U.S. patent application number 11/715420 was filed with the patent office on 2007-11-01 for device for processing workpieces.
This patent application is currently assigned to Herrmann Ultraschalltechnik GmbH & Co.KG. Invention is credited to Gerhard Gnad, Arnold Schneider.
Application Number | 20070251977 11/715420 |
Document ID | / |
Family ID | 38442943 |
Filed Date | 2007-11-01 |
United States Patent
Application |
20070251977 |
Kind Code |
A1 |
Gnad; Gerhard ; et
al. |
November 1, 2007 |
Device for processing workpieces
Abstract
A device for processing workpieces uses ultrasound, with an
resonant system comprising an ultrasound generator, an ultrasound
sonotrode, and an anvil, wherein a workpiece is processed between
the anvil and the ultrasound sonotrode. The ultrasound generator
comprises a regulation means which has a regulation member
connected upstream of the ultrasound generator to receive a
feedback signal from the resonant system and to generate a
regulation variable which is supplied to the ultrasound generator.
A connecting point is provided between the regulation member and
the ultrasound generator, at which the regulation variable of the
regulation member is linked to a process variable from the
processing procedure.
Inventors: |
Gnad; Gerhard;
(Keltern-Weiler, DE) ; Schneider; Arnold;
(Ettlingen-Schluttenbach, DE) |
Correspondence
Address: |
DREISS, FUHLENDORF, STEIMLE & BECKER
POSTFACH 10 37 62
D-70032 STUTTGART
omitted
|
Assignee: |
Herrmann Ultraschalltechnik GmbH
& Co.KG
Karlsbad-Ittersbach
DE
|
Family ID: |
38442943 |
Appl. No.: |
11/715420 |
Filed: |
March 8, 2007 |
Current U.S.
Class: |
228/1.1 |
Current CPC
Class: |
B29C 66/9516 20130101;
B29C 66/92211 20130101; B23K 20/10 20130101; Y10T 83/8821 20150401;
B06B 1/0246 20130101; B06B 2201/72 20130101; B29C 65/08 20130101;
B29C 66/91231 20130101; B29C 66/961 20130101; B29C 66/962 20130101;
B29C 66/96 20130101; G05B 2219/45206 20130101; B23Q 15/00 20130101;
B24B 1/04 20130101 |
Class at
Publication: |
228/1.1 |
International
Class: |
B23K 37/00 20060101
B23K037/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 26, 2006 |
DE |
102006020417.4-22 |
Claims
1. A device for processing a workpiece using ultrasound, the device
comprising: an ultrasound generator; an ultrasound sonotrode
cooperating with said ultrasound generator; an anvil, wherein the
workpiece is processed between said anvil and said ultrasound
sonotrode, said generator, sonotrode and anvil forming a resonant
system; means for generating a feedback signal from said resonant
system; a regulation means having a regulation member and connected
upstream of said ultrasound generator, said regulation means
receiving said feedback signal and generating a regulation
variable; means for extracting a process variable in response to
processing of the workpiece; and connecting means disposed between
said regulation member and said ultrasound generator to link said
regulation variable to said processing variable and to subsequently
pass said regulation variable to said ultrasound generator.
2. The device of claim 1, wherein said process variable is a
processing force of said ultrasound sonotrode.
3. The device of claim 1, wherein said process variable is a
processing temperature of a tip of said ultrasound sonotrode.
4. The device of claim 1, wherein said process variable is a signal
that detects or reflects deformation of said resonant system.
5. The device of claim 1, wherein said process variable is a
predetermined signal that synchronously accompanies processing of
the workpiece.
6. The device of claim 1, wherein in said regulation means has a
PID controller.
7. The device of claim 1, further comprising a scaling element or a
proportional controller for the process variable, disposed upstream
of said connecting point means.
8. The device of claim 7, wherein said scaling element is an
adaptive system.
9. The regulation means of the device for processing a workpieces
of claim 1.
