Rotary expansible chamber devices – Moving cylinder – Rotating
Patent
1994-11-15
1998-06-23
Freay, Charles G.
Rotary expansible chamber devices
Moving cylinder
Rotating
418 1, 173 1, F01C 100
Patent
active
057696209
DESCRIPTION:
BRIEF SUMMARY
This application is the national stage of PCT application PCT/EP 93/01193 filed May 13, 1993, published as WO93/23211 Nov. 25, 1993.
The invention relates to a method for actuating a percussion drilling tool and to a percussion mechanism for a tool working by percussion or rotary percussion.
A method and percussion mechanism of this type is described in Charcut, W.: Essen, 1979, pages 246 to 247, ISBN 3-8027-2647-2. For the reciprocating movement of the percussion piston, the compressed air must be fed into and discharged from the cyclinder spaces upstream and downstream of the piston by travel-dependent control. This control is possible, in principle, in two different ways: namely, via a self-controlling percussion piston, the lifting movement of the percussion piston being controlled by the air feed and air discharge, in that the piston opens and closes the air-feeding and air-discharging control channels, or via a valve body. Valveless percussion mechanisms are considered advantageous on account of the simple design and robust construction, but the impact energy is low, since the floating piston is required for opening and closing the control channels and can therefore execute only a small stroke, so that the piston speed achieved is low, as is consequently the impact energy which is proportional to the square of the speed. The publication states expressly that an increase in the piston travel is possible only if the control of the compressed-air feed is transferred to special control members.
A further conventional method and percussion mechanism of this type is based on the principle that a percussion or floating piston for driving a drilling tool or chisel is set in reciprocating movement by means of a pressure piston moved reciprocatingly in a cavity and designed as a lifting piston. Such percussion hammers are known especially as electropneumatic percussion hammers. The electric motor actuates the pressure piston via a bevel-wheel set or a pendulum ballbearing, with the result that considerable vibrations occur in the percussion hammer.
A percussion drilling machine, in which a cylinder space guiding the percussion piston is alternately loaded by a pressure medium on different of the percussion piston, in order to generate the reciprocating movement, is described in DE 3,439,268 A1. For this purpose, channels extending from a pressuremedium source are opened and closed in a controlled manner by means of valves.
The object on which the invention i s bas ed is to provide a method for actuating a percussion drilling tool or chisel and a valveless percussion mechanism for a tool working by percussion or rotary percussion, by means of which a high percussion energy can be achieved.
This object is achieved by means of the features specified in claims 1 and 5 respectively.
These measures ensure that, without separate control valves and without the intermediary of the floating piston, the compressed air is fed and discharged solely as a result of the rotation of the inner rotor and outer rotor, in order to move the floating piston. As a result, the floating travel can be increased considerably and varied within wide limits in comparison with conventional valveless percussion mechanisms. As a result of the relatively large stroke of the floating piston, a high percussion energy can be achieved even in the case of a relatively light floating piston.
Advantageous embodiments of the method and of the percussion mechanism in terms of construction and mode of operation are the subject of the subclaims.
To transmit the energy of the floating piston to tool, provision can be made, for example, for there to be a percussion pin, to which a percussion or rotary-percussion tool can be coupled and which is guided axially displaceably in a percussion-pin guide provided on the front end face of the inner rotor, and for the percussion pin to be aligned axially with the floating piston and to be actuable by the latter.
In a hammer drill which uses the percussion mechanism and the method, provision is made for there to be a
REFERENCES:
patent: 4946355 (1990-08-01), Old et al.
patent: 5174388 (1992-12-01), Williams et al.
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