GB2405366A

GB2405366A - Hand held grinding machine tool with guard

Info

Publication number: GB2405366A
Application number: GB0417673A
Authority: GB
Inventors: Dietmar Kengeter
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2003-08-25
Filing date: 2004-08-09
Publication date: 2005-03-02
Anticipated expiration: 2024-08-09
Also published as: GB2405366B; DE10339335A1; GB0417673D0; CN100540218C; CN1590020A

Abstract

A hand-held grinding machine tool having a machine housing 12 receives a motor-driven work spindle (16 fig 2) on which a rotary grinding tool (40 fig 4) can be driveably mounted. The grinding tool is in the form of a circular grinding wheel, the circular grinding face serving as the working face. This may be wetted by liquid during grinding, by water guided through the work spindle. The work spindle is surrounded by a hollow-cylindrical guard 26 which assumes a radial spacing from the grinding wheel. The guard is constructed in two parts. The first part 28 being a flat cover arranged centrically about the work spindle and the second part 30 being a casing attached to the first part. The guard has an opening 38 to allow a hose or tube to supply liquid to the grinding wheel.

Description

HAND-HELD GRINDING MACHINE TOOL

The invention takes as its starting point a hand-held grinding machine tool according to the pre-characterising clause of Claim 1.

Hand-held grinding machine tools for wet grinding are already known particularly for stone, ceramics or concrete surfaces. These hand-held grinding machine tools were hitherto operated without guards - guards being used in operationally similar machines for dry grinding the abovementioned material surfaces, e.g. angle grinders. Guards for dry grinders could not be used here for functionally similar wet grinders because the liquid supply means, for example hoses or tubes, impeded these guards and made it impossible to mount them on the neck of the housing of wet grinding machines constructed in the manner of angle grinders.

Operating the corresponding hand-held wet grinding machine tools without a guard is disadvantageous in that the grinding liquid as well as chips and other material removed from the workpiece is dispersed or sprayed uncontrollably over the workpiece and causes the operator to become dirty or injured.

By contrast, the invention having the features of Claim 1 is advantageous in that the hand-held grinding machine tool for wet grinding can be handled in more controlled manner and the operator is not affected by dirt and chips.

As a result of the casing of the guard being axially adjustable, the guard can be adapted in each case to the dimensions of the grinding tool or to its degree of wear so that the gap between the guard casing and the workpiece can always be set to a minimum. As a result of the cover of the guard having a wide cutout for guiding through the tube for the liquid, this tube can be guided along both the right and the left side of the machine housing, enabling the machine to be adapted equally well for both left-handers and right-handers.

As a result of the casing of the guard having a C-shaped cutout, the casing can be displaced a particularly long way upwards in the axial direction until the C-shaped cutout abuts against the corresponding curved profile of the machine housing.

As a result of the cutout in the guard cover corresponding approximately to the area of a semi-circle, it is possible to use the blank of a conventional angle- grinder guard for manufacturing the guard cover.

The invention is explained in more detail below with reference to an exemplary embodiment and associated drawings, which show: Figure 1: a partial view of the hand-held grinding machine tool with guard, viewed at an angle from the above right; Figure 2: a view of the machine from the rear, with the guard facing upwards; Figure 3: a view of the machine from below, with a view of the angle-grinder guard and the driven spindle; Figure 4: a view from below of the wet grinding machine with tool and guard; Figure 5: a guard in detail; and Figure 6: the cover of the guard in detail.

The hand-held wet grinding machine tool 10 shown from the above right in Figure 1 corresponds for the most part to a conventional angle grinder for two- handed operation, whereof the oblong housing 12 has at its front end (as seen in Figure 1) a driven shaft 16 (Figure 2) which projects downwards at a right angle and on which a grinding tool 40 (Figure 4) constructed as a cup-shaped grinding body is mounted in torsion-resistant manner, said grinding tool being surrounded by a hollow-cylindrical guard 26.

Near to the guard, a water hose 20 is guided laterally on the housing 12, said water hose being fixed on the housing by means of a hose clip 21 and being guided almost as far as the driven shaft 16.

The guard 26 comprises a cover 28 which is in the shape of a circular disc and has a central circular cutout having a concentrically arranged, relatively wide, flat annular collar which acts as a clamping element 27 by means of a bent region which is freely movable within a particular range. Leading through the bent ends of the clamping element 27, there are bores through which a clamping bolt and nut reach.

By turning the nut, the clamping element 27 can be clamped to a greater or lesser extent and thus surrounds the neck 14 of the hand-held grinding machine tool 10 with a greater or lesser degree of force fit.

The outer edge of the cover 37 is bent downwards at a virtual right-angle in the shape of a bell and supports a cylindrical casing 30 on this cylindrical edge, it being possible to fix the casing on said cylindrical edge by means of a clamping screw fixed to the edge and a wing nut rotated onto said clamping screw. Here, the screw bolt passes through an elongated hole 34 in the casing 30, which can thus be fixed steplessly in any position in that it is displaceable up and down on the cover 27.

The hollow-cylindrical casing 30 has a concave cutout 36 whereof the contour is adapted to the profile of the housing 12 in the region of its vertical projection towards the housing 12. As a result, when pushed into its axially upper-most position with the concave cutout 36 against the stop, the casing 30 can be guided against the housing 12 so that, in its axial position, the lower edge can be adapted to the particular degree of wear of the grinding tool 40 for the hand-held grinding tool 10.

