Abstract:
A peristaltic pump squeezes a hose between squeezing rollers and a counter bearing to move fluid through the hose. To compensate for production tolerances and non-uniformities in hose thickness, and to also keep the mechanical loading of the hose as low as possible during the operation of the pump, the spacing between the squeezing rollers and the active surface of the counter bearing can be varied. The counter bearing has a conical or cone-shaped adjusting surface which is supported against a complementarily shaped support surface on the pump housing. The spacing between the squeezing elements and the active surface of the counter bearing can be adjusted by moving the counter bearing relative to the support surface.

Description:
FIELD OF THE INVENTION 
     The invention concerns a peristaltic pump. 
     BACKGROUND OF THE INVENTION 
     Such peristaltic pumps are particularly used in the area of medical technology, for example, as infusion pumps or in injection and dialysis devices. A generic peristaltic pump is known, for example, from patent AT 367874. It describes a peristaltic pump with several rollers driven by a central part via a planetary gear, in which the rollers, on at least one hose in which the medium to be conveyed is conducted, roll along its free cross-section while squeezing takes place. The rollers are supported in such a way that they can rotate on a rotating carrier with a large clearance and are in a friction-locking contact with at least one part of their circumference while they lie against the hose with the central part. The rotating movement of the carrier and the rollers causes the squeezed site to move along the hose, wherein the medium conducted in the hose is moved onward in the conveyance direction. 
     By the alternating squeezing, the hose is exposed to a considerable mechanical loading when the pump is running. Especially with the appearance of slack between the surface of the rollers and the hose surface, massive compression and shear forces appear, which stretch and pull the hose. With a high pressure, the hose can therefore be inflated or even destroyed. In order to largely spare the hose and to keep the adjusting effort during the introduction of the hose into the peristaltic pump as low as possible, a counterpressure body pressing the hose against at least one of the rollers is provided in the peristaltic pump known from AT 367874; it is kept on a base plate so it can be moved with respect to the central part of the peristaltic pump in the radial direction and is pretensioned by means of a spring in the direction of the central part. In this way, it is possible to merely place a new hose during the replacement of a hose and to already ensure a sufficient squeezing by the rollers during the pretensioning of the counterpressure body by means of a spring, so as to guarantee the functionality of the pump. Furthermore, tolerances in the pump arrangement and the hoses are compensated by the elastic counterpressure body. 
     This arrangement known from the state of the art has proved, however, to be susceptible to disruption because the springs that produce the pretensioning of the counterpressure body can lose their clamping force in the course of time or even break with material fatigue. The replacement of the springs, however, is cumbersome and time-consuming. Furthermore, the distance between the rollers and the counter bearing varies over their circumference, and the result is a low pump pressure. 
     Proceeding from this, the goal of the invention is to present a peristaltic pump, in which the production tolerances of the pump and the material nonuniformities of the hose are compensated as much as possible and the mechanical loading of the hose during the operation of the pump can be kept as low as possible, wherein, at the same time, as high as possible a pump pressure with a low loading of the hose and a handling of the peristaltic pump with the lowest maintenance possible is to be guaranteed. In particular, the effort to set and adjust the peristaltic pump during or immediately after its production and with regular maintenance is to be reduced. 
     These goals are attained with the peristaltic pump shown and described herein. Preferred embodiments of this peristaltic pump are also disclosed herein. 
