Note: Descriptions are shown in the official language in which they were submitted.
CA 02414117 2002-11-26
FOUR-WHEEL-DRIVE AUTOMATIC SWIMMING POOL CLEANER
FIELD OF THE INVENTION
The present invention relates to swimming pool cleaners and, more
particularly,
to automatic pool cleaners driven by the flow of water therethrough for
purposes of
cleaning. Still more particularly, the invention relates to wheeled automatic
swimming
pool cleaners.
BACKGROUND OF THE INVENTION
Automatic swimming pool cleaners of the type that move about the underwater
surfaces of a swimming pool are driven by many different kinds of systems. A
variety
of different pool cleaner drive devices in one way or another harness the flow
of water,
as it is drawn (or in some cases pushed) through the pool cleaner by the
pumping
action of a remote pump for debris collection purposes, to create forward pool
cleaner
movement. Some of the many kinds of water-driven automatic pool cleaners are
those
driven in various ways by turbines, which translate water movement into
rotational
motion, and those driven in various ways by oscillators, which move back and
back
and forth by virtue of Bernoulli's principle, a motion which can be converted
into
intermittent unidirectional rotation and harnessed in various ways.
Various water-driven automatic pool cleaners of the prior art are four-wheel
structures supported on underwater surfaces by wheels. Wheel rotation by
linkage to a
turbine or other drive mechanism causes propulsion in such prior art devices.
Various
problems and shortcoming exist in such prior devices.
Among the problems and shortcomings not adequately addressed are failures of
certain kinds of cleaners to provide complete cleaning coverage. Obtaining
complete
coverage is particularly difficult or problematic for swimming pools having
certain
kinds of surfaces, surface shapes or obstacles. Complete coverage, and thus
satisfactory cleaning, are difficult to obtain when the pumping pressure
generated by
the pump is weak, such that the driving force of a pool cleaner is seriously
diminished.
Various automatic pool cleaners of the prior art have insufficient speed and
strength of
movement, and this creates and exacerbates problems of weak cleaning ability.
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Some problems, failures or difficulties occur when pool cleaners get hung up
or
caught at an area where its driving wheels are unable to contact the
underwater pool
surfaces, or are at least unable to engage such surfaces with sufficient
traction to allow
movement of the pool cleaner. For some cleaners of the prior art, steering
(that is, the
motions taken by pool cleaners in order to change directions) can be
problematic,
particularly on certain kinds of surfaces and when speed is low and the
steering and
propulsion forces that are generated are low.
Various advances have been made over the years, but there remains a need for
an automatic water-driven pool cleaner, particularly of wheeled kind, having
improved
function in movement and in cleaning ability.
OBJECTS OF THE INVENTION
It is an object of this invention to provide an improved automatic swimming
pool
cleaner, particularly of the water-driven type, which addresses some of the
problems and
shortcomings of the prior art.
SUMMARY OF THE INVENTION
In one aspect, the present invention provides an improvement in a trackless
automatic pool cleaner of the type motivated by the flow of water therethrough
to move
along a pool service to be cleaned, the pool cleaner having four wheels each
in trackless
direct contact with the pool surface. The cleaner has a body with a front
side, a rear side
and opposite sides and the wheels are rotatably mounted with respect to the
body and
include first and second sets of two wheels each, each set including one of
the wheels on
each side of the body. A turbine housing is secured to the body and has a
water-flow
chamber formed by a chamber wall, the chamber having inlet and outlet ports. A
turbine
rotor is rotatably mounted in the chamber and turbine vanes are provided
having
proximal edges connected to the rotor and distal edges freely movable at all
rotational
positions thereabout between extended positions adjacent to the wall and
retracted
positions and which are spaced farther from the wall and closer to the rotor,
thereby to
allow passage of debris of substantial size through the turbine. A drive train
is provided
from the rotor to the first set of wheels and to the second set of wheels for
trackless
driving of all four wheels, whereby all four wheels are driven.
