Welding Transformers

Abstract

The present invention relates to a welding transformer, of the kind in which each of the coils of the primary and secondary circuits is divided into two parts extending parallel to a magnetic shunt member and so arranged on the two transformer legs that the two coil parts of the primary coil are located on the one side of the shunt member and the two coil parts of the secondary coil on the other side, and wherein the amperage is controlled by means of the substantially M-shaped shunt member, which is displaceably arranged between the primary circuit and the secondary circuit.

Description

In connection with welding transformers it has been previously known to control the welding current by means of an additional dissipation (dispersion) field.

In connection with such welding transformers it is most convenient when the welding current can be controlled (regulated) over a large range (area); that the transformers are small in size and light-weighted for transport, etc.

These objects are obtained according to the invention by provision of a welding transformer of the kind described being characterized in that the ratio of the width of the center leg of the magnetic shunt member to that of the outer legs of the same is approximately as 1 to 1, and that the length of the window of the transformer core in the longitudinal direction of the shunt member to the width of the legs of the core is approximately as 2 to 1, so that the center leg of the magnetic shunt member, together with the primary and secondary coil parts fill out the window of the core, while the outer leg and yoke of the shunt member fill out the remaining outer space between the primary and secondary coil parts when the shunt member is in its inserted position.

A maximum welding current is then more rapidly obtained in the adjustment range for the shunt in which the shunt is moved out of the intermediate space and passes the outer limit of the coils. According to the invention the legs of the M-shaped shunt member are so shaped at their end portions that substantially all points of said end surfaces simultaneously pass the outer limits of said intermediate space.

The end surfaces of the shunt member legs are shaped to correspond to the outer circumference of the coils. This is achieved by removing the inner corners of the outer legs of the M-shaped shunt member and also both corners of the center leg, whereby the shunt member obtains concave surfaces substantially corresponding to the outer circumference of the coils.

The large area of the shunt member allows a correspondingly lesser width (approximately one-third of that of conventional welding transformers) so that the primary and secondary coils approach each other to a very high degree, and a substantially higher maximum welding current is obtained.

In order to obtain a simple and vibrationless guiding of the shunt member some of the shunt member plates are narrower than the other plates, thus forming grooves in the center leg of the shunt member, said grooves engaging guide members provided on the inner sides of the transformer core. Those plates forming the side walls of said grooves are bent inwards towards each other, so that they rest resiliently against said guide members. Movement of the shunt member is obtained by means of a spindle cooperating with a nut mounted on the side surface of the shunt member. This method of guiding the shunt member requires very little space and it is therefore not necessary to remove too much of the plate material of the shunt member in order to procure space for the guide arms. Said guide arms are fastened to the transformer core and engage grooves provided in the shunt member. Said guide arms are fastened to the core by means of a clamp device, which simultaneously serves to compress the plates of the transformer core. The guide arm is formed with a step with a pin cooperating with one end of a clamping piece, to the other end of which a bolt is fixedly or detachably mounted, said bolt being inserted into another clamping piece on the other side of the transformer core. These clamping pieces are compressed around the transformer core by means of nuts on said bolt's end portions. The outer ends of the guide arms are supported relative to each other by means of a yoke, on which a rotatable spindle is provided, said spindle cooperating with a nut member on the shunt member. By rotation of the spindle the shunt is moved out of or into the intermediate space of the primary and secondary coils.

Other objects, features and details of the welding transformer according to the invention will become apparent from the following description taken in conjunction with an embodiment.

In the drawings:

FIG. 1 shows the transformer in side elevation, illustrating the magnetic shunt member, the coils and guiding devices.

FIG. 2 shows the transformer in plan view.

FIG. 3 is a perspective view of a guiding provided in the transformer core cooperating with a groove provided in the magnetic shunt member.

FIG. 4 is an exploded perspective view of the clamping device.

The welding transformer comprises a rectangular core 1 having divided primary and secondary coils 2 and 3, an intermediate M-shaped magnetic shunt member 4, the center leg of which, together with the coils 2 and 3, fill out the transformer core window. When the magnetic shunt member occupies its inner (lower) position, its outer leg and yoke will fill out a substantial part of the air space between the coils 2,3 of the primary and secondary circuits.

By correct measurement of the coil parts, the core 1 and the magnetic shunt member 4, in order to obtain an optimally compacted (concentrated) construction of the transformer, the coils 2,2 and 3,3 will be wound in such a manner that approximately full (total) utilization of the available area of the window of the transformer is achieved (excepting the space occupied by the shunt member). Thereby, a certain ratio is established between the width of the center leg and that of the outer leg, said ratio being approximately 2:1. The end surfaces 18, 19,20 of the M-shaped shunt member 4 are shaped in accordance with FIG. 1, so that when the shunt member 4 is moved out of the intermediate space of the primary and secondary coils 2 and 3, substantially all points of said end surfaces will pass the outer limit of said coils simultaneously. The shunt member 4 will thereby leave the magnetic fields of the coils, whereby a maximum amperage is more rapidly obtained.

