US 12,440,952 B2
Hammer drill and method for deep drilling
Simon Hahn, Bochum (DE); Philipp Schroer, genannt Fleutert, Bochum (DE); Volker Wittig, Bochum (DE); and Marian Bunk, Bochum (DE)
Assigned to Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V., Munich (DE)
Filed by Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V., Munich (DE)
Filed on May 31, 2024, as Appl. No. 18/680,598.
Application 18/680,598 is a continuation of application No. PCT/EP2022/084384, filed on Dec. 5, 2022.
Claims priority of application No. 10 2021 213 908.6 (DE), filed on Dec. 7, 2021.
Prior Publication US 2024/0335931 A1, Oct. 10, 2024
Int. Cl. B25D 9/12 (2006.01); B25D 17/06 (2006.01)
CPC B25D 9/12 (2013.01) [B25D 17/06 (2013.01)] 18 Claims
OG exemplary drawing
 
1. A hammer drill comprising
at least one housing having a cylinder bore,
a piston mounted in said cylinder bore such that said piston can move axially between an upper end position and a lower end position,
at least one lower fluid supply adapted to cyclically supply the cylinder bore with drive fluid,
an upper cover and a lower cover closing
the cylinder bore at each end, wherein
the piston is in contact with an inner surface of the lower cover in a lower end position, and wherein
a ring gap is formed between an outer surface of the piston and an inner wall of the cylinder bore, wherein
said ring gap has a gap height H which is greater than
H=2·(Ra,cylinder+Ra,piston)+3·Dparticles, wherein
Ra,cylinder and Ra,piston denote a mean roughness values of the inner wall of the cylinder bore and the outer surface of the piston, respectively and
Dparticle denotes a maximum particle size in the drive fluid.