Attachable/detachable pressure evacuation device

A pressure evacuation device for a compressed gas cylinder having a fixed assembly that is semi-permanently attached to an opening in the cylinder and comprises a retractable bleed valve, and a detachable assembly that can be readily attached to and detached from the fixed assembly and comprises a valve stem to control the bleed valve and a valve tee to direct the flow of gas from the cylinder.

RELATED APPLICATIONS

BACKGROUND OF THE INVENTION

A pressure relief device on a compressed gas cylinder provides a means of venting excess pressure to prevent the rupture of the cylinder. For example, if the cylinder is exposed to extreme heat, the gas within the cylinder will expand, creating the risk of an uncontrolled rupture of the cylinder, which may cause injury, death, and property damage. A reclosing pressure relief device may include a spring-loaded valve that will keep the valve closed under normal pressure conditions. Under high pressure conditions the spring will compress, opening the valve and allowing the gas to vent out of the cylinder. Once safe pressure conditions have been restored, the spring pushes the valve closed. A non-reclosing pressure relief device may include a disk having a design and composition known to rupture at a predetermined pressure. If the gas pressure exceeds that pressure, the disk will rupture allowing the gas to vent. The pressure relief device remains open until the ruptured disk is replaced.

The Compressed Gas Association (CGA) publishes the CGA S-1.1 Pressure Relief Devices Standards representing the minimum requirements for pressure relief devices considered to be appropriate and adequate. However, under the most recent versions of the CGA S-1.1 standard, use of a pressure relief device is now optional in some circumstances. The CGA position is that in the event of a fire, the seals in the cylinder valves and end plugs will leak, which will prevent the buildup of excessive pressure inside the cylinder. As such, without a pressure relief device, the only controllable mechanisms for venting gas in case of an emergency is the primary cylinder valve, but this valve may have been damaged or become inaccessible by the circumstances which caused the emergency in the first place.

As such, there is a need for a pressure evacuation device that can be attached and used in case of emergency and then removed once safe conditions have been restored.

SUMMARY OF THE INVENTION

Embodiments of the present invention solve the problem of venting excessive pressure from a gas cylinder by using a two component pressure evacuation device, the first component comprising a bleed valve inside a bull plug which is inserted into an opening of the gas cylinder and the second component comprising a readily attachable and detachable valve stem and tee.

The bull plug screws into the gas cylinder and becomes a fixed component of the cylinder, except during maintenance of the cylinder. The bull plug has an opening leading to the interior of the cylinder, an opening leading to the exterior of the cylinder, and threaded bleed valve assembly between the openings. Rotating the bleed valve assembly one direction pulls the bleed valve away from its seat and exposes the bleed holes to the opening leading to the interior of the gas cylinder; rotating the assembly the other direction pushes the bleed valve back into the seat and covers the bleed holes to prevent gas from escaping from the cylinder.

Under normal operations, the bleed valve is closed to the cylinder interior and a safety plug covers the external opening in the bull plug. Under emergency operations, the user removes the safety plug and screws the detachable valve stem and tee assembly into the opening in the bull plug. Once the end of the valve stem engages with the bleed valve assembly, the user rotates the valve stem to open the bleed valve, allowing gas to exit the cylinder through the valve tee and out a vent port. Once enough gas has been vented from the cylinder, the user rotates the valve stem to close the bleed valve, unscrews the detachable valve stem and tee assembly from the bull plug, and replaces the safety plug.

Upon review of the drawings and detailed descriptions of the embodiments that follow, those skilled in the art will recognize other embodiments that capture the essential features of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

In describing and claiming embodiments of the present invention, relative terms such as “top,” “bottom,” and the like are sometimes used to identify portions of components. The use of such terms assumes relative orientations suggested by the drawings and does not limit how the embodiments may be oriented in the field.

Further, the following “First Embodiment” section provides a detailed description of the construction and use of one embodiment of the present invention. The “Alternative and Additional Embodiments” section that follows the First Embodiment section provides one of ordinary skill with possible modifications and extensions which complement the essential features of the present invention. Selection of some of these modifications and extensions may affect the quality of the general operation of the present invention in terms of performance when used for particular applications. Implementation of other modifications and extensions may be driven by costs of manufacture, availability of materials, physical constraints, and other factors which may be independent of the general operation of the present invention. The non-exclusive set of examples of alternative and additional embodiments may be mixed and matched as needed and as technically feasible so long as the detachable pressure evacuation device assembly can be readily and safely attached and used in case of emergency conditions and then removed once safe conditions have been restored.

First Embodiment

FIGS.1through30provide an embodiment of a pressure evacuation device which comprises fixed assembly100, which is fitted into an opening of gas cylinder300, and detachable assembly200, which is attached to and detached from fixed assembly100.

