Pressure transmission apparatus

Gas separation: apparatus – Apparatus for selective diffusion of gases

Utility Patent

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Details

C055S495000, C055S503000, C055S511000

Utility Patent

active

06168653

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for the transmission of the pressure in the sterile area of a medical appliance to a non-sterile pressure gauge. Pressure transmission apparatus of this kind, for example, are used in hemo-dialyzers, heart-lung-machines and similar medical appliances, in which a very accurate monitoring of the existing pressures in a sterile hose system is necessary, wherein simultaneously a sterilizing of the corresponding pressure gauges is not possible.
Such pressure transmission apparatus has to be absolutely sealed and free of leakage to prevent the non-sterile air from gaining access into the sterile area of the medical appliances, or to prevent mistakes in the measuring of the pressure. Further, such pressure transmission apparatus should have a so-called “Luer-Lock”-connector on the non-sterile side, preferably consisting of a polyester/polyether-copolymer to provide an easily disconnectable but simultaneously absolutely leak-proof connection with the corresponding stainless steel connectors of the pressure gauges in the medical appliance.
Prior art pressure transmission apparatus of this kind was constructed such that the housing consisted of a sterile half of polycarbonate having a hose connector and a non-sterile half, wherein between these two halves there was positioned a backing of polytetrafluorethylene carrying a polyfluorethylene sheet for the pressure transmission while simultaneously assuring the absolute impermeability. The corresponding “Luer-Lock”-connector on the non-sterile side had to be injection molded in a separate injection molding apparatus when producing the non-sterile side half of the housing. The expert in the art was of the opinion that this kind of production cannot be avoided because the expert had the prejudice that an absolutely sealed and leak-free connection between a part consisting of polyester-polyether-copolymer and a part consisting of polycarbonate was only possible by the cumbersome co-injection molding method, and was not possible by ultrasonic welding. Further, a completely sealed fixing of the backing carrying the polytetrafluorethylene sheet was only believed to be possible between two housing halves consisting of polycarbonate because of the fact that the polyester/polyether-copolymer was too soft for this purpose.
SUMMARY OF THE INVENTION
Starting out from this prior art, one aim of the present invention is to provide a pressure transmission apparatus of the above-identified kind which has the same quality (impermeability and leak-proof) but can be produced in a drastically more simple and cheaper manner.
According to the invention, this aim is achieved by the fact that the non-sterile half of the housing consists of polyester/polyether-copolymer and that the two halves are connected by ultrasonic welding.
Contrary to the prejudice in the related expert field, the present invention is based on the finding that a sufficiently impermeable and leak-proof ultrasonic welding between one housing half of polyester/polyether-copolymer and another housing half of polycarbonate can be produced.
In this connection, it is of special advantage that the backing carrying the polytetrafluorethylene sheet is produced from polyester. This has the substantial advantage that the backing is also welded during the ultrasonic welding of the two housing halves, which leads to a substantially improved fixing and sealing of the backing.
Further, it is preferred that the non-sterile half of the housing has a thin circumferential projection which partly overlies the sterile half of the housing and which forms an ultrasonic welding area. By this, the ultrasonic welding is made not only possible but extremely simple, safe and cheap.
Further, it is especially preferred that within the projection a circumferential groove is provided in the non-sterile half into which a projection of the sterile half meshes. By this, the ultrasonic welding area is enlarged and the impermeability and strength of the connection between the two housing halves is further improved.
It is especially preferred in this connection that the projection on the sterile half has on its exterior a bevel in the direction of the non-sterile half. By this, a narrow, wedge-shaped, circumferential cavity is formed on the non-sterile end of the welding area into which the material softened during the ultrasonic welding can move, whereby the quality of the weld is further improved.
Further, it is especially preferred to provide a bevel on the inner side of the groove. By this, the mounting of the two housing halves is simplified and additional room is created into which the material softened by the ultrasonic welding can move.
The invention is described in more detail with reference to the attached drawings.


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