Patent Application
20110277909
The present patent application for industrial invention relates to a manufacturing method of a seat element made of expandable and reticulable polyolefin material, especially for vehicles.
The term “seat element” refers to seat, back and headrest. The present invention is not exclusively limited to seats for vehicles, and is also extended to interior decoration seats, such as tools, armchairs, sofas and similar items.
As it is known, expandable and reticulable polyolefin materials are characterised by properties of lightness, softness, resistance to wear and water, thus being especially suitable for manufacturing various kinds of seats.
Nevertheless, expandable and reticulable polyolefin materials are generally not used to manufacture seat elements because they are impaired by some drawbacks during the preparation and realisation process.
In fact, these items are manufactured by injecting into the mould plastic material that expands and reticulates inside it. The mould is maintained at a certain temperature in such a way to ensure that, during the cycle-time in which the material is closed inside the mould, the reticulation of the material and decomposition of expanding loads are performed.
When the mould is opened, the product is spontaneously released from the mould because of its violent expansion, continues on expanding and then starts shrinking during cooling. The expansion and shrinking processes cannot be controlled exactly, thus giving high rates of rejects during industrial production.
Consequently, the result would be a seat element that does not comply with the dimensional requirements established at design level and is difficult to use for modular assembly with other elements.
Moreover, it must be considered that expandable materials are mostly soft materials. Therefore, a seat element using these materials should be coupled with a support frame in order to make it stiffer and use it. The coupling of the seat element with the support frame is not simple due the dimensional changes of the seat after moulding, expansion and reticulation. In fact, if the seat element is provided with holes to receive fixing means, these holes may not match the holes of the frame.
Therefore, coupling of the seat element with the frame is complex and expensive, requiring a special adjustment of the seat element and/or frame.
The patent application DE 27 17 268 discloses a seat element made of expanded polyurethane. Although the appearance of expanded polyurethane is similar to expanded polyolefin, it must be noted that the two technologies differ in their production process. Therefore, as it is known, in the polyurethane technology, the seat element is obtained from moulding and left in the mould to cool down.
The patent application DE 20 2006 013633 discloses a seat element comprising a support made of rigid material and a covering coupled with the support in such a way to form a cavity between support and covering. The cavity is filled by injecting a filling material. The covering made of polyurethane, polyolefin or other waterproof material is a premoulded covering. Therefore, the expanded covering (which could also have a polyolefin base) is a stable material that has already been subject to reticulation and consequently is no longer subject to dimensional changes.
The support and premoulded covering are arranged in a mould, in which filling material is injected. The covering made (also) of polyolefin material is subject to thermoforming, but the polyolefin inside the covering is not subject to reticulation or dimensional change.
The purpose of the present invention is to eliminate the drawbacks of the known art, by devising a manufacturing method of a seat element made of expanded material that complies perfectly with the dimensional features of the original design and, at the same time, is inexpensive and simple to produce and install.
This purpose has been achieved according to the present invention, with the characteristics illustrated in the attached independent claim 1.
Advantageous embodiments are disclosed in the dependent claims.
The new manufacturing process provides for a first expansion phase of the seat after opening the mould, and a thermoretraction phase during which the seat is reduced (thermoretraction) to the desired dimensions during cooling.
The use of the template results in a series of advantages:
Additional characteristics of the invention will appear evident from the following detailed description, which refers to merely illustrative, not limiting embodiments, illustrated in the enclosed drawings, wherein:
Referring to
The seat element (1) comprises a body (2) of soft material and a template (3) of rigid material.
The body (2) is made of expandable and reticulable polyolefin material, by means of injection moulding. The polyolefin material is injected into the mould, heated and subject to reticulation process. During the reticulation process the polyolefin material expands, taking the shape of the mould. The expansion of the polyolefin material continues and then the body is released spontaneously from the mould.
It must be considered that the mould is small scale compared to the seat to be manufactured (for example, a mould with cavity 50% smaller than the seat can be made).
The body (2) is provided on the back surface with a perimeter frame (20) that defines a recessed seat (21) adapted to receive the template (3). The internal borders of the perimeter frame (20) define housings in undercut (22) having an overturned-U shape, adapted to receive the borders of the template (3).
Preferably, the housings in undercut (22) are obtained along the entire internal perimeter of the frame (20); however, only two housings in undercut (22) can be provided on opposite sides of the frame (20). Blind holes (23) are obtained in the back seat (21) of the body (2), being adapted to receive fixing means, such as nuts or bolts.
The template (3) consists in a plate made of rigid material, such as for example metal or PVC or Polyamide (Nylon). A flat rectangular template is shown in this first embodiment of the invention; however, the template can also be curved.
The template (3) is provided with through holes (33) to receive fixing means, such as screws or bolts. The holes (33) can also be threaded. In any case the holes (33) of the template are arranged in register with the blind holes (23) of the body (2). The holes (23) of the body have a higher diameter than the holes (33) of the template because they must receive nuts and because they must compensate possible misalignment mistakes.
The template (3) is dimensioned in compliance with the specific dimensions of the seat element to be obtained.
In fact, when the body (2) is spontaneously released from the mould, the material of the body continues its expansion process. Once the expansion process is completed, the template (3) is inserted in the recessed seat (21) of the body (2). As shown in
The body (2) shrinks during cooling. Accordingly, as shown in
In this way the template (3) is firmly anchored to the body (2) and at the same time prevents additional thermoretraction of the body (2). Therefore, the body (2) perfectly complies with the dimensional specifications of the template (3), regardless of the free thermoretraction that would have been suffered by the material of the body (2).
In addition to act as control element of the dimensions of the body (2), the template (3) also acts as stiffening element of the body (2), without the need to provide the body (2) with stiffening ribs that increase the complexity of the mould and without the need to use stiffening inserts that are difficult to match with the body (2).
Moreover, as shown in
In fact, the frame (4) can be provided with screws (40) arranged in register with the holes (33) of the template.
In this case, the body (2) is disassembled from the template (3); then the template (3) is fixed to the frame (4) inserting the screws (40) in the holes (33) of the template and screwing the nuts (41) on the screws (40); finally, the body (2) is assembled again on the template (3) in such a way that the nuts (41) are received in the blind holes (23) of the body (2).
It must be noted that assembly is possible because of the fact that, once it has cooled down completely, the expanded reticulated material maintains the original dimensions also without the template.
In the following text identical elements or elements that correspond to elements that have already been described are indicated with the same reference numerals, omitting their detailed description.
Numerous variations and modifications can be made to the present embodiments of the invention by an expert of the field, while still falling within the scope of the invention as claimed in the enclosed claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| MC2009A000028 | Feb 2009 | IT | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2010/051582 | 2/9/2010 | WO | 00 | 7/26/2011 |
