Abstract:
In a preferred embodiment, a blow molded drum has a port including a neck with exterior buttress threads and a port opening having a shoulder. A snap-in down tube assembly seats with the shoulder and has an upwardly extending nipple. Either a dispense head or a closure seats within and is secured by a threaded retainer nut. The dispense head has a first flow duct extending to a nipple engaging portion to seal with the upwardly extending nipple and a second flow duct leading to an annular space around the nipple for a return fluid line or for providing air or a gas for displacing withdrawn fluid. In a preferred embodiment the threaded nut provides an axial tightening force and also provides an axial removal force that disengages the nipple engaging portion with the nipple as the retainer nut is loosened.

Description:
This is a continuation-in-part of application Ser. No. 09/025,821, filed Feb. 19, 1998 and issuing Jun. 27, 2000 as U.S. Pat. No. 6,079,597. Said application and patent are hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to containment systems and more particularly containment systems particularly useful in the semiconductor processing industry comprising plastic drums with ports and fitting assemblages for connecting to/or closing said ports. 
     Blow molded thermoplastic drums have replaced steel drums in many applications. Particularly in the semiconductor processing industry, the chemicals to be contained are highly pure, quite aggressive and react with, and are contaminated by contact with metals. Such drums are typically blow molded of high density polyethylene. It is appropriate to eliminate any additives in the polyethylene (PE) that contacts the fluid in the drum and the fitting assemblages system since such additives may diffuse into the highly pure chemicals and contaminate same. Such drums are subject to Department of Transportation regulations which require that the exterior of the drum has ultraviolet inhibitors to prevent or minimize the degradation of the drum. The need to have additives in the PE at the exterior of the drum and the need to have highly pure PE on the interior fluid contacting surfaces has been addressed by the use of a multiple layered parison during the blow molding of the drums. 
     Known plastic drum containment systems for use in containing and dispensing highly pure chemicals have been structurally complex with numerous seals and therefore are relatively expensive. The expense often dictates that the system components must be used multiple times rather than allowing a single use. The complexity is due in part to the need to provide port connections and closures of very high integrity while overcoming the deficiencies in the blow molding process. These deficiencies relate primarily to the high tolerances inherent in the formation of threaded surfaces and sealing surfaces at the port during the blow molding process. Conventionally the systems will utilize interior threads on the drum neck which are formed during the blow molding process. Secondary fittings will threadingly engage with the neck and will trap and axially compress sealing rings between the secondary fitting and the top edge or at least an upwardly facing surface of the neck. The injection molded secondary fitting will then provide appropriate precision threaded surfaces and sealing surfaces for attachment of closures or dispense heads. See, for example, U.S. Pat. Nos. 5,526,956; 5,511,692; 5,667,253; 5,636,769; and 5,108,015, all of which are incorporated herein by reference. Conventionally, such connections between the secondary fitting and closure or dispense head will use axially loaded o-rings. In containment systems as such, axially loaded O-rings tend to need replacement more frequently than desired and tightening torques of the dispense heads and closures are more critical than desirable. A sealing system is needed that provides longer lasting O-rings and less critical tightening torque requirements. 
     Moreover, these secondary fittings typically require significant annular space in that they are in engagement with the inside threads of the neck of the drum port. This use of space restricts the space available for flow ducts. Additionally, the inside threads are difficult to clean. 
     Such containment systems may utilize dispense heads and down tube assembles for withdrawal by suction of the chemicals in the drums. Conventionally, such dispense heads and down tube assemblies are structurally complex, have several sealing surfaces, and thus are required to be precisely molded or machined. A containment system is needed that utilizes a simplified dispense head and down tube assembly each with a minimal number of sealing surfaces. 
     A simple containment system is needed that provides sealing and connection surfaces for closures and dispense heads for high purity chemicals such as used in the semiconductor processing industry. Such a system should have structurally simple components, a minimal number of o-rings, and provide connections and closures of high integrity. 
