US2520827A - Mixing machine - Google Patents

Description

Aug. 29, 1950 F. BEKEN 2,520,827

MIXING MACHINE Filed April 8, 1948 Inventor fkrz fi'KE/V Patented Aug. 29, 1950 UN I TED S TAT-ES PATENT ()FF ICE .MIXI-NG MACHINE Fritz Beken, Ilford, England Application A pl'iLS, 1948, Serial No. 19,770

This invention .relates to mixing machines used industrially for such purposes as the preparation of paints, gums in suspension, and similar viscous liquid mixtures.

-Mixing-appara-tus is 'known in which .a power driven shaft having an impeller .on its free end projects downwards into the materials which are to be .mixed together, contained, for example, in a suitable tank, which may be externally heated by a steam jacket or in any other convenient manner. In such apparatus it has also been proposed to provide .a tubular duct open at both ends, suspended or mounted so as to be 'immersed .in the .materials being mixed, coaxial with the impeller-drivingsha'ft, the object being to guide the flow of the .liquid mixture during the mixing operation, so that, for example, the liquids flow upwards externally of the immersed duct and/follow adownward return 'flowepath inside the duct.

Despite the above-described features, known mixing machines are, in many operations, not entirely satisfactory. While the materials in the lower portions-of a tank may beefiectively vmoved by the impeller, the uppermost strata may remain substantially 'unaifected, and even when conditions allow the desired uniform mixture to be attained, considerable time and power is required.

According to the present invention the efficiency of the apparatus is greatly increased by providing means to ensure that, over at least part of their circulatory -flow-path during the mixing operation, the materials are encouraged or constrained to follow asmooth helical .flow. For

this purpose there is provided, submerged in the 7 liquid mass under treatment, a conical funnel coaxial with the impeller shaft. The liquid mass is caused by the impeller to .fiow externally upwards around the external surface of the outer Walls of the cone and over its edge, wherea'fter it flows downwards in and through the conical funnel, there :following .a helical path around the funnel axis. uppermost edge of the funnel may, if desired, be provided with curved vanes adapted to guide the flowing materials into the funnel insuch a manner as to encourage helical flow therein. It is found that the included angle of the cone is of some importance in achieving optimum results, and for the purposes to which the invention is directed it is preferred that this angle shall be not less than 63 and not more than 816'. The form of impeller used may also afiect the results, and according to the invention it is prefer-red to employ .an impeller comprising substantially flat blades extending radially outwards from, and coplanar with the axis of, the impeller :shaft, and having their free outer ends curved forwards in the direction of movement when rotated by the motor.

One form of mixing -apparatus according to the invention (described, however, merely by way of example) is shown in the accompanying drawings showing in Figure 1 a side elevational section; and in Figure 2 a plan view thereof.

Referring to the drawings herewith, there is provided in a mixing machine according to the invention a. shaft 1 having secured at its lower end an impeller --2, running in bearings 3 in a cross-bar 4, and connected by gearing 5 to means such as a shaft 6 and driving wheel 1, whereby it can be driven from any suitable power source. The cross-bar 4 is adapted to rest across the rim of a tank 8 for the liquid and other materials being mixed, and may be removably secured to the edges of the tank by clamps or other suitable means if desired. When the cross-bar 4 is thus in position the lowermost end of the shaft I may run in end bearings 9 in the-bottom of the tank.

The impeller '2 is in the form of two blades, IB, l-l, ext'ending radially in diametrically opposite positions from the shaft l and at their outer ends being curved forward, as shown, towards the direction of rotational movement indicated by arrows in Figure '2.

Suspended from the cross-bar 4 by bolts or rods I2 is aiunnel '1 3 built-of steelor-other metals andcomprising an upper open-mouthed cone portion l4 and a lower open-ended cylindrical portion 15, the whole being substantially coaxial with the shaft 1. At spaced intervals standing "vertically upwards from the edge of the cone l4 and extending obliquely in relation thereto slightly inwards 'of the cone mouth, and outwards until "substantially in contact with the walls "of the tank 8, is a series of van-es l6 of a'rcuate shape, with curvature in such a sense as to encourage the liquid mass flowing from outside the cone l4 into the open mouth thereof to enter it in a helical flow path. The tank 8 may be provided with an outlet tube H and be supportedon angle-iron l'egs l8. If desired the tank may be jacketed "or surrounded by a coiled pipe, allowing it'to be hea'tedby steam or other suitabl'e medium; or it may be "fitted with electrical or other convenient heating means,

While, as will :be appreciated byp'ersons versed in this art, a liquid mass flowing downwards through the cone l4 and its outlet tube l5 will naturally follow a helical path (even in the absence of deflector vanes such as "5), such flow is greatly assisted by the vanes 16; and it is further found that while the effects desired can be partially achieved with apparatus, such as described above, wherein the relative dimensions of the different parts vary over a wide range, nevertheless optimum results are achieved if these dimensions are kept within certain limits. Thus it is preferred that the internally contained angle of the cone I shall be not less than 63 and not greater than 84. Further the radius of curvature of the deflector vanes It should preferably and not greater than The radius of curvature of the tips of the impeller blades H3, II should preferably be not less than and not greater than where R is the radius of the impeller. 'In addition the angle between two planes, containing the axis of the shaft I, one also containing theradial centre lines of the roots of the blades it, if and the other being tangential to the extreme tip of the forwardly-curved ends of the blades H}, H, should preferably be not less than 6 and not greater than 8.

