Patent Description:
The present invention relates to powered fastener drivers, and more specifically to lifter mechanisms of powered fastener drivers.

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. According to its title and abstract <CIT> relates to a fastener driving tool that includes a lift mechanism for moving the driver from a driven position to a ready position. In one embodiment, the lift mechanism is mounted to a movable pivot arm, and the pivot arm is slightly rotated to allow the driver to drive a fastener; when the driver is to be lifted in a return stroke, the lifter subassembly is moved back into engagement with the driver, and multiple lifter pins contact protrusions in the driver to lift the driver from the driven position to the ready position. In another embodiment, the pivotable lifter floats along the driver, and "releases" from contact only to prevent a jam or otherwise undesirable operating condition involving the driver; otherwise, the lifter remains nested in the tool's guide body during all operating states. A solenoid- operated latch also is provided to prevent the driver from moving downward (for driving a fastener).

The present invention provides, in one aspect, a powered fastener driver including a driver blade movable from a top-dead-center (TDC) position toward a driven or bottom-dead-center (BDC) position for driving a fastener into a workpiece, a gas spring mechanism for driving the driver blade toward the BDC position, a lifter assembly having a rotary lifter for returning the driver blade from the BDC position toward the TDC position, and an arm upon which the rotary lifter is supported. The fastener driver also includes a motor which, in a first position of the rotary lifter, provides torque to the rotary lifter to return the driver blade from the BDC position toward the TDC position. The fastener driver further includes a brake mechanism which when activated, prevents the transfer of torque from the motor to the rotary lifter and redirects torque from the motor away from the rotary lifter and toward the arm, causing the lifter assembly to move from the first position toward a second position in which the rotary lifter is not engageable with the driver blade.

In some embodiments, the lifter assembly includes a drive gear between the motor and the rotary lifter for transferring torque from the motor to the rotary lifter. The brake mechanism may include an electromagnetic brake and a planetary gear train which, in the first position of the lifter assembly, receives torque from the drive gear. And, in the second position of the lifter assembly, the planetary gear train and the drive gear are braked.

The present invention provides, inyet another aspect, a powered fastener driver including a driver blade movable from a top-dead-center (TDC) position toward a driven or bottom-dead-center (BDC) position for driving a fastener into a workpiece, a gas spring mechanism for driving the driver blade toward the BDC position, and a lifter assembly having a rotary lifter for returning the driver blade from the BDC position toward the TDC position. The fastener driver also includes a motor that provides torque to a drive shaft upon which the rotary lifter is coupled for selective co-rotation therewith to return the driver blade from the BDC position toward the TDC position. The fastener driver further includes a cam mechanism positioned between the drive shaft and the rotary lifter. During rotation of the rotary lifter, when a reaction torque on the rotary lifter exceeds a predetermined torque limit, the cam mechanism moves the rotary lifter along a rotational axis of the rotary lifter from a first position, in which the rotary lifter is engaged with the driver blade, toward a second position, in which the rotary lifter is disengageable from the driver blade.

The powered fastener driver according to <FIG> is not according to the invention.

With reference to <FIG> and <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>, 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>. 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 cylinder <NUM> and the driver blade <NUM> define a driving axis <NUM>. During a driving cycle, the driver blade <NUM> and piston are moveable between a top-dead-center (TDC) or ready position, and a bottom-dead-center (BDC) or driven position, along the driving axis <NUM>. The fastener driver <NUM> further includes a lifter assembly <NUM>, 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. As explained in greater detail below, the driver blade <NUM> may stop (e.g., become jammed) at an intermediate position that is between the driven position and the ready position. In this situation, the lifter assembly <NUM> is also operable to return the driver blade <NUM> from the intermediate position to the ready position.

With reference to <FIG> and <FIG>, the powered fastener driver <NUM> further includes a frame <NUM> positioned within the housing <NUM>. The frame <NUM> is configured to support the lifter assembly <NUM> within the housing <NUM>. The fastener driver <NUM> further includes a blade guide <NUM> that partially surrounds the driver blade <NUM>.

With reference to <FIG>, the driver blade <NUM> includes a plurality of lift teeth <NUM> formed along an edge <NUM> of the driver blade <NUM>. As described earlier, the driver blade <NUM> defines the driving axis <NUM> along which it moves between the ready position and the driven position. The edge <NUM> extends in the direction of the driving axis <NUM>. In particular, the lift teeth <NUM> project laterally from the edge <NUM> relative to the driving axis <NUM>.

With reference to <FIG>, the motor <NUM> is coupled to a first gear train <NUM> and a second gear train <NUM>. In particular, the first gear train <NUM> is downstream of the motor <NUM> and the second gear train <NUM> is downstream of the first gear train <NUM> such that torque is transferred from the motor <NUM> to the first gear train <NUM>, and then from the first gear train <NUM> to the second gear train <NUM>. Each of the first gear train <NUM> and the second gear train <NUM> is configured as a multi-stage planetary gear train. As shown in <FIG>, a final stage of the first gear train <NUM> is coupled to a first stage of the second gear train <NUM>. More specifically, a carrier <NUM> of the final stage of the first gear train <NUM> includes an input pinion <NUM> for driving the second gear train <NUM> (<FIG>). Furthermore, the fastener driver <NUM> includes a brake mechanism <NUM> operatively coupled to a last stage (e.g., fourth stage) of the second gear train <NUM>. The brake mechanism <NUM> is configured to selectively inhibit the transfer of torque through the second gear train <NUM>.

With reference to <FIG> and <FIG>, the second gear train <NUM> includes a gear case <NUM> and four planetary stages <NUM>, <NUM>, <NUM>, <NUM>. In the illustrated construction of the second gear train <NUM>, the first stage <NUM> includes a first stage ring gear <NUM> and a drive gear <NUM>. The gear case <NUM> is positioned adjacent the first stage <NUM>, and contains therein the remaining three planetary stages <NUM>, <NUM>, <NUM>. The first stage ring gear <NUM>, the drive gear <NUM>, and the gear case <NUM> are positioned between the motor <NUM> and the brake mechanism <NUM> (<FIG>).

