The present invention relates to pumps for dishwashers and the like,
and in particular to a double-delivery bidirectional pump in which the direction
of rotation determines through which delivery the water is delivered. Specific
reference will be made in the following to the application of said pump to a dishwasher,
but it is clear that what will be said can be adapted also to the use of the present
pump in a washing machine or other domestic appliance.
It is known that in modern dishwashers the user is often offered the
possibility of running a "half load", i.e. a washing cycle in which only one of
the sprinklers is used, or an "alternate" wash in which the two sprinklers are
alternately supplied thus allowing to extend the washing of the dishes in one of
the two racks.
This type of program is usually obtained through a single-delivery
washing pump and a flow distribution valve controlled by the control unit of the
machine to direct the water flow to the upper or lower sprinkler. As an alternative,
there may be provided a double-delivery pump with two valves independently controlling
the supply to the two sprinklers.
Other valves may be provided to supply a hydraulic circuit for the
periodical cleaning of the dishwasher filters, or a short-length heating circuit
to reduce the energy waste during the water heat-up phase. In addition to the washing
pump there is also provided a draining pump to drain the water out of the tank
at the end of the washing cycle.
Clearly, the presence of one or more valves and of two pumps implies
an increase in the machine manufacturing cost, as well as a decrease in reliability
since the failure or clogging of a valve or a pump can jeopardize the correct
Therefore the object of the present invention is to provide a pump
which allows to overcome said drawbacks. This object is achieved by means of a
double-delivery pump capable of handling two separate hydraulic circuits simply
by reversing its direction of rotation.
The main advantage of the pump according to the present invention
is exactly that of allowing to dispense with the valve(s) to control the supply
to two different hydraulic circuits, or that of combining the functions of washing
pump and draining pump.
Another advantage of this pump stems from the fact that said functionality
is achieved through a very simple structure substantially without mobile members,
with positive results as to cost and reliability.
These and other advantages and characteristics of the pump according
to the present invention will be clear to those skilled in the art from the following
detailed description of two embodiments, with reference to the annexed drawings
- Fig.1 is a vertical sectional view of the hydraulic group of the pump
in a first embodiment;
- Fig.2 is an exploded vertical sectional view of the members which make
up the pump impeller;
- Fig.3 is a vertical sectional view of the pump showing the path of the
water flow when the pump is driven counter-clockwise;
- Fig.4 is a vertical sectional view of the hydraulic group taken along
line A-A of fig.3;
- Fig.5 is a vertical sectional view of the pump showing the path of the
water flow when the pump is driven clockwise;
- Fig.6 is a vertical sectional view of the hydraulic group taken along
line B-B of fig.5;
- Fig.7 is a vertical sectional view of the pump in a second embodiment;
- Fig.8 is a horizontal sectional view of the hydraulic group taken along
line C-C of fig.7.
Referring to figs.1-6 above, there is seen that the hydraulic group
of the pump according to the invention includes a housing, made up of an external
half-shell coupled to an internal half-shell, and an impeller rotatably arranged
within said housing. More specifically, the impeller is made up of three connected
coaxial members, namely a hub S provided with a blading C, an intermediate ring
R also provided with a blading A as well as with a peripheral rim B, and a cover
The external half-shell has a mouth K, connected to the supply duct,
through which the water enters a first external chamber E which ends at the top
with a first delivery duct H, and is separated by ring R from a second internal
chamber F which ends at the top with a second delivery duct J. The connection between
the two chambers E, F is achieved through the central opening of rings T, R in
that along the periphery rim B is introduced into a corresponding channel D so
as to form a labyrinth seal G.
The novel aspect of the present pump is the particular configuration
of the impeller and delivery ducts, which allows to obtain a "double" pump which
can be driven alternately in one direction or the other. In fact, as shown in figs.4
and 6, while blading C of hub S has a counter-clockwise spiral shape and the relevant
duct J of chamber F is directed leftward, blading A of ring R has an opposite
clockwise shape and the relevant duct H of chamber E is directed rightward.
From the description above and referring in particular to figs.3 and
5, the simple and reliable operation of the pump according to the invention is
When motor M drives the impeller in the counter-clockwise direction
(fig.3), the incoming water flow W is captured only to a very small extent by blading
A which is designed for the clockwise rotation, whereby the water passes through
ring R and is pushed by blading C out through the delivery duct J, which for example
is connected to one of the sprinklers.
Similarly, when motor M drives the impeller in the clockwise direction
(fig.5), the incoming water flow W is captured mostly by blading A, which is exactly
designed for the clockwise rotation, and is pushed out through the delivery duct
H, which for example is connected to the other sprinkler. The water passing through
ring R is just a small amount, and in any case blading C is designed for the counter-clockwise
rotation and therefore results ineffective.
The direction of rotation of the electric motor M and therefore of
the impeller can be controlled in various ways well known to a person skilled in
the art. For example, in the case of a nonsynchronous single-phase motor a switch
may be provided to change the sequence of supply to the windings to obtain the
clockwise or counter-clockwise rotation. This switch may be part of an electromechanical
timer or it can be part of an electronic board to achieve even more sophisticated
functions, such as a slow start at every reversal of the direction of rotation
(to reduce the noise) or the activation on the basis of the signals coming from
sensors which detect the presence of dishes to decide to which sprinkler the water
flow must be directed.
As mentioned in the introductory portion, the two ducts H, J may obviously
be connected to two hydraulic circuits of any kind, not only to those of the upper
and lower sprinkler. Therefore the pump may act as washing pump when rotating
in a first direction, supplying both sprinklers, and the rotation in the opposite
direction may serve to supply a secondary hydraulic circuit for heating the water
or for cleaning the filters.
In the same way it may act as draining pump when rotating in the opposite
direction, thus allowing to dispense with the draining pump. However in this case
it is necessary to separate the supply ducts entering the pump to prevent the dirt
present in the water already used for washing from re-entering the circuit.
To this purpose the hydraulic group may be modified as illustrated
in figs.7 and 8, by providing an intermediate ring R' with a central opening U
which is smaller and shaped with a neck extending outward to which there is connected
a supply duct L separate from the duct connected to mouth K.
In this way the pump can take clean water for washing through a supply
duct and dirty water to be drained through the other duct, the mixing between the
two chambers being negligible.
It is clear that the above-described and illustrated embodiments of
the pump according to the invention are just examples susceptible of various modifications.
In particular, the exact shape of bladings A and C may be somewhat changed as
long as they are designed for rotation in the two opposite directions, and the same
applies to the labyrinth of seal G which may have a different configuration, e.g.
by making it double. Moreover, the direction of rotation may obviously be inverted
with respect to what is depicted in the figures, i.e. by designing the blades for
the counter-clockwise rotation in the external chamber and for the clockwise rotation
in the internal chamber. Similarly, the position of the delivery ducts may be
changed along the periphery of the hydraulic group (e.g. at the bottom or on a side)
as long as the orientation remains consistent with the direction of rotation of
the blading in each chamber.