Patent Publication Number: US-6988648-B2

Title: Adjustable depth of drive device

Description:
The present invention relates generally to fastener driving tools such as combustion powered tools, pneumatic tools, cordless framing tools and the like. More particularly, the present invention relates to improvements in a device which adjusts the depth of drive of the tool. 
   BACKGROUND OF THE INVENTION 
   As exemplified in Nikolich, U.S. Pat. Re. No. 32,452, and U.S. Pat. Nos. 4,552,162; 4,483,473; 4,483,474; 4,404,722; 5,197,646; 5,263,439; 5,558,264 and 5,678,899 all of which are incorporated by reference, fastening tools, and particularly, portable combustion powered tools for use in driving fasteners into workpieces are described. Such fastener-driving tools are available commercially from ITW-Paslode (a division of Illinois Tool Works, Inc.) of Vernon Hills, Ill., under the IMPULSE® brand. 
   Such tools incorporate a generally gun-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 the spark for ignition, and a fan located in the combustion chamber provides for both an efficient combustion within the chamber, and facilitates scavenging, including the exhaust of combustion by-products. The engine includes a reciprocating piston having an elongate, rigid driver blade disposed within a piston chamber of a cylinder body. 
   The wall of a combustion chamber is axially reciprocable about a valve sleeve and, through a linkage, moves to close the combustion chamber when a workpiece contact element at the end of a nosepiece connected to the linkage is pressed against a workpiece. This pressing action also triggers a fuel metering valve to introduce a specified volume of fuel gas into the closed combustion chamber from the fuel cell. The metering valve may take the form of a solenoid valve, which is powered by the battery, or may be a purely mechanical valve. 
   Upon the pulling of a trigger, which causes the ignition of a charge of gas in the combustion chamber of the engine, the piston and driver blade are shot downward to impact a positioned fastener and drive it into the workpiece. As the piston is driven downward, a displacement volume enclosed in the piston chamber below the piston is forced to exit through one or more exit ports provided at a lower end of the cylinder. After impact, the piston then returns to its original, or “ready” position through differential gas pressures within the cylinder. Fasteners are fed into the nosepiece from a supply assembly, such as a magazine, where they are held in a properly positioned orientation for receiving the impact of the driver blade. The power of the tools differs according to the length of the piston stroke, volume of the combustion chamber, fuel dosage and similar factors. 
   Combustion powered tools have been successfully applied to large workpieces requiring large fasteners, for framing, roofing and other heavy duty applications. Smaller workpiece and smaller fastener trim applications demand a different set of operational characteristics than the heavy-duty, “rough-in”, and other similar applications. Other types of fastener driving tools such as pneumatic, powder activated and/or electrically powered tools are well known in the art, and are also contemplated for use with the present adjustment mechanism. 
   One operational characteristic required in trim applications is the ability to predictably control fastener driving depth. For the sake of appearance, some trim applications require fasteners to be countersunk below the surface of the workpiece, others require the fasteners to be sunk flush with the surface of the workpiece, and some may require the fastener to stand off above the surface of the workpiece. Depth adjustment has been achieved in pneumatically powered and combustion powered tools through a tool controlling mechanism, referred to as a drive probe, that is movable in relation to the nosepiece of the tool. Its range of movement defines a range for fastener depth-of-drive. Similar depth of drive adjustment mechanisms are known for use in combustion type framing tools. 
   Existing depth adjusting mechanisms do have some drawbacks. One disadvantage of previous depth adjusting mechanisms is that they will only allow one speed of adjusting, usually gross adjustment. Many projects require the user to accurately set the depth of drive at a specific measurement. This can be difficult to accomplish when the adjusting mechanism only allows for gross adjustments, and therefore the user may have to adjust the depth of drive several times through trial and error in order to obtain the correct measurement for the depth of drive. 
   Consequently, one object of the present invention is to provide an improved depth of drive adjustment drive for use in a fastener driving tool, which allows the user to adjust the depth adjusting mechanism in either a fine or gross adjustment setting. 
   Another object of the present invention is to provide an improved depth of drive device for a fastener driving tool which allows for convenient and easy switching between fine and gross adjustments without releasing latches or other mechanisms. 
   Still another object of the present invention is to provide an improved depth of drive adjustment device for a fastener driving tool which is relatively inexpensive to manufacture and simple to assemble. 
   SUMMARY OF THE INVENTION 
   The above-listed objects are met or excluded by the present adjustable depth of drive device for use on a fastener driving tool, such as a combustion type framing tool or the like. An important feature of the present device is a spring loaded thumb wheel or barrel which is constructed and arranged to adjust the position of the workpiece contact element relative to the nosepiece so that either gross or fine adjustments may be made in virtually the same user motion, without the use of complicated latch mechanisms. 
