US2926006A - Fluid mixing apparatus - Google Patents

Description

Feb. 23, 1960 72 Jzoraye 7a Prams: Syr/fm J. ISREELI FLUID MIXING APPARATUS Filed Jan. 15, 1958 INVENTOR. Ja cl? [area/z M8311 M k $4 M ATTORNEYS FLUID MIXING APPARATUS Jack Isreeli, Tuckahoe, N.Y., assignor to Technicon Instruments Corporation, Chauncey, N.Y., a corporation of New York Application January 15, 1958, Serial No. 709,060 3 Claims. (Cl. 259-7) The present invention relates to apparatus for mixing liquids and, more particularly, pursuant to the primary object of the present invention, to apparatus primarily intended for thoroughly mixing two or more liquids at least one of which is a viscous liquid.

Another object is the provision of apparatus for supplying a continuous flow of a liquid mixture comprising at least two liquids mixed together in predetermined proportion during the flow of the individual liquids to the mixing device.

A further object of the invention is to provide a mixing apparatus which includes a mixing device which is operable to produce a high degree of turbulence of the liquids in the device with consequent thorough mixing of the liquids.

The above and other objects, features and advantages of the present invention will be more fully understood from the following description taken in connection with the accompanying illustrative drawings of the presently preferred embodiment of the invention.

In the drawings:

Fig. 1 is a view, partly in section, illustrating a liquidmixing apparatus of the present invention; and

Fig. 2 is a sectional view along the line 2-2 of Fig. 1.

Referring now to the drawings in detail, there is represented in Fig. 1 a liquid-mixing apparatus which comprises a mixing device 10 and a fixed displacement pump 11, for transmitting the liquids under positive pressure to said mixing device. In order to mix the liquids in predetermined proportions, the pump is a proportioning or metering pump. Said pump is preferably, but not necessarily, of the type which comprises a plurality of resiliently flexible tubes 11a and 11b which are compressed progressively along their lengths against a platen 11c by a plurality of pressure rollers 11d which are moved in unison longitudinally of said tubes by the driven endless chains or belts 11:. The tubes 11a and 11b have predetermined internal diameters according to the proportions in which the liquids are to be mixed in the mixing device 10. A proportioning pump of this type which I presently prefer for this purpose is shown and described in detail in US. application, Serial No. 676,- 086, filed August 5, 1957, by me and Andres Ferrari, Jr. As illustrated more-or-less diagrammatically in Fig. l, the liquids to be mixed are supplied to tubes 11a and 11b and are transmitted by the tubes 11a and 11b to the mixing device 10.

Mixing device 10 comprises a casing 12 formed from a suitable plastic or other material and constituted by a base 14 and a cover 16 which define a mixing chamber 18 therebetween. As shown in Fig. 1 cylindrical recess 18 includes a cylindrical peripheral wall 20 and an end wall 22. Centrally defined in wall 22 is a fluid outlet opening 24. Extending longitudinally through base 14 is a central bore 26 having an enlarged portion 28 at the end thereof in communication with outlet opening 24. Cover 16 is detachably secured to base 14 by means of screws 30 engaging in threaded apertures 32 in base nited States Patent 14. A central recess 17 is provided in cover 16 for a thrust ball bearing 19.

A rotary impeller 34 is mounted in casing 12 and comprises a shaft 38 having a rotary bearing in bore 26 of said casing. The lower end of said shaft engages said anti-friction, end thrust bearing 19. An electric motor 40 is connected to the impeller shaft 38 for rotating the latter.

The impeller is provided with a hub 42 and a plurality of rigid radially extending impeller blades 44 which extend laterally between and close to the inner surface of end wall 22 of chamber 18 and the inner surface of cover 16 which forms the opposite end wall of said chamber. The outer ends of said impeller blades lie close to the cylindrical wall 20 of the mixing chamber. Said impeller blades are integral with or fixed to the -central hub part 42 which is secured to shaft 38. As illustrated in Fig. 2, said hub part 42 is of rectangular contour, and is so dimensioned in relation to outlet opening 24 in end wall 22 that only corner portions of part 42 extend beyond the peripheral edge of said opening and overlap end wall 22 adjacent said peripheral edge, whereby the liquids pumped into chamber 18 and acted upon by said impeller blades may flow out of said chamber through opening 24.

