Patent Description:
The present invention relates to power tools, and more particularly to powered fastener drivers adapted to drive fasteners into a workpiece.

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.), but often these designs are met with power, size, and cost constraints.

<CIT> shows the preamble of claim <NUM> and relates to a gas spring fastener driver including shutter valve. The fastener driver comprises a drive blade movable from a retracted position to an extended, driven position for driving a fastener into a workpiece and a gas spring mechanism for driving the drive blade from the retracted position to the driven position. The gas spring mechanism includes a drive cylinder and a drive piston attached to the drive blade for movement therewith. The drive piston is acted on by a driving force resulting from a pressure differential created by the gas spring mechanism. The fastener driver also includes an adjustable valve for selectively limiting a flow of gas into the drive cylinder above the drive piston, or a flow of ambient air at atmospheric pressure from the drive cylinder beneath the drive piston, thereby changing the pressure differential acting on the drive piston, as the drive piston and the drive blade move from the retracted position to the extended position.

The present invention provides, in one aspect, a gas spring-powered fastener driver. The fastener driver includes a first chamber, and a movable piston positioned within the first chamber. The fastener driver also includes a driver blade attached to the piston and movable therewith between a ready position and a driven position. The fastener driver further includes a second chamber containing pressurized gas. The second chamber is in fluid communication with the first chamber via a flow passage. The fastener driver also includes a throttle mechanism configured to throttle flow of the pressurized gas through the flow passage.

The present invention provides, in another aspect, a gas spring-powered fastener driver. The fastener driver includes a first cylinder defining a first chamber, and a movable piston positioned within the first chamber. The fastener driver also includes a driver blade attached to the piston and movable therewith between a ready position and a driven position. The fastener driver further includes a second cylinder surrounding the first cylinder, and a second chamber defined between the first cylinder and the second cylinder and containing pressurized gas. The second chamber is in fluid communication with the first chamber via a flow passage. The fastener driver also includes a throttle mechanism configured to throttle flow of pressurized gas through the flow passage. The throttle mechanism includes a baffle configured to selectively adjust an area of the flow passage.

<FIG> illustrate a power tool, such as a gas spring-powered fastener driver <NUM>, operable to drive fasteners (e.g., nails, tacks, staples, etc.) held within a magazine <NUM> into a workpiece. In the illustrated embodiment, the fastener driver <NUM> is configured as a multi-shot powered nailer including the magazine <NUM> holding a collated strip of fasteners, allowing the user to perform multiple fastening operations without having to manually reload the fastener driver <NUM> after each driving cycle. The gas spring-powered fastener driver <NUM> includes a gas spring assembly <NUM> for generating a motive force to drive each fastener into the workpiece. The gas spring assembly <NUM> includes a throttle mechanism <NUM> (<FIG>) for varying the power output of the fastener driver <NUM> when performing a fastener driving operation, as will be described in further detail below.

With reference to <FIG> and <FIG>, the gas spring assembly <NUM> includes an inner cylinder <NUM> and a moveable piston <NUM> positioned for reciprocating movement within an inner chamber <NUM> bounded by the inner cylinder <NUM>. The fastener driver <NUM> further includes a driver blade <NUM> that is attached to the piston <NUM> and moveable therewith. The fastener driver <NUM> does not require an external source of air pressure, but rather includes a storage chamber <NUM> filled with pressurized gas and positioned in fluid communication with the inner chamber <NUM>. The gas spring assembly <NUM> also includes an outer cylinder <NUM> positioned about the inner cylinder <NUM>. The storage chamber <NUM> is defined between the inner cylinder <NUM> and the outer cylinder <NUM>. In the illustrated embodiment, the inner cylinder <NUM> and moveable piston <NUM> are positioned within the outer cylinder <NUM>.

With reference to <FIG>, the driver <NUM> further includes a fill valve <NUM> coupled to the outer cylinder <NUM>. When connected with a source of compressed gas, the fill valve <NUM> permits the storage chamber <NUM> to be refilled with compressed gas if any prior leakage has occurred. The fill valve <NUM> may be configured as a Schrader valve, for example.

