GB2322579A

GB2322579A - A grinding plate for a hand-held tool

Info

Publication number: GB2322579A
Application number: GB9803870A
Authority: GB
Inventors: Julian Pfaundler
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1997-02-28
Filing date: 1998-02-24
Publication date: 1998-09-02
Anticipated expiration: 2018-02-24
Also published as: GB2322579B; ITMI980338A1; CN1191792A; IT1298432B1; CN1094814C; GB9803870D0; JPH10264028A

Abstract

A grinding plate 17 with dust extraction means for a hand-held tool (Fig 1, 10) has a flexurally stiff plate 23 on its top side fixedly connected to which is a plate 24 on the underside made of soft material, the plate 23 on the top side being covered substantially over its entire top surface with a soft seating layer 34. The seating layer 34 provides a seal between the grinding plate 17 and the tool (Fig. 1,10) to reduce dust and air leakage as well as providing damping and compensation for manufacturing tolerances. Flanges 36 and 37 are preferably provided on the seating layer 34 and the seating layer 34 is preferably made in one piece with the plate 24 on the underside from a homogenous foam such as polyurethane foam. The top surface of the plate 23 on the top side may be drawn upwards out of the plane of the plate in regions of fastening holes and be substantially free from the seating layer in these regions (Fig. 7).

Description

1 Grinding 121ate for a hand-held electric tool with dust-extraction

Prior art

2322579 The starting point for the invention is a grinding plate for a hand-held electric tool with dust-extraction, of the type defined in the pre- characterising clause of claim 1.

Grinding plates of this kind are known (DE-OS 19 38 350), in which the plate on the top side consists of metal, and in this instance of steel or aluminiurn, and requires mechanical machining. Fixedly connected, for example stuck, to the plate on the top side is a plate on the underside which consists of elastic material such as rubber or plastic. A known grinding plate of this kind poses sealing problems 15 on the top side of the upper plate and at the point where fastening of the grinding plate to the hand-held electric tool takes place. As a rule, the grinding plate is fastened by its top side to a carrier, for example an oscillating plate, by means of screws. For dust-extraction purposes, the carrier has perforations which align with those m the grinding plate. Inadequate sealing between the grinding plate and the 20 carrier results in losses in flow and thus losses in output during extraction, so that the extraction output is reduced in a corresponding manner. There is also the risk of dust passing into the bearing regions of the hand-held electric tool because of deficient sealing.

Advantages of the invention By contrast the grinding plate according to the invention for a hand-held electric tool with dust-extraction, which grinding plate has the features in claim 1, has the advantage that good sealing is achieved because of the seating layer, and so too 2 is damping and also compensation for tolerances. Because of the sealing, dust is prevented from being able to penetrate into bearing chambers or other intervening spaces. Instead, the dust is sucked solely through the intended perforations and ducts. Any losses in flow during extraction are minimised. The extraction output is increased. Nevertheless, the grinding plate is simple, light and inexpensive.

Advantageous flirther developments of, and improvements to the grinding plate indicated in claim 1 are possible as a result of the measures set out in the other claims.

The foam may advantageously be formed from a microcellular foam system, preferably with high mechanical strength values. The plate on the top side may be foarned-round with the foam. In respect of the form of material for the plate on the top side, it may be advantageous if the said plate is formed from sheet metal, in particular light metal, for example aluminium, or is instead shaped from a fibre-reinforced or fabric-reinforced plastic. In this event the plate on the top side may be formed from a polyurethane/glass fibre part. The plate on the underside preferably carries a hook-and-loop adhesive track on its underside.

It may also be advantageous if a sealing cover on the top side is provided for flat sealing of a central aperture in an oscillating plate to which the grinding plate can be fastened.

Drawings The invention is explained in greater detail below with the aid of exemplified embodiments represented in the drawings, in which:

figure 1 shows a diagrammatic axial longitudinal section 3 through part of a hand-held electric tool with dustextraction, figure 2 shows a bottom view of the uncovered underside of a grinding plate, figure 3 figure 4 figure 5 figure 6 figure 7 shows a view of the top side of the grinding plate in figure 2, shows a diagrammatic section along the line IV - IV in figure 3, shows a diagrammatic section along the line V - V in figure 3, shows a diagrammatic section along the line VI - VI in figure 3, and shows an enlarged section through the detail VII M figure 6.