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The automatic swimming pool cleaner of this invention provides important
advantages, including the following: excellent driving force along underwater
surfaces;
excellent traction in a variety of situations; an ability to traverse pool
surfaces of different
types and hard-to-reach pool areas; excellent cleaning coverage of underwater
surfaces;
effective pool cleaner operation at low pressure; good speed and power, even
at low
pressures; reliable take-up of debris; highly-reliable steering; an ability to
avoid and/or
escape situations involving hang-up of the pool cleaner; and good adaptability
to desired
variations in cleaner structure.
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As noted above, the drive mechanism is a turbine including a turbine rotor
secured to the body in position to be rotated by the flow of water. The drive
member is
secured with respect to the rotor and is rotatable with the rotor.
Preferably, the turbine vanes are pivotably mounted with respect to the rotor.
The
vanes are preferably curved and the distal edges of the vanes are able to
contact the
chamber wall in at least some of their extended positions. In highly preferred
embodiments of this type, the rotor has an exterior surface beneath which, for
each vane,
is a corresponding cavity which pivotably holds the proximal edge of the vane.
The
vanes preferably have enlargements at their proximal edges sized for free
insertion into,
and pivotable engagement in, the cavities.
These highly preferred forms of turbine are the subject of United States
Patent
No. 6,292,970 entitled "Turbine-Driven Automatic Swimming Pool Cleaners,"
filed by
Dieter J. Rief and Manuela Rief, both inventors herein, and Rosemarie Rief, on
May 23,
2000.
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Each of the four wheels, of course, has an inward side and an outward side
depending upon how it is mounted on the pool cleaner. In preferred embodiments
of
this invention, the first wheel of the first set has radially-spaced primary
and secondary
wheelgears on its inward side, such wheelgears facing one another, and the
second
wheel of the first set has another primary wheelgear on its inward side, the
primary
wheelgears on the two wheels of the first set being similar to one another.
Preferably,
the drive train terminates at the first and second wheels of the first set in
first and
second drive pinions, respectively, each engaging the primary wheelgear of the
respective wheel of such set; this serves to drive the wheels of the first set
in the
forward direction synchronously, in contact with the underwater pool surface.
In such embodiments, it is highly preferred that the wheelgears of the first
wheel of the first set be concentric with one another, and integrally formed
with the
first wheel itself. The wheelgear of the second wheel of the first set is also
preferably
integrally formed with the second wheel. Most preferably, the first and second
wheels
of the first set are identical, and therefore interchangeable.
As used herein, the term "wheelgear" refers to any gear which is affixed on,
or
formed as part of, a swimming pool cleaner wheel which contacts the surface of
the
pool to propel the pool cleaner.
In preferred embodiments, each of the wheels of the second set of wheels has
what is being called a "final" wheelgear on its outward side. In such
embodiments,
each of the second and third drive-train portions mentioned above includes a
transfer
shaft journaled with respect to the body, a first transfer pinion engaged with
one of the
primary wheelgears, and a second transfer pinion engaged with one of the final
wheelgears. By virtue of these drive-train portions, the wheels of the first
set impart
their rotation of the wheels of the second set. Preferably, each transfer
shaft itself
forms the first and second transfer pinions at the opposite ends thereof.
It is preferred that all four wheels, including the second set each of which
has a
"final" wheelgear on it, have their wheelgears integrally formed with the
wheel. Most
preferably, all four wheels are identical and completely interchangeable.
In preferred embodiments, the drive member is a drive gear and the drive train
includes first and second drive shafts which are journaled with respect to the
body and
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which have proximal and distal ends. In such embodiments, the first and second
drive
pinions, mentioned above, are driven by the first and second drive shafts,
respectively,
and the drive train is a gear train from the drive gear to the first and
second drive
shafts. Preferably, the first and second drive shafts form the first and
second drive
pinions, respectively, at their distal ends.
