Patent Publication Number: US-8522894-B2

Title: Hand machine tool comprising at least one handle

Description:
RELATED ART 
     The invention is based on a power tool with at least one handle according to the preamble of claim  1 . 
     A handle for guiding or holding vibrating devices was made known in DE 87 01 722.9 C1. The handle comprises a grip part having a metal core coated with a vibration-damping plastic. A first piece of sheet metal is connected to the metal core on one end via a screw, which first piece of sheet metal is connected to a second piece of sheet metal via an elastic buffer in the axial direction opposite to the grip part. The second piece of sheet metal, in turn, is connected to a guide shaft of the device via a screw. 
     ADVANTAGES OF THE INVENTION 
     The invention is based on a power tool with at least one handle that comprises at least one grip part that is firmly connected to a mounting part via at least one elastic, vibration-damping element, via which the grip part is affixable to a housing. 
     It is proposed that a connection between the grip part and the mounting part is secured using the elastic element via at least one movable retaining element. If the elastic element becomes damaged, the grip part can be prevented from separating from the housing, and control of the power tool via the grip part can be ensured at all times. Transmission of vibrations via the retaining element can be prevented by means of the movable design of the retaining element when [the power tool is] operated properly. The mounting part is advantageously designed as a piece separate from the housing, although it can also be designed at least partially integrated with the housing of the power tool. 
     In a further embodiment, however, it is proposed that the retaining element is formed by a flexible element, e.g., by a chain or, advantageously, by a plastic or wire rope, etc. When a flexible retaining element is used, a transmission of vibrations can be prevented cost-effectively using a simple design, and the retaining element can be favorably integrated in the elastic element. 
     In order to protect the retaining element from damage during operation of the power tool, and to make a concealed integration of the retaining element in the handle possible, the elastic element advantageously encloses the retaining element. 
     It is further proposed that the retaining element is located in the elastic element in the center along a centerline, by way of which, when a tilting motion takes place, undesired tensile stresses in the retaining element and a transmission of vibration associated therewith can be prevented. 
     If the retaining element, in the installed state, is subjected to compressive stresses, and the elastic element is subjected to tensile stresses, a higher loadability of the elastic element can be achieved than without pretension, and breakage or separation from the grip part and from the mounting part and/or a tearing of the elastic element can be prevented. Moreover, the retaining element can be used advantageously to secure the elastic element to the grip part and to the mounting part, e.g., in that the retaining element applies a contact force necessary for a cemented joint. The compressive stress can be advantageously achieved in the elastic element by tensioning the retaining element, e.g., by tensioning a flexible retaining element—advantageously located in the middle of the elastic element along a centerline—using a fastening screw. 
     In a further embodiment according to the invention, it is proposed that the retaining element is formed by a band that encloses the elastic element. The retaining element designed in the shape of a band can protect the elastic element—formed out of a usually soft material—against outside influences and damage during operation, e.g., against heat, effects of ultraviolet radiation, dust, moisture, and hard objects, etc., by means of its closed surface. The band can be produced out of various materials appearing reasonable to one skilled in the art, e.g., out of fabric tape, etc. Basically, the retaining element can also be formed cost-effectively out of at least one flexible component that is located radially outside of the elastic element, e.g., out of one or more ropes. 
     In order to protect the elastic element from outside influences, it can also be enclosed in a sleeve made of solid material, which sleeve can be secured to the grip part or the mounting part and is located at a distance from the grip part or the mounting part in order to prevent transmission of vibrations. 
     The retaining element can be formed out of a rigid component instead of a flexible component, which rigid component is supported in movable fashion relative to the mounting part and/or the grip part. The retaining element can be designed to be easily installed or removed, so it can be replaced if damaged. Moreover, a maximum displacement of the elastic element from a normal position can be easily determined in at least one tilting direction and/or one sliding direction via the retaining element and, in particular, via a rigid retaining element. An overstretching of the elastic element can be prevented by means of the retaining element, and a long service life can be achieved. 
