Patent Publication Number: US-2021168997-A1

Title: Trimmer Line Spool for a Trimmer Head

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a trimmer line spool for a trimmer head. 
     A trimmer serves for mowing grass, shrub or the like. For this purpose, a trimmer head with a tool is driven in rotation about an axis of rotation of the trimmer head so that the grass is cut off upon contact with the tool. As a tool, in particular trimmer lines are used which are subject to a certain wear in operation of the trimmer line. In order to be able to feed the trimmer line for adjustment, the trimmer line can be unwound from a trimmer line spool of the trimmer head so that mowing with the trimmer head can be continued without impairment of the cutting function without having to perform a complete exchange of the trimmer line. 
     Trimmer heads are known whose trimmer line spool comprises two spool chambers for winding a trimmer line therein, respectively. Each spool chamber is provided with two trimmer line holders that enable clamping of trimmer lines of different thickness. A disadvantage of such trimmer heads is that in operation of such a trimmer head extremely high loads are occurring. 
     It is an object of the invention to further develop a trimmer line spool in such a way that the loads which are acting on the trimmer line spool in operation of the trimmer head can be reduced and at the same time an ergonomic handling of the trimmer line spool is enabled for the operator. 
     SUMMARY OF THE INVENTION 
     In accordance with the invention, this object is solved in that the trimmer line spool for a trimmer head comprises an axis of rotation and a first spool chamber and a second spool chamber for winding a trimmer line therein, respectively, wherein the trimmer line spool comprises at least two holder pairs, wherein the first holder pair of the at least two holder pairs and the second holder pair of the at least two holder pairs each comprise a first trimmer line holder correlated with the first spool chamber and a second trimmer line holder correlated with the second spool chamber, wherein each trimmer line holder comprises an opening for receiving a trimmer line end, wherein the diameter of the openings of the trimmer line holders of the first holder pair is greater than the diameter of the openings of the trimmer line holder of the second holder pair, wherein the openings of the trimmer line holders of a respective holder pair are positioned relative to each other at an angle distance of 150° to 210°, measured around the axis of rotation. 
     The object is further solved in that the trimmer line spool for a trimmer head comprises an axis of rotation and at least one spool chamber for winding a trimmer line therein, wherein the trimmer line spool comprises a first spool wall for delimiting the at least one spool chamber in the direction of the axis of rotation and an actuating device that adjoins in the direction of the axis of rotation the first spool wall and is arranged outside of the spool chamber, wherein the actuating device comprises a holding projection extending in radial direction relative to the axis of rotation for partial engagement from behind by an operator, wherein in the first spool wall at least one grip depression is arranged opposite to the holding projection. 
     The trimmer line spool according to the invention is based on the recognition that the high loads acting on the trimmer head when the trimmer head is operating result from imbalance of the trimmer line spool. This imbalance can be traced back mostly to the arrangement of the trimmer lines in the spool chambers wherein the arrangement of the trimmer lines results, in turn, from the position of the trimmer line holders. In order to reduce the imbalance at the trimmer line spool, the trimmer lines are to be arranged such that the centrifugal forces acting on the trimmer line spool cancel each other or are in mutual force balance. 
     The trimmer line spool according to the invention comprises at least two holder pairs. The first holder pair of the at least two holder pairs and the second holder pair of the at least two holder pairs comprise each a first trimmer line holder correlated with the first spool chamber and a second trimmer line holder correlated with the second spool chamber. Each trimmer line holder comprises an opening for receiving a trimmer line end. The diameter of the openings of the trimmer line holders of the first holder pair is larger than the diameter of the opening of the trimmer line holders of the second holder pair. The openings of the trimmer line holders of a respective holder pair comprise an angle distance of 150° to 210°, measured about the axis of rotation. 
     For operating the trimmer head, the trimmer lines are wound onto the trimmer line spool. For this purpose, a respective trimmer line is inserted into the opening of a trimmer line holder of a holder pair and wound onto the circumference of the trimmer line spool in the respective spool chamber. In operation of the trimmer head, centrifugal forces are acting on the trimmer line holders as well as on the trimmer lines. Since the openings of the trimmer line holders of a holder pair as well as of the trimmer line ends clamped therein are displaced relative to each other about the axis of rotation, the centrifugal forces which are acting on the trimmer lines substantially cancel each other. The imbalance of the trimmer line spool as well as the loads acting on the trimmer head are reduced. Moreover, it has been found that threading the trimmer lines into trimmer line holders that are displaced relative to each other is much easier for the operator. Due to their differently sized openings, the holder pairs assist the operator in regard to which holder pair is to be used for a corresponding trimmer line or into which trimmer line holder a corresponding trimmer line is to be threaded. 
     The trimmer line holders of at least one holder pair are positioned preferably at least partially in a longitudinal plane containing the axis of rotation. Preferably, the trimmer line holders of a holder, when viewed in the direction of the axis of rotation, are arranged relative to each other with rotational symmetry in relation to the axis of rotation. Due to this symmetrical arrangement of the trimmer line holders, a balanced mass distribution of the trimmer line spool, in particular with wound-on trimmer lines, is enabled, and imbalances are avoided when the trimmer line spool is rotated. 
