Hose roller pump and rocker arm for use therein

Abstract

The invention relates to a peristaltic pump for conveying a fluid in a device for extracorporeal blood treatment, comprising a pump housing in which a rotor which can be rotated about a rotor axis is accommodated and which has at least two pressing elements which are offset from one another in the circumferential direction, the pump housing has a support surface extending in an arc shape about the rotor axis and spaced radially from the rotor, the support surface being provided for supporting a hose segment that can be introduced radially between the rotor and the support surface. The rotor carries the pressing element via a rocker arm, which is fixed on the rotor in a pivotal manner and in a spring-loaded manner. The rocker arm itself carries an introduction aid by means of which the hose segment can be pressed into the pump bed during the penetration thereof, and a hose guide element by means of which the hose segment can be oriented centrally relative to the pressing element. The rocker arm consists of high-strength stainless steel with high chemical stability and is produced in a powder injection molding process, preferably in a metal injection molding process.

Description

Technical Field

[0001] The invention relates to a hose roller pump or peristaltic pump, i.e. a volumetric pump, in which the medium to be conveyed is squeezed through the hose by external mechanical deformation of the hose, and to a rocker arm custom-made for the peristaltic pump. Such pumps are usually used in devices for extracorporeal blood treatment, in particular dialysis machines, for conveying fluids, in particular blood. The fluid is conveyed from the low-pressure side to the high-pressure side by means of a peristaltic pump, wherein an elastically deformable fluid line in the form of a hose segment (the hose segment is also referred to as a pump segment) arranged between the low-pressure side and the high-pressure side is deformed, in particular squeezed, by means of at least two squeezing elements between a support surface of a pump bed and a rotor rotating relative to the support surface. Background Art

[0002] Typically, in peristaltic pumps, as are known, for example, from EP 1 749 549 B1 and in Figure 8 and Fig. 9 As schematically shown in FIG. 1 , at least two squeezing elements 320 in the form of elastically supported pressure rollers are arranged offset from each other in the circumferential direction on a rotor rotatably supported in a pump housing. The support surface 330 is formed by an arc surface extending through a sufficiently large central angle greater than 180°. The pressure roller is rotatably supported on a rocker arm 341 by means of a roller shaft 321, and the rocker arm is pivotally fixed to the rotor 310 with the aid of a hinge pin 338 and an axis A338 and is loaded with a radially outwardly directed force FR by a compression spring 336 (see FIG. 1 ). Figure 8 ).

[0003] In order to put the peristaltic pump into operation, it is necessary to Figure 8 A hose segment, i.e. a pump segment, not shown in greater detail, is guided from a connection point PN on the low-pressure side above the rotor 310 in an arc shape following the support surface 330 to a connection point PP on the high-pressure side and is then inserted into the pump bed 307 by manual rotation of the rotor 310 in the direction of the arrow D. As a threading aid or introduction aid for supporting manual threading, the known peristaltic pump has two guide protrusions in the form of hooks 360 carried by the rotor 310, which are arranged between two pressure rollers 320. In contrast to the automatic threading scheme of the pump segment, in which the rotor is automatically oriented into the optimal threading position, in the case of the peristaltic pump known from document EP 1 749 549 B1, the user must take care to insert the hose before the hook 360 in order to prevent it from getting stuck. To this end, the rotor 310 must be manually rotated as in Figure 8 In order to guide the hose section already caught by the hook 360 and to orient it centrally relative to the pressing element, a guide pin 370 inserted into the rotor and serving as a hose guide element is additionally used, which follows the hook 360 .

[0004] In order to simplify the threading process, it is advantageous to integrate the introduction aid and / or the hose guide element into the rocker arm. However, this makes the shape of the rocker arm more complicated, so that the manufacture of the rocker arm is more complicated.

[0005] The rocker arms of the known rotors in blood pumps are therefore either plastic injection-molded parts or parts mechanically produced from plastic or metal.

[0006] Since this type of rocker arm requires high dimensional stability and fatigue strength due to the bending forces that are periodically subjected to, the applicant has also tried to produce a rocker arm with an integrated hose guide made of aluminum and to produce the contour from solid material by milling methods. Even when the hose guide element is designed as a separate pin, in this case, a lot of material must usually be removed by cutting, so that the raw material usage is very high compared to the finished part. Another problem is that the rocker arm must be matched to the roller shaft in order to fasten the extrusion element or the pressure roller. Due to the low strength of aluminum, slight deformations may occur during the matching of the roller shaft. Therefore, in order to avoid scrap, precise process monitoring is required. In addition, the milled aluminum rocker arm must be further anodized to ensure chemical stability. Since anodizing affects the accuracy of the fit in the hole, the hole must be closed with a plug before anodizing. Anodizing and plugging are additional additional costs. When using high-strength materials, mechanical processing becomes more complicated and more cost-intensive. Summary of the invention

[0007] The object of the present invention is to provide a peristaltic pump of the aforementioned type which is distinguished by simplified production with extended functionality and service life.

