U.S. patent number 3,876,148 [Application Number 05/396,823] was granted by the patent office on 1975-04-08 for dishwasher having epicyclic spray system.
This patent grant is currently assigned to General Electric Company. Invention is credited to Donald S. Cushing, Thomas E. Jenkins.
United States Patent |
3,876,148 |
Cushing , et al. |
April 8, 1975 |
Dishwasher having epicyclic spray system
Abstract
There is disclosed a dishwasher having a spray arm providing a
spray opening therein. The spray arm is mounted in order to move
the opening in an epicyclic spray path. In one embodiment of the
invention, the epicyclic spray arm is positioned low in the wash
chamber. Another embodiment of the invention provides the epicyclic
spray arm as elevated above a lower spray arm.
Inventors: |
Cushing; Donald S. (Louisville,
KY), Jenkins; Thomas E. (Louisville, KY) |
Assignee: |
General Electric Company
(Louisville, KY)
|
Family
ID: |
23568760 |
Appl.
No.: |
05/396,823 |
Filed: |
September 13, 1973 |
Current U.S.
Class: |
239/227; 239/246;
134/179; 239/261 |
Current CPC
Class: |
A47L
15/20 (20130101); A47L 15/23 (20130101) |
Current International
Class: |
A47L
15/14 (20060101); A47L 15/23 (20060101); B08b
003/02 (); B05b 003/06 () |
Field of
Search: |
;239/225,97,227,236,243-246,248,249,251,253,255,256,261,DIG.1
;134/176,179 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Wood, Jr.; M. Henson
Assistant Examiner: Kashnikow; Andres
Attorney, Agent or Firm: Boos, Jr.; Francis H.
Claims
We claim:
1. A dishwasher comprising a wash chamber and means for spraying
liquid into the chamber comprising a spray member having at least
one spray opening therein, and means mounting and moving the member
for movement of the opening in a non-repeating epicyclic path which
does not intersect itself in one path revolution.
2. The dishwasher of claim 1 wherein the mounting means comprises a
hub mounting the member for rotation about a first axis, means
mounting the hub for rotation about a second axis parallel to and
spaced from the first axis, the member extending away from the
first axis a distance greater than the spacing between the axes,
the spray opening being spaced from the first axis a distance
greater than the spacing between the axes.
3. The dishwasher of claim 2 comprising means for drivably rotating
the member about the first axis at a first rate and means for
drivably rotating the hub at a second rate, the ratio of the first
and second rates being other than an integer.
4. The dishwasher of claim 3 wherein the first mentioned rotating
means comprises means driving the member in a first direction and
the second mentioned rotating means comprises means driving the
member in a second opposite direction.
5. The dishwasher of claim 4 wherein the first mentioned rotating
means comprises a reaction nozzle on the member facing in the
second direction and the second mentioned rotating means comprises
an arm rigid with the hub having a reaction nozzle thereon facing
in the first direction.
6. The dishwasher of claim 3 wherein the first mentioned rotating
means comprises a reaction nozzle on the member and the second
mentioned rotating means comprises a gear transmission
interconnecting the member and the hub.
7. The dishwasher of claim 3 wherein the first mentioned rotating
means comprises a reaction nozzle on the member, the second
mentioned driving means comprising a driving arm rigid with the hub
having thereon a reaction nozzle.
8. The dishwasher of claim 3 wherein the dishwasher comprises a
pump having an outlet, the member comprising a hollow spray arm,
the hub mounting means comprising a conduit in fluid transmitting
relation to the pump outlet, and the hub including a passage in
fluid transmitting relation between the conduit and the hollow
spray arm.
9. The dishwasher of claim 3 wherein the path meanders between
inner and outer radii of the second axis, the radial distance
between the inner and outer radii being twice the distance between
the axes.
10. A dishwasher comprising a wash chamber and means for spraying
liquid into the chamber comprising a member having at least one
spray opening therein, means mounting the member for combined
rotating and revolving movement about an axis for continuously
moving the opening in a meandering path between inner and outer
spaced limits comprising different radii of the axis, the path
intersecting the limits periodically and proceeding continuously in
the same direction about the axis.
11. A dishwasher comprising a wash chamber and means for spraying
liquid into the chamber comprising a member having first, second
and third spray openings therein spaced at decreasing distances
from a fixed axis intersecting the member; means mounting and
moving the member relative to the axis for movement of each opening
in a continuously meandering path between inner and outer spaced
diameters defining an annular spray zone, the outer diameter of the
third opening spray zone extending at least as far from the axis as
the inner diameter but not as far as the outer diameter of the
second opening spray zone and the outer diameter of the second
opening spray zone extending at least as far from the axis as the
inner diameter but not as far as the outer diameter of the first
opening spray zone.
