Abstract:
The hose pump comprises an eccentric drive with numerous eccentric discs ( 21 ) fastened to a shaft ( 20 ). Each eccentric disc ( 21 ) drives a crank drive ( 24 ) having a connecting rod ( 25 ). At the end of the connecting rod ( 25 ), a pump finger ( 11 ) is borne for compressing a pump hose ( 10 ). A sealing diaphragm ( 27 ) is disposed between the eccentric drive and the pump hose ( 10 ) for preventing liquid from intruding into the interior of the housing ( 16 ). The connecting rod ( 25 ) sealingly passes through the sealing diaphragm ( 27 ). The sealing diaphragm ( 27 ) comprises lateral folds ( 31 ) so that it does not exert any substantial forces upon the crank drive ( 24 ). The hose pump has a low power consumption and permits a small structure.

Description:
RELATED APPLICATIONS 
   This application claims priority from German Utility Model Application No. 202 10 502.4, filed on Jul. 6, 2002, incorporated herein by reference for all legitimate purposes and relied upon for priority. 
   FIELD OF INVENTION 
   The invention relates to a peristaltic hose pump with a shaft comprising several eccentric discs each of which carries a bearing and thus moves a pump finger transversely to a pump hose, and with a sealing diaphragm disposed between the shaft and the pump hose. 
   DESCRIPTION OF RELATED ART 
   Peristaltic hose pumps are often used as infusion or transfusion pumps for conveying liquid substances in the medical field. Linear hose pumps are known wherein numerous pump fingers continuously and cyclically press a straight pump hose against an abutment so that the liquid in the pump hose is moved in the direction of delivery. European Patent Application 0 214 443 A1 describes a peristaltic linear hose pump with numerous eccentric discs fastened to a shaft. Each eccentric disc carries a ball bearing and acts upon a linearly movable pump finger. All the pump fingers are spanned by a sealing diaphragm forming a sealing separation between the drive mechanism and the pump hose. Thereby, damage and contaminations of the pump hose are avoided. On the other hand, the interior of the pump is protected against intruding liquid. A sealing diaphragm arranged in this manner has a negative influence upon the delivery accuracy. It causes a coupling of forces between neighboring pump fingers, whereby the consumption of electrical energy is increased as well. With the diaphragm disposed in this manner, a share of the resetting forces of the pump hose is used to deform the sealing diaphragm against the pump fingers. This may lead to a premature decrease of the resetting forces. Infusion pumps such as peristaltic hose pumps, for example, shall be built to be as small and light-weighted as possible. Therefore, it is important to reduce the requirement of energy in order to dimension components such as accumulator, power pack and drive motor as small as possible. At the same time, the demand to keep to the chosen rate of delivery has to be satisfied, even during long infusion times. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Hereinafter, an embodiment of the invention is explained in detail with reference to the drawings, in which: 
       FIG. 1  shows a perspective representation of a shaft of a peristaltic pump with the eccentric discs and the connecting rods, and 
       FIG. 2  shows a partial cross-section through a peristaltic hose pump. 
   

   DETAILED DESCRIPTION 
   Referring to  FIGS. 1 and 2 , the illustrated hose pump comprises a pump hose  10  in which the liquid to be pumped is located. This pump hose  10  is continuously periodically compressed and relieved by numerous pump fingers  11 , as described in European Patent 0 214 443. 
   The pump hose  10  is included in a receiving channel  12  formed in a guide plate  13 . The guide plate  13  has parallel walls  13   a  and  13   b  laterally defining the receiving channel  12 . The receiving channel  12  is connected with several guide channels  14  in each of which a pump finger  11  is guided transversely to the hose direction. The guide plate  13  is mounted to a front wall  15  of a pump housing  16 . The pump housing has a door attached in front that forms a thrust bearing  17  for supporting the pump hose  10 . The thrust bearing  17  has a projection  18  projecting into the receiving channel  12 . 
   There are about twelve pump fingers  11  altogether, which are driven by an eccentric drive in a sinusoidal manner; accordingly, the movements of neighboring pump fingers have a phase difference. 
   The eccentric drive of the pump fingers has a shaft  20  extending in parallel to the inserted pump hose  10 . To this shaft  20 , several eccentric discs  21 , one for each pump finger  11 , are fastened. A ball bearing  22  bearing an outer ring  23  is seated on each of the eccentric discs. The outer ring  23  is connected with a crank drive  24  comprising a connecting rod  25  projecting radially outward from the outer ring  23 . A joint  26  connects the end of the connecting rod  25  with the pump finger  11 . While the shaft  20  rotates at uniform speed, the described eccentric drive causes a sinusoidal reciprocating movement of the pump fingers  11  relative to the pump hose  10 . 
     FIG. 1  shows the different positions of the connecting rods  25  in a particular rotational position of the shaft  20 . The connecting rods  25  form a period of a sinusoid. 
   In one embodiment of the invention, the ball bearing  22  comprises an inner ring  22   a , an outer ring  22   b , and balls  22   c  arranged therebetween, which are included in a (non-illustrated) ball bearing retainer. In a modified embodiment, the ball bearing  22  is not provided with its own inner ring  22   a  and its own outer ring  22   b . The inner ring is rather formed directly by the eccentric disc  21 . The outer ring of the ball bearing is formed by the outer ring  23  of the crank drive  24 . Preferably, plastic ball bearings are used as ball bearings. 