     SUMMARY OF THE INVENTION 
     The peristaltic pump in accordance with the invention comprises a housing and several squeezing elements, which are preferably designed as squeezing rollers and press the hose, while squeezing takes place, against the active surface of a counter bearing, so that, in this way, the medium conducted in the hose will move on in the conveying direction. The distance between the squeezing elements and the active surface of the counter bearing is thereby variable. In order to make possible a suitable adjustment of the distance between the squeezing elements and the active surface, which exerts the least possible loading on the hose, the invention provides for the counter bearing to have a conical adjustment surface, which is supported against a complementarily shaped supporting surface on the housing. The distance between the squeezing elements and the active surface of the counter bearing can be adjusted by moving the counter bearing relative to the housing along the supporting surface. By the adjustability of the distance between the squeezing elements and the active surface of the counter bearing, it is possible to compensate production tolerances, which inevitably appear during the production of the pump, and any material tolerances in the hose body. The distance between the squeezing elements and the active surface is thereby adjusted for the first time before the first starting of the peristaltic pump and perhaps later with maintenance operations, in such a way that a minimum pressing of the hose is guaranteed, during which the peristaltic pump is functional and the required operating parameters and working points can be attained. An excess pressing of the hose takes place in any case within the framework of admissible hose tolerances. At the same time, the mechanical loading on the entire pump system is reduced and the power consumption in the working points is largely constant, so that a relatively constant electrical power consumption can be attained. On the whole, the service life of the peristaltic pump itself as well as of the hoses used as consumable material can be prolonged. 
     In a preferred embodiment of the peristaltic pump in accordance with the invention, provision is made so that the counter bearing is coupled on an adjusting ring, which is conducted on an outside thread on the housing of the peristaltic pump and can be moved by rotation relative to the housing in an axial direction relative to the housing between an upper limiting position and a lower limiting position. A slider ring lies against the adjusting ring; with an axial movement of the adjusting ring relative to the housing, it is also moved in the axial direction. A pressure ring is affixed to the slider ring; it in turn is connected to the counter bearing. Upon rotating the adjusting ring relative to the housing, therefore, the conical adjusting surface of the counter bearing moves on the adjusting surface of the housing and pulls the counter bearing with respect to the housing inwards or outwards, depending on the rotating direction of the adjusting ring. If the adjusting ring is moved in the direction of its lower limiting position, then the counter bearing is pulled into the interior of the housing, and with a reverse rotation direction of the adjusting ring, is moved outwards. The counter bearing and the pressure ring affixed on it are preferably designed as a ring segment. Upon moving the conical adjusting surface of the counter bearing along the supporting surface of the housing, the diameter of the counter bearing designed as the ring segment is changed, wherein the clearance, that is, the distance between the active surface of the counter bearing and the squeezing elements (in particular, of the outer circumferential surface of the squeezing rollers), is changed. By a rotation of the adjusting ring relative to the housing, the clearance can be adjusted to the optimal value. For the adjusting of the clearance, a gauge is expediently used, which is inserted during the adjusting operation between the active surface of the squeezing element (that is, in particular, the outer circumference of the squeezing rollers) and the active surface of the counter bearing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is explained in more detail below with the aid of an embodiment example with reference to the accompanying drawings. The drawings show the following: 