12. A dishwasher comprising a wash chamber and means for spraying
liquid into the chamber comprising a member having a plurality of
spaced spray openings therein, means mounting the member for
movement relative to an axis for moving the spray openings in
meandering paths between inner and outer diameters defining a
corresponding plurality of annular spray zones of different mean
diameter.
13. The dishwasher of claim 12 wherein the width of all of the
spray zones is substantially the same.
14. A dishwasher comprising a wash chamber and means for spraying
liquid into the chamber comprising a member having at least one
spray opening therein, means mounting the member for movement
relative to an axis for moving the spray opening in a meandering
path between inner and outer diameters defining an annular spray
zone and means for delivering a substantially constant quantity of
liquid per unit area throughout the spray zone.
15. The dishwasher of claim 14 wherein the member provides a
plurality of spray openings spaced therealong and the delivering
means includes means for delivering a substantially constant
quantity of liquid per unit area throughout each spray zone.
Description
The conventional dishwasher presently commercially available
incorporates a spray arm having a plurality of spray openings
therein. The spray arm is mounted for simple rotation. Each spray
opening necessarily repeats or tracks its prior path during
rotation and defines a circular trace, the radius of which is the
dimension from the particular spray opening to the axis of
rotation. Since the liquid spray emitting from any particular
opening travels the same path during successive revolutions of the
spray arm, it is not surprising that there is room for improvement
in washing efficiency. The classic techniques for improving washing
efficiency are to increase liquid volume through the spray device
and to increase spray pressure.
This invention relates to an improved technique for moving a spray
arm to provide an essentially non-repeating path for a spray
opening thereby improving area coverage during washing. There are
devices in the prior art which, either intentionally or inherently,
provide increased area coverage of individual spray openings.
Typical disclosures are found in U.S. Pat. Nos. 2,279,619;
3,468,486; and 3,677,473 as well as U.S. application Ser. No.
252,824, filed May 12, 1972 now U.S. Pat. No. 3,771,725, which
patent is owned by the assignee of this invention. In each of these
disclosures, a main spray arm is mounted for rotation about a
central axis and carries a secondary spray arm near an extremity of
the primary spray arm. The second spray arm is rotated or indexed
about its own axis while the primary spray arm is rotated about its
axis. Consequently, the spray path defined by the openings in the
secondary spray arm meanders in more or less predetermined fashion
between limits comprising radii of different length from the
central axis. The area coverage of compound spray arms of this type
is improved as compared to the conventional spray arms which are
mounted for simple rotation.
One difficulty with the compound spray arms of the prior art is
poor water distribution. The annular spray zone of the compound
spray arms of the prior art is quite large. Since the quantity of
water emitting from any particular spray opening remains generally
constant, the outer portions of the spray zone tends to be
"starved" of wash water while the inner edge of the spray zone
tends to be "flooded."
Another difficulty with the prior art compound spray arms is that
the inertia of the secondary spray arm is quite small compared to
the inertia of the primary spray arm whereby the secondary spray
arm is rotated very rapidly. Rotating the secondary spray arm too
fast tends to break up the spray emitting from the secondary spray
openings into a mist.
The improved spray system of this invention provides a meandering
spray path between relatively narrow inner and outer limits. The
spray path of the openings is epicyclic in nature.
It is an object of this invention to provide a dishwasher
incorporating an improved spray system.
In summary, the dishwasher of this invention comprises a wash
chamber and means for spraying liquid into the chamber including a
member having at least one spray opening therein, means mounting
and moving the member for movement of the opening in a nonrepeating
epicyclic spray path.
IN THE DRAWINGS:
FIG. 1 is an isometric view of a dishwasher, certain parts being
broken away to expose the spray system of this invention;
FIG. 2 is a side view of the dishwasher of FIG. 1, certain parts
being broken away;
FIGS. 3 and 4 are partial top plan views of the compound spray arm
of this invention;
FIG. 5 is a partial exploded view of the mounting mechanism for the
compound spray arm of this invention;
FIG. 6 is a vertical cross sectional view of the spray arms and
mounting means therefor;
FIG. 7 is a trace of one of the spray openings illustrating the
epicyclic path during thirty revolutions of the opening;
FIGS. 8 and 9 illustrate a trace of one of the spray openings for
slightly in excess of one revolution;
FIG. 10 is a trace of one of the spray openings of a typical prior
art compound spray arm;
FIG. 11 is a trace of the spray openings of another typical prior
art compound spray arm;
FIG. 12 is a cross-sectional view of another embodiment of this
invention; and
FIG. 13 is an isometric view of another embodiment of the spray arm
of this invention.
