EP2353790A1 - Manually-operated hammer drill - Google Patents

Abstract

The hammer has a rammer (4) comprising a piston (10) that executes a stroke movement (12) in a cylinder (11) formed in a spindle (3). The piston comprises an annular groove in which an annular seal is arranged. The annular groove comprises a cross sectional profile, that is larger than a cross sectional profile of the annular seal parallel to axis of rotation (6). The profile has an axial region with a maximum spacing of the cylinder at a groove base and another axial region with small distances of the cylinder, where the small distance is smaller than the maximum spacing.

Description

The present invention relates to a hand-held rotary hammer.

Typically, a hand-held hammer drill comprises a spindle which drives a tool holder in rotation about a rotation axis during drilling operation. The spindle itself is usually driven by means of an electric motor. Furthermore, such a hammer drill usually includes a pneumatic percussion hammering in impact mode against an inserted into the tool holder tool. Such a percussion usually has a piston which executes strokes parallel to the axis of rotation in a stroke in a cylinder formed in the spindle. The strokes of the piston to produce pressure oscillations in the cylinder, with the aid of a transmission piston is also driven to lift motions to strike against a percussion piston, so-called striker, which in turn transmits these shocks to the respective tool. In order to produce these pressure oscillations as effectively as possible, the piston is sealed relative to the cylinder appropriate. For this purpose, the piston may have at least one annular groove in which a ring seal is arranged. Due to the stroke movement of the piston, the ring seal is exposed to high wear.

Modern rotary hammers may also be equipped with a percussion stop that allows for drilling without impact operation. For example, this is a drive train between the spindle driving the electric motor and the percussion interrupted, for example by means of a clutch or the like. When the impact mode is switched off, the piston in the cylinder does not perform any lifting movements. In drilling operation, the spindle rotates about the axis of rotation and thus also about the piston. When the impact mode is deactivated This leads to a particularly high load on the ring seal. It can become overheated and damaged. A damaged ring seal reduces the sealing effect between the piston and cylinder, which reduces the effectiveness of the pressure oscillations and thus the efficiency of the hammer drill in impact mode.

The present invention addresses the problem of providing for such a hammer drill an improved embodiment, which is characterized in particular by a reduced wear.

This problem is solved according to the invention by the subject matter of the independent claim. Advantageous embodiments are the subject of the dependent claims.

The invention is based on the general idea to match the annular groove and the ring seal so that the annular seal is movable in the annular groove parallel to the axis of rotation, wherein the annular groove has a varying groove depth parallel to the axis of rotation. The sealing effect between piston and cylinder depends on the contact pressure of the ring seal on the cylinder. The greater this radial contact pressure, the greater the effective frictional forces. Due to the varying groove depth and the adjustability of the ring seal in the annular groove, the ring seal can assume a position in the moving piston, in which a smaller groove depth is present, whereby the sealing effect is increased. As soon as the piston is stopped, for example when passing through a dead center of the oscillating lifting movement, the ring seal can assume a position in which there is a greater groove depth, as a result of which the friction can be significantly reduced. As a result, the wear of the ring seal can be reduced for the drilling operation. This reduction in wear has a particularly significant effect if, by means of an optional impact shut-off the impact mode is deactivated and the piston is permanently stationary during the drilling operation.

In a respect to the axis of rotation axial region of a cross-sectional profile of the annular groove in which the largest groove depth is present, a groove bottom has a maximum distance from the cylinder. Axially adjacent thereto are then smaller distances. If the ring seal is in the range of the maximum distance, it is less biased against the cylinder, whereby the friction between the annular groove and cylinder for the drilling operation is reduced without impact operation. If, however, the ring seal is located in an axial region of the cross-sectional profile with smaller distances, the contact pressure of the ring seal against the cylinder increases, which is accompanied by an increased effectiveness of the sealing effect and consequently an increase in the performance of the hammer drill for impact operation.

It is particularly advantageous to provide the cross-sectional profile of the annular groove parallel to the axis of rotation on both sides of the one area with the maximum distance, each with an area having the smaller distances. This design has the advantage that the ring seal is widened outside the central region with the maximum distance and is thereby biased radially inwardly, whereby the ring seal has the tendency to slide automatically in the middle region with the maximum distance. This can be done especially when the impact mode is off and when the spindle is stopped. When the piston is stationary and the spindle is rotating, the movement of the ring seal in the middle area with the maximum distance is additionally supported, so that the ring seal automatically moves with the piston resting in the area with the maximum distance, in which the smallest friction between ring seal and cylinder occurs. If, however, the impact mode is activated, the strokes of the piston cause the ring seal to move out of the central area and, depending on the stroke direction, into one or the other Area moved in with a smaller distance. This relative movement between ring seal and annular groove can be supported on the one hand by the inertial forces and on the other hand can be promoted by the prevailing between the ring seal and the cylinder friction. In other words, in the moving piston, so activated impact mode, the ring seal within the annular groove automatically takes the positions with the smaller distances, which increases the sealing effect and thus the effectiveness of the impact mechanism.

