Abstract:
A hydraulic torque wrench system automates the tightening process by continuously operating the torque wrench to alternately advance and retract the wrench cylinder when the advance actuator is held by the operator until the desired pressure or torque is reached. If the advance actuator is released by the operator, the wrench retracts fully and stops advancing. If the advance actuator is not pressed for a period of time while the pump is running, the pump is automatically turned off. The pump can be turned off when the fastener has been tightened to the desired torque or pressure set point, or the pump can continue running in which event the reduction in duration of the alternation cycle between advancement and retraction of the torque wrench cylinder will audibly and visibly signal the operator that the fastener stopping point has been reached. The system can store information correlating pressures with torques for the wrench being used and can include a user adjustable pressure relief valve so it can be used similar to a conventional system. The system controller can be provided with a communications port to communicate with an external computer, either directly or over a network.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This claims the benefit of U.S. Provisional Patent Application No. 60/541,996 filed Feb. 4, 2004. 
     
    
     FIELD OF THE INVENTION  
       [0002]     This invention relates to hydraulic torque wrenches, and in particular to pumps for and methods of controlling hydraulic torque wrench tightening operations.  
       DISCUSSION OF THE PRIOR ART  
       [0003]     Conventional torque wrench pumps typically require the operator to advance and retract the torque wrench cylinder numerous times before final tightening of the fastener is achieved. The required torque set point is obtained by setting an adjustable system relief valve to a pressure setting that corresponds to the desired torque.  
         [0004]     A typical sequence requires the operator to press and hold a button (typically an up arrow [⇑]) to advance the torque wrench cylinder, monitor both the system pressure and wrench cylinder position until it is fully extended, then release the button until the wrench cylinder is fully retracted. This interim tightening step must be repeated numerous times until the proper pressure (corresponding to the desired torque setting) is reached prior to full cylinder extension, indicating the proper fastener torque value has been achieved and the final tightening step completed. The entire process can be very tedious, time-consuming, and often necessitates the use of a second individual (one to monitor wrench position and one to monitor system pressure).  
       SUMMARY OF THE INVENTION  
       [0005]     This invention provides a method and apparatus for precisely controlling and automating a hydraulic torque wrench fastener tightening system. In so doing, valve actuation and system pressure representative of the torque is obtained and is used to monitor the tightening of the fastener and determine a final stopping point for terminating tightening. The invention accomplishes this without adding any attachments to the hydraulic torque wrench.  
         [0006]     By utilizing a system controller and system pressure feedback, the tightening (or loosening) process can be automated to substantially simplify operation, reduce cycle time and operator fatigue, and reduce personnel requirements. Such a sequence automates the interim tightening steps, between starting to tighten and reaching the desired torque. The end result is a fastener that reaches a programmable torque set point in a minimal amount of time without continual manual operation of the advance and retract cycles.  
         [0007]     The invention provides a hydraulic torque wrench fastener tightening system having a double acting cylinder that turns a socket of the wrench upon an advance of the cylinder and ratchets backward over the socket without turning the socket upon a retract of the cylinder in which, in response to an operator actuating an advance actuator and holding it actuated, the system alternately: (a) applies a pressure to the cylinder to advance the cylinder until a set pressure is reached; and (b) applies a pressure to the cylinder to retract the cylinder. A system of the invention does this in such a way that when a desired torque of the fastener is reached, the alternation cycle between processes (a) applying a pressure to the cylinder to advance the cylinder and (b) applying a pressure to the cylinder to retract the cylinder is reduced in duration. This reduction in duration indicates to the operator that the fastener has reached the desired torque, and will be apparent both audibly and visually to the operator. In addition, the pump can be automatically turned off after the fastener has reached the desired torque.  
         [0008]     In one aspect, a hydraulic torque wrench system automates the tightening process by continuously operating the torque wrench to alternately advance and retract the wrench cylinder until the desired pressure or torque is reached. Other aspects of the invention include that: if the advance actuator is released by the operator, the wrench retracts fully and stops advancing; if the advance actuator is not pressed for a period of time while the pump is running, the pump is automatically turned off; the pump can be turned off when the fastener has been tightened to the desired torque or pressure set point or the pump can continue running in which event the reduction in duration of the alternation cycle between advancement and retraction of the torque wrench cylinder will audibly and visibly signal the operator that the fastener stopping point has been reached; the system can store information correlating pressures with torques for the wrench being used; the system can include a user adjustable pressure relief valve so it can be used similar to a conventional system; and the system controller can be provided with a communications port to communicate with an external computer, either directly or over a network.  
