EP4182123A1

EP4182123A1 - Hand-held power tool, tool and hand-held power tool system with a certain rotational speed / stroke frequency ratio

Info

Publication number: EP4182123A1
Application number: EP21705567.2A
Authority: EP
Inventors: Maximilian Knyrim; Markus Hartmann; Bastian PLÜMACHER; Olaf Koch
Original assignee: Hilti AG
Current assignee: Hilti AG
Priority date: 2019-08-19
Filing date: 2021-02-22
Publication date: 2023-05-24
Also published as: WO2022012786A1; EP4182124A1; US20230311289A1; EP3845340A1; WO2022012785A1; EP3854532A1; US20230278182A1

Abstract

The invention relates to a hand-held power tool (12), in particular a hammer drill, comprising a tool holder (16), a striking mechanism (32) and a rotary drive (34), wherein the hand-held power tool (12) is designed to rotate a tool (18) accommodated in the tool holder (16) about a longitudinal axis (L) of the tool (18) at a rotational speed n and to drive same along the longitudinal axis (L) with a striking movement at a stroke frequency f, wherein the striking mechanism (32) is designed as a direct electromechanical, electro-pneumatic or electromagnetic striking mechanism. The hand-held power tool is characterised in that the ratio of the rotational speed n to the striking frequency f, at least at a working point of the hand-held power tool (12), is max. 5.0 U/Min./Hz, or, at least at the working point of the hand-held power tool (12), the rotational speed n is max. (0,2*(f/Hz-22)^2+80) U/Min according to the striking frequency f, in particular for striking frequencies f in the region of 20 to 60 Hz. The invention also relates to a tool (18) and a hand-held tool system (10). It allows for a particularly effective and efficient processing of e.g. rocks.

Description

Hand machine tool, tool and hand machine tool system with a specific speed-impact frequency ratio

description

The present invention relates to a hand-held power tool, in particular a hammer drill, with a tool holder, a percussion mechanism and a rotary drive, the hand-held power tool being set up to rotate a tool held in the tool holder at a speed n around a longitudinal axis of the tool and at an impact frequency f along it to drive the longitudinal axis with an impact movement, the impact mechanism being designed as a direct electromechanical, as an electropneumatic or as an electromagnetic impact mechanism. The invention further relates to a tool and a hand-held power tool system.

The contents of the descriptions, the claims and the drawings of the European applications EP19192219A of 08/19/2019, EP19193854 of 08/27/2019 and EP19195363A of 09/04/2019 form part of this description by way of express reference.

For ecological reasons as well as for reasons of cost, there is a particular need for handheld power tools that work particularly effectively and efficiently, for example rotary hammers, associated tools and handheld tool systems, in particular having a handheld power tool and a tool for the handheld power tool.

In order to take account of this need, it is therefore an object of the present invention to provide hand-held power tools, tools and hand-held power tool systems of the generic type that can be operated with particularly high efficiency.

The task is solved by a hand tool, in particular a hammer drill, with a tool holder, a percussion mechanism and a rotary drive, the hand-held power tool is set up to rotate a tool held in the tool holder at a speed n about a longitudinal axis of the tool and to drive it with a percussion movement along the longitudinal axis at a percussion frequency f, the percussion mechanism being designed as a direct electromechanical, electropneumatic or electromagnetic percussion mechanism, where the ratio of the speed n to the impact frequency f is at most 5.0 rpm/Hz at least at one operating point of the handheld power tool or where at least at the operating point of the handheld power tool the speed n depends on the impact frequency f, in particular for impact frequencies f in the range from 20 to 60 Hz, maximum (0.2*(f/Hz-22) ^A 2+80) rpm. amounts to.

A handheld power tool can achieve particularly low friction losses if the ratio of the speed n to the impact frequency f is at most 4.0 rpm/Hz, particularly preferably at most 3.0 rpm/Hz, at least at the operating point of the handheld power tool.

The operating point can correspond to a drill-hammering operation of the hand-held power tool. In particular, it can correspond to full-load operation of the hand-held power tool. Alternatively or in addition, the operating point can correspond to an operating state with the highest possible impact frequency f or the highest possible rotational frequency n depending on the device.

The hand-held power tool can be set up in particular for processing natural or artificial rocks, for example masonry and/or rocks containing cement.

To distinguish it from pure chiseling machines, for example, the speed at the working point can be at least 1 rpm. or depending on the impact frequency f at least f/Hz*0.1 rpm, preferably at least f/Hz*2 rpm.

Alternatively or additionally, a conversion angle, ie the angle by which the tool is offset between two impacts, can be at least 15 degrees, preferably at least 20 degrees, at least at the working point. Alternatively or in addition, the speed n can be at least half of the maximum values mentioned above, depending on the impact frequency f.

