hand-held tool

Abstract

Hand-held work device with a housing (2) that is at least partially made of plastic, wherein a drive motor (6) is arranged in the housing (2) which drives at least one tool of the work device via a drive shaft (8), and wherein the drive shaft (8) is rotatably mounted relative to the housing (2) of the work device by means of at least one first bearing (24) about an axis of rotation (57), wherein the first bearing (24) is supported relative to the housing (2) via an intermediate element (25), wherein the intermediate element (25) is arranged in a receptacle (31) of the housing (2), and wherein the intermediate element (25) is supported on a bearing surface relative to the bottom (44) of the receptacle (31), wherein the total bearing surface is less than 50% of an imaginary annular area (65) between an outer circumference (63) of the first bearing (24) and a circumcircle (64) around the receptacle (31), wherein the circumcircle (64) is a circle.the center point of which lies on a rotation axis (57) of the drive shaft (8) and whose radius corresponds to the distance of the point of the receptacle (31) furthest from the rotation axis (57) to the rotation axis (57), wherein the bearing surface is formed by individual, separate bearing points (54) at which the intermediate element (25) rests on the base (44) of the receptacle (31) against the housing (2), characterized in that the intermediate element (25) has at least one first rib (36) which rests on at least one second rib (48) arranged on the base (44) of the receptacle (31).

Description

[0001] The invention relates to a hand-held work tool such as hedge shears or the like, of the type specified in the preamble of claim 1.

[0002] It is common practice to manufacture the housings of handheld power tools with a drive motor, especially an electric drive motor, from plastic. The drive shaft that powers the tool must be mounted within the tool housing. A problem here is the heat generated during operation, which can lead to damage or destruction of the housing.

[0003] From DE 23 51 204 A1, an electric machine is known in which a thermal insulation zone is provided between the bearing and the housing. The thermal insulation zone can, for example, be designed as a coating of the bearing element with a poorly thermally conductive plastic.

[0004] DE 10 2006 035 387 A1 discloses an electric hand tool with an electric motor whose rotor shaft is mounted in the housing via an elastomer sleeve. The elastomer sleeve has several axially projecting clamping feet that bear axially against the housing.

[0005] CN 101 817 176 A discloses a hedge trimmer whose electric motor has a motor housing with inlet and outlet openings for cooling air. The electric motor drives a fan that draws cooling air for the electric motor through the motor housing.

[0006] The invention is based on the objective of creating a hand-held work tool of the generic type that is simple in design and has a long service life.

[0007] This problem is solved by a hand-held tool having the features of claim 1.

[0008] Instead of a complex coating of the bearing element, the bearing element is arranged on an intermediate element that is positioned in a receptacle of the housing and is supported on a contact surface opposite the base of the receptacle. This contact surface is less than 50% of the area of ​​an imaginary annular circle between the outer circumference of the first bearing and the circumference of the receptacle. The circumference of the receptacle is defined as the circle whose center lies on the axis of rotation of the bearing and whose radius corresponds to the distance from the point of the receptacle furthest from the axis of rotation to the axis of rotation. Because the intermediate element only contacts the base of the receptacle with a maximum of half the area of ​​this annular circle, heat transfer between the bearing and the housing is reduced.The poor heat transfer between the intermediate element and the housing ensures that the heat emitted by the bearing initially spreads evenly within the intermediate element, resulting in a uniform and delayed heat transfer to the housing. This prevents excessive local heating of the housing. A complex bearing coating is therefore unnecessary. The contact surface can be composed of several sub-surfaces, with the specified size of the contact surface referring to the sum of these sub-surfaces.

[0009] The contact area is advantageously less than approximately 40%, particularly less than approximately 30%, and advantageously less than approximately 20% of the annular area between the outer circumference of the first bearing and the circumference around the receptacle. The intermediate element advantageously contacts the housing with only a fraction of the projection area of ​​its circumference as seen in the direction of the axis of rotation. Advantageously, the plastic of the intermediate element has a higher heat resistance than the plastic of the receptacle in which the intermediate element is arranged. The intermediate element is made particularly of polyamide 6.6, while the housing can be made of a more economical, less heat-resistant plastic such as polypropylene. It can be advantageous for the plastic of the intermediate element and / or the plastic of the housing to be glass fiber reinforced. The same plastic can also be used for both the intermediate element and the housing.

