FR2703295A1 - Portable welding pliers for high-frequency welding of plastic sheets. - Google Patents

Abstract

The invention relates to a portable welding clamp comprising an actuation mechanism for manually opening the clamp against the springs associated with clamping the electrodes. According to the invention, the articulation axis (104) of the upper arm (103) is arranged at the level of the proximal end of the main body (101), behind a gripping stick (112) fixed under said body; the actuating mechanism further comprises a maneuvering lever (121) articulated on the main body (101), and a transmission assembly (123) with adjustable mechanical force reduction connecting this lever to a support ramp carried by the upper arm (103).

Description

 The invention relates to the high-frequency welding (H.F.), thermal or otherwise, of plastic sheets, and more particularly to a portable welding clamp designed to perform H.F. welding operations.

 In certain fields of application, the constituent material and the thickness of the sheets to be welded require a more powerful generator than for current applications (such as packaging with polyethylene films for example), and especially a higher clamping pressure between the electrodes of the welding tongs.

 This is the case, for example, for the welding of plastic bags used for the evacuation or the introduction of contaminated materials or wastes under confined continuity. In this case, bags made of weldable polyurethane or ethylvinyl acetate, with a thickness of around 0.3 mm, are used. Such bags are mounted on lids (or "round bags") waterproof glove box, whose diameter generally varies from 100 to 600 mm, with a standard of 186 mm used in European standards.

 It is then a question of welding two thicknesses (the two walls of the bag), or four thicknesses (the bag being rolled up), over a length of 150 to 1000 mm, or 290 mm for the glove boxes with standardized opercules.

 The power of the generator does not pose in general any particular problem, because one uses a generator mounted on rollers or feet. On the other hand, for the portable soldering gun which is connected to the generator by a coaxial cable of several meters in length, it is interesting to have an electrode length as large as possible (to limit the number of passes required to weld a bag in flattened state over its entire width) and also an adjustable electrode application pressure and which can be as high as possible depending on the type of material to be welded.

 Portable welding tongs are known for which the electrodes are clamped hydraulically or pneumatically. In addition to the complication inherent in the hydraulic or pneumatic supply, the "scissor" structure of this type of embodiment results in long-length pliers, in particular about 370 mm for electrodes 110 mm in length. If one sought to lengthen the electrodes to reduce the number of passes, for example with 300 mm electrodes, one would arrive at a clamp of 560 mm in length and relatively high weight, so that even the grip would quickly become uncomfortable .

 To avoid the stress and the cost of a compressor, it has also been studied welding tongs that are manually operable.

 Such tongs are then of the type comprising a main body whose distal end forms a lower arm on which is fixed a welding electrode, the other welding electrode being mounted pendulum at the distal end of an upper arm which is articulated on the main body, and an actuating mechanism for manually opening the welding clamp against the action of elastic return means associated with the clamping of the electrodes.

 These welding tongs have in common to be manipulated by their arms, with a gripping performed at the proximal end of the clamp, using a hand or two hands as appropriate.

 A clamp made of two arms connected to each other at a central articulation is thus known: in front of the articulation, there are the two electrodes (arranged longitudinally or transversely), the back of the clamp then forming an articulated handle similar to that of a pruner, with the interposition of a spring tending to move the two elements of the handle to exert some pressure on the electrodes.

 The main disadvantage of such a clamp lies in the limited pressure exerted by the spring, this pressure must indeed be compatible with the effort that must exert the operator to open the clamp (a force of 10 kg is usually a maximum ). In addition, the size is important (about 700 mm for electrodes of 250 mm), resulting in a cantilever generator fatigue for the operator, this overhang being naturally amplified if the we want to use longer electrodes.

 Scissors-type pliers with amplified pressure are also known. The upper arm of this clamp is articulated in the middle of the main body, so as to form a lower arm forward and a handle rearward. An upper operating lever is further articulated on the main body, slightly behind the axis of articulation of the upper arm, the lever having an eccentric end cooperating with a rear return of the upper arm, with the interposition of spring discs able to exert an adjustable pressure when the lever is lowered to close the clamp.

