Patent Abstract:
A hand-guided jig saw includes a tool housing that houses a drive motor. The drive motor is configured to drive a reciprocating transmission that drives a reciprocating unit connected to a tool receptacle. A vertical axis of the tool receptacle saw is configured to receive a saw blade. In order to enable at least partial free cutting of the saw blade for forming a sawing passage in a workpiece, the tool receptacle, via an electromechanical actuating system, is pivotable by a pre-defined angle about a vertical axis. A pivoting movement of the saw blade is superimposed by at least a reciprocating movement of the tool receptacle.

Full Description:
[0001]    This application claims priority under 35 U.S.C. §119 to patent application no. DE 10 2013 221 092.2, filed on Oct. 17, 2013 in Germany, the disclosure of which is incorporated herein by reference in its entirety. 
         [0002]    The present disclosure relates to a hand-guided jig saw having a tool housing in which a drive motor is disposed for driving a reciprocating transmission which is configured at least for the reciprocating drive of a reciprocating unit which is connected to a tool receptacle, configuring a vertical axis, for receiving a saw blade. 
       BACKGROUND 
       [0003]    From the prior art, a hand-guided jig saw of this type, which is configured in the manner of a so-called “semi-autonomous” jig saw, having an assigned tool receptacle for a saw blade is known. The tool receptacle is configured so as to be pivotable about its vertical axis by means of a servomotor, wherein the servomotor is activated, for example, using signals of an optoelectronic system which acquires the profile of a pre-drawn marking line on an assigned workpiece. On account thereof, the saw blade can always correspondingly align itself in a semi-autonomous manner, that is to say in a self-acting manner, to the profile of the marking line such that a corresponding saw cut can be performed by a user more easily and with higher precision. The saw blade here may display a tooth geometry which is produced by milling and subsequent hardening, wherein the teeth of the saw blade are additionally set in order to avoid sticking of the saw blade in the sawing passage during free cutting with the saw blade for configuring a sawing passage. 
         [0004]    It is disadvantageous in the prior art that a free cutting of the saw blade which is necessary for the free-moving and precise sawing of a corresponding sawing passage cannot be realized independently of the presence of a setting of the teeth of said saw blade. Moreover, a corresponding free-cutting effect of the set teeth is reduced due to wear after a comparatively long period of usage of the saw blade, which is disadvantageously evident in particular when sawing curves. 
       SUMMARY 
       [0005]    It is, therefore, an object of the disclosure to provide a new hand-guided jig saw, in particular a new semi-automatic jig saw, in which at least jamming of an assigned saw blade in a sawing passage to be sawn by said saw blade can be at least largely avoided, independently of the presence of a setting of corresponding teeth of the saw blade. 
         [0006]    This object is achieved by a hand-guided jig saw having a tool housing in which a drive motor is disposed for driving a reciprocating transmission which is configured at least for the reciprocating drive of a reciprocating unit which is connected to a tool receptacle, configuring a vertical axis, for receiving a saw blade. For at least partial free cutting of the saw blade for configuring a sawing passage, the tool receptacle, by means of an electromechanical actuating system, is pivotable by a pre-defined angle about its vertical axis, wherein the pivoting movement of the saw blade is superimposed by at least the reciprocating movement of the latter. 
         [0007]    The disclosure thus enables the provision of a hand-guided jig saw in which, on account of pivoting movements of the saw blade about its vertical axis in an assigned sawing passage, free cutting of said saw blade in the sawing passage is possible, independently of the setting of said saw blade. 
         [0008]    According to one embodiment, the electromechanical actuating system is configured for generating a symmetrically oscillating pivoting movement of the saw blade. 
         [0009]    On account of the preferably periodic pivoting movement, a uniform free-cutting process is ensured, and sticking and/or jamming of the saw blade in the sawing passage can be at least largely prevented. 
         [0010]    Additionally or alternatively thereto, the electromechanical actuating system is moreover preferably configured for generating an asymmetrically oscillating pivoting movement of the saw blade. 
         [0011]    In relation to a cross axis running centrically through the toothed side and a saw-blade rear side of the preferably pivotable saw blade, and to a longitudinal axis of the jig saw (x-axis) as a reference axis, pivot angles α 1 ,α 2  on both sides of the cross axis may in each case be of same size or be of different sizes, wherein at all times the correlation α=α 1 +α 2  applies. 
