Hand-held machine tool system with impact body

Abstract

A hand-held power tool system comprising a hand-held power tool (20), in particular a rotary hammer or chisel hammer, with a percussion unit (1) comprising a striking element (10 / 10' / 10'') for converting a rotary drive movement of a drive device (2) into a linear alternating working movement for a tool (3). The linearly movable striking element (10') is designed to impact the tool. At least two different, interchangeable striking elements (10, 10', 10'') are provided for use in the percussion unit of the hand-held power tool, wherein a first striking element (10) is made of a steel material and is intended for use in the hand-held power tool, and wherein a second striking element (10') is designed as a hybrid striking element and is intended for use in the same hand-held power tool.

Description

[0001] The present invention relates to a hand-held power tool system comprising a hand-held power tool with a percussion unit comprising a percussion body for converting a rotary drive movement of a drive device into a linear alternating working movement for a tool, wherein the linearly movable percussion body is designed for striking the tool.

[0002] The application area of ​​the invention extends primarily to hand-held power tools, such as in particular impact drills, chiseling machines, rotary hammer machines or combination hammer machines, which have in common an impact mechanism integrated into the drive train, which is driven by a drive unit designed, for example, as an electric motor.

[0003] A percussion mechanism serves to convert the rotary drive motion of the electric motor into an alternating working motion for striking the tool, primarily a hammer drill or chisel. Between the percussion mechanism and the tool, a striking element according to the invention – a so-called impactor – is arranged, which, due to its inertia, generates a sufficiently large impulse. State of the art

[0004] According to generally known technology, the combination of high mechanical stress and high abrasive wear on an impactor leads to considerable wear of the impact surface, even when using high-grade steels. Furthermore, high-grade steels require a complex and energy-intensive heat treatment process. This, in turn, leads to increased contact stiffness, which increases the overall stress on the tool and can thus lead to premature tool failure. Since an impactor in an impact mechanism typically comes into contact with a large number of tools over its service life, the wear of the impact surface is more severe than the usual wear at the tool contact points.While there is a user tolerance for the need to replace tools due to wear, the impact elements of an impact mechanism are expected to have a long service life. Furthermore, a deformed impact element due to wear leads to increased tool wear, resulting in a poor sustainability profile.

[0005] Electric hand tools with homogeneously manufactured impact elements are therefore known from the state of the art.

[0006] Furthermore, an electric hand tool is known from DE 10 2010 043 837 A1, the impact mechanism of which acts on an impact body, which in turn impacts a tool. The impact body transmits the impulse via a front-facing stop surface to the coaxially arranged tool and is subjected to particularly high loads. This also applies, to a lesser extent, to the second stop surface on the opposite front face of the impact body, which interacts with the impact mechanism.

[0007] To withstand high impulse loads, the striking surface of the impactor is located on a first impactor part made of a different material than the rest of the impactor part. While the material of both impactor parts is the same, they differ in their heat treatment. This allows the impactor part to be manufactured with higher impact toughness, resulting in a homogeneous impactor.

[0008] However, the production of such striking devices is complex and expensive.

[0009] Against this background, the object of the present invention is to provide a hand-held machine tool system comprising a hand-held machine tool with a percussion mechanism comprising a percussion body, wherein optimized equipment of the hand-held machine is made possible in a structurally simple manner depending on the application. Disclosure of the invention

[0010] The problem is solved by a hand-held power tool system according to the preamble of claim 1 in conjunction with its characterizing features. The following dependent claims specify advantageous embodiments of the invention.

[0011] The invention includes the teaching that interchangeable impact elements are provided for identical hand-held power tools, so that application-optimized impact elements can be easily selected and used. Accordingly, at least two different types of interchangeable impact elements are provided, which are intended for use in the impact unit of one hand-held power tool, wherein a first impact element consists of a steel material and is in particular designed as a homogeneous impact element and is intended for use in the hand-held power tool, and wherein a second impact element is designed as a hybrid impact element and is intended for use in the same hand-held power tool.