The invention is based on the idea that crushing of such rocks, for example to form a borehole, can usually be carried out primarily by the impact movement. In particular, the comminution can take place by means of a tool tip of a tool held in the tool holder, for example a rock drill, in the form of a rhythmic beating, ie a chiselling.

During comminution, the parallel rotating movement usually has the purpose of turning and/or displacing the tool tip so that comminution can take place over a certain processing area, i. H. not just at a single point. In addition, the rotary motion—at least in the case of tools with a helical structure formed along their longitudinal axis, such as, for example, in the case of rock spiral drills—is required to convey drill cuttings produced at the tool tip.

However, with increasing speeds n, there are considerable friction losses, some of which increase disproportionately.

Considerable energy savings can thus be achieved if the hand-held power tool, as provided according to the invention, performs a rotary movement that is slow in relation to the impact frequency, at least at the operating point. Preferably, however, the rotational movement at the working point is still so fast that a sufficient rotational displacement of the tool can take place between two impacts. Depending on the type of tool used, the speed can also be selected as a function of a required drill cuttings conveying speed, in particular if there is a structural connection between them.

The invention also makes it possible to avoid damage to the tool and/or damage to the rock to be worked as a result of overheating due to friction and heat. Occupational safety can also be increased. The invention is therefore also based on the surprising finding that hand-held power tools that allow a combination of an impact movement with a rotary movement at least at the working point can be improved by selecting and/or setting the ratio between the speed n and the impact frequency f at least at this working point .

It is therefore conceivable for a handheld power tool with different operating modes, for example a pure rotary movement or drilling mode and a hammer drill mode corresponding to the operating point, to set up the handheld power tool in such a way that by changing to the hammer drill mode or when the operating point is reached, the speed n is at most the maximum values according to the invention is limited and when leaving the hammer drill mode or the operating point, this limitation is lifted and/or the maximum value of the speed n is set to a higher value.

The hand-held power tool can have a tool recognition device for identifying a type of tool used in the tool holder. Alternatively or additionally, the type of tool used in the tool holder can also be set by a user of the hand-held power tool.

The handheld power tool can also be set up, depending on the type of tool, preferably at least at the operating point, to limit the speed n to a maximum value, which preferably corresponds at most to the maximum values according to the invention, and/or to a minimum value. For example, a particularly low maximum value of the speed n can be set for a tool designed as a suction drill or a hollow drill, whereas a somewhat higher maximum value is set for a tool with a helical structure, but preferably no more than the maximum values according to the invention.

In particular, the hand-held power tool can be set up to calculate the value or the maximum value of the ratio between the rotational speed n and the impact frequency f at different impact frequencies f and/or within different frequency ranges of the impact frequency f, to vary in particular also taking into account a type of tool used. This is based on the idea that at very low frequencies, for example, a minimum speed n can be ensured by this variation. At least in the case of individual tool types, the increase in friction due to the rotary movement can be less than the third power, so that relatively higher speeds n can also be used relative to the impact frequency f.

For this purpose as well as generally for reasons of the range of adjustability of the handheld power tool, it is favorable if the handheld power tool has a multi-stage gear.

The hand-held power tool can be set up to control a gear based on or at least taking into account the determined or set type of tool held, in particular to select one of the gear stages of a multi-stage gear as a function thereof. Alternatively or additionally, in the case of hand-held power tools with at least two drive units, a ratio of the speeds of the two drive units to one another can also be set or adjustable, in particular as a function of the set or determined type of tool held.

Overall, the ratio of the rotational speed n to the impact frequency f can have a U-shaped or at least essentially U-shaped course over the used frequency range of the impact frequency f.

If the total power available from the hand-held power tool is limited, this also makes it possible to direct a larger proportion of the total power to the impact movement, so that the propulsion achieved in the rock can be increased with the same total power. Alternatively or additionally, the total power used can also be reduced while maintaining the propulsion achieved.

An electric impact mechanism can include electromechanically operating impact mechanisms, in particular with a drive that generates a rotation, for example cam impact mechanisms or notched impact mechanisms, electropneumatic, that is, an air chamber for transmission and/or transformation of the percussion movement, percussion mechanisms as well as electromagnetic percussion mechanisms, for example percussion mechanisms based on the principle of a railgun and/or having a linear motor. The hammer mechanism can be a direct hammer mechanism, ie with a drive that is free of rotational movement, or an indirect hammer mechanism, ie with a drive based on a rotational movement.

The hand-held power tool can have at most one drive unit, in particular a motor, for driving the percussion mechanism and the rotary drive. In other words, the hammer mechanism and the rotary drive can be driven by a common drive unit. Alternatively, a separate drive is also conceivable, in particular by means of at least two drive units. The speed n and/or the impact frequency f or their relationship to one another can be fixed or can be fixed by the device. For example, one or more gears of the hand-held power tool can be used and/or selected automatically by the hand-held power tool at the operating point. The gear or gears can have transmission ratios that are matched to the working point.

