US1255944A - Mixing and stirring device. - Google Patents

Description

A. H. S/TEVENS.

MIXING AND STIRRING DEVICE. APPLICATION FILED FEB. 1. 1917.

1,255,944. 'Ia1tent&Feb.12,1918.

2 SHEETS-SHEET 2- A. H. STEVENS.

MIXING AND STIRRING DEVICE.-

APPLICATION FILED FEB. I. 1911.

8 1 9 1 2 1 w E a 2 SHEETS-SHEET1- llIlIIlIlI-IVl. llull'lllillII-lllu-l'lllb IIIIII-ll -llllal lalllll-Il auxme aim sr To all whom it may concern:

Be it known that I, ALFRED H. STEvENs, a citizen of the United States. and a resident 'of the" borough of Brooklyn, in the county of Kings and State of New York, have invented certain new and useful Improvements in Mixing and Stirring Devices, of which the following is a specification.

This invention relates to mixin appara; tus and is particularly designed tor use in connection with the mixing of liquids having different relative speclfic gravities although it may be applied and used in any location and for any purpose for which it is adapted.

In the art of mixing and stirring liquids frequent use has heretofore been made of' mixing apparatus in which an agitating device of a helical or screw-propellerrtype has been caused to rotate about a vertical axis in the midst of a mass of material in a container to thereby intermingle the contents Generally the rotation of' of the container. the agitating device hasbeen in such a direction as to .propel the adjacent material vertically and in either an upward or down ward direction, this action being especially effective in mixing liquids having relatively difi'erent specific gravities. It has been found that the rotative movement of agitating devices of this 'type has had a pronounced' tendency to set the whole mass of liquid in the container into bodily rotation about a vertical axis coincident with the axis of rotation This bodily rotation of the liquid mass, which is ordinarily of such velocity that a vortex is formed in the upper surface, interferes to a considerable extent with the movement of the ascending and descending flow of which is proper mmgling of the difcurrents, the unobstructed essential to the ferent liquids.

Not only is the mixing of the material interfered with in the swirling action referred to, but the effective control of the temperature of the batch, which is essential in carrying out many chemical processes, is

also restricted. In certain operations it is necessary to raise the temperature of the Y ALFRED 'Hl S'IEVENS, or a t r Specification of Letters Patent. Application filed February 1, 1917. Serial No. 145,824.

of the agitating member.

a 1- e nuvrcn.

Patented Feb. i2, ieie.

' batch through the application of externally applied heat by the means surrounding the container. In other'cperations the contrary is the case, and it is necessary to lower the temperature of the material by means of a cooling water jacket. In the case where it is desirable to lower the temperature it has been found in actual practice that the liquidat the central partlof the mass above the propeller is usually maintained at a higher temperature than that of the liquid adjacent the container walls, while where it is desirable to raise the temperature of the batch, the liquid at the central part adjacent the vortex is at a lower temperature than that near the walls. In either event the difi'erence in temperature between different parts of the same batch of material indicates that the stirring operation is not effective to produce a uniform temperature throughout the batch.

It has also been found that the removal of water from a batch of material, after the washing that follows, for example, a n1t ration or sulfonation treatment, has been mpeded by the time required for the swirhng mixture to come to rest and permit the settling and separation of the heavier batch liquid from the lighter water.

The main object of this invention is to provide a mixing and stirring device having means for counteracting the rotating and swirling movement of the material produced by the agitating member.

With this and other objects in view, the invention consists principally in providing a mixing device comprising a container for of a steam jacket a mass of agitable material in which a roaxis of the rotatable member and setting up a complementary counter stream longitudinally, in the opposite direction together with means for counteracting the swirling efl'ect upon the. material of the rotatable member while maintaining the opposed longitudinal streams.

In the accompanying drawing there '15 illustrated a preferred embodiment of the invention, but it is to be understood that the invention may be carried out by other embodiments and by mechanism difierent from 7 that specifically selected for illustration.

Figure 1 is a vertical sectional view of a device embodying the invention.

Fig. 2 is a plan view of the operating member and a modified form of draft tube used in the device.

Fig. 3 is a vertical section of the agitating member and draft .tube taken along the the propeller, the draft tube is provided 7 with stream deflecting vanes set at such an angle as to tend to rotate the ascending stream in a direction counter to that produced in it by the action of the propeller.

In this particular instance a mixing apparatus is shown in which any suitable container, such as 1, is adapted to hold the liquid, or other material, which is to .undergo the mixing or stirring operation.

A propeller 2, carried by the vertical drive shaft 3, is adapted to e rotated about a vertical axis in the liquid near the bottom of the container, the direction of rotation beingsuch that the liquid immediately surrounding thepropeller is forced upwardly through the central. portion of the mass.

In actual practice it has been found that the upward flow of liquid in the vicinity of the propeller and the consequent downward flow adjacent the walls of the container,

arising from the displacement of liquid by the propeller. is interfered with by the rotative or swirling movement of the entire liquid mass which the revolving propeller tends to produce. This interference with the vertically flowing currents, as will be evident, restricts the mixing action to a considerable extent and, as a consequence, an unnecessarily long Interval of time has been neededif io produce the required intimacy of mixture in the batches of material.

