Connecting element for connecting a sensor to a sealed fluid system

Abstract

System element for a detachable sealed connection of a sensor to a fluid system, comprising a measuring chamber (6) that can be connected to the fluid system by flow, wherein the measuring chamber (6) is formed in a housing (1) and a part of the wall of the measuring chamber (6) is formed by a membrane (2) that is significantly more flexible than the remaining part of the wall of the measuring chamber (6), wherein the part of the wall of the measuring chamber adjoining the membrane forms an outer wall (9) with a rim (10) on which the membrane (2) rests, and the membrane (2) has a circumferential bead (11) located on the side of the membrane (2) facing the measuring chamber (6), characterized in that the bead (11) engages in a recess (12) formed in the housing (1) around the outer wall (9), which extends around the measuring chamber (6).and in the area of ​​the recess (12) projecting pins (13) are arranged around the outer wall (9) and wherein holes (14) are provided in the bead (11) of the membrane (2) so that the pins (13) engage in the holes (13) in the bead (11) of the membrane (2).

Description

[0001] The invention relates to a system element for a detachably sealed connection of a sensor to a fluid system, comprising a measuring chamber that can be connected to the fluid system in a flowable manner, wherein the measuring chamber is formed in a housing and part of the wall of the measuring chamber is formed by a membrane that is significantly more flexible than the remaining part of the wall of the measuring chamber, wherein the part of the wall of the measuring chamber adjoining the membrane forms an outer wall with a rim on which the membrane rests, and the membrane has a circumferential bead located on the side of the membrane facing the measuring chamber.

[0002] Such system elements are known in medical technology by the colloquial terms "dome" or "pressure dome," derived from the dome-shaped design of the measuring chamber. A sensor, to which such a dome is typically connected for pressure measurement or monitoring, is known as a "transducer." This term refers to a sensor in a suitable housing that converts the pressures and pressure changes, usually transmitted via the membrane of the pressure dome, into an electrical signal. These devices have traditionally been used to enable the measurement of pressures in liquids during the examination and treatment of humans and animals, preferably via electronic diagnostic and monitoring equipment.The advantage of such an arrangement is the possibility of designing the system element as an inexpensive and easy-to-dispose-of disposable part, while ensuring a hygienically sound and safe closure of the fluid system.

[0003] For example, in DE 42 19 888 A1, a flow-pressure transducer with such a connecting element is described for pressure monitoring during the rinsing of body cavities, which is designed for a large volume flow rate in accordance with the intended area of ​​application.

[0004] To monitor a patient's hemodynamic parameters, especially in intensive care patients, it is now standard practice to include invasive pressures in patient monitoring—that is, the monitoring of the patient's vital functions—in addition to recording an ECG. Depending on the level of monitoring, between one and four pressures (arterial, pulmonary arterial, LAP, and venous) are measured.

[0005] For this procedure, a catheter with an integrated monitoring set is used. The positioning of the catheter's end opening defines the measurement point within the patient's body. A monitoring set is a collection of components, usually single-use for hygienic reasons, that establish the connection between the patient and the monitor. The monitor is the electronic monitoring and recording system that evaluates and displays the relevant measurement data and, if necessary, issues alarm signals when measurement data deviates from predefined target ranges.

[0006] A general description of this can be found in Buchwalsky, Rainer: Einschwemmkatheter: Technik, Bewertung u. prakt. Folgen (Beiträge zur Kardiologie, Bd. 29); Erlangen: perimed Fachbuch-Verlagsgesellschaft, 1985, Seiten 106-109.

[0007] The monitoring set, which is attached to the catheter, consists of a non-vented infusion set for administering infusion solutions to the patient, a flushing system that ensures a continuous flushing rate of typically 3 ml / h at the catheter tip to prevent occlusion by thrombi, optionally with a rapid flushing function for special cases, and a pressure dome. The pressure dome transmits the pressure signal via its flexible membrane to a reusable transducer (pressure sensor). Such a pressure dome has previously been attached to the transducer using a screw or bayonet connection (see DE 42 19 888 A1, column 3, lines 28 to 30).

[0008] Other elements of a monitoring set include the pressure hoses (color-coded) and possibly a three-way stopcock to administer medication, or a blood collection system to take blood for further examinations.

[0009] Disposable transducers, which contain the pressure sensor in a flow-through housing, have a simple tubular design within the flow chamber to prevent air bubbles from being trapped, which significantly impairs their dynamic measurement characteristics. However, they have the disadvantage that the valuable electronics are integrated into the disposable unit and are therefore discarded and disposed of with each change of the monitoring set. To comply with hygiene requirements, such a replacement must occur at least every other day. This not only results in the cost of replacing the still-functional electronics with each change, but also necessitates additional, specialized, and therefore expensive handling as electronic waste during disposal due to the presence of electronic components.

[0010] For this reason, reusable dome systems are once again gaining popularity, at least in Europe. The valuable electronics, especially the pressure sensor, are housed in a special casing. Such a component is usually called a transducer. One or more transducers are integrated into a special mounting plate. The mounting plate is attached to, for example, an IV stand using a clamp or screw mechanism. The pressure measurement data from the transducers in the mounting plate is transmitted to the monitor via one or more cables.