     It is advantageously provided that the trimmer line holders of a holder pair are formed of identical trimmer line chambers. The trimmer line can be inserted preferably only through the opening of the trimmer line holder into the trimmer line chamber. As a result, the trimmer line can be inserted only at one side of the trimmer line holders so that a faulty winding direction of the trimmer line onto the trimmer line spool is prevented. The trimmer line chamber is preferably closed at the side which is opposite the opening and forms a stop for the trimmer line end. The trimmer line, when threaded into the trimmer line chamber, is preferably pushed up to the stop. In this way, the trimmer line ends of both trimmer lines are respectively contacting the stops of the trimmer line chambers of a holder pair so that a symmetric arrangement of the trimmer lines can be ensured. 
     The trimmer line spool comprises a rotational direction wherein the opening is preferably formed at the leading side of the trimmer line chamber viewed in the rotational direction. The rotational direction corresponds to the rotational direction of the trimmer line spool in operation of a trimmer head. 
     It is advantageously provided that the diameter of the openings of the trimmer line holders of the second holder pair amounts to at most 90% of the diameter of the openings of the trimmer line holders of the first holder pair. Due to the openings of the trimmer line holders having different sizes, trimmer lines with differently sized diameters can be secured in the trimmer line holders. In this way, as a function of the intended use, a corresponding trimmer line with a diameter that is suitable for this intended use can be provided. 
     It is advantageously provided that the trimmer line spool comprises a first spool wall, a second spool wall, and an intermediate wall which is arranged between the first spool wall and the second spool wall. The first spool wall, the second spool wall, and the intermediate wall are preferably connected to each other by a circumferential wall extending in the direction of the axis of rotation. The trimmer line holders are preferably contacting the intermediate wall in the direction of the axis of rotation. By arranging the trimmer line holders at the intermediate wall, the mass forces which are generated in operation of the trimmer head at the trimmer line spool are reduced. The first trimmer line holder of one holder pair and the second trimmer line holder of the other holder pair are preferably arranged mirror-symmetrically relative to each other in relation to the intermediate wall. This arrangement contributes also to a balanced mass distribution of the trimmer line spool. 
     The trimmer line spool preferably comprises a contour structure for an indexing device at an end face thereof. In operation of the trimmer head, the trimmer line spool is connected to the housing of the trimmer head with form fit in the rotational direction by means of the contour structure. Upon actuation of the indexing device, the form fit between the housing of the trimmer head and the trimmer line spool is canceled. The trimmer line spool can then be rotated relative to the housing in an unwinding direction, whereby the trimmer line is unwound from the trimmer line spool. The unwinding process is realized in the installed state of the trimmer line spool. Demounting the trimmer head is not required. 
     The trimmer line spool comprises preferably at least one continuous trimmer line channel through which the trimmer line can be pushed and wound. Such a continuous channel enables the operator to wind the trimmer line in the mounted state of the trimmer head. Accordingly, the operator inserts the trimmer line into the trimmer line channel and the trimmer line spool is subsequently rotated relative to the trimmer head. The free ends of the trimmer line then wind respectively into one of the two spool chambers. The trimmer line channel comprises preferably an inlet opening and an outlet opening, wherein the inlet opening and the outlet opening are preferably arranged centrally between two trimmer line holders of a holder pair in circumferential direction. The inlet opening and the outlet opening of the trimmer line channel are arranged preferably in the intermediate wall. This favors a balanced mass distribution of the trimmer line spool for avoiding imbalances. 
     As a further independent invention, it is provided that the trimmer line spool comprises an actuating device that adjoins the first spool wall in the direction of the axis of rotation and is arranged outside of the spool chamber. The actuating device comprises a holding projection extending in radial direction relative to the axis of rotation and configured to be partially engaged from behind by an operator. In the first spool wall, at least one grip depression is formed that is positioned opposite the holding projection. 
     The actuating device serves for actuating the indexing device of the trimmer head. For this purpose, the trimmer line spool is to be pulled against a spring force in the direction of the axis of rotation, whereby the form-fit connection between the housing and the trimmer line spool is canceled, and is subsequently to be rotated relative to the housing in an unwinding direction. In this context, the trimmer line spool is gripped at its actuating device by the operator and is pulled in the direction away from the housing. This is done in that the operator engages from behind the holding projection of the actuating device. Due to the at least one grip depression which is formed opposite the holding projection in the first spool wall, the operator has more room to engage the holding projection from behind. Thus, the grip depression enables the operator to have better grip on the actuating device. 
     The trimmer line spool comprises preferably an intermediate wall and at least one continuous trimmer line channel that extends at least partially in the intermediate wall and through which the trimmer line can be passed preferably completely through the trimmer line spool and wound. The trimmer line channel comprises preferably an inlet opening and an outlet opening. The inlet opening and the outlet opening comprise in particular an angle distance of 150° to 210° relative to each other that is measured around the axis of rotation. The at least one grip depression is preferably arranged in a circumferential region that is positioned between the inlet opening and the outlet opening. Preferably, several grip depressions, in particular two grip depressions are arranged in a circumferential region. 
