Patent Description:
Such a device is intended to machine large objects. For example it may be used to machine flanges of tubular elements for forming for example industrial vessels, pylons for wind turbines or power pylons. For example tubular elements for pylons comprise a rolled tube (shell), varying in diameter between approximately <NUM> and approximately <NUM>, and with a length between <NUM> and <NUM>. A flange of approximately <NUM> thickness is provided at the pipe end, which is connected to the shell by welding. The flange is used to interconnect the tubular element with another tubular element to form the pylon. This flange is machined before welding and meets the required tolerance. However, as a result of the welding of the flange against the tube, a material deformation occurs, with the result that the flatness of the ring-shaped flange often no longer satisfies the required tolerance. Due to the fact that the tube is rolled from raw material, the roundness of the tubular element is not sufficiently accurate to use it as a reference for a clamping process for machining the welded flange. Moreover it is complex to deal with a large, heavy product that is difficult to handle, which must be machined.

In <CIT> a machining assembly is disclosed which has a positioning frame, including a so called "spider", having a plurality of legs. The legs have a screw threaded locking bolt to engage with an internal surface of a pipe, so as to hold the positioning frame fixed inside the pipe. The locking bolts are adjustable to locate the spindle of the support frame at the centre of the pipe. A facing arm is fixed to the spindle. A cutting tool associated with the facing arm is brought in engagement with the surface to be machined. By virtue of the rotation of the spindle the surface is machined.

Such a machining assembly is currently used to machine flanges of relatively large tubular elements. However, it is a dangerous process for the operators, since these machines are not shielded. Furthermore these on-site machining assemblies are difficult to install, must be accurately set and aligned, which takes a lot of time and entails large costs. The result is not always optimal due to the vibration of the unstable cutting tool support. The costs of this machining method are very high.

<CIT> discloses an apparatus according to the preamble of claim <NUM> for surface finishing a flange surface of a pipe. The apparatus moves automatically circumferentially along the flange. It has flange surface rollers that engage the flange surface to be machined at the radially outer circumferential edge region of the flange. Furthermore it has a balance roller that engages the flange surface near a radially inner circumferential edge region of the flange. A power tool having a surface finishing attachment, such as an abrasive disc or brush is provided. The surface finishing attachment is located rearwadly or in front of the flange surface rollers and the balance roller, depending on the direction of movement of the device in the circumferential direction. Examples of surface finishing operations performed by the power tool may include stripping, cleaning, deburring, sanding, grinding, cutting, polishing and the like. This apparatus is not suitable for removing unevenness in the flange surface.

The invention has for an object to provide a simple machining assembly to remove unevenness of circular workpiece surfaces.

This object is achieved by a machining assembly according to claim <NUM>.

The first subframe is used to roughly position the positioning frame against the surface to be machined. The position of the second subframe is adjustable with respect to first subframe. Seen in the direction of movement, the machining head is located between a pair of second support rollers. In an embodiment wherein the pair of rolls flanking the machining head is provided on the second subframe, this allows that the pair of support rollers can be placed and maintained in engagement with the surface to be machined, also when said surface contains unevenness. In another possible embodiment the pair of rollers flanking the machining head is provided on the first subframe. In such an embodiment the first subframe may have some flexibility to allow the support rollers to engage the surface to be machined, while the machining head can be brought in engagement with said surface via the adjustability of the second subframe and then the second subframe can be fixed with respect to the first subframe in that position. In any case, the pair of rollers and the machining head lie in a flat imaginary plane. If the surface to be treated is perfectly flat, the imaginary flat plane is parallel to the surface to be treated and no material will be cut or grinded away. However if the surface is uneven, which is initially the case in practise, the flat imaginary plane will change its inclination in the circular direction with respect to the surface because the pair of rollers follow the uneven surface. At some point the unevenness will end up between the pair of rollers whereby the machining head will engage and machine the uneven surface. At every pass of the entire circular surface by the machining assembly the unevenness will be reduced. After one or more passes by the machining head the surface will be sufficiently flat to satisfy the required tolerance.

In a possible embodiment the positioning frame comprises a console, wherein the console and the first subframe are connected by a first hinge having a first hinge axis. In a further embodiment the first subframe and the second subframe are interconnected by a second hinge having a second hinge axis. In an embodiment having said first hinge and said second hinge, the first hinge axis and second hinge axis are preferably perpendicular. In a possible embodiment the first hinge axis extends in vertical direction and the second hinge axis extends in horizontal direction.