Description
[0001] This application claims Paris Convention priority of DE 10
2006 020 417.4 filed Apr. 26, 2006 the complete disclosure of which
is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] The invention concerns a device for processing workpieces
using ultrasound, comprising an ultrasound generator, an ultrasound
sonotrode, and an resonant system comprising an anvil, wherein a
workpiece is processed between the anvil and the ultrasound
sonotrode, and with a regulation means for the ultrasound
generator, the regulation means comprising a regulation member
connected upstream of the ultrasound generator, which receives a
feedback signal from the resonant system, generates a regulation
variable, and supplies it to the ultrasound generator.
[0003] The invention concerns a regulation device for an ultrasound
generator for processing workpieces, in particular, welding or
cutting them. An ultrasound generator in an resonant system
generates oscillations, using an electroacoustic converter, within
its resonance frequency, i.e. usually between 18 and 60 kHz. These
oscillations operate an ultrasound sonotrode either directly or via
a booster or converter. The ultrasound sonotrode, together with the
anvil, represent the tool for processing the workpiece.
[0004] Conventional ultrasound generator regulation means measure
certain system parameters and system signals which they obtain as
information from the electrical and mechanical resonant system.
These signals and parameters regulate the ultrasound generator.
Changes within the resonant system are thereby detected and the
resonant system is reset at the original value through suitable
algorithms. Internal system parameters and signals are e.g. the
resonant frequency, the current, the reactive current, the voltage,
the phase position etc.
[0005] The main aim of all resonant systems is to keep the
oscillation amplitude at a constant value with maximum efficiency.
Since the resonance frequency of the overall resonant system, which
consists of a mechanical and an electrical resonant circuit,
constantly changes during operation, the regulation process must be
permanently repeated and be as fast as possible. The changes or
disturbances in the resonant system are due to load changes (e.g.
force fluctuations), changes of the geometry due to heating,
fluctuations in the energy supply etc. The regulation improves with
accelerated repetition rate of the regulation process and better
adjustment of the regulation algorithm. Oscillation of the
regulation circuit must be prevented in any case. This means,
however, that the regulation parameters cannot be set at
excessively high values.
[0006] Prior art discloses analog and digital systems (DE-A-40 25
637, DE-A-44 00 210, DE-A-42 30 491, DE-A-42 08 669, EP-A-0 173 761
and U.S. Pat. No. 4,808,948). Irrespective thereof, the parameters
provided in the resonant system are the basis for regulating the
ultrasound generators. These conventional resonant systems are
disadvantageous in that very fast load changes often cause
considerable amplitude fluctuations. These fluctuations can, in
case of excess, cause the limit values of the mechanical components
to be exceeded, thereby damaging them or resulting in insufficient
welding.
[0007] It has turned out that the regulation does not react
sufficiently rapidly. This is mainly due to the system-related
parameters and signals. These change with load changes, but reach
the regulation member of the ultrasound generator with a certain
delay. This delay is mainly predetermined by the speed of sound and
the number of mechanical oscillation components.
[0008] This means, however, that the regulation member reacts to an
event under extreme conditions only when this event is over.
Keeping the oscillation amplitude constant on the basis of the
system parameters and signals is very difficult. Fast load changes
of less than 5 ms therefore produce considerable fluctuations in
the oscillation amplitude.
[0009] It is therefore the underlying purpose of the invention to
further develop a device of the above-mentioned type in such a
fashion that it reduces the amplitude fluctuations during fast load
changes.
SUMMARY OF THE INVENTION
[0010] This object is achieved in accordance with the invention
with a device of the above-mentioned type in that a connecting
point is provided between the regulation member and the ultrasound
generator, at which the regulation variable of the regulation
member is connected to a process variable of the processing
procedure.
[0011] The inventive device, in particular the inventive regulation
device, performs regulation not only on the basis of the parameters
and signals of the resonant system, but also on the basis of at
least one additional, external signal. This additional external
signal is connected to the processing procedure, but is generated
outside of the electric and mechanical resonant circuits. It is
therefore outside of the resonant system, but has a time dependence
which reflects the processing result. This additional external
signal, i.e. the processing variable is not fed into the regulation
system upstream of the regulation member, rather downstream
thereof, and does not pass through the regulation system: i.e. the
regulation variable of the regulation member is therefore
influenced.