[0010] The contact surface is formed by individual, separate contact points where the intermediate element rests against the housing at the bottom of the receptacle. This allows for simple and effective heat transfer from the intermediate element to the housing. The separate contact points, in particular the separate contact areas, provide good mechanical support and high stability with a small contact area.

[0011] A simple design is achieved by the intermediate element having at least one first rib that rests against at least one second rib located on the base of the receptacle. Specifically, the second rib intersects the first rib of the intermediate element, with the intersection point forming a contact point for the intermediate element. The rib structure allows for the simple creation of individual contact points. Simultaneously, the ribs have a significantly larger surface area compared to a solid element, thus considerably improving heat dissipation to the air within the housing.

[0012] This task is also solved by a hand-held tool with the features of claim 5.

[0013] To achieve efficient heat dissipation to the air and prevent all the heat absorbed by the intermediate element from being transferred to the housing, the intermediate element is designed with numerous recesses extending in the direction of the drive shaft's axis of rotation. This increases the surface area and thus improves heat dissipation to the surrounding air. The recesses are designed as openings extending through the intermediate element and through which cooling air flows. This allows for active cooling of the intermediate element by the airflow. The housing advantageously features corresponding openings to permit airflow through the intermediate element.

[0014] This task is also solved by a hand-held tool with the features of claim 6.

[0015] The intermediate element therefore has a grid-like structure formed by intersecting first and third ribs. A single first rib or a single third rib may suffice if multiple third or multiple first ribs are present simultaneously. This grid-like structure easily provides numerous openings for cooling air, a large surface area for efficient heat dissipation, high stability, and a small contact area within the housing.

[0016] Advantageously, the first ribs extend beyond the third ribs in at least one direction. This ensures that only the first ribs, and not the third ribs on the corresponding side, make contact with the housing or bearing. A simple design is achieved if the first ribs extend outwards relative to the axis of rotation of the drive shaft, particularly radially, and if the third ribs are ring-shaped, especially annular. However, a ring shape other than circular, such as an elliptical shape, is also possible. The intermediate element is advantageously designed to be approximately disc-shaped, with the first ribs extending beyond the outer third rib on their outward-facing end faces, extending beyond the inner rib on their inward-facing end faces, and defining a receptacle for the first bearing with their inner end faces.The contact with the first bearing is therefore not full-surface, but only formed by the end faces of the first ribs projecting beyond the inner third rib. It can be advantageous to provide a single third rib, so that the outer third rib is identical to the inner third rib.

[0017] Advantageously, at least one fourth rib is arranged on the bottom of the receptacle, which intersects the third ribs in the direction of the drive shaft's axis of rotation and is spaced apart from the intermediate element. This spacing of the fourth rib from the intermediate element reduces the contact area of ​​the intermediate element on the housing. Advantageously, at least one fifth rib is arranged on the bottom of the receptacle, which intersects the fourth rib and is spaced apart from the intermediate element. This allows ribs extending in both directions to be spaced apart from the intermediate element.

[0018] Advantageously, the drive shaft is supported by a second bearing, which is held in a drive shaft housing. To ensure good cooling of the drive shaft housing and thus also of the bearing, the drive shaft housing is provided with at least one cooling fin on its outer surface. The second bearing is advantageously the bearing located further away from the tool than the first bearing, so that sufficient space is available for guiding the cooling air. Adjacent to the drive shaft housing, at least one first flow guide fin is advantageously arranged, which directs a cooling airflow, conveyed by a fan, past the at least one cooling fin. In particular, at least one second flow guide fin is provided, which directs the cooling airflow over at least a section of the outer surface of the first flow guide fin facing away from the cooling fins.By redirecting the cooling airflow over the second flow guide rib, very good heat dissipation from the drive shaft housing can be achieved.