     Closures for such ports may or not be vented and may have valves for discharging pressure buildup in the drum. Such closures typically are formed of multiple components with exteriorly exposed openings, perforations, tool recesses, and interfaces between the components. Such openings, interfaces, recesses, and perforations may operate as collection points for impurities, contaminants, the contents of the drum, or other matter. Additionally such openings, perforations, and interfaces provide a pathway for leakage of the contents of the drum or for entry of contaminants into the interior of the drum. A closure is needed that has the minimal number of perforations, vents, and interfaces between components. Ideally, such a closure will have a smooth outer shell completely covering the neck without any exposed perforations, openings, or interfaces between components of the closure. 
     Moreover, a closure sealing directly with the inside threads, such as a plug, as opposed to a closure on a secondary fitting, will require tightening said plug directly and the requirement that the closure does not have UV inhibiting additives in contact with the drum contents necessitates that the exterior of the plug also be free of UV inhibitors which is not an ideal situation. A closure is needed in which the component part that is being tightened with the threads on the neck is not the component part which is sealing the neck opening and which is exposed to the contents of the drum. 
     Conventional dispense heads may be attached to ports by a retainer nut securing a flange on the dispense head to the port. Typically, the retainer nut will only provide a downward or tightening force. Removal of the dispense head and disconnection of any fluid couplings within the dispense head are done by a separate manual action. That is, first the retainer nut is loosened and then the dispense head is lifted upward. Where the fluid couplings within the dispense head are axially connected concentric portions, there may be some mechanical resistance associated with said manual separation. Said resistance can create a potential of a sudden unexpected release and separation that can cause the splashing of residual fluid from the concentric portions. Particularly in industries such as the semiconductor processing industry, the fluids involved can be highly caustic presenting a significant personal injury issue. It would be desirable to have a system which provides a controlled safe release of the fluid couplings within a dispense head during disconnection of the dispense head. 
     SUMMARY OF THE INVENTION 
     In a preferred embodiment, a blow molded drum has a port including a neck with exterior buttress threads and a port opening having a shoulder. A snap-in down tube assembly seats with the shoulder and has an upwardly extending nipple. Either a dispense head or a closure seats within and is secured by a threaded retainer nut. The dispense head has a first flow duct extending to a nipple engaging portion to seal with the upwardly extending nipple and a second flow duct leading to an annular space around the nipple for a return fluid line or for providing air or a gas for displacing withdrawn fluid. In a preferred embodiment the threaded nut provides an axial tightening force and also provides an axial removal force that disengages the nipple engaging portion with the nipple as the retainer nut is loosened. 
     In other preferred embodiments, the closure is preferably comprised of a cylindrically shaped interior liner portion for engaging and sealing with the cylindrical sealing surface of the sleeve, such as by an o-ring, and has a pathway which includes the spiral gap between the cooperating buttress threads on the neck and on the retainer. A microporous membrane may be placed in the pathway to allow venting of gases but preclude leakage of the liquid in the drum. 
     An advantage and feature of the invention is that the down tube assembly simply drops in and snaps in place. 
     An advantage and feature of the invention is that the down tube assembly utilizing the nipple provides a simple connection providing a reliable seal of high integrity. 
     An advantage and feature of the invention is that the simplified down tube assembly is easily assembled, is relatively inexpensively manufactured and thus facilitates one-time use of the drum and down tube assembly. 
     An advantage and feature of the invention is that with the closure in place as described on a multiple layer drum, all outwardly exposed polyethylene of the closure may have UV light inhibitors while all of the polyethylene exposed to the contents of the drum will not. Moreover, the sealing is accomplished with the two component parts of the closure only loosely coupled together. That is, the torque is not transferred from the shell to a separate component which is engaging the threads on the neck. Additionally, the criticality of the tightening of the shell portion is minimized in that the radial seal of the cap liner is not dependant thereon. 
     A further advantage and feature of the invention is that the retainer nut provides a controlled disconnection of the fluid connecting portions between the dispense head and the down tube assembly. The controlled disconnect provides a high level of safety during the disconnect. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an elevational view of the containment system with portions of a drum and closure cut-away to reveal particular details. 
     FIG. 2 is a cross-sectional elevational view of a blow mold apparatus for making drums in accordance with the invention herein. 
