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Diaphragm metering pump device for medical use

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Diaphragm metering pump device for medical use

where: Patm=atmospheric pressure, Pvap=vapour pressure of the pumped fluid, ΔPvalve—in=pressure difference between the upstream and downstream side of the inlet valve for opening it, ΔPΔh—in=pressure difference in the upstream pipe between its distal end and the upstream side of the inlet valve as a result of the weight of the column of fluid, ΔPpd=pressure drop in the upstream pipe for the desired flow rate. Patm−(|ΔPvalve—in|+|ΔPΔh—in|+|ΔPpd|)≧P>Pvap This pump comprises a chamber and an annular pumping diaphragm secured to the said chamber and the inner edge of which is secured to a central drive part. This diaphragm has a convex domed profile so that its expulsion stroke results essentially in the energy-generating flexing of the intake stroke. The rigidity of the diaphragm is chosen so that the absolute pressure of the chamber lies within the following range:
Related Terms: Absolute Pressure

Inventor: Jean-Denis Rochat
USPTO Applicaton #: #20120308412 - Class: 417395 (USPTO) - 12/06/12 - Class 417 
Pumps > Motor Driven >Fluid Motor >Common Pumping And Motor Working Member >Collapsible Common Member >Diaphragm

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The Patent Description & Claims data below is from USPTO Patent Application 20120308412, Diaphragm metering pump device for medical use.

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The present invention relates to a metering pump device for medical use comprising a pumping chamber, an annular pumping diaphragm the outer edge of which is secured to the said pumping chamber and the inner edge of which is secured to a central drive part that is more rigid than the said diaphragm, able to be displaced parallel to itself between an extreme return position and an extreme displacement position in its expulsion stroke and its intake stroke, respectively, these two positions lying one on each side of the plane containing the outer edge of the said annular diaphragm, the said pumping chamber comprising an inlet valve and an outlet valve which are respectively opened by a reduced pressure and by a raised pressure in the pumping chamber as a result of the movements of the said annular pumping diaphragm, the intake stroke of the said diaphragm resulting from the energy accumulated by the elastic deformation of the diaphragm during its expulsion stroke.

Pumps of this type are already known. Production of such a pump as a metering pump for medical use, particularly as a single-use perfusion pump, presents numerous problems that known diaphragm pumps are unable to overcome.

This pump needs to be accurate, and small while at the same time providing optimum flow rate, and needs to represent good value for money because it is not re-usable. The outlet valve of the pump has to provide safety against a free flow of liquid under a certain pressure, which is typically that of the column of liquid between a pouch of perfusion liquid and the pump, or the pressure resulting from accidental pressure applied to the pouch of liquid. Given this safety, the pumping diaphragm has to be able to withstand the working pressure, which is made up of a pressure to open the outlet valve that has to remain closed up to a pressure that is determined by safety standards, of a pressure drop in the downstream pipe and of a service pressure at the end of the downstream pipe.

The pumping diaphragm has to be able to take in the liquid by moving from its extreme displacement position to its extreme return position creating enough of a reduced pressure in the presence of the pressure drop in the upstream and downstream pipes of the pumping device and of the pressure threshold of the inlet valve.

This intake has to be achieved as quickly as possible in order to provide an optimum flow rate given the volume of the pumping chamber. However, in order to avoid shockwaves in the pipes, vaporization of the pumped liquid through a pressure drop greater than the vapour pressure of the liquid, and the effects of cavitation, the reduced pressure created by the return of the diaphragm must not be too great.

Admittedly, the pumping diaphragm could be connected to the actuator for a two-way drive. However, such a solution would make the single use more complicated and therefore more difficult to manufacture and would make it more difficult to fit into the drive device. This method of driving also allows great precision in the control of the position of the diaphragm, and therefore great precision in the flow rate.

Meeting all of these conditions, some of which oppose others, is therefore not straightforward.

It is an object of the present invention to provide a solution which is able, at least in part, to meet the aforementioned conditions.

To this end, the subject of the present invention is a metering pump device for medical use according to Claim 1.

The various specifics and advantages of the invention will become better apparent from reading the following description of two embodiments of the metering pump device that forms the subject of the invention which are given by way of examples and illustrated schematically in the attached drawings.

FIG. 1 is a schematic general arrangement of the metering pump device;

FIG. 2 is a diagram illustrating a typical operating pumping range using a flat pumping diaphragm;

FIG. 3 is a cross section through a pumping diaphragm according to the invention intended to be connected to a pumping chamber;

FIG. 4 is a pressure-displacement diagram for a pumping device using the diaphragm of FIG. 3;

FIG. 5 is a comparative pressure-displacement diagram of a pumping device using a flat diaphragm with the same dimensional ratios as the diaphragm of FIG. 3;

FIG. 6 is a diagram showing the pressure sensitivity of the diaphragm of FIG. 3;

FIG. 7 is a comparative pressure-sensitivity diagram for the flat diaphragm of FIG. 5;

FIG. 8 is a diagram of the diaphragm of the pumping device that forms the subject of the invention, showing the characteristic dimensions the dimensional ratios of which will be discussed further in the description.

The metering pump device that forms the subject of the invention is illustrated very schematically in FIG. 1, given that it is the elastically deformable pumping diaphragm 1, and the geometry and structure thereof, which constitute the innovative part of this invention.

Aside from the pumping diaphragm 1, this device comprises a pumping chamber 2 into which there open an upstream pipe 3 controlled by an inlet valve 4, a downstream pipe 5 itself controlled by an outlet valve 6. The pumping diaphragm 1 is intended to move between an extreme displacement position that reduces the volume of the pumping chamber 2, leading to a raised pressure able to open the outlet valve 6 and an extreme return position that induces a reduced pressure able to close the outlet valve 6 and to open the inlet valve 4.

It is a more particular object of the invention to determine how to produce a diaphragm that is able to meet a certain number of conditions.

In order to expel the liquid from the pumping chamber 2, a drive mechanism 7, here symbolically depicted by a pushrod, pushes against the pumping diaphragm 1 in the direction of the inside of the pumping chamber. During the intake phase of the pump, it is the elasticity of the diaphragm which produces the return stroke generating, on the one hand, the intake and, on the other hand, returning the drive mechanism 7 to its starting position. As a result, suitable sizing of the diaphragm 1 is of key importance in order:

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Application #
US 20120308412 A1
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Absolute Pressure

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