Cutting – With work immobilizer – Work-stop abutment
Patent
1995-01-04
1996-10-22
Peterson, Kenneth E.
Cutting
With work immobilizer
Work-stop abutment
8352218, 83581, B26D 701
Patent
active
055666035
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a double-sided miter box for machine tools, in particular for panel saws, comprising two contact rails, which can be moved relative to the driven tool and which are connected to one another, so as to enclose a right angle between them, and which are both mounted pivotably about a rotation axis disposed on an angle bisector near the tool, as well as an electrical measurement transducer for measuring and a display for indicating the pivoting angle of the contact rails relative to a tool plane.
Such miter boxes are mainly used for cutting at an angle wooden or plastic boards and laths on panel saws. Due to the double sided design, workpieces of different widths can easily be cut, so as to form a miter in such a way that the cut surfaces have the same lengths (German Patent 236 451).
To adjust the pivoting angle and thus the cutting angle, the prior art uses indicator scales and electrical measuring systems, the latter, for example, in the form of a rotary potentiometer disposed near the rotation axis. The pivoting angle is sensed mechanically and operation is effected by means of a gear, which steps up the rotation. This system has the disadvantage that a high accuracy of fit is relatively expensive to attain and that the mechanical parts are rather sensitive.
In some cases, the length is also adjusted for adjusting a suitable cutting angle. This is done by moving contact flaps on the contact rails. The difficulty then arises that the distance between a contact flap and the saw blade changes while the pivoting angle is being adjusted. This is due to the circumstance that the rotation axis of the contact rails is disposed at a distance from the plane of the tool. The distance measuring systems, which are usually situated at the contact rails for adjusting and indicating the distance of a contact flap from the saw blade, consequently are only suitable for indicating the true distance for a particular pivoting angle. As a result, the correct length of the workpiece at different miter angles can be obtained only by manually moving a contact flap on the basis of trial and error.
It is consequently an object of the invention to specify a miter box such that the pivoting angle can be measured and indicated easily and reliably and such that workpieces of different lengths can be produced simply and quickly for different pivoting angles.
With a miter box of the type mentioned in the introduction, the inventive solution of this problem is that the electric measurement transducer consists of a magnetically coded measuring tape, which is disposed about the rotation axis along a graduated circle, and of a sensor, which senses the measuring tape without contact, the value measured by this sensor being indicated on the display as an angular measurement of the pivoting angle.
The electrical measurement transducer of an inventive miter box has no mechanical elements that are prone to trouble, and consequently is especially reliable. Furthermore, no step-up gear is needed to increase the resolution, since, by means of a coded measuring tape disposed along the graduated circle, an especially accurate measurement is achieved and the accuracy can be increased by enlarging the radius of the graduated circle. Because the measuring tape is sensed by the sensor without contact, wear phenomena are avoided.
The magnetically coded measuring tape advantageously is attached along the graduated circle, to a surface extending perpendicularly relative to a plane stretched between the contact rails, because the measuring tape, which usually has the form of a flat, flexible strip, can be laid very easily and without mechanical bending stresses on a graduated circle and thus is protected against depositions of dust.
An advantageous embodiment of a miter box with a protrusion thereon, said protrusion being non-pivotable with respect to the tool plane, is one wherein the display and the sensor, which senses the measurement tape, are disposed at one end of the protrusion. Because of the small distance, the display can easi
REFERENCES:
patent: 4158320 (1979-06-01), Kay
patent: 4459750 (1984-07-01), Affa
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