DE29924408U1 - Knee-lever welding tool for automobile body components has fluid-cooled welding electrodes attached to pivoted clamp arm and cooperating jaw acting as counter-bearing - Google Patents

Abstract

The knee-lever welding tool has a clamp head (1) provided with a linear operating drive (2,5), with a piston rod (6) displaced axially relative to the clamp head, cooperating with a knee-lever mechanism (8) at its free end, for pivoting a clamp arm (15) in opposite directions relative a pivot axis (22) in alternation The clamp arm cooperates with a jaw (19) acting as a counter-bearing, each provided with a fluid-cooled welding electrode (17,18), brought together for welding the automobile body component (16) with a high pressure.

Description

Knee lever welding gun for use in bodywork construction

Description Genus

The invention relates to a toggle lever welding gun for use in body construction in the automotive industry.

State of the art

The welding devices commonly used present difficulties when welding body panels that are to be used in the bodywork of the automotive industry due to the often cramped space conditions and also due to the complicated handling. For this reason, relatively complicated devices are often built to guide welding electrodes to the welding points and then remove them again. Since the contours of body panels are often quite complicated depending on the type of car, the welding electrodes also have to be moved past these contours. This means that auxiliary devices have to be built, which often require a

Require several times the total investment costs of the actual welding device. This often involves movements in different planes, such as horizontal lifting movements, which involves relatively complicated auxiliary devices with various motor drives and sequential controls. The investment costs for such auxiliary devices are correspondingly high, not to mention that the non-productive times required for moving the welding electrodes - compared to the actual welding process - are disproportionately high.

Previously known, for example, are C-shaped welding tongs that are transported to the flat components, especially sheets, that are to be welded together.

Also known are tong-shaped structures that have a welding electrode at one end and are connected to each other at the other end via a toggle joint that moves the levers of the welding tongs by motor in order to be able to move the welding electrodes towards and away from each other. These are relatively unwieldy, bulky structures.

When welding body panels, a large number of welding points often have to be placed one behind the other and/or next to the other in quick succession, which results in the welding electrodes moving back and forth in cycles.

In the known welding devices, a distinction is also made between so-called machine welding guns, which are stationary and are arranged on the floor or a foundation and usually only produce one welding point. It is usually not possible to produce numerous welding points in quick succession with such machine welding guns. In addition, the electrodes usually cannot be moved far enough apart to be able to overcome certain contours of the body panels or the like that are to be welded together.

Also known are so-called robot welding guns, which can usually be used to produce a large number of welding points in rapid succession. Robot welding guns are usually assigned to a robot arm.

Furthermore, so-called column welding guns are already known, which are mostly stationary and to which the components to be welded are moved.

The state of the art also generally includes so-called toggle lever clamping devices, which are already known in a variety of designs and are used in particular in the bodywork construction of the automotive industry. They usually consist of a clamping head and an adjoining housing in which the motor drive, for example a piston which is to be pressurized alternately on both sides by pressure medium, in particular by air pressure, is guided longitudinally and in a sealed manner, and which passes axially through the housing and the adjoining clamping head with a piston rod. A toggle lever joint, to which a clamping arm is assigned, is connected via a pivot axis to the free end facing away from the piston. In addition, an abutment known as a jaw is usually arranged on the clamping head. Suitable device parts, for example tools, can be assigned to the clamping arm and jaw by screwing them on. The workpieces to be held, for example sheet metal in the bodywork of the automotive industry, are clamped between the clamping arm and the jaw in order to connect them to one another, for example by clinching or welding -G 91 04 532U1, DE-AS 22 22 686, EP0 778 107A1.

In another design, a drive designed as an electric motor is provided in the housing adjoining the clamping head, which is arranged coaxially to the housing and is provided with a hollow shaft which is geared to a threaded nut, which in turn drives a screw spindle which forms the axially adjustable part, the screw spindle being immersed in the hollow shaft. It is also possible for an electric motor to drive a pinion via a shaft which meshes with a gear wheel which has an internal toothing which drives a screw spindle which forms the axially adjustable part. The axially adjustable part can also be designed as a ball screw drive or as a ball screw spindle - DE 36 13 644 C2.

All in all, the existing welding devices used in particular for welding body panels in motor vehicle construction suffer from the fact that they are either too large and too bulky and therefore in many cases difficult to use due to the limited space available, or they are not able to overcome the contours of body panels, device parts and the like because their welding electrodes cannot be moved far enough away from each other. Furthermore, the existing welding devices are often unprotected against welding spatter and moisture. So-called Rob-CAD analyses (robot simulation analyses) are often carried out to determine whether a

Aside from the fact that such Rob-CAD analyses are expensive and laborious, they do not take into account that in practice hoses and entire bundles of cables often represent additional interference contours, so that despite the most careful evaluation of such simulation programs, difficulties can arise in practice due to such hoses and cables.

A welding gun device is previously known from DE 30 34 700 A1, in which a pair of right and left cam plates are attached to the upper surface of a working cylinder, which holds a stationary gun arm, wherein an arm holder is arranged in a space formed between the cam plates, which arm holder holds a movable gun arm and is connected via a pin to an upper end portion of a piston rod extending from a piston mounted in the working cylinder, wherein the arm holder is engaged via at least one pin with an almost L-shaped cam groove mounted in each cam plate. Furthermore, a positioning member for supporting a workpiece to be machined is provided with a stop plate which carries a guide rod which extends downwards from it. The working cylinder is attached to a central portion of the

Guide rod is slidably arranged and urged downward by a spring. The positioning member is detachably arranged on the support bracket, the stop plate is placed on a support base provided on a lower portion of the positioning member and detachably secured thereto by a screw, the positioning member being replaceable by another positioning member having a support base. The guide rod is connected at its lower end to a drive cylinder to be movable up and down thereby. Furthermore, the guide rod is slidably inserted through a universal joint arranged on the front end portion of a support arm extending from the support bracket. The piston rod is formed in its upper section into a plate-like portion having a shoulder portion at its lower end, the plate-like portion serving to cooperate with a stop arm extending from the stop plate so as to prevent the piston rod from rotating, the shoulder portion serving to cooperate with the stop arm so as to separate an electrode of the stationary gun arm from the workpiece when the two members are tacked together. The pins extend over the cam grooves, guide rollers being provided which are moved further outwards in a nearly arcuate manner at the respective ends of the pins so as to obtain a wide opening angle between the gun arm carrying the welding electrodes.

To close, the movable arm is first moved in an arc and then moved linearly downwards.

From DE 37 43 341 A1, a device for actuating the welding electrode or welding tongs of resistance welding devices in welding machines, robots or similar welding devices is already known, consisting of a cylinder fixed to the frame and a piston guided in the cylinder fixed to the frame and connected to the welding electrode or the actuated arm of the welding tongs. The piston is designed as a sleeve open on one side to accommodate a spindle drive actuated by an electric motor drive and consisting of a threaded sleeve and a threaded spindle. The threaded sleeve is rigidly attached to the piston connected to the welding electrode or the actuated arm of the welding tongs and guided axially movably in the cylinder, with the threaded spindle rotatably mounted in the cylinder being connected to an electric motor drive. Furthermore, the threaded sleeve can be connected in a rotationally fixed manner to the rotor of the electric motor drive and the threaded spindle can be rigidly connected to the piston guided axially in the cylinder.

US 5 201 838 A discloses a robot gripper controlled by a piston with a piston rod, which is driven by a wedge gear and can be used to grip electronic components. Sensors in a housing that accommodates the piston with the piston rod control the position of the piston.

Task

The invention is based on the object of creating a new type of welding device for use in body construction in the automotive industry, which can be used in relatively confined spaces, easily overcomes the contours that usually occur when welding body panels and does not require expensive auxiliary devices (rotating, linear or swivel units = auxiliary devices) that are intended to move the welding electrodes to and from the actual location of use. In addition, the desired new welding device should be protected against welding spatter and the liquids and contaminants that usually occur in body construction production plants.

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Solution

The problem is solved by the features set out in claim 1 .

Some advantages

To solve the problem underlying the invention, an encapsulated toggle-lever welding gun is proposed, which basically uses the design of previously known toggle-lever clamping devices from the automotive industry. In this way, it is possible to connect a welding electrode to the actual clamping arm and another welding electrode to the opposite jaw, which then grip the flat components to be joined together, in particular body panels, between them with high pressure and connect them to one another by spot welding. For example, welding forces in the order of 1 to 10 kN, preferably 2 to 4 kN, can be used. The high welding force can be applied without any problems by the toggle-lever joint automation with initially gentle pressure, i.e. the electrodes do not come into contact with the components suddenly. When the linear motor is designed as a piston-cylinder unit, it is possible to use the compressed air usually used in automotive construction.

preferably only about 6 bar, so that a high-pressure network is unnecessary.

Depending on the available space, piston-cylinder units with different cross-sectional shapes can also be selected, for example, instead of a round cylinder, a cylinder with a slightly rectangular cross-section (so-called flat oval cylinder), which has transition radii on its narrow sides that merge into the narrow sides and the long sides of the cylinder. The piston is adapted accordingly.

The entire mechanism of the toggle-lever welding gun can be protected against dust, moisture and welding spatter by arranging the toggle-lever mechanism and the piston rod itself in the clamping head and/or in the cylinder of the piston-cylinder unit. However, not only the mechanism, but also the electrics and electronics can be safely protected thanks to fully encapsulated housings. The clamping arm and its bearings and, if necessary, an automatic adjustment mechanism for the jaw can also be arranged in protected housing sections, resulting in a very compact toggle-lever welding gun that can be handled as a single component. Such a toggle-lever welding gun can be used in all places where

has also previously used toggle clamping devices in automotive construction, but also where previously known designs failed.

