EP0055244A1 - Outil de percussion pneumatique à main - Google Patents

Abstract

1. A percussive, hand-held compressed-air tool, with a tool cylinder (2) inside whose bore a movable pneumatically operated differential piston (1) is disposed which comprises a piston head (1b) and a piston body (1a) and used for actuating the operating tool and for air cushioning, and with a cushioning ring (4), characterized in that the cushioning ring (4) is disposed in the bore of the tool cylinder (2), acts as a bush for the piston body, and is held in the bore by a retaining member (3a, 3b) which is of deformable material, for example steel, and which is deformable by the differential piston by way of the cushioning ring (4).

Description

The invention relates to a striking, hand-held pneumatic tool, such as is used for a wide variety of purposes, for example for the construction industry in general in industry and mining. Demolition hammers are an example of such tools.

DE-OS 23 26 087 discloses the use of an 0-ring for damping the movement of a striker, which is driven indirectly by an electric motor. A similar damping element is described in DE-OS 25 51 292, where it is arranged between a fixed sleeve of an impacting pneumatic hammer and the housing thereof, which causes the crown to rotate in its up and down movement. However, the percussion piston in the housing is not damped.

One of the essential criteria for durability, service life and handling of such air-powered chisels or hammers is the structural design of the piston buffering in the cylinder. The solution to this problem is particularly important for those pneumatic tools that are exposed to high empty impact stresses, such as chisel hammers for building and plumbing purposes.

The demands placed on a modern compressed air tool consist not only of compliance with the ergonomic guidelines and good efficiency, but above all of the compressed air tools being adequately suitable for empty impact. An empty stroke is understood to mean that the impact surface of the accelerated piston does not come into contact with the impact surface of an intermediate piston or the shaft of the working tool. However, the energy imparted to the piston must be effectively reduced without causing damage, e.g. into heat.

In the case of compressed air tools, the empty impact energy is usually reduced by air buffers with additional safety precautions. So far, the air buffering of the accelerated piston has been achieved in that it is designed in the form of a piston shaft that can move back and forth in the cylinder of the tool and has a piston part of smaller diameter, the piston head, on its front side, that is, it is designed in the form of a stepped piston. An annular compression space remains free between the piston head and the inner wall of the cylinder of the tool, which is delimited at one end by the bushing for the working tool and at the other end by the step in the step piston. The air cushion located there ensures when the piston moves towards the rear end of the shaft of the actual striking tool, e.g. of the chisel, moved due to the compression for an effective buffering of the piston.

In addition to this air buffering, further safety precautions have been taken, e.g. before the collar of the shaft of the striking tool, elastic parts such as a buffer spring, plastic parts, rubber hoses or the like. be arranged so that a metallic impact of the piston inside the cylinder is avoided or weakened, especially when there is an empty stroke.

The disadvantage of this previously used system is, in particular, that the buffering by the abovementioned air buffer decreases rapidly with relatively little wear on the piston skirt. As a result, the buffer spring is overloaded for a longer period of this state. If the bore of the cylinder in which the piston shaft moves is worn, the same effect occurs as if the shaft is worn and if both parts wear out, the number multiplies described lack. In addition, for technical reasons, a recess must be made at the end of the piston head bore; the resulting dead space also has a negative impact on the air buffer. If there is wear on the piston shaft, only the piston has to be replaced; on the other hand, if the piston shaft bore is worn, the entire cylinder including the sleeve for the striking tool itself, for example for the chisel, must be replaced. If the buffer spring breaks or is handled in practice, if the operator refrains from installing the buffer spring when changing the work tool, e.g. the chisel, the pistons will inevitably start to bite even after minor wear of the parts, cylinders and / or piston skirt just described into the end face of the bridge hole, which can ultimately lead to a transverse break of the cylinder in this area. Even before such severe damage, structure-borne noise can also cause secondary breaks in the _. Control body or come in the exhaust clamps of the air tool.

The aim of the invention is to create a striking, hand-held pneumatic tool which does not have the disadvantages mentioned above. The hand-held compressed air tools differ from the others in that they are designed to be relatively small, so that the volume which is used for air buffering must also be kept small, and even with slight leaks the air buffering can no longer be effective.

