EP3463506A2

EP3463506A2 - Dialysis machine and constant flow restrictor

Info

Publication number: EP3463506A2
Application number: EP17728447.8A
Authority: EP
Inventors: Christoph Wiktor
Original assignee: Fresenius Medical Care Deutschland GmbH
Current assignee: Fresenius Medical Care Deutschland GmbH
Priority date: 2016-06-03
Filing date: 2017-06-02
Publication date: 2019-04-10
Also published as: CN109219455B; WO2017207105A3; CN109219455A; US11246968B2; US20190125953A1; WO2017207105A2; DE102016006887A1

Abstract

The invention relates to a dialysis machine, especially for hemodialysis and/or hemofiltration, comprising a dialysate system and a water inlet via which the dialysate system can be connected to an external water supply, characterized in that a constant flow restrictor is mounted between the water inlet and the dialysate system.

Description

Dialysis machine and constant flow restrictor

The present invention relates in a first aspect to a dialysis machine having a dialysate system and having a water inlet, via which the dialysate system can be connected to an external water supply. In particular, it is a dialysis machine for hemodialysis and / or hemofiltration.

Such dialysis machines are usually connected at the place of use to an ultrapure water supply, which provides the dialysate or permeate required for dialysis.

Since the pressure of the external water supply, which is applied to the water inlet of the dialysis machine, can vary greatly from site to site, a pressure reducer is provided in conventional dialysis equipment between the water connection and the dialysate system. Figure 1 shows a schematic diagram of such a dialysis machine according to the prior art. The dialysis machine 1 has a water inlet 2, which can be connected to an external water supply and via which water can flow into an inlet chamber 3 of the dialysate system. To adapt to different pressures of the external water supply is the pressure reducer 4 in the line between the water inlet 2 and the input chamber 3 is provided. Furthermore, an input valve 5 is arranged in the line. When installed at the place of use, the service technician sets the inlet pressure in the inlet chamber of the dialysate system to a desired value by means of the pressure reducer.

Such dialysis machines thus have the disadvantage that a service technician is required to set the pressure reducer at the place of use. Furthermore, an adaptation to fluctuating pressures during the operation is not provided. As a result, an optimal operating behavior is not achieved in all cases. In particular, too low inflows to the input chamber may result in the dialysis machine not achieving optimal performance. Too high inflows lead to an additional burden on the water supply.

The object of the first aspect of the present invention is therefore to provide an improved dialysis machine.

According to a second aspect, the present invention relates to a constant-flow throttle.

From document EP 2 253 352 A1 a constant flow throttle is known, which should ensure a constant outflow of cerebral spinal fluid into other body openings in the case of a hydrocephalus as an implant. The constant flow throttle known from this publication has a housing through which fluid flows, which encloses an inlet, a throttle opening and an outlet. a plunger is slidably disposed in the housing, wherein between the throttle opening and the plunger a dependent of the relative position between plunger and throttle opening, the throttle effect defining throttle channel remains. In EP 2 253 352 A1, the throttle channel is embedded helically in the circumference of the plunger. If the plunger is displaced against the force of a spring by a differential pressure between the inlet and the outlet of the housing, the length of the throttle channel remaining between the throttle opening and the plunger changes. By a corresponding adjustment of the spring force For example, the constant-flow throttle can generate a substantially constant volume flow over its operating pressure range. However, the constant flow throttle known from EP 2 253 352 A1 is designed only for low flow rates and therefore can not be used for dialysis machines.

Another throttle is known from WO 98/38555 A1. Here, a needle-shaped plunger is used, which is shifted in response to a differential pressure relative to a diaphragm. The constant flow restrictor of WO 98/38555 A1 is used in irrigation systems.

The object of the second aspect of the present invention is therefore to provide an improved constant-flow throttle. Preferably, this should be used in a dialysis machine.

The above objects according to the first and second aspects of the present invention are achieved by the independent claims of the present invention. Preferred embodiments of the present invention are the subject of the dependent claims.

According to the first aspect, the present invention comprises a dialysis machine with a dialysate system and with a water inlet, via which the dialysate system can be connected to an external water supply. In particular, the dialysis machine is a device for hemodialysis and / or hemofiltration. According to the invention, it is provided that a constant flow throttle is arranged between the water connection and the dialysate system. Such a constant flow throttle changes depending on the applied pressure difference their flow resistance so that over a given operating range results in an approximately constant, independent of the pressure difference flow.

The use of such a constant flow restrictor in a dialysis machine has the advantage over the known from the prior art pressure reducers that the dialysate system is reliably filled with a reproducible flow. Furthermore, can be dispensed with a setting by the service technician, since the desired flow can be specified by the constant-flow throttle. Furthermore, the constant flow throttle has the advantage that even fluctuating pressures of the external water supply have no influence on the flow with which the dialysate system is filled. A dialysis machine according to the invention can thus be connected without adjustment by a service technician to a wide variety of external water supplies, for example to an ultrapure water ring line of different quality and load, to an ultrapure water location, to a reverse osmosis system, etc.

The constant-flow throttle furthermore ensures that the dialysis machine according to the invention achieves its optimum performance through the correct inflow. Furthermore, unnecessary loads on the water supply are prevented.

