BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 shows a schematic structure of a first embodiment of the inventive device;
FIG. 2 shows a schematic structure of a second embodiment of the inventive device;
FIG. 3 shows a variant of the embodiment of FIG. 2; and
FIG. 4 shows a schematic structure of a third embodiment of the inventive device.
DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1 shows a device for processing a workpiece 12 using ultrasound, which is designated in total with reference numeral 10. The device 10 consists of a first tool part 6, which is formed in FIG. 1 by an ultrasound oscillating structure 14, and a second tool part 8 which is formed by an anvil 16 which is disposed below the ultrasound oscillating structure 14. The anvil 16 is in a machine frame 18, to the arm 20 of which the ultrasound oscillating structure 14 is mounted by a carriage 24 which can be moved in the direction of the double arrow 22. The figure also shows a fixed stop 26 whose position can be adjusted in the direction of the double arrow 28. The ultrasound oscillating structure 14 has a converter 30 and an ultrasound sonotrode 32 whose working surface 34 is supported on the upper side of the workpiece 12. The anvil 16 is provided with an adjusting device 36 which is disposed in the machine frame 18. A force storage 40 formed by a mechanical spring 38, e.g. a helical spring, is mounted to the adjusting device 36, the force storage 40 bearing, in turn, a counter tool 42. The working surface 44 of the counter tool 42, which is shown as a cutting edge in the embodiment, abuts the lower side of the workpiece 12 and is located opposite to the working surface 34 of the ultrasound sonotrode 32.
The ultrasound oscillating structure 14 and anvil 16 have parallel axes, and are, in particular, coaxial to each other. The adjusting device 36 can press the counter tool 42 onto the workpiece 12 with a predetermined force, in particular, a feed force FA. This feed force FS is stored in the spring 38.
The figure also shows that the counter tool 42 is disposed in the machine frame 18 in a bearing 48, such that it can be moved in the direction of the vertical axis 46, wherein the bearing 48 has a bearing friction for damping D. The counter tool 42 has a mass m. The spring 38 moreover has a spring constant c, which results in a resonance frequency fA=f(m,c,D) for the anvil 16 which is determined from the mass m of the counter tool 42, the spring constant c of the spring 38, and damping D of the bearing 48.
FIG. 1 also shows that the carriage 24 presses onto the fixed stop 26 with a travel force Fv which can, in particular, be adjusted. The travel force Fv is thereby substantially larger than the feed force FS(Fv>>FS), such that the workpiece 12 is moved together with the counter tool 42 and the spring 38 is compressed and the force FS is stored in the spring 38.
The function of the device 10 in accordance with FIG. 1 is described below. As mentioned above, the ultrasound oscillating structure 14 is moved by the carriage 24 in the direction of the anvil 16 until the working surface 34 of the ultrasound sonotrode 32 seats on the workpiece 12. The ultrasound sonotrode 32 subsequently compresses the workpiece 12 together with the counter tool 42 in the direction of the adjusting device 36, i.e. downwards in FIG. 1, until the carriage 24 is seated on the fixed stop 26. This builds up a feed force or cutting force FS in the spring 38, by which the working surface 44 abuts the lower side of the workpiece 12 and presses the workpiece 12 onto the working surface 34 of the ultrasound sonotrode 32.
The ultrasound sonotrode 32 is subsequently put into operation such that the working surface 34 oscillates with the adjusted ultrasound, as is indicated at 50. The workpiece 12 is thereby separated and the working surface 44 of the counter tool 42 penetrates into the workpiece 12. The cutting force FS is provided only by the counter tool 42, since the ultrasound sonotrode 32 abuts the fixed stop 26.
As soon as the workpiece 12 has been separated, the working surfaces 34 and 44 temporarily contact, wherein, however, the counter tool 42 remains in this position. The counter tool 42 cannot follow the high-frequency oscillating working surface 34 of the ultrasound sonotrode 32, since the eigen frequency or resonance frequency of the counter tool 42 is substantially lower, in particular by a factor 103, than the oscillating frequency of the ultrasound sonotrode 32. For this reason, the working surface 44 remains at rest. This can be obtained through suitable selection of the mass m, the spring constant c and damping D. Since contact between the working surfaces 34 and 44 cannot be prevented, they have a hardness of at least 55 HRC, which also prevents excessive wear thereof.
In one variant, the working surface 44 of the counter tool 42 is designed not only as a cutting edge but also has a welding surface, such that the counter tool 42 can be used to both cut and weld. In this fashion, workpieces 14 that consist of several layers can be simultaneously cut and the individual layers can be welded together. This is desirable in particular for hose bag systems, wherein the individual hose bags are filled and subsequently separated.
The anvil of FIG. 2 has a cutting edge 44 and a welding edge 52, wherein the welding edge 52 is mounted e.g. to the machine frame 18. The workpiece 12 is then welded and additionally cut. The cutting edge 44 which is sensitive and must be protected is resiliently disposed.
FIG. 3 shows a variant of the device 10 in accordance with FIG. 2. The workpiece 12 is thereby also simultaneously welded and cut. The anvil 18 has welding edges 52 which are resiliently disposed in this case. The associated springs 54 have welding elements 56 that abut the workpiece 12. This variant is advantageous in that it offers a certain flexibility and adaptivity relative to the workpiece 12 and the sonotrode 32. Exact parallel orientation of the anvil relative to the sonotrode 32 is thereby no longer required. The spring force and/or spring rigidity (C) of the welding elements 56 or welding edge 52 is much larger than the spring force and/or spring stiffness (c) of the counter tool 42. Mechanical springs, such as spiral springs, plate springs, or hydraulic or pneumatic springs or springs of elastic materials such as rubber, cork or the like may be used as springs 54.
FIG. 4 shows a third embodiment of the invention, wherein the device 10 has a first tool part 6 which is formed in this case by an ultrasound oscillating structure 14, and comprises a second tool part 8, which is formed by an anvil 16 which is disposed above the ultrasound oscillating structure 14. The structure corresponds moreover substantially to that of FIG. 1.
The converter 30 and the ultrasound sonotrode 32 have a mass m. The spring 38 has moreover a spring constant c. This yields a resonance frequency fU=f(m,c,D) for the ultrasound oscillating structure 14, which is determined from the mass m of the converter 30 and the ultrasound sonotrode 32, the spring constant c of the spring 38 and damping D of the bearing 48.
Patent Application
20070251362
