Abstract:
A drive blade lubrication assembly for use in a powered fastener driver ( 10 ). The powered fastener driver ( 10 ) contains a drive blade ( 42 ) which snap-fits with a reciprocating piston ( 58 ) by a blade seal ( 103 ) assembly. The drive blade lubrication assembly contains a lubricant applying member adapted to apply lubricant to a portion of the drive blade ( 42 ); and a lubricant storing device which is in fluid communication with the lubricant applying member. The lubricating storing device is adapted to replenish the lubricant in the lubricant applying member. A powered fastener driver ( 10 ) containing a drive blade lubrication assembly is also described. The use of the lubricant storing device in the present invention ensures that lubricant is continuously supplied to the drive blade ( 42 ) after long time usage of the powered fastener driver ( 10 ), so that friction between the drive blade and the blade seal assembly is minimized

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to power tools, and more specifically to powered fastener drivers. 
       BACKGROUND OF THE INVENTION 
       [0002]    There are various fastener drivers known in the art for driving fasteners (e.g., nails, tacks, staples, etc.) into a workpiece. These fastener drivers operate utilizing various means known in the art (e.g., compressed air generated by an air compressor, electrical energy, flywheel mechanisms). Among them, the fastener drivers using vacuum as the power source for driving the fasteners, are widely used nowadays which often contain a cylinder-piston structure where vacuum is formed in a portion of the cylinder and its pressure difference with other portions of the cylinder (e.g. in atmosphere pressure) causes the piston to move and drive the fasteners. In some of these fastener drivers there is mechanism for generating vacuum in the cylinder by using a second piston of which the reciprocal movement expels air from a portion of the cylinder, thus creating vacuum thereinside. However, existing pneumatic fastener drivers often do not have a blade lubrication mechanism for reducing the friction between the blade and the blade seal in the second piston. 
       SUMMARY OF THE INVENTION 
       [0003]    In the light of the foregoing background, it is an object of the present invention to provide an alternate fastener driver with an effective blade lubrication mechanism. 
         [0004]    Accordingly, the present invention, in one aspect, is a powered fastener driver containing a cylinder, a reciprocating piston configured within the cylinder to create a pressure differential, a drive blade at least partially accommodated in the cylinder and operable to drive a fastener upon a driving force resulted from the pressure differential; the drive blade passing though the reciprocating piston and slidable with respect to the latter. The power fastener driver further includes a blade seal assembly located in the reciprocating piston, a lubricant applying member adapted to apply lubricant to a portion of the drive blade; and a lubricant storing device which is in fluid communication with the lubricant applying member. The blade seal assembly snap-fits with the drive blade so that the drive blade is adapted to move relative to the reciprocating piston. The lubricating storing device is adapted to replenish the lubricant in the lubricant applying member. 
         [0005]    Preferably, the lubricant applying member is a channel formed in the reciprocating piston which connects fluidly the lubricant storing device to the portion of the drive blade. 
         [0006]    More preferably, the channel is aligned to be substantially perpendicular to a length of the drive blade which is encompassed by the blade seal assembly. 
         [0007]    In another variation, the channel is shielded from the exterior of the reciprocating piston by a covering member. 
         [0008]    In one implementation, the at least a portion of the covering member is superimposed with a dust blocking layer. When the portion of the covering member wears out, the dust blocking layer continues to block dusts in the exterior of the reciprocating piston from entering the channel. 
         [0009]    In one implementation, the lubricant storing device is positioned in the reciprocating piston at a location separated from the blade seal assembly along a longitudinal direction of the drive blade. 
         [0010]    In another implementation, the lubricant storing device is positioned at a location separated from the blade seal assembly along a radial direction of the reciprocating piston. 
         [0011]    Preferably, the lubricant storing device is a hollow portion formed in the reciprocating piston which is capable of storing a volume of the lubricant. 
         [0012]    More preferably, the lubricant is grease oil. 
         [0013]    In another aspect of the invention, a drive blade lubrication assembly for use in a powered fastener driver is disclosed. The powered fastener driver includes a drive blade snap-fitting with a reciprocating piston by a blade seal assembly. The drive blade lubrication assembly further includes a lubricant applying member adapted to apply lubricant to a portion of the drive blade; and a lubricant storing device which is in fluid communication with the lubricant applying member. The blade seal assembly snap-fits with the drive blade so that the drive blade is adapted to move relative to the reciprocating piston. The lubricating storing device is adapted to replenish the lubricant in the lubricant applying member. 
         [0014]    Preferably, the lubricant applying member is a channel formed in the reciprocating piston which connects the lubricant storing device to the portion of the drive blade. 
         [0015]    More preferably, the channel is aligned to be substantially perpendicular to a length of the drive blade which is encompassed by the blade seal assembly. 
         [0016]    In another variation, the channel is shielded from the exterior of the reciprocating piston by a covering member. 