         [0009]     These and other objects and advantages of the invention will be apparent from the detailed description and drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]      FIG. 1  is a schematic block diagram of a hydraulic torque wrench system incorporating the invention;  
         [0011]      FIG. 2  is a schematic circuit diagram of the hydraulics and electronics of the system of  FIG. 1 ; and  
         [0012]      FIG. 3  is a flowchart of an algorithm for the system of  FIGS. 1 and 2 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0013]     Referring to  FIGS. 1 and 2 , a hydraulic torque wrench system  10  of the invention includes a power unit  12  and a torque wrench  14 . The power unit  12  has a hydraulic pump  16 , which may be a fixed displacement pump, driven by an electric motor  18  and supplies hydraulic fluid under pressure through a solenoid operated four way two position valve  20 , which may also be manually operable in addition to operation by the solenoids. The pump  16  draws fluid from reservoir tank  22 , to which fluid is returned from the wrench  14  by the valve  20 . In the position of the valve  20  illustrated in  FIG. 2 , fluid under pressure from the pump  16  is directed to the retract port B of the wrench and from the advance port A of the wrench to tank  22 . When the valve  20  is shifted by the solenoids to its other position, fluid under pressure from the pump  16  is directed to the advance port A of the wrench and from the retract port B of the wrench to tank  22 . The system  10  also includes a pressure relief valve  24  that prevents the pressure in the retract line from exceeding a preset limit.  
         [0014]     The power unit  12  also includes a pressure transducer  26  that produces an electrical signal representative of pump pressure, which signal is input to system controller  28 . The controller  28  also receives as inputs the input from a pendant  30  and from a keyboard button input device  32 , that also has an LCD display to display outputs of the system controller  28 . The controller  28 , pendant  30  and input/display  32  may all be considered part of the power unit  12 , although they may be connected to the power unit  12  and to each other by cables that can be unplugged. The controller  28  has outputs to the pump motor  18  and to the valve  20  solenoids to control them. The pendant  30  typically would have at least two buttons, one button  36  that may be labeled with an up arrow to cause the wrench  14  to advance when it is pressed by the operator and held pressed by continuously alternately advancing and retracting the wrench cylinder until the desired torque is reached, and another button  38  that turns the motor  18  off and on. The button  36  may be a momentary contact switch that has to be held to be kept on, and the button  36  may be a toggle type switch that holds its state of being either off or on. The buttons on the device  32  may include, for example, a button to turn the motor on and off, and three buttons (e.g., a menu button and up and down arrow buttons) to scroll through a menu and/or could include a complete computer keyboard for setting input parameters, calibrating or making other settings for the system  10 .  
         [0015]     The wrench  14  may be of any suitable type. One such type is shown schematically, which is of conventional design. The wrench is designed for extremely rugged and heavy-duty service, having a metal body  40  which a hydraulic cylinder  42  within the body. A piston  44  is slideably received in the cylinder to reciprocate axially as hydraulic fluid is introduced to the cylinder at either the advance A or retract B lines. The piston  44  drives a lever  45  back and forth to rotate the fastener head  52  in one direction. The fastener  52  can be tightened or loosened depending on which side of the wrench is used to drive it.  
         [0016]     A fine-toothed spline drive ratchet pawl  46  engages teeth  48  on the outside of the quill shaft  50 , which is journalled in the body  14  to rotate the quill shaft  50  clockwise on the advance stroke. The quill shaft  50  drives a socket, which engages head  52  of a fastener to rotate and tighten (or loosen) the fastener. On the return stroke, the ratchet pawl chatters in reverse over the teeth of the shaft, preventing rotating of the socket and fastener. The full stroke of the cylinder typically corresponds to a fraction of a rotation, on the order of 20-30 degrees. Hence the process of fully tightening a fastener can require dozens of cylinder cycles.  
         [0017]     The pump unit consists of pump  16 , electrical motor  18 , valve  20 , pressure transducer  26 , pendant  30  and system controller  28  incorporating a microprocessor and may also include the display/button unit  32 . The pendant  30  is the primary interface for the operator, typically containing buttons to both turn the motor on and off (the P button  38 ) as well as advance and retract the torque wrench cylinder. To advance with automatically alternating advance and retract cycles, the ⇑ button  36  is pressed (when the pump is on) and to retract and stop advancing the ⇑ button  36  is released (when the pump is on).  