[0008] This object is achieved with the features according to the invention.

[0009] According to the invention, the rocker arm of the rotor consists of high-strength stainless steel with very good chemical properties, wherein the rocker arm is manufactured by the MIM method (metal injection molding). This production makes it possible to integrate additional functions, such as insertion aids and hose segment guides, while significantly reducing the raw materials used and the production costs compared to cutting production. In this case, the mechanical reworking can be limited to a minimum by the forming MIM method. In addition, fine contours (such as reinforcing ribs) can be achieved by the MIM method, thereby further reducing the mass of the component while maintaining the same strength. These fine contours can only be produced with difficulty or not at all using milling technology. Due to the good surface quality that can be achieved in the MIM method, no special reworking is required in the area of ​​the surface that comes into contact with the hose segment, which can also serve to reduce production costs.

[0010] Tests have shown that such materials, for example austenitic heat-resistant chromium-nickel steel, such as is known, for example, under the name 1.4841 (X15CrNiSi25-21), can be easily produced in the MIM method with a sufficiently high density and that components produced therefrom have optimal properties for peristaltic pumps. Rockers produced in this way are chemically stable to very different media and can be easily produced with only a few cm 3 The minimum amount of material has such a high strength that, on the one hand, the contact force of the rollers during conveying operation of the most different media with the groove structure is ensured and, on the other hand, the fit of the roller shaft is ensured without deformation of the rocker arm. This results in the additional advantage that the chemical properties of the material do not require additional surface treatment, such as painting or anodizing.

[0011] The selection of materials and production methods according to the invention enables the rocker arm to carry out additional functions in a compact design, for example, to integrate a component for guiding a hose section into the rocker arm, i.e., to place the component in the vicinity of the holder of the pressure element or the pressure roller. The rocker arm can thus form the bearing points of the pressure roller on both sides by means of a bridge that surrounds the pressure roller in a frame-like manner, so that forces can be introduced from the pressure roller into the rocker arm reliably and with little deformation.

[0012] In other embodiments of the rocker arm, the operation, in particular the handling, of the pump is facilitated by means of the central position relative to the pressure roller when inserting and / or removing and when guiding the hose section, i.e. the pump section, accommodated in the pump. At the same time, the shape of the rocker arm becomes increasingly complex. When the free space of the rocker arm is produced during the machining of the blank by material removal, only the required material is introduced into the tool in the embodiment of the rocker arm according to the invention. The finished component, for example, has a diameter of only about 4 cm. 3 volume, while components made from complete milling need to have a minimum of 40cm 3 The MIM method can therefore save a considerable amount of raw material. Since even undercut ribs can be produced without any problems with the rocker arm according to the invention, the mass of the rocker arm component can be reduced while maintaining the same strength.

[0013] In addition to the advantages in terms of manufacturing technology, the design of the rocker arm according to the invention also provides advantages in the operation of the peristaltic pump. Since both the introduction aid and the hose guide element are integrated into the rocker arm adjacent to the extrusion element in the direction of rotation of the rotor, the number of components of the pump is reduced and thus also the manufacturing and installation costs are reduced, since only the rocker arm needs to be installed for this purpose. Since the introduction aid is adjacent to the associated extrusion element, i.e., directly in front of the extrusion element in each case, manual insertion of the pump segment is possible without the user having to pay attention to a specific position of the rotor.

[0014] Advantageously, the rocker arm is mounted on the rotor by means of a pivot bearing which is arranged offset relative to the displacement element in the direction of rotation of the rotor, wherein the introduction aid and the hose guide element are seated on the pivot bearing. With this design, the structure of the rocker arm with the integrated introduction aid and hose guide can be designed to be particularly compact.

[0015] Tests have shown that, due to the arrangement according to the invention of the introduction aid on the pivot bearing of the rocker arm, it is sufficient to construct the introduction aid as a simple pin-shaped guide body for protective and secure insertion of the hose segment, which extends from the pivot bearing essentially in a radial direction away from the rotor axis in the direction of the support surface and which, when viewed in cross section, essentially has a rounded wedge shape pointing in the direction of rotation of the rotor, which is inclined toward the pump bed at an acute angle of preferably between 30° and 50°.

