Abstract:
A manually guided implement having a drive motor is provided. For a translatory movement of a tool member, the rotational movement of the drive motor must be converted by a gear arrangement, which has a gear wheel that is coupled with a component that glides on the end face of the gear wheel. To significantly reduce frictional losses and also wear of the pertaining components, a constantly effective, reliable lubricant is required. For this reason, at least one cutout is provided in the main body of the gear wheel and/or in the component that can glide on the end face thereof. Such cutouts are open to a glide plane and serve to accommodate a lubricant.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a manually guided tool or implement, especially a hedge trimmer, having a drive motor. 
     DE 38 16 362 A1 discloses a motor-driven hedge trimmer that includes two trimmer blades that are driven by a gear arrangement disposed between the drive motor and the trimmer blades. The gear arrangement includes, among other things, a gear wheel that is mounted on a king pin and can be coupled with an eccentric wheel. The eccentric wheel comprises a main body that is provided on each end face with an eccentric projection, whereby the two eccentrics are disposed diametrically opposed from one another. The eccentrics engage in openings of coupling levers, which in turn are pivotably connected to the trimmer blades. 
     The coupling levers are embodied in such a way that merely a small surface comes in contact with the end face of the eccentric wheel, which leads to a high pressure per unit of area. However, this causes increased wear since abrasion cannot be avoided at the end faces of the eccentric wheel. 
     It is therefore an object of the present invention to provide a manually guided implement of the aforementioned general type that with a construction that is as straight forward as possible encounters considerably reduced wear. 
    
    
     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 shows the underside of a housing having a gear arrangement and trimmer blades coupled therewith; 
     FIG. 2 is an axial cross-sectional view through the gear arrangement that is accommodated in the housing; 
     FIG. 3 is a view of a gear wheel taken in the axial direction; 
     FIG. 4 is a cross-sectional view taken along the line IV—IV in FIG. 3; 
     FIG. 5 is an enlarged view of the encircled portion V in FIG. 4; 
     FIGS.  6   a - 6   d  illustrate the rotational movement of the gear wheel, and the resulting movement of the trimmer blades, in four different angular positions; 
     FIG. 7 shows a modified embodiment of a gear wheel; 
     FIG. 8 is a cross-sectional view taken along the line VIII—VIII in FIG. 7; and 
     FIG. 9 shows a connecting-rod assembly for a trimmer blade. 
    
    
     SUMMARY OF THE INVENTION 
     The manually guided tool or implement of the present invention is characterized primarily by a gear arrangement that is operatively disposed between the drive motor and a tool member, the gear arrangement including at least one gear wheel and a component, connected to the tool member, that is adapted to glide on an end face of a main body of the gear wheel, wherein the main body is provided with at least two cutouts that serve for accommodating lubricant, and wherein the cutouts in the main body of the gear wheel are open toward both end faces of the main body and form glide planes on each of such end faces. 
     The essential advantages of the present invention are that without additional structural components an effective lubrication of the highly stressed surfaces is ensured, with this lubrication being maintained over a long operating duration of even several hours. The lubricant is a grease having a viscosity that, although it changes as a function of change in temperature, yet does not liquify. The cutouts serve as grease depositories, with the cutouts being open in the direction toward the glide plane, so that the glide surface of the component that is glidable along the end face of the gear wheel is always smeared with the grease that is present at that location. Glide planes are formed on both end faces of the main body, and the cutouts in the main body of the gear wheel are open toward both of these end faces. In this way, the grease depository in each cutout simultaneously serves for lubricating both glide planes. 
     At least two cutouts are expediently diametrically disposed in the gear wheel. This results in a uniform lubricant application over the glide plane, whereby an excess quantity of the lubricant removed from a cutout is given up to the respectively following cutout. A particularly preferred embodiment of the cutouts is provided when such cutouts are slots that extend in the circumferential direction. In this connection, it is expedient for six cutouts to be distributed over the circumference of the main body, with these cutouts being symmetrically disposed relative to a radial axis. 