According to an advantageous embodiment, the cross-sectional profile of the annular groove can be configured with mirror symmetry relative to a plane of symmetry running perpendicular to the axis of rotation. The region with the maximum distance is then arranged centrally in the cross-sectional profile of the annular groove, while the two adjacent end regions are then the same size. This results in substantially the same effects for the ring seal for both stroke directions of the piston.

According to another advantageous embodiment, the maximum distance in the context of manufacturing tolerances can be generated equal to or greater than a maximum diameter of the cross section of the ring seal measured parallel to the distance between the groove base and the cylinder. In other words, the maximum distance is adapted to the ring seal so that the ring seal does not touch the cylinder or virtually force-free when it is in the axial region of the maximum distance. The friction is minimized.

Other important features and advantages of the invention will become apparent from the dependent claims, from the drawings and from the associated figure description with reference to the drawings.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination given, but also in other combinations or in isolation, without departing from the scope of the present invention.

Preferred embodiments of the invention are illustrated in the drawings and will be described in more detail in the following description, wherein like reference numerals refer to the same or similar or functionally identical components.

Fig. 1

eine Seitenansicht auf einen Teil eines handgeführten Bohrhammers,

Fig. 2

eine Schnittansicht des Bohrhammers entsprechend Schnittlinien II aus Fig. 1,

Fig. 3-5

jeweils einen Längsschnitt durch einen Kolben eines Schlagwerks, bei verschiedenen Betriebszuständen,

Fig. 6

ein vergrößertes Detail VI des Kolbens aus Fig. 3 im Bereich einer Ringnut,

Fig. 7

eine Schnittansicht wie in Fig. 6, jedoch stark vereinfacht und bei einer anderen Ausführungsform.

It show, each schematically

Fig. 1

a side view of a part of a hand-held hammer drill,

Fig. 2

a sectional view of the hammer drill according to section lines II Fig. 1 .

Fig. 3-5

in each case a longitudinal section through a piston of a striking mechanism, in different operating states,

Fig. 6

an enlarged detail VI of the piston Fig. 3 in the region of an annular groove,

Fig. 7

a sectional view as in Fig. 6 but greatly simplified and in another embodiment.

According to the Fig. 1 and 2 includes a hand-held hammer drill 1 shown here only partially in a housing 2, a spindle 3 and a pneumatic Schlagwerk 4. The spindle 3 is used in drilling operation for driving a tool holder 5. In drilling operation, the tool holder 5 and the spindle 3 rotate about an axis of rotation 6. In the Fig. 1 and 2 is the axis of rotation 6 in the sectional plane II-II. The spindle 3 itself is for example with an in Fig. 1 indicated electric motor 7 is drive-coupled, which is arranged in a separate portion of the housing 2, which is omitted here for the sake of simplicity.

The striking mechanism 4 is used in a striking operation to hammer against a tool, not shown here, which is used for this purpose in the tool holder 5. For activating and deactivating the percussion mechanism 4, the hammer drill 1 may preferably be equipped with a percussion stop 8. This includes, for example, a manually operable switching element 9, with the impact mode can be turned on and off. For this purpose, for example, interrupts the dash 8 in a suitable manner, for example by means of a clutch, a drive path between the electric motor 7 and the striking mechanism. 4

Corresponding Fig. 2 For example, the percussion mechanism 4 has a piston 10 which in stroke operation in a cylinder 11 carries out lifting movements parallel to the axis of rotation 6. The cylinder 11 is formed in the spindle 3. The spindle 3 is designed to be hollow cylindrical. When the impact mechanism is switched on, the piston 10 performs oscillating strokes corresponding to a double arrow 12, which generate pressure pulsations in the cylinder 11 in a pressure-transmitting space 13. These are transmitted to a transfer piston 14. This transfer piston 14 is thereby also excited to oscillating strokes parallel to the axis of rotation 6. In this case, the transitional piston 14 strikes against a percussion piston 15, which is also referred to as an anvil 15. The percussion piston 15 in turn finally strikes against the tool used in the tool holder 5 tool.

