US2982225A

US2982225A - Rotary pump of tube-compression type

Info

Publication number: US2982225A
Application number: US788550A
Authority: US
Inventors: Ronald E Thompson
Original assignee: Individual
Current assignee: Individual
Priority date: 1959-01-23
Filing date: 1959-01-23
Publication date: 1961-05-02
Anticipated expiration: 1978-05-02

Description

May 2, 1961 R. E. THOMPSON ROTARY PUMP OF TUBE-COMPRESSION TYPE INVENTOR.

are 24 3 Sheets-Sheet l Ronda E 7720172 0501 Filed Jan". 23, 1959 army May 2, 1961 R. E. THOMPSCN ROTARY PUMP OF TUBE-COMPRESSION TYPE Filed Jan. 23, 1959 3 Sheets-Sheet 2 IN VEN TOR A OZJQZC? Z1? 320172 05012 flfz ozfigrz i w' as a May 2, 1961 R. E. THOMPSON ROTARY PUMP OF TUBE-COMPRESSION TYPE Filed Jan. 23, 1959 3 SheetsSheet 5 United States Patent O Ronald E. Thompson, 40 Mountain View Terrace, Cheshire, Conn.

Filed Jan. 23, 1959, Ser. No. 7 88,550

11 Claims. (Cl. 103-149) This invention relates to rotary pumps in general,

audto displacement pumps of tube-compression type in particular.

Pumps of this type are customarily provided with a resiliently flexible tube having inlet and outlet legs and an intermediate fluid-displacing length or section resting against a fixed surrounding track of arcuate extent, and roller means arranged concentrically with respect to, and turnable about, the center axis of the track for cyclically compressing the displacement tube section progressively into complete collapse or closure against the track. With the roller means being thus turned in the proper direction, the fluid in the displacement tube section immediately ahead of the roller-compressed part thereof is displaced therefrom and discharged through the outlet leg of the tube, while the displacement tube section immediately behind the roller-compressed part thereof resiliently recovers from its collapsed state and the ensuing partial vacuum therein draws fluid thereinto from the inlet leg of the tube.

It is an important object of the present invention to provide a pump of this type which has greater output capacity than prior pumps of this type of comparable size.

It is another important object of the present invention to provide a pump of this type which will not only reliably perform, but the output rate of which will also increase with its operating speed, throughout a speed range which extends far beyond that within which prior pumps of this type will perform.

It is a further object of the present invention to provide a pump of this type in which resilient expansion of the tube is introduced and relied on to increase the effective volume of the displacement tube section and also to re-enforce the latter as well as the inlet leg of the tube against collapse under atmospheric pressure, thereby to achieve the aforementioned greater output capacity for a given size of the pump as well as its reliable performance throughout the aforementioned larger operating speed range.

Another object of the present invention is to provide a pump of this type in which the tube is in part restrained against distortion and is in part resiliently expanded for the purposes aforementioned, with the resilient expansion of the tube being achieved solely by the tube-compressing action of the roller means.

A further object of the present invention is to provide a pump of this type in which the aforementioned distortion-restrained tube part is an outer part of the displacement tube section next to and held againstthe surrounding track, and the tube displacement section is of such large width radially of the track as to be resiliently expanded for the purposes aforementioned by the tubecompressing action of the roller means.

It is another object of the present invention to provide a pump of this type in which the displacement section of the tube in non-compressed condition is generally oval in cross-section with its longer axis extending parallel to the center axis of the track, so that the inner non-restrained part of this displacement section offers to the roller means less resistance to its distortion and resilient expansion into more round cross-sectional shape than would a displacement tube section of the same mean cross-sectional area but of circular cross-section. As a result, the tensile stresses to which the displacement tube section is subjected by virtue of its resilient expansion for a contemplated increase of its volume and for adequately re-enforcing the tube against collapse under atmospheric pressure at higher operating speeds of the pump, are of such relatively small magnitude as not appreciably to shorten the useful life of the tube, if at all, and the driving force required by the roller means for the operation of the pump is of accordingly small magnitude. I

