Patent Application
20110271734
This invention relates generally to pipe bending equipment and more particularly concerns machines used to bend steel pipe.
Known pipe bending machines level a pipe against a die with a pin-up located on one side of the die and apply force to the pipe on the other side of the die with a stiff-back, typically powered by hydraulic cylinders, to bend the pipe against the die. The maximum bend typically totals 15-16° and the total is achieved by sequential pulls. In each pull, the pipe is bent approximately ½°. Each pull results in a plastic deformation of the pipe. The cylinders of known machines apply the force directly to the stiff-back. Therefore, known machines generally require large diameter cylinders capable of generating forces in a range of 750,000 pounds. Typically, the cylinders required are in the range of 9-14″ in diameter. Such a requirement imposes serious limitations on capabilities of the machine.
First, the larger the diameter of the cylinder, the greater will be the likelihood of leakage and other defects in cylinder operation. Second, the maximum industry standard cylinder is 8″ in diameter. Therefore, cylinders for this application are currently custom made, usually at two to three times the cost of standard cylinders. Third, even though the custom cylinders are very large, known machines still require the use of tandem cylinders tied together. In this configuration, changes in cylinder orientation occur as the cylinders rotate in slightly different radii. This results in the cylinders competing with each other, reducing the net bending force available. In the worst such cases, the counteracting cylinders may bind. Fourth, the resulting reduced cylinder diameter to stroke ratio can cause the stiff-back to overshoot the intended bending angle of the pipe due to reduced controllability.
It is, therefore, an object of this invention to provide a pipe bending machine that will operate efficiently with standard size cylinders. Another object of this invention is to provide a pipe bending machine in which cylinders are not tied in a possibly competing configuration. It is also an object of this invention to provide a pipe bending machine that reduces the risks of overshooting intended bending angles.
In accordance with the invention, a pipe bending machine has a stiff-back which is driven by a pivoting wedge to provide a significant mechanical advantage against the stiff-back as the stiff-back rotates about its fulcrum.
The pipe bending machine employs a die, a trough pivoted on a first fulcrum, a bed pivoted on a second fulcrum, a wedge disposed between the trough and the pivoted bed and an actuator driving the wedge between the trough and the bed to bend a pipe seated in the trough against the die. Preferably, a linkage applies force from the actuator to the wedge in a direction parallel to a longitudinal axis of the trough.
Preferably, the die is fixed. The trough is pivoted on a first fulcrum about a first axis parallel to a pipe bending face of the die and perpendicular to a longitudinal axis of the pipe. The bed is pivoted on a second fulcrum about a second axis parallel to the first axis. The wedge is disposed between the trough and the pivoted bed. The actuator drives the wedge between the trough and the bed to rotate the trough in relation to the first fulcrum and bend the pipe seated in the trough against the pipe bending face of the die. The linkage applies force from the actuator to the wedge in a direction parallel to a longitudinal axis of the trough as the trough longitudinal axis rotates in relation to the first fulcrum.
Preferably, the pipe bending face is on a downstream portion of the die as the pipe is longitudinally transferred through the machine. The first fulcrum is downstream of the upstream portion of the pipe bending face and facilitates rotation about the first axis and perpendicular to the longitudinal axis of the pipe. The second fulcrum is downstream of the first fulcrum and facilitates rotation about a second axis parallel to said first axis.
According to the method for bending the pipe, the pipe is positioned in the trough which extends longitudinally downstream of the die for application by the die of a first force to one side of the pipe. A second force is exerted in a direction parallel to a longitudinal axis of the portion of the pipe positioned in the trough. The second force is converted into a third force applied to the longitudinal trough on the opposite side of the pipe than and downstream of the first force to bend the pipe against the first force. The third force is maintained in perpendicular relationship to the longitudinal axis of the portion of the pipe positioned in the trough as the pipe is bending against the die. If the pipe is to be bent in incremental steps, the pipe is then repositioned for application of the first force downstream of the previous application of the first force and the previous steps are repeated.
Preferably, the step of maintaining the third force perpendicular to the longitudinal axis of the portion of the pipe positioned in the trough is accomplished by the sub-steps of maintaining the second force parallel to the longitudinal axis of the portion of the pipe positioned in the trough as the pipe is bending against the die and maintaining the third force perpendicular to the second force.
Preferably, the pipe is fed longitudinally with respect to a fixed die and a trough, the trough being pivoted on a fulcrum on an upstream portion of the trough. Feeding of the pipe is stopped at a position in which a leading portion of the pipe is aligned with the trough on one side and a trailing portion of the pipe is aligned with the die on an opposite side. The wedge is driven between the downstream portion of the trough and the bed to pivot the trough about the fulcrum and bend the pipe against the die.
Preferably, the step of driving the wedge is accomplished by the sub-steps of exerting a force on the wedge in a direction parallel to a longitudinal axis of the portion of the pipe seated in the trough and maintaining the exerted force in parallel relationship to the longitudinal axis of the portion of the pipe seated in the trough as the pipe is bending against the die.