Chamber 18 is provided with inlet fittings or nipples 43 for connecting the tubes 11a and 11b to said chamber. The outlet bore 28 communicates with a passage 54 in casing 12, and an outlet fitting or nipple 56 is provided for the connection thereto of a tube or conduit for the liquid mixture. Passage 54 also communicates with a chamber 60 to receive overflow, which may be exhausted through the nipple or outlet 62. Said chamber 60 also provides an off-take for vapors or gases which might be separated from the liquid mixture. As illustrated in Fig. 1, the liquid mixture is transmitted from the mixing chamber by the pressure generated by pump 11 and flows through the outlet 56 to the processing system. If the quantity of the liquid mixture required in the processing system is less than the quantity delivered into passage 54, the excess is exhausted through collection chamber 60 and outlet 62, and if the liquids are such that vapors or foam might formas a result of the mixing operation, said collection chamber provides means which is of aid in the separation of said vapors or foam from the liquid mixture.

The manner in which the fluids are mixed in transit through mixing chamber 18 will now be explained. The normal tendency of the impeller blades 44 is to develop a pressure differential increasing from the root of the impeller blades 44 attached to hub 42 to the tips thereof. The pressure differential tends to urge the flow of fluid from said hub to the tips. However, since the flow of the fluids within the mixing chamber 18 is positively directed by pump 11 from the inlets 43 to the outlet opening 24 and passage 59, the fluids within mixing chamber 18 flow in a direction opposite to the-normal urging of the impeller. This action creates a great deal of turbulence within mixing chamber 18 resulting in an improved intermingling and mixing of the fluids therein. More specifically, as the fluid flows in through the inlets 43 each blade in passing across the inlet opening separates a minute quantity of the fluid from the incoming stream and carries it to the inlet opening supplying the second fluid to be mixed. This operation is repeated by each of the blades. In this mannerthe mixing of the fluids takes place between minute or fractional quantities of the fluids which are thus separated by the' blades from the incoming streams. The mixing action is further increased by the action of the hub 42 in relation to the outlet opening 24. More particularly during the rapid rotation of the impeller the rotation of hub 42 in relation to opening 24 results in the repeated passage of small quantities of liquid from the mixing chamber 18 into outlet passage 28 with increased turbulence and consequent increased intermixing of these small quantities of liquid in the flow of the mixture through passages 28 and 54. It will be noted that the rotation of hub 42 results in division of opening 24 into a plurality of restricted smaller openings or passages which are displaced progressively around the axis of outlet opening 24 during the rotation of the impeller.

Optimum mixing is obtained by rotating the impeller at high speed. By way of example but without limitation, I have found that a speed of 8,000 rpm. of an impeller having four blades gives excellent results, the internal diameter of the chamber 18 being about one inch and its depth, axially of the impeller shaft being about twotenths of one inch and the impeller blades having only a minute clearance between the tips of the blades and the cylindrical wall of the chamber 18 and only a minute clearance between the side edges of the blades and the adjacent surfaces of the end walls, respectively, of said chamber. It will be understood also that other speeds may be employed, and the number of impeller blades may be increased and the impeller operated at lower speeds.

The mixing apparatus of the prment invention is well adapted to mix various liquids. By way of example, but without limitation, this apparatus has been found very effective to convert a very viscous water solution of sugar into a less viscous solution by mixing said vicous sugar solution with water. In this particular example, the decrease in viscosity was necessary or desirable in connection with an analysis of the sugar solution during the flow thereof through a colorimeter with concomitant treatment of the sugar solution during the flow thereof from the outlet 56 of the mixing device 10 to the colorimeter. In this and other processes, the pump 11 may be provided with additional tubes similar to the tubes 11a and 11b for supplying various processing fluids in predetermined proportions either to the mixing device 10 or directly to various devices, without passing through the mixing device, according to the requirements of the process at hand.

