EP1708851B1 - Electric hand tool - Google Patents

Abstract

The invention relates to an electric hand tool comprising a rotatably driven circular tool (22) and a protective cover (28, 32) mounted on the electric hand tool and rotatable about an axis (24) which is parallel or coaxial to a shaft (34) to a limited or partial extent. In a rest position of the protective cover (28, 32), a tool (22) is completely covered. A restoring device exerts a restoring force on the protective cover (28, 32) in the direction of the rest position and the protective cover (28, 32) comprises a stationary part (28). According to the invention, the protective cover (28, 32) comprises two (32a, 32b) or more movable parts that interact with the stationary part (28) to completely cover the tool (22) in the rest position.

Description

The invention relates to an electric hand tool with a rotatably driven disc-shaped tool having a protective hood which can be paralleled or partially rotated about a shaft parallel to or coaxial to a shaft. The tool can be completely covered in a rest position of the protective cover and a restoring force acts on the protective hood in the direction of the rest position by means of a restoring device, and the protective hood comprises a fixed part, in which the protective hood comprises two or more movable parts which completely cover the tool together with the fixed part in the rest position.

Such a hand tool machine, for example, as a hand-held angle grinder or hand-guided circular saw (see US 2003/0041717 A1 ) be formed.

In a hand-held angle grinder known from practice, a disc-shaped tool representing cutting disc is covered about 180 ° of its circumference by means of a solid protective cover. The protective hood can be rigidly mountable or removable and at least partially covers the region of the cutting-off disk pointing in the direction of the user. The remote from the user area of the cutting disc is free and is used for machining the workpiece.

Basically, when working with electric hand tools, which work with a rotating tool, such as a cutting disc, it can lead to breakage of the tool. These commonly used, laterally open guards have very limited Protect the operator against throw-away parts where there is a high risk to the operator.

Another danger potential lies in the trailing tool after switching off the electric hand tool. The still rotating tool can cause accidents or damage when dropped. To reduce the risk u. a. EU safety recommendations, according to which the protective device must inevitably cover the same when idling the tool, as well as after completion of a work, the protection device should return to its original position and a connection for a suction device should be provided.

In a known from practice hand-held circular saw, as for example in the DE 35 05 040 C2 is shown, the disc-shaped tool is formed from a substantially circular disc-shaped saw blade. The saw blade can be almost completely shielded by means of a protective cover pivotable substantially about the axis of rotation of the saw blade. When immersing the saw blade in a plate-like workpiece to be machined, the protective cover opens either automatically or after triggering a lock. Once the saw blade is removed from the workpiece to be machined, the protective cover closes automatically.

Known devices have the disadvantage that the protective devices for a tool change are usually dismantled, and there are no possibilities for adapting to different shaft dimensions.

A hand tool according to the prior art is for example from the DE 101 10 119 A1 known, which describes an electric hand tool with a rotationally driven disc-shaped tool, comprising a pivotable tool cover. It should be the Tool cover may be designed so that the end face of the tool cover on actuation at least a part of the surface of the disc-shaped tool in a direction transverse to the circumferential direction of the same and has a substantially curved end face. Furthermore, a solid protective cover is provided, which covers the tool circumferentially towards the user. The pivot axis for the tool cover is provided eccentrically to the spindle axis of the tool. The disadvantage here, due to the eccentric arrangement of the articulation of the tool cover, that only a pivoting can be done in one direction, so that the machine is not arbitrarily used, for example, for right and left-handers and certain processing situations can be realized only with difficulty.

Furthermore, from the DE 30 37 573 C2 a two-part protective and suction hood for angle grinder known, comprising a stationary hood part and a pivotally mounted hood part, both hood parts are sector-shaped and the sector angle of the first hood part is smaller than the sector angle of the second hood part, wherein by pivoting the pivotable second hood part an additional Work area for a corner processing is free. The disadvantage here is that no complete coverage of the tool is given in the rest position.

Furthermore, the DE 101 07 290 A1 a protective device for electric hand machines, comprising a rigid and a rotatable part, which covers the danger area almost completely. In addition, a return device is provided which ensures pivoting back of the pivotable part in a rest position. The disadvantage here is the low flexibility.

The German utility model G 90 05 339.7 discloses a rotating tool, in particular a pendulum grinding machine, in which a rotatable protective cover is provided in addition to a rigid protective hood, wherein an actuator for the second protective hood is provided, wherein control of the actuator is necessarily carried out in dependence on the operating conditions. Such a construction is expensive and beyond there is no automatic return of the guard.