     The inlet opening and the outlet opening of the trimmer line channel at the intermediate wall cause a locally thickened portion of the intermediate wall. The spool chambers each comprises a height measured in the direction of the axis of rotation. The height of the spool chambers is reduced at the locally thickened portion of the intermediate wall. In order to not additionally reduce the height of the spool chambers and thus reduce the space which is available for winding on the trimmer line, the at least one grip depression, in particular two grip depressions, are arranged in the circumferential region. In this way, between the thickened portion at the intermediate wall and the first spool wall there is sufficient space provided for winding the trimmer line. No additional constriction of the spool chamber is produced at the inlet opening and at the outlet opening of the intermediate wall so that still an easy winding of the trimmer line is ensured. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       Further features of the invention result from the description and the drawing in which embodiments of the invention described in detail in the following are represented. 
         FIG. 1  is a schematic illustration of a trimmer held by an operator. 
         FIG. 2  is a side view of an embodiment of a trimmer head. 
         FIG. 3  is plan view of a trimmer head according to  FIG. 2 . 
         FIG. 4  is a section illustration of the trimmer head in the direction of arrows IV according to  FIG. 3 . 
         FIG. 5  is a perspective illustration of the trimmer line spool according to the invention. 
         FIG. 6  is a side view of the trimmer line spool according to  FIG. 5  showing the rear in relation to  FIG. 5 . 
         FIG. 7  is a lateral section illustration of the trimmer line spool of  FIG. 5  through the trimmer line holders. 
         FIG. 8  is a section illustration of the trimmer line spool in the direction of arrows VIII according to  FIG. 6 . 
         FIG. 9  is a side view of the trimmer line spool in a position rotated about 90° about the axis of rotation relative to  FIG. 6 . 
         FIG. 10  is a side view of an alternative embodiment of the trimmer line spool. 
         FIG. 11  is a perspective illustration of an alternative embodiment of the trimmer line spool. 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 1  shows a trimmer  1  in a schematic illustration. The trimmer  1  is held by an operator  26 . The trimmer  1  comprises a rearward end with a rearward housing  27  and a front end from which a drive shaft  2  ( FIG. 2 ) projects. A shaft  28  connects the rearward end and the front end. Handles  29  for guiding the trimmer  1  are arranged at the shaft  28 . A trimmer head  3  adjoins the front end of the trimmer  1 . The trimmer head  3  is fastened to the drive shaft  2  and is driven in rotation about an axis of rotation  4  by a drive motor  59 , only schematically indicated, in a rotational direction  20 . The drive motor  59  is arranged in the rearward housing  27  wherein a drive shaft is extending in the shaft  28 . It can be provided that this drive shaft is connected inside the shaft  28  immediately to the drive shaft  2  for the trimmer head  3  so that no gearbox is positioned inbetween. In an alternative embodiment, not illustrated, the drive motor  59  which is in particular an electric motor, can also be arranged at a front housing, not illustrated, that is arranged at the front end. Advantageously, in the front housing there is also the gear box. The trimmer head  3  at the side which in operation is facing the operator  26  is provided with a protective shield  40 . The trimmer head  3  comprises at least one tool which—a trimmer line  6 ,  6 ′ in the embodiment—serves for cutting things such as grass, shrubs or the like. A bottom side  42  is formed at the trimmer head  3  and faces the ground  41  in operation; it is arranged at the side of the trimmer head  3  facing away from the shaft  28 . At the side of the trimmer head  3  which is facing the shaft  28 , a top side  43  of the trimmer head  3  is formed. Protective gear that has to be worn mandatorily by the operator  26  for operating the trimmer  1  is not illustrated in the simplified illustration of  FIG. 1 . 
     In  FIG. 2 , the trimmer head  3  is shown in a side view. The trimmer head  3  comprises an axis of rotation  4  about which the trimmer head  3  is rotated in operation of the trimmer. For this purpose, the trimmer head  3  is driven by the drive shaft  2  which is only schematically illustrated. In addition, the trimmer head  3  comprises a housing  44  and a trimmer line spool  7  arranged at the housing. The housing  44  of the trimmer head  3  is cup-shaped and comprises in the embodiment a cover  45  and a circumferential wall  46 . The cover  45  extends, beginning at the axis of rotation  4 , in radial direction away from the axis of rotation  4 . The cover  45  is in particular oriented perpendicularly to the axis of rotation  4  of the trimmer head  3 . The circumferential wall  46  adjoins the cover  45  and extends in the direction of the axis of rotation  4 . 
     As illustrated in  FIGS. 2 and 3 , trimmer lines  6 ,  6 ′ can be attached to the trimmer head  3 . In the preferred embodiment, up to two trimmer lines  6 ,  6 ′, i.e., a first trimmer line  6  and a second trimmer line  6 ′, can be attached. The trimmer lines  6 ,  6 ′ project from the housing  44  of the trimmer head  3 . For this purpose, two trimmer line openings  47  are provided at the circumferential wall  46  of the housing  44  in the preferred embodiment; the trimmer line openings  47  are oppositely positioned in relation to the axis of rotation  4 , and the trimmer lines  6 ,  6 ′ project from the housing  44  through the trimmer line openings  47 . In an alternative embodiment of the trimmer head  3 , it can be expedient to provide a different number of trimmer line openings  47  and a different number of trimmer lines  6 ,  6 ′. 