A particular advantage is that by designing a welding device as a toggle-lever welding gun, it is possible to design the swivel angle of the actual clamping arm to at least 90° or more, so that the electrode connected to the clamping arm can be moved very far away from the electrode assigned to the jaw. In this way, even bulky contours can be overcome, so that the toggle-lever welding gun according to the invention can also be used where previous welding devices failed, i.e. particularly with stationary welding guns. The wide opening angle of the clamping arm allows free, practically vertical component removal, so that an additional swivel unit or other auxiliary devices are not required.

A welding gun according to the invention can be used both as a machine welding gun and as a stand welding gun or robot welding gun.

In summary, the main advantages are as follows:
a) Machine welding gun

Fully encapsulated system, no influence of dirt and welding spatter on bearings and other functional components
Query in cassette technology (revolutionary for welding guns)
Swivel arm opens up to 90°, component can be removed vertically without additional movement
No 12 bar compressed air network required, as the required welding force is achieved by a mechanical toggle lever transmission, conventional 6 bar compressed air supply is sufficient
Flat cylinder creates flat mounting profile in the stations
Knee lever mechanism with curve mechanism for constant welding force with increasing electrode wear

Electrode wear indicator as soon as integrated limit switch indicates wear limit

b) Robot welding gun

also based on the basic principles of machine welding guns, but characterized by the following additional features:

Swivel bracket with integrated transformer cage central balancing cylinder fully encapsulated, integrated in the cylinder base of the drive cylinder

Complete system with integrated query, no "cable tangle" both cylinders, drive cylinder and compensation cylinder controlled via a common valve plate

Housing made of solid aluminum, hard-coated and therefore lightweight and safely protected against welding spatter

c) Column welding gun
Essentially the same as a).

d) Optional clamping function

Simultaneous clamping and welding using clamping pins or contour pieces positioned to the right and left of the welding electrode; spring-supported system that adapts to the conditions even in the event of contour changes and electrode wear

Further inventive embodiments

Further inventive embodiments are described in claims 2 to 39 .

In the case of a design according to claim 2, the sensitive components can be arranged in the clamping head consisting of two halves and sealingly closing with a joint and/or in the housing for the motor drive, which is generally designed as a cylinder, for example any control and interrogation devices, encapsulated against welding spatter, liquid and dust.

When producing several welding points next to or behind each other, it is not actually necessary to let the welding electrodes perform the full stroke, i.e. to move them as far away from each other as possible, because a fast cycle sequence is important.

If the documentation refers to the "step function", this refers to a state in which the welding electrodes do not perform the full opening stroke, but only a "working stroke", which makes it possible to place numerous welding points one behind the other and/or next to each other in rapid succession. In contrast, the welding electrodes are spaced apart by the full stroke when the so-called "pre-stroke" is performed.

Claim 3 describes an advantageous solution. For this purpose, only a small opening stroke of the clamping arm and its electrodes is required, whereby, for example, the welding electrode of the jaw is lowered by a small amount and the welding electrode connected to the clamping arm is pivoted into the open position by a small opening angle. This can be accomplished particularly advantageously and in rapid succession with a compensation and lowering device proposed according to the invention. These different positions, with which a large number of welding points are to be produced in rapid succession, are also referred to as so-called

"Step position". The compensation and lowering device proposed according to the invention is also advantageous when the full opening stroke is required, i.e. when the welding electrode connected to the jaw is to be completely lowered by a certain amount and the welding electrode connected to the clamping arm is to be pivoted into the open position at the same time. In this way, the two welding electrodes can be pivoted open from one another as far as possible, for example by an angle of 90° or more, so that the component can be easily inserted, for example vertically or almost vertically, but can also be removed again.

An advantageous embodiment is described in claim 4. For this purpose, a further piston is arranged in the same cylinder as the piston that drives the piston rod. This results in a space-saving, very compact, cartridge-shaped design for the housing that accommodates the linear drive.

Claims 5 and 6 describe preferred inventive embodiments.

According to claim 7, the clamping arm is assigned a holding-down device which leads during the welding stroke for the flat components to be welded together.

Claim 8 describes such a holding-down device for the jaw. This device makes it possible to clamp and hold the flat components to be welded together, in particular body panels, until they are permanently connected to one another by welding points. This ensures a high degree of dimensional accuracy within narrow tolerances.

Advantageously, the hold-down device according to claim 9 is assigned at least one pre-stressed compression spring, which has the necessary pressure load for the actual hold-down device, by which the flat components are loaded. The compression spring also ensures that the leading hold-down device cannot suddenly touch down.

An advantageous embodiment for a hold-down device is described in claim 10. The dome-shaped bearing enables compressive forces to be introduced without bending or shear stress.

Further advantageous embodiments are described in claims 11 and 12 .

It is of great advantage if, according to claim 13, the welding electrode connected to the clamping arm can be pivoted by more than 90°, preferably 135° or up to 180°, in both directions (A - B) relative to the electrode connected to the jaw. In this way, relatively large contours can be overcome.

An advantageous embodiment is described in claim 14 .

According to the invention, the jaw with its welding electrode is designed to be adjustable and adjustable in the direction of the welding electrode assigned to the clamping arm - protection claim 15.

The embodiment according to claim 16 has the advantage that a relatively constant welding force is achieved despite electrode wear by using the toggle lever cam mechanism. The welding force during welding is greater than, for example, 250 kg at only 5 bar operating pressure. Because the guide walls are curved, a constant or almost constant torque can be delivered, which

I · · «ft· ·

This means that the welding electrodes also grasp and weld the components to be welded together at a certain angle before, possibly above and possibly beyond the otherwise usual dead center position with a constant or almost constant welding force, even if a certain amount of electrode wear occurs.

The curved design of the guide walls or guide grooves thus ensures a high, consistent clamping force between the welding electrodes over a certain pivoting range of the toggle joint.

Claim 17 describes an inventively advantageous alternative to this construction.

Claim 18 describes an advantageous embodiment of the invention, which also applies to the embodiment according to claim 19 .

Advantageously, according to claim 20, the jaw with its support part for the flat components is designed to be adjustable in a special way.

In the embodiment according to claim 21, the adjustability is formed by a piston-cylinder unit, which can optionally be pressurized by pressure medium pressure, in particular by air pressure.

A further advantageous embodiment is described in claim 22. This is particularly suitable for use as a robot welding gun. Both the clamping arm and the jaw are moved together, synchronously and by the same linear drive towards or away from each other via a positive guide.

For this purpose, claim 23 describes an inventive embodiment.

The encapsulated welding gun as claimed in claim 24 can be used with particular advantage as a so-called robot welding gun. For this purpose, the entire encapsulated toggle-lever welding gun is connected in a suitable manner to a robot arm via a swivel axis. Because the lower electrode is arranged so that it can be swiveled, it can be moved synchronously with the clamping arm, but in opposite directions, so that an optimal loading and unloading option for the components is provided. The absolute synchronous operation is achieved by a geared connection between the clamping arm and the lower

electrode. In addition, only one drive needs to be provided to move these two parts.

Advantageously, the geared connection between the clamping arm and the lower electrode in the embodiment according to claim 25 is achieved by using a gear transmission, which ensures absolute synchronization and thus also synchronization of the movements. Conventional involute gears can be considered as the gearing.

A particularly advantageous embodiment is provided in claim 26. In this embodiment, the transformer, which is at least heavy, is arranged in a transformer housing which is associated with the clamping head. This means that no long electrical cables, couplings or the like need to be laid between the transformer and the encapsulated toggle-lever welding gun.

Advantageously, according to claim 27, the transformer housing is designed in a fork-shaped manner. This allows the transformer housing to be integrated into the construction in a structurally advantageous manner by enclosing the clamping head with its two fork legs.

In the embodiment according to claim 28 , the motor drive is designed and arranged in such a way that it can be conveniently arranged below the toggle-lever welding gun and does not cause any interference. By extending and retracting this linear drive, the entire encapsulated toggle-lever welding gun can be pivoted about an axis, which also allows the jaw to be moved away from or towards the clamping arm and thus from the welding electrode assigned to it. In this way, further advantages can be achieved when loading and unloading the toggle-lever welding gun.

Advantageously, according to claim 29, a robot arm is coupled to the transformer housing.

Due to the special design of the welding device as an encapsulated toggle-lever welding gun and the associated toggle-lever transmission, a high-pressure network of, for example, 12 bar is not required to pressurize the linear drive. In many cases, it is sufficient to use 6 bar air pressure, as the toggle-lever technology contains high power reserves - protection claim 30.

As can be seen from claim 31 , with an encapsulated toggle welding gun according to the invention, welding forces of 1 to 10 kN, preferably 2 to 4 kN, can be achieved.

The embodiment according to claim 32 takes into account the requirement for a smaller size and the associated small space requirement. When we talk about "flat oval", we mean cylinder cross-section shapes for the linear drive, preferably a piston-cylinder unit, which is to be pressurized alternately on both sides with compressed air, in which the cylinder wall is flatly curved or straight on the inside and outside on the long sides and either flatly curved or straight on the narrow sides, with the narrow sides merging gently and with large radii into the longer sides of the cylinder. Flat oval, however, also means in the definition of the invention that the cylinder inside and outside, but also the piston that is longitudinally displaceable and sealed therein or the pistons when performing the stepper function, are rectangular in a cross-section that is orthogonal to the longitudinal axis, with the long and wide sides of the rectangular shape merging into one another with gentle radii. In this way, the tightness of the piston seals can also be easily guaranteed. Such "narrow" profiles can also be used in the often cramped space conditions that exist in the

Production equipment available in the automotive body construction industry can be used without any problems.