The dialysate system of the dialysis machine according to the invention may have a water inlet chamber, which is filled by the external water supply with water. In this case, the constant flow throttle is preferably arranged between the water inlet of the dialysis machine and the water inlet chamber of the dialysate system.

The water inlet chamber may further comprise a level detection and / or an input valve. Preferably, a controller of the dialysis machine controls the input valve in response to the level detection to ensure a desired level in the water inlet chamber. In particular, the input valve can be arranged downstream of the constant-flow throttle. In particular, the constant flow throttle and the inlet valve may be arranged in a line which connects the water connection with the water inlet chamber. The input valve may be a switching valve. If this is opened, the constant-flow throttle according to the invention ensures that the input chamber is filled with a reproducible flow. According to a preferred embodiment of the present invention, the constant-flow throttle is designed as a passive flow control element. This makes it possible to dispense with sensors and / or control electronics. In particular, the constant-flow throttle has a throttle element, which is moved by a pressure applied to the constant-flow throttle differential pressure against the force of a spring and changes the flow resistance of the differential pressure throttle. The throttle element may in particular be a plunger, which is displaceable in a throttle opening. The throttle opening, the plunger and the spring are preferably designed so that within an operating range of differential pressures results in a substantially constant, independent of the differential pressure flow through the constant-flow throttle.

In a preferred embodiment of the present invention, the constant-flow throttle used has the following structure: The constant-flow throttle has a housing through which liquid flows, with an inlet, a throttle opening and an outlet. Furthermore, a plunger is provided, which is arranged displaceably in the housing, wherein between the throttle opening and the plunger a dependent of the relative position between plunger and throttle opening, the throttle effect defining throttle channel remains. Furthermore, a spring is provided against the force of the plunger is displaced by a differential pressure which is applied between the input and the output of the housing.

Preferably, the constant-flow throttle is configured as will be described in more detail below. In particular, the constant-flux throttle according to the second aspect of the present invention may be configured.

According to the second aspect of the present invention, which is directed to a constant-flow throttle, the present invention in a first variant comprises a constant-flow throttle with a liquid-flowed housing, which has an inlet, a throttle opening and an outlet. Furthermore, a plunger is provided, which is arranged displaceably in the housing, wherein between the throttle opening and the plunger from the relative position between the plunger and throttle opening dependent, the throttle effect defining throttle channel remains. Furthermore, a spring is provided against the force of the plunger is displaced by a differential pressure which is applied between the input and the output of the housing. According to the invention, it is provided according to the first variant that the minimum flow-through cross section of the throttle channel changes when the plunger is displaced relative to the throttle opening. According to the invention, the minimum flow-through cross-section of the throttle channel is thus changed in order to adjust the flow resistance of the constant-flow throttle as a function of an applied differential pressure. This enables improved performance, especially in an operating range with low differential pressures. Furthermore, this also higher flow rates are possible, which allow use in a dialysis machine.

The constant-flow throttle according to the invention is preferably used in a dialysis machine as described above in accordance with the first aspect. However, the constant flux reactor according to the invention is not limited to use in a dialysis machine, but can be used, for example, in other medical devices.

In one possible embodiment, the length of the throttle channel may be independent of the position of the plunger relative to the throttle opening. In particular, the plunger in this case, the throttle opening always enforce completely. The throttle channel or the throttle opening acts in this case preferably fluidically as a diaphragm. In particular, the throttle opening may be a narrow aperture.

Alternatively, the throttle opening and the plunger may be configured so that change in a displacement of the plunger relative to the throttle opening, both the length, and the minimum flow cross-section of the throttle channel. Preferably, the length of the throttle channel in this case changes in that the plunger is pushed further into the throttle opening with increasing differential pressure, so that the length of the throttle opening, which is penetrated by the plunger, depending on the position of the plunger and thus of the Differential pressure changed. The throttle channel is defined by the region in which the plunger passes through the throttle opening.

Preferably, the plunger and the throttle opening are designed so that the minimum flow cross-section of the throttle channel decreases with increasing differential pressure. The decreasing cross-section increases the flow resistance. Alternatively or additionally, the plunger and the throttle opening may be designed so that the length of the throttle channel increases with increasing differential pressure. This also increases the flow resistance.

Preferably, the plunger, the throttle opening and the spring are designed so that within a range of possible differential pressures results in a substantially constant, independent of the differential pressure flow through the constant flow restrictor. For this purpose, the travel of the spring, the minimum flow cross-section of the throttle channel and optionally the length of the throttle channel are coordinated so that the flow resistance of the constant flux is tracked to the differential pressure so that there is a substantially constant flow over the entire operating range.

The changing minimum flow cross section of the throttle channel is preferably achieved in that the cross section of the plunger and / or the throttle opening over the region in which the plunger is pushed with varying differential pressure in the throttle opening changes.

Preferably, a plunger is used whose cross-sectional area and / or diameter changes over the region with which the plunger is displaced relative to the throttle opening when the differential pressure changes. Preferably, a plunger is used whose cross-sectional area and / or diameter is progressively reduced in a flow direction in a first subregion, ie, at an increasing rate. Preferably, a step area adjoins the first partial area in the direction of flow. In particular, the first subregion and the step region can be arranged on the tappet such that the step region is used in an operating region with lower differential pressures, while the first subregion is used in an operating region having larger differential pressures.

