JPH0445278B2 - - Google Patents

Description

Claim 1: Two base materials 1 and 2 to be welded having circular cavities;
It is a device for aligning and clamping 50 and 51 with each other, and is provided with clamp units for each base metal on both sides of the welding area 9 that receives inert gas supply, and the clamp units are arranged at least in the circumferential direction. Consisting of a clamp member 3 extending in one row, the clamp member is provided in the clamp grooves 36, 39, 42, and the conical flat portions 52, 53 forming the clamp grooves extend in the longitudinal axis direction of the base material. radially expanding by proximity or isolation;
It is designed to contract and has an outwardly sharpened contact clamping surface that contacts the inner circumferential surface of the base material, and when the clamp member 3 expands in the radial direction, the contact clamping surface contacts the base material. In the centering and clamping device configured to position the base material in contact with the inner circumferential surface of the material, the clamp members in each clamp unit are separated by a predetermined distance 57 in the circumferential direction, and A centering and clamping device comprising a spring member having a plurality of continuous spiral filaments 56 or a plurality of disks 60. 2. Device according to claim 1, characterized in that the contact clamping surface (54) is substantially point-shaped. 3. The device according to claim 1 or 2, characterized in that the spring member is an annular helical spring (3). 4. Device according to claim 1 or 2, characterized in that the spring member comprises a spring 59 and a disc 60 aligned at a slight distance above the spring. 5. A device according to any one of claims 1 to 4, characterized in that the circumferential width of the intermediate interval 57 is smaller than the width of the clamp members 56, 60. 6. The device according to any one of claims 1 to 5, wherein the recess 28 to which the inert gas 27 is supplied is provided facing the welding area 9,
Further, the clamp members 56 and 60 are connected to the groove walls 30 and 31.
The apparatus is characterized in that the recess 28 is shielded more widely by the recess 28. 7. The device according to claim 6, characterized in that at least the groove walls 30, 31 closest to the welding region 9 have an outer diameter that is only slightly smaller than the clearance diameter of the circular cavity of the base material. . 8. The device according to any one of claims 1 to 7, characterized in that at least one clamping unit has two rows of clamping members spaced apart by a predetermined distance along the longitudinal axis. A device that does this. 9. The device according to any one of claims 1 to 8, wherein adjacent groove walls belonging to two adjacent clamp units are connected by a sleeve 40 and seated on the holder 21. A device characterized by: 10. The device according to claim 9, wherein the holding body 21 forms groove roots of clamp grooves 36, 39, 42 in which the clamp members are accommodated. 11. Device according to claim 10, characterized in that the groove walls belonging to the same clamping unit are movable together on the holding body (21). 12. The device according to claim 9, wherein the groove wall belonging to each clamping unit is firmly arranged on a holder 21, said holder 21 being supported at least on one side by springs 13a, 13b. A device characterized in that it is placed in a driving force transmission path. 13. Device according to any one of claims 1 to 12, characterized in that only one driving force is applied to both clamp units which can be operated separately, Springs 13a, 1 in which all the clamping grooves of the unit react in sequence with the driving force applied parallel to the clamping groove of one of the clamping units;
3b. 14. The device according to any one of claims 1 to 3, wherein the holder 21 is provided with a refrigerant circuit 2.
2, 23, and 24. 15. The device according to any one of claims 1 to 14, characterized in that an inert gas is used as a pressurized medium for driving. FIELD OF THE INVENTION The present invention is a device for aligning and clamping two base materials to be welded having circular holes, and for each base material to be welded on both sides of a welding area that is supplied with an inert gas. The clamp unit is provided with at least one row of clamp grooves extending in the circumferential direction, and the flat portions of the clamp grooves are arranged axially close to each other and moved radially outward when they are separated from each other. Consisting of clamping members that tighten and relax inwardly, have outwardly pointed clamping surfaces that contact the hole surface of the base material, and are spaced apart a certain distance in the circumferential direction. The present invention relates to a centering and clamping device. BACKGROUND OF THE INVENTION Known devices of this type (West German Patent Publication no.