[0012] It has turned out that very good results can be obtained
when the processing force of the ultrasound sonotrode is used as a
process variable. This processing force depends on the processing
course, but is generated outside of the electrical and mechanical
resonant circuit.
[0013] It is also possible to use the processing temperature as a
process variable, wherein the temperature at the tip of the
ultrasound sonotrode is used. It is also feasible to use a path
signal that reflects the deformation of the resonant system caused
by the process.
[0014] The regulation means that generates the regulation variable
is preferably a PID controller. Such regulation means have proven
to be useful in the past and provide excellent regulation results
in the inventive further development, wherein overswinging is
damped such that disturbances are compensated for after a minimum
time.
[0015] In a further development, a scaling element is provided
upstream of the connecting point where the regulation variable and
the process variable are connected, in particular, a proportional
generator for the process variable. This scaling element adjusts
the process variable such that the regulation variable is optimally
influenced. The value determined by a force sensor is thereby e.g.
multiplied by a factor. The process variable is thereby added to
the regulation variable or subtracted therefrom. This is effected,
in particular, via the scaling element, in particular, the
proportional controller.
[0016] It is, however, also feasible to issue an artificially
generated signal of the regulation variable which is entered
manually. This signal can e.g. simulate a force dependence or the
signal can be matched with time using an incremental generator, and
be supplied to the regulation means. This signal is also not or
only slightly influenced by the ultrasound oscillation.
[0017] In a further development, the scaling element is designed as
an adaptive system. The system may thereby be designed such that it
recognizes recurring changes, and counteracts them in advance.
[0018] Further advantages, features and details of the invention
can be extracted from the dependent claims and the following
description which describes in detail a particularly preferred
embodiment with reference to the drawing. The features shown in the
drawing and mentioned in the description and the claims may be
essential to the invention either individually or collectively in
arbitrary combination.
BRIEF DESCRIPTION OF THE DRAWING
[0019] FIG. 1 shows a diagram of the regulation process; and
[0020] FIG. 2 shows an oscillation curve of the amplitude in case
of a disturbance.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0021] FIG. 1 shows a diagram of a regulation device, in which
reference numeral 10 designates an resonant system which has an
ultrasound generator 12, a booster 14, an ultrasound sonotrode 16
and an anvil 18, wherein the ultrasound sonotrode 16 and the anvil
18 represent the tool for processing a workpiece 20.
[0022] Parameters and signals (u) from this resonant system 10 are
supplied to a regulation means 24 via a return path 22. This
regulation means 24 has a PID controller 26. The regulation means
24 generates a regulation variable (s) which is supplied to the
resonant system 10 and, in particular, to the ultrasound generator
12. The resonant system 10 with regulation means 24 forms a
regulated, electrical and mechanical resonant circuit 28, as is
disclosed in prior art.
[0023] Reference numeral 30 designates a processing procedure, in
particular, a welding process outside of the resonant circuit 28,
since it is not directly influenced by the electrical and
mechanical variables. This processing procedure 30 is connected to
a force sensor 32 which detects the course of the welding force.
The force sensor 32 determines a process variable (p) which is
supplied to a scaling unit 34. This scaling unit 34 provides a
scaled process variable (p') which is supplied to a connecting
point 36. This connecting point 36 is located between the
regulation means 24 and the resonant system 10, such that not only
the scaled process variable (p') is supplied to the connecting
point 36, but also the regulation variable (s). The connected
variables (p') and (s) are supplied to the resonant system 10 and,
in particular, to the ultrasound generator 12.
[0024] It is clearly shown that in the inventive system, a variable
that is generated outside of the resonant circuit 28, i.e. the
process variable (p), is supplied to the resonant system 10.
[0025] FIG. 2 shows the time dependence of the amplitude (A),
wherein 38 indicates a disturbance signal. In conventional systems,
the dependence of the amplitude signal 40 shows strong fluctuations
with overswinging, wherein in the inventive system, the amplitude
signal 42 is regulated much more quickly to the original value. One
can also see that the regulation frequency is shorter than in a
conventional system, in particular half.
* * * * *