The inventor of the present invention has recognized that such a configuration of the plunger, in particular in the range of low differential pressures, makes the constant flow throttle more robust with respect to manufacturing tolerances or an initial sticking of the plunger.

In particular, the first portion with progressively decreasing cross-sectional area and / or diameter allows a particularly effective adaptation to changing differential pressures and thus a high accuracy in setting the desired flow. In contrast, the step area makes the throttle more robust with regard to manufacturing tolerances or mechanical inhibitions at low differential pressures.

Preferably, the constant-flow throttle is configured so that the first sub-range in an operating range with higher differential pressures, the step range in an operating range with lower differential pressures is effective, i. changed the minimum cross-section through.

It is preferably provided that the cross-sectional area and / or the diameter in the first subregion is reduced in accordance with a theoretically optimal curve. In particular, the cross-sectional area and / or the diameter can be reduced so that this theoretically leads to a constant flow over the entire first partial area. Alternatively or additionally, it can be provided that the cross-sectional area and / or the diameter in the step area deviate from a theoretically optimal curve towards a larger cross-sectional area and / or larger diameters. According to the invention, no curve shape is used in the step area, which ensures an optimally constant flow. However, the inventor of the present invention has recognized that, even in a region with low differential pressures, even the slightest deviations from the optimum curve lead to pronounced fluctuations in the behavior of the constant-flow throttle. Furthermore, the inventor has recognized that deviations which lead to an enlargement of the minimally traversed cross section, have greater effects on the flow than deviations, which lead to a reduction of the minimum flow cross section. According to the invention, therefore, the course of the cross-sectional area and / or the diameter deviates from the theoretically optimal curve towards a larger cross-sectional area and / or a larger diameter in the step area, since the constant-flow throttle thereby becomes more robust with respect to manufacturing tolerances and an initial movement inhibition.

Alternatively or additionally, it may be provided that the step region forms an end region of the tappet. As an alternative or in addition, it can be provided that the cross-sectional area and / or the diameter of the plunger in the step area decreases at a decreasing rate or not at all. While the cross-sectional area and / or the diameter in the first partial area thus progressively decreases, it reduces in the step area degressive or not at all.

Furthermore, it can be provided according to the invention that the first subregion terminates in a differential, jolt-free end position of the plunger in front of the throttle opening and / or the narrowest point of the throttle opening. In the differential pressure-free end position of the plunger, the first portion therefore preferably has no influence on the throttle properties and in particular no influence on the minimum flow-through cross section. The narrowest point of the throttle opening is preferably zugt to the point with the smallest cross-sectional area and / or diameter of the throttle opening.

Furthermore, it can be provided according to the invention that the step area extends in the differential jerkless end position of the plunger partially within the throttle opening and partially in front of the throttle opening and / or on both sides of a narrowest point of the throttle opening. Therefore, in the differential pressure-free end position of the plunger, the step area is the area which defines the throttle properties and / or the minimum cross section through which flow passes.

Furthermore, it can be provided according to the invention that the length of the step area is less than 50% of the adjustment path of the plunger. Preferably, the length of the step area is less than 20% of the displacement of the plunger. The step area is therefore preferably used in particular only in a small range of low differential pressures.

Furthermore, it can be provided that the length of the first subregion is more than 50% of the adjustment path of the tappet, preferably more than 80%. Over a wide differential pressure range, in particular via such with the larger differential pressures, so comes the first portion with the progressive reduction of the diameter used.

In a constant flux throttle according to the invention according to the first or second variant, the plunger is preferably pressed by the spring in the absence of differential pressure against a stop. The stop thus defines the differential pressure-free end position of the tappet.

In this position, the current flow may preferably be blocked by and / or past the plunger. In particular, a seal may be provided for this purpose. This ensures that even low differential pressures reliably lead to a movement of the plunger and thus overcome an initial inhibition of the plunger, since the plunger are not flowed around in the differential pressure-free end position can and must therefore first be moved against the force of the spring from the current flow blocking position.

Such an embodiment is also independent of the configuration of the constant-flow throttle according to the first variant of the second aspect of advantage.

The present invention therefore according to a second variant of the second aspect comprises a constant-flow throttle for a dialysis machine with a liquid-flowed housing, which has an inlet, a throttle opening and an outlet. Furthermore, a plunger is provided, which is arranged displaceably in the housing, wherein between the throttle opening and the plunger a dependent of the relative position between plunger and throttle opening, the throttle effect defining throttle channel remains. Furthermore, a spring is provided against the force of the plunger is displaced by a differential pressure which is applied between the input and the output of the housing. According to the invention it is provided that the plunger is pressed in the absence of differential pressure by the spring against a stop, being blocked in this position, the current flow through and / or past the plunger. In particular, this is done by a seal. Such a configuration is not known in the case of constant-flow throttles which would be usable for dialysis machines.

The blockage of the flow of current through and / or past the plunger preferably takes place in that the stop has a sealing geometry which is pressed against a sealing element arranged on the plunger. The sealing element may in particular be made of an elastomeric material. The sealing geometry may in particular be a sealing edge and / or a sealing bead.

