Patent Publication Number: US-2007107236-A1

Title: Hand-Held Cut-Off Machine

Description:
BACKGROUND OF THE INVENTION  
      The invention relates to a hand-held cut-off machine with a motor housing receiving a drive motor, with a cutting wheel driven by the drive motor and supported on an extension arm, and with a conduit for water extending from a water connector to the cutting wheel.  
      Hand-held cut-off machines of known configuration have a cutting wheel that is rotatably drivable about an axis of rotation and is acted on by a drive motor that is in particular embodied as an internal combustion engine. The drive motor is arranged in a motor housing and the cutting wheel is rotatably supported on an extension arm. The extension arm comprises a drive, for example, in the form of a belt drive by means of which the rotary movement of the drive motor is transmitted onto the cutting wheel.  
      In the area of the cutting wheel and in particular in the area of the cover that partially covers the cutting wheel, one or several spray nozzles are provided through which water is guided into the cutting area. The water is provided for binding the grinding dust and for cooling the cutting wheel. For this purpose, the cut-off machine is provided with a water connector through which water from a container or a public water supply system is supplied to the system. A conduit of the cut-off machine leads from the water connector to the cutting wheel and is positioned external to the cut-off machine for maintaining a compact configuration.  
      In operation, the external positioning of the conduit can be disturbing. The conduit can be caught on things and can be damaged. Also, proper guiding during the cutting operation can be impaired.  
     SUMMARY OF THE INVENTION  
      The invention has the object to further develop a cut-off machine of the aforementioned kind in such a way that its susceptibility to failure is reduced.  
      According to the present invention, a cut-off machine is proposed in which a section of the water-carrying conduit is integrated into the extension arm. The integration of this section into the extension arm is more than providing a simple fastening function. In the area of integration, the integrated conduit section is protected from impact and from catching on things. Externally arranged conduit sections extend without protection and are limited with regard to their movability only across a comparatively short distance so that in this area the risk of damage or catching on things is also reduced. The extension arm in usual configurations is suitable for receiving the aforementioned integrated conduit section without this requiring a significantly increased size. The cut-off machine remains compact for enabling excellent handling.  
      The conduit section can be integrated into a supporting element of the extension arm. Preferably, it is integrated into a housing of the extension arm which covers a drive for the cutting wheel. A cross-sectional increase of supporting parts is not required. The extension arm housing including the integrated conduit section can be easily removed for maintenance work. Existing cut-off machines can be retrofitted with minimal expenditure with a extension arm housing that receives the conduit section.  
      It can be expedient to arrange the integrated section of the conduit so as to be only partially recessed within the extension arm. Preferably, the integrated section extends within the contour of a lateral outer surface of the extension arm. Primarily this lateral outer surface is subject to the risk of contact or impact. The extension of the conduit within the contour of this lateral outer surface has the effect that an object impacting the outer surface will slide off the lateral outer surface without the guiding precision of the cut-off machine being impaired significantly and without causing the risk of catching on things.  
      The integrated section of the conduit can be an integrated pipe or a channel. Expediently, the integrated section, in particular the entire conduit, is configured as a flexible hose. This provides an inexpensive water carrying action while avoiding hose couplings, separating locations and the like; if wear occurs, exchange is easy. A complete flexible configuration facilitates adaptation labor and enables with minimal constructive expenditure a swiveling of the protective cover that covers the cutting wheel and has spray nozzles arranged thereat.  
      In a preferred embodiment, the integrated section of the conduit is secured, especially by clamping, in an outwardly open receiving groove. For this purpose, at least one inwardly oriented clamping tooth is expediently provided on an outer edge of the receiving groove, wherein in particular three such clamping teeth are provided that are alternatingly positioned on both edges of the receiving groove and are staggered relative to one another in the longitudinal direction of the groove. The outwardly open receiving groove enables easy mounting of the flexible hose and provides the possibility of visual control by the operator. The clamping tooth or clamping teeth contribute to securing the conduit section within the receiving groove. The alternating arrangement of the three clamping teeth also effects an axial positional securing action of the integrated conduit section. Its clamping action leads to securing against axial sliding but allows at the same time a manual axial position adjustment.  
