WO2008059173A2 - Welding machine having convertible tongs. - Google Patents

Abstract

Welding machine comprising an electrical generator (2), a connection cable (12,62), resistance welding tongs (4,40,140) having two arms (20A,20B) and being connected by the connection table to said generator, and an electrical tool (60), especially an electrical resistance welding gun. This tool is connected to the tongs for its electrical supply, thus avoiding the use of a cable for connection to the electrical generator.

Description

 Welding machine having a convertible clamp

The present invention relates to a welding machine comprising an electric generator, a connection cable, a resistance welding clamp comprising two arms and connected by the connection cable to said generator, and at least one power tool.

Such welding machines are used in automobile repair.

The clamp makes it possible to perform spot welds to secure metal parts of the bodywork.

On this type of welding machine, the electric tool most often encountered is an electric resistance welding gun. The welding gun is then associated with a ground pad.

The welding gun is a multipurpose tool. It allows, for example, resistance welding of sheet metal of small thicknesses, welding of studs, welding of denting pins, or heating with a graphite pencil.

The mass pad is a metal piece that is fixed on the metal assembly on which one intervenes with the tool. The welding current delivered from the welding gun at the weld spot, passes through the metal assembly, returns to the ground pad, and thence back through the ground pad cable to the electrical generator of the welding machine.

It is known to use for the realization of such a machine an electrical generator connected on the one hand to a welding clamp and on the other hand to a power tool. An inverter type inverter is generally used as an electrical generator. The two tools are then powered independently of one another by electric current, by cables connected to the electric generator. The clamp and some power tools that can be mounted on the machine can consume very large currents of up to several thousand amperes. As a result, even if the resistance of the cables is very low, they dissipate a significant amount of energy. To reduce the resistance of the cables as much as possible, cables of large section (several cm ² ) are used. These cables which usually measure 2 to 3 meters are therefore expensive, bulky, and difficult to maneuver.

The resulting congestion is particularly problematic in the limited space of car repair shops. The object of the invention is to overcome the aforementioned drawbacks by providing a welding machine comprising an electrical generator, a connection cable, a resistance welding clamp comprising two arms and connected by the connection cable to said generator, and at least a power tool, and in which the number and / or size of the connecting cables are reduced.

This objective is achieved by the fact that in this machine, the power tool is connected to the clamp for its power supply. The electrical connection cable of the tool on the generator is no longer necessary. To allow the electrical connection of the tool on the clamp, it may include means for turning into a socket for this connection.

The tool may be for example a resistance electric welding gun, another welding clamp having a different configuration of the first, or other.

More generally, the clamp may comprise means allowing all the connections of the tool - and the associated ground shoe in the case in particular of a welding gun - to be made via the clamp. This connection may comprise a power supply connection, a connection of the cooling circuits of the tool, and finally a connection for the exchange of information between the tool and control and control means of the machine.

This machine configuration is particularly suitable for welding machines delivering supply currents of the high frequency clamp, that is to say for frequencies greater than 1 kHz, such as typically 10 kHz.

Indeed at these frequencies it is possible to use a small secondary transformer. This transformer and its rectifying diodes can be integrated into the clamp and housed inside the latter. In this case, the intensity of current flowing in the cable between the electrical generator and the clamp is reduced compared to a traditional configuration in which the transformer is located in the crankcase of the machine; and therefore it is possible advantageously to use a cable of smaller section between the machine and the clamp. The invention will be better understood and its advantages will appear better on reading the detailed description which follows, of embodiments shown by way of non-limiting examples. The description refers to the accompanying drawings, in which:

- Figure 1 is a schematic view of a welding machine according to known techniques.

- Figure 2 is a schematic view of a welding machine according to the invention.

- Figure 3a is a basic representation of a welding machine arranged according to a first embodiment of the invention wherein the welding clamp is converted into a socket for connecting the tool.

FIG. 3b is a schematic view of an alternative welding pliers of a welding machine according to this first embodiment; according to this variant, the clamp comprises a spacer mounted between the arms of the clamp.

FIG. 4a is a basic representation of a welding machine arranged according to a second embodiment of the invention in which the welding tongs perform the function of a mass slider; in this variant, an arm of the clamp is isolated by adding an insulating part. FIG. 4b is a schematic view of an alternative welding pliers of a welding machine according to the second embodiment; in this second variant, a removable arm of the clamp is replaced by a clamping arm.

We will now describe in more detail, in connection with the appended figures, certain embodiments of the invention.

Referring to Figure 1, a welding machine using known techniques will now be described.