It is a further object of the present invention to provide a pump of this type in which the displacement tube section is generally oval in cross-section as aforementioned, and the inlet and outlet legs of the tube are at least near and at their ends circular in cross-section and of a diameter substantially equal to the short axis of the generally oval cross-sectional shape of the displacement tube section, whereby the cross-sectional area of the latter is larger than that of either the inlet or outlet leg of the tube. As a result, the inlet and outlet legs of the tube may readily be connected with conventional cylindrical conduits and, far more importantly, for a given track diameter and,

hence, size of the pump the dimension of the displace menttube section radially of the track, i.e., the short axis of its generally oval cross-section, may be selected without any consideration of the desired fluid holding and displacing volume of this tube section and solely with a view toward achieving a desired maximum resilient expansion of the same by the action of the roller means, yet this tube section may have any desired maximum fluid holding and displacing volume on simply elongating the same cross-sectionally in the direction of its longer axis to the necessary extent.

Other objects and advantages will appear to those skilled in the art from the following, considered in conjunction with the accompanying drawings.

In the accompanying drawings, in which certain modes of carrying out the present invention are shown for illustrative purposes:

'Fig. l is a front view of a pump embodying the present invention;

Fig. 2'is a front view of the same pump with the cover removed to show the parts therein;

Fig. 3 is a longitudinal section through the pump;

Figs. 4 and 5 are transverse sections through the pump as taken on the lines 4-4 and 55, respectively, of Fig. 1;

Fig. 6 is a transverse section through the pump similar to that of Fig. 3, but showing the operating parts of the pump in a different position;

Fig. 7 is a'fragmentary section taken on the line 7-7 of Fig. 6;

Fig. 7A is a section, at a reduced scale, through a prominent part of the pump;

Fig. 7B is a fragmentary section through a pump embodying the present invention in a modified manner;

Fig. 8 is a fragmentary section through a pump ernbodying the present invention in another modified manner;

Figs. 9 and 10 are fragmentary sections through a pump embodying the present invention in a further modified manner;

Fig. 11 is a front view, with certain parts removed, of a a pump embodying the present invention in still another modified manner;

3 lines 13--13 and 1414, respectively, of Fig. 11;

Fig. 15 is a fragmentary section through the modified pump of Fig. 11, showing the operating parts thereof in a certain cycle position;

Fig. 16 is a fragmentary section taken on the line 16-16 of Fig. 15; and

Fig. 17 is a chart depicting the output capacities of the modified pump of Fig. 11 under dififerent conditions.

Referring to the drawings, and more particularly to Figs. 1 to 6 thereof, the reference numeral 20 designates a pump having a casing 22 with rear, bottom and

side walls

24, 26 and 28, respectively, of which the side wall 28 forms an inner arcuate track 30 which presently is substantially semi-circular about a center axis xx. The casing '22 is open at its front and is closed thereat by a removable cover 32. Located in the casing 22 is a resiliently flexible and resiliently stretchable tube 34 which presently is U-shaped, having opposite fluid-conducting legs 36 and-38 and an intermediate fluid displacement length or section 40. The tube 34 normally rests with its displacement section 40 against the track 30, and its legs 36 and 38 are with their ends fixed to the casing 22, presently by being slipped over and clamped at 41 and 43 to the inner ends of

co'nduits

42 and 44, respectively, which are suitably secured in the bottom wall 26 of the casing 22.

