Patent Description:
The present invention relates to powered fastener drivers, and more particularly to a driver blade for use with a powered fastener driver.

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, a flywheel mechanism, etc.) to drive a driver blade from a top-dead-center position to a bottom-dead-center position. A gas spring-powered fastener driver is described in <CIT>. The gas spring-powered fastener driver includes a cylinder, a moveable piston positioned within the cylinder, a driver blade attached to the piston and movable therewith between a ready position and a driven position, a lifter operable to move the driver blade from the driven position to the ready position, a transmission for providing torque to the lifter, a first clutch mechanism permitting a transfer of torque to an output shaft of the transmission in a single rotational direction, and a second clutch mechanism limiting an amount of torque transferred to the transmission output shaft and the lifter. A tool bit is described in <CIT>. The tool bit includes a hexagonal drive portion, a working end made of a first material having a first hardness, and a shank interconnecting the drive portion and the working end. The shank is made of a second material having a second hardness, and the first hardness is higher than the second hardness.

The invention provides, in one aspect, a driver blade for use with a powered fastener driver as defined in claim <NUM>.

The driver blade includes an elongated body defining a longitudinal axis. The body includes a top surface and a bottom surface opposite the top surface. A first edge extends between the top surface and the bottom surface. The driver blade further includes a plurality of teeth formed along the first edge and extending in a direction transverse to the longitudinal axis. The driver blade is manufactured using a metal injection molding process.

The invention provides, in another aspect, a method of manufacturing a driver blade for use with a powered fastener driver as defined in claim <NUM>. The method includes mixing a first material in powder form with a binder composition to yield a first feedstock mixture. The method further includes injecting the first feedstock mixture into a mold to form a rough driver blade. The method further includes removing the binder composition from the rough driver blade, and heat treating the rough driver blade to reduce the porosity of the rough driver blade to yield a finished driver blade that is usable in the powered fastener driver. Heat treating the rough driver blade includes sintering the rough driver blade, and sintering the rough driver blade includes using a hot isostatic pressing process to increase the density of the rough driver blade.

With reference to <FIG>, a gas spring-powered fastener driver <NUM> is operable to drive fasteners (e.g., nails, tacks, staples, etc.) held within a magazine <NUM> into a workpiece. The fastener driver <NUM> includes a cylinder <NUM>. A moveable piston (not shown) is positioned within the cylinder <NUM>. With reference to <FIG>, the fastener driver <NUM> further includes a driver blade <NUM> that is attached to the piston and moveable therewith. The fastener driver <NUM> does not require an external source of air pressure, but rather includes pressurized gas in the cylinder <NUM>.

With reference to <FIG>, the fastener driver <NUM> includes a housing <NUM> having a cylinder housing portion <NUM> and a motor housing portion <NUM> extending therefrom. The cylinder housing portion <NUM> is configured to support the cylinder <NUM>, whereas the motor housing portion <NUM> is configured to support a motor <NUM> and a transmission <NUM> downstream of the motor <NUM>. In addition, the illustrated housing <NUM> includes a handle portion <NUM> extending from the cylinder housing portion <NUM>, and a battery attachment portion <NUM> coupled to an opposite end of the handle portion <NUM>. A battery <NUM> is electrically connectable to the motor <NUM> for supplying electrical power to the motor <NUM>. The handle portion <NUM> supports a trigger <NUM>, which is depressed by a user to initiate a driving cycle of the fastener driver <NUM>.

With reference to <FIG>, the driver blade <NUM> defines a longitudinal axis <NUM>. During a driving cycle, the driver blade <NUM> and piston are moveable between a top-dead-center (TDC) or ready position within the cylinder <NUM>, and a bottom-dead-center (BDC) or driven position, along the axis <NUM>. The fastener driver <NUM> further includes a lifter assembly (not shown), which is powered by the motor <NUM> (<FIG>), and which is operable to return the driver blade <NUM> from the driven position to the ready position.

With continued reference to <FIG>, the driver blade <NUM> includes an elongated body <NUM> having a first planar surface (i.e., a front surface <NUM>) and an opposite, second planar surface (i.e., a rear surface <NUM>). A first edge <NUM> extends between the front surface <NUM> and the rear surface <NUM> along one lateral side of the body <NUM>, and a second edge <NUM> extends between the front surface <NUM> and the rear surface <NUM> along an opposite lateral side of the body <NUM>. The front surface <NUM> is parallel to the rear surface <NUM>. Likewise, the edges <NUM>, <NUM> are also parallel.

The driver blade <NUM> includes a plurality of lift teeth <NUM> formed along the first edge <NUM> of the body <NUM>. The first edge <NUM> extends in the direction of the axis <NUM>, and the lift teeth <NUM> project from the first edge <NUM> in a direction transverse to the axis <NUM>. The lift teeth <NUM> are sequentially engaged with the lifter assembly during the return of the driver blade <NUM> from the driven position to the ready position.

