GB2365818A

GB2365818A - Hand-guided electric tool and cutting head for same

Info

Publication number: GB2365818A
Application number: GB0117290A
Authority: GB
Inventors: Steffen Wuensch; Peter Stierle; Harald Krondorfer; Thomas Schomisch; Siegfried Keusch; Maximilian Ober; Sabine Bocka; Uwe Engelfried; Mario Frank
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2000-07-21
Filing date: 2001-07-16
Publication date: 2002-02-27
Anticipated expiration: 2021-07-16
Also published as: JP5068905B2; GB2365818B; DE10035561A1; JP2002046103A; GB0117290D0

Abstract

In a hand-guided electric tool (6), in particular for face milling, having a cutting head (1) driven rotatably about an axis of rotation (5), having a run-on face (A) formed on the cutting head side and a run-off face (B), the quality of the machined wooden surface is improved and handling of the electric tool is facilitated in that the run-off face (B) is disposed below the axis of rotation (5), uncoupled from rotation of the latter.

Description

2365818 Hand-guided electric too] and cuttinR head forsame The invention

proceeds from a cutting head for a hand-guided electric tool having 5 the generic features of claim I as well as from a hand- guided electric tool having the generic features of claim 6.

Hand-guided electric planes for machining larger surfaces are used to machine flat wooden surfaces, primarily to mechanically remove old layers of paint. Such an 10 electric plane has support faces for positioning both on the unmachined and the machined wooden surface, the so-called run-on and run- off faces. Both support faces are situated in the immediate vicinity of the material removal point and ensure that the electric plane is reliably guidable. Said electric planes are however usable only to a limited extent because of the machining grooves left behind on 15 the surface and the clearly visible steps between the individual plane tracks.

From DE 197 30 087 Al, moreover, a hand-guided electric tool operating on the principle of a face milling tool is known. Said tool comprises a cutting head, which rotates about a vertical axis and on which are disposed blades, which 20 project axially beyond it. Said face milling machine has a height- adjustable runon face, which lies in machining direction upstream of the cutting head. It moreover has a run-off face, which lies in machining direction downstream of the cutting head. This creates the possibility of varying the cutting depth, which is defined by the difference between the planes formed by run-on face and run-off 25 face. Said machine however has the drawback that it easily tilts during operation and so a clean and uniform treatment of the surface is not guaranteed.

Advantages of the invention 30 In contrast, a cutting head according to the invention having the features of claim I as well as a hand-guided electric tool according to the invention having the features of claim 7 have the advantage that they improve the quality of the machined wooden surface and facilitate handling of the tool.

In an electric tool according to the invention two support faces in the immediate 5 vicinity of the material removal point are realized, of which the one is supported on the unmachined workpiece surface and the other on the machined workpiece surface. The run-on and run-off faces thus defined guarantei_ chat a defined chip removal is effected. This leads ultimately to an improved surface quality. The immediate vicinity both of the run-on and the run-off face to the material removal 10 point effectively prevents the electric tool from inadvertently tilting and digging into the surface of the material to be machined. There is an uncoupling of the runoff face from the rotation of the axis of rotation. Thus, even while the cutting head is rotating, the run-off face may be placed onto the surface of the workpiece to be machined without said surface being damaged.

Such an uncoupling is achieved preferentially in that the extension of the support plate is mounted in the cutting head by means of at least one bearing device. This is possible, for example, in a particularly simple and inexpensive manner by means of a ball bearing.

By virtue of the preferred construction of the cutting head with a bladeside recess, in which the support plate is accommodated, the latter may be of a thicker and hence mechanically more stable design.

2S It is particularly advantageous when the opening in the cutting head is pocketshaped and the extension of the support plate is mounted in said opening. It is thereby possible to mount the workspindle, which drives the cutting head, directly in the housing of the electric tool. From a manufacturing viewpoint this is a very simple and, at the same time, stable way of achieving an uncoupling between 30 cutting head and support plate.

Another possible way of achieving said uncoupling is to design the opening as a through-opening, wherein the extension fully penetrates said opening. It is therefore possible for the support plate to be connectable to the housing such as to 5 remain stationary relative to said housing. Thus, the support plate, as it is placed onto the workpiece, need not be braked by a rotational movement, which stems from driving by the cutting head. This helps considerably to prevent damage to the surface of the workpiece. The cutting head is preferentially connected directly via a bearing apparatus to the protective casing. It is particularly advantageous 10 when the support plate is connected to the protective casing so as to be locked against rotation. This is advantageously realized in that a fixing means engages into the fastening apparatus.

It is advantageous when the run-off face on the hand-guided electric tool projects 15 downwards beyond the run-on face, wherein the difference defines the cutting depth. The cutting depth is therefore fixed in a simple manner.

It is further advantageous when the run-on face is fon-ned on a protective casing, which surrounds the cutting head. Thus, support is provided on all sides directly 20 adjacent to the region where chip removal is effected. This increases the tilting stability of the electric tool. The risk of damaging the surface is again reduced when the run-on face is disposed concentrically around the run-off face.

