[0001] The present invention relates to a tray for drying foodstuffs, particularly pasta.
More in detail, the invention relates to a new plastic tray and a preferred process
for realizing said tray.
[0002] Drying treatments are well known in the food industry. A common technique, especially
for pasta, is to load the product on suitable supporting trays which are then inserted
into hot-air drying ovens.
[0003] According to known art, the trays are essentially formed by an external rigid frame,
which supports a net (or grate) where the food product is loaded. The frame is generally
rectangular, with two longitudinal sides and two main cross beams. Some intermediate,
smaller beams may also be provided, to stiffen the tray and to support the net, avoiding
an excessive deformation under the weight of the drying product. The material of the
tray may be wood, plastics, stainless steel or aluminium alloy.
[0004] The frame is made by a number of fixed or screwed elements; the net is fixed to the
frame along its perimeter, at about half-height of the frame itself. The sides of
the frame are shaped on their upper and lower faces, for the trays to be easily stacked
inside the drying oven.
[0005] The direction of the hot air flow is generally parallel to the longitudinal sides
of the trays, i.e. perpendicular to the cross beams.
[0006] The known trays have many disadvantages that have not been solved yet.
[0007] First, the structure made of several parts makes the tray less hygienic and more
difficult to clean. In fact, some small gaps are necessarily formed between the contiguous
parts and around the fixing screws or other fixing means, being very difficult to
clean and thus a good receptacle for dirt, residues, bacteria. A perfect cleaning
of the equipments is of the utmost importance in the food industry, and any obstacle
to this is a major disadvantage.
[0008] The structure made of several joined parts also results in a more expensive and more
complicated item.
[0009] The main cross beams have generally a sharp-edged, square or rectangular cross-section,
and the height of said beams is only a little less than the height of the longitudinal
sides. As a consequence, some negative effects on the hot air flow arise: the flow
is significantly disturbed by the cross beams and the flow resistance is high; when
the trays are stacked in their normal working conditions, a little air passage is
left between the cross beams, further increasing the flow resistance and forming undesired
turbulences.
[0010] The cross beams, being so arranged, are also responsible of a remarkable slip effect
(i.e. detachment of the hot air flow from the surface of the profile). The product
behind the cross beams remains between a more or less turbulent slipstream, and is
not fully exposed to the hot air flow, contrary to the product in the middle of the
tray.
[0011] The disadvantageous effects are: first, the quality of the product is not uniform,
as some product is correctly dried, while some other product - closer to the longitudinal
sides, and more particularly behind the cross beams - is not well exposed to the hot
air flow and remains humid; further, more energy is spent for blowing the hot air,
due to the high flow resistance, and this increased energy consumption, on a long-term
basis, is not negligeable.
[0012] The small beams for supporting the net are further elements disturbing the hot air
flow, particularly under the net.
[0013] It should be noted that, as the drying treatment is very important for the quality
of the product, the hot air flow should be as uniform and well-distributed as possible.
Generally speaking, the tray should be designed to avoid these slip-effects, and to
avoid that some portions of the net are under- or overexposed to the hot air flow.
[0014] Referring now to dry pasta, for example, a correct drying treatment is important
to give the pasta the desired humidity, a brighter yellow colour and better cooking
performance, and to obtain a product free from cracks and breaks.
[0015] Further problems are related to the material of the tray.
[0016] Wood trays are still widely used, but give even more problems from the hygienic point
of view, due to the natural porosity of wood which absorbs humidity and favours the
growth of bacteria. Furthermore, the humid pasta does not slip freely on the wood
surface, so that the uniform distribution of the pasta during the loading phase is
impaired.
[0017] Wood has other disadvantages, including warping and deformation with the passing
of time, being not well suited for an industrial equipment subject to intense use.
The tray may also lose some wood chips, that could be mixed with the product. Wood
trays with metal beams are also realized, but the above problems remain unsolved.