         FIG. 1 : top view of an injection device in which a peristaltic pump in accordance with the invention is used; 
         FIG. 2 : perspective view of a peristaltic pump in accordance with the invention; 
         FIG. 3 : exploded view of the peristaltic pump of  FIG. 2 ; 
         FIG. 4 : sectional view of the peristaltic pump of  FIG. 2  along the A-A plane; 
         FIG. 5 : detailed view of the sectional view of  FIG. 4  in the area of the counter bearing and a guide roller opposite the counter bearing; 
         FIG. 6 : detailed view of a transverse sectional view of the peristaltic pump of  FIG. 2  in the area of the counter bearing and a squeezing roller opposite the counter bearing, wherein  FIG. 6   a  shows the counter bearing in its first (upper) limiting position and  FIG. 6   b , the counter bearing in its second (lower) limiting position; 
         FIG. 7 : top view of the counter bearing of the peristaltic pump of  FIG. 2  and the pressure ring connected with the counter bearing; 
         FIG. 8 : sectional view of the counter bearing and the pressure ring of  FIG. 7 , connected with it along the B-B plane; 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows the injection head of an injection device for the injection of two different or similar contrast agents and a NaCl rinsing solution into the bloodstream of a patient, in which a peristaltic pump  1  in accordance with the invention is used. Such injection devices are used, for example, for the injection of contrast agents in the carrying out of imaging methods, such as computed tomography, ultrasound investigations and magnetic resonance tomography (MRT). The injection device comprises the injection head  20 , which is shown in  FIG. 1  and in which the peristaltic pump  1  is located. The injection head  20  comprises a plastic housing with two circular hand grips  21 ,  22 . A panel  23  is located between the hand grips  21  and  22 ; it can be closed with a lid that is not depicted here in the drawing. In its lower area, the panel  23  has a recess to hold the peristaltic pump  1 . Above it, there are channel-shaped recesses  24 ,  25 , into which the branched hose arrangement (which is not depicted here in the drawing) can be introduced. The hose arrangement is, in particular, a hose arrangement as described in detail in EP 2 011 541 A2. This hose arrangement comprises in total three supply hoses—namely, a first supply hose for a first contrast agent, a second supply hose for a second contrast agent, and a third supply hose for a rinsing solution (in particular NaCl). The three supply hoses are connected to supply flasks for the contrast agents and the rinsing solution, which are also not depicted here in the drawing, and into which branches  24   a ,  24   b , and  24   c  of the recess  24  located in the upper area of the panel  23  are introduced. The three supply hoses coming from the supply containers are brought together into a hose piece, which is conducted to the peristaltic pump  1  and which is introduced in the circular recess  24   d  of the panel  23 . 
     To introduce the hose into the peristaltic pump  1 , a threading device is provided. The mode of functioning and the design of this threading device will be explained below. The hose is finally conducted through the peristaltic pump  1  and placed in the recess  25  in the upper left part of the panel  23 . The end of the hose is connected to a patient hose via which the media conducted in the hose can finally be injected into the bloodstream of the patient. To affix the hose on the panel  23 , an affixing device is provided, which makes possible an affixing of the hose to a first entry-side point  39  and at least one second exit-side point  40  of the peristaltic pump. Appropriately, ultrasound sensors for the detection of air bubbles in the hose are located at the affixing sites  39  and  40 . Other affixing sites of the hose on the panel  23  are possible and are described, for example, in EP 2011541 A1. 
       FIGS. 2 and 3  show the peristaltic pump  1  in detail in a perspective view, wherein  FIG. 3  is an exploded view. The peristaltic pump  1  comprises a lower pump unit with a drive motor  7 , and an upper pump unit with a housing  2 . The housing  2  is subdivided into a lower housing part  2   a  and an upper housing part  2   b . The lower housing part  2   a  can be designed with the upper housing part  2   b  as one part or also in two parts. 