[0012] This allows for the use of highly wear-resistant impact elements during development processes, repairs, specific product lifecycles, and for particular markets with varying wear and service life requirements, without requiring any modifications to the design of the impact mechanism components surrounding the impact element. In applications within markets with high demands, hybrid impact elements can be used, while in markets with lower demands, homogeneous impact elements are particularly suitable. No other modifications to the power tool are necessary.

[0013] The choice of impact element can be selected particularly depending on the desired service life of the hand-held power tool, whereby the homogeneous impact element and the hybrid impact element may differ in terms of mass and / or shape.

[0014] A hybrid striking device is understood here to be a striking device that has at least two different materials that are bonded together.

[0015] In order to make replacing the impact elements particularly easy and especially without further adjustments to the hand-held power tool, the first impact element and the second impact element can have an essentially identical length when viewed in the direction of impact.

[0016] According to another measure improving the invention, it is proposed that the interchangeable impact elements be provided with identical tool-side and / or impact element-side connection diameters. This ensures coordination with the respective adjacent components of the action chain, in particular with regard to an adjacent tool holder.

[0017] In an advantageous embodiment of the invention, the first striking body and the second striking body have essentially an identical external shape.

[0018] In an advantageous embodiment of the invention, the second striking element comprises a steel main component and, on its end face facing the tool, a contact element with a preferably convex impact surface, which is bonded to the steel main component. The contact element is made of a harder material than the main component, in particular a metal matrix composite. This allows for the production of a low-wear impact surface with minimal manufacturing effort. In other words, a contact element made of a metal matrix composite, preferably with a convex (i.e., outwardly curved) impact surface, is attached to a main body manufactured conventionally by turning, forging, extrusion, or the like, on the end face facing at least the tool.

[0019] Thanks to this special choice of material and the geometric design, an almost constant tool load can be achieved over the entire service life of the hand-held power tool, as end-face wear of the impact body is minimized.

[0020] In the hybrid striking body, the contact element can preferably be designed either as a support or as an insert. In the support-type design, the striking body has a connecting surface on its end face facing the tool for attaching the disc-shaped contact element, which preferably has a convex impact surface. In the insert-type design, the contact element is particularly cylindrical or conical, and the striking body has a recess on an end face facing the tool for receiving the contact element, which preferably has a convex impact surface.If a conical contact element is used instead of a cylindrical contact element, its conical basic shape offers an additional self-centering effect in the direction of impact, although this results in an increased joining gap load on the outer surface, which can be reduced by centering strips or similar spacers protruding from the outer surface.

[0021] Preferably, the contact element is bonded to the recess of the striking mechanism body. According to a preferred embodiment, the bond is produced by soldering.

[0022] Preferably, the contact element is bonded to the end face or within the recess of the striking body. This bond can be achieved through adhesive bonding or soldering and should cover the entire contact area between the contact element and the end face / recess of the striking body, both on the end face and, if applicable, on the outer surface, to maximize holding force.

[0023] In a particularly advantageous embodiment of the invention, it is provided that the steel impact body has a recess on the end face facing the tool for receiving a contact element, in which the contact element is at least partially arranged.

[0024] The metal matrix composite material of the contact element preferably contains hard particles held together by a metal matrix. This results in very high impact strength. In contrast, the steel material of the remaining impact body can be conventional case-hardening steel, heat-treatable steel, or tool steel. For example, a tungsten carbide-cobalt cemented carbide (WC-Co) is suitable as the cemented carbide material used within the metal matrix composite. The WC to Co ratio is preferably greater than 6, and particularly preferably greater than 10, to achieve the desired workpiece properties.

