US 3674383 A
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F. [LES PUMPS July 4, 1972 2 Sheets-Sheet 1 Filed Sept. 1 1970 July 4, 1972 2 Sheets-Sheet 2 Filed Sept. 1, 1970 United States Patent 3,674,383 PUMPS Frank Hes, Loscombe, Four Lanes, Redruth, Cornwall, England Filed Sept. 1, 1970, Ser. No. 68,749 Claims priority, application Great Britain, Sept. 5, 1969, 44,040/69; Apr. 16, 1970, 18,296/70 Int. Cl. F04b 43/08, 43/12, 45/06 US. Cl. 417-476 4 Claims ABSTRACT OF THE DISCLOSURE A peristaltic pump comprises a flexible tube in the form of a coil having a single complete convolution encircled by a fixed support, and a member disposed to compress a part of the tube against said support and rotatable about the central axis of the coil. The length of the member in the direction of said axis is such that the member successively compresses all parts of the convolution of the tube during each rotation of the member. The internal surface of the support is conical, and the member is conical or inclined so that the pressure of the member on the tube may be adjusted by axial movement of the member.
The invention relates to pumps of the kind which induce a flow of fluid along a flexible walled tube by repeatedly contracting the tube at a point and moving the contraction along the tube for a distance so as to force a body of fluid along the tube in front of the contraction. Such a pump will hereinafter be referred to as a peristaltic pump.
Accordingly the invention comprises a peristaltic pump of the kind referred to wherein the flexible tube is in the form of a coil having at least one complete convolution encircled by a fixed support and a member disposed to compress a part of the tube against said support and rotatable about the central axis of the coil, the length of said member in the direction of said axis being such that the member successively compresses all parts of at least one complete convolution of the tube during each rotation of the member.
Preferably the coil comprises only a single complete convolution.
It is also preferred that said fixed support comprises a tubular structure encircling the coil or a part thereof.
Preferably the distance of said member from the inner surface of the support is adjustable. For example the inner surface of the support, engaging the tube, may be inclined to the central axis of the coil and the surface of the member may be similarly inclined and be longer than the axial length of said convolution, so that movement of said member in the direction of the central axis of the coil changes the distance of the surface of the member from the inner surface of the support, thus changing the degree of compression of the flexible tube.
Where the fixed support is a tubular structure its inner surface may be in the form of a frustrum of a cone. The member may be a roller in the form of a frustrum of a cone with its axis lying parallel to the central axis of the coil.
Alternatively the member may be a cylindrical roller having its axis inclined to the central axis of the coil and parallel to the inner surface of the support.
The coil is preferably capable of being fixed relatively to said tubular structure. For this purpose the tubular structure may be formed in two parts adapted to be secured together, one part including locating means for one end of the coil and the other part of the tubular structure including locating means for the other end of the coil.
Patented July 4, 1972 The locating means may comprise a slot formed in each part of said tubular structure and blocks capable of sliding in each said slot and of engaging against said tube, to hold it when it extends through said slot, by the clamping of the two parts of said tubular structure together.
The following is a more detailed description of various embodiments of the invention, by way of example, reference being made to the accompanying drawings in which:
FIG. 1 is a plan view of a peristaltic pump, one end of the pump being shown in section;
FIG. 2 is an end view of FIG. 1;
FIG. 3 is a side view of the pump;
FIG. 4 is a detailed view of a part of FIG. 3;
FIG. 5 is a diagrammatic perpsective view of a modified form of pump; and
FIG. 6 is a perspective view showing a fragment of a modified form of tube for use in the pump.
The pump comprises a driving portion 10 and a pump portion 11, both mounted on a base 12. The driving portion 10 comprises an electric motor v13 mounted on the base 12 and capable of sliding movement relatively to the base 12 in the direction of its axis so that its position relatively to the pump portion 11 may be adjusted. The drive shaft 14 of the electric motor 13 carries a disc 15, as best shown in FIGS. 1 and 2. Towards the outer periphery of the disc is mounted a roller spindle 16 (as best shown in FIG. 2) on which is mounted a frusto-conical roller 17 carried on two ball races, one of which is shown at 18, so as to be rotatable on the spindle 16. The roller 17 is circular in cross-section and tapers away from the surface of the disc 15.
The pump housing 11 comprises a pair of blocks 19, 20 which are of frusto-conical internal cross-section having tapered surfaces 21 and 22 respectively. The angle of taper of the surfaces 21, 22 is substantially the same as the angle of taper of the roller 17. The blocks 19, 20 are aligned axially with the motor 13 so that their internal surfaces taper away from the disc 15. Each block is provided with a slot 23 (see FIGS. 3 and 4) on one side thereof, so that when the two blocks 19, 20 are apart, one part of a flexible tube 24 may be inserted into the slot of one block 19, and another part of the flexible tube 24 inserted into the slot in the other block 20 Locking blocks 25, which are formed with curved end surfaces, are then fitted into the slots and, as the blocks are faced together and clamped together by wing nuts 26, the curved end surfaces of the locking blocks 25 engage the flexible tube 24 to hold it firmly in position at the points where it passes through the slots 23. Within the pump assembly 11 the flexible tube 24 is formed into a coil having a single convolution which extends around the tapered surfaces 21, 22 of the two blocks 19, 20.
The roller 17 is so positioned on the disc 15 that it is in contact with the flexible tube 24 as it rotates with the disc 15.
