GB2166381A - Pneumatic hammer damping device - Google Patents

Abstract

In a pneumatic hammer a percussion pin (4) is slidably movable in a bush (8) consisting of a number of separate parts (9), kept assembled together and pressed against the percussion pin by elastic means (10). In this manner a frictional force is produced, that slows down the motion of the percussion pin when the latter is making idle strokes. <IMAGE>

Description

SPECIFICATION Pneumatic hammer damping device This invention relates to a pneumatic hammer damping device suitable in particular for electropneumatic hammers, and capable of acting upon a percussion pin of the hammer to brake the stroke thereof during idling movement of the pin and thus minimise damage to the pin by such movement.

In pneumatic hammers a motor actuates, by means of connecting-rod systems and other known devices, a piston, which acts in turn upon a hammer head causing the latter repeatedly to hit the percussion pin on which a tool is mounted. In some types of conventional pneumatic hammers the hammer head can slide freely inside a cylinder, the ends of which are defined by the percussion pin and the piston respectively.

When working of the hammer is stopped, the hammer head often continues moving by inertia, and it may happen that, depending upon the position of the tool, the hammer head hits heavily one of the ends of the cylinder in which it sides, and causes damage such as breakage. Conventionally in order to avoid this inconvenience, a large size hammer head may be employed which however both adds undesirably to the total weight of the hammer and requires the motor and the other elements of the hammer to be differently sized.

In other cases elastic end stroke devices have been proposed in the form of annular elements made of special elastic material to limit and damp the end of the stroke of the hammer head.

These known devices have not been as successful as desired. For example although various materials have been used for the annular elements, such as Vaiton (registered trade mark), none of them has proved to be sufficiently resistant to the resulting stresses causing the elements quickly to break.

According to the present invention there is provided a pneumatic hammer damping device including means for exerting on a percussion pin of the hammer a frictional force sufficient to slow down motion of the percussion pin during idle strokes thereof.

For a better understanding of the present invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a longitudinal part sectional view through a pneumatic hammer incorporating a damping device of the invention, and Figure 2 is a cross-sectional view taken along the line A-A of Figure 1.

The electropneumatic hammer illustrated in the accompanying drawings, has an end portion 1 on which a tool 2 is mountable.

A piston like hammer head 3 slidably mounted in a cylinder and actuated in a known manner, beats against one end of a slidably mounted percussion pin 4 which in turn at its other end beats against an end 5 of the tool 2 or a part 5 to which the tool is secured. The other end or head of the pin 4 is slidably housed in a cylindrical chamber defined by walls 7. Inside this chamber, around the percussion pin 4, is positioned a bush 8 consisting of a plurality of separate parts 9 (three in number in the present embodiment), which are urged towards each other and against the surface of the pin 4 by a flat spring 10 or the like. The parts 9 forming the bush 8 are therefore detachable, and are shaped so as to assemble together to form a cylindrical chamber 11 inside which the percussion pin 4 slides. Preferably the parts 9 form elongate longitudinal sections of a cylinder.

Spring 10 keeps the parts 9 pressed against the percussion pin 4 which, in order to move, must overcome a frictional force proportional to the force exerted by the spring itself. The bush 8 preferably is as long as the chamber in which it is placed, or alternatively may be slightly shorter. In the latter case, a preferably annular damping element 12 of elastic material for absorbing residual shocks, if any, not completely dampened by the frictional force developed betwen the bush 8 and percussion pin 4. There is thus formed a dampening device capable of exerting on the percussion pin 4 a frictional force sufficient to show down the idle stroke of the latter.

Of course the strength of the spring 10 should be chosen in accordance with the mass of the percussion pin 4, so as to exert a force strong enough to slow down the idle run thereof, without however detrimentally affecting the action of the hammer head 3 which, being heavier, will be affected to a minimum extent by the resistance exerted by the damping device.

Obviously the sizes as well as the employed materials may be vried according to the different requirements of use.

1. A pneumatic hammer damping device including means for exerting on a percussion pin of the hammer a frictional force sufficient to slow down motion of the percussion pin during idle strokes thereof.

2. A device according to claim 1, wherein the frictional force exerting means includes a cylindrical bush for receiving the hammer percussion pin slidably therein, which bush is formed by a plurality of separate parts, and elastic means for resiliently urging the bush parts into contact with side walls of the percussion pin.

3. A device according to claim 2, wherein the elastic means consists of a flat spring.

4. A device according to claim 2 or claim 3, including damping means of elastic material, locatable at one end of the bush.

