Abstract:
A shaft straightening or tube straightening apparatus performs accurate measurements of the linear profile of a metal tube, and then corrects small and large deviations of the tube profile from the ideal centerline along the length of the tube. The tube straightening apparatus is operable to accurately measure a linear profile of the tube positioned in the apparatus. The tube is rotated in the apparatus to locate a pair of low points in the tube profile and a high point of the tube between the two low points. The tube is supported in the apparatus at the pair of low points and the high point of the tube is then deflected beyond the yield point of the metal of the tube to permanently distort the tube and correct the tube&#39;s profile.

Description:
FIELD 
     This disclosure pertains to a shaft straightening or tube straightening apparatus that performs accurate measurements of the linear profile of a metal tube, and then corrects small and large deviations of the tube profile from the ideal centerline along the length of the tube. More specifically, the present disclosure pertains to an automated tube straightening apparatus that is operable to accurately measure a linear profile of a metal tube positioned in the apparatus. The tube is rotated in the apparatus to locate a pair of low points in the tube profile and a high point of the tube profile. The tube is supported in the apparatus at the pair of low points and the high point of the tube is then deflected beyond the yield point of the metal of the tube to permanently distort the tube and correct the tube&#39;s profile. 
     BACKGROUND 
     Aluminum and stainless steel shafts and/or tubes ranging from 1-3½ inches in diameter, and 29-169 inches in length, are often heat treated which typically warps the tube in one or more planes. Deformation of the tubes can range in form from a simple bow along the tube length, to a complex spiral of the tube length. The span of a deformation can range from 4 inches of the overall tube length, to the entire length of the tube. Multiple deformations can occur in each tube. 
     Corrections to the tube deformations or “run out” are currently made manually with a dial indicator, a hand press, and two supporting fixtures for the tube which are moved along the tube length as needed. Corrections are made by profiling the tube length and determining where corrections are needed, and then strategically positioning the tube on the supporting fixtures where the ram of the hand press can be used to deflect the tube to decrease the tube run out and straighten the tube profile. The operator of the hand press positions the ram of the press at the tube high point and then extends the ram a distance to deflect the tube and correct the measured run out of the tube high point by anticipating the spring back of the tube after the force of the ram is removed. An acceptable run out is 5/1000 of an inch over the entire length of the tube. This manual process of correcting tube deformations is labor intensive and requires experienced operators to straighten tubes. This process is a major bottleneck in the aerospace industry manufacturing tubes used for drive shafts and actuator rods. 
     SUMMARY 
     The shaft or tube straightening apparatus of the invention provides an operator controlled or fully automated system that simulates the manual tube straightening operation. 
     The apparatus comprises a frame that supports the apparatus in an upright orientation. The frame has a centrally located open area that is dimensioned to receive a length of shaft or tubing to be straightened by the apparatus. 
     A plurality of holding cylinders or holding devices are supported on the frame. The holding devices are arranged side-by-side on the frame beneath the frame open area. Each of the holding devices has a rod with an end surface that is configured as a holding fixture for holding a portion of a tube engaged by the end surface. Each of the rods is movable in reciprocating movements along an axis of the rod between an extended position of the rod from the holding device, and a retracted position of the rod relative to the holding device. In the rod extended position the rod end surface is moved into the frame open area to engage with a tube that has been positioned in the open area and to support the tube on the rod end surface. 
     The apparatus also comprises a plurality of actuator ram cylinders or actuator devices that are supported on the frame. The actuator devices are positioned side by side on the frame on an opposite side of the frame open area from the plurality of holding devices. Each of the actuator devices has a ram that is movable in reciprocating movements along an axis of the ram between an extended position of the ram from the actuator device, and a retracted position of the ram relative to the actuator device. Each ram has an end surface configured for engaging and exerting a force against an area of the tube positioned in the frame open area. In the extended position of the ram, the ram end surface is moved into the frame open area to engage with a tube that is supported on at least two of the end surfaces of holding device rods that have been extended into the open area. The extended ram end surface engaging with the tube supported in the frame open area bends the tube. As the ram end surface bends the tube it moves the portion of the tube being bent a distance through the frame open area. 
