GB2403171A

GB2403171A - Motor-driven hand grinding tool

Info

Publication number: GB2403171A
Application number: GB0414321A
Authority: GB
Inventors: Joao Jorge Bergner
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2003-06-26
Filing date: 2004-06-25
Publication date: 2004-12-29
Anticipated expiration: 2024-06-25
Also published as: CN1590021A; GB0414321D0; CN1590021B; DE10328967A1; GB2403171B

Abstract

A motor driven hand grinding tool 1, (figure 2, 1', figure 3, 1'') is defined with a simple conversion gear arrangement 21, 31. The grinding tool 1, (figure 2, 1', figure 3, 1'') comprises: a motor 2 with an anchor shaft 20 and grinding plate 4, all of which are mounted in a housing 10, where a drive shaft 30 is associated with the motor 2 and is perpendicularly arranged relative to a grinding surface 41. The conversion gear arrangement 21, 31 is placed between the anchor shaft 20 and the drive shaft 30 where the defection angle a between the anchor 20 and drive shafts 30 is between 40{ and 70{. The grinding tool 1, (figure 2, 1', figure 3, 1'') can have an eccentric cog arrangement (figure 2, 40) and weights provided on the drive shaft 30.

Description

R. 305635 Reference Numeral List 1 Motor-driven hand grinding tool 1'

Eccentric grinder 1" Vibrating grinder 2 Motor 3 Drive plate 4 Grinding plate Work plane Housing Anchor shaft 21 Bevel gear 30 Drive shaft 31 Crown gear 32 Bearing 33 Fixed bearing Eccentric cog 41 Grinding surface 42 Bearing 43 Flexible connection A Drive axis E Eccentric axis M Motor axis Deflection angle 1, - 1 Motor-driven hand grinding tool

Prior art

The invention is based on a motor-driven hand grinding tool with the generic features of claim 1.

Eccentric grinders as well as vibrating grinders are known, comprising motors that are incorporated perpendicularly to the grinding plane. In this connection the height of the eccentric grinder is principally determined by the length of the motor. It follows from this that these electric tools have a height that is dependent on the chosen motor.

The resultant large heights are very inconvenient.

In addition vibrating grinders are known, for example from EP 0 842 011, in which the motor is arranged with its anchor shaft parallel to the grinding plane. Since however the grinding tool has to be driven about a vertically aligned drive axis, a complicated conversion gear arrangement is necessary in order to convert the horizontal rotational movement originating from the motor into a vertical rotational movement. However, although the overall height of the electric tool is reduced, nevertheless it is expensive to produce on account of the complicated conversion gear arrangement.

Advantages of the invention A motor-driven hand grinding tool according to the invention with the features of claim 1 has the advantage, compared to the prior art, that due to the inclined installation of the motor the overall height is less than in the case of a vertical installation of the motor.

Furthermore no complicated conversion gear arrangement is needed to change the drive rotation by 90 , whereby a saving in weight and a favourable location of the centre of gravity are achieved. Due to the incorporation of the motor transverse to the drive shaft of the grinding plate and an arrangement of the motor substantially centrally over the drive shaft (features of claim 2), a very compact design and construction of the hand grinding tool with a favourable location of the centre of gravity is also achieved. The same also applies to a hand grinding tool according to the invention in which the side of the grinding plate remote from the grinding surface is designed as a drive plate (features of claim 3). In addition a saving in weight is also achieved since no additional parts have to be incorporated. Due to a shorter axial distance of the grinding plate from the drive plate (features of claim 4), a very compact design and construction with a favourable location of the centre of gravity are also achieved. All hand grinding tools according to the invention have in addition the advantage that they are very ergonomic.

Due to the fact that the conversion gear arrangement comprises a bevel gear and a crown gear, in which the bevel gear is arranged on the anchor shaft and engages with the crown gear arranged on the drive plate, the said drive plate being connected to the grinding plate, a deflection of the rotation of the anchor shaft onto the grinding plate is achieved in an extremely simple way. Such a design and construction leads not only to a reduction of the height of - 3 the hand grinding tool but also to a saving in cost since no complicated conversion gears are necessary.

Due to the fact that a braking ring is interposed between the housing and the grinding plate, the rotation of the grinding plate in an eccentric grinder can be accurately adjusted.

Due to the fact that the crown gear and/or the anchor shaft drive(s) a fan and/or a device to suck up dust, it is possible in an extremely easy way to drive a fan to cool the motor or drive a suction device to suck up the grinding dust.

Due to the fact that devices for accommodating weights are provided on the crown gear, the weight compensation for the grinding plate can be accomplished in a very simple manner in an eccentric grinder. If the drive plate is made of plastics material, then metal inlay parts may be used as weights.