Also provided in the casing 22 is a rotor unit 46 carrying rollers 48 and being turnable about the center or track axis xx. To this end, a drive or rotor shaft 50, which is journalled in antifriction bearings 52 and 54 in the casing 22 and cover 32, respectively, carries a hub 56 to the ends of which are suitably secured arms 58 and 60. Connecting the adjacent ends of these arms 58 and 60 are cross-pins 62 on which the rollers 48 are journalled, preferably through intermediation of antifriction bearings 64 (Fig. 3). The rollers 48, which presently number two and are diametrically opposite each other, are so spaced from the track axis xx that their peripheries will compress to full closure any adjacent part of the displacement tube section 40 on the track 30 against the latter.

Assuming now that the tube leg 36 is in the inlet leg which through the conduit 42 and a hose connection 66 (Fig. 3) is in communication with a fluid, and in the present example with a supply of liquid L to-be-pumped, the rotor unit 46 will, for proper performance of the pump, be driven by hand or power clockwise as viewed in Figs. 2, 3 and 6. Thus, with the rotor unit 46 passing in its clockwise drive through the momentary angular position of Fig. 6, the presently leading roller 48a approaches the end of its present tube-compression cycle, while the presently trailing roller 48b approaches the start of its next tube-compression cycle, each roller performing a tube-compression or operating cycle while progressively compressing the displacement tube section 40 once against the track 30 throughout. n continued clockwise rotation of the rotor unit 46 beyond the position shown in Fig. 6, the trailing roller 48b will reach the start of its operating cycle before reaching the mo mentary angular position shown in Fig. 3 in which the leading roller 48a has not quite reached the end of its present operating cycle, this by virtue of the fact that the circular extent of the track 30 is presently somewhat in excess of a semicircle. With both rollers 48 thus compressing the adjacent parts of the displacement tube section 40 against the track 30 (Fig. 3), the space in this tube section between the compressed parts thereof and the previously admitted liquid L therein are fully sealed from the remainder of the tube until the leading roller 48a on continued clockwise rotation of the unit 46 reaches the end of its present operating cycle. When the leading roller 48a reaches and moves beyond the end of its present operating cycle, the sealed space in this tube section will open to the outlet leg 38 and the trapped liquid in this tube space will on continued clockwise rotation of the unit 46 be displaced therefrom and discharged through the outlet leg 38, the discharge of this liquid being completed when the trailing roller 48b reaches the end of its presently started operating cycle. Of course, as the trailing roller 48b starts and continues its present operating cycle (Fig. 3), the part of the tube immediately therebehind will more and more resiliently recover from its roller-induced distortion and the ensuing partial vacuum therein will draw liquid thereinto. Thus, the presently trailing roller 48b will during its present operating cycle not only cause liquid to be drawn steadily into the part of the tube immediately therebehind, but it will also discharge the liquid ahead of it in this tube section from the latter and through the outlet leg 38 of the tube. The rollers 48 of the present arrangementthus have alternating operating cycles, with the operating cycle of either roller starting at least simultaneously with,'and in no event subsequent to, the end of an operating cycle of the other roller in order to render the pump at all operative.

In accordance with an important aspect of the present invention, provisions are made resiliently to expand the displacement tube section during each cyclic compression thereof for increased output capacity of the pump for its size. To this end, an outer part of the displacement tube section 40 is retained, or substantially retained, on the surrounding track 30 on the one hand, and the displacement tube section is so dimensioned that the same will resiliently be expanded as and for the aforementioned purpose by the compressing action of the rollers 48 on the other hand.

The tube retaining means is presently in the form of a stiff leaf-like member or liner 70 in the tube 34 which bears against an outer peripheral part of the displacement section 40 thereof and holds the same against the surrounding track 30 rather firmly, and in any event sutficiently firmly to hold it against separation, or at least against appreciable separation, from the track underthe stresses induced in the displacement tube section by virtue of its cyclic compression and ensuing distortion. The ends of the leaf member 70 extend into the tube legs 36 and 38 and are suitably secured to lug

extensions

72 and 74 on the

conduits

42 and 44, respectively.

