Hammer Device

The present invention relates to a hammer mechanism comprising a machine housing, a driving piston which is reciprocably movable in the machine housing, a hammer piston which is arranged to be driven towards a tool by the driving piston via a pressure-gas cushion in a working chamber, and a device for transferring pressure-gas from the working chamber to a channel in the tool.

In a known type of hammer mechanism (Swedish Pat. No. 319.134), the working chamber is continuously connected to the flushing channel of the drill-tool. Through this the maximum driving pressure on the hammer piston is limited. In order to achieve an acceptable impact energy the cross-sectional area of the transferring channel must be limited through which forceful flushing of the bore is made impossible.

The present invention aims at eliminating these drawbacks, which is achieved thereby that the hammer piston is arranged to control the pressure-gas transference when blows are delivered and has an extreme position in which the device for transferring pressure-gas is in continuous communication with the working chamber. Through this is achieved partly a greater impact energy because of a higher maximum driving pressure on the hammer piston and partly a possibility of forceful pressure-gas transference to the channel of the tool because the device for transferring pressure-gas can be given an arbitrarily large cross-sectional area.

An embodiment of the invention is described below with reference to the accompanying drawing on which FIG. 1 shows a hammer mechanism in section whereby the hammer piston is in position for delivering blows to the tool. FIG. 2 shows the hammer mechanism with the hammer piston in impact position. FIG. 3 shows the hammer mechanism with the hammer piston in that position which it takes when its kinetic energy during the return has been transferred to the impact ring. FIG. 4 shows the hammer mechanism on a larger scale with the hammer piston in an extreme position.

The shown hammer mechanism comprises a machine housing 1, which consists of a lower part 17, an intermediate part 18, and an upper part 19. A driving piston 2 is arranged in the machine housing 1 and driven in a reciprocating movement by a crankshaft 20 which suitably is driven by a combustion engine. In the machine housing 1 there is furthermore a hammer piston 3 which is provided with impact means 8. The hammer piston 3 is driven by the piston 2 towards the tool 5 via a pressure-gas cushion in the working chamber 4. The working chamber 4 is supplied with air via an air intake 21. Through draining pressure-gas from the working chamber 4 through a device 14 meant for conducting flushing air to a channel 15 in a tool 5, the return of the hammer piston 3 after the impact against the tool 5 is secured. The return takes place because the driving piston 2 sucks the hammer piston 3 back. An impact ring 7 is arranged concentrically with an glidably around the hammer piston 3 for cooperation with the impact means 8. The impact ring 7 is pressed forward by the pressure in the chamber 22. The chamber 22 is supplied with air from the working chamber 4 via a thin slot arranged between the machine housing 1 and the hammer piston 3. The room 6 continuously communicates with the atmosphere via channels 11, 12 arranged in the impact ring 7 respectively the machine housing 1. The room 6 at its front end provided with a damping chamber 9 which is defined by the machine housing 1, the front part of the hammer piston 3, and the front part of the impact ring 7. A slot 10 is arranged between the impact means 8 of the hammer piston 3 and the front part of the impact ring 7. As shown in FIG. 2 the hammer mechanism is a part of a rock-drilling machine 24 which is provided with handles 25. The slot 10 is so dimensioned that the damping chamber 9 stops the hammer piston 3 essentially without rebound when the rock-drilling machine 24 is lifted by means of the handles 25. In this operation the hammer piston 3 and the tool 5 are brought to take the positions shown in FIG. 4, through which the driving piston 2 is unable to suck the hammer piston 3 back. In the front part of the damping chamber 9 a ring 13 of elastic material is arranged for absorbing that part of the kinetic energy of the hammer piston 3 which may remain when the hammer piston 3 reaches the bottom of the damping chamber 9. When the hammer piston 3 is in the position shown in FIG. 4 the channel 15 in the tool 5 is supplied with approximately double the amount of flushing air as is normal operation. The check-valve 16 has the purpose of preventing recirculation of flushing air. When the hammer mechanism works in a normal way the hammer piston 3 controls the transference of flushing air.

The shown hammer mechanism works in the following way: When the driving piston 2 is driven downwards from the position shown in FIG. 1 it closes the air intake 21 of the working chamber 4. The air in the working chamber 4 is compressed, through which the hammer piston 3 is driven towards the tool 5 and impacts it, which is shown in FIG. 2. The hammer piston 3 hereby produces a connection between the working chamber 4 and the device 14 for transferring pressure-gas to the channel 15 in the tool 5. Because of the recoil from the tool 5 the connection is closed by the hammer piston 3. When the driving piston 2 returns the hammer piston 3 is sucked back and hits with the impact means 8 against the impact ring 7 to which the hammer piston 3 transfers all of its kinetic energy. Directly before this happens the driving piston 2 opens the air intake 21. Through this the hammer piston 3 is given a well-defined stop position, shown in FIG. 3. The impact ring 7 is retarded and returned by the pressure in the chamber 22. In order to achieve a more forceful airflow to the channel 15 in the tool 5 for improved flushing of a bore, the machine 24 is lifted by means of the handles 25. Through this the tool 5 sinks to the position shown in FIG. 4. Because of the chosen dimensioning of the slot 10 and the continuous communication between the room 6 and the atmosphere, the hammer piston 3 is stopped by the damping chamber 9 essentially without rebound and stops in the position shown in FIG. 4. Through this continuous communication between the working chamber 4 and the device 14 for transferring pressure-gas to the channel 15 is achieved. The check-valve 16 prevents recirculation of flushing air. The above described and on the drawing shown embodiment of the invention is only to regard as an example which can be modified within the scope of the subsequent claims.