EP3342506A1 - Force gradient evaluation - Google Patents

Abstract

The invention relates to a Blindnietverfahren using a portable blind riveting and integrated control 101 and integrated traction mechanism 102 for pulling on a mandrel of a blind rivet, wherein the traction mechanism 102 is acted upon by a force which is transmitted to the mandrel and wherein during the pulling operation Gradient of the force is determined by means of the integrated control 101 at least temporarily.

Description

The present invention relates to a blind riveting method and a portable blind riveting apparatus for carrying out the same.

State of the art

Blind riveting are used to connect at least two components (joint partner). A blind riveting method is characterized in that a pre-punching of the components to be joined together is required. A rivet is pressed into the hole and then act on the rivet mandrel until it breaks off. Then the riveting process is completed.

Riveting devices of all types are known, but it is desirable in industrial applications to monitor each individual bonding step, especially to meet the high quality requirements of the riveted joints.

Disclosure of the invention

According to the invention, a blind riveting method and a blind riveting device are proposed. Advantageous embodiments are the subject of the dependent claims and the following description.

A method according to the invention serves for connecting at least two components by means of a blind riveting device. In this case, a portable Blindnietvorrichtung is used with integrated control. This control is intended for stand-alone device control, i. It can take over complex control operations for the blind riveting tool without the need for a superordinate external blind rivet control, in particular also quality monitoring processes and documentation processes, as well as measured value evaluations with respect to individual device components. Also, an integrated tension mechanism is provided for pulling on a mandrel of a blind rivet. The tension mechanism is acted upon by a predetermined force by the control, which is transmitted to the mandrel, wherein during the pulling process by the controller, a force gradient at least temporarily, preferably continuously determined. It may be a temporal gradient, i. Force per time, and / or around a local gradient, i. Power per way, act.

In blind riveting a force as a function of the position or the path of the traction mechanism for a quality assessment of the blind riveting process can be used. In this case, for example, it can be examined whether the force course moves within certain limit values, for example a so-called envelope curve. If the yield point of the rivet mandrel is reached (elongation of the rivet mandrel), then this is just before the demolition, in addition, the gradient drops. If the force gradient is then monitored by the controller (continuously or according to predefinable time segments), the changes in the rivet mandrel can be recorded particularly advantageously and in a very simple manner due to changes in the gradient, and an imminent tear-off process can be detected and thus also influenced.

It is according to the invention, especially in industrial applications, possible to monitor each individual connection step to meet the high quality requirements of the riveted joints.

Preferably, the force gradient is determined during at least one selected time and / or distance range during the riveting operation. Thus, for example, the time or distance ranges can be selected in which experience has shown that the demolition is to be expected. Thus, no monitoring of the entire Blindnietvorgangs is necessary.

Alternatively, it is also preferred if the force gradient is determined during the entire duration or during the entire travel of the rivet mandrel. Thus, the probability is higher to accurately detect the breakpoint, especially if, for example, a demolition occurs at an unusual position or at an unusual time.

Advantageously, the force gradient is determined by means of a time- or path-dependent scanning. In the time-dependent sampling, the force can be detected, for example, with a certain frequency, so that the gradient can be determined. In the path-dependent scanning, the force can, for example, after each covering a certain distance by the traction mechanism, for example. Every 5 microns, are detected. In the path-dependent scanning, for example, a low feed rate can be taken into account insofar as only a small amount of data is obtained. In the case of time-dependent sampling, for example, attention should be paid to a suitable frequency, for example 50 or 100 kHz, so that no excessive amount of data is obtained, but nevertheless a sufficiently accurate detection of a gradient and thus detection of a break is possible.

Preferably, the controller carries out an action by means of the determined force gradient and, in particular, also influences the pulling speed and / or pulling force. This is particularly preferably dependent on at least one gradient parameter and / or on a speed parameter. The gradient parameter particularly preferably defines a force gradient decrease, from which the action is carried out, if a force gradient decrease determined by the control reaches the gradient parameter.

The speed parameter particularly preferably defines a speed change from which the action is executed, if a speed change determined by the control reaches the speed parameter. The control makes it possible to mitigate the severe mechanical jolt of riveting mandrel tearing that occurs with less innovative solutions, since this jerk causes vibrations to the worker's wrist and device mechanics and can therefore contribute to premature wear.

