Patent Publication Number: US-2007095792-A1

Title: Manually guided implement

Description:
The instant application should be granted the priority date of Oct. 29, 2005 the filing date of the corresponding German patent application 10 2005 051 886.9.  
     BACKGROUND OF THE INVENTION  
      The present invention relates to a manually guided implement such as a brushcutter, a trimmer, a pole pruner, or the like.  
      U.S. Pat. No. 5,896,669 discloses an overhead branch cutter according to which the guide rod connects the housing of the implement, in which the drive motor is disposed, with the gear mechanism housing of the implement. The tool is disposed on the gear mechanism housing, which is secured to the guide rod by means of a clamping connection. The gear mechanism housing is connected with the guide rod in an electrically conductive manner.  
      When working with an implement having a driven tool, electrical lines from the tool can become damaged or severed. Electrical devices have safety devices that, if damage or severance of an electrical line occurs, interrupts the supply of current, so that injury to the operator is prevented. However, in rare cases even such safety devices can become damaged or can fail.  
      It is therefore an object of the present invention to provide a manually guided implement of the aforementioned general type that further increases the safety of the operator. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      This object, and other objects and advantages of the present invention, will appear more clearly from the following specification in conjunction with the accompanying schematic drawings, in which:  
       FIG. 1  is a perspective illustration of a manually guided implement;  
       FIG. 2  is a perspective illustration of the gear mechanism housing of the implement of  FIG. 1 ;  
       FIG. 3  is a perspective view of a half shell of the insulating sleeve;  
       FIG. 4  is a side view of the insulating sleeve;  
       FIG. 5  is a side view of the insulating sleeve taken in the direction of the arrow V in  FIG. 4 ;  
       FIG. 6  is a cross-sectional view taken along the line VI-VI in  FIG. 5 ;  
       FIG. 7  is a cross-sectional view taken along the line VII-VII in  FIG. 6 ;  
       FIG. 8  is an end view taken in the direction of the arrow VIII in  FIG. 4 ;  
       FIG. 9  is an end view taken in the direction of the arrow IX in  FIG. 4 ; and  
       FIGS. 10 &amp; 11  are perspective illustrations of manually-guided implements. 
    
    
     SUMMARY OF THE INVENTION  
      The manually-guided implement having a tool pursuant to the present application comprises a guide rod, a drive motor for driving the tool, wherein the drive motor is disposed on a first end of the guide rod and the tool is disposed in the region of a second opposite end of the guide rod, a housing disposed on the guide rod at the second end, and, for avoiding an electrical charging of the guide rod, an electrical insulator disposed between the housing and the second end.  
      Due to the presence of the electrical insulator between the housing at the second end of the guide rod, and the guide rod, a transfer of charges from the housing to the guide rod is avoided. As a result, even if the safety device fails due to being severed or because the electrical line is damaged, a transfer of electrical charges to the guide rod can be avoided. Even if the operator of the implement grasps the guide rod instead of the handle, or accidentally contacts the guide rod, a transfer of electrical charges to the operator is avoided since the guide rod itself is electrically insulated from the gear mechanism housing in the tool. This provides as great a safety for the operator as possible.  
      The housing at second end of the guide rod is preferably a gear mechanism housing in which is disposed a gear mechanism for transferring the drive movement generated by the drive motor to the tool. With such implements it is customary to transfer the drive movement through the guide rod via a drive shaft that is mounted in the guide rod. To convert the drive movement into the drive movement needed by the tool, for example a rotational movement in a direction transverse to the longitudinal direction of the drive shaft, the gear mechanism disposed in the gear mechanism housing is provided. As a result, the drive movement can easily be transferred through the guide rod. The housing is expediently held on the second end of the guide rod by means of a clamping connection. This results in a straightforward configuration. An adequate support of the housing and of the tool on the guide rod can be ensured, so that the housing is fixed on the guide rod and cannot move relative to the guide rod.  
