DE9300577U1 - Butt welding machine for plastic pipes - Google Patents

Description

Rothenberger

Tools-Machines GmbH
Industriestr. 7

W-6233 Kelkheim

"Butt welding machine for plastic pipes"

The invention relates to a butt welding machine for plastic pipes with a machine frame with several clamps for holding the pipe ends, with guides parallel to the common clamp axis for the relative displacement of the clamps to each other and with holding elements arranged on opposite sides of the clamp axis for the optional holding of a milling device and a heating element for the processing and heating of the pipe ends, whereby the holding elements are guided by scissor joint systems in each position of the clamp approximately centrally between the two inner clamps.

Welds made on such butt welding machines must generally comply with the DVS 2207 guidelines. The welding regulations laid down in these guidelines are also taken into account when building the butt welding machine described above. A planer is then used to prepare the weld seam, which brings the ends of the pipes to be welded into a plane-parallel state when clamped. This requires that the heating element and milling device must be interchangeable without changing the clamping of the pipe ends. After the exchange, the pipe ends are moved towards the heating element, whereby specified parameters such as the temperature of the heating element, contact pressure and dwell time must be adhered to with extreme precision, which is usually done by a program control. After heating, the heating element is removed and the pipe ends are brought together, whereby the setting force for joining must be increased quickly from zero to a specified final value. Joining pressure and joining force must be maintained until the weld has cooled down. At the end of this process, a very specific bead formation occurs at the weld point, which in turn must meet certain standard requirements. The basic requirement for achieving the specified quality of the weld is that the pipes or pipe ends are constantly and precisely aligned axially. This is achieved by several clamps arranged on the machine frame, which are usually arranged in pairs on each side of the joint and can be moved in pairs relative to one another.

A butt welding machine of the type described above is known from obvious prior use, in which the plate-shaped heating element is mounted on parallel guides in a housing that is open at the top. Using two handles on opposite sides, the heating element must be moved vertically downwards into its welding position and locked there; the upward movement takes place after being triggered by a remote-controlled trigger element by two energy accumulators.

standing steel belts. The known device requires a relatively large amount of space, is heavy and, due to its numerous guide elements, is complex to construct and maintain, and a not inconsiderable amount of control effort is also required to enable the upward movement of the heating element.

Size, weight and operating speed are decisive criteria for the construction of butt welding machines for plastic pipes. It must be taken into account that the interchangeability of the milling device (planer) and heating element is not only due to the need for alternative use, but also to the fact that the machine frame should not have any permanent structures if possible. It must be possible to pull the machine frame out from under the welded pipe without such structures after a weld has been completed, which is usually laid in a trench, so that space is very limited.

The invention is therefore based on the object of specifying a butt welding machine of the type described above, in which the heating element and the associated components have a small space requirement and a low weight, have only a few, easily maintained moving parts and in which the heating element can be moved automatically from the welding position to the rest position without a complex trigger mechanism.

The solution to the problem is achieved according to the invention in the butt welding machine specified at the beginning by

a) the heating element is mounted so as to pivot about a pivot axis parallel to the clamp axis in a support body which can be exchanged with the heating element,

b) the heating element is weight-relieved with respect to its pivot axis,

c) the heating element is provided with a locking element by means of which it can be locked in the heating position against an upward pivoting movement, and that

d) the locking element is assigned a trigger by which the heating element can be unlocked for upward pivoting after the pipe ends have been heated up and retracted.

In the subject matter of the invention, the heating element is moved on an arc that corresponds roughly to a quarter of a circle. The pivot bearing eliminates the need for complex parallel guidance, so that a much smaller space requirement is created. The weight of the solution according to the invention is also significantly lower, and the heating element and the associated components have only a few moving parts that are easy to maintain. Furthermore, the self-release during the return movement of the movable clamps means that a special remote-controlled release mechanism can be dispensed with.

It is particularly advantageous if the heating element is mounted in the support body by means of a horizontal pivot pin arranged on the heating element in a torsion-proof manner and if a torsion spring is arranged between the pivot pin and the support body, by means of which the heating element is held in its highest position (rest position) in the unlocked state.

The retraction mechanism requires particularly little space if the pivot pin protrudes from the support body at least at one of its ends and carries the torsion spring in the form of a pre-tensioned helical spring in a concentric position along its protruding length.