With reference to <FIG>, the first planetary stage <NUM> includes the first stage ring gear <NUM>, the input pinion <NUM>, a first stage carrier <NUM>, which is also the drive gear, and a plurality of first stage planet gears <NUM>. A plurality of axles (not shown) extend from the front of the drive gear <NUM> upon which the first stage planet gears <NUM> are rotatably supported. In addition, a plurality of axles <NUM> extend from the rear of the drive gear <NUM> upon which second stage planet gears <NUM> are rotatably supported. The first stage planet gears <NUM> are engaged with the input pinion <NUM> for transferring torque to the four planetary stages <NUM>, <NUM>, <NUM>, <NUM>.

With reference to <FIG>, the first stage ring gear <NUM> has an annular portion <NUM> and an arm <NUM> extending therefrom. The annular portion <NUM> includes a plurality of teeth <NUM> (<FIG>) on an inner circumferential surface of the ring gear <NUM> that are meshed with teeth of the first stage planet gears <NUM>. During a portion of each fastener driving cycle, torque from the motor <NUM> is redirected from the drive gear <NUM>, causing the first stage ring gear <NUM> to rotate relative to the first stage planet gears <NUM>, as further discussed below.

With reference to <FIG>, the second planetary stage <NUM> includes a plurality of second stage planet gears <NUM>, a second stage carrier <NUM>, and a second stage ring gear <NUM>. In the illustrated embodiment, the second stage planet gears <NUM> include four planet gears <NUM>. The second stage carrier <NUM> includes a sun gear <NUM> extending from the front of the carrier <NUM>. In addition, a plurality of axles (not shown) extend from the rear of the carrier <NUM> upon which third stage planet gears <NUM> are rotatably supported. The second planetary stage <NUM> is positioned downstream of the first planetary stage <NUM> to receive torque from the first planetary stage <NUM>.

With continued reference to <FIG>, the third planetary stage <NUM> includes a plurality of third stage planet gears <NUM>, a third stage carrier <NUM>, and a third stage ring gear <NUM>. In the illustrated embodiment, the third stage planet gears <NUM> include three planet gears <NUM>. The third stage carrier <NUM> includes a sun gear <NUM> extending from the front of the carrier <NUM>. In addition, a plurality of axles (not shown) extend from the rear of the carrier <NUM> upon which fourth stage planet gears <NUM> are rotatably supported. The third planetary stage <NUM> is positioned downstream of the second planetary stage <NUM> to receive torque from the second planetary stage <NUM>.

The fourth planetary stage <NUM> includes a plurality of fourth stage planet gears <NUM> and the third stage ring gear <NUM>. In the illustrated embodiment, the fourth stage planet gears <NUM> include two planet gears <NUM>. The fourth stage planet gears <NUM> are directly meshed to a pinion <NUM> coupled to an output <NUM> of the brake mechanism <NUM>. The fourth planetary stage <NUM> is positioned downstream of the third planetary stage <NUM> to receive torque from the third planetary stage <NUM>.

With reference to <FIG>, the brake mechanism <NUM> includes the output <NUM>, a plate <NUM>, a spring (not shown), and an electromagnet <NUM> (e.g., electromagnetic coil). The output <NUM> extends from a rear of the plate <NUM> such that the output <NUM> and the plate <NUM> are integrally formed. Therefore, the output <NUM>, the plate <NUM>, and the pinion <NUM> of the fourth planetary stage <NUM> co-rotate together. The spring biases the plate <NUM> and the output <NUM> away from the electromagnet <NUM>. In the illustrated embodiment, the frame <NUM> is configured to support the brake mechanism <NUM> (<FIG>).

When the electromagnet <NUM> is activated, the plate <NUM>, the output <NUM>, and pinion <NUM> are pulled upward (from the frame of reference of <FIG>), against the bias of the spring, such that a front of the plate <NUM> engages the frame <NUM> or a friction plate (not shown) secured to the frame <NUM> to apply a frictional resistance to rotation of the plate <NUM>, the output <NUM>, and the pinion <NUM>, therefore braking rotation of these components. Thus, rotation of the gears <NUM>, <NUM>, <NUM>, <NUM> of the planetary stages <NUM>, <NUM>, <NUM>, <NUM> is also braked. Specifically, the brake mechanism <NUM> prevents the rotation of the fourth stage planet gears <NUM> meshed with the pinion <NUM> when the electromagnet <NUM> is activated, thereby inhibiting the transfer of torque successively throughout the planetary stages <NUM>, <NUM>, <NUM>, <NUM> from the fourth stage <NUM> to the first stage <NUM>.

With reference to <FIG> and <FIG>, the lifter assembly <NUM> includes an offset gear <NUM>, a rotary lifter <NUM>, and a shaft <NUM> (<FIG>) coupling the offset gear <NUM> and the rotary lifter <NUM> for co-rotation. The offset gear <NUM> is enmeshed with the drive gear <NUM> of the second gear train <NUM>, thus receiving torque from the drive gear <NUM> when it rotates. The lifter <NUM> may be coupled for co-rotation with the shaft <NUM> in any of a number of different ways (e.g., by using a key and keyway arrangement, an interference fit, a spline-fit, etc.). The shaft <NUM> is rotatably supported by the arm <NUM> of the ring gear <NUM> and a second arm <NUM>. In the illustrated embodiment, the second arm <NUM> is positioned between the brake mechanism <NUM> and the fourth planetary stage <NUM>, and is pivotably supported by a bearing <NUM> mounted in the frame <NUM> (<FIG>).