dimensions of a machine such as described herein, as well as the overall size of the machine, may readily be varied according to the materials for which the machine is to be used and'the conditions under which it is to be operated. It will be seen that rotation of the impeller sets into motion the liquid mass in the tank 8 asa result of which it rises externally of the tube 15 and cone l4, flowing over the rim of the cone and descending through the cone and tube it, whereafter it is again urged along a similar circulatory path by theimpeller. On account of. the vanes l6 and the form of the cone [4 the liquid mass on entering the mouth of the cone is constrained to circulate about the axis of the shaft I and thus to follow a helical path in passing through the cone and smoothly into the tube I5. No substantial. zone of the liquid mass escapes this enforced circulation, andon account of the smooth helical flow intimate mixing of the in gredients resulting. in a more nearly homogeneous mixture in a shorter time and with less expenditure of energy than heretofore is ensured.

It should, however, be understood that various construction details of the machine described above maybe introduced according to operational requirements, without departing from the scope of the invention as defined in the appendant claims.

What I claim is:

1. Mixing apparatus for mixing solids in liquids comprising a cross-bar for resting across the edges of the container for the mass being mixed, at smooth-surface small-diameter driven shaft extending downwards from said cross-bar, an impeller mounted on the lower end of said shaft and an open-ended funnel device, including an upper inverted conical portion and a lower cylindrical neck, suspended from said cross-bar coaxially with said driven shaft, the space within said funnel device being free from protuberances and obstructions liable to interfere with flow of fluid therein save for said driven shaft projecting Within the above defined limits the relativetherethrough. I I ,7

2. Mixing apparatus for mixing solids in liquids comprising a cross-bar for resting across the edges of a container for the mass being mixed, a smooth-surface small-diameter driven shaft extending downwards from said cross-bar, an impeller mounted on the lower end of said shaft, an open-ended funnel device, including an upper inverted conical portion and a lower cylindrical neck, suspended fro-m said cross-barcoaxially with said driven shaft, the space within said funnel device being free from protuberances and obstructions liable to interfere with flow of fluid therein save for said driven shaft projecting therethrough, and a plurality of curvedupstanding deflector vanes mounted on, and obliquely disposed in relation to, the upper edge of the conical portion of said funnel device. 7, V

3. Mixing apparatus for mixing solids in liquids comprising a cross-bar for resting across the edges of a container for the mass being mixed, a smooth-surface small-diamterdriven shaft extending downwards from said cross-bar, an impeller mounted on the lower end of said shaft, said impeller comprising radially extending fiat strip blades curved at their outer ends forwardly in the direction, of said blades, and an openended funnel device, including an upper inverted conical portion and a lower cylindrical neck, suspended from said cross-bar coaxially with said driven shaft, the space within said funnel device being free from protuberances and obstructions liable to interfere with flow of fluid therein save for said driven shaft projecting therethrough. ,7 I

4. Mixing apparatus according to claim 1 wherein the internal angle of the conical por- 5. A mixing apparatus for mixing solids in liquids comprising a container, a driven impeller adapted to be immersed in a mass to be mixed,

said impellercomprising a plurality of flat blades extending radially from said impeller axis, each blade at its tip being, curved forwardly in the direction of movement of the blade when, said impeller is in operation, an open-ended conical guide member having apertureless smooth internal walls, adapted to be submerged in the mass to be mixedabove said impeller and substantially coaxially with said impeller a plurality of vanes upstanding from the upper edge of said conical guide member and obliquely arranged in relation thereto, said vanes extending to near-contact with the walls of said container, whereby the mass flowing downwards through the conical guide member during the impeller action is constrained to follow a substantially helical flow path.

6. A mixing apparatus according to claim 5 wherein the portion of the container Walls with which the mass contacts above the upper-most level of said conical guide member is in the form of a right circular cylinder coaxial with said impeller axis, and exerts no restraint or deflection upon the flow of liquid from the outside of, over the edge of, and into, said conical guide member.

7. In a mixing machine of the kind comprising a container, a vertical shaft carrying at its lower end a bladed impeller adapted to be immersed in the material to be mixed in the container, and an inverted open-ended frustro-conical flow-guide member above said impeller and substantially coaxial with said impeller axis, the provision of a guide as aforesaid with apertureless, internally smooth walls, the internal angle of said frustro-conical guide being within the limits 63-86, a, smooth-surfaced cylindrical im- REFERENCES CITED The following references are of record in th file of this patent:

UNITED STATES PATENTS Number Name Date 391,787 Friend Oct. 30, 1888 1,055,475 Koolman et a1. Mar. 11, 1913 1,353,166 Johnson Sept. 21, 1920 1,545,082 Cowles July '7, 1925 1,576,018 Wolf Mar. 9, 1926 2,357,640 Ep-penbach Sept. 5, 1944 FOREIGN PATENTS Number Country Date 484,991 Germany Oct. 25, 1929

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