[0011] Previously, if a dual or even triple monitoring set was to be mounted on multiple transducers using the standard screw or bayonet connection found on reusable transducers, the necessary rotational movements were only possible with limitations on the first transducer. When attaching it to the second transducer, the presence of the assembly on the first transducer already interfered. Attaching a second dome to the second transducer was impossible without removing the transducer from a shared mounting plate.

[0012] This complicated handling is not only annoying, it is also an absolute obstacle to designing mounting plates with permanently installed transducers and rear wiring.

[0013] This problem is not solved by a system element of the type described in DE 35 25 536 A1. There, and in EP 0 208 955 A2, a fastening method is proposed to prevent damage, particularly to the diaphragm of the connecting element, which does not require mutual rotation of the connecting element and the transducer. For this purpose, additional fastening elements, such as pivotally mounted clamps or locking hooks, are to be provided at two points on the circumference of the connecting element's housing.

[0014] The proposal suggests that these fastening elements or extensions should protrude downwards beyond the membrane for handling the fasteners. This would allow visual verification that the intended locking mechanism has been engaged. Furthermore, this should simplify handling when removing the connecting element from the transducer. However, this practically precludes combinations with transducers mounted in retaining plates.

[0015] Furthermore, according to the teaching of this publication, the housings of the pressure dome and transducer should directly touch (see there, column 9 / 10), whereby the membranes of the pressure dome and transducer should lie "snugly against each other", but a pre-tension of the membranes should be disadvantageous and avoided (ibid., column 4, lines 21 ff.).

[0016] EP 0 701 830 A1 describes a device and a method, preferably for use in pressure measurement in blood lines in dialysis equipment, hemofiltration, and hemodiafiltration. The pressure is to be measured indirectly via a gas column (air) that is connected to the liquid column in a line through an elastic membrane located in a housing. The pressure of the gas column is detected by suitable and conventional sensors (pressure transducers). To extend the measuring range due to the mechanically limited deflection of the membrane and the compressibility of the gas column, a device and a method are proposed by which the amount of gas in the gas-carrying part of the measuring device is increased or decreased depending on the gas pressure to be measured, thereby maintaining the mobility of the membrane and thus the transmission of pressure changes.

[0017] The gas flow rate is changed via a pumping device in the form of a peristaltic pump controlled by a controller. The compressibility of the gas volume interposed according to the EP application creates a kind of acoustic low-pass filter that dampens or suppresses rapid pressure changes or higher-frequency pressure oscillations. The system described in the publication is practically only suitable for measuring static pressures or for monitoring average values, whereby the calculation of the pressure average can be adjusted by the damping characteristics of the system, e.g., via the gas volume interposed between the diaphragm and the pressure sensor. For arrangements of this type, an upper cutoff frequency of approximately 0.1 Hz for detecting pressure changes is known from prior use.

[0018] German patent DE 29 30 869 C2 describes a pressure measuring capsule for mounting on a pressure transducer, comprising a housing in which a cavity is formed within an annular ridge, closed by a membrane bonded to the annular ridge. The cavity can be filled with a liquid or gas via two connecting tubes.

[0019] The main focus of this description is the design of extensions on the cylindrical housing of the pressure sensor capsule to form a snap-fit ​​connection with correspondingly designed counterparts on a pressure transducer. Particular emphasis is placed on the elastic design of these extensions to create defined, lockable end positions for the components of the snap-fit ​​connection, whereby the pressure sensor and pressure sensor capsule must be rotated relative to each other to establish the mechanical connection. The spring-like design of the pressure sensor capsule-side components of the snap-fit ​​connection is intended to compensate for manufacturing tolerances and achieve a lockable end position between the pressure sensor capsule and the pressure transducer.

[0020] The detent position is intended to simultaneously exert a defined preload force on the pressure sensors, with the inventors envisioning that this force should be so consistently reproducible with different pressure sensors that a zero-point adjustment of the evaluation electronics used is no longer necessary.

[0021] The cited publication describes a Renk connection as particularly advantageous, the known disadvantages of which are in particular a frictional relative movement between the partners to be joined in the Renk connection.

[0022] European patent EP 0 330 891 B1 describes an arrangement for transferring the pressure of one fluid to another. It proposes an elongated housing whose interior, in the form of a rotational ellipsoid, is divided into two compartments by a flexible membrane. These two compartments can be arranged either as adjacent regions of the interior or concentrically. One of the compartments is provided with an inlet and an outlet opening to allow a first fluid, such as blood, to flow through it.

[0023] The second room is provided with a single opening through which a fluid that can be introduced into the second room is to be connected to, for example, an external pressure measuring device in order to measure, for example, the pressure of the blood flowing through the first room.

[0024] The invention is described and claimed as essential to inserting the membrane into the housing in an unstretched or even folded state, whereby the inventors hope to improve the measurement possibilities of pressure and in particular the measurement of negative pressures, without providing any further details.