With reference to <FIG>, the lifter <NUM> includes a body <NUM> and a plurality of pins <NUM> that sequentially engage the lift teeth <NUM> formed on the driver blade <NUM> as the driver blade <NUM> is returned from the driven position toward the ready position. As such, torque from the motor <NUM> is transferred through the first gear train <NUM> and through the first stage <NUM> of the second gear train <NUM>, to the offset gear <NUM>, and subsequently to the lifter <NUM>, which engages the driver blade <NUM>. Specifically, the pins <NUM> of the lifter <NUM> sequentially engage the corresponding lift teeth <NUM> to move the driver blade <NUM> from the driven position toward the ready position.

With reference to <FIG> and <FIG>, the lifter assembly <NUM> is pivotable between an engaged position, in which the rotary lifter <NUM> is engageable with the driver blade <NUM> to return the driver blade <NUM> from the driven positon toward the ready position, and a bypass position in which the lifter assembly <NUM> is pivoted about a pivot axis <NUM> (<FIG>) coaxial with the input pinion <NUM> of the second gear train <NUM> away from the driver blade <NUM>. While the bypass position does not coincide with a single discrete position of the lifter assembly <NUM> about the pivot axis <NUM>, the lifter assembly <NUM> reaches the bypass position when the rotary lifter <NUM> is no longer engageable with the driver blade <NUM>. The lifter assembly <NUM> is biased by a spring (not shown) to return the lifter assembly <NUM> toward the engaged position.

The powered fastener driver <NUM> further includes a controller (e.g., a printed circuit board having one or more microprocessors). The controller is configured to activate and deactivate the motor <NUM> during operation of the fastener driver <NUM>. Specifically, the controller may be electrically connected to one or more sensors for determining, based on an output of the one or more sensors, when to drive the motor <NUM>. For example, the lifter assembly <NUM> may include a sensor, such as a Hall-effect sensor operable to detect a magnet positioned on the lifter <NUM>. When the Hall-effect sensor detects the magnet, the sensor indicates to the controller a rotational position of the lifter <NUM>, which may correlate to the ready position of the driver blade <NUM>. The driver blade <NUM> may also include an onboard magnet (not shown) that is detectable by another Hall-effect sensor (also not shown) in communication with the controller, for example, when the driver blade <NUM> is in the driven position.

The brake mechanism <NUM> is electrically connected to the controller. The motor <NUM> is configured to rotate continuously in one direction (e.g., forward direction) during a driving cycle. The brake mechanism <NUM> is selectively activated by the controller to redirect the torque from the motor <NUM> away from the lifter <NUM> for adjusting the lifter assembly <NUM> from the engaged position toward the bypass position, as further discussed below.

The trigger <NUM> is also electrically connected to the controller such that activation of the trigger <NUM> to initiate a driving cycle may also initiate a timing sequence. In particular, in response to depressing the trigger <NUM>, the controller activates the motor <NUM> and initiates a timer to determine whether, at the expiration of the timer, the driver blade <NUM> has reached the driven position. Upon the driver blade <NUM> reaching the driven position, the controller continues driving the motor <NUM> to return the driver blade <NUM> from the driven position to the ready position. The one or more sensors may be configured to indicate to the controller when the driver blade <NUM> has reached the ready position.

During a normal driving cycle in which a fastener is discharged into a workpiece, the lifter assembly <NUM> returns the piston and the driver blade <NUM> from the driven position to the ready position. As the piston and the driver blade <NUM> are returned to the ready position, the gas within the cylinder <NUM> above the piston is compressed. Once in the ready position, the piston and the driver blade <NUM> are held in position until released by user activation of the trigger <NUM> (<FIG>), which initiates a driving cycle. When released, the compressed gas above the piston within the cylinder <NUM> drives the piston and the driver blade <NUM> to the driven position, thereby driving a fastener into a workpiece. The illustrated fastener driver <NUM> therefore operates on a gas spring principle utilizing the lifter assembly <NUM> and the piston to compress the gas within the cylinder <NUM> upon being returned to the ready position for a subsequent fastener driving cycle. The ready position may be when the piston and the driver blade <NUM> is at the TDC position. In alternative embodiments, the ready position may be when the piston and the driver blade <NUM> is near the TDC position (e.g., <NUM> percent of the way up the cylinder <NUM>) such that the compressed air is partially compressed.

More specifically, when the trigger <NUM> is actuated and the piston and the driver blade <NUM> are at the ready position, the controller activates the motor <NUM> and the brake mechanism <NUM>. The motor <NUM> supplies torque to the first gear train <NUM> and the second gear train <NUM>. Activation of the brake mechanism <NUM>, however, prevents the transfer of torque through the last three stages <NUM>, <NUM>, <NUM> of the second gear train <NUM> such that the planetary gears <NUM>, <NUM>, <NUM>, <NUM> of all the stages <NUM>, <NUM>, <NUM>, <NUM> and the drive gear <NUM> remain stationary, and the torque is redirected toward the first stage ring gear <NUM>. Specifically, when the brake mechanism <NUM> is activated, the electromagnet <NUM> is energized and the plate <NUM>, the output <NUM>, and the pinion <NUM> are pulled upward (from the frame of reference of <FIG>), against the bias of the spring, such that a front of the plate <NUM> engages the frame <NUM> or the friction plate (not shown), applying a frictional resistance and thereby inhibiting rotation of the plate <NUM>, the output <NUM>, and the pinion <NUM>. As such, rotation of the planetary gears <NUM>, <NUM>, <NUM>, <NUM> of all the stages <NUM>, <NUM>, <NUM>, <NUM> and the drive gear <NUM> is inhibited and the first stage ring gear <NUM> rotates (counter-clockwise from the frame of reference of <FIG>) relative to the stationary first stage planetary gears <NUM> to move or pivot the lifter assembly <NUM>, including the arm <NUM>, toward the bypass position. Thereafter, the lifter <NUM> no longer engages the driver blade <NUM>, and the piston and the driver blade <NUM> are thrust downward toward the driven position by the compressed air in the cylinder <NUM> above the piston. As the driver blade <NUM> is displaced toward the driven position, the motor <NUM> and the brake mechanism <NUM> remain activated to continue redirection of the torque away from the lifter <NUM> toward the first stage ring gear <NUM>, maintaining the lifter assembly <NUM> in the bypass position. In some embodiments, the lifter assembly <NUM> may raise the driver blade <NUM> past the ready position toward the TDC position (after the trigger <NUM> is actuated) before the lifter assembly <NUM> is moved to the bypass position.