Referring to FIGS. 1 and 2, there is illustrated a dishwasher 10
comprised of a cabinet 12, a door 14 closing the front of the
cabinet 12, a tub 16 in the cabinet 12 which cooperates with the
door 14 to define a wash chamber 18 and means 20 for spraying
liquid into the wash chamber 18. Suitable article receiving racks
22, 24 reside in the tub 16 for supporting tableware, kitchenware
and the like.
The tub 16 includes a bottom wall 26 providing a sump 28 in
communication with the inlet of a pump 30 positioned under the tub
bottom 26. The pump 30 includes an outlet 32 in sealing engagement
with the tub bottom 26 and in fluid communication with the spray
means 20.
As shown best in FIGS. 1-6, the spray means 20 includes a spray arm
or member 34 having a plurality of generally upwardly facing spray
openings 36 therein spaced at different distances from the center
of the arm 34. The spray arm 34 includes an interior passage 38
providing communication between the center of the arm 34 and the
spray openings 36. One or more of the spray openings 36 may be
laterally inclined with respect to the arm 34 for drivably rotating
the same in a conventional manner. The size or cross sectional area
of the upwardly facing openings 36, or the number of openings,
preferably increases as the spacing thereof from the center of the
arm 34 increases, for purposes more fully explained
hereinafter.
As shown most clearly in FIGS. 5 and 6, the spray means 20 includes
means 40 mounting the spray arm 34 for movement of the spray
openings 36 in an epicyclic spray path.
As used herein, the term epicyclic path is defined as the trace of
a point on the circumference of a first circle that rolls around
the interior of the circumference of a second circle wherein the
diameter of the first circle exceeds the radius of the second
circle. The term non-repeating epicyclic path is here defined as an
epicyclic path of the above type in which the trace does not track
on successive revolutions.
The mounting means 40 includes a hub 42 on which the arm 34 is
mounted for rotation about a first axis 44. The hub 42 is mounted
by a retaining collar 46 onto a stub conduit 48 for rotation about
a second axis 50.
The stub conduit 48 is conveniently molded plastic providing
threads 52 received by the pump outlet 32, an interior passage 54
for transmitting washing liquid, an external flange 56 comprising
part of a bearing assembly, and a lip 58 comprising part of a seal
for preventing leakage through the bearing assembly. Accordingly,
the mounting means 40 not only constrains the spray arm 34 for
movement in the predetermined path but also acts to transmit
pressurized washing liquid from the pump 30 to the interior passage
38 of the spray arm 34.
The retaining collar 46 includes an interiorally projecting flange
60 which acts to captivate a plurality of ball bearings 62 and a
bearing retainer 64 against the flange 56. The upper end of the
retaining collar 46 is of enlarged internal diameter and provides
screw threads 66 for receiving complementary screw threads 68
provided by the hub 42.
The hub 42 is also conveniently made of molded plastic and provides
an interior axial passage 70, a first series of radially directed
passages 72 providing communication between the passages 38, 70 and
a second series of radially directed passages 74 providing
communication between the passage 70 and a driving or auxiliary arm
76. The hub 42 carries a pair of seals 78, 80 for minimizing
leakage between the hub 42 and the spray arm 34 and a seal 82
cooperating with the lip 58 for minimizing leakage between the hub
42 and the stub conduit 48. The hub 42 also provides a series of
threads 84 adjacent the upper end thereof for securing the driving
arm 76 to the hub 42.
The driving arm 76 provides an interior passage 86 leading to a
laterally directed nozzle 88 for rotating the driving arm 76, the
hub 42 and the retaining collar 46 about the second axis 50. The
driving arm 76 may provide upwardly directed spray openings as
desired.
