Note: Descriptions are shown in the official language in which they were submitted.
105009d~ .
VENTILATED MOWER MOTOR
BACKGROUND OF THE INVENTION
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This invention relates generally to the cooling of
electric motors and more particularly, conce~ns the cooling
of electric motors which are providing the motive force to a
mower blade.
The electric motor has been used for many years as
the drive mechanism in a multitude of applications. However,
in recent years the use of electric motors to drive mowing
implements has drastically increased. This large scaled
application of electric motors has produced various problems
in maintaining performance and safety with one such prGblem
being the control and measurement of the temperature of the
motor.
The currently accepted arrangement for measuring
and maintaining a safe motor operating temperature is to use
a thermal switch connected to the motor in conjunction with
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a series of openings through which air is forced to flow.
The thermal switch is of the type which cuts off a supply of
electricity to the motor upon the motor reaching a designated
maximum temperature. The nature of the switch and its
necessary connections require that it be located on an
external surface of the motor elements which are located
within the motor' 9 housing. This location requirement can
produce an inacc~rate temperature sensing since the external
surfaces of the motor within the housing are all exposed to
the air flow through the housing. ~s a result of the artifically
low temperature sense by the switch, the motor will not be
shut down at the desired maximum temperature and it will
overheat thereby damaging its various internal elements. In
addition to these inherent inaccuracie~ in the accepted
arrangement, the environment in which the mower motor must
survive requires that the integrity of the motor be protected
by use of a filtering device which protects the motor's internal
mechanism, e.g. the brushes and commutator, from the dirt
present in the air.
Accordingly it is an object of the present invention
to provide a mower motor arrangement which is air cooled
without the use of a filtering device.
More specifically, it is an object of the present
invention to provide a mower motor arrangement which is air
cooled without a filter device while giving an accurate
temperature reading for the thermal switch of the motor.
Finally, it is an object of the present invention
to provide the above described cooling arrangement which
also minimizes the complexity of the system by utilizing the
mower blade to pump the cooling air.
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SUMMARY OF THE INVI:NTION
The invention contemplates an electric motor for
a mower having a deck. The electric motor includes a
field, brushes and a commutator within a housing mounted
on the deck-, and a thermal switch in close proximity to
the brushes within the housing for sensing the motor
temperature~ The improvement comprises a pressure
differential creating blade rotatably supported below the
~ deck, with the housing having a plurality of inlet apertures
located below the position of the brushes and commutator and
having a plurality of staggered outlet means located below
the field and above and in close proximity to the blade for
creating air flow through the inlet apertures, the housing
and through the outlet means, thus utilizing the pressure
differential to create the air flow.
8RIEF DESCRIPTION OF THE DRAWING
.
Other advantages and objects of the invention will
become apparent upon reading the following detailed description
and upon reference to the drawings in which the figure is a
partial sectional view of a mower incorporating the ventilation
arrangement of the present invention. While the invention
will be described in connection with a preferred embodiment,
it will be understood that it is not intended to limit the
invention to that embodiment. On the contrary, it is intended
to cover all alternatives, modifications, and equivalents as
may be included within the spirit and scope of the invention
as defined by the appended claims.
, DETAILED DESCRIPTION OF THE INVENTION
As shown in the Figure the preferred embodiment of
the present invention has ~the electric motor 10 rigidly
mounted on the mower deck 12 with the cutting blade 14
secured to the output shaft 16 of the mower by connecting
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means 18. The blade 14 of the preferred embodiment has
raised edge 20 which inputs a radial motion to the air
beneath the deck 12 to force the cut material out the
discharge chute (not shown) thereby avoiding clogging of the
blade and deck. The air pump affect of the blade creates a
lower pressure in the area of the output shaft that exists
above the deck around the motor.
The electric motor 10 of the preferred embodiment
is a conventional motor having a rotatable armature 22
centrally located within the field 24. The armature 22
includes an armature winding assembly 26 and a communicator
28 which are attached to the output shaft for rutation
therewith. The communicator 28 contacts brushes 30 which
are carried by the brush holder 32 and biased into contact
by springs 34. The brush holder 32 is rigidly attached to
the housing 36 and also acts as the mounting member for the
thermal switch 38 of the;motor.
In the particular device illustrated the thermal
switch 38 is mounted rigidly on the upper surface of the
brush holder 32 with its connecting wires 40 passing through
an aperture 42 and the cap 44 of the housing 36. In the
preferred embodiment, a thermal switch 38 is connected in
series with the electrical circuitry that supplies the motor
lO with current from the power source (not shown). The
thermal switch 38 is of the conventional type which will
break the connection between the power source and the motor
upon the motor reaching a specified maximum temperature.
In carrying out the invention, there is provided a
plurality of inlet apertures 46 and outlet apertures 48 in
the cup 50 of the motor housing 36. As depicted in the
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- figure, the apertures 46 are positioned below the location
of the thermal switch 38 thereby minimizing the cooling
effect which the cooling air has on the thermal switch, and
the exposure of the commutator and brushes to contaminants
in the cooling air. In the particular device illustrated
the inlet apertures 46 consists of two radially opposed
substantially vertical apertures in the side wall 52 of
the cup 50. In order to maximize the air flow through the
motor, four radially symmetxical outlet apertures 48 are
located in close proximity to the blade 14 in the horizontal
bottom pla.e 54 of the cup 50. In addition to the perpendi-
cularity of the planes containing the inlet and outlet
apertures, the outlet apertures are staggered from the inlet
apertures by being located on radial lines which are
substantially 45 degrees offset from the radial alignment
locating the inlet aper~-ures thereby causing a directional
change in the air flow which makes the contaminants of the
cooling air fall to the bottom piate 54.
Thus, in the present embodiment, there is provided
- 20 a cooling arrangement for an elect.ric mower motor which
maximizes the accuracy of the thermal switches temperature
sensing by minimizing its exposure to cooling air and
eliminates the need for a filter for the cooling air by
locating the inlet apertures below the critical internal
elements and by inducing directional changes in the air
flow to purify the air while minimizing the complexity
of the cooling arrangement-through utilization of the mower
blade as the air pump.
Thus it is apparent that there has been provided,
in accordance with the invention, a ventilated mower motor
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that fully satisfies the objects, aims, and advantages,
set forth above. While the invention has been described
in conjunction with the specific embodiment thereof, it
is evident that many alternatives, modifications, and
variations will be apparent to those sk lled in the art
in light of the foregoing description. Accordingly, it
~ is intended to embrace all such alternatives, modifications,
and variations chat fall within the spirit and broad scope
i of the appended claims.
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