The first hinge allows that the first support rollers can be placed against the circular surface, although this surface may be uneven and contain a waviness. Also, the machining assembly may initially not be exactly aligned with the surface to be machined but will engage initially with one of the first rollers on the surface to be machined, and then by the hinging action at the first hinge the support frame can tilt such that also the other one of the first rollers engages the surface.

A possible embodiment furthermore comprises a top support member from which the console is hingedly suspended by a third hinge, wherein the third hinge has a hinge axis parallel to the hinge axis of the second hinge.

With this top support member the machining assembly may be arranged to a vehicle or other movable support, whereby the assembly can be moved towards and from the workpiece to be machined. In a practical example the top beam may for example be arranged on the fork of a forklift truck and suspended in front of the workpiece. The forklift truck drives forward such that the first support rollers are brought near or against the circular surface to be machined.

In a possible embodiment a first actuator is arranged between the top beam and the console to move the positioning frame towards the workpiece surface and bring the first support rollers in engagement with the workpiece surface.

With the first actuator the machining assembly can be positioned roughly against the workpiece in a controlled manner.

In a possible embodiment a second actuator is arranged between the console and the second subframe to bring the second support rollers in engagement with the workpiece surface.

With the second actuator the second support rollers can be brought in engagement with the workpiece surface and possibly also the machining head.

In a practical embodiment the machining device may be a belt sander.

A belt sander is a relatively low cost device which allows a relatively easy machining of the surface to be machined. The direction of movement of the belt of the belt sander may be oblique with respect to the imaginary flat plane between the second rollers.

In a possible embodiment the position of the first support rollers is adjustable on the first subframe and the position of the second support rollers is adjustable on the first subframe or the second subframe. This enables the positioning frame to be adapted to different diameters of the workpiece surface.

In a possible embodiment the second support rollers are arranged on the first subframe, and a depth adjustment device is arranged between the first subframe and the second subframe to adjust the position of the machining device so as to bring the machining head in the imaginary flat plane defined by the pair of second support rollers.

In a possible embodiment a universal joint is attached to the first subframe. This allows to suspend the frame in a horizontal way above an upstanding tubular element, whereby by the universal or cardanic joint, the first and second support rollers can be brought in engagement with the surface to be machined. The universal joint can be coupled to a rotatable spindle, which can be driven to rotate the positioning frame. The workpiece is then maintained stationary and the machining assembly is rotated around the centre axis of the circular surface. By the universal or cardanic joint the first subframe can set and maintain itself in position with the support rollers against the surface to be machined.

The invention also relates to a method for machining a circular workpiece surface making use of a machining assembly as described in the above, wherein the machining assembly is maintained stationary and the workpiece is rotated around the centre axis of the circular surface.

In practise the tubular element may have a diameter between approximately <NUM> and approximately <NUM>, and with a length between <NUM> and <NUM>. These tubular elements are positioned in a lying fashion on a manipulator, which includes manipulator rollers which support the tubular element and are adapted to rotate the tubular element around its axis. The manipulator may be part of a carriage which can be used to transport the tubular element around the manufacturing site towards different processing units. The machining assembly can thus be positioned against the circular surface of the flange of the tubular element, as described in the above, and then the tubular element can be rotated by driving the manipulator rolls such that the circular surface to be machined passes the machining head. The circular surface may pass the machining head one or more times, during which unevenness or "waviness" is gradually removed by the machining head.

The invention also relates to a method for machining a circular workpiece surface making use of a machining assembly as described in the above, wherein the workpiece is maintained stationary and the machining assembly is moved around the centre axis of the circular surface.

The invention will be further explained in the following description with reference to the drawing, in which:.

In <FIG> is shown schematically a tubular element <NUM>. On an end of the tubular element <NUM> a flange <NUM> is welded. The tubular element <NUM> may be assembled with other similar tubular elements by means of the flanges which are bolted together. By interconnection two or more of the tubular elements <NUM> for example a pylon, such as a pylon for a wind turbine or a power pylon may be assembled. The tubular element <NUM> is made by rolling steel plates and may have in practise a diameter within a range of approximately <NUM> and <NUM>. The tubular element may in practise have a length between <NUM> and <NUM>. The flange <NUM> may have approximately a thickness of <NUM>. It is noted that the mentioned dimensions are merely intended to be indicative for the order of magnitude and should not be considered as limiting.

