DE102022122238A1 - Riveting device with process monitoring - Google Patents

Abstract

The disclosure relates to a riveting device with a process monitor. This includes a pressure generator, which is connected via a quick coupling with a self-closing hydraulic valve with a rivet attachment. A pressure sensor is arranged in a hydraulic area of the pressure generator, via which the force generated by the rivet attachment can be deduced.

Description

field of invention

The invention relates to a hydraulic riveting device with process monitoring. In particular, the invention relates to a hand-held hydraulic riveting tool with a pneumatic-hydraulic pressure booster.

Background of the Invention

It is known to equip riveting tools with a so-called process monitoring device. For example, the disclosure document shows DE 102 48 298 A1 a riveting tool in which a force-displacement or force-time curve can be used to check whether a riveting process has been carried out correctly. In particular, it is known to record a force-displacement or force-time profile and to check whether this profile lies within the process windows stored in the process monitoring device.

For example, if the hole made for the rivet is too thick, the force increases more slowly, which is recognized by the process monitoring device. In such a case, the process monitoring device can interrupt the riveting process or at least provide an error message.

With such riveting devices, the quality can be checked, particularly in the case of stressed structures in which failure of the riveted connection would cause a high risk of accidents, such as in the avionics and automotive sectors.

The prior art mentioned above relates to a hand-held riveting tool in which the handle has a pot-shaped housing for the pneumatic piston and in which a stroke of the pneumatic piston corresponds exactly to a stroke of the hydraulic piston.

The force, which corresponds to the tensile stress, can be measured using a force sensor, such as a strain gauge, which is located on the traction device.

The disclosure document EP 3 360 647 A1 (Inventor Klaus Reitzig) shows a riveting tool in which a pneumatic-hydraulic pressure generator is connected to a riveting attachment. The rivet attachment includes a working piston for a pulling or pressing tool, in particular a blind rivet tool or a rivet clip.

A modular system can thus be provided in which the pressure generator can be used for different types of pressing and drawing tools.

The integration of the process monitoring known from the prior art mentioned above would also be possible with such a tool system. However, this would require that each individual rivet attachment be equipped with a force sensor and the appropriate connections. This is not only expensive, but also disadvantageous insofar as the electronic parts attached to the rivet attachment are at greater risk of being damaged when the tool is used.

object of the invention

In contrast, the invention is based on the object of simply equipping a riveting tool with a rivet attachment that can be connected in a modular manner with process monitoring.

Summary of the Invention

The object of the invention is already achieved by a riveting device with process monitoring according to claim 1 .

Preferred exemplary embodiments and developments of the invention can be found in the subject matter of the dependent claims, the description and the drawings.

The invention relates to a riveting device with process monitoring.

A riveting device is understood to mean, in particular, devices for setting punch rivets, blind rivets, rivet nuts, etc. Such a riveting device comprises, for example in the case of a blind riveting device, a pulling device, by means of which the riveting pin is pulled until it breaks off. There are also rivet brackets that either have a die on the side opposite the pressing device for forming the rivet or are used to process two-part rivets from both sides.

The riveting device includes a pressure generator.

The pressure generator is designed in particular as a pneumatic-hydraulic pressure generator. A pneumatic piston is moved in an oscillating manner and hydraulic fluid is conveyed via a suction and pump valve during the setting process. In this way, high pressures can be generated even with a compact device.

The pressure generator is connected to a rivet attachment via a quick-release coupling.

The quick coupling can have a self-closing hydraulic valve. In this way, hydraulic fluid can be conveyed from the pressure generator into the rivet attachment.

Alternatively, the quick coupling can include a mechanical interface, e.g. with a movable piston, via which the force generated by the pressure generator is passed on to the rivet attachment.

The rivet attachment is the actual riveting tool and includes the working piston, which is used to move the pulling or pressing device. The fluid moved by the pressure generator thus flows into the working piston during the setting process and can flow back after the working process has ended.

The system according to the invention has a modular structure in such a way that various rivet attachments, for example blind rivet attachments, rivet brackets, etc., can be connected to the pressure generator via the quick coupling with the self-closing hydraulic valve.

