US2069975A - Electric spot welding arrangement - Google Patents

Description

Feb. 9, 1937. i D. SCIAKY ELECTRIC SPOT WELDING ARRANGEMENT Original Filed Aug. 6, 1934 DAV\D SQAKY INVENTQ Patented Feb. 9, 1937 UNITED STATES PATENT OFFICE 738,641. 3, 1935, Serial No. 43,304. 1934 3 Claims.

The present invention relates to a device for interrupting the welding circuit in a spot welding machine in such manner that the successive operations of the various elements are carried out in a simple and reliable manner.

Another object of the present invention is the construction of a device comprising electromagnetic control elements which operate in such manner as to avoid shocks during the passage of current which might produce trouble in the control of the elements of the device.

Another object of the invention is to prevent the formation of arcs during the passage of the friction brushes which are disposed in the welding circuits.

Another object of the invention is to construct a device which will be capable of producing welds of similar character as compared with one another.

, Two forms of the invention are illustrated in the accompanying drawing in which Figure 1 is a diagram illustrating an arrangement according to the invention.

Figures 2 and 3 are perspective views showing a constructional detail of this arrangement.

Figure 4 is a diagram illustrating a modified arrangement according to the invention.

In the arrangement illustrated in Figures 1 to 3, a discloses the primary winding and a the secondary winding of a transformer which feeds the contact electrodes. The primary winding a has sundry leads tapped thereto and is supplied with current under the control of the main contactor b and of the switch 0. One of the terminals of said primary winding is connected with a. brush d which makes contact with the periphery of a disc (1 which is partly conductive and partly non-conductive and rotated by a synchronous motor I00. On the said periphery rests another brush d which is connected with the movable armature e of a preparatory relay the coil of which is denoted by c.

When the preparatory relay e is energized its armature e moves against fixed contact e which is connected with the discharge end of the coil e, while when said coil is not energized, armature 6 comes into contact withfixed contact e which is connected with the welding relay b of the main contactor, said relay being connected, also, with a return line.

The starting pedal j for the welding machine is connected with one of the supply conductors I. At rest it contacts with contact spring f which is connected with preparatory relay e. When this pedal is depressed it comes against contact Divided and this application October In France May 30,

spring I which is connected with the cut-out relay 9 of an auxiliary relay having two armatures which are rigidly connected together. The one 9 of said armatures is connected with the discharge end of the cut-but relay g. It is adapted to cooperate with fixed contact 9 which is connected with a return line. The other armature g cooperates with fixed contact g, which is connected with the discharge end of preparatory relay e.

The discharge end of cut-out relay g and the armature g are connected with fixed contacts h and h respectively, which are adapted to coact with the movable contacts In, h rigidly connected with the main contactor b. The contact IL -b is closed when the contactor b is open,

while the contact h. -h is established when the contactor b is closed.

Operation When the pedal 1 is depressed, the circuit feeding the preparatory relay e at rest is interrupted at f Two cases are then possible depending on whether the brushes d and d are or are not connected together, at this moment, by a conducting part of disc (1.

If the brushes are not connected together, the preparatory relay e being no longer energized, its movable contact e engages fixed contact e As soon as the brushes d and d are then connected with each other, the main contactor b will close and remain closed so long as this connection lasts.

If, on the contrary, the brushes (1 and d are connected with each other through a conducting part of disc 11 when the pedal is depressed, preparatory relay e remains energized and maintains the circuit of the welding relay b of the contactor open until said connection ceases. At this moment the movable contact e engages fixed contact e and as soon as the brushes (1 and d are connected again, the current passes through b and the main contactor closes and remains closed so long as the brushes d and d are con nected through d.

In both cases the contactor b closes, therefore, at the same point of a half-cycle and remains closed for the same time, this time being adjusted by the angular distance which separates the brushes d d from'another When closing, the contactor b interrupts the contact between h and h and at the same time closes the contact between it and 71 The cutout relay g is then fed through h n ,1 and ,f and the contact is established between 9 0 on the one hand and 9 g on the other hand. From this moment the cut-out relay g is again supplied with current through g y. Thus this relay remains energized when the contactor b opens at the end of the welding operation and when the contact is broken between )1 and it. On the other hand, the contactor b, when opening, reestablishes the contact between it and h. This has for its result that e is also supplied with current again and that the circuit of the welding relay b of the contactor b is therefore interrupted at c Therefore said relay cannot be energized again as long as the pedal is depressed. When the depression of the pedal ceases the circuit of continuous feeding of e'is re-established at F. At the same time the circuit of g is broken at f and causes the contacts to open at g and g Thus the device is again in the position of rest.