     A plurality of proximity sensors are also supported on the frame. The proximity sensors are positioned side by side adjacent the plurality of actuator devices on the opposite side of the frame open area from the plurality of holding devices. Each of the proximity sensors is operable to sense the distance the tube is moved through the frame open area as the tube is being bent by the actuator device ram engaging the tube. 
     The apparatus also includes a rotation device supported on the frame. The rotation device is positioned adjacent the frame open area and between the plurality of holding devices and the plurality of actuator devices. The rotation device is connectable to the tube positioned in the frame open area and is operable to rotate the tube in the open area. 
     The apparatus also includes a controller that communicates with the plurality of holding devices, the plurality of actuator devices, the plurality of proximity sensors and the rotation device. The controller includes an operator screen or display screen communicating with the controller. The display screen is operable to display a visual indication of the distance sensed by each of the proximity sensors to the portion of the tube in the frame open area that is opposite the proximity sensor. 
     In operation of the apparatus, a length of tube to be straightened by the apparatus is first positioned in the frame open area. The rods of the plurality of holding devices are then extended to precision hard stops of the holding devices that control the extended positions of the rod. The length of tube is supported on the rod end surfaces. The rotation device is connected to an end of the tube to hold the tube against rotation in the frame open area. The plurality of proximity sensors are activated to float on the surface of the tube opposing the proximity sensors. Each of the proximity sensors senses its distance from the tube surface, and the tube profile in one plane is measured from data signals provided by the proximity sensors to the controller. The proximity sensor data is displayed on the display screen. From the displayed data the tube is rotated until the maximum error in the tube&#39;s profile is detected. The best supporting holding devices are identified for supporting the tube at two low points of the tube profile for the desired correction of the tube profile. All of the other holding device rods between the selected two supporting rods are retracted to allow for deflection of the tube between the two supporting rods. 
     The display of the sensor data on the displays screen also identifies a high point in the tube profile. The ram of the actuator device at the high point is then extended from the actuator device to engage against the profile high point of the tube. The engagement of the ram end surface against the tube high point begins to bend the tube and move the tube a distance through the frame open area. The distance the tube is moved through the frame open area as the ram end surface bends the tube is sensed by the proximity sensor associated with the actuator device of the extended ram. The extension of the ram from the actuator device is controlled to bend the portion of the tube at the tube high point and move the portion of the tube a specified distance through the frame open area based on the run out of the tube profile. The bending of the tube is tracked by the controller from the proximity sensor data. When the desired deflection distance of the tube is achieved, the actuator device ram is retracted. The resulting tube profile is evaluated by the plurality of proximity sensors and the controller and the profile correction process is applied again if needed. Once a desired correction of the tube profile is achieved, the rotation device is activated to rotate the tube in the frame open area to identify the next deformation of the tube that is to be corrected using the same procedure. The process is repeated until the run out of the tube is within acceptable specifications. 
     Further features of the apparatus and associated method are set forth in the following detailed description of the apparatus and in the drawing figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a representation of a perspective view of a tube straightening apparatus. 
         FIG. 2  is a representation of an elevation view of a portion of a variant embodiment of the apparatus shown in  FIG. 1 . 
         FIG. 3  is a representation of a display screen of the apparatus. 
         FIG. 4  is a representation of the display screen similar to that of  FIG. 3 , but illustrating a step in the method of operating the apparatus. 
         FIG. 5  is a representation of the display screen illustrating a further step in the method of operating the apparatus. 
         FIG. 6  is a representation of the display screen similar to that of  FIG. 5 , but illustrating a further step in the method of operating the apparatus. 
         FIG. 7  is a representation of a control logical block diagram for the apparatus. 
