EP0663270A1 - Impact hammer with rotative and/or percussive action - Google Patents

Abstract

The electro-pneumatic striker or rotary striker hammer has a free flying striker component which swings forwards and backwards under the influence of pressure fluctuations of an air cushion (27) in a guide cylinder and imparts axial blows rhythmically to a tool or tool holder. A catchment device has an elastically deformable member which is tensioned in the guide cylinder under elastic deformation and catches the striker component in the direction of the tool axis (a-a) when the tool strikes emptily. The catchment device has at least one catch component which with the tool striking emptily, brakes the striker component in a guide area of the hammer coaxial to the tool axis (a-a).

Description

The invention relates to an electropneumatic or electrically driven hammer or rotary hammer according to the preamble of claim 1.

Such devices are usually used in the construction industry and in the artisan sector as portable hammers.

In an electropneumatic impact or rotary hammer known from DE-A 33 09 187, pressure fluctuations of an air cushion are generated with the aid of a drive piston which is controlled to and fro in a guide cylinder and is driven by a crank mechanism. The pressure fluctuations in turn set a striking piston of a striking mechanism, which is designed as a striking element, and which passes the strikes on to a tool or a tool holder. The tool is held in the working position by the contact pressure applied by the operator. In this working position, the rear end of the tool protrudes into the path of the reciprocating percussion piston. If the device is withdrawn or if the tool no longer finds any resistance during the chiseling or drilling process due to the changing strength of the subsurface or when the borehole passes through, the tool will come out of the area of the percussion piston. Since the percussion piston continues to be acted upon by the air cushion, so-called empty blows now occur, which can lead to considerable damage to the device. To reduce the occurrence of empty strikes, it is proposed here to stop the percussion piston in the empty position by means of catch elements. The catching elements are two conical sleeves, of which the outer sleeve is fixed to the housing, while the inner longitudinally slotted sleeve is displaceable in the axial direction with radial deformation when the impact piston strikes. Slowed down will not be the striker that is directly connected to the tool, which can therefore rebound when an empty stroke occurs and brings the strokes back into the striking position. The inner sliding ring is driven axially into the other ring when empty blows occur. This causes a very strong radial deformation, which leads to overstretching and early material fatigue. The sliding ring is therefore very vulnerable to breakage and can cause expensive repairs, since the fragments of the ring inevitably get into the striking mechanism. The braking effect that this configuration can provide is low, since the cones of the two rings working against each other immediately reduce a radial deformation of the ring when the racket strikes, since the ring is clamped both inside and outside diameter. As a result, there is a risk that the percussion piston will be thrown back into its striking position. However, a return of the sliding ring is only left to chance.

From DE-A 27 56 993 an electropneumatic impact hammer or rotary impact hammer is known in which a stepped impact piston is braked against elastically deformable O-rings or catch rings. On the one hand, there is also a separate striker which, even after the stepped piston has been fixed, can free it from its defined position by rebounding. The stepped impact piston has bevels located at a distance from one another, the distance between these bevels being greater than the distance between the two catch rings. The catch rings are fixed axially and are radially deformed when the stepped impact piston hits. The catch rings have no influence on the way of the percussion piston, so that the energy occurring during the braking process can only be reduced between the percussion piston and the catch rings, which contributes to the wear of these parts.

From DE-A 33 35 553 a pneumatic hammer drill is known, in which rubber-elastic ring bodies are provided as a catching device, which are pressed into appropriately prepared recesses when an empty stroke occurs. Here, too, the braking effect takes place in the essential about the deformation of these rubber-elastic elements. Residual energy can be destroyed using an O-ring that is loosely inserted in the machine. However, since the braking movement does not lead to an axial fixation of the rubber-elastic catching device, the O-ring relaxes again after the empty stroke has occurred and can therefore neither contribute to a soft braking of the striker nor influence the pushing back of the percussion piston into the working position.

In order to reduce the empty strokes in CH-PS 590 716 it is proposed to stop the percussion piston in the empty stroke position by a catch ring. This longitudinally slotted catch ring is arranged in an area in front of the percussion piston which is usually not reached in the working position. If there are now empty blows, the percussion piston reaches the area of the catch ring and spreads this catch ring radially outwards. Due to the arrangement of the catch ring in the axial direction, however, only a short braking distance is possible, so that there are rebound forces due to the impact of the percussion piston and the percussion piston is thrown back again, so that several empty strokes are repeated before the percussion piston is stopped.