      In an advantageous embodiment, the integrated section of the conduit, relative to a usual working position of the cut-off machine, is guided toward the cutting wheel in a vertical direction from bottom to top. The water connector at the intake side is positioned in the area of the bottom of the cut-off machine so that it has a sufficient spacing to the grips of the cut-off machine and does not impair the operator during operation. On the other hand, a downstream compensation section of the conduit that extends from the integrated conduit section to the spray nozzle is provided at least partially above the extension arm and thus at a comparatively great spacing relative to the surface to be machined. The extension arm is positioned between the surface to be worked on and the exposed compensation section and therefore provides an additional protective function. Because of the extension in the vertical direction, a significant length of the integrated conduit section extending in the longitudinal direction of the cut-off machine or the lateral surface of the extension arm is prevented. The risk of contact in this area is reduced.  
      For enhancing the protective function, the area of the integrated section is arranged preferably in the area of the grip pipe of the cut-off machine. Relative to the usual working position of the cut-off machine, the integrated section of the conduit is expediently positioned a short distance in front of the grip pipe in longitudinal direction; the grip pipe is guided in an arc shape about an intake section of the conduit that extends in the longitudinal direction. The grip pipe extending in an arc shape about the intake section acts as a protective bow for the intake section and for the integrated section of the water conduit. The lateral projection of the grip pipe provides this protective function not only in the lateral direction but also upwardly, downwardly, at a slant forwardly, and at a slant rearwardly.  
      In a preferred embodiment, a protective cover is provided that covers the cutting wheel partially and is pivotably adjustable; it has at least one spray nozzle that is directed toward the cutting wheel and is in flow connection with the conduit wherein a flexible compensation section of the conduit between the integrated section and the spray nozzle is positioned in an arc shape. The arc-shaped positioning enables a free pivoting action of the protective cover into different pivot positions that are matched to the work to be performed, respectively. Securing the integrated conduit section on the extension arm of the cut-off machine limits the movability of the compensation section positioned in an arc shape to the deformation required for adjustment. Accidental flexible deformations of the compensation section, particularly in the lateral direction, are prevented so that the risk of damage or catching on things is reduced. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      One embodiment of the invention will be explained in more detail in the following with the aid of the drawing.  
       FIG. 1  shows In a perspective side view a cut-off machine according to the invention with a water connector and a conduit section integrated into a housing of the extension arm.  
       FIG. 2  shows in an enlarged detail view the arrangement according to  FIG. 1  in the area of the integrated conduit section with details in regard to a clamping attachment in a receiving groove.  
       FIG. 3  is a plan view onto the cut-off machine according to  FIG. 1  in the area of the extension arm and the protective cover attached thereto showing further details in regard to how the hose is guided.  
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS  
       FIG. 1  shows in a perspective view a hand-held cut-off machine embodied according to the invention with a motor housing  1 , an extension arm  2 , and a cutting wheel  3 . In the motor housing  1  a drive motor  1   a,  not illustrated in detail, is arranged which drive motor  1   a  is an internal combustion engine in the illustrated embodiment but can also be an electric motor. The cut-off machine is shown in its usual working orientation; the arrows  17 ,  18 ,  24  define a vertical direction, a longitudinal direction, and a lateral direction, respectively.  
      Laterally on the motor housing  1  a cable pull starter  32  for starting the internal combustion engine is arranged. Relative to the vertical direction  17  and the longitudinal direction  18 , an upper rear grip  29  is provided on the motor housing  1  on a side facing the operator; for controlling the motor output a throttle lever  30  and also a throttle lock  31  are arranged on the grip. Relative to the longitudinal direction  18 , in front of the rear grip  29  on the end of the motor housing  1  facing away from the operator, a forward grip pipe  19  is provided that extends in an arc shape about the motor housing  1  approximately in a plane defined by the vertical direction  17  and the lateral direction  24 . A lateral grip section  28  of the grip pipe  19  extends approximately in the vertical direction  17  while below the motor housing  1  an adjoining arc-shaped grip section  35  extends approximately in the lateral direction  24  and is attached with its free end on the motor housing  1 . In this area there are also legs  36  for setting down the cut-off machine.  
