The invention relates to a work implement comprising a tool, a housing part, and a stud bolt screwed into the housing part for attachment of the tool to the housing part, wherein the stud bolt projects out of the housing part along an axial direction, wherein the tool comprises an opening, wherein the stud bolt projects at least partially into the opening, wherein the work implement comprises a transmission element for transmitting transverse forces, acting transversely to the axial direction, from the tool to the stud bolt.
GB 2481037 A discloses a work implement with a stud bolt. The work implement has attached thereto a guide bar with saw chain as a tool. Between the guide bar and the stud bolt, a sleeve of silicone is arranged. The stud bolt is fastened in a housing part of the work implement. In operation of the work implement, forces are transmitted from the guide bar to the stud bolt. These forces can damage the connection between the stud bolt and the housing part and, in an extreme case, can even cause the stud bolt to become detached from the housing part. For absorbing these forces, GB 2481037 A employs the sleeve of silicone. The sleeve quickly wears in operation so that the damping action of the sleeve is weakened or completely destroyed. A continued operation of the work implement can then quickly destabilize the connection between stud bolt and housing part.
It is an object of the invention to further develop a work implement of the aforementioned kind such that a wear-resistant and safe operation of the work implement is possible.
In accordance with the invention, this is achieved for a work implement of the aforementioned kind in that the transmission element is embodied as a first element and the first element is at least partially comprised of a first material that comprises a modulus of elasticity of 1 GPa to 80 GPa, or in that the transmission element is embodied as a second element and the second element comprises a spring element, comprised at least partially of a second material with a modulus of elasticity of larger than 80 GPa, and further comprises a free space for a spring travel of the spring element.
According to the invention, it is provided that the transmission element is embodied as a first element and that the first element is comprised at least partially of a first material that has a modulus of elasticity of 1 GPa (1×109 N/m2) to 80 GPa (80×109 N/m2), or that the transmission element is embodied as a second element and that the second element comprises a spring element and a free space for a spring travel of the spring element, wherein the spring element is comprised at least partially of a second material comprising a modulus of elasticity of larger than 80 GPa.
It has been found that even materials with a higher modulus of elasticity than silicone are sufficient, or are even better suited, in order to damp forces that are transmitted from the tool to the stud bolt. Since the first element is comprised at least partially of a first material that comprises a modulus of elasticity of 1 GPa to 80 GPa, the first element wears only by a very small amount and dampens at the same time in a satisfactory manner the transverse forces which are transmitted from the tool to the stud bolt. In this way, the work implement can be operated safely and in a wear-resistant way. Damage of the connection between the stud bolt and the housing part by the transverse forces is effectively prevented in this way. A safe and wear-resistant operation of the work implement is possible in this way. Forces can be transmitted in this way even at high transmission frequency with minimal spring travel.
Since the second element comprises a spring element comprised at least partially of a second material with a modulus of elasticity of larger than 80 GPa and further comprises a free space for a spring travel of the spring element, the second element can be produced of a wear-resistant material. In this way, the second element, in particular the spring element, wears only by a very minimal amount and dampens at the same time sufficiently the transverse forces that are transmitted from the tool to the stud bolt. In this way, the work implement can be operated safely and in a wear-resistant way. Since the second element is comprised at least partially of a second material that comprises a modulus of elasticity of larger than 80 GPa, the second element can be designed to be particularly wear-resistant and exhibit a long service life.
The two variants according to the invention have in common the technical effect that the respective transmission elements achieve a good damping action with minimal wear. The good wear behavior is achieved by materials with a modulus of elasticity of at least 1 GPa. Up to 80 GPa (80 GPa included), the damping action of the materials themselves is sufficient. Above 80 GPa, the transmission element must additionally comprise the spring element and the free space for the spring travel of the spring element in order to achieve a satisfactory damping action. The second element is advantageously designed such that it acts at least partially in a springy fashion due to its shape for the transfer of the transverse forces. The second element is therefore also referred to as a shape spring.
In an advantageous further embodiment of the invention, it is provided that the transmission element in respect to the axial direction extends completely circumferentially around the stud bolt.
Advantageously, the transmission element is arranged between the opening and the stud bolt. In particular, the transmission element is arranged with clearance on the stud bolt. This facilitates mounting and demounting of the tool.
Expediently, the transmission element is fastened to the tool. In this way, an exchange of the tool is possible without there being the risk of losing the transmission element.
In an advantageous embodiment of the invention, it is provided that the opening comprises a rim and that the transmission element is fixed at the rim of the opening of the tool. In this way, the transmission element is captively connected to the tool. The work implement is comprised of a reduced number of individual components and can therefore be mounted and demounted easily.
