GB2466383A

GB2466383A - Power tool with means for determining the type of material of the workpiece

Info

Publication number: GB2466383A
Application number: GB0922239A
Authority: GB
Inventors: Thilo Koeder; Joachim Platzer
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2008-12-22
Filing date: 2009-12-18
Publication date: 2010-06-23
Anticipated expiration: 2029-12-18
Also published as: DE102008055057A1; RU2009147296A; GB0922239D0; RU2533073C2; GB2466383B

Abstract

A power tool such as a hand-held power tool, comprises a sensor device 24 for detecting workpiece conditions, for processing information about the detected conditions and/or for communicating the information to the user. A sensor is provided for determining the type of material of the workpiece 5, such as wood or metal. Preferably, the sensor does not contact the workpiece. The sensor may be an inductive sensor, a capacitive sensor, a Hall effect sensor, or an eddy current sensor. The sensor may be formed by an emitter/receiver unit that operates using electromagnetic waves. The sensor may be provided on the footplate 4 of a compass saw 2, a circular saw, milling tool or planer that is to be positioned on a workpiece.

Description

Description Title

Power tool, in particular a hand-held power tool The invention relates to a power tool, in particular to a hand-held power tool, according to the preamble of claim 1.

Background art

Power tools, in particular also hand-held power tools, offer a growing range of operating options and, linked to the diversity of these operating options, an increasing number of setting options for the user. On the whole, therefore, the number of potential errors is becoming ever greater and accordingly, in order to avoid errors, an increasing level of expertise is demanded of the user. In view of the often only sporadic use of such power tools by the user, actual knowledge of the options and the associated error sources, despite good information material, is however mostly incomplete, in particular non-existent.

Power tools are therefore being equipped to an ever greater extent with in-built aids for the user, such as for example with guiding aids that help the user to follow preset working lines when working with compass saws.

Corresponding in-built support devices frequently operate with computer assistance. On this basis, appropriate guide information is provided for the user optionally in a display. In further stages of development of such compass saws, such as *are known for example from DE 10 2006 052 808 Al, assistance in guiding the tool is also given to the user by the power tool. This is done in that the tool, i.e. in the case of a compass saw the saw blade that is set in reciprocating motion, is rotatable about its reciprocating axis and aligned by the power tool with the respective working line. For this purpose, the working line is visually detected by an in-built sensor device, in particular a camera, and on the basis of a downstream evaluation-and arithmetic unit by means of a positioning device the saw blade is aligned in terms of its rotary position in each case with the preset working line. The result is therefore semi-autonomous operation, whereby the user is at least extensively relieved of the task of guiding the compass saw along the working line and is required substantially only to carry out the rough alignment and support of the compass saw.

The complexity of such compass saws, and in a corresponding manner also of other power tools, entails a higher dependence upon workpiece conditions and, in order to achieve good work results, requires an adaptation of the generally exchangeable tools to the working conditions, including in particular the respective type of material of the workpiece.

Disclosure of the invention

The underlying object of the invention is further to improve a power tool of the initially described type with regard to the support that is made available to the user by the power tool for the handling and use of the power tool.

This object is achieved by the features of claim 1, while advantageous constructions are indicated in the sub-claims.

By virtue of the power tool being equipped with means of detecting the type of material of the respective workpiece to be machined, a large number of the options provided by the power tool for optimizing the work may be used purposefully and in many cases without any kind of intervention by the user, optionally however with additional indications for the user in order to exclude potential error sources. The options discussed include for example, with regard to the type of material of the respective workpiece, providing an automatic adaptation of the rotational speed or stroke rate by the power tool, feedback about whether the tool used in each case is suitable in view of the detected type of material and/or whether the operating mode of the power tool that is set in each case is suitable in combination with the detected type of material for the respective machining of the workpiece.

The determination of the type of material that is provided according to the invention is effected within the scope of the invention by surface detection at the workpiece and may be effected for example inductively, capacitively or by using electromagnetic waves, wherein use may be made of known detection means, such as for example Hall-effect sensors, eddy-current sensors or also scanners, such as are already used i.a. to detect the structure of walls in the

field of construction.

For the purpose according to the invention it is sufficient if the respective materials of the workpieces are detected in a roughly classified manner, i.e. primarily with regard to the type of material, thus for example being classified according to wood, metal, aluminium and/or copper. This allows the outlay for the employed sensor detection systems to be kept low. A further contributory factor to this is that no engagement into the respective workpiece is required, the detection rather being effected at the surface.

On the basis of the detection result it is possible not only to provide indications about the stroke rate or rotational speed that is advantageous in each case and/or about the tool that is preferentially to be fitted in each case but also to check correspondingly set values and fitted tools to ascertain their suitability for use on the respective workpiece, the type of material of which has been detected. The working variables to be influenced by the power tool also include for example the feed rate, the pendulum stroke setting to be set in compass saws, an automatic setting of the torque limitation in screwdrivers.

The invention may further be used in combination with safety queries to protect the power tool.

Over and above the interventions that are to be carried out automatically and hence without any action on the part of the user, it proves advantageous for the user to receive, for example in a display, action guidelines either about the guide work for the power tool, the operating state of the power tool or essential warning information.