The coupling can be designed in particular as a ball coupling. A reliable mechanical connection is established via the ball coupling.

It goes without saying that the rivet attachment is provided with a corresponding coupling piece, which can be connected to the quick-release coupling.

The quick coupling can preferably be operated without tools and can in particular be designed as a rotating or sliding sleeve.

According to the invention, a pressure sensor is arranged in a hydraulic area of the pressure booster, via which the force generated by the rivet attachment can be deduced.

In order to determine the force directly or indirectly, the pressure within the hydraulic area of the pressure intensifier is used according to the invention.

It has been found that the tensile or pressing force generated by the riveting tool can be reliably determined by measuring the pneumatic pressure in the pressure intensifier.

A setting process can be evaluated via corresponding values of a force/time or force/displacement curve that can be determined in this way.

In the process monitoring, tolerance ranges are stored specifically for the respective rivet and the respective rivet attachment, within which the setting process must lie.

If, within the meaning of the invention, a force-displacement or force-time curve is discussed, it goes without saying that the pressure can also be used directly as a measured variable in order to evaluate the setting process, since this is quite reliably linked to the tensile or pressing force correlated.

The pressure can be measured relatively easily using a sensor and does not require a force transducer on the rivet attachment itself.

In a development of the invention, the pressure sensor is arranged on an intermediate piece that is detachably connected to a main housing of the pressure generator.

The use of an adapter also makes it easy to retrofit corresponding riveting tools with process monitoring.

In this case, only the quick coupling has to be removed and the adapter attached to the main housing instead of the quick coupling.

The quick coupling can now in turn be connected to the intermediate piece.

Since it only has to accommodate the quick coupling, the intermediate piece can be of compact design, in particular have a length of less than 5 cm.

The intermediate piece can be connected to the main housing and to the quick-release coupling, in particular by means of a screw connection.

The pressure sensor is preferably designed as an absolute pressure sensor. Silicon, quartz or a metal is preferably used as the sensor material. In particular, the sensor can comprise a piezoelectric sensor, in particular made of zinc oxide or aluminum nitride. Alternatively, it can be a pressure sensor with a strain gauge.

The pressure sensor is preferably firmly connected to the intermediate piece, in particular screwed into the intermediate piece.

The process monitoring preferably uses at least two, preferably three, time windows to check whether the force exerted by the rivet attachment is within a stored tolerance range.

In particular, there can be a window in the elastic range in which the force runs essentially linearly and in which Hooke's law applies.

Another time window can be in the plastic range, in which the rivet begins to deform.

Finally, a third window can be in the so-called flow area, in which the material flows in such a way that the curve flattens out again until, as with a blind rivet, the tear-off force is reached or, when using a rivet clip, the maximum force is reached.

The pressure sensor preferably has a measuring range of up to at least 500 bar, preferably up to at least 800 bar.

The riveting tool is designed in particular as a hand-held riveting tool.

According to one embodiment of the invention, the actuating lever of the riveting tool is arranged on the housing of the pressure generator.

In this embodiment of the invention, the pressure generator is carried by hand and at the same time serves as an actuating element.

In another embodiment of the invention, the pressure generator can also be arranged in a stationary manner and can be connected via a hydraulic line to a grip that includes the actuating member and the quick-action coupling for the rivet attachment.

The invention also relates to a method for monitoring a riveting process, it being possible in particular to use a riveting tool according to an embodiment described above.

The method is used to monitor the setting of a punch rivet. Self-piercing rivets are used in particular to connect sheet metal pairs in car bodies. These have the advantage that no drilling has to be made before processing the rivet. In particular, the rivet punches out the required opening in the pair of holes itself.

In particular, the punch rivet is designed as a semi-tubular rivet. Such a punched semi-tubular rivet punches a hole in at least a first sheet metal layer, the material of the punched hole flowing into the cavity of the rivet and forming a so-called slug there.

