Patent Publication Number: US-7913890-B2

Title: Multistage solenoid fastening device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. patent application Ser. No. 12/402,974 filed on Mar. 12, 2009, now issued as U.S. Pat. No. 7,665,540, which is a divisional of U.S. patent application Ser. No. 11/670,088 filed on Feb. 1, 2007, now issued as U.S. Pat. No. 7,537,145. The entire disclosure of the above applications is incorporated herein by reference. 
    
    
     FIELD 
     The present teachings relate to a cordless fastening tool and more specifically relate to a multistage solenoid that can extend and retract a driver blade of the cordless fastening tool and adjust the magnetic fields of each of the stages of the multistage solenoid based on a position of the armature within the multistage solenoid. 
     BACKGROUND 
     Traditional fastening tools can employ pneumatic actuation to drive a fastener into a workpiece. In these tools, air pressure from a pneumatic system can be utilized to both drive the fastener into the workpiece and to reset the tool after driving the fastener. It will be appreciated that in the pneumatic system a hose and a compressor are required to accompany the tool. A combination of the hose, the tool and the compressor can provide for a large, heavy and bulky package that can be relatively inconvenient and cumbersome to transport. Other traditional fastening tools can be battery powered and can engage a transmission and a motor to drive a fastener. Inefficiencies inherent in the transmission and the motor, however, can limit battery life. 
     A solenoid has been used in fastening tools to drive fasteners. Typically, the solenoid executes multiple impacts on a single fastener to generate the force needed to drive the fastener into a workpiece. In other instances, corded tools can use a solenoid to drive the fastener but the energy requirements can be relatively large and are better suited to corded applications. 
     SUMMARY 
     The present teachings generally include a device including a multistage solenoid having at least a first stage, a second stage and an armature member that travels therebetween. The device also includes a control module connected to the multistage solenoid. The control module detects a position of the armature member relative to at least one of the first stage, the second stage and a combination thereof. The control module adjusts a magnetic field of the at least one of the first stage, the second stage and the combination thereof based on the position of the plunger armature relative thereto. 
     Further areas of applicability of the present teachings will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the various aspects of the present teachings, are intended for purposes of illustration only and are not intended to limit the scope of the teachings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present teachings will become more fully understood from the detailed description, the appended claims and the accompanying drawings, which are each briefly described below. 
         FIG. 1  is a perspective view of an exemplary cordless fastening tool having a multistage solenoid capable of inserting an exemplary fastener and an exemplary workpiece constructed in accordance with one aspect of the present teachings. 
         FIGS. 2A ,  2 B and  2 C are diagrams showing a progression of an exemplary driver sequence of a multistage solenoid that extends a portion of a driver assembly from a retracted condition to an extended condition constructed in accordance with one aspect of the present teachings. 
         FIG. 3  is a diagram of a multistage solenoid having sensors that detect a position of a plunger relative to the stages constructed in accordance with one aspect of the present teachings. 
         FIG. 4  is a diagram of a multistage solenoid having four stages constructed in accordance with one aspect of the present teachings. 
         FIG. 5  is a diagram showing a spring member connected to a plunger of a multistage solenoid that returns the plunger to the retracted condition from the extended condition constructed in accordance with one aspect of the present teachings. 
         FIGS. 6A ,  6 B and  6 C are diagrams of a driver sequence of a multistage solenoid with a plunger having a return spring that extends to contact a separate driver blade that also has a return spring constructed in accordance with one aspect of the present teachings. 
         FIG. 7  is a diagram of a value of current used by the multistage solenoid and shows an inflection point of the value of current associated with a stage in the multistage solenoid in accordance with one aspect of the present teachings. The value of current is shown as a function of voltage and time. 
         FIG. 8  is a flowchart of an exemplary method of use of the multistage solenoid in a fastening tool in accordance with another aspect of the present teachings. 
     
    
    
     DETAILED DESCRIPTION 
     The following description of the various aspects of the present teachings is merely exemplary in nature and is in no way intended to limit the teachings, their application or uses. As used herein, the term module and/or control module can refer to an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that executes one or more software or firmware programs, a combinational logic circuit, other suitable components and/or one or more suitable combinations thereof that provide the described functionality. 
