Abstract:
The invention relates to a device for axially conveying body fluids. The aim of the invention is to embody the inflow and outflow area of an axial pump in such a way that the flow is not separated even when it is diverted, thereby maintaining a substantially non-disrupted flow profile.

Description:
BACKGROUND 
   The invention relates to a device for axially conveying body fluids. 
   In particular, body fluids such as blood which can undergo irreversible changes caused by an energy input, such as in the case of emulsions and dispersions, can run into instable ranges in a disadvantageous manner when being conveyed in corresponding devices such as pumps. 
   Blood is a particularly sensitive fluid system. This opaque red body fluid of the vertebrates circulates in a self-enclosed vessel system where rhythmic contractions of the heart press the blood into various areas of the organism. In this case, the blood transports the respiratory gases oxygen and carbon dioxide as well as nutrients, metabolic-products and endogenous active ingredients. The blood vessel system including the heart is hermetically isolated from the environment so that, in a healthy organism, the blood does not undergo any changes when it is pumped through the body by way of the heart. 
   It is known that, when blood comes into contact with non-endogenous materials or as a result of the effect of energy from an external source, it has a tendency to hemolysis and clot formation. Clot formation can be fatal for the organism because it can lead to blockage in the extensive branching profile of the vessel system. Hemolysis describes the condition where the red blood cells are destroyed within the body beyond the physiological dimension. 
   The causes for hemolysis can be of a mechanical or metabolic nature. Increased hemolysis causes multiple organ damage and can lead to a person&#39;s death. 
   On the other hand it is evident that it is possible in principle, under certain prerequisites with reference to constructive aspects, to support the pumping capacity of the heart or even to replace the natural heart with a synthetic one. However, a continuous operation of implanted heart supporting systems or synthetic hearts is presently only possible with certain limitations heart supporting systems or synthetic hearts is presently only possible with certain limitations because the interactive effects of these artificial products with the blood and the entire organism still always lead to disadvantageous changes of the blood and the organism. 
   In the state of the art, axial blood pumps are known which mainly consist of a cylindrical tube in which a conveying part, which is executed as an externally located motor stator, is located. The rotor which is provided with a so-called blading, conveys the fluid in an axial direction after it has been made to rotate by means of the motor stator. 
   In the WO 00/64030 a device for the protective conveying of single- or multiple-phase fluids is described. Where this device is concerned, and in the direction of flow, an inlet guide facility is arranged upstream of the conveying part (rotor) and, as seen in the direction of flow, an inlet guide facility is arranged upstream of the conveying part (rotor) and, as seen in the direction of flow, an outlet guide facility is arranged downstream of the conveying part. Even though the blood in the flow passage zone of the pump does not undergo essentially any disadvantageous changes, the disadvantage is evident to the extent that, in the inflow zone upstream of the inlet guide facility and in the outflow zone downstream of the outlet guide facility of the pump, disrupted flows can form which can lead to a change of the blood. 
   In the U.S. Pat. No. 4,994,078 a heart pump is described whose outlet and inlet zones have certain flow cross-sections which are characterised by cross-sectional reductions and expansions, respectively. However, this flow pattern of the blood indicated at that location is only inadequately illustrated so that, in the outflow zone, it is not clearly recognisable how the blood flow is conducted further. 
   The invention is based on the task assignment of executing the inflow zone and the outflow zone of an axial pump in such a way that no flow separation occurs with an envisaged deflection of the flow in these zones, but instead a non-disrupted flow profile remains upheld to the greatest extent. 
   SUMMARY OF THE INVENTION 
   Therefore, this is the device according to the invention for the axial conveying of body fluids, consisting of a tube-shaped hollow body ( 1 ) transporting the liquid in an essentially axial manner, and in this hollow body ( 1 ) there is arranged in axial alignment a conveying part that can be rotated by a motor stator ( 3 ) located outside of the hollow body ( 1 ) in a pump casing ( 8 ), where the conveying part ( 2 ) has a rotor blading ( 5 ) and where stationary inlet and outlet guide facilities ( 6 ,  7 ) are arranged in the direction of flow upstream and downstream of the conveying part ( 2 ), and inflow and outflow zones ( 10 ,  11 ) which are positioned at the hollow body ( 1 ) in a flow-direction-changing mode, where in the inflow zone ( 10 ) an intake bend ( 12 ) having an intake bend angle ( 15 ) is positioned at the tube-shaped hollow body ( 1 ) and in the outflow zone ( 11 ) an outlet bend ( 13 ) having an outlet bend angle ( 14 ) is positioned at the hollow body ( 1 ), and where the intake bend ( 12 ) has a cross-sectional reduction in the direction of the inlet guide facility ( 6 ) and the outlet bend ( 13 ) in the direction of flow up to an outlet cylinder ( 19 ) has a cross-sectional reduction, 
   wherein the intake and outlet bends ( 12 ,  13 ) as well as the inlet and outlet channels ( 17 ,  18 ) advantageously consist of flexible material. 
   A flow diffuser ( 25 ) and an outlet channel ( 17 ) are arranged in the direction of flow downstream of the outlet cylinder ( 19 ). 
   I a further embodiment of the invention, the flexible material essentially consists of silicone and/or reinforced silicone (fabric). The flexibility of the material allows an optimal operative insertion of the device according to the invention as well as its function in the thoracic area. 
   In a further embodiment of the invention, the outlet bend and the intake bend only have some individual areas made of flexible material. 
   The radius of the intake bend and the diameter of the inlet of the intake bend are in a ratio of 1:2. 
   The flow diffuser has a cross-sectional expansion in the direction of flow. 
   The formation of the inflow zone and the outflow zone, according to the invention, of a category-related axial pump leads to a situation where the flows can be accelerated very gently without causing disrupted flow regimes. In this case, particularly the formation of the intake bend angle according to the invention, between 45° and 50°, in relation to the change of the flow cross-section, has proved to be very advantageous. The size of the outlet bend angle in this case is between 85° and 95°. The flow profile produced here according to the invention can therefore be characterised by the following advantageous properties:
         special form-shaping of the intake bend with permanent acceleration of the flow in the inflow to the inlet guide facility;   optimised inflow to the conveying part by means of a corresponding configuration of the inlet guide facility;   optimised energy transfer in the conveying part;   conditioning of the flow and pressure recovery in the outlet guide facility;   special configuration of the outlet bend with permanent acceleration of the flow in the bent zone;   conditioning of the flow in the area of the connecting piece to the outlet channel, this connecting piece being preferentially provided with a gradual cross-sectional expansion in form of a rotation-symmetrical diffuser. The device according to the invention receives a particularly advantageous embodiment by the selection of elastically adequately form-stable materials, for the intake and outlet bends which can, in this way, accommodate physically-related permanent movements in the area of the connection of the device to the heart chamber (ventricle) and/or to the aorta.       