In order to counteract the swirling action of the liquid mass and to thereby greatly expedite the mixing operation, in the present invention a draft tube 4 provided with inwardly-extending stream directing vanes 5 is mounted adjacent the bottom of the container on standards 6 in such relation to tube in a counter-clockwise direction.

the propeller 2, that the upwardly flowing stream produced by the propeller is made to flow through the draft tube 4. The vanes 5 are preferably set at an inclination from the vertical and in such a direction that they tend to rotate the stream of liquid passing through the draft tube 4 in a direction opposite that in which the propeller 2 is rotating. That is, if the propeller 2 is rotated in a clockwise direction the vanes 5 are set at such an angle as will tend to rotate the liquid passing through the drf'ft y suitably correlating the inclination of the vanes 5, the velocity of rotation of the propeller 2, and the pitch of the propeller lades, it will be obvious that the stream passing through the draft tube can be caused to emerge therefrom with its rotative tendency wholly or largely dissipated, so that no obstruction is presented to the thorough intermingling of the materials in the container either to effect an intimate mechanical mixture or to produce a desired chemical combination."

It will be noted that the draft tube 4, which preferably has the general formation of a Venturi tube, is spaced from the bottom of the container a suflicient distance to provide for the flow of an ample volume of liquid beneath the lower edge of the tube to restore the balance disturbed by the displacement of the liquid through the draft tube. It has been demonstrated by experiment that a draft tube of this particular form produces more efiicient results than one that has a cylindrical or other formation. The flaring lower inlet end of the tube not only overcomes the tendency of the entering liquid to form eddy currents but, in addition, the out-spreading lower edge causes the. descending streams to pass through the liquid at the angle formed by the junction of the walls with the base of the container and thus insures the agitation of the liquid in this comparatively inaccessible part of the container. The outwardly flaring outlet end of the tube .offers less resistance to the stream from the propeller and also affords a more effective distribution of the ascending material into the portions of the material above than can be obtained with a draft tube that is cylindrical in form.

While a preferred form of draft tube having curved vanes 5 and a minimum height which permits the carrying out of the mixing operation on a batch of material that onlv partially fills the container is shown in Figs. 2 and 3 it will be obvious that not only can a .draft tube of greater length and vanes of,d1fl'erent form, as in use of of the rotatable many modifications as will be best suited for operation on a wide range of materials. Suitable means may be provided ing the inclination of the vanes or for varying the speed of rotation of the propeller as may be required.

struction but a better control of temperature is eflected-when this is desirable. Furthermore the rapid settling and separation which permits of the removal of water from the batch in a very short interval of time following a washing operation, because of the absence of swirling in the liquid mass, materiallyvdecreases the time consumed in the washing operation.

While a propeller of a particular type has been described, the invention is intended to be sufliciently comprehensive to include the means for preventing swirling in combination with any agitating device which tends to produce a swirling operation. It islso pointed out that, while particular reference has been made to the stirring of liquids having different relative specific gravities to form mechanical mixtures or chemical combinations, the apparatus is capable of mixing liquids of the same specific gravity, or liquids and finely divided solids, or solids alone .in granular, pulverulent or. other form capable intermingled,'as may be found desirable.

What iscIaimed, is:

1. A mixing and stirring device comprising: a container for a mass of agitable material, a rotatable member of relatively smaller diameter than that of the container and: disposed within said container causing by its rotation a stream of the material in one direction longitudinally of the axis member and setting up a complementary counter stream longitudina'lly in the opposite direction and means for counteracting the swirling efiect upon the material of the rotatable member while maintaining the opposed longitudinalstreams.

2. A mixing and stirring device comprising: a container for a 'mass of agitable material, a rotatable member of relatively smaller diameter'than that of the container and disposed within said container causing by its rotation a stream of the material in one direction longitudinally of' the axis of the rotatable member and setting up a' comfor varyof being V rection longitudinally of surrounding said rotatable member and in I spaced relation to the walls of the container and having provisi ns for counteracting the swirling effect of the rotatable member upon the material while maintaining the opposed longitudinal streams.

3. A mixing and stirring device comprising: a container for a mass of agitable material, a rotatable member of relatively s'mallerdiameter than that of the container and disposed within said container causing by its rotation a stream of the material in one direction longitudinally of the axis of the rotatable member and setting up a complementary counter stream longitudinally in the opposite'direction and a draft tube of substantially Venturi tube formation surrounding said rotatable member in spaced relation from the wall of the container for counteracting the swirling effect of the rotatable member upon the material while maintaining the opposed longitudinal streams.

4. A.mixing and stirring device compris ing: a container for a mass of agitable material, a screw propeller of relatively smaller diameter than that of the container and dis posed within said container causing by its rotation a. stream of the material in one direction longitudinally of the axis of the screw propeller and setting up a complementary counter stream longitudinally in the opposite direction and a draft tube surrounding. said screw propeller and in spaced relation to the walls of the container and having provisions for counteracting the swirling efiect of the screw propeller upon the material while maintaining the opposed longitudinal streams.

6. A mixing and stirringdevice comprising: a containerfor a mass of agitable material, a screw propeller of relatively smaller diameter than that of the container and disposed rotation a stream of the material in one dithe axis of the rotatable member and setting up a .complementary counter stream longitudinally in within said container causing by its the opposite direction and a draft tube of Signed at New York, in the county of substantially Venturi tube formation sur- New York and State of New .York, this 31 rounding said rotatable member in spaced day of Jan., A. D. 1917. a relation from the wall of the container for ALFRED H. STEVENS.

5 counteracting the swirling effect of the screw Witnesses: propeller upon the material while maintain- ALBERT O. HARTLEY, ing the opposed longitudinal streams. 7 CHARLES J. VOLLMERQ

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