Roller-type blood pump

Abstract

This invention relates to an improved roller-type blood pump in which the rollers are spring-biased toward the raceway while, at the same time, being limited with respect to how close they can come to the latter by means of an adjustable limit stop.

Description

Roller-type pumps are widely used to pump blood in kidney dialysis machines and the like because of their gentle pumping action and also because no part of the pump ever comes into contact with the blood itself. These pumps customarily include anywhere from two to six or more rollers journaled for independent rotation on the extremeties of some sort of rotating impeller. The rollers roll along an arcuate, generally semi-circular, raceway and pinch one or more flexible blood-carrying tubes thereagainst so as to push the fluid on ahead.

Blood is a fluid that must be handled quite gently, especially if it is to be returned directly into the living body from which it was removed as in kidney dialysis. A properly functioning roller pump is ideally suited for the job because blood acts a good deal like greased marbles that squirt out ahead of the advancing roller without being damaged thereby. Unfortunately, not all of the prior art roller pumps function in the manner intended and the net result is that the blood does become damaged during the pumping process. Also, the design of many of the prior art roller pumps is such that they place the blood-carrying tubes under severe strain which is conducive to both permanent deformation and premature rupture or breakage. While a ruptured or broken tube is, admittedly, quite rare, even the remote risk of such an occurrence is to be avoided wherever possible. Far more common, of course, is the gross deformation of the tube due to the rollers pressing thereagainst repeatedly. Excessive elongation can result in kinking and a diminution of the flow. If the tube is pinched so tightly that it is not only compressed but stretched, the wall thickness may change to the point where rupture becomes a real possibility. An even more likely result, however, is that the rollers can no longer pinch the tube closed due to the fact that the combined thickness of its opposite walls becomes less than the gap left between the rollers and the raceway. When this occurs, the overall result is a diminution in flow. Of far greater significance than the loss in flow, however, is the damage to the blood itself that takes place when the rollers roll over and crush it against the raceway rather than squirting it ahead as intended.

Unfortunately, while the prior art roller pumps include provision for adjusting the rollers relative to the raceway so as to set a predetermined gap therebetween, this adjustment, once made, stays the same until readjusted. As such, the gap adjustment is unable to compensate for such things as irregularities in tube wall thickness or the change in wall thickness that takes place over a period of extended use due to tube elongation. Since the ordinary dialysis may run as much as six hours, the tube is subjected to considerable physical abuse which is bound to result in some permanent deformation.

It has now been found in accordance with the teaching of the instant invention that these and other objectionable features in the prior art roller pumps can, in fact, be obviated by the simple, but unobvious, expedient of spring-biasing the rollers toward the raceway while, at the same time, limiting such extension so as to have a pre-set minimum gap therebetween amounting to approximately three-fourths of the combined thickness of the opposed tube walls. Such a pump insures, first of all, that the tube walls will be slightly compressed and that no back flow or crushing of the blood will take place despite normal variations in tube wall thickness regardless of whether such irregularities were a result of poor quality control during manufacture or tube elongation or both. On the other hand, the yieldable mounting of the rollers insures that oversize irregularities can be accommodated and that insufficient pressure will be exerted against the tube to stretch it beyond the reasonable limits expected thereof in such an application. Furthermore, the spring-loaded rollers will self-adjust to changing physical characteristics in the blood-carrying tube that occur during the course of treatment and which cannot be accommodated by the prior art roller pumps due to the fact that the dialysis machine cannot be shut down while manual adjustments are made.

It is, therefore, the principal object of the present invention to provide a novel and improved roller-type pump.

A second objective is the provision of a pump of the type aforementioned wherein the rollers are spring-biased into extended position and, as such, are yieldably mounted so as to accommodate oversize abnormalities.

Another object of the within-described invention is to provide a blood pump having an adjustable stop cooperating with the roller extension spring to limit the gap left between the roller and raceway to a pre-set minimum.

Still another objective is to provide means for adjusting the roller pressure in the rollers of a roller pump.

An additional object is the provision of a roller pump assembly which, when properly adjusted, virtually eliminates any possibility of tube breakage or rupture, kinking, excessive elongation or loss in flow.

Further objects of the invention herein disclosed and claimed are to provide a roller-type pump which is simple, efficient, easy to service, rugged, reliable, compact, relatively inexpensive, versatile and even decorative in appearance.

