WO2005084871A1 - Double-stroke cylinder for soldering tongs - Google Patents

Double-stroke cylinder for soldering tongs Download PDF

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Publication number
WO2005084871A1
WO2005084871A1 PCT/FR2005/000202 FR2005000202W WO2005084871A1 WO 2005084871 A1 WO2005084871 A1 WO 2005084871A1 FR 2005000202 W FR2005000202 W FR 2005000202W WO 2005084871 A1 WO2005084871 A1 WO 2005084871A1
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WO
WIPO (PCT)
Prior art keywords
rod
radial
working
piston
stroke
Prior art date
Application number
PCT/FR2005/000202
Other languages
French (fr)
Inventor
Benoît COUMES
Original Assignee
Finuchem Technologies De Soudage
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Finuchem Technologies De Soudage filed Critical Finuchem Technologies De Soudage
Publication of WO2005084871A1 publication Critical patent/WO2005084871A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K11/00—Resistance welding; Severing by resistance heating
    • B23K11/30—Features relating to electrodes
    • B23K11/31—Electrode holders and actuating devices therefor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B15/00—Fluid-actuated devices for displacing a member from one position to another; Gearing associated therewith
    • F15B15/08—Characterised by the construction of the motor unit
    • F15B15/14—Characterised by the construction of the motor unit of the straight-cylinder type
    • F15B15/16—Characterised by the construction of the motor unit of the straight-cylinder type of the telescopic type
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B15/00—Fluid-actuated devices for displacing a member from one position to another; Gearing associated therewith
    • F15B15/20—Other details, e.g. assembly with regulating devices
    • F15B15/26—Locking mechanisms
    • F15B15/261—Locking mechanisms using positive interengagement, e.g. balls and grooves, for locking in the end positions