     
    
    
     DESCRIPTION 
       FIG. 1  is a representation of a perspective view of an automated tube straightening apparatus  10 . As will be explained, the apparatus  10  provides an operator controlled or fully automated system that simulates the manual tube straightening operation. 
     The apparatus  10  comprises a frame  12  that supports the apparatus in a generally upright orientation. The frame  12  shown in  FIG. 1  is represented as a flat, generally rectangular panel. However, the frame  12  could be any structure that securely supports the component parts of the apparatus  10  in their relative positions to be described. The frame  12  has a centrally located open area  14  with the component parts of the apparatus to be described being positioned on opposite sides of this open area. The open area  14  is dimensioned to receive a length of shaft or tube  16  that is to be straightened by the apparatus. Although the apparatus  10  and its method of operation to be described refer to the apparatus straightening the length of tube  16 , it should be understood that the concepts of the apparatus  10  can be employed in straightening the length of other similar structural features such as shafts, rods, etc. 
     A plurality of holding devices  18 ,  20 ,  22 ,  24 ,  26 ,  28 ,  30  are supported on the frame  12 . In the exemplary embodiment of the apparatus  10  shown in  FIG. 1 , the holding devices  18 ,  20 ,  22 ,  24 ,  26 ,  28 ,  30  are each comprised of a holding cylinder  18   c ,  20   c ,  22   c ,  24   c ,  26   c ,  28   c ,  30   c  and a rod  18   r ,  20   r ,  22   r ,  24   r ,  26   r ,  28   r ,  30   r  that projects from its respective cylinder. In other embodiments of the apparatus the holding devices could be other equivalent types of linear actuators, including pneumatic cylinders, hydraulic cylinders, and motor and screw actuators. Each of the rods is movable in reciprocating movements along an axis of the rod between an extended position of the rod from the holding device, and a retracted position of the rod relative to the holding device. 
     As represented in  FIG. 1 , the holding devices  18 ,  20 ,  22 ,  24 ,  26 ,  28 ,  30  are arranged side-by-side on the frame  12  beneath the frame open area  14 . The rods  18   r ,  20   r ,  22   r ,  24   r ,  26   r ,  28   r ,  30   r  are positioned with their axes parallel. Each of the rods  18   r ,  20   r ,  22   r ,  24   r ,  26   r ,  28   r ,  30   r  has a respective end surface  18   s ,  20   s ,  22   s ,  24   s ,  26   s ,  28   s ,  30   s  on a distal end of the rod from its respective holding cylinder. The rod end surfaces  18   s ,  20   s ,  22   s ,  24   s ,  26   s ,  28   s ,  30   s  are all positioned in substantially a same plane with the rods in their retracted positions relative to their respective cylinders, and are all positioned below the frame open area  14 . Inside its associated holding cylinder, each of the rods  18   r ,  20   r ,  22   r ,  24   r ,  26   r ,  28   r ,  30   r  is provided with a precision hard stop that limits the extension of the rod from its associated cylinder. With each of the rods extended to their precision hard stop, the rod end surfaces  18   s ,  20   s ,  22   s ,  24   s ,  26   s ,  28   s ,  30   s  are all positioned in substantially a same plane and are all positioned in the frame open area  14 . Each of the rod end surfaces  18   s ,  20   s ,  22   s ,  24   s ,  26   s ,  28   s ,  30   s  is configured as a holding fixture for holding a portion of the tube  16  engaged by the rod end surface. In the rod extended positions, the rod end surfaces  18   s ,  20   s ,  22   s ,  24   s ,  26   s ,  28   s ,  30   s  are moved into the frame open area  14  to engage with a tube  16  that has been positioned in the open area and to support the tube on at least two of the rod end surfaces. 
