Patent Document

TECHNICAL FIELD 
     The present disclosure relates, generally, to impact tools and, more particularly, to impact tools having controlled blow impact mechanisms. 
     BACKGROUND 
     An impact wrench is one illustrative embodiment of an impact tool, which may be used to install and remove threaded fasteners. An impact wrench generally includes a motor coupled to an impact mechanism that converts the torque of the motor into a series of powerful rotary blows directed from one or more hammers to an output shaft called an anvil. In typical impact mechanisms, the timing of these rotary blows is mechanically dependent on the rotational motion of the hammer(s). 
     SUMMARY 
     According to one aspect, an impact tool may comprise an impact mechanism including a hammer and an anvil, where the hammer is configured to rotate and to move between a disengaged position in which the hammer does not impact the anvil when rotating and an engaged position in which the hammer impacts the anvil when rotating and where the anvil is configured to rotate when impacted by the hammer, and an electronic controller configured to cause the hammer to rotate in the disengaged position until reaching a threshold rotational speed and to move from the disengaged position to the engaged position in response to the hammer achieving the threshold rotational speed. 
     In some embodiments, the hammer may be configured to move along an axis between the disengaged position and the engaged position. Each of the hammer and the anvil may be configured to rotate about the axis. The electronic controller may be configured to actuate a solenoid valve to cause the hammer to move from the disengaged position to the engaged position. The electronic controller may be further configured to receive user input and modify the threshold rotational speed based on the user input. The impact tool may further comprise a mechanical spring configured to bias the hammer toward the disengaged position. 
     According to another aspect, a method of operating an impact tool with independent rotational and translational hammer motion may comprise rotating a hammer of an impact tool about an axis in a disengaged position in which the hammer does not impact an anvil of the impact tool, measuring a rotational speed of the hammer about the axis, and moving the hammer from the disengaged position to an engaged position to impact the anvil in response to the rotational speed of the hammer achieving a threshold rotational speed. 
     In some embodiments, moving the hammer from the disengaged position to the engaged position may comprise moving the hammer along the axis from the disengaged position to the engaged position. Moving the hammer from the disengaged position to the engaged position may comprise actuating a solenoid valve. The method may further comprise determining the threshold rotational speed as a function of a user input. The method may further comprise moving the hammer from the engaged position to the disengaged position in response to the hammer impacting the anvil. Moving the hammer from the engaged position to the disengaged position may comprise allowing a mechanical spring that biases the hammer toward the disengaged position to move the hammer. 
     According to yet another aspect, an impact tool may comprise an anvil, a hammer configured to impact the anvil when the hammer may be in an engaged position, a motor configured to drive rotation of the hammer to generate a threshold kinetic energy of the hammer, and an actuator configured to move the hammer from a disengaged position to the engaged position to impact the anvil in response to generation of the threshold kinetic energy. 
     In some embodiments, the motor may be configured to drive rotation of the hammer while in the disengaged position to generate the threshold kinetic energy of the hammer. The actuator may be configured to move the hammer from the disengaged position to the engaged position along an axis. The motor may be configured to drive rotation of the hammer about the axis. The impact tool may further comprise a user interface configured to receive user input and modify the threshold kinetic energy based on the user input. The impact tool may further comprise a speed sensor coupled to a rotor of the motor and configured sense a rotational speed of the rotor and an electronic circuit configured to determine a kinetic energy of the hammer based on the sensed rotational speed of the rotor. The rotor may comprise a first end coupled to the hammer, a second end coupled to the speed sensor, and a plurality of fins positioned between the first and second ends. The actuator may be configured to move the hammer from the disengaged position to the engaged position by diverting motive fluid from the motor to a piston coupled to the hammer. 
     BRIEF DESCRIPTION 
     The concepts described in the present disclosure are illustrated by way of example and not by way of limitation in the accompanying figures. For simplicity and clarity of illustration, elements illustrated in the figures are not necessarily drawn to scale. For example, the dimensions of some elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference labels have been repeated among the figures to indicate corresponding or analogous elements. 
