Patent Publication Number: US-7584723-B2

Title: Combustion powered fastener-driving tool with interconnected chambers

Description:
RELATED APPLICATION 
   This is application is a continuation of application Ser. No. 11/182,208 filed Jul. 15, 2005, now U.S. Pat. No. 7,314,025. Priority is claimed under 35 USC §120. 

   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. 
   Combustion tools are known in the art, and one type of such tools, also known as IMPULSE® brand tools for use in driving fasteners into workpieces, is 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; 5,197,646; 5,263,439 and 6,145,724, all of which are incorporated by reference herein. 
   Such tools incorporate a generally pistol-shaped tool housing enclosing a small internal combustion engine. 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 for ignition, and a fan located in a combustion chamber provides for both an efficient combustion within the chamber, while facilitating processes ancillary to the combustion operation of the device. Such ancillary processes include inserting the fuel into the combustion chamber, mixing the fuel and air within the chamber and removing or scavenging combustion by-products. The engine includes a reciprocating piston with an elongated, rigid driver blade disposed within a single cylinder body. 
   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. 
   An operational problem of conventional combustion-powered tools is that as air required for combustion enters the tool, due to the relatively dirty operational environment of such tools, dirt, dust and/or other debris, including but not limited to fragments of nail collation material, sawdust, wallboard particles and the like enters the tool, specifically the cylinder below the piston. This contaminated air enters mainly through air ports located below the exhaust ports as the piston returns to its pre-firing position after combustion. These air ports are typically located below or in close proximity to a shock-absorbing bumper located within the cylinder. Air cannot reenter through the exhaust ports due to the presence of one-way petal valves. Through prolonged tool operation, among other effects, these contaminants deteriorate tool lubricants required for smooth operation of the piston and movement of the reciprocating valve sleeve, the component used to close the combustion chamber. 
   Such tools typically have an air filter located at an upper end of the tool near the combustion chamber fan air intake. However, this filter has been designed to filter air entering the combustion chamber and has no effect on the air located below the piston in the cylinder, where contaminant-caused damage has been known to occur. It has been previously difficult to place a filter in the tool for removing contaminants from air located below the piston because of space considerations, and due to relatively high operational temperatures (in the order of 300° F.) which degrade many filter materials. Also, the size of any such filter would necessarily be relatively large to permit the passage of sufficient air to maintain proper air circulation within the tool. As such, space, material and tool operational factors combine to discourage tool designers from placing a filter on the tool to filter the air in the cylinder below the piston. 
   Thus, there is a need for a combustion-powered fastener-driving tool in which air located below the piston is filtered to remove contaminants encountered in the course of normal tool operation. There is also a need for such a filter which can withstand tool operational temperatures, and which maintains acceptable tool air circulation patterns. 
   BRIEF SUMMARY 
   The above-listed needs are met or exceeded by the present air passageway for a combustion-powered fastener-driving tool. Preferably, the present air passageway takes the form of at least one interconnection tube. One end of each present tube is placed in fluid communication with the air in the cylinder below the piston. This air is typically forced out of the tool as the driver blade is driven towards the workpiece for driving a fastener. In many such tools, this location is in the vicinity of the piston bumper, and where a lower end of the tool housing meets an upper end of the nosepiece. 
   An opposite end of the tube is placed in fluid communication with a filter, preferably the fan motor filter located at the upper end of the tool opposite the workpiece contact element. Alternately, the opposite end of the tube is placed in fluid communication with a separate, preferably supplementary filter, also preferably located remotely from the lower end of the tool housing. In this arrangement, during combustion, the downward movement of the piston will force air into the tube and out the filter, providing a filter cleaning function. As the piston returns to its pre-firing position, air will be drawn into the cylinder below the piston through the tube. This incoming air will have passed into the tool through the filter, thus removing many contaminants. 
