GB2376651A

GB2376651A - Hand-held electric sanding machine with braking rubber and abrasive medium carrier

Info

Publication number: GB2376651A
Application number: GB0213259A
Authority: GB
Inventors: Steffen Wuensch; Werner Neubert
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2000-03-14
Filing date: 2001-03-09
Publication date: 2002-12-24
Anticipated expiration: 2021-03-09
Also published as: GB2376651B; GB0213259D0

Abstract

A hand-held electric sanding machine comprises a housing containing an electric motor which, via an eccentric 13 on its rotor shaft 12, drives a sanding disc 14, a braking rubber 18 for braking the sanding disc 14, the sanding disc 14 having at its underside an abrasive medium carrier 23 made of non-rigid material, the abrasive medium carrier 23 being of a plate-shaped construction and its fastening to the sanding disc 14 being effected by means of a surface bonding means such as a hook and loop material web, which covers the underside of the sanding disc 14 and produces a surface bond with the abrasive medium carrier 23. The sanding disc 14 and the abrasive medium carrier 23 may be penetrated by mutually coaxial holes 21 for extracting dust, and on the underside of the sanding disc 14 annular webs may be formed to engage with the dust extraction holes 21 of the abrasive medium carrier 23.

Description

Hand-held electric sanding machine, m particnlar eccentric sander The invention relates to hand-held electric sanding machines as well as to abrasive medium carriers made of non-rigid material for use on sanding disks of such handheld electric sanding machines.

US-A-5018314 discloses an eccentric sander in which the abrasive medium carner comprises a rubber body fastened to the sanding disk as well as a sanding sheet, which contains the abrasive medium and is fastened exchangeably as an expendable part to the underside of the rubber body. The rubber body is clipped over the outside edge of the sanding disk by means of an annular groove, which is incorporated at the bottom of a central recess at the top surface of the rubber body remote from the sanding sheet.

DE 19708086 Al discloses an orbital sander in which the abrasive medium carrier, referred to there as the sanding plate, is of a plate-shaped construction and is fastened by means of screws to an oscillating plate. The abrasive medium carrier comprises a rigid top plate and a bottom plate of non-rigid material as well as a sanding sheet containing abrasive grains, which is fastened by means of a surface bond detachably to the bottom plate.

The present invention provides A hand-held electric sanding machine comprising a housing containing an electric motor which via an eccentric on its rotor shaft drives a sanding disk, a braking rubber for braking the sanding disk, the braking rubber being formed on the underside of the housing, the sanding disk having at its underside an abrasive medium carrier made of non-rigid material, the abrasive medium carrier being of a plate shaped construction and its fastening to the sanding disk being effected by means of a surface bonding means, which covers

the underside of the sanding disk and produces a surface bond with the abrasive medium carner.

Preferably the abrasive medium carrier is penetrated by congruent holes for extracting dust and at the underside of the sanding disk annular webs are formed, which surround in each case one dust extraction hole of the sanding disk and project axially from the latter and engage positively into the dust extraction holes of the abrasive medium carrier. By virtue of said constructional design the abrasive medium carrier is centred very precisely on the sanding disk, which helps to reduce vibrations in the machine housing.

Preferably, the surface bonding means takes the form of a hook and look material web.

In order that the invention may be well understood, there will now be described some embodiments thereof, given by way of example, reference being made to the accompanying drawings, in which :' Fig. I is a longitudinal section of an eccentric sander with an abrasive medium carrier in accordance with a first embodiment; and Figs. 2-5 are, in each case, cut away cross sections through the abrasive medium carrier in Fig. 1 in accordance with further embodiments- Referring first to Figure 1, there is shown, in longitudinal section, an eccentric sander, which is illustrated in Fig. 1 in longitudinal section as an embodiment of a

general hand-held electric sanding machine which may, for example, also be designed as an orbital sander, comprises a housing 10 containing an electric motor 11, which via an eccentric 13 fastened on its rotor shaft 12 drives a sanding disk 14. The sanding disk 14 is fastened axially to the eccentric 13 by means of a fastening screw 15 inserted into the end face of the latter and is supported against the eccentric 13 via a ball bearing 16 integrated in the sanding disk 14, while the rotor shaft 12 is supported in the housing 10 by means of a ball bearing 17. On the underside of the housing 10 directed towards the sanding disk 14 a braking rubber 18 for braking the sanding disk 14 is formed in such a way that it protects the housing 10 at its greatest diameter from damage. To reduce the cost of manufacture, the electric motor 11 is designed without longitudinal insulation, without an overwound collector, with an unbalanced rotor and a non-fed-in armature winding as well as with a smooth rotor shaft 12 without shoulders or centring. To guarantee the prescribed protective insulation, the fastening screw 15 is covered by a cap 19, which is held captive in the sanding disk 14 and may be only destructively removed. For dust extraction, a fan 20 is fastened to the rotor shaft 12, which fan takes in air from the underside of the sanding disk 14 through dust extraction holes 21 provided in the sanding disk 14 and feeds it to an air discharge adaptor 22, to which a dust collecting filter is usually connected. The dust extraction holes 21 are arranged mutually offset by identical angles at circumference on a separating circle. Each dust extraction hole 21 is in said case surrounded by an annular web 27, which projects axially at the underside of the sanding disk 14.

For sanding workpieces a plate-shaped abrasive medium carrier 23 designed as an expendable part is used, which is fastened detachably to the underside of the sanding disk 14. To said end, the underside of the abrasive medium carrier 23 is covered by a surface bonding means 24, e. g. a hook and loop fastening system

such as Velcro (RTM) web, which together with an opposite surface bonding

layer 25, e. g. a nonwoven, covering me one piate surface of me abrasive medium carrier 23, produces a surface bond between sanding disk 14 and abrasive medium carrier 23. Dust extraction holes 26 are incorporated in the abrasive medium carrier 23 in the same manner as in the sanding disk 14 and, when the abrasive medium carrier 23 is correctly mounted onto the sanding disk 14, are situated coaxially with the dust extraction holes 21 in the sanding disk 14.