Description of the exemplified embodiments

Figure 1 shows, diagrammatically, part of a hand-held electric tool 10 with dust extraction, which tool is advantageously constructed as a grinding appliance, for example an oscillating grinder. The hand-held electric tool 10 has an electric motor, which is contained in a housing of which no more is visible, for driving a shaft 11 on which a fan wheel 13, which serves, above all, for the internal extraction of dust M the direction of the arrow 14, is held in a rotation- proof 4 mariner by means of a sleeve 12. In the construction of the hand-held electric tool 10, for example as an oscillating grinder, there is driven in a revolving manner, by means of the shaft 11, an eccentric sleeve 15 which is disposed on the said shaft in a rotation-proof mariner and on which there is rotatably mounted an oscillating plate 16 to which a grinding plate 17 is detachably fastened by means of screws which are not represented. The oscillating plate 16 is secured in position so as to be elastically movable with respect to a housing part 18. On the left-hand side in figure 1, the housing part 18 has a discharge connection piece, of which no more is represented but through which there is discharged air which is laden with grinding dust and is sucked, through holes in the oscillating plate 16 and also in the grinding plate 17, into a flow chamber 19 by means of the fan wheel 13.

is The oscillating plate 16 contains a central aperture 20 which is sealed, by means of a sealing cover 21 made of plastic, in relation to that side which faces away from the grinding plate 17. The sealing cover 21 serves to catch grease from the arrangement for mounting the oscillating plate 16 by means of a needle bushimg 22, arid also grease which is used for greasing radial shaft-sealing rings and which is centrifuged away by the eccentric sleeve 15. The grinding plate 17 located under the sealing cover 21 is masked by means of the latter on the top side, so that the said top side is kept free from escaping grease or similar contaminants. The sealing cover 21 constitutes an inserted supplementary part.

The extraction of dust takes place transversely through the grinding plate 17 which has a flexurally stiff plate 23 on the top side and, on the underside thereof, a plate 24 on the underside which is made of soft material and is fixedly connected to the plate 23 on the top side. On its underside, the plate 24 on the underside has a hook-and-loop adhesive track 25 which is, for example, stuck on. The hook- and loop adhesive track 25 serves for detachably fitting a grinding sheet, of which no more is shown here. In another exemplified embodiment which is not shown, the hook-and-loop adhesive track 25 is not present and the underside of the plate 24 is, accordingly, uncovered. The said underside is then covered by a grinding sheet which is placed over it and which can be held, for example, by means of holding arrangements 26 on the oscillating plate 16. The uncovered underside of the plate 24 on the underside is shown in figure 2.

For the extraction of dust through the grinding sheet which is not represented, and through the grinding plate 17, the plate 24 on the underside is provided, on its underside (figure 2), with apertures 27 at the edge which are, for example, approximately semi-circular. In addition, the plate 24 is provided with perforations 28, for example bores, which pass through it transversely. The perforations 28 are connected, via recessed ducts 29 which are open towards the underside, with the apertures 27 at the edge, so that the extraction of dust takes place through the perforations 28, and also fresh air and/or dust is sucked in from the outside via the ducts 29 and the apertures 27 at the edge.

The plate 24 on the underside contains holes 30 underneath for the transitional engagement of fastening screws for effecting coupling to the oscillating plate 16.

The hook-and-loop adhesive track 25 contains holes 31 which align with the perforations 28 and holes 30.

The plate 23 on the top side contains openings 32 which align with the perforations 28 and holes 30 in the plate 24 and of which those openings which are smaller in diameter serve as fastening holes, their diameter being smaller than that of the holes 30 in the plate 24. As a result of this there is produced, on the underside of the plate 23, an annular face 33 for supporting the screw head of the fastening screw which is not described in any greater detail.

The grinding plate 17 of the exemplified embodiment shown is rectangular.

Instead of the cross-sectional thickness shown, it may also have a smaller cross- 6 sectional thickness. In another exemplified embodiment which is not shown, the grinding plate 17 has, for example at the right-hand end in figures 2 and 3, a nonperforated extension which can be provided on the top side with, for example, the same hook-and-loop adhesive track 25 as on the underside. In another exemplified embodiment, which is not shown, the extension is not rectangular but is instead delta-shaped. The most varied shapes and dimensions for the grinding plate 17 lie within the scope of the invention.

The plate 23 on the top side is covered, essentially over its entire top side, with a mildly elastic seating layer 34, which also extends along the edge of the plate 23 on the top side, and likewise overlaps the said edge. The plate 23 on the top side may further have, as indicated, centring bores 35 at both ends, which bores are not filled or covered by the seating layer 34. The seating layer 34 advantageously has a uniform layer thickness. The seating layer 34 has at least one upwardly protruding sealing flange, for example a sealing flange 36 running round at the edge. There is additionally provided, in the exemplified embodiment shown, a central, circular ring-shaped sealing flange 37. Since the latter projects in the direction of the oscillating plate 16 and, at that point in the region of the aperture 20, a circular ring-shaped sealing flange 37 in the said region brings about sealing of the chamber 20 against the penetration of dust.