Such relatively large tubular elements <NUM> are moved around the manufacturing sites on a carriage <NUM> which is provided with rows <NUM> of manipulator rollers <NUM>. The manipulator rollers <NUM> support the tubular element <NUM>. The manipulator rollers <NUM> are rotatable around their central axis and are driven by suitable drive means. By rotating the manipulator rollers <NUM> the tubular element <NUM> can be rotated around its central axis and manipulated such that it can be machined or worked on otherwise.

The tubular elements <NUM> are made by rolling and welding and are not perfectly round. In the circumference a certain waviness may occur which is indicated schematically at <NUM>. Therefore the tubular wall of the tubular element <NUM> cannot be used as a reference for further machining.

The flange <NUM> is basically a steel ring which is machined to flatten it to satisfy a certain tolerance range. However, the flange <NUM> is welded afterwards to the end of the tubular element <NUM>. Due to the welding operation the flange <NUM> will be deformed and will show a certain waviness or unevenness in the abutment surface <NUM> with which it abuts an opposing flange <NUM> when assembled to form for example a pylon. The flatness or evenness of the abutment surface <NUM> of the flange <NUM> must satisfy a certain tolerance range, because otherwise the abutment surfaces <NUM> of the flanges <NUM> do not form a tight seal in the assembled state whereby water may reach the bolts with which the flanges <NUM> are tightened together and corrosion issues will arise in the flange structure. Furthermore, when the flanges do not form a tight seal during the installation of the bolts, unwanted forces will rise in the flange connection during this process. These forces can result in unacceptable peak forces in the material, and possible lifetime reduction in the flange connection. Moreover, too much bolt-load will be lost in closing the gap due to a non-tight sealing of the flanges, instead of creating a pretension in the flange connection.

In <FIG> is shown that a forklift truck <NUM> is positioned in front of the end of the tubular element <NUM>. The forklift truck <NUM> has a fork <NUM> which carries a machining assembly <NUM> according to the invention. The machining assembly <NUM> is used to machine the abutment surface <NUM> of the flange <NUM> to remove the unevenness.

The machining assembly <NUM> in this example comprises a positioning frame <NUM>. The positioning frame comprises a first subframe <NUM> and a second subframe <NUM>. The first subframe <NUM> comprises arms <NUM> which are provided with first support rollers <NUM> adapted to roll over the circular abutment surface <NUM> to be machined in a circular direction. Furthermore the first subframe comprises legs <NUM> which are provided with second support rollers <NUM> to roll over the circular surface <NUM> to be machined.

The position of the first and second support rollers <NUM> and <NUM> is preferably adjustable on the arms <NUM> and legs <NUM> of the first subframe <NUM> so as to be able to adapt the positioning frame <NUM> to different flange diameters.

The positioning frame <NUM> furthermore comprises a console <NUM>. The console <NUM> and the first subframe <NUM> are connected by a first hinge <NUM> having a vertical hinge axis. The first subframe <NUM> and the second subframe <NUM> are interconnected by a second hinge <NUM> having a horizontal hinge axis. The position of the second subframe <NUM> with respect to the first subframe <NUM> is adjustable by rotating the second subframe <NUM> with respect to the first subframe <NUM> around the second hinge <NUM>.

The legs <NUM> of the first subframe are interconnected by a bridge part <NUM>. The bridge part <NUM> and the second subframe are interconnected by an adjustment member <NUM>, which may be embodied as a threaded spindle by which the depth position of a machining device <NUM>, which is arranged on the second subframe <NUM>, as will be described below, may be adjusted.

The machining assembly comprises a top support member <NUM>, which in the embodiment shown in the figures is embodies as a plate. The console <NUM> is hingedly connected to the top support member <NUM> by a third hinge <NUM>. The third hinge <NUM> has a hinge axis parallel to the hinge axis of the second hinge. When the top support member is <NUM> attached to the fork of the forklift and lifted, the positioning frame <NUM> is suspended from the third hinge <NUM> which extends approximately in the horizontal direction.

A first actuator <NUM> is arranged between the top support member <NUM> and the console <NUM> to move the positioning frame towards the workpiece surface <NUM> and bring the first support rollers <NUM> in engagement with the workpiece surface <NUM>.

