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(11) | EP 1 316 636 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
| published in accordance with Art. 158(3) EPC |
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| (54) | REINFORCED COVER FOR ELECTRICAL HOUSEHOLD APPLIANCES AND METHOD FOR THE PRODUCTION THEREOF |
| (57) The lid reinforcements consist of parallel equidistant strips (1) perpendicular to
its plane, which are supported on the inner face with a tab (2), provided with a plastic
coating (3) and supported in brackets (4). The lid structure comprises: a plastic
panel (5) clad with melamine or decorated film (6), reinforced with strips (1) and
a frame (7) clasping it at its edges. The manufacturing procedure comprises: Unrolling
(8) the strip, Straightening (9), Profiling (10), Induction preheating (11), Shearing
(12), Robotized transfer (13) to injection machines (14), Robotized feeding (15) of
melaminized paper or decorated film to the injection machines (14), Overinjection
of reinforcement coating, Withdrawal of reinforced panels by the robots (15). Overinjection
of the frame in another injection machine. |
OBJECT OF THE INVENTION
[0001] The present invention refers to a reinforced lid for household electrical appliances, which combines optimum functional capabilities, both from the standpoint of mechanical strength and of preservation in relation to the humid environment in which it has to work, with low manufacturing cost.
[0002] The invention is of specially applicable for producing those lids which form the upper closure of household washing machines.
BACKGROUND OF THE INVENTION
[0004] The well-known and most widely used structure in washing machine lids is formed of a hardboard panel clad with melamine paper and bonded to a moulded plastic frame with adhesives or resins, either directly or else between two frames, the upper and lower.
[0005] In the former case the panel and frame are usually joined by beads of adhesive on each face of the panel, so that they protect its edges not clad with melamine from moisture.
[0006] In the latter case the two frames enclosing the panel are ultrasonically welded, while its outside edge is protected by a rubber seal to make it leaktight.
[0007] In any case, the most lasting and therefore most desirable solution would consist of the replacement on the lid of the hardboard panel whose live matter (wood chips) is highly hygroscopic, which constitutes a permanent risk of degradation due to the inevitable presence of humidity in washing machines.
[0008] Injected plastic lids have been used for this purpose, but they have not given satisfactory results as only those made with thermoplastic materials, which have a prohibitive cost in competitive terms, meet the technical requirements imposed by household electrical appliance manufacturers.
DESCRIPTION OF THE INVENTION
[0009] The purpose of the invention constituting the object of this Patent consists of eradication of the drawbacks entailed in the use of hardboard panels in washing machine lids and replacing them with other suitable materials capable of meeting the requisite technical standards.
[0010] The requirements are basically of two kinds:
a) Mechanical: they tend to forestall and prevent the possible fracturing of the lid, especially
while the washing machine is in operation, due to an excessive and even improper load:
for instance, due to someone getting up onto the lid, in which case the damage occasioned
to the lid would be added to possible injury to the person.
The mechanical strength required is therefore assessed at 1000 Newtons in a 20x20
cm central area of the lid and 800 N at the edges.
b) Chemical: the necessary use of cleaning chemicals (detergents, bleaches, softeners) in washing machines justifies the technical requirement of resistance thereto, something which for precautionary and safety reasons further applies to other chemicals (ammonia, alcohol) and even to beverages (fruit and vegetable juices, alcoholic drinks, colas).
[0011] Resistance to the attack of all these products requires that the appearance of the lid should remain unaltered over at least 16 hours' exposure.
[0012] These basic requirements are supplemented by others of various kinds: thermal (70°C for 7 days), environmental (recycling, absence of formaldehydes), climatic, etc.
[0013] Compliance with all the requirements other than the mechanical ones can be achieved by choice of the right raw materials; these materials, however, do not withstand the required load conditions by themselves, at least with the dimensional limitation imposed by the ceiling of competitive cost.
[0014] The present Patent application claims creation of washing machine lids with metal reinforcements to increase their mechanical strength above the minimum values required.
[0015] The design of the reinforcements has allowed for the fact that the load to be withstood by the lid (1000 N in the central area) is vertical and in an inward direction, so that a principle similar to that of the mechanical performance of reinforced concrete is utilized to offset it, establishing the reinforcements in the areas in which the lid is subject to load bending stress.
[0016] For all these considerations the reinforcements consist of thin steel bands arranged on planes perpendicular to the inside of the lid, parallel to one another and to the lid hinge axis, and equidistant.
[0017] At their end of application to the inner plane of the lid these bands have a little orthogonal bearing tab, while they are overinjected with a plastic coating and protected against lateral deformation (overturn) by means of brackets spread along either side of them.