Although the embodiment according to the second variant can be used independently of the first variant, it is preferred that it be used in combination with the features of the first variant. Preferred embodiments of all variants of the constant flux inductor according to the invention are shown in more detail below:

Preferably, the plunger and the throttle opening are configured and cooperate so that the throttle channel between an outer side of the plunger and an inner side of the throttle opening remains.

According to the invention, the plunger can be designed in the form of a pen.

In one possible embodiment, the throttle opening may be tubular. In this case, the length of the flow channel is preferably predetermined by the length at which the plunger passes through the throttle opening.

In an alternative embodiment, the throttle opening may be designed as a diaphragm, for example as a narrow constriction of a flow channel or as the end of a funnel-shaped tapered channel.

Preferably, the maximum diameter of the plunger in the region in which it passes through the throttle opening, smaller than the minimum diameter of the throttle opening in this area. In one possible embodiment, the plunger and / or the throttle opening may be rotationally symmetrical. Optionally, however, the plunger may also have webs which correspond to the minimum diameter of the throttle opening and guide the plunger in the throttle opening.

In one possible embodiment of the present invention, the cross-sectional area and / or the diameter of the tubular throttle opening may be constant. In particular, it may be a cylinder tube.

Alternatively or additionally, the cross-sectional area and / or the diameter of the tubular throttle opening may increase at least in a partial area in the flow direction. This facilitates removal of the injection molding tool the injection process. Preferably, the cross-sectional area and / or the diameter of the tubular throttle opening over the entire hyperextension increases by a maximum of 10%.

In one possible embodiment, the smallest cross-sectional area and / or the smallest diameter of the throttle opening may be arranged on the side of the throttle opening facing the inlet.

The tubular throttle opening can pass on the output side without transition into a fluid line section. The end of the throttle opening in this case is defined by the point to which the pin is displaced at maximum operating pressure. In a funnel-shaped widening flow channel, only the narrowest point can form the throttle opening, if only this point provides for the actually effective throttling.

In a further embodiment of the present invention, the plunger is connected to a guide region, which is displaceably guided in a guide chamber of the housing. The guide area and the plunger can be made in one piece. Preferably, the plunger is guided by the guide portion in its movement within the housing

In one possible embodiment, the guide area can be cylindrical and guided in a cylindrical guide chamber of the housing slidably. Particularly preferably, the guide region and / or the guide chamber is designed circular cylindrical. However, other cross-sectional shapes are conceivable.

Preferably, the stop for the plunger, against which this is pressed in the differential pressure-free state by the spring, formed by an input-side end of the guide chamber, against which the guide portion is pressed in the absence of differential pressure by the spring. Alternatively or additionally, the guide chamber may have a larger diameter than the throttle opening. In particular, the cross-sectional area and / or the diameter of the guide chamber is so large that a fluid channel remains between the plunger and the guide chamber, which has no relevant throttle effect.

Furthermore, alternatively or additionally, the spring may be arranged in the guide chamber. In particular, the spring may extend between an output-side end of the guide chamber and the guide region of the plunger. Preferably, the spring surrounds the ram arranged on the guide area.

As an alternative or in addition, the guide chamber can be arranged between the inlet and the inlet-side end of the throttle opening.

As an alternative or in addition, the guide region can have one or more openings through which it flows. Preferably, the liquid can flow through the plunger without a relevant throttling action.

According to the second variant of the second aspect, the seal can close off the flow of fluid between the inlet and the one or more openings through which it flows in the position in which the guide area is pressed against the stop.

As described above, the constant-flow throttle according to the invention generates a substantially constant flow over its operating range. Substantially constant in the sense of the present invention preferably means that the flow over the operating range deviates by a maximum of 30% from a maximum value, preferably by a maximum of 10%.

Preferably, the constant-flow throttle according to the invention is designed so that it has a substantially constant flow in its operating range between 500 ml / min and 3000 ml / min, preferably between 1000 ml / min and 1500 ml / min.

Alternatively or additionally, the operating pressure range of the constant flow throttle may include differential pressures between 2 bar and 3 bar. The operating pressure range of the constant flow throttle preferably comprises differential pressures between 1 bar and 5 bar, more preferably between 0.5 bar and 5.5 bar. In a preferred embodiment, the operating pressure range of the constant-flow throttle comprises differential pressures of up to 0.2 bar.

As an alternative or in addition, the operating pressure range of the constant-flow throttle may include input pressures of between 2 bar and 4 bar, preferably between 1.5 bar and 6 bar.

In one possible structural embodiment of the present invention, the housing of the constant-flow throttle according to the invention comprises two parts. The parts can be made in particular as injection-molded parts and / or plastic.

Preferably, the two parts of the housing are screwed or glued together. Alternatively or additionally, a first part may comprise a guide chamber, the throttle opening and the outlet. Alternatively or additionally, a second part may comprise the inlet and optionally a sealing structure against which the plunger is pressed by the spring in the absence of differential pressure. Preferably, the plunger is made of plastic and / or as an injection molded part.

The inlet and / or the outlet of the housing may be tubular, wherein preferably hoses can be fastened to the tubular inlet and / or outlet.

