WO1996030155A1

WO1996030155A1 - Welding arrangement

Info

Publication number: WO1996030155A1
Application number: PCT/SE1996/000413
Authority: WO
Inventors: Torbjörn STÅHL
Original assignee: Staahl Torbjoern
Priority date: 1995-03-29
Filing date: 1996-03-29
Publication date: 1996-10-03
Also published as: SE9501175D0; SE9501175L; SE515818C2

Abstract

The invention relates to a welding device for joining at least two objects (9, 10), comprising at least two electrodes (6, 7) for contacting said objects (11, 12), and a transformer (5) for supplying a current to the electrodes (6, 7). The invention is characterized in that it comprises a rectifier (1) which is connected to an inverter (2), which in turn is connected to the transformer (5), and a frequency control device (3) for controlling the frequency of the inverter (2). The invention provides an improved welding device for welding of sheet-like material, particularly roofing panels.

Description

WELDING ARRANGEMENT

TECHNICAL FIELD:

The present invention relates to a welding device in accordance with the preamble of appended claim 1. The invention is particularly suitable for welding for the purpose of joining roofing panels.

BACKGROUND OF THE INVENTION: In the field of roofing, it is common to use stainless steel panels which are arranged adjacent to each other, thereby forming a roof. The joining of the roofing panels is normally carried out by bending an edge of a certain panel upwards, after which said edge is arranged adjacent to a further bent edge of another roofing panel. After that, the roofing panels are welded together along the bent portion which is formed by the two bent edges.

Conventional welding devices for roofing panels are often of the resistance welding type and comprise a welding head which in turn comprises welding electrodes. The welding head is guided along the bent edge portions formed by two adjacent roofing panels. The welding head is normally connected to a separate transformer which supplies current to the welding head.

The known welding devices are characterized in that they require a very high current, in the range of 3000-4000 A, which in turn demands a relatively large transformer and very thick electrical cables between the transformer and the welding head. This implies that the handling of the welding head will be very heavy and cumbersome, which constitutes a problem in connection with the known welding devices . SUMMARY OF THE INVENTION:

It is an object of the present invention to provide an improved welding device for welding of sheet-shaped material, which has a low weight and which allows simple operation. This object is solved by means of a device of the above-mentioned kind, the characterizing features of which will be apparent from appended claim 1.

BRIEF DESCRIPTION OF THE DRAWINGS: The invention will now be described in greater detail with reference to the annexed drawings, in which

Fig. 1 is a block diagram showing a device according to the present invention,

Fig. 2 is a simplified front view of a welding head according to the invention, and

Fig. 3 is a side view of the welding head according to Fig. 2.

PREFERRED EMBODIMENT:

Fig. 1 shows a block diagram of the electrical components forming part of the welding device according to the present invention. The device comprises a rectifier 1 which is supplied with an alternating voltage, preferably a 380 V three-phase voltage. The rectified voltage is supplied to a dc-ac inverter 2, which converts the rectified voltage to an ac voltage under the control of a frequency control unit 3. The frequency control unit 3 is preferably a voltage- controlled oscillator which is adapted to control the frequency of the inverter 2 so that the voltage is given a frequency of between 500 and 1000 Hz. The frequency control unit 3 can be operated manually by means of an operating device 4. The output voltage from the inverter 2 is supplied to a transformer 5 which transforms the voltage to a lower value. Furthermore, two welding electrodes 6, 7 are arranged at the output of the transformer 5. The transformer 5 supplies a current of approximately 3000-4000 A and a voltage of approximately 2 V to the electrodes 6, 7.

The frequency of the frequency control unit 3 and that of the inverter 2 can suitably be set by an operator by means of the operating device 4. Due to the control of the frequency of the inverter 2, the current supplied by the transformer 5 to the electrodes 6, 7 is also controlled. This makes it possible to adapt the welding operation for example according to the thickness of the material to be welded. Variations of the current will appear as a result of leak inductances in the magnetic circuit.

The transformer 5 and the two electrodes 6, 7 form a welding head 8. Since the welding head 8 has a small number of components, a light-weight apparatus which can be handled easily is obtained, and the above-mentioned drawbacks regarding the heavy and cumbersome cables can be avoided.

Figs. 2 and 3 show a welding head 8 during operation, i.e. during welding of two panels 9, 10. Each one of the panels 9, 10 comprises a section 11, 12 which is bent upwards. The panels 9, 10 are normally in the form of stainless steel in those cases where the welding device is used in order to weld together roofing panels.

The welding head 8 is designed with a recess in the form of a longitudinal groove 13 which serves for guiding the welding head 8 in relation to the upwardly bent sections

11, 12. The two welding electrodes 6, 7 are generally cylindrically shaped and are manufactured from a suitable metal alloy. The welding electrodes 6, 7 protrude a certain distance from the welding head itself 8 and are arranged so that they press against the upwards bent sections 11, 12 of the roofing panels 9, 10. This is carried out by means of a spring mechanism (not shown). Preferably, the device is also provided with a control mechanism adapted to adjust the pressure which the electrodes 6, 7 exert on the upwardly bent sections 11, 12.

