1. Field of the Invention
This invention relates to coupling devices and in particular fluid line coupling devices which are suitable for connecting pneumatic line segments, hydraulic line segments, fuel line segments or other fluid line segments, tubes, ducts, conduits and the like. More specifically, this invention relates to self-locking coupling devices which are designed to prevent inadvertent disassembly and as a result are capable of operating in severe vibrational and thermal cycling environments while maintaining a leak-free fluid connection.
2. Description of the Prior Art
A variety of coupling devices are known in the art for connecting high pressure fluid line segments and the like. Many of these devices have been specifically designed to prevent inadvertent disassembly and catastrophic leakage during operation. These devices include conventional lockwire fluid fittings which consist of threaded fittings coupled together by wired fasteners which prevent the fittings from rotating apart during operation. However, conventional lockwire fluid fittings are labor intensive to install and as a result are not a preferred coupling system where multiple couplings are required in a single installation.
Other prior art devices include for example, U.S. Pat. No. 5,083,819 to Bynum which discloses a threaded fluid coupling equipped with a fastener capture device. The coupling device comprises an internally threaded female fitting formed with external flats about its circumference and an externally threaded male fitting configured with a plurality of tangs mounted above the external threads in a circumferential fashion. Upon engagement of the male and female fittings, the tangs contact the flats with an interference fit and rachet about the junctions between the flats until the fittings are securely coupled. Once coupled, the tangs and the flats cooperate to inhibit rotation of female fitting relative to the male fitting to prevent an inadvertent disassembly of the coupling.
U.S. Pat. No. 5,058,930 to Schlosser discloses a high pressure coupling device consisting of a coupling component with internal threads which engage the external threads of a nipple. The coupling component includes a cylindrical arrangement of cantilevered fingers with bulbous tips at their ends projecting radially inward which, upon engagement of the respective internal and external threads, ride up a frusto-conical ramping surface on the nipple until the tips drop into an annular groove in the nipple wall. Cantilevered forces in the fingers created as the bulbous tips press against the ramping surface act to provide tight engagement of the threads and serve to minimize the effects of vibration thereupon. The bulbous tips seated in the annular groove are intended to prevent a complete disconnecting of the coupling component from the nipple, a separation which would cause a catastrophic leakage at the joint.
Although the above described coupling devices can be used effectively in some applications, these devices lack positive locking features and as a result can be disconnected by simply applying a torsional force to the coupling members sufficient overcome the retaining features which are intended to inhibit relative rotation and prevent disassembly of the coupling.
What is needed and heretofore unavailable is a self-locking coupling device which, once securely coupled, cannot be disconnected regardless of the amount of torsional force applied to the respective coupling members.