GB2336332A

GB2336332A - Clamp for oscillating grinder

Info

Publication number: GB2336332A
Application number: GB9907934A
Authority: GB
Inventors: Werner Neubert
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1998-04-16
Filing date: 1999-04-07
Publication date: 1999-10-20
Anticipated expiration: 2019-04-07
Also published as: FR2777488A1; FR2777488B1; GB2336332B; GB9907934D0; DE19816830A1

Abstract

A clamp for clamping an abrasive sheet 3 onto the grinding plate 1 of an oscillating grinder comprises a clamping member 25 and an adjusting screw 15. One end of the clamping member 25 is hingedly fixed to a face of the plate 1, with the position of the clamping member 25 being adjusted by rotation of the screw 15. Preferably movement of the screw 15 is limited by two axial stops 17 and 18, with the clamping member 25 being engaged between the screw-head 23 and one of these stops 17. Sponge rubber 41 may cover the part of the clamping member 25 which engages with the abrasive sheet 3. Preferably the plate 1 is at least partially hollow and comprises two symmetrical parts joined together along a plane (Fig. 3, E-E) running centrally, longitudinally and perpendicularly to the abrasive sheet 3, with the axes of rotation X-X of the screws 15 lying in this plane.

Description

2336332 1 Oscillating gi:inder

Prior art

1.

The invention relates to an oscillating grinder of the type in claim An oscillating grinder which can be driven by a motor and has an abrasive paper holding system for gripping an abrasive sheet is known from US-PS 3) 3 75 616, 'm which a locking member provided with a sprmig can be moved, with the aid of a slide, into a lifting-off position Mi relation to an opposed surface for the purpose of releasing the abrasive sheet and in which the locking member can be moved into a supporting position in relation to the opposed surface for the purpose of holding the abrasive sheet fast. This holding system consists of a number of separately mounted individual parts which have to be coordinated with one another. Also required are relatively major relocating forces parallel to the grinding plate and a relatively complicated sequence of movements for the purpose of actuating the slide, which makes it more difficult to operate the abrasive paper holdffig system.

Through EP-0558 503, a device for clamping abrasive paper fast on an oscillating grinder is known, in which there serves as a clamping member a bistable tilting over-centre mechanism which can be easily operated but consists of a leaf sprmg which is expensive to manufacture and which, in a first pivotmig position, presses the end of an abrasive paper against the grinding plate and, 'm a second pivoting position, frees the said end of the abrasive paper.

Advantages of the invention The device according to the invention havm"g the charactenismig 2 features in claim 1 has the advantage, compared with the prior art, that it guarantees a contact pressure on the ends of the abrasive paper which remains u'formly high chan i of the said abrasive paper taking place by the turning of m ging 1 1 a hand-operated clamping screw about a small angle of rotation in a converuient and smooth-running manner.

Outside the basic body of the grinding plate, the clamping screw advantageously possesses a handle which acts on a pressure piece. The pressure piece is connected to the base plate via a gripping strap which is directed towards the middle of the basic body, the said gripping strap encompassing the clampmig screw between the base plate and the handle via a slot. The handle may be constructed as a rotary knob, a toggle or a WM'g-nut; the rotary knob may also advantageously be provided with a winglike projection as a grip or a positioning aid. For better distribution of pressure, a supporting washer may be provided between the grip and the gripping strap, or else the grip itself may be provided with a foot in the vicinity of the gripping strap.

The stops may be located inside and/or outside the basic body. In this connection, it is favourable if the stops are shaped Mi the form of discs and are disposed so as to follow one another in the longitudinal direction on the end of the clamp111.111 screw and so as to be separated from one another by the threaded portion of the said clamping screw, which threaded portion is located on the basic body. Under these circumstances, a stop disc is located in the basic body at the opposite end of the clampmig screw from the handle, and prevents the clamping screw from falling out of the said basic body. The other stop disc is located outside the basic body and presses against the gripping strap, when the screw is turned mi the appropriate manner, in order to bring the pressure piece into the freeing position.

In order to ensure that the abrasive paper is held fast with um'fonn clamping pressure, the pressure piece is provided, on its side which is turned towards the web, with a friction-promoting covering or insert. The length of the 3 pressure piece is essentially equal to the breadth of the basic body. The fact that the clamping screw has to be turned, in its position, by a maximum of 180' between the clamping and releasing of the abrasive paper is advantageous. For case of fitting of the device according to the invention, the basic body is constructed in two parts (two halves) and is of hollow construction, at least 'm the vicinity of the clamping screw, the plane of separation of the two parts containing the axis of rotation of the clamping screw and being directed essentially at right angles to the basic body. The basic body advantageously consists of plastic.

