Protective device for suction or blowing channel of a working machine and working machine

Abstract

The invention relates to a protection device for an air suction or blowing channel of a working machine and to a working machine. The protection device (10) comprises at least one rib (11) with a longitudinal direction (12). The at least one rib (11) has at least one rib section (13, 14), wherein the rib section (13, 14) extends from a first end (18) to a second end (19) along the longitudinal direction (12) of the rib (11) and has an inherent frequency itself. An interference body (20) is arranged at the rib section (13, 14) between the first end (18) and the second end (19), which interference body (20) is translatable in vibration with the rib section (13, 14). The rib section (13, 14) and the interference body (20) form a vibration system (21) with a system inherent frequency, wherein the system inherent frequency is different from the inherent frequency of the rib section (13, 14).

Description

Technical Field

[0001] This invention relates to a protective device for the inhalation or exhalation channel of a working instrument. Furthermore, this invention relates to a working instrument with a protective device. Background Technology

[0002] Handheld working devices, particularly air blowers or suction shredders, are known for blowing away or sucking up and chopping green plants such as leaves. Such devices include a blower to generate an airflow. The airflow enters the blower through an intake opening in the housing and exits through an exhaust opening. A grille-like protective device is provided at the opening to prevent interference with the opening and accidental contact with movable or hot drive or motor components. The operation of such devices can result in increased noise levels, which are extremely disruptive to the operator. Summary of the Invention

[0003] Therefore, the present invention is based on the objective of further developing a protective device for the inhalation or blowing passage of such a type of working instrument, so that the operation of the working instrument can be achieved with only a low noise level.

[0004] The task is solved by a protective device for the inhalation or exhalation channel of a working instrument, wherein the protective device includes at least one rib in a longitudinal direction, wherein the at least one rib has at least one rib segment, wherein the rib segment extends from a first end to a second end along the longitudinal direction of the rib and has its own natural frequency, wherein an interfering body is arranged at the rib segment between the first end and the second end, which can translate and vibrate with the rib segment, and wherein the rib segment and the interfering body form a vibration system with a system natural frequency, wherein the system natural frequency and the rib segment natural frequency are different.

[0005] The present invention is based on another objective, namely, to further develop such working machines so that their operation can be achieved with a lower noise level.

[0006] The task is solved by a handheld working device with a protective device for an air intake or exhaust channel for the working instrument, wherein the protective device includes at least one rib in a longitudinal direction, wherein the at least one rib has at least one rib segment, wherein the rib segment extends from one end to a second end along the longitudinal direction of the rib and has its own natural frequency, wherein an interfering body is arranged at the rib segment between the first end and the second end, which can translate and vibrate with the rib segment, and wherein the rib segment and the interfering body form a vibration system with a system natural frequency, wherein the system natural frequency and the rib segment natural frequency are different.

[0007] The inventive concept is based on the knowledge that noise emissions generated during the operation of machinery known in the prior art are at least partially caused by a protective grille installed at the machinery. If airflow passes through the grille, the grille is externally excited and begins to vibrate. If the excitation frequency caused by the airflow corresponds to the natural frequency of the excited grille structure, resonance occurs. This resonant vibration generates noise emissions, which are extremely disturbing to the operator.

[0008] The protective device according to the invention for the inhalation or exhalation passage of a working instrument includes at least one rib in a longitudinal direction. The at least one rib has at least one rib segment, wherein the rib segment extends along the longitudinal direction of the rib from a first end to a second end and has its own natural frequency. At the rib segment, between the first and second ends, a disturbance body is arranged that can translate and vibrate with the rib segment. A translationally vibrating disturbance body should be understood as one that can at least translate and vibrate. It is also possible that the translationally vibrating disturbance body can also rotate and vibrate. The rib segment and the disturbance body form a vibration system with the system's natural frequency. The system's natural frequency and the rib segment's natural frequency are different.