         [0018]     The valve  20  is a dual solenoid operated, four way, two position ( 4 - 2 ) valve which controls the porting of the hydraulic fluid through the system. Referring to  FIG. 2 , actuating solenoid  60  (while deactuating solenoid  62 ) shifts valve  20  leftwardly to connect retract port B to the pump  16  output and connect advance port A to tank  22 . Solenoid  60  may also be referred to as the retract or B solenoid. Actuating solenoid  62  (while deactuating solenoid  60 ) shifts valve  20  rightwardly to connect advance port A to the pump  16  output and connect retract port B to tank  22 . Solenoid  62  may be referred to herein as the advance or A solenoid.  
         [0019]     The display/input unit  32  displays system pressure and pump status, and also incorporates buttons which allow the operator to perform tasks such as entering pressure or torque set points and to cycle through display settings.  
         [0020]     The pressure transducer  26  measures system pressure upstream of the valve  20  and provides feedback to the system controller to determine the cycling set points of the solenoid valve during normal system operation. A calibration program may be provided in the software run by the controller  28  that allows for calibration of the pressure transducer  6  to the microprocessor of the controller  28  and to the display  32  against a certified master gauge.  
         [0021]     The system controller  28  monitors operator inputs from the pendant  30  and input unit  32 , torque wrench pressure as measured by the transducer  26 , and system status. The controller also controls the system operation and provides outputs to the display  32 , the motor  18  and to actuate the valve solenoids  60  and  62 .  
         [0022]      FIG. 3  is a schematic flow chart diagram of the logic used by the controller  28  to control the torque wrench  14 . From start  70 , the motor and both solenoids are turned off at  72  and the on/off motor key (the P key on the pendant or a similar key on the unit  32 ) is monitored at  74 . When a motor on/off key is pressed by the operator, the pump motor  18  is energized by the controller at  76  and the B (retract) solenoid  60  is energized at  78 . The routine then monitors at  79  whether a valid key (either a motor on/off key on the pendant  30  or unit  32  or the ⇑ button  36  on the pendant or a similar advance key on unit  32 ) is pressed within  20  seconds. If no valid key is pressed, the routine goes to  80  where the motor  18  and retract solenoid  60  are de-energized. Both solenoids  60  and  62  are both alternately energized and de-energized twice at  82  (e.g., solenoid  62  on then off, solenoid  60  on then off, solenoid  62  on then off, solenoid  60  on then off) prior to returning to  72  to loop through the above described routine from that point. The on/off valve cycling at  82  is to release oil pressure between the pump, valves, and hoses by allowing trapped oil a path back to tank once the motor has stopped turning. This ensures there is no pressure left in the hoses after the pump motor  18  is shut off and that the display  32  will read zero pressure.  
         [0023]     If a valid key is pressed at  79 , an action is taken at  84 , depending on which key was pressed. Pressing the ⇑ button  36  on the pendant goes to node D at  86  which results in energizing the A (advance) solenoid  62  and de-energizing the B (retract) solenoid  60  at  88 . At  89 , it is determined whether there has been a change in the valid keys, for example, if it had been released. If it had been released, the routine goes to  84  and if no valid key is actuated, the routine is returned to step  78  via node A. If at  89  there is no change in the valid keys, for example if the ⇑ button  36  continues to be pressed, the routine goes to step  90  where the pressure is monitored to determine whether it is above the pressure target, which directly correlates to the torque target if the fastener is being tightened. If it is still below the pressure target, the routine returns to step  89 . If it is above the pressure target, the routine goes to step  91  via node B.  
         [0024]     At step  91 , the B (retract) solenoid  60  is energized and the A (advance) solenoid  62  is de-energized. This would indicate that either the lever of the torque wrench has reached the end of its stroke or that the fastener has been tightened to its target torque. In either case, a retraction stroke is initiated. At step  92 , it is determined if the valid keys have changed, for example if the ⇑ button  36  is released. If so, the routine goes to step  84 . If not, it is determined at step  93  whether the pressure is above the pressure target. If not, step  92  is returned to and the process continues. If the pressure measured by the transducer  26  is above the preset pressure, which indicates that the piston  44  has reached the end of its retraction stroke, the routine goes to node D and picks up at step  88  to continue advancing the wrench.  
         [0025]     If at step  84  it is determined that an on/off motor key at either the pendant  30  or unit  32  is toggled to the off position, the routine goes to node C to enter at step  80  where the motor and B (retract) solenoids are de-energized and the process continues to step  82  as described above.  
         [0026]     If at step  84  it is determined that there is no key activated (⇑ button  36  is released and motor on/off key toggled to off), the routine goes to node A and step  78  where the B (retract) solenoid  60  is energized and the process continues from there.  