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is described in greater detail with the help of a drawing. The drawings show the following: 
       FIG. 1  a schematic cross-sectional illustration of a category-related axial pump with intake and outlet bends; 
       FIG. 2  a schematic cross-sectional illustration of the outlet bend, and 
       FIG. 3  a schematic cross-sectional illustration of the intake bend 
   

   DESCRIPTION OF PREFERRED EMBODIMENT 
     FIG. 1  shows the schematic illustration of a category-related axial pump with an intake bend  12  and an outlet bend  13 . With an intake collar  28 , the intake bend  12  is secured to an inflow zone  10  of a cylindrical hollow body  1 . With an outlet collar  29 , the outlet bend  13  is secured to an outlet flow zone  11  of the cylindrical hollow body  1 . As seen in the direction of flow, the cylindrical hollow body contains a stationary inlet guide facility  6  with a guide blading arrangement  9 , a floating bearing-located conveying part  2 , consisting of a motor rotor  4 , a rotor blading arrangement  5  and a back-up ring  30 . As seen in the direction of flow, and downstream of the motor rotor  4 , a stationary outlet guide facility  7  with an outlet guide blading arrangement  16  is arranged. The motor rotor is caused to rotate by means of a motor stator  3  which is arranged in a pump casing  8 . In an axial pump shown here as an example, a flow diffuser  25  is envisaged at the outlet bend  13 . By way of an inlet channel  18 , the blood to be conveyed enters an inlet cylinder  20  of the intake bend  12  and then, in accordance with the bend routing  24  of the intake bend  12 , it is deflected by an intake bend angle  15  in the direction of flow and led into the intake collar  28 . The intake bend  12  here and downstream has a permanent cross-sectional narrowing up to the inflow zone  10 . The blood is now led via the inlet guide facility  6  and past the motor rotor  4  and by way of the outlet guide facility  7  into the outflow zone  11  of the cylindrical hollow body  1 . At this point, the blood enters the outlet collar  29  of the outlet bend  13  and is deflected in the outlet bend  13  in the direction of flow by an outlet bend angle  14 . Here again, there is a cross-sectional narrowing of the outlet bend  13 . An outlet cylinder  19  of the outlet bend  13  is added here in an exemplary manner at the flow diffuser  25  which has downstream a permanent cross-sectional enlargement in the direction of an outlet channel  17 . Based on the arrangement of the intake bend  12  which deflects the blood flow under the intake bend angle  15 , and the arrangement of an outlet bend  13  which deflects the blood under the outlet bend angle  14 , a non-disrupted flow profile is achieved. 
     FIG. 2  shows in a schematic cross-sectional illustration the outlet bend  13  which leads the blood to be conveyed by way of a pump outlet  27 , the outlet flow zone  11  and a bend  23  into the outlet cylinder  19  and then further into the flow diffuser  25  and the outlet channel  17 . With this routing method of the flow, a separation of the flowing blood from an inner wall  22  of the outlet bend  13  is advantageously avoided. 
   The intake bend  12  as shown in  FIG. 3  in a schematic sectional arrangement deflects the blood coming from the inlet channel  18  via the inlet cylinder  20  around an intake bend angle  15  into the inlet collar  28 . In this case, a permanent cross-sectional narrowing of the intake bend  12  is effected downstream up to the inlet collar  28 . By way of the inflow zone  10 , the blood is then conveyed into the pump inlet  26 . Due to the permanent flow cross-sectional narrowing existing here according to the invention, no separation of the flow from the wall  21  of the intake bend  12  occurs. 
   REFERENCED PARTS LIST 
   
       
         1  Hollow body 
         2  Conveying part 
         3  Motor stator 
         4  Motor rotor 
         5  Rotor blading 
         6  Inlet guide facility 
         7  Outlet guide facility 
         8  Pump casing 
         9  Guide blading 
         10  Inflow zone 
         11  Outflow zone 
         12  Intake bend 
         13  Outlet bend 
         14  Outlet bend angle 
         15  Intake bend angle 
         16  Outlet guide blading 
         17  Outlet channel 
         18  Inlet channel 
         19  Outlet cylinder 
         20  Inlet cylinder 
         21  Wall 
         22  Wall 
         23  Bend 
         24  Bend 
         25  Flow diffuser 
         26  Pump inlet 
         27  Pump outlet 
         28  Inlet collar 
         29  Outlet collar 
         30  Back-up ring