[0009] The interfering element causes a shift in the natural frequency. If the natural frequency of the rib section is still within the resonant range, the arrangement of the interfering element on the rib section creates a vibration system whose natural frequency is outside the excitation frequency and therefore outside the resonant range. The vibration of the rib section with the interfering element is reduced, thereby also reducing noise emissions.

[0010] Advantageously, the protective device is configured as a protective grille and includes at least one additional rib, wherein the additional rib and the at least one rib intersect at a connection point. The connection point forms a suspension point for the adjacent rib section, which is translationally fixed. Therefore, the connection point cannot be translated or vibrated. The additional rib is preferably transverse to, and especially orthogonal to, the orientation of the at least one rib. This creates particularly rigid rib sections.

[0011] Preferably, the at least one rib is divided into a first rib segment and a second rib segment via a connection point, and additional ribs are divided into upper rib segments and lower rib segments. Preferably, at least one interfering element is provided at each of the two, preferably three, and especially four rib segments of the protective device. This results in four vibration systems, each with a different natural frequency relative to its corresponding rib segment. The rib segments preferably have different numbers of interfering elements. The connection point is completely immobile. However, the connection point can rotate if possible. Thus, two adjacent rib segments can completely influence each other in their vibrational behavior via the connection point. If the rib segments, conversely, include different numbers of interfering elements, the different vibration systems also differ from each other at their natural frequencies. Thus, adjacent vibration systems act to reduce each other's vibration.

[0012] Preferably, the interfering bodies have masses of different sizes. Thus, the mass of the vibration system can be changed by the number of interfering bodies in the rib section or by the mass of each individual interfering body. Consequently, the natural frequencies of adjacent vibration systems can be manipulated such that the vibrations of the vibration systems at least reduce or cancel each other out.

[0013] Advantageously, the interfering bodies of the two rib segments are arranged asymmetrically about a plane orthogonal to the rib orientation and intersecting at the connection point. Similarly, the position of the interfering body on the corresponding rib segment is important when the natural frequency of the vibration system changes. The rib segments vibrate in different modes depending on the excitation frequency. Here, the fundamental vibration (Grundschwingung, sometimes also called the natural vibration) of the rib segment corresponds to the first resonance (Harmonischen). However, the rib segment can also vibrate at the second resonance, third resonance, etc. The position of the interfering body on the rib segment is significant depending on the vibration mode. If the two rib segments have the same vibration, the natural frequency of the corresponding vibration system has been changed by the different positioning of the interfering bodies on the rib segments. This asymmetrical arrangement of the interfering bodies generates different natural frequencies of the vibration system and avoids the common vibration of the rib segments.

[0014] Preferably, the rib has an upper side and a lower side opposite to the upper side, wherein preferably, the interfering element of one rib segment is arranged on the upper side and the interfering element of the other rib segment of the same rib is arranged on the lower side. By arranging the two interfering elements on different sides of the rib, the center of gravity of the corresponding vibration system changes. Thus, the corresponding vibration system has different vibration characteristics.

[0015] The mass of the interfering body is preferably at least 2%, especially at least 5%, and preferably about 8% of the mass of the rib. The higher the mass of the interfering body, the greater its influence on the natural frequency of the vibration system composed of the interfering body and the rib segment.

[0016] The interfering element is preferably arranged on the rib section such that it is positioned within the rib along a line of sight perpendicular to the upper side of the rib. In an alternative embodiment, it is also suitable to arrange the interfering element on the rib section such that it extends beyond the rib.

[0017] The interfering element extends longitudinally, with its longitudinal ends aerodynamically rounded for an advantage. This reduces obstruction to airflow.

[0018] The rib and the at least one interfering element are advantageously constructed as a single piece. This single-piece construction allows for simple manufacturing of the protective device. The rib and the interfering element are preferably made of the same material, particularly plastic. Preferably, the rib and the interfering element are manufactured by injection molding. Attached Figure Description

[0019] Further features of the invention will be apparent from the accompanying drawings, in which embodiments of the invention are described in detail below. Wherein:

[0020] Figure 1 A perspective view shows a handheld working device according to the invention with a protective grille at the suction opening.

