Patent Publication Number: US-2023138873-A1

Title: Mobile pipe welding machine

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of International Application PCT/EP2022/076558 filed Sep. 23, 2022 which claims priority to German Application DE 10 2021 128 159.8 filed Oct. 28, 2021. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to a mobile pipe welding machine with (a) a welding unit for welding pipes and (b) a pipe receiver for guiding a pipe to the welding unit, wherein (c) the pipe receiver comprises (i) a distal end facing away from the welding unit and (ii) a proximal end facing towards the welding unit. 
     BACKGROUND 
     Such a pipe welding unit is known, for example, from EP 3 040 592 B1, in which laterally pivotable arms are pivoted towards each other to lift the pipe with a conically tapered roller oriented in the direction of pivoting. The disadvantage of this is that it can result in relatively high surface pressures on the pipe, which is often undesirable. Moreover, this solution usually requires a comparatively material-intensive construction. 
     SUMMARY 
     The invention aims to reduce disadvantages of the prior art. 
     The invention solves the problem by way of a mobile pipe welding machine according to the preamble, the pipe receiver of which comprises, particularly at the distal end, at least one linearly movable contact body for lifting the pipe. In more general terms, the invention solves the problem by way of a mobile pipe welding machine according to the preamble, the pipe receiver of which comprises, particularly at the distal end, at least one non-pivotably mounted, movable contact body designed for lifting the pipe. 
     The invention also solves the problem by way of a method for welding a pipe featuring the steps (a) moving a pipe welding machine according to the invention towards a pipe, and (b) lifting the pipe by linearly moving the at least one contact body towards the pipe, and where applicable (c) guiding the pipe by means of the pipe receiver to the welding unit and/or (d) welding the pipe to a pipe end of a pipeline section. 
     The advantage of the invention is that in many cases, the pipe can be lifted with a reduced surface pressure. For example, the contact body can comprise at least one, preferably rotatably mounted, wheel, particularly two or more wheels, which bear against the pipe to lift the pipe. This reduces the surface pressure. 
     Furthermore, it has been observed that linearly moveable contact bodies can often be produced with less engineering effort than those that can be pivoted. 
     Another advantage may be that a contact body drive, which is provided to move the contact body, can be selected to be comparatively low-powered and/or structurally simple, or to exert a high force on the pipe. This is especially advantageous when pipes with thick walls or large diameters are to be welded. 
     Within the scope of the present invention, a mobile pipe welding machine refers in particular to a machine that has its own running gear with its own motor, such that it can move automatically. For example, the pipe welding machine has a chain drive. The pipe welding machine can then also be referred to as a weld bead. 
     The welding unit is understood to mean a device that is designed to weld pipes, especially plastic pipes and/or steel pipes. In particular, the welding unit is not only suitable for welding as a basic principle, but rather is designed for this task. Specifically, the welding unit is designed to weld automatically. In other words, the welding unit carries out the welding according to a manually or mechanically pre-set start command. 
     The pipe receiver refers in particular to a device that is designed to guide a pipe that is to be welded to the welding unit. For example, the pipe receiver features a longitudinal conveyor, especially a passive longitudinal conveyor. For example, the passive longitudinal conveyor is a roller conveyor. 
     The pipe receiver preferably has a pipe receiver longitudinal axis. This pipe receiver longitudinal axis corresponds to the longitudinal axis of a (imaginary) best-fit cylinder of a pipe, in particular when the latter lies with maximum contact on the pipe receiver. 
     The property that the contact body in particular is not only suitable for lifting the pipe, but is designed for that purpose, is understood specifically to mean that the contact body can be brought into a neutral position and a lifting position. If a pipe lies within an operating area of the contact body, the contact body exerts no force on the pipe when in the neutral position and therefore does not lift it. In the lifting position, on the other hand, the contact body exerts enough force on the pipe in the operating area that the latter is lifted. 
