Hand-held chainsaw with a chain catcher

Abstract

The invention relates to a handheld chainsaw comprising a cutting attachment (8), a housing (1) with a lateral contact surface (2), a sprocket cover (3), and a chain catcher (11) with a catching edge (12). The chainsaw extends in the direction of a longitudinal axis (x) defined by the cutting attachment (8). The chain catcher (11) is arranged on the sprocket cover (3). The contact surface (2) forms a contact plane (13), with the chain catcher (11) abutting the contact surface (2) at a free end (14) without a positive locking mechanism acting backward in the direction of the longitudinal axis (x). The catching edge (12) of the chain catcher (11) has a catching ramp (15) extending away from the contact surface (2), at least in the region of its free end (14).

Description

The invention relates to a hand-guided chainsaw having the features according to the preamble of claim 1.According to relevant construction regulations, manually guided chainsaws must be provided with suitable protective measures in the event of a chain tear. In a widely used design, a so-called chain catcher is used for this purpose, which is arranged on the underside of the respective chain saw close to the drive wheel of the chain. A possibly present chain portion of a torn chain, which runs on the underside of the guide rail backwards in the direction of the housing, is caught by the chain catcher. The chain catcher must be designed to be able to absorb the impact energy of such a chain section. When a chainsaw is allowed, a pendulum impact test is performed as a replacement test for the chain tear in order to verify the correct design.Various designs of such a chain catcher are known in the prior art. In one of these designs, the chain catcher is fastened directly to the housing. In a variant thereof, the chain catcher additionally engages in a positively locking manner in a receptacle of the sprocket wheel cover. In another design, the chain catcher is fastened to the sprocket wheel cover, but engages with its free end likewise in a form-fitting manner in a corresponding receptacle of the housing. In the three cases mentioned, the chain catcher is supported in a solid manner per se. However, the impact energy of the impinging chain section or of the impact pendulum is introduced directly into the comparatively rigid housing, which leads to high loads there because of its lack of flexibility.In a further known design form on which the invention is based here, the chain catcher is arranged on the sprocket wheel cover, wherein it rests with a free end on a contact surface of the housing, without however undergoing here a positive position securing acting in the contact plane. As a result, the impact energy acting is introduced primarily into the comparatively flexible sprocket wheel cover, which dampens the impact acting by a corresponding deformation. The housing can thereby be relieved of load.The deformation that occurs as a result of the strike can lead, in the absence of a positive fit with the housing, to a gap being formed between the free end of the chain catcher and the contact surface of the housing, or to an existing gap being enlarged. A suitable design ensures that the chain delivers its energy completely to the catching edge of the chain catcher without penetrating into the gap between the chain catcher and the contact surface.The invention is based on the object of developing a chain saw of the generic type in such a way that the design of its chain catcher is gaining in robustness.This object is achieved by a chain catcher having the features of claim 1.According to the invention, it is provided that the chain catcher adjoins the contact surface with a free end without a form-fit securing device acting backwards in the direction of the longitudinal axis, wherein the catching edge of the chain catcher has a catching slope pointing away from the contact surface at least in the region of its free end. In particular, the catching slope is designed as a concave catching hook. As a result, the chain is securely caught and held in the region of the catching edge of the chain catcher. Greater energies can be introduced and increased deformations of the sprocket cover for absorbing energy can be realized without the chain being able to pass through between the sprocket cover and the housing. While omitting a positively locking connection to the housing at least toward the rear, the robustness of the chain catcher is increased.In an advantageous development, the catching slope is adjoined on its side facing away from the contact surface by a straight catching edge portion which is at least approximately perpendicular to the contact surface. This ensures that no appreciable force components acting perpendicular to the contact surface are produced at this point. Undesirable lateral deformations and deflections are reduced to a minimum.In a preferred embodiment, a guide slope is positioned on the contact surface of the housing, which slope at least partially covers the catching slope of the chain catcher in the direction of a side axis of the chain saw. In an advantageous development, the guide slope starts in front of the catching slope of the chain catcher with respect to the longitudinal axis of the chain saw and reaches as far as behind the catching slope of the chain catcher. The guide slope deflects the chain already early, even before it strikes the chain catcher, to such an extent laterally away from the contact surface that an increased lateral safety distance from the free end of the chain catcher is achieved, and that the action of the catching slope of the chain catcher is supported.The chain catcher can be designed as a separate