[0021] Figure 2 A handheld working instrument with an intake grille at the intake and exhaust openings is shown in a schematic side view.

[0022] Figure 3 The perspective view shows the data from the rear. Figure 1 Handheld working tools,

[0023] Figure 4 A partial perspective view shows the disassembled state of the device with a protective device at the blow-out opening. Figure 1 Working equipment,

[0024] Figure 5 As shown in the front view, according to Figure 1 Protective device at the blowout opening of the working instrument.

[0025] Figure 6 A schematic cross-sectional view is shown along the... Figure 5 The protective device for arrow VI,

[0026] Figure 7 A schematic cross-sectional view is shown along the alternative embodiment according to Figure 5 The protective device for arrow VI,

[0027] Figure 8 The view below shows the structure with a protective grille at the intake opening. Figure 1 Working equipment,

[0028] Figure 9 The perspective view shows the situation according to Figure 1 The protective grille at the suction opening of the working instrument. Detailed Implementation

[0029] Figure 1 The working device 1 is shown in perspective. In this embodiment, the working device 1 is configured as an inhalation / blowing device. Therefore, the working device 1 can operate not only in an inhalation mode but also in a blowing mode. The inhalation mode and the blowing mode are different operating modes of the working device 1.

[0030] As in Figure 2As illustrated in the schematic diagram, the working apparatus 1 includes a housing 3, which contains a drive motor 4 and a blower 2. The drive motor 4 rotates a blower wheel (not shown in more detail) arranged in the blower 2. In an embodiment, the drive motor 4 is implemented as an electric motor. The electric motor is powered, in particular, by a battery 5. The battery 5 is guided in a battery well open to the outside of the housing, so that the battery 5 can be easily replaced without opening the housing 3. The electric motor can also be powered via electrical wires. Alternatively, the blower 2 can be driven by an internal combustion engine, particularly a two-stroke motor or a hybrid-lubricated four-stroke motor.

[0031] As in Figure 2 As shown, during the operation of the working apparatus 1, the blower 2 draws in air through the intake opening 6 and blows it out through the exhaust opening 7. Here, the airflow 9 passes through the intake opening 6 along a first flow direction 30. The airflow 30 flows from the external surrounding environment 29 of the working apparatus 1 into the internal space 28 of the housing 3 and then to the blower 2. In this embodiment, the blower 2 is configured as a radial blower. The airflow 9 is thus deflected by the blower 2 from the intake opening 6 through the blower helix 40 to the exhaust opening 7. The airflow 9 exits the internal space 28 of the housing 3 through the exhaust opening 7 along a second flow direction 31. The first flow direction 30 and the second flow direction 31 are laterally oriented relative to each other.

[0032] As in Figures 1 to 3 As shown, the working device 1 includes a handle 36. The handle 36 is supported at the housing 3. The handle 36 has a gripping area 38 for gripping the handle 36. The handle 36 is pivotally supported at the working device 1 about a pivot axis 39 and includes working positions for inhalation and exhalation modes respectively. In the case of changing the working device 1 from one working mode to another, the handle 36 is also preferably pivoted 180° about its pivot axis 39 so that the operator can achieve an ergonomic grip and hold in the corresponding working mode of the working device 1.

[0033] As in Figure 1 and 3 As shown, the working device 1 includes a bow-shaped handle 37 in addition to the handle 36. The bow-shaped handle 37 and the blowout opening 7 are arranged on opposite sides of the blower 2. Thus, the reaction force of the airflow 9 escaping from the air pipe 8 can be received very well by the operator using the bow-shaped handle 37. The bow-shaped handle 37 is basically U-shaped. The two ends of the bow-shaped handle 37 are fixed to opposite sides of the working device 1 such that the bow-shaped handle 37 surrounds the blower 2.

