Patent Application
20230058157
This U.S. patent application claims priority to German patent application no. 10 2021 121 577.3, filed Aug. 19, 2021, the entire contents of which is incorporated herein by reference in its entirety.
The present invention relates to a device for grinding saw teeth tipped with hard metal, and to a corresponding method.
In chip removal, hard metal-tipped saw blades and saw bands are of high economic significance and are used expansively. In the trade, electrical saber saws operated with two hands are often used for perpendicular cuts since the hard metal-tipped cutting edges thereof make them suitable for cutting through tree roots in the ground, for disassembling structural components, for cutting through metal by fire fighters and other rescue organizations, as well as for cutting through metals. However, such saw blades and saw bands are also used in the industry for machining metals, plastics or wood. Correspondingly high demands are made on the precision of the tooth geometries, which therefore cannot be produced with the required precision using normal milling processes.
Hard metal-tipped saw blades as well as bands have a large variability with respect to the tooth width and the tooth geometry. They are initially made from a blank in that a metal band is unwound from a coil, optionally turned and straightened. Raw teeth are milled into this metal band and hard metal pins are subsequently welded on in the transition area between the future tooth face and the future tooth back. These hard metal pins are then ground to size in a grinding machine, for the purpose of which diamond grinding wheels are commonly used. After this operating step, tooth face and tooth back are at the final dimension. Depending on the tooth pitch and wedge angle to be produced, a corresponding diamond grinding wheel is used for this purpose. Subsequently, grinding of the two side surfaces of the future saw band takes place, optionally followed by a cutting to the desired length of the finished saw blade or band. The unwinding of the blank from the coil as well as the further operating steps typically follow in a timed manner, in any case within those operating steps with which a hard metal-tipped saw blade/saw band to be manufactured is processed continuously. Here, if necessary, buffer paths between the individual processing stations (machines) have to be planned if the timing cannot be maintained throughout the entire manufacturing line.
The correct grain of the grinding wheels, adapted grinding parameters, as well as an optimal grinding pressure are important parameters for the grinding process on the tooth. Due to the high precision required, it was previously known to use corresponding grinding machines, which in each case process a hard metal-tipped tooth of a saw blade with respect to tooth face and back by means of grinding. Here, the manufacturing time per tooth is usually several seconds because the hard metal layer thickness to be removed often cannot be removed in a single infeed process of the grinding wheel. It is thus known to use a plurality of such processing machines in order to be able to simultaneously process a plurality of bands.
From DE 35 37 059 A1, a method and a device for grinding the teeth of saw blades and saw bands is known, comprising a mechanism for fixing and stepwise advancing a plurality of saw bands which are pressed by a movable gripping claw against a fixed gripping claw, wherein a grinding wheel is movable over the saw bands and grinds teeth of the saw bands.
Also, known from CH 701519 A2 is a device and a method for processing metal bands into saw bands. For this purpose, the device has several reels by means of which the metal bands are brought together to form a stack and are fed into the device in a compressed state. Various clamping and push-down devices are provided in the device, which guide the metal bands rigidly along an axis in the device, where the metal bands are processed by a grinding wheel.
From DE 101 21 370 A1, a grinding machine for grinding teeth of hard metal-tipped saw blades is known, comprising a grinding head with two grinding spindles, each of which has at least one grinding wheel, each grinding spindle being associated with a saw blade.
From WO 96/05931 A1, in addition to a saw blade and a saw tooth, a method for machining a single saw blade is known, in which several teeth in the saw blade are processed simultaneously, and a grinding device capable of doing this.
The present invention has the object of specifying a more efficient device and a more efficient method for grinding teeth.