[0019] An embodiment of the invention is explained below with reference to the drawing. The drawing shows: Fig. 1 a schematic perspective representation of hedge shears, Fig. 2 the hedge shears Fig. 1 with the housing cover removed, Fig. 3 a top view of the hedge trimmer Fig. 2, Fig. 4. a cut along line IV-IV in Fig. 3, Fig. 5 an exploded view of the hedge trimmer Fig. 2, Fig. 6 a perspective view of the housing base of the hedge trimmer with the intermediate element arranged therein, Fig. 7 a perspective representation of the intermediate element, Fig. 8 a perspective view of the recording for the intermediate element, Fig. 9 an enlarged sectional view of the intermediate element and the surrounding area of ​​the housing base, Fig. 10 a top view of the housing base with marked contact points, Fig. 11 a schematic representation of the circular ring area.

[0020] Fig. Figure 1 shows a hedge trimmer as an exemplary embodiment of a hand-held work tool. However, the design provided can also be advantageous for other hand-held work tools, in particular for hand-held work tools with an electric drive motor.

[0021] The hedge trimmer 1 has the in Fig. 1. Housing 2, shown only schematically, on which a rear handle 4 is arranged. On the side of the housing 2 opposite the handle 4, the tool, namely the cutter bars, projects forward, as shown in the illustration. Fig. 1 are surrounded by a guard 5. In the area where the cutter bars connect to the housing 2, a handle 3 is fixed to the housing 2.

[0022] How Fig. As shown in Figure 2, the handle 3 is designed in two parts and has a first handle part 15 and a second handle part 16. The first handle part 15 is pivotally mounted on the second handle part 16 and is spring-loaded relative to it, serving as a safety device. If the two handle parts 15 and 16 are not pressed together by the operator, the drive motor 6 does not run. Fig. As shown in Figure 2, the drive motor 6, located in housing 2, is designed as an electric motor and has a laminated core 14. The drive motor 6 drives a fan wheel 13 located below the laminated core 14. The fan wheel 13 is located on the side of the drive motor 6 facing a gearbox 60. On the side of the drive motor 6 facing away from the cutter bar, a drive shaft housing 9 is located, which is integrated into the gearbox housing 7. A plurality of cooling fins 10 are arranged on the outside of the drive shaft housing 9, which are oriented transversely to the flow direction of the cooling air conveyed by the fan wheel 13. The cooling fins 10 extend approximately radially to the direction shown in Figure 2. Fig. 3 shown axis of rotation 57 of a drive shaft 8. On the upper side of the gearbox housing 7, first flow guide ribs 11 and second flow guide ribs 12 are arranged on both sides of the drive shaft housing 9.

[0023] How Fig. As shown in Figure 3, the two flow guide ribs 11, arranged symmetrically on either side of the drive shaft housing 9, extend in an arc around the drive shaft housing 9, with the first flow guide ribs 11 being spaced apart from the cooling fins 10 on the drive shaft housing 9. A flow guide rib 12 extends along the outer surface 47 of each flow guide rib 11, facing away from the drive shaft housing 9. The flow guide rib 12 connects to the drive shaft housing 9 and directs the cooling airflow along arrow 17 to the outer surface 47 of the flow guide ribs 11. From there, the cooling air flows laterally out of the housing 2 through cooling air slots (not shown).

