U.S. patent application number 09/782658 was filed with the patent office on 2001-07-05 for bursting disc assembly retaining ring with a clover leaf cutting pattern and projection.
Invention is credited to Goddard, John D., Muddiman, G. Scott.
Application Number | 20010006075 09/782658 |
Document ID | / |
Family ID | 23886535 |
Filed Date | 2001-07-05 |
United States Patent
Application |
20010006075 |
Kind Code |
A1 |
Muddiman, G. Scott ; et
al. |
July 5, 2001 |
Bursting disc assembly retaining ring with a clover leaf cutting
pattern and projection
Abstract
In combination with a rupture disc assembly, there is provided
an improvement by using a support ring having a projection and a
continuous, generally clover leaf pattern cutting edge.
Inventors: |
Muddiman, G. Scott;
(Burlington, CA) ; Goddard, John D.; (Burlington,
CA) |
Correspondence
Address: |
WATTS, HOFFMANN, FISHER & HEINKE CO., L.P.A.
Ste. 1750
1100 Superior Ave.
Cleveland
OH
44114
US
|
Family ID: |
23886535 |
Appl. No.: |
09/782658 |
Filed: |
February 13, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09782658 |
Feb 13, 2001 |
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09475182 |
Dec 30, 1999 |
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6220269 |
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Current U.S.
Class: |
137/68.29 ;
220/89.3 |
Current CPC
Class: |
F16K 17/1613 20130101;
Y10T 137/1759 20150401; F16K 17/16 20130101; Y10T 137/1737
20150401 |
Class at
Publication: |
137/68.29 ;
220/89.3 |
International
Class: |
F16K 017/16 |
Claims
I claim:
1. In a rupture disc assembly having a support ring adapted to
support a rupturable rupture disc member; said support ring
including an aperture, spaced upper and lower surfaces, a
continuous side surface and at least one tear-initiation
projection, the improvement wherein said support ring includes
contiguous cutting means about said, aperture, said cutting means
comprising a plurality of arcuately contoured segments having an
innermost arc portion and caution of the arcuate segments spaced
closer to said inner peripheral wall than the other portions of the
arcuate segments.
2. A rupture disc support ring comprising: a substantially flat
support ring having a pair of opposed planar surfaces and a central
aperture extending between said surfaces encircled by said ring; at
least one tear-initiation projection for initiating a tear in a
reverse buckling disc, said projection extending from said planar
support ring inwardly into said aperture and projecting downwardly
and below one of said opposed surfaces; and arcuately contoured
cutting means at least partially surrounding said aperture and
extending either side of said tear-initiation projection, said
cutting means having an innermost segment of the arcuately
contoured cutting means abutting said support ring and projecting
downwardly from said one of said opposed surfaces.
3. The apparatus of claim 1, wherein said support ring includes
means to prevent fragmentation of a reverse buckling disc when said
disc is ruptured.
4. The apparatus of claim 3, wherein said means comprises an
inwardly extending tab associated with said support ring.
5. The apparatus of any one of claim 1, wherein said support ring
is in combination with a reverse buckling rupture disc, said
rupture disc comprising a dome-shaped central member surrounded by
a substantially planar annular flange, said rupture disc having a
transition radius between said flange and said dome-shaped
member.
6. The apparatus of claim 5, wherein said support ring includes a
transition radius between one of said planar surfaces and the
downwardly and inwardly extending tear initiation projection, said
transition radius of said support ring being substantially the same
as the transition radius of said reverse buckling rupture disc.
7. The apparatus of claim 5, wherein said support ring includes a
transition diameter between one of said planar surfaces and the
downwardly and inwardly extending tear initiation projection, said
transition diameter of said support ring being substantially the
same as the transition diameter of said reverse buckling rupture
disc.
8. The apparatus of claim 4, said apparatus including cooperating
first and second holding means for mounting said support ring and
said reverse buckling rupture disc, said first and second holding
means having a central aperture, and means for retaining said first
and second holding means within operative relationship with said
support ring and said rupture disc.
9. The apparatus of claim 8, wherein one of said holding means
includes an aperture having a configuration corresponding
substantially to the aperture configuration of said support
ring.
10. The apparatus of claim 9, wherein said holding means includes a
plurality of support means for supporting said plurality of
spaced-apart tear initiation projection of said support ring.