Further advantageous modifications of the invention are the subject of the subalaims.

Drawings One example of implementation of the invention is described in more detail in the following description and with the aid of the accompanying drawings, in which: - 4 Fig. 1 is a diagrammatic vertical section through a first example of implementation of a motor-driven hand grinding tool according to the invention, Fig. 2 is a diagrammatic vertical section through a second example of implementation of a motordriven hand grinding tool according to the invention, and Fig. 3 is a diagrammatic vertical section through a third example of implementation of a motor-driven hand grinding tool according to the invention.

Fig. 1 shows a motor-driven hand grinding tool 1 that comprises a grinding plate 4 that rotates about a fixed drive axis A. This motor- driven hand grinding tool 1 has a housing 10 in which a motor 2 is arranged. The motor axis M, which is embodied by an anchor shaft 20, has a deflection angle a relative to the drive axis A, which is embodied by the drive shaft 30. Within the scope of the present application the drive shaft 30 is understood to denote not only the conventional use of this term but also a fixed kinematic axis of rotation which, although it does not transmit any drive force, nevertheless has the same action as a conventional drive shaft 30. The drive shaft 30, around which a grinding plate 4 is rotatably arranged, is as in normal grinding tools conventionally aligned perpendicular to the grinding surface 41 of the grinding plate 4. The drive shaft 30 is in the illustrated case connected via a fixed bearing 33 to the housing 10. A bearing 32, for example in the form of a ball bearing race, - 5 is arranged between the drive shaft 30 and the grinding plate 4.

In the present case the grinding plate 4 is designed integrally with a drive plate 3, on the side of which remote from the grinding surface 41 is formed a crown gear 31. This crown gear 31 meshes with a bevel gear 21 that is mounted on the anchor shaft 20 at its end remote from the motor.

A work plane 5 is machined with the grinding surface 41.

Due to the fact that the motor is arranged in the housing 10 along the motor axis M at a deflection angle a relative to the drive axis A, a very small overall height H of the hand grinding tool 1 can be achieved depending on the size of the deflection angle a. It is obvious that the overall height H becomes less the greater the deflection angle a. However, a practical upper limit is imposed on the deflection angle a, which is set by the force transmission by means of the bevel gear 21 to the crown gear 31. If the deflection angle a becomes too large, then a complicated conversion gear arrangement has to be installed instead of this very simple conversion gear arrangement consisting of the crown gear 31 and bevel gear 21, as a result of which the price of the hand grinding tool 1 is increased. In the present case the deflection angle is cat 60 , which means that a very low grinding tool 1 with a very simply realised conversion gear arrangement can be obtained. However, other deflection angles are also possible, which in particular should lie - 6 in the range between 40 and 70 so that the advantages outlined above, namely a simple conversion of the drive rotation as well as a low overall height H can be ensured.

Fig. 2 shows the principle according to the invention for an eccentric grinder 1'. Since the principle and most components are identical or operate in the same way as the hand grinding tool 1 described in Fig. 1, hereinafter reference will be made only to the differences with respect to the first example of implementation described above.

Identical parts or parts having the same effect are provided with the same reference numerals.

Since the grinding plate 4 of an eccentric grinder 1' does not execute a rotational movement - as described in the example of implementation of Fig. 1 - but instead executes an eccentric rotational movement, the drive plate 3 and the grinding plate 4 are no longer designed in one piece. The transfer of the rotational movement from the anchor shaft 20 to the drive shaft 30 functions, as in the example of implementation illustrated in Fig. 1, via the bevel gear 21 and the crown gear 31, which is arranged on the side of the drive plate 3 remote from the grinding plate 4.

In the eccentric grinder 1' the drive shaft 30, which embodies the drive axis A, rotates with the drive plate 3.

To this end it is formed integrally with the drive plate 3 and is rotatably mounted in two bearings 32, for example in ball bearing races, in the housing 10.

At the end of the drive shaft 30 facing the grinding plate 4 the shaft has an eccentric cog 40 that embodies the - 7 eccentric axis E. The eccentric cog 40 is rotatably mounted in the grinding plate 4 via a bearing 42, as is normally the case in eccentric grinders 1, so that this embodiment need not be discussed further here.

During operation of the motor 2 the grinding plate 4 is thus caused to execute eccentric rotational movements. The illustrated eccentric grinder 2' operates exactly in the same way as a known eccentric grinder, though its overall height H. just as in the example of implementation illustrated in Fig. 1, is significantly less than in the case of a parallel arrangement of the motor axis M relative to the drive axis A. Fig. 3 shows a further example of implementation according to the invention, which operates according to the principle of a vibrating grinder 1". This vibrating grinder 1" differs only slightly from the eccentric grinder 1' illustrated in Fig. 2, so that in the following only the differences need be discussed. In addition identical parts or parts having the same effect are identified by the same reference numerals.

