Patent Publication Number: US-2007104599-A1

Title: Peristaltic pump

Description:
The invention refers to a peristaltic pump according to the preamble of claim  1 .  
      Peristaltic pumps of the kind discussed herein are fundamentally known. They are used for conveying different liquid and gaseous media.  
      From the EP 1 137 886, a roller pump for peristaltically conveying of media is known, which is provided with a tube cartridge. The tube cartridge is fixed to the roller pump by means of a lockable cover. The conveying rollers are resiliently supported by a rotation body member. As it is particularly evident from  FIG. 1  of this document, such a roller pump including the tube cartridge has a relatively large length and, accordingly, requires a lot of space.  
      From the WO 02/25112, a peristaltic pump is known, which is provided with a multi-part housing in which a reduction gear box is located. The pressure rollers for squeezing a flexible tube section are integrated into the reduction gear box. Such a pump consists of a multitude of components, is relatively expensive to manufacture and requires a lot of time for assembling.  
      Finally, from the U.S. Pat. No. 5,857,843, a peristaltic pump is known, which comprises a support frame on which the rotor is replaceably supported. The support frame is provided with latch-shaped notch elements, which serve for fixing a plate member constituting the upper portion of the housing. The plate member is concavely shaped at the inner side and serves to receive a flexible tube section. Even if such a pump is of very simple design and can be manufactured at low costs, it has, amongst else, the disadvantage that only a comparatively small tube section and circular arc section, respectively, is available for peristaltic conveying. Moreover, the plate member appears to be relatively unstable, particularly in transverse direction, what has a negative influence on a constant conveying rate. Additionally, the mutual force action of the squeezed tube can result in bending apart the notch elements.  
      It is the object of the present invention to improve a pump designed according to the preamble of claim  1  in such a way that it is compact, that it can be manufactured at low costs, that it can be assembled easily and quickly, and that it is very rigid in assembled form and shows high shape constancy.  
      This object is met with a pump which comprises the characteristics listed in the characterizing portion of claim  1 .  
      Advantageous further developments of the peristaltic pump are defined in the dependent claims  2  to  14 . 
    
    
      In the following, a preferred embodiment of the invention is further explained by means of drawings. Shown in these drawings is in:  
       FIG. 1  an exploded view of the peristaltic pump;  
       FIG. 2  the assembled pump according to  FIG. 1  in a first cross sectional view; and  
       FIG. 3  the assembled pump according to  FIG. 1  in a further cross sectional view. 
    