The object relating to the device is achieved by means of a device for grinding pre-milled and hard metal-tipped teeth of saw bands, comprising a feed device for feeding a temporary workpiece in a timed manner, wherein the temporary workpiece is formed from a plurality of saw bands which are parallel to one another, further comprising a clamping device which clamps the plurality of saw bands against one another, further comprising a grinding unit for simultaneously grinding a plurality of teeth, wherein the grinding unit comprises a grinding wheel with a plurality of grinding profiles, wherein the grinding unit grinds both the tooth backs and the tooth faces to the final dimension in exactly one feed movement. According to the invention, the saw bands are pre-milled and provided with hard metal pins at the tooth tips thus produced, which pins are in particular only attached to the tooth tips but are not pre-machined in a substantial shaping manner by a grinding or milling device. The provision according to the invention of a plurality of grinding profiles on a grinding wheel, in particular a roller-shaped grinding wheel having a multiplicity of tooth face grinding profiles and tooth back grinding profiles, has the highly advantageous result that a block forming a temporary workpiece is made up of a multiplicity of parallel and axially aligned saw bands can be processed simultaneously, thus that a plurality of teeth of a saw band, which in particular directly succeed one another in the axial direction, can be machined simultaneously, wherein the grinding wheel also processes the teeth of the saw bands which are parallel and adjacent to this saw band, of the temporary workpiece. In this case, only one infeed movement of the grinding wheel is required before both tooth back and tooth face are to size. The final dimension according to the invention is to be understood in this context as meaning that the saw bands of the workpiece are each ready for use by an end user and accordingly do not require further regrinding. According to the invention, infeed is understood to mean the grinding movement of the grinding unit, thus, in particular, the linear movement of the grinding unit, during which at least part of the workpiece to be processed is processed. The feed movement is understood to mean the movement by which the workpiece is displaced, in particular linearly, within the device, so that after the feed movement a different part of the workpiece is arranged below the grinding unit for processing than before the feed movement. According to the invention, before a feed movement and after a feed movement, the grinding unit is preferably first pivoted over the workpiece so that the grinding unit is brought closer to the workpiece, and/or a subsequent adjustment of the grinding position is provided so that the grinding unit is arranged relative to the workpiece in such a manner that the teeth of all saw bands are ground over the entire width of the workpiece by a particularly purely linear feed movement over the workpiece. The clamping device ensures that the teeth of the plurality of bandsaw blades, which are parallel to each other, are produced with the same manufacturing quality. Although this requires a longer processing time per temporary workpiece, the multiplicity of simultaneously produced teeth according to the invention results in a significantly shorter manufacturing time per tooth. For this purpose, at least one clearance is provided in at least one, and in particular in all, grinding profiles, which clearance is arranged in particular on the grinding profile in such a manner that it preserves the tips of the teeth during an infeed movement of the grinding unit. The clearances are in particular rounded recesses which do not impair the stability of the grinding unit and take into account the pivot movement of the grinding unit. According to the invention, the clearance is arranged in an area of the grinding profiles which is located at the tooth tip when the grinding unit is in the use state. For this purpose, the clearance is arranged and shaped according to the invention in such a manner that not only is a tooth tip not damaged due to the clearance after an infeed movement, but also both the tooth face and the tooth back remain ground and unimpaired over their entire length, i.e. in particular up to the tooth tip. For this purpose, it has been established according to the invention to arrange the clearance in the area of the tooth tip in the direction of the tooth face, so that the tooth tip in the area of the tooth back is not damaged while the tooth tip in the area of the tooth face is completely ground down to the desired dimension.
In an embodiment of the device, it is provided that it comprises a push-down unit and/or a timing unit and/or a cutting unit. The push-down unit ensures that all tooth backs have the same height above the tooth base, the timing unit advantageously ensures that each temporary workpiece is guided through the device at the correct cycle time, and the cutting unit provides for the cutting of saw bands to be manufactured to the final dimension, if saw blades are to be created. For this purpose, the timing unit is preferably formed by an in particular conical engagement mandrel which simultaneously engages in correspondingly shaped recesses of each saw band.
In an embodiment of the invention, it is further provided that it comprises spacers, preferably band-shaped spacers which can in particular be inserted between two adjacent saw bands of a workpiece, particularly preferably segment-shaped spacers which are arranged in the clamping device in a stationary manner. By means of this advantageous embodiment it is achieved that the hard metal pins which optionally protrude beyond the thickness of the saw band do not result in a negative impact on the processing of the adjacent saw band in the temporary workpiece. Here, the thickness of the spacers preferably corresponds to at least twice the tolerances of the length of the hard metal pins. For this purpose, the spacers are in particular band-shaped spacers, preferably rotating but, according to the invention, preferably segment-shaped spacers, which are arranged in the clamping device in a stationary manner.
Finally, it is advantageously also provided that the device combines 2 to 80, in particular 5 to 60, preferably 20 to 40 metal bands to form a temporary workpiece.
The object relating to the method is achieved by means of a method for grinding hard metal-tipped teeth of saw bands, comprising the steps of: -clamping a plurality of parallel saw bands, which are aligned axially to one another, against one another to create a temporary workpiece, -simultaneously grinding a plurality of tooth backs and tooth faces of the temporary workpiece in exactly one infeed movement,—further transporting the processed temporary workpiece and re-clamping to create a new temporary workpiece. The simultaneous grinding according to the invention of a multiplicity of raw teeth of a bundle of individual saw bands along an axial section of these saw bands highly advantageously leads to very short tooth processing times. During a processing time of several minutes of the multiplicity of raw teeth of the temporary workpiece, significantly more than 1,000 teeth are often completed, depending on the tooth geometry to be manufactured.
