DE102007000386A1 - Percussive electric hand power tool e.g. chisel hammer, has ferromagnetic percussive element with stop surface whose cross-sectional area corresponds to half of cross-sectional area of abutting surface of ferromagnetic plunger - Google Patents

Abstract

The tool (1) has a plunger coil (3) in which a coaxial coil axially moves, and a ferromagnetic plunger (4) with an abutting surface. The ferromagnetic plunger is assigned to a stop surface of a ferromagnetic percussive element (5) in an axial internal area of the plunger coil in an adjacent manner. The cross-sectional area of the stop surface, corresponds to half of the cross-sectional area of the abutting surface. The ferromagnetic plunger and the percussive element are made of shockproof, soft-magnetic material.

Description

Object of the invention

The Invention refers to an at least partially beating electric hand tool with a magnetic impact mechanism, in particular a chisel hammer or a combi hammer.

Usually powerful (in the range of 1000 W power consumption), beating electric hand tool machines are equipped with an air spring impact mechanism, which is driven by an electric motor, for example. According to the principle of US3114423 ,

After US4215297 has a beating electric hand tool a plunger coil, in the coaxial coil inside a ferromagnetic plunger core is arranged axially movable. In a pulse coil energized by a controlled capacitor discharge coil, which pulls the hollow core into its core coil with the highest flux density of the magnetic induction, via a fixedly connected to the plunger core, axially guided percussion means of nonferromagnetic material axially outside the plunger of the power surge on the insertion of a axially limited movably received impact tool in a tool holder. After the impact, a housing-fixed return spring pulls the percussion means back to the rest position with the plunger core.

After the GB258725 . US4553074 or the US4237987 In contrast, the ferromagnetic plunger core within the plunger coils with its impact surface directly axially on the associated abutment surface of an axially projecting axially into the coil inside front end of a partially coaxial within the plunger axially guided insertion of a percussion tool. The over the fixed tool guide axially freely projecting end face of the insertion end has a stop surface whose (magnetically effective) cross section is substantially smaller than the (magnetically effective) cross-section of the abutting surface of the plunger. Thus, in such magnetic impact devices, only the immersion coil principle, in which the core is accelerated via the magnetic induction into the coil interior of a plunger coil with the highest flux density, provides a substantial energy contribution.

The The object of the invention is to increase the performance a magnetic impact mechanism for beating electric hand-held power tools.

The The object is essentially achieved by the features of claim 1 solved. Advantageous developments emerge from the Dependent claims.

So has one along a striking axis at least partially beating electric hand tool on a plunger, in whose coaxial coil inside an axially movable, ferromagnetic Immersion core is arranged with a collision surface, which in the axial inner area of the plunger coil a stop surface axially adjacent directly to a ferromagnetic impact device is, wherein the (magnetically effective) cross-sectional area (under) the stop surface of at least half the cross-sectional area (below) of the impact surface equivalent.

By the comparable cross-sectional areas of the impact surface and the abutment surface of the impactor (i.e., impact tool chisel or striker), which in the axial inner region of the plunger coil are assigned directly adjacent to the magnetic induction be penetrated and thus induce there temporary magnetic poles, provides the physical principle of direct polarity of two (induced) magnetic poles a significant additional Energy contribution to the acceleration of the plunger relative to the percussion means and thereby on the shock pulse of the power stroke or ultimately the Impact energy of impact tool chisel. This energy contribution is also available in a movement phase of the diving core, in which a mere one-piece diving core for reasons of symmetry (Location of maximum field line density) do not absorb any further field energy can.

Here are some physical explanations. In the axial inner region L of an axially elongated cylindrical coil with a ferromagnetic coil core, the magnetic induction B is largely homogeneous and axially oriented inside the coil, whereas it is radially deflected outside the axial inner region and approaches zero extremely rapidly. This is in 2 represented as a physical principle with functional profile of the axial component of the magnetic induction B. If, in the axial inner region L, an air gap of the axial length S (FIG. 3 ) by dividing the ferromagnetic coil core into two parts (plunger core and percussion means), the magnetic induction B passing therethrough temporarily polarizes these parts, causing a pole attraction force between the associated opposite magnetic poles of the magnetized parts to be approximately exponential to the gap length S. ( 3 ) drops. Accordingly, the direct Polanziehung provides just in the relevant for the final impact phase before shock contact an additional, significant contribution to the acceleration of the plunger, after this was pulled in the usual plunger coil by the magnetic flux from its rest position out in the place maximum field density in the interior of the plunger coil and while absorbing kinetic energy and idly lingers in forward motion.