    
       FIG. 1  shows a six channel peristaltic pump in an exploded view. Substantially, the pump consists of a support frame  1 , a tubing holder  2 , a rotor  3  and a connecting element  4  having six tubing sections  43  located thereon. Also evident is a gear wheel  5  for coupling to a not shown driving motor.  
      The support frame  1 , designed to be dimensionally stable, constitutes, together with the tubing holder  2 , the real housing of the pump. For rotatably supporting the rotor  3 , the support frame  1  is provided with two bearing sleeves  11 . The two front faces of the support frame  1  are constituted by panels  12 , which are provided with slots  15   a ,  15   b  for fixing the support frame  1  and the entire pump, respectively. Finally, the support frame  1  is provided with several slot-like cut-outs  13  on both sides, in which notch elements  22  of the tubing holder  2  are clampingly fixable, as will be described further in the following.  
      The tubing holder  2  comprises a tubing bed body member  25 , which is designed essentially in the shape of an Omega and which extends at the inner side in the shape of a circular arc coaxial to the axis of rotation of the rotor  3  over an angle of appr. 130° to constitute a tubing bed. The expression “in the shape of an omega” means in the present case that the tubing bed body member  25  has substantially the shape of a capital omega (Ω). In the end region, the tubing bed body member  25  presents two legs  2   a ,  2   b  which pass over from a concave shape to a convex shape in a smooth transition. The tubing bed is divided into six sections by means of groove-like recesses  21  which serve to receive the flexible tube sections. In place of the groove-like recesses  21  for constituting six sections, also a tubing mat, consisting of six tubes connected to each other, could be used. In this case, the tubing bed body member  25  could be provided with a substantially smooth inner side. The two legs  2   a ,  2   b  of the tubing bed body member  25  are provided, on the outer side, with notch elements  22  by means of which the tubing holder  2  is fixable to the slot-like cut-outs  13  of the support frame  1 . The outer side of the tubing bed body member  25  is provided with radially extending reinforcing ribs  23  as well as with axially extending reinforcing ribs  24 . The radially extending reinforcing ribs  23  extend along appr. 180° of the outer side of the tubing bed body member  25 . In any case, the tubing holder  2  is dimensioned such that the ends of the two legs  2   a ,  2   b  of the tubing bed body member  25  are resiliently flexible in radial direction and make possible a quick fixing of the tubing holder  2  to the support frame  1  in the sense of a snap-on connection.  
      The rotor  3  consists of a rotor body  31 , provided with a central axis  32  which is inserted into the bearing sleeves  11  of the support frame  1 . Three conveying rollers  33 , designed in the shape of barrels, are rotatably supported on the rotor body  31 . Preferably, the rotor body  3  is manufactured of plastic material, while the central axis  32  as well as the conveying rollers  33  preferably consist of metal.  
      The connecting element  4  consists of a base element  41 , to which are fixed twelve pipe sections  42 . Attached to the upper portions of these pipe sections  42  are a total of six flexible tubing sections  43 , which rest on the inner side of the tubing bed body member  25 , once the pump is assembled, and which are squeezable by the conveying rollers  33  for the peristaltic conveying of a medium. It is understood that the design of the inlet and the outlet section is not limited to a six channel pump, but the number of the channels is substantially arbitrarily variable.  
      The assembly of the shown components to a pump can be accomplished with a few simple steps; first, the particular tubing sections  43  are attached to the connecting element  4  and then, the rotor  3  is transversely moved into the tubing sections  43  forming loops. Thereafter, the tubing holder  2  is U-shapely positioned and the rotor  3 , together with the connecting element  4  and the tubing sections  43  attached thereto are slid in from the top. Subsequently, the support frame  1  is positioned upright and a pressure is applied, such that the axis  32  of the rotor  3  as well as the notch elements  22  snap in. Finally, the connecting element  4  is fixed to the support frame  1 . In the embodiment shown here, the connecting element  4  is fixed by means of screws. Alternatively, a snap-on connection can be provided for fixing the connecting element  4 , which ensures a quick connection of the connecting element  4  to the support frame  1 . The entire assembly of the pump can be performed, without the use of tools, from one side, which constitutes an advantage in the case of an automatic manufacture.  
       FIG. 2  shows a first cross sectional view of the assembled pump. In this view, particularly the rotor body  31  together with the three conveyor rolls  33   a ,  33   b ,  33   c  rotatably attached thereto and squeezing the particular tubing section  43  in a rolling motion, the tubing holder  2  with the omega-shaped tubing bed body member  25  as well as the radial and axial reinforcing ribs  23 ,  24  are evident. The reinforcing ribs  23 ,  24  ensure that the tubing holder is dimensionally stable and does not deform in operation under the load of the conveyor rollers  33   a ,  33   b ,  33   c . Due to the omega shaped design of the tubing bed body member  25  with “soft” inlet portion and outlet portion, a continuous substantially pulsation free conveying of the particular medium is ensured. A further advantage of the soft inlet and outlet portions is the reduction of torque peaks which, otherwise, would load the motor and the gear box. Assuming a sense of rotation D in counterclockwise direction, the region designated by reference numeral  35  constitutes the inlet portion, while the region designated by reference numeral  36  constitutes the outlet portion of the pump. The pump can be operated both in clockwise direction and in counterclockwise direction.  