11. The apparatus of claim 10, wherein said holding means has a
plurality of arcuately contoured sides of said aperture extending
between opposed surfaces of said holding means, said arcuately
contoured sides corresponding in shape to the arcuately contoured
configuration of said cutting means of said support ring.
12. The apparatus of any one of claim 6, wherein at least one of
said holding means includes positioning means for positioning said
support ring in a predetermined direction between said holding
means.
13. The apparatus of claim 12, wherein said positioning means
comprises a projection extending from one of said holding means,
the other of said holding means having a recess adapted to receive
said projection, and said support ring having means for receiving
said projection and positioning said support ring between said
holding means.
14. For use with an upper holding member having a bore and a lower
annular surface; a rupture disc and support member assembly
comprising a rupture disc having an annular peripheral section and
a domed central section extending downwardly from said upper
holding member, and a support member having an annular peripheral
section resting on said annular peripheral section of said rupture
disk and at least one cutting projection extending downwardly from
said peripheral section, in close proximity to said domed section
for initiating tear in said domed section, and arcuately contoured
cutting edges extending each side of said cutting projection, said
cutting edges each including an inner arc section coincidental with
said upper holding member when said upper holding member is
positioned on an upper surface of said peripheral section of said
support member.
15. An assembly as claimed in claim 14, including a plurality of
spaced cutting projections.
16. An assembly as claimed in claim 14, including a cord section on
an inner periphery at the annular peripheral section of the support
member, said cord section forming a hinge member.
17. A bursting disc assembly including a reverse buckling bursting
disc comprising: a lower tubular holding member having a bore and
spaced apart annular seating surfaces, an upper surface and a lower
surface; a reverse buckling bursting disc having a peripheral
annular section seated on the upper surface of the lower holding
member and a domed central section extending down into the bore of
the lower holding member; a support member having a peripheral
annular section seated on said annular section of the bursting disc
and at least one tear initiating member extending downwardly within
said domed portion and in close proximity thereto, and arcuately
contoured cutting edges extending on each side of the said tear
initiating member; an upper tubular holding member having a bore
and spaced apart annular seating surfaces, an upper surface and a
lower surface, the lower surface seated on said peripheral annular
section of said support member; and said contoured cutting edges
including innermost arc sections coinciding with the bore of the
upper holding member.
18. An assembly as claimed in claim 17, including a plurality of
space tear initiating members.
19. An assembly as claimed in claim 17, including a chord section,
on an inner periphery of the annular peripheral section of the
support member, said chord section forming a hinge member.
20. An assembly as claimed in claim 17, including support
formations extending down from said upper holding member to support
said tear initiating member or members.
Description
FIELD OF THE INVENTION
[0001] This invention relates to a pressure relief valve, and more
particularly to a pressure relief valve being of a metal rupture
disc in the form of thin rupture members having a metal liner body
with a weakened portion including, in the form of a scored pattern,
where the metal liner is placed in juxtaposition with a bursting
disc.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to safety pressure relief
devices and, in particular, to rupture disc assemblies, including
reverse buckling rupture discs, and also to methods of
manufacturing such rupture discs and assemblies.
[0003] Rupture discs have been known in this art for many years.
Normally, the rupture discs arc manufactured to have a rupturable
membrane to provide a safety mechanism to relieve excessive
pressure within an over-pressurized system or vessel. The rupture
disc and or rupture disc assemblies are typically placed within
such a system or vessel so as to prevent the flow of a liquid or a
gas through such a device until the rupture disc ruptures through
excessive or over-pressure loads. Typically, rupture discs have a
score pattern formed by cuts, machined or by other conventional
methods into the dome portion of the disc to enable the disc to
buckle and to burst when under excessive pressure.
[0004] Rupture discs having support rings providing cutting
projections have been used, but are restricted in use, being
capable of use with gases only and sometimes restricted in pressure
range.
[0005] Obviously, if a rupture disc assembly could be developed
which had better operating characteristics, including the ability
to be used within a gas and or liquid environment capable of low
and or high burst pressures, all without reducing the economic
viability of Such discs, there could be a wider application for the
use of rupture discs assemblies.
