U.S. patent number 3,641,749 [Application Number 05/077,884] was granted by the patent office on 1972-02-15 for baffle for electric lawnmower.
This patent grant is currently assigned to The Black and Decker Manufacturing Company. Invention is credited to John R. Dwyer, Jr., Alvydas P. Karasa.
United States Patent |
3,641,749 |
Dwyer, Jr. , et al. |
February 15, 1972 |
BAFFLE FOR ELECTRIC LAWNMOWER
Abstract
An electric lawnmower which includes a deck mounted on wheels
and a blade mounted for rotation under the deck to cut grass. An
electric motor is supported by the deck for rotating the blade upon
actuation of a switch. The motor extends above the deck and is
enclosed by a shroud. Air passages are defined between the bottom
of the shroud and the deck to permit air to enter and be pulled
through the motor by a fan for cooling purposes. A baffle is
positioned between the motor and the passages to block any straight
line communication therebetween so that the airflow is forced to
turn and contaminants carried thereby are substantially removed
before it enters the motor.
Inventors: |
Dwyer, Jr.; John R. (Timonium,
MD), Karasa; Alvydas P. (Baltimore, MD) |
Assignee: |
The Black and Decker Manufacturing
Company (Towson, MD)
|
Family
ID: |
22140609 |
Appl.
No.: |
05/077,884 |
Filed: |
October 5, 1970 |
Current U.S.
Class: |
56/17.5 |
Current CPC
Class: |
A01D
34/6806 (20130101); A01D 2101/00 (20130101); A01D
2034/6843 (20130101) |
Current International
Class: |
A01D
34/68 (20060101); A01D 34/67 (20060101); A01d
035/26 () |
Field of
Search: |
;310/62,63,88,89
;56/12.8,13.3,13.4,17.5,16.7 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
729,917 |
|
Jan 1943 |
|
DT |
|
1,263,385 |
|
Mar 1968 |
|
DT |
|
Primary Examiner: Askin; Laramie E.
Assistant Examiner: Witkowski; Stanley J.
Claims
We claim:
1. In an electric lawnmower including a deck mounted for movement
over the ground; a blade mounted under said deck for cutting grass
upon rotation thereof; an electric motor extending above said deck
and coupled to said blade for causing rotation thereof upon
energization; and an enclosure for said motor; the improvement
comprising
a plurality of passages defined by said enclosure for admitting air
to cool said motor, said passages being located below the upper end
of said motor; and
a baffle located within said enclosure and disposed to block a
straight line path from said passages to said motor to provide a
curved path from said passages to said motor;
whereby contaminants entering through said passages are
substantially prevented from reaching said motor.
2. A lawnmower as claimed in claim 1 wherein said baffle is
frustoconical in shape whereby air is forced to turn through an
angle greater than 90.degree. after passing through said
passages.
3. A lawnmower as claimed in claim 2 wherein said passages are
defined between the base of said enclosure and upper surface of
said deck.
4. A lawnmower as claimed in claim 3 wherein said baffle extends
from the base of said motor toward said enclosure, the small end of
said baffle being adjacent said motor and the large end of said
baffle being adjacent said enclosure.
5. A lawnmower as claimed in claim 4 wherein said motor comprises a
stationary field supported by said deck, and wherein a flange on
said baffle electrically insulates said field from said deck.
6. A lawnmower as claimed in claim 1 wherein all straight line
paths from said passages to said motor are blocked by said
baffle.
7. A lawnmower as claimed in claim 6 wherein said baffle
substantially surrounds said motor.
8. A lawnmower as claimed in claim 6 wherein said baffle causes at
least one extra turn through 90.degree. in the normal flow path
from said passages to said motor.
Description
The present invention is directed to an improved electric lawnmower
which includes means for preventing water or other contaminants
from entering the electric motor.