In an advantageous variant of the invention, the transmission element is fastened to the stud bolt. In this way, it can be prevented that the transmission element is lost when exchanging the tool. In particular, the transmission element is captively fastened at the stud bolt.
In a particular embodiment of the invention, the transmission element is exchangeably held at the stud bolt. In this way, an adaptation of the stiffness of the system comprised of housing part, stud bolt, transmission element, and tool is possible in a simple manner. For example, when using a different tool, the transmission element can be adjusted to the changed situation by exchange of the transmission element for another transmission element with a different modulus of elasticity. Should the transmission element be worn after an extended period of use, an exchange of the worn transmission element for a new transmission element is possible in a simple manner due to the exchangeability.
Advantageously, the transmission element is a sleeve. Expediently, the sleeve comprises substantially the shape of a hollow cylinder. A substantially hollow cylindrical sleeve can also be a slotted sleeve.
Expediently, the first element consists completely of the first material. In this way, a simple manufacture of the first element is possible. Advantageously, the first material is plastic material. In particular, the first material is no elastomer. It can also be provided that the first material is a light metal. In particular, the first material can be aluminum. The first material can also be an aluminum alloy.
Advantageously, the second element consists completely of the second material.
In particular, the spring element of the second element is arranged between the free space of the second element and the stud bolt.
Expediently, a free space width of the free space of the second element that is measured radially in relation to the longitudinal axis of the stud bolt and perpendicularly to a longitudinal center axis of the tool, amounts to at least 10%, in particular at least 20%, of a spring width of the spring element that is measured radially in relation to the longitudinal axis of the stud bolt and perpendicularly to the longitudinal center axis of the tool. In this way, a shape spring can be formed. Despite the large modulus of elasticity of the spring element of larger than 80 GPa, the second element can be designed such that the damping action of the second element is sufficient.
In particular, the housing part is at least partially made of light metal, in particular of aluminum. In this way, the work implement is lightweight and easy to handle. It can also be provided that the housing part is comprised of an aluminum alloy or a magnesium alloy.
In particular, the tool is free of rotational symmetry with regard to the longitudinal axis of the stud bolt. The tool comprises advantageously no rotational symmetry in relation to the longitudinal axis of the stud bolt. In particular, at least one part of the tool is immobile relative to the housing part in operation of the work implement.
Embodiments of the invention will be explained in the following with the aid of the drawings.
As illustrated in
The stud bolt 3 is comprised of steel. In the embodiment, the stud bolt 3 is comprised of hardened steel. The housing part 2 is comprised advantageously at least partially of light metal, in particular of a magnesium alloy. It can also be provided that the housing part is comprised of a plurality of different materials.
In particular, the housing part 2 can form a part of a crankcase of an internal combustion engine of the work implement 1.
The stud bolt 3 is exchangeable. For this purpose, the stud bolt 3 can be unscrewed from the housing part 2, in particular from the side of the contact surface 33.
The guide bar 8 comprises a rearward end 35. The rearward end 35 comprises the opening 5. The rearward end 35 is facing the handle 9. The tool 4 extends along a longitudinal center axis 48. The longitudinal center axis 48 is the longitudinal center axis of the guide bar 8. The longitudinal center axis 48 extends perpendicularly to the longitudinal axis 49 of the stud bolt 3. The guide bar 8 extends in a plane that is perpendicular to the longitudinal axis 49. In the schematic illustration according to
For attaching the guide bar 8 to the housing part 2, the guide bar 8 with its opening 5 is pushed onto the two stud bolts 3. In the embodiments, the two stud bolts 3 are arranged one behind the other along the longitudinal center axis 48. The two stud bolts 3, considered individually, can be embodied identically. This applies to all embodiments. However, it can also be provided that the stud bolts 3 are differently designed.
At the stud bolt 3, a collar 36 for supporting the guide bar 8 is arranged (see
During mounting, the guide bar 8 is slidable in the direction of its longitudinal center axis 48 relative to the housing part 2 when contacting the stud bolts 3. When the guide bar 8 is in the desired position, the stud bolts 3 are guided through holes in a sprocket cover 37 of the work implement 1. The sprocket cover 37 covers the opening 5 of the guide bar 8 at least partially. The guide bar 8 is arranged between the housing part 2 and the sprocket cover 37. By movement of the guide bar 8 relative to the housing part 2, the saw chain 7 can be tensioned. Nuts as fastening means 32 are screwed onto the portion of the stud bolts 3 projecting from the sprocket cover 37. The nuts force the sprocket cover 37 and the guide bar 8 against the housing part 2. In this way, the guide bar 8 is fastened at the housing part 2. In operation of the work implement 1, at least one part of the tool 4 is immobile relative to the housing part 2. The saw chain 7 circulates about the guide bar 8 in operation of the work implement 1. The saw chain 7 is guided by the guide bar 8. In operation of the work implement 1, the guide bar 8 is immobile relative to the housing part 2.
