Abstract: A changing table has a changing surface on which an individual can lie to be changed or washed. The changing surface is formed from a sheet of semi-rigid material having a longitudinal center axis and having also, parallel to the center axis, first and second edges occupying nominal rest positions with respect to each other when there is no load on the surface, the said edges being fixed to first and second longitudinal members, the sheet and longitudinal members forming together a support system having for the first 10 mm of extension between the said center line and the said nominal rest position of the said first edge and between the said center line and the said nominal rest position of the said second edge an average spring rate in extension of more than 300 N/mm and the said semi-rigid sheet having a torsion coefficient of more than 10 Nm/radian.

Abstract: A changing table has a changing surface on which an individual can lie to be changed or washed. The changing surface is formed from a sheet of semi-rigid material having a longitudinal center axis and having also, parallel to the center axis, first and second edges occupying nominal rest positions with respect to each other when there is no load on the surface, the said edges being fixed to first and second longitudinal members, the sheet and longitudinal members forming together a support system having for the first 10 mm of extension between the said center line and the said nominal rest position of the said first edge and between the said center line and the said nominal rest position of the said second edge an average spring rate in extension of more than 300 N/mm and the said semi-rigid sheet having a torsion coefficient of more than 10 Nm/radian.

Abstract: A rotary valve assembly for a rotary steerable tool is disclosed for directing flow of an abrasive laden drilling fluid; the valve assembly has a first sealing surface rotatably engaging a second sealing surface. At least one of the surfaces has at least about 5% of its area comprising interconnecting voids to an average depth of at least 0.02 mm. The interconnected voids allow fluid pressure to equalize between the sealing faces by flowing through the interconnecting voids to the sealing surfaces. Because the fit of the sealing surfaces of the valve is less than perfect, and because the voids on mating surfaces do not necessarily overlap, the 5% of the surface area comprising interconnected voids can easily translate to a 10% or more reduction in sealed area when both sealing surfaces have the interconnecting voids. The additional reduction in surface area subjected to differential pressure has substantially eliminated the hydraulic lock problem previously encountered upon startup.

Abstract: A rotary valve assembly for a rotary steerable tool is disclosed for directing flow of an abrasive laden drilling fluid; the valve assembly has a first sealing surface rotatably engaging a second sealing surface. At least one of the surfaces has at least about 5% of its area comprising interconnecting voids to an average depth of at least 0.02 mm. The interconnected voids allow fluid pressure to equalize between the sealing faces by flowing through the interconnecting voids to the sealing surfaces. Because the fit of the sealing surfaces of the valve is less than perfect, and because the voids on mating surfaces do not necessarily overlap, the 5% of the surface area comprising interconnected voids can easily translate to a 10% or more reduction in sealed area when both sealing surfaces have the interconnecting voids. The additional reduction in surface area subjected to differential pressure has substantially eliminated the hydraulic lock problem previously encountered upon startup.

Abstract: A downhole unit for use in subsurface boreholes, for example a bias unit for imparting a lateral bias to the drill bit to control the direction of drilling, includes a main body and a number of pads pivotally mounted on the main body for engagement with the walls of the borehole. A thrust member is disposed inwardly of each pivotal pad and is movable along a guide passage in the main body to transmit movement to the pad. Each thrust member is movable by hydraulic pressure and a fluid-tight sliding seal is provided between the thrust member and its guide passage. The outer surface of each thrust member or the inner surface of the guide passage, or both, is in the form of a portion of a toroid centred on the pivot axis of the respective pad so as to minimise lateral movement of the seal as the thrust member moves along the passage. This also allows relative displacement between the thrust member and pad to be avoided, so that the thrust member can be integral with the pad or rigidly connected to it.

Abstract: A rotatable pressure seal between a relatively rotatable shaft and body structure comprises two annular sealing discs concentric with the shaft, one disc being mounted on the body structure and the other disc being carried on the shaft the discs having engaging sealing faces formed of polycrystalline diamond or other superhard material. The pressure seal is particularly for use in a modulated bias unit, for controlling the direction of drilling of a rotary drill bit when drilling boreholes in subsurface formations. The bias unit comprises a number of hydraulic actuators spaced apart around the periphery of the unit, and a selector control valve modulates the fluid pressure supplied to each actuator in synchronism with rotation of the drill bit so that, as the drill bit rotates, a thrust member of each actuator is displaced outwardly at the same selected rotational position so as to bias the drill bit laterally and thus control the direction of drilling.