DE1256917B - Method and device for measuring and displaying the contact forces when adjusting electrical switching contacts - Google Patents

Description

Methods and devices for measuring and displaying contact forces when adjusting electrical switching contacts The invention relates first of all to a method for measuring and displaying the contact forces when adjusting electrical switching contacts using a spring balance with an electrical transducer, the to measuring contact switched to limit value display in an electrical measuring circuit is.

To electrical switching contacts, e.g. B. buttons, switches or relays certain requirements are made with regard to the contact resistance. the Contacts must lie on top of one another with a minimum value of contact force so that the Contact resistance does not become too great. On the other hand, z. B. with relays the contact force not be too big, otherwise the force to be generated by the magnet and thus the electrical power required to operate the relay becomes too great. at Normally closed contacts, these considerations apply to the non-actuated state of the switching device and for normally open contacts for the actuated state. For these reasons, the Contact forces for electrical switching contacts within a specified force range must lie. When assembling a switching device, however, manufacturing tolerances occur very different contact forces. Therefore, with almost all switch contacts the necessary contact forces are set by means of adjustment with the aim of for all contacts of a switching device and continue to be the same for all of them Switching devices to obtain the same contact forces. Every adjustment process goes therefore a measurement of the existing contact force beforehand. Based on the measurement the contact force is increased or decreased. Then another measurement takes place the contact force, etc., until finally the contact force is in the specified range lies.

For the contact force measurement with electrical switch contacts the well-known spring balance is used. The tapping pin of the spring balance is attached to the measuring contact is applied and the force exerted on the spring balance is slowly increased, until it overcomes the contact force and the contact opens. As soon as the contact is opened the measured value becomes the measured value while maintaining the force exerted on the spring balance read on the spring scale. Mostly there is an optical display of the contact status intended. Because now the adjusting person is initially paying attention to it the opening of the contact must direct and only then a reading of the obtained Can make measured value, and because small increases in force or during the reading -approvals cannot be avoided, reading inaccuracies cannot be avoided, especially if during longer working hours the concentration of the adjusting Person gradually wears off. In addition, the measurement cannot be carried out as quickly as desired because the force may only be increased carefully when opening the contact not to hit the deflection of the measured contact spring too far. It is it can be seen that this known measuring and adjustment method is very imprecise and requires considerable time. These disadvantages are particularly evident with small contact forces and noticeable with short contacts, as with sensitive switching devices such as Small relay, either the contact resistance or the response power too high is when the contact forces are not set exactly.

It is known to tap the pointer position on instruments electrically and to an electrical display device. Such a measuring device solves However, the present task of precise contact force measurement is not yet, since the uncertainty caused by the person making the adjustment cannot be eliminated.

It is already known to measure the contact pressure with a probe, which is inserted between the springs carrying the contacts and which in turn consists of two contacts that can be expanded against springs, which are operated by means of hydraulic or pneumatic pressure and indicate the measurement time by opening it. The pressure measured in the shunt by means of a spring balance should then be a measure for be the contact pressure of the contacts to be measured.

In this known device it is not ensured that the contacts to be measured not already opened when inserting the probe will. In fact, only the pressure that is present when the probe is opened is measured. The inertia of the printing system and the inaccuracy of the pressure reading make one Use of the previously known device for measuring within only halfway tolerable tolerances impossible. In another known arrangement, the pressure required to open the contact to be measured in a not specified specified manner used to set a variable electrical resistance, its value via a direct current amplifier as a voltage across the to be measured Contact charged capacitor is communicated and measured on this. The voltage is then a measure of the contact force. This system is among other things with the inaccuracy afflicted that the different electrical resistance from case to case to the Contacts falsify the measurement result. Furthermore, the characteristics of the variable go Resistance and the DC amplifier as a source of error.

According to the invention, to remedy the disadvantages described the method mentioned above uses an analog-to-digital converter, which when exceeded the predetermined limit values that determine the tolerance limits signals in a memory is transferred, is triggered by opening the contact to be measured, the content available in the memory when the contact was opened, regardless of others Signal values from the analog-to-digital converter are recorded and are dependent on the Number of signals given by the analog-digital converter before the contact was opened the area of the contact force is displayed.