         [0012]    According to one embodiment, the pre-defined angle is variable, depending on a local amount of curvature of the sawing passage to be produced. 
         [0013]    On account thereof, the pre-defined angle may be reduced to almost zero in straight portions of the sawing passage, and increased in more heavily curved portions of the sawing passage. 
         [0014]    According to one refinement, the pre-defined angle is pre-selectable, depending on a material of a workpiece to be worked. 
         [0015]    On account thereof, inhomogeneities in a workpiece to be sawed, such as, for example, changes in the material thickness, variations of density, knotholes, changes of materials, etc., and transverse forces acting on the saw blade on account thereof can be at least partly compensated for by a corresponding adjustment of the pre-defined angle. 
         [0016]    According to one refinement, the pre-defined angle is pre-selectable, depending on a feeding rate of the saw blade. 
         [0017]    On account thereof, the size of the pre-defined angle can be adapted to the feeding rate of the saw blade in the material. Preferably, the size of the pre-defined angle is correspondingly reduced as the feeding rate increases. 
         [0018]    In accordance with one design embodiment, a frequency of the pivoting movement is pre-selectable. 
         [0019]    On account thereof, a further parameter for the adjustment of the pre-defined angle is made available. 
         [0020]    In accordance with one embodiment, the electromechanical actuating system displays an electric servomotor for pivoting the tool receptacle about its vertical axis. 
         [0021]    On account thereof, the size of the pre-defined angle can be pre-defined and governed by an electronic control unit. Moreover, adequately high activating forces with a high positioning precision can be achieved with a servomotor. 
         [0022]    In the case of a further design embodiment, the saw blade displays set teeth. 
         [0023]    On account thereof, the sawing passage may also be cut free, independently of the oscillating pivoting movement of the saw blade about its vertical axis in the sawing passage. 
         [0024]    According to a further embodiment, the jig saw is a semi-autonomous jig saw in which the tool receptacle, reacting to a signal of an optoelectronic system, is pivotable by means of the electromechanical actuating system about its vertical axis within an angular range, for aligning the saw blade in a self-acting manner when sawing along a pre-drawn marking line, wherein this pivoting which is based on an assigned profile of the sawing passage is superimposed on the oscillating pivoting movement for free cutting of the saw blade. 
         [0025]    On account thereof, the sensor system and actuating system, which are anyway present in the case of a semi-autonomous jig saw, can be conjointly utilized. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]    The disclosure is described in more detail by means of exemplary embodiments illustrated in the drawings in the following description. In the drawings: 
           [0027]      FIG. 1  shows a perspective view of a jig saw which is configured in the manner of a hand-guided, semi-autonomous jig saw; 
           [0028]      FIG. 2  shows a schematic view of a workpiece having a sawing passage and two symmetrical pivoting positions of the saw blade of the jig saw from  FIG. 1 ; 
           [0029]      FIG. 3  shows a schematic view of a workpiece having a sawing passage and asymmetrical pivoting positions of the saw blade of the jig saw from  FIG. 1 ; and 
           [0030]      FIG. 4  shows a front view of the sawing passage from  FIG. 2 , produced by means of the jig saw from  FIG. 1  in a workpiece. 
       
    
    
     DETAILED DESCRIPTION 
       [0031]      FIG. 1  shows a hand-guided jig saw  10  which, in an exemplary manner, is configured in the manner of a semi-autonomous, hand-guided jig saw  11 , and displays a tool housing  14  which is provided with a handle-type handgrip  12 . The semi-autonomous jig saw  11 , for the mains-dependent power supply, is preferably equipped with a flexible electrical connection line  16 . It should be pointed out, however, that the present disclosure is not to be considered as being limited to a hand-guided semi-autonomous jig saw  11  which is operable in a mains-dependent manner, but rather may be applied also to jig saws of all types which are operable in a mains-independent manner and which, for their power supply, are mechanically and electrically connectable to an assigned rechargeable battery back, for example. It is moreover pointed out that the present disclosure is also not limited to jig saws having tool housings which configure handle-type handgrips, but may also be applied to jig saws having bar-shaped tool housings. 
