Fluid handling – Destructible or deformable element controlled – Destructible element
Reexamination Certificate
2000-02-24
2001-10-09
Buiz, Michael Powell (Department: 3753)
Fluid handling
Destructible or deformable element controlled
Destructible element
C137S086000, C137S910000, C220S089200
Reexamination Certificate
active
06298869
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to polymer rupture disks and specifically to a thermoformed polymer rupture disk that can be economically manufactured and utilized in systems where no metal is desired.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
Reverse buckling rupture disks are, of course, well known in the art. To applicant's knowledge, they are all formed of metal and have score lines therein that enable the disks to buckle or burst in a predetermined fashion.
For many, many years Teflon® film has been thermoformed as liners for metal reverse buckling rupture disks in order to separate the metal from any fluids that may be detrimentally affected by metal contact. Further, flat Teflon® rupture disks have been used for many years. Some of the flat Teflon® rupture disks develop a “domed” center section resulting from room temperature pressure applied thereto.
All such polymer rupture disks in the prior art have a flow area after burst that is relatively small and unpredictable. Second, the burst pressure is difficult to change when the burst pressure is controlled by the construction of the customer's rupture disk holder or flanges.
It would be extremely useful to have a reverse buckling, thermoformed, rupture disk with a relatively large, predictable flow area with buckling pressures controlled by score lines or thin areas or buckling points formed therein.
SUMMARY OF THE INVENTION
The present invention discloses and teaches a reverse buckling, thermoformed, polymer rupture disk with a raised center and having score lines therein, or thinned areas that are in predetermined locations and that provide a predetermined flow area after burst and enable the burst pressure to be changed even though the disk's constraining geometry is controlled by the customer's holder or flanges.
The present reverse buckling polymer rupture disk is thermoformed and has an annular flange and a raised center portion, both having a predetermined thickness. The raised portion may be of various shapes including dome-shaped and has an upstream convex side and a downstream concave side and buckles when pressure is applied to the upstream convex side thereof. It has at least one score line formed in the thermoformed polymer rupture disk to create a line of weakness that forms a predetermined burst pattern when rupturing under a predetermined pressure applied to the upstream convex side.
Note that the disk can buckle independently of the score lines. In some cases the score lines are used to influence the location of the buckling point or the magnitude of the buckling pressure. In the preferred embodiment, the buckling pressure and location are primarily defined by the thermoformed shape and thickness. The score line(s) are primarily used as a means to create a weakened and predictable rupture path.
The score line may be formed in several ways. One of the ways is to cause a predetermined thinning in a predetermined area of the rupture disk during thermoforming by applying a vacuum to the area where it is desired to be thinned.
Another method of forming a score line is to use a razor blade that can cut into the polymer material to a predetermined depth.
Still another method of forming the score line is to utilize a press having a relatively sharp blade extending therefrom in the shape of the score line and apply a force to the blades to force them into the surface of the polymer rupture disk to create the very narrow but deep score lines.
The score lines may be formed in the polymer rupture disk either before, after, or during thermoforming the polymer rupture disk.
The desired score line is formed in the flange of the polymer rupture disk adjacent the dome-shaped center portion and extending at least partially around the dome-shaped center portion.
In another embodiment, the score line is formed in the dome-shaped center portion with two score lines perpendicular to each other.
It is desired that the score line be preferably formed on the downstream side of the rupture disk. However, under certain circumstances, it could be formed on the upstream side thereof.
In addition, because some of the rupture disk holding means have centering recesses formed in the annular base thereof, the rupture disk can have a corresponding raised annual centering ring formed in the annular flange, preferably on the upstream side of the polymer rupture disk, to position the rupture disk in fluid flow line in relation to the holding means having the annular recesses.
Further, where first and second holding means have identical fluid flow orifice sizes, a flat rigid annular plate may be placed in the downstream side of the polymer rupture disk with an orifice therein having a diameter that is less than the fluid flow line holding means diameter to form an offset shoulder on the downstream side of the thermoformed polymer rupture disk with respect to the fluid line inside diameter to provide support to the flange area of the rupture disk and prevent bending of said flange area when pressure is applied to the convex side of the rupture disk. In some cases, the outer portion of the annular rupture disk flange can form as a skirt that extends perpendicular to the plane of the annular flange in the direction of the downstream side of the polymer rupture disk to aid in centering the polymer rupture disk in the flow line and contain the flat rigid annular plate.
Thus, it is an object of the present invention to form the reverse buckling polymer rupture disk by thermoforming the disk.
It is another object of the present invention to use Teflon® as the polymer material forming the rupture disk.
It is yet another object of the present invention to provide a reverse buckling, thermoformed, polymer rupture disk with a relatively large, predictable flow area after rupture and that has a buckling pressure that is controlled by score lines or thinned areas or buckling points created in the thermoforming process.
It is still another object of the present invention to provide a thermoformed reverse buckling polymer rupture disk having a score line therein that penetrates through at least 60% of the polymer rupture disk thickness.
It is yet another object of the present invention to provide a rupture disk wherein the score line is thermoformed into the flange of the polymer rupture disk adjacent its dome-shaped center portion and extending at least partially around the dome-shaped center portion.
It is also an object of the present invention to provide a reverse buckling, thermoformed, polymer rupture disk having a score line that is cut into the annular flange of the polymer rupture disk adjacent the dome-shaped center portion and extending at least partially around the dome-shaped center portion.
It is still another object of the present invention to provide a reverse buckling, thermoformed, polymer rupture disk having a score line mechanically pressed into the annular flange of the polymer rupture disk adjacent the dome-shaped center portion and extending at least partially around the dome-shaped center portion.
It is yet another object of the present invention to provide a reverse buckling, thermoformed, polymer rupture disk wherein the score line is formed in the dome-shaped center portion of the polymer rupture disk.
It is also an object of the present invention to provide a reverse buckling polymer rupture disk having a score line preferably formed on the downstream side of the rupture disk.
It is yet another object of the present invention to provide a reverse buckling, thermoformed, polymer rupture disk that has a raised annular centering ring formed in the annular flange on the upstream side thereof and a skirt formed on the outer portion of the annular flange that extends perpendicular to the plane of the annular flange in the direction of the downstream side of the polymer rupture disk to center a flat, rigid, annular plate placed on the downstream side of the polymer rupture disk. An orifice in the annular p
Buiz Michael Powell
Jones Day Reavis & Pogue
Krishnamurthy Ramesh
Oklahoma Safety Equipment Co.
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