      On the lateral surface of the motor housing  1  shown here, the extension arm  2  is arranged that, beginning at the motor housing  1 , extends essentially in the longitudinal direction  18  and projects past the motor housing  1 . On a forward end  27  of the extension arm  2  that is arranged opposite the motor housing  1  when viewed in the longitudinal direction  18 , the cutting wheel  3  is rotatably supported about axis of rotation  26  wherein the axis of rotation  26  extends in the lateral direction  24 . Within the extension arm  2 , a drive  8  is positioned that in the illustrated embodiment is a belt drive and transmits the motor output of the drive motor onto the cutting wheel  3 . The drive  8 , not shown in detail, is covered by housing  7  of the extension arm  2 . The extension arm housing  7  has a substantially plane outer surface  9  that is positioned approximately in a plane defined by the vertical direction  17  and the longitudinal direction  18 .  
      A conduit  5  for water is provided for binding the grinding dust that is produced in operation of the cut-off machine as well as for cooling the cutting wheel  3 ; the conduit extends from a water connector  4  to the area of the cutting wheel  3 . For this purpose, the water connector  4  has a hose coupling  33  that can be connected to a water container or a public water supply system. In the flow direction downstream of the connector, a control lever  34  is provided in the water connector  4  by means of which the flow rate of the water can be adjusted.  
      It can be expedient to guide the conduit  5  from the water connector  4  to a hub of the cutting wheel  3 , for example. In the illustrated embodiment a protective cover  21  is provided that covers the cutting wheel  3  partially and is provided with a total of two spray nozzles  22 . A first spray nozzle  22  is arranged in a lateral wall of the protective cover  21  while the other spray nozzle  22 , not illustrated here but illustrated in  FIG. 3 , is arranged on the opposite lateral wall of the protective cover  21 . On the inner side of the protective cover  21 , the spray nozzle nozzles  22  are directed onto the lateral surfaces of the cutting wheel  3 , respectively.  
      A bow  25  with grip  39  extends arc-shaped on the outer side of the protective cover  21  from one lateral surface to the opposite lateral surface and realizes a flow-conducting connection between the two spray nozzles  22 . The conduit  5  is connected to the illustrated spray nozzle  22  so as to be in flow communication. A flow of water that is introduced through the water connector  4  and supplied through the conduit  5  is divided at the first spray nozzle  22  illustrated here. A first partial flow is supplied directly to the cutting wheel  3  while a second partial flow is guided through the bow  25  onto the opposite side of the protective housing  21  and is directed against the cutting wheel  3  by means of the spray nozzle  22  ( FIG. 3 ) arranged at the opposite side.  
      The water connector  4  is positioned laterally below the motor housing  1  and extends approximately parallel to the longitudinal direction  18 . The adjoining conduit  5  is configured as a monolithic flexible hose extending between the water connector  4  and the first spray nozzle  22 . A first section of the conduit  5  relative to the flow direction is a supply section  20  that leads away from the water connector  4  approximately parallel to the longitudinal direction  18  and extends to the extension arm  2 . Relative to the lateral direction  24 , the water connector  4  and the conduit  5  are recessed relative to the outer surface  9  of the extension arm  2 . In contrast to this, the lateral grip section  28  projects with a significant length in the lateral direction  24  past the outer surface  9  of the extension arm  2  and is guided together with the lower grip section  35  in an arc shape about the supply section  20 . The lateral grip section  28  effects in the lateral direction a protective function relative to the water connector  4  and conduit  5  while such a protective function in a direction opposite to the vertical direction  17  is provided by the lower grip section  35  and the legs  36 . Because of the comparatively large lateral projecting length of the lateral grip section  28  and the projecting length of the module comprised of the lower grip section  35  and the legs  36  in a direction opposite to the vertical direction  17 , this protective function extends at least partially also in the longitudinal direction  18 .  