     The lower pump unit comprises the drive motor  7  with a drive shaft  10 , which is coupled with the upper pump unit via a gear. The structure of the upper pump unit can be deduced from the sectional view of  FIG. 4 . A gear  6  coupled with the drive shaft  10  of the drive motor  7  is located in the interior of the housing  2 . The gear comprises a sun wheel  30 , which is connected in a non-rotatable manner with the drive shaft  10  of the drive motor  7 . The upper end of the drive shaft  10  is supported so it can rotate via a first bearing  43  in a carrier disk  8 . Several squeezing elements  3  are located on the carrier disk  8 . The squeezing elements  3  are driven squeezing rollers  3  in the embodiment example shown in the drawing here, wherein three such squeezing rollers  3  are uniformly located here on the outer circumferences of the circular carrier disk  8 . The squeezing rollers  3  are supported on the carrier disk  8  in such a manner that they can rotate. For this, each of the three squeezing rollers  3  is mounted on a shaft  9  with an axis  9 ′ and each shaft  9  is supported via a second bearing  15  in a borehole of the carrier disk  8 . The shafts  9  and thus the axes  9 ′ of the squeezing roller  3  run parallel to the drive shaft  10  of the drive motor  7 . The drive motor  7  starts the rotation of the carrier disk  8  and the squeezing rollers  3  with a running pump via the gear  6 . In addition to the sun wheel  30 , the gear  6  comprises planetary wheels  16 , wherein such a planetary wheel  16  is correlated with each squeezing roller  3  and is affixed non-rotatably on the shaft  9 . Each of the planetary wheels  16  is coupled with the sun wheel  30  of the planetary gear, via teeth. In addition to the planetary wheel  16 , a friction wheel  31  is located on each shaft  9 , wherein the friction wheel  31  is non-rotatably affixed on the shaft  9  at a distance to the planetary wheel  16 . A surrounding groove is located on the outer circumference of each friction wheel  31 ; a rubber ring  32  ( 0  ring) is inserted into the groove. Via this rubber ring  32 , the friction wheel  31  is in contact with the inner circumference  2   c  of the pump housing  2 . The inner circumference  2   c  of the housing  2  thus acts as a hollow wheel of a planetary gear. If the drive shaft  10  is made to rotate by the drive motor  7 , then this rotation movement is transferred via the coupling of the planetary wheel  16  on the sun wheel  30  to the shaft  9 , wherein the shaft  9  and the squeezing roller  3  connected with it in a non-rotatable manner are made to rotate. At the same time, the friction wheel  31  on the inner circumference  2   c  of the pump housing  2  rolls, wherein the carrier disk  8  is also rotated, relative to the pump housing  2 . By means of the friction wheels  31 , it is possible also for the drive motor  7  to make the carrier disk  8  rotate if there is still no hose in the peristaltic pump. 
     In addition to the squeezing rollers  3 , guide rollers  11  are also supported on the carrier disk  8 . The guide rollers  11  are used to guide the hose between adjacent squeezing rollers  3  and are not driven. The guide rollers  11  have a groove  34 , which is semicircular in cross-section, on the outer circumference in which the hose is conducted ( FIG. 5 ). The arrangement of the guide rollers  11  and the squeezing rollers  3  on the carrier disk  8  can be deduced, in particular, from the exploded view of  FIG. 3 . 
     To introduce the hose into the peristaltic pump, a threading device is provided, which threads the hose automatically between the squeezing rollers  3  and the counter bearing  4 . The threading device comprises a screw spindle  26  located outside the carrier disk  8 . The screw spindle  26  is located on a shaft  27 , wherein the shaft  27  runs parallel to the axis  9 ′ of the squeezing rollers  3 . The shaft  27  is supported in a housing part  2  of the peristaltic pump in such a way that it can rotate and is coupled with a spindle drive  28  with which the shaft  27  and the screw spindle  26  can be made to rotate, so as to thread a hose placed in the screw spindle into the peristaltic pump. The upper screw flights of the screw spindle  26  protrude in the longitudinal direction of the peristaltic pump (that is, parallel to the axis of the shafts  10  and  27 ) via the upper side of the squeezing rollers  3  and the guide rollers  11 . 
     A counter bearing  4  is located on the upper end of the upper pump unit. The counter bearing  4  is designed in the shape of a circular segment with a recess  38  and appropriately extends over an angle range of 200-300°. The screw spindle  26  is located in the area of the recess  38  of the counter bearing  4 . The counter bearing  4  has an active surface  4   a , which is opposite the outer circumference of the squeezing rollers  3  at a distance d. The hose is threaded into the gap between the active surface  4   a  and the outer circumference of each squeezing roller  3 . 
