EP2852474B1 - Percussion device - Google Patents

Description

The present invention relates to a striking device according to the preamble of claim 1. Such a striking device is known from US 6,073,706 known.

Pressure medium operated impact devices are used in hydraulic hammers, which are used in particular for crushing rock, concrete or other building materials, and in rotary hammers, which are used for drilling holes in rock and other building materials. In most cases, they are grown as attachments or attached to construction equipment, such as excavators, loaders, tracked vehicles or other carrier units and supplied by them with working fluid.
In hydraulic hammers, which are driven with oil as a working fluid, the percussion is hydraulically connected via a pressure line and a tank line with the pump or the tank, for example, an excavator. In the hammer mechanism housing a percussion piston is guided, which has two opposing drive surfaces, which are connected via a control valve (spool) to the pressure or tank line, that the percussion piston repeatedly performs reciprocating movements, wherein it moves in a direction of movement at the end of his Hubes, the Schlaghub, on a tool such as a chisel, a drill rod or a hammer hits. During normal operation, the carrier presses the impactor towards the material to be machined so that the lower end of the tool is pressed against the material to be processed.
The initiated by the impact of the percussion piston on the tool in the tool energy causes high impact force, which is transmitted from the tool to the material and causes destruction of the material.

The percussion piston normally has two piston rods of different diameters and one or more piston collars arranged between the rods, each having a cylindrical outer circumferential surface. The percussion piston is guided in a stepped receiving bore of the percussion mechanism housing which is adapted to the percussion piston diameter, wherein the inner diameter of the receiving bore in the region of the guides is made slightly larger than the corresponding outer diameter of the percussion piston. Since the guide surfaces thus formed each have a cylindrical shape, a gap with a constant height forms at the guide areas between the components.

If there is an oil volume at both ends of the gap, an oil volume flow flows through the gap depending on the pressure difference between the oil volumes. Moves the percussion piston in the receiving bore of the percussion gear housing along its axis of symmetry relative to the percussion mechanism, so takes place due to the friction and adhesion forces between the oil and the component surfaces in addition a transport of oil through the gap. Due to these operations, an oil pressure is established in the gap depending on the pressure difference between the oil volumes and the moving speed of the percussion piston. The pressure of the oil in the gap causes a radial, circumferentially acting force on the piston which pushes it away from the bore wall and exerts a centering effect on the percussion piston.

The guide surfaces of the percussion piston and / or the receiving bore of the striking mechanism housing may have circumferential pressure equalizing grooves having a width and depth of about 1 mm to 3 mm respectively to distribute oil evenly around the circumference of the guide surfaces and thus circumferentially for pressure equalization on the guide surfaces to care. The pressure compensation grooves have a radius in the groove base and perpendicular to the guide surface arranged groove flanks. This pressure compensation reduces the one-sided deflection of the percussion piston transversely to its axis of motion, which would arise as a result of pressure differences.

The chisel of the hydraulic hammer is supported by bushings in the lower part of the percussion mechanism housing, with little play between the chisel and the bushing in the new condition, ie. The chisel may be slightly inclined, causing the chisel axis is no longer parallel to the axis of the bushings. By wear on the chisel and the bushings, the game and thus the inclination can still increase. This inclination causes the end faces of the percussion piston and chisel are no longer aligned exactly parallel to each other and the contact surface formed on the upper chisel end face upon impact of the lower piston end face is not centric to the percussion piston axis. As a result, a force is exerted on the percussion piston during the impact, which acts eccentrically to the impact piston axis and generates a percussion deflecting lateral force.

Partially, the abutting faces of the percussion piston and / or the chisel are chamfered or have a concave contour which has a large radius compared to the chisel diameter to reduce eccentricity when skewed and to reduce surface pressure during impact.

With special coatings on the guide surfaces of the components, which are to increase the wear resistance, either by increasing the surface hardness, by reducing the friction or by smoothing the surfaces is trying to reduce the wear caused by the contact of the components. Such coatings may, for example, be diamond-like carbon layers, graphite layers or molybdenum disulfide layers.

In KR 10-2011-0086289 a percussion piston is described in which the inner surface in the lower part of the cylinder having a plurality of equidistant spaced grooves and in which the inner surface is designed as an inclined surface, wherein the bore progressively widens from the uppermost to the lowermost groove. The bore increases at a constant pitch angle of 0.001 to 0.5 °, which changes the diameter linearly with the distance from the top slot.

In Schlaghubrichtung follows behind the actual guide area with the widening bore an area that has next to a triangular groove, three grooves for receiving seals (s. Fig. 3 the KR 10-2011-0086289 ). The webs between the seals are designed so that their inner diameter corresponds to the smallest diameter of the bore and thus is smaller than the largest diameter of the widening bore.

A disadvantage of the known per se in the prior art impact devices that during the impact of the percussion piston due to an inclination of the bit eccentrically acting force between the faces of percussion piston and chisel a lateral force acting on the percussion piston from which a displacement transverse to the axis of symmetry of Percussion piston results. A shift can also occur by lateral acceleration of the striking mechanism housing, when lateral forces act on the housing and it shifts relative to the percussion piston. In a cylindrical embodiment of the guide surfaces on the percussion piston and striking mechanism housing, the oil pressure in the gap between the percussion piston and receiving bore is often not sufficient to prevent contact between percussion piston and percussion gear housing. The convexity of the faces, the use of pressure equalizing grooves or the use of component coatings are often not sufficient to reduce the lateral force sufficiently to prevent contact between percussion piston and guide surfaces and reduce wear. If the oil pressure dependent load capacity of the oil film in the gap between the guide surfaces is exceeded, there is a contact between the percussion piston and the impact mechanism housing, whereby the guide surfaces can be plastically deformed and scratched.

Due to the cylindrical design of the guide surfaces of the percussion piston is in a misalignment, in which the axis of symmetry of the percussion piston is no longer parallel to the axis of symmetry of the receiving bore of the percussion, at each edge, creating a contact point with a high surface pressure, resulting in damage and wear leads. In addition to a misalignment The piston can also deform due to transverse forces, so that the symmetry axis is no longer straight and one or both ends are bent outwards for a short time.

The axial movement of the percussion piston with respect to the impactor housing causes friction upon contact of these surfaces, thereby generating heat which is in part so high that the component surfaces are locally welded and material is torn out of the one component and at the component surface the other component firmly adheres. If this material is pulled over the guide surfaces, the adhering and protruding material leads to further rapidly progressing damages of the surfaces, which leads to the failure of the impact mechanism and to oil leaks.

Also in the impact device according to KR 10-2011-0086289 disadvantageously occurs in a tilt of the percussion piston in the bore of the percussion piston at the upper edge of the bore (above the groove (8a)) in Appendix, since the angle is chosen so that the percussion piston not with the areas between the groove (8a) and the groove (32) comes into contact. Due to the contact on the upper edge only a very small contact surface between the percussion piston and the bore is present, whereby high surface pressures arise, leading to corresponding damage and wear on the contact surfaces of the piston and bore.

Due to the inner diameter of the webs in the area of the seals, which is smaller than that of the largest inner diameter of the bore, the percussion piston comes into contact with the webs when the percussion piston is tilted in the housing or when the percussion piston deforms. As a result, the guide surfaces of the percussion piston and the web surfaces are damaged.

The gap between the bore and the percussion piston should also act as a sealing gap, which is intended to prevent oil from flowing in large quantities through the gap and to a lying behind the gap Druckentlastungsnut. The throttling effect of Sealing gap is intended to cause the pressure peaks occurring in the groove 33, which propagate into the gap, do not act on the seals 31 at the end of the gap in full height. Due to the continuous widening of the bore over its entire axial extent, the throttling effect of the guide is disadvantageously reduced, which leads to a high leakage volume flow and the presence of high pressure peaks on the seals. The high leakage volume flow degrades the efficiency of the hydraulic hammer.