From the German utility model G 85 32 524.4 is a full protective hood for a portable machine tool, which fully surrounds the cutting tool, especially for angle grinder, with a rigid hood part and a pendulum hood, hood and pendulum hood together form a closed, essentially only in the area of the tool shaft open space and enclose the cutting tool. It is provided that the pendulum hood is to be mounted so that the pendulum hood pivoted in operation by placing on the workpiece with the direction of rotation of the tool shaft to the rear in the upper hood part and after completion of the operation, the pendulum hood slides back to the front and again forms a full protection, although the cutting tool is still rotating.

From the US 2003/0041717 A1 is a hand-held circular saw known with a rotating circular saw blade, which is covered in a rest position by a protective cover, which consists of a fixed and two moving parts, which together span 180 °.

Finally, the shows US 4,711,055 a protective cover for an electric hand tool device with two movable elements that can be pushed into one another and cover the entire circumference. The disadvantage here is that no fixed element is provided and in particular due to the determination of the movable elements no free rotation of the movable elements is possible.

The invention is based on the object to provide a further hand tool that meets the common guidelines and at the same time allows working in all positions.

The invention solves this problem by an electric hand tool having the features of claim 1.

By such a design with a fixed part and at least two or more movable guard parts, wherein in a rest position the tool is completely enclosed, there is the advantage that only a small pivoting or displacement of the individual shares or segments of the movable guard is necessary. In particular, the displacement can be realized in each case proportionally of two adjoining guard parts, so that no large displacement paths are necessary, and yet a variety of processing positions can be achieved. That not only a guard segment is moved to open the movable guard, but at least the two adjacent to a processing station segments, so that only a small movements of the segments are necessary to release a given tool area. It can be provided that the closing is done by spring force, d. H. that the moving parts are biased by a spring force, that they abut against each other. As a result, improved protection of the user and the environment from damage by touching the rotating tool can be achieved. Even with disc breakage improved coverage is achieved. Finally, the flying sparks to the environment as well as the dust pollution can be reduced. The use of two or more movable guard parts increases the freedom of movement compared to conventional protective hoods. Due to the particularly good accessibility of even difficult processing points, the probability that the user of a corresponding electric hand tool performs a disassembly of the protective mechanism, which has often been done in the past, is reduced.

Finally, due to the particularly good coverage of the tool, even in the case of, for example, an angle grinder, a so-called "counter-rotating cut" can be used, which in the Prior art is not used due to dust and flying sparks. Since then, the opposite cut has only been used on circular saws. By using this cutting direction, however, the application forces can be reduced and the cutting speed can be increased.

A positioning of the guard depending on the application is eliminated, reducing the cost of retooling is reduced. Partially unergonomic postures due to detected or only partially movable protective hoods are avoided, which often lead to inadequate fixations, especially at the end of longer separating cuts.

According to a first embodiment can be provided that the electric hand tool has a protective hood with three or more moving parts, which are telescopically segmented and.ininander pushed. Despite this telescoping ability can be provided that between each of the parts or segments and an adjacent part or segment of the processing area can be arranged. Providing more than two telescoping parts significantly improves safety while providing high flexibility of the work area.

The moving parts of the protective hood can extend into the area of the rigid protective hood, which at least partially covers or can accommodate the moving parts.

In contrast to abutting segments or parts of the movable protective hood, wherein either between any or only certain segments, a portion of the Tool as work area can be freed from the guard, an advantage is achieved for the flexibility of the size of the work area by the telescopically telescoping parts. In the telescopic design according to the invention, the movable protective cover spans 360 °. It can be provided that in a telescopic design of the segments can not be defined between each of the individual parts of a workspace. The parts, between which a working area can be defined, can be freely rotated to the respective desired working position without releasing further areas. In this case, for example, spring-loaded, a load of the parts between which spanned the work area. can be in the resting position against each other. If an opening of the working area is now made, then the individual segments slide into each other, wherein, for example, the innermost segment is the segment that is closest to the defined working area. The segments can be partially covered by the rigid protective hood, which covers the area facing the user, and be guided in this. The entire movable protective hood can be pivoted freely with respect to the fixed protective hood, at least in the region which is not covered by the fixed protective hood.

Due to the strong division in particular the necessary space required for the displacement of the individual parts can be reduced. It can be further reduced by Providence of three or more components that are movable, the displacement and thus ensure the safety of the machine over longer cutting paths, since only a small Opening angle and thus only a small exposure of the tool exists.

Furthermore, it can be provided that the fixed part of the protective hood points in the direction of a housing of the electric hand tool or the user and in particular is arranged symmetrically to the longitudinal axis of the housing.

