US2693766A - Rotary pump of the resilient tube type - Google Patents

Description

NOV. 9, 1954 LE 2,693,766

ROTARY PUMP OF THE RESILIENT TUBE TYPE Filed Dec. 12, 1950 2 Sheets-Sheet l Q, Q I H van NOV. 9, 1954 SEYLER 2,693,766

ROTARY PUMP OF THE RESILIENT TUBE TYPE Filed Dec. 12 1950 2 Sheets-Sheet 2 United States Patent ()fiFice ROTARY PUMP OF THE RESILIENT TUBE TYPE Lon Antoine Seyler, Paris, France Application December 12,1950, Serial No. 200,354 Claims priority, application France December 13, 1949 1 Claim. (Cl. 103-149) This invention relates to fluid pumps of the known type including a resilient tube section formed to an arcuate shape, in combination with presser means moved in an arcuate path along said tube section and adapted to flatten it or reduce its cross-sectional area locally, thus creating the travelling flattened area.

It has not been found possible so far to construct pumps of this type having a truly industrial character, that is to say, pump units capable of satisfactory operation with large rates of discharge and at comparatively high pressure heads, and in which the adverse consequences of wear would be minimized by providing the weartaking parts readily interchangeable.

It is a general object of this invention to provide a pump of the type specified free of these limitations. The improvements to which the invention is directed more particularly relate to the construction of the resilient tube which is progressively locally flattened in the operation of the pump, and it is a further object of the invention to prevent any objectionable torsional and other stresses from being set up in said tube under the action of the presser means, and also to provide for a full and accurate flattening of the tube, without any clearance losses of the kind which occurred hitherto in the bending areas. Experience has shown that the tube cannot satisfactorily be made from a straight tube section shaped to an arcuate form, because the opposite wall portions defining the radially inner and outer sides of the arc would then be of different lengths, and are subjected to internal stresses which detrirnentally aifect both the performance and service life of the pump.

According to this invention, the resilient tube section is directly molded to its final shape, so that the inner side of the arc is shorter than the outer side. However, a tube section thus molded to its final arcuate form can only be obtained in the case of a comparatively short fraction of a circumference in no event greater than 180 in extent. Accordingly, the invention provides a special arrangement of the presser members or rollers which enables continuous operation even though the resilient tube may be substantially less than 180 in angular extent.

The above and further objects, features and advantages of the invention will be apparent from the ensuing description, made with reference to the accompanying drawings illustrating some forms of embodiment of the invention by way of non-restrictive examples, and where- Fig. 1 is a diagrammatic view showing the shape assumed by an initially straight tube when pressed by a roller or the like against an arcuate backing surface;

Fig. 2 is a similar view showing the shape assumed under similar conditions by a tube section initially molded to its final arcuate form according to a feature of the invention;

Fig. 3 is a diagrammatic cross-section of an improved pump according to an embodiment of the invention;

Fig. 4 is an axial section of the pump of Fig. 3 on line IV-IV of Fig. 3;

Fig. 5 is a cross-section of a conventional resilient tube in its flattened condition;

Fig. 6 is one embodiment of a tube according to the invention, shown in cross-section together with part of the pump casing;

a vacuum ahead, and a compression beyond,

2 Fig. 7 is similar to Fig. 6, with the tube flattened out;

Fig. 8 is a longitudinal section of the upper wall of an improved form of resilient tube according to this invention;

Fig. 9 is a view similar to Fig. 8 relating to a modification;

Fig. 10 is generally similar to Fig. 6 showing another form of embodiment of a resilient tube according to this invention;

Fig. 11 is generally similar to Fig. 7, showing the tube of Fig. 10 in its compressed or flattened condition;

Fig. 12 is similar to Fig. 3, showing the roller-carrying rotor in its idle or disengaged condition;

Fig. 13 shows a safety device against over-pressure in the tube;

Fig. 14 is an axial section tube; 1

Fig. 15 is an axial section of an improved bearing arrangement; and Fig. 16 diagrammatically illustrates an auxiliary resilient runway for the presser rollers.