Moreover, the non-existing cylindrical portion of the bore, which would have a constant diameter, reduces the bearing capacity of the oil film that forms in the gap, resulting in contact between the percussion piston and the bore and damage and wear of the guide surfaces leads.

Further predominantly hydraulic impact mechanisms are in US 4,005,637 . WO 2010/140922 . US 3,903,972 and EP 2 452 783 disclosed. In these percussion also oscillates a percussion piston within a bore and is supported on Schlagwerkführungsflächen. The Schlagwerkführungsflächen known from these documents are strictly cylindrical and therefore formed linear in cross-section.

The object of the present invention is to remedy the above-mentioned disadvantages and to avoid radial contact between the percussion piston and the impact mechanism housing as far as possible. Furthermore, the oil leakage volume flow is to be reduced by the gap of the guide surfaces. In particular, the wear on the guide surfaces and on the webs between the seals should be prevented.

This object is achieved by the impact device according to claim 1, wherein according to the invention it is provided that the percussion guide surface in the axial direction at least partially has a non-linearly increasing inner diameter, wherein the non-linear magnification of the inner diameter the Schlagwerkführungsfläche parabolic shaped. In order to increase the carrying capacity of the oil film in the gap between the guide surfaces, the guide surfaces of the percussion mechanism housing are thus designed such that a partial region of the lateral surface of at least one guide surface has an inner diameter which increases at least toward one end of the guide surface and non-linearly in the axial direction.

The inventive design prevents the impact piston guide surface comes in an inclined position of the percussion piston in the receiving bore or deformation with the areas of the bore in contact and damage and wear occurs.

When the percussion piston moves in the direction of the narrowing gap in the case of a non-cylindrical percussion guide surface, or, in the case of a non-cylindrical impact piston guide surface, the percussion piston moves in the direction of the widening gap, transport of the oil occurs due to the friction between the oil and the component surfaces Oil in the narrowing gap. As a result, the oil pressure in the narrowing gap against a purely cylindrical design increases significantly, which also causes a pressure increase in the subsequent region with a constant gap height. This increased oil pressure ensures that a sufficient radial force acts on the percussion piston and the carrying capacity of the oil film has been significantly increased and is now sufficient to keep it at a distance from the striking mechanism housing. Since no contact between the moving components occurs, the wear and damage to the guide surfaces are effectively reduced or avoided and increases the service life of the impact mechanism.

Experiments have shown that a non-linear and in particular a parabolic diameter change substantially more effectively avoids contact between the percussion piston and the percussion mechanism, than a linear change in diameter and thus by the non-linear or parabolic diameter change The wear of the components can be reduced more clearly than with a linear change in diameter.

In particular, in the return stroke, after the percussion piston experiences a transverse force after impact on the bit, the nonlinear change in diameter

Forming a more viable lubricating film achieved, whereby the damage to the guide surfaces, the lower piston rod and the corresponding guide surface of the striking mechanism housing can be prevented.

Similarly effective is the change in diameter at the impact piston guide surfaces, in which both ends of the respective piston collar with a, compared to the central cylindrical portion, reduced diameter are executed. As a result, the piston collars have an approximately barrel-shaped outer contour, which ensures an increased load-bearing capacity of the lubricating film in both directions of movement. In the case of several piston collars, it is also possible to provide only the ends of the outer piston collars facing the piston rods with a decreasing diameter.

On the application of complex, expensive and partially environmentally harmful coatings can be dispensed with by the inventive design.

Due to the varying diameter diameter portion extending only over a limited axial length of the guide surface, a cylindrical portion having a constant diameter and a small gap height remains, thereby reducing the leakage volume flow through the gap as compared to a design where the diameter exceeds the diameter the length of the guide surface is changed, reduced and the height of the pressure peaks passed through the gap is reduced. In particular at the percussion guide surfaces an increase in diameter leads only within a partial area to a reduction of the leakage volume flow and the pressure peaks.

In addition, it is achieved by the widening diameter, that in a misalignment of the percussion piston in the housing, in which the axis of the percussion piston is no longer parallel to the axis of the guide or in deformations of the percussion piston, in which the ends of the piston rods are bent outward, the percussion piston not only on the angular inner edges of the guide surfaces of the striking mechanism housing, or the angular outer edges of the guide surfaces of the Impact piston comes to rest, creating a point or line-shaped contact point would arise, but the contact point is in a range in which the diameter changes slightly. In the case of a parabolic diameter, a smooth transition from the cylindrical portion to the enlarged diameter portion is formed. This results in a larger contact surface without edge, which significantly reduces the surface pressure and thus the wear.

The maximum possible angle between the lines of symmetry of the percussion piston and the receiving bore can not be determined exactly because on the one hand due to unavoidable manufacturing tolerances, the clearance between the piston and the receiving bore from percussion to percussion can change and continues to change the angle during the axial piston movement , In general, the maximum theoretically possible skew of the percussion piston results from the game between the receiving bore and the percussion piston, but also from the axial distance between the two contact points between the percussion piston and the receiving bore. If, for example, the position of the upper contact point were defined by the upper edge of the upper percussion piston collar and the lower by the upper edge of the guide surface of the striking mechanism housing for guiding the lower rod, the upper contact point would move with the percussion piston, the lower remain fixed to the percussion mechanism housing, whereby the axial distance of the contact points changed in an axial movement of the percussion piston, which also changes the maximum inclination. An angle change would be recognizable if the contact points were connected to a straight line. If the piston moves downward in the stroke stroke direction in the above-described position of the contact points, the length of the line decreases, but the angle to the axis of symmetry of the receiving bore increases. Thus, it is not possible to perform a linear change in diameter on a guide surface so that the surface carries in the range of the linear change in diameter continuously over its entire length. As the angle changes, the pad moves to one end of the guide surface, whereby an edge forms the contact point on that guide surface. In a non-linear and especially in a parabolic Diameter change always carries the rounded, non-linear or parabolic area with appropriate design.

Due to the larger compared to the adjacent Schlagwerkführungsfläche diameter in the region of the webs between the sealing grooves and between the seal groove and the pressure equalization, or the impact chamber damage and wear of the surfaces of the webs and the percussion piston are prevented because the percussion piston no longer to plant can come.

Preferred embodiments of the present invention will be described below and in the subclaims.

According to a first preferred embodiment, it is provided that the inner diameter of the impact mechanism guide surface has a non-linearly increasing diameter towards at least one of the ends. Preferably, such Schlagwerkführungsfläche a piston rod, wherein the inner diameter of the percussion guide surface to the outer end of the piston rod has a non-linear magnifying diameter.

Impact devices of the type described may have one or more impactor guide surfaces, not all Schlagwerkführungsflächen a striking mechanism must have the inventive design. It is also possible that in one embodiment with two or more spaced Schlagwerkführungsflächen only one or a part of Schlagwerkführungsflächen have the features of the invention. Preferably, the inventive design is applied at least to the leadership of the lower piston rods, where a portion of the guide surface of the striking mechanism housing has a parabolic enlarging diameter, wherein the diameter increases towards the lower end of the guide and formed a tangential transition to the region of constant diameter becomes. The piston rod is cylindrical in the area of the guide surface. A parabolic increase in diameter means that the diameter is not linear but disproportionate increased to the axial distance from the upper edge of the guide or from the transition of the cylindrical to the widening guide area. In a cross section through the central axis of the guide, the course of the inner edge of the guide surface in the striking mechanism housing partially represents a parabolic line.