       FIG. 1A  is a partial cross-sectional view of one embodiment of an impact tool, showing a hammer of the impact tool in a disengaged position; 
       FIG. 1B  is a partial cross-sectional view of the impact tool of  FIG. 1A , showing the hammer in an engaged position; 
       FIG. 2  is a simplified block diagram of one embodiment of a control system of the impact tool of  FIGS. 1A-B ; and 
       FIG. 3  is a simplified block diagram of one embodiment of a method for controlling the impact tool of  FIGS. 1A-B . 
    
    
     DETAILED DESCRIPTION 
     While the concepts of the present disclosure are susceptible to various modifications and alternative forms, specific exemplary embodiments thereof have been shown by way of example in the figures and will herein be described in detail. It should be understood, however, that there is no intent to limit the concepts of the present disclosure to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure. 
     Referring generally to  FIGS. 1A-B , partial cross-sectional views of one illustrative embodiment of an impact tool  100  are shown. The impact tool  100  includes a motor  102  configured to drive rotation of an impact mechanism  104  and thereby drive rotation of an output shaft  108 . The motor  102  is illustratively embodied as a pneumatically powered motor (i.e., an air motor) positioned within an internal cavity  110  of a housing  112  of the impact tool  100 . In the illustrative embodiment of  FIGS. 1A-B , the motor  102  is secured to an inner wall  120  of the housing  112  with motor endplates  122 . The motor endplates  122  securely hold the motor  102  in place to prevent movement of the motor  102  within the internal cavity  110  of the housing  112  (e.g., from vibrations of the motor  102 ). It will be appreciated that, in other embodiments, other mechanisms for securing the motor  102  may be used. U.S. Pat. No. 7,886,840 to Young et al., the entire disclosure of which is hereby incorporated by reference, describes at least one embodiment of an air motor that may be used as the motor  102  of the impact tool  100 . It is also contemplated that, in other embodiments of the impact tool  100 , the motor  102  may be embodied as an electric motor. 
     The motor  102  includes a rotor  114  positioned along a longitudinal axis  116  of the impact tool  100 . As illustratively shown, the longitudinal axis  116  extends from a front output end  136  of the impact tool  100  to a rear end  138  of the impact tool. In the illustrative embodiment of  FIGS. 1A-B , one end of the rotor  114  is coupled to a cam shaft  118  such that rotation of the rotor  114  drives rotation of the cam shaft  118 . For example, in some embodiments, the rotor  114  is taper fit to mate with the cam shaft  118 . In other embodiments, another fastening mechanism may be implemented to secure the cam shaft  118  to the rotor  114  for rotation therewith. In still other embodiments, the rotor  114  and the cam shaft  118  may constitute a monolithic structure, rather than separate components secured to one another. In the illustrative embodiment, where the motor  102  is an air motor, the rotor  114  includes a plurality of fins that are configured to be driven by a supply of motive fluid (e.g., compressed air). 
     As shown in  FIGS. 1A-B , the impact mechanism  104  generally includes the cam shaft  118 , a number of bearings  124 , a piston  126 , a hammer  128 , an anvil  130 , and a mechanical spring  132 . The cam shaft  118  passes through an opening in the hammer  128  (e.g., at the center of the hammer  128 ) and drives rotation of the hammer  128 . The cam shaft  118  includes an axial groove  134  defined longitudinally therein and configured to fit a corresponding structure of the hammer  128 . For example, the contour of the axial groove  134  may match a corresponding contour of a protrusion extending radially inward from the hammer  128 . The axial groove  134  permits the hammer  128  to move freely along the longitudinal axis  116  of the impact tool  100 , independent of the rotational motion of the hammer  128 . 
     In the illustrative embodiment, the piston  126  has a generally annular shape and is coupled to the hammer  128  via one or more bearings  124  that allow rotation of the hammer  128  relative to the piston  126 . The piston  126  is configured to move axially along the longitudinal axis  116  within the housing  112  in response to a motive fluid being applied to the piston  126 . A number of bearings  124  are configured to support the piston  126  for translational movement along the longitudinal axis  116 . It will be appreciated that the shape, location, and number of the bearings  124  may vary depending on the particular embodiment. For example, the bearings  124  may include ball bearings configured to be received in corresponding recesses formed in the housing  112 . 