The tool 4 has no rotational symmetry in relation to the longitudinal axis 49 of the stud bolt 3. The largest distance of an outer edge of the tool 4 in relation to the longitudinal axis 49 amounts to a multiple of the smallest distance of an outer edge of the tool 4 in relation to the longitudinal axis 49. In particular, the largest distance of an outer edge of the tool 4 to the longitudinal axis 49 amounts to at least twice the smallest distance of an outer edge of the tool 4 to the longitudinal axis 49.
In operation of the work implement 1, vibrations of the guide bar 8 may occur. Due to the vibrations but also during sawing with the motor chainsaw, forces are transmitted from the guide bar 8 to the stud bolt 3 and from the stud bolt 3 the force are introduced into the housing part 2. In order to keep the load of the housing part 2 as low as possible or even completely prevent load acting thereon, the work implement 1 comprises a transmission element. The transmission element serves for transmission of transverse forces, acting transversely to the axial direction 50, from the tool 4, in particular from the guide bar 8, to the stud bolt 3.
The first element 10 is comprised at least partially of a first material that comprises a modulus of elasticity of 1 GPa to 80 GPa. The second element 20 comprises a spring element 21 and a free space 22 (
However, it can also be provided that the second element 20 is arranged as a separate component between the guide bar 8 and the stud bolt 3. The springy action of the second element 20 can then be realized, for example, in that the second element 20 at least partially is comprised of a wire mesh structure, not illustrated. The wire mesh structure can be comprised of steel, for example. In particular, the wire mesh structure can comprise substantially the form of a hollow cylinder. Between the wires of the wire mesh structure, free spaces are formed. A section of a wire forms the spring element.
It can also be provided that the transmission element comprises a spring element and a free space for the spring travel of the spring element and that the spring element is comprised at least partially of the first material with a module of elasticity of 1 GPa to 80 GPa, in particular of 60 GPa to 80 GPa. It can be provided that the transmission element is comprised partially of the first material with a modulus of elasticity of 1 GPa to 80 GPa, in particular of 60 GPa to 80 GPa, and also acts at least partially in a springy fashion due to its shape upon transmission of transverse forces.
The first element 10 which is illustrated in
The opening 5 comprises a rim 6. In the embodiments according to
In the embodiments according to
The stud bolt 3 comprises an element stop 45 in all embodiments. The element stop 45 serves as a stop for the transmission element in the direction opposite to the axial direction 50. The transmission element contacts the element stop 45. In the embodiments according to
The element stop 45 extends in relation to the axial direction 50 advantageously completely circumferentially around the stud bolt 3. The element stop 45 is formed by a projection 47 of the stud bolt 3. The projection 47 projects past a bolt base body 46 in radial direction in relation to the longitudinal axis 49 of the stud bolt 3. The element stop 45 projects past the bolt base body 46 in radial direction in relation to the longitudinal axis 49 of the stud bolt 3. The projection 47 forms on its side which is facing the housing part 2 a bolt stop 30 for the stud bolt 3 at the housing part 2. In this way, the screw-in depth of the stud bolt 3 into the housing part 2 is limited. The projection 47 serves for contacting the housing part 2. By means of the projection 47, transverse forces from the stud bolt 3 can be transmitted to the housing part 2 in operation of the work implement 1.
The first element 10 according to the embodiment of
The first element 10 comprises two flat surfaces 12. An open-end wrench can engage the two flat surfaces 12, and the first element 10 can be screwed in this way onto the stud bolt 3 or unscrewed from the stud bolt 3.
