Plastic article or earthenware shaping or treating: apparatus – Shaping surface including means to release or remove product... – By differential gas pressure ejecting means
Reexamination Certificate
1999-11-05
2001-08-28
Nguyen, Nam (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
Shaping surface including means to release or remove product...
By differential gas pressure ejecting means
C425S450100, C425S451900, C425S577000
Reexamination Certificate
active
06280174
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates, in general, to a molding apparatus, and especially, but not exclusively, to a molding apparatus for the manufacture of plastic panes, for example, window panes for passenger cars.
Molding apparatuses, involved here, include a core and a female mold member as well as circumferential peripheral dies, with the peripheral dies being attached to the core for movement in closing direction. The core is completely surrounded by the peripheral dies, with the female mold member so configured in the region of the impact areas of the peripheral dies as to complement these impact areas.
FIG. 1
shows a cross sectional illustration of a conventional molding apparatus of this type which includes a fixed mold clamping pate having attached thereon the female mold member and a movable mold clamping plate having attached thereon the core via a core plate. Upon movement of the movable clamping plate toward the fixed clamping plate, the core descends into the female mold member, whereby the movement of the core is guided by the circumferential peripheral dies which also realize a sealing of the cavity defined between the core and the female member. This conventional molding apparatus suffers the drawbacks that the descending peripheral dies are damaged on both mold halves (injection side and closing side) as a result of:
an imprecise centered descent of the core side into the female mold member;
too narrow dimensions of the female mold member as a consequence of mold shrinkage caused by temperature decrease below the very narrow temperature tolerances;
one-sided contact of the descending dies as a consequence of a floating effect which is encountered during compression injection molding and cannot be offset by greater machine tolerances;
excessive core dimension as a consequence of a mold dilatation caused by temperature deviation above the very narrow temperature tolerances.
Attempts were made to address these drawbacks by providing the core with one or more circumferential peripheral dies which are mounted to the core and movable in closing direction and which are able to bear upon flat areas of the female mold member in closed state. An example of such a mold is described in U.S. Pat. No. 4,707,321 for making optical data carriers. The mold has a circular core which is circumscribed by a circular peripheral die which can be moved by compressed air along the core in direction of the female mold member. The peripheral die is hereby formed in one piece in accordance with the diameter of the circular injection molded part. This peripheral die is unsuitable for use with differently designed injection molded parts.
“Patent Abstracts of Japan, Publication Number 08057922 A” discloses a molding apparatus with several peripheral dies which are wrapped around the core and are mounted to the core for movement in closing direction and completely surround the core. Each individual peripheral die is received in a T-shaped groove which is continuous around the entire circumference of the marginal region of the core and open toward the side of the female mold member and which is formed of two pieces in radial direction. In order to realize a close fit of each peripheral die in this groove, without jamming, but yet being shiftable along the core, both halves of each peripheral die are moved apart by spring elements so as to bear upon confronting inside surfaces of the groove. Provided in the bottom of the groove are spring elements by which the peripheral dies are retained in the direction of the female mold member under prestress. When the mold is closed, the peripheral die, jutting out from the groove, is pressed against the female mold member which has a flat configuration in the contact area of the peripheral die. This molding apparatus is complex, and a replacement of defective or worn-off peripheral dies is very cumbersome. A further drawback resides in the fact that the inner part of the peripheral die is pushed outwards when high injection pressures or compression forces are applied, so that plastic mass can escape and/or flashes are encountered on the injection molded part. Although this could conceivably be avoided by sufficiently biasing the bottom spring, this modification would be accompanied by the drawback that the peripheral die can be moved in the T-groove only at great difficulty or can even jam.
SUMMARY OF THE INVENTION
It is thus an object of the present invention to provide an improved molding apparatus, obviating the afore-stated drawbacks.
In particular, it is an object of the present invention to provide an improved molding apparatus which maintains the advantages of such conventional molds, shown in
FIG. 1
, but yet has a simpler configuration and allows in particular an easy replacement of individual peripheral dies.
These objects, and others which will become apparent hereinafter, are attained in accordance with the present invention by providing a female mold member; a core capable of moving in a closing direction against the female mold member to define a cavity for molding an object, with the core being completely surrounded by peripheral dies which are movable in the closing direction against a complementary impact area of the female mold member; and fasteners for securing each of the peripheral dies laterally to the core, with the fasteners including a retaining element for attaching the peripheral die to the core, and a spacer element fitted in the peripheral die and having a width which slightly exceeds a cross section of the peripheral die to thereby realize a gap between confronting surfaces of the core and the peripheral die.
An essential feature of a molding apparatus according to the present invention resides in the particular configuration of the securement of the peripheral dies to the core. The lateral attachment with spacer and retaining elements allows, on the one hand, a displacement of the peripheral dies along the core, and, on the other hand, the attachment and detachment of the peripheral dies to and from the core can be executed in a simpler manner. The fixed tolerance gap results in constant, minimum frictional conditions, thereby significantly enhancing the availability of the mold. A jamming of the peripheral dies upon the core is prevented even at comparably great temperature fluctuations, because the novel and inventive lateral attachment realizes that the peripheral dies simply “follow” temperature-based dimensional changes of the core.
A molding apparatus according to the present invention is also advantageous for the following reasons. The circumferential gap between the confronting surfaces of the peripheral dies and the core can be kept constant at less than 0.05 mm, preferably in the range of about 0.01 to 0.02 mm, irrespective of temperature fluctuations of the mold or intended temperature changes, irrespective of machine-guide tolerances, and irrespective of components and mold dimensions. In addition, the mold is available for a wide range of applications, and no flash removal or re-finishing operations of the edges of the plastic parts are necessary.
REFERENCES:
patent: 4235576 (1980-11-01), Robinson
patent: 4402659 (1983-09-01), Greenbaum
patent: 4460326 (1984-07-01), Croseck et al.
patent: 4645447 (1987-02-01), Sumitomo
patent: 4707321 (1987-11-01), Segawa et al.
patent: 5040962 (1991-08-01), Waszeciak et al.
patent: 5364253 (1994-11-01), Kojima et al.
patent: 5766407 (1998-06-01), Miwa et al.
patent: 33 15 746 A (1983-11-01), None
patent: 38 20 232 A (1988-12-01), None
patent: 06 344365 A (1994-12-01), None
Patent Abstracts of Japan, vol. 096, No. 007, Jul. 31, 1996 & JP 08 057922 A (Komatsu Ltd.), Mar. 5, 1996.
Feiereisen Henry M.
Krauss-Maffei Kunststofftechnik GmbH
Luk Emmanuel
Nguyen Nam
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