A second actuator <NUM> is arranged between the console <NUM> and the second subframe <NUM> to move the second subframe forward. Via the bridge part <NUM> and the spindle <NUM> the legs <NUM> of the first subframe <NUM> are moved together with the second subframe <NUM>, such that the second support rollers <NUM> are brought in engagement with the workpiece surface <NUM>.

The first actuator <NUM> and second actuator <NUM> may in a practice be embodied as hydraulically or pneumatically operated cylinders.

A machining device <NUM> having a machining head <NUM> is arranged on the second subframe <NUM> such that the machining head <NUM> is located between the second support rollers <NUM> and such that the machining head <NUM> and the engagement surface of the second support rollers <NUM> lie in one flat imaginary plane, which imaginary plane is indicated in <FIG> with reference numeral <NUM>. In the embodiment shown in the figures the machining device <NUM> is a belt sander. One of the rollers <NUM> of the belt sander with the belt <NUM> running over it forms the machine head <NUM> in this embodiment. The machine head <NUM> can be brought in the flat imaginary plane defined by the pair of second rollers <NUM> by means of the adjustment spindle <NUM>.

The machining assembly can be positioned against the circular surface <NUM> of the flange <NUM> of the tubular element <NUM>, by initially approaching the flange with the forklift truck and suspending the positioning frame in front of the flange <NUM>. Next, the first subframe <NUM> is moved forward towards the flange surface <NUM> by means of the first actuator <NUM> until the first support <NUM> rollers are positioned against said surface <NUM>. The positioning frame is now roughly positioned against the flange <NUM> and is supported by the flange <NUM>. The vertical hinge <NUM> facilitates that the first support rollers <NUM> automatically find the engagement with the surface <NUM>. In a following stage the second subframe <NUM> is advanced towards the surface <NUM> by means of the second actuator <NUM>, whereby the lower end of the second subframe <NUM> tilts forward with respect to the first subframe <NUM>. Thereby the second support rollers <NUM>, which are located on the legs <NUM> of the first subframe <NUM>, and the machining head <NUM>, which is located at the lower end of the second subfame <NUM>, are brought in engagement with the surface <NUM> to be machined. This structure ensures that the second support rollers <NUM> are maintained in contact with the surface <NUM>.

In a next stage the tubular element <NUM> can be rotated by driving the manipulator rolls <NUM> such that the circular surface <NUM> to be machined passes the machining head <NUM>. The circular surface <NUM> may pass the machining head one or more times, during which unevenness or "waviness" is gradually removed by the machining head. This will be explained with reference to <FIG>.

In <FIG> the height profile of the surface <NUM> to be machined is shown vs. the position on the circumference of the surface. What is shown is that the surface <NUM> has a certain waviness with a maximum height X between the lowest and highest point. The lowest point is taken as a reference point.

The machining head <NUM> and the second support rollers <NUM> define a flat plane <NUM> as is visible in <FIG>. This flat plane <NUM> can be positioned against the surface <NUM> to be machined. If the surface <NUM> would be perfectly flat the flat plane <NUM> would have the orientation as is illustrated in <FIG> which is parallel to the flat surface <NUM>. However, as mentioned, the surface <NUM> is in practice not flat initially. When the surface <NUM> moves along the machining device <NUM>, the second support rollers <NUM>, which are located in front and behind the machining head in the direction of movement, will follow the height profile of the surface <NUM>. Thereby the orientation of the flat plane <NUM> changes and has a tilted orientation as is shown in <FIG>.

The effect of the changing orientation of the plane <NUM> is illustrated in <FIG>. On the wave profile of the surface <NUM> of <FIG> the flat plane <NUM> will at some points intersect with the wave profile of the surface <NUM> while the surface <NUM> passes the machining head <NUM>, and the machining head <NUM> will come in contact with the surface <NUM> and sand off some material of the surface <NUM>. Thereby the maximum height X of the profile relative to the lowest point will become smaller as is indicated in <FIG>. In the next revolution of the surface <NUM> the same effect takes place and the wave profile of the surface becomes smaller and smaller every rotation, which is illustrated in <FIG>. At some point the maximum height X of the surface profile of surface <NUM> is within the tolerance limits (e.g. <FIG>) and the machining process can be stopped.