[0018] The lid structure comprises: a low mechanical performance plastic panel, formed in a moulding process, which has its upper and outer faces coated with a sheet of melamine bonded with heat-activated glue or a transparent film decorated on the inner face, stuck during the moulding process, the panel being reinforced with metal shapes according to the foregoing description and the assembly overinjected with a high performance plastic frame clasping it by its edges.
[0019] The procedure for manufacturing the reinforced lids, which have technical characteristics as described above, comprises the following consecutive operations:
- Unwinding of the rolls of strip, with simultaneous parallel operation of four rolls.
- Simultaneous straightening of the four strips, in an adjustable position roller train.
- Profiling of the strips in two start and finish wheel trains for continuous forming of the lid reinforcements.
- Preheating, preferably by induction, of the four formed strip lines to prevent an excessive temperature jump during injection, which would bring about cooling and abrupt solidification of the injected plastic in contact with the metal and impede the relative movement between both materials required during the process of injection of reinforcement coating.
- Simultaneous shearing of the four formed strip lines, at the required measurement, so that four reinforcements are obtained at every press stroke.
- Transfer of the four preheated reinforcements by means of a gantry robot shared by two injectors, holding them with its grippers and placing them in the moulds.
- Automatic feeding of melaminized paper or transparent decorated film by means of individual robots.
- Over-injection for panel forming and coating of reinforcements.
- Unloading of injection machines and withdrawal of the reinforced panels by means of the same feeding robots, which deliver them to another injection machine for the over-injection of the frame, whereby the lid is formed.
[0020] In an improved version of the structure of the lid, the low performance plastic panel and the over-injected frame clasping it by its edges are replaced with a single piece forming both the panel and the frame, moulded with low performance material (recycled) and coated entirely with heat-formed transparent film decorated on its inner face for application on the single panel-cum-frame piece.
[0021] As a result of the unification of the panel and frame in a single piece the last injection machine for frame over-injection can be dispensed with in the lid manufacturing process as the lids will come off the two parallel injection machines in an already finished state.
[0022] In another improved version of the lid structure, the low performance plastic panel and the over-injected frame clasping it by its edges are replaced by a single piece forming the panel and the frame, moulded with virgin (first time use) material, with the result that the part of the single piece corresponding to the panel is coated with melaminized paper stuck to the upper face of the lid plane with heat-activated glue.
[0023] As in the previous case, i.e. as a result of the unification of panel and frame into a single piece, the last injection machine for frame over-injection can be dispensed with in the lid manufacturing process as the lids will leave the two parallel injection machines in an already finished state.
[0024] In another improved version of the lid structure, the low temperature plastic panel and the over-injected frame are separated by modifying the arrangement of the panel-cum-frame, so that the latter, instead of clasping the panel by its edges, is superimposed on it round its upper outside edges, both pieces being joined by a bead of adhesive running round the perimeter of the lower or inner face of the panel, between its edge and the inner face of the frame walls, the panel being clad with melaminized paper stuck with heat-activated glue to the upper face of the lid plane.
[0025] In a final improved version of the lid structure, the low performance plastic (recycled) panel and the frame over-injected with unused material are separated by modifying the arrangement of the panel-frame assembly so that the latter, instead of clasping the panel by its edges, is superimposed on it in its upper perimeter area, both pieces being joined by an ultrasonic weld bead running round the upper or outer face of the panel, between its edge and the inner face of the superimposed part of the frame, the panel being clad with melaminized paper stuck with heat-activated glue to the upper face of the lid plane.
DESCRIPTION OF THE DRAWINGS
[0026] To supplement the description of the invention and to assist understanding of the formal, structural and functional characteristics of its object, drawings are attached representing schematically different aspects of a preferred embodiment of the "Reinforced lid for household electrical appliances and procedure for their manufacture", which constitutes the object of this Patent.
[0030] Figure 3 shows a diagram of the plan distribution of the working elements involved in the development of the process claimed.
[0031] Figure 4 shows a vertical plane sectional view of the structure of one of the vertices of the improved lid, according to another embodiment version.
[0032] Figure 5 shows a cross-sectional view of the form and layout of the metal reinforcements in the improved lid of the previous figure.
[0033] Figure 6 shows a vertical plane sectional view of the structure of one of the vertices of the improved lid, according to another embodiment version.
[0034] Figure 7 shows a cross-sectional view of the form and layout of the metal reinforcements on the improved lid of the previous figure.
[0035] Figure 8 shows a vertical plane sectional view of one of the vertices of the improved cover, according to another embodiment version.
[0036] Figure 9 shows a cross-sectional view of the form and layout of the metal reinforcements in the improved lid of the previous figure.
[0037] Figure 10 shows a vertical plane sectional view of the structure of one of the vertices of the improved lid, according to another embodiment version.