According to a further preferred embodiment of the invention, it is provided that the striking mechanism guide surface has a plurality of partial regions, wherein a partial region has a non-linearly increasing inner diameter, which merges into a partial region having a constant inner diameter. Furthermore, a partial region with a linearly widening inner diameter is preferably arranged at the end of the partial region having the largest diameter, and a partial region having a constant diameter is provided at the end of the partial region having the smallest diameter.

Finally, according to a preferred embodiment of the percussion guide surface is provided that on both sides portions are arranged which have non-linearly widening portions in different orientation, wherein the portions are preferably connected to each other over a portion of constant diameter.

The inventive design of guide surfaces is not only provided at Schlagwerkführungsflächen but also at Schlagkolbenführungsflächen. Preferably, the percussion piston here has at least one piston rod and at least one piston collar whose outer surfaces are designed as impact piston guide surfaces. In other words, the embodiment according to the invention is also applied to the guide surface of the piston or collars, wherein the guide surface is cylindrical in Schlagwerkgehäuse, but the guide surface at least one piston collar and at least towards one end, a decreasing diameter. Preferably, the diameter decreases parabolic in the axial direction and with a tangential transition to a region of constant diameter. Does the guide surface of the piston collar on both sides of a parabolic decreasing Diameter, which is preferably provided, have the piston collars on an approximately barrel-shaped outer contour.

In other words, preferably has at least one impact piston guide surface on the side facing away from the tool on an outer portion which has a non-linearly decreasing outer diameter, which preferably parabolic and / or preferably merges into a portion with a constant diameter. In this case, the impact piston guide surface may have two outer subregions which have nonlinearly decreasing outer diameters in a different orientation, which are preferably parabolic. According to a particularly preferred embodiment, provision is made for a partial region with a constant diameter to be arranged between the outer partial regions.

In addition, according to a preferred embodiment of the invention, it is provided that the impact mechanism has a percussion guide surface, which guides a piston rod, wherein a tool with the outer end of the piston rod can be acted upon, and wherein the inner diameter of the percussion guide surface a portion of constant diameter and to the outer Indicates the end of the piston rod, a portion having a parabolic enlarging diameter and the at least one impact piston guide surface has a portion of constant diameter and on the side facing away from the tool has an outer portion having a parabolic outer diameter decreasing.

Furthermore, the inner diameter of the webs within the receiving bore for the percussion piston in the region of the seals and the pressure equalization groove designed to be larger than the smallest inner diameter of the guide portion for the piston rod and preferably designed larger than the largest diameter of the guide portion.

Thereafter, the percussion guide surface is adjoined by at least one region in which peripheral grooves are arranged, the webs between the grooves and the region between a groove and a space arranged behind it having an inner diameter which is greater than the small inner diameter of the guide region.

Fig. 1 und 2:

schematische Darstellungen eines Schlagwerks mit einem Schlagkolben,

Fig. 3 :

schematische Darstellung einer Schlagwerkführungsfläche,

Fig. 4 bis 7:

unterschiedliche Ausführungen von Schlagwerkführungsflächen,

Fig. 8 und 9:

unterschiedliche Darstellungen einer Schlagkolbenführungsfläche,

Fig. 10:

eine Detailansicht eines Schlagwerks und

Fig. 11a bis 11d:

unterschiedliche Detailansichten von Druckausgleichsnuten.

Concrete embodiments of the present invention will be explained below with reference to the figures. Show it:

1 and 2:

schematic representations of a striking mechanism with a percussion piston,

3:

schematic representation of a percussion guide surface,

4 to 7:

different designs of impactor guide surfaces,

8 and 9:

different representations of a striking piston guiding surface,

Fig. 10:

a detailed view of a striking mechanism and

11a to 11d:

different detail views of pressure equalization grooves.

The operation of a hydraulic impact device is in the Fig. 1 and 2 shown schematically. Via a pressure line 1 and a tank line 2, the impact mechanism 3 is hydraulically connected to the pump 4 and the tank 5 of a carrier device, for example. An excavator. On the excavator there is a valve with which the line 1 can be connected to the pump in order to supply pressure oil to the impactor for operation or to disconnect the connection in order to stop the operation of the striking mechanism. To improve clarity, this valve is not shown.

The striking mechanism 3 consists of a striking mechanism housing, in which a percussion piston 6 is guided. The hammer mechanism housing may consist of several components connected by screws, such as a cylinder cover, a cylinder and a bit holder, in which the bit 7 is mounted via bearing bushes 8. Shown is only the simplified inner contour of the receiving bore of the striking mechanism housing, in which the percussion piston 6 is guided. In Fig. 2 are by horizontal Dash-dot lines exemplified the possible separation points between the cylinder cover and the cylinder or between the cylinder and the bit holder. Such a separation is also required to insert the percussion piston in the receiving bore. Between the dash-dot lines is the cylinder.

During normal operation, the carrier presses the percussion mechanism in the direction of the material 9 to be processed, so that the percussion mechanism is supported via the chisel stop 10 arranged in the housing against a contact surface 11 of the upper chisel end and the lower chisel end is pressed against the material to be processed.

During normal operation, the hydraulically powered percussion piston 6 strikes the end of the bit at the end of each stroke and transfers its kinetic energy to the bit. The energy introduced into the bit causes a high impact force, which is transferred from the bit to the material and causes its destruction.

The percussion piston 6 has two piston rods 15, 16 between which two piston collars 17, 18 are arranged. The piston collars 17, 18 each form on the side facing the respective rod side, annular drive surfaces 19, 20, which have different surface areas due to different rod diameter. The lower drive surface 20, via which the return stroke is triggered when pressure is applied, during which the percussion piston moves upwards away from the chisel, is constantly exposed to the pump pressure that prevails in the pressure line 1 during operation. The upper drive surface 19, via which the impact stroke is triggered by means of pressure during which the percussion piston moves towards the chisel, is subjected to the pump pressure or relieved to the tank depending on the position of a control valve 21 by establishing a connection with either the pressure line or tank line becomes. The stroke is possible because the upper annular drive surface 19 has a larger surface area than the lower surface 20, so that upon application of both surfaces with the pump pressure, a resulting, directed to the chisel Force on the percussion piston 6 acts. The moving percussion piston 6 displaces the oil displaced by the small, lower drive surface in the direction of the larger upper drive surface 19 of the percussion piston 6, to which the oil coming from the pump 4 flows during the so-called impact stroke. During the return stroke, the oil flows from the pump 4 exclusively in the direction of the smaller surface drive surface 20, whereas the oil from the larger surface upper drive surface 19 via a return throttle 22, which ensures a smooth running of the hammer, is discharged to the tank 5.

The striking mechanism has a gas reservoir 23, namely a space under gas pressure into which the upper rod 15 of the piston protrudes. The gas pressure in this space exerts on the piston an additional force acting in the direction of the impact stroke. The other, lower bar protrudes into a so-called whipping room 29, which is connected to the atmosphere.

The control valve 21, which is preferably in the cylinder cover, the cylinder or attached to the cylinder cover or cylinder valve block connects depending on the switching position, the larger area upper drive surface 19 either with the pressure line 1, so that there is the operating pressure or relieved during the return stroke this area over the tank line 2, to the tank 5.

Also, the control valve 21 may have two drive surfaces similar to the percussion piston, wherein a first surface 38, the restoring surface, is acted upon by the pressure line constantly with the pump pressure and one of these opposing, larger surface second surface 37, the control surface, optionally applied to the pump pressure or Tank 5 is relieved. Due to the different size of the two surfaces, the control valve can be moved with appropriate pressurization of the surfaces in one of its end positions.