The method used in producing the resilient tube for use in a pump of the kind described herein is of the utmost importance. Were one merely to take an initially straight pipe section, in which the opposite generatrices are normally equal in length, and form it to the desired arcuate shape, the resulting tube will when subjected to the action of the presser means, tend to be distorted both transversely and longitudinally, thus creating friction forces and a displacement of the tube against the casing wall, so that the tube will have a tendency to break away from the backing surface in the casing, as shown in Fig. 1. This figure shows a tube 1 flattened by a presser roller 3 against a casing or backing surface 2. To either side of the point at which the roller 3 exerts its action, the wall of the pipe is seen to separate from the casing wall, as at 39, 39.

According to this invention, a pipe of molded material is used which naturally conforms to the shape of the backing surface or casing wall, as diagrammatically shown in Fig. 2. In this Wa the segment of a torus defined by the tube is, in its idle condition, subjected to no internal stress whatever. This is especially important in the case of large-diameter tubes in which the difference in radii of curvature between the outer and the inner walls of the torus is great. In practice however, it is found that a tube section so formed cannot be provided with an angular extent greater than For, while the removal of the outer mold sections would remain easy to effect, the extraction of the inner core would not be practicable in the case of an are more than 180 in extent. For this reason, the present invention provides a pump in which the resilient tube section has the form illustrated in Fig. 3. As shown, the tube 1 includes a central arcuate section extended to either side'by straight sections 1a and 1b. The tube is contained in a casing 2 preferably consisting of two flanges 19, 19 as shown in Fig. 4. To secure continuous operation of the pump in spite of the fact that the arcuate segment is less than 180 in extent, a special arrangement is provided for the presser rollers 3, as later described.

Moreover, the fact that the tube is molded makes it possible to impart to it a shape in cross section which secures great advantage in the operation of the pump. The tubes used heretofore in pumps of the type under consideration were in the form of a straight cylinder 1 having a uniform wall thickness. When such a cylinder is flattened by a roller 3, it is found that, while the upper and lower walls are flattened against each other, as indicated at 15 in Fig. 5, the bends at the lateral ends of the tube cross-section invariably left residual gaps or clearances 16; this is detrimental both because of the resulting clearance losses detracting from the pumps efficiency factor, and because of the high strains generated in such lateral end parts of the tube material.

Experience has shown that if the side parts of the tube are suitably thinned out at construction, the resulting flattening effect becomes more uniform and the end clearances such as 16 are completely eliminated. Fig. 6 illustrates the cross-sectional configuration of:a

of an end portion of the tube 1 modified according to a feature of the invention,

Patented Nov. 9,1954.-

in that it is provided in each of its sides with a thinnedout area 17 formed by a groove in the outer tube surface. When such a tube is flattened, the shape assumed by it is that shown in Fig. 7, i. e. a substantially regular rectangle with rounded corners, having a uniform line of compression 18 devoid of end gaps or clearances. The periphery of the roller 3 and the casing flanges 19,, 19' are preferably provided with such a shape that the tube when flattened will be pressed by the roller over the full width of the tube against the casing surface.

It has been found in addition, however, that the. flattening action of the roller 3 on the tube causes the tube to be twisted to the extent permitted by the residual clearance space within the casing. It has accordingly been endeavoured to prevent any lateral displacement of the tube, and the tube is for this purpose provided, according to the invention and as shown in Figs. 6 and 7, with a longitudinally-extending rib 20 adapted to cooperate with a complementary groove formed in the casing flanges 19, 19; thus, upon the casing flanges 19, 19' being clamped together by means of the bolts and nuts 21, the rib 20 is firmly blocked in position, preventing any lateral displacements of the. tube. Rather than a continuous rib 20 prevailing over the full length of the tube, as in Fig. 8, separate projections such as 20a, 20b, 206 in Fig. 9, may of course be used.