In the <FIG> a vertical orientation of the framework is shown which is arranged to machine the flange of a lying tubular element. However, it is also possible to machine the flange of an upstanding tubular element <NUM>' which is shown in <FIG>. The tubular element <NUM>' has a flange <NUM>' which has an abutment surface <NUM>' which has to be machined to flatten it.

The machining assembly <NUM> in this example comprises a positioning frame <NUM>. The positioning frame <NUM> comprises a first subframe <NUM>. The first subframe <NUM> comprises two arms <NUM> provided with first support rollers <NUM> adapted to roll over the circular abutment surface <NUM>' to be machined in a circular direction. The first subframe <NUM> furthermore comprises legs <NUM> provided with second support rollers <NUM> to roll over the circular surface <NUM>' to be machined to move with the first subframe <NUM> in the circular direction. The arms <NUM> and legs <NUM> are connected and form an integral unit, i.e. the first subframe <NUM>.

The positioning frame <NUM> furthermore comprises a second subframe <NUM>. The first subframe <NUM> and the second subframe <NUM> are interconnected by a hinge <NUM> having a horizontal hinge axis. The position of the second subframe <NUM> with respect to the first subframe <NUM> is adjustable by rotating the second subframe <NUM> with respect to the first subframe <NUM> around the hinge <NUM>.

A machining device <NUM> having a machining head <NUM> is arranged on the second subframe <NUM> such that the machining head <NUM> is located between the second support rollers <NUM> and such that the machining head <NUM> and the engagement surface of the second support rollers <NUM> lie in one flat imaginary plane, which imaginary plane is indicated in <FIG> with reference numeral <NUM>. Thereto there is a depth adjustment device arranged, comparable to the depth adjustment device illustrated in the previous embodiment of <FIG>. In the embodiment shown in <FIG> the depth adjustment device comprises a bridge part <NUM> which interconnects the legs <NUM> and a threaded spindle <NUM> which extends through a threaded bore in the bridge part <NUM>.

In the embodiment shown in <FIG> the machining device <NUM> is a belt sander. One of the rollers <NUM> of the belt sander with the belt <NUM> running over it forms the machine head <NUM> in this embodiment.

The machining assembly <NUM> is suspended from a fixed suspension point <NUM> which has to be located above the centre of the circle defined by the circular flange <NUM>'. The connection between the positioning frame <NUM> and the fixed suspension point is formed by a rotational joint <NUM> and a universal joint <NUM> (cardan joint). In use the positioning frame <NUM> is rotated and the tubular element <NUM>' remains stationary. In the fixed suspension point a drive means such as an electrical motor can be incorporated to drive the rotational movement of the positioning frame <NUM>. Another option is to drive the rollers <NUM> electrically, pneumatically or hydraulically, in which case the rotational joint is only a suspension and rotation point.

Claim 1:
Machining assembly (<NUM>; <NUM>) for machining a circular workpiece surface, the machining assembly comprising:
- a positioning frame (<NUM>; <NUM>); and
- a machining device (<NUM>; <NUM>) connected to the positioning frame (<NUM>; <NUM>) including a machining head (<NUM>; <NUM>) movable along the circular surface to be machined, and adapted to engage and machine the surface to be machined,
wherein:
the positioning frame (<NUM>; <NUM>) comprises a first subframe (<NUM>; <NUM>) and a second subframe (<NUM>; <NUM>),
the first subframe (<NUM>; <NUM>) is provided with first support rollers (<NUM>; <NUM>) adapted to roll over the circular surface to be machined in a circular direction,
the second subframe (<NUM>; <NUM>) is coupled to the first subframe (<NUM>; <NUM>) such that the position of the second subframe (<NUM>; <NUM>) with respect to the first subframe (<NUM>; <NUM>) is adjustable, and
characterized in that the machining device (<NUM>; <NUM>) is arranged on the second subframe (<NUM>; <NUM>) such that the machining head (<NUM>; <NUM>) is located between a pair of second support rollers (<NUM>; <NUM>) in the direction of movement, said pair of second support rollers (<NUM>; <NUM>) being provided on the first subframe (<NUM>; <NUM>) or the second subframe (<NUM>; <NUM>), and such that the machining head (<NUM>; <NUM>) and the engagement surface of said pair of second support rollers (<NUM>; <NUM>) lie in one flat imaginary plane.