With the method according to the invention, the measurement result is immediate a statement as to whether the measured contact is within the set tolerances or lies outside of it. The method is also free from the disadvantages of the previously known Procedure. It also has the advantage that even with a further deflection of the measured contact spring, the measured value when the contact is opened and so that the exact contact force is recorded.

The method according to the invention is suitable both for measuring the normally closed contacts when the switching device is not actuated and also for measuring the working contacts actuated switching device.

If the mechanical-electrical analog-digital converter is switched on manually brought up the contact to be measured and manually overcome the contact force, then the deflection only needs to be carried out so far that the contact opens. So the measuring person is only indirectly involved in the measuring process, and you The ability to concentrate no longer has any influence on the measurement result.

According to a further development of the method according to the invention, by means of a program-controlled device of the analog-digital converter to the to be measured Contact introduced, the contact force overcome and that of the display device Derived measured value is forwarded to the program control for further evaluation. the Program control can then control the fully automatic adjustment process.

The invention also relates to a device for measuring and displaying the contact forces of electrical switching contacts, in particular according to the above described method with a spring balance with an electrical transducer, a circuit containing the contact to be measured and a memory.

According to the further invention, the pointer position of the spring balance fed directly to a two-digit memory via contact tracks and opened of the contact to be measured interrupted the transmission of the pointer position and the Evaluation of the memory status initiated. The particular advantage of the device according to the invention results from the reliability of the above exercisable with her specified procedure for measuring the contact force.

It is advantageous to use bistable multivibrators as individual memories, via the memory lines with the contact tracks of the analog-to-digital converter are connected, and depending on the pointer code, there is a negative or positive control voltage one or the other stage of the bistable flip-flop switched through. It is it is expedient to set the pointer code and the storage capacity of the memory to the measuring range and to match the desired triggering capacity of the analog-to-digital converter.

The Gray binary code has proven to be the output code of the analog-digital converter proven.

The invention is explained in more detail below with reference to the drawing.

At the F i g. 1 to 3, some of which are shown in schematic form the principle of the invention is explained.

The F i g. 4 to 6 show a partially schematic representation Embodiment of the device for measuring.

The F i g. 7 to 11 show a partially schematic representation Embodiment of a device for adjustment.

In Fig. 1 shows a changeover contact k. If the normally closed contact force is to be measured, then the contact mr is opened. The analog-to-digital converter ADW is applied to the central spring m and the pressure is increased until the contact opens. Is the changeover contact z. B. arranged on a relay, then the relay is not actuated during this measurement. However, if the normally open contact force of the contact in-a is to be measured, the relay must be energized. In this state, the movable contact spring m is to be removed from the working contact piece a. This in turn takes place with the mechanical-electrical analog-digital converter, which emits the force acting on the converter in a corresponding electrical code. As can be seen from this consideration, a contact is opened with every contact force measurement.

The analog-to-digital converter ADW reaches out to FIG. 2 on the one to be measured Contact k an. The force exerted on the transducer tries to open contact k. This force is converted into an electrical code via the analog-digital converter, which is fed directly to a memory Sp. The output of the analog-to-digital converter shows during the entire measuring process the force acting on it in an electrical form Code. As long as contact k is not yet open, this code is available, i. H. this force, also entered in the memory Sp. The force on the converter is now so great increases until contact k opens. then will use this contact self the memory Sp is held on the measured value that is just being generated, even if the measured value still supplied by the analog-digital converter is smaller or larger will. When the storage process is stopped, the display is also initiated. A display device Az takes over the recorded measured value of the memory. the Display is in the same code or can be in any known manner Display code can be converted. Before each measurement, the memory is in the starting position brought and deleted the display on the display device.

