The present invention relates generally to a fluid coupler member for a fluid conduit, and more particularly to a coupler for a self-sealing coupling assembly especially adapted for use in the transfer of liquefied gases, such as liquid carbon dioxide, from a portable storage vessel to a remote location.
Liquid carbon dioxide (CO.sub.2) is utilized by the restaurant industry both as a carbonating agent for soft drink beverages and the like, and to pressurize the vessels in which the beverages are stored and drive the transfer of a medium such as syrup to the dispensers from which the beverages are served. As the restaurant industry has grown, so too has its demand for liquid CO.sub.2. Indeed, many restaurants, and especially those of the "fast-food" food variety that must cater to a high volume of customers, have initiated on-site bulk storage of liquid CO.sub.2. The liquid typically is trucked in a portable storage vessel for transfer to a tank within the restaurant. A flexible supply line or hose is provided to lead from the supply truck for connection to the tank.
The connection between the supply truck and the tank conventionally is effected via a self-sealing coupling assembly which includes a male fitting member, preferably provided as a nipple or the like which may be stationarily mounted to an exterior bulkhead or other wall of the restaurant for defining an inlet port of the tank, and an corresponding female coupler member which terminates the delivery hose for defining an outlet port thereof, and which is configured for a threaded engagement with the male member. In a common configuration, both the male and female members typically include a poppet valve assembly which is spring-biased to be urged into a normally-closed orientation for preventing the escape of fluid when the coupling members are disconnected. These poppet valve assemblies cooperate, however, to establish an internal fluid flow path as the respective male and female members are operatively engaged.
A representative self-sealing coupling of the type herein involved includes an externally-threaded male nipple member which is provided as having a peripheral flange to facilitate the mounting of the member to a bulkhead or other wall. A corresponding female coupler member is provided as having an internally-threaded nut configured for engagement with the external threads of the nipple member. As the two members are engaged and drawn together via the rotation of the coupler sleeve, a generally annular interface seal of the internal poppet valve assembly of the coupler is made to abuttingly engage a corresponding interface land of the nipple for effecting a fluid-tight seal therebetween prior to the opening of any fluid flow path.
As the rotation of the coupler sleeve onto the external nipple threads is continued, a valve sleeve, to which sleeve the interface seal is bonded, is made to retract into the body of the coupler exposing a coaxially-disposed valve stem and opening the normally-closed poppet valve. The valve stem is configured to abuttingly engage an opposing, normally-closed poppet valve of the nipple for opening that valve. With both poppet valves assemblies actuated into an open orientation, an internal fluid flow path thereby is established through the assembly.
Upon disconnection, with the coupler nut being oppositely rotated along the external threads of the nipple, the coupler valve stem is disengaged from the nipple poppet assembly which again returns to its normally-closed orientation. As the disconnecting rotation of the coupler nut is continued, the coupler valve sleeve is urged again toward a fluid-tight engagement with the valve stem which thereby closes the coupler. Thereupon, with further rotation of the coupler nut, the coupler interface seal is disengaged from the interface land of the nipple to allow for the complete disconnection of the members.
Advantageously, the described engagement facilitates "dry break" connects and disconnects with a minimum of air inclusion or liquid spillage, and operates irrespective of whether either or both members of the coupling are pressurized. Other representative coupling arrangements are illustrated in U.S. Pat. Nos. 2,208,286; 2,254,997; 2,485,006; 2,739,374; 2,821,412; 3,117,592; 4,099,726; 5,248,125; and 5,265,844.
The service demands made on fluid couplings include the capability for rapid connection and disconnection without an appreciable loss of the fluid medium or an ingress of air into the fluid system. Most couplings, moreover, generally must be fluid-tight both while separated and while joined. With respect to applications involving the transfer of liquefied gases, cryogenic liquids, or other sub-freezing fluids, the fluid couplings therefor additionally must cope with the problem of "ice-lock." In this regard, and as is detailed in U.S. Pat. No. 4,462,223, the flow of sub-freezing fluid though a fluid coupling is known to effect a localized cooling of the area surrounding the coupling which condenses and freezes ambient atmospheric moisture. This phenomenon, which is most extreme in humid environments, typically results in a build-up of ice both externally on and internally within the coupling which essentially "locks" the male and female members thereof together to an extent that disconnection requires considerably more torque than normal. Upon the attempted uncoupling of an assembly which is in such a condition, the valve seal of the coupling, which conventionally is bonded to the valve sleeve of the coupler member, has been observed to crack or tear. Ultimately, the fluid integrity of the coupling is affected to an extent that the service life thereof is prematurely shortened.
Moreover, with service temperatures which may fluctuate from ambient to less than -45.degree. F. (-42.degree. C.) in under 5 minutes, differences in the coefficients of thermal expansion as between the seal, bonding adhesive, and fitting body often result in the seal being separated from the valve sleeve. This separation further affects the fluid integrity of the coupling.
In view of the foregoing, it will be appreciated that improvements in the design of coupler members for fluid coupling assemblies adapted for use in applications involving the transfer of liquid CO.sub.2 and other sub-freezing liquids would well-received by industry. Especially desired would be a coupler design which is adapted for use with existing nipples, but which is less susceptible to the damaging thermal effects of sub-freezing liquids.