 The gripper is again seized end, so with overhang, and in addition the two hands of the operator must be used (one grasping the fixed handle, the other the mobile operating lever). The length is also important (about 600 mm for electrodes of 200 mm). Finally, if we wanted to increase the length of the electrodes to 300 mm, we would have to choose between lengthening the clamp by as much, or eliminate the free space of about 100 mm, delimited by the upper arm, behind the electrodes, and therefore lose the advantage associated with it, namely to facilitate the storage of a length of sheets already welded in the context of a welding in several passes.

 The object of the invention is precisely to solve this problem by designing a hand-held welding tong that can be operated manually and which does not have the aforementioned drawbacks and / or limitations.

 The object of the invention is therefore to provide a portable welding clamp whose structure makes it possible to have electrodes of considerable length (for example 300 mm) with a reasonable overall length, while improving the comfort of setting and maneuvering the clamp.

 It is more particularly a portable welding clamp for high-frequency welding of plastic sheets, comprising a main body whose distal end forms a lower arm on which is fixed a welding electrode, the other welding electrode being mounted pendulously at the distal end of an upper arm which is articulated on the main body, and an actuating mechanism for manually opening the welding clamp against the action of elastic return means associated with the clamping of the electrodes, characterized in that the axis of articulation of the upper arm is arranged at the proximal end of the main body, behind a grasping grip fixed under said body, and in that the actuating mechanism is constituted by an operating lever articulated on the main body, being arranged just in front of the gripping stock, and by a set of tr mechanical stress reduction transmission connecting this operating lever to a support ramp carried by the upper arm, said support ramp being disposed in front of the axis of articulation of the upper arm.

 Preferably, the operating lever is in the form of an elongated trigger, and its hinge axis is arranged just above the gripping stock.

In particular, the grip handle is fixed below the main body at a central zone, substantially vertical to the center of gravity of the clamp when the lower arm extends horizontally. This provides optimal comfort of wearing and maneuvering.

 According to another particularly advantageous characteristic, the mechanical transmission gear transmission assembly is constituted by the upper end of the operating lever, and by two links articulated together, one of which is articulated on the operating lever and the other on the main body, the latter ending with a roller cooperating with the support ramp carried by the upper arm. Preferably then, the inclination of the support ramp and the dimensions of the transmission assembly are chosen so as to provide a gear ratio at least equal to three.

 It is also interesting that the main body has a notch defining a free space behind the electrodes to facilitate the welding of long sheets in successive passes. For example, the indentation will be formed by the edges of two rear cheeks of the main body between which passes the mechanical gear transmission assembly.

 More preferably, the upper arm is permanently recalled to the closed position by elastic return means arranged on either side of this arm.

 Advantageously then, the elastic return means are essentially constituted by two traction springs, which engage lower on the main body and higher on the upper arm in the rear part thereof. In particular, the two springs cling higher on a transverse axis which is movable in a lumen of the upper arm, and whose position is adjustable by means of an associated actuator, so as to adjust the pressure force at the electrodes.

Other features and advantages of the invention will emerge more clearly in the light of the following description and the accompanying drawings, relating to a particular embodiment, with reference to FIGS.
FIG. 1 illustrates in perspective a portable welding tongs according to the invention
FIG. 2 is a central section of the aforementioned clip, making it possible to better distinguish the arrangement of the associated actuating mechanism;
FIG. 3 is a section on III-III of FIG. 2, showing the arrangement of the springs used to exert the desired pressure between the electrodes when the clamp is closed.

 FIGS. 1 and 2 illustrate a portable welding tongs 100 according to the invention, intended for the welding of plastic sheets, and in particular bags made of weldable polyurethane or ethyl vinyl acetate such as those used for the evacuation or the removal of plastics. introduction of contaminated materials or wastes under confined confinement. It may be a high-frequency welding, thermal type or other (by induction for example) or any other similar welding.

