U.S. patent application number 14/000020 was filed with the patent office on 2014-02-13 for method and device for the quality-assuring production of a crimp.
The applicant listed for this patent is Werner Hofmeister. Invention is credited to Werner Hofmeister.
Application Number | 20140041200 14/000020 |
Document ID | / |
Family ID | 45569604 |
Filed Date | 2014-02-13 |
United States Patent
Application |
20140041200 |
Kind Code |
A1 |
Hofmeister; Werner |
February 13, 2014 |
METHOD AND DEVICE FOR THE QUALITY-ASSURING PRODUCTION OF A
CRIMP
Abstract
A method and a device for producing a crimp are described. A
crimp blank is plastically deformed by a forming tool. In
particular when the forming tool is retracted, the force which the
forming tool exerts on the crimp blank as well as the distance x by
which the forming tool is displaced are measured. A change in the
distance x between a position at maximum force F.sub.max and a
position that for the first time is free from forces provides an
indication of an elastic recovery, i.e., a spring-back, of the
crimp blank. This indication represents a measure of the quality of
the produced crimp.
Inventors: |
Hofmeister; Werner;
(Muehlacker, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hofmeister; Werner |
Muehlacker |
|
DE |
|
|
Family ID: |
45569604 |
Appl. No.: |
14/000020 |
Filed: |
January 31, 2012 |
PCT Filed: |
January 31, 2012 |
PCT NO: |
PCT/EP2012/051534 |
371 Date: |
October 22, 2013 |
Current U.S.
Class: |
29/515 ;
29/283.5 |
Current CPC
Class: |
B30B 15/0094 20130101;
Y10T 29/53996 20150115; H01R 43/0486 20130101; B21D 39/048
20130101; Y10T 29/49925 20150115 |
Class at
Publication: |
29/515 ;
29/283.5 |
International
Class: |
B21D 39/04 20060101
B21D039/04 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 17, 2011 |
DE |
10 2011 004 298.2 |
Claims
1.-10. (canceled)
11. A method for producing a crimp, comprising: providing a crimp
blank; plastically deforming the crimp blank by pressing with a
forming tool; during the pressing, displacing the forming tool by
an approach path in a direction of the crimp blank with the aid of
a forming machine until the crimp blank is pressed with a maximum
pressing force; subsequently displacing the forming tool by a
return path away from the crimp blank; measuring a pressing force
exerted on the crimp blank by the forming tool on the return path;
and measuring a return path length by which the forming tool is to
be displaced on the return path between a state having the maximum
pressing force and a state that is free of pressing forces.
12. The method as recited in claim 11, further comprising:
determining the return path length by measuring a distance between
a first reference point that correlates with a position of the
crimp blank and a second reference point that correlates with a
position of the forming tool.
13. The method as recited in claim 12, wherein the second reference
point correlates with a position of a crimp shaping surface of the
forming tool.
14. The method as recited in claim 11, wherein the return path
length is measured in a contactless manner.
15. The method as recited in claim 11, wherein the return path
length is optically measured.
16. The method as recited in claim 12, further comprising:
outputting information concerning a quality of the crimp on the
basis of the determined return path length.
17. A device for producing a crimp, comprising: an arrangement for
providing a crimp blank; an arrangement for plastically deforming
the crimp blank by a pressing operation; an arrangement for, during
the pressing, displacing the forming tool by an approach path in a
direction of the crimp blank with the aid of a forming machine
until the crimp blank is pressed with a maximum pressing force; an
arrangement for subsequently displacing the forming tool by a
return path away from the crimp blank; an arrangement for measuring
a pressing force exerted on the crimp blank by the forming tool on
the return path; and an arrangement for measuring a return path
length by which the forming tool is to be displaced on the return
path between a state having the maximum pressing force and a state
that is free of pressing forces.
18. The device as recited in claim 17, wherein: the arrangement for
plastically deforming the crimp blank includes a forming tool for
plastically deforming the crimp blank, and the arrangement for
measuring includes a force measuring device for measuring the
pressing force exerted on the crimp blank by the forming tool, the
device further comprising: a crimp blank holder for accommodating
the crimp blank, and a position measuring device for measuring a
position of the forming tool.