The present invention will now be described in more detail with reference to embodiments and drawings. Showing:

Figure 1: a dialysis machine according to the prior art;

Figure 2: an embodiment of a dialysis machine according to the invention according to the first aspect of the present invention;

FIG. 3 shows an exemplary embodiment of a constant-flow throttle according to the first variant of the second aspect of the present invention;

FIG. 4: a diagram which shows the minimum cross-section of the

Throttle channel in response to a differential pressure in the embodiment shown in Figure 3; a schematic representation to illustrate the inventive with a displacement of the plunger relative to the throttle opening changing minimum flow-through cross section of the throttle channel;

FIG. 6 shows a diagram which shows the influence of deviations of the ram geometry from an optimum setpoint geometry on the flow through the constant flow throttle in the exemplary embodiment shown in FIGS. 3 and 4;

FIG. 7 shows the shape of a plunger for a constant flow throttle according to a preferred embodiment of the first variant of the second aspect of the present invention, together with a schematic representation of the flow generated as a function of the differential pressure; FIG. 8 shows a further exemplary embodiment of a constant-flow throttle according to the invention, in which the first and second variants of the second aspect are implemented in combination.

FIG. 2 shows an exemplary embodiment of a dialysis machine 10 according to the invention. The dialysis machine has a water inlet 11 with which it can be connected to an external water supply at the place of use. The external water supply can be, for example, an RO ring line, a single station and / or a reverse osmosis system. The dialysis machine has a dialysis system 12 shown only schematically in FIG. 2 with an inlet chamber 14, which can be filled with water via the water inlet 1. For this purpose, the water inlet 11 is connected via a line 16 to the inlet chamber 14 of the dialysate system 12 in connection.

In line 16 between the water inlet 11 and the inlet chamber 14 of the dialysate system according to the invention, a constant-flow throttle 13 is provided. This is constructed as a passive current control element so that it changes its flow resistance as a function of the pressure difference between the water inlet and the inlet chamber 14 so that sets an approximately constant flow over the entire operating range. In particular, a throttle element is provided, which is displaced by the applied pressure difference between the input and the output of the constant-flow throttle against the force of a spring and thereby changes the flow resistance of the constant-flow throttle. In particular, the throttle element may be a plunger, which cooperates with a throttle opening of the constant flow throttle.

In the exemplary embodiment, the operating pressure range of the constant flow throttle comprises inlet pressures of between 1.5 bar and 6 bar. The constant flow throttle is designed so that it sets a substantially constant flow over the entire operating pressure range between 1000 ml / min and 1500 ml / min. A substantially Constant flow in the sense of the present invention preferably deviates by no more than 35% from a maximum flow, preferably by not more than 20%.

As further illustrated in FIG. 2, the inlet chamber 14 of the dialysate system 12 has a level sensor 17, which is connected to a controller 18 of the dialysis machine. Furthermore, an input valve 15 is provided in the conduit 16 downstream of the constant flow throttle 13. Depending on the data of the level sensor 17, the controller controls the input valve 15 to fill the input chamber 14. Preferably, the input valve 15 is a switching valve.

In the conduit 16 downstream of the constant flow throttle 13, a heat exchanger 19 is further provided, via which the inflowing into the input chamber 14 water can be heated.

The dialysis machine is preferably a device for hemodialysis and / or hemofiltration. An extracorporeal blood circulation, which is usually designed as a disposable, can therefore be connected to the dialysis machine. In the extracorporeal blood circulation, a dialyzer is arranged, which on the one hand forms part of the extracorporeal blood circulation, and on the other hand is connected to the dialysate system of the dialysis machine. During a dialysis treatment carried out by the dialysis machine, the blood and dialysate flow through the two halves of the dialyzer, which are separated from one another by a membrane so as to allow a mass transfer between dialysate and blood. The dialysis machine can in particular have a blood pump and / or a dialysate pump, which are controlled by the controller 18.

In the context of the dialysis machine according to the invention initially any constant flux chokes can be used. However, constant flux chokes are preferably used, which are described in more detail below. The constant flux chokes described in more detail below can be used not only for dialysis machines, but also in other applications, for example in other medical devices.

FIG. 3 shows a first exemplary embodiment of a constant-flow throttle according to the invention. The constant flow throttle comprises a housing 20 with an inlet 21, a guide chamber 22, a throttle opening 23 and an outlet 24. In the housing, a plunger 25 is slidably disposed, which cooperates with the throttle opening 23 and thereby generates the throttle effect of the constant flux.

The inlet 21 and the outlet 24 of the housing are each led out of the housing in a tubular manner, so that in each case a hose nozzle can be pushed onto the inlet 21 and the outlet 24. The input 1 and the output 24 have for this purpose a smaller outer diameter than the central part of the housing. The outer surfaces of the inlet 21 and the outlet 24 forming tubular portion each have a cylindrical portion 35 on which a clamp can be attached, and a bead 36, which prevents removal of the barb after attaching the clamp.

The plunger is arranged on a guide region 26, which is guided longitudinally displaceably in the guide chamber 28. The guide region has a cylindrical outer contour, which rests against the likewise cylindrical inner contour of the guide chamber 22 and is guided on this.