         [0032]    In the tool housing  14 , a drive motor  20  for driving a drive shaft  22  is disposed in an exemplary manner. The drive motor  20  is actuatable, that is to say that it can at least be switched on and off, by a user, for example by way of a hand switch  24  or a hand button, and may be any type of motor, for example an electronically commutated motor or a DC motor. The drive motor  20  is preferably electronically controllable and/or regulatable in such a manner by way of an electronic control unit  26 , that parameters with respect to a desired rotation speed of the drive shaft  22  are implementable, for example. On account thereof, a respective revolution of the drive motor  20 , and conjointly therewith, a corresponding sawing speed and/or a feeding rate of the jig saw  11  inter alia can be easily adapted to variable workpiece properties. The operating mode and the construction of a drive motor  20  of such type and of the electronic control unit  26  are sufficiently known to a person skilled in the art from the prior art, so that a detailed description thereof is dispensed with here in the interest of brevity of the description. 
         [0033]    The drive shaft  22  is mechanically coupled to a reciprocating transmission  28  for driving a reciprocating unit  30  which, in an exemplary manner, displays and/or is fixedly connected to a tool receptacle  32  for clamping an insert tool  36  which, by means of the reciprocating transmission  28 , is drivable in a reciprocating manner substantially in the direction of a double arrow  34 . The insert tool  36  here is configured in a merely exemplary manner as a saw blade  38  having a multiplicity of optionally set saw teeth, wherein merely one tooth, representing all other teeth, is provided with the reference sign  39 . Here, the saw blade  38  runs perpendicularly to a foot plate  40  which is fastened on the tool housing  14  and with which the hand-guided, semi-autonomous jig saw  11  bears on and/or is guidable on an exemplary planar workpiece  42 . Here, the saw blade  38 , proceeding from the tool receptacle  32 , in an illustrative manner, engages, through a clearance  44  provided in the foot plate  40 , onto the workpiece  42 . 
         [0034]    The tool receptacle  32 , in an illustrative manner, has a vertical axis  48  which, in an exemplary manner, coincides with a z-axis of a coordinate system  46 , while an x-axis of the coordinate system  46 , in an illustrative manner, runs parallel to a longitudinal axis  50  of the jig saw  11  and/or the tool housing  14 . Moreover, in deviation from the shown perpendicular alignment of the saw blade  38  in relation to the workpiece  42 , the foot plate  40  may be adjusted to an angle in relation to the vertical axis  48  which deviates from 90°, for example in order to also implement inclined sawing cuts in a simple way and manner. 
         [0035]    In the tool housing  14 , in an exemplary manner, above the reciprocating transmission  28 , an optoelectronic system  52 , by means of which a profile of a pre-drawn marking line  54  on the workpiece  42  can be acquired in a non-contacting manner with high precision, for example with the aid of an optical sensing system or similar which is disposed on a front side, is integrated. A signal  56  generated by the optoelectronic system  52  is preferably supplied at least to the electronic control unit  26 . In this electronic, preferably digital control unit  26 , an evaluation and processing of the signal  56 , emanating from the optoelectronic system  52 , into an output signal  58  which is preferably suitable for the direct activation of a servomotor  60  of an electromechanical actuating system  62 , can take place The electromechanical actuating system  62  and/or the servomotor  60  in turn are mechanically coupled to the tool receptacle  32 , such that the latter together with the saw blade  38  clamped therein, governed by the control unit  26 , can be conjointly pivoted about the vertical axis  48  and/or the z-axis of the coordinate system  46 . On account thereof, it is possible in the semi-autonomous sawing operation to have the saw blade  38  continuously follow the profile of the pre-drawn marking line  54  with high precision, in each case depending on the signal  56  of the optoelectronic system  52 , such that a sawing passage  64  in the workpiece  42 , produced by means of the jig saw  11 , always corresponds with high precision to the pre-defined profile of the marking line  54 . On account thereof, even users with little practice can introduce the sawing passage  64  with high precision and/or dimensional accuracy into the workpiece  42 . 