     It should be noted that the contact body can of course also be in the neutral position and the lifting position when there is no pipe in the operating area. The neutral position and the lifting position are defined in that the at least one contact body can lift a pipe when it lies within the operating area. The operating area is the area in which a pipe can be lifted by the contact body. 
     According to a preferred embodiment, the at least one contact body has a contact surface that comes into contact with the pipe when the pipe is lifted. Preferably, this contact surface is not convex in shape, but rather is at least partially level or at least partially concave, for example. 
     A scratch protection made of an anti-scratch material is preferably arranged on the contact surface. The anti-scratch material is preferably not metallic. For example, the anti-scratch material is a polymer. In particular, the anti-scratch material may be an elastomer, a thermoset, a thermoplastic or rubber. The anti-scratch material preferably exhibits entropy elasticity. It has been observed that in known pipe receivers, the pipe may become scratched at the contact point between pipe and end effector for lifting the pipe. This is due to the comparatively high surface pressures. The pipes are usually designed in such a way that scratches do not present a problem during standard operation of the pipeline. Nevertheless, preventing scratches may result in higher strength pipelines. 
     The contact surface is preferably at least partially concavely curved. As a result, the contact surface can at least partially adapt to the curvature of the pipe. 
     Preferably, the contact surface has a sliding cylinder radius that differs from a nominal diameter of a pipe to be welded by a maximum factor of 3, especially a maximum factor of 2, preferably a maximum factor of 1.5 The sliding cylinder is the (imaginary) cylinder that comes to rest on the contact surface. The sliding cylinder corresponds to the lateral surface of a pipe that rests on the contact surface. 
     The nominal diameter is the diameter for which the mobile pipe welding machine is designed. This nominal diameter is known for all pipe welding machines and is indicated, for example, in operating instructions that are preferably part of the pipe welding machine. 
     According to a preferred embodiment, the at least one contact body has at least one rotatably mounted wheel. In particular, the rotatably mounted wheel is mounted about a wheel rotational axis. It is beneficial if the wheel rotational axis extends at an incline to the horizontal plane. An angle of attack at which the wheel rotational axis extends to the horizontal plane is preferably at least 20°, especially at least 30°. 
     Preferably, a tilt angle between a projection of the wheel rotational axis onto the horizontal plane on the one hand and a projection of the pipe receiver longitudinal axis onto the horizontal plane on the other is is 90°±15°, in particular 90°±5°. 
     It is practical if the at least one wheel is designed to be spherical. Alternatively, the wheel may also have a cylinder barrel-shaped or concave running surface. 
     To achieve the smallest possible wheel force between the pipe and the contact body, it may be advantageous for the contact body to comprise at least one omnidirectional wheel, such as a Mecanum wheel or an omni wheel. 
     The pipe receiver preferably has at least two contact bodies that can be moved towards each other. In particular, the contact bodies are arranged in such a way that they contact a pipe from opposite sides so that horizontally acting force components compensate each other. The contact bodies can preferably be moved linearly towards each other. In particular, the contact bodies are designed to contact the pipe at a height below the longitudinal axis of the pipe and above a height of an underside of the pipe. 
     According to a preferred embodiment, the pipe welding machine has a first contact body drive, which comprises a first contact body longitudinal guide for guided movement of the first contact body. Alternatively or additionally, the pipe welding machine preferably has a second contact body drive, which comprises a second contact body longitudinal guide for guided movement of the second contact body. It is possible that two contact bodies are moved collectively by one, especially the first, contact body drive. 