   More specifically, the present invention provides an adjustable depth of drive device for use on a fastener driving tool having a housing structure which defines an axis, and encloses a combustion chamber, and a nosepiece which extends generally axially from the housing with a workpiece contact element. The device includes a thumb post which is mounted to, and extends from the workpiece contact element. A thumb wheel is adjustably engaged on the thumb post, and a spring member is engagable with the thumb wheel in at least two positions. In a first position, the spring member is frictionally engaged with the thumb wheel to prevent unwanted movement of the thumb wheel relative to the thumb post. In a second position, the spring member is disengaged from the thumb wheel to permit free rotation of the thumb wheel on the thumb post. 
   The spring member exerts a biasing force against the thumb wheel, and in the first position, the thumb wheel is manually movable when the biasing force is overcome, allowing for fine adjustments of the position of the work piece contact element relative to the nosepiece. Also, in the preferred embodiment, the spring member has a thumb lever for moving the spring member into the second position, allowing for gross adjustments of the position of the workpiece contacting element relative to the nosepiece. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of the present adjustable depth of drive device shown assembled and attached to the sleeve of a fastener driving tool; 
       FIG. 2  is an exploded, perspective view showing the structure of the present adjustable depth of drive device and related structures; and 
       FIG. 3  is a perspective view of an alternate embodiment of work piece contact element of  FIGS. 1 and 2 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   As seen in  FIG. 1 , an improved adjustable depth of drive device is generally designated  10 , and is intended for use on a fastener driving tool of the type described above. The tool includes a housing or sleeve structure  12  which defines an axis and encloses a combustion chamber (not shown), and a nosepiece  14  which extends axially from the housing structure, along with a work piece contact element  16 . 
   Referring now to  FIG. 2 , the adjustable depth of drive device  10  includes a thumb post  18  which is mounted to, and extends from the work piece contact element  16 . There is also a thumb wheel  20  which is removably attached to, and adjustably engaged on the thumb post  18 , and a spring member, generally designated  22 , that is engagable with the thumb wheel in at least two positions. In a first position, seen in  FIG. 1 , the spring member  22  is frictionally engaged with the thumb wheel  20  to prevent unwanted movement of the thumb wheel relative to the thumb post  18 . In a second position (not shown), the spring member  22  is disengaged from the thumb wheel  20  to permit free rotation of the thumb wheel on the thumb post  18 . 
   In the first position, the spring member  22  exerts a biasing force against the thumb wheel  20 , and the thumb wheel is manually movable when the biasing force is overcome, allowing for fine adjustments of the position of the work piece contact element  16  relative to the nosepiece  14 . It is an advantage of the present invention to allow a user to make fine adjustments to more accurately set the depth of drive without having to manually disengage the spring member  22 , or any other extra latch member. 
   In both  FIGS. 1 and 2 , it can be seen that the spring member  22  has a thumb lever  24  for moving the spring member into the second position, allowing for gross adjustments of the position of the work piece contacting element  16  relative to the nosepiece  14 . Preferably, a resilient, rubber-like thumb pad  25  is attached to the thumb lever  24 , that provides a user with a cushion to make depressing the thumb lever more comfortable. The present device  10  allows a user to easily switch between fine adjustments and gross adjustments of the depth of drive by simply turning the thumb wheel  20  initially when the spring member  22  is in the first position for fine adjustments, or when the user depresses the thumb lever  24 , placing the spring member in the second position for gross adjustments. 
   In the preferred embodiment as seen in  FIG. 2 , the thumb post  18  has a threaded exterior  26  and the thumb wheel  20  has a threaded interior bore  28 , so that when the thumb wheel is rotated relative to the thumb post in either direction, the position of the thumb post is moved relative to the nosepiece  14 . It is also preferred that the thumb post  18  extends from a clevis  30  that is connected to the work piece contact element  16  by a fastener  32 , preferably a rivet, that extends through a work piece contact element hole  34  and a clevis bore  36 . Upon assembly, the hole  34  and the bore  36  are placed in registry with each other. It is well known in the art that the rivet  32  may be replaced by another securing means such as a screw or other suitable type of fastener. In an alternative embodiment, the work piece contact element  16  and the thumb post  18  could be manufactured as one piece. 
   The spring member  22  itself includes a plate  38  and a securing tab  40  that are disposed in a parallel, displaced relationship with respect to one another. Also included is at least one shoulder flange  42 , which connects the plate  38  to both the thumb lever  24  and the securing tab  40 . As seen in  FIG. 2 , preferably there is a first shoulder flange  42   a  and a second shoulder flange  42   b  that connect the plate  38  respectively to the thumb lever  24  and the securing tab  40 . However, in an alternative embodiment, it is possible for only one flange  42  to connect both the thumb lever  24  and the securing tab  40  to the plate  38 . There is also a locating slot  44  that is defined by the edge of the plate  38 , and a securing hole  46  is defined in the middle of the securing tab  40 . Preferably the spring member  22  is made of steel, however any metal with similar qualities may be used, and even a hard, durable plastic or engineered material may be used for the spring member. 