[0034] Figures 1 to 3A working device 1 assembled as an air blowing device is shown. An air blowing opening 7 is provided at the assembly connector 32, which is part of the housing 4. In the air blowing mode of the working device 1, an air blowing pipe 8 is arranged at the assembly connector 32. A first protective device 10 is provided inside the assembly connector 32. Figure 4 The first protective device 10 is in Figure 2 The diagram illustrates that the first protective device 10 is configured to intervene in the protective element and prevent the operator of the working instrument 1 from grasping into the internal space 28 of the working instrument 1 through the blowout opening 7 at the assembly pipe 32.

[0035] As in Figures 1 to 3 As shown, in the blowing mode of the working apparatus 1, a second protective device 10' is provided at the suction opening 6. The second protective device 10' is constructed as a grille, thereby preventing larger objects from being sucked into the blower 2. Furthermore, the second protective device 10' also forms an intervention protection element. This is particularly important at the blower 2, such as in... Figure 2 It is important that a chopper 33 for chopping leaves is provided as schematically shown. In the blowing mode of the working device 1, the airflow 9 flows from the external environment 29 through the second protective device 10' and into the blower 2 via the intake opening 6. Immediately afterwards, the airflow flows through the exhaust opening 7 into the blowing pipe 8 and from there into the external environment 29.

[0036] In the suction mode of the working device 1 (not shown in more detail), a capture bag can be arranged on the assembly connector 32 instead of the blowing pipe 8 at the blowing opening 7. Furthermore, a suction pipe is arranged at the suction opening 6. Figure 1 and 2 As shown, the second protective device 10' is pivotally fixed to the housing 3 of the working apparatus 1 via a locking member 34 and a rotating joint 35. To switch the working apparatus 1 from blowing mode to suction mode, the locking member 34 of the second protective device 10' should be opened. Afterward, the second protective device 10' can be tilted up and the suction pipe can be inserted into the suction opening 7. In the suction mode of the working apparatus 1, an airflow 9 flows through the suction pipe and from there through the suction opening 6 to the blower 2. The airflow 9 exits the blower 2 in the flow direction 31 and flows through the blowout opening 7 into the capture bag. Using the airflow 9 generated by the blower 2, objects such as, for example, leaves can be sucked in. As shown in the embodiment, a shredder 33 can be provided at the blower 2, which cuts the objects into smaller pieces so that they can be collected in a compact form in the capture bag.

[0037] exist Figure 4In the diagram, the working instrument 1 is partially shown in a disassembled state. The air blowing pipe 8 is detached from the assembly connector 32. Thus, the blowing opening 7 is visible at the assembly connector 32. The assembly connector 32 is tubularly constructed. In this embodiment, the cross-section of the assembly connector 32 is circular. Figure 5 Alternatively, it may be constructed with other cross-sectional shapes (e.g., elliptical, rectangular, etc.). The assembly nozzle 32 includes an outer surface 42 facing outwards to the surrounding environment 29 and a peripheral wall 41 with an inner surface 43 facing away from the outer surface 42. A first protective device 10 is arranged in the assembly nozzle 32. The first protective device 10 is constructed such that it is impossible for an operator to reach through and grasp the assembly nozzle 32 with their hand.

[0038] As in Figure 4 As shown, the first protective device 10 in this embodiment includes two ribs 11 and 15, namely rib 11 and another rib 15. The two ribs 11 and 15 are respectively fixed at their ends to the inner surface 42 of the peripheral wall 41 of the mounting tube 32. The ribs 11 and 15 are preferably constructed in a straight line coaxial with respect to the line of sight of the mounting tube 32 and form the chord of the circular cross-section of the mounting tube 32. Figure 5 In an alternative embodiment of the first protective device 10, the ribs 11, 15 may also be constructed in an arc shape. In an embodiment, the two ribs 11, 15 respectively have longitudinal directions 12, 12'. Figure 5 One of the ribs 11 has a longitudinal direction 12 that differs from the longitudinal direction 12' of the other rib 15. The two ribs 11 and 15 converge at the connection point 22, whereby their longitudinal directions 12 and 12' intersect. Thus, the two ribs 11 and 15 form a protective grille. Alternatively, the two ribs 11 and 15 may be arranged in the mounting nozzle 32 such that they do not contact each other.