19. The device as recited in claim 18, wherein: the position
measuring device measures a distance between a first reference
point that correlates with a position of the crimp blank holder and
a second reference point that correlates with a position of the
forming tool.
20. The device as recited in claim 18, wherein the position
measuring device includes a laser distance measuring device.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a method and a device for
producing a crimp.
BACKGROUND INFORMATION
[0002] "Crimping" is understood to mean a joining process in which
two components are joined together by plastic deformation. In
particular, as the result of crimping, a crimp, i.e., a mechanical
connection between a conductor and a connecting element, for
example a plug or a sleeve, may be produced which is difficult to
disconnect. Such a crimp may be used as an alternative to
conventional connection methods such as soldering or welding, and
when it is correctly produced, may ensure a reliable electrical and
mechanical connection between the two crimped components. In
particular, a gas-tight connection between the two components may
be established by a crimp that is correctly provided, since in the
plastic deformation of a crimp blank and a finely stranded line,
for example, a structure may result which is largely closed off
from the penetration of oxygen, and is thus internally protected
from corrosion. Customarily, for producing a crimp a crimp blank,
for example in the form of a plastically deformable sleeve element
or plug element, is brought into contact with a second component,
such as an end of a cable, to be crimped with the crimp blank. The
crimp blank is subsequently plastically deformed by pressing with a
suitable forming tool which has an appropriately shaped crimp
shaping surface on its side facing the crimp blank, the second
component generally being completely surrounded by the crimp blank
and being squeezed by same. For this purpose, the forming tool is
generally displaced by a distance toward the crimp blank with the
aid of a forming machine until the crimp blank has been pressed and
deformed with a maximum pressing force. The forming tool is
subsequently displaced away from the crimp blank, so that the
component which has been crimped with the crimp blank may be
removed. The forming machine may, for example, be a hydraulic,
pneumatic, or electric press to which the forming tool may be
fastened.
[0003] During production of the crimp, care must be taken that the
crimp is of high quality to be able to ensure a durable, stable
mechanical, and thus electrical, connection between the crimped
components. If during the crimping, for example, a sufficient
pressing force is not exerted or unsuitable contact materials are
used, finely stranded lines, for example, may be insufficiently
pressed to ensure a durable connection. It is thus possible for
oxygen to be present at the individual lines, and for an increased
contact resistance to develop between the lines and a crimp sleeve
due to oxidation. There is also the risk that an incompletely
pressed line may be pulled from the crimp. On the other hand,
during crimping the pressing must not be too great, or the pressing
must not be carried out with a forming tool that is too small,
since for solid, finely stranded lines, for example, the cross
sections may be excessively reduced, so that the resistance could
increase to impermissibly high levels. In addition, when the
pressing force for finely stranded lines is greatly exceeded, there
is a risk that individual conductors may be sheared off.
Furthermore, the crimp may also be damaged by fissures or breaks.
As a rule, quality assurance of a crimp connection is
conventionally carried out by measuring external dimensions of the
crimp, by visually assessing the micrograph, for example through
the center of a crimp perpendicular to the lines, and/or by
force-displacement monitoring during the crimping.
SUMMARY
[0004] An object of the present invention is to provide a method
for producing a high-quality crimp, and a device that is suitable
for carrying out the method.
[0005] It has been found that an internal mechanical pressing state
may be necessary for a reliable crimp connection. Since
high-strength materials are usually used for contacts, and thus for
crimps, it may be advantageous to measure the spring-back of the
crimp. The spring-back reduces an internal compressive stress until
a possibly pretension-free connection results. For stable
electrical connections, the internal pretensioning should be
greater than a relaxation of the materials due to natural aging
during the useful life of the crimp.
[0006] To ensure consistent quality, it may be advantageous to
directly measure a spring-back travel of the crimp during its
production. This may provide a direct conclusion as to the internal
pretensioning state.