The resiliently flexible and stretchable tube 34, which is preferably molded to shape (Fig. 7A), is presently of substantially uniform wall thickness throughout and may be of the same or different cross-sectional shape and size throughout. However, the mean cross-sectional dimensectional dimentions of the displacement tube section 40, in comparison to the track diameter are of real significance for achieving the stated objective of resilient expansion of the displacement tube section for increased output capacity of the pump. Thus, while the described retention of the outer part of the displacement tube section 40 on the track 30 and the firm anchorage of sions of the tube 34, and in particular the mean crossthe ends of the tube legs 36 and 38 to the fixed

conduits

42 and 44 are important factors toward achieving the desired resilient expansion of the displacement tube section 40 under the compression action of the rollers 48, these factors alone will never bring about the desired objective if the mean cross-sectional size of the tube, and particularly of the displacement section thereof, in comparison to the track diameter, is so small that the displacement of the roller-engaged tube parts at any instant is fully compensated by mere cross-secti0nal distortion of the tube length behind the leading roller and without any resilient stretch, cross-sectionally expansionwise, of the displacement tube section between the acting rollers.

-It has been found that the tube 34 (Fig. 7A) is one among several other tubes of different dimensions which in the pump of Figs. 1 to 6 has by the action of the rollers and on each operating cycle of each roller been resiliently expanded for increased output of the pump.

Accordingly, the following data of the tube 34 in Fig. 7A

4 for instance, is of circular cross-section and of the same diameter and wall-thickness througout. The displacement tube section 40 is semicircular in extent about the axis A with the outer periphery 80 thereof having a radius R substantially equal to the track radius r (Fig. 3). The tube legs 36 and 38 lead tangentially from the displacement tube section 40 and they are of sufficient longitudinal extent for their facile slippage over and clamped attachment to the

conduits

42 and 44 when the tube is placed in the pump casing 22 with the rotor unit 46 removed. With the exemplary tube 34 specified as being of the same circular cross-section throughout, the diameter of its circular cross-section is such that the radius R of the inner periphery 82 of the displacement tube section 40 is somewhat less than one-half the length of the radius R of its outer periphery 80 and, hence, of the l track radius r.

i are really fully closed, the leaf member 70 thereat being completely embedded in the tube material and these tube parts being otherwise compressed to full leak-proof closure. With the pump in operation, and assuming that the rotor unit 46 in its exemplary clockwise drive passes through the momentary angular position shown in Fig. 6, the rollers 48 clearly have already displaced the adjacent tube parts beyond the extent at which their displacements would be fully compensated by merecross-sectional distortion without resilient stretch of the rest of the tube between the presently leading roller 48a and the tube anchorage on the inlet conduit 42. Hence, with the roller unit 46 in the momentary position of Fig. 6 and with an outer part of some substantial width of the displacement tube section 40 retained on the track 30 by the, leaf member 70, the resilient stretch to which the non-retained part of the tube between the leading roller 48a and the tube anchorage on the inlet conduit 42 is subjected exerts itself in cross-sectional expansion and, hence, increase in volume of that length of the displacement tube section which presently spans the rollers 48. This cross-sectional expansion and ensuing increase in volume of this roller-spanning length of the displacement tube section in the roller unit position of Fig. 6 is also indicated in Fig. 7 for one cross-section thereof the area of which is larger than it would be if the tube displacement by the rollers were fully compensated by mere distortion without resilient stretch of the tube length behind the leading roller 48a. As the rotor unit 46 turns "beyond the position in Fig. 6 and until the trailing roller 48b starts its next operating cycle, presently before reaching the angular position in Fig. 3, the resiliently stretch of the non-retained part of the tube length behind the pump, the volume of the roller-spanning length of the displacement tube section 4% will through resilient expansion be gradually increased as each roller moves toward its starting positionfor its next operating cycle,