If the pipe is to be bent in incremental steps, the pipe is fed further in the downstream direction. The further feeding of the pipe is stopped at a second position in which a leading portion of the pipe is aligned with the trough on one side and a trailing portion of the pipe is aligned with the die on an opposite side. The wedge is driven between the downstream portion of the trough and the bed to pivot the trough about the fulcrum and bend the pipe against the die. The steps of feeding, stopping and driving at predetermined incremental positions along the pipe are sequentially repeated until the bend is completed.
A pipe bender in accordance with this invention reduces the required hydraulic force by a factor in a range of 4:1 in comparison to known pipe bending machines. It reduces the forces exerted by the cylinder and the opportunity for leaks and defects. It puts the cylinders in a linear non-competing, non-binding configuration.
Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings in which:
While the invention will be described in connection with a preferred embodiment thereof, it will be understood that it is not intended to limit the invention to that embodiment or to the details of the construction or the arrangement of parts illustrated in the accompanying drawings.
Turning first to
Turning now to
The interior components of the machine 10 mounted between the side plates 15 and 25 are illustrated in
The front pipe receiving roller assembly 50 includes a forward extension 51 of the chassis 11 with uprights 53 and 55 supporting a front roller 57 on an axle 59. The rear pipe receiving assembly 60, best seen in
The stiff-back assembly 70 includes the trough or stiff-back 71 which is supported proximate its rearward end by the inboard hydraulic cylinders 21, 23, 31 and 33 which are pivotally connected on the stiff-back lugs 73 and 75 (right side lugs 73 and 75 not shown), respectively, and to the suspension shafts 77 and 79, respectively, extending through the die assembly 80.
The die assembly 80, best seen in
The wedge drive assembly 100, best seen in
Continuing to look at
The operation of the machine can best be understood in reference to
In operation, the bending process begins with the inboard hydraulic cylinders 21, 23, 31 and 33 fully extended and the outboard 121 hydraulic cylinders fully retracted, as seen in
Once the marked pipe is positioned for the first bend, the inboard hydraulic cylinders 21, 23, 31 and 33 are operated to retract lightly until the stiff-back 71 raises the pipe into contact with the die bars 83. The die bars 83 arc across their length so that the pipe substantially makes linear contact across the width of the die assembly 80. When contact is made, retraction is terminated with contact being maintained. The pin-up hydraulic cylinder 99 is then actuated to drive the pin-up wedge 93 between the guide arms 95 and raise the clamp 91 toward the die assembly 80 to pin the pipe against the die bars 83 along the linear contact line. The pin-up hydraulic cylinder 99 is de-actuated with the pipe in the pinned-up condition.
The outboard hydraulic driving cylinders 121 are then actuated to drive the wedge assembly 110 forwardly between the rollers 135 of the stiff-back lift roller assemblies 130 and the rollers 145 of the pivot clamp assemblies 140. The stiff-back lift roller assemblies 130, including its platform 131, are raised as the wedge assembly 110 is driven against the pivoted platforms 141 of the pivot clamp assemblies 140, thus raising the stiff-back 71 about the stiff-back pivot lugs 73 and 75 and the suspension shafts 77 and 79 to bend the pipe against the die bars 83. Pivoting the inboard cylinders 21, 23, 31 and 33 on the suspension shafts 77 and 79 allows inboard cylinders 21, 23, 31 and 33 to operate without competing against each other. Pivoting the stiff-back 71 on the lugs 73 and 75 allows the stiff-back to assume the orientation necessary to conform to the orientation of the pipe. Since the stiff-back 71 is parallel to the roller assembly platform 131 supporting it, the driving force of the extending outboard hydraulic driving cylinders 121 is applied to the wedge assembly 110 in a direction parallel to the stiff-back 71 and the pipe. Since the platforms 141 supporting the wedge assembly 110 are pivoted, the driving force remains parallel to the stiff-back 71 even though the stiff-back 71 is rotating about the lugs 75. Thus, the lifting force applied by the wedge assembly 110 to the stiff-back 71 remains perpendicular to the direction of the driving force of the outboard cylinders 121 and remains constant even though the alignment of the pivoting outboard cylinders 121 varies as the pipe is bending against the die bars 83.
After the first bend is completed, the pin-up cylinder 99 is actuated to withdraw the pin-up wedge 93 and return the pin-up clamp 91 to its lowest position, the outboard cylinders 121 are fully retracted and the inboard cylinders 21, 23, 31 and 33 are fully extended to lower the stiff-back 71 and return the pipe to the front and rear rollers 57 and 67. The pipe will then be advanced to the next mark and the preceding steps repeated until bending of the pipe at all of the marks has been completed.
A pipe bending machine according to the present invention will typically afford a mechanical advantage in a range of 4:1 in comparison to known pipe bending machines. This mechanical advantage reduces the forces exerted by the driving cylinders 121. In some applications, mechanical advantages in a range of 6:1 are possible, depending on the coefficient of friction of the rollers 135 and 145 and the geometry of the wedge assembly 110. The opportunity for leaks and defects is decreased, the cylinders 121 operate in a linear non-competing, non-binding configuration and the cylinders 121 are reduced to standard commercially available sizes.
Thus it is apparent that there has been provided, in accordance with invention, a pipe bending machine that fully satisfies the objects, aims and advantages set forth above. While the invention has been described in conjunction with a specific embodiment thereof, it is evident that many alternatives modifications and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications and variations as fall within the spirit of the appended claims.