     The hammer  128  is rotatable about the longitudinal axis  116  and is configured to impact the anvil  130  (when in the engaged position shown in  FIG. 1B ), thereby driving rotation of the anvil  130  about the longitudinal axis  116 . In some embodiments, the anvil  130  may be integrally formed with the output shaft  108 . In other embodiments, the anvil  130  and the output shaft  108  may be formed separately and coupled to one another. In such embodiments, the output shaft  108  is configured to rotate as a result of corresponding rotation of the anvil  130 . The output shaft  108  may be configured to mate with a socket (e.g., for use in tightening and loosening fasteners, such as bolts). Although the output shaft  108  is shown as a square drive output shaft, the principles of the present disclosure may be applied to an output shaft of any suitable size and shape. The motor  102  and the impact mechanism  104 , which includes the hammer  128  and the anvil  130 , are adapted to rotate the output shaft  108  in both clockwise and counterclockwise directions, for tightening or loosening various fasteners. 
     The hammer  128  includes a forward impact face  142  facing the front output end  136  of the impact tool  100 . A pair of lugs  144  extends forward from the forward impact face  142 . Each of the lugs  144 , which may be integrally formed with the hammer  128 , includes an impact surface configured to impact a corresponding impact surface of the anvil  130 . In some embodiments, the impact surfaces of the lugs  144  are generally perpendicular to the forward impact face  142  of the hammer  128  but, in other embodiments, the impact surface may be otherwise suitably shaped. Although the illustrative embodiment of the hammer  128  includes two lugs  144 , any suitable number of lugs  144  may be utilized in other embodiments. 
     The anvil  130 , which may be integrally formed with the output shaft  108 , includes a rearward impact face  148  facing the rear end  138  of the impact tool  100 . The rearward impact face  148  includes a pair of lugs  150  extending radially outwardly from the output shaft  108 . Each of the lugs  150 , which may be integrally formed with the anvil  130 , includes an impact surface for receiving an impact blow from the lugs  144  of the hammer  128 . The impact surface may be generally perpendicular to the rearward impact face  148  or otherwise shaped. While the illustrative embodiment of the anvil  130  includes two lugs  150 , any suitable number of lugs  150  may be utilized. 
     The mechanical spring  132  is disposed around the cam shaft  118  between the hammer  128  and the anvil  130  to bias the hammer  128  away from the anvil  130 . As shown in  FIG. 1A , when the hammer  128  is not being driven toward the anvil  130  (i.e., toward an engaged position), the mechanical spring  132  biases the hammer  128  away from the anvil  130  (i.e., toward a disengaged position). In other words, the mechanical spring  132  moves the hammer  128  along the axial groove  134  of the cam shaft  118 , toward the rear end  138  of the impact tool  100 , to provide a clearance  152  between the hammer  128  and the anvil  130 . The clearance  152  separates the lugs  144  of the hammer  128  from the lugs  150  of the anvil  130  so that the lugs  144 ,  150  do not contact one another, despite rotation of the hammer  128 . As the hammer  128  is driven forward toward the anvil  130 , as illustrated in  FIG. 1B , the mechanical spring  132  is compressed (i.e., the biasing force is overcome), diminishing the clearance  152  and allowing the hammer lugs  144  to impact the anvil lugs  150  to transfer rotational torque from the hammer  128  to the anvil  130 . 
     Upon impact, the hammer  128  will rebound and be biased away from the anvil  130  by the mechanical spring  132 . In the illustrative embodiment, the axial groove  134  of the cam shaft  118  terminates at an end  154  thereby limiting the displacement of the hammer  128  toward the rear end  138  of the impact tool  100 . In other words, the mechanical spring  132  may only bias the hammer  128  away from the anvil  130  as far as the end  154  of the axial groove  134 . In some embodiments, the impact mechanism  104  may include other mechanisms for biasing or otherwise moving the hammer  128  away from the anvil  130  upon impact and may include other mechanisms for limiting axial displacement of the hammer  128  toward the rear end  138  of the impact tool  100 . For example, as shown in  FIG. 1A , the piston  126  may also seat against one of the motor endplates  122  to limit axial displacement of the hammer  128  toward the rear end  138  of the impact tool  100 . 