[0039] As in Figure 5 As shown, the longitudinal direction 12' of the additional rib 15 is oriented laterally, particularly orthogonally, to the longitudinal direction 12 of one rib 11. The connection point 22 of the two ribs 11, 15 is preferably located approximately at the midpoint of the cross-section of the assembly tube 32. Obviously, the first protective device 10 can also be formed by a single rib 11. If a rib 11 extends approximately through the midpoint 45 of the cross-section of the assembly tube 32, the operator is similarly prevented from gripping the internal space 28 of the working instrument 1 via the assembly tube 32 by a single rib 11. Furthermore, it is obvious that the first protective device 10 can also be formed by more than two ribs 11, 15.

[0040] As in Figure 5As shown, a rib 11 includes at least one rib segment 13, 14. In a preferred embodiment, a rib 11 includes two rib segments 13, 14, namely a first rib segment 13 and a second rib segment 14. It is also suitable to provide more than two rib segments 13, 14. The rib segments 13, 14 extend along the longitudinal direction 12 of a rib 11 from a first end 18 to a second end 19. In an embodiment, the first end 18 of the first rib segment 13 is located at the peripheral wall 41, and the second end 19 of the first rib segment 13 is located at the junction 22 of the two ribs 11, 15. In an embodiment, the first end 18' of the second rib segment 14 is located at the junction 22 of the two ribs 11, 15, and the second end 19' of the second rib segment 14 is located at the peripheral wall 41. Rib segments 13 and 14 can be excited to their eigenmodes for vibration by external excitation, wherein the ends 18, 18', 19, 19' of rib segments 13 and 14 form the suspension points of the rib segments 13 and 14 that perform vibration. Each rib segment 13 and 14 has its own natural frequency.

[0041] As in Figure 5 As shown, a translationally vibrating disturbance body 20 is arranged on at least one rib section 13, 14 of the first protective device 10. The translationally vibrating disturbance body 20 should be understood as a disturbance body capable of at least translational vibration. It is also possible that the translationally vibrating disturbance body can also rotate. Conversely, the connection point 22 of the two ribs 11, 15 does not form a disturbance body 20 because the ribs 11, 15 are so reinforced that translational vibration of the connection point 22 is impossible in the sense of this application. Rotational vibration of the connection point 22 is possible, on the contrary. The disturbance body 20 and at least one rib section 13, 14 form a vibration system 21 with a system natural frequency, wherein the system natural frequency and the natural frequency of the rib section 13, 14 are different. The first protective device 10 is arranged in the assembly nozzle 32, whereby an airflow 9 passes through the first protective device 10 at a high flow velocity. The airflow 9 forms an external excitation for the vibrating rib sections 13, 14. The vibration system 21 formed by the interfering element 20 has a natural frequency that differs from the excitation frequency of the external excitation. This avoids resonance at the rib sections 13 and 14, which would otherwise result in high noise levels. Therefore, the interfering element 20 causes a frequency shift.

[0042] As in Figure 5As shown, the additional rib 15 is similarly divided into two rib segments 16 and 17 via connection point 22, namely upper rib segment 16 and lower rib segment 17. Thus, in this embodiment, four rib segments 13, 14, 16, 17 are provided, with at least one interfering element 20 arranged at each rib segment 13, 14, 16, 17. In alternative embodiments, it may be suitable to provide interfering elements 20 at only one, preferably only two, and especially only three rib segments 13, 14, 16, 17.

