PERISTALTIK PUMP

Description

Technical area

[0001] The present disclosure relates to a hose roller or peristaltic pump, i.e. a positive displacement pump in which the medium to be pumped is pressed through a hose by external mechanical deformation thereof, according to the preamble of patent claim 1. Such pumps are frequently used to pump fluid, in particular blood, in a device for extracorporeal blood treatment, in particular in a dialysis machine. The fluid is pumped from a low-pressure side to a high-pressure side by means of the peristaltic pump, wherein an elastically deformable fluid line in the form of a hose segment, referred to as a pump segment, arranged between the low-pressure side and the high-pressure side is deformed, in particular squeezed, between a support surface of a pump bed and a rotor rotating relative to the latter, having at least two squeezing elements.

[0002] Peristaltic pumps of this type are available in various designs on the market. For example, a pump manufactured by the applicant of document EP 1 749 549 B1, the design of which can be seen from the schematic sectional view according to Figure 8 As can be seen, the torque is transmitted from a drive shaft 310 with axis A by means of a freewheel 320 and a knurled sleeve 330. A rotor base body 340 is mounted on the drive shaft via a small plain bearing point 350 at the free end of the drive shaft, wherein the plain bearing point 350 is axially offset from the knurled sleeve 340, which extends only to the center of the rotor base body 340. The plain bearing point 350 is integrated into the base body 340 of the rotor.

[0003] To ensure coaxiality between the freewheel 310 and the bearing 350, high demands must be placed on the accuracy of the knurled sleeve and the base body. Furthermore, because only a small one-sided bearing of the rotor base body 340 is provided, radial forces and tilting moments can only be absorbed to a limited extent. Although the knurled sleeve has knurling across its entire height, due to its small axial extension and its installation in the axially outer area of ​​the rotor base body 340, the torque to be transmitted is only introduced in the lower area and therefore remains relatively limited.

[0004] Another generic peristaltic pump with the features of the preamble of claim 1 is known, which, as in the Figures 9 and 10 shown. The Figure 9 shows a partial section of a rotor base body with pressed-in freewheel, while Figure 10a sectional view of a knurled sleeve and a bearing ring used in this process. In this peristaltic pump, the torque is transferred from the drive shaft to the rotor base body 440 via a freewheel 420, which is pressed into a knurled sleeve 430. The knurled sleeve 430 is in turn pressed into a cylindrical recess in the rotor base body 440. The freewheel is provided to enable manual threading and unthreading of the pump segment, as well as manual blood return, without having to open a lock. Sleeve freewheels without roller bearings are friction clutches and can only transmit torque. Because they cannot absorb radial forces or tilting moments, the bearing of the rotor base body 440 has two plain bearing points, designated by the reference numerals 450A and 450B. One, peripheral bearing point 450A is integrated into the knurled sleeve 430 below the freewheel, as shown in Figure 9shown. The knurling 435 is located radially outside the bearing point 450A, i.e. where the wall thickness of the knurled sleeve 430 is greater. The second bearing point 450B is formed by a separate bearing ring 470, which according to Figure 8 above the knurled sleeve 430 into a stepped bore in the rotor base body 440. This design requires high manufacturing precision not only for the knurled sleeve 430 and bearing ring 470, but also for the mounting in the rotor base body 440 to ensure coaxiality between the freewheel 430 and the bearing 450A,B. Furthermore, it can be seen that even with this design, the transmittable torque remains limited because it can only be introduced via the knurling 435 arranged on the edge.

[0005] The invention is based on the object of creating a peristaltic pump according to the preamble of claim 1, in which the coaxiality between the freewheel and the bearing is ensured with less manufacturing effort while maintaining a tilt-proof bearing of the rotor base body.

[0006] This problem is solved by the features of claim 1.

