Abstract:
A pipe bending machine has a stiff-back which is driven by a pivoting wedge. A linkage applies force from the actuator to the wedge in a direction parallel to a longitudinal axis of the stiff-back. The stiff-back pivots on a first fulcrum and the wedge slides on a bed which pivots on a second fulcrum. The actuator drives the wedge between the stiff-back and the bed to rotate the stiff-back at the first fulcrum and bend the pipe seated in the stiff-back against the pipe bending face of a die. The conversion of the longitudinal force applied to the wedge into a transverse force applied to the stiff-back provides a significant mechanical advantage which varies directionally as the stiff-back rotates about its fulcrum to maintain a constant force on the stiff-back.

Description:
BACKGROUND OF THE INVENTION 
     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. 
     SUMMARY OF THE INVENTION 
     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. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings in which: 
         FIG. 1  is a free-body diagram of the operating components of the pivoting wedge pipe bending machine; 
         FIG. 2  is a left side elevation view of the pivoting wedge pipe bending machine with the stiff-back in a fully lowered condition; 
         FIG. 3  is a right side elevation view of the pivoting wedge pipe bending machine with the stiff-back in a fully lowered condition; 
         FIG. 4  is a front elevation view of the pivoting wedge pipe bending machine with the stiff-back in a fully lowered condition; 
         FIG. 5  is a rear elevation view of the pivoting wedge pipe bending machine with the stiff-back in a fully lowered condition; 
         FIG. 6  is a perspective view of the front, top and left sides of the pivoting wedge pipe bending machine with the stiff-back in a fully lowered condition; 
         FIG. 7  is a perspective view of the front, top and right sides of the pivoting wedge pipe bending machine with the stiff-back in a fully lowered condition; 
         FIG. 8  is a left side elevation view of the pivoting wedge pipe bending machine with the side plate removed and the stiff-back in a fully lowered condition; 
         FIG. 9  is a left side elevation view of the pivoting wedge pipe bending machine with the side plate removed and the stiff-back in a fully raised condition; 
         FIG. 10  is a perspective view of the pivoting wedge pipe bending machine with the side plate and stiff-back removed and the wedge in a fully retracted condition; 
         FIG. 11  is a perspective view of the pivoting wedge pipe bending machine with the side plate and stiff-back removed and the wedge in a fully extended condition; 
         FIG. 12  is a perspective view of the wedge assembly of the pivoting wedge pipe bending machine; 
         FIG. 13  is an enlarged view of the area  13  of  FIG. 11 ; 
         FIG. 14  is a perspective assembly view of the pivot roller clamp assembly of the pivoting wedge pipe bending machine; and 
         FIG. 15  is a perspective view of the rear, top and left sides of the pin-up clamp assembly of the pivoting wedge pipe bending machine. 
     
    
    