The closing head formed on the opposite side is formed by the collar of the rivet being deformed by the die of the setting tool. It is provided, in particular in the case of stamped semi-tubular rivets, that the bottom sheet metal layer is not stamped through, but is formed into part of the closing head. When the rivet is set, a force-displacement and/or force-time curve is measured. In general, a setting process can be evaluated by measuring the force curve of the setting, with it being checked whether the force curve corresponds to an empirically determined or calculated force curve (plus a tolerance window).

For example, the force can be plotted against time. This is particularly easy since no force transducer, such as a strain gauge or piezo sensor, is required on the setting tool.

In the case of the above-mentioned riveting device, which works as a pneumatic-hydraulic pump, the pumping frequency can also be fixed due to the type of construction. This means that the pumping frequency does not decrease or does not decrease appreciably with increasing force.

A riveting tool is therefore preferably used in which the setting time is proportional to the distance covered. A particularly simple evaluation is thus possible.

Alternatively, it is also possible to provide the setting tool with a displacement sensor. According to the invention, a first force-displacement and/or force-time window is defined empirically or by calculation and it is checked whether the force is within the specified tolerance range within a specified time interval.

In particular, the time from which the minimum setting force is reached in the first window is therefore measured, which elapses until a maximum force is reached which exceeds the maximum force of the first window.

The force-displacement and/or force-time window is used to measure whether the force F lies between a minimum force Fmin and a maximum force Fmax during a period of time t. If t is in a target range between tmin and tmax, the rivet is Operation OK while traversing the first window.

In this regard, the invention is based on the knowledge that in the case of a punch rivet, in particular in the case of a punched semi-tubular rivet, the force initially increases when the rivet punches in the pair of metal sheets. However, due to the flow of the material and/or the punching through of a first layer of sheet metal, the force then drops again, only to then increase again up to a maximum value at which the closing head has formed.

It has been shown that an evaluation of this first time window in particular is elementary when processing self-piercing rivets.

Then, in a second force-displacement and/or force-time window, in which a closing head forms, it is checked whether the second force-displacement and/or force-time window is within a predetermined tolerance range.

In the second window, it is also checked whether a force is reached within a specified tolerance range over a specified period of time.

If, for example, a punch rivet that is defective on the closing head side is processed, the force can increase dramatically. If, for example, an unsuitable die is used, which for example has too large a cavity, the force at the end of the setting process increases too slowly or the specified maximum force is not reached at all.

In a development of the invention, a third force-displacement and/or force-time window is provided, which overlaps the first and the second force-displacement and/or force-time window. The third window can in particular include the entire setting process from the beginning of the punching to the formation of a closing head.

It is understood that for the third window the range between Fmin and Fmax is higher than for the first and second windows. The third measurement window begins in particular when the minimum force Fmin for the first measurement window is reached and ends when the maximum force Fmax is reached at the end of the setting process, ie when the closing head has formed.

This time interval must also match the respective setting process, which means that other possible errors in the setting process can be detected.

If the setting process is not carried out in one of the three measuring windows, the riveting tool can generate an error message.

In addition, the setting process can in particular also be aborted before it is completed, in particular if the first measurement window is not within the specified tolerance range.

As already mentioned at the beginning, the force-displacement or force-time window can be determined empirically. A series of tests is carried out with a specific pair of metal sheets and a specific rivet and the tolerance range for the measuring window is determined on the basis of the test series.

Alternatively or in combination, such force-displacement and/or force-time curves can also be calculated, in particular based on the types of sheet metal used. The sheets can be divided into different groups, for example steel, aluminum and also subdivided based on strength.

The method is preferably carried out in such a way that a program is run on the riveting tool.

In a first step, the user can enter the pair of sheets used into the device.

It goes without saying that a suitably adapted rivet must be used depending on the sheet metal pairing. In the case of punched semi-tubular rivets in particular, the rivet must match the thickness of the pair of metal sheets used with a high degree of accuracy.

For this purpose, suggestions for suitable rivets from which the user can select can already be stored in the memory of the device.

The rivet used can be entered manually. It is also conceivable to automatically read in the rivet used, for example via a barcode or an RFID chip on the packaging from which the rivet is removed.

If the rivet is not suitable for use with the sheet metal pairing entered, the riveting tool generates an appropriate message and informs the user that the use of this rivet is not permitted.