FIGS.1through4provide side, side cutaway, downward, and upward views of bull plug102. Bull plug102has head104having hexagonal prism upper head106and a cylindrical lower head108, and thread110extending downward from head104. Head104is about 4¼ inches in diameter and about 1 inch tall. Thread110is about 3 inches in diameter, about 2 inches tall, and is cylindrical. Bull plug102is constructed from stainless steel.

Crevice112is an annular indentation located on the bottom of lower head108, is about ¼ inch wide, about ¼ inch deep, and positioned slightly wider than thread110. Crevice112is suitable for receiving seals114and116(not shown) when bull plug102is attached to gas cylinder300(not shown) to form a seal between bull plug102and gas cylinder300. Seal114is an o-ring made of a fluoroelastomer (such as the fluoroelastomer commercially available under the brand name Viton™) and seal116is an o-ring made of a fluoropolymer (such as the fluoropolymer commercially available under the brand name Teflon™).

Bull plug opening118provides top access to cylindrical cavity120and is about ¾ inch in diameter. Cavity120comprises upper cavity122, middle cavity124, and lower cavity126. Upper cavity122is about ¾ inch in diameter and about 1½ inches deep and has threaded walls running about halfway down from opening118. Middle cavity194is about ⅝ inch in diameter, about ½ inch deep, and has threaded walls. Lower cavity126is about ⅛ inch in diameter, about 1 inch deep, and has angled bleed valve seat128at the top. Bleed valve housing stop130is formed where upper cavity122meets middle cavity124. Bull plug inlet opening132provides bottom access to cavity120and is about ⅛ inch in diameter.

FIGS.5through8provide side, side cutaway, downward, and upward views of bleed valve housing134. Bleed valve housing134has cylindrical head136about ⅜ inch tall and about ⅞ inch in diameter. Head136connects to cylindrical shank138about ¼ inch tall and about ¾ inch in diameter. Shank138connects to cylindrical thread140about ½ inch tall and about ¾ inch in diameter, Bleed valve housing134has cavity142between the bottom of thread140and shank138, four equally-spaced outlet ports148pass through shank138and into cavity142, and inlet port152in the bottom of thread140which opens into cavity142. Outlet ports148are about ⅛ inch in diameter and inlet port152is about ½ inch in diameter. Cavity142has an upper cavity144and a lower cavity146, and upper cavity144is slightly narrower than lower cavity146to form bleed valve stop154. Valve stem interface156is a cubic cavity in the top of head136and is about ⅜ inch wide and about ⅜ inch deep. Bleed valve housing134is constructed from stainless steel.

FIGS.9through12provide side, side cutaway, downward, and upward views of bleed valve158. Bleed valve158has an upper, middle, and lower portion, where upper bleed valve160is about ⅛ inch tall and about ⅜ inch in diameter, middle bleed valve162is about ⅜ inch tall and about ½ inch in diameter, and lower bleed valve164is about ¼ inch tall and tapers down from about ½ inch in diameter to about ¼ inch in diameter at the tip. Four equally-spaced inlet ports166pass through lower bleed valve164and into cavity170, and outlet port168in upper bleed valve160opens into cavity170. Bleed valve158is constructed from stainless steel.

FIG.13provides a side view of bleed valve assembly174, which is formed by inserting bleed valve158into inlet port152until bleed valve158reaches bleed valve stop154. Air passes freely into bleed valve inlet ports166, through cavity170, and Out outlet ports150.

FIGS.14and15provide side and downward views of safety plug176. Hexagonal prism head178is about ¼ inch tall and about 1¼ inch in diameter. Cylindrical thread180is about ¾ inch tall, about 1 inch in diameter, and is circular. Safety plug176is constructed from brass.

FIG.16provides a side partial-cutaway view of fixed assembly100, which is formed by inserting bleed valve assembly174into opening118(shown inFIG.1) and through cavity120. Bleed valve assembly174is then screwed into the threaded walls of middle cavity124until the tip of lower bleed valve164engages bleed valve seat128. Because of these metal-to-metal engagements, upper cavity122is sealed off from lower cavity126. Safety plug176is then screwed into the threaded walls of upper cavity122, to form an additional seal between upper cavity122and the atmosphere above safety plug176. Bull plug seals114and116are inserted into crevice112.

