Patent Application
20140091129
The present disclosure is related to a welding system, and more particularly, to products, methods, and systems to remotely circumferentially weld cylindrical joints of objects during rotation.
Cylindrical objects often require welds on their interior or exterior circumference. Such cylindrical objects, for example, include pipes, tanks, and the like. Welds are used, for example, to connect two cylindrical objects, seal a cylindrical object, repair a cylindrical object, apply cladding and the like. It is common that remote welding tractors are used within the confined interior space or upon exterior locations of a cylindrical object. To complete a weld, welding tractors travel about the circumference of the cylindrical object. To keep these tractors in contact with the surface of the cylindrical object, the cylindrical object is often rotated about its longitudinal axis. Therefore, the welding tractor maintains its original location in relation to the cylindrical object by moving in the opposite direction and at the same speed as the rotation of the cylindrical object.
Often the cylindrical object is supported and stabilized by two rollers at its base. These rollers rotate forcing the cylindrical object to rotate in the opposite direction. Friction between the rollers and the cylindrical object keep the cylindrical object in motion. To rotate the cylindrical object, the rollers begin rotating from a stopped position. Therefore, the rollers and cylindrical objects rotate at variable speeds. These variable speeds can be experienced before, during, and after welding operations.
In current applications, the welding tractor, which is typically positioned within the cylindrical object before rotation begins, is manually controlled to maintain the correct position. This manual control requires an operator to constantly watch the system and immediately react when changes in the rotational speed of the rollers or the cylindrical object occur. A change in rotation can cause the welding tractor to upset or unsteadily rock from its position on the cylindrical object. Moreover, this may results in unsatisfactory or incomplete welds. In view of these and other deficiencies products, methods, and systems are needed to self-level a welding tractor on or within a cylindrical object during welding operations.
To remotely circumferentially weld a cylindrical object, a welding tractor may be positioned within or on top of a cylindrical object. The welding tractor includes a base. In operative association with the base is a welding assembly, a wire reel assembly, a level sensor, a motor, and wheels. The wire reel assembly supplies welding wire to the welding assembly. The welding assembly welds the cylindrical object. The level sensor determines the levelness of the welding tractor in association with the cylindrical object. This levelness is communicated by the level sensor to a controller. This controller is located in operative association to the base of the welding tractor or in a remote location. This controller uses the angle of inclination or declination of the welding tractor to operate the motor to maintain said angle as close to 0° as possible using the degree of mechanical sophistication normally associated with circumferential welding equipment. The motor drives the wheels rotatably connected to the base of the welding tractor. The wheels are positioned on the base so to support the welding tractor and each of its components above the surface of the cylindrical object. Further, the wheels are each facing the same direction moving the welding tractor in a forward direction.
To travel the entire circumference of the cylindrical object a means for rotating the at least one cylindrical object is applied. One example includes supporting and stabilizing a cylindrical object by placing the cylindrical object upon rollers. Friction between the rollers and the cylindrical object force the cylindrical object to rotate in the opposite direction. As the cylindrical object rotates, the aforementioned welding tractor remains stationary and circumferentially welds the inside of the cylindrical object. To maintain the position of the welding tractor, the forward moving speed of said welding tractor varies as the rotational speed of the rollers and the cylindrical object vary.
In one aspect, a level sensor communicates the levelness of the welding tractor to a controller located on the welding tractor. The controller adjusts the speed of the welding tractor maintaining the position of the welding tractor. As this welding tractor maintains its position, the cylindrical object rotates beneath the welding tractor. The controller adjusts the speed of the welding tractor as the cylindrical object's rotational speed varies.
In another aspect, a level sensor communicates the position the welding tractor to a controller located remotely and communicating with the level sensor and the motor through either a cable or wireless protocol. The controller may be one of a tablet, a cellular phone, a global positioning system and a laptop computer. Using a wireless protocol, the controller maintains the desired speed of the welding tractor by operating the motor thus driving the wheels.
This brief description is provided to introduce a selection of concepts in a simplified form that are further described herein. This brief description is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Furthermore, the claimed subject matter is not limited to implementations that solve any or all disadvantages noted in any part of this disclosure.
Reference is made to the accompanying drawings in which particular embodiments and further benefits of the invention are illustrated as described in more detail in the description below, in which:
Referring now to the figures, several embodiments or implementations of the present invention are hereinafter described in conjunction with the drawings, wherein like reference numerals are used to refer to like elements throughout. The present disclosure is related to a self-leveling welding tractor for welding about the circumference of a cylindrical object. Although illustrated and described hereinafter in the context of various exemplary welding products, methods, and systems, the invention is not limited to the illustrated examples.