[0016] It is further advantageous that the guide body has two functional surfaces, wherein the outer functional surface running in front in the direction of rotation of the rotor and facing away from the middle plane of the rocker arm is constructed as a rounded wedge surface, and the inner functional surface facing the middle plane is formed by a cylindrical segment surface preferably connected to the wedge surface in a stepless manner. When the rotor is rotated manually, the rounded wedge surface presses the hose segment to be inserted gently downward into the pump bed, wherein the rounded geometry prevents damage to the hose segment. The cylindrical segment surface connected to the wedge surface can be used in an advantageous manner to guide the hose segment centrally relative to the extrusion element during the operation of the peristaltic pump. Of course, it should be noted here that the quality of the surface of the guide body that contacts the hose segment is implemented so that the hose segment is protected as well as possible. It has been shown that this surface quality, such as a sufficiently small roughness, can be achieved using the MIM manufacturing method without further processing of the functional surface.

[0017] The MIM method also ensures the dimensional stability of the pin-shaped guide body and its positional relationship to the bearing axis by taking advantage of the linear shrinkage during sintering or by predicting the shrinkage most accurately by sintering samples.

[0018] According to the application, the cross section of the guide body can have very different shapes, as long as the wedge surface and the cylindrical segment surface are formed on the side facing the hose segment. However, if the cross section of the guide body has a center axis, this results in simplified production, especially for the case where the guide body is mounted on the rocker arm as a separate component. For the alternative case, that is, the rocker arm and the guide body are formed in one piece, an additional advantage is that the guide body is additionally supported on the rocker arm by means of a support following the center axis. This design allows the guide body to be constructed in a more sophisticated, but sufficiently stable manner.

[0019] If the guide body is arranged on the pivot bearing hole of the rocker arm, preferably mounted integrally on the pivot bearing hole, the radial supporting forces and bending forces applied to the guide body during insertion can be well introduced into the rocker arm, because the pivot bearing hole of the pivot axis is stably supported and is accordingly subjected to only minimal deformation.

[0020] Another advantageous design of the peristaltic pump is that the rocker arm is provided with a stop surface for the compression spring on its end section facing away from the pivot bearing hole, and the pressing element is arranged, for example, rotatably supported, between the pivot bearing hole and the stop surface. The MIM manufacturing method allows the stop surface to be optimally positioned without making the manufacture of the rocker arm more complicated. In this way, the rocker arm acquires a compact shape, so that sufficient free space is retained on the circumference of the rotor for the construction of other functional surfaces, such as guide surfaces for hose segments. The individual sections of the rocker arm can be reinforced arbitrarily where additional strength is required, for example in the area of ​​the pivot bearing hole or the axis of rotation of the pressure roller, wherein the additional material expenditure required for this purpose is kept to a minimum.

[0021] Preferably, a further second guide body is assigned to the first guide body constituting the above-mentioned introduction aid, which second guide body is constructed and oriented symmetrically to the first guide body relative to a horizontal plane parallel to the pump bed. The cylindrical segment surfaces of the two mirror-arranged guide bodies facing each other thus constitute the functional surface of the hose guide element. Here, the integration of the introduction aid and the hose guide element into the rocker arm is ensured with further reduced manufacturing costs. Due to the mirror-arranged and oriented guide bodies, the guide bodies guide the hose segments in a funnel-shaped and protective manner to the center of the relevant extrusion element when the peristaltic pump is in operation, which has a positive effect on the delivery accuracy of the peristaltic pump.

[0022] The injection mold for producing the rocker arm is simplified if the horizontal plane, with respect to which the two guide bodies are arranged symmetrically, is simultaneously the plane of symmetry of the rocker arm.

[0023] In principle, the material used to produce the rocker arm can be selected so that the surface of the sintered rocker arm is not machined. However, if the introduction aid and preferably the hose guide element are also coated with a material having sliding properties that minimize wear, the hose section can be additionally protected from wear in selected cases.

