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1. WO2020110158 - ELECTRIC RESISTANCE WELDING APPARATUS

Note: Text based on automatic Optical Character Recognition processes. Please use the PDF version for legal matters

[ EN ]

ELECTRIC RESISTANCE WELDING APPARATUS

The present invention relates to a welding apparatus.

As is known, the term "electric resistance welding" identifies a vast category of methods, in which the material to be welded is heated by electric resistance.

Apparatuses are widespread which implement this method and which are equipped with a form of clamp in which the arms have respective electrodes at the free ends (or are constituted by electrodes). From opposite sides the electrodes are kept pressed against the pieces to be welded to each other, and in turn these pieces are in contact: by making a current pass through the electrodes and the pieces, it is thus possible to dissipate sufficient heat to cause the melting of the pieces, and the desired welding.

Solutions of the type described above are adopted in many and varied fields of application, using both permanent installations and solutions that are at least partially portable.

The latter are for example used for welding sheet metal and other parts of automobile bodywork, in repair shops or directly in factories for production and assembly. In such context, conventional apparatuses have a main body, which is composed of a shell that contains the components necessary to the operation and is equipped with grips. The space occupation and the geometry of the arms and/or of the electrodes, which extend from the shell, are designed to be compatible with the shape structure of the bodywork and of the typical areas to be welded, taking account of the fact that the parts to be welded must necessarily be located in the space measuring a few centimeters (or millimeters) comprised between the two electrodes.

That notwithstanding, sometimes, owing to the geometry of the pieces to be welded and/or the shape and space occupation of the arms, it is impossible to position the pieces in the limited space comprised between the electrodes, which are usually locked in a predefined position. Therefore, in order to allow the operator to carry out the welding, conventional apparatuses are equipped with a device for temporarily releasing one of the arms. By acting on such device, the user in fact moves a conveniently contoured lock element, usually placed to interfere with the rotation of one of the arms, which can then be moved in order to temporarily space the electrodes apart. This in fact enables the optimal positioning of the apparatus for the welding (which will be carried out, obviously, only after having brought the electrodes back together and having reactivated the lock).

Release devices must obviously be designed to guard against their accidental activation and therefore, according to modes that are by now widespread, they require the use of an Allen key, which is engaged in a seat directly or indirectly associated with the lock element. Turning the key in fact makes the lock element rotate, and so it is brought from the condition of interference to the condition in which it does not oppose the rotation of the arm.

Such implementation solution is however not devoid of drawbacks.

The Allen key is a tool that is not part of the apparatus, but which the user must be able to obtain at the desired time.

By contrast, it must be noted that often the need to release the arm arises while working, during execution of the welding, for example in order to move to a portion of bodywork that otherwise is not reachable. In such context, in order to not have to leave the workstation, so leading to long stoppages or in any case unwanted extended pauses, the user needs to have previously taken care to bring the Allen key with him or in any case to have it available in the immediate vicinity.

Often it is difficult to observe such prudence in the context of normal activity, which is characterized by frenetic pace and, occasionally, by workplaces that are untidy and chaotic. In any case, even in cases where the user has the Allen key immediately to hand, a pause is necessary in order to put down the apparatus, get the key and grip it, which still results in unwanted pauses in work activity and in unwanted interruptions in the continuity of welding operations

Therefore the need has arisen to rely on a device that, while guarding against the danger of its accidental activation, does not require external equipment or tools for its actuation, insofar as the need to have them constantly available during the welding activity is a cause of inconvenience and slowdowns in the production cycle.

The aim of the present invention is to solve the above mentioned problems, by providing a welding apparatus that offers practical methods of temporarily releasing an arm thereof.

Within this aim, an object of the invention is to provide a welding apparatus that is provided with a device for temporarily releasing an arm thereof which can be easily actuated, without using external tools.

Another object of the invention is to provide a welding apparatus that is provided with a release device that has a low bulk, such as to not be a hindrance during welding operations.

Another object of the invention is to provide a welding apparatus that allows to temporarily release an arm thereof rapidly, while still guarding against the danger of accidental actuation.

Another object of the invention is to provide a welding apparatus that ensures a high reliability of operation.

Another object of the invention is to provide a welding apparatus that adopts an alternative technical and structural architecture to those of conventional apparatuses.

Another object of the invention is to provide a welding apparatus that can be easily implemented using elements and materials that are readily available on the market.

Another object of the invention is to provide a welding apparatus that is low cost and safely applied.

This aim and these and other objects which will become better apparent hereinafter are achieved by a welding apparatus according to claim

1.