and reaches its maximum increased volume as each roller starts its next operating cycle for maximum increase of the output capacity of the pumpv The tube-retaining leaf number in conjunction with the explained resilient stretch of the tube 34 by Virtue of the action of the rollers 48 also secures the important advantage of effectively re-enforcing the tube against collapse under atmospheric pressure at higher operating speeds of the pump. Thus, the leaf member 70, by virtue of its stiff liner function on the outer part of the displacement tube section 40 and the extention of its ends into the tube legs and anchorage to the fixed

conduits

42 and 44 in close proximity to the sides of the tube legs most remote from each other, positively prevents any appreciable collapse under atmospheric pressure of the outer portion of the tube length which leading roller and the described advantages springing therefrom will also be enhanced the closer the conduits '42 and 44 are arranged to each other.

The tube 34 actually shown in the pump 20 (Figs. 4, 5, and 7) is slightly modified from that shown in Fig. 7A by having in the outer part of its displacement section 40 an internal recess 86 of a width and depth to receive the leaf member 70 substantially fittingly. By providing this recess 86 in the tube for substantially fitting reception of the leaf member 70, the tube material will not be pinched by this leaf member under the periodic tube compression when the pump is operating, whereby the useful life of the tube is greatly prolonged.

While the tube 34 in the described pump 20 is provided with the internal recess 86 for protection from the leaf member 70, the tube 34a in the modified pump 20a of Fig. 7B is not so recessed internally and is of uniform wall thickness. However, the tube 34a is protected from the leaf member 70a by virtue of the provision in the track 30a of a recess 90 which receives substantially fittingly that portion 92 of the outer part of the displacement tube section 40:: which is displaced by the leaf member 70a on roller compression of the tube thereat. Fig. 8 shows another modified pumparrangement 20b in which two spaced leaf members 7012 serve to retain an outer part of the displacement tube section 40b on the track 3%. Also, neither the track 3012 nor the displacement tube section 4% is recessed for protection of the tube material from the leaf members, and the rollers are instead peripherally grooved at 94 for this purpose.

While in the pump arrangements described so far the outer part of the displacement tube section is retained on the track by a leaf member in the tube, Figs. 9 and 10 show a pump 290 in which the outer part of the displacement section 400 of the tube 340 is retained on the track 300 by being interlocked therewith. To this end, the outer part of the displacement tube section 40c is provided with an external cross-sectionally dovetailed rib formation 96 which is firmly anchored in a cross-sectionally dovetailed groove 98 in the track 300. For the placement of the tube rib formation 96 and its firm anchorage in the dovetailed groove 98 in the track 300, the casing 220 is formed of two complementary halves or sections 100 and 102 which are provided with complemental parts of the dovetail groove 98 and are secured together by bolts 104.

Figs. 11, 12 and 15 show another pump 20d which -may be of the same overall size as the described pump 20 of Figs. 1 to 6, yet has an output capacity which is considerably larger than that of the pump 20. This considerably larger output capacity of the present pump 20d" in comparison to that of the pump 20 is achieved without any additional parts and in fact without any change of any of the pump parts save a dimensional change in a portion only of the tube 34d. Thus, the larger output capacity of the present pump 20d in comparison to that of the pump 20 is solely predicated on making the displacement section 40d of the tube 34d of a mean crosssectional larger area than that of either of its fluid-conducting

legs

36d and 38d or of that of the displacement section 40 of .the tube 34. Advantageously, and as shown in Figs. 11 and 12, in which the rotor unit 46d is omitted for clearer illustration, the cross-sectional dimension d of the displacement tube section 40d radially of the track 30d is carried uniformly throughout the tube 34d, and this tube dimension d is in the present instance equal to the radial cross-sectional dimension D of the displacement section 40 of the tube 34 (Fig. 7A). However, the cross-sectional dimension d of the displacement tube section 40d parallel to the track axis x'-x' is larger than its dimension d (Fig. 12), whereby the larger crosssectional area of the displacement tube section 40d in comparison to that of either of the