No. 2708040), each clamping groove is provided with a plurality of specially formed clamping wedges that support a clamping shoe on an outer surface facing the circumference of the pipe. At the same time, the clamping shoe is in contact with the inner surface of the pipe to be clamped over a large portion. The clamping wedge is retained within the clamping groove by a plurality of circumferentially extending tension springs. The clamping groove is formed, on the one hand, by a firmly arranged groove wall and, on the other hand, can be axially offset with respect to the groove wall in order to tighten the clamping wedge by filling it with a pressure medium. It is formed by a hydraulic piston. Known clamping devices are suitable for laser welding methods, so that the clamping shoe is relatively immune to damage due to stress due to clamping forces and thermal loads. However, the clamping wedge and clamping shoe used in such devices have a fairly crude construction. A crude construction has the disadvantage of making the overall structure relatively heavy, but it facilitates heat dissipation (Automésion, 1977, p. 59), and for this purpose special cooling is required in the clamping shoe. It is considered advantageous in part because it is possible to provide a channel (U.S. Pat. No. 4,387,845).
In addition, since the clamping shoe is made of large parts, there are other problems such as difficulty in completely exhausting the atmosphere with the inert gas supplied to the welding area. This known device is intended to center the clamping member so accurately that the clamping member arranges the deformed pipe surface into a cylindrical shape. However, the fewer the number of clamp members, the more limited there is to achieving accurate alignment. The object of the present invention is to provide a clamping device similar to the previously known clamping device described above, but with a simple structure, a variable clamping device, with the aim of ensuring proper cooling and reliably eliminating oxygen with an appropriate amount of inert gas. The object of the present invention is to provide a clamping device that can be applied accurately and reliably. SUMMARY OF THE INVENTION According to the present invention, various problems in conventionally known clamping devices can be solved by separating the clamping members in each clamping unit by a predetermined distance in the circumferential direction, and furthermore, by forming a plurality of helical spirals that are continuous in a spiral shape. This problem can be solved by constructing a spring member with a filament or a plurality of disks. According to the present invention, each clamping member is constructed from a large number of small parts rather than a small number of large parts, contrary to conventional design principles. With conventional equipment, it was necessary to intensively apply inert gas to cool the pipe during welding, but the clamp member used in the present invention only extends in the circumferential direction, and in particular, the clamp member does not come in contact with the inner surface of the pipe. Since the surface is small in the circumferential direction, the adverse effects caused by thermal stresses from the welding area on the one hand and from the inner surface of the pipe on the other hand can be minimized. This is because the axial dimensions of the clamping member are relatively large, thus providing a large cooling surface. When removing oxygen from the atmosphere with an inert gas, the clamp members do not become an obstacle, and the narrow gap between the clamp members acts as a uniform squeezing resistance, ensuring even oxygen removal. to promote. The small dimensions of the clamping member thus prevent the formation of pockets of residual oxygen in the atmosphere and prevent the formation of obstructions that would impede the flushing operation. At the same time, since an inert gas is used, not only the clamp member is uniformly cooled, but also the inner surface of the pipe. Furthermore, because the dimensions of the clamping member are small in the circumferential direction, its shape in the radial direction can be reduced, so that the surface of the retaining pair supporting it is close to the inner surface of the pipe, which is favorable for the cooling effect. bring about an effect in a state. It is advantageous for the clamping surface of the clamping member to be a substantially punctiform contact surface,
This is achieved by making the clamping surface an arched outer surface. This reduces heat transfer from the inner surface of the pipe to the clamping member,
Therefore, the possibility of the latter overheating can be reduced. In a particularly preferred embodiment of the invention, the row of clamping elements is formed by a spring having a plurality of disks or coils arranged in each case approximately longitudinally. Meander springs are also suitable for this purpose, but simple annular helical springs are particularly suitable. Annular helical springs are particularly advantageous because they are simple and inexpensive components with clearly defined guide and clamping surfaces that cooperate with the guide surfaces of the clamping groove and the inner surface of the pipe. There was found. Moreover, by fitting it into the holder from the outside, it can be easily installed and replaced. Its point-like contact surface with the pipe inner surface prevents it from overheating and presents a large cooling area for the inert gas. mutually adjacent coils of an annular helical spring;