FIGS.17through19provide front, side, and side cutaway views of valve tee202. Tee202has a cylindrical threaded top connector204which is about 1 inch tall, about 1½ inches in its outer diameter, and about 1 inch in its inner diameter, a cuboid body206which is about 1½ inches tall, about 2 inches wide, and about 2 inches long, and a cylindrical threaded bottom connector208which is about 1 inch tall, about ¾ inch in its outer diameter, and about ⅝ inch in its inner diameter. Cylindrical tee cavity210extends between tee top opening216and tee bottom opening218. Upper cavity212is about 1 inch tall and about 1 inch in diameter and lower cavity214is about 2½ inches tall and about ⅝ inch in diameter. Valve stem stop220is formed within tee cavity210where upper cavity212meets lower cavity214. Tee202also has a cylindrical side connector222which pass through body206, is about 1½ inches tall, about 1½ inches in its outer diameter, and about 1 inch in its inner diameter. The inside wall of side connector222is threaded. Side connector opening224is about 1½ inches in diameter and side connector opening226is about ⅝ inch in diameter. Tee202is constructed from brass.

FIGS.20through22provide side, downward, and upward views of valve stem228. Valve stem228has a threaded cylindrical post230which is about ¼ inch in diameter, a cubic handle interface232which is about ⅜ inch tall, long, and wide, a cylindrical upper stem shaft234which is about 1 inch tall and about ⅝ inch in diameter, a cylindrical middle stem shaft236which is about ½ inch tall and about 1 inch in diameter, a cylindrical lower stem shaft238which is about 3 inches tall and about ⅝ inch in diameter in stem shaft240and about ½ inch in diameter in stem shaft242, and a cubic bleed valve interface244which is about ⅜ inch tall, long, and wide. Valve stem228is constructed from stainless steel.

FIGS.23through26provide side, cutaway, downward, and upward views of valve bonnet246. Bonnet246has a cylindrical upper bonnet248which is about ¼ inch tall and about 2 inches in diameter, a hexagonal middle bonnet250which is about ¾ inch tall and about 2 inches in diameter, and a cylindrical lower bonnet252which is about ¼ inch tall, has an inner diameter of about ⅝ inch, and has an outer diameter of about 2 inches. Valve stem opening254is located in the center of upper bonnet248and is about ⅝ inch in diameter. Valve tee opening256is located in the center of lower bonnet252and is about 1½ inches in diameter. Between valve stein opening254and valve tee opening256, bonnet246has a cylindrical cavity258having a cylindrical upper cavity260and a cylindrical lower cavity262. Upper cavity260has an indentation264. Lower cavity262has threaded walls and an annular valve stem stop268where lower cavity262meets upper cavity260. Annular valve stem stop268has an inner diameter of about ⅝ inch, an outer diameter of about 1⅛ inches, is about 1/16 inch tall. Annular valve seal266is outside of and slightly lower than valve stein stop268and has an inside diameter of about 1⅛ inches and an outer diameter of about 2 inches. Bonnet246is constructed from brass.

FIG.27provides a side partial-cutaway view of detachable assembly200. Valve stem228is inserted into tee202through tee top opening216and through tee cavity210until middle stem shaft236engages valve stem stop220; in this position, lower stem shaft238and bleed valve interface244extend out tee bottom opening218. Sealing o-rings270and272are inserted into bonnet indentation264, thrust washer274is placed onto stem stop268, and sealing ring276is placed onto valve seal266. Sealing o-ring270is made of a fluoropolymer (such as the fluoropolymer commercially available under the brand name Teflon™), sealing o-ring272is made of a fluoroelastomer (such as the fluoroelastomer commercially available under the brand name Viton™), thrust washer274is made of a durable nylon plastic filled with molybdenum disulphide (such as the nylon plastic commercially available under the brand name Nylatron®), and seal ring276is made of stainless steel coated with a fluoropolymer (such as the fluoropolymer commercially available under the brand name Teflon™). Bonnet246is screwed onto tee top connector204. A slight gap between the walls of tee202in lower cavity214and lower stem shaft238allows for enough freedom of movement such that stem228can rotate within tee202and allow the flow of gas between lower valve stem shaft238and the walls of tee202in lower cavity214. This also allows for vertical freedom of movement of middle stem shaft236between thrust washer274and stem stop220. However, an airtight seal is formed between upper stem234and o-rings270and272and between tee top connector204and sealing ring276. Handle280is attached over handle interface232and is secured by screwing handle nut278to post230.

FIG.28provides an external view of safety plug176as installed in a cylinder300. Thread110of fixed assembly100has been screwed into a threaded opening in an end of cylinder300. When installed, only safety plug176and bull plug head104are visible from the outside.

In case of an emergency need to vent gas from cylinder300, the operator performs the following steps:

1. Unscrew safety plug176from the threaded walls of upper cavity122.

2. Screw detachable assembly200into the threaded walls of upper cavity122.

3. Screw in discharge hose301into opening224of side connector222; hose301may lead to a receiving tank302(not shown).FIG.29provides an external view of detachable assembly200and discharge hose301attached to fixed assembly100, which is in turn attached to cylinder300.

