Resilient passage milking-type pump

June 6, 1961

C. W. DANN

2,987,005

RESILIENT PASSAGE MILKING-TYPE PUMP

Filed June 30, 1958

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2,987,005

Patented June 6, 1961

United States Patent Office

2,987,005

RESILIENT PASSAGE MILKING-TYPE PUMP Charles W. Dann, Cambridge, Mass., assignor to Standard

Duplicating Machines Corporation, Everett, Mass., a corporation of Massachusetts

Filed June 30,1958, Ser. No. 745,428

Claims. (Cl. 103—149)

This invention relates to pumps of the type in which a resilient fluid passage is simultaneously acted upon at spaced intervals by two or more compression members such as wheels. More particularly, this invention provides such a pump in which the passage is defined by a pair of members, only one of which was substantial resilience for deformation by the compression members.

In most prior art pumps of the character above referred to, a rubber tube of simple annular cross section has been formed into a loop or arc resting against a generally circular support or casing, and operated upon, over the inner periphery of the tubing arc, by two or more rollers, all operating about a central shaft. See for example U.S. Patents to Lee No. 2,804,023; Ferrara No. 2,102,523; and Connaught No. 2,314,281. Such pumps are subject to a number of disadvantages. First, the life of the rubber tubing is quite short because of wear of two different types, each however being quite substantial. One type of wear is caused by simple stresses within the tubing at the sides; when tubing annular in cross section is squeezed between two flat surfaces, as shown in FIG. 5 of the Lee patent above referred to, great stresses producing rapid wear are set up at the transverse extremities, producing early failure of the wall. Secondly, the rolling of roller compression members on the tubing tends to produce longitudinal stretching by virtue of a sort of squeegee effect; this stretching is compensated only periodically by a slip-back, and this intermittent stretching and slip-back produces additional wear to shorten the tubing life. An additional important disadvantage of these prior art pumps is that they are not of fully positive displacement, inasmuch as almost inevitably when the tubing is pressed there will be small open spaces left along the transverse edges thereof (see FIG. 5 of Seyler U.S. Patent No. 2,693,766). Finally, in pumps of the character above described difficulty has been experienced with transverse displacement of the tubing during operation. Attempts have been made to decrease the stresses along the transverse edges of the tubing in compression and also to prevent openings being left at such edges and nullifying complete positive displacement, by means of giving the tubing special internal configuration (for example, mouth-like, with sharp angles, easily closed at the transverse edges), several of which are disclosed in Seyler, above referred to. An additional configuration is disclosed in an article at page 88 of the February 9, 1956 issue of “Machine Design.” The molding or extruding of such cross sections, however, not only requires expensive, sharp-edged dies, but furthermore only alleviates to some extent the two problems just referred to, and does nothing to cure transverse slippage of the overall tube and longitudinal displacement wear.

It is a primary object of the present invention to provide a novel construction in which life of the resilient member is greatly prolonged, transverse displacement is substantially eliminated and longitudinal displacement is minimized, and in which openings along the transverse extremities of the passage are substantially eliminated to provide full positive displacement action in normal operation. Further objects are to provide a novel assembly which is relatively inexpensive to construct, and which may be assembled, disassembled, and reassembled easily, quickly, and without the need for exercise of any trained judgment; to provide for easy access, as for cleaning or inspection, to the pumping pasage itself or for replacement of the resilient element; and to provide an assembly adaptable to being permanently mounted from the rear, with subsequent partial disassembly as for the purposes indicated being easily possible from the front alone.

Novel features characteristic of the preferred embodiment of the invention include provision of a unit providing an arcuate pumping passage comprising a resilient, tire-like outer member and a non-resilient generally cylindrical hub-like core seated within the tire-like member, provision in the tire-like outer resilient element of a pair of side walls extending partially inwardly over each of the faces of the core, each side wall being formed in part with a bead in a generally semi-torus configuration, of an inner radially partially inwardly extending bulkhead, and of a generally crescent-shaped web integral with each side wall inwardly of the semitorus bead portions thereof and adjacent the bulkhead, and a pumping wall comprising generally parallel inner and outer surfaces defining each substantially an obtuse angle of approximately 135°, with the exception of a flat or relieved portion directly overlying the bulkhead; provision in the core for inlet of fluid through one passage and exit of fluid through another, and for a radially partially inwardly extending notch in the periphery thereof, the fluid inlet and outlet in said core extending each through the outer periphery thereof on respectively opposite sides of said notch, said bulkhead being seated in said notch; provision for holding the tire against the core on each side, to provide a sealed fluid passage, by a pair of members provided each with a circular groove semicircular in cross section to cooperate with the semi-torus, and flat surfaces inwardly and outwardly of said groove for seating against flat portions of the side walls outwardly of the semi-torus portions as well as flat crescentshaped webs inwardly thereof to provide complete sealing all around; fastening means, spring means, and stop means cooperating to provide for axial assembly of the above-mentioned units with a predetermined constant axial force to provide optimum sealing and freedom from stress; and a pair of inwardly biased Teflon tire rollers mounted to roll over the outside of the tire.