The embodiment according to claim 33 describes the arrangement of limit switches or position sensors in the form of microswitches, inductive switches, pneumatic switches or sensors, which signal and display the opening and closing, and possibly intermediate positions (step position) of the electrodes. The known cassette technology can be used to arrange these microswitches or the like. If the compensation and lowering device is arranged on the front, i.e. below the welding electrodes of the cylinder, the query cassette can be arranged as a completely replaceable unit, for example through a narrow slot provided in the longitudinal axis of the housing for the linear drive. However, it is also possible to attach the query cassette transversely to the longitudinal axis of the linear drive, in particular orthogonally to its longitudinal axis. Any control valves can be provided in the bottom of the housing facing away from the clamping head, or on its side, preferably on the back.

Claim 34 describes an advantageous embodiment.

The toggle-lever welding gun according to the invention has, in the embodiment shown in claim 35 , a permanent-magnetic brake which is always in the standby position regardless of the external energy supply, so that when the energy supply (current) to a linear drive designed as an electric motor for the toggle-lever joint is lost, the braking effect is immediately available and the relevant welding electrodes are reliably prevented from moving back. This permanent-magnetic brake essentially only requires two parts which are spaced apart and have pairs of permanent-magnetic poles. Such brakes have practically no wear and tear and are therefore low-maintenance. Like the entire toggle-lever welding rod, they can be encapsulated and housed in the housing in a space-saving manner without the external dimensions of such a toggle-lever welding device needing to be increased compared to the toggle-lever clamping devices usually used in the bodywork of the automotive industry. Such toggle-lever welding guns according to the invention are therefore also compatible with conventional toggle-lever clamping devices. In addition, such a toggle-lever welding gun also enables a space-saving and favorable arrangement of the disc-shaped parts of the permanent magnetic brake, since one part can be arranged in the stator or in the housing itself, while the shaft of the electric motor serves as a bearing for the other part of the magnetic brake.

According to claim 36, the shaft of the electric motor is designed as a hollow shaft into which the linearly driven part of the linear drive, designed as a screw spindle, can be inserted. This results in a space-saving design.

The length-adjustable part, designed as a spindle, can be mounted at both end sections in the clamping head itself and accommodate a screw motor, moving into one or the other opening depending on the drive direction of the shaft of the electric motor in order to pivot a clamping arm or the like up and down, which is coupled to the nut via the toggle joint.

Advantageously, the stop and thus the opening angle of the electrodes can be adjusted and locked from the side facing away from the clamping head.

Further advantageous embodiments are described in claims 37 to 39 .

The invention is illustrated - partly schematically - using several embodiments in the drawing. They show:

Fig. 1 shows a toggle lever welding device according to the invention, partly in side view, partly in section, in welding position;

Fig. 2 the toggle-lever welding device shown in Fig. 1 in the so-called step position, i.e. with the clamping arm partially swung back with the welding electrode and the compensating cylinder loaded accordingly;

Fig. 3 shows the toggle lever welding device shown in Figs. 1 and 2 in the fully open position;

Fig. 4 shows a further embodiment of the invention, also partly in side view, partly in section, corresponding to Fig. 1 in welding position;

Fig. 5 shows the toggle lever welding device shown in Fig. 4 in step position;

Fig. 6 shows the toggle welding device shown in Figs. 4 and 5 in the fully open position;

Fig. 7 is a side view of a hold-down device in clamping position;

Fig. 8 shows a further embodiment of a toggle lever welding gun in welding position, partly in side view, partly in section;

Fig. 9 the knee lever welding gun shown in Fig. 8 in step position;

Fig. 10 the toggle welding gun shown in Figs. 8 and 9 in the fully open position;

Fig. 11 a hold-down device in side view, in clamping position.

Fig. 12 a toggle-lever welding device designed as a robot welding gun according to the invention and shown in side view, partly broken away, in welding position;

Fig. 13 is a plan view of Fig. 12;

Fig. 14 shows the toggle lever welding device shown in Figs. 12 and 13 in the open position;

Fig. 15 shows a detail from Fig. 14, partly broken away, partly in section, with the welding electrodes pivoted into the welding position;

Fig. 16 the step position to Fig. 15 and

Fig. 17 shows a further embodiment of a toggle lever welding gun, partly in side view, partly in section, in particular for use in so-called geometry stations of machine welding guns.

The embodiments shown in Figs. 1 to 11 are particularly suitable for use as "machine welding tongs" or "column welding tongs", while the embodiments according to Figs. 12 to 17 are preferably used as so-called "robot welding tongs".

However, there is nothing to prevent the embodiments according to Figs. 1 to 11 and 17 from being used - at least in principle - in conjunction with robots or robot arms, i.e. as "robot welding guns", if this should be necessary or expedient according to the operating conditions.

While "machine welding guns" and "stand welding guns" are generally stationary, "robot welding guns" are mobile due to the mobility of the robots or robot gripper arms assigned to them. With "robot welding guns" in particular, a so-called "stepping function" is important, i.e. providing many welding points next to or behind each other at the shortest possible intervals on the components to be welded together. They usually clamp and grip the component and bring it to the so-called "geometry station". The aim here is to strictly adhere to the prescribed tolerances, especially in body construction in the automotive industry.

In the case of a "machine welding gun" and "robot welding gun", the stepping function described below may not be used if necessary, or may not be used at all, depending on the operating conditions.

All the embodiments shown in the drawing are "knee-lever welding guns" in which high welding forces are achieved by using the knee lever transmission. What is particularly striking in all embodiments is the compactness and the encapsulated design, the small space required, in particular by using so-called flat cylinders or flat-oval cylinders, and if necessary the use of only 6 bar air pressure to drive the various linear drives to be described below, for example piston-cylinder units.

What is particularly striking in all embodiments is that the mechanics, but also the parts of the linear drive, in particular a piston-cylinder unit, the electrical and electronic components, are arranged in fully encapsulated housings. All of these housings, together with the jaw, the clamping arm and the welding electrodes, are combined to form a single component that can be handled together.

Another important feature of all designs is that the welding electrodes can be placed very far apart from each other, so that free, if necessary vertical component removal is possible thanks to swivel angles of up to 90° or more, without the need for special swivel units, linear guides and handling systems for moving, lowering or lifting with expensive

and time-consuming cycle times with large investment sums as required by the state of the art.

In all or some embodiments, both the clamping head and/or the housing for the linear drive can be made of an aluminum alloy to reduce weight.

In the embodiment shown in Figs. 1 to 3, reference numeral 1 designates a clamping head, to which a cylinder 2 is coaxially connected, in which a piston 5 is arranged, which is sealed by a seal 3 against an inner wall 4 of the cylinder 2 and is longitudinally displaceable in the longitudinal axis direction of the cylinder 2. The piston 5 is integrally connected to a piston rod 6, which partially passes axially through the cylinder 2 and the clamping head 1 and is sealed by a seal 7. The cylinder 2 can be connected to the clamping head 1 detachably by screws (not shown), but can also be sealed by seals (not shown).

A toggle joint arrangement 8 is connected to the piston rod 6 via a pivot pin 9, which is coupled via a joint element 10, for example via a fork head or via tabs, to a toggle joint pin 11, which at its diametrically opposite end sections

φ · ·■

at least one guide roller 12 is guided in guide grooves which are the same size and shape and which are incorporated on opposite sides in the walls of the clamping head 1. Of these guide grooves, only the guide groove 13 has been designated with a reference number. The opposite guide groove is designed accordingly.

The guide grooves 13 are essentially made up of two length sections in the longitudinal axis direction, of which one length section of the guide grooves 13 with its longitudinal axes runs parallel to the longitudinal axis of the piston rod 6, i.e. in a straight line, while the guide grooves 13 run in a curved line on the other length section assigned to the toggle lever joint arrangement 8. The arrangement has been made in such a way that guide rollers (not shown in detail) arranged on the pivot pin 9 are always only guided in the straight section of the guide grooves 13, while the front pair of guide rollers 12 assigned to the toggle lever joint arrangement 8 can enter at least in the transition area, but preferably in the straight section of the guide grooves 13, in the open position, while the guide rollers 12 of the toggle lever joint arrangement 8 are guided by the curved section 14 of the guide grooves 13 at least in a predetermined area.

The walls of the curved section 14 can be shaped like a circular arc, similar to that described in the German utility model 297 13 944.4, which goes back to the applicant.

As can be seen from the drawing, the guide walls of the curved section 14, which are curved in one direction, i.e. to the right in the plane of the drawing, merge seamlessly into the straight section of the guide grooves 13.

The guide rollers of the toggle joint arrangement 8 assigned to the pivot pins 9 do not reach the curved section 14 in any pivoting position, because otherwise jamming could occur. Rather, only the guide rollers 12 of the toggle joint arrangement 8 are guided into the guide groove section 14, which is curved by a radius, i.e. runs in a circular arc, the arrangement being such that a clamping force that is as constant as possible is achieved in a predetermined area, as is also described in connection with the aforementioned German utility model of the applicant. This means that, for example, in a position before the clamping arm 15 is placed with the electrode 17 (to be described below) on sheets of metal or other components 16 or the like to be welded together, the full force is already achieved. In a

Over a very wide range, the clamping force is constant or almost constant, and thus also the force to be applied to the components 16 via the electrodes 17, 18 during welding. This prevents excessive stress, which is otherwise to be feared with pure dead center locking of conventional toggle lever clamping devices. An emergency switch can also be provided which switches off the energy supply if necessary, for example if the toggle lever joint moves too far into the open position due to excessive wear. Theoretically, as is well known, when the dead center is reached, forces occur which are infinite or almost infinitely large, which means that destruction or high wear can occur. This structural design of a toggle lever welding device according to the invention also achieves an automatic readjustment effect in the event of wear on the welding electrodes 17 and 18 of the clamping arm 15 (to be described below) or the abutment 19 designed as a jaw, which is integrally connected to the clamping head 1.