In other words, the cross section of the passage formed by the gap between the spiral filaments acts as a fluid resistance, and as a result, when the inert gas is metered, the inert gas is almost completely spread over the entire circumference. It can be spread evenly. Because the clamping surface that cooperates with the inner surface of the pipe is small and particles are easily pushed away by the elastic action of the annular helical spring during tightening, there are almost no problems caused by particle adhesion. Due to the large number of clamping members formed by the spiral threads of the annular helical spring, they act statistically completely uniformly, so that even the cross section of a deformed pipe can be exceptionally circular. A major advantage of the present invention is that the annular helical spring can be easily replaced at the location where the annular helical spring is used. This is not only particularly advantageous in the event of failure, but also allows the use of annular helical springs with different coil diameters to compensate for the circumferential tolerances of the base material. Thus, for example, the range of diameters for which a particular device is suitable can be extended by using thicker springs. It may also be desirable to vary the annular helical spring if the base material only contacts certain spring materials. However, other embodiments of the clamping member include:
For example, the form of discs aligned with wire springs with no spacing or with slight spacing is also suitable. Balls that are almost lined up without any spacing,
Although their shape sometimes creates undesirably relatively large cross-sectional areas in the passages between the balls, they can be used. The use of balls as clamping members, with large intermediate spacings over the circumference, is itself disclosed in DE 32 33 796, although in relatively small numbers. While the throttling effect on the inert gas is achieved with a pressure drop that makes the ingress of atmospheric oxygen more difficult, the width of the intermediate spacing is generally needs to be made as small as possible. The width of the intermediate spacing is generally less than the circumferential width of the clamping member. If an annular helical spring is used, the helical striations on the inside are apparently contradictory and advantageous. According to another feature of the invention, the groove wall facing the welding area is designed to project radially so as to largely obstruct the clamping member. For this reason, the outer diameter is smaller than the clearance diameter of the hole in the base material by a few percent. Two rows of clamp members are used in at least one of the two clamp units, and the clamp members in both rows are separated along the longitudinal direction of the pipe, so that they not only align the pipe to be clamped, but also align the longitudinal axis. They can also be aligned in the direction. The construction is particularly simple if the clamping groove is constituted by a ring which sits partially displaceably and connected by a sleeve on the holding body which at the same time forms the groove root of this clamping groove. Become. The groove walls belonging to the same clamping unit can be displaced synchronously with respect to the holding body. On the other hand, the groove walls belonging to the other clamping units are firmly arranged in the holding body, and the latter are conveniently arranged in the transmission path of the driving force, so that only one clamping unit is required for driving both clamping units. Only one drive movement is sufficient. According to a further feature of the invention, both clamping units can be operated independently of each other, even though they are driven by the same drive source. This means that all the clamp grooves of the two clamp units are connected one after another against the driving force, and the spring that reacts against the driving force is provided parallel to the clamp groove of one of the clamp units. achieved by. Due to this spring, when the drive is initially applied, the clamp unit assigned to it remains temporarily released from the drive force, so that only the other clamp units can be tightened. This allows the two clamping units to be gradually clamped one after another by applying the driving force slowly so that one of the two base materials to be clamped is first gently clamped and then the other base material is clamped. can be activated. If a drive device filled with pressure medium is used, an average of a magnitude sufficient to tighten one clamping unit, but insufficient to overcome the spring force assigned to the other clamping unit. A switching device can be provided which applies an effective pressure to the drive so that the clamping device can only activate one of the two clamping means. In order to improve cooling, a refrigerant circuit for the holder may be provided. Furthermore, according to the invention, the same pressure medium drive is used for both clamping units, so that the pressure medium consumption is relatively low. Therefore, an inert gas can be used as the pressure medium of the drive device, and by using an inert gas, even if a leak occurs from the drive cylinder, damage will not occur due to the inflow of external pressure medium into the welding area. This does not occur, and there is an advantage that the apparatus can be made lighter and simpler by saving on unnecessary supply of media.

