System elements for measuring pressure in extracorporeal circuits

• US 6,880,404 B2
• Filed: 07/09/2001
• Issued: 04/19/2005
• Est. Priority Date: 07/08/2000
• Status: Expired due to Fees

• Current Assignee: Andreas Uberreiter
• Original Assignee: MHM Harzbecher Medizintechnik GmbH
• Inventors: Überreiter, Andreas
• Primary Examiner(s): Lefkowitz, Edward
• Assistant Examiner(s): ALLEN, ANDRE J
• Application Number:
  US10/332,315
• Publication Number:
  US 20040050168A1
• Time in Patent Office: 1,380 Days
• Field of Search: 737/00, 737/06, 737/08, 737/30, 737/16
• US Class Current: 73/706
• CPC Class Codes: A61M 1/3639 Blood pressure control, pressure transducers specially adapted therefor
• CPC Class Codes: A61M 1/3641 Pressure isolators
• CPC Class Codes: G01L 19/0023 for flowthrough systems having a flexible pressure transmitting element

Abstract

The aim of the invention in particular is to reduce the risk of haemolysis in extracorporeal blood circulation. To this end, a system element for releasably sealingly connecting a transducer to a fluid system comprises a measuring chamber (7) which can be connected to the fluid system in such a way as to allow throughflow. Said measuring chamber (7) is formed in a housing (10). Part of the wall of the measuring chamber (7) is formed by a membrane (11) which is considerably more flexible than the rest of the wall (15) of said measuring chamber (7). The membrane (11) has a peripheral built-up section (20) which is located on the side of the membrane (11) that faces towards the measuring chamber (7). Said built-up section (20) engages in a channel (19) which is formed in the housing (10) and which extends around the measuring chamber (7). The wall (inner wall 16) of the channel (19) that faces towards the measuring chamber (7) is lower than the wall (outer wall 17) of the channel (19) that faces away from the measuring chamber (7) (19). The invention also provides for a system element for releasably sealingly connecting a transducer to a fluid system, containing at least one sensor for converting pressures and pressure changes into electrical signals. The sensor is located in a housing (26) and at least part of the housing (26) is filled with a fluid or gel which transmits pressure. The housing (26) is closed by a transducer membrane (23) on one side. In the area (24) surrounding the transducer membrane (23), the housing (26) is configured for applying one of the system elements (1) according to one of the preceding claims. This surrounding area (24) essentially encompasses the transducer membrane (23) in a ring shape. The measuring range of the sensor has differential pressures of at least −250 mm Hg to +1000 mm Hg in relation to the surroundings. The invention also relates to a set comprising the inventive system elements.

Claims

1. A system element for the releasable sealed connection of a transducer to a fluid system, with a measuring chamber (7) which can be connected to the fluid system in such a way as to allow throughflow, the measuring chamber (7) being formed in a housing (10) and part of the wall of the measuring chamber (7) being formed by a membrane (11) which is considerably more flexible than the rest of the wall (15) of the measuring chamber (7), characterized in that the membrane (11) has a peripheral bead (20) which is located on the side of the membrane (11) that faces toward the measuring chamber (7), the bead (20) engaging in a groove (19) which is formed in the housing (10) and extends around the measuring chamber (7) and the wall (inner wall 16) of the groove (19) that faces toward the measuring chamber (7) being lower than the wall (outer wall 17) of the groove (19) that faces away from the measuring chamber (7).

2. The system element as claimed in claim 1, characterized in that the difference in height of the outer wall (17) with respect to the inner wall (16) of the groove (19) is less than the average thickness of the membrane (11) in the area (21) outside the peripheral bead (20).

3. The system element as claimed in claim 1, characterized in that the membrane (11) protrudes at least approximately 0.1 mm, preferably at least approximately 0.3 mm, beyond the walls (16, 17) of the groove (19) in the area of the bead (20) after insertion of the bead (20) into the groove (19).