[0007] The redesigned peristaltic pump still features two plain bearings to absorb radial forces and tilting moments. However, these are designed so that they are defined on both sides of the freewheel by the geometry of the finished drive sleeve. This offers the particular advantage that the high demands on precise manufacturing are limited to the knurled sleeve and, if necessary, a bearing ring housed within it to ensure coaxiality between the freewheel and the bearing. The rotor base body, on the other hand, can be manufactured with larger tolerances, significantly reducing manufacturing effort. Furthermore, this design opens up the possibility of keeping the installation space for the bearings and torque transmission as small as possible.Because one bearing point is formed by a peripheral, cylindrical inner surface section of the driving sleeve, and the other bearing point is formed by a bearing ring inserted into the driving sleeve with a press fit, the bearing points can be arranged at a large axial distance, which makes it possible to absorb the radial forces and tilting moments even with components such as a drive shaft that require a reduced installation space.

[0008] Advantageous embodiments are the subject of the subclaims.

[0009] A further simplification of production while simultaneously ensuring a high-precision coaxial alignment of the freewheel and bearing is achieved if the driving sleeve has a continuous, i.e. common, fitting surface for the pressed-in freewheel and the bearing ring.

[0010] A further advantageous embodiment consists in forming the drive sleeve on the outside with at least one toothed section that can be pressed into a central recess in the rotor base body, which recess is formed with a draft angle, to create a rotationally fixed, form-fitting connection. In this way, the rotor base body can be formed as an injection-molded part, whereby the recess in the rotor base body no longer requires any further processing.

[0011] If two axially spaced toothing sections are provided, which are located radially outside the bearing points, the torque can be transmitted particularly evenly to the rotor base body, which allows the transmittable torque to be further increased with a small installation size.

[0012] This arrangement is particularly advantageous in conjunction with the design of the rotor base body as a cast part when the toothed sections have different diameters and the central recess of the rotor base body has several sections with different diameters and draft angles. This meets the requirements for an injection-moldable design. Furthermore, it simplifies the pressing-in process of the knurled sleeve and optimizes the angle of the required draft angle.

[0013] Exemplary embodiments of the invention are explained in more detail below with reference to schematic drawings. They show: Figure 1 a perspective central sectional view of a rotor of a peristaltic pump according to a first embodiment; Figure 2 a perspective sectional view of a peristaltic pump according to Figure 1 used knurled sleeve with pressed-in freewheel; Figure 3the sectional view of the knurled sleeve with pressed-in freewheel according to Figure 2 ; Figure 4 in enlarged scale the sectional view of a holder in the rotor base body for the knurled sleeve according to Figures 2 and 3 ; Figure 5 the sectional view of the rotor of the peristaltic pump; Figure 6 a perspective, central sectional view of the rotor body of the Figures 1 to 5 peristaltic pump shown; Figure 7 the sectional view of a modified design of a knurled sleeve fitted into the rotor base body with a pressed-in freewheel; Figure 8 a schematic sectional view of a pump according to the prior art; Figure 9 a schematic partial section of a known rotor base body with pressed-in freewheel; and Figure 10 a sectional view of a pump according to Figure 9 used knurled sleeve and a bearing ring.

[0014] Figure 1shows the central sectional view of a rotor 10 of a peristaltic pump, which can be used in a device for extracorporeal blood treatment, in particular in a dialysis machine. The peristaltic pump has a pump housing (not shown in detail), in which a rotor rotatable about a rotor axis A is arranged, with at least two squeezing elements 46 offset from one another in the circumferential direction (see Figure 5 ), which in the embodiment according to Figures 1 to 6 formed by rollers. The pump housing has a support surface extending in an arc around the rotor axis A and radially spaced from the rotor, which is designed to support a hose segment that can be inserted radially between the rotor and the support surface.

[0015] In the illustrated embodiment, the peristaltic pump has a drive shaft (not shown) with a rotational axis A, with which a rotor base body 40, which carries a rotor cover 45, can be driven. The torque of the drive shaft is transmitted via a sleeve freewheel 20 (see Figures 2 and 3 ) is transferred to the rotor base body 40. For this purpose, a toothed driving sleeve, which is referred to below as knurled sleeve 30 (see Figure 2 ), into which the sleeve freewheel 20 with freewheel rollers 25 is pressed. The freewheel is intended to enable the manual threading and unthreading of a pump segment, as well as the manual blood return, without having to open a lock. The sleeve freewheel is a freewheel without roller bearings and is therefore a type of friction clutch that can only transmit torque.