In another hammer of this type known from DE-PS 25 40 838, a clamping device is provided as an intercepting device. The clamping device comprises an axially fixed inner clamping sleeve and a casing tube into which the shaft of the percussion piston is immersed. If empty blows occur here, there is a limited axial displacement of the casing tube, which leads to jamming of the percussion piston as the distance from the working position increases due to inclined surfaces between the casing tube and the clamping sleeve. However, in order to actually catch the percussion piston, it must first reach a position which enables the percussion piston to run up against the clamping sleeve. Since full braking takes place only at this point, there are rebound effects and repeated empty blows.

In another percussion or rotary percussion hammer of this type according to EP-B 0 218 547, a percussion mechanism is provided in which the percussion piston actuates the tool via a striker. The striker is intercepted by rubber rings, which should allow sufficient fixation by frictional forces, especially when there are no blows. In practice, however, it has been shown that when used in practice, the rubber rings tend to become so soft that they can no longer apply sufficient restraining forces.

Based on this prior art, the present invention seeks to develop a percussion or rotary hammer of the type mentioned in such a way that a lookup is reliably avoided in a simple manner.

This object is solved by the features of claim 1.

In contrast to the prior art, it is assumed that a catch element is at least partially axially fixed in the housing. Instead, the catch element is now axially displaceable in a sleeve which is coaxial with the drilling axis. However, in order to build up a corresponding braking effect due to the displacement path, the catch element is clamped in its guide area with elastic pre-deformation that basically takes place during assembly. If there are now empty blows, the displaceable catch element initially allows a braked displacement to gradually decrease to zero in an area in which a decoupling between the percussion piston and the tool or striker and tool has been achieved. The braking effect is so great that it is also suitable for large empty thrust forces. The braking force can be influenced by changing the excess of the catch element compared to its guidance and by the size of the cross section of the catch element. The braking force is preferably set so that it corresponds approximately to the machine weight, so that no additional force has to be applied when the catch element is pushed back into the working position. This is particularly true for larger machines that are usually used vertically. However, since the impacting element itself, which acts on the tool or tool holder itself, is braked, rebound is avoided.

If the stop on the catch ring is provided with a cone, the axial force is largely converted into a radial force that increases the braking force. If there is still residual energy, it can be absorbed by known elastic end dampers. If a cone angle of more than 5 ° is provided, a small contact pressure is sufficient to bring the catch element back into the working position. All that is required is a single catch ring that is not exposed to strong radial changes, which increases its service life.

In an embodiment according to claim 3, the striker can move freely and unchecked within the catch ring several millimeters in the axial direction, so that no wear occurs on the catch ring and the impact performance is retained. If an empty stroke occurs, the catch ring is pulled forward by the striker and the racket. While a braking effect now occurs initially while overcoming the frictional forces caused by the pre-deformation, braking on the contact edges occurs in the shortest possible way. However, this short braking distance also contributes to a shorter overall length of the entire machine, which increases the ease of use, since only a short distance has to be overcome between the empty position and the working position.

In a configuration of the catch ring according to claim 4, there is a cheaper and simpler production, since the outer surface only has to be finished in the sliding area. At the same time, the cut-out contributes to a reduction in mass and, due to the radial deformation which is thereby facilitated in this area, it can also contribute to energy reduction.

The catch ring can also be moved against the force of a spring, which increases the braking effect and supports the return of the striking element into the working position.

According to claims 7 to 8, a percussion piston can also be provided directly as the striking element, but in this case not only the catch ring but also the guide, which is reset when the tool is reapplied, must be displaced as an interception device.

Fig. 1

Eine Seitenansicht des Schlag- oder Drehschlaghammers in einer ersten Ausführungsform,

Fig. 2

einen vergrößerten Ausschnitt aus Fig. 1 im Bereich des Döppers,

Fig. 3

den Ausschnitt gemäß Fig. 2 in einer weiteren Ausführungsform,

Fig. 4

einen Schnitt nach Linie 4-4 von Fig. 1,

Fig. 5

eine vergrößerte Darstellung des Fangelements,

Fig. 6

eine Darstellung gemäß Fig. 3 in einer dritten Ausführungsform, bei der kein Döpper vorhanden ist.

In the following three embodiments of the invention are explained in more detail with reference to the drawings. Show it:

Fig. 1

A side view of the percussion or rotary impact hammer in a first embodiment,

Fig. 2

2 shows an enlarged detail from FIG. 1 in the area of the striker,

Fig. 3

2 in a further embodiment,

Fig. 4

a section along line 4-4 of Fig. 1,

Fig. 5

an enlarged view of the catch element,

Fig. 6

a representation of FIG. 3 in a third embodiment, in which there is no striker.

The percussion or rotary impact hammer is a portable device that is usually used in the construction industry and in the craft sector.

