EP0066522B1 - Hydraulically actuated diaphragm pump - Google Patents

Abstract

1. Diaphragm for hydraulically-controlled diaphragm pump of which two faces are in contact with two different fluids, said diaphragm forming a cup-shaped member (1) which is substantially spherical and comprises an annular outer edge (2) substantially plane, said diaphragm being characterised in that it is constituted in a manner known per se, by two layers, one (3) in rubber and the other (4) in plastic material such as tetrafluor-ethylene and in that each of the faces of said edge is provided with a bead (2a, 2b) by which the diaphragm is secured in the pump body.

Description

It is usual to use, in hydraulically controlled diaphragm pumps, composite flat membranes, the edge of which is clamped tightly between two moving parts of the body.

When, in the rest position, the pinched membrane is flat, it works in extension, which in the long term causes permanent deformation. This deformation is, in practice, random and constitutes uncertainty as to the operation of the pump.

To remedy the drawback of such a deformation, a membrane with an outside diameter greater than the mounting diameter is sometimes installed in the pump. A buckling then occurs which creates uncertainty as to the position of the membrane at rest.

These deformations, whether desired or not, also have an impact on the operation of controlled compensation systems which may include undesirable hazards. They are a major problem for double diaphragm pumps. It is indeed difficult to correctly fill the intermediate space (between the two membranes) delimited by randomly deformed membranes.

Finally the tightening of the membrane on its periphery leads to a weakening of the latter at this level, weakening which can result in a tear or at least in a less important longevity.

The present invention intends to remedy these drawbacks by proposing a new membrane.

French patent No. 581223 discloses a rubber membrane for a pump, the two faces of which are in contact with two different fluids, this membrane forming a substantially spherical cup which has a substantially planar outer annular edge.

From French patent No. 1547601, a membrane for a vacuum pump is also known, which is made up of two layers, one made of rubber and the other of a tetrafluoroethylene.

From patent US Pat. No. 3,771,907, a membrane for a mechanically driven beverage pump is known, this membrane being fixed in the pump body by a bead projecting from each of the faces of the annular edge of this membrane.

Therefore, according to the invention, the diaphragm for a hydraulically operated diaphragm pump, the two faces of which are in contact with two different fluids forms a substantially spherical cup having a substantially planar outer annular edge, and is formed by two layers, the one made of rubber and the other of plastic such as tetrafluoroethylene, and is provided on each of the faces of its edge with a bead for fixing the membrane in the pump body.

It will also be advantageous for the depth of the interior spherical cup to be of the order of 4 to 6% of the interior diameter of said annular edge.

The present invention also relates to the pump adapted to receive at least one such membrane, the body of which comprises at least two elements between which the membrane is clamped.

This pump is remarkable in that each of said elements is provided with an O-ring groove to receive the aforementioned beads and in that the bringing together of the elements at the end of tightening is limited to approximately 80% of the total thickness of the membrane at the level of its beads, the tightening being carried out only on the beads.

The invention will be better understood during the description given below by way of purely indicative and nonlimiting example, which will make it possible to identify the advantages and the secondary characteristics thereof.

• la fig. 1 est une vue en coupe de la membrane selon l'invention;
• les fig 2 et 2A illustrent une pompe à double membrane dans laquelle la membrane est appliquée, la fig. 2A étant une vue grossie d'un détail de la fig. 2.

Reference will be made to the appended drawings in which:

• fig. 1 is a sectional view of the membrane according to the invention;
• Figs 2 and 2A illustrate a double diaphragm pump in which the diaphragm is applied, fig. 2A being an enlarged view of a detail of FIG. 2.

In fig. 1, we see a membrane according to the invention constituted by a spherical cap 1 of diameter D surrounded by an annular rim 2 substantially planar of width E.

This cap 1 and this rim 2 are in one piece and consist of a composite material, the thickest layer 3 of which is made of rubber (natural or synthetic) and the thinnest layer 4 of which is constituted by a plastic material, in particular by a tetrafluoroethylene. In the case of the figure, the thickness proportion of the two constituents is approximately% for the rubber and ^I k for the tetrafluoroethylene.

The depth of the spherical cap F (or the arrow thereof in the cutting plane) is between 0.04 and 0.06 D.

Finally, it should be noted that the rim 2 has on each of its faces a bead 2a and 2b consisting substantially of a half-torus whose radius R is of the order of the thickness of the membrane. In practice, it has been found that, for all the membranes in a range, an R value equal to 2.5 mm could be adopted.

Fig. 2 schematically illustrates a double diaphragm pump with hydraulic control. The control chamber 5 is associated in a known manner with a piston 6 and with a compensation device 7. A first membrane 8 isolates this chamber from an intermediate chamber 9, itself insulated by a second membrane 10 from the pumping chamber 11.

The membranes 8 and 10 are coupled, as shown in detail in FIG. 2A, by pinching between elements 12a, 12b, 12c of the pump body. These elements are frontally provided with toric grooves 13 to receive the beads 2a, 2b of the membranes.

Once tightened against each other, the elements 12a, 12b, 12c as well as the grooves 13 have dimensions such that, on the one hand, the crushing of the beads 2a, 2b does not exceed 20% of the dimension E (see fig. 1) of the membrane at this location and that, on the other hand, the rest of the membrane located between the above elements is not pinched. Thus, the membranes are embedded only at the level of the beads which cooperate with the elements 12a to 12c in the manner of O-rings to seal between the chambers 5, 9 and 11.

The advantages of the invention lie in the fact that a pump equipped with the above-described membrane has, for equal diameter, a greater capacity. In addition, the longevity of the membrane is increased and its operating performance improved. The tightness ensured during assembly is better (similar to that of the O-ring) with a clamping force lower than that usually practiced on conventional pumps. Finally, in the application to double diaphragm pumps, the intermediate volume is much better defined by the membranes according to the invention and can be much better filled.

The invention finds an interesting application in the field of hydraulically controlled diaphragm pumps, and in particular metering pumps.

Claims (4)

1. Diaphragm for hydraulically-controlled diaphragm pump of which two faces are in contact with two different fluids, said diaphragm forming a cup-shaped member (1) which is substantially spherical and comprises an annular outer edge (2) substantially plane, said diaphragm being characterised in that it is constituted in a manner known per se, by two layers, one (3) in rubber and the other (4) in plastic material such as tetrafluor- ethylene and in that each of the faces of said edge is provided with a bead (2a, 2b) by which the diaphragm is secured in the pump body.

2. Diaphragm according to Claim 1, characterised in that the depth (F) of the internal cup-shaped member is between 4 and 6% of the inner diameter (D) of said annular edge.

3. Diaphragm according to Claim 1, characterised in that the beads (2a, 2b) are substantially semi-annular of outer radius equal to 2.5 millimetres.

4. Hydraulically controlled pump with single or double diaphragm according to any one of Claims 1 to 3, and of which the body comprises at least two elements (12a, 12b) between which the diaphragm (10) is gripped, characterised in that each of said elements is provided with an annular groove (13) to receive said beads and in that the bringing together of the elements at end of tightening is limited to about 80% of the total thickness (E) of the diaphragm at the level of its beads, tightening being applied on the beads only.

Images