AU614630B2 - A jet ring for mixers - Google Patents

Description

6146 3 S F Ref: 98753 FORM COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952 COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE: Class Int Class Complete Specification Lodged: o Accepted: S* Published: SPriority: Related Art:

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Name and Address of Applicant: Flygt AB S-171 25 Solna

SWEDEN

Address for Service: Spruson Fer'iison, Patent Attorneys Level 33 St Martins Tower, 31 Market Street Sydney, New South Wales, 2000, Australia Complete Specification for the invention entitled: A Jet Ring for Mixers The following statement is a full description of this invention, including the best method of performing it known to me/us 5845/4

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Ii I. Karlsson 2-1-2 Revision JET RING FOR MIXERS

ABSTRACT

The mixer includes a driving motor and a propeller which is surrounded by a jet ring. The ring is formed like a funnel having its larger diameter at the inlet and the smaller diameter at the outlet. The transition from the inlet diameter to the outlet diameter being at a predetermined radius in relation to the diameter of the ring.

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ALi L JET RING FOR MIXERS BACKGROUND OF THE INVENTION The Invention concerns a jet ring of the type design to surround the propeller in a propeller type mixer, Mixers of this type include a driving unit, an electric motor, and a propeller mounted on a drilvlng shaft. The propeller may have two or more blades and can be arranged to be driven with varying speeds, all depending on the mixer use, Mixers are used within various fields for homogenizing and suspension maintenance of liquids for different industrial processes, for liquid manure, for waste water etc. The mixer can be arranged to operate horizontally or vertically or at different angles therebetween, The mixer can be designed movable so that the flow from the mixer sweeps over larger areas or is S directed towards certain areas within the liquid tank.

Another field where a mixer may be used is for creation of currents in a S lake to prevent formation of ice, In order to generate an effective mixing or flow, the propeller is normally surrounded by a jet ring with a diameter somewhat larger than the diameter of the propeller and with a normally limited axial extension. If the jet ring is eliminated, a radial flow would occur limiting the axial flow through the machine, since part of the liquid would be sucked back into the propeller due to certain leakage paths occurring between the pressure and the S suction side of the propeller.

,,4,oAccording to know techniques, the jet ring is cylindrically formed and provided with a somewhat outwardly bent collar to make the inflow easier.

Such jet rings are shown in the Swedish Design Registration Nos.: 34601 and 39392. A disadvantage with these known designs is that the flow close to the S ring may be turbulent due to a too sharp transition. This causes a so-called Sdiscontinuance of the boundary layer with an often unstable blocking of the flow as a result. The flow through the machine and thus the mixing ability decreases.

-3- JCD/i557F JCD/155TF i X, Karlsson 2-1-2 RevIgion Another disadvantage with an unsteady or failing flow (blocking) close to the ring is that vibrations generated are easily amplified causing the -tips of the propeller blades to opera-te under conditions for which they are not designed.

Additionally, the cylindrical part of the ring after the propeller extension, forms a relatively large area that is exposed to pressure pulsations causing strain in the material.

In order to overcome the foregoing problems, an improved design of the Jet ring is hereinafter described.

S 0 0 0 0 0 0 o o0 4 0 0. 00! .00 .0 0 00 00 0 SUMMABY.O,..QL.IL YETI An object of the invention is to provide an improved jet ring for mi xers, Accordingly a mixing device is provided comprising: a driving motor having a drive shaft extending therefrom; a propeller mounted on said shaft; a funnel shaped jet ring mounted about the periphery of said propeller; said funnel shaped ring having its larger diameter at its inlet rim and its smaller diameter at Its outlet rim, and the transitional surface between said inlet and outlet rims, In cross-section, is a smooth S curve with a radius not less than ten percent of the smaller diameter of said ring; wherein the inlet rim extends in a direction perpendicular to the shaft and the outlet rim is axially directed, 4 4 C4114 rhk/0333E r i BRIEF DESCRIPTION OF THE DRAWINGS Other objects and features of the invention will best be understood if reference is made to the following detailed description of the preferred embodiment in conjunction with the accompanying drawings, in which: Fig. 1 shows a side view of a mixer provided with a jet ring according to the invention; Fig. 2 shows the jet ring seen in axial direction; and Fig. 3 shows a diagram of the flow losses as a function of the ratio between the radius and the diameter of the jet ring.

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4 4 t S0 4 9 A DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to Fig, 1, a typical submersible pump arrangement is shown including an electric motor 1 with a driving shaft 2, on which Is mounted a propeller 3 having blades 4, A jet ring 5 is mounted by brackets 8a, b about the blades with the inlet rim 6 and outlet rim 7. Brackets 8a, b are fixedly attached to motor brackets lla, b, In order to obtain an effective mixing, the jet ring 5 Is arranaed as shown around the propeller 3 so that an axially directed jet is obtained which pulls in parts of the surrounding fluid mass, The flow is towards and into the propeller and mainly in a direction perpendicular to the axis of rotation, As may be seen additional in Fig. 2 in the axial direction, in order to secure a good flow near the Inside of the jet ring, the ring 5 is designed to have a funnel shaped ring having a significant radial extension from the centre line of the shaft and propeller at its inlet rim 6. The transition between its inlet rim 6, which is perpendicular to the axis of rotation of the blades and its outlet rim 7 which is axially directed, takes place along an even curved surface 9 having a relatively large radius. The ratio between the axial and radial extensions of the jet ring may vary somewhat depending on RPM S of the propeller, the type of mixer, the type and consistency of the liquid to be mixed etc.

It is important however, that the inlet rim be primarily perpendicular to the axis of rotation of the shaft and propeller, and that the transition it I from inlet rim to the outlet rim be along an even curved surface having a S relatively large radius. The curved surface Is dependant on the diameter of S the ring. It has been discovered, as shown in Fig. 3, that the bigger the ratio is between the transition radius and the ring diameter, the smaller the flow losses will be and thereby the disturbances (within certain limits). A ratio between 0.1 and 0.3 is normally sufficient. Larger ratios may cause j manufacturing problems.

-7- JCD/l557F 1. Karisson 2-1-2 Revision According -to the described invention, the jet ring for submersible mixers of different types provides in a simple and effective manner, a ring design which increases the efficiency of -the mixer and simultaneously adds to a diminishing of vibration problems. The vibration is further diminished due to the funnel formed ring being more rigid -than the previously used tube type configuration.

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Claims (4)

1. A mixing device comprising: a driving motor having a drive shaft extending therefrom; a propeller mounted on said shaft; a funnel shaped jet ring mounted about the periphery of said propeller; said funnel shaped ring having Its larger diameter at its inlet rim and its smaller diameter at its outlet rim, nd the transitional surface between said inlet and outlet rims, in cross-section, is a smooth 2 10 Curve With a radius not less than ten percent of the smaller diameter of said ring; wherein the inlet rim extends in a direction perpendicular to the shaft arid the outlet rim is axially directed,

2, The device according to claim 1 wherein the ratio between the radius of the transitional surface and the smaller diameter of said ring is between 0.1 and 0.,

3, The device according to either of claims 1 or 2 wherein the outlet rim extends in a direction parallel to the shaft.

4. A mixing device according to claim 1 substantially as hereinbefore described with reference to the drawings. DATED this TWENTY-SEVENTH day of JUNE 1991 Flygt AB Patent Attorneys for the Applicant SPRUSON FERGUSON rhk/0333E