Manually driven machine

Details Manually driven machine Manually driven machine

1999-02-01

2000-11-21

Rachuba, M.

Cutlery

Cutting tools

Saw

30337, 30342, 83666, 8369841, B23D 4516, B24B 4500, B27B 532

Patent

active

061485268

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The invention relates to a handheld machine tool according to the generic part of claim 1.
A handheld grinding tool known from DE-OS 44 21 480 carries a grinding disk on its driven shaft between two clamping flanges. The outer clamping flange can be tightened against the grinding disk via a thread. The inner flange is supported so as to be rotatable relative to the driven spindle with low friction by means of a solid lubricant. When the outer clamping flange is rotated in the loosening direction, the inner clamping flange can easily be rotated jointly with the grinding disk. Therefore, the outer clamping flange can be loosened by slight force and the grinding disk can be exchanged easily.
This solution has the disadvantage that the outer flange tries to loosen when the grinding spindle is braked abruptly, resulting in the risk that the grinding disk will spin away from the grinding spindle with great force which leads to a corresponding risk of injury to persons in the vicinity.
Since the self-clamping effect in the prior art resulting from the fact that the clamping screw was carried along by the saw blade could be so great that the clamping screw could not be loosened manually but only by means of a tool, it was always necessary to bring along a tool and, in most cases, to use it for changing the saw blade. This was accordingly time-consuming.
EP 0 231 500 discloses fast-clamping systems for easy detachment of grinding disks, saw blades or the like in handheld machine tools which operate satisfactorily, but which, when the tool shaft is stopped, do not automatically reduce the clamping torque in such a way that the tool can be detached easily by rotating the outer clamping flange manually.


SUMMARY OF THE INVENTION

The handheld machine tool according to the invention with the characterizing features of claim 1 has the advantage that when the tool shaft is stopped the outer clamping flange or clamping pin can be easily loosened by hand without additional tools. Due to the fact that the clamping mechanism which automatically loosens and tightens is arranged in the interior of the handheld machine tool, it cannot be lost and is protected against soiling by dust and chips. Further, it is possible to use an inexpensive mass-produced or standard part as a clamping screw or outer clamping flange.
Due to the fact that the clamping mechanism is substantially formed of a pair of disks with rolling bodies arranged therebetween which are held in a determined position by a torsion spring or leg spring, it is especially easy to assemble as a structural component group.
Assembly effort is reduced in that the clamping mechanism can be fitted in a preassembled manner as a constructional unit with the drive pinion for the tool shaft.
Due to the flat head of the head screw and the especially flat outer flange, there is no reduction in the depth of cut when making miter cuts of more than 45.degree. compared with straight cuts because, in spite of the inclined position of the saw shaft, there is no danger of the axially outermost portion of the head screw or of the outer flange striking against the workpiece before reaching the maximum cutting depth for straight cuts.
Due to the fact that the saw shaft bearing is arranged on the outer circumference of the sleeve region of the outer disk, particularly large bearing dimensions can be selected. A large needle bearing of this kind has improved wear behavior compared with needle bearings of comparatively smaller dimensions.
The time expended for changing saw blades is consistently reduced in every case. Further, the previous risk that the saw blade would accidentally detach from the saw shaft in the event that the saw shaft stops abruptly is eliminated.
A further advantage of the invention consists in that the cavities in the pair of disks can be contoured in such a way that the rolling bodies pass through a perceptible pressure point after which the clamping torque ceases to increase. This facilitates handling of the clamping device because the ope

REFERENCES:
patent: 2586530 (1952-02-01), Godfrey
patent: 5107737 (1992-04-01), Tagliaferri
patent: 5447086 (1995-09-01), Wittmaier et al.

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