Patent Publication Number: US-7588096-B2

Title: Cordless fastener tool with fastener driving and rotating functions

Description:
RELATED APPLICATION 
   The present application claims priority under 35 USC § 119(e) from U.S. Ser. No. 60/877,983 filed Dec. 29, 2006. 

   BACKGROUND 
   The present invention relates generally to fastener-driving tools used to drive fasteners into workpieces, and specifically to combustion-powered fastener-driving tools, also referred to as combustion tools or combustion nailers. 
   Combustion-powered tools are known in the art. Representative tools are manufactured by Illinois Tool Works, Inc. of Glenview, Ill. for use in driving fasteners into workpieces, and are described in commonly assigned patents to Nikolich U.S. Pat. Re. No. 32,452, and U.S. Pat. Nos. 4,522,162; 4,483,473; 4,483,474; 4,403,722; 5,133,329; 5,197,646; 5,263,439 and 6,145,724 all of which are incorporated by reference herein. 
   Such tools incorporate a tool housing enclosing a small internal combustion engine or power source. The engine is powered by a canister of pressurized fuel gas, also called a fuel cell. A battery-powered electronic power distribution unit produces a spark combustion within the chamber, while facilitating processes ancillary to the combustion operation of the device. Such ancillary processes include: mixing the fuel and air within the chamber; turbulence to increase the combustion process; scavenging combustion by-products with fresh air; and cooling the engine. The engine includes a reciprocating piston with an elongated, rigid driver blade disposed within a cylinder body. 
   A valve sleeve is axially reciprocable about the cylinder and, through a linkage, moves to close the combustion chamber when a work contact element at the end of the linkage is pressed against a workpiece. This pressing action also triggers a fuel-metering valve to introduce a specified volume of fuel into the closed combustion chamber. 
   Upon the pulling of a trigger switch, which causes the spark to ignite a charge of gas in the combustion chamber of the engine, the combined piston and driver blade is forced downward to impact a positioned fastener and drive it into the workpiece. The piston then returns to its original or pre-firing position, through differential gas pressures within the cylinder. Fasteners are fed magazine-style into the nosepiece, where they are held in a properly positioned orientation for receiving the impact of the driver blade. Upon ignition of the combustible fuel/air mixture, the combustion in the chamber causes the acceleration of the piston/driver blade assembly and the penetration of the fastener into the workpiece if the fastener is present. 
   Such tools are typically employed with nails, brads, or similar fasteners designed for being axially or linearly driven into a workpiece. While these tools have been widely accepted for use in rough framing as well as finish construction, users have been forced to use other tools for installing wallboard to frame members such as metal or wooden studs. In the latter operations, performed on exterior as well as interior construction, users employ corded or cordless drills or fastener drivers for rapidly applying threaded fasteners through the wallboard and into the frame member. 
   One installation factor dealt with by wallboard installers is that, upon driving, the generally large diameter head of the fastener should be flush with, but not pierce the face paper outer layer of the wallboard. If the fastener passes through the face paper, the board is structurally weakened at that point, and may require additional finishing. 
   Another installation factor of wallboard installation is that when wallboard is applied to metal frame members, the fastener typically easily passes through the wallboard, but in some cases has difficulty penetrating the frame member. Even when special cutting or drill tip type fasteners are used, the frame member is pushed away from a rear surface of the wallboard. This type of condition has been experienced when combustion tools drive unthreaded fasteners are used to fasten wallboard to frame members, and also when conventional power drills are used to drive wallboard screws. Thus, in some cases, the fastener pierces the frame member on an angle relative to the wallboard. Subsequent tightening of the fastener by the power applicator tool fails to form a tight connection between the wallboard and the frame member at that point. 
   U.S. Pat. No. 5,862,724 discloses a pneumatic fastener driving tool having both linear and rotational fastener driving functions. One drawback of this tool is that, being pneumatically powered; it requires a remote compressor connected to the tool with a pressure hose. Such hoses are bulky and awkward to work around in many workplaces. Compressors are noisy and cannot always be used indoors. Another drawback of the disclosed tool is that it has insufficient power to drive fasteners into metal frame members. Still another drawback of the disclosed tool is that as the driver blade forces the fastener against the metal frame member, the pneumatic impact force generates recoil which causes a fastener-driving bit at the end of the driver blade to become disengaged from the fastener head. In such cases, a separate tool such as a power screwdriver is needed to complete fastener installation. 
   Thus, there is a need for a fastener driving tool which addresses the above-identified drawbacks of conventional tools. 
