Untitled record

The invention relates to an inert gas welding device according to the preamble of claim 1.

Inert gas welding devices in accordance with DIN 1910, Part 4, or commercially available inert gas welding devices make it possible to set the amount of shielding gas required for a specific welding task on the flow control valve. A solenoid valve is usually provided as the shut-off device and is located in the power source and wire feed unit closest to the welding torch. The torch hose package leads from the central connection of this unit to the torch body. The torch hose package can be up to 12 m long, but is usually only 3 to 4 m long. If the greater distance from the pressure source is to be welded, then at least one intermediate drive unit is used with extended supply lines (for the wire, the electricity, the protective gas and, if necessary, a cooling medium), to whose central connection (individual connections are also conceivable) the torch hose package is connected. The unit closest to the welding torch, to which the torch hose package is connected, usually contains the shut-off device. The flow control fitting can be up to 20 m and more away from the welding torch. When the shut-off element is closed, there is initially high back pressure. When the shut-off device is opened to initiate a welding process, due to the lack of significant throttling, a larger amount of gas undesirably emerges from the gas nozzle over a longer period of time than is set on the flow control valve, until finally a very low flow pressure of only a few tenths for the set amount in the flow path Bar adjusts. This waste of protective gas is very disadvantageous and costly, especially in the case of tack seams with frequent switching on and off. The flow conditions in the flow path between the flow control valve and mainly the central connection of the unit closest to the welding torch are undefined and depend on influences that change during operation, which, however, affect the amount in the gas nozzle at the low flow pressure. Although the set amount is actually maintained over a longer period of time, the amount in the gas nozzle fluctuates noticeably per short unit of time. This has an influence on the quality of the weld and leads to a process uncertainty which is undesirable for the user.

Gas-shielded welding in accordance with DIN 1910, Part 4, includes all common processes such as MSG, MISG, MASG, MSGE, MSGG, MSGP, MAGC, MAGM (metal welding) and WIG, WP, WHG, WPS, WPL, WPSL (tungsten welding) Understood. The central connection of the unit closest to the welding torch is also understood to mean individual connections. Welding devices that work according to the coaxial principle are also affected.

In a protective gas welding device known from EP-A2 0 615 809, a pressure sensor is arranged between a valve, which is arranged in the flow path just behind the protective gas pressure shaft, and the hose package to the welding torch of the flow, a welding wire feed device and / or the power source switches off. The pressure sensor contains a spring-loaded membrane that generates a switch-off signal when the value falls below the threshold. The pressure sensor has no significant throttling effect, but rather senses the actual pressure in the flow path at a relatively large distance from the welding torch. Measuring the gas pressure at such a large distance from the welding torch does not provide any meaningful information about the way in which the shielding gas ultimately emerges in the gas nozzle of the welding torch. Furthermore, due to its distance from the welding torch and its design without a noticeable throttle effect, the pressure sensor is not able to avoid or minimize waste of shielding gas when initiating a welding process or to ensure improved flow conditions in the flow path to the welding torch.

In a shielding gas welding device known from US Pat. No. 4,100,390, a gas quantity measuring device is provided upstream of the hose assembly between line sections and an electromagnetically operated shut-off valve is provided upstream of the gas quantity measuring device. A switch is integrated in the measuring device, which is operated if the gas pressure drops too far. Just measuring the amount of shielding gas by the measuring device does not improve the flow properties in the long flow path to the welding torch. The measuring device has no notable throttle function and is also not able to prevent the escape of too much shielding gas when starting a welding process.

AT 406 838 B

The invention is based on the object of improving a protective gas welding device of the type mentioned at the outset with little structural effort, which can also be retrofitted, in order to waste as little protective gas as possible, and to achieve a uniform welding point at the welding point

To achieve protective gas supply and overall increased process reliability.

The object set is achieved according to the invention with the features of claim 1.

Due to the metering nozzle, which is naturally matched to the protective gas requirement of the gas nozzle and, if necessary, to the type of flow control fitting, a defined working pressure of up to approx. 2 bar or more builds up upstream. The still undefined influences in the flow path upstream of the metering nozzle are no longer noticeable due to the defined and relatively high working pressure. The amount of shielding gas remains constant even over short periods of time. Furthermore, when the shut-off device is opened in the gas nozzle, there is no significant excess amount of protective gas, because the metering nozzle initially throttles very strongly at the high back pressure, automatically relieves the throttling effect as the back pressure drops, and because the flow path to the metering nozzle then acts as a pressure accumulator. A noticeable insensitivity of the system is achieved and the process reliability is significantly increased, the saving of protective gas when opening the shut-off device is significant. The gas nozzle is thus fed very precisely with the correct amount of shielding gas. The metering nozzle is inexpensive and can easily be accommodated (retrofitting) even with given concepts of different inert gas systems.

There is a so-called eco-valve on the flow control valve, which is supposed to prevent the initial overshoot. However, this eco-valve is very expensive and does not improve process reliability with it. It is also known to use a flow nozzle in the form of a capillary in the flow control fitting. However, this only serves to improve the control behavior of the valve.

Appropriate embodiments emerge from the subclaims.

Embodiments of the subject matter of the invention are explained with the aid of the drawing. Show it:

a shielding gas welding device in a schematic representation, a detail in an enlarged sectional view, various concepts of shielding gas welding devices, a section of a detail, and a section of a further detail.