     With reference to  FIG. 1 , an exemplary fastening tool  10  can include a multistage solenoid  12  that can drive a driver assembly  14  between a retracted condition (as shown in  FIG. 1 ) and an extended condition (see, e.g.,  FIG. 2C ) in accordance with one aspect of the present teachings. The fastening tool  10  can include an exterior housing  16 , which can house a first stage  18  and a second stage  20  of the multistage solenoid  12 . The exterior housing  16  can further contain the driver assembly  14  and a control module  22 . While the multistage solenoid  12  is shown in  FIG. 1  with the first stage  18  and the second stage  20 , the multistage solenoid  12  can include additional stages in suitable implementations, examples of which are later described herein. 
     The exemplary fastening tool  10  can also include a nosepiece  24 , a fastener magazine  26  and a battery  28 . The fastener magazine  26  can be connected to the driver assembly  14 , while the battery  28  can be coupled to the exterior housing  16 . The control module  22  can control the first stage  18  and the second stage  20  to magnetically move the driver assembly  14  so that a driver blade  30  can drive one or more fasteners  32  into a workpiece  34  that are sequentially fed from the fastener magazine  26  when a trigger assembly  36  is retracted. The fasteners  32  can be nails, staples, brads, clips or any such suitable fastener  32  that can be driven into the workpiece  34 . 
     With reference to  FIGS. 2A ,  2 B and  2 C, a multistage solenoid  100  can include a first stage  102  and a second stage  104  that can each include one or more coil assemblies that can be selectively energized to establish a magnetic field and de-energized to collapse the magnetic field in accordance with one aspect of the present teachings. By selectively energizing and de-energizing the first stage  102  and/or the second stage  104 , the one or more magnetic fields can establish a generally linear motion of an armature member  106  that moves relative to the stages  102 ,  104 . In one example, the magnetic fields can be selectively energized or collapsed to relatively efficiently drive the one or more fasteners  32  ( FIG. 1 ). The multistage solenoid  100 , however, can save (i.e., not expend) the energy to maintain the magnetic fields by collapsing the magnetic fields at predetermined times and/or locations of the armature member  106  relative to stages  102 ,  104 . 
     The armature member  106  can define (wholly or partially) a plunger member  108  that can move from a retracted condition ( FIG. 2A ) to an extended condition ( FIG. 2C ). In  FIG. 1 , the driver assembly  14  can include the driver blade  30  that can be connected to a plunger member  108   a  via a link member  38 . The plunger member  108   a  can define (wholly or partially) an armature member  106   a  associated with the multistage solenoid  12 . In other examples, additional link members can connect the driver blade  30  to the plunger member  108   a  or the plunger member  108   a  can also be directly coupled to the driver blade  30 . 
     Returning to  FIGS. 2A ,  2 B and  2 C, the plunger member  108  can travel between a top stop  110  and a bottom stop  112 . A portion of the plunger member  108  can define a driver blade  120 , when applicable. The top stop  110  and/or the bottom stop  112  can be a portion of the stages  102 ,  104 , an interior portion of the exterior housing  16  ( FIG. 1 ), a separate component connected to the interior portion of the exterior housing  16  and/or the stages  18 ,  20 , and/or one or more combinations thereof. In any of the above configurations, the driver blade  120  can extend beyond the bottom stop  112 . 
     In various aspects of the present teachings, the driver assembly  14  can cycle through a driver sequence that can drive the fastener  32  into the workpiece  34 , as shown in  FIG. 1 . With reference to  FIG. 2A , the driver sequence can begin, for example, with the plunger member  108  in the retracted condition. The first stage  102  and the second stage  104  can be energized to establish the respective magnetic fields to draw the plunger member  108   a  (i.e., the armature member  106 ) toward the second stage  104 . When the plunger member  108  is connected to a driver blade  120 , the driver blade  120  can begin to move from a retracted condition to an extended condition. The plunger member  108  can end its motion at or near the bottom stop  112 . 
     To return the plunger member  108  to the retracted condition, the first stage  102  and/or the second stage  104  can be energized but the direction of the magnetic field can be reversed so as to reverse the direction of the magnetic force applied to the plunger member  108 . For example, the plunger member  108   a , in  FIG. 1 , can return the driver blade  30  to the retracted condition from the extended condition. As shown in  FIGS. 2A ,  2 B and  2 , the armature member  106  can further define a core member  124  that can be secured to the plunger member  108  with a cap member  122 . In one aspect of the present teaching the cap member  122  and/or the core member  124  can be included, while in other aspects of the present teaching the cap member  122  and/or the core member  124  can be omitted. 