tube legs

36d and 38d is achieved. Advantageously, the displacement tube section 40d is generally oval in cross-section with its longer axis extending parallel to the track axis x'--x', so that the part of the displacement tube section 40d other than that retained on the track 30d by the leaf member 70d offers to the rollers 48d (Fig. 15) less resistance to its distortion and resilient expansion into more round crosssectional shape (Fig. 16) than would a displacement tube section of the same cross-sectional area but of circular cross-section. As a result, the tensile stresses to which the displacement tube section 40d is subjected by virtue of its resilient expansion for a contemplated increase of the volume of the roller-spanning length thereof and for adequately re-enforcing the tube against collapse under atmospheric pressure at higher operating speeds of the pump, are of such relatively small magnitude as not appreciably to shorten the useful life of the tube, if at all, and the driving force required by the rotor unit' 46d for the operation of the pump is of accordingly small magnitude.

The displacement tube section 40d of the tube 34d is of uniform generally-oval cross-section and cross-sectional area throughout its extent between its

ends

106 and 108 at which the same is continuous with the

respective tube legs

36d and 38d. Advantageously, the

tube legs

36d and 38d are near and at their ends of circular cross-section (Fig. 14) for facile connection with the conduits 42d and 44d, the cross-section of these

tube legs

36d and 38d gradually changing from generally oval at their continuations with the displacement tube section 40d to circular near and at their ends with which they are attached to the conduits 42d and 44d. Thus, Fig. 13 shows an intermediate cross-section of the tube leg 36d.

The increased output capacity of the present pump 20d over that of an identical pump with a tube of uniform cross-section of the diameter d throughout is quite apparent, yet the size of the pump remains the same. To demonstrate the elongation of the innermost part of the tube 34d under the action of the rollers 48d, which clearly indicates a quite substantial resilient stretch of the tube behind the presently leading roller 48d in any event, this same innermost part of the tube 34d is in Fig. 15 shown in the dot-and-dash line position which it will assume when the rotor unit 46d is removed from the pump.

The chart of Fig. 17 shows the actual output of a pump, such as that of Figs. 11 and 12, with the exem' plary tube 36d, under ditferent operating conditions. The tube actually used in this exemplary pump performance was molded from rubber and its wall thickness was substantially uniform throughout and somewhat over Its dimension d (Figs. 11, 12 and 14) was approximately 1 /8, and its dimension d (Fig. 12) was approximately 1%". The legs of the tube extended parallel to each other and the outside diameter D' (Fig. 11) of the displacement section thereof was approximately 3%", be-

fore the tube was placed into the pump casing 22d. The tube fairly fitted in the pump casing, with the tube legs brought closer together for their attachment to the conduits 42d and 44d.

The pump was at first operated without the tube retaining leaf member 70d, with the output of the pump indicated by the dotted line in the chart of Fig. 17. Thus, it will be observed from Fig. 17 that the output of the pump increased proportionately with its operating speed up to approximately 55 r.p.m. at which approximately 2 gallons per minute were pumped. The output of the pump continued to increase at operating speeds above 55 r.p.m. but no longer proportionately therewith, and the maximum output was reached in the neighborhood of 110 r.p.m. at which slightly over 3 gallons per minute were pumped. At operating speeds over llO r.p.m. the output of the pump decreased progressively more rapid due to increasing partial collapse under atmospheric pressure of the tube on the intake side thereof.

The same pump was then operated with the leaf member 70d in place, with the output of the pump indicated by the solid line 122 in the chart of Fig. 17. Thus, it Will be observed from Fig. 17 that the output of the pump increased proportionately with its operating speed up to approximately 125 r.p.m. at which approximately 5 gallons per minute were pumped. At operating speeds above 125 r.p.m. the output of the pump still increased, but no longer proportionately with the operating speed. Thus, the output of the pump increased to somewhat less than 7 gallons per minute at an operating speed of approximately 250 r.p.m., and then began to decrease at still higher operating speed.