Definitions

  • the present invention relates to a double-stroke welding clamp cylinder for positioning the clamp in an approach position and then in a working position in a work area.
  • These cylinders comprise a cylinder body in which are housed two rods each secured to at least one piston.
  • a pre-stroke rod is adapted to position the clamp in said approach position from a rest position and a working rod is adapted to position said clamp in a working position.
  • one of the branches of the clamp is fixedly mounted relative to the cylinder body while the other branches which is mounted movably relative to the first, is actuated by the rods of the cylinder. While from the rest position to the approach position, the efforts to implement for the movement of the clamp are small, the setting in working position of the clamp requires more effort.
  • the working rod is held rigidly with respect to the clamp when the piston of the latter is activated; and all the more so as to increase the forces to be applied on the working rod it generally has several stage pistons.
  • mount said clamp directly to the free end of said working rod and to mount said slide working rod through said pre-stroke rod. which is kept away from said work area.
  • the pre-stroke rod has a piston which is further mounted in said cylinder body which is movable in translation relative to said pre-stroke rod.
  • locking means are used to lock together the cylinder body and the pre-stroke rod.
  • the pre-stroke rod being kept at a distance from said working zone, the injection of pressurized fluid into the body and against the piston of the pre-stroke rod translates said body which in turn drives the working rod with the pliers in the approach position. Then, the locking means are activated to lock together the pre-stroke rod and the cylinder body. Then, the working rod is driven into said working position with said clamp, injecting a fluid under pressure into the cylinder body and against the piston or pistons of the working rod.
  • the locking of the pre-stroke rod and the cylinder body is sufficient so that the driving of the clamp to the working position takes place without the cylinder body moving away from said working area, it is relatively relatively easy to fix the pre-stroke rod which is at least partially engaged in the cylinder body and maintain in a fixed position at a distance from this working area. Moreover, the body of the cylinder from which the working rod is driven and guided in translation is maintained only by the pre-stroke rod through which it is slidably mounted, which is likely to increase the clearance clearance. the working rod with respect to the work area.
  • the present invention provides a welding clamp cylinder comprising a body in which are housed two rods each secured to at least one piston, a pre-stroke rod adapted to position said clamp in an approach position and a rod working shaft adapted to position said clamp in a working position, said rods being mounted coaxially in said body and said cylinder further comprising locking means; said pre-stroke rod and its piston being mounted inside said working rod, while said working rod is mounted in said body; and said locking means being adapted to lock in translation, said pre-stroke rod with respect to said working rod when said clamp is positioned in said working position.
  • a feature of the invention lies in the mode of connection between the rods and the cylinder body, the working rod being housed in the cylinder body and the pre-stroke rod which carries the clamp being housed in the working rod .
  • the pre-stroke rod which is kept at a distance from said working zone but the body of the jack, which is much easier for it to maintain in view of its external surface compared to that of the rod. off difference.
  • the rods being mounted telescopically in the cylinder body, the guidance of the clamp and in particular the actuation of the movable branch is perfectly ensured and the rods, in particular the working rod, have no play in travel. As a result, the positioning accuracy of the clamp relative to the work area is increased.
  • the length of the cylinders can be reduced.
  • the piston of the pre-stroke rod is located in the extension of the pistons of the working rod and thus adds an additional stage.
  • the cylinder according to the present invention has a pre-stroke rod piston which is fully housed in the working rod and whose movement takes place in the middle of the working pistons without having to add an extra length.
  • the locking means according to a preferred embodiment, they comprise locking pieces, said locking pieces being movable radially between a position in which said rods are locked in translation and a position in which said rods are free in translation. translation.
  • the radial piston which extends in the radial chamber formed in the working rod and substantially perpendicular to the pre-stroke rod, is adapted to block the pre-travel rod in translation relative to the working rod.
  • the locking means comprise a plurality of radial pistons, for example two, which define equivalent sectors around the pre-stroke rod.
  • said pre-stroke rod preferably has a shoulder, formed for example by means of a ring integral with the pre-stroke rod and against which said radial piston is adapted to come into said bearing position.
  • the pre-stroke rod is locked relative to the working rod, the shoulder abutting against the radial piston which extends at least partially in the radial housing and which then undergoes a shear force.
  • said radial housing is capable of forming two opposite radial chambers delimited by said radial piston, a first radial chamber being adapted to receive a fluid for driving in translation said radial piston in said radial position. 'support.
  • said first radial chamber opposed to the pre-stroke rod with respect to the radial piston reduced when the radial piston is in said disengaged position and fully extends into the radial housing, while is extended when a fluid has been injected under pressure to drive the radial piston to the pre-stroke rod in the support position.
  • said radial chambers are capable of being supplied with fluids by means external supply, so as to control the radial piston from the outside by an independent circuit equipped with solenoid valves.
  • said working rod has an axial housing in which the piston of said pre-stroke rod is adapted to slide by delimiting two opposite axial chambers, a first axial chamber being adapted to receive a fluid under pressure.
  • said pre-stroke rod to be driven from a rest position to said approach position, and said first axial chamber is connected by a conduit to said first radial chamber such that said piston seals said conduit in said position of rest, and releases it into said approach position.
  • the first axial chamber and the first radial chamber are isolated from each other in said rest position and they are in communication in said approach position.
  • the injection of a fluid into the first axial chamber makes it possible to drive the pre-stroke rod into said approach position and then to drive the radial piston into the support position. to block the pre-stroke rod with respect to the working rod.
  • said piston of the pre-stroke rod delimits, particularly advantageously, a second axial chamber and said radial piston delimits a second radial chamber, said chambers being connected together so as to simultaneously drive said radial piston in disengagement from said bearing position and said pre-stroke rod towards said rest position by injecting a fluid into said second axial chamber.
  • the pre-stroke rod has for example returned to said approach position, by injecting a fluid under pressure into the second axial chamber, this the last flows in the second radial chamber and the radial piston is driven into the disengaged position where it is fully housed in the radial housing.
  • the fluid under pressure then drives the pre-stroke rod into said rest position.
  • said locking means are mounted in said pre-stroke rod, and they are movable between an engaged position where they cooperate with said working rod and a disengaged position where they do not cooperate with said working rod.
  • the locking means are activated from the pre-stroke rod.
  • said locking means are adapted to be controlled by electromagnets, which allows great flexibility of control by means of a power supply.
  • said working rod is provided with a plurality of pistons forming a plurality of stages so as to increase the efforts to bring the clamp into the working position.
  • the welding clamp cylinder comprises control means adapted to control the state of said locking means, so as to ensure that the rods are securely locked together before driving the branch in the working position.
  • Figure 1 is a schematic axial sectional view of a welding clamp cylinder according to the invention and in a first position
  • - Figure 2 is a schematic axial sectional view of the cylinder illustrated in Figure 1 in a second position
  • - Figure 3 is a schematic axial sectional view of the cylinder illustrated in Figure 2 in a third position
  • - Figure 4 is a schematic axial sectional view of the cylinder illustrated in Figure 3 in a fourth position.
  • FIG. 1 illustrates a welding clamp cylinder 10 according to the invention and it comprises a body or cylinder 12 in which is adapted to slide a working rod 14 of which is secured a plurality of pistons 16.
  • These pistons 16 are movable in translation in a plurality of chambers 18 delimited by partitions 19 which they divide into two parts.
  • the pistons 16 are in abutment against the lower walls of the partitions 19.
  • the working rod may have only two pistons or even one, when it is desired to shorten the maximum cylinder.
  • the working rod 14 has an axial housing 20 in which extends longitudinally a pre-stroke rod 22 slidably mounted.
  • the pre-stroke rod 22 has a free end 24 passing through a first end 26 of the working rod 14 and which is located outside the axial housing 20 so as to carry a not shown clamp.
  • the axial housing 20 is closed sealingly at the first end 26 by means of an end ring 28 that the pre-stroke rod 22 also freely passes through tightly.
  • the welding clamps have two branches, a first which is mounted in a fixed position, substantially in the axis of the jack and integral with its body, and a second which is mounted movable relative to the first and which is driven by the rods of the cylinder.
  • the pre-stroke rod 22 has a piston 30 of which it is integral and which sealingly joins the inner wall of the axial housing 20 by defining a first axial chamber 32, opposite to a second axial chamber 34.
  • a ring stopper 36 is mounted on the pre-stroke rod in the second axial chamber 34 and is adapted to bear for abutment against the end ring 28 when the pre-stroke rod 22 slides as will be explained hereinafter. - after.
  • the pre-stroke rod 22 has a collar 38 defining a shoulder 40 which makes it possible to form a bearing surface.
  • the working rod 14 has a bulbous end portion 42 adapted to be housed in an internal space 43 of said body 12 in a subsequent phase which will be described next.
  • radial housings 44, 46 which open into the second axial chamber 34.
  • radial housings 44, 46 are mounted to slide two radial pistons 48, 50 which are adapted to be housed entirely in said housings, as shown in Figure 1.
  • These radial pistons have an active part 52 Vietnamese radial chamber 54 opposite said low-cut portion 52 and a second radial chamber 56 where the low-neck portion extends. 52.
  • first radial chambers 54 are connected by a first conduit 58 which opens into the axial housing 20 and which is in this Figure 1 closed by the piston 30 of the pre-stroke rod 22.
  • second radial chambers 56 are connected by a second conduit 60 which opens into the second axial chamber 34.
  • FIG 3 shows the jack 10 in a second approach position in which the oil under pressure in the first radial chambers has driven the radial pistons along the arrow F in a bearing position where the low-cut parts 52 extend partially into the axial housing 20 and precisely against the shoulder 40 of the collar 38 to form locking means.
  • the beveled portions 52 are inserted between the piston 30 and the collar 38 such that the pre-stroke rod 22 is mechanically connected to the working rod 14.
  • the working rod 14 is adapted to be driven in translation by a distance T, to carry the clamp in said working position as shown in Figure 4. Found on this Figure 4 all the elements initially described with the same references.
  • oil is injected, for example, under pressure into the second axial chamber 34, opposite the first 32, taking care to release the pressure in the latter.
  • the oil then flows into the second conduits 60 and into the second radial chambers 56.
  • the radial pistons 48, 50 are driven into an unobstructed position, entirely in their corresponding radial recesses 44, 46, which releases the pre-stroke rod 22 with respect to the working rod 14.
  • the oil under pressure in the second axial chamber then drives the pre-stroke rod via its piston 30 in said rest position initially described with reference to FIG. 1.
  • said locking means comprise locking pieces formed of balls or cylinders, said balls or said cylinders being movable radially between a position in which they block said rods. translation and a position in which they release them.
  • the pre-stroke rod extends entirely in the axial chamber of the working rod, so that the outer surface of the pre-stroke rod is in sliding abutment against the inner wall of the axial chamber.
  • the pre-stroke rod has radial cavities adapted to open opposite radial lights of the working rod. These lights are formed in the thickness of the cylindrical wall of the working rod through which they pass through.
  • these slots are partially housed balls or cylinders which are intended to engage partially in said radial cavities while fully occupying the space of the radial lights.
  • These balls or these cylinders are likely to be held astride in the slots and in the radial cavities by means of a sliding ring mounted on the working rod and which closes said slots to lock the balls or cylinders in position.
  • the ring is slid which then releases the lights and the balls or cylinders can be disengaged from the radial cavities and protrude outwardly from the working rod.
  • the radial cavities have a concave bottom so that the axial translation of the pre-stroke rod relative to the working rod drives the balls or cylinders in radial translation.
  • the radial pistons 48, 50 are held in said bearing position by retractable elastic means. Referring for example to Figures 1 and 2, to describe the operation of one of the radial pistons, 48 according to this last embodiment. Of course, the operation of the other radial piston 50 is identical.
  • spring means are mounted in the first radial chamber 54 and bear on the radial piston 48 so as to drive it to said support position. It is thus no need to provide the conduits 58 to arrive fluid.
  • the radial piston 48 since the radial piston 48 is driven towards the bearing position, it then extends in projection in the second axial chamber 34, at least in the rest position as shown in FIG. 1, and it is necessary at least the active part 52 Vietnameselletée, is bevelled towards the free end 24, so that the collar 38, driven in translation against the active part 52 Vietnameselletée, drives in retraction the radial piston 48; the collar 38 being slidably engaged against the active part 52, cut and tapered.
  • the elastic means are then compressed and as soon as the neck 38, continuing its stroke, is separated from the radial piston 48, the latter driven by the elastic means resumes its projecting position in the second axial chamber 34 and bears against the piston 30 Furthermore, it is intended to chamfer the collar 38 to facilitate the relative movement of the collar 38 against the active part 52 beveled.
  • the clearance of the radial piston 48 is effected identically, in the previous embodiment by injecting a fluid under pressure in the second ducts 60, which also flows under pressure in the second radial chambers 56.
  • the fluid under pressure can obviously be oil but also compressed air.

Abstract

The invention relates to a cylinder for soldering tongs, said cylinder comprising a housing (12) in which two rods (14, 22), each fixed to a piston, are arranged, a pre-stroke rod that is adapted in such a way as to position the tongs in an advancing position, and a working rod that is adapted in such a way that the tongs are positioned in a working position, said rods being coaxially mounted in said housing. The tongs also comprise blocking means, the pre-stroke rod (22) and the pistons (30) being mounted inside the working rod (14), while the working rod (14) is mounted in the housing (12), and the blocking means (40, 48, 50) are adapted in such a way as to block the pre-stroke rod (22) in translation in relation to the working rod (14) when the tongs are positioned in the working position.