This machine comprises firstly an electric generator 2 housed in a metal housing 22. It also comprises a welding clamp 4 and a first cable 12 through which the clamp is connected to the electric generator. It also includes a power tool a soldering gun 6. The latter is connected to the electrical generator by a second cable 8. The ground pad 10 which is associated with the welding gun is connected to the electric generator by means of a third connecting cable. 18. The electrical generator comprises a control and control part 24 by means of which it triggers and adjusts its operation. It also comprises unrepresented connection means for its own power supply.

As the clamp is generally quite heavy and can exceed 10 kg, a suspension device 14 is also provided. It can support the weight of the clamp and possibly the cable or cables to facilitate interventions.

Finally, this type of welding machine is generally mobile on wheels 16, so that it can be easily moved to a car repair shop or other.

Referring to Figure 2, a welding machine according to the invention will now be described.

This machine has the same elements as the machine described above, with the following differences: Instead of having several connection cables (12,8,18) to the electrical generator, one for the clamp, another for the tool, a third for the ground pad, in this machine, only the clamp is connected to the electric generator. The tool - here a welding gun - is connected to the clamp. In addition, the clamp acts as a mass skid. Referring to Figure 3a, a welding machine according to the invention in a first embodiment will now be described.

In this embodiment, the clamp is converted into a socket allowing the particular electrical connection of the tool. Its pinching function, and even more so its welding function, is not used during the interventions with the tool. The clamp arms may or may not be disassembled (if applicable) and have not been shown.

The tool is a resistance electric welding gun, associated with a ground pad. This machine comprises an electric generator 2, a welding clamp 40 connected by a cable 12 to the electric generator; a pistol welding 60, a cable 62 connecting this gun to the welding gun 40; a ground pad 100, a cable 102 connecting this ground pad to the welding tongs 40.

In a simple version, the terminal elements of the clamp are provided to be dismountable; they may be replaced by connecting elements provided at the ends of the cables 62 and 102.

This machine is configured for an intervention on a metal assembly 32 using the welding gun: In the example shown, it is desired to make a weld point between the metal parts 34 and 35 of the metal assembly 32.

For this, the operator connects - or makes the connection if necessary - the welding gun 60 and the ground pad 100 directly on the clamp 40. It also fixes the ground pad on the metal assembly 32, in ensuring a good electrical connection of the ground pad on this set. It then positions the welding gun to the right of parts 34 and 35 to be welded. He can then realize his welding point.

Thus, for the production of the welding point with the welding machine, only the cable 12 for connecting the clamp to the electric generator had to be deployed and connected to the electric generator; the tool could be directly connected to the clamp.

Referring to Figure 3b, a clamp variant of a welding machine made according to the first embodiment of the invention will now be described. This welding clamp comprises a frame 44 on which are fixed the two arms of the clamp (20A, 20B). These two arms are bent towards each other. The clamp has a hinge 46 allowing the two arms to close against each other. Thus, when the two arms are clamped on parts to be welded together and the welding current is delivered by the arms of the clamp through the parts to be welded, a weld spot is made according to a welding operation known in the art. .

In the figures, an articulated clip X is presented.

Naturally, a clamp using any other type of joint, for example a "C" joint, can also be arranged in a welding machine according to the invention. The welding machine also comprises the welding gun 60. This gun comprises an electrode 64 crimped on a housing 68, and a handle 66. It is connected to the welding gun by a cable 62. the clamp towards the gun. In the simplest case, this cable may be a simple electrical conductor in an insulating sheath; it can also be a more complex cable, integrating a set of conductors (for the transfer of current or the exchange of information), as well as cooling fluid lines. The current is returned to the clamp via the mass skid

100 associated with the welding gun 60. This mass pad is constituted by a metal plate 104 adapted to be fixed on a metal sheet or assembly on which it is desired to intervene with the gun. The plate 104 is connected to the welding clamp by a cable 102. The welding clamp 40 also comprises an internal cooling system, not visible in the figures.

The clamp may advantageously have a set of means that can transform it into a socket for connecting the tool, not only for its power supply, but also for its cooling, and the exchange of information with the rest of the machine.

As regards the connection of the tool for its power supply, these means can be for example electrical terminals on which connection plugs can be connected. These terminals can be located either on the frame of the clamp or on the arms.

According to the variant presented in FIG. 3b, these means comprise a spacer mounted between the arms of the clamp and comprising two connection parts electrically insulated from one another and connected respectively to the two poles of the clamp, the tool and a mass slider which can be electrically connected respectively to these two parts by cables.

Advantageously, the spacer thus placed also allows the locking of the arms of the clamp.

