Metal founding – Process – Shaping a forming surface
Reexamination Certificate
2001-05-01
2003-09-16
Swann, J. J. (Department: 3677)
Metal founding
Process
Shaping a forming surface
C164S024000
Reexamination Certificate
active
06619378
ABSTRACT:
BACKGROUND
1. Technical Field
The present invention is directed to a gemstone setting and a method for molding the gemstone setting and, more particularly, to gemstone settings with seats molded directly into the settings and a method for molding seats into gemstone settings using metal molds.
2. Related Art
A variety of gemstone settings (hereinafter “setting” or “settings”) are used in the jewelry industry. The selection of settings is usually made to enhance the beauty of a gemstone (hereinafter “gem”). Settings may be hand-carved, molded, or stamped, and may include prongs that frictionally maintain a gem in the setting. Stamped settings are generally less attractive, and less malleable than those formed from other processes due to the deformation of metal inherent in the stamping process.
A typical molded setting
10
is shown for illustrative purposes only in FIG.
1
. Setting
10
includes a base indicated generally at
12
having a perimeter
14
from which a plurality of prongs
16
having an inner face
22
extend upwardly and slightly outwardly, terminating at upper prong surface
17
. Setting
10
also includes a band
18
approximately midway between the perimeter
14
of base
12
and upper prong surface
17
.
In some instances, inner face
22
of prongs
16
may include a “seat” on which a gem may be fitted or into which it “sits.” Seats may be hand-carved, stamped, or molded directly into the inner face of the prongs of a setting at the upper end of the prongs.
FIG. 2
illustrates such a setting
10
a
, which includes all of the elements of setting
10
, and additionally includes a hand-carved seat
24
formed at upper end
20
of prong
16
on the inner surface
22
of each prong
16
. An expanded side view of seat
24
is illustrated in
FIG. 3
, showing a portion
22
a
of inner surface
22
of prong
16
remaining exposed above seat
24
after hand-carving.
A side view of a typical gem
30
is shown in
FIG. 4
for illustrative purposes only. Gem
30
includes a table
32
, a crown
34
, a culet
36
, a pavilion
38
, and a girdle
40
.
FIG. 5
shows a perspective view of a set gem
50
using, for example, gem
30
and setting
10
a
. As shown, gem
30
is “set” by positioning girdle
40
in seats
24
and folding upper ends
20
a
of prongs
16
downwardly toward crown
34
of gem
30
. The folding process requires the exertion of a great deal of force in order to ensure that surface
22
a
of prong
16
contacts crown
34
, as shown in side view in FIG.
6
. If excessive force is exerted during this process, the gem may shatter. Generally, the intersection of crown
34
and girdle
40
at line L
1
, and the intersection of girdle
40
with pavilion
38
at line L
2
, are the points or lines of intersection at which the seat directly contacts the gem
30
, due to the arcuate shape of hand-carved seats.
Regardless of the method used to form the seats, it is important for aesthetic reasons to ensure that the size and placement of the seats remains substantially the same on each prong of a setting. If the gem is not level with respect to the base of the setting, it will appear crooked to the naked eye. In addition, if the placement of the seats on the prongs of a setting varies, the length of the portion of the prongs (i.e.
22
a
) that is folded onto crown
34
will vary. Both of these are undesirable for aesthetic reasons and consequently for economic reasons.
Hand-carving seats require a great degree of skill and precision on the part of the jewelry maker to ensure that the size and placement of the seats remains substantially the same on each prong. Hand-carved seats have a generally arcuate shape, as shown in FIG.
3
. The arcuate shape of hand-carved seats sometimes may be disadvantageous when attempting to “set” a stone in a setting if the carving has penetrated too deeply into the interior face of the prong, or if the placement of the seat on each prong varies.
One method of addressing the foregoing problems involves molding seats directly into the prongs of a setting using what is known as the “rubber molding process.” The rubber molding process (RMP) involves forming a master setting using conventional means such as would be known to jewelry makers. The master setting is then encased in rubber, and the rubber is allowed to harden. The rubber mold is then split in half, resulting in two complementary mold halves. An exemplary rubber mold halve
60
is illustrated in side view in FIG.
7
. Rubber mold
60
includes a parting surface
62
, with a relief pattern formed in mold halve
60
, fluidly connected to a sprue
64
and gate
66
for receiving fluid material, each which are known to those of skill in the art. The relief pattern includes a plurality of fluidly connected channels or partial channels corresponding to the structure of the desired setting. For example, channel
68
corresponds to base
14
, channel
70
corresponds to band
18
, and channels
72
correspond to prongs
16
.
Because the rubber can flow around and encase the master setting, the rubber mold process can reproduce all the features of the master setting, including the interior surface of the setting. Section
74
of mold
62
includes a relief pattern of the inner surface of the desired setting. For example, section
74
includes grooves
76
corresponding to the inner surface
22
of setting
10
,
10
a
, as well as surface
78
corresponding to hand-carved seat
24
. Thus, the relief pattern also represents the inner surface
22
of prongs
16
of setting
10
a
, including seats
24
.
When the two complementary rubber mold halves are assembled, for example, by clamping, wax may be injected into the assembled rubber mold to form a wax copy of the master setting. The wax copy may be removed from the mold by disassembling the two rubber mold halves. The wax copy of the master setting may then be used to form a precious metal setting.
The remainder of the rubber molding process involves a “lost core” process which is well know to those of ordinary skill in the art. The lost core plaster method involves casting the wax copy or copies in plaster, heating the plaster above the point at which the wax will decompose or carbonize, and injecting molten metal, typically a precious metal, into the plaster. After the metal has hardened, the plaster casting may be shattered to allow removal of the precious metal copy of the master setting.
Thus, if the master setting includes seats, the seats will be reproduced using the rubber molding process. The rubber molding process may be disadvantageous because the flexibility of the rubber mold makes it easy to slightly misalign or distort the mold halves when assembling the mold and during the molding process. This makes it difficult for the jewelry maker to ensure that the size and placement of the seats remains substantially the same on each prong and to maintain reproducibility between settings formed in this manner. Thus, for example, although it is possible to mold seats directly into settings using the rubber mold process, such seats may be at different positions on each of the prongs, resulting in irregularities in the position of the gemstones. In addition, the dimensional accuracy of the settings produced by this method are less than what is desirable due to the number of iterations required to obtain the desired precious metal copy of the original master, i.e. the precious metal copy is a copy of a wax copy, which in turn is a copy of the master setting. Each subsequent copying step reduces the overall accuracy of the final part in comparison to the master setting.
One attempt to overcome the foregoing problems with the rubber molding process involves using metal molds rather than rubber molds. The metal molding process provides greatly improved reproducibility and accuracy of the final setting in comparison to the rubber molding process. However, because metal molds must be machined, it is impossible to provide two mold halves that include a relief pattern of the interior and exterior of the desired setting. By way of explanation, a
Chop Andrea
Findings Incorporated
Salter & Michaelson
Swann J. J.
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