SUMMARY OF THE INVENTION
[0006] With the present invention, it has been found that by
providing a rupture disc assembly having a support ring including a
projection and a predetermined configuration for the continuous
score line, in combination with a rupture disc, the disadvantages
of using standard rupture discs with conventional support rings are
overcome cost-wise and the combination of the present invention
permits a wider range of application for varying liquid and gas
usages, and varying burst pressures.
[0007] The present invention provides a rupture disc combination
which permits the use of rupture disc members in association with a
certain type of rupture disc assemblies which overcomes the
disadvantages with rupture discs assemblies per se, and yet
provides the advantages of certain features of known rupture
discs.
[0008] It is therefore one aspect of the invention to provide in a
rupture disc assembly having a support ring adapted to support a
rupturable rupture disc member; said support ring including an
aperture, an upper and lower surface and a continuous side surface,
the improvement wherein the support ring includes contiguous
cutting means about the inner peripheral wall, the cutting means
comprising a plurality of adjacent arcuately contoured cutting
means having an innermost surface of the arcuate contour spaced at
a closer distance to said inner peripheral wall than outer ends of
the arcuate contour.
[0009] In another aspect of the present invention there is provided
in a rupture disc assembly having a support ring adapted to support
a rupturable rupture disc member; the support ring including an
aperture, an upper and lower surface and a continuous side surface,
the improvement wherein the support ring includes engaging means
for engaging a ruptured disc after rupture of the same, the
engaging means comprising a projection extending upwardly from one
of the surfaces of the support ring and extending inwardly of the
surface over the aperture to thereby engage a displaced ruptured
disc.
[0010] In another aspect of the present invention there is provided
in a rupture disc assembly having a support ring adapted to support
a rupturable rupture disc member; the support ring including an
aperture, an upper and lower surface and a continuous side surface,
the improvement wherein the support ring includes a contiguous
cutting surface operatively associated with said projection, the
cutting surface positioned on said inner peripheral portion on the
support ring, the projection of the cutting surface having a
generally clover-leaf configuration.
[0011] In various alternative embodiments, the device according to
any of the above aspect, the disc further includes a dome having a
pre-determined transition radius between the dome and the support
ring.
[0012] In various alternative embodiments, the support ring
includes a transition radius substantially corresponding to that of
the disc.
[0013] In alternative versions, the support ring transition radius
includes a diameter of the transition radius being smaller than the
transition radius of the disc.
[0014] Desirably, in accordance with the present invention, there
is provided in a rupture disc having a rupturable rupture member
together with a support system including a support ring associated
with the rupture disc, the support ring having a projection formed
within the ring adapted to retain post burst disc material, the
improvement wherein the rupture disc supporting ring comprises a
predetermined continuous score line therein adapted to cut the
rupture disc when the disc buckles at a predetermined pressure, the
support ring with the continuous cut or score line being in
operative association with the projection formed in the support
ring.
[0015] It is therefore another aspect of the present invention to
provide a bursting disc in combination with a support ring having a
projection formed on one side of the ring in combination with a
continuous score pattern is of a generally clover-leaf
configuration.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is an exploded cross-sectional view of a bursting
disc assembly.
[0017] FIG. 2 is a top view of a rupture disc.
[0018] FIG. 3 is a top view of a support ring.
[0019] FIG. 4 is a cross-section view of the disc and support ring
illustrating the transition diameter,
[0020] FIG. 5 is a enlarged view of the portion in circle A of FIG.
4.
[0021] FIG. 6 is a top view of the lower holder,
[0022] FIG. 7 is a view of the upper holder viewed from below,
[0023] FIG. 8 is a side view of the assembled device.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0024] For purposes of description herein the terms upper, lower,
vertical and horizontal along with other directional references
shall be relative to the invention as oriented in FIGS. 1 and 5, as
illustrated in a pressure to non-pressure flow direction. It should
also be understood that the various disclosed embodiments are
merely exemplary and are utilized in a manner as would be readily
understood by a person in the art.
[0025] The assembly as generally indicated by reference numeral 10,
designates a rupture disc assembly including, in a pressure to
non-pressure direction sequential relationship, a lower support
holder or flange 20, a rupture disc 50, a support ring 100 and an
upper support holder or flange 60. The assembly 10 when in use is
securely held in an assembled condition through any conventional
means, such as through the use of bolts or other mounting
arrangements. The support structure 100 includes a projection or
tongue member 120 formed in one side of the ring 100, and a
continuous cutting surface 130 formed in the remaining
non-projection sides of the ring (see FIG. 3).