The transformer 5 is arranged inside or on the welding head 8. The rectifier 1, the inverter 2 and the frequency control unit 3 can be arranged elsewhere. The above- mentioned inverted voltage from the inverter 2 is supplied via an electrical cable 14 (only shown in Fig. 3) to the transformer 5 in the welding head 8.

The device also comprises a handle 15, by means of which the welding head 8 can be guided manually by an operator. Consequently, the guiding of the welding head 8 can be carried out in essentially the same way as a lawnmower or a similar machine. The welding head is guided along the the upwardly bent sections 11, 12, thereby forming a continuous welding seam. Preferably, the handle 15 is provided with a switch (not shown) for switching the welding operation on and off. The handle 15 can also be provided with the above- mentioned operating device 4 for controlling the frequency of the frequency control unit 3 (see also Fig. 1).

Since the transformer 5 and the electrodes 6, 7 will become heated during use, cooling water or some other suitable cooling medium can be supplied to these components via a cooling pipe 16 (shown only in Fig. 3).

The invention is not limited to the above-mentioned embodiment, but can be varied within the scope of the subsequent claims. For example, various designs of the groove 13 and the electrodes 6, 7 are possible.

Furthermore, an engine can be arranged inside the welding head 8 in order to propel it in a forwards direction during operation thereof. Such an engine can be adapted to propel at least one driving wheel contacting any of the upwardly bent sections 11, 12. In this case, the handle 15 can be provided with a further switch by means of which the engine can be operated.

Claims

CLAIMS:

1. Welding device for joining at least two objects (9, 10), comprising at least two electrodes (6, 7) for contacting said objects (11, 12) and a transformer (5) for supplying a current to the electrodes (6, 7), c h a r a c t e ¬ r i z e d i n that it comprises a rectifier (1) which is connected to an inverter (2), which in turn is connected to the transformer (5), and a frequency control device (3) for controlling the frequency of the inverter (2) .

2. Welding device according to claim 1, c h a r a c t e ¬ r i z e d i n that the frequency control unit (3) is constituted by a voltage-controlled oscillator.

3. Welding device according to claim 1 or 2, c h a r a c ¬ t e r i z e d i n that the frequency control unit (3) can be controlled manually for adjusting the frequency of the inverter (2 ) .

4. Welding device according to any one of the preceding claims, c h a r a c t e r i z e d i n that the trans¬ former (5) and the electrodes (6, 7) are arranged in a separate welding head (8) which is adapted to be guided along the objects (9, 10) to be joined.

5. Welding device according to claim 4, c h a r a c ¬ t e r i z e d i n that the welding head (8) comprises a groove-shaped recess (13) which cooperates with the objects (10, 11) to be joined.

6. Welding device according to claim 4 or 5, c h a r a c - t e r i z e d i n that it comprises a handle (15) which is arranged on the welding head (8) and which is adapted for controlling the welding head (8) along the objects (10, 11) to be joined.

7. Welding device according to claim 6, c h a r a c t e ¬ r i z e d i n that the handle (15) comprises at least one switch for controlling at least one function of the welding device.

8. Welding device according to any one of claims 4-7, c h a r a c t e r i z e d i n that the welding head (8) is provided with an inlet pipe (16) for a supply of a cooling medium.

9. Welding device according to any of the preceding claims, c h a r a c t e r i z e d i n that the electrodes (6, 7) are spring biased so as to contact the objects (11, 12) to be joined.

10. Device for joining roofing panels (9, 10) comprising a welding device according to any of the preceding claims.

AME_NDED CLAIMS

[received by the International Bureau on 23 August 1996 (23.08.96); original claims 1,4-6 amended; remaining claims unchanged (2 pages)]

CLAIMS :

1. Welding device for joining at least two objects (9, 10; 11, 12), comprising at least two electrodes (6, 7) for contacting said objects (11, 12) and a transformer (5) for supplying a current to the electrodes (6, 7), c h a r a c ¬ t e r i z e d i n that it comprises a rectifier (1) which is connected to an inverter (2), which in turn is connected to the transformer (5), and a frequency control device (3) for controlling the frequency of the inverter (2).

4. Welding device according to any one of the preceding claims, c h a r a c t e r i z e d i n that the trans¬ former (5) and the electrodes (6, 7) are arranged in a separate welding head (8) which is adapted to be guided along the objects (11, 12) to be joined.

5. Welding device according to claim 4, c h a r a c ¬ t e r i z e d i n that the welding head (8) comprises a groove-shaped recess (13) which cooperates with the objects (11, 12) to be joined.

6. Welding device according to claim 4 or 5, c h a r a c - t e r i z e d i n that it comprises a handle (15) which is arranged on the welding head (8) and which is adapted for controlling the welding head (8) along the objects (11, 12) to be joined.

10. Device for joining roofing panels (9, 10) comprising a welding device according to any of the preceding claims .