Description

Vérin de pince de soudage à double course Double stroke welding clamp cylinder
La présente invention se rapporte à un vérin de pince de soudage à double course, permettant de positionner la pince dans une position d'approche, puis dans une position de travail située dans une zone de travail. Ces vérins comprennent un corps formant cylindre dans lequel sont logées deux tiges solidaires chacune d'au moins un piston. Une tige de précourse est adaptée à positionner la pince dans ladite position d'approche à partir d'une position de repos et une tige de travail est adaptée à positionner ladite pince dans une position de travail. Généralement, l'une des branches de la pince est montée de manière fixe par rapport au corps du vérin tandis que l'autre branches qui elle, est montée mobile par rapport à la première, est actionnée par les tiges du vérin. Alors que de la position de repos jusqu'à la position d'approche, les efforts à mettre en œuvre pour le déplacement de la pince sont peu importants, la mise en position de travail de la pince requiert plus d'efforts. II est donc nécessaire que la tige de travail soit maintenue de façon rigide par rapport à la pince lorsque le piston de cette dernière est activé ; et ce d'autant plus que pour augmenter les efforts à appliquer sur la tige de travail elle présente généralement plusieurs pistons étages. Afin de maintenir ladite tige de travail de façon rigide par rapport à la pince, il a été imaginé, de monter ladite pince directement à l'extrémité libre de ladite tige de travail et de monter ladite tige de travail coulissante à travers ladite tige de précourse qui elle est maintenue à distance de ladite zone de travail. On pourra se référer au document FR 2 781 016 qui décrit un tel dispositif. La tige de précourse présente un piston qui est en outre montée dans ledit corps du vérin qui lui est mobile en translation par rapport à ladite tige de précourse. Par ailleurs, des moyens de blocage permettent de bloquer ensemble le corps de vérin et la tige de précourse. Ainsi, la tige de précourse étant maintenue à distance de ladite zone de travail, l'injection de fluide sous pression à l'intérieur du corps et contre le piston de la tige de précourse, entraîne en translation ledit corps qui lui- même entraîne la tige de travail avec la pince dans la position d'approche. Ensuite, les moyens de blocage sont activés pour verrouiller ensemble la tige de précourse et le corps du vérin. Puis, la tige de travail est entraînée dans ladite position de travail avec ladite pince, en injectant un fluide sous pression dans le corps du vérin et contre le ou les pistons de la tige de travail. Bien que le verrouillage de la tige de précourse et du corps de vérin soit suffisant pour que l'entraînement de la pince vers la position de travail s'effectue sans que le corps du vérin ne s'éloigne de ladite zone de travail, il est relativement mal aisé de fixer la tige de précourse qui est au moins partiellement engagée dans le corps du vérin et de la maintenir en position fixe à distance de cette zone de travail. Par ailleurs, le corps du vérin à partir duquel la tige de travail est entraînée et guidée en translation n'est maintenu que par la tige de précourse à travers laquelle elle est montée coulissante, ce qui est susceptible d'augmenter le jeu en débattement de la tige de travail par rapport à la zone de travail. Un problème qui se pose et que vise à résoudre la présente invention, est alors de fournir un vérin qui permette non seulement de guider parfaitement la tige de travail dans la position de travail, mais aussi qui soit adapté à être maintenu aisément en position fixe et à distance de la zone de travail. Dans ce but, la présente invention propose un vérin de pince de soudage comprenant un corps dans lequel sont logées deux tiges solidaires chacune d'au moins un piston, une tige de précourse adaptée à positionner ladite pince dans une position d'approche et une tige de travail adaptée à positionner ladite pince dans une position de travail, lesdites tiges étant montées coaxialement dans ledit corps et ledit vérin comprenant en outre des moyens de blocage ; ladite tige de précourse et son piston étant montés à l'intérieur de ladite tige de travail, tandis que ladite tige de travail est montée dans ledit corps ; et lesdits moyens de blocage étant adaptés à bloquer en translation, ladite tige de précourse par rapport à ladite tige de travail lorsque ladite pince est positionnée dans ladite position de travail. Ainsi, une caractéristique de l'invention réside dans le mode de liaison entre les tiges et le corps du vérin, la tige de travail étant logée dans le corps du vérin et la tige de précourse qui porte la pince étant logée dans la tige de travail. De la sorte, ce n'est plus la tige de précourse qui est maintenue à distance de ladite zone de travail mais le corps du vérin, qui lui est beaucoup plus aisé à maintenir compte tenu de sa surface externe comparée à celle de la tige de précourse. En outre, les tiges étant montées de façon télescopique dans le corps du vérin, le guidage de la pince et en particulier l'actionnement de la branche mobile est parfaitement assuré et les tiges, en particulier la tige de travail, ne présentent aucun jeu en débattement. De ce fait, on augmente la précision de positionnement de la pince par rapport à la zone de travail. Par ailleurs, grâce à cette caractéristique, la longueur des vérins peut être réduite. Car en effet, selon l'art antérieur, le piston de la tige de précourse est situé dans le prolongement des pistons de la tige de travail et rajoute ainsi un étage supplémentaire. Alors que le vérin selon la présente invention, présente un piston de tige de précourse qui est entièrement logé dans la tige de travail et dont le mouvement s'effectue au milieu des pistons de travail sans avoir à rajouter une longueur supplémentaire. Quant au moyen de blocage, selon un mode de mise en œuvre préférentiel, ils comprennent des pièces de blocage, lesdites pièces de blocage étant mobiles radialement entre une position dans laquelle lesdites tiges sont bloquées en translation et une position dans laquelle lesdites tiges sont libres en translation. Ils comportent selon un premier mode de réalisation particulièrement avantageux, au moins un piston radial formant pièces de blocage, monté dans un logement radial de ladite tige de travail et adapté à coopérer avec ladite tige de précourse, ledit piston radial étant mobile en translation entre une position d'appui pour bloquer ensemble lesdites tiges et une position dégagée autorisant le déplacement de ladite tige de précourse par rapport à ladite tige de travail. Ainsi, le piston radial qui s'étend dans la chambre radiale ménagée dans la tige de travail et sensiblement perpendiculairement à la tige de précourse, est adapté à venir bloquer la tige de précourse en translation par rapport à la tige de travail. Pour des raisons de symétrie et une répartition équilibrée des efforts, les moyens de blocage comportent une pluralité de pistons radiaux, par exemple deux, qui définissent des secteurs équivalents autour de la tige de précourse. Pour ce faire, ladite tige de précourse présente avantageusement un épaulement, formé par exemple au moyen d'une bague solidaire de la tige de précourse et contre lequel ledit piston radial est adapté à venir s'appliquer dans ladite position d'appui. De la sorte, la tige de précourse est bloquée par rapport à la tige de travail, l'épaulement venant en butée contre le piston radial qui lui s'étend au moins partiellement dans le logement radial et qui subit alors un effort en cisaillement. Selon un autre mode particulier de réalisation de l'invention, ledit logement radial est susceptible de former deux chambres radiales opposées délimitées par ledit piston radial, une première chambre radiale étant apte à recevoir un fluide pour entraîner en translation ledit piston radial dans ladite position d'appui. Ainsi, ladite première chambre radiale qui est opposée à la tige de précourse par rapport au piston radial, est- elle réduite lorsque le piston radial est dans ladite position dégagée et qu'il s'étend entièrement dans le logement radial, alors qu'elle est étendue lorsqu'un fluide y a été injecté sous pression pour entraîner le piston radial vers la tige de précourse dans la position d'appui. Selon un mode de mise en œuvre particulier, lesdites chambres radiales sont susceptibles d'être alimentées en fluides par des moyens d'alimentation externes, de manière à commander le piston radial depuis l'extérieur par un circuit indépendant équipé d'électrovannes. Selon un autre mode de mise en œuvre particulier, ladite tige de travail présente un logement axial dans lequel le piston de ladite tige de précourse est adapté à coulisser en délimitant deux chambres axiales opposées, une première chambre axiale étant adaptée à recevoir un fluide sous pression