Fig. 10 illustrates another cross-sectional configuration of the tube which, while difiering from that of Fig. 6 described above, also improves the conditions under which the tube is flattened, eliminates the gaps 16 and correspondingly improves the pumps efliciency. In this modification, the side portions of the tube wall are thinned down by providing V-shaped dents or notches 24, 24 in its inner contour. The inner tube contour further includes somewhat flatted upper and lower sections 22, and a pair of upper inward bosses 23 between the upper flat 22 and the respective dents 24, as well as a pair of lower inward bosses 25, somewhat smaller in radial extent than the upper bosses 23, between the lower flat 22 and the respective dents 24. When a tube of this configuration is flattened out, as shown in Fig. 11, the dents or notches 2.4 co-operate with the related bosses 23 and 25 to. impart to the flattened section a configuration in which the ends 26 are slightly upturned, but are quite free of any gaps. Desirably, the rollers 3 and flanges 19, 19 are in this case formed with a corresponding, shallow U-shaped form, as shown in Fig. ll.

As previously stated, a special arrangement for the presser rollers is used according to the invention in combination with the tube construction shown in Fig. 3, in which the extent of the arc is substantially less than 180 (e. g. about 120), and is extended by straight tube sections la and lb. As shown in Fig. 3, the pump com prises, as known per se, the resilient tube I backed against a fixed casing 2, and a set of presser rollers 3 driven in rotation about a shaft 4 extending through the centre of the arcuate section of the casing 2, are adapted to suecessively engage the inner surface of, and thus locally flatten, the tube 1. The rollers 3 are herein shown as rotatably mounted on their respective pins mounted in equispaced relationship on a rotor structure consist ing of a pair of flanges 6 rotatable with the shaft 4.

Rotation of the rotor in the direction of the arrow creates a depression or vacuum in the tube 1 in the upstream section 1a thereof, and an over-pressure in the downstream end section 1b, thus generating a pumping action.

In known pumps of this type, the resilient tube was either provided with an extent approximating an entire circumference, and was then made to co-operate with a plurality of associated presser rollers adapted to compress the. tube simultaneously at several points thereof, or the tube was made to extend over only a fraction of the circumference, and co-operated with rollers which successively acted on the tube in such a way that the tube, at any given time, was compressed only at one of its points.

Each of these prior arrangements had its limitations:

In the first arrangement, the extent of the arcuate tube on which the rollers were made to act was so great that the tube Was subjected to considerable longitudinal stress, resulting in irregular and repeated distortions damaging the tube within a short time. Moreover, with a tube extending over a near-circumference, the overall size of the pump quickly becomes prohibitively large,

as the discharge rate or capacity of the pump is increased, because the diameter which has to be imparted to said circumference rapidly increases with the tube diameter, if it is desired that the tube retain its circular forrln without any breaks or bends in its radially inner wal In the second above-mentioned'prior arrangement, experience has shown that if, as any one roller begins relieving its pressure on the tube, the next roller has not yet reached its position of full compression, air will penetrate into the tube, reducing the rate of discharge of the pumped fluid owing to the reduction in suction force caused by the ingress of air.

According to the invention, the shape of the casing is so predetermined that the tube bears against it over as short as possible an arcuate extent, slightly greater however, than the angular spacing between any pair of consecutive rollers, whereby, in the first place, the abovementioned distortions are averted, and, at the same time, the tube is at all times subjected to compression at one at least of its points, thus affording a full pumping, seal between the intake and delivery'ends of the pump.

In practice, the number of rollers provided on t e rotor and hence. the arcuate extent of the tube are selected with regard to the design capacity and head of the pumping unit desired.

Thus, for large discharge capacities, the angle between two consecutive rollers should be large enough to allow the tube to return resiliently to its circular form in section. Where on the other hand a large head rather than capacity is desired, the rollers may be brought closer together and thus the arcuate extent of the tube may be reduced. In most cases, satisfactory design characteristics are obtained with an arc of or so and a set of three equispaced presser rollers.

As shown in Fig. 4, the. width of each roller should be at least equal to the width of the tube in its fully compressed condition, to prevent the formation of bulges at the sides, liable to occur in the. absence of a compression force exerted thereat.

As concerns the casing, its inner contour is predetermined in relation to the shape assumed by the tube when flattened, so as to conform to that shape with a. slight amount of clearance, thus preventing friction between the edges of the pipe and the. casing while affording a positive centering action, as already described with reference to Figs. 7 and 11.