[0018] Plastic trays give only a partial solution to these problems, but introduce further
disadvantages. In fact, they are made by an even greater number of parts, compared
to wood trays; they often have two-piece longitudinal sides, with several fixing screws
and, hence, several unhygienic gaps. The frame of known plastic trays is generally
made of U-shaped elements, facing each other, thus forming an internal chamber that
is a dangerous receptacle for dirt and bacteria, and cannot be accessed for cleaning
unless the tray is dismantled.
[0019] Low stiffness is another disadvantage of plastic trays, giving problems during the
handling, loading and unloading of the product. For these reasons, plastic trays have
so far encountered a poor success on the market.
[0020] Metal trays, generally made of aluminium alloys, also comprise several parts, normally
made with extruded beams closed by plastic caps, still having the problem of the unhygienic
gaps.
[0021] Moreover, metal trays are rapidly heated to about the same temperature of the hot
air, which is commonly 70 °C, but in some cases may reach 90 °C, due to their good
heat exchange capability. This however results in another disadvantage, because the
heat absorbed by the tray is obviously a wasted heat, increasing the hot air consumption;
the product that is in direct contact with the hot tray is overdried; hot trays are
difficult to handle for extracting them from the oven, emptying and re-loading.
[0022] The aim of the invention is to eliminate or reduce, as far as possible, the above
disadvantages of known trays for drying pasta and other food products.
[0023] A first aim of the invention is to realize a tray that can be perfectly cleaned and
sanitised, having no gaps or receptacles where dirt and bacteria may accumulate. A
purpose of the invention is also to give the tray a good mechanical stiffness, to
avoid an excessive deformation under the weight of the product and to be more handy.
[0024] A further aim is to keep the hot air flow uniformly distributed on the net, so that
the food product is uniformly dried, following the correct drying cycle, and avoiding
that some product is excessively dry or still humid at the end of the treatment.
[0025] Still another aim is to achieve, through the performance of the tray, a better efficiency
in terms of quantity of dried product vs. hot air consumption.
[0026] These aims are reached by a tray for drying foodstuffs, particularly pasta, characterised
by a plastic single-piece frame structure, comprising longitudinal sides, main cross
beams and a central net for supporting said foodstuffs.
[0027] According to one aspect of the invention, to achieve a better efficiency of the tray,
the main cross beams have a shaped, aerodynamic profile reducuing the perturbation
on the drying hot air flow. The profile of the main cross beams is optimized to reduce
the disturbance to the air flow, particularly slip-effect and formation of turbulences.
Preferably, the cross section of the beams is considerably less high compared to that
of the longitudinal sides, to reduce the inlet losses of the air flow.
[0028] The shaped cross beams, according to a preferred embodiment, have a cross section
substantially oval and asymmetrical with respect to the horizontal plane, as it will
be explained below.
[0029] According to a further aspect of the invention, to optimise practicalness and efficiency,
the tray comprises small beams to support the net, which are part of said single-piece
structure, and are also shaped like the main cross beams.
[0030] Preferably, said small beams are located some millimetres below the net, and comprise
a plurality of supports for supporting the net in discrete points. These discrete
supports allow the hot air to flow directly under the net.
[0031] Any plastic material can be used, provided it is suited for contacting foodstuffs;
the preferred material is polypropylene for foods.
[0032] According to a preferred embodiment, the single-piece structure is obtained with
a frame molded in one piece, forming the longitudinal sides and cross beams, the net
being welded to said frame.
[0033] A preferred process to realize the tray with this structure consists in making the
frame by gas-molding of a single piece, and then welding the net on the frame by hot-blade
process; the net is welded to a suitable step provided on the internal side of the
frame.
[0034] Another embodiment provides a top and a bottom half-frame, each of them molded in
a single piece, which are welded together in correspondence of the plane of the net.
The net is welded between said two half-frames, thus forming a tray with a "monolithic"
single-piece structure.
[0035] A preferred process to obtain the tray with the above structure based on welded half-frames
essentially comprises the following phases: molding of the bottom half-frame, placing
the net; molding of the top half-frame, to weld on said bottom half-frame, obtaining
a single-piece structure free of screws or other connecting means.