At the Shock contact itself deforms (almost always something crowned, elastic) abutment surfaces and abutment surfaces against each other and form a large as possible for a short time common contact surface, which is directly from the magnetic Induction is interspersed and thus the temporary there Magnetic poles (except for the remanence) eleminated, causing the power surge the Polanziehungskraft briefly omitted and the impact process itself or the shock pulse transmission does not inhibit. The Polanziehungskraft is indeed right after the back reflection the diving core again this braking effect, but this is enough do not look to the sluggish backward movement to reverse to the resting position.

Advantageous Both the core and the impact are shockproof, soft-magnetic material, for example of low-carbon soft iron, whereby hysteresis losses are minimized.

Advantageous the plunger coil has an axial coil length, the larger as the core length of the plunger is, which even at Power stroke with completely inside the immersion coil, in which the magnetic induction is largely homogeneous, recorded Immersion core still axial clearance for a portion of the percussion means remains, which is magnetically polarizable, whereby the Polanziehung over a wide, variable axial area works and thus a "hover chisel" with limited allowable axial displacement of the impact tool is possible.

Advantageous is in the rest position, the gap length maximum half, more advantageously less than a fifth the diameter of the plunger core, whereby the Polanziehung the energetic dominant effect with respect to the plunger coil principle and the magnetic impact is axially short executable.

Advantageous the impact means axially limited movably mounted, further advantageous positive fit via radial projections or grooves the impact and corresponding impact-resistant locking means as stop surfaces or locking balls, causing the Positioning of the core-side stop surface in the axial Inside the immersion coil is ensured.

Advantageous the impact means is designed as an anvil, the axial beats directly on the front end of a striking tool, its insertion end received in a striking tool receptacle axially is mounted limited movable, causing the electric hand tool with commercially available tools, especially those with not sufficiently large Axialprojektionsflächen purpose is usable.

Advantageous the rest of the core is assigned a return means axially which is interactively connected to the plunger core, whereby after the Current pulse and pulse transmission of the plunger reliably convertible to its rest position is.

Advantageous is the return means (at least partially) as a spring means formed, for example. As a housing-fixed coil spring or as axial core side at least temporarily closed air spring, creating a realized technologically simple passive return means is.

Advantageous is the return means (at least partially) as a return coil formed, whereby the return operation controlled beinflussbar is. With appropriate active control are thus the impact performance and the beat frequency (in limits) independently of each other selectable.

Advantageous is the plunger coil and the return coil radially outward in an air gap free Trafoblechpaket embedded, which magnetic Magnetically low resistance flux and low-leakage current conducting returns. This will cause the magnetic flux returned in the outer area of the plunger coil. Further advantageous packet air gaps are filled with ferrofluids.

Advantageous is a power electronics available, with the immersion coil (and the return coil) over (one) each from a control means controllable circuit breaker connected to an internal circuit breaker Power source (eg., A power capacitor) is connected to the a power cord connected to the external power supply network is what makes for powerful electric handheld machine tools necessary high power for the magnetic impact technology is provided robustly.

Advantageous is the Magnetschlagwerk via air ducts, the be cooled by a fan, thermally insulated arranged in an outer housing, which has a guide handle training, whereby the electric power tool even under continuous load in chisel operation and the energy losses necessarily associated with it remains.

nevertheless is the inventive magnetic percussion also in part rotating electric hand tool machines with rotating tool holder usable, eg a combination hammer.

The Invention will be with respect to an advantageous embodiment explained in more detail with:

1 as electric hand tool machine

2 as a principle of a cylindrical coil with ferromagnetic coil core

3 as a variant of a detail

To 1 has a along a striking axis A beating electric hand tool 1 a magnetic impact device 2 with a plunger coil 3 on, in the coaxial coil inside a ferromagnetic Tauchkern 4 is arranged axially movable from low-carbon soft iron. The diving core 4 is a ferromagnetic impact agent 5 from low-carbon soft iron axially adjacent directly. That as an anvil for a percussion tool 8th , whose spigot ends in an impact tool holder 11 was recorded, trained percussion 5 and the impact tool 8th themselves are over grooves 9 and locking balls 10 mounted axially limited movable. The diving core 4 is grip side axially as a passive return means an air spring 25 as well as an active return means a return coil 12 assigned. The plunger coil 3 and the return coil 12 are radially outward and frontally into an air gap free Trafoblechpaket 14 embedded. It is one (outside the electric hand tool machine 1 shown) power electronics 15 present with the plunger coil 3 and the return coil 12 via one each, from a tax agent 16 in the form of a microcontroller [my] C controllable, circuit breaker 17 connected to an internal power source 24 is connected to a high-power pulse capacitor C, which itself via a power cord 18 with the external power supply network 19 connected is. The impact position with full-surface impact of the diving core 4 on the percussion 5 illustrated magnetic impact mechanism 2 is thermally insulated in an outer housing 22 arranged, which has a guide handle 23 trains, and is via air ducts 20 from a fan 21 cooled with sucked air.

To 2 , which serves only to explain the physical principle, in the axial inner region L of an axially elongated cylindrical coil with a ferromagnetic coil core inside the coil, the magnetic induction B largely homogeneous and axially oriented, whereas this outside the axial inner region L is deflected radially and extremely in the axial direction quickly goes to zero.

To 3 is in the illustrated rest position, the gap length S about one fifth of the diameter D of the plunger 4 on the flat or slightly convex beater-side stop surface 7 , which is also the diameter of the percussion device 5 (here insertion end of impact tool 8th ) on the flat or slightly convex core-side stop surface 6 equivalent. Thus, their axial projections are the same. The return agent for the diving core 4 is as a spiral spring 26 realized, the transformer sheet package 14 pressure is tight. The plunger coil 3 has an axial coil length with the axial inner region L, which is greater than the core length K of the plunger core 4 is.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - US 3114423 [0002]
• - US 4215297 [0003]
• GB 258725 [0004]
• US 4553074 [0004]
• - US 4237987 [0004]

Claims (12)

An electric hand tool machine with a plunger coil (at least partially beating, at least partially) along a striking axis (A) 3 ), in whose coaxial coil interior an axially movable ferromagnetic core ( 4 ) with an impact surface ( 6 ) is arranged in the axial inner region (L) of the plunger coil ( 3 ) a stop surface ( 7 ) of a ferromagnetic impact agent ( 5 ) is assigned axially directly adjacent, characterized in that the cross-sectional area of the abutment surface ( 7 ) at least half of the cross-sectional area of the abutting surface ( 6 ) corresponds. Electric hand tool according to claim 1, characterized in that both the plunger core ( 4 ) as well as the striking agent ( 5 ) are made of shock-resistant, soft magnetic material. Electric hand tool according to claim 1 or 2, characterized in that the plunger coil ( 3 ) has an axial coil length which is greater than the core length (K) of the plunger ( 4 ). Electric hand tool according to one of claims 1 to 3, characterized in that in the rest position, a gap length (S) between the abutment surfaces ( 6 . 7 ) maximum of half the diameter (D) of the plunger ( 4 ) is. Electric hand tool according to one of claims 1 to 4, characterized in that the impact means ( 5 ) Is mounted axially limited movable. Electric hand tool according to one of claims 1 to 5, characterized in that the impact means ( 5 ) is formed as an anvil axially directly on the front end of a striking tool ( 8th ) is beatable, which in a striking tool holder ( 11 ) received insertion end is axially movable limited. Electric hand tool according to one of claims 1 to 6, characterized in that the plunger core ( 4 ) is assigned a return means axially. Electric hand tool according to one of the claims 1 to 7, characterized in that the return means is designed as a spring means. Electric hand tool according to one of claims 1 to 8, characterized in that the return means as a return coil ( 12 ) is trained. Electric hand tool according to one of claims 1 to 9, characterized in that at least the plunger coil ( 3 ) radially outward into a transformer sheet package ( 14 ) is embedded. Electric hand tool according to one of claims 1 to 10, characterized in that a power electronics ( 15 ) is present, at least with the plunger ( 3 ) via one of a control means ( 16 ) controllable circuit breaker ( 17 ) connected to an internal power source ( 24 ) connected via a power cable ( 18 ) with the external power supply network ( 19 ) is connectable. Electric hand tool according to one of claims 1 to 11, characterized in that the magnetic impact mechanism ( 2 ) via air channels ( 20 ), by a fan ( 21 ) are thermally insulated in an outer housing ( 22 ), which has a guide handle ( 23 ) trains.