Abstract: A down-hole decelerator for decelerating a device dropped down a borehole in a drilling mud column has an elongate casing immersible in the mud flow with its longitudinal axis along the axis of the borehole. A plunger is slidable axially within the casing to vary the volume of two chambers within the casing and terminates outside the casing in a nose for impacting on a landing plate within the borehole when the decelerator reaches the end of its travel on being dropped down the borehole.

Abstract: A rotating centralizer and a centralizing bearing assembly are provided in order to maintain a survey instrument assembly at a fixed angular orientation with respect to a core barrel supported by the bottomhole assembly of a rotating drill string and rotationally isolated therefrom. The centralizer comprises a sleeve having an inner bearing surface providing for rotation of the sleeve with respect to a support sub, and outer bearing surfaces located at the ends of four vanes allowing for rotation of the sleeve with respect to the surrounding drill string. The centralizing bearing assembly comprises a hanger sub, an outer sleeve which is a force fit within a hang-off sub of the drill string and an annular roller bearing unit surrounding the hanger sub and engaging the inner surface of the outer sleeve. The roller bearing unit comprises a plurality of tapered roller bearings having inclined axes of rotation.

Abstract: A downhole probe for use in conditions of high vibration or shock comprises a vibration-sensitive inner unit having a cylindrical outer surface, an outer casing having a cylindrical inner surface within which the inner unit is accommodated, and an intermediate vibration-damping composite sleeve extending between said inner and outer surfaces. The composite sleeve has two coaxial sleeve parts fitting one within the other and consisting of an apertured metal sleeve part and an elastomeric sleeve part having axial ribs which extend through axial slots in the apertured sleeve part. The axial ribs of the elastomeric sleeve part engage the inner surface of the outer casing and inner surfaces of the elastomeric sleeve part engage the outer surface of the inner unit so as to support the inner unit within the outer casing in such a manner as to provide efficient isolation of the inner unit from external vibration and shock.

Abstract: A rotating centralizer and a centralizing bearing assembly are provided in order to maintain a survey instrument assembly at a fixed angular orientation with respect to a core barrel supported by the bottomhole assembly of a rotating drill string and rotationally isolated therefrom. The centralizer comprises a sleeve having an inner bearing surface providing for rotation of the sleeve with respect to a support sub, and outer bearing surfaces located at the ends of four vanes allowing for rotation of the sleeve with respect to the surrounding drill string. The centralizing bearing assembly comprises a hanger sub, an outer sleeve which is a force fit within a hang-off sub of the drill string and an annular roller bearing unit surrounding the hanger sub and engaging the inner surface of the outer sleeve. The roller bearing unit comprises a plurality of tapered roller bearings having inclined axes of rotation.

Abstract: The present invention is directed to an assembly for supporting an electrical circuit board within a tube. The assembly comprises a circuit board, an elongated support spine extending longitudinally along the tube and supporting the circuit board and a shock absorbing device for holding the assembly within the tube. The circuit board is disposed parallel to a support surface of the spine with a gap therebetween and a layer of a vibration absorbing material is disposed in the gap between the circuit board and the spine. The vibration absorbing material preferably is an elastomer. Most preferably, the vibration absorbing material comprises a layer of a thixotropic elastomer together with a layer of a silicon elastomer.

Abstract: An electrical circuit board is supported within a tube by means of an aluminum support spine of semicircular section. The circuit board is mounted on the flat surface of the spine with a continuous layer of vibration-absorbing material between the circuit board and the spine. On the opposite side of the circuit board are a number of regularly spaced aluminum posts capped with rubber bumpers for engaging the inside surface of the tube. In order to hold the assembly within the tube and to absorb shocks, two rubber tubular members are disposed in grooves in the spine parallel to the longitudinal axis. The assembly may be introduced into the tube with the tubular members in a relatively contracted state and may subsequently be held firmly in position within the tube with the tubular members in a relatively expanded state.