[0024] The sectional view in Fig. Figure 4 shows the detailed construction of the hedge trimmer 1. The drive motor 6 is designed as an internal rotor motor and has an internal rotor 18 surrounded by a stator 19. The fan wheel 13 is fixedly connected to the rotor 18. The cooling air conveyed by the fan wheel 13 can flow outwards at the outer circumference of the fan wheel 13. Directly adjacent to the drive motor 6, the drive shaft 8 is mounted in the drive shaft housing 9. The drive shaft 8 is supported by a first, lower bearing 24 in a housing base 26 of the housing 2. A second, upper bearing 23 of the drive shaft 8 is located in the drive shaft housing 9 adjacent to the fan wheel 13. The gearbox housing 7 is formed by a housing shell 61, into which the drive shaft housing 9 is integrated. The gearbox housing 7 is closed at the bottom, on the side facing away from the drive motor 6, by the housing base 26. The drive motor 6 has a drive pinion 20, which is part of the rotor 18.The drive pinion 20 drives a gear 21, which is non-rotatably connected to the drive shaft 8. An overload protection device may be provided in this non-rotatable connection, allowing relative rotation in case of overload. Two eccentrics 33 and 34 are fixed to the drive shaft 8 and drive the two cutter bars 28 and 29 of the hedge trimmer 1. The cutter bars 28 and 29 are held on a guide 27. The guide 27 is held on the housing shell 61. At least one fastening screw (not shown in the figure) is provided for this purpose. A cover strip may be arranged on the cutter bars 28 and 29 on the side facing away from the guide 27 and towards the housing base 26. The eccentrics 33 and 34 drive the cutter bars 28 and 29 in opposite directions, reciprocating. It can also be provided that only one of the cutter bars 28, 29 is driven and the other cutter bar is stationary.

[0025] How the exploded view in Fig. As shown in Figure 5, a spring 22 is arranged on the outer circumference of the drive shaft 8, which serves as a clutch. An intermediate wall 35 is inserted into the gearbox housing 7 adjacent to the drive pinion 20. As the Fig. 4 and Fig. As shown in Figure 5, the first, lower bearing 24 is held in an intermediate element 25, which is arranged in a receptacle 31 of the housing base 26. How Fig. Figure 5 shows that the intermediate element 25 is disc-shaped and has a lattice-like structure. A lattice-like structure is also formed by ribs on the bottom of the inset 31.

[0026] How Fig. As shown in Figure 6, the intermediate element 25 has first ribs 36 and ribs 37 extending radially outwards with respect to the axis of rotation 57. These ribs are annular in shape (in the exemplary embodiment, circular in shape) and connect the ribs 36 to each other. The intermediate element 25 also has a receptacle 56 for the bearing 24. To secure its position in the circumferential direction, one of the ribs 36 is extended, thus forming an outwards projecting pin 40 that engages in a recess 56 formed on the circumference of the receptacle 31. Fig. The opening 41 shown in Figure 8 protrudes and thus secures the rotational position of the intermediate element 25.

[0027] Fig. Figure 7 shows the detailed design of the intermediate element 25. Openings 55 extending in the direction of the axis of rotation 57 are formed between the annular ribs 37 and the radially extending ribs 36. The ribs 36 project beyond the annular ribs 37 both at their opposing flat sides 58 and 59 and with their inner end faces 42 and their outer end faces 43. The inner end faces 42 define the recess 56 for the bearing 24. The bearing 24 therefore does not bear against the ribs 36 over its entire circumference, but only in the area of ​​the end faces 42. The outer end faces 43 form a contact surface against the circumferential wall of the recess 31. Here, too, there is no full-surface contact. A collar 38 is formed on the intermediate element 25, which projects into a recess 62 on the base 44 of the recess 31. The flange 38 transitions via a shoulder 39 into the ribs 36 and 37. The shoulder 39 forms an axial contact surface for the bearing 24.

[0028] How Fig. Figure 8 shows that a grid-like structure is also formed on the base 44 of the receptacle 31. This grid-like structure is formed by ribs 45 extending approximately radially to the axis of rotation 57 and by annular ribs 46 and 48. Two inner, annular ribs 46 and one outer, annular rib 48 are provided. The base 44 of the receptacle 31 can have an opening 30 in the center, which is located in Fig. 8 and Fig. 9 is shown with a dashed line and serves for cooling air guidance.

[0029] How Fig. As shown in Figure 9, the annular ribs 46 have a distance d from the intermediate element 25. The radial ribs 45 have a distance c from the intermediate element 25 that is greater than the distance d. The intermediate element 25 rests only on the outer rib 48 and with a multitude of individual prongs 50 projecting downwards from the intermediate element 25 against the grid structure formed at the base 44 of the receptacle 31. The prongs 50 are cylindrical and arranged evenly distributed over the entire area surrounding the collar 38. The prongs 50 rest against the radial ribs 45, thereby forming individual, separate bearing points 54. Corresponding bearing points 54 are formed between the annular rib 48 and the radially extending ribs 36 of the intermediate element 25.