It is also particularly advantageous if the locking element is a locking pawl mounted on the heating element so that it can pivot radially outwards, which, when pivoted out and in the heating position of the heating element, engages under the adjacent guide of the machine frame, and if the trigger

formed by an extension on the adjacent scissor joint and on a

such a path of motion that the trigger can be actuated by a

By extending the scissor joint the locking pawl can be moved out of its locking position below the guide.

The scissor joint therefore serves in a particularly simple way to cause the heating element to trigger automatically through its positively controlled movement.

It is also particularly advantageous if the scissor joints are designed in three parts with a central double lever and two outer lugs as well as with five pivot pins, of which the two outer pivot pins are attached to the two inner clamps, and if the scissor joints are each assigned a link plate, which

a) carries in its centre the central pivot pin of the double lever,

b) has a horizontal guide groove on each side of the middle pivot pin, which are aligned with each other and with which the guide plate is guided on the two outermost pivot pins, and which

c) has an upward-facing guide rail in its centre onto which the supporting body with the heating element can be placed.

Due to the specified design measures, the two guide plates arranged on opposite sides have a guiding and centering function as well as a supporting function for the heating element and its associated components.

Furthermore - and in contrast to the state of the art - it is also advantageous if the support body for the heating element is supplemented by a chamber closed at the top for accommodating the heating element in its highest position (rest position).

In this way, a chimney effect within the closed chamber is avoided and the temperature of the heating element can be maintained not only with significantly reduced energy consumption, but also with a much more even temperature distribution.

Further advantageous embodiments of the subject matter of the invention result from the remaining subclaims.

An embodiment of the subject matter of the invention is explained in more detail below with reference to Figures 1 to 3.

Show it:

Figure 1 is a side view of a butt welding machine in a

preparation state for preheating the parts to be welded
Pipe ends,

Figure 2 is a partially sectioned side view with view direction according to

the arrow Il in Figure 1 on an enlarged scale,

Figure 3 shows a partial section of Figure 1 at the same scale as Figure 2.

Figure 1 shows a plastic welding machine 1 for plastic pipes 2 and 3, which are made of a thermoplastic material and are to be welded in the plane E-E. The device includes a machine frame 4, which includes skids 5, U-shaped machine stands 6 and 7, as well as spacer tubes 8 and guides 16, to name just the most important components. The guides 16 are also piston rods, which will be discussed in more detail below.

The upper end of the machine stand 6 is also designed as a clamp 9 for the pipe 2. Three further clamps 10, 11 and 12 are arranged on the two guides 16 by means of corresponding holes, of which only the front one is visible in Figure 1. The clamps 9 and 10 are arranged in a fixed position above the machine stand 6 and are held at a fixed distance from one another on both sides by a spacer tab 13.

The other two clamps 11 and 12, which also form a pair, can be moved on the guides 16, but are also held at a fixed distance from one another by a hydraulic cylinder 14 or by spacer bolts 15. Two piston rods 16 extend between the machine stands 6 and 7. Figure 2 shows the spatial position of the piston rods and guides 16, which run parallel to the spacer tubes 8. Pistons (not shown) are arranged on these piston rods and are located inside the hydraulic cylinders 14. By alternatively applying pressure to the two piston surfaces via the pressure medium lines 17 and 18, the two clamps 11 and 12 can be moved a limited distance on the guides 16. The required metered joining forces are also applied by means of the hydraulic cylinders 14. Only a short section of the piston rods 16 can be seen in Figure 1.

The upper parts of the clamps 9, 10, 11 and 12 are completely removable and are clamped against the pipes 2 and 3 during operation by tie rods 19. The clamps 9 to 12 define a common clamp axis A1-A1, which is identical to the pipe axis.

The milling device (planer) that is also part of the butt welding machine as well as the control devices are not shown in the drawing.

Figure 2 shows further details of the machine frame as well as the heating element and the associated components:

The plate-shaped heating element 20, which has an electrical heating resistor inside and whose two flat outer surfaces are provided with a surface coating that repels the plastic, is drawn in solid lines in its lowest position (welding position), and above it with a dot-dash circular line 20a in its highest position (rest position). The center of the heating element 20 is moved on a circular path K. For this purpose, the heating element 20 has a lever-like extension 21 at a circumferential point above the piston rod 16, in the outer end of which a pivot pin 22 is arranged in a rotationally fixed manner. This pivot pin is mounted at two points in a support body 23, which in this case is formed by the lower end of a chamber 24 that is closed at the top and consists of two walls 25 and 26 arranged approximately parallel to one another and a frame 27 between them. (See in particular Figure 3.)