[0043] As in Figure 5 As shown in the illustration, in this embodiment, only one interfering element 20 is provided at the first rib section 13 of a rib 11, and only two interfering elements 20 are provided at the second rib section 14 of a rib 11. Thus, the mass of the vibration system 21 composed of the first rib section 13 and the interfering element 20 is different from that of the vibration system 21' composed of the second rib section 14 and the two interfering elements 20. Although the connection point 22 is translationally fixed, it forms the connection point of the two vibration systems 21, 21', which transmits translational vibrations. Through the different masses of the two vibration systems 21, 21', they act to reduce each other's vibration.

[0044] As in Figure 5 As shown, only one interfering element 20 is arranged at the lower rib section 17 of another rib 15. Conversely, only two interfering elements 20 are arranged at the upper rib section 16 of another rib 15, thus the two vibration systems 21'', 21''' have different masses. Therefore, similar to the above embodiment, the effect of reducing vibration occurs. In the preferred embodiment, the rib sections 13, 14, 16, 17 of each rib 11, 15 have different numbers of interfering elements 20. Therefore, the vibration systems 21, 21', 21'', 21''' of ribs 11, 15 have different masses.

[0045] Alternatively, the disturbance bodies 20 of ribs 11 and 15 can be configured to have different masses. Thus, the vibration systems 21, 21', 21'', 21''' of ribs 11 and 15 can also be constructed with the same number of disturbance bodies 20 having different masses. Clearly, not only the number of disturbance bodies 20 on the corresponding rib segments 13, 14, 16, 17 of ribs 11 and 15, but also the mass of each disturbance body 20 on the rib segments 13, 14, 16, 17 of ribs 11 and 15 is different.

[0046] As in Figure 5As shown, the interfering element 20 is constructed as a bulge on the rib segments 13, 14, 16, 17. Ribs 11, 15 themselves have a preferably constant rib cross-section along their longitudinal direction 12. Thus, the interfering element 20 should preferably be understood as a bulge that extends beyond the constant rib cross-section. The interfering element 20 is preferably constructed as a slightly elongated, particularly rod-shaped bulge on the rib segments 13, 14, 16, 17.

[0047] As in Figure 6 As shown, the interfering element 20 extends longitudinally from its first longitudinal end 25 to its second longitudinal end 26 along the longitudinal direction 27. The interfering element 20 is preferably arranged on the rib sections 13, 14, 16, 17 such that the longitudinal direction 27 of the interfering element 20 is approximately parallel to the flow direction of the airflow 9. This results in less flow obstruction from the interfering element 20. To further reduce flow obstruction, the longitudinal ends 25, 26 of the interfering element 20 are aerodynamically, particularly, teardrop-shaped, rounded.

[0048] To modify the mass of the interfering element 20, it can be constructed geometrically differently. Advantageously, the interfering element 20 may have different lengths and different widths extending along its longitudinal direction 27. It can also be configured such that the interfering element 20 is made of different materials and thus has different masses. In a preferred embodiment, the interfering element 20 is constructed of the same material as the ribs 11, 15, particularly plastic, so that the protective device 10 can be manufactured in the same manner. The protective device 10 is preferably constructed as an injection molded part. The interfering element 20 and the ribs 11 are preferably constructed as a single piece. Preferably, the protective device 10 is constructed as a single piece. The mass of the interfering element 20 corresponds to at least 2%, particularly at least 5%, and preferably about 8% of the mass of the ribs 11, 15. Preferably, the arrangement of the interfering element 20 on the rib segments 13, 14, 16, 17 of the ribs 11, 15 causes a natural frequency shift of at least 2%, preferably at least 5%, and advantageously about 10% with respect to the first and second resonances of the corresponding rib segments 13, 14, 16, 17.

[0049] Essentially, the number and location of the interfering bodies 20 on each of the rib sections 13, 14, 16, 17 are chosen such that the natural frequencies of the vibration systems 21, 21', 21'', 21''' are modified so that they do not resonate with the excitation frequency of the airflow 9. It has proven advantageous that the vibration systems 21, 21', 21'', 21''' of adjacent rib sections 13, 14, 16, 17 have preferably different masses and / or different relative centers of mass. This prevents common vibrations via the connection point 22.