A protective gas welding device V according to FIG a shut-off device (A). The welding torch (B) contains a contact nozzle (1) on an inner tube (2) which is surrounded by a protective gas sleeve (4) which, together with the contact nozzle (1), delimits a protective gas nozzle (3). The inner tube (2) is located in a burner body (6), to whose inert gas connection part (9) a burner hose package (S) can be connected. In the burner body (6) a metering nozzle (Z) is arranged in the flow path of the protective gas, which can be assembled from a nozzle insert (12) in a bore (11) and a retaining screw (10) for the nozzle insert. A shoulder (7) leads from the inner tube (2) into the bore (8). The extension (7) contains at least one passage into the interior of the inner tube, in which the usual guide spiral for the wire electrode (both not shown) is contained. The protective gas coming from the connection part (9) passes the metering nozzle (7) and expands inside the inner tube (2). There it flows up to a gas outlet (5) in the protective gas nozzle (4). The burner hose package (S) has a connection fitting (13) which leads to a connection (C) or a central connection (in the embodiment shown) of the power source and wire feed unit (G) closest to the welding torch (B). For tungsten welding, the unit (G) is of course only a power source and shielding gas supply unit (if necessary with a supply and discharge for a cooling medium) without a wire feed function. A counterpart (14) matching the connection fitting (13) of the burner hose assembly (S) is located in the unit (G). A protective gas nipple (15) is provided on the connection fitting (13), for example, which is connected to a pressure source (Q) for the protective gas via a connection (16) and line sections (17), (18), (19). Between the pipe cuts

Figure 1:

Figure 2:

Figure 3A to 3E: Figure 4:

Figure 5:

AT 406 838 B (17) and (18), the shut-off element (A) is arranged, usually a solenoid valve.

Between the power sections (18) and (19) there is the flow control valve (M) for setting the amount of shielding gas. In connection (C), the current (arrow 20) required for inert gas welding, if necessary the wire (arrow 21), and if necessary a cooling medium (arrows 22) is introduced into the torch hose package (s).

Instead of the metering nozzle (Z) accommodated in the burner housing (6), it can be accommodated with a comparable effect in the area of ​​the connection (C), i.e. for example in the shielding gas nipple (15), in the connection line part (16) or directly in front of its mouth. Appropriately, only one metering nozzle (Z) is provided in the entire flow path. The nozzle size of the metering nozzle is matched to the respective welding task and / or to the flow control fitting (M) used, on the one hand to achieve a relatively high working pressure of approx. 2 To generate bar in the flow path upstream of the metering nozzle (Z), to avoid the overshooting of the amount of protective gas when opening the shut-off device under the high back pressure, and to achieve defined flow conditions that lead to a uniform amount in the protective gas nozzle (3) even with small Time units leads.

Figure 2 illustrates an embodiment of the volume control valve with pressure reducing stages (31). a downstream nozzle (32) (capillary) and pressure or quantity measuring instruments. The line section (18) leads to the shut-off element (A), which is located in the unit (G) closest to the welding torch, ie between line sections (17) and (18).

In the embodiment of the inert gas welding device according to FIG. 3A (for metal welding), the pressure source is arranged in the main unit (H) (the pressure source Q could also be a ring line) and already provided with the flow control valve (M). Since the welding point is close to the main unit (H), the torch hose package (S) is only between 3 and 4 m long. The power source and wire feed unit (G) closest to the welding torch (B), which also contains the shut-off device (A), is installed on the main unit (H). The metering nozzle (Z) is located either in the connection area of ​​the unit (B) or in the welding torch (B) - see Figure 1.

In FIG. 3B, the welding point is further away from the main unit (H), the torch hose package (S) in turn being connected to the unit (G) closest to the welding torch (B) - which contains the shut-off element (A). A longer connection line, for example 5 m, is provided between the unit (G) and another unit (G) on the main unit (H).

In the embodiment according to FIG. 3C, the unit (G) closest to the welding torch (B) is a so-called intermediate drive because the connecting line (33 ') can be up to 30 m long.

In the embodiment according to FIG. 3D, the distance between the welding point and the main unit is even greater, but the torch hose package is connected to the unit (G) containing the shut-off element (A). Intermediate lines (33 and 33 ') connect the unit (G) via an intermediate drive (G¹) with the skin aggregate.

In Figure 3E the torch hose package (3 to 4 m long) is connected to the unit (G) closest to the welding torch (B), which contains the shut-off element (A). The unit (G) is located on a support device (34) and is connected to the main unit (H) via the connecting line (33).

In the prescribed embodiments, the metering nozzle (Z) is located in the flow path between the connection area on the unit (G) closest to the welding torch (B) and the gas nozzle and downstream of the shut-off element (A).

In FIG. 4, the metering nozzle (Z) is inserted into the protective gas nipple (15), for example the connection fitting (13) from FIG. The protective gas nipple (15) has an inner channel (24) for the protective gas, which is drilled and provided with a threaded hole (23) into which a nozzle insert (25) is screwed, which creates a nozzle channel of a predetermined nozzle size (diameter, for example, between 0.6 up to 0.9 mm). To change the nozzle size, another nozzle insert of a nozzle set is screwed in. No further changes are required to the welding device.

In Figure 5, the metering nozzle (Z) is designed in the manner of a rotary tap. A twistable one

AT 406 838 B

The throttle body (28) sits in a bore (29) which intersects the protective gas flow channel (24). Seals on both sides prevent shielding gas from leaking. The throttle body (28) contains a nozzle passage (29) which, depending on the rotational position of the throttle body (28), sets a specific nozzle size. The throttle body (28) is rotatably fixed with a threaded extension (30) and can be rotated from the outside.