[0024] According to an advantageous embodiment, the introduction aid and the hose guide geometry are integrated into the rocker arm. This reduces the production and assembly costs. The hose guide geometry has two regions. Figure 4 The area on the upper guide body or crescent-shaped piece, which is indicated by a dash-dotted line in FIG. , is a rounded bevel, which presses the hose downwards during insertion. The rounded geometry prevents damage to the hose. Figure 4The circular surfaces on the upper and lower guide bodies or crescents, indicated by dashed lines in the figure, guide the hose during operation so that the pump segment is guided centrally on the pressure roller. The quality of the surface is selected in the area of ​​the hose guidance so that the hose is not damaged. The surface quality is achieved without special post-processing. By arranging the introduction aid directly in front of the pressure roller, the user does not have to pay attention to the special position of the rotor during manual threading. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] An embodiment of the present invention is explained in more detail below with the aid of a schematic diagram. It is shown:

[0026] Figure 1 is a perspective view of an exemplary embodiment of a peristaltic pump that can be used in conjunction with an apparatus for extracorporeal blood treatment;

[0027] Figure 2 is based on Figure 1 A three-dimensional view of the rotor used in the peristaltic pump;

[0028] Figure 3 is a perspective view of a rotor base of a peristaltic pump with an attached rocker arm;

[0029] Figure 4 Shown on a strongly exaggerated scale along Figure 2 The direction of observation of the arrow "IV" in Figure 1 and Figure 2 Side view of the rocker arm used in a peristaltic pump

[0030] Figure 5 It is a stereoscopic view of the rocker arm;

[0031] Figure 6 is a rocker with a schematically indicated material volume and Figure 5 The corresponding view, this material volume is necessary for the manufacturing variant;

[0032] Fig. 7A and Figure 7B It is a three-dimensional view of the rocker arm manufactured by cutting process;

[0033] Figure 8 is a top view of a known peristaltic pump; and

[0034] Fig. 9 is based on Figure 8 A stereoscopic view of the rotor used in a peristaltic pump.

[0035] Among them: A-rotor axis; D-rotation direction; PN-low pressure connection part; PP-high pressure connection part; PS-pump segment; ES-symmetry plane; F1-functional surface; F2-functional surface; FR-radial direction; 5-pump housing; 7-pump bed; 10-rotor; 20-extrusion element; 30-support surface; 38-hinge pin; 39-hinge pin retaining block; 40-rotor base; 42-rotor cover; 44-button; 46-guide surface; 48-guide surface; 50-bearing hole; 52-bearing hole; 54-stop surface; 56-compression spring; 58-upper bow arm; 60-lower bow arm; 62-upper supporting part; 64-lower supporting part; 66-rotation axis; 70-upper guide body; 72-lower guide body; 76-pillar; 78-free space; 305-housing; 307-pump bed; 310-rotor; 320-extrusion element; 321-roller shaft; 330-support surface; 341-rocker arm; 336-compression spring; 338-hinge pin; A338-axis line; 341-rocker arm; 360-guide protrusion, hook; 370-guide pin. DETAILED DESCRIPTION

[0036] exist Figure 1 , for example, is used in a dialysis machine. The task of the peristaltic pump is to convey a defined volume of medium, for example blood or dialysis fluid, by deforming and clamping an elastically deformable fluid line. Peristaltic pumps for conveying blood usually convey from the negative pressure side PN (low pressure connection) to the positive pressure side PP (high pressure connection).

[0037] As in Figure 1 As shown in the figure, the peristaltic pump has Figure 1 The rotor or pump housing 5 shown in the figure is unfolded, in which a rotor 10 is accommodated which can rotate about a rotor axis A and has at least two displacement elements 20, in this case pressure rollers, which are offset from each other in the circumferential direction, for example in diameter. The pump housing 5 comprises a pump bed 7 which extends in an arc shape about the rotor axis A and has a support surface 30 which is radially spaced apart from the rotor 10. The support surface 30 is provided for radially supporting a bearing which can be radially introduced between the support surface and the rotor 20 and which is not shown in the drawings but is only Figure 4 The pump segment PS is shown in dashed lines. The squeeze element 20 is supported in a spring-loaded manner on the Figure 1 The rocker arm, which is not shown in detail, is pivotally movable via a hinge pin 38 (see Figure 3 ) is fastened to the rotor 10. The pressing element 20 is rotatably supported on a rocker arm 41 which is supported on the rotor base body 40 in an articulated spring-like manner.

[0038] The hose segments used in peristaltic pumps are referred to below as pump segments. Figure 1The hose section not shown in the drawing is not supported on the pump bed with reference numeral 7, but is positioned centrally relative to the extrusion element by a hose guide element described in further detail below. The support surface 30 is usually formed by a cylindrical surface, but the cylindrical surface can also be recessed in a groove shape. The direction of rotation of the rotor 10 when conveying the fluid is indicated by the arrow D.