[0038] Figure 11 shows a cross-sectional view of the form and layout of the metal reinforcements in the improved lid of the previous figure.
PREFERRED EMBODIMENT OF THE INVENTION
[0039] To show clearly the nature and scope of the advantageous application of the "Reinforced lid for household electrical appliances and procedure for its manufacture" which represents the object of the invention, its structure and manufacturing process are described below, with reference to the drawings.
[0040] The reinforcements consist of thin strips (1) of steel arranged on planes perpendicular to the inside of the lid, parallel to one another and to its hinge axis and equidistant, which at their end of application to the inner plane of the lid have a little orthogonal bearing tab (2), while the aforesaid strips (1) are over-injected with a plastic coating (3) and protected against lateral deformation (turnover) by means of brackets spread along either side of same.
[0041] Their structure comprises: a low mechanical performance plastic panel, formed in the moulding process, which has its upper or outer face clad with a sheet of melamine (6) bonded with a heat-activated glue or with a transparent film decorated on its inner face, bonded in the moulding process, the panel being reinforced with metal shapes (1) and the assembly over-injected with a high performance plastic frame (7) which clasps it by its edges.
[0042] The procedure for manufacturing the lids comprises the following consecutive operations:
- Unwinding (9) of the rolls of strip, with simultaneous parallel operation of four rolls.
- Simultaneous straightening of the four strips, in an adjustable position roller train (9).
- Profiling of the strips in two start and finish wheel trains (10) for continuous forming of the lid reinforcements.
- Preheating, in an induction unit (11), of the four formed strip lines to prevent an excessive temperature jump during injection, which would bring about cooling and abrupt solidification of the injected plastic in contact with the metal and impede the relative movement between both materials required during the process of injection of reinforcement coating.
- Simultaneous shearing of the four formed strip lines, at the required measurement, so that four reinforcements are obtained at every press stroke.
- Transfer of the four preheated reinforcements by means of a gantry robot (13) shared by two injectors (14), holding them with its grippers and placing them in the moulds.
- Automatic feeding of melaminized paper or transparent decorated film by means of individual robots (15).
- Over-injection for coating of reinforcements.
- Unloading of injection machines and removal of the reinforced panels by means of the same feed robots (15), which deliver them to another injection machine for the over-injection of the frame, whereby the lid is formed.
[0043] In an improved embodiment version, represented in figures 3 and 4, the structure is formed of a single piece making up the panel (5') and the frame (7'), moulded with recycled material and wholly coated with thermoformed transparent film (6') decorated on its inner face for application on the single panel and frame piece. The other components of the lid are maintained with the same references as those of the first embodiment of figures 1 and 2 as there is no variation in any of their characteristics.
[0044] As regards the procedure for manufacturing the reinforced lid in accordance with the embodiment of figures 3 and 4, it varies in that the last injection stage described in the first embodiment is omitted and that it is used for over-injecting the frame, as the panel and frame assembly are moulded initially as a single piece, so that the lid assembly leaves the injection machines, which are used for over-injecting the metal reinforcements, in finished condition.
[0045] In another embodiment version shown in figures 5 and 6, the structure is also formed of a single piece making up the panel (5') and the frame (7'), moulded with virgin (i.e. first use) material, where the part of the single piece corresponding to the panel (5') is clad with melaminized paper (6), stuck with heat-activated glue to the upper face of the lid plane. The other components of the lid are maintained with the same references as those of the previous embodiment for there is no variation in any of their characteristics.
[0046] With regard to the procedure for manufacturing the reinforced lid in accordance with the embodiment of figures 5 and 6, it varies in that the last injection stage, which is described in the first embodiment and intended for frame over-injection, is omitted as the panel and frame are moulded initially as a single piece, so that the lid assembly leaves the injection machines, which are used for over-injecting the metal reinforcements, in finished condition.
[0047] In another embodiment version, represented in figures 7 and 8, the configuration defined by the union between the panel (5") and the frame (7") is modified so that, instead of clasping the panel (5") by its edges, said frame (7") is superimposed on it in its upper perimeter area, both pieces being joined by a bead of adhesive running round the lower or inner face of the panel (5"), between its edge and the inner face of the walls of the frame (7"), the panel (5") being clad with melaminized paper (6) stuck with heat-activated glue to the upper face of the lid plane.
[0048] The other components of the lid are maintained with the same references as those of the first embodiment of figures 1 and 2 as there is no variation in any of their characteristics.