[Brief explanation of drawings]

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. 1 to 3 are longitudinal sectional views showing three different embodiments of the centering and clamping device according to the invention. FIG. 4 is a partially enlarged perspective view of the clamp groove and the spring therein, viewed from the radial direction. FIG. 5 is a partially enlarged sectional view of the configuration shown in FIG. 4 viewed along the circumferential direction. FIG. 6 is a side view showing the disc-shaped clamp member.

[Detailed description of the invention]

The alignment and clamping device shown in Fig. 1 clamps the pipes 1 and 2 firmly and in exact agreement with each other at their joints, so that an automatic circumferential welder can be used without problems from the outside. It is used to be welded. An example of an important field of application is the manufacture of pneumatic supply pipes, where it is very important to precisely match the walls of the pipes to avoid troublesome shoulders and steps. The piston 4 is firmly mounted on the piston rod 6, is located in the cylinder 15, and together with the end wall 16 closes off the cylinder chamber 17. Circumferentially, the piston 4 is connected to the cylinder 1 by means of a seal 5.
Sealed against 5. The end wall 16 is sealed by a seal 12 against the piston rod 6 which is displaceable therein. cylinder 1
The other end of the piston rod 5 is closed by a disk 18 having a guide boss 16 of the piston rod 6. The piston rod 6 has a cylindrical shape, with a left end being a closed end and a right end being an open end. In the drawing, a tube 20 extends in the internal cavity of the piston rod 6. Piston rod 6 immediately to the left of piston 7
An opening 7 is formed in the wall through which the pressure medium for actuating the clamping device flows into the cylinder chamber 17, into which the tube 20 communicates. In the drawing, a holder 21 is provided on the left side of the piston-cylinder device, and this holder 21
is essentially constructed as a hollow cylinder, and is freely displaceable in the longitudinal direction, and the right end is connected via a sealing and guiding sleeve 12a, and
At a distance from there, it is coaxially mounted on the piston rod 6 via a pair of guide/sealing sleeves 12b. Inside the holding body 21,
Two sealing sleeves 12a, 12b surround a refrigerant chamber 22 through which a refrigerant, for example water, flows via a refrigerant supply pipe 23 and a refrigerant discharge pipe 24 arranged in the hollow space of the piston rod 6. A pair of sealing and guiding sleeves 12b surround an inner annular chamber 25 that communicates with the hollow portion of the piston rod 6 via one or more holes 26. Further, an outer annular chamber 28 is provided on the outer periphery of the holding body 21.
The outer annular chamber 28 includes a perforated plate 29 that is stretched around the outer annular chamber 28 in order to equalize the flow of pressure medium into the outer annular chamber 28, and a plurality of radially extending holes. It communicates with the inner annular chamber 25 via the hole 27 . Moreover, when the hollow part of the piston rod 6 is filled with inert gas,
This inert gas is supplied to the welding area 9 through the holes 26 and 27. On both sides of the outer annular chamber 28, the holder 21
Two annular projections 30, 31 rise on the cylindrical surface of the annular chamber 28, forming a conical flat on the side facing away from the outer annular chamber 28.
In either case, the cylindrical outer circumferential surface of the holder 21 is continuous with the conical flat portion. A plate 32 having a collar 33 is seated on the left end of the piston rod 6, and this plate 32 is connected to the holder 21.
The left cylindrical portion of the plate 32 is held concentrically, and the conical flat portion (the fifth
A conical flat portion (portion designated by reference numeral 53 in FIG. 5) is formed which is located on the opposite side to the portion designated by reference numeral 52 in the figure and slopes in the opposite direction. The two flat parts together form a clamping groove 36 in which the annular helical spring 3 is accommodated, so that the annular helical spring 3 fits into this clamping groove 3.