[0016] The knurled sleeve 30 is - like the Figures 1 and 5removable - pressed into the base body 40 of the rotor, namely into a centric receptacle 42 with a stop shoulder 44 ( Figure 6 ). For a torsion-proof connection to the rotor base body 40, the knurled sleeve 30 has two straight knurls 35A and 35B, each formed at the axial end portions of the knurled sleeve 30. In the illustrated embodiment, the knurls 35A have different outer diameters D35A and D35B. A smooth recess 36 is located between the knurls 35A and 35B.

[0017] To absorb radial forces and tilting moments, plain bearing points 50A and 50B are provided on both sides of the cup-type freewheel 20. The plain bearing point 50A is formed by a cylindrical annular surface of an end-side inner shoulder 37 of the knurled sleeve 30. The other plain bearing point 50B is formed by the running surface of a bearing ring 39 pressed into the knurled sleeve 30. In this way, the plain bearing points 50A and 50B and their relative positions on both sides of the freewheel 20 are determined by the geometry of the finished knurled sleeve 30. Because the freewheel 20 is already pressed into a fitting surface of the knurled sleeve 30, the required coaxiality between bearing points 50A, 50B and the freewheel 20 can be ensured solely by manufacturing the knurled sleeve 30.In other words, the manufacturing accuracy of the knurled sleeve 30 and the bearing ring 39 alone determines the coaxiality of the freewheel 20 and the bearing of the rotor base body 40, so that the rotor base body 40 can be manufactured with larger tolerances, significantly reducing manufacturing costs. Furthermore, this concept opens up the possibility of keeping the installation space for the design of the bearing points and the torque transmission as small as possible.

[0018] Out of Figure 3 It can be seen that the bearing ring 39 is pressed into a cylindrical joining surface 38, which simultaneously forms the joining surface for the cup-type freewheel 20. This further simplifies production.

[0019] Because the rotor base body 40 can be manufactured with larger tolerances due to the above-described arrangement of the sleeve freewheel 20 and the plain bearings 50A and 50B, it can be produced as an injection-molded part, for example as a metallic or preferably glass-fiber-reinforced plastic injection-molded part, without reworking. The design of the knurls 35A and 35B accommodates this as follows: Because the knurl 35A has a larger outer diameter than the knurl 35B, the receptacle 42 for the knurled sleeve 30 in the base body - as shown in Figure 4shown - into several sub-areas 42A to 42C with different diameters and draft angles. The sub-areas 42A and 42C are slightly conical, for example with a cone angle of 1.5°. These sub-areas 42A and 42C are adapted in terms of their diameter and axial extent to the associated knurls 35A and 35B in such a way that when the knurled sleeve 30 with its straight knurls 35A and 35B is pressed in and the material is displaced as a result, a uniformly firm toothing occurs between the knurled sleeve and the rotor base body 40, so that the torque introduced by the rotor shaft can be distributed as evenly as possible across the rotor base body 40, essentially over its entire height. This is because the positive connection between the knurled sleeve 30 and the rotor base body 40 lies essentially radially outside the bearing points 50A and 50B.The partial area 42B located between the partial areas 42A and 42C is designed as a draft angle with a slightly larger cone angle of 2°.

[0020] In the embodiment described above, the arrangement is such that the knurled sleeve 30 supports the bearing ring 39 on the side on which the knurling 35B with a smaller diameter D35B is formed. The bearing point 50A facing the rotor cover 45 is formed by the knurled sleeve 30. Figure 7 shows a modified embodiment of the assembly unit. In this figure, components corresponding to components of the previously described embodiment are provided with similar reference numerals preceded by a "1".

[0021] Here, the inner shoulder 137 of the knurled sleeve 130 is formed on the side on which the knurling 135B with a smaller diameter is formed. The bearing ring 139 is pressed into the joining surface of the knurled sleeve 130 on the other side, ie radially inside the knurling 135A with a larger diameter. The receptacle 142 formed in the rotor base body corresponds to the receptacle 42 of the embodiment according to the Figures 1 to 6 .