     A longitudinal guide refers to a guide that does not have a fixed pivot point. Preferably, the longitudinal guide extends along a straight line. In particular, the longitudinal guide is designed in such a way that it does not induce a pivot movement, i.e. a movement that can be considered to be pivoting. It is possible, but not necessary, for the longitudinal guide to be completely or partially curved. In this case, the centre point of the circle of curvature, in particular all centre points of the circle of curvature, can be located distally in front of the contact body. In particular, the movement occurs on a linear path. In other words, the longitudinal guide is preferably a linear guide. 
     The at least one contact body preferably features a base body that is guided on the contact body longitudinal guide. The scratch protection is fixed to the contact body. The base body is made of a base body material that has a base body material hardness. The base body material can be, for example, a metal or an alloy, in particular steel or aluminium. 
     Preferably, the base body material hardness is at least 80 HV 10 and/or at most 650 HV 10. 
     An anti-scratch material hardness of the anti-scratch material is preferably lower than the base body material hardness. It is advantageous if the anti-scratch material hardness is at most half, particularly at most one fifth, of the base body material hardness. It is advantageous if the anti-scratch material hardness is at least one five-hundredth of the base body material hardness. 
     For example, the hardness is the Vickers hardness HV 10 in accordance with DIN EN ISO 6507-1:2018 to -4:2018 or the Shore-D hardness in accordance with DIN EN ISO 868, DIN ISO 7619-1 or ASTM D2240-00. 
     Preferably, the anti-scratch material hardness is at most 65 Shore D, in particular at most 58 Shore D, for example at most 45 Shore D, preferably at most 35 Shore D, especially preferably at most 30 Shore D. As a result, the pipe is effectively protected against scratches. 
     According to a preferred embodiment, the anti-scratch material hardness is at least 15 Shore D, in particular at least 20 Shore D. This reduces the wear of the scratch protection. 
     For example, the anti-scratch material is mounted on the base body in a material-locking or form-fitting manner. For example, the anti-scratch material is vulcanized or glued onto the base body. Alternatively or additionally, the anti-scratch material can be screwed, riveted or otherwise fixed onto the base body. 
     It is advantageous if both basic bodies are of the same design, but mirror-symmetrical to each other. 
     It is advantageous if the first and second contact body longitudinal guides extend transversely towards each other. Preferably, the contact body longitudinal guides extend towards each other in a V shape. When the contact bodies move towards each other, i.e. the pipe receivers in particular move towards each other, the contact bodies then move with a movement component in the proximal direction. 
     The first contact body longitudinal guide extends particularly at a first bevel angle to the pipe receiver longitudinal axis that is at least 30°, especially at least 40° and/or at most 85°, especially at most 75°. Alternatively or additionally, the second contact body longitudinal guide extends particularly at a second bevel angle to the pipe receiver longitudinal axis that is at least 30°, especially at least 40° and/or at most 85°, especially at most 75°. 
     The pipe welding machine preferably has a run-up skid for guiding a pipe onto the pipe receiver when a pipe is moving in a proximal direction. In other words, the run-up skid is preferably arranged in such a way that a pipe that is moved onto the pipe receiver is passively lifted from the run-up skid onto the pipe receiver, in particular its longitudinal conveyor. 
     The run-up skid is preferably arranged proximally in the longitudinal direction in relation to the pipe receiver longitudinal axis behind a distal end of the contact body in the neutral position. The run-up skid preferably features a run-up surface that extends transversely to a horizontal plane. A run-up plane angle of inclination at which the run-up skid is inclined on average is preferably at least 15°, especially preferably at least 30° and/or at most 70°, especially at most 60°. If the run-up surface is curved—as provided for according to a preferred embodiment—the run-up surface angle of inclination is the angle of inclination of a compensation surface through the run-up surface. 