In another exemplified embodiment which is not shown, the circular ringshaped sealing flange 37 is omitted. The sealing flange 36 at the edge brings about additional lateral fixing and, at the edge, additional sealing.

The seating layer 34 provided on the top side has a sealing and damping function.

It serves to compensate for and seal tolerances in this region and to give rise to damping. As a result of the sealing which is achieved, the dust is unable to penetrate, during its extraction, either into the bearing chamber of the hand-held electric tool 10 or into other intervening spaces on the oscillating plate side, so that 7 any losses M flow that this might cause are prevented. The dust is transported solely through the extracting ducts. The seating layer 34 may be about 1 mm thick and of white or even coloured design.

As is made clear in figure 7 in particular, the plate 23 on the top side is drawn upwards, out of the plane of the plate, in the region of the openings 32. The top side of this upwardly drawn region is essentially free from the seating layer 34, which is either entirely absent at that point or at least only has remaining a negligible layer thickness, of about 1/10 mm for example, for overlapping purposes, which thickness can then likewise still serve for sealing, damping and compensating for tolerances. The design which is such that this region is essentially free, on the top side, from the seating layer 34, has the advantage that, when the grinding plate 17 is attached, the latter comes to rest with the top side of the plate 23 m the region of the openings 32 flat against that face of the oscillating plate 16 which is turned towards it and deformation of the said grinding plate 17 when the fastening screws are tightened is prevented.

The seating layer 34 is formed firom the same material as the plate 24 on the underside, and is in one piece with the said plate. The seating layer 34 and the plate 24 on the underside are formed from a homogeneous foam made of plastic, in particular polyurethane foam, which may be formed, in particular, from a microcellular foam system, preferably with high mechanical strength values. The plate 23 on the top side is foamed-round on the top side, on the underside and all round with a foam of this kind. Apart from that the plate 24 on the underside also receives its shape during the foaming-round operation, and in particular the apertures 27, the. perforations 28 and the ducts 29, which serve for the extraction of dust, are alike formed with it in the process.

The plate 23 on the top side may be formed from sheet-metal, in particular light metal, for example aluminium. Instead of this, however, the plate 23 on the top 8 side may also be formed from a fibre-reinforced or fabric-reinforced plastic and, in this connection, particularly from a polyurethane/glass fibre part.

The grinding plate 17 in the design described is simple, inexpensive and inherently stable. The high mechanical strength values of the foam for the seating layer 34 and the plate 24 on the underside, result in a high service life for the grinding plate 17.

9

Claims

1. Grinding plate for a hand-held electric tool (10) with dust-extraction, in particular for a grinding appliance, for example an oscillating grinder, with a flexurally stifF plate (23) on the top side, fixedly connected to which is a plate (24) on the underside which is made of soft material and against the underside of which a grinding sheet can be seated, while the plate (24) on the underside has ducts (29) on the underside and/or apertures (27) at the edge and/or perforations (28) aligning with openings (32) in the plate (23) on the top side, for the extraction of dust through the grinding sheet, the plate (24) on the underside and the plate (23) on the top side, characterised in that the plate (23) on the top side is covered, essentially over its entire top side, with a soft, in particular elastically tight seating layer (34).

2. Grinding plate according to claim 1, characterised in that the seating layer (34) has a uniform layer thickness.

3.

Grinding plate according to claim 1 or 2, characterised in that the seating layer (34) has at least one upwardly protruding sealing flange (36, 37).

4. Grinding plate according to claim 3, characterised in that a central sealing flange (37) is provided which extends in a circular ring-shaped manner.

5. Grinding plate according to claim 3 or 4, characterised in that a sealing flange (36) running round at the edge is provided.

6. Grinding plate according to one of claims 1 to 5, characterised in that fastening holes (30 - 32) traversing the structure of the plate are provided, which have a smaller diameter in the plate (23) on the top side than in the plate (24) on the underside, that the plate (23) on the top side is drawn upwards, out of the plane of the plate, in the region of its openings (32), and that the top side of these upwardly drawn regions is essentially free from the seating layer (34).

7. Grinding plate according to one of claims 1 to 6, characterised in that the plate (23) on the top side is bordered, along its edge, by the material of the seating layer (34).

8. Grinding plate according to one of claims 1 to 7, characterised in that the seating layer (34) is formed from the same material as the plate (24) on the underside and is in one piece with the latter.

9. Grinding plate according to one of claims 1 to 8, characterised M that the plate (24) on the underside and the seating layer (34) are formed from a homogeneous foam.

10. Grinding plate according to claim 9, characterised in that the foam is formed from polyurethane foam.

11. Any of the grinding plates for a hand-held electric tool with dust extraction substantially as herein described with reference to the accompanying drawings.