         [0036]    According to one embodiment, for free cutting of the saw blade  38 , a rapid, periodically oscillating pivoting movement of the tool receptacle  32  about the vertical axis  48  is superimposed on a tracking movement of the saw blade  38 , which takes place slowly, in the semi-autonomous sawing operation. This pivoting movement of the tool receptacle  32  and/or the saw blade  38 , which serves for free cutting of the saw blade  38 , is preferably generated with the aid of the electromechanical actuating system  62  and/or by way of the electric servomotor  60 , such that, at least in the case of the semi-autonomous, hand-guided jig saw  11  which is shown here, no additional constructive investment is required. 
         [0037]    For free cutting of the saw blade  38 , pivoting of the tool receptacle  32  and/or of the saw blade  38  about the vertical axis  48  preferably takes place by a pre-defined angle α within an angular range  66  in the shape of a circular sector. The pre-defined angle α here, governed by the electronic control unit  26 , may be varied in many ways and in a corresponding manner to the respective application scenario of the jig saw  10  and/or the semi-autonomous jig saw  11 . For example, the angle α, governed by the control unit  26 , may be varied in a portion-wise manner along the sawing passage  64  on account of a profile of the marking line  54  which has been acquired by the optoelectronic system  52 , depending on the local amount of curvature of the sawing passage  64 . In this manner, the saw blade  38  may be pivoted by a small angle α in largely linear portions of the sawing passage  64  and/or the marking line  54  for example, or the pivoting movement which serves for free cutting is completely suspended. In contrast thereto, a larger value for the angle α may be pre-defined in a self-acting manner by the control unit  26  in those portions of the sawing passage  64  and/or the marking line  54  which display small radii of curvature. 
         [0038]    A user of the semi-autonomous jig saw  11  may moreover manually pre-define by way of the control unit  26  a respective material texture of a workpiece  42  to be sawn and/or a desired frequency of the pivoting movement, such that the control unit  26 , by means of these parameters, can determine the in each case preferred optimal angle α for the pivoting of the tool receptacle  32  which is required for free cutting. Alternatively, these parameters may also be pre-defined in a self-acting manner by the electronic control unit  26 . The term, material texture of the workpiece  42 , in the context of this description defines the material-specific parameters of said workpiece  42 , such as, in particular, material thickness, local variations of density, inhomogeneities, such as, for example, knotholes or inclusions of resin, local changes in material, etc. 
         [0039]    The control unit  26  may preferably furthermore dynamically determine a respective instantaneous feeding rate of the saw blade  38 , for example likewise by means of the signal  56  emitted by the optoelectronic system  52 , and correspondingly adjust and/or adapt the pre-defined angle α, in order to achieve preferably optimal work results. Moreover, the oscillating pivoting movement of the saw blade  38  and/or of the tool receptacle  32  may take place symmetrically in relation to the longitudinal axis  50  and/or to the x-axis of the coordinate system  46 , or asymmetrically to the latter, as is described in the case of  FIGS. 2 and 3 . 
         [0040]      FIG. 2  shows the workpiece  42  with a portion of the sawing passage  64  from  FIG. 1 , and, in an exemplary manner, two symmetrical pivoting positions  80 ,  82  of the saw blade  38  of the semi-autonomous jig saw  11  from  FIG. 1 . The depicted portion of the sawing passage  64 , in an illustrative manner, at least in portions runs with a slight curvature. 
         [0041]    In the operation of the semi-autonomous jig saw  11  from  FIG. 1 , the saw blade  38 , preferably by means of the electromechanical actuating system ( 62  in  FIG. 1 ) of the former, is in each case on both sides of the x-axis of the coordinate system  46  and/or the longitudinal axis  50  from  FIG. 1 , alternatingly brought into one of the two pivoting positions  80 ,  82  by an angle α 1 , α 2 , and on account thereof, cut free, wherein the angles α 1 , α 2  in the attained pivoting positions  80 ,  82  here merely conform in an exemplary manner to the correlation α 1 =α/2 and α 2 =α/2, so that this is a symmetrically oscillating pivoting movement of the saw blade  38 . An unpivoted rest position of the saw blade  38 , which is assigned to each pivoting position  80  and/or  82 , is in each case indicated by a dashed line, while the in each case other pivoting position  82  and/or  80  is in each case visualized by a dotted line. 