     The retaining element is advantageously supported firmly in the mounting part and in movable fashion relative to the grip part, whereby a space in the grip part can advantageously be used for a freedom of motion of the retaining element and a simple installation starting with the grip part can be achieved. Moreover, a fastening screw located in the mounting part can be used for a firm connection of the retaining element. Additional mounting parts for the retaining element can be spared. Basically, however, the retaining element can also be designed to be rigid in the grip part and movable in relation to the mounting part. 
     It is further proposed that the retaining element is formed by a screw that can be screwed particularly advantageously into the fastening screw in the mounting part. A screw is particularly cost-effective and can be installed and removed particularly easily and quickly. Instead of a screw, however, a bolt could be used that can be secured either in the grip part or in the mounting part in positive, non-positive, and/or bonded fashion, e.g., it can be pressed in the fastening screw in the mounting part. 
     In addition to a rigid bar, a screw, a chain, and a rope, furthermore, a spring can be used as the retaining element, in particular a coiled spring. Using a fastening element formed by a coiled spring, a particularly simple installation can be achieved, particularly in automated series production. 
     In order to make an advantageous uniform cooling, and advantageously homogenous microstructure, and an advantageously bonded connection to the mounting part and/or the grip part possible after injection molding of the elastic element, the elastic element comprises a non-circular cross-sectional area at least closely before an advantageously round seating surface with the mounting element and/or with the grip part that is smaller than the seating surface, and, in fact, the cross-sectional area is composed particularly advantageously of a round core area and arched extensions abutting the core area radially on the outside. Using a round contour, an advantageously large seating surface between the elastic element and the mounting part and the grip part can be achieved. The seating region can be cooled advantageously by means of the smaller cross-sectional area abutting this. 
     Moreover, an advantageous microstructure can be enhanced by dissipating heat from an internal region of the elastic element via at least one component during production of the elastic element. The component can be formed by means of a retaining element inserted in the elastic element during production itself, or advantageously by a core that is removed after the elastic element is manufactured, and advantageously forms a recess for the retaining element. Advantageously, the core can be cooled compared to the inserted retaining element using a coolant by means of a cooling passage. When using retaining elements in particular that are formed out of rigid components and that can be installed easily after production of the elastic element, it is advantageous that the elastic element can be cooled by means of a core during production. 
     The means of attaining the object of the invention can be used with various power tools appearing practical to one skilled in the art, e.g., with hammer drills, rotary hammers, drills, power-operated screw drivers, sawing, milling, planing, etc. The means of attaining the object of the invention according to the invention can be used with particular advantage in angle grinders, however, and, in fact, using an additional handle extending transversely to the longitudinal direction, which serves primarily to guide the angle grinder. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       Further advantages arise from the following drawing description. Exemplary embodiments of the invention are presented in the drawing. The drawing, the description, and the claims contain numerous features in combination. One skilled in the art will advantageously consider them individually as well and combine them into reasonable further combinations. 
         FIG. 1  shows a schematic representation of an angle grinder from above, 
         FIG. 2  shows a handle according to the invention comprising a flexible retaining element enclosed in an elastic element, 
         FIG. 3  shows a handle with a retaining element designed in the shape of a rod, 
         FIG. 4  shows a section of an alternative to  FIG. 3 , 
         FIG. 5  shows a view along the line V-V in  FIG. 4  during assembly, 
         FIG. 6  shows a handle comprising an elastic element enclosed by a retaining element designed in the shape of a band, 
         FIG. 7  shows a variant of  FIG. 3 , 
         FIG. 8  shows a view along the line VIII-VIII in  FIG. 7 , 
         FIG. 9  shows a view along the line IX-IX in  FIG. 7 , 
         FIG. 10  shows a view along the line X-X in  FIG. 7 , 
         FIG. 11  shows a view along the line XI-XI in  FIG. 7 , and 
         FIG. 12  shows a handle according to  FIG. 7  during its production. 