     To introduce the hose into the peristaltic pump  1 , the hose piece to be introduced is first affixed via the affixing device on the two affixing sites  39  and  40  on the panel  23 . The hose piece between the affixing devices  39  and  40  then has (as a result of the bounce of the hose piece) the form of a loop. Subsequently, the hose piece is placed in the screw spindle  26 . Then, the pump is started, wherein the drive motor  7  makes the carrier disk  8  rotate. At the same time, the spindle drive  28  makes the screw spindle  26  rotate. For this purpose, the spindle drive  28  is coupled with the control of the drive motor  7 . By means of the rotation of the screw spindle  26 , the hose is conducted from the screw spindle  26  downwards in the direction of the carrier disk  8 . By the rotation of the carrier disk, one of the guide rollers  11  is moved toward the hose and the hose meshes into the groove  34  on the outer circumference of the guide roller  11 . By further rotation of the carrier disk  8 , the guide roller  11  located on it moves on in the conveyance direction of the pump and thereby pulls the hose by fraction in the groove  34 , on the one hand, downwards in the direction of the carrier disk  8  and presses it, on the other hand, in a radial direction outwards against the counter bearing  4 . With a further rotation of the carrier disk  8 , the guide roller  11  pulls the hose further into the peristaltic pump along the inner circumference of the counter bearing  4  shaped as a circular segment as a result of the static friction on the hose surface and the traction in the groove  34  on its outer circumference, until the carrier disk has carried out (almost) a complete rotation with the guide roller  11  located on it, and the hose is pulled completely into the peristaltic pump by further rotation of the carrier disk. By the rotation of the carrier disk, the hose is finally squeezed against the counter bearing  4  by the squeezing roller  3  following on the carrier disk  8  of the guide roller  11 . In this way, the hose is automatically introduced between the outer circumference of the squeezing rollers  3  and the counter bearing  4  and with a further rotation of the carrier disk  8  is squeezed for the conveyance of the liquid conducted therein. 
     If the hose is completely introduced into the peristaltic pump, then the squeezing rollers  3  press the hose while the peristaltic pump is running (that is, with rotating carrier disk  8  and rotating squeezing rollers  3 ) and while squeezing the hose diameter against the active surface  4   a  of the counter bearing  4  in order to further convey in this way the medium conducted in the hose in the conveyance direction (that is, in the rotation direction of the carrier disk  8 ). 
     After ending the pumping operation, the threading device can also be used to thread out the worn hose when a replacement of the hose is required. To this end, the spindle drive  28  is operated when the peristaltic pump is running in the reverse rotation direction. In this way, the screw spindle  26  pulls the hose piece placed in the peristaltic pump upwards so that the meshing of the hose in the groove  34  of the guide rollers  11  is loosened. After a complete rotation of the carrier disk, the hose is pulled completely out of the peristaltic pump and can be removed after loosening the affixing elements on the affixing sites  39  and  40  and can be replaced by a new hose. For the introduction of the threading out of a worn hose, a control routine in the control of the spindle drive  28  is provided, which can be triggered with the pressing of a button by the operator. 
     For the optimal adjustment of the distance between the counter bearing  4  and the squeezing rollers  3 , the counter bearing with its active surface  4   a , in a preferred embodiment example, is placed on the housing  2  in such a way that it can be moved relative to the squeezing rollers  3 . To this end, the counter bearing  4  is connected with a pressure ring  13 . The pressure ring  13  is also a ring with the shape of a circular segment. The counter bearing  4  has an adjusting surface  4   b  opposite the active surface  4   a . It is conical or cone-shaped. The arrangement, consisting of the counter bearing  4  and the pressure ring  13 , is located in the upper opening of the housing  2  in such a way that the conical adjusting surface  4   b  of the counter bearing  4  is supported against a complementary supporting surface  5  on the housing  2 , which has a complementary shape (that is, it is also conical or cone-shaped), wherein the supporting surface  5  on the housing  2  expands conically downwards (that is, into the interior of the housing) ( FIG. 6 , each, above and to the left). 