The driver blade <NUM> further includes a first end <NUM> and a second end <NUM> opposite the first end <NUM>. The front and rear surfaces <NUM>, <NUM>, and the first and second edges <NUM>, <NUM>, extend between the first and second ends <NUM>, <NUM>. In the illustrated embodiment of the driver blade <NUM>, the first end <NUM> includes a threaded post for connection with the piston. The second end <NUM> of the driver blade <NUM> is oriented perpendicular to the axis <NUM> for striking fasteners fed from the magazine <NUM> and driving the fasteners into a workpiece.

<FIG> illustrate another driver blade 26a embodying the invention, with like reference numerals with the letter "a" assigned to like features as the driver blade <NUM> shown in <FIG>. The driver blade 26a includes a plurality of lift teeth 82a extending from a first edge 74a. In addition, the driver blade 26a includes a plurality of projections <NUM> extending from a second edge 78a. In particular, the projections <NUM> extend from the second edge 78a in a direction transverse to the longitudinal axis 58a. In one embodiment, the plurality of projections <NUM> are configured to engage a latch (not shown) of the fastener driver <NUM> for inhibiting the driver blade 26a from moving toward the driven position.

<FIG> illustrates another driver blade 26b embodying the invention, with like reference numerals with the letter "b" assigned to like features as the driver blade <NUM> shown in <FIG>. The driver blade 26b includes a plurality of lift teeth 82b formed along an edge 74b of the driver blade 26b. In particular, the plurality of lift teeth 82b extend from the edge 74b in a direction transverse to a longitudinal axis 58b. Each one of the lift teeth 74b includes an end portion <NUM>. Each of the end portions <NUM>, except for the end portion <NUM> of a lowermost tooth 82b' of the driver blade 26b, has the same shape. In particular, the end portion <NUM> of the lowermost tooth 82b' has a rounded shape. In one example, the rounded shape of the end portion <NUM> of the lowermost tooth 82b' is configured to cooperate with a shape of a roller on the lifter assembly (not shown). In addition, the driver blade 26b includes a plurality of projections <NUM> extending from a second edge 78b of the driver blade 26b.

Conventionally, a forging and/or machining process is used to manufacture driver blades like those shown in <FIG>. However, in the illustrated embodiment, an insert molding process, such as a one-shot metal injection molding ("MIM") process, is used to manufacture the driver blade <NUM>, 26a, 26b. In such a one-shot MIM process, the driver blade <NUM>, 26a, 26b is made of a first material <NUM> (e.g., a metal or metal alloy) having a first hardness. The first hardness of the first material <NUM> is chosen to be at least a minimum value, and at least as hard as the components of the lifter assembly in contact with the lift teeth <NUM>, 82a, 82b to reduce the wear imparted to the driver blade <NUM>, 26a, 26b during use of the fastener driver <NUM>. In one embodiment, the first material <NUM> includes a ferrous alloy composition. For example, the ferrous alloy composition may comprise an alloy of Carbon, Chromium, Iron, Manganese, Molybdenum, Silicon, and/or Vanadium. In the illustrated embodiment of the driver blade <NUM>, 26a, 26b the ferrous allow composition consists essentially of (by weight): between <NUM>% and <NUM> % Carbon, between <NUM>% and <NUM>% Chromium, between <NUM>% and <NUM>% Iron, between <NUM>% and <NUM>% Manganese, between <NUM>% and <NUM>% Molybdenum, between <NUM>% and <NUM>% Silicon, and between <NUM>% and <NUM>% Vanadium.

In another embodiment, the driver blade <NUM>, 26a, 26b may be formed using more than one material such that the driver blade <NUM>, 26a, 26b is manufactured using a multiple-shot MIM process. For example, the body <NUM>, 66a, 66b of the driver blade <NUM>, 26a, 26b may be made from the first material <NUM> having the first hardness, and the lift teeth <NUM>, 82a, 82b (and optionally the projections <NUM>) may be made from a second material <NUM> having a second, different hardness. In this example, the MIM process is a two-shot MIM process. The first and second materials <NUM>, <NUM> are chosen such that the second hardness is greater than the first hardness. Accordingly, the hardness of the lift teeth <NUM>, 82a, 82b is greater than the hardness of the body <NUM>, 66a, 66b to reduce the wear imparted to the lift teeth <NUM>, 82a, 82b during use of the fastener driver <NUM>. Because the dissimilar materials <NUM>, <NUM> of the body <NUM>, 66a, 66b and the lift teeth <NUM>, 82a, 82b, respectively, are conjoined or integrally formed during the two-shot MIM process, a secondary manufacturing process for connecting the lift teeth <NUM>, 82a, 82b to the body <NUM>, 66a, 66b is unnecessary. In one embodiment, the second material <NUM> may also include a ferrous alloy composition.

In other embodiments of the driver blade <NUM>, 26a, 26b, other portions may be made from dissimilar materials to impart different material properties (e.g., hardness) to the respective portions of the driver blade <NUM>, 26a, 26b. For example, the second end <NUM>, 94a, 94b of the driver blade <NUM>, 26a, 26b, which impacts the fasteners during a fastener driving operation, may be made from a harder material than the remainder of the body <NUM>, 66a, 66b.