      A receiving groove  10  is formed in the outer surface  9  of the extension arm housing  7  and has a longitudinal direction  16  that extends approximately in the vertical direction  17 . In the receiving groove  10  an integrated conduit section  6  of the conduit  5  is arranged to be countersunk such that, relative to the lateral direction  24 , it is recessed relative a contour of the extension arm housing  7  as defined by the lateral outer surface  9 .  
      Relative to the longitudinal direction  18 , the receiving groove  10  is positioned with integrated conduit section  6  at a minimal spacing in front of the lateral grip section  28  wherein the supply section  20  that is guided through the arc shape of the grip pipe  19  is bent upwardly near the receiving groove  10  and, extending in the vertical direction  17  from bottom to top, passes into the integrated conduit section  6 . The integrated conduit section  6  and the lateral grip section  28  extends approximately parallel to one another. The supply section  20  and the integrated conduit section  6  are therefore both positioned in the area of the protective action of the grip pipe  19 .  
      In the illustrated arrangement the flow direction of the water within the integrated conduit section  6  is in the vertical direction  17  from bottom to top. In the flow direction, a compensation section  23  adjoins the integrated conduit section  6  and extends in three-dimensional arc approximately in an S-shape from the extension arm  2  to the first spray nozzle  22 . A section  40  of the compensation section  23 , indicated in dashed lines, is positioned relative to the lateral direction  24  between the extension arm  2  and the protective cover  21 . For assisting this course, the compensation section  23  is connected such to the illustrated spray nozzle  22  that it extends in the connecting area parallel to the illustrated leg of the bow  25  approximately from a radial inward position to a radial outward position.  
      The protective cover  21  is pivotably secured on the extension arm  2  wherein a grip  39  is provided on the bow  25  for manually pivoting the cover. A pivot position is illustrated in which the grip  39  is approximately in its rear position. From here, the grip  39  can be pivoted in the longitudinal direction  18  to the front together with the protective cover  20 . The pivot axis of the protective cover  21  is identical to the rotary axis  26  of the cutting wheel  3 . The configuration of the conduit  5  as a flexible hose enables an elastic deformation of the compensation section  23  so that it can follow the pivot movement of the spray nozzle  22 . When pivoting the protective cover  21  to the front, the compensation section  23  as a whole comes to rest above the extension arm  2 . The compensation section  23  opening essentially radially into the bow  25  in combination with integrated attachment of the section  6  on the extension arm  2  lead to the compensation section  23  having no tendency to project in the lateral direction  24  past the outer surface  9 . Instead, upon returning the protective cover  21  by pivot action into the illustrated position, the area  40  of the compensation section  23  is returned automatically into the position between the extension arm  2  and the protective cover  21  in which position it is protected against outer loads.  
       FIG. 2  shows an enlarged detail view of the arrangement according to  FIG. 1  in the area of the receiving groove  10 . The receiving groove  10  is recessed into the housing  7  of the extension arm  2  such that it is open in the lateral direction  24  toward the exterior. Its depth relative to the lateral direction  24  is such that the diameter of the section  6  of the conduit  5  is completely received within the receiving groove  10 . The approximately circular cross-section of the integrated conduit section  6  therefore does not project in the radial direction past the outer surface  9 . Instead, the cross-section of the integrated conduit section  6  is integrated about the entire length of the receiving groove  10  completely within the extension arm  2  in such a way that it extends, relative to the lateral contour that is defined by the outer surface  9 , completely within the extension arm  2  or its housing  7 . As an alternative, a pipe can be provided that extends within the contour of the extension arm  2  and through which the conduit  5  is pushed or which itself forms the integrated conduit section  6 .  
