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The present invention refers to a composite rack adapted to hold and
support the washload items to be handled in a dishwashing machine, in
particular of the kind intended for use in households.
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Racks intended for use in dishwashing machines are largely known to
be made in the majority of the cases with a grid-like structure formed by
metal-wire rods that are so shaped and welded to each other as to define
at least a substantially horizontal resting surface, or bottom wall, and
substantially vertical side walls. The metal wire rods used to form the rack
are additionally coated, after a surface cleaning pre-treatment process,
with a protective polymeric material.
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Metal-wire racks have a number of drawbacks. In particular, their
architecture is undesirably rigid, i.e. limited by problems and
requirements connected with the mechanical processing of the metal-wire,
which must in fact be suitably bent and, possibly, deep-drawn in order to
give the rack a suitable conformation in view of the basic needs that it is
called to meet. It therefore proves practically impossible for a metal-wire
rack of this kind to be made with a structure that is capable of duly
complying with the modern ergonomic and aesthetical requirements that
are becoming increasingly important for the users and consumers in
general.
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In all cases, the manufacture of metal-wire racks for dishwashing
machines usually calls for some extent of manual work to be provided for
positioning and welding special members or items consisting of wire with a
different cross-section area, as for instance this may be the case of the
prongs of the side combs that are usually provided to support cups or
similar items. The resulting impossibility for the rack manufacture on an
industrial scale to be completely automated obviously increases the
related costs.
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In theory, the above mentioned drawbacks could be overcome by
making the racks completely of plastic material, i.e. as an all-plastic
construction. However, this would bring unacceptable problems of a
technical nature with it. In particular, in order to ensure a sufficient
extent of strength and rigidity as required in view of a capability of
adequately supporting the washload items even at the usual drying
temperatures in a dishwashing machine (i.e. approx. 70°C), the racks
should be made with a basic plastic framework of an appropriately large
thickness, which therefore would feature substantially small apertures for
the wash water jets sprayed onto the washload items to adequately pass
therethrough, under a resulting reduction of the washing performance an
d effectiveness of the machine.
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Furthermore, it is a generally known fact that plastic, unlike metal,
does not favour the evaporation of residual water, so that the use of a dish
rack of plastics would generally entail an inferior dish-drying effect.
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Composite racks for dishwashing machines have also been proposed,
which comprise a metal-wire framework on which there may be added,
e.g. by snap-fitting, individual component parts of plastic material that
may be shaped to relatively complex forms owing to technical, ergonomic
and/or aesthetical reasons. Solutions of this kind are described for
instance in GB-A-2 287 874 and EP-A-0 855 166.
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Also known in the art, for instance from the disclosure in GB-A-2 359
248, are composite racks comprising a metal-wire framework on which
there are then added, by an over-injection moulding process, individual
component parts of plastic material such as for instance a peripheral
frame forming an upper edge of the rack.
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Anyway, even in the above cited composite racks the architecture is
undesirably limited by the need arising for the various plastic component
parts to be capable to compliantly adapt to the basic form of the metal-wire
framework, which, as already pointed out earlier in this description,
is scarcely versatile. Furthermore, the fabrication of a composite rack of
the above cited kind is undesirably labour-demanding and cost-intensive
on an industrial scale owing to the need for each one of the individual
plastic component parts to be assembled on to the metal-wire framework.
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It therefore is a main purpose of the present invention to provide a
composite rack for dishwashing machines, which is adapted to be
manufactured quickly and at a low cost, while featuring a versatile
structure and/or appearance and, at the same time, complying with the
technical requirements of strength and convenience in use.
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According to the present invention, this and other aims are reached in
a composite rack for dishwashing machines incorporating the
characteristics as recited and defined in the appended claims.
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Anyway, features and advantages of the present invention may be more
readily understood from the description that is given below by way of nonlimiting
example with reference to the accompanying drawings, in which
- Figure 1 is a schematic view of a first embodiment of the composite
rack according to the present invention, in an assembled state thereof;
- Figure 2 is a schematic view of a second embodiment of the composite
rack according to the present invention, in an assembled state thereof;
and
- Figure 3 is a partially cross-sectional view of a detail of the rack
illustrated in Figure 1.
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The rack according to the present invention has a composite structure
that is made partly of metal wire and partly of plastics and comprises
support members intended to come into substantial contact with the
washload items, such as dishes, pans, glasses and the like.
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In the example illustrated in Figure 1, which refers to a dish rack that
is prevailingly adapted to be slidably positioned in a lower position in the
washing vessel of a dishwashing machine, such support and contact
members comprise substantially vertical prongs 7, or the like, shooting
out from cross-members 8 and/or longitudinal members 9 that form a
base surface.
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Furthermore, the composite structure of the rack comprises a plurality
of structural and/or functional parts, such as a frame 3 delimiting the
rack all along the periphery thereof, an appropriately shaped gripping
handle 4, pins 5 for supporting castors 6 or the like, by means of which
the rack is capable of sliding with respect to side runners provided in the
dishwashing machine in a generally known (and not shown) manner.
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Said structural and/or functional parts provided in the rack may also
comprise hinging and guiding means (not shown) adapted to enable the
prongs 7 to be folded or thrown down, such as this is described for
instance in GB-A―2 287 874.
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The above mentioned support and contact members 7-9 are made in
the form of a metal-wire framework 1. The metal wire used to such a
purpose is particularly fit to ensure a sufficient extent of strength and
rigidity in view of adequately sustaining the washload items, while on the
other hand featuring just a small diameter, so that the entire framework
1 advantageously represents a substantially negligible impediment as far
as the jets of washing and rinsing water are concerned, which in a
generally known (and not shown) manner hit the rack when the
dishwashing machine is in operation.
