WO1996017709A1

WO1996017709A1 - Device for direct-current welding and way of using the device

Info

Publication number: WO1996017709A1
Application number: PCT/SE1995/001308
Authority: WO
Inventors: Bror Gösta PETTERSSON
Original assignee: Pettersson Bror Goesta
Priority date: 1994-12-06
Filing date: 1995-10-26
Publication date: 1996-06-13
Also published as: SE9404223L; SE9404223D0

Abstract

This patent application describes both a method, using a vehicle's standard electric equipment, with which it is possible to perform arc welding, and a device that facilitates switchovers between normal vehicle operation and welding without modification of the standard equipment. The device includes an electrode holder (6) with built-in rectifier (5) and a multifunction selector (14) which in one step takes care of all switchovers necessary for welding. In a special form of design, there are two independent sources of current, one with low-voltage direct current and one with, in relation to the former, high-voltage direct current. These two sources of current are made to work together according to this invention so that arc welding can be performed.

Description

Device for direct-current welding and way of using the device

State of the art Arc welding is today the dominating method of joining metals. There is a long list of machines for this purpose. These machines are electrical apparatuses for generating the form of electrical energy best suited to each purpose. Many of these apparatuses also have devices, in the form of a gas supply, for protecting the arc.

The need for small, lightweight and simple welding sets is great. They may be for small jobs in agriculture, forestry or on contracting machines. Needs of the same type can also arise on boats. It can then be considered an advantage if the welding equipment can be easily used without having to bring along a special machine for the purpose. It is, for example, possible to use a vehicle's modified electrical system. Free-standing combustion- engine powered units are available on the market. There are naturally also welding sets that can be connected to a normal electric socket. Unfortunately, in many cases such a socket is not accessible.

The literature refers to a number of proposed solutions for how to use a vehicle's electrical system to be able to perform arc welding. The American publications 3,681 ,611, 4,853,557 and 4,868,480 can stated specially here.

All the American patents listed above describe methods in which a vehicle's generator (alternator) is replaced by a further developed alternator that permits welding and sometimes also that a normal electric socket with up to 220 V alternating current, including frequency control, is obtained.

Summary of the invention

This invention involves a method with, compared to the methods described in the literature, distinctive power, which implies that without major intervention or with a simple connecting device, can use a vehicle's standard equipment. With that it should be clear that this constitutes commercially favourable equipment with a great industrial potential.

By using two independent sources of current, the battery and the alternator in a 12 V (for which an extra battery must be used) or 24 V system, connected together with a rectifier (diode) to a welding electrode, it is possible to weld, if the work piece and alternator are earthed together with the negative terminal of the battery. This arrangement provides a self- controlling welding system, as regards amperage, for ordinary electrode sizes. A major simplification is achieved if a handle that contains a holder for an electrode is equipped with the necessary rectifier connected to the battery. The decisive factor is that it must be possible to obtain the voltage to strike an arc, which is normally about 70 V, using the alternator, to then, with the normal battery voltage, perform welding with an amperage greater than the alternator's normal rated current.

In another design form of the invention (see Figure 5), another, independent source of direct current (17) can be used instead of the alternator. An example is an alternator with rectification or an existing direct current source connected to the mains. In this form of design, in the same way as described above, this new independent direct current source will be responsible for ensuring that the voltage necessary to strike an arc for the electrode is obtained. Then, another independent source of current (18), such as a battery, will provide the necessary current to permit welding.

More generally, it can be said that there are two independent sources of current. One (18) provides low-voltage direct current (e.g. a battery) and the other (17) a high-voltage (in relation to the first source) direct current. The important feature is that this invention makes these two sources work together so that arc welding can be performed. Detailed description of the invention

To clarify the reasoning below, refer to Figure 1. The intervention specified above aimed at achieving the power sought consists of the following main parts. The alternator (1) is electrically disconnected from the remainder of the vehicle's electrical system. But any earth lead (2) shall be retained.