         [0027]     From an operator&#39;s viewpoint, the sequence of operation is as follows: 
        1. The operator enters the programmable pressure set point into the system controller  28  via the panel unit  32 , which corresponds to the torque desired to be exerted by the wrench  14 . The pressure set point is determined by the operator via a pressure to torque conversion table for the particular torque wrench  14  in use.     2. The operator presses and releases the motor key P on the pendant, which turns on the pump motor and energizes the B (retract) solenoid  60 . Flow from the pump  16  is ported through the valve  20  into the retract port B of the torque wrench  14 . Flow from the advance port A on the torque wrench is ported through the valve  20  into the pump reservoir  22 . The torque wrench piston  44  retracts (if the piston is not in a fully retracted position), ratcheting along the quill shaft  50  and leaving the fastener  52  stationary. The piston  44  continues to retract until either the advance button  36  (or the advance button on the unit  32 ) is pressed or the wrench  14  fully retracts causing the pressure relief setting of the valve  24  to be reached, porting the pump flow to the pump reservoir  22 . If the advance button is not pressed within  20  seconds, the system controller will turn off the motor.     3. The operator presses the advance key  36  on the pendant  30  which energizes the A solenoid  62  and de-energizes the B solenoid  60 . Flow from the pump  16  is ported through the valve  20  into the advance port A of the torque wrench  14 . Flow from the retract port B of the torque wrench  14  is ported through the valve  20  into the pump reservoir  22 . The torque wrench piston  44  advances, engaging the quill shaft  50  and causing the fastener  52  to rotate. The piston  44  continues to advance until either the advance button  36  is released or the programmable pressure set point is reached. The set point is reached one of two ways: the cylinder reaches full stroke, preventing further advancement, causing the hydraulic pressure to increase to the set point; or the cylinder is in mid-stroke, however, the torque required to turn the fastener increases to the desired value, which causes the hydraulic pressure to increase to the set point.     4. With the advance button  36  still pressed, once the programmable pressure set point is reached, the system controller automatically retracts the wrench by de-energizing the A solenoid and energizing the B solenoid. The wrench retracts fully, causing the pump pressure to rise to a factory set point that is programmed into the controller  28 . The system controller then automatically advances the wrench by energizing the A solenoid and de-energizing the B solenoid (as described in step 3).     5. Upon release of the advance button  36 , the system controller will automatically fully retract the wrench, regardless of cylinder position or fastener torque. If the advance button is not pressed again within 20 seconds, the system controller will turn off the motor.        
 
         [0033]     As long as the advance button remains pressed, the system controller will continue this automatic cycling of the wrench (between advance and retract). This saves operation time, as the operator no longer needs to manually identify the end of each advance and retract cycle. It reduces operator fatigue, as the operator no longer needs to press and release control button(s) for each cycle.  
         [0034]     When the torque required to turn the fastener increases to the desired value, additional automatic cycles (advance and retract) will be very short in duration due to lack of fastener movement. This shortened duration will be both audibly and visually apparent to the operator that the fastener is at the desired torque. This saves operation time and reduces the personnel involved, since monitoring system pressure is no longer needed.  
         [0035]     This also provides full pump flow to the wrench right up to the point of the programmable pressure set point. The extra flow reduces wrench cycle time and provides a hydraulic impact through the wrench to the nut, which speeds the tightening (loosening) process (similar to an impact wrench). It also eliminates the need for a user adjustable pressure relief valve on the pump circuit, which reduces product cost.  
         [0036]     Additional features could be programmed into the system. For example, the pump could be automatically shut off when the fastener has reached the desired torque. This could be accomplished by the controller  28  measuring the duration of each advance and retract cycle, and when the duration drops below a corresponding set point, the system controller turns the pump  18  off. Another feature is that the controller could store pre-programmed torque wrench types. This would allow an operator to select from a variety of existing torque wrench models that have torque-to-pressure conversion factors programmed into the system controller. In doing so, the operator could set the tightening (loosening) torque set point to a specific torque value without having to manually look up the conversion value or pressure equivalent. Alternatively, the operator could also manually input a torque-to-pressure conversion factor into the system controller for a specific wrench. In both these cases the equivalent torque value could also be displayed on the LCD display  32  during system operation in lieu of or in addition to pressure. Other features that could be incorporated are that a user adjustable pressure relief valve could be added in the pump circuit to also allow the pump and wrench to be operated in a typical sequence as was used in conventional hydraulic torque wrench systems, and the microprocessor&#39;s communication port could be used to export the operation data live to an external computer.  
         [0037]     Preferred embodiments of the invention have been described in considerable detail. Many modifications and variations to the preferred embodiments described will be apparent to persons skilled in the art. Therefore, the invention should not be limited to the preferred embodiments described, but should be defined by the claims which follow.