     It is advantageous if (a) the pipe receiver has a main section and a foot section, (b) the foot section is arranged at the distal end of the pipe receiver, and (c) the foot section is hinged on the main section such that it can be pivoted. When the pipe welding machine is in the operating position, the foot section preferably extends along the ground and the main section does not extend along the ground, but rather at an angle to it/at an angle of attack of at least 5°, especially 10° and/or at most 35°, especially at most 25°. 
     To enable an automated or at least partially automated lifting of the pipe, the pipe welding machine preferably has a pipe position sensor for recording a position of pipe located in front of the pipe receiver in terms of a direction of travel of the pipe welding machine. 
     The pipe welding machine preferably comprises a control unit that is designed to control the at least one contact body drive if the pipe position sensor falls short of and/or detects a predetermined distance to the pipe. In particular, the control unit is connected to the pipe position sensor and the contact body drive. 
     The pipe position sensor may be a contactless pipe position sensor or a tactile pipe position sensor. For example, the pipe position sensor is an optical sensor. In this way, the pipe position sensor may comprise a light barrier, an ultrasound sensor and/or a camera. The camera may have, for example, an image recognition system and/or a runtime camera. 
     The pipe position sensor may also be an electrical sensor. For example, the pipe position sensor records a change in the dielectric constant. 
     The pipe position sensor is, for example, a touch sensor arranged in such a way that it strikes the pipe when the predetermined distance to the pipe is not reached. If the pipe position sensor is a touch sensor, it can comprise a touch body, for example in the form of a flap, a pin or a cord. 
     According to a preferred embodiment, the pipe welding machine comprises a camera, the contact body being located in its field of vision, for recording images and/or a screen for displaying the images, for example in a driver&#39;s cabin of the pipe welding machine. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       In the following, the invention will be explained in more detail with the aid of the accompanying drawings. They show: 
         FIG.  1    a side view of a pipe welding machine according to the invention, 
         FIG.  2    a perspective view of the pipe receiver of the pipe welding machine according to  FIG.  1   , 
         FIG.  3    a perspective view from above onto the distal end of the pipe receiver, which could also be referred to as receiving head, according to  FIG.  2   , 
         FIG.  4    in the partial  FIG.  4   a   , a frontal view of the distal end of the pipe receiver according to  FIG.  3    and in the partial  FIG.  4   b   , a side view of the distal end of the pipe receiver according to  FIG.  3   , and 
         FIG.  5    a partial sectional view along the line A-A according to  FIG.  4     b,    
         FIG.  6    in the partial  FIG.  6   a   , a perspective view from obliquely above of the receiving head of a pipe welding machine according to the invention, in accordance with a preferred embodiment, in the partial  FIG.  6   b   , a frontal view of the receiving head and in the partial  FIG.  6   c   , a frontal view obliquely from the side of the receiving head and 
         FIG.  7    in the partial  FIG.  7   a   , a view from behind of the receiving head in viewing direction A according to  FIG.  6   c    and in partial  FIG.  7   b   , a view from behind of a pipe receiver head of a pipe welding machine according to the invention, in accordance with a further preferred embodiment. 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    shows a specific view of a pipe welding machine  10  according to the invention, which has a welding unit  12  and a pipe receiver  14 . The welding unit  12  may be arranged in a driver&#39;s cabin  15 . The pipe receiver  14  comprises a distal end  16 , which is spaced apart from the welding unit  12 , and a proximal end  18 . The pipe receiver  14  is fixed at the proximal end  18  to a chassis  20  of the pipe welding machine  10 . An elevation of the proximal end  18  can be changed by means of a movement device  22 . 
     The pipe welding machine  10  has a running gear  24  that is driven by a motor  26 , for example a diesel motor. The pipe welding machine  10  is therefore self-propelled. In the present case, the running gear  24  is designed as a chain drive, so that the pipe welding machine  10  can also be referred to as a weld bead. 