     FIG. 3 is a cross-sectional elevational view of a dispense head and port of a plastic drum. 
     FIG. 3A is a cross-sectional view of a dispense head with an alternate nipple engaging portion. 
     FIG. 4 is a exploded view of a down tube assembly, a dispense head, and a port of a drum. 
     FIG. 5 is a perspective view of a down tube assembly. 
     FIG. 6 is a perspective view of a sleeve in accordance with the invention. 
     FIG. 7 is a cross-sectional view of a closure in place on a port in accordance with the invention. 
     FIG. 8 is a detailed cross-sectional view of a portion of a closure engaged with a port of drum in accordance with the invention. 
     FIG. 9 is a bottom view of a cap liner in accordance with the invention. 
     FIG. 10 is a top view of the cap liner of FIG.  9 . 
     FIG. 11 is a perspective view of a shell portion of a closure. 
     FIG. 12 is an exploded perspective view of a dispense head having the feature of the controlled disconnect. 
     FIG. 13 is an elevational and partial sectional view of the body of the dispense head of FIG.  12 . 
     FIG. 14 is a plan view of the thrust member. 
     FIG. 15 is a sectional view of the body of a dispense head in accordance with the invention herein. 
     FIG. 16 is a sectional view of the body of a dispense head in accordance with the invention herein 
     FIG. 17 is a sectional view of the body of a dispense head in accordance with the invention herein. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring to FIG. 1 a containment system according to the invention is shown and is generally indicated by the numeral  20 . The principal components of the invention are a blow molded drum  22  with a fusion bonded sleeve  24 , a down tube assembly  26 , and a port fitting assemblage  30  which may either be a dispense head  32  or a closure  34 . The drum includes a pair of ports  35 ,  36  each of which have a neck  38  and a port opening  39 . 
     The blow molded drum is similar to those known in the art in the sense that it has a substantially flat bottom  40 , a substantially flat top  42 , an upper chime  44 , and a lower chime  46 . A side wall  48  which is substantially cylindrical and an open interior  50  for holding typically ultrapure chemical contents  52 . 
     Referring to FIG. 2 a cross-section of a blow mold apparatus generally of the type suitable for forming such blow molded drums is illustrated. The blow mold apparatus  56  has a parison extrusion portion  58 , a pair of mold halves  60 ,  62  and a blow pin  64 . The blow pin  64  in the preferred embodiment has a injection molded sleeve  70  inserted thereon prior to the commencement of the blow molding process. When the mold portions come together, the parison is squeezed against said injection molded sleeve portion and is fusion bonded thereto. The mold portions  76 ,  78  will have thread forming surfaces  80  thereon to form preferably exterior buttress threads on the neck  38  of the blow molded drum. The sleeve may have suitable structure to facilitate a secure mechanical connection. 
     Referring to FIGS,  3 ,  4 ,  5  and  6 , details of a port  35 , a port fitting assemblage  30  and the down tube assembly  26  are shown. FIG. 4 is an exploded view of the down hole assembly  26 , the port  35 , and the dispense head  32 . The port  35  includes a neck portion  37  comprised of a neck  38  and the sleeve  24 . The neck  37  has exterior buttress threads  80 , a top edge  82 , as well as the port opening  39 . Within the neck  38  is the sleeve  24  which is shown in perspective view in FIG.  6 . The sleeve has an upper lip  86 , a first engagement structure  90  configured as a shoulder with a seating surface  92 . The sleeve has a inner periphery  94  which is substantially cylindrical and includes an O-ring sealing surface  98  and downwardly facing finger engagement portions  99 . Note that the port  32  has an axis A and the neck and cylindrical periphery  94  are coaxial and concentric. 
     Continuing to refer to FIGS. 3,  4 , and  5 , the down tube assembly  26  is comprised of a down tube  102 , an upwardly extending fluid connection portion configured as a nipple  104 , and an annular support member  108 . The annular support member  108  has a periphery  110  and a plurality of annular passages  112 . At the periphery  110  is second engagement structures  116  configured as downwardly extending fingers with inclined wedge portions  120  and engagement surfaces  122 . The annular support member also has a stop member  126  configured as a flange. 