   More specifically, a combustion tool has a housing with an air intake end and an opposite bumper end, a combustion-powered power source in the housing including a cylinder encircling a reciprocating piston associated with a driver blade, and having at least one air port located at the bumper end below the piston. An air intake is located adjacent the air intake end and is provided with an air filter. At least one air passageway is provided in fluid communication with the at least one air port and in operational relationship with the air filter. 
   In another embodiment, a combustion tool includes a combustion-powered power source having an air intake end and an opposite bumper end, defining a cylinder encircling a reciprocating piston associated with a driver blade, and having at least one air port located at said bumper end below said piston. At least one air intake is provided with an air filter. An air passageway is in fluid communication with the at least one air port and in fluid communication with the air filter for creating a bi-directional air flow between the at least one air port and the at least one air intake during tool operation. The at least one air intake includes a first filtered air intake associated with providing air into a combustion chamber, and a supplemental filtered air intake for supplying air to the passageway and receiving air from the bumper end during tool operation. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a vertical section of a combustion-powered fastener-driving tool incorporating the present interconnection tube; 
       FIG. 2  is a vertical section of an alternate embodiment of the tool of  FIG. 1  showing the tube as part of the housing; and 
       FIG. 3  is a vertical section of an alternate embodiment of the tool of  FIG. 2  showing the tube part of the housing and being in communication with a dedicated air filter. 
   

   DETAILED DESCRIPTION 
   Referring now to  FIG. 1 , a combustion-powered fastener-driving tool suitable for use with the present inventive air passageway is generally designated  10  and preferably incorporates the teachings of the patents referred to above and incorporated by reference herein. However, the present system is considered suitable for many types of combustion-powered fastener-driving tools having a variety of configurations, and not all of the illustrated tool components are described herein as not being directly related to the present air passageway in its various embodiments. 
   A main housing  12  is typically provided in a single piece, in two clamshell-type halves or equivalent configurations as is known in the art, and encloses a combustion power source, generally designated  14 . At an upper end  16  of the housing  12 , the power source  14  is provided with a cylinder head  18  supporting a spark plug  20  and preferably a fan  22  powered by a fan motor  24  as is known in the art. The power source  14  also includes a combustion chamber and a cylinder, described below. 
   Included on the housing  12  is a cap  26  that closes the upper end  16  of the housing and defines an air intake end  28  with an air intake  30  in the cap. An air filter  32  is associated with the  30  as is known in the art and is supported by a protective slatted grille  34 . As is well known in the art, the air filter  32  is releasably secured to the cap  26 . The air filter is made of a porous material such as plastic or metal mesh, foam or the like that is designed to allow the passage of air into the housing  12 , but prevent the ingress of construction debris, dirt and other operational contaminants. 
   Opposite the upper end  16 , a lower end  36  of the tool  10  includes a nosepiece  38  secured to the power source  14  and having a workpiece contact element  40  axially reciprocating relative thereto. A driver blade passageway  42  in the nosepiece  38  slidingly accommodates a driver blade  44  secured at an upper end  46  to a piston  48 . A cylinder  50  is located in the power source  14  and defines a tubular track for the piston  48 . A lower end  52  of the driver blade  44  is configured for engaging fasteners (not shown) fed into the nosepiece  38  through a magazine  54  and driving them into a workpiece as is well known in the art. 
   A bumper end  56  of the housing  12  also defines an end of the power source  14 . An endplate  58  defines a central aperture  60  through which the driver blade  44  passes, as well as air when the piston  48  reciprocates during operation. Thus, the central aperture  60  may also be termed an air port, however it is also contemplated that other air ports may be provided in the end plate  58  or in lower portions of the cylinder  50 . A resilient bumper  62  is located at the bottom end of the cylinder  50  as is known in the art for absorbing the impact of the piston  48  at the end of the combustion stroke. A seal  64  such as a wiping seal or equivalent is located at a lower end of the air port  60  just above an upper end of the nosepiece  38  for preventing air from entering the air port from the outside, thus preventing dirt digestion of the tool, while permitting relative sliding action of the driver blade  44 . 