   BRIEF SUMMARY 
   The above-listed needs are met or exceeded by the present fastener-driving tool which overcomes the limitations of the current technology. In the present tool, pneumatic power is replaced by a combustion power source, eliminating the need for a separate compressor and pressure hose. Thus, the present tool is completely portable. The present tool is provided with a combustion engine for driving the fastener into the workpiece, and an electric motor for rotating the driver blade and the engaged fastener. In addition, the combustion power source provides greater driving force than the prior art pneumatic tool. Also, the present tool controls the combustion-generated driver blade recoil so that the driver blade maintains engagement with the fastener during the rotation phase of the installation process. When used with cutting tip threaded fasteners, wallboard installation time is reduced, and wallboard is more securely attached to the frame members. 
   More specifically, a fastener-driving tool includes a combustion power source configured for driving a driver blade to linearly travel towards a workpiece, and an electrical power source associated with the combustion power source for rotationally driving the driver blade upon completion of the linear travel, both power sources being disposed in the tool. 
   In another embodiment, a fastener-driving tool includes a housing, a combustion power source disposed in the housing and including a cylinder head, a cylinder, a piston reciprocating within the cylinder between upper and lower cylinder ends, and a driver blade connected to the piston configured for linearly driving a driver blade towards a workpiece. An electrical power source is associated with the combustion power source for rotationally driving the driver blade upon the piston reaching the lower cylinder end. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       FIG. 1  is a vertical cross section of a fastener-driving tool incorporating the present combustion and electrical power sources; 
       FIG. 2  is an enlarged fragmentary view of the tool in  FIG. 1  showing the driver blade in an extended position; 
       FIG. 3  is an elevational view of a fastener suitable for use with the present tool; 
       FIG. 4  is a first view of a fastener being properly driven into a metal stud to secure wallboard thereto; and 
       FIG. 5  is a second view of a fastener being improperly driven into a metal stud to secure wallboard thereto. 
   

   DETAILED DESCRIPTION 
   Referring now to  FIGS. 1 and 2 , a fastener-driving tool or combustion nailer incorporating the present invention is generally designated  10  and preferably is of the general type described in detail in the patents listed above and incorporated by reference in the present application. A housing  12  of the tool  10  encloses a self-contained internal combustion power source  14  as is known in the art. Included on the housing  12  is a handle  16  with a trigger  18 . A fuel cell chamber  20  encloses a fuel cell (not shown) which provides pressurized fuel for combustion. 
   Preferably located within the handle  16 , but potentially located elsewhere within the housing  12  is a control system  22  including a central processing unit CPU having a control program  24  (shown hidden). As is known in the art, the control program  24  controls the operation of the tool  10 , including fuel delivery if electronic fuel injection is provided, fan rotation when a fan is located within the combustion chamber, and ignition, among other things. 
   A rechargeable battery (not shown) powers the control program  24  and the control system  22 , and is releasably held within a battery chamber  26  located on a side of the housing  12 . The battery chamber  26  is configured for slidably accommodating the battery so that contacts of the battery electrically engage corresponding contacts (not shown). Alternatively, it is contemplated that the contacts are connectable, as through a line cord, to a source of alternating current. 
   Other features of the tool  10  are a workpiece contact element  28  which contacts a workpiece prior to the driving of a fastener, the workpiece contact element constructed to axially slide relative to a nosepiece  30 , and having a depth adjustment mechanism (not shown) for adjusting the relative spacing of the workpiece contact element  28  to the nosepiece for adjusting the depth of fastener insertion by the tool  10 . A fastener magazine  32  is provided for storing a supply of fasteners (not shown), and is shown connected to the nosepiece  30 . While a rotary magazine  32  is depicted, other magazine configurations are contemplated, including but not limited to linearly operating or strip magazines being part of the housing  12 . 
   As is known in combustion nailers, the power source  14  includes a cylinder head  34  located at a first end  36  of the housing  12 , including a spark plug  38 , and a fan motor  40  powering a fan  42 . 
   A piston  44  connected to a driver blade  46  reciprocates within a cylinder  48  having a first or upper end  50  and a second or lower end  52 . A valve sleeve  54  surrounds and is slidable relative to the cylinder  48 . Connected to the workpiece contact element  28  by a linkage  56  referred to as an upper probe, the valve sleeve  54  is biased out of engagement with the cylinder head  34  by a spring (not shown). 
   A combustion chamber  58  is defined by the cylinder head  34 , the valve sleeve  54 , an upper end  60  of the piston  44  and the first end  50  of the cylinder  48 . The fan  42  projects into the combustion chamber  58  and performs functions identified above and well known in the art. A chamber switch  62  ( FIG. 1 , sometimes referred to as a head switch) is located in proximity to the valve sleeve  54  to monitor its positioning. 
   Depression of the tool housing  12  against a workpiece (not shown) towards the right as seen in  FIG. 1  (other operational orientations are contemplated as are known in the art), causes the workpiece contact element  28  to move relative to the tool housing  12  from a rest position to a firing position. This movement overcomes the normally downward (or rightward as seen in  FIG. 1 ) biased orientation of the workpiece contact element  28 . 