The two connection portions of the spacer 8OA and 8OB are conductive and separated by an insulating member 82. At their ends opposite, they are fixed directly on the arms of the clamp 2OA, 2OB where an electrical contact is established.

The connection cables 62, 102 of the welding gun and the ground pad are respectively connected to these two connection parts.

To make the connection of the welding gun and the ground pad, the arms are separated from the clamp, the spacer is placed between them, and the arms of the clamp are closed. The spacer is arranged such that it maintains the arms of the clamp in a position without mutual contact.

Advantageously, the ends of the spacer may have a shape complementary to the shape of the arms of the clamp, to ensure a stable mounting of the spacer on these arms. For example, if the clamp arms are of circular section, each end of the spacer may be fork-shaped with a passage of cylindrical section between the branches of the fork, the clamp arm being housed and supported in this passage.

Thus very conveniently, in a single mounting operation of the spacer between the arms of the clamp, it ensures the electrical connection of the tool, the ground pad, and blocks the clamp arms in position without mutual contact .

In some cases, the tool has an air or water cooling circuit. The clamp must then naturally include means 48 to allow the connection of this cooling circuit to the clamp.

To allow this connection, these means can be in particular flexible pipes 48 which connect the clean cooling circuit of the clamp to the cooling circuit of the tool. The spacer 80 can integrate a connection interface between these lines 48 and the hybrid cable 62 for connecting the tool. (This cable is called hybrid in the sense that it conveys both the feed current of the tool and its cooling fluid.)

Finally, the operation of the tool may require exchanges of information between the tool and the control and control part of the welding machine. For the sake of simplicity, here we will talk about exchanges of information between the tool and the welding machine. Advantageously, this exchange of information can be done from the tool via the clamp. For example as shown in Figure 3, an information transfer cable 50 is connected between the tool and the clamp and allows the transfer of information between the tool and the welding machine. In a relatively simple first case, the information that one seeks to transmit to the welding machine is simply a tool connection information on the clamp, that is to say the presence of the tool. With this information, the current generator delivers current only for the only operations achievable by the tool, and can not deliver current for operations achievable by the clamp. The safety devices possibly provided for deactivating the clamp are implemented.

In this case, the tool may include an extension up to the clamp, and which allows the welding machine to obtain the connection information of the tool on the clamp.

This extension is typically a cable 50. It can also be a simple link at the end of which is a connector 51. This connector is attached to the clamp when connecting the tool. It establishes an electrical contact through which the connection information of the tool is obtained and transmitted to the welding machine.

Advantageously, the machine comprises means for measuring the temperature of the clamp and / or the tool. Thanks to these measurements, the interventions made with the welding pliers and the tool can be carried out in a finer and more efficient way. Referring to Figures 4a and 4b a second embodiment of the invention with two variants of the welding pliers will now be described.

This embodiment relates in particular to the tools used in association with a mass pad. It consists in using the clamp, not only for the particular electrical connection of the tool, but also as a grounding plug. The clamp is then used pinched on the metal assembly on which one intervenes with the tool, in conjunction with it. As a result, the mass pad can be removed, since the clip performs its function. This embodiment requires firstly that the tool is electrically connected to a first pole of the clamp, and secondly, that the part clamp that performs the clamping on the metal assembly is connected to the second pole of the clamp and isolated from the first pole, to ensure the return of the current to the clamp and from there to the electric generator.

To obtain this result, a first variant is illustrated in FIG. 4a. It consists in that the machine further comprises a removable insulating piece 30 for example a plug, adapted to be inserted between a first arm 20A of the clamp and the part on which it is pinched. The removable part thus isolates the first arm relative to the workpiece on which the clamp is pinched and relative to the other arm. Thus when clamping the clamp on the metal assembly, it is then clamped between the removable insulation part and the second arm and is electrically connected to the second pole of the clamp.

To obtain the above result, a second variant is illustrated in FIG. 4b. It requires that a portion of a clamp arm is removable. The welding machine then has a clamping portion that can be mounted on the clamp instead of this removable portion. One end of the clamping portion is insulated from its attachment point on the clamp or the clamp arm, and cooperates with the other arm of the clamp to provide the clamping function of the clamp. Optionally, this removable part may be the entire arm.

Advantageously, the tool can be connected to the clamp on said clamping part.

This configuration is presented in detail in Figure 4b. The arm 120B of this figure is identical to the arm 20B shown in FIG. 3b. In contrast, the arm 2OA of Figure 3b was removed and replaced by a clamping portion 120A. As this part of the pinching replaces the entire clamp arm, we will speak rather here of clamping arm 120A. This clamping arm comprises a bent electrode 122, the end of which can be opposite the end of the arm 120B, which allows the two arms 120A and 120B to perform the clamping function.

