US 2014/0174779 A1Published application

High frequency fluid driven drill hammer percussion drilling in hard formations

AssigneePen-Rock AS

InventorPer A. Vatne

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Abstract

A fluid pressure driven, high frequency percussion hammer for drilling in hard formations is presented. The hammer piston (20) of the percussion hammer has a relatively large and longitudinally extending bore (41) that provides minimal flow resistance for a drilling fluid flowing through the bore (41) during the return stroke of the hammer piston (20). The bore (41) is closeable in the upstream direction by a valve plug (23) that follows the hammer piston (20) during the stroke. The valve plug (23) is controlled by a relatively long and slender valve stem (49) that is mechanically able to stop the valve plug (23) by approximately 75% of the full stroke length of the hammer piston (20) and separates the plug (23) from a seat ring (40). Thus the bore (41) opens up such that the bore fluid can flow there trough, and the inherent tension spring properties of the valve stem (49) returns the valve plug (23) so rapid that it will be good through flow during return of the hammer piston (20).

Claims10

Dependent claims

A fluid pressure driven high frequency percussion hammer for drilling in hard formations, the percussion hammer comprising:

a housing which in one end thereof is provided with a drill bit designed to act directly on the hard formation;
a hammer piston moveably received in said housing and acts on the drill bit, which hammer piston has a longitudinally extending bore having predetermined flow capacity, and the longitudinally extending bore being closeable in the upstream direction by a valve plug that partly follows the hammer piston during its stroke;
wherein the valve plug is controlled by an associated valve stem slideably received in a valve stem sleeve, said valve stem comprising stopping means able to abruptly stop the valve plug by a predetermined percentage of the full stroke length of the hammer piston and separates the valve plug from a seat seal on the hammer piston, said bore thus being opened and allows the bore fluid to flow through the bore, and that the inherent tension spring properties of the valve stem returns the valve plug with high speed by means of mechanical recoil.

Dependencies are inferred from the claim text.