Further characteristics and advantages of the invention will become better apparent from the detailed description that follows of a preferred, but not exclusive, embodiment of the welding apparatus according to the invention, which is illustrated by way of non-limiting example in the accompanying drawings wherein:

Figure 1 is a front elevation view of the welding apparatus according to the invention, with the supporting arm locked;

Figure 2 is a view from above of the welding apparatus in Figure 1 ;

Figure 3 is a cross-sectional view of Figure 2, taken along the line III-III, and shows the body in the first angular position;

Figure 4 is a perspective view of the device for temporarily releasing, with the rods in the first configuration;

Figure 5 is a side view of the device in Figure 4;

Figure 6 is a cross-sectional view of Figure 5, taken along the line VI-VI;

Figure 7 is a cross-sectional view of Figure 5, taken along the line VII- VII;

Figure 8 is a front elevation view of the device in Figure 4, with an external component removed;

Figure 9 is a front elevation view of the welding apparatus according to the invention, with the supporting arm temporarily released;

Figure 10 is a view from above of the welding apparatus in Figure 9;

Figure 1 1 is a cross-sectional view of Figure 10, taken along the line XI-XI, and shows the body in the second angular position;

Figure 12 is a perspective view of the device for temporarily releasing, with the rods in the second configuration and the first rod rotated with respect to the second rod;

Figure 13 is a front elevation view of the device in Figure 12;

Figure 14 is a side view of the device in Figure 12;

Figure 15 is a cross-sectional view of Figure 14, taken along the line XV-XV.

With reference to the figures, the reference numeral 1 generally designates a welding apparatus, which comprises a main unit 2 which directly or indirectly supports a first electrode 3 a and a second electrode 3b. The electrodes 3a, 3b can be passed through by an electric current for carrying out welding processes (typically but not exclusively using electric resistance), to which pieces placed in advance between the electrodes 3a, 3b are thus subjected.

The methods with which the electrodes 3 a, 3b and in general the apparatus 1 carry out the welding are known, and therefore they are not described further in this discussion. It should be noted however that typically the apparatus 1 is (at least partially) portable, with the unit 2 capable of being gripped by a user, for example by virtue of handles for gripping 4 which extend from the outer shell 5 of the unit 2, and moved freely in a workstation. Usually, in such context the unit 2 is connected by way of wiring to a trolley or to fixed installation, for powering and managing the operation of the unit 2 and of the components inside it (contained in the shell 5).

In a preferred application, which is cited purely for the purposes of non-limiting example, the apparatus 1 is intended for welding parts (metal sheets, for example) of the bodywork of automobiles and vehicles in general, both in production/assembly and in repair. In such context, the user can progressively move the unit 2 along the areas of the bodywork to be welded, keeping the areas between the electrodes 3a, 3b, and so carry out the desired welding.

It has been said and it should be noted in any case that the scope of application of the invention (and the protection claimed herein) extends to welding (by resistance and other means) of other pieces, products or semifinished products, just as the possibility is not ruled out of adopting the solutions described below on fixed apparatuses 1 or in any case on apparatuses of any type.

The unit 2 is associated with a device 6 for temporarily releasing a supporting arm 7 supporting a first electrode 3 a (the arm 7 is part of the unit 2 or extends from it), and the device 6 can be selectively activated in order to temporarily allow the movement of the supporting arm 7 .

Typically in fact the electrodes 3a, 3b are kept immobile at a mutual fixed distance, in order to allow the correct execution of the welding (as in the situation in Figure 1). By contrast, occasionally the very arrangement and the space occupation of the electrodes 3 a, 3 b and of the respective supporting elements (the arm 7 in particular), and also the arrangement and space occupation of the pieces/parts to be welded, do not allow to correctly position the pieces/parts between the electrodes 3a, 3b.

The device 6 makes it possible to temporarily release the supporting arm 7 and therefore makes it possible to separate, even by just a few centimeters, the first electrode 3 a from the other (for example producing the situation shown in Figure 9), thus making it possible to place the pieces to be welded more easily between the electrodes.

It should be noted that the methods with which the second electrode 3b is supported by the unit 2 (directly or indirectly, with or without an additional arm), can be any, as can be the methods with which each electrode 3 a, 3b is kept pressed on the pieces.

It should be noted moreover that the distinction between "first electrode" 3a and "second electrode" 3b is made solely for convenience of identification in this discussion, the term "first" electrode 3a meaning simply the one supported by the arm 7 that is directly affected by the action of the device 6.

