LAMINATED MEMBRANE FOR MEMBRANE PUMP

Abstract

A diaphragm for a pump has a one-piece elastomeric body centered on an axis and formed with an annular outer clamping edge, an annular flexible web extending radially inward from the outer edge, and a core joined by the web to the outer edge and formed in turn by an upper wall and a lower wall axially spaced therefrom. This lower wall is formed on the axis with a throughgoing hole. An insert between the walls extends through the hole, and interengaging formations on the insert and on the lower wall radially couple the insert to the lower wall at an inner edge of the hole.

Claims

1. A diaphragm for a pump comprising: a one-piece elastomeric body centered on an axis and formed with an annular outer clamping edge, an annular flexible web extending radially inward from the outer edge, and a core joined by the web to the outer edge and formed in turn by an upper wall and a lower wall axially spaced therefrom and formed on the axis with a throughgoing hole; an insert between the walls and extending through the hole; and interengaging formations on the insert and on the lower wall radially coupling the insert to the lower wall at an inner edge of the hole.

2. The diaphragm according to claim 1, wherein the interengaging formations include axially oppositely open annular grooves formed on the insert and an annular axially projecting bead formed on the lower wall at the inner edge and gripped axially between the grooves.

3. The diaphragm according to claim 2, wherein the insert includes an annular outer part substantially completely between the upper and lower walls and forming one of the grooves; and an inner part fixed to the outer part, extending through the hole, forming the other of the grooves and axially pressing the inner edge of the lower wall against the outer part.

4. The diaphragm according to claim 3, further comprising locking formations coupling the inner part axially to the outer part.

5. The diaphragm according to claim 4, wherein the locking formations include complementary screwthreads on the inner and outer parts.

6. The diaphragm according to claim 1, further comprising: radially interengaging formations axially coupling the upper wall to the insert.

7. The diaphragm according to claim 6, wherein the formations axially coupling the upper wall to the insert include a radially projecting lip or radially projecting teeth on the wall and a complementary radially open groove on the insert into which engage the lip or teeth.

8. The diaphragm according to claim 7 wherein the teeth fit axially through notches in the upper wall.

9. The diaphragm according to claim 1, wherein the insert is provided with a seat configured for connection to a piston.

10. The diaphragm according to claim 1, wherein the elastomeric body is made of a thermoplastic polymer.

11. The diaphragm according to claim 1, wherein the polymer is polyurethane.

12. The diaphragm according to claim 3, wherein the inner part is T-shaped and has an axially centered threaded stem engaged in the outer part and a radially projecting flange pressing the inner edge of the lower wall against the outer part.

13. The diaphragm according to claim 12, wherein the flange is flush with a lower face of the lower wall.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0029] The above and other objects, features, and advantages will become more readily apparent from the following description, reference being made to the accompanying drawing in which:

[0030] FIG. 1 is a partly sectional perspective view of the membrane according to the invention;

[0031] FIG. 2 is a large scale view of a detail of FIG. 2;

[0032] FIG. 3A is a partial section through a diaphragm according to the prior art;

[0033] FIG. 3B is a view like FIG. 3A but showing the instant invention;

[0034] FIG. 3C is a large-scale view of the detail indicated at IIIC of the prior art of FIG. 3A; and

[0035] FIG. 4 is a bottom isometric view of the invention.

SPECIFIC DESCRIPTION OF THE INVENTION

[0036] FIG. 1 shows the laminated membrane formed in one piece centered on an axis A as a dished elastomeric disk or body 1 having an annular and circular-section outer-edge bead 2 forming a clamping surface 3. The body 1 also has a center portion or core 4 and a flexible annular web 5 connecting the peripheral edge 2 to the core 4.

[0037] The core 4 is formed from an upper and a lower wall 6a and 6b that together define a chamber 7 holding a rigid annular insert 8 between the walls 6a and 6b and having a part-spherical upper surface and a generally planar lower face. The insert 8 extends through a circular axially centered hole 9 in the lower wall 6b and engages with a seal region 10 around an inner periphery of the lower wall 6b. This positively connects the insert 8 and the lower wall 6b at the seal region 10 with respect to one another in a radial direction r.

[0038] Details of the positive connection are shown in FIG. 2 where only the core 4 of the laminated body 1 is shown. It can be clearly seen here that the lower wall 6b has a thickened inner edge 11 surrounding the hole 9 and fitting into a downwardly open annular groove 12a and an upwardly open annular groove 12b of the insert 8.

[0039] How such a sealing structures functions is best understood by comparison with the prior-art system shown in FIGS. 3A and 3C. It should be noted that here too only the core 4 is shown. Due to the stroke movement of the laminated membrane, forces f are produced that are mainly radial and in the case of the prior-art laminated membrane of FIG. 3A lead mainly to spreading or separation of the elastomeric body 1 and the insert 8. This creates a gap between these two parts, into which compressed air can penetrate, as clearly evident from the detail view of FIG. 3C. At the same time surface forces A (FIG. 3A) are also effective that in particular cause the upper wall 6a to detach from the insert 8. As a result, the gap between them becomes larger and larger, so that compressed air penetrates into wide areas between insert 8 and elastomeric body 1 and can lead to component failure.

[0040] With this invention the positive connection in the seal region 10, even when subjected to the radial force f, ensures a solid connection between the insert 8 and the elastomeric body 1, so no gap for entry of the compressed air is formed. At the same time, the thickened edge bead 11 acts together with the circumferential grooves 12a and 12b as an active sealing structure, so that entry of air is blocked at the outermost part of the interface between the insert 8 and the elastomeric body 1.

[0041] In addition, to inhibit separation of the upper wall 6a from the insert 8 caused by the surface forces A, the insert 8 and the upper wall 6a are formed with interengaging formations 13 and 14 constituted by a radially outwardly projecting annular lip 13 on the wall 6a and an inwardly open complementarily annular groove 14 on the inner periphery of the body 8 into which this lip 13 fits.

[0042] FIGS. 1 and 2 also clearly that the insert 8 is formed by two parts, namely a doughnut-shaped or annular part 8a formed with the grooves 12a and 14 and a T-shaped core part 8b having an externally threaded stem extending axially up through the hole 9 in the outer part 8a and in fact screw-threaded into an internally threaded hole of the outer part 8a, and a flat disk-like flange formed with the groove 12b and set flush in the lower wall 6b. Here, the seal region 10 of the lower wall 6b is compressed between the flange of the core part 8b and the lower face of the part 8a to lock the bead 11 in place.

[0043] FIG. 4 also shows how the core part 8b has an internal thread 15 for connection to a piston rod and the lower face of the part 8b is flush with the lower face of the wall 6b