     FIG. 2  shows that between the eccentric drive and the pump fingers  11 , there is a sealing diaphragm  27  extending in longitudinal direction of the receiving channel  12 . The longitudinally extending edges  27   a ,  27   b  of the sealing diaphragm  27  being fastened to the rear side of the housing wall  15 , so that an opening  30 , defined by housing wall  15  and including the guide plate  13 , is closed by the sealing diaphragm  27 . The sealing diaphragm  27  comprises a sealed passage  29  for each connecting rod  25 . The connecting rods  25  are cylindrical and have a round cross-section so that sealing at passage  29  can be effected in a relatively simple manner. The width of the sealing diaphragm  27  is larger than the width of the opening  30  of the housing wall  15  so that folds  31  form in the sealing diaphragm  27  toward either side of the connecting rods  25 . The sealing diaphragm  27  is not taut, but forms a folded structure. The sealing diaphragm  27  prevents liquid from intruding into the interior of the housing  16 . After the door that forms a thrust bearing  17  has been opened, the guide plate  13  can be removed for purposes of cleaning. Similarly, the individual pump fingers can be easily detached from the connecting rods  25 . 
   Since the sealing diaphragm  27  exerts virtually no force upon the pump finger  11  or the connecting rod  25 , the hose pump has a low power consumption. This is even furthered by the use of the ball bearing  22  that has very low friction losses. 
   The present invention according to the embodiment, with the features indicated in claim  1 , provides a peristaltic hose pump that is adapted to be produced in a small size, has a low power consumption and a good delivery accuracy in case of long infusion times. Accordingly, each of the bearings  22  on the eccentric discs  21  of the shaft  20  is connected with a connecting rod  25  which engages on a linearly guided sealing diaphragm  27  facing the pump hose  10  and the connecting rods  25  pass through the sealing diaphragm  27 . 
   Due to the fact that the sealing diaphragm  27  does not span the pump fingers, there is no continuous periodic stretching of the sealing diaphragm between neighboring pump fingers. Thereby, less drive energy is required. The forces for deforming the diaphragm that are still required need not be raised by the resetting forces of the pump hose but are provided by the pump drive. Thereby, the delivery rate accuracy over extended infusion times is improved. Moreover, the wear of the sealing diaphragm is reduced. The use of connecting rods permits a simple and small passage through the sealing diaphragm. The sealing diaphragm should not form a taut surface but should be a loose folded diaphragm adapting to the movements of the connecting rods without substantial material stresses occurring. 
   The invention prevents disturbing influences of the sealing diaphragm upon the delivery accuracy. Also, the sealing diaphragm is not fulled and not squeezed between pump fingers and pump hose. 
   According to a preferred embodiment of the invention, it is provided that the sealing diaphragm has folds at both sides of the pump hose, which permit an adaptation to the transverse movements of the connecting rod. 
   Preferably, a guide plate with a longitudinally extending receiving channel for the pump hose and with guide channels for the pump fingers is provided at the side of the pump hose. Suitably, this guide plate is removable for cleaning purposes. 
   A particular embodiment is constructed such that the eccentric discs  21  of the shaft  20  are integrally formed as part of the shaft so that the shaft forms a crankshaft  24 . The outer jacket of the eccentric discs  21  may be formed such that it simultaneously forms the inner track  22   a  of a ball bearing  22 . The connecting rods  25  may be directly formed to the outer ball bearing rings  23  that are adapted to be injection-molded as well. Due to this configuration, the number of the required components is reduced and the friction is lowered. This, in turn, is accompanied by a lower power consumption. 
   VARIATIONS AND EQUIVALENTS  
   Although the invention has been described and illustrated with reference to specific illustrative embodiments thereof, it is not intended that the invention be limited to those illustrative embodiments. Those skilled in the art will recognize that variations and modifications can be made without departing from the true scope of the invention as defined by the claims that follow. For example, the eccentric discs  21  may be fastened to shaft  20  or integrally formed with shaft  20 . Further, the connecting rods  25  may be fastened to the outer rings  23  of crank drive  24  or connecting rods  25  may be integrally formed with the outer rings  23 . For another example, the bearings,  22  may comprise inner rings  22   a  and outer rings  22   b  or the eccentric discs  21  may form the inner ring  22   a  of bearing  22  and the outer ring  23  of the crank drive  24  may form the outer ring  22   b  of bearing  22 . The bearings may be ball bearings or other friction free bearings or equivalents and may be made of plastic or other materials capable of providing the desired function as a bearing, all without departing from other aspects of the invention. It is therefore intended to include within the invention all such variations and modifications as fall within the scope of the appended claims and equivalents thereof. 
   Spatial references such as “bottom”, “top”, “front”, “side”, “back”, “lower”, “upper”, “under”, and “central” are for purposes of illustration only, relative to the figures shown and are not limited to the specific orientation of the structure or movement directions as described. 
   Although only a few exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many other modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the following claims.