     As illustrated in  FIG. 4 , a hollow pin  60  is projecting coaxial to the axis of rotation  4  away from the cover  45  of the housing  44 . The pin  60  is formed at an inner side  61  of the cover  45  facing the trimmer line spool  7 . At the circumferential side of the pin  60 , the trimmer line spool  7  is arranged. The trimmer line spool  7  is supported on the pin  60  of the housing  44  so as to be rotatable and displaceable in the direction of the axis of rotation  4 , i.e., axially. The trimmer line spool  7  is detachably secured by means of a fastening element  48  on the pin  60  of the housing  44 . The fastening element  48  is embodied as a screw element and is screw-connected to an intermediate element  62  that is fixedly connected to the pin  60 . Between the trimmer line spool  7  and the fastening element  48 , a spring element  49  is arranged which in the embodiment is embodied as a coil spring. The spring element  49  is contacting with one end an inner side of the fastening element  48  facing the trimmer line spool  7 . The spring element  49  is contacting with its other end a stop contour structure  63  of the trimmer line spool  7 . In this context, the spring element  49  exerts a spring force onto the trimmer line spool  7  wherein the spring force acts in the direction of the axis of rotation  4  toward the cover  45 . In an operating position  57  of the trimmer head  3 , the trimmer line spool  7  is tensioned by the spring element  49  against the housing  44  in the direction of the axis of rotation  4 . 
     As shown in  FIG. 4 , the trimmer head  3  comprises an indexing device  30  which enables winding and unwinding of the trimmer line  6 ,  6 ′ from the trimmer line spool  7  in the mounted state of the trimmer head  3 . The indexing device  30  is formed by a contour structure  31  of the trimmer line spool  7  and a counter contour structure  50  of the housing  44  of the trimmer head  3  interacting with the contour structure  31 . The contour structure  31  is formed at the end face  64  of the trimmer line spool  7  facing the cover  45  of the housing  44 . The counter contour structure  50  is provided at the inner side  61  of the cover  45  of the housing  44 . The contour structure  31  is comprised of a plurality of ramps  51  which are arranged in circumferential direction. The ramps  51  comprise an engagement surface  52  which, relative to the rotational direction  20 , is positioned at the trailing end of the ramp  51  and is oriented parallel to the axis of rotation  4 . The ramp  51  comprises in addition a back surface  53  which adjoins the engagement surface  52  and is oriented at a slant to the engagement surface  52  ( FIG. 9 ). In the operating position  57 , the counter contour structure  50  of the housing  44  and the contour structure  31  of the trimmer line spool  7  provide a form fit connection in the rotational direction  20 . In this way, the trimmer line spool  7  is connected to the housing  44  for common rotation in the rotational direction  20  in the operating position  57 . 
     As shown in  FIGS. 4 and 5 , the trimmer line spool  7  comprises a first spool chamber  8  and a second spool chamber  9 . The first spool chamber  8  is the chamber in which a first trimmer line  6  can be wound. The second spool chamber  9  is the chamber in which a second trimmer line  6 ′ can be wound. The trimmer line spool  7  comprises a first spool wall  16 , a second spool wall  18 , and an intermediate wall  17  arranged between the first spool wall  16  and the second spool wall  18 . The trimmer line spool  7  comprises moreover a circumferential wall  19  that connects the first spool wall  16 , the intermediate wall  17 , and the second spool wall  18  to each other. The first spool chamber  8  is delimited in the direction of the axis of rotation  4  by the first spool wall  16  and the intermediate wall  17 . In radial direction relative to the axis of rotation  4 , the first spool chamber  8  is delimited by the circumferential wall  19 . The second spool chamber  9  is delimited in the direction of the axis of rotation  4  by the intermediate wall  17  and the second spool wall  18 . In radial direction relative to the axis of rotation  4 , the second spool chamber  9  is delimited by the circumferential wall  19 . In an alternative embodiment, it can be advantageous to configure the intermediate wall  17  only in sections, in particular in the region of the inlet opening  36  and the outlet opening  37  of the trimmer line channel  35 . In a further alternative embodiment, it can also be advantageous to provide no intermediate wall  17 . In this way, the first spool chamber  8  and the second spool chamber  9  are connected partially, respectively, completely with each other. At the circumferential wall  19 , a web  54  is formed which extends in radial direction relative to the axis of rotation  4  in the direction toward the axis of rotation  4  of the trimmer line spool  7  and connects the circumferential wall  19  to a hub  55  of the trimmer line spool  7 . The trimmer line spool  7  is supported by means of its hub  55  at the pin  60  of the housing  44 . A shoulder  56  with a stop contour structure  63  is formed at the hub  55  and serves for supporting the spring element  49 . The trimmer line spool  7  is tensioned in the direction toward the cover  45  of the housing  44  by means of the spring element  49  resting against the shoulder  56  of the hub  55 . In the operating position  57 , the first spool wall  16  is contacting the end face of the circumferential wall  46  of the housing  44  which is facing away from the cover  45 . In this way, the interior of the housing  44 , which is formed by the cover  45  and the circumferential wall  46  and in which the trimmer line spool  7  is arranged, is closed off and protected against contamination. 
