Tool holding device for hammer drill or chisel hammer with idle stroke and recoil damping

Abstract

The invention relates to a tool holding device for a hammer drill or chisel hammer, comprising a tubular tool holding body (1) for a tool, at an end stop of which a strike ram (2) is provided with a strike mechanism (3) arranged coaxially at the rear, wherein the tool holding body (1) is mounted axially elastically on both sides via at least two elastomeric elements (7, 8), and wherein, for one operating direction, at least one first elastomeric element (7) is arranged axially between the tool holding body (1) and the distal stationary housing stop (9) and, for the other operating direction, at least one second elastomeric element (8) is arranged axially between the tool holding body (1) and the distal stationary housing stop (9). At least one second elastomeric element (8) is arranged axially between the tool holding body (1) and the guide tube (5) of the striking mechanism (3) in order to achieve idle stroke and recoil damping, the elastomeric elements (7, 8) in each case interacting with the associated holding part in order to be fastened to the tool holding body (1) in an axially pre-stressed manner.

Description

Technical Field

[0001] The invention relates to a tool holder for a hammer drill or a chisel hammer, the tool holder comprising a tubular tool holder body for the tool, at the proximal end of which a striking ram of a striking mechanism arranged coaxially at the rear is arranged, on which a piston acts, wherein the tool holder body is elastically mounted axially on both sides via at least two elastomeric elements, wherein for one operating direction at least one first elastomeric element is arranged axially between the tool holder body and a distal stationary housing stop, and for the other operating direction at least one second elastomeric element is arranged axially between the tool holder body and a guide tube of the striking mechanism in order to achieve idle stroke and recoil damping. The invention also relates to a hammer drill or a chisel hammer for machining mineral materials, in particular concrete or rock, comprising such a tool holder.

[0002] The field of application of the invention extends primarily to hand-held hammer drills or chisel hammers, which are equipped with an electric motor drive. Such electric hand tools generate a linear alternating working movement via a mechanical striking mechanism, i.e. a reciprocating movement to be applied to the tool, which is designed as a mortise chisel in the case of a chisel hammer and as a percussion drill in the case of a hammer drill, for working preferably on mineral materials such as stone, concrete, etc. Due to the interaction with the workpiece and the operator's arm system and the internal mass and stiffness distribution, electric hand tools capable of driving the tool for normal striking have a complex vibration behavior, which must be suppressed as much as possible.

[0003] In the context of the electric hand tools of interest here, tool holders are primarily used to secure and guide drilling or chiseling tools in these machines. In the case of a hammer drill, the tool holder transmits the torque to the tool, ensures that the impact pulse is transmitted from the striking mechanism to the workpiece by allowing a limited axial movement, and prevents the tool from accidentally falling out of the machine. In the case of a striking mechanism pulse, the tool holder according to the invention is particularly subject to the so-called idle stroke and recoil stroke. In the case of an acceleration of the tool by the impact pulse of the striking mechanism, an idle stroke occurs, but this impact energy cannot be transmitted to the workpiece because the tool does not rest against the workpiece. When the tool rests too close and / or against an overly hard workpiece, a recoil stroke occurs, so that the impact pulse of the striking mechanism essentially reacts on the machine. Background Art

[0004] US 2020 119 600 A1 discloses a tool holding device of the type described, which is equipped with a component for suppressing idle stroke and recoil stroke. The tool holding device is basically composed of a tubular tool holding body for a tool, which is struck by a striking hammer (so-called rivet die) of a pneumatic striking mechanism at the rear. The tool is locked in the tool holding body by a locking mechanism. For idle stroke and recoil damping, the tool holding body is axially elastically mounted on both sides by two elastomer elements, wherein the first elastomer element is axially arranged between the tool holding body and the distal stationary housing stop. The second elastomer element is axially arranged between the striking hammer of the striking mechanism and the guide tube of the striking mechanism, which rests on the stationary housing stop opposite to the end face. In this case, the two elastomer elements are designed as O-rings and are prestressed via adjacent component structures (such as shoulder flanks, guide rings or sleeves), so that the axial play of the tool holder is reduced and the damping effect of the elastomer element can be optimally utilized. On the other hand, the axial prestressing of the elastomeric element between the tool holding body and the machine housing can cause friction between adjacent components, since the tool holding body can be moved relative to the machine housing, in particular also rotated relative to the machine housing, when the damping element is in the clamped state. With regard to battery-operated electric hand tools, such component friction can lead to energy losses with respect to the battery capacity, which manifests itself in a significant reduction in the machine operating time and, in extreme cases, can also lead to thermal failures due to heat development at the friction points.