The invention is based on the known pneumatic tools just described and relates to a striking, hand-held pneumatic tool with a tool cylinder within its bore, a movable, pressure Air-driven, a piston head and a piston shaft having a stepped piston is arranged, which serves to actuate the working tool and for air buffering and consists essentially in that a buffer ring is arranged in the bore of the tool cylinder, which serves as a bushing for the piston shaft and by a deformable material Holding steel, for example steel, is held in the bore and is deformable via the buffer ring by the stepped piston.

The kinetic energy of the stepped piston is absorbed by the buffer ring in the event of an empty run, which is converted into deformation work and heat in the holding part. The holding part is a replaceable construction element, through which destruction e.g. of the tool cylinder is prevented. By designing the buffer ring as a sleeve for the piston skirt, further guidance for the piston is achieved at the same time.

A particularly simple construction is realized when a compression space for air buffering is formed by the stepped piston, tool cylinder and buffer ring, and at the same time, if the air buffering is reduced in use by wear of the bore or the piston, a better braking of the piston by simply replacing the buffer ring is available again.

If the holding part for the buffer ring is provided in a recess in the bore, it can be arranged at any suitable point in the bore, the transmission of the forces from the holding part to the cylinder being able to be solved particularly well by appropriately designing the recesses.

If the recess is an annular groove in which a preferably cylindrical retaining ring is arranged, one can Even transmission of the forces from the stepped piston to the tool cylinder can be achieved even if the stepped piston moves within the tool cylinder with a larger play.

A structurally particularly space-saving and therefore low-weight solution is obtained if the retaining ring encloses the buffer ring in its entire height.

If the retaining ring on the side facing the working tool protrudes beyond the buffer ring enclosed by it, a particularly gentle buffering of the stepped piston can be achieved, the buffering at the same time having longer distances to reduce the forces.

A particularly simple construction results when the retaining ring is made from one piece together with the buffer ring, the buffer ring being able to have slots, so that particularly simple assembly, e.g. even by inexperienced personnel, can be carried out at the construction site.

If the holding part is made of several parts and it consists of individual springs that are arranged in corresponding grooves in the tool cylinder, the piston can be particularly gently buffered, whereby tilting of the buffer ring can be avoided with certainty by a symmetrical arrangement of at least three holding parts .

A construction that is particularly simple in terms of production technology, but nevertheless highly effective, is obtained when the bore of the cylinder has a constant diameter and the buffer ring and the bushing for guiding the insertion end of the working tool are arranged therein.

The main advantage of the compressed air tool according to the invention is that whenever the buffer spring has not been installed on the tool for any reason and / or there has already been wear on the piston skirt and / or the piston skirt bore and there is therefore an insufficient air buffer, the "soft" catch and retaining ring when the piston is badly buffered converts its impact energy into deformation work. The buffer ring moves in the direction of the impact surface of the working tool and, on the one hand, this increases the compression or buffer space, i.e. the air cushion, and on the other hand, due to the shifting of the impact positions between the piston and the working tool (chisel, hammer), rhythm disturbances occur, which make the need for a Make the exchange of the combination of buffer ring and holding part and, if necessary, the piston clearly recognizable. As a result, the necessary replacement of parts inferior to wear can be provided in good time without difficulty and the damage described above or even the destruction of the expensive cylinder are practically impossible.

As a result of the simplified construction, the replacement of the wearing parts in the pneumatic tools according to the invention is also relatively simple, and the new tools are particularly customer-friendly and service-friendly.

The invention is explained in more detail with reference to the drawing.

• Fig. 1 einen schematischen Längsschnitt durch ein bisher gebräuchliches Druckluftwerkzeug und
• Fig. 2 einen Längsschnitt durch ein erfindungsgemäßes Druckluftwerkzeug.

Show it:

• Fig. 1 is a schematic longitudinal section through a previously used pneumatic tool and
• Fig. 2 shows a longitudinal section through an air tool according to the invention.