[0049] In a last embodiment version, represented in figures 9 and 10, the structure is based on the separation of the low performance (recycled) plastic panel from the frame over-injected with virgin material, specified in the first embodiment of figures 1 and 2, modifying the arrangement of the panel (5"')-frame (7"') union so that, instead of clasping panel (5"') by its edges, the latter is superimposed on it in its upper perimeter area, both pieces being joined by an ultrasonic weld bead (17) running round the upper or outer face of the panel, between its edge and the inner face of the superimposed part of the frame (7"'), the panel being clad with melaminized paper (6) stuck with heat-activated glue to the upper face of the lid plane.
1. Reinforced lid for household electrical appliances, characterised in that its reinforcements consist of thin strips (1) of steel, arranged on planes perpendicular
to the interior of the lid, parallel to one another and to its hinge axis and equidistant,
which have an orthogonal bearing tab (2) at their end of application to the inner
plane of the lid, while the aforesaid strips (1) are over-injected with a plastic
coating (3) and protected against lateral deformation (overturn) by means of brackets
spread along either side of same.
2. Reinforced lid for household electrical appliances, according to Claim 1, characterised in that its structure comprises: a low mechanical performance panel (5 or 5' or 5" or 5"'),
formed in the moulding process, which has its upper or outer face clad with a sheet
of melamine (6 or 6') bonded with heat-activated glue or with a transparent film decorated
on its inner face, stuck in the moulding process, the aforesaid panel being reinforced
with metal shapes (1) and the assembly over-injected with a high performance plastic
frame (7 or 7' or 7" or 7"'), which clasps it along its edges.
3. Reinforced lid for household electrical appliances and procedure for its manufacture,
according to claims 1 and 2, characterised in that the structure of the lid is formed of a single piece making up the panel (5') and
the frame (7'), moulded with recycled material and coated entirely with thermoformed
transparent film (6') decorated on its inner face for application on the single panel-cum-frame
piece.
4. Reinforced lid for household electrical appliances and procedure for its manufacture,
according to claims 1 and 2, characterised in that the structure of the lid is formed of a single making up the panel (5') and the frame
(7'), mould with virgin material, while the part of the single piece corresponding
to the panel (5') is coated with melaminized paper (6), stuck with heat-activated
glue to the upper face of the lid plane.
5. Reinforced lid for household electrical appliances and procedure for its manufacture,
according to claims 1 and 2, characterised in that the panel (5") and the frame (7") are joined in such a way as to define an arrangement
in which, instead of clasping the panel (5") by its edges, the frame (7") is superimposed
on its outer perimeter area, while both pieces are united by a bead of adhesive (16)
running round the lower or inner face of the panel (5"), between its edge and the
inner face of the walls of the frame (7"), the aforesaid panel being clad with melaminized
paper (6) stuck with heat-activated glue to the upper face of the lid plane.
6. Reinforced lid for household electrical appliances and procedure for its manufacture,
according to claims 1 and 2, characterised in that the panel (5"') and the frame (7"') are joined in such a way as to define an arrangement
in which, instead of clasping the panel (5"') by its edges, the frame (7"') is superimposed
on its outer perimeter area, while both pieces are united by a ultrasonic weld bead
(17) running round the upper or outer face of the panel (5"'), between its edge and
the inner face of the superimposed part of the frame (7), the aforesaid panel (5"')
being clad with melaminized paper (6) stuck with heat-activated glue to the upper
face of the lid plane.
7. Procedure for the manufacture of reinforced lids for household electrical appliances
of the technical characteristics described in the foregoing Claims, characterised in that it comprises the following consecutive operations: unwinding (8) of the rolls of
steel strip, with simultaneous parallel operation of four rolls, simultaneous straightening
of the four strips in an adjustable position roller train (9); profiling of the strips
in two start and finish wheel trains (10) for continuous shaping of the lid reinforcements;
preheating of the four formed strip lines in an induction unit (11) to prevent an
excessive temperature jump in the injection, which would bring about cooling and abrupt
solidification of the injected plastic in contact with the metal, and would impede
the relative displacement between both materials needed during the reinforcement coating
injection process; simultaneous shearing (12) of the four formed strip lines at the
required dimension, so that four reinforcements are produced at every stroke of the
press; transfer of the four preheated reinforcements by means of a gantry robot (13)
shared by two injection machines (14), holding them with its grippers and placing
them in the moulds; automatic feeding of melaminized paper or decorated transparent
film into the injection machines by means of individual robots (15); overinjection
for reinforcement coating; unloading of injection machines and reinforced panels by
means of the same supply robots (15), which deliver them to another injection machine
for frame overinjection, so that the lid is thereby formed.
8. Procedure for the manufacture of reinforced lids for household electrical appliances
which includes all the operating phases specified in the preamble of the preceding
claim, characterised in that the last injection machine for frame overinjection is dispensed with, so that the
lid is finally completed when it leaves the injection machines used in the overinjection
of the coating of the metal reinforcements.