Other objects will be in part apparent and in part pointed out specifically hereinafter in connection with the description of the drawings that follows, and in which:

FIG. 1 is a top plan view of the improved roller pump of the present invention;

FIG. 2 is a front elevation of the pump showing one of the tube clamps in open position;

FIG. 3 is a right side elevation;

FIG. 4 is a fragmentary section taken along line 4--4 of FIG. 1;

FIG. 5 is a fragmentary section taken along line 5--5 of FIG. 1;

FIG. 6 is an end view of the impeller to an enlarged scale;

FIG. 7 is a section taken along line 7--7 of FIG. 6;

FIG. 8 is a section taken along line 8--8 of FIG. 6; and

FIG. 9 is a fragmentary section taken along line 9--9 of FIG. 6.

Referring next to the drawings for a detailed description of the present invention and, initially, to FIGS. 1-5, inclusive, for this purpose, reference numeral 10 has been chosen to broadly designate the pump which will be seen to include a stationary base 12 atop which is mounted a trackforming member 14, the inside wall of which is shaped to define a raceway 16 having a semicylindrical section 18 terminating at each end in straight sections 20. An upstanding wall 22 is mounted atop the base in position to extend across the mouth of the track. Recessed within each end of this wall will be found one jaw 24 of a double-jawed hose clamp 26, the second jaw 28 of which is similarly recessed in the face of pivotal block 30 that is hingedly mounted on the base for pivotal movement between the closed position shown on the right in FIG. 2 and the open position shown on the left.

The jaws mate with one another in closed position to define one or more tube-receiving passages 32 arranged one above the other in stacked relation as shown. The base or foot 34 of each block is shaped to define a stop adapted to hold the latter in the partially open position referred to previously. On top of each block, on the other hand, an upstanding pin 36 is provided that cooperates with a conventional releasable latch 38 mounted atop the wall to hold the jaws closed. In pumps designed for a single tube 40, the jaws are modified to provide only one tube-receiving passage 32.

On the underside of the base in coaxial relation to the semi-circular portion 18 of the raceway is attached a tubular shaft journal 42 within which is journaled main impeller drive shaft 44. This shaft, in the actual dialysis unit, is coupled for conjoint coaxial rotation to the output shaft of an electric motor, none of which has been shown as it forms no part of the present invention. The portion of the drive shaft projecting above the impeller 54 is flattened as indicated at 56 to receive a suitable wrench should an emergency arise in which it became necessary to turn the latter by hand.

Impeller assembly 54 has a center section 58 fastened to the drive shaft 44 for conjoint rotation therewith. The drive shaft always rotates the impeller in a clockwise direction as viewed in FIG. 1 when the impeller is arranged as shown, however, by turning the impeller upside down the pump can be turned in the opposite direction. Formed integral with the center section along opposite leading edges of the latter are a pair of oppositely-directed arms 60 with notches 62 in their remote ends. These arms sweep the raceway ahead of their respective roller subassemblies generally indicated by reference numeral 64 that follow closely therebehind while keeping the tube 50 in proper position to be engaged by the rollers 66 thereof.

Next, with particular reference to FIGS. 6-9 of the drawings, the impeller assembly will be described in detail and, more specifically, the novel construction of the roller subassemblies 64 by means of which the rollers 66 thereof are yieldably spring-biased into an adjustable minimum fixed-spaced relation to the raceway 18 will be set forth. Each of the rollers 66 is journaled for rotation upon a shaft 68 that bridges the gap left between the parallel flanges 70 of the generally channel shaped roller mounting frame 72. The web portion 74 of the roller-carrying frame has a pair of vertically-spaced parallel rods 76 projecting horizontally therefrom in a direction opposite to that of the flanges 70. These rods enter sockets 78 provided for the purpose in the web 74 and are fastened therein by pins 80, all of which is most clearly shown in FIG. 8.

The faces 82 of the center section 58 of the impeller that lie next to the integrally-formed arms 60 are drilled to define a pair of rod-receiving sockets 84 within which rods 76 reciprocate. These sockets line up with the tines 86 of the integrally-formed arm 60 projecting from the remote face 82 of the impeller's center section 58. Each tine 86 also has a socket 88 therein arranged in coaxial relation with the corresponding socket 84 coming in from the other direction; however, these aligned sockets are separated from one another by an annular abutment 90 that leaves only a small diameter passage 92 interconnecting same of sufficient sizes to pass the threaded shank 94 of adjusting screw 96 while retaining the head 98 thereof. Now, the remote ends of rods 76 contain internally-threaded sockets 100 adapted to receive the threaded shanks of the adjusting screws.