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Furthermore, the metal wire of which said support and contact
members 7-9 are made, favours the evaporation of the hot water , i.e. an
effect that is normally used in dishwashing machines for drying the dishes
after washing. As a result, unlike what happens in the case of plastic
racks, the dishes can be dried in an optimum manner, in particular
without any substantial scale formation at the contact points with the
members 7-9.
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However, according to an aspect of the present invention, it is only the
support and contact members 7-9 that are provided in the form of a
metal-wire framework 1, whereas the remaining part of the rack is formed
by a single complementary body 2 of plastic material comprising the afore
cited structural and/or functional parts integrally therewith. In addition,
the metal-wire framework and said single-piece plastic body 2 are
mechanically coupled with each other in the manner that shall be
described in greater detail further on.
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The result is that the framework 1 turns practically out to be solely
formed by members 7-9 of metal wire having a relatively small size and
elementary shapes all the way, so that, unlikely what normally happens in
traditional racks made fully or partially of metal, these members are
perfectly capable of being welded together, i.e. to each other, in a fully
automated manner. The resulting advantages in a production on an
industrial scale are fully manifest.
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The single-piece complementary plastic body 2 can in turn be easily
manufactured by a moulding technique, separately from the framework 1,
in such a manner as to incorporate the associated structural and/or
functional parts, as this has already been said earlier in this description,
with a maximum extent of freedom as far as ergonomic conformation,
aesthetical appearance and/or colour is concerned.
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In the example illustrated in Figure 1, these integrally provided parts
will comprise the peripheral frame 3 and, preferably, also the pins 5 for
the wheels 6, as well as one or more possible grips 4. In the case that the
rack also includes hinging and guiding means for folding or pulling down
the prongs 7, as already mentioned earlier in this description, even such
means can be provided integrally with said plastic body 2.
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In conclusion, the composite rack for dishwashing machines according
to the present invention can be advantageously manufactured on an
industrial scale by fabricating the framework 1 on an automatic line that
is adapted to most quickly complete the necessary welding and, possibly,
drawing, "rilsanization" and plastic-coating steps, to which the metal parts
7-9 must be subjected, so as to obtain one or more substantially
standardized structures.
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Separately, and even simultaneously, the single-piece complementary
body 2 can be manufactured by a plastic moulding technique (using for
instance such a plastic material as syndiotactic polystyrene,
polyoxymethylene copolymer or polymethylpentene) to any conformation
and/or colour as actually desired.
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In an assembly station, each standard structure of the metal-wire
framework 1 can be quickly coupled mechanically, preferably by snap-fitting,
to a corresponding single-piece plastic body 2, thereby most
conveniently and quickly obtaining a complete rack having with an
extreme overall versatility in terms of shape, appearance and/or colour
according to the selected ones among the possible combinations of the
various complementary parts 1 and 2. It can be readily appreciated that
such a versatility would turn out as being unpracticably expensive to
obtain in the case of composite racks of a traditional design, in which the
various plastic parts are manufactured, i.e. moulded as individual pieces
that are then applied individually on to a metal-wire base framework.
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The same considerations apply substantially also to the example
illustrated in Figure 2, which refers to a rack that is prevailingly adapted
to be slidably positioned in an upper position in the washing vessel of a
dishwashing machine.
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In a per sè known manner, for instance as described in EP-A-0 901
770, such an upper rack comprises cross-members 7 and longitudinal
members 9 that are bent and shaped in a different manner, and may be
adapted to be mounted in the dishwashing machine with the aid of height-adjustable
side support means as schematically indicated at 10 in Figure
2. In this case, the complementary plastic body 2 integrally comprises at
least part of said height-adjustable side support means 10.
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Furthermore, in the above considered case of an upper rack, the
complementary plastic body 2 preferably comprises in an integral manner
also a part 11 of a water connection conduit that is usually provided in
the dishwashing machine to supply water to the (generally known and not
shown) water spray means that are associated to the same rack.
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It shall of course be appreciated that the composite rack for
dishwashing machines that has been described above by mere way of
example may be the subject of a number of modifications without
departing from the scope of the present invention.
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In any case, the metal framework 1 and the complementary plastic
body 2 are preferably coupled with each other in a loosenable manner, so
as to ensure the selective interchangeability thereof at any time, even in
the field, with the aid of a plurality of quick-release coupling means
distributed all along at least two opposite sides of the rack.
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With reference also to Figure 3, each one of such coupling means
comprises an appropriately shaped receptacle 12 that is provided
integrally in the plastic body 2 and is adapted to accommodate, in a
substantially vertical direction, a correspondingly shaped respective head
portion 13 of a corresponding metal wire of the framework 1 extending
transversally with respect to the above mentioned opposite sides of the
rack, which preferably form a front side 14 and a rear side 15 of the rack,
respectively.
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The head portion 13 of the metal wire is substantially formed in the
shape of a reverse U lying on a plane that is substantially parallel to the
opposite sides 14 and 15 of the rack, wherein an extremity 16 of said U is
free, while the other extremity 17 thereof extends into the metal wire itself,
which preferably forms a longitudinal member 9.
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Such a solution requires the metal wire to just undergo an elementary
bending operation and, at the same time, enables an effective quick-release
coupling system to be provided, which, as this has also been found
and demonstrated experimentally, confers considerable strength and
rigidity, especially in the longitudinal direction, to the entire composite
rack. All this thanks to the fact that the above described structure is
effective in even geometrically compensating the normal distribution of
mechanical stress forces acting in the dish rack.
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Among the advantages deriving therefrom, the possibilities for the
dishes or, for the matter, the washload items in the rack to overturn or fall
off are reduced to a minimum, even in the case that the rack is being
handled in an abrupt manner as this occurs for instance when it is
slidably pulled out/pushed in rapidly from/in the dishwashing machine.