     As illustrated in  FIGS. 4 and 5 , the trimmer line spool  7  comprises an actuating device  32  for actuating the indexing device  30 . The actuating device  32  is arranged adjoining the first spool wall  16  outside of the spool chambers  8 ,  9 . In the preferred embodiment, the trimmer line spool  7  is embodied as one piece together with its actuation device  32 . In the embodiment, the actuating device  32  comprises a holding projection  33  which is extending outwardly in radial direction relative to the axis of rotation  4  and is embodied for engagement from behind by an operator  26 . The unwinding process of the trimmer line  6 ,  6 ′ with actuation of the indexing device  30  will be explained briefly in the following. 
     When winding the trimmer line  6 ,  6 ′ on the trimmer line spool  7 , the trimmer line  6 ,  6 ′ is wound opposite to the rotational direction  20  on the trimmer line spool  7 . For unwinding the trimmer line  6 ,  6 ′, the trimmer line spool  7  is to be rotated relative to the housing  44  in an unwinding direction  25  of the trimmer line spool  7  about the axis of rotation  4 . In this context, the free end of the trimmer line  6 ,  6 ′ projects out of the trimmer line openings  47  of the housing  44 . The trimmer line  6 ,  6 ′ is thus supported at the housing  44  upon unwinding so that the trimmer line portion of the trimmer line  6 ,  6 ′ which is extending from the housing  44  becomes longer. The unwinding direction  25  of the trimmer line spool  7  is opposite to the rotational direction  20 . 
     For unwinding the trimmer line  6 ,  6 ′, the trimmer line spool  7  is to be pulled against the spring force exerted by the spring element  49  in the direction away from the housing  44  into an inoperative position. In this way, the form fit between contour structure  31  of the trimmer line spool  7  and the counter contour structure  50  of the housing  44  is canceled. In the preferred embodiment, the pulling force which is required for overcoming the spring force must be applied by the operator. For this purpose, the operator can grip the trimmer line spool  7  in a simple way at the holding projection  33  of the actuating device  32  and pull the trimmer line spool  7  away from the cover  45  of the housing  44 . In this inoperative position, the trimmer line spool  7  is rotatable in the unwinding direction  25  opposite to the rotational direction  20  relative to the housing  44 . Upon rotation of the trimmer line spool  7  in the unwinding direction  25 , the trimmer line  6 ,  6 ′ is unwound from the spool chambers  8 ,  9 . 
     As illustrated in  FIGS. 4 and 5 , the holding projection  33  of the actuating device  32  forms together with the first spool wall  16  a grip groove  65  into which the operator can extend a hand and thus grip from behind the holding projection  33 . The grip groove  65  is delimited by the first spool wall  16  in the direction of the axis of rotation  4  toward the trimmer line chambers  8 ,  9 . The grip groove  65  is delimited by the holding projection  33  in the direction of the axis of rotation  4  away from the trimmer line chambers  8 ,  9 . In order to provide for a better gripping of the holding projection  33 , at least one grip depression  34  is provided in the first spool wall  16 . In the preferred embodiment, two grip depressions  34  are provided. However, a different number of grip depressions  34  may be expedient. The grip depression  34  is embodied in the form of a curved portion in the first spool wall  16 . Accordingly, the first spool wall  16  is of a curved configuration. The grip depression  34  which is formed in the first spool wall  16  extends in the direction toward the first spool chamber  8 . The grip groove  65  comprises a width d 1  which is measured outside of the grip depression  34  in the direction of the axis of rotation  4  and which corresponds to the distance between the first spool wall  16  and the holding projection  33 . In addition, the grip groove  65  comprises a maximum width d 2  which is measured inside the grip depression  34  in the direction of the axis of rotation  4  and corresponds to the maximum distance between the grip depression  34  and the holding projection  33 . The maximum width d 2  of the grip groove  65  amounts to at least 120%, in particular at least 130%, of the width d 1  of the grip groove  65 . As illustrated in  FIG. 9 , the grip depression  34  extends about the axis of rotation  4  at an angle distance of at least 40°, in particular of at least 60°, preferably approximately of 90°. By means of the partial increase of the width of the grip groove  65  at the grip depression  34 , there is sufficient room provided in order to be able to grip from behind the hold projection  33  of the actuating device  32  in a simple way. 
