Electropneumatic hammer

Abstract

An electropneumatic hammer of the type in which a driving piston is caused to undergo a reciprocating movement of translation under the action of an electric motor and a striking piston is driven by the driving piston, with the striking piston and the driving piston being mounted in a sleeve, the striking piston being disposed in such a manner as to impart a strike to a tool mounted in a tool-holder spindle, the driving piston being adapted to transmit, in the course of its reciprocating movements of translation, an alternating movement of rotation to the sleeve, the sleeve being connected to rotate with the tool through unidirectional connecting means, and means for imparting to the driving piston, in the course of its reciprocating movements of translation, an alternating movement of rotation about an axis parallel to its direction of translation.

Description

BACKGROUND OF THE INVENTION

The present invention relates to an electropneumatic hammer of the type comprising a driving piston caused to reciprocate under the action of an electric motor, and a striking piston driven by the driving piston through resiliently yieldable means, such as an air cushion, the striking piston and the driving piston moving in a common cylindrical sleeve, with the striking piston being disposed in such manner as to strike the rear part of a tool mounted in a tool-holder spindle.

Such hammers are employed, in particular, for making holes in hard walls so as to insert therein sealing or bedding means. In some cases, it is advantageous to arrange for the tool to undergo, in addition to its movement of translation, a movement of rotation about an axis parallel to the direction of translation, with this movement of rotation being superimposed on the striking movement or independent thereof. In the latter case, the rotation generally takes place in the movement of return separating two successive striking movements.

PRIOR ART

Hammers are known for this purpose in which a gear system transmits from the driving means, a movement of rotation directly to the tool or to the cylindrical member with which the tool is connected to rotate. These known devices have the drawback of gear transmissions which are noisy and consume energy. Moreover, these known devices do not allow the extent and the speed of rotation of the tool to be adjusted, which may be very useful for adapting the hammer to materials of various natures.

Hammers are also known in which the driving piston is arranged to transmit, in the course of its reciprocating movements of translation, an alternating movement of rotation to the cylindrical sleeve, with the latter being connected to rotate with the striking tool, through unidirectional connecting means. For example, the sleeve has a helical slot with which an extension integral with the driving piston cooperates.

OBJECT AND SUMMARY OF THE INVENTION

An object of the present invention is to overcome these drawbacks of known hammers by the use of means for adjusting the speed of rotation of the tool.

For this purpose, in the hammer according to the present invention, means are provided for imparting to the driving piston, in the course of its reciprocating movements of translation, an alternating movement of rotation about an axis parallel to its direction of translation, which movement of rotation is preferably adjustable in amplitude.

Preferably, the driving piston is reciprocated by an electric motor through a ball joint and the driving piston is provided with a second extension which co-operates with a slideway fixed to the housing of the hammer and inclinable about a pin integral with the housing and perpendicular to the axis of the sleeve.

An understanding of the invention will be had from the ensuing description with reference to the accompanying drawing in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional view of one embodiment of a pneumatic hammer according to the invention;

FIG. 2 is a sectional view taken on line II--II of FIG. 1, the view looking in the direction of the arrows, and

FIG. 3 is a sectional view taken on line III--III of FIG. 2, the view looking in the direction of the arrows.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

The hammer, according to the invention, comprises a driving piston 1 movable in a cylindrical sleeve member 2, in which is also movable a striking piston 3, which is separated from the driving piston 1 by an air cushion 4. An electric motor 5 rotates through a torque limiter 6, a disc 7 which drives an eccentric arm 8, connected by a ball joint 9 to the rear of the driving piston 1. The sleeve member 2 is mounted on two bearings 10 and 11 integral with a housing 12 of the hammer. A tool holder spindle 13 is connected to the cylindrical sleeve member 2 by a free-wheel system or pawl system 14 so that it is connected to rotate with the sleeve member in only one direction.