      So that the clamping force can be reliably transferred via the insulator from the housing to the guide rod, and so that the electrical insulator has an adequate strength, the electrical insulator can be made of a polymeric material, especially glass fiber reinforced polymeric material. The glass fiber content is in particular approximately 30%. Due to the glass fiber content, a creeping of the electrical insulator under load can also be avoided, thereby ensuring the long-time stability of the clamping connection on the electrical insulator.  
      A straightforward configuration can be achieved if the electrical insulator is formed by an insulating sleeve. In this connection, the insulating sleeve has a cylindrical inner surface and a cylindrical outer surface, as a result of which a good strength of the tolerance-sensitive clamping connection between the housing and the guide rod can be ensured. The insulating sleeve is preferably disposed in a receiver in the housing, whereby the second end of the guide rod extends into the insulating sleeve.  
      The insulating sleeve is preferably formed of two half shells. As a result, the cylindrical shape can be ensured, especially when the insulating sleeve is produced from polymeric material. At the same time, it is easy to remove the two half shelves from the molds, so that manufacturing is simplified and there is no need for additional cores. The two half shells are preferably embodied as identical components, so that only a single mold is required to produce the insulating sleeve, and the inventory is reduced. By constructing the insulating sleeve from two identical half shells, a good accuracy to size of the cylindrical insulating sleeve can be achieved, and low tolerances can be maintained. To fix the position of the two half shells of the insulating sleeves relative to one another, the half shells can overlap in the circumferential direction. One half shell, on at least one longitudinal side that extends parallel to the longitudinal central axis of the insulating sleeve, is preferably provided with a recess that extends parallel to the longitudinal central axis, and the other half shell, on the associated longitudinal side is provided with an edge that extends parallel to the longitudinal central axis, whereby the edge of the one half shell projects into the recess of the other half shell. Where the half shells have an identical construction, each half shell has one edge and one recess, whereby an edge of one half shell respectively projects into the recess of the other half shell.  
      The insulating sleeve expediently has means to fix the position of the insulating sleeve relative to the housing. As a result, the position in the housing can be fixed in a straightforward manner without requiring additional components. Even during installation a correct positioning of the components relative to one another is thereby ensured. The insulating sleeve can be provided with a collar that limits the depth of insertion of the insulating sleeve into the housing. In this connection, the collar is in particular disposed on the front side of the housing. The insulating sleeve is expediently held in the housing in the direction of its longitudinal central axis by means of an arresting connection. The arresting connection in particular prevents movement of the insulating sleeve out of the housing, so that the position of the insulating sleeve, in the direction of its longitudinal central, is fixed by the collar and the arresting connection. To fix the rotational position of the insulating sleeve in the housing, the insulating sleeve is advantageously provided with a longitudinal rib that cooperates with the housing. To fix the position of the insulating sleeve on the guide rod, the insulating sleeve can have a shoulder that forms an abutment for the guide rod. As a result, the relative position of the gear mechanism housing to the guide rod is also fixed by means of the insulating sleeve. The present application is in particular provided for implements where the drive motor is an electric motor, where a severance of the connection cable of the implement can occur.  
      Further specific features of the present application will be described in detail subsequently.  