   Through the linkage  56 , the workpiece contact element  28  is connected to, or in contact with, and reciprocally moves with, the valve sleeve  54 . In the rest position ( FIG. 1 ), the combustion chamber  58  is not sealed, since there are gaps separating the valve sleeve  54  and the cylinder head  34 , and a lower gap separating the valve sleeve and the cylinder  48 . 
   Upon closing of the combustion chamber  58  to ambient through the pressing of the tool  10  against a workpiece, the chamber switch  62  is closed. A dose of fuel is introduced into the combustion chamber  58 , and the fan  42  rotates to circulate the fuel/air mixture within the chamber. Upon depression of the trigger  18  and actuation of an associated trigger switch (not shown, the terms trigger and trigger switch are used interchangeably), a user induces combustion of the fuel/air mixture in the combustion chamber  58  via the spark plug  38 , causing the driver blade  46  to be forcefully driven linearly or axially downward through the nosepiece  30  ( FIG. 1 ). The nosepiece  30  guides the driver blade  46  to strike a fastener that had been delivered into the nosepiece via the fastener magazine  32 . 
   As the piston  44  travels down the cylinder  48 , it pushes a rush of air which is exhausted through at least one petal or check valve  64 . At the bottom of the piston stroke or the maximum piston travel distance, the piston  44  impacts a resilient bumper  66  as is known in the art. With the piston  44  beyond the exhaust check valve  64 , high pressure gasses vent from the cylinder  48  until near atmospheric pressure conditions are obtained and the check valve  64  closes. 
   The operational result of the piston reaching the bumper  66  is that a replaceable bit  68  at a tip of the driver blade  46  strips a fastener from the magazine and forces it through the workpiece, preferably a piece of wallboard  70  backed by a frame member  72  ( FIG. 4 ). As is known in the art, the frame member  72  is either made of wood or 12, 14, 16, 18, 20, 22 or 26 gauge steel. 
   Included in the present tool  10  is an electrical power source, generally designated  80  and associated with the combustion power source  14  preferably but not necessarily within the housing  12  for rotationally driving the driver blade  46  upon completion of the above-described linear or axial travel driven by the combustion power source. In the present application, “in the tool” thus means that the electrical power source  80  as well as the combustion power source  14  are directly movable with the tool  10 , and are not remotely connected by hoses, cords or cables. 
   More specifically, upon the piston  44  reaching the bumper  66 , a sensor  82  disposed in operational relationship to the electrical power source  80 , senses the presence of the piston. Although in the preferred embodiment the sensor  82  is a proximity sensor which senses the arrival of the piston  44 , it is contemplated that other sensors monitoring at least one of pressure, air flow in the cylinder  48 , opening of the exhaust valve  64 , or the shape of the driver blade  46  can potentially trigger the operation of the power source  80 . Preferably a stator motor, the power source  80  includes a fixed stator portion  84 . The stator portion  84  is fixed within the housing  12  between the bumper and a plate  86 . As is known in the art, the combustion power source  14  is fixed within the housing  12 . 
   A bearing race  88 , such as a ball bearing race or the like rotatably supports a rotating armature  90  within the stator portion  84 . At the center of the armature  90  is defined an axial opening  92  having a noncircular shape and preferably polygonal, which forms a keyway filled by the driver blade  46 . At least a portion  94  of the driver blade  46  is provided with a cross-section which is complementary to the keyway  92  for common rotation. 
   Connected through the battery in the battery chamber  26  to the control program  24 , the power source  80  is triggered by the sensor  82 , which is also connected to the control program  24 . Upon being triggered by the piston  44 , the sensor  82 , activates the power source  80 , which rotates the driver blade  46  for a predetermined amount of time, a predetermined number of rotations, or until the trigger  18  is released. These rotations cause the fastener to engage the frame member  72  and draw wallboard  70  to the frame member. 
   Referring now to  FIG. 2 , the above rotation of the driver blade  46  is achieved through a rotatable relationship to the piston  44 . More specifically, an upper end  96  of the driver blade  46  defines a shoulder which receives a washer-like locking plate  98  defining a lower limit of travel of the piston  44 . The piston  44  has an inner bushing  100  which slidably and rotationally engages a threaded cap  102  threadably engaging an upper end of the driver blade  46  and having an annular, radially extending flange  104  which defines an upper limit of axial travel of the piston relative to the driver blade. It has been found that by making the piston  44  axially movable relative to the driver blade  46 , the driver blade is axially movable for more effective fastener engagement and rotational driving after the piston as reached the lower end  52  of the cylinder  48 . Also, the relatively fixed disposition of the electrical power source  80  in the tool  10  absorbs some of the recoil force generated by combustion. 
