string wherein drilling fluids flows the valve comprises blades which are configured so as to be impelled by the flow of the drilling fluid an escapement mechanism is employed to restrain the valve in selected positions thereby at least partially obstructing the flow of the drilling fluid which results in generating positive pressure pulses or waves in the drilling fluid in response to downhole conditions application_number US 84652392 A description referring to fig1 and 2 a preferred embodiment of a rotating pulse valve for inducing positive pressure pulses in drilling fluid is shown generally at 10 in accordance with the present invention a valve 12 is disposed on a shaft 14 for rotation in unison therewith shaft 14 extends diametrically across a channel 16 in a section 18 of drill collar 19 accordingly valve 12 is diametrically mounted in channel 16 shaft 14 is supported at one end in a recess 20 in the drill collar section 18 the other end of shaft 14 extends through an opening 22 into a hatch cavity 24 this hatch cavity 24 is preferably filled with oil or other lubricating fluid maintained at the same pressure as the drill pipe bore seals 26 and 27 prevent leakage of this fluid out or borehole fluids in a seal 27 is provided about shaft 14 within opening 22 to prevent drilling fluid flowing in channel 16 from entering hatch 24 a cover plate 25 includes a seal 26 for enclosing hatch 24 and preventing fluids in the bore hole from entering hatch 24 the direction of flow of drilling fluid e g drilling.