If the application documents refer to "one-piece" and "integrally connected", this is understood to mean both "materially one-piece" and "functionally one-piece". "Materially one-piece" is understood to mean one-piece in which one part cannot be separated from the other without destroying the other, while

in the case of "functional one-piece construction", screwing, pinning, locking or even gluing is possible, i.e. the parts can be separated from one another without destroying them, but can also be reassembled, for example screwed together, if necessary.

It is also possible to produce the curved section 14 using a family of curves, the parts of which are infinitesimally small, although care must be taken to ensure that no sudden stresses, movements or the like occur on the clamping arm 15. The curved section 14 can also be programmed in NC-controlled machines according to a mathematically favorable curve and produced without jumps by removing material, for example by grinding, milling or electrocorrosion.

The reference number 20 designates a joint bracket arrangement which is arranged so that it can pivot over the toggle joint bolt 11 and is coupled so that it can pivot with the clamping arm 15 on the clamping arm pivot bolt 21. The clamping arm 15 is mounted so that it can pivot about a stationary housing pivot axis 22 in the clamping head 1. All axes and bolts run parallel to one another with their longitudinal axes. A bracket arrangement, a fork head or the like is also designated by 23.

The welding electrodes 17 and 18 consist of the materials usually known for electric welding electrodes, primarily copper or a copper alloy, and are water-cooled. The water is fed in the circuit for the welding electrode 17 through lines 24 and 25, respectively, and for the welding electrode 18 through lines 143, 144.

At 26 an electrical line is indicated through which the electrical current required for resistance welding is conducted.

The welding electrode 17 and the welding electrode 18 are each assigned a holding-down device, which are each designated overall with the reference numerals 27 and 28. Each of the holding-down devices 27 and 28 has at least one plunger 29 and 30 and is loaded by at least one pre-stressed compression spring element 31 and 32, the pre-stress of which can be adjusted if necessary, such that the plungers 29, 30 have a tendency to move towards the components 16.

The plunger 29 is arranged in a housing 33 with radial clearance in a blind bore 34 and is enclosed by the compression spring element 31. The

Furthermore, the plunger 29 is guided and supported on part of its length in the blind bore 34 by a spherical bearing element 35 which is supported in a spatially articulated manner to a limited extent in the depth of the blind bore 34. The compression spring element 31 is supported on the one hand with its end section located in the blind bore 34 against this dome-shaped bearing element 35 and on the other hand against a mushroom-shaped head 36 which is also designed as a spherical cap and is mounted in a bearing socket 37 of a lever 38 which is arranged on the housing pivot axis 22 so as to be loosely pivotable via a bore and has the tendency to advance the welding electrode 17 in the direction of the component 16 since it is forced to do so by the compression spring element 31. At its free end, the lever 38 is connected to an upper abutment part 39, which can be fork-shaped or provided with an opening through which the welding electrode 17 passes. The abutment part 39 is spherical or convex on its end face 40 facing the component 16, such that when the clamping arm 15 is pivoted in direction A about the fixed housing pivot axis 22, a gentle and gradual placement of the abutment part 39 on the component 16 is possible. The dome-shaped bearing elements 35 and the dome-shaped head 36 thus ensure that during the pivoting movement, in particular when placing it, no bending stresses are placed on the plunger 29, but rather any

• · Φ··

eccentric or other forces are introduced centrically into the plunger 29.

The plunger 30 is arranged with a piston-shaped thickening 41 in a bore 41a so as to be displaceable against the restoring force of the pre-stressed compression spring element 32 and has a lower abutment part 42 in one piece at its end section protruding from the bore 41a, which can also be fork-shaped or with an opening through which the lower welding electrode 18 extends. The lower abutment part 42 is also spherical or convex on its surface 43 facing the upper abutment part 39. In the case of both surfaces 40 and 43, the convexity can refer to the fact that the crowning is given in the direction of the pivoting movement A or B of the pivoting arm 15, so that the leading surfaces 40 or 43 of the hold-down devices 27 or 28 rest or sit on the components 16 to be welded together after a kind of rolling movement and no hammer-like or shock-like impact effect occurs. This also means that the components 16 do not shift or move, which contributes to dimensional accuracy.

The two welding electrodes 17 and 18 are arranged interchangeably in the components assigned to them.

The hold-down devices 27 and 28, with their abutment parts 39 and 42, ensure that during the welding stroke of the electrodes 17, 18, the leading hold-down devices 27 and 28 grasp the components 16 to be connected to one another by welding points between them with virtually no impact, but then with high force, and fix the components 16 in such a way that they can no longer move against one another when the welding electrodes 17 and 18 are placed. The welding electrodes 17 and 18 then place themselves on the components 16 to be welded together with full pressure, for example with 2 to 4 kN, and press the components against one another with this high force during the welding process, so that particularly good and durable welding points are produced, which is an advantage that should not be underestimated in the body construction of the automotive industry.

The current is supplied to the lower welding electrode 18 via the cable 145.

To close the toggle-lever welding device, pressure medium, in particular compressed air, is supplied via a channel 44, which continues in a central piston guide 45, and via channel 46. The pressure medium supplied via channel 44, primarily air under excess pressure, flows through the

Channel 44 and enters a rod-shaped and central piston guide 45 arranged centrally to a base cover 47 and then flows into a cylinder chamber 48 and acts on the piston 5 here, which results in a displacement of the piston 5 with the piston rod 6 and thus also the toggle lever joint arrangement 8 and via this a pivoting of the clamping arm 15 with the welding electrode 17 and the hold-down device 27 in the direction A.

At the same time, pressure medium is fed into a cylinder chamber 49 via the channel 46, whereby a piston 50 is displaced in the direction Y until it strikes an annular collar 51 and comes to a standstill. The piston 50 is arranged in the cylinder 2 in a pressure-tight manner via a seal 52.

The reference numeral 53 designates a blind bore which penetrates the piston 5 and continues centrally in the piston rod 6 and is capable of penetrating into the piston guide 45 (Fig. 3).

54 designates a seal by means of which the piston 50 is arranged on the piston guide 45 in a pressure-tight manner.

·· tt

• " · &idigr;

At 55, a channel is arranged through which pressure medium pressure, primarily air pressure under excess pressure, is to be led into a cylinder chamber 56 when the clamping arm 15 is to be pivoted in direction B, which will be described further below.

If the pressure medium supply is maintained via the lines 44 and 46, the clamping arm 15 closes and presses the welding electrodes 17 and 18 onto the components or sheets 16 to be welded together. When the current is switched on, the components or sheets 16 are spot welded under high clamping pressure.

If a plurality or a large number of welding points are to be placed next to and/or behind one another, it would be very time-consuming and therefore disadvantageous to always pivot the clamping arm 15 in the fully open position in the direction B. The fully open position can be 90°, but also more than 90°, for example 135°, or even 180°, depending on the operating conditions. When producing several welding points on the components 16, the clamping arm 15 is only pivoted in the direction B in the open position by a comparatively small amount, just enough to place the next welding point and overcome the corresponding contour of the components. This partially open position is referred to below as "step-

: :&Kgr;. &Iacgr;

Position". For example, if the knee lever welding gun according to the invention is located on a robot arm, a corresponding movement takes place, for example to place a welding point next to, in front of and/or behind the previously produced welding point. This can take place in a relatively fast cycle sequence and can be controlled by a sequence control.

The step position for this embodiment is shown in Fig. 2. To achieve this step position shown in Fig. 2, pressure medium is supplied via channel 55 and thus the cylinder chamber 56 and thus the annular piston surface of the piston 5 is pressurized. Before this, the pressure medium supply via channel 44 is switched off and the channel is vented. The pressure medium supply via channel 46 remains so that the piston 50 remains in its upper position shown in Fig. 1, resting on the annular collar 51. By pressurizing the cylinder chamber 56, the piston 5 and thus also the piston rod 6 are moved in the Y direction, which causes a corresponding pivoting of the clamping arm 15 in the B direction into the step position shown in Fig. 2, whereby the welding electrodes 17 and 18 move away from each other. In the step position, the two pistons 5 and 50 lie practically flat on top of each other (Fig. 2). The piston 50 thus serves as a stop for the piston 5.

Also connected to the toggle-lever welding gun according to the invention is a compensating and lowering device 57, which consists of a cylinder 58 and a piston 59 connected to a piston rod 60, which is coupled to a yoke 61, which is part of a carriage 62, which is guided on a carriage guide 63, which in turn is connected to a fixed component 64, for example a machine welding gun, a stand welding gun or, if necessary, also a robot arm (not shown in detail).