   Also, as is well known in the art, the piston  44  is provided with at least one piston ring  106  for maintaining a slidable seal with the cylinder  48 . In the event the speed of rotation of the driver blade  46  and the rotating armature  90  needs to be adjusted, a gear reducer  107  is provided to the power source  80 . 
   In conventional combustion tools, due to internal post combustion pressure differentials in the cylinder  48 , once the combustion has occurred and the exhaust gases vented, the combustion chamber  58  remains closed and the piston  44  is returned to the pre-firing or rest position shown in  FIG. 1 . However, in the tool  10 , the piston  44  must be retained at the second end  52  of the cylinder  48  until the driver blade rotation and associated fastener driving is completed. In the preferred embodiment, a vacuum valve  108  ( FIG. 1 ) such as a petal valve is located at the first or upper cylinder end  50  for releasing the vacuum in the combustion chamber  58  by introducing ambient air. Thus, the differential gas pressures are eliminated, maintaining the piston  44  near the bumper  66  ( FIG. 2 ). 
   If desired, the tool  10  is optionally provided with a supplemental locking device  110  which engages the piston  44  and prevents return until fastener driving is complete, or a specified time expires as controlled by the control program  24 . Such a locking device  110  is a solenoid with a retractable latch  112  projecting through the cylinder  48  in an energized condition to block piston return. 
   Upon completion of the operation of the electrical power source and the rotation of the fastener into the workpiece, the piston  44  is returned to the rest position depicted in  FIG. 1 . If the latch  112  is provided, the control program signals its retraction. 
   In the preferred embodiment, piston return is facilitated by pressurized exhaust gas diverted through a bypass tube  114  having an upper end  116  in communication with the combustion chamber  58  through an opening in the cylinder  48 . Suitable seals such as O-rings, chemical sealant or the like sealingly secure the upper end in place. A lower end  118  is in communication with a gas reservoir  120  preferably containing a compressible bladder  121 . The bypass tube  114  is similar in construction and arrangement to that disclosed in U.S. Pat. No. 7,040,521 which is incorporated by reference. In addition, the bypass tube  114  preferably includes a second leg  122  in fluid communication with a magazine advance cylinder  124  for initiating the advance of a fastener into the nosepiece  30  to be ready for the next combustion cycle. While other materials are contemplated, the tube  114  is made of stainless steel, specifically 11 gauge 304 stainless steel, however other equivalent durable heat resistant materials are contemplated. 
   As is known in the art, the bladder  121  is expandable for retaining pressurized air from the bypass tube  114 . Once rotation of the driver blade  46  is completed and piston return is required, the control program  24  actuates a valve  126  in fluid communication with the bladder  121  which releases the stored, pressurized exhaust gas through a piston tube  128  directed against the piston  44  in a way that assists the return of the piston and the driver blade  46  to the rest position. 
   Referring now to  FIG. 2 , alternatively to, or in conjunction with the bypass tube  114 , a solenoid operated plunger or slide  130  under the control of the control program  24  exerts an impact on the piston  44 , optionally through a collar  132 , sufficient for causing the piston to return to the rest position. As another alternative, the locking device  110  and the latch  112  are used to hold the piston  44  in position against the force of a return spring  134  located near the bumper  66 . Upon completion of rotation of the driver blade  46 , the control program  24  releases the latch  112 , and causes the compressed return spring  134  to push the piston  44  to the rest position. 
   Referring now to  FIGS. 2 and 3 , the replaceable bit  68  is preferably Phillips, hex, TORX® or similarly shaped to drive conventional power driven fasteners such as a fastener  140 , having a head  142  shaped to drivingly engage the bit  68 , a threaded shank  144  and a tip  146  as is known in the art. While a representative suitable fastener  140  has been depicted, it will be appreciated that other fastener configurations may be suitable, depending on the application, and including but not limited to conventional fasteners used with power screwdrivers or the like. 
   Referring now to  FIGS. 4 and 5 , two fastener installation conditions are depicted. In  FIG. 4 , represented by fasteners driven by the tool  10 , the fastener  140  has been driven through the wallboard  70  and into the frame member  72  where sufficient piercing has occurred to allow fastener penetration. As the fastener  140  is rotated by the tool  10 , the wallboard  70  and the frame member  72  are drawn together. In  FIG. 5 , the fastener  140  has pierced the frame member  72 , but only after the frame member has been deflected, causing the frame member to be pushed away from the wallboard  70  and potentially causing a loose wallboard installation. In addition, the deflection of the frame member  72  has caused the fastener head  142  to penetrate the face paper of the wallboard  70 , which is undesirable and results in an insecure installation. By providing greater driving power than conventional tools, the present tool  10  avoids the situation depicted in  FIG. 5 . 
   While a particular embodiment of the present cordless fastener tool with fastener driving and rotating functions has been described herein, it will be appreciated by those skilled in the art that changes and modifications may be made thereto without departing from the invention in its broader aspects and as set forth in the following claims.