permettant l'entraînement de ladite tige de précourse, d'une position de repos vers ladite position d'approche, et ladite première chambre axiale est reliée par un conduit à ladite première chambre radiale de façon que ledit piston obture ledit conduit dans ladite position de repos, et le libère dans ladite position d'approche. Ainsi, la première chambre axiale et la première chambre radiale sont isolées l'une de l'autre dans ladite position de repos et elles sont en communication dans ladite position d'approche. De la sorte, grâce à des moyens hydrauliques uniques, l'injection d'un fluide dans la première chambre axiale permet d'entraîner la tige de précourse dans ladite position d'approche puis d'entraîner le piston radial dans la position d'appui permettant de bloquer la tige de précourse par rapport à la tige de travail. L'entraînement de la tige de travail par des moyens hydrauliques supplémentaires permettant alors d'entraîner la tige de précourse et la pince qu'elle porte vers la zone de travail dans ladite position de travail, sans que la tige de précourse ne se rétracte dans la tige de travail. A l'inverse, dans le but de rétracter la tige de précourse dans la tige de travail après que la pince a été actionnée, ledit piston de la tige de précourse délimite, de façon particulièrement avantageuse, une seconde chambre axiale et ledit piston radial délimite une seconde chambre radiale, lesdites chambres étant reliées ensemble de façon à entraîner simultanément ledit piston radial en dégagement de ladite position d'appui et ladite tige de précourse vers ladite position de repos en injectant un fluide dans ladite seconde chambre axiale. Ainsi, alors que la tige de précourse est par exemple revenue dans ladite position d'approche, en injectant un fluide sous pression dans la seconde chambre axiale, ce dernier s'écoule dans la seconde chambre radiale et le piston radial est entraîné dans la position dégagée où il est entièrement logé dans le logement radial. Le fluide sous pression entraîne ensuite la tige de précourse dans ladite position de repos. Selon une variante d'exécution de l'invention, lesdits moyens de blocage sont montés dans ladite tige de précourse, et ils sont mobiles entre une position engagée où ils coopèrent avec ladite tige de travail et une position dégagée où ils ne coopèrent pas avec ladite tige de travail. Ainsi, selon cette caractéristique avantageuse, les moyens de blocage sont activés depuis la tige de précourse. Avantageusement, lesdits moyens de blocage sont adaptés à être commandé par des électroaimants, ce qui permet une grande souplesse de commande au moyen d'une alimentation électrique. Selon un mode préféré de mise en œuvre, ladite tige de travail est munie d'une pluralité de pistons formant une pluralité d'étages de façon à accroître les efforts pour porter la pince dans la position de travail. Préférentiellement, le vérin de pince de soudage comprend des moyens de contrôle adaptés à contrôler l'état desdits moyens de blocage, de façon à pouvoir s'assurer que les tiges sont bien bloquées ensemble avant d'entraîner la branche dans la position de travail. D'autres particularités et avantages de l'invention ressortiront à la lecture de la description faite ci-après d'un mode de réalisation particulier de l'invention, donné à titre indicatif mais non limitatif, en référence aux dessins annexés sur lesquels : - la Figure 1 est une vue schématique en coupe axiale d'un vérin de pince de soudage selon l'invention et dans une première position ; - la Figure 2 est une vue schématique en coupe axiale du vérin illustré sur la Figure 1 dans une deuxième position ; - la Figure 3 est une vue schématique en coupe axiale du vérin illustré sur la Figure 2 dans une troisième position ; et, - la Figure 4 est une vue schématique en coupe axiale du vérin illustré sur la Figure 3 dans une quatrième position. La Figure 1 illustre un vérin 10 de pince de soudage conforme à l'invention et il comporte un corps ou cylindre 12 dans lequel est adaptée à coulisser une tige de travail 14 de laquelle est solidaire une pluralité de pistons 16. Ces pistons 16 sont mobiles en translation dans une pluralité de chambres 18 délimitées par des cloisons 19 qu'ils divisent en deux parties. Sur cette Figure 1 , les pistons 16 sont en appui contre les parois inférieures des cloisons 19. Bien évidemment, la tige de travail peut ne présenter que deux pistons ou même un seul, lorsque l'on souhaite raccourcir au maximum le vérin. La tige de travail 14 présente un logement axial 20 dans lequel s'étend longitudinalement une tige de précourse 22 montée à coulissement. La tige de précourse 22 présente une extrémité libre 24 traversant une première extrémité 26 de la tige de travail 14 et qui est située en dehors du logement axial 20 de façon à porter une pince non représentée. Le logement axial 20 est refermé de manière étanche au niveau de la première extrémité 26 au moyen d'une bague d'extrémité 28 que la tige de précourse 22 traverse librement de façon étanche également. Les pinces de soudages présentent deux branches, une première qui est montée en position fixe, sensiblement dans l'axe du vérin et solidaire de son corps, et une seconde qui est montée mobile par rapport à la première et qui est mue par les tiges du vérin. En outre, la tige de précourse 22 présente un piston 30 dont elle est solidaire et qui joint de manière étanche la paroi interne du logement axial 20 en définissant une première chambre axiale 32, opposée à une seconde chambre axiale 34. Par ailleurs, une bague d'arrêt 36 est montée sur la tige de précourse dans la seconde chambre axiale 34 et elle est adaptée à venir en appui pour formée butée contre la bague d'extrémité 28 lorsque la tige de précourse 22 coulisse ainsi qu'on l'expliquera ci- après. De plus, la tige de précourse 22 présente un collet 38 définissant un épaulement 40 qui permet de former une surface d'appui. La tige de travail 14 présente une partie d'extrémité 42 renflée apte à venir se loger dans un espace interne 43 dudit corps 12 dans une phase ultérieure que l'on décrira ensuite. Dans cette partie renflée, sont ménagés deux logements radiaux 44, 46, diamétralement opposés qui débouchent dans la seconde chambre axiale 34. Dans ces logements radiaux 44, 46 sont montés à coulissement deux pistons radiaux 48, 50 qui sont adaptés à être logés entièrement dans lesdits logements, tel que l'illustre la Figure 1. Ces pistons radiaux présentent une partie active 52 décolletée adaptée à être entraînée dans ledit logement axial 20 pour bloquer la tige de précourse comme on l'expliquera plus en détail dans la suite de la description. La partie non décolletée forme, elle, piston et délimite le logement radial en deux chambres opposées l'une de l'autre, une première chambre radiale 54 opposée à ladite partie décolletée 52 et une seconde chambre radiale 56 où s'étend la partie décolletée 52. Par ailleurs, les premières chambres radiales 54 sont reliées par un premier conduit 58 qui débouche dans le logement axial 20 et qui est sur cette Figure 1 obturé par le piston 30 de la tige de précourse 22. En outre, les secondes chambres radiales 56 sont connectées par un second conduit 60 qui débouche lui dans la seconde chambre axiale 34. Après avoir décrit les éléments structurels du vérin 10, qui est représenté sur cette Figure 1 , dans une position de repos, on se référera à la Figure 2 pour décrire le même vérin 10 avec les mêmes éléments, dans une première position d'approche. On décrira aussi la transition entre la position de repos et la première position d'approche. Par rapport à la position de repos, un fluide, par exemple de l'huile ou de l'air, a été injecté sous pression par des moyens hydrauliques classiques, dans la première chambre axiale 32, ce qui a provoqué le déplacement de la tige de précourse 22 grâce à son piston 30, dans le sens positif, par rapport à la tige de travail 14, d'une distance P. Ainsi, la bague d'arrêt 36 est venue en appui contre la bague d'extrémité 28, la pince portée par la tige de précourse est, de la sorte, étendue dans une première position d'approche. Simultanément, le déplacement à coulissement du piston 30 de la tige de précourse 22 a libéré les conduits 58 qui débouchent alors dans la première chambre axiale 32 et se faisant, l'huile sous pression est apte à s'écouler dans les premières chambres radiales 54. On retrouve sur la Figure 3 le vérin 10 dans une seconde position d'approche dans laquelle l'huile sous pression dans les premières chambres radiales a entraîné les pistons radiaux selon la flèche F, dans une position d'appui où les parties décolletées 52 s'étendent partiellement dans le logement axial 20 et précisément contre l'épaulement 40 du collet 38 pour former des moyens de blocage. En outre, les parties décolletées 52 sont insérées entre le piston 30 et le collet 38 de telle sorte que la tige de précourse 