DE632750C - Switching device for resistance welding and heating machines or the like, especially for spot welding machines - Google Patents

Description

There are a large number of automatic switching devices for resistance welding machines, in particular spot welding machines, called welding limiters, which pursue the purpose after the welding has ended disconnect the transformer of the welding machine from the mains. The triggering devices used mostly react to the transformer primary or secondary current, with or without a time delay.

These welding limiters are often designed as magnets with hinged armatures. You own the disadvantage of being relatively imprecise and of being dependent on voltage fluctuations in the network. If the setting is wrong the transformer stage by inexperienced workers will definitely lead to faulty welds.

It is already known that instead of magnets with hinged armature, wattmetric induction counter relays to be used as a welding limiter.

But weld limiters of this type are not free from defects either.

as larger resistance welding machines, in particular spot welding machines, namely work with a relatively large Phase shift between welding current and welding voltage. However, the torque of an active consumption counter relay increases with increasing phase shift angle decreases very sharply.

In the diagram shown in FIG. 1, the torque Ό is plotted as a function of the phase shift angle φ .

The torque curve of an active consumption counter relay is denoted by α. The curve clearly shows that the torque is not only relatively small at larger phase shift angles, but is also subject to very strong changes even with only very insignificant fluctuations in the phase shift angle.

It is therefore readily understood that a wattmetric induction counter relay for Resistance welding machines, in particular spot welding machines, being weld limiters is unsuitable because it works too imprecisely.

According to the invention are for with large phase shift angles between Welding current and welding voltage working Resistance welding, heating machines ο. like, especially for point

*.) The inventor has been indicated by the patent seeker;

Georg Hofmann in Nuremberg.

θΒ2750 "·. '

SchweißmasehiHen - this, - type, used as a current limiter "a '" consumption counter relay or with very large * phase shifts a blind consumption counter relay. ■ In Fig. Ι, for example, b denotes the curve 'of a mixed consumption counter adjusted to 45 °. Even with larger fluctuations in the phase shift angle, the torque changes only very insignificantly. The same also applies to a blind consumption meter relay, its. Torque curve in Fig. Ι is denoted by c. In general, you will choose the internal balancing of the counter relay so that it reaches the maximum torque at the phase shift angle with which the machine normally works. In the middle range of the phase shift angle, it is therefore advisable to work with a mixed consumption system, and for very large phase shift angles with a reactive consumption system.

In addition to the driving system, of course, the mixed consumption or reactive consumption meter relay just like the active consumption meter relay, it can be equipped with a further system that, on the one hand, has the Adjustment of the sensitivity of the relay is allowed and, on the other hand, that actuated by the relay Switching device returns to its starting position after welding is complete.

For this second system, which is appropriately referred to as the reverse rotation system, can either a spring (torsion spring) or a second induction motor meter system is used acting either on the same anchor or on an anchor coupled therewith.

"It is immaterial whether the counter moment of the 'Rückdre'hsystems during rotation of the switch axis changes (spring) _barren: remains the same (induction motor counter system).

"If an induction counter system is used as the resetting device, then it may this cannot be switched off with the actual driving system. Also must of course, the torque of the restoring device can be kept smaller than the torque of the driving system.

. The invention is to be explained in more detail with reference to the examples shown in the drawing will.

In Fig. 2 ι is the secondary, 2 the primary controllable part of a spot welding device, which can be connected to the network RT with the primary side 2 via the switch 5 actuated by the foot lever 3 with the interposition of the pawl 4. The main current magnet 61 is connected in series with the switch 5, the voltage magnet 62 is connected in parallel with the secondary side, and the excitation winding of the electromagnet 9 controlling the sink 4 is connected via the switch 8.

"/ The magnets 61, 62 together form a Ferrari drive system known from meter technology, the internal balancing of which is selected so that it works as a mixed consumption or reactive consumption system. It drives the armature 14, which is damped by the permanent magnet 16. The armature shaft is through gears is coupled to the intermediate shaft 13 carrying the control arm 7. The control arm 7 can move between the limit switch 8 and the adjustable start stop 15. It is urged against the stop by the return spring 10. The handle 12 with pointer and scale is used to set the Start stop, the scale is appropriately calibrated in the same sheet metal thicknesses, so that the handle can be set correctly for each sheet metal thickness to be welded.

The facility works in the following way:

After the parts to be connected have been placed between the electrodes of the primary part 1 are, by means of the foot pedal 3 9 <? the switch 5 is closed. Begin with that the weld; the armature 14 rotates until the switching arm 7 reaches the switch 8 and the magnet 9 applies voltage. The Magnei pulls the pawl 4, thereby interrupting the clutch between the foot lever 3 and the switch 5, the switch 5 returns to the Open position back with simultaneous disconnection of all circuits. On that the switching arm 7 is returned to the starting position by the spring 10 (switching arm 15) returned. A new welding process can begin.