The throttle opening is formed by a tubular portion 23 of the housing, which adjoins the guide chamber 22 and has a smaller diameter than the guide chamber itself, and / or by the narrowest point 32 of this section. The plunger 25 is pin-shaped and extends axially from the guide portion 26 to the throttle opening. Depending on the position of the guide region 26, the plunger is pushed into the tubular section at different distances or moved relative to its narrowest point. hereby arises between the inner contour of the throttle opening 23 and 32 and the outer contour of the plunger element 25 a dependent of the relative position between plunger and throttle opening, the throttle effect defining throttle channel.

In the guide chamber 22, a spring 28 is arranged, which extends between the output-side end of the guide chamber 22 and the output-side end of the guide portion 26 and biases the plunger against the flow direction.

The guide portion 26 has in the embodiment, a plurality of through holes 27 through which liquid can flow substantially without throttling action. Due to the enlarged cross section of the guide chamber 22 and the guide chamber itself has no relevant throttling effect. The flow resistance of the throttle is therefore defined by the remaining between the throttle opening 23 and 32 and the plunger 25 throttle channel.

In the exemplary embodiment, the housing 20 is constructed from two elements 29 and 30. The element 29 comprises the output 24, the throttle guide 23 or 32 and the guide chamber 22. The second element 30 comprises the input 21 and a stop region 33, against which the guide portion 26 of the plunger in the case of a lack of differential pressure by the force of the spring 28th is pressed. Both housing elements each have a flange region in which they are screwed together by screws 31. In this case, a sealing element 34, in the embodiment, a sealing ring, is provided, which seals the two housing elements against each other. The housing elements and the plunger are preferably designed as plastic injection molded parts. Preferably, the first housing element 29 is made of a translucent and / or transparent material in order to visually check the function of the constant flux inductor.

In the exemplary embodiment, the throttle channel is designed as an annular gap, which between the outer periphery of the plunger and the inner circumference of the Drosselöff- is running. In the exemplary embodiment, the throttle opening and the plunger have a rotationally symmetrical contour and are arranged coaxially.

The throttle opening 23 may have a constant diameter in a possible embodiment.

In the exemplary embodiment, however, the diameter of the tubular section which surrounds the throttle opening widens in a funnel shape in the flow direction. However, the expansion is only slight, wherein in the exemplary embodiment, the widening of the cross-sectional area of the tubular portion over the entire range of movement of the plunger from the narrowest point 32, starting from a maximum of 10%. In the exemplary embodiment, the section 23 comprising the throttle opening merges directly into the output 24 of the constant-flow throttle.

The narrowest point 32, i. the location with the smallest of the cross-sectional area or the smallest diameter of the throttle opening 23 is provided on the input-side side of the throttle opening 23 in the exemplary embodiment. Therefore, this point defines together with the diameter of the plunger 25 at this point the minimum flow cross-section of the throttle channel. Despite the slight widening of the channel, in one possible embodiment, the actually effective throttling arises essentially only at this narrowest point 32, so that only this acts as a throttle opening.

In this case, the cross-sectional area or the diameter of the plunger changes in the area which is guided past the narrowest point 32 during a movement of the plunger. In particular, the cross-sectional area or the diameter of the plunger in the flow direction decreases. As a result, the minimum cross-section of the throttle channel remaining between the plunger 25 and the throttle opening 23 depends on the relative position between the plunger 25 and the throttle opening 23. According to the invention, the plunger 25 is displaced by a pressure difference between the inlet 21 and the outlet 24 in the flow direction against the force of the spring 28. As a result, the minimum cross-section of the throttle channel remaining between the plunger 25 and the throttle opening 23 changes. In one possible embodiment, the length of the throttle channel may also change and also be used to influence the flow. The change of the cross section and optionally the length is such that an approximately constant flow results.

In the embodiment shown in FIG. 3, the tip of the plunger is in the region of the narrowest point 32 of the throttle opening in the differential pressure-free situation of the constant flow throttle shown in FIG. In this initial situation, the very short, remaining between the tip of the plunger and the narrowest point of the throttle opening throttle channel behaves like an annular gap. The flow rate is determined by the effective area A of the throttle channel, i. the minimum flow cross-section of the throttle channel.

The constant-flow throttle according to the invention is designed so that the minimum cross-section through which flows and thus the effective area A of the throttle channel changes as a function of the pressure difference. This is effected by a corresponding shaping of the plunger.

In Figure 4, the minimum flow cross section of the throttle channel is shown in the embodiment shown in Figure 3 as a function of the differential pressure. As can be seen immediately from FIG. 4, the highest changes in the cross-sectional area occur at low differential pressures.

Since, despite sufficient inlet pressure through flow resistors downstream of the constant flow restrictor, such as a heat exchanger, for example, low pressure differences can result via the constant flow restrictor, this operating range is also relevant when used in a dialysis machine. The relationship shown in Figure 4 between the cross-sectional area of the constant flux and the differential pressure causes a shape of the plunger, in which the diameter of the plunger progressively decreases in the flow direction or in the direction of movement of the plunger with increasing differential pressure. This means that the diameter decreases, with a rate increasing in the flow direction.