22 est liée mécaniquement à la tige de travail 14. A partir de cette position d'approche dans laquelle la tige de précourse 22 forme avec la tige de travail 14 un ensemble rigide, la tige de travail 14 est apte à être entraînée en translation d'une distance T, pour porter la pince dans ladite position de travail telle que représentée sur la Figure 4. On retrouve sur cette Figure 4 tous les éléments initialement décrits avec les mêmes références. Lorsque la tige de travail 14 est entraînée en translation en injectant par exemple de l'huile sous pression dans les chambres 18 derrière les pistons 16 entre parois inférieures et pistons 16, les pistons radiaux 48, 50 transmettent les efforts à la tige de précourse 22, en cisaillement sur l'épaulement 40 du collet 38. Après que la pince a été activée, il y a lieu de rétracter les tiges du vérin 10, tout d'abord en rétractant, par exemple, la tige de travail 14 pour revenir à ladite position d'approche illustrée sur la Figure 3. Lorsque la tige de travail 14 est rétractée, non seulement la bague d'extrémité 28 vient en butée contre la bague d'arrêt 36, mais les parties décolletées 52 sont également en appui contre le piston 30. De la sorte, la tige de précourse 22 est entraînée avec la tige de travail 14, ce qui permet de commander l'ouverture de la pince. Ensuite, on injecte de l'huile, par exemple, sous pression dans la seconde chambre axiale 34, opposée à la première 32, en ayant pris soin de libérer la pression dans cette dernière. L'huile s'écoule alors dans les seconds conduits 60 puis dans les secondes chambres radiales 56. De ce fait, les pistons radiaux 48, 50 sont entraînés dans une position dégagée, entièrement dans leurs logements radiaux correspondant 44, 46, ce qui libère la tige de précourse 22 par rapport à la tige de travail 14. L'huile sous pression dans la seconde chambre axiale entraîne alors la tige de précourse par l'intermédiaire de son piston 30 dans ladite position de repos initialement décrite en référence à la Figure 1. Selon un mode de mise en œuvre de l'invention non représenté, lesdits moyens de blocage comprennent des pièces de blocage formées de billes ou de cylindres, lesdites billes ou lesdits cylindres étant mobiles radialement entre une position dans laquelle ils bloquent lesdites tiges en translation et une position dans laquelle ils les libèrent. Pour ce faire, la tige de précourse s'étend entièrement dans la chambre axiale de la tige de travail, de façon que la surface externe de la tige de précourse soit en appui glissant contre la paroi interne de la chambre axiale. En outre, la tige de précourse présente des cavités radiales adaptées à déboucher en regard de lumières radiales de la tige de travail. Ces lumières sont ménagées dans l'épaisseur de la paroi cylindrique de la tige de travail qu'elles traversent de part en part. Dans ces lumières sont logées partiellement des billes ou des cylindres qui sont destinés à venir s'engager en partie dans lesdites cavités radiales tout en occupant entièrement l'espace des lumières radiales. Ces billes ou ces cylindres sont susceptibles d'être maintenus à cheval dans les lumières et dans les cavités radiales au moyen d'une bague coulissante montée sur la tige de travail et qui vient obturer lesdites lumières pour bloquer les billes ou cylindres en position. Lorsque l'on souhaite libérer les deux tiges, on fait coulisser la bague qui libère alors les lumières et les billes ou cylindres peuvent être dégagés des cavités radiales et ressortir en saillie à l'extérieur de la tige de travail. Pour favoriser le dégagement, les cavités radiales présentent un fond concave de façon que la translation axiale de la tige de précourse par rapport à la tige de travail entraîne les billes ou cylindres en translation radiale. Selon une dernière variante de réalisation de l'invention, non représentée, les pistons radiaux 48, 50 sont maintenus dans ladite position d'appui par des moyens élastiques rétractables. On se référera par exemple aux Figures 1 et 2, pour décrire le fonctionnement de l'un des pistons radiaux, 48 selon cette dernière variante de réalisation. Bien évidemment, le fonctionnement de l'autre piston radial 50 est identique. Ainsi, des moyens formant ressort sont montés dans la première chambre radiale 54 et prennent appui sur le piston radial 48 de manière à l'entraîner vers ladite position d'appui. Il est ainsi nul besoin de prévoir les conduits 58 d'arriver de fluide. En revanche, puisque le piston radial 48 est entraîné vers la position d'appui, il s'étend alors en saillie dans la seconde chambre axiale 34, au moins dans la position de repos telle que représentée sur la Figure 1 , et il est nécessaire qu'au moins la partie active 52 décolletée, soit taillée en biseau vers l'extrémité libre 24, de façon que le collet 38, entraîné en translation contre la partie active 52 décolletée, entraîne en rétraction le piston radial 48 ; le collet 38 étant entraîné en glissement contre la partie active 52 décolletée, et biseautée. Les moyens élastiques sont alors comprimés et dès que le collet 38, poursuivant sa course, est écarté du piston radial 48, ce dernier entraîné par les moyens élastiques reprend sa position en saillie dans la seconde chambre axiale 34 et vient prendre appui contre le piston 30. Par ailleurs, on prévoit de chanfreiner le collet 38 afin de faciliter le déplacement relatif du collet 38 contre la partie active 52 biseautée. En outre, le dégagement du piston radial 48 s'effectue de manière identique, au mode de réalisation précédent en injectant un fluide sous pression dans les seconds conduits 60, qui s'écoule ensuite également sous pression dans les secondes chambres radiales 56. Le fluide sous pression peut bien évidemment être de l'huile mais aussi de l'air comprimé. The present invention relates to a double-stroke welding clamp cylinder for positioning the clamp in an approach position and then in a working position in a work area. These cylinders comprise a cylinder body in which are housed two rods each secured to at least one piston. A pre-stroke rod is adapted to position the clamp in said approach position from a rest position and a working rod is adapted to position said clamp in a working position. Generally, one of the branches of the clamp is fixedly mounted relative to the cylinder body while the other branches which is mounted movably relative to the first, is actuated by the rods of the cylinder. While from the rest position to the approach position, the efforts to implement for the movement of the clamp are small, the setting in working position of the clamp requires more effort. It is therefore necessary that the working rod is held rigidly with respect to the clamp when the piston of the latter is activated; and all the more so as to increase the forces to be applied on the working rod it generally has several stage pistons. In order to maintain said working rod rigidly with respect to the clamp, it has been imagined to mount said clamp directly to the free end of said working rod and to mount said slide working rod through said pre-stroke rod. which is kept away from said work area. We can refer to the document FR 2 781 016 which describes such a device. The pre-stroke rod has a piston which is further mounted in said cylinder body which is movable in translation relative to said pre-stroke rod. Furthermore, locking means are used to lock together the cylinder body and the pre-stroke rod. Thus, the pre-stroke rod being kept at a distance from said working zone, the injection of pressurized fluid into the body and against the piston of the pre-stroke rod translates said body which in turn drives the working rod with the pliers in the approach position. Then, the locking means are activated to lock together the pre-stroke rod and the cylinder body. Then, the working rod is driven into said working position with said clamp, injecting a fluid under pressure into the cylinder body and against the piston or pistons of the working rod. Although the locking of the pre-stroke rod and the cylinder body is sufficient so that the driving of the clamp to the working position takes place without the cylinder body moving away from said working area, it is relatively relatively easy to fix the pre-stroke rod which is at least partially engaged in the cylinder body and maintain in a fixed position at a distance from this working area. Moreover, the body of the cylinder from which the working rod is driven and guided in translation is maintained only by the pre-stroke rod through which it is slidably mounted, which is likely to increase the clearance clearance. the working rod with respect to the work area. A problem that arises and that aims to solve the present invention, is then to provide a cylinder that not only allows to perfectly guide the working rod in the working position, but also that is adapted to be easily maintained