The drive train preferably includes a coupler with opposite ends receiving the
proximal ends of the first and second drive shafts. The proximal end of the
first drive
shaft is a ball joint which allows the first drive shaft to be pivoted off-
axis. This allows
the distal end of the first drive shaft to be moved fore-and-aft between a
driving
position, in which the first drive pinion engages the primary wheelgear of the
first
wheel of the first set, and a steering position, in which the first drive
pinion engages the
secondary wheelgear of such first wheel. This movement, from engagement with a
wheelgear in the form of a ring gear (i.e., with radially inwardly-facing
teeth) to
engagement with a wheelgear having radially outwardly-facing teeth, causes the
first
wheel of the first set to change its direction of rotation -- i.e., to rotate
in a direction
opposite that of the second wheel of the first set. This interrupts the
synchronous
rotation of the wheels on the pool surface, and causes turning of the pool
cleaner.
Highly preferred embodiments include apparatus to achieve the fore-and-aft
movement of the distal end of the first drive shaft. Such apparatus preferably
includes:
a shift bracket assembly which is slidably held by the body and has the first
drive shaft
journaled in it for distal-end movement between the driving and steering
positions; a
cam wheel rotatably secured with respect to the body and engaging the shift
bracket
assembly, the cam wheel having portions of greater and lesser radii; a
reduction gear
assembly secured to the body and linking the drive mechanism with the cam
wheel
such that rotation of the cam wheel is related to rotation of the drive
member; and a
spring which is positioned and supported to bias the shift bracket toward the
cam
wheel. By virtue of this apparatus the cam wheel, acting through the shift
bracket
assembly, alternately holds the distal end of the first drive shaft in the
driving position
and allows the distal end of the first drive shaft to move to the steering
position.
In highly preferred embodiments, the wheels have treads with a multiplicity of
outwardly extending radial fingers. It is most preferred that a small subset
of the radial
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fingers (extending along a very small sector of the wheel) project radially
farther than
the other fingers. With this embodiment, if the pool cleaner for any reason is
hung up
on some obstruction or pool surface feature, the longer treads, when they come
around, tend to provide traction for dislodgement purposes.
In certain preferred embodiments, the aforementioned water inlet faces the
surface of the pool and the pool cleaner includes a skirt secured with respect
to the
body and extending toward the pool surface such that the skirt and the body,
together
with the pool surface, form a plenum from which water and debris are drawn
into the
inlet. The skirt is formed of at least one flap member which has upper and
lower
articulating portions, the upper articulating portion having a proximal end
hinged to
the body and a distal end hinged to the lower articulating portion. Most
preferably, the
skirt is segmented in that it is formed of a plurality of the articulated flap
members in
side-by-side arrangement, each having upper and lower articulating portions.
Such skirt, which is the subject of commonly-owned copending United States
Patent No. 6,131,227, entitled "Suction-Regulating Skirt for Automated
Swimming
Pool Cleaner Heads," filed by Dieter J. Rief, an inventor herein, and Hans
Raines
Schlitzer on May 21, 1999, facilitates relative enclosure of the plenum
despite
encountered irregularities in the pool surface immediately under the pool
cleaner. As
water is drawn into the turbine chamber through the inlet, the skirt minimizes
the
openness between the pool cleaner body and the underwater surface of the pool,
and
this causes a speed-up in the linear flow of water immediately along the
underwater
surface of the pool, at positions under the pool cleaner. Such speed-up of
linear flow
improves the ability of the pool cleaner to ingest debris along with water, so
that the
debris tends to move easily into the turbine chamber, and from there through
the outlet
and into a bag or other collector.
In certain preferred forms, the inventive automatic pool cleaners are suction
cleaners. In other preferred forms, the inventive automatic pool cleaners are
pressure
cleaners. Certain highly preferred forms of swimming pool pressure cleaners
are the
subjects of PCT Patent Application No. PCT/US00/14770, entitled "Swimming Pool
Pressure Cleaner with Internal Steering Mechanism," concurrently filed by the
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applicant herein on an invention of Dieter J. Rief and Manuela Rief, the
inventors
herein.