     DESCRIPTION OF SPECIFIC EMBODIMENTS  
      Referring now to the drawings in detail, in  FIG. 1 a  trimmer  1  is shown as an example for a manually-guided implement. However, the manually-guided implement can also be a brushcutter, a pole pruner or the like. The trimmer  1  includes a motor housing  2  in which is disposed the drive motor  50 , which is schematically indicated in  FIG. 1  and is embodied as an electric motor. To supply energy to the drive motor  50 , the motor housing  2  has an electrical connecting cable  3 . The trimmer  1  also includes a guide rod  5 ; the motor housing  2  is secured to a first, motor-side end  40  of the guide rod  5 . Disposed adjacent to the motor housing  2 , on the guide rod  5 , is a handle  4  for guiding the trimmer  1 . The handle  4  surrounds the guide rod  5 . A portion of the length of the guide rod  5  is surrounded by a grip hose  55  at which the operator can grip the trimmer with his or her other hand. However, a handle could also be secured to the guide rod  5  for guiding the trimmer  1 . A handle frame from which one or two handles are disposed can also be expedient. At the opposite, tool-side end  41  of the guide rod  5  a gear mechanism housing  7  is secured by means of a clamping connection  48 , which is schematically indicated in  FIG. 1 . In this connection, the guide rod  5  extends into a receiver  9  of the gear mechanism housing  7 . A drive shaft  42 , which transfers the drive motion of the drive motor  50  to the gear mechanism housing  7 , extends through the hollow guide rod  5 . Disposed in the gear mechanism housing  7  is a gear mechanism  49  which is schematically indicated in  FIG. 1 . Extending out of the gear mechanism housing  7  is the shearing blade  8  of the trimmer  1 , which is driven by the gear mechanism  49  and is mounted in the gear mechanism housing  7 .  
      The gear mechanism housing  7  is illustrated in an enlarged view in  FIG. 2 . The gear mechanism housing  7  has a sleeve-like portion  26  in which is formed the receiver  9  for the guide rod  5 . The sleeve-like portion  26  has a longitudinal slot  56  that divides the sleeve-like portion  26  into two half shells  13  and  14 , which are connected via the clamping connection  48  ( FIG. 1 ) with the guide rod  5 , which is not shown in  FIG. 2 . However, the gear mechanism housing  7  can also be formed in two parts. Disposed in the sleeve-like portion  26  is an insulating sleeve  10 . The inner surface  51  of the insulating sleeve  10  rests against the guide rod  5  in the installed state, while the outer surface  52  of the insulating sleeve  10  shown in  FIG. 3  rests against the gear mechanism housing  7 .  
      The insulating sleeve  10  is formed of two half shells  11 ,  12  that rest against one another approximately in the plane of separation between the half shells  13  and  14  of the gear mechanism housing  7 . As a result, the first half shell  11  is disposed essentially in the first half shell  13  of the gear mechanism housing  7  and the second half shell  12  is disposed essentially in the second half shell  14  of the gear mechanism housing  7 . The two half shells  11  and  12  of the insulating sleeve  10  are identical, in other words, are embodied as identical components. The identical half shells  11 ,  12  have an outwardly projecting collar  15  that rests against the gear mechanism housing  7  on that side that faces the motor housing  2  of the trimmer  1 ; the depth of insertion of the insulting sleeve  10  into the gear mechanism housing  7  is limited. At the opposite end the two half shells  11  and  12  of the insulating sleeve  10  have an inwardly projecting shoulder  16  that limits the depth of insertion of the guide rod  5  into the insulating sleeve  10 .  
      The two half shells  11 ,  12  of the insulating sleeve  10  overlap one another in the peripheral direction in the region of the plane of separation. For this purpose, the first half shell  11  has an inner longitudinal edge  22  that extends in the longitudinal direction of the insulating sleeve  10 . Adjacent to the inner longitudinal edge  22 , the second half shell  12  has an outer longitudinal edge  21  that rests against the inner longitudinal edge  22  radially outwardly of the inner longitudinal edge. On the opposite side, the second half shell  12  has an inner longitudinal edge  20  that rests against an outer longitudinal edge  23  of the first half shell  11 . As a result, the two half shells  11  and  12  are secured relative to one another in a radial direction. Since the two half shells  11 ,  12  have an identical configuration, the two inner longitudinal edges  20  and  22 , and the two outer longitudinal edges  21  and  23 , respectively correspond to one another.  