The cover 37 has a cutout 38 which is arranged over a region of approximately 120 with respect to the centre of the circular disc-shaped portion of the cover 28 and which, in special cases, can also be 180 so that a conventional angle-grinder guard can be used as the cover 28, at least as a semi-finished product for further processing. Here, the size of the respective cutouts 38, 36 in the cover 28 and the casing 30 is selected to be such that the hose 20 can be detached from the right-hand side of the machine housing 12 (as seen in Figure 1) and the clip 21 positioned there and can be fixed on the opposite side of the housing 12 by means of another clip so that the hand-held grinding machine tool for wet grinding with a guard can easily be changed over as required for right-handed or left-handed use.

Continuing from Figure 1, Figure 2 shows a switch 13 for starting the hand- held grinding machine tool 10 when pressed and switching it off when released. The driven shaft 16, which has a thread 15 at its free end, is clearly shown. A grinding tool 40 constructed as a grinding body having a central cutout (Fig. 4) can be pushed over the free end of the driven shaft so that the end of the thread 15 projects beyond the non-installed grinding body and this latter can be firmly clamped by a clamping - 4 nut 42 screwed onto the thread 15. On the machine side, rotating in torsion-resistant manner with the machine, a portion of the driven shaft 16 is constructed to form a holding flange 44 on which the grinding tool 40, which is clamped on the thread 15 by means of the clamping nut 42, can be supported on the rear side.

A water distributing ring 17 is supported or fixed in torsion-resistant manner on the end face of the neck 14 (Figure 3) of the housing 12, with its side which is remote from the machine flush with the plane of the annular flange 44. The water distributing ring 17 is connected in substantially radially sealed manner to the driven shaft 16 rotating with respect to the water distributing ring 17 - the water pushing through the hose 20 being in communication with a central outlet opening 24 (Figure 3) by means of a radial bore (not illustrated) in the driven shaft 16, which is arranged adjacent to the water distributing ring 17 - and enables water to pass radially through to the centre of the driven shaft 16 from the outside and distributes it evenly to a workpiece to be processed in the region of the grinding body. It is clearly possible to see the C-shaped cutout 36 in the casing, through which the work spindle 16 and the water distributing ring 17 can be seen particularly clearly with the casing 30 pushed into the axially bottom-most position.

In a view from below of the hand-held wet grinding machine tool 10, Figure 3 shows a plan view of the water distributing ring 17 and the manner in which it is mounted on the neck 14 of the housing 12 by means of screws 23. A hose fitting 22 conducts the water flowing through the hose 21 radially inwards from the outside to the driven shaft 16 and out of its central outlet opening 24. The cutout 38 in the cover, which constitutes approximately one third of the circular disc-shaped area of the cover 28, is shown particularly clearly and, if required, can be over half the size in further exemplary embodiments, enabling the use of a conventional angle-grinder guard as the cover. The angled cover edge 29 which supports the casing 30 can be seen on the cover 28.

It is shown from the size of the cutout 38 in the cover that its extent enables the hose 21 to be fixed both on the right-hand side (as in the drawing) or, if required, on the left-hand side of the machine housing 12 (not illustrated). It is therefore optionally possible for the water distributing ring 17 to be rotated and fixed with the two non-used, free openings 25 offset through approximately 30 with respect to those containing the screws 23, so that the hose fitting 22 points towards the opposite side of the housing 12 and the hose 21 can be connected there without being angled too greatly with respect to the hose fitting 22.

Figure 4 is a view from below of the hand-held wet grinding machine tool 10, showing a grinding tool 40 which, continuing particularly from the view in the preceding Figures, is constructed as a cup-shaped grinding body and can be firmly clamped on the flange 44 by means of an annular clamping nut 42. The outlet opening 24 is also shown centrally in the end of the driven spindle 16. The hand-held grinding machine tool 10 moreover has an additional handle 46 projecting laterally above the guard 26 in the radial direction for two-handed operation of the hand-held wet grinding machine 10.

Figure 5 shows an individual guard 26 with the cover 28, the clamping element 27, the collar 31 and the angled edge 29. The cutout 38 in the cover is clearly shown, its contour merging directly into the cutout 36 in the casing so that, together, both form a particularly large through opening for the hose 21.

Figure 6 shows a detail of the cover 28, with the clamping element 27, the angled edge 29 and the cutout 38 in the cover also shown in detail. A guard of this type is particularly economical to manufacture, for example by using unmachined parts used for manufacturing conventional anglegrinder guards.

Claims

CLAIMS: 1. A hand-held grinding machine tool having a machine housing

which receives a motor-driven work spindle on which rotary grinding tools can be driveably mounted, particularly grinding bodies in the form of a circular grinding wheel whereof the circular grinding face serves as the working face which may be wetted by liquid during grinding, particularly by water guided through the work spindle to the tool, characterized in that the work spindle is surrounded by a hollow-cylindrical guard which assumes a radial spacing from a grinding tool provided in the form of a grinding wheel.
2. A hand-held grinding machine tool according to Claim 1, characterized in that, on the machine side, the guard has a through opening for a hose or the like for conveying liquid.
3. A hand-held grinding machine tool according to Claim 1 or 2, characterized in that the liquid runs substantially centrally to the free end of the work spindle.
4. A hand-held grinding machine tool according to one of the preceding claims, characterized in that the guard is constructed in two parts, a first part being constructed as a substantially flat cover and being arranged substantially centrically about the work spindle and a second part which is constructed as a casing surrounding the first part in the manner of a hollow cylinder and being arranged adjustably thereon.
5. A hand-held grinding machine tool according to Claim 4, characterized in that the second part of the guard is mounted such that it can be displaced axially and fixed in position on the first part.
6. A hand-held grinding machine tool according to one of the preceding claims, characterised in that the guard has a wide opening, preferably in the radially outer region, through which a hose or tube can be guided to the grinding spindle for the supply of liquid.
7. A hand-held grinding machine tool substantially as herein described with reference to the accompanying drawings.