In the embodiment according to
In the embodiment according to
In the embodiments according to
The transmission element is exchangeably held at the stud bolt 3. This applies to the first element 10 according to the embodiments of
In the embodiments according to
In the embodiments, according to
When the first material of the first element 10 is plastic material, the plastic material advantageously comprises a modulus of elasticity of 1 GPa to 10 GPa. The first material of the first element 10 is no elastomer. The plastic material of which the first material of the first element 10 is comprised is advantageously polyether ether ketone (PEEK). It can also be provided that the first element 10 of the embodiment according to
When the first material of the first element 10 is metal, the first material of the first element 10 comprises a modulus of elasticity of 10 GPa to 80 GPa, in particular of 50 GPa to 80 GPa. The first material of the first element 10 can be in particular light metal. Advantageously, the metal contains aluminum. Preferably, the metal comprises an aluminum alloy. The first element 10 can consist completely of the first material. It can also be provided that the first element 10 of the embodiment according to
The embodiments show a work implement 1 comprising the tool 4, the housing part 2, and the stud bolt 3 screwed into the housing part 2 for attachment of the tool 4 at the housing part 2, wherein the stud bolt 3 projects from the housing part 2 along the axial direction 50, wherein the tool 4 comprises the opening 5, wherein the stud bolt 3 projects at least partially into the opening 5, wherein the work implement 1, for transmission of transverse forces acting transversely to the axial direction 50 from the tool 4 to the stud bolt 3, comprises the transmission element, wherein the transmission element is selected from a group of a transmission element embodied as first element 10 and of a transmission element embodied as second element 20, wherein the first element 10 at least partially is comprised of a first material that comprises a modulus of elasticity of 1 GPa to 80 GPa and wherein the second element 20 comprises a spring element 21 of at least partially a second material with a modulus of elasticity of larger than 80 GPa and further comprises a free space 22 for a spring travel of the spring element 21.
In the embodiments according to
The first element 10 comprises a maximum thickness d measured radially in relation to the longitudinal axis 49 of the stud bolt 3. It can also be provided that the maximum thickness d is measured radially in relation to the longitudinal axis 49 of the stud bolt 3 and perpendicularly to the longitudinal center axis 48. This is the case in the embodiments according to
In the embodiment according to
In the embodiment according to
In
The free space 22 provides a space for a spring travel for the spring element 21. The second element 20 is designed such that, upon transmission of transverse forces, it is acting like a spring due to its shape.
The longitudinal center axis 48 of the tool 4 and the longitudinal axis 49 of the stud bolt 3 define a center plane. A maximal width b of the spring element 21 measured perpendicularly to the center plane is selected such that the spring element 21 acts like a spring.
In the embodiment according to
The maximum width b of the spring element 21 is measured along an imaginary line on the guide bar 8. This imaginary line with the maximum width b of the spring element 21 marks a separation location between the second element 20 and a base body 23 of the guide bar 8. A plane perpendicular to the longitudinal center axis 48 separates the spring element 21 from the base body 23.
The second element 20 is arranged between the base body 23 and the stud bolt 3. In the embodiments according to
The spring element 21 of the second element 20 is arranged between the free space 22 of the second element 20 and the stud bolt 3. The spring element 21 is a tongue. The tongue originates at the base body 23 of the guide bar 8. The tongue extends substantially along the direction of the longitudinal center axis 48 of the guide bar 8. The spring element 21 comprises a longitudinal end 24. At the longitudinal end 24, the spring element 21 has the maximum width b. The spring element 21 is secured with its longitudinal end 24 at the base body 23 of the guide bar 8. The spring element 21 is an integral component of the guide bar 8. The spring element 21 is monolithic with the base body 23.
The spring element 21 of the second element 20 comprises a spring width b1. The spring width b1 is measured radially in relation to the longitudinal axis 49 of the stud bolt 3 and perpendicularly to the longitudinal center axis 48 of the tool 4. The spring width b1 is measured perpendicularly to the center plane at the level of the longitudinal axis 49 of the stud bolt 3.
The free space 22 is arranged between the base body 23 and the spring element 21. The free space 22 is arranged in relation to the radial direction of the longitudinal axis 49 between the base body 23 and the spring element 21. The free space 22 of the second element 20 has a free space width b2. The free space width b2 is measured radially to the longitudinal axis 49 of the stud bolt 3 and perpendicularly to the longitudinal center axis 48 of the tool 4. The free space width b2 is measured perpendicularly to the center plane at the level of the longitudinal axis 49 of the stud bolt 3. The free space width b2 is measured between the spring element 21 and the base body 23. The free space width b2 is measured upon contact of the spring element 21 at the stud bolt 3. The free space width b2 amounts to at least 10%, in particular at least 20%, of the spring width b1. In the embodiment according to
The free space width b2 amounts to at least 10%, in particular at least 20%, of the maximum width b. In the embodiment according to
The second element 20 is comprised at least partially of a second material that comprises a modulus of elasticity of larger than 80 GPa. The spring element 21 is comprised at least partially of a second material that comprises a modulus of elasticity of larger than 80 GPa. It can also be provided that the second element 20, in particular the spring element 21, is comprised at least partially of a material that comprises a modulus of elasticity of larger than 60 GPa. In the embodiment according to
In the embodiments according to
It can also be provided that the second element 20 is embodied as a wire mesh structure which comprises substantially the form of a hollow cylinder.
The specification incorporates by reference the entire disclosure of European priority document 20 183 204.5 having a filing date of Jun. 30, 2020.
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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20 183 204.5 | Jun 2020 | EP | regional |