Abstract:
The invention relates to a power tool ( 1 ), especially in the form of a hand-held jigsaw ( 2 ). In order to allow for a semi-autonomous operation which assists the user to guide the tool, the tool is provided with a sensor system ( 27 ) for observing a detection surface ( 31, 43 ) within which the desired working direction is detected as a path default ( 23 ) for the saw blade ( 8 ) serving as the tool ( 7 ) with respect to its alignment relative to the jigsaw ( 2 ), the detected path default being intended for downstream control means ( 26 ). Said control means align the saw blade ( 8 ) relative to the path default ( 23 ) by rotating it about its longitudinal axis ( 25 ) so that the user guiding the saw blade ( 2 ) only has to make sure that the path default ( 23 ) extends inside the detection surface ( 31, 43 ).

Description:
CROSS-REFERENCE 
     The invention described and claimed hereinbelow is also described in PCT/EP2009/053046, filed on Mar. 16, 2009 and DE 10 2008 001 757.4, filed on May 14, 2008. This German Patent Application, whose subject matter is incorporated here by reference, provides the basis for a claim of priority of invention under 35 U.S.C. 119 (a)-(d). 
     The invention relates to a power tool, in particular a hand-held power tool. 
     BACKGROUND INFORMATION 
     For users of such power tools, which are typically driven by an electric motor and are often used in practical applications as jigsaws or circular saws, the view of the particular processing point and a related specified path, which is indicated by a marking, in the region of the processing point is often greatly limited. This negatively affects the quality of work that can be achieved. To prevent this, assistance systems in the form of auxiliary devices are used, which support guidance of the power tool in a manner oriented toward the particular specified path as the working path to follow. Power tools of that type, which are designed as jigsaws and circular saws, are therefore often provided with laterally extending guide shoes which are disposed on arms which can be adjusted relative to the power tool, and which rest along a guide track parallel to the specified path and can be displaced in the working direction of the power tool, wherein the guide track can also be formed e.g. by an edge of the work piece that extends parallel to the specified path. 
     Apart from the fact that auxiliary devices of that type are mechanically complex and are limited in terms of their possible uses, they must be adjusted. Furthermore, preliminary work must be performed at times to create such guide tracks. 
     SUMMARY OF THE INVENTION 
     The object of the invention is to provide the user with better ways to guide the power tool in a manner oriented to the specified path. Furthermore, in certain cases, when certain preconditions regarding the power tool exist, to actively support the user in guiding the power tool oriented to the specified path. 
     Improved ways for the user to guide the power tool in a manner oriented to the specified path are initially created by designing the auxiliary device as a sensor system having a detection area that overlaps the working region of the tool, and by providing means in the viewing field of the user for visualizing the position of the detection area relative to the specified path. The detection area therefore provides the user with a much larger observation and/or orientation region, which is based on a starting position with a position of the detection area that is calibrated relative to the specified path, as compared to a specified path in the form of a marking such as a guide line. The depiction of the observation and/or orientation region to the user is not bound to the position of the working region. Instead, the depiction thereof can be presented in any other way in the viewing field of the user. This is accomplished using means for visualizing the detection area and the position of the detection area relative to the specified path. As a result, the visualization of the detection area, overall, becomes an orientation tool for the user. 
     The position of the detection area relative to the specified path can be visualized using mechanical or optical display means; mechanical display means can be formed e.g. by parts of the power tool. In the case of a jigsaw, for example, in the form of a cut-out formed in the base plate thereof, as an at least partial boundary of the detection area. Mechanical display means can also be provided outside of the actual working region e.g. assigned to the base plate as arrow-shaped or triangular cut-outs and projections that point toward the specified path, and therefore, when oriented relative to the specified path, a position of the detection area results that is calibrated relative to the specified path. 
     If optical means are provided for displaying the position of the detection area and/or the position relative to the specified path, they can be formed—relative to the detection area—e.g. by an illuminated field and/or lines of light, light beams, or points of light, the same also applying for optical display means that mark the calibrated position of the detection area relative to the specified path. 
     To visualize the position of the detection area relative to the specified path in a user-friendly manner independently of the position of the detection area relative to the power tool, a display element, in particular an optical display element, can be provided on the housing of the power tool at a distance from the working region, which visualizes the position of the detection area and, therefore, at least indirectly, the position of the working surface and the power tool relative to the specified path; any deviations from the specified path are visualized in a symbolized manner, and possibly symbolized in a manner that is weighted in terms of the degree of the deviation from the specified path. This should be made noticeable to the user, in particular using color, so that the user can guide the power tool accordingly. 