The pneumatic tool shown in FIG. 1 is formed by the cylinder 2, over the end part of which the retaining cap 5 is screwed. The compressed air-operated stepped piston 1 with the piston skirt 1a and a reduced diameter piston head 1b moves within the cylinder 2. The piston head 1b lies with its end face on the end face of the shaft of the working tool 8 pressed against it by the buffer spring 6, e.g. a chisel. The insertion end or the shank of the tool 8 is guided in the tool sleeve 7. Via the return stroke channel 9, the compressed air for return stroke of the piston is supplied after the work cycle. The annular compression space X for buffering the piston is formed between the piston head 1b and the wall of the bore of the cylinder 2. From the figure it can be clearly seen that the cylinder bore has different diameters at different points and that the recess described above, which represents a dead space, is present at the end of the piston head bore.

The compressed air tool according to the invention differs from the previously usual tools, as shown in FIG. 2, in that the piston head 1b of the stepped piston 1 is elongated and in a buffer ring 4, which is made of a deformable material, usually a metal, preferably from a holding part or holding ring soft steel, is enclosed, is guided. The retaining ring can either have a relatively low height 3a and can be pressed into a single-conical annular groove 2a in the cylinder or as a ring with a relatively greater height 3b in a double-conical recess 2b in the cylinder bore with a constant diameter. It becomes a compression space X delimited by the end face of the buffer ring 4, the inner wall of the cylinder 2 and the step from the piston skirt to the piston head formed, which no longer adjoins the end of the shaft of the working tool 8 and the bridge part 7 used for guiding the working tool. The air cushion in the compression chamber X effectively buffers the piston.

There is also the possibility that the buffer ring 4 with the retaining ring 3b is made in one piece, the retaining ring part having axial slots, as a result of which the retaining ring can spring together, so that this unit can be assembled quickly and easily.

Springs can also be provided as holding parts which correspond in section to the holding ring 3b or 3a and are arranged in axially aligned grooves, at least 3 grooves having to be evenly distributed around the circumference.

If due to wear of piston skirt 1a and / or bore the buffering is no longer fully effective and the piston is accelerated with increasing wear against the work tool 8, the buffer ring 4 is moved in the direction of the work tool and the retaining or catch ring 3 takes that from Piston 1 exerted energy on the buffer ring with more or less large deformation. When the buffer ring is moved _: in the direction of the insertion end of the work tool, the above-mentioned rhythm disturbances occur, which clearly indicate the previous wear, so that the parts subject to wear can be replaced in good time.

Claims (9)

1. Striking, hand-held compressed air tool with a tool cylinder within the bore of which a movable, compressed air-operated, piston piston and piston shaft has a stepped piston, which is used to actuate the working tool and to buffer the air. serves, characterized in that a buffer ring (4) is arranged in the bore of the tool cylinder (2), which serves as a bushing for the piston skirt and is formed by a deformable material e.g. Steel (holding part (3a, 3b) is held in the bore, which is deformable via the buffer ring (4) by the stepped piston. 2. Striking, hand-held compressed air tool according to claim 1, characterized in that a compression space (X) for air buffering by step piston, tool cylinder and buffer ring (4) is formed. 3. Striking, hand-held compressed air tool according to claim 1 or 2, characterized in that the holding part (3a, 3b) for the buffer ring (4) is provided in a recess in the bore. 4. Striking, hand-held pneumatic tool according to claim 1, 2 or 3, characterized in that the recess is an annular groove (2a, 2b), in which a preferably cylindrical retaining ring (3a, 3b) is arranged. 5. Striking, hand-held air tool according to one of claims 1 to 4, characterized in that the retaining ring (3a) encloses the buffer ring (4) in its entire height. 6. Striking, hand-held pneumatic tool according to one of claims 1 to 4, characterized in that the retaining ring (3b) protrudes on the side facing the work tool over the buffer ring enclosed by it. 7. Striking, hand-held compressed air tool according to one of claims 1 to 6, characterized in that the retaining ring together with the buffer ring consists of one piece. 8. Striking, hand-held compressed air tool according to one of claims 1, 2 or 3, characterized in that the holding parts are designed as springs which are arranged in corresponding grooves in the tool cylinder. 9. Striking, hand-held pneumatic tool according to one of claims 1 to 8, characterized in that the bore of the cylinder (2) has a constant diameter and therein the buffer ring (4) and the sleeve (7) for guiding the insertion end of the work tool (8 ) are arranged.

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