EP0424720B1 - Attachement for angle grinder - Google Patents

Abstract

Accessory devices for a hand driven tool such as, for example, an angle grinder with the accessory device including an eccentric unit and a resilient coupling for a toolholder whereby an oscillating, elliptical path of movement is imparted to the toolholder in an operating range of the hand driven tool. The eccentric unit and the resilient coupling form one module with the toolholder forming an independent structural assembly thereby enabling the toolholder to be readily exchangeable.

Description

The invention relates to an attachment for an angle grinder, with an eccentric head which can be screwed onto its output spindle and which acts on a tool carrier via an eccentrically arranged ball bearing, the freedom of movement of which, by means of a flexible linkage device attached to the housing of the angle grinder, to a reciprocating movement in accordance with the eccentricity and is limited to an overlapping pivoting movement around the flexible point of the articulation device.

From DE-OS 27 45 129 and DE-GM 76 26 861 eccentric heads are known which can be screwed directly onto the output spindle of hand grinders such as angle grinders and have on their underside a rotary bearing arranged eccentrically to the output spindle, to which the grinding plate is attached. While the grinding disc is driven purely rotating in simple hand-held grinding machines, a relatively slow rotary movement of the grinding disc results when the known eccentric head is interposed, this rotary movement being superimposed on a rapid circular movement in accordance with the eccentricity of the eccentric head. Through this Superimposition of motion results in a very good grinding pattern. However, it is not possible to completely grind surfaces delimited by two converging edge surfaces.

The AEG company has been selling the SS 707 and SS 717 orbital sander types since 1978, in which the tool carrier, which has an eccentric ball bearing, is flexibly articulated by four cylindrical rubber buffers arranged in a rectangle to parts rigidly connected to the drive machine housing in such a way that a rotational movement of the tool carrier is prevented and this only performs a small oscillating circuit movement according to the eccentricity of the ball bearing. These known orbital sanders are designed as attachments for manual drive machines (see catalog AEG DIY system, February 1978). However, they are not suitable for grinding surfaces along edges or in narrow corner areas.

From US-PS 2 350 098 an angle grinder is known, the output spindle is provided with an eccentric, which acts via an eccentrically arranged ball bearing on a strip-shaped tool carrier, the freedom of movement by a bolt attached to the grinder housing, which engages in an elongated hole of the strip-shaped tool carrier , is limited to a to-and-fro movement in the longitudinal direction of the ledge and to an overlapping pivoting movement around the bolt, so that the tool carrier describes an elliptical trajectory at its front free end. The tool carrier carries there a rectangular sanding pad at its front free end. Since the movement of the sanding pad towards the front, ie along the small axis of the elliptical trajectory, is relatively small, this known angle hand grinder is also suitable for sanding and fine sanding on longitudinal edges and in corners. The elliptical, circular movement of the individual abrasive grain enables a very fine sanding, the sanding sheet being worn there almost uniformly over the entire surface. However, this known device must be purchased as a single device, since its eccentric head and the tool carrier linkage are integrated into the basic device and are therefore not designed as an attachment.

From DE-OS 38 05 926 different embodiments of the generic attachment are known, in each of which the tool holder is permanently connected to the eccentric head via the ball bearing and in which, in all embodiments, the tool holder is linked directly to an adapter piece attached to the angle grinder via a flexible rubber buffer is. When changing the tool holder, the entire attachment device must also be replaced there, which leads to a relatively complex set of attachment devices or to a complex replacement in the case of a damaged tool holder.

The invention has for its object to provide a generic attachment for angle grinders in such a way that it can be used for all types of angle grinders available on the market and allows inexpensive production of a set of different tool carriers.

To achieve this object, it is provided according to the invention that the outer ring of the ball bearing is arranged eccentrically in the rotating eccentric head and a central internal threaded bushing is fastened in the inner ring, that the articulation device consists of a tab that can be screwed onto a handle screw hole of the angle grinder and that is flexibly connected to the tab , at the lower end of the threaded bushing, radially projecting cantilever part and that the tool carrier is a structurally separate from the articulation device and the eccentric, which is interchangeable.

The invention provides a number of advantages. On the one hand, the attachment can be attached to almost all commercially available angle hand grinders via the screw-on bracket, since on the one hand the thread of the output spindle of such devices is standardized and the threaded holes on the head of the known angle grinder on both sides for screwing on additional handles are used for the flexible articulation in the invention. There are therefore no longer any special adapter pieces to be attached to the head of the angle grinder. A further decisive advantage is that when the tool holder is changed, the eccentric head including the ball bearing and also the flexible linkage device remain on the angle grinder and therefore only the tool holder - for example when worn against a new one - or against another type of tool holder must be replaced. In this way, a set of different tool carriers can be assigned to an angle grinder in a relatively inexpensive manner. Depending on the grinding task, this can be finger-shaped protruding grinding plates or tool carriers in the form of an arched triangle or, preferably, elongated hexagonal tool carriers, in which the front and rear corners each have an angle of 90 °. Such a grinding plate largely combines the advantages of an arched triangular grinding plate with those of a grinding plate protruding in the form of a finger.