     In one specific embodiment of the present invention, the component that cooperates with the gear wheel is an arrangement for converting a rotational movement into a translatory movement. For this purpose, the component is eccentrically mounted on the gear wheel, with this component having an opening into which an eccentric projection on the end face of the main body engages. With this arrangement according to the connecting-rod principle, the component is a connecting rod that is pivotably connected to a cutting blade. To reduce the number of structural components required for the transmission of power, the component, which is preferably a trimmer blade of a hedge trimmer, can be provided at the rear end of the trimmer blade with an integral ring in which is disposed an opening that operates as a guide means for the eccentric. 
     In order to avoid a hardening of the lubricant as a consequence of aging thereof, it is expedient to act upon the volume of grease in such a way that there is always a slight displacement of the lubricant parallel to the axis of rotation of the gear wheel. In this way, lubricant is constantly delivered to the glide planes, i.e. the glide surface of the component, and is carried along by the component. So that an excess quantity of grease that may have been removed from the lubricant depository is not squeezed to the outside, but rather is conveyed in a directed manner to the subsequent cutout, it is advantageous to provide at least one groove on the main body in the vicinity of a glide surface for the component; this groove extends between two cutouts and interconnects them. In this connection, pursuant to one preferred specific embodiment of the present invention, an annular groove is provided that is tangent to several, and preferably to four, of the cutouts. In a particularly advantageous manner, the groove extends along the peripheral contour at the base of the eccentric, resulting in the effect that the outer surface of the eccentric and the guide means are also lubricated. 
     Further specific features of the present invention will be described in detail subsequently. 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings in detail, FIG. 1 shows the underside of a hedge trimmer  1  having a trimmer blade  10  that is mounted in a housing  2  in such a way as to be longitudinally displaceable. The housing  2  includes a transmission housing  3  in which is disposed a gear arrangement  9  that is coupled with the trimmer blade  10 . The gear arrangement  9  essentially comprises a gear wheel  20 , which is driven by a pinion  8 , as well as a cam or eccentric  15  that is disposed on an end face of the gear wheel  20  and engages an opening  18  of the trimmer blade  10 ; this opening is formed within a ring  13  disposed at the rear end  12  of the trimmer blade  10 . As viewed in the longitudinal direction of the trimmer blade  10 , the opening  18  has an inner dimension that corresponds to the diameter of the eccentric  15 . However, viewed at right angles to the longitudinal direction, the opening  18  is wider, so that the inner peripheral surface of the ring  13  forms a guide means  14  for the surface of the eccentric  15 . Provided in the gear wheel  20  are cutouts  16 ,  17  that are radially spaced from the outer periphery of the gear wheel  20  and extend in the manner of an arc of a circle (also FIG.  3 ). 
     FIG. 2 is an axial cross-sectional view through the gear arrangement  9  as well as through the pinion  8 , which can be coupled with a drive motor. The housing  2  comprises not only the transmission housing  3  but also, integrally therewith, a clutch housing  4 . Disposed within the clutch housing  4  is a clutch drum  6 , on the base  6 ′ of which the pinion  8  is connected in such a way as to be resistant to torque. The shaft  5  of the pinion  8  is disposed adjacent to the base  6 ′ of the clutch drum  6 ; this shaft  5  is accommodated in a ball bearing means  7 . The pinion  8  meshes with the toothed rim  20 ′ of the gear wheel  20 , which comprises a main body  23 , from on the end faces  21 ,  21 ′ of which the eccentric  15  as well as an eccentric  19  project. A shaft  25  is centrally disposed in the gear wheel  20 . This shaft is accommodated in a bearing or support means  24  formed on the transmission housing  3 . As can furthermore be clearly seen from FIG. 2, the hedge trimmer  1  comprises two trimmer blades  10  and  11  that can be moved relative to one another and that are received on the end faces  21 ,  21 ′ of the gear wheel  20  in the same manner although in a mirror-inverted arrangement. In this connection, the opening through which the eccentrics  15  and  19  project is provided in the angled-off rear end  12 , so that the respective ring  13  surrounds the surfaces of the eccentrics  15  and  19 . As a consequence, the rings  13 ,  13 ′ rest against the end faces  21 ,  21 ′ respectively of the main body  23 , so that a glide surface or plane  22 ,  22 ′ is formed between the main body  23  and the ring  13 ,  13 ′. 