[0036] In both cases, gas-molding is preferred, allowing to obtain hollow parts for reducing
the weight and the material used.
[0037] The tray with single-piece structure, free of screws and gaps, is more hygienic and
can be perfectly sanitised; it is also less expensive, it is light and easy to handle,
but strong. The single-piece structure is also advantageous from the point of view
of stiffness, giving a plastic tray with good mechanical performance, contrary to
known plastic trays that have the disadvantage of a low stiffness.
[0038] The aerodynamically shaped cross beams lowers the flow resistance and keep to a minimum
the aforesaid slip-effect. This results in a more uniform hot air distribution on
the net, so that the product can be more uniformly dried; this also results in a lower
energy demand for producing and blowing the hot air, for a given quantity of dried
product.
[0039] The reduced front section of the main cross beams is another advantageous feature,
leaving a sufficient passage for the air, so as to limit the perturbance to the flow
and, again, the flow resistance, when the trays are stacked inside the oven.
[0040] The small beams supporting the net in discrete points allow the hot air flow to lap
the bottom surface of the net, giving a further advantage in terms of uniformity of
the drying treatment.
[0041] The more uniform and less disturbed hot air flow yields a finer quality of the product,
that is dried homogeneously and respecting the parameters of the working cycle.
[0042] These and other features and advantages will be more apparent hereinbelow, with the
help of a description of preferred, non-limitative embodiments, and with the help
of the accompanying figures, wherein:
Fig. 1 is a top view of a tray according to the invention, with frame molded in a
single piece and welded net;
Figs. 2 to 5 are cutaway views of the tray of Fig. 1, according to planes II-II, III-III,
IV-IV and V-V;
Fig. 6 is a top view of a tray according to the invention, made with a frame formed
by two half-frames welded in correspondence of the net;
Figs. 7 to 9 are cutaway views of the tray of Fig. 6, according to planes VII-VII,
VIII-VIII and IX-IX;
Fig. 10 is a representation of the shaped profile of the cross beams of the tray shown
in Fig. 6, according to a preferred embodiment;
Fig. 11 is a sketch showing two trays, like the one of Fig. 1 or the one of Fig. 6,
in their working position inside the drying oven; the hot air flow is also shown.
[0043] Referring now to Figs. 1 to 5, a tray 1 for drying food products, particularly pasta,
is shown, essentially comprising an external frame, made by longitudinal sides 2 and
main cross beams 3, and a net 4 for supporting the drying product.
[0044] The frame of the tray is molded in a single piece, forming the longitudinal sides
2 and main cross beams 3; the preferred material is polypropylene suitable for foods.
[0045] The longitudinal sides 2 (Fig. 2) have a hollow structure, and an upper face 10 and
lower face 11 with matching profiles, allowing the trays to be stacked one onto the
other. More in detail, the upper face 10 exhibits a protruding part on the inner side
(towards the net 4), while the lower face 11 exhibits a protruding part on the opposite
outer side. The matching profiles block the lateral movement between the trays, but
allow longitudinal sliding.
[0046] The sides 2 have an internal face 12, towards the net 4, preferably with a remarkable
lip clearance angle (e.g. 10 degrees) to increase the load capacity of the tray.
[0047] The front section of cross beams 3 is entirely comprised in the height of longitudinal
sides 2, and preferably the height of the cross beams 3 is notably less than the height
of edges 2, about 50%, to leave a wide passage area for the hot air flow when the
trays are stacked in the drying oven.
[0048] In a preferred embodiment, stiffening small beams 13 are also provided, extending
some millimeters below the net 4. Said small beams 13 provide supports 14 for the
above net 4, supporting said net in discrete points, and defining air passages 15
through which the hot air can directly lap the net 4.
[0049] A preferred form of the main cross beams 3 is shown in the cutaway view of Fig. 4,
wherein the beams 3 have a hollow structure and are shaped substantially with an oval
profile. More in detail, the profile of the main cross beams 3 has an upper face 21
following a circular arc, and a lower face 22 also following a circular arc, with
a greater radius. Preferably, the radius of the lower face 22 is about 1.5 times the
radius of the upper face 21.