For oscillating driving of the piston 10, the percussion mechanism 4 may have a crank drive 16 which couples the piston 10 via a connecting rod 17 with a drive wheel 18 which rotates with activated impact operation about a perpendicular to the axis of rotation 6 axis of rotation 19 and arranged eccentrically to the axis of rotation 19 Carrier pin 20 for driving the connecting rod 17 carries. The connecting rod 17 is rotatably coupled to the piston 10. When the impact mode is deactivated, the piston 10 does not carry out a lifting movement, so that it stands still with respect to the axis of rotation 6. The rotation lock between the connecting rod 17 and piston 10, for example, via a pin 23, with which the connecting rod 17 is connected to the piston 10. In the sectional views of the Fig. 3-5 is the cutting plane at 90 ° to the cutting plane of the Fig. 2 rotated, so that there the coupling between the connecting rod 17 and piston 10 via the pin 23 is better visible.

According to the Fig. 3-6 has the piston 10 on an outer side facing the cylinder 11 with respect to the rotation axis 6 in the circumferential direction closed circumferential annular groove 21 into which a ring seal 22 is inserted.

According to the in Fig. 6 shown detail view, the annular groove 21 has a cross-sectional profile 24 which is configured substantially U-shaped. This cross-sectional profile 24 lies in a cross-sectional plane which contains the axis of rotation 6. The cross-sectional profile 24 has two side flanks 25 and a groove bottom 26. In the example, the two side edges 25 are largely planar, wherein they each lie in a plane which extends perpendicular to the axis of rotation 6. Also, the ring seal 22 has a cross-sectional profile 27. In the example, this cross-sectional profile 27 is substantially circular designed. In that regard, the ring seal 22 is preferably an O-ring.

In an in Fig. 6 indicated by a dash-dotted line axial direction 49 which extends parallel to the axis of rotation 6, the cross-sectional profile 24 of the annular groove 21 has a groove width 28 which is greater than a likewise measured parallel to the axis of rotation 6 width 29 of the cross-sectional profile 27 of the ring seal 22. As a result, the Ring seal 22 within the annular groove 21 axially, that is parallel to the axis of rotation 6 adjustable, which in Fig. 6 indicated by a double arrow 30.

At the bottom of the groove 26, the cross-sectional profile 24 of the annular groove 21 has an axial region 31, in which the groove base 26 from the cylinder 11 has a maximum distance 32. Furthermore, the groove bottom 26 has at least one further axial region 33, 34, in which the groove base 26 has at least a smaller distance 35 from the cylinder 11, that is to say at least a distance 35 which is smaller than the maximum distance 32.

In the illustrated, preferred example of Fig. 6 has the cross-sectional profile 24 of the annular groove 21 parallel to the rotation axis 6 on both sides of the maximum distance 32 having region 31 each have a region 33 and 34 with the at least one smaller distance 35. Consequently, the maximum distance 32 provided with an area 31 between the two other areas 33, 34, so that it is also referred to below as the central region 31, while the others are also referred to below as end regions 33, 34.

Preferably, the in Fig. 6 shown symmetrical configuration of the annular groove 21 and its cross-sectional profile 24. In the example, the cross-sectional profile 24 of Ring groove 21 with respect to a plane of symmetry 36 which extends perpendicular to the axis of rotation 6, designed mirror-symmetrically. Further shows Fig. 6 other special features that can be realized optionally. For example, the central region 31 of the groove base 26 is concavely curved toward the ring seal 22. In particular, a circular arc-shaped curvature can be realized here. It is then particularly advantageous to choose an arc radius 37 of this arcuate central region 31 that is larger than a circle radius 38 of the circular cross-sectional profile 27 of the ring seal 22.

In contrast, the end portions 33, 34 are preferably shaped so as to be rectilinear in at least a substantial portion. These rectilinear sections are in Fig. 6 denoted by 39 and 40, respectively. The rectilinear sections 39, 40 of the end regions 33, 34 enclose therebetween an obtuse angle 41, which in particular is greater than 120 ° and can have, for example, 150 ° ± 10 °. The rectilinear sections 39, 40 of the end regions 33, 34 pass tangentially into the curved middle region 31. Likewise, here in the end regions 33, 34 an arcuate, in particular circular arc-shaped transition 42 to the rectilinear flanks 25 of the cross-sectional profile 24 of the annular groove 21 is provided.