The relationships can be derived from the aperture equation as follows. According to the diaphragm equation, the following relationship is established between the flow Q, which is to be set to a constant value, and the effective area A of the diaphragm, the differential pressure ΔP between the inlet pressure P1 and the outlet pressure P3 (ie ΔP = P1-P3), and the viscosity p and a coefficient a:

O = a = const.

The resulting effective area A as a function of the differential pressure Δ P is obtained from the conversion of the formula:

The differential pressure acts on the cross-sectional area of the plunger in the effective range of the constant flow throttle, ie in the exemplary embodiment shown in FIG. 3 in the region of the narrowest point 32 of the throttle opening. The plunger is moved in response to the differential pressure until the spring force and the force generated by the differential pressure force on the plunger are in equilibrium. The position x of the plunger therefore depends on the spring rigidity R and the cross-sectional area A of the plunger in the effective range as follows: F AP * A,

X

RR ^~~

As shown schematically in Figure 5, the effective area A is the remaining area of the throttle opening, which is not blocked by the plunger. Here, A _{0 is} the minimum cross-sectional area of the throttle opening defined by the minimum diameter do and A, the cross-sectional area of the plunger in the region of the narrowest point 32 given by the diameter dj of the plunger at the position x.

The diameter of the plunger dj at the position x is thus given by the difference between the constant outer diameter do of the narrowest point of the throttle opening, which is predetermined by the housing, and the diaphragm surface necessary according to the above formula. The following applies to the effective area A, which is used in formulas 1 and 2:

This results in the following dependence of the diameter dj of the plunger from the position x:

Since the force acting by the differential pressure Δ P on the surface A, in a linear relationship with the position x, resulting in the course of the diameter dj as a function of the position x substantially a curve which the reverse course of in FIG 4 corresponds effective area A corresponds. Thus, the aperture area changes very strongly in the first millimeter. This initial range corresponds to the operating point with little differential pressure. The inventor of the present invention has now recognized that tolerances of the ram diameter and the spring length in this critical range lead to large deviations of the flow. In particular, when the plunger surface is too low due to manufacturing tolerances, or the plunger covers, for example by static friction and / or too stiff or long spring too small a distance, arise in the low differential pressure range too high flows. FIG. 6 shows a simulation result which represents the deviation from a desired flux as a function of tolerances.

In FIG. 6, it can be seen that, with tolerances in the direction of a too large aperture area, the deviation in the flow rate is significantly more dramatic than with the same tolerances in the direction of a flow that is too small.

In the further exemplary embodiments of a constant-flow throttle according to the invention shown in FIGS. 7 and 8, therefore, measures have been taken to reduce such strong deviations in the direction of high flows and to make the constant-flux throttle more robust with respect to manufacturing tolerances and influencing factors such as static friction etc.

FIG. 7 shows an alternative geometry for the tappet tip. The geometry of the ram in the area of the tip deviates from the ideal line of the diaphragm equation calculated above, namely in the direction of larger diameters. For this purpose, instead of the strong reduction of the diameter at the position x = 0, ie the point which is arranged in the difference jerkless position in the region of the narrowest point 32 of the throttle channel, constructively provided a step 40, which prevents the diameter d, falls below a certain level. The diagram in Figure 5 exaggerates the effect of this step on the flow. A region 41 then adjoins the step region 40, in which the diameter dj follows the ideal line and thus progressively decreases in the flow direction, ie opposite to the arrow indicating the position x. Conversely, the diameter d, in the region 41 as a function of the position x decreases in a degressive manner. The area with the largest change of the diameter d, therefore, is that which immediately adjoins the step area 40.

In the embodiments shown, the position x defines the location of the plunger, which is located in the region of the location 32 with the narrowest diameter of the throttle opening. However, the above relationships may alternatively be defined in terms of the throttle opening. This is the case in particular when the throttle opening has a constant diameter.

Furthermore, as shown in Figure 8 constructively prevents the risk of failure due to static friction or too stiff / long spring. For this purpose, the plunger on the back of the guide element 26, which is pressed in the differential pressure-free position by the spring against the input side end of the guide chamber, a seal, which may for example consist of an elastomer. The input-side end of the guide chamber is provided with a sealing geometry 44, in the embodiment with a surrounding the input 21 sealing bead, which is pressed against the seal 43 on the plunger. As a result, a flow through the flow holes 27 of the guide portion 26 is prevented in the differential pressure-free position, as well as a flow around the guide area. This arrangement causes the plunger to be moved to release the flow path. This ensures that small pressure differences are sufficient to overcome the static friction. Another advantage of this arrangement is that the constant-flow throttle has been supplemented by a non-return function.

The dialysis machine according to the present invention has the advantage that the inflow of water into the dialysis system of the device is automatically regulated. Manual adjustment of the pressure, such as during commissioning, is therefore no longer necessary. Furthermore, a cost-effective and simple construction is ensured. The constant flux choke is a passive component, which is maintenance-free. The constant flux chokes according to the second aspect of the present invention are optimized for low differential pressures and high flow accuracy. Furthermore, the second variant has an integrated non-return valve function.

Claims

Dialysis machine and constant flow throttle patent claims

1. Dialysis machine, in particular for hemodialysis and/or hemofiltration, with a dialysate system and with a water inlet via which the dialysate system can be connected to an external water supply,

characterized,

that a constant flow throttle is arranged between the water connection and the dialysate system.