Upon a fastener being driven into a workpiece, the driver blade <NUM> is in the driven or BDC position. As the driver blade <NUM> reaches the driven position, the one or more sensors indicate to the controller that the driver blade <NUM> has successfully reached the driven position. As such, the controller continues driving of the motor <NUM> and deactivates the brake mechanism <NUM>, allowing the lifter assembly <NUM> to move toward the engaged position by the bias of the spring. Deactivation of the brake mechanism <NUM> allows the transfer of torque through the second gear train <NUM> to resume. As such, the second stage, third stage, and fourth stage planetary gears <NUM>, <NUM>, <NUM> freely spin (clockwise from the frame of reference of <FIG>), and the first stage ring gear <NUM> is stationary. The drive gear <NUM> receives the torque from the motor <NUM> to rotate the offset gear <NUM>, and consequently to rotate the lifter <NUM>. Subsequently, a first of the pins <NUM> on the lifter <NUM> engages an uppermost one of the lift teeth <NUM> on the driver blade <NUM>, and continued driving of the motor <NUM> rotates the lifter <NUM>, which returns the driver blade <NUM> and the piston toward the ready position. In some embodiments, one complete rotation of the lifter <NUM> is necessary to return the driver blade <NUM> from the driven position to the ready position.

During a fastener driving cycle, the driver blade <NUM> may stop at an intermediate position between the ready position and the driven position as a result of a fastener jamming within the driver <NUM>. The one or more sensors determine if the driver blade <NUM> stops at the intermediate position if the driver blade <NUM> isn't detected at the ready position at the expiration of the abovementioned timer, at which time the controller implements an error correction mode to allow the user to clear the jammed fastener and to return the driver blade <NUM> to its ready position for a subsequent fastener driving operation. With the driver blade <NUM> is in the intermediate position, the pins <NUM> on the lifter <NUM> may be blocked by the lift teeth <NUM>, depending on the exact position at which the driver blade <NUM> stops. In other words, the driver blade <NUM> may stop at the intermediate position in which the lift teeth <NUM> are blocking the pins <NUM> from reentering the space between the lift teeth <NUM>.

In particular, when the driver blade <NUM> stops at the intermediate position and the controller implements the error correction mode, the controller energizes a solenoid of a driver blade latch mechanism (not shown), thereby moving a latch to engage one of a plurality of latch teeth on the driver blade <NUM> opposite the lift teeth <NUM>. As such, the latch holds the driver blade <NUM> and prevents movement of the driver blade <NUM> toward the driven position, thereby inhibiting unintentional firing of the fastener driver <NUM> when a fastener jamming occurs. The controller continues to drive the motor <NUM> such that the lifter <NUM> continues to rotate. Continued rotation of the lifter <NUM> allows the pins <NUM> to reenter the space between the lift teeth <NUM>. Should the lift teeth <NUM> block the pins <NUM> from reentering the space between the lift teeth <NUM>, the lifter assembly <NUM> is pivotable away from the driver blade <NUM> toward the bypass position by the continued rotation of the lifter <NUM> such that lifter assembly <NUM> pivots slightly away from the driver blade <NUM> against the bias of the spring to overcome the jam. Thereafter, the pins <NUM> are aligned with the space between the lift teeth <NUM> and the spring pivots the lifter assembly <NUM> toward the engaged position. Subsequently, the lifter <NUM> returns the driver blade <NUM> to the ready position from the intermediate position. Once the one or more sensors indicate to the controller that the driver blade <NUM> has reached the ready position, the controller deactivates the motor <NUM> and the latch solenoid, and the fastener driver <NUM> is ready for a subsequent fastener driving cycle.

The lifter assembly <NUM> is operable to automatically overcome a jam when the lifter assembly <NUM> is lifting the driver blade <NUM> from the driven position to the ready position.

<FIG> illustrates a portion of another embodiment of a fastener driver <NUM> and a lifter assembly <NUM>, with like components and features as the embodiment of the fastener driver <NUM> and lifter assembly <NUM> shown in <FIG> being labeled with like reference numerals plus "<NUM>". The lifter assembly <NUM> is powered by a motor <NUM> (<FIG>) and is operable to return a driver blade <NUM> from the driven position (<FIG>) to the ready position (<FIG>) during each fastener driving cycle. If a fastener becomes jammed during a driving cycle, the driver blade <NUM> may stop at an intermediate position between the driven position and the ready position. Like the lifter assembly <NUM> described above, the lifter assembly <NUM> is also operable to return the driver blade <NUM> from the intermediate position to the ready position, thereby resetting the fastener driver <NUM> for a subsequent fastener driving cycle.

With reference to <FIG>, the lifter assembly <NUM> includes a rotary lifter <NUM> coupled for co-rotation with an output shaft <NUM> of the gear train <NUM> (<FIG>). In the illustrated embodiment, the output shaft <NUM> includes external splines <NUM> extending along the length of the output shaft <NUM> and the rotary lifter <NUM> includes a bore defining internal splines <NUM> mated with the external splines on the output shaft <NUM>. As such, the rotary lifter <NUM> receives torque from the output shaft <NUM> when the shaft <NUM> rotates about its a rotational axis <NUM>. However, the mated splines do not axially constrain the rotary lifter <NUM> on the output shaft <NUM>.

With reference to <FIG> and <FIG>, the rotary lifter <NUM> includes a body <NUM> and a plurality of pins <NUM> that sequentially engage lift teeth <NUM> (<FIG>) formed on the driver blade <NUM> as the driver blade <NUM> is returned from the driven position toward the ready position. As such, torque from the motor <NUM> is transferred through the gear train <NUM> and subsequently to the lifter <NUM>, which engages the driver blade <NUM>. Specifically, the pins <NUM> of the lifter <NUM> sequentially engage the corresponding lift teeth <NUM> to move the driver blade <NUM> from the driven position toward the ready position.