While the pump 11 is presently preferred for transmitting the liquids under pressure to and through the mixing device, it is within the scope of this invention to use other types of positive pressure pumps, for example, piston pumps, and it is also within the scope of this invention to provide a separate metering pump for each liquid.

While I have shown and described the preferred embodiment of my invention it will be understood that various changes may be made in the present invention without departing from the underlying idea or principles of the invention within the scope of the appended claims.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1. Fluid mixing apparatus, comprising a mixing chamber having a cylindrical inner wall provided with fluid inlet means for a plurality of fluids supplied thereto under pressure, said fluid inlet means being spaced radially outwardly of the cylindrical axis, said chamber having an end wall provided with fluid outlet means spaced radially inwardly from said inlet means, and a rotary impeller mounted for rotation about said cylindrical axis and provided with a plurality of radial blades positioned in said chamber and terminating in end portions disposed adjacent the cylindrical wall of said chamber and said chamber having opposite ends disposed close to the opposite side edges, respectively, of said blades whereby, upon rotation of said impeller, said end portions of the impeller blades travel in succession across said fluid inlet means and mix successive fractional portions of the incoming fluids with each other in said chamber during the flow of said fluids radially of said chamber from said fluid inlet means to said fluid outlet means, said impeller having a hub which is positioned over said outlet means and has portions which extend beyond the periphery of said outlet means and thereby restricts the passage of fluid from said chamber through said outlet means, the flow of the fluid being from said inlet means, through said chamber in the spaces between the impeller blades, and past the impeller hub to said outlet means.

2. Fluid mixing apparatus comprising a mixing chamber having a cylindrical peripheral wall and flat confronting end walls, and a rotary impeller disposed in said chamber and comprising a plurality of radial blades having their opposite side edges adjacent said end walls, respectively, and having their outer ends disposed adjacent said periperal wall, said chamber having fluid inlet means and fluid outlet means, positioned in spaced relation radially of the axis of rotation of said impeller blades, said fluid outlet means being nearer said axis than said fluid inlet means whereby fluids supplied under pressure to said inlet means passes radially into said mixing chamber toward said axis and is mixed in said chamber by said blades and flows from said chamber through said outlet means, said impeller having a part which is disposed adjacent said outlet and has peripherally spaced portions which extend beyond the peripheral edge of the outlet and divide the latter into a plurality of restricted openings which are progressively displaced around the axis of said opening during the rotation of said impeller, the flow of the fluid being from the inlet means, through said chamber in the spaces between said blades, and radially inwardly of said spaces to said outlet means.

3. Fluid mixing apparatus comprising a mixing chamber having a cylindrical peripheral wall provided with fluid inlet means and spaced confronting end walls, and a rotary impeller disposed in said chamber comprising a plurality of radial blades having their opposite side edges adjacent said end walls, respectively, and having their outer ends disposed adjacent said peripheral wall, fluid outlet means provided in one of said end walls of said chamber inwardly toward the axis of the chamber relative to said inlet means, and means on said rotary impeller in confronting relation to said fluid outlet means and rotatable with said impeller, said last mentioned means having peripherally spaced portions which overlap said one of the end walls adjacent said outlet means for dividing said fluid outlet means into a plurality of restricted openings which are progressively displaced around the axis of said impeller during rotation thereof, the flow of the fluid being from the inlet means, through said chamber in the spaces between said blades, and radially inwardly of said spaces to said outlet means.

References Cited in the file of this patent UNITED STATES PATENTS 1,804,604 Gilbert May 12, 1931 2,432,247 McAnallen Dec. 9, 1947 2,472,802 Bentley June 14, 1949 2,559,516 Russell July 3, 1951 2,736,534 Atkins Feb. 28, 1956 FOREIGN PATENTS 445,291 Germany of 1927

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