[0039] Figure 2 The rotor 10 is shown in detail. The rotor has Figure 3 4 and 42. The rotor 10 can be removed from the drive shaft (not shown in greater detail) by means of a laterally operable button 44.

[0040] The rotor cover 42, which rotates with the rotor 10, carries guide surfaces 46, 48 in the region of the extrusion element 20, wherein one guide surface 46 runs in front of the extrusion element 20 and the other guide surface 48 runs behind the extrusion element 20. The guide surfaces 46, 48 are therefore arranged and designed adjacent to both sides of the extrusion element 20 in the circumferential direction, so that the guide surfaces together with the support surface 30 form an arc-shaped guide channel, in which the pump segment inserted into the pump bed 7 is radially captured with a predetermined clearance fit. The pump segment can be fixed to the pump housing 5 during the operation of the peristaltic pump by means of a matching body, not shown in more detail, which can be fixed in a corresponding connection of the pump housing 5 in a non-movable manner.

[0041] Before the peristaltic pump is put into operation, the hose segment, which is converted into the pump segment during operation of the pump, must be introduced or inserted into the pump bed 7 and positioned centrally with respect to the displacement element 20 .

[0042] For this purpose, a pump segment (not shown) is first inserted into the pump housing 5 so that it extends from the low-pressure side connection point PN in an arc shape over the rotor 10 following the support surface 30 to the high-pressure side connection point PP. Figure 4 In this phase, the rotor 10 (indicated by dash-dotted lines) is still completely above the rotor 10, more precisely above the rotor cover 42. In order to insert the pump segment into the pump bed 7 by manually rotating the rotor 10 in the direction of the arrow D and to keep the stress on the pump segment as low as possible and the handle as simple as possible, the rotor 10 carries an introduction aid, with which the hose or pump segment can be pressed during the insertion of the hose or pump segment into the pump bed 7, and a hose guide element, with which the hose or pump segment can be oriented centrally relative to the pressing element 20.

[0043] The introduction aid and the hose guide element are integrated into the rocker arm 41 according to the invention, which will be described in detail below with reference to the drawings. Figures 3 to 5 Describe in more detail.

[0044] The support of the introduction aid and the hose guide element is in the present invention a rocker arm 41 which is pivotably mounted on the rotor base body 40. More precisely, the introduction aid and the hose guide element are integrated into the rocker arm 41 as follows:

[0045] As shown in FIG. 40 , Figure 3 As shown in FIG. 4 , the rotor cover 42 is removed from the rotor base body, and the rocker arm 41 is pivotally fixed on the hinge pin 38 by means of two pivot bearing holes 50, 52 with a pivot axis A38. Figures 3 to 6 As can be seen in FIG. 1 , the rocker arm 41 has a stop surface 54 for a compression spring 56 on its end section facing away from the pivot bearing holes 50, 52, by which the rocker arm 41 is loaded with a pressure directed away from the rotor base body 40. Figure 5 As can be seen from the illustration, between the pivot bearing holes 50, 52 and the stop surface 54, the rocker arm 41 is designed in the form of a slightly convexly curved frame with two frame arms 58, 60 located in parallel spacing, which are themselves designed for the rotation axis 66 of the pressure roller 20 (see Figure 3 ) bearing points 62, 64. The rocker arm 41 has a symmetry plane ES, relative to which the pressure roller 20 is also centrally positioned in this way.

[0046] The guide bodies 70, 72 which are formed on the pivot bearing, more precisely on the bearing openings 50, 52, i.e. integrated into the rocker arm 41 as close as possible to the pressure roller 20, serve as an introduction aid and guide element for the pump segment PS, and which extend from the pivot bearing, i.e. from the axis A38 of the joint pin 38, essentially in the radial direction from the rotor axis A, i.e. from the rotor base body 40, so far that they (e.g. from the Figure 1 As can be seen in the drawing, however, only the upper guide body 70 is visible in this figure) when the rotor 10 rotates, it comes as close as possible to the support surface 30.

[0047] The upper guide body 70 forms an introduction aid, which is described in more detail below with regard to its function, and the two guide bodies 70 , 72 together serve as a hose guide element, by means of which the pump segment is centered relative to the pressure element or pressure roller 20 .

[0048] At least the upper guide body 70 (in the illustrated embodiment, however, both guide bodies 70, 72) of the introduction aid are formed in cross section and in accordance with Figure 4 In a radial view of the rotor, the rotor has a substantially rounded wedge shape pointing in the direction of rotation D of the rotor, which is at an acute angle WA (see Figure 4 ) is inclined relative to the pump bed 7 and therefore relative to the symmetry plane ES of the rocker arm 41 which is parallel thereto.