in a fixed position and away from the work area. For this purpose, the present invention provides a welding clamp cylinder comprising a body in which are housed two rods each secured to at least one piston, a pre-stroke rod adapted to position said clamp in an approach position and a rod working shaft adapted to position said clamp in a working position, said rods being mounted coaxially in said body and said cylinder further comprising locking means; said pre-stroke rod and its piston being mounted inside said working rod, while said working rod is mounted in said body; and said locking means being adapted to lock in translation, said pre-stroke rod with respect to said working rod when said clamp is positioned in said working position. Thus, a feature of the invention lies in the mode of connection between the rods and the cylinder body, the working rod being housed in the cylinder body and the pre-stroke rod which carries the clamp being housed in the working rod . In this way, it is no longer the pre-stroke rod which is kept at a distance from said working zone but the body of the jack, which is much easier for it to maintain in view of its external surface compared to that of the rod. off difference. In addition, the rods being mounted telescopically in the cylinder body, the guidance of the clamp and in particular the actuation of the movable branch is perfectly ensured and the rods, in particular the working rod, have no play in travel. As a result, the positioning accuracy of the clamp relative to the work area is increased. Moreover, thanks to this feature, the length of the cylinders can be reduced. Indeed, according to the prior art, the piston of the pre-stroke rod is located in the extension of the pistons of the working rod and thus adds an additional stage. While the cylinder according to the present invention, has a pre-stroke rod piston which is fully housed in the working rod and whose movement takes place in the middle of the working pistons without having to add an extra length. As for the locking means, according to a preferred embodiment, they comprise locking pieces, said locking pieces being movable radially between a position in which said rods are locked in translation and a position in which said rods are free in translation. translation. They comprise, according to a first particularly advantageous embodiment, at least one radial piston forming locking pieces, mounted in a radial housing of said working rod and adapted to cooperate with said pre-stroke rod, said radial piston being movable in translation between a bearing position for locking said rods together and an unobstructed position allowing the displacement of said pre-stroke rod by relative to said working rod. Thus, the radial piston which extends in the radial chamber formed in the working rod and substantially perpendicular to the pre-stroke rod, is adapted to block the pre-travel rod in translation relative to the working rod. For reasons of symmetry and a balanced distribution of forces, the locking means comprise a plurality of radial pistons, for example two, which define equivalent sectors around the pre-stroke rod. To do this, said pre-stroke rod preferably has a shoulder, formed for example by means of a ring integral with the pre-stroke rod and against which said radial piston is adapted to come into said bearing position. In this way, the pre-stroke rod is locked relative to the working rod, the shoulder abutting against the radial piston which extends at least partially in the radial housing and which then undergoes a shear force. According to another particular embodiment of the invention, said radial housing is capable of forming two opposite radial chambers delimited by said radial piston, a first radial chamber being adapted to receive a fluid for driving in translation said radial piston in said radial position. 'support. Thus, is said first radial chamber opposed to the pre-stroke rod with respect to the radial piston reduced when the radial piston is in said disengaged position and fully extends into the radial housing, while is extended when a fluid has been injected under pressure to drive the radial piston to the pre-stroke rod in the support position. According to a particular mode of implementation, said radial chambers are capable of being supplied with fluids by means external supply, so as to control the radial piston from the outside by an independent circuit equipped with solenoid valves. According to another particular embodiment, said working rod has an axial housing in which the piston of said pre-stroke rod is adapted to slide by delimiting two opposite axial chambers, a first axial chamber being adapted to receive a fluid under pressure. allowing said pre-stroke rod to be driven from a rest position to said approach position, and said first axial chamber is connected by a conduit to said first radial chamber such that said piston seals said conduit in said position of rest, and releases it into said approach position. Thus, the first axial chamber and the first radial chamber are isolated from each other in said rest position and they are in communication in said approach position. In this way, thanks to unique hydraulic means, the injection of a fluid into the first axial chamber makes it possible to drive the pre-stroke rod into said approach position and then to drive the radial piston into the support position. to block the pre-stroke rod with respect to the working rod. The drive of the working rod by additional hydraulic means then allowing to drive the pre-stroke rod and the clamp it carries to the working area in said working position, without the pre-stroke rod retracting in the working rod. Conversely, in order to retract the pre-stroke rod into the working rod after the clamp has been actuated, said piston of the pre-stroke rod delimits, particularly advantageously, a second axial chamber and said radial piston delimits a second radial chamber, said chambers being connected together so as to simultaneously drive said radial piston in disengagement from said bearing position and said pre-stroke rod towards said rest position by injecting a fluid into said second axial chamber. Thus, while the pre-stroke rod has for example returned to said approach position, by injecting a fluid under pressure into the second axial chamber, this the last flows in the second radial chamber and the radial piston is driven into the disengaged position where it is fully housed in the radial housing. The fluid under pressure then drives the pre-stroke rod into said rest position. According to an alternative embodiment of the invention, said locking means are mounted in said pre-stroke rod, and they are movable between an engaged position where they cooperate with said working rod and a disengaged position where they do not cooperate with said working rod. Thus, according to this advantageous characteristic, the locking means are activated from the pre-stroke rod. Advantageously, said locking means are adapted to be controlled by electromagnets, which allows great flexibility of control by means of a power supply. According to a preferred embodiment, said working rod is provided with a plurality of pistons forming a plurality of stages so as to increase the efforts to bring the clamp into the working position. Preferably, the welding clamp cylinder comprises control means adapted to control the state of said locking means, so as to ensure that the rods are securely locked together before driving the branch in the working position. Other features and advantages of the invention will appear on reading the following description of a particular embodiment of the invention, given by way of indication but not limitation, with reference to the accompanying drawings in which: Figure 1 is a schematic axial sectional view of a welding clamp cylinder according to the invention and in a first position; - Figure 2 is a schematic axial sectional view of the cylinder illustrated in Figure 1 in a second position; - Figure 3 is a schematic axial sectional view of the cylinder illustrated in Figure 2 in a third position; and - Figure 4 is a schematic axial sectional view of the cylinder illustrated in Figure 3 in a fourth position. FIG. 1 illustrates a welding clamp cylinder 10 according to the invention and it comprises a body or cylinder 12 in which is adapted to slide a working rod 14 of which is secured a plurality of pistons 16. These pistons 16 are movable in translation in a plurality of chambers 18 delimited by partitions 19 which they divide into two parts. In this Figure 1, the pistons 16 are in abutment against the lower walls of the partitions 19. Of course, the working rod may have only two pistons or even one, when it is desired to shorten the maximum cylinder. The working rod 14 has an axial housing 20 in which extends longitudinally a pre-stroke rod 22 