[0026] The assembly 10 may be positioned within a safety release
structure (not shown), such as a vent or pressure release valve
assembly, and is normally adapted to prevent the flow of a liquid
or a gas, in high and/or low pressures, through the assembly under
a normal or predetermined burst pressure. The disc 50 is adapted to
rupture or provide relief for excessive pressure when the
predetermined maximum burst pressure of a bursting disc is
exceeded.
[0027] When viewed from a pressure side to the non-pressure side of
the device 10, there is provided a lower support holder or flange
20, which is positioned adjacent the lower surface of a bursting
disc 50. The lower support holder or flange 20 may be constructed
of any suitable material known in the art. The support holder or
flange 20 in use is adapted to provide a secure seal against
leakage between the disc 50 and the portion of the pressure vessel
into which the assembly 10 is placed.
[0028] As illustrated in FIG. 6, the lower support holder or flange
20 is of a generally circular or ring configuration, having a
centralized aperture or bore 22, an inner peripheral wall 24 and an
outer circumferential wall 26, a lower surface 25 (FIG. 1) and an
upper annular surface or inner seating surface 40 around the
centralized aperture 22 of the flange 20. In a preferred
embodiment, the outer wall portion 26 of the lower holder or flange
20 extends above and around the annular surface 40, having a
generally extending peripheral outer rim portion 28. Formed within
the surface 40, through any conventional means such as milling, die
forming, tooling or the like, is a circumferential raised
projection or member 42, spaced inwardly of the outer rim wall 28.
Raised member or projection 42 is adapted to provide a protuberance
against which disc 50 abuts. When the assembly 10 is in a fully
assembled condition, the raised projection or member 43 is adapted
to securely retain the disc 50 against the support ring 110 and the
support holder 20. As the assembly 10 is assembled and secured
through conventional means, the pressure between the flange portion
of the disc and the raised projection or member 42 allows for the
flange portion to form or bend onto the projection thereby
providing a seal and retaining the disc 50 in place.
[0029] In a preferred embodiment, the outer rim 28 is interrupted
and provided with a gap portion or interruption 30. Most preferably
the gap portion 30 is provided or interrupted by a segment 32 of
the outer rim or wall portion, wherein the segment or segments are
adapted to match or fit with a corresponding or mating portion on a
subsequent element of the assembly. In a preferred embodiment, the
raised projection or member 32 is spaced midway between the outer
rim and the inner ring wall 24.
[0030] As illustrated in FIGS. 1 and 3, the support ring 100 handle
portion 120. The support ring 100 is of a generally circular
configuration, having an upper surface 111 and a lower surface 12,
the ring being adapted through dimension and position to fit snugly
within the assembly 10 as shown in FIGS. 1, 4 and 5. The support
ring 100 further includes a central aperture 115, corresponding to
that of the disc and flanges 20 and 60. The support ring has an
inner peripheral edge 116 and an outer circumferential edge 117.
The inner peripheral edge 116 includes a projection or hinge member
120, a series of downward projections 110, and an opening pattern
or cutting edge 130 extend either side of the projections 110. The
projection or hinge member 120 is formed at a predetermined point
along the inner ring surface, the remaining portion providing the
opening pattern or cutting edge 130. The cutting edge 130 has a
generally continuous configuration, which according to the present
embodiment is of a generally clover leaf pattern.
[0031] As shown in FIG. 1, the projections 110 and the cutting edge
130, and projections 110 of the support ring 100, when viewed from
a pressure side to a non-pressure side perspective, depend or
otherwise extend downwardly below the horizontal axis of the
supporting ring 100. As shown in an assembled state, the cutting
edge 130 and projection 120 depend into the concavity of the dome
portion of the disc 50, wherein the transition radius and diameter
is substantially similar to that of the disc. The support ring 100,
including inner peripheral edge 125 and outer peripheral edge 126,
has a predetermined transition radius and transition diameter,
discussed in detail below.