[0049] At least the upper guide body 70 has two functional surfaces F1 and F2, wherein the outer functional surface F1 (which is located at the front in the rotational direction D and faces away from the symmetry plane ES) is Figure 4 The rounded wedge surface is formed by a dot-dash line in FIG. 1 and a functional surface F2 facing the inside of the symmetry plane ES (which is Figure 4 The lower guide body 72 is formed by a cylindrical segment surface which is preferably connected steplessly to the wedge surface. The lower guide body 72 forms at least the inner functional surface F2. The functional surface F1 serves as an introduction aid when inserting the pump segment PS, and the opposite functional surface F2 serves as a hose guide element in order to center the pump segment relative to the pressure element, i.e. the pressure roller 20, when the peristaltic pump is in operation.

[0050] In the exemplary embodiment shown, the cross section of the guide bodies 70, 72 each has a center axis or axis of symmetry, wherein Figure 4 Only the symmetry axis SA70 of the guide body 70 is drawn. Figure 4 It can also be seen in FIG. 7 that the guide bodies 70 , 72 are additionally supported on the rocker arm 41 by means of a strut 76 following the axis of symmetry SA70 .

[0051] Overall, the upper guide body 70 together with the outer functional surface F1 is designed as an introduction aid for the pump segment PS, while the two guide bodies 70 , 72 together with their functional surfaces F2 serve as hose guiding elements.

[0052] This design results in the following working method:

[0053] Starting from any rotational position of the rotor 10, the user can Figure 2 ) The rotor 10 can be rotated manually by grasping the rotor 10 between the guide surfaces 46, 48, on which the rotor is rotated. Figure 4 The inserted pump segment, which is indicated by a dash-dot line in the figure and has the reference symbol PS, extends from the connection point PN to the connection point PP following the support surface 30. In this phase, the guide body 70 does not yet contact the pump segment PS.

[0054] When the rotor rotates further, the outer functional surface F1 of the guide body 70 is Figure 4 As shown in the sequential positions, the guide body 70 slides onto the pump segment PS, and as the rotor 10 rotates further, the functional surface F1 of the guide body 70 continues to press the pump segment PS downward in the direction of the pump bed, so that the pump segment is finally caught by the functional surface F2 in the center relative to the symmetry plane ES because it rests on the support surface 30. This function is also continued when the support surface 30 is swept over, so that the entire pump segment is finally centered relative to the pressure roller in the pump bed 7.

[0055] When the guide body 70, which is offset by 180° from the guide body 70 during further rotation of the rotor and which is not involved in the threading process, encounters the already threaded pump segment PS, the guide bodies 70 and 72 approach the pump segment in this phase so closely that the guide bodies guide the pump segment between the functional surfaces F2 like a funnel and thus orient the pump segment centrally relative to the pressure roller 20. This mode of action occurs whenever the pressure roller is active during operation of the peristaltic pump, whereby the delivery volume of the peristaltic pump can be kept constant.

[0056] Since peristaltic pumps and thus the rocker arm 41 are also used in the medical field and since the mechanical stresses of the rocker arm due to the forces exerted on the pump segment by the pressure rollers are relatively high, the rocker arm 41 is made of high-strength stainless steel with high chemical resistance according to the invention and the rocker arm is produced by the metal injection molding (MIM) method. For example, heat-resistant austenitic chromium-nickel steel (X15CrNiSi25-21), as it is known under the name 1.4841, can be used as the material. This steel is particularly resistant to oxidation and it has been shown that the surface quality that can be achieved in the MIM method is sufficient to make the functional surfaces F1 and F2 sufficiently smooth without further processing in order to press the pump segment PS into the pump bed smoothly and without wear and align it centrally relative to the pressure rollers.