      For the clamping connection  48 , via which the gear mechanism housing  7  is fixed in position on the guide rod  5 , the first half shell  13  of the sleeve-like portion  26  has four jaws  27  that are fixed on the sleeve-like portion  26  and extend outwardly. In this connection, two jaws are disposed on each side of the insulating sleeve  10 . Relative to the plane of the longitudinal slot  56 , four jaws  28  are fixed in position in the second half shell  14  symmetrical to and opposite from the jaws  27 . The jaws  27  are provided with securement bores  25 , and the jaws  28  are provided with securement bores  24 . Tightening screws, which are not shown in  FIG. 2 , extend through the securement bores to clamp the two half shells  13  and  14  together. As a result, the two half shells  11  and  12  of the insulating sleeve  10  are also pressed against one another and against the guide rod  5 . This results in a fixed connection of the gear mechanism housing  7  on the guide rod  5 .  
      The insulating sleeve  10  is expediently made of a polymeric material, especially PA 66 which is reinforced with glass fibers. The glass fiber content is expediently approximately 30%. In this way, a high mechanical strength for the insulating sleeve  10  is achieved, thus preventing creeping of the material during operation. This ensures that the gear mechanism housing  7  is fixedly disposed on the guide rod  5 .  
      FIGS.  3  to  9  show the construction of the second half shell  12  in detail. The first half shell  11  is identical in construction to the second half shell  12 . As shown in  FIG. 3 , adjacent to the collar  15  the first half shell  12  has a longitudinal rib  18 , which extends parallel to the longitudinal central axis  29  of the insulating sleeve  10 . The longitudinal ribs  18  of the identical half shells  11 ,  12  are disposed in the longitudinal slot  56  and thus fix the rotational position of the insulating sleeve  10  in the gear mechanism housing  7  ( FIG. 2 ). At that end opposite the collar  15 , which during operation is disposed within the gear mechanism housing  7 , the half shell  12  is provided with the radially inwardly extending annular shoulder  16 . This annular shoulder  16  merges via a bevel  39  into the outer surface  52 . Adjacent to the annular shoulder  16 , the half shell  12  is provided with a recessed area  19  that is disposed approximately in the middle of the periphery of the half shell  12  and extends radially inwardly from the outer surface  52 . As a result, sufficient installation space is available for components of the gear mechanism housing  7 , especially screws. For the fixation of the half shell  12  in the direction of the longitudinal central axis  29 , the half shell  12  is provided with a transverse fin  17 , which is embodied as an arresting element.  
      As schematically shown in  FIG. 4 , during operation the fin or stop  17  is disposed behind an arresting edge of the gear mechanism housing  7 . The collar  15  rests against a surface  53  of the gear mechanism housing  7 . By means of the collar  15  and the transverse fin  17  the half shell  12  is thus secured in the gear mechanism housing  7  in the direction of the longitudinal central axis  29 .  
      As shown in FIGS.  4  to  9 , the half shell  12  is provided on its longitudinal side  33 , which is disposed toward the front in  FIG. 4 , with the outer longitudinal edge  21 . Radially inwardly of the outer longitudinal edge  21 , the second half shell  12  is provided with a longitudinal recess  35 , which extends parallel to the longitudinal central axis  29 . As shown in  FIG. 2 , the longitudinal recess  35  serves for receiving the inner longitudinal edge  22  of the first half shell  11 . The outer longitudinal edge  21  has an edge section  37  that extends on the annular shoulder  16  at the rear end face  30  of the half shell  12 . The rear end face is that end face that faces away from the collar  15 . Also the longitudinal recess  35  continues with a transverse recess  46  at the annular shoulder  16 . Due to the construction of the half shells  11  and  12  as identical components, the outer longitudinal edge  23  has an identical configuration to the outer longitudinal edge  21 .  
      The opposite longitudinal side  32  of the second half shell  12  has the inner longitudinal edge  20 , which extends parallel to the longitudinal central axis  29  over nearly the entire length of the half shell  12 ; the longitudinal edge  20  continues in an edge section  47  at the annular shoulder  16 . Formed radially beyond the inner longitudinal edge  20  is a longitudinal recess  34  that, as shown in  FIG. 2 , serves for receiving the outer longitudinal edge  23  of the half shell  11 . The longitudinal recess  34  continues at the annular shoulder  16  in a transverse recess  36 . At the front end face  31 , which is disposed adjacent to the collar  15 , the half shell  12  has a bevel  44 , which facilitates insertion of the guide rod  5  into the insulating sleeve  10  during assembly. The inner longitudinal edge  22  of the first half shell  12  is identical in construction to the inner longitudinal edge  20  of the second half shell  12 .  