         [0017]    In one implementation, the at least a portion of the covering member is superimposed with a dust blocking layer. When the portion of the covering member wears out, the dust blocking layer continues to block dusts in the exterior of the reciprocating piston from entering the channel. 
         [0018]    In one implementation, the lubricant storing device is positioned in the reciprocating piston at a location separated from the blade seal assembly along a longitudinal direction of the drive blade. 
         [0019]    In another implementation, the lubricant storing device is positioned at a location separated from the blade seal assembly along a radial direction of the reciprocating piston. 
         [0020]    Preferably, the lubricant storing device is a hollow portion formed in the reciprocating piston which is capable of storing a volume of the lubricant. 
         [0021]    More preferably, the lubricant is grease oil. 
         [0022]    There are many advantages provided by the present invention, one of which is that the solution used in the present invention effectively extends the life cycle of the nailer blade as compared to conventional designs in which no effective lubricant is in place after the initial grease has leaked out. In addition, the use of the lubricant storing device in the present invention ensures that lubricant is continuously supplied to the drive blade after long time usage of the powered fastener driver, so that friction between the drive blade and the blade seal assembly is minimized and the fasteners can be strike out by the maximum force even after a long time of use. 
         [0023]    Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]      FIG. 1  is a perspective view of a powered fastener driver in accordance with an embodiment of the invention. 
           [0025]      FIG. 2  is a perspective view of a drive assembly of the powered fastener driver of  FIG. 1 . 
           [0026]      FIG. 3  shows the cross-sectional perspective view of the drive blade lubrication assembly in the powered fastener driver according to one embodiment of the present invention. 
           [0027]      FIG. 4  shows the cross-sectional perspective view of the drive blade lubrication assembly in the powered fastener driver according to another embodiment of the present invention. 
           [0028]      FIG. 5  shows the cross-sectional perspective view of the drive blade lubrication assembly in the powered fastener driver according to further embodiment of the present invention. 
       
    
    
       [0029]    Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. 
       DETAILED DESCRIPTION 
       [0030]      FIG. 1  illustrates the general structure of a vacuum powered fastener driver  10  according to the present invention, which is operable to drive fasteners (e.g., nails, tacks, staples, etc.) held within a magazine  14  into a workpiece. The fastener driver  10  includes an outer housing  18  with a handle portion  22 , and a user-actuated trigger  26  mounted on the handle portion  22 . The fastener driver  10  does not require an external source of air pressure, but rather includes an on-board vacuum system  30 . The vacuum system  30  is powered by a power source (e.g., a battery pack  34 ), coupled to a battery attachment portion  38  of the outer housing  18 . In alternative embodiments, alternative power sources (i.e., an electrical cord) may provide power to the vacuum system  30 . 
         [0031]    With reference to  FIG. 2 , the fastener driver  10  includes a drive blade  42  actuated by the vacuum system  30  to drive the fasteners into a workpiece. The vacuum system  30  includes a variable-volume vacuum chamber (not shown) defined within a cylinder  50 , between a drive piston (not shown) and an elevator or a reciprocating piston  58 . The drive blade  42  is coupled to the drive piston, and the vacuum chamber  46  creates a driving force as a result of differential pressure acting on the drive piston. The reciprocating piston  58  is driven in a reciprocating manner by a drive assembly  60 . In the illustrated embodiment of the fastener driver  10 , the drive assembly  60  includes a motor  74 , a transmission  70  that receives torque from the motor, a pinion  66  drivably coupled to the output of the transmission  70 , and a rack  62  meshed with the pinion  66  and connected to the drive piston for reciprocation therewith. A vacuum is developed within the vacuum chamber in the cylinder  50  by moving the reciprocating piston  58  away from the drive piston, while the position of the drive piston is held or maintained. A bumper (not shown) is positioned in a bottom portion of the cylinder  50  and absorbs impact forces from the reciprocating piston  58  and the drive piston. 
         [0032]    In the above-mentioned embodiment, the drive blade is at its one end fixedly connected to the drive piston. On the other hand the drive blade snap-fits with the reciprocating piston. As a result, there is a blade seal assembly configured in the reciprocating piston of the fastener driver, which allows for slidably fit between the reciprocating piston and the drive blade, but also separates the vacuum in the vacuum chamber from the other portion of the cylinder, so as to maintain the pressure differential on the two sides. The blade seal is preferably movable between a first position, where the blade seal blocks an air leakage path and thus achieves airtight sealing, and a second position where the leakage path is unblocked and the sealing effect no longer exists. The change of the blade seal&#39;s position can be made by relative movement between the reciprocating piston and the drive blade. However, no matter which position the blade seal is located at, the blade seal always encompasses a certain portion of the drive blade while maintaining a generally tight, sliding fit between the blade seal and the drive blade. In the next part of the description, a drive blade lubrication assembly configured in the powered fastener drivers will be described which effectively introduces and maintains lubricant (such as grease oil) on the portion of the drive blade adjacent to the blade seal. 
