Field of the invention

The present invention relates to an attachment for a brush cutter in the form of a tool holder and more particularly to a multifunctional tool holder for holding different types of tool for performing different tasks.

Back ground of the invention

For management of vegetation in the public space frequent use is made of brush cutters of different types and sizes. The term “brush cutter” is a name for a driven device carried by a person and having a drive member, for instance in the form of a petrol engine or electric motor, operating members and an elongate drive shaft having at one end means for releasable coupling of a tool, such as a cutting blade or a saw blade, or a tool holder for releasable coupling of a tool in the form of for instance a weed brush tuft or a trimmer line. The term “tool” is used here to indicate a part of a device which interferes with the material and/or ground surface to be treated, in this case the material relates mainly, though not exclusively, to the greatest range of vegetation imaginable. The ground surface relates to the soil and paved surfaces. Known tool holders are characterized by a rapid coupling system for exchanging worn or damaged tools for new ones in a user-friendly manner. EP1384419A1 and EP1500349A1 contain descriptions of such tool holders. Known tool holders are intended to hold one type of tool, for instance a tuft, a line or a flail. A tool of a known type, for instance a tuft, is available in different embodiments, for instance with steel wire strands or with plastic filaments. What these tools have in common is that they have similar coupling members, i.e. the parts co-acting with the coupling members of the tool holders in order to establish a coupling.

A frequent occurrence in practice is that the use of a brush cutter with tufts, for instance for removing weeds from a hard surface, is alternated with the use of a brash cutter equipped with a line for trimming and shredding vegetation in the same working environment. In some situations die tool holder with tufts must be exchanged for a tool holder with trimmer line. For such situations it is practical to be able to have a tool holder which can fulfil both functions. The present invention provides such a tool holder.

Summary of the invention

A tool holder for holding weed brush, tufts is tor this purpose characterized according to the invention in that the tool holder also comprises means for holding a trimmer line. The inventive concept of utilizing one and the same tool holder for holding weed brush tufts and for holding trimmer lines goes beyond the prevailing idea that the versatility of the brush cutter is defined by the exchangeable tool holder.

The tool holder according to the invention comprises at least one second, substantially cylindrical drilled hole with a first mouth in the periphery of the tool holder for the purpose of receiving a segment of a trimmer line and damping means for clampingly holding a segment of the trimmer line. In the preferred embodiment the central axis of the second drilled hole lies in a plane perpendicularly of the longitudinal axis of the tool holder and the second drilled hole is a drilled through-hole with a first and a second mouth. The drilled hole and the clamping means provide the option of applying a. known trimmer line. The user is given the choice of using one end of the trimmer line in the work, or both ends simultaneously. Experience in practice shows that working with one end is particularly suitable for trimming vegetation. Working with two ends is particularly suitable for removing weeds from a ground surface susceptible to damage, such as natural stone paving.

The device according to the invention is further characterized in that provision is made for the means for locking a tuft also to serve to clampingly hold the trimmer line. An advantage of this universal provision is that the expansion of the versatility of the tool holder according to the invention is not accompanied by an increase in weight, which would be disadvantageous in respect of the operating comfort.

The invention further provides measures for maximizing the tool life of a trimmer line. These measures comprise a widening of the mouths of the second drilled hole in opposite tangential directions, this minimizing the chance of line breakage.

For the purpose of optimizing the clamping of known serrated trimmer lines the invention provides a projection which engages in the recess between two successive protrusions in a serrated edge.

To increase the convenience of use the tool holder comprises a support base with depth adjusting means in the form of a screw connection, and also arresting means. Brief description of the drawings The invention is elucidated hereiribelow with reference to five figures, in which:

~ figure 1 shows schematically a perspective bottom view of the known Armigo Triplo ^® tool holder;

- figure 2a shows schematically a perspective botom view of a tool holder according to the present invention;

- figure 2b shows schematically a perspective top view of the tool holder according to the present invention;

- figure 3 shows schematically a simplified representation of a flat projection of a radial section of the tool holder;

- figure 4 shows schematically a perspective view of the plunger of the tool holder according to the present invention.

Exemplary embodiment of a device according, to the invention

The invention will be further elucidated below by way of example on the basis of one exemplary embodiment shown in the drawing. Figure 1 shows a perspective view of the Armigo Triplo®, a known tool holder 1 with tufts 4 for brush cutters. The features of this tool holder are described in EP1500349A1. The present invention relates to an improvement in the art of this and similar tool holders, and the invention relates more particularly to an increase in versatility. The increase in versatility contributes to the fact that the brash cutter can be used to perform different functions without the tool holder having to be exchanged for a different type of tool holder.