As already explained at the beginning, the application of the analog-digital converter can also be brought about by means of a device, since now only one force increasing movement has to be carried out, which reliably leads to the opening of the contact to be measured. This method offers the great advantage that a fully automatic contact force measurement and contact adjustment can be set up with it. Like F i g. 3 shows, the measured value which can be derived via the display device Az when the contact k is opened is fed to a program control Pst and used to control the adjustment. The contact force is increased or decreased depending on the measured value. If the measured value is finally in the specified force range, the system switches to the next work step. Such a contact force measurement and adjustment is made possible by the measuring method according to the invention.

In Fig. 4 the conversion of the contact force is indicated in an electrical code. As mechanical electrical analog to digital converter, a known spring scale is used, the pointer Z cl ... grinds s across multiple contact paths. The contact tracks are designed according to the code and the desired resolution of the measuring range. The contact tracks have sections in which the circuit via the pointer Z is closed or interrupted. The individual contact tracks are so different from one another that in each pointer position assigned to a measured value a different connection cl. . . cn is given. The choice of the code is made in such a way that no incorrect output information arises during the transitions to the neighboring measured value. The Gray binary code is particularly suitable for this, in which only one digit changes from code symbol to code symbol, ie in the present exemplary embodiment of the analog-digital converter, the state of one of the contacts cl. . . e n.

In FIG. 5 shows the transmission of the measured values. The contact combination cl ... en set via the analog-digital converter AD W is transmitted to the memory cells of the memory via the memory line spl ... spn (FIG. 6). If the corresponding contact track is not connected to the pointer, e.g. B. c 1, then the positive voltage U 2 reaches through the diode D 1 on the memory line sp l. In the downstream memory cell, a bistable trigger circuit, the transistor T 1 is blocked and the transistor T 1 'is conductive. If, as indicated by contact c2, the pointer circuit z-c2 is closed, then the negative voltage U 1 reaches the corresponding storage line sp 2. In the memory cell connected downstream, the transistor T1 becomes conductive and the transistor T 1 'is blocked. Via the memory lines sp 1 ... Sp n , the memory cells are put into one or the other switching state depending on the state of the associated contact track. Since a memory cell is connected to each contact track cl ... en, the measured value output by the analog-digital converter is always available in the overall memory Sp. The activation of the memory cells has been made dependent on the switching state of the contact k to be measured. At the moment when this contact opens, the control of the memory is stopped, and the bistable behavior of the same means that the exact measured value is recorded. The evaluation and reading of this measured value is, as indicated by a switching means A, initiated at the same moment. The potentials at the outputs A 1-A n of the memory represent the determined measured value in the code of the analog-digital converter. This code can be converted in a known manner to any display code. The resetting of the memory to the rest position takes place automatically when the measured contact k is closed again or when a switch is made to a new contact to be measured. The analog-to-digital converter is also brought into its starting position. The activation of the new contact k also automatically clears the display.

The invention enables the adjustment of electrical switching contacts, in particular while exercising the method described above, with exact measurement results are achieved, which are required for the further adjustment processes and which also suitable for setting up a program-controlled adjustment system. For measurement a mechanical-electrical analog-digital converter is used for the contact force, which corresponds to only two of the minimum and maximum contact force of the contact to be measured Emits output signals, and when the contact is opened, the switching status of held by the two signals controlled switching means and dependent on it the range of the measured contact force is displayed. The distinction is advantageous here of the areas hit in such a way that if both signals are missing, before opening the to measuring contact too small contact force, if only the minimum contact force occurs characteristic signal before the contact to be measured opens, correct contact force and when both signals appear before the contact to be measured is opened, too large Contact force is displayed.

The analog-to-digital converter can be used in this device without any load can be used by the person measuring the contact force, since the electrical Conversion and evaluation of the measured value independent of the deflection of the contact spring is. The contact to be measured is only opened safely via the analog-digital converter. The electrical evaluation and display immediately delivers a signal that has the following Identifies the operation. With such a device for the adjustment of electrical switching contacts, measurement errors are eliminated, and the adjustment process is a pure routine work without special concentration on the measuring process become. If the analog-digital converter provided for the formation of measured values has a Holding device is brought up to the contacts to be measured and moved further, then the signals emitted by the device according to the invention can be used for control purposes of the adjustment tool and of the entire adjustment process so that a fully automatic adjustment of electrical switch contacts can be realized.