[0030] In Fig. Figure 10 shows the support points 54. The support points 54 together form a bearing surface on which the intermediate element 25 is supported against the base 44. The bearing surface is small in relation to the base 44 of the receptacle 31. The bearing surface is less than approximately 50%, particularly less than approximately 40%, advantageously less than approximately 30%, and particularly less than approximately 20% of an imaginary annular area 65 between the outer circumference 63 of the bearing 24 and a circumcircle 64 around the receptacle 31. In the exemplary embodiment, the support points 54 extend over less than 10% of the annular area. The annular area 63 is in Fig. Figure 11 shows a schematic representation. In this embodiment, the circumcircle 64 coincides with the circumcircle wall 51. The circumcircle 64 is a circle whose center lies on the axis of rotation 57 of the drive shaft 8 and whose radius corresponds to the distance of the point on the circumcircle wall 51 furthest from the axis of rotation 57. The recess 31 thus lies completely within the imaginary circumcircle 64.

[0031] Fig. Figure 9 shows the arrangement of the outer end faces 43 of the ribs 36 on the circumferential wall 51 of the inset 31. How Fig. Figure 8 shows that the circumferential wall 51 is supported outwards by approximately radially extending ribs 53.

[0032] How Fig. As shown in Figure 9, the drive shaft 8 is secured in the axial direction by a nut 52, which is located in the area of ​​the collar 38 of the intermediate element 25.

[0033] How Fig.As shown in Figure 9, the outer diameter a of the intermediate element 25 is significantly larger than the outer diameter b of the bearing 24. This allows the heat generated in the bearing 24 to be dissipated over a large area. The intermediate element 25 is made of a more heat-resistant plastic than the housing base 26 with the receptacle 31. Advantageously, the intermediate element 25 is made of polyamide, in particular polyamide 6.6, and the housing is made of polypropylene. The intermediate element 25 and / or the housing 2 can be reinforced with glass fibers.