[0007] The position of the forming tool at maximum crimping force
may be ascertained for measuring the spring-back travel. This
maximum crimping force is generally present directly at the
reversal point of a travel of the forming tool. In addition, the
position of the forming tool may be ascertained as soon as it
leaves the crimp blank, i.e., when it is practically free of force.
The difference in these two positions indicates the spring-back
travel of the crimp.
[0008] This information concerning the spring-back travel thus
ensures an indication of quality for almost all possible defects of
a crimp, including possible material defects of the crimp. Other
possible errors, such as occurrences of friction, may be reduced by
correction factors.
[0009] According to one aspect of the present invention, it is
proposed during the production of a crimp to measure a force
exerted by the forming tool on the crimp blank on the return path,
i.e., after a maximum pressing force effectuated by the forming
tool has been reached and the forming tool is then displaced away
from the crimp blank. In addition, a minimum return path length by
which the forming tool is displaced on the return path between the
state having the maximum pressing force and a state that is
essentially free of pressing forces should be determined In other
words, a distance should be determined between a position in which
the fowling tool presses onto the crimp blank with the maximum
pressing force, and a position which the forming tool reaches when
it is subsequently displaced away from the crimp blank, and at
which for the first time essentially no pressing force is exerted
on the crimp blank by the forming tool.
[0010] In this regard, "essentially free of pressing forces" may be
understood to mean that any forces exerted on the crimp blank by
the forming tool, compared to forces which are necessary for the
plastic deformation of the crimp blank, are negligible. In
particular, "essentially free of pressing forces" may be understood
to mean that a pressing force exerted on the crimp blank by the
forming tool should be less than forces which are empirically
exerted on the forming tool by the crimp blank as the result of
spring-back during the displacement of the forming tool on the
return path.
[0011] By determining the return path length, it may be ascertained
how intensely the crimp blank springs back after the actual
crimping process, i.e., after the maximum pressing force is
reached.
[0012] The information concerning the return path length, and thus
information concerning the spring-back of the produced crimp, may
be subsequently output. It has turned out that such information may
provide a good indicator of the quality of the produced crimp. A
small spring-back, i.e., a short return path length, indicates a
high mechanical internal pressing of the crimp, and thus also
ensures high electrical quality of the crimp. A large spring-back,
i.e., a long return path length, indicates problems in the
production of the crimp or of the contact thus established, and may
thus indicate insufficient quality of the crimp and/or low
electrical stability of the crimp.
[0013] The proposed method results in an option to obtain a
reliable measure of the quality of the crimp directly during
production of the crimp. In particular, such quality may be
ascertained nondestructively, quickly, and cost-effectively, for
example directly during the crimping process.
[0014] The return path length to be determined may be ascertained
by measuring a distance between a first reference point, which
correlates with the position of the crimp blank, and a second
reference point which correlates with the position of the forming
tool. For example, the crimp blank may be accommodated in a crimp
blank holder in which it is held and optionally shaped during the
crimping process. For example, a suitable reference point may be
defined on the crimp blank holder which correlates with the
position of the crimp blank. A reference position on the forming
tool, preferably in the vicinity of the crimp shaping surface, may
be defined as a second reference point. Since the distance between
the two defined reference points progressively increases during the
displacement of the forming tool on the return path of the forming
tool away from the crimp blank, by measuring the distance between
the two reference points on the one hand at a point in time when
the tool exerts the maximum pressing force on the crimp blank, and
on the other hand at a point in time when the forming tool for the
first time no longer exerts force on the crimp blank, the return
path length to be determined may be ascertained.
[0015] For the case, for example, that the position of a crimp
blank holder is fixed and its deformation under the pressing force
is known, and therefore a first reference point may be assumed to
be fixed, using a position measuring device it may be sufficient to
measure only the position of the forming tool or of a second
reference point that correlates with the position of the forming
tool or its crimp shaping surface. In this regard it may be
advantageous to select the second reference point to be as close as
possible to the crimp shaping surface, which during the crimping
process plastically deforms the crimp blank. It may thus be ensured
that by measuring the return path length, the actual spring-back
travel of the deformed crimp blank, situated between the crimp
blank holder and the crimp shaping surface, is determined, and that
influences such as a deformation of the forming tool or of a
machine which moves the forming tool may be largely eliminated.
