Metal working – Method of mechanical manufacture – Shaping mating parts for reassembly in different positions
Reexamination Certificate
1999-03-23
2001-11-20
Hughes, S. Thomas (Department: 3726)
Metal working
Method of mechanical manufacture
Shaping mating parts for reassembly in different positions
C451S123000, C451S050000
Reexamination Certificate
active
06317955
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates generally to a mold for molding resinous domed articles which may be employed as a cover for monitor cameras, and more particularly to a production method of the same.
2. Background Art
Typical monitor cameras employed in stores, banks, etc. are designed to monitor a preselected range across a fixed direction. Cameras of this type have a dead angle so great as not to cover a wide range. In order to avoid this problem, there have been developed monitor devices which turns or pans a single camera horizontally and tilts it vertically for monitoring a wider range. Such prior art monitor cameras are usually suspended from the ceiling and present an appearance persons perceive to be a camera easily, thus giving an unpleasant feeling to customers in the store. Recently, small-sized monitor cameras are, thus, proposed whose major part of the camera and tilt and pan mechanisms are covered with a resinous dome.
FIG. 4
shows such a dome-shaped monitor camera which includes a camera body
1
, a mount ring
2
, a transparent domed cover
3
, an inner cover
4
, a camera lens
5
, a power supply cable
6
, and an output coaxial cable
7
. The inner cover
4
is disposed within the domed cover
3
and made from an opaque or a translucent material. The inner cover
4
has formed therein an opening
4
a through which the camera lens
5
faces the outside. The power supply cable
6
supplied the power to the camera body
1
, a tilt mechanism, and a pan mechanism. The output cable
7
outputs image signals and receives control signals. The domed cover
3
is made from acrylate resin in injection molding and required to have smooth surfaces and a constant thickness for ensuring a given degree of quality of captured images. The domed cover
3
is also required to have substantially a hemispherical surface for vertical and horizontal movements of the camera body
5
over 90° and 360° ranges, respectively.
FIG. 5
shows a conventional mold for forming the domed cover
3
shown in FIG.
4
. The mold consists of an upper block
8
(i.e., a female molding block) and a lower block
9
(i.e., a male molding block). The upper block
8
has formed therein a cavity
10
which consists of a hemispherical wall
10
a and an annular wall
10
b
extending straight from an end of the hemispherical wall
10
a.
The formation of the cavity
10
of the upper block
8
is achieved by rotating the upper block
8
about a vertical axis V passing through the center
0
of a semicircle having the same radius of curvature as that of the hemispherical wall
10
and rotating and moving a grindstone, which has a surface curved outward with the same radius of curvature as that of the hemispherical wall
10
a
, from the top to an end of the semicircle. The annular wall
10
b
of the upper block
8
is grounded by moving the grindstone parallel to the vertical axis V. A hemispherical portion
9
a
of the lower block
9
may be grounded in substantially the same manner as that of forming the cavity
10
, but formation of an annular wall
9
b
extending straight from an end of the hemispherical portion
9
a
requires interruption of the grinding and replacement of the grindstone used in forming the hemispherical portion
9
a
with another one having a flat grinding surface. This is because a comer between the annular wall
9
b
and a flat upper wall
9
c
needs to be formed at right angles. The replacement of the grindstone may result in an error in forming a curved outer surface near an end of the hemispherical portion
9
a
, thereby causing irregularities to be formed on an interface between the hemispherical portion
9
a
and the annular wall
9
b
, which will lead to formation of similar irregularities on an inner surface of the domed cover
3
near its end, thereby contributing to distortion of part of images captured by the monitor camera.
SUMMARY OF THE INVENTION
It is therefore a principal object of the present invention to avoid the disadvantages of the prior art.
It is another object of the present invention to provide a resinous dome-forming mold having smooth surfaces which do not form irregularities on the surfaces of molded articles.
According to one aspect of the invention, there is provided a mold for forming a resinous domed article including a hollow hemispherical portion and a hollow cylindrical portion continuing from an end of the hollow hemispherical portion. The mold comprises: (a) a female block having formed therein a domed mold cavity which includes a hemispherical wall that is just half a sphere and an annular wall extending from an end of the hemispherical wall; and (b) a male block having a domed protrusion mating with the domed mold cavity of the female block. The domed protrusion includes a hemispherical portion and a cylindrical portion which is joined to the hemispherical portion.
According to the second aspect of the invention, there is provided a method of producing a male block of a resinous domeforming mold. The male block has a dome-shaped protrusion which includes a hemispherical section that is just half a sphere and a cylindrical section continuing from an end of the hemispherical section. The method comprises the steps of: (a) preparing a spherical block having a spherical surface ranging over at least more than half a sphere; (b) rotating the spherical block around an axis passing through the center of the spherical block; (c) grinding an area of the spherical surface of the spherical block ranging over more than 180° from a top of the spherical surface through which the axis of rotation passes to a circumference thereof using a grindstone with a curved surface having substantially the same radius of curvature as that the hemispherical section of the male block; (d) cutting off a grounded portion of the spherical block to complete the hemispherical section of the male block; (e) preparing a block on which the cylindrical section of the male block is formed; and (f) joining the cylindrical section to the hemispherical section to complete the male block.
According to the third aspect of the invention, there is provided a method of producing a male block of a resinous dome-forming mold. The male block has a dome-shaped protrusion which includes a hemispherical section that is just half a sphere and a cylindrical section continuing from an end of the hemispherical section. The method comprises the steps of: (a) preparing a spherical block including a hemispherical portion that is just half a sphere and a base portion connected to the hemispherical portion to form a spherical surface ranging over more than 180° of the sphere; (b) rotating the spherical block around an axis passing through the center of the spherical block; (c) grinding an area of the spherical surface of the spherical block ranging over more than 180° from a top of the spherical surface through which the axis of rotation passes to a circumference thereof using a grindstone with a curved surface having substantially the same radius of curvature as that the hemispherical section of the male block; (d) separating the hemispherical portion from the spherical block to complete the hemispherical section of the male block; (e) preparing a block on which the cylindrical section of the male block is formed; and (i) joining the cylindrical section to the hemispherical section to complete the male block.
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patent: 5
Tamura Kazushige
Wada Jyoji
Hughes S. Thomas
Jimenez Marc
Matsushita Electric - Industrial Co., Ltd.
Woo Louis
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