This invention relates to portable combustion powered fastener driving tools, and more specifically to an interchangeable magazine for such a power tool.
Portable combustion powered tools for use in driving fasteners into workpieces are described in commonly assigned patents to Nikolich, U.S. Pat. Nos. Re. 32,452; 4,403,722; 4,483,473; 4,483,474; 4,552,162; 5,197,646 and 5,263,439, all of which are incorporated herein by reference. Such combustion powered tools particularly designed for trim applications are disclosed in commonly assigned U.S. Pat. No. 6,016,622, also incorporated by reference herein. Similar combustion powered nail and staple driving tools are available from ITW- Paslode under the IMPULSE(copyright) brand.
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 or electronic sending 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.
A wall of the 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, or nosepiece assembly, connected to the linkage is pressed against a workpiece. This pressing action also triggers the introduction of a specified volume of fuel gas into the combustion chamber from the fuel cell.
Upon the pulling of a trigger, which causes the ignition of the gas in the combustion chamber, the piston and the 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 xe2x80x9creadyxe2x80x9d position through differential gas pressures within the cylinder. Fasteners are fed into the nosepiece barrel from a supply assembly where they are held in a properly positioned orientation for receiving the impact of the driver blade. The fasteners are then propelled through the length of the barrel by the driver blade, exiting the barrel at the workpiece surface. Force of the driver blade and the momentum of the fastener drive the fastener to penetrate the workpiece.
A convenient manner of supplying fasteners is through a magazine that feeds them in succession to the barrel. When the magazine is emptied, it is detached from the nail gun, refilled and reinstalled to continue the job. Multiple magazines are often used so that the tradesman can continue working while the magazines are refilled by an assistant or stored for later replenishment. It is often necessary to change from among many different types of fasteners. Nails, for example, may be normal or Positive Placement(copyright), clipped head, Roundrive(copyright) or of various lengths. The geometry of the magazine and the shear area that holds the fastener in a proper orientation to receive the impact of the driver blade determines the type of fastener that is appropriate with a particular magazine or shear area.
Firing of the tool produces a great deal of shock and vibration when the driver blade strikes the fastener, driving it into the workpiece. Screws in the vicinity of the shear area tend to work loose from the vibration, frequently requiring tightening to keep the component parts properly aligned. For this reason, magazines have generally been of one-piece construction. Prior art, multi-piece magazines have been fastened with screws adjacent the shear block. In many cases, the screws holding the side rails of the magazine together loosen due to repeated vibration over time. The user of such a magazine must periodically check the magazine to determine if the fasteners need to be tightened. This monitoring requirement is at best inconvenient.
One-piece magazines have been used in the art in an attempt to eliminate disassembly of the magazine. However, units made of a single piece were found to be either very heavy or expensive to manufacture. Windows in the sides of the magazine reduce the weight as well as allow the user to visually confirm operation of the magazine. A single-piece magazine cannot easily be stamped, punched or molded to create the windows and the hollow interior through which the fasteners pass. More expensive fabrication techniques have to be employed to manufacture magazines of this type.
Although they may have detachable magazines, prior art combustion powered tools are not necessarily convertible to handle different sizes or kinds of fasteners. Because the shear area guides the fastener into the barrel, the type of fasteners that can be used is determined by the shear block that surrounds the shear area and is a permanent part of the tool. Detachable magazines can be used to provide a convenient supply of fasteners, but as long as the shear area does not change, the size and shape of the fastener head cannot change from one magazine to another.
It is known in the art to accommodate changes in the length of the fastener by actuating a lever. If the user forgets to move the lever, or places it in the wrong position, the fastener can jam in the barrel of the tool. The barrel must then be opened to clear the jam before work can be resumed. It is contemplated that the use of a lever to accommodate changes in the fastener diameter or the shape of the head would have similar results.
Inclusion of the shear block on the tool can render the tool unusable if the shear block is damaged. If repair or replacement of the shear block is necessary, the entire tool is unusable during the repair time, requiring that the user have another tool as a backup, or else reschedule the workload until the tool becomes available.
Thus, there is a need in the art for a detachable magazine for a tool that accommodates fasteners of different sizes and types. There is also the need for a magazine that does not have screws in the vicinity of the shear block that could loosen due to vibration. Finally, there is a need for a tool to accommodate a magazine with an integrated shear block and where the shear block can be changed merely by attaching a different magazine to the tool.
The present invention features a detachable magazine for a power tool that is interchangeable with similar magazines holding fasteners of different sizes or types for use with the same tool.
More specifically, the present invention provides a tool for driving a fastener from a detachable magazine. The tool includes a tool housing having a proximal end and a distal end and a power source enclosed by the housing. A nosepiece is attached to the housing and has a channel and a first alignment structure. The magazine is removably attached to the tool and has a magazine housing and a shear block that is mounted to the proximal end of the magazine housing. There is a second alignment structure and a face on the shear block such that the channel and the face form a barrel when the first alignment structure is engaged with the second alignment structure and the magazine is removably attached to the tool. Upon firing of the tool, the fastener is propelled by the power source, through the barrel and into the workpiece.
As fasteners move from the magazine into the barrel, they pass through the shear block, which is shaped for fasteners of specific size and type to aid in properly aligning the fastener in the barrel for firing. Mounting of the shear block onto the magazine allows the shear block to be replaced each time the magazine is changed, allowing for rapid conversion to different fasteners. Valuable time is not wasted manually checking lever positions, changing levers or clearing jams if incompatible lever positions are selected.
In a preferred embodiment, a magazine of two-piece construction is used. The magazine housing is made of a first side rail and a second side rail that matingly engage with one another. The shear block is held between the proximal ends of each of the first and second side rails when the first and second side rails are removably attached to each other.
Two-piece construction of the magazine has many advantages over the prior art. Windows, located in each rail to make it lighter, can be die punched when there is only a single thickness of material. A one-piece magazine cannot be die punched. The windows are generally obtained by machining each window, resulting in more labor and higher costs. When each side rail is die punched prior to assembly, the magazine can be made lighter and more quickly at a lower cost compared to a single piece magazine. Additionally, the two-piece magazine can be more economical to repair since each side rail can be independently replaced.
The magazine is easily assembled by a tongue on one side rail in a groove on the bottom edge of the second side rail, then applying fasteners to the top of the magazine. When fasteners are used to hold the magazine together in the vicinity of the barrel, they become loose due to the shock and vibration at each firing of the tool. Use of tongue and groove assembly holds the magazine together in a manner that does not come loose. The magazine is also easier to assemble because fewer fasteners are needed for its construction.