Electric lawnmowers of the type which operate from line voltage
supplied through an extension cord must be designed both to protect
the operator against the possibility of failure of various parts of
the insulation and also must be designed to prevent malfunction of
the lawnmower itself due to such failure. Although the engineering
design of present lawnmowers attempts to compensate for such
possibilities, careless use of the mower by an operator can still
cause a risk of shock or failure. A particularly hazardous example
of this is the case of an operator who may use an electric
lawnmower when the grass is wet or even when a light rain is
falling. In this situation, water may be drawn into the lawnmower
by the fan which produces a flow of cooling air through the motor.
Water can short various parts of the motor and may even produce a
shock hazard to the operator. Similarly, if dust or stone chips are
drawn into the motor by the airflow, damage to the motor may
result.
Accordingly, it is an object of this invention to provide an
improved electric lawnmower which includes means for preventing the
entry of contaminants into the electric motor.
Another object of this invention is the provision of an improved
electric lawnmower including a baffle in the cooling airflow.
A further object of this invention is the provision of a new and
improved baffle construction and airflow path for preventing the
entry of contaminants into an electric lawnmower.
Further objects and advantages of this invention will become clear
as the description and illustration thereof proceed.
Briefly, in accord with one embodiment of this invention, a rotary
electric motor-driven lawnmower is provided which includes a deck
mounted on wheels and adapted to be pushed over the ground by an
operator. A blade is mounted for rotation beneath the deck for
grass cutting in the usual manner. An electric motor is supported
by the deck and extending above it. The rotary armature of the
motor is connected to the blade to cause rotation when electrical
energy is applied to the motor. The motor is enclosed within an
insulating shroud to protect the motor and to prevent operator
contact with live parts of the motor. In accord with this
invention, a plurality of air passages are provided between the
base of the shroud and the deck of the mower. A fan mounted on the
armature draws air through the passages and through the motor to
reduce the operating temperature thereof. In further accord with
this invention, a baffle is provided which interrupts all straight
line paths between the air passages and the entry slots at the top
of the motor. Thus, the airflow is forced to turn a number of times
before it travels from the passages to the motor so that
substantially all contaminants such as water or dust carried by the
airstream are prevented from entering the motor and causing
damage.
In the drawing:
FIG. 1 is a perspective view of a lawnmower which incorporates the
present invention;
FIG. 2 is a cross-sectional view of the lawnmower of FIG. 1 and
illustrating the present invention; and
FIG. 3 is an exploded view of selected parts of FIG. 2.
In FIG. 1, the illustrated lawnmower 10 includes a deck 11
supported on wheels 12 and enclosing a blade 13 which is adapted to
cut grass upon rotation. An electric motor is supported by the deck
within an enclosure 14. Electrical energy is supplied to the motor
via a cord 15 which extends upwardly along the handle 16 to switch
17 and then to an appropriate cord set 18 which is connected to an
extension cord, not shown, which is in turn connected to a
household outlet. The enclosure 14 is supported at one or more
points 19 but a substantial portion of the base thereof, in
cooperation with the upper surface of the deck 11, defines passages
20 through which cooling air is allowed to enter and pass to the
motor for reducing the operating temperature thereof.
FIG. 2 illustrates the interior of the enclosure 14 of FIG. 1 and
the mower construction contained therein. Specifically, the motor
25 which is illustrated is of the permanent magnet type having a
permanent magnet field 26 supported by a steel cylinder 27. The
cylinder 27 is supported on an end casting 28 which is in turn
mounted to the deck 11 by bolts 29. The upper end of the cylinder
28 supports an end bell 30 which carries a pair of brushes, not
shown, to which electrical connection is made via a pair of wires,
one of which is shown at 31, and which are connected to the lead
15. The end bell 30 and the steel cylinder 27 are connected to the
end casting 28 via mounting bolts 32.
An armature 33 is provided to rotate within the permanent magnet
field. The armature is supported by bearings mounted respectively
in the end bell 30 and in the end casting 28. Beneath the casting,
the armature shaft is coupled to the blade 13 and it also carries a
fan 34, the entire assembly being held together by a nut 35. Thus,
when the switch 17 is activated, electrical energy is applied to
the armature whereupon it rotates within the field, causing
rotation of the fan 34 and the blade 13.
