In many industries such as mining, petroleum, construction and chemical production, as well as services such as municipal water and sewer service or emergency services, it is often advantageous to be able to rapidly construct temporary piping networks for the conveyance of pressurized fluids such as water, oil and natural gas. Since such piping networks must often be constructed in the field, with few construction facilities available, it is preferred that the piping comprising such networks be rapidly and securely connectable and disconnectable mechanically without the need for specialized tools or techniques.
To this end, mechanical couplings 10, as shown in FIG. 1, have been developed. Couplings 10 have a male fitting 12 that engages a female fitting 14, compressing a seal 15 within the female coupling. The fittings are secured to one another by one or more cams 16 mounted on the female fitting. Cams 16 comprise a cam body 18 that rotates about an axis 20 offset from the cam body. The offset axis 20 permits the cam body 18 to be rotated into and out of the female fitting 14 and forcibly engage a concave surface 22 on the male fitting 12 to compress the seal 15 and retain the male fitting within the female fitting. Rotation of the cam body is effected manually by a lever 24 that extends from the cam body. The fittings 12 and 14 may be rapidly engaged or disengaged by rotating the cam bodies into and out of engagement with the male fitting.
There are several disadvantages with prior art mechanical couplings using cams to secure fittings together. The disadvantages result from the degree of interference required between the cam body 18 and the concave surface 22 upon engagement in order to secure the fittings together in a fluid-tight fit. The interference results in significant frictional forces between the cam body and the concave surface. The friction causes wear of both the cam body and the concave surface as they move relatively to one another and also results in relatively high actuation forces being required to rotate the cams by means of the levers 24. The frictional forces and wear are further aggravated by the presence of abrasive contaminants such as sand, mud or other particles between the cams and the concave surface. The wear causes the cams and fittings to require frequent replacement, and the high actuation forces make it difficult to manually rotate the levers to engage or disengage the fittings. There is clearly a need for an improved mechanical coupling using cams that does not suffer from high wear between the relatively moving parts or require high actuation forces for engagement and disengagement.
Another disadvantage of the prior art coupling is the lack of a self-locking feature of the cams. Unless additional locking mechanisms are employed, the cams, when closed to effect the joint, are kept in the closed position only by the friction between the cam and concave surface, or by special locking pins or mechanisms designed to hold the cams in place. Under vibration or shock loads, one or more of the cams may disengage and allow leakage or separation of the pipe or hose ends unless locking features are provided.