The control surface 37 is connected to a reversing line 24, which opens into the receiving bore 25, in which the percussion piston 6 is guided, that it is acted upon by the pump pressure depending on the position of the percussion piston 6 or is relieved to the tank 5. In the lower reversing position, in which the percussion piston as in the Fig. 1 shown in the normal operating condition meets the tool, the junction of Umsteuerleitung 24 is connected via a arranged between the piston collars circumferential groove 26 with a likewise opening into the receiving bore tank line 27 in which a low pressure prevails, whereby the control surface of the control valve to the tank 5 relieved is and the control valve assumes a first end position (Rückhubposition), since on the return surface of the spool, the high pump pressure is present and generates a corresponding restoring force. The tank lines 2, 27 are brought together within the impact mechanism and open into a common tank of the carrier, which is shown here for clarity as two tanks. In the return stroke position, the control valve connects via the alternating pressure line 28, the upper drive surface 19 of the percussion piston with the tank line 2. Due to the constant on the lower drive surface 20 of the percussion piston pump pressure, the percussion piston is moved against the Schlaghubrichtung upwards. Via a return throttle 22, the oil displaced by the upper piston drive surface 19 flows throttled to the tank, whereby a pressure level required for smooth running is maintained on the upper drive surface in the return stroke.

Moves the percussion piston 6 during the return stroke from the lower reversing position upwards, the lower piston collar 18 first covers the opening into the receiving bore Umsteuerleitung 24 to a piston stroke, which represents the nominal piston stroke, near the upper reversal point to the lower drive chamber 39 release. Since the lower drive chamber is connected to the pressure line 1, in which the pump pressure is present, this pump pressure now also acts in the reversing line 24 and on the control surface 37 of the control valve 21. Since the control surface 37 is larger in area than the restoring surface 38, acts despite the same Pressure on both surfaces a resultant force on the control valve, which switches it to the other end position (Schlaghubposition). The control valve now connects via the alternating pressure line 28, the upper drive surface 19 of the percussion piston with the pressure line 1. Since the upper Antriebsfäche 19 in terms of area larger than the lower drive surface 20, despite the same pressure on both surfaces, a resulting Power on the percussion piston, which accelerates him in Schlaghubrichtung and on the chisel. During the stroke, the piston again covers the reversing line and connects them, as described above, via the circumferential groove 26 again with the tank line 27, just before the piston strikes the bit. This is followed by a return stroke, etc.

In the illustrated embodiment, the percussion piston on an upper piston rod 15, a lower piston rod 16 and two piston collars 17, 18, between which a circumferential groove 26 is arranged. It is also possible to use only one or more than two piston collars and to use grooves instead of the circumferential groove arranged axially on the rod or a piston collar or a plurality of piston collars, or radial bores. The circumferential groove, grooves or holes are required to take over control functions, depending on the position of the percussion piston relative to the percussion mechanism housing located in the striking mechanism housing circumferential grooves or holes are connected or disconnected via the grooves located on the percussion piston or holes.

The impact piston or the cylinder bore of the housing may have circumferential pressure equalization grooves to distribute oil evenly on the lateral surface of the piston and thus to provide a pressure equalization in the circumferential direction on the lateral surface.

The percussion piston is guided via the impact piston guide surfaces 30 and 31 on the piston collars 17, 18 and over the impact piston guide surfaces 32 and 33 on the rods 15 and 16, which have a slightly smaller outer diameter than the inner diameter of the corresponding percussion guide surfaces 34 and 36 for guiding the rods and the percussion guide surface 35 for guiding the piston collars 17 and 18th

If the percussion piston has more than two guide points, the inner and outer diameters of the respective guide surfaces can be selected by appropriate selection Determine which guide points limit the maximum inclination of the percussion piston in the receiving bore and which maximum inclination is permitted.

The receiving bore in the impact mechanism housing can - as shown - directly represent the Schlagwerksführungsflächen for the percussion piston, but it may alternatively be used sleeve-shaped guide bushes which are arranged with little play around the percussion piston and are used with their outer lateral surfaces in the receiving bore of the striking mechanism housing. If such guide bushes are used to guide the piston rods, they may at the same time have circumferential grooves on the inner circumferential surface into which seals are inserted in order to prevent the escape of gas or working fluid along the piston rods.

The receiving bore has in the region of the guide of the lower piston rod 16 circumferential grooves. The arranged below the Schlagwerkführungsfläche 36 Druckentlastungsnut 40 is connected to the tank line 2 to remove oil, which flows from the lower drive chamber coming through the guide gap between the impact piston guide surface 33 and striking mechanism guide surface 36 to the tank.

Below the Druckentlastungsnut a seal groove 41 is arranged, in which a seal, not shown, is located to prevent the escape of working fluid from the lower drive chamber into the whipping chamber 29 inside. In addition to the sealing groove 41, one or more sealing grooves can also be arranged below the pressure relief groove for receiving a second seal and for receiving a scraper which prevents the entry of dirt from the striking space into the guide region. In addition, a pressure relief groove may be provided between the sealing grooves.

The Druckentlastungsnut can also be connected via a throttle to the tank line or the pressure line. By this pressure relief groove to prevent ensure that the pressure peaks in the lower drive chamber, which may exceed the rated operating pressure, act on the seals, which could damage the seals.

A similar arrangement of sealing grooves and pressure equalizing grooves is also applied to the upper piston rod 15, but for the sake of clarity, not shown. In order to supply oil to the guide surfaces on the upper piston rod during the stroke, a Druckentlastungsnut may be disposed between the guide surfaces and the seals, which is connected to either the pressure line or the tank line.

The inner diameter of the bore in web regions 42 (FIG. Fig. 2 ) between the pressure relief groove and the seal groove and the bore in the land areas 43 (FIG. Fig. 2 ) between the seal groove and the striking space, is made larger than the largest diameter in the region of the guide surface 36 and preferably 0.2 mm to 0.5 mm greater than the smallest diameter of the striking mechanism guide surface 36. This prevents the Impact piston guide surface 33 comes in an inclined position of the percussion piston in the receiving bore or deformations in contact with these areas of the bore in contact and damage and wear occurs.

A similar embodiment can be applied to the upper piston rod, wherein the diameter of web portions of sealing grooves and pressure relief grooves, which are arranged between the guide portion 34 and the gas space 23, are made larger in diameter than the largest diameter of the guide portion.

Due to small differences in diameter between the respective impact piston guide surface and the opposite Schlagwerkführungsfläche arises concentric position of the percussion piston to the receiving bore along the guide surfaces, a gap between the percussion piston and percussion gear housing. The diameter of the striking mechanism housing guide surface 34 is designed so that the inner diameter of this guide surface towards the top, that is, enlarged toward the upper end of the striking mechanism guide surface, wherein a first extending in the axial direction region has a constant diameter and thus represents a cylindrical guide region. The adjoining second region has a parabolic enlarging diameter, ie, the diameter does not change linearly in the second region to the axial distance from the lower edge of the guide, or from the transition of the cylindrical to widening guide region, but disproportionately.

In the case of a cross section through the central axis of the guide, the course of the inner edge of the impact mechanism guide in the region of the widening guide region results in a parabolic line, with a tangential transition to the cylindrical region.

The percussion guide surface 36 for guiding the lower piston rod 16 is designed similarly, wherein the diameter increases towards the lower end of the striking mechanism guide surface.

The diameter of the impact piston guide surface 30 on the collar 17 is also designed with a varying diameter, wherein the diameter of a central region of the guide surface, parabolic reduced towards both ends of the piston collar. As a result, the collar has a substantially barrel-shaped outer contour.

In all cases, a gap between the guide surfaces, which has a changing gap height, is generated by the axially varying diameter of a guide surface, the gap height increasing at least towards one end of the guide surface. By arranged in the percussion circumferential grooves, which are hydraulically connected and filled with oil, the gap between the guide surfaces is also filled with oil.

