Cushion connectors are used to cushion the shock created by the drill bit during drilling and passed through the drill string or drill steel to the drill head of the rig. Such cushion connectors are known and, in general, act to absorb the drilling shocks by moving so as to allow a certain amount of movement between the top of the drill string which is connected to the box end of the cushion connector and the drill drive head which is connected to the pin end of the cushion connector.
From that point of similarity, however, the tools act considerably differently and absorb the shock in a variety of different ways. In one connector, a resilient elastomeric material is inserted into the connector between the housing and the piston which moves relative to the housing and acts principally to absorb compression shocks which are passed from the drill bit to the drill drive head.
A problem with the use of elastomeric material as a compression absorber, however, is that the material inherently has a limited axial elasticity with the result that the stroke available in the connector is limited. It is desirable to have as long a stroke as possible in order to absorb the shocks from the drill bit with maximum efficiency.
A further disadvantage with known cushion connectors is that the drive splines do not act within the axial length of the springs. Rather, the springs are located above or below the drive splines. Such a configuration results in an increased axial length for the cushion connector which is undesirable when it is preferred to keep the axial length to a minimum for more convenient operating characteristics.