component, but is formed in particular integrally on the sprocket wheel cover. In a preferred embodiment, the sprocket wheel cover is formed from plastic. While avoiding local stress peaks, high elastic deformations of the sprocket cover with high energy absorption can be realized, which contributes to the relief of the remaining structure, in particular in the region of the housing.In an expedient development, the sprocket wheel cover has, away from the chain catcher, a form-fitting position securing means acting rearwardly at least in the direction of the longitudinal axis. In particular, the positive position securing is formed by a pin of the sprocket wheel cover, which engages in a corresponding receiving opening of the housing. On the one hand, the deformation potential of the sprocket cover is thereby maintained. On the other hand, a positionally accurate connection of the sprocket wheel cover and a reliable introduction of force into the housing are ensured.In an advantageous embodiment, at least one positioning aid is formed on the contact surface of the housing without a positive position securing means for the chain catcher acting backwards in the direction of the longitudinal axis. The positioning aid permits an exact position finding of the sprocket cover during its assembly, but without significantly impairing the elastic deformation and the energy absorption of the sprocket cover in the event of a chain tear.Exemplary embodiments of the invention are described in more detail below with reference to the drawings. The following are shown: FIG. 1 shows a perspective view of a chainsaw according to the invention, having a housing, having a sprocket cover and having a chain catcher which bears loosely against the housing and is provided with a catching slope designed as a catching hook, FIG. 2 is a partially schematic view from below of the chainsaw according to FIG. 1 in the region of its sprocket cover and of the chain catcher formed integrally thereon, FIG. 3 shows an enlarged detail view of a variant of the chainsaw according to FIGS. 1, 2 with a downwardly acting positioning edge for the chain catcher, and FIG. 4 shows an enlarged detail view of a further variant of the chainsaw according to FIGS. 1, 2 with a guide slope formed on the contact surface of the housing and adjoining the chain catcher.FIG. 1 shows a perspective view obliquely from the front below of a hand-guided chainsaw designed according to the invention. The chainsaw comprises a housing 1, a handle housing 4 and a cutting assembly 8. Alternatively, the housing 1 and the handle housing 4 can also be designed to be rigidly connected. A rear handle 6 is formed on the handle housing 4 and a front handle 5 is fastened. In operation, the chainsaw is held and guided by one hand of the user at the rear handle 6 and at the front handle 5. In front of the handle 5 in the direction of the cutting assembly 9 is a hand guard 7.Mounted laterally at the front on the housing 1 is a cutting assembly 8 which comprises a guide rail 9 and a saw chain 10 which can be driven in a revolving manner around the guide rail 9. The saw chain 10 is driven via a sprocket, not shown, by a drive motor, also not shown, in the form of an internal combustion engine. Alternatively, a mains- or battery-operated electric motor can also be provided as a drive motor for the saw chain 10. The aforementioned sprocket and the region of fastening the cutting assembly 8 to the housing 1 with an associated chain tensioning device are covered by a sprocket cover 3 fastened laterally to the housing 1.The guide rail 9 has a flat and generally elongated design with a longitudinal direction. A longitudinal axis x of the chainsaw is predefined by the longitudinal direction of the guide rail 9. A vertical axis z extends perpendicular to the longitudinal axis x and parallel to the plane of the flat guide rail 9, and a lateral axis y also extends perpendicular to the longitudinal axis x.In the present case, the term "front" with reference to the direction of the longitudinal axis x means the region of the chainsaw with the cutting assembly 8, while the term "rear" also with reference to the direction of the longitudinal axis x means the region of the chainsaw with the handle 6. The term "front" reveals the directional and relative information used here, such as "front" and "front" in the sense of "facing forward" or "facing from the handle 6 to the cutting assembly 8". Analogously, the term "rear" reveals the directional and relative indications used here, such as "rear", "rear", "rearward" in the sense of "pointing rearward" or "pointing from the cutting assembly 8 to the handle 6.".The sprocket cover 3 formed from flexible plastic is provided in the region of its lower edge with respect to the vertical axis z with a chain catcher 11 formed integrally. The chain catcher 11 can, however, also be designed as a separate, for example metallic part and be fastened in a suitable manner to the sprocket wheel cover 3. Corresponding to the chain catcher 11, the housing 1 has a contact surface 2 for the chain catcher 11. The contact surface 2 clamps an imaginary contact plane 13, on which is indicated here by dash-dot lines. The contact plane 13 is parallel to the longitudinal axis x and also to the vertical axis z.FIG. 2 shows a partially schematic view from below of the chainsaw according to FIG. 1 in the region of its sprocket cover 3; it can be seen from the overview with FIG. 1 that the chain catcher 11 formed on the sprocket cover 3 adjoins the contact surface 2 with a free end 14 without a positive position securing means acting backwards in the direction of the longitudinal axis (x) and in particular without a positive position securing means