5. Push stem228downward so that bleed valve interface244enters valve stem interface156; this may require rotation of stem228up to 90° to align bleed valve interface244and valve stem interface156.

6. Turn stem228counter-clockwise using handle280; this screws bleed valve housing134upward, retracting bleed valve158away from bleed valve seat128to open a passageway between inlet ports166and lower cavity126. The pressure of the gas may push middle stem shaft236into stem stop268.

FIG.30shows a side cutaway view of cylinder300, fixed assembly100, and detachable assembly200after completion of steps 1 through 6. The dimensions of the solid components (shown in solid lines and cross-hatch fill) are slightly exaggerated to show the open areas (shown without cross-hatch fill). Since the tip of bleed valve158has been retracted from bleed valve seat128, there is a pathway for gas to travel from cylinder300through bull plug inlet opening132, into lower cavity126, into middle cavity124, into bleed valve inlet ports166, through bleed valve cavity170, out bleed valve housing outlet ports148, into upper cavity122, between the walls of upper cavity122and stem shaft242, between the walls of cavity210, out of valve tee202through side connector222, and into discharge hose301. Note that gas may fill enter cavity210, however seals270,272, and276prevent gas from escaping cavity210except through side connector222.

Once the operator has vented sufficient gas from cylinder300, steps 1 through 6 are effectively performed in reverse:

8. Turn stem228clockwise using handle280; this screws bleed valve housing134downward, unretracting bleed valve158back into contact with bleed valve seat128to close the passageway between inlet ports166and lower cavity126.

9. Pull stem228upward so that bleed valve interface244disengages from valve stem interface156.

Alternative and Additional Embodiments

The present invention as described in the foregoing embodiment may be modified and/or extended by one of ordinary skill without departing from the spirit of the present invention, so long as the modifications and/or extensions do not affect the safe operation of the device. Selection of some of these modifications and extensions may affect the quality of the general operation of the present invention in terms of performance when used for particular applications. Other modifications and extensions may be driven by costs of manufacture, availability of materials, physical constraints, and other factors which may be independent of the general operation of the present invention. The following variations represent a non-exclusive list of examples of other embodiments which may be mixed and matched as needed and as technically feasible without affecting the general functionality.

The dimensions of the various components described in the first embodiment are approximations, and as one of ordinary skill in the art will recognize, in order to function properly, components which engage with one another must have matching diameters and thread sizes. Similarly, components which fit within other components may be sized to accommodate ease of fitting and operation. Further, the components of fixed assembly too and detachable assembly200may be scaled up or down to accommodate larger or smaller sizes of cylinder300.

The various threaded connection mechanisms described in the first embodiment may be replaced with alternative mechanisms provided that the alternative mechanism does not compromise safety or operability of the pressure evacuation device. By way of example and not limitation, in other embodiments side connector222could have its threads on the outside or it could be a cam/groove or camlock style connector.

The first embodiment describes the use of specific materials for the various components of the pressure evacuation device, however the components may be manufactured from other materials provided that alternative materials do not compromise the safety or operability of the pressure evacuation device. By way of example and not limitation, in other embodiments materials other than brass and stainless steel may be used for the metallic components of fixed assembly100and detachable assembly200, materials other than fluoroelastomers and fluoropolymers can be used for seals114and116, materials other than fluoroelastomers and fluoropolymers may be used for rings270and272, a material other than nylon plastic may be used for thrust washer274, and a material other than fluoropolymer-coated stainless steel may be used for seal ring276. Further, some of the sealing mechanisms described in the first embodiment use two components, for example, o-rings270and272, however a given sealing mechanism may comprise any number of components.

In the first embodiment, valve stem interface156is a cube-shaped cavity in the top of head136and bleed valve interface244is a corresponding cube-shaped tip at the end of valve stem228. In other embodiments, other mechanisms could be used to mate the valve stem to the bleed valve, provided that the valve stem can be mated quickly and securely to the bleed valve.

In the first embodiment, bleed valve assembly174comprises bleed valve158and bleed valve housing134. In other embodiments, the functionality of bleed valve housing134could be integrated into bleed valve158to reduce the number of components needed to manufacture the pressure evacuation device.

In the first embodiment, handle280attaches mates with handle interface232on valve stem228and is held in place by nut278on post230. In other embodiments, the functionality of handle280could be provided by a valve wheel or by a fixed or adjustable wrench.

The process for attaching detachable assembly200to fixed assembly100may include application of a lubricant to the threads in upper cavity122and/or wrapping fluoropolymer tape onto bottom connector208in order to ease attaching detachable assembly200to fixed assembly100.