4. The system element as claimed in claim 1, characterized in that the membrane (11) is produced from an EPDM.

5. The system element as claimed in claim 1, characterized in that the membrane (11) is produced from a TPE.

6. The system element as claimed in claim 5, characterized in that the membrane (11) is produced from a TPE of the class SEBS.

7. The system element as claimed in claim 1, characterized in that the membrane (11) seals a negative pressure of 530 hPa with respect to air when a pressing pressure of 60 N is applied to a finely turned steel surface.

8. The system element as claimed in claim 1, characterized in that the membrane (11) has within the bead (20) a diameter of less than 12 mm.

9. The system element as claimed in claim 1, characterized in that the bead (20) has a width of approximately 2 mm in the longitudinal extent of the membrane (11).

10. The system element as claimed in claim 1, characterized in that the membrane (11) has within the bead (20) a thickness of approximately 0.4 mm to approximately 0.5 mm.

11. A system element for the releasable sealed connection of a transducer (12) to a fluid system, containing at least one sensor for converting pressures and pressure changes into electrical signals, the sensor being arranged in a housing (26) and at least part of the housing (26) being filled with a fluid or gel which transmits pressure, and the housing (26) being closed by a transducer membrane (23) on one side, the housing (26) being further configured in the area (24) surrounding the transducer membrane (23) for applying a system element as claimed in one of the preceding claims, the surrounding area (24) essentially encompassing the transducer membrane (23) in a ring shape, characterized in that the measuring range of the sensor covers at least differential pressures with respect to the surroundings of −

250 mm Hg to +1000 mm Hg.

12. The system element as claimed in claim 11, characterized in that the measuring range of the sensor reaches at least down to differential pressures with respect to the surroundings of −

350 mm Hg.

13. The system element as claimed in claim 12, characterized in that the measuring range of the sensor covers at least differential pressures with respect to the surroundings of −

400 mm Hg to +3000 mm Hg.

14. The system element as claimed in claim 11, characterized in that the surrounding area (24) is approximately technically plane and the surface of the surrounding area (24) is smoothed to make it essentially free of scratches, preferably finely turned, ground or polished.

15. The system element as claimed in claim 11, characterized in that the surface of the surrounding area (24) has an averaged peak-to-valley height R_Z of no more than 20 μ

m.

16. The system element as claimed in claim 11, characterized in that the surface of the surrounding area (24) has a maximum peak-to-valley height R_max of no more than 30 μ

m, preferably no more than approximately 20 μ

m.

17. The system element as claimed in claim 11, characterized in that the transducer membrane (23) is slightly pre-curved with respect to the area (24) surrounding it.

18. The system element as claimed in claim 17, characterized in that the transducer membrane (23) is pre-curved with respect to the area surrounding it by no more than 1 mm, preferably no more than 0.6 mm.

19. The system element as claimed in claim 11, characterized in that the transducer membrane (23) is formed from an RTV silicone.

20. The system element as claimed in claim 11, characterized in that the transducer membrane (23) is formed from a polyurethane, preferably a TPE polyurethane.

21. The system element as claimed in claim 11, characterized in that the surrounding area (24) has a width of at least 2 mm.

22. A set comprising a system element as claimed in claim 1, characterized in that the system element is designed as a pressure dome (1).

23. The set as claimed in claim 22, characterized in that at least one coupling device (13, 14) for the mechanical connection of the pressure dome (1) and the transducer (12) is provided and the membrane (11) of the pressure dome (1) is pressed in the area of the bead (20) against the area (24) surrounding the transducer membrane (23), so that an airtight seal takes place between the membrane (11) of the pressure dome (1) and the transducer (12) when the pressure dome (1) and transducer (12) are coupled.

24. The set as claimed in claim 22, characterized in that, when coupling has taken place, the membrane (11) of the pressure dome (1) is pressed in the area of the bead (20) with at least 50 N, preferably by 90-110 N, against the area (24) surrounding the transducer membrane (23).

25. The set claimed in one of claims 22, characterized in that, once coupling has taken place, the membrane (11) of the pressure dome (1) is pressed together in the area of the bead (20) by approximately 0.1 mm to approximately 0.3 mm.