       FIG.  2    shows a perspective view of the pipe receiver  14 . It should be noted that the movement device  22  is designed as a hydraulic drive and features a first hydraulic cylinder  28 . 1 . A height h 18  of the proximal end  18  can be changed by means of the first hydraulic cylinder  28 . 1 . Alternatively, a ball screw drive by an electric motor can also be used, for example. 
     When the first hydraulic cylinder  28 . 1  is extended, a swing arm  30  pivots upward, thereby increasing the height h 18 . The height h 18  is the distance of the proximal end  18  from the ground B on which the pipe welding machine  10  stands. The height h 18  corresponds to a z coordinate in a coordinate system  30  in which the x axis and y axis extend horizontally and at the height of the ground. 
     Extending the hydraulic cylinder  28 . 1  increases the height h 18  of the distal end  16 . 
     The pipe welding machine  10  comprises a pipe centering  32 , which could also be referred to a pipe centering device. The pipe centering  32  features a first support roller  34 . 1  and a second support roller  34 . 2 . The two support rollers  34 . 1 ,  34 . 2  extend at a respective support roller angle σ 1 , σ 2  to the horizontal H (see  FIG.  3   b   ). The support rollers  34 . 1 ,  34 . 2  form a concave support structure for a pipe  36 . The support roller angle σ is measured from the upper edge of the respective support roller to the horizontal H. Only if the support roller is cylindrical does it coincide with the angle between the rotational axis and the horizontal H. 
     The pipe centering  32  features a first guide roller  38 . 1  and a second guide roller  38 . 2 , which are depicted by the dashed line. The two guide rollers  38 . 1 ,  38 . 2  are inclined at a respective guide roller angle φ 1 , φ 2  to the horizontal H. The guide rollers  38 . 1 ,  38 . 2  are fixed to a yoke  40 , the position of which in relation to the support rollers  34 . 1 ,  34 . 2  can be changed by means of a second hydraulic cylinder  28 . 2 . This allows the centering inner circle diameter of a centering inner circle to be adjusted. The centering inner circle corresponds to the outer diameter of the pipe  36  that is touched by all support and guide rollers  34 . 1 ,  34 . 2 ,  38 . 1 ,  38 . 2 . 
     As shown in  FIG.  2   , the pipe receiver  14  features a foot section  42  at the distal end  16 , which is hinged on a main section  44 . The main section  44  is fixed to the chassis  20 . By means of a hydraulic cylinder  28 . 5 , the foot section  42  can be pivoted relative to the main section  44 . 
     The pipe receiver  14  features a plurality of rollers  45 . i  (i=1, . . . , N; 2&lt;N&lt;200, here N=8) that form a roller conveyor. The support rollers  34 . 1 ,  34 . 2  are arranged in extension of the roller conveyor  46 . An imaginary pipe resting on the rollers  45 . i  can roll onto the support rollers  45 . i , preferably without constraining forces that lead to a buckling load of the pipe. 
       FIG.  1    shows that the welding unit  12  has a welding axis A S  that, as a rule, extends horizontally. The welding axis A S  is located at a welding axis height h A  above the ground. When the welding unit  12  welds a pipe (see  FIG.  2   ) to a pipeline part  56 , which may rest on a pipeline guide  58 , the longitudinal axis, i.e. the cylinder axis of the pipe extends at welding axis height h A . By means of the movement device  22  shown in  FIG.  2   , a pipe can always be positioned relative to the welding unit in such a way that a pipe longitudinal axis A R  coincides with the welding axis A S . The pipe receiver  14  has a pipe receiver longitudinal axis A 14 , which corresponds to the pipe longitudinal axis A R  when the pipe  36  rests on the pipe receiver  14 . 
     For receiving the pipe  36 , a machine control unit  47  drives the movement device  22  in such a way that the hydraulic cylinder  28 . 1  initially retracts. This reduces the height h 16  of the distal end  16  until it rests on the ground B. An angle of inclination ν 14  between the main section  44  of the pipe receiver  14  and the horizontal H is then ν 14 =10°, for example. The angle of inclination is determined by means of a pipe that has been received by the pipe receiver  14  on the main section  44 . 
