CA2152293A1

CA2152293A1 - Cooling device for mixers

Info

Publication number: CA2152293A1
Application number: CA002152293A
Authority: CA
Inventors: Hjalmar Fries
Original assignee: Hjalmar Fries; Itt Flygt Ab
Current assignee: Xylem Water Solutions AB
Priority date: 1994-06-22
Filing date: 1995-06-21
Publication date: 1995-12-23
Also published as: AU682589B2; JPH0838874A; SE9402194L; SE9402194D0; SE502118C2; AU2016395A; DE69503981T2; EP0688599B1; EP0688599A1; DE69503981D1

Abstract

A cooling device for the electric motor in a submersible mixer. In order to increase the media exchange at the mantle surface of the motor, the jet ring is extended to surround the propeller, thereby the flow created by the propeller is partly forced to pass through a slot created between the motor surface and the ring and extension thereof.

Description

21~229'~

A COOLING DEVICE FOR VT~

Backqround of the Invention The invention concerns a cooling device for a mixer for operation in viscous liquids where amount of solid bodies are frequent.

Mixers of this type comprise a driving unit such as an electric motor, a propeller and a driving shaft therebetween. The propeller may be designed with two or more vanes and to be driven with various speeds depending on type of use.

Mixers are used within different fields for homogenizing and to keep particles in suspension in liquids for different industrial processes, in farming, for treatment of sewage water, etc. The mixer may be arranged horizontally or vertically or in different angle positions therebetween. It can also be arranged to move in such a way that the flow from the mixer is caused to sweep over larger areas or being directed towards certain spots within the liquid tank.

In order to obtain an effective mixing or flow, a jet ring is often arranged around the propeller having a diameter somewhat exceeding that of the propeller and a normally relatively limited axial extension. With no jet ring present, a dominating radial flow is obtained which means that the axial flow through the machine becomes very limited as the same amount of liquid is rapidly sucked back to the propeller. In addition there is a leakage between the pressure and the suction side of the propeller which further decreases the axial flow. According to known practice the jet ring is normally designed as a cylinder having a somewhat expanding collar at its inlet to facilitate the 21a22~3 inflow. Such jet rings are shown in the Swedish Design Registrations Nos. 34601 and 39392.

The electric motor is cooled by the surrounding medium which calls for a certain flow around the motor, which flow normally is obtained by the mixer itself. When mixing liquids that demand a certain shear stress to be exceeded before any movement is created, Bingham liquids, problems may occur to obtain a flow strong enough. This might cause the motor to be overheated.

The invention concerns a device for solving the problem mentioned above.

Brief Descrition of the Drawings The invention will best be understood by reference to the following description taken in conjunction with the accompanying drawings in which:

Fig. 1 shows a mixer provided with a cooling device according to the invention;
Fig. 2 shows flows around a mixer not provided with a cooling device; and Fig. 3 shows flows around a mixer with a cooling device.

Detailed DescriPtion of the Preferred Embodiment In Fig. 1 there is shown a mixer 1 having a driving electric motor unit 2, a propeller 3, a jet ring 4, and an extension 5 of the jet ring 4 over the propeller 3. A support means 6 is shown between extension S and mixer 1.

21~ 2 2 ~ ~ FRIES-36 With reference to Fig. 2 the conditions when mixing Bingham liquids are illustrated. The mixer here creates a flow symbolized by the arrows in the light part of the drawing.
The area close to the electric motor is not included in the flow which means an insufficient heat exchange between the motor housing and the surroundings, since the flow, as symbolized by the arrows does not pass the motor body.

Fig. 3 shows how the flow increases or extends the area where flow takes place, by means of the invention. The propeller creates an under pressure at its inlet side, inside of the jet ring 4 and extension 5, which means that critical shear stress is exceeded and a flow is obtained through the jet ring 4 along the wall of the motor housing and inside the extension 5 which thus gives an effective cooling to the mixer motor.

In the example above, an extension 5 of the jet ring 4 has been used to obtain an effective cooling of the motor housing. It is, however, possible, according to the invention, to arrange one or several extension sections around the motor which may be spaced from the jet ring, to obtain the necessary flow.

While the principles of the invention have been described in connection with specific apparatus, it is to be clearly understood that this description is by way of example and not as a limitation of the invention as set forth in the accompanying claims.

Claims

1. A cooling device for a mixer comprising an electric motor and a propeller with a driving shaft therebetween, said mixer being meant to operate submersed in the mixed medium, the improvement comprising a cylindrical wall (5) which partly or entirely surrounds the mantel surface of the electric motor (2) for intensifying the media exchange at said surface.

2. A cooling device according to claim 1, wherein the wall (5) is an extended part of a jet ring (4) surrounding the propeller.

3. In combination:
a submersible mixer having an electric motor and a propeller being mounted on the shaft of said motor;
a jet ring surrounding said propeller and an extended part of said ring surrounding at least part of the mantel surface of said motor, whereby when said mixer is operating in a liquid media, the media exchange with said surface is intensified.

4. The combination of claim 3, wherein said extended part includes a flared portion.

5. The combination of claim 4 wherein said extended part substantially surrounds the mantel surface of said motor.