     As the plunger member  108  travels between the stages  102 ,  104 , the respective magnetic fields can be energized or collapsed accordingly to facilitate the motion of the plunger member  108  through the driver sequence and conserve energy consumption during such motion. Specifically, a position of the plunger member  108  (i.e., the armature member  106 ) can be determined relative to the stages  102 ,  104  by detecting, for example, a change in current. The change in current can be caused by a change in inductance of one or more coil circuits in one or more coil assemblies that can be associated with one or more of the stages  102 ,  104 . Specifically, this change in inductance affects the resistance of the one or more coil circuits in the one or more coil assemblies, which can ultimately be measured as a change in current associated with a respective coil circuit. 
     In one aspect of the present teachings and with reference to  FIG. 7 , a diagram  150  shows a value of current  152  as a function of time and direct current voltage. A current inflection point  154  can be detected and can serve as a proxy for the position of the armature member  106  ( FIG. 2 ) in the multistage solenoid  100  ( FIG. 2 ). When the first inflection point  154  is detected, the control module  22  ( FIG. 1 ) can direct full power from the first stage  102  ( FIG. 2 ) to the second stage  104  ( FIG. 2 ). It will be appreciated in light of the disclosure that when a multistage solenoid having more than two stages, see, e.g.,  FIG. 4 , the direction of full power between the stages based on the detection of the inflection point can be repeated as the armature member  106  travels between the stages. Regardless of the amount of stages, the control module  22  can direct full power to each stage and switch power between the stages based on the position of the armature member  106  without the need to modulate the power with, for example, pulse width modulation. 
     The detection of the inflection point  154  can be based on detection of a threshold change of rate of a value of current. By detecting the threshold change of a value of a rate of a current, the control module  22  ( FIG. 1 ) can account for relative changes in voltage due to, for example, changes in remaining battery life and changes in ambient conditions such as ambient temperature. The inflection point can also define a point where the value of the change of rate of current, as illustrated in  FIG. 7 , changes from a positive value to a negative value or vice versa, i.e., the concavity of the slope changes. In this instance, the control module  22  can specifically determine when the value of the rate of change of the value of current changes from a positive value to a negative value, as shown at the inflection point  154 . Put another way, the control module  22  detects the value of the second derivative of current of a period of time, such that when the value of the second derivative becomes negative, the control module can direct power to the subsequent stage. 
     In one aspect of the present teaching and with reference to  FIG. 3 , one or more sensors  200  can be used to detect the position of the armature member  106  relative to the stages  102 ,  104  in the multistage solenoid  100 . In doing so, the position and/or velocity of the armature member  106  and the energizing and collapsing of magnetic fields of the stages  102 ,  104  can be tuned (i.e., adjusted) to further conserve energy and/or increase a force produced by the multistage solenoid  100 . 
     In a further aspect of the present teachings and with reference to  FIG. 4 , a multistage solenoid  300  can include more than two stages: a first stage  302 , a second stage  304 , a third stage  306  and a fourth stage  308 . As a plunger member  310  (i.e., an armature  312 ) is drawn from a retracted condition to an extended condition (not specifically shown), each of the stages  302 ,  304 ,  306 ,  308  can be energized and de-energized in a cascading fashion. To this end, the plunger member  310  can be continuously accelerated toward the next stage (e.g., the second stage  304  to the third stage  306 ) until the travel of the plunger member  310  terminates in the extended condition and/or a portion of the plunger member  310  contacts a second stop  312  that resides on an opposite side of the multistage solenoid  300  from a first stop  314 . The plunger member  310  can define a driver blade  316  or can connect thereto in various suitable fashions. From the extended condition, each of the stages  302 ,  304 ,  306 ,  308  can be energized and then de-energized in a similar but reverse cascading fashion to draw the plunger member  310  from the extended condition back to the retracted condition, as shown in  FIG. 4 . A spring or other suitable elastic member can also be used to move (partially or wholly) the plunger member  310  from the extended condition to the retracted condition, as discussed in greater detail below. 
     In accordance with yet another aspect of the present teachings and with reference to  FIG. 5 , a spring  400  or other suitable elastic member can be attached to a portion of a plunger member  402 . The spring  400  can hold the plunger member  402  in a retracted condition (see, e.g.,  FIG. 6A ) and, when applicable, urge the plunger member  402  to return to the retracted condition from an extended condition (see, e.g.,  FIG. 6B ). It will be appreciated in light of the disclosure that a first stage  404  and/or a second stage  406  of a multistage solenoid  408 , when energized, can hold the plunger member  402  in the retracted condition. In this example, the spring  400  can, in combination with the first stage  404  and/or the second stage  406  (or by itself), also hold the plunger member  402  in the retracted condition. 