     Referring specifically to FIG. 3, the down tube assembly  26  drops down into the port opening  39  “snaps” onto, seats on, and engages the sleeve  24  at the shoulder  90 . The engagement surfaces  122  of the fingers  116  lock on the lower surface  130  of the shoulder. The flange  126  of the annular support member seats on the top of the shoulder. Four second engagement structures  116  are shown in FIG. 3, two of them in cross-section. 
     In the preferred embodiment, the sleeve  24  is fusion bonded at the interface  132  between the neck  38  and the sleeve. Alternate means of sealing engaging may be suitable in particular applications such as welding, adhesives, threaded engagement. 
     Continuing to refer to FIG. 3, the dispense head  32  is comprised of a body  140  with a central first flow duct  142  and a second flow duct  144 . The dispense head  32  has a downwardly extending fluid connection portion configured as a nipple engaging portion  148  shaped as a piece of flared tubing sized to fit and sealing engage with the nipple  104 . FIG. 3A shows an embodiment of the nipple engaging portion  148  configured as a bore  147  with a converging section  149 . Extending around the nipple  104  and the nipple engaging portion  148  is an annular space  152 . Said annular space is in flow communication with the second flow duct  144 . The annular passages  112  also connect to said annular space  152  and thus connect the second flow duct  144  to the interior  50  of the drum adjacent the top  42 . The dispense head also has a retainer  156  configured as a nut and has interior buttress threads  160  shaped and sized to cooperate with the exterior buttress threads on the neck  38 . The dispense head has two connector portions  164 ,  166  for connecting the first flow duct and the second flow duct respectively to tubing. The connector portions as shown are configured as the flared tubing connectors available from Fluoroware, Inc., the assignee of the invention, and sold under the trademark FlareTek®. 
     The body  140  may suitably be injection molded of chemically inert plastic such as fluoropolymers, for example perfluoroalkoxy (PFA) . The body has a cylindrical portion  170  with a circular periphery  174  which in the embodiment shown comprises an O-ring groove. The body also has a flanged portion  180  extending radially outward which engages with the retainer  156  and is clamped between said retainer and the top surface  182  of the sleeve. The primary seal between the dispense head and the port is at the O-ring  186  which in this embodiment provides essentially a pure radially seal. In other words, the axial force provided by the dispense head being clamped to the port by the retainer  156  does not affect the compression of the O-ring  186  or the integrity of the seal provided thereby. The o-ring may suitably be formed of silicon encased in fluorethylene propylene (FEP). Secondary sealing may be provided by the interface  188  between the flange  180  and the top surface  182  of the sleeve. 
     The nipple engaging portion  148  is appropriately sized such that the clamping provided by the retainer positions the shoulder  191  and its annular engaging surface  192  against the upper peripheral surface surrounding the opening  196  of the nipple  104 . The nipple engaging portion  148  thus seals at the upper peripheral surface and also is suitably sized such that there is also a radial seal between the cylindrical portion  198  of said flared tube and the outer cylindrical surface  199  of the nipple. The first flow duct is sized consistent with the bore  206  through the down tube assembly. 
     The down tube assembly may be suitably formed from separate injection molded or machined plastic components, ideally fromchemically inert plastic such as PFA, which are welded or otherwise suitably joined. 
     Referring to FIGS. 7,  8 ,  9 ,  10 , and  11 , views of a port fitting assembly  30  configured as a closure  34  and components thereof are depicted. The closure is comprised of a body  212  configured as a cap liner  220  rotatably engaged within a retainer configured as shell portion  222  which has internal buttress threads  226  at a substantially cylindrical side wall  230  which is integral with a top portion  232  which has a periphery  234 . The cap liner  220  has a downwardly extending cylindrical portion  240  with a circular periphery  242  configured as an O-ring groove supporting the O-ring  244 . Said O-ring radially seals against the inner cylindrical periphery  94  of the sleeve  24 . The liner may be solid, without perforations, or alternatively may have a microporous membrane  250  affixed in a recess  252  with perforations  260  extending through the cap liner into the interior space  264  between the shell portion and the cap liner defining a pathway  270 . The pathway further extends to and is comprised of the spiral gap  266  between the interior buttress threads  226  and the exterior buttress threads  80  of the neck  38 . The buttress threads are configured to have said gap  266  constituting the pathway  270  whether the closure is tightly or loosely secured to the neck  38 . 
