Tool driving or impacting – Automatic control of power operated means – Tool advance causing or controlling means
Patent
1995-10-20
1998-06-30
Smith, Scott A.
Tool driving or impacting
Automatic control of power operated means
Tool advance causing or controlling means
173 8, 173 11, 173141, E21B 4400
Patent
active
057719810
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a control system for a percussion drill.
BACKGROUND OF THE INVENTION
A percussive drilling circuit normally includes a drilling power pack with hydraulic pumps and a power source which may either be an electric motor or a fuel driven engine, a drilling control panel with separate control valves and control means for controlling drill percussion, drill rotation and drill feed, a drill feed and a percussive hydraulic drill. The control means can be either direct control levers to operate main control valves, additional control valves and levers to pilot control the main control valves, or additional control levers for electrical piloting of the main control valves or additional control levers to operate the main valves through operating cables.
Most commonly the percussion, rotation and feed mechanisms have separate direct operated control valves and valve levers. The hydraulic fluid flow from these valves is directed through a drilling control panel.
As a large amount of hydraulic fluid for the percussion mechanism passes through the percussion control valve, in the control panel, relatively thick hydraulic hoses are required and the drilling circuit becomes complex. A complex circuit on the control panel results in an increased likelihood of oil leakages, increased maintenance, greater expense, difficulty in locating malfunctions in the circuit, and heavier demands for satisfactory operator and maintenance personnel training. A large control panel is difficult to mount ergonomically on a drilling machine without affecting the operator's visibility.
Finnish patents Nos. 86008 and 900834 describe different control systems. In the latter case the drilling feeding speed is monitored and hydraulically linked to drill rotation speed, increasing when drilling speed increases and decreasing when drilling speed drops.
The hydraulic connection optimizes the drill rotation speed with the drilling speed thereby minimizing wear of the drill bit.
In the former case the pressure ratio between drill percussion and drill feed is kept constant with an adjustable piloted displacement pump and a hydraulic circuit. The ratio between percussion power and drill feed force is kept constant. By piloting the pump the oil flow to the drill is increased or decreased in direct response to the pressure in the drill fee control circuit.
The aforementioned problems can be avoided by using a variable displacement pump and by controlling the pressure remotely, for example by means of an electric, hydraulic, pneumatic or mechanical pilot control device. However, with this kind of solution, the advantage of using a simple, cheap, dirt-tolerant, fixed displacement pump like a gear pump is lost, and the circuitry becomes complex, difficult to maintain, expensive and, due to the variable displacement pump, sensitive to dirt.
SUMMARY OF THE INVENTION
The invention provides a control system for a percussion drill with a hydraulically actuated drill rotation mechanism and a hydraulically actuated drill feed mechanism which includes control means which in reaction to the hydraulic pressure in the drill feed mechanism or in the drill rotation mechanism or both of these hydraulic pressures, operates to start a percussion movement of the drill.
In one embodiment the control means operates only in reaction to the hydraulic pressure in the drill feed mechanism and, upon starting percussive movement of the drill, simultaneously starts rotary movement of the drill.
The drill feed mechanism may be any suitable device and for example may be a drill feed cylinder.
The system may include a pump, which preferably is a fixed displacement pump such as a dirt tolerant gear pump, for supplying hydraulic fluid to a percussion mechanism of the drill, with the control means comprising valve means for directing the supply of hydraulic fluid from the pump to the percussion mechanism to start the percussion when the drill feed mechanism is pressurized.
The valve means is preferably directly connected to the pump me
REFERENCES:
patent: 4074771 (1978-02-01), Morrison
patent: 4246973 (1981-01-01), Mayer
patent: 4275793 (1981-06-01), Schivley, Jr. et al.
patent: 4711090 (1987-12-01), Hartiala et al.
patent: 5121802 (1992-06-01), Rajala et al.
patent: 5129464 (1992-07-01), Richier
patent: 5131475 (1992-07-01), Beney
Briggs Roger Robarts
Leppanen Jarmo Uolevi
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