     This is expedient, in particular, in combination with a design of the power tool according to the invention as a semi-autonomous jigsaw that includes a saw blade that is pivotable about an axis extending in the longitudinal direction thereof, and that is directionally guided using a servo device oriented relative to the specified path, and so the user—oriented on the position of the detection area relative to the specified path—need only approximately specify the working direction of the power tool since the tool controls the exact positioning of the saw blade relative to the specified path i.e. relative to the jigsaw, with the saw blade oriented accordingly. To this end, the saw blade, which is rotatable about the longitudinal axis thereof, is acted upon by an actuator system that is controlled by a control unit which, in combination with a computer unit, converts the positional values detected by the sensor system into actuator motions for the saw blade which is rotatable about the longitudinal axis thereof. 
     The invention therefore also provides a method for operating a power tool, in particular a power tool of the aforementioned type, in the case of which the position of the detection area of a sensor system and, therefore indirectly the position of the power tool relative to a specified path are signalled. This is carried out in a manner that is easily recognized by a user, wherein the characteristic values detected using the sensor system are converted by the semi-autonomous guidance of the power tool into adjustment values for the tool, in particular for a saw blade, which orient the same relative to the specified path, and therefore, in conjunction with the approximate orientation performed by the user to the position of the detection surface relative to the specified path, precise machining is achieved along the specified path. 
     The detection area, which is large relative to a usually linear specified path, provides the user with the advantage of orientation on an area instead of on a line—which is usually difficult to as certain—as the specified path, and also makes it possible for a warning signal to be triggered and/or for the machine to be shut off if the user guides the power tool carelessly and displaces the detection area from the position thereof in which it overlaps the specified path, thereby ensuring, e.g. by the user becoming accustomed to the semi-autonomous operation, that inattentiveness and errors by the user as he guides the power tool do not result in damage to the work piece. 
     The invention is particularly advantageous for placing the power tool in the correct position on the particular work piece, that is, for making the first cut in the particular work piece at the point marked by the specified path. As the specified path, the detection area specifies a region in which the power tool need be displaced only transversely to the specified path, in particular needing only to be slid while lying on the work piece, until the rotational axis of the tool which lies in the center of the detection area—e.g. the saw blade of a jigsaw—cuts the marking line as the specified path. The user then merely needs to orient the power tool relative to the specified path. In the case of semi-autonomous operation of the power tool, in particular of the jigsaw, and setting the rotary position of the saw blade using an actuator system relative to the specified path, the orientation is implemented by specifying a corresponding rotary position, thereby ensuring that the user mainly only needs to provide support. Power tools that are operated using this assistance function, in particular jigsaws, therefore reduce the work to be performed by the user, even when starting work on a work piece, to primarily placing the machine such that the detection area overlaps the specified path, and then supporting the machine while the orientation relative to the specified path is performed by the machine. 
     Further details and features of the invention result from the claims. Furthermore, the invention is explained below with reference to an embodiment that shows a power tool in the form of a jigsaw which, as a jigsaw to be operated semi-autonomously, comprises a saw blade that is rotatable about the longitudinal axis—as the rotational axis—thereof, the rotary position of which can be adjusted using an actuator system. The drawing shows: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  a perspective depiction of the jigsaw in the working position thereof, in which it is placed on a work piece, 
         FIG. 2  a schematic top view of a display element provided on the front side of the housing—as shown in FIG.  1 —of the jigsaw, and 
         FIGS. 3 and 4  a schematic top view of the working region of the base plate of the jigsaw, through which the saw blade extends. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows, as an example of a power tool  1 , a hand-held machine in the form of a jigsaw  2  that comprises a housing  3  and is supported on a work piece  5  by a base plate  4 . 
     Jigsaw  2  comprises, in the front, relative to the working direction, a saw blade  8  as the working tool  7 . In the working mode, it engages in work piece  5 , on which jigsaw  2  is displaceably supported using base plate  4  thereof. 
     In the embodiment, jigsaw  2  is designed such that a viewing field  10  results for the user that preferably extends at least across the range of working region  9 , which is determined by saw blade  8  and is illustrated in  FIGS. 3 and 4  and, as shown, typically extends beyond working region  9  in working direction  6  to provide the user with the best possible overview of the working conditions, including those to come. 
     Housing  3  of jigsaw  2  is substantially conventional in design and comprises a U-shaped handle  11  which is disposed opposite—in the vertical direction—to base plate  4  which is supported in a manner such that it can be locked in position about a swivel axis that extends in working direction  6 , handlebar  12  of said handle  11  extending in working direction  6  and, on the front side thereof, entering front-wall region  13  of housing  3 . At the top, it transitions into a guide knob  14 . Working direction  6  and, therefore, the swivel axis of base plate  4  extend in the direction of sawing when the saw blade plane contains longitudinal axis  25 , the sawing direction corresponding to the straight-ahead working direction of jigsaw  2 . 