 The welding tongs 100 comprise an elongated main body 101, the distal end of which forms a lower arm 102 on which a soldering electrode 105 is fixed, by means of insulating flanges made of H 106. The insulating flanges 106 will, for example, be made of two complementary parts of hard plastic material, and fixed by associated bolts 106.1 on the upper edge of the arm 102, their H section for clamping the lower electrode 105.

 The other electrode 107 is pendulously mounted at the distal end of an upper arm 103 which is articulated on the main body 101 of the clamp. This pendulum assembly is provided by means of a crossbar 108, which is suspended on an axle 109 mounted transversely on the upper arm 103, the upper electrode 107 being fixed to the crossbar 108 by associated bolts 110. Such an assembly of two electrodes is of conventional type.

 According to the invention, the upper arm 103 is articulated by an axis 104 which is arranged at the proximal end of the main body 101 of the welding pliers, so that the two arms 102 and 103 of the pliers are presented. as a jaw, this gripper being then manipulated by a gripping means which is disposed below the main body 101. This gripping means is here realized in the form of a butt 112 attached to the underside of the main body 101. It is It is interesting to note that the grip handle 112 is fixed under the main body 101 at a central zone, substantially vertical to the center of gravity of the clamp when the lower arm 102 extends horizontally. Such an arrangement then allows easy wearing of the clamp, without overhang, while maintaining a reasonable overall length insofar as this length corresponds only to the length of the articulated arm increased by half a length of electrode.

No longer found gripping by rear handles inducing a cantilever grip of the clamp, but on the contrary a seizure type revolver facilitating considerably the port, and especially, as will be seen later, the actuation of the mechanism associated with the opening of the clamp.

 According to another characteristic of the invention, there is provided a particular actuating mechanism 120 for manually opening the welding clamp against the action of elastic return means associated with the clamping of the electrodes 105 and 107 More specifically, this actuating mechanism 120 is constituted by an operating lever 121 which is articulated by an axis 122 on the main body 101, said lever being arranged just in front of the gripping stick 112, being made under the shape of an elongated trigger, and with its hinge pin 122 disposed just above the gripping stock 112, and also by a mechanical gear transmission transmission assembly ensuring the functional connection between the operating lever 121 and the articulated upper arm 103. The operating lever 121 is extended, beyond its axis 122, by an end 121.1, to which is connected a control system. articulated links cooperating with a support ramp 129 carried by the upper arm 103. In this case, there is provided a set of two rods 123, 124, the rod 123 being hinged at 126 on the operating lever 121 and 127 on the second link 124, the latter being mounted articulated about an axis 125 carried by the main body 101, and ending, beyond said axis, by a roller 128 which cooperates with the support ramp 129 above. The support ramp 129 is disposed in front of the hinge 104 of the upper arm 103, so as to be able to transmit the necessary torque to said upper arm during the actuation of the operating lever 121 by the operator. This support ramp 129 is here removably attached to the upper arm 103, so as to form an interchangeable hard part. There is shown here a rod 123 monoblock therefore of constant length, but we can consider another variant (not shown here) in which the rod is of variable length (for example with a threaded rod connecting two ball joints), so as to adjust the opening of the operating lever 121 and the opening of the upper arm 103 of the clamp.

 The inclination of the support ramp 129, which is here of the order of 300 relative to the longitudinal direction of the electrodes, as well as the relative dimensions of the components constituting the transmission assembly with mechanical force reduction (end upper 121.1 of the operating lever 121, rods 123 and 124) will preferably be selected to provide a predetermined gear ratio, including a ratio of at least three. Thus, one is assured of being able to overcome, by acting with one hand on the actuating lever 121, the action of the elastic return means whose stiffness is calculated so that these means exert a force of at least 30 kg at the adjacent electrodes when the clamp is closed. Thanks to the reduction achieved, the effort to be provided with the hand of the operator remains in any case much less than 10 kg. Such a transmission mechanism with mechanical stress reduction thus makes it possible to envisage high-power elastic return means, realizing a large crushing of the plastic sheets during the actual welding, which could not be envisaged with the grippers. welding of the prior art manually operated.