The piston 59 is sealed by seals and guided longitudinally in the cylinder 58. The piston rod 60 is also sealed from the cylinder

58. By alternately applying pressure to both sides of the piston

59 by means of pressure medium via corresponding channels in the cylinder 58, in particular by means of compressed air, the piston rod 60 can thus be driven parallel to the direction X or Y and thus moved. If pressure medium is applied in such a way that the piston 59 moves in the direction Y, the entire toggle lever collet is lowered in the same direction Y via the slide 62, whereby the welding electrode 18 is also released from the components or sheets 16 to be welded together. This lowering can only be a relatively small amount, for example a few millimeters or even more, and takes place either simultaneously or with a time delay.

accompanied by the opening, i.e. pivoting of the clamping arm 15 in direction B, either to achieve the step position (Fig. 2) or the fully open position (Fig. 3). The respective loading of the various cylinder chambers is controlled by a sequential control via valves (not shown). This makes it easier to move the entire toggle lever welding gun to another welding point or to move away, i.e. also away from the contour of the component 16 to be welded. If the welding position is to be reached again either from the step position (Fig. 2) or from the fully open position (Fig. 3), the piston 59 on the opposite side is subjected to pressure medium pressure, again primarily compressed air, in order to move the device in direction X and thereby bring the welding electrode 18 into the position below the flat components 16 to be welded together, for example body panels in the automotive industry.

The device 57 is thus a combined balancing and lowering device.

If the welding position is to be reached again from the step position shown in Fig. 2, pressure medium is introduced into the blind hole via channel 44.

φ··

53 and introduced via these between the pistons 5 and 50, whereby the piston 5 is displaced in the direction X and thus also the piston rod 6 with the toggle joint arrangement 8 in the same direction, i.e. the clamping arm 15 with its welding electrode 17 is pivoted in the direction A until the welding position shown in Fig. 1 is reached again. Before this, the leading hold-down devices 27 and 28 with the components assigned to them are placed on the components 16 to be welded together and fix them in the welding position before the full welding and clamping force is applied via the electrodes 17 and 18 and the welding current is switched on.

In both Fig. 1 and Fig. 2, the fluid pressure is maintained above the channel 46 so that the piston 50 is pressed against the annular collar 51.

However, if the fully open position (Fig. 3) is to be reached from Fig. 1 or Fig. 2, the channel 46 is also relieved of pressure and at the same time pressure medium is introduced into the cylinder chamber 56 via the channel 55, so that the piston 5 moves in the direction Y and also takes the piston 50 in this direction until it comes to rest against the bottom cover 47 or a stop abutment located here, or against a shock absorber.

The reference numerals 65, 66 and 67 designate contactless sensors in the form of microswitches, inductive switches or the like, which detect the closed position, step position and fully open position and, if necessary, display them optically and/or acoustically on a remote control panel. The sensors, microswitches, inductive switches or the like can be arranged as an exchangeable set on a common circuit board in the form of a uniform component and can be inserted in a seamless and exchangeable manner, for example, through a slot on the rear wall of the clamping head 1. A switching flag 68 dampens the individual sensors 65, 66 and 67. The sensor 67 dictates the fully open position (Fig. 3), the sensor 66 the intermediate or step position and the sensor 65 the welding position (closed position) of the electrodes 17 and 18. By detecting by means of the sensors 65, 66 and 67, a sequence control can be controlled in order to accomplish the necessary loading of the various cylinder chambers and pistons with pressure medium and their venting via valves and multi-way valves.

In the embodiment according to Figs. 4 to 6, the same reference numerals as in the embodiment according to Figs. 1 to 3 have been used for parts with the same function.

In the embodiment according to Figs. 4 to 6, the combined compensating and lowering device 57 is arranged below the jaw 19 such that the slide guide 63 is integrally connected to the jaw 19.

The cylinder 58 with the piston 59 sealed therein, which can be moved in the direction X or Y by a limited amount, is connected to a projection 69 of the slide guide 63 via the piston rod 60. Depending on the pressure medium applied, the cylinder 58 alternately raises the slide 62 from both sides via channels 70 or 71, i.e. moves it in the direction X as seen in the plane of the drawing, or lowers it, i.e. moves it in the direction Y. Since the jaw 19 and also the associated welding electrode 18 and the toggle lever welding gun are coupled to the slide guide 63, these components are also moved in the direction X or Y.

From Fig. 4 to 6 one can also see a connector housing 72 for connecting corresponding electrical lines for the contactless sensors 65, 66 and 67 (inductive switches, magnetic switches, limit switches, microswitches), as shown in Fig. 1 to 6.

Otherwise, the mode of operation is as described in connection with the embodiment according to Figs. 1 to 3. The plug housing 72 can be inserted in one piece with the indicated circuit board 73 into the also indicated slot 74 on the rear wall of the clamping head 1.

In Fig. 7, a hold-down device 75 is shown which differs from the hold-down devices 27 and 28 shown in Figs. 1 to 3, but which can also be used instead of the hold-down device 27, 28 shown in Figs. 1 to 3 in all embodiments, thus also in the embodiment according to Figs. 1 to 3.

The hold-down device shown in Fig. 7 has hold-down housings 76 and 77, in which holes 78, 79 or 80 and 81 are arranged in pairs. A pre-stressed compression spring element 82, 83 or 84 and 85 is arranged in each of these holes, which are supported on the one hand against piston-shaped thickenings 86, 87 or 88 and 89 of hold-down tappets 90, 91 or 92 and 93 with spherical free ends. The hold-down tappets 90, 91 or 92 and 93 are guided in a longitudinally displaceable manner in through holes which are tapered in diameter compared to the holes 78, 79 or 80 and 81 and run with their axes parallel to one another and

are arranged coaxially in pairs and grip the welding electrodes 17 and 18 between them.

If necessary, the hold-down housing 76 can also be assigned a lever 38, as was shown and described in the embodiment according to Figs. 1 to 3. Furthermore, it is possible to use the hold-down shown in Figs. 1 to 3 in the embodiment according to Figs. 4 to 6, or to use the hold-down device according to Fig. 7 in the embodiment according to Figs. 4 to 6. The hold-down device according to Fig. 7 has the advantage that the components 16 to be welded together are pressed against each other with great force on both sides of the welding points and held against each other until the relevant welding point is set.

In the embodiment according to Figs. 8 to 10, the same reference numerals as in the embodiment according to Figs. 1 to 3 or as in the embodiment according to Figs. 4 to 6 have been used for parts with the same function.

Fig. 8 corresponds to the welding position, i.e. the working position, analogous to the representation shown in Fig. 1, while Fig. 9 shows the step position, analogous to Fig. 2, and Fig. 10 the fully open position, analogous to Fig. 3.

However, in the fully open position shown in Fig. 10, only a pivoting of the clamping arm 15 in direction B by around 35° has been shown, as this is sufficient for the assumed application. However, as with all embodiments shown in the drawing, the clamping arm 15 can also be pivoted by 90° compared to the working position in the open position shown in Fig. 8, or by an even larger angle, for example by 135° or 180°. Even with a pivoting angle of 90°, all embodiments practically allow free, vertical component removal. The pivoting angle for the step position can be correspondingly smaller in the open position shown in Fig. 10, and this angle can be correspondingly larger if the pivoting arm can be pivoted by 90°, 135° or up to 180° in direction A or B, for example.

In the embodiment according to Figures 8 to 10, the compensation and lowering device 57 is arranged on a fixed component 94, for example on a robot arm, on a device of a production line or the like, or on a robot welding gun. The compensation and lowering device 57 has a yoke 95, to which two spaced apart and parallel

·

arranged guide elements designed as rods 96 and 97 are assigned, which are arranged in a housing 98 which is integrally but detachably connected to the fixed component 94, for example by screws. The housing 98 has two bores which are parallel to the longitudinal axis and spaced apart from one another, in which the rods 96 and 97 can be adjusted by motor to a limited extent synchronously and in the same direction in the direction X or Y in a manner to be described. For this purpose, the piston 59, which is to be acted upon alternately on both sides by pressure medium pressure, in particular by compressed air, is guided between the two rods 96 and 97 in a longitudinally displaceable and sealing manner in the cylinder 58, which is coupled to a piston rod 60 which extends out of it in a sealed manner and which has a screw bolt at its end, with which the piston rod 60 is locked and coupled to the yoke 95 via one or more nuts. The supply and discharge channels for the cylinder 58 are only indicated, but can be arranged, for example, via the piston rod 60 and/or the cylinder wall of the cylinder 58.

The rods 96 and 97 are mounted so as to be displaceable in their longitudinal axis direction against the restoring force of at least one compression spring element 100 or 101, which is preferably pre-tensioned against the restoring force, with each compression spring element 100 or 101 being on one side against an abutment of the

Housing 98 and at its other end section against an annular collar 102 or 103. This annular collar 102, 103 can be, for example, screw nuts which are adjustable on corresponding bolt-shaped threaded sections 104 or 105 of the rods 96 and 97 in the longitudinal axis direction thereof, whereby the preload of the compression spring elements 100 or 101 can also be changed accordingly.

The jaw 19 is approximately L-shaped in the side view shown in the drawing, with one leg running parallel to the clamping head 1 being connected to the clamping head 1 in one piece but detachably by several screws. Of these screws, only the center lines 106 and 107 are shown. This leg, which is screwed to the clamping head 1 with screws, is designated with the reference numeral 108, while the horizontal leg running at right angles to it, arranged horizontally in the drawing and connected in one piece to the leg 108 is designated with the reference numeral 109. Between the legs 108 and 109 there is a body 110 made of copper or the like, which has several sideways-facing screw holes 111 for arranging lines for coolant, for supplying electrical energy and the like. The clamping arm 15 is fork-shaped and also has

a body made of copper to which the upper welding electrode 17 is connected, while the lower welding electrode 18 is connected to the body 110. The jaw 19, like the clamping arm 15, can be made of aluminum and/or steel.