Although the upper end of the driving arm may be sealed, as by a
suitable closure, there is preferably provided a spray tower 90 in
accordance with the disclosure of U.S. Pat. No. 3,077,200, to which
reference is made for a more complete description thereof. In
summary, the delivery of pressurized washing liquid to the interior
of the mounting means 40 causes the spray tower 90 to move upwardly
therethrough into abutting engagement with a shoulder 92 provided
by the driving arm 76. The spray tower 90 provides one or more
elevated spray openings in order to discharge washing liquid at an
elevated location within the wash chamber 18. When the pump 30 is
turned off and pressurized washing liquid ceases passing through
the mounting means 40, the spray tower 90 falls by gravity through
the passage 70 of the hub 42 and through the passage 54 of the stub
conduit 48. Since the axes of the passages 54, 70 are offset to
each other, the passage 54 is preferably substantially larger in
order to receive the spray tower 90 in any position of the hub
42.
It should now be apparent that the spray arm 34 undergoes compound
movement during the wash cycle of the dishwasher 10. Upon delivery
of washing liquid through the mounting means 40, the spray arm 34
is drivably rotated about the first axis 44 while the first axis 44
is drivably rotated about the second axis 50.
It will be apparent that the distance of any particular spray
opening 36 from the stationary axis 50 will vary depending on the
position of the first axis 44 which in turn is dictated by the
orientation of the hub 42. For purposes of illustration, it may be
assumed that the spray opening 36a is positioned a distance A from
the first axis 44 while the first axis 44 is spaced a distance B
from the axis 50. If the spray arm 34 were held stationary and the
hub 42 rotated as by rotating the driving arm 76, the trace of the
spray opening 36a moves radially with respect to the axis 50
between a first distance A+B and a second distance A-B from the
axis 50. Accordingly, the trace of spray opening 36a moves radially
a distance equal to 2B as suggested from FIG. 7.
Analysis of the movement of the opening 36a during operation of the
dishwasher 10 reveals that the exact pattern or spray path depends
on the speed ratio between the hub 42 and the spray arm 34. When
the speed ratio between the hub 42 and the spray arm 34 is an
integer, the trace of the spray opening 36a repeats or tracks at
each revolution of the spray arm 34. Accordingly, the design speed
ratio between the hub 42 and the spray arm 34 is not an integer. It
is, of course, within the skill of the art to correlate the inertia
of the arms 37, 76 and the frictional forces operating on the seals
78, 80, 82 and on the bearing assembly 56, 60, 62, the liquid
volumes and pressures acting on the various reaction nozzles and
the distance of the reaction nozzles to the axes of rotation to
establish reasonably accurate rotational speeds for the arms 34,
76.
For example, with the spray arm 34 rotating at 30 revolutions per
minute and the driving arm 76 rotating at 17 revolutions per
minute, the speed ratio is somewhat less than 1.8:1 and provides a
1-minute or 30 revolution pattern similar to that shown in FIG. 7,
although it must be admitted that the representation in FIG. 7 is
somewhat more regular than the actual tracing obtaining with a
model of this invention. At a speed ratio of exactly 1.8:1, the
trace of the spray opening 36a should theoretically begin to track
or repeat after 18 revolutions.
In practice the trace of the spray opening 36a does not begin to
track as quickly, if at all, as theory would indicate. The reason
appears to be that the arms 34, 76 cannot be driven at precise
constant rates. The fluctuation of pump outlet pressure or pump
volume as well as the appearance of a gas bubble or food soil
particle at the driving nozzles will affect the instantaneous rate
of rotation of one or both of the arms 34, 76. Accordingly, the
actual rate of rotation of the arms 34, 76 will fluctuate from the
design rate thereof.
It is evident that it is highly desirable to provide as many
consecutive non-tracking revolutions of the spray opening 36a as
practicable. There appear to be two approaches which produce
one-revolution traces of different configurations. The first
approach is to provide an extremely large speed ratio between the
spray arm 34 and the driving arm 76. The second approach is to
provide a speed ratio between the arm 34 and the driving arm 76 of
less than one.
In providing a very large speed ratio, there are several
counterbalancing considerations. First, there are limits on how
fast the spray arm 34 can be rotated. The inertia of the spray arm
34 is substantial since it is filled with water during rotation.
