GB2365380A

GB2365380A - Hand guided electric tool

Info

Publication number: GB2365380A
Application number: GB0116726A
Authority: GB
Inventors: Thomas Schomisch; Albrecht Hofmann; Harald Krondorfer
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2000-07-21
Filing date: 2001-07-09
Publication date: 2002-02-20
Anticipated expiration: 2021-07-09
Also published as: GB2365380B; GB0116726D0; DE10035559A1; JP2002086404A

Abstract

In a hand-guided electric tool (1), more particularly a face milling machine or electric plane, with a base<BR> element (4), with a reference surface (E2) and with a rotatably driven cutter head (11) with at least one<BR> blade (12), whose circular cutting trajectory plane (E1) in relation to the reference surface (E2) defines the cutting depth (t), a structurally very simple and yet robust possibility of adjusting the reference surface (E2) for the cutting depth adjustment is provided in that the reference surface (E2) is formed on a bracket (2), which is to be pivotable in one direction on the base element (4), the bracket (2) being fixable in a selected position relative to the base element (4) by means of a fixing device (8).

Description

2365380 A hand-gwided electric tool State of the art The invention

proceeds from a hand-guided electric tool having the generic features of claim 1.

Electric tools of this type are used for removing surface coatings, in particular paints and varnishes. A face milling tool according to DE 195 43 992 Cl, for example, is used to this end. A device of this type comprises a cutter head, which is provided on its end face and circumferential surface with blades. However, it does not comprise an adjusting device, by means of which the cutting depth can be varied.

However, in order to avoid removing too much material during surface machining with defined cutting, it is necessary to limit the cutting depth by means of at least one reference surface. If a variable cutting depth is to be realised, then the position between the circular cutting trajectory of the milling blade and the reference surface needs to be variable in design. Devices are known, in which this is attained by way of an axial displacement of the cutter head on its drive spindle. This results in an adjustment of the cutting depth in the centre of the cutter head, which can easily result in injury from unintentional contact between the operator's hand and the blades, for example if the adjusting tool slips. Furthermore, the possibility of axial displacement of the cutter head results in an accumulation of functions in a single component. The adjustability and the drive are largely associated with the machine spindle. The complexity of this subassembly renders it sensitive to external loads. Thus, for example, the adjustment of the cutter head can be lost if the machine is put down hard or struck upon the cutter head. In order to obtain maximum evenness of the machined surface, these machines comprise a guide surface, which simultaneously acts as the reference surface for the cutting depth adjustment. This surface is markedly larger than the end face of the cutter head per se.

2 The variation of the cutting depth adjustment is attained, for example, by arranging the guide surface on the base element of the tool via a parallelogram suspension with four swivel joints. A further possibility consists in guiding the reference surface which determines the cutting depth adjustment on an inclined plane on the base element, as is known in the case of the electric hand plane.

Advantages of the invention In contrast, the hand-guided electric tool according to the invention having the characterising features of claim 1 offers the advantage that it represents a structurally very simple but robust possibility of adjusting the reference surface for the cutting depth adjustment.

In this way, the operator can determine the cutting depth in a simple manner.

It is advantageous if the bracket is.connected to the base element via a single swivel joint, since it is then necessary to protect only one axis of rotation against dust and contamination. In addition, there are then no longer several points which are affected by clearance, so that a more precise adjustment of the cutting depth is possible. Furthermore, a swivel joint requires little structural space and simplifies construction, since only a small number of individual parts are required.

Furthermore, it is advantageous if the distance between the swivel joint and the axis of rotation of the cutter head is as large as possible. In this manner, the angle error resulting from the tilting of the reference surface relative to the plane of the circular cutting trajectory is kept to a minimum.

Particularly advantageously, the bracket is L-shaped in construction and the articulation is formed at one end of one of its limbs. This is an embodiment which is particularly simple to manufacture and is at the same time robust.

3 It is also advantageous if the corner point, at which the two limbs of the bracket meet, lies substantially within the plane of the circular cutting trajectory. In this manner, the tilting between the reference surface and the plane of the circular cutting trajectory is kept to a minimum, which results in a reduction in the error in the cutting depth.

A particularly preferred embodiment of the fixing device is a springprestressed screw. An embodiment of this type is characterised on the one hand by structural simplicity and on the other hand by mechanical robustness. The spring prestressing needs to be markedly greater than the pressure exerted by the user, so that the user pressure does not cause the machine to dip.

It is particularly preferred if the free end of the bracket ends in the immediate vicinity of the cutter head. In the case of small cutting depths, which are usually required in the case of a hand-guided electric tool, the angle error is negligibly small on account of the large bearing surface of the reference surface as compared with the cutter head. In this respect, the angle errors appear as a central dip in the track traced by the cutter head. This can be further improved in that the bracket preferably at least partially laterally encloses the cutter head. This results in a further increase in the size of the bearing surface.

Further advantages of the invention form the subject matter of the subclaims.

Drawings An embodiment of the invention will be explained in further detail in the following description with the aid of the associated drawing.

The single figure is a schematic section through a hand-guided electric tool according to the invention.

A hand-guided electric tool 1 rests upon the surface of a workpiece 7 which is to be 4 machined. The electric tool 1 comprises a base element 4, on which two handles 7, 10 are constructed, by means of which the electric tool 1 can be moved over the surface of the workpiece 17 which is to be machined. Arranged on the underside of the base element 4 is a cutter head 11, which is rotatable about a vertical axis of rotation 13. The cutter head 11 is driven by known drive means, in this case by a motor 5 with belt drive 6 shown in broken lines. The drive is not intrinsic to the invention and will therefore not be discussed in further detail. Any other type of drive may also be used.

