[0001] The present invention relates to sprinkling assemblies for dishwashers, and in particular
to a sprinkling assembly comprising a primary revolving sprinkler and a secondary
sprinkler capable of moving with an oscillatory motion in the horizontal plane.
[0002] It is known that conventional revolving sprinklers essentially consist of a single
device pivoted on a vertical axis central shaft and provided with at least one propulsion
nozzle at one end, as well as with other nozzles arranged along said device to sprinkle
the dishes contained in the dishwasher rack. Since the rotation axis of said device
is fixed, the resulting paths of the nozzles consist of circumferences centered on
the rotation axis.
[0003] From this follows that the above-mentioned device directly sprinkles always and only
the surfaces of the dishes which are along said circular paths, with a limited washing
effectiveness. Moreover, the area which can be reached by the water ejected from the
nozzles approximately corresponds to the area of the square circumscribed about the
circular path of the outermost nozzle.
[0004] The simplest solution in trying to overcome this latter limit is that of giving a
greater inclination to the end nozzles of the sprinkler so that the water jets emitted
therefrom reach beyond the area of rotation. For example, it is possible to use a
sprinkler provided with a nozzle inclined at about 75° so as to cover also the foremost
portion of the rack in a dishwasher whose width is smaller than its length (typically
45 x 60 cm).
[0005] This solution has a first drawback of poor washing effectiveness in the end portion
of the rack, since very inclined jets are unable to properly enter between the dishes
arranged side by side like the almost vertical jets emitted by the other nozzles can
do. Moreover, a second drawback stems from the fact that such inclined jets hit the
walls of the washing space with a considerable horizontal component thus causing a
significant noisiness of the dishwasher.
[0006] An improvement with respect to this simple type of sprinkler is the mobile sprinkler
disclosed in
EP 0727176 which is pivoted on a shaft located at the end of a support arm which is in turn
vertically pivoted at its other end to a feed duct integral with the wash tank. This
support arm is therefore provided also with a horizontal reciprocating motion generated
by the sprinkler itself due to the distance between the axis of the shaft on which
it is pivoted and the point where the support arm is pivoted on the feed duct.
[0007] In fact, the inclined jet coming out from a propulsion end nozzle of the sprinkler
generates a reaction force which can be broken up in the horizontal plane into a first
component along the longitudinal axis of the sprinkler and a second component along
a direction perpendicular thereto. While this second component is the one which generates
the rotation of the sprinkler, the component along the longitudinal axis is discharged
on the shaft located at the end of the support arm. This results, therefore, in a
horizontal rotation of said arm pivoted on the vertical axis of the feed duct, moving
alternately from right to left and backwards according to the rotation of the sprinkler,
i.e. according to the direction from which the axial component arrives on the sprinkler
shaft.
[0008] This arrangement allows to sprinkle also the outermost dishes when they are arranged
in a rectangular tank and also increases the surface directly sprinkled by the jets
emitted from the nozzles, since thanks to the combination of the revolving motion
of the sprinkler with the reciprocating motion the nozzle paths have a much more complex
development. However in this type of structure the revolving and reciprocating motions
of the sprinkler are mutually bound, i.e. at each rotation of the sprinkler corresponds
a translation thereof due to the oscillation of the support arm.
[0009] This implies that a high revolving frequency of the sprinkler corresponds to a high
oscillating frequency of the support arm and therefore to a certain noisiness since
the support arm hits the end stops at the end of each travel. Moreover, it is impossible
to reduce said oscillating frequency of the arm without decreasing the revolving speed
of the sprinkler thus negatively affecting the washing effectiveness.
[0010] An improvement over this arrangement is disclosed in
EP 1201178 that provides a sprinkling assembly wherein the ratio between the revolving frequency
of the sprinkler and the oscillating frequency of the support arm is no longer one
but much greater. In other words, it is possible to set a transmission ratio whereby
the oscillation of the support arm occurs only every given number of rotations of
the sprinkler, with the advantage of lower noisiness and lower wear achieved thanks
to the reduction of the oscillating frequency of the support arm.
[0011] To achieve this, in brief, the support arm is provided with two opposite nozzles
suitable to emit jets that cause the oscillation of the arm, the emission of said
jets being controlled by a rotating shutter whose rotation is controlled by the rotation
of the sprinkler through a lower ring externally provided with a tooth suitable to
engage with an adjacent horizontal toothed wheel which is integral with the shutter.