[0016] The return path length is preferably measured in a
contactless manner In particular, the distance between the two
defined reference points may be optically measured, for example
with the aid of a laser distance measuring device. Such a laser
distance measuring device may be designed to emit a laser beam from
one of the reference points to the other reference point, and to
redetect a portion of the laser light reflected from that location,
to be able to obtain information concerning the distance between
the two reference points on the basis of a propagation time
measurement. The contactless measurement of the return path length
may allow a reliable, wear-free determination of the quality of the
crimp. In particular an optical measurement, for example with the
aid of the laser distance measuring device, allows a very accurate
determination of the return path length, for example with an
accuracy in the range of a few microns. A precise indication of the
spring-back travel during the production of the crimp, and thus of
the quality of the produced crimp, may thus be obtained in a
simple, reliable, and wear-free manner.
[0017] It is pointed out that possible features and advantages of
the described present invention are described herein in part with
reference to the proposed method for producing a crimp, and in part
with reference to a device for producing a crimp. Upon study of the
description, those skilled in the art will recognize that the
described features in each case may be combined with one another,
and that further synergy effects may be achieved by such
combinations.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 shows a device for carrying out a crimping process
according to one specific embodiment of the present invention.
[0019] FIG. 2 shows a typical curve of pressing forces during a
crimping process.
[0020] The figures are purely schematic, and are not to scale.
DETAILED DESCRIPTION
[0021] A device is described below with reference to FIGS. 1 and 2,
with the aid of which a method for producing a crimp may be carried
out according to one specific embodiment of the present
invention.
[0022] FIG. 1 illustrates a device 1 with the aid of which a crimp
blank 3 may be crimped. Device 1 has a forming tool 5 in the form
of a punch, and a crimp blank holder 7 in the form of an anvil.
Forming tool 5 is fastened to a fowling machine 9, which is
illustrated purely schematically. Forming machine 9 may move
forming tool 5 back and forth in the vertical direction, as
indicated by arrows 11, 13. Forming tool 5 has a crimp shaping
surface 15 at its lower side facing crimp blank holder 7 which
specifies the contour into which the crimp blank is to be
plastically deformed during the crimping.
[0023] Forming machine 9 is designed to measure with the aid of a
force measuring device 19 the force with which forming tool 5 is
pressed against crimp blank 3 during the crimping process, and to
transmit corresponding measured data to an evaluation electronics
system 17.
[0024] In addition, a position measuring device 21 is provided for
device 1, with the aid of which the position of forming tool 5 may
be measured. In the illustrated example, position measuring device
21 is implemented with the aid of a laser distance measuring device
23 which is fixedly mounted to crimp blank holder 7. Laser distance
measuring device 23 emits a schematically illustrated
time-modulated laser beam 27 in a direction that corresponds to
direction of motion 11, 13 of forming tool 5 during the crimping
process. Laser beam 27 is reflected on a reflector 25 which is
mounted at a lower end of forming tool 5 in the vicinity of crimp
shaping surface 15, protruding at the side. The reflected portion
of laser beam 27 is subsequently detected by a detector of position
measuring device 23. Based on a phase shift to be measured between
the emitted modulated laser light and the detected reflected laser
light, distance x between laser distance measuring device 23 and
reflector 25 may be deduced via a propagation time measurement.
Laser distance measuring device 23 thus allows the position of
crimp shaping surface 15 of forming tool 5 to be determined very
accurately during the crimping process. Appropriate information is
relayed to evaluation electronics system 17.
[0025] In the method for producing the crimp, undeformed crimp
blank 3 is initially arranged on crimp blank holder 7. In this
undeformed state, crimp blank 3 has two brackets 29, 31, which
together with a base 33 of crimp blank 3 essentially enclose a
space 35. Crimp blank 3 may, for example, be an end of a plug or a
socket to which a cable is to be fastened by crimping. The cable or
the plurality of exposed strands 37 of the cable may then be
inserted into space 35.