   Still referring to  FIG. 2 , the adjustable depth of drive device  10  is connectable with a wire form  50  that has a platform  52  and a plurality of arms  54  extending from the platform, generally axially relative to the housing structure  12 . Upper ends  55  of each of the preferably two arms  54  are received in the housing structure  12 . An eyelet guide  56  is attached to the platform  52  and extends perpendicular thereto. There is also a platform hole  58  defined by the platform  52 . A stop block  60  which has a guide opening  62 , has a portion which is insertable through the platform hole  58  so that the eyelet guide  56  is in axial alignment with the guide opening. When the guide opening  62  and eyelet guide  56  are in alignment, the thumb post  18  is insertable through both the eyelet guide and the guide opening, and the thumb wheel  20  is positioned in between the eyelet guide and the stop block  60 , and is engagable with the thumb post. In this position, the thumb wheel  20  secures and, by rotation, adjusts the relative position of the thumb post  18  relative to the housing  12 . 
   Again referring to  FIG. 2 , the platform  52  has at least one upper plate  64  and a lower plate  66 , and the platform has at least one curved shoulder  68  that connects the upper plate to the lower plate in a parallel displaced relationship. In the preferred embodiment, there is a first upper plate  64   a  and a second upper plate  64   b  that are on opposite sides of the lower plate  66 , with a first curved shoulder  68   a  and a second curved shoulder  68   b  that connect the first upper plate and the second upper plate to the lower plate in a parallel displaced relationship. There is a locating lug  70  which is attached to the first upper plate  64   a  and is disposed to engage the locating slot  44  of the spring member  22 . The lower plate  66  defines at least one and preferably two platform securing holes  72 , used by a fastener to attach the wire form  50  to the spring member  22  and the stop block  60 . 
   Also in the preferred embodiment, as seen in  FIG. 2 , the stop block  60  has a first mounting ear  74  connected to an end  78  of the stop block. Each mounting ear  74  and  76  has a mounting ear opening, respectively  74   a  and  76   a . When fully assembled, the stop block  60  is inserted through the platform hole  58 , and the mounting ears  74  and  76  abut the lower plate  66  so that the first mounting ear opening  74   a  and the second mounting ear opening  76   a  are in alignment with the corresponding securing holes  72 . When the spring member  22  is included in the assembly, the securing hole  46  of the securing tab  40  is aligned with the corresponding platform securing hole  72 , so that the flange  42  abuts against the first curved shoulder  68   a  and the locating lug  70  is positioned in the locating slot  44 . In a preferred embodiment, a single rivet  80  is insertable through the securing hole  46 , the platform securing hole  72 , and the second mounting ear opening  76   a , as a way to mount the entire structure together. A second rivet  82  is insertable through one of the platform securing holes  72  and the first mounting ear opening  74   a.    
   Referring now to  FIG. 3 , an alternate embodiment of the workpiece contact element  16  is generally designated  100 . Components of the element  100  which correspond to the element  16  are designated with identical reference numbers. The main difference between the elements  16  and  100  is that the latter is formed in a single piece casting combining elements the thumb post  18 , the clevis  30  and the fastener  32 . In the element  100 , a thumb post  102  is an integral component of the casting. The element  100  otherwise operates in the same manner as the element  16 . 
   When the adjustable depth of drive device  10  is completely assembled and attached to the housing structure  12  as shown in  FIG. 1 , a user may adjust the depth of drive by axially rotating the thumb wheel  20  in either direction. By turning the thumb wheel  20  in a clockwise rotation, the work piece contact element  16  will be moved toward the housing structure  12 , which will decrease the depth of drive. Turning the thumb wheel  20  in a counter-clockwise direction will move the work piece contact element  16  away from the housing structure  12 , which will increase the depth of drive. 
   The present device allows the user to adjust the depth of drive with fine or slow adjustments by turning the thumb wheel  20  in either direction while the spring member  22  is exerting a biasing force against the thumb wheel. The user can adjust the depth of drive with gross, or faster adjustments by depressing the thumb lever  24 , so that it is no longer in contact with the thumb wheel  20  which allows the thumb wheel to rotate freely. The user is allowed to adjust the depth of drive with the present invention when the fastening tool is in an actuated or non-actuated position. 
   While a particular embodiment of the adjustable depth of drive device of the invention has been shown and described, 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.