Accordingly, driving the spray arm 34 at a very rapid rate consumes
a significant amount of energy since the proportion of the
pressurized water used to drive the spray arm 34 become
appreciable. Another factor limiting the rate of speed of the spray
arm 34 is that the spray emitting from the openings 36 can
conceivably be converted to a mist in the wash chamber 18. This is
obviously undesirable and constitutes a practical upper limit from
the rate of rotation of the spray arm 34. Second, there are limits
on how slow the driving arm 76 can be rotated. Since the frictional
forces acting on the seal 82 and the ball bearing 62 fluctuate at
the inception of rotation because of the change of static to
dynamic friction, control over the rate of rotation of the arm 76
is erratic unless it is rotating fast enough. It is accordingly
desirable to rotate the driving arm 76 fast enough to assure that
the friction acting on the seal 82 and the ball bearings 62 is
dynamic friction. The problem of static as opposed to dynamic
friction forces acting on the seals 78, 80 can be resolved in a
slightly different manner. If the driving arm 76 and the spray arm
34 are rotated in the same direction, the rotation sensed by the
seals 78, 80 is the difference in the rate of rotation between the
arms 34, 76. If the arms 34, 76 are driven in opposite directions,
the rotation sensed by the seals 78, 80 is the sum of the
rotational rates of the arms 34, 76. Accordingly, it is desirable
to counterrotate the arms 34, 76 to assure that dynamic friction is
acting on the seals 78, 80.
In practice, the driving arm 76 probably cannot be rotated slower
than five revolutions per minute while the spray arm 34 probably
cannot be rotated faster than 60 revolutions per minute giving a
maximum speed ratio of 12:1. Preferably, the driving arm 76 is
rotated between ten and twenty revolutions per minute while the
spray arm 34 is preferably rotated between twenty and forty
revolutions per minute. Accordingly, the preferred speed ratio lies
in the range of 1:1 to 4:1. As previously mentioned, the speed
ratio should not be an integer to prevent immediate tracking of the
spray path on successive revolutions of the spray arm 34.
Referring to FIG. 8, there is illustrated a trace 94 covering a
slightly more than one revolution of the spray opening 36a when the
speed ratio between the spray arm 34 and the driving arm 76 is
greater than 1:1. For purposes of convenience, the representation
of FIG. 8 constitutes one revolution based on the same parameters
as the thirty revolution representation of FIG. 7. For purposes of
illustration, the spray arm 34 is illustrated as rotating in a
counterclockwise direction commencing at a starting point 96. It
will be appreciated that the axis 44 describes a circular trace 98
about the axis 50 during rotation of the arms 34, 76. For purposes
of illustration, the starting point 96 is positioned at a distance
A+B from the axis 50 which corresponds to the configuration
illustrated in FIG. 6. The axis 44 is accordingly positioned at a
point 100 on the trace 98 at the start of rotation. As the arms 34,
76 commence rotation, the distance from the spray opening 36a to
the second axis 50 begins to shorten in accordance with the degree
of relative rotation between the hub 42 and the spray arm 34.
Assuming that the arms 34, 76 counterrotate, the minimum distance
A-B between the spray opening 36a and the axis 50 is designated by
the point 102 on the trace 94. In this situation, the axis 44 has
moved to a point 104 on the trace 98. The minimum distance between
the axis 50 and the spray opening 36a is illustrated in the
configuration of the arms 34, 76 in FIG. 3. The spray opening 36a
moves along the trace 94 to about the point 106 while the axis 44
moves along the trace 98 to about the point 108.
Somewhat different considerations appear to establish practical
limits on the speed ratio between the arms 34, 76 when operating at
a speed ratio less than one. The problem of static friction acting
on the seals 78, 80, 82 and on the bearing assembly 56, 60, 62 are
no longer governing factors since the arm 76 is rotated relatively
rapidly and since the arms 34, 76 can be counterrotated. The
maximum rate of rotation of the arm 76 issomewhat higher than the
maximum rate of rotation of the arm 34 since the inertia of the arm
76 is substantially less and since it is immaterial if the water
passing through the nozzle 88 is converted to a mist. Although
rotational rates of the arm 76 in excess of one hundred revolutions
per minute appear practicable, rates in the range of 20-80
revolutions per minute seem desirable if for no reason other than
conservation of energy. The arm 34 must be rotated at least fast
enough to provide a substantial number of revolutions during each
wash cycle of the dishwasher 10. For this reason, a rotational rate
of less than five revolutions per minute for the arm 34 is deemed
undesirable. Preferably, the spray arm 34 is rotated between 10 and
40 revolutions per minute. Accordingly, the preferred ratio lies in
the range of 1:1 to 1:8.
Referring to FIG. 9, there is illustrated a trace 110 covering one
revolution of the spray opening 36a utilizing a speed ratio of
about 1:3.8. It will be appreciated that the axis 44 describes a
circular trace 112 about the axis 50 during rotation of the arms
34, 76. As in the representation of FIG. 8, the distance between
any point on the trace 110 and the axis 50 depends on the relative
orientation of the hub 42 and the arm 34.