   An important feature of the present tool  10  is the provision of at least one air passageway, generally designated  70 , in fluid communication with the at least one air port  60  and in operational relationship with the air filter  32 . The at least one air passageway  70  creates bi-directional fluid communication (the preferable fluid being air) between the lower end of the cylinder  50  and the air filter  32 , as well as the air intake  30 . While in the preferred embodiment the air filter  32  is provided for filtering air entering the combustion chamber, it is also contemplated that additional or dedicated air filters and associated air intakes may be provided which are provided specifically for connection to the passageway  70 . For clarity, only the filter  32  will be presently described. 
   Thus, substantially all of the air entering the cylinder  50  as the piston  48  returns to the pre-firing position shown in  FIG. 1  must first pass through the filter  32 . Also, substantially all air forced out the air port  60  during the combustion cycle flows out through both the filter  32  and the air intake  30 . 
   In the preferred embodiment, the passageway  70  is provided in the form of at least one tube, also referred to as an interconnection tube, having a central section  72  generally parallel with an operational axis of the piston  48 , and upper and lower ends  74 ,  76  preferably projecting at generally right angles to the central section formed as radiused bends for effecting connection respectively to the air intake and the at least one air port  60 . The specific angular orientation of the upper and lower ends  74 ,  76  may vary to suit the situation. While depicted as at least one continuous tube, it is also contemplated that the passageway  70  may be defined by tubular segments joined by fixed angle fittings. 
   More specifically, the upper end  74  is preferably secured within an air chamber  78  defined by the cap  26  below the air filter  32  and the cylinder head  18 . Conventional techniques for securing the upper end  74  are contemplated, including but not limited to friction fit, chemical adhesives, clips, rigid fittings or the like. While depicted outside the main housing  12  for clarity, it is preferred that the central section  72 , and at least a majority of the upper and lower ends  74 ,  76  of the passageway  70  extends inside the main housing  12  along the combustion power source  14 . It is contemplated that the passageway  70  may be secured to internal tool components as necessary for support or to enhance performance. If necessary, the main housing  12  can be radially extended to encompass the passageway  70 . The passageway  70  is preferably manufactured of a tubing of sufficient durability to withstand the potential impacts and/or temperatures typically experienced by combustion-powered fastener driving tools. 
   At the lower end  76 , the passageway  70  is placed in fluid communication with the at least one air port  60 . The lower end  76  is ultimately secured to a bottom portion of the cylinder  50  and may pass through the housing  12 , the end plate  58  or other structure on the tool to maintain this fluid communication. Similar fastening techniques described above relative to the upper end  74  are employable for securing the lower end  76  in position. An important consideration is that an opening  82  in the lower end  76  be in close fluid communication with the air port  60 , regardless of the particular location of the air port on the tool  10 . 
   It will be seen that with the provision of the seal  64 , the air port  60  is in essentially sealed fluid communication with the passageway  70 , such that substantially all of the air generated in combustion which is forced down the cylinder  50  by the piston  48  will pass through the airport and into the passageway. Also, it is preferred that the passageway  70  be of sufficient diameter to accommodate the free passage of substantially all of the air forced out the air port  60  by the piston  48  during its normal combustion cycle, as well as draw incoming air from the environment as the piston returns to the pre-firing position. This diameter will vary depending on the type of tool and the- size of the combustion power source  14 . 
   Referring now to  FIG. 2 , an alternate embodiment of the tool  10  is generally designated  90 . Shared components with the tool  10  are designated with identical reference numbers. While it is contemplated that most, if not all of the components of the tools  10  and  90  can be interchanged, a significant distinction between the tools  10  and  90  is that in the tool  90 , instead of being a separate component, the passageway  70 , now designated  92 , is integrally incorporated within and is preferably formed with, the main housing  12 . As is the case with the passageway  70 , the passageway  92  is in fluid communication with at least one air port  60  and also with the at least one air filter  32  for creating a bi-directional air flow between the air port and the at least one air intake  30  during tool operation. As is the case with the passageway  70 , if necessary, it is contemplated that the passageway  92  is secured to internal tool components for additional support. 