         [0042]    On account of the active free-cutting according to the disclosure by way of periodically oscillating pivoting movements of the saw blade  38 , jamming of the latter in the sawing passage  64  is prevented. Moreover, the active free-cutting enables in particular the more pronounced so-called “inward turning” of the saw blade  38  in portions of the sawing passage  64  which have more curvature. On account of the symmetrical pivoting movement of the saw blade  38 , which here takes place merely in an exemplary manner, said saw blade  38  is released on both sides in the sawing passage  64 . An absolute value of the pre-defined angle α here may be up to 120°, but preferably is at most 90°. 
         [0043]      FIG. 3  shows the workpiece  42  with a portion of the sawing passage  64  from  FIG. 1 , and three exemplary asymmetrical pivoting positions  84  to  86  of the saw blade  38  of the semi-autonomous jig saw  11  from  FIG. 1 . As in  FIG. 2 , an unpivoted rest position of the saw blade  38 , which is assigned to each of the pivoting positions  84  to  86 , is in each case symbolized by a dashed line here as well, and an in each case previous position of the saw blade  38  is in each case illustrated by a dotted line. 
         [0044]    In order to attain the pivoting position  84 , in the operation of the semi-autonomous jig saw  11  from  FIG. 1 , the saw blade  38  in the sawing passage  64  is preferably merely pivoted to one side in a periodically oscillating manner by the angle α 1  in relation to the x-axis of the coordinate system  46  from  FIG. 1 , such that the second angle α 2  is always 0°. In the case of the other two pivoting positions  86 ,  88 , in turn a periodically oscillating pivoting movement of the saw blade  38  in relation to the x-axis of the coordinate system  46  and/or the longitudinal axis  50  of the jig saw on both sides takes place. However, said pivoting movements take place with variably large (part-) angles α 1  and α 2 , so that α 1 ≠α 2  applies, wherein however neither α 1  nor α 2  occupies a value of 0°, so that this is an asymmetrically oscillating pivoting movement of the saw blade  38 . 
         [0045]      FIG. 4  shows the sawing passage  64  from  FIG. 2 , which is produced in the workpiece  42  of  FIGS. 1 and 2  by means of the semi-autonomous jig saw  11  from  FIG. 1 . Said sawing passage  64 , in an illustrative manner, disposes of a width  100 . For comparison, a further sawing passage  102 , which is configured when a customary, hand-guided and optionally semi-autonomous jig saw—but without an active free-cutting unit—is used, is drawn having dotted lines, that is to say a jig saw which does not dispose of the electromechanical actuating system  62  from  FIG. 1  for periodically pivoting the saw blade  38  in an oscillating manner for free cutting the latter in the workpiece  42 . Accordingly, an exemplary width  104  of the sawing passage  102 , which is generated with the customary jig saw, turns out to be smaller than the width  100  of the sawing passage  64  which has been introduced into the workpiece  42  by means of the jig saw  11  according to the disclosure, from  FIG. 1 . 
         [0046]    A further significant advantage of the hand-guided, semi-autonomous jig saw  11  from  FIG. 1 , according to the disclosure, is that the sawing passage  64  precisely encloses an angle β of 90° with an upper and a lower side  106 ,  108  of the workpiece  42 , while the sawing passage  102  generated with the customary jig saw runs in an undesirably oblique manner in relation to the upper and lower sides  106 ,  108 , that is to say encloses an angle γ with the latter which is different from 90°. The jig saw  11  according to the disclosure, from  FIG. 1 , thus permits in a simple way and manner the production of a sawing passage  64  and/or a sawing cut which runs in a precisely rectangular manner to the upper and lower sides  106 ,  108 . 
         [0047]    Therefore, with the hand-guided, semi-autonomous jig saw according to the disclosure, the precision of sawing cuts and/or sawing passages can be significantly increased in comparison to customary jig saws. In comparison to saw blades having set sawing teeth in the customary manner, on account of the employment of the jig saw according to the disclosure, the additional advantage that the free-cutting effect is independent of any potential operational wear of the saw blade is derived, and jamming of said saw blade in the workpiece to be worked is reliably and permanently excluded. As a further positive effect, the increased width, in particular in the case of sawing passages running with a curvature with at least in portions small radii of curvature, enables easier “inward turning” of the jig saw and/or the saw blade within the workpiece  42 .

Technology Classification (CPC): 1