Advantageously, the controller recognizes a Dornabriss prematurely by means of the force gradient. The control system preferably returns the traction mechanism to a mechanical starting position at the latest from the time the mandrel breakage is detected, in particular before it has been reached a mechanical end position. If the tension mechanism is returned to its mechanical starting position even before reaching its mechanical end position, this saves processing time because more riveting operations can now be implemented in the same time. It also saves electrical energy and protects the energy supply, eg battery, of the portable blind riveting tool.

Appropriately, the return to the mechanical starting position and / or the tearing takes place by means of a continuous movement profile, for which the controller supplies the position setpoints and which monitors the control. By means of the control, it is thus possible during the tear-off process to reduce mechanical stresses on the device and thus to protect the device and the operator.

In a further embodiment of the invention, the force gradient is also preferably used for detecting a device defect and / or a problem in the manufactured blind rivet connection. By means of the control, it is thus possible, for example, to identify wear-related changes in the tension mechanism prematurely and to initiate maintenance work as a precaution, or to detect connections that do not comply with specifications very early in the process. The defect is preferably detected on the basis of a comparison of the force gradient with at least one force gradient threshold value stored in the controller. It is thus possible to define (also several) maintenance thresholds and to communicate.

Such threshold values can be selected, for example, on the basis of test values or empirical values. A defect can then be detected if the gradient (in terms of amount) exceeds the threshold value. It can be taken into account that, for example, it is only possible to start from a defect at a certain value of the gradient. It is also understood that such threshold values are material-dependent and therefore, for example, can be newly specified or set with each new use of the riveting tool, ie can be specified by a user. In addition to the type of material but may, for example, the thickness of the components to be connected are relevant. It is also conceivable that the use of different threshold values makes a distinction between different types of defects and / or defects on different components, for example, a component and the rivet.

It is also conceivable that a detected defect on display means, for example. A display is displayed. Thus, a defect can be detected quickly and the corresponding components or the rivet can be sorted out. It is also conceivable an acoustic signal indicating the detection of a defect. The blind riveting tool is therefore preferably also provided in order to realize such a signaling.

Particularly preferably, the force gradient is associated with an associated riveting operation and stored in the blind riveting tool, in particular even if a defect or connection error has been detected.

This makes documentation of the riveting process and its quality possible ("logbook function"). For example. In this way defects can later easily be found or explained. In addition, such documentation is often required for industrial applications. It may also be expedient to perform the linking and storage only if a defect has been detected. This avoids unnecessary generation of data. It is also possible in this way to determine a total number of defects occurring during a certain period of time, as a result of which, for example, conclusions can be drawn about the quality of the components or rivets used. By means of the controller, it is thus possible to document prevailing boundary conditions during the connection process. By means of the control, it is thus also possible to document problems that have occurred during the connection process.

It is also advantageous if, in addition to the force gradient, a further method and / or a further quality parameter for a quality evaluation of a connection generated by means of an associated blind riveting operation is determined. The method or the quality parameter may, for example, be a force-displacement or a force-time sequence. In this way, a quality assessment of the entire blind riveting process can take place, which in particular also allows an evaluation of other or additional factors of the blind riveting process in addition to the recognition of the demolition. In addition, in this way also, at least in part, redundant evaluation criteria are possible. Two redundant evaluation criteria are often required for reasons of process reliability. In addition, it can then be taken advantage of the fact that for the force gradient, the force must be detected anyway.

With regard to the claimed portable blind riveting device, reference should be made at this point to the avoidance of repetition to the above statements regarding the method according to the invention.

A control program according to the invention is, in particular programmatically, configured to perform a method according to one of the preceding claims, when it is executed on the controller.

Also, the implementation of the method in the form of a computer program is advantageous because this causes very low costs, especially if an executive controller is still used for other tasks and therefore already exists. Suitable data carriers for providing the computer program are in particular magnetic, optical and electrical memories, such as e.g. Hard drives, flash memory, EEPROMs, DVDs, etc. It is also possible to download a program via computer networks (Internet, intranet, etc.).

Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination indicated, but also in other combinations or in isolation, without departing from the scope of the present invention.

The invention is illustrated schematically with reference to an embodiment in the drawing and will be described in detail below with reference to the drawing.

figure description

• FIG. 1 shows a force-position course in a blind riveting.
• FIG. 2 shows a portable Nietensetzgerät according to the invention.

Detailed description of the drawing

In FIG. 1 an exemplary force-position course is shown in a blind riveting method. In particular, a first gradient region 103, an evaluation zone 104 of the force F and a sloping second gradient region 105 are shown.

In this case, a force F is plotted against a position or a distance s in mm, within which the evaluation zone 104 falls. With F (s) in kN is a course of a force F, which is applied to the removal of the rivet mandrel on this, given as a function of the position s of the tension mechanism during removal. It should be noted that here only one relative position s, i. the distance traveled by the traction mechanism is relevant.

On the course F (s) it can be seen that shortly before the demolition an irregularity occurs in the form of a force drop. Previously, the force relative to the path s changes from a positive slope to a negative slope. With dF, therefore, the decrease of the force F during a path section ds can be designated. This means that there is a (local) gradient dF / ds here. The determination of this gradient 103 and the comparison with a threshold takes over the control and thus coordinates the behavior of the device mechanism shortly before and / or during and / or after the demolition. It is understood that the gradient can be determined not only path-dependent, but also time-dependent. In order to implement the idea according to the invention, the waste 105 of the gradient is detected by means of a computer program executable on the controller which executes the claimed method.

In FIG. 2 is now roughly schematically shown an inventive hand tool 100 in a preferred embodiment. By way of example, the hand tool 100 is designed as a battery-operated hand tool 100. The tool 100 has the following essential components: tool control 101 and traction mechanism 102. In addition, it may be provided: log memory, data storage, power interface for arranging a battery or a mains connection, power supply in the form of a battery, on / off switch, output for receiving a connecting means for Connecting components / workpieces, operating unit (display / keyboard). All these components are preferably at least partially encompassed by a common housing.

This hand tool is preferably designed as a portable battery blind riveting. The tool controller 101 is provided as an integrated stand-alone controller that is configured to perform a method according to the invention. LIST OF REFERENCE NUMBERS Motor operated hand tool 100 tool control 101 draw mechanism 102 gradient 103 evaluation zone 104 Sloping gradient 105

Claims (11)

A blind riveting method for a portable blind riveting apparatus (100) having an integrated controller (101) provided for self-contained apparatus control, and having an integrated pull mechanism (102) adapted to be pulled on a mandrel of a blind rivet, the pull mechanism (102) being one of the control (101) predetermined force is applied, which is transmitted to the mandrel, wherein during the pulling operation of the controller (101), a force gradient is determined at least temporarily. The method of claim 1, wherein the controller (101) performs an action based on the force gradient, and in particular also affects the traction mechanism (102), in particular depending on at least one gradient parameter and / or at least one speed parameter. Method according to one of the preceding claims, wherein the controller (101) detects a mandrel breakage by means of the force gradient. The method of claim 3, wherein the controller (101) upon detection of the mandrel break the traction mechanism (102) moves back to a mechanical starting position, in particular before reaching a mechanical end position. The method of claim 4, wherein the moving of the traction mechanism (102) by means of a continuous motion profile. Method according to one of the preceding claims, wherein the force gradient is also used for a detection of a defect with respect to the device and / or the manufactured Blindnietverbindung. The method of claim 6, wherein the detection of the defect is made on the basis of a comparison of the force gradient with at least one in the control (101) stored force gradient threshold. Method according to one of the preceding claims, wherein the force gradient is associated with an associated riveting operation and stored, in particular even if a defect or connection error was detected. Portable blind riveting apparatus (100), in particular cordless blind riveting apparatus, with integrated pull mechanism (102) for pulling on a mandrel of a blind rivet and with integrated self-contained control (101), which is set up to carry out a method according to one of the preceding claims. A control program that causes a self-contained blind rivet control (100) to perform a method according to any one of the preceding claims when executed on the blind rivet control (100). A machine-readable storage medium having a control program stored thereon according to claim 10.

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