     A switch system  15  is provided in the region of handle  11 , on the underside handlebar  12 , and is used to turn power tool  1  on and off. Different operating modes of jigsaw  2  can be selected using switch device  16  provided on the longitudinal side of housing  3 . 
     Front-wall region  13  of housing  3  is offset in the downward direction, i.e. in the direction toward base plate  4 , in a stepped manner opposite working direction  6 . Resultant step  17  extends over tool fitting  18  for driven working tool  7  formed as saw blade  8 . 
     Saw blade  8  of entirely electrically driven power tool  1  is driven in a reciprocating manner, as indicated by arrow  19 . A servo drive  20  is used to implement a further working mode of saw blade  8 , namely a reciprocating-pendulum mode, in which saw blade  8  can swivel about a swivel axis (not depicted) which extends transversely to the plane of the paper and is superposed on the reciprocating motion. In a third operating mode, which is indicated by arrow  21 , saw blade  8  can be swiveled about a rotational axis  22  which extends in the direction of the longitudinal axis thereof, in addition to performing the reciprocating motion. As a result, as illustrated in  FIGS. 3 and 4 , saw blade  8  can be displaced into working directions that extend at an angle relative to the straight-ahead working direction thereof, thereby enabling jigsaw  2  to be used as a “scrolling jigsaw”, and as a semi-autonomous jigsaw when displaced in a thusly controlled manner. In that case, the user who is holding jigsaw  2  merely moves it forward in the direction roughly defined by working direction  6 . The exact positioning of jigsaw  2 , which corresponds to a specified path  23 , is achieved by setting saw blade  2  in a rotary position that corresponds to particular specified path  23 . 
     In  FIGS. 3 and 4 , specified path  23  is formed by a marking line  24 . In the working situation depicted, marking line  24  has an intersection point with rotational axis  22 , through which longitudinal axis  25 —which is also indicated—of jigsaw  2  extends. Proceeding from rotational axis  22 , specified path  23  extends, in the form of marking line  24 , in working direction  6 , with an increasing lateral offset relative to longitudinal axis  25 . Control means  26  are used to detect such working conditions and orient the rotary position of saw blade  8  to specified path  23 ; control means  26  comprise e.g. a sensor system  27 , a computer unit  28 , and a servo unit  29 . Control means  26  can automate the guidance of saw blade  8  along specified path  23  and the rotatability of saw blade  8  about rotational axis  22  extending in the longitudinal direction thereof, thereby enabling jigsaw  2 —when embodied as a scrolling jigsaw—to be used as a semi-autonomous jigsaw. 
     In the embodiment, sensor system  27  comprises a sensor designed as camera  30 , to which computer unit  28  is assigned. 
     Camera  30  of sensor system  27  is oriented toward a detection area  31  situated in the region of base plate  4 , i.e. in a region through which marking line  24 —which is used as specified path  23 —extends as viewed from above, and toward which saw blade  8  is oriented. Using sensor system  27  comprising camera  30  which is oriented toward detection area  31 , marking line  24  is detected at individual points  32  that lie on search rows  33  which extend transversely to working direction  6  and overlap detection area  31 , and therefore, when analog image processing is used, the data captured using sensor system  27  are forwarded to computer unit  28 , where the trajectory of marking line  24  and, therefore, the course thereof relative to longitudinal axis  25  can be detected. Computer unit  28  transmits control signals to control unit  29  which then sets saw blade angle  34  as a function of the superposed user guidance, using an actuating device comprising a controller e.g. in the form of a stepping motor. The inclination angle of saw blade  8 , which is defined relative to longitudinal axis  25 , is labelled as saw blade angle  34 . 
     In the embodiment depicted in  FIG. 3 , detection area  31  is bounded by dash-dotted line  35 , which overlaps the edges of a cut-out  36  provided in base plate  4 , and so detection area  31  is delimited by the edges of cut-out  36  during use according to the invention. 
     Detection area  31  is primarily symmetrical about longitudinal axis  25 , on which rotational axis  22  of saw blade  8  also lies, saw blade  8  extending via the saw blade plane thereof in the direction of longitudinal axis  25  when longitudinal axis  25  coincides with the marking line. 
     When detection area  31 , which is a preferred solution, lies within the field of view of the user, the user is able to immediately discern the extension of marking line  24  on the basis of angle  34  of saw blade  8  relative to longitudinal axis  25 , wherein, advantageously, the position of longitudinal axis  25  relative to base plate  4  is also marked e.g. using a marking arrow  37  that extends in the direction of longitudinal axis  25 . In the sense of an orientation of jigsaw  2  that is typically aimed for, in which longitudinal axis  25  thereof lies on particular marking line  24 , the user is therefore shown how to guide jigsaw  2  for the particular purpose. 