2. Dialysis machine according to claim 1, wherein the constant flow throttle is arranged between the water inlet and a water inlet chamber of the dialysate system, the water inlet chamber preferably having a level detection and / or an inlet valve, wherein a control of the dialysis machine preferably controls the inlet valve depending on the level detection .

3. Dialysis machine according to claim 1 or 2, wherein the constant flow throttle is designed as a passive flow control element and / or wherein a constant flow throttle according to one of the following claims is used as the constant flow throttle.

4. Constant flow throttle, in particular for a dialysis machine according to one of the preceding claims

- A housing through which liquid flows, which has an inlet, a throttle opening and an outlet

- a plunger which is displaceably arranged in the housing, with a throttle channel which is dependent on the relative position between the plunger and the throttle opening and which defines the throttling effect remaining between the throttle opening and the plunger, and

- a spring, against the force of which the plunger is displaced by a differential pressure between the inlet and the outlet of the housing, characterized in that

that when the plunger is displaced relative to the throttle opening, the minimum flow cross-section of the throttle channel changes.

5. Constant flow throttle according to one of the preceding claims, wherein when the plunger is displaced relative to the throttle opening, both the length and the minimum flow-through cross section of the throttle channel change.

6. Constant flow throttle according to claim 4 or 5, wherein the minimum flow cross section of the throttle channel decreases with increasing differential pressure and / or the length of the throttle channel increases with increasing differential pressure.

7. Constant flow throttle according to one of claims 4 to 6, wherein the cross-sectional area and / or the diameter of the plunger in the flow direction in a first partial area progressively, ie at an increasing rate, reduced, with a step region preferably adjoining the first partial region in the direction of flow.

8. Constant flow throttle according to claim 7, wherein the cross-sectional area and / or the diameter in the first partial area decreases according to a theoretically optimal curve and / or deviates in the step area from a theoretically optimal curve towards a larger cross-sectional area and / or a larger diameter, and/or wherein the step region forms an end region of the plunger and/or wherein the cross-sectional area and/or the diameter of the plunger in the step region decreases at a decreasing rate or not at all.

9. Constant flow throttle according to claim 7 or 8, wherein the first partial area ends in a differentially smooth end position of the plunger in front of the throttle opening and / or a narrowest point of the throttle opening and / or wherein the step area in the differential pressure-free end position of the plunger is partially within the throttle opening and partially extends in front of the throttle opening and/or on both sides of a narrowest point of the throttle opening, and/or wherein the length of the step region is less than 50% of the adjustment path of the plunger, preferably less than 20%, and/or wherein the length of the first partial region is more than 50% of the adjustment path of the plunger, preferably more than 80%.

10. Constant flow throttle according to one of the preceding claims, wherein the plunger is pressed against a stop by the spring in the absence of differential pressure, the flow of current through and/or past the plunger being preferably blocked in this position, preferably by a seal.

1 . Constant flow throttle for a dialysis machine according to one of the preceding claims, with - A housing through which liquid flows, which has an inlet, a throttle opening and an outlet

that the plunger is pressed against a stop by the spring when there is no differential pressure, with the current flow through and/or past the plunger being blocked in this position, preferably by a seal.

12. Constant flow throttle according to one of the preceding claims, wherein the throttle opening is tubular, wherein preferably the cross-sectional area and / or the diameter of the tubular throttle opening is constant or increases at least in a partial area in the flow direction, more preferably the smallest cross-sectional area and / or the smallest diameter is arranged on the side of the throttle opening facing the entrance, and / or wherein the plunger is designed in the shape of a pin.

13. Constant flow throttle according to one of the preceding claims, wherein the plunger is connected to a guide area which is slidably guided in a guide chamber of the housing, the stop for the plunger preferably being formed by an input end of the guide chamber, against which the guide area is pressed by the spring in the absence of a differential pressure, and/or wherein preferably the guide chamber has a larger diameter than the throttle opening and/or wherein preferably the spring is arranged in the guide chamber, in particular between the guide region and a outlet-side end of the guide chamber and/or wherein preferably the guide chamber is arranged between the inlet and the inlet-side end of the throttle opening and/or wherein preferably the guide region has one or more flow-through openings.

Constant flow throttle according to one of the preceding claims, wherein the constant flow throttle sets a substantially constant flow between 500 ml/min and 3000 ml/min, preferably between 1000 ml/min and 1500 ml/min, and/or wherein the operating pressure range of the constant flow throttle has differential pressures between 2 bar and 3 bar, preferably between 1 bar and 5 bar, more preferably between 0.5 bar and 5.5 bar, and / or wherein the operating pressure range of the constant flow throttle includes input pressures between 2 bar and 4 bar, preferably between 1.5 bar and 6 bar includes.

Constant flow throttle according to one of the preceding claims, wherein the housing consists of two parts, which are preferably screwed or glued together, and/or wherein a first part preferably comprises a guide chamber, the throttle opening and the output and/or wherein a second part preferably comprises the input and possibly a sealing structure against which the plunger is pressed by the spring in the absence of differential pressure, and/or wherein the inlet and/or the outlet of the housing is tubular, with preferably a hose at the tubular inlet and/or Output can be attached.