The analog-digital converter with two different electrical output signals adapted to the minimum and maximum contact force according to FIG. 7 is attached to the middle spring m of the contact according to FIG. 1 is applied and the force is increased until the contact opens. Is the changeover contact z. B. mounted on a relay, then the relay is not actuated during this measurement. However, if the normally open force of contact ma is to be measured, the relay must be energized. In this state, the movable contact spring m is to be removed from the working contact piece a. This in turn takes place via the mechanical-electrical analog-digital converter, which only emits an output signal when the minimum or maximum contact force acts. As this observation shows, a normally closed contact is opened with each measurement process and an electrical output signal is generated by the converter when the minimum and maximum contact force is reached.

As shown in FIG. 7, the analog-to-digital converter ADW acts on the contact k to be measured. The force exerted on the transducer tries to open the contact k to be measured. The minimum and maximum contact force is specified for this contact k. With these contact forces, the analog-to-digital converter ADW emits the signals min and max . Both signals control memory switching means. The signal min controls the switching means A, which has two stable positions A “0” and A “1” . The signal max acts on the switching means B with the positions B “0” and B “1” . As long as the contact h to be measured is closed, the signals min and max can act on the downstream memory switching means. Assuming that both switching means assume the starting position A "0" or B "0" at the beginning of a measurement, then during the measurement a signal min before the contact k to be measured opens, the memory switching means A is in the state A »l «Change course. The receipt of the signal max before the contact k to be measured opens causes the memory switching means B to change to state B "1". If the contact k to be measured is opened, the current state of the memory switching means is maintained and used to provide information about the force range of the measured value determined. The outputs A "0", A "1", B "0" and B "1" are combined via logic circuits U1, U2 and U3, whose outputs b1, b 2 and b 3 indicate the force range of the measured value. If no min or max signal occurs before the contact to be measured is opened, then the memory switching means are in states A “0” and B “0”. The combination carried out via the logic circuit U 1 supplies the output signal b 1, which indicates that the contact force is too small. If the signal min occurs before the contact k to be measured opens, the memory switching means are in the states A “1” and B “O”. The AND circuit U2 combines these conditions to form a signal b 2, which indicates the correct contact force. If both signals min and max appear when the contact to be measured is opened, then the memory switching means assume the states A "1" and B "1". These conditions lead via the AND circuit U3 to the signal b3, which indicates that the contact force is too high. As can be seen from the explanation, the three signals required for adjustment are available when the device according to the invention is used. If the adjustment is carried out in a known manner, then the measuring process immediately gives the instruction in which way the adjustment is to be carried out. This makes the adjustment process much easier and faster. In addition, the measurement uncertainties are eliminated. In addition, through the output signals b 1, b 2 and b 3 , the adjustment device offers the advantage that it can be used directly to control the adjustment tools. This allows the construction of a fully automatic adjustment system.

An analog-to-digital converter for the device is shown in FIG. 8 shown. The pointer Z of a spring balance gives contact with the outputs min and max at two specific deflections, which are matched to the minimum and maximum contact force.These contacts are adjustable on a path so that different contact areas can be set. The counter-contact to the movable pointer Z can be a fine elastic wire that is perpendicular to the pointer. The contact force of these measuring contacts is very small so that the characteristics of the analog-digital converter are not influenced. This small contact pressure is sufficient since only control currents for the downstream storage means are switched. Like F i g. 9 reveals, the control voltage U acts on the control switching means only as long as the contact k to be measured is closed. The analog-digital converter emits the signals min and max during the measuring process, namely in the form of the contact connection z-min and z-max. Since the deflection of the contact k is not interrupted immediately after opening, these connections can be made with every measurement. However, the setting of the memory switching means is suppressed after the contact k has opened. In addition, the switching means Ab drops out, which causes the output of the measured value.