Drawings The invention will be explained mi greater detail below with the aid of diagrammatic drawings of two exemplified embodiments, in which:

Figure 1 shows a longitudinal section through a first exemplified embodiment of an abrasive paper clamping device according to the invention, at the left-hand end of a grinding plate; Figure 2 shows a longitudinal section through a second exemplified embodiment of an abrasive paper clamping device according to the invention, at the right-hand end of a grinding plate; Figure 3 shows a plan view of the device according to Figure 1; and Figure 4 shows a plan view of the device according to Figure 2.

Description of the exemplified embodiments

As an individual part without the appertaining oscillating gmder, the left-hand end region, which is represented in longitudinal section 'm Figure 1, of a gnindmig plate 1 shows that a flexible, essentially rectangular abrasive sheet 4 3 is disposed on the underside 2 of the said grinding plate, wraps around an edge 6 and a sharp-edged flange 8 at the extreme left-hand end 4 of the grinding plate 1, and extends, via its end 10, on the upper side 12 of the said grinding plate 1 parallel to the original direction. The night-hand end, which is not included in the representation, of the grindmig plate 1 corresponds to a miTor-miverted design of the left-hand end and is identical, Mi principle, with the night-hand end of the grinding plate 1' according to Figure 2.

The grinding plate 1, which serves as a tool-carrier, is hollow inside, consists of plastic and is driven, so as to circulate without rotating, by the motor of the oscillating grinder for the purpose of grinding workpleces. The grinding plate 1 is joffied together from two essentially identical parts 10 1 102 (Figure 3) in a plane E-E extending longitudinally parallel to the plane of the drawing and, according to Figure 3, centrally.

Disposed near the left-hand end 4 of the grinding plate 1, 'm the upper side 12 of the latter, is a screw bearing 13 having an internal thread, in each case, for the engagement of the external thread on a threaded portion 15 of the shaft 21. The shaft 21 carries two torsion-proof, non-displaceable stop discs 17, 18 which are spaced apart axially and delimit the threaded portion 15, one stop disc 18 being seated, at the bottom, on the end of the threaded portion 15 and a rotary knob 23), which serves as a handle, being seated on the shaft 21 at the top.

Together with the threaded portion 15 and the rotary knob 23, the shaft 21 forms a hand-operated clamping screw having an axis of rotation X-X or Y-Y.

The rotary knob 23 is supported via its underside 24 on the upper side of a pressure piece 25 belonging to a springing, pivot arm-like gripping strap 26. The gripping strap 26 is injection-moulded or glued, by its night-hand side in the direction of viewing, onto the upper side of the grinding plate 1 and is elastically pivotable, by its free end, which is the left-hand end in the direction of viewing, mi relation to the upper side of the base plate 1. The gripping strap 26 engages around the shaft 21 mi a radially contact-free manner via an aperture 31 which is preferably oval or slot-like. If the gripping strap 26 is now swivelled about the axis X-X by means of the shaft 21 as a result of rotation and axial relocation of the said shaft, the shaft 21 and gripping strap 26 cannot become mutually jammed or braced against one another unintentionally. The stop disc 17 entrains the gripping strap 26 on pivoting upwards and the underside 24 of the rotaiy knob 23) on pivoting downwards, it being possible for the stop discs 17, 18 to be in one piece with the shaft 21.

The pressure piece 25 of the grippmg strap 26 is provided, on the underside. with a protruding elastic insert 41, made of sponge rubber for example, which is supported, in the location represented, on the portion 10 of the abrasive sheet 3 and presses the latter onto the upper side 12 of the grinding plate 1. As a result of the pressure and of the high degree of friction between the pressure piece 25 and the portion 10 of the abrasive sheet 3 on the one hand, and between the portion 10 of the abrasive sheet 3 and the upper side 12 of the grinding plate 1 on the other, the abrasive sheet is held in a non-dislocatable manner 'm the location represented in Figures 1 and 2. Under these circumstances, the underside of the gripping strap 26 is at a slight axial distance from the stop disc 17 and the latter is at a slight axial distance from the rim of the threaded hole 13, in order to be able to develop the maximum gripping force on the abrasive sheet 3.

In order to facilitate verification of the gdppmg or releasing position of the rotary knob 23, there is associated with the radial cam or wing 27 on the said rotary knob, in the gripping position according to Figure 1, a marking 28 on the gripping strap 26, up to which marking the wing 27 can be pivoted 'm the gripping position and away from which it can be pivoted 'm the releasing position: If the abrasive sheet 3 is to be freed or changed, the rotary knob 23) is turned towards the left by 180 0 mi accordance with the rotational direction arrow 29, until the wing 27 reaches another mark 30 located on the gripping strap 26. In this 6 position, the stop disc 18 is supported, from below or firom the cavity, against the upper side 12 of the grinding plate and prevents further rotation of the clamping screw 15, 2 1. At the same time, the stop disc 17 has lifted the gripping strap 26, and with it the pressure piece 25, oS the abrasive sheet 33 to a sufficient extent, the said stop disc being axially supported from below on the grippig strap.

