Abstract:
An open end power wrench includes an operating scheme that identifies when the item within the drive socket is an item that should be rotated by the drive socket. The method for controlling the tube nut wrench includes the steps of operating the motor to generate an output torque. The method then measures an angle of rotation through which the drive socket rotates. The angle of rotation is then compared with an angle defined by the clearance opening. The output torque is limited to a minimal torque level when the angle of rotation of the drive socket is less than the angle defined by the clearance opening. The method then increases the output torque to an operating torque level when the angle of rotation of the drive socket exceeds the angle defined by the clearance opening.

Description:
BACKGROUND ART  
         [0001]    1. Field of the Invention  
           [0002]    The invention relates to a method for operating an open end power wrench. More particularly, the invention relates a method for controlling a drive socket on an open end power wrench by measuring parameters thereof.  
           [0003]    2. Description of the Related Art  
           [0004]    Open end power wrenches are used in the manufacturing of products. One type of an open end power wrench is a tube nut wrench. The tube nut wrench is designed to allow the operator thereof to tighten fasteners designed to secure hydraulic and/or pneumatic lines sharing a common centerline with the fastener. The tube nut wrench also facilitates the operator&#39;s ability to maximize torque on a fastener or part when the location of the fastener or part does not allow the operator to have a mechanical advantage over the fastener or part being worked.  
           [0005]    U.S. Pat. No. 5,363,698, issued to Estep et al. on Jun. 10, 1997, discloses a tube nut wrench. This tube nut wrench extends from a tube nut head to a handle. A power cable or air line extends out from a distal end of the handle. The power source provides power to the tube nut wrench.  
           [0006]    In addition, the tube nut wrench disclosed in this reference does not have any means for regulating the speed or torque output of the drive socket as the drive socket rotates through its initial open-to-close rotation. More specifically, neither this reference nor any other tube nut wrench known includes a feature designed to vary or control the speed or torque of the drive socket as the drive socket moves from its starting position through its initial closed position. Such a feature is desirable because so often the drive socket is inadvertently placed on items that are not the item to be rotated. Another situation that occurs is when a fastener is not properly aligned. In this instance, full torque on the fastener may damage the fastener or part assembly.  
         SUMMARY OF THE INVENTION  
         [0007]    The invention is a method for controlling a tube nut wrench. The tube nut wrench includes a tool engaging end, a motor, a switch electrically connected to the motor for selectively operating the motor, a transmission operatively connected to the motor, a housing defining a clearance opening, and a drive socket. The drive socket is connected to the transmission and rotatable with respect to the housing. The drive socket defines a socket opening equal to the clearance opening. The method includes the steps of operating the motor to generate an output torque. The method then measures an angle of rotation through which the drive socket rotates. The angle of rotation is then compared with an angle defined by the clearance opening. The output torque is limited to a minimal torque level when the angle of rotation of the drive socket is less than the angle defined by the clearance opening. The method then increases the output torque to an operating torque level when the angle of rotation of the drive socket exceeds the angle defined by the clearance opening. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    Advantages of the invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:  
         [0009]    [0009]FIG. 1 is a perspective view of a tube nut wrench connected to a power source incorporating one embodiment of the inventive method;  
         [0010]    [0010]FIG. 2 is a perspective view of the tube nut wrench and a fastener to be tightened on a part;  
         [0011]    [0011]FIG. 3 is a top view, partially cut away of a tool engaging head of a tube nut wrench; and  
         [0012]    FIGS.  4 - 1  and  4 - 2  are portions of a logic chart of one embodiment of the inventive method. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0013]    Referring to FIG. 1, one embodiment of an open end power wrench is generally indicated at  10 . For purposes of simplicity, the remainder of the discussion will refer to one type of open end power wrench, i.e., a tube nut wrench  10 .  
         [0014]    The tube nut wrench  10  extends through a longitudinal axis from a handle end  12  to a tool engaging end  14 . The tube nut wrench  10  has a generally cylindrical shape allowing an operator to easily handle it. A surface treatment  16  may extend along a portion of an outer surface  18  to facilitate the handling of the tube nut wrench  10 . While a longitudinal ribbing is used as the surface treatment  16 , it should be appreciated by those skilled in the art that any number of different surface treatments might be used without adding an inventive quality to the tube nut wrench  10 .  
         [0015]    The tube nut wrench  10  includes a power supply  13  (not shown) and a motor, graphically represented at  19  in FIG. 3. The power supply  13  may be a source of electricity or a source of air. In the former case, the motor  19  is electric, whereas, in the latter case, the motor  19  is pneumatic. A plug extending out of the tube nut wrench  10  from the handle end  12  allows the tube nut wrench  10  to be connected to the power supply  13  via an electrical connection  15 . The motor  19  transforms the energy received from the power source  13  into mechanical energy. In particular, the mechanical energy is the rotation of a shaft that extends through the motor  19 . The motor  19  design is not a part of the inventive method.  