[0012] Although this sprinkling assembly provides significant advantages with respect to
the sprinkling assembly disclosed in
EP 0727176, nonetheless it is not free from drawbacks substantially due to the presence of the
cantilevered support arm which still implies problems of cost, complexity and reliability.
[0013] Therefore the object of the present invention is to provide a revolving sprinkling
assembly that overcomes the above-mentioned limits of prior art sprinklers.
[0014] This object is achieved by means of a sprinkling assembly in which the revolving
sprinkler is no longer mounted on a cantilevered support arm but rather on a secondary
oscillating sprinkler which is longer and coaxial thereto. In other words, a mechanism
similar to the mechanism that in
EP 1201178 was used to achieve the oscillation of the support arm only every given number of
rotations of the revolving sprinkler, in this new arrangement is used to achieve a
periodical oscillation of said secondary sprinkler that having a greater length can
reach the portions of the tank not covered by the revolving sprinkler.
[0015] The fundamental advantage of the sprinkling assembly according to the present invention
resides in its greater simplicity, inexpensiveness and reliability obtained thanks
to the elimination of the cantilevered support arm and to the coaxial arrangement
of the two sprinklers in the middle of the wash tank.
[0016] A further advantage stems from the possibility of easily setting within a certain
range the transmission ratio between the two sprinklers, i.e. the time interval between
the oscillations of the secondary sprinkler.
[0017] These and other advantages and characteristics of the sprinkling assembly according
to the present invention will be clear to those skilled in the art from the following
detailed description of two embodiments thereof, with reference to the annexed drawings
wherein:
Fig.1 is a diagrammatic, partially sectional side view of a first embodiment of the sprinkling
assembly;
Fig.2 is an enlarged view of detail A of Fig.1.
Fig.3 is a diagrammatic exploded view of the sprinkling assembly;
Fig.4 is an enlarged view of detail B of Fig.3;
Fig.5 is a diagrammatic top plan view of the sprinkling assembly placed at the center of
the wash tank of a dishwasher whose width is smaller than its length;
Fig.6 is an enlarged view of detail C of Fig.5; and
Fig.7 is a diagrammatic top plan view of a second embodiment of the sprinkling assembly
placed in the same wash tank of Fig.5 but at an eccentric position.
[0018] Referring to figures 1 to 6, there is seen that the sprinkling assembly according
to the present invention essentially consists of a primary revolving sprinkler 1 and
a secondary oscillating sprinkler 2, with the former coaxially pivoted on the latter
which is in turn pivoted on a support 3 arranged at the end of a water supply duct
(not shown).
[0019] In practice, as shown in the detail of Fig.2, sprinkler 1 is centrally snap-fitted
on sprinkler 2 through a bottom ring 4 that engages a top socket 5 of sprinkler 2,
which is in turn centrally snap-fitted through a bottom ring 6 that engages support
3 and is in communication with the top socket 5. In this way, the supply duct reaching
support 3 feeds both sprinklers 1 and 2.
[0020] The primary sprinkler 1 is a conventional hollow sprinkler with two opposite arms
provided with a wash and propulsion nozzle 1a at the end of each arm and with wash
nozzles 1b along its length, which substantially corresponds to the shorter side of
the rectangular tank in which it is located (the width in the illustrated example).
[0021] The secondary sprinkler 2 has a shape similar to the primary sprinkler 1 but, on
the contrary, its length substantially corresponds to the longer side of the rectangular
tank (the length in the illustrated example) and it is provided only with wash and
propulsion nozzles in the end portions projecting beyond the primary sprinkler 1,
said nozzles being arranged in two opposite pairs 2a, 2b at the end of the first arm
and two opposite pairs 2c, 2d at the end of the second arm.
[0022] As a consequence, while the primary sprinkler 1 is a simple revolving sprinkler that
continuously revolves in the same direction, the secondary sprinkler 2 is an oscillating
sprinkler that alternately moves in the two directions thanks to the push of the jets
sequentially emitted from the end nozzles 2a, 2b, 2c and 2d as explained hereafter.
