);

iii) continuously sweeping the closed chamber (20) by introducing an inert gas under positive pressure into the closed chamber (20) through a gas inlet (22);

iv) continuously exhausting the inert gas from the closed chamber (20) through a gas outlet (24); and

v) controlling a pressure level within the closed chamber (20), when continuously exhausting the inert gas, to within about 0.125 kPa.

14. The process of claim 13, wherein the pressure level within the closed chamber (20) is controlled within about 0.062 kPa.

15. The process of claim 13, wherein the pressure level within the closed chamber (20) is controlled within about 0.031 kPa.

16. The process of claim 13, wherein the process is capable of measuring a 20 kg mass of material within +/−

0.1 gm.