[0025] WO 97 / 39679 A1 describes a coupling of a type of pressure dome with a transducer, whereby the measuring chamber of the "pressure dome" is not sealed off from the environment by a membrane, but by an insulating gel. During assembly of the pressure dome and transducer, the fluidity of the gel is intended to allow air to be forced out between the pressure dome and the transducer through venting channels.

[0026] US Patent 4,562,845 A describes a screw connection that results in a tight coupling of a pressure dome to a transducer. Since the device described therein is intended to be part of a system also described therein for monitoring other transducers for malfunction and for detecting air bubbles in blood pressure monitoring systems, the pressure dome described therein does not have a membrane for sterile sealing of the fluid system from the environment and the transducer.

[0027] From US 4,462,409 A, a pressure dome is known, which, however, is not intended for insertion into an extracorporeal circuit or for flow through with an infusion solution, but rather as the termination of a branch line that can be hydraulically coupled to a patient's circulatory system via an infusion system for pressure transmission. The measuring chamber of this pressure dome is separated from a transducer by a membrane. The transducer comprises a two-part housing, wherein a first housing part (53) has a connection surface for the attachment of the pressure dome's membrane. A rib (63a) is provided on this connection surface of the housing part, which is intended to ensure a secure fit of a bead of the membrane in a groove in the housing and thus a reliable seal of the measuring chamber.

[0028] However, the pressure dome is permanently connected to the housing part of the transducer by welding (ibid., column 4, lines 60-67), so that an arrangement with a disposable dome and a reusable transducer is not possible.

[0029] US Patent 4,920,972 A describes a system consisting of a disposable dome and a reusable transducer, in which the measuring chamber in the dome and the transducer are each sealed by a membrane. Furthermore, this document deals with replacing oil for pressure transmission within the transducer with a gel that, after being introduced in liquid form into the transducer housing, hardens into the desired gel form only after the transducer is heated to 65°C for four hours. This arrangement is intended to increase the upper cutoff frequency of a transducer.

[0030] From US 5,551,300 A, a set consisting of a disposable pressure dome and a reusable transducer is known, in which both the measuring chamber of the pressure dome and a liquid-filled measuring chamber of the transducer are sealed by a flat membrane bonded to the respective housings. In the transducer, pressure equalization of the liquid-filled measuring chamber is provided such that the measuring chamber is in flow communication with a compensating vessel, which is sealed from the environment by an elastic membrane.

[0031] The liquid system should be filled with a slight overpressure to ensure contact between the two pressure-transmitting membranes and thus the system's operational capability. To prevent pressure equalization in the transducer's liquid system during measurement, which is a prerequisite for accurate pressure measurement, it is proposed that the transducer membrane protrude slightly and that the liquid-filled measuring chamber of the transducer be connected to the pressure equalization reservoir via a hole on the transducer's front face, which is also covered by the transducer membrane. By connecting to the pressure dome, the membrane is mechanically pressed against the transducer housing, thereby closing the equalization opening. This ensures that only the liquid remaining in the transducer's measuring chamber can dampen signal transmission to a piezoelectric sensor.

[0032] From DE 44 19 593 A1, a device for measuring the pressure of a medium is known, in particular for pressure measurement in extracorporeal blood circuits, e.g., a dialysis system. This device comprises a disposable element containing a measuring chamber and having two hose connections. The measuring chamber is closed by a membrane that is inserted into a circumferential groove and secured therein by means of a metallic clamping ring or by adhesive bonding. It is particularly advantageous that a circumferential bead, in particular an O-ring, is formed around the part of the measuring chamber that is in contact with the membrane. This bead raises the membrane above the surface of the element in the area of ​​the connection to the measuring chamber.This should make it possible to achieve good coupling of the diaphragm to a pressure sensor when the element is placed in a drawer of the measuring system and the pressure sensor is preferably moved pneumatically or via a spindle towards the element.

[0033] Furthermore, the device according to DE 44 19 593 A1 requires an extremely high assembly effort for the measuring element, particularly with regard to the assembly of the membrane. This also leads to considerable effort in verifying the quality of the assembly for product liability reasons. Moreover, the large number of parts, and especially the cavities formed between the membrane and the O-ring, can also cause problems with sterilization. Considering the assembly and quality assurance effort, this results in such high costs that such a measuring system is unacceptable for single-use applications.

[0034] Furthermore, the corresponding arrangement of the pressure sensor requires an enormous amount of equipment, especially with regard to the movement device for the sensor and the calibration of the sensor which depends on the travel distance, so that such a system is unsuitable for everyday clinical and laboratory use due to the handling effort and the enormous costs.

[0035] From DE 21 29 670 A, a so-called vacuum capsule is known in which an elastic diaphragm is arranged in a rigid metal capsule. The essential features of the invention are described as the design of the diaphragm and its attachment to a plunger, such that during manufacturing the diaphragm rests against one side of the capsule and, after pre-tensioning by a spring, performs an actuating action via the plunger depending on the absolute atmospheric pressure applied to the diaphragm on one side. In particular, depending on the pre-tension via the spring, the diaphragm can execute a considerable stroke. However, this device is not designed to allow flow through it and, due to its design and purpose, is entirely unsuitable for measuring pressures, especially in extracorporeal circuits.