It is advantageous when the run-off face has rounded-off edges. Handling of the 25 electric tool, especially when it is being guided along a curve over the workpiece, is thereby improved.

The run-off face is advantageously of a circular disk-shaped design. As the cutting head is generally of an annular design, the run-off plate fits particularly 30 well into the cutting head.

Further advantageous refinements of the invention are the subject matter of the sub-claims.

5 Drawings In order that the invention may be better understood, there now follows a detailed description of two embodiments thereof with reference to the accompanying drawings, in which

Fig. I shows a diagrammatic partial section through a first embodiment of a hand-guided electric tool according to the invention, Fig. 2 shows a view both of the first and of the second embodiment in direction 11 of Figures I and 3, and 15 Fig. 3 shows a diagrammatic partial section through a second embodiment of a hand-guided electric tool according to the invention.

Figure I shows a hand-guided electric tool 6 for face milling. Said tool comprises a cutting head 1, which rotates about a vertical axis of rotation 5. The cutting 20 head I is connected to a driving spindle 19, which is set in rotation via a belt drive 4. As the drive for the belt drive 4 is of a known design and not essential for the invention, its construction is not described in detail.

Provided on the periphery of the cutting head I is a blade 2 which projects, 25 relative to the axis of rotation 5, axially beyond the cutting head 1. At the side remote from the driving spindle 19 the cutting head I has a recess 14. Inside the recess 14 a pocket-shaped opening 17 is formed concentrically with the axis of rotation 5 in the cutting head 1. In the opening 17 a support plate 3 is mounted by means of a bearing device 16, here a ball bearing, so as to be rotatable about the 30 axis of rotation 5 relative to the cutting head 1. The support plate 3 is T-shaped in section, comprising an extension 12, which projects into the opening 17, and an end part 13, which at its side remote from the cutting head I has a flat run-off face B. The edge 18, which delimits the support plate in radial direction, is roundedoff. The run-off face B lies in the plane defined by the rotating blade 2, i.e. the 5 flight circle plane. The cutting head I is radially surrounded by a protective casing 7. Adjacent to the cutting head I the protective casing 7 is designed in such a way that a flat run-on face A is formed. The run- on face A is aligned substantially parallel to the run-off face B while being set back relative to the runoff face B. The distance between run-on face A and run-off face B defines the 10 cutting depth t. The mounting of the driving spindle 19 in the protective casing 7 is effected with the aid of a bearing apparatus 15, here in the form of two ball bearings, so as to guarantee rotation about the axis of rotation 5 which is as free of friction as possible.

is The electric tool 6 operates as follows. After it has been connected, the cutting head I rotates about the axis of rotation 5 and drives the support plate 3, which is mounted therein, because of the bearing friction in the bearing device 16. The support plate 3 rotates at the same speed as the cutting head I so long as the electric tool 6 is not in engagement with a surface (not shown) which is to be 20 machined. When the electric tool 6 is placed by the run-off face B of the support plate 3 onto the surface to be machined, the support plate 3 is slowed to a standstill by the friction between it and the surface. In tests with different wooden materials and differently coated surfaces it has emerged that, in said case, there is no risk of damage to the workpiece surface. During machining the support plate 3 25 is stationary because the friction force between the workpiece surface and the support plate 3 is greater than the bearing friction in the bearing device 16 between the extension 12 of the support plate 3 and the opening 17 of the cutting head 1.

30 Machining of the surface is effected in that the run-off face B is guided flat along the already treated surface and the run-on face A is supported at least partially on the not yet treated surface. Thus, the cutting depth t is precisely as great as the difference between the planes defined by the run-off face B and the run-on face A. An advantage of the present invention is that by virtue of the central support plate -5 3 being stationary during machining a support and/or rest for the tool 6 is provided in the immediate vicinity of the material removal point. This effectively prevents the machine from inadvertently tilting and digging into the surface of the material to be machined. Good protection from injury is guaranteed for the operator of the electric tool 6 by the protective casing 7, which laterally surrounds 10 the cutting head 1.

Figure 2 shows the spatial arrangement of the run-on face A, the run-off face B and the cutting head I plus blade 2. The end part 13 of the support plate 3, which forms the flat run-off face B, is of a circular disk-shaped construction. The 15 cutting head I is disposed in the shape of a ring around the run-off face B. The cutting head I has a single blade 2, which is disposed substantially radially relative to the axis of rotation 5 in the cutting head. A cutting head I may equally well carry a plurality of blades 2. The latter are then advantageously distributed on the annular cutting head I such that in each case adjacent blades 2 are 2o equidistant from one another. The support plate 3 is embedded in the recess 14, which may be seen as a narrow, annular gap between the cutting head I and the support plate 3. The protective casing 7 of the electric tool 6 radially surrounds the cutting head I and leads to the previously described safety for the operator. In the drawing to the left of the cutting head 1, the protective casing 7 is designed as 25 a flat run-on face A. Said arrangement is however selected only by way of example. For predominantly orbital machining of a surface, on the other hand, it is advantageous to dispose the run-on face A concentrically around the run-off face B. The electric tool 6 is then supported substantially by the central support plate 3) on the machined surface, while the outer, in said case annular run-on face 30 A is only partially supported on the unmachined surface.