      A soft and continuous inlet portion and outlet portion means that both the inlet portion  35  and the outlet portion  36  are designed such that the tubing cross section relevant for conveying is continuously decreased and increased, respectively, by the conveying roller  33   a ,  33   c  rolling along the particular flexible tubing portion  43 . In this connection, it is important that the tubing bed body member  25  is accurately manufactured and that it exhibits a high dimensional stability in operation such that the predetermined distances between conveying roller  33   a ,  33   b ,  33   c  and tubing bed body member  25  are maintained.  
      Besides the already mentioned advantage, further advantages result from a continuous inlet portion and outlet portion; for example, the torque fluctuations emerging from the rotation of the rotor  3  are minimized. This is additionally favored by the facts that the rotor  3  is provided with three conveying rollers  33   a ,  33   b ,  33   c  and that the inlet portion  35  is offset around the axis of rotation of the rotor  3  by about 240° relative to the outlet portion  36 , such that the first conveyor roller  33   a  is located approximately in the middle of the inlet portion  35  when the third conveyor roller  33   c  is located approximately in the middle of the outlet portion  36 . By means of the design shown in the drawings, moreover, a high efficiency is realized and the mechanical load on the tubing sections  43  is reduced, thus increasing their service life. Since the pump is designed symmetrically, it can be operated bi-directionally, i.e. in both senses of rotation. Additionally, as the view shown in  FIG. 2  exhibits, that the particular tubing section  43  is not fully squeezed in the inlet portion  35  and in the outlet portion  36 , while it is fully squeezed after the inlet portion  35  by the corresponding conveyor roller  33   b  to enable a peristaltic conveying of the particular medium. A pump designed in such a way is also particularly suitable for conveying fluid media in a way gentle to cells, for example blood, because the blood corpuscles are prevented from damage by the particular design of the inlet and outlet portions  35 ,  36 .  
      The design of the tubing holder  2  with a dimensionally stable tubing bed body member  25  and with elastically resilient legs  2   a ,  2   b  ensures a very quick and simple assembling, i.e. by simply clicking in the tubing holder  2  into the support frame. Even if the legs  2   a ,  2   b  have to be elastically resilient for assembly, the tubing bed body member  25  has to maintain its dimensional stability and a precise geometry. This goal is met, amongst else, by the fact that the elastically resilient parts are positioned and stiffened by means of an outer positive fitting support on the support frame  1 .  
      From  FIG. 3 , showing a cross sectional view of the assembled pump taken between two tubing sections  43 , particularly the clamping fixation of the tubing bed body member  25  to the support frame is evident. The notch elements  22  located at the outside of the tubing bed body member  25  engage the slot-shaped cut-outs  13  of the support frame  1 . Moreover, the notch elements  22  positively engage an upper web  14  of the support frame, delimiting the slot-shaped cut-outs  13 . In order to ensure a high stiffness in the flexible region of the tubing bed body member  25  fixed to the support frame  1 , the legs  2   a ,  2   b  of the tubing bed body member  25  are positively supported at the outside by the web  14  of the support frame  1 . This design particularly also ensures a precise observation of the optimized distances between the conveyor rollers  33   a ,  33   b ,  33   c  and the inside of the tubing bed body member  25 .  
      The individual elastic tubing sections  43  additionally support the fixing of the tubing bed body member  25  at the support frame  1 , since the conveyor rollers  33   a ,  33   b ,  33   c  of the rotor  3  load the tubing bed body member  25  in radial direction via the tubing sections  43 , such that the fixation thereof to the support frame  1  is additionally supported.  
      The connecting element  4  is designed such and matched to the tubing holder  2  and to the rotor  3  such that the individual tubing section  43  is led essentially in tangential direction into the tubing bed body member  25  of the tubing holder  2  and also led out there from.  
      Even if, in the foregoing, reference has made to the embodiment shown in the drawings of a pump with three conveyor rollers, it is understood that the number of conveyor rollers can be practically arbitrarily varied as long as one stays within the scope of the present invention defined in the claims. Thereby, the tubing bed body member  25  has to enlace the rotor  3 , depending on the number of conveyor rollers, to such a degree that always at least one conveyor roller  33   a ,  33   b ,  33   c  is active, i.e. engages the particular tubing section and squeezes it. The minimal enlacement and the minimum angle of enlacement, respectively, can be calculated as follows: 
 
Enlacement=360°/number of conveyor rollers. 
 
      In the case of using such a pump for higher pressure, moreover, it can be advantageous to have always two conveyor rollers engage the flexible tubing section. In this case, the enlacement can be calculated by using the following formula: 
 
Enlacement=2×360°/number of conveyor rollers. 
 
      The calculated enlacement is to be understood as a minimal amount of enlacement. Preferably, the enlacement is chosen about 10° higher than the angle of enlacement calculated by means of the foregoing formula. The expression “enlacement” shall be understood as that part of the tubing bed that coaxially surrounds the rotor.  
      In recapitulation, the following advantages of a peristaltic pump designed according to the invention may be noticed: 
          It is of simple design and consists of only a few parts;     It can be assembled from one side and, thus, is suitable for automatic manufacturing;     It can be assembled quickly and without tools;     It shows a high dimensional stability (stiffness) after having been assembled;     It can be manufactured at low costs;     It is compact and light;     It can be designed as one channel or multiple channel pump;     It is suitable for conveying for example blood, gently conveying the blood cells;     It can be operated bi-directionally and universally used;     It reduces pulsation, torque peaks, is resistant to wear-out and, thereby, has a higher efficiency.