In particular, the solid part can cover substantially 120 ° of the grinding wheel. In contrast to conventional machines, which sometimes cover up to 180 ° of the grinding wheel, so a larger angular range can be used for machining workpieces. It can be provided that the movable parts of the protective cover each cover substantially 180 ° and at an opening of the protective cover, the movable parts telescopically within the fixed part telescopically, so that regardless of the angular position on the tool, which are used for processing should always, the entire remaining area of the tool is enclosed by the protective hood.

Alternatively, only a coverage of a quarter, so 90 ° or an overlap of 180 ° by the fixed portion be given. In particular, it may be provided that the movable protective hood parts are preferably divided over the free circumference, which is not covered by the fixed protective hood part, into equal parts.

It can be provided that the fixed part is permanently connected to the machine housing. In particular, too the movable part to be permanently connected, so as to prevent disassembly on the part of the user.

According to a particularly preferred embodiment it can be provided that the protective cover is opened automatically by the contact with the workpiece to be machined, wherein the opening takes place only as much as must necessarily be exposed by the tool for machining.

For this purpose, it can be particularly preferably provided that on one or more of the moving parts of the guard in the region of the contact points between the moving parts, which are provided to release a work area, feeding means are provided for a workpiece. As a result, easier opening and easier positioning of the tool of the electric hand tool on the workpiece is achieved. Slipping with the guard on the workpiece can thus be largely avoided.

Alternatively or additionally, it can also be provided that a manual actuation of the protective hood can take place, wherein, for example, an opening device provided for opening the protective hood can be arranged in the region of a holding handle provided on an electric hand tool.

Finally, to further improve the working conditions as well as to reduce the environmental impact, it may be provided that a suction device can be connected to the electric hand tool, wherein the suction device may have a connection possibility, in particular in the region of the fixed part of the protective cover.

By an appropriate arrangement of the suction device, no impairment of the safety devices is caused by the suction device, in particular on

Housing of the electric hand tool, the supply to the suction can be done safely or appropriate dust collection devices can be attached.

Figur 1

einen Winkelschleifer in einer Seitenansicht und

Figur 2

den Winkelschleifer gemäß Figur 1 in einer Ansicht von unten.

Further advantages and features of the invention will become apparent from the remaining application documents. The invention will be explained in more detail below with reference to an embodiment shown in a drawing. Showing:

FIG. 1

an angle grinder in a side view and

FIG. 2

according to the angle grinder FIG. 1 in a view from below.

FIG. 1 shows an angle grinder in a side view, which is provided in its entirety by the reference numeral 10. The angle grinder includes a machine housing 12 having a longitudinal axis 14 along which the machine housing extends. In this case, the machine housing 12 comprises a tool-side end 16 and an opposite end 18 to which a cable 20 is provided for connection to a power supply network. In the machine housing 12, a drive motor is provided, which rotates a tool, in this case a grinding wheel 22, via a shaft. In addition, a deflection gear (not shown) is provided, via which the rotational movement in the direction of the axis 14 in a rotational movement in the direction of an axis 24, which corresponds to the axis of rotation of the tool 22 and passes through the center of the tool, is deflected. The deflection gear is in this case arranged in a gear housing 26, which is connected to the motor housing or machine housing 12. Integral with the engine or. Machine housing 12 is a rigid part of a protective hood 28 connected, which serves to partially cover the tool 22, wherein the fixed portion of the protective cover 28 in the direction of the machine housing and thus directed towards an operator of the electric hand tool at a normal operating position.

The housing 12 may be made of plastic, in particular in the form of a two-shell housing, which is produced by injection molding. In the fixed portion of the protective cover 28 may further integrally connected thereto a nozzle 30 may be arranged to which an external dust extraction device can be connected, whereby the dust can be significantly reduced in particular grinding. As a result, the environmental impact, but also the burden on the operator is reduced with some hazardous to health sanding dust.

The housing 12 itself serves as a first handle, the housing 12 being grasped by the operator with one or both hands, so that the machine can be held and positioned in this way.

In order to comply with the safety guidelines and to ensure a particularly ergonomic work even on difficult to reach positions or over longer processing distances, a movable portion of the guard 32 is further provided, which consists of at least two parts. In this case, the movable part 32 of the protective cover covers the part of the tool 22 directed away from the operator. In the side view shown, the protective cover engages around the tool both on its upper side and on its underside, leaving only an opening for the tool-carrying opening on the underside Shaft 34 which is coaxial with the longitudinal axis 24 of the grinding tool.