Thus, the impact piston guide surfaces and the corresponding percussion guide surface do not wear excessively, which may occur due to contact between the guide surfaces, it is necessary that forms a sufficiently viable oil lubricating film between the guide surfaces. The lubricating film is intended to center the percussion piston as far as possible in the receiving bore and to absorb forces acting radially on the percussion piston in order to allow a low-friction and low-wear movement of the percussion piston in the receiving bore, without resulting in direct contact between the percussion piston and the percussion mechanism housing.

If there is a gap with a constant height in a cylindrical embodiment of the impact piston guide surface and the striking mechanism guide surface, the carrying capacity of the lubricant film can be exceeded, especially at low relative speeds, strong mechanical transverse accelerations of the percussion piston or percussion mechanism housing or other transverse forces. If the carrying capacity is exceeded, a contact between the guide surfaces, whereby faster wear of the components occurs, resulting in rapid failure of the percussion mechanism.

If two opposing guide surfaces, which have oil volumes in the form of grooves at both ends, move against each other, oil will adhere to the surfaces of the guide surfaces due to the adhesion forces. The adhering oil is entrained and partially transported into the gap between the guide surfaces. Due to cohesive forces within the oil, oil, which is slightly spaced from the surfaces, is also partially transported into the gap.

Moves the percussion piston in the receiving bore of the percussion mechanism housing during the return stroke up, so remains on the impact piston guide surface 33 oil due to the adhesion forces and friction and is entrained by the percussion piston. The entrained oil is conveyed into the narrowing gap. The adhesion and friction between the oil and the impactor guide surface act a back flow of the oil in the direction of pressure equalization groove 40, whereby a pressure builds up in the gap.

The pressure profile within the gap is dependent on the pressure difference between the oil volumes before and after the gap, the geometry of the guide surfaces and the speed of movement of the percussion piston. The pressure of the oil in the gap causes a radial force acting on the circumference on the piston, which causes a centering of the percussion piston in the receiving bore.

Since the pressure level is increased by the above-described embodiment of the geometry of the guide surfaces compared to purely cylindrical guide surfaces, the load capacity of the oil film increases in the gap, since the oil pressure exerts a stronger radial force on the percussion piston to keep it at a distance from the striking mechanism housing , A contact between percussion piston and impact mechanism housing is effectively prevented and the wear of the components significantly reduced.

In addition, is achieved by the parabolic widening diameter of the striking mechanism guide surface 36 that at a misalignment of the percussion piston, in which the axis of the percussion piston is no longer parallel to the axis of the receiving bore of the striking mechanism housing, the lower piston rod not only at the lower inner edge of the striking mechanism 36th comes to rest, creating a point or linear contact point would arise, but comes to a larger area to the plant. This larger contact surface is created by the parabolic geometry, through which the piston rod comes to rest on a slightly curved surface of the striking mechanism guide surface. As a result, the surface pressure and the wear at the contact point are significantly reduced.

A disproportionate change in diameter as described above can be performed on all guide surfaces 30, 31 of the percussion piston and on the percussion guide surfaces 34, 35, 36, wherein it is possible to provide a change in diameter only on one side of the gap, as on the guide surfaces 34 and 36th is shown or on both sides of the guide surface, as it is on the piston collar 17th is shown. If the diameter change is provided on the impact piston guide surfaces, the change in diameter is carried out so that the outer diameter decreases at least toward one end of the guide surface, in contrast to the diameter change on the impactor guide surfaces where the inner diameter increases at least toward one end.

The piston collar 18 is in Fig. 1 shown with constant diameter and represents the prior art, this piston collar analogous to the collar 17 can also be performed with a variable diameter.

Regardless of the variation in diameter, the outer ends of the guide portions and the transitions between the cylindrical guide portions and the enlarged diameter portion may be radiused, thereby avoiding sharp edges or angular transitions in diameter changes (in Figs Fig. 1 and 2 not shown).

Also, the wear of the guide surfaces of the bit 7 and the bushings 8 can be reduced by parabolic diameter changes to the inner guide surfaces of the bushings. The diameters at each end of the bushings facing a bit end preferably increase in a parabolic manner, with decreasing distance to the respective end of the bearing bush. In an inclined position of the bit in the bushes, the bit is no longer at the respective outer edges of the bearing bushes, but at the area with a parabolic enlarging diameter, which increases the contact surface and reduces the surface pressure and wear.

Fig. 3 shows an embodiment of the impact piston guide surface 33 and the striking mechanism guide surface 36, wherein the illustration shows a section through the percussion piston axis and only one half of the symmetry to the percussion piston axis contours are shown. The contours represent only a limited in the direction of the percussion axis axis.

The horizontal coordinate axis 47 corresponds to the axis of symmetry of the percussion piston and the receiving bore of the striking mechanism housing. The vertical distance between the horizontal coordinate axis and the thick contour lines of the impact piston guide surface 33, and the striking mechanism guide surface 36 represents the radius of the percussion piston, or the receiving bore of the striking mechanism housing.

On the horizontal coordinate axis, the axial extent of the guide area and on the vertical axis of the diameter is shown. The radii, the diameter, the change in diameter, the gap height, the axial extent of the guide surfaces and the position of the transition from the cylindrical portion to the widening portion do not correspond to the practical meaningful values, but are not reproduced to scale the invention idea to scale.

The upper thick line shows the contour of the percussion guide surface 36 between the lower drive chamber 39 and the pressure relief groove 40. Within an axial range Z, the percussion guide surface is made cylindrical, i. the diameter DZ, or the distance of the line to the horizontal coordinate axis is constant up to the transition point 46. Within the range L, the diameter of the percussion guide surface 36 increases linearly with the distance from the transition point 46 and reaches its maximum value DM at the end of the percussion guide surface.

The lower thick line represents the contour of the impact piston guide surface 33 and has the diameter DK, which is constant at least within the area of the striking mechanism guide surface 36.

The gap height results from the half of the difference of the diameter of the striking mechanism guide surface and the impact piston guide surface and is marked in the area Z with H and reaches the maximum value HM at the right end of the striking mechanism guide surface.

The contours of the areas outside the percussion guide surface, such as the Druckentlastungsnut 40 or the lower drive chamber 39 are not shown here and can have diameters larger than the diameter DM and DZ.

The percussion piston also has a constant diameter DK at least over a limited length laterally of the area shown.

The arrow 44 indicates the movement of the percussion piston, during which the illustrated embodiment of the guide surfaces causes an improvement in the carrying capacity of the lubricating film. The percussion piston moves parallel to the horizontal coordinate axis, towards the narrowing gap 49. Due to the adhesion forces and friction, oil adheres to the surface of the impact piston guide surface and is entrained in the direction of arrow 45. Cohesive forces within the oil ensure that oil is also carried along, which is further away from the impact piston guide surface. Near the impact piston guide surface, the speed at which the oil moves in the direction of the arrow is high, but decreases with increasing distance from the impact piston guide surface. As the gap height decreases in the arrow direction, the entrained oil thus accumulates in the gap, resulting in an increase in the pressure, which increases the carrying capacity of the oil film in the gap and the centering effect due to the force generated by the oil pressure radially acting on the percussion piston force ,

In the embodiment according to Fig. 4 the diameter of the percussion guide surface 36 is not increased linearly to the distance from the transition point 46 at which the cylindrical region Z ends, but disproportionately, resulting in a parabolic course within the region P with a tangential transition in the Z area.

mit

• DZ = Durchmesser der Schlagwerkführungsfläche im zylindrischen Bereichs der Führungsfläche,
• k= Konstanter Faktor, der abhängig von der axialen Erstreckung des erweiterten Führungsbereiches P gewählt wird. Dieser Faktor beeinflusst, wie stark sich der Durchmesser pro axialer Lageänderung a verändert.
• a= axialer Abstand einer senkrecht zur Symmetrieachse liegenden Ebene zum Übergangspunkt 46, wobei die Ebene innerhalb des Bereiches P liegt.