         [0016]    A switch  20  also extends out from the handle end  12  of the tube nut wrench  10 . The switch  20  selectively closes the circuit between the motor  19  and the battery. In the embodiment shown, the switch  20  is a dead-man switch designed to receive the palm of a hand of the operator. Other types of switches  20  may be used.  
         [0017]    The motor  19  is operatively connected to a drive socket, generally indicated at  22 . The drive socket  22  is the part of the tube nut wrench  10  that comes in direct contact with the piece, i.e., a fastener  23 , that is to be rotated by the tube nut wrench  10 . The rotation of the motor  19  is bidirectional. The drive socket  22  utilizes both directions of the motor  19  to move from its start orientation to its stop orientation and back again. Once the drive socket  22  has completed its operative rotation, it backtracks to its start orientation so that it may re-orient a socket opening  26  (discussed subsequently) of the drive socket  22  in the proper position for the next fastener  23  to be accessed. It should be appreciated that the backtracking does not occur until the drive socket  22  is removed from the fastener  23 .  
         [0018]    Referring to FIG. 3, the drive socket  22  includes a circular drive  24 . The circular drive  24  defines a circular periphery that extends around the majority of the circular drive  24 . The circular periphery is broken by the socket opening  26  that provides access into a portion of the interior of the drive socket  22 . The socket opening  26  provides access to the fastener  23  when a tube  27  extends therethrough. The circular drive  24  may be characterized as a sector gear in that gear teeth  28  extend along the outer periphery that is circular. The interior of the drive socket  22  is a plurality of sides  30 . While there may be any number of sides  30 , the embodiment shown in FIG. 3 includes ten sides  30 . The ten sides  30  correspond to receive a nut or bolt  23  in the shape of a hexagon. The eleventh and twelfth sides are missing because it provides for the socket opening  26 .  
         [0019]    A transmission  32  extends between the motor and the drive socket  22 . The transmission  32  includes two drive gears  36 ,  38  and two engaging gears  40 , 42 . The three drive gears  34 ,  36 ,  38  extend out from the motor  19  and transmit the rotational force generated by the motor  19  out to the drive socket  22 . The two engaging gears  40 ,  42  are used to directly engage the gear teeth  28  of the drive socket  22  to rotate the drive socket  22  in the desired direction. Two engaging gears  40 ,  42  are required so that the transmission of the rotational force is not interrupted when the socket opening  26  passes thereby. Therefore, the two engaging gears  40 ,  42  must be spaced from each other along the circular drive  24  a distance greater than the length of the socket opening  26 , and in the embodiment shown, greater than the length of one of the sides  30 .  
         [0020]    One of the drive gears  38  includes an interior stop  44 . The interior stop  44  is a surface that is designed to be an abutment for a pawl  46 . When the drive gear  38  is rotated (in the clockwise direction for FIG. 3), the pawl  46  hits the interior stop  44  and prevents the drive gear  38  and, hence, the drive socket  22 , from rotating therepast. The interior stop  44  is positioned such that when the pawl  46  abuts thereagainst, the drive socket  22  is in its start position (FIG. 3).  
         [0021]    The tool engaging end  14  of the tube nut wrench  10  includes a housing  48 . The housing  48  holds the drive socket  22  in place with respect to the tool engaging end  14 . The housing  48  is forked and defines a clearance opening  50 . The clearance opening  50  is slightly larger than the socket opening  26 . In the embodiment shown in the Figures, the socket opening  26  defines an angle of sixty degrees whereas the clearance opening  50  is slightly larger than that. The clearance opening  50  is oriented such that the housing  50  and socket  26  openings are aligned when the drive socket  22  is in its rest or starting position (FIG. 3).  
         [0022]    Referring to FIGS.  4 - 1  and  4 - 2 , the logic chart for the inventive method is generally indicated at  52 . The method  52  begins at  54  by determining whether a foreign object mode is active. If not, an indicator is activated at  56  to identify to the operator that this mode is not active.  
         [0023]    Regardless of whether the foreign object mode is on or off, the next step of the method is to determine whether the switch  20  has been released at  58 . If the switch  20  has been released, i.e., the tube nut wrench  10  is off, then the method  52  loops until the switch  20  changes states resulting in the motor being activated. If the switch  20  has not been switched to an off state, it again tests the state of the switch  20  at  60 .  
         [0024]    If the switch  20  has now been turned off, it is determined at  62  whether the tube nut wrench  10  has attempted to rotate the drive socket  22 . If not, the method  52  does not run at  64  preventing the drive socket  22  from being rotated. It should be appreciated by those skilled in the art that the method  52  may replace the no run step  64  with a stop command. This would be a positive signal to tell the tube nut wrench  10  that the drive socket  22  is not to be rotated. Conversely, if the tube nut wrench  10  has run, the method  52  then reverses the motor  19  and the drive socket  22  at  66  to return the drive socket  22  to its start or home position (FIG. 3).  
         [0025]    If the switch  20  is still active, it now calculates a full torque command at  68 . The full torque command is not necessarily the full capability of the tube nut wrench  10 , but the designed full torque for that particular job or task. The torque command is generated in a control unit (not shown). The full torque command is stored until it is determined that the drive socket  22  can be driven at a full torque level. It should be appreciated by those skilled in the art that the force is being identified when torque measurements are taken. Measuring a parameter to affectively measure force without measuring torque would be considered an equivalent of measuring torque.  