According to a preferred embodiment of the invention, the cantilever part can consist of a cup which largely encloses the eccentric head and which protrudes toward the tab and which can be clamped together with the tool carrier by means of a single cap screw on the internally threaded bushing. As a result, the manufacturing effort and labor for changing the tool holder are reduced.

Further features of the invention are specified in the subclaims.

Fig. 1

in einer vereinfachten perspektivischen Darstellung ein Vorsatzgerät nach der Erfindung, zusammen mit einem typischen Winkelhandschleifer,

Fig. 2

einen Vertikal-Längsmittelschnitt durch ein Vorsatzgerät nach Fig. 1,

Fig. 3

das Vorsatzgerät in Fig. 2 von rechts in Richtung des Pfeiles III gesehen,

Fig. 4

eine Draufsicht auf das Vorsatzgerät,

Fig. 5

eine schematische Darstellung zu den Bewegungsbahnen bei einem sechseckigen Schleifblatt,

Fig. 6

ein zweites Ausführungsbeispiel des Gerätes nach der Erfindung und

Fig.7 und 8

ein drittes Ausführungsbeispiel.

The invention is described below with reference to three exemplary embodiments shown in the drawing. The drawing shows:

Fig. 1

a simplified perspective view of an attachment according to the invention, together with a typical angle hand grinder,

Fig. 2

2 shows a vertical longitudinal central section through an attachment according to FIG. 1,

Fig. 3

2 seen from the right in the direction of arrow III,

Fig. 4

a plan view of the attachment,

Fig. 5

1 shows a schematic representation of the trajectories in a hexagonal sanding sheet,

Fig. 6

a second embodiment of the device according to the invention and

Fig. 7 and 8

a third embodiment.

Fig. 1 shows an angle grinder 1, the output spindle 2 is provided with a standardized thread and has two threaded holes 3, 4 provided on both sides of the angle grinder head for optionally screwing on additional handles.

The attachment consists of an eccentric head 5 which can be screwed onto the output spindle 2 by means of a threaded bore 6 and rotates with the latter. At the lower end, the eccentric head 5 carries in an eccentric receptacle 8 with respect to the axis 7 of the threaded bore 6 the outer ring 9 of a deep groove ball bearing 10, on the inner ring 11 of which an internally threaded bushing 12 is clamped by means of a cap screw 13 screwed into the internally threaded bushing 12 from above. The outer ring 9 of the ball bearing is clamped to the eccentric head 5 by a plurality of pan head screws 14 distributed over the circumference. The tool carrier 16, which is designed as a grinding plate, can be connected to the eccentric ball bearing 10 by means of a cap screw 15 inserted into the internally threaded bushing 12 from below.

To achieve a purely oscillating drive of the tool carrier 16, i. H. In order to avoid rotation of the grinding plate, the attachment is provided with a flexible articulation device 17, which is only shown schematically in FIG. 1 and in constructive detail in FIGS. 2 to 4.

The articulation device 17 comprises a cantilever part 18 which can be clamped directly onto the end face of the internally threaded bushing 12 and between whose radially projecting projection 19 and a tab 20 an elastic rubber buffer 21 is clamped. The tab 20 is directed approximately perpendicular to the tool carrier 16 and is provided with an elongated hole 22 and is fastened by means of a cap screw to the screw hole 4 lying rearward in FIG. 1. To take into account the different angle grinders, a group of different cap screws 23 with washers 24 is assigned to the attachment.

The cantilever part 18 of the flexible articulation device 17 consists of a cup 25, which largely encloses the eccentric head 5, on the inner bottom of which a hexagon receptacle 26 is attached for the lower end of the threaded bushing 12 designed as a congruent hexagon head 27. On the outside of the cup 25 there is provided the radially protruding projection 19, which is directed towards the rear during assembly of the attachment, ie under the angle grinder 1, and which has a clamping surface 28 perpendicular to the tool carrier 16, on which the rubber buffer 21 by means of it penetrating head screw 29 is tightened such that the axis of the cylindrical rubber buffer 21 is directed parallel to the tool carrier 16 and at the same time parallel to the transverse central plane of the attachment.