     As illustrated in  FIGS. 5 and 6 , the trimmer line spool  7  comprises at least one continuous trimmer line channel  35 . The trimmer line  6 ,  6 ′ can be completely pushed all the way through the trimmer line channel  35  and wound onto the trimmer line spool  7 . In the preferred embodiment, the trimmer line spool  7  has two continuous trimmer line channels  35 ,  35 ′. The continuous trimmer line channel  35  extends at least partially in the intermediate wall  17 . The trimmer line channel  35 ,  35 ′ comprises an inlet opening  36  and an outlet opening  37 . The inlet opening  36  and the outlet opening  37  of a trimmer line channel  35 ,  35 ′ comprise an angle distance β measured about the axis of rotation  4  of preferably 150° to 210°, in particular of 160° to 200°. The inlet opening  36  and the outlet opening  37  of the trimmer line channel  35 ,  35 ′ are arranged in the intermediate wall  17 . The inlet opening  36 , the outlet opening  37 , and the trimmer line channel  35  cause a locally thickened portion  66  of the intermediate wall  17 . As illustrated in  FIG. 6 , the first spool chamber  8  has a first height h 1  which corresponds to the distance measured outside of the grip depression  34  and outside of the thickened portion  66  in the direction of the axis of rotation  4  between the first spool wall  16  and the intermediate wall  17 . In addition, the first spool chamber  8  has a second height h 2  which corresponds to the distance measured between the first spool wall  16  and the intermediate wall  17  in the direction of the axis of rotation  4  at the thickened portion  66 . The first spool chamber  8  comprises in the region of the grip depression  34  a reduced third height h 3  measured in the direction of the axis of rotation  4 . The third height h 3  corresponds to the distance between the first spool wall  16  at the grip depression  34  and the intermediate wall  17 . The third height h 3  is less than the first height h 1 . The first height h 1  of the first spool chamber  8  is larger than the second height h 2  of the first spool chamber  8 . In order to avoid an additional constriction of the first spool chamber  8  at the thickened portion  66 , the at least one grip depression  34  is arranged displaced relative to the thickened portion  66  in the circumferential direction about the axis of rotation  4 . Accordingly, the at least one grip depression  34  is arranged in a circumferential region  38  of the trimmer line spool  7  wherein the circumferential region  38  is positioned between the inlet opening  36  and the outlet opening  37  of the trimmer line channel  35 ,  35 ′. Accordingly, an additional constriction of the first spool chamber  8  at the thickened portion  66  of the intermediate wall  17  can be avoided. Due to the arrangement of the thickened portion  66  and the grip depression  34  displaced relative to each other in circumferential direction about the axis of rotation  4 , sufficient space for winding the trimmer line  6 ,  6 ′ can be provided along the entire first spool chamber  8 . 
     As illustrated in  FIG. 5 , the trimmer line spool  7  has two holder pairs  21 ,  22 . The first holder pair  21  of the two holder pairs  21 ,  22  comprises a first trimmer line holder  10  correlated with the first spool chamber  8  and a second trimmer line holder  11  which is correlated with the second spool chamber  9 . The second holder pair  22  of the two holder pairs  21 ,  22  comprises also a first trimmer line holder  10 ′ correlated with the first spool chamber  8  and a second trimmer line holder  11 ′ correlated with the second spool chamber  9 . Each trimmer line holder  10 ,  10 ′,  11 ,  11 ′ comprises an opening  14 ,  14 ′,  15 ,  15 ′ for receiving a trimmer line end. The trimmer line  6 ,  6 ′ is fixed with its trimmer line end in the trimmer line holder  10 ,  10 ′,  11 ,  11 ′ and subsequently wound onto the trimmer line spool  7 . This process will be explained later on in more detail. 
     As illustrated in  FIGS. 4 and 5 , the trimmer line holders  10 ,  10 ′,  11 ,  11 ′ are formed at the circumferential wall  19  of the trimmer line spool  7 . Accordingly, the trimmer line holders  10 ,  10 ′,  11 ,  11 ′ are arranged as close as possible to the axis of rotation  4  in order to obtain an inertia moment as small as possible of the trimmer line spool  7 . The first trimmer line holders  10 ,  10 ′ of the holder pairs  21 ,  22  are arranged in the first spool chamber  8 . The first trimmer line holders  10 ,  10 ′, are positioned in this context at the intermediate wall  17 , i.e., at the side of the intermediate wall  17  opposite the first spool wall  16 . The second trimmer line holders  11 ,  11 ′ of the holder pairs  21 ,  22  are arranged in the second spool chamber  9 . The second trimmer line holders  11 ,  11 ′ are positioned in this context at the intermediate wall  17 , i.e., at the side of the intermediate wall  17  positioned opposite the second spool wall  18 . In the preferred embodiment, the first trimmer line holders  10 ,  10 ′ of one holder pair and the second trimmer line holder  11 ,  11 ′ of the other holder pair are positioned opposite each other relative to the intermediate wall  17 , in particular mirror-symmetrical thereto. The inlet opening  36  and the outlet opening  37  of the continuous trimmer line channel  35 ,  35 ′ are arranged in circumferential direction centrally between two trimmer line holders  10 ,  10 ′,  11 ,  11 ′ of a holder pair  21 ,  22 . 
