GB2304407A

GB2304407A - Hand machine tool with dust extraction device

Info

Publication number: GB2304407A
Application number: GB9616898A
Authority: GB
Inventors: Klaus Wurst
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1995-08-19
Filing date: 1996-08-12
Publication date: 1997-03-19
Anticipated expiration: 2016-08-12
Also published as: CH691283A5; CN1065466C; GB9616898D0; DE19530542A1; ITMI961740A0; ITMI961740A1; GB2304407B; CN1151343A; IT1283790B1

Description

2304407 1 Hand machine tool with dust extraction device

Background art

The invention proceeds from a hand machine tool having a dust bag or filtering bag as well as from an adapter connectable to the hand machine tool for receiving a dust bag or filtering bag according to the type of claims 1 and 5.

From DE-GM 93 16 626 a hand machine tool of the described type having a dust extraction device is known, the dust bag or filtering bag of which is securely and tightly connectable to the air injection nozzle of the hand machine tool, it being impossible however for the air injection nozzle or the fan chamber of the hand machine tool to be sealed off from a possible return flow of dust and swarf. Dust and swarf therefore pass into the air injection nozzle and into the interior of the fan chamber when the hand machine tool is carried around with a full dust bag connected thereto. Upon a subsequent start-up, this may lead to jamming of the fan in the fan chamber and to blocking of the motor. This in turn may lead to burn-out of the motor winding and to serious damage to the hand machine tool or at the workplace. There is also the risk that dust and swarf which have passed into the extraction nozzle when the hand machine is stopped will, after removal of the dust bag, be hurled out into the environment when the tool is subsequently set in operation.

Advantages of the invention In contrast, the hand machine tool according to the invention and the fitting piece for receiving filtering bags or dust bags having the characterizing features of claims 1 and 5 have the advantage that when the extraction fan is switched off, 2 i.e. when the motor is switched off, the extraction nozzle and hence the fan chamber of the hand machine tool are automatically closed so that dust and swarf cannot pass back into the interior of the fan chamber or be moved counter to the dust-conveying direction, i.e. are also not hurled into the environment upon subsequent operation of the tool without a dust bag connected thereto.

When the dust bag is removed jointly with the fitting piece from the product, the fitting piece closes the inlet opening of the dust bag. The dust bag may therefore be taken away for disposal without any risk of dust escaping.

Further advantageous refinements of the invention are indicated in the dependent claims.

Drawings There follows a detailed description of an embodiment of the invention with reference to the accompanying drawings.

Of said drawings, Figure 1 is a longitudinal section of a hand machine tool according to the invention with dust bag, Figure 2 an enlarged cutout of the region according to Figure 1 which carries the dust bag, Figure 3 the view according to Figure 2 with the motor switched off and Figure 4 a three-dimensional view of the fitting piece according to the invention.

Description of the embodiment

The hand machine tool 10 shown in Figure 1 comprises a housing 11 with a handle 12, which carries a switch button 13 for operating an electric switch and has an electric connecting cable 15 emanating from its back end.

At its bottom end, the hand machine tool 10 carries a grinding disc 14 with extraction openings 16, which is drivable by a 3 motor (not described in detail) in a rotatory and gyratory manner. Disposed in the bottom region of the housing 11 in a fan chamber 20 immediately above the grinding disc 14 is a fan 18, which is drive- connected to the motor (not described in detail) and upon start-up of the motor blows the air out of the fan chamber 20 through an extraction nozzle 22, thereby producing at the underside of the grinding disc 14 a vacuum which entrains dust and swarf from the workpiece. Movement arrows 36 illustrate the direction of flow of the extraction air and extraction material.

The extraction nozzle 22 terminates at an outlet opening 24, through which the extraction material leaves the housing 11 and which is overlapped by a fitting piece 26 carrying a dust bag 28. The bag opening 30 of the dust bag 28 overlaps the fitting piece 26 in such a manner that the dust bag is secured against loss. The top region of the dust bag 28 directed towards the handle 12 carries a clip 32, into which is insertable a supporting rail 34 which is displaceably supported on the housing 11 in the region of the handle 12.

Figure 2 is an enlarged view of the region of the extraction nozzle 22. The latter is non-positively encompassed by the fitting piece 26. The fitting piece 26 comprises a front, thick-walled region 38 illustrated in a hatched manner, which has a wall thickness of around 2 to 40mm.

Adjoining the first region 38 of the fitting piece 26 is a second region 40, the outside and inside diameter of which widens towards the free end and which has a wall thickness of around 0.2 mm.