The mechanical connection between the engine and alternator shall be retained to ensure the engine's other essential functions (cooling, air conditioning, etc.). Disconnection may be achieved either by using normal hand tools to remove the terminal connections or by fitting a suitable connecting device. The connecting device then permits disconnection between the alternator and the electrical system and makes the following additional connections. A lead is connected between the work piece and the vehicle's chassis (3) or the battery's negative terminal (11). To the battery's positive terminal (12) is connected by a cable (4) a device that consists of a rectifier (5) placed either in the vehicle or in a handle (6). Further, a cable is connected from the battery's positive terminal directly to the alternator's excitation winding (7). Finally, a lead is required from alternator's positive terminal (9) to the lead downstream of the rectifier (8). After this connection, the alternator can no longer charge the battery (10).

The battery's positive terminal (12) is, however, still connected to the vehicle's electrical system.

The connecting device mentioned above need not necessarily be used but it does provide great practical advantages. It will be specially advantageous if the connecting device is used for simplification as described above and is combined with the rectifier being placed in a handle, which is at the same time the attachment device for the welding electrode. This provides a very simple device that permits practical and fast use of the device.

To describe the connecting device and handle in greater detail, refer to Figures 2 and 3. Figure 2 indicates the appearance of the connecting device. This device can now be placed in the cab of the vehicle, for example. It is also possible to place the device under the bonnet or on the outside of the vehicle, to simplify the switchover.

The connecting device is best described in detail as follows: Using a connecting device with several connecting functions, the following functions can be effected. The battery's positive terminal (12) is connected on activation to the weld electrode holder via the rectifier (5). The alternator's charging terminal (positive terminal) (9) is connected on activation to the weld electrode holder (6), but downstream of the rectifier (5). The alternator's excitation winding (7) is connected directly to the battery's positive terminal (12). Other connections to the alternator (16) are disconnected from the system.

The handle can be designed as shown in Figure 3. It is then practical that the rectifier be placed in the handle. The lead from the battery (4) and the lead from the alternator (17), which are in a joint cable are connected using a plug.

To illustrate the mode of operation of the device, refer to Figure 4. After the necessary connections, the engine may be started. Set the engine speed so that the voltage necessary to strike an arc is generated for the electrode against the work piece (V₀). The voltage from the alternator drops, in accordance with the first part of the graph in Figure 4. to the battery's working voltage (VB). The amperage from the alternator (I_j) then assumes a value, which is the alternator's rated current. The arc's further energy demand in the form of current (I2 - I_j) at the battery's working voltage is supplied by the battery. As an example it can be stated that if the alternator's rated current is 50 A and 2.5 mm electrodes are used, the possible welding time will be equal to the time the battery requires for recharging. In step with the battery discharging during the course of welding recharging will be required. This can be achieved in the following way: The electrode holder is attached to the pin (15), after which the alternator's energy is supplied to the battery in the form of a quick charge at the alternator's rated current. According to the example above, the charging time will be equal to the effective welding time. During charging the handle cools as the rectifier (the diode) heats up during welding.

Claims

Patent claims

1

Device to permit, inter alia, arc welding using coated electrodes by simultaneous use of two independent sources of current characterized in that one of the independent sources of current generates the voltage necessary to strike an arc (17) with the electrode and the other independent source of current (18) generates the current necessary for welding and the two sources of current work together during welding.

2

Device to permit, inter alia, arc welding using coated electrodes by simultaneous use of a battery and alternator included as standard equipment in a vehicle, as the energy generator, in which a diode is used to electrically connect the battery characterized in that the alternator (1) generates for use the necessary starting voltage over and above the rated voltage of the battery (10) and the battery (10) supplies the current over and above the rated current of the alternator (1) necessary for continued operation, for which the alternator (1) is driven by a source independent of the battery (10) and the device is driven intermittently so that the remaining time can be used for the necessary charging of the battery (10) and cooling of the diode (5).