      As shown in the cross-sectional view of  FIG. 6 , in the interior of the half shell  12  the annular shoulder  16  forms an abutment  38  for the guide rod  5 , which is not shown in  FIG. 6 . At the end face  30 , the half shell  12  has an opening  43 , which is delimited by the annular shoulder  16 . By means of the opening  43 , the drive shaft  42  of the trimmer  1  can extend through the insulating sleeve  10  to the gear mechanism  49  that is disposed in the gear mechanism housing  7 .  
      As shown in  FIG. 7 , the transverse fin  17  extends over an angle α, which is preferably approximately 60°. The longitudinal recesses  34  and  35 , and the longitudinal edges  20  and  21 , each extend over the plane  54  of the longitudinal slot  56  of the gear mechanism housing  7 . The longitudinal recesses  34  and  35 , and the longitudinal edges  20  and  21 , have a height a that is preferably 10 to 20% of the inner diameter of the insulating sleeve  10 . At those edges that face the longitudinal central axis  29 , the longitudinal edges  20  and  21  are provided with a bevel  57 ,  58 .  
      Since the two half shells  11  and  12  of the insulating sleeve  10  are designed as identical components, the description of the second half shell  12  also pertains to the identical first half shell  11 . Due to the fact that a respective longitudinal edge of one half shell cooperates with a recess of the other half shell, a construction having identical components is possible.  
       FIG. 10  shows a pole pruner  61 . The construction of the pole pruner  61  corresponds essentially to the construction of the trimmer  1  shown in  FIG. 1 . However, the tool of the pole pruner  61  is a saw chain  63  that is schematically illustrated in  FIG. 10  and circulates about a guide bar  62 . The guide bar  62  is fixed in position on a gear mechanism housing  7  of the pole pruner  61  and is driven by a gear mechanism  49  that is disposed in the gear mechanism housing  7 . The gear mechanism housing  7  has a receiver  9  in which the guide rod  5  is disposed in an insulating sleeve  10 , which is not shown in  FIG. 10 . As a result, the saw chain  63  is electrically separated from the guide rod  5 . As a result, injury to the operator is avoided if an electrical line is severed by the saw chain  63 , even if the safety device fails and the operator accidentally contacts the guide rod  5 .  
       FIG. 11  schematically illustrates a brush cutter  71 , which is guided by an operator  74 . The brushcutter  71  has a motor housing  2  that is fixed at one end of a guide rod  5 . Disposed at the other end of the guide rod  5  is a gear mechanism housing  7 , which is fixed on the guide rod  5  by means of an insulating sleeve  10  that electrically insulates the guide rod  5  from the gear mechanism housing  7 . A blade  72  is rotatably driven on the gear mechanism housing  7 . Fixed on the gear mechanism  7  is a guard  73 , which screens the blade  72  on that side facing the operator  74 . Fixed on the guide rod  5  is a handle frame  75  on which are disposed two handles  76  for guiding the brushcutter  71 . Furthermore fixed on the guide rod  5  is a carrying strap  77  that the operator carries over the shoulder to absorb the weight of the brush. The structural configuration of the insulating sleeve  10  of the brushcutter  71  corresponds to the construction of the insulating sleeve shown in FIGS.  2  to  9 . The arrangement of the drive motor, the drive shaft and the gear mechanism, which are not shown in  FIG. 11 , correspond to the arrangement of the trimmer shown in  FIG. 1 .  
      The specification incorporates by reference the disclosure of German priority document 10 2005 051 886.9 filed Oct. 29, 2005.  
      The present invention is, of course, in no way restricted to the specific disclosure of the specification and drawings, but also encompasses any modifications within the scope of the appended claims.