According to the invention, the device 6 comprises an axially

symmetric hollow body 8, which is supported by the unit 2 with the possibility to axially rotate between at least one first angular position (in which it is arranged in Figures 1-3) and a second angular position (Figures 9-1 1).

In the first angular position at least one axial portion 8a thereof (preferably intermediate, and even more preferably equidistant from the ends) is arranged in interference with the rotation of the arm 7. Effectively, the axial portion 8a is identified by the section of the body 8 that is longitudinally aligned with the arm 7. The first angular position is clearly shown in Figure 3, where it can be seen that the body 8, with its portion 8a, opposes the rotation of the arm 7, which otherwise could occur about a pin 9.

In the second angular position however, which corresponds to a rotation of the body 8 with respect to the first angular position about its own longitudinal axis, a window 10 provided along the lateral surface of the portion 8a is arranged along the rotation path of the arm 7 (about the pin 9), in order to allow the movement of the arm. As can be seen from Figure 11 , which shows the body 8 in the second angular position, in such situation the arm 7 does not immediately encounter the opposition of the lateral surface of the body 8 (of the portion 8a), but rather the window 10, which allows a rotation at least of a few degrees, sufficient in any case to separate the electrodes 3a, 3b from each other, thus obtaining the desired object.

Furthermore, the device 6 comprises a lever 1 1 for actuating the body 8, which can rotate with respect to the body 8 and which comprises a first rod 12a and a second rod 12b, which are mutually articulated at a common end 12c.

The rods 12a, 12b can slide between a first configuration and a second configuration. In the first configuration they are aligned and accommodated in the body 8 (Figure 6 for example clearly shows such first configuration). Then, in the second configuration, the first rod 12a is extracted from the body 8 (Figures 12-13-14), while the second rod 12b is kept at least partially inside (Figure 15).

The body 8 has a seat 13 which is configured for coupling by interlocking with the first rod 12a, when the latter is arranged in the second, axial configuration and rotated with respect to the second rod 12b about the common end 12c, with respect to the condition of mutual alignment. By virtue of the coupling by interlocking between the body 8 (at the seat 13) and the lever 1 1 (the first rod 12a) it is thus possible to command the rotation of the body 8 between the aforementioned angular positions by way of the movement (rotation) of the first rod 12a, and therefore with the latter it is possible to obtain the release of the arm 7, without resorting to external tools or equipment and thus already achieving the set aim.

It should be noted furthermore that in the second configuration the rods 12a, 12b are moved until the axial portion 8a (Figures 14-15) is empty, and therefore the window 10 gives onto an empty chamber (in order to increase the space available for the arm 7 to rotate).

It should likewise be noted that, after the release, the possibility exists of providing apparatuses 1 that enable the complete disengagement of the arm 7 from the unit 2 (for example, by offering the possibility to slide the arm 7 off the pin 9, after having rotated it about the latter), where the circumstances and the requirements require it.

In particular, in the preferred embodiment, illustrated in the accompanying figures for the purposes of non-limiting example of application of the invention, the seat 13 is defined at a protruding end of the body 8, directed outward, and is constituted by a radial notch of width substantially corresponding to the diameter of the first rod 12a. Thus, the body 8 is coupled by interlocking with the first rod 12a when the latter is arranged in the second, axial configuration (i.e. it is extracted from the body 8) and rotated until it assumes an orientation perpendicular to the second rod 12b (as can be seen in Figures 12-14 for example, and also in Figures 9- With further reference to the embodiment in the accompanying figures, which are illustrative and non-limiting, the body 8 is substantially shaped like a straight circular cylinder (along which the portion 8a is therefore defined). The body 8 has an enlarged head 8b protruding at an end thereof (the end affected by the seat 13). Furthermore, the window 10 is ideally defined between two generatrices of the cylinder and two axially aligned (and at right angles to the axis of the cylinder) arcs, which are chosen to have a measure preferably less than 180°. In particular, the angle of the arcs (and therefore the width or transverse dimension of the window 10) can be freely chosen, as a function of the mechanical strength that it is desired to give to the portion 8a and/or as a function of the space that it is desired to leave for the arm 7 to rotate.

In a possible embodiment of the invention, the rods 12a, 12b can slide within a longitudinal duct which is provided coaxially inside the body 8.

Conveniently, in an alternative embodiment to the preceding one, the rods 12a, 12b can slide within a longitudinal channel 14 that is provided eccentrically inside the body 8 (i.e., the longitudinal axis of symmetry of the channel 14 does not coincide with that of the body 8, even though it is parallel thereto). Such geometric choice is clear in particular from the cross-section in Figure 7.