The diameter change in the region P results from: $$\mathrm{D}\left(\mathrm{a}\right)=\mathrm{DZ}+\left(\mathrm{k}\cdot {\mathrm{a}}^2\right).$$

With

• DZ = diameter of the percussion guide surface in the cylindrical area of the guide surface,
• k = Constant factor which is selected as a function of the axial extent of the extended guide region P. This factor influences how much the diameter changes per axial change of position a.
• a = axial distance of a plane perpendicular to the axis of symmetry plane to the transition point 46, wherein the plane is within the range P.

The length of the area P divided by the total length of the guide area (Z + P) is 0.5 in the illustrated embodiment. The guide portion may also have a continuous parabolic enlarging diameter, but a ratio of 0.3 to 0.9, preferably 0.5 to 0.7, has been found to be the preferred embodiment.

The amount of the difference between the diameter DZ in the region Z of constant diameter and the diameter DM at the end of the range at which the diameter change reaches its maximum is 0.01 mm to 0.08 mm, preferably 0.02 mm to 0, 05 mm.

berechnet werden, wenn die axiale Länge P des Bereiches mit veränderlichem Durchmesser und die maximale Durchmesseränderung (DM-DZ) vorgegeben ist.The factor k can according to the formula $$\mathrm{k}=\left(\mathrm{DM}-\mathrm{DZ}\right)/\left({\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="imgf0001.png"\; state="\{\{state\}\}">P</figure-callout>}}^2\right)$$

calculated when the axial length P of the variable diameter portion and the maximum diameter change (DM-DZ) is predetermined.

In the embodiment according to Fig. 5 become the embodiments after Fig. 3 with those of Fig. 4 combined. At the area Z of constant diameter of the percussion guide guide surface, starting from the transition point 46, a region L with a linearly increasing diameter adjoins the second transition point 50, from which a region P with a parabolic enlarging diameter adjoins.

The transition between the cylindrical to linearly increasing diameter can be provided in the region of the transition point 48 with a radius, so that in the course of the contour no corner, or edge is formed, but results in a tangential transition.

It is also possible to carry out the change in diameter of the guide region such that a region P with a parabolic enlarging diameter adjoins the area Z of constant diameter of the percussion guide surface from the transition point 48 and a region L with a linearly increasing diameter from the second transition point 50.

Fig. 6 shows a further concrete embodiment of a striking mechanism guide surface. This version corresponds to the one in Fig. 4 shown, but here the position of the impact piston guide surface 33 is shown, which results when the percussion piston in the receiving bore is so far wrong until the impact piston guide surface comes to rest against the percussion guide surface. In such a misalignment, the symmetry axis 52 of the percussion piston, which is shown here as a dash-dot line, no longer runs parallel to the axis of symmetry 47 of the receiving bore of the percussion mechanism housing, which is represented by the horizontal coordinate axis, and the area of the impact piston guide surface shown on the right shifts in the direction of the arrow 63 to the striking mechanism guide surface 36. The inclination results in contact between the impact piston guide surfaces and the impactor guide surfaces, with the impact piston guide surface 33 of the piston rod 16 abutting the outer end of the impactor guide surface 36. Such a condition can occur, for example, with exceptionally high transverse forces acting on the percussion piston, in which the carrying capacity of the lubricating film is exceeded or at low percussion piston speeds at which no sufficiently viable lubricating film can form in the gap between the guide surfaces and an exact centering is no longer present ,

Due to the parabolic shape of the contour of the percussion guide surface in the area P, there is no contact of the outer, angular edge of the percussion guide surface 36 with the impact piston guide surface 33, but the contact region 51 lies in the parabolic portion P. By this parabolic rounding in Area P is the contact area increased, whereby the surface pressure in the contact area is significantly reduced, which greatly reduces damage and wear of the guide surfaces. In a purely cylindrical design of the impactor guide surface, the outer pointed edge of the striking mechanism guide surface would come to rest on the impact piston guide surface, so that high surface pressures and wear would be the result. Even with a linear change in diameter instead of a parabolic, as in Fig. 3 is shown, would be at the outer end of the percussion guide surface and at the transition point between the cylindrical portion and the area in which the diameter changes linearly to the distance from the transition point, angular edges exist that would lead to high surface pressures and thus damage to the guide surfaces and to increased wear.

The specific embodiment according to Fig. 7 is the in Fig. 4 However, the percussion guide surface 36 has on both sides of the cylindrical portion Z, or at both ends of Schlagwerkführungsbereiches, areas P1 and P2 with parabolic enlarging diameter, so that in both directions of movement 44, 54 of the percussion piston 16 by a in the axial direction changing lubricating gap height, an improvement in the carrying capacity of the lubricating film is achieved. The lengths of the areas P1 and P2 and the maximum diameter changes can be adapted to the circumstances and can have different values in the areas P1 and P2.

When the percussion piston moves in the direction of the arrow 44, the parabolic region P2 - and in the opposite direction of movement according to arrow 54 the parabolic region P1 - causes an improved pressure build-up in the gap between the guide surfaces by moving oil from the surface of the impact piston guide surface narrowing in the corresponding direction of movement Gap is transported into it. At the outer ends of the guide surface, which adjoins the pressure equalization groove or the lower drive chamber and the diameter changes significantly, additional chamfers 55 or radii 56 may be provided, which are shown by dashed lines by way of example. Through these chamfers or radii, the installation of the percussion piston is facilitated in the receiving bore of the striking mechanism housing, since they serve as insertion aids and center the percussion piston with a small lateral offset to the striking mechanism housing. Furthermore, these radii or bevels reduce the risk that the sharp edges without radii or chamfers would be damaged and flaked off under load. The axial extent of the chamfers or radii is smaller than the axial extent of the parabolic area P. Contrary to the illustration, the difference in diameter within the area of the chamfers or the radii is greater than the diameter difference within the parabolic area P.

Fig. 8 shows a further embodiment of a striking piston guide surface. Herein, the guide area and the lubricating gap 49 are shown in the region of the piston collar 17. Compared to the Fig. 3 to 7 In this embodiment, the impact piston guide surface 30 has a contour with a varying diameter, and the impact mechanism guide surface 35 is cylindrical.

Shown are the contours of the impact piston guide surface 30 and the striking mechanism guide surface 35, wherein the representation is a section through the impact piston axis 52 and only a half of the impact piston axis 52 symmetrical contours is shown. The contours represent only a limited in the direction of the percussion axis axis.

The vertical distance between the impact piston axis or symmetry axis 52 and the thick contour lines of the impact piston guide surface 30, or the percussion guide surface 35 represents the radius of the percussion piston or the receiving bore of the percussion mechanism housing.

On the horizontal coordinate axis, the axial extent of the guide area is shown. The radii, the diameters, the change in diameter, the gap height, the axial extension of the guide surfaces and the position of the transitions from the cylindrical region Z to the widening regions P1, P2 do not correspond to the practical values. Rather, the values for better representation are not true to scale and shown enlarged.

The thick line represents the contour of the percussion guide surface 35, within a partial area between the upper drive chamber 53 and the lower drive chamber 39. Within this range, the percussion guide surface has a constant diameter DG.

The upper thick line represents the contour of the impact piston guide surface 30, in the region of the upper piston collar 17.

Within a central axial region Z, the impact piston guide surface is cylindrical, i. the diameter DZ, or the distance of the line to the axis of symmetry is constant up to the two transition points 46. Within the areas P1, P2, the outer diameter of the impact piston guide surface decreases disproportionately from the distance from the transition points 46 and reaches at the ends of Schlagwerkführungsfläche its minimum diameter DM. The gap height is equal to half the difference between the diameter of the striking mechanism guide surface and the impact piston guide surface and is marked H in the area Z. At the outer ends of the impact piston guide surface, the gap height assumes the maximum value HM.