The inner cylinder <NUM> and the driver blade <NUM> define a driving axis <NUM>, and during a driving cycle the driver blade <NUM> and piston <NUM> are moveable between a ready position (i.e., top dead center; see <FIG>) and a driven position (i.e., bottom dead center; see <FIG>). The fastener driver <NUM> further includes a lifting assembly <NUM>, which is powered by a motor <NUM> (<FIG>), and which is operable to move the driver blade <NUM> from the driven position to the ready position.

In operation, the lifting assembly <NUM> drives the piston <NUM> and the driver blade <NUM> to the ready position by energizing the motor <NUM>. As the piston <NUM> and the driver blade <NUM> are driven to the ready position, the gas above the piston <NUM> and the gas within the storage chamber <NUM> is compressed. Once in the ready position, the piston <NUM> and the driver blade <NUM> are held in position until being released by user activation of a trigger <NUM> (<FIG>). When released, the compressed gas above the piston <NUM> and within the storage chamber <NUM> drives the piston <NUM> and the driver blade <NUM> to the driven position, thereby driving the fastener into a workpiece. The illustrated fastener driver <NUM> therefore operates on a gas spring principle utilizing the lifting assembly <NUM> and the piston <NUM> to compress the gas within the inner chamber <NUM> and the storage chamber <NUM>. Further detail regarding the structure and operation of the fastener driver <NUM> is provided below.

With reference to <FIG> and <FIG>, the fastener driver <NUM> includes a housing <NUM> having a cylinder support portion <NUM> (<FIG>) in which the outer cylinder <NUM> is at least partially positioned, and a transmission housing portion <NUM> in which a transmission <NUM> (<FIG>) is at least partially positioned. The transmission <NUM> is a component of the lifting assembly <NUM>, which raises the driver blade <NUM> from the driven position to the ready position. The motor <NUM> is also a component of the lifting assembly <NUM> and is coupled to the transmission housing portion <NUM> for providing torque to the transmission <NUM> when activated. A battery pack <NUM> (<FIG>) is electrically connectable to the motor <NUM> for supplying electrical power to the motor <NUM>. In alternative embodiments, the driver may be powered from an AC voltage input (i.e., from a wall outlet), or by an alternative DC voltage input (e.g., a DC power support).

With reference to <FIG>, the transmission <NUM> receives torque from the motor <NUM> via a motor output shaft <NUM>, and includes a transmission output shaft <NUM> to which a lifter <NUM> of the lifting assembly <NUM> is rotationally affixed (<FIG> and <FIG>). The transmission <NUM> provides torque to the lifter <NUM>, causing the lifter <NUM> to rotate about an axis <NUM> (<FIG>) and return the driver blade <NUM> from the driven position to the ready position. A fan <NUM> is rotatably coupled to the motor shaft <NUM> to generate cooling airflow within an interior of the fastener driver <NUM>.

With reference to <FIG>, the gas spring assembly <NUM> will now be described in further detail. The inner cylinder <NUM> includes an open end <NUM> that fluidly communicates with the storage chamber <NUM>. An end portion <NUM> of the outer cylinder <NUM> is located adjacent the open end <NUM> and substantially surrounds the open end <NUM>. A flow passage <NUM> is defined between the open end <NUM> and the end portion <NUM>, and fluidly connects the inner chamber <NUM> with the storage chamber <NUM>. The pressurized gas flows between the inner chamber <NUM> and the storage chamber <NUM> via the flow passage <NUM>.

The gas spring assembly <NUM> further includes the throttle mechanism <NUM> that selectively increases or reduces an area of the flow passage <NUM> to throttle the flow of pressurized gas between the inner chamber <NUM> and the storage chamber <NUM>. The throttle mechanism <NUM> includes a sliding sleeve or baffle <NUM> that surrounds the inner cylinder <NUM> adjacent the open end <NUM>. The baffle <NUM> is slidable in an axial direction relative to the inner cylinder <NUM>, so that a portion of the baffle <NUM> may extend beyond the open end <NUM> and into the flow passage <NUM>. As the baffle <NUM> slides beyond the open end <NUM> (e.g., <FIG>), it obstructs and effectively reduces the area of the flow passage <NUM>, thereby inhibiting the flow of pressurized gas between the inner chamber <NUM> and the storage chamber <NUM>. The baffle <NUM> is movable between a no-choke position (<FIG> and <FIG>) corresponding to a highest power output of the fastener driver <NUM>, a choked position (<FIG> and <FIG>) corresponding to a lowest power output, and one or more partially-choked positions (<FIG> and <FIG>) corresponding to an intermediate power output.