In an embodiment of the method, it is provided that it further comprises a method step after the step of simultaneously grinding a plurality of tooth backs and tooth faces in only one infeed movement, after which the remaining tooth backs and tooth faces of the temporary workpiece are ground in further infeed movements. This method step is particularly necessary for particularly long saw bands whose length exceeds the length of the corresponding side of the grinding unit. Thus, the length of the grinding unit does not necessarily have to correspond to that of the saw bands to be manufactured. According to the invention, it is possible to move the grinding unit or the workpiece itself between the grinding processes on two areas of a temporary workpiece in such a manner that in a next infeed movement, the grinding unit processes an unprocessed area of the workpiece.
In one embodiment of the method, it is provided that it further comprises one or more of the following steps:—pre-milling of raw teeth in desired areas of the metal band,—unwinding a plurality of metal bands, each comprising pre-milled raw teeth and welded-on hard metal pins, from a coil in each case,—turning and aligning the respective metal bands,—inserting spacers between two adjacent metal bands,—pushing down a temporary workpiece during grinding,—winding up a plurality of processed metal bands to form a coil in each case.
In one embodiment of the method it is provided that it comprises a step of cutting processed the metal band to length instead of winding it up.
The invention will be described in an exemplary manner in a preferred embodiment with reference to a drawing, wherein further advantageous details of the figures are apparent from the drawing. Functionally identical parts are provided with identical reference numerals.
In detail, the figures of the drawings show:
In
According to the invention, the clearance 15 is designed in particular in such a manner that both the tooth back 27 and the tooth faces are ground in only one infeed movement and the tooth tip remains intact. For this purpose, the clearance 15 has an area which, in a state applied to the tooth tip, runs parallel to the tooth back 27 but does not rest against it. This allows a straight cut of the tooth back 27 and a clear tooth tip without any roundings. The entire tooth face 26 is ground over its entire length despite the clearance since the grinding wheel 8 is designed as a roller 10 and thus various angular sections of the grinding wheel 8 come into contact with the tooth face 26 during an infeed movement. For the reasons mentioned, the clearance allows simultaneous processing of the tooth backs 27 and the tooth faces 26 by only one infeed movement.
Depending on the different tooth geometries to be manufactured, in particular relating to the clamping angle at the tooth face and the free angle at the tooth back, the grinding unit 7 is pivoted about a corresponding angle by means of a pivoting device 20, which is arranged downstream of the base plate 19 (on which the grinding unit 7 is mounted).
The pivoting device 20 consists of a stable pivot bearing 21 comprising a high-resolution rotary encoder 22 for the exact angle adjustment as well as an NC-controlled drive 23 (pivoting movement initiated via a tooth pinion and a tooth segment) as well as an automatic fastening device 24.
To support the unwinding process of the individual coils on the inlet side, a supply device 26, which is timed with the same timing as the feed device 4, is provided to the right of the clamping device 6.
Like the feed device 4, the supply device 25 consists of a clamping unit, a guide unit and a drive unit.
The invention thus achieves tooth processing times that are a factor of 20 or more below the present processing times, even if up to several minutes of machining time are required per temporary workpiece. However, since often more than 2,000 teeth are finished here at the same time, or even more depending on the tooth geometry, the tooth processing times are correspondingly short.
In a highly advantageous manner, the grinding process according to the invention allows for high manufacturing speeds while simultaneously ensuring highest processing precision, for the purpose of which a grinding wheel and a saw band bundling had to be developed.
For this purpose, the core method according to the invention consists of the steps of clamping a plurality of parallel saw bands, which are aligned axially to one another, against one another to create a temporary workpiece, simultaneously grinding the temporary workpiece at a plurality of locations which are axially spaced apart, and further transporting the processed temporary workpiece, and re-clamping to create a new temporary workpiece. The following steps are added for a complete manufacturing process: pre-milling of raw teeth in desired areas of the metal band, unwinding a plurality of metal bands, each comprising pre-milled raw teeth and welded-on hard metal pins, from a coil in each case, turning and aligning the respective metal bands, inserting spacers between two adjacent metal bands, pushing down a temporary workpiece during grinding, as well as after the core steps of winding up a processed metal band to form a coil, alternatively cutting a processed metal band to length instead of winding it up.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2021 121 577.3 | Aug 2021 | DE | national |