[0032] The opening pattern or cutting edge 130 in the example shown
in FIG. 2, is of a generally clover leaf configuration, extending
continuously along an inner peripheral portion 116 of the
supporting ring 100 Most desirably, the cutting member 130 having a
generally clover leaf configuration depends from the horizontal
plane of the support ring 100 towards and within the dome portion
of the disc 50. The cutting edge 130 includes the tear initiation
points 110, and arcuately curved continuous cutting portions 134,
the cutting edge has an angle generally being between 50 and 70
degrees, and most desirably about 60 degrees. The arcuately curved
cutting portions 134 include inner arcs which substantially
coincide with the bore of an upper support holder 60.
[0033] This provides for a non-fragmenting burst pattern of the
disc, although other suitable angles may be used. A method of
forming this cutting pattern is described in further detail
below.
[0034] As shown in FIG. 3, the outer circumferential edge of the
support ring 100 includes the projection 120. Formed within the
projection 120 through any conventional means is a slot or aperture
106, adapted to aid in the proper assembling of the assembly 10 by
being able to receive member 32, on the lower holding member
20.
[0035] As illustrated in FIGS. 1 and 2, the disc 50 is of a
conventional type commonly referred to as a reverse buckling disc,
fabricated from a conventional metal material such as steel, steel
alloy or other, and is adapted to tear upon reversing along the
predetermined cutting pattern 130 on the support ring 110 when a
pressure load exceeds the predetermined pressure load of the
rupture disc 50. The rupture disc 50 includes a central portion or
dome portion 52, and a flange or rim portion 54, and is adapted to
be positioned with the dome 52 facing in a pressure flow direction
between the support structure 100 and the lower flange 20. Disc 50,
when in use and under excessive pressure, is adapted to reverse
buckle towards the support ring 110 and the projection member 120.
The dome portion 52 of the disc 50 is cut or otherwise opened
against the clover leaf pattern immediately after which the burst
or buckled disc is wrapped around the projection 120.
[0036] Disc 50 may be of any conventional type, such as a
non-scored reverse bursting disc. When utilized in accordance with
the present invention, no score lines are required as the support
ring 110 as described in detail below includes a cutting formation
which provides for the serration and non-fragmentation of the disc
50. According to a preferred embodiment, when using a non-scored
reverse buckling disc, the present invention is able to be utilized
within both gaseous and liquid environments, and for both high and
low burst pressures in both gaseous and liquid environments.
[0037] Most preferably, the disc 50 includes a transition region 45
having a predetermined transition radius and diameter. The
transition radius between the dome portion of the rupture disc and
the peripheral portion is approximately identical in both the
rupture disc and the support ring. Desirably, the diameter of the
transition radius of the support ring is approximately 0.010" to
0.020" smaller than the transition radius of the disc.
[0038] As illustrated in FIGS. 4 and 5, the transition diameter and
radius of the support ring and the disc, as indicated above, are
substantially similar, with the support ring being adapted through
dimension and position to coincide with the disc 50. The transition
diameter of the support ring 110, as generally indicated by
reference numeral 90, has a predetermined diameter and radius
corresponding to that of disc 50. This ratios of course will vary
depending upon the size and diameter of the disc being used, as
will be understood by one skilled in the art.
[0039] A second upper holder or flange 60 is positioned abutting
the support ring 100, as shown in FIGS. 1 and 8, on the
non-pressure side of the disc 50. The upper support holder or
flange 60 is adapted to provide a secure seal against leakage
between the non-burst disc 50 and the non-pressure side of the
assembly 10 when placed within a pressure vessel. The upper support
holder 60 is similar to that of the lower support holder or flange
20, wherein the upper or non-pressure side support holder or flange
60 has a generally cylindrical configuration including a central
aperture 62, having a defined bore dimension, a continuous side
wall 64 and upper and lower surfaces 66 and 68, respectively. The
upper support holder 60 includes a corresponding or mating portion
70 having a circumferential or annular seat to that of the outer
rim of flange 20. Alternatively, the mating portion 70 of the upper
support holder 60 is interrupted by spaced apart projections 74 and
76, extending from the side wall 64. Projections 74 and 76 are
dimensioned to correspond with the gap portions 30 and 32 of the
outer rim 28. The corresponding projections of the upper support
holder 60 aid in the proper seating and assembly of the ring
assembly 10 by ensuring that the gap portions and projections are
mated correctly in an abutting relationship. If the upper and lower
support holders 20 and 60 are not properly fitted together, they
will not properly align, and the assembly would not be able to be
assembled in the relationship illustrated in Figure 1.