This is found to be of considerable practical interest: in fact, in this manner the cross-section of the body 8 (of the axial portion 8a) that is intended to oppose the rotation of the arm 7 in the first angular position is increased (with respect to the choice to provide the duct coaxially with the body 8), with benefits in terms of mechanical strength and rigidity, and therefore of safety and reliability of the invention.

Advantageously, the apparatus 1 comprises detachable means for locking the rods 12a, 12b, which can be selectively activated in the first configuration to obstruct (prevent) the accidental transition to the second configuration and therefore the involuntary actuation of the device 6. Evidently, the means increase the safety of use of the invention, in that by virtue thereof it is possible to guard against or in any case further reduce the risk that, during the execution of welding for example, the rods 12a, 12b could accidentally be brought to the second configuration from which, as has been seen, with an additional rotation of the first rod 12a, it is possible to release the arm 7.

In particular, in the preferred but not exclusive embodiment, the means for locking comprise a latch 15 which is mounted transversely on the first rod 12a (Figures 12-14 for example). The latch 15 is configured for bayonet coupling in a respective contoured recess 16, provided inside the body 8 (preferably but not exclusively proximate to the protruding end). Such coupling can occur only following a rotation of the lever 1 1 (about its own longitudinal axis) with respect to the body 8, imparted with the rods 12a, 12b in the first configuration (in that only in the first configuration is the first rod 12a arranged at such a longitudinal height that the latch 15 is located at the recess 16). According to methods that are known per se, the bayonet coupling occurs by virtue of the mutual engagement of inclined planes provided along the latch 15 with chutes and ramps defined along the recess 16.

Obviously, the latch 15 is in turn contoured so as to not obstruct the extraction of the first rod 12a, during the transition from the first configuration to the second configuration (for example, by making it align with the radial notch).

It should be noted that the means for locking can be provided differently to what is described above, while remaining within the scope of protection claimed herein. For example, there could be an external threading of an adapted component (substituting the latch 15), which can engage a female thread provided on the body 8 (in place of the recess 16).

Conveniently, the apparatus 1 comprises an indication mechanism 17,

which is automatically activated during the rotation of the body 8 (about its own longitudinal axis) with respect to the main unit 2 upon reaching the second angular position.

It should be noted in this regard that, as a function of the width of the window 10 and in general of the geometric and shape parameters involved, it could be possible to obtain the release of the arm 7 at further angular positions of the body 8, with respect to the designated second angular position. At the same time however, in such further angular positions for the arm 7 a very limited rotation travel may be permitted, precisely because of the non-optimal positioning of the window 10 with respect to the arm 7.

Noting likewise that it may be difficult for the user to identify the moment when the body 8 reaches the second angular position, when this occurs the mechanism 17 emits a signal (optical, acoustic, or of any other kind), thereby overcoming the possible drawback explained above.

In particular, in the embodiment proposed in the accompanying figures for the purposes of non-limiting example of application of the invention, the mechanism 17 comprises a sensor anchored to the body 8, which is configured to detect its alignment with a nick 18 (of any shape and size) arranged along the lateral surface of the body 8 (and preferably along the head 8b). By virtue of a suitable placement of the nick 18 on the body 8 (in particular with respect to the window 10), the condition of alignment between the nick 18 and the sensor is chosen to correspond to the point where the body 8 (which is thus indirectly detected by the sensor ) reaches the second angular position. The information thus obtained can be transmitted to the user with a signal of any kind, according to the specific requirements.

More specifically, the sensor comprises a sprung tip element 19 (Figures 2 and 9), which is usually kept pressed elastically against the lateral surface of the body 8 (and preferably of the head 8b). The tip element 19 (by virtue in fact of the elastic reaction of the spring) moves

automatically upon the alignment of the sensor with the nick 18 (by being inserted, even only partially, into the nick). The user can thus recognize when the second angular position is reached by seeing a small click of the tip element 19 (and/or by hearing the associated noise).

To increase the practicality of use of the apparatus 1 according to the invention, advantageously the lever 1 1 is provided with a knob 20 for gripping, which is fitted on the first rod 12a at the opposite end from the common end 12c. The knob 20 (which is typically but not exclusively spherical) thus defines a facilitated handle at least for moving the rods 12a, 12b between the first configuration and the second configuration and for rotating the first rod 12a with respect to the second rod 12b, in the second configuration.

Operation of the welding apparatus according to the invention and of its device for temporarily releasing is the following.