With reference to <FIG>, the body <NUM> of the lifter <NUM> includes a first flange <NUM> and a second flange <NUM> parallel with the first flange <NUM>. The pins <NUM> extend between the flanges <NUM>, <NUM>. While the first flange <NUM> is generally circular, the second flange <NUM> has a recess <NUM> in its outer peripheral surface, thereby exposing an axial face portion <NUM> of the first flange <NUM>. A first pin 1238A and a second pin 1238B of the plurality of pins <NUM> are positioned on the axial face portion <NUM>, with the distal ends of the respective pins 1238A, 1238B being exposed.

With continued reference to <FIG>, the second flange <NUM> includes a first cam portion <NUM> and a second cam portion <NUM> that extend from the second flange <NUM> away from the first flange <NUM>. The first and second cam portions <NUM>, <NUM> are positioned opposite each other with the rotational axis <NUM> therebetween. But, relative to the rotational axis <NUM>, the first cam portion <NUM> is spaced farther in a radially outward direction on the second flange <NUM> than the second cam portion <NUM>. Each of the first and second cam portions <NUM>, <NUM> includes a first surface <NUM> that is inclined relative to the rotational axis <NUM> and an adjacent second surface <NUM> that is perpendicular to the rotational axis <NUM>. The second surfaces <NUM> are hereinafter referred to as landing surfaces <NUM>.

With reference to <FIG>, the frame <NUM> includes a third cam portion <NUM> and a fourth cam portion <NUM> extending toward the rotary lifter <NUM>. Like the first and second cam portions <NUM>, <NUM>, the third and fourth cam portions <NUM>, <NUM> are positioned opposite each other with the rotational axis <NUM> therebetween. But, relative to the rotational axis <NUM>, the third cam portion <NUM> is spaced farther in a radially outward direction than the fourth cam portion <NUM>. Also, each of the third and fourth cam portions <NUM>, <NUM> includes a first surface <NUM> that is inclined relative to the rotational axis <NUM> and an adjacent second surface <NUM> that is perpendicular to the rotational axis <NUM>. The second surfaces <NUM> may be defined as landing surfaces <NUM>. The inclined surfaces <NUM> of the third and fourth cam portions <NUM>, <NUM> are engageable with the inclined surfaces <NUM> of the first and second cam portions <NUM>, <NUM>, respectively. And, the landing surfaces <NUM> of the third and fourth cam portions <NUM>, <NUM> are engageable with the landing surfaces <NUM> of the first and second cam portions <NUM>, <NUM>, respectively.

With reference to <FIG>, the lifter assembly <NUM> further includes a spring <NUM> for biasing the lifter <NUM> along the rotational axis <NUM> toward an interior surface <NUM> of the frame <NUM> from which the cam portions <NUM>, <NUM> project (<FIG>) to position the lifter <NUM> in an engaged position in which the pins <NUM> on the rotary lifter <NUM> are engageable with the corresponding teeth <NUM> on the driver blade <NUM> (<FIG>). Engagement between the first and second cam portions <NUM>, <NUM>, and the third and fourth cam portions <NUM>, <NUM>, respectively, by rotation of the lifter <NUM> axially moves the lifter <NUM> on the output shaft <NUM>, along the rotational axis <NUM>, away from the interior surface <NUM> of the frame <NUM> against the bias of the spring <NUM> (thus away from the engaged position of the lifter <NUM>). In particular, the axial movement of the lifter <NUM> away from the engaged position also moves the pins <NUM> "out of plane" with the driver blade <NUM> where, when the landing surfaces <NUM>, <NUM> of the respective cam portions <NUM>, <NUM>, <NUM>, <NUM> are engaged, a gap <NUM> is created between a rear surface <NUM> of the driver blade <NUM> and the distal ends of the respective pins 1238A, 1238B (<FIG>). When the lifter <NUM> is moved a sufficient distance to create the gap <NUM>, the lifter <NUM> is located in a bypass position.

During a normal driving cycle in which a fastener is discharged into a workpiece, the lifter <NUM> returns the piston and the driver blade <NUM> from the driven position to the ready position. Once in the ready position (e.g., <FIG>), the piston and the driver blade <NUM> are held until released by user activation of a trigger <NUM> (<FIG>), which initiates a driving cycle. When released, the compressed gas above the piston drives the piston and the driver blade <NUM> toward the driven position (<FIG>), thereby driving a fastener into a workpiece. The piston and driver blade <NUM> are then returned again toward the ready position, which is near a true TDC position of the piston and driver blade <NUM>.

Prior to initiation of a fastener driving cycle, the inclined surfaces <NUM> of the first and second cam portions <NUM>, <NUM> are spaced circumferentially from the inclined surfaces <NUM> of the third and fourth cam surface <NUM>, <NUM>, as shown in <FIG>. When the trigger <NUM> is actuated and the piston and the driver blade <NUM> are at the ready position, the controller activates the motor <NUM>. The motor <NUM> supplies torque to the gear train <NUM> and begins rotating the lifter <NUM>. After a small amount of rotation, the pin 1238C of the lifter <NUM> disengages the lowermost tooth <NUM> on the driver blade <NUM>, and the piston and the driver blade <NUM> are thrust downward toward the driven position by the compressed air above the piston. In some embodiments, the lifter <NUM> may raise the driver blade <NUM> past the ready position toward the TDC position before the driver blade <NUM> is driven toward the driven position.

