Abstract: In order to form a noise suppressor in a hose of e.g. a motor vehicle, modular portions are connected in series to define suppression chambers with particular noise suppression characteristics. Those characteristics are due to the volume of each chamber, to the size of the apertures from the chambers to the central duct of the suppressor, and optionally due to spacers which are inserted into at least one aperture of the chambers to alter the effective open area of that aperture. Such spacers may also be used in which the noise suppressor is not modular. Where modular portions are used, it is preferable that each chamber is bounded by parts of two modular portions. A wall of one modular portion may then close the chamber in another modular portion, making the manufacture of the modular portions easier. Also disclosed is the use of a mass acting as a damper, which may be a noise suppressor as previously discussed, within a hose. The mass is connected to the hose by resilient means, e.g. electrometric material.

Abstract: In order to form a noise suppressor in a hose of e.g. a motor vehicle, modular portions are connected in series to define suppression chambers with particular noise suppression characteristics. Those characteristics are due to the volume of each chamber, to the size of the apertures from the chambers to the central duct of the suppressor, and optionally due to spacers which are inserted into at least one aperture of the chambers to alter the effective open area of that aperture. Such spacers may also be used in which the noise suppressor is not modular. Where modular portions are used, it is preferable that each chamber is bounded by parts of two modular portions. A wall of one modular portion may then close the chamber in another modular portion, making the manufacture of the modular portions easier. Also disclosed is the use of a mass acting as a damper, which may be a noise suppressor as previously discussed, within a hose. The mass is connected to the hose by resilient means, e.g. electrometric material.

Abstract: A modulated bias unit is provided for controlling the direction of drilling of a rotary drill bit when drilling boreholes in subsurface formations. The unit comprises a plurality of hydraulic actuators spaced apart around the periphery of the unit and having movable thrust members hydraulically displaceable outwardly for engagement with the formation of the borehole being drilled. Each actuator has an inlet passage for connection to a source of drilling fluid under pressure and an outlet passage for communication with the annulus. A selector control valve connects the inlet passages in succession to the source of fluid under pressure, as the unit rotates, and a choke is provided to create a pressure drop between the source of fluid under pressure and the selector valve. A further choke is provided in the outlet passage from each actuator unit. The actuators and control valve arrangements may take a number of different forms.