Valveless down-the-hole drill
US4790390A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jan 25, 1988 |
| Grant date | Dec 13, 1988 |
| Priority date | — |
| Expiry date | Jan 25, 2008 |
Classification
- Technology area (CPC B)Performing Operations; Transporting
- CPC primaryB23Q1/0036
- WIPO fieldMachine tools
- WIPO sectorMechanical engineering
Abstract
A valveless down-the-hole hammer drill is actuated by fluid such as compressed air. The drill includes a piston disposed within a chamber defined within an outer wear sleeve, an air diverter at one end and a suspendably mounted drill bit at the other end, wherein the piston has a slidable contact surface with the chamber towards each end of the piston, such that the piston is slidably reciprocable within the chamber. Porting and exhaust arrangements alternately supply and exhaust live pressure fluid to either end surface of the piston to reciprocate it and cause it to repeatedly strike the drill bit. An intermediate compression chamber is defined between the two sliding contact surfaces of the piston between the piston and the outer wear sleeve. Air trapped in the intermediate chamber is compressed so as to apply a retarding force on the piston towards the end of the return stroke, and to provide additional impetus to the piston on the commencement of the drive stroke. Sealing arrangements to reduce air leakage past working clearance gaps are also disclosed.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.