         [0033]    Turning now to  FIG. 3 , in one embodiment of the present invention there are grease pools  101  formed in the reciprocating piston  158 . The grease pools  101  are hollow portions formed in the reciprocating piston  158 , and each is capable of storing a volume of grease oil therein. As shown in  FIG. 3 , each grease pool  101  is formed with a trapezoidal cross-sectional shape, and two such grease pools  101  are symmetrically located on two side of the drive blade  142 . The grease pools  101  are positioned in the reciprocating piston  158  at a location separated from a blade seal  103  along a longitudinal direction of the drive blade  142 . In other words, the grease pools  101  are located adjacent to a portion of the drive blade  142  while the blade seal  103  is also located adjacent to the drive blade  142  but at a different point along the length of the drive blade  142 . The blade seal  103  and the grease pools  101  are actually placed in a parallel manner along the length of the drive blade  142 . 
         [0034]    As shown in  FIG. 3 , there is also an outlet configured for each grease pool  101 , which is a channel  105  connecting the grease pool  101  to a portion of the surface of the drive blade  142 . The channel  105  as shown in this embodiment is aligned to be substantially perpendicular to a length of the drive blade  142  which is encompassed by said blade seal  103 . The channel  105  is also referred as a lubricant applying member in this embodiment, since it functions to apply the lubricant to the surface of the drive blade  142 . The grease pools  101  are also referred as lubricant storing devices in this embodiment, and the grease pools  101  are adapted to replenish lubricant in the channel  105  since each channel  105  is in fluid communication with its corresponding grease pool  101 . 
         [0035]    During continuous usage of the powered fastener driver, any grease oil originally applied on the surface of the drive blade (for example applied during manufacture of the fastener driver) will gradually leak out through the movement of the drive blade relative to the blade seal. In addition, the grease oil may gradually diffuse and thus leaves the blade surface. However, due to the presence of the grease pool, any loss of the grease oil on the drive blade will be replenished by that in the grease pool. The drive blade therefore can be always kept at the status where grease oil is present on the drive blade to reduce the friction between the blade and the blade seal. As a result, the performance of the powered fastener driver will not deteriorate over time because of depletion of the grease oil, and the fasteners will always be strike out by the powered fastener driver without any impedance resulted from friction between the blade and the blade seal. 
         [0036]    In another embodiment as illustrated in  FIG. 4 , the reciprocating piston  258  like that in  FIG. 3  also contains a blade seal  203  where the drive blade  242  slidably fits with the blade seal  203 . However, the difference of the reciprocating piston  258  compared to that in  FIG. 3  is that the grease pools  201  are no longer placed adjacent to the drive blade  242  and separated from the blade seal  203  from a distance along the length of the drive blade  242 . Rather, in  FIG. 4  the grease pools  201  are placed on the exterior of the blade seal  203 . That is to say, the grease pools  201  are positioned at locations separated from the blade seal  203  along a radial direction of the reciprocating piston  258 . As a result, the channels  205  configured to fluidly connect the grease pools  201  to the portion of the drive blade  242  are longer than those shown in  FIG. 3 . 
         [0037]    In another embodiment as illustrated in  FIG. 5 , the reciprocating piston  358  like that in  FIG. 3  also contains a blade seal  303  where the drive blade  342  slidably fits with the blade seal  303 . However, one can see that the grease pools  301  in this embodiment are placed substantially parallel to the channel  305 , and each of the grease pools  301  is formed with a rectangular cross-sectional shape, with the length of the grease pool  301  being parallel to the radial direction of the reciprocating piston  358 . What is more, the grease pools  301  and the channel  305  are covered by a dust covering member  309 , which shields the channels  305  from the exterior of the reciprocating piston  358 . The covering member  309  is preferably made of polyoxymethylene materials. There is further a blocking layer  307  placed outside the covering member  309 . The covering member  309  is superimposed with the dust blocking layer  307 , so that during use of the fastener driver when the portion of the covering member  309  near the interface of blade seal  303  and drive blade  342  wears out due to abrasion, the dust blocking layer  307  continues to block dusts in the exterior of the reciprocating piston  358  from entering the channel  305 . The dust blocking layer  307  is preferably made of materials much harder than that of the covering member  309 . 
         [0038]    While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only exemplary embodiments have been shown and described and do not limit the scope of the invention in any manner. It can be appreciated that any of the features described herein may be used with any embodiment. The illustrative embodiments are not exclusive of each other or of other embodiments not recited herein. Accordingly, the invention also provides embodiments that comprise combinations of one or more of the illustrative embodiments described above. Modifications and variations of the invention as herein set forth can be made without departing from the spirit and scope thereof, and, therefore, only such limitations should be imposed as are indicated by the appended claims. 
         [0039]    In the above embodiment the lubricant used in the drive blade lubrication assembly is grease oil, although those skilled in the art would appreciate that any other types of liquid lubricant can also be used in the drive blade lubrication assembly of the present invention.