GB2420519A

GB2420519A - Guide device for the sanding plate of a hand held tool

Info

Publication number: GB2420519A
Application number: GB0523364A
Authority: GB
Inventors: Gyoeri Szabolcs
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2004-11-17
Filing date: 2005-11-16
Publication date: 2006-05-31
Anticipated expiration: 2025-11-16
Also published as: CN1775474A; DE102004055270A1; GB0523364D0; CN1775474B; GB2420519B

Abstract

A guide device for a hand held power tool (figure 1, 12) is described. A guide slot 14 is provided to be penetrated by an eccentrically drivable engagement shaft 16 of said power tool. This slot 14 guides the engagement shaft 16 in a first operating mode along a first degree of freedom 18. A switchable locating element 20 for locating the position of an engagement shaft 16 in the guide slot 14 in a second operating mode is also defined. The characterising feature being that the locating element 20 is rotatably mounted. A handle element 38 may also be provided to manually rotate the locating element 20.

Description

_______ 2420519 Guide device

Prior Art

The invention is based on a guide device according to the preamble of claim 1.

A hand-held power tool with a guide device integrated into a sanding pad is known from GB 2 338 197 A. The sanding pad has a guide slot in the form of an elongated hole for guiding an eccentrically drivable engagement shaft of the hand-held power tool and a switchable locating element for locating a position of the engagement shaft in the guide slot.

The locating element has a first region with a contour which corresponds to a part of the contour of the guide slot. In a second operating mode this region is superimposed by the guide slot and the engagement shaft is freely movable within the guide slot. If the engagement shaft is driven eccentrically, it oscillates in a longitudinal direction of the guide slot and displaces the sanding pad via lateral edges of the guide slot, oscillating in a linear manner in a direction which extends perpendicular to the longitudinal direction of the guide slot.

The locating element further comprises a second region with a contour which forms a pitch circle, the radius of which is substantially equal to the radius of the engagement shaft. In a first operating mode this region superimposes the guide slot and engages around the engagement shaft. The locating element is fixedly connected to the sanding pad in the direction of the degree of freedom, so that the locating element in the first operating mode locates a position of the engagement shaft relative to the sanding pad in this direction, whilst the position is located by the guide slot in a second direction extending perpendicular to the degree of freedom. As a result, the sanding pad follows the eccentric movement of the engagement shaft and during operation oscillates on an orbital path.

To switch between the first and the second operating mode, the locating element is mounted translationally displaceably on the sanding pad. Whilst the first operating mode, characterised by circular orbital motions, for example when using the solution according to the invention in connection with an orbital sander, is particularly suited for sanding surfaces, the second operating mode characterised by linear oscillating motions is particularly suitable for sanding in the region of edges.

Advantages of the invention The invention is based on a guide device of a hand-held power tool with a guide slot which is provided to be penetrated by an eccentrically drivable engagement shaft of the hand-held power tool and to guide the engagement shaft at least in a first operating mode along a first degree of freedom and with a switchable locating element for locating a position of the engagement shaft in the guide slot in at least a second operating mode.

It is proposed that the locating element is rotatably mounted. As a result, a guide device may be achieved which is at least substantially free from jamming and which may be switched between the operating modes. An area swept over by the locating element on the guide device may be designed to be advantageously small, whereby a robust and space- saving switchable guide device can be achieved. As a smaller area is swept over, the risk of the locating element jamming on the guide device caused by soiling of the area, may be advantageously reduced.

In this connection, designed' and equipped' are also intended to be understood by the term provided' Particular advantages are revealed when using the solution according to the invention in connection with a handheld power tool configured as an orbital sander and, in particular, with a hand-held power tool with a rectangular sanding pad. It may be achieved that an oscillating motion of the sanding pad extends parallel to a side edge of the rectangular sanding pad. As a result, an advantageous use may be achieved in a region of an edge of the workpiece. In principle, however, embodiments of the invention are also conceivable in which the hand-held power tool comprises an oscillating tool, which is triangular and/or delta-shaped or round. Use in connection with a random orbital sander is also conceivable.

In an embodiment of the invention, it is proposed that a rotational axis of the locating element coincides with a centre point of the guide slot. A pivot region over which the locating element sweeps during rotary motion, may therefore be avoided.

It is additionally proposed that the guide slot is configured as an elongated hole. As a result, the engagement shaft may be guided more securely in the guide slot. In this connection, a length of the elongated hole advantageously corresponds to the sum of the diameter of a circular motion of the eccentrically driven engagement shaft and the diameter of the engagement shaft itself and/or a guide sleeve of the engagement shaft, so that the engagement shaft in the direction of the degree of freedom defined by the longitudinal axis of the elongated hole has a movement tolerance of the order of magnitude of double the eccentricity of the movement of the engagement shaft.

For the guiding to be achieved with at least substantially zero clearance, one lateral dimension of the elongated hole is at least substantially equal to the diameter of the engagement shaft and/or a guide sleeve of the engagement shaft.

In a further embodiment of the invention it is proposed that the locating element comprises at least one guide face which in at least one rotational position of the locating element is superimposed by a guide face of the guide slot.

As a result, in the corresponding rotational position the locating element advantageously prevents a reduction of the movement tolerance of the engagement shaft and in the corresponding rotatioal posftion, the locating element may advantageously assist the guide slot in its guiding function.

It is further proposed that the guide slot comprises lateral stop faces for defining a freedom of movement of the engagement shaft. As a result, lateral slipping of the engagement shaft out of the guide slot may be avoided.

If the locating element comprises a slot which is at least substantially similar to the guide slot, it can result in the slot being completely superimposed by the guide slot.

Due to the similarity of the slots, a production process may also be advantageously and inexpensively designed. The term!similar! is intended in this connection to be understood in the geometric sense.

If the locating element comprises a slot which is of convex form, it may be advantageously achieved that during rotary motion of the locating element the occurrence of a concave region of an engagement slot, defined by the slot being superimposed by the guide slot, is avoided. The existence of such concave regions has the risk of the engagement shaft jamming in the engagement slot.

If the guide device comprises at least one sleeve element for providing the engagement of the engagement shaft in the guide slot, the engagement shaft may be advantageously easily fitted into the guide slot. By means of a suitable choice of material and/or design of sleeve element, sliding friction, which may occur during movement of the engagement shaft within the guide slot, may be kept advantageously low.

In this connection, this sliding friction is almost completely avoidable if the sleeve element comprises at least one roller bearing. Ball bearings or needle bearings may be used as roller bearings.

If the guide device comprises at least one retaining element for locating the locating element in at least one rotational position, inadvertent displacement of the locating element out of the rotational position which is advantageously associated with an operating mode, may be avoided.

The locating element may be particularly comfortably locked if the guide device comprises a latching device which includes the retaining element.

A further gain in comfort may be achieved when the guide device comprises a handle element for manually rotating the locating element. In this connection, the handle element may be rigidly connected in a robust manner to the locating element or, however, indirectly, in mechanical cooperation with the locating element, for example by means of a cable control.

The locating element may be particularly inexpensively and securely mounted on the guide device if the guide device comprises a round depressed region, which is provided to accommodate the locating element.

Moreover, embodiments of the invention are conceivable in which the handheld power tool comprises a sensor unit by means of which the locating element may be automatically switched. For example, a hand-held power tool configured as an orbital sander or random orbital sander may advantageously have a lateral sensor unit which is actuated when approaching an edge and automatically switches on or switches off the locating unit.

Drawings Further advantages are revealed from the following description of the drawings. An embodiment of the invention is shown in the drawings. The drawings, the description and the claims contain numerous features in combination. The person skilled in the art will also expediently consider the features individually and combine them to form meaningful further combinations.

The drawings show: Fig. 1 an orbital sander with an oscillating tool, Fig. 2 the oscillating tool with a guide slot, a locating element and with an engagement shaft in an exploded view, Fig. 3 the oscillating tool with the locating element of Figure 2 in a first operating mode, Fig. 4 the oscillating tool with the locating element of Figures 2 and 3 in a second operating mode and Fig. 5 an alternative oscillating tool with a switching mechanism in a diagrammatic view.

Description of the embodiment

Figure 1 shows a hand-held power tool 12 constructed as an orbital sander with an oscillating tool 10 constructed as a sanding pad, the underside of which having a Velcro cover by means of which the sanding paper may be attached to the oscillating tool 10. A guide device is integrated in the oscillating tool 10. The hand-held power tool 12 comprises a grip 42 with an integrated switch 44 for switching on and switching off the hand-held power tool 12 and a dust collection bag 46. A body of the hand-held power tool 12 is contained by a plastics housing which accommodates a motor, not shown here, which is powered by a power supply cable 48. The oscillating tool 10 is attached to the body of the hand-held power tool 12 via spring struts which produce a spring force against which the oscillating tool 10 may be deflected by a few millimetres in a plane, created when the oscillating tool 10 is clamped, relative to the body of the hand-held power tool 12.

In the region of a gap 52 existing between the oscillating tool 10 and the body, spanned by the spring struts, a handle element 38 is arranged, via which an operator switches between a first operating mode in which, during operation, the oscillating tool 10 performs linear, one dimensional oscillating motions aligned parallel to one side edge 50 of the oscillating tool 10 and a second operating mode. In the second operating mode the oscillating tool 10 moves, during operation, on rotary and/or orbital paths during which a centre point of the oscillating tool 10 moves in a circular motion, whilst a rotational position of the oscillating tool 10 relative to the body of the hand-held power tool 12 remains constant.

The motor has a rotatably driven motor shaft, not shown here, onto which an engagement shaft 16 may be pressed (Figure 2) . The engagement shaft 16 has an offset so that a cylindrical part of the engagement shaft 16 facing away from the motor shaft and facing the oscillating tool 10, is displaced with its axis of symmetry about an eccentricity relative to an axis of the motor shaft, so that a rotary motion of the motor shaft creates an eccentric motion of the cylindrical part of the engagement shaft 16 in which the axis of symmetry rotates in a circle with a radius provided by the eccentricity in a parallel manner about the axis of the motor shaft.

A sleeve element 32 is placed on the cylindrical region of the engagement shaft 16 and which provides engagement of the engagement shaft 16 in a guide slot 14 in the form of an elongated hole extending perpendicular to the side edge 50.

In one engagement region the sleeve element 32 comprises a roller bearing with an inner race which is rotationally fixedly connected to the engagement shaft 16 and to an outer race which is in contact with the guide slot 14.

A centre point of the guide slot 14 forms a centre point of a circular, round depressed region 40 which is provided to accommodate a disc-shaped locating element 20 which comprises a slot 30 which has the form of an elongated hole and is of convex form and is geometrically similar to the guide slot 14. The locating element 20 is rotatably mounted in the depressed region 40, a rotational axis 22 of the locating element 20 coinciding with a centre point of the guide slot 14.

In a first rotational position of the locating element 20 (Figure 4) which is associated with the first operating mode, the slot 30 of the locating element 20 is congruent with the guide slot 14. The slot 30 and the guide slot 14 comprise semi-circular front faces which form lateral stop faces 28, 28' which define a freedom of movement of the engagement shaft 16 within the guide slot 14 and within the slot 30. Both the locating element 20 and a cover plate of the oscillating tool 10 are configured as stamped flexible sheet metal parts. The guide slot 14 and the slot 30 respectively have a peripheral, integral collar. The inner faces of the collar in the region of the long sides of the slot 30 of the locating element 20 form guide faces 24, 24' which in the first rotational position are superimposed in the axial direction by guide faces 26, 26' which are formed from the inner faces of the collar in the region of the long sides of the guide slot 14, so that, as pairs, the guide faces 24, 24', 26, 26' are respectively coplanar.

In the first rotational position the engagement shaft 16 may be displaced within the limits defined by the lateral stop faces 28, 28' along the longitudinal direction of the guide slot 14, whilst the guide faces 24, 24', 26, 26' prevent a displacement perpendicular to the longitudinal direction of the guide slot 14. The guide slot 14 defines a degree of freedom 18, namely a degree of freedom of movement of the engagement shaft 16 relative to the oscillating tool 10.

If the engagement shaft 16 moves on its orbital path whilst the locating element 20 is in the first rotational position, a component of the movement parallel to the longitudinal direction of the guide slot 14 effects a displacement of the engagement shaft 16 along the degree of freedom 18, whilst a component of the movement extending perpendicular to the degree of freedom 18 effects a deflection of the oscillating tool 10 relative to the body of the hand-held power tool 12 against the spring force of the spring struts.

The handle element 38 is attached to the locating element 20 and projects radially outwardly through the gap 52 where an operator may grip said handle element and by means of the handle element 38 may manually rotate the locating element 20 in the depressed region 40 within an angular range of 9Q0 which is defined by stop elements not shown here. In a second rotational position rotated by 900 relative to the first rotational position, a longitudinal axis of the slot 30 extends perpendicular to the longitudinal axis of the guide slot 14 (Figure 3) In positions of the handle element 38 associated with the first and second rotational position, bulge-shaped retaining elements 34, 34' are formed on the oscillating tool 10 via which the handle element 38 slides away when an operator rotates it out of the corresponding position, the handle element 38 deforming resiliently, so that the operator has to use force. The handle element 38 and the retaining elements 34, 34' thus form a latching device 36 by means of which the locating element 20 is located in the first rotational position and in the second rotational position.

In the second rotational position, the guide faces 24, 24' of the guide slot 14 prevent a movement of the engagement shaft 16 in a direction perpendicular to the longitudinal axis of the guide slot 14 and/or parallel to the slot 30 of the locating element 20. The guide faces 26, 26' of the locating element 20 prevent a movement of the engagement shaft 16 along the degree of freedom 18, whereby the locating element 20 in the second rotational position locates a position of the engagement shaft 16 in the guide slot 14. By rotating the locating element 20 said locating element may therefore be switched and exhibits its locating effect in the second rotational position.

If the engagement shaft 16 moves on its orbital path whilst the locating element 20 is in the second rotational position, the motion of the engagement shaft 16 and/or the axis of the engagement shaft 16 is transferred into an orbital and/or rotary motion of the oscillating tool 10 relative to the body of the hand-held power tool 12.

Figure 5 shows an oscillating tool 10 with an alternative guide device in a diagrammatic view. Similar features are provided with the same reference numerals. In the description it is substantially intended that further details are given about the differences from the embodiment shown in Figures 1-4. With regard to features remaining the same, reference may be made to the description for the embodiment shown in Figures 1-4.

The oscillating tool 10 shown in Figure 5 comprises a switching mechanism 54 and two sensing elements 56, 56' for sensing the ambient parameter, namely an edge of a In a first operating mode, a locating element 20 is freely rotatably mounted about a rotational axis 22 on the oscillating tool 10 and, during operation, is alternately oscillated by an engagement shaft not shown here, whilst the engagement shaft moves in a guide slot 14 along a degree of freedom 18 and produces an alternating motion of the oscillating tool 10 in a direction extending perpendicular to the longitudinal direction of the guide slot 14.

The switching mechanism 54 automatically switches the guide device into the first operating mode when the hand-held power tool 12 approaches an edge of the workpiece. If the edge comes into contact with one of the sensing elements 56, 56', said sensing element pivots inwardly about its respective axis 58, 58' and displaces a locking element 60 via a stop 64 and which is displaceably mounted on the oscillating tool 10 in a direction facing away from the locating element 20, whereby an engagement of a fork-shaped end region of the locking element 60 with a pin of the locating element 20 is automatically released and the locating element 20 may follow the motion of the engagement shaft.

If no pressure acts on the sensing elements 56, 56', a spring element 62 automatically displaces the locking element 60 in the direction of the locating element 20 and the fork-shaped end region of the locking element 60 slides over the pin of the locating element 20, so that the position of the locating element 20 and the position of the engagement shaft 16 within the guide slot 14 are located.

The guide device is then switched into a second operating mode in which the oscillating tool 10 has rotary motion.

Claims

Cia ims 1. Guide device of a hand-held power tool (12) with a guide slot

(14) which is provided to be penetrated by an eccentrically drivable engagement shaft (16) of the hand-held power tool (12) and to guide the engagement shaft (16) at least in a first operating mode along a first degree of freedom (18) and with a switchable locating element (20) for locating a position of the engagement shaft (16) in the guide slot (14) in at least a second operating mode, characterised in that the locating element (20) is rotatably mounted.
2. Guide device according to claim 1, characterised in that a rotational axis (22) of the locating element (20) coincides with a centre point of the guide slot (14)
3. Guide device according to any one of the preceding claims, characterised in that the guide slot (14) is configured as an elongated hole.
4. Guide device according to any one of the preceding claims, characterised in that the locating element (20) comprises at least one guide face (24, 24') which in at least one rotational position of the locating element (20) is superimposed by a guide face (26, 26') of the guide slot (14).
5. Guide device according to any one of the preceding claims, characterised in that the guide slot (14) comprises lateral stop faces (28, 28') for defining a freedom of movement of the engagement shaft (16)
6. Guide device according to any one of the preceding claims, characterised in that the locating element (20) comprises a slot (30) which is at least substantially similar to the guide slot (14)
7. Guide device according to any one of the preceding claims, characterised in that the locating element (20) comprises a slot (30) which is of convex form.
8. Guide device according to any one of the preceding claims, characterised by at least one sleeve element (32) for providing the engagement of the engagement shaft (16) in the guide slot (14)
9. Guide device according to claim 8, characterised in that the sleeve element (32) comprises at least one roller bearing.
10. Guide device according to any one of the preceding claims, characterised by at least one retaining element (34, 34') for locating the locating element (20) in at least one rotational position.
11. Guide device according to claim 10, characterised by a latching device (36) which includes the retaining element (34)
12. Guide device according to any one of the preceding claims, characterised by a handle element (38) for manually rotating the locating element (20)
13. Guide device according to any one of the preceding claims, characterised by a round depressed region (40) which is provided to accommodate the locating element (20)
14. Guide device according to any one of the preceding claims, characterised by an automatic switching mechanism (54) for switching the locating element (20)
15. Guide device according to any one of the preceding claims, characterised by a sensing element (56) for sensing an ambient parameter.
16. Guide device according to claims 14 and 15, characterised in that the switching mechanism (54) can be triggered by the sensing element (56)
17. A guide device substantially as herein described with reference to the accompanying drawings.
18. Hand-held power tool (12) with a guide device which comprises a guide slot (14) which is provided to be penetrated by an eccentrically drivable engagement shaft (16) and to guide the engagement shaft (16) at least in one operating mode along a first degree of freedom (18) and with a switchable locating element (20) for locating a position of the engagement shaft (16) in the guide slot (14) in at least a second operating mode, characterised in that the locating element (20) is rotatably mounted. p
19. A hand-held power tool comprising a guide device according to any one of claims 1 to 17.