6 is seated in a pre-tensioned state so that its circumference is at its minimum. Coils of this annular spiral spring 3 that are spirally continuous with each other, that is, spiral filaments constitute each clamp member,
At the minimum circumferential length position where the circumferential length is the minimum, the spiral filaments are substantially in contact with each other. On the other side of the outer annular chamber 28, a sleeve 40 is movably mounted on the cylindrical portion of the holder 21, and both end surfaces of the sleeve 40 are formed into conical flat portions. The left conical flat part of the cannula 40 in the drawings is the same as the conical flat part of the annular projection 31.
It surrounds a clamp groove 39 having the same configuration as the clamp groove 36 and having an annular helical spring 3 . Mantle 40
The conical flat part on the right side is a clamping groove 42 for the annular helical spring 3 whose other side is restrained by a conical flat part formed in the hollow cylindrical extension part 44 of the cylinder 15 that grips the outer periphery of the holder 21. is formed. Compression springs 13a, 13b acting in the longitudinal direction
is used as a centering spring between the holder 21 and the plate 32, and between the holder 21 and the end wall 1 of the cylinder 15.
The compression springs 13a and 6 are respectively interposed between the compression springs 13a and 6.
generates a larger compressive force than the compression spring 13b. A flexible tube 10 is firmly connected to the right open end of the piston rod 6 and is used for supplying inert gas, as well as tubes, namely refrigerant tubes 23, 24,
If a pressure medium is to be supplied separately, a bundle 11 of pipes 20 and the like for this purpose is housed. The clamping groove 36, together with its associated parts, constitutes a clamping unit for the pipe piece or bent pipe 2; the clamping grooves 39, 42
belongs to the clamp unit assigned to pipe 1. The device is used as follows. In the relaxed state of the device, the annular helical spring 3 is at its minimum circumference inside the clamping groove in which it is housed, and exhibits an outer diameter smaller than the inner diameter of the pipes 1, 2. The device is thus adapted to be brought into position such that the welding site is radially forward of the outer annular chamber 28. Cylinder chamber 17 of piston-cylinder device
When filled with pressure medium, the piston rod 6 moves to the right relative to the cylinder 15, so that the holding body 21 approaches the cylinder 15 while the plate 3
2. Spring 13a and spring 13b via holder 21
is compressed from the left end of the piston rod. At the same time, the clamp grooves 39, 42 become narrower, so that the annular helical spring 3 in the clamp grooves 39, 42 becomes narrower.
is forced outwardly as shown in dotted lines until it abuts the inner periphery of the pipe 1, thus at least temporarily aligning and securing the clamping device inside this pipe. Become. At this time,
Care is taken that the edge of the pipe 1 to be welded is radially forward of the outer annular chamber 28. Spring 13a
The force is chosen in such a way that in such a situation, the clamping unit corresponding to the clamping groove 36 is not yet functional and the pipe 2 can still be adjusted. Then spring 1
3a is also compressed, thereby narrowing the clamping groove 36 of the left-hand clamping unit, so that the annular helical spring 3 in its clamping groove 36 ensures that the pipe 2 is also aligned and clamped. is pushed radially outward to the position shown in dotted lines until it is pressed. At the same time, the annular spiral spring 3
As shown by solid lines and dotted lines, the pipe expands outward in the radial direction and moves in the longitudinal direction, thereby mutually clamping the contact surfaces with the pipe. When the clamping device is ready to be clamped as described above, inert gas is supplied to the outer annular chamber 28 as described above, with the result that atmospheric air is removed from the annular chamber 28 and thus from the welding site. do. The device is now ready for automatic welding from the outside. During actual welding, in order to prevent the device from overheating, the holder 21 is cooled by supplying refrigerant to the refrigerant chamber 22. FIG. 2 shows a clamping device for clamping pipe 50 to flange end 51. FIG. Components that are the same as those described with reference to FIG. 1 are designated by the same reference numerals. Inside the pneumatic cylinder 15, a cylinder chamber 17 is formed between the piston 4 and the fixed cylinder end wall 16. On the right side of the drawing, the piston 4 is firmly connected to a pipe 34, which is provided at one end with a connector socket 35 for connection to a pressurized gas hose, the supply of which can be controlled by a device not shown. Further, the piston rod 6 is firmly connected to the piston 4, extends to the left side of the piston 4 when viewed from the drawing, and is connected to the inside of the pipe 34,
An opening for supplying pressurized gas for operating the clamp device is formed toward the cylinder chamber 17 at a location indicated by 7 . The cylinder 15 has a flange end 51 to be welded.