The percussion or rotary hammer 10 is driven electrically. A guide cylinder 14 is arranged in the rear housing 24. Another housing part 22 surrounds the so-called tool holder 21. A free-flying striking element is arranged in the guide cylinder, which is moved axially back and forth rhythmically by pressure fluctuations of an air cushion. The pressure fluctuations of the air cushion are generated in the exemplary embodiment by a drive device 23, which allows an excitation piston 28 to oscillate back and forth in the guide cylinder.

In the first two exemplary embodiments of FIGS. 1 to 5, the percussion piston transmits its vibrations to a striker 12, which in turn actuates the tool 11. In the third embodiment on the other hand, the percussion piston 13 'has a shaft 13c' which extends as far as the tool 11, so that here the blows are transmitted directly from the percussion piston 13 to the tool.

In all of the exemplary embodiments, an interception device is provided which is penetrated by the striking element, regardless of whether striking piston 13 itself or striker 12. The interception device has a catch element which intercepts the striking element when the tool is empty. In the exemplary embodiment, the catch element is a single catch ring 15, 15 ', but the braking function in the guide region 14a can also be achieved by a plurality of catch rings, catch elements or catch ring parts which act with one another or one behind the other. The catching element is clamped in a guide area 14a with elastic pre-deformation. Only when the tool 11 strikes empty is it axially movable in the guide region 14a and produces a gradual braking effect, while the striking element is otherwise free and can be moved freely in the catch ring if necessary. The guide area 14a can be part of the guide cylinder, but can also be a separate part of the hammer. The catch element is a catch ring 15, 15 'provided with a longitudinal slot 15g. The catch ring 15 has an oversize compared to its guide region 14a. This has the consequence that the clamping ring must be pre-deformed during installation and is therefore clamped in the guide region 14a coaxial to the tool axis a-a due to its elastic deformation. This clamping force results in an increased frictional force between the guide area 14a and the catch ring 15, 15 ', which, despite the axial displacement, enables the build-up of a braking force by increasing the contact pressure on the guide area when empty blows occur. However, the possibility of axial displacement also minimizes the radial load on the retaining ring, since jamming is excluded, and thus material fatigue.

In the first two exemplary embodiments, a head 12a of the striker 12 is movably mounted within the catch ring. In the working position, as long as no empty blow occurs, it is guided on a cylindrical section 15b of the catch ring in such a way that a free and unbraked movement is possible without wear of the catch ring 15. At the same time, the striker is guided with a shaft 12d on a guide 20. The head part 12a of the striker 12 has bevels 12b, 12c which cooperate with appropriately shaped stops 15c and a cone 15a of the catch ring to limit the maximum path of the striker within the catch ring. The stop on the tool side is formed by the cone 15a. In the specific exemplary embodiment, this stop has an angle of 15 °. Any other angle can also be selected. The selection of the cone angle influences the conversion of the axial force into a radial force which increases the braking effect, that is to say into a normal force on the guide region 14a. The larger the angle, the smaller the brake boost. The smaller the angle, the greater the brake boost. At an angle of less than 5 ° there is a risk of wedging, which makes it difficult to return the catch ring from the empty position to the working position.

From Figure 5 it is clear how the catch ring is designed. The cone 15a is provided at the tool end. At the opposite end is the stop 15c. The cylindrical section 15b lies between these two stops. On the outer surface, the catch ring 15 has a finely machined sliding area 15d and a cutout 15e, which on the one hand contributes to a reduction in mass and on the other hand makes production easier. In addition, a bevel 15f is also provided which, in the working position, allows contact with the stop 14b of the guide cylinder. The percussion piston 13 has a nose 13a, the length l of which is greater than the maximum possible path s of the striker within the catch ring. This reliably prevents the percussion piston 13 from striking the catch ring directly when the striker suddenly gives way to the front when an empty stroke occurs.

In this embodiment as well as in the other two, when an empty stroke occurs, there is initially a movement of the striking element to the front, which causes an axial displacement of the catch ring. Due to the braking force, the catch ring is gradually axially braked. Depending on the intensity of the blank stroke, the catch ring can come to a standstill before reaching the stop ring 18. However, if the catch ring reaches the stop ring 18, which is cushioned by elastic elements 19, 19 ', the residual energy still present is destroyed there. The axial displacement of the catch ring 15, 15 'adapts to the energy of the empty stroke: high energy, long braking distance; low energy, short braking distance. But even with a long braking distance, the catch ring is not deformed more than with a short braking distance.