     The apparatus  10  also comprises a plurality of actuator devices  32 ,  34 ,  36 ,  38 ,  40 ,  42 ,  44  that are supported on the frame  12 . In the exemplary embodiment of the apparatus  10  represented in  FIG. 1 , each of the actuator devices  32 ,  34 ,  36 ,  38 ,  40 ,  42 ,  44  is comprised of an actuator cylinder  32   c ,  34   c ,  36   c ,  38   c ,  40   c ,  42   c ,  44   c  and a ram  32   r ,  34   r ,  36   r ,  38   r ,  40   r ,  42   r ,  44   r  that projects from its respective cylinder. Each of the rams is movable in reciprocating movements along an axis of the ram between an extended position of the ram from the actuator device, and a retracted position of the ram relative to the actuator device. The reciprocation axes of the rams  32   r ,  34   r ,  36   r ,  38   r ,  40   r ,  42   r ,  44   r  are all parallel to each other and are coaxial with the respective reciprocation axes of the holding device rods  18   r ,  20   r ,  22   r ,  24   r    26   r ,  28   r ,  30   r . The actuator devices  32 ,  34 ,  36 ,  38 ,  40 ,  42 ,  44  are positioned side by side on the frame  12  on the opposite side of the frame open area  14  from the respective holding devices  18 ,  20 ,  22 ,  24 ,  26 ,  28 ,  30 . 
     In the exemplary embodiment represented in  FIG. 1 , the closeness of adjacent rams  32   r ,  34   r ,  36   r ,  38   r ,  40   r ,  42   r ,  44   r  is limited by the diameter dimensions of their respective actuator cylinders. For example, if each of the actuator cylinders  32   c ,  34   c ,  36   c ,  38   c ,  40   c ,  42   c ,  44   c  has a 4 inch diameter dimension, then the closest adjacent rods  32   r ,  34   r ,  36   r ,  38   r ,  40   r ,  42   r ,  44   r  could be to each other is 4 inches. However, in a variant embodiment of the apparatus represented in  FIG. 2 , by staggering the positions of the actuator cylinders  32   c ,  34   c ,  36   c ,  38   c ,  40   c ,  42   c ,  44   c  and providing every other actuator device with a ram having a different axial length, the distances between adjacent rams  32   r ,  34   r ,  36   r ,  38   r ,  40   r ,  42   r ,  44   r  can be reduced to substantially half of that in the embodiment of the apparatus represented in  FIG. 1 . 
     Referring back to  FIG. 1 , each of the rams  32   r ,  34   r ,  36   r ,  38   r ,  40   r ,  42   r ,  44   r  has a respective end surface  32   s ,  34   s ,  36   s ,  38   s ,  40   s ,  42   s ,  44   s  on a distal end of the ram from its respective actuator cylinder. In the retracted positions of the rams, the ram end surfaces  32   s ,  34   s ,  36   s ,  38   s ,  40   s ,  42   s ,  44   s  are positioned in substantially a same plane above the frame open area  14 . Each ram end surface  32   s ,  34   s ,  36   s ,  38   s ,  40   s ,  42   s ,  44   s  is configured for engaging and exerting a force against an area of the tube  16  positioned in the frame open area  14 . In the extended position of the rams, the ram end surfaces  32   s ,  34   s ,  36   s ,  38   s ,  40   s ,  42   s ,  44   s  are moved into the frame open area  14  to engage with the tube  16  that is supported on at least two of the holding device rod end surfaces  18   s ,  20   s ,  22   s ,  24   s ,  26   s ,  28   s ,  30   s  that have been extended into the open area  14 . Each ram end surface can be selectively moved into the frame open area  14  to engage with the tube supported in the frame open area and bend the tube. As the ram end surface bends the tube it moves the portion of the tube being bent a distance through the frame open area  14 . 
