MARTEAU PERFORATEUR

L'INVENTION CONCERNE UN MARTEAU PERFORATEUR COMPORTANT UN PISTON D'ENTRAINEMENT ET UN PISTON DE PERCUSSION, LEDIT PISTON D'ENTRAINEMENT ETANT ACTIONNE PAR UN ARBRE A EXCENTRIQUE MONTE PERPENDICULAIRE A L'AXE DU PISTON.LE PALIER 14 DE L'ARBRE A EXCENTRIQUE 21 PEUT TOURNER AUTOUR DE L'AXE DE PISTON ET L'ENTRAINEMENT DE L'ARBRE A EXCENTRIQUE EST EFFECTUE PAR ROULEMENT SUR UNE COURONNE DE ROULEMENT 25, LE PALIER EXECUTANT UN MOUVEMENT RELATIF PAR RAPPORT A LA COURONNE; POUR L'ENTRAINEMENT DE L'ARBRE A EXCENTRIQUE 21, CELUI-CI ET LA COURONNE 25 COMPORTENT DES DENTURES 24, 26 EN PRISE L'UNE AVEC L'AUTRE. A hammer drill is arranged to rotate and also apply percussive force to a tool receptacle. The percussive force is transmitted from a shaft to a drive piston which, in turn, reciprocates a percussion piston which drives the tool receptacle. The hammer drill includes a housing and a bearing rotatably mounted in the housing. The shaft is rotatably mounted in the bearing and its axis extends perpendicularly of the axis of rotation of the bearing. The bearing supports a contact rim which is in meshed engagement with the shaft. The contact rim is displaceably into frictional contact with a brake member for holding the contact rim against rotation while the bearing rotates carrying with it the shaft. Due to its meshed engagement with the contact rim, the shaft rotates about its own axis causing the drive piston to reciprocate.