The invention relates to a trimmer head for mounting on a drive shaft of a trimmer.
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, trimmer lines are used which are subject to a certain wear in operation of the trimmer head. During operation of a trimmer head, the trimmer line must be readjusted several times so that a sufficient length of trimmer line is available and the cutting function of the trimmer head is not impaired. When the trimmer line is completely unwound from the trimmer line spool, a new trimmer line must be inserted into the trimmer head.
It is advantageous when the operator is enabled to anticipate an upcoming change of the trimmer line. This enables the operator to keep at hand a replacement trimmer line and to change at the site of use the trimmer line, as needed. The operator, in preparation before even beginning work, can change the trimmer line so that an interruption of the work on site is not necessary.
WO 2018/153424 A1 discloses a trimmer head with a trimmer line wherein the trimmer line comprises sections of different color. Based on the differently colored sections of the trimmer line, the user can recognize how much trimmer line is already used up and when to expect a necessary exchange of the trimmer line. A disadvantage of such systems is that the recognition of the residual trimmer line length is possible only as a function of the trimmer line type.
It is an object of the invention to develop a trimmer head with an alternative residual trimmer line indicator.
In accordance with the invention, this is achieved by a trimmer head for mounting on a drive shaft of a trimmer, wherein the trimmer head comprises a housing and a trimmer line spool for winding and unwinding a trimmer line, wherein the trimmer line spool is rotatably supported in relation to the housing about an axis of rotation, wherein the trimmer line spool comprises, in relation to the housing, a first rotational direction and a second rotational direction opposite to the first rotational direction, wherein the trimmer head comprises a counting device for detecting the residual trimmer line length, wherein the counting device is operatively connected to the trimmer line spool such that the counting device is counting up upon rotation of the trimmer line spool in the first rotational direction in relation to the housing and is counting down upon rotation of the trimmer line spool in the second rotational direction in relation to the housing.
The trimmer head according to the invention comprises a trimmer line spool for winding and unwinding a trimmer line. The trimmer line spool comprises, in relation to the housing, a first rotational direction and a second rotational direction opposite to the first rotational direction. The trimmer head comprises a counting device for detecting the residual trimmer line length. The counting device is operatively connected to the trimmer line spool in such a way that the counting device counts up upon rotation of the trimmer line spool in the first rotational direction in relation to the housing and counts down upon rotation of the trimmer line spool in the second rotational direction in relation to the housing.
When the trimmer line is wound onto the trimmer line spool, the counting device counts up. When the trimmer line is unwound from the trimmer line spool, the trimmer line spool rotates in the second rotational direction in relation to the housing and the counting device counts down. In this context, the counter value is indicated by the counting device at least indirectly. In this way, the operator is advised by the counting device how much residual trimmer line length is still remaining on the trimmer line spool. The determination of the residual trimmer line length is realized independent of the configuration of the trimmer line.
Preferably, the counting device comprises a counter wherein the counter determines the relative rotation between trimmer line spool and housing. Advantageously, the counter is a mechanical, an electronic, or an electromechanical counter. By means of the counter, the relative rotations between trimmer line spool and housing can be measured by which the trimmer line is wound onto the trimmer line spool.
It is advantageously provided that at the trimmer line spool of the trimmer head at least one actuating element is provided wherein the counter is actuated at least once by means of the at least one actuating element for each relative rotation between the trimmer line spool and the housing. In this way, the counter counts the numerical value up or down by 1 for each revolution. Advantageously, a plurality of actuating elements can be provided also wherein the counter for each revolution determines a counter value which corresponds to the number of actuating elements.
The actuating element is preferably a tooth element which is arranged at the trimmer line spool. It is advantageously provided that the actuating element is a ring gear which is arranged at the trimmer line spool, wherein the counter is continuously actuatable by the ring gear at the trimmer line spool. By use of a ring gear, an extremely precise determination of the relative rotation between trimmer line spool and housing and thus of the trimmer line length that is wound onto the trimmer line spool is enabled.
It is advantageously provided that the actuating element is a pulse generator arranged at the trimmer line spool, wherein the counter is embodied as a pulse counter for recording the pulses that are emitted by the at least one pulse generator. The pulse counter is preferably an optical sensor, in particular an inductive or a capacitive proximity sensor. In this configuration, the counting process can be realized without mechanical contact between the actuating element and the counter. The counter is preferably embodied as a rotary encoder. In this way, a precise indication of the rotation angle can be provided.
The counting device comprises preferably an output element coupled with the counter, wherein the counter value which is determined by the counter is indicated at least indirectly by the output element. The output element is preferably arranged on the housing so as to be visible by the operator of the trimmer head. In this way, the operator can detect how much residual trimmer line length is still wound on the trimmer line spool even in the installed state of the trimmer line spool.
The counting device is preferably configured such that the counting device has a zero position when the trimmer line has been unwound from the trimmer line spool. When winding trimmer line onto the trimmer line spool, the counter counts up so that the operator based on the output element can recognize the trimmer line length that has been wound onto the spool. Upon unwinding the trimmer line from the trimmer line spool, the trimmer line spool is rotated in relation to the housing in the second rotational direction and the counter counts down until the trimmer line has been completely unwound and the counting device has again reached the zero position.