     A plurality of proximity sensors  46 ,  48 ,  50 ,  52 ,  54 ,  56 ,  58  are also supported on the frame  12 . The proximity sensors are capable of precise, accurate measurements, for example, to about 0.0001 inches. For example, the proximity sensors could be inductive proximity sensors or other equivalent types of sensors. The proximity sensors  46 ,  48 ,  50 ,  52 ,  54 ,  56 ,  58  are positioned adjacent the respective actuator devices  32 ,  34 ,  36 ,  38 ,  40 ,  42 ,  44  and on opposite sides of the frame open area  14  from the respective holding devices  18 ,  20 ,  22 ,  24 ,  26 ,  28 ,  30 . As represented in  FIG. 2 , each of the proximity sensors  46 ,  48 ,  50 ,  52 ,  54 ,  56  is directed at a respective target  46   t ,  48   t ,  50   t ,  52   t ,  54   t ,  56   t  that follows the position of the tube and is operable to sense the distance a portion of the tube  16  in the frame open area  14  is from the proximity sensor. Each of the proximity sensors  46 ,  48 ,  50 ,  52 ,  54 ,  56 ,  58  can thereby sense the distance the portion of the tube  16  opposite the sensor is moved through the frame open area  14  as the tube is being bent by the adjacent actuator device ram  32   r ,  34   r ,  36   r ,  38   r ,  40   r ,  42   r ,  44   r  when the adjacent ram engages with and bends a portion of the tube. 
     The apparatus  10  also includes a rotation device  60  supported on the frame  12 . As represented in  FIG. 1 , the rotation device  60  is positioned on the frame  12  adjacent the frame open area  14  and between the plurality of holding devices  18 ,  20 ,  22 ,  24 ,  26 ,  28 ,  30  and the plurality of actuator devices  32 ,  34 ,  36 ,  38 ,  40 ,  42 ,  44 . The rotation device  60  includes a clamp  62  that is selectively connectable to an end of the tube  16  positioned in the frame open area  14 . When connected to the tube  16 , the rotation device  60  is operable to rotate the tube  16  in the frame open area  14 . 
     The apparatus also includes a programmable logic controller  66  that communicates with the plurality of holding devices  18 ,  20 ,  22 ,  24 ,  26 ,  28 ,  30 , the plurality of actuator devices  32 ,  34 ,  36 ,  38 ,  40 ,  42 ,  44 , the plurality of proximity sensors  46 ,  48 ,  50 ,  52 ,  54 ,  56 ,  58  and the rotation device  60 . The controller  66  includes an operator screen or display screen  68  communicating with the controller. The display screen  68  is operable to display a visual indication of the distance sensed by each of the proximity sensors  46 ,  48 ,  50 ,  52 ,  54 ,  56 ,  58  to the portion of the tube  16  in the frame open area  14  that is opposite the proximity sensor. This enables the display screen  68  to provide a visual indication of the profile of the tube  16  in the particular orientation of the tube held by the rotation device  60  in the frame open area  14 . The location of the tube&#39;s upper surface or the surface directed toward the proximity sensors is displayed, providing a visual indication of the location of the tube&#39;s upper surface above the ideal zero reference. The controller  66  also includes a pair of joysticks  72 ,  74  on opposite sides of the controller. One of the joysticks  72 , the left joystick shown in  FIG. 3  has a thumb wheel  76  on the distal end of the joystick and the other joystick, the right joystick  74  shown in  FIG. 3  has a trigger  78  on the distal end of the joystick. In manual mode of the apparatus  10 , using the left joystick  72 , the operator can translate or rotate the tube  16  until a pair of desired supporting low point portions of the tube and a desired deflection high point portion of the tube are displayed on the display screen  68 . 
     In operation of the apparatus  10 , the length of tube  16  to be straightened by the apparatus is first positioned in the frame open area  14 . One end of the tube  16  is firmly grasped by the clamp  62  of the rotation device  60 . The holding device rods  18   r ,  20   r ,  22   r ,  24   r ,  26   r ,  28   r ,  30   r  are then extended by an operator operating the program logic controller  66 . The rods are extended to the precision hard stops of the holding devices  18 ,  20 ,  22 ,  24 ,  26 ,  28 ,  30 . These position the rod distal end surfaces  18   s ,  20   s ,  22   s ,  24   s ,  26   s ,  28   s ,  30   s  in substantially a same plane. The length of tube  16  is supported on at least some of the end surfaces of the rods due to its warped profile. 
