Abstract:
The invention relates to a gearing, in particular for portable electric power tools, preferably for angle grinders, comprising an automatic locking device ( 6, 15 ). According to the invention, provision is made for damping elements ( 20 ) to be integrated in the locking device module.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a transmission, in particular for electric hand-held power tools, and preferably for angle grinders. 
     With angle grinders, a manually operated locking device (spindle lock) is usually provided on the transmission housing. By pressing and holding a button, it is ensured that the spindle does not rotate when the grinding disk is installed or removed. This is attained by the fact that, when the locking device is actuated, a bolt engages in a recess in the driven gear, thereby preventing it from rotating. Since the driven gear is fixedly connected with the spindle, the spindle is also prevented from rotating. Manual locking devices for electric hand-held power tools are known, e.g., from U.S. Pat. No. 4,448,098 and U.S. Pat. No. 3,802,518. 
     Automatic locking devices are also known with drills, drill/drivers, and rotary hammers. The known locking devices automatically block the spindle when torque is transferred from the spindle to the drive. When torque is transferred from the drive to the spindle, the spindle is automatically released. Electric hand-held power tools of this type with automatic locking devices are described in DE 100 03 773 A1 and U.S. Pat. No. 5,016,501. 
     From publication DE 102 59 519 A1 it is known to dampen vibrations in the drive train of electric hand-held power tools using resilient damping elements located between the driven gear and the spindle. 
     BRIEF SUMMARY OF THE INVENTION 
     The object of the present invention is to provide a transmission with an automatic locking device, with which vibrations in the drive train are reduced and that requires only a small amount of installation space. 
     This object is achieved via the features of claim  1 . Advantageous embodiments of the present invention are defined in the subclaims. 
     The present invention is based on the idea of integrating a locking device (spindle lock) and transmission damping in a transmission, in particular for angle grinders. To reduce the amount of axial installation space required, it is provided according to the present invention that the transmission damping is an integral component of the locking device. In other words, the locking device and the transmission damping are a single assembly. According to the present invention, the vibrations in the drive train are absorbed by at least one resilient damping element located in the circumferential direction between a driving element of the driven gear and a counter-element of the locking device that is non-rotatably coupled with the spindle. The driving element is adjustable relative to the counter-element in the circumferential direction about a limited circumferential angle. When the driven gear is acted upon with a torque by the driving gear, which is driven by the drive, the damping element is pressed by the driving element against the counter-element in the circumferential direction, thereby elastically deforming the damping element and damping the vibrations in the drive train. The vibrations that occur are due, e.g., to production-related tolerances. By providing the at least one damping element, is vibrations are reduced, operating noises are minimized, and the peak loads on the toothed structure that occur during start-up of the drive and during operation are reduced. Rubber-like material may be used, e.g., as the damping material. It is also feasible to use fluids—viscous fluids, in particular—filled in small cushions. 
     A decisive factor in realizing the present invention is the fact that the resilient damping element engages with the counter-element, which is non-rotatably connected with a component of the locking device, or it is connected therewith as one piece. The counter-element is preferably located on a clamping disk of the locking device. Blocking elements, in particular rolling elements, may be clamped between the clamping disk and the circumferential wall that encloses the locking device. Given that the clamping disk is non-rotatably coupled with the spindle, the spindle—which is used to attach tools, in particular cutting disks—is also prevented from rotating. 
     To minimize the installation space in the axial direction, it is provided in a refinement of the present invention that either the driving element or the counter-element is designed as an axial extension that engages axially in a pocket. The pocket therefore forms the counter-element and/or the driving element. To transfer torque, the extension—which extends axially into the pocket—bears against a radial wall of the pocket. According to a preferred embodiment, the counter-element is designed as a pocket, and the driving element is designed as an extension. The pocket is formed in the side of the clamping disk that faces the driven gear. The extension, which is non-rotatably coupled with the driven gear, is displaceable in the circumferential direction inside the pocket about a circumferential angle limited by the distance between the radial walls of the pocket. The distance between the radial walls in the circumferential direction therefore defines the circumferential angle about which the driven gear is rotatable relative to the spindle. With transmissions that may be driven in both circumferential directions, it is advantageous when at least one damping element is located on both sides of the extension in the pocket. The damping material may be positioned in various manners. It is feasible for the damping element to be placed loosely in the intermediate space between the extension and the pocket wall. It is also possible to fixedly connect the damping elements with the driving element and/or the counter-element using suitable measures, e.g., vulcanizing. 
     Instead of the combination of pocket and extension as the counter-element and driving element, it is feasible to provide two extensions, which may be brought to bear against each other. 
     It has proven advantageous to not attach the driving element directly to the driven gear or to design it as a single piece therewith, but rather to locate it on a driving disk, which is non-rotatably connected with the driven gear, or to design it as a single piece therewith. The driving element may also be located directly on the driven gear, however. 