     The shell portion  222  of the closure in the preferred embodiment will have ultraviolet light inhibitor additives. The cap liner  220  is preferably formed of an ultrapure polyethylene without having additives such as ultraviolet light inhibitors. The cap liner may be formed of the same highly pure polyethylene that is on the interior contact surface  290  of the drum. Referring to FIG. 7, three layers of the wall are portrayed by way of the dashed lines. The inner layer  290  will be of ultrapure polyethylene. The exterior layer  292  will typically be formed of a polyethylene with the ultraviolet light inhibitors. The inner layer  294  can be comprised of recycled scrap polyethylene originating from the molding process or from recycled drums. Thus with a multiple layer drum and the closure of FIG. 7, no polyethylene with UV light inhibitors is exposed to the contents of the drum and no ultrapure polyethylene is exteriorly exposed when the closure is in place. 
     Referring to FIG. 8, and particularly the o-ring  242 , a significant aspect of the invention is depicted. The o-ring sealing surface  98  is on the upright, substantially vertical, non grooved cylindrical side wall  298 . Thus, a seal is provided with minimal or no axial loading on the o-ring, a substantially pure radially loaded seal which facilitates longer seal life and less critical tightening of the retainer  222 . 
     Referring to FIGS. 12,  13 , and  14 , details of the controlled disconnect feature of a particular embodiment of the invention are illustrated. The dispense head body  140  has a flanged portion  180  which the retainer nut  156  compresses against the neck of the port. In this embodiment, a gusset  312  with a cutaway portion  314  provides an engagement portion  316  upon which a thrust member  322  acts when the retainer nut  156  is unscrewed for removal of the dispense head and disconnection of the fluid connecting portions, such as the nipple and nipple engaging portion. Similarly a second engagement portion  320  positioned opposite the first engagement portion  316  provides a thrust-receiving portion. The thrust member  322  is made from a resilient and rigid plastic that has a slit  330  that allows the thrust member to be opened to be applied to and positioned above the retainer nut and below the first and second engagement portions  316 ,  320 . The thrust member further has a thinned portion  336  that further facilitates said placement and removal on the dispense head body  140 . A resilient O-ring  340  fits in a circumferential groove  344  to retain the thrust member properly positioned on the dispense head body  140 . The aperture  344  in the thrust member is appropriately shaped to follow the exterior shape of the dispense head body. This is particularly appropriate where the wall thickness of the dispense head body is kept to a minimum. 
     With the retainer nut and dispense head secured on the neck of a port, unscrewing the retainer nut pushes upward on the thrust member and also on the engagement portions  316 ,  320  of the dispense head body. This causes the nipple engaging portion to axially slide on the nipple to disconnect from same. The threaded portions  348  of the retainer nut and the length of the nipple engaging portions are suitably sized to allow separation of the nipple and nipple engaging portions before the retainer nut is totally unscrewed from the neck of the port. 
     Referring to FIGS. 15,  16 , and  17 , alternate engagement members are illustrated that can provide engagement with the retainer nut or an intermediate thrust member to provide the upward disconnect force on the dispense head body for disconnecting the fluid connecting portions. These embodiments all use the lifting mechanism  139  of the threaded retainer nut and threaded neck. FIG. 15 illustrates additional threads  352  on the dispense head body  140  and a threaded engagement member  354  that provides an adjustment feature to the positioning of the engagement member. FIG. 16 illustrates an integral wedge shaped engagement member that the retainer nut can slide over in the downward direction and effectively prevents sliding upward capturing the retainer nut. FIG. 17 illustrates a plastic pin  360  press fit into the dispense head body. 
     The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof, and it is therefore desired that the present embodiment be considered in all respects as illustrative and not restrictive, reference being made to the appended claims rather than to the foregoing description to indicate the scope of the invention.