The horizontal leg 109 designates an adjustable stop 112 in the form of a screw that can be screwed in and out and which interacts with an industrial shock absorber 113 provided in the compensation and lowering device 57.

The compression spring elements 100 and 101 tend to move the jaw 19 and thus the entire toggle welding gun upwards relative to the fixed component 94. By applying pressure to the piston 59, the entire toggle clamping device, and thus also the jaw 19 and the lower welding electrode 18 connected to it, can be lowered and thus moved away from the components 16. The housing 98 can be arranged as a cube-shaped body in the lateral projection next to a flat oval or approximately rectangular cylinder 2 and below the horizontal leg 109 of the jaw 19, so that it does not take up any additional space. Several blind holes with threads can be provided on the side facing away from the cylinder 2, by means of which the

The entire toggle welding gun together with the housing 98 can be exchangeably attached to the fixed component 94.

If a pressure medium is supplied to the side that moves the piston 59 in the Y direction, this results in a corresponding movement of the yoke 95 via the piston rod 60 and thus a displacement of the two rods 96 and 97 against the restoring force of the compression spring elements 100 and 101, with the result that the entire toggle-lever welding gun with the lower welding electrode 18 is lowered in the Y direction by a limited amount. Conversely, a pressure medium application to the opposite ring side of the piston 59 leads to a movement of the entire toggle-lever welding gun in the X direction, whereby the compression spring elements 100 and 101 can have a supporting effect.

From Fig. 11, a holding-down device associated with the toggle-lever welding gun according to Figs. 8 to 10 can be seen, which is designated overall with the reference number 114. In the body 110, bores 115 and 116 with different diameters are provided, in which holding-down plungers 117 and 118 are arranged to be longitudinally displaceable by a limited amount against the restoring force of the compression springs 119 and 120. Piston-shaped thickenings 121 and 122 limit the displacement path of the

Hold-down plungers 117 and 118 in the holes with different diameters. The hold-down plungers 117 and 118 are spherical at their front end sections facing the components 16 to be welded together and grip the lower welding electrode 18 between them.

Upper hold-down tappets 123 and 124 are arranged diametrically and coaxially opposite the hold-down tappets 117 and 118, which are also arranged against the restoring force of compression springs 125 and 126 in the swivel arm 15 or in the body 127 provided here, which is also made of copper. The body 127 can be provided with suitable threaded holes (not shown) through which the cooling liquid, electric current or the like is fed to the welding electrode 17.

The compression springs 125 and 126 on the one hand and 119 and 120 on the other hand load the associated hold-down plungers 123 and 124 or 117 and 118, so that they act in advance in the direction of the components 16 to be welded together and securely hold and fix the components 16 to be joined together before the welding electrodes 17 and 18 hit them, before the welding electrodes 17 and 18 press them together with high forces generated by the toggle lever mechanism.

applied forces against each other and are joined together by welding under this high pressure.

In the embodiment according to Figs. 12 to 17, the same reference numerals have again been used for parts with the same function.

This shows a toggle-lever welding gun for use with a so-called geometry station of a machine welding gun. The clamping arm 15 and the lower electrode 18 can move synchronously and in opposite directions in directions A and B, respectively, so that they can be moved towards and away from each other to the same extent, by a single linear drive, in this case by a piston-cylinder unit. The toggle-lever joint arrangement 8 is in turn driven via the piston rod 6 and pivots the clamping arm 15 in directions A and B, respectively. The forced movement is ensured by toothing elements 128 and 129, which in this case are designed as tooth sectors lying on a circular arc that mesh with one another. The tooth sector 128 is assigned to the clamping arm 15 as a pivot axis and has the housing pivot axis 22 as its axis of rotation, which the clamping arm 15 also has as a pivot axis. The tooth sector 129 has an axis 130 for the electrode 18 as a housing-fixed axis. Of course, the toothing elements 128 and 129 can also be designed as semicircles or full circles instead of as sectors.

It is also possible to provide other coupling elements that achieve absolute synchronous operation. In Figs. 15 and 16, the curved section 14 of the guide grooves has not been shown for the sake of simplicity. Of course, this curved section 14 can also be provided with guide rollers, as in the embodiments described above. The toggle lever arrangement 8 can also be designed in the same way as was described, for example, in connection with Figs. 1 to 3.

As can be seen, a transformer housing 132 is connected to the clamping head 1 via a pivot axis 131 running orthogonally to the longitudinal axis of the piston rod 6. In the plan view shown in Fig. 13, the transformer housing is approximately U-shaped in cross section, with a welding transformer 133 arranged between the spaced U-legs and secured here by screws or the like. The transformer housing 132 is coupled to a robot arm 134 or the like by screws or the like.

On its side facing away from the clamping arm 15, in the drawing plane at the bottom, the transformer housing has a projection 135, which is connected via a pivot bearing 136 to a linear drive 137, in this case a linear drive which is alternately actuated on both sides by pressure medium pressure, primarily by air pressure.

is connected to a piston-cylinder unit which is acted upon by a force, the piston rod 138 of which is pivotally connected to the projection 135 via the pivot bearing and the cylinder 139 of which is pivotally connected to a bearing projection 141 of the cylinder 2 via a pivot bearing 140 with its pivot axis running parallel to the pivot axis 136. By applying appropriate pressure medium, the piston rod 138 can be extended and retracted to a greater or lesser extent, so that a tilting movement in the direction A or B occurs. In this way, the welding electrode 18 can also be lowered downwards from the component 16 and the clamping arm 15 can also be pivoted in the direction A and B, for example by 90° or more, for example by 135° or 180°, so that even bulky contours do not cause any problems when loading and unloading this toggle lever welding gun.

From Fig. 17 it can be seen that even in a toggle-lever welding gun designed, for example, as a machine welding gun, a lever 38 as in the embodiment according to Figs. 1 to 3 can be used, to which a similar hold-down device 27 as in the embodiment according to Figs. 1 to 3 is assigned, so that in the interest of avoiding repetition with regard to the function, reference can be made to the description of Figs. 1 to 3. It can be clearly seen from Fig. 17 that the lever 38 is designed to run loosely, since it is mounted on a circular axle section 142

which runs coaxially to the axis 22. For reasons of simplification, no special linear drive corresponding to the linear drive 137 and the connection of this toggle welding gun to the robot arm are shown in Fig. 17. The transformer housing 132 is also missing.

The features described in the claims and in the description as well as those apparent from the drawings may be essential for the realization of the invention both individually and in any combination.

List of reference symbols

1 clamping head

2 cylinders, housing

3 Seal

4 Interior wall

5 pistons

6 Rod, piston rod

7 Seal

8 Knee lever joint arrangement

9 Swivel bolt

10 Joint element

11 toggle joint bolt

12 Leadership role

13 Guide groove

14 Section, curved

15 Clamping arm

16 Component, flat component

17 Welding electrode, upper

18 Welding electrode, lower

19 Jaw, abutment

20 Joint plate arrangement

21 Clamping arm pivot pin

22 Housing pivot axis

23 Tab arrangement Housing 24 Line 25 Jl 26 Line, electrical 27 Hold-down device 28 29 Pestle 30 IJ 31 Compression spring element 32 &eegr; 33

34 Blind hole

35 Bearing element, spherical cap shape

36 Head, mushroom-like, spherical

37 Bearing pan

38 Lever, hold-down swivel arm

39 Abutment part, upper

40 Front side of

41 Thickening, piston-shaped 41a bore

42 Abutment part, lower

43 Surface

44 Channel

45 Piston guide, central

46 Channel

47 Floor cover

48 Cylinder, cylinder chamber 49

50 pistons, additional; step piston

51 Ring collar

52 Seal

53 Blind hole

54 Seal

55 Channel

56 Cylinder crown

57 Compensation and lowering device

58 cylinders

59 pistons

60 Piston rod

61 yoke

62 sledges

63 Slide guide

64 Component

65 Sensor; Micro switch; Inductive switch; Limit switch; Pneumatic switch

^' » jj Jj Jj &ugr;

68 Switch flag

69 Lead

70 Channel 71

72 Connector housing

73 board

74 Slot

75 Holding down device

Hold-down housing

drilling

Compression spring element

Thickening, piston-shaped

Hold-down ram

Component, fixed yoke

96 Rod; guide element

98 Housing

100 compression spring element, compression spring 101

102 Ring collar, nut

104 Threaded section, bolt-shaped

106 Center line

107 „

108 Thighs of the jaw 109

110 bodies

111 Screw hole

112 stop

113 Industrial shock absorbers

114 Holding down device

115 Bore

116 „

117 Hold-down plunger 118

119 compression spring element, compression spring

121 Thickening, piston-shaped

123 Holding down device, upper

125 compression spring element, compression spring

127 bodies

128 Gear element 129

130 Swivel axis 131

132 Transformer housing

133 Welding transformer

134 Robot arm

135 Lead

&KHgr; ^: · &Lgr;

136 swivel bearing

137 Linear drive, piston-cylinder unit

138 Piston rod

139 cylinders

140 swivel bearing

141 Bearing approach

142 Axis

143 Line

144 „

145 Cable

A Swivel direction

Y shift direction

Claims (39)