     In  FIG.  2   , the foot section  42  and the main section  44  are depicted in their unfolded position, in which they are arranged behind each other. To facilitate transportation of the pipe welding machine  10 , the foot section  42  can be folded up into a folded position: it then extends along the main section  44 . Compared to the angular position in the folded position, the foot section  42  in the unfolded position is pivoted by approximately 180°. 
     During operation, the machine control unit drives the running gear  24  in such a way that the pipe welding machine  10  moves forwards in a direction of travel F towards the pipe  36 . This pushes the pipe  36  onto the foot section  42 . To protect a face of the pipe  36 , it is advantageous to lift the face of the pipe  36  by means of a pipe lifter  50 . 
       FIG.  2    shows that the pipe lifter  50  has two contact bodies  52 . 1 ,  52 . 2 , which are spaced apart from each other transversely to the longitudinal direction of the pipe. By means of at least one contact body drive  54 . 1  (see  FIG.  3   ), which is, for example, a hydraulic cylinder, the contact bodies  52 . 1 ,  52 . 2  can be moved towards each other. This lifts the pipe  36 . When the pipe welding machine  10  continues to move forward, the pipe  36  then moves onto rollers  55 . j  (j=1, 2, 3, 4) of the foot section  42 . The rollers  55 . j ,  45 . j  and the support rollers  34 . i  form a support for the pipe  36 . 
     As an option, the hydraulic cylinders  28 . 1 ,  28 . 2  can be subsequently extended. This reduces the angle of inclination ν 14 . The pipe welding machine  10  now continues to move forward until the pipe is received on the pipe receiver  14 . It is possible, but not necessary, for the pipe to rest across its entire length on the pipe receiver  14 . 
     Subsequently, the hydraulic cylinders  28 . 1 ,  28 . 2  can continue to be extended until the entire pipe receiver  14 , i.e. the main section  44 , assumes an angle of inclination of ν&gt;0°, for example. The pipe  36  located on the pipe receiver  14  then slopes downward towards the proximal end  18  and pushes in this direction. However, it is also possible that the inclination of the pipe receiver  14  remains unchanged, while the pipe  36  is pushed upwards onto the pipe receiver  14 . 
     The extension of the hydraulic cylinders  28 . 1 ,  28 . 2  also raises the pipe  36 , so that its pipe longitudinal axis A R  coincides with the welding axis A S . The pipe is subsequently welded to the existing pipeline section, i.e. a pipe end of a pipeline section, by means of the welding unit. 
       FIG.  3    shows that the first contact body  52 . 1  comprises a first wheel  70 . 1 , which is rotatably mounted about a first wheel rotational axis D 70.1 . The second contact body  52 . 2  has a second mounted wheel  70 . 2 , which is rotatably mounted about a second wheel rotational axis D 70.2 . As an option, the contact bodies  52 . 1 ,  52 . 2  may each feature at least one additional wheel  70 . 3 ,  70 . 4 , which are rotatably mounted about corresponding rotational axes D 70.3 , D 70.4 . In the present case, the wheels  70 . k  are designed to be spherical. However, this is not essential. 
     The rotational axis D 70.1  of the first wheel  70 . 1  extends at an angle of attack α 1 , (see  FIG.  4   a   ). The rotational axes D 70.k  of the remaining wheels  70 . k  extend accordingly at an angle of attack α k . It is preferable, but not necessary, for the angles of attack to be the same. In the present case, the angle of attack is α 1 =40°. 
     The first contact body  52 . 1  is linearly guided by means of a first contact body longitudinal guide  72 . 1  (see  FIG.  3   ). When the first contact body drive  54 . 1  is activated, the first contact body  52 . 1  moves towards the second contact body  52 . 2  as well as in the proximal direction, i.e. towards the driver&#39;s cabin  15 . 
     Accordingly, the second contact body  52 . 2  is linearly guided by means of a second contact body longitudinal guide  72 . 2 . When the second contact body drive  54 . 2  is activated, the second contact body  52 . 2  also moves towards the first contact body  52 . 1  as well as in the proximal direction. 
       FIG.  5    shows that in the present case, a first bevel angle β 1 , at which the first contact body longitudinal axis  72 . 1  extends to the pipe receiver longitudinal axis A 14  is β 1 =65°. In general, the bevel angle can lie between β 1 =30° and β 1 =120°, for example. In the present embodiment, the first bevel angle β 1  corresponds to a second bevel angle β 2 , at which the second contact body longitudinal guide  72 . 2  extends to the pipe receiver longitudinal axis A 14 . However, this is not essential. 