The movement described in FIGS. 8 and 9 is to be contrasted with
that in FIG. 10 which is representative of the traces which are
obtained from the disclosures in U.S. Pat. Nos. 2,279,619;
3,468,486 and 3,677,473 when the secondary spray arms counterrotate
relative to the primary spray arm. An axis 114 illustrated in FIG.
10 corresponds to the axis of rotation of the primary spray arm. A
trace 116 describes the path taken by one of the spray openings in
the secondary spray arm. It will be apparent from a comparison of
FIGS. 8-10 that the individual spray openings of this invention
cover a relatively narrow annulus as compared to the relatively
broad annulus between the inner and outer circles 118, 120. One
disadvantage of the prior art spray patterns is poor water
distribution. It is obviously desirable that the quantity of water
emitting from each spray opening be substantially constant per unit
area of dishes exposed to the spray.
For purposes of illustration, the radius r.sub.1 of the inner
circle 118 is assumed to be one unit, the radius r.sub.2 of the
circle 122 is assumed to be two units and the radius r.sub.3 of the
circle 120 is assumed to be three units. The circle 122 constitutes
the trace of the axis of rotation of the secondary spray arm.
Elementary calculations will reveal that the area of the annular
segment r.sub.3 -r.sub.2 is greater than the area of the annular
segment r.sub.2 -r.sub.1 by a factor of 1.67. It is apparent that
the spray opening on the secondary spray arm resides exact half the
time in the annular segment r.sub.3 -r.sub.2 and exactly half the
time in the annular segment r.sub.2 -r.sub.1. Accordingly, the
quantity of water sprayed in each annular segment r.sub.3 -r.sub.2
and r.sub.2 -r.sub.1 are equal. Since the area of the outer annular
segment r.sub.3 -r.sub.2 is substantially greater, the conclusion
is unmistakable that the outer annular segment is relatively
starved of wash water while the inner annular segment is relatively
flooded with wash water. It is thus apparent that the water
distribution pattern of the prior art is not desirable.
As may be seen from FIG. 10, the trace 116 is basically of clover
leaf design and is illustrated as having six loops or leaves
indicating a speed ratio of approximately six. It is apparent that
the water distribution pattern of the prior art is not improved by
changing the speed ratio between the primary and secondary spray
arms since each secondary spray opening resides in the inner
annular segment r.sub.2 -r.sub.1 for exactly the same time that it
resides in the outer annular segment r.sub.3 -r.sub.2 independent
of the number of loops or leaves on the trace 116.
As mentioned previously, the trace 116 is achieved with the primary
and secondary arms counterrotating. As shown in FIG. 11, a trace
130 with somewhat different configuration is obtained if the
primary and secondary spray arms of the prior art devices rotate in
the same direction. An axis 132 corresponds to the axis of rotation
of the primary spray arm with the spray zone being defined between
inner and outer circles 134, 136. The loops or leaves of the trace
130 are inverted to intersect the inner circle 134 with the trace
segment 138 between the loops being adjacent the outer circle 136.
As in the configuration of FIG. 10, the circle 140 represents the
trace of the secondary spray arm axis so that each spray opening
resides for equal periods of time in the inner annular segment
defined by the circles 134, 140 and the outer annular segment
defined by the circles 140, 136. It will accordingly be apparent
that a greater quantity of water per unit area is delivered to the
inner annular segment than to the outer annular segment.
It will be noted that the traces 116, 130 intersect during one
revolution thereof about the axis 114, 132 respectively. This is
inherent in the prior art since the distance between the secondary
spray opening and the secondary arm axis is less than the distance
between the primary and secondary arm axes. For the same reason,
the traces 116, 130 do not continuously proceed in the same
direction about the axis 114, 132 respectively but instead proceed
in the opposite direction adjacent the apex of each loop.
In contrast to the relatively wide spray zone of the prior art,
each spray opening of this invention covers a relatively narrow
annular spray zone of predetermined cross sectional area which may
be calculated quite readily from the dimensions A, B as shown in
FIGS. 6-8. Since the annular spray zone of each spray opening
increases in area as the distance from the spray opening to the
axis 50 increases, the spray openings 36 desirably increase in size
(or number) as the distance thereof from the axis 50 increases so
that the delivered water per unit area of each annular zone is
relatively constant. The spacing between the spray openings 36,
such as the openings 36a, 36b in FIG. 1, is preferably such that
the corresponding annular spray zones 126, 128 illustrated in FIG.