acting overall in the contact plane 13. In other words, it only rests loosely on the contact surface 2. A contact resting directly on top does not necessarily have to be present. It may also be sufficient if a narrow gap is present between the free end 14 of the chain catcher 11 and the contact surface 2 of the housing 1.A positive position securing means, in particular backwards in the direction of the longitudinal axis x, is understood here to mean a positive fit which prevents a change in position of the relevant component under the action of the impinging torn chain at least to the rear and instead absorbs the corresponding impact energy. The lack of such a form-locking securing of the position of the chain catcher 11 on the contact surface 2 thus means that the chain catcher 11 on the side of the housing 1 or the contact surface 2 does not receive any direct form-locking support at least to the rear, i.e. under the action of the impinging chain can spring or yield unimpeded at least to the rear and thereby deform the sprocket cover 3. This excludes corresponding energy-absorbing supporting measures acting directly on the chain catcher 11. In particular, it is excluded that the free end 14 of the chain catcher 11 dips into a corresponding receiving opening of the contact surface 2, for example.On the chain catcher 11, a catching edge 12 pointing forward in the direction of the longitudinal axis x toward the cutting assembly 8 (FIG. 1 ) is formed for an impinging chain section of a possibly torn saw chain 10. The catching edge 12 has a catching slope 15 pointing or inclined away from the contact surface 2. In other words, in the drawing plane defined here by the longitudinal axis x and the lateral axis y, an edge normal direction 20 perpendicular to the capture slope 15 and a surface normal direction 21 perpendicular to the contact surface 2 enclose an angle <90°, so that the edge normal direction 20 points away from the contact surface 2 in the direction of the lateral axis y and forwards in the direction of the longitudinal axis z, i.e. away from the rear handle 6 and towards the cutting assembly 8 (FIG. 1 ).The catching slope 15 can pull over the entire length of the catching edge 12 and thereby form the catching edge 12 overall. In the exemplary embodiment shown, it extends only over the region of the free end 14 of the chain catcher, wherein the catching slope 15 is adjoined on its side facing away from the contact surface 2 by a straight catching edge section 16 which is at least approximately perpendicular to the contact surface 2. The catching slope 15 can run in a straight line or in another suitable manner. In the preferred exemplary embodiment shown, it is designed as a concave catch hook with straight and concavely curved edge sections.Furthermore, it can also be seen in FIG. 2 that the sprocket cover 3 has, away from the chain catcher 11 and at a distance therefrom, a positive position securing means 23 acting at least in the direction of the longitudinal axis x rearward or rearward, in particular acting in all directions of the contact plane 13. The positive position securing means 23 is located behind the chain catcher 11 with respect to the longitudinal axis x. In the exemplary embodiment shown, a pin 18 is formed for this purpose on the sprocket wheel cover 3, which pin engages in a corresponding receiving opening 19 of the housing 1, which is only schematically indicated here.FIG. 3 shows an enlarged detail view of a variant of the chainsaw according to FIGS. 1, 2 In this exemplary embodiment, a positioning edge 22 is formed on the lateral contact surface 2 below the free end 14 of the chain catcher 11, the free end loosely bearing against said positioning edge. However, this is not a form-fit position securing means as in the case of the pin 18 and the receiving opening 19 (FIG. 2 ). The positioning edge 22 protrudes only so little beyond the contact surface 2 that the chain catcher 11 can execute a quasi unimpeded deformation movement at least to the rear without significant local introduction of force into the housing 1 during the simulated or actual chain breakage.FIG. 4 shows, in an enlarged detail view, a further variant of the chainsaw according to FIGS. 1, 2, and in this exemplary embodiment, a guide slope 17 is formed on the lateral contact surface 2 below the free end 14 of the chain catcher 11, which slope, starting from its front end with respect to the longitudinal axis x, rises above the contact surface 2 with a height increasing toward the rear and then extends below the chain catcher 11 as far as behind at least its catch slope 15. In the present case, it even extends as far as behind the chain catcher 11 as a whole. In the direction of the lateral axis y, the inclined catch surface 15 of the chain catcher 11 is at least partially covered or protruding beyond by the inclined guide surface 17. This is also not a form-fitting position securing means as defined above. Like the positioning edge 22 (FIG. 3 ), the guide slope also protrudes only so little beyond the contact surface 2 that the chain catcher 11 can execute a quasi unimpeded deformation movement at least toward the rear without significant local introduction of force into the housing 1 during the simulated or actual chain breakage. Alternatively, the guide slope 17 can also be arranged above the chain catcher 11. It is also possible to arrange the guide slope 17 at the same height as the chain catcher 11, wherein the guide slope then preferably ends directly in front of the chain catcher 11.In the remaining features and reference numerals, the exemplary embodiments according to FIGS. 3, 4 correspond to one another and to the exemplary embodiment according to FIGS. 1, 2.