In comparing the output of the same pump with and without the leaf member 70d, it becomes strikingly apparent that the presence of the leaf member in the tube more than doubles the output capacity of the pump. This far greater capacity of the pump with the leaf member in place is, of course, due to the ensuing resilient stretch of the tube in action which, as explained, not only increases the volume of the roller-spanning length of the displacement tube section, but cooperates with the leaf member in greatly re-enforcing the tube against partial collapse under atmospheric pressure at its intake side. It appears from the comparative output of the exemplary pump with and without the leaf member (Fig. 17) that the re-enforcement of the tube at its intake side against partial collapse under atmospheric pressure by virtue of the presence of theleaf member in the tube is particularly pronounced and accounts to a large extent for the extraordinary increase of the output capacity of the pump over that of the same pump with the leaf member removed. However, the chart of Fig. 17 also shows that the output of the pump with the leaf member in place is definitely increased over that of the same pump Without the leaf member, solely by virtue of the resilient expansion and, hence, increase in volume of the roller-spanning length of the displacement tube section when the leaf member is in place. Thus, the straight part of the solid line 122 rises more steeply than the straight part of the dotted line 120, indicating clearly the displacement of a larger volume of liquid per roller cycle when the leaf member is in place than when the same is removed. For example, the pump without the leaf member delivered 2' gallons per minute at a relatively low operating speed of somewhat over 50 r.p.m., while the same pump with the'leaf member in place and at the same relatively low operating speed delivered approximately 2 /5 gallons. While this particular increase of the output of the pump with the leaf member in place, which is due solely to resilient expansion and, hence, increase of the volume of the roller-spanning length of the displacement tube section, is not overly large in the present exemplary pump, nevertheless the increase of the output of the pump solely by virtue of this resilient tube expansion is definite and proves the point in question. Moreover, the dimensions of the tube may readily be selected so that the increase in the output capacity of the pump solely by virtue of resilient expansion and ensuing increase in volume of the roller-spanning length of the displacement tube section, will be considerably larger.

The invention may be carried out in other specific ways than those herein set forth without departing from the spirit and essential characteristics of the invention, and the present embodiments-are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.

What is claimed is:

1. In a pump, the combination of a casing providing an inner arcuate track with a center axis, a resiliently flexible and resiliently stretchable tube in said casing having fiuid conducting legs fixed to the latter and an intermediate fluid displacement section surrounded by said track; means holding against said track an adjacent outer part of said intermediate tube section; and a rotor unit mounted in said casing for rotation about said track axis and having a plurality of rollers equally radially spaced from said track axis so that each roller will with its periphery compress to full closure an adjacent part of said intermediate tube section against the adjacent track with said rollers being also so equi-angularly spaced from each other that successive rollers will in at least one angular position of said unit compress to full closure the respective adjacent parts of said intermediate tube section against said track, and said intermediate tube section in its non-compressed condition being of a Width radially of said track to extend toward said track axissufficiently closer than any roller periphery that an inner part thereof is resiliently stretched by and between successive rollers of the driven rotor unit on their closing of said tube section for periodic resilient expansion of the latter into a larger volume than it would have if said inner part thereof were resiliently non-stretched.

2. The combination in a pump as set forth in claim 1, in which said tube holding means is a stiif liner in said tube bearing against said outer part of said intermediate tube section and extending through said tube legs and being secured with its ends to said casing.

3. The combination in a pump as set forth in claim 1, in which said tube holding means is a stiif leaf mem ber in said tube bearing against said outer part of said intermediate tube section and extending through said tube legs and being secured with its ends to said casing, and said outer tube section part is internally recessed for substantially fitting reception of said leaf member.

