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Rolling diaphragm pump

Rolling diaphragm pump description/claims

The benefits of U.S. Provisional Application No. 60/886,919 filed Jan. 26, 2007 and entitled “Rolling Diaphragm Pump” are claimed under 35 U.S.C. § 119(e), and the entire contents of this provisional application are expressly incorporated herein by reference thereto.

The invention relates to a pump and product delivery. More particularly, the invention relates to rolling diaphragm type pumps.

In a rolling diaphragm type pump, a small amount of positive differential pressure is needed to keep the diaphragm in the correct orientation (convoluted orientation). However, if the differential pressure is too high, the diaphragm will wear out at a faster rate or even burst in extreme cases.

Prior art rolling diaphragm pump designs create a positive differential pressure by sizing the driving cylinders to match the diaphragm diameter. This limits the diaphragm size to one that will match with commercial cylinders. Additionally, the greater the mismatch, the more the differential pressure will vary with the pump's output pressure.

In a prior art rolling diaphragm pump, the differential pressure across the diaphragm is determined by the pump dimensions and the working pressure. For a given pump size, the differential pressure increases as the working pressure increases. This not only reduces the lifetime of the diaphragms but also limits the maximum pressure of the pump.

A dual-unit pump, e.g., a rolling diaphragm piston pump, is disclosed in U.S. Pat. No. 4,543,044, the entire contents of which are incorporated herein by reference thereto. The pump is suitable for pumping an abrasive high-viscosity slurry, and is adapted to operate at a constant flow rate by means for detecting and correcting a pressure differential in the two units before the units switch from the pumping cycle to the filling cycle and vice versa. The flow of liquids is controlled by valves of the type which switch the flow to and from the units with essentially no volume change in the liquid inlet and outlet lines.

Turning to FIG. 1, a rolling diaphragm pump 10 of the prior art is shown. Piston 12, which for example may be formed of nylon, is disposed within a cylindrical housing 13 and seated with respect to top-hat shaped rubber diaphragm 14. A working fluid 16 such as oil and a discharge fluid 18 (the fluid that is being pumped) are shown. A standard hydraulic cylinder 19 (such as a double-rodded cylinder with a vented top) includes a fluid region 20 such as having oil therein, rods 22a and 22b, and a vented region 24. Piston 12 is used to maintain the shape of diaphragm 14. Diaphragm 14 is coupled along its circumference to housing 13 at regions 27 along axis 25b which is normal to axis 25a (along which rods 22a, 22b for example are axially disposed).

In FIG. 1, P1 is the discharge pressure of the medium that is being pumped (e.g., to a packaging machine so that the medium may be used to fill a chub), P2 is the pressure of the hydraulic fluid under piston 12 (e.g., the working fluid pressure), P3 is vented to atmosphere and assumed as zero pressure with respect to atmosphere, and P4 is connected to P2 and thus is the same as the pressure of the hydraulic pressure P2. In addition, for the purposes of this analysis, A1 is the effective area that pressure P1 acts upon to produce force in a direction parallel to axis 25a, A2 is the effective area that pressure P2 acts upon to produce force in a direction parallel to axis 25a, and A3 is the internal area of the hydraulic cylinder 19 about a plane normal to axis 25a. Product is discharged from pump 10 in direction E. Preferably, P1>P2 in FIG. 1.

According to the design of pump 10 in FIG. 1, the downward force is determined by the following Equation 1 below:

Fdown=P1·A1+P2·A4+P3·(A3−A4)  (Eq. 1)

The upward force is determined by Equation 2 below:

Fup=(P2·A2)+[P4·(A3−A4)]  (Eq. 2)

• Provisional Patent
• Utility Patent

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