[0050] As an example, in a tray for drying pasta where the sides 2 are 60 mm high, the profile
of the upper face 21 follows an arc with a radius of 25 mm, while the lower face 22
follows an arc with a radius of 45 mm. The front section is about 28 mm.
[0051] Fig. 5 shows a preferred form of the small beams 13, wherein the cross-section of
said beams 13 appears as a "C" facing downwards.
[0052] A preferred process to fix the net 4 to the tray 1 is the following: to this purpose,
the tray 1 is realized with a step 30 (Figs. 2 and 3), that is heated and locally
melted with a hot blade device; the net is placed on the heated step 30 and then is
cold-pressed; the edges of the net 4 penetrate through the hotted material of the
step 30, which is softened by the high temperature and flows through the holes of
the net 4 itself; when cooled, the net 4 remains "trapped" into the frame, no gaps
or holes are formed between the net and the frame and, obviously, no fixing screws
are required.
[0053] The net is continuously fed from a roll, or previously cut to the desired dimensions.
[0054] Turning now to Figs. 6 to 10, another embodiment of the tray 1 is shown, wherein
the main components are still a frame made of lateral sides 2 and main cross beams
3, and a net 4 fixed to said frame.
[0055] The frame (Fig. 7) is made essentially with a top half-frame 105 and a bottom half-frame
106. Both the top half-frame 105 and bottom half-frame 106 are molded in a single
piece, and coupled, preferably by welding, along a rim 107, about in a median position
substantially corresponding to the plane of the net 4.
[0056] The half frames 105 and 106 are intended as realized in a single piece with the exception
of possible non-structural accessories, that is when the main elements, i.e. the longitudinal
sides and cross beams, are parts of a single body and are not to be assembled with
screws, couplings or equivalent means.
[0057] The longitudinal sides 2 have an upper face 110 and a lower face 111 with matching
profiles, allowing the trays to be stacked. The sides 2 have an internal face 112,
towards the net 4, preferably with a remarkable lip clearance angle (e.g. 10 degrees)
to increase the load capacity of the tray.
[0058] As above, the main cross beams 3 have a shaped profile, to reduce the flow resistance
and disturbance to the hot air flow, and the front section of cross beams 3 is such
to leave a wide passage area for the hot air flow when the trays are stacked in the
drying oven.
[0059] The tray may comprise small stiffening beams 113, which in this embodiment may be
formed with the lower half-frame 106.
[0060] Preferably, the small beams 113 have a shaped profile like the main beams 3, and
are located some millimeters below the net 4, with supports 114 extending towards
the above net 4, for supporting said net in discrete points. Said supports 114 keep
the net 4 distanced from the small beams 113, defining passages 115 for the hot air
directly lapping the net 4.
[0061] A preferred section of cross beams 3 (Fig. 10) is substantially oval with an upper
face 121 and a lower face 122 substantially following a circular arc, the lower face
with a greater radius. Referring to Fig. 10, the radius R2 of the lower face 122 is
preferably about 1.5 times the radius R1 of the upper face 121. Fig. 10 refers to
an embodiment where sides 2 are about 60 mm high, R1 is about 30 mm, R2 is about 45
mm, R3 is about 8 mm. The front section "d" is about 28 mm.
[0062] The profile of small beams 113 may be similar to that of main beams 3 (Fig. 9), or
an open, C-shaped profile like that of Fig. 5.
[0063] A preferred process for making the tray according to the embodiment of Figs. 6-10
is the following: molding of bottom half-frame 106; placing the net 4 on said bottom
half-frame 106; molding of top half-frame 105, to weld on said bottom half-frame 106;
[0064] This process realizes a tray which is actually a single piece, with no screws, linking
means or those gaps between contiguous elements, which are found in known trays formed
by a plurality of parts.