The clampm'g screw, not represented, which is requu"ed for doublesided clamping of the abrasive sheet 3 on the grinding plate 1 and is disposed, in a mirror-inverted manner, at the opposite end of the said grinding plate 1 may have, depending upon the room for movement available for the wing 27, a thread which runs 'm the opposite direction to the first clamping screw 15, 21, 23, thereby resulting mi oppositely-directed rotational movements which are ergonomically favourable for the simultaneous operation of both clamping screws with both hands, so that the abrasive sheet 3 can be rapidly released at both ends 10, 11 simultaneously.

The night-hand end region of the grinding plate F, which end region is represented m longitudinal section in Figure 2 as an individual part without the appertaining oscillating grinder, shows, in a manner which is identical, m prmciple, to the exemplified embodiment according to Figure 1, that there is disposed on the underside 2' of the said end region a flexible, essentially rectangular abrasive sheet 3' which is guided round an edge 7 and a sharp-edged flange 9 at the extreme right-hand end 5 of the grinding plate 1' and extends, via its end, on the upper side 12' of the grinding plate F, parallel to the original direction.

The grinding plate F, which serves as a tool-carrier, is hollow Inside, consists of plastic and is driven, so as to circulate without rotating, by the motor of the oscillating grinder for the purpose of grinding workpleces. The grindmig plate F Is joffied together from two essentially identical parts 10F, 102' (Figure 4) in a plane E-E extending longitudinally and parallel to the plane of the drawing 7 and, according to Figure 3, centrally. In Figure 2, the plane E-E coincides with the plane of the drawing. In the vicinity of the end 5, there is located M the upper side 12' a screw bearing 14 having an internal thread, M each case, for a threaded portion 16 havm'g an external thread and two stop discs 19, 20 disposed fixedly on the end of the shaft 22 Mi each case, the shaft 22 forming M each case, together with the corresponding threaded portion 16, a clarripwig screw having an axis of rotation X-X or Y-Y, in relation to which the stop discs 19, 20 are directed essentially at right angles.

As distinct from the exemplified embodiment according to Figure 1, a gripping strap 32 is screwed or fastened M some other way, on its side which is remote from the end 5, to the grinding plate V. At that firee end of the gripping strap 32 which is located in the vicinity of the end 5, there is provided a pressure piece 33, of which that face 34 which is turned towards the abrasive sheet 3 has a structure of the ffiction covering type. A toggle 40 which can be pivoted, Mi the directions indicated by a double arrow 37, between the "OPEN" and TLOSEW positions designated by marks 35, 36 is attached, mi a manner stiff agaffist torsion, to that end of the shaft 22 which is averted from the grinding plate 1.

In the location represented, the clamping screw consisting of the threaded portion 16 and the shaft 22 is adjusted or screwed upwards, so that the stop disc 20 presses agaffist the upper side 12 of the grinding plate 1' and thereby keeps the shaft 22 from being screwed out. The gnppmg strap 32 is pressed upwards by means of the stop disc 19, and the pressure piece 33 lifted off from the folded-over portion 11 of the abrasive sheet Y. By this means, the abrasive sheet 3' can be removed and freed for changing purposes. The shaft 22 also projects through an aperture 38 in the gripping strap 32 which is shaped so as to be sufficiently large and slightly oval, so that the clamping screw 16, 22 is not impeded in its rotating movement by the pivoting movement of the gripp mig strap 32, or vice versa.

8 For the purpose of clamping the abrasive sheet 3 fast on the grindmig plate 1, the toggle 40 is pivoted towards the mark 36 in a direction designated by the double arrow 37. In the process, the clamping screw 16, 22 is screwed into the grinding plate 1 until the stop disc 19 is applied against the upper side 12 of the said grinding plate 1. At the same time, the toggle 40 presses, via its lower face 39, against the gripping strap 3-)2 and thereby presses the pressure piece 33 agamist the portion of abrasive sheet 11 and clamps it fast on the grinding plate 1.

It is self-evident that, of the devices described above in connection with Figures 1 and 2, two identical ones are used on the grinding plate 1, F, which are mounted in the vicinity of the ends 4, 5 of the said grinding plate 1, V. Under these circumstances, the clamping screws may be provided, at each end, with external threads which run 'm opposite directions to each other in each case, depending upon the room for movement available for the toggle 40.

The division of the "" ding plate 1, l' in the plane E-E is ninportant for the fitting of the device according to the invention and, mi particular, of the stop discs 18, 20 located in the said grinding plate 1, V.