In the vibrating grinder 1" too, the grinding plate 4 and the drive plate 3 are arranged separately from one another.

Flexible connections 43 in the form of vibrating feet are arranged between the side of the grinding plate 4 remote from the grinding surface 41, and the housing 10. The movement of the grinding plate 4 characteristic of a vibrating grinder 1" is thereby generated, which is - 8 sufficiently well known and therefore does not need to be discussed further.

Here too a reliable hand grinding tool is obtained, again with a low overall height H and an inexpensive and simple conversion gear arrangement, as has already been illustrated and described in the two examples of implementation in Figs. 1 and 2.

The grinding plate 4 in the three illustrated examples of implementation may be of any conceivable shape. As examples of shapes, only the following need be mentioned here: rectangular, square, round, angular or a combination of the aforementioned shapes.

Common to all the illustrated examples of implementation is the fact that the force transmission from the motor 2 to the grinding plate 4 does not take place in the region of the interior of the grinding plate 4, but at its peripheral end in the region of its outer edge. - 9 -

Claims

Claims 1. Motor-driven hand grinding tool (1, 1', 1") with a housing (10)

in which is arranged a motor (2) with an anchor shaft (20), and with a grinding plate (4) mounted in the housing (10) whose drive shaft (30) is perpendicular to the grinding surface (41) and is driven by the anchor shaft (20), characterized in that a conversion gear arrangement (21, 31) is arranged between the anchor shaft (20) and the drive shaft (30) and the deflection angle (a) between the anchor shaft (20) and the drive shaft (30) is greater than 0 and less than 90 , and is preferably between 40 and 70 .
2. Motor-driven hand grinding tool (1, 1', 1") with a housing (10) in which is arranged a motor (2) with an anchor shaft (20), and with a grinding plate (4) mounted in the housing (10) whose drive shaft (30) is perpendicular to the grinding surface (41) and is driven by the anchor shaft (20), characterized in that the motor (2) is arranged transverse to the drive shaft (30) of the grinding plate (4) and substantially centrally over the drive shaft (30) of the grinding plate (4).
3. Motor-driven hand grinding tool (1, 1', 1") with a housing (10) in which is arranged a motor (2) with an anchor shaft (20), and with a grinding plate (4) mounted in the housing (10) whose drive shaft (30) is perpendicular to the grinding surface (41) and is driven by the anchor shaft (20), characterized in that the side of the grinding plate (4) remote from the grinding surface (41) is designed as a drive plate (3) and is provided in particular with a crown gear (31).
4. Motor-driven hand grinding tool (1, 1', 1") with a housing (10) in which is arranged a motor (2) with an anchor shaft (20), and with a grinding plate (4) mounted in the housing (10) whose drive shaft (30) is perpendicular to the grinding surface (41) and is driven by the anchor shaft (20), characterized in that the grinding plate (4) has a very small axial distance to the drive plate (3).
5. Hand grinding tool (1, 1', 1") according to one of the preceding claims, characterized in that the conversion gear arrangement comprises a bevel gear (21) and a crown gear (31), in which the bevel gear (21) is arranged on the anchor shaft (20) and engages with the crown gear (31) arranged on a drive plate (3), wherein the drive plate (3) is connected to the grinding plate (4).
6. Hand grinding tool (1, 1', 1") according to one of the preceding claims, characterized in that the drive shaft (30) is connected via a fixed bearing (33) to the housing (10) and a bearing (32) is arranged between the grinding plate (4) and the drive shaft (30).
7. Hand grinding tool (1, 1', 1") according to one of claims 1 to 3, characterized in that the drive shaft (30) is rotatably arranged in the housing (10) via a . - 11 bearing (32) and has an eccentric cog (40) that is rotatably connected to the grinding plate (4) via a bearing (42).
8. Hand grinding tool (1, 1', 1") according to one of the preceding claims, characterized in that a brake ring is interposed between the housing (10) and the grinding plate (4).
9. Hand grinding tool (1, 1', 1") according to one of the preceding claims, characterized in that the crown gear (31) and/or the anchor shaft (20) drives a fan and/or a device for sucking up dust.
10. Hand grinding tool (1, 1', 1") according to one of the preceding claims, characterized in that devices for accommodating weights are provided on the drive shaft (3).
11. Hand grinding tool substantially as herein described with reference to the accompanying drawings.