[0050] As in Figure 5As shown, the two ribs 11, 15 each have upper sides 23, 23' and lower sides 24, 24' opposite to the upper sides 23, 23'. In an embodiment, at least one interfering element 20 is arranged on the upper sides 23, 23' of the two ribs 11, 15 and at least one interfering element 20 is arranged on the lower sides 24, 24' of the two ribs 11, 15. At a first rib section 13 of a rib 11, the interfering element 20 is arranged on the upper side 23 of the rib 11. At a second rib section 14 of a rib 11, the interfering element 20 is arranged on the lower side 24 of the rib 11, and preferably an additional interfering element 20 is also arranged on the upper side 23 of the rib 11. Furthermore, at a lower rib section 16 of another rib 15, the interfering element 20 is arranged on the upper side 23' of the other rib 15. At the upper rib segment 17, the interfering element 20 is arranged on the lower side 24' of another rib 15, and preferably additionally on the upper side 24' of another rib 15. Therefore, in the embodiment, the number of interfering elements 20 is preferably different for adjacent rib segments 13, 14, 16, 17 of ribs 11, 15. Furthermore, it is advantageous that the interfering elements 20 of two adjacent rib segments 13, 14, 16, 17 are also arranged on different sides 23, 23', 24, 24' of ribs 11, 15.

[0051] As in Figure 5 and 6 As shown, the interfering elements 20 of adjacent rib segments 13, 14, 16, 17 of ribs 11, 15 are arranged asymmetrically with respect to a plane 46 orthogonal to the respective rib 11, 15 and intersecting at connection point 22. Plane 46 extends parallel to the longitudinal direction 27 of the interfering elements 20. In other words, the spacings a, a', b, b' of two interfering elements 20 arranged on adjacent rib segments 13, 14, 16, 17, measured along the longitudinal direction 12 of the respective rib 11, 15, are different.

[0052] As in Figure 6 As shown, in a preferred embodiment, the interfering element 20 is arranged on the rib segments 13, 14, 16, 17 such that, along a line of sight perpendicular to the upper side 23, 23' of the ribs 11, 15, the interfering element 20 is positioned within the ribs 11, 15. Therefore, the interfering element 20 does not extend beyond the ribs 11, 15. In an alternative embodiment, it is also suitable that the interfering element 20 is constructed on the ribs 11, 15 such that the interfering element 20 extends beyond the ribs 11, 15.

[0053] As in Figure 7As shown, the interfering element 20 may also be positioned differently depending on its longitudinal direction 27. Ribs 11, 15 have flow edges 47 facing the airflow 9. In a preferred embodiment, the flow edges 47 extend parallel to the longitudinal direction 12 of the ribs 11, 15. The interfering elements 20 have spacings c, c' relative to the flow edges 47. The spacings c, c' of two interfering elements 20 arranged on adjacent rib segments 13, 14, 16, 17 of ribs 11, 15 are different in a preferred embodiment.

[0054] exist Figure 8 The working apparatus 1 is shown in the view below. In this view, a second protective device 10' can be identified. The second protective device 10' is constructed as a suction grille and has a significantly finer mesh than the first protective device 10. Even in the case of the fine-mesh protective device 10', increased noise emissions can occur due to resonant vibrations. (As in...) Figure 9 As schematically shown, the rib sections may also be provided with interfering elements 20. Regarding the number and positioning of the interfering elements 20 on the rib sections, given the applicable principles of the first protective device 10, these principles can also be applied to the second protective device 10'. In principle, at each protective device of the working instrument 1, and especially at each protective grille, a corresponding interfering element 20 is provided, given that airflow can cause external excitation and excite vibration of the individual ribs or rib sections. This is particularly applicable to cooling air grilles used for cooling airflow directed at the drive motor 4.

