Metal tools and implements – making – Saw-making or furbishing device or machine – Sharpening and gumming
Reexamination Certificate
1999-12-02
2001-12-25
Watts, Douglas D. (Department: 3724)
Metal tools and implements, making
Saw-making or furbishing device or machine
Sharpening and gumming
C076S037000, C076S041000
Reexamination Certificate
active
06332375
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application claims the priority of German Application No. 198 55 773.6 filed Dec. 3, 1998, which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
The invention relates to a saw blade sharpening machine provided in particular for saw blades having hard-metal inserts.
In circular saw blades the teeth have to be laterally set off relative to the planar saw blade faces. Such an offset may be obtained by a setting of the teeth or a widening thereof, particularly in the region of the tooth face. Such a widening process is used in particular for saw blades having hard metal inserts. Each tooth carries at its leading side a hard metal piece on which the cutting edges of the tooth are formed. The frontal, forwardly-oriented edge face of the hard metal piece constitutes the tooth face, while its opposite, lateral surfaces define the tooth flanks. The principal cutting edge is defined between the tooth face and the tooth land. In many instances, in manufacturing or sharpening a saw blade, however, not only the principal cutting edge has to be provided or restored but also, the tooth flanks must be given a defined shape.
German Offenlegungsschrift (application published without examination) No. 42 44 180 discloses a grinding machine for the bilateral sharpening of tooth flanks of saw blades provided with hard metal inserts. The grinding machine has two grinding heads, each having a driven grinding disk supported for rotation about an axis. The axes of rotation of the two grinding heads are oriented parallel to one another. Each grinding head is supported on a linear guide whose direction of guidance forms an acute angle with the rotary axis of the grinding spindle. The guiding directions of the two linear guides determine the feed directions with which two sleds are simultaneously advanced to thus simultaneously grind both flanks of the tooth. The two guides are, in turn, carried by guiding sleds, by means of which the grinding heads are adjustable in a direction transverse to the saw blade. Both sleds are driven by a joint threaded spindle and are adjustable so that upon rotation of the threaded spindle the sleds are moved towards or away from one another.
The above-outlined conventional construction requires an accurate alignment of the saw blade with respect to a desired central plane. Such an arrangement may lead to problems particularly when the grinding machine is changed over to saw blades having different blade thicknesses.
German Patent No. 41 20 567 discloses a machine for a multi-stage machining of circular saw blades. The machine has a first grinding device provided with two grinding disks for the tooth flanks and a facing second grinding device having a grinding disk for the tooth land. The two grinding devices may be adjusted independently from one another. The grinding device for grinding the tooth flanks is designed such that the tooth flanks are simultaneously ground and the desired free tooth flank angle may be set according to requirements. The grinding disks are movable back and forth radially of the saw blade with a center sleeve by means of a piston-and-cylinder unit for positioning the grinding disks relative to the tooth flanks.
German Patent No. 41 13 854 shows a similar grinding machine for sharpening-saw blades. This machine too, has a grinding head with two grinding disks supported such that their rotary axes are parallel to one another. The grinding disks are used mainly for grinding the tooth land. The distance between the grinding disks is fixed. The two rotary shafts are supported in a rigid holder which may be pivoted about a pivot axis lying in the plane of the saw blade and which may be displaced in three mutually perpendicular directions. This construction is not adapted for the simultaneous grinding of both tooth flanks of one tooth.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an improved saw blade sharpening machine which may be adapted in a simple manner to different tooth shapes and tooth sizes.
This object and others to become apparent as the specification progresses, are accomplished by the invention, according to which, briefly stated, the saw blade sharpening machine includes a receiving and positioning chuck assembly for setting a saw blade in a grinding position in a plane corresponding to a main saw blade plane; and a grinding device which has a first and a second grinding head for grinding opposite tooth flanks of a saw tooth of the saw blade and an arrangement for moving the first and second grinding heads independently from one another towards and away from the saw blade plane in a direction perpendicularly thereto.
Thus, the saw blade sharpening machine has a chuck assembly for receiving and positioning the saw blade by tightly clamping the saw blade in the grinding position. After completing the grinding work on one tooth or several teeth, the chuck assembly rotates the saw blade by one tooth division and again firmly clamps the saw blade in the successive working position.
According to the invention at least one work station has a grinding device provided with two grinding heads which are movable independently from one another transversely to the plane of the saw blade. For the displacement of the grinding heads displacing or driving devices preferably formed as numerically-controlled shafts (NC-shafts) are used. When the grinding disks of the two grinding heads are simultaneously in engagement with a tooth of the saw blade, the grinding motions of the two grinding heads may be controlled independently from one another. As a result, different special tooth shapes may be ground, and thus the saw blade sharpening machine is not configured specifically for particular tooth types. For example, tooth flanks may be ground which alternatingly project laterally from the saw blade plane to different distances, or saw blade teeth may be ground where wider teeth alternate with narrower teeth. Further, the saw blades may be of uniform or non-uniform pitch. The axial thickness of the saw blade to be worked and thus the position of the central plane of the saw blade have only a subordinated role. The two grinding heads provided for grinding the tooth flanks may be separately moved to the desired respective positions. Such a feature permits a high-diversity use of the saw blade sharpening machine even in case of unusual tooth shapes and alternating tooth sizes. The grinding disks may be moved along very complicated curves by numeric control.
Further, if required, a feed motion transversely to the saw blade plane may be effected so that with relatively few setting axes and unitary grinding disks different tooth shapes and particularly different free angles at the tooth flanks may be produced. The free angles may be obtained by superposing a feed motion oriented transversely to the saw blade plane with a further motion of the respective grinding head.
If required, the grinding heads may be arranged for a linear displacement radially to the saw blade or tangentially to its circumference. For such displacements preferably NC-shafts are used, whereby a complete computer control of the grinding motion is possible. As a result, for the two grinding heads essentially any desired motion curve may be obtained by providing a total of four displacement shafts: for the motion of the grinding heads transversely to the blade plane each grinding head has its own, separate displacement shaft, whereas for the radial and tangential motions the two grinding heads have common displacement shafts. By combining the motion of the two grinding heads in the radial direction and in the tangential direction in a single NC-shaft each, the required setting devices are reduced to a low number, resulting in a clear arrangement, a simple construction and a superior grinding accuracy. In particular, none of the grinding heads have more than three sequential setting possibilities.
In addition to the grinding heads for the tooth flanks, one or more grinding heads for a separate grinding of the tooth la
Motzer Willi
Randl Johann
Kelemen Gabor J.
Venable
Walter AG
Watts Douglas D.
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