     On the outside of the housing  2 , an affixing ring  36  affixed on the housing (which had to be omitted in  FIG. 3  for reasons of clarity) is provided with affixing flanges  37  to affix the housing  2  on the panel  23  of the injection head  20 . Moreover, in the transition area between the lower housing part  2   a  and the upper housing part  2   b , an adjusting ring  12  is located on the outside of the housing  2 . The adjusting ring  12  is a circular ring, which has an inner thread  50  on the inside surface of the circle. An outside thread  52 , which is complementary to this inside thread  50 , is provided on the outside of the housing  2 . The adjusting ring is coupled with the housing  2  via this thread arrangement in such a manner that by a rotation of the adjusting ring  12  relative to the housing  2 , the adjusting ring can be continuously moved in the axial direction between an upper limiting position and a lower limiting position with respect to the housing  2 . Several boreholes  33  with which a pin can engage are provided on the outer circumference of the adjusting ring  12  for the rotation of the adjusting ring  12  relative to the housing  2 . 
     A slider ring  14  fits against the underside of the adjusting ring  12 . The slider ring  14  is composed of two semi-circular ring segments  14   a  and  14   b  and is connected via several bolts  29  with the pressure ring  13  ( FIG. 3 ). 
     The distance d between the squeezing rollers  3  and the active surface  4   a  of the counter bearing  4  can be adjusted via the arrangement consisting of the counter bearing  4 , the pressure ring  13 , the slider ring  14 , and the adjusting ring  12 . 
     In order to maximize the distance d between the outer circumference of the squeezing rollers  3  and the active surface  4   a , the counter bearing  4  is brought to its first (upper) limiting position ( FIG. 6   a ). Proceeding from here, the distance d can be reduced in that the adjusting ring  12  on the housing  2  is rotated in the direction of its lower limiting position. In this way, the adjusting ring  12  moves from its upper limiting position downwards. Thus, the slider ring  14 , which fits against the underside of the adjusting ring  12 , is also moved downwards relative to the housing. Since the slider ring  14  is connected with the pressure ring  13  via the bolts  29 , the pressure ring  13  with the counter bearing  4  affixed thereon is also moved downwards in this way. The adjusting surface  4   b  of the counter bearing  4  on the conical supporting surface  5  thereby slides along the housing  2 . With this movement, the counter bearing  4  with the shape of a circular segment is readily constricted and reduces its diameter, wherein the active surface  4   a  is pressed in the radial direction toward the squeezing rollers  3  or the guide rollers  11 . By means of this movement, the distance d between the active surface  4   a  and the outer circumference of the squeezing roller  3  is reduced. If the adjusting ring  12  arrives at its lower limiting position with a further rotation, then the underside of the pressure ring  13  sits on a base  61  of the housing  2 . In this position, the distance d between the active surface  4   a  and the outer circumference of the squeezing roller  3  or the guide rollers  11  is in a minimal position ( FIG. 6   b ). 
     By this arrangement of the counter bearing  4 , the clearance (that is, the distance d) between the active surface  4   a  and the outer circumference of the squeezing rollers  3  can be adjusted to a value that is optimal for the operation of the pump. This adjustment takes place for the first time before the starting of the peristaltic pump. For the adjustment of a desired distance d, a gauge is appropriately used, whose thickness corresponds to the clearance to be set and which is placed between the active surface  4   a  and the outer circumference of the squeezing rollers  3 . Subsequently, the adjusting ring  12  is rotated relative to the housing until the active surface  4   a  and the outer circumference of the squeezing roller  3  fit closely against the outer surfaces of the gauge. The clearance can be readjusted if necessary when maintenance is carried out on the peristaltic pump. 
     The invention is not limited to the described embodiment example. Thus, the invention can be used not only in radial peristaltic pumps but rather, for example, also in peristaltic pumps with a linear mode of action, such as in so-called linear peristaltic pumps or travelling wave pumps. The use of the peristaltic pump in accordance with the invention is furthermore not limited to injection devices, but rather extends also to other pump devices, such as infusion pumps.