Welding tractor 110 includes base 150, welding assembly 160, wire reel assembly 170, level sensor 140, motor 190 and at least two wheels 200. Welding assembly 160 applies weld 240 to cylindrical object 120. Wire reel assembly 170 supplies welding wire 220 to welding assembly 160. As illustrated in
Level sensor 140 identifies and communicates the degree of horizontal planarity of welding tractor 110 to controller 210. Controller 210 may be in operative association with the base 150 or in a remote location wherein controller 210 is, for example, a tablet, a cellular phone, a global positioning system, or a laptop computer. Controller 210 further communicates with and operates motor 190 through a wire or wireless interface. Controller 210 operates motor 190 in response to the welding tractor's 110 levelness communicated to controller 210 by level sensor 140. Motor 190 drives at least one wheel 200 forcing welding tractor 110 forward thus maintaining a levelness of the welding tractor 110 as cylindrical object 120 rotates in the opposite direction. Concurrently or on demand, weld reel assembly 170 supplies welding wire 220 to welding assembly 160, and welding assembly 160 applies weld 240 to cylindrical object 120.
In this example, welding tractor 110 is at least partially placed inside cylindrical object 120. In the alternative,
As illustrated in
As additionally illustrated in
Another embodiment for welding a cylindrical object 120 includes placing an oval object on at least two rollers 130 positioned below the horizontal centerline of the oval object. Rollers 130 are positioned apart a distance less than the shortest axis of symmetry of the oval object. Additional rollers 130 can be used to further stabilize an oval object.
While the focus of the previous discussion has been on monitoring the position of welding tractor 110 in a level or horizontal position, the invention is not limited to the above. Rather the invention encompasses monitoring welding tractor 110 at a predefined angle of inclination or declination, and holding this angle essentially constant during the circumferential welding process. In a preferred embodiment the predefined angle is 0°, although both positive and negative angles from horizontal are within the scope of this invention, varying at least between +30° to −30° from horizontal, but within the confines of sound engineering judgment.
In practicing the process of the invention, a method for circumferentially welding at least one cylindrical object is described in which at least the following steps are employed: inserting a welding tractor into a cylindrical object for performing a circumferential welding operation, the welding tractor comprising a base, a welding assembly in operative associated with the base, a wire reel assembly in operative associated with the base for supplying welding wire to the welding assembly, and a level sensor in operative association with the base for determining the angle of inclination or declination of the welding tractor; rotating the cylindrical object about its longitudinal axis; continuously monitoring the angle of inclination or declination of the welding tractor; and generating a signal proportional to the magnitude of said angle of inclination or declination of said welding tractor; interfacing said signal with at least one drive wheel on said welding tractor to control a speed of said at least one drive wheel responsive to said signal to maintain said speed of said welding tractor so that said angle of inclination or declination is essentially 0°. The step of interfacing is often wireless.
There are instances when the angle of inclination or declination is sought to be maintained at a predefined angle, which may vary from +30° and −30° with respect to a horizontal plane. In this instance, the angle of inclination or declination of the welding tractor is continuously monitored, and a signal is generated proportional to the magnitude of the difference between the angle of inclination or declination of the welding tractor and the predefined angle. The signal is interfaced with at least one drive wheel on the welding tractor to control the speed of said at least one drive wheel responsive to the signal to maintain the speed of the welding tractor so that the difference between the angle of inclination or declination and the predefined angle is essentially 0°.
While the above discuss has focused on proportionately matching the rotational speed of the pipe to the rotational speed of the welding tractor wheels, the invention is not limited to such. In fact, in an alternative embodiment, powered cross slides are employed in place of wheels and the angle of the torch and/or position of the welding tractor positioned on a cross slide is controlled by communication with a level sensor positioned directly (or indirectly) within the pipe. The communication is either wired or wireless as discussed hereinabove.
In a preferred embodiment, controller is a PID controller (Proportional Integral Derivative controller). Proportional means that there is a linear relationship between two variables. Proportional control is an excellent first step, and will reduce, but never eliminate, the steady-state error and typically results in an overshoot error. To improve the response of a proportional controller, integral control is often added. The integral is the running sum of the error. Therefore, the proportional controller tries to correct the current error and the integral controller attempts to correct and compensate for past errors. The derivative controller attempts to predictively correct error into the future. That means that the error is expected to be the current error plus the change in the error between the two preceding sensor sample values. The change in the error between two consecutive values is the derivative. While a PID controller is preferred, the system will benefit from the use of just a proportional controller, a proportional-integral controller, or a proportional-derivative controller.
This written description uses examples to disclose the invention, including the best mode, and also to enable one of ordinary skill in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that are not different from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.