4. The combination in a pump as set forth in claim 1. in which said tube holding means is a stiif leaf member in said tube bearing against said outer part of said intermediate tube section and extending through said tube legs and being secured with its ends to said casing, and said track is adjacent said outer tube section part provided with a recess of such dimensions as to receive sub stantially fittingly that portion of said outer tube section part displaced by said leaf member on compression to full closure of any part of said intermediate tube section against said track.

5. The combination in a pump as set forth in claim by said leaf member on compression to full closure of any part of said intermediate tube section against said in which said intermediate tube section is in non-stretched condition of generally oval cross-section with the longer axis thereof extending substantially parallel to said track axis.

7. In a pump, the combination of a casing providing an inner part-circular track with a center axis; a resiliently flexible and resiliently stretchable tubein said casing having an intermediate fluid displacement section surrounded by said track and opposite fluid conducting legs leading tangentially from said intermediate section and being fixed at their ends to said casing; means holding against said track an adjacent outer part of said intermediate tube section; and a rotor unit mounted in said casing for rotation about said track axis and having a plurality of rollers equally radially spaced from said track axis so that each roller within the angular confines of said track will with its periphery compress to full closure an adjacent part of said intermediate tube section against said track, with said rollers being also so equi-angularly spaced from each other that successive rollers will in at least one angular position of said unit be within the angular confines of said track, said intermediate tube section in its non-compressed condition having a mean cross-sectional area larger than that of either of said tube legs and being of a width radially of said track to extend toward such track axis sufficiently closer than any roller periphery that an inner part thereof is resiliently stretched by and between successive rollers of the driven rotor unit on their closing of said tube section for periodic resilient expansion of the latter into a larger volume than it would have if said inner part thereof were resiliently non-stretched.

8. The combination in a pump as set forth in claim 7, in which two conduits lead from and are fixed to said casing with said tube legs slipped over the inner ends of the respective conduits and secured thereto, and said tube holding means is a stiff leaf member in said tube bearing against said outer part of said intermediate tube section and extending into said tube legs and being secured with its ends to said inner ends of the respective conduits.

9. The combination in a pump as set forth in claim 7, in which said track is of substantially semi-circular extent, said rollers are two in number and are diametrically opposite each other with respect to said track axis, two closely adjacent conduits lead from and are fixed to said casing with said tube legs slipped over the inner ends of the respective conduits and secured thereto, and said tube holding means is a stiff leaf member in said tube bearing against said outer part of said intermediate tube section and extending into said tube legs in close proximity to their sides most remote from each other and being secured with its ends to said inner ends of the respective conduits.

10. In a pump, the combination of a casing providing an inner track of substantially semi-circular extent about a center axis; a resiliently flexible and resiliently stretchable tube in said casing having an intermediate fluid displacement section surrounded by and resting against said track and opposite fluid conducting legs leading tangentiaily from said intermediate section and being fixed at their ends to said casing; means holding against said track an adjacent outer part of said intermediate tube section;and a rotor unit mounted in said casing for rotation about said track axis and having two diametrically opposite rollers equally spaced from said track axis so that each roller within the angular confines of said track will compress to full closure an adjacent part of said intermediate tube section against said track, the crosssection of said intermediate tube section in non-compressed condition being such that its one axis parallel to said track axis is at least as long as its other axis radially of said track axis and the length of said other axis exceeds one-half the length of the track radius sufficiently so'that an inner part of said tube section is resiliently stretched by and between said rollers of the driven rotor unit on their closing of said tube section for periodic resilient expansion of the latter into a larger volume than it would have if said inner part thereof were resiliently non-stretched.

11. The combination in a pump as set forth in claim 10, in which the mean cross-sectional area of said intermediate tube section in noncompressecl condition is larger than that of either of said tube legs, the crosssection of said intermediate tube section in non-compressed condition is generally oval with said one axis thereof being longer than said other axis, and said tube legs are at least at their ends circular in cross-section and of a diameter substantially equal to said other axis.

References Cited in the file of this patent UNITED STATES PATENTS 314,851 Kelly Mar. 31, 1885