[0023] In fact, a fraction of the pressurised water arriving through the supply duct and
support 3 rather than flowing into the primary sprinkler 1 is laterally diverted into
a chamber 7, open at the top, which is formed in the first arm of the secondary sprinkler
2 next to the top socket 5. Said chamber 7 has four lateral openings 7a, 7b, 7c, 7d
putting it into communication with four ducts 8a, 8b, 8c, 8d extending in the two
arms between chamber 7 and nozzles 2a, 2b, 2c, 2d respectively.
[0024] The bottom ring 4 of the primary sprinkler 1 is externally provided with a tooth
4a that at each rotation of sprinkler 1 engages an adjacent horizontal toothed wheel
9 which is integral with an underlying cylindrical shutter 10. Said shutter 10 is
provided with a lateral opening 10a and rotatably snap-fitted within chamber 7 so
as to close it at the top and allow the water out only through said lateral opening
10a.
[0025] In practice, as shown in the detail of Fig.6, opening 10a has a size equal to the
size of openings 7a, 7b, 7c, 7d and when it is aligned with one of said openings it
allows the water to flow out into the relevant duct 8a, 8b, 8c, 8d so as to reach
the respective end nozzles 2a, 2b, 2c, 2d.
[0026] The simple and effective operation of the sprinkling assembly according to the invention
is therefore readily understood in the light of the description given above.
[0027] Assuming that nozzles 1a are oriented to rotate sprinkler 1 clockwise (as seen from
above), it follows that tooth 4a at each rotation causes a partial counter-clockwise
rotation of the toothed wheel 9. The number of rotations of sprinkler 1 corresponding
to a complete rotation of the toothed wheel 9 is obviously defined by the transmission
ratio between said members 1 and 9, namely in practice by the number of teeth of wheel
9 (twelve in the illustrated example). However, both ring 4 and the toothed wheel
9 could have a different number of teeth so as to obtain a different transmission
ratio.
[0028] Consider to start from the position of Fig.6 where opening 10a of shutter 10 has
just arrived into alignment with opening 7a of chamber 7. In this position the water
flows into duct 8a and reaches nozzles 2a generating jets that cause a counter-clockwise
oscillation of the secondary sprinkler 2, as indicated by the arrow in Fig.5. Sprinkler
2 thus reaches the position indicated in broken lines in Fig.5, defined by and end
stop, and along its path nozzles 2a sprinkle the rear portion of the wash tank not
covered by the nozzles of the primary sprinkler 1.
[0029] Since in the illustrated example the transmission ratio between sprinkler 1 and the
toothed wheel 9 is 12:1, upon the following rotation of sprinkler 1 the toothed wheel
9 will rotate through 30° and the same applies to shutter 10 integral therewith. Therefore
opening 10a will no longer be aligned with opening 7a thus stopping the jets emitted
from nozzles 2a, and the same applies for the following rotation through 30° during
which opening 10a is still along the wall of chamber 7 between openings 7a and 7b.
[0030] At the third rotation through 30°, opening 10a arrives at opening 7b whereby the
water can flow into duct 8b and reach nozzles 2b generating jets that cause a clockwise
oscillation opposite to the preceding one, thus taking the secondary sprinkler 2 back
to the position of Fig.5. This position is obviously also defined by an end stop and
along the path nozzles 2b sprinkle the rear portion of the wash tank.
[0031] The oscillating cycle of the secondary sprinkler 2 is completed with a similar back-and-forth
oscillatory movement when the following rotations of shutter 10 take opening 10a into
alignment first with opening 7c and then with opening 7d, whereby the water is emitted
from nozzles 2c, 2d that sprinkle the front portion of the wash tank not covered by
the nozzles of the primary sprinkler 1.
[0032] Therefore it is clear how this simple structural arrangement allows to oscillate
the secondary sprinkler 2 only every three rotations of the primary sprinkler 1, and
it is also clear that it is sufficient to change the number of teeth of wheel 9 and/or
of ring 4 to change said oscillating frequency. Moreover, if one desires to extend
the pushing and sprinkling time of the end nozzles 2a, 2b, 2c, 2d there can be provided
openings 7a, 7b, 7c, 7d and/or an opening 10a having a greater width, e.g. extending
over an arc of rotation of 60° rather than 30° such that chamber 7 remains in communication
with the respective duct 8a, 8b, 8c, 8d through two rotations of the primary sprinkler
1.
