JPH0214869Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an alarm device for a foot-operated spot welding machine.

As is well known, in this type of welding machine, by depressing a foot lever, an electrode tip is applied to pressurize the object to be welded and energize it, thereby performing the required spot welding. However, if the foot pedal level is returned before sufficient welding current flows, the current supply will be stopped, resulting in insufficient welding.

The purpose of this invention is to notify by an alarm that welding is insufficient due to the quick return of the foot lever.

This device is designed so that when the foot lever is returned to its original position during welding before a predetermined welding current is flowing, an alarm is issued to notify the user that it is too early to return the pedal. Features.

An embodiment of this invention will be explained with reference to the drawings. In FIG. 1, 1 is a welding machine main body, and 2 is a movable arm installed on the upper surface of the main body 1, which is swingable about a shaft 3, and supports an electrode chip 4 at one end thereof. Reference numeral 5 designates an electrode chip that is paired with the electrode chip 4, and is supported by a fixed arm 6.
A workpiece to be welded is inserted between both electrode chips 4 and 5 and welded. Reference numeral 7 denotes a foot lever, which is swingable about a shaft 8 as a fulcrum; 9 is a foot lever; 10 is a foot lever 7;
is the return spring. A pressure rod 11 is connected to the tip of the foot lever 7, and when the foot lever 7 is depressed, it rises and rotates the movable arm 2. Due to this rotation, both electrode tips 4 and 5 pressurize the object to be welded inserted between them.

These structures are not particularly different from ordinary welding machines of this type. In this design, the foot lever 7
The foot lever 7 is used to detect the position of the pedal.
A first switch LS ₁ that operates when the foot lever 7 is depressed and moves away from the top dead center, and a second switch LS ₂ that operates when the foot lever 7 is then depressed to the bottom dead center are provided. Switch LS ₁ is always installed in the fixed position (top dead center), but Switch LS ₂ is
When the foot lever 7 is depressed to this position, the electrode tip 4 is placed at a position sufficient to pressurize the object to be welded with a predetermined pressing force. Therefore, when changing the pressing force or depending on the thickness of the object to be welded, the position is adjusted vertically as appropriate.

In Figure 2, T is the terminal of the welding power source, Mg is the electromagnetic switch, Mga is the contact, AT is the welding transformer, S ₁ and S ₂ are switches, R ₁ to R ₅ are relays, and TM
is a timer and BZ is an alarm, for example, it may be a buzzer and/or an indicator light. CT is a welding current detection device such as a cycle counter, and input is given via a transistor Tr that is turned on every half-wave voltage of the welding voltage given from the transformer TS. R ₁ a~R ₁ c are contacts of relay R ₁ , R ₂ a~
R ₂ c and R ₂ a' are contacts of relay R ₂ , R ₃ a, R ₃ b are contacts of relay R ₃ , R ₄ a, R ₅ a are contacts of relays R ₄ , R ₅ , TMa is timer TM This contact operates when the time-limited operation ends and time-up occurs. _CT1 is a contact that operates when the cycle counter CT counts a predetermined number of inputs.

In the above configuration, it is assumed that the switch LS ₁ is normally off, the switches S ₁ and S ₂ are both on, and that the foot lever 7 is now depressed.

Then, switch LS ₁ is first turned on. Based on this ON relay _R1 operates and its contacts
R ₁ a and R ₁ c are turned on, and contact R ₁ b is turned off. Cycle counter CT is activated by turning off contact _R1b .
The reset is canceled and contact R ₁ c turns on.
Timer TM starts operating.

When the timer TM ends a preset time, its contact TMa is turned on. However, if the foot lever 7 reaches a predetermined bottom dead center before the timer ends, the switch is turned on. LS ₂ turns on, relay R ₂ operates, and its contact R ₂ a self-holds, and contact R ₂ b turns on, so electromagnetic switch Mg operates and its contact closes.
Mga is turned on and welding begins.

On the other hand, when the contact R ₂ c is turned off (or the b contact LS _{2 '} of the switch LS 2 is turned off), the timer TM is de-energized and its time-limiting operation is stopped. In other words, the operation of the timer TM stops before the timer time expires.

Cycle counter by operation of switch LS ₁
CT starts operating. That is, when relay R ₁ operates as described above, contact R ₁ b is turned off. As a result, the reset of the cycle counter CT is canceled and it becomes possible to accept pulse input. At the same time, contact R ₁ a is turned on.

The foot pedal is further depressed and the switch is turned on.
When LS ₂ is turned on, relay R ₂ and transformer TS
The primary coil of is energized. Excitation of relay R ₂ turns on contact R ₂ a, and relay R ₂ is self-held.