     When the second stage  406  is energized and draws the plunger member  402  toward a second stop  410  and into the extended condition (not specifically shown), the spring  400  can be elongated and thus produce a spring force that can act to return the plunger member  402  to the retracted condition. As the second stage is de-energized, the spring  400  can begin to pull the plunger member  402  toward a first stop  412  and into the retracted condition. In this case, not only does the magnetic field generated by the first stage  404  and/or the second stage  406  draw the plunger member  402  back to the retracted condition, the spring force generated by the spring  400  in the elongated condition can also draw the plunger member  402  back to the retracted condition. 
     The plunger member  402  can define a driver blade  414 . It will be appreciated in light of the disclosure that the first stage  404  and/or the second stage  406  need not be used in lieu of using the spring  400  or other suitable elastic member to return the plunger member  402  back to the retracted condition. Because the first stage  404  and/or the second stage  406  need not be energized (or a field generated by the first stage  404  and/or the second stage  406  need not be as strong) to move the plunger member  402  to the retracted condition, battery life can be extended. 
     In another aspect of the present teachings and with reference to  FIGS. 6A ,  6 B and  6 C, a driver assembly  500  can include a two-piece assembly. Specifically, the driver assembly  500  can include a plunger member  502  that can move independently of a driver blade member  504 . The plunger member  502  can be moved between an extended condition ( FIG. 6C ) and a retracted condition ( FIG. 6A ) by energizing and de-energizing at least a first stage  506  and/or a second stage  508  of a multistage solenoid  510 . The plunger member  502 , when moved from the retracted condition to the extended condition by one or more of the stages  506 ,  508  can strike and, therefore, impart a force on the driver blade member  504 . The force from the plunger member  502  can move the driver blade member  504  from a retracted condition ( FIG. 6A ) to an extended condition ( FIG. 6C ) to, for example, drive a fastener into a workpiece in a similar fashion to the driver blade  30 , as shown in  FIG. 1 . 
     A spring  512  or other elastic member can be attached to the plunger member  502  and a portion of a first stop  518  and can assist with the movement of the plunger member  502  from the extended condition ( FIG. 6C ) back to the retracted condition ( FIG. 6A ). In addition, a spring  514  or other suitable elastic member can be attached to the driver blade member  504  and a block member  516 . In one example, the block member  516  can be contained with a suitable tool housing. The spring  514  attached to the driver blade member  504  can move the driver blade member  504  from the extended condition ( FIG. 6C ) back to the retracted condition ( FIG. 6A ). 
     The first stage  506  and/or the second stage  508  can be energized to draw the plunger member  502  from the retracted condition to the extended condition. As the plunger member  502  is drawn toward the second stage  508 , the plunger member  502  can strike the driver blade member  504  to move the driver blade member  504  from the retracted condition to the extended condition. It will be appreciated in light of this disclosure that the larger the velocity achieved by the plunger member  502 , the larger amount of energy (e.g., an impulsive force) that is delivered to the driver blade member  504 . 
     From the extended condition, the spring  514  or the suitable elastic member can pull the driver blade member  504  back to the retracted condition. After the plunger member  502  has imparted the force on the driver blade member  504 , the stages  506 ,  508  can be energized to draw the plunger member  502  back to the retracted condition. In lieu of, or in addition to, the magnetic force of the stages  506 ,  508  the springs  512 ,  514  or other suitable elastic member can (wholly or partially) draw the plunger member  502  and/or the driver blade member  504  back from the extended condition to the retracted condition. 
     As noted, the two or more stages of the multistage solenoid can be energized in a cascading fashion to move a driver assembly that can have a driver blade in a similar fashion to an electric motor and a transmission. When compared to the electric motor and the transmission, however, the multistage solenoid can be shown to provide relatively better battery life. In addition, the fastening tool using the multistage solenoid can provide a relatively lighter, more balanced and more compact tool. 
     With reference to  FIG. 1 , the nosepiece  22  can include a contact trip mechanism  50  as is known in the art. Briefly, the contact trip mechanism  50  can be configured to prevent the fastening tool  10  from driving the fastener  32  into the workpiece  34  (e.g., inhibit power to the multistage solenoid) unless the contact trip mechanism  50  is in contact with the workpiece  34  (i.e., in a retracted position). 