     
    
    
     DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENT 
       FIG. 1  shows an angle grinder having an electric motor (not shown) supported in a housing  56 , via which a cutoff wheel clamped in the toolholder is driveable. The angle grinder is guidable via a first handle  58  integrated in the housing  56  on the side opposite to the cutoff wheel  54  and extending in the longitudinal direction, and via a second handle  10  secured to a gearbox housing  60  in the region of the cutoff wheel  54  or the toolholder and extending transversely to the longitudinal direction. The handle  10  comprises a grip part  12  that is firmly connected via an elastic, vibration-damping plastic element  14  to a mounting part  16 , via which the grip part  12  is secured to the gearbox housing  60  of the angle grinder via a set screw  18  integrally molded to the mounting part  16 . The elastic plastic element  14  is integrally extruded on the grip part  12  and the mounting part  16  and, as a result, is firmly connected to them. 
     According to the invention, the grip part  12 , in addition to the elastic plastic element  14 , is connected to the mounting part  16  via a movable retaining element  20  ( FIG. 2 ). The retaining element  20  is formed by a flexible component in the form of a wire rope and is located in the elastic plastic element  14  along a centerline. Threaded sleeves (not shown) are secured to the ends of the retaining element  20 , via which the retaining element  20  is screwed to the grip part  12  and the mounting part  16 . The elastic plastic element  14  encloses the retaining element  20 . The retaining element  20 , in the installed state, is subjected to tensile stresses, and the elastic element  14  is subjected to compressive stresses. 
       FIG. 3  shows a further embodiment of a handle  26  according to the invention, in which a retaining element  22  is formed by a rigid rod supported in movable fashion and enclosed in an elastic plastic element  24  applied by injection molding, to the ends of which washers  30 ,  32  are secured in each case. Components that are essentially identical are labelled with the same reference numerals in the exemplary embodiments presented. With regard for features and functions that remain the same, reference is made to the description of  FIG. 1 . 
     One sleeve  34 ,  36  each is secured to the mounting part  16  and the grip part  12 , each of which comprises a washer  38 ,  40  having coaxial openings  42 ,  44  in the direction toward the elastic plastic element  24 . The sleeves  34 ,  36  and the washers  38 ,  40  each abut a space  46 ,  48  filled via injection with an elastic material, into which the retaining element  22  with its washers  30 ,  32  is inserted. The washers  30 ,  32  of the retaining element  22  have a larger diameter than the openings  42 ,  44  and are held captive in the spaces  46 ,  48 . 
     For installation, the washer  30  can be unscrewed from the rod-shaped part of the retaining element  22 . The retaining element  22  can then be inserted into this—before installation of the sleeves  34 ,  36  with the grip part  12  or the mounting part  16 —and the washer  30  can be screwed to the rod-shaped part once more. The sleeves  34 ,  36  are connected to the grip part  12  or the mounting part  16  via threaded joints (not shown). After the sleeves  34 ,  36  are connected to the grip part  12  and the mounting part  16 , the retaining element  22  is coated with elastic plastic applied by injection molding. 
     The sleeves  34 ,  36 , with their washers  38 ,  40 , advantageously produce a positive connection between the grip part  12  and the elastic plastic element  24 , and between the elastic plastic element  24  and the mounting part  16 . Basically, however, the elastic plastic element could be designed with the retaining element, the sleeves, and the washers as an assembly capable of being preassembled, which is then screwed and cemented to the grip part and the mounting part. 
     A maximum displacement of the elastic plastic element  24  is determined by a freedom of motion of the washers  30 ,  32  of the retaining element  22  in the spaces  46 ,  48 , in all directions, in fact. In order to prevent a transmission of vibrations via the retaining element  22 , the retaining element  22  is situated at a distance—filled with an elastic material—from the sleeves  34 ,  36  and the washers  38 ,  40  when [the power tool] is operated properly. 