When the eccentric head 5 rotates, the internally threaded bushing 12 and the region of the grinding plate immediately below it execute a circular movement path 30, cf. the schematic representation in Fig. 5. Since the backing plate is held at its rear end over the rubber buffer 21, it performs a back and forth movement in the longitudinal direction according to the double arrow 31, which with an eccentricity of, for example, 0.5 millimeters between the Drive axis 7 and the axis 32 of the internally threaded bushing or the ball bearing 10 means a stroke of 1 millimeter. The rubber buffer 21 is constantly bent back and forth on this end 31 by this path 31, which means only an uncritical loading of the rubber buffer. The transverse component of the circular movement path 30 is, however, suppressed by the rubber buffer 21 at the rear end of the tool carrier 16, so that the back and forth movement of the grinding plate overlaps a pivoting movement around the articulation point 33 and the grinding plate in its front region 34 has an elliptical movement path 35 executes, which is, however, shown greatly enlarged in Fig. 5. Due to the swiveling movement, the rubber buffer is minimally loaded for compression or expansion, which is indicated by the short arrows on the front side S of the buffer. The buffer is not subjected to torsion. In the case of the tool carrier or grinding plate 16 shown, which has the shape of an elongated hexagon and in which the screwing point 36 is offset on the longitudinal axis L next to the center M of the grinding plate, there is an eccentricity of 0.5 millimeters in the front region 34 of the grinding plate an elliptical trajectory, the short axis is 1 millimeter and the long axis is about 2 to 3 millimeters. The hexagonal tool carrier 16 has at its two opposite ends in the longitudinal axis L each at a right angle R, so that with such a grinding tool optimally along the edge and in the corner of a workpiece 37, which is, for example, a drawer acts, can be worked. The grinding plate is provided on both sides of its longitudinal center M with screw-through openings 38, so that when the front area 34 wears out, the tool carrier can be converted into a position turned through 180 ° and screwed on again.

6 shows a modified embodiment for the flexible articulation 39 of the attachment on an angle grinder. The tab 40 here has at its lower, forwardly bent end a downwardly directed bolt 41 which engages in a horizontal elongated hole 42 in the shoulder 43 of the cantilever part 44. The elongated hole 42 has a width equal to the diameter of the bolt 41, so that the bolt 41 acts as a hinge axis. The length of the elongated hole 42 should be significantly greater than the sum of the diameter of the bolt 41 and the stroke length according to the double arrow 31, for example 20 millimeters, since this facilitates the adaptation of the attachment to the respective angle grinder devices.

In the embodiment according to FIGS. 7 and 8, the articulation device 45 consists of an approximately parallel to the plane of the tool carrier 16 Connecting member 46 which is pivotally mounted on the cantilever 47 and the tab 20 about axes perpendicular to the plane of the tool carrier. For this purpose, a hinge sleeve 48 is screwed onto the tab 20 and a sleeve 49 is inserted into the collar part 47. The articulation axes 50, 51 are here made in one piece with the connecting member 46 consisting of round material, which thus has an overall U-shape. Instead of simple bearing sleeves, ball bearings can also be provided to reduce the bearing friction.

The invention is not restricted to the exemplary embodiments shown. Rather, the tool attachment can be assigned different tool carriers with tools for grinding, polishing, corner grinding, scraping or slitting.

Claims (8)

1. Attachment for an angle-grinder, with an eccentric head (5), attachable by screwing to the downward-drive spindle (2) thereof, which, via an eccentrically arranged ball-bearing (10), influences the operation of a tool-holder (16), whose freedom of movement is limited, by a flexible coupling (17) fixed to the casing of the angle-grinder (1), to a back-and-forth movement dictated by the eccentricity and a superimposed rotatory movement around the flexible point (33) of the coupling (17), characterized in that the outer ring (9) of the ball-bearing (10) is located eccentrically in the rotating eccentric head (5) and a central internal-thread bush (12) is fixed in the inner ring (11), in that the coupling (17) consists of a bracket (20) which may be screwed on to a handle-connection-hole (4) in the angle-grinder (1) and a collar unit (18) connected flexibly to the bracket (20), fixed to the lower front face of the threaded bush (12) and projecting radially, and in that the tool-holder (16) is constructed as a separate component from the coupling (17) and the eccentric head (5), this component being replaceable.
2. Attachment as claimed in Claim 1, characterized in that the collar unit (18) consists of a cup (25) surrounding the eccentric head (5) as completely as possible and a projection (19) aligned parallel to the bracket (20), which together with the tool-holder (16) may be fastened to the internal-thread bush (12) by means of a single cap-screw (15).
3. Attachment as claimed in Claims 1 and 2, characterized in that the collar unit (18) and the bracket (20) are connected to one another via an elastic buffer (21) whose parallel connecting surfaces are aligned perpendicular to the plane of the tool-holder (16) and parallel to the vertical transverse central plane of the attachment.
4. Attachment as claimed in Claims 1 and 2, characterized in that the collar unit (44) has a longitudinal hole (42) aligned parallel to the longitudinal axis of the angle-grinder, into which the bracket (40) engages with an underneath bolt (41), as an articulated axle.
5. Attachment as claimed in Claim 1, characterized in that the coupling (45) consists of a connecting-member (46), aligned parallel to the plane of the tool-holder (16), and which rests, rotatable around axes perpendicular to the plane of the tool-holder, on the collar unit (47) and the bracket (20).
6. Attachment as claimed in Claim 1, characterized in that the tool-holder (16) is a grinding-plate in the form of a longitudinal hexagon, in which the opposite corners lying on the longitudinal axis (L) are each a right-angle (R).
7. Attachment as claimed in Claim 6, characterized in that the screw-on point (36) of the grinding-plate (16) is displaced from but adjacent to the longitudinal centre (M) thereof.
8. Attachment as claimed in one or more of Claims 1 to 7, characterized by a set of various different complementary tool-holders for grinding, polishing, angle-grinding, scraping or slotting.

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