In the embodiment of Fig. 1 the abrasive medium carrier 23 comprises a backing layer 28, which carries the opposite surface bonding layer 25, and a sanding sheet 29, which contains the abrasive medium and is detachable from the backing layer 28 and is fastened via a surface bond detachably to the side of the backing layer 28 remote from the opposite surface bonding layer 25. In said case, the resistance to peeling of the surface bond between backing layer 28 and sanding sheet 29 is lower than the resistance to peeling of the surface bond between abrasive medium carrier 23 and sanding disk 14 so that, when the worn-out sanding sheet 29 is exchanged, the abrasive medium carrier 23 is left clinging to the sanding disk 14 and is not simultaneously pulled off. The surface bond between backing layer 28 and sanding sheet 29 is effected by means of a Velcro (RTM) web 30, which covers the sanding sheet 29, and a counterpart web 31, e. g. velour or felt, which covers the backing layer 28, or vice versa. The abrasive medium carrier 23 is manufactured from non-rigid material and projects markedly beyond the sanding disk 14 so that, as the abrasive medium carrier 23 wears out, the hard sanding disk 14 is prevented from striking laterally against the workpiece. To optimise sanding processes, the abrasive medium carrier 23 is stocked in different styles of material, e. g. soft, extra-soft or hard. To denote said degree of softness or hardness of the abrasive medium carrier 23, the opposite surface bonding layer 25 made e. g. of velour is of a coloured design, wherein e. g. the colour red is chosen for a soft

abrasive medium carrier 23, the colour white for an extra-soft and the colour black for a harder abrasive medium carrier 23.

In Figs. 2-5 further embodiments of an abrasive medium carrier 23 are illustrated diagrammatically in a cutout manner.

In the case of the abrasive medium carrier 23 shown in Fig. 2, abrasive grains are contained throughout the material which also simultaneously realizes the opposite surface bonding layer for producing the surface bond relative to the abrasive medium carrier 23. For said purpose, the abrasive medium carrier 23 preferably takes the form of an open-cell nonwoven containing abrasive grains.

In Fig. 3 the abrasive medium carrier 23 is inseparably composed of two layers 32,33, which contain abrasive grains and are of differing granularity. Here too, an open-cell nonwoven containing abrasive grains may be used for each layer so that by pressing the abrasive medium carrier 23 against the surface bonding means 24 in each case the surface bond is produced.

In the embodiment of Fig. 4, the abrasive medium carrier 23 has a backing layer 28, e. g. ofmicrocellular rubber, as well as a layer 32, preferably of a nonwoven, which contains abrasive grains and is applied non-detachably to the backing layer 28. At its top side remote from the layer 32 containing abrasive grains, the backing layer 28 is provided with the opposite surface bonding layer 25.

In the embodiment of Fig. 5, a layer 32,33 containing abrasive grains is applied non-detachably to each side of a backing layer 28, wherein the two layers 32,33 are of differing granularity. The two layers 32,33 may be realized likewise by an open-cell nonwoven containing abrasive grains so that, when the abrasive medium

carrier 23 is mounted by one or the other layer 32,33 onto the underside of the sanding disk 14, the surface bonding means 24 provided there effect a surface bond with the abrasive medium carrier 23. Depending on the application, either the coarser-grained layer 33 or the liner-grained layer 32 of the abrasive medium carrier 23 may be used to sand the workpiece.

Reference is made to British Application No. 0105861.9 from which the present application has been divided out.

Claims

Claims 1. A hand-held electric sanding machine comprising a housing containing an electric motor which via an eccentric on its rotor shaft drives a sanding disk. a braking rubber for braking the sanding disk, the braking rubber being formed on the underside of the housing, the sanding disk having at its underside an abrasive medium carrier made of non-rigid material, the abrasive medium carrier being of a plate shaped construction and its fastening to the sanding disk being effected by means of a surface bonding means, which covers the underside of the sanding disk and produces a surface bond with the abrasive medium carrier.
2. A hand-held electric sanding machine according to claim 1, wherein the sanding disk and the abrasive medium carrier are penetrated by mutually coaxial holes for extracting dust and on the underside of the sanding disk annular webs are formed, which surround in each case one dust extraction hole of the sanding disk and project axially from the latter to engage positively into the dust extraction holes of the abrasive medium carrier.
3. A hand-held electric sanding machine according to claim 1 or claim 2, wherein the surface bonding means on the sanding disk takes the form of a hook and loop material web, which forms a surface bond with an opposite surface bonding layer which is disposed on the abrasive medium carrier.
4. A hand-held electric sanding machine according to claim 3, wherein the abrasive medium carrier comprises a backing layer, which carries the

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opposite surface bonding layer, and a sanding sheet, which contains the abrasive medium and is detachable from the backing layer and between the backing layer and the sanding sheet there is a surface bond, the resistance to peeling of which is lower than the resistance to peeling of the surface bond between sanding disk and abrasive medium carrier.
5. A hand-held electric sanding machine according to claim 4, wherein the surface bond between sanding sheet and backing layer is produced by means of a hook and loop material web, which covers the sanding sheet, and a counterpart web which covers the backing layer, or vice versa.
6. A hand-held electric sanding machine according to claim 5, wherein the counterpart web is formed from velour or felt
7. A hand-held electric sanding machine according to claim 3 or claim 4, wherein the surface bonding layer is formed from velour or felt.
8. A hand-held electric sanding machine according to the preceding claim, wherein the electric sanding machine is an eccentric sander.