slidably mounted. The pre-stroke rod 22 has a free end 24 passing through a first end 26 of the working rod 14 and which is located outside the axial housing 20 so as to carry a not shown clamp. The axial housing 20 is closed sealingly at the first end 26 by means of an end ring 28 that the pre-stroke rod 22 also freely passes through tightly. The welding clamps have two branches, a first which is mounted in a fixed position, substantially in the axis of the jack and integral with its body, and a second which is mounted movable relative to the first and which is driven by the rods of the cylinder. In addition, the pre-stroke rod 22 has a piston 30 of which it is integral and which sealingly joins the inner wall of the axial housing 20 by defining a first axial chamber 32, opposite to a second axial chamber 34. Moreover, a ring stopper 36 is mounted on the pre-stroke rod in the second axial chamber 34 and is adapted to bear for abutment against the end ring 28 when the pre-stroke rod 22 slides as will be explained hereinafter. - after. In addition, the pre-stroke rod 22 has a collar 38 defining a shoulder 40 which makes it possible to form a bearing surface. The working rod 14 has a bulbous end portion 42 adapted to be housed in an internal space 43 of said body 12 in a subsequent phase which will be described next. In this bulged part, are provided two diametrically opposite radial housings 44, 46 which open into the second axial chamber 34. In these radial housings 44, 46 are mounted to slide two radial pistons 48, 50 which are adapted to be housed entirely in said housings, as shown in Figure 1. These radial pistons have an active part 52 décolletée adapted to be driven into said axial housing 20 to block the pre-stroke rod as will be explained in more detail in the following description . The non-turned part forms the piston and delimits the radial housing in two chambers opposite to each other, a first radial chamber 54 opposite said low-cut portion 52 and a second radial chamber 56 where the low-neck portion extends. 52. Moreover, the first radial chambers 54 are connected by a first conduit 58 which opens into the axial housing 20 and which is in this Figure 1 closed by the piston 30 of the pre-stroke rod 22. In addition, the second radial chambers 56 are connected by a second conduit 60 which opens into the second axial chamber 34. After describing the structural elements of the cylinder 10, which is shown in this Figure 1, in a rest position, reference is made to FIG. describe the same jack 10 with the same elements, in a first approach position. We will also describe the transition between the rest position and the first approach position. With respect to the rest position, a fluid, for example oil or air, has been injected under pressure by conventional hydraulic means, into the first axial chamber 32, which has caused the displacement of the rod. 22 with its piston 30, in the positive direction, relative to the working rod 14, a distance P. Thus, the stop ring 36 is abutting against the end ring 28, the Gripper carried by the pre-stroke rod is, in this way, extended in a first approach position. Simultaneously, the sliding displacement of the piston 30 of the pre-stroke rod 22 has released the ducts 58 which then open into the first axial chamber 32 and in doing so, the pressurized oil is able to flow into the first radial chambers 54 FIG. 3 shows the jack 10 in a second approach position in which the oil under pressure in the first radial chambers has driven the radial pistons along the arrow F in a bearing position where the low-cut parts 52 extend partially into the axial housing 20 and precisely against the shoulder 40 of the collar 38 to form locking means. In addition, the beveled portions 52 are inserted between the piston 30 and the collar 38 such that the pre-stroke rod 22 is mechanically connected to the working rod 14. From this approach position in which the pre-stroke rod 22 forms with the working rod 14 a rigid assembly, the working rod 14 is adapted to be driven in translation by a distance T, to carry the clamp in said working position as shown in Figure 4. Found on this Figure 4 all the elements initially described with the same references. When the working rod 14 is driven in translation by injecting for example pressurized oil into the chambers 18 behind the pistons 16 between lower walls and pistons 16, the radial pistons 48, 50 transmit the forces to the pre-stroke rod 22 shearing on the shoulder 40 of the collar 38. After the clamp has been activated, it is necessary to retract the rods of the cylinder 10, first by retracting, for example, the working rod 14 to return to said approach position shown in FIG. 3. When the working rod 14 is retracted, not only does the end ring 28 abut against the stop ring 36, but the notched portions 52 also bear against the piston 30. In this way, the pre-stroke rod 22 is driven with the working rod 14, which allows to control the opening of the clamp. Then, oil is injected, for example, under pressure into the second axial chamber 34, opposite the first 32, taking care to release the pressure in the latter. The oil then flows into the second conduits 60 and into the second radial chambers 56. As a result, the radial pistons 48, 50 are driven into an unobstructed position, entirely in their corresponding radial recesses 44, 46, which releases the pre-stroke rod 22 with respect to the working rod 14. The oil under pressure in the second axial chamber then drives the pre-stroke rod via its piston 30 in said rest position initially described with reference to FIG. 1. According to one embodiment of the invention not shown, said locking means comprise locking pieces formed of balls or cylinders, said balls or said cylinders being movable radially between a position in which they block said rods. translation and a position in which they release them. To do this, the pre-stroke rod extends entirely in the axial chamber of the working rod, so that the outer surface of the pre-stroke rod is in sliding abutment against the inner wall of the axial chamber. In addition, the pre-stroke rod has radial cavities adapted to open opposite radial lights of the working rod. These lights are formed in the thickness of the cylindrical wall of the working rod through which they pass through. In these slots are partially housed balls or cylinders which are intended to engage partially in said radial cavities while fully occupying the space of the radial lights. These balls or these cylinders are likely to be held astride in the slots and in the radial cavities by means of a sliding ring mounted on the working rod and which closes said slots to lock the balls or cylinders in position. When it is desired to release the two rods, the ring is slid which then releases the lights and the balls or cylinders can be disengaged from the radial cavities and protrude outwardly from the working rod. To promote the clearance, the radial cavities have a concave bottom so that the axial translation of the pre-stroke rod relative to the working rod drives the balls or cylinders in radial translation. According to a last variant embodiment of the invention, not shown, the radial pistons 48, 50 are held in said bearing position by retractable elastic means. Referring for example to Figures 1 and 2, to describe the operation of one of the radial pistons, 48 according to this last embodiment. Of course, the operation of the other radial piston 50 is identical. Thus, spring means are mounted in the first radial chamber 54 and bear on the radial piston 48 so as to drive it to said support position. It is thus no need to provide the conduits 58 to arrive fluid. On the other hand, since the radial piston 48 is driven towards the bearing position, it then extends in projection in the second axial chamber 34, at least in the rest position as shown in FIG. 1, and it is necessary at least the active part 52 décolletée, is bevelled towards the free end 24, so that the collar 38, driven in translation against the active part 52 décolletée, drives in retraction the radial piston 48; the collar 38 being slidably engaged against the active part 52, cut and tapered. The elastic means are then compressed and as soon as the neck 38, continuing its stroke, is separated from the radial piston 48, the latter driven by the elastic means resumes its projecting position in the second axial chamber 34 and bears against the piston 30 Furthermore, it is intended to chamfer the collar 38 to facilitate the relative movement of the collar 38 against the active part 52 beveled. In addition, the clearance of the radial piston 48 is effected identically, in the previous embodiment by injecting a fluid under pressure in the second ducts 60, which also flows under pressure in the second radial chambers 56. The fluid under pressure can obviously be oil but also compressed air.

