Method and an apparatus for measuring the flow in oscillating displacement pumps

• US 5,047,950 A
• Filed: 06/02/1989
• Issued: 09/10/1991
• Est. Priority Date: 12/27/1985
• Status: Expired due to Fees

• Current Assignee: LEWA Herbert OTT GmbH & Company
• Original Assignee: LEWA Herbert OTT GmbH & Company
• Inventors: Benken, Josef, Fritsch, Horst
• Primary Examiner(s): Lall, Parshotam S.
• Assistant Examiner(s): MELNICK, STEVEN A
• Application Number:
  US07/343,073
• Time in Patent Office: 830 Days
• Field of Search: 364/510, 364/509, 417/18, 417/19, 417/20, 417/43
• US Class Current: 702/47
• CPC Class Codes: G01F 3/20 having flexible movable walls, e.g. diaphragms, bellows

Abstract

In a method and apparatus for measuring and monitoring the flow in oscillating displacement pumps, the basis for measurement used is the working principle of the pump itself and, accordingly, the mathematically unambiguous relation between the displacer kinematics and the compression or expansion time of the displacer is utilized, in particular via a microcomputer. For this purpose the compression time and expansion time are measured as the time difference between the back and the front dead point position of the plunger, respectively, and the coupling pressure peak at the beginning of the feeding process and the suction process, respectively, which is effected in particular by sensors.

Claims

1. An oscillating pump for pumping a fluid, said pump comprising a piston plunger disposed within a piston cylinder, said piston plunger being adapted to move within said piston cylinder between front and back dead points, said piston plunger being further adapted to act on a chamber whereby, in a forward stroke said piston feeds fluid from said chamber, fluid being drawn into said chamber by suction of a vacuum caused by a backstroke of said piston plunger, said oscillating pump further comprising;

pressure sensors for measuring a pressure response in said piston cylinder,

means for determining a time t₂ at which a positive pressure surge associated with said suction occurs, and times at which said piston reaches said back dead point t₁, and said front dead point t₃, and

means for calculating a volume flow of said pump based upon the determined times, using the kinematic equation of said piston.

2. The apparatus of claim 1 wherein said pump is a diaphragm pump.

3. An oscillating pump for pumping a fluid, said pump comprising a piston plunger disposed within a piston cylinder, said piston plunger being adapted to move within said piston cylinder between front and back dead points, said piston plunger being further adapted to act on a chamber whereby, in a forward stroke, said piston plunger feeds fluids form said chamber, fluid being drawn into said chamber by suction of a vacuum caused by a back stroke of said piston plunger, said oscillating pump further comprising;

pressure sensors for measuring a pressure response in said piston cylinder,

means for determining at time t₄ at which a negative pressure surge associated with fluid feed occurs, and times at which said piston plunger reaches said front dead point t₃ and said back dead point t₁, and

means for calculating a volume flow of said pump based on the determined times using the kinematic equation of the piston.

4. The apparatus of claim 3 wherein said pump is a diaphragm pump.

5. An oscillating pump for pumping a fluid, said pump comprising a piston disposed within a piston cylinder, said piston plunger being adapted to move within said piston cylinder between front and back dead points, said piston plunger being adapted to act on a chamber whereby, in a forward stroke, said piston feeds fluid from said chamber, fluid being drawn into said chamber by suction of a vaccum caused by a backstroke of said piston plunger, said oscillating pump further comprising;

means for sensing a positive pressure surge Δ

P_S at the beginning of said suction, at a time t₄, means for determing the time at which said piston plunger reaches said back dead point t₁, means for sensing a negative pressure surge Δ

P_D at the beginning of the fluid feed t₂ and a time at which said plunger reaches said front dead point t₃ and,

means for calculating volume stream V_D relative to system pressure P_D, volume stream V_S relative to suction pressure P_S and a degree of pump feeding X, based on the determined times, using the kinematic equation of the piston.

6. The oscillating pump of claim 5 wherein said piston plunger moves in harmonic motion and X, V_D, and V_S can be calculated by the following formulae ##EQU4## wherein A_K is the area of the plunger surface and h equals the stroke height of said piston plunger.

7. The oscillating pump of claim 6 wherein said means for calculating is a microcomputer.