     According to a particularly advantageous design of the locking device, the clamping disk includes—on its outer circumference—at least one, and preferably three recesses located in the circumferential direction with separation between them. These first recesses extend across a circumferential section and widen radially in a first circumferential direction (the direction of rotation). Blocking elements, preferably rolling elements, are located in the recesses. The diameter of the blocking elements is dimensioned such that the blocking elements are clampable in the narrow region of the recess between the inner wall of the recess and the circumferential wall that encloses the locking device. The circumferential wall is preferably formed by the transmission housing. The blocking elements are accommodated in the wider region of the recess in such a manner that the clamping disk may rotate within the circumferential wall. When the clamping disk is rotated in the direction of the widening recess, the blocking elements travel—due to their inertia—into the narrower region and thereby prevent the clamping disk—and, therefore, the spindle, which is non-rotatably coupled with the clamping disk—from rotating further. 
     If the spindle should also be blockable in the opposite circumferential direction, e.g., to release the tool, then, according to the present invention, at least one second recess—and preferably at least three second recesses—is/are provided with blocking elements, and the second recesses widen in the radial direction—as do the first recesses—in the opposite circumferential direction. 
     To release the spindle when it is driven via the driven gear by the drive—which is an electric motor in particular—it is provided in a refinement of the present invention to provide at least one finger that extends in the radial direction, with which the blocking elements may be transferred from the narrower region to the wider region and held there when the driven gear is rotated in the direction of the wider region of the recesses, thereby preventing the blocking elements from traveling back into the narrower recess region and preventing the spindle from rotating further. If the transmission is drivable in both circumferential directions, the finger must slide the blocking elements—depending on the direction of rotation—into the first recesses, or it must slide the blocking elements into the second recesses in the direction of rotation. It is feasible to assign a separate finger to each blocking element, the finger engaging behind the particular blocking element in the radial direction. 
     Advantageously, the extension and the finger are located on the driving disk. The circumferential angle around which the finger is displaceable is limited by the distance between the radial walls of the pocket into which the extension engages axially. To ensure that the finger may displace the associated blocking element in the circumferential direction, it is advantageous when the blocking element extends axially out of its recess in the direction of the finger, so that the blocking element may be captured by the finger when the finger is rotated. It is also possible to design the finger with a bent shape, so that it engages in the pocket. 
    
    
     
       BRIEF DESCRIPTION THE DRAWING(S) 
       Further advantages and advantageous embodiments are depicted in the further claims, the description of the figures, and the drawing. 
         FIG. 1  shows an exploded view of the inventive transmission, 
         FIG. 2  shows a cross section of the transmission, which is installed in the transmission housing, as viewed from the pinion toward the spindle, which is driven in the clockwise direction by a drive, but without transmission damping, 
         FIG. 3  shows a cross section of the transmission when the locknut is tightened on the spindle, with the drive shut off, but without transmission damping, 
         FIG. 4  shows a cross section of the transmission when the locknut is loosened on the spindle, with the drive shut off, but without transmission damping, and 
         FIG. 5  shows a cross section of the transmission with transmission damping integrated in the locking device. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Identical components and components with the same functionality are labelled with the same reference numerals in the Figures. 
     A transmission  1  for an angle grinder is shown in the figures. The components of transmission  1  are shown in an exploded view in  FIG. 1 . Transmission  1  includes a spindle  2  with a thread  3  located on its free end for securing a not-shown grinding disk using a not-shown locknut. 
     The transmission also includes a ball bearing  4  with an outer bearing flange  5 . In the installed state, spindle  2  is connected with ball bearing  4  via pressing. Transmission  1  also includes a clamping disk  6 , which, in the installed state, is also non-rotatably coupled with spindle  2  via pressing. Clamping disk  6  is also retained via two wedges  7 —which extend radially inward and in the axial direction—in two grooves  8 —which also extend in the axial direction—formed in the outer circumference of spindle  2 . Clamping disk  6  is therefore connected with spindle  2  in a form-fit and non-positive manner. 
     On the outer circumference, clamping disk  6  includes three first recesses  9  and three second recesses  10 , which are offset relative to first recesses  9 . First recesses  9  widen radially in the clockwise direction. Second recesses  10  narrow radially in the clockwise direction. First blocking elements  11  and second blocking elements  12  are located in recesses  9 ,  10  of clamping disk  6 . Blocking elements  11 ,  12  rest on base  13  of clamping disk  6  and are free to move in the radial and tangential directions. On the side opposite to base  13 , blocking elements  11 ,  12  are limited by a driven gear  14  designed as a crown wheel. It is even more advantageous when the blocking elements are not located on a base  13  that is non-rotatably connected with clamping disk  6 , but rather on a disk that is non-rotatably connected with bearing flange  5 . The adjusting behavior of blocking elements  11 ,  12  is improved as a result. 
