Abstract:
A closure for the end of a male quick disconnect fluid coupling has an  innal plug that displaces the plug normally provided in the male quick disconnect coupling, and the closure also has an outer plug wall with balls that can be radially cammed inwardly by a rotatable sleeve on the closure.

Description:
STATEMENT OF GOVERNMENT INTEREST 
     The invention described herein may be manufactured and used by or for the government of the United States of America for governmental purposes without payment of any royalties thereon or therefor. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention generally relates to fluid couplings and more particularly to a self-sealing, quick disconnect (QD) cap for a male coupling to isolate it from external pressures. 
     2. Description of the Prior Art 
     Standard self-sealing couplings for fluids are designed to seal themselves from internal pressures only. However, in a Vertical Launch System (VLS), the missile tube has a quick disconnect coupling located therein. When a Capsule Launch System (CLS) is loaded into the missile tube, a sensing line from the CLS is connected to the QD coupling forming a path from the missile tube&#39;s differential pressure transducer to the CLS. However, when a ballast cam is loaded into the missile tube in place of a CLS, no sensing line is connected to the missile tube&#39;s QD coupling and the QD coupling&#39;s self-sealing plunger could be subjected to an external pressure. This situation can arise in the event of a flooded tube. If the plunger is opened under this circumstance, it would subject the different pressure transducer to sea pressure which would destroy it. There is thus a need for a pressure cap on the coupling which protects the differential transducer and the QD coupling against an external pressure. 
     SUMMARY OF THE INVENTION 
     This invention relates generally to fluid couplings, and deals more specifically with a cap or closure for the male portion of such a coupling for use when the coupling is not connected to a female coupling portion in order to prevent any external fluid pressure from entering the line to which the male coupling is secured. 
     In accordance with conventional fluid coupling design the male coupling portion is of annular shape, and has an external surface of revolution that includes an outwardly facing annular groove spaced from the end of the male coupling. An internal surface of revolution includes an inwardly facing annular groove fitted with an O-ring seal. This annular male coupling end portion is adapted to be closed with a pressure tight cap that includes a plug having an inner portion adapted to be received inside the male coupling, and having an outer annular wall cooperating with this inner plug portion to define an annular slot for receiving the annular end of the male coupling. 
     The outer wall of the plug has openings for receiving ball elements that are adapted to move radially in these openings so that these ball elements have portions that can project inwardly of the outer plug wall and into the above-mentioned annular slot. 
     A ball biasing sleeve is threadably received on the plug for movement between first and second axially spaced positions relative to the plug. The sleeve includes an annular camming surface for biasing the ball elements radially inwardly as the sleeve is threaded in one direction on the plug. 
     The plug inner portion has an external cylindrical surface of such a diameter that the O-ring of the male fluid coupling portion seals against it as the sleeve is so threaded on the plug. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a conventional fluid coupling with the male and female portions illustrated in exploded relationship. 
     FIG. 2 shows a pressure cap of the present invention adapted to be received on the male fluid coupling portion, the pressure cap in this view is illustrated in an unlocked condition. 
     FIG. 3 is a view of the pressure cap in its locked condition on the male fluid coupling to provide a secure seal whereby the quick disconnect male coupling portion is adapted to resist external pressure. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Turning now to the drawings in greater detail, FIG. 1 shows a conventional fluid coupling with the male and female portions illustrated in exploded relationship. The male coupling portion 10 does have a spring loaded plug 12 which is biased into the closed position shown by a spring 14. Upon inserting the male fluid coupling portion into the female coupling portion this plug 12 will be displaced providing a passageway for the fluid to pass through the fluid coupling. The present invention seeks to provide a pressure cap for such a male fluid coupling portion in order to secure the line associated with this male coupling portion from external pressure or force. In the event that the plug 12 were to be inadvertently displaced from the position shown for it in FIG. 1 the seal would be broken and the conventional design has been found to be less than satisfactory in some applications as a result of this defect. 
     Still with reference to the male coupling portion 10 the end portion thereof has a generally annular shape in the area indicated generally by reference numeral 10a and this annular shape defines an external surface of revolution that includes an outwardly facing annular groove 10b spaced from the end of the male coupling portion so as to receive ball elements of the type indicated generally at 16 in the female coupling end portion. 
     Again with reference to the male coupling end portion an internal surface of revolution is also provided with an inwardly facing annular groove 10c that is preferably fitted with an O-ring. This O-ring in the groove 10c is adapted to seal against the external cylindrical surface of plug 12. 
     Turning now to a description of the pressure cap or closure of the present invention, FIG. 2 shows a preferred embodiment wherein a ball retaining plug 20 is provided with an outer annular wall 20a and with an inner portion 20b that cooperate to define an annular slot 20c therebetween. Ball elements 24 are provided in openings defined for this purpose in the outer annular wall 20a of this plug and these ball elements can be positioned as shown in FIG. 2 so that the ball retaining plug and the pressure cap itself can be inserted on the annular end portion of the male fluid coupling. The annular end portion 10a of the fluid coupling 10 is received in the slot 20c. 
     As the pressure cap is so positioned on the end of the male fluid coupling portion the &#34;built-in&#34; plug 12 will be displaced axially inwardly by the end wall 20d of the central portion of the plug 20. Once the parts have been so positioned an outer ball locking sleeve 26, threadably received on the plug portion 20e as shown in FIG. 2, can be rotated in order to achieve axial displacement of the sleeve 26 relative to the plug 20. As the sleeve 26 is moved relative to the plug 20 an annular camming surface 26a acts on the ball elements 24 to urge these ball elements radially inwardly of their openings in the ball retaining plug outer wall 20a so that these balls will be received in the annular slot 10b of the male fluid coupling portion described earlier. 
     The center plug portion 20b of the plug 20 defines an external cylindrical surface which is fitted to the internal diameter of the male fluid coupling portion 10 so that the O-ring seal provided in the slot 10c acts on this surface 20b of the plug creating a seal therebetween. 
     It will be apparent that as so constructed and arranged the pressure cap illustrated in FIG. 2 can be used to seal the male fluid coupling portion from pressure and from forces external to the fluid coupling male portion 10 in a manner not possible with the prior art plug 12 provided in the coupling itself.