[0005] The object of the present invention is therefore to further develop a tool holding device of the type described with lost motion stroke and recoil damping in such a way that the friction of the components caused by the damping element is effectively reduced by simple technical means. Summary of the invention

[0006] This object is achieved by a tool holder for a hammer drill or a chisel according to the preamble of claim 1 in combination with its characterizing features. The following dependent claims describe advantageous developments of the invention. With regard to a hammer drill or a chisel having a tool holder according to the invention, reference is made to claim 10.

[0007] The invention includes the following technical teaching, namely, in order to axially elastically mount the tool holding body on both sides, the elastomeric elements used for this purpose interact in each case with the associated holding part in order to be fastened to the tool holding body in an axially prestressed manner. The tool holder according to the invention is thus mounted in a floating manner and thus has reduced friction.

[0008] In other words, in the solution according to the invention, an elastomer element is used to dampen axial impacts, which is prestressed in the tool holder and therefore does not press against the transmission housing or the accessories arranged immovably thereon. The component friction in the area of ​​the tool holder is thereby significantly reduced. At the same time, the damping effect of the elastomer element on axial impacts is ensured in the sense of idle stroke and recoil damping. Due to the fact that the holding part fastens the elastomer element to the tool holding body in an axially prestressed manner, a certain degree of movement play occurs between the corresponding holding part and the component of the tool holding device adjacent to the housing, which play can be the size of the minimum gap width, so that the component friction can be completely eliminated thereby, and the relatively stiff spring characteristics of the prestressed elastomer element can nevertheless be fully utilized. This is because, without prestressing, the spring deflection of the elastomer element would initially be too soft before the damping effect appears. By fastening the elastomer element directly prestressed on the tool holding body realized according to the invention, an initially soft spring deflection is thereby avoided, which does not contribute to effective idle stroke and recoil damping.

[0009] According to a preferred embodiment, the retaining components according to the invention each have a stop ring or a stop sleeve for the associated elastomeric element and each have a locking ring for forcibly fastening the stop ring or the stop sleeve to the tool holding body in an axial position that produces the prestress. Thus, only two components that are easy to manufacture are sufficient to produce the prestress in the elastomeric element. In this case, the locking ring can be designed as a snap ring made of spring steel, and the corresponding stop ring or stop sleeve can be made from sheet metal as a stamped and bent part.

[0010] According to a first embodiment, the stop ring for the first elastomeric element should have an L-shaped cross section, which stop ring surrounds the first elastomeric element on the outer wall side of the tool holding body by means of two legs. Since the damping point associated with the first elastomeric element is realized on the outer circumference of the tool holding body, a stop ring that surrounds the first elastomeric element is ideal in order to save installation space.

[0011] The first elastomeric element preferably has a rectangular cross section to match the shape of the aforementioned stop ring. Thus, the entire space formed between the L-shaped stop ring and the corresponding housing shoulder on the tool holding body can be filled with elastomeric material to the greatest extent, which in turn allows for an optimal size design.

[0012] Similarly, it is proposed in the context of a preferred embodiment that a stop ring for the second elastomeric element, which likewise preferably has an L-shaped cross section, is arranged on the tool holding body so that the outer sides of its axial legs rest against the inner wall of the tool holding body. The mounting position of the second stop ring is therefore on the inner circumference of the tool holding body and preferably opposite its tube shoulder, against the outer side of which the first elastomeric element rests. In order to prestress the second elastomeric element in this mounting position, the associated stop ring can be pushed into the tubular tool holding body and fixed in the target position by a locking ring. On the side of the elastomeric element opposite to the stop ring, there is an additional stop ring between the elastomeric element and the tool holding body, which additional stop ring forms an end stop in the entry direction of the striking hammer, which end stop is recoil-damped by the second elastomeric element.