If the hand-held power tool has a pneumatic, in particular an electro-pneumatic, drill cuttings conveying device, then particularly low speeds n can be used since drill cuttings can be conveyed by the drill cuttings conveying device. The drill cuttings conveying device can be a suction device or can have such a device.

The increases in effectiveness and efficiency achieved according to the invention are particularly useful when the hand-held power tool is designed as a portable device. In particular, the hand-held power tool can weigh a maximum of 25 kg. The power delivered by the impact mechanism can be limited to a maximum of 2 kW, particularly preferably to a maximum of 1 kW.

The handheld power tool can particularly preferably be operated wirelessly. It can preferably have an accumulator, in particular an accumulator containing lithium. The hand-held power tool can, for example, have a portable power storage device, for example a rechargeable battery. This can be through the invention achieved increases in effectiveness and efficiency achieve particularly long runtimes with a single battery charge.

According to the invention, the gear or gears can have particularly high, for example 50:1, reduction ratios. Therefore, handheld power tools are particularly preferred that include at least one overrunning clutch, a crank mechanism or a rotary thrust mechanism. For example, combinations of the overrunning clutch with the link gear and/or the circular thrust gear are also conceivable. Further details according to the invention on particularly advantageous configurations of the overrunning clutch, the slotted link mechanism and the circular thrust mechanism can be found in the European patent applications mentioned at the outset, which are incorporated by reference as part of this description.

In the case of a tool having a helical structure for a hand-held power tool according to the invention, the pitch of the helical structure can be increased compared to known helical structures, in particular of tools for working rock.

The scope of the invention also includes a tool for a handheld power tool according to the invention, comprising a tool tip, a tool shank and a shank for receiving the tool in the tool holder of the handheld power tool, with a material transport channel being formed at least along the tool shaft, the material transport channel having a Minimum cross-sectional area of 19 mm ² or at least 6%, particularly preferably at least 12%, of the cross-sectional area of the borehole that can be produced by the tool. In particular, when working at comparatively low speeds n, larger drill cuttings particles can increasingly arise, which can also be safely transported away due to the comparatively large material transport channel. A blockage of the tool can thus be avoided even at low speeds n in relation to the impact frequency f.

In general, the tool can be designed as a hollow drill. Such a tool enables drill cuttings to be conveyed particularly efficiently either through the material transport channel or through a flushing fluid which is preferably transported via the material transport channel to the tool tip, so that drill cuttings can be flushed away from the tool tip for transport.

In general, the tool and/or the hand-held power tool can be set up to convey the drill cuttings mechanically, pneumatically or hydraulically.

In particular, the tool can be designed as a suction drill. The drilling conveyor device can have a suction device that is in particular adapted to the tool.

Also within the scope of the invention is a use of a tool according to the invention for processing a natural or artificial rock.

The object is also achieved by a hand-held power tool system comprising a hand-held power tool according to the invention and a tool according to the invention.

The handheld power tool system can be set up for processing natural or artificial rocks.

Further features and advantages of the invention result from the following detailed description of exemplary embodiments of the invention, using the figures of the drawing, which shows details essential to the invention, from the claims and from the description and the figures of the drawing, which also shows details essential to the invention, by Reference to incorporated European patent applications mentioned at the outset. The features shown there are not necessarily to be understood to scale and are presented in such a way that the special features according to the invention can be made clearly visible. The various features can each be implemented individually or in groups in any combination in variants of the invention. In the schematic drawing, exemplary embodiments of the invention are shown and explained in more detail in the following description.

The only figure (Fig. 1) shows a hand tool system.

A handheld power tool system 10 has a handheld power tool 12 . The handheld power tool 12 can be operated wirelessly. For this purpose it has a rechargeable accumulator 14 . It is designed as a portable device.

It also has a tool holder 16 .

A tool 18 is accommodated in this. For this purpose, the tool 18 has a tool shank 20, at one end of which an insertion end 22 and at the other end of which a tool tip 24 are formed.

The tool 18 is designed as a hollow drill and in particular as a suction drill. For this purpose, it has a material transport channel 26 running inside the tool shank 20 and shown schematically in FIG.

The material transport channel 26 has a cross-sectional area of 15% of the cross-section of a borehole to be created by the tool 18 .