After driving a fastener into a workpiece, the driver blade <NUM> is in the driven or BDC position (<FIG>). After the driver blade <NUM> reaches the driven position, the inclined surfaces <NUM> of the first and second cam portions <NUM>, <NUM> engage the inclined surfaces <NUM> of the third and fourth cam surface <NUM>, <NUM>, as shown in <FIG>. Continued rotation of the lifter <NUM> causes the inclined surfaces <NUM> of the first and second cam portions <NUM>, <NUM> to slide along the inclined surfaces <NUM> of the third and fourth cam portions <NUM>, <NUM> (<FIG>), thereby translating the lifter <NUM> against the bias of the spring <NUM> along the rotational axis <NUM> away from the engaged position and toward the bypass position. The lifter <NUM> continues translating (as well as rotating) until the landing surfaces <NUM> of the first and second cam portions <NUM>, <NUM> reach the landing surfaces <NUM> of the third and fourth cam portions <NUM>, <NUM>, respectively (<FIG>). Thereafter, the lifter <NUM> stops translating, at which time the first pin 1238A has been moved out of plane with the driver blade <NUM>. The lifter <NUM> is at the bypass position (i.e., the farthest axial position from the driver blade <NUM>) when the landing surfaces <NUM> of the first and second cam portions <NUM>, <NUM> are in sliding contact with the landing surfaces <NUM> of the third and fourth cam portions <NUM>, <NUM>, respectively (<FIG>).

Continued activation of the motor <NUM> continues to rotate the lifter <NUM> such that the landing surfaces <NUM> of the first and second cam portions <NUM>, <NUM> move circumferentially past the landing surfaces <NUM> of the third and fourth cam portions <NUM>, <NUM> respectively, as shown in <FIG>. At this time, the spring <NUM> rebounds, translating the lifter <NUM> from the bypass position toward the engaged position again. Subsequently, as shown in <FIG>, the first lifter pin 1238A on the lifter <NUM> engages an uppermost one of the lift teeth <NUM> on the driver blade <NUM>. Because the distal ends of the lifter pins 1238A, 1238B are exposed by the recess <NUM> defined in the second flange <NUM>, the uppermost one of the lift teeth <NUM> cannot contact or jam against the second flange <NUM> as the lifter <NUM> is moved back into the engaged position (i.e., back into plane with the driver blade <NUM>). Continued activation of the motor <NUM> rotates the lifter <NUM>, which returns the driver blade <NUM> and the piston toward the ready position. In some embodiments, one complete rotation of the lifter <NUM> is necessary to return the driver blade <NUM> from the driven position to the ready position.

In particular, the first and second cam portions <NUM>, <NUM> (and the third and fourth cam portions <NUM>, <NUM>) are positioned at predetermined circumferential positions to reciprocate the lifter <NUM> between the engaged position and the bypass position after the driver blade <NUM> reaches the driven position, but before the first lifter pin 1238A engages the uppermost one of the lift teeth <NUM> on the driver blade <NUM> to begin returning the driver blade <NUM> toward the ready position. The reciprocating lifter <NUM> is moved out of plane, and then back into plane with the driver blade <NUM>, with every single revolution of the lifter <NUM> for each fastener driving cycle.

During a fastener driving cycle, the driver blade <NUM> may stop at an intermediate position (<FIG>) between the ready position (<FIG>) and the driven position (<FIG>) as a result of a fastener jamming within the driver <NUM>. With the driver blade <NUM> in the intermediate position and with the lifter <NUM> in the bypass position, the first lifter pin 1238A may be blocked by one of the lift teeth 1094A (<FIG>), depending on the exact position at which the driver blade <NUM> stops. In other words, the driver blade <NUM> may stop at the intermediate position in which one of the lift teeth <NUM> is blocking the first lifter pin 1238A from reentering the space between adjacent lift teeth <NUM>. In such a situation, the lift tooth 1094A prevents the lifter <NUM> from returning to the engaged position by the rebounding spring <NUM>. Consequently, the landing surfaces <NUM> of the first and second cam portions <NUM>, <NUM>, which have moved past the landing surfaces <NUM> of the third and fourth cam portions <NUM>, <NUM> respectively, as shown in <FIG>, are prevented from axially moving toward the interior surface <NUM> of the frame <NUM>.

Continued rotation of the lifter <NUM> moves the landing surfaces <NUM> of the first and second cam portions <NUM>, <NUM> circumferentially past the landing surfaces <NUM> of the third and fourth cam portions <NUM>, <NUM> respectively, and slides the distal end of the first lifter pin 1238A along the rear surface of the driver blade <NUM> until the first lifter pin <NUM>8A can reenter the space between adjacent lift teeth <NUM>. Thereafter, the spring <NUM> rebounds and translates the lifter <NUM> toward the engaged position (shown in <FIG>), where the remainder of the pins <NUM> are aligned with the respective spaces between the lift teeth <NUM> and again moved into plane with the driver blade <NUM>. Subsequently, the lifter <NUM> returns the driver blade <NUM> to the ready position from the intermediate position. Once the one or more sensors indicate to the controller that the driver blade <NUM> has reached the ready position, the controller deactivates the motor <NUM> and the fastener driver <NUM> is ready for a subsequent fastener driving cycle.

<FIG> illustrates a portion of another embodiment of a fastener driver <NUM> and a lifter assembly <NUM>, with like components and features as the embodiment of the fastener driver <NUM> and lifter assembly <NUM> shown in <FIG> being labeled with like reference numerals plus "<NUM>". The lifter assembly <NUM> is powered by a motor <NUM> (<FIG>) and is operable to return a driver blade <NUM> (<FIG>) from the driven position to the ready position during each fastener driving cycle. If a fastener becomes jammed during a driving cycle, the driver blade <NUM> may stop at an intermediate position between the driven position and the ready position. Like the lifter assemblies <NUM>, <NUM> described above, the lifter assembly <NUM> is also operable to return the driver blade <NUM> from the intermediate position to the ready position, thereby resetting the fastener driver <NUM> for a subsequent fastener driving cycle.