 For the embodiment that is shown here, the main body 101 has, in its rear part, a set of two cheeks 114 which delimit between them an intermediate space 115 in which is housed the transmission assembly with mechanical gear reduction. effort. This housing 115 also allows to pass a coaxial cable 111 (Figure 2) which provides electrical power to the electrodes for high-frequency welding.

 The elastic return means associated with the articulated upper arm 103 will now be described so as to ensure the exercise of a constant high application pressure of the upper electrode 107 against the lower electrode 105 before and during the welding.

 Here is illustrated a particularly efficient and compact embodiment, which also has the merit of clearing a notch 117 formed by the front edges of the two rear cheeks 114 of the main body 101, this notch defining a free space 116 behind the electrodes 105 and 107 to facilitate the welding of long length sheets in successive passes.

 As is more clearly visible in FIGS. 1 and 3, the elastic return means referenced 130 are here essentially constituted by two traction springs 131 arranged on either side of the articulated upper arm 103, these two springs hanging lower on the main body 101 and higher on the upper arm 103, in the rear part thereof. More specifically, there is provided here a fixed lower transverse axis 132, passing right through the two cheeks 114 of the main body 101, this axis serving for the attachment of the lower ends of the two springs 131. For attachment in the upper part of these springs, on the other hand provided a transverse axis 133 which is movable in an associated elongated slot 134 formed in the upper arm 103, the upper end of the two springs 131 then catching on both lateral ends of the axis The light 134 is elongate in the same direction as the axis of the springs 131, so that the position of the transverse axis 133 is easily adjustable to adjust the pressure force at the electrodes 105, 107: in this case, there is provided a screw 135 screwing on the transverse axis 133, so that it is sufficient to use a tool adapted to easily change the stiffness of the springs, and therefore the pressure force at the level of the electrodes 105, 107. It will be possible, as is illustrated in FIGS. 2 and 3, to provide a counterplate 136 interposed between the head of the adjusting screw 135 and the corresponding upper face of the articulated arm 103. hard material counterplate avoids a marking by the head of the screw 135 of the upper arm 103 which will generally be cast aluminum. It is interesting to note that the axes of the turns of the springs 131 extend in a transverse plane passing through the center of the inclined ramp 129, which makes it possible to avoid parasitic bending forces.

 For operation, it is sufficient that the operator grasps the welding tongs 100 by its butt 112, and exerts sufficient pressure on the trigger-shaped lever 121 to move the two electrodes 105 and 107 away from each other, to insert the two or four thicknesses of plastic to be welded. Once these sheets set up, it is sufficient for the operator to release the operating lever 121, which allows an application of the two electrodes against each other with a high pressure given by the springs 131. It will naturally be possible to provide to have a contactor 140 under the main body 101, said contactor intervening when the operating lever 121 is in the released position (as shown in Figure 2) so as to send a signal to the control unit associated with the high-voltage generator. frequency, to initiate the planned welding cycle. It is thus possible to produce a weld line whose width corresponds to that of the electrodes, that is to say about 8 mm, and especially with a length that can easily reach 300 mm, insofar as the problem of the cantilever that was found on the portable welding tongs of the prior art. If the length to be welded is important, then it is sufficient to carry out a new welding pass, backing up and creasing the length already welded in the space 116 which thus constitutes a sort of reserve magazine, until the correct positioning of the weld a new length to be welded between the two open electrodes. In particular, if European-standard standardized glove boxes are used, the length to be welded is approximately 290 mm, so that a single weld pass is now sufficient.

 As an indication, it is possible to make a welding clamp such as that described here, with electrodes 300 mm long, for an overall length of 400 to 450 mm. So we managed to get a very long welding length while maintaining a minimum overall length for the welding clamp.