Claims

REVENDICATIONS
1. Vérin de pince de soudage comprenant un corps (12) dans lequel sont logées deux tiges (14, 22) solidaires chacune d'au moins un piston, une tige de précourse adaptée à positionner ladite pince dans une position d'approche et une tige de travail adaptée à porter ladite pince, de ladite position d'approche vers une position de travail, lesdites tiges étant montées coaxialement dans ledit corps et ledit vérin comprenant en outre des moyens de blocage ; caractérisé en ce que ladite tige de précourse (22) et son piston (30) sont montés à l'intérieur de ladite tige de travail (14), tandis que ladite tige de travail (14) est montée dans ledit corps (12) ; et en ce que lesdits moyens de biocage (40, 48, 50) sont adaptés à bloquer en translation, ladite tige de précourse (22) par rapport à ladite tige de travail (14) lorsque ladite pince est portée dans ladite position de travail. 1. Welding clamp cylinder comprising a body (12) in which are housed two rods (14, 22) each secured to at least one piston, a pre-stroke rod adapted to position said clamp in an approach position and a working rod adapted to carry said clamp, from said approach position to a working position, said rods being mounted coaxially in said body and said cylinder further comprising locking means; characterized in that said pre-stroke rod (22) and its piston (30) are mounted inside said working rod (14), while said working rod (14) is mounted in said body (12); and in that said biocage means (40, 48, 50) are adapted to block in translation, said pre-stroke rod (22) relative to said working rod (14) when said clamp is carried in said working position.
2. Vérin de pince de soudage selon la revendication 1 , caractérisé en ce que lesdits moyens de blocage comprennent des pièces de blocage, lesdites pièces de blocage étant mobiles radialement entre une position dans laquelle lesdites tiges sont bloquées en translation et une position dans laquelle lesdites tiges sont libres en translation. 2. Welding clamp cylinder according to claim 1, characterized in that said locking means comprise locking pieces, said locking pieces being movable radially between a position in which said rods are locked in translation and a position in which said rods are free in translation.
3. Vérin de pince de soudage selon la revendication 1 ou 2, caractérisé en ce que lesdits moyens de blocage comportent au moins un piston radial (48, 50) formant lesdites pièces de blocage, montés dans un logement radial (44, 46) de ladite tige de travail (14) et adapté à coopérer avec ladite tige de précourse (22), et en ce que ledit piston radial (48, 50) est mobile en translation entre une position d'appui pour bloquer ensemble lesdites tiges et une position dégagée autorisant le déplacement de ladite tige de précourse (22) par rapport à ladite tige de travail (14). 3. Welding clamp cylinder according to claim 1 or 2, characterized in that said locking means comprise at least one radial piston (48, 50) forming said locking pieces, mounted in a radial housing (44, 46) of said working rod (14) and adapted to cooperate with said pre-stroke rod (22), and in that said radial piston (48, 50) is movable in translation between a support position to lock said rods together and a position clear allowing the movement of said pre-stroke rod (22) relative to said working rod (14).
4. Vérin de pince de soudage selon la revendication 3, caractérisé en ce que ladite tige de précourse (22) présente un épaulement (40) contre lequel ledit piston radial (48, 50) est adapté à venir s'appliquer dans ladite position d'appui. 4. Welding clamp cylinder according to claim 3, characterized in that said pre-stroke rod (22) has a shoulder (40) against which said radial piston (48, 50) is adapted to come to be applied in said position d 'support.
5. Vérin de pince de soudage selon la revendication 3 ou 4, caractérisé en ce que ledit piston radial (48, 50) est maintenu dans ladite position d'appui par des moyens élastiques rétractables. 5. Welding clamp cylinder according to claim 3 or 4, characterized in that said radial piston (48, 50) is held in said bearing position by retractable elastic means.
6. Vérin de pince de soudage selon la revendication 3 ou 4, caractérisé en ce que ledit logement radial (44, 46) est susceptible de former deux chambres radiales opposées délimitées par ledit piston radial (48, 50), une première chambre radiale (54) étant apte à recevoir un fluide pour entraîner en translation ledit piston radial (48, 50) dans ladite position d'appui. 6. Welding clamp cylinder according to claim 3 or 4, characterized in that said radial housing (44, 46) is capable of forming two opposite radial chambers delimited by said radial piston (48, 50), a first radial chamber ( 54) being able to receive a fluid for driving in translation said radial piston (48, 50) in said support position.
7. Vérin de pince de soudage selon la revendication 6, caractérisé en ce que lesdites chambres radiales sont susceptibles d'être alimentées en fluides par des moyens d'alimentation externes. 7. Welding clamp cylinder according to claim 6, characterized in that said radial chambers are capable of being supplied with fluids by external supply means.
8. Vérin de pince de soudage selon la revendication 6, caractérisé en ce que ladite tige de travail (14) présente un logement axial (20) dans lequel le piston (30) de ladite tige de précourse (22) est adaptée à coulisser en délimitant deux chambres axiales opposées, une première chambre axiale (32) étant adaptée à recevoir un fluide sous pression permettant l'entraînement de ladite tige de précourse (22), d'une position de repos vers ladite position d'approche, et en ce que ladite première chambre axiale (32) est reliée par un conduit (58) à ladite première chambre radiale (54) de façon que ledit piston (30) obture ledit conduit (58) dans ladite position de repos, et le libère dans ladite position d'approche. 8. Welding clamp cylinder according to claim 6, characterized in that said working rod (14) has an axial housing (20) in which the piston (30) of said pre-stroke rod (22) is adapted to slide in delimiting two opposite axial chambers, a first axial chamber (32) being adapted to receive a pressurized fluid allowing the driving of said pre-stroke rod (22), from a rest position towards said approach position, and in this that said first axial chamber (32) is connected by a conduit (58) to said first radial chamber (54) so that said piston (30) closes said conduit (58) in said rest position, and releases it in said position approach.
9. Vérin de pince de soudage selon la revendication 8, caractérisé en ce que ledit piston (30) de la tige de précourse (22) délimite une seconde chambre axiale (34) et ledit piston radial (48, 50) délimite une seconde chambre radiale (56), lesdites chambres étant reliées ensemble de façon à entraîner simultanément ledit piston radial (48, 50) en dégagement de ladite position d'appui et ladite tige de précourse (22) vers ladite position de repos en injectant un fluide dans ladite seconde chambre axiale (34). 9. Welding clamp cylinder according to claim 8, characterized in that said piston (30) of the pre-stroke rod (22) delimits a second axial chamber (34) and said radial piston (48, 50) delimits a second chamber radial (56), said chambers being connected together so as to simultaneously drive said radial piston (48, 50) in release of said support position and said pre-stroke rod (22) towards said rest position by injecting a fluid into said second axial chamber (34).
10. Vérin de pince de soudage selon la revendication 1 ou 2, caractérisé en ce que lesdits moyens de blocage sont montés dans ladite tige de précourse, et en ce qu'ils sont mobiles entre une position engagée où ils coopèrent avec ladite tige de travail et une position dégagée où ils ne coopèrent pas avec ladite tige de travail. 10. Welding clamp cylinder according to claim 1 or 2, characterized in that said locking means are mounted in said pre-stroke rod, and in that they are movable between an engaged position where they cooperate with said working rod and an open position where they do not cooperate with said working rod.
11. Vérin de pince de soudage selon l'une quelconque des revendications 2 à 4 ou 8, caractérisé en ce que lesdits moyens de blocage sont adaptés à être commandé par des électroaimants. 11. Welding clamp cylinder according to any one of claims 2 to 4 or 8, characterized in that said locking means are adapted to be controlled by electromagnets.
12. Vérin de pince de soudage selon l'une quelconque des revendications 1 à 11 , caractérisé en ce que ladite tige de travail (14) est munie d'une pluralité de pistons (16) formant une pluralité d'étages. 12. Welding clamp cylinder according to any one of claims 1 to 11, characterized in that said working rod (14) is provided with a plurality of pistons (16) forming a plurality of stages.
13. Vérin de pince de soudage selon l'une quelconque des revendications 1 à 12, caractérisé en ce qu'il comprend des moyens de contrôle adaptés à contrôler l'état desdits moyens de blocage. 13. Welding clamp cylinder according to any one of claims 1 to 12, characterized in that it comprises control means adapted to control the state of said locking means.
PCT/FR2005/000202 2004-02-06 2005-01-31 Double-stroke cylinder for soldering tongs WO2005084871A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR0401166 2004-02-06
FR0401166A FR2865950B1 (en) 2004-02-06 2004-02-06 WELDING CLAMP CYLINDER WITH DOUBLE RUN.

Publications (1)

Publication Number Publication Date
WO2005084871A1 true WO2005084871A1 (en) 2005-09-15

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/FR2005/000202 WO2005084871A1 (en) 2004-02-06 2005-01-31 Double-stroke cylinder for soldering tongs

Country Status (2)

Country Link
FR (1) FR2865950B1 (en)
WO (1) WO2005084871A1 (en)

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5115113A (en) * 1990-09-24 1992-05-19 General Motors Corporation Spot welding method and apparatus having weld electrode lock-up
EP0914896A2 (en) * 1997-10-25 1999-05-12 NIMAK Automatisierte Schweisstechnik GmbH Piston-cylinder for welding gun
FR2781016A1 (en) * 1998-07-08 2000-01-14 Aro CYLINDER WITH PRECOURSE OF APPROACH AND WORK RACE, FOR THE HANDLING OF A TOOL
EP1398105A1 (en) * 2002-09-10 2004-03-17 Gerbi & Fase S.p.A. Two-stage actuating cylinder, particlulary for opering a welding gun

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5115113A (en) * 1990-09-24 1992-05-19 General Motors Corporation Spot welding method and apparatus having weld electrode lock-up
EP0914896A2 (en) * 1997-10-25 1999-05-12 NIMAK Automatisierte Schweisstechnik GmbH Piston-cylinder for welding gun
FR2781016A1 (en) * 1998-07-08 2000-01-14 Aro CYLINDER WITH PRECOURSE OF APPROACH AND WORK RACE, FOR THE HANDLING OF A TOOL
EP1398105A1 (en) * 2002-09-10 2004-03-17 Gerbi & Fase S.p.A. Two-stage actuating cylinder, particlulary for opering a welding gun

Also Published As

Publication number Publication date
FR2865950B1 (en) 2007-04-20
FR2865950A1 (en) 2005-08-12

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