[0013] An elastomeric element with a circular cross section is preferably used for the above-mentioned second damping point. Since there is sufficient installation space in the radial direction at this damping point, a thick cross-sectional shape can be omitted.

[0014] Preferably, the idle stroke and recoil damping consists of exactly two annular elastomeric elements, which are arranged concentrically with the axis of rotation of the tubular tool holding body. In this case, the two elastomeric elements are each fastened to the tool holding body with an axial prestressing path of 1% to 30% of the axial element length. On the one hand, this prestressing path is sufficient not to excessively restrict the spring characteristics of the elastomeric element by the prestressing and, on the other hand, to apply sufficient prestress in the tensioning area to achieve an optimal spring characteristic for the intended use, as described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Other measures to improve the present invention are described in more detail below together with the description of the preferred embodiment reflecting the prior art. In the drawings: Figure 1 shows a partial longitudinal section of a tool holding device for a hammer drill or chisel hammer with lost motion stroke and recoil damping according to the prior art; and Figure 2 A partial longitudinal section is shown of a tool holder according to the invention for a drill hammer or a chisel hammer with lost motion stroke and recoil damping. DETAILED DESCRIPTION

[0016] As from Figure 1 As can be seen, the tool holding device known in the prior art and therefore conventionally used for hammer drills or chisel hammers, which are not shown in detail here, usually consists of a tubular tool holding body 1, into which the slotted distal end area of ​​the tool, which is also not shown here, can be inserted and then locked in a conventional manner.

[0017] In the locked state, the striking hammer 2 of the striking mechanism 3, which is arranged coaxially at the rear with respect to the tool, acts on the tool. The pneumatic striking mechanism 3 comprises a striking plunger 4, which is coaxially arranged on the striking hammer 2 and is accommodated in a dynamically sealed manner in a guide tube 5, on which a connecting rod drive 6 in turn acts in a generally known manner.

[0018] The tool holding body 1 of the conventional tool holding device is axially elastically mounted on both sides via two annular elastomeric elements 7 and 8. The first elastomeric element 7 provided for one operating direction is arranged axially prestressed between the tool holding body 1 and the distal stationary housing stop 9. The housing stop 9 is a component of a housing extension 11, which is non-movably attached to the machine housing 10 and extends it in the tool direction. The first elastomeric element 7 is surrounded by a stop ring 12, which is arranged to be displaceable relative to the tool holding body 1 and is loose in this respect.

[0019] For the other operating direction of damping, a second elastomer element 8 is used, which acts axially between the tool holding body 1 and the guide tube 5 of the striking mechanism 3, arranged as a component fixed to the housing on the positioning side. A bridging stop sleeve 13 is also provided here, which rests on the second elastomer element 8 on one side and on the guide tube 5 of the striking mechanism 3 on the other side. Opposite the second elastomer element 8 in the direction of the tool holding body 1 is a stop ring 14, which is also a bridging stop ring and serves as an end stop for striking the hammer 2 in the entry direction.

[0020] according to Figure 2 , the two elastomer elements 7 and 8 for idle stroke and recoil damping are not arranged in the tool holding device in order to be prestressed via the housing component. In the following description of the solution according to the invention, the same names and reference numerals as used in the context of the above description of the prior art apply to the corresponding components, and additional components are provided with further reference numerals and names.

[0021] Therefore, according to the invention, the two annular elastomeric elements 7 and 8 are each provided with an associated retaining component for axially prestressed attachment to the tool holding body 1, which retaining component attaches the retaining ring 12 to the tool holding body 1 with an additional locking ring 15 relative to the first elastomeric element, so that the first elastomeric element 7, which is rectangular in cross-section here, is prestressed between the visible housing shoulder of the tool holding body 1 and the retaining ring 12.