The action of the pump is as follows. The flexible tube 24 forms part of a delivery conduit containing a fluid which it is desired to pump. For example, the pump may be used for pumping blood since the blood does not come into contact with any of the moving parts of the pump but only contacts the tube 24 which may be easily sterilised. The electric motor 13 is started and the disc 15 is rotated by the drive shaft 14, so rotating the spindle 16 on which is mounted the roller 17. Due to the action of the bearings 18 the roller may rotate relatively to the spindle 16 as the disc 15 rotates. As the disc 15 rotates the roller 17 compresses the surface of the coil of flexible tubing 24 causing a wave of high pressure to move in front of the roller 17 and a wave of low pressure to follow the roller 17. As the roller 17 reaches the end of the convolution of flexible tubing 24 which lies closest to the disc it comes again into contact with the beginning of the convolution which is furthest away from the disc 15. Thus the fluid being pumped is always prevented by the roller from passing back round the convolution and is continually forced through the tube.
The fact that the pump housing 11 is formed in two parts 19, enables a tube to be used which is a part of a continuous circuit, without the need for disconnecting either of the ends of the tube.
The rate of fiow of liquid through the tube 24 may be varied in one of two ways. Firstly, the motor 13 may be adjusted relatively to the base 12 in the direction of its axis to move the roller 17 in and out of the pump housing. The movement of the motor 13 towards or away from the pump housing may be achieved by means of a screw thread arrangement which is connected to the motor 13 and is mounted for movement relatively to the base 12. In such an arrangement the motor 13 is slidably mounted on the base 12 and rotation of the screw thread by means of a hand wheel or the like moves the motor 13 either forwards or away from the pump housing. If the roller 17 is withdrawn from the housing, the action of the complementary tapered surfaces of the roller 17 and the blocks 19 and 20 means that the surface of the roller 17 moves further away from the surfaces 21, 22 and consequently exerts less pressure on the surface of the flexible tube 24. Thus the magnitude of the pressure wave decreases and consequently the rate of pumping also decreases. Movement of the electric motor 13 towards the pump housing 11 closes the gap between the surfaces and increases the pressure exerted by the roller 17 on the flexible tube 24, so increasing the rate of pumping.
The second method of varying the rate of pumping is to vary the speed of rotation of the motor 13. This method is not capable of achieving such fine variations in the rate of flow as the first method.
It will be appreciated that as long as at least one complete convolution of flexible tubing is provided within the block assembly 11 the length of the coil may be varied at will, the only condition being that the roller must be in contact with such a coil along the whole length of at least one convolution. It will also be appreciated that a number of rollers may be provided around the disc 15, which will result in a corresponding increase in the rate of pumping.
In the modified form of pump shown in FIG. 5, the tube 24, at either end of the convolution, is fixed in position by the tubular structure. In order to fix the tube in its coiled position in the convolution, a tape 31 made of nylon, glass fibre or other suitable materials, is placed round the tube at the top point of the convolution. The two ends are clamped between the pump housing blocks 19 and 20, as shown in FIG. 5. Other tapes may be similarly fixed at other points in the coil if so required. To ensure a constant length for the tape, one end is secured to the pump housing block 20, by a retaining stud 32 which acts as the mate unit for a press fastener (not shown) on the opposite end of the tape.
Alternatively, as shown in FIG. 6, the tube could be manufactured in plastics with a lug 33 moulded in, which could be clamped between the pump housing blocks.
A further modification employed in the construction of FIG. 5 is that the locking blocks 25 are integral with the blocks 19 and 20 instead of being separately formed as in the arrangement of FIGS. 1 to 4.
Also in FIG. 5, the roller 17, instead of being tapered is cylindrical and the axis of rotation of the roller is inclined inwardly slightly towards the central axis of the coil so as to be parallel to the tapered internal surfaces of the blocks 19 and 20. It will be appreciated that in this arrangement also, axial adjustment of the motor 10 will bring the roller 17 closer to or further from the tapered surfaces of the blocks 19 and 20' and will thus vary the pumping rate.
If two pumps are run-coupled together so that one motor and one drive shaft serve both, and the pumps are run out of phase, not only can the pumps be operated at identical speeds but any slight pulse in the one pump can be cancelled out by the pulse in the other.
1. A peristaltic pump comprising a flexible tube in the form of a coil having at least one complete convolution; a fixed support encircling the convolution of the tube; a member disposed to compress a part of the tube against said support; and means to rotate the member about the central axis of the coil, a length of said member in the direction of said axis being such that the member successively compresses all parts of at least one complete convolution of the tube during each rotation of the member; the inner surface of the support, engaging the tube, being inclined to the central axis of the coil and the surface of the member being similarly inclined and longer than the axial length of said convolution, the distance of said member from said inner surface of said support being adjustable so that movement of said member in the direction of the central axis of the convolution changes the distance of the surface of the memher from the inner surface of the support to change the degree of compression of the flexible tube.
2. A pump according to claim 1 wherein the fixed support is a tubular structure the inner surface of which is in the form of a frustum of a cone.
3. A pump according to claim 1 wherein the member is a roller in the form of a frustum of a cone with its axis lying parallel to the central axis of the convolution.
4. A pump according to claim 1 wherein the member is a cylindrical roller having its axis inclined to the central axis of the convolution and parallel to the inner surface of the support.
References Cited UNITED STATES PATENTS 2,679,807 6/1954 Bruckmann 4l7476 X 2,930,326 3/1960 Simer et al. 417-477 X 2,752,852 7/1956 Offutt 4l7474 3,427,986 2/1969 Cornell 417-474 3,584,983 6/1971 Hindman et a1 417-476 CARLTON R. CROYLE, Primary Examiner R. E. GLUCK, Assistant Examiner US. Cl. X.R. 418-45; 92-l3.2