It should further be observed that the arcuate section of the tube 1 merges tangentially with the straight. sections 1a and 1b, extending through side apertures in the casing, in order to minimize wear on the tube and-re duce pressure. losses in the conduits. It is further to be noted that in the case of large-capacity pumping units, the arrangement is desirably such that the intake branch 1a and the delivery branch 1b, are respectively directed downwards and upwards. This will eliminate the. use of elbow connections in, the lines, liable to impede the flow. A I further advantage of such arrangement is that, on step ping pump operation, it is only necessary to rotate the rollers backwards once, on order to. drain the pump empty of liquid, thus avert-aing the danger of freezing, etc. Such drainage may, however, also be obtained merely byrelieving the compression of the rollers, as by un-blocking the eccenter to be presently described.

Further to prevent distortion of the tube, the inventron provides. disengaging means: for relieving; the pressure of the rollers when the pump is. idle.v Inasmuch as there is always at least one roller engaging the tube, the pres sure of such roller would: be exerted against the same point of the tube thlOughQUt. anyidleperiod of the pump; if the pump were to. remain idle for aconsiderable length of time, this might lead to. local ovalization, reducing the efficiency factor, and-to premature wear.

The disengaging means of, the invention eliminates such local pressure when the pump is idle. The. rotor shaft. 4-

is rotatable in a. preferably bronze. disc 7, the shaft being mounted eccentrically in the disc 7. The. disc 7 in turn is rotatably ad ustable in a concentric outer bushing or ring 8, e. g. of steel. Keying means 9 are provided to; block the disc 7 in either one of two positions relatively to the ring 8, namely an operative position shown in Fig. 3, in which the rollers 3 engage the tube 1 to flatten it, and anidle position, shown in Fig. l2, in which the rollers 3 are disengaged from thetube. To shift from the operative to the idle condition or vice versa, it is simply necessary to disengage the key means 9 and rotate the shaft 4, acting for instance on the drive pulley 4a. To facilitate this operation, a lever (not illustrated) may be provided integral with the bushing 7 to rotate it from either one to the other of its positions. As shown in Fig. 4, the assembly including disc 7, bush 8 and keying means 9 is provided at each of the two bearings of the shaft 4 in the casing. The degree of eccenter of the shaft 4 in the disc 7 is of course predetermined in relation to the diameter of the tube. It may be seen that, should the shaft inadvertently be left in its idle condition when the pump is started, this would merely result in harmless idle operation of the pump.

Fig. 13 illustrates a further safety device which is provided according to a preferred aspect of this invention. Should the delivery outlet of the pump be accidentally stopped or obstructed during operation, an over-pressure would result liable to cause the tube to burst. As a safeguard against this, the pins 5 of the rollers may, as shown in Fig. 13, be mounted in radially-extending slots 10 formed in the rotor flanges 6, and carried by clevises 11 subjected to the radially-outward urge of springs 12 surrounding guide pins 13 and abutted inwardly on the periphery of a flange 14 of the shaft 4. The strength of the springs 12 is so predetermined as to be higher than the resistance opposed by the tube 1 in normal operation of the pump, so that the rollers will normally act to compress the tube as though they were rigidly connected with the shaft 4, but lower than the resistance opposed by the tube When subjected to abnormally high internal pressure as may result from an obstruction of the delivery pipe. In the event of such obstruction, therefore, the springs will yield and allow the rollers to be retracted inwards, so that the pump will rotate idly until the obstruction is removed. The device just described will also serve as a safeguard for protecting the pump against the consequences of the ingress of a solid body into the tube. In this case, one of the springs 12 would yield, retracting the related roller and allowing the foreign body to pursue its course to the outlet of the tube.

A further feature of the invention relates to the arrangement at the outer end of each tube section 1a and 1b. As shown in Fig. 14, end flanges or beads 1' are provided to prevent longitudinal displacements of the tube both at the inlet end 1a and at the outlet end 1b, the bead 1 being confined in a groove formed in the related casing connector flange 27, and the bead 1' slightly projecting, as shown, beyond the radial surface of said connector flange. Upon connection of a rigid pipe section 28 by means of a coupling flange 29 co-operating with the flange 27 through bolts 30 or the like, the protruding end of the bead 1 of the resilient tube 1 will fulfill the function of a sealing gasket for the coupling. If the pipe 28 to be coupled is a flexible one, a coupling flange such as 29 may be adapted thereto to co-operate with the casing coupling flange 27 as described.