      Relative to the longitudinal direction  18 , the receiving groove  10  is delimited by a forward edge  11  and a rear edge  12  that are both oriented in the longitudinal direction  16  of the receiving groove  10  and are both positioned in the plane of the lateral outer surface  9  of the extension arm housing  7 . Centrally at the forward edge  11  a clamping tooth  14  is arranged that extends past the leading edge  11  in a direction opposite to the longitudinal direction  18  into the receiving groove  10 ; in the lateral direction  24 , it extends from the outer surface  9  or the edge  11  to the bottom  37  of the receiving groove  10  illustrated in  FIG. 3 . The opposing edge  12  is provided with two additional clamping teeth  13 ,  15  that are mirror-symmetrical to the clamping tooth  14  and are identical to it otherwise. Relative to the vertical direction  17  or the longitudinal direction  16  of the receiving groove  10 , the clamping teeth  13 ,  14 ,  15  are arranged alternatingly on the two edges  11 ,  12  so that the clamping tooth  14  on the edge  11  is arranged above the clamping tooth  15  on the edge  12  and the clamping tooth  13  on the edge  12  is arranged above clamping tooth  14 . Between these clamping teeth  13 ,  14 ,  15  and the oppositely positioned sidewalls of the receiving groove  10 , the integrated conduit section  6  of the conduit  5  in the form of a flexible hose is secured by clamping in the receiving groove  10 . The clamping action acts in all direction  17 ,  18 ,  24  and secures the integrated conduit section  6  but allows for manual position adjustment of the integrated conduit section  6  in the longitudinal direction  16  of the receiving groove  10 .  
       FIG. 3  shows a plan view of the arrangement according to  FIG. 1  in the area of the extension arm  2  and the protective cover  21 . It can be seen that the lateral grip section  28  of the grip pipe  19  projects in the lateral direction  24  past the lateral outer surface  9  of the extension arm  2  by an amount that is greater than a spacing of the integrated conduit section  6  extending in the longitudinal direction  16  from the grip pipe  19 .  
      The receiving groove  10  integrated into the extension arm housing  7  has an approximately C-shaped cross-section wherein a bottom  37  of the receiving groove  10  relative to the lateral outer surface  9  is recessed in the lateral direction  24 . In the area of the bottom  37  the receiving groove  10  has a width that is greater than the opening width between the edges  11 ,  12  in the longitudinal direction  18 . An exterior side of the integrated conduit section  6  is at least partially surrounded or covered by the edge  11  wherein the cross-section of the integrated conduit section  6  is recessed relative to the lateral outer surface  9  and the edges  11 ,  12  in the lateral direction  24 . The edge  11  and optionally also the edge  12  assist the clamping teeth  13 ,  14 ,  15  illustrated in  FIG. 2  in the clamping fixation of the integrated conduit section  6 . The spacing of the two edges  10 ,  11  in the longitudinal direction  18  can be smaller than the diameter of the flexible integrated conduit section  6  so that, for mounting, this section must be pressed into the receiving groove  10  with elastic cross-sectional deformation so as to snap into place.  
      The illustration according to  FIG. 3  also shows that relative to the lateral direction  24  between the extension arm  2  and the protective cover  21  an intermediate space  38  is provided. Starting at the integrated conduit section  6  or the receiving groove  10 , the compensation section  23  extends first in an arc shape in the lateral direction  24  to the intermediate space  38  from where it continues on to the spray nozzle  22 . It can be seen that the bow  25  is arranged mirror-symmetrically to a center plane of the protective cover  21  and is provided with two diametrically opposed spray nozzles  22 . About the circumferential contour of the protective cover  21 , a water channel not illustrated, extends through the bow  25  for guiding the water flow from the compensation section  23  and the first spray nozzle  22  to the second spray nozzle  22 .  
      The specification incorporates by reference the entire disclosure of German priority document 10 2005 049 766.7 having a filing date of Oct. 18, 2005.  
      While specific embodiments of the invention have been shown and described in detail to illustrate the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles.