Abstract:
A combination of two or more jaw assemblies for mounting onto a self-centering power chuck to move an irregular workpiece to the axial centerline of the power chuck after it has been clamped. Each jaw assembly has a independent hydraulic system which, when activated, reduces the length of the jaw assembly, thereby moving the workpiece clamped in the power chuck. The imperfect pipe&#39;s average centerline can be moved to any location within the combined adjustable range of all the jaw assemblies. Each jaw assembly consists of a base jaw that is affixed to the power chuck, a connecting block that moves when the hydraulic system is actuated, a piston, a cylinder, and an interchangeable swivel insert with a serrated gripping surface.

Description:
FIELD OF THE INVENTION 
     The present invention relates to an assembly and method of positioning a workpiece, such as pipe, tubing or any other part that, when clamped, does not line up to the true centerline of a self-centering power chuck due to imperfections of roundness, wall thickness and straightness. The present invention will move the imperfect part&#39;s average centerline to the true centerline of the self-centering power chuck. The present invention uses at least two chuck jaw assemblies, each of which is adjustable by means of an independent internal hydraulic system. 
     BACKGROUND OF INVENTION 
     When a workpiece, such as pipe, tubing or another part to be machined (hereinafter simply referred to as “pipe”) is clamped in a machine tool lathe for threading, it is usually held in place with a self-centering power chuck on the front and rear of the lathe, and the remaining length of the pipe or tubing is supported by rollers. Pieces of pipe or tubing, which come in various sizes and lengths, are not perfectly round or straight from end to end. These imperfections cause the surface area to be machined and threaded to run out from the true centerline of the self-centering power chuck. 
     Presently, the primary method of correcting the pipe&#39;s centerline runout is to insert shims between the chuck laws and the pipe or tubing. When a shim is used, the chuck must be opened allowing the pipe to move from the clamped position, and a shim must be placed in the correct location to adjust the part&#39;s average centerline with respect to the centerline of the power chuck. The shim must be held in place while the chuck is closed. This process may have to be performed repeatedly until the pipe is at an acceptable location. The process is dangerous and time consuming. In addition, the shim can also reduce the holding properties of the chuck jaw&#39;s gripping surface, which could cause the pipe to slip or move during the machining process. 
     Other methods for correcting the runout include the use of specialized chucks such as a self-compensating chuck or a sequencing chuck. In both cases, the machine operator has less control of the pipe&#39;s location. A self-compensating chuck, which relies on an external locating device to hold the pipe in place before the pipe is clamped by the chuck, does not always locate the pipe in an acceptable location due to the various imperfections of the pipe. Also, the weight of the pipe has some negative effects on the external locating device. A sequencing chuck has a locating device built into the chuck that retracts into the chuck body after the part is located and clamped. This chuck is very expensive and also has the same locating problems with the various imperfections of the pipe described above. In addition, when these specialized chucks are used the jaws and the locating device must be changed for each size pipe to be machined, increasing the time and cost to set up the specialized chucks. 
     None of the present methods provides an economical method of locating a pipe for machining. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes the problems present in the prior art by providing a means for clamping a pipe, then adjusting the imperfect pipe&#39;s average centerline by moving one or more of the chuck jaw assemblies by activating its independent, closed hydraulic system in order to adjust the length of the chuck jaw assembly. As the length of a chuck jaw assembly is reduced, the imperfect pipe&#39;s average centerline moves toward that chuck jaw assembly and all the other chuck jaws follow the pipe due to the dynamic clamping properties of a power chuck. On a power chuck with two or more jaws, the imperfect pipe&#39;s average centerline can be moved to any location within the combined adjustable range of all the jaw assemblies. 
     The jaw assemblies of the present invention can be mounted onto the power chuck&#39;s master jaw or can incorporate the master jaw as combined assemblies. 
     Each jaw assembly consists of a base jaw that is affixed to the chuck, a connecting block that moves when the hydraulic system is actuated, and an interchangeable swivel insert with a serrated gripping surface. The swivel insert, which is sized according to the diameter of the pipe being machined, compensates for the roundness imperfections of the pipe and reduces the distortion of the pipe caused by the clamping pressure of the chuck by equally distributing the forces across the entire gripping surface of the swivel insert. Each of the swivel inserts for the jaw assemblies is attached to the connecting block with a single bolt so that it can be quickly changed, depending on the diameter of the pipe being machined. 
     To activate the invention, the chuck must be clamped on the pipe to be machined. The clamping force of the chuck pressurizes the hydraulic system in each jaw assembly. The hydraulic system consists of a single action cylinder, which is built into the connecting block; a piston, which is affixed to the base jaw; a diverting ball valve assembly; two reservoirs; and a check valve assembly. In the unclamped position, the cylinder is completely extended and full of hydraulic oil. In the clamped position, the hydraulic oil in the cylinder is pressurized. With the hydraulic oil under pressure in the cylinder, a fixed amount of the hydraulic oil is removed from the cylinder by the diverting ball valve. The diverting ball valve has three ports: one port to the cylinder; one port to a spring-loaded fixed area reservoir, which is always open to the center of the ball passage, and one port to a spring-loaded hydraulic oil holding reservoir. When the ball valve is turned, opening the passage from the cylinder through the ball, a fixed amount of hydraulic oil fills the spring-loaded fixed area reservoir, reducing the distance between the base jaw and the swivel insert. The measure of the distance reduced is set by the volume of hydraulic oil held in the spring loaded fixed area reservoir, which is adjustable. The resulting reduction in length of the jaw assembly moves the pipe clamped by the chuck jaws toward that particular jaw. When the ball valve is turned to open the passage to the spring-loaded hydraulic oil holding reservoir, since the minimum spring pressure of the spring-loaded fixed area reservoir is greater than the maximum spring pressure of the spring-loaded hydraulic oil holding reservoir, all of the hydraulic oil from the fixed area reservoir is forced into the hydraulic oil holding reservoir, ending one adjustment cycle. Each jaw assembly can be adjusted in the same fashion in order to move the clamped pipe to any location within the adjustable range of the combined jaw assemblies. The number of cycles which one jaw assembly can be adjusted depends on the volume of hydraulic oil in the cylinder. 
     When the pipe is unclamped from the chuck, the spring pressure of the spring loaded hydraulic oil holding reservoir forces all the hydraulic oil back to the cylinder through a check valve. This action restores the original length of each of the jaw assemblies for the next pipe to be clamped. 
     The jaw assemblies could also be activated by an external mechanical device controlled by a machine tools computer program, resulting in a completely automated process. In that event a spool valve rather than a diverting ball valve would be used. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 a  is an isometric bottom view of the jaw assembly of the present invention. 
     FIG. 1 b  is an isometric top view of the jaw assembly of the present invention 
     FIG. 2 is a view of an imperfect pipe that is clamped by three jaw assemblies of the present invention mounted on a power chuck. 
     FIG. 3 is an isometric view of the jaw assemblies of the present invention mounted on a power chuck. 
     FIG. 4 is a top view of the jaw assemblies of the present invention mounted on a power chuck. 
     FIG. 5 is a diagrammatic view of the jaw assemblies of the present invention mounted on a power chuck, holding a pipe on a machine tool lathe. 
     FIG. 6 is an exploded view of the jaw assembly of the present invention. 
     FIG. 7 is a top view of the jaw assembly of the present invention showing its moveable parts. 
     FIG. 8 is a sectional view of the ball valve assembly of the hydraulic system within each jaw assembly of the present invention. 
     FIG. 9 is a sectional view of the jaw assembly of the present invention. 
     FIG. 10 is a side view of the jaw assembly of the present invention. 
     FIG. 11 is a sectional view of the jaw assembly of the present invention. 
     FIG. 12 is an isometric view of the back of the base jaw of the present invention. 
     FIG. 13 is an isometric view of the front of the base jaw of the present invention. 
     FIG. 14 is an isometric view of the piston in the hydraulic system of the present invention. 
     FIG. 15 is a front view of the piston in the hydraulic system of the present invention. 
     FIG. 16 is a sectional view of the piston in the hydraulic system of the present invention. 
     FIG. 17 is a sectional view of the check-valve assembly in the hydraulic system of the present invention. 
     FIG. 18 is an isometric view of the back of the connecting block of the present invention. 
     FIG. 19 is an isometric view of the front of the connecting block of the present invention. 
     FIG. 20 is an isometric view of the front of the swivel insert of the present invention, showing the gripping surfaces. 
     FIG. 21 is an isometric view of the back of the swivel insert of the present invention. 
     FIGS. 22 a - 22   e  is a series of diagrammatic views representing the stages of operation of the internal hydraulic system of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     As shown in FIGS. 1 a  and FIG. 1 b , each jaw assembly  1  of the present invention has a base jaw  2 , a piston  3  (not visible), a connecting block  4 , and a swivel insert  5 . The base jaw  2  will be affixed to a power chuck  20  (not shown) in typical fashion. A swivel insert  5  is attached to the connecting block  4  by shoulder bolt  7 , which fits into threaded hole  8 , allowing the swivel insert  5  to rotate about the axis of the shoulder bolt  7 . The swivel insert  5  can be interchanged with other inserts, depending on the pipe diameter to be machined. Gripping surfaces  6   a ,  6   b  make contact with the surface of the pipe to be machined, in order to prevent slippage. On the bottom of the base jaw  2  are locating surfaces  10   a  and  10   b , which mate to a power chuck  20  (not shown), and a groove, or locating keyway  11 , to align the jaw assembly  1  to the power chuck  20  (not shown). Fixing holes  12  and  13  are used to bolt the jaw assembly  1  to the power chuck  20  (not shown). The locating surfaces  10   a ,  10   b  and the locating key way  11  on jaw assembly  1  vary in configuration depending on the type and model of the power chuck used. The actuator knob  9  is turned, using a hex wrench, to actuated internal hydraulic system. 
     FIG. 2 shows a typical imperfect pipe  14  that is clamped by a power chuck  20  using the jaw assemblies  1   a ,  1   b  and  1   c  of the present invention. The chuck centerline  17  is the center of rotation of the power chuck  20 , the cutting centerline of the machine tool lathe. The pipe centerline  16  is the average center of the imperfect pipe  14 , which varies from the chuck centerline  17  due to the variation in wall thickness  15 . The present invention is designed to move the pipe  14  to the optimum location before machining by reducing the mid-length  18   b  of jaw assembly  1   b  and the mid-length  18   c  of jaw assembly  1   c , without changing the mid-length  18   a  of jaw assembly  1   a . These adjustments will move the pipe  14  in the direction  19 , which moves the pipe centerline  16  to the same location as the chuck centerline  17 , the optimum location for machining the pipe  14 . The swivel inserts  5   a ,  5   b ,  5   c  are able to rotate about the axes of shoulder bolts  7   a ,  7   b ,  7   c , respectively. 
     In FIG.  3  and FIG. 4, three of the jaw assemblies  1   a ,  1   b ,  1   c  have been mounted onto a three jaw, self-centering power chuck  20 . 
     FIG. 5 shows the jaw assemblies  1   a ,  1   b , ( 1   c ) of the present invention used in conjunction with a machine tool lathe  21 . The assemblies  1   a ,  1   b , ( 1   c ) are mounted onto the power chuck  20 , which holds a pipe  22  to be machined. The pipe  22  is supported by standard work holding jaws  24   a ,  24   b  ( 24   c ) on a rear chuck  23  and roller device  25 . The surface to be machined  26  will be cut by the cutting tool in tool holder  27 . 
     The exploded view of FIG. 6 shows all the parts of the jaw assembly  1  of the present invention. The base jaw  2  is the main valve body of the hydraulic system. The internal parts of the base jaw  2  are the diverting ball valve assembly  28 , the metering pistons  45   a ,  45   b , cup seals  46   a ,  46   b , washers  47   a ,  47   b , button head cap screws  48   a ,  48   b , compression springs  49   a ,  49   b  and adjusting caps  50   a ,  50   b , the holding pistons  52   a ,  52   b , cup seals  53   a ,  53   b , button head cap screws  54   a ,  54   b , compression springs  55   a ,  55   b  and caps  56   a ,  56   b . Also shown are the piston  3 , and a spring-loaded check valve assembly  57 , which consists of a check valve cage  58 , compression spring  59 , ball  60 , O-ring  61  and hollow setscrew  75 . O-ring  62  and backup ring  63  in groove  80  is the dynamic seal for piston  3 . O-ring  64   a ,  64   b  seal the hydraulic oil passages  78  (not seen) and  79  (not seen) in the piston  3  to the hydraulic oil passages  72  (not seen) and  73  (not seen) in the base jaw  2 . The piston  3  is located from hole  76  (not seen) to the base jaw  2  with dowel pin  66  to hole  71  (not seen) and fixed with socket head cap screw  65  through hole  69  (not seen) in base jaw  2  to hole  77  (not seen) in piston  3 . Spring  68  forces the connecting block  4  away from piston  3  and spiral retainer ring  67  holds connecting block  4  to piston  3 . The swivel insert  5  is attached to the connecting block  4  through hole  84  with shoulder bolt  7 , which is affixed to hole  8 , allowing the swivel insert  5  to rotate about the axis of the shoulder bolt  7 . When not in contact with a clamped pipe, the swivel insert  5  is centralized by spring plunger  88   a ,  88   b.    
     FIG. 7 shows the moving parts of the jaw assembly  1 . The motion line  87  shows the swivel of the swivel insert  5  about the axis of the shoulder bolt  7 . The swivel insert is centralized by spring plunger  88   a ,  88   b  when not in contact with the clamped pipe (not shown), thereby maintaining the maximum contact between the swivel insert  5  and the part to be machined. The rotating movement  89  shows the movement to actuate the hydraulic system namely turning the actuator  9 . The distance  90  represents the distance between the base jaw  2  and the connecting block  4 , which is changed by actuating the hydraulic system, thereby moving a clamped pipe (not shown). Also shown are cutting line  8  and cutting line  9 . 
     FIG. 8 is a sectional view showing the ball valve assembly  28  of the hydraulic system inside each jaw assembly  1 . The ball valve assembly  28  is comprised of valve stem  30 , which when rotated diverts the flow of hydraulic oil through the valve assembly  28 . A hex wrench is used to rotate the actuator  9 , which is affixed to the valve stem  30  by two setscrews  42   a  and  42   b , thereby rotating the valve stem  30 . The valve stem  30  is sealed by the stem seal  33 , set in place by spacer  32  and the two peek seals  35   a  and  35   b . The coefficient of friction to rotate the valve stem  30  is reduced by the plane bearing  38  and the thrust washer  31  against packing gland  29 . The peek seals  35   a  and  35   b  are set in place by the valve set retainers  34   a  and  34   b . The valve set retainers  34   a  and  34   b  are set in place by the backup rings  37   a  and  37   b  and seat glands  39   a  and  39   b . The valve set retainers  34   a  and  34   b  are spring loaded by spring washers  36   a ,  36   b ,  36   c  and  36   d , which maintain constant force on peek seals  35   a  and  35   c  to the ball on valve stem  30 . The seat glands  39   a  and  39   b  are sealed by O-rings  40   a ,  40   b ,  41   a ,  41   b ,  41   c , and  41   d.    
     The sectional view of the jaw assembly  1  in FIG. 9 shows the base jaw  2  located to the piston  3  with the dowel pin  66  and fixed in place with socket head cap screw  65 . Connecting block  4  held on to the piston  3  with the spiral retainer ring  67 . Spring  68  sets the distance  90  to the maximum position. An interchangeable swivel insert  5  is fixed to connecting block  4  with shoulder bolt  7 . 
     FIG. 10 is a side view of the assembly  1 , showing the cutting line  11 . 
     FIG. 11 is a sectional view of the jaw assembly  1 . Inside the jaw assembly  1  are the pair of spring-loaded metering reservoirs, comprising metering pistons  45   a ,  45   b , cup seals  46   a ,  46   b , washers  47   a ,  47   b , button head cap screws  48   a ,  48   b , compression springs  49   a ,  49   b  and adjusting caps  50   a ,  50   b , and the pair of spring loaded holding reservoirs, comprised of holding pistons  52   a ,  52   b , cup seals  53   a ,  53   b , button head cap screws  54   a ,  54   b , compression springs  55   a ,  55   b  and adjusting caps  56   a ,  56   b.    
     In FIG. 12, the base jaw  2  has cylinder bores  44   a ,  44   b , of the spring-loaded metering reservoirs. 
     The view in FIG. 13 shows cylinder bores  51   a ,  51   b  of the spring-loaded holding reservoirs. The hole  69  is for a socket head cap screw  65  (not shown), which connects the piston  3  (not shown) to base jaw  2 . Piston  3  (not shown) is located in hole  70  and aligned with dowel pin  66  (not shown) in hole  71 . Holes  72  and  73  are hydraulic oil passages to the ball valve assembly  28  (not shown) from piston  3  (not shown). 
     FIG. 14 shows the piston  3 , with threaded fixing hole  77  and alignment hole  76 . 
     In FIG. 15, the front view of the piston , 3  shows the hole  74  for spring  68  (not shown) and cutting line  16 . 
     FIG. 16 shows the piston  3  with hole  78  and hole  79 , which mate to hole  72  and  73  in the base jaw  2  (not shown) and O-ring groove  80 . Also shown is the check valve assembly  57  inside the piston  3  as detail  17 . 
     The detail drawing, FIG. 17 shows the check valve assembly  57 , comprising a check valve cage  58 , compression spring  59 , ball  60 , O-ring  61  and hollow setscrew  75 . 
     As shown in FIG. 18, the connecting block  4  has the cylinder  81 , spiral ring groove  82  for spiral ring  67  (not shown) and hole  83  for spring  68  (not shown). 
     The view in FIG. 19 shows the connecting block  3  with the swivel hole  84  for shoulder bolt  7  (not shown) and locating surface  85  to locate a swivel insert  5  (not shown). 
     FIG. 20 shows the gripping surfaces  6   a ,  6   b  on the swivel insert  5 , which make contact with the pip e (not shown) to be machined. 
     FIG. 21 shows the surface  86  on the swivel insert  5 , which mates to surface  85  on the connecting block  3  (not shown). Hole  8  accommodates shoulder bolt  7  (not shown) 
     FIG. 22 a  through  22   e  represent the movements of a jaw assembly  1  when the hydraulic system is activated. 
     In FIG. 22 a , jaw assembly  1  is not clamped on a pipe (not shown). The ball valve assembly  28  is closed to oil passage  72 ; no force is present in an unclamped state. 
     In FIG. 22 b , clamping force is applied. The ball valve assembly  28  remains closed to oil passage  72 . The clamping force pressurizes the hydraulic oil  91 , which forces the check valve assembly  57  to close oil passage  73 . 
     In FIG. 22 c , with clamping force applied and the ball valve stem  30  (not shown) of the ball valve assembly  28  has rotated 90 degrees from the position in FIG. 24 b , which is open to oil passage  72 , diverting oil  91  from cylinder  81  to the cylinders  44   a ,  44   b . The volume of oil  91  diverted from cylinder  81  moves the connecting block  4  (not shown) toward the base jaw  2  (not shown) the distance  90 . The distance  90  can be pre set by adjusting the area in the cylinders  45   a ,  45   b  with the adjusting caps  50   c ,  50   d  (not shown). 
     FIG. 22 d  with clamping force applied and the ball valve stem  30  (not shown) of the ball valve assembly  28  has rotated 180 degrees from the position in FIG. 22 b , which is open to oil passage  72 , diverting oil  91  from cylinders  44   a ,  44   b  to cylinders  51   a ,  51   b  where the oil  91  is stored until the jaw assembly  1  (not shown) is unclamped or force is no longer applied. 
     FIG. 22 e  shows the state of the hydraulic system after the ball valve stem  30  (not shown) of the ball valve assembly  28  has been rotated several revolutions. 
     When the jaw assembly  1  (not shown) is unclamped or when no force is applied, the hydraulic system returns to the state shown in FIG. 22 a.