While the drive mechanism included in the pool cleaner of this invention is
preferably a turbine, and most preferably a turbine having the particular
features
referred to above, the drive mechanism can be other kinds of devices which are
capable
of rotating a drive member. For example, oscillating drive mechanisms which
utilize
Bemoulli's principle to establish and maintain oscillation of an oscillator
may be used.
As is known to those skilled in the art, oscillating rotation can be
translated into
intermittent unidirectional rotation by ratcheting or other devices; thus,
oscillators can
drive the rotatable drive member referred to above.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGURE 1 is a perspective view of a preferred automatic pool cleaner in
accordance with this invention, taken generally from the rear. The device is a
suction
cleaner.
FIGURE 2 is a front elevation of the device of FIGURE 1.
FIGURE 3 is a left side elevation of the device of FIGURE 1.
FIGURE 4 is a rear elevation of the device of FIGURE 1.
FIGURE 5 is a top plan view of the device of FIGURE 1.
FIGURE 6 is a detailed top sectional of the device of FIGURE 1.
FIGURE 7 is a side sectional taken along stepped section 7-7 as indicated in
FIGURE 6, but with certain parts and details not included to enhance clarity.
FIGURE 8 is a perspective of one of the drive wheels, with its annular tread
piece removed.
FIGURE 9 is a perspective of the tread piece.
FIGURE 10 is a schematic sectional side elevation illustrating portions of
another embodiment of the invention, a swimming pool pressure cleaner.
DETAII.ED DESCRIPTION OF PREFERRED EMBODIMENTS
FIGURES 1-9 illustrate a preferred automatic swimming pool cleaner 20 in
accordance with this invention. Pool cleaner 20 has four identical drive
wheels marked
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by numeral 22, including left front drive wheel 22a, right front drive wheel
22b, and
left and right rear drive wheels 22c and 22d. All four drive wheels are driven
to
provide forward movement of pool cleaner 20. Rear drive wheels 22c and 22d are
driven by separate linkages from front wheels 22a and 22b, respectively.
Left front drive wheel 22a, which is normally driven in a forward direction,
is
periodically temporarily driven in a reverse direction. When this occurs, left
rear drive
wheel 22c is also driven in a reverse direction by virtue of the linkage
between drive
wheels 22a and 22c. During such brief intermittent periods of reverse
rotation, the
direction of travel of pool cleaner 20 changes. This steering function,
together with
the power provided by four-wheel drive of this invention, provides excellent
cleaning
coverage of underwater pool surfaces.
Pool cleaner 20 includes a body 24 which is preferably formed of two or more
plastic pieces designed to accommodate the parts and features of the
invention. Front
drive wheels 22a and 22b are rotatably mounted with respect to body 24 on
wheel
shafts 26, as shown in FIGURE 6. Attached to body 24 are rear wheel supports
28,
and rear wheels 22c and 22d are rotatably mounted thereon by wheel shafts 30.
Front
wheels 22a and 22b have gearing (hereafter described) on their inward
surfaces, i.e.,
the surfaces facing each other. Rear wheels 22c and 22d have the same gearing
on
their outward surfaces. Drive wheels 22a-d are identical to each other, and
thus are
interchangeable.
The gearing on wheels 22a-d includes concentric radially-spaced primary and
secondary wheelgears 32 and 34. Primary and secondary wheelgears 32 and 34 are
radially spaced from one another by a distance in excess of the diameter of a
pinion
gear (hereafter described) which alternately engages such gears on drive
whee122a.
While all wheels are interchangeable, only drive wheel 22a uses both
wheelgears; on
drive wheels 22b-d, only wheelgear 32 is used.
Pool cleaner 20 includes a drive mechanism which utilizes the flow of water
through the pool cleaner to create rotary motion which is transferred to the
wheels by
a drive train. More specifically, pool cleaner 20 includes a turbine 36, part
of which,
notably turbine housing 38, is secured to body 24. (As used with respect to
turbine
housing 38 and body 24, the term "secured to" includes having been formed
together.)