Fig. 6 shows another special feature that can be realized as an option. In Fig. 6 the ring seal 22 is arranged in the central region 31 of the annular groove 21. It is thus located in the region of the annular groove 21, which has the largest groove depth, ie the maximum distance 32. This maximum distance 32 can now be chosen equal to a preferred embodiment as a diameter 43 of the cross section 27 of the ring seal 22, said diameter 43rd is measured parallel to the distance between groove base 26 and cylinder 11. The diameter 48 is measured parallel to the distance 32, since the originally circular cross section of the ring seal 22 under radial stress, which is also in the state of the Fig. 6 can be present, is deformed more or less oval or elliptical. Since the production of the annular groove 21 and the production of the ring seal 22 are exposed to manufacturing tolerances, the wording "equal to" is to be understood that the maximum distance 32 in the context of conventional manufacturing tolerances is equal to the diameter 43. Tolerance-related deviations can therefore occur and should also be recorded. By the specific embodiment proposed here, there is a quasi-force-free contact or just no contact between the ring seal 22 and the cylinder 11. Consequently, the friction is minimal when the piston 10 and rotating spindle 3 between ring seal 22 and cylinder 11. It is also possible to choose the maximum distance 32 greater than the diameter 43 of the ring seal 22.

In the example, the cross-sectional profile 24 of the annular groove 21 in the axial direction 49, ie parallel to the axis of rotation 6 at least 20% greater than the cross-sectional profile 27 of the ring seal 22 in the same direction, ie parallel to the axis of rotation 6. Expediently, the cross-sectional profile 24 of the annular groove 21 is parallel to the axis of rotation 6 at most 50% greater than the cross-sectional profile 27 of the ring seal 22nd

At the in Fig. 7 In the embodiment shown, the central region 31 is designed such that it extends in a straight line and parallel to the axial direction 49 and thus parallel to the axis of rotation 6. In that regard, the annular groove 21 has a constant portion in the cross-sectional profile 24 in the central region 31 in the axial direction 49. The two end regions 33, 34 are curved and pass tangentially into the rectilinear central region 31. In particular, the end regions 33, 34 can be curved in a circular arc, wherein they then each have a radius 50 or 51. The two radii 50, 51 are suitably the same size; However, they can be different in size. The respective radius 50, 51 is greater than the radius 38 of the cross-sectional profile 27 of the ring seal 22, which is present at least in the relaxed state of the ring seal 22. The end portions 33, 34 thereby form ramps along which the ring seal 22 is lifted radially outward as the ring seal 22 moves within the annular groove 21 from the central region 31 into one of the end regions 33, 34.

To power the electric motor 7, the hammer drill 1 can be connected with a cable, not shown here to a power grid. It is also possible to equip the hammer drill 1 with a battery, whereby the hammer drill 1 can be operated independently of a power grid. Such a battery is in Fig. 1 but not shown. It usually closes in relation to the presentation in Fig. 1 at the bottom of the housing 2 at.

With reference to the Fig. 3-5 the operation of the hammer drill 1 presented here or the special design of the annular groove 21 is explained in more detail below.

Fig. 3 represents an operating state in which with the help of the impact stop 8 the impact mode is deactivated. As a result, the piston 10 performs relative to the cylinder 11 no strokes; the piston 10 is. In this case, the ring seal 22 automatically positioned within the annular groove 21 in the central region 31, in which the maximum distance 32 prevails. As a result, the ring seal 22 has a minimum outer diameter 44, which generates a minimum friction with respect to the rotating spindle 3. With hammer mechanism 4 deactivated, the ring seal 22 automatically assumes this middle position, since the end regions 33, 34 act like ramps which center the ring seal 22 in the middle region 33. The ring seal 22 is driven by the inner bias of the ring seal 22, which experiences this when it is widened in the end regions 33, 34 by the ramp effect. This condition according to Fig. 3 can also occur when activated impact mode, and always when the piston 10 reverses the direction of movement when passing through one of its dead centers and is temporarily stationary.

In the 4 and 5 are reproduced states that occur when the piston 10 performs strokes. This is the case when the percussion mode 8 is activated by means of the impact cut-off 8 and thus the percussion mechanism 4 is switched on. These strokes then occur between the dead centers of the piston 10 and the piston movement.

