Stock material or miscellaneous articles – Sheet including cover or casing – Filled with gas other than air; or under vacuum
Reexamination Certificate
1999-02-03
2001-07-24
Gupta, Yogendra (Department: 1751)
Stock material or miscellaneous articles
Sheet including cover or casing
Filled with gas other than air; or under vacuum
C428S054000, C428S068000, C428S070000, C428S071000, C428S076000, C428S077000, C428S096000, C428S142000, C428S147000, C428S158000, C428S159000, C428S167000, C428S168000, C428S304400
Reexamination Certificate
active
06265044
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a vacuum covering method in which a sheet is drawn by vacuum or suction down onto a profiled surface of a base member to effect bonding therebetween to cover the profiled surface with the sheet. It also relates to a sheet particularly suitable for use in the vacuum covering method.
2. Description of the Related
FIG. 29
shows in cross section a portion of a vehicle instrument panel which exemplifies an article produced in accordance with a conventional vacuum covering method. The article (instrument panel) has a sheet bonded by adhesion to a profiled surface of a base member through the vacuum process.
Conventionally, the instrument panel is produced as follows.
At first, a base member
101
injection-molded from synthetic resin and a sheet
102
of double layered structure having a facing layer
103
and a foam layer
104
of polypropylene are provided. Then, the base member
101
is set on the lower mold member (not shown) of a vacuum mold assembly. Subsequently, a primer
105
a
is coated on a rear surface (foam-layer side) of the sheet
102
, and an adhesive
105
b
is coated on a front surface of the base member
101
. After heating the base member
101
and the sheet
102
at desired temperatures, the sheet
102
is placed over the base member
101
. In this instance, the sheet is stretched in one direction. Then, an upper mold member is lowered toward the lower mold member to close the vacuum mold assembly with the sheet
102
and base member
101
held therein. While the vacuum mold assembly is kept closed, air is evacuated from vacuum holes
101
a
in the vacuum mold assembly so that the sheet is drawn by vacuum or suction down onto the base member to thereby effect adhesive bonding between the sheet
102
and the base member
101
.
A typical material eligible for the base member
101
is acrylonitrile-butadiene-styrene (hereinafter abbreviated as “ABS”) resin. The facing layer
103
of the sheet
102
is made from polyvinyl chloride (hereinafter abbreviated as “PVC”), and the foam layer
104
of the sheet
102
is made from polypropylene (hereinafter abbreviated as “PP”).
In general, the base member
101
of ABS resin is produced by injection-molding. The injection-molded base member
101
undergoes thermal shrinkage as it becomes cool. The PP is advantageous over the ABS resin from a recycling point of view. However, the PP is a crystalline polymer and hence has a large rate of shrinkage. Accordingly, in the case of a base member
101
made from PP, it occurs likely that due to thermal shrinkage concentrated on an area surrounding a vacuum hole
101
a
, an annular shrink mark (also called “sink mark”) is formed around the vacuum hole
101
. As a result of generation of the shrink mark, an edge portion
101
b
of the vacuum hole
101
a
is forced to swell or project outwardly from a surface of the base member
101
. Thus, a sheet
102
which is bonded to the surface of the base member
101
including the projecting edge portion
101
b
necessarily has a projection
102
a
on its front surface at a position corresponding to the position of the projecting edge portion
101
b
. The projection
102
a
thus formed makes the sheet
102
unsightly in the appearance and lowers the product value of the instrument panel.
SUMMARY OF THE INVENTION
It is accordingly an object of the present invention to provide a vacuum covering method which is capable of covering a profiled surface of a base member with a sheet by effecting bonding between the sheet and the base member reliably through the vacuum process without involving generation of a recess or a projection on a facing layer of the sheet.
Another object of the present invention is to provide a sheet which is particularly suitable for use in the vacuum covering method.
According to a first aspect of the present invention, there is provided a method of covering a profiled surface of a base member with a sheet by bonding together the sheet and the base member under vacuum, comprising the steps of: (a) providing a base member having a profiled surface and a sheet of thermoplastic material; (b) setting the base member on an outside surface of a mold member of a vacuum mold assembly with the profiled surface facing outward, the mold member having a plurality of vacuum holes opening at one end to the outside surface of the mold member and connected at the other end to a vacuum source; (c) providing one of the profiled surface of the base member and one surface of the sheet with a portion forming vacuum passages extending across the profiled surface of the base member and said one surface of the sheet; (d) while keeping the sheet in a prestretched condition, placing the sheet over the base member so that the vacuum passages formed by said portion are provided between the profiled surface of the base member and said one surface of the sheet and held in fluid communication with at least one of the vacuum holes in the first vacuum mold member; and (e) activating the vacuum source to evacuate air from the vacuum passages through the vacuum hole in the first mold member so that the sheet is drawn by vacuum down onto the profiled surface to thereby effect bonding between the sheet and the profiled surface.
In one preferred form of the present invention, the step of providing a portion forming vacuum passages comprises providing a plurality of spaced vacuum grooves extending across the profile surface of the base member when the base member is formed by injection molding from a synthetic resin material. Preferably, the parallel spaced vacuum grooves have a pitch set to vary inversely with the elongation of the sheet on the base member. The sheet may have a laminated structure including a facing layer of olefin thermoplastic elastomer, and a cushioning foam layer of polypropylene, wherein the vacuum grooves have a width ranging from 0.3 mm to 0.9 mm and a depth ranging from 0.3 mm to 2.0 mm.
In another preferred form of the invention, the step of providing a portion forming vacuum passages comprises providing small resin particles between the profiled surface of the base member and said one surface of the sheet with a predetermined distribution. Preferably, the resin particles are applied to said one surface of the sheet. The resin particles may be polypropylene particles having an average diameter ranging from 0.1 mm to 0.3 mm.
The sheet may include a facing layer, a cushioning foam layer and a barrier layer laminated in the order named. The barrier layer provides one surface of the sheet to be bonded to the profiled surface of the base member. The barrier layer has a greater modulus of elasticity than the facing layer. It is preferable that the facing layer has a modulus of elasticity ranging from 0.02 to 2.0 kg/cm
2
, and the barrier layer
73
has a modulus of elasticity ranging from 3.0 to 5.0 kg/cm
2
Preferably, the facing layer is made from olefin thermoplastic elastomer, the foam layer is made polypropylene, and the barrier layer is made from polypropylene.
REFERENCES:
patent: 784503 (1957-10-01), None
Apr. 26, 1999, Search Report form UK Patent Office for application No. GB 9902545.4.
Chujo Kenichi
Furuya Tamio
Kameshima Akihiro
Saita Junichi
Boyer Charles
Gupta Yogendra
Honda Giken Kogyo Kabushiki Kaisha
Merchant & Gould P.C.
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