The support body 23 rests on opposite sides of the clamp axis A1-A1 on holding elements 28 and 29, which include locking knobs 28a and 29a. The special design of the holding elements 28 and 29 will be discussed in more detail below in connection with Figure 3.

The heating element 20 has a locking element 32 in a chord-shaped recess 30 that can be pivoted to a limited extent around an axis 31 and that has an arcuate cutout at its upper end with which it engages under the piston rod and guide 16 in the pivoted-out position. The heating element 20 is held in its welding position by the locking element 32, which functions as a locking pawl. In order to enable the heating element 20 to be automatically released to return to its rest position (position 20a) after the pipe ends have been heated up, a trigger 33 is assigned to the locking element 32, the construction and operation of which will be discussed in more detail in connection with Figure 3. On both sides of the device, at the height of the two piston rods, there is a

16 each have a scissor joint system 34 or 35, the construction and mode of operation of which will also be explained in more detail using Figure 3. The cables for the power supply and the temperature sensor are not shown specifically in Figure 2, but are naturally present.

The chamber 24 has a handle 36 at its upper end, with which the chamber 24 and thus the (upwardly pivoted) heating element 20 can be lifted off the holding elements 28 and 29 after releasing the locking knobs 28a and 29a. It can be seen very clearly from Figure 2 that the chamber 24 is designed to be very space-saving and, in particular, has no annoying corners in its upper area that would make the chamber 24 bulky and hinder handling. It can be seen in particular from Figure 3 that the chamber 24 is also designed to be very narrow, since no guide devices have to be arranged in the chamber itself, as would be the case with a parallel stroke of the heating element 20.

Figure 3 also shows the following:

The pivot pin 22 is guided out of the support body 23 or the chamber 24 at both ends and has a torsion spring 37 on one end, which brings about the inventive weight relief of the heating element 20 about its pivot axis A2-A2 or about the pivot pin 22. This torsion spring 37 is designed as a helical spring and is held in a concentric position on the pivot pin 22. It is connected at one end in a torsion-proof manner to the pivot pin 22, and at the other end in a likewise torsion-proof manner to the support body 23. It is also pre-tensioned to such an extent that the heating element 20 returns to its highest position (position 20a) after the locking element 32 is released (Figure 2). The other end of the pivot pin 22 carries a hand lever 38 with a handle 38a, which is fixed against rotation and is used to pivot the heating element 20 into its heating position (Figure 2, below).

When the hand lever 38 is operated, the torsion spring 37 is naturally further tensioned.

Figure 3 shows additional details of the two scissor joint systems 34 and 35: Each of these scissor joint systems is designed in three parts and has a central double lever 39 and two outer tabs 40 and 41 as well as a total of five pivot pins 42, 43, 44, 45 and 46. The two outer pivot pins 42 and 46 are attached to the two inner clamps 10 and 11. Each scissor joint system is assigned a link plate 47, of which only the front one is visible. This link plate 47 carries the central pivot pin 44 of the double lever 39 in its center. A horizontal link groove 48 and 49 is arranged on either side of the central pivot pin 44, with the two link grooves being aligned with one another. By means of these guide grooves 48 and 49, the guide plate 47 is guided on the two outermost pivot pins 42 and 46. It is clear that when the clamps 10 and 11 are pushed together or pulled apart, the middle pivot pin 44 is always guided exactly in the middle between the two outer pivot pins 42 and 46. As a result, the plane E-E (Figure 1) is always exactly in the middle between the clamps 10 and 11.

According to Figure 3, the link plate 47 also has an upwardly pointing guide rail 48 in its middle, which is slightly beveled at its upper ends and bent inwards to make it easier to place the support body 23 on it. The unspecified threaded pins of the locking knobs 28a and 29a are also attached to these guide rails 48 (Figure 2). The vertically upwardly pointing guide rails 48 also contribute to the easy and precise positioning of the chamber 24 with the heating element 20, as can easily be seen from Figure 3.

One of the two scissor joint systems, namely the scissor joint system 34 has a special feature with regard to the trigger 33 according to the invention for

the locking element 32. The outer tab 40 of the scissor joint system 34 is extended beyond the pivot pin 43 that connects it to the double lever 39. This creates an extension 49 that reaches directly to the pivoting area of the locking pawl 32 of the heating element 20. At its free end, the extension 49 carries a release body that is designed as a roller 50.