 The springs 131, whose stiffness is particularly high, can easily accommodate a quadruple thickness to be welded, which can be the case when using a rolled bag. Alternatively, as illustrated in Figure 1, wrap each of these springs 131 by a smooth protective sleeve 137, to contain a grease anti-wear. Also shown in Figure 1, an actuating button 113, mounted on the grip handle 112, and for triggering the welding. If a contactor such as the switch 140 above is used, it will of course be possible to provide for inhibiting the control of the button 113 until the switch 140 has been triggered. Finally, FIG. 1 shows a connecting end piece 111.1 which is associated with the coaxial cable 111 shown schematically in FIG. 2.

 It has thus been possible to produce a portable welding clamp whose structure makes it possible to have electrodes of considerable length (for example 300 mm) with a reasonable overall length (for example from 400 to 450 mm), while improving comfort. gripping and maneuvering the gripper.

 The invention is not limited to the embodiment which has just been described, but on the contrary covers any variant using, with equivalent means, the essential characteristics mentioned above.

Claims (10)

 1. Portable welding forceps for high-frequency welding of plastic sheets, comprising a main body whose distal end forms a lower arm on which is fixed a welding electrode, the other welding electrode being mounted pendulum to the distal end of an upper arm which is articulated on the main body, and an actuating mechanism for manually opening the welding clamp against the action of elastic return means associated with the clamping electrodes, characterized in that the axis of articulation (104) of the upper arm (103) is arranged at the proximal end of the main body (101), behind a grasping grip (112) fixed under said body, and in that the actuating mechanism (120) is constituted by an operating lever (121) articulated on the main body (101), being arranged just in front of the gripping stick (112), and by a transmission assembly (121.1, 123, 124) with mechanical gear reduction connecting said operating lever (121) to a support ramp (129) carried by the upper arm (103), said support ramp being arranged in before the articulation axis (104) of this upper arm.  2. Welding forceps according to claim 1, characterized in that the actuating lever (121) is formed in the form of an elongated trigger, and its hinge axis (122) is arranged just above the butt gripping device (112).  3. Welding pliers according to claim 1 or claim 2, characterized in that the gripping stock (112) is fixed under the main body (101) at a central zone, substantially vertical to the center of gravity of the clamp when the lower arm (102) extends horizontally.  4. Welding forceps according to one of claims 1 to 3, characterized in that the mechanical gear transmission transmission assembly is constituted by the upper end (121.1) of the operating lever (121), and by two links (123, 124) hinged together, one (123) is articulated on the operating lever (121) and the other (124) on the main body (101), the latter ending in a roller (128) cooperating with the support ramp (129) carried by the upper arm (103).  Soldering pliers according to claim 4, characterized in that the inclination of the bearing ramp (129) and the dimensions of the transmission assembly (121.1, 123, 124) are selected to provide a ratio reduction ratio at least equal to three.  Welding pliers according to one of claims 1 to 5, characterized in that the main body (101) has a notch (117) defining a free space (116) behind the electrodes (105, 107) to facilitate the welding of long leaves in successive passes.  7. Welding pliers according to claim 6, characterized in that the notch (117) is formed by the edges of two rear flanges (114) of the main body (101) between which the transmission assembly (121.1, 123) passes. , 124) with mechanical reduction.  8. welding pliers according to one of claims 1 to 7, characterized in that the upper arm (103) is permanently biased to the closed position by elastic return means (130) arranged on either side of this arm.  9. welding pliers according to claim 8, characterized in that the elastic return means (130) consist essentially of two traction springs (131), which clings below on the main body (101) and upper on the upper arm (103) in the rear part thereof.  10. Welding pliers according to claim 9, characterized in that the two springs (131) cling superiorly on a transverse axis (133) which is movable in a slot (134) of the upper arm (103), and whose position is adjustable by means of an associated actuator (135), so as to adjust the pressure force at the electrodes (105, 107).