As it is noted, in order to carry out the welding activity , the apparatus 1 can be used according to methods that are traditional per se, by positioning the parts (metal sheets for example) to be welded between the electrodes 3a, 3b and keeping them pressed against the first electrode, while an electric current passes through them.

The device 6 offers the possibility to temporarily separate the electrodes 3a, 3b, or in any case to move the first with respect to the designated placement for the welding, in order to allow the user to reach areas that would otherwise be inaccessible, owing to the encumbrances and geometries of the components in play. In fact, as seen, the device 6 makes it possible to release the arm 7 that supports the first electrode 3a, in order to turn it even by just a few degrees, but enough to increase/change the distance between the electrodes 3a, 3b and indeed facilitate a repositioning of the apparatus 1.

The simple and rapid methods of interaction with the device 6, which do not require the use of external equipment, allow the user to operate the release even while working, with minimal pauses and without requiring him or her to leave the station. For example, even during the execution of a welding cycle, the user can temporarily release the arm 7 in order to move to a portion of the bodywork of a car that otherwise would be inaccessible, and then restore the welding conditions and recommence the cycle.

In more detail, it has already been seen that during the welding activity, with the electrodes 3 a, 3 b locked and adequately close together (Figure 1), the body 8 is arranged in the first angular position (Figure 3) and opposes, with its axial portion 8a, the rotation of the arm 7. The lever 11 is arranged in the first angular position (i.e., the rods 12a, 12b are accommodated in the body 8, as for example in Figures 4-8). Furthermore, preferably the rods 12a, 12b are rotated (about their own longitudinal axis) with respect to the body 8 so that the latch 15 performs bayonet coupling with the recess 16, in order to prevent accidental movements.

If the user wishes to release the arm 7 and move the first electrode 3 a, he or she first of all has to rotate the lever 1 1 about its own longitudinal axis (for example by gripping the knob 20), in order to deactivate the means for locking (in order to disengage the latch 15 from the recess 16). Then the user has to pull out (extract) the lever 1 1, bringing the rods 12a, 12b from the first configuration to the second configuration (fully extracting the first rod 12a from the channel 14). Having reached such second configuration, it is then possible to rotate the first rod 12a with respect to the second rod 12b about the common end 12c, until the coupling by interlocking occurs between the first rod 12a and the seat 13 provided on the body 8 (Figures 12-14 for example), thus rendering the latter temporarily integral with the lever 11.

At this point, the user has to impose a further rotation on the lever 1 1 (in this case, about the longitudinal axis of the body 8, which is rendered integral with it), for example by acting once again on the knob 20. In this way, the body 8 is brought from the first angular position to the second

angular position (Figure 9), in which it is the opening defined by the window 10 that is arranged along the rotation path of the arm 7, and no longer the mass of the axial portion 8a. The user can then grasp the arm 7 and move it as desired. Optionally, as a function of the position of the window 10 with respect to the arm 7, during rotation the latter can turn the body 8.

Obviously, by carrying out the operations listed above in reverse it will then be possible to restore the welding conditions and continue work as desired.

It should be noted therefore that the few operations described above, required for the release, can be carried out by the user in a few seconds, effectively by acting exclusively on the lever 1 1 (the knob 20 for example), i.e. a component of the apparatus 1.

The apparatus 1 according to the invention therefore offers convenient methods of temporarily releasing an arm 7 thereof, by using a device 6 that does not require external tools.

At the same time, the means for locking guard against the danger of accidental actuation, while the indication mechanism 17 offers the user the certainty of identifying the exact moment when, during the rotation of the body 8, the second angular position is actually reached.

It should be emphasized that in the first configuration (maintained during execution of the welding) the lever 1 1 with its rods 12a, 12b is completely contained within the body 8 (protruding at most only with the knob 20), with the body 8 in turn being fully insertable (rotatably) into the unit 2, without resulting in any increase in space occupation with respect to the unit.

During welding operations therefore, the device 6 does not impede the welding operations in any way, in fact maintaining a very reduced space occupation and being practically hidden from the user (so as not to create any hindrance for the user).

Finally, it has likewise been seen that the choice to arrange the rods 12a, 12b inside a longitudinal channel 14 that is eccentric (and not coaxial to the body 8) ensures greater rigidity and mechanical strength, in particular in the portion 8a.

The invention, thus conceived, is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims. Moreover, all the details may be substituted by other, technically equivalent elements.

In the embodiments illustrated, individual characteristics shown in relation to specific examples may in reality be substituted with other, different characteristics, existing in other embodiments.

In practice, the materials employed, as well as the dimensions, may be any according to requirements and to the state of the art.

Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.