7 abut or overlap to afford substantially complete area coverage.
As is apparent from FIG. 7, the coverage of each spray opening 36
within its corresponding spray zone is quite good leading to good
washing efficiency. Since the area coverage of each spray opening
36 is so complete, the openings 36 may be designed to create a
solid jet of water rather than a fan-shaped spray. It will be
evident that this provides substantial erosion action on food soil
particles adhering to tableware and kitchenware in the racks 22,
24. Also contributing to good washing efficiency is that the spray
jet passes each point in its zone at different angles of
attack.
Another difference between the spray zones of this invention and
that of the prior art resides in the mean diameter of the spray
zones 126, 128. From FIG. 7, it is apparent that the mean diameter
of the spray zone 126, which is the inner diameter plus one-half of
the width of the spray zone, is the distance from the spray opening
36a to the axis 44 which is designated A in FIG. 6. Similarly, the
mean diameter of the spray zone 128 is the distance between the
axis 44 and the spray opening 36b. Consequently, the mean are of
each of the spray zones of this invention re of different length.
In the prior art spray patterns represented in FIG. 10, the mean
diameter of the outermost opening spray zone on the secondary spray
arm is the distance between the trace 122 and the axis 114 which is
the distance between the axes of the primary and secondary spray
arms. Assuming for purposes of illustration that the secondary
spray arm of the prior art provides a spray opening closer to the
axis of the secondary spray arm, this spray opening defines an
annular spray zone having inner and outer diameters 142, 144 having
a mean diameter corresponding to the trace 122. Consequently, the
spray zones of the prior art have a common mean diameter. Thus in a
multi spray opening secondary spray arm of the prior art, there is
a substantial quantity of water per unit area delivered between the
diameters 118, 144. There is a relatively small quantity of water
per unit area delivered in the annular zone defined by the
diameters 120, 144.
It will accordingly be apparent that the spray zones of this
invention may abut or overlap but none of the spray zones are of
sufficient width to wholly encompass another of the annular spray
zones.
Referring to FIG. 12, there is illustrated another embodiment of
the invention comprising spray means 146 including a spray arm or
member 148 having a plurality of generally upwardly facing spray
openings 150 therein spaced at different distances from the center
of the arm 148. The spray arm 148 includes an interior passage 152
providing communication between the center of the arm 148 and the
spray openings 150. One or more of the openings 150 may be
laterally inclined with respect to the arm 148 for drivably
rotating the same in a conventional manner. The size or cross
sectional area of the spray openings 150 preferably increases as
the distance thereof from the center of the arm 148 increases as
previously discussed.
The spray means 148 includes means 154 mounting the spray arm 148
for movement of the spray openings 150 in an epicyclic spray path.
The mounting means 154 includes a hub 156 on which the arm 148 is
mounted for rotation about a first axis 158. The hub 156 is mounted
by a retaining collar 160 onto a stub conduit 162 for rotation
about a second axis 164. The stub conduit 162 is conveniently
molded plastic and includes threads received by a pump outlet 166,
an interior passage 168 for transmitting washing liquid, an
external flange 170 comprising part of a bearing assembly, and a
lip 172 comprising part of the seal for preventing leakage through
the bearing assembly. Accordingly, the mounting means 154 not only
constrains the spray arm 148 for movement in the predetermined path
but also acts to transmit pressurized washing liquid from the pump
(not shown) to the interior passage 152 of the spray arm 148.
The retaining collar 160 includes an interiorally projecting flange
174 which acts to captivate a plurality of ball bearings 176 and a
bearing retainer 178 against the flange 170. The upper end of the
retaining collar 160 is of enlarged internal diameter and provides
screw threads for receiving complementary screw threads provided by
the hub 156.
The hub 156 is also conveniently made of molded plastic and
provides an interior axial passage 180 and a series of radially
directed passages 182 providing communication between the passages
152, 180. The hub 156 carries a pair of seals 184, 186 for
minimizing leakage between the hub 156 and the spray arm 148 and a
seal 188 cooperating with the lip 172 for minimizing leakage
between the hub 156 and the stub conduit 162. The hub 156 also
provides an upstanding conduit 190 for cooperation with an
extendable spray tower 192.
A major distinction between the embodiment of FIG. 12 and the
previously described embodiment resides in the means for rotating
the hub 156 and retaining collar 160 about the second axis 164. In
the embodiment of FIG. 6, the driving arm 76 effects this rotation.