5. A pneumatic hammer damping device substantially as hereinbefore described with reference to the accompanying drawings.

6. A pneumatic hammer including a damping device according to any one of claims 1 to 5.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Pneumatic hammer damping device This invention relates to a pneumatic hammer damping device suitable in particular for electropneumatic hammers, and capable of acting upon a percussion pin of the hammer to brake the stroke thereof during idling movement of the pin and thus minimise damage to the pin by such movement. In pneumatic hammers a motor actuates, by means of connecting-rod systems and other known devices, a piston, which acts in turn upon a hammer head causing the latter repeatedly to hit the percussion pin on which a tool is mounted. In some types of conventional pneumatic hammers the hammer head can slide freely inside a cylinder, the ends of which are defined by the percussion pin and the piston respectively. When working of the hammer is stopped, the hammer head often continues moving by inertia, and it may happen that, depending upon the position of the tool, the hammer head hits heavily one of the ends of the cylinder in which it sides, and causes damage such as breakage. Conventionally in order to avoid this inconvenience, a large size hammer head may be employed which however both adds undesirably to the total weight of the hammer and requires the motor and the other elements of the hammer to be differently sized. In other cases elastic end stroke devices have been proposed in the form of annular elements made of special elastic material to limit and damp the end of the stroke of the hammer head. These known devices have not been as successful as desired. For example although various materials have been used for the annular elements, such as Vaiton (registered trade mark), none of them has proved to be sufficiently resistant to the resulting stresses causing the elements quickly to break. According to the present invention there is provided a pneumatic hammer damping device including means for exerting on a percussion pin of the hammer a frictional force sufficient to slow down motion of the percussion pin during idle strokes thereof. For a better understanding of the present invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a longitudinal part sectional view through a pneumatic hammer incorporating a damping device of the invention, and Figure 2 is a cross-sectional view taken along the line A-A of Figure 1. The electropneumatic hammer illustrated in the accompanying drawings, has an end portion 1 on which a tool 2 is mountable. A piston like hammer head 3 slidably mounted in a cylinder and actuated in a known manner, beats against one end of a slidably mounted percussion pin 4 which in turn at its other end beats against an end 5 of the tool 2 or a part 5 to which the tool is secured. The other end or head of the pin 4 is slidably housed in a cylindrical chamber defined by walls 7. Inside this chamber, around the percussion pin 4, is positioned a bush 8 consisting of a plurality of separate parts 9 (three in number in the present embodiment), which are urged towards each other and against the surface of the pin 4 by a flat spring 10 or the like. The parts 9 forming the bush 8 are therefore detachable, and are shaped so as to assemble together to form a cylindrical chamber 11 inside which the percussion pin 4 slides. Preferably the parts 9 form elongate longitudinal sections of a cylinder. Spring 10 keeps the parts 9 pressed against the percussion pin 4 which, in order to move, must overcome a frictional force proportional to the force exerted by the spring itself. The bush 8 preferably is as long as the chamber in which it is placed, or alternatively may be slightly shorter. In the latter case, a preferably annular damping element 12 of elastic material for absorbing residual shocks, if any, not completely dampened by the frictional force developed betwen the bush 8 and percussion pin 4. There is thus formed a dampening device capable of exerting on the percussion pin 4 a frictional force sufficient to show down the idle stroke of the latter. Of course the strength of the spring 10 should be chosen in accordance with the mass of the percussion pin 4, so as to exert a force strong enough to slow down the idle run thereof, without however detrimentally affecting the action of the hammer head 3 which, being heavier, will be affected to a minimum extent by the resistance exerted by the damping device. Obviously the sizes as well as the employed materials may be vried according to the different requirements of use. CLAIMS

1. A pneumatic hammer damping device including means for exerting on a percussion pin of the hammer a frictional force sufficient to slow down motion of the percussion pin during idle strokes thereof.

2. A device according to claim 1, wherein the frictional force exerting means includes a cylindrical bush for receiving the hammer percussion pin slidably therein, which bush is formed by a plurality of separate parts, and elastic means for resiliently urging the bush parts into contact with side walls of the percussion pin.

3. A device according to claim 2, wherein the elastic means consists of a flat spring.

4. A device according to claim 2 or claim 3, including damping means of elastic material, locatable at one end of the bush.

5. A pneumatic hammer damping device substantially as hereinbefore described with reference to the accompanying drawings.

6. A pneumatic hammer including a damping device according to any one of claims 1 to 5.