Further details and features of the invention arise from the claims, the description and the drawing, which shows in a perspective representation a compass saw, as an example of a hand-held power tool, that is positioned on a The power tool 1 depicted as a compass saw 2 comprises a housing 3, which is supported via a footplate 4 in a displaceable manner on a workpiece 5. The straight-forward working direction of the compass saw 2 is indicated by the arrow 6. The plane of the saw blade 8, which forms the working tool 7 of the power tool lies in straight-forward working direction.

The saw blade 8 is held in a tool holder 9 and driven so as to be movable along its stroke axis in accordance with the arrow 10. In the illustrated embodiment of the compass saw 2, an ability of the saw blade 8 to rotate about an axis of rotation 12 corresponding to its stroke axis is moreover provided in accordance with the arrow 11. pendulum drive 13 for the saw blade 8 is additionally provided, by means of which the saw blade 8 is movable in a pendulum manner about an axis that is not shown and extends at right angles to the axis of rotation 12 and transversely of the working direction 6.

Given this design, work may be carried out by the compass saw 2 in different modes of operation, which may be selected by means of a switching device 15 and of which one, in the form of a standard work setting, corresponds to the straight-forward working direction 6. Connection of the pendulum drive 13 to the system gives rise to the so-called pendulum stroke operation, and in combination with the rotatability of the saw blade 8 about the axis of rotation 12 the compass saw 2 is to be operated as a so-called "scrolling jigsaw", i.e. in a semi-autonomous mode of operation. In this mode of operation the user undertakes substantially only the respective support of the recoil resulting from the working operation as well as the feed of the compass saw 2, the saw blade 8 of which is aligned by the power tool with the respective preset straight or curved working line and follows this line.

Switching-on and -off of the compass saw 2 is effected via a switching arrangement 14 that is provided in the handle region of the housing 3.

The front region 16 of the housing 3 in its bottom region 17 projecting like a step from the tool holder 9 accommodates a sensor device 18, which is oriented towards the working region of the saw blade 8 and hence towards the respective working line and by means of which the position of the saw blade 8 relative to the respective working line on the workpiece is to be visually detected. In the embodiment the working region of the saw blade 8 is delimited within the footplate 4 positioned on the workpiece 5 by a, here, only partially visible recess 19, through the region of which that overlies the workpiece 5 the respective working line also extends.

A display 20 that is provided in the front region 16 and lies in the visual range of the user is further indicated, which is used in particular to display information of relevance to the user.

Depicted only diagrammatically on the front region 16 are an arithmetic unit 21 forming part of the compass saw 2, control electronics 22 and a positioning device 23 for the saw blade 8, by means of which the saw blade 8 may be aligned in terms of its rotary position with the respective For determining the type of material of the workpiece 5 at least one sensor device 24 is further provided, which depending on the nature of its design may be provided for example adjacent to the sensor device 18 in the part of the front region 16 that is set back in a step-like manner but is preferably disposed in particular in a position as immediately adjacent to the workpiece 5 as possible, hence for example in a position 25 in the edge 26 surrounding the footplate 4. The illustrated, preferred position 25 in this case lies in the edge region that is open down towards the recess 19, thereby resulting in a minimal and uniform spacing relative to the workpiece surface 27.

The sensor device 24 may be formed by inductive or capacitive sensors, Hall-effect sensors or alternatively sensors in the form of emitter-receiver units that enable a determination of the type of material of the respective workpiece 5 on the basis of electromagnetic waves. On the basis of simply designed, inexpensive sensors it is therefore already possible to carry out a rough classification of materials, such as for example wood, metal, aluminium or plastics material by way of the electrical or mechanical properties thereof, wherein the measurement is effected at the workpiece surface. In principle, it also lies within the scope of the invention to use a combination of a plurality of types of such sensors 24 if further information in addition to a rough classification of the workpiece 5 with regard to its type of material is required.

Via the determination of the type of material the inexperienced user in particular may be provided with diverse information about the power tool setting and the tooling, for example information about selection of the appropriate tool for the respective material and, in particular also with due regard to this selection, suitable rotational speed and/or stroke rate values for the working tool 7, wherein according to the invention preferably rotational speed and/or stroke rate values of the working tool 7 may also be adapted automatically to the tool that is clamped in each case, this being advantageous particularly in connection with a corresponding coding of the tool 7. Given a corresponding design of the appliance with such tool identification based on RFID technology or alternatively with coding bumps, it is moreover even possible to carry out a plausibility check, so that for the user handling of the power tool is substantially simplified and incorrect tool selection and power tool setting on the part of the user may be avoided. In the case of a compass saw designed for pendulum stroke operation, with due regard to the type of material the correct pendulum stroke setting in each case may moreover also be optionally indicated in the display 20 but preferably set automatically, the same applying also to selection of the feed rate. In connection with power tools 1 designed as screwdrivers or drills, in particular automatic setting of the torque limitation with due regard to the type of material and/or the tool fitted in each case in dependence upon the nature and size thereof also presents itself within the scope of the invention.

Such information is helpful also in the case of further appliances, and particularly so with regard to practices that in the case of non-professional users are often not common knowledge. Thus, for example in the case of sanders default settings for the grain, in the case of old-type saws information about the hardness of the material, in the case of power drills and milling tools information about the rotational speed. In general, a plausibility check is moreover expedient and for the user also advantageous as confirmation during operation.