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Turbine housing 38 has a chamber 40 in it which is formed by a chamber wall
42. Chamber 40 includes an inlet port 44 and an outlet port 46. Turbine 36
also
includes a rotor 48, which is rotatably mounted within chamber 40, and a
number of
turbine vanes 50, each of which has proximal and distal edges 50a and 50b.
Proximal
edge 50a of each vane 50 is generally cylindrical in shape and is loosely
received within
a generally cylindrical void in rotor 48, formed just below the outer surface
of the
rotor. Thus, vanes 50, which are of a curved configuration, freely move
between fully
extended positions in which they contact chamber wal142 and retracted
positions in
which their distal edges 50b are closer to rotor 48 and spaced from chamber
wall 42.
This provides free adjustability of vanes 50 to allow large pieces of debris
to pass
through chamber 40 without interfering with operation of the turbine.
Turbine 36, shown in FIGURE 7, serves two functions, providing power to
drive wheels 22a-d through linkages (hereafter described) and providing power
for
operation of a steering device (hereafter described), both of which occur as
water and
debris are drawn through it by the action of a remote pump. A flexible hose
(not
shown) is rotatably attached to hose coupling 52 (in known fashion) and draws
water
from beneath pool cleaner 20 through inlet port 44, turbine 36 and outlet port
46.
Beneath pool cleaner 20, water inlet port 44 faces the pool surface 54. Pool
cleaner 20 includes a segmented skirt which has forward and rearward portions,
each
of which includes a number of flap members 56 arranged in side by side
relationship.
Together, flap members 56 and body 24 form a plenum 62. Each flap member 56
includes an upper articulating portion 58 and a lower articulating portion 60.
Upper
portion 58 has a proximal end 58a which is hinged to body 24 and a distal end
58b
which is hinged to a proximal end 60a of upper portion 60. By virtue of this
design,
flap members 56 self-adjust to the contours of the pool surface 54. Flap
members 56
serve to keep plenum 62 substantially closed, which provides flow
characteristics
favorable for collection of debris from beneath pool cleaner 20 by the suction
action.
While pool cleaner 20 is a suction cleaner, an alternative pool cleaner 63,
which
is a pressure cleaner, is shown in FIGURE 10. Pressure cleaner 63 has a
turbine 68
and related portions which differ from their counterparts in pool cleaner 20.
Pressure
cleaner 63, instead of operating by harnessing the suction of water through a
pool
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cleaner, operates by harnessing a positive flow of water to a pool cleaner
through a
pool cleaner hose (not shown), which is attached to a swiveling hose coupling
(not
shown). The water from the hose flows through conduits 64 and conduit branches
64a
and 64b, and ultimately through venturi jets 66a and 66b into turbine 68. It
should be
remembered that FIGURE 10 is schematic; it omits a number of parts and does
not
purport to show the location or the structure providing conduits for flow of
water
from the hose to the venturi jets.
As shown in FIGURE 10, turbine 68 has a larger inlet 70 facing the pool
surface (not shown) than is used in pool cleaner 20, described above. Venturi
jets 66a
and 66b are located at or near inlet 70 and are oriented to direct water
upwardly into
inlet 70 and toward outlet 72. The venturi jets, particularly venturi jet 66a,
are located
to cause rotation of the rotor of turbine 68 to provide driving and steering
power for
pressure cleaner 63. A venturi action caused by venturi jets 66a and 66b draws
water
and debris from beneath pool cleaner 63 into inlet port 70, and causes such
water and
debris to flow upwardly through turbine 68 and outlet port 72 into a
collection bag 74,
which acts as a filter.