1. Knee lever welding gun, for use in bodywork construction in the automotive industry, with a housing-like clamping head ( 1 ) and with a linear drive connected to it in axial extension - piston-cylinder unit actuated alternately on both sides by pressure medium pressure, primarily pneumatically; electric motor; Hollow shaft motor - which drives a rod ( 6 ) which axially passes through the cavity of the clamping head ( 1 ), wherein at the free end of the rod ( 6 ) within the clamping head ( 1 ) a toggle joint arrangement ( 8 ) is arranged in an articulated manner, which is coupled to a clamping arm ( 15 ) which can be driven by the linear drive ( 2 , 5 ) to pivot alternately in opposite directions about a housing pivot axis ( 22 ) fixed to the housing, with an abutment opposite the clamping head ( 1 ) and designed as a jaw ( 19 ), wherein both the clamping arm ( 15 ) and the jaw ( 19 ) are each assigned at least one welding electrode ( 17 , 18 ) which can be supplied with controlled electrical current and is preferably liquid-cooled, by means of which components assigned between the welding electrodes ( 17 , 18 ) ( 16 ) can be welded together under high pressure while avoiding shock-like stresses when the welding electrodes ( 17 , 18 ) are placed on the components ( 16 ). 2. Knee lever welding gun, characterized in that the clamping head ( 1 ) and the linear drive ( 2 , 5 ) are designed as encapsulated components which are protected from dust and, if possible, splash liquid and which are connected to one another to form a manageable structural unit. 3. Knee lever welding gun according to claim 1 or 2, characterized in that at least the jaw ( 19 ) with its welding electrode ( 18 ) is associated with a compensating and lowering device ( 57 ) which can be driven alternately in both directions and which enables a joint and simultaneous synchronous movement of the welding electrode ( 18 ) and the jaw ( 19 ) by a limited amount away from the components ( 16 ) to be welded together or directed towards them. 4. Toggle-lever welding gun according to claim 1 or one of the subsequent claims, in which a piston-cylinder unit ( 2 , 5 ) is assigned a piston ( 5 ) which is to be acted upon alternately on both sides by pressure medium pressure and which drives the rod ( 6 ), characterized in that in the same cylinder ( 2 ) of the piston ( 5 ) a further piston ( 50 ) is guided in a sealing manner on a rod-shaped piston guide ( 45 ) between a base cover ( 47 ) and an end stop, for example designed as a ring collar ( 51 ), both with respect to the inner wall ( 4 ) of the common cylinder ( 2 ) and with respect to the piston guide ( 45 ), and that the further piston ( 50 ) serves as a stop for the piston ( 5) connected to the rod (6 ) for the so-called step position, such that the gap between the two pistons ( 5 , 50 ) can be connected to the pressure medium supply via a channel ( 44 ), while a cylinder chamber ( 49 ) located between a base cover ( 47 ) and the step piston ( 50 ) can also be connected to a pressure medium source via a further channel ( 46 ), and that the cylinder chamber ( 56 ) on the side of the rod ( 6 ) can also be connected to a channel ( 55 ) for supplying pressure medium, the rod ( 6 ) being provided with a blind bore ( 53 ) for immersing the piston guide ( 45 ), while the compensating and lowering device ( 57 ) is also formed by a piston-cylinder unit ( 58 , 59 ), the piston ( 59 ) of which is connected via a piston rod ( 60 ) to a yoke ( 61 ) or the like and a slide ( 62 ), while the carriage guide ( 63 ) is arranged on a fixed component (64, for example on a robot arm, device part), and that the toggle lever clamping device, in particular the clamping head ( 1 ) is coupled to the carriage ( 62 ), the compensating and lowering device ( 57 ) being arranged on the rear side of the toggle lever clamping device opposite the welding electrodes ( 17 , 18 ). 5. Toggle-lever welding gun according to claim 4, characterized in that in the same cylinder ( 2 ) of the piston ( 5 ) a step piston ( 50 ) is guided in a pressure-tight manner on a rod-shaped piston guide ( 45 ) between a bottom cover ( 47 ) and an end stop, for example designed as a ring collar ( 51 ), both with respect to the inner wall ( 4 ) of the common cylinder ( 2 ) and with respect to the piston guide ( 45 ), and that the step piston ( 50 ) serves as a stop for the piston ( 5 ) connected to the rod ( 6 ) for the so-called step position, such that the cylinder space ( 48 ) provided between the two pistons ( 5 , 50 ) can be connected to the pressure medium supply or vented via a channel ( 44 ), while a pressure medium supply between a bottom cover ( 47 ) and the step piston ( 50 ) can also be connected to a pressure medium source via a further channel ( 46 ), and that the cylinder space ( 56) on the side of the rod (6 ) can also be connected to a channel ( 55 ) for supplying pressure medium, the rod ( 6 ) being provided with a blind bore ( 53 ) for immersing the piston guide ( 45 ) , while the compensating and lowering device ( 57 ) is also formed by a piston-cylinder unit ( 58 , 59 ), the piston ( 59 ) of which is coupled to a slide guide ( 63) via a piston rod (60 ) , while the slide is arranged on a fixed component (64 - robot arm, device part) and that the jaw ( 19 ) is coupled to the slide guide ( 63 ), the compensating and lowering device ( 57 ) is arranged on the side of the toggle lever clamping device facing the two welding electrodes ( 17 , 18 ), below the jaw ( 19 ). 6. Toggle lever welding gun according to claim 4 or 5, characterized in that in the same cylinder ( 2 ) of the piston ( 5 ) a step piston ( 50 ) is guided in a sealing manner on a rod-shaped piston guide ( 45 ) between a bottom cover ( 47 ) and an end stop, for example designed as a ring collar ( 51 ), both with respect to the inner wall ( 4 ) of the common cylinder ( 2 ) and with respect to the piston guide ( 45 ), and that the step piston ( 50 ) serves as a stop for the piston ( 5 ) connected to the rod ( 6 ) for the so-called step position, such that the cylinder space ( 48 ) provided between the two pistons ( 5 , 50 ) can be connected to the pressure medium supply or vented via a channel ( 44 ), while a ( 50 ) lying cylinder chamber ( 49 ) can also be connected to a pressure medium source via a further channel ( 46 ), and that the cylinder chamber ( 56 ) present on the side of the rod ( 6 ) can also be connected to a channel ( 55 ) for supplying pressure medium, the rod ( 6 ) being provided with a blind bore ( 53 ) for immersing the piston guide ( 45 ), while the compensating and lowering device ( 57 ) is also formed by a piston-cylinder unit ( 58 , 59 ), the piston ( 59 ) of which is connected via a piston rod ( 60 ) to a yoke ( 95 ) to which two rods ( 96 , 97 ) are connected, which are spaced apart and run parallel to one another with their longitudinal axes and which act against the restoring force of prestressed compression spring elements ( 100 , 101 ) can be driven in directions offset by 180 degrees from one another, wherein the rods ( 96 , 97 ) are coupled - optionally indirectly - to the jaw ( 19 ) and that the compensating and lowering device ( 57 ) is arranged below the jaw ( 19 ). 7. Toggle lever welding gun according to claim 1 or one of the subsequent claims, characterized in that the clamping arm ( 15 ) is assigned at least one hold-down device ( 27 ) leading during the welding stroke for the flat components to be welded together. 8. Knee lever welding gun according to claim 1 or one of the subsequent claims, characterized in that a hold-down device ( 28 ) is also assigned to the jaw ( 19 ). 9. Toggle-lever welding gun according to claim 1 or one of the subsequent claims, characterized in that the hold-down device ( 27 , 28 ) is pressure-loaded by a pre-stressed compression spring element ( 31 ) in the direction of the components to be welded ( 16 ) and is arranged with one end section in a recess, blind bore or the like ( 34 ) and cooperates with its other end with a lever ( 38 ) which is arranged so as to be freely pivotable about an axis ( 22 ) fixed to the housing in the clamping head ( 1 ) below the clamping arm ( 15 ). 10. Toggle lever welding gun according to claim 1 or one of the subsequent claims, characterized in that the hold-down pivot arm ( 38 ) has a bearing cup ( 37 ) against which a plunger ( 29 ) with a dome-shaped head ( 36 ) loaded by the compression spring element ( 31 ) rests and is arranged with its plunger-like end in a likewise dome-like bearing element ( 35 ) or the like in the deepest part of a blind bore ( 34 ). 11. Knee lever welding gun according to claim 10, characterized in that the pivot axis ( 22 ) of the hold-down swivel arm ( 38 ) coincides with the housing-fixed pivot axis ( 22 ) for the knee lever joint arrangement ( 8 ) or the clamping arm ( 15 ) and that the hold-down swivel arm ( 38 ) has at its free end a spherical or convex abutment part ( 39 ) which acts against the components ( 16 ) to be welded together and that the abutment part ( 42 ) connected to the jaw ( 19 ) for placing the components ( 16 ) to be welded together is also spherical or convex in such a way that the spherical or convex parts of the hold-down swivel arm ( 38 ) and the jaw ( 19 ) are directed towards each other with their spherical or convex surfaces. 12. Knee lever welding gun according to claim 1 or one of the subsequent claims, characterized in that both the clamping arm ( 15 ) and the jaw ( 19 ) are assigned a plurality of hold-down plungers ( 90 , 91 or 92 , 93 ; 123 , 124 or 117 , 118 ) loaded by a prestressed compression spring, between which the welding electrodes ( 17 , 18 ) are arranged. 13. Knee lever welding gun according to claim 1 or one of the subsequent claims, characterized in that the clamping arm ( 15 ) can be pivoted relative to the jaw ( 19 ) by 90° or more, preferably by 180°, in the open position. 14. Knee lever welding gun according to claim 1 or one of the subsequent claims, characterized in that the welding electrodes ( 17 , 18 ) are designed to be automatically adjustable according to their wear and burn-off. 15. Knee lever welding gun according to claim 1 or one of the subsequent claims, characterized in that the jaw ( 19 ) with the welding electrode ( 18 ) is designed to be automatically adjustable and settable in the direction of the welding electrode ( 17 ) associated with the clamping arm ( 15 ). 