Assuming, as will become clear presently, that each roller frame 72 is spring-biased away from the center section 58 of the impeller and toward the raceway 18 (FIG. 1), it will become apparent that adjusting screws 96 with their heads 98 abutting stops 90 provide the means by which a fixed minimum spacing between the surface of the roller and raceway can be maintained at all times. One need only insert an Allen wrench or other hex-bladed tool into socket 88 in the tines of the integral arm and turn the adjusting screws 96 to move the rollers relative to the raceway. The preferred spacing or gap is approximately three-fourths of the combined thicknesses of the opposite tube walls. This gap insures that the tube will be squeezed tight, yet, can accommodate a thinning of the walls resulting from tube elongation.

Finally, with reference to FIGS. 6, 7 and 9, the center section 58 of the impeller will be seen to include a third socket 102 located approximately midway between sockets 84 and in parallel essentially coplanar relation with each of the two vertically-aligned pairs thereof. A coiled compression spring 104 fits loosely in said socket and bears against the web 74 of roller frame 72 biasing same outwardly toward the raceway and functioning in a no-load condition to keep the heads 98 of the adjusting screws 96 snugged up against stops 90. Under load, of course, this spring provides a yieldable bias on the roller frame that allows the roller associated therewith to retract upon coming into contact with any obstruction of sufficient magnitude to overcome such bias.

The conditions under which the pump is operated vary considerably due to such things as using different members of tubes. Also, the size and wall thickness of the tubes may vary as well as their ability to resist deformation. In any event, a constant bias exerted on the roller frame by spring 104 leaves no room to accommodate these different operating conditions; therefore, an internally-threaded continuation 106 of passage 102 is provided in the central section 58 of the impeller to receive adjustable spring abutment 108. In the particular form shown, continuation passage 106 is smaller in diameter than the main passage and it opens onto face 82 of the impeller between the tines 86 of the integral arm 60 as shown most clearly in FIGS. 6 and 7. Also, a washer 110 has been shown interposed between the spring 104 and adjustable abutment 108. As was the case with the adjusting screws 96, access to the head of the adjusting screw is had through continuation passage 106 where it can be turned with a simple hex-bladed wrench inserted into the socket in its head.

Claims

What is claimed is:

1. In a roller pump of the type having a base, an upstanding wall atop the base defining a concave semi-cylindrical raceway, latch means located at opposite ends of said raceway adapted to releasably hold an arcuate section of flexible tubing in position against said raceway, a shaft journalled for rotation within the base about an axis coincident with the cylindrical surface of said raceway, and an impeller assembly movable by said shaft for causing fluid movement through the tubing by collapsibly distorting said tubing, the improvement which comprises: providing said impeller assembly with an elongate arm mounted on the shaft for conjoint rotation about an axis intermediate the ends of said arm; a pair of roller frames each having one end adapted for attachment to an end of the arm and another end notched to accept a roller for rotation within said notch; a cylindrical roller mounted for rotation within the notched end of each roller frame; telescopable connecting means interconnecting said one end of each roller frame to an end of the arm for independent relative movement between an extended position and a retracted position, said connecting means including at least one rod projecting from one of said interconnected ends and a corresponding opening positioned and adapted to telescopically receive said rod in the other of said interconnected ends; biasing means interposed between said interconnected ends of said arm and roller frame independently biasing said roller frame into extended position; and, adjustable stop means operative upon actuation to independently limit the maximum extension of each roller frame relative to the end of said arm to which said roller frame is connected, said stop means including an enlarged head carried by a portion of said rod telescoped within the opening receiving said rod and a section of said opening cooperating to define a shoulder positioned to engage said enlarged head upon movement of said roller frame toward extended position, said head being mounted for adjustment in the direction of the length of said rod to vary the distance separating said head from the interconnected end from which said rod projects.

2. The improvement as set forth in claim 1 in which: the telescoped portion of said rod terminates in an end containing an internally-threaded socket; an externally-threaded member is screwed into said internally-threaded socket forming an adjustable extension of said rod; and, in which the enlarged head is carried by a portion of said externally-threaded member outside said socket.

3. The improvement as set forth in claim 1 in which: the openings within which the rods telescope lie in transversely-spaced parallel relation to one another on opposite sides of the axis of shaft rotation and open onto both ends of the arm; the enlarged head is accessible through the end of said opening opposite the end into which the rod carrying said head enters; and, in which the portion of said head accessible through said end of said opening is shaped to receive an adjusting tool inserted therethrough.