[0036] From DE 93 17 751 U1, a pressure indicator device is known that, upon reaching a specific predetermined pressure value, displays a color change from green to red or vice versa, visible under a transparent disc, and / or can actuate an electrical switch or push button via a plunger. For this purpose, a liquid is enclosed in the space between a diaphragm and a measuring housing. If a limit pressure on the other side of the diaphragm, corresponding to the liquid's boiling point, is undershot, the liquid evaporates, and the diaphragm, together with an attached plunger, performs a sudden stroke, allowing the plunger to actuate a pressure switch or similar device. The liquid is colored to obscure the view of a signal-colored disc on the diaphragm, which becomes instantly visible when the liquid evaporates, thus serving as a signal.

[0037] It is readily apparent that this device is not suitable for the continuous measurement of pressures.

[0038] Finally, WO 99 / 37 983 A2 discloses a pressure dome which is specially designed and suitable for use in extracorporeal blood circuits, e.g. in blood purification, and which is also particularly easy to handle due to a detachable snap connection for attachment to a transducer.

[0039] From DE 198 02 615 A1 and WO 99 / 37 983 A2, a pressure dome is known in which the measuring chamber has an inlet opening and an outlet opening at the level of opposing parts of the wall that form an edge of the measuring chamber, in the part of the wall opposite the membrane that forms a roof of the measuring chamber, and the roof is drawn inwards in a central area of ​​the measuring chamber, so that an annular channel-shaped part of the measuring chamber with a larger distance between membrane and roof and a central area of ​​the measuring chamber with a smaller distance between roof and membrane results, and the wall of the measuring chamber is designed without edges (rounded) except for the inlet and outlet openings and the transition from membrane to the remaining part of the wall.

[0040] In the area of ​​the membrane, a device for mechanically coupling the connecting element with the sensor is provided, which is part of a detachable expansion joint formed by claw-shaped retaining elements in the form of hooks for engagement in a corresponding groove or undercut of the sensor or an associated fastening device.

[0041] From DE 100 32 616 A1, WO 02 / 003 854 A1, US 6 880 404 B2, and DE 201 22 806 U1, a pressure dome is known in which the diaphragm has a circumferential bead located on the side of the diaphragm facing the measuring chamber. This bead engages in a groove formed in a housing, which extends around the measuring chamber. The inner wall of the groove facing the measuring chamber is lower than the outer wall of the groove facing away from the measuring chamber. The described design, particularly in conjunction with a suitable sensor, is intended to prevent air from being trapped between the diaphragms when the pressure dome is placed on the transducer, thus improving the measurement characteristics for negative pressures and the dynamic transmission behavior of the overall assembly.

[0042] A one-way pressure dome with an attached three-way stopcock and a check valve is known from the apparent prior use of Smiths Medical, London, UK, under the type designation MX848X2SC. In this known pressure dome, the diaphragm is also provided with a circumferential bead that is inserted into a groove surrounding the outside of the measuring chamber. The groove, with the portion of the diaphragm contained therein, is partially covered on the outside by an annular disc that is welded or bonded to the housing of the pressure dome.

[0043] Tests have shown that when subjected to higher pressures than those typically used in human blood pressure monitoring—i.e., pressures significantly above 260 mmHg—the membrane of such a pressure dome, without mechanical support from an attached transducer, bulges so far that the material's high elasticity pulls the ridge holding the membrane out of its groove, without the annular disc being able to prevent this. However, this membrane slippage is unacceptable, as it compromises the seal of the fluid system, leading to contamination of the surrounding environment and the fluid itself, which must be avoided under all circumstances in many applications.

[0044] Therefore, system elements of the type mentioned at the beginning have so far been considered unsuitable for use at higher pressures and especially outside of the monitoring of vital functions in medicine.

[0045] A system element according to the preamble of claim 1 is known from US patent 2003 / 0200812A1.

[0046] A pneumatic or hydraulic pressure sensor with a pressure dome for determining the hydrostatic pressure of the water filling in the washing basket of a washing machine is known, for example, from document US 4 163 964 A.

[0047] The invention is therefore based on the objective of providing inexpensive disposable system elements for pressure monitoring for use in other areas outside of monitoring vital functions in medicine.

[0048] This problem is solved according to the invention by a system element of the type mentioned at the outset, in which the bead engages in a recess formed in the housing around the outer wall, which runs around the measuring chamber, and in the area of ​​the recess around the outer wall projecting pins are arranged and wherein holes are provided in the bead of the membrane so that the pins engage in the holes in the bead of the membrane.

[0049] The inventor has discovered that, due to the inventive design, the membrane does not deform as much under high pressure as in known system elements, and in particular, the membrane is virtually eliminated from slipping off the housing. This opens up a further field of application for the proven, cost-effectively manufactured system elements, which are disposable and environmentally friendly, including in industrial settings where a hygienically sealed fluid system is essential, e.g., in the field of biotechnology.