Claims

[1] Hand-held work device with a housing (2) which is at least partially made of plastic, wherein a drive motor (6) is arranged in the housing (2) which drives at least one tool of the work device via a drive shaft (8), and wherein the drive shaft (8) is rotatably mounted relative to the housing (2) of the work device by means of at least one first bearing (24) about an axis of rotation (57), wherein the first bearing (24) is supported relative to the housing (2) by means of an intermediate element (25), wherein the intermediate element (25) is arranged in a receptacle (31) of the housing (2) and wherein the intermediate element (25) is supported on a bearing surface relative to the bottom (44) of the receptacle (31), wherein the total bearing surface is less than 50% of an imaginary annular area (65) between an outer circumference (63) of the first bearing (24) and a circumcircle (64) around the receptacle (31), wherein the circumcircle (64) is a circle,the center point of which lies on a rotation axis (57) of the drive shaft (8) and whose radius corresponds to the distance of the point of the receptacle (31) furthest from the rotation axis (57) to the rotation axis (57), wherein the bearing surface is formed by individual, separate bearing points (54) at which the intermediate element (25) rests on the base (44) of the receptacle (31) against the housing (2), , characterized by , that the intermediate element (25) has at least one first rib (36) which rests on at least one second rib (48) arranged on the bottom (44) of the receptacle (31). [2] Working tool according to claim 1, characterized by , that the bearing area is less than 30% of the circular annular area (65) between the outer circumference (63) of the first bearing (24) and the circumcircle (64) around the receptacle (31). [3] Working equipment according to claim 1 or 2, characterized by, that the intermediate element (25) and the receptacle (31) are made of plastic and that the plastic of the intermediate element (25) has a higher heat resistance than the plastic of the receptacle (31). [4] Working tool according to claim 1, characterized by , that the second rib (48) crosses the first rib (36) of the intermediate element (25), the intersection point of the ribs (36, 48) forming a support point (54) of the intermediate element (25). [5] Hand-held work device with a housing (2) which is at least partially made of plastic, wherein a drive motor (6) is arranged in the housing (2) which drives at least one tool of the work device via a drive shaft (8), and wherein the drive shaft (8) is rotatably mounted relative to the housing (2) of the work device by means of at least one first bearing (24) about an axis of rotation (57), wherein the first bearing (24) is supported relative to the housing (2) by means of an intermediate element (25), wherein the intermediate element (25) is arranged in a receptacle (31) of the housing (2) and wherein the intermediate element (25) is supported on a bearing surface relative to the bottom (44) of the receptacle (31), wherein the total bearing surface is less than 50% of an imaginary annular area (65) between an outer circumference (63) of the first bearing (24) and a circumcircle (64) around the receptacle (31), wherein the circumcircle (64) is a circle,the center point of which lies on a rotation axis (57) of the drive shaft (8) and whose radius corresponds to the distance of the point of the mount (31) furthest from the rotation axis (57) to the rotation axis (57), wherein the intermediate element (25) has a plurality of recesses extending in the direction of the rotation axis (57) of the drive shaft (8), , characterized by , that the recesses are designed as openings (55) which extend through the intermediate element (25) and through which cooling air flows. [6] Hand-held work device with a housing (2) which is at least partially made of plastic, wherein a drive motor (6) is arranged in the housing (2) which drives at least one tool of the work device via a drive shaft (8), and wherein the drive shaft (8) is rotatably mounted relative to the housing (2) of the work device by means of at least one first bearing (24) about an axis of rotation (57), wherein the first bearing (24) is supported relative to the housing (2) via an intermediate element (25), wherein the intermediate element (25) is arranged in a receptacle (31) of the housing (2) and wherein the intermediate element (25) is supported on a bearing surface relative to the bottom (44) of the receptacle (31), wherein the total bearing surface is less than 50% of an imaginary annular area (65) between an outer circumference (63) of the first bearing (24) and a circumcircle (64) around the receptacle (31), wherein the circumcircle (64) is a circle,whose center point lies on a rotation axis (57) of the drive shaft (8) and whose radius corresponds to the distance of the point of the mount (31) furthest from the rotation axis (57) to the rotation axis (57), , characterized by , that the intermediate element (25) has a lattice-like structure formed by intersecting first ribs (36) and third ribs (37). [7] Working tool according to claim 6, characterized by , that the first ribs (36) extend beyond the third ribs (37) in at least one direction. [8] Working equipment according to claim 6 or 7, characterized by , that the first ribs (36) extend outwards with respect to the axis of rotation (57) of the drive shaft (8), and that the third ribs (37) are ring-shaped. [9] Working tool according to claim 7 or 8, characterized by, that the intermediate element (25) is disc-shaped, wherein the first ribs (36) project beyond the outer third rib (37) at their outwardly facing end faces (43), wherein the first ribs (36) project beyond the inner third rib (37) at their inwardly facing end faces (42), and wherein the first ribs (36) with their innerly facing end faces (42) define a receptacle (56) for the first bearing (24). [10] Working tool according to any one of claims 6 to 9, characterized by , that at least a fourth rib (45) is arranged on the bottom (44) of the receptacle (31), which crosses the third ribs (37) in the direction of the axis of rotation (57) of the drive shaft (8) and which has a distance (c) to the intermediate element (25). [11] Working tool according to claim 10, characterized by, that at least a fifth rib (46) is arranged on the bottom (44) of the receptacle (31), which crosses the fourth rib (45) and which has a distance (d) to the intermediate element (25). [12] Working device according to any one of claims 1 to 11, characterized by , that the drive shaft (8) is supported by a second bearing (23) which is held in a drive shaft housing (9), the drive shaft housing (9) having at least one cooling fin (10) on its outside. [13] Working tool according to claim 12, characterized by , that adjacent to the drive shaft housing (9) at least one first flow guide rib (11) is arranged, which directs a cooling airflow conveyed by a fan wheel (13) past the at least one cooling rib (10). [14] Working tool according to claim 13, characterized by, that at least a second flow guide rib (12) is provided which directs the cooling airflow over at least a section of the side (47) of the first flow guide rib (11) facing away from the at least one cooling rib (10).

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