     A driving disk  15  is located between driven gear  14  and clamping disk  6 , which is non-rotatably connected with the underside of driven gear  14  using suitable measures, such as screwing or welding. Three fingers  16 , which engage behind first blocking elements  11  in the radial direction, extend away from driving disk  15  in the radial direction. Three driving elements  17  designed as extensions extend in the axial direction, toward clamping disk  6 . In the installed state, driving elements  17  engage in associated pockets  18  in top side of driving disk  15 . Via driving elements  17 , the torque applied to driven gear  14  is transferred to counter-elements of clamping disk  6  designed as pockets  18 . The torque is transferred by driving elements  17  to radial walls  19  of pockets  18 . In the installed state, damping elements  20 —with which vibrations in the drive train may be damped—are located between radial walls  19  and driving elements  17 . When torque is transferred, the damping elements deform elastically and are clamped between walls  19  and driving elements  17 . If the intention is to use transmission  1  shown, e.g., in a drill with two directions of rotation, it is advantageous when damping elements are also located between walls  21  of pockets  18  opposite to walls  19 , and driving elements  17 . 
     Driven gear  14  is supported on spindle  2  in such a manner that it may rotate freely. In the upward axial direction, driven gear  14  is held in its position by a snap ring  22 . At the bottom, driven gear  14  rests on clamping disk  6 . 
     Driven gear  14  is driven via a drive gear, which is designed as pinion  23 , meshes with driven gear  14 , and is driven by an electric-motor drive via a shaft. 
     The function of the locking device, which is composed of driving disk  15  with driving elements  17 , clamping disk  6  with pockets  18 , recesses  9 ,  10 , and blocking elements  11 ,  12 , will be described in greater detail below with reference to  FIGS. 2 through 4 . For clarity, damping elements  20  are not shown in  FIGS. 2 through 4 . They are located in the circumferential direction between driving elements  17  and front—as viewed in the clockwise direction—walls  19  of pockets  18 . 
       FIG. 2  shows a cross section of a locking device that has been installed in a transmission housing  24 , as viewed from drive gear  23  in the direction toward ball bearing  4 .  FIG. 2  shows the operating state, i.e., driven gear  14  and driving disk  15  non-rotatably connected thereto are driven in the direction of rotation indicated by the arrow. Driving elements  17  engage in pockets  18  of clamping disk  6 . The torque is transferred by driven gear  14  via driving disk  15  with driving elements  17  to clamping disk  6  and, therefore, spindle  2 . At the same time, fingers  16  move the three first blocking elements  11 —of the six blocking elements  11 ,  12  in all—in the clockwise direction out of their blocked position in the region of radially narrow circumferential section of recesses  9 . This is necessary, because first blocking elements  11  would otherwise get stuck between inner wall  25  of first recesses  9  and non-rotatable circumferential wall  26  formed by transmission housing  24  (spindle lock function or locking function). 
     Due to their inertia, the three second blocking elements  12  are pressed against the rear—as viewed in the clockwise direction—radial wall of associated second recesses  10 . This effect is improved further when blocking elements  11 ,  12  do not rest on a base  13  that is non-rotatably connected with clamping disk  6 , but rather on a disk that is non-rotatably connected with bearing flange  5 . Inner walls  25  of second recesses  10  are slanted differently than the inner walls of first recesses  9 . Second blocking elements  12  therefore travel to the wider side of the recesses, where they cannot become stuck. 
     Driving disk  15  is not shown in  FIG. 3 .  FIG. 3  shows the state that exists when the not-shown locknut is being tightened in the counterclockwise direction (in the direction of the arrow). The drive is shut off during this procedure. When a tightening torque is applied to the not-shown locknut, spindle  2  rotates and, therefore, clamping disk  6  also rotates by a small amount in the counterclockwise direction, until three second blocking elements  12  travel in their second recesses  10  along inner walls  25  into narrower region of second recesses  10  and become stuck between circumferential wall  26  and inner wall  25  of clamping disk  6 . Spindle  2  is therefore prevented from rotating further and the tightening torque may be applied to tighten the locknut. 
     Driving disk  15  is not shown in  FIG. 4 , either. The state in which the locknut is being loosened is shown here. During the loosening procedure, three first blocking elements  11  travel along inner wall  25  of first recesses  9  into the narrower region of recesses  9  and become stuck between circumferential wall  26  and inner walls  25  of first recesses  9 . The torque for loosening the locknut may therefore be applied without also rotating spindle  2 . 
       FIG. 5  shows the state in  FIG. 2 , but with damping elements  20  made of rubber-like material shown between driving elements  17  and radially extending walls  19  of pockets  18 . With the configuration shown, vibrations are damped when driving takes place in the clockwise direction. It is feasible to also locate additional damping elements on the sides of driving elements  17  opposite to damping elements  20 . Since damping elements  20  are integrated in pockets  18  formed in the clamping disk, the axial installation height of transmission  1  is minimal. With driving elements  17  located on clamping disk  6 , pockets  18  could just as easily be located in driving disk  15  or in driven gear  14 .