     A further exemplary embodiment of a handle  62  is shown in  FIGS. 4 and 5 , in which a retaining element  64  is formed by a rigid rod supported in movable fashion and comprising a coating of an elastic plastic element  24  applied by injection molding, the ends  66 ,  68  of which are designed in the shapes of washers. With regard for features and functions that remain the same, reference is made to the description of  FIG. 3 . 
     One structural part  74 ,  76  each is integrally molded to a mounting part  70  and a grip part  72 , each of which is designed in the shape of a washer in the direction toward the elastic plastic element  24  and which comprise coaxial openings  78 ,  80 . 
     The structural parts  74 ,  76  each abut a space  82 ,  84  filled with an elastic material applied by injection, into which the retaining element  64 —designed as a single piece—is inserted with its washer-shaped ends  66 ,  68  during assembly. The retaining element  64  with its rod-shaped part is thereby guided transverse to the longitudinal direction of the handle  62  through lateral openings  86 ,  88  in the structural parts  74 ,  76  ( FIG. 5 ). The retaining element  64  is then secured in the structural parts  74 ,  76  against the direction of its insertion  90  by means of the openings  86 ,  88  by pushing structural parts  92 ,  94 —each of which has an L-shape in the longitudinal view—perpendicular to the direction of insertion  90  and transverse to the longitudinal direction with one opening  96 ,  98  each over the rod-shaped part of the retaining element  64 . The rod-shaped ends  66 ,  68  of the retaining element  64  have a greater diameter than the openings  78 ,  80  and are held captive in the spaces  82 ,  84 . The retaining element  64  is then coated with plastic applied by injection molding. 
     A width  100  of the openings  86 ,  88  transverse to the longitudinal direction of the handle  62  and perpendicular to the direction of insertion  90  of the retaining element  64  is advantageously designed smaller than a diameter  102  of the rod-shaped part of the retaining element  64 , so that the retaining element  64  must be pushed through the openings  86 ,  88  against resistance and then locks in place in the openings  78 ,  80  of the structural parts  74 ,  76 . The retaining element  64  is secured in the openings  78 ,  80  of the structural parts  74 ,  76 , and the structural parts  92 ,  94  can be advantageously spared. 
       FIG. 6  shows a further exemplary embodiment of a handle  50  in which, according to the invention, a retaining element  28  is formed by a flexible fabric tape that encloses an elastic plastic element  52 . The band-shaped retaining element  28  is designed to be essentially non-elastic in the longitudinal direction of the handle  50  and comprises a plastic flange (not shown) abutting the grip part  12  and abutting the mounting part  16  in each case, with which the band-shaped retaining element  28  is firmly connected to the grip part  12  or with the mounting part  16  via arresting connections. 
     In order to prevent a transmission of vibrations via the retaining element  28 , it is designed longer than the elastic plastic element  52 . The elastic plastic element  52  is protected by the retention element  28  against outside influences and damage while the angle grinder is in use. Moreover, a maximum displacement of the elastic plastic element  52  from its normal position is determined by the retention element  28  and, in fact, in the directions of push, tilt, and pull. In the maximum displacement positions, the retention element  28  is tensioned and prevents a further displacement of the elastic plastic element  52 . 
     A handle  104  that is an alternative to the exemplary embodiment in  FIG. 3  is shown in  FIGS. 7 through 12 . The handle  104  comprises a mounting part  110  that is firmly connected via an elastic plastic element  108  with a grip part  106 . The connection between the mounting part  110  and the grip part  106  is secured via a retention element  112  formed by a screw ( FIG. 8 ). 
