Tool driving or impacting – Impacting devices – Hammer head constitutes piston of drive motor
Patent
1995-10-20
1998-08-18
Smith, Scott A.
Tool driving or impacting
Impacting devices
Hammer head constitutes piston of drive motor
173 13, 173128, 91300, 91321, B25D 914
Patent
active
057947171
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates generally to a rock drill percussion mechanism and more particularly to a valve arrangement for controlling reciprocating movement of a piston in a percussion drill.
The applicants are aware of a wide variety of percussion rock drills. These drills are usually made from a number of different sections which are bolted together and a chosen type o valve construction is used to control the flow, of hydraulic fluid which powers a reciprocating piston. It is for example known to make use of pilot controlled spool valves or pilot controlled check valves and mechanical valves.
Spool and check valves are riot easily built large enough in order to obtain the opening speed and immediate hydraulic fluid flows for the piston. This is critical particularly with large rock drills. Mechanical valves on the other hand, which are subjected to mechanical shocks, are easily damaged.
It is known for example from U.S. Pat. No. 4,070,949 to make use of a pilot sleeve type distributor valve which is positioned around the piston. This valve has the advantage of providing immediate hydraulic fluid float to the piston. On the other hand the piston is in close contact with the breaks, the valve and its casing will be damaged at the same time.
Other valve arrangements are described for example in the specifications of Swiss patent No. 559088 and of U.S. Pat. Nos. 4,852,664, 4,073,350 and 5,002,136.
FR-A-2 383 757 discloses a rock drill with a percussion mechanism according to the pre-characterising part of claim 1.
According to one aspect of the present invention, there is provided a rock drill with a percussion mechanism which includes a piston, a body in which is formed a chamber, a first cylinder which is located in the chamber, a second cylinder which is engaged with the first cylinder, and a valve, for controlling movement of the piston, which is located in a volume defined by opposing surfaces of the two cylinders, the first cylinder, on an inner side, forming at least part of a sleeve for the piston, and the valve being located on an outer side of the first cylinder and on an inner side of the second cylinder, characterised in that the valve is movable relatively to the first and second cylinders which are stationary relatively to the body, in that the valve is guided for movement between two limiting positions formed by respective shoulders, and in that stop means is provided to prevent the valve from being removed from the volume.
Ports can be provided through the cylinders for directing hydraulic fluid flow from and to the valve.
Preferably the stop means is integrally attached to at least one of the cylinders by means of at least one of the following: an adhesive, welding, fusion, an interference or friction fit, or by mechanical deformation of the stop means or at least one of the cylinders.
According to another aspect of the present invention, there is provided a method of assembling a control valve mechanism for a percussion drill, which is characterised in that it includes the steps of mounting a control valve in an operating space in a housing wherein the valve is guided for movement between two limiting positions formed by respective shoulders and integrally attaching stop means to the housing to prevent the control valve from being removed from the operating space.
For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawing, in which:
FIG. 1 is a side view partly sectioned of a percussion mechanism for a rock drill according to the invention, and
FIG. 2 is a side view partly sectioned of portion of the mechanism shown in FIG. 1, on an enlarged scale, and
FIG. 3 is a view similar to FIG. 2 illustrating the way in which a control valve is secured in position according to the invention.
DESCRIPTION OF PREFERRED EMBODIMENT
FIGS. 1 and 2 illustrate a percussion mechanism 10 for a rock drill according to the invention. The mechanism includes a main body 12 i
REFERENCES:
patent: 3955478 (1976-05-01), Feucht
patent: 4070949 (1978-01-01), Salmi
patent: 4878550 (1989-11-01), Chuang
Briggs Roger Robarts
Leppanen Jarmo Uolevi
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