[0057] By integrally attaching the guide bodies 70, 72 to the rocker arm 41 and more specifically to the pivot bearing holes 50, 52, respectively, a relatively complex shape is obtained for the rocker arm 41, which can be seen in the figure and can be produced with a minimum expenditure of material using the MIM method. At the same time, material can be omitted in places that are not important for the function. In this way, it is possible to, for example, Figure 5 As shown in the view of FIG. 4 , the rocker arm 41 is designed to have many material gaps on the one hand and to reinforce the sections at the locations where the mechanical strength needs to be increased on the other hand. The reinforced bearing holes 50, 52 can thus be used to support the originally rather delicate guide bodies 70, 72 using the struts 76 on the rocker arm 41. At the same time, the free space between the pivot bearing holes 50, 52 can be increased so that a more robust hinge pin retaining block 39 (see FIG. 4 ) of the rotor base body 40 is axially enclosed between the two pivot bearing holes. Figure 3 The support arms 58, 60 connecting the pivot bearing holes 50, 52 to the stop surface 54 are also designed to save material in order to provide a lot of space for accommodating the pressure roller. The bearing points 62, 64 are reinforced in order to be able to connect the rotation axis 66 to the support arms 58, 60 in a rotationally and displacement-proof manner.

[0058] In the production method, the blank which is injection molded from the mixture of metal powder and binder can already have all the geometrical features of the finished rocker arm 41. These geometrical features are not lost during the removal of the usually organic binder or during sintering, because the shrinkage which occurs during sintering usually proceeds linearly up to 96% of the final density, so that after sintering, the surface of the rocker arm with sufficient quality is also good enough to fulfill the above-mentioned functions of the rocker arm while protecting the pump segment well. In addition, the correct excess factor can be accurately determined by sample sintering.

[0059] Figure 6 It is shown what kind of material saving can be achieved with the rocker arm according to the invention compared to a rocker arm manufactured by cutting. 3 The metal block from which approximately 36 cm of 3 Correspondingly, the material consumption of the rocker arm is only about cm 3 , thus achieving significant raw material savings.

[0060] from Fig. 7A It can be seen how a rocker arm which can be manufactured with machining at reasonable manufacturing costs differs from a rocker arm manufactured and designed according to the invention. It can be seen that only a base body with relatively simple surfaces without struts can be manufactured, to which the components for the introduction of auxiliary parts and hose guide elements must then also be connected. The struts cannot be produced at reasonable cost. Only materials that are easy to machine are considered as materials, so that additional costs for surface treatment are required.

[0061] Use basis Figure 7B The illustration of shows the additional material expenditure required when producing a rocker arm by means of conventional milling methods, wherein hose guide elements in the form of pin-shaped guide bodies 70 , 72 are integrated in one piece into the rocker arm.

[0062] In contrast, the rocker arm according to the present invention is Figure 6 As shown in , this results in a component which, despite a low material usage, is highly rigid, wherein further processing of the surface can be dispensed with.

[0063] Of course, deviations from the described embodiments are possible without departing from the essential idea of ​​the invention.

[0064] If necessary, the guide bodies 70 , 72 can also be additionally coated with a material having sliding properties that minimize wear.

[0065] Other powder injection molding methods, such as ceramic powder injection molding, can also be used to produce the rocker arm 41 .

[0066] It is also possible to design the guide bodies 70 , 72 as separate components and then connect these to the rocker arm 41 to form an integral structural unit.

[0067] In the above-described peristaltic pump, two extrusion elements are provided, which are arranged rigidly or at a fixed angle of 180° to each other in a relative position of 180°. However, it can also be provided that there are more than two extrusion elements and that these extrusion elements are designed to be positionable relative to each other in the direction of rotation at an angle. For this purpose, the extrusion elements can be arranged on a rotor arm, which can be designed to be pivotable relative to the rotor in the circumferential direction.

[0068] The pressing elements do not have to be designed as pressing rollers or pressure rollers, which advantageously roll on the fluid line in a material-protecting manner. Sliding shoes that slide on the hose section can also be provided.

[0069] The invention therefore provides a peristaltic pump, in particular for conveying fluids in an apparatus for extracorporeal blood treatment, the peristaltic pump having a pump housing, in which a rotor rotatable about a rotor axis is accommodated, the rotor having at least two extrusion elements offset from each other in the circumferential direction, and the pump housing having a support surface extending in an arc shape about the rotor axis and radially spaced from the rotor, the support surface being provided for supporting a hose segment that can be radially introduced between the rotor and the support surface. The rotor carries the extrusion element via a rocker arm, which is pivotally and spring-loadedly fixed to the rotor. The rocker arm itself carries an introduction aid, with the aid of which the hose segment can be pressed into the pump bed during its insertion, and a hose guide element, with the aid of which the hose segment can be centered relative to the extrusion element. In order to provide a peristaltic pump characterized by simplified manufacturing with an extended functionality and service life, the rocker arm is composed of a high-strength stainless steel with high chemical resistance and the rocker arm is manufactured by a powder injection molding method, preferably a metal injection molding (MIM) method.