[0025] The impact mechanism used in the hand-held power tool system according to the invention is preferably designed as a pneumatic impact mechanism and comprises an eccentric drive for converting the rotary drive movement into a linear alternating movement by means of coupling to an exciter piston with a connecting rod, which is guided slidably in a guide tube, in order to interact with an impact piston arranged opposite it in the guide tube via the compressed air column generated between them. The impact piston in turn corresponds to the designed impact body. Detailed description based on drawing

[0026] Further measures improving the invention are described in more detail below, together with a description of preferred embodiments, with reference to the figures. The figures show: Fig. 1 shows a schematic longitudinal section through an exemplary impact mechanism of a chisel hammer of a hand-held power tool system with a tool inserted; Fig. 2 shows a schematically detailed longitudinal section through the impact mechanism according to Fig. 1 To illustrate the impact chain; Fig. 3a shows a longitudinal section through a homogeneous impact body for the chisel hammer according to Fig. 1 ; Fig. 3 Longitudinal section through a hybrid impact body for the chisel hammer according to Fig. 1 ; and Fig. 3 shows a longitudinal section through an alternatively designed hybrid impact body for the chisel hammer according to Fig. 1 .

[0027] In Fig. 1 A hand-held power tool 20 designed as a chisel hammer, part of a hand-held power tool system 30, is shown. According to Fig. 1A percussion arrangement 25 for the chisel hammer 20 essentially consists of a percussion unit 1 for converting a rotary drive movement of a drive device designed as an electric motor 2 into a linear alternating working movement for a tool 3, which here is designed as a chisel.

[0028] The pneumatic percussion unit 1 comprises an eccentric drive 4 for converting the rotary drive motion generated by the drive motor 2 into a linear alternating motion by coupling it to an exciter piston 5 with a connecting rod 6. The exciter piston 5 is guided slidably in a guide tube 7, forming a piston-cylinder unit. Opposite the exciter piston 5, a percussion piston 8 is also arranged slidably in the guide tube 7. A damping air column is generated between the exciter piston 5 and the percussion piston 8 as a result of the linear alternating motion.

[0029] The impact unit 1 acts on an adjacent impact body 10, made of a steel material, which is also slidably housed in an extension 9 of the guide tube 7. The impact body 10 has a rotationally symmetrical shape and, within the action chain, acts in a backward-percussive manner on the tool 3.

[0030] According to Fig. 2 The two end faces 11a and 11b of the striking body 10 are each provided with a convex impact surface. Along the chain of action, the global stress on the striking components is minimized. However, the local stress on the striking components at the contact points is very high. The convexly shaped end faces 11a and 11b of the striking body 10 reduce the contact stiffness of the impact transmission and stretch the temporal contact force curve, which has a stress-reducing effect.

[0031] Fig. 3a shows the striking body 10 according to Fig. 1Uniquely positioned. The impact piston 10 is homogeneous and manufactured in one piece from a single steel material. Figs. 3b and 3c Further impact bodies 10' or 10" of the hand tool system 30 are shown, wherein the impact bodies 10' or 10" are also intended and suitable for use with the chisel hammer 20.

[0032] All striking elements 10, 10', 10" have an essentially identical length L, an essentially identical diameter D1 in the region of the end face 11a, and an essentially identical diameter D2 in the region of the end face 11b. Overall, the shape of the striking elements 10, 10', 10" is essentially identical, so that the striking elements 10, 10', 10" can all be used without modification of the striking mechanism 1 or other components of the chisel hammer 20 and are interchangeable.

[0033] In contrast to the striking element 10, the striking elements 10' and 10" have a hybrid shape. This means that a contact element 12' or 12" is provided on the tool side, respectively.

[0034] The impact body 10' has a steel main part 14' in which a recess 13 is provided for receiving the contact element 12'. The contact element 12' has a convex contact surface for interaction with the tool 3. In this embodiment, the contact element 12', which is cylindrical in its basic form, consists of a metal matrix composite material containing a tungsten carbide-cobalt cemented carbide to increase its impact strength. The contact element 12' is designed as an insert.

