1. Field of the Invention
The invention relates to a composite diaphragm for diaphragm pumps comprises of an elastomer body and a polytetrafluoroethylene (PTFE) coating on the product side. This elastomer body has the shape of a circular dish that comprises an edge of the dish with a clamping area; a bottom; and a flexible section of the diaphragm connecting the edge of the dish with the bottom.
The composite diaphragm is clamped in a diaphragm pump along the side of the edge, whereas the bottom performs lifting movements. The flexible section of the diaphragm is turned inside out with each lifting movement, whereby roll-off movements of the flexible material are observed in a radial section. Technically speaking, the flexible section of the diaphragm can therefore be referred to as a rolling loop in a tech.
2. The Prior Art
When composite diaphragms are used, where the flexible section of the diaphragm is a smooth ring surface and where the PTFE coating contains radial white staining in the form of lines, this indicates the onset of damage to the material. As this damage to the PTFE material progresses, the composite diaphragm loses its chemical resistance to aggressive conveyed media. The development of this damage as described above limits the useful life of the diaphragm.
U.S. Pat. No. 5,349,896 shows a composite diaphragm that has the structure specified above, wherein the flexible section of the diaphragm is stiffened by radial ribs. Such ribs extend from a transition area adjoining the bottom, up to the edge of the dish of the elastomer body. Thus, these ribs make it possible to prevent the damage described above from developing; however, the roll-off property of the flexible section of the diaphragm deteriorates and the resistance to roll-off increases to a considerable extent.
It is an object of the invention to provide a composite diaphragm for diaphragm pumps that permits a long useful life without damage to the PTFE coating. This design contains good roll-off properties during the operation of the pump.
This object is achieved by a composite diaphragm in which the flexible section of the diaphragm has a multitude of naps, cups or protrusions forming elevations in the PTFE coating. These naps are preferably in the form of cups with a circular or elliptic base area. These naps, as defined by the invention provide the flexible section of the diaphragm with punctual stiffening elements. In addition, the areas disposed between the naps are flexible, so that the flexible section of the diaphragm can be turned inside out with low pressure. Thus there are no folds caused by compression or lines caused by buckling. When in use, the composite diaphragm performs defined rolling movements, whereby the resistance to roll-off of the rolling fold is low. Furthermore, the napped structure of the composite diaphragm as defined by the invention creates superior adhesion between the elastomer body and the PTFE coating. The superior adhesion of the layered composite is attributed to a cogging effect of the naps or a larger surface area obtained as a result of the nap-like embossing.
These naps are preferably arranged lined up in at least two concentric circles with an angular division of between 5° and 30°. The naps, burls or protrusions are arranged in concentric circles and can be lined up in the radial direction in lines extending through the center of the circles. However, the invention also covers an embodiment in which the naps are arranged in adjacent concentric circles at offset angles in relation to each other so that in the radial direction, one nap is disposed in front of each gap between two naps when these naps are lined up in the peripheral direction. Furthermore, these naps are arranged in the circle wherein all have the largest diameter and/or the smallest diameter and form a chain without gaps in the peripheral direction.
Other objects and features of the present invention will become apparent from the following detailed description considered in connection with the accompanying drawings which disclose at least one embodiment of the present invention. It should be understood, however, that the drawings are designed for the purpose of illustration only and not as a definition of the limits of the invention.
In the drawings, wherein similar reference characters denote similar elements throughout the several views:
a to 3h each show other exemplified embodiments by a top view of the product side; and
Referring in detail to
As in
The instruction as defined by the invention also covers composite diaphragms with a bottom not containing any metal core incorporated therein by vulcanization, but a center opening for the connection with the piston rod.
In another embodiment as shown in
Accordingly, while at least one embodiment of the present invention has been shown and described, it is to be understood that many changes and modifications may be made thereunto without departing from the spirit and scope of the invention as defined in the appended claims.
Number | Date | Country | Kind |
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102 27 193 | Jun 2002 | DE | national |
Number | Name | Date | Kind |
---|---|---|---|
3435734 | Bushway et al. | Apr 1969 | A |
3911796 | Hull et al. | Oct 1975 | A |
3947156 | Becker | Mar 1976 | A |
4270441 | Tuck, Jr. | Jun 1981 | A |
5349896 | Delaney et al. | Sep 1994 | A |
5699717 | Riedlinger | Dec 1997 | A |
Number | Date | Country | |
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20030230191 A1 | Dec 2003 | US |