Other objects, features and advantages will appear from the following description of a preferred embodiment, taken together with the drawings thereof, in which:

FIG. 1 is an exploded isometric view of a pump according to the invention;

FIG. 2 is a front elevation of said pump, partially broken away;

FIG. 3 is a sectional view, partially broken away, at 3—3 of FIG. 2; and

FIG. 4 is a sectional view, partially broken away, taken at 4—4 of FIG. 3.

Referring now to the drawings, there is shown in FIG. 1 a rear plate assembly comprising a rear plate 10, and a pair of posts 12 and a hub 14 rigidly mounted thereon. Seated within the hub 14 is a bronze bearing 16 through which extends a drive shaft 18, which may be driven by any suitable means (not shown). Secured to the drive (shaft 18 as by brazing is a rotor disk 20 on which are rigidly mounted a pair of roller arm studs 22 and a pair of spring anchor posts 24. Pivotally mounted on each roller arm stud is a roller arm assembly comprising a roller arm 26 supporting near the inner extremity thereof a roller shaft 28, on which is rotatably mounted a wheel with a metal hub 30 characterized by a milled or grooved surface embedded in a Teflon tire 32. Springs 34 extending between the roller arms 26 and the anchor posts 24 bias the roller arms and rollers inwardly, although holes 36 in the rotor disk 20 set a limit to the in2,987,005 ward travel of the rollers, inasmuch as the roller shafts extend substantially through the holes 36, which are generally concentric with the roller shafts when the latter are in normal operating position, but which are somewhat larger so as to provide the desired freedom of movement in two directions while at the same time providing a stop against excess movement of the roller arms in either direction.

A front plate 38 has secured thereto by fastening means 40 the brass front disk 42, which has on its rear face, slightly inwardly of its outer periphery, a circular groove 43, which is semicircular in cross section. Urged toward the front disk 42 by means of screw 44 passing through bushing 46 and a hole 48 in the front disk 42 into the threaded inner portion 50 of the fastening member 40 are the disk spring 52, the rear disk 56, the tire-like element 58, and the core 60. All these elements, being secured to the front plate 38, may be removed from the elements above described by removing said plate. The screw 44 can be tightened down only a predetermined distance as determined by the length of the bushing 46, and the beryllium copper bent disk spring 52, acting between the flange 54 of the bushing 46 and the brass rear disk 56, when the bushing 46 is seated against the front disk 42, provides a predetermined amount of pressure between the rear disk 56 and the front disk 42, so that these parts hold together the resilient passage-defining element 58 and the non-resilient core 60 with the desired force without need for exercise of judgment on the part of the assembler.

The resilient passage-defining member 58, which in the preferred embodiment is rubber and very much resembles a tire, includes a pair of side walls 62. Around the outermost periphery of the side walls 62 is a flat surface 62α lying in a plane perpendicular to the axis of the tire-like element 58. Adjacent the flat surface 62α and inwardly thereof is a semi-torus 626 extending around the entire periphery on each side wall; these portions 62b of the side walls are seated in the grooves 43 and 64 of the front and rear disks respectively. Around most of the outer surface 66 of the pumping wall of the tire-like element 58, the same is defined by rotating two symmetrically disposed lines, at an obtuse angle to each, other of approximately 135°, about the axis of the element. The inner surface of the pumping wall is parallel with the outer surface 66; both are thus centrally bulged away from the outer surface 72 of the core 60. At one portion of the periphery, a flat 68 is provided. Extending radially inwardly of the tire-like element 58, from just below the center of the flat 68, is a bulkhead or wall 70. Adjacent the bulkhead 70 and a part of the side walls 62 are a couple of generally crescent-shaped webs, the outer surfaces 62c of which are in the same planes as the respective surfaces 62α.

Seated within the tire-like element 58 is the core 60, which may suitably be made from metal, and in the preferred embodiment is provided with a Teflon coating. The core 60 is provided with a cylindrical outer surface 72 in which is provided a notch 74 in which the bulkhead 70 fits. On each side of' the notch 74 is provided an opening into the cylindrical surface 72, and extending inwardly therefrom, an outlet port 76, and an intake port 78. These ports are integrally joined respectively with tubes 80 and 82. Extending around the side walls 84 of the core 60 on each side thereof and slightly inwardly from the outer surface 72 thereof, are a pair of grooves 86, into which the rubber of the tire-like element may be deformed slightly to improve the seal. The tubes 80 and 82 extend through holes 88 and 90 in the front plate 38 and aligned corresponding holes in the front disk 42, and may be connected with tubing leading from and to the zones between which pumping is desired.