Owing to the arrangement just described, the resilient tube 1a1--1b may be bodily removed from the pump casing when worn out or otherwise damaged and replaced by a new tube, the end beads 1 serving as abutments for positioning the newly inserted tube relatively to the casmg.

According to a subsidiary feature, to prevent the resilient tube from collapsing under the efiect of suction creat ed therein in operation, a metal ring or the like may be incorporated in the tube, adapted to resiliently resist such collapse.

The invention further provides an improvement in the mounting arrangement of the rollers 3 on their pins, especially useful where the pump is designed to handle acid or other corrosive liquids. Even though the liquids being pumped are at no time in contact with any part of the pump mechanism, flowing as they do through the resilient tube throughout the pump assembly, yet there remains the danger of corrosive vapors surrounding the pump and attacking the ball-bearings of the rollers. Moreover, the bearings being arranged on either side of the roller, a certain amount of play may occur between the roller and the part securing the bearing on the roller pin, resulting in lateral displacement and friction in operation. According to this invention, a protecting and securing element is provided at the end of the roller pin. As shown in Fig. 15, the roller 3 is mounted on a pin 5 which further supports the inner race 31 of the ball-bearing 32. A disc or flange 33 is secured on the end of the pin 5, firmly engaging and abutting the inner ball-race 31 as at 35 while overlapping the outer race 34 at a slight spacing therefrom as at 36. This eliminates the afore-mentioned drawbacks.

A further improvement according to this invention is for reducing wear on the resilient tube at its inlet end, as caused by the sudden impact thereon of each successive roller as the latter, after having left the outlet end of the tube and thus having been allowed to assume a greatly increased speed of rotation or impetus about its pin, first contacts the inlet tube section. As shown in Fig. 16, an arcuate guide or runway 37 made of resilient material is provided along the path of the rollers between the point where they leave the tube outlet section and the point where they re-engage the inlet section. The runway 37 is thus adapted to play the part of the tube section 1 with respect to the rollers 3 throughout the extent of the path of the rollers from which the tube is actually absent. The runway 37 merges substantially tangentially with the tube 1 as at 38. Said runway 37 may either consist of a single unbroken element as shown, or it may consist of two or more separate parts leaving a free intermediate space, to promote the cooling of the rollers 3 during the idle part of their travel. In any case, the rollers will be provided with practically the same rate of rotation about their axes at the beginning and at the end of the active part of their travel, and there will be no appreciable impact at the point where they first engage the intake end 1a of the tube.

What I claim is:

A rotary pump comprising a housing having an arcuate inner surface portion and means defining inlet and outlet channels adjacent said arcuate surface, a rotor rotatably mounted in said housing, said rotor carrying a plurality of circumferentially spaced rollers movable with said rotor in an are substantially concentric with said arcuate surface, an elastic tube disposed in said housing, said elastic tube having an arcuate portion corresponding in curvature with said arcuate surface and adapted to lie against said arcuate surface and to be engaged by the rollers of said rotor upon rotation thereof, the arcuate portion of said tube extending over an are substantially equal to the space between two of said circumferentially spaced rollers of said rotor and having substantially rectilinear extensions tangently merging with the ends of said arcuate portion and extending through said inlet and said outlet channels, the wall portions of said tube between the portion engageable with the housing and the portion engageable by the rollers being thinner than the remainder of the tube.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 314,851 Kelly Mar. 31, 1885 496,559 Fraser et al. May 2, 1893 513,315 Funk Jan. 23, 1894 1,988,337 Santiago Jan. 15, 1935 2,314,281 Knott Mar. 16, 1943 2,403,572 Wittenberg July 9, 1946 FOREIGN PATENTS Number Country Date 190,811 France of 1888 438,536 Italy Aug. 17, 1948 851,636 France Jan. 12, 1940 954,019 France Dec. 16, 1949

Images