When the catch ring is axially displaced, the striker 12 comes into contact with the catch ring in the region of the cone 15a and is held at a distance from the percussion piston 13 by the cone tension, so that no look-up occurs. If the machine is reattached, the striker will also be reset due to the movement of the tool, whereby the selected cone angle enables easy release from the cone clamping. When pushing back, the striker then comes into contact with the stop 15c, so that the catch ring 15 is also pushed back with the striker 12 until the striker is in the area of the percussion piston.

A comparison of Figures 2 and 3 shows that the main difference between these two embodiments is that in Figure 3 the catch ring is axially displaced against the force of a spring. Here too it is ensured that a frictional force is brought about between the sliding region 15d of the catch ring and the guide region 14a of the guide cylinder over the entire displacement path. With the axial displacement, the spring force must now also be overcome, which contributes to increasing the braking force. On the other hand, this spring force also contributes to a quicker transfer to the working position when the tool and the catch ring are reset. However, the spring cannot reset the catch ring alone.

In the third exemplary embodiment according to FIG. 6, the percussion piston acts directly on the tool via a shaft 13c '. In this respect, the percussion piston cannot be guided within the slotted retaining ring that is stored under pre-deformation. The catch ring 15 'therefore has a cone 15a 'which cooperates with a bend 13b' of the percussion piston. When empty blows occur, the catch ring 15 'is now moved forward in a manner comparable to that in the first two exemplary embodiments, but takes the guide 26 of the shaft 13c' of the percussion piston 13 'with it. Both elements together form the interception device. The maximum path of this displacement unit is limited by the stop 31a of the tool holder 31. If the device is now to be returned to the working position, the reset takes place in that folds 11a of the tool engage folds 26a of the guide bush 26 and bring about the reset of both the guide bush 26 and the catch ring 15 '. Here too, the cone 15a 'is chosen so that there is a slight reset. In all exemplary embodiments there is a targeted resetting of the interception device by abutment of the impact element on the interception device.

Claims (8)

Electropneumatic percussion or rotary hammer (10) with a free-flying percussion element, which swings back and forth in a guide cylinder (14) under the influence of the pressure fluctuations of an air cushion (27) and gives rhythmic, axial impacts to a tool (11) or tool holder, and with an interception device which has an elastically deformable catching element which is clamped in the guide cylinder (14) under elastic pre-deformation and intercepts the striking element with an empty tool with axial displacement in the direction of the tool axis (aa), characterized in that the interception device from which the tool (11) or the impact element acting on the tool holder itself is penetrated and has at least one catch element (catch ring (15, 15 ') which brakes the impact element on a guide region (14a) of the impact or rotary hammer which is coaxial with the tool axis (aa) when the tool is empty. Impact or rotary impact hammer according to claim 1, characterized in that a cone (15a, 15a) is the only catch element that has a longitudinally slotted catch ring (15, 15 ') to increase the braking force at the point where the impact element runs onto the catch ring when the tool is empty ') with an angle of preferably more than 5 °, which cooperates with bends (12b, 13b') of the striking element. Impact or rotary impact hammer according to claim 1 or 2, characterized in that the impact element is a striker (12) acted upon by an impact piston (13) which, in the working position, freely reciprocates within a cylindrical section (15b) of the catch ring (15). is held in a swinging manner, the striker (12) having bevels (12b, 12c) on its head part (12a), which with correspondingly shaped stops (15c, cone 15a) of the catch ring to limit the maximum path of the striker (12) within the catch ring ( 15) interact. Impact or rotary impact hammer according to one of the preceding claims, characterized in that the catch ring (15) with a sliding area (15d) of its outer lateral surface partially abuts the guide area (14a) of the guide cylinder (14) and in the remaining area of the outer lateral surface there is a relief on the tool side (15e). Impact or rotary impact hammer according to one of the preceding claims, characterized in that a spring (16) is mounted on the tool side in front of the catch ring (15) to cushion it. Percussion or rotary hammer according to one of claims 3 to 5, characterized in that the percussion piston (13) has a nose (13a), the length (l) of which is greater than the maximum possible path (s) of the striker (12) within the Catch rings (15). Percussion or rotary impact hammer according to claim 1 or 2, characterized in that the percussion piston (13) designed as a striking element is guided in a guide bush (26) which, together with the catch ring (15 '), forms the interception device and also axially between a stop ( 31a) of the tool holder (31) and the catch ring (15 ') which can be stopped at a stop (14b) of the guide cylinder (14). Percussion or rotary impact hammer according to claim 7, characterized in that the guide bush (26) has a stop (26a) on the tool side, which interacts with folds (11a) of the tool (11) to reset the catch element.

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