Claims

Hand-guided chain saw comprising a cutting assembly (8), a housing (1) with a lateral contact surface (2), a sprocket cover (3) and a chain catcher (11) with a catching edge (12), wherein the chain saw extends in the direction of a longitudinal axis (x) predetermined by the cutting assembly (8), wherein the chain catcher (11) is arranged on the sprocket cover (3), wherein the contact surface (2) clamps a contact plane (13), and wherein the chain catcher (11) adjoins the contact surface (2) with a free end (14) without a positive locking position acting backwards in the direction of the longitudinal axis (x), characterised in that the catching edge (12) of the chain catcher (11) has a catching slope (15) pointing away from the contact surface (2) at least in the region of its free end (14).Hand-guided chain saw according to claim 1, characterised in that the catching slope (15) is designed as a concave catching hook.Hand-guided chainsaw according to claim 1 or 2, characterised in that the catching slope (15) is adjoined on its side facing away from the contact surface (2) by a straight catching edge portion (16) which is at least approximately perpendicular to the contact surface (2).Hand-guided chainsaw according to one of claims 1 to 3, characterised in that a guide slope (17) is positioned on the contact surface (2) of the housing (1), which guide slope at least partially covers the catching slope (15) of the chain catcher (11) in the direction of a lateral axis (y) of the chainsaw.Hand-guided chainsaw according to claim 4, characterised in that the guide slope (17) starts before the catching slope (15) of the chain catcher (11) with respect to the longitudinal axis (x) of the chainsaw and extends to behind the catching slope (15) of the chain catcher (11).Hand-guided chainsaw according to one of claims 1 to 5, characterised in that the chain catcher (11) is formed integrally on the sprocket cover (3).Hand-guided chainsaw according to one of claims 1 to 6, characterised in that the sprocket cover (3) is formed from plastic.Hand-guided chainsaw according to one of claims 1 to 7, characterised in that the sprocket cover (3) has a positive position securing means (23) acting rearwardly at least in the direction of the longitudinal axis (x) away from the chain catcher (11).Hand-guided chain saw according to claim 8, characterised in that the positive position securing means (23) is formed by a pin (18) of the sprocket wheel cover (3) which engages in a corresponding receiving opening (19) of the housing (1).Hand-guided chainsaw according to one of claims 1 to 9, characterised in that at least one positioning aid (22) is formed on the contact surface (2) of the housing (1) without a positive position securing means for the chain catcher (11) acting backwards in the direction of the longitudinal axis (x).

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