In accord with this invention, the fan 34 is of the centrifugal
type and accordingly, it produces a downward airflow through the
motor and through slots 36 in the end casting 28. To provide for
this flow of air, entry slots 37 are provided in the end bell 30.
In further accord with this invention, provision is made for
removing contaminants from the airstream prior to its entry into
the motor by eliminating any openings in the enclosure 14 except
for the passages 20 adjacent its base. Due to this configuration,
air drawn by the fan can only enter the enclosure 14 adjacent the
base thereof and its path must then be upward along the outside of
the motor until it enters the motor through slots 37. As previously
noted, water or abrasive dust could easily be carried by the
relatively large volume of air which passes through the motor.
To prevent this possibility, and to provide means for removing
these contaminants from the airstream, a baffle 40 is provided in
the path of the airstream to force the air to turn at least twice
as it travels from the passages 20 to the slots 37. Since the
contaminants are less easily turned than the airstream, the
contaminants encounter the baffle and are substantially removed
therefrom. In the preferred embodiment of this invention which is
illustrated in FIG. 2, the baffle 40 is frustoconical in shape and
has a small lower end 41 adjacent the motor and a larger upper end
42 which is closer to the enclosure 14. This conical shape
increases the effect of the baffle on the airstream by forcing the
air to turn through an angle greater than 90.degree.. This further
contributes to the removal of contaminants from the airflow. If
desired, a simple cylindrical baffle could also be provided. In
either case, a significant feature of this invention is the
provision of the baffle 40 in such a position that it blocks all
straight lines paths from the passages 20 to the motor 25.
Accordingly, both the main airstream which is passing toward the
air slots 37 and air which may escape the main airstream are
prevented from reaching either the outside or the inside of the
motor without first passing through a relatively tortuous path
which reduces the quantity of contaminants entrained therein.
FIG. 2 and FIG. 3 illustrate a further feature of this invention,
namely, the provision of an additional layer of insulation by a
flange 43 on the baffle which projects radially inward under the
motor. Specifically, the cylinder 27 of the motor is supported on
an insulating ring 44 which provides a barrier of insulation
between the motor and its mounting. The radially inwardly extending
flange 43 of the baffle 40 underlies this insulating ring 44 and
also provides an insulating barrier between the motor 25 and the
end casting 28. In this embodiment, the ring 44 may be a dielectric
material such as nylon and the baffle 40 may be any thermoplastic
material.
Alternatively, if the material is suitable, the baffle 40 may be
manufactured, for example by molding, so as to include a structure
similar to that of the ring 44 as an integral path of the flange
43. In either case, the portion of the baffle which extends under
the motor forms a significant part of the insulating barrier
between the motor and accessible metal such as the deck 11.
In the foregoing description, reference has been made to a
specific, preferred embodiment of this invention. It will be
recognized by those skilled in the art, however, that many changes
and modifications can be made without departing from the basic
concept disclosed herein of providing a path for cooling air in an
electric lawn mower which forces the air to travel upward from the
bottom of the motor enclosure through a baffled path before it
reaches this point of entry into the motor. In addition to the
advantage of contamination removal provided by the baffle itself,
the upward travel of the air from the passages 30 to the top of the
motor also contributes significantly to this process. Furthermore,
the presence of the passages 20 adjacent the bottom of the motor
enclosure permit the escape of contaminants, particularly water,
which might otherwise be retained within the enclosure and
eventually cause corrosion or malfunction. As an additional
feature, all of the electrical connections and wires of the motor
are retained by the baffle in case of breakage and prevented from
reaching the deck or other accessible metal. Accordingly, it is
intended that the appended claims cover all changes and
modifications from the specifically illustrated embodiment as may
fall within the true spirit and scope of this invention.
* * * * *