With reference to <FIG>, the MIM process includes in sequence a feedstock mixing process <NUM> to mix the first material <NUM> with a binder composition <NUM>, an injection molding process <NUM> using a mold <NUM>, a debinding process <NUM> to eliminate the binder composition <NUM>, and a heat treating process <NUM>.

During the feedstock mixing process <NUM>, the binder composition <NUM> is added to the first material <NUM> to facilitate processing through the injection molding process <NUM>. As a result, the first material <NUM>, which is in a powder form, is homogeneously mixed with the binder composition <NUM> to provide a first feedstock mixture <NUM> of a determined consistency. If it is a two-shot MIM process, the second material <NUM>, which is also in a powder form, is also homogeneously mixed with the binder composition <NUM> to provide a second feedstock mixture <NUM> with substantially the same consistency as the first mixture <NUM>. In the illustrated embodiment of the driver blade <NUM>, 26a, 26b, the binder composition <NUM> includes a thermoplastic binder. Alternatively, the binder composition <NUM> may include other appropriate binder compositions (e.g., wax). The amount of binder composition <NUM> in each of the first and second feedstock mixtures <NUM>, <NUM> is chosen to match the shrink rates of the body <NUM>, 66a, 66b and the lift teeth <NUM>, 82a, 82b respectively, during the sintering process <NUM> described below.

The injection molding process <NUM> includes processing the first and the second feedstock mixtures <NUM>, <NUM> through an injection molding machine <NUM>. Particularly, the process <NUM> includes injecting the first feedstock mixture <NUM> into the mold <NUM>. If it is a two-shot MIM process, than the first feedstock mixture <NUM> is injected into a first portion of the mold <NUM>, and the second feedstock mixture <NUM> is injected into a second portion of the mold <NUM>. Upon completion of the injection molding process <NUM>, a temporary or rough (otherwise known in the MIM industry as a "green") driver blade <NUM> is produced that includes the first material <NUM> (and the second material <NUM> if it is a two-shot MIM process) and the binder composition <NUM>. The "green" driver blade <NUM> is larger than the final driver blade <NUM>, 26a, 26b due to the presence of the binder composition <NUM>.

After the injection molding process <NUM>, the "green" driver blade <NUM> is removed from the mold <NUM> and proceeds through the debinding process <NUM>. The debinding process <NUM> eliminates the binder composition <NUM>. During the debinding process <NUM>, the "green" driver blade <NUM> transforms into a "brown" driver blade <NUM> (as it is known in the MIM industry) that only includes the first material <NUM> (and the second material <NUM> if it is a two-shot MIM process). In the illustrated embodiment, the debinding process <NUM> includes a chemical wash <NUM>. Alternatively, the debinding process <NUM> may include a thermal vaporization process to remove the binder composition <NUM> from the "green" driver blade <NUM>. The "brown" driver blade <NUM> is fragile and porous with the absence of the binder composition <NUM>.

To reduce the porosity of the "brown" driver blade <NUM>, the heat treating process <NUM> is performed to atomically diffuse the "brown" driver blade <NUM> to form the final tool bit <NUM>, 26a, 26b. The heat treating process <NUM> exposes the "brown" driver blade <NUM> to an elevated temperature to promote atomic diffusion allowing atoms to interact and fuse together. In the illustrated embodiment, the heat treating process <NUM> includes a sintering process <NUM>. Alternatively, the debinding process <NUM> and the heat treating process <NUM> may be combined as a single process such that, at lower temperatures, thermal vaporization will occur during the debinding process <NUM> to eliminate the binder composition <NUM>. And, at higher temperatures, atomic diffusion will reduce the porosity in the "brown" driver blade <NUM> to yield the final, finished driver blade <NUM>, 26a, 26b.

In the invention, the sintering process <NUM> includes a hot isostatic pressing (HIP) process that utilizes high pressure and temperature for a predetermined amount of time to impart a higher density to a part, such as the driver blade <NUM>, 26a, 26b. In one example, the "brown" driver blade <NUM> is positioned in a high temperature furnace, which is enclosed in a pressure vessel. Any voids within the "brown" driver blade <NUM> collapse and fuse together under the high pressure and temperature to eliminate any defects within the "brown" driver blade <NUM>, 26a, 26b. As such, the driver blade <NUM>, 26a, 26b subjected to the HIP process may have an increase in density, a decrease in porosity throughout the driver blade <NUM>, 26a, 26b and/or a decrease in micro-cracking.

Claim 1:
A metal injection molded driver blade (<NUM>) for use with a powered fastener driver (<NUM>), the driver blade (<NUM>) comprising:
an elongated body (<NUM>) defining a longitudinal axis (<NUM>), the body (<NUM>) including
a top surface (<NUM>) and a bottom surface (<NUM>) opposite the top surface (<NUM>),
a first edge (<NUM>) extending between the top surface (<NUM>) and the bottom surface (<NUM>); and
a plurality of teeth (<NUM>) formed along the first edge (<NUM>) and extending in a direction transverse to the longitudinal axis (<NUM>).