Patent Publication Number: US-4484864-A

Title: Peristaltic pump

Description:
The working principle of a peristaltic pump resides in the crushing of an elastically deformable tube in at least one point, so as to divide its inner volume into two chambers sealed one with respect to the other, and in the displacement of this crushing point along the tube so as to push the product contained inside the tube upstream of said crushing point, and also in drawing-in said product behind the said crushing point due to the suction effect caused by the tube tending to elastically recover its initial shape. A high pressure chamber and a low pressure chamber are thus created inside the pump, which chambers are separated by a movable tight zone, on the quality of which depends the operation of the pump. 
     The quality of the tightness is dependent on the crushing of the tube which is itself dependent on the nature of the material used and on its degree of wear. Consequently, it is necessary to be able to regulate to a certain extent the tube crushing value to allow for these particular parameters. 
     The object of the invention is to propose a peristaltic pump which comprises means permitting to regulate easily the crushing and overcrushing of the tube to, either adjust this value in relation to the required suction and delivery pressures, or to compensate for the wearing down of the tube which can badly affect the efficiency and performance of the pump, or to select the maximum crushing value permitting to obtain the most wear from the tube depending on the work or works to be carried out. This control also enables to adapt the crushing value so as to obtain a regular flow for pumps working at low speeds thus permitting to carry out proportioning operations with such pumps. 
     Such a pump comprises a stator, an elastically deformable tube placed along a surface supporting the stator, and a rotor provided with a plurality of members designed to crush the tube against the said supporting surface, and evenly distributed around the rotor, each of said crushing members being coupled to the rotor by way of an element for regulating the radial distance separating it from the axis of rotation of said rotor. 
     Said rotor comprises at least one reference face parallel to the axis of rotation of the rotor and said regulating element is constituted by a support of the axle of rotation of the roller provided with a reference surface held in contact with the said reference face of the rotor, whereas at least a plurality of orifices are provided in the rotor and at least one orifice is provided in the said support and is designed to be placed over one of the orifices from the said plurality of orifices, by moving the support with respect to the rotor along the said reference face and surface, inside a radial plane of the rotor, and to receive a traversing connecting member. 
     Moreover, in the case where the pump comprises two diametrically opposite crushing rollers, the rotor comprises two reference faces parallel together, each one cooperating with a corresponding support. 
    
    
     The invention will be more readily understood on reading the following description with reference to the accompanying drawings, in which: 
     FIGS. 1 and 2 are cross-sectional views of a pump according to the invention, taken along line I--I of FIG. 2 and along line II--II of FIG. 1, respectively. 
     FIG. 3 is an external view of only the rotor of the pump according to FIGS. 1 and 2. 
     FIG. 3A illustrates one embodiment of a regulating element according to the invention. 
    
    
     With reference to FIGS. 1 and 2, we recall hereafter the constitution of a peristaltic pump. In a stator 1 which comprises a fixed surface 1a (semi-cylindrical in this case) is placed an elastically deformable tube 2, clamped by its ends to the stator 1 and placed along the surface 1a. A rotor 3 rotates inside the stator 1 about an axle 4 situated on the axis of the cylindrical surface 1a. This rotor comprises two crushing members 5 (in the illustrated example, rollers mounted for rotating on the rotor about axles 6) which members are diametrically opposite and flatten the tube 2 against the surface 1a by creating a sealed zone 7 which divides the inner volume of the tube into two chambers, a delivery chamber upstream and a suction chamber downstream. It will be noted that other types of pump can work on the same principle and comprise a plurality of tube-crushing rollers. In this case, the rollers are regularly distributed around the rotor and the surface 1a is limited to a portion of cylinder, the center angle of which is equal to the angular offset of two successive rollers. 
     For the pump to work well, one of the important parameters to determine is the quality of the tube-crushing which is conditioned by the distance D separating the stress-bearing generating line of the roller 5 of the supporting face 1a. This distance should be adjustable in order to obtain an optimum crushing effect which will ensure a good tightness for the said zone 7 without really overcrushing the tube (which would give rise to fatigue and excessive wearing down of the tube). This adjustment is essentially dependent on the nature of the tube, of the product to be transported and of the conditions in which the pump is used. 
     It is also necessary, after initial adjustment of the value of distance D, to be able to alter it to allow for the variations of the mechanical characteristics of the tube and of its wear as time goes by. 
     To this effect, a device is provided for adjusting the radial position of the rollers 5 with respect to the axle 4 of the rotor 3. In FIGS. 1, 2, 3 and 3A, this device consists in a support 8 for the axle 6 of the rollers, which support is removably fixed to the rotor 3. Said support is constituted by two side members 8a and 8b, equipped at one of their ends with a bearing 8c for the axle 6 and which comprise, perpendicularly to the axle of said bearing, a reference surface 9. The rotor 3 is also provided with a reference surface 10 which is perpendicular to its rotation axle 4 to receive the surface 9. Moreover, the support 8 and the rotor 3 have corresponding indexing means 11 to mark the position of the support on the rotor which means are constituted by at least one orifice 12 provided in each of the said side members 8a and 8b and a plurality of orifices 13 provided in the rotor. When orifice 12 is placed over one of the orifices 13, a tightening pin 14 can be fitted in to fix the support to the rotor. It is also possible for the plurality of orifices 13 to be provided on the support and for the orifice 12 to be provided on the rotor. Moreover, and as illustrated in the figures, the support 8 comprises a plurality of orifices 12a, 12b, 12c (to be more precise, a double plurality to allow the aforesaid fixation by two pins 14) each orifice having its corresponding orifice in the plurality of orifices 13a, 13b, 13c of the rotor. 
     FIG. 3 shows that by placing orifices 12a over orifices 13a, a position 8&#39; of the support is obtained. The positions 8&#34; and 8&#34;&#39; are obtained respectively by placing orifice 12b over orifice 13b and orifice 12c over 13c. The cooperation of the reference faces 9 and 10, remaining in contact, guide the passage from one to the other positions. It is thus clear that if position 8&#39; defines a distance A separating the bearing 6 of the roller from the rotation axle 4 of the rotor 3 (which distance can be minimum), the positions 8&#34; and 8&#34;&#39; define distances B and C which are by construction different one from the other and from the distance A, and larger than A if the latter is minimum (meaning if the straight line joining the axle 4 to the bearing 6 in its position 8&#39; is perpendicular to the surface 10). This being a means to regulate the radial distance separating the rollers from the rotor axle and therefore a means to regulate the said distance D. 
     For the rollers to keep the same angular offset (in this case 180°), the dispositions to regulate the support 8 of the other roller will be symmetrical to those described with respect to the axle of the rotor 4. 
     The invention is in no way limited to the description given hereinabove, but on the contrary covers any variant that can be brought thereto without departing from its scope or its spirit.