In order to accelerate the return of the switching arm 7, instead of the permanent magnet 16 an electro-brake magnet connected together with the voltage magnet 62 is used will. ~

A further embodiment is shown in FIG. 3. ■ It essentially corresponds to that of FIG. 2, but here the counter relay is provided with a second plate 17 onto which a E ^a system 18 exerts a torque corresponding to the system 6r, 62 counteracts. The torque of the system 18 is smaller than that of the system 61, 62; depending on the type of welding, it is 10 to 90 ° / _{0 of} the other torque. The system 18 is preceded by a resistor 19 provided with taps, which can be short-circuited by a switch coupled to the switch 5. The taps of the resistance 19

632? 5Ö

are led to the regulating switch 20, the movable part 21 of which with the handle 12 connected is. The return spring for the switching arm 7 is omitted.

During the welding process, the movement of the is driven by the system 61, 62 Armature not only by the brake magnet 16 but also by the system 18 depending on Position of the controller 20 more or less delayed. After the welding process has ended, the system 61, 62 switched off at the same time as the welding current by the switch 5 as in FIG. 2; Therefore

. the switch 22 closes the series resistor 19 short. The system 18 now brings with it the unimpaired Torque the switching arm 7 back into the starting position.

In addition to the system 18, a return spring can also be used to accelerate the return be used. Again, instead of the brake magnet 16, a Disengageable -Electromagnet step. By accelerating the return of the switch arm the welding breaks can be reduced to a minimum.

In order to increase the regulation range of the device, the current coils of the Counter relays with adjustable resistors, the voltage coils with the same series resistors be provided. The coils can also have taps. .

The return of the switching arm 7 (Fig. 2) can also be accelerated in that between the arm and the shaft 13 a disengageable, suitably electromagnetic actuated clutch is switched on. The clutch is activated when the foot pedal is depressed 3 engaged, disengaged after completion of the welding process. The clutch can engage an electromagnet that is switched on and off by switch 5. The switching arm 7 then returns under the Action of the spring 10 freely back against the stop 15 and does not need turn back the relay armature 14.

In the embodiment of FIG. 3, the reverse and counter-rotation system 18 also remains Return of the switching arm 7 to the stop 15 is switched on. About unnecessary energy consumption to prevent by the system, an off switch can be attached to the stop 15 be that after the return of the arm, the system 18 de-energizes. Instead of this can also be done by a special switching device coupled to the switching arm 7 be used.

In Fig. 3, the armatures 14 and 17 sit on a common shaft; instead it can also be used for the two systems 61, 62 and 18 a common anchor can be used. However, the anchors 14 and 17 can also be separated from each other and via a differential gear, the first part of which with the armature 14, the second part of which with the armature 17 and the third part of which with the 6g Arm 7 is coupled, act on the arm 7.

The invention offers the advantage that for switching off the welding current commercial meters can be used with minor changes and that the switch-off device in every way the different - types of welding, - sheet thicknesses etc. can be customized.

τ-,

Claims (9)

Patent claims: 1. Switching device for with a large phase shift between Resistance welding and heating machines operating welding current and welding voltage or the like, in particular - for spot welding machines with an induction counter relay to switch off the welding current is used with a preferably adjustable retraction force acting on the armature, characterized in that that driving on the armature either a mixed consumption or a very large phase shift Reactive consumption system acts. 2. Device according to claim 1, characterized in that the driving a second induction motor meter system acting on the armature of the relay counteracts this on the same anchor or on a special anchor mechanically coupled to it. 3. Device according to claims 1 and 2, characterized in that the The system counteracting the forward turning system at the same time as a reverse turning system serves and that it is after. The forward rotating system is switched off remain. 4. Device according to claims 1 and 2, characterized in that on A switch is attached to the start stop of the switch arm, which rotates backwards or the counter-rotating system switches off when the switching arm reaches the start stop achieved, or that with the switching arm a circuit breaker acting in the same way for the opposite or reverse rotating system is connected. 5. Device according to claim 1 or 2, characterized in that for the purpose of acceleration the switch arm return is temporarily uncoupled from the drive relay, a relay armature the damping electromagnet is switched off during the return movement or • is at least weakened, the rotary Moment des Rückdrehsystenis during the return ^ is increased or that several of these measures are applied at the same time. 6. Device according to claim i, characterized in that the magnetic windings of the counter relay are provided with taps, adjustable series or shunt resistors. 7. Device according to claims ι and 6, characterized in that with the setting device for .the start stop or the limit switch, a regulating device is connected for at least one relay winding, in particular for the winding of the reverse rotation system. 8. Device according to claim i, characterized in that the switch arm restoring spring or gravity adjustable and the adjustment device ao device is appropriately connected to that of the start stop. 9. Device according to claim 1, wherein the anchor during the welding process moves from a start stop to a limit switch, at least one of which is against the other is adjustable, characterized in that this adjustment device is provided with a scale that is calibrated according to the thickness of the sheets to be welded. 1 sheet of drawings