As can be seen from a joint examination of Figures 2 and 3, the roller 50 of the release mechanism 33 moves on a path of movement when the clamps 10 and 11 are pulled apart, in that its axis remains at least essentially within the plane E-E. At the same time, however, the roller 50 moves upwards and in doing so strikes the correspondingly beveled outer edge of the locking element 32 (pawl), which is thereby pressed away from the guide (piston rod 16) (Figure 2). It is understood that the path of movement of the roller 50 in relation to the outer edge of the locking element 32 is designed in such a way that the locking element 32 is only unlocked after the plasticized ends of the pipes 2 and 3 are sufficiently far away from the two heating surfaces of the heating element 20.

Claims (10)

Protection claims: 1. Butt welding machine (1) for plastic pipes (2, 3) with a machine frame (4) with several clamps (9, 10, 11, 12) for holding the pipe ends with guides (16) parallel to the common clamp axis (A1-A1) for the relative displacement of the clamps to one another and with holding elements (28, 29) arranged on opposite sides of the clamp axis for holding a heating element (20) for heating the pipe ends, wherein the holding elements (28, 29) are guided by scissor joint systems (34, 35) in each position of the clamps approximately centrally between the two inner clamps, characterized in that a) the heating element (20) by an angle parallel to the clamp axis (A1-A1)
Swivel axis (A2-A2) swiveling in a with the heating element
replaceable support body (23), b) the heating element (20) with respect to its pivot axis (A2-A2)
is weight-relieved, c) the heating element (20) is provided with a locking element (32),
and that d) the locking element (32) is associated with a trigger (33), by
After the pipe ends have been heated and retracted, the heating element (20) can be unlocked for upward pivoting. 2. Butt welding machine according to claim 1, characterized in that the heating element (20) is mounted in the support body (23) by means of a horizontal pivot pin (22) arranged on the heating element in a rotationally fixed manner and that a torsion spring (37) is arranged between the pivot pin and the support body, by means of which the heating element is held in its highest position in the unlocked state. 3. Butt welding machine according to claim 2, characterized in that the pivot pin (22) projects from the support body (23) at at least one of its ends and carries the torsion spring (37) in the form of a prestressed helical spring in a concentric position over its projecting partial length. 4. Butt welding machine according to claim 3, characterized in that the other end of the pivot pin (22) has a hand lever (38) for pivoting the heating element (20) into its heating position. 5. Butt welding machine according to claim 1, characterized in that the locking element (32) is a locking pawl mounted on the heating element (20) so as to be pivotable radially outwards, which in the pivoted-out state and in the heating position of the heating element (20) engages beneath a guide (16) of the machine frame (4) adjacent to it, and in that the trigger (33) is formed by an extension (49) on the adjacent scissor joint system (34) and is movable on a path of movement such that the trigger can move the locking pawl out of its locking position beneath the guide (16) during an extension movement of the scissor joint system (34). 6. Butt welding machine according to claim 1, characterized in that the scissor joint systems (34, 35) are designed in three parts with a central double lever (39) and two outer plates (40, 41) as well as with five pivot pins (42, 43, 44, 45, 46), of which the two outermost pivot pins (42, 46) are attached to the two inner clamps (10, 11), and that the scissor joint systems are each assigned a link plate (47), which a) carries in its centre the central pivot pin (44) of the double lever (39). b) on both sides of the central pivot pin (44) a horizontal
link groove (48, 49) which are aligned with each other and with which the
Slide plate (47) on the two outermost pivot pins (42, 46)
is conducted, and c) has an upwardly pointing guide rail (48) in its centre, on
onto which the supporting body (23) with the heating element (20) can be placed. 7. Butt welding machine according to claims 5 and 6, characterized in that one of the outer tabs (40) of one scissor joint system (34) is extended beyond the pivot pin (43) which connects it to the double lever (39) of the scissor joint system (34), that the extension (49) of the relevant tab (40) reaches directly to the pivoting area of the locking pawl (32) of the heating element (20), and that the extension (49) carries a release body for the locking pawl at its free end. 8. Butt welding machine according to claim 7, characterized in that the release body is designed as a roller (50). 9. Butt welding machine according to claim 1, characterized in that the support body (23) for the heating element (20) is supplemented by an upwardly closed chamber (24) for receiving the heating element in its highest position (20a). 10. Butt welding machine according to claim 9, characterized in that the walls (25, 26) of the chamber (24) are provided with an insulating coating.