Claims

1. A protective device (10, 10') for the inhalation or blowing passage of a working instrument, in, The protective device (10, 10') includes at least one rib (11) with a longitudinal direction (12), wherein the at least one rib (11) has at least one rib segment (13, 14), wherein the rib segment (13, 14) extends from a first end (18) to a second end (19) along the longitudinal direction (12) of the rib (11) and has its own inherent frequency. The feature is that an interfering body (20) that can translate and vibrate with the rib section (13, 14) between the first end (18) and the second end (19) is arranged therein. Furthermore, the rib sections (13, 14) and the interfering body (20) form a vibration system (21) with the system's natural frequency, wherein the system's natural frequency is different from the natural frequency of the rib sections (13, 14).

2. The protection device according to claim 1, characterized in that, The protective device (10, 10') is constructed as a protective grille and includes at least one additional rib (15), wherein the additional rib (15) and the at least one rib (11) intersect at a connection point (22).

3. The protection device according to claim 2, characterized in that, The additional rib (15) is oriented transversely to the at least one rib (11).

4. The protection device according to claim 2, characterized in that, The at least one rib (11) is divided into a first rib segment (13) and a second rib segment (14) through the connection point (22), and the other rib (15) is divided into an upper rib segment (16) and a lower rib segment (17).

5. The protection device according to claim 2, characterized in that, At least one interfering element (20) is provided at each of the two rib sections (13, 14, 16, 17) of the protective device.

6. The protection device according to claim 2, characterized in that, The rib segments (13, 14, 16, 17) of ribs (11, 15) have many different interfering bodies (20).

7. The protection device according to claim 5, characterized in that, The interfering body (20) has a mass of different sizes.

8. The protection device according to claim 5, characterized in that, The interfering bodies (20) of the two rib segments (13, 14, 16, 17) of the rib (11, 15) are arranged asymmetrically with respect to a plane orthogonal to the orientation of the rib (11, 15) and intersecting the connection point (22).

9. The protection device according to claim 5, characterized in that, The rib (11) has an upper side (23) and a lower side (24) opposite to the upper side (23), wherein the interfering body (20) of one rib segment (13,14,16,17) of the rib (11,15) is arranged on the upper side (23) and the interfering body (20) of the other rib segment (13,14,16,17) of the same rib (11,15) is arranged on the lower side (24).

10. The protection device according to claim 1, characterized in that, The mass of the interfering body (20) corresponds to at least 2% of the mass of the ribs (11, 15).

11. The protection device according to claim 9, characterized in that, The interfering element (20) is arranged on the rib sections (13,14,16,17) such that the interfering element (20) is arranged within the ribs (11,15) along a line of sight perpendicular to the upper side (23) of the ribs (11,15).

12. The protection device according to claim 1, characterized in that, The interfering body (20) extends in the longitudinal direction, wherein the longitudinal ends (25, 26) of the interfering body (20) are aerodynamically rounded.

13. The protection device according to claim 1, characterized in that, The ribs (11, 15) and the at least one interfering body (20) are constructed as a single piece.

14. The protection device according to claim 1, characterized in that, The ribs (11, 15) and the interfering body (20) are made of the same material.

15. The protection device according to claim 3, characterized in that, The additional rib (15) is orthogonal to the orientation of the at least one rib (11).

16. The protection device according to claim 5, characterized in that, At least one interfering element (20) is provided at each of the three rib sections (13, 14, 16, 17) of the protection device.

17. The protection device according to claim 16, characterized in that, At least one interfering element (20) is provided at each of the four rib sections (13, 14, 16, 17) of the protection device.

18. The protection device according to claim 10, characterized in that, The mass of the interfering body (20) corresponds to at least 5% of the mass of the ribs (11, 15).

19. The protection device according to claim 18, characterized in that, The mass of the interfering body (20) corresponds to 8% of the mass of the ribs (11, 15).

20. The protection device according to claim 14, characterized in that, The ribs (11, 15) and the interfering body (20) are made of plastic.

21. A handheld working tool having the protective device (10, 10') according to claim 1.

Images