The front plate 38 seats through the holes 92 against the abutting surfaces 94 of the posts 12 and is held down thereagainst by the screws 96.

In operation, the shaft 18 is driven to rotate the disk 20 which in turn rolls the two Teflon, or tetrafluoroethylene resin, tires 32 over the outer surface 66 of the pumping wall of the resilient passage-defining element 58, compressing it against the cylindrical outer surface 72 of the non-resilient core 60 to completely collapse the passage defined therebetween. As the rollers roll along, slugs of fluid ahead of each roller are forced toward the opening to outlet port 76 thereby, while in springing back to its normal position behind each roller said pumping wall draws in fluid from the opening of the intake port 78, whereby the desired pumping is achieved. The inner surface 98 of the pumping wall of the tire-like element 58 is substantially parallel with the outer surface 66 throughout. This configuration permits the outer, or pumping, wall of the resilient element, defined between the surfaces 66 and 98, to be flattened against the surface 72 by the rollers without any particular stress being imposed on the rubber at the transverse edges of the passage (i.e., adjacent the side walls 62), or elsewhere in the resilient element; substantially the entire deformation is in desirable compression rather than in undesirable tension. Additionally, this arrangement eliminates any openings alongside the transverse edges of the passage defined between the core 60 and the resilient element 58, so that positive displacement with full efficiency is achieved. In view of the positive grip on the sidewalls 62, including the semi-torus portions 626, of the flexible element by the disks 42 and 56, the problem of transverse movement of the resilient element is eliminated. And longitudinal displacement of the flexible element, with large intermittent back-slipping, is minimized to an extent hitherto unknown not only by the firm grip between the disks 42 and 56 on the flexible element completely therearound, which minimizes slippage or the squeegee effect, but additionally by provision of the Teflon tires 32, which permit easy continuous back-slippage rather than large intermittent backslippage. An extra similar desired effect is produced in the preferred embodiment by the Teflon coating on the core 60; though, of course, most of the advantages of the invention may be obtained without any use of Teflon as a part of any of these members.

Easy uniform rolling of the rollers about the entire periphery of the resilient element 58 is provided, for by the flat 68; because of the thickness of solid rubber over the bulkhead 70, the flat 68 is desirable to produce this smoothness of operation and avoid jumping of the rollers. The web surfaces 62c (like the wall surfaces 62α) extending inwardly of the semi-torus portions 626 are gripped between the side walls 84 of the core 60 and the abutting walls of the disks 42 and 56, and provide positive sealing alongside and inwardly of the bulkhead 70.

The unit is ideally adapted to be permanently mounted from the rear, as on a panel, the shaft 18 being if desired permanently mounted together with driving means therefor. The parts of the unit which may require periodic disassembly for inspection, cleaning or replacement of the resilient element, may be easily removed therefrom simply by unscrewing the two screws 96 and removing the front plate 38. to which all the parts on which the rollers operate are secured. This unit may be called the stator assembly. Though the rollers are inwardly biased, the stop means 36 above described limit the inward travel when the front plate 38 and associated parts are withdrawn, so that the latter may be easily reinserted without any need to separate the rollers beyond the separation enforced by the stop means 36. Disassembly of the stator assembly is completed simply by removing the screw 44, after which the front and rear disks 42 and 56 may be separated, the front disk remaining permanently attached to plate 38 by member 40, which is knurled along parallels to its axis to prevent relative rotation and force-fitted into the front disk; and the core 60 removed from the flexible element 58. Cleaning is thus very simple, as is repalcement. The stator

2,987,005 assembly is disassembled into only four separate parts: the front plate 38 (with attached front disk 42), the core 60, the resilient member 58 and the permanent rear disk assembly which consists of bushing 46, snap ring 99, spring 52 and rear disk 56. As the screw 44 is removed, the spring 52 relaxes, pulling bushing 46 out of disk 56 a little until snap ring 99 comes to rest on the bottom of counterbore 56α. The snap ring becomes thereby inaccessible which reduces the likelihood of tampering with the rear disk assembly (which is never taken apart while the axial freedom of bushing 46 in disk 56, as limited between the snap ring and the flange of bushing 46, permits the free clamping function of spring 52 above described). By reducing in this way the number of normally separate parts, errors in reassembling are made almost impossible. Reassembly is equally simple, and the desired degree of compression of the flexible element 58 between the disks 42 and 56 is easily and automatically achieved by the disk spring 52 when the screw is turned down until the bushing 46 seats against the front disk 42.

Although only one embodiment of the invention has been above described, other embodiments within the spirit and scope of the invention and the appended claims will of course occur to those skilled in the art. For example, the beads might be inwardly directed to cooperate with grooves provided therefor in the core.