     During production of the handle  104 , the mounting part  110  and the grip part  106  are first produced out of plastic via injection molding, and a fastening screw  114  is inserted in the mounting part  110  and coated via injection molding with positive engagement in the axial direction and in the direction of rotation, which fastening screw  114  comprises an external thread  118  as well as an internal thread  120  for fastening to a machine housing in the direction of the grip part  106 . The fastening screw  114  could also be pressed into a mounting part afterwards. After applying a coating to the fastening screw  114  via injection molding, the mounting part  110  with the fastening screw  114  and the grip part  106  are placed in a casting mold  140  in order to become bonded to the elastic plastic element  108  in an injection molding procedure ( FIG. 12 ). The casting mold  140  is shaped so that the elastic plastic element  108  comprises a non-circular cross-sectional area  116  closely before a round seating surface  146  with the mounting part  110  and a round seating surface  134  with the grip part  106 , each of which is smaller than the seating surfaces  134 ,  146  and, in fact, the cross-sectional areas  116  each comprises a round core area  122  abutted radially on the outside by four arched extensions  124 ,  126 ,  128 ,  130  ( FIGS. 9 and 11 ). More or fewer than four arched extensions  124 ,  126 ,  128 ,  130  would also be possible. The elastic plastic element  108  comprises a round cross-sectional area  136  in a center region ( FIG. 10 ). 
     Moreover, a core  142  cooled via a fluid passage  148  is placed in the casting mold  140  that forms a recess  144  for the retention element  112 , via which core  142  heat is dissipated from the interior region of the elastic plastic element  108  during production. The grip part  106  is designed hollow inside and comprises a recess  138  in the direction of the mounting part  110  through which the core  142  extends, and which is partially filled with the elastic plastic element  108  applied via injection, so that a flange  150  of the elastic plastic element  108  grips behind an edge region of the recess  138 . 
     Once the elastic plastic element  108  has cooled and the core  142  has been removed, the retention element  112  of the grip part  106  is guided through the recess  144  formed by the core  142  in the direction of the mounting part  110  through the elastic plastic element  108  and is screwed into the interior thread  120  in the fastening screw  114 . The retention element  112  comprises a screw head  132  that, when the retention element  112  is installed, is situated at a distance from the grip part  106 , so that the retention element  112  is supported in movable fashion relative to the grip part  106 . The screw head  132  is larger than the recesses  138  and  144 , so that, if the elastic plastic element  108  becomes damaged, the grip part  106  is connected to the mounted part  110  in captive fashion. The distance between the screw head  132  and the grip part  106  determines a maximum permissible displacement of the elastic plastic element  108 . Direct contact between the screw head  132  and the grip part  106  is prevented and transmission of vibrations is largely prevented by means of the flange  150  when maximum displacement occurs. 
     REFERENCE NUMERALS 
     
         
           10  handle 
           12  grip part 
           14  element 
           16  mounting part 
           18  set screw 
           20  retaining element 
           22  retaining element 
           24  element 
           26  handle 
           28  retaining element 
           30  washer 
           32  washer 
           34  sleeve 
           36  sleeve 
           38  washer 
           40  washer 
           42  opening 
           44  opening 
           46  space 
           48  space 
           50  handle 
           52  element 
           54  cutoff wheel 
           56  housing 
           58  handle 
           60  gearbox housing 
           62  handle 
           64  retaining element 
           66  end 
           68  end 
           70  mounting part 
           72  grip part 
           74  structural part 
           76  structural part 
           78  opening 
           80  opening 
           82  space 
           84  space 
           86  opening 
           88  opening 
           90  direction of insertion 
           92  structural part 
           94  structural part 
           96  opening 
           98  opening 
           100  width 
           102  diameter 
           104  handle 
           106  grip part 
           108  element 
           110  mounting part 
           112  retaining element 
           114  fastening screw 
           116  cross-sectional area 
           118  external thread 
           120  internal thread 
           122  core area 
           124  extension 
           126  extension 
           128  extension 
           130  extension 
           132  screw head 
           134  seating surface 
           136  cross-sectional area 
           138  recess 
           140  casting mold 
           142  component 
           144  recess 
           146  seating surface 
           148  fluid passage 
           150  flange