     The operator at the operator&#39;s screen  68  then activates the rotation device  60  to rotate the tube  16  in the frame open area  14 . As the tube  16  is rotated by the rotation device  60 , each of the proximity sensors  46 ,  48 ,  50 ,  52 ,  54 ,  56 ,  58  senses the distance of the portion of the tube surface opposite the sensor and produces a signal that is representative of this distance. These signals are transmitted to the programmable logic controller which then controls the display screen  68  to display a visual representation of the distance of each proximity sensor to the portion of the tube surface opposite the sensor. The operator, using the left joystick  72  of the controller  66  controls a translation of the tube  16  and rotation of the tube in the frame open area  14  until a desired warped profile of the tube surface opposite the proximity sensors is displayed on the display screen  68 . 
       FIG. 3  is a representation of the profile of the tube  16  displayed on the display screen  68 . Referring to  FIG. 3 , the display screen  68  displays sensed distance representations  82 ,  84  from the proximity sensors  46 ,  58  that are opposite the respective holding devices  18 ,  30  that are positioned at the two tube low points. By moving the right joystick  74  left and right, these holding devices  18 ,  30  are selected by the operator at the screen  68  to support the tube  16 . This is represented in  FIG. 4 . The rods  20   r ,  22   r ,  24   r ,  26   r    28   r  of the remaining respective holding devices  20 ,  22 ,  24 ,  26 ,  28  are retracted. This provides clearance between the two supporting holding devices  18 ,  30  for deflection of the tube  16 . 
     The display screen also displays a sensed distance representation  86  from the proximity sensor  50  that is opposite the high point of the tube profile. Using the right joystick  74 , the operator at the screen  68  then selects the actuator device  36  that is opposite the highest portion of the tube profile sensed by the proximity sensor  50 . This is represented in  FIG. 4 . In a manual mode of operation, the controller  66  and display screen  68  then prompt the operator to select a deflection distance using the right thumb wheel  76  as represented in  FIG. 5 . When operating the apparatus manually the operator guesses how much deflection is required to bend the tube beyond the yield point so that it will spring back to the desired state and enters the desired deflection value. This requires multiple corrections with each part being straightened through trial and error. However, during normal operations, the programmable controller performs mathematical calculations based on the tube&#39;s wall thickness, diameter, Young&#39;s Modulus for the material being used, the span between the two supporting dies, the second moment of inertia for the bend, the measured error value, the geometry of the stress-strain curve, and a number of approximations. From this the required deflection is calculated. The selected distance is represented in  FIG. 6 . The ram  36   r  of the selected actuator device  36  is then extended at a controlled rate until the ram end surface  36   s  comes into contact with the portion of the tube surface opposite the selected actuator device  36 . The actuator ram  36   r  is then continued to move a desired distance that is either selected by the operator or calculated by the programmable logic controller  66  to deflect the tube  16  or bend the tube through the frame open area  14 . The deflection of the tube is tracked dynamically by the programmable logic controller  66  from the signals received from the proximity sensors  46 ,  48 ,  50 ,  52 ,  54 ,  56 ,  58 . When the designated deflection distance of the tube  16  is achieved, the selected actuator device  36  is then deactivated. 
     The resulting profile of the tube  16  is then evaluated from the data received by the programmable logic controller  66  from the proximity sensors  46 ,  48 ,  50 ,  52 ,  54 ,  56 ,  58  and the correction process is applied again if needed. Once the desired correction in the tube profile is achieved, the programmable logic controller  66  is operated by the operator to again activate the rotation device  60  to rotate the tube  16  in the frame open area  14  until the next deformation of the tube  16  is identified and corrected using the same procedure. This process is repeated until the run out of the tube  16  is within specifications. 
     Although the apparatus described herein and its method of use have been described by reference to a particular embodiment of the apparatus, it should be understood that modifications and variations to the apparatus and method could be made without departing from the intended scope of the claims appended hereto.