On the other hand, when the primary coil of the transformer TS is excited,
An induced voltage is generated in the secondary coil, which is half-wave rectified by a diode and then transformed into a transistor by a resistor.
By adjusting the input voltage of the Tr (voltage drop effect), a regulated half-wave rectified voltage is applied as the base voltage of the transistor Tr.

The transistor Tr is a switching transistor, and when the half-wave rectified voltage reaches a certain level, conduction occurs between the collector and emitter. This is done for each wave of the half-wave rectified voltage.

As a result, current is input from the common terminal of the cycle counter CT to the input terminal in the form of square wave pulses, and the cycle counter CT counts the number of square wave pulses.
That is, the frequency of the spot welding current from the commercial frequency power source is counted.

When the cycle counter CT counts the predetermined number of inputs as described above, the contact
CT ₁ is turned on. This activates relay R ₃ and turns off its contact R ₃ a, thereby returning electromagnetic switch Mg to its original state, thereby completing welding.

After this, when the foot lever 7 is released from the foot, it will rise due to the elasticity of the return spring 10. Then, switches LS ₂ and LS ₁ are restored, and along with this, relays R ₁ and R ₂ are also restored, so that cycle counter CT is reset and its count value becomes zero.

With the above steps, one welding operation is completed.

However, at first Switch LS ₁ was set to foot lever 7.
Assume that the switch LS ₂ has not yet entered the operating state by the foot lever 7 when the timer time set in the timer TM has elapsed after the switch LS 2 is operated. At this time, when the timer TM times up, the relay _R2 is not in an operating state, so the contact _R2c remains on. Then, the contact TMa is turned on due to the time-up, so
Alarm BZ will operate and notify you of this. contact
When TMa is turned on, relay _R5 is operated and its contact _R5a is turned on. Relay R ₅ by contact R ₅ a
is self-maintained and alarm BZ continues to operate.
On the other hand, since the switch LS ₂ is not in the operating state at this time, the relay R ₂ is not operating, and therefore the electromagnetic switch Mg is not in the operating state, so no energization for welding is started. As a result of the above, it is reported that the foot lever 7 is insufficiently pressed, and therefore the workpiece to be welded is insufficiently pressurized, and energization is not started.
If you release the foot lever 7 at this point, the foot lever 7 will rise and switch LS ₁ will operate in this process, so the relay and cycle counter CT that were in the operating state will be restored and reset. This is the same as described above.

In the above explanation, the timer detects the case where the foot lever 7 is not energized at all due to insufficient foot pressing.Next, we will explain the case where the foot lever 7 is returned while the welding current is insufficient.

As described above, the operation of switch LS ₂ causes relay R ₂ to operate and cycle counter CT to count the input value. It is clear that this input counts half-wave cycles of the welding current.
Here, if the foot is removed from the foot lever 7 before the count reaches a predetermined value (that is, before the necessary welding current has finished flowing), the foot lever 7 is raised by the return spring 10. This will cause the switch
LS ₂ and its b contact LS ₂ ' are restored. At this point, contact CT ₁ is not turned on, so relay R ₃
is not working yet. And at this time the relay
Since R ₂ is still self-holding, its contacts
R ₂ a′ is in the on state, so this contact
Alarm BZ is activated via R ₂ a', R ₃ b and switch LS ₂ ', and gives an alarm to that effect.

At the same time, relay _R5 is activated, contact _R5a is turned on and self-maintained, and the alarm continues. When the foot lever 7 rises to a predetermined position, the switch LS ₁ operates in the process, so the relays R ₁ and R ₂ are reset, and the electromagnetic switch Mg is also reset, cutting off the welding current. . To reset the alarm BZ once activated, simply open the switch S ₂ or S ₁ or weld it again.

As detailed above, according to this invention, after starting energization by depressing the foot lever,
If the foot lever is returned to its original position before sufficient welding current has finished flowing, an alarm will be activated to notify the operator that the return is too soon, so the operator will immediately know that the return is too soon. Therefore, it is possible to perform welding by depressing the foot lever again to ensure reliable welding.

[Brief explanation of the drawing]

FIG. 1 is a schematic side view of a welding machine according to an embodiment of this invention, and FIG. 2 is a control circuit diagram. 7...Foot lever, LS ₂ ...switch, Mg...electromagnetic switch, Mga...electromagnetic switch contact, CT...cycle counter, CT ₁ ...cycle counter contact,
R ₃ ...Relay, R ₃ b...Relay R ₃ contact, BZ...Alarm.

Claims (1)

[Scope of utility model registration request] A switch that operates when the foot lever reaches a predetermined bottom dead center, and an electromagnetic switch that allows welding current to flow from the time the switch starts operating until the predetermined welding current finishes flowing to the workpiece. an alarm for a foot-operated spot welding machine, the alarm being activated when the foot lever rises from the bottom dead center and the switch returns before a predetermined welding current finishes flowing through the workpiece. Device.