The driving piston 1 carries a radial stud 15 which co-operates with a helical slot 16 provided in the sleeve member 2. The driving piston 1 also carries a radial pin 17 having a free end portion which extends through the sleeve member 2 and carries a roller 18 co-operating with a rectilinear slideway 19. The slideway 19 is mounted on the housing 12 to rotate about a shaft connected to this housing, and the inclination of the slideway 19 with respect to the axis of the cylindrical sleeve member 2 being is adjustable by a control knob 20 (FIG.2). The hammer further is provided with a grip 21 integral with the housing 12 and having a button 22 for actuating the motor 5 which is supplied with current through a cable 23.

When the motor 5 is supplied with current, the driving piston 1 is caused to undergo a reciprocating movement of translation in the sleeve member 2 through the eccentric arm 8 and the ball joint 9. It causes the striking piston 3 to move in translation through the air cushion 4.

The co-operation of the stud 15 with the slot 16 causes, in the course of the reciprocating movements of translation of the driving piston 1, the sleeve member 2 to undergo an alternating movement of rotation about its axis of revolution, with this rotation being transmitted to the tool-holder spindle 13, and consequently to the striking tool (not shown), only in respect of one direction of rotation, preferably the direction corresponding to the rearward return movement of the driving piston 1. The co-operation of the roller 18 with the slideway 19 causes, if the slideway is not parallel to the axis of the sleeve member 2, the driving piston 1 to undergo an alternating movement of rotation about its axis when the driving piston reciprocates in the sleeve member 2. This rotation of the driving piston 1, which is allowed by the ball joint 9, is added to or substracted from, depending on its direction of rotation, the rotation imparted by the driving piston 1 to the sleeve member 2 and consequently to the tool. The extent to which the tool rotates, and therefore its speed, are adjustable over a wide range.

Claims

What I claim is:

1. An electropneumatic hammer of the type including a rotatable sleeve member having an axis, a driving piston mounted in said sleeve member for reciprocating movement along the axis of the sleeve member, an electric motor for effecting the reciprocating movement, a tool-holder spindle, and a striking piston mounted in said sleeve member and driven by said driving piston, the striking piston being disposed in such a manner as to impart a strike to a tool mounted in the tool-holder spindle, the improvement comprising:

means for causing reciprocal rotational movement of said sleeve member about its axis upon reciprocation of said driving piston in a direction parallel to the axis of said sleeve member,

means for causing reciprocal rotational movement of said driving piston about the axis of said sleeve member upon the reciprocating movement of said driving piston which can add to or subtract from the reciprocal rotational movement of the sleeve member imparted to it by the reciprocation of the driving piston, and

means for translating the reciprocal rotational movements of the sleeve member into unidirectional rotation of the toolholder spindle.

2. The hammer as claimed in claim 1 further including means for adjusting the amount of reciprocal rotational movement of said driving piston so that the amount of reciprocal rotation of said sleeve member can be varied.

3. The hammer as claimed in claim 2 wherein said means for causing reciprocal rotational movement of said sleeve member includes a cam slot in said sleeve member and a projection attached to said driving piston and extending into said slot.

4. The hammer as claimed in claim 3 wherein the means for causing the reciprocal rotational movement of said driving piston includes a slideway mounted exteriorly of the sleeve member and means projecting from said driving piston and sleeve member into engagement with said slideway.

5. The hammer as claimed in claim 4 further including means for mounting said slideway so that it is inclinable about an axis perpendicular to the axis of said sleeve member.

6. The hammer as claimed in claim 5 further including a ball joint connection between said driving piston and said electric motor.

7. The hammer as claimed in claim 6 further including a torque limiter interposed between the electric motor and the ball joint connection.

8. The hammer as claimed in claim 4 further including a free-wheel mechanism connecting said sleeve member and the tool-holder spindle.

9. The hammer as claimed in claim 4 further including a pawl system connecting said sleeve member and the tool-holder spindle.

10. The hammer as claimed in claim 4 including a housing, the sleeve member extending axially of and being mounted in the housing, and the slideway being mounted in the housing.