Abstract: A downhole pulsing apparatus having a tubular housing, a first valve assembly positioned in the housing, first and second turbine stages each comprising a stator and a rotor positioned in the housing below the first valve assembly and a second valve assembly positioned in the housing. There is a tubular mandrel connected for rotation of the rotors of the turbine stages and to a second valve assembly. The first valve assembly includes a valve element which is movable between a first position wherein pressurized fluid flow entering the housing is directed to the first turbine assembly, and a second position wherein the fluid flow is directed primarily axially through the apparatus so as to partially bypass the first turbine stage.

Abstract: A pulsing apparatus for use in a conduit through which is flowing a liquid. The pulsing apparatus includes a housing in which is positioned a valve generally at the inlet of the housing, the valve controlling flow of fluid down a central passageway of the housing. There is also flow through an annulus of the housing formed in part by at least one rotor and one stator, the rotor rotating in response to fluid flow impinging on the vanes of the rotor. There is a second valve provided in the lower end of the housing through which flow can be intermittently interrupted to cause pressure pulses in the mud flow and hence in the conduit in which the pulsing apparatus is disposed, the second valve being operatively connected to the rotor.

Abstract: A downhole pressure pulsing apparatus comprising: an upper sub that comprises a tube having a hollow interior through which fluid can flow; a middle sub that comprises a tube having a hollow interior through which fluid can flow; a lower sub that comprises a tube having a hollow interior through which fluid can flow; wherein said upper sub is connected to said middle sub by a connection such that the hollow interior of said upper sub 1 is in fluid communication with said middle sub's hollow interior; wherein said middle sub is connected to said lower sub by a connection such that the hollow interior of said middle sub is in fluid communication with said lower sub's hollow interior; an impeller assembly, wherein said impeller assembly comprises an impeller that is rotatably mounted inside said middle sub's hollow interior; a stator, wherein said stator is housed inside said upper sub's hollow interior and wherein said stator directs fluid flow into said impeller; a cam assembly mounted within said lower sub's