     In the illustrative embodiment shown in  FIGS. 1A-B , the impact tool  100  further includes a valve  156 , which is configured to control the flow of motive fluid. The valve  156  is configured to move between a first position (shown in  FIG. 1A ) in which motive fluid is supplied solely to the motor  102  to drive rotation of the rotor  114  and a second position (shown in  FIG. 1B ) in which motive fluid is at least partially diverted from the motor  102  to drive axial movement of the piston  126 . As such, the valve  156  and the piston  126  together act as a pneumatic actuator to move the hammer  128  from a disengaged position to an engaged position to impact the anvil  130 . The valve  156  may be embodied as any suitable type of valve, such as an electronically controlled solenoid valve. 
     In other embodiments (e.g., in embodiments in which an electric motor is used to drive rotation of the hammer  128 ), the impact tool  100  may include a mechanical or electromechanical actuator, which may be formed with or coupled to the cam shaft  118 , to drive movement of the hammer  128  along the longitudinal axis  116  toward the anvil  130 . In such embodiments, the actuator may additionally move the hammer  128  away from the anvil  130 , without a need for the mechanical spring  132 . Although the hammer  128  has been discussed above as traveling along the longitudinal axis  116  to impact the anvil  130 , it is contemplated that the hammer  128  may travel along a different trajectory in other embodiments. For example, the hammer  128  may translate along an arced path (e.g., via hinged actuation) in order to impact the anvil  130 . 
     The impact tool  100  also includes one or more sensors  158  configured to sense, directly or indirectly, a rotational speed of the hammer  128 . As shown in the illustrative embodiment of  FIGS. 1A-B , one or more the sensors  158  may be coupled to an end of the rotor  114  opposite the end coupled to the camshaft  118  and the hammer  128 . It will be appreciated that, in other embodiments, the sensors  158  may be positioned elsewhere in the impact tool  100 . In the illustrative embodiment, the sensors  158  are configured to sense data that may be used by an electronic controller  202  of the impact tool  100  to determine when to drive the hammer  128  toward the anvil  130 . Accordingly, the sensors  158  may be configured to sense, for example, the rotational speed that various components of the impact tool  100  are traveling (e.g., the hammer  128 , the cam shaft  118 , or the rotor  114 ). As such, the sensors  158  may include, for example, proximity sensors, optical sensors, light sensors, motion sensors, and/or other types of sensors. It should be appreciated that the foregoing examples are merely illustrative and should not be seen as limiting the sensors  158  to any particular type of sensor. As discussed below, once a threshold rotational speed of the hammer  128  has been achieved, the controller  202  may instruct the actuator (e.g., via electrical signals sent to valve  156 ) to move the hammer  128  from the disengaged position to the engaged position to impact the anvil  130 . 
     Referring now to  FIG. 2 , the impact tool  100  includes an electronic control system  200 . It should be appreciated that certain mechanical and electromechanical components of the impact tool  100  are not shown in  FIG. 2  for clarity. The control system  200  generally includes an electronic controller  202 , the valve  156 , the sensor(s)  158 , and a user interface  216 . In the illustrative embodiment, the electronic controller  202  constitutes part of the impact tool  100  and is communicatively coupled to the valve  156 , the sensor(s)  158 , and the user interface  216  of the impact tool  100  via one or more wired connections. In other embodiments, the controller  202  may be separate from the impact tool  100  and/or may be communicatively coupled to the valve  156 , the sensor(s)  158 , and the user interface  216  via other types of connections (e.g., wireless or radio links). The controller  202  is, in essence, the master computer responsible for interpreting signals sent by the sensor(s)  158  and the user interface  216  of the impact tool  100  and for activating or energizing electronically-controlled components associated with the impact tool  100 . For example, the controller  202  is configured to monitor various signals from the sensor(s)  158  and the user interface  216 , to control operation of the valve  156 , and to determine when various operations of the impact tool  100  should be performed, amongst many other things. In particular, as will be described in more detail below with reference to  FIG. 3 , the controller  202  is operable to identify when to move the hammer  128  from the disengaged position to the engaged position to impact the anvil  130 . 
     To do so, the controller  202  includes a number of electronic components commonly associated with electronic controllers utilized in the control of electromechanical systems. In the illustrative embodiment, the controller  202  of the impact tool  100  includes a processor  210 , an input/output (“I/O”) subsystem  212 , and a memory  214 . It will be appreciated that the controller  202  may include additional or different components, such as those commonly found in a computing device. Additionally, in some embodiments, one or more of the illustrative components of the controller  202  may be incorporated in, or otherwise form a portion of, another component of the controller  202  (e.g., as with a microcontroller). 