In this case, the fixed portion 28 and the movable portions 32 of the protective cover together also substantially a circular shape, wherein the diameter of the Protective hood is larger than the diameter of the tool 22 is designed.

FIG. 2 now shows the angle grinder 10 in a view from below in the direction of arrow II. It can be seen in the bottom view of the division of the guard in fixed 28 and movable components 32. The fixed portion 28 encloses substantially a range of 120 ° of the tool 22, wherein the arrangement of the fixed part 28 extends symmetrically to the longitudinal axis 14 of the housing 12.

In this case, the movable components 32a and 32b respectively enclose essentially 180 ° of the tool, wherein the movable part 321 can be inserted telescopically into the movable part 32a and, moreover, both movable parts are guided telescopically within the rigid part 28.
Moreover, the movable members 32a and 32b are provided with a feeding means 36 constituted by two protrusions on the circumference of the movable parts 32a and 32b in the area of the contact surfaces between the movable parts of the protective hood, the two protrusions having a V-shaped area between include, provided that the protective device is in the rest position and the workpiece to be machined inserted in the direction of arrow 38 between the projections and securely guided by the V-shaped gap and so leads to a spread apart of the movable components 32 a and 32 b of the protective hood, wherein the components are rotated about the longitudinal axis 24.
Both movable components of the protective hood 32a and 32b are biased by a spring, wherein the spring force acts in each case in the direction of the other protective hood component 32a and 32b. In this way, as well as by the arrangement the movable hood components over 180 ° is achieved that only a small proportion of the tool is released, which at any time the widest possible coverage of the tool and thus the greatest possible security of the environment and the operator is achieved.

As an alternative to the feed device, which leads to an automatic opening of the protective hood 32 in contact with a workpiece, a manual opening device 40 can also be provided which can be attached to an additional handle 42, wherein the additional handle 42 on the fixed protective hood 28 is arranged. The additional handle 42, the hand tool can be performed even safer in two-handed operation, even with larger forces acting.

In this way, an angle grinder can be provided, which ensures the greatest possible protection and at the same time enables a particularly ergonomic work in the largest possible angular range over the tool 22.

Claims (11)

1. Hand-held power tool comprising a rotatably drivable disc-shaped tool (22) with a protective hood (28, 32) which can be fastened to the hand-held power tool (10) and which is rotatable, in part and at least to a limited degree, about an axis (24) which is parallel to or coaxial with a shaft (34), the tool (22) being able to be covered completely in a rest position of the protective hood (28, 32) and a resetting force being exerted on the protective hood (28, 32) in the direction of the rest position by a resetting means, the protective hood (28, 32) comprising a fixed component (28), the protective hood (28, 32) comprising two (32a, 32b) or more mobile components, which in the rest position, together with the fixed component (28), completely cover the tool (22), characterised in that the mobile components of the protective hood can be slid into one another in a telescopic, segmented manner and encompass 360° of the tool, and the mobile components, between which the working region is defined, are rotatable in a freely movable manner into the working position desired in each case.
2. Hand-held power tool according to claim 1, characterised in that the protective hood (28, 32) has three or more mobile components.
3. Hand-held power tool according to either claim 1 or claim 2, characterised in that the fixed component (28) is arranged in the direction of a housing (12) of the hand-held power tool (10), and in particular symmetrically to the longitudinal axis (14) thereof.
4. Hand-held power tool according to any one of the preceding claims, characterised in that the fixed component (28) covers substantially 120° of the tool (22).
5. Hand-held power tool according to any one of the preceding claims, characterised in that two mobile components (32a, b) each cover substantially 180° of the tool (22) in the rest position.
6. Hand-held power tool according to any one of the preceding claims, characterised in that the fixed component (32) is undetachably connected to the machine housing (12).
7. Hand-held power tool according to any one of the preceding claims, characterised in that the resetting means is a spring which is pre-tensioned in the direction of the rest position.
8. Hand-held power tool according to any one of the preceding claims, characterised in that the mobile components (32a, b) are movable, and in particular separable from one another, by being brought into contact with an object, in particular a workpiece.
9. Hand-held power tool according to any one of the preceding claims, characterised in that on one or more of the mobile components (32a, b), in the region of the points of contact with further components of the protective hood (28, 32), a supply means (36) for a workpiece is provided.
10. Hand-held power tool according to any one of the preceding claims, characterised in that a manual opening means (40) for opening the protective hood (28, 32) is provided.
11. Hand-held power tool according to claim10 , characterised in that the opening device (40) is provided in the region of a handle (42) which is provided on the hand-held power tool (10).

Images