1. Field of the Invention
This invention relates to a bellows sealed ball joint and, more particularly, to a bellows ball joint for use in a gas turbine engine.
2. Description of Related Art
In the design of gas turbine engines, bellows sealed ball joints are often used in ducting systems of the gas turbine engine. Typically, a bellows sealed ball joint is used to provide a flexible joint with leak proof angulation. The bellows sealed ball joint provides flexibility which may be required in order to physically deflect the ducting line so as to improve installation ease with other parts of the turbine engine and, primarily, to accommodate thermal growth in the ducting line.
A typical bellows ball joint comprises an inner shell or ball, an outer shell or socket, and a bellows. A problem common to all bellows ball joints is in getting the bellows inside both the ball and socket of the ball joint. A typical manner in which this was done was to simply cut an outer spherical section of the socket, insert the bellows in the ball portion of the joint, insert the ball and bellows inside the socket, and then weld the outer spherical section back together. A disadvantage with this approach is that welding the outer spherical section back together is time consuming and costly and often distorts the spherical form of the outer shell such that the ball and socket sections no longer angulate freely.
German Patent Specification No. 413263, issued on May 4, 1925, discloses a ball joint having a bellows therein. The ball joint comprises a smaller hollow element C having a catch hook C1. An outer hollow element comprises a catch hook C2 and a plurality of slits C4. The slits C4 enable the catch hook C1 of the smaller hollow element to be inserted therein and rotated such that when the ball joint flexes the catch hook C1 and C2 cooperate to ensure that the smaller and larger hollow elements do not become disconnected. A problem with this design and structure is that the catch hooks C1 and C2 are subjected to considerable force and stress when the ball joint is pivoted. In addition, the catch hooks C1 and C2 require additional material and complicate the manufacturing of the smaller and larger hollow elements.
What is needed is an inexpensive and lightweight flexible bellows ball joint which can be easily assembled and wherein the force between the outer and inner shells is distributed evenly over the spherical surfaces of the shell when the ball joint pivots.