The ftirther embodiment illustrated in Figure 3 is described only in so far as there is a difference from the first embodiment illustrated in Figure 1. Parts which are identical or have an identical effect are provided with the same reference 5 characters. The main difference from the first embodiment is that the support plate 3 is firmly connected to the protective casing 7. This is achieved in that the opening 17 in the cutting head 1 is a through- opening and is penetrated by the entire length of the extension 12 of the support plate 3. The cylindrical extension 12, at its opposite end to the end part 13, has a fastening means 10 in the form of 10 an internal thread, which is aligned along the axis of rotation 5. In alignment therewith the protective casing 7 has a hole 11. A fixing means 9 in the form of a screw engages through the hole 11. Said fixing means 9 is screwed into the fastening means 10 of the support plate 3. The extension 12 of the support plate 3 therefore offers a - with regard to the protective housing 7 - fixed abutment, 15 around which the cutting head I is rotatably mounted. The mounting is effected via a bearing device 8 in the form of two ball bearings. The shape of the recess 14 of the cutting head I is designed so as to converge conically inwards. The side of the end part 13 of the support part 3 directed towards the recess 14 is likewise of a conical design. This contributes towards the mechanical stability of the end part 20 13. By virtue of the fact that the support plate 3 with its run-off face B is constantly fixed relative to the protective casing 7, upon placing of the electric tool 6 with a rotating cutting head I onto a surface damage to said surface is ruled out.

25 With said refinement, essentially the same advantages arise as were described with reference to Figure I and the possibilities for further development are also identical to those of the first embodiment. The view from below, i.e. in the direction of the arrow 11, is illustrated by Figure 2. The above statements made in said connection apply.

Claims

1 Cutting head (1) for a hand-guided electric tool, in particular for face 5 milling, which cutting head is rotatable about an axis of rotation (5) and comprises at least one blade (2), which projects axially beyond the cutting head (1), characterized in that along the axis of rotation (5) it has an opening (17), disposed in which is a 10 support plate (3), which comprises an axial extension (12) and a flat end part (13) with a run-off face (B), wherein the run-off face (B) lies substantially level with the flight circle of the blade (2), and which is mounted by its extension (12) rotatably relative to the cutting head (1).

15

2. Cutting head (1) according to claim 1, characterized in that the extension (12) of the support plate (3) is mounted by means of at least one bearing device (8, 16) in the cutting head (1).

3. Cutting head (1) according to claim I or 2, characterized in that on the 20 blade side it has a recess (14), in which the support plate (3) is accommodated.

4. Cutting head (1) according to one of the preceding claims, characterized in that the opening (17) is pocket-shaped and the extension (12) of the 2S support plate (3) is mounted in said opening.

5. Cutting head (2) according to one of claims I to 3, characterized in that the opening (17) is a through-opening which is fully penetrated by the extension (12).

6. Hand-guided electric tool (6), in particular for face milling, having a cutting head (1) driven rotatably about an axis of rotation (5), having a run on face (A) formed on the cutting head side and a run-off face (B), characterized in that 5 The run-off face (B) is disposed below the axis of rotation (5), uncoupled from rotation of the latter.

7. Hand-guided electric tool (6) according to claim 6, characterized in that the cutting head (1) is designed according to one of claims I to 5.

8. Hand-guided electric tool (6) according to claim 6 or 7, characterized in that the run-off face (B) projects downwards down beyond the run-on face (A), wherein the difference defines the cutting depth (t).

is

9. Hand-guided electric tool (6) according to one of claims 6 to 8, characterized in that the run-on face (A) is formed on a protective casing (7), which surrounds the cutting head (1).

10. Hand-guided electric tool (6) according to one of claims 6 to 9, 20 characterized in that the run-on face (A) is disposed concentrically around the run-off face (B).

11. Hand-guided electric tool (6) according to one of claims 6 to 10, characterized in that the run-off face (B) has rounded-off edges (18).

12. Hand-guided electric tool (6) according to one of claims 6 to 11, characterized in that the run-off face (B) is of a circular disk-shaped construction.

30

13. Hand-guided electric tool (6) according to one of claims 6 to 12, characterized in that the cutting head (1) is connected directly by a bearing apparatus (15) to the protective casing (7).

14. Hand-guided electric tool (6) according to one of claims 6 to 12, 5 characterized in that the support plate (3) is connected to the protective casing (7) so as to be locked against rotation.

15. Hand-guided electric tool (6) according to claim 14, characterized in that a fixing means (9) engages into the fastening apparatus (10).

16. A cutting head substantially as described herein with reference to the accompanying drawings.

17. A hand-guided electric tool substantially as described herein with reference 15 to the accompanying drawings.