[0035] The rotationally symmetrical contact element 12' can be bonded to the recess 13 of the striking body 10' by means of a soldered connection. Alternatively, the contact element can be conical and have several centering strips or spacers arranged circumferentially along a surface and projecting from the surface. Alternatively or additionally, spacers can also be provided in the area of ​​an end face.

[0036] The striking body 10" also has a contact element 12". Unlike the contact element 12', the contact element 12" is not located in a recess, but rather on an end face 15 of a steel main part 14" of the striking body 10". The contact element 12" is disc-shaped and is bonded to the main part 14" via a flat contact surface, for example, by a soldered connection. The contact element 12" is specifically made of a metal matrix composite material comprising a tungsten carbide-cobalt cemented carbide, which ensures increased impact strength under high loads. The contact element 12' is designed as a support and has a convex contact surface for interaction with the tool 3.

[0037] The invention is not limited to the preferred embodiments described above. Rather, variations thereof are also conceivable and are included within the scope of protection of the following claims. For example, it is also conceivable that, under suitable geometric conditions, a press fit is created between the contact element and the impact body, piston, or tool to join the two components. If a material-bonded connection is chosen, it is also conceivable to implement this, for example, as an adhesive bond. Reference symbol list

[0038] 1 Impact mechanism 2 Electric motor 3 Tool 4 Eccentric drive 5 Exciter piston 6 Connecting rod 7 Guide tube 8 Impact piston 9 Tool holder 10 Impact element 11 End face 12 Contact element 13 Recess 14 Main part 15 End face 20 Chisel hammer 25 Impact mechanism assembly 30 Hand tool system Diameter Length

Claims

1. Hand-held power tool system (30) comprising a hand-held power tool (20), in particular a rotary hammer or chisel hammer, with a percussion unit (1) comprising a percussion body (10, 10', 10") for converting a rotary drive movement of a drive device (2) into a linear alternating working movement for a tool (3), wherein the linearly movable percussion body (10, 10', 10") is designed for striking the tool (3), characterized by the fact that at least two different interchangeable striking bodies (10, 10', 10") are provided, which are intended for use in the impact unit (1) of a hand-held power tool (20), wherein a first striking body (10) is made of a steel material and is intended for use in the hand-held power tool (20), and wherein a second striking body (10' or 10") is designed as a hybrid striking body and is intended for use in the same hand-held power tool (20).

2. Hand-held power tool system according to claim 1, characterized by the fact that The first striking body (10) and the second striking body (10`, 10") have an essentially identical length extension (L) when viewed in the direction of impact.

3. Hand-held power tool system according to claim 1 or 2, characterized by the fact that the impact bodies (10, 10`, 10") are designed with essentially the same tool-side and / or piston-side connection diameters (D1, D2).

4. Hand-held power tool system according to one of the preceding claims, characterized by the fact that the first striking body (10) and the second striking body (10`, 10") have essentially an identical external shape.

5. Hand-held power tool system according to one of the preceding claims, characterized by the fact thatthe second impact body (10`, 10") has a steel main component (14") and in the area of ​​its end face (15) facing the tool (3), a contact element (12`, 12") joined to the steel main component (14`, 14") with a preferably convex impact surface, wherein the contact element (12`, 12") is made of a harder material than the main component (14`, 14"), in particular a metal matrix composite material.

6. Hand-held power tool system according to claim 5, characterized by the fact that the contact element (12`, 12") is designed in the form of a pad or in the form of an insert.

7. Hand-held power tool system according to claim 6, characterized by the fact that The striking body (10') has a recess (13) on the end face facing the tool (3) for receiving the cylindrical or conical contact element (12').

8. Hand-held power tool system according to one of the preceding claims, characterized by the fact thatthe percussion unit (1) is designed in the manner of a pneumatic percussion unit, comprising an eccentric drive (4) for converting the rotary drive movement into a linear alternating movement by coupling to an excitation piston (5) with connecting rod (6), which is guided slidably in a guide tube (7) in order to interact with an opposing percussion piston (8) via a compressible air column generated between them.

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