Blades 12 are arranged on the side of the cutter head 11 remote from the base element 4. These project beyond the surface of the cutter head and thereby define a circular cutting trajectory plane E 1. The cutter head 11 is arranged at one end, in this case the rear end of the base element 4. At the other end of the base element 4, a bracket 2 is mounted via a swivel joint 3 so as to be pivotable in the pivoting direction 14 illustrated by a double arrow. In this manner, the distance a between the swivel joint 3 and the vertical axis of rotation 13 of the cutter head 11 is as large as possible, which results in a minimum angle error. In this respect, the swivel joint 3 is constructed at the free end of a first limb 15 of the bracket 2. The bracket 2 comprises a second limb 16, which is arranged perpendicular to the first limb 15, resulting in an L-shaped bracket in cross section. The free end of the second limb 16 is disposed in the immediate vicinity of the cutter head 11. The corner point 9, at which the first limb 15 meets the second limb 16, is disposed substantially within the circular cutting trajectory plane El. A fixing of the bracket 2 relative to the base element 4 is attained by means of a fixing device 8. In the illustrated example, this is a screw 18, which engages through the second limb 16 of the bracket 2 and can be screwed into a thread 20 in the base element 4. Arranged between the base element 4 and the second limb 16 of the bracket 2 is a spring 19, which encloses the screw 18 and attempts to push the bracket 2 away from the base element 4.

For the machining of the workpiece 17, the electric tool 1 is moved with the cutter head 11 rotating over the surface, the electric tool being moved along the reference surface E2 defined by the second limb 16. The reference surface E2 is tilted relative to the circular cutting trajectory plane El, the tilting angle being dependent upon the angle at which the bracket 2 is fixed to the base element 4. The cutting depth t is defined by the difference between the circular cutting trajectory plane E1 and the reference surface E2 at the free end of the second limb 16 of the bracket 2. During the machining of the workpiece 17, chips having a thickness corresponding to the cutting depth t are removed from the surface of the workpiece. As a result of the tilting between the reference surface E2 and the circular cutting trajectory plane El, an error results, which is equal to the difference between the circular cutti ng trajectory plane E 1 at the end of the cutter head 11 remote from the bracket 2 and at the end of the cutter head 11 facing the bracket 2. However, the error can be almost negligible in the case of the maximum cutting depths t of 0.5 min usually used for hand-guided electric tools 1, or is at least not visible to the eye, so that it is shown exaggerated in the drawing.

As a result of a bracket 2 as described above, a structurally very simple and yet robust possibility of adjusting the cutting depth on the electric tool 1 in a problemfree manner is made available. Many different variations in the design of the bracket 2 are possible. For example, it is possible for the second limb 16 to be plate-shaped in plan view, i.e. when viewed in the direction of the axis of rotation 13. In this manner, a tilting of the electric tool 1 during machining of the workpiece 17 is almost impossible. The wider the plate-shaped second limb, the smaller the danger of the electric tool 1 tilting. In this manner, the danger of unintentional damage to the surface of the workpiece 17 which is to be machined is also reduced.

6 List of reference characters 1 Hand-guided electric tool 2 Bracket 3 Swivel joint 4 Base element Motor 6 Belt drive 7 Handle 8 Fixing device 9 Corner point Handle 11 Cutter head 12 Blade 13 Axis of rotation 14 Pivoting direction First limb 16 Second limb 17 Workpiece 18 Screw 19 Spring Thread E1 Circular cutting trajectory plane E2 Reference surface a Distance: swivel joint - axis of rotation t Cutting depth At Error

Claims

7 Claims

1. A hand-guided electric tool (1), more particularly a face milling machine or electric plane, with a base element (4), with a reference surface (E2) and with a rotatably driven cutter head (11) with at least one blade (12), whose circular cutting trajectory plane (E1) in relation to the reference surface (E2) defines the cutting depth (t), characterised in that the reference surface (E2) is formed on a bracket (2), which is to be pivotable in one direction on the base element (4), the bracket (2) being fixable in a selected position relative to the base element (4) by means of a fixing device (8).

2. An electric tool (1) according to claim 1, characterised in that the bracket (2) is connected to the base element (4) via a single swivel joint (3).

3. An electric tool (1) according to claim 2, characterised in that the distance (a) between the swivel joint (3) and the axis of rotation (13) of the cutter head (11) is as large as possible.

4. An electric tool (1) according to one of the preceding claims, characterised in that the bracket (2) is L-shaped in construction and the articulation is formed at one end of one of its limbs (15, 16).

5. An electric tool (1) according to one of the preceding claims, characterised in that the corner point (9), at which the two limbs of the bracket (2) meet, lies substantially in the circular cutting trajectory plane (E1) defined by the rotating blade (12).

6. An electric tool (1) according to one of the preceding claims, characterised in that the fixing device (8) is a spring-prestressed screw.

7. An electric tool (1) according to one of the preceding claims, characterised in 8 that the free end of the bracket (2) ends in the immediate vicinity of the cutter head (1).

8. An electric tool (1) according to one of the preceding claims, characterised in that the bracket (2) at least partially laterally encloses the cutter head (11).

9. A hand-guided electric tool substantially as herein described with reference to the accompanying drawings.