Cutlery – Cutting tools – Saw
Patent
1993-07-09
1995-07-11
Seidel, Richard K.
Cutlery
Cutting tools
Saw
30276, 302984, B27B 538
Patent
active
054309441
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to an electric hand-operated rotary machine tool, in particular a hand-operated circular saw.
In such hand-operated rotary machine tools the end side of the housing hood of the machine tool advantageously serves as a standing surface for resting the machine tool when changing the rotary tool. The standing surface is constructed in such a way that the machine tool stands on it in a stable balanced state. To change the rotary tool, it is necessary to loosen a clamping screw which presses the rotary tool against a positive-engagement member which is arranged on the drive spindle so as to be fixed with respect to rotation relative thereto. In so doing, a component of the drive train--which includes the drive motor, power take-off shaft, transmission, and drive spindle--must be secured against rotation by the spindle locking arrangement.
For this purpose, in a known hand-operated circular saw of the type mentioned above, the radially projecting locking pin at the machine tool housing is manually depressed so that it projects into the locking slot and thus locks the drive spindle. The locking pin must be held down manually while loosening and tightening the clamping screw. This results in an ergonomic disadvantage when exchanging the saw blade since one hand must be used in part for actuating the spindle locking arrangement.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an electric hand-operated rotary machine tool, and in particular a hand-operated circular saw, which avoids the disadvantages of the prior art.
In keeping with these objects and with others which will become apparent hereinafter, one feature of the present invention resides, briefly stated, in an electric hand-operated rotary machine tool, particularly a hand-operated circular saw, which has an actuating slide projecting from a standing surface at a machine tool housing and supported in the machine tool housing so as to be axially displaceable, and the actuating slide is coupled with a locking pin of a spindle locking arrangement for fixing a drive spindle when changing the rotary tool, so that when the actuating slide is axially displaced until arriving behind the standing surface the locking pin is inserted into the locking slot of the spindle locking arrangement when the latter is in an aligned position.
When the electric hand-operated rotary machine tool is designed in accordance with the present invention, it has the advantage over the prior art that the spindle locking arrangement is actuated automatically when the machine tool is set down on the standing surface for changing the rotary tool. Accordingly, there is a substantial improvement with respect to ergonomics when exchanging the rotary tool in that the operator now has both hands free for loosening the clamping screw and changing the rotary tool. When the machine tool is lifted again the restoring spring automatically pushes back the locking pin and also returns the actuating slide via the coupling of the locking pin and actuating slide so that the drive spindle is unlocked on the one hand and the end of the actuating slide again projects out of the cover over the standing surface on the other hand.
According to a preferred embodiment form of the invention, the coupling between the locking pin and actuating slide can be realized in that a displacing piston arranged at right angles to the actuating slide is held in the machine tool housing so as to be axially displaceable and carries a displacing ramp extending at an acute angle to the piston axis, the actuating slide contacting this displacing ramp by an actuating surface extending at an acute angle to the slide axis. The locking pin which is arranged coaxially relative to the displacing piston is coupled with the latter via the restoring spring. The restoring spring which exerts a restoring force directed radially outward is supported on one side at the machine tool housing and on the other side at a spring disk located at the l
REFERENCES:
patent: 2539468 (1951-01-01), Pihl
patent: 2702098 (1955-02-01), Staak
patent: 2993518 (1961-07-01), Bork
patent: 4402241 (1983-09-01), Moores, Jr.
patent: 4434586 (1984-03-01), Muller et al.
Robert & Bosch GmbH
Seidel Richard K.
Striker Michael J.
Woods Raymond D.
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