The venturi action is caused by the accelerated flow of water created by jets
66a and 66b. The accelerated flow of water creates a pressure differential
which
causes an upward suction of water and debris from adjacent on the pool surface
into
inlet 70. Thus, the venturi jets serve two purposes -- driving the turbine and
creating
an upward flow from beneath the pool cleaner for cleaning purposes. The size
and
orientation of venturi jets 66a and 66b not only cause these actions, but
serve to
facilitate an essentially quick straight-line movement of debris into
collection bag 74.
In every other respect, pressure cleaner 63 is like suction cleaner 20.
Referring again to pool cleaner 20 of FIGURES 1-9, the following is a
description of the manner in which the rotation of rotor 48 is transmitted to
drive
wheels 22a-d. FIGURE 6 is particularly helpful in illustrating the drive train
and its
three different portions. The three different portions include: (1) a first
portion which
extends from a first drive gear 76, affixed to rotor 48, to left and right
front wheels 22a
and 22b; (2) a second portion which extends from front wheel 22a to rear
whee122c;
and (3) a third portion which extends from front wheel 22b to rear whee122d.
(The
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second and third portions of the drive train are identical to each other.) All
four
wheels are driven by first drive gear 76; a second drive gear 78, which is
affixed to the
opposite side of rotor 48, is used to control the steering of pool cleaner 20.
(First and
second drive gears 76 and 78 are integrally formed with rotor 48 and are
affixed to a
rotor shaft 79 which is rotatably mounted with respect to body 24.)
The first drive train portion includes left and right drive shafts 80 and 82,
sometimes referred to herein as "first" and "second" drive shafts. Drive
shafts 80 and
82 are aligned end-to-end. The first drive train portion also has a gear train
including
gears 84a, 84b and 84c. Gear 84c serves as a coupler to receive the proximal
ends 80a
and 82a of drive shafts 80 and 82. (Proximal end 80a of drive shaft 80 forms a
ball-
joint coupling with coupling gear 84c, for steering purposes described below.)
Drive
shafts 80 and 82 terminate at their distal ends in pinion gears 86a and 86b,
which are
integrally formed with the shafts. Gears 86a and 86b engage primary wheelgears
32 of
drive train wheels 22a and 22b, respectively. Thus, the rotation of rotor 48
causes
synchronous rotation of front drive wheels 22a and 22b, each in the same
direction.
The rotation of front drive wheels 22a and 22b causes rotation of rear drive
wheels 22c and 22d, by means of the second and third portions of the drive
train,
which will now be described. Each of these identical drive-train portions end
up
engaging primary (or final) wheelgear 32 of one of rear drive wheels 22c and
22d.
Adjacent to each rear wheel is a transfer shaft 88 which is journaled in body
24 by
means of appropriate bearings. The opposite ends of each transfer shaft 88
include
pinion gears 90a and 90b, which are formed as part of transfer shaft 88. Each
pinion
gear 90a engages primary wheelgear 32 of one of front drive wheels 22a or 22b,
at a
position spaced about 180 from the point of engagement of pinion gear 86a or
86b
therewith. Each pinion gear 90b engages primary (or final) wheelgear 32 of one
of
rear drive wheels 22c and 22d.
The operation of the steering mechanism will now be described. Left drive
shaft 80, which is generally in exact axial alignment with right drive shaft
82, can be
moved off-axis by virtue of the ball-joint at its proximal end 80a. More
specifically,
pinion gear 86a, which is formed at the distal end of left drive shaft 80, is
movable in
fore-and-aft directions depending upon forces applied to drive shaft 80, as
hereafter
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described. FIGURE 7 shows an oblong opening 92 in a portion of body 24 which
accommodates such movement of left drive shaft 80.
Pool cleaner 20 includes a shift bracket assembly 94 which is slidably held
within a cavity 96 formed in body 24. Left drive shaft 80 is journaled by
suitable
bearing means in shift bracket assembly 94. Shift bracket assembly 94 includes
a roller
98 at its rearward end for engagement by a cam wheel 100 which serves the
purpose of
controlling the position of shift bracket assembly 94, either fore or aft. A
spring 102 is
located within cavity 96 in a position between a fixed surface of body 24 and
the
forward end of shift bracket assembly 94. Spring 102 biases shift bracket
assembly 94
into firm engagement with cam wheel 100.