[0033] Similarly, the rotating shutter 10 could be provided with a second opening 10a diametrically
opposite to the first opening illustrated above so as to put chamber 7 in communication
simultaneously with the two arms, i.e. with ducts 8a, 8c or ducts 8b, 8d. In this
way it is possible to achieve the sprinkling of both the front portion and the rear
portion of the wash tank at every oscillation of the secondary sprinkler 2.
[0034] If support 3 is located not at the center of the rectangular wash tank but at an
eccentric position such that the primary sprinkler 1 arrives close to three sides
of the tank, the portion not reached by the wash nozzles is on one side only of the
tank. In this case it is possible to adopt the second embodiment illustrated in Fig.
7 that is different from the first embodiment in that the secondary sprinkler 2',
while still being coaxially pivoted on the primary sprinkler 1, only has one arm extending
beyond the latter with the relevant end nozzles 2a', 2b' fed through ducts 8a', 8b'.
[0035] The members defining the oscillating frequency of the secondary sprinkler 2', namely
ring 4, chamber 7', toothed wheel 9 and rotating shutter 10 may remain the same or
be consequently changed, providing a different transmission ratio and/or openings
greater in number and/or larger in size. When retaining the same members of the first
embodiment it is obvious that the oscillating frequency of the secondary sprinkler
2' is reduced by half.
[0036] It is clear that the number of nozzles of sprinklers 1, 2 and 2' can change with
respect to the number of nozzles of the illustrated embodiments and that the secondary
sprinkler 2, 2' could also have "uncontrolled" ducts, i.e. ducts constantly in communication
with the supply duct, provided with simple wash nozzles that continuously sprinkle
without affecting the oscillation.
[0037] Finally, it should be noted that the illustrated embodiments relating to a sprinkling
assembly located at the bottom of the tank under the bottom rack are mere examples,
since the same structure can be similarly applied in other ways. For example, the
sprinkling assembly can be located also above the top rack by turning it upside down,
since in that case support 3 extends downwards from the tank ceiling and the sprinkling
takes place from above, or below the top rack by swapping the positions of the primary
and secondary sprinklers since in that case support 3 extends downwards from the top
rack and the sprinkling takes place from below.
1. A sprinkling assembly for dishwashers including a primary revolving sprinkler (1)
centrally pivoted on a support (3) through which water under pressure is fed, characterized in that it further includes a secondary oscillating sprinkler (2; 2') coaxially pivoted on
said primary sprinkler (1) and provided with at least one arm having such a length
as to project beyond the primary sprinkler (1), said at least one arm being provided
with opposite wash and propulsion nozzles (2a, 2b, 2c, 2d; 2a', 2b') located in the
end portion(s) projecting beyond the primary sprinkler (1), and in that the emission of water jets from said wash and propulsion nozzles (2a, 2b, 2c, 2d;
2a', 2b') is controlled by a rotating shutter (10) provided with at least one opening
(10a), the rotation of said rotating shutter (10) being controlled by the rotation
of the primary sprinkler (1) according to a transmission ratio greater then unity.
2. A sprinkling assembly according to claim 1, characterized in that the rotation of the shutter (10) is controlled by the primary sprinkler (1) through
a lower ring (4) externally provided with at least one tooth (4a) suitable to engage
with an adjacent horizontal toothed wheel (9) which is integral with the shutter (10).
3. A sprinkling assembly according to claim 1 or 2, characterized in that the shutter (10) is fitted within a cylindrical chamber (7) in which there are formed
four lateral openings (7a, 7b, 7c, 7d) that put said cylindrical chamber (7) in communication
with four ducts (8a, 8b, 8c, 8d) extending between the chamber (7) and the respective
wash and propulsion nozzles (2a, 2b, 2c, 2d).
4. A sprinkling assembly according to claim 3, characterized in that the shutter (10) is provided with two diametrically opposite openings (10a) so as
to put the chamber (7) in communication simultaneously with two opposite ducts (8a,
8b, 8c, 8d).
5. A sprinkling assembly according to any of the preceding claims, characterized in that the secondary sprinkler (2; 2') is pivoted between the primary sprinkler (1) and
the support (3).
6. A dishwasher with a rectangular wash tank, characterized in that it includes at least one sprinkling assembly according to any of the preceding claims.