Note: Descriptions are shown in the official language in which they were submitted.
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FRIES-36
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
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FRIES-36
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.
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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.
