| 摘要 |
A pneumatic hammer comprises an external cylinder 30 defining an internal cylindrical cavity in which a movable element 40 is mounted for axial sliding, this element being of a lesser axial length than said cylindrical cavity so as to define alternately and/or simultaneously a lower chamber 11 and an upper chamber 10 within the said cylindrical cavity, and means for connecting the movable element to a tool to be actuated by the element, wherein the said movable element 40 has two axially-extending passages, 6, 4, the first of which, 6, communicates with the upper face of the movable element and the second, 4, with the lower face of the movable element, the first passage communicating through a first branch passage 5 of the element with the external surface of the movable element at the lower half of the element and the second passage communicating through second and third branch passages 8, 3 of the element with the external surface of the movable element respectively at the upper half and at about the mid-section of the surface, and wherein the external cylinder 30 has two passages 1, 9 which open on to the internal cylindrical surface thereof and are for communication respectively with a pressurised fluid source and with the atmosphere; the axial distance between the two internal openings of the external cylinder being substantially equal to the axial distance between the first and the second branch passages of the movable element. <IMAGE> |