     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. 
     DETAILED DESCRIPTION 
     Turning first to  FIG. 1 , the pipe P is to be bent against a die D. The pipe P will be advanced along its longitudinal axis L in a downstream direction in incremental steps past the die D. “Downstream direction” is relative and describes the movement of the pipe P in relation to the machine M. In practice, the machine M moves upstream in relation to the pipe P which is stationary. The pipe P is initially advanced to a position at which it can be rested in a trough T, commonly referred to as a stiff-back, which extends longitudinally downstream of the die D. The trough T is pivoted on a first axis A 1 , as shown on the upstream portion of the trough T below the die D but downstream of the anticipated contact point C of the pipe P with the die D. The downstream end of the trough T is supported by a wedge W which is supported by and reciprocally slides on a bed B which is pivoted on a second axis A 2 . When the pipe P is in the initial position, a wedge driving force F 1  which is directionally variable in relation to a third axis A 3  is applied at a fourth pivotal axis A 4  to the wedge W in a direction parallel to the longitudinal axis L of the pipe P and the trough T. This results in a trough lifting force F 2  being exerted on the trough T in a direction perpendicular to the wedge driving force F 1  applied to the wedge W. The application of the lifting force F 2  to the free end of the trough T bends the pipe P against the opposing force F 3  of the die D to conform the portion of the pipe P downstream of the contact point C to the shape of die D. As the sliding of the wedge W between the bed B and the trough T causes the trough to rotate about its pivotal axis A 1 , the direction of the longitudinal force F 1  changes. However, the bed B and the wedge W pivot on their respective axes A 2  and A 4  to maintain the force F 2  perpendicular to the longitudinal axis L of the pipe P and trough T as the pipe P is bending against the die D. After being bent to the desired contour in initial position, the pipe P will be advanced along its longitudinal axis L in the downstream direction in incremental steps past the die D, repositioning the pipe P for application of the bending force F 2  downstream of the previous application of the bending force F 2 . The steps are repeated until bending of the pipe P has been completed. 
     Turning now to  FIGS. 2-7 , a preferred embodiment of the machine  10  has a chassis  11  mounted on a pair of idler tracks  13 . One side plate  15 , as shown on the left side of the machine  10 , supports an operator platform  17 , a pneumatics platform  19  and inboard hydraulic cylinders  21  and  23 . Another side plate  25 , as shown on the right side of the machine  10 , supports an hydraulics platform  27 , a power system platform  29  and inboard hydraulic cylinders  31  and  33 . Looking at the left side plate  15  in  FIGS. 2 ,  4 ,  5  and  6 , a bender operation control box  35  is mounted on the operator platform  17 . An air tank  37  is mounted below and an air compressor  39  is mounted on the pneumatics platform  19 . Looking at the right side plate  25  in  FIGS. 3 ,  4 ,  5  and  7 , the engine  41  is mounted on and the fuel tank  43  is mounted under the power system platform  29 . The engine control box  45  is mounted on the operator platform  17  on the left side plate  15 . An hydraulic pump  47  is mounted behind the engine  41  and an hydraulic tank  49  is mounted on the hydraulic platform  27 . 
     The interior components of the machine  10  mounted between the side plates  15  and  25  are illustrated in  FIGS. 4 and 5  and in  FIGS. 8 and 9  in which the left side plate  15  and its associated platforms and exterior components are removed, except for the inboard cylinders  21  and  23 . The inboard components include front and rear pipe receiving roller assemblies  50  and  60 , respectively, the stiff-back assembly  70 , the die assembly  80 , the pin-up clamp assembly  90  and the wedge drive assembly  100 . 
     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  FIGS. 10 and 11 , includes uprights  63  and  65  from the chassis  11  supporting a rear roller  67  on an axle  69 . 
     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  FIGS. 10 and 11 , includes nesting plates  81  securing the die bars  83  in shape and position to bear against the pipe in the bending process. The pin up clamp assembly  90 , best seen in  FIG. 15 , includes a short trough or clamp  91 . A pin-up wedge  93  is positioned between the clamp  91 , which is guided by left and right arms  95  (right side arm  95  not shown), and a slide  97 . The wedge  93  is reciprocally driven by a pin-up hydraulic cylinder  99  pivotally mounted on the chassis  11  to raise and lower the clamp  91  between the guide arms  95  toward and away from the die assembly  80 . 
     The wedge drive assembly  100 , best seen in  FIGS. 8-11 , includes a wedge assembly  110 , left and right outboard hydraulic driving cylinder assemblies  120 , left and right stiff-back lift roller assemblies  130  and left and right roller pivot clamp assemblies  140 . The wedge assembly  110 , shown in greater detail in  FIG. 12 , includes a support plate  111  connected along the hypotenuse edges of opposed side plates  113 . Guides  115 , as shown with chamfered leading ends and extending on the outboard sides of the wedge assembly side plates  113  parallel to the support plate  111 , are provided to keep the wedge assembly  110  centered in the bender chassis  11  between the machine side plates  15  and  25 . Holes  117  are provided in the trailing ends of the wedge side plates  113  for connecting the wedge assembly  110  to the driving cylinder assemblies  120 . Each of the driving cylinder assemblies  120  includes a driving cylinder  121  pivotally mounted at its rearward end to the chassis  11  on an axle  123 . The forward end of each driving cylinder  121  is pivotally connected to the wedge assembly  110  by a pin  125  through its corresponding hole  117  in the wedge assembly  110 . The leading end of the wedge assembly  110  slides reciprocally between the stiff-back lift roller assemblies  130  and the roller pivot clamp assemblies  140  in response to the extension and retraction of the driving cylinders  121 , as best seen in  FIGS. 8 and 9 . 
     Continuing to look at  FIGS. 8 and 9 , each stiff-back lift roller assembly  130  includes a platform  131  seated on the wedge assembly  110  and supporting the forward portion of the stiff-back  71 . Looking at  FIG. 14 , channel guides  133  have rollers  135  forming tracks in the channel guides  133 . Returning to  FIGS. 8 and 9 , one guide  133  on each side of the underside of the platform  131  receives the upper edges of the wedge assembly side plates  113  onto the rollers  135 . Turning to  FIGS. 13 and 14 , each roller pivot clamp assembly  140  includes a platform  141  and a channel guide  143  with rollers  145  forming a track in the channel guide  141 . The channel guide  143  is mounted on top of its platform  141  and receives the lower edges of the wedge assembly side plates  113  under the rollers  145 . A shaft  147  engaged in a bushing formed by upper and lower clamp members  149  and  151 , respectively, pivotally supports the roller pivot clamp assembly  140  on the chassis  11 . 
     The operation of the machine can best be understood in reference to  FIGS. 8-11 .  FIGS. 8 and 10  show the stiff-back  71  in a fully lowered condition in which the inboard hydraulic cylinders  21 ,  23 ,  31  and  33  are fully extended and the outboard hydraulic wedge driving cylinders  121  are fully retracted.  FIGS. 9 and 11  show the stiff-back  71  in a fully raised condition in which the inboard hydraulic cylinders  21 ,  23 ,  31  and  33  are fully retracted and the outboard hydraulic wedge driving cylinders  121  are fully extended. 
     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  FIG. 8 . The pipe is generally, though not always, pushed into the machine  10  via its back end. A mandrel (not shown) aligned and sitting in the stiff-back  71  is inserted into the pipe to maintain the pipe circularity during bending. The air tank  37  and compressor  39  of the machine  10  are intended to serve a pneumatic mandrel used for this purpose. As The pipe is loaded into the machine  10 , it passes across the rear roller  67  and onto the front roller  57  and eventually rests on the rollers  67  and  57  and above the stiff-back  71 . As the pipe is loaded, it is marked to identify the points along the pipe at which “pulls” will be sequentially made, it generally taking multiple “pulls” to achieve a full bend. 
     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.