     FIG. 3 is a view in the axial direction showing the gear wheel  20  as an individual component. As indicated previously, the gear wheel  20  is provided on its outer periphery with a toothed rim  20 ′. In addition, the central portion of the gear wheel  20  has a hole  26  for receiving the shaft  25  that is illustrated in FIG.  2 . Disposed in the main body  23 , radially inwardly from the toothed rim  20 ′, are a total of six cutouts,  16 ,  17 ,  27 ,  16 ′,  17 ′ and  27 ′, that extend in the manner of an arc of a circle and have the shape of slots. In this connection, the cutouts  27 ,  27 ′ are wider in a radial direction than the cutouts  16 ,  17 ,  16 ′,  17 ′. When viewed relative to the axis A, which extends perpendicular to the axis of rotation of the gear wheel  20 , the cutouts  17 ,  27 ,  16 ′ and  16 ,  27 ,  17  are symmetrically arranged. It can also be clearly seen from FIG. 3 that the mass centers of the eccentrics  15  and  19  are also disposed on the axis A and each have the same radial spacing relative to the axis of rotation, so that the gear wheel  20  practically does not suffer from an unbalance. Extending along the peripheral surface of the eccentric  15  is a circular groove  28 , the outer peripheral edge of which intersects radially inwardly disposed regions of the cutouts  16 ,  17 ,  27  and  27 ′; in other words, the annular groove  28  is tangent to four of the six cutouts of the main body  23 . 
     FIG. 4 is a cross-sectional taken along the line IV—IV in FIG.  3 . From this view, it can be seen that the main body  23  has a respective eccentric  15 ,  19  on the end faces  21  and  21 ′ respectively; these eccentrics have the same size and the same radial spacing relative to the axis of rotation D. Disposed on the peripheral surface of the eccentric  15  is the annular groove  28 , which is disposed at the base of the eccentric in the end face  21 . A corresponding annular groove  28 ′ is disposed on the eccentric  19 , i.e. on the end face  21 ′. 
     FIG. 5 is an enlarged view of the encircled portion V in FIG.  4 . Disposed in the main body  23  is the annular groove  28 , which extends precisely along the peripheral surface of the eccentric  15 , with the outer rim thereof being formed by the end face  21  of the main body  23 . 
     FIGS.  6   a - 6   d  are respective views of the gear wheel  20  illustrated in FIG. 3, and in particular in each case once without the pertaining end  12  and once with the pertaining end  12  of the trimmer blade  10 . In this connection, FIG.  6   a  shows the position of the gear wheel  20  at an angle of rotation of 0° or 360°, FIG.  6   b  shows an angle of rotation of 90°, FIG.  6   c  shows an angle of rotation of 180°, and FIG.  6   b  shows an angle of rotation of 270°. Reference numerals for the same parts correspond to those of FIG.  3 . 
     As shown in FIG.  6   a , the eccentric  15  is disposed in the uppermost position, and hence is disposed in a region of the ring  13  in which the guide means  14  of the opening  18  has a curved shape, with the curve of the arch corresponding to the surface of the eccentric  15 . From this position, the gear wheel  20  is rotated about the axis of rotation D in the direction of the arrow P, so that the eccentric  15  of the gear wheel  20  passes into the position illustrated in FIG.  6   b . In so doing, the peripheral surface of the eccentric  15  moves along the guide means  14  in that portion thereof in which the guide means  14  extends linearly, as a consequence of which the ring  13  moves toward the left in the drawing and hence the trimmer blade  10  is also pulled to the left. The ring  13  glides along the surface  21  of the gear wheel  20  and is provided with a lubricant charge due to the movement along the cutouts  16 ,  17 ,  27 , which serve as lubricant depositories. 