[0050] It is particularly advantageous if the pins are arranged evenly distributed around the outer wall. The number of pins is advantageously at least three, preferably four to twelve, and most preferably six to ten. In an embodiment successfully tested, eight pins are provided.

[0051] To avoid the risk of the membrane cracking due to notch effect and cross-sectional weakening of the bead, it is advantageous if the pins have a length greater than width in the circumferential direction around the outer wall, in particular a curved oval base.

[0052] It has proven advantageous if the length of the tenons is approximately 2 / 3 of the distance between two tenons.

[0053] For high resistance to membrane peeling, it has proven advantageous if the pins rise approximately coaxially to the outer wall and the height of the pins is at least half the height of the recess relative to the edge of the outer wall, in particular if the height of the pins is approximately 2 / 3 the height of the recess relative to the edge of the outer wall.

[0054] A particularly advantageous embodiment of the invention has proven to be one in which a retaining ring is provided that encompasses the edge of the outer wall of the measuring chamber and is fixed against the housing, especially when the retaining ring at least covers the gaps between the pins. Tests have shown that the overpressure at which the system element remains leak-tight without the support of a sensor is limited only by the burst pressure of the diaphragm, and no longer by the diaphragm's attachment to the housing.

[0055] The arrangement is particularly stable if the retaining ring also at least partially covers the diaphragm's bead on its radially outer side. This also protects the outer surface of the bead from mechanical damage that could impair its strength, such as that which might occur, for example, if the system element is carelessly placed onto the sensor. For this purpose, the retaining ring advantageously comprises a radial wall section and an axial wall section.

[0056] A system element according to the invention is particularly secure if the retaining ring is connected to the housing in such a way that the retaining ring cannot be removed from the housing in the axial direction without damage. For this purpose, it is advantageous if the retaining ring is bonded to the housing by a material-bonded connection, e.g., by suitable welding processes. It is particularly advantageous if the retaining ring is made of the same material as the housing.

[0057] From a manufacturing perspective, it is particularly advantageous if the retaining ring is connected to the housing by an expansion joint (snap connection). This avoids the negative effects of a welding process on the diaphragm, depending on the diaphragm material.

[0058] To enable simple and quick mounting and removal of a system element according to the invention onto or from the sensor (transducer), it is advantageous if the housing is further preferably provided with two spring-elastic extensions for mechanically coupling the connecting element to the sensor (transducer), which are part of a detachable expansion joint formed by claw-shaped retaining elements in the form of hooks on the extensions for engagement in a corresponding groove or undercut of the sensor.an associated fastening device, wherein the system element further comprises a retaining ring having a non-annular shape, with a first operating position in which the retaining elements are radially movable around the measuring chamber so that the system element can be placed on or removed from the sensor, and a second operating position in which the retaining elements are held in a position so that the system element and sensor cannot be separated without damage.

[0059] The use of the retaining ring virtually eliminates the risk that, particularly in the event of large pressure spikes or fluctuations, especially when the intended maximum system pressure is exceeded due to malfunctions, the engagement of the hooks in the groove or undercut of the sensor or an associated mounting device could loosen. Without the support provided by the sensor, the diaphragm would be overloaded and rupture, allowing fluid to escape from the system. In any case, however, it is ensured that ongoing measurement or monitoring will not be interrupted by a system component slipping out of place.

[0060] For transport and handling before mounting on a sensor, it is particularly advantageous if the retaining ring has a protective plate on its side facing away from the housing. This plate is connected to the body of the retaining ring via predetermined breaking points and covers the diaphragm. The protective plate can be easily broken off and removed by the user, but until then, it protects the diaphragm from any mechanical damage that could reduce the pressure resistance of the system component.

[0061] For use in bioreactors and filtration systems, it is particularly advantageous if the membrane is attached to the housing in such a way that it does not detach from the housing when there is an overpressure in the measuring chamber relative to the environment of at least 6,000 hPa, without being connected to a sensor.

[0062] The invention will be explained in more detail with reference to exemplary embodiments shown in the accompanying drawings, which are not to be understood as limiting. The drawings show: Fig. 1 a perspective view of a housing of a first embodiment of a system element according to the invention from a low angle; Fig. 2 a perspective view of the housing of a system element according to the invention made of Fig. 1 from diagonally above; Fig. 3 a top view of a membrane of a system element according to the invention; Fig. 4 a sectional view of the membrane Fig. 3; Fig. 5 a sectional view of the housing made of Fig. 1 and Fig. 2 ; Fig. 6 a sectional view of a system element according to the invention with a housing according to. Fig. 5 and mounted membrane; Fig. 7 an exploded view of a further embodiment of a system element according to the invention with an additional retaining ring; Fig. 8 a bottom view of the embodiment of a system element according to the invention with an additional retaining ring made of Fig. 7; Fig. 9 a sectional view of the system element with additional retaining ring made of Fig. 7 and Fig. 8; Fig. 10 a perspective view of the system element with additional retaining ring made of Fig. 7, Fig. 8 to Fig. 9 from the bottom diagonal; Fig. 11 a perspective view of a retaining ring of a system element according to the invention from an oblique angle above with the protective plate broken out; Fig. 12 an underside view of a retaining ring made of Fig. 11 with protective plate; Fig. 13 a perspective view of a further embodiment of a system element according to the invention with a retaining ring with a protective plate from an oblique angle above; and Fig. 14 a perspective view of the system element with retaining ring with protective plate made of Fig. 13 from the bottom diagonal.