In the embodiment of FIG. 12, there is provided a gear transmission
194 for rotating the hub 156 about the axis 164 in response to
rotation of the spray arm 148 about the axis 158. The gear
transmission 194 includes a first stationary annular gear 196
having inwardly projecting gear teeth provided by the stub conduit
162. The gear transmission 194 also includes a second movable
annular gear 198 having inwardly projecting gear teeth provided by
the rotatable spray arm 148. Interconnecting the annular gears 196,
198 is a member 200 comprising a first circular gear 202 rigid with
an axle 204 which is inturn connected to a second circular gear
206. The axle 204 extends through a boss 208 rigid with the hub
156.
Rotation of the spray arm 148 rotates the movable annular gear 198
thereby rotating the first circular gear 202. Coaction between the
gears 196, 206 constitutes a reaction member causing the axle 204
to orbit about the second axis 164. Since the axle 204 is received
by the boss 208, orbiting of the axle 204 causes the hub 156 and
the retaining collar 160 likewise to revolve about the second axis
164.
The gear reduction ratio afforded by the transmission 194 is
selected to provide desirable spray patterns as previously
discussed. In the particular design illustrated in FIG. 12, the
ratio between the gears 198, 202 is greater than the ratio between
the gears 196, 206 which provides for rotation of the hub 156
faster than the spray arm 148 providing a spray pattern similar to
that shown in FIG. 9 where the trace of any particular spray
opening 150 will intersect the inner and outer diameters of the
spray zone more than once. For purposes of illustration, the gear
202 may comprise 10 teeth, the gear 198 may comprise 112 teeth, the
gear 206 may comprise 15 teeth and the gear 196 may comprise 70
teeth. One revolution of the gear 198 causes 11.2 revolutions of
the gear 202 which necessarily effects 11.2 revolutions of the gear
206. Eleven and two tenths revolutions of the gear 206 causes 2.4
revolutions of the axle 204 about the axis 164 thereby providing a
speed ratio between the arm 148 and the hub 156 of 1:2.4.
The arrangement of FIG. 12 provides several advantages over the
device of FIG. 6. A substantial advantage is that the speed ratio
between the arm 148 and the hub 156 may be determined quite
directly rather than taking into account all of the dynamically
variable forces acting on the driving arm 76. Eliminating the
driving arm 76 also provides a lower wash arm of lower profile
which may be desirable in many instances.
Referring to FIG. 13, there is illustrated another embodiment of
this invention comprising spray means 210 including a lower spray
arm 212 spaced from an upper spray arm 214 by a central conduit
216. The length of the conduit 216 is preferably such that the
upper spray arm 214 resides directly beneath an upper rack, such as
the rack 22 illustrated in FIG. 2. The lower rack, such as the rack
24 in FIG. 2, is provided with a central slot in order to pass the
conduit 216 allowing movement of the lower rack 24 into and out of
the wash chamber 18 as is conventional.
The lower spray arm 212 includes a hub 218 mounted for simple
rotation about an axis 220 on the pump outlet (not shown). Mounting
of the hub 218 may be effected in substantially the same manner
that the retaining collar 46 is mounted for rotation. The lower
spray arm 212 provides a plurality of upwardly directed spray
openings 222 for discharging wash liquid in the wash chamber and a
reaction nozzle 224 for drivably rotating the spray arm 212 about
the axis 220. It will accordingly be seen that the lower spray arm
212 may be of typical design.
The conduit 216 conveniently projects upwardly from the hub 218
concentric with the axis 220. The upper spray arm 214 provides a
hub 226 mounting the spray arm 214 for rotation about an axis 228
offset with respect to the axis 220. The hub 226 may comprise a
base 230 threaded into the top of the conduit 216 in much the same
manner that the hub 42 is threaded into the top of the collar 46.
Suitable seals are provided in the hub 226 for sealing between a
rotating circumferential band 232 and a relatively stationary hub
body 234. The spray arm 214 preferably includes a pair of balanced
oppositely projecting arm segments 236, 238 providing a plurality
of spray openings 240 and a reaction nozzle 242 respectively.
The embodiment of FIG. 13 has many functional similarities to the
embodiment of FIG. 6. The lower spray arm 212 functions in much the
same manner as the driving arm 76 to orbit the hub 236 about the
axis 220. The speed ratio between the lower spray or driving arm
212 and the upper spray arm 214 is subject to control based on the
design parameters discussed in relation to FIG. 6.
It will accordingly be seen that there is provided an improved
spray system for dishwashers.
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