   In operation, both embodiments  10  and  90  operate in the same manner. During the firing cycle, a combustion chamber  94  is closed and separated from the air chamber  78 . After combustion, the piston  48  moves downward in the cylinder  50  towards the bumper  62 . Air from the cylinder  50  located below the piston  48  escapes partially through an exhaust valve  96  and partially through the air port  60 . The exhaust valve  96  is a petal type or other one-way flow structure for preventing air intake, but in fluid communication with ambient in both embodiments  10  and  90 . After the piston  48  passes below the exhaust valve  96 , the air escapes primarily through the air port  60 , which now travels through-the passageways  70 ,  92  and cleans the filter  32  of accumulated debris by pressurized reverse flow of air. 
   Another difference between the embodiments  10  and  90  is that a lower end  98  of the passageway  92  is in fluid communication with at least one air port  100  located in the side of the cylinder  50  near the bumper  62 . In this version, the air port  60  in the end plate  58  has been eliminated, so that air remaining in the cylinder  50  as the piston  48  passes below the exhaust valve  96  is forced out the air port  100 . Only one air port  100  is shown for clarity, however it is contemplated that multiple ports  100  are provided, preferably with multiple passageways  92 . 
   During the return cycle, the piston  48  and the driver blade  44  move upward, driven by differential gas pressure, and the vacuum created in the combustion chamber  94  and the cylinder  50 . Outside air now enters the cylinder  50  primarily through the passageways  70 ,  92 , which are now filtered. Since the air filter  32  is located remotely from the relatively hot cylinder  50 , it is not subjected to high operational tool temperatures. 
   Referring now to  FIG. 3 , another embodiment of the present tool is generally designated  110 , and shared components with the tools  10  and  90  are designated with identical reference numbers. Also, it is contemplated that the construction of the passageway  70 ,  92 , and the positioning of the air ports  60 ,  100  may be interchanged with that disclosed in  FIG. 3  to suit the situation. As is the case in the tool  90 , in the tool  110  a passageway is generally designated  112  and is integrally formed with the housing  12 . 
   A main difference between the tool  110  and the tools  10  and  90  is that an upper end  114  of the passageway  112  is not in communication with the air intake  30 , but is in fluid communication with at least one supplemental air intake  116  located in a specially reconfigured upper end  118  of the main housing  12 . However, both the air intake  30  and the supplemental air intake  116  are preferably located at or adjacent the air intake end  28 . The supplemental air intake  116  is preferably provided with its own filter  120 , protective grille  122  and a supplemental chamber  124  with which the upper end  114  is in fluid communication. In some applications, it is contemplated that the filter  120 , the protective grille  122  and the chamber  124  would be eliminated. It is also contemplated that the at least one supplemental air intake  116  may be located on the main housing in any suitable location which is satisfactorily remote from the relatively high operational temperatures of the combustion power source  14 . 
   While the upper end  114  of the passageway  112  is shown as a vertically projecting extension of the central portion  72 , other angular orientations or other configurations are contemplated as long as fluid communication with the air port  100 ,  60  is maintained. Also, as is the case with the tools  10  and  90 , while the passageway  112  is shown on a periphery of the housing  12 , an internal disposition is also contemplated. Also, while the lower end  98  of the passageway  112  is shown in communication with the cylinder  50  through the port  100 , it is also contemplated that the passageway  112  could be in communication with the air port  60  as shown in  FIG. 1 . The operation of the embodiment  110  is substantially the same as described above in relation to the embodiments  10  and  90 , with the primary difference being that the chamber  124  does not also supply air to the combustion chamber  94 . 
   While a particular embodiment of the present combustion-powered fastener-driving tool with interconnected chambers 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.