Measuring and testing – Gas content of a liquid or a solid – By vibration
Patent
1996-09-04
1998-09-22
Williams, Hezron E.
Measuring and testing
Gas content of a liquid or a solid
By vibration
604 65, G01N 2900
Patent
active
058116591
DESCRIPTION:
BRIEF SUMMARY
The invention relates to an infusion hose for an infusion device with a bubble detector of the type specified in the preamble of claim 1.
When infusion devices are used in medical applications the column of liquid in the infusion hose is monitored for included bubbles of air, for such air bubbles must not be allowed to pass into the patient's bloodstream.
Although a wide variety of methods is available for monitoring the column of liquid for included air bubbles, the use of ultrasound sensors is preferred.
On such method and apparatus for carrying out this method are for example described in unexamined German Patent Application DE-OS 3141576. This involves arranging an ultrasound transmitter plate and an ultrasound receiver plate on the mutually facing inner surfaces of the free side-pieces of a U-shaped supporting body, the distance between the ultrasound transmitter plate and the ultrasound receiver plate being such that the hose or line is squeezed between these plates, deforming its circular cross-section. The size of the signal received by the ultrasound receiver will depend on whether there is liquid or air in the infusion hose in the region of the acoustic signal, thereby enabling the electrical signal output from the ultrasound receiver to be evaluated and used to detect air inclusions.
Undesirably, however, the transmitted acoustic signal is relayed not only by the column of liquid, or rather inclusions of air, but also by the free hose sections which form between the free side-pieces of the U-shaped supporting body, with the result that the signal-to-noise ratio is small and this may mean that perfectly reproducible results are not obtained.
This problem is further intensified by the fact that in many cases a plastics body fitting exactly into a mating part in the infusion device is drawn over the infusion hose to produce a good contact with the ultrasound transmitter and receivers and to fix the position of the hose. This plastics body may also be a specially shaped connection nipple featuring two connection fittings to which two different grades of hose are joined, particularly when an infusion device with a roller pump is used on which the hose segment located in the roller pump is silicone hose whilst a less expensive material is used for the remaining part of the infusion hose.
Although this plastics body makes it possible to properly position the ultrasound transmitter and receiver, it very strongly conducts the acoustic signal independently of the hose, thereby further deteriorating the signal-to-noise ratio.
It is the object of the invention to create an infusion hose for an infusion device with a bubble detector of the type mentioned at the beginning that makes it possible for air inclusions in the column of liquid to be detected better.
This object is achieved by the features indicated in claim 1.
Advantageous embodiments and refinements of the invention can be taken from the subsidiary claims.
Designing the infusion hose in accordance with the invention enables the acoustic signal to be communicated in a defined manner to the column of liquid, or rather to the interior of the infusion hose, thereby enabling reproducible results with a high signal-to-noise ratio to be obtained which can be satisfactorily reproduced, since the contacts and the filters and/or dampers can be manufactured both inexpensively and in an accurately reproducible manner by straightforward shaping of a plastics part.
The plastics body is preferably constructed as a connection nipple for connecting two hose sections of the infusion hose made from different materials, or alternatively it may be drawn onto an infusion hose in a tight fit.
Additional measuring elements may also be arranged inside the plastics body, for example an impeller wheel used to monitor the rate of flow; the path travelled by this movable body intersects the acoustic signal and thus the movement of this movable body can be derived in the electric signal output by the ultrasound receiver.
The invention will now be explained in more detail with r
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Politzer Jay L.
Williams Hezron E.
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