     As shown in  FIGS. 7 and 8 , the diameter a of the openings  14 ,  15  of the trimmer line holders  10 ,  11  of the first holder pair  21  are larger than the diameter b of the openings  14 ′,  15 ′ of the trimmer line holders  10 ′,  11 ′ of the second holder pair  22 . The diameter b of the opening  14 ′,  15 ′ of the trimmer line holder  10 ′,  11 ′ of the second holder pair  22  amounts to at most 90% of the diameter a of the opening  14 ,  15  of the trimmer line holder  10 ,  11  of the first holder pair  21 . The diameter b of the openings  14 ′,  15 ′ of the trimmer line holders  10 ′,  11 ′ of the second holder pair  22  amounts to at least 60% of the diameter a of the openings  14 ,  15  of the trimmer line holders  10 ,  11  of the first holder pair  21 . The different diameters a, b of the openings  14 ,  14 ′,  15 ,  15 ′ of the holder pairs  21 ,  22  enable the use of trimmer lines  6 ,  6 ′ with different diameters. Thus, the holder pair  21  with the trimmer line holders  10 ,  11  with larger diameter a of the openings  14 ,  15  can hold trimmer lines  6 ,  6 ′ with large diameter; the holder pair  22  with the trimmer line holders  10 ′,  11 ′ with small diameter b of the openings  14 ′,  15 ′ can hold trimmer lines  6 ,  6 ′ with small diameter. 
     As illustrated in  FIG. 8 , the openings  14 ,  15  of the trimmer line holders  10 ,  11  of the holder pair  21  and the openings  14 ′,  15 ′ of the trimmer line holders  10 ′,  11 ′ of the holder pair  22  have an angle distance α, measured about the axis of rotation  4 , of 150° to 210°, in particular of 160° to 200°, approximately of 180°, relative to each other, respectively. In the preferred embodiment, the trimmer line holders  10 ,  10 ′,  11 ,  11 ′ of at least one holder pair  21 ,  22  are positioned at least partially in the longitudinal plane  5  containing the axis of rotation  4 . Due to the displaced arrangement of the first trimmer line holder  10 ,  11  and of the second trimmer line holder  10 ′,  11 ′ of the respective holder pairs  21 ,  22  in the circumferential direction of the axis of rotation  4 , the ends of the trimmer lines  6 ,  6 ′ are also clamped displaced about the corresponding angle distance relative to each other in the trimmer line holders  10 ,  10 ′,  11 ,  11 ′. The trimmer line openings  47  at the housing  44  have an angle distance of approximately 180°. The trimmer lines therefore exit displaced at an angle distance of approximately 180° relative to each other from the housing  44 . 
     Due to the displaced trimmer line holders  10 ,  10 ′,  11 ,  11 ′ and the displaced trimmer line openings  47 , a symmetrical winding of the trimmer lines  6 ,  6 ′ can be realized and thus also a uniform mass distribution in relation to the axis of rotation  4 . Therefore, the centrifugal forces acting on the trimmer line  6 ,  6 ′ in operation of the trimmer head  3  cancel each other mutually. In this way, imbalance of the trimmer line spool  7  and thus also of the trimmer head  3  are avoided. 
     As illustrated in particular in  FIG. 7 , the trimmer line holders  10 ,  10 ′,  11 ,  11 ′ of at least one holder pair  21 ,  22  are formed of identical trimmer line chambers  12 ,  13 . The trimmer line chambers  12 ,  13  are accessible through openings  14 ,  14 ′,  15 ,  15 ′ of the trimmer line holder  10 ,  10 ′,  11 ,  11 ′. In this context, the opening  14 ,  14 ′,  15 ,  15 ′ is formed at the leading end of the trimmer line chamber  12 ,  13  viewed in the rotational direction  20 . At the rearward side of the trimmer line chamber  12 ,  13  viewed in rotational direction  20 , a stop  23  for the trimmer line end is formed. For clamping the trimmer line  6 ,  6 ′ in the trimmer line holder  10 ,  10 ′,  11 ,  11 ′, the trimmer line  6  can be inserted via the opening  14 ,  14 ′,  15 ,  15 ′ of the trimmer line holder  10 ,  10 ′,  11 ,  11 ′ into the trimmer line chamber  12 ,  13  and can be pushed all the way against the stop  23  into the trimmer line holder  10 ,  10 ′,  11 ,  11 ′. In the preferred embodiment, the trimmer line  6 ,  6 ′ can be inserted only via the opening  14 ,  14 ′,  15 ,  15 ′ of the trimmer line holder  10 ,  10 ′,  11 ,  11 ′ into the trimmer line chamber  12 ,  13 . It can be provided that at the trailing side of the trimmer line chamber  12 ,  13  viewed in rotational direction  20 , a further opening is provided which serves only for cleaning the trimmer line holder. In this context, the diameter of this opening is designed to be so small that the trimmer line  6 ,  6 ′ stops however at the stop  23  in any case. Pushing the trimmer line  6 ,  6 ′ through the opening provided at the stop  23  is not possible. In the preferred embodiment of the trimmer line spool  7 , as illustrated in  FIG. 8 , the trimmer line chamber  12 ,  13  is closed at the side which is positioned opposite the opening  14 ,  14 ′  15 ,  15 ′, i.e., is closed at the stop  23 . 
     In the preferred embodiment as illustrated in  FIG. 5 , between the first trimmer line holders  10 ,  10 ′ and the first spool wall  16  as well as between the second trimmer line holders  11 ,  11 ′ and the second spool wall  18 , a reinforcement rib  67  is provided at the circumferential wall  19 , respectively. The trimmer lines  6 ,  6 ′ are laid about the reinforcement ribs  67  when wound on the trimmer line spool  7 . The forces which are acting through the trimmer line  6 ,  6 ′ onto the trimmer line spool  7  are distributed in a mechanically favorable manner by the reinforcement ribs  67  to the circumferential wall  19  so that peak loads at the circumferential wall  19  of the trimmer line spool  7  are avoided. 