         [0026]    At the same time the torque command is being generated, the tube nut wrench  10  measures the amount of torque currently being applied to the drive socket  22  by the motor  19  via the transmission  32  and the angle of rotation at which the drive socket  22  is currently positioned. This step is performed at  70 . It is then determined at  72  whether the torque or angle targets have been hit. If so, a run command is not issued at  74  and the method  52  loops back to test when the switch  20  is again activated at  58 .  
         [0027]    Referring to FIG. 4- 2 , the method  52  continues by again testing in which mode the tube nut wrench  10  is operating. More specifically, it is determined at  76  whether the tube nut wrench  10  is operating in the foreign object mode. If the tube nut wrench  10  is not in the foreign object mode, the method  52  produces a command at  78  to output full torque. A full torque output may be factory set or it may be set by the operator. Regardless, when a full torque output command is created, the torque created by the tube nut wrench  10  will be the designated full torque. The method  52  then returns to test whether the switch  20  is still active at  60 . The full torque output will continue running through the loop allowing the angle and torque measurements to be taken until one of the targets is hit or when the switch  20  is deactivated by the operator releasing it.  
         [0028]    If the tube nut wrench  10  is operating in the foreign object mode, the angle of rotation of the drive socket  22  is measured and compared at  80  with an angle defined by the clearance opening  50 . In the preferred embodiment, the compare step  80  uses an angle defined by the clearance opening  50 . In the embodiment shown with a drive socket  22  having the plurality of sides  30  equating to receiving a nut or bolt  23  hexagonal in shape, the clearance opening  50  equals approximately sixty degrees.  
         [0029]    If the angle of rotation is greater than the angle defined by the clearance opening  50 , the method  52  operates the tube nut wrench  10  in the full output torque mode as shown at  78 .  
         [0030]    If the angle of rotation is less than the angle defined by the clearance opening  50 , the tube nut wrench  10  limits the torque output by the motor  19  at  82 . The limitation of torque prevents the tube nut wrench  10  from damaging a foreign object or a misaligned part.  
         [0031]    Once the limit torque command has been issued, step  82 , it is determined whether a measured torque generated by the tube nut wrench  10  is greater than a set torque at  84 . If the measured torque is equal to or greater than the set torque, a predetermined value for the particular job being performed, then the tube nut wrench  10  is stopped at  86 . Depending on the method incorporated into the tube nut wrench  10 , it may automatically reverse to its start or home position, after which, the method returns to the point of determining whether the switch  20  has been released at  58 . If the measured torque is not equal to or greater than the set torque, a second test is performed at  88 . The second test determines whether a time of drive socket  22  rotation is greater than a set time. If the measured or elapsed time is equal to or greater than the set time, a predetermined value for the particular job being performed, then the tube nut wrench  10  is stopped at  86 .  
         [0032]    If the measured time is not equal to the set time, a third test is performed at  90 . This test measures current across the motor  19  to determine whether a change occurs. In the electrical embodiment, the current is an electric current. In the pneumatic embodiment, the current is the pressure of air building up against a motor  19  that may not be turning. In the instance of an electric motor  19 , if the change in the measured current is an increase greater than a predetermined value while the angle of rotation is less than the angle defined by the clearance opening  50 , the tube nut wrench  10  is stopped at  86 . In the instance of a pneumatic motor  19 , if the change in the measured current reduces the measured current to a value approaching zero while the angle of rotation is less than the angle defined by the clearance opening  50 , the tube nut wrench  10  is stopped at  86 .  
         [0033]    In an alternative pneumatic embodiment, the current measurement could be a measure of the flow of air as opposed to air pressure. In this instance, any flow decrease would indicate an object is present in the clearance opening  50  of the drive socket  22 .  
         [0034]    The three steps of measuring torque  84 , measuring time  88  and measuring current  90  are performed sequentially as set forth above. In alternative embodiments, these steps  84 ,  88 ,  90  may be incorporated into the inventive method independently and exclusively of one another. In addition, derivatives of these steps may also be performed. By way of example, a test may be a measure of the angle as a function of time. This measurement could be performed in terms of revolutions per minute. As the RPMs reduce to zero, it would indicate an object is obstructing the free movement of the drive socket  22 .  
         [0035]    Again, in an alternative embodiment, a test directly measuring RPMs may be included as an independent or subsequent test at  92 . A sensor (not shown) on a shaft of the motor  19  could indicate each rotation thereof. As the RPMs reduce to zero, an indication of an object being present would result in the stopping of the tube nut wrench  10  at  86 .  
         [0036]    The invention has been described in an illustrative manner. It is to be understood that the terminology, which has been used, is intended to be in the nature of words of description rather than of limitation.  
         [0037]    Many modifications and variations of the invention are possible in light of the above teachings. Therefore, within the scope of the appended claims, the invention may be practiced other than as specifically described.