[0022] The invention thus provides a peristaltic pump, in particular for conveying fluid in a device for extracorporeal blood treatment, comprising a pump housing in which a rotor rotatable about a rotor axis is accommodated, having at least two squeezing elements offset from one another in the circumferential direction. The pump housing has a support surface extending in an arc around the rotor axis and radially spaced from the rotor, which is designed to support a hose segment that can be inserted radially between the rotor and the support surface. The rotor is driven by a rotor shaft, the rotational movement of which is transmitted to a rotor base body via a freewheel pressed into a toothed driver sleeve, and a plain bearing for the base body is provided on both sides of the freewheel.In order to ensure the coaxiality between the freewheel and the tilt-proof bearing of the rotor base body with minimal manufacturing effort, the plain bearing positions on both sides of the freewheel are defined by the geometry of the finished drive sleeve. List of reference symbols

[0023] A Axis 20 Sleeve freewheel 25 Freewheel roller 30 Knurled sleeve 35A, BRilling 36 Recess 37 Inner shoulder 38 Joint fit surface 39 Bearing ring 40 Rotor base body 42 Mounting 42A, B, C Sections of 42 44 Stop shoulder 45 Rotor cover 46 Squeeze elements 50A, B Plain bearing points 120Freewheel 130Knurled sleeve 135A, BRnurlings 139Bearing ring 310Drive shaft 320Freewheel 330Knurled sleeve 340Rotor base body 350Bearing point 420 Sleeve freewheel 430 Knurled sleeve 435 Knurling 450A, B Plain bearings 470 Bearing ring

Claims

1. A peristaltic pump, specifically for conveying fluid in an apparatus for extracorporeal blood treatment, comprising a pump housing in which a rotor (40, 45) rotatable about a rotor axis (A) and including at least two squeezing elements (46) offset against each other in the circumferential direction is accommodated and which includes a support surface extending in a curved shape around the rotor axis (A) and being radially spaced apart from the rotor, said support surface being arranged to support a tube segment to be radially inserted between the rotor and the support surface, wherein the rotor (40, 45) is driven by means of a rotor shaft, the rotary movement of which can be transmitted to a rotor base body (40) via a freewheel (20) press-fitted into a toothed driver sleeve (30), and a plain bearing position (50A, 50B) for the rotor base body (40) is provided on both sides of the freewheel (20), characterized in that the plain bearing positions (50A, 50B) are defined on both sides of the freewheel (20) by the geometry of the finished driver sleeve (30), wherein one bearing position (50A; 150B) is formed by an edge-side cylindrical inner surface portion of the driver sleeve (30; 130) and the other bearing position (50B; 150A) is formed by a bearing ring (39; 139) inserted with press-fit into the driver sleeve (30; 130).

2. The peristaltic pump according to claim 1, characterized in that the driver sleeve (30) has a continuous fitting area (38) for the press-fitted freewheel (20) and the bearing ring (39).

3. The peristaltic pump according to one of the claims 1 or 2, characterized in that the driver sleeve (30) on the outside has at least one toothing section (35A, 35B) which can be pressed into a centric recess (42) of the rotor base body (40) to establish a rotationally fixed positive or form fit connection.

4. The peristaltic pump according to claim 3, characterized in that two axially spaced toothing sections (35A, 35B; 135A, 135B) are provided which are located radially outside the bearing positions (50A, 50B; 150A, 150B).

5. The peristaltic pump according to claim 4, characterized in that the toothing sections (35A, 35B; 135A, 135B) have differently sized diameters (D35A, D35B), and the centric recess (42) of the rotor base body (40) includes plural sections (42A, 42B, 42C) having different diameters and draft angles.

6. The peristaltic pump according to claim 5, characterized in that the sections (42A, 42B, 42C) of the centric recess (42) are each conical with a cone opening in the same direction.

7. The peristaltic pump according to claim 6, characterized in that the cone angles of the sections (42A, 42C) receiving the toothing sections (35A, 35B; 135A, 135B) are smaller than the cone angle of the intermediate section (42B).

8. The peristaltic pump according to one of the claims 1 to 7, characterized in that the rotor base body (40) is in the form of an injection-molded part, preferably made of glass-fiber reinforced plastic or light metal.