Abstract:
A hose pump is provided having an elastically deformable hose ( 3 ) for a medium ( 7 ) to be conveyed, and a hose bed ( 2 ), over which the hose ( 3 ) is guided. Furthermore, at least one squeeze element ( 6 ) is provided that is movable along the hose bed ( 2 ), for deforming the hose ( 3 ) on the hose bed ( 2 ) in order to this way move forward the medium ( 7 ) inside the hose ( 3 ). The hose bed ( 2 ) is provided at least partially with a friction-reducing coating ( 8 ).

Description:
INCORPORATION BY REFERENCE 
       [0001]    The following documents are incorporated herein by reference as if fully set forth: German Patent Application No. DE 10 2014 112 324.7, filed Aug. 27, 2014. 
       BACKGROUND 
       [0002]    The invention relates to a hose pump. Such a hose pump comprises an elastically deformable hose for a medium to be conveyed, a hose bed, via which the hose is guided, as well as at least one squeeze element, which can be moved along the hose bed. The squeeze element deforms the hose on the hose bed and conveys the medium forward inside the hose, when it moves along the hose bed; the deformation site of the hose moving along the hose bed with the squeeze element, which usually completely blocks the hose and drives the medium to be conveyed forward inside the hose. A vacuum inside the hose at the input side of the pump is normally generated by its elastic return force, by which it is returned into its original form behind the squeeze element. 
         [0003]    Hose pumps of the present type are also called peristaltic pumps or sometimes constricted tube pumps. They are generally used at locations, where slow quantities of a medium to be conveyed must be moved at high dosing precision, or where a medium is conveyed, which due to its chemical aggressiveness, radioactive contamination, or particularly due to such reasons that the medium shall not contact any moving pump elements, because it is chemically ultra-pure or serves medical purposes. Accordingly, hose pumps of the present type are preferably used in medical technology, in which such advantages are particularly relevant, for example in an infusion of saline solution with or without any pharmaceutically effective content, contrast agents, or the like. 
         [0004]    In the simplest design a hose pump of the present type shows a pump head with an approximately semi-circularly shaped internal contour. The hose bed is arranged inside the internal contour of the pump head, into which the hose is inserted. A pump wheel arranged inside the semi-circle usually carries two or more squeeze elements in the form of rolls, which roll over the hose when the pump wheel is rotated and this way squeeze it against the hose bed. The pump wheel is moved by an electronically controlled drive, with the electronic control regulating the dosing of the medium conveyed via the hose pump. Such hose pumps are known for example from DE 20 2012 103 619 U1, DE 20 2010 000 282 U1, or DE 20 2012 009 626 U1. 
         [0005]    A known problem of hose pumps of the present type is the strong mechanic stress applied upon the hose. In order to generate the necessary conveyance pressure, the hose must be strongly squeezed and this force largely compromises its life span. In order to solve this problem, in the above-mentioned DE 20 2012 103 619 U1 as well as DE 20 2013 100 124 U1 it is suggested to use multilayered hoses, with in the latter-most publication of prior art mentioned also the use of mechanically elastic squeeze elements and/or a mechanically elastic hose bed being suggested. 
         [0006]    Another problem of the use of hose pumps in medical technology, and here particularly relating to hose pumps connected via catheters to the vascular system of a patient, is given in the generation of pressure pulses and minor separations of charge during the deformation of the hose. Due to the fact that the separations of charge generated during the pumping action as well as the mechanic pulses introduced via the hose and the catheter into vascular system of the patient, under certain circumstances, ongoing ECG-measurements may be disturbed, namely on the one hand due to electric charges, which interfere in case of ECG-measurements an electric signal determined at very high Ohms and with extreme precision, and which may alter the signal shape of the ECG-signal evaluated by the physician, and on the other hand by the mechanic pulses, with their frequency being in the range of the heart rate measured by the ECG, and this way may interfere the measurement or even falsify it. 
       SUMMARY 
       [0007]    The present invention is therefore based on the objective to optimize a hose pump of the type mentioned at the outset, particularly for the use in medical applications, with regards to potential interferences upon ECG-measurements, and to improve it for all applications with regards to the life span of the hose. 
         [0008]    This objective is attained in a hose pump with one or more features of the invention. Preferred embodiments and further developments of the hose pump according to the invention are described below and in the claims. 
         [0009]    A hose pump of the type mentioned at the outset is also modified according to the invention such that the hose bed is provided at least partially with a friction-reducing coating, namely preferably on a running surface of the hose. This friction-reducing coating adheres preferably fixed at the hose bed and can essentially be made from plastic, such as particularly PTFE (polytetrafluoroethylene) or perylene and/or graphite, diamond-graphite, and/or a hard fat. 