[0026] During the crimping process, forming tool 5 is now
progressively displaced vertically downwardly in the direction of
arrow 11 by forming machine 9. Crimp shaping surface 15 comes into
contact with brackets 29, 31 and deforms same as forming tool 5
moves further downwardly. A deformation which is largely plastic
takes place in this initial stage. As forming tool 5 moves further
downwardly, brackets 29, 31 are pressed increasingly intensely onto
strands 37 present in space 35, so that on the one hand the strands
are situated close to one another, and on the other hand the
material of brackets 29, 31 flows in a partially plastic manner
into the spaces between strands 37. The deformation of crimp blank
3, including strands 37 accommodated therein, occurs in a partially
plastic manner and in a partially elastic manner
[0027] Force F exerted on crimp blank 3 by forming tool 5 is
continuously measured during the progressive downward displacement
of forming tool 5. The magnitude of the force is not crucial for
these measurements; only the points of maximum pressing force and
minimum pressing force are to be ascertained. To avoid possible
error effects due to deformations of the forming machine and/or of
the forming tool, the measuring device should be placed close to
the crimp blank. For example, laser distance measuring device 23
may advantageously be mounted close to the support surface of the
crimp blank on crimp blank holder 7, and reflector 25 used as a
counterpart may be mounted, for example, in the vicinity of crimp
shaping surface 15 on forming tool 5.
[0028] During the crimping process, forming tool 5 is displaced
vertically downwardly until force measuring device 19 indicates
that the force with which forming tool 5 presses on crimp blank 3
corresponds to a maximum pressing force F.sub.max. After a defined
approach path, the forming tool moves upwardly until it leaves the
crimp blank.
[0029] Curve 39 in FIG. 2 illustrates a typical progression of
exerted pressing force F as a function of downward displacement x.
During deformation of the crimp blank, pressing force F slowly
increases during the plastic, elastic deformation of crimp blank 3,
and upon further displacement arrives at an area in which the
pressing force rises at an increasingly higher rate with the
displacement. This may be regarded as an indicator that, in
addition to the plastic deformation, an elastic deformation of
crimp blank 3 together with strands 37 accommodated therein takes
place with an increasingly greater contribution. The downward
movement of forming tool 5 is terminated when maximum pressing
force F.sub.max is reached.
[0030] Forming tool 5 is subsequently moved vertically upwardly, as
indicated in FIG. 1 by arrow 13, in order to be displaced away from
crimp blank 3 on a return path. Also during this return path, force
F exerted on crimp blank 3 by forming tool 5 is continuously
measured with the aid of force measuring device 19.
[0031] As illustrated in FIG. 2 by curve 41, force F decreases
approximately linearly over the return path as a function of
displacement Ax. This may be explained in that, during the raising
of forming tool 5, the elastic portion of the deformation of crimp
blank 3 is once again progressively relaxed. As soon as the elastic
deformation has completely diminished, crimp blank 3 no longer
exerts any force on forming tool 5, which may thus be displaced
upwardly, essentially free of pressing forces.
[0032] During the displacement of forming tool 5, distance x
between laser distance measuring device 23 and reflector 25 is
continuously measured with the aid of position measuring device 21.
In particular, distance x.sub.max is measured at the instant at
which forming tool 5 exerts maximum pressing force F.sub.max on
crimp blank 3. In addition, distance x.sub.0 is measured at which
the force exerted on crimp blank 3 by forming tool 5 during the
return path for the first time is at least essentially zero. Travel
difference .DELTA.x=x.sub.max-x.sub.0 indicates information
concerning the elastic deformation of the crimp blank, i.e., the
spring-back of the crimp blank during the retraction of forming
tool 5.
[0033] This information .DELTA.x represents an indicator of the
quality of the produced crimp. The smaller the value of .DELTA.x,
i.e., the less the spring-back, the better the general quality of
the crimp. In particular when .DELTA.x deviates from otherwise
ascertained values for a certain crimp, this may be an indicator of
production defects.
[0034] As a result of the described method and the device which
makes this method possible, a crimping process may be directly
monitored, and a quality of the produced crimp may be easily and
reliably analyzed based on the ascertained force-displacement
diagram.
* * * * *