It is firmly connected to a plate 37, hereinafter referred to as a locking plate since it constitutes a locking part for positioning. This locking plate 37 has a cylinder 1
A cylindrical collar 38 is mounted on the side facing away from 5. The piston rod 6 is connected to the locking plate 3
7 and a collar 38, it is guided concentrically in the longitudinal direction and is movable. The free end of the piston rod 6 is firmly connected to a plate 32 having a collar 33. Cylindrical holding body 21
is disposed between the two collars 33, 38 and is fitted into the inner cavities of these collars 33, 38. Alternatively, the piston rod 6 may be guided so as to be movable in the longitudinal direction by sealing/guiding sleeves 12a and 12b provided on the bosses of the end walls, in which case the spring 13b causes the collar 38 to be It is supported on the base. A cylindrical sleeve 40 is mounted on the holder 21, and both enlarged end faces of the sleeve 40 form conical flats. The end flat of the collar 33 is also correspondingly conical and forms, opposite the conical flat of the sleeve 40, a clamping groove 36 in which the annular helical spring 3 is arranged. In this embodiment as well, each spiral filament of the annular spiral spring 3 forms a clamp member. The sleeve 40 is longitudinally movable on the holder 21, but a sleeve 40', which is arranged similarly to the sleeve 40 on the holder, is firmly connected to the holder 21. Further, the sleeve 40' is also formed with annular protrusions 30 and 31 having conical flat parts at both ends thereof, one of which is formed on the sleeve 40'.
The other side faces the clamp groove 39 of the annular spiral spring 3, and the other side faces the clamp groove 39 of the annular spiral spring 3.
1. A longitudinally movable ring 41 provided around the circumference of 1.
A clamping groove 42 of the annular spiral spring 3 is formed together with the ring 41 so as to face the conical flat portion of the ring 41 . When the device is in the relaxed state as shown, a gap is formed between the end face of collar 38 and ring 41. Between the annular projections 30 and 31, the holding body 21
A hole 27 is formed in the sleeve 40' and the sleeve 40'.
Further, a hole 26 is also formed in the piston rod 6 in the portion of the holder 21. The inert gas, which is also used as pressurized medium to supply the cylinder chamber 17, flows through these holes 26 to the welding region 9 of the pipe 50 and the flange end 51 to be clamped together. The clamp grooves 36, 39, together with their related parts, are configured in the clamp unit of the pipe 50, and the clamp groove 42, together with their related parts, are configured in the flange end 51.
It constitutes the second clamp unit. The apparatus constructed as shown in FIG. 2 operates as follows. In the relaxed state shown, the pipe 50 and flange end 51 are attached to the clamping device as shown. For example, 5
When supplied with the initial average effective pressure of the crowbar, the piston rod 6 moves to the right in the drawing, and the pressurizing force increases to the collar 3.