Information regarding the matrix to be used can also be stored on the device. For example, the display of the riveting tool can show which die has to be used for the selected rivet.

The force-displacement and/or force-time window for the measurement process to be carried out is then generated on the basis of the sheet metal pairing and the rivet. As explained above, these can be stored directly on the device as an empirically generated data set. Furthermore, the riveting device can also include an algorithm which calculates the force-displacement and/or force-time window based on the respective sheet metal pairing and the respective rivet.

The invention also relates to a riveting tool which is designed to carry out the method described above.

The riveting device includes a memory and a processor. Data sets relating to the force-time and/or force-displacement windows are stored in the memory and/or an algorithm is used to calculate them. The riveting tool can also include a display. This can be designed in particular as a touch screen.

character list

• 1 ist eine Seitenansicht eines Ausführungsbeispiels eines Druckerzeugers.
• 2 ist eine Seitenansicht eines Ausführungsbeispiels eines Nietaufsatzes.
• 3 ist eine schematische Darstellung eines gesetztes Stanzhalbhohlniets.
• 4 zeigt schematisch einen typischen Kraft-Zeit-Verlauf.
• 5 ist ein Flussdiagramm eines Ausführungsbeispiels eines erfindungsgemäßen Verfahrens.

The invention is intended below with reference to an exemplary embodiment using the drawings 1 until 4 be explained in more detail.

• 1 12 is a side view of an embodiment of a pressure generator.
• 2 Figure 12 is a side view of one embodiment of a rivet cap.
• 3 Figure 12 is a schematic representation of a set punch semi-tubular rivet.
• 4 shows a typical force-time curve.
• 5 FIG. 12 is a flowchart of an embodiment of a method according to the invention.

Detailed description of the drawings

1 shows a side view of an embodiment of a pressure generator 1, which in combination with the 2 shown rivet attachment 30 can be coupled to a riveting tool.

The pressure generator 1 comprises a main housing 2 with a pneumatic connection 3.

In the main housing there is an oscillating moving pneumatic piston, which drives a hydraulic piston. The pressure generator is therefore designed as a pneumatic-hydraulic pump, in particular essentially as shown in FIG EP 3 360 647 A1 is described.

In this exemplary embodiment, the complete pressure generator 1 is carried along by hand.

In another exemplary embodiment, not shown here, the pressure generator is arranged in a stationary manner and is connected to a handle by means of a hydraulic hose.

The pressure generator 1 includes a quick coupling 5.

The quick coupling 5 is designed as a ball coupling and includes an integrated self-closing hydraulic valve.

The quick coupling 5 can be designed as a sliding sleeve, for example.

The sleeve of the quick coupling 5 is pulled in the proximal direction from the position shown here in order to be able to uncouple the rivet attachment.

Between the main housing 2 and the quick coupling 5 there is an intermediate piece 10 which is provided for process monitoring.

The intermediate piece is bolted to the main body 2.

For its part, the intermediate piece 10 includes a thread, in particular an internal thread, for the quick coupling 5 with the self-closing hydraulic valve.

The channel for hydraulic fluid leading to the quick coupling 5 is thus lengthened by the intermediate piece.

This axial channel 11 is shown schematically as a dashed line.

A channel 12 extends in the radial direction from the channel 11 to the pressure sensor 22.

In this exemplary embodiment, the channel 12 initially runs radially outwards and is then angled in the proximal direction.

This has the advantage that the pressure sensor 20 can be arranged approximately parallel to the main housing 2 .

The pressure sensor can be located in particular in an extension arm 13 which is angled laterally in the proximal direction.

This arrangement is compact and protects the pressure sensor 20 from damage.

The pressure sensor 20 is designed as a screw sensor in this embodiment and comprises a thread 21 which is screwed into the intermediate piece 10.

The pressure sensor 20 also includes an output 22, in which the signal from the pressure sensor 20 can be picked up and forwarded to an external unit.

Instead of such an electrical connection 22, in an exemplary embodiment not shown here, a pressure sensor can also be used, which communicates with a process monitoring device via a wireless communication device.