In an exemplified embodiment of the invention which has not been included in the representation, the grinding plate is in one piece and is not hollow, but is instead constructed from solid material, there being provided on the outside of the grinding plate, instead of stop discs, stops which prevent the clamping screi.s from falling out of the threaded holes 13, 14.

In another exemplified embodiment of the grinding plate which is not represented, the clamping screws carry a thread which reaches as far as the handle and is more advantageous from the production engm'eenng point of view, the region of the thread located above the upper stop then being inoperative.

In a further exemplified embodiment of the invention which is not represented, the gripping straps do not extend, on their fasterning sides, over the entire breadth of the grinding plate. They may be shaped Mi the form of a V or U, 9 under which circumstances they are preferably fastened to the grinding plate via the pomit of the V or the ends of the legs of the U.

Instead of the rotary knob or of the toggle, use may also be made of a gnut. The individual features of the above exemplified embodiments can be interchanged with one another or varied mi manifold ways for the purposes of the ffivention.

Claims

Hand-held oscillating grinder having a motor-driven grinding plate (1, F) for receiving an abrasive sheet (3, J3) which can be gripped fast on the said grinding plate (1, 1) by means of a clamping device (15, 21 or 16, 22) carried by the latter, the said clamping device having a pressure piece (25 or 33)) which, at one end, is fixedly disposed, particularly 'm a hinge-Uke manner, on the uppeir side of the grinding plate (1, 1) and via which the abrasive sheet (3), 3) can be clamped against the upper side of the grinding plate (1, V), characterised in that the clamping device contains a clamping screw (15, 21 or 16, 22) which is mounted on the upper side of the grinding plate (1, 1) mi such a way as to be screwable in relation to the latter, the clamping screw (15, 21 or 16, 22) being in engagement, via its region above the grinding plate (1, V), with the pressure piece (25 or 33) mi such a way that the said pressure piece can be adjusted, when the clamping screw (15, 21 or 16, 22) is turned, so as to pivotm" a rocker- like manner in relation to the said grinding plate (1, V).
2. Oscillating grinder according to claim 1, characterised 'm that the clamping screw (15, 21 or 16, 22) is adjustable so as to be limited, preferably by two axial stops (17, 18 or 19, 20), 'm a screw bearing (13), 14), and holds the pressure piece (25 or 33) fast between its handle, which is designed as a screwhead-like rotary knob (23) or a toggle (40), and the stop disc (17, 19).
Oscillating grinder according to claim 1, characterised in that the pressure piece (25 or 33) merges into a gripping strap (26 or 32), the latter being articulated on the gnindmig plate (1, F).
4.

Oscillating grinder according to claim 3, characterised in that the 11 pressure piece (25 or 3) has an aperture (3 1 or 3 8) through which the shaft (15, 16) of the clamping screw (15, 21 or 16, 22) passes, the diameter of the handle (233 or 40) and also of the stop disc (17, 19) being greater than the diameter of the aperture (3 1 or 3 8).
5. Oscillating grinder according to claim 4, characterised mi that the handle (23 or 40) is designed as a rotary knob having at least one winglike projection (27).
6. Oscillating grinder according to one of the preceding clains, characterised M" that the clamping screw (15, 2 1; 16, 22) carries, mi each case, two stop discs (17, 18; 19, 20) between which there extends, 'm each case, a threaded portion (15 or 16) which is in threaded engagement with the screw bearing (13), 14) on the grinding plate (1, V).
7. Oscillating grinder according to claim 1, characterised in that the pressure piece (25) is provided with a friction covering (4 1) on its face (34) which is turned towards the upper side of the grinding plate (1).
8. Oscillating grinder according to claim 1, characterised in that the clamping screw (15, 21; 16, 22) is pivotable, preferably by 1.80% between end positions on the upper side of the grinding plate which are designated by markings (28, 30; 35, 36).
9. Oscillating grinder according to claim 1, characterised m that the grinding plate (1; V), which is at least partly hollow, consists of two, 'm particular symmetrical, parts which can be joined together at a p!ane of division (E- E) running centrally, longitudinally and perpendicularly to the abrasive sheet (3 - Y), 12 the axes of rotation (X-X; Y-Y) of the clamping screws (15, 21; 16, 22) being directed in the plane of division (E-E) and parallel to the longitu dinal direction of the gonffiding plate (1, 1').
10. Oscillating gninder according to claim 1, characterised in that the length of the pressure piece (25 or 3 333) is essentially equal to the breadth of the grinding plate (1, F).

A hand-held oscillating grinder substantially as herein described with reference to Figures 1 and 3, or Figures 2 and 4 of the accompanying drawing.

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