Furthermore, the hand-held power tool 12 has an operating mode selector switch 30 for switching between different operating modes, in particular for switching between a pure drill mode, a pure chisel mode and a hammer drill mode. In the position of the mode selector switch 30 shown, the hammer drill mode is selected. The hand-held power tool 12 can be set in motion by means of an actuating lever 31 and, in particular, can be operated at an operating point with the highest possible speed determined by the device. The hand-held power tool 12 also has an electropneumatic percussion mechanism 32 and a rotary drive 34 . The percussion mechanism 32 and the rotary drive 34 are driven by a common drive unit 36, an electric motor. The handheld power tool 12 is set up to rotate the tool 18 accommodated in the tool holder 16 at a speed n about a longitudinal axis L of the tool 18 and to drive it with an impact frequency f along the longitudinal axis L with an impact movement.

In this exemplary embodiment, the ratio of the rotational speed n to the impact frequency f at the working point is 4.0 rpm/Hz.

In alternative exemplary embodiments A2, A3, A4, A5 and A6, which can be constructed in principle, in particular structurally identically, to the exemplary embodiment described above, this ratio depends on the impact frequency f at the respective operating point, in this exemplary embodiment with impact frequencies f in the range from 20 to 60 Hz, as can be seen from Table 1 below. However, the speed n does not exceed (0.2*(f/Hz-22) ^A 2+80) rpm.

Table 1

It can be seen that the ratio is slightly increased at particularly low impact frequencies f. In this case, even with low impact frequencies f, this enables a rock to be machined to be crushed evenly. A particularly energy-saving operation results at medium impact frequencies f.

On the other hand, in the range of high comminution performance, ie at higher impact frequencies f, the ratio increases again.

In order to be able to set these different ratios, the hand-held power tool 12 has a multi-stage gear (not shown in FIG. 1). The transmission can have, for example, an overrunning clutch, a link mechanism or a circular thrust mechanism in accordance with the European patent applications mentioned at the outset and incorporated by reference.

Claims

patent claims

1. Hand tool (12), in particular a hammer drill, with a

tool holder (16), an impact mechanism (32) and a rotary drive (34), the hand-held power tool (12) being equipped with a tool (18) held in the tool holder (16) at a speed n about a longitudinal axis (L) of the tool (18) and to be driven with an impact movement along the longitudinal axis (L) with an impact frequency f, the impact mechanism (32) being designed as a direct electromechanical, electropneumatic or electromagnetic impact mechanism, characterized in that the ratio of the speed n to the impact frequency f at least at one operating point of the handheld power tool (12) is at most 5.0 rpm/Hz or that at least at the operating point of the handheld power tool (12) the speed n is a function of the impact frequency f, in particular for impact frequencies f in the range of 20 to 60 Hz, at most (0.2*(f/Hz-22) ^A 2+80) rpm. amounts to.

2. Hand tool according to the preceding claim, characterized in that the ratio of the speed (n) to the impact frequency (f) at least at the operating point of the hand tool is at most 4.0 rpm / Hz, particularly preferably at most 3.0 rpm /Hz.

3. Hand tool according to one of the preceding claims, characterized in that the hand tool (12) has at most one drive unit, in particular a motor, for driving the impact mechanism (32) and the rotary drive (34).

4 Hand-held power tool according to one of the preceding claims, characterized in that the hand-held power tool (12) has a tool recognition device for identifying a type of tool (18) used in the tool holder (16) and/or that it is set up in such a way that the type of tool in the tool (18) used in the tool holder (16) can be adjusted by a user of the hand-held power tool (12).

5 Hand tool according to one of the preceding claims, characterized in that the hand tool has a multi-stage gear.

6 Hand tool according to one of the preceding claims, characterized in that the hand tool has a pneumatic, in particular an electro-pneumatic, drill cuttings conveyor (28).

7 Hand tool according to one of the preceding claims, characterized in that the hand tool (12) is designed as a portable device.

8 Hand tool according to one of the preceding claims, characterized in that the hand tool (12) can be operated wirelessly, it preferably having an accumulator, in particular a lithium-containing accumulator.

9 Hand tool according to one of the preceding claims, comprising at least one overrunning clutch, a link mechanism or a circular thrust mechanism.

10. Tool (18) for a hand-held power tool (12) according to one of the preceding claims, comprising a tool tip (24), a tool shank (20) and an insertion end (22) for receiving the tool (18) in the tool holder (16). Hand tool machine (12), wherein at least along the tool shank (20) a material transport channel (26) is formed, characterized in that the

Material transport channel (26) has a minimum ^{cross-sectional area of 19 mm 2} or at least 6%, particularly preferably at least 12%, of the cross-sectional area of the borehole that can be produced by the tool.

11 . Tool according to the preceding claim, characterized in that the tool (18) is designed as a suction drill.

12. Hand tool system (10), comprising a hand tool (12) according to any one of claims 1 to 9 and a tool (18) according to any one of claims 10 or 11.