       FIG.  5    shows that a run-up skid  74 . 1  is arranged at the distal end of the contact body  52 . 1 . The run-up skid  74 . 1  features a run-up surface  76 . 1  that extends transversely to the horizontal plane. In the present case, the run-up surface  76 . 1  extends at a run-up surface angle of inclination of ν 76.1  to the horizontal plane (compare  FIG.  6   b   ). In the present case ν 76.1 =47°. The run-up surface angle of inclination ν 76.1  may lie between 30° and 60°, for example, or be greater or smaller. 
     When the pipe welding machine  10  moves towards the pipe  36  (see  FIG.  3   ), without the pipe  36  being lifted by the contact bodies  54 . 1 ,  54 . 2 , the face of the pipe  36  comes into contact with the run-up surface  76  and is raised in such a way that it is lifted onto the roller conveyor  46 . 
     However, this may cause the face to deform. This requires subsequent treatment, especially machining of the damaged parts of the face, which is time-consuming and therefore undesirable. During standard operation, therefore, the pipe  36  lifted by the contact bodies  52 . 1 ,  52 . 2  before it reaches the run-up skid  74 . 
     To facilitate the activation of the contact bodies  52 . 1 ,  52 . 2  for an operator, for example in the driver&#39;s cabin  15 , the pipe welding machine  10  can have a pipe position sensor  78 . The pipe position sensor  78  may be formed by or feature a camera  80 , for example. The camera records images that can be displayed on a screen  82  (see  FIG.  1   ), not depicted, in the driver&#39;s cabin. Alternatively or additionally, the camera is equipped with an image recognition system, by means of which a position of the pipe  36  relative to the pipe receiver  14  can be detected. 
     The pipe position sensor  78  may also feature at least one light barrier  80 , depicted here by the dashed line. However, other pipe position sensors  78  are conceivable, such as those that measure tactilely or electrically. 
       FIG.  5    depicts the tilt angles γ 1 , γ 2  between a projection of the wheel rotational axis D 70.1  or D 70.2  onto the horizontal plane E h  on the one hand and a projection of the pipe receiver longitudinal axis onto the horizontal plane E h  on the other. The tilt angles γ 1 , γ 2  are preferably 90±15°. 
       FIG.  4   a    shows a side view of the foot section  42 .  FIG.  5    is the section along the line A-A. 
       FIGS.  6   a  and  6   b    show that the first linearly moveable contact body  52 . 1  comprises a first base body  84 . 1 . The second linearly moveable contact body  52 . 2  has a second base body  84 . 2 . Both base bodies  84 . 1 ,  84 . 2  are made of metal, for example, in particular steel or aluminum. 
     A scratch-protection  86 . 1  is arranged on the first base body  84 . 1 . In the present case, the scratch protection  86 . 1  comprises multiple scratch protection elements  88 . 1 . 1 , . . . ,  88 . 1 . 6 , each of which is made of hard rubber that has been vulcanized onto a support strip. The anti-scratch material, for example the hard rubber in the present case, preferably exhibits a hardness of 22 to 40 Shore D. 
     The scratch protection elements are screwed to the base body  84 . 1 . Accordingly, a scratch protection  86 . 2  is arranged on the second base body  84 . 2  that is also made up of multiple scratch protection elements  88 . 2 . 1 , . . . . Parts of the surfaces of the scratch protection  86 . 1  and  86 . 2  form a contact surface  90  of the contact body  52 , in that the contact body comes into contact with the pipe  36  when it is lifted.  FIG.  6   c    shows a perspective view of the contact bodies  52 . 1 ,  52 . 2 . The contact bodies  52 . 1 ,  52 . 2  and the contact body longitudinal guide  72  form a receiving head  91 . 
       FIG.  7   a    depicts a view in viewing direction A. It should be noted that the first contact body  52 . 1  is connected for movement purposes by means of the first drive  54 . 1 , here in the form of a hydraulic cylinder. The second contact body  52 . 2  can be moved by means of the second drive  54 . 2 , here in the form of a second hydraulic cylinder. 
       FIG.  7   b    depicts an alternative embodiment of the receiving head  91  with a concavely curved contact surface  90 . A sliding cylinder radius R 90  of a sliding cylinder  94  corresponds in particular at least to the nominal diameter R 36  of the pipe  36 . In the present case, the sliding cylinder radius R 90  is 1.05 times a nominal diameter R 36 . 
     