     The processor  210  of the controller  202  may be embodied as any type of processor(s) capable of performing the functions described herein. For example, the processor  210  may be embodied as one or more single or multi-core processors, digital signal processors, microcontrollers, or other processors or processing/controlling circuits. Similarly, the memory  214  may be embodied as any type of volatile or non-volatile memory or data storage device capable of performing the functions described herein. The memory  214  stores various data and software used during operation of the controller  202 , such as operating systems, applications, programs, libraries, and drivers. For instance, the memory  214  may store instructions in the form of a software routine (or routines) which, when executed by the processor  210 , allows the controller  202  to control operation of the impact tool  100 . 
     The memory  214  is communicatively coupled to the processor  210  via the I/O subsystem  212 , which may be embodied as circuitry and/or components to facilitate I/O operations of the controller  202 . For example, the I/O subsystem  212  may be embodied as, or otherwise include, memory controller hubs, I/O control hubs, firmware devices, communication links (e.g., point-to-point links, bus links, wires, cables, light guides, printed circuit board traces, etc.), and/or other components and subsystems to facilitate the I/O operations. In the illustrative embodiment, the I/O subsystem  212  includes an analog-to-digital (“A/D”) converter, or the like, that converts analog signals from the sensors  158  of the impact tool  100  into digital signals for use by the processor  210 . It should be appreciated that, if any one or more of the sensors associated with the impact tool  100  generate a digital output signal, the A/D converter may be bypassed. Similarly, in the illustrative embodiment, the I/O subsystem  212  includes a digital-to-analog (“D/A”) converter, or the like, that converts digital signals from the processor  210  into analog signals for use by the valve  156  of the impact tool  100 . It should also be appreciated that, if the valve  156  operates using a digital input signal, the D/A converter may be bypassed. 
     The user interface  216  is also communicatively coupled to the processor  210  via the I/O subsystem  212 . The user interface  216  permits a user to interact with the controller  202  to, for example, control operation of the motor  102  and/or modify a threshold value (e.g., threshold rotational speed or kinetic energy of the hammer  128 ) at which the hammer  128  should be moved from the disengaged position to the engaged position to impact the anvil  130 . As such, in some embodiments, the user interface  216  includes a keypad, a touch screen, a display, switches, knobs, and/or other mechanisms to permit I/O functionality. 
     Referring now to  FIG. 3 , one illustrative embodiment of a method  300  of operating the impact tool  100  of  FIGS. 1A-B  is shown as a simplified flow diagram. The method  300  represents one illustrative embodiment of operating an impact tool  100  in which the hammer  128  is capable of independent rotational and translational motion. The method  300  is illustrated in  FIG. 3  as a number of blocks  302 - 312 , which may be performed by various components of the impact tool  100  or, more specifically, of the control system  200  described above with reference to  FIG. 2 . 
     The method  300  begins with block  302  in which the impact tool  100  increases the rotational speed of the hammer  128 . In some embodiments, block  302  may be performed in response to such an instruction from the controller  202 . As described above, the motor  102  drives rotation of the hammer  128  via the cam shaft  118 . The controller  202  may transmit a control signal to the motor  102  to begin rotation of the hammer  128  in response to user input (e.g., a user holding a trigger of the impact tool  100 ). Additionally, as described herein, the controller  202  may cause the speed of the hammer  128  to be increased in response to determining that the hammer  128  is in a disengaged position (i.e., the clearance  152  is present between the hammer  128  and the anvil  130 , as shown in  FIG. 1A ) and that a threshold value (e.g., a threshold rotational speed of the hammer  128 ) has not yet been achieved. 