Since left drive shaft 80 is journaled in shift bracket assembly 94, the
position
of pinion gear 86a is determined by the fore-or-aft position of shift bracket
assembly
94. In the forward position, pinion gear 86a engages primary wheelgear 32 of
left
front wheel 22a; in the rearward position, it engages secondary wheelgear 34
of left
front whee122a. Left front wheel 22a moves in a forward direction when pinion
gear
86a engages primary wheelgear 32; however, since the reverse side of pinion
gear 86a
is what engages secondary wheelgear 34 when pinion gear 86a is in the aft
position,
such engagement results in reverse rotation of left front wheel 22a. And, by
virtue of
the driving linkage between left front whee122a and left rear wheel 22c, the
aft
position of pinion gear 86a also reverses the rotational direction of left
rear drive wheel
22c. In other words, the periodic movement of shift bracket assembly 94 moves
left
drive shaft 80 and its pinion gear 86a to the aft position, and this
interrupts the
synchronous rotation of the drive wheels and causes turning of pool cleaner
20.
A major portion of cam wheel 100 has a fixed radius sufficient to allows cam
wheel 100 to hold shift bracket assembly 94 in a forward position. Cam wheel
100
also has one or more smaller portions of lesser radius which allow shift
bracket
assembly 94 to move to its aft position under the biasing force of spring 102.
Cam wheel 100 is rotatably supported on an extension 104 of rotor shaft 79 at
a position spaced from rotor 48. Also rotatably supported on extension 104 are
several gear members of a reduction gear assembly 106, the purpose of which is
to
reduce rotational speed such that cam wheel 100 turns slowly -- at a rate such
that its
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portions of greater or lesser radial dimension dwell in contact with roller 98
of shift
bracket assembly 94 for reasonable periods of time. More specifically, the
gearing and
cam design are such that the pool cleaner 20 will move in a forward position
most of
the time, and only intermittently change directions for short periods of time.
Primary and secondary wheelgears 32 and 34 are integrally formed with each of
the drive wheels 22a-d. FIGURE 8 illustrates the main portion of one such
drive
wheel, with its tread piece removed.
FIGURE 9 illustrates a resilient elastomeric tread element 108 which is shaped
for firm engagement about the periphery of the main portion of each drive
wheel and
to provide good traction. Tread element 108 has many outwardly extending
resilient
radial fingers 110. These tread features on the drive wheels of the present
invention
provide increased traction on slippery surfaces. This tread in combination
with the
large size of the drive wheels, which are essentially as large in diameter as
the pool
cleaner is high, allows the cleaner to ride over commonly encountered
impediments
and obstacles in the pool environment, including main drains, pool liner
wrinkles, and
uneven, convex and concave surfaces. Such drive wheels in the four-wheel-drive
pool
cleaner of this invention also allow the pool cleaner to navigate a vertical
wall which
joins a pool bottom surface without any curved transition (or "radius").
While elastomeric flexible treads are normally best, in certain applications,
notably involving submerged tile surfaces, it may be preferable to fit the
drive wheels
with synthetic foam treads. When foam tread is used, effective grip and
suction can be
maintained on even the most slippery submerged inclined and vertical tile
surfaces.
As shown in FIGURE 9, three consecutive radial fingers 110a-c project radially
farther than the others. As explained above, this serves to provide additional
traction
for dislodgement of the pool cleaner 20, if needed. Radial finger 110b extends
slightly
farther than radial fingers 110a and 110c.
Most of the parts of the pool cleaners of this invention may be formed using
rigid plastic parts, as is well known in the art. Suitable materials- for all
of the parts
would be apparent to those skilled in the art who are made familiar with this
invention.
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While the principles of this invention have been described in connection with
specific embodiments, it should be understood clearly that these descriptions
are made
only by way of example and are not intended to limit the scope of the
invention.
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