In order to provide a simple and vibrationless guiding between the transformer core 1 and the magnetic shunt member 4, the center plates of the center leg of the latter may be narrower than the other (see FIG. 3), so that grooves 5 are formed, such grooves 5 engaging guide members 6, provided on the inner portion of the core. Those plates forming the side walls 7 of the groove 5, are bent somewhat inwards towards each other, so that a resilient connection between the guide member 6 and the groove 5 is obtained. FIGS. 1 and 4 illustrate a guiding device between the core 1 and the magnetic shunt member 4, said device comprising clamping means compressing the plates of the core. The clamp device comprises a first clamping piece 25 and a second clamping piece 26,both having a U-shaped section and adapted to compress the plates of the core 1 by means of bolts 8 and 9. One (8) of said bolts 8,9 is fixedly (rigidly) connected with the clamping piece 26 and the other detachably connected with the clamping piece 26 by means of a pin 11 projecting from a step 10 adapted to engage a hole 12 in the clamping piece 26. A guide arm 13 is at its free end supported relative to another guide arm 13 by means of a yoke 15. On said yoke 15 a rotatable spindle 16 is provided, said spindle engaging a nut member 17 provided on the side surface of the shunt member 4. By turning the spindle 16 the shunt member 4 is moved into or out of the intermediate space between the primary and secondary coils.

The flanges of the clamping pieces 25, 26 serve as distance pieces for the coil parts 2,3.

According to the invention, transformers of the kind described become smaller in size and weight than ordinary welding transformers possessing the same maximum amperage. According to the invention a lower amperage is obtainable as compared with conventional transformers of this kind.

Claims

What is claimed is:

1. Welding transformer, in which the coils (2,3) of the primary and the secondary circuits each is divided into two parts extending parallel to a magnetic shunt member (4) and so arranged on the two transformer legs that the two coil parts (2,2) of the primary coil are located on the one side of the shunt member (4) and the two coil parts (3,3) of the secondary coil on the other side, and wherein the amperage is controlled by means of the substantially M-shaped shunt member (4), which is displaceably arranged between the primary circuit and the secondary circuit, characterized in that the ratio of the width of the center leg of the magnetic shunt member (4) to that of the outer leg of the same is approximately as 2 to 1, and that the ratio of the widths of the outer legs is approximately as 1 to 1, and that the ratio of the length of the window of the transformer core (1) in the longitudinal direction of the shunt member to width of the legs of the core is approximately as 2 to 1, so that the center leg of the magnetic shunt member, together with the primary and secondary coil parts (2,2; 3,3) fill out the window of the core (1), while the outer leg and the yoke of the shunt member (4) fill out the remaining outer space between the primary and secondary coil parts when the shunt member (4) is in its inserted position.

2. Welding transformer according to claim 1, characterized in that the legs of the M-shaped shunt member (4) at their end portions are so shaped in relation to the circumference of the primary and secondary coils (2,3) that substantially all points of the end surfaces (18, 19,20) of said legs, when the shunt member is moved out of or into the intermediate space of said coils, approximately simultaneously pass the outer limits of said intermediate space.

3. Welding transformer according to claim 1 characterized in that grooves (5) are formed in the side surfaces of the center leg of the magnetic shunt member (4), said grooves (5) being formed by selecting a smaller width of some of the shunt member plates than for the remaining plates, and that these grooves (5) correspond to or cooperate with guide members (6) provided on the inner side surfaces of the transformer legs, and that the plates forming the side walls (7) of the groove (5) are bent inwards towards each other, in order to rest resiliently against the guide members (6).

4. Welding transformer according to claim 1 characterized in that a guide device for the shunt member (4) comprises guide grooves provided on the shunt member (4) and guide arms (13) provided on the core (1), said guide arms (13) forming a part of a clamp device for compression of the core plates.

5. Welding transformer according to claim 4, characterized in that said clamp device comprises a first clamping piece (25) having holes for insertion of bolts (8,9) fixedly or detachably mounted on a second clamping piece (26), one (9) of said bolts (8,9) being extended beyond said second clamping piece (26), said bolt extension forming said guide arm (13).

6. Welding transformer according to claim 5, characterized in that the clamping pieces (25,26) have outwardly projecting flanges, acting as distance pieces for the coils (2,3).

7. Welding transformer according to claim 6, characterized in that the extended bolt (9) has a projection or gradation provided with a pin (11) for engaging one end of said second clamping piece (26), said extended bolt (9) and said other bolt (8) being inserted into the holes of the first clamping piece (25), in order to compress the core plates and simultaneously providing a fastening for the guide arm (13).

8. Welding transformer according to claim 7, characterized in that said guide arms (13) at their free ends are supported relative to each other by means of a yoke (15), on which a rotatable spindle (16) is provided, said spindle cooperating with a nut (17), mounted on the side surface of said shunt member (4) and being adapted to move said shunt member out of or into the intermediate space of the primary and secondary coils, when said spindle is rotated.