The clamping arm further comprises an insulating sleeve 124. This sleeve rigidly supports the electrode 122 and isolates it from the rest of the clamp. It is fixed on a connecting piece 126 which allows the electrical connection of the tool 60 (the welding gun) on the first pole of the clamp 140, and the mechanical fixing of the clamping arm 120A on the clamp. Thus, the tool is electrically powered via its tip 126 connected to the first pole of the clamp; on the other hand, the arm 122 can be gripped with the second arm of the clamp on the metal assembly on which the intervention with the tool is made, electrically connecting the metal assembly to the second pole the clamp, without risk of electrical contact with the first pole of the clamp.

This second embodiment with respect to the welding machine according to known techniques, allows the removal of the connection cable of the tool to the electric generator, but also the removal of the ground pad and its connecting cable, the function of mass slider being directly ensured by the welding pliers.

From this second embodiment, it is possible to derive a clamp comprising an arm from which a removable part can be dismounted in order to connect in its place the power supply of the tool or the cable of a ground pad. Of course this removable part can be the entire arm.

Note that in this document the term cable refers to a cable in the broad sense, that is to say one or more cables, each of these cables possibly being a hybrid cable that is to say a cable carrying one or several streams among electrical or optical signals, electric currents, coolants, or the like.

Claims

1. Welding machine comprising an electric generator (2), a connection cable (12,62), a resistance welding clamp (4,40,140) comprising two arms (20A, 20B) and connected by the connection cable to said generator, and at least one electric welding tool (60), characterized in that said tool is connected to the clamp for its power supply. 2. Welding machine according to claim 1, characterized in that the tool (60) is an electric resistance welding gun. 3. Welding machine according to claim 1 or 2, characterized in that the frequency of the feed current of the clamp is greater than 1 kHz. 4. Welding machine according to any one of claims 1 to 3, characterized in that a current transformer and its rectifying diodes is integrated in the clamp. 5. Welding machine according to any one of claims 1 to 4, characterized in that the clamp further comprises means for converting it into a socket for the electrical connection of the tool. 6. Welding machine according to any one of claims 1 to 5, characterized in that a spacer (80) mounted between the arms (20A, 20B) of the clamp further ensures the maintenance of the arms of the clamp in a position without mutual contact. 7. Welding machine according to claim 6, characterized in that said spacer (80) comprises two connection portions (80A, 80B) electrically insulated from each other and respectively connected to the two poles of the clamp, the tool (60) and a ground pad (100) electrically connectable respectively to these two parts by cables (62, 102). 8. Welding machine according to any one of claims 1 to 6, characterized in that a portion of an arm is removable and can be disassembled to connect in its place the power supply of the tool or the cable of a mass skid. 9. Welding machine according to any one of the claims 1,2,3,4,5 or 8, characterized in that the clamp (140) is used as mass taken by being pinched on a metal assembly on which one intervenes with the tool (32). 10. Welding machine according to claim 9, characterized in that to use the clamp (140) as ground, said machine further comprises a removable insulation piece (30) adapted to be interposed between a first arm of the clamp and the piece on which it is pinched, and thus isolate the first arm relative to the part on which the clamp is pinched and relative to the other arm. 11. Welding machine according to claim 9, characterized in that to be able to use the clamp as ground, a portion of a clamp arm is removable and said machine further comprises a clamping portion, said removable portion being replaced by said nip portion, one end of which is insulated from its attachment point on the clamp or the clamp arm and cooperates with the other arm of the clamp to provide the pinching function of the clamp. 12. Welding machine according to claim 11, characterized in that the tool is further connected to the clamp on said clamping portion. 13. Welding machine according to any one of claims 1 to 12, characterized in that all the connections of the tool are made via the clamp. Welding machine according to one of claims 1 to 13, characterized in that an information transfer cable (50) between the welding machine and the tool (60) is connected to the clamp (40). 15. Welding machine according to any one of claims 1 to 13, characterized in that an extension (50) of the tool up to the clamp (40) allows the welding machine to obtain the connection information of the tool (60) on the clamp. 16. Welding machine according to any one of claims 1 to 15, characterized in that it comprises clamping temperature measuring means (4, 40, 140). Welding machine according to one of claims 1 to 16, characterized in that it comprises means for measuring the temperature of the tool (60). 18. Welding machine according to any one of claims 1 to 17, characterized in that the tool (60) comprises a cooling circuit by air or by water. 19. Application of the welding machine according to any one of claims 1 to 18 for the repair of motor vehicles.