[0065] Although Figs. 6 to 10 show sides 2 and cross beams 3 with a solid section, they
may also have a hollow structure obtained e.g. by gas molding.
[0066] The preferred material is polypropylene, for both the tray 1 and the net 4. Equivalent
embodiments are also possible with other plastic materials and/or with a net made
of a material different from that of the tray, to remain incorporated in the plastic
frame.
[0067] During the use, the trays are loaded with pasta or another vegetal or animal food
product, and stacked inside the drying oven as shown in Fig. 11.
[0068] Referring to said Fig. 11, two trays are shown as 1 a and 1b; the respective main
cross beams are shown as 3a and 3b, and the nets are shown as 4a and 4b. The hot air
flow is indicated as F; the minimum section S available to the hot air flow, between
cross beams 3a and 3b, is also shown.
[0069] The hot air flow F follows the shaped profiles of beams 3a and 3b, thus reducing
undesired slip effect, vortexes and turbulences; also the product resting behind the
beams 3a and 3b is exposed to the hot air flow and correctly dried.
[0070] Thanks to the above described arrangement of cross beams 3a and 3b, the section S
is greater than the same section of known trays, wherein the cross beams are rectangular
or squared, with about the same height as the longitudinal sides. In practice, the
section S does not create a sharp throttle for the flow F, avoiding slip-effect and
turbulence, and limiting losses and energy consumption.
[0071] The above arrangement of the small beams 13, 113 and net supports 14, 114 further
contributes to uniformity of hot air flow F.
[0072] The tray according to the invention meets the above aims and purposes, being easy
to handle, perfectly cleanable, with the aforesaid advantages of product quality and
working efficiency.
1. A tray (1) for drying foodstuffs, particularly pasta, characterised by a plastic single-piece frame structure, comprising longitudinal sides (2), main cross
beams (3) and a central net (4) for supporting said foodstuffs.
2. A tray according to claim 1, characterised by said main cross beams (3) having a shaped profile adapted to reduce the perturbation
of the drying hot air, during the use.
3. A tray according to claim 1 or 2, characterised by said structure comprising small beams (13, 113) connecting the longitudinal sides
(2), and disposed to support said net (4) between the main cross beams (3), said small
beams (13, 113) having a shaped profile adapted to reduce the perturbation of the
drying hot air, during the use.
4. A tray according to claim 3, characterised by said small beams (13, 113) comprising a plurality of supports (14, 114) extending
towards the net (4) and supporting said net (4) in discrete points, defining passages
(15, 115) between said supports (14, 114) for the hot drying air under said net (4).
5. A tray according to claim 2, characterised by the fact that the shaped profile of said main cross beams (3) is substantially oval,
having an upper face (21, 121) following a circular arc of a first radius, and a lower
face (22, 122) following a circular arc of a second radius, greater than the first.
6. A tray according to any one of preceding claims, characterised by the fact that said structure comprises a frame molded in a single piece to form said
longitudinal sides (2), cross beams (3) and, when provided, small beams (13) and supports
(14), and said net (4) is welded along the perimeter of said frame.
7. A tray according to any one of preceding claims, characterised by the fact that said structure comprise a frame formed by a top half-frame (105) and
a bottom half-frame (106), both molded in a single piece and coupled at about the
plane of said net (4).
8. A tray according to claim 7, characterised by the fact that the small beams (113) are molded in a single piece with said bottom
half-frame (106).
9. A process for realizing a tray for drying food, said tray having a structure according
to claim 6,
characterised by the following steps:
- a step (30) provided on the tray (1) to support the net (4) is heated with a hot-blade
device;
- the net (4) is positioned on the heated step (30);
- the net (4) is cold-pressed, so that the edges of the net penetrates through the
hotted material of the step (30).
10. A process for realizing a tray for drying food, said tray having a structure according
to claim 7,
characterised by the following steps:
- molding of the bottom half-frame (106);
- placing the net (4) on said bottom half-frame (106);
- molding of top half-frame (105), to weld on said bottom half frame (106).