     In an alternative embodiment of the trimmer line spool  7  according to the invention in accordance with  FIG. 11 , a reinforcement wall  68  can be provided instead of the reinforcement ribs  67 . The reinforcement wall  68  extends in the direction of the axis of rotation  4 , beginning at the first trimmer line holder  10 ,  10 ′, all the way to the first spool wall  16 . In this context, the reinforcement wall  68  is part of the trimmer line holder  10 ,  10 ′ so that the reinforcement wall  68  extends completely from the intermediate wall  17  to the first spool wall  16 . In the same embodiment, a further reinforcement wall  68  is provided extending in the direction of the axis of rotation  4 , beginning at the second trimmer line holder  11 ,  11 ′, all the way to the first spool wall  18 . Preferably, the reinforcement wall  68  extends across the entire length c of the trimmer line chamber  12 ,  13  (see  FIG. 8 ). 
     The operator can choose between two possibilities for winding the trimmer line  6 ,  6 ′ on the trimmer line spool  7 . When the trimmer head  3  is demounted, the operator can insert the first trimmer line  6  into the first trimmer line holder  10 ,  10 ′ of a holder pair  21 ,  22  and the second trimmer line  6 ′ into the second trimmer line holder  11 ,  11 ′ of the same holder pair  21 ,  22 . Subsequently, the trimmer line spool  7  is to be rotated in a winding direction  24  that is opposite to the unwinding direction  25 . The trimmer lines  6 ,  6 ′ are to be held by hand such that they are wound onto the trimmer line spool  7 . In this context, the trimmer lines  6 ,  6 ′ bend beginning at the trimmer line holders  10 ,  10 ′,  11 ,  11 ′ by approximately 180° so that the trimmer line ends are held by being clamped in the trimmer line holders  10 ,  10 ′,  11 ,  11 ′. Subsequently, the trimmer line spool  7  with the trimmer lines  6 ,  6 ′ wound into the first spool chamber  8  and into the second spool chamber  9  is to be positioned in the trimmer head  3  so that the free ends of the trimmer lines  6 ,  6 ′ project out of the trimmer line openings  47  of the housing  44  of the trimmer head  3 . 
     When the operator does not want to remove the trimmer head  3  from the trimmer, the operator can insert a trimmer line  6 ,  6 ′ from the exterior through the trimmer line channel  35 ,  35 ′ and subsequently can rotate the trimmer line spool  7  in the winding direction  24  relative to the housing  44 . In this context, the trimmer line spool  7  runs across the back surfaces  53  of the ramps  51  at the counter contour structure  50  and moves in the direction of the axis of rotation  4  against the spring force of the spring element  49  away from the housing  44  until the ramp  51  locks in the corresponding counter contour structure  50 . Applying a pulling force on the actuation device  32 , as it is required for unwinding the trimmer line, is not required. It is sufficient to rotate the trimmer line spool  7  in the winding direction  24  relative to the housing  44  because the shape of the ramps  51  automatically leads to overcoming the geometry of the counter contour structure  50 . Such functional principles are also known from pawl devices. Thus, the trimmer line channel  35 ,  35 ′ provides an alternative fastening possibility in relation to the trimmer line holders  10 ,  10 ′,  11 ,  11 ′ for fastening the trimmer line  6 ,  6 ′ in the spool chambers  8 ,  9 . 
     In  FIG. 10 , a further trimmer line spool  7  according to the invention is illustrated which differs from the embodiment of  FIG. 5  only in the arrangement of the trimmer line holders  10 ,  10 ′,  11 ,  11 ′. The trimmer line holders  10 ,  10 ′,  11 ,  11 ′ are arranged in the intermediate wall  17  of the trimmer line spool  7 . In this context, the first trimmer line holders  10 ,  10 ′ are arranged adjacent to the inlet opening  36  of the trimmer line channel  35  and the second trimmer line holders  11 ,  11 ′ adjacent to the outlet opening  37  of the trimmer line channel  35 . Preferably, the trimmer line holders  10 ,  10 ′,  11 ,  11 ′ are arranged relative to each other such that the trimmer line holders  10 ,  11  of the first holder pair  21  are embodied with axial symmetry relative to the axis of rotation  4  and the trimmer line holders  10 ′,  11 ′ of the second holder pair  22  are also embodied with axial symmetry to the axis of rotation  4 . The longitudinal direction of the trimmer line holder  10 ,  10 ′,  11 ,  11 ′ intercepts in this context the circumferential wall  19 . This results in the same functional operation in accordance with the invention and the same advantages for the trimmer line spool  7  according to  FIG. 10  as disclosed for the trimmer line spool  7  according to  FIG. 5 . 
     The specification incorporates by reference the entire disclosure of European priority document 19 213 583.8 having a filing date of Dec. 4, 2019. 
     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.