     With the contact trip mechanism  50  in a retracted condition, the trigger assembly  36  can be retracted to initiate the driver sequence. Further details of an exemplary contact trip mechanism are disclosed in commonly assigned U.S. patent applications entitled Operational Lock and Depth Adjustment for Fastening Tool, filed Oct. 29, 2004, Ser. No. 10/978,868; Cordless Fastening Tool Nosepiece with Integrated Contact Trip and Magazine Feed, filed Oct. 29, 2004, Ser. No. 10/878,867; and U.S. Pat. No. 6,971,567, entitled Electronic Control Of A Cordless Fastening Tool, issued Dec. 26, 2005, which are hereby incorporated by reference as if fully set forth herein. 
     In one aspect of the present teachings and with reference to  FIG. 8 , an exemplary method is illustrated in a flow chart that can be used with the multistage solenoid  100  and, for example, the fastening tool  10  having the multistage solenoid  12  that drives the driver assembly  14 , as shown in  FIG. 1 . In  600 , the contact trip mechanism  50  ( FIG. 1 ) associated with the fastening tool  10  is engaged, e.g., retracted against the workpiece  34  ( FIG. 1 ). In  602 , a user can retract the trigger assembly  36 . Upon detecting the retraction of the trigger assembly  36 , the control module  22  can direct power to the first stage  18 . In  604 , the first stage is energized and can establish a magnetic field that can exert a force on the armature member  106   a  ( FIG. 1 ). In  606 , the control module  22  can monitor the value of the current over time to determine when a value of the current establishes an inflection point. 
     In  608 , while the control module  22  is watching for the current inflection point, the control module  22  ( FIG. 1 ) can determine whether the value of current is indicative of a tool jam condition and/or a low battery condition. In one example, the value of current can be relatively higher when the tool jam condition and/or the low battery condition occur. When the value of current is indicative of the tool jam condition and/or the low battery condition, the method continues at  620 . When the value of current is not indicative of a tool jam condition and/or a low battery condition, the method continues at  610 . 
     In  610 , the control module  22  ( FIG. 1 ) can determine whether the current inflection point has been detected. When the control module  22  detects the current inflection point, the method continues at  612 . When the control module  22  does not detect the current inflection point, the method continues at  620 . In  612 , the control module  22  can determine whether a threshold period of time has expired before the detection of the current inflection point. When the control module  22  detects the current inflection point before the expiration of the threshold period of time, the method continues at  614 . When the control module  22  detects the current inflection point after the expiration of the threshold period of time, the method continues at  620 . 
     In  614 , the control module  22  ( FIG. 1 ) can shift power from the first stage  18  ( FIG. 1 ) to the second stage  20  ( FIG. 1 ) based on the detection of the first inflection point. It will be appreciated in light of the disclosure that in an instance where the multistage solenoid  12  ( FIG. 1 ) has more than two stages, the method can loop back to  606  and wait to detect a second inflection point. When the second inflection point is detected, the control module  22  can send power from the second stage to a third stage of the multistage solenoid. This can continue until power is sent to the last stage of the multistage solenoid  12 . 
     In  616 , the control module  22  ( FIG. 1 ) can remove power from all of the stages, so that each stage is not applying a force to the armature member  106   a  ( FIG. 1 ). In  618  and with reference to  FIG. 1 , a suitable return spring or other suitable mechanism can return the driver assembly  14  to the retracted condition, i.e., returning the armature member  106   a  to the first stage  18 . It will be appreciated in light of the disclosure that the fields generated by the stages of the multistage solenoid  12  can be reversed to direct the armature member  106   a  ( FIG. 1 ) in a direction opposite, as discussed above, to return the driver assembly  14  to the retracted or beginning condition. Returning to  FIG. 8 , the control module  22  ( FIG. 1 ), in  620 , can remove power from all of the stages, so that each stage does not apply a force to the armature member  106   a  ( FIG. 1 ). From  618  and from  620 , the method ends. 
     While specific aspects have been described in the specification and illustrated in the drawings, it will be understood by those skilled in the art that various changes can be made and equivalence can be substituted for elements thereof without departing from the scope of the present teachings. Furthermore, the mixing and matching of features, elements and/or functions between various aspects of the present teachings may be expressly contemplated herein so that one skilled in the art will appreciate from the present teachings that features, elements and/or functions of one aspect of the present teachings may be incorporated into another aspect, as appropriate, unless described otherwise above. Moreover, many modifications may be made to adapt a particular situation, configuration or material to the present teachings without departing from the essential scope thereof. Therefore, it is intended that the present teachings not be limited to the particular aspects illustrated by the drawings and described in the specification as the best mode presently contemplated for carrying out the present teachings but that the scope of the present teachings includes many aspects and examples following within the foregoing description and the appended claims.