       
         
           
               
             
               
                   
               
               
                 Reference list 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 10 
                 pipe welding machine 
               
               
                   
                 12 
                 welding unit 
               
               
                   
                 14 
                 pipe receiver 
               
               
                   
                 15 
                 driver&#39;s cabin 
               
               
                   
                 16 
                 distal end 
               
               
                   
                 18 
                 proximal end 
               
               
                   
                 20 
                 chassis 
               
               
                   
                 22 
                 movement device 
               
               
                   
                 24 
                 running gear 
               
               
                   
                 26 
                 motor 
               
               
                   
                 28 
                 hydraulic cylinder 
               
               
                   
                 30 
                 coordinate system 
               
               
                   
                 32 
                 pipe centering 
               
               
                   
                 34 
                 support roller 
               
               
                   
                 36 
                 pipe 
               
               
                   
                 38 
                 guide roller 
               
               
                   
                 40 
                 yoke 
               
               
                   
                 42 
                 foot section 
               
               
                   
                 44 
                 main section 
               
               
                   
                 45 
                 roller 
               
               
                   
                 46 
                 roller conveyor 
               
               
                   
                 47 
                 machine control unit 
               
               
                   
                 48 
                 hydraulic unit 
               
               
                   
                 50 
                 pipe lifter 
               
               
                   
                 52 
                 contact body 
               
               
                   
                 54 
                 contact body drive 
               
               
                   
                 56 
                 pipeline section 
               
               
                   
                 58 
                 pipeline guide 
               
               
                   
                 70 
                 wheel 
               
               
                   
                 72 
                 contact body longitudinal guide 
               
               
                   
                 74 
                 run-up skid 
               
               
                   
                 76 
                 run-up surface 
               
               
                   
                 78 
                 pipe position sensor 
               
               
                   
                 80 
                 camera 
               
               
                   
                 82 
                 screen 
               
               
                   
                 84 
                 base body 
               
               
                   
                 86 
                 scratch protection 
               
               
                   
                 88 
                 scratch protection element 
               
               
                   
                 90 
                 contact surface 
               
               
                   
                 91 
                 receiving head 
               
               
                   
                 α 
                 angle of attack 
               
               
                   
                 β 
                 bevel angle 
               
               
                   
                 γ 
                 tilt angle 
               
               
                   
                 ν 76   
                 run-up surface angle of inclination 
               
               
                   
                 ν 14   
                 angle of inclination 
               
               
                   
                 A 
                 viewing direction 
               
               
                   
                 A 14   
                 pipe receiver longitudinal axis 
               
               
                   
                 A R   
                 pipe longitudinal axis 
               
               
                   
                 A s   
                 welding axis 
               
               
                   
                 B 
                 ground 
               
               
                   
                 D 70.k   
                 wheel rotational axis 
               
               
                   
                 D 
                 centering inner circle diameter 
               
               
                   
                 D 64   
                 cradle rotational axis 
               
               
                   
                 E h   
                 horizontal plane 
               
               
                   
                 F 
                 direction of travel 
               
               
                   
                 H 
                 horizontal 
               
               
                   
                 h 16   
                 elevation 
               
               
                   
                 h A   
                 welding axis height 
               
               
                   
                 j 
                 running index of rollers 
               
               
                   
                 j 
                 running index of rollers 
               
               
                   
                 k 
                 running index of wheels 
               
               
                   
                 K 
                 centering inner circle 
               
               
                   
                 R 
                 direction of movement 
               
               
                   
                 R 90   
                 sliding cylinder radius 
               
               
                   
                 R 36   
                 nominal diameter 
               
               
                   
                 v 
                 angle of inclination