[0022] With regard to the second elastomeric element 8, although the stop ring associated therewith also has an L-shaped cross section, it is oriented in a different installation position relative to the adjacent components. This is because the short leg of the L-shaped stop ring 16 with its outer surface rests on the inner wall of the tool holding body 1 and is fixed to the tool holding body 1 in the target position, thereby prestressing the elastomeric element 8 via the associated locking ring 17. The second elastomeric element 8 has a circular cross section.

[0023] Due to the floating mounting of the tubular tool holding body relative to the stationary housing assembly in the tool holding device (this is achieved by means of two annular elastomeric elements 7 and 8), no friction-inducing axial forces act on the housing assembly or its accessories due to the prestressing of the elastomeric elements 7 and 8 achieved on the tool holding body, and therefore the relative movement does not cause friction.

[0024] The invention is not restricted to the preferred exemplary embodiments described above. On the contrary, modifications thereof are also conceivable, which modifications are covered by the scope of protection of the following claims. Thus, it is also possible to design a retaining component that applies a prestress on the tool holding body in a different way than an L-shaped retaining ring, for example. More precisely, other retaining components are also conceivable, such as flat rings, pressure sleeves, etc., as long as they can be accommodated in the tool holding device. Instead of an annular elastomeric element, a plurality of separate elastomeric elements can also be provided, which are arranged around the tubular tool holding body, for example, at a distance from each other.

[0025] List of Reference Numerals 1 Tool holding body 2 Strike hammer 3. Attack institutions 4 Impact plunger 5 Guide tube 6-link drive 7. First elastic element 8 Second elastic element 9 Shell shoulder 10 Machine housing 11 Shell extension 12First stop ring 13 Stop sleeve 14First stop ring 15First locking ring 16 Second stop ring 17 Second locking ring

Claims

1. A tool holding device for a hammer drill or a chisel hammer, the tool holding device comprising a tubular tool holding body (1) for the tool, at the proximal end of which is arranged a striking hammer (2) of a striking mechanism (3) arranged coaxially at the rear, the tool holding body (1) being axially elastically mounted on both sides via at least two elastomeric elements (7, 8), at least one first elastomeric element (7) being arranged axially between the tool holding body (1) and a distal stationary housing stop (9) for one operating direction, and at least one second elastomeric element (8) being arranged axially between the tool holding body (1) and a guide tube (5) of the striking mechanism (3) for the other operating direction, in order to achieve idle stroke and recoil damping, It is characterized in that The elastomeric elements (7, 8) interact in each case with an associated holding component in order to secure the tool holding body (1) in an axially prestressed manner.

2. The tool holding device according to claim 1, It is characterized in that The retaining components each have a retaining ring (12, 16) for the associated elastomeric element (7; 8) and each have a locking ring (15; 17) for positively fastening the retaining ring (12; 16) to the tool holding body (1) in a prestressed axial position.

3. The tool holding device according to claim 2, It is characterized in that The retaining ring (12) for the first elastomeric element (7) has an L-shaped cross section and surrounds the first elastomeric element (7) on the outer wall side of the tool holding body (1) by means of two legs.

4. The tool holding device according to claim 3, It is characterized in that The first elastomeric element (7) has a rectangular cross-section.

5. The tool holding device according to claim 2, It is characterized in that The retaining ring (16) for the second elastomeric element (8) has an L-shaped cross section and is arranged on the tool holding body (1) so that the outer sides of its axial legs bear against the inner wall of the tool holding body (1).

6. The tool holding device according to claim 5, It is characterized in that The second elastomeric element (8) has a circular cross-section.

7. A tool holding device according to any one of the preceding claims, It is characterized in that The locking ring (15, 17) is designed as a snap ring made of spring steel.

8. A tool holding device according to any one of the preceding claims, It is characterized in that For lost motion stroke and recoil damping, exactly two annular elastomeric elements (7, 8) are provided, which are arranged concentrically with the axis of rotation of the tubular tool holding body (1).

9. A tool holding device according to any one of the preceding claims, It is characterized in that The elastomeric element (7, 8) is fastened to the tool holding body (1) with an axial prestressing path of 1% to 30% of the axial element length.

10. A drill hammer or a chisel hammer for machining mineral material, in particular concrete or rock, having a tool holder according to any of the preceding claims.

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