The actual process monitoring device, which preferably includes a screen, is not shown here. However, such process monitoring devices are known and can in particular also be embodied as mobile devices.

The corresponding parameters for the various rivets are stored within the process monitoring device.

If a setting process is not within the stored target values, the process monitoring device can output a corresponding signal (optical or acoustic) and/or display an error message.

2 shows a side view of an embodiment of a rivet attachment 30.

The rivet attachment 30 is designed as a blind rivet attachment.

This includes a coupling 31, which also has a self-closing hydraulic valve and which includes a groove in which the balls of the quick coupling of the pressure generator engage when assembled.

The rivet attachment also includes a housing 32 in which the working chamber of a hydraulic piston is located, via which the pulling device of the blind rivet attachment is operated.

The claws for holding the rivet pin are located in a conventional manner in a head piece 33 connected to the housing 32.

In this exemplary embodiment, the housing 32 can be pivoted via a pivot bearing 34 . The swivel bearing includes a rotary feedthrough for hydraulic fluid.

In this way, even hard-to-reach places can be reached in a simplified manner.

3 shows a semitubular punched rivet that has already been processed in a schematic sectional view, with respect to which the method according to the invention is used to evaluate the setting process.

The punched semi-tubular rivet 40 comprises an annular section which punches through the metal sheet and which forms a closing head 43 at the end of the setting process.

As per the illustration 3 as can be seen, the punched semi-tubular rivet 40 completely punches through a first layer 41 of the metal sheet. A slug 44 is formed, which is arranged in the cavity of the punched semi-tubular rivet 40 at the end of the setting process.

In this exemplary embodiment, the closing head is formed by the material of the rivet 40 , by the slug 44 and by the formed sheet metal of the lower sheet metal layer 42 .

4 shows the time-force curve when setting the rivet in a schematic graphic.

The time is plotted dimensionlessly on the x-axis and the force is plotted dimensionlessly on the y-axis.

Due to the system, the course of the force during the setting process is plotted from right to left in this representation.

Starting from the right, the setting process ends with a maximum force at which the closing head has formed. The maximum force can preferably be set on the riveting tool and is adjusted depending on the pairing of the rivet and sheet metal.

Starting from the right, the force initially increases as the self-pierce rivet hits the pair of sheets and begins to punch the sheet.

In the case of a punch rivet, in particular in the case of a semi-tubular punch rivet, the force then drops again within the first force window, in particular when the first sheet metal layer has been punched through.

It turned out that the time t1, within which the force lies in the first force window, is decisive for the assessment of the setting process of a semi-tubular punch rivet. A minimum time and a maximum time for t1 (and also t2 and t3, not shown) are defined.

If t1 is not within a predetermined time interval, for example if the maximum force of the first window is exceeded early, the setting process is evaluated as faulty.

A region of plastic, approximately linear deformation then occurs until the second, upper force window is reached, within which the closing head forms.

At the end of the setting process, the increase in force over time (or distance) decreases as material is now flowing into the die in which the closing head is formed. The setting process ends when a defined maximum force is reached.

The second force window defines a time interval t2 within which the closure head forms. t2 must also be within a specified interval.

For example, if the wrong die is used, where the cavity is too large for the closing head, the force in the second force window will increase too slowly.

Furthermore, a third window is defined by the invention, which is identified here as a distance-time window.

The third window is defined by time t3. This is the period of time from reaching the minimum force of the first force window until reaching the specified maximum force Fmax at the end of the setting process.

t3 must also be within a specified range. Due to tolerances, the maximum force of the second and third window is greater than force Fmax at the end of the setting process.

t2 and t3 can either be measured until the force Fmax is reached, or until the riveting tool ends the setting process with a slight delay when the force Fmax is reached.

The flow chart according to 5 shows schematically how the riveting tool in 4 shown assessment of the setting process is started by the user. The user first enters a sheet metal pairing, in particular the thickness and type of sheet metal to be riveted.

A rivet is then either entered manually or read in by the device.

If the rivet is not suitable, an error message will be generated advising the user.

If the rivet is suitable, a first, second and third force window data set is generated or read from an empirically determined data set.

This data set corresponds to the representation according to 4 .

