GB2420518A

GB2420518A - Eccentric device

Info

Publication number: GB2420518A
Application number: GB0523260A
Authority: GB
Inventors: Gyoeri Szabolcs
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2004-11-17
Filing date: 2005-11-15
Publication date: 2006-05-31
Also published as: DE102004055271A1; GB0523260D0; CN1776257A

Abstract

An eccentric device for a hand tool machine (figure 1, 12) that converts the rotary motion 10 of a motor (figure 1, 52) to oscillatory motion 14 of a hand tool component (figure 1, 16) is described. The eccentric device is characterised in that setting means (figure 1, 18) is provided for setting the eccentricity (figure 3, 20) of the oscillatory motion 14. The hand tool may be a sanding machine (figure 1, 12) and the hand tool component may be a sanding plate (figure 1, 16). The eccentric unit 24 may be provided with an integral fan impeller 42. The eccentric units 22, 24 can twist relative to one another when the direction of rotation of the motor (figure 1, 52) varies, therefore altering the eccentricity of the component (figure 1, 16).

Description

Eccentric device

Background art

The invention proceeds from an eccentric device according to the preamble of claim 1.

It has already been proposed to equip a hand tool machine with an eccentric device that is suitable for converting a rotary motion of a motor of a hand tool machine to an oscillatory motion of a tool component. Sanding machines in particular often comprise such an eccentric device, which converts the rotary motion of the motor of a sanding plate of a sanding machine.

Advantages of the invention The invention proceeds from an eccentric device, which is provided for converting a rotary motion of a motor of a hand tool machine to an oscillatory motion of a tool component, in particular to an oscillatory motion of a sanding plate of a sanding machine.

It is proposed that a setting means is provided for setting the eccentricity of the oscillatory motion. The effect achievable thereby is that the eccentricity is advantageously adaptable to specific conditions of an actual operative range of the hand tool machine and/or of a material to be machined. Particularly in the case of a sanding machine with an exchangeable abrasive covering, an adaptation of the eccentricity to a specific choice of abrasive covering may be enabled.

By "provided" in this connection, "designed" and "equipped" are also to be understood. As oscillatory motion in this connection a generally periodic or quasi-periodic motion is also to be described, in particular however an eccentrically orbital motion on an elliptical path.

Besides such developments of the invention, in which a manual adaptation of the eccentricity occurs, developments of the invention are conceivable, in which the hand tool machine uses the setting means for automatic adaptation of the eccentricity, for example, in dependence upon a sensor signal.

A particularly rugged eccentric device is achievable when the eccentric device comprises at least one eccentric unit having at least two eccentric bearing points. The eccentric bearing points are in said case particularly advantageously characterized by parallel-running axes of rotation.

When the setting means is provided for setting a relative phase between two eccentric units supported rotatably about a bearing point, an eccentric device that is advantageously adjustable continuously and/or within a wide range may be achievable, which is simultaneously rugged and economical to manufacture.

Inadmissible and/or dangerous settings of the eccentric device may be avoided in a constructionally simple manner when the eccentric device has at least one stop element for limiting a setting range of the phase.

When the setting means is provided for varying a direction of rotation of the motor, a reliable changeover between at least two basic configurations of the eccentric device may be achieved.

In said case, a particularly comfortable change of configuration is achievable when the eccentricity varies automatically upon a variation of the direction of rotation, namely in particular because of a motor force and an inertia of at least one of the eccentric units.

Overheating of a bearing of the eccentric unit may be prevented when the eccentric device comprises at least one eccentric unit, on which a fan impeller is integrally formed. The fan impeller may be used also to cool other components. Developments of the invention are further conceivable, in which the fan impeller is fastened to the eccentric unit. For example, the fan impeller might be slipped onto a flange of the eccentric unit. Developments of the invention are also conceivable, in which the eccentric unit is glued, screw-connected or riveted to the fan impeller.

In order to guarantee a defined orientation of the eccentric units relative to one another and/or relative to an eccentricity of the device, rotationally fixed connections of the eccentric device are preferably designed in such a way that they may be closed only in a specific position of relative rotation. For example, a shaft, onto which the fan impeller is slipped, might by virtue of a flattened area differ from a circular cross section and the fan impeller might have a corresponding shape in a central opening.

A vibrating of the entire hand tool machine that is uncomfortable for an operator may be avoided when the eccentric device comprises a counterweight for counterbalancing centrifugal forces of the tool component.

In said case, components may be spared when at least one eccentric unit has at least one eccentrically disposed counterweight and when the counterweight is in particular formed integrally on the eccentric unit.

A reliable setting of the eccentricity without large play may be achieved when the eccentric device has a guide device for guiding a setting motion. In said case, such a guide device is realizable in a constructionally simple, economical manner by means of a guide groove and a guide pin, which runs in the guide groove and may be integrally formed on the eccentric unit.

Drawings Further advantages arise from the following description of drawings. In the drawings, an embodiment of the invention is illustrated. The drawings, the description and the claims contain numerous features in combination. The person skilled in the art will consider the features expediently also individually and combine them into meaningful further combinations.

The drawings show: Fig. 1 an orbital sander having an eccentric device comprising a setting means, Fig. 2 an oblique view of two eccentric units of the eccentric device of Figure 1 in a first configuration, Fig. 3 a section along the line 111-111 in Figure 2, Fig. 4 a sectional view of the eccentric units of Figures 2 and 3 in a second configuration and Fig. 5 an exploded view of the eccentric units of Figures 1 - 4 and a detail of a sanding plate of the orbital sander of Figure 1.

Description of the embodiments

Figure 1 shows a hand tool machine 12 in the form of an orbital sander, having a housing 54 and having a tool component in the form of a sanding plate 16, on which abrasive paper of differing grain size may be clamped.

Disposed in the housing of the hand tool machine 12 is a motor 52, which is designed as an electric motor with adjustable brush plate and is illustrated here merely diagrammatically.

A setting means 18 takes the form of a slide switch, which is disposed displaceably in peripheral direction of an axis of rotation 64 of the motor 52 on the housing 54 of the hand tool machine 12 and which engages through an outer shell of the housing 54 into the brush plate of the motor 52. By displacing the setting means 18, an operator may rotate the brush plate about the axis of rotation and therefore bring about a phase displacement of the electric currents in armature windings of the motor 52 that ultimately produces a reversal of the direction of rotation of the motor 52.

When the hand tool machine 12 is switched on, the motor 52 is provided for generating a rotary motion 10 of a motor shaft (not explicitly illustrated here), which is connected in a rotationally fixed manner to a first eccentric unit 22 in the form of a metal casting. For establishing this connection, the motor shaft has gearing that meshes with internal gearing (not shown here) of a fastening point 26 of the first eccentric unit 22.

The first eccentric unit 22 comprises a counterweight 44, which in axial plan view takes the form of a segment of a circle having an internal angle of approximately 90 . The eccentric unit 22 further has a bearing point 28, which is designed as a circular recess in a surface lying opposite the fastening point 26 and which is provided for receiving and rotatably supporting a second bearing point 30. The second bearing point 30 is integrally formed on a second eccentric unit 24 in the form of a moulded plastic part and takes the form of a stud of a complementary shape to the circular recess.

A swivelling axis 66 of the first bearing point 28 and the second bearing point 30 is displaced parallel by a first eccentricity 56 relative to the axis of rotation 64 of the motor shaft and to an axis of symmetry of the fastening point 26 respectively.

In addition to the second bearing point 30, the second eccentric unit 24 at a side facing the first eccentric unit 22 has a semicircular guide groove 58, the centre of which is formed by the swivelling axis 66 of the first bearing point 28 and the second bearing point 30 and which forms part of a guide device 48 for guiding a setting motion 50.

In addition to the guide groove 58, the guide device 48 comprises a guide pin 60, which is provided for engagement into the guide groove 58. During the setting motion 50 the first eccentric unit 22 rotates relative to the second eccentric unit 24 through 180 about the first bearing point 28 and the second bearing point 30, wherein the guide pin 60 slides in the guide groove 58 of the guide device 48. During the setting motion 50 a relative phase 34 of the eccentric units 22, 24 varies by 180 . The ends of the guide groove 58 form stop elements 36, 38, against which the guide pin 60 strikes at the limits of the setting motion 50.

At a side remote from the first eccentric unit 22, the second eccentric unit 24 has an integrally formed shaft, which forms a third bearing point 32 and is provided for engagement into a ball bearing 62 connected to the sanding plate 16, 50 that the second eccentric unit 24 is connected in a rotatable and axially fixed manner to the sanding plate 16. An axis of rotation 68 of the ball bearing 62 and/or of the third bearing point 32 is displaced by a second eccentricity 40 relative to the swivelling axis 66.

When the motor 52 drives the motor shaft and, with it, the first eccentric unit 22 in positive direction, the guide pin 60 swivels about the swivelling axis 66 in the guide groove 58 up to attainment of a first configuration (Figure 2) . Via the stop element 36 the guide pin 60 then transmits a torque from the first eccentric unit 22 to the second eccentric unit 24.

In the first configuration the swivelling axis 66 lies in a plane between the axes of rotation 64, 68, so that the first eccentricity 56 is added to the second eccentricity and an eccentricity 20 of the axis of rotation 64 relative to the axis of rotation 68 arises as the sum of both eccentricities 56, 40.

When the motor 52 drives the motor shaft and, with it, the first eccentric unit 22 in negative direction of rotation, the guide pin 60 swivels about the swivelling axis 66 in the guide groove 58 up to attainment of a second configuration (Figure 4). Via the stop element 38 the guide pin 60 then transmits a torque directed in negative direction from the first eccentric unit 22 to the second eccentric unit 24.

In the second configuration the axis of rotation 68 lies in a plane between the axis of rotation 64 and the swivelling axis 66, so that the second eccentricity 40 and the first eccentricity 56 are destructively superimposed and the eccentricity 20 of the axis of rotation 64 relative to the axis of rotation 68 arises as the difference of both eccentricities 56, 40 and is therefore smaller than the eccentricity 20 in the first configuration.

When an operator, starting from a positive direction of rotation of the motor 52, actuates the setting means 18, the motor 52 reverses its direction of rotation and the first eccentric unit 22 swivels about the swivelling axis 66 into the second configuration, wherein the phase 34 varies by 1800, so that the setting means 18 is suitable for setting the phase 34 between the eccentric units 22, 24 supported rotatably about the bearing points 28, 30.

The third bearing point 32 and/or the axis of rotation 68 then executes an orbital oscillatory motion 14 having a radius that is defined by the eccentricity 20 in the second configuration and/or by the difference of the eccentricities 56, 40.

When an operator, starting from a negative direction of rotation of the motor 52, actuates the setting means 18, the motor 52 reverses its direction of rotation and the first eccentric unit 22 swivels about the swivelling axis 66 into the first configuration, wherein the phase 34 between the first eccentric unit 22 and the second eccentric unit 24 is displaced because of the inertia of the second eccentric unit 24 and the components connected thereto.

The third bearing point 32 and/or the axis of rotation 68 then executes an orbital oscillatory motion 14 having a radius that is defined by the eccentricity 20 in the first configuration and/or by the sum of the eccentricities 56, 40. The oscillatory motion 14 is transmitted from the third bearing point 32 via the ball bearing 62 to the sanding plate 16.

When the eccentric device is situated in the second configuration, the third bearing point 32 and/or the axis of rotation 68 executes an orbital oscillatory motion 14 having a radius that is defined by the eccentricity 20 in the second configuration and/or by the difference of the eccentricities 56, 40. The oscillatory motion 14 is transmitted from the third bearing point 32 via the ball bearing 62 to the sanding plate 16. The sanding plate 16 is connected to the housing 54 by oscillating feet (not shown here), which allow a limited elastic movement of the sanding plate 16 relative to the housing 54 in a plane defined by the sanding plate 16, whereas the oscillating feet are rigid in a direction extending at right angles to the plane of the sanding plate 16.

Provided on the housing 54 in the region of the setting means 18 is a mark visually indicating to the operator the magnitude of the eccentricity 20 to be expected depending on the position of the setting means 18. A tactile mark would also be conceivable, namely in that a region of the surface of the housing 54 in a first region, in which the setting means 18 is disposed when the eccentric device is being operated in the first configuration, has a coarse grain and in that a second region of the surface of the housing 54 in a region, in which the setting means 18 is disposed when the eccentric device is being operated in the second configuration, has a fine grain. In this way the operator may directly determine an advantageous position of the setting means 18 in dependence upon the grain of the abrasive paper clamped onto the sanding plate 16.

At a side remote from the first eccentric unit 22 and facing the ball bearing 62 and the sanding plate 16, the second eccentric unit 24 has blades, which extend radially outwards relative to the axis of rotation 58 and form a fan impeller 42 integrally formed on the second eccentric unit 24.

Integrally formed on the second eccentric unit 24 between some of the blades is a second counterweight 46, which in the first configuration is directed towards the first counterweight 44 and in the second configuration lies opposite the first counterweight 44. The masses of the counterweights 44, 46 are so selected that they counterbalance centrifugal forces, which the sanding plate 16 supports because of the oscillatory motion 14 at the third bearing point 32, in a way that prevents these centrifugal forces from being transmitted to the motor shaft and hence to the housing 54.

Claims

R. 308515 11.11. 04 ROBERT BOSCH GMBH, 70442 Stuttgart Claims 1. Eccentric

device, which is provided for converting a rotary motion (10) of a motor (52) of a hand tool machine (12) to an oscillatory motion (14) of a tool component (16), in particular to an oscillatory motion of a sanding plate of a sanding machine, characterized in that a setting means (18) is provided for setting an eccentricity (20) of the oscillatory motion (14)
2. Eccentric device according to claim 1, characterized by at least one eccentric unit (24), which has at least two eccentric bearing points (30, 32)
3. Eccentric device according to one of the preceding claims, characterized in that the setting means (18) is provided for setting a relative phase (34) between two eccentric units (22, 24) supported rotatably about a bearing point (28, 30)
4. Eccentric device according to one of the preceding claims, characterized by at least one stop element (36, 38, 60) for limiting a setting range of a phase (34)
5. Eccentric device according to one of the preceding claims, characterized in that the setting means (18) is provided for varying a direction of rotation of the motor (52).
6. Eccentric device according to claim 5, characterized in that the eccentricity (20) varies automatically upon a variation of the direction of rotation of the motor (52).
7. Eccentric device at least according to claims 3 and 6, characterized in that the eccentric units (22, 24) twist relative to one another when the direction of rotation of the motor (52) varies.
8. Eccentric device according to one of the preceding claims, characterized in that at least one eccentric unit (24) comprises an integrally formed fan impeller (42)
9. Eccentric device according to one of the preceding claims, characterized by a counterweight (44, 46) for counterbalancing centrifugal forces of the tool component (16).
10. Eccentric device according to one of the preceding claims, characterized in that at least one eccentric unit (22, 24) has at least one integrally formed, eccentrically disposed counterweight (44, 46)
11. Eccentric device according to one of the preceding claims, characterized by a guide device (48) for guiding a setting motion (50).
12. Hand tool machine (12) having an eccentric device, which is provided for converting a rotary motion (10) of a motor (52) to an oscillatory motion (14) of a tool component (16) , in particular to an oscillatory motion of a sanding plate of a sanding machine, characterized in that a setting means (18) is provided for setting an eccentricity (20) of the oscillatory motion (14)
13. An eccentric device in or for a hand tool, substantially as herein described with reference to the accompanying drawings.