Adjusting of the time of welding The time of closure of the contactor b and, consequently, the time during which the welding current passes, can be made adjustable by making the brush d (Figures 2 and 3) movable. When both brushes are side by side (Figure 3) the closing time of b is a maximum, while it is naught when the angular spacing of both brushes corresponds (Figure 2) to the angle occupied by the conducting part on the disc d. By making also the contact d movable, it is possible, furthermore, to adjust the point of the halfcycle where the welding current begins to pass.

Embodiment according to Figure 4 In the embodiment according to Figure 4 the disc d coacts with the contactor b for controlling the passage of the current in the welding machine. The purpose of this is to diminish the absolute error of time in the passage of the current by closing the primary circuit of the welding machine through a contact sliding on d, while avoiding any deterioration of said contact at the breaking point by effecting the breaking through the contactor.

The primary circuit passes through the body of disc d, a brush i and the main contactor b. Another brush (1 rests on disc (1. It is shifted about a certain angle with respect to i in the opposite direction to the rotation of the disc d. This angle is a function of the constant of time of the contactor. The brush d is connected with the fixed contacts e e of a relay equivalent to the relays e---e of the unit according to Figure 1. In this case both movable contacts 6 0 are connected, one with the outlet of the preparatory relay e, and the other at one end of the welding relay b of the main contactor. When the welding machine is at rest, the preparatory relay e is supplied with current without interruption, its circuit is closed through I and the pedal 1, e, e is then in contact with e while the contact is broken between c and c When the pedal is depressed the permanent feeding circuit of the preparatory relay eis broken.

Two cases are then also possible.

(1) The brush at is at this moment on a nonconducting part of disc d. Preparatory relay e is then no longer energized, the contact is broken between e and e and established between e and c Consequently, as soon as the conducting part of d comes against the brush a, welding relay bl is energized and the contactor closes. However, the circuit of the welding machine is closed only afterwards, when the conducting part of the disc d comes against the brush 2.

For the breaking the non-conducting part of disc :2 comes first against the brushd This has -for its result that the energization circuit of b is broken and that the contactor opens, consequently, before the insulating part of disc (1 has come against the brush 2'. Thus the current is already interrupted when the sliding contact opens.

(2) If, at the moment of the depression of the pedal, the brush d is in contact with a conducting part of d, the preparatory relay e remains energized through e e (1 d. Thus the circuit of b remains broken until (1 is engaged by the nonconducting part of d and so long as it is not engaged by its conducting part. Then -the device operates as in the foregoing case.

I claim:

1. In a commutator device for feeding the electrodes of a welding machine, a starting pedal, a preparatory relay controlled by said pedal, feeding means for continuously feeding said preparatory relay during the rest position thereof, a cutout relay for restoring energization of the preparatory relay as soon as a Weld has been completed, a synchronous motor fed from a current source, a rotary commutator provided with contacts controlled by the synchronous motor and controlling the preparatory relay, a welding relay controlled by the preparatory relay, and controlling the welding circuit.

2. In a commutator device for feeding the electrodes of a welding machine, a starting pedal, a preparatory relay controlled by said pedal, feeding means for continuously feeding said preparatory relay during the rest position thereof, a cutout relay for restoring energization of the preparatory relay as soon as a weld has been completed, a synchronous motor fed by a current source, a disc consisting of an insulating portion and a conductive portion, said disc being rotated by said synchronous motor, two brushes in engagement with said disc and adjustable with respect to each other, the first brush being connected to a current source, whereas the second brush is connected to the preparatory relay, a welding relay controlled by the preparatory relay and controlling the welding circuit.

3. In a commutator device for feeding the electrodes of a welding machine, a starting pedal, a preparatory relay controlled by said pedal, feeding means for continuously feeding said preparatory relay during the rest position thereof, a cut-out relay for restoring energization of the preparatory relay as soon as a weld has been completed, a synchronous motor fed by a current source, a rotary commutator operated by said synchronous motor and disposed directly in the welding circuit, said commutator carrying a brush, the latter being connected to the preparatory relay and a second brush disposed in the welding circuit, a welding relay comprising a contact disposed in series with the said second brush of the rotary commutator.

DAVID SCIAKY.

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