It is preferably provided that the trimmer line spool comprises at least one continuous trimmer line channel through which the trimmer line can be pushed and then wound onto the spool. For winding the trimmer line, the trimmer line has to be pushed through the trimmer line channel and subsequently the trimmer line spool is to be rotated in the first direction relative to the housing. Preferably, the trimmer line spool comprises at least two holding devices for fastening two trimmer lines. In this way, one trimmer line can be fixed at each holding device and the trimmer lines can be subsequently wound onto the trimmer line spool.
Further features of the invention result from the description and the drawing. Embodiments are illustrated which will be described in detail in the following.
In
As illustrated in
For winding the trimmer line 6 on the spool, the trimmer line spool 5 has a continuous trimmer line channel 54 through which the trimmer line 6 can be pushed and then wound onto the spool. Such a continuous trimmer line channel 54 enables the operator to wind the trimmer line 6 onto the spool in the mounted state of the trimmer head 2. In such a state, the trimmer line spool 5 is held in the housing 4 of the trimmer head 2. The operator pushes the trimmer line 6 into the trimmer line channel 54 and aligns it in such a way that trimmer line ends of approximately the same length project from the trimmer line channel 54 at the respective ends of the trimmer line channel 54. Subsequently, the trimmer line spool 5 is rotated in a first rotational direction in relation to the housing 4. Each free end of the trimmer line 6 then is wound into one of the spool chambers 45, 45, respectively. In the embodiment, such a trimmer line channel 54 is provided in the intermediate wall 47 of the trimmer line spool 5.
Instead of or in addition to the trimmer line channel 54, the spool chambers 45, 45′ can be provided with trimmer line holders at which a respective trimmer line 6 can be held. The trimmer line 6 is fixed at the trimmer line holder and, by a rotation of the trimmer line spool 5 relative to the housing 4, is subsequently wound onto the trimmer line spool 5 in one of the spool chambers 45, 45′. In this way, several trimmer lines 6 can be wound onto the trimmer line spool 5.
When in operation of the trimmer head 2 the trimmer line 6 is worn at its ends, it must be unwound from the trimmer line spool 5 for lengthening the ends extending from the housing 4. For this purpose, the trimmer head 2 comprises an indexing device 50. As illustrated in
In an alternative embodiment, the indexing device 50 can also be designed such that, for canceling the rotational connection between the trimmer line spool 5 and the housing 4, the trimmer line spool 5 must be pulled in the direction away from the cover member 39 of the housing 4 in the direction of the axis of rotation 7. Subsequently, the trimmer line spool 5 is to be rotated by hand relative to the housing 4 in order to unwind the trimmer line 6 from the trimmer line spool 5.
As illustrated in
For winding the trimmer line 6 onto the trimmer line spool 5, the trimmer line spool 5 is to be rotated in the first rotational direction 8 about the axis of rotation 7 relative to the housing 4. For unwinding the trimmer line 6 from the trimmer line spool 5, the trimmer line spool 5 is to be rotated in the second rotational direction 9 opposite to the first rotational direction 8.
As illustrated in
Upon winding the trimmer line 6 onto the spool, the counting device 10 provides for initializing the length of the trimmer line 6. Accordingly, the length of a trimmer line 6 is determined. Therefore, the use of a trimmer line of a predetermined length is not required for a correct determination of the residual trimmer line length. It is possible for the operator to use trimmer lines of various lengths.
The counter 11 can be a mechanical, in particular an electromechanical, preferably electronic counter 11. In the embodiment of the counter 11 as a mechanical counter, preferably an actuating element 13, here embodied as a tooth element, is provided at the trimmer line spool 5 and actuates the counter 11 with each revolution. A compensation weight 14 for an imbalance-free weight distribution of the trimmer head 2 is provided for the counting device 10. Such a compensation weight 14 can be designed as simple weighting elements. Also, a second counting device with output element is conceivable that is designed to be symmetrical to the first counting device 10 in relation to the axis of rotation 7.
In addition, in an alternative embodiment according to the invention of the trimmer head 2, it can be expedient to distribute a plurality of actuating elements 13 at the trimmer line spool 5 in the circumferential direction of the axis of rotation 7 in order to actuate the counter 11 several times per revolution. With increasing number of actuating elements 13, a more exact determination of the residual trimmer line length is possible. Alternatively, a ring gear can be provided instead of individual tooth elements at the trimmer line spool 5, wherein the ring gear is operatively connected to the counter 11. Preferably, a gear unit is provided between the counter 11 and the ring gear so that a continuous determination of the residual trimmer line length is possible. The counter 11 is illustrated schematically in
In an alternative embodiment of the trimmer head 2, the counter of the counting device 10 can be embodied as an electromechanical or electronic counter. As shown in
As shown in
As illustrated in
As illustrated in
Alternatively, a computational conversion, based on the diameter of the trimmer line spool 5, to the actual residual trimmer line length can be realized so that the output element 12 indicates the residual trimmer line length as a unit of length.
In an alternative embodiment, it can be expedient to design the trimmer head 2 such that the counter 11 is fixedly connected to the trimmer line spool 5 and the actuating element 13 is fixedly connected to the housing 4.
The specification incorporates by reference the entire disclosure of European priority document 19 218 095.8 having a filing date of Dec. 19, 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.
Number | Date | Country | Kind |
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19 218 095.8 | Dec 2019 | EP | regional |