Then the setting process is carried out, which is automatically checked whether according to 4 specified value ranges for t1 t2 and t3 in the respective window are observed.
If this is the case, the setting process is evaluated positively, for example by the display of the riveting tool showing that the setting process is OK.

If this is not the case, this is also indicated by the riveting tool.

The riveting tool can include a memory in which the values of each individual setting operation are stored. In this way, the quality of each individual setting process can be documented as part of quality assurance.

The invention made it possible to reliably monitor the process even in the case of riveting tools with a separate pressure generator.

reference list

1

pressure generator

2

main body

3

pneumatic connection

4

actuator

5

quick coupling

10

spacer

11

axial canal

12

channel to the pressure sensor

13

boom

20

pressure sensor

21

thread

22

Connection

30

rivet attachment

31

coupling

32

Housing for the working piston of the rivet attachment

33

headpiece

34

swivel bearing

40

semi-tubular rivet

41

1st layer

42

2nd layer

43

locking head

44

hickeys

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 10248298 A1 [0002]
• EP 3360647 A1 [0007, 0084]

Claims (15)

Riveting device with process monitoring, comprising a pressure generator which is connected to a rivet attachment via a quick coupling, a pressure sensor being arranged in a hydraulic area of the pressure generator, via which the force generated by the rivet attachment can be deduced. Riveting tool according to the preceding claim, characterized in that the pressure sensor is arranged on an intermediate piece which is detachably connected to a main housing of the pressure generator. Riveting tool according to one of the preceding claims, characterized in that the quick coupling comprises a self-closing hydraulic valve. Riveting tool according to one of the preceding claims, characterized in that the quick coupling is arranged on the intermediate piece, in particular is releasably connected to the intermediate piece. Riveting tool according to one of the preceding claims, characterized in that the process monitoring uses a pressure-time curve to check whether a riveting process is within a stored tolerance range. Riveting tool according to the preceding claim, characterized in that the process monitoring uses at least two, preferably three, time windows to check whether the force exerted by the rivet attachment is within a stored range. Riveting tool according to one of the preceding claims, characterized in that the pressure sensor is screwed into the housing, in particular the intermediate piece, from the outside. Riveting tool according to one of the preceding claims, characterized in that the pressure sensor has a measuring range of up to at least 500 bar, preferably up to at least 800 bar. Riveting tool according to one of the preceding claims, characterized in that the pressure generator is designed as a pneumatic-hydraulic pump, with a pneumatic piston being moved in an oscillating manner, which drives a hydraulic piston, which in turn pumps hydraulic fluid into the riveting attachment via a pressure and suction valve. Riveting tool according to one of the preceding claims, characterized in that the riveting tool is designed as a hand-held riveting tool and/or that the intermediate piece has an axial fluid channel from which a channel leads transversely, in particular vertically, leading to the pressure sensor. Method for monitoring a riveting process, in particular with a riveting tool according to one of the preceding claims, wherein when setting a punch rivet, in particular a semi-tubular rivet, a force-displacement and / or force-time profile is measured, characterized in that the force-displacement - and/or force-time profile in at least a first force-displacement and/or force-time window, in which the rivet punches a pair of metal sheets, it is checked whether the first force-displacement and/or force-time window is in a predetermined tolerance range, and that in a second force-displacement and/or force-time window, in which a closure head forms, it is checked whether the second force-displacement and/or force-time Window is within a specified tolerance range. Method according to the preceding claim, characterized in that in a third force-displacement and/or force-time window, which overlaps the first and the second force-displacement and/or force-time window, it is checked whether this is within a specified tolerance range. Method according to the preceding claim, characterized in that the third force-displacement and/or force-time window begins when a minimum force of the first window is reached and ends when a predetermined maximum force is reached. Method according to one of the preceding claims, characterized in that a time t1, t2 and/or t3 is assigned to the first, second and/or third force-displacement and/or force-time window, with the setting process being evaluated as faulty , if t1, t2 or t3 is not within a specified tolerance range. Riveting tool, comprising a memory and a processor, wherein the riveting tool is designed to carry out a method according to one of the preceding claims.

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