In Fig. 10 shows a bistable multivibrator with the two transistors T 1 and T 1 '. This circuit is activated via the input early, that is, this flip-flop represents the memory switching means A. The flip-flop changes its state with every positive pulse that comes in via the line min. Before each measurement, the circuit is reset, as indicated by the contact r . In the starting position A "0" , the transistor T 1 is conductive, so that the output A "0" carries ground potential. If the analog-digital converter emits the signal min before the contact k to be measured is opened, then the memory switching means A is switched to the state A "1". The transistor T 1 ' becomes conductive and the transistor T 1 is blocked. This state of the memory switching means is retained even if the contact z-min on the analog-digital converter is opened again. If only the signal min was emitted by the converter before the opening of the contact k to be measured, then the memory status A "1" and B "0" is fixed at this moment, Signal max is formed. When the contact k to be measured is opened, the evaluation of the memory status is also initiated. This can be done in the simplest way by connecting the supply voltage to the logic output circuits U1, U2 and U3.

F i g. 11 shows e.g. B. the logic circuit U2,. Which supplies the signal b 2 when the measured contact force is correct. The changeover contacts connected to the voltage - Uo via the resistors R 4 are simulations of the output circuit of the memory switching means. The outputs A "1" and B "O" of the memory switching means are combined via resistors R 5 and connected to the control electrode of the NPN transistor T2. As long as one of the outputs still has negative potential - U0, transistor T 2 remains blocked. The voltage - U 2 is to be selected somewhat smaller than half the voltage - Uo. If both outputs A "1" and B "0" are at ground potential, transistor T2 will be conductive. The potential U2 occurs at the output b2 . The logic circuits U1 and U3 are constructed in a similar manner. They are controlled by the outputs A “0” and B “0” or A “i” and B “1” and deliver the output signal b 1 or b 3. These output signals characterize the further work process. When the output signal b I. occurs, the contact force must be increased. This is done manually or is initiated via the program-controlled system. If the signal b 3 occurs, the contact force is reduced, and the adjustment process is ended at the signal b 2. The switchover to a new contact takes place. Before the new measurement of the contact force, the memory switching means must be brought into their starting position. This can also be done in that the pointer Z of the transducer returns to its zero position O. The min and max signals only become effective again when the contact k to be measured is closed. The deflection of the contact spring to be measured leads to the electrical signal b 1, b 2 and b 3, and when the contact spring is reset, the device is automatically returned to its starting position.

Claims (5)

Claims: 1. A method for measuring and displaying the contact forces when adjusting electrical switching contacts using a spring balance with an electrical transducer, the contact to be measured being switched into an electrical measuring circuit for limit value display, characterized in that an analog-to-digital converter ( ADW) is used, which transfers signals to a memory (Sp) when the tolerance limits (min, max) that determine the tolerance limits (min, max) are exceeded Memory content is retained regardless of further signal values from the analog-digital converter and that the range of the contact force is displayed depending on the number of signals emitted by the analog-digital converter before the contact is opened. 2. The method according to claim 1, characterized in that the spring balance with the analog-digital converter (ADW) operated by means of a program-controlled device and the display of the contact force range is forwarded to the program control for further evaluation. 3. Device for Measuring and displaying the contact forces when adjusting electrical switching contacts, in particular for carrying out the method according to claim 1 or 2, with a spring balance with an electrical transducer, a circuit containing the contact to be measured and a memory, characterized in that the pointer position of the spring balance is fed directly to a two-digit memory via contact tracks and that through the opening of the contact to be measured interrupts the transmission of the pointer position and the evaluation of the memory status is initiated. 4. Apparatus according to claim 3, characterized in that the contact tracks can be set to two predeterminable values are. 5. Apparatus according to claim 3 or 4, characterized in that as a memory bistable circuits are used. Publications considered: German Utility model nos. 1759 626, 1711958, 1682 513; U.S. Patent No. 2,789 430, 2,776,561; "Werkstattstechnik" magazine, 1960, issue 10, pp. 537 to 547.