A control knob <NUM> is coupled to the baffle <NUM> via a scotch-yoke mechanism <NUM> and is operable to slide the baffle <NUM> in the axial direction relative to the inner cylinder <NUM>. The scotch-yoke mechanism <NUM> includes an eccentric pin <NUM> coupled to the control knob <NUM> and rotatable therewith. The eccentric pin <NUM> engages a slot <NUM> formed in the baffle <NUM>. As the control knob <NUM> rotates between the no-choke position (<FIG>) and the choked position (<FIG>), the eccentric pin <NUM> engages the slot <NUM> to adjust the axial position of the baffle <NUM> relative to the inner cylinder <NUM>.

In operation, the control knob <NUM> is adjusted to select an appropriate choke position for the throttle mechanism <NUM>, based on a given fastener driving application. For example, if the given fastener driving application requires a relatively high power output (e.g., for driving fasteners into relatively harder workpieces such as masonry, concrete, etc.), the control knob <NUM> is rotated to the no-choke position (<FIG> and <FIG>). The eccentric pin <NUM> engages the slot <NUM> to move the baffle <NUM> away from the flow passage <NUM>, such that the baffle <NUM> vacates the flow passage <NUM> and does not extend beyond the open end <NUM>. When a fastener driving sequence is initiated, the compressed gas within the storage chamber <NUM> flows relatively rapidly through the flow passage <NUM> unimpeded by the baffle <NUM>, resulting in the highest power output for the fastener driver <NUM>. The compressed gas drives the piston <NUM> and the driver blade <NUM> to the driven position, thereby driving the fastener into the workpiece.

If a subsequent fastener driving application requires a relatively low power output (e.g., for driving fasteners into relatively softer workpieces such as softwood products, engineered wood products, etc.), the control knob <NUM> is rotated to the full choke position (<FIG> and <FIG>). The eccentric pin <NUM> engages the slot <NUM> to move the baffle <NUM> toward the flow passage <NUM>, such that the baffle <NUM> extends beyond the open end <NUM> and constricts the flow passage <NUM>. When a fastener driving sequence is initiated, the compressed gas within the storage chamber <NUM> flows relatively slowly through the flow passage <NUM>, which is constricted by the baffle <NUM>, resulting in the lowest power output for the fastener driver <NUM>. The compressed gas drives the piston <NUM> and the driver blade <NUM> to the driven position, thereby driving the fastener into the workpiece.

If an intermediate power output is desired, the control knob <NUM> can be rotated to any intermediate position between the no-choke position and the choked position. In some embodiments of the fastener driver <NUM>, a detent mechanism may be used with the control knob <NUM> to define a plurality of predefined rotational positions of the control knob <NUM> coinciding with the no-choke position, the choked position, and one or more intermediate positions.

Claim 1:
A gas spring-powered fastener driver (<NUM>) comprising:
a first cylinder (<NUM>) defining a first chamber (<NUM>);
a movable piston (<NUM>) positioned within the first chamber;
a driver blade (<NUM>) attached to the piston and movable therewith between a ready position and a driven position;
a second cylinder (<NUM>) surrounding the first cylinder;
a second chamber (<NUM>) defined between the first cylinder and the second cylinder and containing pressurized gas, the second chamber being in fluid communication with the first chamber via a flow passage (<NUM>);
a throttle mechanism (<NUM>) configured to throttle flow of the pressurized gas through the flow passage, the throttle mechanism including a baffle (<NUM>) configured to selectively adjust an area of the flow passage.
wherein the first cylinder defines an open end (<NUM>) that communicates with the second chamber, and the flow passage is defined between the open end of the first cylinder and an end portion (<NUM>) of the second cylinder; characterized in that
the baffle is configured as a sliding sleeve supported about the first cylinder adjacent the open end.