16. Toggle-lever welding tongs according to claim 1 or one of the subsequent claims, wherein guide rails or guide grooves ( 13 ) arranged parallel to one another for guiding the rod ( 6 ) and/or the toggle-lever joint ( 8 ), primarily via roller bearings, are arranged in the axial direction of the rod ( 6 ) in the clamping head ( 1 ) through which the rod (6) passes, characterized in that the opposite guide walls of the guide grooves or guide rails ( 13 ) for the toggle-lever joint arrangement ( 8 ) are arranged to run curved ( 14 ) according to only one radius towards one side of the piston rod longitudinal axis, such that with the workpiece clamping arm ( 15 ) over a predetermined pivoting range of the workpiece clamping arm ( 15 ) an equal or approximately constant welding clamping force can be achieved on the welding electrodes ( 17 , 18 ) without achieving a dead center position. 17. Toggle lever welding gun according to claim 16, characterized in that the opposite guide walls of the guide grooves or guide rails ( 13 ) are each limited on their length section serving to guide the toggle lever joint ( 8 ) on one side of the longitudinal axis of the rod ( 6 ) by a group of curves which merge into one another as seamlessly as possible, such that with the clamping arm ( 15 ) over a predetermined pivoting range of the clamping arm ( 15 ) without achieving a dead center position, an equal or approximately constant welding force is achieved on the welding electrodes ( 17 , 18 ). 18. Knee lever welding gun according to claim 16 or 17 with a coupling bolt for gear coupling of the rod ( 6 ) with the knee lever joint arrangement ( 8 ) and a knee lever joint bolt, characterized in that both the coupling bolt and the knee lever joint bolt are guided in the guide grooves via at least one pair of guide rollers each. 19. Knee lever welding gun according to claim 1 or one of the subsequent claims, characterized in that both the welding electrode ( 17 , 18 ) connected to the clamping arm ( 15 ) and the welding electrode ( 19) connected to the jaw (19 ) are connected to lines ( 24 , 25 and 143 , 144 respectively) through which cooling liquid can be supplied and removed. 20. Knee lever welding gun according to claim 1 or one of the subsequent claims, characterized in that the entire knee lever welding gun is adjustable via a linear drive, in particular a compressed air cylinder, as a whole relative to a fixed component connected to a robot arm, or to a welding gun or to a stand welding gun. 21. Knee lever welding gun according to claim 20, characterized in that the adjustability of the lower welding electrode ( 18 ) with the jaw ( 19 ) can be carried out by a piston-cylinder unit. 22. Toggle-lever welding gun according to claim 1 or one of the subsequent claims, characterized in that the jaw ( 19 ) and the clamping arm ( 15 ) are designed to be driven jointly, synchronously and, for example, by the same linear drive towards or away from each other via a positive guide, in particular a gear. 23. Knee lever welding gun according to claim 22, characterized in that the jaw ( 19 ) and the clamping arm ( 15 ) are connected to one another by a gear transmission ( 128 , 129 ). 24. Toggle-lever welding gun according to claim 1 or one of the subsequent claims, characterized in that the jaw ( 19 ) is mounted in the clamping head ( 1 ) so as to be pivotable about a pivot axis ( 131 ) whose longitudinal axis runs parallel to the stationary pivot axis ( 22 ) of the clamping arm ( 15 ). 25. Toggle lever welding gun according to claim 24, characterized in that at least one gear wheel, one gear ring or one toothed sector ( 128 , 129 ) is arranged on the pivot axis ( 22 ) of the clamping arm ( 15 ) as well as on a pivot axis ( 131 ) for the opposite welding electrode ( 18 ), and that the teeth are in engagement with one another at least over a certain pivoting range of the electrodes ( 17 , 18 ). 26. Toggle-lever welding gun according to claim 23 or one of the subsequent claims, for use as a robot gun, characterized in that a transformer housing ( 132 ) in which a welding transformer ( 133 ) is arranged is connected to the clamping head ( 1 ) via a pivot axis ( 131 ) running parallel to the pivot axis ( 22 ) of the clamping arm ( 15 ). 27. Knee lever welding gun according to claim 26, characterized in that the transformer housing ( 132 ) is fork-shaped and is arranged between the legs of the welding transformer ( 133 ). 28. Knee lever welding gun according to claim 26 or one of the subsequent claims, characterized in that a motor drive ( 137 ) acting in both directions, in particular a piston-cylinder unit to be alternately acted upon by pressure medium on both sides, is arranged on the lower side facing away from the pivot axis ( 131 ), which is connected on one side - optionally indirectly - to the transformer housing via a pivot axis and on its other side via a pivot axis to the knee lever clamping device and that the entire knee lever welding gun is pivotally mounted about the pivot axis ( 131 ) via the motor drive ( 137 ). 29. Toggle welding gun according to claim 27 or 28, characterized in that a robot arm ( 134) is coupled to the transformer housing (132 ) . 30. Toggle lever welding gun according to claim 4 or one of the subsequent claims, characterized in that both the piston ( 5 ) of the linear drive and the step piston ( 50 ) additionally arranged in the same cylinder ( 2 ) can be alternately pressurized on both sides by compressed air of 6 bar. 31. Toggle lever welding gun according to claim 1 or one of the subsequent claims, characterized in that the welding electrodes ( 17 , 18 ) act on the components ( 16 ) to be welded together with a clamping welding force of 1 to 10 kN, preferably 2 to 4 kN. 32. Toggle lever welding gun according to claim 1 or one of the subsequent claims, characterized in that the cylinder ( 2 ) of the linear drive is flat-oval on the inside and outside in a cross-section orthogonal to its longitudinal axis and that the pistons which are longitudinally displaceable and sealingly guided in it are correspondingly shaped at their periphery with their seals and their shape dimensions. 33. Toggle welding gun according to claim 1 or one of the subsequent claims, characterized in that it is equipped with a clamping head ( 1 ) which is rectangular in cross-section and which is orthogonal to the longitudinal axis of the rod, which is constructed from two housing parts which can be clamped against one another in a sealing manner, and with a cylinder ( 2 ) which is connected in axial extension to the end of the clamping head ( 1 ) on the inside of the cylinder, in which a piston ( 5 ) which is to be acted upon alternately on both sides by air pressure and a step piston ( 50 ) are guided longitudinally displaceably and sealingly, which extends axially through the cylinder ( 2 ) and the cavity of the clamping head ( 1 ) with its rod ( 6 ), a toggle joint arrangement ( 8 ) being fastened to the free end of the rod ( 6 ), which is coupled to a clamping arm ( 15 ) which has one or more welding electrodes ( 17 , 18 ) with limit switches or position sensors ( 65 , 66 , 67 ) in the form of microswitches, inductive switches, pneumatic switches or sensors, which are integrated in a space of the clamping head ( 1 ), wherein the switches are adjustable relative to one another and are arranged and fastened to a holder forming the cover for this as a completely exchangeable query cassette ( 73 ) in the form of a circuit board in the region of a slot ( 74 ) in the axial direction or transversely thereto of the clamping head ( 1 ), wherein the query cassette ( 73 ) is inserted from the side of the housing of the clamping head ( 1 ) facing away from the welding electrodes ( 17 , 18 ) through the narrow slot ( 74 ) extending in the direction of the longitudinal axis or transversely thereto and while retaining the possibility of attaching the toggle lever welding device from at least three sides, in particular also from the rear, in such a way that the profile of the query cassette ( 73 ) seals the slot ( 74 ) towards the outside as tightly as possible. 34. Toggle-lever welding gun according to claim 1 or one of claims 2 to 32, characterized in that a query cassette ( 73 ) is inserted from the side of the housing of the clamping head ( 1 ) through a narrow slot extending in the direction of the longitudinal axis or transversely thereto of the rod ( 6 ) and, while retaining the possibility of attachment, also from both side surfaces of the encapsulated toggle-lever welding gun, in such a way that the profile seals the slot towards the outside as tightly as possible. 35. Toggle-lever welding gun according to claim 1 or one of the subsequent claims, wherein the linear drive is an electric motor drive which is located in a housing ( 2 ) adjoining the clamping head ( 1 ), characterized in that a permanent-magnetic brake is associated with the electric motor, one part of which is immovably associated with the housing ( 2 ) or the stator and the other part of which is rotatably associated with the shaft of the electric motor with a gap. 36. Toggle lever welding gun according to claim 35, characterized in that the two parts of the permanent magnetic brake are disk-shaped, one part of which is arranged and locked in a bearing block for the bearing of the shaft and the other part on the free end section of the shaft of the electric motor. 37. Toggle-lever welding gun according to claim 1 or one of the subsequent claims, characterized in that the shaft of the electric motor is designed as a hollow shaft and has a screw motor at its end section facing the clamping head, in which the linearly drivable part designed as a screw spindle is arranged so that it can be screwed in and out. 38. Knee lever welding gun according to claim 1 or one of the subsequent claims, characterized in that the linearly drivable part is immersed in the shaft of the electric motor. 39. Knee lever welding gun according to claim 38, characterized in that a spindle is mounted at both end sections in the clamping head and that a screw motor can be screwed onto this spindle in one direction or the other depending on the drive direction of the electric motor and a link of the knee lever joint ( 8 ) is pivotally coupled to this screw motor via a pivot axis.