[0040] Desirably, as shown in FIG. 1, the bore of the upper support
holder 60 is provided with depending projections 80 adapted to
support the cutting member 130. Depending support 80 include
corresponding support projections 82 adapted to aid in supporting
the support ring cutting or tear initiation points 110. Depending
support 80 includes arcuately curved sections 84 adapted to
reinforce or support arcuately curved members 134. The depending
support 80, aids in supporting the cutting member 130 when the
predetermined burst pressure of a reverse rupture disc has been
exceeded and the disc reverses and is cut open on the tear
initiating members 110 and the cutting edge 130. Typically, this
pressure is substantial and the bursting of the disc 50 is quite
rapid and places pressure upon the support ring cutting member. As
such it is desirable to support the cutting pattern in such a way
that substantially all of the cutting surfaces are supported
against undesirable bending or twisting during the serration or
cutting of the disc 50. Most preferably the projections have the
substantially similar transition radius and transition diameter to
that of the support ring and rupture disc. By having the innermost
segments of the contoured configurations coincide with the defined
bore of the upper support holder, the present invention enables a
bursting disk to be applicable for both gas and liquid applications
and for high and low pressure applications.
[0041] In use, the assembly 10 is clamped in a pressure line (not
shown). The lower support holder or flange 20 is placed toward the
pressure flow, followed in an abutting and sealed sequential
relationship, a reverse buckling disc 50, a support ring 100 and an
upper support holder or flange 60, positioned such that any
pressure must first contact the disc 50. When pressure in the
vessel is greater than the rupture pressure of the rupture disc 50,
the disc reverse disc pressure load is exceeded and upon rupture,
the pressure is relieved through the assembly 110.
[0042] As the reverse buckling disc 50 reverses upon itself, the
dome or concave convex portion of the disc is forced against the
cutting edge pattern 130 of the support ring 110. The cutting
pattern 130 effectively cuts the disc 50 along the continuous
cutting edge such that the cutaway portion of the disc folds or
hinges along the projection member 120.
[0043] In a further alternative embodiment, the upper support
holder or flange 60 includes a depending projection, having a
substantially similar configuration to that of the cutting pattern
of the support ring 110. This depending projection provides for
additional support of the cutting member 130 during the bursting of
the disc 50.
[0044] Desirably, a method for forming the support ring includes
providing a blank for use as a support ring is manufactured through
conventional means, ie pressing, cutting etc., resulting in a
bulged out or domed shape configuration. Ideally, once formed, the
disc 50 includes a flange portion, and a concave/convex dome, and a
pre-determined transition region having a transition radius and
transition diameter substantially equal to that of a corresponding
disc member. As understood, the term transition radius used herein
is used to describe the area between the flange portion of the disc
and the dome portion of the disc having a predetermined radius and
angle. The transition diameter is understood to describe the length
of the area between the flange sides.
[0045] In a preferred embodiment, the transition diameter of the
support ring 110 has a predetermined length alpha, which is
substantially similar to that of the of the transition diameter
beta of the disc 50. The substantially similar transition diameters
provide for a closer or more snug fit between the disc 50 and the
support ring 110 which allows for less movement of the disc upon
burst and aids in the efficient cutting of the disc 50 upon the
tear initiation points or cutting points 132 and arcuate cutting
members 134.
[0046] A preferred method of forming the cutting pattern 130 of the
support ring 110 is utilizing a precision cutting means, such as a
laser, to effectively cut or otherwise form the clover leaf cutting
pattern 130 in the pre-formed blank. This provides for a more
precise cutting of the support ring surface, as the laser optimally
cuts at a 90 degree angle to the ring surface. The laser provides
(or forms) a cutting edge having a predetermined angle extending
for at least a major portion of the pattern. As stated, the cutting
edge has a predetermined angle of between 50 and 70 degrees, and
most preferably has a cutting angle of approximately 60
degrees.
[0047] Although embodiments of the invention have been described
above, it is not limited thereto and it will be apparent to those
skilled in the art that numerous modifications form part of the
present invention insofar as they do not depart from the spirit,
nature and scope of the claimed and described invention.
* * * * *