3, the clamp groove 36, the annular spiral spring 3 in the clamp groove 36, the sleeve 40, and the clamp groove 3
9, it is transmitted to the spring 13b via the annular spiral spring 3 in the clamp groove 39, the sleeve 40', the holder 21, and the sleeve 12a. At that time, the spring 13b
is such that under this moderate pressure it behaves practically firmly or is not compressed further than corresponds to the magnitude of the distance between the collar 38 and the sleeve 40. Its dimensions are determined. For, up to this pressure limit, only the annular helical springs 3 in the clamping grooves 36, 39 are forced outwardly by the conical flats of the latter in order to orient and clamp the pipe 50. . Care is therefore taken to ensure that the end face of this pipe to be welded is exactly aligned with the center of the welding area 9 surrounded by the annular projections 30,31. Thereafter, the pressure is further increased so that the spring 13b is compressed. Then, relative movement occurs in the longitudinal direction between the pipe 50 that is being clamped at that time and the locking plate 37 so that the flange end 51 is pressed against the pipe 50. As soon as the gap between the adjacent rings 41 is overcome, the rings 41 act on the collars 38 and the annular helical springs 3 of the clamping grooves 42 are forced radially outwards, so that the flanges 51 are aligned. It is clamped together. At the end of this operation, the pipe 50 and the flange end 51 are aligned and their end faces abut each other with a clamping action, and the inert gas has flushed the weld area 9. It is clear that this device is exceptionally simple in construction and can be operated as a welding clamp device with the simplest control means and only with inert gas as the control medium. Further, the annular spiral spring 3 close to the welding part 9 is shielded from the welding part by the annular protrusions 30 and 31, and is widely incorporated into the cold parts of the clamping device, so that the inert gas can evenly flow. This results in good cooling, and on the other hand, the heat from the machined pipe 50 and the flange end 51 is only gradually transferred to them due to the point-like reduction of the contact surface. The device according to FIG. 3 is identical to the device according to FIG. 2, but instead of the only clamping groove 42 corresponding to the flange end 51 in the configuration according to FIG. 2, two clamping grooves 42, 42a are provided. It is formed. In addition, in the configuration shown in FIG. 3, the pipe on the right side is not only aligned between the clamp grooves 42 and 42a, but is also movable on the holder 21 so that its direction is determined so as to be smooth. A sleeve is provided. Furthermore, the locking plate 37 is omitted. Instead, two sliding rings 43 are provided which are made of plastic with a low coefficient of friction and project somewhat radially outwards from the annular projection forming the clamping groove. This sliding ring 43 facilitates movement of the clamping device inside the closed pipeline. The spring 13b is arranged at the end of the holder 21 on the opposite side from the cylinder 15. This allows the clamp unit, which is far away from the cylinder 15 and corresponds to the clamp grooves 36 and 39, to
Close to the cylinder 15, clamp grooves 42, 42a
The clamp unit can be clamped after the corresponding clamp unit. Needless to say, this device is suitable for clamping straight pipe sections. If the pipe on one side of the welding area is a bent pipe, the clamp unit on the left side of FIG. 3 must have a short structure with one clamp groove as shown in FIG. 4 and 5 constitute a clamp member,
Moreover, the conical flat portions 52 and 53 of the clamp groove 36
It shows two coils or helical filaments 56 of the annular helical spring 3 held between them. Furthermore, the fourth
The figure corresponds to a view viewed from above along the radial direction of each annular spiral spring, and FIG. 5 corresponds to a view viewed along the circumferential direction of each annular spiral spring. Each spiral filament 5 of each annular spiral spring 3
6 is constructed by bending a wire rod with a circular cross section, so it makes point contact with the inner circumferential surface of the base material to be clamped, as shown in the drawing with a very small point-like contact clamping surface 54. , has an outwardly sharp curved surface. These point-like contact clamping surfaces 5
4 is approximately smaller than the outer dimension 58 of each helical filament, the inert gas flow 55 flowing through the very small intermediate spacing 57 is smaller than the size of the punctiform contact clamping surface 54. The surface of each spiral filament will be twice as large. Thereby,
The helical filament of the annular helical spring is effectively cooled and there is no risk of overheating. FIG. 6 shows a similarly effective clamping member arrangement using a plurality of disks 60, which are circular in shape, held at a distance 57 by an intermediate disk 61, and tensioned by a wire spring 59. It shows that it is possible.