[0063] The figures illustrate various embodiments of a system element according to the invention for a detachable, sealed connection of a (not shown) sensor to a fluid system in the form of a so-called pressure dome. Suitable sensors include transducers already used in medical technology, as described in the prior art above.

[0064] In a first embodiment of the invention, a system element or pressure dome according to the invention consists of a housing 1 and a membrane 2. One embodiment of a housing 1 is described in the Fig. 1, Fig. 2, and others shown, another in the Fig. 13 and Fig. 14. The housing 1 has openings 3 as inlet and outlet for connection to a fluid system, such as an infusion device, and to a patient, e.g. via a glued-in three-way stopcock, or for insertion into an extracorporeal blood circulation, e.g. a dialysis machine, a heart-lung machine or a cell separator, or also another fluid system such as a filtration system or a bioreactor.

[0065] The inlet and outlet have corresponding connections, e.g. in the form of a conical sealing seat 4, as e.g. in Fig. 5, a glue-in groove or another tight connection system commonly used in medical technology or bioprocess engineering. The dimensions of the connections 4 can, for example, comply with DIN 13090. The connections 4 can, for example, include lockable Luer-lock connections with a loose threaded part or with a fully threaded external section, as specified, for example, in DIN 13090 Part 2, or hose fittings 5 ​​(also called hose clamps), as, for example, in the Fig. 13 and Fig. 14 shown.

[0066] Suitable diameters for inlet and outlet openings 3 are in the range of over 1 mm for measurements with static liquid columns, and up to 10 mm for use in extracorporeal blood circulation. For connecting the fluid system to standard transducers used as measuring sensors in medical technology, the diameter can also be up to one inch, corresponding to over 25 mm.

[0067] The housing 1 contains a measuring chamber 6, which is in flow communication with the inlet and outlet openings 3. The housing 1 is particularly economical as a one-piece injection-molded part, preferably made of a sterilizable plastic, e.g., polycarbonate. Part of the wall of the measuring chamber 6 is formed by the elastic membrane 2 (in Fig. 3 and Fig. (4 shown) formed, for example, from EPDM, TPE, preferably SEBS class TPE, or any other suitable material that is resistant to the intended fluid in the fluid system, sterilizable, and optionally physiologically harmless. Gamma irradiation is also a suitable sterilization method.

[0068] Thus, in a first embodiment, the system element preferably consists only of the membrane 2 and a one-piece injection-molded plastic part as the housing 1, as shown in Fig. Figure 6 shows that for a proven good pressure transmission to commercially available transducers, the material of the diaphragm and its processing during manufacturing, e.g. injection molding, should result in a diaphragm that, with a contact pressure of 60 N against a finely machined steel surface, seals a vacuum of 530 hPa against air.

[0069] Furthermore, a device for mechanically coupling the connecting element with the measuring sensor (transducer) is provided, which is part of a detachable expansion connection formed by claw-shaped retaining elements in the form of hooks 7 for engagement in a corresponding groove or undercut of the measuring sensor or an associated fastening device.

[0070] The hooks 7 are formed by spring-elastic extensions of the housing 1 and are formed in pairs, each integrally with a handle 8. A total of four evenly spaced hooks 7 are provided. This allows the system element to be assembled and disassembled blindly with one hand by squeezing the handles 8 together.

[0071] For measuring pressures under ambient pressure, it is advantageous if the spring-elastic connection of hook 7 with the housing 1 is designed in such a way that a preload force of at least approximately 60 N can be maintained.

[0072] Instead of hook 7 and a corresponding undercut on the transducer (not shown), other known coupling mechanisms are also possible, although a rotating movement between diaphragm 2 and the transducer diaphragm should be avoided. For example, the hook and undercut can be interchanged. Alternatively, a different snap connection can be provided, e.g., as proposed in WO 99 / 37 983 A2 or US 6 880 404 B2. Furthermore, bayonet connections (locking connections), preferably with a locking ring, are also suitable, as is a screw connection if excessive tightening of the connection is prevented by suitable spacers or the like. Finally, pivotally mounted clamps or toggle latches similar to locking hooks can be provided.