Fig. 4 Due to inertial forces and / or due to the friction between the ring seal 22 and cylinder 11 while the ring seal 22 is axially displaced within the annular groove 21 against the stroke direction 45, causing them in the area 33 is moved, which faces the tool holder 5. In Fig. 4 the hub 45 is oriented to the right, so that the ring seal 22 is adjusted in the left end portion 33. It comes to the left flank 25 of the annular groove 21 to the plant. Since in this end region 33 of the smaller distance 35 is effective, there is a radial expansion of the annular seal 22, so that this has an outer diameter 46 in the sequence, which is greater than that in Fig. 3 shown outside diameter 44, the ring seal 22 has at rest piston 10.

In contrast, shows Fig. 5 the situation with a stroke 47 oriented in the direction of the tool holder 5. The forces acting on the ring seal 22 now displace more the ring seal 22 within the annular groove 21 in a direction away from the tool holder 5, ie again counter to the stroke 47 Fig. 5 the hub 47 is oriented to the left. Accordingly, the ring seal 22 moves within the annular groove 21 to the right, ie in the Right end region 34. There, too, due to the reduced distance 35 in the end region 34, there is a radial widening of the ring seal 22, as a result of which again a diameter 48 is present. Also, this diameter 48 is larger than that in Fig. 3 shown diameter 44, which is present when the piston 10 is stationary. Suitably, the two larger diameters 46 and 48 are the same size, which is the case in particular in a symmetrical embodiment of the annular groove 21.

The larger diameter 46, 48, which automatically adjusts during impact operation, increase the contact pressure of the ring seal 22 on the cylinder 11 and thereby improve the sealing effect and thus the performance of the striking mechanism 4 or of the hammer drill 1.

Claims (10)

Hand-held hammer drill, - With a spindle (3) which drives a tool holder (5) in rotation about a rotation axis (6), with a pneumatic percussion mechanism (4) hammering against a tool inserted into the tool holder (5) in impact mode, - wherein the percussion mechanism (4) has a piston (10), which in stroke operation in a spindle (3) formed in the cylinder (11) lifting movements (12) parallel to the axis of rotation (6), - wherein the piston (10) has at least one annular groove (21) in which a ring seal (22) is arranged, - wherein the annular groove (21) has a cross-sectional profile (24) parallel to the axis of rotation (6) is greater than a cross-sectional profile (27) of the annular seal (22) and the groove base (26) a region (31) with a maximum distance ( 32) of the cylinder (11) and at least one region (33, 34) with smaller distances (35) from the cylinder (11), which are smaller than the maximum distance (32). Hammer drill according to claim 1,
characterized,
that the cross-sectional profile (24) of the annular groove (21) to the rotational axis (6) on both sides of the one region (31) with the maximum distance (32) each have a region (33, 34) with the smaller distances (35) in parallel. Hammer drill according to claim 2,
characterized,
that the cross-sectional profile (24) of the annular groove (21) with respect to a perpendicular to the axis of rotation (6) plane of symmetry is designed mirror-symmetrically. Hammer drill according to one of claims 1 to 3,
characterized,
that the maximum distance (32) in the context of manufacturing tolerances is equal to or greater than a maximum diameter (43) of the cross section (27) of the ring seal (22) measured parallel to the distance. Hammer drill according to one of claims 1 to 4,
characterized, - That the one area (31) is concavely curved with the maximum distance (32) to the ring seal (22), - In particular, it may be provided that the area (31) with the maximum distance (32) with a radius of curvature (37) which is greater than a circular radius (38) of the circular cross-sectional profile (27) of the ring seal (22), curved arcuate , Hammer drill according to one of claims 1 to 4,
characterized,
in that the one region (31) with the maximum distance (32) extends in a straight line parallel to the axis of rotation (6). Hammer drill according to one of claims 1 to 6,
characterized, - That the respective region (33, 34) with the smaller distances (35) is rectilinear or has a rectilinear portion (39, 40), or - That the respective region (33, 34) with the smaller distances (35), in particular circular arc-shaped, curved or a curved, in particular circular arc-shaped, section has. Hammer drill according to one of claims 1 to 7,
characterized,
that the respective region (33, 34) merges with the small distances (35) tangentially in the region (31) with the maximum distance (32). Hammer drill according to one of claims 1 to 8,
characterized,
that the cross-sectional profile (24) of the annular groove (21) parallel to the rotational axis (6) at least 20% and / or a maximum of 50% greater than the cross-sectional profile (27) of the ring seal (22). Hammer drill according to one of claims 1 to 9,
characterized, - That a battery for powering the electric motor (7) for driving the spindle (3) and / or the striking mechanism (4) is provided, and / or - That a stroke shutdown (8) is provided, which allows a drilling operation without impact operation.

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