         [0010]    According to the invention it has been acknowledged that by the friction between the hose and the hose bed a relatively strong milling of the hose occurs, and this milling leads to unnecessary and unintentional squeezing inside the hose body. The friction-reducing coating of the hose bed allows little evading motions of the hose on the hose bed, resulting in a more gentle deformation and undesired squeezing being avoided. This naturally increases the life span of the hose. 
         [0011]    Furthermore it has been acknowledged according to the invention that a more gentle deformation of the hose on a hose bed provided with a friction-reducing coating is also suitable to significantly reduce disadvantageous pressure pulses and reduce the separations of charge developing when deforming many common hose materials. According to observations of the applicant this is connected to the fact that the hose on the hose bed according to the invention is not deformed by to the squeeze element as abruptly as in prior art. 
         [0012]    The hose pump according to the invention is therefore considerably improved in reference to prior art, particularly for the use in medical technology, due to its significantly lower perturbation potential for ECG-measurements. Furthermore, the life span of the hose used in the hose pump is increased, and last but not least also the noise development of the hose pump is advantageously reduced. 
         [0013]    The present invention provides particular advantages when the hose pump according to the invention is also connected to a cardiac catheter, because here the pressure pulses and/or micro-pulses generated by the deformation of the hose as well as the also generated separation of pulses can be guided directly into the heart of the patient, even if they might be very low, where they can significantly compromise the ongoing ECG-measurement. 
         [0014]    Within the scope of the present invention it has also proven advantageous for a hose bed to be provided with a modified profile. This profile is symmetrically or asymmetrically shaped concavely with regards to a central line extending in the longitudinal direction of the hose, with a central area comprising the central line showing a first radius of curvature and two second radii of curvature adjacent to the central area, which are greater than the first radius of curvature. Beneficially the transition between the radii of curvature is embodied in a constant fashion. The hose bed therefore tapers slightly flatter next to its central area, which has beneficial consequences for the intentionally gentle deformation of the hose during the conveying movement of the squeeze element. Primarily in the context with the friction-reducing coating of the hose bed according to the invention the hose can here be gently deformed. 
         [0015]    Surprisingly it has shown that additional benefits develop when the profile of the hose bed is not flattened even further towards the outside, but for the profile to show two edge sections, which in turn show a smaller radius of curvature than the flattened neighboring sections of the central area. This supports the hose during the deformation process. Preferably the edge sections of the profile taper towards the outside with a convex curvature such that even at this point no undesired clamping and squeezing of the hose occurs. 
         [0016]    Within the scope of the present invention it is preferred to use rolls as squeezing elements, which roll on the hose and deform it against the hose bed. If necessary, these rolls may be adapted to the profile of the hose bed. 
         [0017]    The squeeze element is preferably guided in reference to the hose bed such that initially during a motion along the hose bed it deforms the hose only slightly and with increasing length of the path of motion it increasingly deforms it until completely clamping it off. This way, the deformation of the hose occurs in a particularly gentle and gradual fashion, which additionally contributes particularly to the reduction of undesired pressure pulses. As known per se, within the scope of the present invention the hose may be produced from PVC, PTFE, or silicon, which provides advantages particularly for applications of medical technology. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    In the following an exemplary embodiment of a hose pump according to the invention is described and explained in greater detail with reference to the drawings. Shown are: 
           [0019]      FIG. 1  a schematic cross-sectional illustration of parts of a hose pump according to the invention essential for its function; 
           [0020]      FIG. 2  a perspective illustration of a part of the hose bed of  FIG. 1 ; 
           [0021]      FIG. 3  a side view of the hose bed of  FIG. 2 ; 
           [0022]      FIG. 4  a diagram of electric voltages measured in the hose with a hose bed according to prior art; 
           [0023]      FIG. 5  a diagram of measured electric voltages in the hose with a hose bed according to the invention; 
           [0024]      FIG. 6  a diagram to illustrate the squeezing of the hose on the hose bed. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0025]      FIG. 1  shows a schematic cross-sectional illustration of the parts of a hose pump embodied according to the invention, essential for the function. A pump head  1  with a semi-circular internal contour  14  carries at this internal contour  14  a hose bed  2 , into which a hose is inserted. The semi-circular internal contour  14  of the hose head  1  continues in a straight inlet section  15  and a straight outlet section  16 . Within the semi-circular internal contour  14  a pump wheel  4  rests on a drive shaft  5  (not shown), which is driven by an electrically controlled drive engine. A squeeze element  6 , which in the present case is embodied as a rotationally supported roll, rests on the pump wheel  4 . 
         [0026]    By rotating the pump wheel  4  in the clockwise direction the squeeze element  6  rolls over the hose  3  and presses it against the pump bed  2  such that the hose  3  deforms about the squeeze element  6 . Along the semi-circular internal contour  14  of the pump head  1  the hose  3  is completely clamped off by the squeeze element  6 , causing any medium  7  present in the hose  3  to be pushed forward. At the rear of the deformation site the hose  3  returns to its original shape, generating a vacuum for the medium  7  to be conveyed. 