The increase in versatility stems from the inventive concept of taking measures that provide a tool holder with means for holding tufts for sweeping and for removing weeds from paving, and with means for holding a trimmer line for trimming vegetation and for removing weeds from vulnerable paving, for instance natural stone paving.

The application of trimmer line as trimming tool is known. Trimmer line is supplied on roils and as individual line pieces, for tool holders with holders for respectively rolls and pieces of trimmer line. Trimmer line is usually manufactured from plastic and lias a round or angular cross-section. The known trimmer lines also include trimmer lines with two or more serrated edges oriented in the longitudinal direction. The present invention relates to a tool holder for tufts and for trimmer line in the form of individual line pieces. The term “trimmer line” is used in the following to indicate a line piece of trimmer line.

The biggest challenge in expanding the versatility of known tool holders without compromise is limiting the negative consequences for the weight of the tool holder. Any increase in weight results in a decrease of the user comfort. The embodiment of the inventive concept must be viewed mainly in this light.

Figures 2a and 2b show schematically a perspective bottom and top view of the preferred embodiment of tool holder 2 with means for holding tufts and trimmer lines according to the invention. The upper side of tool holder 2 indicates the side which in mounted state faces toward the drive shaft of the brush cutter, the underside faces toward the area to be heated during intended use.

Figures 2a and 2b show, among other things, recesses 3 for receiving a head of a tuft 4 adapted thereto, recesses 5 for weight reduction, shaft hole 6 for mounting tool holder 2 on the driving shaft of a brush cutter, first drilled holes 7 with manually pressable plungers 8 for locking and unlocking a tuft 4, and locking pins 9 serving as stop for plungers 8. Tool holder 2 comprises second drilled holes 10 (not shown) for holding the trimmer lines 11. Tool holder 2 as shown in figures 2a and 2b further comprises means, to be further described, for clampingly holding the respective trimmer lines 11.

For a further description of the features of the present invention reference is made to figure 3. Figure 3 shows a highly simplified schematic view of a radial, flattened section of tool holder 2. According to the preferred embodiment of the invention, the central axes of the second drilled holes 10 lie in one plane, perpendicularly of the longitudinal axis of tool holder 2, and second drilled holes 10 intersect the respective first drilled holes 7. In the preferred embodiment each second drilled hole 10 with diameter D ₁ is a drilled through- hole through tool holder 2, wherein first and second mouths 12 and 1.3 are formed on the periphery. Figure 3 shows that plunger 8 is pressed with a stop 15 against locking pin 9 by a spring 14 in the situation where no external force is exerted on plunger 8 (F = 0 N). The stop 15 is formed by a boundary of a first recess 16 along the side of plunger 8, in the form of a cylinder segment. Locking pin 9 also prevents twisting of plunger 8 in first drilled hole 7, and thereby fulfils an important function. The outer end of plunger 8 that is in contact: with the spring 14 is referred to as the first outer end of plunger 8.

Plunger 8 is provided with a second recess 17 which in known tool holders plays a role In locking a tuft in a recess 3 of tool holder 2. According to the invention, plunger 8 comprises a radial drilled through- hole 18 with diameter D ₂ , for which it is the case that D ₂ ≥ D ₁ . For the orientation and the position of drilled through-hole 18 it is the case that, within the path along which plunger 8 is displaceable, the path being bounded here by respectively the stop 15 and the fully compressed spring 14, there is a position for which it is the case that the central axis of drilled through-hole 18 of plunger 8 coincides with the central axis of the second drilled hole 10 and wherein the spring 14 is at least largely compressed. In this position of plunger 8 a trimmer line 11 can be earned via. the second drilled hole 10 through the drilled through-hole 18 of plunger 8. In the preferred embodiment the central axis of drilled through-hole 18 coincides with the axis of symmetry of the second recess 17.

Three configurations A, B and C are described further with reference to figure 3. In configuration A tool holder 2 comprises a tuft 4 in locked state, as described in EP1500349A1. In this configuration the brush cutter with tool holder 2 is eminently suitable for brushing a ground surface. Configuration B, without tuft 4, is characterized in that a force F is exerted manually on plunger 8, such that plunger 8 takes up a position wherein drilled through-hole 18 of plunger 8 lies in line with second drilled hole 10. In this configuration trimmer line 11 can be moved freely In tool holder 2 and can he placed into tool holder 2, displaced so as to be placed in the desired position, or be removed.