At the end of the impact piston guide surface 30 of the piston collar 17 shown on the right, the upper piston rod 15 connects, which projects into the upper drive chamber 53, in which the upper drive surface 19 is located. At the left end, the circumferential groove 26 connects.

mit

• DZ = Durchmesser des zylindrischen Bereiches der Schlagkolbenführungsfläche
• k= Konstanter Faktor, der abhängig von der axialen Erstreckung des sich erweiternden Führungsbereiches P gewählt wird. Dieser Faktor beeinflusst, wie stark sich der Durchmesser pro axialer Lageänderung a verändert.
• a= axialer Abstand einer senkrecht zur Symmetrieachse liegenden Ebene zum Übergangspunkt 46, wobei die Ebene innerhalb des Bereiches P liegt.

The change in diameter in the areas P1, P2 results from the formula: $$\mathrm{D}\left(\mathrm{a}\right)=\mathrm{DZ}-\left(\mathrm{k}\cdot {\mathrm{a}}^2\right).$$

With

• DZ = diameter of the cylindrical portion of the impact piston guide surface
• k = Constant factor which is selected as a function of the axial extension of the expanding guide region P. This factor influences how much the diameter changes per axial change of position a.
• a = axial distance of a plane perpendicular to the axis of symmetry plane to the transition point 46, wherein the plane is within the range P.

The length of the regions P1, P2 divided by the total length of the guide region (Z + P1 + P2) is approximately 0.27 in the illustrated embodiment. A ratio of the length of the region P to the total length of the impact piston guide region of 0.1 to 0.4, preferably from 0.2 to 0.3 has proved to be a preferred embodiment.

The amount of the difference between the diameter DZ in the region Z of constant diameter and the diameter DM at the outer end of the region P at which the diameter change reaches its maximum is 0.005 mm to 0.03 mm, preferably 0.01 mm to 0, 02 mm.

wenn die axiale Länge P des Bereiches mit veränderlichem Durchmesser und die maximale Durchmesseränderung (DZ-DM) vorgegeben wird.The factor k results $$\mathrm{k}=\left(\mathrm{DZ}-\mathrm{DM}\right)/\left({\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="imgf0001.png"\; state="\{\{state\}\}">P</figure-callout>}}^2\right).$$

when the axial length P of the variable diameter portion and the maximum diameter change (DZ-DM) are set.

The arrow 44 indicates the return stroke of the percussion piston and thus the piston collar 17 parallel to the axis of symmetry, during which the parabolic contour within the region P2 causes an improvement in the carrying capacity of the lubricating film. Due to the adhesion forces, oil in the gap remains adhered to the surface of the percussion guide surface which moves relative to the percussion piston and is drawn against the direction of the arrow 44 into the narrowing lubricating gap, causing the pressure inside the percussion device to increase Gap leads. This increased oil pressure in the gap leads to an improved bearing capacity of the oil lubricating film and improves the centering effect due to the generated by the increased oil pressure, radially acting on the percussion piston force. Instead of the parabolic contour, the contour can analogously to the execution of Fig. 3 are also designed so that the diameter of the impact piston guide surface varies linearly to the distance from the transition point 46, wherein a parabolic contour further increases the carrying capacity of the lubrication gap with respect to a linear contour and further reduces wear.

The embodiment according to Fig. 9 corresponds to the embodiment according to Fig. 8 , wherein here the position of the impact piston guide surface 30 is shown, which results when the percussion piston in the receiving bore of the percussion mechanism so far skewed until the impact piston guide surface 30 comes to rest against the striking mechanism guide surface 35. In such a misalignment, the axis of symmetry 52 of the percussion piston no longer runs parallel to the axis of symmetry 57 of the receiving bore of the percussion mechanism housing and the end of the impact piston guide surface shown on the right shifts in the direction of the arrow 63 on the percussion guide surface. The inclination leads to a contact between the impact piston guide surfaces and the striking mechanism guide surfaces, the impact piston guide surface 30 of the piston collar 17 comes to rest near the outer edge of the piston collar on the striking mechanism guide surface 35. Such a condition can occur, for example, with exceptionally high transverse forces acting on the percussion piston in which the carrying capacity of the lubricating film is exceeded or at low percussion piston speeds at which no sufficiently viable lubricating film can form and an exact centering is no longer present.

In the illustration, for the purpose of better illustration, the skew and the change in diameter are not true to scale, but shown greatly exaggerated and do not correspond to the practical meaningful values.

Due to the parabolic shape of the contour of the impact piston guide surface in the area P, in which the diameter of the impact piston guide surface increasingly reduces toward the outer end of the impact piston guide surface, it comes with a tilt not to contact the outer angular edge of the impact piston guide surface with the striking mechanism guide surface, but the contact area lies in the parabolic area P. By means of this parabolic rounding in the area P, the contact area is increased, as a result of which the surface pressure in the area of contact is considerably reduced, which greatly reduces damage and wear of the guide surfaces. In a purely cylindrical design of the impact piston guide surface, the outer sharp edge would come to rest, resulting in high surface pressures and wear would be the result. Even with a linear instead of a parabolic diameter change, similar to the contour Fig. 3 would be at the outer end of the impact piston guide surface and at the transition point from the cylindrical portion to the region in which the diameter is reduced linearly to the distance from the transition point, angular edges exist that would lead to high surface pressures and thus damage to the guide surfaces and increased wear ,

It is also possible to provide the change in diameter on the impact piston guide surface, in particular with a parabolic course, only at the respective ends of the respective impact piston guide surfaces which point to the piston rods. Thus, in the illustrated embodiment, a change in diameter could be performed on the collar 17, for example, only at the end pointing to the rod 15 (in the area P2).

In Fig. 10 is a section of the striking mechanism housing in the area of the striking mechanism guide surface 36 is shown, which serves to guide the piston rod 16 of the percussion piston. The dash-dot line represents the line of symmetry 52 of the percussion piston and the receiving bore 25 of the impact mechanism housing. On the percussion guide surface 36 are circulating approximately equal distance pressure equalization grooves 58 are provided which ensure that in the gap between the striking mechanism guide surface 36 and the impact piston guiding surface prevailing pressure in Compensates circumferential direction, so that the radially acting on the piston pressure causes no transverse deflection of the percussion piston in relation to the receiving bore. However, the pressure equalization grooves can not prevent contact between the guide surfaces of the percussion piston and percussion mechanism occurring at a low relative speed between percussion piston and percussion mechanism or with a high lateral force acting on the percussion piston.

The impact piston guide surfaces on the piston collars 17, 18 and the Schlagwerkführungsflächen may have circumferential pressure equalization grooves, and it is also possible that both impact piston guide surfaces and Schlagwerkführungsflächen are performed with pressure equalization grooves. These pressure compensation grooves can also be arranged in the regions L or P, in which the diameter of the guide surface changes linearly or parabolically.

Also shown are in Schlaghubrichtung seen behind the guide area pressure relief groove 40 and three sealing grooves 41st

The Fig. 11a to 11d show detail views of the pressure equalization grooves 58. In particular, cross sections are shown, the sectional plane extends parallel to the axis of symmetry 52 of the receiving bore 25 of the impact mechanism housing. The illustrations show only a section of the total cross-section. The illustrated pressure compensation grooves differ in their cross-sectional shape, especially in the transition from the percussion guide surface 36 to the groove flank surfaces 59.

The symmetry axis of the receiving bore is not shown, but extends horizontally above the contour shown, as well as the impact piston guide surface, which is not shown, but lies horizontally between the axis of symmetry and the striking mechanism guide surface 36.