With reference to <FIG>, the lifter assembly <NUM> includes a rotary lifter <NUM> coupled for co-rotation with a drive shaft <NUM> (<FIG>) of the gear train <NUM> (<FIG>). The rotary lifter <NUM> includes a body <NUM> and a plurality of pins <NUM> (<FIG>; only some of which are shown) that sequentially engage lift teeth <NUM> (<FIG>) formed on the driver blade <NUM> as the driver blade <NUM> is returned from the driven position toward the ready position. Torque from the motor <NUM> is transferred through the gear train <NUM>, to the drive shaft <NUM>, and subsequently to the lifter <NUM>, which engages the driver blade <NUM>. Specifically, the pins <NUM> of the lifter <NUM> sequentially engage the corresponding lift teeth <NUM> to move the driver blade <NUM> from the driven position toward the ready position.

With continued reference to <FIG>, the lifter <NUM> has two cam grooves <NUM> (only one of which is shown) equally spaced from each other about an inner periphery of the body <NUM> of the lifter <NUM>. Each of the cam grooves <NUM> includes a portion 2414A of which is inclined relative to the rotational axis <NUM> defined by the drive shaft <NUM> (<FIG>).

With reference to <FIG>, the drive shaft <NUM> includes two cam grooves <NUM> (only one of which is shown) equally spaced from each other about an outer periphery of the drive shaft <NUM>. Like the respective portions 2414A of the cam grooves <NUM> in the lifter <NUM>, each of the cam grooves <NUM> is inclined relative to the rotational axis <NUM>. More specifically, each cam groove <NUM> includes a first end <NUM> and a second end <NUM>, and the respective cam groove <NUM> extends from the first end <NUM> to the second end <NUM> at an oblique angle A relative to the rotational axis <NUM>. The respective pairs of cam grooves <NUM>, <NUM> in the lifter <NUM> and the drive shaft <NUM> are in facing relationship such that a cam member (e.g., a ball <NUM>) is received within each of the pairs of cam grooves <NUM>, <NUM> (<FIG>). The balls <NUM> and the cam grooves <NUM>, <NUM> effectively provide a cam arrangement between the lifter <NUM> and the drive shaft <NUM> for transferring torque between the lifter <NUM> and the drive shaft <NUM>. As such, the rotary lifter <NUM> receives torque from the drive shaft <NUM> when the shaft <NUM> rotates about its rotational axis <NUM>. Furthermore, similar to the lifter <NUM> of <FIG>, the lifter <NUM> is axially movable on the drive shaft <NUM>.

With reference to <FIG>, the lifter assembly <NUM> further includes a spring <NUM> for biasing the lifter <NUM> along the rotational axis <NUM> toward an engaged position. Specifically, the spring <NUM> biases the lifter <NUM> toward an interior surface <NUM> of the frame <NUM> in which a bearing <NUM> is mounted to position the lifter <NUM> in the engaged position in which the pins <NUM> on the rotary lifter <NUM> are engageable with the corresponding teeth <NUM> on the driver blade <NUM>. The spring <NUM> extends between a retaining ring <NUM> on the drive shaft <NUM> and the lifter <NUM>. The bearing <NUM> rotatably supports the drive shaft <NUM> at the upper interior surface <NUM> of the frame <NUM>, whereas another bearing <NUM> rotatably supports the opposite end of the drive shaft <NUM> in the frame <NUM>.

During normal operation of the nailer <NUM>, torque from the drive shaft <NUM> is transferred through the cam arrangement <NUM>, <NUM>, <NUM> to the lifter <NUM>, causing the lifter <NUM> to rotate. However, should the reaction torque applied to the lifter <NUM> (e.g., by a jammed driver blade <NUM>) exceed a predetermined torque limit, the drive shaft <NUM> will rotate relative to the lifter <NUM>, causing the balls <NUM> to ride downward within the cam grooves <NUM> from the frame of reference of <FIG>. As the balls <NUM> move in this manner within the cam grooves <NUM>, <NUM>, a downward displacement is imparted to the lifter <NUM> to move axially (along axis <NUM>) away from the bearing <NUM>, against the bias of the spring <NUM>, and thus away from the engaged position shown in <FIG>.

The cam grooves <NUM>, <NUM> are inclined at the oblique angle A corresponding to the predetermined torque limit allowed between the output shaft <NUM> and the lifter <NUM>, before the lifter <NUM> will be moved away from the engaged position. In other words, once the predetermined torque limit is exceeded, relative rotation between the drive shaft <NUM> and the lifter <NUM> applies a force on the balls <NUM> via the cam grooves <NUM> having components resolved in a direction that is transverse to the rotational axis <NUM> and a direction that is parallel with the rotational axis <NUM>. The component force acting in the direction that is parallel with the rotational axis <NUM> displaces the lifter <NUM> away from the engaged position (shown in <FIG>, against the bias of the spring <NUM>) and toward a bypass position (shown in <FIG>). The selection of the oblique angle A, and the stiffness of the spring <NUM>, allows for a sufficient amount of torque transmission between the drive shaft <NUM> and the lifter <NUM> before the reaction torque on the lifter <NUM> moves the lifter <NUM> toward the bypass position.

The axial movement of the lifter <NUM> away from the engaged position also moves the pins <NUM> "out of plane" with the driver blade <NUM>. Specifically, when the balls <NUM> move from the first end <NUM> toward the second end <NUM> of the respective cam groove <NUM> thereby axially moving the lifter <NUM>, a temporary gap <NUM> (<FIG>) may be created between a rear surface <NUM> of the driver blade <NUM> and the distal ends of the respective pins 2238A, 2238B (<FIG>) on the lifter <NUM>. This may allow the pins 2238A, 2238B to slide behind the rear surface <NUM> of the driver blade <NUM>. Alternatively, the spring <NUM> may rebound quick enough such that the spring <NUM> may bias the distal end of one of the pins 2238A, 2238B against the rear surface <NUM> causing the pin 2238A, 2238B to contact the rear surface <NUM> of the driver blade <NUM> as the lifter <NUM> moves toward the bypass position. As such, the distal ends of the pins 2238A, 2238B may slide against the rear surface <NUM> of the driver blade <NUM> as the lifter <NUM> is moved toward the bypass position.