[0073] The part of the wall of the measuring chamber 6 adjoining the membrane 2 forms an outer wall 9 with a rim 10 on which the membrane 2 rests. The membrane 2 has a circumferential bead 11 located on the side of the membrane 2 facing the measuring chamber 6. The bead 11 engages in a recess 12 formed in the housing 1 around the outer wall 9, which extends around the measuring chamber 6, as shown particularly in the Fig. 1 and Fig. 5 can be seen. In the area of ​​the recess 12 around the outer wall 9, protruding pins 13 are arranged. Corresponding holes 14 are provided in the bead 11 of the membrane 2, either as through holes, as in particular in Fig. 4, or as blind holes (not shown), so that the pins 13 engage in the holes 14 in the bead 11 of the membrane 2, thus providing increased security against the membrane being pulled off by the internal pressure in the measuring chamber 6. A system element according to the invention with housing 1 and mounted membrane 2 is well illustrated in the sectional view in Fig. 6 can be seen.

[0074] A suitable distribution, shape and size of the holes 14 in the membrane 2 is shown in the top view in Fig. 3 can be seen. Eight holes are 14 and in the Fig. 1 and Fig. Figure 7 shows eight pins 13, which are evenly distributed around the outer wall 9. The number of pins 13 (and corresponding holes 14) should be at least three; better pull-off protection is achieved with four to twelve, preferably six to ten, pins 13. A larger number of pins 13, when sized to fit the aforementioned standard transducers, would result in very small pins and holes, and thus the desired greater mechanical strength of the connection between diaphragm 2 and housing 1 would hardly be achievable. However, a larger number of pins 13 and holes 14 can be advantageous for larger system components.

[0075] To achieve a good holding effect between membrane 2 and pins 13 with minimal material weakening due to the notch effect of the holes 14 on membrane 2, the pins 13 and the holes 14 have a length greater than width in the circumferential direction around the outer wall and are curved around the measuring chamber 6. It has proven practical that the length of the pins 13 is approximately two-thirds of the distance between two pins 13.

[0076] The pins 13 rise approximately coaxially to the outer wall 9. Since the bead 11 of the membrane 2 is advantageously set back from the contact plane with a sensor in order to obtain the least possible interference with the membrane-membrane coupling, it is advantageous that the height of the pins 13 is approximately 2 / 3 of the height of the setback 12 from the edge 10 of the outer wall 9, as well shown in Fig. 6 can be seen.

[0077] Fig. Figure 7 shows an exploded view of a further embodiment of a system element according to the invention with an additional retaining ring 15. Fig. Figure 9 shows a sectional view of this embodiment of the invention, wherein the membrane 2 and retaining ring 15 are mounted on the housing 1 in this illustration. A bottom view shows Fig. 8, Fig. 10. A perspective view from a low angle. How well in the Fig. 8 and Fig. As shown in Figure 9, the retaining ring 15 surrounds the edge 10 of the outer wall 9 of the measuring chamber 6 and, with its radial wall section 16, covers the bead 11 of the diaphragm 2 in the area of ​​the pins 13, shown here and preferably over its entire circumference. This coverage is necessary for an improved fit of the diaphragm 2, at least in the area of ​​the gaps between the pins 13. With its axial wall section 17, the retaining ring 15 covers the bead on its radially outer side. This provides mechanical protection for the bead 11 and allows the retaining ring 15 to be securely connected to the housing 1, preferably by welding, so that the retaining ring 15 cannot be removed from the housing 1 in the axial direction without damage. For this purpose, it is advantageous if the retaining ring 15 is made of the same material as the housing 1.

[0078] In this embodiment, it is practically impossible for the membrane 2 to deform due to pressure from the measuring chamber 6 to such an extent that it could slip off the housing 2. Rather, tests have shown that the membrane 2 will tear in the area of ​​the measuring chamber 6 beforehand.

[0079] Instead of welding, a connection of the retaining ring 15 to the housing 1 by means of an expansion joint is also possible.

[0080] In the Fig. 13 and Fig. In the embodiment of a system element according to the invention shown in Figure 14, a retaining ring 18 is also provided, as shown in Figure 18. Fig. Figure 11 shows that the retaining ring 18 is not annular in shape, but rather has two circular sections 21 lying on a first axis 19, which, for example, have knurling on their outer surface for improved handling. A section 22 is arranged in a second axis 20 of its base, perpendicular to this axis, in which the retaining ring is extended to an approximately rectangular shape. In this area, detent recesses 23 are provided on the upper surface of the retaining ring 18.

[0081] In a first operating position of the retaining ring 18 (not shown), the spring-elastic extensions of the housing 1 with the hooks 7 are movable in a radially outward direction with respect to the measuring chamber 6 in the extended section 22 of the retaining ring 18, so that by squeezing together the handles 8 the hooks 7 can be moved in order to place the system element on or remove it from a transducer.

[0082] The retaining ring 18 can be rotated into a second operating position, as described in the Fig. 13 and Fig. Figure 14 shows that in this position, the retaining elements with the hooks 7 are held in place, preventing the system element and the sensor from being separated without damage. However, in this position of the retaining ring 18, the system element also cannot be placed onto a transducer by squeezing the handles 8 together and thus spreading the hooks 7. In this operating position, the retaining ring 18 is secured against accidental rotation by the locking recesses 23 engaging with the housing part forming the inlet and outlet openings 3. This position is also advantageous for transporting and storing a system element according to the invention.