     As the gear wheel  20  continues to rotate in the direction of the arrow P about the axis of rotation D, the eccentric  15  passes into the position shown in FIG.  6   c , where the eccentric  15  is disposed in the lowermost position. As a consequence of this movement of the eccentric  15 , the ring  13 , and hence also the trimmer blade  10 , are again moved toward the right, and by means of a further rotation of the gear wheel  20  the trimmer blade is shifted still further in the longitudinal direction thereof, as a consequence of which the eccentric  15  rests against a linear portion of the guide means  14 . This movement sequence leads to a gliding of the ring  13  over the end face  21  and over the lubricant-filled cutouts  16 ,  17 ,  27 ,  16 ′,  17 ′,  27 ′, so that the ring  13  is constantly smeared within an adequate quantity of lubricant. Excess lubricant is conveyed by the movement of the ring  13  to the following cutouts or is pressed into the annular groove  28 , via which the lubricant can be conveyed to one of the openings that is tangent to the annular groove  28 . 
     As a consequence to the lubricant being carried along by the movement of the ring  13 , and the pressing-in of a portion of lubricant into the following cutouts, a pump effect results that keeps the lubricant supply moving. In so doing, the lubricant volume pressed into the cutouts by the ring  13  presses upon the lubricant already present in a cutout, so that this lubricant gradually passes in an axial direction to the other end face of the main body, from where it is taken along by the ring that slides on this end face. There thus results a circulation of the lubricant, which counteracts a solidification or gumming. As a consequence of the heating up of the gear mechanism, the viscosity of the lubricant also alters, although liquification is avoided. 
     FIG. 7 shows a gear wheel  30  that is provided in the middle with a central opening  26  for receiving a rotary shaft. A toothed rim  30 ′ is disposed on the outer periphery. Spaced radially not only relative to the central opening  26  but also to the toothed rim  30 ′ are diametrically opposed cutouts  32 ,  32 ′ that serve for accommodating lubricant. In addition, further uniformly distributed cutouts  34  can be provided that serve as lubricant depositories. 
     FIG. 8 is cross-sectional view taken along the line VIII—VIII in FIG.  7 . In this embodiment, the main body  33  of the gear wheel  30  has planar end faces  31  and  31 ′; in other words, no eccentrics are formed on the end faces. 
     FIG. 9 shows an arrangement for converting the movement of a gear wheel  40  to a trimmer blade  36  via a gear arrangement  29  in the from of a connecting-rod assembly. In this connection, a main body  43  of the gear wheel  40  is provided on the front side  41  with an eccentric  42  and on the rear side with an eccentric  42 ′, with these two eccentrics being disposed diametrically relative to one another. Disposed in the middle of the gear wheel  40  is a central hole  26 , with a toothed rim  40 ′ being formed on the outer peripheral edge. In the region most remote from the central hole  26 , the eccentrics  42  and  42 ′ are each provided with a respective concave curvature  45  or  45 ′. Disposed in the main body  43  are two cutouts  44  and  44 ′. The cutout  44  on the front side  41  is covered nearly entirely by the eccentric  42 , and the cutout  44 ′ on the back side is similarly covered to a large extent by the eccentric  42 ′. 
     Disposed on the eccentric  42  is a ring  39  that is formed on one end of a connecting rod  38  and that thus surrounds the outer surface of the eccentric  42 , whereby radial play is provided between the ring  39  and the eccentric  42 . At the other end, the connecting rod  38  is mounted on a pin  37  of a trimmer blade  36 , so that the circular movement carried out by the eccentric  42  is converted into a longitudinal movement of the trimmer blade  36 . An opening is formed between the inner peripheral surface of the ring  39  and the concave curvature  45  of the eccentric  42 ; this opening provides a communication between the cutout  44  and the outside. As a consequence of the gliding movement of the ring  39  along a circular path, the ring  39  takes up lubricant as it passes over the cutout  44 ′, in the manner described in conjunction with the previous embodiments, and hence takes care of lubricating the glide surfaces. As a consequence of the heat that occurs during operation of the implement, the viscosity of the grease or lubricant is reduced so that the lubricant, enhanced by centrifugal force, can more easily exit the cutout  44  into the lubricating gap. Abrasion particles that accumulate in the cutout are also flushed out with the lubricant and can, due to the radial play between the ring  39  and the eccentric  42 , pass to the outside without any binding occurring. To the extent that it is necessary to refill the cutouts with lubricant, the lubricant can be applied to the end face  41  of the gear wheel  40  in the vicinity of the toothed rim  40 ′; from there, the connecting rod  38  spreads the lubricant into the cutout  44 . 
     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.