During a normal driving cycle in which a fastener is discharged into a workpiece, the lifter <NUM> returns the piston and the driver blade <NUM> from the driven position to the ready position. Once in the ready position, the piston and the driver blade <NUM> are held until released by user activation of a trigger <NUM> (<FIG>), which initiates a driving cycle. When released, the compressed gas above the piston drives the piston and the driver blade <NUM> toward the driven position, thereby driving a fastener into a workpiece. The piston and driver blade <NUM> are then returned again toward the ready position, which is near a true TDC position of the piston and driver blade <NUM>.

Specifically, when the trigger <NUM> is actuated and the piston and the driver blade <NUM> are at the ready position, the controller activates the motor <NUM>. The motor <NUM> supplies torque to the gear train <NUM> and begins rotating the lifter <NUM>. After a small amount of rotation, the last pin <NUM>8C of the lifter <NUM> disengages the lowermost tooth <NUM> on the driver blade <NUM>, and the piston and the driver blade <NUM> are thrust downward toward the driven position by the compressed air above the piston. In some embodiments, the lifter <NUM> may raise the driver blade <NUM> past the ready position toward the TDC position before the driver blade <NUM> is driven toward the driven position. After driving a fastener into a workpiece, the driver blade <NUM> is in the driven or BDC position. Throughout the fastener driving cycle, the balls <NUM> remain proximate the first end <NUM> of the respective cam groove <NUM> for transferring the torque from the drive shaft <NUM> to the lifter <NUM>.

During a fastener driving cycle, the driver blade <NUM> may stop at an intermediate position (<FIG>) between the ready position and the driven position as a result of a fastener jamming within the driver <NUM>. When the driver blade <NUM> is in the intermediate position, the first pin <NUM>8A may jam against one of the teeth <NUM> on the driver blade <NUM>, imparting a reaction torque on the lifter <NUM> that exceeds the predetermined torque limit. As described above, the lifter <NUM> is moved from the engaged position (<FIG>) toward the bypass position (<FIG>) against the bias of the spring <NUM>.

The drive shaft <NUM> rotates relative to the lifter <NUM> such that the balls <NUM>, guided along a path defined by the respective pair of cam grooves <NUM>, <NUM>, apply a downward axial force to the lifter <NUM> thereby moving the lifter <NUM> from the engaged position (<FIG>) toward the bypass position (<FIG>). Although the lifter <NUM> is only shown at its bypass position (i.e., its farthest axial position relative to the interior surface <NUM> of the frame <NUM>) in each of the <FIG>, <FIG>, and <FIG>, the lifter <NUM> progressively moves from the engaged positon to the bypass position in response to one of the lift pins (e.g., first lift pin 2238A) becoming jammed against one of the drive teeth <NUM> when the driver blade <NUM> is stopped at the intermediate position as shown in <FIG>. Once in the bypass position, the first pin 2238A clears the particular drive tooth <NUM> against which it was jammed, permitting the lifter <NUM> to resume rotation with the drive shaft <NUM>. At this time, with the lifter <NUM> in the bypass position, the first pin <NUM>8A passes behind the rear surface <NUM> of the tip of the drive tooth <NUM> (as shown in <FIG>). In some embodiments of the driver <NUM>, the spring <NUM> biases the first pin 2238A to contact the rear surface <NUM> of the drive tooth <NUM> as the first pin <NUM>8A slides behind the drive tooth <NUM>. And, in other embodiments of the driver <NUM>, the gap <NUM> shown in <FIG> is maintained while the first pin 2238A passes behind the rear surface <NUM> of the drive tooth <NUM>, such that the first pin 2238A skips over the drive tooth <NUM>.

Once the lifter <NUM> reaches the bypass position, the balls <NUM> are located proximate the second end <NUM> of the cam grooves <NUM> as shown in <FIG>. Subsequently, the jam is cleared between the first pin 2238A and the drive tooth <NUM>, and the lifter <NUM> begins to rotate with the drive shaft <NUM>, thereby positioning the first pin 2238A in alignment with the space between the lift teeth <NUM>. The spring <NUM> then rebounds and translates the lifter <NUM> to the engaged position (<FIG>) from the bypass position (<FIG>). Subsequently, the pins <NUM> are in plane with the drive teeth <NUM> and the lifter <NUM> returns the driver blade <NUM> to the ready position from the intermediate position. Once the one or more sensors indicate to the controller that the driver blade <NUM> has reached the ready position, the controller deactivates the motor <NUM> and the fastener driver <NUM> is ready for a subsequent fastener driving cycle.

Unlike the lifter assemblies <NUM>, <NUM> of the previous embodiments, the reciprocating lifter <NUM> is moved out of plane, and then back into plane with the driver blade <NUM>, only when a fastener jam occurs (i.e., not with every single revolution of the lifter <NUM>, <NUM> for each fastener driving cycle).

Claim 1:
A powered fastener driver (<NUM>) comprising:
a driver blade (<NUM>) movable from a top-dead-center (TDC) position toward a driven or bottom-dead-center (BDC) position for driving a fastener into a workpiece;
a gas spring mechanism for driving the driver blade (<NUM>) toward the BDC position;
a lifter assembly (<NUM>) having a rotary lifter (<NUM>) for returning the driver blade (<NUM>) from the BDC position toward the TDC position;
an arm (<NUM>) upon which the rotary lifter (<NUM>) is supported;
a motor (<NUM>) which, in a first position of the rotary lifter (<NUM>), provides torque to the rotary lifter (<NUM>) to return the driver blade (<NUM>) from the BDC position toward the TDC position; and
a brake mechanism (<NUM>), characterised in that the brake mechanism, when activated, prevents the transfer of torque from the motor (<NUM>) to the rotary lifter (<NUM>) and redirects torque from the motor (<NUM>) away from the rotary lifter (<NUM>) and toward the arm (<NUM>), causing the rotary lifter (<NUM>) to move from the first position toward a second position in which the rotary lifter (<NUM>) is not engageable with the driver blade (<NUM>).