[0083] To protect the membrane during transport and storage with the retaining ring in place, it is particularly advantageous that the retaining ring 18 has a protective plate 26 on its side facing away from the housing 1, which is connected to the body 25 of the retaining ring 18 via predetermined breaking points 24, as shown in Fig. 12 shown. This protective plate 26 covers the membrane 2 when the retaining ring 18 is placed on the housing 1 of the system element, as shown in the Fig. 13 and Fig. Figure 14 shows the protective plate 26, which can be easily broken out and removed by the user when the system element is to be placed on a transducer.

[0084] Tests have shown that the inventive improvement of known system elements results in the membrane 2 not detaching from the housing 1 even in the absence of a support provided by the membrane of a transducer at an overpressure in the measuring chamber 6 relative to the environment of at least 6,000 hPa, and thus proven and cost-effective disposable pressure domes can also be used for industrial applications in the future with the inventive improvement.

Claims

[1] System element for a detachable sealed connection of a sensor to a fluid system, with a measuring chamber (6) that can be connected to the fluid system by flowing fluid through it, wherein the measuring chamber (6) is formed in a housing (1) and a part of the wall of the measuring chamber (6) is formed by a membrane (2) that is significantly more flexible than the remaining part of the wall of the measuring chamber (6), wherein the part of the wall of the measuring chamber adjoining the membrane forms an outer wall (9) with a rim (10) on which the membrane (2) rests, and the membrane (2) has a circumferential bead (11) located on the side of the membrane (2) facing the measuring chamber (6), characterized by, that the bead (11) engages in a recess (12) formed in the housing (1) around the outer wall (9), which extends around the measuring chamber (6), and in the area of ​​the recess (12) projecting pins (13) are arranged around the outer wall (9), and wherein holes (14) are provided in the bead (11) of the membrane (2) so that the pins (13) engage in the holes (13) in the bead (11) of the membrane (2). [2] System element according to one of the preceding claims, characterized by , that the pins (13) are evenly distributed around the outer wall (9). [3] System element according to claim 2, characterized by , that the number of cones (13) is at least three. [4] System element according to claim 3, characterized by , that the number of cones (13) is four to twelve, preferably six to ten. [5] System element according to claim 4, characterized by , that eight pins (13) are provided. [6] System element according to one of the preceding claims, characterized by , that the pins (13) have a length greater than width in the circumferential direction around the outer wall (9). [7] System element according to claim 6, characterized by , that the length of the pins (13) is 2 / 3 of the distance between two pins (13). [8] System element according to one of the preceding claims, characterized by , that the tenons (13) rise approximately coaxially to the outer wall (9) and the height of the tenons (13) is at least half the height of the recess (12) relative to the edge (10) of the outer wall (9). [9] System element according to claim 8, characterized by , that the height of the tenons (13) is 2 / 3 of the height of the recess (12) opposite the edge (10) of the outer wall (9). [10] System element according to any one of the preceding claims, characterized by, furthermore, a retaining ring (15) is provided which surrounds the edge (10) of the outer wall (9) of the measuring chamber (6) and which is fixed against the housing (1). [11] System element according to claim 10, characterized by , that the retaining ring (15) at least covers the gaps between the pins (13). [12] System element according to claim 11, characterized by , that the retaining ring (15) furthermore covers at least partially the bead (11) of the membrane (2) on its radially outer side. [13] System element according to claim 12, characterized by , that the retaining ring (15) comprises a radial wall section (16) and an axial wall section (17). [14] System element according to one of claims 10 to 13, characterized by , that the retaining ring (15) is connected to the housing (1) in such a way that the retaining ring (15) cannot be removed from the housing (1) without damage in an axial direction. [15] System element according to one of claims 10 to 14, characterized by, that the retaining ring (15) is materially bonded to the housing (1). [16] System element according to one of claims 10 to 14, characterized by , that the retaining ring (15) is connected to the housing (1) by an expansion joint. [17] System element according to any one of claims 10 to 16, characterized by , that the retaining ring (15) is made of the same material as the housing (1). [18] System element according to any one of the preceding claims, characterized by, that the housing (1) preferably has two spring-elastic extensions for mechanically coupling the connecting element to the sensor, which are part of a detachable expansion joint formed by claw-shaped retaining elements in the form of hooks (7) on the extensions for engaging a corresponding groove or undercut of the sensor or an associated fastening device, wherein the system element further comprises a retaining ring (18) having a non-annular shape, with a first operating position in which the retaining elements are radially movable around the measuring chamber (6) so that the system element can be placed on or removed from the sensor, and a second operating position in which the retaining elements are held in a position so that the system element and sensor cannot be separated without damage. [19] System element according to claim 18, characterized by , that the retaining ring (18) has on its side facing away from the housing (1) a protective plate (26) connected to the body (15) of the retaining ring (18) via predetermined breaking points (24), which covers the membrane (2). [20] System element according to any one of the preceding claims, characterized by , that the membrane (2) is attached to the housing (1) in such a way that it does not detach from the housing (1) when there is an overpressure in the measuring chamber (6) relative to the environment of at least 6,000 hPa, without being connected to a sensor.

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