The back region 40 of the fitting piece 26, when extraction air flows through it, is held by said inflation effect in the manner of a tube directed straight along the axis of the extraction nozzle 22.

4 Figure 3 shows the view according to Fig.2 with the motor switched off and the fan 18 consequently at a standstill, with the result that there is no extraction air flowing through the extract on nozzle 22 or through the fitting piece 26. In the absence of an extraction air flow and hence of an inflation effect, the back thin-walled region 40 of the fitting piece 26 collapses in on itself and folds downwards under the effect of gravity, thereby acting as a valve flap which closes the fitting piece 26 and hence the extraction nozzle 22. As a result, neither dust nor swarf may pass from the interior of the dust bag 28 through the fitting piece 26 into the extraction nozzle 22 and the fan chamber 20. The risk of jamming of the fan 18 is therefore eliminated. Particularly during transport of the hand machine tool and in the event of shaking motions and when the motor is switched off, it is ensured that the contents of the dust bag 28 are unable to pass outwards or into the interior of the hand machine tool.

The front region of the fitting piece 26 has a collar 42, which is embraced by the bag opening 30 and which secures the dust bag 28 against loss.

Figure 4 is a three-dimensional view of the fitting piece 26, from which it is evident that the thick-walled front region 38 has an oval shape, which is adapted to the extraction nozzle 22 and verges rearwards in the direction of the back region 40 into a circular cylindrical shape. The back region 40 widens in the shape of a funnel towards its free end, which leads to a deceleration of the flow rate of the dust-laden air flowing through and prevents fine dust escaping from the dust bag 28.

The back region 40 of the fitting piece 26 forms a floppy tube which, in the absence of an inflation effect caused by the extraction air flow, collapses in on itself, folds downwards and acts as a valve flap.

The location and extent of downward folding are determined by the preselected ratio of length and wall thickness of the fitting piece.

The bottom of the dust bag is provided with a zip fastener for waste disposal purposes.

6

Claims

Claims

Hand machine tool (10) having an extraction nozzle (22), which carries a dust bag (28) or filtering bag, which with its bag opening (30) detachably encompasses the extraction nozzle (22), characterized in that the extraction nozzle (22) at its free end carries a valve (26), which closes the extraction nozzle (22) as soon as the extraction process ends and releases the extraction nozzle (22) as soon as the extraction process begins.
Hand machine tool according to claim 1, characterized in that the valve (26) takes the form of a diaphragm valve or valve flap.
Hand machine tool according to claim 1, characterized in that the valve (26) takes the form of a thin-walled tubular piece which, under its own weight, collapses in on itself and folds over in such a way that, in the absence of an extraction air flow or upon an interrupted air injection process, it closes the extraction nozzle (22) in a dust-proof manner.
4. Hand machine tool according to claim 3, characterized in that the valve (26), particularly in the form of a tubular piece, is refined into a fitting piece which is mountable onto the extraction nozzle (22) so as to be secured against accidental detachment and carries the dust bag (28) secured against accidental detachment.
Hand machine tool according to claim 4, characterized in that the fitting piece (26) is secured elastically by 7 means of frictional engagement by its inner surface on the extraction nozzle (22) and carries the dust bag (28) secured against loss in that the latter is latched, in particular over an annular bead on its outer surface.
Hand machine tool according to one of claims 1 to 5, characterized in that the valve (26) is opened by the extraction air flow and closes in the absence of an extraction air flow.
7. Fitting piece (26) for fastening to the extraction nozzle (22) of a hand machine tool according to the preamble of claim 1 and for receiving the dust bag (28), characterized in that the fitting piece at its free end carries a valve (40), which releases the extraction nozzle (22) - opened by the extraction air flow - and closes the extraction nozzle (22) in the absence of an extraction air flow.
Fitting piece according to claim 7, characterized in that its front region (38) directed towards the extraction nozzle (22) has a wall thickness of around 2 to 4 mm and its cross section is adapted to that of the extraction nozzle (22), being in particular oval, and that the back region (40) of the fitting piece (26) forms a floppy tube with a circular cross section, the wall thickness of which is less than 1 mm.
9. Fitting piece according to claim 8, characterized in that the back region (40) of the fitting piece (26) has a wall thickness of 0.1 to 0.5 mm and its diameter increases and hence widens in the manner of a funnel towards its free end.
10. Fitting piece according to one of the preceding claims, characterized in that it is made of a rubber-elastic material.
8 Fitting piece according to one of the preceding claims, characterized in that it has a predetermined folding point which lies between the back region (40) and the front region (38).
12. A hand machine tool substantially as herein described with reference to the accompanying drawings.
13. A fitting piece substantially as herein described with reference to the accompanying drawings