The transition from the percussion guide surface to the Nutflankenflächen is designed so that increases the diameter of the percussion guide surface near the Druckausgleichsnut with decreasing distance to the Nutflankenflächen out. As a result of this change in diameter, the transition can take the form of a slope with a linear course and a slight inclination, a slope with a parabolic course, a chamfer or a radius, combinations of chamfers or bevels with bevels being also possible.

The embodiments of pressure compensation grooves described below show pressure equalization grooves on the impactor guide surface 36. Similar embodiments can also be performed on the striking mechanism guide surfaces 34 and 35 and the impact piston guide surfaces 32 and 33, but preferably on the impact piston guide surfaces 30 and 31.

The cross section of a pressure equalization groove 58 according to Fig. 11a in a plane parallel to the axis of symmetry of the receiving bore of the hammer mechanism housing, has a radius R in the groove base, so that the groove base merges tangentially into the groove flank surfaces 59. The diameter D of the percussion guide surface 36 increases slightly linearly with decreasing distance to the Nutflankenflächen, so that the contour of Schlagwerkführungsfläche in this area on both sides of the Nutflankenflächen 59 each forms a slope 62 with low pitch.

The bevels support the build-up of pressure in the lubrication gap between the percussion guide surface and the impact piston guide surface and further prevent damage to the sensitive groove edges 61 since they are slightly spaced from the impact piston guide surface by the bevels. The groove is symmetrical, so that the contours of the bevels on both sides of the pressure equalization groove is present. It can also be performed only one side with a slope. The slopes can also be performed with a parabolic contour with a tangential transition to the percussion guide surface.

The radius at the groove bottom is between 0.75 mm and 1.75 mm, the distance between the groove flanks is between 1.5 mm and 3.5 mm. The groove depth is between 0.8 mm and 3 mm.

In comparison, in the embodiment according to Fig. 11b the diameter change significantly more pronounced, whereby at the groove edges bevels in the form of chamfers with a slope of about 45 ° are available. The groove edges 61 formed in this way at the transition of the bevels to the groove flank surfaces are substantially more stable with respect to stresses that can arise due to mechanical contact, cavitation or flow forces. Flow forces and cavitation can occur when high velocity oil flows in from the gap between the guide surfaces into the pressure equalization grooves. The groove depth is chosen so that the slopes pass directly into the radius R of the groove bottom.

Cavitation refers to the process when, for example, eddies are created on edges around which fast flowing oil flows, which generate a strong pressure drop locally, so that gas bubbles can form in the oil. If these gas bubbles reach areas of higher pressure, these gas bubbles collapse again, which accelerates the liquid around the gas bubbles very much. If the collapse of the gas bubbles takes place close to component surfaces, in particular of angular edges, the accelerated oil can hit the component surfaces so hard that they are damaged.

Compared to the execution after Fig. 11b are in the design after Fig. 11c the bevels or chamfers replaced by radii R, so that the groove surfaces merge into one another and no more angular edges more, but tangential transitions between the Schlagwerkführungsfläche and the Druckausgleichsnutinnenflächen are present. The radii in the groove bottom and at the transitions can be the same or different. The rounding provides stable edges and transitions which further reduce turbulence of the oil flowing into the pressure equalization groove and thus reduce cavitational tendency.

Finally, the embodiment detects Fig. 11d compared to the execution after Fig. 11c the pressure equalization groove at the transitions 60 paragraphs 63, resulting in a stepped Druckausgleichsnut with oblique Nutflankenflächen 59. The groove base has a radius R. The transitions between the Nutflankenflächen 59 and the paragraph 63 are also provided with radii, so that no angular groove edges are present. The heel is intended to redirect the flow of oil flowing from the gap between the impact piston guide surface and the impactor guide surface into the pressure equalization groove so as to reduce the swirl and flow velocity in the groove bottom and reduce the pressure between the oil pressure in the gap and the oil pressure the pressure equalization groove is gradual. The distance of the percussion guide surface 36 to the bottom of the pressure equalizing groove divided by the distance between the percussion guide surface 36 and the shoulder 63 is 0.25 mm to 0.5 mm.

Claims (12)

1. An impact tool with an impact mechanism housing having a receiving bore in which an impact piston (6) is mounted such that it is movable along the longitudinal axis, wherein at least one impact mechanism guide surface (34, 36) having an inner diameter is formed in the receiving bore and at least one impact piston guide surface (30, 31) having an outer diameter is formed on the impact piston (6), wherein the impact mechanism guide surface (34, 36) has in the axial direction at least in regions an inner diameter that increases non-linearly,
   characterized in that
   the non-linear increase in the inner diameter of the guide impact mechanism guide surface (34, 36) is parabolic in design.
2. The impact tool as claimed in claim 1 characterized in that the inner diameter of the impact mechanism guide surface (34, 36) has a diameter that increases non-linearly toward at least one of the ends.
3. The impact tool as claimed in claim 2 characterized in that the impact mechanism guide surface (34, 36) guides a piston rod (15, 16) wherein the inner diameter of the impact mechanism guide surface (34, 36) has a diameter that increases non-linearly toward the outer end of the piston rod.
4. The impact tool as claimed in one of claims 1 to 3 characterized in that the impact mechanism guide surface (34, 36) has several partial regions wherein one partial region (P) has a non-linearly changing inner diameter that merges into one partial region (Z) with a constant inner diameter.
5. The impact tool as claimed in one of claims 1 to 4 characterized in that at the end of the partial region (P) having the largest diameter there is a partial region (L) arranged with a linearly widening inner diameter, and at the end of the partial region (P) having the smallest diameter there is a partial region (Z) arranged with a constant diameter.
6. The impact tool as claimed in one of claims 1 to 4 characterized in that the impact mechanism guide surface (34, 36) has on each side partial regions (P1, P2) that have partial regions widening non-linearly in different orientation, wherein the partial regions (P1) and (P2) are preferably connected to one another via a partial region (Z) with a constant diameter.
7. The impact tool as claimed in claim 1 characterized in that the impact piston (6) has at least one piston rod (15, 16) and at least one piston collar (17, 18) whose outside surfaces are designed as impact piston guide surfaces (30, 31).
8. The impact tool as claimed in claim 7 characterized in that at least one impact piston guide surface (30, 31) has on the side facing away from the tool an outer partial region (P2) having a non-linearly decreasing outer diameter that preferably runs parabolically and/or preferably changes into a partial region (Z) with a constant diameter.
9. The impact tool as claimed in claim 8 characterized in that the impact piston guide surface (30, 31) has two outer partial regions (P1, P2) that have outer diameters that decrease non-linearly in different orientation and preferably run parabolically.
10. The impact tool as claimed in one of claims 7 to 9 characterized in that a partial region (Z) with a constant, diameter is arranged between the outer partial regions (P1, P2).
11. The impact tool as claimed in one of claims 1 to 10 characterized in that the impact mechanism has an impact mechanism guide surface (35) that guides a piston rod (15), wherein a tool can be loaded with the outer end of the piston rod (16), and wherein the inner diameter of the impact mechanism guide surface has a partial region (Z) with a constant diameter and pointing toward the outer end of the piston rod, a partial region (P) with a parabolically increasing diameter, and that at least one impact piston guide surface (30, 31) has a partial region (Z) with a constant diameter and on the side facing away from the tool an outer partial region (P2) having a parabolically decreasing outer diameter.
12. The impact tool as claimed in one of claims 1 to 11 characterized in that the impact mechanism guide surface (34, 36) is adjoined at least by a region in which there are peripheral grooves (40, 41) arranged wherein the webs between the grooves (40, 41) and the region between a groove (41) and a space (23, 29) arranged behind same have an inner diameter that is greater than the smallest inner diameter of the guide region (34, 36).

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