Configuration C, likewise without tuft 4, is characterized in that no external force is exerted on plunger 8 (F = 0 N). In this configuration trimmer line 11 is clampingly held by the force being exerted on a segment of the trimmer line 11 by spring 14 via plunger 8. In the operational mode this force is increased by the centrifugal force experienced by plunger 8. In this configuration the brush cutter with tool holder 2 is eminently suitable for trimming and shredding vegetation and for removing weeds from a ground surface susceptible to damage.

During use trimmer line 11 comes under strain of bending by a centrifugal force as a res ult of the ro tation of tool holder 2 and as a result of the resistance experienced by trimmer line 11 during trimming. Extreme bending can result in damage to trimmer line 11, particularly at the mouth 12 of second drilled hole 10. Measures have therefore been taken at mouth 12 of second drilled hole 10 to reduce the bending moment. These measures comprise a gradual widening, directed toward the periphery of tool holder 2, of the outlet mouth of second drilled hole 10 in tangential direction and substantially opposite to the rotation direction R, resulting in an oval mouth 12.

In the preferred embodiment the second drilled hole 10 comprises a drilled hoie all the way through, with a first and second mouth 12 and 13. This feature of tool holder 2 gives the user the option of carrying the trimmer line 11 through tool holder 2 so as to use both ends of a trimmer line 11 simultaneously. This configuration of trimmer line 11 has been found particularly suitable in practice for removing weeds from ground surfaces, such as natural stone, which are unable to withstand the aggressi ve action of the known weed brush tufts.

The known trimmer lines 11 include trimmer lines 11 embodied with serrated edges. Compared to smooth trimmer lines 11 , the use of serrated trimmer lines 11 is accompanied by a relatively great tensile force which attempts to pull trimmer line 11 from tool holder 2. Tests have shown that clamping holding of such a serrated trimmer line 11 improves greatly when drilled through-hole 18 of plunger 8 comprises a projection which engages in a recess in the serrated edge. A further enhancement is achieved when the drilled through-hole 18 comprises a recess with a projection for simultaneously guiding and arresting a trimmer line 11 with a serrated edge. These measures are shown schematically in figure 4. Figure 4 shows a perspective view of a plunger 8 and a drilled through-hole 18, wherein the wall of drilled through-hole 18 directed toward spring 14 is provided from both mouths with third recesses 19 and 19’ and a projection 20 between the two recesses 19, 19’. In a preferred embodiment the depth di of recess 19, 19’ is a minimum of 1 mm and the height iij of the projection is likewise a minimum of 1 mm, while the width bi of the projection amounts to a maximum of 1 mm. In the preferred embodiment the projection 20 has a sharp edge which engages aggressively on the trimmer line 11 in placed situation.

An embodiment which is characterized by one recess 19 and a projection 20 with the same dimensions likewise falls within the scope of the invention.

It follows from the above description that the objective stated in the preamble lias been achieved in an effective manner. An advantageous feature of the tool holder according to the invention is that the expansion of the versatility of the tool holder is not accompanied by an increase in weight. This feature is related to, among other things, die clever adaptation of the known plunger, whereby the plunger fulfils two functions: locking a tuft and clampingiy holding a trimmer line.

The features of the preferred embodiment, as one of the embodiments of the present invention, are related to, among other factors, the manner in which the tool holder can be manufactured. “Drilled holes” and “drilled through-holes” are thus used to indicate respectively blind and open cylindrical channels. Such channels can however also form part of a cast piece or a workpiece of a 3D printer. Such embodiments, having essentially similar features, are understood to fall within the scope of the invention. The description further relates to an embodiment wherein the central axes of the first and second drilled holes 7 and 10 intersect perpendicularly and plunger 8 comprises a radial drilled through-hole 18. Embodiments for which it is the case that the central axes of the first and second drilled holes 7 and 10 do not intersect perpendicularly but at an angle and drilled through-hole 18 of plunger 8 is not oriented radially are likewise understood to fall within the scope of the invention.

The preferred embodiment developed here relates to a tool holder for holding three tufts or three trimmer lines. Tool holders with similar means for more or fewer tufts/trimmer lines are likewise understood to fall within the scope of the invention.

The invention further provides a support base 21 for supporting a brush cutter with a tool holder 2 on the surface to be treated. For this purpose support base 21 serves as support means for maintaining the working height. Support base 21 is provided with screw thread and co-acts with a recess (not shown) on the underside of tool holder 2 , which recess is for this purpose likewise provided with screw thread. The trimming height can be controlled by screwing support base 21 further of less far into the recess. The invention also provides means for fixing a set trimming height, for instance in the fours of clamping or arresting means.