     Detection area  31  also delimits the region in which jigsaw  2  is guided semi-autonomously with reference to values captured using sensors, and is therefore oriented toward particular marking line  24  via the automated adjustment of saw blade angle  34  independently of the user&#39;s requirements. If marking line  24  leaves the region that is identified using sensors and is used as detection area  31 , the user therefore also loses the support of the machine in guiding jigsaw  2  along a particular marking line  24 ; thus, when marking line  24  wanders out of the detection area, a signal is advantageously triggered, in particular an acoustic signal, which is advantageously accompanied by the machine being automatically shut off. 
     Since the semi-autonomous guidance of jigsaw  2  ensures that the user need only orient jigsaw  2  toward particular marking line  24  in an approximate manner, it is typically not necessary for the user to follow and observe marking line  24  exactly; instead, it is sufficient for the user to be informed that marking line  24  still extends through detection area  31 , thereby enabling the user to focus on detection area  31  and on information regarding critical deviations. This can take place e.g. using related color schemes in the region of detection area  31 , or using color schemes of separate display elements  38 , one of which is disposed on the end face of housing  3  and comprises an upwardly facing display field  39  which is shown alone in a top view in  FIG. 2 . Display field  39  advantageously comprises color fields  40 ,  41  and  42 , of which central color field  40  is e.g. green, outer color fields  41  are red, and color fields  42  situated therebetween are yellow, thereby ensuring that the user is easily informed about the regions in which he is moving and, when one of the outer color fields  41  illuminates, is notified that jigsaw  2  is being operated just within the limits within which the guidance thereof is automatically supported. 
     Optionally, related color markings can also be depicted within detection area  31 . In the embodiment shown in  FIG. 3 , detection area  31  is mechanically delimited or marked. In contrast, the embodiment depicted in  FIG. 4  shows a base plate  4  which is closed outside of a working region  9  around saw blade, and is preferably at least partially transparent, in particular in the region of detection area  43  which is likewise indicated using a dash-dotted line. 
     Considering that, during practical application, only one acute-angled region  44  which is symmetric about longitudinal axis  25  in particular comes into play in regards to the rotation of saw blade  8 , detection area  43  shown in  FIG. 4  is delimited in a trapezoidal shape, it being possible to display this delimitation on base plate  4  in a manner that is visible to the user, or to mark it in any other manner. In the same manner as explained with reference to  FIGS. 2 and 3 , the detection area can also be used here as a display field, and can therefore also be used as an optical display field. 
     Preferably in the region of the transition to step  17 , an illumination source  45  can also be provided in the front-wall region  13  of housing  3 , which points toward working region  9  and/or detection area  31  or  43  and which can be used, given an appropriate marginal sharpness of the illuminated field, to emphasize the detection area accordingly and thereby depict it in a delineated manner. In conjunction with such a solution in particular, it can also be advantageous to work with color codings, wherein different color fields can be provided in the sense of the explanations provided above, each one being irradiated by an illumination source of the particular color. 
     It is likewise possible to use detection area  31 ,  43  as a whole to characterize a particular operating state and to thereby present only the particular state in a coded manner by illuminating the detection area or parts of the detection area using a single color. 
     Transition states can also be signalled, in particular, using optical means i.e. flowing color transitions. 
     If this is implemented using mechanical means, it can be advantageous—as indicated in  FIG. 3  using dash-dotted lines—to provide projections on the edge of the detection area, which extend toward longitudinal center line  25  and therefore away from the diametrically opposed edges of cut-out  36 , and which are used during observation of marking line  24  to indicate that marking line  24  is approaching the limits of detection area  31 . In particular, projections  46  can also coincide with search rows  33 , therefore forming points  32  to be detected by camera  30 , which lie between search rows  33  and marking line  24 , similar to the intersection points, limited to the relevant edge regions in the overlap with marking line  24 . 
     In summary, the invention provides a power tool  1 , in particular in the form of a hand-held jigsaw  2  to be operated—using a sensor system  27  for observing a detection area  31 ,  43 —in a manner that is semi-autonomous in particular and supports the user in terms of guidance; within detection area  31 ,  43 , the orientation of the target working direction, as specified path  23  for saw blade  8 , which is being used as tool  7 , is detected relative to jigsaw  2 , for downstream control means  26  which are used to orient saw blade  8  to specified path  23  via rotation about longitudinal axis  25  thereof, thereby ensuring that the user, while guiding jigsaw  2 , need only make certain that specified path  23  extends within detection area  31 ,  43 . 
     The embodiment of the power tool according to the invention also makes it easier, in particular, for the user to place the tool on the work piece with great precision.