Claims

1. A peristaltic pump, in particular for conveying fluid in an apparatus for extracorporeal blood treatment, the peristaltic pump having A pump housing (5) in which a rotor (10) rotatable about a rotor axis (A) is accommodated, the rotor having at least two extrusion elements (20) offset from one another in the circumferential direction, and the pump housing having a support surface (30) extending in an arc shape about the rotor axis (A) and radially spaced from the rotor (10), the support surface being provided for supporting a hose section (PS) which can be radially introduced between the rotor (10) and the support surface (30), in, The rotor (10) The squeezing element (20) carries a rocker arm (41) which is pivotally and spring-loadedly fastened to the rotor (10), an introduction aid (70, F1), and a hose guide element (70, 72), by means of which the hose section (PS) can be pressed during its insertion into the pump bed (7), and by means of which the hose guide element can be centered with respect to the squeezing element (20), characterized in that The rocker arm (41) is made of high-strength stainless steel with high chemical resistance and is produced by a powder injection molding method, preferably a metal injection molding (MIM) method.

2. The peristaltic pump according to claim 1, It is characterized in that The functional surface of the rocker arm is not subjected to any further surface smoothing treatment after the sintering process.

3. The peristaltic pump according to claim 1 or 2, It is characterized in that Both the introduction aid (70, F1) and the hose guide element (70, 72, F2) are integrated into the rocker arm (41) adjacent to the pressing element (20) in the direction of rotation (D) of the rotor (10).

4. A peristaltic pump according to any one of claims 1 to 3, It is characterized in that The rocker arm (41) is mounted on the rotor (10) by means of a pivot bearing (38), which is arranged offset in the rotational direction relative to the displacement element (20), wherein the introduction aid (70, F1) and the hose guide element (70, 72, F2) are mounted integrally on the pivot bearing (38).

5. The peristaltic pump according to claim 4, It is characterized in that The introduction aid (70, F1) is formed by a pin-shaped guide body (70), which extends from the pivot bearing (38) essentially in a radial direction away from the rotor axis (A) and which, when viewed in cross section, essentially has a rounded wedge shape pointing in the direction of rotation (D), which is inclined at an acute angle (WA) relative to the pump bed (7).

6. The peristaltic pump according to claim 5, It is characterized in that The guide body (70) has two functional surfaces (F1, F2), wherein the outer functional surface (F1) running in front in the direction of rotation (D) of the rotor (10) and facing away from the center plane (ES) is designed as a rounded wedge surface, and the inner functional surface (F2) facing the center plane (ES) is formed by a cylindrical segment surface preferably continuously connected to the wedge surface.

7. The peristaltic pump according to claim 4 or 5, It is characterized in that The cross section of the guide body (70) has a central axis (SA70), wherein the guide body (70) is preferably additionally supported on the rocker arm (41) by means of a strut (76) following the central axis (SA70).

8. A peristaltic pump according to any one of claims 3 to 7, It is characterized in that The guide body (70) is preferably integrally mounted on the pivot bearing hole (50) of the rocker arm (41).

9. The peristaltic pump according to claim 8, It is characterized in that The rocker arm (41) is configured with a stop surface (54) for a compression spring (56) at its end section facing away from the pivot bearing eye (50, 52), wherein the pressure element (20) is arranged, for example rotatably supported, between the pivot bearing eye (50, 52) and the stop surface (54).

10. A peristaltic pump according to any one of claims 3 to 9, It is characterized in that A further second guide body (72) is assigned to the first guide body (70) which constructs the introduction aid (70, F1), and is constructed and oriented symmetrically to the first guide body (70) with respect to a horizontal plane (ES) parallel to the pump bed (7), so that the facing cylindrical segment surfaces (F2) of the two guide bodies (70, 72) constitute the functional surfaces of the hose guide element (70, 72, F2).

11. The peristaltic pump according to claim 10, It is characterized in that The second guide body (72) is preferably arranged integrally on the other pivot bearing eye (52), and the two pivot bearing eyes axially surround the pivot pin retaining block of the rotor base body (40).

12. The peristaltic pump according to claim 10, It is characterized in that The horizontal plane (ES) is the symmetry plane of the rocker arm (41).

13. A peristaltic pump according to any one of claims 1 to 11, It is characterized in that At least the introduction aid (70, F1) and / or the hose guide element (70, 72, F2) are made of and / or coated with a material having sliding properties that minimize wear.

14. A rocker arm for a peristaltic pump having the features according to any one of claims 1 to 12.

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