     After block  302 , the method  300  proceeds to block  304  in which the controller  202  determines whether a particular threshold value for an attribute of the hammer  128  has been achieved. The particular attribute and value defining the threshold value may vary depending on the particular embodiment and the particular sensors  158  used. For example, in an embodiment in which the sensors  158  are used to determine the rotational speed of the hammer  128 , the controller  202  may compare the sensed speed values to a threshold rotational speed to determine whether the threshold rotational speed has been achieved (i.e., met or exceeded). It will be appreciated that sensed values may be used to derive other values that may be compared to a threshold. For instance, the controller  202  may use the sensed rotational speed of the hammer  128  to derive a kinetic energy of the hammer  128 , which may then be compared to a desired kinetic energy as the threshold value. Additionally, in some embodiments, a user of the impact tool  100  may set or otherwise modify the threshold value to be used, via the user interface  216 . 
     If the controller  202  determines in block  304  that the threshold value has not been reached, block  304  may involve the controller  202  returning the method  300  to block  302 . As such, in the illustrative embodiment of  FIG. 3 , blocks  302 ,  304  will be repeated until the threshold value has been reached. If the controller  202  instead determines in block  304  that the threshold value has been reached, the method  300  proceeds to block  306  in which the impact tool  100  moves the hammer  128  from the disengaged position to the engaged position to deliver an impact to the anvil  130 . In particular, block  306  may involve block  308  in which the controller  202  transmits a signal to the valve  156  of the impact tool  100 , providing motive fluid to the piston  126  to move the hammer  128  along the longitudinal axis  116 . In other embodiments, block  306  may involve the controller  202  transmitting a signal to an electromechanical actuator to move the hammer  128  from the disengaged position to the engaged position. 
     After block  306 , the method  300  proceeds to block  310  in which the impact tool  100  returns the hammer  128  to the disengaged position. In particular, block  310  may involve block  312  in which the hammer  128  is returned to the disengaged position by virtue of the mechanical spring  132 . As discussed above in reference to  FIGS. 1A-B , the mechanical spring  132  biases the hammer  128  away from the anvil  130  toward the rear end  138  of the impact tool  100 . After rebounding from impact with the anvil  130 , the hammer  128  is moved (i.e., via the spring bias) from the engaged position to the disengaged position in which there is clearance  152  between the hammer  128  and the anvil  130 . More specifically, air may be supplied to engage the hammer  128  with the anvil  130 . Upon impact, the controller  202  may transmit a signal to the electromechanical actuator (i.e., to energize or de-energize the actuator, depending on the particular embodiment) to cause air to be vented and evacuated from the piston  126 , thereby allowing the mechanical spring  132  to disengage the hammer  128  from the anvil  130  via mechanical bias. 
     In other embodiments, block  310  may involve the controller  202  transmitting a signal to an electromechanical actuator to move the hammer  128  from the engaged position to the disengaged position. In yet another embodiment, the piston  126  may be embodied as a double action air piston. In such an embodiment, the impact tool  100  need not include the mechanical spring  132 . Rather, a control valve may shuttle air between both sides of the piston  126  such that, in one state, the air engages the piston  126  (e.g., to cause the hammer  128  to engage the anvil  130 ) and, in the other state, the air disengages the piston  126  (e.g., to cause the hammer to disengage the anvil  130 ). In some embodiments, the mechanical spring  132  may be positioned at the rear end of the hammer  128  and configured to bias the hammer  128  toward the anvil  130  (i.e., toward the engaged position). In such embodiments, air may be supplied to overcome the spring bias and to cause the hammer  128  to disengage the anvil  130 . It should be appreciated that the hammer  128  may engage and disengage the anvil  130  in another way and/or using another mechanism and may do so using, for example, an electric or air powered actuator. After block  310 , the method  300  returns to block  302 . It is contemplated that the method  300  may be repeated rapidly for tightening or loosening a fastener using the impact tool  100 . 
     While certain illustrative embodiments have been described in detail in the figures and the foregoing description, such an illustration and description is to be considered as exemplary and not restrictive in character, it being understood that only illustrative embodiments have been shown and described and that all changes and modifications that come within the spirit of the disclosure are desired to be protected. There are a plurality of advantages of the present disclosure arising from the various features of the apparatus, systems, and methods described herein. It will be noted that alternative embodiments of the apparatus, systems, and methods of the present disclosure may not include all of the features described yet still benefit from at least some of the advantages of such features. Those of ordinary skill in the art may readily devise their own implementations of the apparatus, systems, and methods that incorporate one or more of the features of the present disclosure.

Technology Category: b