         [0027]    By the circular motion of the squeeze element  6  and the straight inlet section  15  for the hose  3  the squeeze element  6  therefore impinges the hose  3  rather gently, so that it initially deforms it only slightly, with increasing traveling path inserts more and more into the hose  3 , and thus gradually and increasingly deforms it to the completely clamped off state shown in  FIG. 1 . 
         [0028]      FIGS. 2 and 3  show a part of the hose bed  2  in a perspective view ( FIG. 2 ) and a side view ( FIG. 3 ). According to the invention the hose bed  2  is provided with a PTFE-coating  8 , which acts in a friction-reducing fashion in reference to the hose  3  such that it slightly moves on the hose bed  2  during the deformation and can evade undesired, suddenly occurring squeezes. In the present case, the coating  8  is applied over the entire area of the hose bed  2 . However, it is possible within the scope of the present invention that only partial areas of the hose bed  2  are provided with a friction-reducing coating  8 , in order to yield the advantages according to the invention. 
         [0029]    In order to allow for the hose  3  to perform evading motions on the hose bed  2 , which reduced undesired clamping and pressure pulses, the friction-reducing coating  8  has not only been applied to the hose bed  2 , but it also shows a profile at which a central area  10  with a radius of curvature is provided about a central line  9 , at which laterally two neighboring sections  11  abut with flattened contours; in the present case this contour also shows a (second) radius of curvature, which however is greater than the first radius of curvature of the central area  10 . At the outside of the neighboring section  11 , then edge sections  12  abut, which in turn show a (third) radius of curvature, which is smaller than the second radius of curvature of the neighboring sections  11  and in the present case is approximately equivalent to the first radius of curvature of the central section  10 . Towards the outside the edge sections  12  taper in a convex curvature. 
         [0030]    In the present exemplary embodiment the combination of the special profile of the hose bed  2  with the friction-reducing coating  8  ensures that the hose  3 , during the deformation by the squeeze element  6 , is deformed more gently than previously possible in prior art, and particularly can perform minor evading motions in the lateral and the longitudinal direction, in order to avoid undesired sudden squeezes and compressions, and to dampen the motion of deformation which is mandatory as the movement of conveyance. This damping finally ensures that the pressure pulses generated by the conveyance motion as well as the electric voltages resulting from the charge of separations in the hose are reduced significantly. 
         [0031]    The  FIGS. 4 and 5  show two measuring diagrams, with their lines respectively showing the progression of an electric voltage over time that can be measured in the hose.  FIG. 4  represents a measurement diagram of a hose pump, which is embodied according to prior art, thus a hose bed without a friction-reducing coating and without a modified profile.  FIG. 5  shows the measurement diagram of a hose pump embodied according to the invention, thus comprising a hose bed with a modified profile and a friction-reducing coating. 
         [0032]    The voltage signal  13  is embodied considerably more distinct in the hose pump according to prior art ( FIG. 4 ) than in the hose pump embodied according to the invention ( FIG. 5 ); the scales of the diagrams of  FIGS. 4 and 5  are identical. The amplitudes of the voltage signal  13 ′ of the diagram of  FIG. 5  (hose pump according to the invention) amount, in the present measuring design selected, not even to one fourth of the amplitudes of the voltage signal  13  in  FIG. 4  (prior art). As discernible based on this voltage signal  13 ,  13 ′, the electric voltage that can be measured in the hose is very significantly reduced (to a few microvolts). This difference can be decisive in order to keep from lastingly influence particularly an ECG-signal. 
         [0033]    Two peaks each are discernible in the voltage signals  13 ,  13 ′ of  FIGS. 4 and 5 . This represents the reference signal, which is not connected in any way to the electric voltage measurable in the hose and the reduction thereof according to the invention. 
         [0034]    Due to the fact that in medical-technical applications the treating physician monitors the heart rate of the patients via ECG and they simultaneously are given an infusion, which uses the ECG-signals for the diagnosis and evaluates them, here voltage signals  13  may have very disadvantageous consequences if they significantly interfere with the ECG-measurement signal. This risk is eliminated with the present invention. 
         [0035]    In  FIG. 6  the changes in the deformation of the hose of a hose pump according to prior art and a hose pump according to the invention are shown in a common diagram. For this purpose, the amplitude of the deforming motion of the hose over time is drawn over a pumping cycle. 
         [0036]    A first curve  14  shows the deformation changes of the hose in a hose pump according to prior art. It is easily discernible that the hose is deformed with steep flanks, thus very abruptly and suddenly. Contrary thereto, it is discernible from a second curve  15 , which shows the deformation changes of the hose in a hose pump according to the invention, that here a more gentle deformation of the hose occurs, with the amplitude of the deforming motion over time falls short of exceeding a maximum value of 40% of the maximum value according to prior art.